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July 12, 1996 <br />Mr. James C. Stevens <br />State of Colorado <br />Division of Minerals and Geology <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />RE: Costilla Landfill Pit, Costilla County, Colorado <br /> <br />III IIIII~~IIIIII III <br />•:1` • ~" <br />o~rFIVED <br />JUL 17 1996 <br />Division of Minerals & Geology <br />1~'~ ~ <br />2~ <br />Dear Mr. Stevens: <br />Greystone is submitting this letter on behalf of Costilla County to provide you with the data <br />collected during the quarterly groundwater monitoring and sampling site visit conducted on <br />June 6, 1996, at the above referenced site. A site map is included as Figure 1. Groundwater <br />samples were obtained from the four monitor wells (MW1 through MW4). The groundwater <br />samples were submitted for laboratory analysis. The samples were analyzed for volatile organics <br />using EPA Method 624, semi-volatile organics using EPA Method 625, pesticides using EPA <br />Method 608 and herbicides using EPA Method 8150. The samples were also analyzed for <br />Human Health Standards and Secondary Drinking Water Standards listed in the Colorado <br />Department of Health, Water Quality Control Commission, The Basic Standards for Ground <br />Water. In addition, all monitoring wells were measured for depth to water to determine the <br />groundwater gradient and flow direction. <br />Prior to sampling, each well was purged of a minimum of three well volumes of water or until <br />the well was dry and allowed to recharge. On-site measurements of electric conductivity, pH, <br />and temperature were recorded to ensure that the well stabilized so that a representative sample <br />of the aquifer was collected. Copies of the field activity forms are attached. The bailer used <br />to develop the wells was decontaminated with aphosphate-free detergent and distilled water <br />between each well. Samples were collected with a Teflon disposable bailer and placed on iced <br />until delivery to the laboratory for analyses. The samples analyzed for phenols, odor, <br />radiochemistry, cyanide, foaming agents, metals, nitrates, nitrites, fluoride, alkalinity, chloride, <br />color, total dissolved solids (TDS), sulfides, and pH were filtered in the field (.45 microns). <br />Chain-of-custody forms accompanied the samples throughout the shipment and are included with <br />the attached analytical report. <br />Laboratory results indicate that samples obtained from wells MWl through MW4 were below <br />detection limits for pesticides, PCBs, herbicides, semi-volatile organics, and volatile organics. <br />TDS were within the acceptable range for groundwater. The remaining analyses, identified in <br />the Human Health Standards and Secondary Drinking Water Standards tables with The Basic <br />Standards for Groundwater were below the method detection limits or below the respective <br />standards. Analytical results for the Human Health Standards and Secondary Drinking Water <br />5990 Greenwood Plaza Blvd. Suite 250 Englewood, CO 80111 <br />(303) 550-09,3Q Fax (303) 721•y29$ <br />i <br />