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IRONMENTAL SOLUTIONS " <br /> C WWI <br /> pr� November 30, 1998 <br /> 1 d" D <br /> Protect 20805-147 OOS <br /> Ms Carol Oz <br /> San Joaquin County Public Health Services Environmental Health Division <br /> 304 East Webber, Third Floor <br /> Stockton, California 95202 <br /> Re Depth Discrete Groundwater Sampling at ARCO Service Station 2186 located at <br /> 3212 N California Street, Stockton, California <br /> Dear Ms Oz <br /> On behalf of ARCO Products Company, Pinnacle Environmental Solutions, a division of <br /> EMCON (Pinnnacle), is providing this letter regarding the proposed depth discrete <br /> sampling of well MW-1 at the subject site The San Joaquin County Public Health <br /> Services (SJCPHS) requested vertical delineation of Impacts near MW-1 in a letter dated <br /> May 13, 1998 In response to this request, the SJCPHS, ARCO, and Pinnacle met in <br /> September 1998 to discuss the known impacts to soil and groundwater At that time, <br /> collection of a depth discrete groundwater sample from MW-1 was discussed <br /> ARCO intends to collect one depth discrete sample from MW-1 during the fourth quarter <br /> groundwater monitoring event scheduled for December 1, 1998 to assess the vertical <br /> extent of groundwater impacts at the site The proposed sample will be a grab sample <br /> collected using a bomb sampler that allows collection of a depth discrete sample The <br /> bomb sampler is a stainless steel and teflon unit that complies with EPA sampling <br /> protocols The bomb sampler will be slowly lowered through the water column present in <br /> MW-1 to the base of the well at approximately 75 4 feet below ground surface (bgs) The <br /> sampler will be raised approximately 1 foot to the target sample depth of approximately <br /> 74 5 feet bgs This depth interval coincides with the lower portion of the well screen in <br /> MW-1 When the target depth is reached, the sampler will be opened using a pull line <br /> After the sampler is filled, the pull line will be released to reseal the sampler The sampler <br /> will then be retrieved In order to minimize the disturbance to the water column in MW-1, <br /> the sample will be collected prior to conducting the water level survey or other site <br /> sampling activities <br /> The sample will be analyzed at the ARCO approved and state-certified analytical <br /> laboratory for total petroleum hydrocarbons as gasoline using USEPA Method 8015, <br /> SACK 1MSOFFICFIWINWORDIARCOPR--112186121865AMP DOC-961'?? I <br /> `� 3939 Cambridge Road Suite 220 Cameron Park California 95682 (530)676 6884 (530)676 6885 Fax <br />