Laserfiche WebLink
ENVIRONMENTAL HEALTH EPARTMENT <br /> SAN JOAQUIN COUNTY <br /> ).• 'A� Unit Supervisors <br /> Donna K Heran,R.E.H.S. Carl Borgman,R.E.H.S. <br /> Director 304 East Weber Avenue,'Third Floor 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 /> Program Manager Telephone: (209)468-3420 Margaret Lagorio,R.E.H.S. <br /> �iFOR Laurie A.Cotulla,R.E.H.S. Robert McClellon,R.E.H.S. <br /> Program Manager Fax: (209)464-0138 Mark Barcellos,R.E.H.S. <br /> JOHN DAVIS OCT 2 4 2002 <br /> MCDOWELL & DAVIS TOWING <br /> 1360 ESCALON AVE <br /> ESCALON CA 95320 <br /> RE: McDowell & Davis Towing SITE CODE: 1486 <br /> 1360 Escalon Ave. <br /> Escalon CA 95320 <br /> San Joaquin County Environmental Health Department(SJC/EHD)has received the September <br /> 2, 2002 correspondence from your consultant M.J. Kloberdanz&Associates (MJK)regarding the <br /> above referenced site and has the following comments. ` <br /> SJC/EHD recently reviewed the"Risk Assessment and Conceptual Site Model"report dated May <br /> 23,2002 that was submitted on your behalf by MJK. In that report MJK concluded that there was <br /> an indoor air exposure risk at a building on site, and recommended that the interior of the <br /> McDowell & Davis Towing office be monitored for the possible migration of contaminant vapors, <br /> and that a passive soil vapor survey of areas of exposed soil be conducted. Responding to that <br /> document by letter dated August 6, 2002,SJC/EHD requested additional data and <br /> reconsideration of the default values presented in the risk assessment model. MJK has <br /> apparently misunderstood and taken exception to some of SJC/EHD's comments and requests. <br /> SJC/EHD had considered this site to be of fairly low risk and moving toward a closure <br /> consideration when an undirected and unrequested Risk Based Corrective Action (RBCA) model <br /> was presented by MJK that calculated a cancer risk and a health hazard to people working in the <br /> building on the site. SJC/EHD cannot give a closure consideration to a site that has been <br /> demonstrated by the responsible party's consultant to pose both a health risk and hazard without <br /> further study and perhaps site assessment. <br /> SJC/EHD did not expect the findings of the RBCA model that the site contamination presented a <br /> cancer risk and health hazard to the buildings workers,as the extent of impacted soil appeared to <br /> be limited; thus SJC/EHD inquired regarding the default values used in the model,which may be <br /> too conservative, the implication being that the model be rerun with site-specific-Values which <br /> may present more favorable results. In particular, SJC/EHD notes that effective-porosity is not <br /> the same as total porosity. While 0.38 is probably a good estimate of total pofosity, the effective <br /> porosity is probably much lower,typical averages ranging from 0.21 to 0.27 for poorly graded fine <br /> sand to poorly graded coarse sand, respectively, and from 0.08 to 0.18 for silt. Mix sand and silt <br /> together and the effective porosity would be less. SJC/EHD believes that 0.20 may be closer to <br /> actual conditions than 0.38, but recommends that MJK reevaluate the parameter. Also, the <br /> groundwater gradient in the model(0.18)appears to be too high as the gradients determined <br /> from the groundwater monitoring events ranged from 0.004 to 0.018. Again, SJC/EHD <br /> recommends that each value utilized in the model be reexamined and be as site-specific as <br /> possible, and that the model be rerun. <br /> i <br />