What A Blast
The OBUC overdevelopment is mainly planned for the space currently occupied by car parking.
To replace these parking spaces and provide an inadequate number of spaces for the residents, visitors and congregation, the OBUC are proposing an underground parking garage.
The creation of the underground car park will require extensive blasting through solid granite (the entrance of the parking garage is on Granite Street). But this is not normal granite - the Geological Survey of Canada says this is harder than normal granite. The granite has metamorphosed and recrystallised.
The developers have made available their geotechnical report
This webpage has 4 sections:
1. An analysis of the geotechnical report
2. A review of the dangers of blasting, particularly carbon monoxide percolating through the rock into surrounding houses
3. A review of literature on urban blasting
4. Insurance and Inspections
1. An analysis of the geotechnical report
Some members of the CCN-OakBay have analysed the report from a layman’s point of view. A copy of the report, with passages marked, is available here
The highlights of the report follow, in page number order. Comments or observations are in italics:
Page 1 Details of 1.8 m / 6’ retaining wall
Another document states this retaining wall is to be demolished and replaced.
Under Oak Bay Zoning Bylaw 4.17.1 "No retaining wall shall have an exposed face with a vertical distance from bottom to top exceeding 1.2 m (3.9 ft). "
We have not seen a zoning variance requesting permission for this over height, dangerous, retaining wall. Will there be a child-proof fence at the top of this wall, especially as some family units are planned?
Page 1 “… the south where one corner of the parkade would extend all the way to the church”.
Are the congregation aware of this?
Looking at the plans, during construction there will be a 23’ / 7 m deep hole within 1’ / 30 cm of the foundations of the church building.
This image is part of the next image showing the drill holes and shows how close the excavation is to the church building. Plans of the underground car parking (obtained under a Freedom of Information Request) show the excavation to be even closer to the existing building.
Page 2 They tested the ground with a drill to see find how deep the soil went before they hit bedrock.
At the northern edge of the property the bedrock is only 0.2 m below ground surface.
0.2 m is only 8", so bedrock is very close to the surface at the front of the site. They don’t know how deep the bedrock is, but they assume it to be solid.
As can be seen, below, the test holes only cover about 1/3 of the area to be excavated so it hasn’t been established how deep the bedrock is on most of the site.
Page 3 As noted above, the south corner of the parkade would extend all the way to the church.
The report states “Underpinning or shoring below the existing church will be required, the extent of which will depend on the depth of the existing footings, the horizontal distance from the excavation, and the thickness of the soils overlying bedrock. Minimal shoring is anticipated elsewhere, although such may be required to maintain support to the neighbouring property to the east if pockets of deeper soils are encountered during construction.”
And continues “Where the excavation borders the existing church in the west and neighbouring property in the east, some underpinning and/or shoring will be required where space is not available for open soil cuts, as discussed below.”
Underpinning of the church is one problem but underpinning and/or shoring of the neighbours will be very intrusive and disruptive to the owners and other occupants.
As we haven’t seen any of the financials for the project we don’t know if budget allows sufficiently for such costs or has enough to cover overruns.
What happens if the underpinning is not successful? What happens if the 100+ year old church starts to crumble into the excavation? Will they then decided to turn the whole site into a massive development of 150 to 200 units? Will the OBUC / contractor’s insurance cover damage to their own property? How many many unanswered questions surround this project?
Page 3 “We expect perimeter cuts to be on the order of 6 to 7 m in height.”
7 meters is 23 feet in depth, much of which is through solid granite.
Page 4 “As noted, it will be necessary to maintain support to the existing church during construction.”
Again, are the congregation aware of this? How risky is this process? How expensive is this?
Page 4 East Excavation Perimeter
“However, where any pockets of fill or soil deeper than approximately 1.2 m are encountered, shoring will be required if permission to encroach for open cutslopes cannot be arranged.”
This means they may need to ask the neighbours for permission to dig up part of the neighbours’ yards and gardens. Given how dismissive the OBUC-DT has been of the local community throughout the planning of this project, how likely is it that neighbours would accommodate such a request? The OBUC-DT is being arrogant if they assume such permission might be forthcoming.
Page 4 Blasting Considerations / Rock Slopes
“The bedrock will contain localized fractures and joints.”
This is particularly relevant to the discussion on carbon monoxide poisoning – see below.
“On past projects with near vertical cuts, we have recommended making an additional allowance of 10 to 15% of the overall excavation cost to cover works associated with rock stabilization. Direction for such would be provided at the time of excavation.”
Have the OBUC Development Team’s estimates taken this into account? We haven’t seen any of the financials.
Page 5 Blast Vibrations
“Blasting must be undertaken with care using controlled techniques so as to limit the intensity of the ground vibrations in order to avoid impacting adjacent structures, properties, and infrastructure.
“Drilling and blasting operations will create noise and ground vibrations that will be experienced by neighbouring residents. Complaints from neighbours should be anticipated. It should be noted that vibrations from blasting may result in damage to nearby structures in close proximity if the blast is not properly managed. Safe blasting procedures should be followed, and initial assessments of surrounding structures are recommended prior to undertaking the excavation/blasting works.”
So, they anticipate complaints from neighbours. Perhaps adequate and earnest consultation with the immediate (100 m) neighbours could improve relationships and outcomes. But previous experience of the OBUC’s idea of consultation is to ignore or tell, never to discuss or consult.
One of the scariest sentences in the whole report is: “Safe blasting procedures should be followed”. Not “MUST.” Just should!
“Despite suitable precautions, even minor blast vibrations which are not sufficient to result in structural damage can result in minor cosmetic cracking in adjacent buildings, as a result of release of existing stresses within building materials.”
So, they also recognise, that despite suitable precautions there will be cracking in adjacent buildings.
“We expect that lifts of maximum 0.3 m thickness can be adequately compacted by several passes of a large vibratory drum roller.”
So after all the drilling and blasting the neighbours will have to endure the sounds and vibrations of a large vibratory drum roller :(
This is what large vibratory drum roller looks like https://bit.ly/2QZG0A6
Page 7 “It is not recommended to have engineered fill cross the property boundary”
That is not to say that they won’t ask to try to place the fill into neighbour’s yards.
2. A review of the dangers of blasting, particularly carbon monoxide percolating through the rock into surrounding houses.
In March 2012 the Quebec equivalent of WorksafeBC (du ministère de la Santé et des Services sociaux) issued a guide “Les intoxications au monoxyde de carbone et les travaux de sautage - Guide de pratiques preventives” which I believe translates to “Carbon monoxide poisoning and blasting - A guide to preventative practices”.
A report on this guide ( https://www.asp-construction.org/bulletin-prevenir-aussi/magazine/dl/automne-2012 page 12) says
“According to the Ministry of Health and Social Services of Quebec, more than 20 incidents related to blasting work in residential environment have occurred since 2009 and have resulted in serious intoxication in residents near construction sites.
“Indeed, during blasting work, carbon monoxide is produced and if it does not dissipate in the open air, it can move in the ground to buildings, trenches, manholes for public services and cause poisoning. The guide that we present to you, proposes preventive measures to be implemented place before carrying out the work to avoid poisoning.
“If, despite these measures, an infiltration of carbon monoxide occurring, an emergency response should be made and it is also an aspect of which the document deals. The guide is for so to all those who perform excavation work [with] explosives - contractors, contractors’ workers - as well as municipal emergency services (police and fire) to the directorates of public health.”
All urban properties near a Quebec blasting site need to receive http://publications.msss.gouv.qc.ca/msss/en/document-000854/?&txt=carbon%20monoxide&msss_valpub&date=DESC
There is no such requirement to give an equivalent guide here in BC.
Carbon Monoxide is not only a problem out east. For example, The District of Oak bay has this report on its website: https://www.oakbay.ca/municipal-hall/news/blasting-2285-woodlawn-crescent
Blasting at 2285 Woodlawn Crescent
December 10, 2014
A blasting permit was issued to 2285 Woodlawn Crescent. As a condition of the permit, as is standard practice, the District of Oak Bay is indemnified from any damage resulting from the blasting.
A stop work order was issued yesterday afternoon to 2285 Woodlawn Crescent preventing any further blasting from occurring at this location until further notice. Although a very rare occurrence, there is a possible connection between the blasting and the release of carbon monoxide from the ground.
The Oak Bay Fire department responded to a carbon monoxide alarm at 2281 Woodlawn Crescent on Friday evening December 5. After a thorough investigation of the home and proper venting protocols, they could not determine the cause. The home was rendered safe for occupancy. Blasting had been occurring on the adjacent property, 2285 Woodlawn Crescent.
On Monday, blasting resumed and on Monday evening, the carbon monoxide alarm sounded again at 2281 Woodlawn Crescent. The Oak Bay Fire Department arrived on scene and confirmed that carbon monoxide levels were significant enough to warrant the home cleared. It was determined that the carbon monoxide was entering the home through the floor drain in the crawl space. When the home ventilation system was activated, the carbon monoxide levels increased. Following protocols of public safety, the Oak Bay Fire Department advised the family to leave their home until the source of the carbon monoxide could be confirmed and mitigated, and instructed the home owners to contact their insurance company.
While the property owner at 2285 Woodlawn Crescent prepares to respond to the stop work order with appropriate geotechnical information, the District of Oak Bay is attempting to mediate a cooperative solution between the neighbours. The issue at hand is between the two property owners.
What is shocking is that WorksafeBC are not concerned about this problem because it doesn’t affect the workers on the worksite. If the neighbour is not on OBUC’s premises, WorksafeBC has no jurisdiction.
3. A review of literature on urban blasting
I also obtained a copy of “Best Practices Guide for Urban Blasting Operations” from http://iseewest.org/images/downloads/Best_Practices_Guide_for_Urban_Blasting/best_practices_guide_for_urban_blasting_operations_1st_edition_draft.pdf
Even though this was published in 2016, there is no mention of carbon monoxide.
I contacted the publishers, The International Society of Explosives Experts – Western Canada Chapter and asked:
1. Have I missed references to the danger of carbon monoxide to nearby residents in your Best Practices Guide? If so, what pages are they on?
2. If there aren’t any in your guide, can you explain why the Quebec authority reports “According to the Ministry of Health and Social Services of Quebec, more than 20 incidents related to blasting work in residential environment have occurred since 2009 and have resulted in serious intoxication in residents near construction sites.” https://www.asp-construction.org/bulletin-prevenir-aussi/magazine/dl/automne-2012 (that was in less than 3 years)
3. Do you recommend members distribute brochures like the attached when blasting in residential areas? Do you have an equivalent brochure available? If not, why not?
I received the following in reply:
My name is Mike Witham and I am chairman of the Urban Blasting Committee. Our committee develops, reviews and updates the Best Practices Guide for Urban Blasting Operations.
Your questions are under review by our committee. We are currently working on our 2nd Edition of the Best Practices Guide for Urban Blasting Operations which we are planning to release in 2019.
I am not the first person in Oak Bay to have come across this problem. The publisher of the attached document Blasting Near Existing Buildings which I believe is based on the French document reference above.
This 5 page document is well worth the read.
Another interesting read is “Urban Construction Blasting in Canada - Complaints and Associated Municipal Bylaws” http://www.hrpub.org/download/20131215/CEA1-14801317.pdf
The Abstract reads:
Blasting in urban environments frequently results in both legitimate and frivolous complaints even though effective blasting practices and associated protective measures exist. Analysis of blasting-related complaints and the existing state of blasting regulations applicable to Canadian municipalities was conducted. Provincial blasting regulations typically do not prescribe the need for notification of planned blasts, pre-blast surveys, and blasting monitoring. In the absence of these requirements, some municipalities have developed their own blasting bylaws. Anecdotal results suggest that when a well-designed municipal blasting bylaw is present and is enforced, then complaints from the public are greatly reduced. To aid municipalities, this paper presents a generic blasting bylaw along with recommendations for a blast-notification protocol that were developed with input from blasting contractors and consultants. Key features in the bylaw require the blaster to 1) obtain a municipal blasting permit, 2) notify residents within a specified distance from the blast site of impending blasts, 3) carry out pre-blast surveys, and 4) use a third-party vibration-monitoring consultant.
I can’t find an Oak Bay bylaw requiring these things.
Insurance and Inspections
While the OBUC and the contractors should have insurance, and will most likely do an inspection, all local residents are advised to talk to their insurance company or broker BEFORE demolition and excavation commences.
Confirm that your insurance will provide cover for any damage, particularly delayed damage. We have heard of damage appearing after the contractor’s 12 month’s cover has expired.
Also see if your insurer recommends an independent inspection of your property, so you have a neutral baseline assessment.
As a minimum, get and install Carbon Monoxide monitors for your basement / crawl spaces.