Challenge. Operate and maintain systems designed to protect the environment and public health from issues associated with a 77-acre former municipal landfill where over 1.5 million tons of solid waste was placed in an abandoned sand and gravel quarry between 1978 and 1983

Solution. INTERA has provided operations and maintenance (O&M) and related services for a landfill gas (LFG) extraction system and a soil vapor extraction/air injection (SVE/AI) system to address vadose zone and shallow aquifer contamination by volatile organic compounds. For the 60-well LFG extraction system, we have performed well field balancing (optimization of methane concentration), groundwater sampling, and LFG monitoring, and have maintained the blower/flare station condensate recovery system, a pilot system microturbine unit, and indoor methane detection systems. Our efforts have resulted in the LFG extraction system being operational for more than 99.9% of the time. One of our first tasks associated with the SVE/AI system involved troubleshooting injection performance which had degraded over time and could no longer support the needed extraction rate. To improve injection performance, we installed two new injection wells and upgraded components including pre-injection buffering tanks, a new pump-skid building, an injection pump system, pre-injection filters, actuated backflush and injection globe valves, flow meters, and a chemical sequestering agent delivery system. When mineral precipitant started to negatively impact extraction operations, INTERA developed and implemented a well-rehabilitation program using a mild acid and aggressive swabbing and bailing. To permanently address the clogging issue, we designed and installed a sulfuric acid delivery system for pH adjustment of the treated water. This has produced a SVE/AI system operational run time of over 99%. Beyond the routine O&M activities performed at the landfill, INTERA has responded to a number of unique and challenging issues. The perpetual decomposition of waste material causes differential settling. This issue results in unequal stresses to buried and surficial infrastructure and causes drainage issues across the site. To address this, INTERA developed a formal grading and drainage plan for the landfill and have conducted annual grading and drainage work in accordance with this plan. We have removed relic electrical infrastructure that posed a constant hazard to site workers and the public (the landfill site is used for recreational vehicle parking during the annual Albuquerque International Balloon Festival [AIBF]); developed a Public Access Plan; remedied the unequal settlement of the SVE building footings with a new foundation design that allows for adjustments to be made to the building as subsidence continues; and prepared the landfill site for the annual AIBF.