An SCS Advice from the Field blog.
Self-priming pumps can provide excellent performance in the design of a landfill leachate removal system. Landfill owners and operators prefer them to help control construction and maintenance costs too.
A typical system for removing leachate from landfill disposal cells is to have a collection point (sump) inside the lined area of the disposal cell at the toe of the landfill perimeter berm slope with large riser pipes extended from the top of the berm to the bottom of the sump. Removal of leachate from the sump takes place by placing specialized submersible pumps inside the large riser pipes with electric controls for ON-OFF switches inside the control panel of the pumps located at the top of the landfill perimeter berm. The pumps are equipped with wheels that roll down the riser pipe and are positioned in the horizontal portion of the riser pipe at the bottom of the sump. The discharge line from the pump extends up through the riser pipe, and after exiting the riser pipe at the top of the berm, connects to a leachate force main in the perimeter berm. Leachate in the sump flows into the riser pipe through perforations in the riser pipe and reaches the intake of the submersible pump for removal from the sump.
Maintenance of such submersible pumps is not easy; the entire pump assembly including the power cable connected to the pump, level control leads, discharge line, and the pump is taken out of the riser pipe to have access to the pump. Normally, the entire pump assembly is soiled with leachate and slime sticking to the pipes, lines, and the pump while submerged in leachate. The discharge line could be a 2-inch diameter solid HDPE pipe long enough to reach the sump bottom from the top of the perimeter berm. Depending on the depth of the landfill from the top of the perimeter berm, the discharge lines could be long; which means the technician has to handle the extraction of a long and heavy pipe connected to a heavy pump at the lower end of the pipe, out of the rise pipe. Technicians handling the maintenance of the submersible leachate pumps must be well trained about safety aspects of the activities involved in the maintenance of such pumps. The structure located at the top of the berm, where the riser pipes and leachate piping are located, should be watertight to prevent liquids generated during maintenance activities from escaping into the berm structure and entering the environment. It is a safe practice to have more than one technician attempting to remove a submersible pump for maintenance purposes.
For landfills with depth to the bottom of the disposal cell less than the water column vacuum pressure (for practical purposes less than 15 ft.), self-priming pumps may be a feasible replacement for specialized submersible pumps. Self-priming pumps are not specialized pumps, come in all sizes, are much less expensive than the submersible pumps, and can easily be installed inside the structure at the top of the perimeter berm with a 2-inch line extended to the bottom of the riser pipe for leachate removal. Maintenance of such pumps is significantly less cumbersome than submersible pumps, with one technician able to handle replacement or maintenance of the pump in a much shorter period than that of a submersible pump. The work is not necessarily a dirty job where the technician has to handle a significant amount of leachate and slime. For maintenance of the pump, the 2-inch diameter pipe inside the riser pipe for removal of leachate does not need to be extracted. The self-priming pumps are normally designed to prime easily after each maintenance session. A check valve on the intake of the pump and a check valve near the bottom of the removal pipe prevents the liquid inside the pump and the removal pipe from flowing back down to the sump when the pump goes OFF, which prevents the need for priming the pump on the next ON cycle. The leachate level control can be a bubbler system installed inside the pump control panel with the air hosing extended to the bottom of the riser pipe. The initial setting of the bubbler system allows to control ON and OFF levels of the pump.
Self-priming pumps could also be used for double lining systems equipped with a secondary sump and a primary sump. A secondary pump removes liquids from the secondary sump and a primary pump removes leachate from the primary sump. In areas where freezing conditions during the wintertime are expected, self-priming pumps can also be used as long as the pumps and exposed piping are located inside an enclosed housing to prevent frost.
The author, Ali Khatami, Ph.D., P.E., has used self-priming pumps in his designs, where applicable, for over the past 20 years and has experienced very satisfactory performance results from the pumps, even those included in very large pumping networks. Testimonials from his clients regarding ease of maintenance and lesser capital cost for construction of the system is a good track record for a sound system to be used in the future.
Liquids Management and Landfill Design
The updates to air regulations intend to remove redundant requirements and reduce compliance burdens where environmentally appropriate.
The U.S. Environmental Protection Agency (EPA) proposed updates to the oil and natural gas industry national standards. The proposal intends to remove regulatory duplication while maintaining health and environmental regulations on oil and gas sources that the agency considers appropriate. The proposal is the result of EPA’s review of the 2016 New Source Performance Standards (NSPS) for the oil and natural gas (O&G) industry conducted in response to Executive Order 13783 – Promoting Energy Independence and Economic Growth. The goal was to review existing regulations that could potentially “burden the development or use of domestically produced energy resources,” including oil and natural gas.
The resulting regulatory impact analysis from EPA estimates that the proposed amendments could save the O&G industry $17-$19 million a year, for a total of $97-$123 million from 2019 through 2025.
“EPA’s proposal delivers on President Trump’s executive order and removes unnecessary and duplicative regulatory burdens from the oil and gas industry,” said EPA Administrator Andrew Wheeler. “The Trump Administration recognizes that methane is valuable, and the industry has an incentive to minimize leaks and maximize its use. Since 1990, natural gas production in the United States has almost doubled while methane emissions across the natural gas industry have fallen by nearly 15%. Our regulations should not stifle this innovation and progress.”
In its primary proposal, the agency is proposing to remove sources in the transmission and storage segment of the O&G industry from regulation. These sources include transmission compressor stations, pneumatic controllers, and underground storage vessels. The agency is proposing that the addition of these sources to the 2016 rule was not appropriate, noting that the agency did not make a separate finding to determine that the emissions from the transmission and storage segment of the industry cause or significantly contribute to air pollution that may endanger public health or welfare.
The primary proposal also would rescind emissions limits for methane, from the production and processing segments of the industry; keeping emissions limits for ozone-forming volatile organic compounds (VOCs). These sources include well completions, pneumatic pumps, pneumatic controllers, gathering and boosting compressors, natural gas processing plants and storage tanks. The controls to reduce VOCs emissions also reduce methane at the same time, so separate methane limitations for that segment of the industry are redundant.
In an alternative proposal, EPA would rescind the methane emissions limitations without removing from regulation any sources from the transmission and storage segment of the industry.
The agency also is seeking comment on alternative interpretations of EPA’s legal authority to regulate pollutants under section 111(b)(1)(A) of the Clean Air Act.
This proposal is in addition to a September 2018 technical action that proposed targeted improvements to help streamline implementation, reduce duplication of EPA and state requirements, and significantly decrease unnecessary burdens on domestic energy producers. EPA is currently reviewing comments received on that technical package and expects to issue a final rule in the upcoming months.
EPA will take comment on the proposal for 60 days after its publication in the Federal Register, and will hold a public hearing. EPA will announce details of the hearing shortly.
More information, including a pre-publication version of the Federal Register notice and a fact sheet, is available at https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-industry
Link to the proposal: https://www.epa.gov/sites/production/files/2019-08/documents/frn_oil_and_gas_review_2060-at90_nprm_20190828revised_d.pdf
Link to fact sheet:
Air Monitoring at SCS Engineers / O&G Services
Do you really need to use a drinking straw? With most beverages, probably not! Make this one change and help America reduce the amount of plastic going into our landfills.
Click to learn more about Sustainable Materials Management.
The initiative to optimize the residential waste and recycling collection system for current and future operations exemplifies the County’s commitment to safe, efficient, and excellent civic services for residents.
The County of Sacramento, Department of Waste Management & Recycling (DWMR) is contracting with SCS Engineers to study and analyze how to optimize the routing, collection, and disposal of municipal solid waste, green waste, organics, and single-stream recycling in the unincorporated area of the county. The analyses will help Sacramento control costs, provide quality services to residents, and lower their carbon footprint.
Using a three-cart system, the DWMR provides weekly residential garbage collection, every other week recycling, green waste collection, and other waste collection services to approximately 155,000 residents in unincorporated Sacramento County.
Currently, vehicles cover 71 routes and collect a total of 151,000 tons of municipal solid waste, 77,000 tons of green waste and organics, and nearly 37, 000 tons of single-stream recycling annually. Materials go to appropriate locations, including the county-owned and operated North Area Recovery Station and the Waste Management owned and operated Sacramento Recycling Center and Transfer Station.
Approximately 60 percent of residential collection activity occurs in the northern half of unincorporated Sacramento County and 40 percent in the southern half. DWMR will use SCS Engineers’ comprehensive analyses and the current residential waste collection and disposal operations to identify options for charting a path forward that will optimize collection efficiencies and reduce collection costs. The analyses examine these areas, as follows:
Regulatory compliance, including comprehensive, cost-effective adherence to all applicable known and anticipated regulations and ordinances
Financial and contractual controls, such as long-term agreements with haulers, processors, contractors, key suppliers, and vendors; infrastructure maintenance and construction
Route logistics and vehicle controls, for example, the number of routes, type of vehicles, safety, carbon footprint reductions, workloads
Community satisfaction with clear communications, ease of disposal, overall convenience, and other factors to continuously improve residential service
The SCS analyses include a model for creating alternative collection scenarios for waste and recycling operations and performing cost modeling. The model gives the County the benefit of insight into many potential options while considering various technology, best practices of the operations staff and fleet crews, and rate structures. The SCS model is in use in cities and counties across the U.S.
“The data and the way it is analyzed and interpreted will lay the foundation for collecting waste and recycling in the unincorporated area of the County,” stated Tracie Bills of SCS Engineers. “The cost savings and environmental benefits are significant supporting Sacramento residents into the future.”
This proposed MSW Landfills Federal Plan includes the same elements as required for a state plan: identification of legal authority and mechanisms for implementation; inventory of designated facilities; emissions inventory; emission limits; compliance schedules; a process for the EPA or state review of design plans for site-specific gas collection and control systems (GCCS); testing, monitoring, reporting and record-keeping requirements; public hearing requirements; and progress reporting requirements. Additionally, this action summarizes implementation and delegation of authority of the MSW Landfills Federal Plan.
This proposed action addresses existing MSW landfills and associated solid waste management programs. For the purpose of this regulation, existing MSW landfills are those that accepted waste after November 8, 1987, and commenced construction on or before July 17, 2014.
Tables 1 and 2 in the publication list the associated regulated industrial source categories that are the subject of this action and the status of state plans. The EPA tables are not intended to be exhaustive but do provide a guide for readers regarding the entities that this proposed action is likely to affect. The proposed standards, once promulgated, will be directly applicable to the designated facilities.
The document contains the full text and how/when to comment or appear at the public hearing. Feel free to share this document or page with others using the icons at left.
I read your informative blog regarding recommendations for jet cleaning leachate collection pipes. I have a question.
QUESTION: Say a landfill only has access to one end of a leachate pipe. This would be a situation where a new cell was built, where the uphill side of the cell butts up against an existing, pre-subtitle D cell with no leachate collection pipe. In other words, the uphill side of the new leachate pipe simply terminates rather than tie into an existing pipe.
To add to the issue, no vertical cleanout/riser pipe was installed on the uphill end (as this may impede waste operations in the area). There are of course riser and cleanout pipes and a sump on the downhill side for normal leachate collection. I would imagine that pumping water from the accessible side would push out any solids through the perforations into the leachate aggregate bedding, and may cause clogging there.
Is it possible, or reasonable, to flush this new leachate line?
ANSWER: There is always a possibility that a portion of dislodged material from the interior walls of the pipe will pass through pipe perforations and enter the gravel bedding around the pipe. However, due to the pipe slope, the great majority of the separated material flows down the pipe to the lowest point where it can be removed using a vac-truck.
Keep in mind also that, it’s true that leachate can partially flow through the bedding gravel toward the sump, but the role of the gravel is primarily protecting the pipe against compressive loads of waste above. Partial clogging of gravel around the pipe should not be considered as a malfunction of the system. Partial clogging of gravel normally may occur near the bottom portion of the gravel pack, which still allows leachate flow through gravel to pipe perforations above any clogged zone below.
In several instances, when a portion of a leachate collection pipe was opened up after being in service for a while, it did not support the idea of a clogged zone in the gravel pack. What was observed, included discolored gravel due to fine particles settling (from filtered leachate through geotextile) on gravel particles and a bit of the same particles near the bottom of the gravel pack.
I’ve never observed severe clogging of the gravel pack.
Thanks for your interest in the subject, and please stay in touch with any other questions. SCS freely shares best practices and advice within our industry; email us at
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 over 40 years of research and professional experience in mechanical, structural, and civil engineering.
A recent article in Waste Advantage Magazine features a detailed and comprehensive operation, the Sussex County, NJ Municipal Utilities Authority (SCMUA). The SCMUA team continuously looks for innovative solutions that will not only make operations more efficient but also help them to ‘be a good neighbor ’and resource to the surrounding communities.
“We are self-sufficient. Right now, we can manage our own solid waste through 2066, depending on a number of factors—recycling rates, population growth and what the regulations are going to be in 20 years, etc.,” says John Hatzelis, SCMUA Administrator.
The SCMUA is headed by a nine-person Board of Commissioners, and employs about 70 people, including wastewater, solid waste and central services staff, and receives support from SCS Engineers.
According to Tom Varro, Executive Director and Chief Engineer, “Everyone who works here knows their job and does it well. With the amount of traffic, 20,000 customers per month, 240,000 per year, that is a lot of potential for complaints. Every once in a while, you get someone that wasn’t happy, but for the most part, we get a lot of positive feedback, like ‘I love this place’, ‘I go here every Saturday’, ‘The guys are helpful’, etc. That is part of what we do as a service to the county and I think we’ve worked hard to get the staff trained and motivated.”
Learn more about this landfill operation’s best practices and outreach program in Waste Advantage.
Solar Ready CCR Site Closures Help Energy Companies Move Toward a Sustainable Future
Electricity is the one big energy source that can be free of carbon emissions. You can make it from the sun. You can make it from the wind. Tap the heat of the Earth, hydropower. While all utilities are moving in a sustainable, environmentally friendly direction, Aliant Energy stands out for making progress and keeping rates reasonable for consumers.
At the recent USWAG Workshop on Decommissioning, Repurposing & Expansion of Utility Assets held October 2019, Eric Nelson presented on the opportunities for solar generation at closed CCR sites and provided an overview of civil and geotechnical considerations when redeveloping closed sites as solar generating assets. His presentation demonstrated these considerations through the use of a case study.
SCS Engineers has assisted Alliant Energy with the design and/or construction of multiple coal combustion residual (CCR) surface impoundment closures. Two of the completed closures are the former Rock River Generating Station in Beloit, Wisconsin, and the M.L. Kapp Generating Station in Clinton, Iowa.
Both sites were closed by incorporating Alliant Energy’s vision to create “solar ready” sites. The Rock River site is now home to just over 2 megawatts (MW) of solar photovoltaic (PV) generating capacity, which was developed on the footprint of the now-closed on-site landfill and ash ponds. Although no solar assets have been developed at the site, the M.L. Kapp ash pond closure represents another opportunity for Alliant Energy to repurpose a closed ash pond for clean power.
Two additional closure designs are in process that incorporates similar elements, making them available for future solar generating asset development.
For more information visit SCS Engineers
Eric J. Nelson, PE, is a Vice President of SCS Engineers and one of our National Experts for Electric Utilities. He is an experienced engineer and hydrogeologist.
We recommend reading this article series to stay abreast of relevant knowledge from Bryan Staley, president and CEO of the Environmental Research & Education Foundation (EREF); Anne Germain, vice president of technical and regulatory affairs for the National Waste & Recycling Association (NWRA); Viraj deSilva, SCS Engineers wastewater treatment director; and testing results from New Hanover County whose capital investment in landfill infrastructure has proven to successfully treat effluent water to meet higher standards.
In September the City of Bangor will formally move over to a new arrangement in which residents will throw all of their recycling in with their trash and leave the mixed waste to be picked up from the curbside every week, as now happens with trash.
Bangor will also close their local recycling station as part of the city’s switch to a new integrated waste conversion plant in Hampden developed by Coastal Resources of Maine with Fiberight technology. The new facility includes a materials recovery facility (MRF), organic processing, plastics processing, anaerobic digestion (AD) and wastewater treatment. The integrated technology is intended to increase recycling rates without the need for extensive outreach programs and is easier for customers to use. According to Coastal Resources of Maine, the benefits are:
The advanced technologies are undergoing final testing at the Hampden, Maine facility, and are already in use at automated material recovery facilities in the United States and in Europe. The end product is cleaner and provides more diverse types of materials that can then be reused to create new products.
The Hampden facility’s advanced MRF has a high degree of separation, recovery, and monetization of commodity products, and then employs additional processes for generating clean cellulose, engineered fuels, and biogas from traditionally non-recyclable materials. Hired for the firm’s technical expertise and experience planning large municipal solid waste and biogas programs and facilities, SCS provided an in-depth examination and analysis of the technologies, program sustainability, and potential economic impacts of the facility.
The facility will serve 116 municipalities and public entities represented by the Municipal Review Committee, a non-profit organization that currently manages the waste disposal activities in Eastern and Northern Maine. The facility is planning to start accepting waste from its municipal customers shortly.
“With the planning and cooperation of many, Fiberight’s providing a truly sustainable solution in Maine while solving several challenges when consumers separate their recyclable materials and eliminating contamination,” stated Bob Gardner, SCS Engineers Senior VP. “The facility is capable of reusing nearly 150,000 tons of what formerly went into a landfill, is processing more municipal solid waste into high-value commodities, and is helping local municipalities and private waste haulers offset the cost of recycling.”
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