California Code, Government Code - GOV § 14529.8

(a) Funds may be allocated by the commission for each project element during the fiscal year that is identified in the state transportation improvement program and the funds shall be available for expenditure during that fiscal year and the following two fiscal years.  Any funds not allocated, or allocated but not encumbered, during the period specified in this section, shall remain in theState Highway Account or Public Transportation Account, or be returned tothat particular account, as the case may be.

(b) Upon a finding that an unforeseen and extraordinary circumstance beyond the control of the responsible agency has occurred that justifies an extension, the commission may extend the deadlines specified in subdivision (a).  The deadline extensions shall not exceed the period of delay directly attributed to the extraordinary circumstance and in no event be more than 20 months.  The commission shall not grant more than one extension.