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UST Terminology


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ACA - Active Corrective Action

Physical actions taken to reduce the concentrations of CoCs.

AFVR Aggressive Fluid Vapor Recovery

A high-pressure vacuum is attached to recovery wells.  It removes petroleum vapors, contaminated groundwater and the petroleum product.

Air Sparging

Oxygen is pumped underground to evaporate petroleum products.


ATG Automatic Tank Gauge

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The act of offsetting buoyancy factors of a tank by filling it with a liquid (typically water or fuel).

BFVV Ball Float Vent Valve

An overfill prevention device that is designed to be installed inside a tank where the vent line makes contact with the tank.  The ball float is designed to temporarily prevent venting during a delivery at the 90% full level.  This allows enough pressure to build in the tank so when the tank is close to 95% full, the rate of fuel being delivered is noticeably slowed so the truck driver will realize the fuel drop should stop thus preventing an overfill event.


Microorganisms that live underground “eat” the petroleum products and convert the product to water and carbon dioxide.  Air and nutrients will be injected underground to assist the microbes in removing the petroleum products.

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CASE - Corrective Action System Evaluation

A report that documents corrective action activities during a certain time period.

Chemical Oxidation

Oxygen-rich chemicals are injected underground to change the petroleum products into harmless coumpounds (water and carbon dioxide).

Class I Contractor

Contractors performing work involving the collected and interpretation of investigative data. 

Class II Contractor

Contractors performing work involving routine investigative activities (soil sampling).

CNFA Conditional No Futher Action

A decision by the Division based on historical data trends and CoCs are below SSTLs.

CoC Chemical of Concern

A specific constituent that is identified for evaluation in the risk assessment process (i.e. benzene, MTBE).

CP Cathodic Protection

Technique to prevent corrosion of a metal surface.  Two types: Impressed Current and Sacrificial Anode.

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Equipment attached at the end of a piping run designed for transferring fuel from the tank to a vehicle (suction dispenser, pressure dispenser).

DP – Delivery Prohibition

DTSO - Drop Tube Shut Off Valve

An overfill prevention mechanism installed within a drop tube located in a fill riser of a tank.  It is designed to abruptly stop the flow of fuel into the tank when the tank capacity reaches 95%.  When activated it makes the delivery hose jerk noticeably so the delivery driver can halt the delivery so as not to overfill the tank.

EOU – Extended-Out-Of-Use

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FP - Free Product

Free phase petroleum greater than 0.01 foot floating on top of the water table.

FR - Financial Responsibility*

GAC - Granulated Active Carbon Filter

A carbon filter that is installed on a water supply well to filter out petroleum chemicals.

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IGWA - Initial Groundwater Assessment

An assessment to determine the presence of soil and groundwater CoCs by the installation of one monitoring well.

IM Interstitial Monitoring

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Leak Detector (electronic or mechanical)

Mechanism typically installed on a submersible pump head and designed to “watch” pressurized product lines for releases.  (Minimum requirement is to find a 3.0 gph leak with a 95% confidence level when the line pressure reduces to 10 PSI or less).

LTT - Line Tightness Test

MNA - Monitored Natural Attenuation

Petroleum and petroleum by-products naturally break down over time through chemical, physical, and biological processes. These processes are called natural attenuation.

Metal Components

Piping of a UST system that routinely contains product (i.e. piping from the tank to the dispenser, manifold piping connecting one tank to another, flex connectors, swing joints). Vent piping and riser access piping for ATG probes, STP, and vapor recovery do not fall into this category.

NFA - No Further Action

A decision by the Division based on soil and groundwater reports that levels of CoCs are below the risk levels to human health and the environment.

NOVA - Notice of Alleged Violation

A letter issued to a tank owner/operator stating that violations may be present and documentation is requested to prove compliance.

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Overfill Prevention

Devise designed to stop or slow the flow of fuel or alert the delivery driver when the tank reaches 90-95% full (depends on the device used). Common types are: Drop Tube Shut Off Valve, Ball Float Vent Valves, or Electronic Alarms.


The extent of petroleum chemicals of concern typically in groundwater both horizontally and vertically.

QAPP - Quality Assurance Program Plan

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Rain Cap

Equipment installed atop typical vertical vent pipes designed to prevent intrusion and potential blockage from rain water, insects, and debris from entering the vent line and allowing the tank to “breathe” when temperature fluctuations, dispensing actions, or fuel deliveries occur.

RBSL - Risk Based Screening Levels

Risk-based, non site-specific, corrective action target levels for CoCs.


Persons, structures, utilities, surface water bodies, sensitive habitats, water supply wells, or any living organisms that are, or may be, affected by a release.

Rectifier Box

Part of an impressed current cathodic protection system. The box converts normal A/C power into D/C current. This current, in conjunction with buried anodes, changes the polarity of the soil surrounding the UST system enough to stop the metal parts from rusting.

Relay Boxes

Electronic switches (typically red or blue boxes), usually installed in the back room near the breaker boxes.  These switches supply power to submersible turbines that pump the fuel to the dispenser when someone picks up the nozzle to fuel their vehicle. They usually make an audible “click” each time they turn on.


Any spilling, leaking, emitting, discharging, escaping, leaching or disposing from an underground storage tank into subsurface soils, groundwater, or surface water.

Release Detection

Determining whether a release of a regulated substance has occurred from the UST system into the environment or into the interstitial monitoring space between the UST system and its secondary barrier or secondary containment around it.

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Secondary Containment

Shear Valve (Impact Valve, Emergency Valve)

Valve typically installed only on pressurized piping systems at the point of the level of the concrete dispenser island. The valve is designed to break in half upon impact of a vehicle or debris large enough to knock over a dispenser. The break causes to the valve to close preventing fuel from being released to the environment during the accident and therefore, limiting the fire and/or explosion hazards.

SIR - Statistical Inventory Reconciliation

Site Check

Soil Boring

A bored, drilled or driven shaft, or a dug hole, where depth is greater than the largest surface dimension.

Soil Excavation

A bored or dug hole for purpose of removing soil that has been impacted by petroleum CoCs.

Soil Vapor Extraction

Removes chemicals using a vacuum system.

Spill Bucket

A container typically installed underground around the fill riser with a lid at ground level. It is designed to catch and contain fuel during the delivery process to prevent petroleum releases to the environment.

SSTL - Site Specific Target Levels

Risk-based corrective action target level for a CoC developed for a particular site under the Tier 2 and Tier 3 evaluations.

Steel Flex Connector

Flexible hose with braided stainless steel mesh covering the outside.  Initially they were utilized to dampen vibration from the STP to fiberglass piping to prevent stress related piping failures. Now they are often utilized for attaching piping runs at both ends because of ease of termination due to flexibility and range of motion.

STP - Submersible Turbine Pump

Pump used to pressurize the product line and push fuel to the dispenser. The turbine is suspended on a supply line and hangs close to the bottom of the tank. The supply pipe is attached to the pump head which sits on top of the tank and can be seen by opening a manway cover.

SUPERB - State Underground Petroleum Environmental Response Bank

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Tier I

Three monitoring wells and eight soil borings, to determine soil and groundwater chemicals of concern, hydraulic properties and risk.

Tier II

A scope of work proposed by a certified site rehabilitation contractor, consisting of established tasks/components in order to provide a comprehensive risk-based assessment of soil and groundwater chemicals of concern, hydraulic properties and risk.

TTT - Tank Tightness Test

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UST - Underground Storage Tank

Any one or combination of tanks (including underground pipes connected thereto) that is used to contain an accumulation of regulated substances and the volume of which (including the volume of underground pipes connected thereto) is 10 percent or more beneath the surface of the ground.

Vapor Recovery

Stage 1: Equipment typically installed attached to the vent line where it exits the tank underground with access at ground level. During a delivery, the driver hooks up a second hose, which removes vapors from the tank and puts them back into the tanker truck.& This prevents the majority of vapors (gas fumes) from being released to the atmosphere. Stage 2: Equipment designed to remove vapors from motor vehicles via a vacuum pump back into the UST during fueling events.

Vent Lines

Piping attached to the top of the UST underground extending above ground (typically 12 feet or greater in height) to allow air to flow freely enabling the tank to “breathe”.  This prevents pressure and vacuum issues that could damage the structural integrity of the tank.

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For more information please contact the Bureau of Land & Waste Management at (803) 898-2000 or visit our offices (note new location).