SWCR systems

The third part, called the surface water collection and removal (SWCR) system, lies above the waste system in a cap or closure above the closed facility. Its purpose is to redirect surface water coming through the cover soil from the flexible membrane in the cap to the outside perimeter of the system. The location of all three parts of the liquid management system is illustrated in Figure 26.21. 

FIGURE 26.29 Design methodology to estimate cover soil infiltration into the SWCR system. (Adapted from U.S. EPA, Requirements for Hazardous Waste Landfill Design, Construction, and Closure, EPA/625/4-89/022, U.S. Environmental Protection Agency, Cincinnati, OH, August 1989.)... 

This section describes the elements in a closure or cap system of a completed landfill, including flexible membrane caps (FMCs), SWCR systems, gas control layers, biotic barriers, and vegetative top covers. It also discusses infiltration, erosion control, and long-term aesthetic concerns associated with securing a completed landfill. 

The SWCR system is built on top of the FMC. The purpose of the SWCR system is to prevent infiltration of surface water into the landfill by containing and systematically removing any liquid that collects within it. Actual design levels of surface water infiltration into the drainage layer can be calculated using the water balance equation or the HELP model.36 37... 

In designing an SWCR system above an FMC, three issues must be considered5 ... 

The impact of settlement is a major concern in the design of the SWCR system. A number of facilities have settled 6 ft in a single year, and 40 ft or more over a period of years.5 The Meadowlands site in New Jersey, for example, was built at a height of 95 ft, settled to 40 ft, and then was rebuilt to 135 ft. Uniform settlement can actually be beneficial by compressing the length of the FMC and reducing tensile strains. However, if waste does not settle uniformly, it can be caused by interior berms that separate waste cells. 

Figure 26.30 shows details of a gas vent pipe system. The two details at the top left of the illustration show close-ups of the boot seal and flange seals located directly at the interface of the SWCR system with the FMC. To keep the vent operating properly, the slope of the closure system should... 

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