2007-01-31_REVISION - M1986015 (2)

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i Requirement: The actual arrangement of sediment basins may vary a[ [he discretion of the i operator so long as all basins have 9t least one side with an unsealed connection to adjacent i unmined land and a significant portion of the groundwater is allowed to flow completely through I the backfilled area. ~ I Mini i g Plans for the New Phase 2 STEP 1: Strea i bank Strengthening and Protection Issues Requirement: Prior to mining Phai a 2, streambank strengthening and stabilization shall be installed along the river bank south' of Phase 2 at all locations where it is expected that erosion may i occur. The preference will be for [hie installation of closely spaced (20 feet, more or less) jetties keyed into [he bank and extending a short ways into the river Dow. Prior to installation approval from the U.S. Army Corps of Engineers may be required. i I I DISCUSSION: In eariy Jhly of 2006, the entire I-25 corridor from Colorado Springs [o i Pueblo and lands as far west as Canon City were subjected to a series of intense thunderstorms that created the largest flood event since the floods of late April 1999. Roads were flooded or washed out, streams overflowed and sometimes cflanged course, and major rivers like [he Arkansas River spread floodwaters [o about the 25 to 50 year~ or greater storm event elevation in the floodplain. For the most part, damages were less significant than had occurred as a result of the three day long event in 1999. But where conditions ware suitable, major damage to streambanks did occur. On August 26, 2006, a large line i of intense thunderstorms swept across the Pueblo area flooding streets and intersections and producing another major flood event. As a result of [he first flood, the pit in Phase 1 was breached at one location and was subjected to overflow erosion in another location. The setbacks were appropriate and secure. The breach was primarily caused by a sandbar located upstream from the breach. The sandbar forced [he high water into the bank which undercut the bank. Overflow pliobably also occurred, but there was a protective berm in place that should have kept overflow to a minicellIum unless the overflow even overtopped the berm. Once the river bank was cut through, the river rushe$ into the pi[, completely filling it and leaving about a 300 foot wide I hole in the southeastern wall of the pit. If the gravel bar had not been there it is highly unlikely that the breach would have occurred, unless i~ was primarily an overflow event. Unfortunately, [he actual breaching was not witnessed so nobody can be sure of exactly what happened. The second flood on Angus[ 26, breached the pit again. Although repairs of the first breach i created in July were well along and a majority of [he water had been pumped out of [he pit, the river once Pueblo East Pit Amendment 3 (2007) Exhibit D Page 22 of 34