2008-03-13_PERMIT FILE - C1992081 (8)

Home Browse Search

4.0 ANALYSIS AND CONCL~ISIONS • 4.1 Sources of :Flow The similarity between stream quality quality for samples collected dui-ing Diagram) indicates that Dry and Sage, Dowden Gulches are fed from seepage f Another strong indication o~ this is the streams above the Twentymile sand crop in the Hayden Gulch and Dowden G and the ground iYater the study (see the Stiff Creeks and Hayden add rom the aquifers: the absence of €low in stone aquifers dut= uleh drainages: Figure 8 shows the drainages of the gages in relation to the study area geology: All of the drainages are in either the Lewis Shale, .the Williams Fork Formation or the Iles Formation. Only the lower stations on Sage and Dry Creeks inelude mtieh of the the Lewis Shale in their drainage. The increase ih dissolved solids in these streams is caused by seepage from the Lewis Shale. Seepage from shales is typically very high in dissolved solids, particularly in sodium and sulfate; as was the case in samples from these streams: Shall seepage also contributed to the increased concentrations of iron and manganese, prbb- • ably because of ion exchange reactions between the water and clay in the shale. 4.2 Mining-Related Ef.feC.ts.ori Water Rg~b:ur.ces Mining-related effects dri surface water will be negligible because the mine is hear a drainage divide; acid therefore little water flows through the proposed mine area besides that from snow or rain falling on the site: Fldw iii Hayden and Dowden gulches will also remain unaffected, since the Twentymile Sandstone aquifer will not be altered: The upper portions of Sage Creek should not 6e affected; since it does hot inelude either .the mine or the corridor. Upper Dry Creek is expected to show ari increase in suspended solids during the construction of the haulage. road; but norm<<lly there should be no other measurable change: The quality of the lower portions of Sage and Dry Creeks is affected by seei~- age from the Lewis Shale to the extent thaf fhe xater is un- suitable for domestic use and is a questionable, source of irrigation water during most of the time that the .streams do flow. \.