Underground Storage Tanks

PREAMBLE
(37107-37125)

 

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IV. Analysis of Today's Rule

A. Program Scope

1. Applicability

2. Regulatory Exclusions

3. Deferral of Regulations

4. Definitions

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IV. ANALYSIS OF TODAY'S RULE

A. Program Scope

1. Applicability

As described previously, this rule generally applies to all owners and operators of UST systems containing regulated substances. Regulated substances consist of either petroleum or any substance defined in section 101(14) of CERCLA (but not including any substance regulated as a hazardous waste under Subtitle C). The following sections discuss the tank systems subject to exclusions from today's requirements and the deferral of regulation for other UST systems.

2. Regulatory Exclusions

The regulatory exclusions in today's final rule are based on a number of statutory provisions and regulatory considerations. Section 9003(a) of RCRA requires the Administrator to establish an UST program "as may be necessary to protect human health and the environment." In addition, Section 9003(b) allows the administrator to consider such factors as tank size and quantity of substances stored when establishing necessary requirements. The Agency believes that this statutory language allows some flexibility for EPA to concentrate its resources on tanks that pose the greatest potential environmental threat. Section 9001 defines the universe of the UST program and indicates that EPA should regulate tanks containing an "accumulation" of regulated substances. Section 9001 also excludes tanks regulated under Subtitle C from the jurisdiction of Subtitle I. Finally, section 1006 of RCRA generally requires integration of RCRA with the Federal Water Pollution Control Act; the Safe Drinking Water Act; the Marine Protection, Research, and Sanctuaries Act; and the Atomic Energy Act.

Based on these provisions, the Agency is today excluding from regulation several types of tank systems. These exclusions will decrease the regulatory burden on implementing agencies so they can focus their resources on types and classes of tanks that pose a significant threat to human health or the environment. Unlike statutory exclusions, regulatory exclusions may be modified by the Agency in the future should new information show that regulation of such an excluded tank type is necessary.

Four classes of tanks are excluded from regulation in the final rule: UST systems containing mixtures of hazardous waste and regulated substances; equipment and machinery that contain regulated substances for operational purposes; wastewater treatment tanks regulated under the Clean Water Act; and UST systems excluded via one of three de minimus exclusions. A specific regulatory exclusion for UST systems containing mixtures of hazardous waste and regulated substances was included in the proposed rule (52 FR 12687). The preamble of the proposal also discussed de minimus exclusions. The other two regulatory exclusions were regulatory deferrals in the proposal. The rationale for these exclusions is discussed below.

a. Tanks Regulated Under Subtitle C of RCRA. Because USTs containing a mixture of hazardous wastes (regulated under Subtitle C of RCRA) and regulated substances (regulated under Subtitle I) are subject to dual jurisdiction from Subtitle C and Subtitle I, EPA is today excluding these tanks from Subtitle I regulation. As evidenced by the exclusion of substances covered under Subtitle C within the statutory definition of "regulated substance," the Agency believes that this exemption is consistent with Congressional intent not to have redundant requirements under these two programs. Because of the continued coverage of these tanks by Subtitle C, the exclusion of these tanks from Subtitle I regulations will not present a risk to human health and the environment, and, thus, Subtitle I regulation is not "necessary to protect human health and the environment."

Several commenters pointed out that in the proposed rule this exclusion applied only to mixtures of hazardous wastes and hazardous substances. This wording would subject tanks that contain mixtures of hazardous wastes and petroleum to regulation under both Subtitle C and Subtitle I. The commenters requested that the wording be changed so that all mixtures with hazardous wastes regulated under Subtitle C would be excluded from these regulations.

The original wording in the proposal was based upon the statutory jurisdiction of the program. Under section 9001(2)(A), the exclusion of tanks regulated under Subtitle C pertains only to tanks containing hazardous substances, not to tanks containing petroleum. EPA, however, agrees with the commenters that dual regulation of tanks containing hazardous wastes and petroleum is not necessary and has changed the wording of this exclusion appropriately. This exclusion now applies to all tanks subject to regulation under Subtitle C that contain mixtures of hazardous wastes and either petroleum or non-petroleum regulated substances.

b. Equipment and Machinery that Contain Regulated Substances for Operational Purposes. Equipment and machinery that contain regulated substances for operational purposes, such as hydraulic lift tanks and electrical equipment, are excluded from today's regulations. These specific tank categories were deferred from regulation in the proposal, and the Agency requested comments on whether, and to what extent, these tanks should be subject to regulation under the UST program. Several commenters responded to this request and gave several reasons why these tanks should not be regulated as USTs. Their comments included three main points: the tanks are self-monitoring; the tanks pose a minimal risk to human health and the environment; and there have been few leaks.

Because these tanks contain regulated substances solely for operational purposes, the commenters argued that the loss of regulated substance would be accompanied by faulty operation of the equipment or machinery and thus the equipment is "self-monitoring." Second, the threat to human health and the environment was judged to be minimal because the tanks contain small amounts of regulated substances. Also, the commenters said that these devices rarely leak. Data submitted for leaks from electrical equipment, for example, show a leak incidence much lower than that for other types of tanks such as those at service stations.

This category of tanks includes hydraulic lifts and electrical equipment. Although commenters did not suggest other specific types of tanks that would fall within this class, EPA believes that other tanks of this type would also be included, provided that the tanks meet two major criteria: the equipment or machinery contains small amounts of regulated substances solely for operational purposes; and a loss of regulated substance is accompanied by faulty operation of the equipment or machinery, such that a loss of fluid causes knowledge of the loss.

In excluding this category of tanks, the Agency agrees with the commenters that these types of tank systems pose a relatively low level of risk compared to other types of storage tanks for the reasons given above. Moreover, the Agency recognizes that these tanks, although within Subtitle I jurisdiction, are not central to the Congressional concerns that created this program. Thus, regulation of these tank systems appears at this time to be unnecessary under section 9003(a).

EPA also believes that this potentially overwhelming large universe would require considerable effort on the part of implementing agencies even for just notification, with very little discernable environmental benefit. For example, the universe of hydraulic lift tanks alone has been estimated at 350,000 to 600,000 lifts. These figures do not include elevator lifts. Regulation of these types of tanks would unnecessarily divert implementing agency resources from other, more serious health threats. Therefore, today's final rule excludes such tanks.

c. Wastewater Treatment Tanks Regulated Under the Clean Water Act. The Agency is today excluding all wastewater treatment tanks, including any oil-water separators, that are subject to regulation under either section 402 or 307(b) of the Clean Water Act (CWA) (33 USC 1151 and following). These tanks, including tanks at most publicly owned treatment works and many private treatment facilities, would otherwise be subject to dual regulation. Because these tanks are subject to regulation under the CWA, further regulation under Subtitle I is unnecessary to protect human health and the environment and would be inconsistent with section 1006(b) of RCRA. This exclusion is analogous to the "wastewater treatment unit" exclusion under the RCRA Subtitle C program (see 40 CFR 260.10, 264.1, and 265.1).

In addition, tanks that treat wastewater or storm water, but which are not covered by the applicable sections of the CWA, are being deferred from today's final regulations. Such tanks might include many oil-water separators found at various facilities. Further discussion of these tanks can be found under the deferral section of this preamble.

d. De Minimis Exclusions. Today's final rule has been modified to exclude the following tanks: (1) those that have a capacity of less than 110 gallons; (2) those holding a very low concentration of regulated substances; and (3) those that serve as emergency backup tanks, hold regulated substances for only a short period of time, and are expeditiously emptied after use.

The statutory definition of tank includes all devices that "contain an accumulation of regulated substances." Although legislative history provides no guidance on the meaning of the phrase "accumulation of regulated substances," the Agency believes the statutory language provides some flexibility to define the universe of regulated facilities in a manner that focuses regulatory resources on the tanks posing substantial risk from storage of regulated substances and, thereby, fosters development of a program that most effectively protects human health and the environment. Thus, sections 9001 and 9003(a) authorize EPA to exclude from its regulations tanks containing de minimis amounts of regulated substances. EPA requested comment in the proposed rule concerning de minimis exclusion criteria.

A number of comments addressed the issue of including a de minimis exclusion in the rule for tanks that hold a small quantity of regulated substances. The overwhelming majority of the commenters believed that such an exclusion should be part of the final rule. Some commenters suggested that a small-capacity exclusion would reduce the regulatory burden on the implementing agencies and, thus, result in a more effective program. Some commenters believed that a small-capacity exclusion was justified because small quantities of regulated substances pose less of a health risk than do larger quantities.

In deciding to include a regulatory exclusion for tanks that contain small quantities of regulated substances in today's rule, the Agency had to balance the benefits and drawbacks of such an exclusion. The Agency agrees with the commenters who thought that without an exclusion such as this, the regulated universe could be overwhelmingly large. Such a large universe would require considerable efforts by the implementing authorities even for notification, diverting their attention away from other, more potentially environmentally hazardous classes of tanks. The Agency agrees that small tanks pose less danger to the environment than larger tanks, generally, due to the smaller quantity of regulated substances available to leak. In certain cases, however, the mismanagement of even small quantities of regulated substances could pose serious danger to human health and the environment. Nevertheless, the Agency has decided that the detriments of attempting to regulate these small tanks greatly outweigh any potential benefits from regulation of this class of tank and has, therefore, adopted this exclusion.

Several comments were received with suggested sizes for a de minimis cutoff. These sizes ranged from 100 gallons to 5,000 gallons. State and local agencies with de minimis exclusions use cutoffs that range from 60 to 2,100 gallons. Because it was apparent that there was no standard size for the de minimis exclusion, the Agency chose the size limit of 110 gallons capacity. According to one commenter, this size is below the smallest petroleum product tank routinely mass produced (275 gallons), and a 110-gallon level coincides with the Department of Transportation definition for minimum portable tank for the transportation of hazardous materials. Tanks likely to be exempted under this exclusion include many small sumps and other atypical tanks.

The Agency is also today excluding tanks that contain de minimis concentrations of regulated substances. Because "an accumulation of regulated substances" could include within the regulated universe USTs holding regulated substances in any amount, no matter how small, the regulated universe could include a vast number of tanks that contain regulated substances only in small concentrations. These very small concentrations could occur accidentally (through contamination) or by design (for example, underground tanks storing food that contains a preservative that is a regulated substance). The Agency has not included a specific percentage threshold as the de minimis cutoff because of the many difficulties with measuring tank contents for low concentrations. Instead, on a case-by-case basis, the implementing agencies will determine if tanks that hold very low concentrations of regulated substances are excluded via the de minimis concentration rationale. Tanks that are likely to meet this criteria include those that are used to treat storm water and municipal wastewater, tanks that store potable water that has been treated with chlorine, and in-ground swimming pools. EPA believes that such tanks pose a minimal threat to human health and the environment, and the inclusion of such tanks in the regulated universe would impose an undue burden on the implementing agencies because of the potentially large numbers of such tanks. Other types of tanks with very low concentrations of regulated substances may also be excluded.

The third de minimis exclusion included in today's rule pertains to tanks that are emergency spill protection tanks or overflow tanks, and are emptied expeditiously following use. This exclusion is analogous to the exclusion for emergency response treatment and containment under the RCRA Subtitle C program (see 40 CFR 264.1 and 265.1). Included in this category are many types of sumps and secondary barrier tanks. This exclusion does not specify a maximum time a tank may hold material, but applies only to tanks that are rarely used and are emptied shortly after use. The purpose of this exemption is to allow appropriate immediate response to emergency situations. These tanks are used for temporary storage of substances in response to a leak, spill, or other unplanned occurrences. Regulation of such tanks is unnecessary because they are rarely used and expeditiously emptied and, therefore, are unlikely to have any long-term leaks. Many of these tanks may also be able to be visually inspected because they rarely hold regulated substances. Several commenters expressed concern that the way the proposed rule was written, the Agency may have been requiring infinite layers of secondary containment. For example, in the proposal, an UST system was defined to include a secondary containment system, but there were references to requiring secondary containment for a hazardous substance UST system. Thus, it appeared that secondary containment was required to surround secondary containment. By including this exclusion in the final rule, the Agency believes that any potential confusion regarding the need for secondary barriers (containment) for secondary barrier (containment) systems has now been eliminated.

Sumps designed to store petroleum or hazardous substances during periodic cleaning or maintenance of machinery or equipment are not included in this exclusion. An example of this type of sump is turbine oil sumps that are used during maintenance of electric power generation turbines.

3. Deferral of Regulations

In the proposal preamble (52 FR 12687), EPA discussed its proposed deferral of requirements for the following categories of UST systems: wastewater treatment tanks, sumps, systems containing used oil, systems containing radioactive waste, systems containing electrical equipment, underground bulk storage tanks, and hydraulic lift tanks. The Agency requested comments on whether the deferrals were appropriate for each category and, if not, what regulations would be necessary.

In today's final rule, the Agency has revised the proposal in several ways. As a result of these revisions, tanks in some of these categories will fall within the scope of the regulatory exclusions described above, some will be subject to full regulation, and some will continue to be deferred from regulation. Tanks that are deferred rather than excluded are subject to interim UST requirements, but excluded tanks are not subject to any regulatory requirements. These revisions are briefly summarized below:

o Wastewater treatment tanks now fall under two parts of today's final rule. Wastewater treatment tanks, including oil-water separators, that fall under the jurisdiction of sections 402 or 307(b) of the CWA are excluded from today's regulatory requirements (as discussed above in IV.A.2.). The remaining wastewater treatment tanks continue to be deferred from Subparts B, C, D, E and G of today's regulations, but are subject to interim requirements under Subpart A and corrective action under Subpart F.

o Many sumps are excluded from regulation under the CWA-regulated wastewater treatment exclusion, and others via one or more of the de minimis exclusions; others may be excluded as part of the statutory exclusion for storm-water and wastewater collection systems. Many of those that are not excluded continue to be deferred from Subparts B, C, D, E and G under the "field-constructed tank" deferral. Such UST systems are subject to the interim prohibition under Subpart A and corrective action under Subpart F. Sumps that are neither excluded nor deferred from regulation are subject to today's regulation.

o Field-constructed tanks, which include many tanks classified as underground bulk storage tanks in the proposal, are deferred from Subparts B, C, D, E and G but are subject to interim requirements under Subpart A and corrective action under Subpart F.

o UST systems that contain radioactive wastes and other radioactive materials have been deferred from Subparts B, C, D, E and G but are subject to interim requirements under Subpart A and corrective action under Subpart F.

o UST systems containing electrical equipment and hydraulic lift tanks, which had been deferred in the proposal, are both examples of equipment or machinery using regulated substances for operational purposes. As discussed above in IV.A.2., both types of tanks have been excluded from regulation under Subtitle I.

o Tanks containing used oil are no longer deferred but are subject to full regulation under today's final rule.

Today's final rule also includes deferral of some subparts of the regulations for the following additional categories of tanks:

o Airport hydrant fueling systems and tanks storing diesel fuel for emergency power generation at plants regulated by the Nuclear Regulatory Commission are deferred from the technical standards set forth in Subparts B, C, D, E and G but are subject to interim requirements under Subpart A and corrective action under Subpart F.

o UST systems that store fuel solely for use by emergency power generators are deferred from the release detection requirements under Subtitle D. All other regulatory requirements apply to these tanks.

EPA's decision making on these various tank types is discussed in more detail in the sections below.

a. Wastewater Treatment Tanks. In the proposal, EPA deferred wastewater treatment tanks from UST regulation in order to gather more information on the need to regulate these tanks and the appropriate type of regulation. EPA included oil-water separators (which are considered treatment tanks) within the scope of wastewater treatment tanks.

In the proposal preamble, EPA specifically requested comments on whether wastewater treatment tanks should be regulated under Subtitle I (52 FR 12687). Almost all comments submitted were opposed to regulating wastewater treatment tanks under UST regulations. The commenters stated that wastewater treatment tanks are process devices and flow-through process tanks, not storage tanks; thus, they should not be regulated under the UST program. Several commenters also stated that wastewater treatment tanks contain large volumes of water and only small amounts of oil or hazardous materials and, thus, pose no major threat to human health or the environment. It was also stated that wastewater treatment tanks that are currently excluded by RCRA are, however, currently covered by the CWA. They should not, therefore, be regulated under UST regulations. In addition, several commenters pointed out that if wastewater treatment tanks were to be included in the final rule, there is presently no practical method of performing a tightness test on these tanks because the tanks are typically open to the atmosphere. Inventory reconciliation is not feasible because the very high throughput would require more accurate metering than is currently available.

EPA does not agree with the commenters who argued that wastewater treatment tanks are outside the scope of Subtitle I as "flow-through process tanks" or part of a storm-water or wastewater collection system, which are excluded from the jurisdiction of this program under section 9001(1). Wastewater treatment tanks are not part of a production process, nor are they part of a collection system. See section IV.A.2. for further discussion of the scope of the flow-through process tank and storm-water and wastewater collection system exclusions. EPA does, however, agree with commenters that the universe of treatment tanks could add a large administrative burden that could reduce the ability of the implementing agencies to regulate more serious threats to the environment.

After review of all available information, EPA now believes that wastewater treatment tanks that are currently covered by sections 402 and 307(b) of the CWA should be excluded from UST regulations as discussed in the previous section. In addition, some of these treatment devices, such as those treating municipal sewage, typically contain de minimis concentrations of regulated substances and are therefore excluded under today's rule.

Wastewater treatment tanks not covered by the CWA or otherwise excluded will continue to be deferred under these regulations. Oil-water separators and other similar treatment devices fall under the definition of "wastewater treatment tank" under today's rule. The deferral for those wastewater treatment tanks not regulated by the CWA reflects the Agency's uncertainty regarding the nature of this tank population and the appropriateness of some of the UST regulations for these tanks. For example, some types of leak detection (such as tightness testing) and inventory reconciliation would not appear to apply to treatment tanks.

b. Sumps. In the preamble of the proposal (52 FR 12687), the Agency requested that commenters submit information on the number, location, and substances stored in sumps; how sumps are protected to prevent releases from occurring; leak history; and whether the proposed UST regulations would be appropriate for sumps. Most of the commenters who responded believed that regulations for sumps should continue to be deferred because sumps are small, temporary storage facilities that are frequently visually monitored and that contain mostly water and only small amounts of petroleum or hazardous substances. Also, commenters stated that regulation of sumps would pose an unmanageable regulatory burden for the implementing agencies and would require an individualized approach for each location. Some commenters suggested that de minimis size, time, and throughput exclusions be developed to prevent sumps from becoming subject to the regulations. The only commenters who supported regulation of sumps did not believe that Subtitle I was the appropriate regulatory authority.

Although commenters did not submit data that would enable EPA to determine the total number of sumps nationwide, the Agency realizes that that the number of sumps potentially subject to Subtitle I is very large and could pose an unmanageable regulatory burden. In addition, the Agency agrees with the commenters that many sumps are small, temporary storage facilities that contain only small amounts of petroleum or hazardous substances. No information was submitted concerning whether sumps pose a significant threat to human health or the environment.

As discussed above, today's final rule contains de minimis size, time, and concentration exclusions that are expected to apply to many sumps. Also, sumps that are part of a storm-water or wastewater collection system are excluded by statute from UST regulations. These exclusions will allow the implementing agencies to focus their resources on UST systems that are a more significant threat to the environment and human health. The Agency believes, however, that large sumps that contain significant quantities of regulated substances over a period of time do not warrant such exclusion, because they are indistinguishable from other regulated tanks. Therefore, factory-built sumps are subject to all requirements under today's final rule if they are not subject to any other exclusion. Field-constructed tanks, including field-constructed sumps, are deferred until information can be obtained on what regulations (if any) are appropriate for these systems as discussed in the following section. Therefore, the final rule no longer contains a deferral for sumps.

c. Field-Constructed Tanks. In the proposal preamble, EPA specifically requested comments concerning the applicability of Subtitle I (52 FR 12688) to underground bulk storage tanks (UBSTs). In the proposal preamble, EPA considered UBSTs as those tanks whose total capacity was 20,000 gallons or greater. Several commenters stated their belief that because UBSTs pose a major environmental concern and are closely related to other USTs, they should be regulated under Subtitle I in the final rule. It was also stated by some commenters that secondary containment of UBSTs is feasible and other existing leak detection methods are applicable to UBSTs. On the other hand, there were some commenters who opposed the inclusion of UBSTs in the regulation stating that the differences between UBSTs and normal USTs are too great and that many leak detection and leak prevention methods are not applicable to UBSTs. There were also requests by some commenters that the definition of UBST be clarified and included not only in the preamble but also in the final regulation.

After reviewing the comments, EPA has modified the deferral of UBSTs to a deferral for tanks that are field-constructed. Although many bulk tanks are expected to be deferred because they are field-constructed, the capacity of these tanks no longer determines their regulatory status.

Field-constructed tanks are usually constructed of steel or concrete, shaped like flat vertical cylinders, and have a capacity of greater than 50,000 gallons. In contrast, factory-constructed bulk tanks are typically long, horizontal cylinders and are less than 12 feet in diameter. Tanks that are principally factory-built but are assembled in the field are considered factory-built tanks. For example, welding two halves of a factory-constructed tank together in the field does not qualify the tank as a field-constructed tank.

The deferral of regulation for field-constructed tanks is largely based on the fact that design and construction methods for field-constructed tanks are different from those for factory-built tanks. EPA has not had sufficient time to develop appropriate regulations related to design and construction for such tanks.

Comment was divided on the applicability of present leak detection and leak prevention methods to bulk tanks. Some commenters argued that existing leak detection methods are applicable to UBSTs, while others stated that the differences between UBSTs and normal USTs are too great to use most presently available leak detection and prevention methods for such tanks. EPA believes that the division of bulk tanks into field-constructed and factory-built tanks simplifies this issue.

EPA believes that because of the different design and construction methods used for field-constructed tanks, as well as the very large size of some field-constructed tanks, the majority of the leak detection methods presently available do not work for such tanks. Leak prevention methods may also differ for such tanks. The deferral for these tanks is due in part to this restricted availability of appropriate leak detection methods.

By contrast, EPA believes that currently available leak detection methods are applicable to factory-built tanks. Factory-built tanks, even those that are very large, generally conform to standard design and construction methods that allow the use of widely available leak detection methods.

EPA agrees with commenters that tanks that hold large amounts of regulated substances do pose a relatively larger potential danger to human health and the environment than other, smaller tanks. However, until regulations are developed to govern design and construction of field-constructed tanks, they will be deferred.

d. Systems Containing Radioactive Materials. At proposal, the Agency requested comment on the issue of whether tanks containing radioactive materials, including high-level radioactive waste and tanks containing mixtures of low-level radioactive waste and other materials, should meet the proposed standards or whether separate standards should be developed. No commenters supported regulation of these USTs under Subtitle I. The commenters stated that radioactive waste and materials tanks at nuclear facilities are regulated by the Nuclear Regulatory Commission (10 CFR 50.34a) and that further regulation of these tanks under Subtitle I would be duplicative and possibly inconsistent. One commenter noted that these tanks are typically made of stainless steel and have a capacity of approximately 1,000 gallons. The tanks are pressure tested before the nuclear facility is licensed to operate and are retested every 10 years. In addition, they are constantly monitored for loss of pressure and radiation leakage. Commenters also noted that the current Department of Energy management program for tanks containing high-level radioactive waste is as stringent as, and in some cases exceeds, the proposed UST rule.

Because tanks containing radioactive wastes and other radioactive materials at nuclear facilities are regulated by the Nuclear Regulatory Commission, these tanks could be subject to overlapping jurisdiction under Subtitle I and the Atomic Energy Act of 1954 (42 U.S.C. 2011 and following). The Agency, however, lacks complete information on whether these regulations fully cover all appropriate areas addressed under Subtitle I. The Agency, therefore, is deferring regulation of these tank systems until more information can be gathered.

e. Systems Containing Electrical Equipment. Under the proposed definition of "tank," large numbers of utility units in urban and residential areas (e.g., underground transmission cables and vaulted transformers for large trunk lines) could be subject to regulation. At the time of the proposal, the Agency deferred regulation of these structures based on its belief that inclusion of these structures in the UST program would be impractical and unnecessary. EPA requested that commenters submit information on the number, location, and substances stored in these units; how they are protected to prevent releases; leak history; and whether the proposed regulations would be appropriate for these units.

All of the commenters in this area were opposed to inclusion of electrical equipment structures in the UST program. The commenters stated that these units are not primarily used for storage and that the utilities industry already takes many precautions to prevent releases. Dielectric fluids, typically naphthenic mineral oil and synthetic fluids such as polybutene or alkylbenzene, are used in underground cable piping and vaulted transformers to prevent the cables and transformers from overheating. Underground cable piping is cathodically protected and is coated to prevent corrosion. The piping is subjected to pressure tests both before and after insertion of the cable and addition of the dielectric fluid. Electronic monitors at the utility's control center indicate potential releases of fluid (i.e., when the required oil pressure cannot be supplied by the associated pumping station). In addition, transmission line routes are routinely inspected to identify potential sources of piping damage, such as the misuse of construction equipment. Information submitted by commenters showed that from 1978 to 1985, utilities nationwide reported an average of less than 1 leak per 100 circuit miles of cable. In 1985, there were 23 reported leaks involving low-pressure systems and 6 reported leaks involving high-pressure systems. Of the low pressure system leaks, only one occurred belowground.

The Agency believes that there are already strong incentives for the utilities industry to prevent releases from underground equipment because these leaks could result in system malfunctions and widespread power outages. The industry has developed release response procedures for notification, containment, and cleanup in the event of a release. In addition, despite its widespread use, underground electrical equipment appears to pose a minimal threat to the environment because of the low leak incidence for such UST systems. Moreover, many of these systems also fall within the statutory exclusion for storage tanks situated on or above the floor of underground areas, such as basements and cellars. Therefore, to allow the implementing agencies to focus their limited resources on more significant potential threats, the Agency has decided to exclude underground electrical equipment from the final rule as equipment and machinery that contain regulated substances solely for operational purposes.

f. Hydraulic Lift Tanks. In the proposal preamble, EPA deferred the application of the proposed technical standards to hydraulic lift tanks; however, these tanks would have been subject to Subparts F and G of the proposed rule (i.e., corrective action). "Hydraulic lift tanks" are those tanks used to store fluid used in hydraulic lifts at service stations and similar devices such as lubrication oil reservoirs for elevators. After review of all available information, EPA has now decided that, like the electrical equipment tanks discussed above, hydraulic lift tanks will be excluded in the final rule as equipment or machinery that contain regulated substances solely for operational purposes.

In the proposal preamble, EPA specifically requested comments on whether hydraulic lift tanks should be regulated, and if regulated, to what extent (52 FR 12689). In response, several commenters stated that hydraulic lift tanks should not be regulated under the final rule because they are not used for storage and many of them are almost completely aboveground. It was suggested by several other commenters that hydraulic lift tanks not be regulated because they pose either minimal or no threat to human health or the environment and are self-monitoring. If problems do arise, the lifts cease to operate when they lose fluid. It was also mentioned by several commenters that due to the location of hydraulic lift tanks (e.g., under buildings), the cost impact involved in bringing these tanks under regulation would be substantial. Finally, several commenters stated that the inclusion of hydraulic lift tanks in the regulation would cause severe impacts on the implementing agency; the number of hydraulic lifts has been estimated at over 800,000. Several commenters suggested, however, that special standards be developed specifically for hydraulic lift tanks. It was also suggested that only those hydraulic lift tanks that exceed 100 gallons be regulated under the final rule.

EPA deferred regulation of hydraulic lift tanks at proposal to allow time to gather additional information on the subject. In the preamble to the proposal, however, EPA identified several reasons why, based on preliminary information, the Agency felt that regulation of such tanks would be unnecessary. After reviewing all comments submitted, EPA believes that it is appropriate to exclude all hydraulic lift tanks from regulation. EPA agrees with those commenters who stated that hydraulic lift tanks pose a minimal threat to the environment and are self-monitoring. The Agency is today excluding these types of tanks as equipment that contains regulated substances solely for operational purposes (see section IV.A.2.b. above).

g. Used Oil USTs. The Agency proposed to defer regulation of used oil USTs. The Agency indicated, however, that it might apply the proposed technical standards to used oil USTs in the final rule following public comment on the appropriateness of the technical standards for used oil USTs. EPA considered the many comments received on this issue and has decided to include used oil USTs in the final regulation. Public comments received by EPA and proposed revisions to the final rule as they relate to the appropriateness of the technical standards for used oil USTs are discussed below.

In the preamble to the proposed regulations, EPA requested comments on the following issues relating to used oil:

o Are the petroleum UST requirements appropriate for recycled used oil and/or used oil bound for disposal?

o Do the minor constituents found in used oil (such as water and metals) alter the appropriateness of the requirements?

o Is it appropriate to have different standards for relatively smaller tanks, such as those used by used oil generators and burners, than for larger tanks, such as those used by used oil processors?

In addition, EPA also requested comment on the impact of the proposed regulations on the recycling of used oil.

In a supplemental Federal Register Notice (52 FR 48638, December 23, 1987), EPA requested comment on the appropriateness of using alternative methods of release detection for used oil USTs, to supplement those listed in § 280.41 of the proposed rule. The Agency specifically requested comments on the use of static inventory control as a method of release detection for smaller used oil USTs. This request was prompted by the Agency's belief that some of the release detection methods proposed in § 280.41 may not be practical or effective for used oil USTs due to the physical characteristics of used oil. On the other hand, the Agency believes that the static inventory method of release detection may be very effective and practical for use with small used oil USTs. "Static inventory control" has been renamed as "manual tank gauging" in the final rule and in the rest of this preamble's discussion of this method of release detection.

The Agency believes that the risks associated with releases from used oil USTs may be different from those of other USTs, but the overall level of risk is similar to that of other petroleum products. Releases from used oil USTs may be less likely to occur than from petroleum USTs, but the health risks posed may potentially be greater because of the possibility of contaminants in the used oil. The appropriateness of further regulation, under RCRA Subtitle C, will be determined by results of studies currently in progress. At this time, the Agency has determined that used oil USTs should be regulated under Subtitle I because there is evidence of leaks that indicates a significant threat to human health and the environment.

In reply to EPA's request for comments about the appropriateness of the proposed regulation for used oil USTs, public comment was divided. Several commenters stated that used oil USTs should be covered by Subtitle I regulations because the risk to ground water was essentially the same as for other petroleum products, and that management of all underground tanks at a facility that had both used oil tanks and other Subtitle I regulated tanks (e.g., a service station) would be facilitated by a single, inclusive regulation (Subtitle I). In contrast, some commenters stated that the risk from used oil USTs was insignificant and, thus, used oil USTs should permanently be exempted from regulation. Others stated that used oil USTs should be regulated under RCRA Subtitle C because the hazardous constituents in used oil make it more dangerous than other petroleum products.

The Agency agrees with those commenters who noted that used oil presents risks similar to other petroleum products and that Subtitle I regulations are appropriate. Today's final rule reflects this by applying the petroleum UST requirements to used oil USTs, with limited exceptions discussed below. Releases from both used oil USTs or other petroleum USTs can be prevented, or at least limited, by sound management practices. As a result, the Agency has decided to require used oil USTs to meet the same upgrading, operation and maintenance, corrosion protection, corrective action, and closure requirements that are applicable to other petroleum USTs.

The Agency received comments requesting an exemption from Subtitle I regulations for small tanks. Recommended cutoff sizes ranged from 100 to 3,000 gallons. In addition, several commenters also requested regulatory exemptions for small vessels used to trap used oil, as well as tanks holding regulated substances for short time periods. As discussed above, in today's final rule EPA is exempting from the regulations USTs that are 110 gallons or less. Thus, small traps are excluded from regulation. With respect to tanks that hold regulated substances for short periods of time, today's rule includes an exemption for emergency spill collection tanks. The regulations do, however, apply to any other used oil USTs, the majority of which are the 500- and 550-gallon tanks often found at gasoline service stations. Most of these USTs are old and are believed to be a common source of releases of used oil. USTs that contain used oil that is used as substitute for heating oil are excluded.

The Agency received several comments noting particular characteristics associated with used oil or used oil USTs that make some of the proposed technical standards in Part 280 inappropriate for used oil USTs holding less than 1,100 gallons. In response to these comments, today's final rule contains different requirements for small used oil USTs in two areas: release detection and overfill/spill protection. First, with respect to release detection, many commenters noted their support for manual tank gauging (formerly called "static inventory control") by itself as an alternative leak detection method for used oil USTs. Today's final rule allows the use of this alternative release detection method as the sole method of release detection for any petroleum UST with a capacity of 550 gallons or less. Manual tank gauging may be used in combination with periodic tank tightness testing on petroleum tanks with a capacity between 55 and 1,000 gallons. (These provisions are discussed in more detail in section IV.D. of this preamble.)

Today's final rule also provides an exemption from the rule's spill and overfill protection controls for USTs that are filled in small increments. (This is also discussed in more detail later in this preamble under spill and overfill prevention for new USTs.) The Agency agrees with the commenters that used oil USTs that are filled manually in small increments do not pose the same risk to human health and the environment from spills and overfills as other USTs.

The Agency received additional comments related to design standards and agrees with those who requested cathodic protection for new used oil tanks. In addition, EPA is requiring that owners and operators upgrade or replace their used oil USTs according to the time period of today's final rule (10 years). EPA disagrees, however, with the commenters who argued that these tanks should be subject to secondary containment. Because the physical and chemical characteristics of used oil are similar to petroleum products, the release detection and corrective action technologies should be similarly applicable to used oil. Thus, the final rule subjects used oil USTs to the release detection requirements applicable to petroleum UST systems rather than secondary contaminant required for hazardous substance UST systems.

h. Airport Hydrant Fueling Systems. A number of commercial airports and airports at Department of Defense bases use hydrant fueling systems. These systems generally consist of one or more bulk storage tanks that may be either below or aboveground and that are connected by underground piping to various aircraft fueling locations on the airport. Hydrants, otherwise known as fuel dispensers, are connected to the pipe networks and dispense fuel into aircraft. These systems are, in some cases, very large in size and contain great volumes of fuel. Many airports have miles of piping, which is typically 8 to 24 inches in diameter, and the total capacity of the systems can be many millions of gallons.

Through a brief investigation of these systems, the Agency believes that some of these systems do not meet the statutory definition of an UST system, and are thus outside of the jurisdiction of Subtitle I. Hydrant systems that have aboveground storage tanks are not regulated tank systems unless 10 percent or more of the capacity of the system is in the belowground pipelines.

However, hydrant systems with belowground storage tanks and those with aboveground storage tanks but whose pipelines account for 10 percent or more of the system's capacity are within to Subtitle I jurisdiction as UST systems. The special problems posed by requiring hydrant systems to meet many of the requirements in today's final rule have motivated the Agency to look further at these systems, and have led to today's deferral of regulations for these systems.

The Agency continues to examine questions regarding the construction, operation, maintenance, and monitoring of hydrant systems. Preliminary information indicates that hydrant systems typically have cathodic protection, and are monitored for leaks on a daily, monthly, and annual basis. Inventory monitoring is often used, but the sensitivity of this technique is very limited due to the large volume these systems typically handle. No single leak test, however, appears to be an industry standard.

Since proposal, the Agency has become aware of several leak incidents from hydrant systems that resulted in environmental damage. Because of limited information on this subject, however, the Agency is unclear about the extent of this problem. In addition, to the nature of these systems, especially the typically large amount of piping, certain requirements in today's rule (such as leak detection for piping systems) may not be feasible for hydrant systems. For these reasons, the Agency is deferring regulation of Subparts B, C, D, E and G for all airport hydrant systems, including the underground tank portions of those systems, to allow more time to gather information.

i. Backup Diesel Tanks at Nuclear Facilities. Following publication of the proposed regulations, a commenter raised the issue of the applicability of the UST regulations to tanks at nuclear power plants that store diesel fuel for use in emergency situations. According to the commenter, these tanks are already extensively regulated by the Nuclear Regulatory Commission (NRC), and further regulation by EPA could result in an overly burdensome program if the regulations were inconsistent. Not only would these nuclear facilities be required to meet dual regulatory programs, but structural changes to the systems as a result of the UST regulations could result in an amendment to the plant's license, according to a commenter. The commenter also pointed out that any shutdown of the backup fuel system (e.g., for retrofitting) could result in the entire nuclear power plant being shut down.

The Agency is today deferring the requirements of Subparts B, C, D, E and G for these tanks pending completion of a review of the NRC regulations (10 CFR 50 Appendix A) governing these tanks to determine whether further regulation is necessary to protect human health and the environment or would be inconsistent with NRC regulations for proposes of section 1006. If this research indicates that the NRC regulations are not adequate or are not as complete as the UST regulations, EPA may require these tanks to be subject to Subtitle I regulations, or it may develop a separate set of standards applicable to this class of tank.

j. UST Systems Associated with Emergency Generators. In today's rule, EPA is deferring Subpart D requirements for UST systems associated with emergency power generators. Such tanks are common in the telephone industry and the electric utility industry. These tanks often store diesel fuel which serves as a source of backup power in remote locations (for example, at telephone switching locations). This is a deferral of the release detection requirements only; owners and operators of these systems must comply with all other subparts of this rule.

Several commenters argued that these tanks should not be regulated at all for the following reasons: they are generally small in size (typically under 500 gallons); most are less than 5 years old; they are often at unmanned stations in remote locations; they contain diesel fuel, which is less mobile than gasoline due to its higher viscosity; and many are filled only annually.

The Agency does not agree that these reasons merit an exclusion from the UST regulations. The requirement that these tanks be monitored each month is unworkable, however, because they are often located in remote areas and are visited very infrequently. Therefore, EPA is deferring Subpart D requirements for these tanks to allow time to develop workable release detection requirements for these tank systems.

4. Definitions

The following sections address many of the terms that are used in the statutory language and elsewhere in the final regulations. Since proposal, many terms have been redefined or clarified as a result of comments. The following sections contain the revised definitions, the rationale for the changes, and the Agency's interpretation of these terms.

a. Definitions of Terms in the Statute. (1) Underground Storage Tank. Underground storage tank is defined in the statute as any one or a combination of tanks (including underground pipes connected thereto) that is used to contain an accumulation of regulated substances, and the volume of which (including the volume of the underground pipes connected thereto) is 10 percent or more beneath the surface of the ground.

Today's rule sets forth the following definitions for terms used in the statutory definition of underground storage tank:

(a) Tank is a stationary device designed to contain an accumulation of regulated substances and constructed of non-earthen materials (e.g., concrete, steel, plastic) that provide structural support.

Several commenters stated that the definition of tank in the proposed rule was too broad, and included devices that do not store regulated substances but rather use, treat, collect, or capture regulated substances. By expanding the scope of tank beyond just storage tanks, say the commenters, EPA departed from its Congressional mandate and created a program that is overly inclusive and difficult to manage. The commenters also argued that the inclusion of hydraulic lift tanks, electrical equipment, oil-water separators, sumps, treatment tanks, and other devices not normally regarded as storage tanks would overwhelm the Agency's ability to adequately enforce the regulations. Also, the added burden of regulating these devices would be disproportionate to their potential environmental harm. Few of these devices have documented leak histories, according to the commenters.

Throughout the development of the UST regulations, where there has been ambiguity in the terms defining the jurisdiction of the Subtitle I program, it has been the Agency's policy to define the scope of the UST regulations broadly and interpret the exclusions relatively narrowly. By taking this approach, the Agency hoped to avoid prematurely eliminating from its jurisdiction tanks that may pose an environmental threat. This policy has afforded the Agency the opportunity to gather more information on the various classes of tanks in the potential regulated universe. EPA has retained the prerogative to narrow the scope of the program by regulation rather than statutory interpretation, taking into account potential environmental and health risks, implementability, and administrative burden. The Agency decided that this approach would result in a program that provides maximum protection to human health and the environment while taking into account the regulatory burdens associated with the program. Further explanation of these regulatory exclusions is found earlier in this preamble under IV.A.2. Regulatory Exclusions, many of which deal with precisely those tanks about which commenters expressed concern.

Accordingly, EPA disagrees with commenters who argued that EPA's definition of "tank" results in an unauthorized expansion of its regulatory program under Subtitle I. Although EPA acknowledges that this program includes only "storage" tanks, Congress defined "storage" in section 9001 of RCRA as "containing an accumulation of regulated substances." EPA's interpretation of the Subtitle I jurisdiction to encompass any devices holding an accumulation of any regulated substances (unless subject to a statutory exclusion) is thus not inconsistent with the statute. Moreover, this definition is the same as that which has been used in the Subtitle C tank program for years.

(b) Underground pipes connected thereto means all underground piping, including valves, elbows, joints, flanges, and flexible connectors attached to a tank system through which regulated substances flow. For the purpose of determining how much piping is connected to any individual UST system, the piping that joins two UST systems should be allocated equally between the systems. Tanks that are simply manifolded together are considered as one UST system. However, if an exempt tank is connected by piping to a regulated tank, half of the piping is allocated to each tank system. This allocation of connected piping is an attempt to reconcile two conflicting statutory provisions: section 9001(1) states that an UST system includes the tank and all underground pipes connected thereto but also states that a statutorily excluded UST system also includes all of the piping connected to it. As a result, half of the piping is allocated to the regulated tank system and half to the excluded tank system if two are connected.

In the RCRA Subtitle C tank rules, the starting point of the "connected piping" is the point at which the contained substance is initially considered to be a hazardous waste. It should be noted that the above terms as they apply here, while similar, are different than the Subtitle C definition.

(c) Regulated Substance. Today's definition of "regulated substance" in the final rule codifies the statutory definitions of "regulated substance" and "petroleum" and provides additional clarificati on concerning the coverage of certain substances and mixtures of these substances under the regulations.

(i) Overview. In the April 17 proposal, the Agency codified the statutory definition of regulated substance. Thus, "regulated substance" was defined to include: (1) any substance listed under section 101(14) of CERCLA, except those regulated as hazardous waste under Subtitle C of RCRA; and (2) petroleum, including crude oil or any fraction of crude oil that is liquid at standard conditions of temperature and pressure. The term "petroleum" was also separately defined as crude oil, crude oil fractions, and refined petroleum fractions including gasoline, kerosene, heating oils, and diesel fuels. The proposal addressed mixtures of petroleum and any hazardous substance with a "50 percent rule," and under which, for example, an UST system containing a mixture that was 50 percent or more petroleum was proposed to be a "petroleum UST system."

In the Supplemental Notice of December 23, 1987, the Agency proposed further clarification of these definitions by requesting public comment on a specific list of substances and blends that would be subject to the petroleum UST requirements. This list was intended to be comparable to the list of CERCLA hazardous substances (not including hazardous wastes). Thus, an owner or operator would have to comply with the UST regulations only if one or more of the stored substances were on either of the two lists of regulated substances. The proposed list of petroleum substances would also be used to determine, for purposes of release detection requirements, if a substance would be regulated as a petroleum UST system.

The few comments the Agency received about the proposed definition of regulated substance asked for further clarification of the term petroleum. The commenters' concern was whether the release detection requirements for new hazardous substance USTs (i.e., secondary containment), or those for new petroleum USTs, applied to particular substances. EPA also received numerous comments on the proposed list of petroleum substances contained in this Supplemental Notice. In general, most commenters expressed preference for this proposed list because it was more specific and clarified which substances had to meet the release detection requirements for petroleum USTs. However, some other commenters questioned this approach because of the difficulty in preparing a complete list and the loss of flexibility such a specific list would entail as the composition of petroleum products changed over time. Numerous commenters provided suggestions for adding or deleting specific substances from the list.

In today's final rule, the proposed list of petroleum substances in the Supplemental Notice is not used, although the general categories from the list have been included in the final definition of regulated substance. Thus, the definition of regulated substance retains the statutory language that was originially proposed, except that it has been revised to reference the petroleum refining process and include a list of seven basic categories of petroleum or petroleum-based substances considered by EPA to be "regulated substances." This addition to the federal definition is intended to respond to those commenters who requested more clarity about the scope of petroleum substances included within Subtitle I jurisdiction. The final rule also includes definitions for hazardous substances UST systems and petroleum UST systems for the purpose of clarifying, as requested by some commenters, which regulated substances are subject to the secondary containment requirements for new USTs storing hazardous substances and which are subject to the release detection requirements for new USTs storing petroleum or petroleum products. (These terms and their use to discern how mixtures are treated are discussed in section IV.A.4.b.)

(ii) Revisions in the final rule and public comments on the proposal. In the final rule regulated substance is defined as: "(a) any substance defined in section 101(14) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (but not including any substance regulated as a hazardous waste under Subtitle C), and (b) petroleum, including crude oil or any fraction thereof that is liquid at standard conditions of temperature and pressure (60 degrees Fahrenheit and 14.7 pounds per square inch absolute). The 'regulated substance' includes but is not limited to petroleum and petroleum-based substances comprised of a complex blend of hydrocarbons derived from crude oil through processes of separation, conversion, upgrading, and finishing, such as motor fuels, jet fuels, distillate fuel oils, residual fuel oils, lubricants, petroleum solvents, and used oils." In summary, the proposal's codification of the statutory definition of "regulated substance" has been retained in sections (a) and (b) of the final definition (see above). Also, the proposal's elaboration of the meaning of petroleum in a separate definition of the term has been deleted (see section (iii) below), but several general categories in that proposed definition have been listed in the final definition of regulated substance to respond to some commenters' requests for clarification of the scope of the substances covered by the regulations.

The first part of today's final definition of regulated substance (section (a)) refers to the specific list of substances (both chemicals and discarded chemical products) that are defined by regulation under CERCLA (see 40 CFR Part 302). The Subtitle I program covers all hazardous substances except those that are hazardous wastes. Few comments were submitted concerning this list or section (b) of the proposed definition (the statutory definition of petroleum). The two questions raised in most public comments were (1) whether the storage of a particular substance was regulated under Subtitle I, and (2) what release detection was required for new UST systems storing a particular substance (see section (iii) below).

EPA originally proposed to define petroleum as crude oil, any fractions of crude oil and refined petroleum fractions, such as gasoline, kerosene, heating oils, and diesel fuels. In the Supplemental Notice to the proposal, EPA requested comment on the appropriateness of adding to the definition a specific list of substances that was based on the fundamental petroleum refinery process. Many commenters agreed with the proposed use of the crude oil separation processes as the basis for determining which substances should be subject to petroleum UST standards. However, others believed that basing the definition of petroleum strictly on the steps in the separation process was inappropriate. These commenters pointed out that this approach could result in similar substances being regulated differently, such as unleaded motor gasoline being considered a petroleum substance and leaded motor gasoline a hazardous substance because lead is added in steps subsequent to basic separation processes. Other commenters pointed out the difficulty in determining the exact point in the refinery process at which a substance is considered petroleum and at which point it becomes a chemical product distinct from petroleum.

In the refinery process, separation involves two steps: atmospheric and vacuum distillation. Heat is applied to crude oil, which separates into individual fractions because of differences in boiling points or boiling ranges. Some of these fractions can be used directly from a distillation tower; however, many of the products must go through further treatment. This treatment is known as conversion, which includes such processes as hydrocracking, catalytic cracking, coking, and alkylation. These processes are used to change the molecular weight and boiling ranges of the fractions. Upgrading is the process of improving the quality of the petroleum fraction by removing sulfur, nitrogen, and oxygen. The heating involved with this process adds stability and removes waxes, allowing lower pour points. Finishing does not mean distillation to pure chemical products, but is the final step before a petroleum product is sold at retail. An example of finishing is the addition of certain chemicals to motor gasoline. Additives may include octane enhancers, which either raise or lower octane ratings, dyes for product identification by color, and detergents that remove deposits from engines. These additives may be listed hazardous substances. The complexity of this process, the variety of chemical products produced, and the variety of chemical additives mixed with petroleum products in the refinery process has led to some confusion about which substances are "petroleum" or "hazardous substance" under Subtitle I.

To overcome this confusion and respond to comments received on the proposal, the final rule does not include a separate definition of petroleum. Instead, the final rule language for "regulated substance" has been amended to clarify what petroleum and petroleum-based substances, hazardous substances, and mixtures are within the regulated universe.

The final definition of regulated substance has been revised to refer to products from the refinery process, and it lists seven general categories of petroleum and petroleum-based substances so that the breadth of the coverage of the regulations is clear. Each of these general categories in fact consists of many specific individual products or substances. By not individually listing these different products and grades, EPA intends that any future adjustments in specific product composition (for example, changes made to respond to market demands) will not affect the product's classification as a "regulated substance." These seven categories correspond to the major categories in the list of petroleum substances and mixtures proposed in the Supplemental Notice. Nearly all petroleum products in use today are included in the seven categories listed in the definition. The general reference in the definition to the products from the refining process (discussed above) will aid in identifying the remaining unlisted regulated substances. Under this approach, EPA will not need to continually update the list (for example, motor gasolines is a category of regulated substance now and in the future, although new blends of motor gasoline, such as "mid-grade," may be developed or new additives may be used).

The Agency believes that this approach will make it easier to determine the regulatory status of an individual substance or blend under Subtitle I and ease the implementation burdens on the UST owner and operator, and the implementing agency. Any owner or operator trying to determine whether a tank system contains "regulated substances" and is subject to Subtitle I requirements must first determine if the substance belongs to one of the seven general categories of regulated petroleum substances. If not, then the owner or operator next must determine whether the stored material is included within the production process and physical properties description for petroleum products. If not, then the owner or operator must finally determine whether the substance is listed as a hazardous substance under section 101(14) of CERCLA (see 40 CFR Table 302.4), except for those listed as "hazardous wastes" under Subtitle C of RCRA. If the substance has not met one of these three definitions, then it is not a regulated substance.

(iii) Petroleum. The proposed definition of petroleum has been deleted from the final rule. A separate definition of petroleum was not included in the final rule because now no regulatory distinctions are based solely on whether the stored substance is "petroleum" or a "hazardous substance." However, regulatory distinctions concerning the selection of release detection equipment are based on whether a new tank system is a "petroleum UST system" or a "hazardous substance UST system." All other technical requirements are the same for all UST systems storing regulated substances.

In response to commenters' concerns about how to determine what type of release detection is applicable to a new UST system, the final rules include definitions that distinguish between "petroleum UST systems" and "hazardous substance UST systems." Owners and operators of new petroleum UST systems may utilize a variety of release detection methods because petroleum or petroleum-based substance releases are more predictable in their fate and transport underground, create relatively well-known exposure risks, and are subject to more widely available release detection and corrective action technologies. For regulatory purposes, petroleum UST systems may store petroleum or petroleum-based substances, petroleum and de minimis hazardous substance mixtures (e.g., used oil), or hazardous substances with properties similar to petroleum products. Thus, the types of stored substances subject to the release detection requirements for new petroleum UST systems are somewhat broader in scope than what constitutes simply "petroleum." This is reflected in a revised definition of "petroleum UST system," which includes a replacement of the proposal's 50-percent rule for petroleum-hazardous substance mixtures with a de minimis rule. (See the discussion in section IV.A.4.b. concerning the definitions of "hazardous substance UST system" and "petroleum UST system.")

The Agency will continue to use the statutory definition of "petroleum" for purposes of the LUST Trust response program under section 9003(h). Except for the requirement that petroleum must be a liquid at standard conditions of temperature and pressure, the term has the same definition as the term "petroleum" defined under CERCLA sections 101(14) and 101(33). The Agency interprets these terms to include the same substances, i.e., crude oil and refined fractions of petroleum, including gasoline and diesel fuels. The term "petroleum" includes the inherent "hazardous substance" constituents in crude or refined oil but does not include contaminants present in or mixed with the petroleum. Under section 9003(h), the Agency may undertake or order corrective action with respect to a release of petroleum from an UST system. The response program, however, is not limited to UST systems containing solely petroleum but, rather, requires only that the release from the UST contain petroleum. Thus, petroleum-hazardous substance mixtures would also be subject to the section 9003(h) corrective action authorities. This is consistent with Congressional statements concerning the jurisdiction of the section 9003(h) program. (See H.R. Conf. Rep. No. 962, 99th Congress, 2d. Sess., p. 228 (1986).)

(d) A tank is 10 percent or more beneath the surface of the ground if its volume (including the volume of its connected underground piping) is 10 percent or more beneath the ground surface or otherwise covered with earthen materials.

This definition reflects the intent of the UST regulations to govern underground tanks that could leak directly into the ground undetected. Thus, the following types of tanks are included within UST jurisdiction: tanks that are underground; in-ground open-top tanks; and tanks that are above grade but are covered with earthen materials (for example, to comply with fire codes). Tanks that are above the ground surface and are covered with non-earthen materials are not included within the scope of this definition.

The phrase "so that physical inspection is precluded" has been removed from this definition since proposal. One commenter argued that this phrase could be construed to bring under the jurisdiction of the UST program any totally aboveground tank that is permanently covered or shielded from view (e.g., by insulation). EPA agrees with this commenter that such tanks, as long as their volume, including the volume of connected underground piping, is not 10 percent or more beneath the surface of the ground, are not the focus of this program and should not be subject to UST regulations. These tanks are not subject to the same corrosive forces as are underground tanks and may be more easily inspected visually than other belowground tanks.

Other commenters referred to aboveground tanks that are enclosed in concrete vaults and are surrounded by inert material such as sand or vermiculite. The commenters believed that these tanks should not be defined as USTs. Under the changes to this definition in today's rule, aboveground tanks surrounded by sand would be within the scope of these regulations, because sand is an earthen material and has the potential to create corrosion. Vermiculite is not considered an earthen material and would not promote corrosion, and, therefore, tanks that are covered by this material are not considered USTs.

The statute excludes nine types of tanks from the definition of underground storage tank. Eight of these nine types of exclusions are described below. The ninth, on septic tanks, is not discussed because no changes have been made to the proposal and no comments were submitted to EPA on this exclusion.

(2) Farm or Residential Motor Fuel Tank Exclusion. The first group of tanks excluded by the statute is "farm or residential tanks of 1,100 gallons or less capacity used for storing motor fuel for noncommercial purposes." Following are definitions for the key terms of this exemption.

(a) A farm tank is a tank located on a tract of land devoted to the production of crops or raising of animals, including fish. To be exempt from UST jurisdiction, a farm tank must be located on the farm property. "Farm" includes fish hatcheries, rangeland, and nurseries with growing operations.

"Farm" does not include laboratories where animals are raised, land used to grow timber, and pesticide aviation operations. Moreover, this definition does not include retail stores or garden centers where the product of nursery farms is marketed, but not produced. This definition, as promulgated, is unchanged from the proposal.

One commenter argued that tanks at golf courses are essentially the same as tanks at sod farms; both types are used to hold fuel in support of sod and turf development. For these reasons, the commenter contended, these tanks deserve to be included under the farm exemption. The Agency does not agree that the similarities between sod farms and golf courses merit inclusion of tanks at golf courses within the farm tank exclusion. The Agency does not believe the term "farm" under section 9001 of RCRA, reasonably interpreted, includes golf courses or other places dedicated primarily to recreational, aesthetic, or other non-agricutural activities.

(b) Motor Fuel in today's rule means petroleum or a petroleum-based substance that is motor gasoline, aviation gasoline, No. 1 or No.2 diesel fuel, or any grade of gasohol, and is typically used in the operation of a motor engine.

As originally proposed, motor fuel was defined as petroleum-based fuel used in the operation of an engine that propels a vehicle for transportation of people or cargo. In the general interpretation of this phrase, motor fuel was limited to motor gasoline and diesel fuel used in automobiles, trucks, and buses. Many commenters felt that gasohols should be added to the list of motor fuels, because alcohol-type fuels are an alternative energy source encouraged by many states such as California. Commenters also felt that the term motor fuel should not be restricted to vehicles used for transportation purposes because some motors are stationary engines. The Agency agrees that the proposed definition was unnecessarily restrictive.

The final rule lists five types of motor fuel that are typically used to operate motor engines. Gasohols are included as motor fuels because EPA agrees with public comment that these are commonly used as and understood to be motor fuels. The proposed language restricting "motor fuel" to fuels used in transportation has been deleted from the definition because the term "motor fuel" does not in itself describes a use of the fuel, but rather describes a type of fuel. The statutory exclusion already contains a "use" limitation by restricting the exclusion to motor fuels stored for "noncommercial" purposes.

Accordingly, today's final rule defines motor fuel in terms of specific types of fuel. The definition lists typical uses to give descriptive, not restrictive, information about these substances. The final rule thus includes fuels used in stationary motors. The structure of this definition parallels that of heating oils.

(3) Heating Oil Tanks Exclusion. The second group of tanks excluded from UST jurisdiction by statute are tanks used for storing "heating oil for consumptive use on the premises where stored." Following are definitions for key terms of this exclusion:

(a) Heating Oil means petroleum that is No. 1, No.2 , No. 4-light, No. 4-heavy, No. 5-light, No. 5-heavy and No. 6 technical grades of fuel oil; other residual fuel oils (including Navy Special Fuel Oil and Bunker C); and other fuels when used as substitutes for one of these fuel oils. Heating oil is typically used in the operation of heating equipment, boilers, or furnaces.

The proposed rule defined heating oil as either one of eight technical grades of fuel oil (No. 1; No. 2; No. 4-light; No. 4-heavy; No. 5-light; No. 5-heavy; No. 6; and residual) or fuel oil substitutes such as kerosene or diesel when used for heating purposes. This definition has been revised in the final rule to clarify which technical grades of fuel oil the Agency believes are heating oil. In addition, the definition has been revised in response to comments on the use of heating oil substitutes.

The list of grades of fuel oils has been reworded because, since proposal, the Agency has discovered that "residual" is not a specific technical grade of fuel oil, but refers to several grades of fuel derived from certain operations in the refinery p rocess. Also, Navy Special Fuel Oil and Bunker C are included in the final definition as examples of residual fuels.

Several commenters suggested changes to the definition to modify the applicability of the heating oil exclusion to tanks storing fuel oil substitutes. Several commenters stated that both No. 2 diesel fuel and kerosene should be included as heating oil because their chemical makeup is similar to each other and No. 2 fuel oil. Additional commenters thought that the exclusion should not be limited to oil used for heating purposes. The Agency agrees that the heating limitation is inconsistent with the statutory language of the exclusion that limits "use" only by requiring "consumptive" use. The final rule definition, therefore, includes heating as a typical use of the fuels but does not limit the exclusion to fuels so used. The exclusion does, however, limit the use of substitutes to those situations where the substitute is actually used in place of one of the technical grades of fuel oil. For example, tanks that contain used oil at a typical retail gas station are not excluded unless the used oil is consumed on-site as a substitute for fuel oil (burned in an on-site space heater, for example). Tanks that store used oil awaiting recycling pickup are not heating oil tanks. Another example of a tank that is not a heating oil tank is one that stores diesel fuel for an on-sit