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Appendix F - Detailed Description of Alternative 3: DoEIRI.,2oo1-1 t
Entombment with Internal Waste Disposal Rev. e Dr•e
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1 (2 in.] or less) resulting from movement in the 3:11 to I:V side slope of the environmental cap
2 would be outside the waste area requiring infiltration protection from the engineered barrier.
3 With Ihese layout parameters addressed, the environmental cap could provide the required
4 containment during a 500-ycar life. During final design of the environmental cap, a finite
5 element analysis method should be used to define the final cap layout dimensions and confirm
6 that the engineered barrier components are propcrty sized for the design seismic event.
7 Additional discussion of the barrier is provided in Section 4.0 of this final FS report.
8
9 F.3.2 Revegetate Site
10
11 The excavations from demolition activities would be backf lled with compacted clean soil and
12 clean concrete rubble. Fill contours would match adjacent contours. Material for backfill would
13 come from both stockpiled material and the borrow source. The borrow source is assumed to be
14 within the Hanford Site, but has not yet been idcntified.
15
16 All areas disturbed by demolition activities would be prepared for surface restoration. If
17 required under the industrial land use for the 200 Areas, the majority of restoration would be
18 application of an approved native grass seed mixture. Existing roads damaged by the demolition
19 would be roturned to their pre-project condition.
20
^31 F33 Cleanup Complex
22
23 Before leaving the complex, the demolition contractor would clear the site of all equipment and
24 materials.
25
26 1F3.4 Sustain Post-Closure
27
28 This alternative would require institutional controls and maintenance of a monitoring system.
29 Institutional controls could consist of both physical and legal batriers to prevent access to
30 contaminants. In addition, certain activities would need to be prohibited to verify protection of
31 the groundwater and the Columbia River. Post-closun: care would consist of periodic
32 inspections and maintenance to verify the success of the revegetation effort.
33
34 F3A.1 Establish Institutional Controls. Specific institutional controls associated with this
35 alternative would be developed as the remedy is further dcfined in the remedial design report and
36 implemented through an update to the Sitewide fRrtirutional Controls PlanjorHanjord CERCIA
37 Response Actions (DOE-RL 2002). Generally, these activities would include physical and legal
38 methods of controlling land use. Physical methods of controlling access to waste sites are signs,
39 entry control, excavation permits, artificial or natural barriers, and active surveillance. Physical
40 access controls would be designed to preclude unintentional trespassing and minimize wildlife
41 access. Physical restrictions are effective in protecting human health by reducing the potential
42 for contact with contaminated media and avoiding adverse environmental, worker safety, and
(O'N33 community safety impacts that arise from the potential release of contaminants. They require
44 ongoing monitoring and maintenance. Public notices and community relation efforts would
Final Feeslbiliry Study for the Canyon DitpnrNion Inidmive (221-U Facility)
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