Potentiometric Surface The term “Potentiometric Surface” means the hydrogeological surface that represents the total hydraulic head of groundwater from a confined aquifer or semi-confined aquifer that’s under pressure. The Potentiometric Surface of an aquifer is defined by the level to which water will rise in a groundwater monitoring well (that’s exclusively screened within said aquifer).

Dip-Slip Fault Dip-Slip Fault: In geology, a dip-slip fault is any fault in which the earth’s movement is parallel with the dip of the fault plane. For example, a normal fault, reverse fault, or listric fault. The opposite of a dip-slip fault is a strike-slip fault.

Trench Dam Trench Dam: Per the Los Angeles Department of Building and Safety (LADBS) Methane Code, Ordinance Number 175790, a trench dam is part of a methane mitigation system. A trench dam is essentially a subsurface barrier that exists within a furrow or ditch, that is adjacent to the foundation of a building in a…

Rotational Slide (Slump) Definition Rotational Slide (Slump):  A rotational slide is a type of landslide movement that occurs in a turning moment, about a pivot point that is above the center of gravity. This is typically due to an increased normal force on a slope, as well as a reduced cohesion factor of the soil…

Gap-Graded The term “Gap-Graded” is used by geologists, engineers, and soil scientists in the geotechnical engineering field to describe the gradation of a soil sample, specifically when some particle sizes are missing. Aside from being “gap graded,” a soil sample can be described as “well-graded” (also referred to as poorly sorted), or “poorly graded” (or…

Subsidence “Subsidence” is a geologic condition, in which a localized mass movement occurs, resulting in the downward settlement of the earth over time. When subsidence occurs, the actual ground surface elevation is lower. This occurrence of the ground surface sinking is typically caused by groundwater table and aquifer reductions, by which the soils become more…