Restoring a 39-year-old parking garage while it remains in active use presents a set of challenges that push the limits of conventional demolition methods. When Arguson Projects Inc. took on the restoration of a multi-level parkade in Toronto’s East End, the project called for the removal of 200,000 square feet of chloride-contaminated concrete from the second and third suspended slabs. The structure had to stay open. Building tenants needed parking access. A school and hotel sat nearby, demanding strict noise and vibration controls. The solution required methods that go far beyond traditional jackhammering. For a broader look at demolition methods for large-scale structures, see our guide on Building Demolition and Implosion Mechanical Demolition Methods Explosive.
The Scale of Active Parking Garage Restoration
Restoring an active parking garage is fundamentally different from new construction or vacant building demolition. The constraints are tighter, the logistics more complex, and the margin for error narrower. Contractors must coordinate material removal, structural repair, and waterproofing while vehicles, pedestrians, and building operations continue around them.
Chloride Contamination and Structural Deterioration
Suspended slabs in parking structures are especially vulnerable to chloride ion penetration. Road salt carried in by vehicles during winter months seeps into the concrete, reaches the rebar, and triggers corrosion. The corrosion expands, cracking the surrounding concrete and accelerating deterioration. In the Toronto project, engineering firm RJC Engineers identified heavy chloride contamination across the entire second and third levels of the parkade. The concrete needed removal to depths of 4 to 5 inches in most areas to reach sound substrate.
The typical progression of chloride damage follows a predictable pattern:
- Chloride ions penetrate the concrete cover through surface cracks and pores
- Rebar corrosion begins once chloride concentration exceeds the threshold at the steel surface
- Corrosion byproducts (rust) occupy more volume than the original steel, generating tensile stress
- Cracking propagates upward through the concrete cover, creating spalls and delaminations
- Water and chlorides reach the rebar more easily, accelerating the cycle
Occupancy Constraints That Drive Method Selection
Several factors made this project especially demanding from an occupancy standpoint:
- The building has a roof deck with tenant amenities that had to remain accessible
- A prep school with athletic facilities sits immediately south of the parking structure
- A nearby hotel imposed nighttime noise restrictions
- The parking facility had to stay open for building tenants throughout the restoration
- Part of the building sits directly on the roof deck, making vibration control critical
These constraints eliminated traditional demolition methods from consideration early in the planning phase.
Why Hydrodemolition Excels in Noise-Sensitive Environments
Hydrodemolition uses high-pressure water jets to remove deteriorated concrete without impact forces. The Aqua Cutter 710V robot deployed on this project operates at pressures between 14,500 and 40,000 psi. The water jet penetrates pores and micro-cracks in weakened concrete, widening them until the material separates from the sound substrate beneath. Because the process applies no mechanical impact, it generates zero vibration and produces significantly less noise than traditional methods.
Noise Level Comparison Across Demolition Methods
| Demolition Method | Typical Noise Level (dB at 6m) | Vibration Level | Suitable for Active Occupancy |
|---|---|---|---|
| Hydrodemolition (with Ecosilence pump) | 63 dB | None | Yes |
| Pneumatic jackhammers (handheld) | 95-110 dB | High | No |
| Hydraulic breakers (skid-steer mounted) | 90-105 dB | Very High | No |
| Diamond wire sawing | 80-90 dB | Low | Limited |
| Expansive grout (non-explosive) | Silent | None | Yes |
Conterra paired their Aqua Cutter robot with an Aquajet 700 Ecosilence high-pressure pump. The pump and diesel engine are enclosed inside a sound-dampened container. Combined with a hoarding system around the work area, the team achieved noise levels of 63 dB at a range of six meters. For context, normal conversation measures around 60 dB. This allowed crews to work during daytime hours without disturbing the school, hotel, or building tenants.
Vibration-Free Demolition Benefits
The absence of vibration carries structural advantages beyond noise compliance. Impact-based demolition methods create micro-fractures in the concrete that remains in place. These micro-fractures weaken the bond between new and old concrete, reducing the long-term durability of repairs. Hydrodemolition removes only the deteriorated material. The water jet stops naturally when it reaches sound concrete, leaving a clean, rough surface ideal for bonding new overlay. The rebar is cleaned and descaled by the water jet without being damaged or dislodged.
As Philip Sarvinis, P.Eng., Managing Principal with RJC Engineers noted, the process works extremely well with the added bonus that it does not physically damage the remaining concrete left in place compared to traditional jackhammering operations. For more on parking structure design considerations, see Parking Space Types and Multi Level Car Parking.
Equipment Systems for Sustainable Concrete Removal
The Toronto parkade restoration deployed three pieces of equipment that worked as an integrated system: the demolition robot, the pump, and the water treatment unit. Each played a specific role in enabling productive, environmentally responsible concrete removal.
The Aqua Cutter 710V Hydrodemolition Robot
The 5,181-pound Aqua Cutter 710V is a tracked robot controlled remotely by a single operator. Its high-pressure water jet removes concrete at rates of 600 to 1,000 square feet per eight-hour shift. Key specifications include:
- Operating pressure range: 14,500 to 40,000 psi
- Removal depth: programmable, typically 4 to 5 inches per pass
- Automated detection: the robot finds and removes all deteriorated concrete, even areas invisible to visual inspection
- Clean substrate: leaves a sound, rough surface for superior bonding of new concrete overlay
- Rebar-safe: cleans and descales reinforcement without damage
The robot’s ability to detect weak concrete by sensing changes in resistance during removal ensures comprehensive remediation. As David Porciello, General Manager for Conterra, explained, the robot finds what most engineers cannot see every millimeter of bad concrete. This gives the restoration team a clean slate for stronger, longer-lasting repairs.
The Ecosilence High-Pressure Pump
The Aquajet 700 Ecosilence pump delivers 56 gallons per minute at 18,700 psi. Its distinguishing feature is sound insulation. The pump and diesel engine are enclosed in a container that dampens noise to the point where it can run outside a downtown window and remain quieter than normal traffic. The unit also allows year-round operation, functioning even at temperatures as low as -4 degrees Fahrenheit.
The EcoClear Water Treatment System
Hydrodemolition uses large volumes of water. This project required an estimated 10 million gallons over its duration. Without on-site treatment, this volume would have to be trucked away using vacuum trucks at significant cost and carbon emissions. The EcoClear system treats blast water on-site in real time.
The treatment process addresses two main contaminants:
- High pH: Blast water starts at pH 12.5 due to cement alkalinity. EcoClear uses carbon dioxide (not mineral acid) to reduce pH to between 7.5 and 8.5, eliminating the risk of over-acidifying the water
- Suspended solids: The system reduces solids to 50 ppm or less, with documented results as low as 15 ppm
After treatment, the water can be discharged into the sanitary sewer system. Treatment costs less than one penny per gallon. The system processes up to 5,283 gallons per hour. Conterra is the only contractor in Ontario with equipment that can provide documented, quantifiable on-site water treatment results on demand.
Closed-Loop Water Recirculation
Conterra planned to implement a closed-loop system that recirculates treated water back to the Ecosilence pump. In this setup, blast water is treated in the EcoClear, then the clean water is reused in the hydrodemolition process. A small percentage is lost to evaporation, but the system can collect, treat, and recirculate up to 75% of the water used. Some contractors have achieved recapture rates as high as 90%. For more on sustainable parking structure design, see Designing Greener Parking Structures How Mobility Changes Are.
Project Execution and Lessons for Contractors
The restoration was organized in two phases over two years, beginning in December 2019. The staging area was set up outside the parkade to house the Ecosilence pump and EcoClear system. Depending on the day, the Aqua Cutter robot operated up to 615 feet away and several stories above the pump, connected by high-pressure hoses routed through the structure.
Crew Structure and Productivity
One of the economic advantages of robotic hydrodemolition is its minimal crew requirement. A single operator manages the Aqua Cutter robot with assistance monitoring the EcoClear treatment system. A small team follows behind to remove demolished concrete, while other crews handle through-slab removal, forming, and related tasks.
Porciello estimates that achieving the same productivity with manual methods would require a crew of 20 workers averaging 30 square feet per person per day. The comparison is striking:
| Metric | Hydrodemolition Robot | Manual Jackhammering |
|---|---|---|
| Removal rate (per 8-hr shift) | 600-1,000 sq ft | ~30 sq ft per worker |
| Crew size for equivalent output | 2-3 operators | 20 workers |
| Noise level | 63 dB at 6m | 95-110 dB |
| Vibration | None | High (risk of micro-fractures) |
| Work schedule | Daytime | Overnight only |
Water Management Strategy
The team took advantage of the structure’s existing drainage to manage wastewater. Water flows through existing drains and a clear stone filtration system to a catch pit near the staging area, then is pumped through the EcoClear on its way to the sanitary sewer. This gravity-assisted approach minimizes pumping requirements and reduces energy consumption.
Adapting to Unforeseen Disruptions
The project lost 13 weeks due to COVID-19 shutdowns. Productivity from the robotic equipment helped recover much of that lost time, with final completion scheduled for spring 2022. The use of remotely operated equipment also made it easier to implement social distancing protocols, allowing work to continue while other jobsites required reorganization.
Environmental and Economic Benefits
The combination of robotic hydrodemolition and on-site water treatment delivered environmental benefits that factored into the project’s bottom line:
- Eliminated vacuum truck trips for water removal, saving fuel and exhaust emissions
- Minimized crew size, reducing commuting emissions and labor costs
- On-site water treatment avoids the carbon cost of trucking 10 million gallons of wastewater
- Closed-loop recirculation recaptures up to 75% of water for reuse
- Carbon dioxide used for pH adjustment is safer to handle than mineral acids
Conterra’s full-service approach also gave them an advantage in bidding subsequent phases of the project, which included pouring new concrete, applying waterproofing systems, and marking parking lines. Decades of experience in parking structure restoration, combined with the productivity and environmental advantages of their equipment package, made their bid competitive. For more on parking garage facade and cladding considerations, see Metal Panels for Parking Garage Facades Material Performance.
The Toronto parkade restoration demonstrates that hydrodemolition is not just a demolition method. It is a systems-level approach that solves noise, vibration, productivity, and environmental challenges simultaneously. For contractors facing active occupancy constraints, the combination of robotic precision, sound-dampened pumping, and on-site water treatment represents a viable path through the tightest of project parameters.