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Section 3 <br /> Supplemental Site Characterization, <br /> Groundwater Modeling, and Monitoring <br /> This section documents supplemental exploratory drilling, new monitoring well construction, <br /> aquifer test analysis, hydrogeological observations, and the results of quarterly groundwater <br /> i monitoring that was conducted in 1995. This phase of site characterization involved the <br /> following field activities: <br /> • Drilling six exploratory borings and groundwater sampling by Hydropunch <br /> • Installing an upgradient monitoring well <br /> • installing a downgradient deep and shallow well pair <br /> • Aquifer testing at the two downgradient wells <br /> • Collecting quarterly groundwater samples and level measurements <br /> Exploratory Drilling and Hydropunch Sampling <br /> Exploratory groundwater samples were collected to further identify the lateral extent of <br /> gasoline contamination in groundwater and provide information for placing upgradient and <br /> downgradient monitoring wells. <br /> Permitting Requirements <br /> Before beginning exploratory drilling and sampling, Del Monte obtained several permits. An <br /> Encroachment Permit for drilling in a public right-of-way and a Revocable Permit for the <br /> right to install a permanent monitoring well were obtained from the City of Stockton. The <br /> San Joaquin County PHS/EHD required a well permit for each parcel of land where wells <br /> j were to be installed. These city and county permits required a signed statement from adjacent <br /> property owners indicating that they were aware of the drilling activity (which Del Monte <br /> obtained). <br /> } <br /> Del Monte did not pursue permits for exploratory drilling on Caltrans property to the south of <br /> the site because the-historic required approval time has been several months for a Standard <br /> Encroachment Agreement. Discussion with Mr. Syed Ali of Caltrans District 10 revealed that <br /> during the recent excavation for construction of Route 4, no groundwater contamination was <br /> encountered and no monitoring wells were installed near the Disco site (post mile R18.77). <br /> Field Work <br /> Two methods of exploratory groundwater sampling were evaluated. The first method was <br /> cone penetration or push point sampling. The second method was drilling with a hollow <br /> r stem auger followed by Hydropunch sampling. Push point sampling by cone penetration can <br /> be faster and less expensive, but soil blow counts were too high to allow push points to reach <br /> f SF010030982.DOC 3-1 <br />