2008-04-03_REVISION - M1980149

• Permit No: M1980149
• IBM Index Class Name: REVISION
• Doc Date: 4/3/2008
• Doc Name: Adequacy review comments ‎(part 1)‎
• From: Applegate Group, Inc.
• To: DRMS
• Type & Sequence: AM3
• Email Name: ESC
• Media Type: D
• Archive: No

a-pplegate
Group, ~n~.
Apri13, 2008
Colorado Department of Natural Resources
Division of Reclamation, Mining, and Safety
Attn: Ms. Erica Crosby
1313 Sherman Street, Room 215
Denver, Coloradlo 80203
R;~CE~~IE®
APR 0 3 ZOQS ~
Division ui t<eciamation,
Mining and Safety
RE: Adequacy Review Comments #2; Weld County; Hokeatra Pit; M-80-149
C~-~3)~
Dear Ms. Crosby:
This letter is provided in response to the adequacy review comments dated March 10, 2008. Thank you
for taking the time to review our responses. We appreciate your time and effort regarding this project and
feel that we have; adequately addressed your concerns.
1. A map showing all adjacent land owners has been provided. Adjacent landowners were also added to
Exhibit C-1.
2. The application has been revised to reflect the approved (AR-04) penrr-it boundary acreage of 172
acres.
3. The stability analysis indicates that the slopes of reservoir III and IV which will be surrounded by a
slurry wall v~rill be stable. The XSTABL model assumed the following.
• The slurry wall will be minimum of 12 feet from the reservoir embankment.
• Gaslines are located outside of the slurry wall. .
• The slurry wall does not infringe upon the easements for the existing gaslines.
• Reservoir slopes are at a 4:1 and are native sand and gravel.
• The ;material properties for the shale bedrock were taken from on-site tests. The sand and
gravel properties are from the Bureau of Reclamation's "Design of Small Dams", Third
Edition, 1987. These properties are shown in the table accompanying the answer to
comment 5 in this letter.
The model was run in both a rapid draw down condition and a static condition. The model showed
that the reservoir side slopes were stable.. A factor of safety of 1.74 was. generated in the rapid
drawdown scenario. The static scenario produced a slough failure with at a factor of safety of 2.83.
Neither failw~e plane impacted the slurry wall. The gaslines will be outside of the slurry wall and
therefore their stability was also not affected. The results of this analysis are attached.
During construction where the slurry wall crosses the gaslines, the County will have crossing
agreements with the gasline companies and supply copies of those agreements to the DRMS before
construction of the slurry wall begins. .
1499 West 120th Avenue, Suite 200 [phone] • Fax .[phone]
Denver, Colorado 80:?34-2759 www.applegategroup.com ,