Code of practice for storage tank systems containing petroleum and allied products: appendix B

Appendix B: explanatory material

B.1.4.2 Allied petroleum product - It is understood that a number of chemicals not included in this definition may be stored in underground storage tanks. This definition, however, represents combustible and flammable products that are directly petroleum-based and are the most widely used petroleum products in the manufacturing sector.

B.1.4.2 Interstitial space includes the following space:

  1. outside the storage tank bottom and above a synthetic membrane liner or prepared soil layer;
  2. between the storage tank bottom and a secondary bottom creating a leak containment space;
  3. between two pipes of a double-wall piping system;
  4. between a pipe and a synthetic membrane liner; or
  5. space between a storage tank and a secondary containment system.

B.1.4.2 Used oil - The definition of used oil was taken from the 1989 Canadian Council of Ministers of the Environment (CCME) publication, PN 1042, "Code of Practice for Used Oil Management in Canada " with the following modifications.

  1. the category of "metal-working fluids" has been removed as this product class is considered to be sufficiently different from the definition of petroleum products. Since metal-working fluids may include a substantial amount of water, further consideration would have to be given to the need to line steel tanks.
  2. the category of "insulating fluids or coolant" has been modified for similar reasons, and now reads as "insulating oils".

Used oil contains primarily hydrocarbons; however, it may also contain additives (for example, a total of 14% by volume of detergents and viscosity-improvers in lubricating oils for gasoline engines). It contains physical and chemical impurities (for example, solids, metals, and chlorinated organics) due to physical contamination and chemical reactions occurring during its use. Contamination of used oil may also occur from mixing with other oily fluids or fluid wastes when it is collected for recycling.

This Code does not treat used oil exclusively as a hazardous waste. Used oil may or may not be designated as a hazardous waste depending on the types and amounts of chemical impurities it contains. For example, used oil containing 50 ppm or more of Polychlorinated biphenyls (PCBs) is designated as a hazardous waste in most Canadian jurisdictions. If the used oil is designated as a hazardous waste, other requirements for its storage may apply. Consult the authority having jurisdiction.

B.3.2.6 The CCME "Guideline for Controlling Emissions of Volatile Organic Compounds from Aboveground Storage Tanks" applies to storage tanks having a capacity of more than 4000 L, designed to contain a petroleum product that has a vapour pressure of 10 kPa or greater. The published document is available from Manitoba Statutory Publications.

B.3.3.1(1) (e)(ii) The overfill alarm system required shall be in addition to the alarm or gauging system that is routinely used. This system shall be used as a back-up system when the primary means of detecting a high level has failed.

B.3.5.1 (2) It is important to note that the requirements of the fire authorities must be met if any used oil collection tank is considered for use indoors.

B.3.8.1(1) The use of certain secondary containment techniques may preclude the use of cathodic protection and in some cases cause accelerated corrosion of the storage tank bottom. A corrosion expert shall be consulted.

B3.9.2 (2)(a) The authority having jurisdiction may specify an acceptable material for a secondary containment impermeable barrier based on local conditions or previous experience. Regardless of material, proper installation and ongoing maintenance of a secondary containment impermeable barrier is important.

B.3.9.3 (1) The installer shall advise the electrical contractor that synthetic membrane liners have been used and ensure that the liner is not punctured by grounding rods. It is recommended that grounding rods not be inserted within the dyked areas where a synthetic membrane or clay liner has been used for secondary containment. If penetrations are required, locating the penetrations at a high point reduces the likelihood of leaks.

B.4.2.7 Abandonment in-place of an out-of-service storage tank is not normally an acceptable practice. Storage tanks shall not be located near or under building foundations or in locations where the ultimate removal of the storage tank would be impractical.

B.4.5.3 (1)(b) Stray current from an impressed current system can cause corrosion to storage tank systems that are cathodically protected by sacrificial anodes.

B.4.5.3 (2) The anodes on a cathodically protected storage tank that conforms with Canada/Underwriters' Laboratories of Canada (CAN/ULC) S603.1, "Standard for Galvanic Corrosion Protection Systems for Steel Underground Tanks", are designed to protect the tank only. Inadequate corrosion protection of such cathodically protected storage tanks can occur if the storage tank is not electrically isolated from the piping or other storage tanks.

B.4.5. Rectifier shall have a non-resettable 115V. AC elapsed time indicator with 99,999 hour capacity. A battery powered downtime counter of the same hour capacity is an optional alternative.

B.5.2.5 Mechanical joints, such as flanged joints or couplers, shall not be used below ground. Additionally, it is good practice to minimize the use of threaded joints below ground.

B.6.2.6 Continuous in-tank leak detection system (CITLDS) method combines use of an Automatic Tank Gauge probe to collect data and sophisticated data analysis used in Statistical Inventory Reconciliation (SIR) techniques. An underground storage tank is monitored continuously without interfering with normal tank operations. These systems are designed to meet the monthly monitoring performance standard of detecting a leak of 0.76 L/hr or 567 L per month with 95% probability and 5% false alarm.

B.6.2.11. (1)(h) The determination of an appropriate procedure for a leak detection test of piping with a volume greater than 1000 L is based on several variables, including the ability to drain and isolate the line, line volume, product characteristics, the availability of test equipment, and the reliability of procedures to detect leaks. The best results will be generated when the product is drained from the line, the line is blinded or isolated at each end, and the line is pressurized with an inert gas. The length of time that the line is pressurized should be consistent with its volume. Industry's best practices should also be taken into consideration. Typically, refineries and terminals will use an inert gas to pressurize a line at one and one half times normal operating pressure and monitor the pressure for four or more hours.

B.6.2.13 (1) Numerous technologies are available to conduct a precision leak detection test and determine the presence of leaks in a storage tank, associated connections, risers, connected equipment and the vent system. Commonly used methods include vacutech, mass measurement, volumetric, and acoustics. The various test systems have specific preparation requirements, operating procedures, and technical limitations. These requirements have been determined by the equipment manufacturer and are based on the design of the technology. Failure to follow the procedures or operate within these parameters can impact the accuracy of results and scope of the evaluation.

The test equipment has also been designed to evaluate various areas of the storage tank and associated equipment. In some cases, more than one test must be competed in order to evaluate the underfill area (below the fluid level) and the ullage space (above the fluid level). For example, a mass measurement or volumetric test could be used to evaluate the area below the fluid level. An acoustics test would be used in conjunction with the underfill test to evaluate the ullage space, risers and vent system. However, in some cases a test procedure can be used in more than one application. An ullage test could also be used to test an empty tank.

Various factors, including tank type - aboveground, underground, single-wall or double-wall, - interstice space design, and product level, must be considered and will influence the selection of an appropriate test. Underground storage tanks require an evaluation of the primary containment, connections, risers, connected equipment and the vent system. An aboveground storage tank requires an evaluation of the floor or any area of the tank that cannot be visually inspected for leaks. Tank components and leak detection test requirements are outlined in table 10:

Table 10: tank components and leak detection test requirements
Tank description Product level Test type
Single-wall underground tank empty ullage test
Single-wall underground tank with product complete tank test
Double-wall underground tank empty ullage test
Double-wall underground tank with product ullage test and low-pressure inert gas or vacuum leak detection test (LPVLDT) on the interstice; or complete tank test
Double-wall underground tank with brine or vacuum interstice monitor empty ullage test
Double-wall underground tank with brine or vacuum interstice monitor with product ullage test; or complete tank test
Single-wall aboveground tank with product underfill test
Double-wall aboveground tank empty ullage test
ullage test and LPVLDT on the interstice
Double-wall aboveground tank with product underfill test
underfill and LPVLDT on the interstice

B.6.3.1 (2) When the leak detection device is not an electrical device (such as a monitoring well or statistical inventory reconciliation), electrical interlocks may not be possible.

B.6.3.2 Even with the present mechanical type of line-leak detectors, a line leak within a submersible pump system can result in large volumes of product being pumped into the ground. Leaks from submersible pump systems have been the cause of some of the largest environmental and safety incidents. Where line-leak detectors are used, they shall not be bypassed when problems are encountered while dispensing the product.

The authority having jurisdiction may choose to prohibit the use of remote or submersible pump systems unless the pipes and pumps are within an acceptable secondary containment system.

B.6.5.3 The soil shall consist of gravels, coarse or medium sands, coarse silts, or other permeable material.

B.6.5.8 A filter pack is a porous medium usually consisting of sand or pea gravel.

B.6.5.13 Monitoring wells shall not be constructed of Schedule 20 polyvinyl chloride (PVC) "sewer" or leach field piping.

B.6.7.2 (1) A mechanical line leak detector (MLLD) is unable to reliably detect small leaks. From the effective date of this code and at the discretion of the authority having jurisdiction, an MLLD is not recognized as a method of detecting leaks in pressurized piping. Additional methods of leak detection may be used, or alternatively, the MLLD can be replaced by an electronic line leak detector (ELLD).

Inventory control for a storage tank is a form of inventory monitoring for motive fuel storage tanks. However, inventory control by itself is not an acceptable form of leak detection. Inventory control combined with acceptable statistical inventory reconciliation is an acceptable form of leak detection for the entire storage tank system.

An under-pump check valve is located directly below the pump of a suction system and is the only check valve installed on the system. With continuous slope back to the tank, a leak in the pipe will cause product to drain into the tank.

B.7.3.4 (2)(b) Allows a field-erected storage tank to simply follow the requirements of American Petroleum Institute (API) Std 653-01, "Tank Inspection, Repair, Alteration, and Reconstruction." Strict adherence to API Std 653-01, "Tank Inspection, Repair, Alteration, and Reconstruction." is required. API Std 653-01, "Tank Inspection, Repair, Alteration, and Reconstruction." requires periodic corrosion monitoring. Once a corrosion rate is established, subsequent corrosion monitoring and repairs to the tank bottom can be performed prior to the occurrence of any perforations. If perforations do occur, it can be assumed that the provisions of API Std 653-01, "Tank Inspection, Repair, Alteration, and Reconstruction." have not been strictly followed. If this occurs, stronger preventive steps are specified.

B.8.3.2 (1)(a) To facilitate early detection of leakage from an underground storage tank system, proper inventory records must be developed, maintained, and reviewed continuously for any developing trends that may signify a loss of product. The traditional method of doing this has been to "dip" the storage tanks. Dipping is the actual measurement of the liquid contents of the storage tank with a graduated stick (dip stick). This measurement combined with the storage tank chart (suitable for use with the specific tank) can be converted to the liquid volume of the storage tank. A measuring device (generally a recording type of pump) that will measure the amount of product withdrawn from the storage tank is also an integral part of the inventory control system. Finally, it is necessary to reconcile the product in storage with the amount recorded (daily/weekly) as having been withdrawn. Any continuous discrepancy (shortage) must be investigated as a possible leak from the underground storage tank system.

B.8.4.1 (2)(b) Frequent visual inspections of an aboveground storage tank system is required to provide early detection of equipment failures and product spills. The authority having jurisdiction may decide that operators of tanks of 5000 L and less capacity do not have to do daily checks. In addition, it may not be possible or practical to inspect a storage tank at unattended remote sites.

B.8.5.2 (1)(b) The National Fire Code of Canada (NFCC) requires that a vehicle operator remain in close proximity to the discharge control valve. There is concern that a vehicle operator may interpret ‘close proximity’ to include sitting in the cab of the tank vehicle, out of sight of the delivery point. Many overfills occur because the tank vehicle operator is not observing the filling operation and is unaware that the storage tank is overfilling. Therefore sentence 8.5.2(1)(b) is more specific and requires a vehicle operator to be more attentive.

B.8.5.3 (2) A significant number of the spills that occur at aboveground storage tank facilities result from improper procedures during routine activities. These accidents can be reduced or eliminated if operating personnel are properly trained about correct safety procedures and the importance of following them to prevent injury and environmental incidents. Training must be periodically followed up to ensure that proper procedures are being followed.

B.8.6.1 (1) Cathodically protected potentials are required on all parts of the tank bottom in order for it to be considered to be cathodically protected. when a perimeter anode type cathodic protection system is used, the potential at the tank centre can be much different than that measured at the tank perimeter and a corrosion expert should be consulted

B.8.7 The Canadian Petroleum Products Institute (CPPI) "Code of Practice for Management of Water Effluent Quality at Petroleum Storage and Distribution Facilities" may be useful for anyone who owns or operates an oil-water separator.

An oil-water separator does not remove the soluble fraction of oil that is in the water or storm runoff. Therefore, it shall be noted that even if an oil-water separator produces an effluent that has an oil and grease or hydrocarbon content that is below provincial or territorial discharge limits, the effluent may still be acutely toxic to fish.

It is recommended that the designer shall ensure that when an oil-water separator is to be installed that a proper design basis is used. The owner shall control sources to the separator and remove the free oil layer and accumulated separated solids as required by the manufacturer's operating instructions.

B.8.7.5 Detergents and cleaning solutions cause oil to emulsify in water and prevent effective separation. Never wash trucks with such products in areas that drain to an oil-water separator.

B.8.8.3 At the time of a change of ownership, an environmental assessment or investigation of site contamination shall be conducted on real property on which storage tanks are located.

B.8.12.1 (1) The tank bottom water from the bottom of a storage tank normally contains water, insoluble hydrocarbon, and dissolved hydrocarbons. The concentration of dissolved or soluble hydrocarbons is often sufficiently high that the tank bottom water would be considered toxic if a biological toxicity test were conducted. Since oil-water separators, such as an API separator, only separate insoluble oil from water, the tank bottom water shall be segregated in a holding tank and sent to a wastewater treatment facility either on- site or off- site (and not directly to an oil-water separator).

B.9.3.1 Corrosion is the major factor which limits the life of a steel storage tank system and corrosion can be controlled for an indefinite period of time if corrosion protection is maintained. When cathodic protection system is used it is only effective when the system is "on". Therefore, the cathodic protection system must be maintained and operated continuously.

B.9.5.3 (1) The authority having jurisdiction could consider any of the following as reasonable conditions for allowing the owner to abandon a storage tank in place:

  1. located in whole or in part beneath a permanent building or other facility so that excavation of the storage tank is not practicable;
  2. so large or of a type of construction that the excavation of the storage tank is not practicable;
  3. inaccessible to the heavy equipment necessary for removal of the storage tank; or
  4. situated so that removal of the storage tank would endanger the structural integrity of nearby buildings or other facilities.

B.9.5.5 (1) Sand, gravel, or concrete are examples of what is considered acceptable inert material. Foam shall not be considered an acceptable inert material.

B.9.5.4 A precision leak detection test conducted in conformance with section 8.10, or borehole sampling of the soil may be required to satisfy the authority having jurisdiction that the soil under and around the storage tank has not been contaminated by a petroleum product or allied petroleum product.

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