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f i <br /> STATE OF CALIFORNIA PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL VALLEY REGION 1 �� <br /> 3443 ROUTIER ROAD, SUITE A t <br /> SACRAMENTO, CA 95827-3098 \� <br /> PHONE: (916) 361-5600 <br /> FAX: (916) 361-5686 <br /> 12 July 1991 EN,� �iZISEVGE�SH <br /> PERM <br /> Mr. Abel Haines <br /> Director of Environmental Program Office <br /> Defense Distribution Region West, Sharpe Site <br /> Lathrop, CA 95331 <br /> REVIEW OF THE WELL SAMPLING FREQUENCY RECOMMENDATIONS, DEFENSE DISTRIBUTION <br /> REGION WEST (DORN) , SHARPE SITE, SAN JOAQUIN COUNTY <br /> We have reviewed the Well Sampling Frequency Recommendations submitted on <br /> 11 February 1991 by the U. S. Army Toxic and Hazardous Materials Agency <br /> (USATHAMA) for the DDRW, Sharpe Site. We acknowledge that our review is <br /> submitted late, however, we believe that our comments may be useful for future <br /> revisions to the monitoring program. The monitoring program must be a dynamic <br /> data gathering process because the needs of the program will change as the site <br /> moves forward from the remedial investigation to the cleanup phase. <br /> In general , we are pleased that Sharpe has made an evaluation of the existing <br /> monitoring program. Many of the proposed changes are reasonable and are adequate <br /> to assess the extent of the plume and effectiveness of the extraction systems. <br /> However, we believe that the monitoring program should ultimately be changed to <br /> quarterly and semi-annual , rather than a quarterly and annual monitoring program, <br /> due to the apparent seasonal fluctuations in the hydraulic system at the site. <br /> The proposed quarterly monitoring should be reduced and the proposed annual <br /> monitoring should be increased to semi-annual . <br /> We are also concerned that quarterly or annual monitoring frequently does not <br /> include all of the monitor wells in a cluster. We find this to be confusing. <br /> We recommend that all of the wells in a cluster be monitored at the same <br /> frequency so that the vertical as well as the horizontal extent of the plume can <br /> be defined. We also have several comments on the specific wells proposed for <br /> monthly, quarterly and annual monitoring. Our comments can be found in the <br /> enclosed memorandum. <br /> If you have any questions, please call me at (916)361-5670. <br /> ��r,GI�JrC'kl>C�r <br /> CAMILLA WILLIAMS <br /> Engineering Geologist <br /> CKW:cw <br /> Enclosure <br />