2008-04-30_REPORT - M1973021 ‎(3)‎

• Permit No: M1973021
• IBM Index Class Name: REPORT
• Doc Date: 4/30/2008
• Doc Name: Geotechnical Addendum/ 2007 Annual Report
• From: Tetra Tech
• To: DRMS
• Permit Index Doc Type: Annual Reclamation Report
• Media Type: D
• Archive: No

~~~ ~~~""~ 1900 S. Sunset Street, Suite I-F Longmont, CO 80501
Tel: [phone] Fax: [phone]
MEMORANDUM
TO: Matt Hall, Aggregate Industries Inc.
FROM: Gary Linden, Rich Tocher, Eric Bergstrom, Tetra Tech
RE: Review of Mining Activities; North Quarry, Morrison Quarry, Morrison, CO
Tetra Tech Job No. 133-23514.08002
DATE: February 7, 2008
BACKGROUND
Tetra Tech has completed a review of geotechnical data collected for the North Quarry of the
Morrison Quarry located at 18131 Highway 8, Morrison, Colorado. Aggregate Industries (AI) started
mining in the North Quarry in 2002 and mining is nearing completion. Upon the completion of
mining, the North Quarry will be reclaimed as a below grade water storage reservoir for the Town of
Morrison.
The geotechnical data review was performed to review the rock conditions encountered during
mining. The rock conditions affected the mining slope and mining depth achieved during mining.
Ultimately, the rock conditions affected the maximum depth of the North Quarry and the storage
capacity of the water storage reservoir.
OUARRYDEVELOPMENT PLAN
The Morrison Quarry is permitted with the State of Colorado under mine permit M-1973-021 which
contains five amendments and three technical revisions. The North Quarry was first included in the
permit in Amendment #2 with minor expansions in Amendments 3, 4, and 5. The limit of disturbance
for the North Quarry included 60 acres of minable reserves.
• The approved development plan for the quarry called for highwalls to be developed at 40 to 80 feet
high with benches 40 to 80 feet wide. Highwalls in areas visible from Highway 8 were generally
outlined to be 40 feet high with 40 feet wide benches to accommodate fill material for improved
reclamation. Highwalls below the visible area were generally outlined to be up to 80 feet high with
• benches 40, 60 or 80 feet wide. The development plan for the North Quarry specifically included 40
or 80 feet highwalls with corresponding 40 or 80 feet benches (resulting in an overall slope of 1:1
i horizontal:vertical) above elevation 6,455 and 80 feet highwalls with 40 feet benches below elevation
• 6,455 (resulting in an overall slope of/2:1 H:V) with a bottom at elevation 5,770.