If you are performing work in tidal waters in Washington State, you must identify the limits of the Corps jurisdiction. Under Section 10 of the Rivers and Harbors Act, the limits of the Corps' jurisdiction is the line of Mean High Water. Under Section 404 of the Clean Water Act, the limits of the Corps' jurisdiction is the High Tide Line (HTL) and adjacent wetlands.
Per 33 CFR 328.3, the term high tide line means the line of intersection of the land with the water's surface at the maximum height reached by a rising tide. The high tide line may be determined, in the absence of actual data, by a line of oil or scum along shore objects, a more or less continuous deposit of fine shell or debris on the foreshore or berm, other physical markings or characteristics, vegetation lines, tidal gages, or other suitable means that delineate the general height reached by a rising tide. The line encompasses spring high tides and other high tides that occur with periodic frequency but does not include storm surges in which there is a departure from the normal or predicted reach of the tide due to the piling up of water against a coast by strong winds such as those accompanying a hurricane or other intense storm.