Section 329IAC9-7-4. Methods of release detection for tanks

   Each method of release detection for tanks used to meet section 2 of this rule must be conducted in accordance with the following:

(1) Product inventory control, or another test of equivalent performance, must be conducted monthly to detect a release of at least one percent (1.0%) of flow-through plus one hundred thirty (130) gallons on a monthly basis in the following manner:

(A) Inventory volume measurements for regulated substance inputs, withdrawals, and the amount still remaining in the tank are recorded each operating day.

(B) The equipment used is capable of measuring the level of product over the full range of the tank's height to the nearest one-eighth (⅛) of an inch.

(C) The regulated substance inputs are reconciled with delivery receipts by measurement of the tank inventory volume before and after delivery.

(D) Product dispensing is metered and recorded within the local standards for meter calibration or an accuracy of six (6) cubic inches for every five (5) gallons of product withdrawn.

(E) The measurement of any water level in the bottom of the tank is made to the nearest one-eighth (⅛) of an inch at least once a month.

(F) Deliveries must be made through a drop tube that extends to within one (1) foot of the tank bottom.

(2) Manual tank gauging must meet the following requirements:

(A) Tank liquid level measurements are taken at the beginning and ending of a period of at least thirty-six (36) hours during which no liquid is added to or removed from the tank.

(B) Level measurements are based on an average of two (2) consecutive stick readings at both the beginning and ending of the period in clause (A).

(C) The equipment used is capable of measuring the level of product over the full range of the tank's height to the nearest one-eighth (⅛) of an inch.

(D) A leak is suspected and subject to 329 IAC 9-4 if the variation between beginning and ending measurements exceeds the weekly or monthly standards in the following table:

Nominal Tank Capacity	Weekly Standard (1 Test)	Monthly Standard (Average of 4 Tests)
550 gallons or less	10 gallons	5 gallons
551–1,000 gallons	13 gallons	7 gallons
1,001–2,000 gallons	26 gallons	13 gallons

(E) The following requirements apply:

(i) Only tanks of five hundred fifty (550) gallons or less nominal capacity may use manual tank gauging as the sole method of release detection.

(ii) Tanks of five hundred fifty-one (551) to two thousand (2,000) gallons may use manual tank gauging in place of product inventory control in subdivision (1).

(iii) Tanks of greater than two thousand (2,000) gallons nominal capacity must not use manual tank gauging to meet the requirements of this rule.

(3) Tank tightness testing, or another test of equivalent performance, must be capable of detecting a one-tenth (0.1) gallon per hour leak rate from any portion of the tank that routinely contains product while accounting for the effects of the following:

(A) Thermal expansion or contraction of the product.

(B) Vapor pockets.

(C) Tank deformation, evaporation, or condensation.

(D) Location of the water table.

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

(A) The automatic product level monitor test can detect a two-tenths (0.2) gallon per hour leak rate from any portion of the tank that routinely contains product.

(B) Inventory control, or another test of equivalent performance, is conducted under subdivision (1).

(5) Testing or monitoring for vapors within the soil gas of the excavation zone must meet the following requirements:

(A) The materials used as backfill are sufficiently porous to readily allow diffusion of vapors from releases into the excavation area. The materials used as backfill may include any of the following:

(i) Gravel.

(ii) Sand.

(iii) Crushed rock.

(B) The stored regulated substance or a tracer compound placed in the tank system, which may include gasoline as an example, is 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.

(C) The measurement of vapors by the monitoring device is not rendered inoperative by the:

(i) ground water;

(ii) rainfall;

(iii) soil moisture; or

(iv) other known interferences;

so that a release could go undetected for more than thirty (30) days.

(D) The background level for contaminants in the excavation zone must not interfere with the method used to detect releases from the tank.

(E) The vapor monitors are designed and operated to detect any significant increase in concentration above background of any of the following:

(i) The regulated substance stored in the tank system.

(ii) A component or components of the regulated substance stored in the tank system.

(iii) A tracer compound placed in the tank system.

(F) In the UST excavation zone, the site is assessed to:

(i) ensure compliance with clauses (A) through (D); and

(ii) establish the number and positioning of observation wells that will detect releases within the excavation zone from any portion of the tank that routinely contains product.

(G) Observation wells are clearly marked and secured to prevent damage and unauthorized access and tampering.

(6) Testing or monitoring for liquids on the ground water must meet the following requirements:

(A) The regulated substance stored is immiscible in water and has a specific gravity of less than one (1).

(B) Ground water is never more than twenty (20) feet from the ground surface. The hydraulic conductivity of the soil between the UST system and the observation wells, monitoring wells, or monitoring devices is not less than one-hundredth (0.01) centimeter per second. The soil may consist of any of the following:

(i) Gravel.

(ii) Coarse to medium sand.

(iii) Coarse silt.

(iv) Other permeable material.

(C) The slotted portion of the observation well casing must be designed to:

(i) prevent migration of natural soils or filter pack into the well; and

(ii) allow entry of regulated substance on the water table into the well under both high and low ground water conditions.

(D) Observation wells must be sealed from the ground surface to the top of the filter pack.

(E) Observation wells, monitoring wells, or monitoring devices must be located as follows:

(i) An observation well intercepts the excavation zone.

(ii) A monitoring well that meets the requirements of rules of the natural resources commission at 312 IAC 13 is installed as close to the excavation zone as is technically feasible if an observation well cannot intercept the excavation zone.

(iii) A monitoring device intercepts the excavation zone or is as close to the excavation zone as is technically feasible.

(F) The continuous monitoring devices or manual methods used can detect the presence of at least one-eighth (⅛) of an inch of free product on top of the ground water in the observation wells or monitoring wells.

(G) Within and immediately below the UST system excavation zone, the site is assessed to:

(i) ensure compliance with clauses (A) through (E); and

(ii) establish the number and positioning of observation wells, monitoring wells, or monitoring devices that will detect releases from any portion of the tank that routinely contains product.

(H) Observation wells and monitoring wells are clearly marked and secured to prevent damage and unauthorized access and tampering.

(7) Interstitial monitoring between the UST system and a secondary barrier immediately around or beneath it may be used, but only if the system is designed, constructed, and installed to detect a leak from any portion of the tank that routinely contains product and also meets one (1) of the following requirements:

(A) For a double-walled UST system, the sampling or testing method can detect a release through the inner wall in any portion of the tank that routinely contains product.

(B) For an UST system with a secondary barrier within the excavation zone, the sampling or testing method used can detect a release between the UST system and the secondary barrier. The following must be completed:

(i) The secondary barrier around or beneath the UST system consists of artificially constructed material that is sufficiently thick and impermeable (no more than 1 × 10^-6 centimeters per second for water) to direct a release to an observation well and allow its detection.

(ii) The barrier is compatible with the regulated substance stored so that a release from the UST system will not cause a deterioration of the barrier allowing a release to pass through undetected.

(iii) For cathodically protected tanks, the secondary barrier must be installed so that the secondary barrier does not interfere with the proper operation of the cathodic protection system.

(iv) The ground water, soil moisture, or rainfall must not render the testing or sampling method used inoperative so that a release could go undetected for more than thirty (30) days.

(v) The site is assessed to ensure that the secondary barrier is always above the ground water and not in a twenty-five (25) year flood plain unless the barrier and observation well designs are for use under such conditions.

(vi) Observation wells are clearly marked and secured to prevent damage and unauthorized access and tampering.

(C) For tanks with an internally fitted liner, the following must be completed:

(i) An automated device that can detect a release between the inner wall of the tank and the liner.

(ii) The liner is compatible with the substance stored.

(8) Any other type of release detection method, or combination of methods, may be used if one (1) of the following is completed:

(A) The release detection method or combination of methods must meet the following requirements:

(i) Capability to detect a two-tenths (0.2) gallon per hour leak rate or a release of one hundred fifty (150) gallons within a month.

(ii) Probability of detection of ninety-five hundredths (0.95) and a probability of false alarm of five-hundredths (0.05).

(iii) The method is third party certified.

(B) The commissioner may approve another method if the owner and operator can demonstrate that the method can detect a release as effectively as any of the methods allowed in subdivisions (3) through (7) and clause (A). In comparing methods, the commissioner shall 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 and operator shall comply with any conditions imposed by the commissioner on the method's use to ensure the protection of human health and the environment.

(Solid Waste Management Division; 329 IAC 9-7-4; filed Jul 19, 1999, 12:00 p.m.: 22 IR 3725; readopted filed Jan 10, 2001, 3:25 p.m.: 24 IR 1535; filed Aug 30, 2004, 9:35 a.m.: 28 IR 175)