The Renewal of Stormwater Systems Using Trenchless Technologies

Wednesday, March 6, 20192:00-3:30 PM ET

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Purpose

Discuss NCHRP Synthesis Report 519: The Renewal of Stormwater Systems Using Trenchless Technologies.

Learning Objectives

At the end of this webinar, you will be able to:

• Describe the current trenchless renewal methods and their state of the practice

• Differentiate between each method and when they are applicable

The Renewal of Stormwater Systems Using Trenchless

TechnologiesPresented by: David C. Ward, PE, LEG

Moderated by: Mohammad Najafi, PhD, PE

Synthesis Objectives

• Provide an understanding of the successful practices and associated limiting factors for using trenchless technologies to renew stormwater facilities.

• Characterize the decision criteria used by facility owners when choosing a renewal method.

• Characterize how state departments of transportation (DOTs) and local agencies are using trenchless technologies.

• Summarize new, emergent, and underutilized methods and technologies that might be used in highway applications and suggest further research needs.

WebinarLearning Objectives

Differentiate between each method and when they are applicable

Understand current trenchless renewal methods for stormwater systems and their state of the practice

Outline

Background

Types of trenchless renewal methods

Emerging methods

DOT current practices and experiences

Conclusions\Summary

Background

• Why Trenchless Renewal?• Facilities reaching or exceeding

their design life.• Structural/Functional Repairs• Minimize negative impacts and

maximize the cost benefits

Photo: Ohio Department of Transportation

Trenchless Renewal

• Extend service life:• Corrosion, abrasion, erosion,

infiltration/exfiltration• Structural repair/improvement• Improve hydraulic capacity (sometimes)

• Limit surface disruption by moving work outside of travel lanes

Stormwater Application

• 12 in to 12 foot diameter

• Corrugated metal, concrete, plastic and brick pipe

• Circular and non-circular cross-sections

• Spot repair to thousands of linear feet

Trenchless Renewal versus Installation

Trenchless Renewal: Upgrading, rehabilitating, repairing, and renovating the performance and increasing the design life of existing stormwater facilities using trenchless technology.

Trenchless Installation: Constructing a new stormwater conveyance system to replace an existing stormwater facility along a new alignment using trenchless technology such as pipe ramming, pipe jacking, auger boring, microtunneling, or horizontal directional drilling.

Types of Trenchless Renewal

Cured-in-place pipe (CIPP)

01Sliplining (SL)

02Modified sliplining (MSL)

03In-line replacement (ILR)

04Spray-in-place pipe (SIPP)

05Close-fit pipe (CFP)

06

Cured-in-place pipe (CIPP)

• Insertion, expansion, and curing of a flexible fabric and a thermosetting resin lining system (hot water, steam, UV).

• Up to 108-inch typical (120-inch has been completed)

• Maximum length, depending on diameter 1,000 to 2,000 feet

Cured-in-place pipe (CIPP)

Existing Pipe Type• Concrete• Steel• Plastic• Brick

Installation of a 60-inch diameter CIPP liner using the air inversion method (Courtesy: Michels Corporation).

Cured-in-place pipe (CIPP)

ADVANTAGES CHALLENGES

• Small construction footprint.• Excavation typically not required.• Grouting not required.• Minimal reduction in culvert size.• No joints.• Accommodates most bends.• Noncircular and varying cross-sections.

• Flow bypass required.• Typically manufactured for specifically for each

project.• Toxic resins associated with some variants.• Capture and disposal of cure water requires

additional consideration.• Relative high volumes of steam and water

required for some methods.

Sliplining (SL)

• Insertion of new smaller diameter pipe into the existing pipe. Typically includes grouting the annular gap. Commonly new pipe is HDPE or PVC.

• Up to 160-inch• Lengths up to 1,000 feet

Sliplining (SL)Existing Pipe Type• Concrete• Steel• Plastic• Brick

Sliplining a culvert (Courtesy: Advanced Drainage Systems, Inc.).

Sliplining (SL)

ADVANTAGES CHALLENGES

• Flow bypass not always required.• Structural renewal.• Can accommodate large radii bends.• Noncircular and varying cross-sections

• Large insertion pits and construction area typically required. Can be mitigated with use of segmental pipe.

• Limited to smallest diameter of existing pipe.• Excavation may be required.• Bulkheading and grouting of annulus requires

additional considerations.

Modified sliplining (MSL)

• Construction of a new liner for existing pipes 48-inch-diameter or larger and noncircular shapes. Includes spiral wound lining, pipe panels, pipe segments, and split-can liner.

• Personnel accessible size (48-inch or larger – up to 14 feet).

• Length about 1,000 feet for spiral wound, no limit on other variants.

• Commonly grouted annular space.

Modified sliplining (MSL)

Existing Pipe Type• Concrete• Steel• Plastic• Brick

Spiral-wound liner (Courtesy: Contech Engineered Solutions, Inc).

Modified sliplining (MSL)

ADVANTAGES CHALLENGES

• Flow bypass not always required.• Structural renewal.• Smaller construction footprint.• Noncircular and varying cross-sections.• Accommodates some bends.• Grouting not always required.

• Specialized equipment needed for some products.• Excavation may be required at some bends.• Typically manufactured for specifically for each

project.

In-line replacement

(ILR)

• In situ replacement of the existing pipe. Common methods include pipe bursting, pipe reaming, pipe eating, and pipe ejection/extraction.

• Pipe bursting• Split and push outward• Mainly replacing plastic pipe, up to 36-inch

and 1,000 feet• Pipe removal

• Reaming/crushing into small pieces or pushing/pulling intact pipe sections out of the ground.

• Pipe reaming (HDD - limits), Pipe eating (microtunneling - limits), Pipe ejection (thrust capacity of original pipe, length, diameter, backfill, etc.)

In-line replacement (ILR)

Existing Pipe Type• Unreinforced or

lightly reinforced concrete

• Steel• Plastic

Completed pipe bursting of a CMP (Courtesy: Hammerhead Trenchless Equipment).

In-line Replacement (ILR)

ADVANTAGES CHALLENGES

• Structural renewal.• Can upsize existing pipe size.• Accommodates some bends.

• Flow bypass typically required.• Larger construction footprint.• Excavation may be required.• Can damage adjacent structures and

improvements.• Not suitable for all soil conditions.• Can exaggerate line and grade defects.

Spray-in-place pipe (SIPP)

• Sprayed cementitious or polymer liner for existing pipes. Includes lining for structural and non-structural renewal.

• Clean pipe and bypass flows• Diameters 3 to 276 inches• Lengths up to about 1,500 feet

Spray-in-place pipe (SIPP)

Existing Pipe Type• Concrete• Steel• Brick

Example of cementitious SIPP (Courtesy: Centri-Pipe).

Spray-in-place pipe (SIPP)

ADVANTAGES CHALLENGES

• Small construction footprint.• Noncircular and varying cross-sections.• Can incorporate reinforcement.• Larger diameter can be accommodated.• Protects against corrosion.

• Flow bypass required.• Specialized equipment and training required.• Surface preparation is critical.

Close-fit pipe (CFP)

• Installation of a new liner using the fold and formed, drawdown, rolldown, or similar process.

• Deformed and reformed, up to 60-inch diameter, no bends.

• Folded and formed, up to 30-inch diameter, up to 30 degree bends.

• Maximum length about 2,500 feet.

Close-fit pipe (CFP)

Existing Pipe Type• Concrete• Steel• Plastic• Brick

Deforming the HDPE pipe in a reduction dye (Courtesy: City of Fort Collins).

Close-fit pipe (CFP)

ADVANTAGES CHALLENGES

• Annular grouting not required.• Structural renewal.• Accommodates some bends.

• Flow bypass required.• Infiltration sealed• Larger construction footprint.• Limited to circular cross-sections.

Emerging Methods

• Variations of ILR using pipe ramming• Pipe crushing– steel wedges inside

rammed casing• Pipe swallowing – engulf existing pipe

and use second piece of equipment to break pipe to facilitate removal

(Courtesy: HammerHead Trenchless Equipment).

Emerging Methods

• Geosynthetic cementitious composite mats• Personnel accessible pipes• Similar to invert paving• Flexible cement impregnated cloth with a PVC

backing.• Secured and hydrated

• Steel-reinforced composite system• Personnel accessible pipes• Continuously wrapped, high strength, steel wires

embedded in a spin-cast or spray-applied cementitious or polymeric matric sandwiched between two epoxy-impregnated, fiber-reinforced polymer sheets.

DOT Current Practice and ExperienceSynthesis goal to answer questions regarding:• Relative Frequency of Use• Decision process to use trenchless renewal• Method selection process• Relative use and satisfaction with the methods• Costs and degree that costs are tracked

DOT Current Practice and ExperienceSynthesis• Literature search• Questionnaire• Interviews

Experience

Experience with

Trenchless Renewal

40 Respondents

Breadth of Experience37 Respondents

• 60% have experience with 2 or fewer methods

• 40% have experience with 3 or more methods

Methods and Frequency Used

Frequency Various

Methods are Used

36 Respondents

Does not consider the number of projects performed.

Experience with Various Methods37 Respondents

Relative Frequency Methods are Used37 Respondents

Satisfaction with Methods Used

Relative Satisfaction

36 Respondents

100% = Always0% = Never

Increasing Trenchless Renewal Use

Experienced Agencies37 Respondents

• Typical cost information• Agency experience with applicable

methods (case studies)• Decision criteria used by facility

owners• Limiting factors to the applicability

of specific methods• Emergent technologies

Non-experienced Agencies4 Respondents

Reasons agencies elect not to use trenchless

Experienced Agencies37 Respondents

• Existing pipe condition• Reduction in hydraulic capacity• Economics/Costs

Non-experienced Agencies4 Respondents

• Reduction in hydraulic capacity not acceptable

• Limited organization experience• Preference for new construction• Uncertainty regarding design

life/performance of trenchless methods

• Condition of existing pipe

Method Selection

Standardized Process (Y/N)4 Respondents (Yes) and 34 Respondents (No)

• Experience• In-house expert/consultation• Own equipment/crews

Reasons for Using Trenchless Renewal

Reasons for using trenchless renewal34 Respondents

• Height of fill (cover) over the structure• Limiting surface disruption• Perceived economic/cost benefit• Faster than open-cut• Temporary or permanent deferral of

constructing a larger replacement pipe

Temporary and Structural Renewal35/36 Respondents

• Trenchless renewal is commonly (70%) considered to be a permanent repair rather than a temporary repair to defer replacement.

• Trenchless renewal is commonly (74%) considered to be a structural repair

Defects Commonly Mitigated and Satisfaction

Defects Mitigated36 Respondents

• Corrosion• Leaks/infiltration• Loose or open joints• Crack, breaks, or splits

Satisfaction Mitigating Defects38 Respondents

Costs

Frequency Cost Overruns Occur32 Respondents

Sources of Claims

Two most common reasons for claims:• Difference in existing pipe condition• Differing groundwater/soil conditions

Fourteen Comments:• Existing pipe condition and/or size different than anticipated (three respondents)• Differing site conditions (two respondents)• Additional liner thickness required• Wrong method selected for conditions• Difficulty with the annular void filling• No claims on trenchless renewal projects (6 respondents)

Conclusion/Summary

WebinarLearning Objectives

Differentiate between each method and when they are applicable

Understand current trenchless renewal methods for stormwater systems and their state of the practice

Summary• Trenchless renewal methods are commonly considered to be

“permanent” (70 percent) rather than as a temporary repair to defer replacement.

• Trenchless renewal is also commonly considered to be a structural repair (74 percent).

• 89 percent of respondents overwhelmingly relied on previous experience, in-house experts, or the fact that they had their own equipment and experienced crews to decide on which trenchless method to use.

Summary• The four most common reasons for using trenchless renewal were

identified as:• Height of fill (cover) over the structure,• Limiting surface disturbance,• Perceived economic/cost benefit, and• Faster than open-cut.

Summary• The three most common reasons for DOTs with trenchless renewal

experience for not using trenchless renewal when it is technically feasible were identified as:

• Condition of existing pipe,• Reduction in hydraulic capacity not acceptable, and• Economics/costs.

Summary• The surveyed DOTs have the most experience with sliplining (SL) (89

percent), cured-in-place pipe (CIPP) (62 percent) and spray-in-place pipe (38 percent).

• The respondents are generally satisfied with SL (88 percent) and CIPP (90 percent). The reported satisfaction rates for the other methods may not be representative because they are not frequently used.

Summary• The respondents are generally satisfied or very satisfied with the

ability of trenchless renewal to mitigate the common defects, such as corrosion, leaks/infiltration, loose/open joints, and cracks/breaks/splits.

• The most common cause of cost overruns and claims is changed or differing conditions associated with the existing pipe (59 percent).

• Sixty-four percent of respondents indicated that cost overruns were generally less than 10 percent of the original project cost.

Today’s Speakers• Mohammad Najafi, Center for

Underground Infrastructure Research and Education, University of Texas at Arlington, najafi@uta.edu

• David Ward, Shannon & Wilson, Inc., dcw@shanwil.com

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