Cal. Health & Safety Code § 25296

(a) If there has been any unauthorized release, as defined in Section 25294 or subdivision (a) of Section 25295, from an underground storage tank containing motor vehicle fuel not under pressure, the permitholder may repair the tank once by an interior-coating process if the tank meets all of the following requirements:
1. (1) One of the following tests has been conducted to determine the thickness of the storage tank:
  1. (A) An ultrasonic test.
  2. (B) Certification by a special inspector that the shell will provide structural support for the interior lining. The special inspector shall make this certification by entering and inspecting the entire interior surface of the tank and shall base this certification upon the following procedures and criteria:
    1. (i) If the tank is made of fiberglass, the tank is cleaned so that no residue remains on the tank wall surface. The special inspector shall take interior diameter measurements and, if the cross-section has compressed more than 1 percent of the original diameter, the tank shall not be certified and shall also not be returned to service. The special inspector shall also conduct an interior inspection to identify any area where compression or tension cracking is occurring and shall determine whether additional glass fiber reinforcing is required for certification before the tank may be lined.
    2. (ii) If the tank is made of steel, the tank interior surface shall be abrasive blasted completely free of scale, rust, and foreign matter, as specified in the American Petroleum Institute’s recommended practice 16-31, relating to white metal blasting. The special inspection shall sound any perforations or areas showing corrosion pitting with a brass ballpeen hammer to enlarge the perforation or break through a potentially thin steel area. Tanks that have any of the following defects shall not be certified or returned to service:
      1. (I) A tank which has an open seam or a split longer than three inches.
      2. (II) A tank which has a perforation larger than one and one-half inches in diameter, or a gauging opening larger than two and one-half inches in diameter.
      3. (III) A tank with five or more perforations.
      4. (IV) A tank with 20 or more perforations in a 500 square foot area.
      5. (V) A tank with a perforation larger than one-half inch.
  3. (C) A test approved by the board as comparable to the tests specified in subparagraph (A) or (B).
    If the person conducting the test determines that the test results indicate that the tank has a serious corrosion problem, the local agency may require additional corrosion protection for the tank or may prohibit the permitholder from making the repair.
2. (2) The material used to repair the tank by an interior-coating process is compatible with the motor vehicle fuel that is stored, as approved by the board by regulation.
3. (3) The material used to repair the tank by an interior-coating process is applied in accordance with nationally recognized engineering practices such as the American Petroleum Institute’s recommended practice No. 1631 for the interior lining of existing underground storage tanks.
4. (4) Before the tank is placed back into service following the repair, the tank is tested in the operating condition using the tank integrity test.
(b) The board may adopt regulations, in consultation with the State Fire Marshal, for the repair of underground storage tanks, which may include, but are not limited to, a requirement that a test be conducted to determine whether the interior-coating process has bonded to the wall of the tank. The standards specified in subdivision (a) shall remain in effect until the adoption of these regulations.
(c) The board shall, by regulation, require that monitoring systems be installed when a repair is made pursuant to this section. For purposes of this subdivision, “monitoring system” means a continuous leak detection and alarm system which is located in monitoring wells adjacent to an underground storage tank and which is approved by the board.
(d) If there has not been an unauthorized release, as defined in subdivision (a) of Section 25295, from an underground storage tank containing motor vehicle fuel not under pressure, the permitholder may line the interior of the tank as a preventative measure. If an unauthorized release occurs from a tank which was lined as a preventative measure, the permitholder shall not reline the tank again.