Contrary to mining industry claims ("Modern mining is much safer, no threat to Minn.," Aug. 24) the proposed PolyMet sulfide mine is not "modern" mining designed for environmental and safety performance. PolyMet is a bargain-basement project that would fail to protect northern Minnesota's priceless water resources and that would put public health at risk.

The sad truth is that PolyMet is proposing to mine a low-grade, disseminated copper-nickel ore deposit in Minnesota's Lake Superior Basin. More than 99 percent of what is blasted out of the ground would end up as waste rock and tailings. Mining this low-quality deposit and managing its mountains of waste would be costly. In addition, copper prices have dropped 29 percent since 2011, falling this month to their lowest price since July 2009. Business analysts note that, as the price of copper has fallen, it is approaching the marginal cost of production where new mining no longer makes economic sense.

It's time to admit that PolyMet is, at best, a marginal project. Mining of a low-grade deposit on the cheap would not include best available technology to protect Minnesota waters.

One striking example of PolyMet's cut-rate approach is the company's failure even to analyze the alternative of dry-filtered tailings storage to reduce the risk of seepage and catastrophic dam failure at PolyMet's proposed tailings waste impoundment.

After Canada's Mount Polley disaster last year at a sulfide mine tailings impoundment similar to that proposed for PolyMet, an independent panel of experts determined that the tailings dam failed due to its design. The expert panel recommended the "best available technology" of filtered, dried and compacted tailings, emphasizing that there were no technical barriers to widespread use of this storage method.

Mining industry experts have explained for years that the dry-filtered tailings technology recommended by the Mount Polley experts has high sheer strength and prevents liquefaction of tailings and catastrophic dam collapse. According to Mike Davies, a pre-eminent AMEC (Association of Mining and Exploration Companies) tailings engineer, in addition to reducing the risk of dam failure, dry-tailings disposal requires minimal water management post-closure and facilitates reclamation.

Perhaps most important in Minnesota's water-rich environment, as compared with the cheap slurry approach proposed at PolyMet, dry-filtered tailings produce only one-tenth of 1 percent of the contaminated seepage of wet slurry tailings waste heaps.

Environmental groups and thousands of Minnesota citizens have called for the best-available dry-tailings technology to reduce the threat of contaminated seepage and dam failure at PolyMet. Across the globe, use of dry-tailings storage has dramatically increased since 1990. Yet neither PolyMet nor the agencies that should be responsible for protecting Minnesota waters have even analyzed this alternative technology.

More than six years ago, before PolyMet's first draft environmental-impact statement was released to the public, PolyMet and the "responsible" agencies rejected tailings-waste improvements, even as they admitted that placing tailings in a lined facility or reducing water in tailings would mitigate environmental harms. These better technologies to reduce water-quality impacts were screened out in 2009, because the operational costs "would be high." Neither of these safer alternatives has been analyzed since.

Rejecting best-available technology for tailings waste is cheaper and, so far, PolyMet has gotten away with it.

Minnesota deserves better than PolyMet's second-rate offer. It is inexcusable that Minnesota's first proposed sulfide mine won't even evaluate the dry-tailings alternative to reduce risks of dam failure, polluted seepage and long-term post-closure liability. A modern mine, at the very least, requires use of best-available technology to mitigate harm from tailings waste, not a penny-wise and pound-foolish approach that places our clean waters at risk.

And, as Minnesotans consider whether to assume the risks of sulfide mining's long-term pollution and costs, we should realize that experts in the business of mining agree that recycled metal is fundamentally cheaper as well as more sustainable than mined metal. Copper recycling has burgeoned in the U.S. Market consultants advise that the richest new source of platinum group metals may not come from mining at all, but from recycling catalytic converters from cars.

If Minnesota wants a truly "modern" method to produce metals and enhance environmental performance, that choice is recycling. It certainly is not PolyMet.

Paula Maccabee is advocacy director and counsel for WaterLegacy (waterlegacy.org), a nonprofit formed to protect Minnesota's water resources.