OSPE - The Voice - Winter 2019 - 35

COVER

the groundwater drawdown to as
close to the sand-clay interface
as practically feasible, while
highlighting that construction
would remain demanding.
The ground held many
challenges. Excavation unearthed
three thin clay horizons within
the rarely excavated lower part of
the aquifer, ranging between a few
inches and a few feet in thickness.
Critically, regardless of the
thickness, a continuous clay layer
inhibits the downward drainage
of water, significantly reducing
the effectiveness of the surface
dewatering system in achieving
the drawdown to the base of the
excavation. A contingency plan
was implemented comprising
arrays of wellpoints targeting the
clay interfaces, installed from
various locations within the machine-bored tunnels and from
within the partially completed mined cavern. WJ implemented
24-hour operations within the tunnels to make sure that the
ground was always dry ahead of the excavation. WJ was able to
complete this feat, without any delay to the mining schedule.
This is significant, as NATM construction costs run to tens of
thousands of dollars a day, and as everyone who knows anything
about NATM works: the mining can never stop!

Groundwater drawdown models of Eglinton Station

Even with more than half the caverns complete, the dewatering
along Eglinton remains a day-to-day challenge. Tight timelines
and access constraints requires a collaborative and flexible team
able to adapt to the new demands that this exciting project
brings. As WJ's dewatering efforts continue to be successful,
we are achieving what we set out to do by providing a quality
service and innovative solutions in a unique and challenging
construction environment.

Clay interfaces within the soil matrix
encountered at the bottom of the
excavation at Oakwood Station

Winter 2020

THE VOICE

35



OSPE - The Voice - Winter 2019

Table of Contents for the Digital Edition of OSPE - The Voice - Winter 2019

OSPE - The Voice - Winter 2019 - Cover1
OSPE - The Voice - Winter 2019 - Cover2
OSPE - The Voice - Winter 2019 - 3
OSPE - The Voice - Winter 2019 - 4
OSPE - The Voice - Winter 2019 - 5
OSPE - The Voice - Winter 2019 - 6
OSPE - The Voice - Winter 2019 - 7
OSPE - The Voice - Winter 2019 - 8
OSPE - The Voice - Winter 2019 - 9
OSPE - The Voice - Winter 2019 - 10
OSPE - The Voice - Winter 2019 - 11
OSPE - The Voice - Winter 2019 - 12
OSPE - The Voice - Winter 2019 - 13
OSPE - The Voice - Winter 2019 - 14
OSPE - The Voice - Winter 2019 - 15
OSPE - The Voice - Winter 2019 - 16
OSPE - The Voice - Winter 2019 - 17
OSPE - The Voice - Winter 2019 - 18
OSPE - The Voice - Winter 2019 - 19
OSPE - The Voice - Winter 2019 - 20
OSPE - The Voice - Winter 2019 - 21
OSPE - The Voice - Winter 2019 - 22
OSPE - The Voice - Winter 2019 - 23
OSPE - The Voice - Winter 2019 - 24
OSPE - The Voice - Winter 2019 - 25
OSPE - The Voice - Winter 2019 - 26
OSPE - The Voice - Winter 2019 - 27
OSPE - The Voice - Winter 2019 - 28
OSPE - The Voice - Winter 2019 - 29
OSPE - The Voice - Winter 2019 - 30
OSPE - The Voice - Winter 2019 - 31
OSPE - The Voice - Winter 2019 - 32
OSPE - The Voice - Winter 2019 - 33
OSPE - The Voice - Winter 2019 - 34
OSPE - The Voice - Winter 2019 - 35
OSPE - The Voice - Winter 2019 - 36
OSPE - The Voice - Winter 2019 - 37
OSPE - The Voice - Winter 2019 - 38
OSPE - The Voice - Winter 2019 - Cover3
OSPE - The Voice - Winter 2019 - Cover4
https://www.nxtbook.com/dawson/ospe/thevoice_2021winter
https://www.nxtbook.com/dawson/ospe/thevoice_2021summer
https://www.nxtbook.com/dawson/ospe/thevoice_2020Winter
https://www.nxtbook.com/dawson/ospe/covid_19_Provincial
https://www.nxtbook.com/dawson/ospe/covid_19_Federal
https://www.nxtbook.com/dawson/ospe/thevoice_2020Fall
https://www.nxtbook.com/dawson/ospe/thevoice_2020summer
https://www.nxtbook.com/dawson/ospe/thevoice_2020spring
https://www.nxtbook.com/dawson/ospe/thevoice_2019winter
https://www.nxtbook.com/dawson/ospe/thevoice_2019fall
https://www.nxtbook.com/dawson/ospe/thevoice_2019May
https://www.nxtbook.com/dawson/ospe/thevoice_2019March
https://www.nxtbook.com/dawson/ospe/thevoice_2018dec
https://www.nxtbook.com/dawson/ospe/thevoice_2018Sept
https://www.nxtbook.com/dawson/ospe/thevoice_2018june
https://www.nxtbook.com/dawson/ospe/thevoice_March2018
https://www.nxtbook.com/dawson/ospe/thevoice_december2017
https://www.nxtbook.com/dawson/ospe/thevoice_September2017
https://www.nxtbook.com/dawson/ospe/thevoice_June2017
https://www.nxtbook.com/dawson/ospe/thevoice_March2017
https://www.nxtbook.com/dawson/ospe/thevoice_2016winter
https://www.nxtbook.com/dawson/ospe/thevoice_september2016
https://www.nxtbook.com/dawson/ospe/thevoice_june2016
https://www.nxtbook.com/dawson/ospe/thevoice_march2016
https://www.nxtbook.com/dawson/ospe/thevoice_december2015
https://www.nxtbook.com/dawson/ospe/thevoice_2015fall
https://www.nxtbook.com/dawson/ospe/thevoice_2015summer
https://www.nxtbook.com/dawson/ospe/thevoice_2015winter
https://www.nxtbook.com/dawson/ospe/thevoice_2014fall
https://www.nxtbook.com/dawson/ospe/thevoice_2014spring
https://www.nxtbook.com/dawson/ospe/thevoice_2013fall
https://www.nxtbook.com/dawson/ospe/thevoice_2013summer
https://www.nxtbook.com/dawson/ospe/thevoice_2012fall
https://www.nxtbookmedia.com