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2� <br /> San Joaquin County Public Health Service <br /> Environmental Health Division <br /> December 15, 1995 <br /> Page 2 <br /> • Evaluate groundwater quality for total petroleum hydrocarbons as diesel (TPH-d) <br /> in groundwater samples in the vicinity of the former underground storage tanks; <br /> and <br /> 0 Analyze soil samples for TPH-d following the five-year groundwater monitoring <br /> program to evaluate the rate of natural biodegradation of TPH-d in soils at this <br /> site. -- _.r -. ... . -AL__� .. <br /> The duration of this proposed monitoring program is five years. At the conclusion of the <br /> program, assuming results are consistent with conclusions reached to date, you indicated that <br /> final closure of the tanks would be approved. The frequency of each type of analysis is <br /> summarized in the table below. <br /> Summary of Proposed Monitoring Program <br /> Total No. <br /> No. Samples <br /> Monitoring Activity Media Analyte Frequency locations 15 years} <br /> Groundwater Level Groundwater Water level (ft) Semi-Annual (July 511) 50 <br /> and January,1996 <br /> to 2001) <br /> Groundwater Sampling and Groundwater TPH-d (Method Annually (July 1996 50' 25 <br /> Analysis 8015M) to 2001) <br /> Soil Monitoring Soil TPN-d (Method One Time (July 2(2) 10 <br /> 8015M) 2001) <br /> ..- <br /> i - <br /> I11 Locations of the five monitoring wells are shown in Figure 1. <br /> (2) Locations for the two soil borings will be adjacent to SB-19 and SB-20;soil samples will be•callected from 20,25,30,35,and 40 feet below <br /> ground surface. <br /> This testing program is appropriate for the stated objectives and; was developed from previous <br /> investigation and monitoring work at the site, including the most recent analyses of soil and <br /> groundwater samples reported in the Evaluation of Hydrocarbon Mobility (Dames"& Moore, <br /> 1995). <br /> Methods <br /> Groundwater measurements and soil sampling will be conducted using the methods described <br /> in the Work Plan for Additional Soil Sampling and Monitoring Well installation (Dames & <br />{ <br /> SAC180.02 <br />