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October 13, 1997 <br />~crE!~'ED <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 />OCT 1 ~ 1997 <br />~11A"~'~il ~~ n~~iICI~IJ G UUC~~~~y <br />RE: Costilla Landfill Pit, Costilla County, Colorado <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 August <br />28, 1997 at the above referenced site. <br />A regional site map is provided as Figure 1. A site map displaying the location of [he monitor <br />wells is provided as Figure 2. A groundwater elevation map is included as Figure 3. <br />Groundwater elevations were calculated using the measured groundwater elevation data and the <br />surveyed well casing elevations. The survey data and groundwater level measurements are <br />included in Table 1. A groundwater elevation contour map is included as Figure 3. <br />The groundwater gradient observed on August 28, 1997 ranged from 0.003 to 0.018 feet per foot <br />(ft/ft) to the southwest. Depth to water ranged from 34.90 ft below grade in well MW4 to 43.15 <br />ft below grade in well MWS. <br />A site map displaying the location of the monitor wells is included as Figure 2. Groundwater <br />samples were obtained from the three monitor wells (MW1, MW4 and MW5). Monitor wells I <br />MW2 and MW3 were dry. The groundwater samples were submitted for laboratory analysis. The <br />samples were analyzed for volatile organics using EPA Method 624, semi-volatile organics using <br />EPA Me[hod 625, pesticides using EPA Method 608 and herbicides using EPA Method 8150. <br />The samples were also analyzed for Human Health Standards and Secondary Drinking Water <br />Standards listed in the Colorado Department of Health, Water Quality Control Commission, The <br />Basic Standards for Ground Water. In addition, all monitoring wells were measured for depth to <br />water to determine the groundwater gradient and flow direction. <br />5990 Greenwood Plaza Blvd. Suite 250 Englewood, CO 80111 <br />(303)850-0930 Fax(303)721-9298 <br />:. >s <br />