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Royal Oak Savings & Loan 510 N Main Street, Manteca, CaliforniaQuartPage 2 eHy Ground Winter Sampling Repots October, 1992 -January, 2993 Previous investigations had shown that relatively low level contamination I water had occurred. of ground AM-1, drilled in the area where the underground tank was removed, showed an nntnal concentration of 11 mg/l, and 10 months later, a concentration of 37 mg/1 of total Petroleum hydrocarbons (TPH). The soil samples taken, at the time of the well installation, showed a maximum level of 4,800 mg/kg of total hydrocarbon. Wells MW 2, 3 and 4 were all installed at a later date by Harding & Lawson Associates. All were sampled initially on January 26, 1989. Monitoring Well 2 (MW- 2) showed a substantial increase from the initial sampling to the second sampling seven (7) months later. MW-3 showed a decrease to a "none detected" level and MIV-4 showed a slight increase m the benzene level. MW-5, 6 and 7 were installed in December of 1990, by WSF. Wells 5 and 6 showed "none detected" levels, and MW-7 showed significant levels of BTX&E. Minor hydrocarbon contamination was visually detected in soils at a 20 foot depth in Mw-7. After the Pump test and well development, a sampling round was conducted and all wells showed "none detected" in February of 1991. A subsequent around was taken m I March of 1991, and this round showed all wells "none detected", except Well 2. Well 2 had Benzene in it at 1.1 ppb. Groundwater gradient has been measured in several durections over the life of this project. These measuremeftts show swings from southeast to east to northeast The Regional Water Quality Control BoardWQCB) and the San Joaquin County Envmnmental Health down grachent is .northeast and had asked for a monitoorinDepartment grtwen to be tailed to the I northeast. IOn May 2, 1991, MW-8 was installed, northeast of the remedial excavation. 'Phis well was installed at the direction of the RWQCB to determine if groundwater had migrated to the northeast portion of the site. Soil and groundwater samples tested negative for BTXE and gasoline. In the July, 1991, sampling round, all wells I and MW-8) showed "ND" for BTXE and gasoline. bur,and-5, MW-6, MW-7 W 7 MW-2 and MW-7 had low levels of some compounds. The January, 1992 sampling showed low levels of Benzene and Xylene an MW-2. In the April and July, 1992 samplings, MW-2, MW-6 and MW-7 were tested. All three (3) wells showed "ND" levels for BTXE and gasoline.