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Conclusions and Recommendations <br /> Soil exploratory bonngs were used to ascertain the extent of petroleum contaminants <br /> downgradient of a former underground storage tank location at M & M Automotive. <br /> Exploratory soil borings and reconnaissance groundwater sampling show that <br /> contaminants were not observed in soil at the capillary fringe, nor dissolved in <br /> groundwater. In our opinion this contaminant distribution is indicative of plume <br /> migration under a shallow flow gradient in clayey sediments. The plume appears to <br /> have migrated slightly downgradient of the former tank area Reconnaissance <br /> boring location B-9 showed field evidence of earlier presence, however, the <br /> chemical analytical data shows contaminants were not detected. <br /> Wright recommends performing an interim source abatement at the former tank <br /> location to excavate and remove contaminated soil from the immediate pit vicinity <br /> and underlying capillary fringe laterally up to the curb along 10th Street. This <br /> should remove an ongoing contributor observed in Well MW-1 Confirming soil <br /> samples should be collected from excavation sidewalls above the capillary fringe and <br /> analyzed for TPHG, BTEX and MTBE at the extent of excavation. <br /> Wright further recommends that one groundwater monitoring well be placed <br /> downgradient of the former tank location as close as possible to the building fronts <br /> in the alley opposite 10th Street across from the site This downgradient well would <br /> be added to quarterly monitoring to meet the requirements of the San Joaquin <br /> County Public Health Services-Environmental Health Division and Regional Water <br /> Quality Control Board for underground tank petroleum releases <br /> The data collected in this periodic monitoring program can be used to track <br /> hydrocarbons in groundwater These concentrations are anticipated to decline <br /> through natural biodegradation processes with time. Wright recommends that <br /> quarterly monitoring continue to observe flow gradient and water quality in order <br /> to confirm the anticipated trends As a declining and/or none detected analytical <br /> trend is documented, a proposal for site closure can be made to PHS-EHD following <br /> the fourth quarterly monitoring showing non-detectable concentrations of TPHG, <br /> BTEX and MTBE. <br /> Limitations <br /> This report has been prepared by Wright Environmental Services, Inc specifically <br /> for the M & M Automotive site The interpretations, conclusions and <br /> recommendations made herein are based on the data and analysis for the soil and <br /> water samples collected on-site and should be reviewed in the context of the whole <br /> report. Please note that reports of contamination must be submitted to the agencies <br /> in a timely manner. Wright Environmental Services, Inc is not responsible for <br /> errors in laboratory analysis and reporting, or for information withheld during the <br /> course of the study and no warranty or guarantee is expressed or implied therein. <br /> M&MAuromotive Project No. 4070-T Page b <br /> I <br />