Y--MOUTH OF THE COLUMBIA RIVER NORTH JETTY LAGOON FILL

BACKGROUND The mouth of the Columbia River (MCR) is located at the river's confluence with the Pacific Ocean between Oregon and Washington and is known as one of the most treacherous coastal inlets in the world. Consistent navigation through MCR bar was finally secured by construction of three rubble-mound jetties, which included the North Jetty. Since initial construction, approximately 2,100 feet of the North Jetty head has deteriorated and is no longer functional. Structural degradation of the North Jetty has accelerated in recent years because of storm activity, loss of sand shoal material at its foundation, and continued recession of the jetty head. Along with the degredation of the jetty itself, the landward side of the North Jetty between stations 10+00 to 60+00 is eroding and has created a depression, or tidal lagoon, that fills with water on the incoming tide. This lagoon appears to be formed primarily by the erosion and piping of accreted sand with tidal exchange and wave surge through the deteriorated jetty structure. Surface water flow and groundwater flow from McKenzie Head Lagoon on the north side of Jetty Road also likely contributes to the loss of material through the jetty. PROJECT DESCRIPTION The work includes filling the lagoon with sand and rock fill up to an elevation of 15 feet NAVD88. The lagoon fill work includes construction of a filter zone (consisting of riprap, shot rock, and gravel) adjacent to the jetty stone to prevent sand migration through the jetty, followed by upland bulk filling with imported and on-site borrow sand. An Erosion Protection zone shall also be part of the lagoon fill at it's west end. On-site borrow sand will be excavated from the borrow area at the eastern part of the site. The resulting borrow pit shall be reclaimed as an intertidal wetland. In addition, an existing 48 inch diameter corrugated culvert that extends under Jetty Road, and associated with the McKenzie Head Lagoon system, shall be replaced, and the road surface repaired in the culvert area. Guardrails shall also be installed associated with the culvert replacement work. Construction shall meet all environmental restrictions. The sequence of construction shall accommodate high tides, storms, and groundwater levels. LOCATION The work shall be located landward and north of the North Jetty, between jetty stations 10+00 and 60+00. The North Jetty is located at Cape Disappointment State Park (formerly Fort Canby State Park) in Pacific County, Washington, near the town of Ilwaco. Access to the site from Ilwaco is by way of Highway 101, which connects to State Route 100, which connects to Fort Canby Road, which connects to Jetty Road, as shown on drawings. Contractor access to the work site will be from Jetty Road. Project Street/Location: Cape Disappointment State Park, Jetty Road Nearest City: Ilwaco State: Washington ZIP Code: 98624 County: Pacific