How do single liners and double liners differ?

How do single liners and double liners differ?

• A. Single liners consist of one barrier layer with a leachate drainage layer on top; double liners consist of two single liners separated by a leak detection layer.
• B. Single liners use two barrier layers; double liners use one.
• C. Single liners have a drainage layer below; double liners have two drainage layers.
• D. Single liners are used in Subtitle C; double liners in Subtitle D.

Answer: (C)

In this question, the idea is about how liner systems are built to keep leachate from migrating. A single liner uses one impermeable barrier with a drainage layer beneath to collect liquids that are managed by the system. A double liner stacks two impermeable barriers separated by an interstitial space that includes a leak-detection layer, and it involves two drainage layers—one associated with each barrier—to capture liquids at both levels. This arrangement provides redundancy and an early warning if the upper barrier starts to leak, which is why it’s described as having two drainage layers. The other choices mix up the placement of drainage layers or the regulatory context, so they don’t match how these liner systems are typically constructed.

In this question, the idea is about how liner systems are built to keep leachate from migrating. A single liner uses one impermeable barrier with a drainage layer beneath to collect liquids that are managed by the system. A double liner stacks two impermeable barriers separated by an interstitial space that includes a leak-detection layer, and it involves two drainage layers—one associated with each barrier—to capture liquids at both levels. This arrangement provides redundancy and an early warning if the upper barrier starts to leak, which is why it’s described as having two drainage layers. The other choices mix up the placement of drainage layers or the regulatory context, so they don’t match how these liner systems are typically constructed.