FY 1986

Dynamics of Commencement Bay and approaches

Ebbesmeyer, C.C., C.A. Coomes, J.M. Cox, E.T. Baker, C.S. Smyth, and C.A. Barnes

NOAA Tech. Memo. NOS OMA-24, 79 pp (1986)

Oceanographic and hydraulic model data were examined to determine pathways of water and suspended particulate matter (SPM) in Commencement Bay, a small urban embayment adjoining Puget Sound's Main Basin and the City of Tacoma's waterways. The SPM enters the Bay with the Puyallup River plume as a thin surface layer, and some of the SPM moves into the waterways past industrial facilities. Because water flows into these waterways near both the surface and bottom, trapping of SPM and adsorbed materials may occur in the waterways. The circulatory pattern may be partially responsible for lower concentrations (eight-fold) of lead and PCB in the bottom sediments of Commencement Bay as compared to Elliott Bay adjacent to Seattle. There are countercurrents within the Bay that may change in velocity structure in response to long-term trends of currents observed in Puget Sound.