May 2009 Report from Regional Water Quality Control Board on MTBE in Cambria

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The Regional Water Quality Control Board for the Central Coast Region (Central Coast Water Board) met last Friday (May 8). On the agenda was an update on Cambria’s MTBE situation. According to the report, the Central Coast Water Board staff oversees cleanup activities on numerous petroleum underground storage tank (UST) cases involving methyl tertiary-butyl ether (MTBE).  Here is the part of the staff report concerning Cambria (the new information is presented in italics):

Chevron Cambria service station, located on the corner of Main Street and Burton Drive in Cambria, has been a Central Coast Regional Water Quality Control Board (Central Coast Water Board) lead groundwater investigation and cleanup case since December 1993. In 1995 Chevron Products Company commissioned the removal of a UST system and transferred ownership of the service station to an independent ownerloperator who installed a new UST system. Chevron is cleaning up a petroleum hydrocarbon discharge, including the fuel additive MTBE, from the original UST system. The discharge threatened groundwater in Cambria Community Service District (CCSD) Wells No. 1 and 3, which provide supplemental water to the community of Cambria.
As part of interim corrective action beginning in May 2000, Chevron continuously pumped MTBE contaminated water from four onsite wells. Currently, there are 15 shallow groundwater extraction wells in operation. Beginning in November 2000, Chevron began full operation of groundwater extraction and high-vacuum, dual-phase extraction systems. Both systems operate continuously,
except for periodic system upgrade, mechanical breakdowns, and system maintenance activities. Extracted and treated groundwater is stored in an onsite, 15,000-gallon tank until it is trucked offsite for disposal at the Santa Maria Wastewater Treatment Plant.
During a November 2001 technical work group meeting with Central Coast Water Board staff, CCSD representatives, and Chevron representatives, the CCSD indicated the new temporary high school well had been connected to the Cambria municipal drinking water supply. The CCSD needs the high school well as an alternative water supply. The CCSD installed a wellhead treatment system on their Santa Rosa Creek wells which will enable well use in the event of an emergency. The Santa Rosa Creek Wells have not been impacted with IMTBE. On May 18, 2004, the Central Coast Water Board’s Executive Officer rescinded Cleanup or Abatement Order (CAO) No. 00-28. The CAO required Chevron to provide CCSD with alternative water supply due to loss of CCSD’s Well Nos. 1 and 3. The settlement agreement between CCSD and Chevron explicitly resolves all of CCSD’s claims against Chevron, including claims for an alternative water supply.

Since the Last Staff Report:
The Fourth Quarter 2008 Groundwater Monitoring and Remediation Status Report indicates fhe following:
Monitoring wells within the plume boundaries continue to exhibit MTBE and tertiary butyl alcohol (TBA) concentrations exceeding the cleanup goals of 5 micrograms per liter (pg/L)and) 12 pg/L, respectively; however, current concentrations have decreased significantly compared to historical maximum values. The fourth quarter 2008 maximum MTBE concentration was detected in piezometric well P-5 at 620 pg/L and the maximum TBA concentrations was detected in monitoring well MW-7 at 170 pg/L.  Historically, maximum concenfrations of MTBE and TBA were as high as 5,500 pg/L and 8,80Opg/L, respectively. Shallow-zone MTBE and TBA isoconcenfration maps are shown on Attachments 1 and 2, respectively. Monitoring wells historically located beyond the plume boundaries continue to be free of detectable concentrations of MTBE and TBA. The high-vacuum, dual phase extraction system was not operated during the fourth quarter 2008. Chevron started an oxygenated groundwater infiltration system at the site to enhance the biodegradation of the petroleum hydrocarbon plume. The groundwater extraction and treatment (GWET) system operated during the reporting quarter. The GWET system extracted and treated approximately 15,000 gallons of groundwafer during the fourth quarter; 10,000 gallons were aerated and re-infiltrated into the subsurface (as described in the following bullet) and the remaining 5,000 gallons were disposed at the City of Santa Maria wastewater plant. On October 15, 2008, Stantec Consulting Corporation (Stantec) initiated the infiltration of oxygenated water at the site. Approximately 10,000 gallons of treated and oxygenated groundwater were infiltrated into the source-zone via infiltration wells MW-IR, HVE-4 and HVE-11. Stantec will continue the oxygenated groundwater infiltration activities, sample collection and analysis to evaluate performance of the enhanced in-situ bioremediation technology.

Read the full report and past reports at the geotracker website.

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