Project Detail
Habitat in the Northeast Basin was created by beneficially using approximately 87,000 m3 of dredge material from the Southern Intertidal Area (resulting from the creation of the Southwest Channel), and approximately 95,000 m3 of imported clean fill material, to raise the elevation of the existing substrate. Fraser River sand was utilized as additional fill material. This imported material was placed over the dredge material from the Southwest Channel to form the upper sediment layer in the Northeast Basin. Construction of a rock dyke was required to contain the fill material needed to establish the intertidal and shallow subtidal areas in the Northeast Basin. Subtidal rock reef habitat south of the rock dyke, at the southernmost end of the Northeast Basin, was constructed by placing appropriately sized rock material between approximately -3.0 m and -4.0 m CD. The rock reef habitat was constructed using rock of varying diameter, with an average (median) diameter (D50) of approximately 600 mm. A total of approximately 8,500 m3 of rock material is anticipated to be placed in the Northeast Basin. Rock reef habitat was also be created in the Southern Intertidal Area following dredging of the Southwest Channel. The Southwest Channel improves tidal flushing in the Maplewood Basin and enhance nutrient transport, improve water quality, reduce siltation of marine vegetation, and facilitate suspension and distribution of eggs and larvae of pelagic spawning fish and invertebrates, including marine vegetation spores. A total of approximately 14,000 m3 of rock material was placed in the Southwest Channel, both along the base of the channel to function as subtidal rock reef habitat, and along the side slopes of the excavated Southwest Channel to protect against scour from tidal currents as well as to function as rock reef habitat.
Pacific Pile & Marine Civil Constructors utilized barge-mounted construction equipment that was required to cross over the shallow Southern intertidal area during a high tide before the start of dredging. The Southwest Channel was dredged using the barge-mounted clam-shell dredge to facilitate placement of material from the Southwest Channel into the Northeast Basin.