Buildings: Prison Precast
At the Central Nova Scotia Correctional Facility in Dartmouth, high-strength precast concrete walls and cell components protect the building from vandalism by inmates.Those who design correctional fac...
At the Central Nova Scotia Correctional Facility in Dartmouth, high-strength precast concrete walls and cell components protect the building from vandalism by inmates.
Those who design correctional facilities have to stay one step ahead of the inmates’ ability to cause havoc by anticipating where the prisoners might do damage to themselves or cell property. Someone like John Dobbs, an architect from Halifax who specializes in correctional facilities, spends his days thinking up designs for things like sprinkler heads to ensure that an inmate in a cell can’t use the device to hang him or herself. The problem, Dobbs says, is that to be suicide-proof the sprinkler head has to detach easily, which means the prisoners easily knock them out and cause flooding.
Though Dobbs is still wrestling with the sprinkler problem, he and a team of consulting engineers, architects, contractors and precast manufacturers, have solved many other security issues in a large new correctional facility that opened last year near Halifax. The Central Nova Scotia Correctional Facility is the first new prison built in the province for about 40 years. Located in an industrial park in Dartmouth, part of the Halifax regional municipality, the prison has 310 cells for male and female prisoners serving sentences of two years or less. There is a separate forensic psychiatry centre adjacent to the prison, which is run by the district health authority. The entire $60 million project covers 256,000 s.ft./23,782 s.m., of which 175,000 s.f. are the correctional facilities.
A design-build team under Reid Management (a local developer who will also lease the jail to the province for 25 years) won the competition for the project with an innovative approach. They used precast high strength concrete walls and cell components as opposed to the more standard reinforced concrete masonry units. Strescon, a local precast fabricator with a plant five miles down the road, made a total of 2,611 pieces of precast which fit together “like a jigsaw puzzle.”
The exterior loadbearing walls, for example, are 8-ft. wide sandwich panels consisting of 6* high-strength concrete on the inside, 3* rigid insulation, and 3* ribbed concrete on the outside. The walls have cast-in windows with 5* mullion bars, and cast-in door subframes.
Using precast had the advantage of speed. The steel frame could be erected while the precast components were being made. Once the basic frame and roof truss were installed, the building was quickly enclosed.
The walls are also extremely strong. Rioting prisoners have been known to break out — literally — through solid walls using table legs, stools or anything else they can find. Dobbs and the team rigged up a sledgehammer test, and found their proposed panels were much stronger than reinforced masonry or a regular precast wall. The 8* reinforced concrete block wall succumbed after 100 blows; the 5* precast wall was penetrated after 200 blows; but the high-strength sandwich precast panel was still intact after 600 blows.
While precast prison cells have been built in the United States, they tend to be stacked, loadbearing three-dimensional forms that are expensive to develop. The Nova Scotia prison cells are a kit of parts using commonly available technology.
Precast elements prevent equipment in the cell from being used as a weapon or being vandalized. Between each pair of cells is a shared precast mechanical/electrical service chase which runs as a V-shape wedge up one corner of the party wall. The chase holds the plumbing for the stainless steel combination toilet/sink and sprinkler water supply, and it houses the electrical conduit for the lights, smoke detector, intercom and alarms. The chase also acts as the return air exhaust plenum.
Each cell has an L-shaped precast bunk bed. The beds measure 26* wide by 67* long in each unit, but were manufactured four cells long, i.e. in approximately 30-ft. segments. Set inside the L is the supply air duct (there’s no air-conditioning). Heating is by a radiant underfloor system, fed by plastic pipes buried in the concrete, which means there are no radiators for prisoners to rip out and use as weapons. The radiant heat is energy efficient, since the heat only has to be maintained at 90F-100F in the pipes. The building was designed to meet the energy efficiency requirements of NRCan’s Commercial Buildings Incentive Program i.e. to use 25% less energy than a building designed according to the Model National Energy Code for Buildings. The cell floors are so warm, Dobbs says, some of the inmates prefer to sleep there on their mattresses rather than on the bunks.
Keeping an eye on the prisoners and guards are over 250 high-definition cameras strategically placed around the prison, such as in corridors at the interlocking gates, and at the perimeter fencing. They are triggered into action by a detection system, and will zoom in so that the controllers in the central operations room or in each of the pods can see what’s happening. Around the perimeter of the facility is a proprietary “First Defence” curved-pole fencing system that has vibration disturbance sensors. The fence curves inwards at the upper half and the mesh gets smaller above to give little chance of getting a foothold. Walk-through metal detectors regularly screen offenders and x-ray scanners are used to inspect incoming parcels.
Project name: Central Nova Scotia Correctional Facility
Client: Nova Scotia Department of Justice
Developer: Reid Management
Prime consultant: John K. Dobbs & Associates (John K. Dobbs, Ross MacIntosh) in association with William Nycum & Assoc. (Harold Foley)
Mechanical & electrical: Morris & Richard Consulting Engineers (Hari Singh, P.Eng., Don MacDonald, P.Eng.)
Civil & structural: CBCL Consulting Engineers (Macdara Woodman, P.Eng.)
Precast fabricator: Strescon (John Fraser, P.Eng.)
Precast cell design: Gratec Engineering (Calvin Gray, P.Eng.)
General contractor: Tidewater Construction
Detention hardware consultant: Simpson Detention
Access control/CCTV/intercom/fire alarm/sprinklers: