2008-01-15_HYDROLOGY - M2004078 - Laserfiche WebLink

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1.0 INTRODUCTION The following report describes the results from the October 2007 Sampling Event and analyzes the results of the sampling • events over the past year. The sampling results are then used to establish background or "baselinep levels for the parameters that have been tested in wells CRMW09 and CRMW16 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 Mining Reclamation and Safety (DBMS). Baseline levels have been modified in wells CRMW01, CRMW02 and CRMW41 since there has been no active mining in this portion of the site and groundwater impacts from mine activity is highly unlikely. Site wide baseline levels for dissolved iron concentrations have also been determined. 2.0 OCTOBER GROUNDWATER MONITORING RESULTS The October 2007 Sampling Event included monitoring wells (CRMW) 01, 02, 04, 05, 06, 09, 16, 40, 41, and 42. Two recharge sites have also been sampled and reported. 2.1 Primary Drinkina Water Standards Sampling results from December 2006 through October 2007 show that the Primary Drinking Water Standards (PDWS) were exceeded for nitrates, fecal coliform, and arsenic. Following is a general description and discussion of results related to PDWS analytes: Nitrate (as N) exceeded PDWS in eight of the ten wells sampled across the site ranging from undetected up to 71.26 milligrams per liter (mg/L). The site wide nitrate baseline levels proposed in 2006 were exceeded in wells CRMW01 CRMW02 and CRMW41. These three wells are located in the northwest corner of the site well away from any active mining during the sampling period and should not be considered to be influenced by mining activity. New baseline levels are proposed for these three wells below. Nitrate levels in the south and north recharge areas both exceeded the PDWS but did not exceed the site wide baseline levels. • Fecal coliform exceeded PDWS in three of the ten wells sampled across the site ranging from undetected up to 13 most probably number per 100 milliliters (mpn/100m1). Fecal coliform was detected in wells CRMW01, CRMW04, and CRMW06 in the April and October 2007 sampling events. The test detection limit is 2 mpn/100m1 with a site wide baseline level of 1 mpn/100m1. CRMW01 is located in northwest corner of the site well away from any active mining during the sampling period and should not be considered to be influenced by mining activity. CRMW04 is located cross gradient from the active mining activities and also cross gradient from an existing residence and downgradient from an existing auto salvage yard and repair shop. CRMW06 is located downgradient of the active mining area and cross gradient with a prefabricated concrete business. CRMW06 is also located within an active petroleum remediation site with an air Sparge system. • Total arsenic exceeded PDWS in two of the four wells sampled in April 2007 ranging from undetected up to 0.023 mg/L. There were no arsenic concentrations that exceeded the proposed site wide baseline level of 0.03 mg/L. • Mercury exceeded the site wide baseline level of 0.0002 mg/I in one sample from CRMW04 during April 2007. There were no detections of mercury in the October 2007 samples. • Fluoride did not exceed the PDWS or the baseline levels from December 2006 through October 2007. 2.2 Secondary Drinkina Water Standards Sampling results from December 2006 through October 2007 show that the Secondary Drinking Water Standards (SDWS) were exceeded for total dissolved solids (TDS), iron, sulfate, and chloride. Following is a general description and discussion of results related to SDWS analytes: • Chloride exceeded SDWS in one of the ten wells sampled in December 2006, April 2007, and October 2007. . CRMW09 did not have a sufficient amount of data collected in the 2006 annual report to establish a baseline level. However, with the additional data collected in 2007 a baseline level has been established for this well. The baseline Annual 2007 Sampling Report -Lupton Lakes -1- January 2008