The Yukon Water Board has approved a plan for additional monitoring of water quality at Tatchun Creek where waste rock from the Minto Mine is being used for bank stabilization.

The board halted the placement of waste rock earlier this month following recent concerns raised by the Little Salmon-

Carmacks First Nation regarding the potential for metals leaching out of the rock.

The board last Tuesday ordered the Department of Highways and Public Works to develop a plan to conduct further analysis of the waste rock and examine the potential for the rock to leach toxic metals.

It's also instructed the department to prepare a water monitoring program for Tatchun Creek, as well as develop a contingency plan to remove the material if a problem arises.

The order remains in effect until tomorrow, or until the board issues a new directive, according to the decision last week.

The Tatchun Creek Bridge is being replaced at an estimated cost of $4.5 million.

Waste rock from the Minto is being used as rip rap, and the board has already approved its use, though it decided to have another look at it given the concerns raised in mid-May by the First Nation.

Assistant deputy minister Allan Nixon of the highways branch said he's hoping test results from additional rock and water samples will be available for the board this week so that the placement of rip rap can continue.

The board's order has not affected all construction work at the bridge site but has caused delays, though there has been no indication from the contractor about whether the delays will cause an increase in the project cost, he said.

In an interview last Thursday afternoon, Nixon emphasized the use of waste rock from the Minto Mine was fully examined by experts retained by the department as part of the application for a water licence submitted in October 2012.

The water licence issued by the board in February 2013 approved the use of the waste rock from the mine site, he pointed out.

In its decision last week, the board notes it's taking the measures to re-examine the use of waste rock because of the First Nation's concerns.

Nixon said the new management plan requested by the board was delivered last Thursday.

It's the department's hope the board will be satisfied by the test results from the additional samples taken in the last couple of days and will lift the stop-work order with regard to the placement of rip rap, he said.

Nobody, said Nixon, provided submissions to the water board during the initial process to screen the application for a water licence, and the First Nation was invited to participate.

He said he does respect the First Nation's right to raise the matter now. It could, however, put the squeeze on because the government only has a four-week window to work in the creek before the chinook salmon arrive, Nixon explained.

Chief Eric Fairclough said in an interview last week rain runoff from the pile of waste rock stockpiled for use at the bridge is already showing discolouration.

This is not waste rock, but rather low-grade ore containing minerals, the chief contends.

Fairclough said he isn't sure how the use of the waste rock passed in the first place.

Even the tiniest fraction of copper released into the water – eight parts per billion – can cause harm to the salmon's ability to navigate and harm their defensive system, he said.

Tatchun Creek, the chief insisted, provides very important spawning grounds.

The government's new management plan required by the water board was approved last Friday.

If the placement of waste rock is allowed to continue, water sampling on Tatchun Creek will be conducted at six sites every two days while the rip rap is being placed.

There will be two sites upstream of the bridge project, one on each side of the creek bank.

Also planned are two more sites 10 metres downstream of the rip rap zone and two more sites 200 metres below the bridge project.

Monitoring will be reduced to weekly for a month after completion of the waste rock placement, then to monthly for a full year.

After a year, it's proposed the monitoring will be reduced to once in the summer and once in the winter, though the schedule could vary, depending on the views and needs of the water board, according to the government's management plan.