Vent Riser in Methane Mitigation Vent Riser in Methane Mitigation: As per the Los Angeles Department of Building and Safety (LADBS) Methane Code, Ordinance Number 175790, a vent riser is a cast iron or ABS pipe that runs through the building walls (vertically). A vent riser is part of a methane mitigation system and has…

Sand Boil A “Sand Boil” is a cone-shaped deposit of sand that is formed during an earthquake. A Sand Boil occurs when subsurface sand layers liquefy and are then blown to the surface through cracks.

Asthenosphere Asthenosphere: The asthenosphere underlies the lithosphere. The Asthenosphere comprises the upper mantle, where isostatic adjustments are made, and where magma is generated. It is also in this part of the earth, where seismic waves strongly attenuate.

Unconfined Aquifer Unconfined Aquifer: In the hydrogeology branch of geology, an unconfined aquifer is an aquifer that has a water table. In fact, an unconfined aquifer can only be the uppermost hydrogeologic unit and is particularly one that has no hydraulic head (or pressure) that is equal to atmospheric pressure. To illustrate, depth to groundwater…

“Toe” of a Slope Definition The “toe” of a slope is essentially the bottom, or baseline section, of the soil mass comprising the slope. It is also defined as the outermost margin of displaced material during a landslide. The toe of a slope is farthest away from the head scarp.

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).