The Renewal of Stormwater Systems Using Trenchless...
Transcript of The Renewal of Stormwater Systems Using Trenchless...
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, [email protected]
• David Ward, Shannon & Wilson, Inc., [email protected]
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