GENERAL40615

• Permit No: C1981013
• IBM Index Class Name: General Documents
• Doc Date: 7/5/2006
• Doc Name: 2006 Vegetation Study Plan Memo
• From: Dan Mathews
• To: Kent Gorham & Sandy Brown
• Permit Index Doc Type: Vegetation
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: (303) 832A106
DATE: July 5, 2006
TO: Kent Gorham and Sandy Brown
FROM: Dan Mathews
RE: Golden Eagle Mine 2006 Vegetation Study Plan
Permit No. C-81-013
COLORADO
DIVISION OF
MIN SRALS
GEOLOGY
REC LAMATION•NINING
SAf ETY•SCIENCE
Bill Owens
Governor
Russell George
Executive Director
Ronald W. Gattany
Division Director
Natural Resource Trustee
I have reviewed the referenced study plan, dated June 12, 2006, and have a couple comments, which
follow.
1. At the end of the Herbaceous Production Sampling section on page 4, narrative indicates
that "if sample adequacy is not achieved with fifteen through twenty-nine transects, data
collection will cease with the thirtieth transect and revegetation success evaluated utilizing a
two sample reverse null t-test". This approach would be acceptable, but there aze a couple
points the operator may want to consider.
First, it may be in the operator's interest to sample more than 30 transects to demonstrate that
the reclaimed azea mean is greater than the reference azea mean. The DMG rules merely
require a minimum sample size of 30, if the reverse null approach is used. Second, a one
sample reverse null t-test would be acceptable in the event that sample adequacy is
demonstrated in the reference azea but not in the reclaimed area [see the specific formula for a
one sample reverse null t-test in Rule 4.15.1 ] (2)(c)]. Operator may want to include the one
sample reverse null approach as an option in the study plan. If sample adequacy is not
demonstrated for either the reclaimed area or the reference area, a two sample reverse null t-
test incorporating Satterthwaite standard error and adjusted degrees of freedom will be
required, as indicated in my memo of Apri124, 2006.
Operator should consider these points and revise the study plan as warranted.
2. On page 4, under Post Mining Success Demonstration, the one sample t-test to be used in the
event that reclaimed area sample mean is less than 90% of the reference azea sample mean is listed.
The appropriate one and two sample reverse null t-test formulas, as applicable depending on the
sampling results, are not presented. A commitment to submit the appropriate reverse null
formulas for Division approval prior to submittal of success demonstration is requested.
Office of Office of Colorado
Mined Land Reclamation Active and Inactive Mines Geological Survey