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.
FREE ON-DEMAND WEBINAR & Q/A – RECORDED JAN.21, 2021
Landfills, compost facilities, transfer stations, and renewable energy plants are cognizant of odor issues and strive to minimize odors. Proactive odor management is critical to the continued success and operation of these facilities.
More so than ever before, the solid waste industry faces complex and challenging odor issues based upon public, regulatory, and legal actions. Since odors are generally enforced through nuisance regulations, compliance can be difficult to achieve, not to mention almost impossible to define. Enforcement of odor nuisances is subjective, usually at the discretion of an environmental inspector or Air Pollution Control Officer, and often based upon citizen complaints. When citizen complaints mount, and enforcement action is leveraged, lawsuits often surface as an added ongoing challenge to waste facility operations. Now politicians are demanding action and using alleged odor violations as part of their environmental platforms. Facing odor issues can be costly and threaten the intended land-use designs that waste facilities require to serve their local communities.
SCS Engineers’ January webinar was for those who want to learn more about the proactive strategies and practices you can implement at your critical solid waste facilities. This free webinar will help you develop capabilities to assess the potential for odor issues and, by doing so, set realistic benchmarks toward cost-effective and meaningful mitigation measures.
Our panelists bring comprehensive expertise to the table, including facility design and planning, technical experience in air quality compliance and pollutant dispersion and air measurement programs, atmospheric dispersion and transport of airborne pollutants, particularly in the area of complex terrain. They will provide decades of strategies, resources, and best practices and technologies based on successful solutions that help support your facility as you prepare for, and likely will, experience odor complaints.
The team answers questions throughout the presentation, and the second portion of the program is devoted to Q&A and idea exchange.
In implementing the EPA’s federal requirements for Coal Ash Residual – CCR sites, the Texas Commission on Environmental Quality’s CCR program needs to be at least as protective as the requirements of the self-implementing federal CCR rules. The TCEQ also is charged with making the Texas CCR program consistent with other TCEQ regulatory programs. As such, the TCEQ incorporated various provisions of state permitting programs and procedures into Chapter 352.
Whereas many of the EPA’s federal requirements are adopted directly by reference to the federal CCR rules (40 Code of Federal Regulations, as amended through April 17, 2015, issue of the Federal Register (80 FR 21301)), other requirements were tailored and, or expanded to be consistent with TCEQ programs. Following are select examples correlating the EPA and TCEQ requirements:
There were also five provisions of the federal CCR regulations that the TCEQ did not include in its permit program. These are addressed in EPA’S announcement regarding the TCEQ’s application requesting partial approval of their CCR state permit program. See https://www.epa.gov/coalash/us-state-texas-coal-combustion-residuals-ccr-permit-program
SCS Engineers and Florida East Coast Industries (FECI) are to be honored at the annual conference in Florida planned for August 2021. The firms will receive a 2021 Engineering Excellence Award by the American Council of Engineering Companies of Florida. The honor acknowledges SCS for the environmental engineering firm’s innovative design that integrates groundwater remediation with the stormwater management system on a 500-acre former landfill site. The design enabled the developer to remediate the former landfill into the Countyline Corporate Park in Southeast Florida.
Industrial real estate is in high demand, but former landfills and brownfields present environmental challenges that can become cost-prohibitive to redevelop without sound environmental expertise. FECI retained the professional services of SCS Engineers to provide consulting and design services addressing the environmental concerns preventing the transformation of a former landfill into a state of the art business park.
Environmental guidelines require 28% (or about 140 acres) of the site to be set aside for stormwater retention. The set aside would require the relocation of several thousand cubic yards of waste and prevent the 140 acres’ redevelopment. The estimated loss of $300 million in potential real estate sales, coupled with the groundwater remediation expense, made the site redevelopment cost-prohibitive. Unless resolved, the problem also impeded FECI’s corporate sustainability goals.
SCS’s experts in landfill design, closure, and remediation, developed a solution tying together the groundwater remediation and stormwater management systems. The integrated system allows for shallow aquifer recharge with stormwater and captures impacted groundwater at the site’s boundary. “We were able to provide an alternative design acceptable to all the permitting agencies, eliminating the need to set aside large areas for stormwater retention,” said Mr. Som Kundral, P.E., SCS’s senior project manager.
SCS’s remedial actions protect public health while opening the site for reuse. The project will be completed in phases. Phase I, consisting of 160 acres, is complete, with two million square feet of occupied businesses and a 30-acre community park. Development of the other three phases, which include another six million square feet, is underway.
The development will create hundreds of new jobs, deliver several hundred million dollars to the city and county tax base, and provide a 30-acre public park. “The engineering solution protects the environment while meeting FECI’s strategic, social, economic, and sustainability goals,” said Mr. Eduardo Smith, P.E., SCS’s senior vice president of client success.
Learn more about these related topics, events, and case studies at SCS Engineers:
EPA is hosting a free workshop in January on landfill monitoring and emissions. The workshops are scheduled twice, over half-day sessions. These sessions will include presentations highlighting the latest technological developments for monitoring and measuring landfill gas emissions.
Dates and Times: Register once for both sessions.
If you have any questions, please contact Shannon Banner at or John Evans at .
As large tracts of geographically desirable vacant land become scarcer, residential and commercial property developers are increasingly turning to old landfills or former dumps. However, such redevelopment is complex and rife with uncertainties. When compared to greenfield development, the land acquisition costs are lower. Still, any savings are typically offset by greater environmental and infrastructure costs associated with the foundation, landfill gas management, stormwater management, groundwater impacts, meeting closure requirements, and multiple regulatory agency coordination. Therefore, it is important to maximize the developable area while providing engineering solutions to make the project economically feasible. In this blog, we identify some options to reuse challenging sites and lessons learned to contribute to successful redevelopment projects.
Deep Dynamic Compaction
Old landfills or dumps present some unique soil stability challenges. Deep dynamic compaction (DDC) is a ground stabilization technique that has gained popularity in recent years to improve subsurface soil conditions. DDC involves dropping 6 to 30-ton weights from a height between 30 and 75 feet to achieve the desired soil compaction. DDC can effectively apply to a range of subsurface materials, including former C&D debris or municipal solid waste dumps.
DDC provides a stable foundation for future development, minimizes differential settlement while leaving the landfill waste in place, and eliminates the costs associated with removing, transporting, and disposing of buried waste, costing millions of dollars. For simplicity’s sake, let’s consider a 1-acre old landfill or a dumpsite with an average of 15 feet of waste. If excavating the waste and replacing it with clean fill, the disposal fee costs for the excavated waste alone could exceed $400,000. Alternatively, DDC costs range from $1.50 to $2.00 per square foot or $65,000 to $87,120 per acre, excluding mobilization, which costs around $30,000.
Gas Mitigation Systems
Constructing buildings on top of dynamically compacted areas generally requires a combustible gas barrier layer below the building foundation to manage subsurface combustible gases (typically methane). The barrier is required because the waste remains in place. In its simplified form, gas mitigation systems include:
These gas mitigation systems can be either a passive or an active system with a blower. The cost of such systems varies depending on the size of the building, location, and type of liner system used. Typical capital costs for passive systems are in the range of $7 to $9 per square foot for the spray-applied liner and $3 to $4 per square foot for the HDPE liner. For an active system using blowers, add $3 to $4 per square foot. The designer configures a system from these options to address the client’s risk preference and considering future tenant preferences.
Using innovative approaches, impaired lands are increasingly attractive to developers. Beyond the cost-saving benefits to developers realized through DDC and an appropriate gas mitigation system, such projects also create local jobs, increase the tax base, and protect public health and the environment.
About the Authors:
Somshekhar Kundral – Mr. Kundralis, PE, is a Senior Project Manager with over 12 years of broad and diverse environmental engineering experience that includes projects in landfill redevelopment, landfill gas management system design, site assessment, groundwater remediation system design, stormwater management, and injection well system construction. Som is experienced with site permitting, compliance reporting and construction administration services, and remediation systems’ operation and management.
Maura Dougherty is joining SCS’s Southwest Business Unit as a Senior Project Manager in the solid waste engineering practice. Dougherty will execute engineering design, operations support, and construction quality assurance projects. She is responsible for project management, client service, business development, technical leadership, and overseeing professional staff teams. Dougherty reports to Vice President and Southwest Business Unit Director of Engineering, Vidhya Viswanathan, P.E., from SCS’s Pleasanton office.
“Maura is a senior professional with proven extensive success in solid waste engineering, construction, and construction quality assurance solutions,” said Viswanathan. “Her experience managing landfill and landfill gas collection and control system engineering and construction projects strengthen our efforts to support our solid waste and recycling clients.”
Dougherty is a registered Professional Engineer in California, Oregon, Washington, and Hawaii. She brings over 20 years of experience overseeing landfill engineering and construction projects, coordinating with regulatory staff, conducting design and technical reviews, and supporting construction work. Dougherty earned her B.S.E. in civil engineering at the University of Princeton and her M.S. in environmental engineering from U.C. Berkeley.
Register for SCS Engineers’ January webinar to learn more about the proactive strategies and practices you can implement at your critical solid waste facilities. This free webinar will help you develop capabilities to assess the potential for odor issues and, by doing so, set realistic benchmarks toward cost-effective and meaningful mitigation measures.
DATE: Thursday, January 21, 2021 TIME: 2 p.m. ET
Our panelists bring comprehensive expertise to the table, including facility design and planning, technical experience in air quality compliance and pollutant dispersion and air measurement programs, atmospheric dispersion and transport of airborne pollutants, particularly in the area of complex terrain. They will provide decades of strategies, resources, and best practices and technologies based on successful solutions that help support your facility as you prepare for, and likely will, experience odor complaints.
The team answers questions throughout the presentation, and the second portion of the program is devoted to Q&A and idea exchange.
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.
On November 30, 2020, the Environmental Protection Agency announced it is aggressively addressing per- and polyfluoroalkyl substances (PFAS) in the environment. The agency announced two steps that it states would help ensure that federally enforceable wastewater monitoring for PFAS can begin as soon as validated analytical methods are finalized.
First, EPA issued a memorandum detailing an interim National Pollutant Discharge Elimination System (NPDES) permitting strategy for addressing PFAS in EPA-issued wastewater permits.
EPA’s interim NPDES permitting strategy for PFAS advises EPA permit writers to consider including PFAS monitoring at facilities where these chemicals are expected to be present in wastewater discharges, including from municipal separate storm sewer systems and industrial stormwater permits. The PFAS that could be considered for monitoring will have validated EPA analytical methods for wastewater testing. The agency anticipates being available on a phased-in schedule as multi-lab validated wastewater analytical methods are finalized. The agency’s interim strategy encourages the use of best management practices where appropriate to control or abate the discharge of PFAS and includes recommendations to facilitate information sharing to foster adoption of best practices across states and localities.
Second, EPA released information on progress in developing new analytical methods to test for PFAS compounds in wastewater and other environmental media.
In coordination with the interim NPDES permitting strategy, EPA is developing analytical methods in collaboration with the U.S. Department of Defense to test for PFAS in wastewater and other environmental media, such as soils. The agency is releasing a list of 40 PFAS chemicals that are the subject of analytical method development. This method would be in addition to Method 533 and Method 537.1 that are already approved and can measure 29 PFAS chemicals in drinking water. EPA anticipates that multi-lab validated testing for PFAS will be finalized in 2021. For more information on testing method validation, see https://www.epa.gov/cwa-methods.
EPA continues to expand its PFAS Action Plan to protect the environment and human health. To date, it has assisted more than 30 states in helping address PFAS, and the agency is continuing to build on this support. Across the nation, the EPA has addressed PFAS using a variety of enforcement tools under SDWA, TSCA, RCRA, and CERCLA (where appropriate), and will continue to protect public health and the environment.
The agency is also validating analytical methods for surface water, groundwater, wastewater, soils, sediments, and biosolids; developing new methods to test for PFAS in air and emissions; and improving laboratory methods to discover unknown PFAS. EPA is developing exposure models to understand how PFAS moves through the environment to impact people and ecosystems.
Related Information
This blog references information issued from the US EPA, Office of Public Engagement.
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