Perched Water Table

An accumulation of groundwater that is above the regional groundwater table in an unsaturated zone.

Performance Specification

Establishes the performance criteria the constructed product must meet. A performance specification leaves the selection of means and methods to the contractor.

Periphery

Circumference or perimeter of a circle, ellipse, pipe-arch, or other closed curvilinear figure.

PFA

Pulverized Fuel Ash; a fine powder residue after burning carbon based products. Especially from electricity generating stations.