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,%Joe Lapon L f��t " x�� ,L H~A� i PE��R,{ - �F"4'v c '-Ttr93 OCT 12 PH 2: O 7 October 7, 1993 Mr. Michael Collins Environmental Health Specialist San 7aoquin County Public Health Services, Environmental Health Division P.O. Box 2009 Stockton, California 95201 Dear Mr. Collins: Pursuant to our telephone conversation today I am sending you this letter describing the soil boring and vadose well installation procedures for the property located at 4555 North Pershing Avenue in Stockton, California. Enclosed with this letter is the permit application for the installation of the vadose well at the subject site. A total of eight soil borings will be completed to a total approximate depth of 26 feet below grade. The soil borings will be completed utilizing a direct push sampling rig. A direct push rig consists of a hydraulically-driven soil coring system mounted to a vehicle. The rig utilizes two nested sampling rods driven simultaneously: small-diameter inner sampling rods (1 1/2- inch), lined with brass sleeves, are used to obtain and retrieve the soil cores; the larger diameter outer rods (1 518-inch) serve as temporary drive casing. After being driven three feet the inner rods are removed from the borehole with a hydraulic winch. The brass sleeves containing the soil samples are removed from the drive sampler, and can then be preserved for chemical analysis or used for lithologic identification. After adding new stainless steel sleeves, the drive sampler and inner rods are than lowered back into the borehole to the previous depth, and an additional three foot section of rods (both inner and outer) is attached, and the process is repeated until the desired depth is reached. An on-site California state approved mobile laboratory will be analyzing the soil samples and providing data the same day of sampling. Based on the analytical data, the specifications and location of the proposed vadose zone well will be determined. The vadose zone well may or may not be constructed in one of the soil borings completed utilizing the direct push sampling rig. All other soil borings will be grouted with portland cement to within one foot of the existing grade and capped with concrete. A hollow stem auger drill rig will be utilized to advance the soil boring in which the vadose zone well will be constructed. The soil boring will be completed with a 10 inch diameter auger. The specifications of the vadose well can not be determined at this time because the well design is dependent on the analytical data. 1 oo7ied4 1135 Atlantic Avenue,Alameda,CA 94501 (510)52I-5200 FAX(510)521-1547 f •fYincrc*d POW