PERMFILE67748

• Permit No: M2000113
• IBM Index Class Name: Permit File
• Doc Date: 4/9/2001
• Doc Name: FAX COVER SHEET
• From: DMG
• To: BALAZ & ASSOCIATES
• Media Type: D
• Archive: No

LEAVENWORTH & IiARP, P.• •
Army Corps Public Notice Number: 200175036
Page 4
March 30, 2001
2. HEC-RAs Analysis
To further identify the hydrologic and geomorphologic impacts of Applicant's gravel mine,
the Ciry of Rifle, at its own expense, performed aHEC-RAS analysis of the proposed mining
operation. See Exhibit C, HEC-RAS prepared by Schmueser Gordon Meyer, Inc. (The
conclusions of that analysis are summarized in the letter dated March 29, 2001 by Jeff Simonson,
P.E., of Schmueser Gordon Meyer, attached hereto as Exhibit B.) According to that analysis,
almost all of Applicant's project will be located within the floodplain of the Colorado River
between Mamm Creek and the City of Rifle. Therefore, during 10-year and 100-year flood
events, the proposed mining areas will be overtaken by water. Further, due to the meandering
nature of the Colorado River, physical activity such as mining could change the course of flow
of the stream, accelerating stream channel changes in the mining area and downstream. 'T'hose
stream channel changes may include a shift in the main stream channel from its current location
into the mining area. Finally, the berms, stockpiles and ponds created by the mine will be subject
to erosion and sediment transport. See Exhibit B.
There are several possible detrimental effects of the aforementioned circumstances created
by the mine, as detailed in Exhibit B. First, there is a possibility that the stream channel may
shifr, overtaking the wetlands mitigation areas and preventing Applicant from performing the
necessary wetlands mitigation. Second, the downstream effect on property owners and wetlands
areas may be significant due to the high potential for main stream channel changes. Third, the
project may have significant long-term impacts on water quality due to the erosion of berms,
stockpiles and ponds, as well as the erosion of previously stable channels and the mining areas
themselves. See Exhibit B.
The impacts referenced above could have a significant effect on the City's water quality
and water supply, as the City of Rifle relies on the Colorado River as the City's water source.
Currently, the City's water intake structure lies along the main channel of the Colorado River.
See Exhibit A, Floodplain Study Map. As detailed in the Floodplain Study, a disruption in an
ofd, abandoned river channel due to Applicant's proposed mining operation could alter the course
of flow of the Colorado River, thereby isolating the Ciry of Rifle's water intake structure. See
Exhibits A and C. Such an impact could effectively cut off the City's water supply.
Due to the potential impact of Applicant's mining operation on the City of Rifle's water
intake structure and supply, as well as the other potential geomorphologic and hydrologic impacts
referenced above and detailed in the attached exhibits, the City requests that Applicant's CWA
§§ 401 and 404 permit applications be denied. )n the alternative, the Ciry requests that an
Environmental Assessment or Environmental Impact Statement be prepared in order to more fully
evaluate the environmental impacts of the proposed project.
I:\1A01\Clie`us\RIFI,EV!-7J\l.erters-Memos\CWA r01~04 conu,t,twpE