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Mr, Jeff Cosgray and Ken Yea <br /> • -2 ' 23 October 2009 <br /> Mountain House Site#4 . <br /> and KMPL at MH Site #4. The OVP carried crude oil (crude) from Bakersfield to <br /> Chevron's refinery in Richmond from the early 1900s to the 1970s. On 6 May 2009, <br /> Central Valley Water Board staff issued a No Further Action Required (NFAR) letter for <br /> the OVP at MH Site #4. <br /> Our comments are presented below. <br /> 1. The results of fingerprint analyses conducted by Chevron have failed to clarify <br /> whether the refined product detected in the vicinity of the active pipelines originated <br /> from KMEP or Chevron. This may be a result of commingling of OVP, BAPL and <br /> KMPL releases. KMEP's and Chevron's pipeline integrity investigations showed no <br /> evidence of releases from the active pipelines at MH Site #4. However, the <br /> laboratory analytical results showed that the samples are weathered. Therefore, any <br /> spills could have predated record keeping for these events. Additionally, the lateral <br /> and vertical extents of the groundwater pollution at the MH Site #4 have not been <br /> delineated. <br /> These findings uphold the need for a soil and groundwater investigation work plan, <br /> as stated in the Central Valley Water Board staff's 4 December 2008 letter. The work <br /> plan should be prepared cooperatively by both KMEP and Chevron. The purpose of <br /> the work plan is to delineate the lateral and vertical extent of refined petroleum in soil <br /> and groundwater at MH Site #4. Once the extent is defined, a feasibility study may <br /> be required to determine an appropriate cleanup method. <br /> 2. Regarding soil cleanup levels, Chevron should be aware that the Central Valley <br /> Water Board does not use San Francisco Bay Regional Water Quality Control Board <br /> Environmental Screening Levels (Region 2 ESLs) as threshold criteria for evaluating <br /> soil data. Soil contamination levels below ESLs do not constitute sufficient <br /> justification to discount site cleanup. Furthermore, the Central Valley Water Board's <br /> Basin Plan states that, unless specified otherwise, all Central Valley groundwater is <br /> considered a potential drinking water source. To determine soil cleanup levels to <br /> protect this beneficial use, we suggest using the June 1989 Designated Level <br /> Methodology for Waste Classification and Cleanup Level Determinations (DLM). The <br /> calculation must include a discussion of any assumptions and the rationale for the <br /> values used in the calculation. The DLM may be downloaded from our website at <br /> htt ://www.waterboards.ca. ov/centralvaile / laps oliciesl uidance/index.shtml. <br /> By 30 December 2009, please submit a site assessment work plan for the MH Site #4. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4811 <br /> or by email at betaylor@waterboards.ca.gov. <br /> y; BRIAN TAYLOR, P.G. <br /> Engineering Geologist <br /> cc list on Page 3 <br />