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On 11 December 1992, passive skimmers were installed in wells RW3 and VI to recover liquid-phase hydrocarbons (LPH) The skimmers were checked for LPH on 18 May 1993, but no LPH was found in either of the skimmers or in any of the monitoring wells A Shell service station and a 7-11 store that dispense gasoline are located, respectively, on the ' southwest and northwest corners of the intersection of North Pershing Avenue and Rosemarie Lane Soil and groundwater investigations have been conducted at the Shell site, which is ' upgradient of former Exxon RS 7-3942 ' 3. CURRENT FIELD INVESTIGATION Groundwater monitoring well MW13 was installed approximately 300 feet northeast of former ' Exxon RS 7-3942, in the parking lot of the Chateau Convalescent Hospital (MW13, Figure 2) Two air-sparging wells were installed at the northern corner of the former tank field and the site itself where vapor extraction will be focused (SW1, SW2, Figure 2) to enhance the removal of dissolved and entrapped petroleum hydrocarbons from the groundwater and the soil beneath static water. On 18 May 1993, the wells were monitored for the presence of hquid-phase hydrocarbons, and groundwater samples were collected from I 1 wells ' 3.1 MONITORING WELL Groundwater monitoring well MW13 was drilled to better define and monitor the downgradient extent of dissolved petroleum hydrocarbons The borehole was drilled using a truck-mounted rotary drill and 10-inch outside-diameter hollow-stem augers The borehole ' was drilled 45 feet below ground surface (see the soil boring log, Appendix A) The borehole was completed as a groundwater monitoring well by installing 4-inch Schedule 40 PVC. The screened casing is 20 feet long and has 0 020-inch slots The bottom of the screen was ' placed 44 5 feet below ground surface The annular space around the screen was filled with #3 Monterey sand from below the casing to 15 feet above the top of the screen The sand filter pack was sealed with 1 foot of bentonite pellets which were hydrated, and the remaining ' space was filled to the surface with a cement-bentonite grout The well head was secured with a watertight steel monitoring well cover ' Soil samples were collected at 5-foot intervals for soil classification and field screening for hydrocarbon content with an OVA Samples were labeled and placed in an ice-filled cooler ' Selected samples were sent to Pace Incorporated, where they were analyzed for Total Petroleum Hydrocarbons as gasoline (TPH-g) by Cal EPA-modified EPA Method 8015 and for benzene, toluene, ethylbenzene and xylenes (BTEX) by EPA Method 8020 ' The well was located and the elevation of the top of casing was surveyed relative to monitoring well RW4 Well MW 13 was developed and purged, and groundwater samples ' were collected from it when the groundwater samples were collected from the other wells during the regular quarterly sampling on 18 May 8373942(2yRO1693lrX 3 2