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July 2, 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, Roont 215 <br />Denver, Colorado 80203 <br />~ ~ ~~~ <br />~~ <br />~,~ <br />iii iiiiiniuiiiiii <br />oao <br />RECEIVED <br />'JUL 0'7 1998 <br />Division of t~erals-&-G~ <br />~~ <br />ItE: Costilla Landfill Pit, Costilla County, Colarado <br />Dear Mr. Stevens: <br /> <br />Greystone is submitting this setter on behalf of Costilla County to provide you with the data <br />collected during die quarterly groundwater monitoring and sampling site visit conducted on June <br />4, 1998 at the above referenced site. <br />A regional site map is provided as Figtrre 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 usurg 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 June 4, 1998 ranged from 0.02 to 0.03 feet per foot (ft/ft) <br />to the southwest. llepth to water ranged from 34.86 ft below grade in well MW4 to 49.77 ft <br />below grade in well MW2. <br />A site map displaying the location of the monitor wells is included as Figure 2. Groundwater <br />samples were obtained from one monitor well (MW5). Monitor wells MWI, MW2., MW3 and <br />MW4 have been excluded from quarterly sampling and were not sampled. <br />The sample was analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) using EPA <br />Method 602, and total dissolved solids (TllS) using EPA Medtod 160.1. Standards are presented <br />in Tables 4 and 5. The sample was also analyzed for Human Health Standards (total colifotm, <br />barium, fluoride, lead, and nitrate+nitrite), Secondary Drinking Water Standards (chloride, iron, <br />rrlanganese, pH, and zinc) listed in the Colorado Department of Health, Water Quality Control <br />Commission, The Basic St~r~dards for Ground Water and for pesticides using EPA Method 603 <br />and herbicides using EPA Method 8150. Standards are presented in Tables 2 and 3. In addition, <br />all morti[oring wells were measured for depth to water to determine the groundwater gradient and <br />flow direction. <br />5231 South Quebec Strcet • Greenwood Village, Colorado 8011 l <br />Phone (303) 850-0930 • Fas (303j 721-9298 <br />Web Site: www.greystone-consuhants.com • E-mail greystone@greystone-consultants.com <br />Environmental Planners, Scientists, and Engineers <br />