Standardized Test Method to Quantify Environmental Impacts of Stormwater Pipe Rehabilitation Materials

About the report:

The purpose of this study was to develop a standardized test method that the Virginia Department of Transportation (VDOT) can apply to evaluate the environmental impact of stormwater infrastructure materials. Three laboratory stormwater infrastructure material leaching protocols named static, stirbar, and modified Toxicity Characteristic Leaching Procedure (mTCLP) were developed. These protocols were evaluated for their ability to predict field stormwater quality and aquatic toxicity caused by a pipe rehabilitation material. Cured-in-place pipe (CIPP) was used in this study as a model rehabilitation material because there was prior evidence this technology could cause environmental damage. The study objective was achieved, and during this project it was discovered that the material installation process itself was the main cause of environmental pollution, more than the material. Additional materials and installation processes should be examined in future work.

Freshly cured CIPP samples were removed from the field and were submerged in synthetic stormwater and deionized water (54 hr, 23°C, pH 7.2, 120 ppm as CaCO3). Every 18-hour extractant water was analyzed for chemical oxygen demand (COD), UV254 absorbance, and styrene levels along with nonvolatile organic contaminants. CIPP weight gain measurements were also conducted to understand polymer composite water interaction.

Results showed that the greatest CIPP weight increase occurred during the first contact period and was roughly 2% to 3%. Water pH and alkalinity levels were unaffected by contact with CIPP specimens. The mTCLP method resulted in the greatest chemical leaching as shown by elevated COD, UV254 absorbance, and styrene levels, while the static and stirbar methods both poorly predicted field stormwater quality levels. For mTCLP testing, COD, UV254 absorbance, and styrene levels for the material leaching protocols were roughly 12, 43, and 4 times less than levels observed in the field stormwater, respectively.

Water type, exposure duration, and agitation methods were found to be statistically significant factors influencing chemical release. Four tentatively identified chemicals were detected in both the laboratory and field testing that included styrene, benzene, 4-(1,1-dimethyl)-cyclohexanol, and 4-(1,1-dimethyl)-cyclohexanone. Several (18) contaminants found in field stormwater were not detected during laboratory material leaching tests. With the exception of styrene, the concentration of detected chemicals was not quantified. None of the laboratory material leaching test extractant waters was acutely toxic to Daphnia magna for any exposure period.

As shown by the results of this study, chemicals other than styrene were released by CIPP into stormwater. Any further CIPP testing should not be limited to a few contaminants but be expanded to include other contaminants of environmental and human health concern. Further work is necessary to determine the ability of the mTCLP method to predict field stormwater levels at multiple installation sites, for broader range of materials, and evaluate additional water quality and toxicity indicators. Additional materials that should be examined with this method include at least those that are created in-situ by chemical reactions such as spray-on coatings and liners. Further testing with additional model systems and individual compounds and at field sites is recommended.

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