Total Petroleum Hydrocarbons (TPH) Total Petroleum Hydrocarbons (TPH): The term “Total Petroleum Hydrocarbons” represents the complete carbon chain of hydrocarbon compounds that originate from petroleum. In general there are three ranges of TPH: Gasoline Range Total Petroleum Hydrocarbons (TPH-g); Diesel Range Total Petroleum Hydrocarbons (TPH-d); and Oil Range Total Petroleum Hydrocarbons (TPH-o). Gasoline range TPH represents the…

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…

Transgression Transgression: In geology, the term transgression is the formation of a specific sequence of sedimentary and metamorphic layers, that are the result of ocean water advancing onto land. To illustrate, when transgression occurs over millions of years, geologists find a layer of sand, overlain by shale, and overlain again by limestone. The opposite of…

What is an Embankment Dam? An Embankment Dam is a freshwater-retaining structure comprising excavated rock, soil, or a combination of rock and soil from nearby geological formations.  In fact, Embankment Dams are known as an “Earthfill Dam” when filled with soil, and a “Rockfill Dam” when filled with rocks. Earthfill Dams are most common. The…

What is a Concrete Gravity Dam? A Concrete Gravity Dam is also known as “Gravity Arch Dam,” and is a freshwater-retaining concrete structure that has a wider footing (base) than the top-section. The purpose of a Concrete Gravity Dam is to maintain a low center of gravity, in order to avoid collapsing in the event…

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.