N.J. Admin. Code § 7:14B-6.5 - Methods of release detection for tanks

(a) The owner and operator shall use each method of release detection for tanks according to the requirements of N.J.A.C. 7:14B-6.2 , 6.3, and 6.4, and in accordance with the following:

1. Product inventory control shall be conducted monthly to detect a release of at least 1.0 percent of throughput plus 130 gallons on a monthly basis in the following manner:

i. Inventory volume measurements for regulated substance inputs, withdrawals, and the amount still remaining in the tank shall be recorded each operating day;

ii. The equipment used shall 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;

iii. The regulated substance inputs shall be reconciled with delivery receipts by measurement of the tank inventory volume before and after delivery;

iv. Deliveries shall be made through a drop tube that extends to within one foot of the tank bottom;

v. Product dispensing shall be metered and recorded within the standards for meter calibration pursuant to 13:47B-1.20;

vi. The measurement of any water level in the bottom of the tank shall be made to the nearest one-eighth of an inch at least once a month; and

vii. The practices described in American Petroleum Institute, Recommended Practice 1621 "Bulk Liquid Stock Control at Retail Outlets," may be used, where applicable, as guidance in meeting the requirements of N.J.A.C. 7:14B-6.5(a)1i through vi above.

2. Manual tank gauging shall meet the following requirements:

i. Tank liquid level measurements shall be taken at the beginning and ending of a period, as appropriate, to the minimum duration of test value given in the table at (a)2v below, during which no liquid is added to or removed from the tank;

ii. Level measurements shall be based on an average of two consecutive stick readings at both the beginning and ending of the period;

iii. The equipment used shall 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;

iv. Only tanks of 550 gallons or less nominal capacity and tanks with a nominal capacity of 551 to 1,000 gallons that meet the tank diameter criteria in the table in (a)2v below may use manual tank gauging as the sole method of release detection. Tanks of 551 to 2,000 gallons nominal capacity may use the method in place of manual inventory control as set forth in (a)1 above. Tanks of greater than 2,000 gallons nominal capacity may not use manual tank gauging to meet the requirements of this subchapter; and

v. A release shall be suspected and subject to the requirements of N.J.A.C. 7:14B-7 if the variation between beginning and ending measurements exceeds the weekly or monthly standards in the following table:

Nominal Tank Capacity	Minimum Duration of Test	Weekly Standard (one test)	Monthly Standard (average of four tests)
550 gallons or less	36 hours	10 gallons	5 gallons
551 to 1,000 gallons (when tank diameter is 64 inches)	44 hours	9 gallons	4 gallons
551 to 1,000 gallons (when tank diameter is 48 inches)	58 hours	12 gallons	6 gallons
551 to 1,000 gallons (also requires periodic tank tightness testing)	36 hours	13 gallons	7 gallons
1,001 to 2,000 gallons (also requires periodic tank tightness testing)	36 hours	26 gallons	13 gallons

3. Tank tightness testing shall be capable of detecting a 0.1 gallon per hour leak rate from any portion of the tank that routinely contains product while accounting for the effects of thermal expansion or contraction of the product, vapor pockets, tank deformation, evaporation or condensation, and the location of the water table.

4. Equipment for automatic tank gauging that tests for the loss of product and conducts inventory control shall meet the following requirements:

i. The automatic product level monitor test shall detect a 0.2 gallon per hour leak rate, from any portion of the tank that routinely contains product, when performing a test in one of the following modes:

(1) In-tank static testing conducted with passing results at least once every 30 days; or

(2) Continuous in-tank leak detection operating either on an uninterrupted basis, or with a process that allows the system to gather incremental measurements to ensure an accurate, passing test at least once every 30 days; and

ii. Inventory control (or another test of equivalent performance) shall be conducted in accordance with the requirements of 7:14B-6.5(a)1.

5. Testing or monitoring for vapors within the soil gas of the excavation zone shall meet the following requirements:

i. The materials used as backfill shall be sufficiently porous (for example, gravel, sand, crushed rock) to readily allow diffusion of vapors from releases into the excavation area;

ii. The stored regulated substance, or a tracer compound placed in the tank system, shall be sufficiently volatile to result in a vapor level that is detectable by the monitoring devices located in the excavation zone in the event of a release from the tank;

iii. The measurement of vapors by the monitoring device shall not be rendered inoperative by the ground water, rainfall, soil moisture or other known interferences so that a release could go undetected for more than 30 calendar days;

iv. The level of background contamination in the excavation zone shall not interfere with the method used to detect releases from the tank;

v. The vapor monitors shall be designed and operated to detect any significant increase in concentration above background of the regulated substance stored in the tank system, a component or components of that substance, or a tracer compound placed in the tank system;

vi. In the underground storage tank excavation zone, the site shall be assessed to ensure compliance with the requirements in (a)5i through iv and to establish the number and positioning of monitoring wells that will detect releases within the excavation zone from any portion of the tank that routinely contains product; and

vii. Monitoring wells shall be clearly marked and secured to avoid unauthorized access and tampering.

6. Testing or monitoring for liquids floating on the ground water shall meet the following requirements:

i. The regulated substance stored shall be immiscible in water and has a specific gravity of less than one;

ii. Ground water shall never be more than 20 feet from the ground surface and the hydraulic conductivity of the soil(s) between the underground storage tank system and the monitoring wells or devices is not less than 0.01 cm/sec (for example, the soil should consist of gravels, coarse to medium sands, coarse silts or other permeable materials);

iii. The slotted portion of the monitoring well casing shall be designed to prevent migration of natural soils or filter pack into the well and to allow entry of regulated substance on the water table into the well under both high and low ground-water conditions;

iv. All monitoring systems using screen and casing shall be constructed and permitted in accordance with the Subsurface and Percolating Waters Act (N.J.S.A. 58:4A-4.1 et seq.) unless constructed in the manner described in N.J.A.C. 7:14B-4.1(c) or sealed from the ground surface to the top of the filter pack in accordance with N.J.A.C. 7:14B-4.1(d);

v. Monitoring wells or devices shall intercept the excavation zone or are as close to it as is technically feasible;

vi. The continuous monitoring devices or manual methods used shall detect the presence of at least one-eighth of an inch of free-phase non-aqueous phase liquid on top of the ground water in the monitoring wells;

vii. Within and immediately below the underground storage tank system excavation zone, the site shall be assessed to ensure compliance with the requirements in (a)6i through v 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

viii. Monitoring wells shall be clearly marked and secured to avoid unauthorized access and tampering.

7. Interstitial monitoring between the underground storage tank system and a secondary barrier immediately around or beneath it may be used, but only if the monitoring system is designed, constructed, and installed to detect a leak from any portion of the tank and/or piping that routinely contains product and also meets one of the following requirements:

i. For double walled underground storage tank systems, the sampling or testing method shall detect a leak through the inner wall in any portion of the tank and/or piping that routinely contains product;

ii.For underground storage tank systems with a secondary barrier within the excavation zone, the sampling or testing method used shall detect a leak between the underground storage tank system and the secondary barrier. The secondary barrier shall meet the following requirements:

(1) The secondary barrier shall consist of artificially constructed material that is sufficiently thick and impermeable (at least 10-6 cm/sec for the regulated substance stored) to direct a leak to the monitoring point and permit its detection;

(2) The secondary barrier shall be compatible with the regulated substance stored so that a leak from the underground storage tank system shall not cause a deterioration of the barrier allowing a release to pass through undetected;

(3) For cathodically protected underground storage tank systems, the secondary barrier shall be installed so that it does not interfere with the proper operation of the cathodic protection system;

(4) The ground water, soil moisture, or rainfall shall not render the testing or sampling method used inoperative so that a release could go undetected for more than 30 calendar days;

(5) The site shall be assessed to ensure that the secondary barrier is always above the ground water and not in a 25-year flood plain, unless the barrier and monitoring designs are for use under such conditions; and

(6) Monitoring wells shall be clearly marked and secured to avoid unauthorized access and tampering; or

iii. For tanks with an internally fitted liner, an automated device shall detect a leak between the inner wall of the tank and the liner, and the liner shall be compatible with the substance stored.

8. Any other type of release detection method, or combination of methods, including statistical inventory reconciliation (SIR), can be used if the method can detect a 0.2 gallon per hour leak rate or a release of 150 gallons within a month with a probability of detection of 0.95 and a probability of false alarm of 0.05.

i. Statistical inventory reconciliation release detection methods based on the application of statistical principles to inventory data shall, in addition to (a)8 above:

(1) Report a quantitative result with a calculated leak rate;

(2) Use a threshold that does not exceed one-half the minimum detectible leak rate; and

(3) Be conducted at least once every 30 days.

9. The Department shall approve another method, through the issuance of a permit for a substantial modification issued pursuant to N.J.A.C. 7:14B-10, if the owner and operator can demonstrate that the method can detect a release as effectively as any of the methods allowed in (a)3 through 8 above. In comparing methods, the Department shall consider the size of release that the method can detect and the frequency and reliability with which it can be detected. The owner and operator shall obtain a permit issued by the Department pursuant to N.J.A.C. 7:14B-10 and comply with any conditions imposed by the Department on its use to ensure the protection of human health and the environment.

Notes

N.J. Admin. Code § 7:14B-6.5

Amended by 50 N.J.R. 409(a), effective 1/16/2018