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EEC 5411-4 UniFirst Stockton September 17,2002 <br /> Waste oil remaining in the drum was transferred to plastic storage containers by UniFirst <br /> personnel. The oil will be disposed along with other waste material generated at the <br /> facility. <br /> Following the discovery of the waste-oil drum,UniFirst contacted EEC to investigate <br /> whether underground storage tanks (USTs) or additional debris might be present at the <br /> site, and based on those findings, determine the steps necessary to properly remove tanks, <br /> debris, or any impacted soil that may be uncovered. <br /> Remediation Activities <br /> On Wednesday August 7, 2002, EEC mobilized to the site to determine if USTs or other <br /> debris was present. EEC subcontracted the service of Gasch and Associates, Inc. (Gasch) <br /> of Rancho Cordova, California,to perform a subsurface geophysical survey to determine <br /> if UST's or other debris is present beneath the site. Gasch performed the survey by <br /> dividing the 90 foot by 100 foot site into 10 foot grids. The geophysical survey was <br /> conducted utilizing a cesium vapor magnetometer. <br /> The geophysical survey identified several large magnetic anomaly within the survey area. <br /> Based on the results of the geophysical survey, EEC excavated several test pit locations <br /> to determine if underground storage tanks and associated pipelines were present. <br /> Excavation of the test pits revealed the presence of underground piping near the northern <br /> property boundary. This underground piping appeared to be a combination of sewer <br /> pipelines and fuel dispensing piping. On August 7, 2002, as excavation progressed, <br /> hydrocarbon odors and soil discoloration were identified in the northernmost test pits. <br /> The discolored soil extended to a depth of at least 5 feet bgs, the maximum depth <br /> excavated. Due to the presence of the discolored soil,EEC halted excavation activities, <br /> until the San Joaquin County Environmental Health Department SJCEHD could be <br /> notified. <br /> On August 14, 2002, Gasch re-evaluated their geophysical data and provided EEC a new <br /> interpretation for the possible location of the USTs. EEC continued test pit excavations <br /> at those locations to determine if USTs were present at the site. Excavations were <br /> extended to approximately 7.0 feet below ground surface (bgs),but no USTs were <br /> located. All anomalies appear to be associated with abandoned buried piping. <br /> Once it was determined that no USTs were present,EEC proceeded to remove discolored <br /> soil and soil with hydrocarbon odors that were located within the footprint associated <br /> with the construction of the new laundry facility. EEC terminated the excavation at the <br /> construction limits and/or at the depth where field screening instruments and visual <br /> observations indicated that no hydrocarbon-impacted or discolored soil remained. All <br /> soil with evidence of hydrocarbons was removed. The majority of the excavation <br /> activities were focused in the northwest portion of the site. The configuration of the <br /> excavation is shown on Figure 3. All discolored soil was stockpiled and cover until it <br /> could be properly removed,profiled, and disposed. It is unclear whether hydrocarbons in <br /> the soil were related to a release from the underground piping. <br /> 2 <br />