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Work Plan For UST Removal and Over-Excavation-Tosco 76 Branded Facility No. 11193 . 1 i November 18;.1998 i A • Groundwater monitoring wells MW-5 through MW-7 were installed in March 1994. • One vadose zone well (VW-1) was installed and two.Hydropunch borings,.(THP-1 and THP-2) Jwere drilled in November 1994. Soil samples TD-2 and TD-3 were.also collected beneath the dispensers: SCOPE-OF WORK I' GR will collect the required compliance samples from the UST excavation and beneath the product ` piping .and dispenser islands.: Groundwater'is likely to be encountered,in.the UST excavation . preventing collection.of soil samples from the base of the excavation. If petroleum hydrocarbon- impacted soil is encountered and Tosco elects to excavate the,impacted soil, GR will observe the over- excavation activities and collect confirming soil samples from the base and lateral 'limits of the, E `excavation. GR field methods and procedures are.attached. To implement this scope of work, GR " proposes the following tasks: Task 1. Compiiance Sampling Three USTs, the associated product piping and dispensers -will be removed by Paradiso - Mechanical, Inc. (Paradiso). Compliance soil samples will be collected from the UST excavation, ` the product piping trenches, and beneath'the dispensers in accordance with,the SWRCB LUTT r' Manual, the RWQCB Tri.-Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites, and SJCPHS guidelines which specify the locations for a minimum number of soil samples to,.be collected:upon routine UST.removal. GR anticipates groundwater.being encountered during UST removal and'.will collect a grab groundwater sample from the .UST excavation. Removal and disposal of USTs and related equipment, soil and groundwater sampling' and disposal of excavated backfill materials'will'be conducted according to the methods outlined in the Tank Closure Permit Application submitted to the.SJCPHS'.on , behalf of Paradiso. Task 2. Over-Excavation of Impacted Soil If either subjective field evidence or.analytical data indicate soil beneath the site has been impacted by hydrocarbons, Tosco may elect to excavate the impacted soil. ':The feasibility.and necessity G of over-excavation of impacted soil can only be-determined after UST removal and compliance sampling: Over-excavation maybe necessary in, but not limited to the`areas shown oh-Figure 2• ` Groundwater levels at the site will limit the depth of over-excavation to approximately 11 feet below ground surface(bgs): Based on the size of the.areas defined.on Figure 2,and the depth to .groundwater; the potential amount of over-excavated soil is not likely to-exceed.4W cubic yards. ' If Tosco elects'to over=excavate hydrocarbon-impacted soil, GR will observe the excavation activities. Excavated soil will be screened in the field for the presence of volatile,organic vapors using a,photoionization detector. ' When possible,. clean and impacted soil will.be segregated. 140205.03-1 2