Enclosure (1) TO COMDTINST 16478.12
bottom types, including mud, sand, rock, and shells; and water depths ranging
0 to 50 feet. The data reported here, for the Chesapeake Bay, Tampa Bay,
Tennessee River, and Puget Sound, represent the majority of depths,
salinities, and bottom types where AtoNs are located. Based on this
representation, generalizations can be made about most fixed AtoNs operated by
the Coast Guard, with respect to the number of batteries likely to be found,
the condition of the batteries, the level of mercury likely to be found in
sediments. Generalizations can even by made about cleanup time and expected
costs.
Unusually sensitive environment, such as a coral reef area providing
endangered species habitat, is the only type of location not yet addressed.
Such an area has been chosen for special study in the near future. These
results are not expected to vary significantly from the data already gathered.
Chesapeake Bay
The Chesapeake Bay, located on the east coast of the United States, is one of
the largest and most productive estuaries in the world. The main stem of the
Bay extends approximately 190 miles from Cape Henry, Virginia, to the mouth of
the Susquehanna River. The Chesapeake Bay is a submerged river valley, a
remnant of the Susquehanna River Valley which was inundated with rising sea
level after the most recent glacial period.
The most important feature that distinguishes an estuary from a river or ocean
is the temporal and geographic variations in salinity levels. In the
Chesapeake, salinities range from about 35 parts per thousand at its outlet
to the ocean to near zero at the head of the Bay and its estuarine
tributaries. This variation in salinity is directly related to the quantity
of freshwater inflow to the Bay from its tributaries. The estuary is fed by
however, 90 percent of the freshwater contributed to the Bay originates in
five major tributaries: the Susquehanna, Potomac, James, York, and
Rappahannock Rivers. The Susquehanna, draining from Pennsylvania and New
York, provides approximately half of the Bay's freshwater.
As with most estuaries, the Chesapeake Bay supports a highly productive
biological community. This, in turn, supports a large commercial and sport
fishery quite important to the regional economy. The Bay is also an important
recreation area for the region's nearly 15 million residents and, in turn,
provides a lucrative source of tourism for the economy. The Bay has also
served for centuries as a commercial shipping center, with two major port
complexes connected by interstate highway, air, and rail systems to important
inland points.
Several different bottom types and AtoN structures were characterized in the
study on the Chesapeake. These ranged from a large, caisson structure
2-5
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