EIS-0113_Section_11 - Hanford Site

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P-6 Why was it assumed that TRU wastes are uncmnplexed solutions? The
references suggest that they are complexed solutions.
P-7 Why is Sm assumed to behave chemically similar to Am?
APPENDIX Q APPLICATION OF GEOHYDROLOGIC MODELS TO POSTULATED RELEASE
SCENARIOS FOR THE HANFORD SITE
G
shown on a map of the Hanford area (Figure Q.5, page Q.32). Two irrigation
scenarios are developed in Section Q.8. The two irrigation scenarios
assume, first, a very few (10 percent) deep percolation rate with one
irrigated acreage and, second, a higher percolation rate (20 percent) with
what appears to be a lesser irrigated area. The degree of conservatism of
these scenarios cannot be assessed from infomation presented in the DEIS;
however, Table Q.17 (page 0.36) indicates either scenario can substantially
reduce the thickness of the Sateen zone in the 200-areas; which would lead
to proportionate or greater reduction in times required for contaminants to
reach the accessible environment.
LIT
W
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Appendix Q presents a series of groundwater contaminant pathway
analyses for the four alternative disposal methods. Analytical results are
presented for two climatic scenarios, a drier climate represented by
0.5 cm/yr average`annual recharge, and a wetter climate represented by
5.0 cm/yr recharge. For the wetter climate case, consequences of two
barrier-failure scenarios are also analyzed.'
Groundwater travel times in the vadose zone were computed manually,
using a fixed vadose-zone thickness of 64 meters. Travel times for the
saturated zone were analyzed using numerical simulation. The boundary
conditions, solute transport assumptions, and output of this numerical model
are described generally..
Quantitative overall radionuclide travel times, from disposal to the
200-Areas to peak arrival in the accessible environment, and peak nuclide
concentrations/fluxes are tabulated for each disposal alternative. Two
points of contaminant release to the accessible environment were considered,
the Columbia River, and a hypothetical domestic well 5 km downgradient of
the 200 disposal areas.
Separate subsections summarize radionuclide transport from the
300 disposal areas and describe water table .changes . resulting from potential
irrigation scenarios. -
LrrC E , and Uncertainties
Because the radionuclide travel time analyses incorporate assumptions
described earlier in the DEIS, most of the errors and uncertainties
discussed for appendices M, 0, and P are Compounded in the quantitative
trans p ort assessments tabulated in Appendix Q. The net effect is that these
results are non-conservative. In addition to this compounding of earlier
Problems, Several new errors or uncertainties are manifest in Appendix Q.
DEIS section Q.3 summarizes some of the in p ut data assumptions and
results of vadose zone modeling. The table at the bottom of page Q.3
indicates a vadose zone thickness of 64 meters was used to calculate
unsaturated travel times for all recharge scenarios. This assumption
contradicts information presented elsewhere in Appendix Q. Specifically:
a) Oat.. from figure 0.3 (page Q.8) and table 9.17 (page Q.36)
.indicate the depth to groundwater beneath the 200-areatank
bottoms would ran ge between about 37 and 57 meters for 5 cm/yr
average recharge.
b) Scenarios re garding off-site irrigation after site closure or loss
of institutional control, presented in section Q.8 (Table Q.17,
page 0.36), indicate vadose zone thicknesses beneath the 200-area
tank bottoms as small as 15 meters.
c) For situations not involving site closure,. artificial recharge of
Coming and waste waters at Hanford cannot conservatively be
assumed to cease.. In this case, vadose zone thicknesses beneath
the 20D-area tanks should be less than the present 59-meter
average, to account for continued artificial recharge.
Each item (a through c) above implies significantly Shorter vadose zone
travel times than are indicated on pages 0.3 and O.S. This is true for the
0.1, 5.0, and 15.0 cm/yr recharge and in cases (b) and (c) probably the 0.5
Cm/yr recharge. rates as well.
Questions
0-1 In view of a number of factors indicating much smaller possible
vadose-zone thicknesses, why is 64. meters used in all calculations
of unsaturated zone travel times for the 2OD disposal areas?
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The most significant of these errors or uncertainties includes the
development of the off-site irrigation scenarios, and the apparent omission
of these scenarios in any of the quantitative analyses of radionuclide
transport, long-term performance assessment, or probability and consequence
analysis. DEIS section Q.8 (page Q.31) states "After site closure or less
of institutional control, the passibility of irrigation on Hanford land
becomes real.-Areas likely to be f rmed are discussed on page Q.31 and
Q-2 .DEIS section Q.4 on aquifer modeling discusses the simulated
steady-state configuration of the water table corresponding to the
0.5 and 5 cm/yr infiltration (recharge) scenarios. The modeling
implies that with 0.5 cm/yr recharge, the water table drops to
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