Turbidity Barriers Turbidity Barriers –– Mine Site Reclamation ProjectMine Site Reclamation Project

Presented by: Murray Banting, R.E.T.

Turbidity Curtains Turbidity Curtains -- HistoryHistoryFirst put to use in early 1970First put to use in early 1970’’s. Got s. Got started in logging industry when nets started in logging industry when nets were suspended from log booms to catch were suspended from log booms to catch log debris. Later the nets were replaced log debris. Later the nets were replaced with fabrics such as canvas to confine mud with fabrics such as canvas to confine mud and finer debris. The term and finer debris. The term ““LogLog”” still is still is used today to describe the floating PVC used today to describe the floating PVC and polyand poly--booms used today. booms used today.

Bottom Anchor

Boom/FloatsTensioning Cable

Permeable Silt Skirt

AGES Turbidity CurtainTypical Detail

Depth Variesto suit max. waterdepth

Curtain bottom conforms toriver bed to block suspendedparticles

Low WaterHigh Water

A turbidity curtain or barrier consists of a floating top boom section attached to a skirt constructed of either impermeable or permeable materials. The skirt is equipped with a ballast chain or other weight to anchor and “seal” it to the bottom.

Turbidity Barriers optional anchoring detailsTurbidity Barriers optional anchoring details

Typical Applications of Turbidity BarriersTypical Applications of Turbidity Barriers1.) Minimize migration of fines during in1.) Minimize migration of fines during in--water water construction construction –– i.e.: intake structures, pipeline i.e.: intake structures, pipeline crossings, lakeshore rehabilitation, etc.crossings, lakeshore rehabilitation, etc.2.) Spill containment 2.) Spill containment –– booms and curtains used booms and curtains used to confine sludge or floating debris to specific to confine sludge or floating debris to specific areas.areas.3.) To create 3.) To create forebaysforebays in sedimentation ponds, in sedimentation ponds, storm water ponds, tailings ponds to replace storm water ponds, tailings ponds to replace conventional earthenconventional earthen--fill dykes.fill dykes.4.) To trap pollutants suspended in the water 4.) To trap pollutants suspended in the water column column –– i.e.: protect water intakes, beaches etc.i.e.: protect water intakes, beaches etc.

Storm Pond - Bridlewood

Advantages over conventional meansAdvantages over conventional means

-- Low cost compared to other permanent structuresLow cost compared to other permanent structures-- Portable, movable and able to install rapidlyPortable, movable and able to install rapidly-- Minimal disturbance to environmentMinimal disturbance to environment-- Minimal access required Minimal access required –– usually deployed fromusually deployed from

a small boat by handa small boat by hand-- Regulatory authorities (DFO) are familiar with Regulatory authorities (DFO) are familiar with turbidity curtains and recommend use.turbidity curtains and recommend use.

Air Photo of BayAir Photo of Bay

Photo of Galena Bay looking southPhoto of Galena Bay looking south

17 km

Blue Bell mineBlue Bell mineProject: Located on east shore of Project: Located on east shore of Kootenay Kootenay Lake approx. Lake approx.

75 km N. of Creston 75 km N. of Creston Project Engineers: Project Engineers: Bel Bel MK MK –– CalgaryCalgaryEnvironmental Monitors: Environmental Monitors: Morrow EnvironmentalMorrow Environmental--

Cranbrook Cranbrook Contractor: Contractor: McKay Const.McKay Const.-- KimberlyKimberlySupplier of Turbidity Curtains: Supplier of Turbidity Curtains: AGES Inc. CalgaryAGES Inc. Calgary

Project ParticipantsProject Participants

Remedial DesignRemedial Design

•• Source removal was selected as the remedial Source removal was selected as the remedial approach.approach.

•• Necessary to recover process fines to a depth of Necessary to recover process fines to a depth of 0.5 m below low water to prevent ARD/ML.0.5 m below low water to prevent ARD/ML.

•• Cap process fines to a depth of Cap process fines to a depth of 5 m5 m below low below low water.water.

•• Construct an engineered beach that would resist Construct an engineered beach that would resist becoming rebecoming re--contaminated by offshore tailings contaminated by offshore tailings during peak storm events.during peak storm events.

Challenges associated with implementing the remedial Challenges associated with implementing the remedial design included:design included:

1)1) Recovering contaminated sediments from Recovering contaminated sediments from KootenayKootenay Lake;Lake;

2)2) Constructing a beach that would cap Constructing a beach that would cap submerged contaminated sediments;submerged contaminated sediments;

3)3) PPreventing contamination of the lake by reventing contamination of the lake by sediment and/or metalsediment and/or metal--containing water; andcontaining water; and

4)4) OObtaining necessary approvals and permits in btaining necessary approvals and permits in a ninea nine--week period. week period.

Remedial DesignRemedial Design

1)1) Build a temporary dam across the bay, Build a temporary dam across the bay, dewater and work in a dewater and work in a ““drydry”” environment. environment.

2)2) Build a temporary dyke across the bay and Build a temporary dyke across the bay and work in a saturated environment. work in a saturated environment.

3)3) IInstall sheet piling and work in a saturated nstall sheet piling and work in a saturated environment.environment.

4)4) IInstall floating silt barriers and work in a nstall floating silt barriers and work in a saturated environment. saturated environment.

Working in Lake Working in Lake -- OptionsOptions

Selected Approach to Working in LakeSelected Approach to Working in Lake•• Floating silt barriers were selected as the Floating silt barriers were selected as the

preferred approach to working in the lake due preferred approach to working in the lake due to:to:-- Minimal disruption to bottom of bay;Minimal disruption to bottom of bay;-- Quick deployment;Quick deployment;-- Bay geometry;Bay geometry;-- History of successful use in marine History of successful use in marine

environments in the USA; andenvironments in the USA; and-- Cost effectiveness.Cost effectiveness.

Turbidity Curtain Assembly & InstallationTurbidity Curtain Assembly & Installation

Siltation Siltation Barrier Material/ConstructionBarrier Material/Construction

Turbidity Curtain DeploymentTurbidity Curtain Deployment

Adding oil absorbent skimmerAdding oil absorbent skimmer

Recovery of Deep Process Fines Recovery of Deep Process Fines

300 NTU 300 NTU vs vs 3 NTU3 NTU

Lake Water Quality on May 4th, 2001 Lake Water Quality on May 4th, 2001

Tota

l As

Dis

. As

Tota

l Cd

Dis

. Cd

Tota

l Pb

Dis

. Pb

Tota

l Zn

Dis

. Zn

TSS

Turb

idity

Outside Secondary

Inside SecondaryOutside Primary

Inside Primary0

50

100

150

200

250

ug/L (Metals)

mg/L (TSS)

NTU (Turbidity)

Can turbidity curtains fail ?Can turbidity curtains fail ?Yes Yes -- Most turbidity curtain projects are Most turbidity curtain projects are required only in difficult situations. Any required only in difficult situations. Any marine environment exposes many marine environment exposes many hazardous and often unpredictable hazardous and often unpredictable situations. Build in safety factors such as situations. Build in safety factors such as redundancy, extra strength, heavy cables redundancy, extra strength, heavy cables and robust materials are important. and robust materials are important. Monitoring and inspection on regular Monitoring and inspection on regular basis also important.basis also important.

Compromised ContainmentCompromised Containment

…and just when you thought it was safe to go in the water….

Mud slide occurred on lake bottom due to earthwork activities and unstable fine deposits. Additional weight of the new fill and constant vibration was determined to be cause of rapid slumping of debris along sloping lake shore below water level.

AGES Inc.

Repair work being done on shore once curtains pulled from lake. Excavator and tug boat used to extract curtains from under debris.

Damage caused Damage caused to sides of to sides of curtain from curtain from mud slide and mud slide and removal efforts.removal efforts.

Performance of Containment SystemPerformance of Containment System

0.1

1

10

100

1000

3/20 3/30 4/9 4/19 4/29 5/9 5/19 5/29 6/8 6/18

Date (month/day)

Tu

rbid

ity (

NT

U)

Inside Primary Inside Secondary Outside Secondary DATE

Sediment Transport ControlSediment Transport Control

Exposed Final Upper ForeshoreExposed Final Upper Foreshore

Beach ReconstructionBeach Reconstruction

Evaluation of Sediment Control ProgramEvaluation of Sediment Control Program

•• The floating silt barriers were effective in The floating silt barriers were effective in minimizing the transport of contaminants further minimizing the transport of contaminants further into Galena Bay.into Galena Bay.

•• Floating silt barriers were an appropriate control Floating silt barriers were an appropriate control method given the environmental settingmethod given the environmental setting..

•• Open communication with regulatory agencies Open communication with regulatory agencies resulted in a positive, cooperative working resulted in a positive, cooperative working relationship.relationship.

Evaluation of Sediment Control ProgramEvaluation of Sediment Control Program

•• Intercepting groundwater seepage and diverting Intercepting groundwater seepage and diverting HammilHammil Creek prevented an unnecessary flux of Creek prevented an unnecessary flux of water and sediment into the contained area.water and sediment into the contained area.

•• Working from Working from ““top downtop down”” minimized the amount of minimized the amount of time that the contractor was working below low time that the contractor was working below low waterwater..

•• PitPit--run fill material with a lower percentage of silt run fill material with a lower percentage of silt would have reduced the sediment loading to the would have reduced the sediment loading to the curtain.curtain.

Evaluation of Sediment Control ProgramEvaluation of Sediment Control Program

•• The primary containment barrier was deployed too The primary containment barrier was deployed too close to shore.close to shore.

•• The design of the other barrier components could be The design of the other barrier components could be improved to function better in a lake environment.improved to function better in a lake environment.

•• Earlier routine underwater inspections may have Earlier routine underwater inspections may have resulted in resulted in mitigativemitigative action being taken sooner in action being taken sooner in some situations.some situations.

Thank YouThank You

www.ageswww.ages--corp.comcorp.comGo to Project Updates for a PDF file of article Go to Project Updates for a PDF file of article

published on this project.published on this project.

Special thanks to Morrow Environmental Special thanks to Morrow Environmental Consultants for technical data & photosConsultants for technical data & photos