REP28949

• Permit No: M1993041
• IBM Index Class Name: Report
• Doc Name: ATTACHMENT 1
• Media Type: D
• Archive: No

ROCKY MOUNTAIN CONSULTANTS. INC.
~J
October 13, 1993
Mr. Bill McIntyre
Senior Professional Engineer
Office of the State Engineer
1313 Sherman Street, Room 816
Denver, CO 80203
~~~
700 Florida Avenue
Suite 500
Longmont, CO 80501
[phone]
Metro [phone]
FAX [phone]
RE: Southwestern Portland Cement, Dowe Flats Mine, CMLRB Reclamation Permit,
File No. M-93-041, Boulder County Permit Docket No. SU-93-4/V-93-8,
Sections 9, 10, 15, 16, 21 & 22, T3N, R70W, 6th P.M.
Water Division 1, Water District 5
Dear Mr. McIntyre:
We have reviewed the water supply plan and water requirements for
Southwestern's proposed mine and reclamation plan at Dowe Flats, adjacent to
its existing Lyons cement plant. This report is to address the concerns of
your office in your referral responses that you had insufficient data to
evaluate the adequacy of a water plan for the project.
Out-of-priority depletions, if any, resulting from the mining operation
will occur from dust suppression; from exposure of a maximum of 2 surface
acres of groundwater in the mined pits; and from irrigation of the trees and
shrubs during reclamation. The water resources available to Southwestern are
more than adequate to offset estimated water usage for these purposes.
Based on 150,000 gallons per day, 5 days per week and 30 weeks per year,
dust suppression will require an estimated 70 acre-feet per year. Dust
suppression is not needed for approximately 22 weeks per year due to bad
weather, rain and snow. About 75% of the dust suppression will occur from May
through October, requiring approximately 53 acre-feet of water. The
remaining 17 acre-feet will be needed during the non-irrigation season.
Evaporative depletions from the two acres of water surface created by
the mining will be approximately 5 acre-feet per year. From current site
characterization, groundwater as presented occurs in a bedrock aquifer and in
an alluvial aquifer. From groundwater elevations measured in exploration
drill holes at the site, free water in the bedrock will not be encountered
within the first 3 to 4 years of mining. During the initial phases of mining,
shallow groundwater within the alluvium (which appears to be a perched system
resulting from surface water recharge such as drainage and ditch leakage) will
be encountered. Thus, the alluvial groundwater will likely not occur outside
the irrigation season. The total surface area of exposed groundwater, either
alluvial or bedrock, will not exceed two acres. .
•
CIVIL AND ENVIRONMENTAL ENGINEE2ING • PLANNING