Physical Security Considerations of High Security Sites
The street-facing defences of a nicely designed high security building.
Physical security devices including gates, fences, turnstiles and barrier systems play a vital role in providing extreme protection on high security sites from determined attacks by intruders using vehicles or on foot.
PHYSICAL security is the application of barriers that deny or slow down intrusion into a protected site. Such barriers may take the form of walls, gates, bollards, doors, trenches, grills, bars, gatehouses or natural barriers like banks, streams or elevated garden beds. Clever use of physical security significantly increases a site’s overall protection. Such barriers are one of the key elements of an effective security solution and they’re either natural or structural.
Importantly, barriers don’t just form a physical defence that increases the delay between an attempted intrusion and a breach. They also represent a psychological deterrent to potential intruders. And despite the fact we’re talking about high security physical barriers here, it’s important to point out that physical barriers must be supported by electronic systems that allow an appropriate and early response to an escalating event. There’s no point building a strong wall and failing to detect an intrusion on it until the defences are breached.
In the most basic definition, a classic onion skin barrier defence might incorporate a perimeter fence, a building with barred windows and locked doors, a room with a locked door and a locked safe in a corner of that room. Each of these layers will take some getting through and an effectively defended site will incorporate electronic security support of these barriers to ensure there’s response to the intrusion long before the last layer is breached. One of the most important aspects of external physical perimeters is an effective gate and/or manned gatehouse. While on low security sites these gates might be basic framed and hinged chain mesh, on high security sites rising barriers and huge sliding steel barriers will be needed.
Growth in global terrorism and the fact Australia is clearly a target of that terrorism means some applications demand the physical onion skin be seriously tough. While many higher security sites use a double layer of chain link with sabre tape crowns, this is not enough to guarantee protection against a determined attacker in a vehicle. This means providing gates, walls and structural defences that cannot be breached by any ground-based means short of assault by heavy military vehicles.
Security managers need to bear in mind that a perimeter is devalued if adjacent fences fail to meet the specifications of high security gates. This element of physical security is a serious challenge, particularly on very large sites. In some cases, matching fence security levels to those of the best gates may mean building earth banks or ditches that ensure vehicles are unable to approach a fence-line, altering its risk profile. You can’t simply install chain link on boundaries and a massive gate at your entrance and feel physical security requirements are completely covered.
For intruders on foot, powered fence solutions offer a proactive solution. These powered fences have electrical properties that allow them to give intruders a sharp shock that’s entirely harmless. Intrusion events are reported to a central location, or passed to an alarm panel for communication with a monitoring station. They comprise a series of pulsed and earthed wires interspersed with standard galvanised wire. But while they are ideal defence against humans on foot even the best fences need strong support on high security sites. High security fences should be no further from the ground than 2 inches and they should have a height of at least 2m and a post gap of no more than 2m. Concrete sills or metal spikes should be used to anchor fence mid-sections to the earth.
One way to effectively protect free standing fences from determined assault by vehicles is with banks or ditches. The key element of bank or ditch design is the ‘wavelength’ of the structure. Gentle slopes may defeat attacks by large, long wheelbase vehicles but they will not stop short wheelbase 4WDs. Not only do the banks or ditches need to be 1-1.5 metres, they need to be steep – that means slope angles of 60 degrees or higher – additionally, the smaller the bank or the shallower the ditch, the closer to 90 degrees this slope angle needs to be.
Another effective defence against vehicles is the installation of concrete blocks but depending on the perimeter length these are far more expensive than earth works. They’ll also give your site all the aesthetic appeal of the Maginot Line. Bollards are another useful solution that allows foot traffic to pass but denies entry to vehicles. There’s a good range of bollards now available capable of stopping heavy vehicles and some options can be integrated with electronic security solutions and controlled remotely.
In the past, all high security sites had high, solid walls built of concrete or masonry. Huge sandstone or concrete and masonry ramparts are extremely effective barriers against all forms of attack but they have problems you don’t get with fences. The biggest problem is poor surveillance characteristics and inability to support some fence mounted sensing technologies. Supporting solid walls with CCTV will allow a security team to see what’s going on just outside a facility. Just remember that it’s important that solid walls are constructed with plenty of pillar support, additional support at corners and adequate drainage.
But just how far you can push physical security when it comes to foot traffic is going to depend on budget and the genuine risk factors your site faces. Very high security sites will need 2 sets of gates with a DMZ between them – a man trap for vehicles just like the entry way of a high security monitoring station. Such a design allows gatehouse security teams to assess risks and undergo search or authentication procedures while ensuring the site’s integrity is not compromised. If you can’t afford this, the gate house should be located outside the high security gate and a rising barrier used to providing a perceived sterile zone.
Under no circumstances should unidentified or unauthorized vehicles be allowed through the high security gate until they have been cleared by security staff and on high risk sites with single gates, drivers should be asked to leave their vehicles while waiting in the queue for entry to the site. Speed of gate operation will be the key here – you don’t want a gate that takes a long time to open and close, affording attackers plenty of time to tailgate legitimate traffic or to swerve into your facility unannounced and bypass the gatehouse altogether. Applying tyre shredders to adjacent lanes can assist security staff here.
Along with vehicles security you will need to think about foot traffic. Smart design will keep the staff carpark and the visitors’ carpark separate and it will keep both carparks outside the security perimeter. This means all staff will be required to pass through an access controlled security turnstile on foot while entering the facility and they’ll be checked long before they reach the foyer area. Some locations won’t be laid out in a way that allows security managers to deliver this sort of design, but it works well where the real estate exists around a facility to support it.