2008-09-15_HYDROLOGY - M2004078 - Laserfiche WebLink

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CIVIL RES 2URCES,LLC ENGINEERS & PLANNERS r? September 11, 2008 Mr. Eric Scott Division of Reclamation Mining and Safety 1313 Sherman Street, Room 215 Denver, Colorado 80203 RE: July 2008 Groundwater Quality Monitoring Results, Lupton Lakes Gravel Mine Permit No. M•2004-078 Dear Mr. Scott: The following letter report describes the results from the July 2008 Sampling Event. This report is being submitted in general compliance with approved Groundwater Sampling and Analysis Plan (GWSAP) included in Technical Revision 2 (TR2) to the Lupton Lakes Gravel Permit issued by the State of Colorado Division of Reclamation Mining and Safety. Dewatering began in the area of the south sediment pond near Weld County Road 6 in June 2007 and stopped in May of 2008. Dewatering began in the area of the north sediment pond in April 2008. The dewatering water was placed into an infiltration basin located near the northeast corner of the project until a sixteen (16) inch High Density Polyethylene Pipe (HDPE) pipe was installed. The sediment in the water was allowed to settle out then it was discharged through the HDPE pipe into the South Platte River. Discharge into the South Platte River began in May 2008. Groundwater Monitoring Results The July 2008 Sampling Event includes monitoring wells CRMW01, CRMW04, CRMW06, CRMW09, CRMW16, and CRMW41. CRMW02 was not sampled because a conveyor belt was placed over the well and there is no access. The dewatering volume is being pumped from the site under Hwy 85 and into the South Platte River. Following is a listing of the major results and conclusions: • Fluoride, Chloride, Iron, pH, and Total Dissolved Solids did not exceed the Primary Drinking Water Standards (PDWS) or the Secondary Drinking Water Standards (SDWS). Nitrate (as N) exceeded PDUVS in three of the six samples with nitrate concentration levels ranging from <0.04 mg/L up to 16.53 mg/L in CRMW41. The PDWS for nitrate is 10 mg/L. The currently proposed site wide baseline level for nitrate is 29.9 mg/L. The baseline level for well CRMW41 is 29.9 mg/L. Nitrate levels in all of the wells were below either the proposed site wide or individual well baseline levels. Nitrate concentrations have consistently exceeded the PDWS before and during mining operations. • Secondary Drinking Water Standards (SDWS) were exceeded for the sulfate concentration level reported in well CRMW09. The sulfate concentration in CRMW09 did exceed the proposed individual well baseline level by 14.6 mg/L. The remaining SDWS parameters tested for including pH and Iron did not exceed the SDWS. Additional parameter test results and the summary of all laboratory analysis results are contained in the attached table. 323 Fw-rH STREET 0 P.O. Box 680 0 FREDERICK, 00 80530 0 PHONE (303) 833-1 41 6 0 Flax (303) B33-2850