33 CFR §117.892

The drawspan for the Oregon State Highway Drawbridge across South Slough at Charleston must open on signal for the passage of vessels, except that between the hours of 7 a.m. and 7 p.m., from June 1 through September 30, the drawspan need be opened only on the hour and half-hour. This exception does not apply to commercial tugs and/or tows or public vessels of the United States.