PGE and the Confederated Tribes of Warm Springs are entering the final phases of constructing the underwater tower that will restore fish passage on the Deschutes River. Over the next two months, crews will make the final connections and test the equipment on the 273-foot-tall structure in Lake Billy Chinook.

The tower was built in three main sections on barges anchored near the Round Butte dam, then towed to its final destination on the other side of the lake.

• The bottom section was completed in October of 2008. Crews towed it across the lake, sunk it and attached it to the bottom of the lake in front of the existing powerhouse intake.
• The top structure has been towed into place and the 40 foot diameter pipe will be lowered to its final location (on top of the bottom section) in late April. The top structure will be attached to a steel bridge that anchors it to the shore. This segment of the tower will capture the migrating fish.
• After the fish are captured in the top structure, they are transferred by a pipe to the Fish Transfer Facility. PGE personnel will then sort and mark the fish and eventually transport them below the dam to the Deschutes River where they can continue their journey to the ocean.

Once the construction is complete, engineers and crews will spend the next month thoroughly testing and balancing the system. This unique tower is designed to selectively draw cold water from the bottom of Lake Billy Chinook and warm water from the surface during different parts of the year to meet downstream water temperature and quality requirements. Withdrawing water from the surface of the lake will also create surface guidance current to attract migrating young salmon and steelhead into the floating top structure. Engineers will be fine-tuning the equipment to achieve optimal flow balance. For more information on the tower design, see Underwater Tower.

Most of the structure is underwater, but you can see the top structure of the tower near the original power intake tower. By late April, if you go to the viewpoint above Lake Billy Chinook, you should be able to see the surface current created by the tower guiding the young seaward migrating fish into the V-shaped openings of the Selective Water Withdrawal structure.

The bridge to the underwater tower has been attached to the shore. The other end will be connected to the top structure of the underwater tower.

The Fish Transfer Facility is being pushed and towed to its final location next to the access bridge on the left.

This photo shows the top structure with its large V screens nearing completion along side Round Butte Dam When completed in mid April, it will be towed over and attached to the end of the access bridge. On the top of the dam is one section of the 40-ft diameter vertical flow conduit that will be attached the top structure to the bottom structure.

When operating, water will enter the open end of each large V. Water for generation will move through the sides of each V and down the vertical flow conduit while the fish will be captured at the apex of each V. After capture the fish will be moved in water through a large fish pump over to the Fish Transfer Facility attached to the side of the access bridge. After marking, the young salmon will be loaded onto a truck at the base of the bridge, then transported and released into the lower Deschutes River.

This entry was posted on Friday, March 27th, 2009 at 9:30 am and is filed under Construction, Media Gallery. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.