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,- <br /> <br />RE: Inspection Report on Henderson Mine/Mill Visit July 27, 1981 <br />Inspector Add Roy Cox and Brad Jones to the list of 5 other <br />inspectors. <br />Rule 6.1,A(2) Natural drainage patterns on the mine yard slopes <br />are being identified and erosion preventative measures are being <br />designed. A diversion trench above the administrative building was <br />completed in August of this year which effectively eliminated an <br />erosion gully. This system of trenching appears to be an effective <br />control and will be applied on other mine 'yard slopes where <br />appropriate. <br />Rule 6.1,B(1)a Bench <br />back toward the dam. <br />the brow of the bench <br />erosion or infiltrate <br />top surfaces will be graded so water drains <br />This will eliminate the incidence ~~f water on <br />where it could spill over and cause surface <br />and induce sloughing of the brow. <br />Rule 6.1,B(1)b The soil dressing on the tailing dam fac~~ does vary <br />in thickness from top to bottom but still provides a top dressing <br />that supports vegetation. There are very few spots which are <br />devoid of soil dressing. Any revegetation effort rarely achieves <br />100$ cover on the first application. For this reason ou:- revegeta- <br />tion program consists of retreatment and maintenance as necessary <br />until we are satisfied that the vegetation is self-sustaining. <br />Rule 6.1,B(1)c Our geological engineer advises that a 1•-2' high by <br />3' wide berm along the brow of the bench would very unlikely be <br />enough weight to be a significant "locus of tensional sei:tlement <br />cracking." <br />Revegetation (1) There are no tailing revegetation test plots on <br />pure tailing sands at the Henderson tailing pond at this time. <br />Revegetation (2) There are divergent views on the revegetation <br />process with respect to the use of exotics versus native::. One <br />viewpoint holds that a vegetative cover of whatever may he adapt- <br />able should be established as soon as practical on a suri:ace <br />disturbance to conserve soil and water. In the inspection report <br />under Topsoil Handling (1) recognition of this procedure is iden- <br />tified with regard to a stockpile area which "has been stabilized <br />with an excellent stand of grass." Natives will eventually <br />reinvade and succession and diversity will be reestablished. This <br />process will not be complete in 2-3 years but the protective cover <br />of introduced grasses will facilitate the eventual recovery. <br />Customarily tailing deposits are not reclaimed until the mine/mill <br />closes. We are attempting to begin reclamation on the tailing dam <br />faces as the dam goes up. This will provide additional lead time <br />for vegetation to form a self-sustaining stabilizing star,.d of grass <br />on the dam faces. This early effort to revegetate the dam faces <br />has the additional esthetic benefit of ameliorating the otherwise <br />