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January 8, 1997 Mr. James C. Stevens State of Colorado Division of Minerals and Geology Department of Natural Resources 1313 Sherman Street, Room 215 Denver, Colorado 80203 / Q~ ,`~~ %~, ~~,~ V`N RE: Costilla Landfill Pit, Costilla County, Colorado Dear Mr. Stevens: III IIIIIIIIIIIII III oao iun, ~ 1997 ,,.1y}, t;^. Greystone is submitting this letter on behalf of Costilla County to provide you with the data collected during the quarterly groundwater monitoring and sampling site visit conducted on December 4, 1996, at the above referenced site. A regional site map is included as Figure 1. A site map displaying the location of the monitor wells is included as Figure 2. Groundwater samples were obtained from the two monitor wells (MW1 and MW4). Monitor wells MW2 and MW3 were dry and not sampled. The groundwater samples were submitted for laboratory analysis. The samples were analyzed for volatile organics using EPA Method 624, semi-volatile organics using EPA Method 625, pesticides using EPA Method 608 and herbicides using EPA Method 8150. The samples were also analyzed for Human Health Standards and Secondary Drinking Water Standards listed in the Colorado Department of Health, Water Quality Control Commission, The Basic Standards for Ground Water. In addition, all monitoring wells were measured for depth to water to determine the groundwater gradient and flow direction. A groundwater elevation contour map was not constructed because only two monitor wells contained water. Prior to sampling, each well was purged of a minimum of three well volumes of water or until the well was dry and allowed to recharge. On-site measurements of electric conductivity, pH, and temperature were recorded to ensure that the well stabilized so that a representative sample of the aquifer was collected. Copies of the field activity forms aze attached. The bailer used to develop the wells was decontaminated with aphosphate-free detergent and distilled water between each well. Samples were collected with a Teflon disposable bailer and placed on iced until delivery to the laboratory for analyses. The samples analyzed for phenols, odor, radiochemistry, cyanide, foaming agents, metals, nitrates, nitrites, fluoride, alkalinity, chloride, color, total dissolved solids (TDS), sulfides, and pH were filtered in the field (.45 microns). Chain-of-custody forms accompanied the samples throughout the shipment and are included with the attached analytical report. 5990 Greenwood Plaza Blvd. Suite 250 Englewood, CO 80111 (303)850-0930 Fax(303)721-9298