Landfills across the country are experiencing a trend ─ black goo, pluggage, and scaling in their leachate and gas collection systems. These organic and inorganic deposits are difficult to treat once they’ve seeped into liquid and GCCS systems, the pluggage slows equipment and pipes, impacting the extraction of liquids and landfill gas.
Our team of engineers, scientists, and landfill-landfill gas operations experts will provide a comprehensive discussion in May of what we are seeing and piloting in the field.
Live on Thursday, May 19, 2022
2:00 pm Eastern Time for 1 hour
Register to receive on-demand access following the live forum.
Prevent chemical deposits and pluggage before your pipes slow landfill gas and leachate collection.
This educational, non-commercial webinar with a Q&A forum throughout is free and open to all who want to learn more about landfill pluggage concerns and preventative treatments to consider. We recommend this month’s discussion for landfill owners/operators, landfill gas technicians, environmental engineers, and environmental agency staff. A Certificate of Attendance is available on request following the live session.
Landfill efficiency: every landfill owner or operator knows that landfills are distinctly unique. Consequently, landfill gas collection and control systems (GCCS) and leachate management systems with highly engineered components are configured precisely to tailor to each landfill’s needs. North American landfills have always tried to be good neighbors, but now are making greater strides toward reducing emissions and protecting groundwater with master planning and technology. These plans keep the effectiveness of these systems running as efficiently as possible and help prevent expensive and extensive repairs.
Today’s blog takes us out in the field examining how to plan for these flexible high-dollar infrastructure systems. These plans are taking landfill operations into the future and are adaptable to changing regulations around emissions and the evolving waste streams that affect gas production.
We’ll also provide resources to similar articles about leachate systems, remote monitoring systems, drones, and carbon sequestration that are helping to keep your carbon footprint even lower and support landfill efficiency.
In the April issue of WasteAdvantage Magazine, Professional Engineers Vidhya Viswanathan and Maura Dougherty discuss how operators with 5-year and master plans in place get a payoff with a system that serves them well and costs less. They can prepare early for capturing their gas, use the plan to install gas collection infrastructure on a timely basis, and help guide them through post-closure among the daily benefits. Read Master Plan to Lower Your Landfill GCCS Infrastructure Investments here.
Planning/Managing Leachate/PFAS
Remote Monitoring and Control and Drones
(l) Liquids addition. The owner or operator of a designated facility with a design capacity equal to or greater than 2.5 million megagrams and 2.5 million cubic meters that has employed leachate recirculation or added liquids based on a Research, Development, and Demonstration permit (issued through Resource Conservation and Recovery Act (RCRA), subtitle D, part 258) within the last 10 years must submit to the Administrator, annually, following the procedure specified in paragraph (j)(2) of this section, the following information:
(1) Volume of leachate recirculated (gallons per year) and the reported basis of those estimates (records or engineering estimates).
(2) Total volume of all other liquids added (gallons per year) and the reported basis of those estimates (records or engineering estimates).
(3) Surface area (acres) over which the leachate is recirculated (or otherwise applied).
(4) Surface area (acres) over which any other liquids are applied.
(5) The total waste disposed (megagrams) in the areas with recirculated leachate and/or added liquids based on on-site records to the extent data are available, or engineering estimates and the reported basis of those estimates.
(6) The annual waste acceptance rates (megagrams per year) in the areas with recirculated leachate and/or added liquids, based on on-site records to the extent data are available, or engineering estimates.
(7) The initial report must contain items in paragraph (l)(1) through (6) of this section per year for the most recent 365 days as well as for each of the previous 10 years, to the extent historical data are available in on-site records, and the report must be submitted no later than June 21, 2022.
(8) Subsequent annual reports must contain items in paragraph (l)(1) through (6) of this section for the 365-day period following the 365-day period included in the previous annual report, and the report must be submitted no later than 365 days after the date the previous report was submitted.
(9) Landfills in the closed landfill subcategory are exempt from reporting requirements contained in paragraphs (l)(1) through (7) of this section.
(10) Landfills may cease annual reporting of items in paragraphs (l)(1) through (6) of this section once they have submitted the closure report in § 62.16724(f).
If you need assitance meeting the regulations, please contact your project manager or send a request to
Engineering News Report publishes the ENR Top 500 List, which ranks global design/engineering firms by revenue. SCS Engineers again ranks in the top 100, moving up this year from #73 to #59. We thank our clients and our employee-owners for helping SCS continue to rank as a top-tier environmental services engineering, consultanting, and construction firm.
ENR is one of the premier companies tracking the A&E industry, and these rankings are closely followed as they publish throughout the year. SCS Engineers is also recognized in the Sewer & Waste List of Top 20 companies globally, ranking at #5, up from #10 the previous year.
Climate change and reducing our nation’s carbon footprint are important challenges facing our planet. SCS Engineers remains a leader in recovering and utilizing methane from landfills, a potent greenhouse gas. In the last decade, we’ve been expanding our role to include more utilization of biogas from agriculture, carbon sequestration, management of other greenhouse gas and environmental impacts for multiple sectors while reducing methane production in landfills by diverting organics.
SCS designs and supports innovative environmental solutions with our in-house award-winning technologies to help our clients. With more data and control available 24/7, our clients can make more informed decisions, operate more efficiently, running cleaner and safer while delivering essential services, products, and properties.
Join EPA, SCS Engineers, and the GWPC for the 2022 Annual GWPC & UIC Conference in Salt Lake City, from June 21 through June 23. This year’s event features two experts from SCS, Kacey Garber and Stephanie Hill. In today’s blog, we take a dive into their presentations, where both women use case studies to highlight safely using deep injection wells, and what can happen during operations to plan for more sustainable operations.
Thursday, June 23 at 8:30-10:00 Class VI UIC
“Sensitivity of Aquifer Chemistry to Changes in Carbon Dioxide Partial Pressure: Implications for Design of Groundwater Monitoring Protocols,” Kacey, Julie O’Leary, and Charles Hostetler are all with SCS Engineers. The team will discuss Carbon Sequestration and Storage (CSS) solutions. Great care is taken in the design and operation of the injection of carbon compounds to ensure that the sequestration is effective and permanent. Each injection site also has permitting requirements for groundwater monitoring in any overlying aquifer as a protective measure. Because the duration of the injection and sequestration periods are long, it is essential for CSS projects to have a cost-effective groundwater monitoring program with a robust sensitivity to detect any leakage.
In this case study, the SCS team has examined the sensitivity of aquifer chemistry (major and minor cations and anions) to the partial pressure of carbon dioxide using an aqueous speciation/solubility/sorption model. They examined a number of hydrochemical facies, both natural and synthetic, to determine which geochemical parameters are most likely to be affected by changes in the partial pressure of carbon dioxide. The team anticipates that the regulatory framework and practice for CSS will be similar to that of Municipal Solid Waste (MSW) and Coal Combustion Residue (CCR) disposal sites. Prior to the injection of carbon compounds, the overlying aquifer is characterized and background values for key parameters are established. During the injection and post-injection phases of the project, there is periodic monitoring of the groundwater parameters, which they anticipate will be compared to the established background. When Statistically-Significant Increases (SSIs) are found, an Alternate Source Demonstration (ASD) will have to be prepared that attributes the SSIs to the CSS operation or to some other source. By establishing a groundwater monitoring protocol that is specific to the site, sensitive to changes in the partial pressure of carbon dioxide, and relative insensitive to natural variability and hydrochemical facies changes, optimal and cost-effective groundwater protection can be implemented.
Kacey Garber is an experienced groundwater project manager for active and closed landfills, including routine groundwater monitoring and statistical analyses; reports and permit applications; designing sampling and analysis plans; special groundwater studies; and conducting groundwater well construction planning and design. She has also been involved in PFAS workgroups. Ms. Garber has a Master’s in Geoscience from the University of Iowa, and a BS in Geology from Illinois State University Her field experience includes collecting groundwater, surface water, landfill leachate, industrial and municipal wastewater, and soil; oversight of groundwater monitoring well installation; logging and sampling soils for well-drilling operations; groundwater well maintenance and development; inspection of final landfill covers for post-closure care; and routine wetland monitoring and delineation activities.
Thursday, June 23 at 10:30 – 12:00 Class I UIC
“Microbially Influenced Corrosion in Injection Wells: A Case Study in a Class I Well for Coal Combustion Residuals,” with Stephanie Hill. Stephanie will discuss microbially influenced corrosion (MIC) is known as a direct cause of mechanical integrity failure in injection wells. While premature failures of expendable components, such as casing and packers, are inconvenient and expensive, this is not the only reason to proactively address downhole biological issues. Stringent control and mitigation of biological activity are imperative to minimizing borehole fouling and subsequent plugging of an injection reservoir. If left untreated, a well’s long-term reservoir health and operational efficiency may be jeopardized.
This presentation will summarize a case study of MIC-related failure in a Class I injection well used for leachate disposal from a coal combustion residuals facility. The well failed to maintain internal mechanical integrity just six months after being commissioned. We’ll walk through the investigation process, which includes annular pressure testing, downhole caliper logging, casing thickness detection, injection fluid analysis, and metallurgical analysis to identify the cause of failure. Following the replacement of the injection casing and packer, injection tests were conducted to assess the potential impacts of MIC on the reservoir’s ability to accept injected fluids. A proactive disinfection plan was customized based on the unique investigative results and implemented to prevent future MIC-related issues.
Stephanie Hill is a hydrogeologist, program leader for SCS Engineers’ Carbon Sequestration and Deep Well Injection practice, and licensed Professional Geologist. She earned a BS in Geosciences at the University of Texas, emphasizing hydrogeology and geomorphology. Stephanie’s early career focused on environmental compliance for mineral and fossil fuel industries at the Texas Commission on Environmental Quality (1996 to 2000) and the Railroad Commission of Texas (2000 to 2012). Currently, she leads a team of geologists and engineers to advise SCS clients of various industries on geologic storage options for carbon neutrality and disposal solutions for liquid residuals.
Our panelists this month discuss best practices for identifying, treating, and possibly even preventing chemical deposits (black goo, scaling, foaming) before and after they occur within your infrastructure. We’ll also include what landfill field operations can do to identify and treat conditions that appear symptomatic of possible future issues.
No one has all the answers ─ each site’s conditions are unique. Our team of engineers, scientists, and landfill-landfill gas operations experts will provide a comprehensive discussion in May of what we are seeing and piloting in the field.
Live on Thursday, May 19, 2022
2:00 pm Eastern Time for 1 hour
Prevent chemical deposits (black goo, scaling, foaming) bofore your pipes plug or slow landfill gas and leachate collection. RSVP to receive a copy of the recording for on-demand access.
If you thrive in a friendly, collaborative, and client-focused company, SCS Engineers is the place for you, and we’re growing! We’re looking for field technicians to work collaboratively on our Field Services teams nationwide. Specific information is posted for each open position. Use our job search to find your desired location.
Under general supervision, our technicians operate, monitor, and maintain gas migration control and recovery systems, including gas well monitoring and adjustment, troubleshooting, and system repairs. These systems capture emissions that keep our planet cleaner. SCS clients entrust us with the management of more than 35 million metric tons of anthropogenic CO2e greenhouse gases every year. We collect and beneficially use or destroy enough to offset greenhouse gas emissions from 7.4 million passenger cars annually.
Become one of the growing engineers, consultants, scientists, and technicians helping private and public entities run cleaner and more efficiently. A very rewarding place to have a career!
It isn’t often that you have the oppotunity to have a full bench of experts at your disposal for free. At SCS, it happens monthly. Join us for our next free forum covering sticky situations that clog your landfill gas and leachate pipes. Keep the gas and liquids flowing with our scientists, engineers, and field experts. Ask questions anonymously for privacy, and learn the latest strategies for preventing and mitigating pluggage.
Live on Thursday, May 19, 2022
2:00 pm Eastern Time for 1 hour
Managing Liquids Extracted From Landfills
Environmental engineers specializing in landfills can successfully design disposal sites and infrastructure to mitigate how much liquid enters the waste matrix. If liquids do infiltrate the waste or gas extraction system, these professionals effectively capture and direct them to the bottom of the leachate collection system, where it belongs.
But success brings different challenges following extraction.
“You pull liquid and leachate from your landfill and landfill infrastructure, but now the question is, where do I send it? And there are no simple solutions. It’s a hard wastewater stream to manage, especially as operators grapple with increasing volumes and strength,” says Bob Dick of SCS Engineers.
As precipitation increases in many regions and operators take in wetter special wastes like sludges, finding an economically and logistically viable means to offload leachate quickly is daunting. Tightening regulations around what publicly owned treatment works (POTW) will accept adds even more pressure.
There are three main issues resulting from higher leachate quantities and its quality. Those issues are:
Storage tank capacity
“I have clients with two tanker trucks cycling 24 hours a day, taking leachate to the POTW, but they still can’t keep up with their volumes. So, they can’t be as aggressive as they want in moving it out. It’s coming out of their landfills, and they have nowhere to store it all,” Dick says.
Transportation limitations
Operators can’t transport leachate fast enough to keep pace with steadily accumulating volumes. It takes time to load tanker trucks, drive long distances, return, and repeat the process, Dick says. Even finding a facility to accept it can be difficult, compelling some of them to ship it on barges or haul it by rail—costly processes.
Wastewater treatment plant issues
Increasingly, POTWs faced with permit restrictions limit how much leachate they will take or refuse altogether, either because of the volume, quality, or characteristics.
This problem magnifies as high concentrations of several specific constituents are now often seen, including high ammonia and nitrogen. Other offenders increasingly coming into play are total suspended solids (TSS) such as clay, sand, and silt and total dissolved solids (TDS), smaller particles than TSS, including minerals and microorganisms.
Mixing leachates adds complexity
Some liquids inevitably make their way into gas extraction wells above the leachate collection system. A common solution is pumping them out so gas can enter the pipes and injecting them into nearby leachate piping. There it mixes with leachate from the bottom of the landfill.
This method may solve one problem but presents another challenge: gas dewatering liquid is a much higher strength than filtered leachate at the bottom. Mixing them could disrupt the POTW’s system due to biological changes in the material, explains Eric Peterson of SCS Engineers. He’s seen this headache escalate as POTWs adopt more sophisticated technology; it treats most leachate better, but liquids from gas wells interfere with the newer process.
“We’ve seen POTWs who refuse the liquid because it’s stronger than previously, and the plant can no longer manage it. We have also seen upsets at on-site treatment plants that may be designed for the leachate conditions at the bottom of the landfill; now they must deal with a more polluted gas dewatering liquid,” Peterson says.
Ensuring this liquid can work in either facility type requires pretreatment. Even with the more benign liquid extracted from the bottom and sent to the force main, pipes are prone to clogging, requiring due diligence in preventative maintenance.
Strategies to manage extracted leachate
Currently, three options offer alternatives to the time and money intensive process of trucking high volumes long distances:
Leachate evaporator
This system heats liquids and evaporates the water molecules, reducing leachate volume by 70 to 90 percent, enabling operators to return the sludge-like residual to the landfill. Managing liquids on-site leveraging this technology eliminates dependency on drivers and the POTW.
“The idea is that the residual is small enough that you can effectively manage it in your landfill. But regulations may require another step to solidify the liquid residue,” says Zach Mahon of SCS Engineers.
Solidification of waste
Solidifying high-strength liquids entails mixing them with an amendment such as sawdust or lime that adsorbs them, removing them from the water phase, and strengthening them to dispose of in the landfill safely.
But this process is often a temporary fix. “You are typically just imposing a management technique that slows movement,” Dick says.
On-site leachate treatment
This option can clean the material to POTW-acceptable standards or enable it to discharge into the environment safely. Reverse osmosis (RO) is a common treatment of choice, where leachate flows through a membrane, separating contaminants that collect in a solution. RO can reduce contaminated water by 90 percent, typically rendering it clean enough to discharge directly to surface water with appropriate permits. Or, it can be discharged to the city sewer, eliminating the permitting step.
Mahon recently assessed all three options for a Midwestern client and a fourth solution that he believed fit this landfill’s particular needs. The operator’s 20,000-gallon tank was filling up so fast that it had to be hauled to the POTW nearly daily.
“The quality and volume were acceptable to the POTW; it was just an operational issue for the landfill. So, the solution is to install a force main that automatically pumps directly to the POTW, solving the challenges of scheduling trucks and drivers, quickly loading and unloading the vehicles,” Mahon says.
His team’s design enables the addition of RO should regulators’ requirements change or the POTW plant intensifies its discharge limits.
Still, solutions continue evolving. Landfill operators work with liquids management experts to keep up with the latest proven technologies. Many promising solutions are on the horizon, but you need a proven solution when investing capital.
Dick says the best defense is to remain proactive. Even with careful planning, some liquid will contact waste and become leachate. The best course is for robust engineering designs and sound operational practices to minimize leachate to the greatest extent possible.
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There’s science, engineering, and careful maintenance happening inside and outside of a landfill, but it’s all there to capture emissions. We thank landfill owners and operations teams across North America for strategically managing landfill system integration and running these complex systems. These well-trained and educated teams include field technicians, landfill and environmental engineers, geologists, technologists, and specialized operations staff, to name a few. They work hard and smart to make sure each landfill remains a good neighbor while delivering essential services.
Slope failure
Side slope failures are not common but, depending on circumstances, can be catastrophic. When they happen, wet waste and soil that hold up the walls are often the leading catalyst. When moisture content increases, the friction angle (the angle at which waste is stable) decreases, and waste and soil slide down the hill.
Keeping a close watch for warning signs and taking proactive measures even before they emerge are landfill operators’ greatest defenses against disastrous failure; once the slope moves, it’s nearly impossible to stop it.
One general guideline is to monitor landfill liquid levels. Regulations require no more than 12 inches of liquid at the bottom of the site. An exceedance will reduce the slope stability significantly. But there are plenty more strategies to stay ahead of the curve and prevent major issues.
Three primary types of slope failures
The primary failures are circular, block-type or wedge, and veneer. Veneer failure is confined to the final geomembrane cover system; it’s minor and fixable, says James Law of SCS Engineers, an expert in geotechnical engineering.
Circular failures occur in the waste mass and affect the entire slope. In most cases, they are relatively minor, remaining near the mound’s surface. Less commonly, circular failures occur deep in the mass, which are major events.
“In either scenario, circular failures occur when the waste mass is uncompacted. It’s less dense and therefore weaker and susceptible to failure,” Law explains.
Block failure can be complex. It begins at the crest and descends to the bottom liner system, where the failure ultimately occurs. How it happens is there are multiple interfaces of soil and geosynthetic material that each contribute to a weakening zone of material at the bottom. That’s when a failure occurs, and it is serious.
Law advises operators to use a vetted engineering analysis to avoid block failure. “This analysis enables us to define the sheer strength of the interfaces at the bottom of the landfill to ensure sufficient resistance against failures and select soil or geosynthetic layers to accomplish this properly,” he says.
Early signs of failure and next course
Early signs of a failure of any type are tension cracks near the crest of the slope that runs parallel to the structure’s crestline. Especially lookout for an accelerated cracking pace, advises Bob Dick of SCS Engineers.
There may also be a barging or raising of the ground near the lower part of the slope or at the toe, indicating that the slope has moved.
Don’t simply fill in the tension cracks and walk away, Dick and Law advise.
“The chance is that they will reappear, especially during wet seasons. And each time they emerge, they will get worse. Eventually, the whole slope will collapse without proper attention,” Law says.
Once warning signs emerge, the best course of action is to bring in a geotechnical expert with landfill design expertise to analyze and set up instrumentation to monitor movement closely. That expert analysis will determine whether the slope failure is within the waste at the surface or the bottom of the landfill.
If it’s shallow within the waste, operators can be confident the integrity of the liner and collection system is not compromised. They can then turn their attention to addressing the material moving down the hill. But a failure deeper in the mass calls for immediate action to deal with complex, interacting systems at the bottom of the landfill.
Measuring slope movement
Settlement monuments and inclinometers— determine if the slope is moving, the location, and the direction of that movement. The settlement monument is a concrete block that gauges vertical and lateral movement at the surface, determining if and to what degree the surface dropped. The inclinometer is a PVC pipe installed below ground in the waste mass to measure the lateral movement of the entire slope.
Operators can also use a measuring instrument to gauge liquid above the liner, typically through a leachate collection clean-out pipe.
“If it is slowing, it may stop, but normally, nothing can stop it once it starts. We need to measure systematically to know if it’s accelerating; you have to get off the slope if it is. It’s not safe anymore. But these instruments could help save lives or equipment if they detect early signs of failure,” Law says.
Best practices to stay ahead of the curve
If the movement is very slow or stopped, landfill engineers can improve its stability by flattening or removing the upper portion of the slope. Removing this impervious surface increases safety by decreasing the weight of soil and waste pushing downward.
Another important proactive practice is installing a sump with a pump system to remove liquid and ensure it is low.
Leachate seeps
Leachate seeps are another ongoing challenge that relates to slope conditions. These breakouts happen when saturated waste becomes impermeable. Unable to penetrate, leachate can’t travel its intended route: straight down through the waste mass to the bottom of the landfill. With nowhere else to go, it runs horizontally and comes out the surface of the side slopes.
Uncontrolled seeps can be a big problem. They are a source of odors, can cause erosion, and the leachate can contaminate groundwater if it infiltrates stormwater.
Leachate can also seep below the final cover, causing a different set of problems: a pool of leachate at the toe of the slope that continues to grow. And slope instability due to excess moisture under the final cover geomembrane at the toe of the slope.
“Seeps indicate something is going on behind the slope. They typically are a condition tied to landfill operations. And it takes a lot of practice and planning to prevent or manage them,” Law says.
Some best practices are to break up daily covers before moving to the next cell. Operators may trench it or reuse it. Ultimately removing the impermeable surface enables leachate to drain straight down to the collection system.
Using plants and trees may also serve as a preventive measure. Their root systems can help secure the soil and minimize erosion and runoff depending on plant type.
In the case of an active seep, operators typically excavate a pit at its origin to encourage leachate to travel vertically to the drainage layer. The pit is backfilled with stone surrounding a perforated pipe, covering the structure with low-permeability soil. This practice usually proves successful as a first corrective action, Dick says.
But continuous, pervasive flow calls for more aggressive action. Dick advises in this scenario, operators may need to install perforated pipes with a pump in the stone excavation. This rock sump is a more substantial measure for when a long-term solution is needed, though it requires operational upkeep.
Whether a leachate stone pit is sufficient or whether the sump is also needed depends on the quantity of leachate seeping out and its frequency. Specifically, whether seeps occur only during precipitation or are continuous, Dick says.
Leachate seeps can tie to slope stability issues, particularly when excess moisture accumulates in the material under the final cover geomembrane at the toe of the slope.
Preventing leachate outbreaks and the overall job of maintaining strong, secure slopes comes back largely to managing liquids efficiently and proactively. It’s about preventing problems in the first place.
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Tomorrow we publish Part IV about managing liquids extracted from landfills.
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