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' • k`■ KLEINFELDER 1 EXECUTIVE SUMMARY ' This report presents results for a limited soil and groundwater assessment conducted at 1785 N. Corral Hollow Road, in Tracy, California. The assessment was conducted for Fitzpatrick Homes ' as a result of discolored soil noted during grading operations while developing the site for residential lots. The site was previously owned by R&B Trucking Company from the late 1960's to about 1990. During the soil assessment discolored soil with a petroleum-like odor was removed from three excavations, totaling approximately 4100 yards of soil. A total of 44 soil samples were collected ' from the excavation of which 40 soil samples were analyzed primarily for petroleum constituents. During the subsequent groundwater assessment four temporary wells were installed ' in the vicinity of the two larger excavations. A groundwater sample from each well was also analyzed primarily for petroleum constituents. Groundwater flow direction and gradient was also calculated based on groundwater soundings from these four wells. ' The three excavations are identified as Shallow Excavation A (SE-A), Small Excavation B (SE- B) and Large Excavation C (LE-Q. See Plate 2 for locations. The primary contaminants appear to be both purgeable and extractable hydrocarbons, but primarily extractable hydrocarbons. The following is brief summary of Kleinfelder's findings and recommendations. Please refer to Sections 6 (Discussion of Findings) for additional details. • No additional mitigation or sampling is recommended for Excavation SE-A ' . The majority of petroleum affected soil was removed from SE-B, however a portion of affected soil was left in place at the western boundary fence. Contaminated soil may be located offsite. • The bulk of contaminated soil appears to have been removed from Excavation LE-C. ' However field observation and/or analytical soil sampling results indicate that contaminated soils still exist along the northern sidewall and part of the eastern sidewall. Kleinfelder recommends excavation and removal of this soil with subsequent confirmation soil sampling. ' • Groundwater flow and gradient was estimated towards the northeast at a gradient of 0.0028 ft./ft. ' • Groundwater sampling results were none detect for all requested analytes (See Section 5.1.4), with the exception of xylenes detected in a single water sample at a concentration of 0.75 ' µg/1. This groundwater sample was collected from a well located cross-gradient of SE-B and LE-C and downgradient of a former tank area operated previously by R&B Trucking Company. Groundwater sampling results appear to indicate that contaminated soil from SE- ' B and LE-C have not adversely affected groundwater. 20-4341-11.E01/201IR959 Pagel of31 Copyright 2001,Kleinfelder,Inc. August 21,2001