Wednesday, May 3, 2017

Butte, Montana - The richest hill on earth

One of our overnight stops was in Butte, Montana. One of the most noticeable features of the town is a ring of mining headframes on the hills around the town. Mining began here when gold was discovered in a little creek called Silver Bow Creek in 1862. Placer mining started soon and went on for a while. With the arrival of the railroad in 1874, it became economical to mine silver, iron, and copper, as the ore could now be shipped for processing. The timing was especially great as the electric age was just beginning, and the demand for copper was sky rocketing.

By 1896 this 5 square mile area was producing 26% of the world's copper supply, more than half of the  United State's, and employing some 8,000 men.The first underground mine started producing in 1882, the last one closed in 1980, and the deepest was about a mile deep.  By the mid 1950's, with more powerful earth moving machinery available, it became more economical to switch to open pit mining. The pit we visited, Berkeley Pit, was operational from 1955 through 1982. However, mining still continues in adjacent areas.

A fascinating account of the mining history of Butte can be found on the website of the Mining History Association, including the "War of the Mining Barons".  For those of you interested in the social aspects, we were surprised to learn about the early unions, both miners labor unions for miners and the women's protective union.

This is a view into Berkeley Pit from the visitor center overlook. When it was closed in 1983, it was 7,000 feet long, 5,600 feet wide, and more than 1,800 feet deep.

When a mine is operating, pumps are used to keep groundwater from filling it up. The pumps here were turned off in 1982 and water started flowing back into the underground workings and Berkeley Pit.

The water has a very high concentration of copper, cadmium, cobalt, iron, zinc, manganese, and arsenic. It also is very acidic with a pH of 2.7. Even with all the metals and acidity, water boatmen (an aquatic beetle) live here.  In 200-, students and professors from Montana Tech discovered a new kind of algae living in the water that appears to digest iron.

At this point in time, solid bedrock is containing the contaminated waters. However, as the water level rises, there is the danger of groundwater contamination. As the graphic below shows, this critical level is 5410 ft above sea level. As long as the water level is kept below this, the groundwater should be safe. To ensure this, a water treatment plant has been built  that can treat 7 million gallons of water per day and then discharge clean water into Ssilver Bow Creek.

The Berkeley Pit Public Education Committee maintains an amazing website called pitwatch with the most recent data, articles on scientific research, sampling methods, and history of the pit.

The Silver Bow Creek/Butte Area site is located in Butte, Montana and covers about 26 miles of stream and streamside habitat. Since the late 1800's, mining crews dumped mining wastes into on-site streams and wetlands near mining operations. These activities contaminated soil, groundwater and surface water with heavy metals. Now a EPA superfund site, the area is being restored and re-developed into community parks, a sports complex, picnic area, wetlands, and an extensive trailsystem .

Here's a picture of the channelized stream bed of Silver Bow Creek.  This is a very common practice where streams are straightened to improve water passage and speed water flow downstream.  The banks are sloped to create a trapezoidal cross-section.  The problem, is that this is really, really bad for stream organisms.  There's no habitat.

Blacktail Creek is a tributary to Silver Bow Creek seen above.  Blacktail Creek already has restoration well under way.

Workers created meanders in the stream bed, and removed the trapezoidal cross section.  They also planted riparian (stream bank) vegetation.  We saw ducks, geese, and fish here.

This has a nice paved trail system alongside that runners, riders, and walkers use a lot.

You can see that its clean enough and natural enough that beavers are inhabiting the stream.  Here, you can see where they were chewing down these trees.

This vegetation on the sides provides shade and cover for fish, as well as keeping the water temperatures cold, which many fish need.

An important aspect of stream restoration is having lots of woody debris, such as logs, in the water.  Many aquatic species need this cover for their habitat.  Logs and the like create eddies which retain sediment and cause natural meanders that a stream is supposed to have.

For intance, in this meander site, you can see the rush growing on the left side, that helps push the water into the right side.  Sediment builds on the left and is taken away from the right.  In time, the creek will meander off to the right side.

Students at the University (or someone else) had a system of depth sensors installed at several locations to monitor stream flow.

So, if you compare the aquatic and terrestrial ecosystem around Blacktail Creek above to that to Silver Bow Creek below (so named because it looked like a silver ribbon), you see the incredible restoration results.  We didn't see any ducks, geese, fish, or beavers in Silver Bow Creek - just a shopping cart, oddly enough a pile of socks, and a lot of garbage.

I really like this kind of thing.  You watch the news, you read, and it seems that the environment is going to hell in a hand basket.  However, there are lots of really good and cool examples where the environment is getting better and past wrongs are being righted.

No comments:

Post a Comment