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AIIanUC Richfield Company Page 6 ARCO Station No 4932,Stockton California August 29 2002 gradient ranging from approximately 0 002 to 0 04 ft/ft Depth to groundwater measurements and hydraulic gradient data reported through the third quarter 2002 are Included in Tables 2 and 3, respectively A map Illustrating groundwater flow patterns constructed from water level data in shallow and deep water bearing zones collected during the third quarter 2002 monitoring event on July 12, 2002 are presented as Figures 4 and 5 2.4 Updated Sensitive Receptor Survey In 2001, SECOR personnel performed a door-to-door survey of businesses and residences in the area to Identify any water supply wells within a 500-foot radius of the site Where no response was observed, a questionnaire and stamped envelope addressed to SECOR was placed in a conspicuous place Verbal and written survey results suggest that no water supply wells are located within a 500-foot radius of the site Nearby wells were located approximately 1/2 mile east of the site at the Stockton State Hospital and approximately 2,000 feet northwest at the intersection of Wyandotte and Commerce (As Indicated by SJCPHS in their letter dated Nov 21, 2000) The Sensitive Receptor Survey is presented in SECOR's report Additional Site Assessment Report dated November 9, 2001 Water supply well data is included in Table 4 2.5 Utility Survey SECOR evaluated the potential for migration of petroleum hydrocarbons through utility corridors or underground improvements near the site Depth to water at the site is approximately 27 feet bgs and no underground improvements or utilities were identified near this depth Since underground improvements and utilities do not intersect the water table, low migration potential for contaminants in groundwater exists through these areas Higher potential exists for vapor phase contaminant migration through these areas I I IARM49321PARTAR doc