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.”
When Doug Doerr got a call from a Colorado-based landfill operator with a hot gas probe at his site’s boundary, Doerr’s day kicked into high gear. Chasing down gas migration problems is nothing new in an SCS client manager’s life, but that reality makes the job no less complex. And in this scenario, he was dealing with a site that he occasionally got called to visit, so to understand the problem fast, he needed the site’s historical data and the current information to fully picture what was happening.
Doerr started with basic landfill gas information from the client: the monitoring probe’s location and a drawing of the gas collection system to determine where the probe was in relation to the gas system. But as you know, that is one small slice of a king-sized pie.
“All the LFG data that I would typically wade through to identify the problem can be overwhelming, but I had a recourse enabling me to get up to speed quickly. It didn’t take long to assess the problem,” he says. That recourse is a combination of quick teamwork from his peers nationwide and sophisticated technology developed by SCS practitioners for landfill owners and operators.
“I queried our in-house landfill gas technical group (engineers, geotechnical experts, and field personnel). And got over 25 responses within several hours with suggestions, one of which came from Ken Brynda in SCS Field Services, who leveraged DataServices to help me identify and narrow down the potential cause of the problem,” recalls Doerr.
DataServices, a module of the SCS eTools® digital platform, collects, stores, manages and analyzes large volumes of continuously accumulating landfill gas data for individual sites or multiple landfills. The module provides a quick method to view landfill gas scenarios.
The beauty of it is that it generates maps and charts to visualize every well and every probe. These system components are viewed in relation to one another and in relation to the perimeter, where the methane on that Colorado site flowed. Further, SCS Field Services’ landfill gas gurus, such as Ken Brynda, plug-in specific parameters that keep a close watch on any well or a group of wells.
“I logged into DataServices and pulled data from the five wells closest to the hot probe, which showed we had vacuum, flow, and gas quality, indicating the wells were pulling hard enough. I shared the results with our landfill gas technical group responders in a table and range map I’d created. And they started chiming in,” Brynda recalls.
As responders viewed initial results from their respective bases around the country, Brynda churned out more information in a few hours, running point charts to capture the balance gas, methane, flow, temperature, supply vacuum, and the vacuum applied to each well. He looked for trends that narrow down cause and point to solutions.
Eliminating the Possibilities – Rule Out Well System Malfunctions
“It can take days if we’d had to do it the old school way with spreadsheets laid out in a lot of rows. But we could identify the potential problem in a matter of hours, backed by a comprehensive evaluation for the landfill operator in eight hours,” Doerr says.
When Field Services staff work to solve a problem with a probe, they look for an outlier, something from a group of wells that’s not behaving like the other wells. In this case, Brynda determined that the wells near the hot probe were functioning properly. DataServices eliminated potential problems by slicing through and analyzing large chunks of data confirming the system was working efficiently.
Next, we observed that the wells are likely too far away to pull gas back from waste, adjacent to the probe in question, where there are no wells.
“DataServices helped rule out malfunctions, and that’s a big deal because if you can confirm the landfill system is working properly, you have narrowed your focus and can look toward other possibilities, ultimately leading to corrective options,” Doerr says. Brynda and Doerr suggested putting in temporary wells in that area to avoid odor migration and health and safety issues.
Doerr continues watching the situation and is prepared with a several-point action plan to mitigate exceedances and avoid falling out of compliance. “We continue watching the data to ensure the gas collection system continues to function well. Should there be issues again, we’re able to fully identify the gas migration pathways and anything in the system that looks out of the ordinary,” Doerr says.
If the client decides to add wells in time, data from the expanded infrastructure will be added to the app and monitored. “As the number of wells grows, DataServices grows with it, adding any, and as much, monitoring and collection data as the operator wants. DataServices will always be in the background to monitor, collect and analyze LFG data in real-time, whenever we need it,” he says. Being able to store, organize, dissect and analyze unlimited volumes of information from one location is powerful. And not just because it helps operators identify problems as they are happening, but because it and our teams can support them in looking for trends over time. Keeping an eye on the activities that keep the systems in balance is less costly.
For Doerr, who spends time in the field but longer hours with his clients, DataServices and the ability to interact quickly with experts like Brynda help SCS deliver more value to clients. “As much as I’d love to master DataServices, I need to focus all of my time on my clients’ business and goals; having support from Field Services and DataServices makes us all more efficient.”
Landfill Technologies and Comprehensive Expertise
SCS eTools® and SCS DataServices®, now with SCS MobileTools® for viewing data and charts anywhere; available to pull landfill data into DataServices for analyzing. You can customize and focus on exactly what you need fast. As Doug and Ken emphasize, it’s info that you likely already have, but may not be able to use quickly for troubleshooting.
SCS RMC®, remote monitoring and control of landfill equipment and systems.