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A 1. <br /> E1�VICES OR4tU!N .O� <br /> PUBtc HEALTH S � :� . <br /> SAN JOAQUIN COUNTY ': <br /> JOGI KHANNA M.D.,M.P.H. '• <br /> Health Officer <br /> P.O. Boz 2009 a (1601 Bast Hxwkm AvWW) Stockton,C Mmiia 95201 ;� oRe► <br /> (209)4683400 <br /> ROBERT BURICK <br /> 350 VIA CONCHA AUG 3 0 <br /> APTOS CA 95003 <br /> RE: 1129 West Eleventh Street SITE CODE: 9024 <br /> Tracy, CA <br /> San Joaquin County Public Health Services,Environmental Health Division (PHS/EHD) has reviewed your <br /> letter, dated April 5, 1993, requesting groundwater monitoring as a remedial alternative to abate the <br /> groundwater pollution caused by a release from the former underground storage tanks on this property and <br /> has the following comments. <br /> Please be advised that 0.70 parts per billion benzene, as noted in the letter, is not an acceptable level of <br /> benzene contamination in groundwater nor are the levels of the other contaminants detected in the <br /> groundwater at this site considered acceptable. The remedial alternative chosen to remediate the gasoline <br /> pollution in the groundwater at this site must be sufficient to achieve nondetectable levels of hydrocarbons <br /> using accepted detection limits as noted in the LUFT Manual(Leaking Underground Storage Tank Manual). <br /> Although the data from monitoring well MW#2 has indicated a general decreasing trend for contaminant <br /> concentrations since the well was installed in 19879 that data alone does not support passive groundwater <br /> monitoring as the most effective remedial alternative for this site for the following reasons. <br /> Monitoring well MW#2 is currently the only monitoring point located within the groundwater contaminant <br /> plume. The levels being measured in this monitoring well may not reflect the concentrations of the entire <br /> contaminant plume. Additional wells within the plume will provide data to estimate the total contaminant <br /> mass of the plume and to use in evaluating the feasibility of several cleanup alternatives. This additional <br /> groundwater contaminant plume definition, previously requested of you in a letter from PHS/EHD dated <br /> February 8, 1993, is warranted for this reason. <br /> The shallow soils in and around the former tank pit area have not been investigated for petroleum <br /> hydrocarbons and may act as a source to the groundwater contamination indefinitely. This investigation,also <br /> requested in the February 8, 1993 letter,would provide data on any possible remaining soil contamination <br /> threatening groundwater that may need remediation. <br /> The data generated from this additional investigation is needed to evaluate at least two forms of active <br /> remediation. In addition to this data,feasibility studies(studies conducted on-site to determine if a particular <br /> form of remediation would be effective at this particular site and the appradmate cost) must be conducted <br /> to generate the data to support or justify the particular remedial approach chosen. The remedial approach <br /> chosen must be the most efficient,cost effective alternative. <br /> You may propose to continue to monitor the groundwater plume as a form of passive remediation. However, <br /> you still must generate the physical data to indicate that this alternative would be the most efficient, cost <br /> effective approach over at least two other active remediation approaches. Passive groundwater monitoring <br /> would be a long term remediation alternative and the cost of monitoring the groundwater for several years <br /> to decades must be considered when evaluating remedial alternatives for this site. <br /> A Division of San JoKpAn County Halm Fare SerAces <br />