Sea Outfall in Sochi, Russia, Breaks Record

— Jun 13, 2013

WastewaterA modern wastewater treatment plant is being constructed in the Sochi district of Bzugu, Russia, so that the city is well prepared for the Winter Olympics.

The plant is part of an initiative by the local administration and Moscow's government, which aims to comprehensively increase the capacity of the entire local wastewater system. The project will also lead to sustainable protection of the environment. A piping system conducts the wastewater treated at the plant into the Black Sea so far away from the coast that residents and the environment are not affected.

The Russian Utility Tunneling expert ZAO PRiSS from St. Petersburg drilled the connection from the Bzugu wastewater treatment plant to the coast and from the coast out to the Black Sea using an AVN2000AH (slurry-supported tunneling system) made by Herrenknecht. A navigation system from the company VMT GmbH of the Herrenknecht Group took over the precise navigation of the driller. The machine started excavating the sea outfall in the 25-m deep shaft in February 2012. Tunneling operations along a length of 1,411 m were completed in August 2012. High abrasiveness of the mainly encountered limestone meant extreme demands on the excavation tools and the pumps of the slurry circuit. The machine mastered this challenge under the direction of ZAO PRISS without any problems, achieving top daily performances of up to 30 m per day. The tunnel builders stopped the machine at the target point on Aug. 28, 2012, beneath the seabed around 800 m away from the coast. Herrenknecht equipped the machine with a rescue module to ensure safe recovery. This additional equipment allows the machine to be sealed at the bottom of the sea by means of a bulkhead and separates it from the tunnel using cylinders and the necessary hydraulic supply. The machine can then be lifted by a crane or with balloons to the sea surface.

After recovery of the machine in October, the AVN was completely refurbished and employed in the second project. The plan is to connect a new wastewater treatment plant in the Adler district of Sochi with the sea through a sea outfall. From mid-December 2012 to the end of March 2013 — within 100 days — the AVN2000 installed a total of 2,014 m of pipeline with top performances of up to 37 m per day. In the DN 2000 (2.5 m) diameter range, this constitutes a previously unachieved world record.

The large-scale infrastructure package in Sochi includes the construction of new roads and railway connections. An EPB Shield (Ø 10,630 mm) and a Single Shield TBM (Ø 13,210 mm) from Herrenknecht excavated a road tunnel (3.1 km) and a railway tunnel (3.1 km) in the years 2010 to 2012.
Herrenknecht AVN or Slurry Machines with a cone crusher are all-rounders for safe tunneling in the diameter range of 0.1 to around 4 m. The microtunneling experts demonstrate their full potential in non-accessible machine dimensions in particular. The slurry-supported excavation concept makes it possible to use the machines in ground conditions of all kinds: ranging from silt to clay to incohesive soils, gravel and rock. Depending on the diameter, this is possible both in pipe jacking and for segment lining.

 With the exception of Mexico City and Beijing, almost all metropolitan areas in the world are located next to coastal waters. In addition, more than half of the world’s population lives within 60km from the coastline. Therefore, the construction of outfall tunnels is often an effective and sustainable solution to improve the quality of life in the coastal areas. With the help of sea outfalls, wastewater can be discharged far away from the coast. The self-purifying power of nature is used by first diluting the wastewater, after which micro-organisms start to breakdown the substances. Another important area of sea outfall use are intakes and outlets for desalination plants. 

Sea Outfall Sochi, Russia


Machine data M-1103M


Project data


Machine type:




Diameter (OD):

2,525 mm



Installed power:

315 kW

Tunnel lengths:

1,411 m and




2,014 m

Max. torque:

780 kNm


limestone, clay




This article was submitted by Herrenknecht AG.

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