There are more than 20,000 regulated above-ground storage tanks (ASTs) currently in use across Minnesota.
Product types in the tanks can range from food-based to petroleum to hazardous materials. When properly designed and operated, ASTs are very safe. However, ASTs and their associated piping are subject to construction flaws, corrosion, stress, cracking, weld and valve failures, overfills, spills during transfers, and occasionally tank rupture.
When ASTs leak or spill, the stored substances may flow into lakes and rivers, migrate through the soil to the water table, or catch fire, thereby contaminating soil, ground water, or surface water and creating hazards to aquatic life and human health.
ASTs which store liquid substances that may pollute the waters of the state are regulated by Minnesota Rules, Chapter 7151, if site capacity is less than one million gallons. Larger facilities (facilities with a capacity of one million gallons or more) are regulated by permits negotiated with MPCA. The goal of regulating ASTs is to prevent spills and leaks by providing storage tank owners with various safeguard options. These options include safeguards such as: secondary containment to minimize the impact of a release, corrosion protection and overfill prevention to prevent releases, and tank monitoring for leak detection. The level of protection needed depends on the type of product stored, the size of the tank, and the date that the tank was installed.
Which ASTs are subject to MPCA regulation?
Most tanks located above ground containing liquid substances (i.e., not gaseous or solid at ambient temperature and pressure) are subject to the MPCA's rules for design and operation of ASTs. Tank appurtenances such as piping, valves, containment areas, and loading areas, are also covered. Definitions in the rules can be found at this link. Minnesota Rules, Chapter 7151.1200
Some types of ASTs are exempt from the regulations:
- ASTs with a capacity of 500 gallons or less;
- farm ASTs;
- residential ASTs storing 1,100 gallons or less of motor fuel used for noncommercial purposes;
- ASTs holding 1,100 gallons or less used to store heating oil for on-site consumption;
- wastewater treatment equipment including a wastewater clarifier, wastewater treatment basin a tank regulated by a National Pollutant Discharge Elimination System permit (NPDES), Sewage Disposal System permit (SDS), or another pretreatment system permit;
- equipment holding substances used for operational purposes like integral hydraulic lift tanks, lubricating oil reservoirs for pumps and motors, and electrical equipment;
- ASTs containing hazardous wastes subject to a treatment or storage permit;
- stormwater collection systems and septic systems;
- ASTs containing agricultural chemicals regulated under Minnesota Statutes Chapter 18B, Chapter 18C, Chapter 18D;
- a vehicle like a tank truck or a railroad car designed to transport substances from one location to another unless it remains in the same location more than 30 days;
- ASTs containing drinking water, filtered surface water, demineralized water, noncontact cooling water, or water stored for fire or emergency purposes;
- ASTs with a capacity of 1,100 gallons or less that are not located within 500 feet of Class 2 Surface Water;
- tote tanks (See Tote Tanks fact sheet - t-a2-02)
- indoor tanks (See Indoor Storage Tanks fact sheet)
- compressed gas tanks
- stainless steel tanks containing any substance that is not a petroleum product or hazardous substance; and
- a surface impoundment, pit, pond, or lagoon.
Owners of ASTs with a capacity of 500 gallons or more, which contain petroleum or hazardous substances used commercially, must notify the MPCA of the existence of these tanks.
At the federal level, the Environmental Protection Agency requires non-transportation-related facilities with a total above-ground oil storage capacity of greater than 1,320 gallons to meet Spill Prevention, Control, and Countermeasure (SPCC) requirements. Both petroleum and non-petroleum oils (e.g., vegetable oil) are regulated according to SPCC. Other federal requirements relate to spill response and spill reporting.
MPCA's Tank Compliance and Assistance Program provides assistance to tank owners and evaluates compliance of facilities through inspection and investigations, and determines appropriate enforcement actions when violations are discovered.