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' California Regional Water Quality Control Board <br /> Central Valley Region <br /> Katherine Hart, Chair 0 <br /> Linda S. Adams Arnold <br /> Secretary for 3685E Street,Fresno,California 906 Schwarze <br /> Environmental (559)445-5116•Fax(559)445-59191nE0 98er <br /> http://www.waterboards.i�a.gov/centralvalley Governor <br /> Protection <br /> TO. Shelton R. Gray FROM: C. Dean Hubbard <br /> Senior Engineering Geologist Engineerin eologist <br /> t <br /> DATE: 6 August 2010 SIGNATURE: <br /> SUBJECT: SOIL AND GROUNDWATER INVESTIGATION REPORT, MOUNTAIN HOUSE <br /> DEVELOPMENT SITE#6, MOUNTAIN HOUSE, SAN JOAQUIN COUNTY <br /> Chevron Environmental Management Company (Chevron) submitted the 25 February 2010 <br /> report entitled Soil and Groundwater Investigation Report (Report), Mountain House <br /> Development Site #6 (Site), Mountain House, San Joaquin County. The Report was prepared <br /> on behalf of Chevron by Science Applications International Corporation -- Benham Companies, <br /> LLC (SAIL). I have reviewed the Report and related 2001 to 2010 project file reports and my <br /> comments are provided below. <br /> The Site, northwest of the intersection of West Byron Road and Wicklund Road, northwest of <br /> Tracy, is within an area predominated by agricultural fields and rural residences. The Site lies <br /> within the West Byron Road and Union Pacific Railroad (UPRR) right-of-way easements. The <br /> historical Old Valley Pipeline (OVP) is parallel to and west of West Byron Road and the former <br /> Tidewater Associated Oil Company (TAOC) pipeline easements, between the road and the <br /> railroad tracks. In addition, two refined petroleum products pipelines are reported to be within <br /> ' the utility corridor easements, but the alignment/locations are unknown. Several soil and <br /> groundwater investigations have been completed at the Site by SAIC and other Chevron <br /> consultants since 2001; copies of historical documents are contained in our files. <br /> ' Previous) based on findings provided in a Jul 2008 soil and groundwater investigation <br /> Y� 9 p Y <br /> report, SAIC determined that crude oil affected soil and groundwater was not defined and <br /> ' additional characterization was needed. SAIC recommended additional borings to investigate <br /> the lateral and vertical extent of impacted soil and groundwater onsite and offsite to the east- <br /> northeast. A workplan was approved by Central Valley Regional Water Quality Control Board <br /> ' (Central Valley Water Board) staff in November 2009. SAIC proceeded to drill soil borings and <br /> obtain soil and groundwater samples for analysis. Previous fuel fingerprint evaluation <br /> determined that the crude oil present was consistent with degraded San Joaquin Valley crude <br /> oil from the historical Chevron pipelines. <br /> According to the findings, affected soil and groundwater were identified at two separate areas, <br /> ' designated as Areas 1 and 2. Area 2 was previously described as two separate impacted <br /> areas but based on the recent reports, were combined collectively into, and henceforth will be <br /> referred to as, Area 2. SAIC's February 2010 Report describes the approximate dimensions of <br /> crude oil affected soil within Area 1 as about 150 feet across. Area 2 consists of one <br /> elongated area of crude oil affected soil, parallel to and within the historical OVP/TAOC <br /> pipelines' alignment, with an approximate dimension of 75 feet to 200 feet across and about <br /> ' California Environmental Protection Agency <br /> ' (rFecyded Paper <br />