West Valley Environmental Services, LLC engaged McMahon & Mann to design a groundwater barrier and a geomembrane cover for the Nuclear Regulatory Commission Disposal Area at the West Valley Demonstration Project site to limit the amount of groundwater infiltration and storm water seepage into the facility. McMahon & Mann prepared technical specifications and drawings showing the barrier wall, re-graded ground surface and drainage structure details. We provided construction monitoring services during the barrier wall and cover construction.

The State-Licensed Disposal Area (SDA) was capped in the early 1990’s with a geomembrane cover. After 20 years, the geomembrane showed signs of wear and distress. In addition, settlement had occurred in some areas, resulting in ponding of surface water. McMahon & Mann designed a replacement geomembrane cover and grading plan using light weight fill to create a positive slope for surface water runoff. During construction, we provided construction oversight services.