Subj: CVN 68 CLASS WATER DEPTH REQUIREMENTS
clearance criterion established as a result of sea chest fouling problems at
Norfolk. Port specific fouling clearance studies can be performed it
requested and funded. Note that this criterion also provides clearance for
divers (5 feet) while at the pier. The dredging project depth can be traded
off with tides to obtain the necessary water depth in inner channels and
turning basins with the corresponding operational restrictions; however, tide
tradeoffs cannot be used at piers. Localized pier dredging in way of sea
chests can save 2 feet of dredging costs outside of the sea cheat area;
however, operational restrictions may result (e.g. less
transit time in tide window and limited diver access). In ports with large
amounts of debris on the bottom, locally dredged areas will tend to collect
debris requiring more frequent maintenance dredging.
4.
In the outer channel, wave action usually dominates the depth
requirements and can have a large variance. A ship motions analysis was
performed for the outer channels of San Diego and Mayport to account for the
statistical nature of the tides and wave action. The ship motions analyses of
the remaining home ports and shipyards will be completed within 6 months after
receipt of funding. Dredging to support unrestricted access is clearly
unaffordable. Consequent1y, the selection of a project depth is a tradeoff
between cost, operational requirements, and the risk of grounding.
5.
Many of the factors that affect channel transit are operational issues
such as operating schedule and contingencies; port operations; ship
displacement, trim, list, and speed; as well as weather and tides. Actual
transit situations will vary and will involve different combinations of these
factors. Consequently, a given transit could require more or less water
depth. Enclosure (3) describes efforts underway or proposed to improve
onboard shallow water navigation aids that predict ship's motion, provide real
time channel condition measurement, improve ship's draft and attitude
indication, and provide a load management system.
6, The NAVSEA point of contact is W. Page Glennie, NAVSEA 03D37, (703) 4I8-
8876.
M. S. FIREBAUGH
Deputy Commander for Engineering
Copy to: (w/encls)
OPNAV (Code N43)
NAVFAC (Code 15)
COMNAVAIRLANT (Code N43, N02N)
COMNAVAIRPAC (Code N43, N7N)
CINCLANTFLT (Code N4, N43)
CINCPACFLT (Code N4, N43)
NSWC-CD (Code 1561)
NAVSEA DET PERA CV (Code 1824)
B-2
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