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4 � <br /> PUBLIC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY s Py <br /> ENVIRONMENTAL HEALTH DIVISION :( <br /> Karen Furst, M.D., M.P.H., Health Officer ' <br /> 304 East Weber Avenue, Third Floor - Stockton, CA 95202 <br /> 2091468-3420 <br /> MAY 17 2000 <br /> FRANK GUINTA JAMES RAMSEY <br /> 2072 W YOSEMITE AVE 840 LA CONTENTA DRIVE <br /> MANTECA CA 95336 VALLEY SPRINGS CA 95252 <br /> RE., FRANKS EXXON SITE CODE: 1426 <br /> 2072 W VOSEMITF AVE <br /> MANTECA CA <br /> San Joaquin Count} Public Health Services Enironmentc] Health Division (PH511=HD) has reviewed the <br /> Aqua Science Engineers Inc (ASE)"Report oJSotl and Oro undivai r.fssessment"received May 11, 2000 <br /> As a result of reviewing the report PHS/HHD provides the following comments and directives <br /> Multilevel monitor wells and piezometers installed w the site have been used to document the presence of <br /> several groundwater contaminants, many above established Maximum Contanuriant Letiels (MCL's) <br /> including MtBE and benzene Contanunants include separate phase fuel hydrocarbons (free-product) PCE, <br /> 1,2-Dichloropropane, TPH-gasoline, TPH-diesel, toluene, ethylbenzene, xylenes, TAMS, TBA, McOH and <br /> EtOH <br /> Through previous reports ASE has established the potential risk to nearby receptors All groundwater zones <br /> (0 to greater than 100 feet bgs) evalu to-A tet eip4fN..4 l.t <br /> t.wuatruiranis Dcpth to water is <br /> approximately 13 feet below grade surface (bgs) Greater 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 mrilpling and <br /> analyses of the closest drinking water wells, ASE buts seven addresses for the first round of analyses <br /> t 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 well (100 feet bgs) to complete the non- <br /> linear 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 systema <br /> Remediation system feasibility studies may be presented to PHS/EHD in workplan fomut, <br /> PHS/EHO does not concur with recommendations to modify quarterly groundwater sampling at this time <br /> Please continue to sample all monitor wells op a quarterly bast$until further written notice from this office <br />' A Di�tslon of San Joaquin County Health Care services <br /> IClC 'd s r�zszeEez s xraraz1 wd 9Z. 60 CIO-9z—A0W <br />