Duwamish Gardens Estuarine Rehabilitation Design
Request for Additional Funding
Project Description:
The City of Tukwila will create shallow water habitat on a 2.16 acre site (and on adjacent WADNR aquatic lands) on the right bank of the Duwamish River immediately downstream of river mile 7.0. The site is in the high priority "transition zone" between fresh and salt water, which provides the appropriate range of salinities for juvenile Chinook and chum to transition to salt water. Off channel and shallow water habitats in this stretch of the Duwamish will provide opportunities for juvenile fish to move out of the main channel to habitats where they can feed and rear. Longer residence times in the estuary allow for larger, healthier smolts prior to ocean migration. The property is among the largest remaining pieces of under-developed sites for habitat restoration remaining in the Duwamish corridor. When restored, it will be the largest off-channel habitat between the Codiga Farms restoration at RM 8.5 and North Wind's Weir restoration at RM 6.4.
The new habitat will be created by excavating 55,000 cubic yards of material to establish approximately 2.0 acres of shallow water mudflat and marsh habitat and approximately 0.8 acre of uplands planted with native vegetation.
The project will provide another viewpoint on the river across from the popular Green River Trail. The viewpoint will include interpretive signs on the pre-contact use, historical, and ecological features of the site. The project is immediately below the Sound Transit LINK light rail bridge and viewed by thousands of riders each day.
Additional Funding Request:
The City of Tukwila is requesting an additional $50,045 from the Salmon Funding Recovery Board to cover unanticipated costs for design and permitting of the Duwamish Gardens project. Previous grants awarded include a Salmon Funding Recovery Board grant in 2009 ($197,299) and King Conservation grant in 2010($52,929). The contractor has been selected for the design and Tukwila staff is in the process of negotiating a scope of work. The current fee schedule totals $316,066, which is $66,021 greater than originally estimated, with the biggest cost increase is for soils investigations. The project design had originally planned to use a substantial amount of soils information from the North Winds Weir project but the consultant advised not to do this as a way of reducing costs. He cautions that substantial costs could be incurred during construction if further contaminated soils are discovered or if the subsurface conditions are not as described.
Funding Strategy:
Funding Source / AmountSalmon Funding Recovery Board (2009) / 197,299
King Conservation District – WRIA 9 Forum / 50,000
King Conservation District – Jurisdictional Funding / 2,929
Additional RCO Request / 50,045
Additional City of Tukwila Funds / 15,976
Total Design / $316,249
FundingStrategy8-11-11