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1 <br /> Harding Lawson Associates <br /> 94 SEP 29 PM 1: 09 <br /> September 26, 1994 <br /> 293504 <br /> Mr. James Brathovde <br /> California Regional Water Quality Control Board <br /> 3443 Routier Road <br /> Sacramento, California 95827-3098 <br /> Pond Closure Addendum <br /> Confirmation Soil Borings <br /> USC/A Division of Hydrite Chemical Company <br /> 1448 Shaw Road <br /> Stockton, California <br /> Dear Mr. Brathovde: <br /> INTRODUCTION <br /> Harding Lawson Associates (HLA) is pleased to present this addendum to the August 12, 1994 revised <br /> pond closure plan presented to the California Regional Water Control Board (RWQCB) on behalf of <br /> USC/A Division of Hydrite Chemical Company (USC). The site is located at 1448 Shaw Road in <br /> Stockton, California. The revised pond closure plan described the procedures to be employed for <br /> removal of the remaining contents in the pond and a proposed sampling plan to establish clean <br /> closure of the pond. Based on the findings of recent sampling, deeper confirmation borings are <br /> necessary. <br /> BACKGROUND <br /> Pond contents have been removed. Currently, confirmation samples have been collected from eight <br /> locations within, and one location outside the pond as shown on the attached Plate. Samples have <br /> been collected between the depths of 6 and 8 feet in all the borings. Based on the analytical results, <br /> which have shown sodium levels at concentrations above background, additional sampling at depth is <br /> required. <br /> ADDITIONAL SAMPLING <br /> To evaluate the sodium levels, HLA will drill seven borings to 20 feet below the existing base of the <br /> pond. Boring locations will coincide with the existing confirmation sampling locations (SIA, S113, <br /> S213, S3, S4, S5, S6, and S7 (see attached Plate). The borings will be drilled using hollow stem auger <br /> drilling equipment. Samples will be collected at 8.0, 10.0, 12.0 14.0, 16.0, 18.0, and 20.0 feet bgs. <br /> The samples will be collected using a split barreled sampler lined with stainless steel liners. Upon <br /> collection, the samples will be capped, sealed, labeled, and placed in a chilled container. The samples <br /> will be transported to an analytical laboratory under chain of custody procedures. Samples submitted <br /> to the laboratory will be analyzed for sodium. <br /> Upon completion of the borings, they will be backfilled with bentonite chips. The bentonite chips will <br /> be hydrated with 5 gallons of water every 5 feet. <br /> Engineering and 3247 Ramos Circle,Sacramento.CA 95827 9161364-0793 FAX 916/364-5633 <br /> Enwonmentai Services ASWrriJie,r<fHardinF A+soriara•Ohre+Nori,.x,d, <br />