1 - paducah environmental information center

Paducah Site
at the south end of the plant. The sediments
deposited on this erosional surface are termed
continental deposits. The lower portion of the
continental' deposits dmsists of approximately 9
m (30 ft) of stream gravel and sand.
Over time, sediments from the retreating
glaciers dammed the river valley, causing the
formation of a lake. Silts and clays with thin
zones ofsapd and occasional gravel were
deposited in the lake, forming the upper portion
of the continental deposits. These deposits range
from approximately 1.5 to 17 rh (5 to 55 ft) thick.
Finally, loess, a wind~blown silt, overlies
the continental" deposits throughout the site.
Thickness of loess deposits varies f~om
approximately 1.5 to 8 m (5 to 25 ft), averaging
approximately 4.6 II1 (15 ft). 'The local
groundwater flow system at the Paducah, Site
contains four major components: the McNairy
flow system, the Regional Gravel Aquifer
(RGA), the Upper Continental Recharge System
(VCRS), and the terrace gravels.
• The McNairy flow system consists
, of interbedded and interlensing sand,
silt, and clay of the McNairy Formation.
"Sand facies ,account for 40 to 50% of the
'total formation thickness of
approximately 69 m (225 ft).
• TheRGA consists of san4 and gravel
facies in the lower continent3I deposits,
gravetand coarse sand portions in the
upper McNairy that are directly adjacent
to ,the lower continental deposits, coarse~
grhlned sedimfmts at the base of 'the
upper continental deposits, and alluvium
adjacent to the Ohio River. These
depo'sits have an average thickness of 9
m (30 ft) and range up to 21 m (70 ft)
along an axis that trends east-west
'through the site. The RGA is the
uppermost and primary aquifer, formerly
used by private residences north of the
Paducah Site.
• The UCRS consists mainly of clayey
silt with interbedded sand and gravel in
the upper continental deposits. The
system is so named because of its
characteristic recharge to the RGA.
• The terrace gravels consist of
shallow Pliocene gravel deposits in the
southern portion of the plant site. These
deposits usually lack sufficient thickness
and saturation to constitute an aquifer
but 'may be an important source of
groundwater recharge to the RGA.
Groundwater flow ongmates south of the
Paducah Site within Eocene sands and the
terrace gravels. Groundwater within the terrace
gravels either discharges to local streams or
recharges the RGA, although the flow regime of
the terrace gravels is not fully understood.
Groundwater flow through ,the UCRS is
ultimately downward, also recharging the RGA.
From the plant site, groundwater flows generally
northward in the RGA toward the Ohio River, the
local base level for the system.
Uses of Groundwater in the
Vicinity
The WKWMA and some lightly populated
farmlands are in the immediate vicinity of the
Paducah Site. Homes are sparsely located along
rural roads in the vicinity of the site. Three
communities lie within 3.2 kilometers (2 miles)
of the plant: Magruder Village to the southwest
and Grahamville and Heath to the east.
Both groundwater and surface water
sources have been used for water supply to
residents and industries in the plant area. Wells
in the area are screened at depths ranging from
4.6 to 75 m (15 to 245 ft). The majority of these
wells are believed to' be screened in the RGA.
The Paducah Site continues to provide
municipal water to all residents within the area of
9-8 '
Groundwater