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ENVIRONMENTAL HEALTH DEPARTMENT <br /> Pp U, IN SAN JOAQUIN COUNTY <br /> �o._� • ..co` Unit Supervisors <br /> _Donna K. Heran, R.E.H.S. 304 East Weber Avenue, Third Floor Carl Bergman, R.E.H.S. <br /> Director Mike Huggins, R.E.H.S., R.D.I. <br /> Al Olsen., R.E.H.S' Stockton, California 95202-2708 Douglas W. Wilson, R.E.H.S . <br /> Prop am Manager Telephone: (209) 468-3420 Margaret Lagorio, RE.H .S , <br /> 4 F 0 Laurie A. Cotulla, R.E.H.S. Fax: (209) 464_0138 Robert McClellan, R.E.H.S. <br /> Program Manager Mark Barcellos, R.E.H.S . <br /> NOV 0 9 2004 <br /> JAY COFFEY <br /> CITY OF STOCKTON <br /> DEPARTMENT OF HOUSING AND REDEVELOPMENT <br /> 22 EAST WEBER AVENUE , ROOM 350 <br /> STOCKTON CA 95202 - 2317 <br /> RE: Former San Joaquin County Motor Pool Site SITE CODE: 1150 <br /> 130 North Hunter Street RO: 0495 <br /> Stockton, CA 95202 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Investigation Work <br /> Plan dated November 4, 2004, that was prepared by Treadwell & Rollo, Inc. (Treadwell & Rollo) <br /> on your behalf. In the above-referenced document, Treadwell & Rollo proposes to advance five <br /> borings to 30 feet below ground surface (bgs) and excavate three test pits to approximately six to <br /> ten feet bgs to further investigate soil and groundwater contamination at this site. Three of the <br /> proposed borings will be advanced approximately four feet from the east curb on North Hunter <br /> Street to delineate soil and groundwater west of this site; one proposed boring will be advanced <br /> approximately 10 feet northeast of the former pump station and one proposed boring will be <br /> advanced approximately 10 feet southeast of the former pump station. The three pits are to be <br /> excavated at the former pump station and along each of the two former product lines. <br /> EHD approves the excavation of three test pits at the proposed locations and the collection of up <br /> to three soil samples from each pit. However, if field conditions demonstrate that the soil is <br /> contaminated, EHD directs you to remove the soil instead of backfilling the pits with the <br /> excavated soil. <br /> EHD recommends the following to better ensure assessment of the vertical and lateral extent of <br /> impacted soil and groundwater: <br /> • Advancement of the five proposed borings to a minimum depth of 60 feet bgs, instead of <br /> 30 feet bgs. Current analytical data demonstrate that soil and groundwater are impacted <br /> at 30 feet bgs near the proposed boring locations. Historical data document that <br /> groundwater was at approximately 60 feet bgs in 1978, therefore soil and groundwater <br /> should be investigated to 60 feet bgs or greater, based on field observations. <br /> • Relocation of the five borings from their presently proposed locations to at least ten feet <br /> in each prospective direction further away from the source area. EHD believes that <br /> contamination boundaries projected by Ramage Environmental, Inc. are conservative, <br /> and relocating the borings further away from the source area in each direction will <br /> provide better delineation as to the lateral fringes of the contamination plume. <br />