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5.1.02
Corps of Engineers statement on Mead plume and Platte
West Project
The Corps involvement in the M.U.D. EIS process is triggered by the proposed
placement of fill (pipelines and vertical wells) in waters of the United
States associated with the expansion of the M.U.D. well field.
The placement of fill for M.U.D.'s preferred alternative would require
a Clean Water Act Section 404 permit. The permit process and associated
Environmental Impact Statement (EIS) was begun in 1994.
Two public meetings and a Section 404 hearing have been held within the
past three years.
The final EIS recently was distributed to the public.
After a 30-day "no action" period, the Corps will begin the
permit decision process, and should have a decision on the permit by this
fall. The Corps' options with the permit decision process are:
- Issue the permit,
- Issue the permit with conditions, or
- Deny the permit.
The groundwater concerns are in regards to RDX and TCE from the former
Nebraska Ordnance Plant (NOP) located near Mead, Nebraska.
This active clean-up site is located approximately three miles west of
the Saunders County portion of the Platte West well field. The groundwater
investigation and containment of the contaminated water is being managed
by our Kansas City District.
The project manager for this effort, Tom Graff, has been contacted and
has provided factual information associated with this clean-up effort.
- The proposed Platte West well field would be located more than two
miles northeast of the eastern extension of the area of containment of
the contaminated plume. The proposed well field is considered well beyond
the range of any potential adverse impact from the contaminated plume,
even under the most severe case that was modeled.
- Groundwater modeling was originally conducted as part of the M.U.D.
EIS by a contractor for M.U.D. The Kansas City District and their contractor
have developed a preliminary groundwater model using information supplied
by M.U.D. on their Platte West Project. This modeling was performed
to verify the groundwater model developed by the M.U.D. contractor which
showed the Mead plume would not migrate toward the M.U.D. well field. The
modeling used a steady state pumping scenario (the most severe case) of
50 million gallons per day (mgd) from wells in the Platte River aquifer.
With this scenario, 18 wells in the M.U.D. well field were active at a
pumping rate of 2.8 mgd/well. Of the 18 wells, six are located north of
the Platte River and will have no impact on the Mead plume. Therefore,
12 wells were active in the model simulation for a total of 33.6 mgd. Modeling
has indicated that groundwater would be drawn down one foot near the eastern
portion of the contaminant plume in the Platte Valley. Under this modeled
scenario, the contaminated plume would be drawn a maximum of 1,000 feet
to the east, and indicated that some containment of the plume would be
lost from the southeast containment well. Because of the slow rate of movement
in the contamination plume, the quarterly monitoring that is currently
being done will easily detect this highly unlikely scenario and allow for
the installation of additional measures to intercept and contain it.
- Sentry groundwater monitoring wells are also planned to be installed
beyond the eastern extent of the plume in the Platte Valley to monitor
any changes in ground water quality. If a permit for the Platte West Project
is issued, a condition of that permit would be for M.U.D. to reimburse
the Kansas City District if pumping from the M.U.D. well field results
in the need for additional remedial tasks to prevent further migration
of the contaminated plume.
- Kansas City District already conducts semi-annual groundwater monitoring
in and around the containment area to ensure that the Mead plume remains
contained.
- In the Fall of 2001, an additional and unanticipated area of groundwater
contamination was found at the southwestern portion of the former ordnance
plant. This area is, however, even farther away from the proposed M.U.D.
wellfield and much less likely to create any problems than those already
modeled. This area is approximately seven miles southwest from the proposed
Platte West Project and well outside the area of influence of the proposed
Platte West well field. Additional tests will be conducted during the spring
of 2002 to determine the extent of this plume of contamination.
Based on the information from the Kansas City District, as well as the
information in the EIS, the groundwater proposed for the Platte West
water supply would not become tainted with the contaminated groundwater
and the public would not be at risk from this proposal.
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