Aboveground
containment systems have advanced to higher levels of versatility
and price/performance with the introduction of modularity in their
design, fabrication and installation. Among advantages reported
for prefabricated modular tanks, including secondary containment,
are lower costs, and rapid availability and shipment for emergency
storage, spill containment and site remediation. In addition, these
systems can be easily customized from standard components into almost
any right angle configuration for irregularly-shaped areas: "L",
"T" and "S" shapes are typical.
They bolt together
quickly with standard hand tools and can be knocked down for relocation
or compact storage. When disassembled, the steel components of a
300,000-gallon tank can be stored on pallets in an 8 foot x 10 foot
space. Modular tanks are equipped with various types of corrosion
and chemical resistant flexible membrane liners for the storage
and handling of virtually all liquids, hazardous wastes and sludges.
Among available
application-specific flexible membrane liners are XR-5, Hypalon,
PVC, HDPE and potable water grade polypropylene. Most often the
appropriate liner is precut, sometimes seam-welded at the shop to
the exact dimensions of the tank, and delivered with its metal components
in one package.
These systems
may also be resized by adding or subtracting panels and refitting
them with appropriate liners. Modular tanks from 250 to millions
of gallons accept inlet/outlet piping, sumps and other product handling
plumbing equipment, as well as floating covers. Leak detection can
also be incorporated through geotextile or drainage net layers between
the tank's primary and secondary liners.
Squaring
the circle
Modular storage systems are not new when considering that many of
today's typical round tanks are designed and installed with modular
curved panels which are repeatedly bolted or welded together in
sequence. What is new is modularity as a total design concept unique
to the rectilinear tank whose standardized parts can be configured
to site patterns.
Tank installation
can be completed on prepared, compacted ground free of depressions
and sharp objects, or on concrete or asphalt beds as environmental
regulations mandate. For example, assembled as an "L,"
a tank could be cornered around obstructions. Modularity serves
almost any asymmetrical configuration that is compatible with the
available space.
Modularity also
means accessibility--tanks that go most everywhere and fit anywhere,
indoors or out. Hand-carried through doorways, hatches or windows,
modular components bolt together rapidly in hard-to reach locations
like basements, tunnels, upper floors, laboratories, rooftops and
utility areas. Modular tanks could be the sensible alternative to
breaking through walls to retrofit plant interiors with additional
storage capacity.
A demonstration
of the kind was performed when installing storage for fuel oil and
hydraulic fluid in a salt mine chamber 2,500 feet below ground level.
Hand-carried components for two 10,000 gallon modular tanks with
covers were transported via the mine's elevator and tunnel for bolt-together
assembly in the deep site--averting the hazards of welding fumes
trapped in poorly ventilated spaces.
Other
savings in time and applications
An often underappreciated cost factor in tank installation is that
of transportation. In the case of modular rectangular tanks, all
components are strapped to standard skids--each weighing approximately
3,000 lbs for site delivery by commercial flat bed trucks.
Heavy duty containment
systems have met extremely hostile weather conditions on the North
Slope of the Alaskan pipeline, and were successfully erected on
tight deadlines in mid-winter at the Halifax and Montreal airports.
In a challenging North American installation, a million gallon (U.S.)
tank for emergency containment was shipped the next day and operational
within three days.
Modular rectangular
containment systems are believed to be nearing full partnership
with conventional round tanks as facilities for hazardous materials
containment, handling and treatment.
By
Reed Margulis, President ModuTank Incorporated
