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STATE OF CALOORNIA GEORGE DEUKMEJIAN,Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL VALLEY REGION ..� <br /> 3443 ROUTEER ROAD <br /> SACRAMENTO,CA 95827-3098 <br /> 17 May 1989 <br /> Ms. Diane Hinson <br /> San Joaquin Local Health District <br /> P. 0. Box 2009 <br /> Stockton, CA 95201 <br /> PROPOSED WORK PLAN FOR PROBLEM ASSESSMENT REPORT FOR UNOCAL STATION NO. 2859, <br /> 1665 PACIFIC AVENUE, STOCKTON, SAN JOAQUIN COUNTY <br /> We have reviewed 7 February 1989 work plan for investigative work at this <br /> site. Although the proposed work is too limited to define soil and ground <br /> water contamination, we will accept it with the understanding that additional <br /> work will be necessary to adequately assess the problem at the site. All <br /> necessary permits to conduct the proposed work are to be obtained from the <br /> appropriate local agencies. <br /> We have the following comments on the proposed work plan: <br /> 1 . A Health and Safety Plan needs to be submitted. <br /> 2. All monitoring wells at the site should be sampled for total petroleum <br /> hydrocarbons (TPH) and benzene, toluene, xylene and ethylbenzene (BTX&E) <br /> analysis. <br /> 3. Ground water levels should be made in all monitoring wells for gradient <br /> and flow direction calculations. <br /> 4. Because of the proximity of commercial and residential buildings to this <br /> site, we recommend that the possibility of vapors migrating to these <br /> areas be investigated and some type of air monitoring be conducted. <br /> We have the following comments regarding the scope of the additional work <br /> necessary to define the problem at this site: <br /> 1. An additional monitoring well needs to be installed south of <br /> MW-2 to define the southern extent of the ground water contamination. <br /> It may need to be installed in the street in front of the Bank of <br /> America if there is no other accessible location. The results from the <br /> two proposed monitoring wells, MW-4 and MW-5, should be useful in <br /> selecting the appropriate distance from MW-2 to install this new well . <br /> 2. Additional on-site soil borings are necessary to define the extent of <br /> soil contamination reported in soils from MW-2. <br />