North Korea's Underground Navy: A Review

Many countries have underground facilities for their navies. Places to protect submarines, places to defend against surprise or nuclear attacks, underground storage, places that have all kinds of purposes.

One large example was the Soviet base in Balaklava, Crimea. China currently maintains at least six underground submarine bases. The United States has an enormous underground fuel storage site in Hawaii.

North Korea is no different.

North Korea has a tremendous amount of experience digging tunnels. I have found hundreds of tunnels across the country, hundreds of artillery sites that pop out of tunnels, scores of underground factories, and quite a few underground naval sites.

Bounded on two sides by the ocean and with 2,495 km of coastline, the Korean People's Navy has a strength of 60,000 men and over 800 vessels, making it one of the largest navies in the world in terms of vessel numbers. And while most of their naval technologies are decades behind the West, Kim Jong Un has been focusing on modernizing the fleet. Furthermore, what they lack in technology they can make up (some of that gap) by sheer numbers.

North Korea has 70-80 submarines, which places them on par with the United States (based on numbers) and far outpaces South Korea. Their navy has been able to inflict substantial damage in attacks like the Second Battle of Yeonpyeong in 2002.

And so, it makes sense to marry navy and tunnel together. Underground naval bases provide safety in the event of attack and secrecy to develop, arm, refuel, and launch attacks. Having multiple sites also makes it more difficult for an attacking country to quickly knock out North Korea's navy.

The country has 13 identified underground naval sites. Some can accommodate submarines but most currently serve various types of surface ships. Interestingly, North Korea's main submarine base for the Sea of Japan (East Sea), which is based on Mayang Island, lacks any apparent underground facilities.

(Click on images for larger view)

The facilities range from simple tunnels to more complex facilities that are accessed from the sea and cover a large footprint.

Starting with the Yellow Sea (West Sea) bases:

Taewha-do Underground Base: 39°25'59.69"N 124°37'2.39"E

Taewha-do is on an island (the -do suffix means island) and consists of a small underground facility and a turntable to enable vessels to be moved around the base on a short rail system. There is only a single dual entrance/exit point to the underground facility (UGF) but the island's size could theoretically accommodate an enormous UGF inside. However, it only appears to house small patrol boats and the island garrison is no larger than battalion sized.

Very little information about the base is publicly available and most of the information that does exist relates to a series of small military actions during the Korean War, before the UGF was construction. The island rises steeply out of the ocean and can provide up to 600 feet of solid rock on top of the UGF, giving it excellent protection.

Sok-do is not necessarily an underground base but rather it is a set of four hardened pens that allow craft to be protected. Located at 38°38'7.33"N 125° 0'26.27"E, it doesn't appear to be in use. It lies just 5 km from Pip'a-got, which is a primary naval base.

Pip'a-got is the largest naval base immediately outside of the West Sea Barrage, which cuts off direct access to the Taedong River and Pyongyang.

Pip'a-got naval base.

The base consists of a large protected harbor (created by a set of breakwaters), hundreds of buildings, and seven distinct ship handling sites (dry docks, main harbor, UGF, etc). It covers approx. 5 square kilometers.

The underground component consists of a 600-meter long tunnel that connects a turntable (that can take ships from a slip and bring them to the tunnel entrance) to an exit that enters directly into the sea, bypassing the large seawalls.

The tunnel could include other facilities like fueling, loading weapons, and repair, but the interior layout is not known. The hill it cuts beneath rises from ~90 feet at the turntable to a maximum height of ~250 feet along the path of the tunnel.

Sunwi-do & Sagot (Ryongho) Bases
Sunwi-do has a small base at the far northeast end of the island. It is across from the larger Sagot base on Ryongho Island 4 km to the north. Both bases are in South Hwanghae Province are the southernmost underground naval facilities on the west coast. The base at Sunwi-do lies a 31 km from the South Korean island of Yeongpyeong.

The base on Sunwi Island, 37°46'11.59"N 125°20'21.45"E

At its height, the island provides ~180 feet of rock over the Sunwi tunnel which runs for 250 meters.
North Korea has several classes of patrol boats and Sunwi seems to be a base for them. In the imagery provided by Google Earth, at no time has there been more than 13 ships and none over ~28 meters in length.

In this image of Ryongho, four classes of ship can be seen. Upwards of 36 ships have been seen at Ryongho but some may have actually been small fishing vessels along with the military craft.

Sagot base is split between two main facilities. One is at the town of Sagot, on the mainland 1.8 km to the north, and the second is the UGF on Ryongho Island (37°48'17.24"N 125°21'9.58"E).
A direct line from the Ryongho entrance to the exit runs 290 meters but the full tunnel path isn't a straight line. It is likely at least 365 meters in total length. Between 150 and 250 feet of rock sits above the site, depending on location.

The exit has apparently silted up and cannot be used as a direct exit point for sailing into the sea. Any vessel must be towed down the "hump" from the UGF exit point to the water. Why this hasn't been corrected would only be speculation, but it has been the case since at least 2004.

NK-01 antiship cruise missiles (a local variant of the Soviet P-15 Termit (aka Styx) are believed to be deployed at the base.

Along the northeast edge of the island is a series of small tunnels for terrestrial vehicles and other equipment. This is a common feature found at many bases across the country.

East Sea (Sea of Japan) Bases

Puam-dong is the first base on the east coast. (Going north to south, as I did for the Yellow Sea bases.) Located at 41°19'17.15"N 129°46'4.71"E it is a primary navy base and has a large harbor protected by ~470 meters of breakwaters.

The base has been called a submarine base (and some of its features support that conclusion) but no submarines are visible in the available imagery. Other vessels stationed at the base include the Sohung-class PTG (guided missile patrol boat). This has been a key base for them since at least the 1980s.

Puam-dong is divided into two sections because of a hill in the middle of the base. The main section has headquarter facilities, barracks, and other buildings. The second section (to the south) is for maintenance.

The tunnel runs for at least 425 meters and the hill provides ~270 feet of rock above. The base also has a small underground storage facility higher in the hills at 41°20'12.02"N 129°45'24.94"E.

Cha'ho is a major submarine base located at 40°12'18.28"N 128°38'59.31"E in S. Hamgyong province. Including the harbor, it covers approx. 7.7 square kilometers.

Development of Cha-ho began in 1961 and it was transformed from a small base for patrol craft to a major submarine facility. By 1968 the underground portion was under construction. Unlike many other bases, it has rail access.

Unlike land-based underground facilities, where large piles of debris can be seen and analyzed to yield the approximate volume of the UGF, sea-based sites tend to lack any visible debris (since it can just be dumped under water) making it almost impossible to determine its size or layout using traditional methods. (Technology does exist that can shed light on the internal nature of the site using special techniques, but those are beyond the reach of most.)

However, at least a portion of the quay positioned between the entrances of the UGF may be made up of excavated debris based on a review of declassified images.

Taking the curved shape into account, the tunnel runs at least 330 meters and is protected by upwards of 200 feet of rock. I suspect that the main tunnel is placed farther back than I have it drawn, but that's why things are labeled "approximate".

Throughout the base Sang-O class (mini subs) and Romeo-class submarines can be seen. Romeo's are Chinese built, Soviet originated submarines that North Korea first acquired in 1973.

Ryoho-ri (Toejo-dong) Base is the location of the East Sea Fleet Command. It goes by several designations, Ryoho-ri, Yŏho-ri (an alternate spelling), and Toejo-dong (the name of the bay and also commonly used). Its location is 39°52'33.92"N 127°46'43.45"E.

As if signifying the base's importance, one of North Korea's many leadership residences is adjacent to the base. Ryoho is also serviced by rail.

The base doesn't appear to have any shipbuilding capabilities, but it does have a small repair facility for patrol boats. As mentioned, it is the headquarters for the East Sea Fleet and commands all of the bases and associated facilities along the east coast. One of the subordinate units at the base is KPA Unit 158.

The underground facility follows the same basic design as all the others. Its tunnel is ~315 meters long and is covered by roughly 200 feet of rock.

Samil-ri is a small UGF that consists of a single entry point. Located at 39°22'18.03"N 127°26'18.43"E it is on a small peninsula that's part of the much larger Munchon Naval Base.

Across from it on the other side of the peninsula (over 900 meters away) is a turntable but it doesn't appear to have been used in years and the images available on Google Earth make it difficult to confidently assert that there's a tunnel connecting the two points.

It's hard to gauge how active this site is, particularly since the turntable doesn't appear to be in use, but the wider Munchon area has been the focus of a large modernization and expansion program which has been ongoing since 2014. The Munchon-Wonsan region is an important military and industrial area, and various improvement projects have occurred there including the Kalma International Airport, Wonsan-Kalma tourist zone, and the nearby Hodo missile test facility.

Of note, various materials can be seen at the entrance site in recent images that could be used in a restoration project.

Sindo & Yodo island bases

Sindo is a small, narrow island in Yonghung Bay, off of Wonsan. It has a small underground site but unlike Samil-ri it definitely doesn't have an exit point. It is located at 39°13'18.11"N 127°31'10.04"E and would have a maximum length of 85 meters (based on the particulars of the island). The island's garrison seems to be geared toward operating coastal defense artillery and is located nearly a kilometer to the east.

The Yodo island site is located 8.7 km east of the Sindo site. Like Sindo, it doesn't have a second entry/exit point, but it does have a turntable. This allows approx. 8 vessels to sit on the beach and then individually brought into the tunnel for servicing and then moved back out and onto the "holding yard".

If you look closely at the image, you can see a vessel halfway in (or out) of the tunnel entrance.

Yodo has a much larger garrison and even has a small grass runway that extends for 660 meters (although a dirt path cuts across it near the southern end). The naval tunnel may run for 180 meters into the hill to reach 140-150 feet of rock depth. Directly across is a hardened coastal artillery battery and those tend to have small tunnels connecting them to the outside. If we assume the tunnel comes close to the battery, then the tunnel may run as much as 200-230 meters.

Namae Navy Base

Located at 38°48'9.76"N 128° 8'18.58"E Namae is a large navy base with a breakwater that creates 38 hectares of protected harbor. The northern end of the base contains the underground facility. Namae has the facilities available to service all of North Korea's surface fleet and may be able to dock submarines.

The entrance is approx. 20 meters in width and could be covered by as much as 200 feet of rock. There does appear to have been an exit point built, but the tunneling work was either never finished or there was some other problem. An exit structure was built but is in a state of disrepair.

By 2013 a hole had appeared in the roof of the possible exit structure and by 2019 the roof had collapsed entirely. Had the entire facility been completed, the tunnel would have run 515 meters and would make it the second longest confirmed tunnel after Pip'a-got.

Possible exit structure with collapsed roof.

The last of North Korea's underground navy sites is at Changjon, 38°43'59.96"N 128°12'45.45"E.

It's the southernmost naval facility on the east coast and lies a mere 18 km from the military demarcation line.

Changjon is divided into two sections. The northern section contains a large active navy base, the southern section (~1.8 km away) has the underground facility but it appears to have been abandoned. No military vessels can be seen in Google Earth images (which go back to 2005), and there is a civilian dock with a floating restaurant just a kilometer away. It's part of the Kumgang tourism system.

At the same time, a small naval unit is still directly connected to it and the base did serve as a "frontline base for North Korean submarines" before being suspended as part of the creation of the aforementioned tourist zone. However, Kim Jong Un has recently expressed a desire to enlarge the base, so this portion of it may become active again in the future.


Additional reading:
Work on Major Hovercraft Base Advances, AccessDPRK, 1/17/2020


I would like to thank my current Patreon supporters: Amanda O., GreatPoppo, Kbechs87, Planefag, Russ Johnson, and Travis Murdock.

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Nuclear Fallout Part II: the health consequences of Pyongyang's nuclear program

Pollution and health risks exists at every point along the nuclear weapons’ development chain, from the initial mining and milling operations to the enrichment process, and finally from testing nuclear devices. In this two-part article I will examine each of those areas and the health risks associated with them.

In this second part, I finish discussing the health consequences of North Korea’s nuclear program by examining issues related to their underground testing. (Part I can be read here.)

Testing

After producing the needed nuclear fuel and solving the other matters associated with creating a nuclear device, the next step is testing.

After decades of work the regime was able to test its first nuclear device in 2006. The underground test was carried out within Mount Mantap at the Punggye-ri nuclear test site. However, there is no such thing as a safe nuclear test, even when they’re underground. The original tunnel for the 2006 test was closed up shortly after the test as a result of radiation releases according to 38 North. Since 2006, five additional tests have been carried out in different tunnels. Further reporting indicates that another delayed leak was also detected as a result of post-tunneling activities in 2013.

Even under the best circumstances, underground nuclear testing still can release some radionuclides into the atmosphere. Less than optimal testing can pose a much greater radiation risk to those downwind of the test site. Initial radiation releases from a containment failure occur through “venting” but releases can continue for longer through “seeps”, where radiation finds its way out of the underground site through small fissures and openings in the overlying rock. Radioisotopes of xenon (such as ¹³³Xe and ¹³⁵Xe) are almost impossible to contain and can travel across the globe, as Canadian detectors picked them up after the very low-yield 2006 test.

Punggye-ri is in a mountainous area with little population but the main tunnel entrances are less than 2 miles away from the boundary of the Hwasong Concentration Camp. Due to the extreme human rights violations facing prisoners, we can’t hear their stories or send professionals over to determine how much radiation they have been exposed to. Residents within the larger area, however, have been able get their experiences to the broader world.

In 2017, South Korea reported that four defectors who lived in the area around Punggye-ri showed signs of radiation exposure. Defector Lee Jeong Hwa, who lived in Kilju County, said, "So many people died we began calling it 'ghost disease’…We thought we were dying because we were poor and we ate badly. Now we know it was the radiation." Unfortunately, the inability to do detailed testing on people still living in the area and gather more definitive evidence prevents us from knowing the full effects of the testing.

Negative health impacts from underground nuclear testing is easily supported by looking at the results of underground testing in the United States. According to the US National Cancer Institute, some 2,800 annual cases of thyroid cancer within the US can be attributed to the “underground era” of 1962-1992, when the United States (and the Soviet Union) was limited to testing nuclear devices underground by treaty. While North Korea has only had a limited number of tests, those tests have increased radiation levels for the region and caused an unknown level of damage to the population. Of particular concern are the 20,000 Hwasong prisoners, who are also suspected of being used as slave labor to help dig the tunnels used at Punggye-ri.

The stability of portions of Mount Mantap is also of concern after six tests, and surface changes as a result of ground shifting have been studied in detail. The first two (of four) tunnels are likely to be unusable for any future testing. Worries over accidental radiation releases from collapsing tunnels spurred China to install additional radiation detectors along their border with North Korea in 2017 and at a newly constructed border crossing in 2019.

The other two tunnels exist to the west and south and have not been used to-date. Their entrances were demolished in May 2018; however, questions remain about the irreversibility of those closures.

Occasional rumors of a possible future above-ground test (for which there are very few potential testing sites) raises the stakes even more. Radiation would flood over Japan and would reverse decades of atmospheric radionuclide decline around the globe.

Conclusion

The known risks associated with the chemicals and processes involved in mining, milling, and enriching uranium, as well as in the production of other radioactive materials, supports the descriptions of illnesses as told by unrelated sources, each with first-hand knowledge of the locations discussed.

Despite the guarantees of the North Korean constitution and international law regarding the right to favorable working conditions and the right to pick one’s career (or to leave it), expert and defector testimonies, coupled with satellite imagery, paints a very different and dangerous story. It can be said that a major humanitarian and health crisis is brewing within North Korea as we know the substandard state of their nuclear program – not just in terms of technology but also safety.

Most of the facilities within Punggye-ri’s 17-kilometer-long compound still stand, waiting to be used again. Yongbyon continues to grow and thousands of additional scientists, laborers, and their families have been moved in under Kim Jong Un. The mines and milling plants still produce materials to be sent to enrichment facilities. And the regime keeps working on their abilities to deliver ballistic missiles to any part of the globe. It is clear that the sixty years of nuclear harm now affecting the tens of thousands of North Koreans who have worked to develop Pyongyang’s nuclear program over three generations of Kim will continue into the future, causing more harm, more sickness, and will likely require the efforts of multiple countries to finally resolve once the Kim Era is over.

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Jacob Bogle, 12/26/2019

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Wollo-ri: Much Ado About Something

A counter-analysis examining known nuclear facilities and important civilian facilities reveals there are still many questions surrounding the site at Wollo-ri (also spelled Wonro-ri), and that a conclusion as to its purpose cannot yet be ascertained based on publicly available information.

Note: to save this report and read it later, you can download the PDF version here.

On July 8, 2020, CNN reported on research done by experts from the Middlebury Institute of International Studies on a facility in the village of Wollo-ri (near Pyongyang) that claims the facility is part of North Korea’s nuclear program and is likely involved in either warhead production or warhead storage.

Jeffrey Lewis and fellow researchers Catherine Dill, David LaBoon, and Dave Schmerler then published a more detailed account of their line of reasoning on the Arms Control Wonk blog. The post listed a number of visual signatures about Wollo-ri that led them to suspect the facility was part of the country’s nuclear program. That suspicion was then bolstered by a mention in Ankit Panda’s new book Kim Jong Un and the Bomb, in which Panda says that the US intelligence community assesses that there is an undeclared nuclear facility in Wollo-ri. Having that public mention of the facility led to Lewis et. al going public with their own research.

After the reporting, a number of experts commented^A and gave the general view that there is nothing specific to Wollo-ri that would make it a suspected nuclear facility. I happen to agree. However, there hasn’t been a point-by-point counter-analysis of why some experts may disagree with the assessment by Lewis et. al. That is the purpose of this report.

Before I go on, I want to be clear that none of this should be construed to mean that Wollo-ri isn’t a nuclear facility. It might be and it might not be. What I am attempting to show is that while the possibility exists, the probability of it is low based on the available evidence (especially whether it’s a storage facility), and that more research needs to be done before coming to any conclusion.

 

In the Arms Control Wonk post, five points are listed to support the group’s conclusion that this facility is likely an undeclared nuclear site. I would like to go through each of those points and give my reasoning for why I don’t think they are necessarily, either individually or collectively, direct signatures of a nuclear facility.

The signature elements described are:

1. A strong security perimeter

2. On-site housing

3. Monuments commemorating unpublicized leadership visits

4. The existence of underground facilities (UGFs)

5. Lewis also uses a description by US officials in September 2018 that talk about an undeclared warhead storage facility. The unnamed officials are cited as saying North Korea “built structures to obscure the entrance to at least one warhead storage facility” and that “the U.S. has also observed North Korean workers moving warheads out of the facility.”

 

On the security perimeter

The facility is surrounded by a wall that runs along the full perimeter of the site and is approximately 1,460 meters long. Lewis points out the fact that the nearby Ryongaksan Spring Water Factory doesn’t have any such perimeter wall, and so the wall’s existence helps to key us onto the fact that the facility is important.

Typically, this is true. Most civilian facilities lack a defined perimeter. However, many military sites lack them as well. In fact, few military sites have more than a guard post at the entrance let alone full perimeter security. There is even an artillery base located a mere 60 meters from Wollo-ri’s perimeter that doesn’t appear to be surrounded by anything; no wall, no fence, nothing. 

And while most civilian sites lack a wall, some do have one. An example is the nearby Mangyongdae Chicken Farm (39° 2'47.29"N 125°38'44.50"E) which has its own 2.9-kilometer-long wall.

When examining known nuclear-related facilities, we do find that most have a perimeter wall. The Pyongsan uranium processing and milling plant has one, each of the laboratories and research compounds within Yongbyon have their own walls, and sites associated with their WMD/missile programs also have them like the Kim Jong Un National Defense University. But while looking at these places, a key difference between them and Wollo-ri becomes apparent. 

The Wollo-ri facility has three entrances into the complex. There is a primary entrance at the southwest corner and then two others along the eastern portion of the wall. Every other known and suspected nuclear facility only has one direct entrance, including the suspected uranium enrichment site at Kangson which Lewis described in 2018.

The entrances at Wollo-ri are also fairly basic and do not appear to include anything substantial blocking the entry points, just small guard huts. No gate or movable fencing to impede forced entry.

Having multiple entry/exit points raises the security risk that something could be stolen. And having multiple sets of guards raises the risk that someone could be bribed to let in an unauthorized person(s).

Facilities like Yongbyon and the Punggye-ri nuclear test site, where substantial nuclear components and functional nuclear devices are held, take a multilayered approach to security. To get to the actual testing tunnels at Punggye-ri, one has to travel along several kilometers of narrow road and make it through multiple checkpoints. If Wollo-ri is where nuclear warheads are either being produced or stored, only the strictest security measures make sense.

Of on-site housing

Image showing apartment buildings ("A") at both Kangson and Wollo-ri.

Using Kangson as an example, Lewis cites what are likely apartment blocks within the perimeter as evidence that the facility may be part of the country’s nuclear program because having on-site housing (within a walled complex) is quite rare, and Kangson also has on-site housing. On-site housing is indeed unusual in North Korea but most nuclear facilities, in fact, do not have such an arrangement. Neither the Pyongsan or Pakchon uranium milling plants have housing, Yongbyon is a closed city with a defined housing district but no housing within the individual research and production areas, and the Academy of National Defense Science (Sanum-dong) lacks it as well. Other sites may have housing but part of that is due to the expansive size or remoteness of the facilities in question.

To be short, on-site housing at any facility would indicate it has some level of importance, but it is not a unique identifier of nuclear facilities.

Another thing to consider is how the housing relates to Wollo-ri’s potential purpose.

Wollo-ri lacks any obvious substantial electrical infrastructure which would point to the existence of energy-intensive industrial activity or to a large underground facility. When the site at Kangson was constructed, an electrical substation was built nearby as well to help provide the needed electricity. Lacking its own substation or major transmission lines, this would suggest that whatever is going on at Wollo-ri wouldn’t be intense industrial activity or producing large numbers of parts.

At the same time, there are six apartment blocks at the facility. I estimate that there are as many as 406 apartment units^B; each given to a worker and their family. Assuming some couples work together, let’s make it an even 450 employees.

North Korea’s nuclear inventory has less than 100 warheads and it is estimated that they can produce no more than twelve bombs per year at maximum output. The country already possess an industrial base known to produce a range of electrical components for their ballistic missiles and other weapon systems, and more dangerous components (like the explosive lenses) are manufactured elsewhere, so an undeclared production facility would likely be used in the production of specialty parts. But you wouldn’t necessarily need 450 employees to produce a handful of small devices each year.

 

The monuments

Monuments can be an indicator of the importance of a facility. Whether it educational, industrial, agricultural, or military, the type of monument(s) seen at a site can help give a fairly unambiguous ranking for the place. They can also indicate if Kim Jong Un (or his predecessors) has visited before.

Wollo-ri possesses two monuments: a Tower of Immortality and an apparent joint mural of Kim Il Sung and Kim Jong Il.

A typical example of a Tower of Immortality.

Towers are found in every town in the country and they are dedicated to the “eternal” lives of Kim Il Sung and Kim Jong Il. They can also be found at universities, factories, and other sites the regime deems worthy. During my 2019 survey of North Korean monuments, I found at least 5,175 Towers across the country.

Joint murals are found in county seats and at even more rarified civilian and military facilities.

In some places you can clearly see the faces of the Kims through satellite imagery. Unfortunately, the mural view at Wollo-ri isn’t the greatest quality. But what is obvious is that there are two images being shown (interpreted as busts of the Kims) and the rest of the monument’s surface appears to be white. This is indicative of a joint mural. Unlike the thousands of Towers, fewer than 300 were identified during the monument survey.

The existence of the mural at Wollo-ri is important, however, it isn’t a signature of a nuclear facility, even when combined with the Tower. The headquarters of North Korea’s air force has at least seven monuments and a joint statue of Kim Il Sung and Kim Jong Il, the highest honor any North Korean site can be bestowed. The headquarters also has a defined perimeter and on-site housing.

Monument at the Mangyongdae Children’s Camp commemorating visits by Kim Il Sung in 1974 and Kim Jong Un in 2016. | Screenshot provided by Colin Zwirko.

In the Arms Control Wonk post, it is claimed that the monuments at Wollo-ri indicate visits to the facility by the country’s leadership. That is simply incorrect. As I have described, Towers and joint murals are found in many locations and none are directly connected to leadership visits, rather, they are daily reminders of the Kim family cult and (when taken in combination) can ascribe a level of importance to a given site. Commemorative monuments are much smaller and are typically rectangular blocks of stone with a brief inscription carved into the surface.

These can be found at many (but not all) places visited by the Kims. In the event of multiple visits, instead of having an ever-growing wall of monuments, a museum will be built. This was the case with Korean People’s Army Farm No. 1116 which has received annual visits by Kim Jong Un since 2013. Even if visits to Wollo-ri weren’t publicized, the facility would still be awarded with a monument.

Wollo-ri only has the Tower and mural.

Underground facilities

In the most simplistic terms, an underground facility (UGF) could be defined as any useful structure with an inch of dirt placed on top. However, most wouldn’t consider a root cellar or simple basement a genuine underground facility. Particularly for the purpose of secure and clandestine manufacturing or storage, underground facilities are located multiple meters below the ground if they are placed underneath an existing building or they are excavated deep into hills and mountains.

North Korea probably has more identified underground sites than any country on earth. Some are enormous arms production facilities (like the Kanggye General Tractor Plant, the largest known underground arms manufacturing plant in North Korea) and others are smaller facilities used for storage or that sit empty until needed in the event of a conflict. They are all clearly identifiable once you know what to look for.

There are two hardened structures at Wollo-ri at the front end of the complex that were built in 2011-2012. (Coordinates: 39° 3'9.59"N 125°37'8.36"E) Neither is larger than 20 meters wide and there was no evidence of excavation work during their construction to suggest they cover an underground entrance. Small hardened structures like these are common enough and are often used to store fuel or for other benign purposes.

There is also a small trench-like structure that is barely two meters wide that lies in the northeast section. (Coordinates: 39° 3'19.82"N 125°37'15.41"E) It does not connect to any building and doesn’t match the design of any other underground entry point one can find throughout the country. If it is supposed to be part of a UGF, I would say construction is just in the initial stages.

Most underground facilities are easy to spot.

One such facility is between the cities of Pyongsong and Sunchon, beneath Mt. Sonje. It has four entry points and there are piles of debris that were excavated from inside the hill during construction. 

In other cases, where a building hides the entry point, the building is flush with the hillside. None of the main buildings at Wollo-ri are flush with the hillside. The other buildings at Wollo-ri could only hide a UGF that was constructed directly beneath them and there is no evidence of that having occurred. (Construction wasn’t caught on imagery and no large debris piles are evident.)

In the event where you connect a UGF to a building that isn’t flush with the surrounding landscape, a connecting structure is built. A prime example of that is a connecting tunnel that was built in 2017 and connects a building in the Armed Forces District of Pyongyang to a massive underground complex. It is approx. 6 meters wide and extends a maximum of 20 meters to reach the hill. Prior to this connecting structure, the main entrance, 660 meters away from the newer one, was still identifiable.

Warhead storage possibility

Lewis’ addition of the description of an unidentified nuclear warhead storage facility is interesting but there was nothing in the description that mentioned Wollo-ri or that gave a specific location. The officials simply said there’s a warhead storage site somewhere. In terms of storage, there are other more suitable places suspected of being warhead storage facilities, including one near the city of Kusong.

And when looking at known warhead storage sites around the world, a few trends become clear. Namely, very tight security and underground storage. The largest warhead repository in the world is the Kirtland Underground Munitions and Maintenance Storage Complex in the scrublands around Albuquerque. The underground portion alone covers roughly 57,000 square meters (not including the potential for multiple levels).

It has a single entry point, it is surrounded by fencing, and has three watchtowers. Plus, it is situated in the middle of a larger military complex.

Incirlick AB with US/NATO nuclear storage site highlighted. | Image source: Federation of American Scientists/Hans Kristensen

Turkey’s Incirlik Air Base is another place that houses American/NATO warheads (up to 50). They are stored underground in the center of the air base which is the most secure area.

The lack of any identifiable underground facilities at Wollo-ri, its questionable security, and the lack of any direct mention of the site specifically as a storage facility leads me to conclude that while it may have a role to play in North Korea’s nuclear program, the probability of it being a warhead storage facility is almost zero. Adding to that assessment are the additional facts that Wollo-ri is located far away from any long-range missile bases and the fact that it is located just a few miles of an elite section of Pyongyang.

In order for North Korea’s ballistic missiles to be a credible threat, they must be near the warheads. Wollo-ri is nearly 70 km away from the nearest known ballistic missile base and that journey would take hours across miles of winding road and rail – an easy target to destroy.

And while North Korea does have a habit of meshing military and civilian areas together, any direct hit to a nuclear storage site would spread radioactive material across a wide area thanks to fire and wind currents, contaminating the city with highly enriched uranium and/or plutonium (depending on the type of weapons stored there).

 

Political University?

I’d like to briefly discuss an alternative explanation put forth by an alleged North Korean official. He claimed that the facility is actually the “Pyongyang Anti-aircraft Unit Command’s Political Military University”. I and many others deeply question this explanation. There is a state security academy nearby at 39° 2'39.39"N 125°38'1.49"E, and it and all of the other known political and security schools follow a very specific pattern. Wollo-ri does not comport with that pattern and deviates from it in a number of ways. While I am not convinced that Wollo-ri is a nuclear-related facility, I reject the assertion that it is a mere political university.

 

Conclusions

While there aren’t any other “unusual” facilities around Wollo-ri that could instead be the nuclear facility, the evidence provided for the site in question, in my estimation, doesn’t rise to a likely probability – particularly when it comes to the question of it being a warhead storage site. The specific parts of Wollo-ri described are common to many other facilities (military, industrial, and educational), and it seems the claim rests largely on the book mention, for which other questions need to be answered before having the confidence to connect the intelligence assessment with this specific location.

Even when looking at all of the signatures discussed on the Arms Control Wonk post in combination, the perimeter, housing, monuments, etc. they don’t add up to a unique identifier. To demonstrate this, one need only look at the Samchon Fish Farm (which underwent an expansion in 2019). It, too, has a security wall, on-sight housing, multiple monuments, and it also has its own electrical substation and a water supply system that is partially underground.

But back to Wollo-ri. As a village it is unassuming, so the Wollo-ri facility certainly sticks out among the structures surrounding it. It just doesn’t stick out in any specific manner. There are also less conspicuous (aka not unusual looking) military facilities in the area, some that include underground sites, that could theoretically serve as a production site. (The underground facilities at the Panghyon Aircraft Plant are thought to have played an early role in the country’s enrichment program.)

Last note

On a personal note, I have never openly debated the analytical work of anyone before, so I want to take a moment to address this. Lewis and the other experts who took part in analyzing Wollo-ri are brilliant. That’s rather self-evident when you look at each of their careers. I am not saying they are wrong, rather, I disagree with the conclusions drawn based on the evidence presented.

Wollo-ri is a “puzzle” in certain ways, as David LaBoon told me, and I agree with that. The fact the village has been mentioned in connection with the country’s nuclear program by an intelligence official is intriguing, but the facility’s aspects are vague, yet also show importance. Importance to what is the question.

As interest in North Korea grows and the tools available for open-source intelligence improves, the body of work relating to the country has exploded (pardon the pun). Having an open dialogue about differing analysis creates a fuller and more nuanced picture and serves to better inform the public and policy makers going forward.

Footnotes

A.

1. Shin Jong-woo of the Korea Defense and Security Forum said, "It may be a facility for another military purpose, not for nuclear warhead development."

2. Olli Heinonen, former deputy director general of the International Atomic Energy Agency (IAEA) told Voice of America that there is little possibility that there is a nuclear facility around Wollo-ri and that, “the report does not provide clear evidence that the facility is nuclear-related.”

3. A report by the Korean Broadcasting Service also noted, “South Korea’s military and intelligence authorities have dismissed a CNN report that said activity suspected of being nuclear warhead production.”

B. There are five apartment buildings in a cluster and a likely sixth (that’s of a different layout) near the southern end of the facility. Each building is seven stories tall. Estimating the first five buildings have 10 apartment suites on each floor, that comes to 350 units. And the sixth building has eight suites or 56 units for the building. That totals 406 apartment units. Depending on the actual layout of the units, there could be fewer or substantially more.

I would like to thank my current Patreon supporters: Amanda O., Anders O. GreatPoppo, Kbechs87, Planefag, Russ Johnson, and Travis Murdock.

--Jacob Bogle, 7/23/2020
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Construction at Huichon

Huichon is an industrial city in Chagang Province, North Korea that has been experiencing a construction boom over the last few years.

This latest round of work would likely not have occurred if it weren't for the completion of Huichon Hydroelectric Dam No. 2 - a project that was mired in complications and may have played a role in Kim Jong Il's death. The dam along with ten other hydroelectric generating stations built along the Chongchon River from ca. 2010-2019, have a combined generating capacity of 420,000 kW.

At the start of Dam No. 2's construction, approximately ninety multi-family housing buildings were also constructed in downtown Huichon that provided space for around 500 families. 

This current ongoing construction boom began in 2020. Some of the projects have been reported on by DPRK media such as in the Rodong Sinmun and in a television program titled "The Look of a New Town" which aired in July 2020. But others haven't been officially acknowledged yet. With that in mind, I'd like to highlight some examples that can be seen via satellite imagery. 

To start, there is a kilometer-long road tunnel (40.198067° 126.278119°) that connects two other projects I'll be discussing with the rest of Huichon and the Huichon Industrial Cooperative, which is a collection of factories near the center of the city. 

Satellite imagery reveals new spoils piles, suggesting that the interior of this tunnel is either being renovated or that the tunnel is being enlarged in some way.

The tunnel area as seen on October 2, 2020.

New work at the tunnel site as seen on Sept. 1, 2022.

Although the tunnel looks like a typical road and can be accessed from one of the city's main arteries, the road only leads to and from the Chilsong Electrical Appliance Factory. This feature becomes more interesting when you consider that the hill it runs through contains a warren of other tunnels, suggestive of a large underground facility (discussed further below).

Chilsong Electrical Appliances Factory as seen in 2018.

This tunnel leads directly to the Chilsong Electrical Appliance Factory (40.202665° 126.278621°) which is in the process of being completely rebuilt.

Little is publicly available about the specifics of the factory, but Kim Jong Il visited it in March 2010 and said that the factory was an important part of the country's economic future. However, that's the only leadership visit to the factory I can find in online sources. Regardless of the exact role of the factory, the fact it is being doubled in size attests to its continued importance. 

The factory is undergoing expansion. As seen in November 2022.

In 2018, the overall factory area covered approximately 12.5 hectares. In 2019/2020 the old factory was demolished and construction of a new factory campus began. This new area covers approximately 30 hectares and includes not only typical industrial buildings but will also have a stadium (somewhat common at large industrial sites), factory museum, revolutionary history/Juche museum, a health clinic for workers, and other amenities. 

The early stages of construction seem to have been carried out quickly, but it has since stalled. Little new activity is visible between October 2020 and December 2022. This may be a reflection of the COVID-19 pandemic's economic toll on the country.

Foundations for new apartment blocks across from the Chilsong Factory.

Across from Chilsong (at 40.208419° 126.281558°) the foundations for 21 apartment buildings have also been constructed, perhaps as new worker housing for the expanded factory. Previously, only farmland and a few small houses existed on the site, but they were cleared away for the new apartments sometime between 2019 and 2020. However, like the stalled progress on the factory, only the foundations of the apartment buildings have been constructed, and the work appears relatively inactive as of Dec. 2022.

As mentioned earlier, the Chilsong factory is connected to the rest of Huichon via a tunnel. The hill the tunnel runs through has several other smaller tunnels that indicate the presence of a large underground facility (UGF) at 40.188214° 126.275511°.

The hillside is encircled by a newly built 3.5-km-long perimeter road (yellow) that can also be used to reach Chilsong and that connects to the six other tunnels (white) clustered at the southwest of the hill. There is no way to know how the tunnels are actually arranged or if there are large rooms within the hill, but I've created a speculative map of the interior tunnel arrangements based upon the location of each entrance and service adit.

There are three main entrance points to the hill. These are located together, and each entrance is protected by a small, covered structure. Previously, a series of greenhouses existed on the site as well but those have been demolished. 

Excluding the main road tunnel, if my estimated tunnel layout is considered, there are at least 3 kilometers of tunnels inside the hill.

After reviewing the available imagery, there isn't enough visual evidence to say if a factory complex exists underground or if the site is being used as a hardened storage facility. However, other "electrical appliance" factories are known to be involved in North Korea's armaments industry, and the closed-off nature of the underground facility and Chilsong factory raises further questions.

The Huichon COVID-19 isolation ward.

Within the new complex of the Chilsong Factory is one of over 80 (and counting) suspected COVID-19 isolation wards. Located in an out-of-the-way building (40.201310° 126.281072°) at the inactive construction site, the COVID ward was established in 2021. The 180-square-meter building is surrounded by a wall, has two guard posts, and all of that is surrounded by a perimeter fence. 

Public information is sparse about these facilities, but because of their high security and relatively small size, I surmise that they are used to isolate those who test positive for COVID-19 or have an otherwise unidentified fever until they either recover or need to be transported to a hospital that can provide intensive care (at least, North Korea's version of intensive care). 

As part of the overall construction in the Huichon area, this school (40.205530° 126.244176°) and nearby housing have been reconstructed. The school will be 2-3 stories in height and there have been 14 new housing buildings constructed. Each building contains 2-4 individual housing units.

Across the river from the school a further 78 houses were built totaling 156 family units. The houses are in the new "countryside" architectural style promoted by Kim Jong Un in recent years.

The last construction project I want to discuss is the ongoing work at the Hagap Underground Facility (40.081244° 126.188535°).

Hagap is an underground complex 13-km south of Huichon that has an uncertain purpose. Construction began in 1991 but after several years of work it was apparently never completed. Following a prolonged period of inactivity, activity resumed in 2016. I have written about the progress at Hagap a couple of times (in 2017 and in 2019), and work is still ongoing.

Construction activity in 2016-2019 had been focused on improving access roads and building new tunnels, but since 2019 temporary worker's housing and workshops were constructed at the front of the complex, suggesting work is now being carried out in the interior of the main underground area.

As seen in the above image, construction work and landscaping have been completed at this auxiliary entrance site.

Secret nuclear facility, underground state archive, or something else, after 32 years of construction Hagap's purpose still isn't known. However, unlike the neglected underground facility at Kumchang-ni, North Korea seems intent on giving Hagap life and warrants continual monitoring.

I would like to thank my current Patreon supporters who help make all of this possible: Alex Kleinman, Amanda Oh, Donald Pierce, Dylan D, GreatPoppo, Jonathan J, Joel Parish, John Pike, JuneBug, Kbechs87, Russ Johnson, and Squadfan.

--Jacob Bogle, 4/23/2023

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