May 23, 2018
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Mining track record brings worries for Maine

By Ernest W. Hilton, Special to the BDN

Jeff Reardon of Trout Unlimited recently wrote an OpEd in the BDN in opposition to a legislative initiative to amend Maine mining laws to facilitate open pit mining in the Bald Mountain area northwest of Ashland. His major premise was that the sulfide mineralization in Maine rock and soils will result in what is known as “acid mine drainage,” or AMD, degradation of the streams and rivers in those parts of Maine where such mining takes place — whether Bald Mountain northwest of Ashland or elsewhere.

As a mining engineer I write to reinforce and validate his concerns.

My experience has not been in hard rock mineral mining but in the northern Appalachian coal fields of Pennsylvania, Ohio and West Virginia. Coal is obviously a different mineral than gold, silver or copper, but the rock around it, the so-called overburden or country rock, in much of that region is generally a sulfide and therefore creates a parallel set of problems of massive amounts of sulfide rock stripped off (in the case of coal), or both stripped off and ground up (in the case of these minerals).

As water leaches down through this stripped off material it reacts with those sulfides, acidifies into sulfuric acid and acidifies the streams and brooks into which it flows.

What’s more, mitigating the formation of AMD from coal mining overburden is, if anything, far easier than with the mining and processing of mineral ores. Coal overburden is simply blasted and shoveled out of the way to reach the coal which is usually in a fairly discrete seam.

But in the case of mineral mining, once overburden soils are removed, mineral ores after blasting are themselves usually crushed and milled to gain better access for separating out the ore. These ores only contain mere ounces of gold, silver or copper per ton of ore. Crushing creates more surface area for chemical extraction of the mineral sought. But enlarging the available surface area also facilitates contact of water with the sulfides and initiates the acidification process.

Throughout the Appalachians there are literally thousands of miles of acidified streams. And, while not recognized in Maine or acknowledged by the mining industry, they still find it financially unfeasible to initiate practices that would stop acidification or other pollution of streams. Indeed, more miles of acidified and otherwise polluted streams are being added all the time with the current widespread use of mountaintop mining.

Restoring these streams — mitigating the damage — has generally been possible only with the input of many millions of dollars for even short sections of streams and generally to less than satisfactory results. Indeed, federal and state taxpayers right here in Maine are still dealing with the aftermath of a copper mining project on the coast in Brooksville, a small project at that, which was closed in 1972, was declared a Superfund site some years ago and has required years of work to mitigate.

Fifteen years ago, the state went through a very lengthy process of developing a statute and a set of rules for dealing with ore mining, specifically in anticipation of mining at Bald Mountain. Mining and mineral processing technology has changed little since then. There is no reason to modify either the statute or the rules. Once these streams are acidified and polluted with the chemicals used for mineral extraction, which they will be, there is little likelihood of getting them back. The hastily acquired jobs will not have been worth it.

Ernie Hilton lives in Starks.

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