Dennett Dam no longer serves a function, and has been an in-stream partial barrier to fish passage for over 60 years. It has also been a navigation hazard to recreational boating through Modesto due to the powerful hydraulic forces associated with the concentrated overflow near the middle of the dam. This project will greatly improve safety for swimmers, boaters, and anglers who are currently at high risk near the dam, which has tragically been the site of three drowning deaths within the last five years, including two children.
Originally built in the 1930s to create a seasonal recreational lake, Dennett Dam partially failed during high flows within a decade of its completion. The Tuolumne River Trust’s involvement has been not only building public, governmental and agency support for its removal, but also pursuing funding for the necessary planning, engineering, environmental studies, and construction necessary for removal. The Trust ultimately seeks to restore the river channel and enhance the surrounding landscape, resulting in a vastly improved native riparian habitat and recreational experience.
Complete removal of Dennett Dam would support extensive coordinated restoration efforts on the Tuolumne, which historically had the largest fall Chinook runs in the San Joaquin River system, by facilitating upstream access during the fall to prime salmon and steelhead spawning gravels between Basso Bridge and Old La Grange Dam (visible on our canoe trips), as well as downstream outmigration during spring high flows. Dam removal would also eliminate conditions conducive to native and non-native predator species that likely feed on outmigrating juvenile salmonids.
With the dam removed, Chinook salmon, steelhead, pacific lamprey, and river lamprey will have unimpeded access to 37 miles of upstream habitat. Central Valley steelhead is an anadromous fish listed under both the State and Federal Endangered Species Act, and Central Valley fall-run Chinook salmon and Pacific lamprey are anadromous species of concern or candidates for listing.
The dam is located just west of the 9th Street Bridge in Gateway Park (Modesto), which is part of the Tuolumne River Regional Park (TRRP). The Trust has supported development of TRRP and its associated trail system as part of the overall economic redevelopment of this Central Valley town. When completed the Tuolumne and Dry Creek trail system will stretch over 16 miles of scenic riverfront, providing Modesto with a fantastic amenity to its quality of life.
Removal would also complement efforts by the Tuolumne River Coalition to complete the Lower Tuolumne River Parkway, a mosaic of 25 park and habitat projects along the 52 miles of the Lower Tuolumne, and support development of a planned boat trail through this portion of the river.
To learn more about the Tuolumne River Trust's efforts to remove Dennett Dam, please contact Jesse Roseman at jesse.roseman@tuolmne.org or call (209) 236-0330.
