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MINING NEWS: BLM reclaims historic mining properties Environmental conditions at Nome Creek and Harrison Creek watersheds in Interior Alaska have been significantly improved Sarah Hurst For Mining News
Fortunately for Alaska, there are relatively few abandoned mine sites in the state that pose a hazard to the public. Historically, placer mining was widespread in Alaska, which means there aren’t too many deep adits where necks can be broken. But there is still reclamation work to be done, and when there is no new owner to take responsibility on federal lands, the Bureau of Land Management steps in. Over the past few years staff from BLM’s Fairbanks office have been working at two sites on Harrison Creek and Nome Creek in Interior Alaska.
Nome Creek is in the White Mountains National Recreation Area and Harrison Creek is in the Steese National Conservation Area, and both creeks drain into national wild rivers that flow into the Yukon Flats National Wildlife Refuge, BLM’s Linda Musitano explained May 16 at the Northern Latitudes Mining Reclamation Workshop in Juneau. Both the Recreation Area and the Conservation Area are closed to further mineral entry, but there are still a handful of active mining claims in the Harrison Creek drainage, she added.
The scale of the Harrison Creek project was much larger than that of the Nome Creek project. “The Nome Creek area was mined historically by dredge and dragline, while Harrison Creek was mined primarily by heavy earth-moving equipment, and the access to the sites differs as well,” Musitano said. Nome Creek is about 30 miles north of Fairbanks and a state-maintained road goes there, while Harrison Creek is only accessible via a seasonal mining road.
Nome Creek a popular recreation area BLM’s concern about Nome Creek was heightened because it is a popular recreation area for activities that include camping, fishing and gold panning. The upper middle reaches of Nome Creek were dredged and extensively placer mined from the late 1800s to about 1980. Evidence of mining, such as old dredge buckets, still remains there today. “Most of Nome Creek’s stream channel and associated floodplain were disturbed by dredges and the earth-moving equipment and much was left in an unreclaimed state,” Musitano said. “It had been diverted and its banks totally reworked until it was almost unrecognizable as a stream in some parts. By 1980, when it became part of the White Mountains Recreation Area, over seven miles of the stream were disturbed by mining.”
The overall project goal at Nome Creek was to reduce the erosion problem by stabilizing the channel and creating a functioning floodplain. BLM began a streamflow monitoring project at Nome Creek in 1989 and the information was used to help design a new stream channel and a suitable floodplain for the upper reaches of the drainage. Peak flow gauges were installed at two sites on Nome Creek and one site on Moose Creek in 1989, and 10 years later an automated water level recorder was installed.
Reclamation work began with filling in the settling pond by using the material from the surrounding tailing piles and then grading the area as flat as possible with the grade not to exceed 3:1. A pilot channel was then dug, avoiding the filled-in ponds. For revegetation work, BLM worked with the Plant Materials Center in Palmer, testing various grass species and willow planting techniques.
“We had good results with the grass seed mixture that was spread on the tailing piles,” Musitano said. “At the beginning of the project the seeding rates were at about 55 pounds per acre. This was continued for about three years and then it was observed that the grasses were probably interfering with the natural revegetation of the willows, so the rates were reduced to 36 pounds per acre, and they were only put on the areas that were highly erodable. Fertilizer was also applied annually to the newly constructed floodplains ... at rates ranging from 330 pounds per acre to 400 pounds per acre. The sites treated annually with the fertilizer exhibited faster rates of return for natural revegetation of willows than the sites that were not treated with the fertilizer.”
Results from the project showed that site selection, planting techniques and summer weather routines all factor into plant survival. Dormant cuttings had higher survival rates than the willows that were cut on site. Another challenge was large overflowing ice that occurred when the stream froze down to the bed. This kind of ice filled the valley in the springs of 1996 and 1997. “Not only does it cause problems to the floodplain that was recently constructed, but it also delays revegetation of the reclaimed areas,” Musitano said.
During several summers there were also severe storms that caused extensive flooding in Nome Creek. “The pilot channel that was put in place remained largely intact, but other areas suffered from lateral erosion and braiding,” Musitano said. “While overestimating channel dimensions may increase construction costs and possibly cause braided channels, the results of underestimating can be channel failure and catastrophic floodplain damage,” she added.
Harrison Creek project lasted only a few weeks The Harrison Creek reclamation program was much more short-term than the one at Nome Creek, lasting only for two weeks in July and August 2006. It did require a few years of planning, though, after BLM received funding for the project from the federal Abandoned Mine Lands program in 2001. BLM then contracted with the United States Geological Survey to collect hydrologic information about the watershed so that the reclamation program could be designed. Engineering firm USKH provided a literature review for BLM, covering what had already been written about the area.
As at Nome Creek, BLM wanted to create a functional floodplain to reduce the erosion problem at Harrison Creek and to encourage native species to grow there. “Some specific objectives were to design river reaches that mimicked the undisturbed areas both upstream and downstream of the reclamation project. To reduce the environmental degradation by getting rid of the spoil piles, and to rehabilitate the riparian habitat,” Musitano said.
Reclamation activities included pushing over and flattening tailings piles, excavating floodplains along channel margins, filling in braided channels, cutting back stream banks to lower the angle of the bank, and redistributing topsoil and organic material where possible. A bulldozer operated for about 20 hours a day for 14 days. About 80,000 cubic yards of tailings material was moved and 4.3 acres of topsoil was salvaged and spread on the new floodplain. In 2008 and beyond BLM will look at reclaiming some other stretches of Harrison Creek.
In-house work reduced Nome Creek cost In total, 2,400 operator hours were spent at Nome Creek over a period of almost 20 years. At Harrison Creek 353 operator hours were spent in two weeks. Nevertheless, the cost of the Harrison Creek project was about $680,000 (with 1.46 stream miles reclaimed), compared to $344,000 at Nome Creek (with five stream miles reclaimed). The biggest difference was that Nome Creek was done in-house and Harrison Creek required outside help, including $50,000 to create a topographic contour map; this kind of map was already available for Nome Creek.
“Based on our experience at Nome Creek we found that what appears to produce the most labor- and cost-effective results in terms of revegetation is to apply fertilizer for several years after reclamation to encourage native species coming in, but not conducting additional willow plantings. If you are going to do willow plantings, the dormant cuttings were pretty time-consuming,” Musitano said.
The use of a single bulldozer at Nome Creek was effective because only a small portion of the valley was being reclaimed each year, according to Musitano. “At Harrison Creek our idea was to get a larger area reclaimed in a very short period of time and so the use of two bulldozers was not nearly as effective, probably because the pushing distance was pretty far, and to balance the cut-and-fill it was taking a lot of time, so they recommended that we use an excavator and dump trucks for future projects there,” she said.
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