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44 e <br /> Conclusions From Tank Removal Soil Sample Analysis <br /> The concentration of TPHd is the highest under the south end of the 12000-gallon diesel tank.Lower <br /> concentrations were found to graduate to the north end of the tank.Most likely a spill occurred near <br /> the south end of the 12000-gallon diesel tank. <br /> THE PROPOSED WORK PLAN <br /> SUMMARY OF THE WORK PLAN <br /> Tank removal soil samples indicate that a diesel spill occurred at or near the south end of the 12000- <br /> gallon diesel storage tank. To determine the vertical extent of contaminated soil at that point, <br /> Foothill Engineering proposes that a single soil bore and monitoring well be installed as close as <br /> possible to the south end of the excavation of that diesel storage tank. <br /> The groundwater gradient of existing on site monitoring wells will be determined. Groundwater <br /> samples from the proposed and existing down gradient monitoring wells will be analyzed for diesel <br /> fuel contamination. <br /> PROCEDURE <br /> Analysis of Existing Monitoring Wells on the Site <br /> Foothill Engineering proposes to determine the elevation and gradient of the groundwater on the site <br /> by survey and sounding of the existing monitoring wells.Groundwater samples from down gradient <br /> monitoring wells in relation to the 12000-gallon diesel tank will be extracted for analysis by methods <br /> standard to the industry. <br /> Soil Boring and Sampling <br /> Foothill Engineering proposes to place a single eight inch soil bore to ten feet below first <br /> groundwater. Soil samples will be extracted at five foot intervals by a standard BX split spoon soil <br /> sampler through an eight-inch hollow stem auger. Standard 2"x 6" soil sample tubes will be capped <br /> with Teflon sheets and plastic caps. The caps will be secured with duct tape and stored on ice. <br /> Sample Analysis <br /> Samples will be transported under chain of custody on ice to an approved state certified laboratory <br /> for analysis.Samples will be analyzed by EPA methods 8015 for BTEX and TPHd.Samples selected <br /> by the PHS/EHD inspector on the site will be analyzed for oxygenates by EPA method 8260. Soil <br /> samples will not be analyzed for heavy metals as diesel tank removal samples indicate that none of <br /> the contaminated areas contain heavy metals above detectable levels.Water samples will be analyzed <br /> by the same methods as soil samples. <br /> Monitoring Well Construction <br /> A two-inch PVC monitoring well will be installed in the proposed soil bore. Twenty feet of 0.01 <br /> PVC screen will be set to the bottom of the soil bore. The#2 x416 sand filter will extend two feet <br /> above the screen section and a two-foot bentonite plug will be placed above the filter. Cement grout <br /> will be placed to the surface above the bentonite plug. The monitoring well will be secured with a <br /> locked cap and flush cover. <br /> 2 <br />