Sec. 598.6. Underground tank systems—testing and inspection

(a) Testing and inspections of ancillary equipment.

Beginning August 11, 1995, the owner or operator must inspect ancillary equipment as follows:

(1) Monthly inspection must be made of vents, pressure relief devices, gauges, alarms, overfill prevention equipment, cathodic protection monitoring equipment, other monitoring equipment, warning alarms and safety systems. Equipment must be visually inspected for cleanliness, leakage, corrosion, and operability.

(2) Annual testing of automatic line leak detectors and cathodic systems, providing protection to tanks or pipes subject to corrosion, must be performed to ensure the equipment is operating properly. Cathodic protection systems must be checked by a qualified technician to ensure that adequate structure to electrolyte potential exists for corrosion protection. If any line leak detector or cathodic protection system fails to provide the necessary protection, action must be taken in accordance with section 598.9(a)(2) of this Part.

(b) Leak detection for underground tanks.

Beginning August 11, 1995, the owner and operator must check underground tanks for leakage using one or more of the following:

(1) Inventory monitoring may be used if it detects a leak of one percent of flow-through plus 130 gallons on a monthly basis and is coupled with an annual tightness test. Inventory monitoring must be done in accordance with the standards set forth in 40 CFR section 280.43(a) (see section 598.1[j] of this Part).

(2) Weekly monitoring of the interstitial space of a double-walled tank may be practiced using pressure monitoring, vacuum monitoring, electronic monitoring or manual sampling.

(3) Vapor wells for monitoring soils in the excavation zone may be used. Vapor monitoring systems must be designed and installed by a qualified engineer or technician in accordance with generally accepted practices. Wells must be protected from traffic, permanently labeled as a “monitoring well” or “test well-no fill” and equipped with a locking cap, which must be locked when not in use so as to prevent unauthorized access and tampering. Vapor monitoring may be used only under the following conditions:

(i) soils in the excavation zone must be sufficiently porous to allow for the movement of the vapors from the tank to the vapor sensor. Gravel, coarse sand and crushed rock are examples of porous soils;

(ii) the stored substance or a tracer compound placed in the tank must be sufficiently volatile so as to be detectable by the vapor sensor;

(iii) vapor monitoring must not be hindered by groundwater, rainfall or soil moisture such that a leak could go undetected for more than 30 days;

(iv) background contamination must not mask or interfere with the detection of a release;

(v) the system must be designed and operated to detect increases in vapors above background levels. Monitoring must be done at least once per week; and

(vi) the number and positioning of vapor monitoring wells must be sufficient to ensure detection of releases from any portion of the tank and must be based on a scientific study. Wells must be at least four inches in diameter.

(4) Groundwater monitoring wells designed and installed by a qualified engineer or technician may be used. Wells must be protected from traffic, permanently labeled as a “monitoring well” or “test well-no fill” and equipped with a locking cap which must be locked when not in use to prevent unauthorized access and tampering. Groundwater monitoring may be used only under the following conditions:

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

(ii) the groundwater table must be less than 20 feet from the ground surface. The hydraulic conductivity of the soil between the tank and well must not be less than one hundredth cm/sec. Gravel and coarse to medium sand are examples of such soil;

(iii) the slotted portion of the well casing must be designed to prevent migration of soils into the well and must allow entry of the hazardous substances into the well under both high and low groundwater conditions;

(iv) wells must be at least four inches in diameter and be sealed from the ground surface to the top of the filter pack to prevent surface water from entering the well;

(v) wells must be located within the excavation zone or as close to it as technically feasible;

(vi) the method of monitoring must be able to detect at least one eighth of an inch of free product on top of the groundwater. Monitoring must be done once per week; and

(vii) the number and positioning of the groundwater monitoring well(s) must be sufficient to ensure detection of releases from any portion of the tank and must be based on a scientific study.

(5) Automatic tank gauging equipment may be used if it can detect a leak of two tenths of a gallon per hour or larger with a probability of detection of 95 percent and probability of false alarm of five percent or less with a maximum threshold for declaring a leak of one tenth of a gallon in one hour. Monitoring must be done once per week.

(6) Other equivalent methods as approved by the department if the method can detect a leak of two tenths of a gallon per hour with a 95 percent probability of detection and probability of false alarm of five percent.

(c) Leak detection in underground and on-ground piping.

(1) Beginning August 11, 1995, the owner and operator must check underground and on-ground piping for leakage. The method to be used must be designed to detect a leak from any portion of the piping that routinely contains a hazardous substance and may include any method accepted for tanks under subdivision (b) of this section, except for paragraph (b)(5) of this section. Note exception for suction piping in paragraph (3) of this subdivision.

(2) If the underground piping is pressurized, then an automatic line leak detector which alerts the owner or operator to the presence of a leak must also be installed. The detector must be capable of restricting or shutting off flow or triggering an alarm. The line leak detector must also be capable of detecting a leak of three gallons per hour at 10 pounds per square inch line pressure within one hour with a probability of detection of 95 percent and probability of false alarm of five percent or less. An annual test of the operation of the leak detector must be conducted using procedures established by the manufacturer.

(3) Leak detection is not necessary for suction piping which meets all of the following conditions:

(i) operates at less than atmospheric pressure;

(ii) is sloped so that the contents of the pipe will drain back into the tank if the suction is released;

(iii) has only one check valve in each line; and

(iv) where the check valve is located directly below and as close as practical to the suction pump.

(d) Inspection of lined tanks.

Within 10 years after a lining is affixed to an underground tank, the tank must be internally inspected and found to be structurally sound with the lining still performing in accordance with original design specifications. Reinspection must be performed every five years thereafter.

(e) Criteria for tightness tests.

(1) A tightness test is a test acceptable to the department which will determine if a tank and piping system is tight or not tight. This shall include:

(i) a test capable of detecting a tank or pipe leak of one tenth gallons per hour (gph) with a probability of detection of 95 percent and probability of false alarm of five percent or less with a maximum threshold for declaring a leak of five hundredths of a gallon in one hour accounting for variables such as vapor pockets, thermal expansion and contraction of product, temperature stratification, groundwater level, evaporation, pressure and tank deformation; or

(ii) a structural inspection performed in accordance with the requirements of section 598.7(d) of this Part.

(2) If it is technically impossible to perform a meaningful tightness test, then an alternative test or inspection which is acceptable to the department must be performed.

(f) Qualification of technicians.

All tightness tests must be performed by a qualified technician who has an understanding of the variables which affect the test and is trained by the manufacturer or his representative in the performance of the test.

(g) Uninspected facilities.

If, for any reason, testing or inspection is not performed as required in this section, the owner and operator must take the uninspected portion of the tank system out-of-service pursuant to the requirements of section 598.10 of this Part.