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Singapore – 11 November 2016
Underground Waste
Depositing at Odda, Norway
Anne Hommefoss, MSc.
Engineering Geologist
Multiconsult ASA, Oslo, Norway
Underground Waste Depositing at Odda – Anne Hommefoss
Singapore – 11 November 2016
Stakeholders
Owner: Boliden Odda AS
Site management: Boliden Odda AS
Contractor caverns no. 17 and no. 18: Lemminkäinen Norway AS
Contractor caverns no. 15 and no. 16: Skanska Norway AS
Contractor caverns no. 13 and no. 14: NCC Construction AS
Design and geological supervision: Multiconsult ASA
Environmental consultant: Multiconsult ASA
Underground Waste Depositing at Odda – Anne Hommefoss
Singapore – 11 November 2016
Underground Waste Depositing at Odda, Norway
- Boliden Odda AS zinc refinery plant is located on the southwest coast of Norway.
- Founded in 1924.
- The world’s fifth largest producer of zinc metal from smelters
- Eight largest producer of metal in concentrate from mines.
- The repository is located 2 km from the zinc plant.
Singapore – 11 November 2016
History- Waste from zinc refining was discharged directly to the narrow fjord at Odda.
- Created a severe pollution problem.
- The narrow fjord in Odda were previously called «The most contaminated fjord in theworld».
- State Pollution Control Authority asked Boliden to develop an alternative method of wastedisposal.
- After 1st of July 1986 no discharge of residue to the fjord was permitted!
- Depositing in rock caverns was the most attractive alternative.
1958 1970 1992 2004
Singapore – 11 November 2016
Today Boliden Odda is probably the most environment
friendly zink production plant in the world!
- Studies for alternative disposal of waste started in 1975.
- The rock formation Mulen, 2 km from the zink plant, was selected as location
for caverns.
- Solid waste are mixed with water – form a slurry.
- The slurry is transported through a 2 km long pipeline to the storage
caverns.
- Today, the storage plant consists of 18 caverns and about 1 km connecting
tunnels.
Singapore – 11 November 2016
Singapore – 11 November 2016
First generation of caverns
- First generation caverns, no. 1-12
- Total volume of these caverns
varies from 65.000m3 to
140.000m3.
- Excavation is by drill and blast
method, top heading and
benching.
- Rock support mainly consists of
bolts, and a minimum of shotcrete.
- A pipeline system in the cavern
roof transports slurry into the
caverns.
Singapore – 11 November 2016
Second generation caverns
- The second generation caverns is a result of a more comprehensiveengineering process.
- Cavern no. 13: storage capacityof 180.000m3.
- Cavern no. 14: storage capacityof 210.000m3.
- Cavern no. 17 and no. 18 (completed in 2013 and 2014): 25 m wide, 60-63 m high and 250 m long – storage capacity of300.000m3.
- In the future the caverns will be even larger.
- A preliminary goal is cavernvolumes of 400.000m3.
Singapore – 11 November 2016
Geological- and hydrogeological conditions
- The main reason for storing the material inside the caverns is to prevent
hazardous heavy metals from reaching the biosphere.
- Rock quality has been a key factor for location and design of the storage.
- The rock has low permeability, and the gradient is into the cavern.
Singapore – 11 November 2016
Singapore – 11 November 2016
Excavation
- New caverns are carried out to a deeper level by introducing an additional
access tunnel 30 m below the main level.
- Heading and bench are excavated by drill and blast
- The lower tunnel serves as transport opening for the rock mass.
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Excavation sequenceScanned model
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Rock support- During and after the second level of
benching, the roof is checked manuallyfrom lifting platforms.
- The rock stress level is high, resulting in rock spalling and some cracking sounds.
- Systematic patterns of end-anchored bolts (4-5 m long) and steel fibre reinforcedshotcrete (E1000,80mm).
- Stabilizing local jointing and weaknesszones; grouted rebar bolts and thickershotcrete.
- Systematick rock support of the wall area; 7 m long grouted 2 pcs 16 mm steelstrands per hole, spacing of 4 m.
- Additional support of jointed rock at thesurface; end-anchored 2-4 m long rock bolts, supplemented by fiber reinforcedshotcrete.
Singapore – 11 November 2016
Controlled dispose of blasted rock
- Barge is used for controlled dumping into the 130 m deep fjord.
- Covering existing contaminated deposits in the fjord.
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Sub-title
Top heading excavated Installation of rock support
Scaling after excavating twobenches
Scaling after threebenches Fourth bench is
starting
Singapore – 11 November 2016
Singapore – 11 November 2016
Scanning of cavern no. 18
Singapore – 11 November 2016
Cavern and sea water level
Singapore – 11 November 2016
Sub-titleThank you
for yourattention!