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Small Diversion Dam Upgrades

Coandă-Effect Screens Allow Fish Passage and Reduce Maintenance at Three Sierra Dams

The upgrades to three diversion dams on the Middle Fork American River Project were designed to improve operations and maintenance, enhance environmental resources, and meet the requirements specified in new environmental programs and measures required for FERC licensing. This project included the design of a self-cleaning, Coandă-effect screen intake system along the spillway crest of existing diversion dams to increase efficiency, reduce maintenance, and improve riparian habitat by allowing fish and sediment migration over the dams. The designs maintained required variable minimum instream flows, allowing for fish bypass.

  • Duncan Creek has a 100-foot-wide dam with 400 cfs diversion. Engineering design also included a maintenance access road extension and culvert to connect the new intake structure to the existing diversion tunnel
  • North Fork Long Canyon has a 95-foot-wide dam with 100 cfs diversion
  • South Fork Long Canyon has a 60-foot-wide dam with 200 cfs diversion

Bennett Engineering Services provided project management, analysis of the existing system hydraulics, and assessment of feasibility study design with modifications to meet regulatory agency requirements. The team worked closely with PCWA engineers and planners to develop creative design solutions to meet the needs of the operators, license requirements, and resource agencies for all three diversions.