VI. B. 1. Types of Structures |
There are many types of overwater structures that currently exist within the nearshore zone of Puget Sound and Bainbridge Island. This discussion focuses primarily on four popular floating and fixed structures within the nearshore, including floating docks, fixed piers, marinas, and mooring buoys. Pilings are generally associated with these structures to support their load. Many of these structures are designed for boat use, which have associated impacts (anchor chain drag, prop wash/scour, grounding, and accidental littering/discharge) that are also addressed here.
Floating docks and fixed piers provide access to water resources for commercial and recreational activities. A fixed pier is an overwater structure supported by pilings that extends out above the water from the shoreline (Mulvihill et al. 1980). A fixed pier may or may not have a floating dock associated with it (Figure VI-10). Floating docks are generally composed of a frame mounted on floats of encapsulated styrofoam or wood, anchored in place to pilings via sliding hardware (Figure VI-11). Mooring buoys are floating surface structures used for private and commercial vessel moorage. These buoys are typically anchored outside of the intertidal zone in areas where boats will not ground on benthic substrate. Pilings, which are associated with several of these structures, are long timber, steel, reinforced concrete or composite posts that have been driven, jacked, or cast vertically into the ground to support a load (Mulvihill et al. 1980). Marinas are typically a collection of fixed piers, breakwaters, and floating docks that provide moorage for private and commercial marine vessels. Marinas are typically located close to or along a shoreline, with a fixed pier that connects the shoreline with a series of floating docks containing moorage slips.
Figure VI-10. Pier with float. (© WA Dept of Ecology 2000).
Figure VI-11. Floating dock. (Source: Applied Environmental Services, Inc.).
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