View Document Here - Hanford Site

Appendix G - Detailed Description of Alternative 4: DoFJRI.-20oI-1t
^ Entombment with Internal and Eirte'rnal Waste Disposal Rev. I Draft n
Redlinc/Strikeout
1 at the ERDF (Casbon 1995). The 3 horizontal to I vertical (horizontal:vertical) slope for the
2 liner system is anticipated to pose construction challenges because it would need to be built in
3 stages as engineered fill is placed around the facility. The liner starts from the intersection of a
4 45-degree line projected from the bottom slab of 221-U and the bottom of the engineered barrier
5 (see Figure G-2). The liner extends downward toward 221-U and transitions into a flat section
6 prior to intersecting the building's exterior face. An impermeable barrier would also be required
7 along the building face above the liner, and a method for transitioning from the wall to the liner
8 would be defined during final design. To serve the operational period, the building face barrier
9 could use a waterproof-type paint system.
10
l I The area of liner system is estimated as 15,100 mz (162,476 ftz), which includes the 3,800 mz
12 (40,100 ftz) of painted wall area. The total volume available for placement in this external waste
13 disposal area is 50,100 0 (65,463 yd).
14
15 The waste envisioned for placement within this disposal area is soil remediation-type waste. It
16 would be delivered and placed in compacted lifts, from a 0.6-m (2-ft)-thick clean working
17 surface, similar to the ERDF operations. Due to the location of the disposal area, lining and
18 placing waste would be difficult. Irke ERDF, the open working area would be limited to reduce
19 the potential for release of contaminants. Upon completion of waste placement, an interim cap
20 would be placed on the waste. Its purpose would be to limit the potential for infiltration during
^ 21 waste placement activities until the engineered barrier could be constructed during closure
22 activities.
23
24 Construction of the liner system for Alternative 4 would be challenging because it must address
25 scheduling requirements to maintain near-equal levels between internal and external waste
26 placement and the technical issues associated with the liner installation. I.iner installation
27 scheduling could present a delay to the placement of waste internally while the liner system was
28 completed. Technical design issues include selection of an appropriate paint system for the
29 canyon exterior, the connection of the liner to the wall, and a liner system that could be installed
30 satisfactorily in "lifts" over an extended period of time.
31
32
33 G3 CLOSE THE COMPLEX
34
35 This function consists of completing construction of the environmental cap over 221-U,
36 demolition debris, and external waste disposal area that was placed immediately adjacent to it. It
37 would also involve restoring the disturbed sites (access roads and equipment staging areas) to a
38 grade consistent with the natural surface topography. Closure of the complex for Alternative 4
39 would also require institutional controls and maintenance of a monitoring system. Institutional
40 controls could consist of both physical and legal barriers to prevent access to contaminants.
41 A closeout report would be prepared for regulatory agency approval.
42
^ 43 G3.1 Construct Environmental Cap
44
Final Feasibility Stady jor rlu Canyon Disposition Initiative (221-U Facility)
„ • 100 G-20