the environmental implications of road culvert repair ......pipe repair •in the u.s., $23 trillion...
TRANSCRIPT
The Environmental
Implications of Road
Culvert Repair
Technologies
Bridget Donaldson
Senior Research Scientist
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Presentation Overview
• Culvert repair technologies
• Past and ongoing research by VCTIR
– Cured-in-Place Pipe repair study and resulting
specifications
– Other lining technologies being
evaluated
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Pipe Repair
• In the U.S., $23 trillion in water and sewer
infrastructure needs to be spent in next
20 yrs
• Pipe/culvert repair
technology has grown rapidly
• Repair technologies originated
for underground pipes
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Culvert Repair
Deterioration of culverts is an increasing
problem for transportation agencies
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Open cut
Trenchless
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Trenchless Technologies
Six Main Categories:
• Slipliners
• Spiral wound liners
• Fold and form liners
• Spray-on liners
• Cured-in-place pipe liner
• Pneumatically applied concrete (Shotcrete)
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Slipliners
PVC or steel inserted into host pipe, annular space
is grouted
- Benefits: no chemicals or resins
- Disadvantages: reduction in flow capacity
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Spiral Wound Liners
Sections of PVC wound and
welded around spiraling
machine, annular space
grouted
- reduction in flow capacity
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Fold and Form Liners
Folded liner, unfolds and expands to
fit shape of damaged pipe
- minimal reduction in flow capacity
- 18”-21” max diameter
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Spray-on Liner Epoxy spray, solidifies immediately
- Disadvantages: pipe must be completely dry,
environmental issues?
- Advantages: cures quickly, no reduction in flow capacity
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Cured-in-place (CIPP) Liners Flexible liner coated with resin, expands to fit shape of
damaged pipe,
- minimal reduction in flow capacity
- environmental issues
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Pneumatically Applied Concrete Concrete application along culvert bottom
- Raises bottom elevation (at least 4 in)
Costs
Longevity
Highest $
Varies greatly depending on pipe and site
conditions
Lowest $
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VCTIR study: Are there any environmental
implications of these pipe repair methods?
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Trenchless Technologies
Six Main Categories:
• Slipliners
• Spiral wound liners
• Concrete (Shotcrete)
• Spray-on liners
• Cured-in-place pipe liner
• Fold and form liners
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Trenchless Technologies
Six Main Categories:
Slipliners
Spiral wound liners
Concrete (Shotcrete)
• Fold and form liners
• Spray-on liners
• Cured-in-place pipe liner
Steel, PVC, HDPE + grout
Entail a chemical
transformation
Increased enforcement of
permitting regulations
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Trenchless Technologies
Six Main Categories:
Slipliners
Spiral wound liners
Concrete (Shotcrete)
• Fold and form liners
• Spray-on liners
• Cured-in-place pipe liner
Steel, PVC, HDPE + grout
Entail a chemical
transformation
Increased enforcement of
permitting regulations
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Trenchless Technologies
• Fold and form liners
• Spray-on liners
• Cured-in-place pipe liner
Will be evaluated this year
Lab study (2009) found no env
effects, would like to evaluate in field
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Cured-in-place Pipe Repair
• CIPP operations span the U.S. and 40
other countries
• Most common repair method for
underground pipes
• Repair method used by nearly all U.S.
DOTs, and for approx 1/2 of VDOT’s
culvert repair projects before 2007
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CIPP (conventional)
• A resin-saturated felt liner is pulled or inverted through host
pipe
• Water or steam inflates the liner, conforms to shape of host
pipe
• Heated water or steam re-circulates and cures the resin
• Cool-down period, then ends of cured liner are cut open
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CIPP (conventional) Resin is 30-50% styrene
• Styrene is an EPA priority pollutant, potentially carcinogenic
- Max Contaminant Level (MCL) for drinking water: 0.1 mg/L
• Styrene from uncured resin from CIPP installations has
caused fish kills (FL, Canada) and damaged water treatment
plants
- Toxicity level for rainbow trout: 2.2 mg/L
• Vapor from styrene in CIPP installations has entered buildings
and homes and exceeded allowable exposure levels
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CIPP study (VCTIR)
• Monitored 7 CIPP installations in VA
• Collected water samples before, during,
and after installations
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CIPP
Observations:
• Discharge of hot cure water
• Uncured extruded resin
• Algal blooms
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CIPP
Water Sampling Test Results
• Styrene concentrations were as high as 77 mg/l and were detected up to 88 days post installation
- 770 times the MCL for drinking water
- 31 times toxicity values for rainbow trout and water flea
• Styrene concentrations exceeded the toxicity values of the rainbow trout and water flea at four of the seven monitored project sites (for up to 24 days post installation)
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CIPP Styrene concentrations detected in water samples
resulted from one or a combination of the following:
• Installation practices that did not capture condensate
containing styrene
• Uncured resin that escaped from the liner during
installation
• Insufficient curing of the resin
• Some degree of permeability in the felt lining material
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CIPP: VDOT Response
• VDOT immediately placed a stop work order on all
styrene-based CIPP repair projects contracted by VDOT
(2007)
• A VDOT task group led by VDOT’s Environmental
Division was formed to evaluate further the use of
steam- and water-CIPP repair projects containing
styrene
• VDOT developed new specifications for CIPP repair
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VDOT’s CIPP Specifications
• VDOT project inspector must provide oversight
• Thermocouples required during installation
• Additional lining materials are required to ensure capture of extruded uncured resin
• Finished liner must be rinsed before reinstating water flow
• Cure water and rinse water must be captured and disposed
• Contractors must hire independent labs to test water before and after each project
California has reduced its use of CIPP
New York State DOT has also issued new CIPP specifications
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Other CIPP Methods being
Evaluated Epoxy (styrene-free) CIPP
- small amount of uncured, extruded
resin observed
- some samples exceeded aquatic
species toxicity thresholds
- water volume and
dilution have important
effect on chemical
concentrations
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UV-CIPP
(styrene)
- Uses 1/3 of the resin as compared to conventional method
- Fiberglass liner, inner and outer impermeable foil
- Produces no effluent
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UV-CIPP
Preliminary test results: Many samples were non-detect, but some exceeded aquatic species toxicity thresholds
Recommended Considerations for
New Lining Products
• Field-test and monitor new products before
approval
• Detailed specifications for projects requiring
resin or spray
- rinse liner, capture and dispose of effluent
and rinse water, test water samples after
installation
• Installation oversight with trained inspectors
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Final VCTIR report will be available 2012
Will include information to assist with pipe
repair product selection and specification
development