Chester Creek Alignment and Channel Improvements

Bristol realigned a portion of Chester Creek to remove barriers to fish passage, reconnect stream segments, reduce flooding, and improve water quality. The project included demolition, bank stabilization, new stream and pond construction, toe and slope protection, box culvert installation, erosion control, in-water work, storm drainpipe slip lining, riprap placement, straw wattles, landscaping, pavement, and concrete. 

To reroute the creek, Bristol first installed a temporary 650-foot creek diversion trench to collect flow waters from crossing culverts. Excavation activities occurred within temporary construction easements provided by the Municipality of Anchorage. Super Sacks® were placed at the beginning of the existing creek channel, preventing flow waters from re-entering the existing creek channel during the installation of the proposed storm drain system. The Super Sacks® were filled with excavated material from the temporary creek diversion and were placed to prevent breaching of flow waters. Upon completion of the new storm drain system installation, the temporary diversion trench was backfilled and compacted using the previously excavated material. The new stream channel now has an average slope of 1.5%, mimicking the natural stream channel 

This project included the challenging task of closing one of Anchorage, Alaska’s busiest intersections for 84 hours to complete box culvert and storm drain modifications. This required the Bristol team to have all materials, equipment, personnel, and back-ups ready to work 24 hours a day during a holiday weekend closure. Work was completed ahead of the scheduled closure time with no safety near misses or accidents.

Levee Rehabilitation Desimone-Briscoe

The Desimone-Briscoe School Levee along the Green River in Tukwila, Washington, required significant repairs after a flood had damaged portions of the existing levee toe and slope. US Army Corps of Engineers (USACE) Seattle District awarded Bristol this rehabilitation project as a task order under the Multiple Award Task Order Contract (MATOC) for Design Build and Horizontal Construction to repair approximately 780 feet of levee toe and slope of the approximately 11,600-foot-long Desimone-Briscoe levee. 

The Muckleshoot Indians rely on the Green River for fishing. Any construction along this corridor must adhere to strict environmental requirements to protect wildlife and habitat. Additionally, the general public relies on the integrity of the levee to protect against flooding, prevent damage to adjacent property, and prevent disruption of civil infrastructure. This project included clearing and grubbing along the riverbank as well as demolition of a 12-foot asphalt trail and an asphalt parking area. 

The levee repairs included riverward side slope work with a layback of the slope to 2H:1V, a 12-foot crown, rock armor with a launchable toe, and a mid-slope bench. Bristol matched the levee top elevation to the top of the concrete cap beam and provided two parking spaces and access to the tribal fishing trail for tribal members throughout construction in order to allow maintained fishing access. In order to provide erosion control and bank stabilization in heavy flood events, significant rock work was completed via installing class 4 riprap. Bristol placed topsoil to stabilize the bank, followed by a layer of jute mat, and completed the project by hydroseeding the entire levee area.