This specific category includes diversified finds as it unites all the objects that are potentially dangerous for safety of navigation, fishery, coastal construction, underwater pipeline or cable laying, and also a threat of ecological disasters and catastrophes. Unfortunately, the bottom of Gulf of Finland and especially its east part abounds with such objects. Three times in XX century high-intensity battlefield with extensive use of mine weapon took place in this water area. Though formally the gulf water area is designated on a map as «former mine-dangerous areas open for navigation», practice shows the presence of a very big number of explosive objects which have remained at the bottom since war and post-war time. It is known, that the international program of their inspection and demining has been executed in coastal zone of the Baltic countries since 1995 till nowadays. In first three years works were executed by 5 ships of Naval Forces of Sweden (2. Mine Warfare Group Royal Swadish Navy), and then the ships of Germany, Holland, Norway joined to them. The find number is estimated in several tens each season. Not without reason even the Museum of «caught and weighed» sea mines is organized in Tallinn. Similar programs are carried out by Naval Forces of Germany and Naval Forces of Finland in their own waters.
In the Russian Federation similar works are executed within the limited areas connected with coastal construction only, and the basic method is diving inspection of the bottom. In 2002 mine clearing was carried out in the region of the oil terminal construction in Primorsk, in 2003 - at tourist center arrangement in Suurkjule bay on Gogland Island, in 2004 – in Ust-Luga port development zone, in 2005 – in areas of access fairway to projected passenger port in Saint Petersburg routing and water areas near Vysotskoj oil terminal. And each time finds of dangerous objects took place. As bright examples of recent date it is possible to name an incidental find of the wartime Finnish mines near a military berth in Primorsk port in July, 2005 and detection of "two tens of service projectiles» in the Oryol pond in Strelna town in December, 2005. The last works were executed within the limits of “Big Eight” countries summit safety measures.
However there is no purposeful constant program of dangerous objects search and destruction in the Russian Federation.
The truth is that the governmental order of the Russian Federation of February, 21st, 2002 #124 (:200312) «On underwater potentially dangerous objects in internal waters and the territorial sea of the Russian Federation safety declaring» is now in force in Russia. It assigns a duty of special «underwater objects safety declarations» development to proprietors of these objects. However the problem is that the property rights to the sunk objects and especially concerning dangerous objects are not determined in the Russian Federation. It is known, that all the state and private organizations would like to become proprietors of the underwater objects of commercial or cultural historical value. Equally all these organizations would not like to be proprietors of dangerous objects and it is clear why.
As a result the register of potentially dangerous underwater objects is rather insignificant. For example, the Ministry of Emergency Measures, Gosakvspas and “Typhoon" scientific-production association executed the expedition on 17 potentially dangerous objects of the Second World War time search and inspection in the Baltic Sea in June, 2005. They had the sunk ships for an object. But the real number of such objects is more than several thousands. And it is necessary to add a little bigger number of small objects. Analyzing materials of our sunk objects database it is possible to define four basic groups of potential danger according to the order mentioned above.
1. Separate explosive items lying at the bottom. What is meant here is mines, mine defenders, torpedos, dud air bombs, shells and depth charges. Their total quantity according to our estimations makes several tens of thousands items. And as their incidental finds show, they are a real danger till nowadays.
Let us remind, that active and large-scale minelaying was carried out in Gulf of Finland even during First World War, Civil War and intervention, "Winter" Soviet-Finnish War. There is no exact information on minelaying scale, but the available incomplete information analysis allows to estimate them in 60000 items. (Only minelaying of the Russian imperial fleet in 1914-1917 have made 38932 mines). Thus no more than 25 % mines were destroyed by post-war minesweeping by expert estimations. The given statistics includes also numerous cases of mines and shells flooding at the bottom. For example on December, 17th, 1918 minelayer «Narova» has dropped 159 pin mines to the bottom to the west of Kotlin Island escaping the bombardment. They should lie at the bottom till nowadays, being a nest of mines with a 20.67-ton lump of trotyl.
Another case – flooding of several thousands of artillery shells in Chudskoe Lake during civil war.
Available data on the Second World War allow to estimate volumes of minelaying in the Baltic sea in 85000 pieces, 52000 of which were laid by Naval Forces of Germany. Thus in the east of Gulf of Finland from Kotlin island to Gogland island 41750 mines and mine defenders, i.e. almost half of all mines, were laid. At the same time, it is known that only 8364 mines and 1783 mine defenders were destroyed at mine clearing during post-war years, i.e. no more than 12 % of the laid mines. Considering that approximately 30 % of mines were destroyed by ices and sea motions, there should be more than a half of the laid mines at the bottom. The most dangerous of them are bottom influence mines with a large explosive charge. It is known, that 1162 mines have been laid in the east of Gulf of Finland, and only 407 mines were destoyed during post-war minesweeping in 1946-1962. Let us remind, that at Leningrad protective constructions complex building in 1980s more than 80 mines were found by builders in the ground.
The number of dud torpedos lying at the bottom is, according to our estimations, several hundreds as at the big number of the Soviet torpedo boats attacks, the number of hits was rather insignificant.
2. Transportations of military cargoes are one of the basic kinds of navigations during war. And losses of water crafts transported an ammunition were significant. It is enough to tell, that, for example, ammunition transportations were carried out in both directions on Ladoga Lake.
During the blockade the Leningrad factories supplied "continent" with the production. Unfortunately, information on transport water crafts with an ammunition loss is secret till nowadays. However it is possible to mention as authentic examples the following:
- On August, 11th 1941 a barge with ammunition in tow was sunk by enemy aviation near Seskar island;
- On August, 18-20th, 1941 2 self-propelled barges with an ammunition were sunk by enemy aviation during parts of 168 rifle division evacuation from Kilpola region to Valaam Island;
- On the night of the 22nd/23rd of August, 1941 2 not self-propelled barges were lost at evacuation of an equipment and ammunition of 32 separate artillery battalions from Pukkio, Patio and Lajtsaljmi islands in Gulf of Finland. One was sunk by enemy artillery, the second sank owing to tow breakage at strong sea motion. Today these barges can be especially dangerous as they were lost somewhere in the north German gas pipeline laying region.
- On September, 17th, 1941 a barge with ammunition was lost on Ladoga Lake during a storm. According to official information the total quantity of ammunition on 7 barges lost at passages in September-October, 1941 is 1000 tons;
- On November, 4th, 1942 a barge with ammunition damaged at passage by a storm sank on Ladoga Lake;
This list can be continued. According to our estimations the total number of sunken water craft with ammunition is more than 300 items, though these number include information on losses of German and the Finnish barges and transports which reliability is not confirmed by foreign archives.
3. The combat ships with large charge.
Certainly all the armed ships lost during battles had ammunition load onboard. But patrol boats or minesweepers which ammunition load comprised only machine-gun cartridge and a hundred of shells for a light gun are not very dangerous.
Another matter is the artillery ships which were armed with the big calibre gun and several hundreds of shells and mines. This group can undoubtedly include two German heavy floating batteries SAT-1 «Ost» and SAT-27 «West» sunk in 1943. Their arms consisted of 5 guns at each battery. The remains of four German torpedo boats of the project «39» lost in the summer of 1944 are not less dangerous. Each of them was armed with 4 guns of 105 mm calibre, 4 guns of 37 mm calibre, 6 torpedo launchers 4 anti-submarine mortar. The lump of an explosive in charge of each torpedo boat was 8 tons. Except for that it is necessary to consider, that three torpedo boats (-22, -30, -32) were lost at minelaying approach having 50 anchor mines onboard.
Soviet submarines lost at battle task run, having onboard a full stock of torpedos, shells and diesel fuel, are also especially dangerous. Their number includes, first of all, submarine «-405» lost on the night of the 12th/13th of June, 1942 between Seskar and Moshjnij islands. The archival materials analysis shows that it can lie directly on the main waterway, having onboard 12 torpedos, 1000 shells and 55 tons of diesel fuel. It is necessary to add minimum 4 submarines to «-405». Theoretically remains of bombers lost at bombardment run can also be dangerous.
4. The ships having reserves of liquid fuel onboard. This group includes the already mentioned submarines with reserves of diesel fuel, and also German torpedo boats of type «» and type «Z» used liquid fuel. Besides tank vessels, towing vessels, fuel oil barges are also dangerous. The total number of such ships is not so great, but considering great reserves of oil or fuel in their tanks the damage can be much more significant rather than at weapons load or bottom mine explosion.
Possibly it is necessary to include also such potentially-dangerous objects as cargo containers laying at the bottom in this group. They occured rather often. Certainly, it can be just containers with the goods washed off overboard during a storm. But, in the light of the western publications, it is quite probably that they were sunk specially, by loading them with barrels flanks with used oil or other ship waste.