ARCHIVED REPORTS_XR0008188 - Laserfiche WebLink

Home Browse Search

i Appendix A - Historical Background round g PACIFIC MINI-MART 4511 Pacific Avenue, Stockton, California SITE USAGE The site is located at the northwest corner of Pacific Avenue and Rose Marie Lane in Stockton, California and currently operates as a gasoline dispensing station and mini-mart The facility consists of a building and three pump islands with a covered canopy STRATIGRAPHY Light brown to brown, dry, sandy silt was encountered at 30 to 35 feet below surface grade (bsg) Gray or tan, wet, coarse-sandy gravel was encountered from depths of 35 to 40 feet bsg An indurated clay generally underlaid the sandy gravel at depths of 40 to 60 feet bsg ' UNDERGROUND STORAGE TANK REMOVAL In February 1991, a broken coupling in a product line was discovered and repaired During repair ' procedures,hydrocarbon-impacted soil was discovered beneath the product line Subsequently,the EHD required an assessment of the vertical and lateral extent of the hydrocarbon impact ' Between 1991 and 1993, three soil borings, one vapor extraction well and three ground water monitoring wells were installed at the site by Geological Audit Services, Inc (GAS) The vertical and lateral extent of hydrocarbon-impacted soil and ground water were delineated to the satisfaction ' of the San Joaquin County Environmental Health Department (EHD) On 08 April 1994, six USTs were removed from the site Details of the USTs removal and soil ' sampling were presented in a report prepared by GAS In May 1994, two 12,000-gallon USTs and associated piping were installed at the site to replace the removed tanks 1 SITE ASSESSMENT Between 1991 and 1997, four soil borings, one vapor extraction well and seven ground water monitoring wells were installed at the site The vertical and lateral extent of hydrocarbon-impacted soil has been delineated,however,the lateral extent of hydrocarbon-impacted ground water has not been delineated to the satisfaction of the EHD Data collected from the site during the investigation of the former UST site indicated that hydrocarbon-impacted soil is present in the vadose zone from depths of appioximately 5 to 55 feet bsg Rising ground water elevation has greatly exceeded the screened intervals of monitoring wells MW-1, MW-2 and MW-3, rendering data collected form these wells suspect Hydrocarbon-impacted ground water has been encountered north and east of the property in the down-gradient direction from the suspected former source of the unauthorized hydrocarbon release, but was not well constrained in these directions These factors necessitate