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Mr. Sam Savig ,,,� � Project 880-040.1A December 12, 2001 Page 2 Product line upgrade began on January 7, 2000. After the removal of dispenser plumbing, soil obviously impacted by petroleum hydrocarbons was discovered below the western dispenser islands. Soil samples were collected from beneath the dispensers and along the product lines at a depth of approximately 3.5 feet below ground surface (bgs). Remedial activities conducted on January 26, 2000 included removal of approximately 262 tons of impacted soil in the area below dispenser and product lines. Excavation areas were selected based upon the results of January 7, 2000 sampling. Excavation was restricted laterally by concrete canopy footings and asphalt surfacing. Maximum excavation depth was 10 feet bgs due to close proximity of groundwater. Results of soil sampling and excavation were reported in IT's Product Line Upgrade and Soil Excavation Report dated March 15, 2000. The SJCEHD requested further delineation of soil and groundwater impacts in their April 24, 2000 letter. A total of five Geoprobe—>borings (GP-1 through GP-5) were completed on August 15 and 16, 2000 using a direct push rig. The borings were advanced to groundwater at which time a discrete water sample was collected. Following groundwater sample collection the borings were continued to a maximum depth of 30 feet bgs. Three groundwater monitoring wells (MW-1 through MW-3) were installed on September 6, 2000 at the locations shown on Figure 2. The well locations were selected based upon results of the Geoprobe---> investigation. Quarterly groundwater monitoring has been conducted at the site since the First Quarter 2001 event. PROPOSED SCOPE OF WORK Task 1 —Installation of Two Down Gradient Wells. A map presenting the analytical data from the fourth quarter 2001 sampling event is included as Figure 2. This map was developed to evaluate the approximate downgradient limits of MtBE. The data was used to evaluate appropriate locations of additional shallow zone monitoring wells. Flow in the shallow water-bearing zone has been consistently to the north at an approximate gradient of 0.002 feet/feet. The concentration map shows that highest concentrations of MtBE are localized in an area immediately downgradient of the UST complex and adjacent to the dispenser islands and MW-1. Based on these results IT proposes to install one monitoring well at the north corner of the site to define the boundary of the MtBE plume to the north. Another monitoring well is proposed on Access Road Easement to define the boundary of the MtBE plume to the northeast (Figure 3). \\SACRFPI\COMMON\sacDP\200]\PRJ\PJ8\8800401 A.1 ac.doc 12/12/01