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• Phase I field work will consist of soil and groundwater sampling <br /> using a Geoprobe system to define the extent of contamination. <br /> Based on field observations, screening, and preliminary chemical <br /> analyses, Geoprobe sampling will progress outward from each site <br /> until the extent of contamination in soil and groundwater is <br /> approximately defined. <br /> • Phase H field work will be based on the analytical results of Phase I <br /> sampling and will consist of the installation of monitoring wells <br /> (using the hollow-stem auger drilling method) and subsequent <br /> development, purging, and sampling of the monitoring wells. A <br /> minimum of one upgradient and two downgradient monitoring <br /> wells will be installed at each site to provide for long-term <br /> monitoring. <br /> For this investigation, sump sites will not be assessed beyond the <br /> Phase I level. However, if evidence indicates that groundwater has <br /> been impacted at either or both sump sites, ERM will recommend to <br /> the Navy that a "Phase H" investigation may be required. <br /> RI Methodologies <br /> This section describes the overall technical approach of the RI and the <br /> rationale for the types and locations of sampling activities. <br /> Descriptions of field methods and procedures to be used during this <br /> investigation are provided below. <br /> Phase I-Geolrobe Sampling <br /> To determine the extent of contamination at each site, soil and <br /> groundwater samples will be collected using a Geoprobe system. The <br /> primary advantage of the Geoprobe is that it can collect a large number <br /> of samples per day while generating little waste. The proposed number <br /> of sampling points may vary depending on field conditions. Table 1 <br /> summarizes the proposed number of Geoprobe locations and soil <br /> samples to be collected at each site. <br /> Geoprobe sampling locations will be based on previous analytical data, <br /> if available, and will progress outward from the former UST until the <br /> extent of the fuel-affected soil and groundwater is approximately <br /> defined. Because Geoprobe sampling locations will be determined by <br /> the results of upcoming sample analyses, figures showing approximate <br /> Geoprobe locations have not been prepared for this workplan. Because <br /> the depth to groundwater is relatively shallow throughout the base, <br /> 4-2 <br />