Hudson River Dredging
Project
Site Description
The Hudson River flows in a generally southerly direction approximately
315 miles from its source at Lake Tear-of-the- Clouds on Mount
Marcy in the Adirondack Mountains to the
Battery in New York City. The Hudson River PCBs Superfund Site
extends nearly 200 river miles (320 km) from the Fenimore Bridge
in Hudson Falls (River Mile [RM] 197.3) to the Battery in New
York City (RM 0) at the tip of Manhattan Island. The Superfund
site traditionally has been divided into the Upper Hudson River
and the Lower Hudson River, based on physical and chemical characteristics.
The Upper Hudson River extends from the Fenimore Bridge in Hudson
Falls to the Federal Dam at Green Island in Troy (RM 153.9), a
distance of about 43 river miles. The Lower Hudson River extends
from the Federal Dam to the Battery (RM 0).
The Upper Hudson River was further divided into
three sections in the Feasibility Study to evaluate remedial alternatives
(see map). River Section 1 consists of
the Thompson Island Pool, and extends about 6.3 miles from the
former Fort Edward Dam (RM 194.8) to the Thompson Island Dam at
RM 188.5.
The first 2.5 miles from the Fenimore Bridge to
the former Fort Edward Dam are not a major focus of the Proposed
Plan because the sediment PCB contamination has largely been addressed.
This area consists primarily of rocky outcrops and little sediment,
or areas of sediment that have already been remediated (i.e.,
the Remnant Deposits, which are discussed in greater detail in
Site History). The area between the former Fort Edward Dam and
the northern/upstream end of the Thompson Island Pool, a distance
of 0.2 miles, contains shallow, fast moving water and primarily
course-grained sediments that are believed to have minimal PCB
inventory. River Section 2 extends from the Thompson Island Dam
to the Northumberland Dam (sometimes referred to as Lock 5) near
Schuylerville (RM 183.4) an extent of about 5.1 river miles. River
Section 3 extends from below the Northumberland Dam to the Federal
Dam at Troy, an extent of about 29.5 river miles.
The mean annual flow of the Hudson River at Fort
Edward is approximately 3,800 cubic feet per second (cfs). Downstream
of Fort Edward, the river is joined by several tributaries; the
largest in the Upper Hudson River is the Hoosic River near Schaghticoke.
The combined total of the tributaries nearly doubles the flow
of the Upper Hudson by the time it reaches Waterford, where the
mean annual flow of the river is approximately 7,100 cfs.
Within the Superfund site, there are eight dams
with locks that form a series of pools in the Upper Hudson. The
flow in the Upper Hudson is controlled by these dams and, to a
lesser degree, by wetlands and backwaters in the vicinity of the
river that act as buffers for high and low flow conditions. The
flow in the Upper Hudson is also controlled by several reservoirs
above Glens Falls, the most significant of which is Great Sacandaga
Lake. The mean gradient of the Upper Hudson River is about 3 feet/mile.
The gradient within each pool is smaller than the mean gradient
for the Upper Hudson River overall, with elevation drops between
the pools at the dams. The width of the Upper Hudson above Lock
4 in
Stillwater is approximately 400 feet. The Upper Hudson has an
average depth of less than 8 feet in the shoal areas and approximately
18 feet in the channel, with a maximum depth of more than 45 feet
in a section below Thompson Island Dam. The total surface area
of the Upper Hudson River is approximately 3,900 acres.
The Champlain Canal is coincident with portions
of the Upper Hudson River, extending from Waterford (RM 158) on
the Hudson to Whitehall at the southern end of Lake Champlain.
The Champlain Canal is 60 miles long, including 37 miles of canalized
Upper Hudson River from Waterford to Fort Edward and 23 miles
of land-cut sections. The canal diverges from the river at Fort
Edward just below Lock 7 and proceeds in a northeasterly direction
to Lake Champlain. Additional land cut areas exist at Stillwater,
Northumberland, and Fort Miller. The Hudson River between the
Federal Dam at Troy and Lock 1 at Waterford is part of the Champlain
Canal and the Erie Canal.
Return to Hudson River
Dredging Page One
