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<br /> <br />Arcadis U.S., Inc. <br />735 Tank Farm Road <br />Suite 150 <br />San Luis Obispo <br />California 93401 <br />Phone: 805 706 2805 <br />Fax: 805 782 9273 <br />www.arcadis.com <br /> <br /> <br /> <br />1/3 <br />Mr. Brian Hitz, P.G. <br />Engineering Geologist <br />Central Valley Regional Water Quality Control Board <br />1685 E Street <br />Fresno, CA 93706 <br /> <br />Date: August 30, 2021 <br />Our Ref: 30063795 <br />Subject: Case Status Update <br /> Chevron Surland Homes <br /> Lowell Avenue <br /> Tracy, California 95376 <br /> GeoTracker Case No.: SL0607766006 <br /> <br /> <br />Dear Mr. Hitz, <br /> <br />On behalf of Chevron Environmental Management Company (CEMC), Arcadis U.S., Inc. (Arcadis) has prepared <br />this letter in response to the Central Valley Regional Water Quality Control Board (Central Valley Water Board) <br />letter dated June 30, 2021 (Attachment A). The subject of the June 30, 2021 letter was a Request for Status Report <br />for the Chevron Surland Homes site located in Tracy, California (the “site”). In their letter, the Central Valley Water <br />Board requested that CEMC provide an update of all site activities for the installation and sampling of soil vapor <br />probes, including maps showing completed and proposed soil vapor probe locations and the sampling results. In <br />addition, the Central Valley Water Board requested a proposed due date for the Additional Subsurface Investigation <br />Report and Human Health Risk Screening Evaluation (Report). <br />A total of five proposed soil vapor probe locations were approved in the Central Valley Water Board Letter dated <br />October 3, 2019 (Attachment A). Arcadis made multiple attempts to execute an access agreement for each of the <br />five residential properties. As of August 2021, Arcadis has executed access agreements for two of the residential <br />properties including 2532 Dorset Avenue and 2502 Dorset Avenue. Site activities were completed at these two <br />properties, as described below. <br />In December 2019, two soil borings (B-12 and B-13) were advanced at 2532 Dorset Avenue (Figure 2). Soil boring <br />B-12 was advanced to a total depth of approximately 10 feet below ground surface (bgs). Soil samples were <br />collected from 4.5 to 5 feet bgs and 9.5 to 10 feet bgs. After reaching total depth, approximately 14 inches of <br />groundwater entered the borehole, and a hydrocarbon sheen was observed. The soil boring was then abandoned <br />and a step-out boring (B-13) was completed. Soil boring B-13 was advanced to a total depth of approximately 8.25 <br />feet bgs. Soil samples were collected from 4.5 to 5 feet bgs and 7.5 to 8 feet bgs. Dual-nested soil vapor probes <br />were then installed at approximately 5 and 8 feet bgs and soil vapor samples were collected in January 2020. The <br />soil analytical results are provided as Attachment B. The soil vapor analytical results are provided as Attachment <br />C. <br />In October 2020, two soil borings (B-14 and B-15) were advanced at 2502 Dorset Avenue (Figure 2). Soil boring B- <br />15 was advanced on the western side of the property to a total depth of approximately 4 feet bgs when groundwater <br />was encountered. As a result, the boring was abandoned and a step-out boring was completed on the eastern side