Prior to 1954, the natural flow rate of Steel Creek was approximately
one cubic meter per second (m3/sec). Steel Creek first
received thermal effluents in early 1954, when P Reactor went on-line.
From early 1954 until mid-1954, thermal discharges from P Reactor
resulted in flow rates of 5.7 m3/sec, or 200 ft3/sec,
in Steel Creek. Flow rates increased to 11.4 m3/sec in
mid-1954 when effluents from L Reactor also were routed into Steel
Creek. Thermal discharges into Steel Creek from P and L Reactors peaked
at 24 m3/sec (865 ft3/sec) in 1961 and then
decreased in 1963 as a result of the construction of Par Pond, which
sub-sequently received effluents from P and R Reactors. L Reactor
continued discharging thermal effluents into Steel Creek at a rate
of 11.3 m3/sec until early 1968, when the reactor was placed
on standby. Since that time, no further thermal effluents have been
discharged directly into Steel Creek, although heated effluents did
enter the creek after passing through L Lake. During the period of
thermal discharge, water temperatures where Steel Creek enters the
Savannah River floodplain often exceeded 45oC. These high temperatures
destroyed the original swamp forest and the area of tree loss was
extended to the southeast as a result of flooding. Since 1968, a vegetation
community dominated by early successional plant species has developed
in the Steel Creek corridor and delta, but the original swamp forest
has not become reestablished. As a result of reactor operations, approximately
261 curies of cesium-137 were released into Steel Creek from 1961
to 1973. Radiocesium still is confined primarily to the channel and
floodplain of Steel Creek and the Savannah River because it has not
migrated into the terrestrial ecosystem.
SREL Research in Steel Creek...
SREL research in Steel Creek has focused on the effects of past thermal
effluents on the natural vegetation and aquatic invertebrates of
the stream system, as well as on the effects of contaminants on natural
communities and the distribution and movement of contaminants through
this stream system. Additional studies have concentrated on use of
Steel Creek by the federally endangered Wood Stork. More recent studies
are examining the potential for wildlife to serve as vectors for transport
of contaminants off of the SRS. Other studies are examining the movement
of fish into and out of Steel Creek and the levels of radiocesium
in fish that typically are harvested from the Savannah River by the
Vegetation and wildlife studies
|SREL researcher in the
Steel Creek delta, late 1970's.
vegetation of Steel Creek and the delta now is dominated by early
successional plant species, such as willows and shrubs, rather than
the cypress and tupelos found in this region prior to thermal impacts.
- Fish communities of thermally impacted streams such as Steel Creek
show elevated fish densities dominated by large numbers of a few
species, particularly sunfish, some minnows, suckers, and mosquitofish,
that are tolerant of conditions associr operations, and their effects
on swamp water levels, greatly affected when, where, and how federally
endangered ated with more open canopies of willows and shrubs.
- Former reactor operations, and their effects on swamp water levels,
greatly affected when, where, and how federally endangered Wood
Storks foraged in the Steel Creek delta and the Savannah River swamp.
- Continued monitoring after cessation of reactor operations has
shown that Wood Stork use of the Steel Creek delta and Savannah
River swamp now is linked to river management and rainfall patterns;
Wood Storks now forage primarily in more natural areas of the SRS,
such as Carolina bays.
- Fish communities in Steel Creek have been influenced by the presence
of L Lake, resulting in an increased abundance of some reservoir
species, such as largemouth bass.
- Studies conducted in the 1980s found levels of radiocesium
contamination in Steel Creek soils to be among the highest reported
for any natural system studied at that time; relatively high radiocesium
concentrations also were reported from plants and arthropods from
- Radiocesium was found to desorb easily from the clays that are
characteristic of Steel Creek, making this contaminant more available
to biological systems in Steel Creek when compared to aquatic systems
in other regions of the U.S. which also were contaminated with radiocesium.
Further studies documented a high variability in radiocesium uptake
by plants in Steel Creek, with uptake often varying independently
of the concentration of radiocesium in soils.
- Radiocesium levels were found to be higher in the eggs of female
Wood Ducks that foraged in contaminated areas of the SRS. Similarly,
natural populations of vertebrates including various species of
snakes, green tree frogs, herons, and game species such as Wood
Ducks, which are consumed by the public, also have been documented
to have higher levels of radiocesium contamination in Steel Creek
than in noncontaminated regions of the Site.
- Studies over several decades have shown striking differences in
the long-term rates of radiocesium decline in Steel Creek biota;
contaminant burdens of animals, in general, have tended to decline
much more rapidly than those of plants.
- Fish in Steel Creek have higher concentration ratios of radiocesium
than fish from most other aquatic systems on the SRS, probably because
of this creeks soft water and low potassium concentration.
- High populations of largemouth bass in Steel Creek represent a
potential vector of contamination to the public off-site.
to Research Snapshots)