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31 <br />General Engineering and Environmental Management Services <br />Winston - Salem, North Carolina <br />PIGGYBACK LANDFILL <br />HDR designed, permitted, and <br />provided construction administration <br />services for the 37 -acre expansion of <br />the existing Hanes Mill Road Sanitary <br />Landfill. In accomplishing this task, <br />HDR redesigned the side slopes and <br />final cap of the existing landfill facility <br />to "piggyback" or overlay the liner <br />system of the new unit along the <br />common slope of the current fill area. The ovediner includes a <br />double liner, a witness zone to facilitate the monitoring of potential <br />leachate generation, and a single composite base liner. This facility is the first ovediner permit issued in the state of <br />North Carolina. <br />To address the potential for settlement in the design, settlement devices were installed in the old waste and then loaded <br />with soil overburden to simulate the increased weight of the future waste. Settlement coefficients were developed to <br />model short- and long -term stresses on the liner. <br />MSW LANDFILL EXPANSION <br />HDR completed preparation of the required permit application for the City's 347 - <br />acre (90 lined acres) expansion site. This project began with development of a Key Elements: <br />Master Plan of the site followed by preparation of the Site Study Report. With ' 347 -acre expansion <br />over 12,000 people living within 2 miles of the site, coordination with the public permittingidesign <br />■ First permitted "piggyback" liner in <br />was a critical aspect of the project. HDR prepared computer - generated imagery North Carolina <br />of the site to help represent the before and after views of the landfill from vantage ■ First permitted alternate liner in <br />points around the facility. Screening methods were evaluated, including use of North Carolina <br />tree cover and engineered berms. Each of the screening options was also - 44-acre closure completed in 1999 <br />9 9 P ■ 40 -acre closure completed in 2007 <br />analyzed for sound attenuation qualities using computer modeling. The permit to ■ 72 acres of subtitle D Landfill <br />construct the first phase was issued in November 2001, and construction of the constructed <br />first cell began in April 2002. The landfill piping system is designed for future <br />bioreactor operation. A permit to operate for the 21 -acre Cell 1 was obtained in October 2004. Construction of the 14- <br />acre Cell 2 was permitted to operate in March 2007. HDR is currently performing the hydrogeologic investigation for <br />Phase 2 of the expansion landfill. <br />MSW LANDFILL CLOSURE <br />HDR completed the design and provided construction administration and monitoring service on the 40 -acre piggyback <br />landfill closure. The closure has a permit modification to use an alternative cap liner system consisting of a geosynthetic <br />clay liner on the 8% slope top. HDR is currently conducting post - closure inspections of the closed facility. <br />GROUNDWATER CLEANUP PILOT STUDY <br />HDR is currently performing a pilot study injecting a food -grade product into the subsurface to enhance chemical <br />degradation of contaminants in the groundwater from the unlined landfill on -site. In addition, HDR is evaluating the type <br />of contamination (i.e., leachate or gas) by conducting specific geochemical tests on groundwater samples that would <br />indicate the source. <br />Page 16 f al <br />