Short- and long-term leakage through composite liners. The 7th Arthur Casagrande Lecture¹This lecture was presented at the 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, Toronto, Ont., October 2011, and a pre-print appeared in the conference proceedings.

Abstract

The factors that may affect short-term leakage through composite liners are examined. It is shown that the leakage through composite liners is only a very small fraction of that expected for either a geomembrane (GM) or clay liner (CL) alone. However, the calculated leakage through holes in a GM in direct contact with a clay liner is typically substantially smaller than that actually observed in the field. It is shown that calculated leakage taking account of typical connected wrinkle lengths observed in the field explains the observed field leakage through composite liners. Provided that care is taken to avoid excessive connected wrinkle lengths, the leakage through composite liners is very small compared to a typical GM or CL alone. It is shown that the leakage through composite liners with a geosynthetic clay liner (GCL) is typically much less than for composite liners with a compacted clay liner (CCL). Finally, factors that will affect long-term leakage through composite liners are discussed. It is concluded that composite liners have performed extremely well in field applications for a couple of decades and that recent research both helps understand why they have worked so well and provides new insight into issues that need to be considered to ensure excellent long-term liner performance of composite liners — especially for applications where the liner temperature can exceed about 35 °C.

Using Geomembrane Liners to Reduce Seepage through the Base of Tailings Ponds—A Review and a Framework for Design Guidelines

“…These include modeling seepage routes and rates, and estimating the ability to prevent or minimize leakage throughout the life cycle of the mine. Analytical methods are usually used in calculation of the specifics [79], while numerical modeling is used in assessing the behavior of the entire pond or the movement of seepage waters [80][81][82]. Analytical calculations are based on the theory of fluid movement in pipe systems (Bernoulli equation) and the flow of a fluid through a porous medium (Darcy's law).…”

“…Analytical calculations are based on the theory of fluid movement in pipe systems (Bernoulli equation) and the flow of a fluid through a porous medium (Darcy's law). Many studies have also developed empirical formulae for leakage calculations in various composite solutions [81,[83][84][85][86][87]. Sufficient modeling accuracy can often be achieved by 2D examination, but 3D modeling is required when, e.g., modeling groundwater head beneath the facility of valley fill [42].…”

A Generic Method for Predicting Environmental Concentrations of Hydraulic Fracturing Chemicals in Soil and Shallow Groundwater

“…A similar chemical migration pathway exists if pipes transporting produced water leaked (Source 4 in Figure 1). Even when appropriately designed and installed, lined ponds are known to cause small leaks over time [33][34][35][36]. Moreover, when highly saline fluids are stored, the permeability of clay lined ponds will increase [37,38].…”

“…Current engineering practices for lining landfills and storage ponds consider double liner systems which incorporate leakage collection systems. While generally low, leakage (the combination of advective and diffusive migration of chemicals) from a composite liner (GM combined with either a CCL or a GCL) cannot be avoided and is mainly due to the fact that a GM installed as part of liner system will generally have some holes [36,39,40]. (10) and deep (6 to 8) groundwater, and via surface runoff (9) during the depressurization phase.…”

Ageing of exposed geomembranes at locations with different climatological conditions

“…High density polyethylene (HDPE) geomembranes (GMBs) are used as barriers to liquids and gas in many geotechnical and geoenvironmental engineering applications, such as landfills, reservoirs, lagoons, and dams (e.g., Reddy and Butul 1999;Koerner and Hsuan 2003;Rowe et al 2004;Rowe 2005Rowe , 2012Richardson and Zhao 2009). Since the late 1990s, HDPE GMBs have typically comprised (by weight) medium-density polyethylene resin (96% to 97.5%), carbon-black (2% to 3%), and antioxidants (>0.5%) Scheirs 2009).…”