EIS-0113_Section_11 - Hanford Site

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near its natural (pre-1945) condition, while 5 cm/yr recharge
table rise and minimum and average assume zone thicknesses beneath
3 . 5 , 2 a 30V
causes the water tattle to rise above its present level. the 200-area tank bottoms that would result from this more
conservative scenario?
a) To what extent did these simulations use actual measured
aquifer properties?
0-9 Have the reduced contaminant travel times due to water-table rises
associated with off-site irrigation been incorporated in the
b) The simulation of 1983 water table (figure Q.3, page Q.T) overall analyses of, a) long-term performance of waste disposal
differs from the water table observed in fall, 1982, as
systems, or b) probability and consequence of radionuclide release
depicted on figure 4.8 (page 4.18). To what extent were
and transport after disposal? If not, why?
attempts made to calibrate simulations of the 0.5 and 5 cm/yr
recharge scenarios against pre-1945 and later water level
data?
APPENDIX R ASSESSMENT OF LONG-TERN PERFORMANCE OF WASTE DISPOSAL SYSTEMS
.
Q-3 DEIS section Q.T (page Q.30) computes badose .zone travel times in General Comments
the 300-area TRU burial grounds at 14 and 114 years, respectively,
for 5.0 and 0.5 cm/yr recharge. According to the unit hydraulic
Appendix R presents an extensive series of tables assessing :long-Leon
gradient model (Ap pendix 0)-, these values imply average soil
performance of each of the four disposal alternatives, in terms of maximum
moisture contents of 8.15 percent and 7.125 parcent, respectively, radiation rdozes. Three main. sources of radiation exposu e are considered:
- for 5.0 and 0.5 cm/yr recharge, versus 6.4 percent and 7.8 percent a drinking-water well 5 km doengradient of the disposal area; a well used
assumed on page P.6 for the 200-areas. A finer-textured soil is for irrigation and stock watering in addition to drinking water; and the
implied in the 300-areas. is this supported by actual soil
Columbia River. Concentrations of radionuclides are tabulated for the well
moisture characterization? sources using the wet climate scenario (0.5 and 5 cm/yr average recharge),
-
- and for the Columbia River using both wetter and drier (0.5 cm/yr average
Q-4 What I. USDOE's estimate of the probability of occurrence of the recharge) climate scenarios.. Barrier failure scenarios are considered for
off-site irrigation scenario discussed in Section Q.8?
the wet-climate cases.
0-5 The two off-site irrigation scenarios developed in Section Q.8 Inaddition to the above combinations of scenarios, the potential
describe off-site land areas that are or may be irrigated in the impacts of A number of other disruptive events areconsidered in varying
future. Do historic soil surveys indicate significant
detail.
agricultural potential of any other areas tributary to or
overlying the unconfined aquifer modeled in the DEIS?
Errors or Uncertaint i ei
0-6 Irrigation losses to the groundwater table of 10 percent and 20 A combines results from nearly all the preceding e appendices.
percent are used in DEIS section Q.8, analyzing water-table Non- cAppendix Pointed out in this review in appendices is,
effects of future. irrigation. These figures appear
therefore , compounded in Appendix R, An example of this is the migration
non-conservative it relation to average deep parcel ation rates. analysis presented in DEIS Section R.1.3 (pa g e R.4) in which.. groundwater
Probably only trickle- systems or intensively managed sprinkler travel times are reported based an assumptions. which we judged in our review
systems could attain these rates in the relatively sandy soils of of Appendix 0 (this chapter) to be non-conservative.
the Hanford region. Would the capital and operational costs for
- such systems, compared to the incremental costs of pumping
-
Effects of Compounded Non-COrmeraatism. For.. Appendix R as a whole, the
additional water from the basalt aquifer and/or Columbia River, CDMPOundina of n cohhservativa assumptions and results from elsewhere in
Justify such low deep percolation rates?
the DEIS has the end result of makino the computed maximum. radiation doses
-. (tabulated in Tables R.2 through R.61 and others) unconservatively low for
04 What specifically is the quantitative effect of the irrigation all disposal alternatives. It also makes the results of the evaluation of
scenarios presented in Section Q.8 on contaminant travel times maximum radiation doses appear more similar for the geolcgi-, in-place
from the 200-areas?
stabilization, and reference alternatives than is reasonable, given the
current state of knowledge.We believe toe consequences of the in-place
Q-8 Deep percolation losses of 20 percent (or greater) in combination stabilization and reference alternatives differ from consequences of the
with irrigation of all potentially irrigable land would appear to geologic disposal alternative by a greater degree than is indicated in the
represent a reasonable but more conservative irrigation scenario DEIS.
than those presented in Section Q.B. What is the maximum water
3.5.2.30
4.1.21
4.1.21
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