PERMFILE132941

• Permit No: M2006003
• IBM Index Class Name: Permit File
• Doc Date: 5/8/2006
• Doc Name: Groundwater Model Review
• From: DMG tas
• To: DMG
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room z l s C O L D RA D O
Denver, ColOmdo 80203 DIVISION O F
Phone: [phone] M I N E RA L S
FAx: [phone]
GEOLOGY
0.EC LANATION•NINING
EAiETY•EUENCE
DATE: May 8, 2006
TO: Erica Crosby, Carl Mount clGV~no
~ Rus:en ceorae
FROM: Tom Schreiner Executive Director
Ronald W. Cattany
Division Director
Natursl Rewura Trustee
RE: Groundwater Model Review, "Parker-Dersham Gravel Mine'; Hall-Irwin Corporation
File M-2006-003, Class: Permit
Per your request, I have reviewed the Apri128, 2006 Groundwater Study for the above
referenced Regular 112 Application prepared by Civil Resources, LLC. The results of the study
are based on input from 16 months worth of water level measurements collected at the proposed
site as well as expected pit de-watering and reclaimed pit conditions at a number of aggregate
operations in close proximity. The results of the study indicate the alluvial aquifer being drawn
down up to seven (7) feet due to de-watering and a mounding effect of up to two (2) feet due to
slurry wall installation. The applicant has proposed a variety of mitigation measures to ensure
minimization of impacts to groundwater users in the surrounding area. To completely address
the Division's concerns regarding impacts to groundwater in the surrounding area, per Rule
3.1.6(1), the applicant will need to provide the following information and/or commitments:
The applicant must commit to a groundwater level monitoring program with monthly
water level measurements at the six (6) existing piezometers throughout the life of the
operation, or until such time that the Division determines that the monitoring schedule of
groundwater levels at the Pazker-Dersham Gravel Mine may be revised or is no longer
needed.
The applicant must commit to an action level or "trigger" that will prompt the need for
mitigation measures to be implemented. (The Division suggests that the applicant
consider a trigger of 3' beyond the observed baseline groundwater elevation, as the
natural seasonal fluctuation at most piezometers appears to be 2').
• The applicant must specify provisions for reporting of action levels encountered during
mining as well as the reporting of annual water monitoring data and summary results to
the Division. The applicant may also want to specify measuring criteria to be used to
verify that a true exceedance of an action level has occurred.
• In the event that an action level is met during the life of the operation, the applicant will
be required to submit a revision to the permit within 30 days of summarizing the
mitigation measures employed and verification that de-watering impacts to surrounding
groundwater users have been adequately mitigated.
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey