Cal. Pub. Util. Code § 29034.6

(a) Not later than 1991, the district shall proceed to commence construction of an extension of its facilities to West Pittsburg, or to a point east of that location, if the funding described in subdivision (b) is sufficient and all of the following occur:
1. (1) The voters of Contra Costa County, at the November 8, 1988, general election, approve an additional one-half of 1 percent sales tax for transportation purposes.
2. (2) An increase in San Francisco Bay area bridge tolls, as proposed by Senate Bill No. 45 of the 1987–88 Regular Session, is approved.
3. (3) Sufficient funds are provided to the district from paragraphs (1) and (2) which, together with funds identified in subdivision (b), would result in the generation of at least four hundred twenty-five million dollars ($425,000,000) for the West Pittsburg BART extension.
(b) The district board of directors shall set aside at least thirty-four million dollars ($34,000,000) from district reserve funds and, if the district receives two hundred million dollars ($200,000,000) from the San Mateo County Transit District as a result of an agreement between the district and the San Mateo County Transit District, the district board of directors shall set aside at least an additional seventy-four million dollars ($74,000,000) for the purposes of this section. The district shall seek other funding as may be available from state and other sources to meet the objective of completing construction of an extension to West Pittsburg.
(c) It is the intent of the Legislature that the district extend its service and facilities to eastern Contra Costa County as far as the four hundred twenty-five million dollars ($425,000,000) funding amount will permit.
(d) If funds generated from the additional Contra Costa County transportation sales tax or the increase in bridge tolls do not become available to the district, it is the intent of the Legislature that the district proceed with service and facilities extension as far as available funding sources permit.