The Estes Landfill WQARF site is located in Phoenix, Arizona. The groundwater contamination plume is bounded approximately by the Salt River to the north, the Sky Harbor Expressway (Hwy. 153) to the east, Magnolia Street to the south, and S. 37th Street to the west. Groundwater contamination from the landfill extends in an oval shape for approximately one-half mile to the west and north of the landfill.
The plume boundaries depicted on the site map represent the Arizona Department of Environmental Quality’s (ADEQ) interpretation of the data available at the time the map was constructed. The map is intended to provide the public with basic information as to the estimated extent of known contamination as of the date of map production. The actual extent of contamination may be different. Therefore, the plume boundaries may change in the future as new information becomes available.
ADEQ sampled 17 monitor wells in March 2013. Trichloroethene (TCE) was detected in four groundwater samples. Concentrations ranged from 0.64 micrograms per liter (µg/L) to 1.2 µg/L. TCE concentrations were below the Aquifer Water Quality Standard (AWQS) of 5.0 µg/L. Vinyl chloride (VC) concentrations exceeding the AWQS were found in eight wells. Concentrations ranged from non-detect (<0.50 µg/L) to 16 µg/L.
A community advisory board (CAB) has been formed for the site. These meetings are open to the public. The CAB is not currently meeting regularly. Past CAB meeting agendas and minutes can be viewed at the Information Repositories listed below.
1953 - 1973: The Estes Landfill was privately owned and operated from 1953 until 1973 when it was permanently closed. The unregulated landfill was reported to have accepted industrial, commercial, residential and liquid wastes. Liquid wastes which would now be considered hazardous were discharged into ponds excavated in the refuse pits.
1980 - 1982: Groundwater contamination was discovered in two industrial supply wells located down gradient of the landfill. One of these wells was located on the Bradley Landfill and one on the former Tanner property west of 40th Street. The primary contaminants detected in the supply well were 1,2-DCE and vinyl chloride, which are degradation products of TCE. Groundwater sampling of eight wells, four on the Estes Landfill and four on the Bradley Landfill through the mid-1980s, confirmed the presence of groundwater contamination in the area. The greatest contaminant concentrations were in the vicinity of a former liquid waste disposal pit on Estes Landfill.
1997: The COP submitted a draft remedial investigation (RI) report for ADEQ’s review in September.
During a routine groundwater monitoring event, the maximum PCE concentration observed throughout the site was 3,000 µg/L.
1998 - 1999: The site was placed on the WQARF Registry in April 1998 with an eligibility and evaluation score of 45 out of a possible 120. Until 1999, ADEQ provided regulatory oversight and technical review of site investigations and activities performed by the COP. In March 1999, ADEQ took over responsibility of completing the RI, feasibility study (FS) and other site activities. ADEQ completed the RI report in July 1999. The report defined the extent of soil and groundwater contamination emanating from the landfill.
2001 - 2003: The Land and Water Use Study was issued on July 9, 2001 as a supplement to the July 1999 RI report. With the issuance of the remedial objectives (RO) report in January 2002, the RI report for the site was final. After completion of the FS for the site, the proposed remedial action plan (PRAP) was issued for public comment on June 30, 2002.
2007: Bi-annual groundwater monitoring was performed in March and August to evaluate groundwater flow patterns and chemical migration patterns. Depth-to-water measurements were collected in September. A site visit was conducted in November to evaluate the current status of the site.
2008: In January, landfill vapor samples were collected. The samples were analyzed for volatile organic compounds (VOCs) and methane. Groundwater elevation measurements were collected in February and September to evaluate groundwater flow and chemical migration patterns. TCE concentrations ranged from <0.5 µg/l to 2.8 µg/l. Well EW-6 was the only monitor well where cis-1,2-DCE concentrations exceeded the AWQS of 70 µg/l. The highest concentration of vinyl chloride was detected in on-site Well EW-6 at a concentration of 510 µg/l. Other VOCs detected in the groundwater samples did not exceed their respective AWQSs.
2009: ADEQ personnel met with the COP on August 24th to discuss the Responsiveness Summary and ROD.
2011: Groundwater samples were collected in February and September.
2012: ADEQ sampled 19 monitor wells in March. TCE was detected in seven groundwater samples with concentrations ranging from 0.61 µg/L to 1.9 µg/L. TCE concentrations were below the AWQS of 5.0 µg/L. Detected cis-1,2 dichloroethene (cis-1,2-DCE) concentrations were also below their AWQS of 70 µg/L. Vinyl chloride (VC) concentrations exceeding the AWQS were found in eight wells at concentrations ranging from non-detect (<0.50 µg/L) to 42 µg/L.
2013: ADEQ sampled 17 monitor wells in March. TCE was detected in four groundwater samples with concentrations ranging from 0.64 µg/L to 1.2 µg/L. TCE concentrations were below the AWQS of 5.0 µg/L. Detected cis-1,2 dichloroethene (cis-1,2-DCE) concentrations were also below their AWQS of 70 µg/L. Vinyl chloride (VC) concentrations exceeding the AWQS were found in eight wells at concentrations ranging from non-detect (<0.50 µg/L) to 130 µg/L.
The current contaminants of concern in soil include arsenic, lead and thallium. The contaminants of concern in groundwater include vinyl chloride, cis-1,2-dichloroethene (cis-1,2-DCE), TCE, benzene, bis(2-ethylhexyl)phthalate, arsenic, barium, chromium, lead, and manganese. Contaminants of concern at the site may change as new data become available.
Although the groundwater beneath the landfill is contaminated, there are no known drinking water wells within the area of contamination. Drinking water provided by the COP and it is tested regularly to ensure that it meets all state and federal water quality standards.
The site is underlain by approximately 115 to 175 feet of heterogeneous alluvial sediments and several hundred feet of consolidated sedimentary bedrock. The alluvium beneath the site contains sediments (cobbles, gravel, sand and fines) of similar composition with differing hydraulic properties. Four distinct alluvial hydrostratigraphic units have been identified at the site.
The major hydrologic feature in the study area is the Salt River immediately adjacent to the site. The Salt River is normally dry, but periods of above average precipitation and/or releases from upstream reservoirs have caused river flows to occur that have exceeded 100,000 cubic feet per second. These river flows cause rapid recharge to the underlying aquifer.
Groundwater flow is generally west to northwest across the site during “dry” river conditions and west to southwest during sustained river flow events. Water levels have fluctuated historically, between 25 to 70 feet below ground surface at the site and are significantly influenced by recharge from river flow events. Depth to groundwater is currently approximately 60 feet bgs at the site.
*In Arizona, but outside the Phoenix area, call toll-free at (800) 234-5677.
Interested parties can review site information here on this page and at the ADEQ Record Center located at 1110 W. Washington Street, Phoenix, Arizona. Please contact (602) 771-4380 or (800) 234-5677 ext. 6027714380 for hours of operation and to schedule an appointment. To review site information at a location near you, please contact the designated Community Involvement Coordinator.Site Map
Remedial Investigation Report