This manual includes a summary volume (Volume 1) and the following four supporting technical documents:

•Volume 2 – Theory and Background;
•Volume 3 – Site Characterization and Numerical Analyses of Cover Performance;
•Volume 4 – Field Performance Monitoring and Sustainable Performance of Cover Systems; and
•Volume 5 – Case Studies.

The basic theory discussed in Volume 2 focuses on unsaturated zone hydrology as it relates to the design of cover systems. Volume 2 is divided into two sections. Section 1 presents the background theory and fundamental concepts pertinent to soil cover design. The topics are grouped into four key areas: moisture storage, moisture flow, evaporation and transpiration, and oxygen transport. Moisture storage includes discussion of the topics of volume / mass relationships, the definition of soil suction, and an introduction to the relationship between soil suction and water content, referred to as the soil water characteristic curve. Moisture flow is divided into liquid flow, and includes a description of the hydraulic conductivity function and vapour flow, as well as a discussion on vapour diffusion. Lastly, evaporation, transpiration, and oxygen transport, specifically oxygen diffusion, are discussed.

Section 2 of this volume introduces applications of the basic theory to issues encountered with soil cover design. Examples illustrating the basic theory and concepts are provided. This section is divided into four subjects: moisture flow issues, moisture storage, capillary barriers, and oxygen transport. Flow issues discussed include bypass flow, basal inflow, wetting, and pore-water velocity. For the discussion of storage, an example is given for calculation of the storage capacity of a soil cover. Capillary barriers are also discussed, along with issues of capillary barriers on sloping surfaces and an example of a diversion length calculation. Lastly, the mechanisms of oxygen ingress are discussed.