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Monitoring Stations of Sites within the confluence area of the above creeks are listed below: <br />• Station 301 is located on Trout Creek upgradient of the confluence with Middle Creek, Flow: 14-16 <br />cfs in summer; TDS: average 320 mg/I (Figure 33, AHR 1993; data sheets) <br />• Station 69 is located downgradient from the confluence of Middle Creek, but upgradient from the <br />confluence of Fish Creek. Flow: 5 cfs in summer; TDS: average 578 mg/I (Figure 33, AHR 1993; <br />data sheets) <br />• Site 1002 is located on Fish Creek and is the last site above the confluence with Trout Creek. Water <br />in Fish Creek flows through Site 16 and Site 115 before reaching Site 1002. Flow: 3.35 cfs in <br />summer; TDS: average 1828 mg/I (Table 3 this report). <br />The calculations used to determine the theoretical impact of each stream on total dissolved solid (TDS) <br />concentrations in Trout Creek are discussed below: <br />Trout Creek (TC) background (Site 301) combined with Middle Creek (MC) (Site 29): <br />(TC flow x TC TDS cont) + (MC flow x MC TDS cont) =Average TDS Concentration <br />(TC flow + MC flow) <br />The calculations used to determine the theoretical TDS concentration in Trout Creek at site 1005 downstream from <br />the confluence of Trout Creek and Fish Creek are as follows: <br />(5.Ocfs x 43 3m / L) + (3.35cfs x 1,828mg / L) <br />• (S.Ocjs + 3.35cjs) — <br />— Average TDS Concentration = 922mg / L TDS Concentration <br />This theoretical calculated average of 922 mg/L is comparable to the value of 982 mg/L actually measured in <br />August 1994 at site 1005 downstream from the confluence of Fish Creek and Trout Creek. <br />EASTERN MINING DISTRICT <br />Prior work has been conducted on the alluvial valley floor determination, and the Division has made a positive <br />finding of the existence of alluvial valley floor downstream on Foidel and Middle Creeks. Twentymile is in the <br />process of generating data to modify the designation of the mid -reaches of Foidel and Middle Creeks as alluvial <br />valley floors due to the land use criteria. <br />Map 15, Alluvial Valley Floors and Water Rights, presents the alluvial valley floor designations. As shown on the <br />map, the confluence area of Middle and Foidel Creeks is the major alluvial valley floor in the area. This area, <br />along with the other mid -reaches of Foidel and Middle Creeks, will be undermined and subsided; but, based upon <br />the work done by Twentymile (refer to Fish Creek alluvial valley floor study. Technical Revision No. 14), <br />agricultural activities will not be interrupted, precluded, or discontinued on the valley floor. The present <br />monitoring work has not shown any changes to the stream and its valley floor. During late August or early <br />September 1993, longwall mining of panel number 9 Right will commence: this will provide further data as to the <br />impact to the stream and valley floor. As projected, approximately 1.5 feet of subsidence will occur in the stream <br />channel. However, as indicated in the projections, no impacts are anticipated to the stream and the valley floor. <br />(I ScJs x 320mg / L) + (2.Ocfs x 1,756mg / L) <br />= <br />(15cfs + 2.Ocfs) 489mg / L TDS Concentration <br />MR 97-154 2.06-23 12/09/97 <br />