REV101675

• Permit No: C1981039
• IBM Index Class Name: Revision
• Doc Date: 4/27/1989
• Doc Name: GRASSY GAP BOND
• From: MLRD
• To: CATHY BEGEJ
• Type & Sequence: MT1
• Media Type: D
• Archive: No

III IIIIIIIIIIIII III
999
STATE OF COLORADO
Roy Romer, Governor
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DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Dlreetor
DATE: April 27, 1989
T0: Cathy Begej
FROM: Susan Mowry ~.
RE: Grassy Gap Bond
At the request of Rockcastle, I have re-evaluated my bond calculations of
December 1988. I therefore submit the following set of calculations for
your consideration. The changes which you will note are as follows:
Substitute use of 631E scrapers, four of them, and a D9N dozer for the
637E push-pull scrapers.
Deleted the road maintenance team, water truck and grader, and therefore
increased rolling resistance.
I changed the material weights and descriptions for overburden and
topsoil to more closely agree with the weights that Rockcastle presented
at our April 1989 meeting.
I used a lower swell factor, that of clay and gravel mix, according to
the Cat Handbook. I believe this figure to be appropriate based on a
demonstration submitted by Peabody Coal Company for the Seneca II permit.
I have deleted the cost for demolition of the shop building based on the
letter from A&B Repair which Rockcastle submitted.
I have also deleted the cost for rough grading the backfill based on
conversations with staff.
Therefore, while comparing my new calculations to those submitted by
Rockcastle the following differences arise:
Rockcastle did not adjust for altitude, I did.
Rockcastle used an 8% grade figure, I used 6% based on their maps. This
slight difference results in negligible difference when summing the haul
and return times. Therefore our total cycle time estimates are very
close (4.4 vs. 4.33).
215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]