A leachate is any liquid that, in the course of passing through matter, extracts soluble or suspended solids, or any other component of the material through which it has passed.
Geosynthetics are synthetic products used to stabilize terrain. They are generally polymeric products used to solve civil engineering problems. This includes eight main product categories: geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, geofoam, geocells and geocomposites. The polymeric nature of the products makes them suitable for use in the ground where high levels of durability are required. They can also be used in exposed applications. Geosynthetics are available in a wide range of forms and materials. These products have a wide range of applications and are currently used in many civil, geotechnical, transportation, geoenvironmental, hydraulic, and private development applications including roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, erosion control, sediment control, landfill liners, landfill covers, mining, aquaculture and agriculture.
Geotextiles are versatile permeable fabrics that, when used in conjunction with soil, can effectively perform multiple functions, including separation, filtration, reinforcement, protection, and rebuilding the coastline. Typically crafted from polypropylene or polyester, geotextile fabrics are available in two primary forms: woven, which resembles traditional mail bag sacking, and nonwoven, which resembles felt.
A pond liner is an impermeable geomembrane used for retention of liquids, including the lining of reservoirs, retention basins, hazardous and nonhazardous surface impoundments, garden ponds and artificial streams in parks and gardens.
Geocomposites are combinations of two or more geosynthetic materials for civil engineering applications that perform multiple geosynthetic functions. Such composite materials may enhance technical properties of the soil or the geotechnical structure and minimize application costs.
A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common.
Geosynthetic clay liners (GCLs) are factory manufactured hydraulic barriers consisting of a layer of bentonite or other very low-permeability material supported by geotextiles and/or geomembranes, mechanically held together by needling, stitching, or chemical adhesives. Due to environmental laws, any seepage from landfills must be collected and properly disposed of, otherwise contamination of the surrounding ground water could cause major environmental and/or ecological problems. The lower the hydraulic conductivity the more effective the GCL will be at retaining seepage inside of the landfill. Bentonite composed predominantly (>70%) of montmorillonite or other expansive clays, are preferred and most commonly used in GCLs. A general GCL construction would consist of two layers of geosynthetics stitched together enclosing a layer of natural or processed sodium bentonite. Typically, woven and/or non-woven textile geosynthetics are used, however polyethylene or geomembrane layers or geogrid geotextiles materials have also been incorporated into the design or in place of a textile layer to increase strength. GCLs are produced by several large companies in North America, Europe, and Asia. The United States Environmental Protection Agency currently regulates landfill construction and design in the US through several legislations.
Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.
A geonet is a geosynthetic material similar in structure to a geogrid, consisting of integrally connected parallel sets of ribs overlying similar sets at various angles for in-plane drainage of liquids or gases. Geonets are often laminated with geotextiles on one or both surfaces and are then referred to as drainage geocomposites. They are competitive with other drainage geocomposites having different core configurations.
Solid waste landfills can be affected by seismic activity. The tension in a landfill liner rises significantly during an earthquake, and can lead to stretching or tearing of the material. The top of the landfill may crack, and methane collection systems can be moved relative to the cover.
In-Situ Capping (ISC) of Subaqueous Waste is a non-removal remediation technique for contaminated sediment that involves leaving the waste in place and isolating it from the environment by placing a layer of soil and/or material over the contaminated waste as to prevent further spread of the contaminant. In-situ capping provides a viable way to remediate an area that is contaminated. It is an option when pump and treat becomes too expensive and the area surrounding the site is a low energy system. The design of the cap and the characterization of the surrounding areas are of equal importance and drive the feasibility of the entire project. Numerous successful cases exist and more will exist in the future as the technology expands and grows more popular. In-situ capping uses techniques developed in chemistry, biology, geotechnical engineering, environmental engineering, and environmental geotechnical engineering.
Final cover is a multilayered system of various materials which are primarily used to reduce the amount of storm water that will enter a landfill after closing. Proper final cover systems will also minimize the surface water on the liner system, resist erosion due to wind or runoff, control the migrations of landfill gases, and improve aesthetics.
Novel polymeric alloy (NPA) is a polymeric alloy composed of polyolefin and thermoplastic engineering polymer with enhanced engineering properties. NPA was developed for use in geosynthetics. One of the first commercial NPA applications was in the manufacturer of polymeric strips used to form Neoloy® cellular confinement systems (geocells).
Electrical liner integrity surveys, also known as leak location surveys are a post-installation quality control method of detecting leaks in geomembranes. Geomembranes are typically used for large-scale containment of liquid or solid waste. These electrical survey techniques are widely embraced as the state-of-the-art methods of locating leaks in installed geomembranes, which is imperative for the long-term protection of groundwater and the maintenance of water resources. Increasingly specified by environmental regulations, the methods are also applied voluntarily by many site owners as responsible environmental stewards and to minimize future liability.
Ronald Kerry Rowe, OC, BSc, BE, PhD, D.Eng, DSc (hc), FRS, FREng, NAE, FRSC, FCAE, Dist.M.ASCE, FEIC, FIE(Aust), FCSCE, PEng., CPEng. is a Canadian civil engineer of Australian birth, one of the pioneers of geosynthetics.
Jean-Pierre Giroud is a French geotechnical engineer and a pioneer of geosynthetics since 1970. In 1977, he coined the words "geotextile" and "geomembrane", thus initiating the "geo-terminology". He is also a past president of the International Geosynthetics Society, member of the US National Academies, and Chevalier de la Légion d'Honneur.
Jorge G. Zornberg is Professor and Joe J. King Chair in Engineering in the geotechnical engineering program at the University of Texas at Austin. He has over 35 years' experience in geotechnical and geoenvironmental engineering. He is also one of the pioneers of geosynthetics.
The Neoloy Geocell is a Cellular Confinement System (geocell) developed and manufactured by PRS Geo-Technologies Ltd. Geocells are extruded in ultrasonically welded strips. The folded strips are opened on-site to form a 3D honeycomb matrix, which is then filled with granular material. The 3D confinement system is used to stabilize soft subgrade soil and reinforce the subbase and base layers in flexible pavements. Cellular confinement is also used for soil protection and erosion control for slopes, including channels, retention walls, reservoirs and landfills.
Patrick J Fox, Ph.D., P.E., BC.GE, F.ASCE is an American civil engineer and currently the Dean of the Russ College of Engineering and Technology at Ohio University. His field of expertise is geotechnical and geoenvironmental engineering, with specializations in slope stability, retaining walls, landfills, and settlement. He obtained a Ph.D. in civil and environmental engineering from the University of Wisconsin–Madison in 1992.
A double liner is a fluid barrier system that incorporates two impermeable layers separated by a permeable drainage layer also called a leak detection layer. Typically the impermeable layers are made from geomembranes with a permeable layer in between. The uppermost layer is called the primary liner while the lower layer is called the secondary liner. This combination of layers is designed to prevent hydraulic head from building on the secondary liner thereby limiting or preventing any permeation into the secondary liner. Due to the difficulty of constructing a single large scale impermeable layer without any defects, a double liner system is more robust by accounting for leakage through the primary liner. A double liner system is required by the United States EPA for landfill, surface impoundments, and waste piles.
