FAQ

What was mined?

Limestone between the 1870’s until 1946

What was it used for?

Cement made at the plant across the highway

When was this created?

1963

By who?

Medusa Cement

Why?

GSA contract to store Civil Defense Hospital supplies 

How deep underground is the mine?

Between 100’-200’

How thick is the rock?

The Vanport limestone layer is typically 20’ thick. The limestone was mined leaving approximately 4’ of limestone on the ceiling and varying amounts on the floor. Our buildings have a typical height of 16’ 6”.

How is the roof supported?

The roof is supported by pillars of limestone left during mining.

How big are the pillars?

Approximately 30’ diameter (varies)

How many pillars are there?

Over 1,500

How big is the facility?

  • Over 300 acres on the surface
  • 1 mile from end to end
  • 2.5 million sq. ft. subsurface
  • 1,000,000 sq. ft. used for recreational vehicle storage
  • 1,100,000 sq. ft. developed into buildings and roadways
  • 750,000 sq. ft. of warehouse (leased and public)
  • 225,000 sq. ft. of office, record center, light industrial, maintenance, and corridors
  • 125,000 sq. ft. of climate controlled vehicle warehouse
  • 20 dock doors

How long does it take to build space?

90 to 150 days but construction can be completed throughout the entire year.

How do you measure space?

Square footage is measured by useable floor space excluding the pillars.

What does electric typically cost?

Approximately $.25/sf/year.

What about dampness?

All of the buildings are equipped with dehumidification units that keep the relative humidity at approximately 50% inside the buildings.

What about the temperature?

Building temperatures are a steady 62 degrees, while the mine remains at a constant year round temperature between 50-55 degrees.

Has there ever been a cave in?

The majority of roof failures occur during the mining process or relatively soon thereafter. Usually they are caused due to excessive blasting. Since mining activity ended over sixty years ago we have had a long period of time to evaluate this subsurface as stable. We also do regular measurements to record significant changes in the structure of the subsurface. The pillars over time go through a self scaling process where smaller loose rocks do fall. Our facility is inspected on a quarterly basis by the PA DEP Bureau of Deep Mines.

The majority of roof failures occur during the mining process or relatively soon thereafter. Usually they are caused due to excessive blasting. Since mining activity ended over sixty years ago we have had a long period of time to evaluate this subsurface as stable. We also do regular measurements to record significant changes in the structure of the subsurface.

The pillars over time go through a self scaling process where smaller loose rocks do fall. Our facility is inspected on a quarterly basis by the PA DEP Bureau of Deep Mines.

What about not seeing the sun?

It is not unlike working in a warehouse or office. Not everyone has a window. But there are advantages: our cars never gets melting hot in the summer. We never have to scrape ice off of our windshields in the winter. We never have to go out in the rain. During the summer we go outside at lunch like everyone else.

Interesting facts:

  • Since 1994 there has been over 5 million dollars invested in facility improvements including a new truck entrance, interior and exterior roadways, truck docks, 400,000 sq ft. of additional space.
  • George Romero’s “Day of the Dead” filmed at the facility Site for other films and continue to be considered as a potential site for film projects in the Pittsburgh area.

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