Our next SCS Client Webinar will focus on landfill gas maintenance and how Landfill Operators create more efficient operations using monitoring data. Scott Messier, Site Operations Manager at the Monterey Regional Waste Management District, will join us to describe how he finds efficiencies using SCS eTools.
This lively panel will discuss common operational challenges and demonstrates how maps, charts, and graphs created from your collected data, can enhance technician productivity when:
• Locating new LFG wells,
• Locating the cause of odors or surface emission monitoring hits,
• Determining the cause of LFG migration to probes,
• Identifying obstructions in the header network,
• Getting more gas for a power plant and preventing migration,
• Identifying elevated temperature conditions,
• Creating report libraries for regulatory compliance.
SCS’s format allows you to ask questions throughout the event and ask anonymously if you prefer. We realize September is an extraordinarily busy time this year, so if you register but cannot attend, we’ll send you the recording.
Register to join the live event or receive a link to the session recording if you can’t make it. SCS respects your privacy; you will only receive an event confirmation and reminder.
Accumulating liquids are problematic for landfills taking sludges and other wet wastes not traditionally part of the incoming waste stream. Add to the mix increasing precipitation, and operators could be staring down the perfect storm—especially as they work to optimize their gas extraction systems. Here’s the challenge, explains Pete Carrico, SCS Engineers Senior Vice President and national expert on liquids management:
“Trash is porous, and the soils used for daily and intermediate cover usually aren’t, so liquid gets trapped between alternating trash layers as the landfill fills. These “perched” liquids can drain into well columns and block the slotted portion of the extraction well piping that withdraws gas from waste and into the gas collection system.”
Even a robust vacuum on the wells will not pull gas once pipes fill with fluid. With no path to move it from trash into the collection infrastructure, operators work harder to stave off odor and slope stability issues, among potential resulting problems.
The good news is they have a recourse to remove the liquids, unblock well perforations, and extract more gas. They do it by installing dewatering systems: an intricate network of pneumatic pumps, air lines to power them, and conveyance lines, also known as force mains, to remove liquid.
Manufacturers have designed and redesigned their pumps to try and address problems specific to landfill gas extraction systems. And the equipment does the job but requires meticulous attention and skill to keep all the moving parts going. These liquids are rough on pumps due to their harsh nature. The suspended solids and biological material they contain are the biggest challenges, and if the landfill has high temperatures, these liquids can heat up, further taxing the system, Carrico says.
“No pump indefinitely survives the challenging conditions you have in landfills. So, where we can make the biggest difference is with these maintenance programs,” Carrico says. You’re spending O&M budget on what provides the most impact.”
SCS uses dedicated, factory-trained pump crews who focus solely on operating and maintaining gas extraction dewatering systems. These crews help ensure the infrastructure functions as it should, and gas moves through well piping slots, into the gas header piping, and to the blower/flare station for beneficial end-use.
“Operations run more smoothly with these crews in place. An SCS field crew is as unique as each landfill. Our specialists have various skill sets, i.e., gas collection system monitoring, surface emissions monitoring, or pump maintenance expertise. That’s how we produce better outcomes in terms of pump performance. If you effectively maintain and repair the pumps, you will restore them to their designed specifications, pump more liquids, and with greater ease,” Carrico says.
The teams, who work on landfills across the country, stay busy. One site can have five to 300-plus pumps, each with multiple components, and they must be removed and cleaned frequently.
Replacing worn, fouled, or damaged components is an especially tedious and complex job.
Some wells are 70 to 100 feet deep. Pulling air lines, liquid lines, and pumps out from that depth is hard and requires special equipment to do safely. SCS crews know how to take them apart and put them back together; they don’t just lower them back in the ground after working on them. But hook them up to air and water lines and watch them work at capacity before returning them to service.
It’s a value add; with a good maintenance plan and the right crew, pumps can be kept at their designed specifications and run efficiently for many years. They can typically be cleaned and reset for a fraction of their replacement cost.
“We leverage our size and resources. We have a deep bench of in-house experts and engineers willing to share information to help with problems, which is important as conditions vary at each site, as can problems and solutions. So, it’s important not to do this in a silo but rather pull from our broader knowledge base,” Carrico says.
Technology helps too, especially with tracking, maintaining, and reporting progress to clients. A geographical information system (GIS) maps each well’s location, and pump technicians upload data corresponding to each one from wireless tablets almost instantaneously.
The ability to automate tracking and display critical information right away on a dashboard has increased our program’s efficiency. Technicians spend less time tracking and look at analyses of all the landfill conditions to know where to concentrate their efforts, Carrico says.
A few landfills are working to avoid pumping liquids altogether. They are building large gabion rock structures at the landfill’s base, with piping that connects to the extraction well system, creating a conduit. Liquids automatically drain to the bottom where leachate is intended to go while effectively pulling more gas into the gas collection system.
“This is a newer trend that some of our clients are already doing. And we are involved supporting the well designs,” Carrico says.
For now, in most cases, achieving the best outcomes is about investing in pumps and a good maintenance program.
“Monitoring and regularly measuring—checking stroke-counters, which show how many times a pump cycles, and checking flow meters to know how many gallons a day a system produces are key to finding savings. It’s how you reduce or prevent catastrophic failures,” says Greg Hansen, Senior Project Manager with SCS Field Services Operations, Maintenance & Monitoring.
To execute properly, Hansen provides this advice for operators setting up a pump program:
Have pump maintenance areas with water, electricity, disposal means for waste liquids, and storage facilities for spare parts and tools. More specifically:
Operators planning on doing maintenance in-house should train their technicians on cleaning, servicing, and testing pumps. Either SCS or the pump manufacturer can provide this training.
Above all, Hansen says, “You need a comprehensive OM&M program. The better the job tuning pumps, the better they do in the field, and the longer they work before being cleaned or repaired. It’s a continual process.”
With the frequency and severity of storms on the rise, municipal solid waste landfill operators have to think differently to keep their workers and environment safe. Planning is key to safely hit the ground running in the wake of severe weather.
Federal law does not hold household hazardous waste (HHW) to the same standards as what is classified as hazardous waste (generated by businesses and received at subtitle C landfills). Yet, these materials have the same compounds and are potentially dangerous too.
“Subtitle D landfills routinely receive these wastes, but under normal conditions, it’s in much smaller quantities, and they are typically segregated. So managing them is not a big deal. But, after a storm, operators can be inundated with these oxidizers, corrosives, flammable gases, and flammable solids. It’s all coming in at once and mixed with other storm debris, posing a risk for reactions and workers’ safety,” says Mike Knox, SCS Quality Advisor. He supports landfill operators in safely managing hazardous wastes. Storm season is a busy time for him and his clients. Those unprepared find themselves pulled in multiple directions and need to act quickly and smartly.
If a structure blows down, it may generate waste that contains gallons of dangerous liquid, gas containers, propane tanks, and pesticides mixed in. It’s dangerous, especially if a waste worker does not see it.
Mike’s Planning Advice
Operators set themselves up for success when they’re ready to go with a plan before that first 80-mile-an-hour wind gust hits.
“You must know how to identify hazardous wastes ahead, train staff ahead, and look at worse-case scenarios ahead,” Knox says.
He and his team start by looking at operators’ facilities and identifying materials, workers’ roles, and available equipment and assets. They identify safety areas and set up classrooms. Important are preparing the staging areas to manage the influx, screen, and segregate by waste type.
Then they look at government rules; help operators determine what they need to do; and execute a plan.
Operators need to secure waste, make sure it’s packaged right, and minimize it where possible to stave off mishaps.
The safety of people and equipment is part of a proactive strategy. Trucks can tip over with heavy, wet loads, so do not overload them. Space trucks in the tipping area are at least 10 feet further apart than the dump trailer is long. For a 30-foot trailer, that’s 40 feet.
Setting up this extra space can be difficult unless you’ve established a large tipping area, and don’t take chances with dump trailers; the results have proven deadly in the past, Knox advises.
Check that backup alarms and strobe lights are working. Train equipment operators to look for vehicles and pedestrians. Do not allow cell phones at the working face; a distraction that no one needs. Mandate the use of high-visibility vests and restrict people to stay within five feet of their vehicle. Strictly control scavenging. People cannot wander and pull items from the trash.
Fuel is the item most often overlooked in Knox’s experience.
“Having enough fuel to operate heavy landfill equipment and hauling fleets is essential to keep waste moving. Severe storms have impacted fuel supplies for several days to a week or more, so stock up,” he recommends. Mike typically arranges for temporary fuel storage tanks so haulers and heavy equipment operators can stay on their mark through and after the storm.
Scenarios in Preparation
Part of safety management is asking “what if” and then answering ahead of a problem. Depending on where ‘what if’ leads, you prioritize and go after the big things first. One big one is, what if floods occur? That question leads to more specifics to plan for, such as roads likely to be impacted and establishing alternate routes available. What other actions will help traffic flow?
Remember: if there’s a lot of rain or clay, trucks can slip going up hills. So alternate tipping areas that are lower and flatter may be needed to accommodate inclement weather access. “And that takes preparation. Sometimes you have to build a road to reroute to an area you are not using. It can take days,” Knox says.
Building wet weather access roads are important, as are measures like cleaning out stormwater ditches. Nevertheless, know that, depending on location, rising water may flood out areas despite these efforts. Pumping water into berms and ponds from flooded ditches can be a temporary solution if your plan and local regulations allow it. Coordinate with regulatory and permit agencies to set up such actions.
You will want to bolster protections of maintenance facilities, the scale house, and other structures that could be damaged or lose power – stock up on tarps, lumber, and power generators.
Many operators find waste screening towers to be especially useful. Knox and his team will build them in advance to prepare for what’s coming. Waste screeners at the gate radio to active face supervisors if hazardous materials are arriving so they can properly place them, ensuring they are covered with dirt before sending staff to the active face.
Knox completes quality evaluations guided by a 200-item checklist to ensure proper procedures are in place. He compliments this list with many questions to prepare.
Know Your Jurisdiction’s Rules and Storm Accommodations
Operators check local permit conditions to take advantage of possible modifications they may make. Some jurisdictions have more lenient weight restrictions for hauling vehicles or the option to set up temporary staging areas.
Knox also suggests coordinating with the local permit and regulatory agencies following the storm to take advantage of emergency relief funds and coordinate across the area’s public and emergency services.
Local government, emergency responders, regulatory and permitting agencies often have Emergency Operations Centers (EOC) to coordinate resources, information, and crisis management. Mayors, County Commissioners, fire departments, hospitals, police, environmental regulatory agencies, and other key industry leaders are typically part of this team.
These groups practice response coordination and stage tabletop exercises or mock disasters. “Take time to participate and plan with the EOC. Check for whatever else may be available in your area to help prepare, and work as a team with these local entities to respond to severe weather or other emergency events,” Knox says.
Circling Back to Planning
“Knowing what to do before the storm hits will make your recovery easier. You will keep your employees, your community, and your site safe. And be ready to go back to normal operations much faster.”
About the Author: Mike Knox has over 30 years of Ordnance and Hazardous Materials experience. He is a Regional OM&M Compliance Manager with extensive supervisory abilities in hazardous waste emergency response and large-scale clearance operations.
The Solid Waste Association of North America (SWANA) is hosting a virtual Landfill Challenges Summit on Thursday, June 17.
This half-day, virtual event will bring together landfill, landfill gas, and biogas professionals from throughout the United States and Canada. Industry experts from the public and private sectors will discuss current and future challenges that are expected to impact landfill operations and landfill gas production, and what lessons can be applied as we move forward.
The virtual summit will be followed by an on-line networking event.
Here at SCS, we work for developers, industry, and manufacturers to help them run cleaner, safer, and more efficiently. This PBS video provides insight into how SCS brings value to the waste industry, our clients, and, most importantly, our communities.
You may ask yourself, don’t pig farms create pollution? Yes, but even that waste is reusable!
Did you know the food you buy in the grocery is supported by our environmental experts? Learn more about SCS’s environmental engineers and consultants who bring contaminated properties back to life, lower and capture greenhouse gases for fuels and renewable energy, and make possible a brighter future.
If you are interested in becoming an SCS Engineers employee-owner, watch our comprehensive video to see the breadth of services our teams offer.
Recorded Live Thursday, June 10 at 2:00 pm ET
GIS improves operational efficiency at waste facilities, landfills and helps keep development projects on schedule. GIS technology transforms volumes of collected data into maps and easy-to-understand dashboards – making staff assignments and decisions more precise and timely.
Our panelists use case studies to demonstrate how they use this proven technology in new ways to improve forensic, diagnostic, and planning activities. Join us to learn how your operation may also leverage GIS to address these challenges:
Landfills: Operators make diagnostic and forensic use of GIS to address maintenance tasks faster. We’ll cover modeling 3D wells and liquid level data, showing how GIS embedded dashboards and infographics pinpoint exactly where to assign staff. At the same time, supervisors monitor completed assignments seeing real-time results and what still needs attention.
Siting Facilities: Decision-makers use multi-criteria decision analysis incorporated into a geographic information system to account for relevant technical data, environmental, social, and economic factors during the site selection of a waste transfer station. The resulting maps and infographics are useful at public meetings too.
Property Development: Time is money on development projects. Environmental engineers use GIS to more accurately pinpoint potential contamination sources, conduct site assessments, strategize remediation solutions, and see sampling results weeks faster. Infographics and dashboards show if and exactly where to continue sampling without waiting weeks or months for reports.
Among the extensive list of landfill operating costs are those incurred for landscaping to keep the slopes trimmed. While regularly mowing large spaces is expensive, keeping sites well-groomed is essential for protecting landfill covers and providing other safeguards. Putting sheep and other grazing livestock to work eliminating invasive plants and other vegetation from properties difficult to traverse for two-legged workers could be a good alternative. Grazing is an often useful technique for maintaining traditional native plants while reducing weeds and unwanted vegetation, mitigating risk for growth to dry out and possibly catch fire or intrude on a site’s pipelines and infrastructure.
In municipal solid waste landfills near urban areas, such as in Pennsylvania, Arizona, and California, grazing animals are helping with slope management. These locations also reap environmental benefits of reduced soil erosion; improved air and water quality; better plant diversity, vigor and production; and improved wildlife habitat.
As with all landfill operations, planning is everything. The choice of grazing animal (i.e., sheep, goats, cattle, or horses) and the number of animals necessary is site-specific. To determine the best choices, SCS Engineers looks at site characteristics such as the age of the plants and the proportion of grass species present, the local climate, and wildlife species present.
A landfill operator in California using sheep to groom landfill slopes is pleased with the results after three months and plans to continue the grazing method in the upcoming years. “We use 400 sheep per acre, per day, and have 600 on-site.”
“We talked about it for years before we implemented this method,” he says. “We needed time to research the feasibility and the costs, but that isn’t a challenge for SCS; their environmental scientists have landfill expertise in gauging air, soil, water, inorganic and organic content. These are all conditions requiring careful consideration before bringing in sheep to graze.”
The operator was sold on grazing, seeing the environmental, economic, and safety benefits of this alternative to herbicides and staff maneuvering trimming equipment on steep slopes. Finding a shepherd was the next step. With all its benefits, the method does require human oversight.
Luis lives at the landfill in a trailer home, his base of operations. He grew up in Peru, herding sheep. The landfill operations staff trained him on landfill safety, and Luis, in turn, teaches landfill staff what to expect from the 600 sheep.
The herd grazes during daylight hours, clearing patches of mustard grass and weeds. “Sheep are a better choice than goats here; they are more selective and won’t eat native plants or damage the infrastructure by trying to eat it too,” says the landfill operator.
As the sheep graze on invasive grasses, they are preventing tumbleweeds and destroying the seeds while chewing. A further benefit is the fertilizer they leave behind supports the growth of native plants that require minimal grooming, are tolerant of dry conditions, and facilitate the protection of the landfill cover.
“Around here, where the climate is very dry, preventing tumbleweeds and flammable conditions is a priority. The herd is packing the groundcover down while they’re eating, providing a great alternative to mowing while helping control runoff,” says the operator.
The herd is low maintenance, thriving outdoors without shelter and needing only to have their water troughs filled. The shepherd has two helpers, a border collie for herding the sheep to new locations and another larger dog to help protect the sheep from coyotes. Both the dogs and the wildlife help cut down the number of burrowing animals, which for obvious reasons are not landfill-friendly.
Occasionally, the landfill operation staff helps Luis move the herd. He sets up new locations across the landfill as the sheep are grazing in another area. Then the dogs help move the herd to the new location. Keeping the sheep going in the right direction is hard work, explains SCS’s Regional Manager. “If one sheep breaks off, twenty more will follow. Depending on where we’re moving them, Luis may need extra hands.”
This natural “landscaping” alternative with all its landfill-specific benefits is working well. The sheep can do some damage, they sometimes rub along exposed pipelines scratching themselves, but the staff is quickly alerted to anything broken. Luis uses a lightweight grid fence to corral the animals. The battery-powered fencing helps protect the sheep at night from coyotes with a light “shocking” deterrent, similar to static electricity. It’s enough to keep the carnivores at bay along with the dogs’ help.
The SCS landfill operations team has adopted the two dogs. Their Field Services Regional Manager points out, “We didn’t plan on adopting them, but we just couldn’t help ourselves. These are hardworking animals, and Guardian, the dog protecting the sheep at night, can get Foxtail, a grass-like weed, caught in his fur. The seeds can injure dogs, so we inspect and brush them, and we watch to ensure they stay healthy. These dogs, like the sheep, are part of the team and important to helping maintain the landfill − not to mention they’re special to us.”
The sheep, dogs, and Luis are doing an exemplary job. The operator expects in two or three seasons to see a significant improvement in maintenance; each consecutive year, there is less undesirable vegetation. “It’s working well; next year, we will start grazing in January to help prevent more invasive new growth earlier in the season,” he says.
“Environmentally, I like to think we’re helping our client be a good neighbor,” he continues. “And we save the landfill 66 percent of their landscaping budget every year; that helps us all sleep better.”
The U.S. Environmental Protection Agency recommends ecological restoration and revegetation of landfills, abandoned dumps, mines, and other site containment systems designed to protect people and the environment from exposure and prevent contaminant migration. Grazing is one cost-effective and efficient option to consider supporting these priorities.
The Solid Waste Association of North America (SWANA) is hosting a virtual summit in place of SOAR this June 17th. The Landfill Challenges Summit presents sessions from 12:00 – 5:00 pm EDT and on-demand sessions throughout the conference.
The Landfill Challenges Summit brings together landfill, landfill gas, and biogas professionals throughout the United States and Canada. Industry experts, including those at SCS Engineers, will discuss current and future challenges that are expected to impact landfill operations and landfill gas production and what lessons can be applied as we move forward.
As vacant land becomes more scarce, developers are turning to former landfills, which are often large tracts in prime locations, are now use. Daniel Cooper and Somshekhar Kundral use examples demonstrating how landfills and lakefills may be reclaimed, allowing the community to realize economic benefits in previously unusable areas for development while improving environmental protection. However, redevelopment on such site poses several environmental and geotechnical challenges. The design concepts of methane gas management systems vary based on the site’s subsurface conditions, building footprint, and the perceived risk tolerance of building owners. Several gas management barriers are available in the market today and can be broadly classified into the asphaltic spray-applied liner and the HDPE liner. The use of these liner systems depends on subsurface conditions and the size of the building. SWANA CEU: .50
SCS Engineers periodically prepares SCS Technical Bulletins – short, clear summaries of U.S. Environmental Protection Agency (EPA) rules and plans. On May 21, 2021, the EPA published a Federal Plan to implement the new Emission Guideline (EG) rule for municipal solid waste (MSW) landfills. The Federal Plan is published under Title 40 of the Code of Federal Regulations (CFR) Part 62, Subpart OOO.
Read, share, download the Federal Plan for Landfill EG Rule Tech Bulletin here.
It goes without saying: landfill operators are forever working to stay on top of odors, especially when the community smells something and points to the landfill or when regulators come calling. This blog shares two odor stories: one around landfill gas and another around trash. Then it looks at what happened when an operator got a permit restriction over alleged hydrogen sulfide emissions; odor was not the problem here. It was a perceived health risk; learn how SCS proved a predictive model was off the mark.
Is Landfill Gas a Source of Community Odors? And Ensuring Compliance
Living up to landfill odor nuisance standards is tough. The underlying premise is that odors must limit peoples’ ability to enjoy life or property to create a public nuisance, but it’s a subjective call. How strong an odor is and sometimes even if it exists depends on perception, so the question becomes: when they aren’t sure what they are being measured against, how do operators comply and prove compliance?
SCS recently helped a client figure out how to accomplish this after receiving odor complaints from the community, ultimately leading to a state agency-issued violation.
“We needed to thoroughly investigate to identify and mitigate odors, then prove compliance to the state regulator. Making a strong, valid case without having a numeric standard to go by takes both creativity and a scientific approach,” says Pat Sullivan, SCS senior vice president.
Sullivan, a biologist and his team of meteorologists, air dispersion modelers, and engineers, had a good starting point. They knew landfill gas was the source of the problem. But they needed more data to get to the root of that problem, and the operator’s required surface monitoring did not tell enough of the story.
The team launched a series of studies relying on multiple investigative tools.
“When we may have to put in more gas collection components, as we did here, we want to be sure we install them exactly where they are needed. This entails going above and beyond the standard modeling with a more rigorous methodology to get a comprehensive landfill gas emissions footprint,” Sullivan says.
SCS began by bringing out a drone to reach more landfill areas than technicians on foot for better coverage. The drone can fly over slopes, areas too dangerous to walk due to constant movement of heavy equipment, and areas inaccessible because of snow and ice. As it flies, it shoots a laser, which identifies methane based on the light refraction by methane molecules—then incorporates the data into a map for a comprehensive, visual picture.
Knowing methane concentrations at specific locations is important, but determining where to be more vigilant in controlling landfill gas also requires knowing hydrogen sulfide (H2S) concentrations. Sometimes overall methane levels are within acceptable limits, but the hydrogen sulfide in it is elevated, which could be a problem, Sullivan explains.
Getting a good grasp on H2S’s potential impact is tricky, as levels can vary radically from one area of the landfill to another. Pat Sullivan, SCS senior vice president, has seen them range from 100 parts per million to as high as 100,000 at different locations.
SCS used a Jerome meter, a highly sensitive tool that precisely quantifies H2S down to low-level part per million levels. SCS took it across the landfill and then into the community in search of H2S hot spots.
At the same time that the team investigated surface emissions of H2S, they went deeper down, sampling each landfill gas extraction well for levels of this volatile sulfur compound to identify potentially problematic spots within the landfill gas system.
“For this, we used Dräger sampling tubes, a resourceful tool in that rather than sending 100 samples to the lab, we analyze them ourselves and get immediate results,” Sullivan says.
Technicians get accurate quantitative results within plus or minus about 20% and can view concentration readings out in the field. Results are recorded on field logs and entered into a database for future analysis.
SCS overlaid the methane data from the drone study with the H2S data on both surface emissions and wells to develop a roadmap to design a landfill gas system upgrade. It includes new wells and piping in focused areas and more blowers for increasing the vacuum to pull more gas.
“We saw immediate results,” Sullivan says.
“Total gas collected went up 15 to 20 percent. Complaints went down significantly, and our client has not received another violation since.”
Of course, as the landfill takes in more trash, it will generate more gas, so due diligence is ongoing.
“Problem-solving is a phased approach. You do what you determine to be most effective; evaluate; then do additional work to improve. We will continue to follow this site and fine-tune where needed to keep the system running efficiently and keep the community and regulators happy,” Sullivan says.
Taking Down Landfill Odors from Trash
New garbage on a landfill’s active face can be a source of offsite odors, but determining if the waste facility is responsible, and determining when, where, and how odors travel, takes forensic work. Landfill odor experts rely on multiple data sets and tools to understand what can be complex issues and ultimately devise the most effective odor mitigation program when necessary.
In a couple of recent scenarios in Southern California, SCS combined complaint data, meteorological data, and smoke studies to get a full picture that verified the decomposing waste was the odor source. Then staff helped nail down specific times the problem occurred and under what conditions; providing a concise window can save operators labor and other resources because they can execute proactive measures only when needed.
“We look at complaint data to learn the location, day, and time of the complaint, but these accounts are not reliable by themselves. So, we overlay this information with meteorological data to determine the wind conditions during those days and times. Weather-related data is important in vetting offsite odors because if the landfill is not upwind of the location when the complaints happen, there likely is another source,” says Pat Sullivan, SCS senior vice president.
Sullivan and his team begin their investigations in two possible ways – setting up meteorological stations at strategic areas on the landfill to capture wind-related data or capturing data from already situated stations. Then they produce wind roses from their findings, which graphically represent wind speed; how often the wind blows from certain directions; and how these two correlate. In these two scenarios, graphing wind data times during each day helped determine exactly when specific wind conditions are prevalent.
In one of the two cases, odors occurred in the summer and almost always in the morning. The data not only showed where the winds were coming from at those times, but also showed they were traveling at low to moderate speeds.
“We matched that information to complaints and confirmed that the wind conditions were indeed driving the odors,” Sullivan says, explaining the speeds were just enough to carry the odor molecules into the community but not high enough to disperse and dilute them.
“Now we have painted a picture of wind conditions that we can focus on to get more information. We are getting closer to designing a multi-tiered odor mitigation program,” he says.
The next step was a smoke study, which reveals how odors move offsite, identifying the exact pathways and movement trajectory. These details are important because to treat or disrupt odor molecules; operators need to intersect the odor plume before it leaves the site.
SCS odor experts release colored smoke at the time and location they believe odors are, based on the meteorological data. They film from a drone to get a bird’s eye view of the smoke plume as well as get a camera filming from a different angle, following the plume movement to identify its path out of the landfill. This method enables them to determine where to intersect the odors as they move through the air before leaving the site.
From this research came three recommended measures to take during unfavorable wind conditions:
One of the landfill operators now has the problem under control and has received no further violations.
The other site made many of the same changes and plans to open a second disposal area for smelly loads. This client has seen a significant reduction in complaints and violations, but it’s a work in progress. The next true test will come when Sullivan and his team reevaluate in the summer.
“We will see then if any improvements are needed and tweak the solution if needed.”
And as with our other clients, we are training operators on how to be proactive. We teach them how to identify and grade odors and how to follow set procedures. And we help them with strategy implementation,” he says.
Odor mitigation is an ongoing undertaking. The team continually assesses and quantifies emissions and potential impacts.
“We look for changes that will control odors or prevent them in the first place. And we provide clients with the know-how and support to stay ahead today and into the future. Landfills and waste volumes are growing and changing. It’s a dynamic scenario. And we continue to build on what we have proven and adjust to keep up to make more progress,” Sullivan says.
Showing That a Model Can Over Predict H2S Emissions
Hydrogen sulfide (H2S) can be problematic even at very low concentrations, so this volatile sulfur compound is on federal, state, and local regulators’ radar. Some jurisdictions require the evaluation of air toxic emissions to determine potential health impacts to nearby communities.
They are also calling for these evaluations during permitting or to decide when controls are needed. To make these impact determinations, regulators typically rely on standard H2S risk assessments leveraging air dispersion modeling that predicts concentrations at locations away from the source.
However, this methodology, which includes estimates of emissions and predicts offsite concentrations based on algorithms that mimic how air moves, is not always accurate. Inaccuracy proved to be the case at one SCS client’s site. The model overpredicted offsite measurements of H2S that the state and local agency classifies as toxic.
Ultimately, the client entered into an enforcement agreement with the state because the operator had a permit limit, based on results of the risk assessment that it could not meet.
“Respectfully, the agency came in maintaining that the levels were out of compliance; it came as a surprise and seemed questionable to our team given our experience. We felt that the air modeling and risk assessment results derived from this modeling were not accurate,” says Sullivan.
First, his team tried to adjust model inputs and variables that would yield what they believed would be more accurate data. Even though they could show improvements, the model adjustments could not obtain readings that showed compliance with the risk-based limits.
Next, they began going out monthly and measuring real concentrations at receptor locations. The team used a Jerome sensor, a highly sensitive handheld device that detects H2S down to single-digit parts per billion levels with good accuracy.
When they compared the predictions from the standard model to their readings on the same days of each month and same times of day, they confirmed the concentrations were well below the acceptable risk threshold.
“Because we did this over an extended period, we have continuous readings and a large data set from many locations that give a history and statistical validity,” Sullivan says. Every monitored value was substantially lower than the values predicted by the model.
“What that means is we could show that while there were onsite emissions, they were not escaping the landfill at levels that would exceed risk-based thresholds. That was useful in proving to the regulators that the landfill was actually in compliance with the standard, even when the model suggested it was not,” Sullivan says.
Now SCS is asking for revising its client’s permit and that the limitations are made more flexible based on real-time, longer-term findings. While the team is still waiting on the final permit decision, they’re confident they have proof that the site complies with the risk-based limit.
The outcome of this project has potential beyond possibly changing one permit for one operator, Sullivan surmises.
“We think the data developed from this study showing how the models can overestimate real-world conditions can ideally help other operators build a sound case in circumstances where they truly are in compliance.”
Staying Ahead of Odor Management at Solid Waste Facilities – This video recording is from a live session about the challenges of odors, including measuring them and the science behind them. Throughout the recording, the speakers’ field questions as they make recommendations for assessing and avoiding odors, regulatory issues, litigation, and responding to complaints.
The presentation and Q&A run for 1 hour 41 min. It’s well worth your time, with plenty of questions posed by solid waste facility operators, landfill managers, and composting operators answered.
SCS Engineers encourages you to share this video or any from our Learning Center. You can embed them at events and use them for in-house training. Look for our next webinar in June 2021. If you’d like to attend a live session or request our presentation slides, please email us at .