I am doing some very preliminary research on the construction of an underground data secure data storage center. This is VERY preliminary - I am hoping that this research will teach me which questions to ask when I get to the final research. All of the properties being looked at now are either in Arizona, Nevada or New Mexico. They are not in desert land but are in very sandy soil that does support the growth of brush and shrub - maybe that will tell you something about the soil condition. The data center will be a round dome 30 feet high and 80 feet in diameter. There is a requirement to have 10' of soil on top of the dome, so the pit will have to be about 43 feet deep. The excavated soil does not need to be removed from the property. The soil does not have to be lifted out of the hole - a ramp can be built so that equipment can drive up and down to retrieve/dump the soil, and the area can be backfilled later. It is better if the excavation can be done in 4 weeks or less. What is the least expensive method to dig this pit? Blasting is permissible in 5 of the 7 counties being considered. The work will most likely need to be done during the summer months.
I did the math as a square building 80x80x43 ( because I'm not sure how to do area figures on a cylinder ) and got a little over 10,000 yards. If its all dirt and no rock any competent earth mover should be able to pull that off in a week or less. Now if rock is involved and your gonna blast it may take a little long. You may also have to consider crushing the rock for backfill or importing it from somewhere else and that's more time and money.
When bidding site unseen, it's best to have a rock clause in the bid or send a local driller to put some holes down to feel the ground out. Depending on the site at 43' deep you may also need the 3/1 slope or several benches. I would think the diameter would be closer to 100' at the bottom and 358' at the top giving a min ten foot working around at the bottom and the slope to the top?. Looks like a good job for a trackhoe and a off road tipper or two.
Not trying to be a wiseguy or anything, unless there is some reason it must be done on a "time and materials" basis I think the best thing to do would be advertise for bids from excavating contractors who work in the area, and let the contractor who wins the job use the method they figured their bid with. As for blasting, that is something that is done as needed, (if you hit rock, that is) I am extra curious what this is for, 10 feet of dirt on top sounds like a bomb shelter or something.
While the DOD or DOE probably don't concern themselves a bunch with the extra cost of blasting etc. relative to the entire cost of there programs, test wholes (drilled) prior to deciding on the exact location may be prudent, and even if the location is definite will provide for a much better bid. Keep us posted please as some aon here may be very interested in bidding!!
The "ten feet of earth on top"....you can think of it as a bomb shelter but it is to protect corporation's data. By keeping the servers and backup media underground it is easier to control access to, easier to protect, easier for climate control, etc. There is almost nothing burnable in these kinds of buildings (no wood in the building), but if a fire does break out, it is very easy to contain. I will keep you posted, but it is likely to be more than a year from now before things get put out to bid. Right now we have to deal with the question of accessing fiber optic cable for the center. Thanks for helping me know how to plan!
This kind of project would be a normal job for many contractors in my area. With enough room for construction around the outside, say 20', and 1.5:1 slopes for safety, the hole would be around 45,000 cy. Excavation of this would be a couple of weeks unless there were unforseen conditions like rock, groundwater, or environmental issues. The soil to backfill around the sides and top will likely need to be screened to something like 3" minus so there are no rocks or debris to damage the walls or roof. There will also likely be waterproofing and subdrains to handle groundwater and condensation. All in all, the excavation will be one of the easiest parts of the project.
Without "complications" and without backfilling, is $20-40K a reasonable ballpark figure for the excavation?
That would require pricing well below $1.00 per cy, and those prices have not been seen for work like this for over 30 years. Try adding a 1 in front of those numbers and you may be close enough for a budget.
This may sound crazy, but look into a retired missile complex (Atlas D) Most of what you are looking for may already exist
Pretty funny you mention the retired missile complex Jimbo. I just had a conversation with my dad about them, because the site I am developing used to be a control station for one or something like that. At least that is what I have been told. But anyway there used to be another one in the area, They put a housing plan on the site and filled the silo and put a house on top of it. Thought that was kind of funny. sorry for the hijack
If I'm thinking of the same one you are Eric that was a early detection radar site during the cold war. There are a bunch of these all over the country that were used to detect incoming missiles from the reds.
Well, Buckfever, they were actual missile silos in the ground. They were loaded and ready to launch to take down anything the reds sent at us. Pittsburgh had a large number of them because of the steel mills. I think there were 17 of them just in PA. My dad is into them, knows a lot about them.