Laserfiche WebLink
I I'i <br /> Page 2 <br /> I <br /> 2103 Country Club Blvd . <br /> The residual sorbed contaminant mass was only estimated for benzene and MTBE , and the <br /> estimate was based on the last monitoring event dissolved concentrations and the partition <br /> coefficient between sorbed , dissolved and vapor phases which depends on a number of <br /> assumptions . Arcadis focused only on benzene and MTBE ; however, TPHg is a contaminant <br /> that has Water Quality Objectives (WQOs) that must be achieved and is part of determining the <br /> plume extent which needs to be addressed . The most impacted groundwater is in the " B" zone <br /> at 40 to 50 feet bsg which has not been adequately or fully delineated . The maximum extent of <br /> the delineated plume so far is approximately 190 feet toward the north from the assumed source <br /> area to MW-13B; the maximum extent toward the WNW - the predominant flow direction has not <br /> been delineated . If plume length is not reasonably demonstrated then the correct LTCP criteria <br /> cannot be identified . In this case , the maximum benzene concentration of 3 , 200 ug/L in MW-2B <br /> exceeds the criteria for either the groundwater specific criteria (2d) or (4d) on the LTCP <br /> checklist . <br /> The EHD recommends that the following actions be taken in order to move the site towards <br /> closure consideration : <br /> 1 ) Complete the characterization of impacted groundwater in the " B" zone ; <br /> 2) Proceed with the currently approved remedial actions addressing the " B" zone <br /> groundwater and overlying impacted soil ; <br /> 3) Include the TPI-Ig as a constituent of concern for plume delineation , time to reach water <br /> quality objectives and determining distance from plume margin to sensitive receptors . <br /> With the above listed items adequately addressed the EHD will be able to reevaluate the site for <br /> closure. <br /> If you should have any questions please contact Lisa Medina at (209) 468-3455 or by email at <br /> Imedina(i�Ncehd . com . <br /> Lisa Medina Nuel C. Henderson , Jr. , PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> l c: James Barton , CVRWQCB 11020 Sun Center Drive, ##200 Rancho Cordova , CA 95670 <br /> Mark Springs, 3535 Windham Circle , Stockton , CA 95209 <br />'I <br /> h <br /> Justin Sobieraj , Arcadis U . S . , Inc. , 2000 Powell Street 7 Floor, Emeryville , CA 94608 <br /> i <br />