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ENVIRONMENTAL HEALTH DEPARTMENT <br /> Pau,N SAID JOAQUIN COUNTY <br /> o c <br /> Unit Supervisors <br /> Q Donna K.Heran,R.E.H.S. g Carl Bor man,R.E.H.S. <br /> Dsectar <br /> < 304 East Weber Avenue, Third Floor <br /> 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 /> • c.;: ..':`P Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E:H.S. <br /> �iFoa Laurie A.Cotulla,R.E.H.S. <br /> Fax: (209) 4'64-0138 Robert Mcclellon,R.E.H.S. <br /> Progr aea�Llnnnger Mark Barcellos,R.E.H.S. <br /> DAVID A ROSso APR a 8 2005 <br /> STOCKTON CENTER SITE AUTHIFOOR ITY <br /> 401 GOLDEN SHORE, SECOND <br /> LONG BEACH CA 90802 4210 <br /> RE: California State University Stanislaus <br /> 1252 N. Stanislaus Street RO 0700 <br /> Stockton, CA 95205 <br /> San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Additional Groundwater Investigation and Remediation Feasibility <br /> Evaluation Work Plan (WP) dated 25 January 2005, prepared by Condor Earth <br /> Technologies, Inc, (Condor), received by EHD on 09 February 20'05. <br /> In the WP, Condor proposes, to install 3 shallow and 3 deeper groundwater <br /> monitoring wells to further characterize the vertical and lateral extent of impacted <br /> groundwater, and to collect soil and groundwater samples to evaluate natural <br /> attenuation and bench-test for site suitability for ozone or oxygen injection. Total <br /> depth for the proposed shallow wells is 55 feet below surface grade (bsg) and for <br /> the deeper wells is 95 feet bsg. <br /> Review of the cross sections in the WP indicate that the current shallow wells are <br /> screened across a' thin sand unit at 40 feet bsg and that most of these wells' <br /> screens are in clayey soil. The clayey interval extends as deep as 52 to 55 feet <br /> bsg and overlies a variable silt-silty sand and `stiff fine-grained' interval between <br /> approximately 52/55 feet bsg to 65/68 feet,bsg. The variable silt-silty sand unit is <br /> underlain by a thinner clayey unit that generally occurs between 62/65 and 68/78 <br /> feet bsg. The lower clayey interval may not have great lateral extent. Beneath the <br /> lower clayey unit more mixed sand, silty sand, silt and 'stiff fine-grained' soil <br /> types occur. <br /> Based on the cross section, the deeper wells appear to be,targeting a poorly <br /> graded sand interval and are approved, although the western well may be better <br /> placed near MW-1 ; still an up-gradient location, that will allow triangulation .for <br /> groundwater flow direction determination. Three wells in a Tine cannot be utilized <br /> to characterize flow direction. <br />