Canadian Consulting Engineer

BUILDING STUDY: Casino Nova Scotia

BMR Structural EngineeringF.C. O'Neil Scriven & AssociatesOn a 3.5 acre site off Upper Water Street at the north end of Halifax's waterfront, a large new casino and entertainment complex opened in Apr...

December 1, 2002   Canadian Consulting Engineer

BMR Structural Engineering

F.C. O’Neil Scriven & Associates

On a 3.5 acre site off Upper Water Street at the north end of Halifax’s waterfront, a large new casino and entertainment complex opened in April 2000. Casino Nova Scotia’s location directly on Halifax Harbour allowed the mechanical-electrical engineers, F.C. O’Neil Scriven, to take advantage of the cold Atlantic Ocean as a primary source of cooling for the building. The harbour location also led to an interesting design by structural engineers BMR: almost one-third of the building footprint is suspended over the water.

Built for a Las Vegas Corporation (the Nova Scotia government gets a share of profits), the $44 million complex was a design-build project, with a fast track schedule of 24 months.

The engineers note that while the project involved many innovative design and construction methods and was “definitely not the kind of engineering we do on a daily basis,” most of the solutions were very cost effective. The 12,825-m2 building and 550-car parking garage were completed on time and on budget.

Structure

The casino is supported on two miles of steel pipe caissons filled with high strength concrete. The pipe caissons are socketed as much as 21 metres deep into bedrock in the harbour floor. With a life expectancy of 100 years, the steel pipe helps protect the concrete from the seawater.

The main cast-in-place floor slab, which supports the large gaming area, is a complex structure, partly because it is built over the water and has to accommodate a layer of insulation. The floor also has to support heavy change carts (“mules”), and it is inlaid with hundreds of conduits and cables to provide radiant heat, and communications cable connecting the slot machines.

The steel support system for the pre-cast cladding on the superstructure was another engineering challenge, especially the framing for the towers and domes. Concrete was used extensively in the project because of its ability to withstand the salt air environment better than any other economical building material. Also it is locally available and uses local labour — factors that were important given some of the controversy that surrounded the project.

All the building’s concrete that is over Halifax Harbour or in contact with the water, including the caisson infills, uses a ternary blend of low alkali cement and Class F fly ash. The fill concrete has a specified minimum 28 day compressive strength of 40 MPa, and a maximum water to cementing materials ratio of 0.36. The average strength for all the marine concrete was 65 MPa.

Ocean cooling

At a depth of 90 feet, the temperature of water in the harbour is about 6C in June and peaks to a high only in late September. During the hot summer weather, therefore, it is cold enough to be used in the building’s cooling coils. This ability meant the building could be cooled at the cost of a 25-hp pump instead of a 260 kW chiller.

Cold ocean water is pulled from near the bottom of the harbour approximately 500 feet from shore through a 12″ diameter polyethylene suction line. The water is then pumped through two titanium plate heat exchangers to cool the water in the buildings’ closed loop chilled water system. If the sea water cannot lower the water to the required set point, one of the heat exchangers is switched out of the chiller water loop into the condenser water loop.

To minimize water lifting, the sea water pumps are located as close to the water surface as practical, with the centre line at the high tide elevation. A vacuum system is used to raise the sea water to the pump intake and to maintain prime levels.

The two main design challenges of using sea water are its corrosive nature and biological fouling. To deal with the corrosiveness, polyethylene DR21 with fibre reinforced plastic fittings is used for the intake and all the piping on the sea water side of the heat exchangers. Equipment flanges are 316 grade stainless steel. The heat exchangers’ titanium plates are highly resistant to corrosion, and the pumps incorporate copper, nickel and stainless steel.

The biological fouling problem is addressed using an electrolytic copper ion dosage technique. Cathodes are placed at the entrance to the intake bell and they release ions during electrolysis which combine with those released from the sea water to form an environment that prevents minute organisms from entering the system.

Nicotine attack

Intense ventilation was necessary because the casino allows smoking in most of its areas. Multiple fans in built-up air conditioning systems supply a total of 157,000 cfm air (approximately three times the rate for a typical office building) to the gaming, restaurant and kitchen areas. Two-thirds of the supply air is always outside air.

To control energy consumption, five heat wheels with variable frequency drives extract up to 80% of the heat in the exhaust air stream and transfer it to the incoming outside air. Air laden with cigarette smoke is discharged from these systems upwards through a short stainless steel stack on the roof to avoid recirculating the air back into the intake louvres.

Separate modular units serve areas on the upper floor, where there are offices and a ballroom. Each unit can introduce up to 100% outside air to allow for free cooling, and consists of a filter section (30% pre-filter and 85% final filter), heating coil, cooling coil, pressure atomizing humidifier, supply fan and return fan.

Theatrical effects

Incorporating more than 2,000 receptacles, 15,000 light fixtures, 200 security cameras and 300 kilometres of wire and cable, the casino requires a 2400 ampere 347/600 volt secondary service. The power is obtained from a utility padmount transformer and extended underground.

In the main gaming area is a feature ceiling made to simulate the sky. Floodlit from hidden sources, the sky has a lighting sequence that starts at sunrise and changes through the day. After dusk, thousands of stars, created by individually placed fibre optic fibres, dot the night sky. A GoBo in a programmable projector causes the moon to move, while the selective actuation of some fibres simulates shooting stars. General lighting in the gaming area uses fluorescent cove lighting, with low voltage MR16 downlights at each gaming table.

Seven separate sound systems with 23 amplifiers provide background music, telephone page and microphones throughout the complex, all connected through a digitally controlled analogue matrix. The sound systems in the gaming and special events areas have automatic gain control, by which the sound pressure level is maintained above the ambient noise using microphones in the speakers.

Over 200 closed circuit security cameras continually record proceedings in the casino. The fire protection system has addressable devices and an alarm that includes speakers, horns and strobe lights.

Owner: Park Place Entertainment

Structural: BMR Structural Engineering (Roy McBride, P.Eng., Mark Reynolds, P.Eng., Peter Richardson, AScT)

Geotechnical/concrete: Jacques Whitford & Assoc. (Gordon Leaman, P.Eng.)

Mechanical & electrical: F.C. O’Neil Scriven & Assoc. (Lloyd Schofield, P.Eng., Rick Moulton, P.Eng., Glenn Brunt, CET, Glen Rockett, P.Eng.)

Architects: Lydon Lynch Architects

General contractor: J.W. Lindsay Enterprises


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