18 Alaska Admin. Code § 78.065

Current through September 25, 2024

Section 18 AAC 78.065 - Release detection methods for tanks

(a)General requirements. Each method of release detection for tanks that is used to meet the requirements of 18 AAC 78.060 must meet the requirements of this section.

(b)Inventory control.Inventory control must be capable of detecting a release of at least 1.0 percent of flow-through plus 130 gallons monthly. Inventory control must be conducted monthly as follows:

(1) inventory volume measurements are recorded each operating day for petroleum

(A) inputs;

(B) withdrawals; and

(C) amount remaining in the tank;

(2) the equipment used is capable of measuring the level of petroleum over the full range of the tank's height to the nearest one-eighth of an inch;

(3) at the time of delivery, inputs of petroleum are reconciled with delivery receipts, by measurement of the tank inventory volume before and after delivery;

(4) deliveries are made through a drop tube that extends to within one foot of the tank bottom;

(5) dispensing is metered and recorded within state standards for meter calibration;

(6) at least once a month, the measurement of any water level in the bottom of the tank is made to the nearest one-eighth of an inch; and

(7) the information generated under this subsection must be reviewed analyzed, and certified by signature monthly by the owner or operator; and

(8) to meet the requirements of this subsection, an owner or operator shall ensure that one of the following are used:

(A) practices described in the American Petroleum Institute Recommended Practice RP 1621, Bulk liquid Stock Control at Retail Outlets, Fifth Edition, May 1993, adopted by reference; or

(B) another procedure, code, or standard that is no less protective of human health and safety and the environment and approved by the department.

(c)Manual tank gauging. Manual tank gauging must meet the following requirements:

(1) tank liquid level measurements must be taken at the beginning and end of a period, using the appropriate minimum duration of test value in Tab le A of this subsection, during which no liquid is added to or removed from the tank;

(2) level measurements must be based on an average of two consecutive stick readings at both the beginning and ending of the period;

(3) the equipment used must be capable of measuring the level of product over the full range of the tank's height to the nearest one-eighth of an inch;

(4) testing must be conducted at least once each week, and the four weekly results must be averaged to obtain a monthly result; a release is suspected and subject to the requirements of 18 AAC 78.200 - 18 AAC 78.280 if the variation between beginning and ending measurements exceeds the weekly or monthly standards in Table A of th is subsection; and

(5) owners and operators of tanks with a nominal capacity of 550 gallons or less, and owners and operators of tanks with a nominal capacity of 551 to 1,000 gallons and a tank diameter of 48 or 64 inches may use the method in this subsection as the sole method of release detection; owners and operators of all other tanks with a nominal capacity of 551 to 2,000 gallons may use the method in this subsection in combination with periodic tank tightness testing in place of inventory control in (b) of this section; owners and operators of tanks with a nominal capacity greater than 2,000 gallons may not use the method in this subsection to meet the requirements of this section.

TABLE A

Nominal tank capacity	Minimum duration of test	Weekly standard (one test)	Monthly standard (four test average)
550 gallons or less	36 hours	10 gallons	5 gallons
551-1,000 gallons, when tank diameter is 64 inches	44 hours	9 gallons	4 gallons
551 - 1,000 gallons, when tank diameter is 48 inches	58 hours	12 gallons	6 gallons
551 - 1,000 gallons, when tank diameter is not 48 or 64 inches	36 hours	13 gallons	7 gallons
1,001 - 2,000 gallons	36 hours	26 gallons	13 gallons

(d)Tank tightness testing. Tank tightness testing, or another test of equal performance, must be capable of detecting a 0.1 gallon per hour leak rate from any part of a tank, including the associated piping, that routinely contains petroleum, while accounting for the effects of thermal expansion or contraction of the petroleum, vapor pockets, tank deformation, evaporation or condensation, and the location of the water table. To satisfy the requirements of this subsection,

(1) the owner or operator may use only tank tightness tests that have been developed and reviewed by a nationally recognized association or third-party testing laboratory and that meet or exceed the criteria for the detection of leaks set out in the United States Environmental Protection Agency's manuals Standard Test Procedures for Evaluating Leak Detection Methods: Volumetric Tank Tightness Testing Methods, March 1990 (EPA/530/UST- 90/004), and Standard Test Procedures for Evaluating Leak Detection Methods: Nonvolumetric Tank Tightness Testing Methods, March 1990 (EP A/530/UST-90/005), the provisions of which are adopted by reference;

(2) the tests required under this sub section must be performed by a person certified under this chapter;

(3) the owner or operator shall submit to the department a certified copy of the evaluation results indicating that the criteria have been met or exceeded and a copy of the manufacturer's test protocol;

(4) an owner or operator may use tank tightness testing only if

(A) the UST meets the performance standards set out in 18 AAC 78.025 or 18 AAC 78.030; and

(B) the owner or operator complies with the monthly inventory control requirements set out in (b) of this section or the manual tank gauging requirements set out in (c) of this section;

(5) if tank tightness testing is used, the test must be conducted every five years for 10 years after the tank is installed or upgraded, whichever is later;

(6) the combination of tank tightness testing and either inventory control or manual tank gauging is a temporary release detection method and may not be used for more than the period of time indicated in 18 AAC 78.060(e)(1)(A); after that period, a permanent monthly release detection method must be used; and

(7) the department may disapprove a tank tightness test or testing system under this subsection if the

(A) test or testing system fails to disclose leaks that fall within the boundaries of the criteria stated in this subsection; or

(B) tester is not certified by the manufacturer of the test or testing system.

(e)Automatic tank gauging. Equipment for automatic tank gauging that tests for the loss of petroleum and conducts inventory control must meet the following requirements:

(1) the automatic product level monitor test must be able to detect a 0.2 gallon per hour leak rate from any part of the tank that routinely contains petroleum and a release of 150 gallons within a 30-day period;

(2) the automatic tank gauging equipment must meet the inventory control, or other test of equivalent performance, requirements of (b)(6) of this section; and

(3) the test must be performed with the system operating in one of the following modes:

(A) in-tank static testing conducted at least once every 30 days; or

(B) continuous in-tank leak detection operating on an uninterrupted basis or operating within a process that allows the system to gather incremental measurements to determine the leak status of the tank at least once every 30 days.

(f)Soil gas vapor monitoring.Vapor monitoring may be used only at certain sites and only with department approval. The department will, in its discretion, approve the testing or monitoring of soil gas vapors in the excavation zone if the following requirements are met:

(1) material used as backfill is sufficiently porous to readily allow diffusion of vapors from a release into the excavation area; for purposes of this paragraph, gravel, sand, or crushed rock are "sufficiently porous" materials;

(2) the stored petroleum, or a tracer compound placed in the tank system, is sufficiently volatile to result in a vapor level that is detectable by the monitoring devices located in the excavation zone if a release from the tank occurs; for purposes of this paragraph, gasoline is "sufficiently volatile;"

(3) the measurement of vapors by the monitoring device is not rendered inoperative by groundwater, rainfall, soil moisture, other local climatological, geologic, or hydrogeologic conditions, or other known interference so that a release could go undetected for more than 30 days;

(4) the level of background contamination in the excavation zone will not interfere with the method used to detect a release from the tank;

(5) the vapor monitors are designed and operated to detect any significant increase in concentration above background of

(A) petroleum stored in the tank system;

(B) a component or components of the petroleum; or

(C) a tracer compound placed in the tank system;

(6) the UST excavation zone is assessed as required by 18 AAC 78.090 to

(A) ensure compliance with (1) - (4) of this subsection; and

(B) establish the number and positioning of observation wells that will detect a release within the excavation zone from any part of a tank that routinely contains petroleum; and

(7) observation wells are clearly marked and secured to avoid unauthorized access and tampering.

(g)Groundwater monitoring. Groundwater monitoring may be used with department approval. Testing or monitoring for liquids in the groundwater must meet the following requirements:

(1) the petroleum stored must be immiscible in water and must have a specific gravity of less than one;

(2) groundwater may not be, at any point, more than 20 feet from the ground surface and the hydraulic conductivity of the soil between the UST and the monitoring wells or devices may not be less than 0.01 centimeters per second;

(3) the slotted portion of the monitoring well casing must be designed to prevent migration of natural soils or filter pack into the well and to allow entry of petroleum on the water table into the well under both high and low ground water conditions;

(4) monitoring wells must be sealed from the ground surface to the top of the filter pack;

(5) monitoring wells or devices must intercept the excavation zone or be as close to it as is technically feasible;

(6) the continuous monitoring devices or manual methods used must be able to detect the presence of at least one-eighth of an inch of free product on top of the groundwater in the monitoring wells;

(7) within and immediately below the UST excavation zone, the site must be assessed to ensure compliance with the requirements in (1) - (5) of this subsection and to establish the number and positioning of monitoring wells or devices that will detect releases from any portion of the tank that routinely contains product; and

(8) monitoring wells must be clearly marked and secured to avoid unauthorized access and tampering.

(h)Interstitial monitoring.Interstitial monitoring between the UST or pipe and a secondary barrier immediately around or beneath the UST or pipe may be used only if the system

(1) is designed, constructed, and installed to detect a leak from any part of a tank or pipe that routinely contains petroleum; and

(2) meets one of the following requirements:

(A) for a double-walled UST, including piping, the sampling or testing method is capable of detecting a release through the inner wall in any part of a tank or pipe that routinely contains petroleum;

(B) for a UST with a secondary barrier within the excavation zone, the sampling or testing method used is capable of detecting a release between the UST and the secondary barrier as follows:

(i) the secondary barrier around or beneath the UST consists of artificially constructed material that is sufficiently thick and impermeable to direct a release to the monitoring point and permit its detection; for purposes of this clause, "sufficiently thick and impermeable" means have a permeability of at least 10-6 cm/sec for the petroleum stored;

(ii) the barrier is compatible with the petroleum stored so that a release from the UST will not cause a deterioration of the barrier and allow a release to pass through undetected;

(iii) for a cathodically protected tank, the secondary barrier must be installed so that it does not interfere with proper operation of the cathodic protection system;

(iv) groundwater, soil moisture, or rainfall will not render the testing or sampling method inoperative so that a release could go undetected for more than 30 days;

(v) the site is assessed to ensure that the secondary barrier is always above the groundwater and not in a 25-year floodplain, unless the barrier and monitoring designs are for use under those conditions; and

(vi) monitoring wells are clearly marked and secured to avoid unauthorized access and tampering; or

(C) for a tank with an internally fitted liner, an automated device is capable of detecting a release between the inner wall of the tank and the liner, and the liner is compatible with the substance stored.

(i)Statistical inventory reconciliation. Third-party reviewed and certified release detection methods based on the application of statistical principles to inventory data similar to those described in (b) of this section must meet the following requirements:

(1) the release detection methods must be capable of detecting a leak rate of 0.2 gallons per hour or a release of 150 gallons not later than 30 clays;

(2) the release detection methods must use a threshold that does not exceed one-half the minimum detectible leak rate; and

(3) the release detection methods must report a quantitative result with a calculated leak rate.

(j)Other methods.Any other type of release detection method, or combination of such other methods, may be used with prior approval, if the method or combination of methods can, for volumetric release detection methods, detect a 0.2 gallon per hour leak rate or a release of 150 gallons in a 30-day period with a probability of detection of 95 percent and a probability of a false alarm of five percent. For non-volumetric release detection methods, the department may approve another method of release detection not described in (d) - (i) of this section, if the owner or operator shows that the method can detect a release as effectively as any of the methods allowed in (d) - (i) of this section. In comparing methods, the department will consider the size of release that the method can detect and the frequency and reliability with which it can be detected. If the method is approved, the owner or operator shall comply with any conditions imposed by the department on its use to ensure the protection of human health and safety and the environment.

(k)Certification of performance standards.The National Work Group on Leak Detection Evaluations' List of Leak Detection Evaluations for Storage Tank Systems, 17th Edition, January 11, 2010 shall be used to determine compliance with the applicable performance standards for automatic tank gauging, statistical inventory reconciliation, tightness testing, electronic interstitial monitoring, and automatic line leak detectors. The List of Leak Detection Evaluations for Storage Tank Systems, 17th Edition, January 11, 2010, is adopted by reference.

18 AAC 78.065

Eff. 3/25/91, Register 118; am 8/21/91, Register 119; am 11/3/95, Register 136; am 6/25/99, Register 150; am 1/30/2003, Register 165; am 7/25/2012, Register 203; am 9/27/2018,Register 227, October 2018

1. The American Petroleum Institute Recommended Practice 162 1, Bulk liquid Stock Control at Retail Outlets, Fifth Edition, May 1993, adopted by reference in 18 AAC 78.065(b), may be reviewed at the Department of Environmental Conservation's office in Anchorage.

2. The provisions outlined in the Steel Tank Institute's Standard for Dual Wall Underground Steel Storage Tanks, F841, revised January 2006, may be used as guidance for aspects of the design and construction of underground steel double-walled tanks as described in (h)(2)(A) of this section.

3. The National Work Group on Leak Detection Evaluations' List of Leak Detection Evaluations for Storage Tank Systems, 17th Edition, January 11, 2010, adopted by reference in 18 AAC 78.065, may be reviewed at the Department of Environmental Conservation's office in Anchorage or may be obtained on the Internet at http://www.nwglde.org.

4. The tank tightness documents referred to in Notes 1 and 2 may be reviewed at the Department of Environmental Conservation's office in Anchorage or may be obtained from the publisher at the address listed in the editor's note at 18 AAC 78.025.

5. The United States Environmental Protection Agency tank tightness testing documents referred to in 18 AAC 78.065(d) may be reviewed at the Department of Environmental Conservation's office in Anchorage or may be obtained from:

United States Environmental Protection Agency (EPA), Office of Underground Storage Tanks, 1200 Pennsylvania Ave., NW, Mail Code 5401P, Washington, D.C. 20460; telephone (703) 603-9900; Internet address: http://www.epa.gov/oust;

United States Government Bookstore, 717 North Capitol St. NW, Washington D.C. 20401; telephone: (866) 512-1800; facsimile: (202) 512-2104; Internet address: http://bookstore.gpo.gov/.

Authority:AS 46.03.020

AS 46.03.365

AS 46.03.375