Hazardous materials in existing buildings

Two weeks before demolition of level 2 was due to start, a drywall foreman named Andre lifted a ceiling tile in a corridor to check the route for a new cable tray and found grey, fibrous insulation wrapped around an old steam pipe. The hazardous materials survey in the bid documents listed asbestos pipe insulation in the mechanical rooms but showed this corridor as clear. Andre put the tile back, told Gareth Lowe, and Gareth closed the corridor ceiling and called Calloway Environmental, the hospital's hazardous materials consultant. A sample came back the next day at 40 % chrysotile asbestos. The survey had missed the corridor because the original surveyor had been unable to access it while the hospital was occupied. That one ceiling tile changed the schedule of phase 2, added an abatement contract and became the first lesson for every new worker on the project: if you are not sure what a material is, stop and ask.

Buildings constructed before the 1990s often contain materials that were legal and common when installed but are now known to harm health when disturbed. Renovation disturbs them. Cutting, drilling, sanding, demolishing and even moving ceiling tiles can release fibres, dust or vapours that workers and occupants breathe. The East Wing, built in 1974 and renovated several times, contained most of the common ones.

The usual suspects

Asbestos deserves particular attention because it was used so widely and because the harm it causes can appear thirty or forty years after exposure. It is generally safe when intact and undisturbed. It becomes dangerous when it is damaged, cut or removed and its fibres become airborne. Materials are often described as friable, meaning they can be crumbled by hand pressure and release fibres easily, or non-friable, meaning the fibres are bound in a hard material such as floor tile or cement board. Friable materials need the most stringent controls.

Finding hazards before the work starts

In Ontario, the Occupational Health and Safety Act requires an owner to determine whether designated substances, including asbestos, lead, silica and mercury, are present at a project site and to include a list of them in the tender documents, so that bidders can price and plan the work. Owners usually meet this duty by hiring a consultant to prepare a designated substances and hazardous materials survey. The asbestos regulation for construction projects, O. Reg. 278/05, adds requirements to identify asbestos-containing materials before work that may disturb them. Other provinces have similar rules.

A survey is only as good as its access. Surveys done while a building is occupied often cannot open every wall or ceiling, and many surveys state that further sampling is needed when areas become accessible. Calloway's original survey for the East Wing said exactly that, in a paragraph on page 31 that nobody on the bid team had read carefully. A pre-demolition survey, done after the hospital moved out of an area and before demolition starts, fills those gaps. On Ashgrove, after the corridor discovery, Harbourline and the hospital agreed that Calloway would do a pre-demolition survey of each phase, opening walls, ceilings and floors as needed, before any demolition was released.

Classifying and controlling the work

Ontario's construction asbestos regulation classifies work into Type 1, Type 2 and Type 3 operations, from lower to higher risk, and sets precautions for each. In broad terms, work with non-friable materials that does not create much dust, such as removing intact floor tiles by hand with wetting, falls in Type 1. Removing small amounts of friable material, or using power tools on non-friable material with dust control, falls in Type 2. Removing or disturbing more than a small area of friable material, generally about one square metre or more, falls in Type 3, which needs full enclosure under negative pressure, decontamination facilities, air monitoring, trained workers and advance notice to the Ministry of Labour. Abatement on Ashgrove was done by a specialist subcontractor working to Calloway's specification.

Whatever the jurisdiction, high-risk asbestos removal follows a recognizable pattern: isolate the area, build a sealed enclosure under negative pressure with HEPA filtration, provide a decontamination unit for workers to change and shower, wet the material to keep fibres down, remove and bag it, clean the enclosure, test the air to confirm fibre levels are low enough, and only then take down the enclosure. The same negative pressure principles from lesson 2 apply, with stricter limits and independent air testing.

Lead

Lead in paint and other materials becomes a hazard when it is sanded, scraped, cut, burned or demolished. Ontario treats lead as a designated substance, and the province's guideline for lead on construction projects sets out work classifications and precautions, from wet scraping by hand to abrasive blasting and torch cutting, with increasing controls. In the East Wing, Calloway found lead-based paint on door frames and in the stairwells, and lead sheet lining a former X-ray room on level 1. The childcare room was to be built in that part of level 1, so Ashgrove decided to treat the area as if it were a facility for young children: lead paint was removed rather than painted over, and the room was cleaned and tested with dust wipe samples before it opened, using clearance levels its consultant recommended.

Silica, mould and the rest

Crystalline silica is created by the trades themselves whenever concrete, block, tile or stone is cut, cored, ground or chipped. It is controlled by engineering methods at the tool: water delivery to the blade, shrouds with HEPA vacuum extraction, and enclosed cabs, backed by respirators where needed. On Ashgrove, every saw and core drill used water or vacuum extraction, and the concrete chipping on level 2 used vacuum-shrouded tools inside the containment described in lesson 2.

Mould usually shows up where water has leaked for years: behind old sinks, under windows, around roof drains. Small areas can be removed with containment and HEPA vacuums by trained workers; larger areas need an abatement approach similar to asbestos. In a hospital, mould also matters because of infection risk to patients, so Dr. Moreau's team reviewed every mould abatement plan. Light ballasts were checked for PCBs and bagged for regulated disposal, fluorescent tubes and mercury thermostats were collected for recycling, and refrigerant in the old cooling units was recovered by a licensed technician before removal.

# Abatement shifts and classification (Ontario, metric)
items = [  # name, quantity, unit, friable?, rate per shift
    ('Floor tile and mastic', 1600, 'm2', False, 160),
    ('Pipe insulation',        420, 'm',  True,   35),
    ('Textured ceiling',        12, 'm2', True,    6),
]
total = 0
for name, qty, unit, friable, rate in items:
    shifts = -(-qty // rate)        # round up
    kind = 'Type 3 (enclosure)' if friable else 'Type 1 or 2'
    total += shifts
    print(f'{name:22s} {qty:6,} {unit:3s} {kind:18s} {shifts:3d} shifts')
print('Total crew-shifts:', total)

Floor tile and mastic   1,600 m2  Type 1 or 2         10 shifts
Pipe insulation           420 m   Type 3 (enclosure)  12 shifts
Textured ceiling           12 m2  Type 3 (enclosure)   2 shifts
Total crew-shifts: 24

When an unknown material turns up

No survey finds everything. Workers on renovation projects need a simple rule they can follow without thinking: if you uncover a material you are not sure about, stop, leave it alone, keep others away, and tell your supervisor. The supervisor arranges sampling before work in that area continues. Harbourline's orientation showed pictures of the common materials, and every work area had a laminated card with the stop-work rule and the phone number of Calloway's site representative. The corridor insulation that Andre found was the first of nine unexpected finds during the project, and in every case work stopped before anything was disturbed.

Unexpected hazardous materials also have contract consequences. Most contracts treat the discovery of hazardous materials that were not disclosed as the owner's responsibility: the contractor must stop work in the affected area and notify the owner, and is entitled to an adjustment of time and price for the delay and extra work, provided it did not cause or knowingly disturb the material. Lesson 5 shows how the corridor discovery was priced and scheduled.

Clearance and records

An area is not safe for general construction, or for occupants, until testing shows it is clean. After asbestos removal, independent air samples are taken inside the enclosure and compared with clearance criteria before the enclosure comes down. After lead work, dust wipe samples are compared with clearance levels. Clearance results are signed by the consultant, kept in the project file and given to the owner, because they may be needed decades later to show that the work was done properly.

The hazardous materials records for the East Wing filled three binders by the end of the project: surveys, abatement plans, notifications, worker training and medical records summaries, daily logs, air and dust sampling results, waste manifests showing that material went to licensed disposal sites, and clearance certificates. Harbourline's closeout package, covered in lesson 11, included a full copy, and the hospital updated its asbestos management records to show which materials had been removed and which remained in other parts of the campus.