INSPEC34776 - Laserfiche WebLink

Home Browse Search

III. COMMENTS -COMPLIANCE Below are comments on the inspection. The comments include discussion of observations made during the inspection. Comments also describe any enforcement actions taken during the inspection and the facts or evidence supporting the enforcement action. This was a complete quarterly inspection of the Fruita mine site conducted by Dan Mathews and Janet Binns of DMG. In addition to the quarterly inspection, vegetation cover sampling was conducted to provide data in support of Phase II bond release and sediment pond removal demonstrations. The Fruita Mine reclamation plan did not specify removal of the pond embankment, and the Division does not contemplate such removal. However, initial assessment based on vegetation cover data and site conditions indicate that the sediment pond is no longer necessary to control disturbed area sedimentation. If this initial assessment is confirmed, the Division will propose to discontinue monitoring and maintenance of the sediment pond embankment and spillway structures. Site conditions were largely unchanged from those described in the March 2005 and December 2004 inspections. The only change of note is the seasonal growth of vegetation, which is particularly lush this year, Revegetation/Reclamation Success Perennial grasses and shrubs have exhibited impressive growth due to the above normal fall/winter/spring precipitation. Rubber rabbitbrush and shadscale saltbush in particular were notable for the amount of annual growth produced, with longer leaves and stem leaders than normal. In addition to the vigorous appearance of the shrubs that were seeded in 2000 and previously, high numbers of seedling four-wing and shadscale saltbush, and rubber rabbitbrush were noted in various locations throughout the reclaimed area. There has also been a flush of annual vegetation, with significantly higher densities of annual grasses, particularly cheatgrass brome and little barley, along with annual fortis including tumble mustard, flixweed, blue mustard, storksbill, various buckwheats, and others. The flush of annual vegetation is not limited to the disturbed mine areas, but is apparent all along the base of the bookcliffs and the semi-desert lowlands to the south of the bookcliffs, in western Colorado and eastern Utah. Thirty randomly located, 10 meter vegetation cover transacts were run. At each transact, a tri-pod mounted ocular 10 point frame was set up every 2 meters, for a total of 50 readings per transact. A complete vegetation assessment report has not been prepared, however an initial cover summary has been prepared, and is attached. Tha sole vegetation standard applicable to the Fruita Mine is vegetation cover (because of the extensive pre-law disturbance at the site). The mine was never permitted under the permanent regulatory program, but the Division had proposed a cover standard of 25% in a findings document that was prepared prior to forfeiture of the reclamation bond. Based on the data collected, the standard was easily exceeded this, year. The applicable criteria is 22.5% vegetation cover (90% of the approved standard). The sample mean from the cover data collected by the Division was 43.2%, based on the sample size of 30 transacts. Statistical sample adequacy was not met (30 transacts run vs. 31 calculated for adequacy), however a statistically valid "reverse null" demonstration of success was made. The 90% lower confidence limit on the mean is 38.83°k, which easily exceeds the standard. This result is confirmed by the reverse null t-test, in which the calculated t value of 7.66 exceeds the table t value of 1.311. Because the calculated t value exceeds the table t value, the null hypothesis of equality is rejected, and success is demonstrated.