Redfern Resources Ltd., developer of the Tulsequah Chief Project in northwestern British Columbia, is advancing an ingenious and economical way to access the remote mine site.
But the idea to build a year-round transportation system that would use Alaska waterways instead of a contentious 96-mile access road to the mine site from Atlin, B.C., is also encountering opposition.
Redfern, a subsidiary of Vancouver, B.C.-based Redcorp Ventures Ltd., has been working since the 1990s to re-open Tulsequah Chief, an underground zinc-copper-lead-gold-silver mine near the B.C.-Alaska border that closed in 1957. In 1998, Redfern obtained permits from the B.C. government to move forward with the project, using the road-access option.
The junior believes Tulsequah Chief has enough mineral reserves for eight years of production, with a strong possibility that more ore will be discovered at greater depth and immediately adjacent to the known ore body.
Multi-metal processing plannedRedfern plans to build a new underground mine and physical plant with a 200-worker camp to support processing 2,000 metric tons of ore per day, or 730,000 tons per year with an availability of 92 percent.
The ore will be crushed in two stages and filtered to yield four products — gold concentrate, bulk copper-lead flotation concentrate, zinc concentrate and tailings with pyrite. The gold concentrate will be refined onsite to produce gold bullion; and the pyrite with inert tailings will be mixed with cement and pumped underground as paste backfill. The remaining neutral tailings will be mixed with limestone to ensure no acid generation and sent to a tailings pond.
Redfern began a C$6 million exploration drilling program for 2007 in May and is gearing up for construction of a temporary camp and access road on its land and mineral claims and installation of a sewage system at the mine site this summer.
Redfern estimates capital costs for the project of about C$202 million.
The company unveiled the alternate transportation plan last fall in a feasibility study. It involves using the Taku River as the primary access and transportation route for the project, eliminating the need for a $50 million access road and trucks to haul concentrate to port.
The study is based on probable reserves of 5.4 million metric tons, grading 1.40 percent copper; 1.20 percent lead; 6.33 percent zinc; 2.59 grams per ton gold; and 93.69 grams per ton silver, which incorporates a downdip extension.
Water access viewed as best optionRedfern proposes to use air cushion barges towed by amphibious tugs to bring in supplies and equipment and haul out mineral concentrate in 40-tonne sea containers. In Juneau, the concentrate will be transshipped via scheduled commercial barge service to the Skagway Ore Terminal where it will be loaded onto container ships for transport to Asian smelters.
The air cushion barges would operate year-round with some potential weather delays due to high winds on the Taku River.
ACBs look a lot like hovercraft, but are very different. Unlike hovercrafts, ACBs travel at very slow speeds and sit in the water at a depth of about 18 inches rather than skimming the surface, Redfern said.
While hovercrafts are loud, ACBs only require diesel engines to fill their skirts and are relatively quiet. Their engines are enclosed in containers to dampen their noise to about the level of a semi-trailer truck, the company said.
ACBs generate minimal wakes in the water and carry much larger loads than hovercrafts.
Redfern said it will require two ACBs to carry payloads up to 450 metric tons each.
On average, 316 dry tonnes (341 wet) of concentrate will be produced from the operation each day, so less than one trip per day will be required, the company said.
The ACBs will be towed by an amphibious tug, called an “amphitrac.” This vessel is a converted Rolligon that uses Archimedes screws as a primary means of propulsion over water and ice and wheels for travel over ice when exiting the water up a ramp or beach, the company said
Alternative will save moneyRedfern aims to build a landing site for loading and unloading the ACBs about five miles south of the mine site on the banks of the Taku River near its confluence with the Tulsequah River.
A modest facility will be constructed, comprising a graded beach, fixed points for the ACBs to be winched to an unloading ramp, and a storage yard for the concentrate containers and incoming supplies, the company said.
The ACBs will not be used to transport the mine’s workers. Instead, personnel will be flown to the site on charter planes.
Redfern said the water transportation system represents a capital cost reduction of C$46.5 million (including contingency) and an operating cost savings of C$64 per metric ton of mineral concentrate (or $10 per metric ton mined).
Redfern is currently pursuing amendments to its Canadian permits and seeking necessary approvals from Alaska regulators to proceed with the new plan.
State has lots of questionsAlaska regulators and at least one environmental group have raised concerns about the potential for the ACBs and amphitracs to cause environmental damage to sensitive fish habitat in shallow areas of the Taku River.
The Office of Habitat Management and Permitting in the Alaska Department of Natural Resources is leading the state’s review of Redfern’s proposal. But several agencies have raised questions about the plan, said Tom Crafford, acting director of DNR’s Division of Mining, Land and Water.
“It’s clear that there is a lot more we need to know,” said Crafford. He observed that ACBs are a known phenomenon in Alaska, dating back to the 1970s when they were used on the Yukon River to support construction of the trans-Alaska oil pipeline.
“The concerns are related not so much to when the barge and amphitrac are in navigable waters but when they exit to land. Also using it year-round and traversing a variety of land forms, plus the winds on the Taku River are outrageous. So we are concerned how this system would work,” he said.
Crafford said the untested nature of the amphitrac also raises questions in his mind, especially about transitions from water to ice at the mouth of the Taku River as well as which route it will take on the river.
“We’re talking about a new technology. None of us have ever seen one of these vehicles. None has ever been built at full scale, to my knowledge,” he said. “It sounds pretty intriguing, so we are eager to know more.”
Crafford said state regulators expect Redfern to submit a detailed description of the alternate transportation by the end of July.
“Both vessels were chosen for their capabilities and environmental sensitivities as well as economic advantages,” Redfern spokeswoman Salina Landstad said July 17.
Terminal talks under wayThe Alaska Industrial Development and Export Authority, meanwhile, has held initial discussions with Redfern about the company shipping Tulsequah Chief concentrate to Asia via the Skagway Ore Terminal.
The talks are ongoing and the mine project could end up using about 25 percent of the terminal’s capacity, John Wood, AIDEA’s project manager, said July 18.
“With the change in access, we now have a more direct relationship with Alaska and as such we are working with various businesses in Alaska to provide supplies, equipment and fuel to the mine site, which we estimate could represent $30 million in annual expenditures in the state, Landstad added.