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& STATE OF CALIFORNIA—ENVIRONMENT#TECTION AGENCY PETE WILSON Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— ...�°""` <br /> CENTRAL VALLEY REGION ,�1'� { i�l ALTH - <br /> 3443 ROUTIER ROAD, SUITE A Jh '1x s` r t� + <br /> SACRAMENTO, CA 95827-3098 r �l "7ERVICE q' � <br /> PHONE: (916) 255-3000Y r �� �• O� w�?" "VP <br /> FAX: (916) 255-3015 J 1 6 <br /> 20 May 1993 <br /> Mr.Wes Johnson <br /> San Joaquin County Department of Public Works <br /> 1810 East Hazelton Avenue <br /> Stockton,CA 95201 <br /> NORTH COUNTY LANDFILL,SAN JOAQUIN COUNTY(CASE#3161) <br /> The staff of the Regional Water Quality Control Board has been putting together revised Waste <br /> Discharge Requirements(WDRs)and a Water Quality Monitoring Program for the North County <br /> Landfill. The Proposed Water Quality Monitoring Program we received from you in June of 1992 <br /> lists upper tolerance limits (UTLs),or concentration limits,for the surface water quality monitoring <br /> parameters also proposed in the program. The concentration limits proposed are based on the range <br /> of monitoring parameter concentrations recorded at background surface water monitoring point,S-1, <br /> at the landfill site. <br /> In the First Quarter 1992 Water Quality Monitoring report,chloride,TDS,and EC concentrations <br /> were reported at significantly higher levels than historical values. The downstream sampling at S-2 <br /> did not show this increase,and therefore,we believe that the sampling done at S-1 may not have been <br /> representative of the general conditions near S-1 at that time. We feel that the 1st quarter 1992 <br /> monitoring results for S-1 should be treated as outlier data and not included in any statistical analysis <br /> for the landfill. <br /> Article 5 is designed with a mechanism to change the monitoring status of a landfill from detection <br /> monitoring to evaluation monitoring if the concentration limits are exceeded at any monitoring point. <br /> The historical groundwater quality data included in the Proposed Monitoring Program indicate that <br /> the concentration of TDS and the value of EC at S-1 have already exceeded the limits proposed in the <br /> program. <br /> Based on the overall quality of the surface water at the landfill site,we suggest that the surface water <br /> quality concentration limits for chloride,TDS,and EC be based on the historical data excluding the <br /> 1st quarter 1992 sampling event. We request the revised concentration limits by 15 June 1993 so that <br /> we may proceed with revision of the landfill's WDRs. <br /> If you have any questions,please call Robert Evans at(916)255-3136. <br /> Robert Evans <br /> Project Representative <br /> BJS <br /> cc: Mr.Brad William,CIWMB,Sacramento <br /> Mr. Ed Padilla,San Joaquin County Public Health Service,Stockton <br />