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ENVIRONMENTAL HEALTH JEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Donna K. Heran, R.E.H.S. Unit Supervisors <br /> Director 304 East Weber Avenue, Third Floor Carl Bergman, R.E.H. S . <br /> Jul. 4 ` Laurie A . Cotulla, R.E.H.S. Stockton, California 95202-2708 Mike Huggins, R.E.H.S ., R.D.I. <br /> Program Manager Douglas W. Wilson, R.E.H.S . <br /> q � / .FOPN Telephone : (209) 468-3420 Margaret Lagorio, R.E. H .S . <br /> Fax : (209) 464-0138 Robert McCtellon, R.E.H. S . <br /> Website : www. sjgov. org/ehd/ Jeff Carruesco, R.E.H.S . <br /> VELMA MASTERSON APR 1 1 2006 <br /> BENETO INC <br /> PO BOX 980220 <br /> WEST SACRAMENTO CA 95798 <br /> RE : DARPETRO, INC Site Code: 1060 <br /> 749 E CHARTER WAY <br /> STOCKTON, CA 95202 <br /> San Joaquin County Environmental Health Department (EHD ) received and reviewed <br /> Re: Updated Monitoring Well Installation Work Plan (MW- 17, MW- 18) (WP-MW), dated <br /> 21 March 2006 and Amended Work Plan for Soil Vapor Extraction Pilot Test (W P-SVE ), <br /> dated 28 March 2006 , both prepared and submitted by California Geophysical Group <br /> (CGG) on your behalf. <br /> The WP-MW is an improvement on the original work plan , but contains some <br /> inconsistencies . The text descriptions of the well designs are inconsistent and the well <br /> design diagrams are not scaled or have well component dimensions labeled to resolve <br /> the text inconsistencies. Examination of one inconsistency illustrates the other <br /> inconsistencies : the text indicates the well will have 10 feet of screen section at the <br /> bottom ( 125 feet to 135 feet below surface grade) and have a sand filter pack extending <br /> from total depth to 5 feet over the screened interval - which would be 120 feet to 135 <br /> feet below surface grade (bsg). The text then states that a transitional seal (bentonite) <br /> will be placed above the sand from 120 to 125 feet bsg . The sand and the transitional <br /> seal cannot occupy the same 5 feet of space . This inconsistency is repeated for the <br /> second proposed well and also affects the depth of placement of the annulus cement. <br /> These inconsistencies may seem trivial , but if the WP-MW is approved with these <br /> inconsistencies the actual well construction may not conform to what EHD thought was <br /> intended in the WP-MW , or there may be disagreement between the driller, the <br /> consultant and the EHD inspector at the site at the time of the well installation . <br /> The WP-MW does not provide a technical justification for collection and laboratory <br /> analysis of soil and groundwater samples . EHD can infer reasons for soil sampling , i . e. <br /> to confirm the CPT log interpretations, to fill in data gaps , etc, but collection and <br /> analysis of water samples from the pilot boring for a monitoring well is less apparent. <br /> The technical justifications should be provided . <br /> The WP-SVE is also an improvement on its original work plan , but EHD would like to <br /> know how the vapor samples will be collected from the individual wells into the tedlar <br />