U.S. Army Corps of Engineers

07/31/2020 | Press release | Distributed by Public on 08/01/2020 18:36

20-041 Diffuser block rehabilitation to result in trail closures at Rooks Park

Walla Walla, WA -- The U.S. Army Corps of Engineers' Walla Walla District (Corps) will be rehabilitating the diffuser blocks at the base of the diversion dam at Rooks Park beginning August 3, resulting in trail detours and trail closures in Rooks Park.

The rehabilitation project will involve hydro-excavating down the old diffuser blocks, located at the base of the dam, and pouring new blocks in their place. Safety improvements will also be made to gates that pass water to the lake, allowing increased safety for workers that maintain them.

'The current diffuser blocks are original to the dam, which was completed in 1942. While the blocks were utilized every year for the past 78 years, they have sustained freeze-thaw damage over the years. The likely culprit for their current distress is the method in which they were constructed,' Natural Resources Specialist Jeremy Nguyen said. 'Newer concrete-pouring methods eliminate the majority of the air bubbles, and the new diffuser blocks should last even longer than the originals,' he added.

The $550,000 contract for the diffuser block rehabilitation project and other work to rehabilitate the diversion dam was awarded to TDX Power Services, based out of Anchorage, Alaska.

Additional construction projects taking place at Mill Creek Dam and Bennington Lake over the summer include replacing the downstream fish ladder at the first division works, which is underway and has closed access to the yellow footbridge over Mill Creek and detoured part of the paved levee trail; Reservoir Road repaving, which will result in the closure of Reservoir Road; closure of the Mill Creek Project parking lot for maintenance building construction; and restroom installation at Bennington Lake, which will result in the closure of the Bennington Lake parking lot. Almost every aspect of the Mill Creek Dam and Bennington Lake area will be affected by temporary closures throughout the summer.

'It is really great that we are getting so much work accomplished this summer. The added benefit of getting people back to work in these unprecedented times will have positive impact well beyond the boundaries of Mill Creek Dam and Bennington Lake. Unfortunately the timing of the closures happens to be in the same year as closures due to flooding followed by restrictions from COVID-19. Our biggest mission this summer will be to keep visitors informed of the various closure to reduce frustrations people may be feeling about not being able to visit one of the busiest and appreciated recreation areas in the vicinity,' Nguyen said.

More information about upcoming construction will be released once contracts are finalized. More information can also be found on the Mill Creek Facebook page at