MILLER-RICE ISLANDS PILE DIKE SYSTEM REPAIRS

This award announcement is for the construction/repair of the Miller-Rice Islands Pile Dike System located between River Mile 22 and River Mile 25 on the Columbia River in Wahkiakum County, Washington. The project consists of enhancing and connecting the enrockments of PD 23.82 and PD 23.71 and repairing and enhancing PD 24.63. The enrockment for PD 23.71 and PD 23.81 will be raised uniformly and enhanced to connect the two pile dikes.

The repair and enhancement of the centerline of PD 24.63 will be approximately 10 feet downstream (west) of the existing pile dike piles centerline. This placement allows for enhanced enrockment construction without the need for removal of existing piles. The offset placement of the enhanced enrockment may also allow for phased placement over time as the existing pile dike continues to degrade.

Furthermore, locating the enhanced enrockment slightly downstream eliminates the need for removal of large amounts of debris on the upstream side of the existing pile dike. The enhanced enrockment crest will be raised from an existing elevation of approximately El. -15 feet NAVD88 to El.-5 feet NAVD88. For the northern (nearshore) portion of the dike, from Sta. 1+00 to Sta.

0+25 the enhanced enrockment crest will slope downward from El. -5 feet NAVD88 to El. -12 feet NAVD88, from Sta 0+25 to 0+04 the enhanced enrockment crest will have an El. of -12 feet NAVD88. The northern (nearshore) end of the enhanced enrockment will terminate in 14 foot wide by 4-foot-thick rock scour apron. For the southern (offshore) 480 feet of the dike (Sta.

8+00 to 12+80), the crest will slope downward from El. -5 feet NAVD88 to El. -16 feet NAVD88 at the offshore end where it will tie into the existing enrockment at a 2H:1V slope. The enhanced enrockment will have an 8-foot crest width and 1.5H:1V side slopes. The design includes construction of 8 new hazard marker piles to designate the locations of the submerged enrockments. The new hazard marker piles are driven mono pile structures. Hazard marker pile design is a steel pipe monopile. The hazard marker pile will have a 3-foot by 3-foot navigation hazard sign affixed to the top. The top of the pile is positioned at 20 feet NAVD88.