WATER QUALITY GUIDANCE MANUAL...TOC-2 TRWD Water Quality Manual June 2018 3.4.3 Design Criteria 3-17...

WATER QUALITY GUIDANCE MANUALPlanning and Implementing Stormwater Quality Practices

June 2018

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TABLE OF CONTENTS

1.1 Purpose and Introduction ........................................................................................................................... 1-1 1.2 How to Use This Manual .............................................................................................................................. 1-4 1.3 Water Quality Impacts from Development .......................................................................................... 1-5 1.4 Applicable Water Quality Protection Zones ........................................................................................ 1-5 1.5 Authorities and Jurisdictions..................................................................................................................... 1-6 1.6 BMP Submittal Requirements ................................................................................................................... 1-6 1.7 Alternative Approaches ............................................................................................................................... 1-8 1.8 Project Review Process ................................................................................................................................ 1-8

2.1 BMP and Site Planning .................................................................................................................................. 2-1 2.1.1 Site Layout ............................................................................................................................................ 2-1 2.1.2 Impervious Surfaces ......................................................................................................................... 2-2 2.1.3 Siting BMPs .......................................................................................................................................... 2-2

2.2 BMP Selection ................................................................................................................................................... 2-3 2.3 Calculation of Water Quality Volume ..................................................................................................... 2-4 2.4 BMP Design ....................................................................................................................................................... 2-6 2.5 BMP Submittal Requirements ................................................................................................................... 2-5

3.1 Sand Filters ........................................................................................................................................................ 3-1 3.1.1 Description of BMP ........................................................................................................................... 3-1 3.1.2 Applicability ......................................................................................................................................... 3-3 3.1.3 Design Criteria .................................................................................................................................... 3-3 3.1.4 Maintenance Considerations for Design and Construction.............................................. 3-5

3.2 Bioretention Basins ...................................................................................................................................... 3-6 3.2.1 Description of BMP ........................................................................................................................... 3-6 3.2.2 Applicability ......................................................................................................................................... 3-6 3.2.3 Design Criteria .................................................................................................................................... 3-7

3.2.3.1 Centralized Bioretention Basins .................................................................................... 3-7 3.2.3.2 Distributive Bioretention Basins (Rain Gardens) ................................................... 3-9

3.2.4 Maintenance Considerations During Design and Construction .................................. 3-113.3 Constructed Wetlands ............................................................................................................................... 3-12

3.3.1 Description of BMP ........................................................................................................................ 3-123.3.2 Applicability ...................................................................................................................................... 3-12 3.3.3 Design Criteria ................................................................................................................................. 3-133.3.4 Maintenance Considerations During Design and Construction .................................. 3-15

3.4 Wet Basins ...................................................................................................................................................... 3-16 3.4.1 Description of BMP ........................................................................................................................ 3-16 3.4.2 Applicability ..................................................................................................................................... 3-17

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TRWD Water Quality Manual June 2018

3.4.3 Design Criteria ................................................................................................................................. 3-17 3.4.4 Maintenance Considerations During Design and Construction .................................. 3-19

3.5 Retention / Irrigation Basin .................................................................................................................... 3-19 3.5.1 Description of BMP ........................................................................................................................ 3-19 3.5.2 Applicability ...................................................................................................................................... 3-19 3.5.3 Design Criteria ................................................................................................................................. 3-21 3.5.4 Maintenance Considerations During Design and Construction .................................. 3-24

3.6 Extended Dry Detention Basin ............................................................................................................... 3-25 3.6.1 Description of BMP ........................................................................................................................ 3-25 3.6.2 Design Criteria ................................................................................................................................. 3-23 3.6.3 Maintenance Considerations During Design and Construction .................................. 3-28

3.7 Vegetative Strip ............................................................................................................................................ 3-28 3.7.1 Description of BMP ........................................................................................................................ 3-28 3.7.2 Applicability ...................................................................................................................................... 3-29 3.7.3 Design Criteria ................................................................................................................................. 3-29 3.7.4 Maintenance Considerations During Design and Construction .................................. 3-30

3.8 Grass Swale .................................................................................................................................................... 3-30 3.8.1 Description of BMP ........................................................................................................................ 3-30 3.8.2 Applicability ...................................................................................................................................... 3-31 3.8.3 Design Criteria ................................................................................................................................. 3-31 3.8.4 Maintenance Considerations During Design and Construction .................................. 3-32

3.9 Permeable Surfaces .................................................................................................................................... 3-33 3.9.1 Description of BMP ........................................................................................................................ 3-33 3.9.2 Design Criteria ................................................................................................................................. 3-34 3.9.3 Maintenance Considerations During Design and Construction .................................. 3-34

Section 4 Permanent BMP Design Components ................................................................................. 4-1 4.1 Stormwater Inlets ........................................................................................................................................... 4-4

4.1.1 Curb Cut / Depressed Curb............................................................................................................ 4-5 4.1.2 Trench Drain ........................................................................................................................................ 4-5 4.1.3 Gutter Apron ........................................................................................................................................ 4-5 4.1.4 Manufactured At-Grade Inlet ........................................................................................................ 4-6 4.1.5 Flow Splitter ........................................................................................................................................ 4-6 4.1.6 Distribution Pipe ................................................................................................................................ 4-7

4.2 Pre-Treatment/Post-Treatment ............................................................................................................ 4-13 4.2.1 Vegetated Filter Strip .................................................................................................................... 4-14 4.2.2 Sediment Forebay .......................................................................................................................... 4-14 4.2.3 Floatable Separators ..................................................................................................................... 4-15 4.2.4 Hydrodynamic Separator ............................................................................................................ 4-15 4.2.5 Gravity (Oil Grit) Separator ........................................................................................................ 4-15 4.2.6 Grass Swale ....................................................................................................................................... 4-16 4.2.7 Micropool ........................................................................................................................................... 4-16

4.3 Energy Dissipation ...................................................................................................................................... 4-19 4.3.1 Splash Pad .......................................................................................................................................... 4-20 4.3.2 Sump .................................................................................................................................................... 4-20

4.4 Area Protection ............................................................................................................................................. 4-24

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4.4.1 Curb ...................................................................................................................................................... 4-25 4.4.2 Bollards ............................................................................................................................................... 4-22

4.5 BMP Media ...................................................................................................................................................... 4-30 4.5.1 Bioretention or Engineered Soil ............................................................................................... 4-31 4.5.2 Sand ...................................................................................................................................................... 4-33 4.5.3 Storage Aggregate .......................................................................................................................... 4-33

4.6 Media Barriers .............................................................................................................................................. 4-36 4.6.1 Sand ..................................................................................................................................................... 4-37 4.6.2 Pea Gravel (No. 7 or 8) ................................................................................................................. 4-37 4.6.3 Permeable Geotextile .................................................................................................................... 4-38 4.6.4 Geomembrane Liner ...................................................................................................................... 4-39 4.6.5 Clay Liner ........................................................................................................................................... 4-40

4.7 Landscaping ................................................................................................................................................... 4-42 4.7.1 Chart for Application of Landscaping .................................................................................... 4-44 4.7.2 Seed Mixes ........................................................................................................................................ 4-44

4.7.2.1Nurse Crop Seed Mix ......................................................................................................... 4-44 4.7.2.2 Seed Mix 1: Dry/Wet Conditions – Bottom and Sides ........................................ 4-44 4.7.2.3 Seed Mix 2: Dry/Wet Conditions – Bottom ............................................................. 4-45 4.7.2.4 Seed Mix 3: Dry Conditions – Upper and Back Slopes ........................................ 4-46 4.7.2.5 Seed Mix 4 – Overseed: Wet and Moist Conditions – Regular Drainage or Seepage Along Bottom ................................................................................................................... 4-46 4.7.2.6 Seed Mix 5: Access Roads or Pedestrian Access Ramps .................................... 4-47 4.7.2.7 Plant List 1: Bioretention ............................................................................................... 4-47 4.7.2.8 Plant List 2: Deep Water Zone (6’ Deep to 18” deep) ......................................... 4-49 4.7.2.9 Plant List 3: Aquatic Bench (18” Deep to Normal Water Level) .................... 4-50 4.7.2.10 Plant List 4: Wetland Plants (Normal Water Level to +6”) ............................ 4-50 4.7.2.11 Plant List 5: Semi-Wet Zone (Normal Water Level to +4’) ............................ 4-51 4.7.2.12 Plant List 6: Wooded Vegetation (+6” Above normal Water Level and Up) .... .................................................................................................................................................................. 4-52 4.7.2.13 Plant List 7: Periodically Inundated (+4’ and Up) ............................................. 4-53 4.7.2.14 Plant List 8: Infrequently Inundated ...................................................................... 4-53

4.7.3 Maintenance ..................................................................................................................................... 4-55 4.8 Outlets/Piping ............................................................................................................................................... 4-58

4.8.1 Underdrain ........................................................................................................................................ 4-59 4.8.2 Cleanout .............................................................................................................................................. 4-59 4.8.3 Overflow Riser ................................................................................................................................. 4-60 4.8.4 Multi-Stage Outlet Structure ...................................................................................................... 4-60 4.8.5 Observation Well ............................................................................................................................ 4-61 4.8.6 Anti-Seep Collar ............................................................................................................................... 4-61 4.8.7 Utility Sleeve ..................................................................................................................................... 4-61

4.9 Permeable Surfaces .................................................................................................................................... 4-70 4.9.1 Permeable Pavers ........................................................................................................................... 4-70 4.9.2 Porous Pavers .................................................................................................................................. 4-71

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Section 5 Water Quality Requirements Specific to Zone 1 (Panther Island) ........................... 5-1 .1 Introduction and Background ................................................................................................................... 5-1 .2 Requirements Specific to Zone 1 .............................................................................................................. 5-1

List of Figures Figure 1.1 Water Quality Zones for the Trinity River ............................................................................. 1-3 Figure 2.1 Water Quality Depth (in watershed inches) for the 85th Percentile

Capture of Runoff ............................................................................................................................. 2-4 Figure 3.1 Conceptual Rendering of a Concrete Sand Filter ................................................................ 3-2 Figure 3.2 Conceptual Rendering of Distributive Bioretention Basin .............................................. 3-7 Figure 3.3 Conceptual Rendering of a Constructed Wetland ............................................................ 3-13 Figure 3.4 Conceptual Rendering of a Wet Basin................................................................................... 3-16 Figure 3.5 Conceptual Rendering of a Retention / Irrigation Basin .............................................. 3-20 Figure 3.6 Conceptual Rendering of an Extended Dry Detention Basin ....................................... 3-26 Figure 3-7 Conceptual Rendering of Permeable Pavers ..................................................................... 3-33 Figure 4.1 Example of Design Components in Bioretention BMP ...................................................... 4-1 Figure 5.1 Distribution of Stormwater Quality Practices by Type for Zone 1 (Panther Island) ......................................................................................................................................................................... 5-3

List of Design Criteria DM-DC 4.1.1 Curb Cut / Depressed Curb ..................................................................................................... 4-9 DM-DC 4.1.2 Trench Drain .............................................................................................................................. 4-10 DM-DC 4.1.3 Gutter Apron............................................................................................................................... 4-11 DM-DC 4.1.4 Distribution Piping .................................................................................................................. 4-12 DM-DC 4.2.1 Vegetated Filter Strip .............................................................................................................. 4-18 DM-DC 4.3.1 Splash Pad ................................................................................................................................... 4-22 DM-DC 4.3.2 Energy Dissipation Sump ...................................................................................................... 4-23 DM-DC 4.4.1 Curbing ......................................................................................................................................... 4-27 DM-DC 4.4.2 Bollard ........................................................................................................................................... 4-28 DM-DC 4.8.1 Underdrain .................................................................................................................................. 4-63 DM-DC 4.8.2 Cleanout ....................................................................................................................................... 4-64 DM-DC 4.8.3 Outflow Riser ............................................................................................................................. 4-65 DM-DC 4.8.4 Multi-Stage Outlet Structure ................................................................................................ 4-66 DM-DC 4.8.5 Observation Well ...................................................................................................................... 4-67 DM-DC 4.8.6 Anti-Seep Collar ........................................................................................................................ 4-68 DM-DC 4.8.7 Utility Sleeve ............................................................................................................................... 4-69 DM-DC 4.9.1 Permeable Pavers ..................................................................................................................... 4-73

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List of Tables Table 2.1 Pollutant Reductions by BMP ........................................................................................................ 2-3 Table 2.2 Equations for Required Water Quality Depth ........................................................................ 2-5 Table 4.1 Minimum Applicable Design Components by BMP Practice ............................................ 4-2 Table 4.2 Maximum Permissible Entrance Velocities Typical BMP Surface Materials .......... 4-19 Table 4.3 Compost for Bioretention Soil Mix Testing Parameter Requirements ..................... 4-31 Table 4.4 Expanded Shale Gradation Requirements ............................................................................ 4-32 Table 4.5 Bioretention Soil Mix Testing Parameter Requirements ................................................ 4-32 Table 4.6 Crushed Rock Aggregate Gradation......................................................................................... 4-34 Table 4.7 No. 3 Aggregate Storage Gradation Requirements ........................................................... 4-34 Table 4.8 No. 7 and No. 8 (Pea Gravel) Gradation Requirements ................................................... 4-38 Table 4.9 Permeable Geotextile Requirements ...................................................................................... 4-39 Table 4.10 Geomembrane Requirements ................................................................................................. 4-39 Table 4.11 Sizing Perforated Pipes .............................................................................................................. 4-59

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Appendices Appendix A – Design Review Resources

Appendix B – BMP Fact Sheets

Appendix C – Planting Palettes

Appendix D – Design Component Inspection and Maintenance

Appendix E – BMP Spreadsheets

Appendix F – Zone Maps

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List of Acronyms

BMP best management practice CFW City of Fort Worth CGP Construction General Permit cm/s centimeters per second ft/sec feet per second GSI green stormwater infrastructure HDPE high density polyethylene iSWMTM integrated Stormwater Management lbs. pounds lbs/sq yd pounds per square yard LID low impact development NOI notice of intent NRCS Natural Resources Conservation Service O&M operation and maintenance oz/cm3 ounces per cubic centimeter PCB polychlorinated biphenyl PVC polyvinyl chloride STD standard SWPPP Storm Water Pollution Prevention Plan TCEQ Texas Commission on Environmental Quality TPDES Texas Pollutant Discharge Elimination System TRWD Tarrant Regional Water District TxDOT Texas Department of Transportation USCS Unified Soil Classification System UWRI Urban Water Resources Institute

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TRWD WATER QUALITY MANUALPLANNING AND IMPLEMENTING STORMWATER QUALITY PRACTICES

SECTION 2

BMP Process and Plan DevelopmentProper planning for development projects and implementation of BMPs is important for the mitigation of impacts to water quality and protection of receiving water bodies. Implementing a plan that considers the existing hydrology of the site and protects pervious areas and existing vegetation can help minimize both the cost and the footprint of structural drainage practices.

This section provides a brief overview of the BMP planning processes and outlines the plan submittal requirements for new development and re-development projects. This includes adiscussion to support integration of water quality BMPs into site development and recommendations to help determine the type and layout of BMPs for a specific site layout.Additional detail is provided in Sections 3 and 4.

2.1 BMP AND SITE PLANNING

Proper BMP planning includes consideration of site layout and BMP placement early in the process. These steps can help to provide important water quality benefits. The recommended steps for the planning of the site and BMPs are:

1. Identify protected and sensitive features and opportunities to protect these. This may includedevelopment of a setback for impervious areas from creeks, wetlands, riparian areas, anddense and / or desirable vegetation. Other planning practices include:

Locate the development in less sensitive areas of the site

Fit the design to the terrain

2. Define the areas that are most suitable for development, areas to be landscaped, and areas tobe conserved. Conform site layout along natural landforms and avoid excessive grading andsoil disturbance. Avoid construction on steep slopes, in floodplains, and on erodible soils.

3. Assess opportunities to minimize overall impervious coverage on the site.

4. Locate BMPs with consideration for capturing stormwater runoff from areas with a highpotential for pollutant loading, such as parking lots.

2.1.1 SITE LAYOUT

Careful consideration of the site layout can help mitigate the water quality impact of the development and, as a result, reduce the water quality volume (WQV) that must be treated and the required BMP footprint.

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The existing site conditions that serve important hydrologic functions such as reducing runoff or pollutant loads downstream should be identified for protection early in the site assessment process. Natural and sensitive features that should be protected include:

Bodies of water such as streams, rivers, ponds, and lakes

Natural drainage paths

Riparian areas

Floodplains

Wetlands

Aquifer recharge areas

Steep slopes

Erodible soils

Areas of dense vegetation

Areas with seasonal high groundwater

Other site-specific features that may impact hydrology

The developer should take steps during planning and construction to protect these features. It is important to consider that the disturbance of soil during construction can enable large quantities of sediment to be mobilized during stormwater events. These sediment loads can harm natural features and clog or otherwise damage BMPs. Temporary construction controls should be implemented as per City of Fort Worth and TCEQ requirements to prevent erosion and sediment transport.

2.1.2 IMPERVIOUS SURFACES

The developer should minimize the amount of impervious cover in the site design where possible to help reduce the size and cost of structural BMPs. WQV and BMP size are calculated based on the impervious cover for new and re-development sites. Therefore, reducing the amount of impervious cover can reduce the volume, cost, and land required for BMPs. Approaches might include using more vertical construction (reducing building footprints), utilizing pervious pavement, and designing the site for efficient vehicle circulation, reducing pavement area.

Disconnecting impervious surfaces can also be an effective way to reduce the required WQV treated by structural BMPs. This can be performed at an individual lot level and at the larger development site level. At an individual lot or property, impervious surfaces can be disconnected by directing gutter downspouts to pervious areas, installing rain gardens, and implementing other small scale BMPs or pre-treatment devices. Similar strategies can be implemented at the larger development scale by draining runoff to pervious areas. Other examples of this may include using stable grass swales instead of curb and gutters and natural channel paths instead of storm sewers. Both of these alternatives could function as pre-treatment based on compliance with the design standards outlined in this manual.

2.1.3 SITING BMPS

The developer should consider potential sources of high pollutant loading and locate BMPs to capture stormwater runoff from these areas. Roof runoff and parking lots will require pre-treatment before treatment by approved BMPs. Section 4 of this manual outlines the options for pre-treatment.

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2.2 BMP SELECTION

The planning for the types and locations of BMPs to be implemented on a site should be performed with consideration of the pollutants of concern, available right-of-way, existing soil types and infiltration rates, pollutants of concern, and the development goals that impact aesthetics of the development. Table 2.1 summarizes the level of treatment that each type of BMP provides for pollutants of concern.

Table 2.1 Pollutant Reductions by BMP

Sand and

Media Filters*

Bioretention Basins*

Constructed Wetlands

Wet Basins

Retention and Irrigation

Basin

Detention Basin

Vegetated Filter Strips/

Grass Swales*

Permeable Surfaces

Sediment High High High High High Moderate Moderate to High High

Nutrients Low to Moderate Moderate Moderate

to High** Moderate to High**

Moderate to High

Low to Moderate

Low to Moderate Low

Trash High High High High High High Low to Moderate High

Metals Moderate to High

Moderate to High Moderate Moderate High Moderate Low to

Moderate Moderate

Bacteria Moderate to High High High** High** High Moderate

to High Low High

Oil and Grease High High High High No Data No Data Moderate to

High Moderate

Organics Moderate to High Moderate High** High** No Data Low Moderate to

High Low

Source: SARA, 2013; NCTCOG, 2014; TCEQ, 2005; ISWBD, 2017 * Removal effectiveness varies dependent on infiltration capacity and design ** Wetlands, Wet Basins, and other BMPs with wildlife habitat can have high internal loads of bacterial indicators, nutrients, and organics

Section 3 of this manual outlines the requirements and benefits of the post-construction BMPs that can be implemented to comply with the water quality requirements for areas covered in this manual. The fact sheets (Appendix B) summarize the effectiveness of the BMPs for removal of different pollutants.

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2.3 CALCULATION OF WATER QUALITY VOLUME

The required WQV to be treated is calculated based on the runoff volume from the 85th percentile runoff event. A continuous hydrologic simulation model assessment was performed to define the WQV. The model assessment considered routing through the capture basin, infiltration in the tributary drainage area, and the recapture of infiltration and other losses during dry periods in the Trinity River watershed.

For a development within Zones 1 and 2, the water quality volume can be estimated using Figure 2.1 or Table 2.2. The process to estimate is also summarized in the callout on this page.

First, the developer should define the drainage areas within the project site and calculate the size of each of the drainage areas (step 1). Note that the project area may have more than one drainage area, and one or more BMPs should be used for each drainage area where there will be new impervious or redevelopment. Only the portion of each drainage area within the site boundaries will need to be treated.

Next, the developer should estimate the amount of impervious cover and the percentage of impervious cover within each drainage area (step 2). This should be done for each drainage area within the site. The developer should thenidentify the BMP type(s) that may be used to treat stormwater runoff on the site and evaluate the drainage time and components for the BMP(s) (step 3 and step 4).

Figure 2.1 provides a graphical representation of the Water Quality Depth (WQD) expressed ininches as a function of the percent impervious area of a development and the design drain time for the selected BMPs. Equations to estimate the WQD are also provided in Table 2.2. To calculate the total water quality volume for each drainage area within the project site, use the percent impervious for that drainage area and the drain time for the selected BMP to estimate the WQD (step 5). Multiply the WQD by the drainage area to calculate the total WQV for that drainage area (step 6). The WQD and WQV should be estimated for each drainage area separately.

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Figure 2.1 Water Quality Depth (in watershed inches) for the 85th Percentile Capture of Runoff Volume

As noted, the equations provided in Table 2.2 can also be used to calculate the WQD for BMPs based on the amount of impervious in the drainage area and the drain time of the BMP. As described for Figure 2.1, multiply the WQD by the drainage area to calculate the WQV.

Table 2.2 Equations for Required Water Quality Depth

Drain Time Water Quality Depth

48 hour y = 0.0093x + 0.0104

24 hour y = 0.0080x - 0.0009

12 hour y = 0.0068x - 0.0132 Where: x = percent impervious (%) for drainage area to BMP y = water quality volume in inches

Section 3 and the design spreadsheets included in Appendix E also include guidance for these estimates. The WQV is based on the percent of the drainage area with impervious cover. By reducing the amount of impervious cover, a new development or re-development project can reduce the required footprint of BMPs.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100

Wat

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ualit

y D

epth

(Inc

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% Watershed Impervious

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2.4 BMP DESIGN The design guidance in this manual is based on components. The components for each BMP are the critical elements required for that BMP to meet the water quality goals. Based on the type of BMP, components may include inlets, pretreatment, energy dissipation, area protection, storage media, media barriers, planting media, landscaping, and outlets/piping. To allow flexibility for specific sites, this manual provides alternatives for components that meet the design criteria. The required design specifications and components for each BMP are outlined in Section 3. Design sheets and conceptual layouts for the components are provided in Section 4.

ADDITIONAL RESOURCES

1 City of Fort Worth. December 20, 2012. Standard Construction Specification Documents. 2 North Central Texas Council of Governments (NCTCOG). September 2014. “iSWM Technical

Manual: Water Quality: 1.0 Water Quality Protection Volume and Peak Flow”, Arlington, Texas, April 2010, Revised September 2014, http://iswm.nctcog.org/Documents/technical_manual/Water%20Quality_9-2014.pdf

4 San Antonio River Authority (SARA). 2013. San Antonio River Basin Low Impact Development Technical Guidance Manual.

5 Texas Commission on Environmental Quality (TCEQ). July 2005. Complying with the Edwards Aquifer Rules: Technical Guidance on Best Management Practices.

6 International Stormwater BMP Database. Accessed September 2017. BMP Database Tool: Texas BMPs. http://bmpdatabase.org/retrieveBMPs.asp

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SECTION 3

Post-Construction Storm Water Quality Control MeasuresThis section provides information about the Best Management Practices (BMPs) that can be implemented to comply with the water quality requirements for Zones 1 and 2 (as presented in Section 1.4). The BMPs included in this section, if sized for the Water Quality Volume (WQv) (defined in Section 2) and designed in compliance with this manual, meet the water quality requirements for new and re-development projects in Zones 1 and 2, with two exceptions: grass swales and vegetated filter strips. These two BMPs are intended to treat only small impervious areas or act as pre-treatment or post-treatment for other BMPs. Specific requirements unique to Zone 1 (Panther Island) are discussed in Section 5. The following sections provide 1) a short description of each BMP, 2) information about the application of the BMP, 3) design criteria, and 4) maintenance considerations for design and construction. The design criteria describe the required components for each type of BMP and criteria for the components.

The general approach to identifying and designing appropriate BMPs includes the following steps:

1) Review the descriptions and applicability information provided in this section to determine what BMPs are most appropriate for the development.

2) Review the design criteria in this section to determine the necessary components and design elements for compliance with water quality requirements. The design criteria include references to applicable design details and specifications in Section 4. Review the maintenance considerations for design in this section to make any design adjustments that would simplify maintenance.

3) Identify the component details and specifications in Section 4 based on the components and references described in this Section. See Table 4.1 for major components.

Additional support included in Appendix E will assist in performing design calculations, sizing BMP structures and developing project submittal support information. The BMP design plan sheets and calculations, inspection and maintenance plans, as-builts, and other supporting information for projects in Zones 1 and 2 with WQV treatment requirements must be submitted for review to TRWD.

3.1 SAND FILTERS

3.1.1 DESCRIPTION OF BMP

Sand filters and other types of media filters filter stormwater through sand or other media to remove pollutants. These BMPs can be implemented to treat a relatively large (generally up to 10-

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acres) drainage area. This manual focuses on sand as the filtration media; other types of media may be considered on a case by case basis but are not specifically detailed in this section.

Two of the primary components are the sediment forebay (also referred to as sedimentation chamber) and the filtration chamber. The sediment forebay should be included for sand filters with drainage areas over 2-acres and can be included in smaller sand filters to remove floatables, large materials, and sediment before storm water is filtered through the sand or other media. The volume of water conveyed to the treatment system must be controlled by a diversion structure to prevent inflow rates that exceed the capacity of the BMP.

Component details and specifications are provided in Section 4. Figure 3.1 provides a conceptual rendering of a Concrete Sand Filter with major components identified for reference. The components may depend on the size and type of sand filter; these are described further in Section 3.1.3.

Figure 3.1 Conceptual Rendering of a Concrete Sand Filter

Due to the inherent dangers associated with confined spaces, which complicates routine inspections and maintenance, as well as the out-of-sight nature and inherent potential for neglect, underground structures/vaults are not discussed. Developers wishing to propose buried structures must provide conclusive supporting documentation regarding maintenance access and equivalent performance compared to above grade filters. These sand filters must be in compliance with all applicable confined space rules and regulations.

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3.1.2 APPLICABILITY

The layout of sand filters is highly flexible. They can be incorporated within new development or as retrofits in re-development sites and can be used at locations with limited space or where other BMPs would be difficult to fit2. Although versatile in their potential application, sand filters are best suited for areas with highly impervious drainage areas. However, sites that produce heavy sediment loads will clog filtration media and without frequent maintenance, will render this BMP ineffective2.

3.1.3 DESIGN CRITERIA

This section provides the design criteria for sand filters. The structural criteria provide information about the necessary components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General Criteria

a. Runoff from all impervious surfaces should be directed to a BMP.

b. The maintenance plan for sand filters must include, as a minimum, trash removal, accumulated sediment removal, inspection for standing water, and inspection for 24-hour drawdown in accordance with the Stormwater Facility Maintenance Agreement – Water Quality Devices and oultlined in Appendix D.

2) Site Conditions

a. Drainage area – Sand filters are recommended for drainage areas less than 10-acres in size. Larger areas should be subdivided and treated by multiple devices.

b. Depth to water table – A minimum of 2-feet are required between the bottom of the sand filter and the elevation of the seasonally high-water table.

c. Soils – An underdrain is required for soils that do not allow sufficient infiltration.

d. Floodplain – Where feasible, the BMP should be located outside of the 100-year floodplain. Where not feasible, the top of walls / embankments for the BMP should be above the 100-year floodplain and the BMP should be designed to protect against surcharge from downstream waters.

e. Space required to achieve WQV – Function of available head at the site, the holding time, WQv, and the surface area of the sand layer for the BMP (see design calculation procedures in Appendix E).

3) Structural Criteria

a. Emptying / drain time – Design to drain within 24-hours.

b. Minimum head – The elevation difference needed at a site between the inflow and the outflow is generally 5-feet.

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c. Pre-treatment - A sediment forebay must be used for all sand filters treating over 2-acres and is recommended for all sand filters.

i. The forebay should be designed to hold at least 25% of the WQv.

ii. The sediment forebay should have a length-to-width ratio of at least 2:1.

iii. Inlet and outlet structures should be located at opposite ends of the chamber to prevent short-circuiting (see Section 4.1 for additional information on inlet structures, Section 4.2 on the design of the sediment forebay, and Section 4.8 on outlet structures).

iv. A vegetated filter strip or grass swale can be implemented in lieu of a sediment forebay where the drainage area is less than 2-acres.

d. Energy dissipation – Required to dissipate energy and prevent erosion at the inlet to the BMP (see Section 4.3).

e. Sand filter chamber – The structure of a surface sand filter may be constructed of impermeable material such as concrete or using earthen embankments and slopes.

i. Size – The filtration chamber must be designed to hold 100% of the WQv (see Sections 4.5 and 4.6 for additional information on layout criteria).

ii. Depth – Maximum design depth of WQv within filtration basin shall not exceed 5-feet. Note that surface area and depth of captured stormwater impacts maintenance requirements; a larger surface area (and resulting reduced stormwater depth) increases the ability of the sand filter to store sediment without clogging. Therefore, a depth greater than 3-feet may increase the frequency of required maintenance to keep the BMP effective.

iii. BMP media – Primary BMP media used is sand consisting of 18-inch (minimum) to 24-inch layer of clean washed medium sand. A storage aggregate layer shall be placed at the bottom of the sand filter chamber for additional water storage capacity. (see Section 4.5 for material, gradation, and design criteria). Filter fabric can be used between the sand and gravel to prevent migration of fines; however, the material can clog and require additional maintenance. Alternatively, an aggregate layer is not required if a slotted underdrain is used to prevent sand from flowing into the underdrain pipe.

iv. Media barrier – A geomembrane liner should be used to line the bottom and side slopes of the structure before installation for sand filters with earthen embankments (see Section 4.6). An impermeable liner must be used for installations adjacent to streets to prevent water from getting under the pavement into the base material.

v. Underdrain - If the system includes an underdrain, the BMP media shall be located above the underdrain system and the underdrain shall be located within the storage aggregate layer (see Section 4.8).

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vi. Note - Texas Commission on Environmental Quality (TCEQ) Dam Safety requirements shall be accounted for as required with higher depth structures.

f. Diversion structure – The diversion structure must be capable of passing the peak flow rate of the ten (10) year annual chance storm into the stormwater quality BMP and passing excess runoff, including up to the 100-year storm, through the diversion structure without overtopping the sidewalls of the pond. (see Section 4.1 for additional information on diversion structures).

3.1.4 MAINTENANCE CONSIDERATIONS FOR DESIGN AND CONSTRUCTION

Routine inspection and maintenance of sand filters is critical to their performance. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D, the “BMP Inspection and Maintenance” section of this manual. The following should be considered during design and construction of the BMP:

Access – Adequate access must be provided for all sand filter systems for inspection and maintenance, including the appropriate equipment and vehicles. An access ramp with a minimum width of 10-feet and a maximum slope of 25% shall be provided.

Fencing – To prevent risk to the public, it is recommended that sand filter facilities be fenced in accordance with the City of Fort Worth requirements.

Include cleanouts as discussed in Section 4.8. These can be used for inspection to make sure that the underdrain is intact, and for ongoing maintenance during and after construction.

For earthen systems, include vegetated side slopes to pre-treat runoff and reduce the frequency of maintenance2.

The BMP should be kept offline until the construction activities are completed. However, the BMP excavation can be used as a sediment trap during construction before filtration or other media are placed in the basin. In that case, the bottom of the basin should not be excavated below 2-feet of the final grade. Temporary BMPs should be in place as detailed in the project Sediment and Erosion Control Plan to protect receiving waters during construction activities (the Sediment and Erosion Control Plan requirements are not discussed in this manual). Sediment discharged during construction can clog the system and would require additional maintenance.

______________________________________ City of Austin. (2017). Design Guidelines for Water Quality Controls. Environmental Criteria Manual. 2 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

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3.2 BIORETENTION BASINS


Bioretention basins (also referred to as rain gardens, biofiltration basins, or biofilters) use the chemical, biological, and physical properties of plants, microbes, and soils to remove pollutants from stormwater runoff via a system of distributed micro-scale storm water treatment devices.1 The filter medium is an engineered mix of highly-permeable natural media, which are usually mixtures of soil, sand and organic matter, that facilitate pollutant removal via sedimentation, filtration, sorption, and precipitation.1 The defining characteristic of a bioretention system is the integration of plants and microorganisms that are rooted in the filter medium and can provide more treatment of runoff, directly and by uptake by the filter medium2. Plants help sustain the permeability of the medium for longer periods and enhance removal of pollutants1,2. The composition of the BMP media is key to the system’s overall effectiveness.1

More information on the components for bioretention basins can be found in the design criteria discussion in Section 3.2.3 and the component details and specifications are provided in Section 4.

There are two types of bioretention basins that are addressed as part of this handbook – centralized and distributed bioretention basins. Centralized bioretention basins must be implemented for larger drainage areas and have additional elements as detailed below. These include a two-cell system. Distributive bioretention basins (i.e., rain gardens or green street infrastructure) can be implemented for drainage areas of 1-acre or less. These are smaller and shallower than the centralized systems and are often placed adjacent to the impervious cover runoff source. The primary components for these are different. Figure 3.2 provides a conceptual rendering of a distributive bioretention basin with the components identified. The components that are fundamental for distributive bioretention basins are shown in the figure. For larger centralized bioretention facilities, pre-treatment should be included. Additional area protection may also be considered.

3.2.2 APPLICABILITY

Given the variability of design as it relates to the drainage area and allowable ponding depth within the system, the selection of a bioretention basin design depends largely on the size of the contributing drainage area. Large centralized bioretention basins are well suited to service large residential subdivisions. However, these may also be used to treat commercial and industrial sites, although pretreatment should be considered, especially if there are high sediment loads anticipated. Bioretention basins are not recommended to treat drainage areas greater than 5-acres. Small bioretention basins (rain gardens) may serve these land use types; however, they are limited to sites that are less than an acre. Therefore, on large sites, the developer should consider distributing smaller systems throughout the site. Given the ability of a rain garden to be incorporated into the landscape, its use is extremely flexible and makes it ideal for roadway median strips and curb bump outs, parking lot islands, and roof downspout catchment areas3.

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Figure 3.2 Conceptual Rendering of Distributive Bioretention Basin


The following sections provide design criteria for both centralized and distributed bioretention basins. As noted above, the primary differences between the two are the allowable drainage area size and inclusion of the sediment forebay.

3.2.3.1 CENTRALIZED BIORETENTION BASINS

This section provides the design criteria for large centralized bioretention basins (those serving drainage areas up to 5-acres). Note that some of the primary differences between sand filters and the centralized bioretention basin described in this section are the bioretention media and landscaping.

1) General Criteria


b. Maintenance plans – Maintenance plan contains a guarantee of maintenance in accordance with the Stormwater Facility Maintenance Agreement – Water Quality Devices and confirms with requirements in Appendix D.

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2) Site Conditions

a. Drainage Area – Not recommended for drainage areas greater than 5-acres; there is no minimum drainage area limitation. If proposed for drainage areas greater than 5-acres, additional information must be provided to ensure that the basin will perform effectively, and additional maintenance and inspections may be required to verify.

b. Depth to Water Table – Consider depth of 4-feet to groundwater table when identifying appropriate locations for bioretention. A high groundwater level could damage the bioretention basin or limit the treatment by infiltration.

c. Soils – the characteristics of the native soils will determine if infiltration would occur naturally outside of the bioretention basin.


e. Space Required – The BMP footprint is a function of the available head at the site, the size of the drainage area, and the designed surface area for the BMP.

3) Structural criteria

a. Emptying / drain time – The optimal drain time for the BMP is 12-hours, but the drain time should be not be greater than 24-hours.

b. Minimum Head – The elevation difference required at a site from the inflow to the outflow is generally 3 to 5-feet.

c. Pre-treatment – For inlets where there is concentrated flow, the centralized bioretention cells should have a sediment forebay. The sediment forebay should be designed to hold 10% of the bioretention volume. For areas with sheet flow, the bioretention system should have vegetated filter strips or gravel to dissipate energy, minimize erosion, and capture sediment (see Section 4.2).

d. Bioretention cell - The structure of the bioretention cell is constructed through the use of excavations and earthen embankments.

i. Size – The bioretention cell must hold 100% of the WQV (see Sections 4.5 and 4.6 for additional information on layout criteria).

ii. Length to width – The bioretention cell should maximize the length-to-width ratio (see Section 4.1 for additional information on inlet structures and Section 4.8 on outlet structures).

iii. Maximum depth – The maximum depth for captured WQv within the basin is 12-inches.

iv. Area Protection – Curbing is advised in locations with pedestrian traffic and vehicular traffic. Bollards are advised in locations with vehicular traffic (see Section 4.4).

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v. BMP Media – Centralized bioretention basins require a 30-inch (minimum) to 48-inch (maximum) layer of bioretention or engineered soil medium. A storage aggregate layer shall be placed below the centralized bioretention for additional water storage capacity (see Sections 4.5).

vi. Media barrier – Depending on site conditions, a permeable geotextile or geomembrane liner should be used to line the bottom and sides of the BMP before installation of the underdrain system and BMP media. A media barrier is also recommended between the bioretention or engineered soil and the storage aggregate layer to reduce sediment migration into the storage aggregate layer; permeable geotextile is not recommended because of the tendency for the material to clog and thus prevent water migration into the storage layer (see Section 4.6). An impermeable liner must be used for installations adjacent to streets to prevent water from getting under the pavement into the base material.

vii. Vegetation – Vegetation must be provided, and mulch used for areas where there is bare soil. Organic enhancers may be added to promote vegetation growth and use of heavy tackifier with hydro mulch and erosion mats staked to the soil can be used to help vegetation establish and stabilize the site (see Section 4.7). Appendix C provides planting palettes for BMP facilities. These areas should not receive any fertilizers, pesticides, or herbicides. Vegetation on the pond embankments should be mowed as appropriate to prevent the establishment of woody vegetation.

viii. Underdrains - If the system includes an underdrain, the bioretention medium shall be located above the underdrain system and the underdrain shall be located within the storage aggregate layer (see Section 4.8).

e. The diversion structure must be capable of passing the peak flow rate of the ten (10)-year storm into the stormwater quality BMP and bypassing excess runoff, including up to the 100-year storm, away from the BMP (see Section 4.1 for additional information on diversion structures).

f. Note – Texas Commission on Environmental Quality (TCEQ) Dam Safety requirements shall be accounted for as required with higher depth structures.

3.2.3.2 DISTRIBUTIVE BIORETENTION BASINS (RAIN GARDENS)

This section provides the design criteria for distributive bioretention basins (hereafter referred to as rain gardens).

1) General criteria


b. Maintenance plans – Maintenance plan contains a guarantee of maintenance in accordance with the Stormwater Facility Maintenance Agreement – Water Quality Devices and confirms with requirements in Appendix D.

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2) Site conditions

a. Drainage Area – Maximum drainage area of 1-acre.

b. Depth to Water Table – Consider depth of 4-feet to groundwater table when identifying appropriate locations for bioretention. A high groundwater level could damage the bioretention basin or limit the treatment by infiltration.

c. Soils – the characteristics of the native soils will determine if infiltration would occur from the bioretention basin. Engineered media is required for the bioretention filtration media to perform effectively.


e. Space Required – The BMP footprint is a function of the available head at the site, the size of the drainage area, and the designed surface area for the BMP.


a. Emptying / drain time – The optimal drain time for the BMP is 12-hours, but the drain time should be not be greater than 24-hours.

b. Minimum Head – The elevation difference needed at a site from the inflow to the outflow is generally 3 to 5-feet.

c. Energy dissipation – Energy dissipation is recommended, especially for areas with concentrated flow. Gravel or vegetated filter strips can be used to dissipate energy (see Section 4.3).

d. Bioretention cell – The structure of the bioretention cell is constructed through excavation and the construction of earthen embankments.

i. Size – The entire treatment system must be designed for 100% of the WQv (see Sections 4.5 and 4.6 for additional information on layout criteria).

ii. Maximum depth – The maximum depth of water within the rain garden bioretention cell is 12-inches.

iii. Area Protection – Curbing is advised in locations with pedestrian traffic and vehicular traffic. Bollards are advised in locations with vehicular traffic (see Section 4.4).

iv. BMP Media – The BMP media consists of 30-inch (minimum) to 48-inch layer of bioretention or engineered soil medium. A storage aggregate layer shall be placed at the bottom of the distributive bioretention for additional water storage capacity (see Sections 4.5).

v. Media barrier – Depending on site conditions, a permeable geotextile or geomembrane liner should be used to line the bottom and sides of the BMP before installation of the underdrain system and BMP media. A media barrier is also recommended between the bioretention or engineered soil

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and the storage aggregate layer to reduce sediment migration into the storage aggregate layer; permeable geotextile is not recommended because of the tendency for the material to clog and thus prevent water migration into the storage layer (see Section 4.6). An impermeable liner must be used for installations adjacent to streets to prevent water from getting under the pavement into the base material.

vi. Vegetation – Vegetation must be provided, and mulch used for areas where there is bare soil. Organic enhancers may be added to promote vegetation growth and use of heavy tackifier with hydro mulch and erosion mats staked to the soil can be used to help vegetation establish and stabilize the site (see Section 4.7). Appendix C provides planting palettes for BMP facilities. These areas should not receive any fertilizers, pesticides, or herbicides. Vegetation on the pond embankments should be mowed as appropriate to prevent the establishment of woody vegetation.

vii. Underdrains - If the system includes an underdrain, the underdrain shall be located within the storage aggregate layer below the bioretention soil media (see Section 4.8).

3.2.4 MAINTENANCE CONSIDERATIONS DURING DESIGN AND CONSTRUCTION

Inspection and maintenance are critical to the performance of bioretention systems. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Access – For centralized bioretention, adequate access must be provided for inspection and maintenance, including the appropriate equipment and vehicles. For larger facilities where access may be an issue, an access ramp with a minimum width of 10-feet and a maximum slope of 25% shall be provided. Distributive bioretention should be accessible for inspection and maintenance including the appropriate equipment; however, due to the smaller facilities, no access ramp is necessary.

Fencing (optional) – To prevent access and damage to vegetation, it is recommended that centralized bioretention facilities be fenced to prevent public access and in accordance with City of Fort Worth requirements.

The use of vegetation is preferred to mulch. Mulch can float and clog outlets. However, there must be effort taken to ensure successful implementation of the vegetation3.

Maintenance should be considered during the design and layout. For example, pruning and mowing of vegetation and accessibility to features that will need to be maintained3.

Include cleanouts as discussed in Section 4.8. These can be used for inspection to make sure that the underdrain is intact, and for ongoing maintenance during and after construction.

Keep the BMP offline until the construction activities are completed. Temporary BMPs should be in place as detailed in the project Sediment and Erosion Control Plan to protect receiving waters during construction activities (the Sediment and Erosion Control Plan requirements

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are not discussed in this manual). Sediment discharged during construction can clog the system and would require additional maintenance.

Consider making the bioretention basin shallower, to make maintenance easier3.

1 Hsieh, C.-h., & Davis, A. P. November 2005. Evaluation and Optimization of Bioretention Media for Treatment of Urban Storm Water Runoff. Journal of Environmental Engineering, 1521-1531. 2 City of Austin. (2017). Design Guidelines for Water Quality Controls. Environmental Criteria Manual. 3 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

3.3 CONSTRUCTED WETLANDS


Constructed wetlands generally serve large drainage areas where the WQv is both stored and treated in the wetland facility. They may also provide additional capacity for flood control management. For water quality, these practices are often referred to as stormwater wetlands. The purpose of the constructed wetland is to provide treatment by way of a functional pool resulting in the settlement, filtration, and uptake of pollutants by a viable wetland ecosystem. Constructed wetlands sized for the WQv and designed in compliance with this manual meet the water quality requirements for new and re-development in Zone 2.

A Design/Review spreadsheet has been developed specifically for use with this document and is included in Appendix E. Figure 3.3 provides a conceptual rendering of a constructed wetland with major components identified. As will all detention facilities, constructed wetlands need to be designed such that public safety is maintained (such as using benching to keep deeper water further from shore and/or barriers on lookouts, walkways and the like, or where benching can’t be accomplished cost-effectively.

3.3.2 APPLICABILITY

The selection of a constructed wetland depends largely on the ability to make sure the system is viable as a wetland ecosystem, performs the key functions of stormwater treatment, and minimizes potential vectors to protect human health. As such, considerable design expertise beyond hydrology, hydraulics, and water quality needs to be engaged to provide a sustainable wetland ecosystem that meets these criteria. Constructed wetlands are best suited for large areas often where flood control detention is also required and where the wetland can contribute additional value to the setting (e.g., such as a park system with trails where birdwatching, environmental education, and the like could occur). Therefore, the final condition of the developed site and the availability of a perennial source of water (and whether a wetland system can be viable with interruptions in water supply) should be considered before choosing constructed wetlands. Poorly designed constructed wetlands can become public nuisances because they lack the natural ability to mitigate mosquito populations. As such, other practices (such as extended dry detention) should be considered before constructed wetlands where wetland viability is questionable. Practices like extended dry detention can be designed with attractive landscape elements as well for inclusion in open spaces, park systems, etc.

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Figure 3.3 Conceptual Rendering of a Constructed Wetland


This section provides the design criteria for constructed wetlands. The structural criteria provide information about the components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General Criteria


b. Maintenance plans – Maintenance plan for constructed wetlands must contain a guarantee of maintenance in accordance with the Stormwater Facility Maintenance Agreement for Water Quality Devices and be in conformance with the requirements outlined in Appendix D. The plan must be submitted for review by TRWD.

2) Site Conditions

a. Drainage area – Constructed wetlands should be implemented at locations where there is a larger drainage area or where a wetland system is viable.

b. Depth to water table – 2-feet are required between the bottom of the constructed wetland and the elevation of the seasonally high-water table.

c. Soils – Infiltration into soils is not recommended to maintain a permanent pool. Permeable soils are not ideal for maintaining water levels within the constructed wetlands. An impermeable barrier may be needed to minimize water loss from the

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permanent pool (See Section 4.6 for additional information on media barriers). A geomembrane liner must be used for installations adjacent to streets to prevent water from getting under the pavement into the base material.


e. Space – The space required for the BMP is a function of available head at the site, treatment WQv, and availability of make-up water.


a. Energy dissipation – The constructed wetland must be designed with energy dissipation structures at the inlet if the entrance velocities exceed the erosive velocity requirement of the BMP surface material (See Section 4.3).

b. Diversion structure – The diversion structure should be sized to bypass flows from the 10-year annual probability storm and the channel should be able to convey flows from the 100-year annual probability storm without overtopping.

c. Sediment forebay – The constructed wetland must have a sediment forebay to prevent sediment accumulation in the wetland.

i. Size – The forebay volume should be sized to contain 0.1-inches of runoff from the impervious portion of the contributing drainage area. For example, for a two-acre drainage basin with 60% impervious cover, the forebay should be designed to hold 0.1 inches of runoff from 1.2 acres.

ii. The length to width ratio of the forebay should be at least 2:1 (length:width) and have a side slope ratio no steeper than 3:1 (horizontal:vertical).

iii. Drawdown – The forebay outlet should be sized such that the forebay drains within 24-hours.

d. Constructed wetland basin

i. Size – The basin should be sized to contain a permanent pool volume equal to 100% of the WQv and a surcharge volume sized to contain 120% of the WQv. The purpose of the additional storage volume is to account for the total volume lost through sediment accumulation over time. Ideally, constructed wetlands should have sinuous flow paths, a length to width ratio of 4:1, and side slopes no steeper than 3:1 (horizontal: vertical) (See Section 4.4 for additional information on area protection). It is recommended that the basin be lined with a filter fabric if constructed with earthen embankments.

ii. Depth – The permanent pool depth of the constructed wetland should have varying depths as outlined below, ending with a micropool before the outlet that is no more than 6-feet in depth. The surcharge depth should be 2-feet or less. Below are the different permanent pool depth zones that should be included in a constructed wetland.

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1. Semi-Wet Zone – This zone lies at or above the permanent pool and is only inundated following storm events. (See Section 4.7 for Plant List 4 through 8).

2. Aquatic Bench Zone – This zone has a depth of 18-inches below the permanent pool elevation. (See Section 4.7 for Plant List 3).

3. Deep Water Zone – This zone has a depth from 18-inches to 6-feet below the permanent pool elevation. (See Section 4.7 for Plant List 2).

iii. Vegetation – appropriate vegetation is a critical component of the effectiveness of the wetland system. The different zones must be planted with the appropriate vegetation for the depth of inundation (see Section 4.7). Appendix C provides planting palettes for BMP facilities. These areas should not receive any fertilizers, pesticides, or herbicides. Vegetation on the pond embankments should be mowed as appropriate to prevent the establishment of woody vegetation.

iv. Outlet – Design the outlet properly with the fine trash rack in front of the outlet orifices and is submerged the full depth of the micropool. This allows flow under the clogged portions of the trash rack.

v. Emptying / drain time – The surcharge of the wetland above the permanent pool volume should drain within 24-hours. (See Section 4.8 for additional information on outlets/piping).


Inspection and maintenance are critical to the performance of constructed wetlands. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Maintenance requirements should be considered during the design and layout. For example, pruning and mowing of vegetation and accessibility to features that will need to be maintained1. Access should be provided to the constructed wetland, particularly to the sediment forebay. A maintenance ramp should be a minimum of 10-feet in width and have a maximum slope of 25%. For mowing, it is recommended to keep side slopes at a maximum of 3:1 (horizontal:vertical). Sediment accumulation in the forebay should be monitored using vertical depth markers indicating when sediment accumulation equals 20% of the forebay volume.

The BMP should be kept offline until the construction activities are completed. However, the BMP excavation can be used as a sediment trap during construction before filtration or other media are placed in the basin. In that case, the bottom of the basin should not be excavated below 2-feet of the final grade. Temporary BMPs should be in place as detailed in the project Sediment and Erosion Control Plan to protect receiving waters during construction activities (the Sediment and Erosion Control Plan requirements are not discussed in this manual). Sediment discharged during construction can clog the system and would require additional maintenance.

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Monitor and minimize use of fertilizers that can increase nutrient concentrations in discharge and cause algal blooms1.

1 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

3.4 WET BASINS


Wet basins are designed to retain stormwater in ponds between runoff events to allow the retained volume to be treated for an extended period. These BMPs are also referred to as wet ponds, stormwater ponds, or retention ponds. They are best suited to treat large drainage areas and require a source of water to maintain the permanent pool. Wet basins sized for the WQv and designed in compliance with this manual meet the water quality requirements for new and re-development in Zone 2.

Wet basins remove pollutants by retaining stormwater and allowing for settling and plant uptake during that period. A design/review spreadsheet has been developed specifically for use with this document and is included in Appendix E. Figure 3.4 provides a conceptual rendering of a wet basin with major components identified. Area protection should also be considered.

Figure 3.4 Conceptual Rendering of a Wet Basin

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3.4.2 APPLICABILITY

The selection of a wet basin depends largely on the availability of space, a large contributing drainage area, and the availability of a water source to ensure a permanent pool throughout the entire year. Having a source of water available to maintain a permanent pool is an important consideration when considering the use of wet basin as a BMP.


This section provides the design criteria for wet basins. The structural criteria provide information about the components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General Criteria


b. Maintenance plans – Maintenance plan for wet basins must contain a guarantee of maintenance in accordance with the Stormwater Facility Maintenance Agreement for Water Quality Devices and be in conformance with Appendix D. The plan must be submitted for review by TRWD.

2) Site Conditions

a. Drainage area – Wet basins should be implemented at locations where there is a larger drainage area or a potential source of baseflow to maintain the water level.

b. Depth to water table – 2-feet are required between the bottom of the wet basin and the elevation of the seasonally high-water table.

c. Soils – Infiltration into soils is not recommended to maintain a permanent pool. Permeable soils are not ideal for maintaining water levels within the wet basins. An impermeable barrier may be needed to minimize water loss from the permanent pool. (See Section 4.6 for additional information on media barriers). A geomembrane liner must be used for installations adjacent to streets to prevent water from getting under the pavement into the base material.


e. Space – The space required for the BMP is a function of available head at the site, required treatment WQv, and availability of make-up water.


a. Energy dissipation – The wet basin must be designed with energy dissipation structures at the inlet if the entrance velocities exceed the erosive velocity requirement of the BMP surface material (see Section 4.3).

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c. Sediment forebay – The wet basin must have a sediment forebay to prevent sediment accumulation in the basin.

i. Size – The forebay volume should be sized to hold 0.1-inches of runoff depth from the impervious portion of the contributing drainage area. For example, for a two-acre drainage basin with 60% impervious cover, the forebay should be designed to hold 0.1 inches of runoff from 1.2 acres.

ii. The recommended length to width ratio is no less than 2:1 (length:width), and side slopes no steeper than 3:1 (horizontal:vertical).

iii. Drawdown – The forebay outlet should be sized such that the forebay drains within less than 24-hours.

d. Wet Basin

iv. Size – The wet basin should be designed to contain a permanent pool volume equal to or greater than the WQv and a surcharge volume of 120% of the WQv (See Section 4.4 for additional information on area protection). The purpose of the additional storage volume is to account for the total volume lost through sediment accumulation over time. The basin should be lined with a filter fabric if constructed with earthen embankments.

v. Depth – The wet basin surcharge should have no more than 5-feet of depth. The wet basin should have a safety bench, or littoral zone, which makes up 15% of the total surface area of the basin.

vi. Vegetation – Appropriate vegetation is a critical component of the effectiveness of the wetland system. The different zones must be planted with the appropriate vegetation for the depth (See Section 4.7). Appendix C provides planting palettes for BMP facilities. These areas should not receive any fertilizers, pesticides, or herbicides. Vegetation on the pond embankments should be mowed as appropriate to prevent the establishment of woody vegetation.

vii. Outlet – Design the outlet properly with the fine trash rack in front of the outlet orifices and is submerged the full depth of the micropool. This allows flow under the clogged portions of the trash rack.

viii. Drawdown – The surcharge of the wet basin should drain within 12-hours. (See Section 4.8).

e. Note – Texas Commission on Environmental Quality (TCEQ) Dam Safety requirements shall be accounted for as required with higher depth structures. For ponds with significant earthen embankments, prevent planting of woody vegetation in berms to comply with state dam safety rules.

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Inspection and maintenance are critical to the performance of wet basins. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Maintenance should be considered during the design and layout. For example, there must be easy accessibility to the outlet structure and other features that will need to be maintained1. Access should be provided to the wet basin, particularly to the sediment forebay. A maintenance ramp should be a minimum of 10-feet in width and have a maximum slope of 25%. For mowing, it is recommended to keep side slopes at a maximum of 3:1 (horizontal:vertical). Sediment accumulation in the forebay should be monitored using vertical depth markers to indicate when sediment accumulation equals 20% of the forebay volume.

The BMP should be kept offline until the construction activities are completed. However, the BMP excavation can be used as a sediment trap during construction before filtration or other media are placed in the basin. In that case, the bottom of the basin should not be excavated below 2-feet of the final grade.

Temporary BMPs should be in place as detailed in the project Sediment and Erosion Control Plan to protect receiving waters during construction activities (the Sediment and Erosion Control Plan requirements are not discussed in this manual). Sediment discharged during construction can clog the system and would require additional maintenance.

Monitor and minimize use of fertilizers that can increase nutrient concentrations in discharge and cause algal blooms

______________________________________ 1 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

3.5 RETENTION / IRRIGATION BASIN1 The following description and design criteria is consistent with that provided in the Complying with the Edwards Aquifer Rules: Technical Guidance on Best Management Practices prepared by Michael E. Barrett, Ph.D., P.E. for the TCEQ (June 20, 2005). Figure 3.5 provides a conceptual rendering of a retention / irrigation basin with major components identified. Area protection should also be considered in the design.

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Figure 3.5 Conceptual Rendering of a Retention / Irrigation Basin

* Note – wet well should be separated from wet basin where possible


Retention / irrigation refers to the capture of stormwater runoff in a holding pond, then use of the captured WQv for irrigation of appropriate landscape areas. Collection of roof runoff for subsequent use (rainwater harvesting) also qualifies as a retention / irrigation practice but should be operated and sized to provide adequate capture volume. Rainwater harvesting design will not be described in Section 3.5.

Retention / irrigation systems represent a highly effective approach to stormwater quality control. The goal of this technology is to use infiltration and evapotranspiration to treat runoff. Pollutant removal effectiveness is accomplished through physical filtration of solids in the soil profile and uptake of nutrients by vegetation. The primary drawback of this approach is the potentially high maintenance requirements for the irrigation system, which must remain operational for this BMP to function effectively.

Retention / irrigation can replace or reduce the use of potable water for irrigation. When properly designed, constructed, operated, and maintained, retention / irrigation systems are considered to be highly effective at removing pollutants for the water quality capture volume.

3.5.2 APPLICABILITY

Retention / irrigation systems depend heavily on available land for irrigation. Land uses should be limited to residential, commercial, or light industrial developments. Given the high infiltration rate of the designed system, this system should not be used for areas with the potential to contaminate groundwater such as areas with high levels of toxic compounds. Irrigation is assumed in this section; however, other uses of the retained water may be considered and submitted for consideration.

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The system includes mechanical components; therefore, observation and maintenance will be required to ensure the system is performing as designed. Active sites that are routinely inspected and maintained are preferred. The long-term availability of irrigated lands should be considered during BMP selection.


This section provides the design criteria for retention / irrigation basins. Capture of stormwater in retention / irrigation systems can be accomplished in virtually any kind of runoff storage facility ranging from fully dry, concrete- lined to vegetated with a permanent pool. The design of the storage system can be quite flexible. The pump and wet well system should be automated with a rainfall or soil moisture sensor to allow for irrigation only during periods when required infiltration rates (based on soils, evapotranspiration rates, etc.) can be realized.

The structural criteria provide information about the components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General Criteria


b. Maintenance plans – Maintenance plan for retention / irrigation basins must contain a guarantee of maintenance in accordance with the Stormwater Facility Maintenance Agreement for Water Quality Devices and be in conformance with Appendix D. The plan must be submitted for review by TRWD.

2) Site Conditions

a. Drainage area – Retention / irrigation basins should be implemented at locations where there is a larger drainage area. It is recommended that sites be less than 128-acres2.

b. Depth to water table – 2-feet are required between the bottom of the retention basin and the elevation of the seasonally high-water table.

c. Floodplain – Where feasible, the BMP should be located outside of the 100-year floodplain. Where not feasible, the top of walls / embankments for the BMP should be above the 100-year floodplain and the BMP should be designed to protect against surcharge from downstream waters.

d. Space – The space required for the BMP is a function of available head at the site, required treatment WQv, and availability of make-up water.

e. Irrigated area – The irrigated area must be pervious and have an overall slope no greater than 10%. The area must be distinct from areas that are used for wastewater effluent irrigation, and it should be at least 100-feet from wells, septic systems, natural wetlands, and streams. The minimum area requires intermittent irrigation over a period of 60-hours at low rates to use the entire WQv without allowing runoff. This intensive irrigation may be harmful to vegetation that is not adapted to long periods of wet conditions (see Section 4.7). In practice, a much larger

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irrigation area will provide better use of the retained water and promote a healthy landscape.

f. Soils – The permeability of the soils in the area proposed for irrigation should be assessed. This can be determined using a double ring infiltrometer (ASTM D 3385-94) or from county soil surveys prepared by the Natural Resource Conservation Service. A geomembrane liner must be used for retention basin installations adjacent to streets to prevent water from getting under the pavement into the base material. There should be a minimum of 12-inches of soil cover for irrigated areas. If maintaining a permanent pool, minimize water loss by using an impermeable barrier to prevent infiltration.


a. Energy dissipation – The retention / irrigation basin must be designed with energy dissipation structures at the inlet if the entrance velocities exceed the erosive velocity requirement of the BMP surface material (see Section 4.3).

b. Diversion structure – The diversion structure elevation should be equal to or greater than the surface elevation of WQv in the BMP. The diversion structure should be sized to bypass flows from the 10-year annual probability storm and the channel should be able to convey flows from the 100-year annual probability storm with less than 1-foot over the diversion weir.

c. Runoff storage facility configuration and sizing – The design of the runoff storage facility is flexible as long as an appropriate pump and wet well system can be accommodated.

d. Sediment forebay – The retention / irrigation basin should have a sediment forebay to prevent sediment accumulation in the basin and to protect the pumps and irrigation system.

i. Size – The forebay volume should be sized to contain 0.1-inches of runoff from the impervious portion of the contributing drainage area. For example, for a two-acre drainage basin with 60% impervious cover, the forebay should be designed to hold 0.1 inches of runoff from 1.2 acres.

ii. The length to width ratio should be no less than 2:1 (length:width), and the side slopes should be no steeper than 3:1 (horizontal: vertical).

iii. Drawdown – The forebay outlet should be sized such that the forebay drains within 24-hours.

e. Retention basin

i. Size –Three typical options for retention basins consist of dry, concrete-lined basin, vegetated basin, and vegetated basin with permanent pool. The permanent pool is sized to contain 100% of the WQv. The retention basin must be sized to contain the WQv, plus the permanent pool volume if included. The retention basin should allow enough freeboard such that the retention basin can pass the 100-year storm over the diversion structure without overtopping the side walls.

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ii. Vegetation – If applicable, consult Section 4.7 for a list of appropriate vegetation for the retention basin.

iii. Outlet – Design the outlet properly with the fine trash rack in front of the outlet orifices.

iv. Drawdown – The surcharge of the retention basin must drain to the wet well within 72-hours. (See Section 4.8).

v. Fencing – To prevent risk to the public, it is recommended that retention basins be fenced in accordance with the City of Fort Worth requirements. The contours of the retention basin should be managed to eliminate drop-offs and other hazards. Landscaping can also be used to impede access to the retention basin.

f. Note – Texas Commission on Environmental Quality (TCEQ) Dam Safety requirements shall be accounted for as required with higher depth structures.

g. Pump and wet well system - A reliable pump, wet well, and rainfall or soil moisture sensor system should be used to distribute the WQv.

i. Pumps – The pumps should be able to provide 100% of the design capacity and operate within 20% of their best operating efficiency.

ii. The valves should be located outside of the wet well on the discharge side of each pump to allow the pumps to be isolated for maintenance and throttling if necessary.

iii. A high/low-pressure pump shut off system should be installed in the pump discharge piping.

iv. Wet well – The wet well should be constructed of precast or cast in place concrete and located separate from the retention basin. The wet well and pump must be designed to be low enough to completely evacuate the retention basin.

h. Irrigation area and system - The details and specifications for irrigation systems are not part of this manual, and the specifications must be approved by a PE licensed in the state of Texas and submitted for review by the TRWD.

i. Pipes and valves should be marked to indicate that they contain non-potable water.

ii. The irrigation schedule should not begin within 12-hours of the end of the rainfall event so that direct storm runoff has ceased, and soils are not saturated.

iii. The length of active irrigation period is 60-hours with a cycling factor of ¼. The irrigation system should cease in the event that another rainfall event begins during the active irrigation period and should not begin within 12-hours of the end of the rainfall event. Continuous application on any section should be designed to prevent surface runoff from the irrigated area.

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iv. Valves – All valves should be designed specifically for sediment bearing water and be of appropriate design for the intended purpose. All remote control, gate, and quick coupling valves should be located in 10-inch or larger plastic valve boxes.

v. Sprinklers – Sprinklers should operate at the required rate and distribute water in a uniform manner and not beyond the limits of the designated irrigation area. Sprinkler heads should be capable of passing solids that may pass through the intake. Sprinkler heads should be protected from mowing and service equipment.

vi. Vegetation – The irrigation area should have native and high water tolerant vegetation or be restored or re-established with native and high water tolerant vegetation (see Section 4.7). Appendix C provides planting palettes for BMP facilities. These areas should not receive any fertilizers, pesticides, or herbicides. Vegetation on the pond embankments should be mowed as appropriate to prevent the establishment of woody vegetation.


Inspection and maintenance are critical to the performance of retention / irrigation basin. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Maintenance should be considering during the design and layout. Depth markers should be installed in the forebay to monitor sediment accumulation and removal. The basin should be maintained when sediment accumulation is no more than 20% of the forebay volume. Earthen side slopes should not exceed 3:1 (horizontal:vertical) and should terminate on a flat safety bench area.

Water from the retention basin should pass through a screen or filter to remove solid material and prevent clogging of pipes and sprinklers. The pump and other internal components of the wet well should be accessible through a locked cover to prevent unauthorized access. An isolation valve to prevent flow from the retention basin to the wet well during maintenance activities is recommended.

Alarms - An alarm system should be provided that is protected against vandals and exposure to weather. The alarm system should be highly visible and should alert when the pumps are not functioning correctly. This could include the water level not being drawn down, the pump not shutting off with low levels of water, or issues with pump pressure.


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Monitor and minimize use of fertilizers that can increase nutrient concentrations if there is runoff.

To the greatest extent practicable, irrigation areas should remain in their natural state. However, vegetation must be maintained in the irrigation area such that it does not impede the spray of water from the irrigation heads. Tree and shrub trimmings and other large debris should be removed from the irrigation area.

1 Barrett, Michael E. Ph.D., P.E. Complying with the Edwards Aquifer Rules Technical Guidance on Best Management Practices. TCEQ RG-348. Revised July 2005 with Addendum Sheet (updated January 2017). 2 “Retention/Irrigation” Highland Lakes Watershed Ordinance Water Quality Management Technical Manual. LCRA. (2007). 7th ed. 4-31 to 4-36.

3.6 EXTENDED DRY DETENTION BASIN 3.6.1 BMP DESCRIPTION

Extended dry detention basins are depressed basins that temporarily store stormwater runoff following a storm event. The water quality benefit of extended detention is achieved through the extended time for particulate pollutants to settle out and incorporating features to promote the capture of sediment, trash, and debris. Detention systems have traditionally been used for flood control to mitigate or regulate flow; however, by extending the detention time from flood control facilities and adding key features that improve water quality, these systems are effective at reducing pollutants. The City of Fort Worth also requires dry detention basins for streambank protection and flood control mitigation. The design and components of extended dry detention basins defined in this manual expand on these requirements and provide additional water quality features (COFW Stormwater Criteria Manual).

When used as a pre- or post-treatment or in conjunction with other water quality treatment systems (i.e. grass swales, vegetated filter systems, sand filters, bioretention basins, constructed wetlands) the performance of the overall BMP approach is increased. Extended dry detention basins must be designed following the criteria specified below and used in conjunction with pre- or post-treatment or other water quality treatment facilities. Figure 3.6 provides a conceptual rendering of an extended detention basin with major components identified. Area protection should also be considered.


This section provides the design criteria for extended detention basins. The structural criteria provide information about the components and include references to the component design section of this manual (Section 4); the details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

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Figure 3.6 Conceptual Rendering of an Extended Dry Detention Basin

A general overview of design criteria for consideration at the BMP selection stage of the site design process is provided below.

1) General Criteria


b. Maintenance plans – Maintenance plan for extended dry detention basins must contain a guarantee of maintenance in accordance with the Stormwater Facility Maintenance Agreement for Water Quality Devices and be in conformance with Appendix D. The plan must be submitted for review by TRWD.

2) Site Conditions

a. Drainage area – Extended dry detention basins should be implemented at locations serving a drainage area greater than 5-acres but less than 100-acres. For larger basins, additional information must be provided to ensure that the basin will perform effectively, and additional maintenance and inspections may be required to verify.

b. Depth to water table – 2-feet are required between the bottom of the extended dry detention basin and the elevation of the seasonally high-water table.

c. Soils – Determine if native soils on site are sufficient for infiltration. A geomembrane liner must be used for installations adjacent to streets to prevent water from getting under the pavement into the base material.

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e. Space – The space required for the BMP is a function of available head at the site, required treatment WQv, and availability of make-up water.


a. Energy dissipation – The extended dry detention basin must be designed with energy dissipation structures at the inlet if the entrance velocities exceed the erosive velocity requirement of the BMP surface material (see Section 4.3).


c. Forebay – The extended dry detention basin must have a sediment forebay to prevent sediment accumulation in the basin.

i. Size – The forebay volume should be sized to contain 10% of the WQv. The length to width ratio should be no less than 2:1 (length:width), and the side slopes no steeper than 3:1 (horizontal:vertical).

ii. Drawdown – The forebay outlet should be sized such that the forebay drains within 24-hours.

d. Basin

i. Size – The extended dry detention basin should be designed to contain 100% of the WQv. Side slopes of the basin should be no steeper than 3:1 (horizontal: vertical). (See Sections 4.4 for additional information on area protection).

ii. Trickle channels should have a design slope of at least 3%. Extended dry detention basins should have a micropool that is at least 2.5-feet in depth at the end of the basin. The micropool does not have to drain within 48-hours.

iii. Landscaping – The extended dry detention basin should be appropriately seeded for temporary inundation (see Section 4.7).

iv. Outlet – Design the outlet properly with the fine trash rack in front of the outlet orifices and submerged the full depth of the micropool. This allows flow under the clogged portions of the trash rack.

v. Drawdown – The extended dry detention basin should drain the WQv within 40 to 48-hours. (See Section 4.8).

e. Note – Texas Commission on Environmental Quality (TCEQ) Dam Safety requirements shall be accounted for as required with higher depth structures. For ponds with significant earthen embankments, prevent planting of woody vegetation in berms to comply with state dam safety rules.

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Inspection and maintenance are critical to the performance of extended detention basins. The activities, schedule, and additional maintenance considerations and requirements are included in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Maintenance should be considering during the design and layout. For example, pruning and mowing of vegetation and accessibility to other features that will need to be maintained1. Adequate access must be provided for inspection and maintenance, including the appropriate equipment and vehicles. An access ramp with a minimum width of 10-feet and a maximum slope of 25% shall be provided.



______________________________________ 1 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

3.7 VEGETATED FILTER STRIP

3.7.1 DESCRIPTION OF BMP1

Vegetated filter strips are gently sloped flat vegetated areas designed to receive and maintain sheet flows over the entire width of the strip2. They are typically linear facilities that run parallel to the impervious surface. These systems are not intended to be used as a stand-alone or primary BMP system for a development. However, if a vegetated filter strip BMP system is used within close proximity to small, low-density impervious areas, the WQv for this area can be treated. For these areas, the area that drains to the BMP can be reduced from the total site area. Therefore, the WQV from that area is reduced from the total WQV for the site.

Vegetated filter strips treat stormwater runoff and can reduce velocity2. Vegetated filter strips remove pollutants by sedimentation, filtration, and infiltration. To function correctly, vegetated filter strips require shallow slopes and well drained soils that increase contact time and remove pollutants. Pollutant removal efficiencies are highly variable and primarily depend on the longitudinal slope, the length of the filter strip, and the amount of vegetation. These variables correspond to the contact time for filtration. The extent of infiltration also depends on the type of soil, the drainage capacity of the soil, as it relates to infiltration, the density of the grass, and the slope of the strip3.

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3.7.2 APPLICABILITY

These BMPs can be used most effectively in areas with low density impervious cover or linear impervious cover or as pre- or post-treatment for other water quality BMPs. Vegetated filter strips are intended to treat sheet flow only. They are commonly used to receive runoff from roads and highways, roof downspouts, very small parking areas, walkways and driveways, as well as pervious surfaces1,3. Filter strips can be easily integrated into the site design.


This section provides the design criteria for vegetative filter strips. The structural criteria provide information about the components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General criteria

a. Maximum depth of sheet flow over the filter strip should not exceed 2-inches for the water quality event; 1-inch is preferred.

b. Maintenance plans – The maintenance plan must contain a guarantee of maintenance and conform with requirements in Appendix D and the Stormwater Facility Maintenance Agreement – Water Quality Devices.

2) Site conditions

a. Drainage Area – The length of the contributing drainage area in the direction of flow should not exceed 75-feet. A flow spreader device can be placed at the top of the filter strip for large flow lengths to promote sheet flow.

b. Soils – Soils should have a minimum depth of 12-inches and must allow for dense vegetative coverage.

c. Space Required – To achieve the desired level of treatment, the length of the filter strip in the direction of flow should be no less than 15-feet, and 25-feet is preferred. However, vegetated areas will provide some level of treatment at less than 15 feet. Therefore, if the available space does not allow for the length of the filter strip to be at least 15-feet, then including vegetated areas is still encouraged to help reduce sediment loads.

d. Pedestrian traffic across filter strips shall be limited through channeling onto sidewalks.


a. Slope – The longitudinal (direction of flow) slope of a filter strip should be no less than 2% and no greater than 6%.

b. Landscaping – An appropriate planting pallet should be selected to ensure vegetation is sustained over the course of wet and dry periods, capable of withstanding large rain events, and able to withstand relatively high velocity flows at the entrances in order to prevent erosion rills (see Section 4.7).

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c. Permeable berms – Installed for enhanced filter strips should have a maximum height of 12-inches with a 3:1 side slope. They should be level and constructed with a non-settling core to prevent erosion or channelized flow downstream of the berm resulting from high flow storm events.


Inspection and maintenance are critical to the performance of vegetated filter strips. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Access - Limit pedestrian access across filter strips by directing pedestrians to sidewalks or other marked walkways.

Maintenance should be considering during the design and layout. For example, pruning and mowing of vegetation and accessibility to features that will need to be maintained4.

Consider installing vegetated filter strips 1 to 3-inches below adjacent impervious surfaces4.

Include soil amendments to improve plant establishment and reduce need for irrigation4.

1 Barrett, Michael E. Ph.D., P.E. Complying with the Edwards Aquifer Rules Technical Guidance on Best Management Practices. TCEQ RG-348. Revised July 2005 with Addendum Sheet (updated January 2017). 2 King County. April 2016. Surface Water Design Manual 3 North Central Texas Council of Governments. September 2014. iSWMTM Technical Manual. 4 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

3.8 GRASS SWALE


Grass (vegetated) swales are gently sloped channels that are designed to receive and treat stormwater as it is conveyed to a standalone or primary BMP or after discharge from a BMP2. These systems are not intended to be used as a stand-alone or primary BMP system for a development. However, if a grass swale BMP system is used within close proximity to small, low-density impervious areas, the WQv for this area can be treated. For these areas, the area that drains to the BMP can be reduced from the total site area. Therefore, the WQV from that area is reduced from the total WQV for the site.

These remove pollutants primarily by maintaining shallow flow through vegetation that encourages sedimentation or particle settling and infiltration2. These processes can be enhanced by resistance of vegetation to flow2. To a much lesser degree, pollutants may adhere or sorb to grass and thatch2. Swales generally do not remove dissolved pollutants effectively, although some infiltration to underlying soils may occur depending on the nature of those soils1.

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The pollutant removal efficiency of swales is highly variable and primarily depends on the density of the vegetation, the width of the swale and depth of flow, the length of the vegetated swale, which corresponds to the contact time for filtration, as well as the drainage capacity of the soil as it relates to infiltration3. There are two types of grass swales: simple and enhanced. An enhanced version includes the use of berms, check dams, or dense or specialized vegetation to slow the flow and increase the residence time. This section discusses each in further detail.

3.8.2 APPLICABILITY

They can be used most effectively in areas with low density impervious cover or linear impervious cover, such as roadways or sidewalks, or as pre- or post-treatment for other water quality BMPs. Grass swales are intended to treat shallow concentrated flow. They are commonly used to receive and convey runoff from road and highways, roof downspouts, parking areas, walkways and driveways, as well as pervious surfaces1,3.

To function correctly, grass swales require shallow slopes and well drained soils that increase contact time and remove pollutants. They can be easily integrated into the site design.


This section provides the design criteria for grass swales. The structural criteria provide information about the components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General criteria

a. Maximum depth of sheet flow over the filter strip should not exceed 4-inches during the water quality event.

b. Maintenance plans – Maintenance plan must include a guarantee of maintenance and conforms with the requirements in Appendix D and the Stormwater Facility Maintenance Agreement – Water Quality Devices.

2) Site conditions

a. Drainage Area – Less than 5-acres. If the practices are used on larger drainage areas, the flows and volumes through the channel become too large to allow for filtering and infiltration of runoff.

b. Soils – Generally unrestricted. Swales should not be used on soils with infiltration rates less than 0.27-inches per hour if infiltration of small runoff flows is intended.

c. Space Required – Dependent on the contributing drainage area and anticipated flow.


a. Cross section design - The swale should have a trapezoidal or parabolic cross section with relatively flat side slopes (generally 3:1 or flatter).

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b. Channel bottom – The bottom of the channel should be between 2 and 6-feet wide. The minimum width ensures an adequate filtering surface for water quality treatment, and the maximum width prevents braiding, which is the formation of small channels within the swale bottom. The bottom width is a dependent variable in the calculation of velocity based on Manning’s Equation. If a larger channel is needed, the use of a compound cross section is recommended.

c. Slope – Relatively flat slopes of less than 4%; channel slopes between 1% and 2% are recommended.

d. Maximum Velocity - Target maximum velocity less than 1.0-foot per second.2

e. Vegetation – An appropriate planting pallet should be selected to ensure vegetation is sustained over the course of wet and dry periods, as well as capable of withstanding large rain events, in order to prevent erosion rills (see Section 4.7). These areas should not receive any fertilizers, pesticides, or herbicides. Vegetation on the pond embankments should be mowed as appropriate to prevent the establishment of woody vegetation.

f. Permeable berms – Should have maximum height of 12-inches with a 3:1 side slope. They should be level and constructed with a non-settling core to prevent erosion or channelized flow downstream of the berm as a result of high flow storm events.

g. Riprap - Riprap-protected side slopes shall be no steeper than 2:1.2

h. Check Dams – If check dams are installed, then the ponding depth behind check dams shall be designed to infiltrate or drain stormwater runoff within less than 48 hours.


Inspection and maintenance are critical to the performance of grass swales. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Access - Limit pedestrian access across filter strips by directing pedestrians to sidewalks or other marked walkways.

Maintenance should be considering during the design and layout. For example, mowing of vegetation and accessibility to features that will need to be maintained3.

Include soil amendments to improve plant establishment and reduce need for irrigation3.

1 King County. April 2016. Surface Water Design Manual 2 North Central Texas Council of Governments. September 2014. iSWMTM Technical Manual. 3 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

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3.9 PERMEABLE SURFACES


Permeable surfaces include permeable pavers, porous concrete, porous asphalt, and grassed modular grid systems. Permeable surfaces require careful design, construction, and maintenance in order to provide good service life and proper drainage. Permeable surfaces have been used to replace or use in place of impervious surfaces and be used to temporarily store water in the storage aggregate layer. This manual focuses on the use of permeable pavers. Other surfaces can be submitted for review. Porous asphalt is not allowed for compliance with water quality requirements. There are many types of proprietary permeable pavement systems on the market today. When applicable, and unless modified by a civil engineer’s signed/sealed design, the manufacturer's recommendations should be strictly followed.

Permeable pavers are not recommended in areas with high sediment loads due to the potential for clogging and may require frequent maintenance to remain effective2. To prevent clogging, permeable pavers are recommended at a ratio of treatment drainage area to permeable paver surface area of 1.5 to 1. It is also recommended that impervious surfaces that drain to Permeable Surfaces are regularly swept by street sweepers. Figure 3.7 provides a conceptual rendering of a permeable paver system with an adjacent small bioretention basin.

Figure 3.7 Conceptual Rendering of Permeable Pavers

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This section provides the design criteria for permeable pavers. The structural criteria provide information about the components and include references to the component design section of this manual (Section 4). The details and specifications for the components are provided in that section. The design/review spreadsheet in Appendix E outlines the design steps and calculations for the BMPs.

1) General conditions

a. Specifications for permeable must contain technical information as detailed in Section 4.9.

b. Maintenance plan for sand filters must include, at a minimum, trash removal, accumulated sediment removal, inspection for standing water, and inspection for 24-hour drawdown as specified in Appendix D

2) Site Conditions

a. A minimum of 4-feet of clearance is recommended between the bottom of the gravel base course and underlying impermeable layers or the seasonally high groundwater table.

b. Permeable pavers are recommended at a ratio of treatment drainage area to permeable paver surface area of 1.5 to 1.


a. Pretreatment – Vegetated filter strips are recommended to be installed for permeable surfaces that receive runoff from vegetated surfaces such as open fields or playgrounds.

b. Slopes – Permeable paver systems should not be used on slopes greater than 5% with slopes of no greater than 2% recommended. For slopes greater than 1% barriers perpendicular to the direction of drainage should be installed in sub-grade material to keep runoff in the media from flowing downstream and surfacing at the toe, thus not providing the needed WQv under the pavement.

c. Signage – A warning sign should be placed at the facility that states, “Permeable pavers used on this site to reduce pollution. Do not resurface with non-porous material or sand during icy weather.”


Inspection and maintenance are critical to the performance of permeable pavers. The activities, schedule, and additional maintenance considerations and requirements are attached in Appendix D “BMP Inspection and Maintenance” of this manual. The following should be considered during design and construction of the BMP:

Maintenance should be considering during the design and layout.

Consider installation of an observation well to monitor drain time of the pavement over time.

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The BMP must be protected until the construction activities are completed. Temporary BMPs should be in place as detailed in the Sediment and Erosion Plan to protect permeable pavers and receiving waters during construction activities (this will not be covered in this manual). Sediment discharged during construction can clog the system and would require additional maintenance. A pre-construction meeting should be held to ensure the contractor is aware that the permeable pavers should be protected from sediment load. A construction fence can also be used during construction to prevent compaction

1 King County. April 2016. Surface Water Design Manual 2 Urban Drainage and Flood Control District (UDFCD). (2010). Urban Storm Drainage Criteria Manual (USDCM): Volume 3 Stormwater Quality.

ADDITIONAL RESOURCES

1 City of Fort Worth. December 20, 2012. Standard Construction Specification Documents. 2 NCTCOG. September 2014. “iSWMTM Technical Manual: Water Quality: 1.0 Water Quality

Protection Volume and Peak Flow”, North Central Texas Council of Governments, Arlington, Texas, April 2010, Revised September 2014, http://iswm.nctcog.org/Documents/technical_manual/Water%20Quality_9-2014.pdf

3 Placer County, et. al. West Placer Storm Water Quality Design Manual. April 2016. 4 Texas Commission on Environmental Quality. November 2015. Rules and Regulations for Public

Water Systems. 5 UWRI. October 5, 2015. Comparison of Water Quality Capture Volume Needs for Ft. Worth, TX

Region to Capture of 85th Percentile Runoff Volume and Runoff Events, Urban Watershed Research Institute.


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Curb CutSpecify Width(See Note 1)

Standard Curb

Saw Cut Curb(See Note 2)

Notes

1. A curb cut is a cut in an existing curb, and a depressed curb is a curb poured in-place with a tapered opening. Width and angle of curb cut ortaper varies based on site and stormwater capture requirements. If existing curb is damaged beyond extents specified for cut, curb shall bereplaced to the nearest joint.

2. Curb cuts must be saw-cut such that all edges are square and edges beveled to a min 14" radius. Saw-cut per City of Fort Worth STDSpecification 02 41 15.

3. Horizontal surface must have positive slope toward BMP installation.

4. Concrete curb materials shall conform to City of Fort Worth STD Specification 32 13 13. All exposed surfaces shall have a broom finish.

5. Depressed curb shall transition to typical curb section per City of Fort Worth STD DWG D534.

Bevel Edges ofCurb to MIN 1/4" R

Pavement(See Note 3)

Angle Varies

Cut Depth to At-Grade Elevation or asSpecified (See Note 3)

CurbCurb Cut/Depressed CurbStormwater Inlet

BMPEnergy Dissipation(See Section 4.3)

PLAN

Flow

Dire

ctio

n

Pavement

TARRANT REGIONAL WATER DISTRICT REVISED: JANUARY 2018

Curb Cut / Depressed Curb DM-DC 4.1.1

Concrete Curb(See Note 4)

Formed FinishedEdge (Typ)

Pavement

Bevel edges of curbto MIN 1/4" R

Specify Length(See Note 1)

Specify Width(See Note 1)

ELEVATION

ELEVATIONCurb Cut

Depressed Curb

Trench DrainCover,Pattern/GratingMay Vary(See Note 1)

Bolt and Frame per Manufacturer'sRequirements (See Notes 2 and 4)

PLAN

SECTION A-A

Curb

Specify Outlet PipeSize and Inverts (IfApplicable)

Sidewalk

ConcreteTrench

Specify TrenchLength Based on

Pavement Extents

Pavement

6"MIN

Provide Elevationsand Inverts (Typ)

Provide TrenchElevations andInverts (Typ)

Storage Aggregate-CrushedRock (Section 4.5.3)

Notes

1. Grated located in walking surface shall have openings no greater than 1/2" in one direction, and elongated openings shall beplaced so that the long dimension is perpendicular to the dominant direction of travel per Texas Accessibility Standards.

2. If trench drain assembly includes metal frame and channel, install per manufacturer instructions.

3. Cross slope and longitudinal slope of trench channel bottom may vary by design.

4. Bolt down grate and frame is required. All bolts shall be flush with existing grade of the paved surface.

5. Trench drain materials, installation, and other considerations shall comply with City of Fort Worth STD Specification 33 46 02including compliance with AASHTO HS-20 loading.

SpecifyDepth

AA

Expansion joint(Typ)

Provide TrenchElevations andInverts (Typ)

Trench DrainStormwater InletSpecify Width

TARRANT REGIONAL WATER DISTRICT

Trench Drain DM-DC 4.1.2

Flow

Flow

Flow

FlowDirection

A

APLAN

18" (Typ)

Pavement

25% MAX (See Note 2)

Flow

Dire

ctio

n

Notes

1. Max Slope of apron parallel to thecurb is 16.67% per City of Fort WorthSTD DWG D405.

2. Max Slope of gutter apron cross slopeis 25% per City of Fort Worth STDDWG D405. Slopes will be governedby stormwater capture requirementsand entrance velocities.

3. Concrete shall conform to City of FortWorth STD Specification 32 13 13.

ELEVATION

FlowDirection

Curb

Stormwater Entrance

Gutter Apron Existing Gutter

BMP

Curb Cut/Depressed Curb(Section 4.1.1)

(See Note 1) (See Note 1)

Specify Length(3' MIN)

Transition toTypical GutterSection

Existing Gutter

Crushed Rock per City STDSpecification 33 05 10

Compacted Subgrade

Transition toTypical GutterSection

BMP

SECTION A-A

Pavement

Existing Gutter

Energy Dissipation (See Section 4.3)

6" MIN

6" MIN

Front of Curb6"

(Typ)


Gutter Apron DM-DC 4.1.3

6" (Typ)

Front of Curb

2' MIN

Notes

1. Acceptable pipe materials shall be in accordance with City of Fort Worth STD Specification 33 46 00.

2. Distribution piping shall include a backflow prevention device such as a check valve, a flap gate, or other appropriatemeasure to prevent the flow of ponded water back into the inlet structure.

Solid DistributionPiping

PROFILE

Stone Aggregate-CrushedRock (Section 4.5.3)

PerforatedDistributionPiping


Distribution Piping DM-DC 4.1.4

4" MIN

4" MIN

BackflowPrevention (Typ)(See Note 2)

INLETSTRUCTURE

End Cap

DecorativeGravel/River Rock

DecorativeGravel/River Rock3' MIN

PerforatedDistributionPiping

Stone Aggregate-CrushedRock (Section 4.5.3)

4" MIN

A

A

SECTION A-A

0.5% (Typ)

BMP

BMP

VegetatedFilter Strip

Distance SiteSpecific

(See Note 1)

SECTION A-A

Provide SpotElevations (Typ)

Pavement

Slope Varies(See Note 3)

Vegetated FilterStrip

Provide SpotElevations (Typ)

BMP

A

APLAN

Pavement Ribbon Curb

Notes

1. For optimal filtration performance, a vegetated filter strip shall have a minimum length of 15-feet in the direction of theflow unless site constraints prevent meeting this requirement.

2. The longitudinal (direction of flow) slope of a filter strip should be no less than 2% and no greater than 6%. Thetransverse slope should be no more than 2% and preferably 1%.

3. Filter strip shall be parallel to the adjacent pavement grade.

Distance SiteSpecific

(See Note 1)


Vegetated Filter Strip DM-DC 4.2.1

Ribbon Curb

4" MIN(Typ)

2"- 3"Spacing

4" - 6"Stone Size

Surface Stone Free ofJagged Edges and TopsFlush with Invert Opening

8" MIN ConcreteBedding per City of Fort Worth

STD Specification 03 30 00

PLAN

Pavement

Specify Surface Material(See Note 2)

BMP


Specify Length(See Note 1)

AA

SECTION A-ARock Splash Pad

Embedded inConcrete

SECTION A-ABrick Splash Pad

Embedded inConcrete

Curb

Stormwater Inlet(Section 4.1)

Mortar Joints Specify Brick Materialand Pattern

BMP

4" MIN Crushed Rock Per City of Fort Worth


4" MIN ConcreteBedding per City of Fort Worth


Welded Wire MeshPlaced in Bottom 13 ofConcrete

CompactedSubgrade

CompactedSubgrade

4" MIN Crushed Rock Per City of Fort Worth


Notes

1. Dimensions of splash pad are dependent on inlet size and type, and the velocity of stormwater entering the BMP. Width ofsplash pad shall be greater than total stormwater entrance width and consider potential for erosion adjacent to splash pad.

2. Surface material shall be clean washed aggregate or clay bricks. Splash pad not embedded in concrete must use aggregatewith a minimum 2" diameter surrounded with permanent edging, such as anchored angle iron or concrete, to prevent materialfrom migrating into the BMP. Loose surface material shall require a permeable geotextile (Section 4.6.3) to separate theenergy dissipation aggregate and underlying BMP media.

3. A minimum 3" of freeboard is required between the top of energy dissipation material and the inlet grade elevation to accountfor sediment accumulation.

4"x2.5"x8" Full Brick,Stand on End (Typ)4"x2.5"x4" Half Brick,Stand on End (Typ)


Splash Pad DM-DC 4.3.1

BMP

Flow

Dire

ctio

n


Mortar Bed 1/2" Thick

Flow

Dire

ctio

n

Pavement

Notes

1. Dimensions of sump are dependent on inlet size and type, and the velocity of stormwater entering the BMP.

2. A minimum of 3" of freeboard is required between the top of energy dissipation sump and inlet to account for sedimentaccumulation.

3. Steel reinforcement shall be determined by the engineer.

4" (MIN)

PLAN

SECTION A-A

Pavement

Curb Cut/DepressedCurb (Section 4.1.1)

4" (MIN)

BMP

BMP

A

A

StormwaterEntrance

StormwaterEntrance

SpecifyLength

(See Note 1)


Curb

TARRANT REGIONAL WATER DISTRICT Energy Dissipation

Sump DM-DC 4.3.2

BB

4" (MIN)6" Concrete

SECTION B-B

2" Opening

6" Concrete 2" Opening

MIN 3" Depth(See Notes 1 & 2)

Thickness to beDetermined by

Engineer


Full Height Curb

Notes

Curbing shall conform to City of Fort Worth STD DWG D534 - Standard Curb and Gutter.

Combination curb and gutter is preferred for curbing on existing curb and gutter street sections.Straight bac curb per may be used where curb is proposed for existing non-curb and gutter streetsections, permeable pavement applications, and for sidewa butting the BMP.

Curb heights exceeding on the front face shall be considered a curb with retaining wall and shallconform to City of Fort Worth STD DWG D534.

Concrete curb materials shall conform to City of Fort Worth STD Specification 32 13 13. All exposedsurfaces shall have a brushed finish.

Ribbon curb may be used to facilitate overland sheet flow to BMP where applicable. Ribbon curb shallhave the same design as the standard curb, with the exception that the top of curb elevation shall beflush with the surrounding grade.

Street

Specify Slope

CompactedSubgrade to

0 Density

SpecifyDepth

Adjacent SidewalCurb Per City of FortWorth STD DWGD534 (See Note 3)

Curb Per City of FortWorth STD DWG D534

BMP

Specify Slope

SECTIONStraight Curb

Subgrade Per City ofFort Worth STD Specifications32 13 13.

CompactedSubgrade

Designerto Specify

Depth

SpecifyDepth

SECTIONCurb Gutter

SpecifyDepth

SpecifyDepth

12" MA

Front Face(See Note 5)

Front Face

12" MA


Curbing DM-DC 4.4.1

3" R

3" R

12" R

34" per ft

Bars

BMP

BMP

40" MIN


Notes

1. When BMP is applied adjacent to on street parking zones, a minimum 2' clearance for vehicular door openings will be requiredbetween the back of curb or edge of pavement and the edge of the BMP. Bollards applied at intersections must not obstruct theminimum sight triangles per City of Fort Worth Public Work's Traffic Engineering Design Standards and Policy Guidelines.

2. Bollard design shall conform to manufacturer specifications and requirements. Product manufacturer or equal shall be specified onthe detail.

3. Bollard post embedment shall be site specific. Footing may be embedded directly in BMP planting media or within adjacentsidewalk area. Bollards that require embedment for additional or traffic rated stability shall be designed by an engineer licensed inthe State of Texas.

4. Bollards located within sidewalk area shall maintain a minimum 3' clear zone in the pedestrian pathway per ADA requirements.See City of Fort Worth STD DWG D546 for minimum sidewalk widths.

5. For Bollards located in BMPs without curb, local DOT standards shall be used to determine placement of bollard.

PavementSpecify Slope

Post Embedment and Footing(See Note 3)

Specify HighIntensity ReflectiveSheeting Size andShape

Specify BollardMaterial and Pattern

SpecifyDepth

24" MIN

Footing shall extend to bottom of BMP section to subgradeor aggregate bedding layer for sufficient stability


Bollard DM-DC 4.4.2

Concrete Curb orEdging

•

•

o

o

o

•

•

•

•

•

•

•

•

MIN Slope 0.5%

Notes

1. Acceptable pipe materials shall be in accordance with City of Fort Worth STD Specification 33 46 00.

2. Lateral or parallel underdrains may be installed if necessary depending on size and slope of BMP. Intersecting underdrains shall beinstalled such that flow enters the pipe in the downstream direction.

3. A flow control mechanism such as a valve, orifice, or upturned elbow is highly recommended to be installed on the downstream end ofunderdrains to control discharge from the BMP.

4. Anti-seep collar should be completely free of bedding.

Cleanout (Section 4.8.2)

PLAN

PROFILE

200' (MAX) Spacing Between Cleanouts

Typical BMP Installation

Anti-seep Collar(Section 4.8.6)(See Note 4)

Connect Underdrain to Storm Seweror Open Channel ThroughUnperforated HDPE or PVC Pipe

Typical BMP Installation

6" MIN

4" (MIN)

Outflow Control Device(See Note 3)


Solid PVC or HDPE Pipe

Connect Underdrain to Storm Seweror Other Free-flowing Outlet

6" (MIN) Perforated Pipe(See Note 1)

Outflow Control Device(See Note 3)

Cleanout(Section 4.8.2)


Media Barrier (Section 4.6)

Valve Box/Access Structure


Underdrain DM-DC 4.8.1

12" MIN From OD of Pipe

Upstream End of UnderdrainShall Terminate With Two45-Degree Bends and Riser

Notes

1. Cleanouts in vegetated BMPs shall extend aminimum 6" above finished grade. Cleanouts inpaved areas shall be flush with adjacent grade.Cleanout cast iron box & lid required in paved areasused for traffic purposes and shall be flush with thepaved surface.

2. Acceptable pipe material shall be in accordancewith City of Fort Worth STD Specification 33 46 00.

3. Cleanouts shall be required at the upstream anddownstream ends of an underdrain or distributionpipe system with a maximum spacing distance of200 feet between cleanouts.


Cleanout DM-DC 4.8.2

6"

Cleanout Shall Extend Above GradeWithin Vegetated BMPs (See Note 1)

6"

PVC Cleanout Lid

CLEANOUT IN SOILCast Iron Box and LidBass & Hays Detail #340-1"Stormwater" or ApprovedEqual (See Note 1)

6" MIN Solid PVC or HDPERiser (See Note 2)

45 Degree Bend

45 Degree WyeFitting

Underdrain (Section 4.8.1) orDistribution Pipe (Section 4.1.4)

CLEANOUT IN PAVED SURFACE

Crushed Rock Per Cityof Fort Worth STD

Specification 33 05 10

6" MIN Solid PVC or HDPE(See Note 2)

FlowDirection

Concrete Footer for CastIron Box Per Manufacturer'sSpecifications

Notes

1. Nyoplast Drain Basin or equal is an acceptable alternative to standpipe overflow. Bedding and anchoring details shallbe per manufacturer requirements.

2. Riser piping shall be made of soil tight seals and fittings and conform to City of Fort Worth STD Specification 33 31 20.

3. Overflow elevations shall be set at or above design ponding height such that overflow occurs only as necessary toprevent flooding of BMP facility and surrounding area.

4. Vegetation placed in the vicinity of the outlet shall maintain a minimum distance of 12-inches to prevent plant debrisfrom clogging the structure.

5. Surface of the BMP shall be graded for positive drainage towards the outlet.

SECTION

Nyoplast Dome Grate (Specify Diameter)or Approved Equal, (See Note 1)

Typical BMP Installation(See Notes 4 & 5)

Crushed Rock PerCity of Fort WorthSTD Specification33 05 10

Concrete Surround

6"

Overflow Elevation Above Top of BMPto be Specified, (See Note 3)

• • ••• • • • • ••• • • ••••••••••••••••

Connect to Storm Sewer or OtherFree-Flowing Outlet

HDPE or PVC SpecifyDiameter (See Note 2)

Specify Depth(See Note 3)


Outflow Riser DM-DC 4.8.3


Notes

1. BMP Drain to be used for watering BMP during maintenance activities.

2. Use of multi-stage orifice to be determined by engineer.SECTION

Install MechanicalPlug/Valve Gate WhenDrain is Not in Service


Multi-Stage Outlet Structure DM-DC 4.8.4

Beehive Grate

Multi-Stage OutletOrifice (Optional)(Note 2).

Typical BMPInstallation

ALTERNATIVE BEEHIVEGRATE OPTION

Connect to StormSewer or OtherFree-Flowing OutletStorage Aggregate-

Crushed Rock(Section 4.5.3)

Solid BMP MaintenanceDrain Pipe

Perforated Underdrain(Section 4.8.1)(Where Applicable)

Grate

Cast Iron Box and Lid Bass & HaysDetail #340-1 "Stormwater" orApproved Equal (See Note 2)

PVC Cap

SECTION

6"

1'-6"

4" PVC SCH 40 Slotted WellScreen With 0.01" Slot size(See Note 4)

Notes

1. If the observation well is located within a parking area, then it shall be flush with the paved surface. Not recommended toplace observation wells in areas with high vehicular traffic due to safety concerns.

2. Well covers shall be secured in concrete surround if not secured in pavement surface restoration. Well covers inpavement shall be flush with finished grade.

3. Area surrounding well shall be restored in kind with the adjoining area. Any geotextile filter fabric penetrated duringinstallation shall be cut and wrapped to a height of 6" upward along the solid well section.

4. Larger piping material may be required to accommodate need for monitoring or data recording equipment.

6"

Specify Depth

HDPE or PVCPipe (4" MIN)(See Note 4)

Concrete Surround


BMP Installation

4" MIN

Bottom Plug

6" Solid PVC

Crushed Rock Per City of Fort WorthSTD Specification 33 05 10

Observation Well DM-DC 4.8.5


6" MIN Above Slotted Pipe

Notes

1. Anti-seep collars used in conjunction with Utility Sleeves (Section 4.8.7) shall be installed on the upstream anddownstream end of the piping at each edge of the BMP facility. Anti-seep collars and Utility sleeves shall also beinstalled on all utility piping joints, bends, and splices that are within the BMP.

2. 'W' shall be 3' for pipes 12" and smaller.

3. Collar shall be constructed of 4000 psi compressive strength concrete or other material providing watertight connectioncompatible to pipe, as approved by a PE and reviewed by the TRWD.

4. Geomembrane Liner (Section 4.6.4) shall be used where anti-seep collars are required on vertical sides of the BMP.Liners shall be minimally cut to allow for the collar and sealed with the external sheets of the anti-seep collar.

5. All fittings and seals to be installed and tested to a water-tight seal per manufacturer specifications.

6. Hydrophilic water stops may be an allowable substitute for anti-seep collars for situations where the utility or other pipingpasses through a concrete structure.

ELEVATION

Concrete Collar

SECTION

Piping (Section 4.8) orUtility Service

W(See Note 2)

W

Align Collar With Edge ofBMP Installation

See Note 4

6" MIN.


Anti-Seep Collar DM-DC 4.8.6

Concrete ReinforcementPer City of Fort WorthSTD DWG D416

Notes

1. Length of required utility sleeve dependent on type of utility service and location within or adjacent to the BMP.

2. Seal surface of utility, utility sleeve and anti-seep collar (if necessary) with non-shrink grout or other sealant.

3. Anti-seep collars (Section 4.8.6) used in conjunction with utility sleeves shall be installed on the upstream anddownstream end of the piping at each edge of the BMP facility. Anti-seep collars and Utility sleeves shall also beinstalled on all utility piping joints, bends, and splices that are within the BMP.

Anti-Seep Collar(Section 4.8.6)

Utility Service Line

Utility Sleeve(See Note 1)

Specify Diameter of PipeSleeve Dependent onService Line Size

Non-shrink grout orwatertight sealant(See Note 2)


Utility Sleeve DM-DC 4.8.7

Specify Length (See Note1)


PROFILE

SECTION

Permeable Pavers(See Note 1)

Joint Material(See Note 3)

Sand (Section 4.6.1)or No. 8, 89 or 9Aggregate (See Note 3)


Specify JointSpacing

Per Manufacturer(See Note 3)

Notes

1. Permeable Paver material shall be either brick paver per City of Fort Worth STD Specification 32 14 16 or permeableinterlocking concrete paver per ASTM C936. All pavers shall be laid in an interlocking pattern for increased stability. Attentionshall be paid to joint material to ensure uniform spacing is achieved for application that do not use interlocking pavers.

2. Thickness of brick paver shall be a minimum of 2.25" unless specified per City of Fort Worth STD Specification 32 14 16.Thickness of a permeable interlocking concrete paver shall be dependent on usage (minimum of 2.75" for vehicular use and2.25" for pedestrian use).

3. Joint material shall either be sand per Section 4.6.1 or No. 8, 89, or 9 per ASTM C33. For interlocking concrete paversystems, open joints with no jointing material may be acceptable per manufacturer requirements. Open joints shall notexceed 1/2" openings per Texas Accessibility Standards.

4. Pavers shall have chamfered edges.

5. See Section 3 for full pavement section requirements for permeable pavers.

1"

SpecifyThickness

(See Note 2)

Soldier Course Installed atCurb (4"x 8"x 3 18" unlessotherwise specified)


Permeable Pavers DM-DC 4.9.1

Curbing(Section 4.4.1)

5-1


SECTION 5

Water Quality Requirements Specific to Zone 1 (Panther Island)

5.1 INTRODUCTION AND BACKGROUND

To cost-effectively meet water quality goals from stormwater runoff originating from Panther Island, TRWD is requiring revised procedures for selecting and implementing water quality practices in Zone 1 (maps of which are included in Appendix F). The Panther Island form-based code implemented by the City of Fort Worth is designed to provide for high-density, mixed use developments. While the practices and procedures for Zones outside of Panther Island could be applied in Zone 1, it would be much costlier to property owners and also place more restrictions on how an owner/operator/developer of a property could use their available footprint to achieve theneeded water quality goals while meeting other requirements expressed by the form-based code as each developer would be trying to individually place and maintain stormwater quality practices on their property.

The water quality requirements for Zone 1 are designed to achieve the same results in pollutant removal as they would from Zone 2. However, by constraining the number of available water quality practices that can be used in Zone 1 and placing them predominantly in the public right-of-way instead. This results in several benefits to TRWD, TRVA, and owner/operator/developers of properties:

1) It improves consistency with the Panther Island Form-Based Code (which is designed in-part to maintain look and feel compatibility among the many properties that will be built onthe Island).

2) It removes most of the responsibility for operating and maintaining any stormwater qualitytreatment system from the owner/operator of the property and shifts it to PublicImprovement District (PID) planned for Panther Island.

3) Because the number of available practices is constrained for Zone 1, this greatly increasesthe efficiency of stormwater quality management, substantially lowers the aggregatefootprint (square footage) needed for stormwater treatment, and substantially reduces thecost of stormwater treatment for developers.

5.2 REQUIREMENTS SPECIFIC TO ZONE 1

TRWD’s requirements for Zone 1 (Panther Island) in many ways simplify the implementation of this manual. The following are the specific requirements and restrictions for Zone 1:

5-2


1) The vast majority of stormwater treatment will be operated and maintained by the aforementioned PID (those treatment practices within a public right-of-way);

2) Placement and type of practice required will be reviewed and approved by TRWD for Zone 1 in accordance with this manual. Placement and type of practice may be adjusted accordingly based on additional evaluation by TRWD and reflected in subsequent versions of this manual. Therefore, those working to comply with this manual are encouraged to make sure they are working with the most recent version of the manual.

3) Currently, only bioretention basins (sections 3.2.3.3.1 and 3.2.3.2) and permeable surfaces in the form of pervious pavers (Section 3.9) may be used in public right-of-way locations approved by TRWD. Predominantly these will be distributive bioretention basins (Section 3.2.3.2).

4) Because of groundwater conditions on the island, all practices must have underdrains to collect and convey treated stormwater to stormwater drainage infrastructure.

5) Because of groundwater conditions on the island, it is critical that all practices, especially bioretention, have positive-side waterproofing consistent ASTM Standards (see references). Because groundwater is shallow, the significant incursion of groundwater into biorientation facilities may cause plants to die from excess water around root systems.

6) Additional treatment of stormwater may be required by TRWD for installation, operation, and maintenance by property owner/operators where the risk of pollutant discharge is increased such as in any directly-connected impervious surface (an example would be parking-garage rooftops with drainage directly to the Panther Island waterway or canals and no treatment between the two).

7) Larger detention practices (serving a larger number of properties) may be prescribed by TRWD and implementation of any larger practices for stormwater treatment is at TRWD’s sole discretion in coordination with TRVA and its implementation of the Panther Island form-based code.

Figure 5.1 shows the current distribution of stormwater practices in the public right-of-way by practice-type and is subject to revision by TRWD.

5.3 REFERENCES

The following references are useful in specifying either elastomeric sheet waterproofing or hot fluid-applied, rubberized asphalt waterproofing (two of the more common techniques used to prevent groundwater intrusion). Other references will be needed for design purposes.

ASTM International. ASTM C 1305: Test Method for Crack Bridging Ability of Liquid-Applied Waterproofing Membrane. West Conshohocken, PA: ASTM, 2008.

ASTM D 5329: Test Methods for Sealants and Fillers, Hot-Applied, for Joints and Cracks in Asphaltic and Portland Cement Concrete Pavements. 2009.

ASTM D 6622: Guide for Application of Fully Adhered Hot-Applied Reinforced Waterproofing Systems. 2001 (Reapproved 2009).

ASTM E 96/E 96M: Test Methods for Water Vapor Transmission of Materials. 2010.

5-3


Sealant, Waterproofing, and Restoration Institute. Below Grade Waterproofing Manual. Kansas City, MO: SWRI, 2000, (Available at www.swrionline.org)

ASTM International. ASTM D 5295: Guide for Preparation of Concrete Surfaces for Adhered (Bonded) Membrane Waterproofing Systems. West Conshohocken, PA: ASTM, 2000 (Reapproved 2006).

ASTM D 5898/D 5898M: Guide for Standard Details for Adhered Sheet Waterproofing. 1996 (Reapproved 2013).

NM

AIN ST

STREET F

CALHOUN ST

6TH ST

4TH ST

7TH ST

HENDERSON ST

WHITE SETTLEMENT RD

STREET A

N COMM

ERCEST

8TH ST

STR

EET

B

STREET D

N THROCKMORTON ST

Zone 1 Drainage Area

Canal or Other Areas To Be Determined by TRWD/TRVA

Right of Way Boundaries

Stormwater Treatment Practices from TRWD Water Quality Manual

Bioretention Basins (Section 3.2.3.2)

Pervious Pavers (Section 3.9)

Potential Regional Pratice

Figure 5.1: Distribution of Stormwater Quality Practices

300 0 300150 Feet

TRWD Water Quality Manual (June 2018)

by Type for Zone 1 (Panther Island)

De

sig

n G

uid

an

ce:

All

runo

ff fr

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perv

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sur

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s sh

ould

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site

geo

logy

and

soi

ls, b

ut a

n un

derd

rain

ca

n be

add

ed if

site

soi

l inf

iltra

tion

capa

city

is

insu

ffici

ent

May

be

subj

ect t

o dr

aina

ge a

rea

size

lim

itatio

ns

Bior

eten

tion

Basi

n

Bior

eten

tion

Basi

n w

ith C

ompo

nent

s Lab

eled

(CD

M S

mith

, 20

17)

Ov

erv

iew

:

Bior

eten

tion

basi

ns a

re c

omm

only

us

ed B

est M

anag

emen

t Pra

ctic

es

(BM

P) d

ue to

the

effec

tiven

ess

for

pollu

tant

load

redu

ctio

n an

d vi

sual

ap

peal

. The

re a

re tw

o m

ain

type

s of

bi

oret

entio

n ba

sins

out

lined

in th

is

man

ual:

cent

raliz

ed a

nd d

istr

ibut

ive.

Ce

ntra

lized

bio

rete

ntio

n ba

sins

are

in

tend

ed fo

r lar

ger d

rain

age

area

s an

d in

clud

e a

sedi

men

tatio

n fo

reba

y.

Dis

trib

utiv

e bi

oret

entio

n ba

sin

can

be im

plem

ente

d fo

r dra

inag

e ar

eas

less

than

1-a

cre.

The

se a

re o

ften

pl

aced

adj

acen

t to

impe

rvio

us

surf

aces

to c

aptu

re ru

noff

dire

ctly

. Bi

oret

entio

n ba

sins

util

ize

infil

trat

ion

and

filtr

atio

n th

roug

h so

ils a

nd

vege

tatio

n in

dep

ress

ed b

asin

s or

la

ndsc

ape

area

s to

pro

vide

bot

h w

ater

qua

ntity

and

wat

er q

ualit

y be

nefit

s. Th

e ve

geta

tion,

mic

robe

s, an

d so

ils in

bio

rete

ntio

n ba

sins

pr

ovid

e ad

ditio

nal t

reat

men

t an

d re

mov

al o

f pol

luta

nts

from

st

orm

wat

er ru

noff.

Rend

erin

g of

Bio

rete

ntio

n w

ith C

ompo

nent

s (T

RWD

Dev

elop

er M

anua

l, 20

18)

Bior

eten

tion

Basi

n

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

2 of

the

TRW

D D

evel

oper

M

anua

l. Th

is ta

ble

cont

ains

the

mai

n ca

lcul

atio

ns fo

r siz

ing

the

BMP.

Refe

renc

e Se

ctio

n 3.

2 an

d A

ppen

dix

E fo

r the

spe

cific

des

ign

calc

ulat

ions

and

crit

eria

.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e bi

oret

entio

n ba

sin

cont

inue

s to

op

erat

e th

roug

hout

its

lifes

pan.

Reg

ular

in

spec

tion

also

indi

cate

s w

hen

cert

ain

mai

nten

ance

pra

ctic

es a

re

nece

ssar

y. L

ike

insp

ectio

n, re

gula

r mai

nten

ance

kee

ps th

e BM

P op

erat

ing

smoo

thly

and

pro

long

s, or

elim

inat

es, t

he n

eed

for i

nten

sive

re

habi

litat

ion

such

as

side

slo

pe re

stab

iliza

tion

or re

plac

ing

of

corr

oded

pip

es. T

he ta

ble

belo

w o

utlin

es th

e re

gula

r and

as-

need

ed

mai

nten

ance

pra

ctic

es fo

r bio

rete

ntio

n ba

sins

. Spe

cific

info

rmat

ion

on

insp

ectio

n an

d m

aint

enan

ce re

quire

men

ts c

an b

e fo

und

in A

ppen

dix

D

of th

e TR

WD

Dev

elop

er M

anua

l.

ST

EP

1W

AT

ER

QU

AL

ITY

VO

LU

ME

ft3

Cont

ribut

ing

Dra

inag

e A

rea

(DA

)ac

Capt

ure

Dep

th fo

r 12

Hou

r or 2

4 H

our D

raw

dow

n Ti

me

(dt)

in

ST

EP

2S

ED

IME

NT

FO

RE

BA

Y V

OL

UM

E

ft3

ST

EP

3T

OT

AL

AV

AIL

AB

LE

BIO

RE

TE

NT

ION

S

TO

RA

GE

VO

LU

ME

ft

3

Top

of p

ondi

ng s

urfa

ce a

rea

(SA

T)ft

Bott

om o

f pon

ding

sur

face

are

a (S

AB)

ftPo

ndin

g de

pth

(dh)

inVo

id ra

tio

-St

orag

e ag

greg

ate

dept

h (d

f)in

ST

EP

4O

RIF

ICE

DIA

ME

TE

R

in

Max

. dis

char

ge o

f WQ

v (Q

o)

ft3 /s

Dra

in ti

me

(td)

hrO

rifice

ope

ning

are

a (A

o)in

2

Orifi

ce c

oeffi

cien

t (c)

-Av

erag

e he

ad (H

avg)

ft

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E A

CT

ION

FR

EQ

UE

NC

YM

ow g

rass

y ar

eas

Ann

ually

or m

ore

freq

uent

ly d

urin

g gr

owin

g se

ason

Prun

e ex

cess

ive

vege

tatio

n/br

anch

esA

nnua

lly o

r mor

e fr

eque

ntly

dur

ing

grow

ing

seas

onRe

plan

t ann

uals

Befo

re c

orre

spon

ding

gro

win

g se

ason

Clea

ring

tras

h, d

ebris

, and

folia

ge

Mon

thly

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

FR

EQ

UE

NC

YSt

andi

ng w

ater

aft

er d

esig

n st

orm

ev

ent a

nd d

raw

dow

n tim

eCh

eck

the

inle

t/ou

tlet f

or c

logg

ing.

Cle

ar

if pr

esen

t. Ch

eck

for e

xces

sive

fine

s/ha

rd-

pack

ing

on th

e su

rfac

eFo

ul o

dors

or i

nsec

ts s

uch

as

mos

quito

sPr

omot

e in

sect

pre

dato

rs a

nd/o

r pre

vent

st

agna

nt w

ater

In

let/

outle

ts c

logg

ed w

ith d

ebris

Clea

r out

acc

umul

ated

deb

ris. I

nsta

ll de

bris

sc

reen

s.Ac

cum

ulat

ed s

edim

ent/

debr

is

Dre

dge

or re

mov

e ac

cum

ulat

ed s

edim

ent

or d

ebris

to d

esig

n el

evat

ions

. Vac

uum

cl

ogge

d pe

rmea

ble

surf

aces

. Po

or v

eget

ativ

e he

alth

/ in

vasi

ve

spec

ies

Repl

ant v

eget

atio

n an

d re

mov

e in

vasi

ve

spec

ies,

taki

ng c

are

not t

o sp

read

see

ds/

spor

es.

Exce

ssiv

e or

ove

rgro

wn

vege

tatio

nPr

une

the

exce

ssiv

e/ov

ergr

own

vege

tatio

n.

Bank

s/sl

opes

ero

ded

Repa

ir ba

nks/

slop

es s

uch

that

they

mat

ch

desi

gn s

lope

s. In

stal

l ene

rgy

diss

ipat

ers

or

flow

div

ersi

ons.

Sign

s of

cha

nnel

ing

or w

orn

path

sM

ow o

r pos

sibl

y re

grad

e.Pi

pe c

orro

sion

Repl

ace

pipi

ng. C

onsi

der d

iffer

ent m

ater

ial

or c

over

ing

the

pipe

with

a c

orro

sion

re

sist

ant c

oatin

g.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:P

OL

LU

TA

NT

RE

MO

VA

L E

FF

EC

TIV

EN

ES

S*

Sedi

men

tH

igh

Nut

rient

sM

oder

ate

Tras

h H

igh

Met

als

Hig

h-M

oder

ate

Bact

eria

Hig

hO

il an

d G

reas

eH

igh

Org

anic

sM

oder

ate

(SAR

A, 2

013;

iSW

M, 2

014;

and

TCE

Q, 2

005)

*Rem

oval

effe

ctiv

enes

s var

ies d

epen

dent

on

infil

trat

ion

capa

city

and

des

ign

Refe

renc

es o

r Fut

ure

Read

ing:

“Com

plyi

ng w

ith th

e Ed

war

ds A

quife

r Rul

es: T

echn

ical

Gui

danc

e on

Bes

t Man

agem

ent P

ract

ices

”. Jul

y 20

05. T

CEQ

. RG

-348

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//w

ww

.stor

m-t

ex.c

om/w

p-co

nten

t/up

load

s/20

16/0

4/TC

EQ_R

G-3

48.p

df >

. “iS

WM

Tech

nica

l Man

ual:

Site

Dev

elop

men

t Con

trol

s”. (2

014)

. Nor

th C

entr

al Te

xas C

ounc

il of

Gov

ernm

ents

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//isw

m.n

ctco

g.or

g/D

ocum

ents

/tec

hnic

al_m

anua

l/Site

_D

evel

opm

ent_

Cont

rols

_9-2

014.

pdf >

.Ro

ach,

V. (

CDM

Sm

ith).

Mar

ch 6

, 201

7. “G

reen

Infra

stru

ctur

e D

esig

n in

You

r CSO

Long

Term

Con

trol

Pla

n”. N

J Wat

er E

nviro

nmen

t Ass

ocia

tion:

Win

ter T

echn

olog

y Tr

ansf

er S

emin

ar. N

ew Je

rsey

. Pre

sent

atio

n.

Acce

ssed

Sep

tem

ber 2

017.

“San

Ant

onio

Riv

er B

asin

Low

Impa

ct D

evel

opm

ent T

echn

ical

Des

ign

Gui

danc

e M

anua

l”. (2

013)

. San

Ant

onio

Riv

er A

utho

rity.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttps

://w

ww

.sara

-tx.

org/

wp-

cont

ent/

uplo

ads/

2015

/05/

Full-

LID

-Man

ual.p

df >

.“T

arra

nt R

egio

nal W

ater

Dis

tric

t Dev

elop

er M

anua

l”. (2

018)

. Tar

rant

Reg

iona

l Wat

er D

istr

ict (

TRW

D).

(WQ

v =

DA

*[d

t/(1

2in

/ft

)]*

43

,56

0ft

3/a

c)

(do=

2*

(Ao/π

)0.5

)

(Vb

c =

10

%W

Qv

) (if

requ

ired)

De

sig

n G

uid

an

ce:

All

runo

ff fr

om im

perv

ious

sur

face

s sh

ould

be

dire

cted

tow

ards

the

BMP.

Impo

rtan

t site

co

nsid

erat

ions

dur

ing

desi

gn in

clud

e th

e dr

aina

ge

area

and

the

prop

ortio

n of

whi

ch is

impe

rvio

us,

dept

h to

the

wat

er ta

ble,

per

mea

bilit

y of

soi

ls,

dow

nstr

eam

wat

er s

urfa

ce, a

nd o

vera

ll sp

ace

requ

ired

for t

he B

MP.

A lo

ng, s

inuo

us fl

ow p

ath

prom

otes

pol

luta

nt re

mov

al. A

mic

ropo

ol h

as b

een

adde

d at

the

outle

t to

impr

ove

mai

nten

ance

and

pr

ovid

e ad

ditio

nal t

reat

men

t bef

ore

disc

harg

e.

The

wat

er q

ualit

y vo

lum

e (W

QV

) sho

uld

drai

n w

ithin

24

hour

s. Th

e m

inim

um c

ompo

nent

s fo

r a

cons

truc

ted

wet

land

incl

ude,

a s

torm

wat

er in

let,

pre-

and

pos

t-tr

eatm

ent,

ener

gy d

issi

patio

n,

area

pro

tect

ion,

land

scap

ing,

and

out

lets

/pip

ing.

Re

fer t

o Se

ctio

n 4

of th

e TR

WD

Des

ign

Man

ual

for s

peci

fic in

form

atio

n on

thes

e co

mpo

nent

s.

Be

ne

fits

:

Wel

l sui

ted

for r

emov

al o

f par

ticul

ate

mat

ter

and

som

e di

ssol

ved

cont

amin

ants

(TCE

Q, 2

005)

Pro

vide

s an

aes

thet

ical

ly p

leas

ing

spac

e fo

r the

su

rrou

ndin

g co

mm

unity

Pro

vide

s w

ildlif

e ha

bita

t (se

e no

te b

elow

on

bact

eria

l ind

icat

or lo

ads)

Effe

ctiv

e fo

r lar

ge tr

ibut

ary

area

s

Po

ten

tia

l C

on

stra

ints

a

nd

Co

nsi

de

rati

on

s:

Req

uire

s co

ntin

uous

sou

rce

of b

ase

flow

(i.e

. st

orm

wat

er a

nd d

ry w

eath

er in

flow

or m

ake-

up

wat

er in

flow

)

Pot

entia

l sig

nific

ant m

aint

enan

ce c

osts

and

la

rge

amou

nts

of s

edim

ent r

emov

al to

pre

vent

po

nd s

tagn

atio

n, fl

oatin

g de

bris

, scu

m, a

lgal

bl

oom

s, an

d un

plea

sant

odo

r (TC

EQ, 2

005)

.

Pot

entia

l acc

umul

atio

n of

sal

ts a

nd s

cum

that

ca

n be

dis

char

ged

durin

g la

rge

stor

m e

vent

s

Pro

per d

esig

n m

ust b

e us

ed to

pre

vent

hab

itat

for u

ndes

irabl

e in

sect

s su

ch a

s m

osqu

itos

May

not

be

appr

opria

te fo

r loc

atio

ns w

ith

high

gro

undw

ater

leve

ls d

ue to

pot

entia

l for

co

ntam

inat

ion

Ove

rgro

wth

and

sed

imen

t acc

umul

atio

n m

ay

redu

ce h

ydra

ulic

cap

acity

Wild

life

are

a po

tent

ial s

ourc

e of

bac

teria

in

dica

tor l

oads

Cons

truc

ted

Wet

land

s

(iSW

M, 2

014;

EPA

, 200

9)

Ov

erv

iew

:

Cons

truc

ted

Wet

land

s, al

so re

ferr

ed

to a

s st

orm

wat

er w

etla

nds,

are

desi

gned

to p

erm

anen

tly h

old

wat

er a

nd in

crea

se d

eten

tion

time

betw

een

stor

m e

vent

s fo

r im

prov

ed

trea

tmen

t. Th

is B

est M

anag

emen

t Pr

actic

e (B

MP)

requ

ires

mor

e la

nd

than

oth

er B

MPs

and

a c

onst

ant

sour

ce o

f infl

uent

wat

er. H

owev

er,

cons

truc

ted

wet

land

s ca

n be

an

exce

llent

opt

ion

for i

mpr

ovin

g w

ater

qua

lity.

Con

stru

cted

w

etla

nds

empl

oy c

ompl

emen

tary

m

echa

nism

s (i.

e. p

hysi

cal a

nd

biol

ogic

al) t

o eff

ectiv

ely

trea

t st

orm

wat

er in

flow

. The

slo

w, s

inuo

us

flow

and

ext

ende

d de

tent

ion

time

prom

otes

par

ticle

set

tling

and

pl

ant u

ptak

e. B

ecau

se th

is B

MP

is n

ot in

tend

ed fo

r infi

ltrat

ion,

its

stor

mw

ater

runo

ff vo

lum

e re

duct

ion

is m

inim

al, e

xcep

t thr

ough

ev

apor

atio

n an

d ev

apot

rans

pira

tion.

A

s su

ch, c

onst

ruct

ed w

etla

nds

are

idea

l at t

he e

nd o

f a s

torm

-to-

stre

am

sequ

ence

for fi

nal t

reat

men

t bef

ore

disc

harg

e in

to a

str

eam

. Con

stru

cted

w

etla

nds

can

prov

ide

site

aes

thet

ics

and

prov

ide

habi

tat f

or lo

cal w

ildlif

e.

Cons

truc

ted

Wet

land

Re

nder

ing

(TRW

D

Des

ign

Man

ual,

2018

)

Cons

truc

ted

Wet

land

s

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

3 of

the

TRW

D D

esig

n M

anua

l. Th

is ta

ble

cont

ains

the

mai

n ca

lcul

atio

ns fo

r siz

ing

the

BMP.

Refe

renc

e Se

ctio

n 3.

3 an

d A

ppen

dix

E fo

r the

spe

cific

des

ign

calc

ulat

ions

and

crit

eria

.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e co

nstr

ucte

d w

etla

nd c

ontin

ues t

o op

erat

e th

roug

hout

its l

ifesp

an. R

egul

ar

insp

ectio

n al

so in

dica

tes w

hen

cert

ain

mai

nten

ance

pra

ctic

es a

re

nece

ssar

y. L

ike

insp

ectio

n, re

gula

r mai

nten

ance

kee

ps th

e BM

P ru

nnin

g sm

ooth

ly a

nd p

rolo

ngs,

or e

limin

ates

, the

nee

d fo

r int

ensi

ve re

habi

litat

ion

such

as s

ide

slop

e re

stab

iliza

tion

or re

plac

ing

of c

orro

ded

pipe

s. Th

e ta

ble

belo

w o

utlin

es th

e re

gula

r and

as-

need

ed m

aint

enan

ce p

ract

ices

fo

r con

stru

cted

wet

land

s. Sp

ecifi

c in

form

atio

n on

insp

ectio

n an

d m

aint

enan

ce re

quire

men

ts c

an b

e fo

und

in A

ppen

dix

D o

f the

TRW

D

Des

ign

Man

ual.

Refe

renc

es o

r Fut

ure

Read

ing:

“Com

plyi

ng w

ith th

e Ed

war

ds A

quife

r Rul

es: T

echn

ical

Gui

danc

e on

Bes

t Man

agem

ent P

ract

ices

”. Ju

ly 2

005.

TCE

Q. R

G-34

8. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

ww

w.s

torm

-tex

.com

/wp-

cont

ent/

uplo

ads/

2016

/04/

TCEQ

_RG

-348

.pdf

>.

“iSW

M Te

chni

cal M

anua

l: Si

te D

evel

opm

ent C

ontr

ols”.

(201

4). N

orth

Cen

tral

Texa

s Cou

ncil

of G

over

nmen

ts. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

isw

m.n

ctco

g.or

g/Do

cum

ents

/tec

hnic

al_

man

ual/

Site

_De

velo

pmen

t_Co

ntro

ls_

9-20

14.p

df >

.Cl

ary,

J. e

t al.

“Int

erna

tiona

l Sto

rmw

ater

BM

P Da

taba

se 2

016

Sum

mar

y St

atis

tics:

Fin

al R

epor

t”. (2

017)

. The

Wat

er E

nviro

nmen

t & R

euse

Fou

ndat

ion.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//w

ww

.bm

pdat

abas

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cs/0

3-SW

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h%20

BMP%

20Da

taba

se%

2020

16%

20Su

mm

ary%

20St

ats.

pdf >

. “

San

Anto

nio

Rive

r Bas

in L

ow Im

pact

Dev

elop

men

t Tec

hnic

al D

esig

n Gu

idan

ce M

anua

l”. (2

013)

. San

Ant

onio

Riv

er A

utho

rity.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttps

://w

ww

.sar

a-tx

.org

/wp-

cont

ent/

uplo

ads/

2015

/05/

Full-

LID-

Man

ual.p

df >

.“S

torm

wat

er W

et P

ond

and

Wet

land

Man

agem

ent G

uide

book

”. Fe

brua

ry 2

009.

EPA

. EPA

833

-B-0

9-00

1.

“Tar

rant

Reg

iona

l Wat

er D

istr

ict D

evel

oper

Man

ual”.

(201

8). T

arra

nt R

egio

nal W

ater

Dis

tric

t (TR

WD)

.

*(SA

RA M

anua

l, 20

13; C

lary

, J. 2

017)

** W

etla

nds o

r oth

er B

MPs

with

wild

life

habi

tat c

an h

ave

high

inte

rnal

load

s of b

acte

rial

indi

cato

rs, n

utrie

nts,

and

orga

nics

ST

EP

1W

AT

ER

QU

AL

ITY

VO

LU

ME

ft3

Cont

ribut

ing

Dra

inag

e A

rea

(DA

)ac

Capt

ure

Dep

th fo

r 24

Hou

r Dra

wdo

wn

Tim

e (d

t)in

ST

EP

2Se

dim

ent F

oreb

ay V

olum

e

ft3

Impe

rvio

us D

rain

age

Are

a (A

imp)

ft2

ST

EP

3Ba

sin

Volu

me

ft3

Perm

anen

t Poo

l Vol

ume

(VP)

= 10

0% W

Qv

ft3

Surc

harg

e Po

ol V

olum

e (V

S) =

120%

WQ

vft

3

ST

EP

4O

rific

e D

iam

eter

in

Max

. dis

char

ge o

f WQ

v (Q

o)

ft3 /s

Dra

in ti

me

(td)

hrO

rifice

coe

ffici

ent (

c)-

Aver

age

head

(Hav

g)ft

Orifi

ce o

peni

ng a

rea

(Ao)

in2

(WQ

v =

DA

*[d

t/(1

2in

/ft

)]*

43

,56

0ft

3/a

c)

(Vfb

= 0

.1in

pe

r im

pe

rvio

us

ac

re

of

dra

ina

ge

are

a)

(VB =

VP +

VS)

(do=

2*

(Ao/π

)0.5

)

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E A

CT

ION

FR

EQ

UE

NC

YCl

ear t

rash

, deb

ris, w

eeks

, and

fo

liage

Mon

thly

or a

s ne

eded

Mow

gra

ssy

area

sA

nnua

lly, b

ut m

onth

ly d

urin

g gr

owin

g se

ason

Befo

re c

orre

spon

ding

gro

win

g se

ason

Prun

e ex

cess

ive

vege

tatio

n /

bran

ches

Ann

ually

, but

mon

thly

dur

ing

grow

ing

seas

on

Repl

ant A

nnua

lsBe

fore

cor

resp

ondi

ng g

row

ing

seas

on

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

FR

EQ

UE

NC

YSt

andi

ng w

ater

aft

er

draw

dow

n pe

riod

Chec

k th

e in

let/

outle

t for

clo

ggin

g.

Foul

odo

rs o

r ins

ects

suc

h as

m

osqu

itos

Retr

ofit B

MP

to p

reve

nt s

tagn

ant w

ater

Inle

t/ou

tlets

clo

gged

with

de

bris

Clea

r out

acc

umul

ated

deb

ris. I

nsta

ll de

bris

sc

reen

s.Ac

cum

ulat

ed s

edim

ent/

debr

is h

ighe

r tha

n lim

itD

redg

e or

rem

ove

accu

mul

ated

sed

imen

t or

debr

is to

des

ign

elev

atio

ns. V

acuu

m c

logg

ed

perm

eabl

e su

rfac

es.

Poor

veg

etat

ive

heal

th /

inva

sive

spe

cies

Repl

ant v

eget

atio

n an

d re

mov

e in

vasi

ve s

peci

es,

taki

ng c

are

not t

o sp

read

see

ds/s

pore

s.Ex

cess

ive

or o

verg

row

n ve

geta

tion

Prun

e th

e ex

cess

ive/

over

grow

n ve

geta

tion.

Bank

s/sl

opes

ero

ded

Repa

ir ba

nks/

slop

es s

uch

that

they

mat

ch

desi

gn s

lope

s. In

stal

l ene

rgy

diss

ipat

ers

or fl

ow

dive

rsio

ns.

Sign

s of

cha

nnel

ing

or w

orn

path

sA

sses

s dr

aina

ge c

ondi

tions

. Con

side

r reg

rade

.

Brok

en o

r mis

sing

are

a pr

otec

tion

Repa

ir or

repl

ace

area

pro

tect

ion.

Pipe

cor

rosi

onRe

plac

e pi

ping

. If r

eocc

urrin

g is

sue,

con

side

r di

ffere

nt m

ater

ial o

r cov

erin

g th

e pi

pe w

ith a

co

rros

ion

resi

stan

t coa

ting.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:

PO

LL

UT

AN

T

RE

MO

VA

L E

FF

EC

TIV

EN

ES

S*

Sedi

men

tH

igh

Nut

rient

sM

ediu

m to

Hig

hTr

ash

Hig

hM

etal

sM

ediu

mBa

cter

iaH

igh*

*O

il an

d G

reas

eH

igh

Org

anic

sH

igh*

*

Con

stru

cted

Wet

land

(CD

M S

mith

, 201

7)

Be

ne

fits

:

Easi

ly in

corp

orat

ed in

to a

seq

uenc

e of

BM

Ps fo

r ho

listic

trea

tmen

t of s

torm

wat

er

Pro

vide

s te

mpo

rary

sto

rmw

ater

sto

rage

to

miti

gate

dow

nstr

eam

floo

ding

Effe

ctiv

e fo

r lar

ger d

rain

age

area

s

Can

be

used

for r

ecre

atio

n be

twee

n st

orm

ev

ents

Rel

ativ

ely

low

cos

t com

pare

d to

oth

er B

MPs

su

ch a

s w

et p

onds

due

to le

ss e

xcav

atio

n

Req

uire

s le

ss s

trin

gent

mai

nten

ance

than

ot

her B

MPs

whi

ch m

aint

ain

perm

anen

t poo

ls

thro

ugho

ut th

e ye

ar

If p

rope

rly p

reve

nted

, les

s ch

ance

of h

arbo

ring

pest

s su

ch a

s m

osqu

itoes

than

oth

er B

MPs

with

pe

rman

ent p

ools

of w

ater

Po

ten

tia

l C

on

stra

ints

an

d

Co

nsi

de

rati

on

s:

Lim

ited

effec

tiven

ess

for s

ome

pollu

tant

s. Co

ordi

nate

with

oth

er B

MPs

whe

re p

ossi

ble

or

incl

ude

pre-

/ po

st-t

reat

men

t

Wat

er q

ualit

y tr

eatm

ent i

s lim

ited

to s

mal

l to

mod

erat

e st

orm

eve

nts

De

sig

n G

uid

an

ce:

The

first

ste

p in

des

ign

is to

acc

urat

ely

delin

eate

th

e dr

aina

ge a

rea

of th

e BM

P. N

ext,

all r

unoff

fr

om im

perv

ious

sur

face

s sh

ould

be

dire

cted

to

war

ds th

e BM

P. Im

port

ant s

ite c

onsi

dera

tions

du

ring

desi

gn in

clud

e th

e dr

aina

ge a

rea

and

the

port

ion

of w

hich

is im

perv

ious

, dep

th to

the

wat

er ta

ble,

per

mea

bilit

y of

soi

ls, d

owns

trea

m

Exte

nded

Dry

Det

entio

n Ba

sins

Exte

nded

Dry

D

eten

tion

Basin

Pl

an a

nd P

rofil

e (C

olum

bus

Stor

mw

ater

D

rain

age

Man

ual,

2012

)

Ov

erv

iew

:

Exte

nded

dry

det

entio

n ba

sins

ar

e a

type

of B

est M

anag

emen

t Pr

actic

e (B

MP)

use

d fo

r tem

pora

ry

stor

age

of s

torm

wat

er d

urin

g sm

all

to m

oder

ate

stor

m e

vent

s. Th

is

BMP

is d

esig

ned

to p

rovi

de fl

ood

cont

rol b

y m

itiga

ting

or re

gula

ting

runo

ff w

hile

the

exte

nded

sto

rage

pr

omot

es p

artic

le s

ettli

ng.

Exte

nded

dry

det

entio

n ba

sins

ca

n be

com

bine

d ea

sily

with

oth

er

wat

er q

ualit

y tr

eatm

ent B

MPs

for

holis

tic s

torm

wat

er m

anag

emen

t an

d ar

e m

eant

for l

arge

r dra

inag

e ar

eas.

Unl

ike

wet

pon

ds a

nd

cons

truc

ted

wet

land

s, ex

tend

ed

dry

dete

ntio

n ba

sins

sho

uld

drai

n co

mpl

etel

y af

ter a

sto

rm a

nd

rem

ain

dry

betw

een

stor

m e

vent

s.

Exte

nded

Dry

Det

entio

n Ba

sin,

City

of

Lene

xa, K

S

wat

er s

urfa

ce, a

nd o

vera

ll sp

ace

requ

ired

for t

he

BMP.

Mic

ropo

ols

shou

ld b

e in

clud

ed a

t the

out

let

for m

aint

enan

ce a

nd w

ater

qua

lity

bene

fits.

The

wat

er q

ualit

y vo

lum

e (W

Qv)

sho

uld

drai

n w

ithin

40

to 4

8 ho

urs.

The

min

imum

com

pone

nts

for a

n ex

tend

ed d

ry d

eten

tion

basi

n in

clud

e, a

sto

rmw

ater

in

let,

pre-

and

pos

t-tr

eatm

ent,

ener

gy d

issi

patio

n,

area

pro

tect

ion,

land

scap

ing,

and

out

lets

/pip

ing.

Re

fer t

o Se

ctio

n 4

of th

e TR

WD

Dev

elop

er M

anua

l fo

r spe

cific

info

rmat

ion

on th

ese

com

pone

nts.

Rend

erin

g of

an

Exte

nded

D

ry D

eten

tion

Basin

an

d Co

mpo

nent

s Afte

r a S

torm

(T

RWD

Dev

elop

er M

anua

l, 20

18)

Exte

nded

Dry

Det

entio

n Ba

sins

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

6 of

the

TRW

D D

evel

oper

M

anua

l. Th

is ta

ble

cont

ains

the

mai

n ca

lcul

atio

ns fo

r siz

ing

the

BMP.

Refe

renc

e Se

ctio

n 3.

6 an

d A

ppen

dix

E fo

r the

spe

cific

des

ign

calc

ulat

ions

and

crit

eria

.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e ex

tend

ed d

ry d

eten

tion

basi

n co

ntin

ues

to o

pera

te e

ffect

ivel

y th

roug

hout

its

lifes

pan.

Reg

ular

in

spec

tion

also

indi

cate

s w

hen

cert

ain

mai

nten

ance

pra

ctic

es a

re

nece

ssar

y. L

ike

insp

ectio

n, re

gula

r mai

nten

ance

kee

ps th

e BM

P ru

nnin

g sm

ooth

ly a

nd p

rolo

ngs,

or e

limin

ates

, the

nee

d fo

r int

ensi

ve

reha

bilit

atio

n su

ch a

s si

de s

lope

rest

abili

zatio

n or

repl

acin

g of

cor

rode

d pi

pes.

The

tabl

e be

low

out

lines

the

regu

lar a

nd a

s-ne

eded

mai

nten

ance

pr

actic

es fo

r ext

ende

d dr

y de

tent

ion

basi

ns. S

peci

fic in

form

atio

n on

in

spec

tion

and

mai

nten

ance

requ

irem

ents

can

be

foun

d in

App

endi

x D

of

the

TRW

D D

evel

oper

Man

ual.

(iSW

M, 2

014;

TCE

Q, 2

005;

Inte

rnat

iona

l Sto

rmw

ater

BM

PD

atab

ase,

201

7)*n

utrie

nt, m

etal

s, an

d or

gani

cs re

mov

al w

hen

boun

d to

sedi

men

ts th

at a

re re

mov

ed

Refe

renc

es o

r Fut

ure

Read

ing:

“Com

plyi

ng w

ith th

e Ed

war

ds A

quife

r Rul

es: T

echn

ical

Gui

danc

e on

Bes

t Man

agem

ent P

ract

ices

”. Ju

ly 2

005.

TCE

Q. R

G-34

8. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

ww

w.s

torm

-tex

.com

/wp-

cont

ent/

uplo

ads/

2016

/04/

TCEQ

_RG

-348

.pdf

>.

Exte

nded

Dry

Det

entio

n Ba

sin.

“Gre

en In

fras

truc

ture

”. (n

o ye

ar p

ub.).

City

of L

enex

a, K

ansa

s. Im

age.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//w

ww

.lene

xa.c

om/g

over

nmen

t/de

part

men

ts_

__

divi

sion

s/ra

in_

to_

recr

eatio

n/le

arn_

mor

e/gr

een_

infr

astr

uctu

re/ >

.“F

acili

ties”.

Sto

rmw

ater

Par

tner

s. Im

age.

Acc

esse

d Ja

nuar

y 20

18. <

htt

p://

ww

w.s

torm

wat

erpa

rtne

rs.c

om/f

acili

ties/

inde

x.ht

ml >

. “i

SWM

Tech

nica

l Man

ual:

Site

Dev

elop

men

t Con

trol

s”. (2

014)

. Nor

th C

entr

al Te

xas C

ounc

il of

Gov

ernm

ents

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//is

wm

.nct

cog.

org/

Docu

men

ts/t

echn

ical

_m

anua

l/Si

te_

Deve

lopm

ent_

Cont

rols

_9-

2014

.pdf

>.

“San

Ant

onio

Riv

er B

asin

Low

Impa

ct D

evel

opm

ent T

echn

ical

Gui

danc

e M

anua

l”. (2

013)

. San

Ant

onio

Riv

er A

utho

rity.

1st

edi

tion.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttps

://w

ww

.sar

a-tx

.org

/wp-

cont

ent/

uplo

ads/

2015

/05/

Full-

LID-

Man

ual.p

df >

.“C

olum

bus S

torm

wat

er D

rain

age

Man

ual”.

(201

2). T

he C

ity o

f Col

umbu

s: D

ivis

ion

of S

ewer

age

and

Drai

nage

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttps

://w

ww

.col

umbu

s.go

v/up

load

edFi

les/

Publ

ic_

Utili

ties/

Docu

men

t_Li

brar

y/Pu

blic

atio

ns/S

ewer

/Sto

rmw

ater

Drai

nage

Man

ual.p

df >

.“T

arra

nt R

egio

nal W

ater

Dis

tric

t Dev

elop

ers M

anua

l”. (2

018)

Tarr

ant R

egio

nal W

ater

Dis

tric

t (TR

WD)

.“B

MP

Data

base

Tool

: Tex

as B

MPs

.” (2

016)

. Int

erna

tiona

l Sto

rmw

ater

BM

P Da

taba

se. A

cces

sed

Augu

st 2

017.

<ht

tp:/

/bm

pdat

abas

e.or

g/re

trie

veBM

Ps.a

sp>

ST

EP

1W

ate

r Q

ua

lity

Ca

ptu

re V

olu

me

ft

3

Cont

ribut

ing

Dra

inag

e A

rea

(AD)

acCa

ptur

e D

epth

for 4

8 H

our D

raw

dow

n Ti

me

(dt)

in

ST

EP

2S

ed

ime

nt

Fo

reb

ay

Vo

lum

e

ft3

ST

EP

3B

asi

n V

olu

me

ft

3

ST

EP

4O

rifi

ce D

iam

ete

r in

Max

. dis

char

ge o

f WQ

v (Q

o)

ft3 /s

Dra

in ti

me

(td)

hrO

rifice

ope

ning

are

a (A

o)in

2

Orifi

ce c

oeffi

cien

t (c)

-Av

erag

e he

ad (H

avg)

ft

(WQ

v =

AD

*[d

t/(1

2in

/hr)

] *

43

,56

0ft

3/a

c)

(Vfb

= 1

0%

WQ

v)

(VB =

10

0%

WQ

v)

(do=

2*

(Ao/π

)0.5

)

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E I

TE

MS

FR

EQ

UE

NC

YCl

ear t

rash

, deb

ris, w

eeks

, and

fo

liage

Mon

thly

or a

s ne

eded

Mow

law

nA

nnua

lly, b

ut m

onth

ly d

urin

g gr

owin

g se

ason

Repl

ant A

nnua

lsBe

fore

cor

resp

ondi

ng g

row

ing

seas

on

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

FR

EQ

UE

NC

YSt

andi

ng w

ater

aft

er d

raw

dow

n pe

riod

Chec

k th

e in

let/

outle

t for

clo

ggin

g. C

heck

fo

r exc

essi

ve fi

nes/

hard

-pac

king

on

the

surf

ace

Foul

odo

rs o

r ins

ects

suc

h as

m

osqu

itos

Retr

ofit B

MP

to p

reve

nt s

tagn

ant w

ater

Inle

t/ou

tlets

clo

gged

with

deb

risCl

ear o

ut a

ccum

ulat

ed d

ebris

Ac

cum

ulat

ed s

edim

ent/

debr

is

high

er th

an li

mit

Dre

dge

or re

mov

e ac

cum

ulat

ed s

edim

ent.

Vacu

um c

logg

ed p

erm

eabl

e su

rfac

es.

Poor

veg

etat

ive

heal

th /

inva

sive

sp

ecie

sRe

plan

t veg

etat

ion

and

rem

ove

inva

sive

sp

ecie

s.Ex

cess

ive

or o

verg

row

n ve

geta

tion

Prun

e th

e ex

cess

ive/

over

grow

n ve

geta

tion.

Ba

nks/

slop

es e

rode

dRe

pair

bank

s/sl

opes

suc

h th

at th

ey m

atch

de

sign

slo

pes.

Inst

all e

nerg

y di

ssip

ater

s or

flo

w d

iver

sion

s if

reoc

curr

ing

issu

e.Si

gns

of c

hann

elin

g or

wor

n pa

ths

Mow

or p

ossi

bly

regr

ade.

Brok

en o

r mis

sing

are

a pr

otec

tion

Repa

ir or

repl

ace

area

pro

tect

ion.

Pi

pe c

orro

sion

Repl

ace

pipi

ng. C

onsi

der d

iffer

ent m

ater

ial

or c

over

the

pipe

with

a c

orro

sion

resi

stan

t co

atin

g.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:

PO

LL

UT

AN

T

RE

MO

VA

L E

FF

EC

TIV

EN

ES

S*

Sedi

men

tM

ediu

mN

utrie

nts

Low

to M

ediu

mTr

ash

Hig

hM

etal

sM

ediu

mBa

cter

iaM

ediu

m to

Hig

hO

ils a

nd G

reas

eN

o D

ata

Org

anic

sLo

w

De

sig

n G

uid

an

ce:

The

first

ste

p is

acc

urat

e de

linea

tion

of th

e dr

aina

ge

area

of t

he B

MP.

Impo

rtan

t site

con

side

ratio

ns

durin

g de

sign

incl

ude

the

drai

nage

are

a an

d th

e po

rtio

n of

whi

ch is

impe

rvio

us, d

epth

to th

e w

ater

tabl

e, p

erm

eabi

lity

of s

oils

, dow

nstr

eam

w

ater

sur

face

, and

ove

rall

spac

e re

quire

d fo

r th

e BM

P. W

hen

delin

eatin

g th

e dr

aina

ge a

rea

and

cons

ider

ing

use

of p

erm

eabl

e pa

vers

, the

re

com

men

ded

ratio

of t

reat

ed d

rain

age

area

to

perm

eabl

e pa

vers

sur

face

are

a is

1.5

to 1

. The

w

ater

qua

lity

capt

ure

volu

me

(WQ

v) s

houl

d dr

ain

bet

wee

n 12

hou

rs to

48

hour

s af

ter

the

stor

m e

vent

. The

min

imum

com

pone

nts

for

perm

eabl

e pa

vers

are

as

follo

ws:

are

a pr

otec

tion,

BM

P m

edia

, med

ia b

arrie

rs, o

utle

ts/p

ipin

g, a

nd

perm

eabl

e su

rfac

es. R

efer

to S

ectio

n 4

of th

e TR

WD

D

M fo

r spe

cific

info

rmat

ion

on th

ese

com

pone

nts.

Be

ne

fits

:

Perm

eabl

e pa

vers

are

eas

ily a

dapt

ed to

site

la

yout

pla

n

Can

be

effec

tive

at re

duci

ng ru

noff

rate

and

vo

lum

e in

stea

d of

trad

ition

al im

perv

ious

are

as

Can

redu

ce s

torm

wat

er in

fras

truc

ture

foot

prin

t re

quire

men

ts o

f dow

nstr

eam

BM

Ps

Pro

mot

es d

ual-p

urpo

se u

sage

of p

avem

ent a

s a

tran

spor

tatio

n su

rfac

e an

d w

ater

trea

tmen

t m

edia

Can

be

used

to re

duce

sto

rmw

ater

pol

luta

nts

load

ing

to d

owns

trea

m s

urfa

ce w

ater

s

Po

ten

tia

l C

on

stra

ints

an

d

Co

nsi

de

rati

on

s:

Reg

ular

mai

nten

ance

requ

ired

to p

reve

nt

clog

ging

of p

orou

s m

edia

by

sedi

men

t, w

hich

m

ay re

sult

in re

duce

d po

lluta

nt re

mov

al

effec

tiven

ess

(SA

RA M

anua

l, 20

13)

Per

mea

ble

surf

aces

hav

e po

tent

ial t

o co

mpr

ess

and

lose

per

mea

bilit

y w

hen

inst

alle

d in

are

as

subj

ect t

o he

avy

vehi

cle

load

s.

Res

tric

ted

to s

urfa

ces

with

min

imal

slo

pes

Res

tric

ted

to g

rade

s of

5%

or l

ess.

2% o

r les

s is

re

com

men

ded.

Perm

eabl

e Su

rfac

esO

ve

rvie

w:

Perm

eabl

e su

rfac

es a

re a

type

of

Best

Man

agem

ent P

ract

ice

(BM

P)

that

trea

ts s

torm

wat

er s

heet

flow

ov

er w

hat w

ould

alte

rnat

ivel

y be

co

nven

tiona

l im

perv

ious

sur

face

s. Th

is ty

pe o

f sto

rmw

ater

BM

P co

nsis

ts o

f per

mea

ble

pave

rs, p

orou

s co

ncre

te, p

orou

s as

phal

t, an

d gr

asse

d-m

odul

ar g

rid s

yste

ms.

The

TRW

D D

evel

oper

Man

ual (

DM

) onl

y co

vers

the

use

of p

erm

eabl

e pa

vers

. Pe

rmea

ble

pave

rs c

an b

e us

ed to

re

plac

e or

in p

lace

of i

mpe

rvio

us

surf

aces

and

to te

mpo

raril

y st

ore

wat

er in

the

stor

age

aggr

egat

e la

yer.

The

over

all p

erfo

rman

ce o

f pe

rmea

ble

surf

aces

is v

aria

ble

base

d on

des

ign,

dur

atio

n of

use

, an

d fr

eque

ncy

of m

aint

enan

ce.

Perm

eabl

e pa

vers

and

por

ous c

oncr

ete

side

wal

k (C

DM

Sm

ith, 2

017)

Perm

eabl

e pa

vers

an

d ra

in g

arde

ns

(Har

roch

, W.,

et a

l.,

2017

)Re

nder

ing

of p

erm

eabl

e pa

vers

with

com

pone

nts a

fter

a st

orm

(T

RWD

DM

, 201

8)

Perm

eabl

e pa

vers

–

aggr

egat

e jo

ints

(S

. Lan

dgre

n,

2011

)

Perm

eabl

e Su

rfac

es

*(SA

RA, 2

013;

Inte

rnat

iona

l Sto

rmw

ater

BM

P D

atab

ase,

201

7)**

Rem

oval

occ

urs w

hen

asso

ciat

ed w

ith re

tain

men

t of n

utrie

nt- a

nd m

etal

-bou

nd

sedi

men

ts o

r filte

ring

oil/g

reas

e on

und

erly

ing

soil

med

ia.

Refe

renc

es o

r Fut

ure

Read

ing:

Har

rouc

h, W

., Ro

ach,

V.,

and

M. D

odso

n (C

DM S

mith

). O

ctob

er 2

3, 2

017.

“Tu

rnin

g Ul

tra

Urba

n In

to U

ltra

Gree

n fo

r CSO

Con

trol

in th

e Br

onx”

. Mai

n St

orm

wat

er C

onfe

renc

e. P

ortla

nd, M

aine

. Pre

sent

atio

n. A

cces

sed

Sept

embe

r 201

7.

“iSW

M Te

chni

cal M

anua

l: Si

te D

evel

opm

ent C

ontr

ols”.

(201

4). N

orth

Cen

tral

Texa

s Cou

ncil

of G

over

nmen

ts. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

isw

m.n

ctco

g.or

g/Do

cum

ents

/tec

hnic

al_

man

ual/

Site

_De

velo

pmen

t_Co

ntro

ls_

9-20

14.p

df >

.La

ndgr

en, S

. “H

artf

ord,

CT

Gree

n Ca

pita

ls P

roje

ct”.

(201

1). C

DM S

mith

. Pho

togr

aph.

“P

ervi

ous P

avem

ent”.

(no

year

). N

atio

nal A

ssoc

iatio

n of

City

Tra

nspo

rtat

ion

Offi

cial

s. A

cces

sed

Sept

embe

r 201

7. <

htt

ps:/

/nac

to.o

rg/p

ublic

atio

n/ur

ban-

stre

et-d

esig

n-gu

ide/

stre

et-d

esig

n-el

emen

ts/s

torm

wat

er-m

anag

emen

t/pe

rvio

us-p

avem

ent/

>.

Roac

h, V

. (CD

M S

mith

). M

arch

6, 2

017.

“Gre

en In

fras

truc

ture

Des

ign

in Y

our C

SO L

ong

Term

Con

trol

Pla

n”. N

J Wat

er E

nviro

nmen

t Ass

ocia

tion:

Win

ter T

echn

olog

y Tr

ansf

er S

emin

ar. N

ew Je

rsey

. Pre

sent

atio

n. A

cces

sed

Sept

embe

r 201

7.“S

an A

nton

io R

iver

Bas

in L

ow Im

pact

Dev

elop

men

t Tec

hnic

al D

esig

n Gu

idan

ce M

anua

l”. (2

013)

. San

Ant

onio

Riv

er A

utho

rity.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttps

://w

ww

.sar

a-tx

.org

/wp-

cont

ent/

uplo

ads/

2015

/05/

Full-

LID-

Man

ual.p

df >

.“T

arra

nt R

egio

nal W

ater

Dis

tric

t Dev

elop

er M

anua

l”. (2

018)

. Tar

rant

Reg

iona

l Wat

er D

istr

ict (

TRW

D).

“Ten

ness

ee P

erm

anen

t Sto

rmw

ater

Man

agem

ent a

nd D

esig

n Gu

idan

ce M

anua

l”. D

ecem

ber 2

014.

Tenn

esse

e De

part

men

t of E

nviro

nmen

t and

Con

serv

atio

n. 1

st e

d. A

cces

sed

Sept

embe

r 201

7. <

htt

ps:/

/app

.box

.com

/s/p

dl1a

fehg

00s1

ww

qa94

d8qm

izyp

txw

3i/fi

le/2

5367

6926

45 >

.

Perv

ious

Pav

emen

t, N

atio

nal A

ssoc

iatio

n of

City

Tra

nspo

rtat

ion

Offi

cial

s

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

8 of

the

TRW

D D

evel

oper

M

anua

l. Thi

s tab

le c

onta

ins t

he m

ain

calc

ulat

ions

for s

izin

g th

e BM

P. Re

fere

nce

Sect

ion

3.8

and

Appe

ndix

E fo

r the

spec

ific

desi

gn c

alcu

latio

ns

and

crite

ria.

ST

EP

1W

ate

r Q

ua

lity

Ca

ptu

re V

olu

me

ft

3

Cont

ribut

ing

Dra

inag

e A

rea

(DA

)ac

Capt

ure

Dep

th fo

r 24

Hou

r Dra

wdo

wn

Tim

e (d

t)in

ST

EP

2R

eq

uir

ed

Pe

rme

ab

le S

urf

ace

Are

a

ft2

ST

EP

3O

rifi

ce D

iam

ete

rin

Max

. dis

char

ge o

f WQ

v (Q

o)

ft3 /s

Dra

in ti

me

(td)

hrO

rifice

ope

ning

are

a (A

o)in

2

Orifi

ce c

oeffi

cien

t (c)

-Av

erag

e he

ad (H

avg)

ft

(WQ

v =

DA

*[d

t/1

2

*4

3,5

60

ft3/a

c)

(SA

P =

DA

/1.5

)

(do=

2*

(Ao/π

)0.5

)

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E I

TE

MS

FR

EQ

UE

NC

YCl

ear t

rash

, deb

ris, a

nd fo

liage

Mon

thly

or a

s ne

eded

Vacu

um s

wee

ping

Ann

ually

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

AC

TIO

NPo

olin

g of

wat

er o

ver s

urfa

ce

cour

se 4

8 ho

urs

afte

r sto

rm e

vent

Addi

tiona

l vac

uum

sw

eepi

ng w

hen

dry

Sign

ifica

nt d

eter

iora

tion

of s

urfa

ce

cour

se o

r pav

ers

and

stru

ctur

al

inte

grity

of p

avem

ent,

inle

ts/

outle

ts, a

nd o

bser

vatio

n w

ells

Poss

ible

repl

acem

ent o

f sur

face

cou

rse,

pa

vers

, inl

ets/

outle

ts, a

nd o

bser

vatio

n w

ell

com

pone

nts

depe

ndin

g on

sev

erity

Inle

t/ou

tlets

clo

gged

with

deb

risCl

ear o

ut a

ccum

ulat

ed d

ebris

. If n

eede

d an

d no

t ins

talle

d pr

evio

usly

, ins

tall

debr

is

scre

ens.

Pipe

cor

rosi

onRe

plac

e pi

ping

. If r

eocc

urrin

g is

sue,

con

side

r di

ffere

nt m

ater

ial o

r cov

erin

g th

e pi

pe w

ith a

co

rros

ion

resi

stan

t coa

ting.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:P

OL

LU

TA

NT

R

EM

OV

AL

EF

FE

CT

IVE

NE

SS

*Se

dim

ent

Hig

hN

utrie

nts

Low

**Tr

ash

Hig

hM

etal

sM

ediu

mBa

cter

iaH

igh

Oil

and

Gre

ase

Med

ium

Org

anic

sLo

w

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e pe

rmea

ble

pave

rs c

ontin

ue to

op

erat

e th

roug

hout

thei

r life

span

. Re

gula

r ins

pect

ion

also

indi

cate

s w

hen

cert

ain

mai

nten

ance

pra

ctic

es

are

nece

ssar

y. L

ike

insp

ectio

n, re

gula

r mai

nten

ance

kee

ps th

e BM

P ru

nnin

g sm

ooth

ly a

nd p

rolo

ngs,

or e

limin

ates

, the

nee

d fo

r int

ensi

ve

reha

bilit

atio

n su

ch a

s si

de re

plac

ing

pave

rs. T

he ta

ble

belo

w o

utlin

es

the

regu

lar a

nd a

s-ne

eded

mai

nten

ance

pra

ctic

es fo

r per

mea

ble

pave

rs.

Spec

ific

info

rmat

ion

on in

spec

tion

and

mai

nten

ance

requ

irem

ents

can

be

foun

d in

App

endi

x D

of t

he T

RWD

DM

.

De

sig

n G

uid

an

ce:

Firs

t, ac

cura

tely

del

inea

te th

e dr

aina

ge a

rea

of

the

BMP.

Nex

t, al

l run

off fr

om im

perv

ious

surf

aces

sh

ould

be

dire

cted

tow

ards

the

BMP.

Impo

rtan

t site

co

nsid

erat

ions

dur

ing

desi

gn in

clud

e th

e dr

aina

ge

area

and

the

port

ion

of w

hich

is im

perv

ious

, dep

th

to th

e w

ater

tabl

e, p

erm

eabi

lity

of so

ils, d

owns

trea

m

wat

er su

rfac

e, a

nd o

vera

ll sp

ace

requ

ired

for

the

BMP.

Rete

ntio

n/irr

igat

ion

basi

ns ra

nge

from

dr

y-co

ncre

te b

asin

s to

vege

tate

d ba

sins

with

a

perm

anen

t poo

l. St

ored

wat

er d

rain

s to

a w

et w

ell

outs

ide

of th

e ba

sin

and

is th

en p

umpe

d to

irrig

ate

a la

ndsc

aped

are

a. T

he m

inim

um c

ompo

nent

s fo

r an

exte

nded

dry

det

entio

n ba

sin

incl

ude,

a

stor

mw

ater

inle

t, pr

e- a

nd p

ost-

trea

tmen

t, en

ergy

di

ssip

atio

n, a

rea

prot

ectio

n, la

ndsc

apin

g, a

nd

outle

ts/p

ipin

g. R

efer

to S

ectio

n 4

of th

e TR

WD

D

evel

oper

Man

ual f

or sp

ecifi

c in

form

atio

n on

th

ese

com

pone

nts.

Rete

ntio

n/irr

igat

ion

basi

ns a

lso

requ

ire w

et w

ells

, pum

ps, a

nd a

n irr

igat

ion

syst

em.

Be

ne

fits

:

Exc

elle

nt p

ollu

tant

rem

oval

thro

ugh

filtr

atio

n of

sed

imen

ts, p

ollu

tant

-bou

nd s

edim

ents

, oils

, gr

ease

s, an

d ot

her o

rgan

ics

as w

ell a

s up

take

of

nut

rient

s an

d so

me

met

als

by v

eget

atio

n w

hen

prop

erly

des

igne

d, c

onst

ruct

ed, a

nd

mai

ntai

ned

Ben

efici

al fo

r are

as th

at d

o no

t hav

e m

uch

rain

fall

beca

use

it ca

n re

duce

irrig

atio

n de

man

d on

gro

undw

ater

Can

pro

vide

indi

rect

gro

undw

ater

rech

arge

th

roug

h in

filtr

atio

n

Po

ten

tia

l C

on

stra

ints

an

d

Co

nsi

de

rati

on

s:

Mai

nten

ance

requ

irem

ents

and

cos

ts to

kee

p th

e irr

igat

ion

syst

em o

pera

tiona

l are

pot

entia

lly

high

(TCE

Q, 2

005)

Mus

t mat

ch th

e am

ount

of i

rrig

ated

land

to th

e ca

ptur

ed s

torm

wat

er v

olum

e

Pot

entia

l for

gro

undw

ater

con

tam

inat

ion

if in

adeq

uate

soi

l cov

erag

e ov

er ir

rigat

ed a

reas

(T

CEQ

, 200

5; iS

WM

, 201

4)

Thi

s sy

stem

requ

ires

mec

hani

cal c

ompo

nent

s su

ch a

s pu

mps

, irr

igat

ion

syst

em, a

nd e

lect

rical

po

wer

whi

ch a

dds

addi

tiona

l cos

t to

the

BMP

Rete

ntio

n &

Irrig

atio

n Ba

sin

Rete

ntio

n/irr

igat

ion

basi

n an

d co

mpo

nent

s ren

derin

g af

ter

stor

m e

vent

(TRW

D D

evel

oper

Man

ual,

2018

)

Ov

erv

iew

:

Rete

ntio

n/irr

igat

ion

basi

ns a

re

a Be

st M

anag

emen

t Pra

ctic

e (B

MP)

use

d to

col

lect

sto

rmw

ater

ru

noff

with

the

inte

ntio

n of

usi

ng

it fo

r irr

igat

ion

of a

ppro

pria

te

land

scap

e ar

eas.

Unl

ike

othe

r BM

Ps

such

as

exte

nded

dry

det

entio

n ba

sins

or w

et b

asin

s, re

tent

ion/

irrig

atio

n ba

sins

use

mec

hani

cal

com

pone

nts

such

as

pum

ps, w

et

wel

ls, a

nd a

n irr

igat

ion

syst

em.

Rete

ntio

n/irr

igat

ion

basi

ns ty

pica

lly

are

used

in la

rge

cont

ribut

ing

drai

nage

are

as, b

ut s

ite s

elec

tion

mus

t be

bala

nced

with

ava

ilabl

e la

ndsc

ape

area

to ir

rigat

e. T

his

BMP

relie

s on

the

infil

trat

ion

capa

city

of t

he ir

rigat

ed a

reas

to

disc

harg

e th

e fu

ll ca

ptur

ed w

ater

qu

ality

vol

ume

(WQ

v). W

hile

the

sedi

men

t for

ebay

rem

oves

the

maj

ority

of t

he s

uspe

nded

sol

ids,

colle

cted

wat

er is

trea

ted

furt

her

thro

ugh

infil

trat

ion

and

plan

t up

take

in th

e irr

igat

ed a

rea.

Rete

ntio

n irr

igat

ion

pond

(City

of A

ustin

W

ater

shed

Pro

tect

ion

Dep

artm

ent,

TX)

Rete

ntio

n ba

sin,

out

let,

and

inle

t str

uctu

re (K

anna

n, 2

014)

Rete

ntio

n &

Irrig

atio

n Ba

sin

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

5 of

the

TRW

D D

evel

oper

M

anua

l. Th

is ta

ble

cont

ains

the

mai

n ca

lcul

atio

ns fo

r siz

ing

the

BMP.

Refe

renc

e Se

ctio

n 3.

5 an

d A

ppen

dix

E fo

r the

spe

cific

des

ign

calc

ulat

ions

and

crit

eria

.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e re

tent

ion/

irrig

atio

n ba

sin

cont

inue

s to

ope

rate

th

roug

hout

its

lifes

pan.

Reg

ular

in

spec

tion

also

indi

cate

s w

hen

cert

ain

mai

nten

ance

pra

ctic

es a

re

nece

ssar

y. L

ike

insp

ectio

n, re

gula

r mai

nten

ance

kee

ps th

e BM

P ru

nnin

g sm

ooth

ly a

nd p

rolo

ngs,

or e

limin

ates

, the

nee

d fo

r int

ensi

ve

reha

bilit

atio

n su

ch a

s si

de s

lope

rest

abili

zatio

n or

repl

acin

g of

cor

rode

d pi

pes.

The

tabl

e be

low

out

lines

the

regu

lar a

nd a

s-ne

eded

mai

nten

ance

pr

actic

es fo

r ret

entio

n/irr

igat

ion

basi

ns. S

peci

fic in

form

atio

n on

in

spec

tion

and

mai

nten

ance

requ

irem

ents

can

be

foun

d in

App

endi

x D

of

the

TRW

D D

evel

oper

Man

ual.

Refe

renc

es o

r Fut

ure

Read

ing:

“Com

plyi

ng w

ith th

e Ed

war

ds A

quife

r Rul

es: T

echn

ical

Gui

danc

e on

Bes

t Man

agem

ent P

ract

ices

”. Ju

ly 2

005.

TCE

Q. R

G-34

8. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

ww

w.s

torm

-tex

.com

/wp-

cont

ent/

uplo

ads/

2016

/04/

TCEQ

_RG

-348

.pdf

>.

“iSW

M Te

chni

cal M

anua

l: Si

te D

evel

opm

ent C

ontr

ols”.

(201

4). N

orth

Cen

tral

Texa

s Cou

ncil

of G

over

nmen

ts. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

isw

m.n

ctco

g.or

g/Do

cum

ents

/tec

hnic

al_

man

ual/

Site

_De

velo

pmen

t_Co

ntro

ls_

9-20

14.p

df >

.Ka

nnan

, N.,

Jeon

g, J.

, Arn

old,

J., G

osse

link,

L. “

Hyd

rolo

gic M

odel

ing

of a

Ret

entio

n Irr

igat

ion

Syst

em”.

(201

4). A

mer

ican

Soc

iety

of C

ivil

Engi

neer

s: Jo

urna

l of H

ydro

logi

c Eng

inee

ring:

19(

5). A

cces

sed

Sept

embe

r 201

7. <

htt

p://

asce

libra

ry.o

rg/d

oi/f

ull/

10.1

061/

(ASC

E)H

E.19

43-

5584

.000

0867

>.

“Ret

entio

n Irr

igat

ion

Pond

s”. T

he C

ity o

f Aus

tin: W

ater

shed

Pro

tect

ion

Depa

rtm

ent.

Imag

e. A

cces

sed

Janu

ary

2018

. < h

ttps

://a

ustin

texa

s.go

v/co

nten

t/13

61/F

AQ/2

483

>.

“Tar

rant

Reg

iona

l Wat

er D

istr

ict D

evel

oper

Man

ual”.

(201

8). T

arra

nt R

egio

nal W

ater

Dis

tric

t (TR

WD)

.

* (iS

WM

, 201

4)**

Dep

ends

on

vege

tatio

n in

the

rete

ntio

n po

nds f

or n

utrie

nt u

ptak

e

ST

EP

1W

ate

r Q

ua

lity

Ca

ptu

re V

olu

me

ft

3

Cont

ribut

ing

Dra

inag

e A

rea

(DA

)ac

Capt

ure

Dep

th (d

t)in

ST

EP

2S

ed

ime

nt

Fo

reb

ay

Vo

lum

eft

3

Impe

rvio

us D

rain

age

Are

a (A

imp)

ft2

ST

EP

3R

ete

nti

on

Ba

sin

Vo

lum

eft

3

ST

EP

4O

rifi

ce D

iam

ete

rin

Max

. dis

char

ge o

f WQ

v (Q

o)

ft3 /s

Dra

in ti

me

(td)

hrO

rifice

ope

ning

are

a (A

o)in

2

Orifi

ce c

oeffi

cien

t (c)

-Av

erag

e he

ad (H

avg)

ft

ST

EP

5Ir

rig

ati

on

Are

ain

Soil

perm

eabi

lity

(r)

in/h

r

(WQ

v =

DA

*[d

t/(1

2in

/hr)

] *

43

,56

0ft

3/a

c)

(Vfb

= 0

.1in

pe

r im

pe

rvio

us

ac

re o

f d

rain

ag

e a

rea

)

(VR

B =

10

0%

WQ

v o

r 2

.2W

Qv

if

inc

lud

es

a p

erm

an

en

t p

oo

l)

(do=

2*

(Ao/π

)0.5

)

(AI=

[(1

2in

/ft)

WQ

v]/

[60

r])

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E I

TE

MS

FR

EQ

UE

NC

YCl

ear t

rash

, deb

ris, w

eeks

, and

fo

liage

Mon

thly

or a

s ne

eded

Mow

law

nA

nnua

lly, b

ut m

onth

ly d

urin

g gr

owin

g se

ason

Prun

e ex

cess

ive

vege

tatio

n /

bran

ches

Ann

ually

, but

mon

thly

dur

ing

grow

ing

seas

on

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

AC

TIO

NSt

andi

ng w

ater

aft

er d

esig

n st

orm

ev

ent a

nd d

raw

dow

n tim

eCh

eck

the

inle

t/ou

tlet f

or c

logg

ing.

Cle

ar if

ne

cess

ary.

Che

ck fo

r exc

essi

ve fi

nes/

hard

-pa

ckin

g on

the

surf

ace.

Foul

odo

rs o

r ins

ects

suc

h as

m

osqu

itos

Retr

ofit B

MP

to p

reve

nt s

tagn

ant w

ater

Inle

t/ou

tlets

clo

gged

with

deb

risCl

ear o

ut a

ccum

ulat

ed d

ebris

.Ac

cum

ulat

ed s

edim

ent/

debr

is

high

er th

an li

mit

Dre

dge

or re

mov

e ac

cum

ulat

ed s

edim

ent o

r de

bris

to d

esig

n el

evat

ions

. Po

or v

eget

ativ

e he

alth

/ in

vasi

ve

spec

ies

Repl

ant v

eget

atio

n an

d re

mov

e in

vasi

ve

spec

ies.

Exce

ssiv

e or

ove

rgro

wn

vege

tatio

nPr

une

the

exce

ssiv

e/ov

ergr

own

vege

tatio

n.

Bank

s/sl

opes

ero

ded

Repa

ir ba

nks/

slop

es. I

nsta

ll en

ergy

di

ssip

ater

s or

flow

div

ersi

ons.

Sign

s of

cha

nnel

ing

or w

orn

path

sM

ow o

r pos

sibl

y re

grad

e.Br

oken

or m

issi

ng a

rea

prot

ectio

nRe

pair

or re

plac

e ar

ea p

rote

ctio

n.

Pipe

cor

rosi

onRe

plac

e pi

ping

. Con

side

r diff

eren

t mat

eria

l or

cov

erin

g th

e pi

pe w

ith a

cor

rosi

on

resi

stan

t coa

ting.

Pum

p/Irr

igat

ion

Equi

pmen

t Fai

lure

Repl

ace

or re

pair

equi

pmen

t.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:

PO

LL

UT

AN

T

RE

MO

VA

L E

FF

EC

TIV

EN

ES

S*

Sedi

men

tH

igh

Nut

rient

sM

ediu

m to

Hig

h**

Tras

hH

igh

Met

als

Hig

hBa

cter

iaH

igh

Oil

and

Gre

ase

No

Dat

aO

rgan

ics

No

Dat

a

Be

ne

fits

:

Offe

r des

ign

flexi

bilit

y an

d ca

n be

impl

emen

ted

in u

rban

retr

ofits

or n

ew d

evel

opm

ent p

roje

cts

Effe

ctiv

e in

the

rem

oval

of s

uspe

nded

sol

ids,

oil

and

grea

se, h

eavy

met

als,

and

part

icle

-bou

nd

nutr

ient

s an

d pa

thog

ens

Can

be

used

to re

duce

pea

k ru

noff

rate

s fo

r re

lativ

ely

freq

uent

sto

rms

Can

inco

rpor

ate

deep

er p

ondi

ng d

epth

s of

up

to 5

-feet

to li

mit

the

requ

ired

foot

prin

t

Po

ten

tia

l C

on

stra

ints

an

d

Co

nsi

de

rati

on

s:

San

d fil

ters

in b

asin

s w

ith h

eavy

sed

imen

t lo

ads

are

subj

ect t

o cl

oggi

ng a

nd re

quire

mor

e fr

eque

nt m

aint

enan

ce to

mai

ntai

n op

timal

fil

trat

ion

rate

Fre

quen

t tra

sh re

mov

al m

ay b

e re

quire

d fo

r si

tes

with

hig

h tr

affic

volu

me

Can

lack

aes

thet

ic a

ppea

l

Sta

gnan

t wat

er d

ue to

clo

ggin

g an

d /o

r in

adeq

uate

mai

nten

ance

may

cre

ate

bree

ding

ha

bita

t for

nui

sanc

e co

nditi

ons

Sand

and

Med

ia F

ilter

s

Sand

Fi

lter R

ende

ring

and

Com

pone

nts (

TRW

D

Dev

elop

er M

anua

l, 20

18)

Ov

erv

iew

:

Sand

and

med

ia fi

lters

are

a

vers

atile

, wel

l-est

ablis

hed

stru

ctur

al

Best

Man

agem

ent P

ract

ice

(BM

P) th

at p

rovi

des

trea

tmen

t of

stor

mw

ater

runo

ff by

filtr

atio

n th

roug

h sa

nd o

r oth

er fi

ltrat

ion

med

ia. T

o im

prov

e tr

eatm

ent

effec

tiven

ess,

sand

and

med

ia fi

lters

ar

e pa

ired

with

a p

re-t

reat

men

t BM

P to

rem

ove

larg

e de

bris

and

se

dim

ent f

rom

the

runo

ff in

flow

. Th

is B

MP

is e

asily

inco

rpor

ated

into

ne

w d

evel

opm

ents

or a

dapt

ed fo

r re

trofi

ts in

re-d

evel

opm

ent s

ites.

The

sand

and

med

ia fi

lters

are

su

itabl

e fo

r rel

ativ

ely

larg

e, h

ighl

y im

perv

ious

dra

inag

e ar

eas.

Exam

ple

of S

urfa

ce S

and

Filte

r (Be

nder

Wel

ls C

lark

Des

ign,

SA

RA, 2

013)

Surf

ace

Sand

Filt

er S

enec

a Be

st

Man

agem

ent P

ract

ice.

DEP

Mon

tgom

ery

Coun

ty, M

D.

De

sig

n G

uid

an

ce:

Firs

t, de

linea

te th

e dr

aina

ge a

rea

of th

e BM

P. N

ext,

all r

unoff

from

impe

rvio

us s

urfa

ces

shou

ld

be d

irect

ed to

war

ds th

e BM

P. Im

port

ant s

ite

cons

ider

atio

ns d

urin

g de

sign

incl

ude

the

drai

nage

ar

ea a

nd th

e po

rtio

n of

whi

ch is

impe

rvio

us,

dept

h to

the

wat

er ta

ble,

per

mea

bilit

y of

soi

ls,

dow

nstr

eam

wat

er s

urfa

ce, a

nd o

vera

ll sp

ace

requ

ired

for t

he B

MP.

Sand

and

med

ia fi

lters

in

clud

e m

ultip

le c

ham

bers

: a s

edim

ent f

oreb

ay

or s

edim

enta

tion

cham

ber,

and

a fil

trat

ion

cham

ber.

If th

e dr

aina

ge a

rea

is le

ss th

an 2

acr

es,

then

a v

eget

ated

filte

r str

ip o

r gra

ss s

wal

e ca

n be

use

d in

lieu

of a

sed

imen

t for

ebay

. The

dep

th

of th

e fil

trat

ion

basi

n m

ust b

e ba

lanc

ed w

ith th

e fr

eque

ncy

of re

quire

d m

aint

enan

ce. T

he d

eepe

r the

fil

trat

ion

basi

n, th

e m

ore

freq

uent

the

mai

nten

ance

. Th

e w

ater

qua

lity

volu

me

(WQ

v) in

the

sand

and

m

edia

filte

r sho

uld

drai

n in

24

hour

s. Th

e m

inim

um

com

pone

nts

for t

he s

and

and

med

ia fi

lter i

s as

fo

llow

s: s

torm

wat

er in

let,

pre-

and

pos

t-tr

eatm

ent,

ener

gy d

issi

patio

n, a

rea

prot

ectio

n, B

MP

med

ia,

med

ia b

arrie

rs, l

ands

capi

ng, a

nd o

utle

ts/p

ipin

g.

Refe

r to

Sect

ion

4 of

the

TRW

D D

evel

oper

Man

ual

for s

peci

fic in

form

atio

n on

thes

e co

mpo

nent

s.

Sand

And

Med

ia F

ilter

s

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

1 of

the

TRW

D D

evel

oper

M

anua

l. Th

is ta

ble

cont

ains

the

mai

n ca

lcul

atio

ns fo

r siz

ing

the

BMP.

Refe

renc

e Se

ctio

n 3.

1 an

d A

ppen

dix

E fo

r the

spe

cific

des

ign

calc

ulat

ions

and

crit

eria

.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e sa

nd a

nd m

edia

filte

rs

th

roug

hout

th

eir l

ifesp

an. R

egul

ar in

spec

tion

also

indi

cate

s w

hen

cert

ain

mai

nten

ance

pra

ctic

es a

re n

eces

sary

. Lik

e in

spec

tion,

regu

lar

mai

nten

ance

kee

ps th

e BM

P ru

nnin

g sm

ooth

ly a

nd p

rolo

ngs,

or

(SAR

A, 2

013;

iSW

M, 2

014;

and

TCE

Q, 2

005)

* rem

oval

effe

ctiv

enes

s var

ies d

epen

dent

on

infil

trat

ion

capa

city

and

des

ign

** S

ourc

es h

ave

rang

ed fr

om lo

w re

mov

al to

hig

h re

mov

al

Refe

renc

es o

r Fut

ure

Read

ing:

“Com

plyi

ng w

ith th

e Ed

war

ds A

quife

r Rul

es: T

echn

ical

Gui

danc

e on

Bes

t Man

agem

ent P

ract

ices

”. Jul

y 20

05. T

CEQ

. RG

-348

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//w

ww

.stor

m-t

ex.c

om/w

p-co

nten

t/up

load

s/20

16/0

4/TC

EQ_R

G-3

48.p

df >

. “iS

WM

Tech

nica

l Man

ual:

Site

Dev

elop

men

t Con

trol

s”. (2

014)

. Nor

th C

entr

al Te

xas C

ounc

il of

Gov

ernm

ents

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//isw

m.n

ctco

g.or

g/D

ocum

ents

/tec

hnic

al_m

anua

l/Site

_D

evel

opm

ent_

Cont

rols

_9-2

014.

pdf >

.“S

an A

nton

io R

iver

Bas

in Lo

w Im

pact

Dev

elop

men

t Tec

hnic

al D

esig

n G

uida

nce

Man

ual”.

(201

3). S

an A

nton

io R

iver

Aut

horit

y. A

cces

sed

Sept

embe

r 201

7. <

htt

ps://

ww

w.sa

ra-t

x.or

g/w

p-co

nten

t/up

load

s/20

15/0

5/Fu

ll-LI

D-M

anua

l.pdf

>.

“Tar

rant

Reg

iona

l Wat

er D

istr

ict D

evel

oper

Man

ual”.

(201

8). T

arra

nt R

egio

nal W

ater

Dis

tric

t (TR

WD

). Yo

ung,

G.K

., et

al.

1996

. “Ev

alua

tion

and

Man

agem

ent o

f Hig

hway

Run

off W

ater

Qua

lity”

. U.S

. Dep

artm

ent o

f Tra

nspo

rtat

ion.

Fed

eral

Hig

hway

Adm

inis

trat

ion:

Offi

ce o

f Env

ironm

ent a

nd P

lann

ing.

Pub

licat

ion

No.

FH

WA-

PD-9

6-03

2.

ST

EP

1W

ate

r Q

ua

lity

Ca

ptu

re V

olu

me

ft

3

Cont

ribut

ing

Dra

inag

e A

rea

(DA

)ac

Capt

ure

Dep

th fo

r 24

Hou

r Dra

wdo

wn

Tim

e (d

t)in

ST

EP

2S

ed

ime

nt

Fo

reb

ay

Vo

lum

eft

3

ST

EP

3S

urf

ace

Are

a o

f

Fil

tra

tio

n C

ha

mb

er

ft3

Filtr

atio

n ch

ambe

r dra

in ti

me

(Tf)

days

ST

EP

4T

ota

l A

va

ila

ble

Sa

nd

Fil

ter

Wa

ter

Qu

ali

ty S

tora

ge

Vo

lum

e

ft3

Surf

ace

area

top

of b

asin

pon

ding

sto

rage

(SA

T)ft

2

Surf

ace

area

bot

tom

of b

asin

pon

ding

sto

rage

(SA

B)ft

2

Dep

th o

f pon

ding

(Hf)

ftD

epth

of s

tora

ge a

ggre

gate

(Hag

g)ft

Void

ratio

-

ST

EP

5S

an

d F

ilte

r C

ha

mb

er

To

tal

De

pth

ft

Filte

r med

ia d

epth

(Hf)

inFi

ltrat

ion

cham

ber d

epth

(Hm

)ft

ST

EP

6O

rifi

ce D

iam

ete

rin

Max

. dis

char

ge o

f WQ

v (Q

o)

ft3 /s

Dra

in ti

me

(td)

hrO

rifice

ope

ning

are

a (A

o)in

2

Orifi

ce c

oeffi

cien

t (c)

-Av

erag

e he

ad (H

avg)

ft

(WQ

v =

DA

*[d

t/1

2*

4

3,5

60

ft3

/ac

)

(Vfb

= 2

5%

WQ

v)

(Af =

WQ

v/[

kT

f] w

here

k=3

.5ft

/day

)

(Ht =

[H

f/(1

2in

/ft)

]+H

m)

(do=

2*

(Ao/π

)0.5

)

elim

inat

es, t

he n

eed

for i

nten

sive

reha

bilit

atio

n su

ch a

s m

edia

re

plac

emen

t. Th

e ta

ble

belo

w o

utlin

es th

e re

gula

r and

as-

need

ed

mai

nten

ance

pra

ctic

es fo

r san

d an

d m

edia

filte

rs. S

peci

fic

info

rmat

ion

on in

spec

tion

and

mai

nten

ance

requ

irem

ents

can

be

foun

d in

App

endi

x D

of t

he T

RWD

Dev

elop

er M

anua

l.

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E I

TE

MS

FR

EQ

UE

NC

YCl

earin

g tr

ash,

deb

ris, a

nd fo

liage

M

onth

ly o

r as

need

ed

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

AC

TIO

NSt

andi

ng w

ater

aft

er d

raw

dow

n tim

eCh

eck

the

inle

t/ou

tlet f

or c

logg

ing.

Cle

ar if

ne

cess

ary.

Fo

ul o

dors

or i

nsec

ts s

uch

as

mos

quito

sRe

trofi

t BM

P to

pre

vent

sta

gnan

t wat

er

Inle

t/ou

tlets

clo

gged

with

deb

risCl

ear o

ut a

ccum

ulat

ed d

ebris

.Ac

cum

ulat

ed s

edim

ent/

debr

isD

redg

e or

rem

ove

accu

mul

ated

sed

imen

t or

deb

ris.

Surf

ace

med

ia s

pent

Repl

ace

the

top

of th

e su

rfac

e m

edia

Br

oken

or m

issi

ng a

rea

prot

ectio

nRe

pair

or re

plac

e ar

ea p

rote

ctio

n.

Pipe

cor

rosi

onRe

plac

e pi

ping

. If r

eocc

urrin

g is

sue,

con

side

r di

ffere

nt m

ater

ial o

r cov

erin

g th

e pi

pe w

ith

a co

rros

ion

resi

stan

t coa

ting.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:

PO

LL

UT

AN

T

RE

MO

VA

L E

FF

EC

TIV

EN

ES

S*

Sedi

men

tH

igh

Nut

rient

sTr

ash

Hig

hM

etal

sM

ediu

m to

Hig

hBa

cter

iaM

ediu

m to

Hig

hO

il an

d G

reas

eH

igh

Org

anic

sM

ediu

m to

Hig

h

De

sig

n G

uid

an

ce:

Firs

t, de

linea

te th

e dr

aina

ge a

rea

of th

e BM

P. N

ext,

all r

unoff

fr

om im

perv

ious

su

rfac

es s

houl

d be

di

rect

ed to

war

ds th

e BM

P(s)

. Im

port

ant s

ite

cons

ider

atio

ns d

urin

g de

sign

incl

ude

asse

ssm

ent

of th

e im

perv

ious

por

tion

of th

e dr

aina

ge a

rea,

de

pth

to th

e w

ater

tabl

e, p

erm

eabi

lity

of s

oils

, do

wns

trea

m w

ater

sur

face

, and

ove

rall

spac

e re

quire

d fo

r the

BM

P. VF

S ty

pica

lly h

ave

one

gent

le s

ide

slop

e w

here

the

shee

t flow

runo

ff is

tr

eate

d. G

rass

sw

ales

are

mor

e ch

anne

lized

, hav

ing

shal

low

sid

e sl

opes

on

both

sid

es o

f the

cha

nnel

pe

rpen

dicu

lar t

o th

e lo

ngitu

dina

l flow

pat

h. V

FS

and

gras

s sw

ales

can

be

enha

nced

by

cons

truc

ting

chec

k da

ms

alon

g th

e flo

w p

ath

to s

tore

and

trea

t th

e st

orm

wat

er fo

r an

exte

nded

per

iod.

Wat

er

shou

ld n

ot p

ool i

n th

ese

BMPs

. If c

heck

dam

s ar

e in

stal

led,

then

the

pond

ing

behi

nd th

e da

ms

mus

t dr

ain

with

in 4

8 ho

urs.

The

min

imum

com

pone

nts

for V

FS a

nd g

rass

sw

ales

are

as

follo

ws:

sto

rmw

ater

in

let,

pre-

and

pos

t-tr

eatm

ent,

ener

gy d

issi

patio

n,

area

pro

tect

ion,

BM

P m

edia

, med

ia b

arrie

rs,

land

scap

ing,

and

out

lets

/pip

ing.

Ref

er to

Sec

tion

4 of

the

TRW

D D

evel

oper

Man

ual f

or s

peci

fic

info

rmat

ion

on th

ese

com

pone

nts.

Be

ne

fits

:

VFS

and

gra

ss s

wal

es a

re re

lativ

ely

sim

ple

and

low

cos

t to

desi

gn a

nd c

onst

ruct

Bot

h ca

n be

use

d fo

r pre

trea

tmen

t and

re

duct

ion

of s

edim

ent f

rom

sto

rmw

ater

Bot

h ha

ve s

impl

e, a

esth

etic

ally

ple

asin

g qu

aliti

es a

nd p

rovi

de la

ndsc

apin

g op

port

uniti

es

Low

mai

nten

ance

requ

irem

ents

VFS

and

gra

ss s

wal

es a

re e

ffect

ive

alon

g lin

ear,

narr

ow, i

mpe

rvio

us s

urfa

ces

and

are

easi

ly

dist

ribut

ed a

roun

d a

site

Po

ten

tia

l C

on

stra

ints

an

d

Co

nsi

de

rati

on

s:

May

not

be

suita

ble

for i

ndus

tria

l site

s or

larg

e dr

aina

ge a

reas

, unl

ess

used

to c

onve

y su

b-ar

eas

as re

plac

emen

t for

sto

rm s

ewer

s

VFS

requ

ires

shee

t flow

acr

oss

vege

tate

d ar

eas

Req

uire

mild

slo

pes

to a

llow

veg

etat

ion

to

prov

ide

filtr

atio

n an

d to

mai

ntai

n lo

w v

eloc

ities

App

licat

ion

in a

rid a

reas

is li

mite

d be

caus

e of

th

e ne

ed fo

r den

se v

eget

atio

n

Doe

s no

t pro

vide

suffi

cien

t att

enua

tion

of

peak

flow

s, un

less

che

ck d

ams

or o

ther

sto

rage

m

echa

nism

s ar

e in

stal

led

to

the

gras

s sw

ale

Vege

tate

d Fi

lter S

trip

s an

d G

rass

Sw

ales

Vege

tate

d G

rass

Sw

ale

(Dot

t Ar

chite

ctur

e, 2

010)

Gra

ss S

wal

e (N

iska

yuna

Bus

ines

s Pa

rk-D

EC, N

Y, 2

005)

Ov

erv

iew

:

Vege

tate

d Fi

lter S

trip

s (V

FS)

and

Gra

ss S

wal

es c

an b

e us

ed

to tr

eat s

torm

wat

er ru

noff

from

lo

w d

ensi

ty im

perv

ious

are

as o

r al

ong

linea

r im

perv

ious

sur

face

s, su

ch a

s ro

adw

ays

or s

idew

alks

. VF

S ar

e lin

ear s

trip

s of

nat

ural

, gr

ass

vege

tatio

n ex

tend

ed o

ver

a ge

ntle

slo

pe w

hich

use

the

biol

ogic

al a

nd p

hysi

cal p

rope

rtie

s of

the

vege

tatio

n an

d in

filtr

atio

n to

rem

ove

sedi

men

t and

oth

er

pollu

tant

s in

she

et fl

ow ru

noff.

G

rass

sw

ales

are

gra

ss-li

ned

ditc

hes

that

can

be

used

to c

onve

y an

d tr

eat s

hallo

w c

once

ntra

ted

flow

. The

se B

est M

anag

emen

t Pr

actic

es (B

MPs

) sho

uld

not b

e us

ed a

s a

stan

d-al

one

BMP

for

deve

lopm

ents

and

can

be

used

as

pre

- or p

ost-

trea

tmen

t alo

ng

with

oth

er w

ater

qua

lity

BMPs

.

Gra

ss S

wal

e (D

omin

ican

Col

lege

-DEC

, NY,

20

07)

Vege

tate

d Fi

lter S

trip

s A

nd G

rass

Sw

ales

Siz

ing

Cri

teri

a:

The

crite

ria b

elow

are

from

Sec

tion

3.7

of th

e TR

WD

Dev

elop

er M

anua

l. Th

is ta

ble

cont

ains

the

mai

n ca

lcul

atio

ns fo

r siz

ing

the

BMP.

Refe

renc

e Se

ctio

n 3.

7 an

d Ap

pend

ix E

for t

he sp

ecifi

c de

sign

cal

cula

tions

and

crit

eria

.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e VF

S an

d th

e gr

ass

swal

es

cont

inue

to o

pera

te a

t the

ir de

sign

ed

thro

ugho

ut

life

span

. Reg

ular

insp

ectio

n al

so in

dica

tes

whe

n ce

rtai

n m

aint

enan

ce p

ract

ices

are

nec

essa

ry. V

FS a

nd g

rass

sw

ales

requ

ire

less

mai

nten

ance

than

oth

er B

MPs

, but

con

sist

ent i

nspe

ctio

n an

d m

aint

enan

ce k

eeps

the

BMP

runn

ing

smoo

thly

and

pro

long

s, or

elim

inat

es, t

he n

eed

for i

nten

sive

reha

bilit

atio

n su

ch a

s si

de

ST

EP

1W

AT

ER

QU

AL

ITY

CA

PT

UR

E V

OL

UM

E

Gra

ss S

wal

e: C

ontr

ibut

ing

Dra

inag

e A

rea

(DA

) les

s th

an 5

ac?

VFS:

Len

gth

of c

ontr

ibut

ing

drai

nage

are

a in

dire

ctio

n of

flow

less

th

an 7

5-fe

et?

ST

EP

2U

PS

TR

EA

M O

R D

OW

NS

TR

EA

M B

MP

? IF

NO

T,

JUS

TIF

ICA

TIO

N?

ST

EP

3IN

FL

OW

PA

RA

ME

TE

RS

Gra

ss S

wal

e: L

ess

than

4 in

ches

of s

heet

flow

? G

rass

Sw

ale:

Ene

rgy

diss

ipat

ion

at th

e in

let t

o re

duce

cha

nnel

ized

w

ater

vel

ociti

es to

< 1

-ft/

s?VF

S: L

ess

than

2 in

ches

of s

heet

flow

?

ST

EP

4V

FS

OR

GR

AS

S S

WA

LE

PA

RA

ME

TE

RS

Gra

ss s

wal

es: L

ongi

tudi

nal s

lope

less

than

4%

with

max

. wat

er

velo

city

less

than

1-f

t/s?

Gra

ss s

wal

e: S

ide

slop

es n

o st

eepe

r tha

n 3:

1 (h

oriz

onta

l:ver

tical

) and

ch

anne

l bot

tom

bet

wee

n 2-

feet

and

6-fe

et?

VFS:

Flo

w p

ath

at le

ast 1

5-fe

et w

ith 2

% to

6%

long

itudi

nal s

lope

and

tr

ansv

erse

slo

pe le

ss th

an 2

%?

VFS:

Min

imum

of 1

2-in

ches

of s

oil c

over

and

den

se v

eget

ativ

e co

ver?

ST

EP

5C

HE

CK

DA

M P

AR

AM

ET

ER

S

Doe

s it

drai

n w

ithin

48-

hour

s?

Dam

has

max

. hei

ght o

f 12-

inch

es w

ith 3

:1 s

ide

slop

es?

Refe

renc

es o

r Fut

ure

Read

ing:

“Dom

inic

an C

olle

ge D

ry S

wal

e.” (2

007)

. New

Yor

k St

ate

Dep

artm

ent o

f Env

ironm

enta

l Con

serv

atio

n. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

ww

w.d

ec.n

y.go

v/la

nds/

5933

2.ht

ml >

.“iS

WM

Tech

nica

l Man

ual:

Site

Dev

elop

men

t Con

trol

s”. (2

014)

. Nor

th C

entr

al Te

xas C

ounc

il of

Gov

ernm

ents

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//isw

m.n

ctco

g.or

g/D

ocum

ents

/tec

hnic

al_m

anua

l/Site

_D

evel

opm

ent_

Cont

rols

_9-2

014.

pdf >

. “N

iska

yuna

Bus

iess

Par

k D

ry S

wal

e.” (2

005)

. New

Yor

k St

ate

Dep

artm

ent o

f Env

ironm

enta

l Con

serv

atio

n. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

ww

w.d

ec.n

y.go

v/la

nds/

5933

5.ht

ml >

.“S

an A

nton

io R

iver

Bas

in Lo

w Im

pact

Dev

elop

men

t Tec

hnic

al D

esig

n G

uida

nce

Man

ual”.

(201

3). S

an A

nton

io R

iver

Aut

horit

y. A

cces

sed

Sept

embe

r 201

7. <

htt

ps://

ww

w.sa

ra-t

x.or

g/w

p-co

nten

t/up

load

s/20

15/0

5/Fu

ll-LI

D-M

anua

l.pdf

>.

“Sus

tain

able

pra

ctic

es fo

r lan

dsca

pe d

esig

n: v

eget

ated

swal

es”. (

2010

). D

ott A

rchi

tect

ure.

Acc

esse

d Se

ptem

ber 2

017.

< h

ttps

://do

ttar

chite

ctur

e.co

m/2

010/

06/0

3/su

stai

nabl

e-pr

actic

es-fo

r-la

ndsc

ape-

desi

gn-

vege

tate

d-sw

ales

/ >.

“Tar

rant

Reg

iona

l Wat

er D

istr

ict D

evel

oper

Man

ual”.

(201

8). T

arra

nt R

egio

nal W

ater

Dis

tric

t (TR

WD

).

slop

e re

stab

iliza

tion.

The

tabl

e be

low

out

lines

the

regu

lar a

nd a

s-ne

eded

mai

nten

ance

pra

ctic

es fo

r VFS

and

gra

ss s

wal

es. S

peci

fic

info

rmat

ion

on in

spec

tion

and

mai

nten

ance

requ

irem

ents

can

be

foun

d in

App

endi

x D

of t

he T

RWD

Dev

elop

er M

anua

l.

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E I

TE

MS

FR

EQ

UE

NC

YCl

ear t

rash

, deb

ris, w

eeds

, and

fo

liage

Mon

thly

or a

s ne

eded

Mow

law

nA

nnua

lly, b

ut m

onth

ly d

urin

g gr

owin

g se

ason

As-N

eede

d M

aint

enan

ceIN

SP

EC

TIO

N I

SS

UE

AC

TIO

NSt

andi

ng w

ater

aft

er d

raw

dow

n tim

eCh

eck

for e

xces

sive

fine

s/ha

rd-p

acki

ng o

n th

e su

rfac

eFo

ul o

dors

or i

nsec

ts s

uch

as

mos

quito

sRe

trofi

t BM

P to

pre

vent

sta

gnan

t wat

er

Inle

t/ou

tlets

clo

gged

with

deb

risCl

ear o

ut a

ccum

ulat

ed d

ebris

.Ac

cum

ulat

ed s

edim

ent/

debr

is

high

er th

an li

mit

Dre

dge

or re

mov

e ac

cum

ulat

ed s

edim

ent

or d

ebris

. Po

or v

eget

ativ

e he

alth

/ in

vasi

ve

spec

ies

Repl

ant v

eget

atio

n an

d re

mov

e in

vasi

ve

spec

ies.

Exce

ssiv

e or

ove

rgro

wn

vege

tatio

nPr

une

the

exce

ssiv

e/ov

ergr

own

vege

tatio

n.Ba

nks/

slop

es e

rode

dRe

pair

bank

s/sl

opes

suc

h th

at th

ey m

atch

de

sign

slo

pes.

Inst

all e

nerg

y di

ssip

ater

s or

flo

w d

iver

sion

s.Si

gns

of c

hann

elin

g or

wor

n pa

ths

Mow

or p

ossi

bly

regr

ade.

Pipe

cor

rosi

onRe

plac

e pi

ping

. If r

eocc

urrin

g is

sue,

co

nsid

er d

iffer

ent m

ater

ial o

r cov

erin

g th

e pi

pe w

ith a

cor

rosi

on re

sist

ant c

oatin

g.

Po

llu

tan

t R

em

ov

al

Eff

ec

tiv

en

ess

:

PO

LL

UT

AN

T

RE

MO

VA

L E

FF

EC

TIV

EN

ES

SSe

dim

ent

Med

ium

to H

igh

Nut

rient

sLo

w to

Med

ium

Tras

hM

etal

Low

to M

ediu

mBa

cter

ia*

Oil

and

Gre

ase

Org

anic

s(S

ARA,

201

3; iS

WM

, 201

4)

* Rem

oval

effe

ctiv

enes

s will

var

y ba

sed

on re

mov

al m

echa

nism

(i.e

. ads

orpt

ion

to

sedi

men

t or v

eget

atio

n or

infil

trat

ion)

De

sig

n G

uid

an

ce:

Firs

t, de

linea

te th

e dr

aina

ge a

rea

of th

e BM

P. N

ext,

all r

unoff

fr

om im

perv

ious

su

rfac

es s

houl

d be

di

rect

ed to

war

ds th

e BM

P. Im

port

ant s

ite

cons

ider

atio

ns d

urin

g de

sign

incl

ude

asse

ssm

ent

of th

e po

rtio

n of

whi

ch

is im

perv

ious

, dep

th to

th

e w

ater

tabl

e, p

erm

eabi

lity

of s

oils

, dow

nstr

eam

w

ater

sur

face

, and

ove

rall

spac

e re

quire

d fo

r the

BM

P. Th

e w

et b

asin

doe

s no

t var

y in

dep

th a

s m

uch

as th

e co

nstr

ucte

d w

etla

nd, t

houg

h, 1

5% o

f the

to

tal s

urfa

ce a

rea

of th

e ba

sin

mus

t be

mad

e up

of

a lit

tora

l zon

e, o

r saf

ety

benc

h. L

ike

the

cons

truc

ted

wet

land

, it h

as a

mic

ropo

ol a

t the

out

let f

or

addi

tiona

l tre

atm

ent b

efor

e di

scha

rge.

The

wat

er

qual

ity v

olum

e (W

Qv)

sho

uld

drai

n w

ithin

12

hour

s. Th

e m

inim

um c

ompo

nent

s fo

r a w

et b

asin

incl

ude,

a

stor

mw

ater

inle

t, pr

e- a

nd p

ost-

trea

tmen

t, en

ergy

di

ssip

atio

n, a

rea

prot

ectio

n, la

ndsc

apin

g, a

nd

outle

ts/p

ipin

g. R

efer

to S

ectio

n 4

of th

e TR

WD

DM

fo

r spe

cific

info

rmat

ion

on th

ese

com

pone

nts.

Be

ne

fits

:

Wel

l sui

ted

for r

emov

al o

f par

ticul

ate

mat

ter

and

som

e di

ssol

ved

cont

amin

ants

(TCE

Q, 2

005)

Pro

vide

s an

aes

thet

ical

ly p

leas

ing

spac

e fo

r the

su

rrou

ndin

g co

mm

unity

Pro

vide

s w

ildlif

e ha

bita

t. Se

e no

te b

elow

on

bact

eria

l ind

icat

or lo

ads

Effe

ctiv

e fo

r lar

ge tr

ibut

ary

area

s

Po

ten

tia

l C

on

stra

ints

an

d

Co

nsi

de

rati

on

s:

Req

uire

s co

ntin

uous

sou

rce

of b

ase

flow

(i.e

. st

orm

wat

er in

flow

or m

ake-

up w

ater

inflo

w)

Pot

entia

l sig

nific

ant m

aint

enan

ce c

osts

and

la

rge

amou

nts

of s

edim

ent r

emov

al to

pre

vent

po

nd s

tagn

atio

n, fl

oatin

g de

bris

, scu

m, a

lgal

bl

oom

s, an

d un

plea

sant

odo

r (TC

EQ, 2

005)

.

Pot

entia

l ac

cum

ulat

ion

of s

alts

and

sc

um th

at c

an

be d

isch

arge

d du

ring

larg

e st

orm

eve

nts

Pro

per d

esig

n m

ust b

e us

ed to

pre

vent

hab

itat

for u

ndes

irabl

e in

sect

s su

ch a

s m

osqu

itos

May

not

be

appr

opria

te fo

r loc

atio

ns w

ith

high

gro

undw

ater

leve

ls d

ue to

pot

entia

l for

co

ntam

inat

ion

Ove

rgro

wth

and

sed

imen

t acc

umul

atio

n m

ay

redu

ce h

ydra

ulic

cap

acity

Wet

Bas

ins

Wet

bas

in (C

DM

Sm

ith, 2

017)

Rend

erin

g of

a w

et b

asin

aft

er a

stor

m (T

RWD

DM

, 201

8)

Wet

bas

in m

ulti-

stag

e ou

tlet

(SAR

A M

anua

l, 20

13)

Ov

erv

iew

:

Wet

bas

ins

are

a Be

st M

anag

emen

t Pr

actic

e (B

MP)

des

igne

d to

reta

in

stor

mw

ater

bet

wee

n ru

noff

even

ts

to a

llow

the

reta

ined

vol

ume

to

be tr

eate

d fo

r an

exte

nded

per

iod.

Th

ese

BMPs

are

als

o kn

own

as

wet

pon

ds, s

torm

wat

er p

onds

, or

rete

ntio

n po

nds.

They

are

si

mila

r to

exte

nded

dry

det

entio

n ba

sins

, but

this

BM

P m

aint

ains

a

perm

anen

t poo

l thr

ough

out t

he

year

. Wet

bas

ins

rem

ove

pollu

tant

s fr

om th

e su

rcha

rge

prim

arily

th

roug

h pa

rtic

le s

ettli

ng a

nd p

lant

up

take

of n

utrie

nts.

This

BM

P is

not

inte

nded

for i

nfiltr

atio

n.

Ther

efor

e, th

e st

orm

wat

er ru

noff

volu

me

redu

ctio

n is

min

imal

, ex

cept

thro

ugh

evap

orat

ion

and

evap

otra

nspi

ratio

n. W

et b

asin

s re

quire

larg

e am

ount

s of

spa

ce

and

cont

ribut

ing

drai

nage

are

a.

A s

ourc

e of

inflo

w is

nee

ded

to m

aint

ain

a pe

rman

ent

pool

thro

ugho

ut th

e ye

ar.

Wet

bas

in (T

enne

ssee

Per

man

ent S

W M

gmt

and

DG

M, 2

014)

Wet

Bas

ins

Siz

ing

Cri

teri

a:

The

calc

ulat

ions

bel

ow a

re fr

om S

ectio

n 3.

4 of

the

TRW

D D

M. T

his t

able

co

ntai

ns th

e m

ain

calc

ulat

ions

for s

izin

g th

e BM

P. Re

fere

nce

Sect

ion

3.4

and

Appe

ndix

E fo

r the

spec

ific

desi

gn c

alcu

latio

ns a

nd c

riter

ia.

Insp

ec

tio

n a

nd

Ma

inte

na

nce

Re

qu

ire

me

nts

:

Insp

ectio

ns h

elp

to e

nsur

e th

at th

e w

et b

asin

con

tinue

s to

ope

rate

a

thro

ugho

ut it

s lif

espa

n. R

egul

ar in

spec

tion

also

indi

cate

s w

hen

cert

ain

mai

nten

ance

pra

ctic

es a

re n

eces

sary

. Lik

e in

spec

tion,

regu

lar m

aint

enan

ce k

eeps

the

BMP

runn

ing

smoo

thly

an

d pr

olon

gs, o

r elim

inat

es, t

he n

eed

for i

nten

sive

reha

bilit

atio

n su

ch

as s

ide

slop

e re

stab

iliza

tion

or re

plac

ing

of c

orro

ded

pipe

s. Th

e ta

ble

belo

w o

utlin

es th

e re

gula

r and

as-

need

ed m

aint

enan

ce p

ract

ices

fo

r wet

bas

ins.

Spec

ific

info

rmat

ion

on in

spec

tion

and

mai

nten

ance

re

quire

men

ts c

an b

e fo

und

in A

ppen

dix

D o

f the

TRW

D D

M.

Refe

renc

es o

r Fut

ure

Read

ing:

“Com

plyi

ng w

ith th

e Ed

war

ds A

quife

r Rul

es: T

echn

ical

Gui

danc

e on

Bes

t Man

agem

ent P

ract

ices

”. Jul

y 20

05. T

CEQ

. RG

-348

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//w

ww

.stor

m-t

ex.c

om/w

p-co

nten

t/up

load

s/20

16/0

4/TC

EQ_R

G-3

48.p

df >

. “iS

WM

Tech

nica

l Man

ual:

Site

Dev

elop

men

t Con

trol

s”. (2

014)

. Nor

th C

entr

al Te

xas C

ounc

il of

Gov

ernm

ents

. Acc

esse

d Se

ptem

ber 2

017.

< h

ttp:

//isw

m.n

ctco

g.or

g/D

ocum

ents

/tec

hnic

al_m

anua

l/Site

_D

evel

opm

ent_

Cont

rols

_9-2

014.

pdf >

. Cl

ary,

J. e

t al.

“Inte

rnat

iona

l Sto

rmw

ater

BM

P D

atab

ase

2016

Sum

mar

y St

atis

tics:

Fina

l Rep

ort”.

(201

7). T

he W

ater

Env

ironm

ent &

Reu

se F

ound

atio

n. A

cces

sed

Sept

embe

r 201

7. <

htt

p://

ww

w.b

mpd

atab

ase.

org/

Doc

s/03

-SW

-1CO

h%20

BMP%

20D

atab

ase%

2020

16%

20Su

mm

ary%

20St

ats.p

df >

. “S

an A

nton

io R

iver

Bas

in Lo

w Im

pact

Dev

elop

men

t Tec

hnic

al D

esig

n G

uida

nce

Man

ual”.

(201

3). S

an A

nton

io R

iver

Aut

horit

y. A

cces

sed

Sept

embe

r 201

7. <

htt

ps://

ww

w.sa

ra-t

x.or

g/w

p-co

nten

t/up

load

s/20

15/0

5/Fu

ll-LI

D-M

anua

l.pdf

>.

“Tar

rant

Reg

iona

l Wat

er D

istr

ict D

evel

oper

Man

ual”.

(201

8). T

arra

nt R

egio

nal W

ater

Dis

tric

t (TR

WD

). “T

enne

ssee

Per

man

ent S

torm

wat

er M

anag

emen

t and

Des

ign

Gui

danc

e M

anua

l”. D

ecem

ber 2

014.

Tenn

esse

e D

epar

tmen

t of E

nviro

nmen

t and

Con

serv

atio

n. 1

st e

d. A

cces

sed

Sept

embe

r 201

7. <

htt

ps://

app.

box.

com

/s/p

dl1a

fehg

00s1

ww

qa94

d8qm

izyp

txw

3i/fi

le/2

5367

6926

45 >

.

Regu

lar M

aint

enan

ceM

AIN

TE

NA

NC

E I

TE

MS

FR

EQ

UE

NC

YCl

ear t

rash

, deb

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TRWD Water Quality Manual June 20184-26

Cereal RyeSecale cereale L.

Buffalo Grass Buchloe dactyloides

Blue GramaBouteloua gracilis

Little Bluestem Grass Schizachyrium scoparium

Side Oats Grama / Bouteloua curtipendula

Big BluestemAndropogon gerardii

Green SprangletopLeptochola dubia

Herbaceous Species - Grasses

BermudagrassCynodon dactylon


Eastern GamagrassTripsacum dactyloides

SwitchgrassPanicum virgatum

Sand LovegrassEragrostis trichodes

Western WheatgrassPascopyrum smithii

Cane BluestemBothriochloa barbinodis

Texas CupgrassEriochloa sericea

Sand DropseedSporobolus cryptandrus

Prairie WildryeElymus canadensis


IndiangrassSorghastrum nutans


Curly Mesquite Hilaria belangeri

White tridensTridens albescens


Bushy BluestemAndropogon glomeratus

Halls PanicumPanicum hallii

Broomsedge BluestemAndropogon virginicus

Regal Mist Gulf MuhlyMuhlenbergia capillaris‘Regal Mist’

Lindheimer MuhlyMuhlenberia lindheimeri

Cherokee SedgeCarex cherokeensis

Emory’s SedgeCarex emoryi


Texas BluegrassPoa arachnifera

WitchgrassPanicum cappillare

Virginia WildryeElymus virginicus

Inland Sea OatsChasmanthium latifolium



Plains Coreopsis Coreopsis lanceolate

Blackeyed SusanRudbeckia hirta

Scarlet SageSalvia coccinea

Cutleaf DaisyEngelmannia peristenia

Pink Evening PrimroseOenothera speciosa

Illinois BundleflowerDesmanthus illinoensis

Clasping ConeflowerDracopis amplexicaulis

American BasketflowerCentaurea americana

Maximilian SunflowerHelianthus maximiliani

Herbaceous Species – Perennials


Lemon MintMonarda citriodora

Purple Prairie CloverDalea purpurea

White Prairie CloverDalea candida

Partridge PeaChamaecrista fasciculata

GayfeatherLiatris spicata

Texas BluebonnetLupinus texensis

Indian BlanketGaillardia pulchella

Giant Goldenrod Solidago gigantea

Tall GoldenrodSolidago altissima



Gregg’s MistflowerConoclinium greggii

Mealy Blue SageSalvia farinacea

Turk’s CapMalvaviscus drummondii

Tall Aster / Symphyotrichumpraealtum var. Praealtum

Joe Pye WeedEupatorium fistolosum

Zexmenia / Wedeliaacapulcensis var. hispida

Aromatic Aster / Symph-yotrichum oblongifolium

Texas Yellow StarLindheimera texana

Cardinal Flower Lobelia cardinalis



Late BonesetEupatorium serotinum

Cinnamon FernOsmunda cinnamomea

Royal FernOsmunda regalis

Texas BluebellsEustoma grandiflora

Common Milkweed Aesclepias syriaca

Halberdleaf HibiscusHibiscus laevis

Dwarf TickseedCoperopsis tinctoria

Louisiana IrisIris ser. Hexagonae

Obedient PlantPhysostegia virginiana

Herbaceous Species - Perennials


Autumn SageSalvia greggii

Purple ConeflowerEchinacea purpurea

Texas Gayfeather / Liatrispuncata var. mucronatum

Butterfly WeedAsclepias tuberosa

Herbaceous Species - Perennials


American Beautyberry Callicarpa americana

Dwarf PalmettoSabal minor

Dwarf WaxmyrtleMorella cerifera var. pumilla

Common ButtonbushCephalanthus occidentalis

Pale Leaf YuccaYucca pallida

Cast Iron PlantAspidistra elatior

Dwarf Yaupon HollyIlex vomitoria ‘Nana’

Shrubs


Reverchon HawthornCrataegus reverchonii

Eve’s NecklaceSophora affinis

Shantung MapleAcer truncatum

PossumhawIlex decidua

Yaupon Holly - MaleIlex vomitoria

Texas Redbud / Cerciscanadensis ‘Texensis’

Mexican Redbud / Cerciscanadensis ‘Mexicana’

Oklahoma Redbud / Cercis canadensis ‘Oklahoma’

Yaupon Holly - FemaleIlex vomitoria

Ornamental Trees


Wafer AshPtelea trifoliata

Southern WaxmyrtleMyrica cerifera

Ornamental Trees


Montezuma CypressTaxodium mucronatum

Pond CypressTaxodium ascendens

Cedar ElmUlmus crassifolia

Green AshFraxinus pennsylvanica

PecanCarya illinoensis

Slippery ElmUlmus rubra

Bald CypressTaxodium distichum

Texas AshFraxinus albicans

Common Persimmon Diospyros virginiana

Trees


Live OakQuercus virginiana

Chinkapin OakQuercus muhlenbergii

Shumard OakQuercus shumardii

Bur OakQuercus macrocarpa

Trees


SweetflagAcrous calumus

Caric SedgeCarex spp.

Square Stem SpikerushElocharis quadrangulata

Swamp SunflowerHelianthus angustifolius

Soft RushJuncus effusus

Fragrant WaterlilyNymphaea odorata

SpatterdockNuphar luteum

Yellow WaterlilyNymphaea mexicana

Rice Cut GrassLeersia oryzoides

Aquatic Plants – Perennials and Grasses


PickerelweedPontederia lanceolata

Lance-leaf ArrowheadSaggitaria landifolia

Duck PotatoSaggitaria latifolia

Lizard’s TailSaururus cernuus

Three-squareScirpus americanus

Smart Weed / Polygonum hydropiperoides

PickerelweedPontederia cordata

Green ArumPeltandra virginica

Giant Bulrush Scirpus californicus



Virginia Chain FernWoodwardia virginica

Softstem BulrushScirpus validus


Service Layer Credits: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong),

0 1,200 2,400

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Zone 2 - Floodway Corridor

Zone 3 – Water Quality Zone (Conceptual)

Zone 4 - City of Fort Worth

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C2

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