Section 2631 - Design and Construction Requirements for New Underground Storage Tanks(a) All new underground storage tanks including associated piping used for the storage of hazardous substances shall have primary and secondary containment. Primary containment shall be product-tight. Secondary containment may be manufactured as an integral part of the primary containment or it may be constructed as a separate containment system. Secondary containment systems shall be designed and constructed such that the secondary containment system can be periodically tested in accordance with section 2637.(b) Except as provided in subdivision (j) below, the design and construction of all primary containment including any integral secondary containment system, shall be approved by an independent testing organization in accordance with industry codes, voluntary consensus standards, or engineering standards. Except as provided in subdivision (j) below, all other components used to construct the primary containment system, such as special accessories, fittings, coatings or linings, monitoring systems, and level controls shall also be approved by an independent testing organization. These requirements became effective on July 1, 1991 for underground storage tanks; January 1, 1992 for piping; and January 1, 1995 for all other components. The exterior surface of underground storage tanks shall bear a marking, code stamp, or label showing the following minimum information: (1) Engineering standard used;(2) Nominal diameter in feet;(3) Nominal capacity in gallons;(4) Degree of secondary containment;(5) Useable capacity in gallons;(6) Design pressure in pounds per square inch gauge;(7) Maximum operating temperature in degrees Fahrenheit;(8) Construction materials;(9) Year manufactured; and(10) Identity of manufacturer.(c) A primary containment system with or without an integral secondary containment system shall have wear plates (striker plates) installed, center to center, below all accessible openings. The plates shall be made of steel or other appropriate material if steel is not compatible with the hazardous substance stored. The width of the plate shall be at least eight inches on each side, or shall be equal to the area of the accessible opening or guide tube, whichever is larger. The thickness of the steel plate shall be at least 1/8 inch and those made of other materials shall be of sufficient thickness to provide equivalent protection. The plate, if under 1/4 inch thick, shall be rolled to the contours of the underground storage tank and all plates shall be bonded or tack welded in place. A drop tube-mounted bottom protector may fulfill this requirement.(d) A secondary containment system which is not an integral part of primary containment shall be designed and constructed according to an engineering specification approved by a state registered professional engineer or according to a nationally recognized industry code or engineering standard. The engineering specification shall include the construction procedures. Materials used to construct the secondary containment system shall have sufficient thickness, density, and corrosion resistance to prevent structural weakening or damage to the secondary containment system as a result of contact with any released hazardous substance. The following requirements apply to these secondary containment systems: (1) The secondary containment system shall be constructed to contain at least the following volumes: (A) One hundred percent of the usable capacity of the primary containment system where only one primary container is within the secondary containment system.(B) In the case of multiple primary containers within a single secondary containment system, the secondary containment system shall be large enough to contain 150 percent of the volume of the largest primary container within it, or 10 percent of the aggregate internal volume of all primary containers within the secondary containment system, whichever is greater. When all primary containers are completely enclosed within the secondary containment system, the restrictions of this subdivision do not apply.(2) If the secondary containment system is open to rainfall, it shall be constructed to accommodate the volume of precipitation which could enter the secondary containment system during a 24-hour, 25-year storm in addition to the volume specified in subdivision (d)(1) above.(3) If backfill material is placed in the secondary containment system, the volumetric requirements for the pore space shall be equal to the requirement in subdivision (d)(1) above. The available pore space in the secondary containment system backfill shall be determined using standard engineering methods and safety factors. The specific retention and specific yield of the backfill material, the location of any primary container within the secondary containment, and the proposed method of operation for the secondary containment system shall be considered in determining the available pore space.(4) The secondary containment system shall be equipped with a collection system to accumulate, temporarily store, and permit removal of any liquid within the system.(5) The floor of the secondary containment system shall be constructed on a firm base and, if necessary for monitoring, shall be sloped to a collection sump. One or more access casings shall be installed in the sump and sized to allow removal of collected liquid. The access casing shall extend to the ground surface, be perforated in the region of the sump, and be covered with a locked waterproof cap or enclosed in a surface security structure that will protect the access casing(s) from entry of surface water, accidental damage, unauthorized access, and vandalism. A facility with locked gates will satisfy the requirements for protection against unauthorized access and vandalism. The casing shall have sufficient thickness to withstand all anticipated stresses with appropriate engineering safety factors and constructed of materials that will not be structurally weakened by the stored hazardous substance and will not donate, capture, or mask constituents for which analyses will be made.(6) Secondary containment systems using membrane liners shall be approved by an independent testing organization in accordance with industry codes, voluntary consensus standards, or engineering standards. A membrane liner shall contain no primary nutrients or food-like substances attractive to rodents and shall meet the requirements in Table 3.1 after a 30-day immersion in the stored hazardous substance. Table 3.1 |
Standards for Membrane Liners |
Some Acceptable Test Methods |
(See Appendix I, Table A) |
Property | Unsupported Liners | Supported Liners | Requirement |
| (A) | Tensile strength | ASTM D638 | ASTM D751 | |
| Tensile strength at yield | | Procedure B (Cut Strip | >300 lbs/in of width |
| Tensile strength at break | | Method) | >200 lbs/in of width |
| | | | |
| (B) | Permeability | ASTM E96 | ASTM E96 | <0.65 gram/meter2-hr |
| | | | |
| (C) | Seam strength | ASTM D413 | ASTM D751 | = Parent material |
| | | | |
| (D) | Solubility | ASTM D471 | ASTM D471 | <0.10% by weight |
| | | | |
| (E) | Puncture | | FTMS 101C Method 2031 | 350 lbs. |
| | FTMS 101C Method 2065 | | 80 lbs. |
| | | | |
| (F) | Tear | | ASTM D751 | 125 lbs. |
| | ASTM D1004 DIEC | | 50 lbs. |
(7) A membrane liner, if used, shall be installed under the direct supervision of a representative of the membrane liner fabricator or a contractor certified by the fabricator.(8) The excavation base and walls for a membrane liner shall be prepared to the membrane liner fabricator's specifications and shall be firm, smooth, and free of any sharp objects or protrusions.(9) The site shall be assessed to ensure that the secondary containment is always above the ground water and not in a 25-year flood plain, unless the containment and monitoring designs are for use under such conditions.(e) Laminated, coated, or clad materials shall be considered single-walled and do not fulfill the requirements of both primary and secondary containment.(f) Underground storage tanks with integral secondary containment systems, which satisfy the construction requirements of subdivision (b) above, fulfill the volumetric requirements for secondary containment specified in subdivision (d)(1) above.(g) Underground storage tanks with secondary containment systems shall be so designed and installed so that any loss of a hazardous substance from the primary containment will be detected by an interstitial monitoring device or method.(h) An underground storage tank which contains motor vehicle fuel and which is designed with an integral secondary containment system shall provide 100 percent secondary containment unless it is equipped with overfill prevention equipment in accordance with section 2635(c)(1)(C). In this case, the top portion of the tank, no greater than two feet wide along the length of the tank, may be single-walled.(i) Tanks designed and constructed pursuant to the provisions of this section shall be monitored according to the provisions of section 2632.(j) Effective June 1, 2012, if an independent testing organization approval for containment or components described in subdivision (b) above, does not include the compatibility of the hazardous substance stored or to be stored, an owner or operator may submit to the local agency a written, affirmative statement of compatibility for the specific hazardous substance from the manufacturer(s) of the containment or components. The written, affirmative statement of compatibility along with the independent testing approval specified in subdivision (b) above, shall satisfy the requirements in subdivision (b) above, that all primary containment including any integral secondary containment system and all other components used to construct the primary containment system be approved by an independent testing organization as compatible with the specific hazardous substance stored or to be stored. If an affirmative statement of compatibility made by a manufacturer conflicts with a later determination by an independent testing organization on the compatibility of the hazardous substance stored or to be stored, the written, affirmative statement of compatibility shall no longer satisfy the compatibility requirements of subdivision (b) above.(k) Subdivision (j) above, applies only to underground storage tanks that meet the construction requirements contained in Health and Safety Code sections 25291, excluding subdivision (a)(7), 25290.1, or 25290.2, as applicable.(l) On and after October 1, 2018, owners or operators shall demonstrate compatibility, 30 days before beginning to store or changing the hazardous substance, for all components used to construct the underground storage tank system which may come into contact with the hazardous substance to be stored and are not subject to subdivisions (b) or (d) above, such as spill containers, overfill prevention equipment, and ancillary equipment, by submitting to the local agency one of the following: (1) A written approval from an independent testing organization, in accordance with industry codes, voluntary consensus standards, or engineering standards, for use with the hazardous substance to be stored;(2) A written approval from a state registered professional engineer for use with the hazardous substance to be stored. The approval shall contain an affirmative statement of compatibility with the substance and a specified acceptable range of blends or concentrations of the substance. The component shall be designed and constructed according to an engineering specification. The engineering specification shall include the construction procedures. Materials used to construct the component shall have sufficient corrosion resistance to prevent damage to the component as a result of contact with the hazardous substance; or(3) A written affirmative statement of compatibility from the manufacturer(s) of the components for use with the hazardous substance to be stored. The statement shall contain an affirmative statement of compatibility with the hazardous substance and a specified acceptable range of blends or concentrations of the hazardous substance.(m)(1) On and after January 1, 2020, and except as provided in paragraph (2) below, diesel containing up to 20 percent biodiesel meeting the 2019 American Society of Testing and Materials International standard D7467, hereby incorporated by reference, shall be recognized as equivalent to diesel for purposes of satisfying subdivisions (b), (d), and (l) above, and section 2630(d) for all underground storage tank systems meeting the construction requirements contained in Health and Safety Code sections 25290.1, 25290.2, or 25291, excluding subdivision (a)(7).(2)(A) Paragraph (1) may not be used for any material or component of the underground storage tank system for which the applicable approver required in subdivisions (b), (d), or (l) above, or section 2630(d) has determined is not compatible with diesel containing up to 20 percent biodiesel meeting the American Society of Testing and Materials International standard D7467.(B) Within 30 days from the date of a determination from the applicable approver required in subdivisions (b), (d), or (l) above, or section 2630(d) that any material or component of the underground storage tank system is not compatible with diesel containing up to 20 percent biodiesel meeting the American Society of Testing and Materials International standard D7467, the owner or operator shall repair the underground storage tank system in accordance with section 2631.1(a).Cal. Code Regs. Tit. 23, § 2631
1. Amendment filed 8-9-91 as an emergency; operative 8-9-91. Text remains in effect uninterrupted pursuant to Health and Safety Code section 25299.7 (Register 92, No. 14).
2. Editorial correction of printing errors in HISTORY 1 (Register 92, No. 43).
3. Amendment of section heading and text filed 4-5-94; operative 5-5-94 (Register 94, No. 14).
4. Amendment of subsection (a) and NOTE filed 5-14-2001; operative 5-14-2001 pursuant to Government Code section 11343.4 (Register 2001, No. 20).
5. Amendment of subsection (b) and new subsections (j) and (k) filed 4-10-2012; operative 5-10-2012 (Register 2012, No. 15).
6. Amendment of subsections (a), (b), (b)(6), (d)(1)(B)-(d)(3), (e), (f), (h), (j) and (k), new subsections (l)-(l)(3) and amendment of NOTE filed 8-27-2018; operative 10-1-2018 (Register 2018, No. 35).
7. New subsections (m)(1)-(m)(2)(B) filed 11-6-2019; operative 1-1-2020 (Register 2019, No. 45). Note: Authority cited: Sections 25299.3 and 25299.7, Health and Safety Code. Reference: Sections 25281, 25284.1 and 25291, Health and Safety Code; and 40 CFR §§ 280.20 and 280.32.
1. Amendment filed 8-9-91 as an emergency; operative 8-9-91. Text remains in effect uninterrupted pursuant to Health and Safety Code section 25299.7 (Register 92, No. 14).
2. Editorial correction of printing errors in History 1 (Register 92, No. 43).
3. Amendment of section heading and text filed 4-5-94; operative 5-5-94 (Register 94, No. 14).
4. Amendment of subsection (a) and Note filed 5-14-2001; operative 5-14-2001 pursuant to Government Code section 11343.4 (Register 2001, No. 20).
5. Amendment of subsection (b) and new subsections (j) and (k) filed 4-10-2012; operative 5-10-2012 (Register 2012, No. 15).
6. Amendment of subsections (a), (b), (b)(6), (d)(1)(B)-(d)(3), (e), (f), (h), (j) and (k), new subsections (l)-(l)(3) and amendment of Note filed 8-27-2018; operative 10/1/2018 (Register 2018, No. 35).
7. New subsections (m)(1)-(m)(2)(B) filed 11-6-2019; operative 1/1/2020 (Register 2019, No. 45).