2011-05-20_REVISION - M2001107

• Permit No: M2001107
• IBM Index Class Name: Revision
• Doc Date: 5/20/2011
• Doc Name: Adequacy Review
• From: DRMS
• To: NCCI
• Type & Sequence: TR5
• Email Name: MAC
• Email Name: AJW
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
May 20, 2011
Mr. Doug Graff
Northern Colorado Constructors, Inc. Aggregate Div
COLORADO
D I V I S I ON OF
RECLAMATION
MINING
SAFETY
John W. Hickenlooper
Governor
Mike King
Executive Director
9075 WCR 10 Loretta E. Pineda
Ft. Lupton, CO 80621 Director
RE: NCCI Pit #1; DRMS File No. M-2001-107; Technical Revision No. 5 - Adequacy
Review
Dear Mr. Graff,
The Division of Reclamation, Mining and Safety (Division) received Technical Revision - 05
(TR05) for the above referenced site on May 5, 2011 and the application was filed for review on
May 18, 2011. The decision date for this application is June 17, 2011. The Division has reviewed
the TR05 proposal and has the following comments which must be addressed by the decision
date.
1. The groundwater monitoring plan approved under Technical Revision - 03 (TR03) specified
that piezometers would be monitored monthly for one year beginning when the recharge
ditches were in use and once the defined cone of depression had stabilized. Please specify
when the monthly monitoring to determine baseline levels began.
2. The Operator committed to establishing seasonal baseline levels under TR03. It appears the
baseline levels provided with this submittal were based on a twelve month average for each
monitoring well. Upon reviewing the groundwater monitoring data, it is apparent the
groundwater levels fluctuate greatly throughout the year. The mean of a data set is sensitive
to outliers and can result in a baseline level which may be impractical to maintain. The
Division believes it would be more appropriate to establish baseline levels based on the
standard deviation of each monitoring well data set, with the standard deviation used to
create the upper and lower levels at which groundwater will be maintained. Please determine
the upper and lower baseline levels for each monitoring well using the data collected from
2007 through 2010.
3. The groundwater monitoring plan approved under TR03 did not contain a provision for
notifying the Division in the event groundwater levels exceeded the established trigger
levels. Typically the trigger point is based off of three consecutive months of variation from
baseline data. Please commit to notifying the Division in writing within 48 hours in the event
the monthly average of any of the monitoring wells exceeds the upper or lower baseline
levels by 24 inches for three consecutive months.
- p Ii=i
Office of I ?-Office of
Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines