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<br />Aspen Highlands SJrj Area. Draft EnvironmeltlaI Impact SttUemenl <br /> <br />POTENTIAL MITIGATION MEASURES <br />Measures 10 mitigate impaclS on biodiversity would be the same as those included under wildlife for reducing the <br />loss of snags and forest debris habitat elemenlS. habitat fragmentation. and critical habitat areas for forest interior <br />and edge-sensitive species. <br /> <br />AQUATIC RESOURCES <br /> <br />AFFECTED ENVIRONMENT <br />On-mountain streams within the analysis include three perennial spring-fed streams in the CCW and two <br />perennial spring-fed streamS in the MCW. all of which are too small to support fisheries. Ski terrain development <br />within CCW is less than I percent of the total composite watershed area. This low concentration of developed <br />area. combined with good vegetative cover. and relatively stable catwalks. roads. and ski runs. minimizes <br />oMimP.ll'a'ion to on- and off-mountain streams within the analysis area. The critical impact issue in the MCW <br />ct:fI1erS on the erosion and slope instability problems this area has experienced. Ski area development within the <br />MCW comprises 15 percent of the total composite watershed area. with many of the ski runs being graded. <br />Where vegetative cover has been restored there appears to be few erosion problems. However. there are some <br />critical areas in the watershed where nmoff and erosion control have long been concerns. as discussed previously <br />in the Water Resources section. <br /> <br />Off-mountain streams include Castle and Maroon creeks. both of whicb are 4th-order streams which converge <br />and eod in the Roaring Fork River near Aspen. Maroon Creek experiences relatively high bedload movement and <br />experiences an average monthly discharge of 5.474 acre-feet during maximum snowmelt. Fishery surveys of <br />Castle Creek found two game species. brook trout and rainbow trout. and one non-game species. mottled sculpin. <br />Flsbery surveys of Maroon Creek found two game species. brook trout and Colorado River cutthroat trout. and <br />no non-game species. Both Castle and Maroon creeks are stocked annually with catchable rainbow trout. <br /> <br />The USFWS identified the Colorado squawfish (Ptychocheilus lucius). razorback sucker (Xyrauchen texanus). <br />bonytail (Gila elegans). and humpback chub (Gila cypho) as federally listed species that may occur within the <br />Aspen Highlands area or that could be impacted by the project. Nooe of the above-listed species have been <br />reported in the Roaring FOlk drainage. but all four are located in the upper Colorado River basin. The Colorado <br />River cutthroat trout (Oncorhynchus clarki pleuriticus) is on the Forest sensitive list and a fishery survey of <br />Maroon Creek done by CDOW in 1973 located one individual. <br /> <br />ENVIRONMENTAL CONSEQUENCES <br />While the Aspen Highlands water righlS are junior to the 14 cfs minimum instream flow. it is possible that winter <br />depletions could adversely impact the aquatic habitat in Maroon Creek even if they do not violate the minimum <br />instream flow. This is because streams that undergo extremely low flows. especially during November and <br />December. could be subject to stream icing (anchor ice. shelf ice. and ice dams). Larger substrate exposed <br />through reduced streamf10ws can result in reduced stream temperatures and accelerating ice formation. Anchor <br />ice in particular can be damaging to beothic macroinvenebrates which occupy the stream substrate. In addition. <br />potential impacts to Maroon and Castle creeks under all alternatives would include spring/summer events <br />resulting from increased water yield from expanded snowmaking operations and winter water depletions from <br />Marocm Creek for snowmaking and municipal usage. The combination of construction and clearing for ski area <br />facilities and increased Stlowpack from soowmaking could result in elevated overland flow volume and velocity. <br />and consequently increase the sediment load transponed to waterways. In most cases. vegetation clearing would <br />take place sufficient distances from both Maroon and Castle creeks to prevent sedimentatioo to these streams. <br />Water depletions 10 Castle Creek are expected to be negligible. and therefore not a coocern for this project. Water <br />depletions to Maroon Creek. however. are greater and could impact aquatic resources. None of the alternatives <br />would cause violation of a 14 cfs instream flow right for Maroon Creek. <br /> <br />24 <br /> <br />Section III <br />AqlUllic Resources <br />