Laserfiche WebLink
^ h <br /> a <br /> Page 4 <br /> Trust of Mary Gardella <br /> June 26, 2003 <br /> Soils <br /> An excavation may be considered in localized areas of suspected residual relatively shallow soil <br /> contaminants. However soil vapor extraction (SVE) could cost effectively target the excavation <br /> backfill and the 15-30 foot zone immediately below the former tank pit with the heaviest soil <br /> contamination. The SVE well would be placed in the vicinity of MW-2 and within the former <br /> tank pit. Well and SVE equipment design requires a review of site stratigraphy, preparation of <br /> geologic cross sections and an understanding of the relative permeability's of the soil strata at the <br /> target depths. Lead times required in obtaining permits to construct and operate from the San <br /> Joaquin County Air Pollution Control District (SJAPCD) will determine the time required to <br /> deploy the SVE system. <br /> Ground Water <br /> The emphasis for source area interim cleanup would be in the aquifer at the 35-50 foot zone (that <br /> is the area of current monitoring well slotted interval) where a large residual contaminant presence <br /> is located (Well NI -2 currently shows the most elevated dissolved concentration). Previous <br /> discussions suggested the use of ozone bubblers to initially address this largest contaminant <br /> problen-L The successful use of ozone sparging requires effectively delivering the ozone to the <br /> dissolved phase hydrocarbons. The feasibility and system design depend on an understanding of <br /> the site stratigraphy, the hydrogeology, the potential for channeling and the extent of dissolved <br /> phase contamination. Dissolved phase concentrations and mass affect the dosage and time <br /> required for cleanup. Where the stratigraphy is suitable, ozone bubblers deliver ozone to the <br /> contaminant area and have been a cost effective approach to degrading contaminants relatively <br /> quickly. <br /> A detailed evaluation of the geologic cross sections, ground water concentrations and other site <br /> data may indicate that other technologies such as oxygen releasing compounds (ORCs) are more <br /> suitable for this site. Should these other technologies be indicated `Wright will review the <br /> alternative technology with the PHS EHD before making a decision. However, Wright proposes a <br /> conceptual approach using ozone technology and possibly using one of the existing monitoring <br /> wells to deliver the ozone into the contaminated aquifer. <br /> Page 4 of 6 <br />