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Appendix F - Detailed Description of Alternative 3: DoEIRt.2001-11
Entombment with Internal Waste Disposal Rev. et ra
Redline/Strileout
I As part of the grouting effort, a 0.75-m (2.5-ft)-thick layer of grout would be placed on top of the
2 filled containers. This layer would act as both shielding and a working surface for the next layer
3 of containers. Grout amendments, such as fly ash or zeolite clays, would be considered for the
4 grout to reduce potential for leaching of radioactive isotopes. In the final design, a reinforced
5 concrete stab could be installed as the top section of the grout layer. The concrete slab would
6 provide a smoother surface for operation of the forklifts during waste placement of the next
7 layer. The grout, or possibly reinforced concrete slab, would be designed for the wheel loads of
8 the forklift.
10 The next waste placement would be inside the craneway. An opening in the southwest end wall
11 would be cut to provide access to the craneway. Guide rails would be installed and cargo
12 containers delivered into the craneway similar to waste placement in the galleries.
13 Approximately 39 containers could be placed in the craneway. The containers would be grouted
14 inside and out as was done in the galleries.
15
16 After placing, grouting, and pouring the topping grout or concrete layer on the third layer of
17 cargo containers, the height from the grout layer to the underside of the canyon roof would be
18 approximately 2 in. This would be too short to allow placement of cargo containers. Rather than
19 fill this large void with grout, placement of waste-filled burial boxes (1.2 m by 1.2 m by 2.4 m
r,20 long [4 ft by 4 ft by 8 ft]) would be performed. For this final FS, it is assumed that 960 boxes of
(.> 1 this size could be placed into a fourth and final layer of waste within the canyon. With tighter
22 packing, the number of boxes placed could be increased to 1,500. Void spaces on the interior of
23 the boxes would be filled with grout prior to placement. As a final step in placement of waste
24 inside the canyon, holes would be drilled through the canyon roof. Flowable grout would be
25 delivered into the canyon through these holes to fill around the boxes. Pressure grouting would
26 be used to fill voids not reached by previous grouting.
27
28 Upon completion of waste placement within 221-U, available space within the facility would be
29 filled with waste and/or grout. The containment provided by the grouting the waste inside
30 openings in the canyon would eliminate a111arge voids. These steps would stabilize 221-U and
31 ready it for placement of the environmental cap.
32
33 F.2.2.3 Install Engineered Fill. As the canyon is filled with waste, engineered fill would be
34 compacted in lifts around the exterior of 221-U. The engineered fill elevation would be
35 maintained within a few meters of the same level as the grouted wastes within 221-U. This
36 would prevent an excessive load across the canyon walls, including the end walls. The
37 engineered fill would also provide an access ramp to the south end of 221-U for container
38 delivery.
39
40 The engineered fill would be clean, compacted granular material, which would be placed in lifts.
41 Its source is assumed to be a Hanford Site borrow pit within 24 km (15 mi) of the 221-U Facility.
42 The actual source location has not been identified. The volume of engineered fill for
^33 Alternative 3 is approximately 1,169,700 m3 (1,529,869 yd'). The extent of the engineered fill
44 and environmental cap is shown in Figure F-1.
45
Final Feasibility Stndy/6rthe Canyon Di.ryrosltion Inftrative (221 •U Facility)
n,e 200-1
F- 19