PERMFILE67186

• Permit No: C1981028
• IBM Index Class Name: Permit File
• Doc Date: 6/15/2006
• Doc Name: Revegetation Success Criteria
• Section_Exhibit Name: Appendix TR-37
• Media Type: D
• Archive: No

• 4.2 1995, 1997, 1998 Reclamation Areas
4.2.1 Total Vegetation Cover
The overall form of the best-fit predictive curve for total vegetation cover in the
reclamation areas changed from the 2002 investigation with the use of this data from a
convex polynomial to a concave polynomial or logarithmic exponential. Using 1998-2002
data, the correlation coefficient was particularly high (0.9867}, decreased slightly with the
addition of the 2003 data, and decreased significantly with addition of the 2004 data. Two
potential factors affecting the predictive ability; stand age and drought conditions are
discussed below. Overall, the use of 2002-2004 data from the 1995, 1997, and 1998
Reclamation Areas did not improve the predictive ability of best-fit curves and equations,
over that developed from reclamation azeas in the 2002 investigation.
4.2.2 Total Herbaceous Production
Use of total herbaceous production data from the 1995, 1997, and 1998 Reclamation
Areas did not significantly change the overall shape of the best-fit predictive curves. The
overall rate of increase in biomass production and value (at higher precipitation levels)
decreased greatly from that predicted in the 2002 investigation as did values of the
correlation coefficients (from 0.9431 in the 2002 investigation to 0.7562 with the 1998-
2002 data, and ultimately to 0.4716 with inclusion of the 1998-2004 data). As with total
• vegetation cover, it was hypothesized that stand age and drought conditions may have
significantly affected the predictive ability with use of the 2002-2004 data.
4.2.3 Conclusions: 1995,1997, and 1998 Reclamation Areas data
Overall, the use of total vegetation cover and total herbaceous production data from the
1995, 1997, and 1998 Reclamation Areas from 1998-2004 did not improve the correlation
or predictive ability of best-fit curves and equations from those developed in the 2002
investigation.
4.3 Effects of Drought Conditions
Table A3 presents a record of precipitation at the Keenesburg Mine from 1993 to the
present. Precipitation in the years 2002-2004 was highly variable and droughty. In 2002,
annual precipitation was 38.7 percent below average and September-July precipitation for
2002 was 43.9 percent below average. In 2003, annual precipitation was 1.5 percent
below average, though September-July precipitation was 9.2 percent above average. In
2004, drought conditions again prevailed with annual precipitation being 22.0 percent
below average and September-July precipitation 40.5 percent below average.
It is hypothesized that these variable and drought conditions influenced both total
. vegetation cover and total herbaceous production in unaccounted ways, ultimately leading
to unpredictable growth, particulazly in the reclamation azea.
Coors Energy Company Keeneeburg Mine Page 9
2005 Addendum to Kevisbn of Revegetataon Success Criteria