ARCHIVED REPORTS XR0006513 - Laserfiche WebLink

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' LO } INTRODUCTION On October 1, 1998, Blakely Environmental Investigations, Inc (BEII) was contracted by Wickland Properties to review all groundwater and soil test data for the former Regal Station # ' 603, located at 6425 Pacific Ave , Stockton, Ca , and to recommend appropriate remediation It was identified that greater than 99% of the benzene mass has been removed from the soil and groundwater during the initial seven years of vapor extraction and groundwater treatment at this ' site it was further identified that the rate of benzene removal has decreased to approximately intrinsic levels after the first four years of vapor extraction and groundwater treatment since less than 1% of the initial dissolved benzene mass has remained available for removal ' Based upon the effective removal of the dissolved aromatic gasoline constituents, benzene, toluene, ethyl benzene and xylene (BTEX) and remediation in accordance with the Tri-Regional ' Board staff recommendations, BEII proposes that no further remedial action be required for this site ' 2.0) CRifTERIA FOR NO FURTUER ACTION After completion of soil vapor extraction for an eight year period of operation, soil and ' groundwater analytical results support that all of the following remedial criteria have been met 1 No contaminants remain in the vadose zone which may reverse or threaten to reverse the mass reduction rate of groundwater pollutants Confirmation borings drilled in 1997 identified no detectable levels of TPH nor BTEX in the vadose zone Please see section 5 0, Soil Confirmation Testing 2 Separate h p phase product has been removed to that extent practicable No free phase gasoline has been reported since 1992 in site wide quarterly monitoring performed on the shallow groundwater Section 6, Groundwater Monitoring ' 3 No existing water supply wells, deeper aquifers, surface waters or other receptors are threatened by pollutants remaining in the shallow aquifer A search performed by Western Geo-Engineers identified no municipal nor domestic drinking water wells ' screened in this aquifer within 900' of the site Please see Section 7, Vicinity Water Supply Wells and Appendix A 4 The total pollutant mass remaining in the ground water is decreasing at predicted intrinsic rates and neither creates, nor threatens to create, a -.11,4C toy har an health and safety or future beneficial uses of the shallow aquifer Dissolved petroleum aromatic constituents in onsite groundwater monitoring wells have decreased to asymptotic or less than detectable levels in every case The extent of dissolved gasoline and its aromatic constituents, benzene, toluene, ethyl benzene, and xylene has decreased consistently since initial measurement in 1990 during remediation by soil vapor l