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I� GAVIN NEwsoM <br />Sp. 0U �,\ �i4 ,; GOVERNOR <br />enuPonx lq U .JARED BLUMENFELD <br />SECRETARY FOR <br />later Boards ENVIRONMENTAL PROTECTION <br />Central Valley Regional Water Quality Control Board <br />REC F IVED <br />26 May 2021 <br />Michael N. Oliphant <br />Chevron Environmental Management Company <br />6001 Bollinger Canyon Road ENV1Ro N N I F, ►:l►, ��►':;�1;►'►i <br />P.O Box 6012 uLP,�►r► N►L��►' <br />San Ramon, CA 94583 <br />REVIEW — 2021 ANNUAL GROUNDWATER MONITORING REPORT, ALDEN PARK, <br />TRACY, SAN JOAQUIN COUNTY <br />Chevron Environmental Management Company (Chevron) submitted the 2021Annual <br />Groundwater Monitoring Report (Report) dated and submitted to Geotracker on 30 April <br />2021, for the Alden Park site (Site) in Tracy. The Report was prepared for Chevron by <br />the consultant Arcadis U.S., Inc. (Arcadis), and submitted to Central Valley Regional <br />Water Quality Control Board staff (Staf). Staff reviewed the Report and prepared a <br />summary and comments that are contained in this letter. <br />According to Arcadis, groundwater sampling and monitoring was conducted in <br />accordance with Monitoring and Reporting Program MRP R5-2019-0903 (MRP). The <br />Report provides an annual summary of the 2021 groundwater monitoring analytical <br />results for the former Old Valley Pipeline fuel oil reservoir Site, now occupied by the City <br />of Tracy's Alden Park. <br />Report Summary <br />There are 14 monitoring wells associated with the Site. Six wells were sampled <br />using HydraSleeves, and the remaining eight wells were not sampled due to the <br />presence of separate phase hydrocarbons (SPH). <br />• Depth to groundwater was measured in six wells and ranged between 14.19 and <br />15.65 feet below top of casing. The depth to groundwater increased by less than <br />1 foot since the 2020 monitoring event in five of the wells, with exception of well <br />MW -9 which had decreased by approximately 0.6 feet. The groundwater flow <br />direction was north-northwest with a gradient of 0.003 feet- per- foot. <br />• Analytical results indicated total petroleum hydrocarbons as diesel (TPHd) at <br />concentrations of 97micrograms per liter (pg/L) in well MW -7, 1,200 pg/L in well <br />MW -21, and 1,300 pg/L for the duplicate sample collected from well MW -21. <br />TPHd did not exceed laboratory the reporting limit of 50 lag/L in the remaining <br />wells. <br />KARL E. LONGLEY SCD, P.E., CHAIR I PATRICK PULUPA, ESO., EXECUTIVE OFFICER <br />1685 E Street, Fresno, CA 93706 1 www.waterboards.ca.gov/centralvalley <br />