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Supplementary Information - 1984 Annual Report Henderson Mine March 26, 1985 Page 3 The spillway-pipeline would probably cross thE~ dam on the northwest end, proceed along the existing peri- meter access road at the toe of the tail dam, and outlet into the northwest end of the seeo water canal. This pipeline-spillway affords a backup to the already-existing decant and flood bypass pipelines which underlay the tailing deposition area and drain surface water from the basin. 5,000 feet of 36" reinforced concrete F~ipe at $35/linear foot would cost a total of appro~:imately $175,000.00. Excavation and backfill for installa- tion of the pipe would cost approximately $23,500.00, bringing the total to approximately $200,000.(10. Question 5: Page 4, Area 9 references "Revegetation Peri. Road" with a cost per acre of $700.00. Page 2 of this attachment referenced reclamation costs of $].,045.00 per acre. Please specify why a lower am~~unt is required in this area. Answer: The effective cost per acre for the treatment of the 94 acres in Area 9 is $700/acre because portions of the areas and roads included in this total acreage have been treated, were only partially disturbed by timber clearing for the canal ROW, or are recovering unaided due to invasion of adjacent plant and seed material. The costs were arrived at in the following manner: (Thousands) a) Reveg. tailing, 715 acres @ $4,068/acre $2,909 b) Flood control 200 c) Reveg. peri.road, 62 acres @ $1,045/acre 65 d) Fe rt. peri.road, 32 acres @ $33/acre 1 e) Perm. use, Canal/road, 40 acres 0 f) Buffer , 1,597 acres 0 $3,175 As you can see, the 94 acres of perimeter road treatment is further broken down as shown it items c) and d). This breakdown was not detailed in the Annual Report. $66,000.00 to revegetate 94 acres is an average of $700.00 per acre.