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Spring Lane and Hendren StreetProposed Flood Relief ProjectNovember 12, 2013
www.phillywatersheds.org
Outline
Review of Past Problems and Project ObjectivesPWD Involvement and InitiativesWatershed and Neighborhood FindingsPWD Proposed Contributions to SolutionsHomeowner InvolvementChoices and Decision Making
Hendren Street and Spring Lane
Review of original problemStabilize the Spring Lane OutfallProtect the existing 4” force mainAddress the flooding impacts experienced by residents
Infrastructure Damage: Failed Outlet-700 Block Spring Lane
Infrastructure Damage: Failed Outlet -700 Block Spring Lane
Impaired Driver Safety: Standing Water-700 Block Spring Lane
PONDED WATER LIMITS AFTER JUNE 2013 THUNDERSTORM
Impaired Driver Safety: Sediment Deposition @ Hendren & Spring Intersection
Roadway/Lawn Interface Deterioration Eroded gutter@ Hendren & Spring Intersection
Homeowner Impacts: Erosion and Pavement Damage- 600 Block Hendren Street
PWD Involvement and Initiatives
Initiative 1: Homeowner Surveys
Quantify number of homeowners adversely affected by stormwater runoffConcurrently gather data to evaluate provision of sanitary sewer service
Initiative 2: Analysis
Determine Source(s) and destinations of problematic runoffEvaluate Potential remedies
Initiative 3: Recommendations
PWD Survey Response Summary
45 Surveys Distributed / 19 Responses (42%)15 Surveys on Spring Lane/ 7 Responses (47%)30 Surveys on Hendren / 12 Responses (40%)
PWD Survey Summary: Septic
ID Good Condition Fair Condition Poor Condition
Spring Lane 4 2 1
Hendren Street 3 5 4
Total 7 7 5
PWD- Analysis- Source of Runoff
Drainage Area to Spring Lane is approximately 25 Acres
Runoff Sources: Manatawna Avenue to Spring Lane
Runoff Sources: Hendren Street and Yards to Spring Lane
Summary of Observations:
PWD’s installation of storm sewers/inlets in Manatawna Avenue, Hendren Street and Spring Lane will provide control of stormwater from city streets and public rights-of-way, however, runoff from private property, driveways and roof tops will need to be directed and connected to this infrastructure.
Manatawna Stormwater Improvements
Inlets can be added in Manatawna to intercept this street runoffHOWEVER, this represents only a small fraction of the total land area currently contributing to Hendren and Spring flooding.
PWD Analysis: Runoff Path
YardsHendren StreetColonial Swale and YardsResidencesLow Point in Spring (Damaged Storm pipe and Headwall)
Runoff Paths: Colonial Gutter
Runoff Paths: Yards-Hendren to Spring
Runoff Paths: Streets- Spring to Field
Runoff Paths: Streets -Low Point Spring
PWD Analysis: Significant Runoff Generators
Surface Character affects the amount of runoffImpervious Surface like roofs, drives, streets and walks prohibit infiltration of stormwater. Nearly 100% RunoffPervious, Vegetated Surfaces absorb some runoff, however runoff still occurs, especially in more intense storms
Watershed Statistics: Impervious Surface
25 Acres Total Drainage Area
25% Impervious (6.3 acres)2.3 acres streets (public)4.0 acres roof tops and driveways (privately owned)
75% Pervious (18.6 acres – privately owned)
Public vs. Private Runoff Generators
Runoff from streets and public rights-of-way 2.3 Acres or 9%
Yards, roofs and driveways 18.5 acres + 4 Acres = 22.5 Acres or 91%
Sanitary Sewer Service
Existing Sanitary ChallengesOf the respondents to the survey, 62% indicated that their existing septic system was only in “fair” or “poor” condition
Sanitary Sewer Design Considerations
Spring LaneSouth side of Spring served by a standard depth gravity sewer.
A new pump station will require acquisition of additional right-of-way
Sanitary Sewer Design Considerations
Hendren StreetSouth side residents (uphill) can be served by standard depth (8-feet Separate) sewersNorth side residents (downhill) are below standard depth sewers
PWD Stormwater Remedies:
Localized Damage solution is available; Repair damage at Spring Lane outfall
Interim: Armor and reinforce
Typical Repair of Damaged Outfall
PWD Stormwater Remedies:
Construction of a Storm Sewer pipe and inlet system in public rights of way is possible
Will provide for safe conveyance of captured runoff
Will fortify repair of damaged Spring Lane outfall and protect forcemain
Actions Required beyond PWD’s Proposed Stormwater Remedies:
Doesn’t Solve the Entire ProblemRequires that private property runoff be redirected to intercept 100% of runoffWill not resolve homeowner flooding emanating from private property runoff
Stormwater: Increase Effective Runoff Collection – Connect All Roofs to Proposed Main
Stormwater: Increase Effective Runoff Collection – Connect All Roofs to Proposed Main
PWD Sanitary Sewer Remedies:
Construction of Sanitary Sewer and Pump station is possible
Will provide alternative to replacement of failing septic systemsRequires additional efforts to provide service to entire neighborhood
Downslope properties that have plumbing discharge below street level may need to install ejector/grinder pumps
Choices Related to PWD Action
Construction Impacts
Financial and Action Commitment
Choices Related to PWD Action
Construction ImpactsPotential roadway changes
WideningADA WalksCurbs or swalesDriveway crossings
Tree, Shrubbery and Fence Removal Probable
Construction Choices Related to PWD Action: Fence POTENTIALLY at Risk
Construction Choices Related to PWD Action: Fence POTENTIALLY at Risk
Construction Choices Related to PWD Action: Trees POTENTIALLY at Risk
Construction Choices Related to PWD Action: Shrubbery POTENTIALLY at Risk
Construction Choices Related to PWD Action: Shrubbery and Specimen Tree at Risk
Consequences of PWD Action:Shrubbery and Specimen Tree at Risk
ALTERNATIVE APPROACH
Reduced extent of curbing and street wideningIntercept Runoff with Roadside Swales in-lieu of Curbing
Retain Neighborhood CharacterProvides Infiltration
Reduces Runoff VolumeImproves Water Quality
Alternative Approach: Hendren Street Section @ Regulated Width
Alternative Approach: Hendren Street
Section - Retained Narrow Width- No Curb
Choices Related to PWD Action:Financial and Action Commitment
PWD Responsibility Homeowner Responsibility3540 feet of Storm Water Main: Construct, Own & Maintain
3293 feet stormwater laterals and appurtenances from downspouts to edge of street: Construct, Own & Maintain
462 feet stormwater laterals to edge of street: Construct only. (will be owned and maintained by homeowner)
Decommission septic system
3075 feet of Sanitary Sewer Main: Construct, Own & Maintain. 453 feet sanitary laterals to edge of street: Construct only. (will be owned and maintained by homeowner)
3806 feet sanitary laterals and appurtenances from house to edge of street including : Construct, Own & Maintain
Pump station and + 700 Feet of Forcemain: Construct, Own & Maintain
Grinder Pump (if required): Construct, Own & Maintain
Inlets: Construct, Own & MaintainSwales: Construct, Own & Maintain
Pay Assessment fee: $9.00/lineal foot of frontage
Driveway restoration in area of disturbance only Pay monthly service fee
Remove vegetation within construction limits*
Acquire permits and approvals for construction within the public rights-of-way, Only
Acquire permits and approvals for construction within homeowner property limits
* Landscaping outside the right of way that is affected by construction will be replaced with young nursery stock of similar species. Landscape replacement within the right of way will be replaced depending on the situation. Utility, safety and maintenance issues will be evaluated.
Steps to Obtain Public Sewers
Residents signed petition to PWD or their CouncilpersonCity Council Ordinance is required for a public sewerProcess from Ordinance to construction can take a few years
Impact to Customers
Each property owner is assessed at the rate of $9.00 per linear foot of property frontage Plumbing which drains to the back of the house needs to be redirected to the front of the house (PWD has zero interest loans available)Yard drains, downspouts should be connected to new stormsewer via new stormwater lateral (PWD has zero interest loans available)
Benefits of PWD Actions
Reduced runoff from street and connected roofs…reduced property damageImproved Driver Safety-Reduced standing waterElimination of maintenance associated with on-lot septic systemAlternative to replacement of expensive on-lot septic systemImproved marketability of property
Homeowner Solution Choices
PWD Installation of Stormwater and Sanitary Sewer conveyance System?
…or
Limit PWD’s actions to Repair of Damaged Spring Lane outfall?
Other?