Landfills, Maintenance, and Success
Minimize repair costs...and maximize profits.
If there is one idea that a landfill operator has to keep in mind, it is the fact that maintenance and repair are two different things entirely. Maintenance is what is done to prevent having to perform repairs. Maintenance is performed at regular planned intervals. Repair is unscheduled and performed as needed. Maintenance is an anticipated cost of doing business. Repair is an unanticipated expense that affects the bottom line. Maintenance is proactive. Repair is reactive. Maintenance saves money. Repair costs money.
Since an ounce of prevention really is worth more than a pound of cure, the time and money spent on maintenance is always preferable to the additional costs and lost productivity due to downtime caused by repairs. “Saving” money by neglecting necessary maintenance is the ultimate example of a false economy. This article will apply these principles to landfill operations and landfill systems to illustrate the cost effectiveness of a well-planned and properly budgeted maintenance program.
Landfill Systems and Support Facilities
Precipitation is a primary concern as it becomes either surface water runoff or leachate. Surface water runoff control structures have to be maintained to direct flows and prevent downstream flooding. Leachate extraction and storage systems are needed to remove potentially dangerous leachate head buildups from the landfill. Similarly, some sites require the onsite pretreatment of leachate prior to transport and disposal offsite. Permanent groundwater control structures that utilize gravity discharge can often be found below the landfill. Similarly, above the landfill, there are wells, vents, and piping that manage the landfill gas produced by decomposing organic waste, necessitating the care and maintenance of landfill gas extraction systems. Vegetative cover has to be maintained in order to prevent erosion and sedimentation. Earthworks have to be preserved to ensure their structural integrity. Monitoring systems have to be maintained to detect and evaluate any adverse environmental impacts.
|Photo: HJ Industries
In addition to the landfill and system that operate directly on or with the landfill structure, there are two other support facilities found at most landfills: truck scales and wheel washes. In-ground scales are separate structures that are installed either below grades (to provide a weighing surface flush with adjacent ground or road surface) or on existing grades (requiring approach ramps to reach the elevated weighing platform). The truck drives over the in-ground scale as it enters and leaves the site so it can be weighed. The scale is the cash register and is an important part of required data collection. Similarity, the truck drives through wheel-wash facilities when it exits the facility to remove accumulated waste and dirt from its tires. Wheel washes can be passive pools and/or active spray systems that also utilize rumble strips designed to vibrate caked on dirt off of the wheels.
Cardinal Scale is a manufacturer of in-ground and aboveground truck scales for multiple applications. Typically, landfill scales are located in the entrance to the facility and are subject to high traffic. The trucks are mostly tractor-trailer trucks coming onto the scale at a little higher rate of speed and exerting a greater dynamic force on the scale platform. They also are typically in more rural areas and subject to dirt and water, so more housekeeping is required by the maintenance personnel. And with the higher dynamic forces resulting from continuous use, a scale is going to need more attention to the adjustment bolts used to check the platform. If the scale is a free-floating deck, the bumps will need to be adjusted more often. Inspections should be performed regularly to make sure that no debris is under or wedged in the end of the scale deck. This can cause inaccurate weights.
Landfill scales are typically located in more rural areas and are subject to more dirt, snow, ice, and adverse weather conditions. Therefore, scale cleaning is required on a more frequent basis. The dirt and debris buildup under and around the scale can inhibit the accurate operation. Another item of concern is that of rodents, including rabbits and squirrels, which in a rural area can destroy the load cell cable if left unprotected. This is why it is very important to spend the few extra dollars to place the load cell cable in a conduit or provide a metal-shielded cable. The scale, if it has a volume of 10 to 20 trucks per day, should be tested every six months. Typically, the state department of weights and measures will test the scale once per year. If the volume is higher—and some landfills and transfer stations can have several hundred weighs per day—the test maybe should be every three months or even every two months. The scales should be well grounded to help prevent lightning or other surges to damage the load cells. The electronic instrumentation should have a computer grade surge protector to help inhibit any electrical surges. The mechanical aspect of the scale must be reviewed during the housecleaning to make sure the scale deck is free of any dirt or debris. The person performing the housecleaning can look for and signs of wear in the cleaning systems, the bumper system, and the deck, whether steel or concrete. All scales have a means to inspect the load cell mounts, and they should be inspected to look for wear in the components.
Fairbanks Scales makes the Trident, Talon, and Triton series of truck scales. Maintenance is based on regular inspections. While performing inspections, the operator should check for accumulations of solid material under the scale that may affect the accuracy (ice, frozen mud, debris), inspect load cells and bearing cups for damage to the ends/cables, check cups and O-rings for damage, and inspect and adjust all check bolts using anti-seize on the threads. Mechanical faults need to be found and corrected as well. Inspectors should check for all clearances around the scale for any obstructions or interference with the free movement of the platform, including bolt clearances both with and without a concentrated load over each section, one at a time, while ensuring that the load cells and the scale deck are plumb and level.
Columbia Industries LLC portable tippers are an efficient way of unloading solid waste trailers in landfills. They have proved to be safe, reliable and efficient, with an average of less than one downtime hour per 1,000 hours of operation and an approximate three-minute cycle time allowing for a throughput of 10 to 12 trailers per hour. Visual inspections of all operating parts and systems should be done daily with repairs performed prior to operations. During the weekly lubrication schedule, the operator should check the lower lift cylinder mounting brackets for cracks, bending, distortion, loose bolts, or the lift cylinder universals (trunnion mount) for cracks, bending, distortion, and bearing retainer bolt tightness. Observations should be made for weld cracks or bending and cylinder misalignment.
Neptune Automated Wheel Wash Systems is an automated tire washing system that can save the operator significant costs by a simple regular maintenance schedule. Before any maintenance is performed on any Innovative Equipment Solutions equipment, the control power must be disconnected at the control panel and source. The customer should utilize a “lock-out/tag-out” procedure while the maintenance is being performed. Each day, the operator should check the nozzles for any trapped debris, removing excess sediment and adjusting the floater valve as needed. Monthly maintenance involves inspection of all hoses/pipes/tubes for wear, connections for leakage, and pumps and control panel for faults and proper grounding (which is also inspected annually for the entire system).
Cold-weather operation is one of the tougher challenges for an operator. From experience, the hardest challenge is operating in the range of 32 to 18 degrees. The water from any system freezes in this range. The ambient and latent heat from the ground and the tires, however, causes the ground to thaw. Below 18 or so degrees, the ground remains solid, and there are limited issues with trackout. In cold weather environments, we strongly recommend the use of a dry flocculent that is not sensitive to the temperature. In preparation for winter, the operator should unhook the various components, storing separately wet flocculent in a non-freezing location, and draining all pipes and reservoirs.
Surface Water Runoff Controls
Surface water runoff controls include the following structures: the final cap and cover system constructed on top of the final waste disposal grades, surface water runoff interception berms and diversion channels that prevent sheet flow and gully formation by concentrating surface water flows into manageable flow paths, surface-water discharge structures that take the collected runoff and direct it down grade in a safe manner, and detention basins that detain the accumulated flows for a certain design period that allows a controlled discharge to offsite surface waters. These are often found on intermediate waste disposal slopes as well as on final waste grades.
Working in conjunction with surface-water runoff structures are sedimentation and erosion controls that are designed to trap water-borne soils and prevent them from leaving the site. These include temporary structures such as silt fences and straw bale dikes, as well as in-channel structures such as rock dams, and large finishing structures such as sedimentation and detention ponds. Ponds are typically designed for double duty, both retaining sedimentation particles and detaining surface-water flows.
The primary means of maintaining surface-water controls and erosion management structures is by dredging of accumulated sediments and maintenance of vegetative cover. Certain surface-water control structures are designed to be essentially self-cleaning, with anticipated flow velocities sufficient to keep sediments suspended and transported to their discharge points. However, due to local topography or the settlement of underlying waste, this may not always be possible. In either case, sediment has to be trapped before it can leave the site, creating the necessity of cleaning out the trap. Depending on its size, shape, and depth, a sediment trap can be dredged using a simple backhoe, or the accumulated muck can be pushed out by a low-ground pressure dozer. The excavated settlement can be transported to a disposal location or (if free from contaminants) stockpiled for future use onsite.
In addition to the accumulation of sediments, there is the problem of gully formation caused by the loss of soil. These are usually discovered during quarterly or annual site inspections and often require extensive manual work to back fill the gullies, compact the soil in place, and apply seed, fertilizer, and mulch to what are often irregular and confined areas of erosion.
Leachate Collection and Extraction Systems
Precipitation (both rainfall and snowmelt) that enters the landfill and comes into contact with the waste mass becomes leachate. Once formed, leachate has to be managed by systems that contain it and prevent it from contaminating lower groundwater, collect it and remove it so it does not build up on the landfill’s floor, extract it from the landfill and transmit it to storage and/or treatment units. The landfill’s liner (typically a composite layer consisting of compacted clay and welded geomembrane sheets) provides leachate containment. Collection pipes installed on top of the liner allow for the collection of leachate into sump located along the perimeter of the landfill’s floor. Leachate accumulating in the sumps is removed by extraction pumps set in riser pipes that discharge the leachate to transmission pipelines. The transmission pipelines carry the leachate to onsite pretreatment facilities and storage tanks or ponds.
There are many mechanical and electrical systems associated with leachate collection and extraction that require regular maintenance. These include leachate collection pipelines, collection sump extraction pumps, and leachate head buildup pressure sensors.
Leachate collection pipes must be cleaned out on a regular basis. Small particles carried by the leachate and biological growth generated by the leachate can together clog a collection pipe, reducing its flow capacity. This can be done either by flushing (pushing water forward from a hose nozzle as it advances through the pipe) or by jetting (pushing water backwards from a jet at the end of a hose as it advances through the pipe, in fact, the force of the jets pushing backwards helps move the hose forward). There are practical limits to how far a leachate collection pipeline can be cleaned. Typically that is no more than 1,400 linear feet, though some states (such as Wisconsin, which limits pipe-cleaning distances to no more than 1,200 linear feet) limit the cleanout distance—and effectively the maximum length of the pipe—either through regulation or guidance. Leachate collection pipes should have a minimum diameter to allow for cleanout along its entire length. For example, 6-inch diameter pipes can be cleaned out along a longer length than four 4-inch diameter pipes.
Leachate extraction pumps need to be removed for maintenance and cleaning at regular intervals. A good design for a leachate extraction system has two riser pipes emerging from each collection sump. This allows for the easy placement of replacement pumps while the other is removed for maintenance and cleaning, or conversely it allows for the placement of an additional pump should the current pump get stuck or otherwise hung up in the riser pipe, making it impossible to remove or operate.
Pressure sensors used to measure leachate head buildup in the collection sump and on the lined floor of the disposal cell can be either installed separately or as part of the extraction pump itself. If installed separately, it will need its own maintenance regimen.
The Blackhawk Technology Co. is in the business of manufacturing and marketing of piston-pump systems for landfill leachate, gas-well dewatering, remediation, and other uses. Since their drive motors are located above the wellhead, not in the well itself, maintenance is needed far less frequently than with air-lift or submersible pumps. When it is required, servicing also takes much less time than with other pump styles because the above-well mechanicals are cleanly and safely away from the liquid being pumped. As there is no pump pulling, no worker ever comes into contact with leachate, and no pumps are lost by being hung up or caught down in the well. The down-hole components are simply designed to be sturdy and rugged, requiring little if any attention. Every landfill situation is different, as such actual maintenance requirements can vary with leachate composition, landfill siting, local conditions, and several other factors affecting individual performance.
Blackhawk has four main lines of pneumatic pumps: the Atlas, the Trident, and the Big Bertha (the largest pneumatic pump which shares operational characteristics with the other three). With only two large rugged seals and a simple, three-input control located on the motor’s side frame, maintenance for the Atlas is simpler and faster. Replaceable seals on the Vector make the pump field serviceable. The Blackhawk drivers employ rugged seals that are easily replace in the field, above the wellhead. These include pneumatic seals for Vector and Atlas, and liquid seal plates for all models, both pneumatic and electric drivers. The stainless-steel down-hole pump cylinder of the Trident is compatible with the Blackhawk drive motors, which makes possible a long down-hole life, critical in standing up to the tough grit and silt environments of landfills
Leachate Storage and Treatment Facilities
The transmission pipelines carry the leachate to onsite pretreatment facilities and storage tanks or ponds.
The transmission pipelines consist of double-encased, solid-walled force mains. Pumps and lift stations transmit the extracted leachate through the force mains to final storage or treatment destination.
There are also many mechanical and electrical systems associated with leachate transmission. These include leachate storage (typically in aboveground storage tanks), onsite pretreatment systems (such as aerators for leachate with high levels of BOD), lift station pumps, condensate pumps, electronic pump controls, and flow-monitoring systems.
Aside from the obvious care and maintenance required for sophisticated electronic controls and remote monitoring systems, basic physical maintenance is required for the storage tanks and their appurtenances. This is especially true of the cathodic protection needed to prevent the rusting out of the tank wall and foundation.
Groundwater management systems are utilized to isolate the site from groundwater by either cutting off or lowering the elevation of the groundwater. Permanent systems include slurry walls and underdrains, while temporary groundwater management can be provided by wick drains or well points. Like leachate collection pipes, groundwater collection pipes need regular cleaning. Furthermore, groundwater discharge pipes typically window out to the surface via riprap-lined aprons. These also have to be inspected to ensure that their structural integrity has been maintained and that they are still protecting the area around the discharge point from erosion and gully formation.
Landfill-gas management systems include gas extraction wells (either passive vents or attached to an active extraction system), associated pipelines (laterals and headers), blower, and flare apparatus. Landfill-gas destruction or utilization is provided by ignition, containment, or energy production systems. Like leachate management systems, landfill gas management systems consist of multiple electronic and mechanical systems that require regular maintenance for proper functioning. These include pressure and flow gages, blower apparatus, and flare stacks.
Enercon Engineering custom designs and manufactures switchgear, controls, and SCADA systems for landfill-gas management. Enercon Engineering also provides packaging for the generators, in-house services (such as testing), and maintenance resources to its customers. Its staff of engineers and technicians can provide support, maintenance and start services worldwide, along with technical support training to customer personnel.
There are several tasks that should be regularly undertaken to ensure that SCADA system remains operational and performs up to the required standard. These include producing a complete and thorough inventory of every piece of equipment in the SCADA’s telemetry system. This should include all single items of equipment, repair of any immediate system faults, a check from the central site computer monitoring, and repair as needed any faulty equipment items. Functional checks of each piece of equipment should be performed weekly to ensure that they are functioning properly. Physical maintenance (cleaning each site of dust, debris, and vermin) should be performed monthly as should test telemetry operations. A complete and thorough audit of the entire system should be performed at least annually.
Dust and Odor Suppression
Buffalo Turbine has been manufacturing Turbine Style Blower that utilizes 14-inch Turbine Blower to generate the perfect combination of air volume and air velocity much more efficiently than larger traditional style fans. The Buffalo Turbine Monsoon utilizes a gyratory atomizing nozzle driven by the turbine style blower to create a water droplet size and coverage area that best fits your desired application for dust suppression and or odor control.
The Monsoon Misting System also has the capability to direct the atomized water particulates right at the source of the dust, or oscillate up to 80 degrees to obtain over 12,000 square feet of coverage. The Monsoon can be utilized for misting water for dust control or many varieties of odor neutralizers or masking agents to help control nuisance odors at landfills, waste transfer stations, water treatment facilities, and many other applications. Buffalo Turbine offers complete monsoon units with oscillation powered by gas, diesel, and electric as well as hydraulic and PTO-driven units.
Efficient machine operation requires that the belts always be properly tensioned to adjust the belt. Other maintenance concerns include having a qualified tire dealer or repair service perform required tire maintenance, lubricate the machine as required by the maintenance schedule (using only clean, approved lubricants), remove all debris that has settled between the blower wheel fan and the stationary vanes, inspect and replace driveshaft bearings, and follow all safety procedures while performing these maintenance tasks.
Benzaco Scientific makes chemical formulations that neutralize noxious odors. They also manufacture and produce high-quality automated odor control systems. Benzaco distinguishes itself from other manufacturers by providing odor control systems that require minimal maintenance. While typical odor control systems are plagued with rusted plumbing, clogged nozzles, and inferior thin-walled tubing, Benzaco odor control systems that are engineered with the solid waste professional in mind. That means far less maintenance for the owner.
Since various environmental and atmospheric factors affect the time of day that the odors are more prevalent, each site is assessed, and the system is timed accordingly. “On average a site will program the odor control systems to turn on from 6 a.m. to 2 p.m., then again from 4 p.m. to 8 p.m.,” says Rick O’Sadnick, senior scientist at Benzaco. “The odors are more concentrated in the morning and the evening. The heat from the sun and the winds tend to disperse the odors in the afternoon hours. Also, people who are affected by the odors are at home more in the morning and evenings. But it all depends—there are some sites that run 24 hours. All of our systems are designed to run with minimal maintenance in all scenarios.”
Standard maintenance for most odor control systems includes keeping an eye on outgoing pressure, changing water filters, and the maintaining the chemical supply. Each week, the operator should examine all nozzles to ensure a proper spray pattern. If a site is not going to run its system during the winter, odor control systems should be winterized by disconnecting the hoses from the unit, and clearing out the hoses and nozzles with high-pressure air.
While high-pressure, water-based odor neutralization is widely recognized as the preferred method for controlling transient odors, Benzaco designs and manufactures a variety of system options for effective odor control including waterless, freeze-proof, and mobile systems.
St. Croix Sensory Inc., rents and sells sampling equipment, such as the unique Nasal Ranger for the measurement of ambient air/odor around a landfill and the Odor GIS system, which is used by landfills to automatically map the odors (or lack thereof) around a landfill and in the surrounding community. Their odor-testing laboratory receives samples that are collected by engineers and operators of landfills and are evaluates for odor parameters (strength, character, etc.). The Ranger’s mask has three openings: a nasal port designed to match the geometry of the human face, an inhalation inlet that connects to the Filed Olfactometer, and an exhalation outlet.
Check valves are installed with both the inhalation and exhalation outlets. The check valves are replaceable if they become dirty or damaged. The valves are pressed into the respective ports and can be removed by applying pressure to the outer rim of the valve from inside the Nasal Mask. Replace of both cartridges can be performed in accordance with an established “cartridge change schedule,” or the user may decide to replace the cartridges before each use of the Nasal Ranger Field Olfactometer.
Though landfill tarps are normally known for their role in daily cover, that same capability provides excellent dust, odor, and litter control, features that Rogers, AR–based Southwestern Sales contends will help keep your landfill out of the public’s cross-hairs. Besides saving valuable airspace, the company’s tarpARMOR limits the amount of wind-borne trash, contains odors, reduces the chance of fire, and curtails disease from birds, animals, and insects feeding on waste. Tarps are available in 50- and 100-foot sizes.
Structural Integrity: Earthworks and Geosynthetics
Liner system and stable foundation designed to contain leachate and final cover systems designed to prevent leachate from forming can only function provided that they remain structurally stable. Structural elements of a landfill can be undermined by consolidation of the waste slopes, settlement of the underlying soil foundation, burrowing animals and seismic activity.
Proper care and maintenance of a landfill’s structural components begins with good siting and construction of the landfill in areas with stable (nonorganic) foundation soils and without natural karst topography or man-made underground mines. Second, the types of soils used to construct foundations and structural fill berms should have sufficient strength and compaction characteristics to ensure their stability. Finally, the contractor must ensure the proper manufacture, transport and care (once they arrive onsite) of the geosynthetics used to construct the liner and leachate, and final cap and cover systems.
Postconstruction inspections should be done at the same frequency as the other site walkovers and sampling visits. The inspector should look for telltale cracking of exposed embankments and berms that may result from differential settlement, equipment loadings, vibratory loads, or seismic activity.
Should such damage be apparent, a skilled and experienced geotechnical engineer should assess the situation and prepare remedies for repairing and shoring up the damaged slope area.
Environmental Monitoring systems include landfill gas probes, groundwater monitoring wells, surface-water runoff monitoring points, leachate samplings, collection lysimeters, and other leak-detection devices. These monitoring systems provide the information necessary to evaluate potential environmental impacts and allow for modification of the construction or operation of the landfill.
In-Situ, Inc is a manufacturer of water-quality monitoring equipment, pressure transducers/data loggers (Level TROLL) and conductivity/level/pressure/temp data loggers (Aqua TROLL), as well as pH and pH/ORP Combination Sensors. The Level TROLL has been designed to withstand harsh field conditions. However, as with any electronic instrument, it can be permanently damaged if used outside its operating specifications. Accuracy can be adversely affected by improper care and handling, lightning strikes and similar surges exceeding operating temperature and pressure limits, physical damage, or abuse. Factory calibration every 12 to 18 months is recommended.
Carlson Software products include machine-control software for landfill operators. Carlson Landfill Grade provides the ultimate in landfill maintenance capability, the ability to maximize airspace utilization. Using this software guidance package, machinery can avoid adverse impacts with existing landfill structures such as gas wells and leachate-extraction riser pipes. Overfill is eliminated in real time, avoiding the possible slope instability issues and the need to go back in later to dress up the slope.
Carolina Software (WasteWORKS) produces software packages for solid waste management, including WasteWORKS (its core system for ticketing, billing and reporting), WasteWIZARD (a scale lane automation system), and WasteWALKER (a handheld, mobile ticket system), which all come standard with a comprehensive support and maintenance package. This maintenance and support package provides customers with unlimited 24/7/365 phone and remote support as well as all version upgrades. Customers who continue to pay for these services are considered “active” and are privy to this customer support. Given its lengthy time in service WasteWORKS is a very stable product and typically requires a low level of support for ongoing operations.
In addition to maintenance, regular upgrades are an important part of the support package. Customers are encouraged to update their systems on a regular basis as new versions are made available for download at all times. New versions not only provide customers with useful enhancements and features, but they also make customers more supportable. Basically, customers who are up to date are immune from issues that have been addressed in recent versions. New versions of the software are provided to customers via FTP. The WasteWORKS-SQL application provides a tool that automatically propagates updated versions to client workstations. Local IT staff places the upgrade in a central location, and the upgrades happen automatically when users open the program.
Because its automation system and handheld devices are “hardware-heavy,” it also provides front-line support and troubleshooting for a wide range of equipment. With remote access the company is able to analyze hardware issues quickly and provide an appropriate plan for replacement or repair. As with any hardware-based system, having spare parts is a necessity. Hardware warranties are typically provided by the manufacturer, and they provide liaison services for customers in need of repairs or warranty work.
Author's Bio: Daniel P. Duffy, PE, writes frequently on the topics of landfills and the environment.
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