ASTs: Above and Beyond

Due to their many advances in design, modern aboveground storage tanks are able to store a wide range of hazardous substances successfully while protecting human health and the environment

The other day a person preparing to make a presentation on small aboveground storage tanks (ASTs) asked me for a "sexy spin" on fuel tanks. I wasn't sure if I should be amused or upset. Fuel tanks are designed to hold fuel. That's it. There isn't anything at all sexy about them in my mind and you surely don't want them to make your life exciting. ASTs are one of those things that irritate you if your neighbor has one with a problem, cause you considerable stress if you have one with a problem, and something you don't particularly think about if you have one that is performing its job correctly. However, even though we often take ASTs for granted, they play a crucial role in protecting people and the environment from the adverse affects of accidental releases of hazardous substances like petroleum hydrocarbons.

AST Overview
ASTs can be broken down into two basic groups: 1) tanks manufactured under American Petroleum Institute (API) requirements, and 2) tanks manufactured under Underwriter's Laboratory (UL) 142 standard. Tanks manufactured under API requirements are large usually field fabricated tanks typically used by oil companies and distributors. Tanks manufactured under UL or SWRI requirements are normally shop-fabricated tank s and are small enough to be transported over the road. The shapes can be vertical cylindrical, horizontal cylindrical, rectangular, or horizontal oval. Typical AST sizes range from 100 gallons to 12,000 gallon, although they can be made larger. There are a large number of these smaller shop-fabricated tanks located around your town, state, country, and world. You can find them everywhere, at the phone company, the dry cleaner, the cemetery, the hospital, the hotel, the marina, the airport, the car dealer, the road department, and on farms.

Currently, there are three different types of small ASTs being used. The simplest is an unprotected tank, which can be single wall or double wall, and is manufactured according to UL 142 requirements. The next step up is a "fire-resistant" tank manufactured according to UL 2080 requirements, and the third is a "protected" tank manufactured according to UL 2085 requirements. Fire resistant and protected tanks are required by the listing to incorporate secondary containment and are not required by most fire codes to have a dike area around them so long as they are not larger than 12,000 gallons. The U.S. Environmental Protection Agency (EPA) recognizes the integral secondary containment with the stipulation that the tanks have "overfill prevention measures that include an overfill alarm and an automatic flow restrictor or flow shut-off" and all product transfers are constantly monitored.

SPCC Rule Update
There are several areas of recent changes in the small AST arena, including an update in the rule related to preventing accidental releases. Most AST facilities are currently subject to the Spill Prevention Control and Countermeasures (SPCC) rule if the facility has the capacity to store more than 660 gallons of fuel, although the 2002 rule update has raised the cutoff to 1,320 gallons. Fines for the failure to prepare and implement a SPCC plan can be substantial. Tank owners/operators should find out how much capacity their site has, and if applicable, should make themselves knowledgeable about the SPCC rule. The implementation dates for the SPCC rule, which was enacted on July 17, 2002, have twice been extended, partially to "provide sufficient time for the regulated community to undertake the actions necessary to prepare and update their plans in light of a recent partial settlement of litigation." The new compliance deadlines are as follows: February 17, 2006 to amend an existing SPCC plan, and August 18, 2006 to implement the amended SPCC plan. Affected facilities that become operational after August 18, 2006, must prepare and implement an SPCC plan before starting operations.

Tank Inspection Guidelines
One of the items recognized in implementing a strong spill prevention program is an ability to inspect the tank. Historically, regulated tanks were of the large American Petroleum Institute (API) version, so it was natural that the API requirements should be brought forward into the new regulations. Large tanks typically sit on the ground, so inspecting under the tank is a problem, and a failure is a major event. However, there is a tremendous difference between the structure and design of field erected tanks and shop-fabricated tanks, especially the fire resistant and protected versions. Most of the API tests are not applicable or impossible to perform. Additionally, those tanks were designed to overcome many of the liabilities of field-erected tanks, such as being able to inspect under the tank. A leaking fire resistant or protected tank contains the fuel in the integral secondary containment and, while a leak is not pleasant, it is far from have the catastrophic impact that an accidental release from a field-erected tank can cause.

At the request of EPA, the Steel Tank Institute (STI) drafted a shop-fabricated tank inspection standard, STI SP-001. Unfortunately, parts of the standard were too vague to be very useful, while other parts of the standard were written from a noticeably single manufacturer's view. In order to improve this standard, a team of consultants, tank owners, and testing experts on the committee with STI manufacturers are currently working on an update to STI SP-001. The update is expected to be finished some time in 2005.

Enhanced Vapor Recovery Program
The California Air Resources Board (CARB) is working to reduce emissions from gasoline storage tanks and delivery systems through a program known as enhanced vapor recovery (EVR). As part of the process, it has been discovered that tanks, which are uninsulated ASTs, lose considerably more vapors over the course of a year than do underground storage tanks (USTs) or insulated ASTs. While not technically part of the EVR program, owners of uninsulated ASTs can realize a reasonably quick return on investment (ROI) by purchasing a fire resistant or protected tank. Although testing is still in progress, the ROI appears to be a few months. Both of these tank styles stabilize the fuel temperature and reduce vapor emissions, which aids in keeping the gasoline in the tanks instead of having expensive fuel vaporize into thin air.

For those who cannot justify the major expense of buying a new tank, they can choose the less expensive alternative of replacing their existing atmospheric vent with a pressure/vacuum vent, which is a minimal expense of approximately $60.00. This choice helps reduce vapor emissions to a certain extent.

The proper selection of the most efficient ASTs for your facility can aid in lowering fuel costs. As well, appropriate maintenance of your ASTs helps to prevent accidental discharges and ensure better protection of your workers and the environment.

This article originally appeared in the 07/01/2005 issue of Environmental Protection.

About the Author

David P. Harris is an engineer and vice president of marketing with Convault Inc.

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