Former Eureka MGP Site Gas Pipeline Relocation

PIVOX Corporation served as construction contractor for site preparation, gas pipeline relocation, stormwater management/treatment and restoration at PG&E’s former Eureka Manufactured Gas Plant (MGP) site.   This project is one of 20 MGP remediation projects successfully completed by PIVOX for utility clients throughout California.

The Eureka manufactured gas plant (MGP) was constructed in Eureka, CA in 1907 and operated through the 1940’s. Since the abandonment and removal of the plant’s features in the early 1950s, MGP wastes and related impacts to soil, vapor and groundwater have been documented at the site during previous site investigations.

As part of the site preparation activities prior to site-wide remediation, a natural gas pipeline that resided within the footprint of the proposed remediation area was relocated to the perimeter of the property within a dedicated 20-foot-wide easement. PIVOX corporation completed removal of contaminated soils to a depth of approximately six feet below grade within the easement and backfilled the excavation with clean fill to allow the pipeline contractor to relocate the active natural gas line without potential exposure to MGP impacted materials. Due to the site’s proximity to Humboldt Bay, the water table beneath the site ranged from four to six feet below ground surface.

PIVOX Corporation installed a groundwater treatment system (GWTS) at the project site capable of treating up to 200 gallons per minute of impacted groundwater collected from within the open excavation. Due to the relatively small size of the project site, the GWTS installation setup had to be installed within a compact footprint to ensure that truck access routes were not obstructed. The system influent settling tank, bag filters, granular activated carbon treatment vessels, effluent tanks, and associated transfer pumps. The treatment system was installed within secondary containment to prevent accidental releases of untreated groundwater during system operation. Treated groundwater was sampled within the effluent tank and analyzed prior to discharge into the municipal sewer system.