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The Tanks Compliance and Technology Unit is responsible for compliance evaluations, regulatory determinations and reviews of new technology. The Tanks Compliance and Technology Unit also provides technical assistance to members of the regulated community, underground storage tank (UST) manufacturers and equipment providers, environmental consultants, and any other parties that have questions concerning underground storage tank laws and regulations. This unit also oversees the inspection program and reviews documentation to determine facility compliance with the laws and regulations, and, if necessary assists facilities in their efforts to return to compliance.

In addition, this unit is responsible for updating the operational portion of the UST regulations. For news about upcoming rule changes, visit our webpage at Changes to the Underground Storage Tank Regulations

Operational Compliance
The statute that provides underground storage tank regulatory authority is the Missouri Petroleum and Underground Storage Tank Law, Chapter 319, Section 127, Revised Statutes of Missouri. The regulations applicable to underground storage tanks in Missouri can be found at Underground Storage Tank Regulations. For questions concerning regulatory interpretation or technical assistance, please contact the department's Tanks Compliance and Enforcement Unit at 573-522-5665 or by email.

If you would like information and updates on compliance issues, visit the Tanks Operational Assistance Bulletin to sign up for the electronic newsletter. This email service will provide you with clarification of regulatory requirements, information about upcoming changes, commonly cited violations and other technical assistance. Newsletter archives are available at Operational Tanks Assistance Listserv Archive.

  • New UST system installations
    • The new installation requirements will now apply to the installer. Installers must:
      • Notify the department at least 30 days prior to beginning an installation (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 or interstitial sensors.
      • Have proof of financial responsibility on file with the Missouri Department of Agriculture.
      • Pre-test the tanks prior to installation in accordance with the manufacturer and PEI 100 or API 1615.
      • Test the entire system (0.1 gallon/hour leak threshold) prior to bringing the system into use.
      • Conduct an approved form of release detection if the tank is ballasted with product (if ballasted with water, release detection is not necessary).
    • New installation restrictions (as of Jan. 1, 2012):
      • Ball float valves may not be installed for overfill prevention. If they are to be installed for any other purpose, they may only be installed above 98% of the tank’s capacity.
      • Containment sumps must be installed at:
        • Tank top areas (submersible turbine pump areas or suction piping-tank top junctions).
        • Sub-dispensers.
        • Piping transition/ball valve locations (e.g. manifold piping ball valves, piping unions or splice

      The department also has the authority to shut down an installation that is not being conducted in accordance with the manufacturers’ written procedures or guidance or is not in compliance 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.

      The owner of the new underground storage tank system must register no later than 30 days after bringing the tank into operation (dispensing fuel or using the product for its intended purpose).

  • Cathodic Protection and Interior Lining systems

    Unprotected underground metal components of the underground storage tank 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 underground storage tank 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. More information on allowable NACE certifications, is available on EPA's website.

      Cathodic protection tests must include:

      • Tester, certification and date.
      • Testing standard used.
      • System readings (for impressed current systems, tests must also include the instant off and the decay values, if using the 100mV depolarization).

      For additional guidance on cathodic protection system test reports, please refer to the department’s checklist of information needed to review a cathodic protection system test.

      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, here 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 department may consider written requests for extensions.

      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.)

      Cathodic Protection Test Reports presentation

    For additional guidance on meeting the corrosion protection requirements, please visit EPA’s Office of Underground Storage Tank's corrosion protection.

  • Spill and Overfill prevention equipment

    Many releases at underground storage tank 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. Underground storage tanks 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 underground storage tank 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. Ball float valves may not be installed on any underground storage tank system after Jan. 1, 2012 for overfill prevention and may only be installed for alternative purposes if the ball float valve is installed above 98% tank capacity and proper overfill prevention equipment is in use.

    For additional guidance about the spill and overfill prevention requirements, EPA’s Office of Underground Storage Tank's spill and overfill prevention.

  • Release Detection
    All regulated tanks and piping must have release detection so leaks are discovered quickly before contamination spreads from the underground storage tank site. You must provide your underground storage tank system with release detection (often also called "leak" detection) that allows you to meet three basic requirements:
    1. You can detect a leak from any portion of the tank or its piping that routinely contains petroleum.
    2. Your leak detection is installed, calibrated, operated and maintained in accordance with the manufacturer's instructions.
    3. Your leak detection meets the performance requirements described in the state and federal regulations.

    All release detection equipment (except for manual measuring sticks used for inventory control or statistical inventory reconciliation) must be approved by the National Work Group on Leak Detection Evaluations, (NWGLDE).  All release detection equipment must not only be operated and maintained in accordance with the manufacturer’s requirements, but also in accordance with 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, and specific guidance documents on properly conducting each method of release detection, from inventory control to automatic tank gauging. Visit EPA's Office of Underground Storage Tank's leak detection page for additional information.

  • Statistical Inventory Reconciliation, or SIR
    • Statistical Inventory Reconciliation 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, owners/operators must:
      • 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 the National Work Group on Leak Detection Evaluations.
      • Conduct SIR in accordance with the NWGLDE certification and the manufacturer’s protocol.
      • The monthly data must be submitted, evaluated and reported by the 15th of the following month (e.g., June’s data must be submitted to the vendor or input in the software program, evaluated, and the final report back to the owner/operator 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 underground storage tank 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. Please note, 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. In addition, 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). This monitoring must be conducted every 15 days.
      • Continuous In Tank Leak Detection Systems, which must include a continuous reconciliation feature (SCALD or CSLD testing is not sufficient). This method of release detection conducts constant evaluations to determine if a system is leaking and to monitor inventory leak calculation trends. A Continuous In Tank Leak Detection 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
    • The new regulations require tanks that store fuel for emergency generators to be monitored for leaks. Owners/operators will have to conduct monitoring just like any other tank regulated under the Missouri Underground Storage Tank tank law and regulation. Most of these tanks are already conducting a method of release detection, specifically, an automatic tank gauge. For additional information about release detection options, please review EPA’s guidance document Straight Talk on Tanks: Leak Detection Methods For Petroleum Underground Storage Tanks And Piping or visit its release detection webpage.

      Pressurized piping connected to emergency generators, though, may use interstitial monitoring (e.g., containment sump sensors) with an alarm in lieu of an automatic line leak detector. An alternative option is an electronic line leak detector, equipped with an alarm but not the shutdown function. A mechanical line leak detector is not recommended on pressurized piping connected to an emergency generator tank as it could shutdown fuel flow at a critical moment.
  • Out of use tanks and permanent closure
    • Any tank that is in use (contains product) must comply with all related underground storage tank 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.

      Out of use means that the tank has been emptied so that no more than one inch of product remains, or that no more than 0.3% by weight of the total capacity remains.

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

      • Stop maintaining and inspecting the cathodic protection system or interior lining (only recommended if the owner/operator does not intend to ever use the tank again).
      • Maintain the cathodic protection system or interior lining (conduct all scheduled inspections and associated repairs, ensure 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.

      Once a tank is taken out of use, the following steps must be taken:

      • Within one year/12 months, a site assessment must be conducted.
      • Within five years of being taken out of use (not associated with the date of the assessment), the tank must be permanently closed.

      A site assessment must include sampling of soils and groundwater in the areas where a release would have most likely occurred. Soil borings should be advanced on each side of the underground storage tanks, piping and pump islands/dispensers in accordance Section 5 of the Risk Based Corrective Action Process for Petroleum Storage Tanks, or another process approved by the department.  These sampling points should be advanced so that groundwater samples can be collected, if groundwater is encountered. 

      Note: Sample data conducted for the site assessment may be used for the closure report upon permanent tank closure only if:

      • The tank has not contained any regulated substances since the data was collected.
      • No new or additional signs of a release have been reported or found.
      • A written request to use the data as part of a closure plan has been approved by the department.
      • Additional soil samples underneath the tanks are taken during tank removal. 
      • The permanent closure must be completed in accordance with Section 4 of the Risk Based Corrective Action Process for Petroleum Storage Tanks, or another process approved by the department. Please be aware that additional sampling and requirements may be needed to complete the closure of the tanks. 

      Permanent closure of the tank must be conducted within five years of the date the tank was emptied. 

      The regulations also clarify all regulated tanks that have not been permanently closed, even those out of use prior to 1989, must still be permanently closed in accordance with the regulations. For tanks out of use prior to Aug. 28, 1989, the person(s) who owned the tank immediately prior to its being taken out of use is/are the person(s) responsible for complying with the closure requirements

The department requires all regulated underground storage tank owners and operators to maintain compliance with the laws and regulations concerning underground storage tanks. The Tanks Section works closely with the Tanks Compliance and Enforcement Unit and encourages compliance through conference, conciliation and persuasion. For further information on compliance issues, please email the Tanks Compliance and Enforcement Unit or call 573-522-5665.

Fact sheets and guidance documents for owners and operator of petroleum and underground storage tank systems are available online including:

For Information about Stage I and Stage II vapor recovery please contact the department's Air Pollution Control Program.


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