Monday, May 23, 2011

Northern Tier Spring Meeting

This morning, after a general meeting, we all came out to the Homestake gold mine in Lead, SD. We had a series of presentations by the Sanford science staff explaining what they were trying to do if they get continued funding. The Homestead mine goes down to about 8000' underground, has 375 miles of tunnels and has been converted to a large science laboratory. When the site was turned over from being an operational gold mine the mine had water to ~4000' level. It is still in the process of being pumped out and needs to go through quite a bit of treatment to lower the temperature and get rid of the iron and arsenic.

They are in the process of outfitting the 4850' level as the Sanford Underground Lab with quite a bit of construction going on including expanding rooms, running adequate power and data down the shafts, installing clean rooms and lining all of the walls with a spray on concrete to contain any dirt or pebbles falling from the ceiling. Some of the "rooms" they are planning to build would be able to house Mt. Rushmore. These are much larger than the chambers needed to support the gold mining activity. This is the top of the one (of two) of the elevator shafts taking workers and equipment down to the 4850' level. There is another shaft that starts at the 4850' level and goes down to the 8000' level. There, the plans are to build DUSEL or the Deep Underground Science and Engineering Laboratory at the 8000' level. There is a desire to extend the lab down another 8000'. Many in the group were hoping to be able to go down into the mine but it just wasn't in the cards. I'm told that that was the original plan until a short time ago. There was a lot of water in the mine from recent heavy rains plus a lot of construction underground. Those in charge thought it would be better not to have a bunch of tourists underground.

This is a shot inside the building shown above at the top of the Yates shaft. The cables supporting the elevator cars are about 1½ inches in diameter and wind around these huge drums in the next building. There are two elevators in this particular shaft which is still not in use yet. Normally, it takes about 15 minutes to make the trip to the 4850' level but the elevators are capable of going up to 40 mph making for a much speedier thrill ride.

This is a small scale test version of one of the initial big science experiments to go down into the 4850' level. One of the reasons for going underground is to minimize the background from all of the other particles from the sun. The dirt and rock shields out most of the particles (just letting neutrinos through since they don't interact with anything) from reaching the experiment. It is being assembled and tested on the surface before being disassembled and taken down the elevator to be reassembled in one of the large vaults. The physicist leading the tour said it is much easier to identify and resolve problems on the surface. If you are down there and you forgot a tool or a fitting it is over a 30 minute ride to retrieve it.

One of the two giant winches used to raise and lower the cage. It isn't that the cage is so heavy but it's the weight of 5000' of 1½" of cable. The winches are driven by DC motors for better control. In the next room were the DC generators being driven by AC motors. One of the engineers mentioned that power down in the mine is pretty unreliable since all of the infrastructure is simply bolted to the walls of the tunnels.

6 comments:

redlegsrides said...

Cool stuff Richard and thanks for explaining why they had to go deep underground....interesting stuff, way above my meager understanding of physics I am sure but still interesting.

dom


Redleg's Rides

Colorado Motorcycle Travel Examiner

RichardM said...

I'm still very interested in physics and trying to learn the new material since I got out of school (physics degree). A LOT of new stuff or else I have a real bad memory. Both options are plausible.

Jack Riepe said...

Dear RichardM:

I found this blog episode simply fascinating, and I have a few questions. While you alluded to arsenic and iron, you also mentioned flooded tunnels due to rainwater.

1) If the elevatir shafts are covered, how does the rainwater get into the mine?
2) Is most of this rain water or seepage? Wouldn't it be just like a giant well?
3) Is the water pure, or is the water table loaded with arsenic?
4) Air gets thinner the higher you go. Does it get denser as you get lower?
5) Do your ears pop in reverse?

I realize you didn't get down into the mine, but I wondered if any of this came up in construction.

Very interesting.

Fondest regards,
Jack / Reep
Twisted Roads

RichardM said...

Jack / Reep:

I'll take a shot at these questions.
1&2) Adjacent to the mine is an open pit mine and the bottom of the pit is around the 300' level. There are several routes for the water from the pit into the mine through permeable rock layers. They have an elaborate pumping system to bring the water to the surface in stages with holding tanks at various levels. Otherwise the pressure required would be enormous. The same problem with water and sewage in large skyscrapers. The couple of inches of rain resulted in about 20 million gallons all of which needs to be run through the treatment plant.

3) The water in and near the mine have arsenic due to the chemical process of extracting the gold from the pulverized rock.

4&5)Yes, it gets denser as you go lower and I believe that your ears would "pop" as you descend. Even though the elevator will go up to 40mph, they only run it at a third of that when transporting people.

This was a really interesting trip...

BeemerGirl said...

Many family members worked in that mine while it was an active gold mine. I hadn't heard it was being reopened for these purposes. Awesome!

Like Jack, a question. If it flooded with a couple inches of rain, how will they prevent it in the future when it is "the lab"?

-Lori

RichardM said...

Lori:
They are installing a whole sequence pumps, intermediate holding tanks and water tight doors to manage the water. When the mine was turned over to them, the pumps weren't working.