Glossary

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UNAUTHORIZED RELEASE:

Any reportable unauthorized release of petroleum from a UST, unless authorized by the Board or Regional Board.

UNDERGROUND INJECTION:

The placing of fluids below the surface of the ground through wells. Fluids injected include hazardous wastes, brine from oil and gas recovery, liquids used in mining, radioactive waste, sewage, natural gas and oil products and storm water runoff. EPA and states regulate underground injection under the Safe Drinking Water Act and RCRA. 

UNDERGROUND INJECTION:

The placing of fluids below the surface of the ground through wells. Fluids injected include hazardous wastes, brine from oil and gas recovery, liquids used in mining, radioactive waste, sewage, natural gas and oil products and storm water runoff. EPA and states regulate underground injection under the Safe Drinking Water Act and RCRA. 

UNDERGROUND STORAGE TANK (UST):

A tank and any underground piping connected to the tank that has 10 percent or more of its volume (including pipe volume) beneath the surface of the ground. These tanks are used to store petroleum or certain hazardous chemicals.

UNDERGROUND UTILITY CHECK:

A check for the location of buried utilities such as power, gas, and telephone to prevent accidents during site work.

UNSATURATED ZONE:

The zone immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. These zones differ from an aquifer, where the pores are saturated with water.

UPGRADIENT:

In the direction of increasing potentiometric (piezometric) head. The direction water and contaminant would normally flow from without any other influences.