Showing posts with label Sindo. Show all posts
Showing posts with label Sindo. Show all posts

Monday, February 20, 2023

North Korea's Expanding Coastline

Seawall construction at the Honggongdo Tidelands Project. Image via KCNA, 2017.

Land reclamation has history dating back centuries around the world. Whether it's draining marshes to grow more food or building islands to handle a growing population, the land reclamation process has helped save nations and encourage economic growth.

North Korea's leaders have recognized the potential land reclamation represents and have embarked on a series of projects that span nearly the whole history of the country.

From news reports or watching changes in satellite imagery, one can see North Korea's coastline change year after year due to port expansions, new rice paddies, and aquaculture facilities. The hope surrounding these projects is that the country can become more self-sufficient regarding food supplies and improve their maritime trade and transportation networks.

Land reclamation has taken several forms in North Korea, but predominantly it's an act of simply allowing natural erosion to slowly fill in enclosed spaces while draining water. 38 North has an article on some reclamation projects that goes into greater detail on the process. 

Each generation of Kim has left their mark on the peninsula's geography. Through reclamation, one can see marshes drained, tidal flats infilled, and networks of islands connected to each other in order to build expansive new fields. 

After looking through publicized projects, historical satellite imagery including declassified imagery from the 1960s and 70s, topographical features, and old maps of coastal areas dating back to the 1940s, by my measurements, a total of 1,049 sq. km of land has either been reclaimed or is currently undergoing active reclamation in North Korea. This doesn't include future projects but represents land one can walk on right now or will be able to very soon.

The vast majority of the new land has been for agriculture with smaller amounts created to expand port facilities or to set up aquaculture/fish farming. Of this new land, over 97% of it has been added along the country's west coast.

In this article I will explore ten key land reclamation projects on the west coast, moving from north to south, and then six on the east coast. 

With 97% of all reclamation projects, North Korea's west coast has grown by 1,025 sq. km.


West Coast

Sindo District Reclamation Project (39.828238° 124.231714°)

What is now North Korea's largest island, Sin-do, was once an archipelago of over seven islands and islets including Maando, Maldo, Nojeokdo, Sari, and the Jangdo Islands that lie at the mouth of the Yalu River. In 1958 over 40 km of embankments and sea walls were constructed and an area of over 52 sq. km. was allowed to fill with river silt, creating the island as it appears today.

Sin-do is used as a major source of reeds that can be used for a wide variety of purposes from creating baskets to plastics. And the project stands out in North Korean history and state propaganda as the largest early land reclamation project, and as an example of the people's revolutionary spirit. All three Kims have visited the island to give "guidance". 


Taegyedo Tideland Reclamation Area (39.796157° 124.487555°)

There have been plans to reclaim the tidelands around Taegye Island (Taegyedo) for several decades. Initial work began in the early 1980s and envisioned reclaiming 8,800 hectares (88 sq. km.). However, the original immediate coastal area, some 3,800 hectares (38 sq. km.), had already been reclaimed in the years prior.

Approximately 15 km of seawalls (completed in 1985) were constructed, connecting Taegye Island with several other islands and to the mainland, creating a large enclosure of tidal flats and water channels.

From there, small rivers and streams were allowed to flow into the protected enclosure, enabling silt to accumulate while the water level was carefully controlled via a system of three dams. These allowed for continued fishing operations within the enclosure (predominantly shellfish) and for the silt to not get washed away with each tide.

Throughout the process, as one area became more filled, embankments were constructed and each section converted into usable farmland.

Thirty-eight years later and the project is a little more than halfway finished. Once complete, the entire Taedye-do/Yamju-gun coastal area (including those areas filled prior to 1985) will have had added 125 sq. km. of new territory.

 

Honggongdo-Sinmido Tidelands Project (39.651977° 124.860447°)

Click on image for a larger view. 

This has been a very ambitious reclamation project that was first announced in 2012. Currently some 10,200 hectares of land are in the process of being reclaimed in a project that has connected Sinmi Island with the mainland and employed over 45 km of seawalls to subdivide the area to create more manageable spaces for filling.

The outer seawalls for the first polder were completed in 2016, a second polder was created in 2017, a third the following year, and a fourth in 2019.

Most of polder #1 has been filled and around half of polder's #2 and #4 have been. Polder #3 is still completely flooded. However, a small section of Polder #3 is being used for fish farming.

According to the Korean Friendship Association (a pro-North Korea group), the heavy construction equipment used to build the seawalls is a mix of domestically manufactured equipment and imports from Slovakia.


Kwaksan-Oejangdo Project (39.556794° 125.112628°)

The area along the coast south of Kwaksan to the island of Oejangdo has been reclaimed through the creation of three polders, with work first beginning in the early 1980s.

By 2000 polder no. 1 was about 80% filled, the seawalls for polder no. 2 were completed in 2012 and it was two-thirds filled by 2020. Work on the third polder began in 2019 and the sea walls were completed in 2020-2021. 

Once completed, the whole project will have created 48 sq. km. of dry land. Nearly 20 islands and islets will have been incorporated into the mainland in the process.

Chongnam Stream (39.440982° 125.374683°)

Land reclamation doesn't only mean major projects involving thousands of hectares. It also includes small scale works like reclaiming marshes and small river islands.

In a small tidal stream near Chongnam, between 2014 and 2019, four plots of marshes and mud flats have been reclaimed to add to the area's farmland. Along with a fifth plot that was reclaimed ca. 1990, a total of 23.1 hectares were reclaimed through this small-scale work.

The act of enclosing a stream or riverbank to add a few hectares of farmland here and there can be seen throughout North Korea's western plains. They remain prone to flooding but can still contribute to the food supply in a country where every bushel counts.


Namyang Saltern (39.351779° 125.413742°)

The Namyang Salt Farm (saltern) is a 17 sq. km. saltern in Pyongwon County. I couldn't find much information about its creation but based on a review of Korean War-era military maps and declassified KH-9 satellite imagery, the northern sections had been completed by the 1950s and the rest was reclaimed by 1968.

Off-nadir image example of the Namyang Saltern from 1972. Declassified image from the KH-9 satellite program operated by the CIA.

Google Earth image showing the numerous evaporation ponds within the saltern.

In North Korea, salt is produced either by allowing sea water to flood small ponds or by pumping out ultra-saline water from underground sources, both methods then require the water to evaporate in the open air that causes the salt to precipitate and form large crystals of pure salt which are then collected for use. For Namyang, part of the saltern was converted to use pumped saline groundwater after 2008.


Nampo Coastline

Starting at the West Sea Barrage and moving north into Chungsan County is 42 km of reclaimed land representing basically the entire coastline there. The three largest projects in that region have been the Ansok and Kumsong tideland reclamation projects, and the Kwisong Saltern. In total, that 42 km stretch of coast represents 116.5 sq. km. of reclaimed land.

The Ansok project (38.944434° 125.185589°) began in the 1970s and was partially completed and reclamation reached just a portion of the project's envisioned extent. The original seawalls were finally completed in 2019 and work on seawalls for a second polder began in 2020. Roughly 13 sq. km. remains empty, but infilling has actively resumed. 

For Kumsong (38.759244° 125.172644°), some land was reclaimed several decades ago but work on seawalls for the largest sections didn't start until the late 1980s, after the West Sea Barrage was completed. The walls were finished by 1993 and reclamation began in earnest. Currently, about 85% of the enclosed area has been filled, with only the deeper reaches of the former Taedong River estuary remaining under water. Those underwater portions aren't going unused, however. Two aquaculture facilities totaling 7.6 sq. km. were built to take advantage of the water and aid in fish harvesting.

The Kwisong Saltern had its beginnings before the 1980s but it has been expanded over the decades and now encompasses 25.9 sq. km. In 2014, 150 hectares were converted to use pumped saline groundwater and has a capacity to produce 7,000 tons of salt annually. 


Taedong Reservoir (38.685108° 125.297410°)

Low-lying areas within the Taedong River estuary have been slowly reclaimed over the last 70 years. Additionally, the reservoir created by the construction of the West Sea Barrage in 1986 has allowed sediment and silt to build up, furthering the creation of new land whether intentional or not.

Between marshes and tidal flats that have been filled and converted to agricultural use, some 90.5 sq. km. of land has been reclaimed including the large marshes that once nearly encircled the city of Nampo.


Kangryong Bay (37.864756° 125.456633°)

The southern coast of South Hwanghae Province has seen numerous reclamation projects over the years, and a number are still in the early stages of completion. But one that stands out has been the result of the Kangryong Bay Dam.

Built in 1986-87, the 960-meter-long dam cut off Kangryong Bay from the sea. This has resulted in parts of the bay silting up and marshes drained, and that land then being converted into farmland. There are twelve sections of land that have since been developed totaling 17.6 sq. km.


Ryongmae (37.858348° 125.879742°)


First envisioned in the 1970s, the project has had a series of fits and starts. The full extent was going to be nearly 62 sq. km. in area, but the northern section (outlined in white) was never finished. By 1984 a 12.5 sq. km. section was completed and some additional work carried out, but the seawalls were breeched during a storm in 1997, and the site reflooded. The 'grand plan' was put on hold until 2011 when construction of the seawalls for the entire project (except the area in white) were erected.

This was done in two stages, 2011-2015 and 2019-2020. Today over 90% of the area has been drained and rice paddies and salterns have been built.


Yonan-gun Saltern (37.758135° 126.120169°)

The Yonan-gun Salt Farm, also called Yonbaek, is perhaps the oldest reclamation area I'll discuss. I couldn't actually find when the 16.7 sq. km. site was constructed, but it clearly shows on US Army maps of the region from 1951. Given its proximity to Seoul, it's possible that it was built out of the mudflats sometime before the Japanese occupation of Korea in 1910 because salt production has always been a necessary industry for human survival and the capital of dynastic Korea would have needed a steady supply.

However, I'm including it in this article because the internal layout of the saltern has changed over the decades and adjacent areas have also been reclaimed in more recent times, creating a larger conglomeration of reclaimed land covering 21 sq. km.

Along with two other salterns, Yonan was partially converted to accept pumped groundwater as the source of saline for its operations in 2008.

Many reclaimed areas are built on tidal mudflats, but they often don't reclaim the whole tidally affected territory. Yonan, on the other hand, extends right up to the main channel of the Han River and has a series of piled stone "groins" (similar to jetties) reaching out into mud like spokes to help protect the saltern from erosion. 


East Coast

Rason (Rajin & Songbon sites)

Area highlighted shows that this portion of the Rajin (Najin) port was planned to be reclaimed while Korea was under Japanese occupation. Image: US Army Map Service, 1944. Digital copy via the Perry-CastaƱeda Library Map Collection, University of Texas. Highlight markings by AccessDPRK. 

The port city of Rajin (Najin) in the Rason Special Economic Zone has seen a lot of investment since the late 2000s, with thousands of new homes, scores of businesses, and numerous parks/recreational facilities constructed in the last 15 or so years. Part of that improvement has been extending the city's waterfront.

The planned reclamation area (42.239161° 130.303417°) highlighted in the above image was initially designed by the Japanese but never carried out. However, from 2011-2013, work was done on a modified reclamation plan and 7.1 hectares were added to the city. The land was used to build decorative gardens and a waterpark. 

To the north of Nanjin is Sonbong. Sonbong had traditionally been the more important of the two cities prior to the establishment of the special economic zone when it was superseded by Rajin. Still, resources have been spent on improving the city and on reclaiming land that had been a brackish lake and marshes (42.334866° 130.372910°). In total, 65 hectares have been drained since 2006.


Tanchon port expansion (40.416884° 128.918915°)

Tanchon is a key city in South Hamgyong Province and is home to zinc and magnesia foundries, as well as serving as the gateway to the major Komdok mining region. Yet, it lacked modern port facilities until 2012. Including the surrounding wetlands, Tanchon's new port construction resulted in 21 hectares being reclaimed. 

Some 1,500 meters of repaired and elongated breakwaters were also built to create the protected harbor.

Cha'ho Submarine Base (40.202812° 128.654004°)


North Korea has thirteen underground naval facilities, the largest are submarine bases. One such base is Cha'ho. To build the base, two tunnels were excavated for submarines and a new supply wharf was also created. The excavated spoils were used to create new land for berthing and other base activities.

In total, over 62,000 sq. meters of land was reclaimed. 


KEDO Lakes (40.098358° 128.339233°)

The Korean Peninsula Energy Development Organization (KEDO) was established in 1995 to implement parts of the 1994 Agreed Framework in which North Korea was to suspend its activities at the Yongbyon nuclear facility and in return KEDO would build two light water reactors for civilian energy production.

The site chosen for these reactors is located 28 km south of Cha'ho. The site was covered by rice paddies and two small lakes. The paddies had already been created through draining portions of the lakes, but additional reclamation work needed to be done to secure the foundations for the power plant.

In total, 300 hectares of new land has been created at the site, both before and as a result of the KEDO construction project. 

Unfortunately for global nuclear disarmament, North Korea violated the terms of the Agreed Framework and KEDO eventually shut down in 2006. What's left of the site is an industrial wasteland, with giant foundation trenches and piles of construction materials left over. The site seems to now be used to store raw materials like stone and sand, and occasional vehicle movements can be seen on satellite but they're unrelated to any on-site construction.


Wonsan Bay Marshes (39.409847° 127.442985°)

The largest reclamation example on the east coast involves the marshlands of the Chontan and Ryonghung rivers as they merge into a single delta and empty into Wonsan Bay. 

Three tracts of land totaling 16.1 sq. km have been reclaimed since the 1980s. One tract is used as a saltern and the other two are rice paddies. 


Future of Reclamation

As stated at the beginning, all of these reclamation projects have created 1,049 sq. km. of land, and that's taken 70 years. In 2012, Kim Jong Un said that he wanted land reclamation to rise to 3,000 sq. km. It's difficult to see how that goal would be possible without completely enclosing the waters between Sinmi Island and Sohae, enclosing the Chongchon River delta, and destroying the remaining bays of South Hwanghae Province. It's also difficult to see this happening within a single lifetime.

Nonetheless, despite natural disasters and financial problems, North Korea has a strong history of slow but steady land reclamation progress. Over 200 sq. km. of water have already been enclosed since 2010, and there has been improved progress at stalled projects. 

Although North Korea has less arable land than South Korea, the two countries actually have a similar amount of land actively under plough. And Pyongyang is trying to solve the country's food problems through sheer volume, since it refuses to address the underlying economic policies that have left one in five young children with stunted growth due to malnourished. 

As I have shown, reclaimed land is predominately used for agriculture (particularly rice and reeds), salterns, and to a lesser extent aquaculture and port facilities. While this may benefit the nation in the short-term, serious long-term questions have been raised about their sustainability and impact on coastal ecosystems.

Nearly all of the reclaimed land was built over wetlands and tidal flats, two ecosystems at-risk all around the world. Wetlands also provide buffers against storms and wave damage. Without them, typhoon storm surges can cause even greater coastal damage and flood farther inland.

If the seawalls aren't high enough, North Korea could see thousands of hectares of valuable farmland inundated as precedent has demonstrated (as with Ryongmae and elsewhere). Additionally, rising sea levels due to climate change put these sites at risk of not merely flooding but also saltwater infiltration that could make their agricultural output plummet. 

There are several ways to mitigate the risks to climate change, and maintaining sufficient coastal wetlands can offset storm damage while also improving regional biodiversity. However, the North Korean government have not been forthcoming when it comes to these mitigation plans, if it has any at all. 

In the face of these issues and knowing that North Korea will be reclaiming ever greater amounts of land, one must look at their overall impact with skepticism. Food security is obviously a necessary goal to achieve, but if those efforts result in the destruction of hundreds or thousands of square kilometers of wetland and tidal areas or if the new lands can't be protected from flooding, then their creation may not actually benefit future generations. 


Note: if you would like the polygons from Google Earth to explore all of these sites and those I didn't include, just email me


I would like to thank my current Patreon supporters: Alex Kleinman, Amanda Oh, Donald Pierce, GreatPoppo, Jonathan J., Joel Parish, John Pike, JuneBug, Kbechs87, Russ Johnson, and Squadfan.

--Jacob Bogle, 2/19/2023

Sunday, May 10, 2020

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.

--Jacob Bogle, 5/9/2020
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