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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.

Singapore – 11 November 2016

Excavation sequenceScanned model

Singapore – 11 November 2016

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.

Singapore – 11 November 2016

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!