INSPEC06977 - Laserfiche WebLink

Home Browse Search

(Page 2) MINE~ID # OR PROSPECTING ID # M-77-342 INSPECTIOCJ DATE 5/24/99 Ir15 PECTOR'S INITIALS ACS OBSERVATIONS Three primary elements related to the Henderson Mill site and the reclamation permit were addressed through this inspection; (1) Inspection of the acreage under consideration for release from the permit area under Acreage Reduction Revision AR-001, (2) Inspection of the acid storage yard outside and just north of the mill building, (3) Inspection of the ore conveyor corridor currently under construction. The acreage under consideration for release from the permit area is located in Lost Creek up gradient from the proposed Lost Creek dam and reservoir site. The proposed release acreag~^ was field located using the topographic maps included in the AR-001 submittal. The acreage has been subject to timber harvest at some time in the past, but there has been no mining, mineral processing cr other disturbance related to the Henderson Mine and Mi11 reclamation permit. The logged area has stabilized through the establishment of grass and the regrowth of small trees. Based on these observati~>ns, AR-001 will be approved. An approval letter will be sent under separate cover. The acid storage yard is the location of two 50,000-gallon tanks used to store hydrochloric (HC1) acid for use in the milling circuit. A leak developed in the south tank during May 1999. A portion of the HC1 from the leaking tank was transferred to the north tank by an emergency dedi cited transfer pump, but the seals in the pump failed before the transfer was complete. The HC1 that leaked from the tank was fully contained in the bermed tank basin. This basin is lined and filled wi t~z crushed limestone for acid neutralization. The acid storage ycr3 is an Environmental Protection Facility as defined in Rule L.1(15) of the Hard Rock/Metal Mining Rules and Regulations. The Environmental Protection Plan (EPP) describes the facility as having primary containment (the tanks), and secondary containment cf an 84,000-gallon bermed basin lined with limestone. The acid storage facility has been substantiall}• upgraded since the submittal of the EPP. In particular, a geomembrane has been installed in the se~:ondary containment basin, the emergency transfer pump described previously has been installed, dout~le piping has been installed to transfer the HC1 into the mill, and concrete curbing has been installed to contain any spills that may occur during tank filling operations. The operator should provide a report to update the EPP and incorporate improvements in the acid storage yard into the plan. The four topsoil stockpiles related to construction of the conveyor corridor were inspected. The largest topsoil stockpile is located at the north end of East Branch reservoir adjacent to the County Road. Side slopes of this stockpile were measured with an Abney level to be as steep as 28 degrees or 1.9H:1V. Silt fence had been installed around the down gradient perimeter of the stockpile, but many lengths of the silo fence were in need of maintenance. A crew was working on silt fence repairs at the time of this inspection. There are two topsoil stockpiles located at the south end of East Branch reservoir. One of these piles contains the topsoil salvaged from wetlands distur.oed during conveyor construction. This wetland soil will be used during construction of wetland cells this summer in accordance with the individual 404 permit issued for the project. Side slopes on the topsoil pile located east of the north conveyor access road were measured to be as steep as 25 degrees or 2.1H: 1V. The silt fence around this pile was in need of maintenance. The fourth topsoil s'.ockpile is located adjacent to the REC-6 rectifier, just west of [he ore haulage rail line. Potential problems with the configuration of this pile were noted during the 8/6/98 DMG inspection of the site. Since that time, the pile has been sloped to 3H:lV and is now in a stable configuration. All of the topsoil stockpiles were hydroseeded and mulched at the end of the 1998 construction season. Some germination of grass was observed on all piles, but it is too early to maY.e an assessment of whether the vegetation established through the 1998 seeding will be adequate tc provide long term stabilization of the scot kpil es. Until a stand of grass is established on the stockpiles, silt fence or other runoff controls must be maintained. The terms of the topsoil stoc kpil i~ig plan approved in amendment AM-03 to the Henderson reclamation plan specify that "stockpiles will be graded to slopes no greater than 3H:1V in contoured configurations within one month of the topsoil salvage operation." As documented above, this permit condition has not been adhered [o for the three stockpiles around East Branch Reservoir. It was discussed on site that topsoil from these three stockpiles would be used in