BOARD00069

• Board Meeting Date: 5/24/1999
• Description: ISF Section - Colorado River Basin Issues - San Juan/Chama Project - ISF By-Pass Issues
• Board Meetings - Doc Type: Memo

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later in the century. Reports by trappers in the 1820's brought prospectors and _
miners, and eventually permanent settlers. -

Studies of the possibility of diverting San Juan River Basin waters into the
Rio Chama, a tributary of the Rio Grande, began immediately after the First World
War. In 1933, the Bunger Survey began surveys of the features involved. That
survey was continued in 1936, as a part of the Rio Grande Joint Investigations, to
determine the need for such a project. The investigations established the basis for
recognizing, in the Rio Grande Compact, the possibility of a transmountain diversion
to bring water from the San Juan River into the Rio Grande Basin. The Colorado River
Basin report, issued by Reclamation in 1946, established the quantity of water that
was considered for transmountain diversion during negotiation of the Upper Colorado
River Basin Compact.

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In 1950, in the interest of coordination, the Secretary of the Interior appointed
a committee known as the San Juan River Technical Committee. Its summary report
was prepared in May 1950, and the committee presented progress reports in 1951
and 1952. Field survey work was resumed at the beginning of 1951, and Reclamation
prepared interim reports through 1955, followed by a feasibility study. That study
was supplemented in 1957 and was followed by authorization of the project, as
preciously mentioned. Volume I of the definite plan report, covering diversion and
regulation elements of the project, was approved on August 10, 1 964.

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Project Features

The northernmost facility is Blanco Diversion Dam on the Rio Blanco. It diverts
water to Blanco Tunnel, a closed conduit of 520 cubic feet per second (ft'/s) capacity,
designed to carry water 8.6 miles from the Rio Blanco southward to the Little Navajo
River. There, the Little Oso Diversion Dam diverts water from the Little Navajo River
to the Oso Tunnel to join with flows from Blanco Tunnel. Oso Tunnel is a
concrete-lined structure of 650 ft'/s capacity and 5.1 mile length conducting water
from the Little Navajo River to the Navajo River. The southernmost facility is Oso
Diversion Dam, which diverts water from the Navajo River to Azotea Tunnel to join
with flows from Oso Tunnel. The 12.8-mile, concrete-lined Azotea Tunnel, with a
capacity of 950 ft'/s, conveys water from the Navajo River, under the Continental
Divide to Azotea Creek in the Rio Grande Basin.

These imported waters flow down Azotea and Willow Creeks 11.8 river miles
to Heron Reservoir. The regulating and storage reservoir is formed by Heron Dam, on
Willow Creek just above the point where Willow Creek enters the Rio Chama. The
dam is an earthfill structure, 269 feet high, which forms a reservoir with a
conservation capacity of 401 ,320 ac-ft and surface area of 5,950 acres. Its spillway
has a capacity of 660 ft'/s, and the outlet works has a capacity of 4,160 ft'/s.

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