Cal. Food & Agric. Code § 13149

(a) Within 90 days after the active ingredient, other specified ingredient, or degradation product of a pesticide is detected under any of the conditions listed in paragraph (1) or (2), the director shall determine whether the detection resulted from agricultural use in accordance with state and federal laws and regulations, and shall state in writing the reasons for the determination.
1. (1) An active ingredient, other specified ingredient, or degradation product of a pesticide has been found at or below the deepest of the following depths:
  1. (A) Eight feet below the soil surface.
  2. (B) Below the root zone of the crop where the active ingredient, other specified ingredient, or degradation product was found.
  3. (C) Below the soil microbial zone.
2. (2) An active ingredient, other specified ingredient, or degradation product of a pesticide has been found in the groundwaters of the state.
(b) Upon a determination by the director that a pesticide meets any of the conditions specified in paragraph (1) or (2) of subdivision (a) as a result of agricultural use in accordance with state and federal laws and regulations, the director shall immediately notify the registrant of the determination and of the registrant’s opportunity to request a hearing pursuant to subdivision (c).
(c) Any pesticide that meets any of the conditions in subdivision (b) shall be subject to Section 13150 if the registrant of the pesticide requests, within 30 days after the notice is issued, that the subcommittee conduct a hearing, as described in Section 13150. Notwithstanding any other law, if the registrant does not request the hearing within 30 days after the notice is issued, the director shall cancel the registration of the pesticide.
(d) For purposes of this section, any finding of a pesticide shall result from either an analytical method approved by the department that provides unequivocal identification of a chemical, such as mass spectroscopy, or from verification, within 30 days, by a second analytical method or a second analytical laboratory approved by the department.