Representatives from Constantine Metal Resources met with the Haines Borough Assembly on Tuesday to answer questions about the Palmer Project, a mineral exploration site in the Chilkat Valley. Recently the company completed a waste management permit application and a reclamation plan for its second phase of exploration
At the meeting on Tuesday, Liz Cornejo, Constantine’s Vice President of Community and External Affairs gave an overview of the plans for the second phase of exploration at the Palmer Project.
“Moving forward we are looking to transition into a phase of underground exploration,” Cornejo said.
Constantine plans to excavate a 2,000 meter underground ramp to provide easier access to the main mineral deposit at the Palmer Project.
“Having underground access would allow us to do year-round work,” Cornejo said. “Currently most of our work is in the summertime. The drilling is in the summertime.”
Excavation for the ramp will require removing over one hundred thousand tonnes of rock. The company has proposed to use some of the waste rock for construction purposes and store the rest above ground in stockpiles.
In response to concerns about the possibility of unearthing acid generating rock Cornejo explained that the site has a high ratio of acid neutralizing minerals to potentially acid generating minerals. According to Constantine, all the samples they have taken so far have more than twice as many basic minerals as acidic minerals.
“If any potentially acid generating rock is encountered that rock will all be placed back underground at closure. So nothing would be left on surface that would be acid generating,” Cornejo said.
Part of Constantine’s waste management plan for the second phase of exploration involves treating water that has seeped into the proposed underground ramp. This seepage would come in contact with wall rock and explosive residue. The company has proposed developing two settling ponds to treat seepage water before discharging it to the surrounding environment through a diffusing system.
This was a concern for Assemblymember Heather Lende.
“What happens there with the water that comes out of the ponds and with the water that comes out of the pipes that goes through those filter systems? Is there a way that that’s going to be filtered out so it doesn’t end up in the creeks or particularly in Glacier Creek and run down into the Klehini?” Lende asked.
Jack Dimarchi, a consultant for the Palmer Project responded that the seepage water will be discharged 10 feet under the ground but 20 feet above the water table. He said that the seepage water would not be discharged directly into nearby creeks because they flow on the surface above the water table. But he did acknowledge that water flows downhill and eventually connects downstream.
“You know we all have to agree that all water eventually goes downgradient and connects up and flows downstream,” Dimarchi said.
Constantine will monitor the chemistry of the groundwater. Cornejo said that the Department of Environmental Conservation (DEC) has set trigger limits for certain minerals and chemicals in the groundwater.
“Those trigger limits are really set around natural conditions. We’ve collected water samples of the surface water and the groundwater and DEC has used those to establish their trigger limits.”
Constantine’s waste management permit application states that levels of dissolved aluminum, manganese and vanadium in discharged seepage water are expected to exceed Alaska water quality guidelines. However, the document notes that the aluminum concentration in the wastewater discharge is still lower than natural background aluminum concentrations when measured as total aluminum.
Total metals analysis includes the metals both dissolved in the water and present in the particulates in the water. A dissolved metals analysis is performed by removing the particulates with a filter, then analyzing the filtered water for metals.
The Department of Natural Resources (DNR) is currently accepting public comments on Constantine’s waste management and reclamation plans.
Kyle Moselle with DNR’s Large Mine Permitting Team says he has received seven comments so far. Several have requested an extension of the public comment period.
The deadline to submit comments is May 15th.