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LJ <br />The aforementioned eelcuiated Changes in baatn parameters that will result from mining the <br />• Nuela East area are 1Skely exprease0 in reclaimed areas st the Nuela Mina. However, duo <br />to the lack of premi ni ng (before 1960'a) topographic mapping at a suitable scale (7 inch <br />400 feet), meaningful estimates of the pram ning basin parameters for the Nuela H1 ne <br />cannot be determined. <br />A final impact to drat page basins fn both areas is the temporary loss of topsoil <br />structure. This could potenti el ly reduce the infiltration capacity of the soil and <br />increase ovarl and runoff. <br />In sumaary, Impacts from ml ning on the local geomorphology wt11 be long tens, but appear <br />• to be of Mni nal si gnificancs. Tha reestab7 ished reach of the Nast Return Ditch will <br />result in a shorter, slightly steeper stream channel. The potenti ai for increased <br />sediment loeda in Me Neat Return Di teh (once the 001 aedi moot pond {s removed) should ba <br />offset by the stable banksidas and Cho relatively small change In overall gradient. The <br />f nereaaed runoff and consequent erosi an potentS al on disturbed basins in eS thar mining <br />area due tc the temporary loss oT topsoil structure should ba of minimal significance. <br />Contour rippi m~, wulcht ng and revegetati on have been demonstrated to minimize soil erosion <br />• and will be used to ml ti gate the increased runoff potential until the topsoil struetu re is <br />davel oiled. <br />Effects of Sediment Ponds on Channel Charaeteiiatlca and Downstream Users. During the <br />permit period of boN the Nuela Nine and the Nuela Eaat mining arses, seven sediment ponds <br />will be utilized to Smpoun0 Cho runo}f fray disturbed areas and provi da for'suffieiant <br />detention ti ms before any water is discharged trap the poMa. Six of these ponds have <br />ei ready been constructed at the Nuele Nine (Ponds 001, 002, 003, 004, 005 and 006, see <br />Exhibit 13-4, Tab 13). The seventh pond, 007, will be conseructetl near the southern <br />boundary of the Nue7a Eaat mining area (sae Exhibit 73-5). Impeeta to the channels as a <br />raault of these ponds ere expected es Eoll owe. <br />The ponds that coilaee flow iron larger drainages doml oared by irri gati an tailwatar (001, <br />006 aM 007) wiil eventually reach an equiltbri uo with water gains (inflow) aM lasaea <br />(seepage, evaporation and discharge). Channel reaches imsndiately below these ponds will <br />bscase inctssd with smaller, actively meandering channels whaaa geasetri ea will be <br />4uncti on of reduced runoff potential, channel gradlenta and sediment load perti eta si za <br />ranges. VOgeEati on will begin encroaching on the edpsc of the new ecti ve channels as <br />there will be inauffi.cient runoff to remove it. <br />t7-7fi RevT sad 04/71/88 <br />\J <br />REVISED MARCH 2006 Attachment 2.05.6(3}2-87 <br />