Underground Waste Depositing at Odda, Norway

Transcription

1 Underground Waste Depositing at Odda, Norway Anne Hommefoss, MSc. Engineering Geologist Multiconsult ASA, Oslo, Norway Underground Waste Depositing at Odda Anne Hommefoss

2 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

3 Underground Waste Depositing at Odda, Norway - Boliden Odda AS zinc refinery plant is located on the southwest coast of Norway. - Founded in 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.

4 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 the world». - State Pollution Control Authority asked Boliden to develop an alternative method of waste disposal. - After 1st of July 1986 no discharge of residue to the fjord was permitted! - Depositing in rock caverns was the most attractive alternative

5 Today Boliden Odda is probably the most environment friendly zink production plant in the world! - Studies for alternative disposal of waste started in 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.

6

7 First generation of caverns - First generation caverns, no Total volume of these caverns varies from m 3 to m 3. - 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.

8 - The second generation caverns is a result of a more comprehensive engineering process. - Cavern no. 13: storage capacity of m 3. - Cavern no. 14: storage capacity of m 3. - Cavern no. 17 and no. 18 (completed in 2013 and 2014): 25 m wide, m high and 250 m long storage capacity of m 3. - In the future the caverns will be even larger. - A preliminary goal is cavern volumes of m 3. Second generation caverns

9 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.

10

11 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.

12 Excavation sequence Scanned model

13 Rock support - During and after the second level of benching, the roof is checked manually from 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 reinforced shotcrete (E1000,80mm). - Stabilizing local jointing and weakness zones; grouted rebar bolts and thicker shotcrete. - Systematick rock support of the wall area; 7 m long grouted 2 pcs 16 mm steel strands per hole, spacing of 4 m. - Additional support of jointed rock at the surface; end-anchored 2-4 m long rock bolts, supplemented by fiber reinforced shotcrete.

14 Controlled dispose of blasted rock - Barge is used for controlled dumping into the 130 m deep fjord. - Covering existing contaminated deposits in the fjord.

15 Sub-title Top heading excavated Installation of rock support Scaling after excavating two benches Scaling after three benches Fourth bench is starting

16

17 Scanning of cavern no. 18

18 Cavern and sea water level

19 Thank you Sub-title for your attention!