TABLES SIMPLIFY DELUGE OF U.S. STORAGE TANK REGULATIONS

Philip E. Myers Chevron Research & Technology Corp. Robert L. Ferry Conservatek Industries Inc. Chapel Hill, N.C. Tank owners and operators are faced with an increasing number of complex regulations governing aboveground storage tank emissions. Three tables have been prepared to help operators compare any new regulations to 40CFR60, Sub-part Kb, thus determining the extent of applicability of the new rule.

June 7, 1993

9 min read

Philip E. Myers
Chevron Research & Technology Corp.

Robert L. Ferry
Conservatek Industries Inc.
Chapel Hill, N.C.

Tank owners and operators are faced with an increasing number of complex regulations governing aboveground storage tank emissions. Three tables have been prepared to help operators compare any new regulations to 40CFR60, Sub-part Kb, thus determining the extent of applicability of the new rule.

CLEAN AIR ACT

The Clean Air Act Amendments of 1990 (CAAA) were a U.S. Environmental Protection Agency (EPA) legislative mandate that unleashed a deluge of new regulations affecting every sector of the Petroleum industry. Many of these rules have provisions that will affect aboveground tanks storing petroleum-related products.

Faced with hundreds of pages of confusing, and sometimes conflicting, regulations, the bottom line for tank owners and operators is often, "What will I haze to do to my tanks?"

To understand the impact of the CAAA, it is instructive to review the pre-1990 regulators scenario.

The emphasis of earlier storage tank regulations was to reduce emissions of volatile organic compounds (VOCs) under the smog-reduction authority of Title 1 of the Clean Air Act. VOCs combine with nitrogen oxides (NOx) in the presence of sunlight to form ozone. Ozone in the lower atmosphere is the primary constituent of smog.

Before 1990, EPA had issued two control techniques guidelines (CTGs) to guide the states in regulating existing storage tanks in ozone nonattainment areas. EPA also issued three new source performance standards (NSPS), which imposed rules for new construction nationwide.

The NSPS were published as a series of revisions to 40CFR60, the most recent rule being Subpart Kb, published in 1987. This "Kb level of control" seems to be EPA's benchmark for subsequent tank rules,

KB LEVEL OF CONTROL

It is useful to understand the Kb level of control before trying to grasp the new and proposed rules. The Kb rules essentially prohibit the use of uncontrolled, fixed-roof tanks. The following alternative options, however, are acceptable:

External floating-roof tanks (EFRTs)
Internal floating-roof tanks (IFRTs)
External floating-roof tanks that have been converted to internal floating-roof tanks
Fixed-roof tanks with vapor collection and processing systems.

The Kb controls also contain detailed hardware specifications-applicable to each of the allowed options-that mitigates emissions release. For example, the types of floating-roof seals and seal fit requirements are specified, as are requirements for fittings. These rules also contain inspection and monitoring requirements.

The authors suggest that, as new regulations are issued, tank owners and operators compare these new rules to Subpart Kb. Tables that simplify this task have been prepared.

Table 1 addresses the applicability of a rule as a function of the capacity of the storage tank and the true vapor pressure of the product stored. The tank capacity and vapor-pressure limits of Subpart Kb are summarized on the first line.

Tanks within these limits must then comply with the fittings controls described in Table 2, and the floating-roof rim seal requirements in Table 3.

In addition to the information in these tables, there are operating, record-keeping, and permitting requirements. The purpose here, however, is to summarize the tank design options allowed under these rules.

NESHAPS

Many of the new regulations generated by the CAAA will be under Title 3-Air Toxics. These rules are known as national emissions standards for hazardous air pollutants, or Neshaps. Title 3 lists 189 hazardous air pollutants (HAPs), some of which are found in the petroleum industry.

Fig. 1 is a decision tree for the applicability of Neshaps storage tank provisions.

A benzene-storage Neshaps, published in 1989, is the second regulation summarized in the accompanying tables. It is evident from a review of the tables that this rule requires the same control options as found in the Kb rules.

Neshaps rules are promulgated by the categories of sources that handle HAPs. In other words, various industries will be regulated separately by rules specifically tailored for them.

For example, the first Neshaps with storage tank provisions to be issued under the CAAA is the proposed hazardous organic Neshaps (HON). These rules will apply only to the synthetic organic chemical manufacturing industry (Socmi). Similar rules are being developed for petroleum refineries and other industrial source categories.

The HON rule is the third regulation summarized in the tables. The control descriptions clarify some requirements that were implied, but not expressly stated, in Kb.

These clarifications include the requirement for a gasketed float in slotted guide-poles, and stipulations of the controls required for EFRTs that have been converted to IFRTs by retrofitting with a fixed roof, such as an aluminum dome (Fig. 2).

Fig. 3 shows a drawing of a slotted guide-pole. In the wall of the guide-pole are a series of holes, or slots, that allow the liquid to mix freely inside the guide-pole. These slots ensure that the liquid in the guide pole has the same composition and liquid level as the product in the tank.

Although Subpart Kb did not expressly address slotted guide-poles, it did include catch-all language requiring that openings in the roof be equipped with a gasketed cover, seal, or lid that has no visible gaps. Many local regulatory agencies have interpreted this as requiring floats in slotted guide-poles, and the EPA has expressed a similar opinion.

The HON on the other hand, specifically includes the guide-pole float requirement:

"Each slotted guide-pole well shall have:

(A) A gasketed sliding cover or a fabric sleeve seal, and

(B) A gasketed float inside the guide-pole."

Even if one does not agree with the interpretation that Kb requires the float, the authors advise the reader to accept this now, because upcoming rules will clearly stipulate it.

In fact, the Bay Area Air Quality Management District (Baaqmd), in San Francisco, not only requires a gasketed float in the slotted guide-pole, but also mandates that the top of the float be level with the top of the roof at all times or it will not be accepted as complying with the CAAA.

Because of the difficulty of complying with this interpretation of the regulations, many companies have eliminated the use of slotted guide-poles in their tanks, or have sealed the slots in the guide-poles to achieve compliance.

Another clarification involves retrofitting EFRTs with fixed roofs, effectively converting them to IFRTs. This conversion has been acknowledged in EPA documents at least as far back as the fourth edition of AP-42, issued in September 1985.

AP-42 is EPA's emissions-estimating procedure document, which describes IFRTs as follows:

"There are two basic types of internal floating-roof tanks, tanks in which the fixed roof is supported by vertical columns within the tank, and tanks with a self-supporting fixed roof and no internal support columns. Fixed-roof tanks that have been retrofitted to employ a floating deck are typically of the first type, while external floating-roof tanks typically have a self-supporting roof when converted to an internal floating-roof tank. Tanks initially constructed with both a fixed roof and a floating deck may be of either type."

Subpart Kb accommodated this conversion by expressly allowing a mechanical shoe seal as an acceptable rim-closure device for IFRTs. Some state regulators, however, still require these converted tanks to comply with the rim seal requirements for external floating roofs (i.e., to install a secondary seal over the mechanical shoe seal).

The HON has clarified the circumstance of EFRTs converted to IFRTs by expressly requiring that the roof comply with IFRT requirements for rim seals and EFRT requirements for fittings.

Thus, HON has essentially the same control requirements as Kb. The primary differences are that HON applies to a different industry sector-Socmi-and it extends to smaller tank capacities and lower vapor pressures.

It is apparent from Table 1 that Subpart Kb applies only to new tanks with capacities greater than 20,000 gal, whereas HON applies to new tanks of 10,000 gal or greater.

Products with a true vapor pressure less than 4.0 psia, stored in tanks smaller than 40,000 gal, were exempt from the control requirements under Kb. The HON, however, pushes this cutoff down to 1.9 psia.

In a similar manner, the Kb cutoff for tanks larger than 40,000 gal is 0.75 psia, but the HON applies to products with vapor pressures as low as 0.1 psia in these larger tanks. What is being introduced by HON, then, is not so much new controls, but rather a wider range of tanks to which these controls apply.

WHICH RULE APPLIES?

Because the Kb level of control appears to be a given, the question becomes, "Is this the regulation that imposes these controls on my tanks?"

This is determined as a function of:

The industry or source category that the facility belongs to
The product stored in the tank
The size of the tank
Whether the tank is existing or new construction.

The local enforcing agency, of course, has the last word regarding the applicable regulation and its interpretation.

There will be cases in which a new regulation applies to a tank that had been controlled under a previous regulation. Because the EPA trend is to standardize the Kb level of control, a tank with controls installed under one post-1990 regulation generally will be in compliance with other EPA rules.

It should be noted, however, that state and local regulations may vary from the federal rules. The use of the summary tables, however, will readily highlight those variations.

This is illustrated by the inclusion of Baaqmd requirements in the tables as an example of how one of the most stringent air management districts in the country has decided to enforce the CAAA requirements on aboveground storage tanks.

FUTURE

The CAAA will result in the proliferation of many new regulations impacting storage tanks. The trend, as the authors see it, is that these new rules will call for essentially the same controls as now required by the NSPS for volatile organic liquids (VOL) storage (40CFR60, Subpart Kb).

The difference will not be a new level of control technology, but rather the extension of the Kb level of control to a much larger tank population. The accompanying tables provide a method of readily comparing the tank capacity and vapor pressure cutoffs for the various rules, and reviewing the required control options.

These options should be evaluated for a given application on the basis of cost feasibility, maintenance and operating considerations, and emissions reduction.