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PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION w < <br /> Karen Furst, M.D., M.P.H., Health Officer ' <br /> 304 East Weber Avenue, Third Floor - Stockton, CA 95202 <br /> 2491468-3420 <br /> MAY 1 7 2000 <br /> FRANK OVINTA JAMES RAMSEY <br /> 2072 W YOSEV.1 E AVE ?40 14A CO?vTENTA Dr,:VE <br /> EXXON SITE CODE, 1426 <br /> 2072 W YOSEMITE AVE <br /> MANTECA CA <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EliD) has reviewed the <br /> Aqua Science Engineers Inc (ASE)"Report of Soil and Croundwnter,issessrnent"received May 11, 2000 <br /> As a result of reviewing the report PHS/EHD provides the following comments and directives <br /> Multilevel monitor wells and piezometers installed at the site have been used to document the presence of <br /> several groundwater contaminants, many above established Maximum Contaminant Levels (MCL's) <br /> including MtDE and benzene Contaminants include separate phase Lel hydrocarbons (free-product) PCE, <br /> 1,2-Dichloropropane, TPH-gasollne, TPH-diesel,toluene, cthylbenzene,xylenes, TAME, TBA, McOH and <br /> EtpH <br /> Through previous reports ASE has established the potential risk to nearby receptors All groundwater zones <br /> (0 to greater than 100 feet bell evalwecl to date »r. tMrac1ed WWI ±rGutairuhants Depth to water is <br /> approximately 13 feet below grade surface (bgs) Oreater than 57 shallow water wells are present within <br /> 2000 feet of this site Groundwater off-site is impacted with fuel hydrocarbons The lateral and vertical <br /> characterization of the groundwater plume is currently undefined. Gradient and groundwater flow is <br /> variable with depth, and a downward vertical flow component is evident Groundwater flow direction and <br /> gradient in the deeper zones of the aquifer(100 feet bgs)cannot be plotted because only two of the required <br /> three non-linear points exist to date <br /> PHS/EHD concurs with the majority of ASE's recommendations The first priority is sampling and <br /> analyses of the closest drinking wattr wells, ASE lists seven addresses for the first round of analyses <br /> Contact PHS/EHD to schedule field work for this purpose as soon as possible, Other water wells may <br /> require sample collection and analyses as the groundwater plume is defined Full scan EPA Method 8260 <br /> analyses is recommended <br /> Additional groundwater monitor wells are needed A third deep Kell (100 feet bgs) to complete the non- <br /> liriear three point evaluation should be installed during the next well installation mobilization Monitor <br /> wells in the shallow and intermediate zone should be installed in down gradient positions as soon as <br /> possible in order to evaluate risk to regional groundwater supplies and design of remediation systems, <br /> Remediation system feasibility studies may be presented to PHS/EHD in workplan format, <br /> PHS/EHD does not concur with recommendations to modify quarterly groundwater sampling at this time <br /> Please continue to sample all monitor wells on a quarterly basis until farther written notice from this office <br /> A Divislon of San loaquln County Health Care s4rvlces <br /> TS d 9i£t�Z669Z 5�NN"6-3 Wd 9Z- 60 013-97---J,dW <br /> 401rin7 Gni nn n7 KOut nan 1 a'1'.a ll <br />