For the purposes of this article, the orphan share shall be determined in the following manner:

(a) The orphan share shall be expressed as a percentage in multiples of five, up to, and, including, but not greater than, 75 percent.

(b) The potentially responsible party filing a claim for reimbursement of the orphan share shall provide the administrator of the fund with a written potentially responsible party search report that shall include a list of all potentially responsible parties identified for the site, the factual and legal basis for identifying those parties, and a proposed orphan share percentage. The potentially responsible party shall also provide the administrator with the factual documentation necessary to support the proposed orphan share percentage.

(c) Upon receipt of the information required by subdivision (a), the administrator of the fund shall invite all identified potentially responsible parties and the department and the regional board to submit any additional information relating to the proposed orphan share percentage or to the list of identified potentially responsible parties.

(d) The administrator of the fund, in consultation with the department or the regional board, shall determine a final orphan share percentage based on the volume, toxicity, and difficulty of removal of the contaminants contributed to the site by the party or parties responsible for the orphan share. The administrator shall determine the orphan share timely and efficiently and is not required to precisely determine all relevant factors, as long as the determination is generally equitable. In addition, the administrator may consider the results of any apportionment or allocation conducted by voluntary arbitration or mediation or by a civil action filed by a potentially responsible party, or any other apportionment or allocation decision that is helpful when determining the orphan share percentage.

(e) A potentially responsible party shall not assert, and the administrator of the fund shall not determine, that the orphan share percentage includes the share of liability attributable to a potentially responsible party’s acts that occurred before January 1, 1982, unless that share of responsibility is attributable to a person who is defunct or insolvent.

(f) In determining the orphan share percentage under this section, the administrator of the fund may perform any of the activities authorized in subdivisions (b) and (d) of Section 25358.1.

(g) The administrator of the fund shall issue all orphan share percentage determinations in writing, with notification to all appropriate parties. The decision of the administrator with respect to either apportionment or payment of claims is a final agency action for the purposes of judicial review of the decision by any party to the proceedings resulting in the decision; however, judicial review of the administrator’s decision is limited to a showing of fraud by a party submitting information under this subdivision. The administrator shall be represented by the Attorney General in any action brought under this article.

(Amended by Stats. 2016, Ch. 145, Sec. 4. (AB 2893) Effective January 1, 2017. See operational conditions in Section 25390.9.)