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anuary 30, 1998 <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 />Dear Mr. Stevens: <br /> <br />RECEIVED <br />FEB 02 1998 <br />Oivisi0n olMinerals 8 Geology <br />Z .- <br />lj <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 />December 18, 1997 at the above referenced site. <br />A regional site map is provided as Figure 1. A site map displaying the location of the 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. <br />The groundwater gradient observed on December 18, 1997 ranged from 0.02 to 0.03 feet per foot <br />(ft/ft) to the southwest. Depth to water ranged from 38.08 ft below grade in well MW4 to 48.65 <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 two monitor wells (MWl and MWS). Monitor wells MW2, MW3 <br />and MW4 have been excluded from quarterly sampling and were not sampled. The groundwater <br />samples were submitted for laboratory analysis with MW 1 placed on "hold" pending results of <br />MWS. Should MWS exceed the permit limits, MW1 will be analyzed for corresponding <br />parameters. <br />The samples were analyzed for volatile organics using EPA Method 602, total dissolved solids <br />(TDS) using EPA Method 160.1, pesticides using EPA Method 608 and herbicides using EPA <br />Method 8150, Tables 4 and 5. The samples were also analyzed for Human Health Standards <br />(total coliform, barium, fluoride, lead, and nitrate+nitrate) and Secondary Drinking Water <br />Standards (chloride, iron, manganese, pH, and zinc) listed in the Colorado Department of Health, <br />Water Quality Control Conunission, The Basic Standards for Ground Water, Tables 2 and 3. In <br /> <br />5231 South Quebec Street • Greenwood Village, Colorado 80111 <br />Phone (303) 850-0930 • Fax (303) 721-9298 <br />i Web Site: www.greystone-consuhants.com • E-mail: greystone@greystone-consultants.com <br />Eirvirortmenta( Planners, Scientists and Engineers <br />