bc hydro rock bay remediation project
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›BC Hydro Rock Bay Remediation Project›Management and Technical Achievementsof a Major Remediation ProgramIan Mace, SNC-Lavalin Inc.Ryan Stewart, BC Hydro & Power Authority
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A world leaderFounded in 1911, SNC-Lavalin is one of the leading engineering and construction groups in the world and a major player in the ownership of infrastructure. Fromoffices in over 50 countries, SNC-Lavalin's employees are proud to build whatmatters. Our teams provide EPC and EPCM services to clients in a variety of industrysectors, including oil and gas, mining and metallurgy, infrastructure and power. SNC-Lavalin can also combine these services with its financing and operationsand maintenance capabilities to provide complete end-to-end project solutions.
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Overview
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› Site History
› Tailored Project Management Approach
› Remediation History
› Key Technical Achievements
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Manufactured Gas Plant
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History of Rock Bay
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Rock Bay
1884 Shoreline
Gov
ernm
ent S
treet
Former MGP
Pembroke Street
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Project Management – Working Areas
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Rock Bay
Working Area 4
Working Area 3
Working Area 1
Working Area 2
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Risk Register - Background
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›A Risk Register is a management tool for monitoring the risk management process within the project. It is used to identify, assess and manage risks down to acceptable levels*.
›Risk Register – implemented due to project complexity and importance of overall project schedule.›* https://www.simplilearn.com/risk-management-framework-article
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Risk Register - Implementation
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› Regular ongoing review (every 2 – 3 months)› Risks separated into 40 different categories› Risk levels assigned based on probability and consequence severity
Risk LevelConsequence Severity
Insignificant Minor Moderate Major Catastrophic
Probability
Rare Low Low Low Medium Medium
Unlikely Low Low Medium Medium High
Possible Low Medium Medium High High
Likely Medium Medium High High Very high
Frequent Medium High High High Very high
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Risk Register – “Shelf-Ready” Solutions
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• Early review and engagement with CSAP. Potential concerns were brought forward early allowing them to be addressed.
REGULATORY: CSAP requires more work to be done following
review.
• BC Hydro Project Manager responsible for early communication and negotiation with third parties.
OFF-SITE PARTIES: Inability to conclude working
agreements with off-site third parties.
• Excavation in this area to include all of weathered clay to ensure all DNAPL is removed.
SITE/GROUND/FACILITIES: DNAPL may be present at
greater depth at SW corner of WA3
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Remedial Program – History
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Rock Bay
WA4 Risk Assessment
2014/5 (54,000 tonnes)
2004/5 (110,000 tonnes)
2013 (11,000 tonnes)
2004/5 (130,000 tonnes)
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Preservation of Heritage Buildings
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›Rock Bay (Powerhouse) Building
›Instrumentation Building
›Administration Building
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Shoring Techniques
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›Project size and variability required multiple types of shoring› Options considered based on depth of excavation, stratigraphy, access and
presence of utilities› Project team received input from contractors and BC Hydro construction team
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Shoring Techniques – Secant Wall
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›Secant Wall› Interlocking concrete piles with reinforcing H-piles› Extended to design depth (15.0 m bgs) or keyed into
bedrock› Capable of drilling through 1 – 2 m diameter
sections of rip rap› Excavation to 8 m bgs without slot cutting
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› Identified during the excavation around the perimeter of the Former Instrumentation Building
› 1.9 m diameter / 14 m depth› Estimated to contain 26,000 litres of
coal tar NAPL
Shoring Techniques – Tar Well
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Shoring Techniques – Tar Well
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› Overlapping unreinforced secant piles installed surrounding the tar well
› Tar stabilized in-situ with hog-fuel to satisfy treatment facility requirements
› Tar well void backfilled with CDF to encapsulate any residual contamination
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Shoring Techniques – Sheet Pile
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› Used where rip rap not present / removed mechanically and in areas of utilities› Excavation to 4 to 5 m bgs without slot cutting› Excavation to 8.1 m bgs with additional support and/or slot cutting
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WA3 - Modified Sheet Pile
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›Excavation to the property line was required within HW area at WA3› Sheet pile wall with backing steel plate installed› Material within the void subsequently removed to the depth of excavation (hydrovac)› Minimal water infiltration through sheet pile wall observed.
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Hazardous Waste Transport
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› Reduction of vapours / odours was achieved by wrapping the HW soil with poly
› Reduce potential for spillage during transport
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Stockpile Soil Tracking
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› Soil classified based on in-situ data› Tracking system implemented to insure
proper stockpiling of excavated material› Coloured card provided to driver › Material Movement Approval forms used
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WA3 - Over-excavation into Underlying Clay
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›Purpose: to reduce the potential for residual contamination to negatively effect the post-remediation groundwater quality› Excavation extended 0.5 m into the underlying weathered clay› Within the HW area, excavation extended 1 - 2 m to remove weathered clay
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WA3 - Storm Water Pipe Reroute
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› 0.9 m diameter storm water discharge pipe - southern area of WA3 excavation
› Located in area of HW contamination requiring excavation to 8 m bgs
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WA3 - Storm Water Pipe Reroute
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› Contractor implemented design› Two new manholes installed› Utility rerouted in area previously
excavated using a gravity feed system› Former storm water pipe replaced
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WA4 – Source of Contaminant
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› MGP-contaminants migrated across the bay
› Contaminants deposited at bottom of unfilled Rock Bay and buried (primarily between 1884 to 1918) during the filling of portions of the bay;
› Buried sediments called Bay Bottom Sediment
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WA4 - Approach
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›Risk Assessment of MGP-Sourced Contamination•Contamination
› Difference between pre and post-industrial era sediment quality› Widespread contamination in present from surface to BBS› MGP contaminant of concern in BBS - PAH and LEPH
•CofC Approach
› BC Hydro only responsible for MGP sourced contamination› Residual contamination (within the BBS) addressed by means of risk assessment
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Rock Bay Achievements
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› 11 of 16 Certificates of Compliance with remaining 5 expected shortly› 2017 Association of Consulting Engineering Companies BC – Awards for Engineering
Excellence› 2017 BROWNIE Award› Property ready for
redevelopment
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QUESTIONS?
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