I. Introduction

Bílinská kyselka is a rare source of cold pure alkaline kyselka, the only one of its kind in the Bohemian Massif. It emerged in several springs at the foot of the slope on the left bank of the Bílina (Bělá) river valley, about 2 km southwest of the town of Bíliny, near the Bořeň hill.
Balneologically, it is valued for its high content of sodium bicarbonate (4400 mg/l) with a relatively low content of sulphates (570 mg/l) and iron (around 1 mg/l) and a higher content of free carbon dioxide (over 2 g/l). Almost all the mineral water is bottled, only a small part is used in local spas to treat post-operative stomach conditions and non-specific respiratory diseases.
In the years 1959–1965, at the request of the Central Bohemian Springs NP, I designed, managed and evaluated exploration work aimed at achieving increased yield of acid water. The exploration, which ended with the construction of collection wells, completed the gradual development of capturing acid water from shallow spring wells through a deep collection shaft of unique dimensions.
At the suggestion of Professor Dr. Ing. Ota Hynie, DSc., I have supplemented the manuscript and am submitting it in this form as a candidate dissertation. I also gratefully remember the bright memories of Professor Dr. Odolen Kodym, DSc., who was my first supervisor.

II. Overview of older works

Bílinská kystelka has received (especially in the last century) considerable attention from both geologists and chemists. Most of the works deal with Teplice, and the article about Bílinská kystelka forms the conclusion, as it was recommended as a complementary treatment to Teplice treatment.
The oldest mention of Bílinské kystelka dates back to 1607. The physicist from Görlitz C. Schwenckfeldt dedicated the last chapter of his work on Teplice to Bílina. From the test results, he states that the water contains salt and limestone, and therefore instead of the name kyselka Sauerbrunn recommends labeling Salsula-SältzlingIt provides a long list of diseases that Bílina water treats.

W. Sparmann (1733) cites the chronicle of Václav Hájek and states that drinking cures were introduced by D. Zittmann. The first chemical analysis by J. Berzelius is known from 1786. Two years later, the first scientific monograph on Bílina acid was published by F. A. Reusse (1788), which describes in detail the natural conditions. D. Hufeland (1815) places Bílinská kystelka in first place in Central Europe for its high CO content₂ (49 cubic inches per 1 pound).
The fundamental contribution was the work from 1886–1898, described in the monograph W. Gintl, G. Laube and F. SteinerG. Laube describes the geological conditions and W. Gintl tries to explain the genesis of water as a product of the action of CO₂ on phonolite and basalt.

III. Development of source capture and expedition

It is not possible to reconstruct the method of the first capture from literary sources today. It was probably a shallow well. In 1761 the wells were lined with stone blocks and in 1781 a bottling plant was built.
According to J. Löschner (1859), the expedition of sour wine grew as follows. Originally, it was filled into fired ceramic jugs with a narrow, short neck; the jug's content was 0,7 l; the closure was a cork stopper with a cracked lead foil.

Three other higher-lying springs were found in 1810–1820: Josef, Carolina a Municipal. In 1852 the wells were reconstructed again. In 1870–1871 the spa building was built and a spring was discovered. MoritzAt that time, the "Rock Spring" was also being mined with a constant yield of 14,4 m³/day.
In 1903–1904, the A. Scherrer company carried out a massive reconstruction. It was moved over 150,000 m³ of rock and a 26 m deep collection shaft was created. Nevertheless, the yield in 1932 dropped to a critical 5,17 l/min. J. Päckert solved the critical situation with "irrigation", but the need for a stable source led to the decision to conduct a new survey in 1959.

IV. Geological conditions

The wider surroundings of Bílina are built up of rocks of the Ore Mountains crystalline rocks, Upper Cretaceous sediments and Tertiary volcanics. Volcanic bodies are of fundamental importance for the genesis of the acid lake, especially phonolite of Bořeň HillThis massive laccolith broke through the chalk layers and created a system of cracks.
An important finding from the boreholes (V-1, V-2, V-3) is that the gneiss is affected by hydrothermal transformations (sericitization, chloritization) to a considerable depth. The cracks in the gneiss are often filled with calcite or quartz.

The output of Bílinská kyselka is decisive the so-called "Bílina break"Detailed measurement of cracks revealed a maximum of cracks in the direction h 2 (approximately SJ to NNE-SJW). This direction turned out to be the main supply route of the gasified mineral water from the depths.

V. Design and methodology of drilling work

Based on the analysis of geological conditions, it was decided to abandon the surface pits. The goal was to capture the exit routes at depth. The most suitable method was chosen core drilling.

Drilling and insulation technology

The drilling was carried out by a rig ZIF-300 and Craelius. In order not to damage the structure of the mineral water, it was used as a rinse clean water, not clay leaching. The key moment was the isolation of Cenomanian sandstones by cementation to separate the fresh water from the mineral water.

VI. Hydrogeological verification and testing

After drilling, it was necessary to demonstrate the hydraulic connection with the original shallow springs. A key experiment was to monitor the response of the water level in the old collection shaft to pumping from the new V-1 well.
The result was clear: As soon as the deep well V-1 began to be pumped, the water level in the shallow shaft began to fall. This confirmed that The V-1 well intercepted the same exit route (fracture h-2), but at a much greater depth. When the V-1 well was fully opened, the overflow of the old springs completely stopped - the new well "stole" them and eliminated losses.

During the tests, it was shown that the V-1 well behaves like a “gas lift.” When the level drops, bubbles of CO are released₂which pull water upwards.

VII. Hydrochemical conditions and genesis

The chemical composition of Bílinská kyselka is the result of complex geochemical processes. According to the classification, it is pure alkaline acid (type Na – HCO₃) with an increased content of silicic acid and fluorides. Analyses from 1963–1964 confirmed that the water from the depths is identical to the original one, but is more stable.

Genetic model and comparison with the world

The question of origin was resolved as follows: CO₂ It is of deep, post-volcanic origin. The gas-saturated water reacts with gneiss (hydrolysis of feldspars), thereby enriching itself with sodium and bicarbonates. Finally, it rises through the cracks h-2.
Prof. Mladějovský has already pointed out the striking similarity of Bílinská kyselka with the famous springs in Vichy, France. Chemical comparison shows that Bílinská is their colder and more strongly gasified equivalent.

VIII. Conclusion of the report

The work carried out in the narrower spring area (1959–1964) was aimed at verifying the possibility of increasing the usable yield of the springs. The original collection system was replaced by two inclined and one vertical collection wells. The acid collected by the wells on its way out has been used for bottling purposes since 1960.
By capturing the mineral water on its outlet path, the originally usable amount was increased from 5 to 7 l/min to 34 l/min. Of this, 27 l/min will be used for the bottling plant and 7 l/min for the natural carbonated baths (for the first time in the history of Bílina).
Based on a comparison of the conditions of the emergence of acid lakes in the Bohemian Massif, the thesis is expressed that their formation is conditioned by the causal and spatial unity of these factors: the existence of Variscan plutons, Variscan tectogenesis, Saxon tectonics and the formation of neovolcanites.