It is not out of the ordinary to see several different landfill designers providing services at a specific site over many years. Each landfill designer brings his/her preferences and designs to the owner, depending on the urgency of the projects and the owner’s willingness to accept new concepts.
Experienced landfill designers review the prior history of design work at the facility and ensure that their new design work is compatible with previously developed cells and final covers. Lack of such due diligence could impede landfilling operations following implementation of the design with implications that may survive for many years to come at a high cost to the owner.
Proper due diligence may reveal issues that the owner may not be aware of. In such cases, the new landfill engineer attempts to explain the observed issues from a previous design to the owner’s attention during one or more meetings or through a narrative report including documentation of the issues and measures to address each issue. The owner may accept or reject the technical matters brought to their attention by the new landfill designer. If accepted, authorize the new design engineer to prepare proper plans and details, and assist in retaining a contractor to fix noted problems. If rejected, the new landfill engineer can feel confident he/she is professionally conducting himself/herself considering the ethical obligations in his/her profession.
If the new landfill engineer had not brought up issues discovered during the due diligence, the owner could blame the new designer claiming that he/she should have known better. Such situations do not get resolved easily and could lead to another change in the design team.
The cost of performing thorough due diligence may not be in the first task order’s budget. However, it will certainly pay off over time with back-to-back task orders from the owner when confidence n the designer’s capabilities build over time.
Changes to the landfill personnel may occur similar to any other organization. Landfill general managers, operation managers, site engineers, or compliance engineers may leave, and the position filled by a new person who has no site familiarity or history. These types of rotations can provide the opportunity for inexperienced landfill designers to influence the site’s long-term plans. Mistakes by inexperienced designers can last decades in some instances, while new and remaining personnel must deal with the consequences.
SCS’s project management protocols require project managers to constantly learn about the site’s history and review documents representing the backbone of the facility development over the long-term life of the site to the present. This type of continual learning of important matters and minute nuances of the site history equips a project manager to address technical and permitting issues based on knowledge of prior work performed at the facility. Implementation of new ideas based on prior knowledge of the site history is considered the backbone of properly managing projects and serving the client in consideration of their business priorities.
Past knowledge comes from documents prepared by prior designers and knowledge of site personnel who have been working at the site for a long time. Competent engineers welcome opportunities to interview and discuss site history, especially with long-term site personnel. The knowledge these people carry with them is not found in any document that the designer, if lucky enough to get his/her hands-on, may obtain by review. The knowledge of the changes to existing systems during original construction and a later date, which may not have been documented, can lead the engineer to concepts that otherwise would not have been envisioned without the long-term employee’s information of the site.
About the Author:
Ali Khatami, Ph.D., PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design, Construction Quality Assurance, and Elevated Temperature Landfills. He has over 40 years of research and professional experience in mechanical, structural, and civil engineering.
Landfill engineers rely heavily on topographic maps in their design work. Topographic maps present elevation contours, known as contour lines, for changes in the ground surface. Surveying companies create contour lines by performing land surveys, Light Detection and Ranging (Lidar) surveys, or aerial mapping. In all cases, the topographic maps are generated based on a standard coordinate system.
Basing horizontal systems on geodetic coordinates worldwide, they may be updated every few years or decades. An example of the horizontal coordinate system is the North American Datum (NAD). A datum is a formal description of the Earth’s shape and an anchor point for the coordinate system. Using the NAD system, engineers can make horizontal measurements in consideration of the anchor point information.
NAD 27 and NAD 83 are two versions of the NAD system with slightly different assumptions and measurements. A point with specific latitude and longitude in NAD 27 Datum may be tens of feet away from a point with similar latitude and longitude in NAD 83 Datum.
The latitude and longitude of an initial point (Meads Ranch Triangulation Station in Kansas) define the NAD 27 Datum. The direction of a line between this point and a specified second point and two dimensions define the spheroid. Conversely, NAD 83 Datum uses a newer defined spheroid, the Geodetic Reference System of 1980 (GRS 80). GRS 80 is an Earth-centered or geocentric datum having no initial point or initial direction.
Similarly, vertical systems provide surveyors the means to measure vertical measurements based on a standard system. Examples of the vertical datum are the National Geodetic Vertical Datum 1929 (NGVD 29) and North American Vertical Datum 1988 (NAVD 88).
Using topographic maps, solid waste engineers pay special attention to the standard coordinate system used for generating the topographic map made available to them for their design work. Engineers will want to check for additional topographic maps using another Datum for the same site. Checking eliminates the possibility of discrepancies in the design documents.
Typically, the standard system set for a landfill site remains unchanged for consistency among topographic maps generated over the years. If the standard system must change, document the conversion making it available to the solid waste engineers working at the site. The conversion information is valuable for converting engineering plans to prevent the older plans from becoming obsolete and unusable for practical engineering work.
A solid waste engineer that begins work for the first time at an existing landfill site pays special attention to the standard system (horizontal or vertical). The engineer wants to ensure the time spent producing design documents and plans aren’t wasted. For optimum efficiency, landfill owners contracting with new solid waste engineers should provide conversion information from the old to the new system upon the contract’s commencement.
The United States National Spatial Reference System NAD 83(2011/MA11/PA11) epoch 2010.00, is a refinement of the NAD 83 datum using data from a network of very accurate GPS receivers at Continuously Operating Reference Stations (CORS). A new Global Navigation Satellite System (GNSS) will replace the National Spatial Reference System NAD 83 and the NAVD 88 in 2022, according to the National Geodetic Survey Strategic Plan 2019-2023. The GNSS will rely on the global positioning system and a gravimetric geoid model resulting from the Gravity for the Redefinition of the American Vertical Datum (GRAV-D) Project. The new systems’ intention is easier access and maintenance than NAD 83 and NAVD 88, which rely on physical survey targets that deteriorate over time.
Solid waste engineers should be aware of the upcoming changes to adapt site designs as necessary and to check with landfill owners and operators to check for any implementations at their facilities.
About the Authors:
Ali Khatami, Ph.D., PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design, Construction Quality Assurance, and Elevated Temperature Landfills. He has over 40 years of research and professional experience in mechanical, structural, and civil engineering. Dr. Khatami has been involved for more than 30 years in the design and permitting of civil/solid waste/environmental projects such as surface water management systems, drainage structures, municipal solid waste landfills, hazardous solid waste landfills, low-level radioactive waste landfills, leachate and wastewater conveyance and treatment systems, gas management systems, hazardous waste impoundments, storage tank systems, waste tire processing facilities, composting facilities, material recovery facilities, landfill gas collection and disposal systems, leachate evaporator systems, and liquid impoundment floating covers. Dr. Khatami has acquired extensive experience and knowledge in the areas of geology, hydrogeology, hydrology, hydraulics, construction methods, material science, construction quality assurance (CQA), and stability of earth systems. Dr. Khatami has applied this experience in the siting of numerous landfills.
William Richardson, EIT is Project Professional at SCS, and part of our Young Professionals organization. Will has two years of experience with landfill design projects, including permit modifications and siting requirements. He is currently working in Virginia Beach under the tutelage of Dr. Khatami.
Landfills are large and dynamic systems that can take several decades to develop. Unlike many other infrastructure projects that have a beginning and an end to the construction of the project, landfills constantly grow and change due to many factors, including but not limited to:
From an engineering perspective, it is very common to see changes to the engineering team over time. Each team brings about their ideas and preferences to the operator, and if they present technically competent and economically solid ideas, they can change the course of the landfill development. The course change could be shaped by what will get constructed, how it will get constructed, when it will get constructed, and what sequence it will get constructed. In most cases, the owner is in the loop, but the owner may not be intimately familiar with the nuances that such designs and modifications entail. Therefore, the owner may not necessarily realize hidden problems or mishaps that may happen in the future, which could be prevented by the engineer at an earlier stage of work.
Competent engineers starting work at an existing landfill site for the first time need to review years of data to become familiar with the history of the site before they can begin design work. The history of the site involves, but is not limited to, land use approvals, permitting, designs, modifications, environmental impacts, subsurface conditions, environmental improvements, leachate and gas collection and disposal, existing and future planned developments, operation requirements, and many other features that vary from site to site. Without such knowledge, the engineer is working in the dark without the owner’s knowledge that the engineer’s path lacks familiarity with details. Work products generated by an engineer with limited familiarity with the site are, at best, not reliable. Even potentially having significant impacts on the owner to fix issues that otherwise are preventable with sufficient due diligence.
For example, tasking an engineer to close a portion of the landfill, the engineer must investigate any plans set for landfill development, in the area planned to close. The engineer and owner can discuss any problems discovered by the engineer’s early due diligence, and solutions will be developed and adopted to address issues during the design. This level of due diligence provides the opportunity to generate sound designs and develops a level of confidence in the engineer in the mind of the owner.
SCS landfill design professionals train regularly to be thorough and comprehensive in their familiarization with a site. They spend significant effort to foresee potential problems that might arise many years down the road and find solutions for them now.
About the Authors:
Ali Khatami, Ph.D., PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design, Construction Quality Assurance, and Elevated Temperature Landfills. He has over 40 years of research and professional experience in mechanical, structural, and civil engineering. Dr. Khatami has been involved for more than 30 years in the design and permitting of civil/solid waste/environmental projects such as surface water management systems, drainage structures, municipal solid waste landfills, hazardous solid waste landfills, low-level radioactive waste landfills, leachate and wastewater conveyance and treatment systems, gas management systems, hazardous waste impoundments, storage tank systems, waste tire processing facilities, composting facilities, material recovery facilities, landfill gas collection and disposal systems, leachate evaporator systems, and liquid impoundment floating covers. Dr. Khatami has acquired extensive experience and knowledge in the areas of geology, hydrogeology, hydrology, hydraulics, construction methods, material science, construction quality assurance (CQA), and stability of earth systems. Dr. Khatami has applied this experience in the siting of numerous landfills.
William Richardson, EIT is Project Professional at SCS, and part of our Young Professionals organization. Will has two years of experience with landfill design projects, including permit modifications and siting requirements. He is currently working in Virginia Beach under the tutelage of Dr. Khatami.
About the Author: Ali Khatami, Ph.D., P.E.
There are several hundreds of Municipal Solid Waste (MSW) landfills in the United States. Many of these landfills are anticipated to remain active for decades to come, and Federal and state rules require slopes reaching permitted final elevations to be closed within 180 days. This means partial closure of slopes is part of the operational requirements of MSW landfills.
Federal and State Rules
Subtitle D of the Resource Conservation and Recovery Act (RCRA), enacted on October 21, 1976, requires the final cover of MSW landfills to include a barrier layer with hydraulic conductivity that is substantially equivalent to or less than the hydraulic conductivity of the bottom liner. State-level regulations developed following the enactment of the federal law also required similar standards for MSW landfills. Many states, pursuing the federal guidelines, require at a minimum, the bottom lining system of MSW landfills include at least one primary barrier layer consisting of Polyvinyl chloride (PVC), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE). Naturally, the final cover barrier layer should also be PVC, HDPE, LLDPE as well.
According to the Federal and state regulations, following the completion and closure of a MSW landfill, the facility owner maintains the landfill for a minimum of 30 years beyond the final closing date. Extension of the long-term care period beyond the 30-year post-closure period is a hot subject among solid waste professionals. Some states have already implemented matrices for such time extensions; it is anticipated that the remaining states will require similar extensions for MSW landfills over the next several years. Even if regulatory agencies approve completion of the post-closure period for a specific landfill, the landfill’s final cover system is expected to perform for many more years to come. Otherwise, environmental issues associated with a lack of performance may force the regulatory agency to spend money for repairs no longer available through a financial instrument.
Long-Term Performance Designs
For the past few decades, SCS has specifically designed and permitted final cover systems with special features to prolong the final cover system’s performance beyond the post-closure period of the landfill. The final cover system designs:
Less Maintenance
The first partial final cover with these features was constructed in 1998, and since then, many more partial closures with these types of features have been constructed. All partial closures are performing satisfactorily without failure. Regular maintenance of the final cover vegetation and occasional cleaning of drainage swales, which are common maintenance activities, have been the only measures taken by the operators of the facilities with these final cover systems.
The features incorporated into the final cover systems were:
The features above have financial, performance, and stability benefits for the facility for many years to come. So far, such final covers have been constructed on 3H:1V slopes as long as 550 ft. in length with no terraces. Several of the completed final covers were partial closures on a 3H:1V slope, where the next phase was constructed directly above a previous phase with the two phases tied together at the phase boundary.
Want more advice from our designers? Select articles and blogs for further reading:
Landfill operators have known about elevated temperature conditions in landfills for nearly a decade. Some operators have already incurred numerous expenses to control adverse environmental and operational issues at these landfills, and some operators have set aside large amounts of money in their books to address future liabilities associated with such landfills. Due to the complexities of controlling elevated temperature conditions and the compliance issues arising from such conditions, it can force operators to temporarily, or permanently close their landfills.
Can design address elevated temperature conditions?
The operators of larger landfills have been monitoring and analyzing data to identify triggering factors, while others continue controlling the environmental impacts. Environmental Research & Education Foundation (EREF) initiated several research projects to identify the triggering factors with the excellent scientific work of highly qualified researchers. These are on-going projects.
In the meanwhile, operators of larger landfills are developing strategies, basing strategic-decisions on the data and conditions collected during operations over long periods. After analyses, they have the means to reduce the impacts by making changes in their operations and landfill designs. The most effective changes include eliminating certain waste types from the waste stream and improving the movement of liquid and gas through the waste column with new designs.
Are design innovations consistently implemented?
The pioneering designs feature preventative measures, intending to avert the formation of elevated temperature conditions in future disposal cells. Implementing these new design features requires careful consideration and functional analyses, as some of the recommendations can be costly, affecting the bottom line. The urgency in controlling compliance issues associated with elevated temperatures and the associated financial impacts of such conditions objectively prescribe that local managers work closely with their designers and field expertise to bring non-compliance issues under control.
Is this an executive risk management strategy?
Until the on-going research more clearly identifies the triggering factors and the means to prevent the development of elevated temperature conditions, it seems logical to invest in implementing preventative measures that are currently available. When more research results are accessible, then the local managers will be able to make decisions that are even more informed. Those wanting to address the likelihood of future liabilities proactively will need executive-level funding and superior technical support, all of which are possible.
Is there much sharing of newer designs and strategies within the solid waste industry?
Yes, there is a fair amount of collaboration among the technical community and within solid waste associations. Most operators share their preventative designs within the engineering community and help contribute to funded research. Their actions and results will help to strengthen an industry application until such time that research results and the means to prevent the development of elevated temperature conditions are well understood. We all know that progress in technology and science depends on sharing new knowledge.
Let’s continue with the combination of serious research, innovative designs, proactive operational changes, and sharing knowledge among our industry professionals that will lead to more precise solutions in the near future. Here are a few resources available now:
About the Author: Ali Khatami, Ph.D., PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Elevated Temperature Landfills, plus Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Learn more at Elevated Temperature Landfills
On July 7, 2020, the City of Brownsville Commission approved a recommendation by the Engineering and Public Works Department to continue an existing multi-year partnership with SCS Engineers. SCS is an environmental consulting and contracting firm that will serve the City for an additional five years. The environmental contracts support the Landfill Gas Collection and Control System (GCCS) expansion and provide landfill engineering, compliance, monitoring and operations assistance.
Project Director, J. Roy Murray, an SCS vice president, and the team’s principal consulting engineer will continue to serve the City’s citizens and staff. Mr. Murray has decades of experience in civil and environmental permitting, design, and construction at municipal solid waste landfills (MSW), including 20 years serving the Brownsville Landfill. Mr. Murray states:
The City staff and Commission continues to entrust SCS Engineers to help the landfill staff with the safe, efficient, and compliant operation of the landfill. We are honored by their trust. The City of Brownsville MSW Landfill Operations team serves the City well. The facility is the primary solid waste disposal site for surrounding communities, carefully engineered and maintained regularly even during severe weather and now a pandemic. The forethought of the Landfill Division, their leadership, and innovative practices provide the citizens with stellar services while protecting the environment.
The initial installation of the City Landfill’s Gas Collection and Control System (GCCS) completed in 2011, was part of an Energy Efficiency and Conservation Block Grant the City received from the American Recovery and Reinvestment Act of 2009. SCS Engineers assisted with the application process, and as a result of the collaboration, the City received a $1.7 million grant to install a landfill gas collection system at the landfill. With GCCS operation, the City has reduced its greenhouse gas emissions. The landfill infrastructure and emission reductions were voluntary at the time, but the Texas Commission on Environmental Quality (TCEQ) Air Quality rules and regulations, and EPA’s New Source Performance Standards, now require them.
The Gas Collection and Control System consists of 16 landfill gas extraction wells and currently provides coverage of 32 acres of the City Landfill’s disposal footprint. The City plans to expand the GCCS during 2021, to support landfill’s growth and stricter air permit regulations. The expansion includes 38 additional wells covering 120 acres of the landfill footprint. The new wells will integrate with the collection system and integrate with liquids management, leachate control, and stormwater systems, among others.
About SCS Engineers
SCS Engineers’ environmental solutions and technology are a direct result of our experience and dedication to solid waste management and other industries responsible for safeguarding the environment. For more information about SCS, please follow us on your preferred social media channel, or watch our 50th Anniversary video.
Landfill slopes that have reached final grades, or will receive waste in the distant future have maintenance challenges. Environmental elements continually affect surface conditions, and remedial work is required routinely to prevent negative outcomes of exposed slopes. Consider using a geomembrane temporary cap to address much of the maintenance. Here’s a list showing how the cap can help:
Landfill Maintenance Challenge
With Geomembrane Temporary Cap
The significant maintenance savings by using a temporary cap make the payoff period for the investment attractive. Based on my experience and site variations, the return on investment is usually three to six years. The period is considerably shorter if your landfill does not have a leachate disposal or treatment system, or deep injection well. The difference is the high cost to have the leachate hauled away.
Temporary caps potentially reduce routine maintenance work, leaving operation staff available for other tasks. The cap provides peace of mind that slopes remain in compliance; regulators don’t need to report non-compliance conditions of exposed slopes during inspection events.
After completing 25 temporary cap projects in the U.S. Southeast alone, we highly recommend using a thick geomembrane. It’s tempting to try to save money using a thinner geomembrane, such as 12 mils or 20 mils, but these can damage more easily and will negatively affect your return. The majority of SCS clients chose to use the recommended 40 mils thick geomembrane, which will survive severe weather conditions.
Ballasting the geomembrane and using the right materials for ballasting is significantly important. We recommend using ultraviolet (UV) resistant rope and sandbags, a tried and true system. UV resistant straps are a decent replacement for ropes. Anchoring mechanisms are also important. We typically recommend using 4×4 treated wood posts at 10-ft spacing, installed in anchor trenches, and tied to ballasting ropes. Depending on the site and operator’s preference, the supporting architecture may be to lay the post horizontally, while tied to the ballasting ropes, at the bottom of the anchor trench buried in the anchor trench’s backfill material.
Over the years, landfill operators have experienced the savings and value that temporary caps bring to landfill operating budgets, and we’re placing more temporary caps every year. If considering this option, SCS can assist you by evaluating the slopes at your site for the caps. We’ll also prepare estimates for the purchase of material and installation costs and estimated time of recovery for your project.
About the Author: Ali Khatami, Ph.D., PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Elevated Temperature Landfills, plus Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Learn more at Landfill Engineering
Landfills located in areas with high precipitation usually experience leachate seeps on slopes. The location of leachate seeps varies, and the reason behind the seeps appearing on the slopes varies as well.
As long as the slope does not have its final cover, you can attempt to control leachate seeps no matter where the seep location. There are many remedies known to landfill operators for controlling seeps before the final cover, but leachate seeps below the final cover are not controllable. The reason is the seeps are out of reach, and you have no means to control or mitigate the situation. The only potential solution is a seep management system built under the final cover geomembrane at the time of final cover construction.
For landfills with slopes extending up to the top of the landfill without terraces, construct a leachate toe drain system (LTDS) at the toe of the slope adjacent to the landfill perimeter berm. The design will collect and convey liquids emanating from seeps further up on the slope (below the final cover geomembrane) to the leachate collection system. See Figure 1.
For landfills with terraces on the slope, construct LTDSs at every terrace. Best practices call for the location at the toe of the slope, above the terrace, the lowest point of that slope. Consequently, the terrace width prevents seep liquids from flowing further down the slope, and the LTDS at the terrace prevents the accumulation of leachate behind the final cover geomembrane at the interior line of the terrace. See Figure 2.
At the lowest point of the terrace, locate a downspout to convey liquids to the leachate collection system at the bottom of the landfill. You will also need a LTDS at the toe of the slope adjacent to the landfill perimeter berm, as discussed above. You may connect the terrace downspouts to the LTDS located adjacent to the perimeter berm to drain the liquids collected at terraces.
To prevent erosion of fines by small streams of liquids flowing down the slope below the final cover geomembrane use this best practice. This design will prevent depressions forming in the top surface of the final cover. First, place a LTDS geocomposite panel from the source of any leachate seep that you identify on the slope right before the construction of the final cover. Connect the panel to the LTDS pipe-gravel burrito at the terrace or perimeter berm. This solution provides a preferential path for liquids coming out of the seep without causing erosion. See Figures 1 and 2.
Place the LTDS geocomposite below the LTDS burrito when simultaneously constructing the burrito and the LTDS geocomposite. When constructing the LTDS burrito ahead of time, place the LTDS geocomposite above the burrito later. In either case, the contact area between the LTDS burrito and the LTDS geocomposite must be free of soil, which could impede the free flow of liquids to the LTDS burrito.
SCS has a 20-year record of accomplishment solving leachate seeps below the final cover geomembrane. Feel free to contact our landfill designers for advice.
About the Author: Ali Khatami, Ph.D., 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 nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Learn more at Landfill Engineering
Landfills, especially large regional landfills, are huge enterprises with many different operations ongoing daily. A landfill’s tangible assets are equipment, buildings, machinery, construction materials in the ground, or stockpiled to support various operations. Of all these, the most significant asset is the permitted airspace. It’s undoubtedly a non-tangible asset when permitted, but gradually this asset gets consumed as it turns into revenue.
Creating landfill airspace during a design/permitting process involves the operator hiring a landfill engineer to develop the concept of the airspace, prepare an appropriate design with engineering methods, and obtain a permit for it through regulatory agencies. In a sense, a portion of your future revenue is in the hands of your landfill engineer. You depend on this engineer to create the maximum amount of airspace, generating the maximum amount of revenue for your operation over time. Your engineer is supposed to be your trusted partner, and you are investing an enormous amount of capital for the design, permit, and construction based on the work performed by the engineer.
In some instances, the operator leaves most of the technical decision making to the engineer. On other occasions, the operator is in the loop during the engineer’s design, but the operator is not heavily involved in the nuances of the disposal cell’s layout in consideration of the existing terrain. In either case, the engineer is significantly responsible for achieving the maximum amount of airspace. The multi-million dollar question is whether you could have had another 3 million or 5 million cubic yards of additional airspace in your permit. How do you check if your landfill engineer maximized airspace in the design?
Assuming proper training, most landfill engineers can design adequate landfills. Still, very few landfill engineers have the unique talent and experience that can maximize airspace within specific design parameters. You, as the operator want engineers with a proven track record of maximizing airspace in their landfill designs, and do not let relationships or political nuances affect your judgment during selection because tens of millions of dollars of additional revenue are at stake.
A trained landfill engineer may miss details that a highly qualified engineer would not. Incidentals here and there, if recognized and accounted for, can add significant airspace to the design. These details vary from site to site, and it’s up to the engineer to recognize the benefits of geometric and regulatory opportunities to add to the covered airspace. These details could be in the form of:
The operator chooses the project manager or the primary engineer for the design of a greenfield landfill or an expansion to an existing landfill, knowing that the work performed by the selected engineer could potentially add to or take away hundreds of millions of dollars from the bottom line of your enterprise. So, pick your engineer based on the engineer’s prior design track record and make sure the engineer is an expert in maximizing landfill airspace.
SCS is an expert, highly experienced landfill designer – relied on by many landfill operators as a trusted partner. Our culture is to serve our clients as if their project is our own, and we do not consider ourselves successful unless our clients are satisfied. These close relationships help us serve the majority of our clients on a long-term basis, with decades of continuous service and value.
SCS will gladly evaluate scenarios for your landfill expansions that you are planning to design and permit, and provide you with a preliminary estimate of airspace gain and revenue that an SCS design could bring, potentially increasing your primary asset by another tens of millions of dollars. Now that’s a value statement!
About the Author: Ali Khatami, Ph.D., 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 nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Learn more at Landfill Engineering
The industry is designing and building more substantive drainage features and larger collection systems from the bottom up, that maintain their integrity and increase performance over time, thus avoiding more costly problems in the future.
Waste360 spoke with three environmental engineers about what landfill operators should know about liquids’ behavior and what emerging design concepts help facilitate flow and circumvent problems such as elevated temperature landfills, seeps, and keep gas flowing.
The engineers cover adopting best practices and emerging design concepts to facilitate flow. They cover topics such as directing flow vertically to facilitate movement to the bottom of the landfill, drainage material, slope to the sump percentages, vertical stone columns, installing these systems at the bottom before cells are constructed, and increasing cell height to prevent the formation of perched zones.
Ali Khatami, one of the engineers interviewed, has developed standards for building tiered vertical gas wells that extend from the bottom all the way up. He frequently blogs about landfill design strategies that his clients are using with success. His blog is called SCS Advice from the Field. Dr. Khatami developed the concept of leachate toe drain systems to address problems tied to seeps below the final cover geomembrane. These seeps ultimately occur in one of two scenarios, each depending on how the cover is secured.
Read Waste360’s Emerging Design Concepts to Facilitate Flow of Liquids on Landfills
Related Resources
More resources and case studies are available here Landfill Design, Build, OM&M
Landfill Gas Header: Location and Benefits By continuing to design gas header construction on landfill slopes, all of the components end up on the landfill slope as well. You can imagine what type of complications the landfill operator will face since all of these components are in areas vulnerable to erosion, settlement, future filling, or future construction. Additionally, any maintenance requiring digging and re-piping necessitates placing equipment on the landfill slope and disturbing the landfill slope surface for an extended period.
AIRSPACE, the Landfill Operators’ Golden Egg Airspace is a golden egg, the equivalent to cash that a waste operating company will have overtime in its account. With each ton or cubic yard of waste received at the landfill, the non-monetary asset of airspace converts positively to the bottom line of the …
Gas Removal from Leachate Collection Pipe and Leachate Sump Keeping gas pressure low in and around the leachate collection pipe promotes the free flow of leachate through the geocomposite or granular medium drainage layer to the leachate collection pipe and improves leachate removal from the disposal cell. Using gas removal piping at leachate sumps is highly recommended for warm or elevated temperature landfills where efficient leachate removal from the leachate collection system is another means for controlling landfill temperatures.
Leachate Force Main Casing Pipe and Monitoring for Leaks Landfill operators may add a casing pipe to their leachate force main for additional environmental protection. Consequently, the leachate force main is entirely located inside a casing pipe where the leachate force main is below ground. In the event of a leak from the leachate force main, liquids stay inside the casing pipe preventing leakage …
Pressure Release System Near Bottom of Landfills Pressure Release System Near Bottom of Landfills – Essential Component for Proper Functioning of the Landfill Drainage Layer. Landfill designers are generally diligent in performing extensive leachate head analysis for the design of the geocomposite drainage layer above the bottom geomembrane barrier layer. They perform HELP model analyses considering numerous scenarios to satisfy all requirements …
Landfill Leachate Removal Pumps – Submersible vs. Self-Priming Pumps 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 …
