Elliott Bay Nearshore Restoration Project

Location: Western shore of Elliott Bay between Seacrest Park and Duwamish Head.

Funding Source: City of Seattle/Metro Settlement

Project Goals:

• To improve nearshore marine habitat conditions by enhancing productivity of epibenthic infauna,
• To increase the distribution and density of macroaglae and other primary producers, and
• To improve the attributes that support resident and migratory marine and estuarine fish species.

Site Summary

The Elliott Bay Nearshore Habitat Restoration Project was selected by the Elliott Bay/Duwamish Restoration Program (EB/DRP) based on criteria identified in the Panel's Concept Document (see summary).

The project had a number of objectives the EB/DRP wanted it to meet, including:

• Increase diversity of bottom substrates
• Increase area of limiting hard bottom substrates
• Provide suitable substrates at proper horizons for eel grass
• Increase volume of physical protective structures for juvenile and adult resident invertebrates and fishes
• Increase hard structure surfaces for macroalgae
• Remove undesirable bottom debris
• Provide substrate improvements that are compatible with commerce, navigation, tribal and sport fishing, and recreational shoreline uses
• Provide public educational and involvement opportunities
• Provide information useful to subsequent substrate enhancement projects
• Design improvements to be sustainable.

The Elliott Bay Nearshore project site is located along the western shore of Elliott Bay between Seacrest Park and Duwamish Head. The initial phase was constructed in two nodes: one is slightly west of the Duwamish Head Light in about -35 feet (MLLW) and the second is off Seacrest Park between -2 and -35 feet.

The Duwamish Head unit consisted of four alternating plots or "mounds" roughly ten feet square containing approximately five cubic yards of rock cobble (2 inches, river-run, diameter) and quarry spalls (2-12 inches diameter) located along the 35-foot contour on a featureless sandy bottom near an eel grass bed.

The Seacrest Park unit consisted of four plots of different substrates: two 10-ft by 20-ft mounds, one of pea gravel and the second of oyster shells in bands between -2 and -12 feet (MLLW); and two 10-foot square mounds of cobble and quarry spalls at approximately -35 feet.

This Panel habitat restoration project partnered with the Washington Department of Natural Resources (DNR) and the U.S. Army Corps of Engineers (Corps). DNR was the property owner and approved the project without fee as an enhancement of public lands without interfering with commerce, navigation, or fishing uses. The Corps provided the construction management and implementation under a cooperative cost-sharing basis with King County Department of Natural Resources. King County served as the project manager for the Panel. Preliminary habitat surveys had been conducted for the Panel by the Washington Department of Fish and Wildlife and a local SCUBA-diving instructors training group.

The first phase of this project was completed in March of 1998. Materials were emplaced from a barge into the eight separate plots using a crane and clamshell bucket. None of the plots were more than 18 inches in height.

The Panel released a monitoring program report for this project in December 2000 (Panel Publ. #26) discussing the efficacy of the various substrates on nearshore bottom habitats for macroalgal production and juvenile fish and invertebrate use. The conclusion was that the substrates were effective in providing macroalgal and sessile invertebrate attachment sites. Fish and epibenthic invertebrates were using the macroalgae as cover. A study of the oyster shell habitat (Panel Publ. #19) suggested that the emplacement depths may have been too deep for juvenile Dungeness crabs (a primary target) but were very successful for other crab and shrimp species. Where practicable, volunteer community stewards have been used to conduct the monitoring. Initially, Explorer Scouts from Garfield High School were used to conduct the quarterly video surveys; the King County Sheriff's Deputy dive unit provided this service later. The U.S. Environmental Protection Agency (EPA) dive team provided a detailed underwater survey of the plots two years after placement; the University of Washington Fisheries Research Institute Wetlands Team quantitatively evaluated the epibenthic faunal use. A reference site between the two units was used for comparing enhanced productivity and use.

Activities

11/98. Construction of Oyster Shell Habitat Plots in Elliott Bay: Evaluation of Crab Settlement and Habitat Utilization.

05/00. (2724KB) Publication of Elliott Bay Nearshore Substrate Enhancement Monitoring Plan

12/00. (3487KB) Publication of Elliott Bay Nearshore Substrate Enhancement Monitoring Report: Evaluation of the Utilization of Substrate Diversity and the Production of Prey Taxa Important to Juvenile Salmonids in 1998 and 1999. December 2000 Report (1857KB) and appendices (1631KB).