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Well Abandonment and Soil and Groundwater Investigation Work Plan US Can-Welty Road September 2007 • Replace the oleophilic socks in wells MW-1 and MW-2 on an annual rather than quarterly basis as these wells contain immeasurable hydrocarbon sheen,and a total of only 0.34 gallon of separate-phase hydrocarbons (SPH)has been removed from these wells. • Discontinue collecting groundwater samples from WFSMW-1 as the fuel-fingerprint analyses from the samples collected during the first and second quarters of 2007 demonstrate the well is impacted with gasoline-range hydrocarbons that are not attributable to crude oil of the OVP or TAOC pipelines. • Destroy wells MW-3 and MW-4 because the water volumes in these wells are consistently insufficient for adequate sample collection(originally proposed in SAIC's Second Quarter 2007 Groundwater Monitoring and Sampling Report). The RWQCB concurred with these recommendations(RWQCB,2007). Monitoring Well Destruction Evaluation. In September 2007, SAIC evaluated historical groundwater monitoring well sampling analytical results using the following criteria, to determine whether monitoring wells may be destroyed: 1. COCs in a well must be less than WQOs and ESLs for at least last four sampling events;or 2. CDCs in a well must be stable or declining for at least eight consecutive events where the overall plume is defined. SAIC's review indicated that monitoring wells MW-4 and MW-5 should be destroyed. No COCs have ever been detected above ESLs or WQOs in MW-5. Laboratory analytical results for all COCs have been non-detectable in MW-4 for the previous four sampling events. TPHd levels in MW-3 have declined from a high of 6,700 pg/L on July 21,2005 to 60 pg/L on November 8,2006. The TPHd spike in MW-3 appears to have been caused by residual petroleum or naturally-occurring organic matter that adhered to sediments entrained in the groundwater sample, as TPHd concentrations in the well prior to July 2005 were similar to more recent groundwater concentrations. The November 8,2006 concentration of 60 pg/L is believed to be representative of the dissolved TPHd in groundwater at MW-3. The RWQCB agreed that monitoring wells MW-3 and MW-4 should be destroyed,provided that the results of one additional groundwater sampling event satisfy the monitoring well destruction criteria (RWQCB,2007). The RWQCB also recommended a final sampling event for MW-5. However, SAIC recommends the destruction of MW-5 without additional sampling and analysis,because access to the well for this purpose has been denied by the property owner and because the well is unaffected by crude oil of the OVP or TAOC pipelines. SAIC is currently working on behalf of CEMC to (re)-gain access to MW-5 to destroy the well. 3. SCOPE OF WORK The objectives of the proposed scope of work are: (1)collect groundwater samples from monitoring wells MW-3 and MW-4 and analyze for the COCs,to confirm that the wells satisfy the well destruction criteria; (2)properly destroy monitoring wells MW-3,MW-4,and MW-5 (provided the criteria for well destruction are satisfied after one more sampling event); and(3)advance 11 borings from which samples will be collected and tested for the COCs to delineate the extent of soil and groundwater affected by former OVP and TAOC facilities at the site. The proposed soil boring locations are shown on Figure 3, and boring details are listed in Table 1. 3.1 PERMITTING,ACCESS,AND SITE SAFETY Before initiating the field investigation, SAIC will implement the following: • Obtain boring and abandonment permits from San Joaquin County Environmental Health Department(SJCEHD); 7 == == WIW M=/rel�..._ From Sc e;ce!o Sc mutrons