Evaluation of Environmental Impacts of Two Common Restoration Methodologies for Pipes that Convey Stormwater Runoff

About the report:

The Virginia Department of Transportation (VDOT) is responsible for the maintenance of underground pipes that convey stormwater runoff from roadways and other relatively impervious surfaces.  Due to normal fatigue, cracks can develop in these pipes over time.  Excavation and replacement of the damaged pipe section are expensive, intrusive, and time-consuming.  As an alternative, VDOT has used pipe-repair technologies that involve the insertion of the synthetic liner material inside the damaged pipe.  Although this technology can effectively seal water leaks caused by cracks in the pipe, the environmental impact of chemicals that leach from the liner materials into water in the pipe are not known.  In this work, we have investigated two common commercial pipe-repair technologies: Ultraliner and Troliner.  Both technologies employ a synthetic liner material.  Troliner installation also requires the use of grout that helps to provide an effective seal between the synthetic liner and the original host pipe wall.

Review of the materials safety data sheets of the liner materials revealed three possible plasticizers of potential environmental concern: bisphenol A (BPA), bis(2-ethylhexyl) phthalate (DEHP), and benzyl butyl phthalate (BBP).  A high-performance liquid chromatography (HPLC) analysis methodology was developed to quantify trace concentrations of these compounds in water.  In addition, a generic gas-chromatography scan with a flame ionization detector (GC-FID) was developed to identify other possible organic constituents that could possibly leach from the liner materials.  Kinetic batch experiments were conducted to determine if contaminants were leaching from Ultraliner, Troliner, and/or the grout.  In all cases and for all incubation times up to 48 hr., none of the three plasticizers was detected in water in contact with any of the pipe-repair materials.  In addition, the generic GC-FID scan did not detect any unidentified compounds relative to control samples.

It is possible that one or more of the target analytes were released from the liner materials at concentrations below the analytical detection limit.  To investigate this possibility, a mathematical model of plasticizer leaching from the pipe-liner material was developed with the assumption that the leached pollutant concentration after a 48-hr period exactly equals the analytical detection limit.  By normalizing this leaching rate to the surface area of the liner materials, the concentration of each plasticizer in pipe water could be estimated as a function of time, pipe diameter, and discharge of water through the pipe.  Both flowing and stagnant conditions were considered.  In all cases, simulated aqueous concentrations of the target analytes were well below drinking-water limits.  In summary, these experiments and analyses suggest that both Ultraliner and Troliner are technologies that are not expected to have any significant, adverse environmental impact.

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