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vPqu IN..c /� <br /> g� C J I THOMAS R.FLINN <br /> c. DEPUTY DIRECTOR <br /> DEPARTMENT OF PUBLIC WORKS <br /> R O.BOX 1810-1810 E.HAZELTON AVENUE <br /> 4ciFbaP STOCKTON,CAUFORNIA95201 `, .THOMAS M.GAU <br /> (209) 3000 DEPUTY DIRECTOR <br /> MANUEL LOPEZ FAX(209)468-2999 <br /> DIRECTOR <br /> STEVEN WINKLER <br /> DEPUTY DIRECTOR <br /> April 25,2001 <br /> Wendy Arano <br /> California Regional Water Quality Control Board <br /> 3443 Routier Road,Suite A <br /> Sacramento,California 95827 <br /> SUBJECT: HEXAVALENT CHROMIUM RETESTS AT HARNEY LANE SANITARY LANDFILL AND <br /> NORTH COUNTY RECYCLING CENTER AND SANITARY LANDFILL <br /> Dear Ms.Arano: <br /> During the fourth quarter 1999 monitoring event,Hexavalent Chromium was detected in downgradient well G-4 at <br /> the North County Recycling Center and Sanitary Landfill(NCRCSL),and in downgradient wells MW-3 and MW-4 <br /> at the Harney Lane Sanitary Landfill. In response to these detections the Regional Board requested these wells be <br /> retested for the presence/absence of Hexavalent Chromium. The retests have been completed,and the analytical <br /> results are enclosed. <br /> Results from the retest conducted at the NCRCSL showed no detection of Hexavalent Chromium in well G-4. <br /> Therefore,the County believes this to be either sampler or laboratory error,and not a release from the landfill. <br /> Results from the retest at the Harney Lane Sanitary Landfill indicate the presence of Hexavalent Chromium in both <br /> down gradient wells. The results also show that the detected concentrations in each well have apparently switched. <br /> The concentration in MW-4 was now approximately half that of the concentration in MW-3,where previously the <br /> concentration in MW-4 was more than twice that of the concentration in MW-3. Due to this unusual occurrence the <br /> County requested our consultant to investigate this occurrence further. Our consultant felt that the laboratory <br /> detection limits were unusually low and requested verification from the laboratory. As a result of this,our <br /> consultant suggested taking a second set of samples and sending them to a separate laboratory for verification. <br /> Therefore,the County had a second set of samples taken and sent to a laboratory that runs a different analysis that <br /> has been proven to detect Hexavalent Chromium at very low concentrations. The results from the second retest <br /> confnmed the presence and concentration levels found in our first retest. <br /> If you have any questions please contact me at(209)468-3066. <br /> Sincerely, <br /> Aww <br /> MICHAEL KALISH <br /> Associate Engineer <br /> Enclosure <br /> c: Robert McClellon,Public Health Services,Environmental Health Division <br /> MK:NZ:vn <br /> N:\Michael\HL\GWmon\Cr_VI_retest.wpd <br /> LA 64201 <br />