Water Quality Implications of Culvert Repair Options: Vinyl Ester Based and Ultraviolet Cured-in-Place Pipe Liners

About the report:

Specifications of the Virginia Department of Transportation (VDOT) allow for the use of several “trenchless” pipe or culvert repair technologies whereby existing underground culverts are repaired in place rather than by the use of the conventional method of unearthing and replacing damaged sections.  However, water quality implications of these trenchless alternatives are not completely understood.  A previous evaluation found water quality impacts from installations of conventional cured-in-place pipe (CIPP).  This trenchless rehabilitation technology includes saturating a flexible liner with a styrene-based resin and curing the liner onsite with steam or hot water.  VDOT subsequently implemented new specifications for styrene-based CIPP to prevent water quality impacts from its installation or use.  The current study included an environmental evaluation of two unconventional CIPP technologies available for use by VDOT: vinyl ester based (styrene-free) CIPP and styrene-based ultraviolet (UV) CIPP.

To evaluate the potential for vinyl ester based and UV CIPP technologies to impact water quality, water samples were collected from field installations and simulations for up to 120 days.  Samples were analyzed for product constituents listed in material safety data sheets.  Results were then compared with established regulatory standards and published toxicity criteria for aquatic species.

For the vinyl ester based CIPP liner evaluated, concentrations of the primary resin constituent exceeded toxicity thresholds for aquatic species in six subsequent water sampling events.  Adherence to VDOT’s CIPP specifications for styrene-based liners is expected to minimize contaminant leaching from the installation and use of this product.  Following UV CIPP installations, no water quality impacts were documented from culvert outlets with water flow but styrene concentrations following one of the installations exceeded toxicity thresholds for aquatic species in standing water. 

The study recommends that VDOT consider revising its current CIPP specifications such that styrene-based CIPP requirements also apply to non–styrene-based CIPP installations.  Because the water quality evaluations conducted in this study could not capture the range of potential field scenarios and installation variables, the VDOT specification that requires the collection and analyses of water and soil samples following CIPP installations would provide VDOT with additional sampling results from liners installed in varying field conditions and help ensure that VDOT is using this lining technology with appropriate environmental safeguards.

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