Learn about our environmental activities at Topock

Map of Topock Compressor Station near Needles, California and the Colorado River

We are committed to safety, reliability, and environmental stewardship at the Topock Compressor Station. That commitment includes the investigation and cleanup of groundwater and soil at and near the station. The California Department of Toxic Substances Control (DTSC) and the U.S. Department of the Interior (DOI) oversee our efforts, and we also work closely with several nearby communities and Native American Tribes. We regularly meet with and invite input from several communities, Tribes, agencies, and organizations both upstream and downstream of the station. Tribal representatives also play a vital role in monitoring our project activities.


Comprehensive Environmental Program

Extensive environmental studies have been conducted or are in progress at the Topock Compressor Station and surrounding area. These studies help guide cleanup and stewardship activities and ensure compliance with all operating permits and regulatory requirements. This page summarizes our environmental activities.


Groundwater Investigation and Cleanup

All data collected to date confirm that no chromium has reached the Colorado River: chromium has never been detected in any river water or sediment sample collected during the long-term monitoring program overseen by DTSC and DOI.


Other findings and cleanup activities include:


  • Interim cleanup measures have been actively treating groundwater since 2005 and will continue until the final remedy selected by DTSC and DOI is approved, constructed, and operating as designed.
  • The final remedy design and decision-making process included an extensive effort to include input from technical experts and several local communities, Native American Tribes, and other organizations and stakeholders.
  • The cleanup method is a proven technology and involves installing a line of “in-situ” (in-place) treatment wells along the National Trails Highway corridor north of the station. Fresh water and recirculated treated/amended water will be injected to the west of the affected groundwater, helping to push the groundwater through the in-situ treatment zone where hexavalent chromium will be treated. Extraction wells near the river will capture the treated water and recirculate it. This recirculation and "flushing" action will help speed up the treatment process and overall time needed to achieve cleanup goals.
  • Construction is expected to begin in 2018, with the first phase of work complete in about 2020 and remaining work by about 2022. Long-term monitoring of the remedy will continue for many years to confirm the design is working and that cleanup goals and all other requirements are met.

Explore more details about our groundwater cleanup activities on DTSC’s Groundwater Cleanup webpage.



Person showing a soil sample from Topock

Soil Investigation and Next Steps

With oversight by DTSC, DOI, and Tribal Monitors, all approved soil sampling activities have been completed. Results to date show that impacts from historical operations are mostly on and near the station property.


Additional sampling may be performed, if determined by the agencies, until the nature and extent of affected soil is defined. All sampling locations are carefully monitored to respect, avoid, and protect sensitive cultural and biological resources.


Soil investigation results will help DTSC, DOI, and PG&E determine what next steps may be needed. Meanwhile, some soils have already been fully characterized and removed from the property.


Protecting Cultural and Biological Resources

We take great care during all our project activities because the station is located within a culturally and ecologically rich area.


For example, we:


  • Consult with several Tribes to make sure we understand the history and current sensitivities in the area
  • Integrate Tribal Monitors into our field work to help ensure that we properly respect, avoid, and protect archeological resources and culturally significant areas
  • Work with DTSC, DOI, and other agencies to study, map, and protect plants and animals nearby
  • Collaborate with interested stakeholders to avoid or reduce the effects of field work on our neighbors and the sensitive species and cultural sites that share the area with us

Learn more about the Topock program

Visit our Topock Compressor Station page and DTSC’s project website.


Program schedules are subject to change but continually updated as needed and posted on DTSC’s project website.