Bull Run Dam 2 Tower Improvements
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The Bull Run watershed is 102 square miles and is located 26 miles east of downtown Portland and serves as the primary drinking water source to the City of Portland and a few surrounding communities.

The City of Portland was faced with a problem of trying to address competing demands between preserving the drinking water supply and releasing water for Endangered Species Act (ESA) listed fish in the river below their reservoirs. As part of their Habitat Conservation Plan effort, a hydrodynamic and water quality model was previously developed (CE-QUAL-W2) for the two drinking water reservoirs and the river below the reservoirs. The results of the modeling study were used to assist the City in making upgrades to the Reservoir 2 Dam intake tower to allow water to be withdrawn from multiple depths and not just the bottom of the reservoir. The construction of the new Dam 2 Intake Tower was completed and became operational.

Geosyntec's Scope of Services

Geosyntec assisted the City of Portland Water Bureau (PWB) in performing hydrodynamic and temperature modeling using CE-QUAL-W2 to support management decisions pertaining to improvements to the Dam 2 Intake Tower where a selective withdrawal structure was added. Geosyntec also collaborated with PWB staff to increase their familiarity with the model and allow the PWB staff to independently develop future management scenarios as needed.

Geosyntec’s acquired model files from the PWB needed to simulate previous conditions and confirmed the previously developed models were able to run successfully. Geosyntec developed a technical memorandum describing the results, including tabulating and plotting temperatures at key locations within the reservoir and in the outflows. Next, Geosyntec collaborated with the PWB to identify and develop modeling scenarios using previous models. Our staff also developed a CE-QUAL-W2 model to simulate previous conditions. A key part of the project was working closely with PWB staff in developing the model files for the recent year and increasing their familiarity with the model such that they can work with it as needed in the future. Finally, Geosyntec updated the models to the most recent version of CE-QUAL-W2.

Notable Accomplishments

The results of the modeling study were used to assist the City in making upgrades to the Reservoir 2 Dam intake tower to allow targeted water releases for fish habitat downstream. Geosyntec further developed the reservoir temperature model to ensure it was able to reproduce reservoir temperatures with the new tower in place. The calibrated model was utilized to explore alternative reservoir operations management scenarios. This project required a substantial amount of work in a short period of time.