History of the Cave Creek Landfill
Cave Creek Landfill (CCL) began operations around 1965 in the area known as the “Old Landfill.” (See maps in "Maps and Images".) Somewhere around 1984, operations shifted to the “New Landfill.” The CCL stopped accepting waste to be buried in the landfill in 1998. (A transfer station continues to operate, but all waste is hauled offsite.) The CCL was permitted to accept residential and commercial municipal solid waste and other wastes including: appliances, barnyard and stable waste, demolition material, non-infectious medical waste, domestic animals (large and small), green waste, foods, and inert materials. As was typical with landfills operated during those times, liners were not required.
As required by law in 1993, the County installed two groundwater monitoring wells (south and southeast of the landfill) and began to monitor these wells along with continuing to monitor an already existing well north of the landfill. Each of these wells is located on County property. In December 1997, trichloroethene (TCE) above the Aquifer Water Quality Standard of 5.0 micrograms per liter (ug/L) was found in the monitoring wells. In 1999, Maricopa County entered into a Consent Order with the Arizona Department of Environmental Quality (ADEQ) which assigns the responsibility for site remediation to the County. The Consent Order has been updated since, most recently in 2016. ADEQ also approved a Remedial Action Plan (RAP) submitted by the County in 2008, and continues to approve periodic revisions to the plan.
The groundwater contamination from CCL is over 700 feet below the ground surface and does not impact any drinking water sources or any other known sources of water use.
There are two critical steps in remediating the contamination, 1) removal of contaminated vapors in the soil, and 2) treatment of contamination in the ground water. Efforts to remove contaminated vapors in the soil have been underway since 2011, beginning with pilot testing of a Soil Vapor Extraction system (SVE). Additional pilot tests were conducted at other vapor wells and a permanent SVE system was constructed and started in 2015. To date, the County has removed more than 46,000 pounds of contaminants using the SVE. The second step of removing contamination is to clean the groundwater through a Groundwater Treatment System (GWTS). Work to construct a system to remove, treat and re-inject water began in 2017. The GWTS will remove contaminated water from under the landfill, clean it to meet Federal drinking water standards, and return the clean water to the aquifer. (See Remediation Activities.) Delays due to permitting, construction and the need for custom built GWTS system components have pushed the completion and start up into 2022.
Maricopa County is committed to this remediation project and has accelerated the pace of the treatment efforts. This compresses the timeline of construction activities to try and keep the impact on the neighborhoods near the landfill to the shortest time possible. Once the current construction phase is over (currently estimated for late 2022) activities will be operational with periodic maintenance of equipment. The impact on the surrounding area should be negligible.
Remediation is ongoing and will continue until complete to the satisfaction of ADEQ.