Penetration Rate

Instantaneous excavation distance per time while the MTBM is operating, typically measured in inches per minute or millimeters per minute.

Percent (%)

A dimensionless number with the ratio of one (1) to one hundred (100). In the construction industry, it is mostly used to give the rise of fall of a pipe line, or road, in feet per 100 feet (i.e., a one (1) foot rise in one hundred (100) feet would be a plus 1% (one percent) grade).

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.