Laserfiche WebLink
Page 2 <br /> 1817 Fresno Avenue <br /> f <br /> In the Report, Clearwater recommends updating the current Site Conceptual Model (SCM) <br /> with the data obtained from SB- 11 and SB- 13 . The EHD considers that the Report and the <br /> recommendations for additional work should have been presented in the context of an <br /> updated SCM; therefore the EHD approves updating the SCM , or appropriate portions of the <br /> SCM , each time newly acquired data and interpretation dictates. <br /> In the interest of reducing costs, the EHD recommends implementing the following modified <br /> sampling regimen : <br /> 1 . Quarterly sampling of wells MW-513 , MW-7 and MW-8 . <br /> 2 . Semi-Annual sampling of wells MW- 1 and MW-6 . <br /> 3. Annual sampling of wells MW-2, MW-3 and MW-4. <br /> 4. All sample analyses should include total petroleum hydrocarbons as gasoline , <br /> benzene, toluene, ethylbenzene and xylenes. <br /> 5 . Well MW-513 and MW-7 groundwater samples should also be analyzed for fuel <br /> oxygenates, ethylene dibromide and 1 ,2-dichloroethane . <br /> 6 . All wells should be monitored on a quarterly basis for calculation of the groundwater <br /> gradient and flow direction . <br /> In Third Quarter 2008 Groundwater Monitoring and iSOC Remediation Activity Report, dated <br /> October 28 , 2008 , Clearwater recommended implementing a low-flow, minimal-drawdown <br /> purging method . To show that sample results collected from low-flow purging would give <br /> comparable results to the site's analytical history, the EHD recommends conducting both <br /> methods at the next quarterly event. Groundwater samples should be collected first using the <br /> low-flow technique , followed by traditional purging of three casing volumes and collection of <br /> another set of samples . If the analytical results from both samples are comparable, the EHD <br /> would approve the switch to low-flow purging method at his site. <br /> If you have any questions please call Lori Duncan at (209) 468-0337. <br /> Sincerely, <br /> Lori Duncan , REHS Nuel C . Henderson, Jr. , PG <br /> Registered Environmental Health Specialist Engineering Geologist <br /> c: James Barton , CVRWQCB, 11020 Sun Center Drive #200 , Rancho Cordova, CA 95670 <br /> Raga Mani , Clearwater Group, 229 Tewksbury Avenue , Point Richmond , CA 94801 <br />