Ayer Closed Wastewater Treatment Plant Sludge Landfill O&M
The Town of Ayer, Massachusetts selected Weston & Sampson to provide solid waste engineering services related to the operation and maintenance (O&M) of their closed wastewater treatment plant sludge landfill. O&M activities initially included quarterly groundwater, surface water, and sediment sampling and analysis, along with soil gas monitoring for landfill gas parameters including methane, hydrogen sulfide, and volatile organic compounds. However, Weston & Sampson had the monitoring frequently reduced to semi-annually by submitting a request with technical justification to the Department of Environmental Protection (DEP). In addition, Weston & Sampson inspects the landfill final cover system integrity for erosion and differential settlement. Monitoring results and recommendations are summarized in a report and submitted to DEP in accordance with the Massachusetts Solid Waste Regulations.
Prior to conducting O&M activities, Weston & Sampson provided engineering services related to the closure of the landfill as part of the closure process. As part of the closure process, Weston & Sampson conducted a combined initial and comprehensive site assessment (ISA/CSA) for the landfill, implemented a groundwater and landfill gas monitoring program, and designed the landfill cap system.
The sludge landfill is bordered by wetlands on two sides. Weston & Sampson performed a topographic survey of the landfill to determine the existing grades of the site. In order to locate the limit of waste beneath the daily cover, test pits were excavated along the perimeter of the landfill. Weston & Sampson used this information to design the cap and stormwater controls for the landfill.
Weston & Sampson’s landfill cap design consisted of HDPE flexible membrane liner, manufactured loam, grass-lined swales, rip-rap downchutes, and stormwater retention basins. The manufactured loam was selected as a cost-saving material with the benefit of additional erosion control.
Weston & Sampson provided construction administration services during construction of the landfill cap and stormwater controls. The project was completed under budget.