Wisconsin Administrative Code, Subchapter V, Section ATCP 93.515 - Leak detection methods | Wisconsin Administrative Code

(1) GENERAL.

(a) Leak detection methods for tank systems shall meet the requirements of this section.

(b) The leak detection test information reports submitted to the department, or maintained on site as required in s. ATCP 93.500(9), shall include at least all of the following:

1. Site information including the name of the business, the street address, and the municipality in which the site is located.

2. Tank system information including the department-assigned tank identification number, the site identification number designated by the owner or operator, the tank capacity, the product in the tank, the type of pipe system, and whether there are pipe manifolds in the tank system.

3. Test method information including the name of the method or equipment used, the material approval number as issued under s. ATCP 93.130, the date the test was performed, the threshold value used to declare a leak, the rate of volumetric change, whether the final result was a pass or fail, and the name and certification of the technician performing the test.

(2) INVENTORY CONTROL.

(a) General methodology. Inventory control that is used as the leak detection method shall be conducted in accordance with API 1621 and with this subsection.

(b) Prescriptive requirements. Product inventory control shall be conducted monthly and reconciled to detect a leak rate of at least 0.5 percent of throughput on a monthly basis, in the following manner:

Note: A leak rate of 0.5 percent is equal to 5 gallons out of every 1,000 gallons of throughput.

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

2. 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.

3.

a. The inputs shall be reconciled with delivery receipts by measurement of the tank inventory volume before and after delivery.

b. Where tanks are interconnected by a manifold, reconciliation may address all of the interconnected tanks as a group rather than as individual tanks.

4. The measurement of any water level in the bottom of the tank shall be electronically or manually gauged to the nearest one-eighth of an inch at least once a month and recorded.

(c) Product losses. Tank systems that exceed the losses allowed under par. (b) for 2 consecutive months shall follow the requirements in ss. ATCP 93.575 to 93.585 for assessing and responding to a release.

(d) Precision tightness test. A precision tightness test shall be performed in accordance with sub. (4) within 10 business days of notification from the authorized agent or the department for any of the following reasons:

1. Failure to provide monthly inventory control data for the past 12 months.

2. Incomplete or inconsistent data entry reflected during any 2 months of data entry out of the most recent 3 months of inventory control record keeping.

(3) MANUAL TANK GAUGING.

(a) Where allowed.

1. Manual tank gauging may be used as the sole method of leak detection for tanks that have a capacity of 1,000 gallons or less for the life of the tank.

2. For tanks that have a capacity of more than 1,000 gallons to 2,000 gallons, manual tank gauging may be used if all of the following conditions are met:

a. The tank system has a precision tightness test performed in accordance with sub. (4) at least once every 5 years from the date of installation until the tank is ten years old.

b. The tank is less than 10 years old.

c. The piping either receives an annual precision tightness test or has electronic line leak detection testing, and this tightness test or leak detection testing is performed in accordance with the capabilities specified in s. ATCP 93.130(3) (b).

3. Tanks which have a capacity of more than 1,000 gallons to 2,000 gallons and which are more than 10 years old shall be provided with monthly monitoring in accordance with sub. (5), (6), or (7).

4. Tanks that have a capacity of more than 2,000 gallons may not use manual tank gauging as the method of required leak detection.

(b) Manual tank gauging procedures. Manual tank gauging shall meet all of the following requirements:

1. Liquid level measurements shall be taken with a gauge stick that is marked to measure the liquid to the nearest one-eighth of an inch over the full range of the tank's height.

2. Tank liquid level measurements shall be taken at the beginning and ending of the test duration periods given in Table 93.515, during which no liquid may be added to or removed from the tank and shall be based on the average of 2 stick readings taken at both the beginning and ending of the period.

3. A leak is suspected and subject to the requirements of ss. ATCP 93.575 to 93.585 if the variation between beginning and ending measurements exceeds the weekly or monthly standards in Table 93.515.

Table 93.515

Test Duration and Standards

Nominal Tank Capacity	Minimum Test Duration	Weekly Standard (One Test)	Monthly Standard (Average of 4 Tests)
550 gallons or less	36 hours	10 gallons	5 gallons
551-1000 gallons, tank diameter of 48 inches	58 hours	12 gallons	6 gallons
551-1000 gallons, tank diameter of 64 inches	44 hours	9 gallons	4 gallons
551-1,000 gallons and using precision tightness testing every 5 years	36 hours	13 gallons	7 gallons
1001-2000 gallons1	36 hours	26 gallons	13 gallons

1 Requires precision tightness testing every 5 years. This method is only allowed until the tank is 10 years old.

(4) PRECISION TIGHTNESS TESTING.

(a) Precision tightness testing shall be conducted in one of the following ways:

1. By a certified tank system tightness tester, using methods approved under s. ATCP 93.130 to perform precision tightness testing for tanks or piping.

Note: The approval criteria in s. ATCP 93.130 include capability of detecting a leak rate of 0.1 gallons per hour.

2. With permanently installed leak detection equipment as approved under s. ATCP 93.130 to perform precision tightness testing for tanks or piping.

(b) Where a certified tank system tightness tester is used, the tester shall include the date and the beginning and end times in the test results report.

(c) Precision tightness testing of double-wall underground product piping shall include testing of both the inner and outer wall.

(d) Precision tightness testing shall be recorded on the department's tank precision tightness testing form, TR-WM-152, or line tightness testing form, TR-WM-125, as applicable and shall be maintained onsite in accordance with s. ATCP 93.500(9) (a). Alternative forms may be used with the permission of the department.

(5) AUTOMATIC TANK GAUGING. Automatic tank gauging shall meet all of the following requirements:

(a)

1. No more than 30 days may elapse between monthly monitoring tests using an automatic tank gauge.

2. Monthly monitoring tests shall have the capabilities specified in s. ATCP 93.130(3) (b).

3. An automatic tank gauge shall be placed in the center of the tank and no closer than 12 inches from the fill pipe and the submersible pump.

(b) Automatic tank gauges shall be provided with a printer that provides at least all of the following information:

1. The starting date and time and ending date and time of the test.

2. The volume of liquid in the tank during the test.

3. The measured leak rate in gallons per hour and whether this leak rate indicates a pass or a fail.

4. The specific identification of the tank, associated piping, or sumps used for interstitial monitoring that are being tested.

Note: See s. ATCP 93.130(3) (b) 1. for approval requirements for automatic tank gauges.

(c) Automatic tank gauges shall be programmed to provide an audible and visual alarm in the event of a tank or line test failure, a periodic monthly tank or line test not performed within a 30-day interval, or a tank or line interstitial sensor actuation. Manual operator action shall be needed to silence the alarm.

(6) STATISTICAL INVENTORY RECONCILIATION.

(a) Leak detection methods based on the application of statistical principles to inventory data shall meet the requirements of 40 CFR § 280.43(h) including:

1. Report a quantitative result with a calculated leak rate;

2. Be capable of detecting a leak rate of 0.2 gallon per hour or a release of 150 gallons within 30 days; and

3. Use a threshold that does not exceed one-half the minimum detectable leak rate.

(b) Tank systems or portions of tank systems using statistical inventory reconciliation as the primary method of leak detection shall be monitored and evaluated for leaks at least every 30 days with a conclusive result of pass or fail within the 30-day monitoring period.

(c) The daily tank system product inventory records shall be kept current and shall be maintained on site.

(d) Tank product level measurements shall be recorded using an electronic inventory probe or an automatic tank gauge.

(e) The operator shall have an effective process to submit their data to the vendor according to the vendor requirements for producing an evaluation report within the 30-day monitoring period.

(f) The statistical inventory reconciliation vendor shall analyze the data and supply an evaluation report to the operator within the 30-day monitoring period.

(g) If the result of the 30-day monitoring period is inconclusive or missing, another method of leak detection shall be used to determine a conclusive pass or fail for that monitoring period.

(h) If during the initial 30-day monitoring period, a conclusive result has not been obtained, another method of leak detection shall be used to determine a conclusive pass or fail for that monitoring period.

(i) Operators using statistical inventory reconciliation shall review the vendor summary report within 24 hours of receipt. If the summary report indicates a failure, the operator shall take immediate action in accordance with the requirements in ss. ATCP 93.575 to 93.585 for assessing and responding to a leak or release.

(j) Statistical inventory reconciliation may not be used as a method of precision tightness testing.

(l) Before changing from another method of leak detection to statistical inventory reconciliation, the operator shall provide the department with proof that precision testing was performed in accordance with sub. (4) within the previous 12 months, showing the tank system to be liquid-tight.

(7) INTERSTITIAL MONITORING. Interstitial monitoring between an underground tank system and a secondary barrier immediately around it may be used only if the system is installed and maintained to detect a leak from any portion of the tank that could contain product, and the system meets one of the following requirements:

(a) System testing. Post-installation testing shall be performed on the interstitial monitoring system to verify that the system operates in accordance with the manufacturer's specifications.

(b) Double-walled systems. For double-walled systems, the sampling or testing method shall be capable of detecting a leak through the inner or outer wall in any portion of the tank or piping that routinely contains product.

(c) Systems with internally fitted liners.

1. For tank systems with an internally fitted liner, a monitoring system shall be installed that is capable of detecting a leak between the inner wall of the tank and the liner.

2. The liner shall be chemically compatible with the substance stored.

(d) Systems with a barrier in the excavation zone. Systems with a secondary barrier within the excavation zone shall meet all of the following requirements:

1. The testing method shall be capable of detecting a leak between the system and the secondary barrier.

2. The secondary barrier around the system shall consist of manufactured material which is impermeable to at least 10 -6 cm/sec for the regulated substance stored, and which will direct a leak to the monitoring point, to be detected.

3. The liner shall be chemically compatible with the substance stored.

4. For cathodically protected tanks, the secondary barrier shall be installed so that it does not interfere with the proper operation of the cathodic protection system.

5. The test method shall be designed, installed, and maintained so groundwater, soil moisture, and rainfall do not render the method inoperative, so that a leak could go undetected.

6. The site shall be investigated to ensure that the secondary barrier is always above groundwater and not in a 25-year flood plain, unless the barrier and monitoring designs are for use under such conditions.

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

(e) Interstitial monitoring sensors. Interstitial monitoring sensors shall be capable of providing an audible or visual alarm in the event of a tank or line interstitial sensor actuation. Manual operator action shall be needed to silence the alarm.

(8) METHODS OF LEAK DETECTION FOR PIPING.

(a) General. Leak detection for piping shall follow the requirements of s. ATCP 93.510(4) and this section.

(b) Automatic line leak detectors.

1. Underground piping systems serving a storage tank with a submersible pump or pressurized booster pump shall be provided with an automatic line leak detector that alerts the operator to the presence of a leak by restricting or shutting off flow from the pump, when it detects leaks of 3 gallons per hour at 10 pounds per square inch line pressure within one hour.

2. New or replacement automatic electronic line leak detection shall be provided with a printer that provides at least all of the following information:

a. The date and time of the test.

b. The measured leak rate in gallons per hour and whether this leak rate indicates a pass or a fail.

c. The specific identification of the associated piping or sumps used for interstitial monitoring that are being tested.

3. Automatic electronic line leak detection shall be programmed to provide an audible and visual alarm in the event of a line test failure or if a periodic monthly line test is not performed within a 30-day interval. Manual operator action shall be needed to silence the alarm.

4. Any of the methods in sub. (7) may be used in lieu of complying with subd. 1. if they are designed and approved under s. ATCP 93.130 to detect a leak from any portion of the underground piping that routinely contains product.

(c) Line tightness testing.

1. In addition to the automatic line leak detection required by par. (b), a periodic precision tightness test of piping shall be performed in accordance with sub. (4), except as provided in subds. 2. and 3.

2. Where piping leak detection is installed that has the capability to perform monthly monitoring, a separate precision tightness test is not required.

3. Any of the methods in subs. (6) and (7) may be used in lieu of complying with subd. 1. if they are designed and approved under s. ATCP 93.130 to detect a leak from any portion of the underground piping that routinely contains product.

(d) Interstitial sensors. Sensors used for interstitial line monitoring shall be programmed to provide an audible or visual alarm. Manual operator action shall be needed to silence the alarm. The operator shall respond to the alarm within 30 minutes.

(e) Periodic line leak detection equipment testing.

1. A start-up functionality test of the operation of the leak detector shall be conducted in accordance with the manufacturer's procedures for testing to the leak thresholds in par. (b) by inducing a physical line leak.

2. A functionality test of the operation of a mechanical line leak detector shall be conducted annually in accordance with the manufacturer's procedures for testing to the leak thresholds in par. (b) by inducing a physical line leak.

3. A functionality test of the operation of an electronic line leak detector shall be conducted at least annually in accordance with the manufacturer's procedures for periodic testing to the leak thresholds in par. (b) by inducing a physical line leak.

5. Annual functionality verification shall be recorded on the department's electronic-mechanical line leak detector annual functionality form, TR-WM-123, and shall be maintained onsite in accordance with s. ATCP 93.500(9) (a).

(9) OTHER METHODS. The department may approve other methods of leak detection in accordance with s. ATCP 93.130.

(10) ULLAGE TESTING. Tightness testing of the ullage portion shall be performed in one of the following ways:

(a) As specified in NFPA 30 section 21.5, by or under the direct supervision of a certified installer or tank system tightness tester.

(b) By or under the direct supervision of a certified tank system tightness tester, with leak detection equipment and methods as approved under s. ATCP 93.130 that measure the tightness of the ullage portion.

(11) ORDERED CONVERSION OF LEAK DETECTION METHODOLOGY.

(a) The authorized agent or the department may order an operator, in writing, to terminate the use of a leak detection method and convert to an approved electronic methodology with history-generation capabilities for any of the following reasons:

1. The operator has a history of failing to perform monthly leak detection for a total of 6 months or more during a 24 month period, or for 3 consecutive months.

2. Statistical inventory reconciliation reports reflect pass for a total of 6 months or more during the preceding 24 months, or for 3 consecutive months, and the data points are not consistent with the material approval criteria in s. ATCP 93.130.

3. The operator fails to review monthly leak-detection reports as required by the applicable leak detection method under this section.

4. The operator enters data into an inventory record that is not supported by actual probe-generated data.

(b) The operator shall complete a conversion under par. (a) within 30 days of the date of the order or as determined by the department. Daily inventory verification as specified in s. ATCP 93.503(2) is acceptable as a temporary monthly leak detection method during the conversion period.

Wisconsin Administrative CodeDepartment of Agriculture, Trade and Consumer ProtectionATCP 90-139 - Trade and Consumer ProtectionChapter ATCP 93 - Flammable, Combustible, And Hazardous LiquidsSubchapter V - General UST Storage and Underground PipingSection ATCP 93.515 - Leak detection methods

Wisconsin Administrative Code
Department of Agriculture, Trade and Consumer Protection
ATCP 90-139 - Trade and Consumer Protection
Chapter ATCP 93 - Flammable, Combustible, And Hazardous Liquids
Subchapter V - General UST Storage and Underground Piping
Section ATCP 93.515 - Leak detection methods