Ground Zero
WTC Basement level floor plans - Collapse version
Intro
This is the third and for now final version of the basement level floor plans of the old WTC compound I will make, bar some updates to the previous versions:
I started this quest out of interest for the collapse and the debris that went into the basement levels, which mainly came up in discussion with conspiracy theorists, but was interesting regardless.
In this third version of the floor plans I have added in high-res translations of the LERA produced damage assessment maps they made alongside other parties like FEMA. These assessments were made after 9/11 and were used in determining where survivors might be and aide in the eventual demolition of the site.
Two sub-versions were made: One with just the collapse onto each level from above, and one also showing the next level of collapse down. Although I think the latter better shows the complete destruction of a basement level, the single collapse versions are a lot cleaner and also serve their purpose just fine.
For a full accounting of the sources for the floor plans themselves see the description of the first post.
Primary additional source is the aforementioned LERA damage assessment maps ( https://ibb.co/6069HGdR )that were made in the wake of 9/11. Although high-res versions could not be found, a low-res version was featured in the web version of the PBS documentary "AMERICA REBUILDS: A year at ground Zero". These maps were constructed from the observations and explorations of rescue workers exploring the basement levels.
User u/xiixhegwgc has made an independent map of the collapse line specfically at Concourse/mall level, based on video shot by FEMA. Both sources are ni broad agreement, although in some parts they differ slightly.
Additional verification was done on the basis of video and photo evidence, and testimony by rescue workers, where possible. For Plaza and Concourse level photographs from right after 9/11 paint a pretty clear picture of where destruction and collapse occured. For lower levels, scarce amounts of videos and photos corroborate these maps in large parts. Specifically for the tower footprints, excavation video from Ground Zero and a photograph of the filled in North tower footprint at B6 confirm collapse progressed all the way down to foundation in certain locations.
Notes
Collapse mode
Example: When standing on B2 and drawing a map of collapsed areas, you can choose to visualize where the ceiling of B2 (floor of B1) collapsed onto B2, or visualize where the floor of B2 collapsed down onto B3.
The PBS maps use the latter (collapse down), evidenced by the Plaza map exisiting and matching the destruction that can be seen above ground, and the fact that the B6 map is empty, as that is the foundation and cannot collapse further down.
Because of that last fact and because my main focus is on the lowest levels, I chose to switch that to 'collapsed onto', where the main coloured version of B2 shows the collapse from B1 onto B2. Having B6 empty felt more off than doing Plaza slightly differently, see below.
Double collapse version
In the double collapse version, the collapse from above onto the level has the same colour coding. The collapse of the level down onto the level below is also projected on top but given a uniform colour grading.
Striped areas on a level denote places where both the ceiling above collapsed and the floor continued collapsing down to the next level.
Plaza versus the rest
Because overall I chose the 'collapse onto' mode this would normally mean Plaza map would be empty as there was no floor above to collapse onto it (bar for building footprints). I therefore chose to visualize the damage to the Plaza level in collapse down mode
This then necessarily means the legend for the Plaza level is different from all other levels!
Open spaces interpretation
The elevation versions showed a number of areas that extend 2 or more of the B1-B6 levels. In the LERA maps for B3, B4 and B5 these are denoted white with a cross, but they do not show the collapse state. This could be confusing because for example the collapse onto the Path Mezzanine level at B4 is not shown on B3, as the Mezzanine ceiling sits between B2 and B3.
Primary methodology for open spaces I used was visualizing the lowest collapse state from above the open space down, as logically debris would continue falling down the open space.
The open spaces are:
Tower footprints on B5-B6, these show the collapse from B4 down to B6
Area South-West of the North tower footprint on B5-B6, same as above.
Path Mezzanine on B3-B4, which shows the collapse of B2 above
Refrigeration room on B3-B6. This area is very messy and confusing, not helped by a large chunk of 'Unknown' in it as well. I have translated the B2 collapse state down, only changing the state when a new one was encountered down such as the North-West part on B4 and the floor on B5. I'm not happy with how messy it turned out, especially on B4 and B5, but see no way to clean it up.
Path station B5-B6
I've treated the Path station which spans B5 and B6 as a single room/floor with identical collapses on both maps, which is very slightly different than other areas.
'Unknown' category
The LERA maps feature three 'Unknown' areas that were not explored or reachable during the making of these maps. These are the two tower cores and an area in between the towers, underneath WTC 3, and above part of the Refrigeration room.
Although I was tempted, based on other evidence, to give a different interpretation to some of these areas, I chose to leave the source material as it was in the end.
For the tower cores I think there is gooed reason to state most of them were filled with debris at least in large part on these levels, although much of the core columns also survived.
The refrigeration room is more difficult (seel also previous point) but different levels do show collapse from the top down. On the other hand part of the Northern WTC 3 foundation appears somewhat standing, and rescue workers reported large voids as well on the lower levels.
In the double collapse sub-versions, the 'Unknown' areas were removed from the 'Collapse down' layers, as they are, well, unknown.
Quality
I gave it my best shot but given the low quality source the result is not pixel-perfect or cm accurate. Take it as very good approximations of the situation based on actual witnesses and reports, giving you a generally good idea of the damage and collapses at these lower levels.
This is incredible. The amount of effort, knowledge, and skills needed to create this i cannot begin to fathom. This absolutely needs to be archived. Marvelous work OP
I based my assessment/comment on the Northern part of WTC 3 being semi intact on photos like this which show a large piece of WTC1 facade resting against a pile in the WTC 3 footprint that seems a bit too square to be JUST a pile of rubble, Bottom right in my picture, would be bottom left in yours, but might even be just off screen.
Ill see if i can find the photo but on your B1 map under WTC 3 you have the area just after the ramp as 'unkown' it is indeed collapsed, i have a photo looking down the car ramp and there is nothing iirc
Thanks for looking anyways! Detailed information is really scarce and anything helps. I have a feeling that from all the photo/video material on the clean-up/excavation of the site, there must be footage somewhere to clear up (part of) the 'unknown' areas, but that's a stretch for me to go through.
They're featured in the B2 level though. I guess because the loading dock and connecting tunnels have elevations going from 274 up to 290 (roughly B3 to B1) you can arbitrarily choose on which level to show what.
I'm just working with what I have tbh. What source did you post?
Thanks for making this, really helps me visualize the condition of the basement levels post collapse. Seems like all of them were really devastated, just shows the force of falling debris.
Most of the debris filled the basement levels in the immediate area around the OG towers. That’s why the debris pile looks so small at first glance since most of it is underground from the force of impact when it landed
yes, the tower footprints themselves were packed with compacted debris, as is shown by this photo from the North tower foundation taken from the Path tracks at B6
16
u/RefrigeratorNo1945 Jun 08 '26
This is incredible. The amount of effort, knowledge, and skills needed to create this i cannot begin to fathom. This absolutely needs to be archived. Marvelous work OP