New commercial satellite imagery from May 1, 2014 indicates a significant increase in activity in the West Portal area of North Korea’s Punggye-ri Nuclear Test Site related to the excavation of a new test tunnel begun one year ago. At the same time, there appears to be a drawdown in activity in the South Portal area, believed to be the likely location of North Korea’s next nuclear test. Specifically:
- In the West Portal area, imagery indicates that Pyongyang is continuing and perhaps stepping up excavation activities resumed in late April after repairing a collapsed track leading from a new test tunnel entrance to the spoil pile. On May 1, mining carts are visible on the tracks. Moreover, they may also be present on an older set of rails leading to a different dumpsite last used in 2009.
- There is new logging activity just outside the fence line a short distance up the mountain just north of the tunnel entrance. No activity was present on April 25, but four days later there appeared to be two log skid trails with trees removed. By May 1, a third skid trail is seen and more trees have been removed. The logs may be used to shore up the tunnel under excavation or for new construction of a nearby small building. (Work began in late April on that building and as of May 1, construction material appears piled up.) Also between April 29 and May 1, part of the main building at the West Portal appears to have been removed. One possible explanation is that this area was a vehicle shelter or carport that has been taken down.
- In the South Portal area, the May 1 imagery shows continued vehicle activity—two dark color vehicles are on or near the bridge over an adjacent creek and a white box body truck is parked on a spoil pile across the road from the left tunnel entrance.
- The crates or boxes that had been present near the entrance of that tunnel have been removed as of May 1. There is now sufficient room in front of the entrance to bring in earthmoving equipment to seal the tunnel in preparation for a nuclear test. As of May 1, there was no indication this was being done.
- Between April 29 and May 1, the number of crates outside the right tunnel entrance in the same area has decreased to one, probably indicating continued activity inside the tunnel.
Despite statements last week by the ROK Ministry of Defense that a North Korean nuclear test was imminent and could well happen during the visit of US President Barack Obama to Seoul, almost a week has gone by with no detonation. The passage of time may indicate that, in fact, a test may not be imminent.
Leaving aside Pyongyang’s recent statement implying that a test might not be in the immediate works, the May 1 imagery of Punggye-ri indicates a number of developments that would tend to lead to the same conclusion. Most important is the stepped up excavation and construction activity at the West Portal area, which would be cleared of personnel in the event of an imminent test. Moreover, in the South Portal area, movement of crates near one tunnel entrance reinforces the conclusion that activity is still ongoing inside the tunnel. Even at the second South Portal test tunnel, where activity has been greatest in the past week, even though crates have been cleared from the entrance, there is no evidence to suggest that the tunnel has been sealed in preparation for a detonation.
Figure 1. Activity stepped up at the West Portal including beginning construction on a small building and a bypass road.
Figure 2. Construction activities continue at the West Portal.
Figure 3. Logging trails down the mountainside are visible.
Figure 4. South Portal activity continues near the tunnel entrances.
 As the design of the tunnels is unknown, it is unclear how the tunnels will be stemmed or if stemming is necessary at all.