Perlenbachtalsperre

Perlenbachtalsperre
Drain:	Perlenbach → Rur
Major cities nearby:	Monschau
	North Rhine-Westphalia , Germany
Coordinates	50 ° 32 ′ 21 ″ N , 6 ° 14 ′ 21 ″ E Coordinates: 50 ° 32 ′ 21 ″ N , 6 ° 14 ′ 21 ″ E
	Data on the structure
Lock type:	dam
Construction time:	1953-1956
Height above valley floor:	19 m
Height above foundation level :	21 m
Height above the river bed :	19.7 m
Height of the structure crown:	467 m above sea level NN
Building volume:	50,800 m³ (125,000 m³?)
Crown length:	117 m
Crown width:	5.3 m
Slope slope on the air side :	1: 1.75 / 1: 3
Slope slope on the water side :	1: 1.75
Operator:	Water supply association Perlenbach
	Data on the reservoir
Altitude (at congestion destination )	464.3 m above sea level NN
Water surface	15 ha
Storage space	0.76 million m³
Total storage space :	0.9 million m³
Catchment area	61.5 km², according to other information 64.4 km²
	Average annual inflow: 57 million m³

The Perlenbachtalsperre is located near Monschau in the Aachen city region in North Rhine-Westphalia . On the west side of the lake is the federal road 399 , while on the east side a hiking trail runs from the dam to the Höfener Mühle . The structure dams the Perlenbach . The water from the dam is used to supply drinking water and to generate electricity through hydropower. It was completed in 1956 and is operated by the Perlenbach water supply association.

description

Construction of the dam began in 1953 . Because of the high strength at low cost, the planners decided to build a rock embankment, designed for a storage capacity of 800,000 cubic meters. The 120 meter long and altogether 18 meter high dam has a drivable road on the five meter wide crown and its visual design blends in harmoniously with the landscape.

The catchment area of the Perlenbachtalsperre covers 64.4 square kilometers, of which almost two thirds are on Belgian territory. The source and early course of the Perlenbach are located at the Belgian military training area in Elsenborn . In addition to the main tributary Perlenbach, the Hasselbach, Königsbach, Römerbach and Höfener Bach also form important inflows to the dam.

The pipes for the drinking water extraction and the bottom outlet with which the dam can be emptied are located in a tunnel running transversely under the dam .

The water for underwater delivery is used by a hydropower plant to generate energy. Extreme floods can be channeled through the flood relief system past the dam and into the lower reaches of the Perlbach.

Six wells in the dam body enable the seepage water to be observed . The stability of the dam body, for example in the event of an earthquake, as well as the efficiency of the flood relief were proven in complex computer-aided processes.

Drinking water treatment

The raw water of the Perlenbachtalsperre is taken from a depth of twelve meters by means of two DN 300 extraction pipes. It goes through a tunnel to the pre-treatment plant for flocculation and filtration that went into operation in 2001. This has a maximum output of 700 cubic meters per hour, whereby the actual capacity is usually around 400 to 600 m³ / h. Every year around 3.65 million (as of 2008) cubic meters of raw water are processed into drinking water. First, milk of lime (Ca (OH) ₂ ) is added to the raw water before it enters two 35 cubic meter reaction chambers. At a pH of 10, manganese dissolved in the water oxidizes and is filtered off. The addition of milk of lime and carbon dioxide also increases the hardness of the soft reservoir water and lowers the pH value to 6.3. In six self-sufficient flocculators, the flocculant (FeCl ₃ ) transforms the turbid substances in the water into a filter that can be filtered off. Mesh stirrers increase this formation of voluminous flakes, which can then be easily filtered out. Each filter has a filter area of 30 square meters and is made up of two layers: The upper and coarser layer consists of hydro-anthracite (hard coal) with a height of 1.4 meters, the lower one of a 90 centimeter thick layer of quartz sand (primary flocculation).

The older part of the drinking water treatment system consists of two filter systems operated in parallel. The older one was built in 1956 using the open construction method and renovated in 2007, including a complete lining with stainless steel. The second filter system is the closed double-deck filter in filter house 3, which was built in 1973. Flocculant (Al ₂ (SO ₄ ) ₃ ) is added to the upstream reaction chambers, the upper single-layer filters hold back the flocs that have formed. The lower filter is used for deacidification to a pH value of 8.5 and for hardening. The filter material consists of half-burnt dolomite and removes excess, corrosion-promoting carbon dioxide from the water (secondary flocculation).

Finally, the water is disinfected with chlorine gas and dosed with a phosphate mixture in order to protect the pipeline network from corrosion. The drinking water is fed into the 380 cubic meter pure water chamber, pumped into the elevated tanks and finally reaches the end customer via the distribution network. The water supply association Perlenbach supplies seven communities in the northern Eifel. The water is very soft (hardness range I) and therefore aggressive to lime.

Hydropower

The hydropower plant has an output of 100 kW. The flood relief has a 27 m wide fixed overflow and an 8.5 m wide fish-bellied flap . In order to use the energy of the water that flows through the Perlenbachtalsperre effectively and ecologically sensible, a hydropower plant was built. In 2004 it was put into operation after three years of construction and planning. The annual work of between 850,000 and 1.2 million kilowatt hours corresponds to a saving of around 900 tons of fossil-generated CO ₂ . Around 300 households can be supplied with electricity in this way. The system was funded with 150,000 euros by the state of North Rhine-Westphalia. The inlet to the hydropower system is below the water level. The water enters the power house via a 160 meter long pipe with a drop height of 18 meters and flows into the turbine, which drives a generator. The water returns to the lower reaches of the Perlenbach stream. In dry times, the output of the system is throttled or completely switched off - the drinking water supply remains the primary task of the Perlenbachtalsperre.

Renovations

For the period from February 15, 1997 to December 3, 2001, i.e. for almost five years, the health department of the Aachen district has issued a boiling recommendation due to the poor quality of the drinking water supplied by the Perlenbach water supply association. The Aachen public prosecutor's office started investigations into violation of the Federal Disease Act . In January 2002 the chairman of the association assembly announced the end of the boiling recommendation.

In 2001 a so-called "closed" drinking water treatment plant was put into operation. After completion and leak testing of the weld seams, the filters were finally filled with new sand. In 2007, after around a year of construction, the open filter system went back into operation.