Regulatory and siting restrictions are such that many solid waste operators prefer to expand their existing landfill footprint as much as possible instead of finding a new disposal footprint at a different location. As landfills are getting larger in height and greater in footprint area, the location of leachate tanks, leachate ponds, or discharge points to an on-site or off-site leachate treatment plant usually does not change. A larger footprint means leachate force mains are getting longer forcing the existing pumps to work harder to push leachate through the system to a target point. Some operators carry on with the same pumps for decades and do not monitor the performance of the pumps after expanding the landfill footprint, which could be more costly in the long-term.
Hydraulic Evaluations for Lateral Expansion
The longer leachate force main with possibly additional bends in the line increases friction in the line and causes flow rates to reduce to unexpected levels. We recommended that landfill operators evaluate the performance of the existing pumps along with new pumps when designing a lateral expansion. Such an evaluation may require hydraulic analysis of the entire network of pipes along with pumps, or only the segment of the network affected by the expansion. However, the effort is minimal in comparison to the operating costs of inefficient flow and overtaxing the equipment.
Sometimes the results of a hydraulic evaluation may require up-sizing all or specific pumps in leachate sumps because not enough flow can go through the force main due to high friction loss in the expanded leachate force main. Up-sizing pumps may be achievable depending on the type of the leachate sump, i.e., riser system or vertical manholes. If the up-sized pump in a riser system is too long to fit inside a riser system, or so long that it makes routine maintenance too cumbersome, your engineer may consider enhancing the functionality of the design.
Inline and Offline Pumps
Booster pumps located along an expanded leachate force main can certainly be an option. Booster pumps can be the inline or offline type. Install the inline pumps on the actual force main, and position the offline type on the side so that liquids go through bends and elbows to reach the pump, and again through bends and elbows to get back in the force main. In either case, the booster pump adds hydraulic energy to the flow inside the force main to push the liquids at a compensated pressure through the remainder of the force main and to the target point.
Operators need to be aware of the dynamic nature of the leachate piping network and the role of booster pumps in the dynamic environment. Changes to the flow in the force main may change following a landfill expansion when the new cells are coming online increasing leachate generation. Alternatively, after closing portions of the landfill slopes, that decreases leachate generation over time. Sometimes booster pumps have to be up-sized or downsized depending on the flow and pressure in the system.
Optimizing Performance, Reduce O&M Costs
The cost of replacing pumps, up-sizing, or downsizing, is insignificant compared to the revenue that landfills generate. Proper adjustment of the pumping system keeps the entire network operating at the appropriate range of pressure, and velocity in the line; increasing the life of the pumping system. Less wear and tear on the system produces a reduction in maintenance costs along with less equipment downtime.
Lower maintenance requirements may also reduce the number of personnel required to keep the system in operational condition. Landfills with a large pumping system employing a second technician because of the high maintenance of multiple pumps may find a single technician sufficient for the upkeep of the system. Proper sizing of pumps and operating the pumping system as designed within the evaluation parameters can significantly reduce the cost and frequency of pump maintenance.
About the Author: Ali Khatami, PhD, PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Landfill Engineering and Leachate Management
SCS Engineers promotes Carlo Lebron to lead the Southeastern region operations, including all environmental consulting, landfill, landfill gas, and solid waste business. He commences his responsibilities immediately, under the title Business Unit Director, and is managing the staff and business operations of six offices in Florida and Georgia, and including projects in Puerto Rico. His primary office is located in Tampa, Florida.
Reflection, as a means of self-evaluation of the robustness of your refrigeration management system, is critical to the continuing success of your program.
Proper planning is another vital element of your program. Together, they will help ensure the continuing safety of you, your employees, and the public.
Bill Lape, a Certified Industrial Refrigeration Operator and a member of the National
Board of Directors of RETA is a Project Director for SCS Engineers. In his most recent article, Bill provides advice to use January and early February as a time of reflection and a planning period. We need to look closely at our ammonia refrigeration management programs, be they Process Safety Management (PSM) / Risk Management Plan (RMP) or Ammonia Refrigeration Management (ARM) for facilities with less than 10,000 pounds of
ammonia in their process.
Click to read the article, and thank you for interest in maintaining safety standards.
Process Safety Management, Risk Managment Plans, Ammonia Refrigeration Management information.
At EUEC 2019 learn how SCS can minimize leachate and contact water management at coal combustion residual (CCR) landfills using good design, physical controls, and operational practices.
Through this SCS presentation of case studies, you will learn how to assess leachate and contact water management issues and implement techniques to minimize leachate and contact water management at your landfill.
Leachate management and contact water management at CCR landfills can be expensive, cause operational headaches, and divert valuable resources from other critical plant needs. Our presentation will provide you with useful tools to ensure your landfill is designed and operated to effectively reduce leachate and contact water and alleviate operator stress. We will present case studies that highlight how design features, physical controls, and operational practices have effectively decreased leachate and contact water management at CCR landfills.
2019 EUEC in San Diego, February 25-17, 2019. Conference details here.
Even the simplest impoundment closures come with design challenges. It is a challenge to navigate project constraints, whether technical, regulatory, or financial, to design and implement an effective closure strategy. Cost often helps to determine the “balance” between project constraints when the future end use of a closed CCR surface impoundment or the property it occupies is undefined. When a post-closure end use is defined, finding balance among project constraints to best serve that future use provides rewarding challenges.
SCS Engineers has navigated this balancing act on impoundment closure projects during generating facility decommissioning. Through a presentation of case studies, you can learn how this team has approached ash pond closure planning and execution where the future use of the impoundment site ranged from undefined to the home of a new solar photovoltaic installation. Examples also include potential future industrial use or property sale.
Case studies will highlight how geotechnical, hydrological, regulatory, or simple physical constraints have influenced the design and implementation of CCR surface impoundment closures.
EUEC 2019 in San Diego, February 25-27, 2019. Conference details here.
Today’s landfill design professionals can help eliminate unsafe configurations and institute features that can proactively warn of and minimize hazards for operator and customer safety. Designers consider subgrade conditions, geotechnical factors and regulatory requirements when specifying how steep a landfill may be constructed.
The practical aspects of landfill operations and maintenance play a significant role in slope configurations since the landfill must provide safe access to monitoring points, environmental control features, and mowing.
Bob Gardner highlights the most important features to consider for landfill cells, including the design and construction phases of the entire landfill’s infrastructure. Bob covers a broad range of topics including:
Many states regulate the maximum design slope, and although these vary, it is up to the landfill designer to take practical, safety and regulatory considerations into account when establishing the slope configuration. Bob recommends working closely with the field staff to incorporate a design that is user-friendly, effective and safe.
Read the WasteToday article “Ensuring safety during landfill design,” by clicking here.
About the Author: Bob Gardner, PE, BCEE
One of the most important regulatory requirements on landfill bottom lining system drainage layer is that the maximum head of leachate over the liner should not exceed 1 ft. When this requirement was developed, the consensus was that the drainage layer consisted of granular materials. Later, when geonets and geocomposites entered the market, the unwritten consensus among solid waste engineers and regulators was that the maximum head of leachate at the base should not exceed the thickness of the geonet or geocomposite drainage layer.
With that in mind, the reduction in hydraulic transmissivity of geocomposite laid over steeper slopes can adversely affect the maximum leachate head over the liner. When hydraulic transmissivity value reduces due to steeper slope at the base, the hydraulic conductivity reduces in turn as well. Reducing hydraulic conductivity results in an increase in the maximum head of leachate passing through the geocomposite.
Read Dr. Ali Khatami’s design advice for cell base slopes under these circumstances to maximize hydraulic transmissivity; recently published in the winter edition of Talking Trash.
Additional Resources:
Downhole scaling of organic compounds presents challenges in Class I disposal wells. Once chemical and physical conditions drive biological growth and mineral precipitation, the resulting downhole scale must be confronted with expensive workovers, stimulations, or even plugging and abandonment. In one Midwest case study, an electric utility is battling ferric, carbonate, and sulfate precipitate driven by fluctuating pH in its coal combustion residuals (CCR) leachate. Using a variety of geochemical models, we are taking a proactive approach to eliminate expensive fixes by simulating the saturation indices of key mineral species under defined parameters that drive the formation of downhole precipitate under temperature and pressure.
Using a variety of chemical equilibrium models such as PHREEQC, MINTEQ, WATEQ4F, and Geochemist’s Workbench, conceptual scenarios are run at the surface and in the mixing zone of the downhole reservoir using site-specific water-quality data, pressures, and temperatures. Each scenario provides anticipated mineral saturation states, used to estimate mass removal or chemical neutralization to prevent downhole precipitation. To mirror the dynamic nature of the CCR leachate water chemistry, modeling will continue as an iterative process whereby we will continue to collect data and run simulations to stay ahead of changes that could affect the downhole well chemistry.
This proactive approach will reduce the potential for downhole scaling to increase operational efficiency, reduce maintenance costs, and extend the life of this Class I well.
Meet Stephanie Hill and the SCS team at the Groundwater Protection Council’s 2019 Underground Injection Control conference. Tuesday, Feb. 26 from 10:30 a.m. – 12:00.
Stephanie Hill obtained a Bachelor of Science degree from the University of Texas at Austin in geological sciences with a focus on hydrogeology. She serves clients nationwide with the SCS Engineers team as a senior project manager and oversees the St. Louis area operations. Stephanie’s project experience includes hydrogeological evaluations, liquids management solutions, and Class I injection well permitting, design and operation.
If you use hazardous substances or store oils or fuels on-site at your facility, you need to be prepared to respond appropriately to a release. Having a written plan is your company’s first step to protecting human health, the environment, and your company’s assets from the aftermath of a spill.
Not all of your employees are qualified to clean up all releases. Training may be required if there are potential risks. Choosing the correct level of training and the right people to train is essential to maximizing your facility’s spill preparedness. Read more about spill response teams here.
Spill planning and reporting can be subject to rules from multiple agencies, depending on what spilled, where the spill happened, and whether it leaves your property.
Which Plan Does My Facility Need?
Where do I Start?
You can start by assessing your facility’s spill potential. Take an inventory of the chemical products at your facility. You will want to include some details in your assessment such as the related hazards of each product, the amount you store on-site, the biggest container, and where these are stored and used in relation to employee workstations and other operations at the facility. This assessment may already be incorporated into your written plans.
Ask yourself these questions:
Based on your answers, choose the level of spill response training that best suits your needs…continue by reading Cheryl Moran’s article on spill response training.
Are you ready for the 2019 Environmental Reporting season?
Don’t let the deadlines sneak up on you. Use these reporting overviews from SCS Engineers to help you get ahead of your compliance requirements.
Each guide includes the due dates for the most common environmental reports due at the federal and state levels, including a short overview of each report.
Need more help sorting out details like which reports apply to you, or step-by-step support on how to prepare your reports?
Contact SCS Engineers’ environmental reporting experts today for help complying with your 2018 reporting requirements. In the Upper Midwest contact Ann O’Brien or Cheryl Moran at
For other SCS Engineers locations, please contact us at .
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