an underground storage tank installation in a lined pit

An underground storage tank, also called a UST, is defined as a tank and any underground piping connected to the tank, that has at least 10 percent of its combined volume underground. In 1984, the federal Resource Conservation and Recovery Act established a regulatory program for USTs, found under RCRA Subtitle I. For information about what is happening at the national level, visit the U.S. Environmental Protection Agency's (EPA) Underground Storage Tanks (USTs) webpage. This particular website is a tremendous resource with federal regulations, frequently asked questions, information from all 50 states, technical bulletins and fact sheets.

Depending on what is or was stored in the UST and the USTs purpose, the UST may be regulated under Missouri's Underground and Petroleum Storage Tank Law, found in Missouri Revised Statues, sections 319.100 to 319.139, RSMo. The Underground Storage Tank Regulations are found in Code of State Regulations 10 CSR 26-2. The department's goal is to protect human health and the environment by building conditions under which good management of UST systems is common business practice. For information about financial responsibility requirements, visit Underground Storage Tank Financial Responsibility. For information about UST cleanup and closure, visit Regulated Storage Tank Cleanup and Closure

Note: The Missouri Department of Natural Resources does not regulate the operation of above ground storage tanks, also referred to as ASTs. For information about AST operation and inspection regulations, please contact the Missouri Department of Agriculture by telephone at 573-751-5636.


The department, tank owners and operators, installers, fuel suppliers and insurance providers all recognize that properly installing USTs, piping and monitoring systems is essential. The technical regulations regarding USTs can be found in Code of State Regulations 10 CSR 26-2. Before installing a new UST system, please be aware that vapor recovery requirements may also apply to your facility. Please visit the department's Vapor Recovery webpage to learn more about vapor recovery requirements in Missouri. If you have additional questions, please contact the department's Air Pollution Control Program

New Installation Requirements

Installers must: 

  • Have proof of financial responsibility on file. The Missouri Department of Agriculture requires all installers to be registered and provide proof of financial responsibility before installing a new UST system. For more information concerning this requirement, review the department's Financial Responsibility for Installers and Manufacturers of Underground Storage Tanks - PUB2423 fact sheet. You may also contact the Missouri Department of Agriculture, Weights, Measures and Consumer Protection Division, by telephone at 573-751-5636.
  • Notify the department at least 14 days before beginning an installation. The installer must complete and submit to the department, a Notification Installation of New Underground Storage Tank System MO 780-1949 form. New installation notifications expire after 180 days. 
  • Comply with PEI RP 100 or API RP 1615 and the manufacturer(s)’s installation guidance, practices and instructions.
  • Comply with all manufacturer certification or training requirements for equipment including, but not limited to, tank, piping, automatic tank gauge, line leak detector and interstitial sensors. 
  • Pre-test the tanks before installation, according to the manufacturer and PEI RP 100 or API RP 1615. 
  • Test the entire system (0.1 gallon/hour leak threshold) before bringing the system into use. 
  • Conduct an approved form of release detection if the tank is ballasted with product. Please note, you must install approved spill and overfill prevention equipment before receiving a fuel delivery.  Also, if you are in St. Louis City, St. Louis County, St. Charles County, Franklin County or Jefferson County, you must also install vapor recovery equipment before receiving the delivery. If ballasted with water, release detection is not necessary.

Additional Information

Please notify the department at least five days before work begins to install the UST system, in order to schedule the inspector's visit. In addition, please notify the department of any scheduling changes or delays. The purpose of these inspections is to not only confirm equipment installed, but to help identify and minimize any potential concerns before installation is complete. To schedule the inspection, please contact the department's installation inspection staff by telephone at 800-361-4827 or 573-522-5665, or by email at

The department has the authority to shut down an installation that is not being conducted according to the manufacturers’ written procedures or guidance, or does not comply with PEI RP 100 and API RP 1615. The shutdown may be restricted to the portion of the installation in question. The shutdown will be released upon approval by: a) the equipment manufacturer (if appropriate), b) the tank owner/operator or c) the department. 

All regulated USTs must be registered with the department. The owner of the new UST system must register no later than 30 days after bringing the tank into operation (dispensing fuel or using the product for its intended purpose). For more information about UST registration, visit Underground Storage Tanks Registration.


Missouri has a composite inspection program for underground storage tank inspections. The Missouri Department of Natural Resources and Petroleum Storage Tank Insurance Fund (PSTIF) have a joint contract inspection program, which consists of contract inspectors, department inspectors and compliance review staff.

The current contract inspector is Rounds and Associates. Their inspection manager is Mr. Brian Wiegert. He may be contacted at 855-808-8686.

All regulated facilities will be inspected at least once every three years, according to the requirements outlined in the federal Energy Policy Act. In addition to the required active and out-of-use facility inspections, department inspectors are inspecting new tank and piping installations. Inspectors may also investigate complaints and suspected releases.

The facility will receive a notification letter before a contract inspection. For non-PSTIF insured facilities, this notification will include a Request for Underground Storage Tank Records MO 780-1968 form. These records must be submitted to the department's Underground Storage Tanks Compliance and Enforcement Unit. If you have any questions, contact the department's Underground Storage Tanks Compliance and Enforcement Unit.


The department's main goal is to help facilities achieve and maintain compliance with the standards, laws and regulations concerning USTs. The department is responsible for new technology compliance evaluations, regulatory determinations and reviews. The department oversees the UST inspection program, reviews documentation to determine facility compliance with the laws and regulations and, if necessary, assists facilities in their efforts to return to compliance. The department also provides technical assistance to members of the regulated community, UST manufacturers and equipment providers, environmental consultants and any other parties that have questions concerning UST laws and regulations. For questions concerning regulatory interpretation or technical assistance, please contact the department's Tanks Compliance and Enforcement staff by telephone at 800-361-4827 or 573-522-5665, or by email at Information about proposed rule changes is available in the Regulatory Action Tracking System

If you would like to receive regular information and updates about environmental compliance issues, please click on the "Get Updates on this Issue" button to the right to subscribe to the department's Operational Tanks Assistance Bulletin electronic newsletter. The bulletin is directed towards those involved in properly maintaining, operating, testing and monitoring USTs and designed to keep all facilities informed so they can meet or exceed the environmental requirements. The bulletin provides clarification of regulatory requirements, information about upcoming changes or additions to federal or state regulations, commonly cited violations and other technical assistance. For information about other hazardous waste issues, visit the department's Hazardous Waste Compliance and Assistance webpage.

Operational Compliance

Any tank that is in use (contains product) must comply with all related UST regulations (financial responsibility, release detection, corrosion protection, including cathodic protection and lining requirements). Once a tank is brought into operation for the first time, “in use” is based solely on whether the tank contains product and is not related to whether or not product is being used or dispensed.

UST Operator Training

The Missouri operator training regulations, found in 10 CSR 100-6, require the owner or operator to designate at least one trained Class A/B Operator and designate trained Class C Operators for each of their in use facilities. At least a trained Class C Operator must be present anytime the tank is dispensing product. The Petroleum Storage Tank Insurance Fund Board of Trustees created an online operator training program, which is free to Missouri operators. State-issued certifications from Arkansas, Oklahoma, Kansas, Iowa, Illinois, Kentucky or Tennessee are also accepted. Complete and submit to the department a Class A/B & Class C Operator Designation Form and Class C Operator Training Certification MO 780-2636 form.

New UST System Installations

* For compliance information, please refer to the Installation tab above.

Cathodic Protection and Interior Lining Systems

Unprotected underground metal components of the UST system can corrode and release product through corrosion holes. In addition to tanks and piping, metal components can include flexible connectors, swing joints and turbines. All metal UST system components that are in contact with the ground, soil or water and routinely contain product must be protected from corrosion. 

  • Cathodic protection system testers must be certified (current at the time of the test) by either NACE International, Steel Tank Institute (sacrificial systems only) or International Code Council. For more information on allowable NACE certifications, visit EPA's Underground Storage Tanks (USTs) webpage. 
  • Cathodic protection tests must include the following information. For additional guidance on cathodic protection system test reports and information needed to review a cathodic protection system test, review the Cathodic Protection Test Report Minimum Guidelines.
    • Tester, certification and date
    • Testing standard used
    • System readings
    • For impressed current systems, instant off and the decay values, if using the 100mV depolarization
  • Tank owners/ operators must maintain a log of the rectifier readings. These logs must now include relevant system data (e.g., green or red light, voltage or amperage meter readings or hour meter readings). If any of these readings change, the owner/ operator must investigate and confirm that the cathodic protection system is still operating properly and providing adequate protection for the steel system components. While you are not required to use any specific form for this rectifier log, the department's Cathodic Protection System Rectifier Check Log Sheet is an example of an acceptable form.
  • An integrity test, which evaluates the actual thickness of the steel shell, must be conducted if:
    • The cathodic protection system has been off, unhooked or damaged for more than 90 days
    • The system failed during a routine test and was not adequately repaired or re-tested with passing readings within 90 days
  • The interior lining of a steel tank may not be repaired, replaced or re-lined without first conducting, and passing, an integrity assessment of the tank shell. All integrity assessments must include actual steel shell thickness readings.
  • All lined tanks, whether lined for upgrades, repair or compatibility, must be routinely inspected, maintained and repaired, if warranted. The tank must be inspected within 10 years of the initial lining and every five years thereafter, regardless of whether or not the tank is re-lined. A tank is not granted another 10 years before inspecting the interior lining simply because the tank was re-lined. 

The department may consider written requests for extensions. For additional guidance about meeting the corrosion protection requirements, visit EPA’s Release Prevention for Underground Storage Tanks (USTs) webpage.

Spill and Overfill Prevention Equipment 

Many releases at UST sites come from spills made during delivery. Spills usually result from human error and can be avoided if everyone involved in the fuel delivery follows industry standard practices for tank filling.

  • USTs must have a spill bucket sealed around the fill pipe to contain small spills.
  • If a tank is accidentally overfilled, large volumes of product can be released. Your UST must have overfill protection equipment, unless deliveries are less than 25 gallons. The three main types of overfill protection devices are:
    • Automatic shutoff devices
    • Overfill alarms
    • Ball float valves
  • All deliveries must use a “lock-on” delivery connection, unless the department has approved a written, alternative delivery plan that adequately prevents spills and overfills.
  • Ball float valves may not be used with safe suction systems, suction systems with check valves that are not completely contained within a building, with any open vapor release port (e.g., open tank top fittings or co-axial drop tubes) or pressurized deliveries.
  • Spill and overfill equipment must be tested at least triennially. Please note, ball float valves are no longer acceptable overfill devices. Existing sites may continue to use them as long as they pass their triennial test. However, if they fail, then the facility must install an automatic shut off device or an audible, outside overfill alarm.

For additional guidance about the spill and overfill prevention requirements, visit EPA’s Release Prevention for Underground Storage Tanks (USTs) webpage.

Release Detection

All regulated tanks and piping must have release detection so leaks are discovered quickly before contamination spreads from the UST site.

  • You must provide your UST system with release detection, also called "leak" detection, that allows you to meet three basic requirements: 
    • Detect a leak from any portion of the tank or its piping that routinely contains petroleum
    • The leak detection is installed, calibrated, operated and maintained according to the manufacturer's instructions
    • The leak detection meets the performance requirements described in the state and federal regulations
  • Except for manual measuring sticks used for inventory control or statistical inventory reconciliation, all release detection equipment must be approved by the National Work Group on Leak Detection Evaluations (NWGLDE).
  • All release detection equipment must be operated and maintained according to both the manufacturer’s requirements and the NWGLDE certification. 

In addition to the state regulations, EPA provides guidance documents about release detection, both general criteria and the basics of approved methods. EPA also provides specific guidance documents on properly conducting each method of release detection, from inventory control to automatic tank gauging. For additional information, visit EPA's Release Detection for Underground Storage Tanks (USTs) webpage. 

Statistical Inventory Reconciliation

Statistical Inventory Reconciliation (SIR) has been approved as an “other” or alternative release detection method for years, but is now officially outlined in the regulations. To properly conduct SIR, tank owners/ operators must meet these criteria: 

  • Take readings to at least the nearest 1/8th inch. Using an automatic tank gauge meets this criteria
  • If using a tank stick to take measurements, a drop tube must be installed
  • If using a tank stick, the correct tank chart must be used for converting the height reading to gallons
  • Be able to accurately measure the full range of the tank height 
  • Check for water at least once every 30 days
  • Compare delivery reports to pre- and post-delivery measurements
  • The SIR vendor or program must be approved by NWGLDE
  • Conduct SIR according to both the manufacturer’s requirements and the NWGLDE certification
  • The monthly data must be submitted to the vendor or input in the software program, evaluated and the final report back to the owner/ operator by the 15th of the following month (e.g., June’s data must be submitted, evaluated, and reported no later than July 15)
  • Retain all supporting data, including the daily inventory, sales, deliveries, overages/ shortages, monthly detailed reports and exception information, if applicable
  • Evaluate independent tank systems separately, even if they contain the same products. Manifolded systems are typically evaluated as one system
High-throughput Facilities

High-throughput facilities are those facilities with at least one UST system (a single tank or a manifolded tank system) through which more than 800,000 gallons of product is dispensed or used per month. The following requirements apply only to the high-throughput system or systems. The high-throughput tank system must be monitored for leaks using either: 

  • Interstitial Monitoring - Continuous, electronic interstitial monitoring may be used for any double-walled or secondarily contained tank or piping system. The secondary containment or outer wall must be able to contain any leak from the inner wall, with the interstitial monitoring system able to detect any failure of the inner wall. The secondary containment or outer wall must also prevent water intrusion or water interference from affecting the interstitial monitoring system. 
  • Vapor Monitoring - Must be compatible or approved for the product stored. Standard vapor monitoring is not approved for diesel, but chemical marker testing is. Vapor monitoring must be conducted every 15 days. 
  • Continuous In-Tank Leak Detection (CITLD) System - The system must include a continuous reconciliation feature. Statistical continuous automatic leak detection (SCALD) or continuous statistical leak detection (CSLD) testing is not sufficient. This release detection method conducts constant evaluations to determine if a system is leaking and monitor inventory leak calculation trends. A CITLD System is more precise and is specifically designed for high-throughput facilities. 
  • Another method approved by the department that is appropriate for high-throughput facilities. 

Please note, these requirements apply only to the high-throughput tanks and do not necessarily apply to all tanks at a facility.

Emergency Generator Tanks

USTs storing fuel for emergency power generators must meet the release detection requirements required under 10 CSR 26-2. EPA recently revised its determination on emergency generators tank release detection requirements. Beginning Jan. 1, 2020, it is a requirement to perform a monthly visual inspection of the emergency generator's day or belly tank. This can be included in the monthly walk through inspection log to satisfy the release detection requirements. For emergency generator UST systems installed before July 1, 2017, you may use one of the methods:

  • Secondary containment with interstitial monitoring
  • Automatic tank gauging (ATG) systems (performing in-tank static tests)
  • Continuous in-tank leak detection (CITLD)

Emergency generator UST systems installed on or after July 1, 2017, must be secondarily contained with sump sensors and use interstitial monitoring upon installation. To make sure your release detection equipment is working properly, you must be doing the following: 

  • Test your release detection equipment yearly
  • Conduct walkthrough inspections every 30 days to visually check your release detection equipment and maintain applicable records of those checks
  • Conduct yearly walkthrough inspections to visually check containment sumps and hand-held release detection equipment, such as tank gauge sticks and groundwater bailers

EPA recently reevaluated The Energy Policy Act of 2005 concerning UST emergency generators systems. Day tanks and belly tanks that are part of the emergency generators will now require a monthly visual check as part of the release detection check. 

For more information about release detection options, visit EPA’s Straight Talk on Tanks: Release Detection Methods For Underground Storage Tanks And Piping or Release Detection for Underground Storage Tanks (USTs) webpages.

Out of Use Tanks and Permanent Closure

When a UST is out of use, it means the tank has been emptied so that no more than one inch of product remains, or that no more than 0.3 percent by weight of the total capacity remains. Once a tank is taken out of use, a site assessment must be conducted within 12 months. Tanks that remain out of use must be permanently closed within five years of being taken out of use (not associated with the date of the assessment). The regulations clarify all regulated tanks that have not been permanently closed, even those out of use before 1989, must still be permanently closed according to the regulations. For tanks out of use before Aug. 28, 1989, the person(s) who owned the tank immediately before it being taken out of use is the person(s) responsible for complying with the closure requirements. For information about how to perform a UST site assessment or closure, visit the department's Regulated Storage Tank Cleanup and Closure webpage.

The cathodic protection system/ interior lining on an out of use tank does not have to be maintained after completing the site assessment. The tank owner/ operator has the following options for their out of use tank(s):

  • Stop maintaining and inspecting the cathodic protection system or interior lining. This is only recommended if the owner/ operator does not intend to ever use the tank again. 
  • Maintain the cathodic protection system or interior lining by conducting all scheduled inspections and associated repairs, ensuring the cathodic protection system is on, functioning and is being monitoring. 

If an owner/ operator chooses option one but then opts to reopen the tank, the tank must pass a tank assessment/ tightness test. If the tank is steel:

  • Lining: The lining must either pass inspection or be repaired/ reinstalled
  • Cathodic Protection: The cathodic protection system must be redesigned or re-evaluated and re-energized by a cathodic protection expert