REP52112

• Permit No: C1981021
• IBM Index Class Name: Report
• Doc Date: 2/8/1999
• Doc Name: 1998 EVALUATION OF REVEGATATION SUCCESS AT THE WALDEN COAL CO MINE SITE
• Permit Index Doc Type: ANNUAL RECLAMATION REPORT
• Media Type: D
• Archive: No

L
EVALUATION OF SAMPLE ADEQUACY
' Sample adequacy was obtained for cover and production in each of the two
reference areas (Table 12}. Shrub density data were not collected in 1998 because the
' standard for reclamation success was based on a stipulated value rather on the basis of
comparison with a reference area.
For the two reclaimed areas, sample adequacy was obtained for cover,
production and shrub density in both areas (fable 12).
EVALUATION OF REVEGETATION SUCCESS
i ,
Cover and Production. The Colorado Division of Minerals and Geology
Guideline Regarding Selected Coal Mine Bond Release Issues (March 17, 1995) provides
approaches for evaluating the success of revegetation on coal mined lands. For the
reclaimed areas at the Walden Coal Company Mine, the approach titled "Technical
Standard or Simple Reference Area Comparison Weighted Sampling in Bond Release
~' Block" was used to evaluate success for cover and production. With this approach,
pooled weighted mean and standard error of the mean values are obtained for
combinations of reclaimed areas. To conduct this analysis, the cover and production
data for the 1984 and 1988 areas were pooled using the approach outlined on page 22 of
the guideline referenced above. Pooled values are weighted based on the areal extent of
each of the reclaimed areas. For the 1984 area at the Walden Site, the weighing factor
was 29/112 (0.25893) and for the 1988 area, the weighting factor was 83/112 (0.74107).
Weighted means for the reclaimed area were calculated as follows:
Mean Total Vegetation Cover = 29/112 x (31.1) + 83/112 x (33.2) = 32.66 percent
Mean Total Ground Cover = 29/ l12 x (66.53) + 83/ ] 12 x (79.25) = 75.96 percent
' Mean Total Production = 29/112 x (20.8) + 83/112 x (70.1) = 57.3 g/m2
These pooled mean values were then compared to values obtained from the two
sampled reference areas. Since two reference areas were used, pooled mean values for
cover and production were used to obtain the initial comparison values. Since the
sample sizes for cover and production were the same in both reference areas, the pooled
mean values were computed as the simple means between the two areas. The pooled
' mean values were:
100 % Mean Total Vegetation Cover = 35.5 percent
' 100 % Mean Total Ground Cover = 81.6 percent
100 % Mean Total Production = 38.40 g/m~
The actual mean values were then converted to the cover and production
standards by taking 90 % of the pooled mean values:
90 % Mean Total Vegetation Cover = 31.95 percent
90 % Mean Total Ground Cover = 73.44 percent
' 90 % Mean Total Production =34.56 g/mz
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