Mesa Property Set for Return to the Navy

Mesa Location

The San Onofre Nuclear Generating Station (SONGS) sits on land leased from the Navy which is part of Marine Corps Base–Camp Pendleton. Next month, a portion of the land on the eastside of Interstate 5 will be returned to the Navy after years of demolition and restoration work.

Known as “the Mesa,” the property was utilized as a support facility for SONGS, though not part of the site licensed by the Nuclear Regulatory Commission. The dismantlement work began soon after the SONGS plant was officially retired. The overall project has been guided by the decommissioning principle of Environmental Stewardship.

“The Mesa was its own city,” said Jeffrey Roland, project manager for the Mesa work, who has worked at SONGS since 2011. “It had medical services, fire, fabrication, engineering, and support groups. Personnel who worked (at SONGS) before 2013 all reported here to the Mesa for in-processing and training.”

There were garage operations, machine shop activities, warehouses and a learning center including a state of the art simulator for operator training. The Mesa also had a campground for temporary workers who helped construct parts of the SONGS facility and who would perform work at SONGS during maintenance shutdowns.

The Project

Many of the structures on the Mesa had been demolished prior to SCE’s Environmental Services Department becoming involved in the project. The Navy requested SCE to return the site in a condition with no land use restrictions. Such an effort would require environmental assessments to be done.

“We entered into what’s called a Voluntary Cleanup Agreement with California EPA’s Department of Toxic Substances Control so we could demonstrate that whatever actions were necessary to make the site suitable for unrestricted use, we would take them,” said John Johnsen, an SCE senior environmental science advisor.

Johnsen, a registered California Environmental Health Specialist for more than 30 years, joined the project in 2016 to assist with site characterization and any necessary remediation. While the Mesa was not home to work involving radionuclides, industrial chemicals were used at the site and processes, such as sand-blasting, would require some ground clean-up. Subsequently, several rounds of soil sampling, soil vapor sampling, and groundwater sampling were required to fully characterize the site to the satisfaction of the DTSC and the Navy. That included 860 soil borings, and installing 929 soil vapor probes, and 20 groundwater monitoring wells.

20200710_093213
Soil is excavated from the Mesa property.

Once it was determined that soil excavation would be the optimal method of remediating the site, truckloads of soil material were removed from the area and backfilled with native soils from another Camp Pendleton location. Subsequent testing of the site has shown the clean-up work was successful.

Getting to that end state required a focus on safety. “The drilling of the soil samples, the drilling of the soil vapor probes, the drilling of groundwater wells are all high-risk activities,” Johnsen said. “Further, excavating a hole to 30 feet below the surface must be done with the utmost attention to potential safety issues. The whole project team did an excellent job in that respect, even with the COVID-19 restrictions.”

Johnsen says the partnerships forged throughout the project helped bring it to closure, including with state agencies, environmental consultants, and the Navy.

“I feel like it brings to closure a chapter in SONGS history,” Roland said. “When the keys are turned over, this project team can walk away knowing that SCE gave the Navy the Mesa back in the condition that was requested and did it safely and successfully.”

(Posted May 27, 2021)