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About Tri-Dam


Tri-Dam Project is a joint venture (partnership) between the Oakdale Irrigation District and the South San Joaquin Irrigation District. Together they developed, operate and maintain the Beardsley, Donnells and Tulloch projects including the dams, tunnels, penstocks, powerhouses, communications systems, and general offices. These facilities are located on the Middle Fork of the Stanislaus River in Tuolumne County, California.

Tri-Dam Power Authority is a similarly governed and managed entity, but separate from Tri-Dam Project, with responsibility for the Sandbar hydroelectric plant also located on the Middle Fork of the Stanislaus River.

Originally the Districts were interested in water development projects and continue to be responsible for providing irrigation water to their service territories in the greater Oakdale and Manteca areas. The Beardsley, Donnells and Tulloch facilities provide Oakdale and South San Joaquin Irrigation Districts with storage reservoirs necessary to meet this water obligation. The historical cost to add electric generating facilities to the water storage projects was relatively minor.

Water is currently used to irrigate about 117,500 acres of land on farms in San Joaquin and Stanislaus counties. The irrigated land supports almonds, walnuts, grapes, pasture, and truck crops.

The “Upper Works” include Donnells and Beardsley dams, reservoirs, powerhouses and appurtenant facilities. The “Lower Works” refer to the Tulloch development below Jamestown reaching into both Calaveras and Tuolumne Counties.

Tri-Dam Project is governed by a joint board of directors composed of the five member boards of the two Districts. The day to day activities of Tri-Dam Project and Tri-Dam Power Authority are managed by a General Manager who reports to the board. The administrative offices of Tri-Dam Project are located in Strawberry, California.

Contact Tri-Dam Project or Tri-Dam Power Authority by:

Email –
Telephone – (209) 965-3996
Fax – (209) 965-4235

Mailing Address:
PO Box 1158
Pinecrest, CA 95364-0158