Management of Commercially Generated Radioactive Waste - U.S. ...

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layers. The volume of water entering the repository is generally directly related to repo-
sitory size and will be greatest during the last stages of construction-operation when the
repository is near its maximum size. For granite the estimated inflow of water could be
about 1500 m 3 /day (400,000 gal/day). Much of this water will be removed as water vapor by
the mine ventilation system, although some of the water will probably require collection in
sumps in the mine and pumping to the surface. Nonradiological water quality standards will
have to be met before this effluent is released to land or surface waters. Disposal of this
water will only be necessary until the repository is sealed off. However, the maximum vol-
ume of water that would likely need treatment and disposal probably will be less than
760 m3/day and is not expected to create ecological problems.
5.4.4.3 Ecological Effects for a Repository in Shale
In the case of a deep geological repository in shale about 3.5 x 107 MT of rock would
be mined and 1.4 x 107 MT would require disposal. The mined material would be crushed
before it is brought to the surface, a practice that will reduce the release of dust above
ground. Several disposal methods may be applicable for mined shale not required for back-
filling of the mine. These methods are surface storage, ocean disposal, and placement in
abandoned mines. Each of these alternatives has some potential for causing ecological
impact. Mine storage may contaminate ground-water supplies that may, in turn, impact ecolo-
gical systems; some local but poorly defined impacts may result from ocean disposal; and
surface storage may remove land from the available natural habitat and be a source of acid
runoff.
Shale may contain up to 0.5% iron pyrite, which will produce sulfuric acid when exposed
to oxygen and water. Runoff from storage piles, water pumped from the mine, leaching of
shale if it were disposed of in abandoned mines, storage, and ocean disposal may provide
sources of this acid waste to the environment. The actual quantities and acidity of this
waste water have not been defined. Potential ecological impacts will probably be localized
and highly site specific. Factors such as the ambient pH of the soil and receiving water,
their buffering capacity and the interaction with other physical and chemical parameters
will be important in controlling the affects. To afford a moderate level of protection for
aquatic life, the pH of freshwater systems should be between pH 6.0 and 9.0, and there
should be no change greater than 1.0 units outside the estimated seasonal maximum and mini-
mum (Jones 1964). In marine waters, the addition of foreign material should not reduce the
pH below 6.5 or raise it above 8.5, and within the normal range the pH should not vary by
more than 0.5 units. Natural plants and animal communities are found on soils ranging from
acid bogs to highly alkaline arid environments, and limits of appropriate release would be
site specific.
As was the case with the granite repository, shaft and mine liquid effluents are
expected to seep into the shale repository during construction. The estimated maximum
inflow during the last stages of construction will be about 19,000 m 3 /day (5,000,000 gal/
day). Most of this water will be collected in sumps, pumped to the surface and treated.
One or more holding ponds will be used to retain the water prior to cleanup and release to