2023 California Code › Health and Safety Code - HSC › DIVISION 20 - MISCELLANEOUS HEALTH AND SAFETY PROVISIONS › CHAPTER 6.7 - Underground Storage of Hazardous Substances › Section 25291.

25291. Every underground storage tank installed after January 1, 1984, shall meet all of the following requirements:
(a)  The underground storage tank shall be designed and constructed to provide primary and secondary levels of containment of the hazardous substances stored in it in accordance with the following performance standards:
(1)  Primary containment shall be product-tight and compatible with the substance stored.
(2)  Secondary containment shall be constructed to prevent structural weakening as a result of contact with any released hazardous substances, and also shall be capable of storing the hazardous substances for the maximum anticipated period of time necessary for the recovery of any released hazardous substance.
(3)  In the case of an installation with one primary container, the secondary containment shall be large enough to contain at least 100 percent of the volume of the primary tank.
(4)  In the case of multiple primary tanks, the secondary container shall be large enough to contain 150 percent of the volume of the largest primary tank placed in it, or 10 percent of the aggregate internal volume of all primary tanks, whichever is greater.
(5)  If the facility is open to rainfall, then the secondary containment shall be able to additionally accommodate the maximum volume of a 24-hour rainfall as determined by a 25-year storm history.
(6)  Single-walled containers do not fulfill the requirement of an underground storage tank providing both a primary and a secondary containment. However, an underground storage tank with a primary container constructed with a double complete shell shall be deemed to have met the requirements for primary and secondary containment set forth in this section if all of the following criteria are met:
(A)  The outer shell is constructed primarily of nonearthen materials, including, but not limited to, concrete, steel, and plastic, which provide structural support and a continuous leak detection system with alarm is located in the space between the shells.
(B)  The system is capable of detecting the entry of hazardous substances from the inner container into the space.
(C)  The system is capable of detecting water intrusion into the space from the outer shell.
(7)  Underground storage tanks for motor vehicle fuels installed before January 1, 1997, may be designed and constructed in accordance with this paragraph in lieu of the requirements of paragraphs (1) to (6), inclusive, if all of the following conditions exist:
(A)  The primary containment construction is of glass fiber reinforced plastic, cathodically protected steel, or steel clad with glass fiber reinforced plastic.
(B)  Any alternative primary containment is installed in conjunction with a system that will intercept and direct a leak from any part of the underground storage tank to a monitoring well to detect any release of motor vehicle fuels.
(C)  The system is designed to provide early leak detection and response, and to protect the groundwater from releases.
(D)  The monitoring is in accordance with the alternative method identified in paragraph (4) of subdivision (b) of Section 25292. This subparagraph does not apply to tanks designed, constructed, and monitored in accordance with paragraph (6).
(E)  Pressurized piping systems connected to tanks used for the storage of motor vehicle fuels and monitored in accordance with paragraph (4) of subdivision (b) of Section 25292 also meet the conditions of this subdivision if the tank meets the conditions of subparagraphs (A) to (D), inclusive. However, any pipe connected to an underground storage tank installed after July 1, 1987, shall be equipped with secondary containment that complies with paragraphs (1) to (6), inclusive.
(b)  The underground tank system shall be designed and constructed with a monitoring system capable of detecting the entry of the hazardous substance stored in the primary containment into the secondary containment.
(c)  The underground storage tank shall be provided with equipment to prevent spills and overflows from the primary tank.
(d)  If different substances are stored in the same tank and in combination may cause a fire or explosion, or the production of flammable, toxic, or poisonous gas, or the deterioration of a primary or secondary container, those substances shall be separated in both the primary and secondary containment to avoid potential intermixing.
(e)  If water could enter into the secondary containment by precipitation or infiltration, the facility shall contain a means of monitoring for water intrusion and for removing the water by the owner or operator. This removal system shall also prevent uncontrolled removal of this water and provide for a means of analyzing the removed water for hazardous substance contamination and a means of disposing of the water, if so contaminated, at an authorized disposal facility.
(f)  Underground pressurized piping that conveys a hazardous substance shall be equipped with an automatic line leak detector and shall be tightness tested annually.
(g)  Before the underground storage tank is covered, enclosed, or placed in use, the standard installation testing for requirements for underground storage systems specified in Section 2-7 of the Flammable and Combustible Liquids Code, adopted by the National Fire Protection Association, (NFPA 30) as amended and published in the respective edition of the Uniform Fire Code, shall be followed.
(h)  Before the underground storage tank is placed in service, the underground tank system shall be tested in operating condition using a tank integrity test.
(i)  If the underground storage tank is designed to maintain a water level in the secondary containment, the tank shall be equipped with a safe method of removing any excess water to a holding facility and the owner or operator shall inspect the holding facility monthly for the presence of excess water overflow. If excess water is present in the holding facility, the permitholder shall provide a means to analyze the water for hazardous substance contamination and a means to dispose of the water, if so contaminated, at an authorized disposal facility.
(Amended by Stats. 2002, Ch. 999, Sec. 18.5. Effective January 1, 2003.)