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Richard Mills <br />Page 2 <br />March 13, 1998 <br />in which flow in the stream was completely disrupted." Indeed, at that time, Foidel creek was <br />Flowing over this crack, with no visually noticeable loss of flow. It is DMG's opinion that, rather <br />than the crack in the Twentymile sandstone unit being sealed by fine-grained material, the crack <br />was completely saturated and filled with water in the vicinity of the creek channel. As <br />characterized by aquifer data for the Twentymile sandstone, this unit would likely not have the <br />ability to absorb this water as compared to the rate the creek flow was entering the crack. <br />Therefore, at some point after the crack developed to it's full extent, the crack would fill with <br />water and flow would be restored in the stream bed over this recharge area of the Twentymile <br />sandstone. DMG is interested in any measurable loss of Flow, crack dimensions, estimated <br />saturated area of the crack, associated recharge to the sandstone from the increased saturated area. <br />Have other cracks developed in areas subsided since the Fall of 1996? DMG would like <br />clarification of the statement "The data shows that sealing process was completed in <br />approximately 66 days after the initial cracking". Is it TCC's contention that there was a <br />measurable loss of flow for 66 days or 8 hours? What information led to this conclusion? What <br />determines when the sealing process is complete? How will this sealing process work along <br />17,500 feet of Fish Creek? What kind of flow interruption can DMG expect along Fish Creek, <br />and where? How will downstream uses be impacted by a loss of flow in the Fish Creek? <br />No response was provided to the remainder of the original question, repeated below. <br />A relationship has been established benveen site 8, upstream of the EMD, and site 900, <br />downstream ojthe subsided area ojthe EMD. According to information submitted by TCC in the <br />/996 Annual Hydrology Report, the average flow for the period ojrecord (1979-1996) for site 8 <br />is 3.589 cjs. The average flow for site 900 for the period ojrecord (1976-1996) is 6.06 cfs. The <br />Division's prior understanding ojthe flow relationship between the two sites was that site 900. <br />flow was less than the flow at site 8, possibly due to recharge to the Twentymile sandstone <br />upstrenm of site 900. The average flow information does not seem to support this understanding. <br />Additionally, the information collected and reported in Table 72 for site 900 does not match the <br />information presented in the /996 AHR for site 900 for the same day. Why? <br />A few sentences ojtext and data from 26 monitoring visits to Foidel Creek during subsidence <br />cnused by one panel of mining in the EtLID is not sufficient injormatiorr for the Division to <br />approve mining and subsidence of /7,500 feet of Fish Creek. Amore detailed analysis of the flow <br />relationship between site 8 and site 900 in necessary. This analysis should estimate the loss of <br />flow along Foidel Creek due to subsidence, considering the length ojstream affected by <br />subsidence, while considering the geology, hydrology, and geomorphology of creek. This <br />information should be used to develop the probable hydrologic consequences for Fish Creek, <br />including long-term loss ojflow in the creek due to subsidence as well as evaporative loss Jere to <br />po»ding. Detailed, concise, and accurate flow information along Fish creek at the various <br />historic monitoring stations can be used in conjunction with subsidence predic[ion models for <br />Fislr Creek to estimate irnpncts. The channel response ojFoidel Creek due to subsidence and the <br />sire and location of ponded areas can also be used to estimate impacts along the length ojFish <br />Creek to be subsided. !t should be noted [hat the probable hydrologic consequences injornration <br />submitted with PR-Oa for the ErLID and the NMD (beginning on page 2.O.i-12a p) contained no <br />injormnlion estimating loss ojstreanrJlox~ dere [o subsidence. <br />