2016-08-10_GENERAL DOCUMENTS - M1981185 (2)

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Final -Restoration and Compliance Plan for May Day Idaho Mine Complex Administrative Order for Compliance, Docket No. CWA-08-2012-0011 5.0 INFORMATION FOR REMOVAL AND RESTORATION PLAN 5.1 EXISTING PHYSICAL CONDITIONS The following describes the physical conditions at the Chief Portal and Mine Access Road sites. included is a description of wetlands at the sites, per a wetland delineation completed for the Mine Affected Area, as described in more detail in Section 5.2. 5.1.1 Chief Portal Area The Chief Portal area is located along Little Deadwood Gulch approximately 3,200 feet upstream of the confluence with the La Plata River (see Figure 2). Little Deadwood Gulch is a high-gradient stream with swell-armored channel (see Photos 1 to 6 in Appendix C). Based on a longitudinal slope of 12 percent in the reach of the Chief Portal, the channel would be classified as an "Aa+ Stream Type" according to Rosgen 1996. This stream type is very steep (slope of greater than 10 percent), well entrenched with a low width/depth ratio and is totally confined. The channel consists of boulders and cobbles in the vicinity of the Chief Portal (see Photos 1, 2, and 5 in Appendix C). Further downstream where the slope of Deadwood Gulch is not as steep (less than 10 percent), Little Deadwood Gulch would be classified as an "A Stream Type" according to Rosgen 1996. Little Deadwood Gulch is an intermittent stream, with flow primarily derived from snowmelt in the spring and periods of no or very little flow later in the year. Approximately 5 gallons per minute (gpm) of flow was observed upstream of the fill in the gulch in May 2012, but the gulch was dry in early June 2012. There are no springs or seeps in the Chief Portal area. The channel of Little Deadwood Gulch consisfs primarily of cobble ar~d boulder-sized rr~ate~iai, with a thin, poorly developed soil matrix. Woody debris is evident in and near the channel. The aquatic resource value of the channel is relatively limited due to the lack of perennial water and wetlands. For example, a cursory survey in May 2012 did not find any macroinvertebrates or other aquatic life in the channel upstream or downstream of the portal. The channel of Little Deadwood Gulch at the Chief Portal site would be considered an active channel. Several measurements were taken of the limit of the ordinary high water mark (OHWM), as defined by the limit of large rock in the channel bottom, break in side slope, and limit of vegetation. The average of the field measurements of the OHWM is approximately 9 feet. June 2016 Bikis Water Consultants, a division of SGM Page 7 Case 1:16-cv-02008-WYD Document 2 Filed 08/08/16 USDC Colorado Page 37 of 82