History and Overview of Cleanup

Geothermal Inc The Geothermal Inc. (GI) property is the site of a former geothermal waste disposal facility that is located about 2.5 miles southeast of Middletown on Butts Canyon Road, Lake County, California (Site). The facility, which operated from 1976 to 1986, consisted of evaporation ponds and solid waste disposal trenches where companies disposed mud and waste generated from exploratory/development drilling and waste from the power generation operations at the nearby Geysers Energy Field. PG&E was one of 17 companies and agencies who used the facility and who cooperated to close the Site after the former facility operator, Geothermal Inc., went bankrupt. PG&E purchased the property in 2003 and subsequently took over the responsibility for the facility.

From 2003 to 2006, PG&E conducted Site closure activities under the oversight of the California Regional Water Quality Control Board, Central Valley Region (Water Board). The Water Board is responsible for protecting the waters of the State and in particular, California’s water supply. The following activities were performed to close the facility in accordance with an approved closure plan:

Crews Installing Landfill
  • Solar evaporation of 21 million gallons of pond water;
  • Excavating and mixing 186,000 cubic yards of waste with clean soil and the consolidation of these materials into a 15-acre landfill covering four of the original evaporation ponds on the Site;
  • Filling/re-grading the remaining waste evaporation ponds with clean soil;
  • Installation of an engineered cover over the landfill to prevent surface water infiltration into the landfill;
  • Grading of 90-acres around the landfill to promote rain water runoff away from the landfill;
  • Lowering the neighboring Freeman Lake and planting 32-acres of Eucalyptus and poplar trees around the landfill to lower groundwater levels;
  • Installing water supply and irrigation systems for the tree plantations and fire protection; and
  • Constructing four acres of new wetlands and constructing additional ecological habitat.

The final cover that was installed on the landfill consists of a layer of high-density plastic covered by two feet of clean soil. The soil was then planted with grasses. Eucalyptus and poplar trees were specifically chosen for planting around the landfill to tap into the groundwater and lower groundwater in the vicinity of the landfill.

Since 2006, PG&E has performed post-closure maintenance activities that include inspection and maintenance of the closed landfill, tree plantations, and surrounding parts of the property; as well as semi-annual groundwater and surface water monitoring. PG&E also grazes the area around the landfill to reduce the threat of wildfire.

Grasses on landfill Tree on landfill

Project Status Update

In 2012, PG&E submitted a Closure Evaluation Report to the Water Board, which concluded that all Water Board closure requirements were achieved, except the required year-round separation between groundwater and the waste in the landfill. Separation is being achieved during most of the year for the entire landfill; however, there are limited areas of the landfill where separation between the groundwater and the waste in the landfill is not achieved during part of the year. Since this report, PG&E has been performing additional studies to further define the complex geological, surface water, and groundwater conditions at the Site. In the winter of 2014, PG&E will submit a report to the Water Board that will further evaluate the implemented closure and assess whether it will achieve the required year-round separation between groundwater and the waste in the landfill or if additional measures are needed. PG&E will continue to keep the public informed about this project as more data become available.

Connecting with our Community

Middletown High School Field TripAs part of its commitment to community engagement in the local area, PG&E works with various organizations including the Middletown High School to promote opportunities for local youth to participate in learning activities at the Site. Most recently, PG&E invited students from the Middletown High School Advanced Placement Environmental Science class to learn more about the diversity of ecological habitats and wildlife at the Site through bird and wildlife monitoring and hands-on science activities.

Wildlife Habitat Council Overview and Certification

Integrity of Landfill CapThe closure activities PG&E implemented at the Site required the removal of some wildlife habitat – including wetland and riparian areas and some oak trees. Working with regulatory agencies, PG&E replaced these resources, creating new wetlands and replacing trees on the property.

PG&E employees and contractors also went beyond the regulatory requirements and created additional wildlife habitat on the property. Logs and brush from removed trees were arranged into piles to enhance habitat for ground and shrub nesting birds, reptiles, and small mammals. Two ponds were created to supplement wildlife habitat and provide water during the hot and dry summer/fall months.  In addition, a permit was secured from the State Water Board to maintain Freeman Lake as wildlife habitat. Owl nesting boxes were installed around the perimeter of the closed landfill to house barn owls that naturally limit the population of ground squirrels and gophers, which are considered pests on capped landfills because of the borrows they create.

In November 2010, the Wildlife Habitat Council (WHC) awarded PG&E a Wildlife at Work certification for its wildlife enhancement efforts at the property. WHC is a non-profit, non-lobbying organization dedicated to restoring and enhancing wildlife habitat by promoting partnerships with corporations and community members to conserve and restore wildlife habitats on corporate lands.

Frequently Asked Questions

Wildlife Habitat Who oversees PG&E’s work at this site?
The Water Board, part of the California Environmental Protection Agency, is the regulatory agency responsible for overseeing and approving the work. Some work also requires permits from other agencies, including Lake County, the US Army Corps of Engineers, and the California Department of Fish and Wildlife.

What chemicals were found in the soil and groundwater?

Waste in the landfill contains drilling muds, construction debris, sulfur compounds from geothermal energy production, and naturally-occurring mineral compounds and elements from the surrounding region. Elevated concentrations of total dissolved solids, chloride, boron, and sulfate are present in the groundwater in the vicinity of the landfill. Testing has determined that the geothermal waste material in the landfill is not hazardous. This has been confirmed by the Water Board. The groundwater impacts are confined to the property and the impacted groundwater has remained stable since groundwater monitoring at the site began in the early 1990s.

Why did PG&E choose to consolidate and cap the wastes as opposed to removing them?
An evaluation  of cleanup alternatives was performed that was based on a prescribed list of factors including effectiveness, feasibility, regulatory and public acceptance, overall protection of human health and the environment, and cost. Based on this evaluation, the Water Board determined that consolidating and capping the wastes on-site was the best cleanup alternative.

Vernal PoolsHas PG&E completed the closure of the landfill?
PG&E has achieved all the requirements of the Water Board’s remedy for the closure of the landfill except the required year-round separation between the groundwater and landfill waste. Separation has been achieved during most of the year for the entire landfill; however, there are currently limited areas of the landfill where separation is not achieved during part of the year. PG&E is currently engaged in further studies and conversations with the Water Board to determine whether separation can be achieved. If the Water Board determines that additional remediation or closure activities are necessary, PG&E will then inform the community.

Can surface water or groundwater impacted by the site spread to my property or impacted groundwater in the area outside the property?
PG&E has a robust groundwater monitoring well network and performs surface- and groundwater monitoring on a semi-annual basis and the results are submitted to the Water Board. Since 1992 monitoring results indicate that surface- and groundwater have not impacted neighboring properties. In addition, results indicate the area of impacted groundwater remains stable, on-site, and has not moved for over two decades. PG&E will continue to conduct semi-annual surface- and groundwater monitoring and report these results to the Water Board, which is consistent with the agency’s monitoring plan for the Site.

Why do I see PG&E crews at the former landfill?
PG&E regularly monitors and maintains the landfill, tree plantations, and the property to ensure the effectiveness of the landfill closure and to implement the fire prevention plan for the Site. PG&E also conducts semi-annual monitoring of the surface and groundwater conditions.

What would happen if there was a fire and the tree plantations burned?
PG&E has a robust fire prevention program that includes annual goat grazing and brush clearing to reduce fire hazards, maintenance of the tree plantations, maintenance of the on-site fire suppression facilities and water supplies, and maintenance of a network of roads and turnouts throughout the Site to facilitate access and segregate the tree plantation stands. While a major tree plantation fire is unlikely, if they were to burn in a fire to the point where they could not recover, PG&E would actively work with the Water Board to develop a replacement program to maintain groundwater levels.

What would happen to the landfill in an earthquake?
The landfill was designed to withstand an earthquake and the mixed waste and clean soil is firm enough that it is not expected to be damaged. The landfill would be inspected following significant earthquakes and any settlement repaired.

For More Information

Wildflowers Blooming Further information about this site as well as an archive of all quarterly reports can be found on the Water Board’s GeoTracker website at:

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