How to Close USTs by the Book

Many thousands of U.S. tanks still must be closed to meet the 1998 deadlines. John Hartmann explains what tank owners must do to satisfy the requirements, while protecting workers, the public and the environment.

This article focuses on some of the more significant technical requirements and practices related to permanent UST closures. These requirements and practices are designed to protect the environment from leaking UST systems; the public from fires and explosions; and workers from the safety and health hazards involved in tank closures.

Prior to the adoption of the UST regulations by EPA in 1988, the national fire codes, API standards, OSHA, and other codes and standards included provisions related to the safe and effective closure of storage tanks. The 1988 EPA regulations adopted many of those provisions by reference, including the following requirements that must be met when any UST is temporarily or permanently closed:

• For temporary closures (less than three months), tanks must continue to meet corrosion protection and release detection requirements that apply to tanks in use. This is true also for temporary closures up to 12 months duration, so long as: (1) the vents are left open and are functioning; and (2) all other piping, pumps, manways and ancillary equipment are capped and secured.
• Tanks out of service for more than 12 months must be permanently closed if they do not meet the performance standards for new USTs or the upgrading requirements for old USTs (except for the spill and overfill equipment requirements). Substandard USTs must be permanently closed after the 12-month period, unless an extension is obtained.

Permanent UST closures (and changes-in-service) are much more complex than temporary closures and must comply with considerably more technical requirements. The remainder of this article deals with permanent closures.

Excavation has been done to the top of tank. Piping is still attached.

Getting the right guidance
Closure of a tank that has contained motor fuel or other flammable or combustible liquids, leaded fuel or benzene is a hazardous exercise—one that should be done only by properly trained personnel. Responsible managers should review all pertinent EPA and OSHA regulations as well as API, PEI and NFPA standards, as this information provides guidance on work procedures, as well as safety, fire and environmental requirements for closures.

The EPA regulations on permanent UST closure are in 29 CFR 280.71-74 (Technical Standards for Owners and Operators of Underground Storage Tanks). The regulations require that advance notice (usually at least 30 days) be given to the implementing agency before beginning closure. The closure procedures include emptying and cleaning the tanks, and either removing them from the ground or filling them with a solid inert material.

The EPA regulations specifically cite the following API documents as UST cleaning and closure procedures that may be used to comply with the regulations:

• RP 1604, Removal and Disposal of Used Underground Petroleum Storage Tanks. At the time the regulation was established, the current edition of RP 1604 was 1987. However, according to API, compliance with the 1996 edition meets the requirements of the 1987 edition.
• Pub. 2015, Cleaning Petroleum Storage Tanks.
• RP 1631, Interior Lining of Underground Storage Tanks.

In addition to the above, NFPA 30-2-4.4.2, Temporary and Permanent Closure of Underground Storage Tanks, contains significant and valuable guidance on tank closures.

Worker monitors tank atmosphere before removal.

Permanent closure
No matter whether the tanks are to be left in the ground or removed, the planning and execution of the work must include or consider the following:

Scope of work. Determine why the owner wants to close the tanks. Find out if there have been indications of leakage. If an assessment of the site reveals environmental damage, federal regulations require corrective action to stop leaks, contain spills and prepare a plan for cleaning the site.

Other site characteristics. Inspect the site to make sure adequate access is available for equipment. If tanks will be removed from the ground, determine where they can be temporarily stored. Determine the location of underground and overhead utilities, products stored and associated hazards and precautions. Check clearances of overhead utility lines.

Safety/health hazards. Determine what products have been stored in the tanks. Usual hazards are flammable and combustible liquids, benzene and lead; however, USTs at industrial facilities may have been used to store a wide variety of products.

Determine the upper and lower explosive limits for use of these products for monitoring purposes during construction. You can find this information from material safety data sheets from OSHA. Also, identify and provide the needed personal protective gear, as well as the meters (properly maintained and frequently tested) for measuring the atmosphere for hazardous vapors and, in some cases, oxygen. Formal HazWoper training may be required for workers.

Site safety/health plan. OSHA regulations require a site safety plan for tank closures. The plan must include general information about the scope of the project; a hazard evaluation; a listing of required personal protective equipment; a description of the decontamination procedures; information in case of an accident; and so on. The individual placed in charge of ensuring adherence to the site plan throughout the project must acknowledge his responsibilities by signing the plan.

Other safety measures. Means for barricading the site, signs prohibiting smoking, means for bonding and grounding of spark producing equipment, particularly that used for purging and inerting, must be provided. There are numerous stories of “yank-a-tank” accidents, usually resulting from reliance on under-trained or under-supervised employees to recognize the hazards and appropriate precautions necessary.

Excavating around sides will release tank for removal.

Notification of responsible agencies. Find out where the federally required advance notice of the closure must go. Depending on the jurisdiction, this notice may need to go to the State UST administrator and the state and local fire authorities.

Securing permits. Tank closure work may require a variety of permits, depending upon local rules. For instance, a permit may be required for the disposal of tanks to be removed from the site. Since issuance of permits may sometimes involve a delay of two months or more, start the process early.

Weather. Atmospheric conditions are a significant factor in the degree of hazard at a site on a particular day. Vapors tend to accumulate more on hot, windless humid days. We do not recommend closure of tanks during rain, particularly if it is attended by lightning. (Static discharge occurs more frequently on very dry days.)

Product and sludge removal. At some point early in a closure job, liquid or sludge from the tank must be removed. Piping should be drained into the tank before disconnecting. The materials removed must be classified and disposed of according to environmental regulations.

Excavating. Excavating is required to close or remove an UST. Excavating near piping and tank top appurtenances should be done by hand until the location of all sources of product leakage are identified. Since the area may contain vapors in the explosive range, care to avoid sparks and static discharge are essential.

Monitoring. Frequently monitor the tank atmosphere with a combustible gas indicator to determine if the tank is safe to remove, fill or transport. Monitor before and during purging and inerting and always before cutting. Also monitor tanks already made safe as it is not uncommon for the mixture of air and fuel in an already purged tank to become explosive due to the release of vapors from sludge, scale and rust.

Removal of an old and previously leaking tank is a cumbersome process.

Purging. The tank’s internal atmosphere typically exceeds the upper explosive limit (UEL). Purging the tank vapors requires diluting them to below the lower explosive limit (LEL) by replacing the potentially explosive mixture of fuel and air inside the tank with air. It is considered safe to proceed with the work when the mixture is 10 or 20 percent of the LEL for petroleum tanks.

Air can be introduced by using a diffused-air blower or by a ventilation system employing an eductor. Large volumes of air are passed through the tank and vented to the atmosphere. Ground purging devices prevent static discharge.

The tank must vent at least 12 feet above the ground to prevent concentrations of vapors from developing.
WARNING: During the purging process, the tank atmosphere will pass through the explosive range.
During this time of maximum danger, non-essential work should be suspended in the tank area.

Inerting. Inerting reduces the concentration of oxygen by replacing the tank vapors with a heavy inert material, such as carbon dioxide or nitrogen. Carbon dioxide, usually in the form of dry ice, is crushed and poured into several openings along the top of the tank. Nitrogen is provided in cylinders under pressure.

The tank atmosphere is monitored with an oxygen meter. The tank is considered safe when the oxygen content of the tank atmosphere is one to 10 percent.

Air may re-enter the tank during monitoring or through holes. Plug all openings to prevent air from finding its way into the inerted tank, which will prevent an explosive mixture from being re-established.

Ground the gas source as well as the tank to prevent static discharge.

Storage. There is a possibility that some of the excavated materials will be contaminated. An area for temporary storage of excavated materials must be identified and provided with a means to prevent release into the atmosphere and soil.

Record-keeping. Document everything. There is no better way to resolve disputes than to take accurate notes of all aspects of the project, including the size, types and location of tanks.

Preparing to transport

Closure in place
Closure in place requires the removal of all fuel and sludge from the tank to prevent it from leaking into the soil after closure; cleaning the tank surfaces; disconnecting and plugging piping; and then filling the tank with an inert material. To accomplish this, excavating is generally required to expose the tank top, and sufficient openings are made in the tank to introduce the inert material.

Inert materials. In most cases, sand or a lightweight cement slurry is poured into openings along the tank top until the tank is completely filled.

Expanding foam. Expanding foam products are available and approved in some jurisdictions. As the foam is injected into tank openings, it expands to fill the tank. Foam is generally placed in layers for maximum benefit.

Plastic covers the spoil that is temporarily stockpiled on-site. This practice minimizes rain and surface water infiltration.

UST removal, handling and disposal
Removal of an UST can commence after it is purged or inerted.

Piping must be disconnected or plugged. Tank openings are tightly plugged except for one plug that must have a G inch hole through it to permit the tank to vent and to prevent over- or under-pressurization.

Excavating the area around the tank is necessary to facilitate removal. The vacuum which may exist between the tank and the surrounding soil may be broken by forcing compressed air beneath the tank. Spoil from the excavation may be hauled away or stockpiled on-site, depending on its condition. Plan ahead for on-site storage.

After removal, holes found in the tank are sealed to prevent air or fuel from re-entering or residue from leaking out. The UST must be secured from movement by chocking and periodic monitoring of the tank’s atmosphere must continue.

The excavation must be inspected and tested for the presence of contamination to determine the need for additional soil or ground water removal. This testing and evaluation should be made by a person qualified to do environmental assessments or by the authority having jurisdiction over environmental conditions not covered here (40 CFR 280.72).

Following completion of any required environmental work, the excavation should be filled with uncontaminated soil.

“Jaws” hydraulic shear is used to cut tanks up at scrap yard.

Disposal and Handling. Plans for disposal of the tank must be made in advance. The disposal method will be determined by the tank material of construction, whether or not there are tightly adhering internal or external coatings and the possible presence of lead residue.

The removed tank should be lifted, not rolled. Unless it is to be immediately hauled off-site, the UST must be stored in a secure area not open to the public. The G inch vent hole should be inspected to ensure it is open.

The tank should be clearly labeled with its former contents, present vapor state, the vapor-freeing method employed and a warning against reuse. Rules in many jurisdictions require such tanks to be disposed of only in designated locations and also require that they not be used for non-petroleum purposes, such as farm water tanks.

The UST should be hauled from the site the same day as it is removed. The UST must be secured to the transport and warning signs posted. Before loading and leaving the site, retest the tank atmosphere and make any adjustments to ensure the tank is gas free. When the tank arrives at the disposal site, a sufficient number of holes should be cut in the tank to render it unusable except as scrap.

Changes in Service. In some cases, the materials stored in tanks may change. If the characteristics of the new materials are similar to those of the old, there is no problem. However, if the characteristics of the contents differ, the tank should be cleaned internally and recertified to meet all of the regulations for installation of new tanks.

The closure is in place, with the tank top opened to place inert material (sand).

Documentation
All aspects of the project, from bidding to wrap-up, must be carefully documented. This is not only an environmental regulation (40 CFR 280.74), but also good common sense. If something goes wrong and you have no documents to support your position, the consequences can be devastating. On the other hand, your accurate and timely documentation can save you from a lot of unnecessary aggravation in the future.

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