The Next Step for UST Leak Detection

Interstitial monitoring is likely to be mandated in environmentally sensitive areas, such as over sole source aquifers or in proximity to drinking water supplies. Sully Curran provides insight into what might be around the corner and the relevant codes, which might mandate secondary containment.

This column focuses on the current and the proposed future mandates that are likely to occur for continuous monitoring or secondary containment UST systems. Based on this information, I will predict the direction of future leak detection standards and policies.

Making it possible-In the last decade, technology has been available for reliable continuous leak detection monitoring of underground single-wall tanks and piping. Also, until recently, the interstitial area in some previous secondary containment systems could not be monitored and periodically tightness-tested. For example, an early method to secondarily contain USTs was to use an excavation liner system with a piping trench gutter system. However, there is no practical method to tightness-test the liner at the time of installation or periodically thereafter.

The lack of a tightness-testing method for the open gutter trench liner system also reduced the effectiveness of double-wall tanks when the extent of leaks from piping was recognized. Developing cost-effective systems has been made possible by new continuous leak detection and double-wall tank and piping technology, improved sumps and simplified annular leak detection methods. UST owners are electing to use either continuous monitoring or double-wall containment. For example, 70 percent of the fiberglass tanks being installed today are double-wall.

Leak detection changes-In addition to advances in technology, several other key factors are proving to be instrumental in bringing about changes in leak detection practices for USTs. These factors include:

• Ethanol and Methanol
Federal tax incentives for alternative fuels were increased when Congress passed the 1997 balanced budget agreement. This agreement reduced alternate-fuel federal excise taxes by applying them on a BTU equivalent basis to gasoline. This additional incentive will likely encourage the use of methanol and ethanol-based fuels, but triggers the requirement to handle them in secondarily contained USTs.

Gasohol (i.e., 10 percent ethanol or 5 percent methanol in gasoline) is defined as a "motor fuel" by the EPA, and is compatible with and may be stored in existing single-wall fiberglass and steel USTs. However, methanol and ethanol in higher percentages than in gasohol are classified by the EPA as a hazardous substance, and new or upgraded USTs designed for handling such substances must utilize secondary containment with at least monthly interstitial monitoring.

• Sole Source Aquifers
The EPA groundwater classification system groups aquifers or portions of aquifers according to their water quality and use. There are special classifications for sole sources of drinking water in a geographical region and sensitive areas such as aquifer recharge zones. As a result of EPA established groundwater classifications, state and local zoning ordinances have been required to control contaminating activities over sole source aquifers and in recharge areas of confined aquifers.

Therefore, secondarily contained USTs are now required by state or local (e.g., Long Island, NY, and Austin, TX) ordinances, and double-walled USTs with interstitial monitoring are the accepted systems.

• State and Local Regulations
Secondary containment of all USTs in motor fuel service is required by several states and local governments. States such as California, New York, New Hampshire and Texas (Austin) implemented their requirements before 1989. Later, Florida made secondary containment retroactive for existing USTs.

In addition, California expanded its secondary containment and interstitial monitoring requirement in September 1977 to include all riser pipes (e.g., fill pipe, vent lines) if a ball float valve is used as an overfill protection method.

Proposed International Fire Code
Historically, there have been four model fire codes in the U.S.:

• Building Officials and Code Administrators International's (BOCA), National Fire Prevention Code;

• International Fire Code Institute's (IFCI) Uniform Fire Code;

• Southern Building Code Congress International's (SBCCI) Standard Fire Prevention Code, and the

• National Fire Prevention Association's (NFPA) Fire Prevention Code.

However, recently the International Code Council (ICC) was formed by BOCA, ICBO and SBCCI; now they and NFPA are developing a single national fire code. This fire code will be known as the International Fire Code (IFC). The first draft is available for review; public hearings are scheduled; and the code is scheduled to be published in the year 2000.

The draft language contained in Chapter 35, "Flammable and Combustible Liquids," includes a provision that states, "An approved method of secondary containment shall be provided for underground tank systems" (Section 3504.35 "Underground Tanks"). This provision would mean that all new or replacement USTs (i.e., tanks and piping) containing flammable and combustible liquids will be secondarily contained.

This proposal is subject to a lengthy review process that begins with formal comments due on January 5, 1998. While secondary containment is recognized as a method to rapidly detect a primary tank leak, the new code should also recognize that continuous monitoring of a single-wall system is also a proven method of early leak detection and corrective action. Further, this is a practical solution-should there be a need to retrofit existing single-wall UST systems.

Setting the standard-It is likely that continuous monitoring of single-wall or double-wall underground tanks and piping systems will become the future standard for new and replacement petroleum motor fuel storage. While single-wall USTs, in combination with a periodic leak detection method, has been an accepted technology, more of the authorities having jurisdiction (AHJ) are considering either continuous monitoring or secondary containment.

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