Trailers, Containers, and Transporters Rolling the Job SIte
Rarely showing up as line items for particular tasks, transportation costs usually get placed under indirect overhead costs. But they are required nonetheless. Without their supporting roles, there would be no job site in the first place.
There are two broad categories of excavation and grading equipment: those that are wheeled and those that are tracked. This article will examine the broad range of functions provided by the former. However, the emphasis will be on the operational characteristics and capacities of those unsung wheeled vehicles (office trailers, storage trailers and containers, or equipment trailers for hauling other equipment to the site) that indirectly affect the job site.
These pieces of equipment don’t directly do any work. No contractor can directly make money off of them. Such rolling equipment does cost money for the operator to lease or to purchase, however.
Trailers for Heavy Equipment
The reason for acquiring or leasing an equipment trailer is to provide transport for other construction equipment, such as backhoes, dozers, trenchers, compactors, graders, and even other tool carriers. Aside from preventing this heavy equipment from tearing up the pavement of public roads between job sites, utilizing an equipment trailer saves on wear and tear of the equipment itself. Even wheeled construction equipment is seldom designed for long road distances. This reduces transport times, labor costs, and fuel costs, which in turn minimize repair and servicing costs. Once delivered to the site, the use of separate equipment trailers makes it easier for the truck hauling them to drop off the equipment in a confined area.
(Historical note: The first widespread use of equipment trailers was the use of tank-hauler rigs during World War II. From the earliest days of armored warfare, it was noted that long-range, cross-country movement of tanks resulted in frequent breakdowns, knocking out more tanks than actual combat. Hollywood movies and even newsreels of the day that show tanks advancing on their own across country roads for long distances don’t show the far less dramatic logistical reality.)
Equipment trailers come in two broad varieties: flatbed and tilted bed. The flatbed trailer has a fixed flat surface where the equipment is parked for transportation. Access to this surface is provided by lowering a ramp hinged on the back of the flatbed. When fully laid out, the ramp has a typical approach angle of 8 or 10 degrees to the horizontal. This allows for easy access of the flatbed. These ramps are referred to as beavertails or dovetails. These can be full-size ramps that extend as one or two pieces the entire width of the flatbed, or they can be two separate ramps that resemble ladder frames wide enough to handle the width of the tires or the tractor treads of the equipment being transported. The positions of the separate ramps can be adjusted so that the distance between can match the wheelbase or undercarriage width of the equipment. Once the equipment is loaded and in place, the ramps are lifted back up and locked into an upright position for transport.
The other type of equipment trailer is the tilted-bed model. Instead of using a fold-down ramp, the entire bed tilts on a midpoint pivot until the back end comes into contact with the ground. Again, the usual approach grade is about 8 or 10 degrees to the horizontal. As the equipment rolls up onto the tilted bed, the weight of the equipment combined with the lowering motion of the bed itself returns the bed to its original horizontal position. The bed is then locked in place and is ready for transport. To steady the trailer during loading and unloading, landing jacks located at each corner of the rear of the bed are extended to the ground to ensure that it stays level. Some models come equipped with a winch for mechanical loading.
Standard features of any heavy-duty equipment trailer typically include the following: an air-lift assembly that can pneumatically raise or lower the bed depending on the weight of the load and still be light enough to be towed by a three-quarter- or 1-ton truck; a diamond plate-walk on the sides to improve friction contact; heavy-duty landing jacks (10,000 pounds capacity minimum) mounted on each corner; dual-axle, load-sharing suspension; a mechanical override braking system (with brakes on each axle); restraint straps and chains; a reinforced steel floor; heavy-duty axles and frames; and an auxiliary Pintel hitch.
Standard equipment trailer sizes range from 2-ton capacity to 25-ton capacity. The deck height ranges from 30 inches to 36 inches, making it possible to load packages and materials onto the bed from the side with forklifts. Most tail ramps measure 5–6 feet in length. Axle widths may be as long as 102 inches with bed lengths as long as 30 feet. Some trailers are combination trailers capable of hauling bulk items and equipment alike. These provide greater transport flexibility but often are limited in regard to the size of equipment they can carry. Eight-lug wheels with 10-ply tires are often used for heavy transport.
Storage Containers and Trailers
Two types of “boxes” are available for onsite storage: storage trailers and ground-level containers. Storage trailers are distinct from ground-level containers in that they can be maneuvered and hauled on their own set of wheels, whereas ground containers are equipped with rollers that allow them to be hauled onto the back of a flatbed truck for transport. Ground-level containers tend to be more ruggedly built, some using 14-gauge steel siding and often being airtight as well as watertight, since they tend to be more permanently located or used as shipping units. Containers can be used to store a wide variety of construction equipment, supplies, materials, parts, tools, documents, and records. They typically range 12–40 feet in length. Containers provide security against theft or damage.
Mobile storage is provided by storage trailers. Their function is to serve as a warehouse on wheels, combining both storage and transport functions. They typically range in size from 28 feet to 48 feet in length. Their doors can either roll up or swing open. Storage trailers are typically loaded from loading docks. Being high off the ground also provides greater protection from the elements, especially flooding.
A specialized form of storage trailer is the tool trailer. Usually much smaller than the typical storage trailer, the tool trailer is often manufactured specifically for individual customers, making each tool trailer a one-of-a-kind structure. Each tool trailer has a unique storage configuration and organization scheme, depending on the customer’s needs. These are not just places to hang and store hand tools and other parts (appurtenances, adhesives, lubricants, or fasteners); these trailers also serve as mobile workshops. The working space can be inside and sheltered from the elements or the sides of the trailer can open up to expose the work bench and minimize space requirements. Tool trailers are built in anticipation of rugged use, reinforced with heavy steel frames and aluminum siding along with their own electrical outlets and lights. Unlike other types of trailers, tool trailers are typically owned by the contractor and are not leased for a particular job.
Office Trailers: Construction and Installation
Office trailers are a form of premanufactured (or prefabricated) buildings. They are constructed in a factory and then hauled out to the site. This factory assembly ensures that the buildings and their components are built strong enough to stand the stresses and strains of being hauled over roads and hills. However, they should be distinguished from modular buildings and other similar premanufactured structures. Modular buildings are permanent structures set on fixed foundations and are usually built to the owner’s specifications. They also tend to be much larger than office trailers, usually requiring that the building be brought out in pieces for onsite assembly.
Office trailers are smaller, temporary structures delivered to the job site for a fixed lease period to provide office space and storage capacity for the duration of the project. They are mostly used by contractors and subcontractors, though they are also used as onsite work space for architects, engineers, consultants, sales representatives, regulatory agencies performing oversight, and other employees.
Office trailers come in a variety of sizes, layouts, and auxiliary functions. Widths vary from 8 feet to 14 feet (at 2-foot intervals). Lengths range from 16 feet to 60 feet. The term single-wide refers to a single, stand-alone office trailer measuring, for example, 12 feet by 60 feet. Two such office trailers installed side by side and joined together into a single office unit measuring 24 feet wide by 60 feet long are referred to as a double-wide.
The exterior finishes of the manufactured office trailers can be modified to meet needs, preferences, and budgets. The plainest of these (simple featureless boxes) are considered construction-grade and represent the low end of exterior finish options. Each trailer should come equipped with entrance stairways (preferably prefabricated metal frames with equipment to clean the soles of muddy boots) and entrance ramps for handicapped access if required by law. Trailers have a gap between the ground surface and the bottom of the trailer itself (where their wheels are located). Usually, some sort of decorative skirt or framing is installed to hide this gap.
Besides costing more, larger office trailers are typically leased for longer periods of time than smaller trailers. Office trailers are rarely sold outright to customers. They represent too large of a capital investment for purchase (along with all the personnel, support vehicles, and equipment necessary for transport, delivery, and installation). Office trailers may be obtained either from local dealers (according to reputation or personal contacts) or from nationwide vendors (according to their wide selection of models and types).
The type of trailer to be used depends on its function at the job site. The first question to ask is that of how many people will use the trailer on a regular basis. Sufficient room is provided by the previously mentioned 12-foot-by-60-foot office trailer for up to five or six personnel to work comfortably. The floor plan of the trailer can be set up to provide a meeting room, a changing room, additional storage closets, a bathroom, or a kitchen.
Siting the office trailer once it is delivered to the job site involves ensuring ready access to the trailer while making sure that the trailer itself does not block access or violate set-back requirements. Security in the form of fencing and gates usually encompasses the entire job site (unless the site is a land development project covering hundreds of acres). Fencing can also be provided around the office trailer and adjacent parking areas. Parking is usually provided by gravel paved areas adjacent to the office trailer and connected to the site’s main access road. Parking is usually set aside for lightweight cars, trucks, and vehicles. Heavy vehicles and construction equipment are parked in their own separate area. Access to the office park is usually by gravel roads connecting to local public service roads.
Each office trailer will have a unique construction area footprint based on local topography and the dimensions of the trailer. Many municipalities have stringent building codes for office trailer installation. Many require even temporary trailers be installed on concrete or asphalt pavement (not grass or gravel). The pavement design and thickness must be such that it can support the weight of the trailer. Often the trailer is required to be anchored into the underlying pavement by means of anchor straps set at a 45-degree angle to the horizontal to prevent overturning. The location of the trailer in relation to the site’s property lines may also be governed by local codes. These codes limit how close a trailer can be installed to a property line, and they establish set-back distances from the trailer to adjacent streets, fences, walls, utilities, rights of way, and other buildings.
Once the job is complete and the trailer no longer needed, it should be broken down and removed from the site. All office equipment, furniture, and storage items that are owned by the operator and did not come with the trailer need to be removed. Anchors, stairs, and skirts are removed in order to make the trailer mobile again. The supplier then comes out to the site, hitches it to a hauling truck, and pulls it offsite. Once the trailer is gone, good housekeeping measures should be undertaken to clean and repair damage caused by temporary installations or use of temporary facilities. Drainage should be restored, and the land should be evenly graded, seeded, or planted as necessary. The goal is to leave the location of the trailer equal to or better in appearance than the original.
Office Trailers: The Utilities
An office trailer is not much good for anything but bulk storage and basic shelter from the elements without its utilities. If the office trailer is the “brains” of the job site, its utilities are the nervous system that lets the brain function. There are several key utilities required by every office trailer: electricity, lighting, heat, telephone, water, and sanitation. In addition to these traditional utilities, Internet access is now as important as telephone hookups.
Electrical power is provided either by hookups to adjacent power lines and their transformers, or by mobile generators. When hooking up to existing power lines, a 120-V single-phase service line is typically provided (though some sites are adjacent to three-phase power).
Exterior temporary lighting is installed once the electrical hookups are complete to allow for completion and observation of work being performed (including the installation of the office trailer itself). The interior of the office should be provided with overhead fluorescent lights, lamps, wiring, switches, sockets, and similar appurtenances for the supply of electrical power for lighting, small power tools, and office equipment. All electrical systems need to meet the national electrical code, while illumination for the work site has to meet state code requirements.
Heat can be provided either by baseboard electrical units or by propane gas furnace. Of the two, the propane system is typically more expensive to construct but cheaper to operate. So electrical baseboard heating is usually found in smaller office trailers with propane furnaces in larger units.
Air conditioning is almost always provided by window-mounted units, except in the largest of models. When utilizing propane gas furnaces, provisions should be made for regular delivery of the fuel to the job site and the purchase of the gas accounted for in the site’s operating budget. Additionally, the furnace should be maintained in accordance with the manufacturer’s schedule. The ducts that deliver the hot air generated by the propane furnace throughout the office trailer should be checked for mold and cleaned on a regular basis. Furthermore, disposable air filters should be provided and replaced as needed.
Temporary space heaters are sometimes used, but this is not recommended for the duration of the project for reasons of safety and space utilization.
Telephone connections remain important even in this age of the cell phone and wi-fi connections. Often, telephone lines are collocated in the same easement as the power lines. Touch-tone telephone service is not the only use for these lines. Fax machines will also utilize these lines to send contract and purchase documents. Internet connections are vital to any business, especially those using isolated job sites. If no landline is available or if the site is within easy reach of a wi-fi hot spot, then wireless connections can be made. However, those worried about proprietary information may want the greater security and privacy afforded by a landline.
Rarely is a water main located near enough to the job site to allow for direct access to potable water. Even if a water main was conveniently nearby, the costs of a tap-in, obtaining the permit from the water department, and the installation of the feeder pipeline may be too expensive, especially for a temporary facility. Delivery of bottled water is the method of choice for providing drinking water to an office trailer. One exception to this rule is the accessing of fire hydrants, whether for cleaning purposes, pipe flushing, or fire control. Permits should be obtained beforehand for hydrant access and/or agreements made with the local fire department for opening the hydrant valves for site use.
Also lacking on a typical job site are existing sanitary facilities such as washbasins and flush toilets. Fortunately for most large-size office trailers (8 feet by 30 feet or larger) restrooms are a common feature. Toilets are almost always chemical toilets, not that different from the portable toilets found on all job sites. These restrooms tend to be large and also provide cleanup facilities, including emergency eyewash basins. Some office-trailer suppliers will also provide chemical toilet evacuation services and provide the necessary paper supplies, although the site operator usually has to obtain these services from a separate subcontractor.
The lack of direct water service should not in any way impair the facility’s ability to fight fire. A minimum of one all-purpose fire extinguisher should be provided for each office trailer (two for a double-wide), and office-trailer personnel should be trained in its use.
The trailer itself should come equipped with a smoke detector and an automatic alarm that signals the local fire department. The manager of the office trailer should keep important documents (contracts, insurance policies, purchase agreements, or ready cash) in a fireproof safe.
Author's Bio: Daniel P. Duffy, PE, writes frequently on the topics of landfills and the environment.