In Romania, underground lakes and caves are built over mines. The lack of geotechnical investigations guarantees the collapse of constructions

The town’s mayor admitted that no one knew what lay beneath, although in a heavily populated urban area with apartments, a kindergarten and a police station, it should have been known if there was such a danger. To find out what is under the fallen portion will be the same types of geotechnical studies that should have been in place before the road and buildings were built there. Specialists in geotechnical studies say that the problems could have been avoided if the studies were done on time.

The portion of the street that collapsed in Slănic Prahova could be caused by the existence of an underground gallery of an old salt mine. 42 families were evacuated from nearby buildings, a kindergarten can no longer function and a police station may close. It is not the only case of this kind in the areas with salt mines. In 2011, a Kaufland store built on top of a mine gallery at Ocnele Mari collapsed.

But the situation is much more tragic, because almost no geotechnical studies were done in Romania after the legislation was changed in 2007. The companies that did feasibility studies closed down, remaining without contracts, and on this market more there are very few such companies that take the risk of working with 10-15% of the total sums that would be needed for the drilling required in such studies.

They are looking for the culprits among the politicians

Initially, an area of ​​about 60 square meters collapsed, the depth of the crater being about two meters, but in the following days the area expanded and deepened. The first hypotheses show that under the collapsed road there is an old salt mine or several underground galleries that were not taken into account when the area above was developed as part of the settlement.

The President of the Prahova County Council, Iulian Dumitrescu, is suspended for acts of corruption investigated by the DNA, and now he is running for the same position, for a new mandate, being in full electoral campaign. He was accused by the locals of having contributed to the disaster.

Several residents of the city say that the surprise on 23 August street would be the effect of the activity of the president of the CJ, because he would have brought in some “house companies” to do a work on the gas network, and because of that recent intervention the water table or rainwater would have been diverted and thus the salt vein below the collapsed surface would have been destroyed.

The hypothesis was strengthened by the statements of Prime Minister Marcel Ciolacu, who said that he had information regarding the construction of the street over a salt mine, for which those who gave the authorizations would be responsible. Rainwater seepage into the soil has also been considered, but surveyors say it’s less likely that the soil was eroded by rainwater.

The salt pan is half a kilometer away

There have also been accusations against Salrom, which owns the nearby salt mine, but company representatives say it can be proven that there is no connection between the mine’s activity and what happened in the collapsed area. The place where the explosion occurred is approximately 500 meters from Salina Slănic Prahova – where, at a depth of more than 200 meters, is the Unirea Mine, with an area of ​​more than 50 thousand square meters.

However, two other salt mines are known to be located a short distance away and are now closed, and it is assumed that there is one such mine under the affected area. In this case, the area in question should not have been built on.

Specialists who were on site during the first days of research do not rule out the hypothesis of surprise due to an underground watercourse either, because the level of a lake in the area has inexplicably dropped by 2-3 meters in just a few weeks – which means that such a salt gallery below the collapsed area may have been flooded, but the cause of such an accident has not yet been established.

Feasibility studies are skipped

Regardless of the cause of the surprise, geotechnical studies specialists say that it should have been known from the beginning what the structure of the soil is and what the dangers are, and the urban area should not have been built over such a salt mine.

Before 1990, it happened to build on dangerous surfaces, but later measures were taken to avoid disasters. The situation changed for the worse after 2007, when the legislation on geotechnical studies was amended.

“What happened in that area of ​​the street could also happen in the block area and it would be a disaster. Probably no borings were made, or they were made, but not where the gallery was. You are not allowed to work there until you prospect the situation in depth, until you have the technical foundation of the location. If the investigation is not done before building, anything can happen. The legislation is valid for absolutely all constructions. You are not allowed to build even a toilet without a geotechnical study. But the law is not taken into account. The fact that blocks of flats were built in such an area is very serious”, university professor explained to Jurnarul. Dr. Nicolae Boțu, expert in geotechnical studies.

GPR can be used

He also says that all investigations should be done at least now, to see if it is a mine or another phenomenon generated by water courses. “The collapse is over a fairly large area and it’s probably a salt mine that would be underneath. Ground-penetrating radars could be used to see what was at depth. For example, in Focșani and Iași, we did such studies and discovered such routes below, even at a depth of 9 meters. That’s what the investigations are for,” says the expert.

Even if the road and buildings are built before 1990, these investigations should be done in such areas, especially because the potential hazards are known, where there are mines and old underground galleries of salt or limestone, which can fell easily.

These investigations are no longer done at all. Experts say legislation should be changed to make them mandatory because such crashes happen frequently.

The field of geotechnical research was destroyed

In Ocna Mureș, in 2011, a store built without a feasibility study collapsed. Nicolae Boțu says that the situation is the same with regard to highways. “Everything that geotechnics means in Romania has been destroyed, from 2007 until today, and no one discusses this issue. It all started in 2007, when a regulation appeared to govern the entire activity in our field. The one who coordinated this standard has never done a geotechnical survey in his life and introduced the preliminary geotechnical survey, that is, without drilling or with very little drilling. Then work started to be done only on the basis of these preliminary studies, in order not to pay for the real geotechnical studies. For the Târgu Mureș – Iasi highway, the representatives of a company came to me for the geotechnical study, I gave them an offer, and after 6 months we met and they told me that they were only asked for the preliminary study and none was done drilling. Then they drilled 3 boreholes, along the entire length of the section, only to not show any boreholes in the study. That’s how we do things,” explained the specialist.

Those who were in charge of the feasibility studies insisted that the legislation be amended to return to normality. “In 2014, we managed to remove the term “preliminary” from the regulations, and the situation should have changed, but nothing has changed. The bad part is that the companies that did geotechnical investigations have almost completely disappeared from the Romanian market, and there are no longer tenders for works, but direct assignments”, explains Nicolae Boțu.

It also happened in communism

During the communist period, even a combine hall collapsed, due to construction on land with a risk of collapse. There are situations where collapse cannot be accurately predicted by geotechnical studies, but it can be specified in the terrain details that the hazard may occur at any time.

For example, in the 70s, in Călăraşi, a section of the steel plant collapsed into an unsuspected void that formed below. In 2007, a building in Mangalia was destroyed by such a natural landslide. Cristian Lascu, former editor-in-chief of National Geographic magazine, known as a speleologist, but who was for a long time one of the best Romanian experts in geological and geotechnical studies, explained to Jurnalul that these catastrophes are called “karst collapses” and many they took place in Dobrogea and on the banks of the Danube.

The building in the center of the city of Mangalia was affected by such a collapse in progress, resulting in a “karst funnel” seven meters deep. Such “funnels” evolve near the Mangalia Stud and in several other points in the area, where human intervention has ruined the natural balance – explained Lascu.

Exactly this phenomenon saved the southern Romanian coast from being transformed into an industrial area, in the 70s, when Cristian Lascu was the one who did the land studies and warned about the imminent danger of collapse. He demonstrated that the area is a real “karst sponge” and thus abandoned the construction.

Periodic investigations would be the solution

Periodic geotechnical studies should have existed in all mining areas or where there are caves, but not only is no money allocated for them, in order to prevent possible collapse hazards, but even building permits have been issued on dangerous surfaces, the decision being left to the mayors of localities and local councils who can vote anything.

For example, in the south of the coast, where the Limanu Cave is located, dug by sea water into a fragile limestone structure with a very thin ceiling, land has been given to build houses above the cave, although geologists and speleologists have warned permanently in relation to the danger of collapse.

Landslides can be anticipated

The same is the case with landslides that could be anticipated and avoided, through consolidation works or by abandoning construction projects. Such a case is happening right now in Cluj, where a section of the street collapsed on April 25.

The City Hall of Cluj-Napoca has only now taken measures to reduce traffic and would be doing consolidation work on Strada Uliului, following the landslide, although the incident could have been avoided if a good geotechnical study had been done before the start street construction works or even afterwards, if these investigations were done periodically.