Many commonly used culvert rehabilitation technologies entail the use of a resin or coating that cures to form a rigid liner within the damaged culvert. However, the potential environmental impacts of leaching or release of contaminants during normal installation practices have not been well studied. Evaluations of previous culvert repair operations by the Virginia Department of Transportation (VDOT) were conducted for conventional (styrene-based) cured-in-place pipe and fold and form repair technologies. The study reported herein included an evaluation of two additional technologies available for use by VDOT: a polymer-enhanced cement mortar (or cementitious) spray-on liner and a polyurea spray-on liner.
To evaluate the potential for these lining technologies to impact water quality, installations were monitored up to 49 days. Three water quality tests were conducted for each installation, and water samples were analyzed for water quality indicators and constituents listed in material safety data sheets. Tests included a water flow simulation with low dilution potential; an immersion test to simulate a standing water scenario; and a laboratory leaching test. Results were then compared against established regulatory standards and published toxicity criteria for aquatic species.
For the cementitious spray-on liner evaluated, pH and alkalinity exceeded specified Virginia water standards in laboratory tests but pH and other evaluated compounds were within the acceptable range in water flow and immersion tests. For the polyurea spray-on liner evaluated, elevated water quality indicators (i.e., biochemical oxygen demand, chemical oxygen demand, total organic carbon, and total nitrogen) in laboratory tests suggested that contaminants were released from the polyurea liner, particularly during its initial contact with water, but water quality impacts were not detected in the other tests. Water flow, dilution, and volatilization appear to play an important role in reducing water quality impacts from contaminant leaching.
The study recommends that VDOT specifications include protective controls for spray-on liners to prevent exceeding water quality standards or toxicity thresholds for aquatic species in receiving waters with low flows and little dilution potential.