ARCHIVED REPORTS_XR0007997 - Laserfiche WebLink

Home Browse Search

' Updated Site Conceptual Model and Second Quarter 2002 Monitoring and Remediation Report Cleanup and Abatement Order No 5-00-707 EAI Project No 1232 1 1 3 Unocal Site ' The property located at 5606 Pacific Avenue contained a gasoline station between approximately 1955 and 1985 (see Figure 2) In 1985, the station was closed and the USTs removed After completing investigations of the site, Unocal in 1988 excavated approximately 6,000 cubic yards of soil from the site The excavated soil was aerated, and based on the analytical testing results associated with the aerated soil, 5,800 cubic yards of the aerated soil was reused on-site as fill, and 200 cubic yards transported off-site for disposal On August 25, 1989, the RWQCB issued a letter for the Unocal site confirming that the soil contamination at the site has been adequately cleaned up, but, that the extent of ground water impact has yet to ' be defined Between 1992 and 1999, additional soil and ground water investigations associated with the Unocal site were conducted In February 2001, seven new wells (MW-I8D, MW-23S, MW-23D, MW-24S, MW-24D, MW- 25S, and MW-25D) were installed to assist in defining the vertical and lateral extent of hydrocarbon impacted ground water at the Unocal site and around the Robinhood Irrigation Well (see Section 1 1 3) In September 2001, four additional wells (MW-8D, MW-9, AS-26 and MW-27) were installed to further define vertical and lateral hydrocarbon-impacted ground water (see Figure 2) 1 14 Robinhood Irrigation Well RIW San Joaquin Delta College owns and formerly operated a ground water extraction well ' identified as the "Robinhood Irrigation Well' (RIW) (a k a Delta College Well) The RTW was located southwest of the intersection of Robinhood Drive and Pacific Avenue (see Figure 2) The RIW was installed in 1950 and is reported to be 322 feet deep with perforations in multiple ' zones beginning at depths as shallow as 40 feet below ground surface (bgs) According to the Water Well Driller's Report for the RIW, "no strata were sealed against pollution " Ground water from the RIW was formerly used to irrigate portions of Delta College's campus Ground water monitoring data for the Unocal and Wards sites show that historical pumping of the RIW influenced and changed the natural direction of ground water flow in the area from ' easterly, to south southwesterly, i e , towards the RIW Sampling of the RIW by Unocal and/or Wards for dissolved petroleum constituents began in 1997 and continued through June 15, 2000 w In August 2000, Delta College students and staff complained of a gasoline odor from the water ' derived from. the RIW As requested by the RWQCB, the RIW was taken out of service as of 6 00 AM August 22, 2000 The RWQCB in a letter dated February 26, 2001, requested that the RIW be destroyed ' DHM 123280231 -2- ENVIRONMENTAL AUDIT, INC