A substantial landfill with sharp, angled slopes required an innovative and reliable capping solution.
Peter Ceribelli
Operators at a thermal plant in Mallorca, Spain, had a problem. The plant’s adjacent sun-beaten Mediterranean landfill was at capacity with coal combustion by-products (CCB), or coal ash, and needed an impermeable and durable capping solution. The landfill had originally been lined with a bentonite-enhanced sand (BES) barrier and an HDPE geomembrane. With waste that contained high concentrations of inorganic salts and heavy metals, it was paramount that the capping solution be compatible with the existing bottom liner to support the long-term performance of both.
The size of the proposed capped site was substantial: 130,000 m2with 40,000 m2of slopes, which were inclined at 3H:1V and ranged from 5 meters to 35 meters. The size of the slopes presented the greatest challenge to a pure BES installation, which risked instability issues as well as time constraints (the BES lining solution was only seven centimeters thick, which the operator feared would not hold up in the area’s sunny climate). In early 2013, operators contacted CETCO to help solve the problem at hand due to our decades of experience and expertise in geosynthetic containment design.
As the world’s leading supplier of geosynthetic clay liners (GCLs), CETCO offers a full range of products to address design challenges such as hydrostatic pressure, shear strength, and chemical compatibility. CETCO’s engineered solutions include best-in-class lining systems, part of a larger portfolio of innovative environmental products.
The Solution
The landfill operators required a capping solution that would not only match the chemistry of the landfill waste, but also offer long-term durability (avoiding instability issues) and allow for rapid installation. CETCO performed a detailed assessment of the site, carrying out leachate analyses taken from the site and conformance tests at our lab in Szczytno, Poland. Over a period of two months, the tests helped identify two ideal product solutions: RESISTEX® ST GCL to cover the landfill cell, and CETCODRAIN, a drainage geocomposite, which would be placed atop RESISTEX ST GCL and serve to collect and drain excessive rainwater.
The RESISTEX® GCL line of products is a polymer-modified bentonite GCL designed to deliver superior chemical compatibility for hydraulic barrier performance in extremely aggressive leachate environments — a perfect match for the waste stored at the Mallorca landfill. A recipient of the 2015 GeoMe award for “Best Geosynthetics Innovation and Technology,” RESISTEX GCLs are compatible with a wide range of pH, electrical conductivity and ionic strengths, and have proven more effective than standard bentonite when working in contaminated chemical environments.
CETCODRAINgeocomposite consists of two superimposed polyethylene high-density wires crossed at 60-degrees, which form channels with high water evacuation capacity, even under heavy loads and under reduced conditions. The biaxial design of the material allows for drainage in two directions, an essential feature to adapt to all types of terrain. Geotextiles protrude at about 10 cm from the geocompositeso that the continuity of the draining surface is not lost. In addition, CETCODRAIN is resistant to chemical and biological attacks normally present in natural soils and in organic or inert waste.
Capping Success
Installation was seamless for the operator and adhered closely to schedule. Daily installation included roughly 3,500 m2, with total installation of the 130,000 m2taking less than two months. Feedback from the operator ad the project’s general contractor has been very positive on the quality of the solution and speed of its deployment. In fact, the RESISTEX GCL solution has proven so successful that the Mallorca team has selected the RESISTEX ST GCL in the subsequent four phases of the landfill operation, with new cells deployed in 2014 and 2018, and new capping performed in 2016 and 2019. In these latter installations, the consultant added a HDPE 2.0 mm geomembrane over the RESISTEX ST GCL, which offered improved performance of the lining system.
The RESISTEX ST GCL delivered the performance durability that the operator needed at an effective price point. It has been more than six years since the original installation of the RESISTEX ST GCL and the operator has required no additional maintenance or servicing of the capping solution – demonstrating the long-term effectives of CETCO’s innovative products in challenging conditions.
Peter Ceribelli is the Vice President of CETCO, a subsidiary of Minerals Technologies Inc. Peter has over 35 years of experience in the manufacturing, engineering, consulting and construction industries and manages the company’s Building Materials and Environmental Products Businesses. He can be reached at [email protected].