Understanding the Environmental Implications of Cured-in-place Pipe Rehabilitation Technology

About the report:

Cured-in-place (CIPP) rehabilitation is a commonly used technology for pipe repair, and transportation agencies are using CIPP technology to repair damaged pipe culverts. In typical CIPP applications, a lining tube saturated with a thermosetting resin is installed into the damaged pipe and cured with a heat source to form a pipe-within-a-pipe. This study focused on CIPP installations that use forced steam through the lining tube both to press the liner to the inside dimensions of the host pipe and to harden the resin-impregnated liner material. Of the thermosetting resins used in CIPP applications, styrene-based resins are the most common. This research focused on styrene-based CIPP products. To evaluate the potential for impacts on water quality from the steam-cured CIPP process, seven CIPP installations in surface water and stormwater conveyances were identified and observed over the course of a 1-year study in Virginia. Water samples were collected from each project site and analyzed for styrene. The results were then evaluated for compliance with established regulatory standards and published aquatic toxicity criteria. Water samples collected from pipe outlets at five of the seven CIPP installations showed detectable levels of styrene. Styrene concentrations were generally highest in water samples collected during and shortly following installation. The maximum duration that styrene was detected at any site was 88 days following the CIPP installation. Although the sites in this study were not directly linked to sources of drinking water, styrene levels at five sites were higher than the U.S. Environmental Protection Agency's maximum contaminant level for drinking water of 0.1 mg/L. Styrene was detected at five sites for a minimum of 5 days to at least 71 days after installation and was detected at these sites up to 40 m downstream. Certain measurements were also found to exceed the values for EC50 (the concentration required to have a defined effect on 50 percent of a study population) or LC50 (i.e., the concentration required to kill 50 percent of a study population) for several freshwater aquatic indicator species. The findings suggest that the elevated styrene levels could have resulted from one or a combination of the following: (1) installation practices that did not capture condensate containing styrene, (2) uncured resin that escaped from the liner during installation, (3) insufficient curing of the resin, and (4) some degree of permeability in the lining material. A summary of the actions taken by the Virginia Department of Transportation (VDOT) in response to the preliminary findings of this study is also provided in this report. VDOT suspended the use of styrene-CIPP for pipes that convey surface or stormwater while further evaluating CIPP repair and subsequently developing new requirements for these installations. The new measures include substantial modifications to VDOT's CIPP specifications; an inspector training program; increased project oversight; and water and soil testing prior to and after CIPP installation. Reinstatement of statewide VDOT CIPP installations using the new procedures and specifications is planned for May 2008.

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