2020-05-05_REVISION - M2008017

• Permit No: M2008017
• IBM Index Class Name: REVISION
• Doc Date: 5/5/2020
• Doc Name: Request for Technical Revision
• From: J&T Consulting, Inc.
• To: DRMS
• Type & Sequence: TR4
• Email Name: ECS
• Email Name: MAC
• Email Name: AWA
• Media Type: D
• Archive: No

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J&T Consulting, Inc, REEVED
MAY 0 5 2020
DIVISION OF RECLAMATION
May1, 2020TRO4 MINING AND SAFETY
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ECS/mac c
Mr. Eric Scott co
Environmental Protection Specialist
State of Colorado m •
Division of Reclamation, Mining, & Safety
1313 Sherman Street— Room 215
Denver, CO 80203
RE: Broken Arrow Investments, LLC— Derr Pit— Technical Revision No. 4 Request
File No. M-2008-017
Dear Mr. Scott, m
halo
Broken Arrow Investments, LLC requests a revision to their existing permit to address the following 1 ,1
2
items:
1. Slurry Wall Construction: Revision of the existing permit to reflect that benching is proposed in
order to construct the slurry wall because of the depth to bedrock and key into bedrock.
2. Change Depth of Phase 5a: Revision of the existing permit to reflect that surface mining for the
area was from 8'-10' and will now change to a depth not exposing groundwater.
3. Change of grading for disturbed areas: Revision of the existing permit to reflect proposed
grading in disturbed areas on east side of original permit boundary.
A detailed description of the revision is below:
Slurry Wall Construction: Revision of the existing permit to reflect that benching is proposed in
order to construct the slurry wall because of the depth to bedrock and key into bedrock.
This letter will serve as notice to the DRMS that Broken Arrow Investments, LLC requests a technical
revision to address the construction of the slurry wall as benching will be required to complete the
construction due to the depth of the bedrock and key into bedrock. There are several areas that the
bedrock is over 80 to 90 feet below the surface. The slurry wall construction equipment (PC 1250 with
Pierce Pacific Boom and Stick) can dig to a depth of 75 feet including key into bedrock. In order to
complete the slurry wall successfully the construction must occur by benching down 5 to 15 feet based
on the depths to bedrock.
Material will be removed along the slurry wall alignment to bench down to the level needed to achieve
excavation into bedrock to complete the key into bedrock and the slurry wall to a 75 feet maximum
depth. Once the slurry wall is completed to the surface of the bench elevation, the bench area will be
backfilled. After the bench area is backfilled the slurry wall will be excavated to the surface tying into the
completed slurry wall at the bench elevation and the slurry wall will then be completed to the surface
elevation. Attached are updated mining plan exhibits for your review showing the details of the
benching for the slurry wall construction. Slope stability analysis has been provided to show the 1.5:1
bench slope is safe for the areas where the slurry wall will be benched to construct.
•V 305 Denver Avenue—Suite D•Fort Lupton CO 80621 •Ph: 303-857-6222• Fax: [phone]