SCS Engineers, a top-tier ENR environmental consulting and construction firm, welcomes Professional Engineer Mary Kennamer to its environmental services team in Raleigh, N.C. As a Senior Project Professional, Mary is responsible for designing and engineering solutions to help landfills, manufacturers, and businesses comply with federal and state environmental regulations.
As a chemical engineer, Mary’s background and degree are useful to help North Carolina landfill owners prepare to meet more stringent federal and local air regulations. She will advise on air compliance issues, air permitting, compliance reporting, and consulting for landfills and manufacturing.
“Mary’s previous consulting experience and work with the US EPA is a tremendous asset and value for our landfill and manufacturing clients,” states Kenton Yang, the Raleigh office’s project director. “We’re excited to add another bright star to the Raleigh office.”
In order to permit new or expanding plants and facilities, there are complex environmental policies to meet. As an environmental and chemical engineer, Mary researches, plans, and completes the technical work for air permitting and compliance, SPCC, and due diligence that keeps owners in compliance and projects moving forward.
About SCS Engineers
SCS Engineers’ environmental solutions and technology directly result from our experience and dedication to solid waste management and other industries responsible for safeguarding the environment. For more information about SCS, please visit our website at www.scsengineers.com/, contact , follow us on your preferred social media, or watch our 50th Anniversary video.
SCS Engineers – Raleigh specializes in permitting and meeting comprehensive clean air, water, and soil goals and provides a range of services such as PFAS treatment, solid waste master planning, landfill technology, risk management, groundwater monitoring, pre-closure and landfill closures, and Brownfields remediation.
SCS Engineers is a leading environmental consulting and contracting firm with over 50 years of expertise in designing, permitting, constructing, and operating landfills. The firm is a pioneering force in developing landfill design technologies in use today by most landfill designers in the United States and internationally. Dr. Khatami describes several of the more prominent of these technologies below.
Landfills without Terraces
SCS is one of the first landfill designers to develop the concept of straight-up 3:1 slopes for landfills with no terraces. The modern version of tack-on swales (also known as tack-on berms) for control of surface water runoff came about along with this concept. This technology simplified waste filling operations for landfill operators and added significant additional airspace to landfill facilities. This concept’s financial benefits for SCS’s clients over the past three decades exceed one billion dollars.
Pipe Downchutes
SCS developed the single-barrel downchute and double-barrel downchute systems combined with the tack-on swales for landfill slopes during final cover installation. SCS has been designing and constructing these systems since the early 1990s, and none of the constructed systems have experienced failure. System performance for such a long time is a clear indication of the design’s suitability in combination with the tack-on swales. These concepts eliminate numerous problems that arise with open surface downchutes and other downchute systems combined with terraces on landfill slopes. The construction simplicity and rapid system installation make them the most useful systems for our clients.
Leachate Toe Drain System
SCS was the first landfill designer that developed the concept of a toe drain to collect and properly dispose of leachate seeps below the final cover geomembrane. SCS coined the term leachate toe drain system or LTDS for standardizing the design over 20 years ago. The LTDS is currently an essential component of all landfill designs that experience leachate seeps on exterior slopes, and landfill designers are catching up with the concept.
Rainwater Toe Drain System
SCS was a pioneering landfill designer in developing the proper means for collecting and removing water from the final cover drainage layer located above the final cover geomembrane. SCS coined the term rainwater toe drain system, or RTDS, to standardize the design over 20 years ago. The RTDS concept is currently an integrated component of all closure projects designed and constructed by SCS and many other landfill designers.
Sustainable Landfill Design Concepts
SCS revolutionized the landfill base grades design by developing the Landfill Green Design concept over two decades ago. Many regional landfill owners welcomed the concept and its numerous benefits, including savings in construction material and increasing airspace, to name a few. Introducing the second generation of the landfill green design within a few years, SCS addressed solid waste rules in several states. The improvements apply to very long disposal cells, minimum slope values for the leachate collection pipes, and minimum slope for a disposal cell’s base area. Coining the second generation design a Landfill Green-H Design, with “H” for hybrid, SCS reflects the combination of the landfill green design concept and the traditional herringbone concept. Readers of the SCS Advice from the Field blog can look forward to an upcoming blog on the term herringbone soon!
Over the past two decades, SCS has increased the airspace of many large regional landfills by modifying their solid waste permits incorporating the first and second generations of these concepts. The savings in construction material for these facilities exceeds $130,000,000, and the added financial benefit related to extra airspace is nearly $300,000,000. These SCS design concepts not only reduce construction costs and increase landfill airspace; they also have other sustainable benefits that landfill owners and operators value to help meet their sustainability goals.
The third generation of SCS’s Landfill Green Design is now available. Landfill Green+ Design provides its predecessors’ benefits with a higher degree of sustainability to our clients.
Tiered Vertical Gas Wells
SCS developed the concept and coined Tiered Vertical Gas Well, or TVGW, for the largest waste operator in the world as part of the developing standards for preventing elevated temperature conditions forming in deep and wet landfills. TVGWs collect landfill gas from the entire vertical column of waste from the bottom lining system to the final cover system. SCS developed additional concepts for horizontal blankets and fingers around the TVGWs to improve gas collection and rapid vertical movement of leachate through the vertical column of waste, allowing leachate to migrate vertically down to the leachate collection system rapidly. TVGWs have been a necessary component of new disposal cell construction at deep and wet landfills since their introduction to the industry.
Recently, SCS developed the second generation of TVGWs, known at SCS as TVGW+. TVGW+ simplifies the construction of intermediary pads and improves the connection of the pads to the vertical wells. Horizontal blanks and fingers can integrate easily into the TVGW+.
Gas Release System at Lining System
SCS developed the concept and coined the term Gas Release System (GRS) for the largest waste operator in the world as a part of the developing standards for preventing the formation of elevated temperature conditions in deep and wet landfills. The GRS releases high-pressure landfill gas near the bottom of the landfill. Excessive pressure can adversely impact leachate flow within the geocomposite drainage layer above the lining system geomembrane. Landfill owners and operators can apply the GRS concept to non-wet or shallow landfills as long as gas pressure near the bottom lining system is an issue.
Clog-Free Leachate Collection Pipe System
Over five years ago, SCS developed a design for leachate collection pipes without geotextile, which is a primary source of clogging in the vicinity of leachate collection pipes. SCS coined the term Clog-Free LCS Pipe or CFPIPE to standardize the design. Leachate from the geosynthetic drainage layer flows directly into the gravel around the LCS pipe and then into the pipe without passing through a geotextile. Since its introduction to the industry, SCS incorporates the CFPIPE into the design of landfills requested by clients looking for sustainable and clog-free systems.
Superior Ranking
The development of these technologies and many other SCS Firsts illustrates the value that the combination of our engineers, consultants, field staff, and scientists brings to each client. Our landfill designers work in combination with other highly sophisticated landfill related technologies developed by SCS, such as landfill gas systems, renewable energy systems, SCS RMC® remote monitoring and control, SCS eTools® for data management and decision making, and stellar operation and maintenance services.
As environmental industry pioneers, we never stop striving to be the most valuable landfill full-service provider. We highlight industry Firsts on our website just beneath the photo headlines.
State regulatory agencies normally require landfill slopes reaching final grades to close within a certain period. This requirement leads to closing landfill slopes in phases, normally referred to as partial closure. Generally, partial closures start from the bottom of the landfill slope up to a certain elevation, with geosynthetics in the final cover temporarily anchored along the partial closure’s sides and upper boundary. Engineers propose different designs for securing the lower boundary of partial closures at the bottom of the landfill slope. Some engineers propose an anchor trench outside the bottom lining system anchor trench to secure the final cover geosynthetics. Others specify welding the cover geomembrane to the bottom lining system geomembrane.
Experience with anchor trenches at the bottom of the landfill slope for the final cover geosynthetics has not been positive because of these issues:
To eliminate the issues above, engineers weld the final cover geomembrane to the bottom lining system geomembrane for cases when there is a bottom lining system below the waste. The welding completely seals the landfill interior space from the outside environment and keeps regulated materials, such as waste, leachate, and gas, within the sealed system. Of course, the engineer should design proper means to address these behind the sealed system; designs may include:
Leachate toe drain system is a concept originally developed by SCS and incorporated into landfill final cover designs over the past 20 years. Unfortunately, many solid waste engineers are unaware of the need for LTDS, so their designs lack this important feature. LTDS saves a tremendous amount of repair money in the long run by avoiding complications for landfill operators.
A rainwater toe drain system removes water that moves laterally within the final cover geocomposite toward the slope’s bottom. The RTDS includes a perforated HDPE pipe encased in gravel and wrapped in geotextile. Also, install the RTDS on terraces along the depression on the interior side of the terrace. Along the landfill slope’s bottom, position the RTDS behind a HDPE flap welded to the final cover geomembrane. The RTDS is sloping with high and low points along the RTDS alignment. Lateral drain pipes located at low points remove water from the RTDS to the perimeter ditches.
Other designs involving extending the geocomposite to daylight at the slope surface cause problem such as those listed below:
Similar issues can also occur at the outlet of such systems on landfill terraces, making the RTDS a superior design.
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.
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:
The Dallas City Council recently authorized a three-year service contract, with two one-year renewal options, for environmental monitoring and engineering consulting services supporting Dallas’s Department of Sanitation Services. SCS Engineers will use its integrated specialized practices to support the City’s McCommas Bluff Sanitary Landfill, Bachman Transfer Station, Fair Oaks Transfer Station, and Southwest Transfer Station.
Vice President Ryan Kuntz, P.E., the team’s principal consulting engineer, said, “SCS is privileged that the City of Dallas entrusts us to partner with the City’s staff to maintain the landfill and the transfer stations’ safe and efficient operations. The Department of Sanitation Services support the citizens and the environment; we’re honored to be of assistance.”
Landfills are extraordinarily complex systems integrating liquids and gas management systems, and the City’s McCommas Bluff Landfill is one of the largest landfills in the State of Texas. Transfer stations also require expertise in technical and regulatory issues for successful operation.
The City finds it cost-effective to employ an engineering firm, such as SCS, that specializes in solid waste engineering. SCS enhances environmental services with its specialized in-house practices, providing comprehensive capabilities and advanced technologies that improve efficiency and help control costs.
SCS Engineers will provide monitoring and engineering support staff from the firm’s Bedford, Texas office, along with the help of our minority/women-owned business partners. The SCS Bedford team’s professionals and field technicians are experienced and knowledgeable of regional and local geology, regulatory policies, and technical challenges.
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 watch our 50th Anniversary video.
… according to the experts, and continue through its active life. All along, operators should consider what they will need to show regulators once they are ready to install the final cap.
Choosing the right designer for liquids and gas management is critical. The complexity of landfills varies from site to site, and issues related to conflicts among gas and liquids pipes, and pipes and final cover geosynthetics vary depending on the geometry and other landfill features involved at each location. In short, your designers must understand and work closely with your operations and monitoring team.
The best way to resolve conflicts before the closure is to have a coordinated effort among parties involved in the design to discuss and find solutions to every conflict at the design stage.
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
