WALLA WALLA, Wash. – Portions of the walking trails along the federally managed section of the Mill Creek Levee System will be temporarily closed to all visitors starting Tuesday, Oct. 24, to accommodate the completion of levee-maintenance activities, U.S. Army Corps of Engineers officials announced today.
Fall-Winter 2017 phase-2 repair work begins on the south levee in an area just downstream of the wooden pedestrian bridge, progressing upstream toward the Mill Creek diversion dam. Repair and maintenance work in this area is anticipated to be completed in early November. Contractors will likely be onsite this weekend to place safety barriers and stage equipment, which occupy the horse trailer parking area near the Mill Creek Project office. Workers will be accessing the levee with heavy equipment and vehicles to remove the tree roots and re-compact levee material.
Work on the north levee – in the area about 1,500 feet upstream of the metal division works and progressing upstream toward the dam -- will likely begin about a week after the start of work on the south levee and require temporary closure of the paved trail and pedestrian access to Rooks Park.
Safety barriers and signs will be placed to alert visitors to the temporary closures and encourage public safety. A map of visitor trails which will require temporary closures to accommodate levee work activities is available on the Corps’ website at www.nww.usace.army.mil/Missions/Projects/MillCreekLeveeMaintenance.aspx
. The Walla Walla District will continue to announce work progress and temporary impacts to visitor access. Visitors are also encouraged to look for trail-closure updates on information kiosks located at major trailheads and on the Mill Creek Project’s Facebook page www.facebook.com/millcreekdam
Phase-2 of restoring the federally managed portion of the Mill Creek Levee System, about half of which was conducted during Winter 2016-2017, includes removing tree roots that intruded into the levee cross section from the landside slope and replacing levee material in accordance with geo-technical and design criteria. District Geotechnical Section engineers (levee experts) examined several test pits excavated at various points along the mile-long levee and determined removing problematic roots would require “grubbing” roughly two feet into the levee. In some locations, where tree roots have extended deeper into the levee cross section, more extensive excavation and repairs may be required.
The contract to perform phase-2 work was awarded to KEU Inc., of Vancouver, Washington, on Sept. 14, 2016. Because of the large scope of work and the narrow timeframe to accomplish it -- between bird-nesting and flood seasons – phase-2 work was planned to occur during multiple years. Fall-Winter 2017 phase-2 levee-repair work is anticipated to be completed in mid-December, depending upon weather and soil conditions.
This maintenance is necessary to meet National Levee Safety Program requirements in accordance with Corps headquarters regulations and policies. Phase-1 work began on Oct. 8, 2015, and was completed on Dec. 31, 2015. Problematic vegetation was removed from the surface of the levee slopes and 15-feet landward from the levee’s design toe. Non-compliant vegetation on levees blocks visibility for inspections, access for maintenance, hinders flood-fighting operations, and adds uncertainty to structural performance and reliability, which increases risk to the public. The inability to inspect, maintain and flood fight typically delays emergency response and contributes to the risk of levee failure. Life safety is paramount for the Corps’ operations.
Environmental-compliance documents, maps, photos, videos and other information about this levee-maintenance project is available on the Corps’ website at www.nww.usace.army.mil/Missions/Projects/MillCreekLeveeMaintenance.aspx