Municipal safety centers typically combine
police, fire, 9-1-1 and other emergency
services and must remain operational at all
times. If communications systems fail,
dispatchers are helpless, emergency workers
can't find each other and the public could be at
COMTEC, the county's impressively rebuilt, 25,000 square feet safety center in Mt. Clemens, Michigan is in the up and running since they're often dealing with life-and-death southeastern part of the state. It's critical that all communications services remain situations in their 9-1-1 dispatch center. All communications systems need antenna towers, which naturally invite lightning strikes that can cause damage to a center's sensitive equipment.
The solution: equip the towers with robust,
correctly designed and properly installed
lightning protection and grounding systems to
direct lightning energy away from sensitive
equipment and harmlessly into the earth before
it damages equipment.
Victoria Wolber, Macomb County's director of
emergency management and communications
based at COMTEC, said that they knew they
had to call in experts who understood lightning
protection and grounding fields, knew their
systems and how to protect their critical assets.
Since then, she said that COMTEC has never
had any lightning-caused downtime.
Wolber and her electrical contractor hired Greg
Fair, a project manager and field
superintendent with Guardian Equipment
Company, a Michigan-based firm that
specializes in lightning protection. Since
COMTEC was relocating to an existing
structure with a pre-existing tower, the
challenge was to formulate a system that met
the applicable codes and accommodate the
During reconstruction, the building's open
walls helped Guardian Equipment advise the
engineers on designing and concealing the
new grounding system. The building's antenna
tower had previously been grounded, but the
existing mechanical connection method was
found to be inadequate. Existing connections
to the tower showed signs of aging. They were
mechanical, in one case using a simple water
pipe connector, and had become loose over time.
There was also some corrosion, which increases
To aid in the new grounding system design, Fair
and his team referenced several codes that dealt
specifically with grounding for lightning protection:
Underwriters Laboratories' UL96A: "Installation
Requirements for Lightning Protection Systems,"
the National Fire Protection Association's NFPA
780: "Standard for the Installation of Lightning
Protection Systems" and the Lightning
Protection Institute's LPI 175: "Standard for the
Design – Installation – Inspection of Lightning
Protection Systems". The well-known and often
used Motorola 56A, which also deals with towers,
did not fall within the scope of work.
Fair and his team began with a site survey to
guide their engineers in designing the work.
Afterward, the team installed air terminals at 20
foot intervals along the roof's perimeter and
elsewhere on the roof. The perimeter cable was
used as a ring ground from which to drop down-conductors
to driven 10 feet x ¾-inch copper-clad
electrodes in the ground below. Approximately 15
driven electrodes were spaced about 100 feet
apart surrounding the structure. Two of them
specifically bonded to the ring-ground surrounding
The tower was grounded with 28R cable, a special
Class II lightning conductor consisting of 28
strands of bare, braided AWG 14-gauge wire.
Class II cable is used for structures taller than
75 feet. It is also good when conductors have to
be exothermically welded to ground rods,
building steel, or in this case, to the tower itself.
All services, such as electric, water and gas were
bonded together at a common ground potential
and bonded to the building's grounding system,
in accordance with code requirement. Fair tags his
installations where appropriate to inform workers
of the code-sensitivity of those connections.
Fair said they also bonded to exposed building
steel. Bonding the grounding system to building
steel is also a code-mandatory practice. However,
while building steel might provide a de facto
ground/earth connection, a continuous electrical
path cannot always be verified and grounding
connections should properly be made via
adequately sized copper down-conductors bonded
to appropriately spaced, driven electrodes.
A rooftop level ring-ground surrounding the
structure might also be employed, as was done
at the COMTEC facility. The ring simplified
installation of the lightning protection/
grounding system, and its copper down-conductors,
blended in well with the center's
Macomb County operates several auxiliary
transmission facilities that are located such that
they provide emergency communications to the
county's 850,000 residents throughout the large
479 square miles jurisdiction. The auxiliary
facilities are each equipped with a tower. The
towers, as well as the facilities themselves, are
protected from lightning strikes by robust, all copper
Notably, neither the COMTEC facility nor any
of the county's properly grounded auxiliary
transmission stations have ever experienced a
lightning-induced service disruption. For that,
Macomb County residents can thank smart
decisions by COMTEC management, proper
design and installation, regular maintenance,
and of course, robust, all-copper grounding and
lightning protection systems.
The full article with more details and images may
be found at www.copper.org.
Emergency Management Coordinator
Macomb County, MI
Greater Detroit Area