WSP07875

• File Number: 8220.116.I
• Description: Fruitland Mesa Project
• State: CO
• Basin: Gunnison
• Water Division: 4
• Date: 1/1/1976
• Title: Comments re: Draft Environmental Statement
• Water Supply Pro - Doc Type: EIS

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~stern State College of Colorado, Gunnison, Colorado 81230

October 7, 1976

Bureau of Reclamation
Grand Junction, CO

Dear Sirs:

I would like to comment on the geologIcal aspects of the Fruitland Mesa
project especially concernIng the Soap Park Dam site and the Black rAesa
tunnel. I feel qualified to comment on these aspects since I am a Professor
of Geology at Western State Col lege and have been here for' over I I years. .
Further, I was a member of a U.S. Geological Survey team that evaluated the
minerai potential of the West Elk Wi Iderness area In the summers of 1971,
1972 and 1973. I have spent some time doing geologic mapping. in the area.

First, I .would like to emphasize the extreme landslide potential that
Is found In Big Soap Park and Little Soap Park. Although this is discussed
In the Draft Environmental Statement, I feel that the Bureau has greatly
understated the hazard. Both areaS ?Ire absolutely full of old landslide
scars and are Indeed great complexes Of old slump systems. The 'fluctuating
reservoir wi II almostcerta'inly caUSe reactivation of some of these systems
and although catastroph i c lands Ii ding into therese.rvoi r I s not anti ci pated,
slow landslldlng on a major scale is very I ikely. This would displace water
out of the reservoir. This will require constant attention by heavy e?lrth .
moving equipment and the slight possibll ity of a dam spillover is. present.
To put it bluntly, the reservoir si.te Is In hlghly.unstable rock and is
going to create significant problems which may .easlly require costly malnt;",
".,enance and mitigation procedures. I .

Secondly, 'there appear to be major consIderations in the geology of the.
tunnel that are eIther not stated In the Draft EnvIronmental .Sta:tement or
not understood by the Bureau. It is stated that the tunnel bore wI II start
out in Mancos shale in Little Soap Park (which is true) and probably continue
for most of the tunnel although some uncertainty Is expressed due to the fact
that the tunnel bore wll I be closely parallel to an unconformlty.with the
Wes.t. Elk Breccia. However, west of Curecanti creek the West Elk Brecci~ rests
directly on the Precambrian metamorphic complex and most of the tunllel wi.il
probably be bored In either of these two rocks, notfheMancos Shale. . These
rocks are highly fractured ?lnd altered and wi II present signifICant engineering
di fficultles. Although the draft statement showed no estimates of costs, I
would suggest that the above mentioned diffkultieswill significantly increase
the estimated costs of the tunnel; 'Further, experience in Colorado (the
Eisenhower Tunnel) and other areas makes ally.person highly suspect of official,
origInal cost estimates. Overruns of several hundred percent are not uncommon.
What wou I d a 100% cost ove rrun on the. tunne I do the the cost Ibenef It rat i 01

Dlylslon of Natural Sciences and Mathematics

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