WJ News

Latest News and Updates from WJ Groundwater and across the Industry.

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Eductor systems for PATH Toronto

PATH Toronto – the background

Torontonians have long considered near incessant construction on the arterial roads of the city a part of everyday life in a vibrant and ever growing metropolis.

In order to try and minimize this disruption and as part of the development of the new lake front South Core district, a new pedestrian tunnel was required to be constructed underneath York Street, forming part of the PATH pedestrian walkway system that spans more than 30km of downtown Toronto.

Phase 1

Phase 1 of the new tunnel project, under the southbound lanes of York Street, was beset by extensive issues with the dewatering contractor unable to control the seepage flows in to the excavations. This lead to project delays and frustrations for commuters, the City and the General Contractor. One of the most important skills for those in the construction industry is learning from previous projects, therefore for the second Phase of the project, under the northbound lanes, the client was determined to recoup the lost time and therefore adopted a different approach to the project – part of which involved getting WJ on board!

UOIT multilevel excavation
New UOIT development

Meeting project constraints

The General Contractor, PCL, the second largest in Canada, chose to partner with WJ for the tunnel dewatering works upon the recommendations of the structural consultants for the project.

Due to the nature of the site, a small compact rig with a capability of drilling with water flush was essential, therefore we used our trusty SM5 drilling rig to install an eductor dewatering system in Toronto’s characteristic low permeability silty sandy lake deposits which overly the deeper bedrock.

The eductor system was chosen as, based on our extensive experience of working in downtown Toronto, it is best suited to the generally low permeability soils with occasional high permeability layers that are generally encountered.

Ahead of schedule

This installation method and system was so successful we were able to complete our works AHEAD of schedule, and this, coupled with the absence of problematic groundwater in the challenging reclaimed land of the South Core district, enabled the client to make up much of the time lost during the first phase of the works.

  • LOCATION: Toronto
  • MAIN CONTRACTOR: PCL

“This installation method and system was so successful we were able to complete our works AHEAD of schedule.”

WJ wellpoint installation at UOIT September 2019
WJ dewatering in Oshawa
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WJ Group AdminEductor systems for PATH Toronto
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Eductor wells 543 Richmond Condominiums

Our first residential dewatering in Canada

WJ have a long established history of providing dewatering for residential developments in the UK, Middle East and mainland Europe. Whilst 543 Richmond Condominiums will for many just be another block amongst the forest of condos in downtown Toronto, it will always be special to WJ as our first residential dewatering project in the country.

The challenge

As with all city centre projects across the globe, access and space is always at a premium. In the case of the Richmond Condos project, the footprint of the excavation took up almost 100% of the site. This meant space for the installation of dewatering wells and storage of pumping plant and equipment was sparse. However, WJ showed our trademark flexibility by working with the project client to locate our plant, equipment and materials to maximize the available resources.

UOIT multilevel excavation
New UOIT development

Installing eductor wells

The programme of works was key on this project. In order to dewater Toronto’s characteristic silty sandy lake deposits, WJ mobilized two drilling rigs from our extensive, modern drilling fleet to install 55no eductor wells around the perimeter of the excavation.

A successful result

The highly stratified ground conditions, of predominantly low permeability soils with occasional higher permeability layers, made this project challenging… but we love a challenge at WJ and, as of summer 2020, the pumping and construction works are successfully underway, with the first apartments scheduled to open in 2022.

“543 Richmond Condominiums will always be special to WJ as our first residential dewatering project in the country.”

WJ wellpoint installation at UOIT September 2019
WJ dewatering in Oshawa
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WJ Group AdminEductor wells 543 Richmond Condominiums
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Wellpoints at UOIT, Oshawa

The University of Ontario Institute of Technology in Oshawa, located approximately 70km east of WJ’s Head Offices in Toronto, is one of Canada’s leading universities. It was the site of one of our earliest projects in the region not associated with the Crosstown LRT works.

An unexpected dewatering requirement

Groundwater control strategies are conventionally developed during the early planning stages of a project. But it’s not uncommon for unexpected groundwater to be encountered on a project where dewatering was not initially anticipated to be required. In these instances it’s important to be able to mobilise a reliable dewatering contractor to site at short notice to minimize the risk of potentially costly programme delays.

During the early construction works for a new building, housing the Faculty of Health Sciences, Office of Student Life and the new Ontario Tech University Students Union, the client unexpectedly encountered groundwater and got in touch with WJ.

Our response

Fortunately due to our extensive fleet of installation and pumping plant and equipment (not to mention talented and experienced staff!) we were able to prepare an appropriate dewatering design for the works, installation of the system and achieve the desired drawdown all in a few weeks, to the relief of the client.

UOIT multilevel excavation
New UOIT development
WJ’s Baby Giraffe drilling rig installing wells around the perimeter of the UOIT excavation

The approach – innovative wellpoints

The project would comprise a wellpoint dewatering system to dewater the bulk excavation and a deeper central sump structure. Normally an excavation of this depth, size and in these ground conditions would require an expensive perimeter eductor dewatering system.

However with good drilling techniques from our ‘Baby Giraffe’ drilling rig, WJ’s innovative wellpoints, and clever positioning of the pumping equipment, we were able to able to avoid having to install an energy inefficient and space hungry eductor system. This ultimately saved our client $1,000s!

This 100no wellpoint system, was able to achieve drawdown significant enough for the client to dig to 5m depth in dry conditions; a depth which would not normally be considered feasible with this type of system.

Communication was key

Close and regular liaison with the client was vital on this project due to the nature of the works. As the new buildings would be linked in to existing and active buildings on site, space was of a premium.

Additionally the phasing of the construction works had been planned prior to the requirement for dewatering being determined. A deep central sump excavation was amongst the first to be scheduled and as a result a big drawdown was required initially prior to the full system being installed.

Installing the wellpoints with the Baby Giraffe

WJ chose to use the ‘Baby Giraffe’ for both phases of wellpoints. Its extendable mast allowed us to install wellpoints without the need for the construction of excavating rig platforms or access ramps, saving further time and unnecessary expense.

You can learn more about this project on the Ontario Tech University website.

WJ wellpoint installation at UOIT September 2019
WJ dewatering in Oshawa
UOIT Oshawa New Block August 2020

“We were able to able to avoid having to install an energy inefficient and space hungry eductor system, saving our client $1,000s”

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WJ Group AdminWellpoints at UOIT, Oshawa
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Sump Pit Completion at Caledonia Station

The Eglinton Crosstown represents the largest transit expansion in Canada. It will completely change how residents and visitors in Toronto get around this great city. 19 kilometres of new light rail – 10km underground – that starts in the west end and travels right through the city to the east end, with 25 new stations and stops linking to 54 bus routes, three subway stations and various GO transit lines. That means shorter commutes, reliable and convenient transit and cleaner air.

But that kind of huge infrastructure project doesn’t come without more than its fair share of challenges! This was exactly the case at the Caledonia Station site. The ground conditions we encountered there were among the most challenging we’ve had to deal with in WJ’s long and successful involvement with the Eglinton project. However, we were confident that given our decades of experience and industry-leading practices, we were up for the challenge!

Eglinton Crosstown Caledonia Station dewatering
Eglinton Crosstown Caledonia Station dewatering
Eglinton Crosstown Caledonia Station dewatering

Multiple clay layers ran through the site, cutting up the aquifer into many different pieces. Factor in a massive 30m deep excavation, shored by soldier pile and lagging, and we had all the ingredients for a dewatering nightmare.

After coming in to rescue project developers, CTS, from an inferior dewatering system that couldn’t tackle these site conditions, WJ got to work with Crosslinx to uncover these layers. Our expert water management consultants deciphered the geology of ancient glacial lake bottom deposits that lay buried deep underground across Toronto.

However, in the world of dewatering, clay is clay. No matter how thin, a continuous layer can quickly change dewatering requirements.

Our deductions were proved correct when we uncovered a 1-inch thick layer of clay across the entire site. Working tireless to dewater each and every layer, WJ battled the water towards the base of the sump pit. From there. our sump pit dewatering actions provided a site suitable for CTS to complete their excavation and commence construction of the station from the bottom-up.

Eglinton Crosstown Caledonia Station dewatering
Eglinton Crosstown Caledonia Station dewatering
Eglinton Crosstown Caledonia Station dewatering

“WJ helped the Caledonia team through some very challenging conditions at Caledonia. They were committed and worked with us every step of the way. WJ’s can-do attitude was refreshing and much appreciated on this difficult and challenging site.”

– Daniel Sanchez, Project Manager, Caledonia and Keelesdale Stations.

Eglinton Crosstown Caledonia Station dewatering
Eglinton Crosstown Caledonia Station dewatering
Eglinton Crosstown Caledonia Station dewatering
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WJ Group AdminSump Pit Completion at Caledonia Station
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Quick Turnaround Dewatering at Science Centre Station

Being the largest transit expansion in Canada, with significant on-going disruption to Toronto’s population, any delay to the development of Eglinton Crosstown LRT is not welcome news. Especially when that delay is totally unexpected. That’s exactly what happened when the construction crew discovered groundwater where there wasn’t supposed to be any!

Early one morning, WJ Canada received a call for help. The CTS construction team, working at the Science Centre Station, encountered groundwater at the bottom of the excavation. The Science Centre Station is the longest excavation on the entire Eglinton Crosstown project, at 800m in length, with the deepest part being underneath Don Mills Road.

dewatering at Science Centre Station
dewatering at Science Centre Station
dewatering at Science Centre Station

According to a previous hydrogeological investigation, there was not supposed to be water present. Yet, to their surprise, as the CTS crew approached the bottom of an aquifer on a clay Till, they were greeted by approximately 1m of water. This prevented the last section of excavation and concrete placement. It also meant a potentially serious delay to the project!

Once we’d received CTS’s call for help, WJ was on-site within just a few days and we wasted no time in getting straight to work. This involved drilling inclined well-points on both the north and south side of the excavation. We worked from the bottom of the shaft, through the lagging wall, and got the entire system commissioned in record time.

dewatering at Science Centre Station
dewatering at Science Centre Station
dewatering at Science Centre Station

Just two weeks after receiving their call for help, WJ had dewatered the Science Centre Station site. CTS were able to resume excavation in dry conditions. Within 3 months, CTS had completed all concrete and waterproofing systems and WJ was able to decommission the system.

“WJ came in on very short notice and executed a professional and effective dewatering solution. Their solution was cost effective and efficient as the wells were short and installed from the base of the excavation. The solution was tailored to our needs as they allowed us to complete our station build-back all the while remaining functional behind the waterproofing membrane. I would recommend WJ to any contractor in need of a dewatering partner.”

– Diego Ocampo, Project Manager, Science Centre Station

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WJ Group AdminQuick Turnaround Dewatering at Science Centre Station
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Cross Cut Completion at Oakwood Station

The Eglinton Crosstown Light Rail Transit (ECLRT) project consists of 19.7 km of light rail transit running along Eglinton Avenue from Mount Dennis in the west to Kennedy in the east. The project is being designed and constructed by Crosslinx Transit Solutions (CTS).

With such an important and flagship infrastructure project, under constant public scrutiny, given the build disruption to local communities, the stakes were high. CTS needed a true water management partner who would work with them right through to the end.  And that’s where WJ came in.

WJ was called in from the UK to take a look at dewatering requirements of the Eglinton Crosstown Project – a challenging commission, which combines difficult dewatering conditions with innovative construction techniques. Several of the stations within the Eglinton project are being constructed using a unique soil mining technique, known as the New Austrian Tunnelling Method. This meant that our dewatering solutions had to be just as innovative in order to succeed.

Right from the start, the Oakwood main entrance access (called the cross-cut) was flagged as the most challenging aspect of the project. A silty, low-permeability soil matrix that fines towards the bottom of the excavation was located just above a clay interface. Using, wellpoints, ejectors, and deep wells, from the road surface and from confined spaces in TBM tunnels and mined caverns, WJ was able to complete this substantial dewatering feat, without any delay to the CTS mining schedule.

As everyone in mining knows: the mining can never stop!

WJ ensured it never did.

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WJ Group AdminCross Cut Completion at Oakwood Station
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Provost Driver Court, Renfrew

This contract took WJ to Renfrew, in the suburbs of Glasgow, not far from our Scottish Office in the Scottish capital, to help contribute to an award winning project.

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Dan CarpenterProvost Driver Court, Renfrew
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Royal Hospital For Sick Children, Edinburgh

The Royal Hospital for Sick Children has been based on it’s existing site in the heart of Edinburgh since 1895, however in 2005 it was decided by the local NHS Trust that a more modern facility should be constructed adjacent to the existing Edinburgh Royal Infirmary at Little France on the south-east edge of the city.

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Dan CarpenterRoyal Hospital For Sick Children, Edinburgh