De-Watering System in Methane Mitigation De-Watering: In accordance with the Los Angeles Department of Building and Safety (LADBS) Methane Code, Ordinance Number 175790, a de-watering system is a permanent water removal system in a methane mitigation system. In the mitigation process, a de-watering system consists of perforated horizontal pipes, gravel pockets, sump areas with pumps,…

Rock Stratigraphic Unit In the field of geology, a rock stratigraphic unit, or a lithostratigraphic unit, is a geologic formation that is identifiable by a specific lithology, as well as a consistent stratigraphic position. For example, the Monterey Formation is a rock stratigraphic unit, as it tends to consistently comprise the same gravel and sand…

Direct Shear Test A Direct Shear Test is a geotechnical engineering laboratory procedure that measures the shear strength value of a soil sample.

Transmissivity Transmissivity: In geology and hydrogeology, transmissivity (T) represents the capacity of an aquifer to transmit water of the prevailing kinematic viscosity. Formula T=Kb, where b = saturated thickness of the aquifer. Dimensions are gallons per day per foot (gpd/ft) or feet squared per day (ft^2/day).

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.

Thrust Fault Thrust Fault: In the field of geology, a thrust fault is a reverse fault in which the fault plane dipping angle is less than 45 degrees. Thrust faults are dip-slip faults, and can also be listric faults. For instance, the fault underlying the western embankment of the historical St. Francis Dam in Saugus,…