[Federal Register Volume 63, Number 202 (Tuesday, October 20, 1998)]
[Notices]
[Page 56047]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-28031]
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DEPARTMENT OF THE INTERIOR
Bureau of Reclamation
Arrowrock Dam Outlet Works Rehabilitation, Boise, ID
AGENCY: Bureau of Reclamation, Interior.
ACTION: Notice of intent to prepare an environmental impact statement.
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SUMMARY: Pursuant to the National Environmental Policy Act (NEPA) of
1969, as amended, the Bureau of Reclamation (Reclamation) intends to
prepare an environmental impact statement (EIS) for the proposed
rehabilitation of the outlet works at Arrowrock Dam on the Boise River
near Boise, Idaho. The purpose of the proposed rehabilitation is to
reduce the maintenance requirements of the existing outlet works, which
are past their useful life, while meeting the operational needs of the
dam for irrigation and flood control. The current proposal is to remove
some of the existing outlet works and install 10 clamshell gates. This
work will require operational changes during construction, including
prolonged drawdown of Arrowrock Reservoir.
FOR FURTHER INFORMATION CONTACT:
Mr. Steve Dunn, telephone (208) 334-9844.
ADDRESSES: Bureau of Reclamation, Snake River Area Office, 214 Broadway
Avenue, Boise, Idaho 83702.
SUPPLEMENTARY INFORMATION: Arrowrock Dam is located on the Boise River,
about 13 miles east of Boise, Idaho. Reclamation completed construction
of the dam in 1915, and at that time it was the highest dam in the
world. The downstream face of the dam was resurfaced and the height was
increased by 5 feet in 1937.
Arrowrock Dam is one of three instream storage dams on the Boise
River. Anderson Ranch Dam is located upstream of Arrowrock Dam on the
South Fork Boise River, and Lucky Peak Dam, constructed by the U.S.
Army Corps of Engineers, is located on the Boise River downstream of
Arrowrock and impounds water up against Arrowrock Dam when full.
Arrowrock Reservoir is operated for irrigation and flood control in
combination with Anderson Ranch and Lucky Peak Reservoirs. In general,
water is stored in Arrowrock Reservoir during the winter and spring
according to predicted runoff and flood control requirements. Beginning
in April water is released for irrigation from Arrowrock and Anderson
Ranch Dams until early September when Lucky Peak Reservoir is drafted
to meet irrigation demands. Lucky Peak water elevation is kept high
through most of the summer for recreation.
The ensign valves controlling releases from Arrowrock Dam are the
original valves installed in 1915. These valves have reached the end of
their useful life, resulting in complex operational and maintenance
concerns. Most of the valves have been damaged through prolonged use,
and there is an increasing need for frequent inspection and repair.
Three of the 10 ensign valves in the lower bank are no longer usable.
In order to ensure against malfunctioning valves, inspection and
maintenance should be performed about every 5 years, which requires the
reservoir level to be below the outlets. Under normal operations the
upper row of ensign valves are out of the water by the end of summer
and easily accessed. However, in order to dewater the lower bank of
valves, the sluice gates must be used. There is some concern about use
of the sluice gates since they too are over 80 years old and are in
need of repair. If one of the sluice gates were to stick open,
uncontrolled releases from Arrowrock would occur which could empty the
reservoir.
The existing ensign valves also limit Arrowrock Dam's operational
flexibility. The lower bank of ensign valves cannot be used under high
water pressure when the reservoir is full. This reduces the dam's
capability to release water for flood control operations in years with
high runoff.
Reclamation has developed a proposal to replace the 10 lower ensign
valves with ``clamshell gates.'' The clamshell gates would allow
releases at any reservoir level, providing more operational
flexibility. The remaining upper row of 10 ensign valves and the sluice
gates could be abandoned which would significantly reduce maintenance.
The clamshell gates would be designed to allow inspection and
maintenance without dewatering.
Reclamation has studied several other engineering alternatives to
the proposal which involve different configurations of outlet control
structures and rehabilitating the existing outlet works. Reclamation
will also study operational alternatives to be implemented during the
construction phase. Other alternatives to the proposal may be developed
through the public scoping process. It is expected that the presence of
threatened bull trout in Arrowrock Reservoir and the requirements of
the Endangered Species Act may also influence the range of
alternatives. All reasonable alternatives which meet the purpose and
need for the project will be evaluated in the EIS.
Federal, state and local agencies, tribes, and the general public
are invited to participate in the EIS process. Scoping meetings to
obtain input about concerns and issues associated with this proposal
will be held but are not yet scheduled. Notification of meeting dates
will be provided in a Federal Register notice, as well as through local
media.
Anyone interested in more information concerning the EIS or who has
information that may be useful in identifying significant environmental
issues, should contact Mr. Dunn at the telephone number or address
indicated above.
Dated: October 14, 1998.
Steven R. Clark,
Acting Regional Director, Pacific Northwest Region.
[FR Doc. 98-28031 Filed 10-19-98; 8:45 am]
BILLING CODE 4310-94-M