Copy of Development

Geological Positioning

Perfection in Stone

The caverns are located on the Southern side of the Puster valley. Specifically, they are in the Brixner quartz phyllite zone in a dome-shaped rock which is closed in on all sides. 
An extended geological engineering and rock mechanics investigation (including drillings, seismic and geo-structural photos, as well as a pilot gallery) resulted in an ideal alignment of the caverns and produced clear instructions for the planning and carrying out of the gallery construction works (joints, stratification/cleavage, mechanical defects, rock mass classification, required stabilisation and support system measures, etc.) 

Rock Mass Classification 
All caverns were classified as being class III (RMR = 60-41) according to Bieniawsky, with exception of the shaft inset area. 
Structurally, the fault zones were predicted to be class IV, while the remaining areas were estimated to be class III. 
With relation to the project, the complicated intersecting and cutting areas were assessed as being class IV.

Planning and Construction

Together, reaching the goal faster

The building contractors' consortium of the autonomous province Bozen, South Tyrol was commissioned with the estate finding and planning and with the execution of construction works. The building contractors consortium is an association of qualified local contractors whose objective is to increase their productivity and competitive ability.


- Selection of the six construction 
  companies through the South 
  Tyrolean building contractors' 
- Resolution of the 
  provincial government 
- Decision for awarding of a license 
- Contract to the building 
  contractors' consortium

- Signing of the contract 
- official authorisation 
- First blastings 
- Drilling of the inlet gallery 
  with a TBM by ILLBAU

1992 - 1993
- Blast and drill according to the New 
  Austrian Tunnelling Method (NATM) 
  in three caverns 
- 200.000 m3 solid material 
- 220 tonnes explosives

1993 - 1994
- Concrete works 
- Concrete: 50,000 m3 
- Reinforcing steel: 
  approx. 1,500 tonnes

- Assembling of the electro-technical 
  and mechanical-technical plant 
- On schedule clearance of the 
   plant for operational tests

3. Juli 1996
- Punctual opening of plant
  after completing the 
  operational tests

Year 1998
- Start up sludge dryer

2004 - 2005
- Installation and Start up   thermal recycling plant

March – July 2008
- new sludge head dryer 

Tunnel construction

The excavation, as well as the stabilisation and support system works were carried out according to the New Austrian Tunnelling Method (NATM). The support system was done in two phases, one with shotcrete and expansion anchors and one with mortar anchors, welded wire meshes, and shotcrete. 
The rock stabilisation functioned as a permanent supporting structure ("single-lining permanent support"), whereby higher standards were necessarily placed on the quality of the materials and on the construction. 13 measurement check points were installed for the technical measuring supervision of the support system (convergence measurements with five convergence bolts each, multiple extensometers, levellings, etc.). Work was done around the clock with three different shifts. 

Stabilisation and Support System 
"Single-lining permanent support": The rock stabilisation functions as a permanent supporting structure. 


- 2 - 5 cm shotcrete (sealer) 
- First layer: shotcrete 10-15 cm, welded wire meshes diameter 5/20/20, grouted anchors, N = 4,5-6,0-7,50m GEWI bar diameter 28 mm 
- Second layer: shotcrete 10 cm HS Cement, welded wire meshes diameter 5/20/20

Structural Composition of Wall - Rock


Inlet gallery 

The inlet gallery has a diameter of 3.9 m and a length of 930 m. Drilling was done with a TBM. At the same time, the inlet gallery served as a development drilling and reconnaissance gallery. In the area where the river Gader and the river Rienz merge, the single sewers are lead into the inlet galleries' intake structure. As a result of the sewer's depth level (5.0 m below the water level), substantial water containment works were necessary. 

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a) Central Gallery 

Area of preliminary treatment Area of technical chambers
Central Gallery
consisting of:

Coarse Screen
Aerated grit chamber
Dump Station
Pre - thickeners
Technical rooms
Technical Data
Central Galley:

Galley lenght: approx 325 m
Full section 65 - 180 m²
Excavation volume approx. 35.000 m³

 b) Side Galleries

Nitrification basins Final clarifiers
Side Galleries
consisting of:

Preliminary clarifier
Final clarifier
Technical Data
Side Galleries:

Galley lenght: approx . 325 m
Full section 190 - 200 m²
Excavation volume approx. 75.000 m³ je Stollen

Cavern Technical Data

Excavations total:
Surface support:
Concrete Spritz:
Welded Steel Mesh:
Quantity of explosives:
  approx. 200.000 m³
approx. 50.000 m²
approx. 12.000 m³
approx. 50.000 m
approx. 200.000 kg
approx. 150.000 kg
  Total Cavern 

Concrete regularization:
Concrete structures:
Steel Formwork:
  approx. 2.000 m³
approx. 22.000 m³
approx. 1.500.000 kg
approx. 50.000 m²


Constructional Part

a) Clarification

Aerated grit chamber and grease trap 2 x 200 m³
Preliminary clarifier 8 x 260m3 = 2.080 m³
(retention period during dry weather flow approx. 1 h - lateral flow)
Denitrification basin 4 x 3.250 m3 = 13.000 m³
Aeration basin 4 x 6.350m3 = 25.000 m³
(retention period during dry weather flow approx 3,7 h. fine bubbly in depth aeration)
Final clarifier 8 x 1.400m3 = 11.200 m³
(surface load during dry weather flow approx. 0,75 m/h - retention period during dry weather flow approx . 2,8 h)
TOTAL EFFECTIVE volume 50.000 m²


b) Service Building

The service building is built at the bottom of the mountain slope and incorporated into the landscape. It consists of the following sectors:

- Gasometer: Effective volume 2,000 m3 
- Gas engine room, heating installation, technical rooms 
- Service and administration area 
- Sludge dewatering and sludge drying

Technical Data:
Build over area: approx. 2.700m2
Excavated material: approx. 13.000m3 Loose material: ca. 12.000 m³ Rock and slope stabilisation respectively. Rock excavation: ca. 3.000m2
Need of:
Reinforcing steel:
approx. 5.000m3
approx. 20.000m2
approx. 4.000m2
approx. 400.000kg


c) Digestion Chambers

The two digestion chambers have an effective volume of 2,000 m_ each and they are built into the rocky mountain slope. Only the upper area rises up into the open because for safety reasons.

Technical Data:
Excavated material: Rock excavation: approx. 13.000 m³
Loose material: approx. 7.000 m³
Need of:
Welded wire meshes:
Reinforcing steel:
approx. 500 m³
approx. 2.000 m
approx. 3.000 m²
approx. 2.000 m³
approx. 150.000 kg
approx. 5.000 m²



d) Concrete Works

The concrete works required:
Reinforcing steel:
50.000 m³
approx. 1.500 tonnes
This is equivalent to approx. 4,160 mixer conveyor trucks or approx. 60 truck loads!

Mechanical-Technical Installations

a) Water Line 

- Coarse screen, fine screen installations with screw conveyor 
- Grit chamber: compressors and shield scraper 
- Preliminary clarifier scraper as shield scraper 
- Final clarifier scraper as chain scraper 
- Mixing device for the dentrification zone 
- Messner plates as ventilation system with frequency controlled compressors 
- Eccentric screw pumps and submersible motor driven pumps (80) 
- Pipelines (approx. 20 km) 
- Pneumatic valves (125) 
- 2 Transformer stations 2 x 630 kVA 
- Approx. 165 km cables' length (energy, control system, light, power) 
- Lime milk dosing device for pH regulation 
- Precipitant solvent station with dosing devices

b) Technical Equipment

Ventilation system cavern and service building 
Heating, ventilation and sanitary installations

c) Sludge Line

Mechanical and static sludge pre-dewatering / strainpress 
Heat exchanger with heat recovery 
Digestion tower turning with gas injection 
Sludge dewatering with belt filter presses 
Sludge drying plant 
Thermal recycling plant

d) Gas Line

Ring membrane gas accumulator 
Block-type thermal power station 
Heating installation

Electro-technical Installations

- Interconnecting station

- Medium voltage switch controls

- Transformer stations (2 x 630 kVA)

- Low voltage rooms caverns

- Low voltage main distributor (2)

- Low voltage subsidiary distributor (10)

- Cabling (165 km)

- No-break power supply installations with 16 kVA each (2)

- Radio telephone facility

- Fire alarm system

- Gas warning installation (60 gas sensors)

- Pneumatic installation

- Intruder alarm

- Process visualisation and data processing

- Mimic switch diagram in the form of a dynamic big screen

- Optic fibre lines

Measurement and Automatic Control Techniques

Measurement technique:

- Temperature sensors 
- Level probes (ultrasonic, pressure and capacitive) 
- pH measuring instruments 
- O2 measuring instruments 
- Dried matter measuring instruments 
- Quantity measuring (IDM, double flow velocity sensors in the sewer) 
- Gas sensors 
- On-line measuring instruments (NO3-N, NH4-N, PO4-P)

Field cabling and on-site service stations 
Substations process control system configuration 
(Simatic S5; CPU 135, 115, 95)

- Analogue input: 4,500 
- Analogue output: 3,000 
- Digital input: 2,500 
- Digital Output: 500

Field bus system and local networks 
Process control level and control technology 
Energy management system (electrical and thermal)

Process Engineering

Primary denitrification

- Denitrification regulation with on-line analysing instruments (see Figure 1) 
- Nitrification regulation with on-line analysing instruments (see Figure 2) 
- Phosphate filling with on-line analysing instruments (see Figure 3) 
- pH value regulation of biology (see Figure 4) 
- Excess sludge regulation with on-line analysing instruments (see Figure 5)

Construction Expenses, Companies Involved, Planning and Supervision of Construction

Construction Expenses

The total costs of the plant amounted to 125 billions Lira - Euro 64,557,112. These costs include the galleries construction, sewage purification plant, service building and access road. 

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Breakdown of Costs
Caverns, access road, and inlet gallery 49 Bn. Lire
Euro 25.306.388
Building contractor's work 33 Bn. Lire
Euro 17.043.078
Mechanical engineering 23 Bn. Lire
Euro 11.878.509
Electronic installations, measurement and automatic control techniques 15 Bn. Lire
Euro 7.746.853
Drying plant 5 Bn. Lire
Euro 2.582.284
Thermal recycling plant Euro 4.300.000

Companies Involved
Constructional component
Fa. PANA S.p.A. Brixen
Fa. UNIONBAU S.r.l. Sand in Taufers
Fa. HOBAG S.p.A. Sand in Taufers
Fa. ZIMMERHOFER S.r.l. Sand in Taufers
Fa. MOSER & CO. S.r.l. Bruneck
Fa. WIESER Karl S.n.c. Mühlen
Mechanical technical equipment
Fa. ATZWANGER S.p.A. Bozen
Electro-technical equipment
Fa. LINEL S.r.l. Bozen
Fa. ELPO S.r.l. Bruneck

Planning and Supervision of Construction
Total project and supervision of construction
Project leader, process engineering, measuring technology and automatic control engineering
Dr. Ing. Konrad ENGL Bruneck
Pre-project - process engineering and consulting
Ingenieurbüro KUSTER & HAGER Schweiz
Gallery ventilation system
PRIGHEL Thermostudio Walter Bruneck
Dr. Ing. Alois STADLER Autonomous province Bozen
P. Ing. Georg SIMEONI Autonomous province Bozen
Manfred STEIN Autonomous province Bozen