a topic summary by
Jerome Edinger
| I. Introduction
This paper focuses on the technical records that are required in Texas for underground storage tanks (UST's) and includes summary check boxes which summarizes the UST's record keeping requirements. Since the author is an instructor of Corrosion Technology at Kilgore College and NACE certified Corrosion Specialist and Consultant, this paper shows the corrosion point of view and does not necessarily consider all the regulatory aspects of UST record keeping. The information included in this paper was collected from the Texas Administrative Code Title 30 Chapter 334 Subchapter C but the record keeping examples and procedures discussed will in many cases apply to other states and EPA requirements. This topic is important because many owners and operators of UST systems are finding out that "legible copies of all required records pertaining to a UST system" must be maintained "in a secure location on the premises of the UST facility" and must be "immediately accessible for reference and use by the UST system operator, and shall be immediately available for inspection upon request by commission personnel". This does not mean that all records must be kept forever and it does not mean that only current records are required. The purpose of this paper is to help sort out the records and storage requirements that a UST owner or operator needs available at the UST facility and to demonstrate the reasoning behind the corrosion requirements. |
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General records Temporary Records Copies of the results of the various required tests described in this paper must also be maintained by the owner and operator of UST's for at least five years after the date of the test. These include the following:
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| III. Corrosion
Prevention Aspects The corrosion prevention requirements can be categorized into 3 areas. Internal corrosion prevention of the UST and components, external corrosion prevention of the UST, and external corrosion prevention of UST components. It is necessary to consider the UST separately from the UST components because there are distinctions in the regulations that will require different records as will be shown. |
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IV. Corrosion Protection
Prerequisites
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Examples
of typical codes that apply to UST's are shown on this table.
| Standard or Code | Examples | |
| Bare Steel | Inspection according
to a Code, Standard, or Independent Laboratory |
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Coated Steel with Factory Installed CP |
UL-58 UL-1746 Part I |
Sti-P3 |
| Coated Steel
with Field- Installed Cathodic Protection |
UL-58 NACE Control of External Corrosion on Liquid Storage Systems |
Approved Manufacturers |
| FRP | UL-1316, ASTM D4021 |
FRP |
| Steel/FRP Composite
or Steel with FRP Cladding |
UL-1746 Part
II ACT 100-U |
Perma-Tank, Watco, Futura-Thane 527 |
| Alternative Methods |
| V. UST Internal
Protection Records This diagram shows the procedure to determine the requirements of UST's depending upon the date of installation. If the UST was installed before 12/22/88 there must be permanent records to verify that the tank was upgraded to the current standards and codes. These records may include tank tightness testing, lining, or other methods listed in Title 30 Chapter 334. If the UST was installed after 12/22/88 and is in compliance with the current standards and codes, there must also be records showing that the material of construction is compatible with the store substance and that striker plates were installed below all of the openings. In summary the following records should be available:
If the above records
are available, there are additional requirements for UST's that contain
hazardous substances. Hazardous substance UST's must also include secondary
containment systems and monitoring records. |
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| VI. Piping and Components
Internal Protection Records The piping and related components of an UST system must first be constructed of materials that are compatible with the stored substance and then the rules depend upon whether the piping is pressured, suction, or gravity fed. The diagram shows that pressured piping requires automatic line leak detection systems and testing and monitoring records to prove their performance. If the piping is not a suction system (gravity fed), there must be records showing the 3 year pipe tightness tests and the monthly release detection procedures. Suction piping systems do not require leak detection or tightness testing. Required records may include;
If the stored material is hazardous, there are additional requirements already described in the UST section V. |
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VII. UST External
Protection Corrosion protection of the external surfaces of UST's is often the most costly aspect of the UST rules. It is important to remember that all 5 options require records to verify compliance. These records may include;
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| TAC 334.49(b)(1-5)
lists the 5 options for corrosion protection of UST's, AST's and their
components. Option #1 is to utilize a "non-corrodible material" which is compatible with the stored substance. An example of this type is a fiberglass reinforced plastic UST that is suitable for the substance being stored. Permanent records should verify that the material is suitable, by meeting a standard of construction such as UL Standard 1316 or ASTM Standard D 4021 and there may also be testing records for tightness tests, secondary containment, and release detection if the stored substance is classified as hazardous or if the tank was upgraded. Option #2 is to insure that the UST is "electrically isolated from the corrosive elements " such as in the case of a tank placed into an open area such as a sump, vault, etc. This allows for visual inspection to insure that the tank is not leaking. Option #3 requires a secondary containment device that must be designed and installed in accordance with an applicable code or standard of practice. An example of this option is a double walled tank or a suitable liner. Option #4 allows for a steel/fiberglass-reinforced plastic composite tank or a steel tank with a bonded fiberglass-reinforced plastic external cladding or laminate designed and installed in accordance with an applicable code or standard of practice. Option #5 is a coated steel tank with the application of cathodic protection that is described in the next slide. |
| VIII. Corrosion
Cell In order to understand the value of cathodic protection it is helpful to see how the typical corrosion process happens by studying a corrosion cell. NACE has identified the 4 requirements for electrochemical corrosion of metal. Ordinary underground corrosion cannot proceed without the presence of an anode, a cathode, a metallic connection, and an electrolyte. Since metal atoms are held together by their electron attractions, this cell provides the mechanism for electrons to leave thus removing the "glue" that holds metal atoms together and resulting in metal loss. Most metals contain zones with high energy called anodes, which tend to give up electrons and lower energy zones called cathodes, which will accept electrons. It can be shown that soil provides the electrolyte and the tank metal provides the metallic path so that all 4 components are available on an underground storage tank to produce a corrosion cell. |
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| IX. Cathodic Protection
When cathodic protection is installed, a new more powerful anode is connected to the circuit that overcomes the previous anodes, which turns the entire metal (tank) into a huge cathode. This is why the term "Cathodic Protection" is used. Since the cathode of a corrosion cell does not corrode, neither does the tank since it is now a single cathode. The previously corroding areas become cathodic and stop corroding. |
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| X. Sacrificial Cathodic
Protection There are two common methods of achieving cathodic protection. The first method is called a sacrificial system or galvanic system. The driving force for this method is the energy difference between the anode usually magnesium or zinc and the steel tank. Sacrificial cathodic protection systems are often factory installed such as the sti-p3 system, which consists of magnesium anodes mounted to the tanks, which provide a small amount of current. Records for this type of system include the following:
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XI. Impressed
Cathodic Protection
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| XII. Cathodic
Protection Limitations Regardless of the type of cathodic protection, there are several limitations that must be considered when controlling corrosion. Attenuation refers to a reduction or lessening of protective current on the structure furthest away from the anode or groundbed. Many times one anode is not sufficient to "reach" all the surfaces of the tanks and piping that need protective current. It should also be remembered that neither internal surfaces nor above ground surfaces will be protected by an underground cathodic protection system. Other problems such as shielding and interference may result if the groundbed system is not placed carefully. It is possible to actually cause corrosion by misplacement of groundbed anodes. It is also possible to over protect a tank that could possibly damage coatings or set up interference currents. Additional problems can result from stray dc or ac current from nearby electrical systems. |
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| XIII. Installation
Problems This slide lists the common installation problems that must be considered when choosing either the sacrificial or impressed cathodic protection systems. Galvanic systems are extremely dependent upon the soil resistivity and can not be used economically for bare metal surfaces if the soil resistivity exceeds 3000 ohm-centimeters. The size, depth, and location of galvanic anodes is also critical to achieve satisfactory results. Calculations should be done to insure that the life of the anode is adequate. Fortunately, factory applied galvanic systems take these factors into consideration but if any of the di-electric bushings are shorted, the life of the galvanic anodes will be compromised. It is also important that the entire galvanic anode be placed deep enough to remain moist to produce a uniform current. Impressed current systems can overcome most of the problems of the galvanic anodes but have their own set of problems. Impressed systems can be adjusted to compensate for most high soil resistivities; however, the higher operation voltages and currents may cause interference. There is also more maintenance required to keep the rectifier operating and additional record keeping. Another problem is the corrosion of the positive wires that must be prevented by keeping the insulation free of all nicks. Any splices of the positive cable of an impressed current system must be completely and permanently waterproof or the wire will corrode through in a short time. I have a sample of a large positive wire that separated by corrosion after moles chewed on the insulation in West Texas. Finally, the voltage readings taken on an impressed system must be read carefully because it is possible to connect the wires backwards and produce a positive voltage on an UST which would promote corrosion rather than stop it. |
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| XIV. Cathodic Protection
Records This drawing compares the records required for galvanic systems to impressed current systems and shows the 60-day records on the impressed system which are not required for galvanic or sacrificial systems. |
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| XV. UST Components
External Corrosion Protection In this last drawing you can see two categories of materials which may be protected by the same 5 options as the UST. There is however a sixth option for "other underground components of a UST system (including vent lines, fill risers, submersible pump risers and housings, spill containment vessels, and tank fittings (e.g. bunghole plugs)) which do not routinely contain regulated substances". This second category may be protected from external corrosion by thorough coating or wrapping with a suitable dielectric material that is compatible with the stored regulated substance. TAC30I334.49(b)(6) Records therefore should show the option that was chosen and any tests that are a part of the chosen corrosion control method.
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| XVI. Summary In summary, there are a variety of records both permanent and temporary that must be kept at the UST site which demonstrate compliance with all aspects of the TNRCC Title 30 rules. An audit should be done by owners or operators to insure that the required documents are available for an official inspection. This paper can be used as a guide to see if there are sufficient records available to satisfy the requirements of the TNRCC of Texas and most regulatory agencies responsible for UST compliance. |
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