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Innovative Use of Sliding Rail Shoring, Installation of
Vertical Hanging Barriers, & Under Pinning
SMART Remediation Toronto
By: Gerry Parrott, P.Geo., QP & Shannon Marceau
CLAYBAR
January 2016
CONTRACTING INC.
Topics
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Site Setting
Objectives
The Game Plan
Constraints
Scope Developed
Shoring Options and Shoring Cost Evaluation
What We Did, How It Worked, & Challenges
Key Factors That Led to Success
Site Setting
• 1950s, two storey commercial/industrial building
in an industrial subdivision in north Toronto
• 700 m2 building occupied about a third of the 2.5
acre property
• Location of a 24 hour, 7 day-a-week call-centre
• Adjacent manufacturing buildings to the north
and south, road to the east, residential to the
west
Site Setting
Environmental Conditions
• Table 3 (non-potable) site condition standards,
medium and fine textured soils
• COCs were BTEX and PHC fractions F1 to F3
• Free product observed in soil north and south of the
building, but not under building
• Perched water table (~2m) and deeper aquitard
(~6m) that was historically breeched
• Impact from 4, former USTs; 2 on the north side, 2
on the south side
Objectives
• Comply with TSSA Order to i)
remove USTs, ii) delineate, and iii)
implement remedial plan
• Conduct work while operations
(call-centre) continued
• Remove as much source (impacted
soil and groundwater) as possible
and all free product
• Prevent further migration off-Site
The Game Plan
• Our Game Plan, in a nut-shell:
• Excavate impacted soil and
groundwater around building,
under footings, and ~1 m under
building
• Install property line barriers
• Assess vapour intrusion risk
• Conduct due diligence risk
assessment
• Sounds simple enough, right?
Let’s see….
Constraints
Constraints
• Building could NOT be vacated (call-centre)
• Free product under and adjacent to exterior of footings
• How do we remove product with a +50 year old building that can’t be
vacated?
• Un-cooperative neighbours to the north and south = no
access (and no off-Site investigation – but that’s another storey)
• 6 m to north property line, then 4 m more to edge of building
(~10 m wide strip)
• 7.5 m to south property line, then 1 m more to edge of
building (~8 m wide strip)
• Deep excavation (up to 7 mbgs at some locations)
Constraints
• Free product adjacent footings
Constraints
• View of North laneway
Scope of Work
• Use a shoring system along property lines to facilitate
excavation of impacted soil and groundwater beyond
building footprint and up to property lines – but don’t go
off-Site!
• Install property line barriers – or don’t bother doing any
work at all…
• Underpin foundation and up to ~1m under building to
remove liquid product
• Conduct soil vapour intrusion assessment
• Implement risk management plan after completion of
due diligence RA
Shoring Challenge
• What shoring will work…
• In the limited space available?
• That allows us to install a liner along the property
lines (81 linear metres)?
• Up to 7m deep
• That’s cost effective
• And won’t hinder, and may even help us to install
underpinning
Shoring Options – Caisson Walls
PROS
CONS
 Liner easy to X Expensive
install
 Good
X Long duration
structural
support
 Tried and true X Need space
X Have to go offSite
X Part of wall will
be off-Site
Shoring Options – Lagging and Piling
PROS
CONS
 Liner easy to X Expensive
install
 Good
X Long duration
structural
support
 Tried and true X Need space
X Have to go offSite
X Tie backs offSite
Shoring Options – Sheet Piling (Waterloo)
PROS
 Built-in liner
CONS
X Expensive
 Easy to install X Long duration
 Good
X Need space
structural
support
 Tried and true X Have to go offSite
Shoring Options – Sliding Rail Shoring
PROS
CONS
 Can install
liner
X Depth
limitations
 No need to
access offSite*
X Little structural
support
 Quick
 Lowest cost
Shoring Costs
• Conventional shoring requires off-Site access
• Even if that could have been addressed, the cost for 80 m
of Caisson shoring was estimated to be ~$500k
• Sliding Rail Shoring: $150k; < ½ the cost of conventional
shoring
Option
Cost
Caisson Walls
$650/m2 + excavation costs
Soldier Piling
$550/m2 + excavation costs
Sheet Piling
$450 to $650 (Waterloo) + excavation costs
Sliding Rail
$150/m2 (including excavation costs!)
What We Did
• North portion completed December 2015
• Installed sliding rail shoring between building and property line to
approx. 5 mbgs to 7.5 mbgs
• Placed 2 cells in series to facilitate installation of liner
What We Did
https://www.youtube.com/watch?v=7MR53K4LcVA
What We Did
• Installing Liner
What We Did
• Liner Material (Paraseal R)
• Self-sealing expandable layer of granular
bentonite laminated to HDPE
• Permeability 2.7x10-13
What We Did
Excavated 23, 1.2 m
wide slots below
building foundation,
and ~1m under
building, in a piano key
fashion, and backfilled
with 10 MPa concrete
Challenges and Solutions
Challenge...
• Deep excavation for
sliding rail
Solution!
• Stripped top 2 m then
started sliding rail
Challenges and Solutions
Challenge...
• Installing posts causing too
much vibration
Solution!
• Pre-drill posts
Challenges and Solutions
Challenge...
• Very Soft Clay >5 mbgs
bowing up from base of cells
Solution!
• Excavate last 2m in each cell
under supervision of geotech
engineer and backfill
immediately after reaching
target depth
Challenges and Solutions
Challenge...
• How do we “hold up” soil
behind footings and under
floor slab when excavating
under building
Solution!
• Install re-bar through
foundation to hold up soil like a
basket
Challenges and Solutions
Challenge...
• How do we install the sliding
rail on the property when the
track is centred on the corner
posts
Solution!
• Claybar modified the corner
post rail system so panels slide
on the outside of the posts
Key To Success
1. Non-routine projects require a team of experts, not
any one individual
2. Problems often have simple solutions if you think
outside of the box and brainstorm with the Team
3. Never assume there aren’t any options – don’t settle
for the status quo
4. The cost for up-front planning, strategizing and brainstorming can be the best money spent and ultimately,
can save lots of $s in the end
5. Get a good team, with experience, and the willingness
to be your Trusted Advisor
Thank You – Questions?
Gerry Parrott, P.Geo.
T: 416 407 9769
Hemmera
Shannon Marceau
T: 416 819 7313
Claybar Contracting
CLAYBAR
CONTRACTING INC.