Waste Programs Division: Cleanups: Topock Compressor Station Groundwater VRP Site

Topock Station

Pacific Gas and Electric Company's (PG&E) Topock Compressor Station is located in eastern San Bernardino County, approximately 12 miles southeast of Needles, California, along the Colorado River. The nearest communities are Moabi Regional Park, California (one mile northwest); Topock, Arizona (one-half mile east, across the Colorado River); and Golden Shores, Arizona (five miles to the north, across the Colorado River).

In 1996, the California Department of Toxic Substances Control (DTSC) entered into an agreement with PG&E to investigate the nature and extent of hexavalent and total chromium contamination resulting from releases from the PG&E Topock Compressor Station in Needles. Under the terms of the agreement, PG&E is following an investigation and cleanup process governed by a federal law known as the Resource Conservation and Recovery Act (RCRA). Additionally, because some of the property affected by operations at the compressor station is owned by the U.S. Department of the Interior (DOI), DOI is overseeing remedial actions at the site pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). Due to the Topock Compressor Station's proximity to the Colorado River, ADEQ participates in investigation activities as they relate to the Colorado River and potential future impacts to Arizona's groundwater.

Arizona's Involvement in Current Groundwater Investigations

Arizona Well Drill Topock Compressor Station

In 2005, ADEQ initiated a yearlong groundwater study in Arizona to assess whether there was a potential threat to human health from hexavalent chromium in the drinking water supplies for the Arizona communities of Topock and Golden Shores. At the time of the document review, the study concluded that there was no immediate threat to human health from use of groundwater for drinking water in Arizona. However, available information at the time did not allow ADEQ to completely assess potential long-term threats to the future water supply because the eastern extent of hexavalent chromium contamination in groundwater was not defined. As such, the study recommended the installation of groundwater monitoring wells in Arizona. The final report is available at ADEQ's Phoenix office and at the document repositories listed below.

In December 2006, PG&E entered ADEQ's Voluntary Remediation Program (VRP) in order to initiate a Colorado River investigation that would include the Arizona side of the river. PG&E submitted a work plan in March 2007 with the primary goal to define the eastern extent of the hexavalent chromium plume emanating from the Topock Compressor Station. The VRP approved the work plan in May 2007.

The well installations proposed in the work plan were completed in spring 2008. Three wells were installed, including a slant well beneath the Colorado River, a vertical well at the Havasu National Wildlife Refuge (HNWR), and a vertical well at the Topock Marina. Data for total chromium and hexavalent chromium as of April 2015 are shown below:

Well Name: Sample Date: Hexavalent Chromium (ug/L): Total Chromium (ug/L):
“Slant Well” MW-56S 04/28/15 <0.2 <1.0
“Slant Well” MW-56M 04/28/15 <2.0 <1.0
“Slant Well” MW-56D 04/28/15 <2.0 <1.0
“HWNR Well” MW-54-85 04/28/15 <1.0 <1.0
“HWNR Well” MW-54-140 04/28/15 <1.0 <1.0
“HWNR Well” MW-54-195 04/28/15 <2.0 <1.0
“Topock Marina Well” MW-55-45 04/29/15 <0.2 <1.0
“Topock Marina Well” MW-55-120 04/29/15 6.7 7
ug/L: micrograms per liter
<1.0: compound was not detected by the laboratory above the reporting limit.

As of January 2014, the Federal Safe Drinking Water Act and Arizona's Aquifer Water Quality Standard for total chromium is 100 ug/L. Effective July 1, 2014 the California Safe Drinking Water Act established a standard for chromium VI of 0.010 milligrams per liter (mg/L). There is not a separate drinking water standard for hexavalent chromium in Arizona. At this time, there is no indication that the chromium concentrations identified in the Topock Marina Well are from a source emanating from the Topock Compressor Station.

Groundwater Monitoring Program and Surface Water Monitoring

In addition to the groundwater well installations, the groundwater and Colorado River surface water monitoring activities that began in 1997 continue to this day. The current Groundwater Monitoring Program includes more than 100 monitoring wells with quarterly and semi-annual sampling. Additionally, quarterly surface water samples are collected from four shoreline wells and ten river channel locations. To date, Colorado River sampling results consistently indicate that the river is not impacted by chromium.

At this time, the U.S. DOI and California Department of Toxic Substances Control (DTSC) continue to oversee the larger study area as part of the RCRA and CERCLA investigations. The VRP remains active as a stakeholder in these investigative activities and also continues to monitor the surface water data and quarterly sampling data obtained from all wells included in the Groundwater Monitoring Program.

Timeline -- (PDF)

Topock Compression Station Soil Digging

Soil Investigation

PG&E is conducting soil investigation and remedial activities at the site under RCRA and CERCLA, pursuant to agreements with DTSC and DOI, respectively. The soil is in the RCRA Facility Investigation/Remedial Investigation (RFI/RI) phase of the cleanup process. Soil and related investigation activities are being conducted at several areas located outside and inside of the Topock Compressor Station fence line. The perimeter areas adjacent to the Topock Compressor Station fence line and the storm drains leading from the Topock Compressor Station to areas outside the fence line are also included in the investigation.

Community Notice -- (PDF)
Timeline -- (PDF)

See Also:

For detailed information regarding all aspects of the investigation and remediation aspects of the Topock Compressor Station, please visit:

Document Repositories

Arizona Department of Environmental Quality
ADEQ Records Center
Phoenix, Arizona 85007
(602) 771-4380
(602) 771-4389 - Fax
Monday through Friday: 8:30 am to 4:30 pm
Saturday and Sunday: Closed

Looking East Topock Compresor Station

Golden Shores/Topock Library Station
13136 Golden Shores Parkway
Topock, Arizona 86436-1086
Phone: (928) 768-2235
Library Hours:
Monday, Friday and Sunday: Closed
Tuesday, Thursday and Saturday 9 a.m. to 1 p.m.
Wednesday 2 p.m. to 5 p.m.

Lake Havasu City Branch Library
1770 McCulloch Boulevard
Lake Havasu City, Arizona 86403
Phone: (928) 453-0718
Library Hours:
Monday and Wednesday- 9 a.m. - 6 p.m.
Tuesday and Thursday- 9 a.m. - 8 p.m.
Friday and Saturday - 9 a.m. - 5 p.m.
Sunday - Closed

Parker Public Library
1001 South Navajo Avenue
Parker, Arizona 85344
Phone: (928) 669-2622
Library Hours:
Monday through Thursday - 10 a.m. - 7 p.m.
Friday through Sunday - Closed

California DTSC

PG&E Topock Compressor Station, Needles, California - Environmental Investigation and Cleanup Activities