A number of temporary storage sites have been commissioned to contain soils and wastes generated from the decontamination works after the accident at Tokyo Electric Power Company’s Fukushima Dai-ichi Nuclear Power Plant. At these sites, volume reduction has been observed in the flexible container bags caused by the dehydration and decomposition of the decontamination waste inside. This situation leads to uneven settlement of the top of these flexible container bags in these temporary storage sites, and might result in problems such as leakage through top and bottom liners installed to contain these container bags. To deal with these problems immediately, the Geomembrane Technical Committee, Japan Chapter of International Geosynthetics Society has conducted deliberations and made reports on procedures for selection and installation of storage containers that are to prevent polluted water from leaking outside of storage sites, structures, and barrier materials, a new inspection procedure for seaming of cover geomembranes, installation of cover materials that are to counter uneven settlement of soil, and also temperature control procedures to prevent natural ignition of waste. This paper summarizes the deliberations and the procedures adopted.

View full abstract

We have developed gas-permeable/waterproof sheet (GPWS), comprising a micro-porous sheet which is waterproof and have gas permeability, coated with nonwovens to protect and reinforce it, and carried out many experiments in both laboratories and fields. GPWS has been applied as cover sheet for temporary storage sites of decontamination waste due to the Fukushima nuclear accident. On the other hand, geomembrane which is waterproof but gas-impermeable has also employed as cover sheet of the decontamination waste in conjunction with gas-vent pipes. In this study, temperature and oxygen-concentration of the decontaminated wastes, over which GPWS and geomembrane were installed respectively, were experimentally measured in real temporary storage site to compare the influence of weather condition. As the results, it was demonstrated that GPWS can achieve sufficient performances as the cover sheet in that both temperature and oxygen-concentration, closely relating with the consistency of gas permeability in the cover system, was less influenced by weather condition.

View full abstract

In the last two years, several large infrastructure projects were successfully constructed in the Netherlands with the use of HDPE vertical barriers. The executed schemes used HDPE screens made of 2mm thick HDPE liner welded to patented HDPE Geolock profiles. The screens have a width of 2.5 meter and lengths ranging from 8 meter to 26 meter. During the installation, a hydrophilic swelling cord was incorporated into the locks to create a complete seal. This article describes the application of the HDPE barrier on six different projects. It includes the design aspects, installation methods as well as laboratory measurements with regards to the durability of the material used, water tightness of the system and swelling capacity of the swelling cord when used in salt water. In the projects described, the barriers were used to prevent horizontal flow of water. On the projects the screens were installed by different contractors using equipment supplied by the manufacturer of the HDPE screens. In four projects (three near the city of Leeuwarden and one at the N381), the screens were used in the construction of aqueducts and underpasses. The screens were installed with a special installation plate in narrow trenches, made using partial predrilling and displacement, as well as in ‘ mixed-in-place’ walls up to a depth of 18 meters. Near Nijmegen the screens were used in a river widening project to prevent the flow of water to the low lying land during high river discharges. The screen was installed using a reclaimable weight down to a depth of 26m in a ‘ cement-bentonite’ trench made by a diaphragm wall grab. In a project near Rotterdam the screens were also installed in a diaphragm wall. They were installed to prevent ground water inflow into a long low lying section of a new highway.

View full abstract

Construction Quality Assurance (CQA) plays an important role in producing a quality containment system. Electrical liner integrity surveys are non-destructive CQA tests that help locating leaks and reducing defects at post-installation of the liner systems and even after geomembranes are covered with soil and water. A new and innovative geomembrane, GSE Leak Location Liner incorporates a thin layer of electrically conductive layer on the bottom surface of an insulating geomembrane that allows it to be 100% sparked tested for defects. Liner integrity surveys on electrically conductive geomembranes have been tested and verified as the most effective and accurate candidate in locating leaks in installed geomembranes after cover soil installation. Based on large scale field tests and commercial scale tests that have been performed by third party surveyors, the leak surveys demonstrate that an electrically conductive geomembrane can significantly increase the quality of electrical liner integrity surveys by improving both speed, accuracy and expanding detection limits. It also allows the use of liner integrity surveys in applications that were previously impossible such as multiple-layer systems, on side slopes and in situation where wrinkling has occurred in the liner.

View full abstract

Geomembrane liner has been widely accepted as standard components of geosynthetic lining systems in many containment facilities. Among the plastic materials utilized for geomembranes, high density polyethylene (HDPE) geomembranes are the most widely used geosynthetic lining materials adopted for various containments applications include waste landfill, liquid containment and mining ponds, etc. This is mainly attributed to its superior hydraulic and mechanical properties in combination with its very low permeable characteristics, greater chemical resistance and ultra violet light (UV) degradation resistance. It is always engineers’ major concern regarding the lifetime of geomembranes. The paper presents an evaluation of HDPE geomembrane liner that was left exposed to the extreme continental climate with long, cold winters and short summers in Northern Mongolia. After more than 16 years of service and exposure, geomembrane samples were evaluated for physical property integrity and engineering performance. The laboratory test results presented in this paper demonstrate that after 16 years in active service, HDPE geomembrane liners are working in their desired function and performance under exposed condition.

View full abstract

This paper presents the experimental results of the diffusion of phenolic compounds through a flexible polypropylene geomembrane. The study considers the partition and diffusion of two chlorophenol contaminants: 2,4,6-tricholophenol and 2,3,5,6-tetrachlorophenol that are known to be toxic even at very low concentrations. The concentration dynamics in the source and receptor chambers of the diffusion cells were interpreted using the numerical code Pollute. The values of diffusion coefficients are respectively equal to 1.2×10^-13 m²/s and 2.5×10^-13 m²/s for 2,4,6-TCP and 2,3,5,6 TeCP. Values of partitioning coefficients were respectively equal to 504 and 357 for 2,4,6-TCP and 2,3,5,6 TeCP. Values of diffusion coefficients obtained are similar to values previously obtained for an HDPE geomembrane. Partitioning coefficients are one order of magnitude larger than values obtained for an HDPE geomembrane, thus resulting in a larger permeation coefficient in PP than in HDPE geomembranes by one order of magnitude

View full abstract

A combination of high-density polyethylene (HDPE) geomembranes (GMs) and geosynthetic clay liners (GCLs), is widely used for protecting groundwater from contaminated water in landfill liners and brine ponds. While a low-permeability and chemically-resistant GM prevents downward flow of water, the GCL acts as a diffusive and advective buffer against the flow under defects in the GM. However, it has been shown that GCLs may desiccate due to thermal gradients. Downward flow of water vapour from the GCL towards cooler areas near the aquifer is the main mechanism expected to control the water content of GCL. Defects in the GM are clearly undesirable because they can lead to contaminant migration though the liner. On the other hand, defects may also allow water to rehydrate the GCL. Little is known, however, about this potential for rehydration. In this study, we validate a thermo-hydro-mechanical model of composite liner systems, based on computer software CODE_BRIGHT, and use it to simulate hydration-dehydration dynamics of composite GCLs in a landfill liner. Specifically, we assess the extent to which downward water flow through a defect can counteract desiccation. We find that close to the defect, stresses in the bentonite remain compressive and the likelihood of desiccation is thus reduced. However, under the low transmissivity conditions encountered for GCLs, the effect seems localised and disappears away from the defects.

View full abstract