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April 1, 1998
Daniel Costello and James T. Dinneen
The "integrated" in integrated solid waste management takes on new meaning as competition between providers becomes more intense. For example, in order for a transfer station to be a viable part of an efficient, integrated system, owners and operators must understand the variables that will make their business successful - or not.
Haulers know that collection costs are usually twice as much as disposal costs and that disposal costs are often beyond their control. As a result, they must find ways to collect and transfer waste as efficiently as possible to gain a competitive advantage.
For example, Sacramento County, Calif., is focusing on increasing its collection efficiency by rerouting and implementing a four-day-per-week collection system and by routing more material through low-cost transfer operations.
That's only the beginning. The costs of transfer must be understood. They include:
* the station's annual operating expenses, including: debt on the capital cost to site and build the station(s), debt on the rolling stock and equipment, labor; maintenance/repair and utilities;
* longhauling materials transferred to disposal or market destinations;
* collecting and hauling materials to the station(s); and
* disposal less net revenues from recycling materials recovered.
More to Consider But wait, there's more. Other areas that affect overall transfer cost include basic design and planning. For example, it is important that a transfer facility is properly sized when it is designed.
The basic elements - the scale facility, circulation roadways and queuing areas, the tipping floor and the transfer load-out areas - should be sized based on accurate existing and realistic future traffic and tonnages. Excessively conservative and unrealistic future projections can make the venture appear uncompetitive.
Two simple strategies for keeping capital costs under control are:
* Plan the design based on a 10- to 15-year period instead of guesstimating the tonnage and traffic volumes for 25 to 30 years in the future. Plan for additional growth through easy expansions, such as adding another bay on the tipping floor or adding a second scale). Alternatively, tonnage and traffic growth can be managed by increasing the operating hours.
* Use existing facilities and infrastructure such as industrial warehouses or other large structures. For example, the city of Portland, Ore., converted an old steel mill into a material recovery facility (MRF) and Montgomery County, Ohio, expanded a facility originally designed for incineration into a transfer station (see "Montgomery County Shapes up, Ships out" on page 44).
What's Your Operating Cost? Labor, operation and maintenance costs can represent up to 50 percent of total annual costs. To keep labor and operating costs as low as possible, planners in Sacramento County, Calif., are considering the following options at their two existing 300 to 400 ton-per-day (tpd) stations and one planned 300 tpd station:
* Centralizing different functional operations when making material recovery improvements. For example, one person manages both sets of containers when they are set side-by-side - the roll-off containers used by the public for recyclables and the containers for loading recovered materials from the tipping floor.
* Because the new transfer station will eliminate all self-haul traffic at the landfill, the county will defray system-wide cost increases by transferring unneeded landfill equipment and staff to the proposed transfer operations.
* Instead of implementing costly mixed waste processing and sorting operations, the county plans to incorporate material recovery improvements at its transfer stations that provide incentives for the public to separate recyclable materials.
These include constructing a free tip area for recycling certain materials. A waste exchange also will be established to encourage customer recycling. Another improvement will be a new, reduced-rate tipping area so that customers can dispose of materials such as clean loads of inerts, wood, white goods and yard waste.
Longhaul Costs Typically, longhauling materials from the transfer station to the landfill is the most expensive element. Factors that contribute to high longhaul costs include low payloads, inefficient loading/unloading and inefficient round-trip travel times.
The most effective step toward minimizing longhaul costs is to reduce the amount of time and the number of longhaul miles traveled annually. Tactics to maximize payloads include:
* breaking up and running over the waste on the tipping floor to increase density prior to loading transfer vehicles;
* using tamping equipment to increase the material density in open-top transfer trailers; and
* using mechanical compactors.
Preload compactors and lightweight trailers also can minimize longhaul's costs. However, for preload compactors to be cost-effective, haul-cost savings must offset the additional capital and the compactors' operating costs. A comparison between open-top and preload technologies must include the following to determine the lowest per-ton cost:
* Annual debt service on capital costs. At about $1 million for a large, high-capacity preload compactor and associated infrastructure, pre-load compaction costs are considerable. Conversely, the cost of tamping equipment must be considered for open-top stations.
* Station labor costs. Labor costs for tamping equipment operation is higher than that for preload compactors, which can be operated either by loader operators or truck drivers.
* Maintenance, repairs and consumables costs for both the compactors and tamping equipment.
* Longhaul costs, consisting of debt service on transfer vehicles, driver labor, fuel and lubricants, tires, vehicle repairs and maintenance, taxes, insurance and licensing.
Payloads depend on the size and type of the transfer trailers used and the over-the-road weight limits. Payload optimization must be evaluated by project to identify the most cost-effective operation.
For example, in Montgomery County, the transfer stations primarily are handling packer truck waste using tamping cranes with open-top trailers. Even with a 50-mile, one-way haul, this system provides the lowest-cost operation.
In contrast, at Sacramento County's North Area transfer station, which primarily handles self-haul and low-density waste materials, pre-load compaction is the lowest-cost operation with a 25-mile, one-way haul.
In congested metropolitan areas, longhaul costs can be reduced by scheduling the transfer outside of heavy traffic hours.
While no cookie-cutter plan exists, your transfer station can remain competitive if it is properly designed, built and operated.
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