We tend to think that in a trade-off there are positives that outweigh the negatives, but as many colloquial expressions attest, some things don’t lend themselves to a trade-off. The Chinese say you can’t have a horse that runs fast yet consumes no food; the Danish say you can’t both blow and have flour in your mouth; and the Germans say it’s an impossibility to want someone to “Please wash me, but don’t get me wet.” In English, we say “You can’t have it both ways.”Approximately 200 miles southwest of Anchorage lies Bristol Bay, sometimes characterized as the type of salmon “factory” that doesn’t exist anywhere else on the planet anymore. The bay is fed by a vast, pristine network of rivers, lakes and wetlands. The water in the tributaries is so pristine, fish biologists use the word “distilled” to describe its purity. Not only do all five Pacific species of salmon spawn in these freshwater tributaries, but so many spawn that as many as half of the ones fished in Bristol Bay can be caught sustainably because a single spawning event can produce up to 60 million fish. So wouldn’t you know it, right in the midst of this remote and uninhabited part of the Bristol Bay watershed an international consortium, called Pebble Limited Partnership, has assembled mineral leases over 330 square miles of state land for the purpose of developing an open-pit mine. It would be large enough, according to former Republican Alaska state Sen. Rick Halford, to hold three open-pit mines the size of Bingham (Kennecott) Canyon Mine in Utah.To give you a sense of Pebble’s potential size, Bingham Canyon Mine is more than six-tenths of a mile deep and 2 1/2 miles wide, and covers 1,900 acres. This mine is the largest man-made excavation in the world and is visible from space with the naked eye. Imagine something three times bigger.At this point I’m sure you can guess the problem. What the Pebble Partnership sees as a wonderful trade-off, fishermen, Native Americans, fish biologists and the Environmental Protection Agency see as a “you can’t have it both ways” situation. The Pebble Limited Partnership is 50 percent owned by Anglo American (United Kingdom) and 50 percent by Northern Dynasty Minerals Ltd. (Canadian). Its stockholders are UK, Canadian, Australian and Japanese companies. These are big-time international players that project the value of the deposits at Pebble in excess of $300 billion at 2010 prices for copper, gold, and other metals. The tax revenue to Alaska on mining returns is 1.5 percent. This could eventually be a bonus for Alaska, but it’s a much greater bonus for the Pebble Partnership.To those who oppose the development of the Pebble deposit, it’s a trade-off not worth taking because the potential loss of salmon and water, and damage to the environment can’t be reclaimed. Because the Pebble Deposit lies between the two branches of the pristine watershed, building the infrastructure alone (an 86-mile road; a new port; a power project) involves major disruption to the salmon-spawning habitat. If built, an open-pit mine there would be termed wet climate mining, which Rick Halford refers to as “experimentation” because there has to be “perpetual remediation” in terms of keeping the open-pit mine dry. Keeping the open pit dry, in turn, involves extensive and continual “de-watering” or pumping of the streams, which depletes the water the spawning salmon need. Even if the water is returned to the streams as discharge, the chance of it being identical to the pristine original water the salmon know by scent as the location where each was spawned is slim, if not nonexistent. Copper is toxic, and distilling copper creates huge amounts of waste or tailings. At Pebble, estimates are there would be up to 10 billion tons of waste, which would have to be stored and monitored forever in order to prevent acid mine drainage, the most serious threat to the environment. The proposed plan is to build a series of huge earthen dams, the largest one over 4 miles long and 700 feet high. These dams would be able to hold 20 times the waste of those at the Anaconda mine here in Nevada and would be among the largest man-made structures in the world. Over time, it’s possible that a toxic plume of these dissolved metals could eventually leak from the tailing dams into nearby rivers and Lake Iliamna (15-20 miles south of the Pebble Deposit). Other possible dangers include large storms that overwhelm the storm-retaining capacity the dams were designed for, and earthquakes.Everything on this Earth is finite: copper, natural gas, oil, water, salmon, us. What can we invent if we run out of copper, natural gas, oil, and fresh water to drink?Probably something. But can we invent fish, birds, deer, bear, corn, wheat, life?A number of sources were consulted for this column, including the PBS Frontline program “Alaska Gold.”• Ursula Carlson, Ph.D., is professor emerita at Western Nevada College.