Manholes are located at strategic locations throughout most municipal water, wastewater, and other underground utility systems. Manholes are designed to provide access to the underground utilities, and therefore they are potential entry points to a system. For example, manholes in water or wastewater systems may provide access to sewer lines or vaults containing on/off or pressure-reducing water valves. Because many utilities run underneath other infrastructure (roads, buildings), manholes also provide potential access points to other critical infrastructure as well as water and wastewater assets. In addition, because the portion of the system to which manholes provide entry is primarily located underground, access to a system through a manhole increases the chance that an intruder will not be seen. Therefore, protecting manholes can be a critical component of guarding an entire community.

A "manhole lock" is a physical security device designed to delay unauthorized access to the utility through a manhole. Locking a manhole that provides access to a water or wastewater system can mitigate two distinct types of threats. First, locking a manhole may delay access of unauthorized personnel to water or wastewater systems or assets through the manhole. Second, locking manholes may also prevent the introduction of hazardous substances into the wastewater or storm water system.

There are currently three basic design types for manhole locks: a bolt-type manhole lock, a clamp-type manhole lock, and a pan-type manhole lock. These three design types are discussed below.

McGard, Inc., has developed a bolt-type manhole lock called the Intimidator Man-Lock™. This product is a specialized bolt that is installed at two separate locations in the top of the manhole cover, anchoring the cover to the frame beneath the cover. The holes that are drilled into the manhole cover down through a portion of the manhole frame must be aligned in order to insert the bolt. This is called indexing. The top of the bolt has a uniquely designed groove that can only be turned with a matching "key wrench." The bolt therefore serves as a locking mechanism and helps prevent unauthorized persons from opening the manhole cover.

STABILOC® has developed a clamp-type manhole lock called the STABILOC® Model 911. This product is a spring loaded lever and clamp mechanism that is placed into a receiver unit which is installed in the manhole cover. The STABILOC® is locked by pressing down on the bolt head in the top of the lock. This releases a catch and rotates a lever arm against the manhole frame. The top portion of the lock is pressed down against the receiver and the lever arm is pressed upward against the frame of the manhole. The bolt is then tightened down to lock the clamp, securing the manhole cover in place. When locked, the STABILOC® is flush with the manhole cover surface, and the manhole cover remains flush with its frame, thereby minimizing the potential for the manhole cover or STABILOC® to be dislodged (i.e., if it was hit by a snowplow, etc.).

The bolt used to secure STABILOC® is available in a variety of stock configurations, or it can be custom configured. It can only be turned with a matching socket provided by the manufacturer. A strong, tamper evident, UV inhibited plastic cap locks into the STABILOC® body to cover the recessed bolt head. The disposable cap is designed to protect the bolt head and to keep dirt and debris out of the lock body.

One advantage of this technology over the bolt-type manhole locks is that because the clamp works effectively on any part of the manhole frame, indexing (aligning the cover with a certain part of the manhole frame) is normally not necessary. Only when STABILOC® is used in conjunction with previously installed bolts (normally when a watertight seal is used) is indexing required.

The pan-type manhole lock design consists of a steel pan that is inserted within the manhole and locked into place. This design does not lock the manhole cover on the manhole, but it physically obstructs the manhole entrance. The pan is typically 10 to 12 gauge stainless steel and has a flared edge that rests on the same base or frame ledge as the manhole cover. The body of the pan is more narrow than the manhole opening and is slightly recessed into the manhole. The locking mechanism is located in this recessed portion of the pan.

Two manufacturers currently market pan-type manhole locks. The No Access™(patent pending) manhole security device by Henkels & McCoy consist of a pan which has two cutouts in its sidewalls, opposite from one another. Stainless steel pins are inserted horizontally from inside the pan through each cutout so that they extend outside the pan and under the manhole casement. An eyelet on each pin is matched to an eyelet welded to the interior wall of the pan next to each cutout. A padlock is then inserted through each eyelet pair to secure the pin in place. The manhole cover is then replaced over the pan and the manhole.

The LockDown-LockDry™ pan locking system, manufactured by Barton Southern Company, has been used since 1996. This pan locking system, secures the pan in the manhole with a "bolt and bar" system. After the manhole cover is removed, the steel "bar" portion of the system is tilted and lowered into the manhole. A threaded rod with a cable attached at the top is then screwed into the center of bar, forming a "t." The pan is then seated on the same ledge where the manhole cover normally sits. The pan has a hole through the center, and the cable attached to the threaded rod is pulled up through the center of the pan. As the cable is raised, the threaded rod is also pulled up through the center of the pan. A lock nut on the cable above the threaded rod is tightened down onto the threaded rod.

This pulls the steel bar upward towards the manhole frame, while compressing the pan down on the frame edge. This forms a seal between the manhole frame and pan and secures the pan in place. The threaded rod also has a hole bored through it. As the locknut is tightened, the threaded rod is pulled further upward, eventually exposing the hole. Once the hole is raised above the locknut, a padlock can be inserted through the hole. This prevents the loosening of the locknut and the lowering of the horizontal bar. The padlock is protected with a standard lock guard to deter unauthorized personnel from tampering. In addition, the entire lock, lock guard, and lock nut sit in a recessed portion of the pan, which is then concealed underneath a hinged cover plate to protect it from water and other contaminants. The manhole cover is then replaced over the pan and the manhole.

As stated above, a standard padlock can be used to secure the locknut and pan locking assembly in place. For added security, more sophisticated locks are available that can sound an alarm or send out an electronic signal if they are disturbed. This can notify the owner of attempted unauthorized access to the manhole. These types of locks are available separately and are not part of the standard pan locking system supplied by the vendors.

An important security feature of each of the pan-type manhole locks is their seal against the manhole casement. A tight seal prevents groundwater inflow into the manhole. In addition, the seal can also be an effective barrier against the introduction of hazardous substances into the water or wastewater system. The LockDown-LockDry™ pan style locking system is designed to form a watertight seal with the manhole frame. The No Access™ pan locking system can be custom manufactured to form a watertight seal with the manhole frame.

Some utilities have constructed makeshift locks that consist of a steel bar bolted over a manhole. The bars are secured by padlocks, and the padlocks must be unlocked before the steel bar can be removed and the manhole can be accessed. These makeshift locks are usually located in off-street areas so that they do not impede vehicle traffic over the manhole.

The Intimidator Man-Lock™ bolt locking system uses a specialized bolt that is installed at two locations in the top of the manhole cover, anchoring it to the frame beneath the cover. The product is designed with several security features. First, the top of the bolt has a uniquely designed, patterned groove that can only be turned with a specially designed matching "key wrench." These specialized patterns are regionally distributed so that no two like patterns coexist in the same geographical region. Each bolt type lock is also fitted with a threaded plastic cap to prevent debris from obstructing the keyed groove. To provide additional security, the bolt is either countersunk in the cover or has a special angled head to further protect against tampering with common gripping devices. Finally, Intimidator Man-Lock? manhole cover locks are constructed from alloy or stainless steel, which can deter attacks from common tools and also withstand various environmental conditions. Custom plating is applied to suit a variety of different environments and applications. The vendor can be consulted to determine which grade of steel and plating is appropriate for a particular situation.

As described above, the Intimidator Man-Lock™ manhole cover locks can only be opened with specialized key wrenches. These specialized wrenches are tightly controlled and available only to authorized persons registered by the end-user so that they can access the manholes as needed. An inventory of wrenches and their serial numbers are generally kept by a municipality so that the location of all wrenches is known. Controlling access using these patented keys minimizes the potential for unauthorized access to the manholes.

Intimidator Man-Lock™ manhole cover locks do not require specialized knowledge to install. They can typically be installed by the owner's maintenance crews only with a special heavy duty electromagnetic drill and carbide-tipped drill bits. Drilling though a manhole cover and frame can prove time consuming, however, installation instructions are provided by the vendor. The vendor can also be consulted to determine the appropriate bolt size for a given application, or to determine where to drill holes in different types of manhole covers. This type of manhole lock is suitable for retrofitting in place for concrete, steel and cast iron access covers of any size and shape. In addition, this lock can be retrofitted into manhole covers that are already fitted with non-locking bolts that secure the cover to the frame. Many of the current installations are in manholes which have been custom-ordered with pre-drilled holes in the manhole. These locks do not typically require maintenance, except for periodic greasing, and thus overall installation and maintenance costs are low.

The Intimidator Man-Lock™ can also be used to secure other infrastructure assets. For instance, this product can also be installed on most storm water and sewer grates, which could delay intruders from entering the storm water system.

As described above, the STABILOC? is a clamp-type manhole lock that uses a specialized spring loaded lever and clamp mechanism fitted through a receiver in a manhole cover. The STABILOC? is made from military grade 17-4 heat-treated stainless steel to maximize strength, security, and longevity in harsh environments. The anchor bolt used to tighten the STABILOC? is available in a variety of head configurations. These include:

Sockets matching the bolt head configuration are also provided by the manufacturer. All data and information related to bolt shapes is kept confidential. For added security, STABILOC? also offers an optional high security bolt with a tungsten carbide insert. The insert helps to deter drilling through the bolt head.

The manufacturer recommends that each manhole cover be fitted with two STABILOCs?. The cover must be machined using a Vertical Machining Center (VMC) to accept the STABILOC? receivers. All cutter path programs are provided to the machine shops by STABILOC?. STABILOC? can also provide custom cast manhole covers configured for their locking system. Once a manhole cover is equipped to receive the STABILOC?, the clamp-type lock can be installed or removed in about two minutes.

STABILOC? also has available an optional intrusion sensor that resides under the disposable plastic cap. The sensor is activated when the cap is removed. Manhole intrusion sensors will be discussed in a future Product Guide. For further information on this particular intrusion sensor, please contact STABILOC?.

Pan-type manhole locks are constructed from strong, durable, corrosion-resistant stainless steel. They require no special tools for installation, and installation requires no modifications to the manhole cover or frame. A typical installation can be accomplished by one person in a few minutes. The most important factor in choosing a pan-type manhole lock is choosing the right size for the manhole; therefore, taking proper measurements of the manhole diameter prior to ordering the pan-type manhole lock is essential. Vendors can help with any questions and will generally be willing to send a representative to take the required measurements if necessary. Standard padlocks can generally be used to secure the assembly, although vendors may recommend a specific type suitable to the owners' unique requirements.

The Intimidator Man-Lock™ bolt-type manhole locks range from about $10.00 per lock for orders over 1000 to around $20.00 per lock for orders less than 50. The manufacturer recommended that each manhole be fitted with two separate manhole locks to ensure security. The large t-shaped key wrench sells for around $40.00. They also make a smaller key adaptable to a regular socket wrench that costs about $16.50. Keys are available only to registered users.

The STABILOC? is available for around $200 per unit. The corresponding socket sells for about $20. As mentioned above, the manufacturer recommends each manhole be fitted with two separate locks to ensure security. The cover must be retrofitted to receive the STABILOCs?. Retrofitting a manhole cover must be done by a qualified machine shop and generally takes about one hour of machine time. This cost is in addition to the hardware costs. STABILOC? can also procure covers and have them custom fitted, or will work with foundries to produce the covers configured for STABILOC? and arrange for shipping. Pricing for these services vary due to size, material type, and quantity ordered. Please contact the manufacturer for pricing. The disposable plastic caps that cover and protect the bolt head cost about $0.50 each.

Prices for the No Access™ manhole locking system by Henkels & McCoy, Inc. range from about $495 to $600 apiece depending on the manhole size and quantity ordered. Each No Access™ locking system is custom manufactured to the precise manhole dimensions required with each order.

Pricing for the LockDown-LockDry™ pan locking system from the Barton Southern Company ranges from about $390 to $525 apiece depending on the manhole size and quantity ordered. They can be ordered from standard sizes or they can be custom designed for specific needs.