(1) Unexplained differences in daily inventory reconciliation values that, over a 30-day period, exceed 1.0% of the product throughput;

(2) Unexplained losses detected through statistical analysis of inventory records;

(3) Detection of product in a monitoring well or by other leak detection methods;

(4) Failure of a tank or piping precision test, hydrostatic test or other tank or piping tightness test approved by the department; and

(5) Discovery of oil off site on or under the premises or abutting properties, including nearby utility conduits, sewer lines, buildings, drinking water supplies and soil.

The rules may not require the reporting of a leak or discharge of oil above ground of 10 gallons or less that occurs on the premises, including, but not limited to, spills, overfills and leaks, when those leaks or discharges do not reach ground water groundwaters or surface waters of the State and are cleaned up within 24 hours of discovery, if a written log is maintained at the facility or the owner's place of business in this State. For each discharge the log must record the date of discovery, its source, the general location of the discharge at the facility, the date and method of cleanup and the signature of the facility owner or operator certifying the accuracy of the log;

Sec. 9. 38 MRSA §564, sub-§2-A, as amended by PL 1995, c. 493, §10, is further amended by amending the last paragraph to read:

The requirements in paragraphs A and B do not apply to the following tanks provided the associated piping has secondary containment or a suction pump product delivery system or another leak detection system approved by the commissioner and provided that the tank and associated piping have been installed and are operated in accordance with the requirements of this subchapter, including rules adopted under this subchapter: tanks providing product to a generator; double-walled tanks with continuous interstitial space monitoring; and existing tanks constructed of fiberglass, cathodically protected steel or another