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<br />002891 <br /> <br />Because coal seams act as aquifers in the basin, substantIal areal strip- <br />pIng of the major seams located at or near the land surface may affect the <br />local ground-water regime by reducing recharge to downgradient streams. De- <br />pending upon availability of data and operational models, some form of quanti- <br />tative analysis will be attempted of localized ground-water systems In exist- <br />ing or potential mining-affected areas. Transport of conservative contami- <br />nants will be investigated, in view of possIble geochemical changes occurring <br />from the stripping of overburden or the removal of coal strata, A related <br />concern is the practice of depositing waste materials in old mine pits. For <br />example, fly ash from the Hayden power-generation plant presently is disposed <br />of in the nearby Peabody Seneca mine and covered with strIpped overburden. <br /> <br />Water Qua Ii ty <br /> <br />By documenting the various alternate coal-resource development proposals <br />for the Yampa River basin, specific areas of potential environmental stress <br />will be delineated for analysis. In thIs regard, approximately one-quarter of <br />the 85 areal reconnaissance sites (Steele and others, 1976) will be sampled <br />quarterly for 12 to 18 months. Interpretation of these data will help to In- <br />dicate continuing data needs and to determine model ing appl ications. <br /> <br />A major thrust of the basin assessment involves determining the extent to <br />which alternative residuals-management plans are likely to affect water quality. <br />Interactions among environmental controls of air, water, and land resources <br />need to be evaluated to assess projected effects on water-qual ity conditIons. <br />Discussed below are several water-quality modeling efforts proposed for incor- <br />poration into the basin assessment. In several cases, modeling alternatives <br />are presented. Further evaluation of these will be required after more-detail- <br />ed specifications on desired modeling accuracies and refinement have been made. <br /> <br />Dissolved Oxygen, Biochemical Oxygen Demand, <br />and Selected Nutrients <br /> <br />For the Yampa River mainstem near areas of projected large population <br />growths--primarily Steamboat Springs--an analysis of the dIssolved oxygen (DO), <br />biochemical oxygen demand (BOD), and several conservative substances will be <br />made for present and projected waste loadings of the stream, A procedure used <br />in a previous study in Arkansas (Jennings and Bryant, 1973) will be considered, <br />A steady-state segmented DO model similar to the model developed by Bauer and <br />Jennings (1975) is being applIed in the Yampa River basin ~ssessment. <br /> <br />As pointed out by Bauer and Jennings (1975), it is necessary to first cal- <br />ibrate the model near the reference 7-day 10-year low flow. Data for DO, BOD, <br />selected nutrient species, temperature, specific conductance, and pH are need- <br />ed for the model (Bauer and Jennings, 1975). These data need to be collected <br />over a 24-hour cycle of a low-flow period. Discharge and stream-geometry data <br />also are requIred by the model. For the Yampa River mainstem, all the requir- <br />ed data for a modeling analysis were not readily available. To supply the nec- <br />essary data for a waste assimilative capacity modeling analysis a field data <br />collection was made during September 1975 for a reach of the Yampa RIver be- <br />tween Steamboat Springs and Hayden (Steele and others, 1976). After the model <br /> <br />19 <br /> <br />, <br />~ <br />