The second phase of the Program involves the renovation of the Basement and Mezzanine, which started in September 1994. One third of the Basement has been renovated with many areas now occupied. The original basement slab was lowered in order to accommodate an entirely new level between the basement and the first floor. When completed, this new Mezzanine level will add close to 320,000 square feet of office space to the Pentagon.
The Mall and River sides of the building have a Basement area which includes a partial Mezzanine.
[The Pentagon site]"...is situated between a large man-made lagoon...[and] the highlands of Arlington National Cemetery."
The decision to move the Pentagon downstream from its planned location placed it within the flood plain of the Potomac River.
Building Condition extensive discourse on the basement and under terraces
Pentagon Renovation & Construction Program Office Project Information
March 2000 Basement/Mezzanine
Basement and Mezzanine levels exist under three fifths of the Pentagon. This area has been divided into three segments. Segment 1 has been renovated and is now occupied by 1,200 Air Force personnel and the new DiLorenzo TRICARE Health Clinic. Segments 2 and 3 have been demolished and abated of all hazardous materials.
The basement floor slab was excavated and lowered two feet. This allowed enough room to build and entirely new mezzanine level, an addition of 240,000 square feet of space.
October 1999 Basement Segment 2A2
June 2003 Navy Build-out 2A1
Navy requires approximately 25,000 square feet of space in the Pentagon. The area designated for this project in Basement Segment 2A1 is the only available space.
Early basement renovation in Segment 1.
October 2000 Basement Segment 3A Demolition and Abatement
Navy Build-out 2A1
Completion Date of March 2003, with tenant move in expected in April 2003· NTP sent out on 09/25/01. Over 200 Helical screwed piles being installed through the existing slab on grade to support a new structural floor slab. (Phoenix NOV 2003)
"Core and Shell construction is underway in the basement. Gilford is currently saw cutting the floor slab for installation of helical piers, a new ductbank and plumbing for future build-out. To date they have installed approximately 200 piles within the Navy space's concrete slab. Piles are placed in preparation for a new concrete slab that is to be poured on top of the existing slab. A new structural slab must be poured due to settlement of the existing slab over the years."THE PENTAGON ATTACK PAPERS Seven Hours in September: The Clocks that Broke the Lie, by Barbara Honegger, M.S. Sept. 6, 2006
"Immediately after the second WTC tower was struck at 9:03 am, Andrews and his aide left his office and ran as fast as they could down to the Secretary of Defense’s West section basement Counterterrorism Center (CTC), beneath the ground-level location of the violent event in the building."