The Harrison Road Landfill accepted municipal solid waste from 1972 until it closed in 1997. Data indicates soil vapor contaminated with volatile organic compounds (VOCs), specifically tetrachloroethene (PCE), migrated from the waste to the groundwater table and caused groundwater contamination of PCE at levels above regulatory standards. The City operated a deep soil vapor extraction (SVE) system to remove the source of the groundwater contamination, and a groundwater pump and treat system to control and clean up the PCE contaminated groundwater. In addition, a landfill gas flare system was constructed to control the migration of methane and VOCs from the waste. The site is regulated under the Arizona Department Environmental Quality (ADEQ) Solid Waste Unit. The groundwater pump and treat system was shut-down in December 2015 as VOC concentrations have been below regulatory standards since 2013.
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January, April, July, & October
The City conducts quarterly landfill gas monitoring at perimeter probes during these months every year to monitor for methane migration at the property boundary.
May & November
The City monitors the groundwater quality semiannually at site wells and a downgradient private production well. Monitoring reports are prepared documenting the results.
April & October
The City conducts closed landfill site inspections during these months. A report documenting site conditions will be prepared after the inspections.
The groundwater pump and treat system was shut down as VOC concentrations have been below regulatory standards since 2013. The groundwater is monitored quarterly at select wells. Should concentrations rebound, the system will be turned back on.
The Arizona Department of Environmental Quality (ADEQ) provides approval to turning-off the groundwater treatment system. The remediation system has successfully cleaned-up the groundwater for tetrachloroethene (PCE) and trichloroethene (TCE) to concentrations below regulatory standards. The city will develop a work plan prior to shutting down the system for continued monitoring of the groundwater. Should concentrations in the groundwater rebound, the system can be turned back on.
The city installed the new downgradient groundwater well HLM-550 along Wingate Road. The well is monitored quarterly and all VOC results are below the AWQS.
An existing groundwater monitoring well was converted to an extraction well to better contain the plume.
Groundwater pump and treat system began operation. The sytem is designed to remove and treat groundwater impacted with volatile organic compounds (VOCs), primarily tetrachloroethene (PCE) and trichloroethene (TCE). The treatment system consists of two 4,500 pound granular activited carbon (GAC) vessels. The treated water is re-injected into the groundwater.
1999-2002 & 2005-2006
Operation of the deep SVE and air injection system (AI) began in order to remove and treat VOCs from the deep soil vapor. The system removed and treated 18,034 pounds of VOCs. This system is currently not operating, but the City monitors the vapor wells periodically and will return the system to operation if needed.
The City acquired land rights and installed groundwater extraction wells, monitoring wells, injection wells, infrastructure and piping for the groundwater extraction and treatment system.
ADEQ Solid Waste Unit approved the use of an SVE system to remove the source of the contamination, and a groundwater extraction and treatment system to contain and clean up the PCE plume.
A landfill gas extraction and flare system was installed and is still in operation today. From 1995-1998 a temporary emergency flare was in operation.
The City closed the landfill according to Federal and State regulations. Closure included construction of the landfill cover for the landfill, including a graded earthen cap and landscaping to prevent erosion. This date marks the beginning of the 30-year post-closure monitoring and management period.
The City stopped accepting waste at the Harrison Landfill.
Groundwater investigation completed to characterize the aquifer properties and extent of the contamination.
The City installed shallow landfill gas monitor probes to monitor methane concentrations between the landfill and nearby homes and businesses and began routine monitoring.
Groundwater contamination of PCE was first discovered in monitoring wells that were not used to provide drinking water supply. Additional groundwater monitoring wells were installed to characterize the extent and migration rate of the contamination. The City commissioned studies to determine the best method of groundwater remediation.