Quantcast Entrances and Harbors site specific criteria

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Channel Approaches (Outer Channels) site specific criteria
a. Coordinate dimensions of approaches with the NAVFAC Criteria Office,
should be given to traffic lanes, local commercial traffic, navigational aids, magnetic anomalies,
electronic navigation aids, waves, winds, currents, use-frequency, pilotage and tugs. Contact the
US Coast Guard for navigational marking requirements and bridge clearances.
b. The geometrics of the approaches (depth, width, and course) are dependent on many
operational and environmental factors. The wave environment greatly affects the required depth
to transit the approach. Local commercial traffic affects the width. Maneuverability is the
primary driver for the course. Consequently, the planner must examine each channel approach
separately. Contact the NAVFAC Criteria Office to assist in evaluating or designing channel
c. Contact the local NAVFAC representative, who will contact the US Army Corps of
Engineers to address environmental and material disposal issues.
Entrances and Harbors site specific criteria
a. Entrance Restrictions Entrance channels provide access between deep water
subjected to a strong wave environment to sheltered harbors. Contact local Port Authority for
any operational restrictions.
b. Entrance Currents - Strong currents greatly affect the usability of entrance channels.
These currents should be quantified and the impact assessed during the planning stages.
c. Minimum Entrance Depth - CVN's require 50.0 feet of water during transit of
channels (usually during mean to high tides) greater than 1000 ft. wide. Narrower channels
require greater depths. Tides and waves should be quantified and the impact assessed to
determine if a dredge depth of greater than 50.0 feet is required. Siltation occurs in most channels
and shall be quantified initially. The design depth should then be deeper than the requirement to
accommodate siltation. Expected siltation can be addressed through advance maintenance
dredging or other means. More detail is contained in "ITG CVN Dredge Depth Criteria,"
NAVFACENGCOM, dated 4 March 1997. That ITG includes NAVSEA ltr 11460 Ser
03D3/242, dated 3 Jan 95, "CVN 68 Class Water Depth Requirements".
d. Minimum Entrance Channel Width (outside breakwaters) depends on wave and
current environment but generally at least 800 ft. at toe of slope, assuming no bends in the channel
and one way traffic during transit.
e. Vertical Bridge Clearances - 250 ft. Mean Higher High Water (MHHW) when ship is
in light condition. Light condition occurs when ship has no aircraft, airwing, ammunition, and has
55% of JP-5, 10% of provisions and stores, 10% of potable water, aircraft handling vehicles, and
25% onboard discharge tank water. This height is based on the older CVs. If the facility is
designed explicitly for Nimitz class, use 230 ft. MHHW.


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