Waste

Keeping Transfer Station and MRF Infrastructure Costs in Line

Operating a solid waste facility presents an ongoing challenge to meet ever-changing demands, and needs for capital expenditures can arise for many different reasons.

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Predicting the future and exactly where the funds to make changes will come from is difficult. Plus, most facility owners want to minimize their capital expenditures. But the fact is, improvements and expansions will always be needed: so, how can operators plan for and keep those costs in line?

Unfortunately, controlling transfer station and materials recovery facility (MRF) infrastructure costs can be challenging—on the order of climbing a mountain or wrestling a bear. But fortunately, there are many tools and much information available to facility owners for planning and managing capital improvement costs.

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Ever-increasing demands for greater recycling and landfill diversion, along with stricter regulations for mitigation of environmental impacts, may dictate solid waste facility improvements and expansions that can require significant capital investment. Additionally, by their very nature, transfer stations and MRFs are subjected to extensive wear and abuse, requiring frequent—and sometimes extensive (and, of course, expensive)—repairs and replacement.

Although transfer stations and MRFs should be designed to resist excessive wear and tear, with the future in mind, the need for repair and improvements is inevitable. The costs for repair and the costs for future improvements are very different, and keeping them in line requires different approaches. This article will discuss effective strategies for facility owners when addressing both.

Managing municipal solid waste is more than landfilling: publicity, education, engineering, long-term planning, and landfill gas waste-to-energy are specialties needed in today’s complex environment. We’ve created a handy infographic featuring 6 tips to improve landfill management and achieve excellence in operations. 6 Tips for Excellence in Landfill Operations. Download it now!  

Improvements and Expansions
The need to be bigger and better: higher recycling goals, more processing, advances in technology, new rules and regulations—all of these can create needs for facility improvements and expansions. Forecasting and controlling costs for these future improvements and expansions requires planning ahead, which in turn requires good technical analysis and design.

Preparation of a master plan to identify foreseeable improvements and expansion needs is a good way to manage expectations, establish priorities, and minimize the future capital and operating costs. This process starts with completing an inventory of current operations. What works well, and what doesn’t work well? What is missing?

After completion of the inventory, the focus must shift to long-term needs. These could include added capacity, new and expanded services, new systems and processes to increase materials recovery, and diversion or alterations to comply with regulatory changes.

Once a needs inventory has been completed, necessary improvements can be identified and quantified. These may include building expansions, site modifications, or new equipment and processes.

Based on this information, a master site plan can be prepared to examine how these improvements can be incorporated into the facility. This plan must consider phasing to minimize impacts to current operations, traffic circulation, and safety.

The next step is to prepare an Implementation Schedule for all improvements and phases. At this point, capital cost projections can be prepared, and a Capital Improvement Program can be developed for the desired period—say five to 10 years.

This technical schedule and cost information will become the basis for the master plan. The described process, besides creating a valuable planning, informational, and consensus-building document, will most likely result in the soundest strategy for facility growth and the lowest cost for implementation.

A recent example of how a community accomplished this is Redding, CA. The City of Redding Recycling and Transfer Station was constructed in 1996. By 2010, the existing facilities were not adequate to handle the volume of customer traffic and the new services that had been added over the years. In addition, the State of California passed new legislation requiring jurisdictions to recycle more materials for the commercial wastestream.

The City of Redding and JR Miller and Associates, its consultant, worked to complete a total inventory of the existing facilities and assess how the site could be retrofitted to meet existing and future needs. The planning process focused on creating more space on the site to relocate the outdated recycling drop off and household hazardous waste operations and expanding the transfer station to add more equipment to process commercial waste in the future. The Master Plan was completed, and a 15-year capital plan was prepared to forecast revenue requirements and prepare an Implementation Schedule and Financial Plan for the improvements. In 2016, the City will complete Phase 1 of a multi-year plan to improve and expand the facility.

Repair and Replacement
Wear and damage to a solid waste facility can be reduced through good operations and maintenance, but the need for eventual repairs and replacements is unavoidable. Realizing and planning as far ahead as possible will allow time for the consideration and evaluation of the widest array of options.

Repair and replacement projects almost always affect existing operations and may require temporary shutdowns. The opportunity cost of these operational inefficiencies and possible loss of revenue must be included in the analysis. Once all feasible options have been identified and evaluated, a facility owner can make better decisions that will keep their costs in line and establish timelines to ensure sufficient funds are available when needed.

The most common repaired and replaced item in a solid waste facility is the tipping floor. Transfer station and MRF tipping floors are subjected to constant and sometimes extreme abuse, including impacts from unloading of vehicles, wear from traffic and loaders, and chemical attack from the waste materials. These forces combine erode tipping floor slabs, and the erosion can lead to weakening, loss of reinforcing, and even premature structural failure.

Compounding this problem is that floor wear is never consistent throughout the tipping area. In high traffic areas, such as truck loading or in front of in-feed conveyors, tipping floors can be expected to erode anywhere from ¼ inch, to ½ inch or more per year. In lower-traffic areas, erosion may be less, but where waste materials are staged, chemical attack may be even more detrimental.

Proper slab design and concrete specifications can minimize slab deterioration and delay the necessity for repairs. Tipping floor slabs should be designed using a high-strength concrete, for instance 5,000 psi. Admixtures and cement types to reduce shrinkage and permeability should be used.

Despite the best design and materials, tipping slabs will erode, and eventual repair or replacement is inevitable. A common strategy to extend the inevitable is to simply increase the thickness of the slab above what is determined through structural analysis. A typical amount of increase is 2 inches, which represents between four and eight years of wear in high-traffic areas. This resulting sacrificial layer should not be an independent, unbonded slab, but rather increased thickness of the base slab itself.

Tipping floor repair can be accomplished through a wide range of fixes with an equally wide range of capital cost and operating cost impacts, depending on the degree and extent of the wear. Therefore, monitoring slab wear through regular floor-level surveys or wear indicators is essential to planning for repairs or replacement. In addition to indicating total wear, proper monitoring will differentiate between high- and low-wear areas and serve as the basis for determining the extent of a topping or replacement slab.

The three primary categories of slab repair are: 1) the placement of a specialty topping, 2) the placement of a reinforced concrete topping slab, or 3) complete removal and replacement. Since few reliable life cycle cost analyses are available, there are a variety of opinions regarding the best methods, and therefore all three will be discussed below.

Specialty Topping
Specialty toppings are high-density, fine cement, metallic aggregate mixtures, specifically developed for the repair of concrete slabs that receive high wear or impact. Due to the high cost of these toppings, they are typically used only for slabs with low wear (generally less than 3 inches) concentrated in a small portion of the tipping floor.

The primary benefit of specialty toppings is that they can be placed, cured, and ready for operations to resume within a short time, typically a weekend. As a result, there can be very minor loss of operations resulting in insignificant operational cost impacts and very little loss of revenues. Also, since these toppings can be applied in thin layers (1 ½ inches), transitioning from high-wear areas to areas with little or no wear is relatively straightforward with little long-term operational impact.

The ability to minimize the cost of the application of a specialty topping comes from a consistent monitoring program. The best time to install a specialty topping is when the maximum slab wear is approximately 2 inches. This not only limits the thickness, but also will limit the extent.

Reinforced Concrete Topping
For slabs that have worn more than the 3 inches but have remained structurally sound, a reinforced concrete topping slab may be the best repair solution. Preparing the existing slab surface, forming, setting reinforcing steel, and placing a reinforced concrete topping slab can be a time-consuming process—perhaps as much as five to seven days. In addition, operations should not resume until the concrete has had sufficient curing time (recommended seven days).

While a reinforced concrete topping slab may be a less-expensive solution construction-wise, the total cost, considering operational cost impacts, can be more when compared to a specialty topping. In addition to the costs resulting from loss of use, there can be long-term operational costs from floor surface differential. This is because the minimum thickness for a reinforced concrete topping slab should be 6 inches, and the transitions to areas of little or no wear are more difficult. As an example, if the base slab surface is only 3 inches lower than its original level, and a 6-inch topping slab is placed over it, the new surface is 3 inches higher. The presence of that 3 inches differential can cause operational problems, particularly for the movement of materials by loaders.

Complete Replacement
When the wear is too extensive, the structural integrity of the slab has been compromised, or there is additional damage from impacts, the remaining slab may be no longer structurally sound, and full replacement will be required. Removal and replacement of an existing slab is typically the most time-consuming slab replacement solution with the highest operational cost impacts and is likely to be the highest life cycle cost solution.

In summary, tipping floor repair or replacement is inevitable. Cost to repair can vary from perhaps as much as $50 per square foot. However, facility owners can minimize the costs and operational impacts through preventative monitoring and proper planning for repairs on an identified schedule.

Loading Ports
Typically, even more difficult for a Transfer Station or MRF with a below-grade tunnel for top-loading is the repair of loading ports. Most top-loading ports are constructed entirely of reinforced concrete or of steel framing with concrete slab. For both types, maintaining the structural integrity of the concrete section is crucial to the ability of the structure to safely support the operational loads, including loader wheel loads and weight of waste materials.

There is simply no option for repairing a loading port when it reaches a point where the possibility of structural failure exists. Good design and detailing of the port perimeter can help prolong the life of a loading port. This can be best accomplished by placing the steel rim 2 to 3 inches, with an embedded leading edge below the slab surface, and by carefully checking the wear on a frequent basis. But, as with tipping floor slabs, repairs are inevitable.

Since most facilities have two or fewer loading ports, their repair is extremely intrusive to facility operations, often requiring shut down an individual port or possibly suspension of the entire top-loading operation. Obviously, taking a port out of service will have significant operational cost impacts. This is true even for a facility with multiple ports, because they are typically in close proximity.

For a facility with a single port, during the repair some other type of loading will be necessary, typically loading over the side of a trailer that is sitting at the same level as the loader. This type of loading operation is a slow, costly, and potentially dangerous process with substantial cost impacts, but is normally the only option.

Loading port repair requires a very high level of planning if operational cost impacts are to be minimized. Routine monitoring of the wear around the port perimeter is essential. By starting with proper surveillance and observation, an owner can plan ahead for repairing the loadout port.

Next, determine the best time of year when waste volumes are the lowest and build into your operations alternate methods for transfer truck loading. Remember to schedule construction in off hours to minimize interference between repair activities and operations. These efforts will enable the facility owner to minimize cost impacts and achieve the best possible bottom line.

Conclusion
As the information in this article has demonstrated, capital cost expenditures for facility repairs and improvements are inevitable, but can be managed. The key to better management is rigorous and timely planning to evaluate alternatives, identify solutions, and have necessary funds available.  MSW_bug_web

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