text: United States Environmental Protection Agency (EPA) standards, published in 40 CFR Parts 280 and 281, mandate double-walled piping for many below-ground transport systems in wastewater treatment plants and at sanitary or hazardous-waste landfills or remediation sites. These and other regulations affect below-grade transport of hazardous materials in fuel storage systems, tank farms, drainage or runoff from process plants, and some food-processing and related applications. Double-walled containment systems are also used for certain classes of toxic or corrosive chemicals, mostly gases, used in semiconductor fabrication. Double-walled pipes may also be used where a waste water pipe traverses a drinking water catchment area.