An essential part of landfills accepting organic matter is the gas collection and control system (GCCS) for controlling odors and landfill gas (LFG) emissions into the environment; the piping network. GCCS design and construction have evolved significantly over the past four decades, from passive venting trench systems to a sophisticated and elaborate piping systems with specialized components for handling LFG, landfill liquids, and condensate flowing through the piping network.
This detailed article discusses best practices and recommendations that GCCS designers keep in mind; careful attention to these details can potentially save landfill operators significant modification costs and inconveniences prior to and during construction of the final covers.
Read the full article published in MSW Magazine.
About the Authors: Ali Khatami, Ph.D., PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. Srividhya Viswanathan, PE, is a Senior Project Manager with over 10 years of engineering experience. David Fisher is an SCS National OM&M Compliance Manager with 18 years of environmental experience.
We continue SCS’s Advice from the Field blog series with guidance from an article in MSW Magazine by Daniel R. Cooper, Jason Timmons, and Stephanie Liptak.
The authors of a recent article in MSW Management Magazine present engineering ideas that provide for more efficient construction of a GCCS. Gas system operators will benefit by having fewer pumps to operate and maintain and shallower headers that are more easily accessible. Odor management will be easier along with other benefits.
Read the full article here to learn about the design elements for maximizing long-term benefits, impacting: bottom liners, location of the blower/flare station, leachate risers, extraction well targets, and external header piping.
Landfill operators are making significant investments developing comprehensive lining systems to protect human health and the environment. These lining systems are normally equipped with drainage layers to convey leachate reaching the lining system to collection pipes and sumps for removal from the landfill. Landfill operators are also heavily investing in collecting and removing landfill gas for disposal or conversion to renewable energy.
After three decades of experience with these systems, landfill liquids may still accumulate in some gas wells adversely impacting gas removal efficiencies. In these situations installing a pneumatic submersible pump in the gas well to lower the liquid head in the well, restoring gas removal efficiencies is standard practice. However, this remediation technique requires additional capital investment.
An Alternative Solution Exists
A more recent alternative, constructing vertical drains from the bottom up where gas wells are located, may be a better solution. Construction of a vertical drain/gas well begins by constructing a gravel pad at the bottom of the landfill after completion of the lining system and placement of the protective soil cover over the lining system. The gravel pad may be 15 ft. by 15 ft. in lateral dimensions by 10 ft. in height. Gravel pads are normally constructed where future vertical wells are planned to be drilled. The center of each pad is surveyed, and the information is used to locate future gas wells at some vertical distance above waste that is placed in the new cell over time. The gas well drilling continues until it reaches the gravel pad at the bottom of the landfill. The connection between the gas well gravel pack and the gravel pad at the bottom makes it possible for landfill liquids to flow down and drain directly into the leachate collection system below the gas well.
Vertical drains help landfill liquids reaching the gas well gravel pack to flow to the leachate collection system at the bottom of the landfill; thus preventing watering out the gas wells. This sustainable alternative keeps gas production efficient and is environmentally sound, requiring less capital investment.
About the Author: Dr. Ali Khatami
Related Advice, Whitepapers, and Articles
SCS Engineers will provide landfill and landfill gas engineering and construction management services to the Authority. Consulting services will include technical and financial advisory services related to the operation, expansion, and development of the Authority’s landfills, and work with utilities and regulatory agencies.
SCS Engineers has been awarded a contract to provide professional engineering services to the Solid Waste Authority (Authority) of Palm Beach County, Florida. The Authority selected SCS as its preferred full-service provider based on the firm’s wide range of expertise and local presence. SCS Engineers will provide the Authority with professional engineering and consulting services for landfill, landfill gas (LFG), and other solid waste facility management projects.
SCS will provide the technical, construction quality assurance, regulatory, and financial expertise necessary to provide safe, sustainable solutions. The landfill, solid waste management, and LFG support will vary according to task and can include civil, structural, mechanical, environmental, and electrical engineering. SCS’s general responsibilities will include landfill siting, expansions, closures, end use operations, and other improvements or modifications as needed by the Authority to continually improve its landfill and LFG services keeping its landfills in compliance with Federal and Florida Department of Environmental Protection (FDEP) regulations.
“Landfills are complex ecosystems that require the expertise of many types of technical professionals to ensure that the County’s systems are built to last, continue to meet the needs of the community, and safeguard the community’s general health and welfare,” said Eddy Smith, SCS senior vice president. “The planning, design, construction, and maintenance phases of a landfill require a mix of professional engineers and specialists in geotechnical, geological, hydrogeological, environmental, and civil engineering all working on the same team in collaboration with the Solid Waste Authority of Palm Beach County and the FDEP.”
SCSeTools® gives you the ability to instantly map air leaks, vacuum distribution, wells that are “over pulling” and wells that are underutilized – valuable tools for every wellfield technician to maximize system performance beyond simple compliance tracking and reactive wellhead tuning.
As a field technician, you walk a fine line – tuning to a threshold, pulling as hard as you can, as safe as you can. When important data factors start to wander you need to troubleshoot quickly to keep collecting as much as gas as possible without over compensating and adjusting wellheads multiple times. SCSeTools® makes troubleshooting faster and more efficient by turning your data into maps identifying important conditions in the field and the wellheads that need tuning. Field technicians know how to balance the wellfield without killing bacteria and without diluting the gas.
A map of your field with your specific tuning range quickly shows data that are typically missed in reams of data. SCSeTools alerts you to these indicators using a map of each wellhead in the wellfield. Where you formerly needed months for these changes to become apparent, SCSeTools tells you at the touch of a button when a change began occurring and which wellheads are impacted. As a technician you know what you need to tune and which wellheads need your attention.
Using SCSeTools pick any parameter that the GEM collects and create custom ranges or use specified guidelines to quickly identify trends throughout the landfill. Tuning ranges can be adjusted to specific conditions found at individual landfills. Smooth a saw tooth collection pattern and learn from your data for maximum vacuum and maximum collection without risk.