By Ali Khatami
MSW sanitary landfills constantly face the issue of aesthetics due to leachate seeping out of the landfill slopes. Of course, the problem goes away after the construction of the final cover, but the final cover construction may not take place for many years after seeps show up on slopes. To the public, leachate seeps represent a problem with the design of the landfill and possible malfunction of the leachate collection system below the waste, which is an incorrect perception. Such arguments are common and difficult to counter.
Landfill operators use different means to control leachate seeps from landfill slopes and to clean up the unpleasant view of the seep as soon as they can. Innovative solutions to address the issue have been observed and noted in the industry. The degree of effectiveness of the solution to some extent depends on the amount of money spent to address the problem. Some landfills are located in rural areas and the operator may not mind the unpleasant appearance of the slopes, so naturally no urgency in addressing the issue or no money available to take care of the problem.
The environmental side of the leachate seep issue is the impact to surface water quality. If leachate seeps remain unresolved, liquids coming out of slope may eventually reach the landfill perimeter and mix with stormwater in the landfill perimeter ditch. At that point, the operational issue turns into a compliance issue, and regulatory agencies get involved. If the public around the site is on top of their game concerning their opposition to the landfill, they can take the non-compliance issue and turn it into a political issue. At that point, the landfill operator finds himself or herself on the hot plate dealing with the agency and the public on an environmental impact matter.
It always makes sense to stay ahead of the issues and address any potentially sensitive condition before it turns into a major problem. As discussed above, addressing leachate seeps can be done in many different ways, and the operator needs to be prepared to fight for funds to address leachate seeps as they appear on slopes. Availability of funds and willingness of the operator to take necessary action are the primary required elements to stay ahead of the game.
SCS has developed methodologies to address all sorts of leachate seeps on landfill slopes and is uniquely equipped to assist you with a solution. Reach out to a local SCS office for a consultation if you have leachate seep problem at your site.
By Ali Khatami, Ph.D, P.E., SCS Engineers National Expert
Leachate seeping out of a landfill slope can be a major issue during the active life of a landfill, and waste operators undertake significant efforts to control and manage it. Uncontrolled seeps can cause soil erosion on the slope, odor issues, and unpleasant scenery on the landfill slope which is visible to adjacent public roads or properties. Leachate can also travel beyond the liner boundaries into perimeter ditches.
Leachate also can seep below the final cover, and that causes a different set of problems. Leachate seeps below final landfill covers are rarely discussed because of the general consensus that they become inactive after construction of the final cover system. That may be true under certain conditions, but very often, leachate seeps remain active as long as the source of water remains active and continues discharging through the seep locations. Leachate seeps below final covers can potentially:
If the final cover geomembrane is not welded to the bottom liner geomembrane, leachate seeping to the toe of the slope can reach the landfill perimeter ditch and contaminate the surface water, or it can percolate into the ground and cause ground water contamination that may be detected in nearby groundwater monitoring wells. Leachate seep also may enter the perimeter berm structure and saturate the berm to the point that the stability of the landfill slope becomes a concern.
If the final cover geomembrane is welded to the bottom liner geomembrane, the only way to address the accumulation of leachate under the cover at the toe of the slope is to open the geomembrane, remove the leachate, and close the geomembrane again. However, this process does not solve the seep problem, which will continue to recur.
SCS has designed various leachate toe drain systems to collect and dispose of leachate that flows below the final cover geomembrane. Leachate toe drains have become a standard feature in the final cover designs for some of our clients who have experienced the benefits of the system.
If you have leachate seep issues at your landfill, please contact SCS. We can develop a design specific to your landfill and the conditions at your facility. We also provide construction recommendations and a preliminary cost estimate for implementation of the system. SCS has extensive experience with the permitting of these systems; we prepare modification applications for permitting purposes and obtain approval from the state regulatory agency. SCS can also prepare the construction plans. We also offer design-build options, employing our SCS Field Services Construction group to construct the system, which often can be a cost-effective way to implement your system.
Questions? Contact Ali Khatami, PhD, PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering. 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 and the remediation of hazardous waste contaminated sites.