2014-06-12_HYDROLOGY - M1977300

• Permit No: M1977300
• IBM Index Class Name: Hydrology
• Doc Date: 6/12/2014
• Doc Name: Mine Phase 1- 2013 Mitigation Monitoring Report
• From: IRIS Mitigation and Design, Inc.
• To: COE and DRMS
• Permit Index Doc Type: Hydrology Report
• Email Name: TAK
• Media Type: D
• Archive: No

IRIS MITIGATION AND DESIGN,INC.
IRIS 2022 Arapahoe Street
' MITIGATION AND DESIGN,INC. Golden,Colorado 80401
Environmental Consulting Phone: [phone]
[e-mail]
PHASE 1 MITIGATION AREA CREATION
' In June 2012, American Civil Contractors ("ACC') completed Schwartzwalder Mine - Phase 1
construction activities to install an upstream concrete cutoff wall to bedrock across the valley.
ACC also completed excavation of three required riparian mitigation areas located just upstream
of the cutoff wall (0.16 acre total) and one upland restoration area also located upstream of the
' cutoff wall (0.09 acre total). As planned, the 0.04 acre riparian creation area located farthest to
the west had approximately 2 feet of soil excavated with the top 6 inches of topsoil cleaned of
' rocks and debris and restored to the site (see Table 1). Approximately 6 inches of soil including
rocks and debris were removed from the 0.03 acre central and eastern riparian mitigation areas.
' These two areas then received an addition of approximately 6 inches of imported topsoil. The
' 0.09 acre riparian restoration area was cleaned of rocks and debris before having approximately
6 inches of imported topsoil added. Lastly, an approximately 0.09 acre of upland located
' directly adjacent to the installed cutoff wall was restored through the removal of rocks and
debris and through the addition of approximately 6 inches of imported topsoil (see Table 1). All
mitigation areas were then seeded with either the upland, transitional or wetland seed mixes as
' detailed in the IRIS August 2011 Biological Assessment and hydro-mulched in July 2012.
Seeding and hydro-mulching activities were completed at all seeded areas to stabilize the soil
following Phase 1 construction activities.
' The mitigation sites located on the north side of the Creek (approximately 0.16 acre total) were
' trampled by several cattle which strayed across the site in late August/early September 2012.
The 0.09 acre restored upland area located just south of the cutoff wall was not trampled. Due
' Schwartmalder Mine Phase 1 -2013 Mitigation Monitoring Report Page 2
May 31,2014