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existence of flood irrigation and the presumed capability of these areas to support subirrigation during a portion of <br />• the growing season." Negative findings on all identified alluvial valley floor areas were also issued. <br />The information submitted to the division in the permit application for Colorado Yampa Coal Company's Mine #3 <br />(Permit C-84-062) addressed the issue of subirrigation in two of these AVF areas. Both the fmdings document and <br />permit materials are presented in Exhibit 42b. These areas are: <br />on Fish Creek near the Fish Creek Tipple and <br />the confluence area of Foidel and Middle Creeks <br />The data presented strongly indicates that subirrigation is not occurring during the "moisture-stress" portion of the <br />growing season in either of these two areas. The Proposed Decision and Findings of Compliance for the Mine #3 <br />permit application did not accept the data as representative of the entire growing season on the basis that the study <br />was performed in October, 1980. in order to supplement the previously submitted material, additional water level <br />data for the period 1981-1985 has been compiled for alluvial monitoring wells in these two AVF areas. These data <br />are presented as hydrographs for well 008-AV-2 in the Foidel Creek/ Middle Creek confluence area (Figure 3f) and <br />for well 008-AU-3 in the Fish Creek area (Figure 3g). These hydrographs also indicate the relative depth of the <br />observed root zone in the two AVF areas. Figure 3f is updated with water level data through the 1998 water year. <br />Additionally, the historic data collected by P & M for this azea was used to construct a peizometric surface along <br />Fish Creek. The well location and profile is shown on Figure 3-i. The profile is based on a surface elevation range <br />for the period of November, 1979 through February, 1981. Figure 3j provides the monthly water level elevation for <br />this period. <br />• The hydrographs clearly show that the alluvial ground water table during October is representative of the moisture- <br />stress portion of the growing season and that typically the water table is 3 to 4 feet below the root zone during these <br />periods. The capillary zone in both areas was estimated to be between 2.5 and 3 feet above the water table based on <br />neutron probe soil moisture measurements. On this basis the upper limit of saturation would still fall below the root <br />zone during most of the growing season. In addition, when evaluating subirrigation, greater concern should be placed <br />on the rate of upward movement of water in order to enhance vegetative growth. Kohnke (1968), states that in fine <br />textured soils the capillary rise becomes exccedingly slow so that plants seldom gain from the presence of ground <br />water if its level is greater than 2.6 feet below the roots. <br />On the basis of previously submitted information and the supplemental alluvial monitoring well data included in this <br />permit application it is TCC's contention that subirrigation is not an essential hydrologic function of the two alluvial <br />valley floor areas described above. These areas are acknowledged to be alluvial valley floors on the basis of <br />historical and existing artificial flood imgation activities only. <br />An area in the Foidel Creek drainage in sections 21, 22 and 28 has been designated an alluvial valley on the basis of <br />the potential for subimgation. The U.S. Department of Interior, Office of Surface Mining, Division of Reclamation <br />and Enforcement released in June 1985, Reconnaissance Maps to Assist in Identifying Alluvial Valley Floors in <br />Northwestern Colorado. The reconnaissance map of potential alluvial valley floors for the Yampa and Danforth <br />Hills Coal Field of Northwest Colorado (Eastern half) delineates the subject area as having the potential for flood <br />irrigation but not for subirrigation. This evaluation is consistent with information submitted in the permit for the <br />Eckman Park Mine including an analysis of infrared photography taken in September, 1978 which showed no <br />evidence of subirrigation in this area (Permit #79-177, pages 785-IS to 785-16). The azea has numerous zones of <br />surficial salt deposits which tends to suggest that the underlying alluvial ground water is probably of high salinity <br />• which would limit plant growth by subirrigation even if the alluvial water table was high enough to be tapped by <br />plant roots. <br />APPROVED JUN 2 8 2000 <br />PR 99-OS 2.06-8 8/27/99 <br />