ARCHIVED REPORTS_XR0007337 - Laserfiche WebLink

Home Browse Search

' 1.0 INTRODUCTION Mittelhauser Corporation (Mittelhauser) has prepared this report for Unocal Corporation (Unocal) to document the remediation activities that have occurred at ' former Service Station #6348 located at 3788 Tracy Boulevard in Tracy, California (see the Site Location Map, Figure 1 ) The successful intent of this work was to identify and remove sods containing hydrocarbons by removing the underground storage tanks (USTs) and preforming overexcavation in the affected areas The subject site was in operation from 1972 until March 1992 for the retail sale of unleaded gasoline and maintenance of automobiles Mittelhauser performed an initial ' series of exploratory drilling beginning in July, 1991 (see the Predemolrtion Site Plan, Figure 2) ' 20 PREVIOUS INVESTIGATIONS AND REMEDIATION ACTIVITIES In June 1990 an underground waste-oil storage tank located near the northeast corner ' of the station building was removed because of suspected leaks During the removal, the pit was over-excavated to remove hydrocarbon-affected soil In Jul 1991, four monitoring wells (MW-1 through MW-4) were installed and Y 9 9 ' additional soil borings were drilled to assess the level and extent of hydrocarbons in soil and groundwater Total petroleum hydrocarbons as gasoline (TPH-G) were ' identified in soil near the fill spout of the southern 10,000 gallon UST The results of the investigation were presented in the Preliminary Investigation and Evaluation Report ' by Mittelhauser dated January 31 , 1992 (Appendix A) Quarterly groundwater sampling results indicated persistent levels of dissolved hydrocarbons in well MW-3 located adjacent to the USTs Dissolved hydrocarbons ' have generally not been detected in the site perimeter monitoring wells (MW-1 , MW-2, / 1ittelhauser q C O R P O k A T 1 0 N P21 68R008 wp[03l941 1 r