Rural Transfer Stations: Built For The Long Haul

Erik E. Colville and Nancy J. McFeron

Transfer stations in rural areas are growing to larger numbers than ever. rural transfer stations handle a waste flow of less than 200 tons per day and serve approximately 60,000 people. A typical station handles less than 60 tons per day and serves approximately 20,000 people.

A rural transfer station includes solid waste services and a minimum of recycling and/or household hazardous waste collection services. Customer vehicles usually are not weighed, and often a rural transfer station is not attended full-time by an operator.

At a rural transfer station, residents can dump their garbage at the least possible cost. Because sites are often unattended, design the site layout and signs to clearly direct users to the transfer and recycling areas and to provide enough capacity so that the transfer or roll-off containers do not need to be changed more often than necessary.

Station Types Rural transfer stations fall into two main categories: roll-off or drop box stations, which use roll-off containers to receive customer waste; and transfer stations, which use transfer trailers to receive waste.

A typical roll-off container is 24 feet long by eight feet wide and six feet tall, with a capacity of 40 cubic yards or seven tons of garbage. The roll-off containers are transported on a straight body truck with a tilting frame and winch for loading and un-loading the container onto or off of the truck. Transfer trailers are typically 40 feet long by eight feet wide by 14 feet tall with a capacity of 109 cubic yards or 16 tons of garbage.

For smaller communities, roll-off stations accommodate only one container; larger stations use two or more containers, depending on the capacity needed and the desired frequency of changing the containers.

Stations may be uncovered, have only a roof or walls, or may be enclosed within a building. Nearly all roll-off stations are configured so customers dump their waste directly into roll-off containers.

Transfer stations also may accommodate one or more trailers, and may not be enclosed, surrounded by walls or covered with a roof, or may be enclosed within a building. In these facilities, customers drop their waste directly into the transfer trailer or onto a flat concrete slab.

In direct dump stations, customers drop their waste directly into the trailer; in tipping floor stations, customers dump onto a concrete slab. At a tipping floor station, a rubber-tired loader pushes the waste across the floor and over the edge of a retaining wall into a transfer trailer below.

Some transfer trailer stations use a conveyor to transport customer waste to the transfer trailer. A few stations have a shallow pit for customers to unload their waste, then a rubber-tired loader pushes the waste into an opening in the floor where it drops into a transfer trailer below. Neither type is commonly used in rural applications because they are generally more expensive to build operate.

Although direct dump stations are the least expensive to construct, operate and maintain, they can be dangerous and it is difficult to unload while a trailer is being changed. It is also difficult to check the waste for prohibited materials or to remove recyclable materials before it enters the transfer trailer.

At tipping floor transfer stations, the customers dump their waste onto a flat floor rather than into a trailer. The operator of the rubber-tired loader is trained to notice and remove unacceptable waste materials as the waste is moved toward the transfer trailer. Transfer trailers can be changed without affecting the customer unloading operations.

Characteristics Selecting a station type should be determined by economics, including the construction and/or operations and maintenance (O&M) costs. A roll-off station is the least expensive transfer facility to construct and operate. A roll-off application can be used for waste flows of less than 15 tons per day.

It is also important to consider the distance to the disposal site. If a long haul to the disposal site is required, the additional capital cost of a transfer trailer station could be offset by the reduced cost of hauling fewer of the larger transfer trailers.

Unless project budget restrictions or local preferences dictate otherwise, transfer and roll-off stations should at least be covered and, preferably, enclosed. The only way to control wastewater, litter, dust and odor is to provide some shelter for the waste handling area.

The physical size of the transfer station can be determined by identifying the number and type of customer vehicles served. Unless the customer vehicle size can be accurately predicted or controlled, it is best to plan for 22-to-25-foot maximum height.

The station width must be at least as great as the length of the transfer trailer or roll-off container. The number of customer vehicles that must unload simultaneously (to minimize the waiting time for other customers) will affect the station width. To determine the number of dumping stalls, use a vehicle queuing analysis that considers the hourly distribution of customer vehicles during a peak vehicle day and the average time it takes to unload.

The station depth depends on the station type. A direct dump station needs a depth of 12 feet for each transfer trailer or roll-off container and 15 to 20 feet for customer vehicles. A tipping floor station must have 12 feet for each transfer trailer and a minimum of 40 feet of tipping floor. Additional tipping floor depth may be added to provide a few days of waste storage capacity to the floor.

Public perception is the main difference between rural and urban transfer stations. For example, in an urban area, customers are more accustomed to being rigorously protected from falling hazards and heavy equipment. Customers in rural areas generally know to watch out for their own safety.

Another example is the public perception of what constitutes an environmental impact. Urban residents are accustomed to air that doesn't have a noticeable odor. Many rural areas have dairies and feedlots that emit a distinct but acceptable odor.

Siting And Equipment The station's design must be coordinated with local fire and public health officials to determine the type of fire protection at the site and the handling of wastewater and runoff.

Environmental controls necessary at any transfer station include diversion of surface water from off-site areas away from the site; control of surface water run-off from the site; collection and disposal of wastewater from the waste handling and trailer storage areas; litter, odor, dust and pest control; and a limited waste storage time.

In some areas, simply locating and purchasing a vacant piece of property is adequate for siting a rural transfer station. In other areas, possible sites are brought to local officials for selection. Some areas may even require an open, public nomination, ranking and selection process.

In all areas, the siting process can become political, since those in favor of or against the project lobby their local elected officials.

Successful siting can be accomplished by objectivity and allowing for public input.

To minimize siting difficulty, consider the following characteristics: * No residences, restaurants, day care centers or other sensitive neighbors located within 1,000 feet.

* Site topography allowing the station to be hidden or at least screened from view by neighbors.

* Access to the station on a public, paved road wide enough for two vehicles to easily pass and

* Site topography that allows the station orientation to minimize wind blown debris.

More technical site characteristics to consider include sufficient site size, appropriate site shape, acceptable soil geology and groundwater conditions, access to water and electric utilities and access road characteristics.

After the site has been identified and its benefits documented, it is best to commission the local officials to make the final decision. This allows the public to feel that they can affect the decision and helps to avoid disputes during the conditional use permit and planning and zoning permit phases.

Compared to urban transfer stations, rural transfer stations are less expensive to construct, operate and maintain. A basic rule for keeping costs down is to eliminate or minimize any equipment that isn't absolutely necessary for day-to-day operation.

To determine the equipment needed, ask the following questions: * Will the equipment pay for itself in five to seven years by reducing some other cost

* Will the equipment reduce the number of employees or allow the site attendant to manage another transfer station site?

* Is the project budget for the station sufficient to allow the purchase of the equipment?

In general, the only equipment needed at a rural station is a rubber-tired loader, a yard tractor and a knuckleboom crane. The rubber-tired loader is needed only when the transfer station is a tipping floor type. If wood or yard waste services are available at the transfer station site, a loader is more easily justified.

A yard tractor is necessary if more than one trailer will be filled and needs to be changed during the operating day. A knuckleboom crane adjusts the distribution of waste in transfer trailers and increases the waste density so that the maximum amount of waste can be loaded into the transfer trailer. If the knuckleboom crane will reduce the number of trailers or containers hauled from the site over a five-to seven-year period by an amount sufficient to pay for itself, it is a good investment.

For a facility that offers such services as basic solid waste transfer, recyclables drop-off and white goods, yard waste and tire collection services, five to 10 acres are needed. For construction debris disposal or yard and wood waste composting services, the site should be larger than 10 acres.

Although not required, a slope is helpful for surface water control and conveyance and helps to achieve the elevation difference needed for tipping activities without extensive site regrading. The slope should allow the transfer building to be oriented with blank walls (no doors or openings) exposed to the prevailing wind. If the site has little or no slope, or if the slope runs contrary to the direction needed for proper building orientation, earth-moving construction can create the necessary slope, at a cost.

The site should be arranged to present recycling services to customers as they approach the transfer building, using the power of suggestion as an incentive for recycling. For customers with only recyclables, an exit should bypass other services they do not need.

On-site roads should be arranged to avoid or minimize turns across traffic. Roads for transfer trailers or roll-off trucks should be separated, if possible, from the roads used by customers. Site roads should be long enough so that, during the busiest traffic, all vehicles will fit on the site and not block public access roads.

Consider Costs Because a rural transfer station is designed to minimize costs, consider the following planning-level construction costs: * Uncovered roll-off transfer station: $70,000;

* Covered roll-off station: $90,000;

* Enclosed roll-off transfer station: $190,000;

* Uncovered single trailer transfer station: $220,000;

* Enclosed single trailer transfer station: $320,000;

* Enclosed double trailer transfer station: $420,000;

* Enclosed single trailer tipping floor station: $600,000; and

* Enclosed double trailer tipping floor station: $750,000.

These actual costs are based on a rural transfer system constructed in southern Idaho last summer. Twelve transfer stations were sited, designed, permitted and constructed under a $490,000 engineering contract (approximately $41,000 each). The approximate construction cost of the stations was $3,370,000. A rural transfer station in central Washington has a construction cost of $750,000 and an engineering contract of $160,000 for siting, design and permitting.

Budgets for rural transfer station projects are typically limited. Before beginning a project and spending unnecessary money, contact an experienced designer to guide you through the process.