The Board of Directors of the Expo Line Construction Authority voted on Thursday evening to approve the final environmental impact report for the light rail line from Culver City to Santa Monica.

The vote allows design and construction work of the line to go forward. The seven-mile, $1.5-billion line is scheduled to open in 2015. The first phase of the Expo Line, from downtown Los Angeles to Culver City, is currently under construction.

The vote was six yeas with one abstention from Dan Rosenfeld, the senior deputy for Supervisor Mark Ridley-Thomas who was voting as an alternate for Ridley-Thomas. Rosenfeld said the main issue was Metro’s grade-crossing policy and that Ridley-Thomas’ office does not believe it takes into account pedestrian traffic and future economic development created by the line

Despite the approval of the report, some residents who live near the Expo Line — mostly in the West Los Angeles area in neighborhoods near the Westside Pavilion — said they are planning to file a lawsuit alleging that the environmental report is flawed. In particular, they allege that the report failed to take into consideration the full traffic and safety impacts of building the line at street level across Overland Avenue and Westwood and Sepulveda boulevards.

It remains unclear how such a lawsuit would impact construction of the Expo Line. But residents said that if such a suit was filed they would likely seek an injunction to stop construction until the report is redone to their satisfaction. They are seeking to have the line built underground between Overland and Sepulveda.

County Supervisor Zev Yarosvlasky — who serves on the Metro Board and the Expo Line Board — said that he believed the impacts of the train could be mitigated and that it simply was not financially practical to build underground rail lines everywhere residents wanted them.

An amendment by Yaroslavsky kept open the option of the train crossing Sepulveda on a bridge. There have been discussions that the developer of a large mixed-use development at Sepulveda and Pico might pay for the bridge, but that is not a done deal and the development yet been approved by the city of Los Angeles.

Los Angeles City Councilman Paul Koretz said that he expected to vote as an alternate to board member Bernard C. Parks but that Parks changed his mind this week and decided to vote. Koretz — whose district includes the disputed stretch of the Expo Line — told the Board that while he supports the line, he would have voted against the EIR because he thought that Metro’s grade-crossing policy was flawed and the line should be grade-separated at Overland and Sepulveda.

Koretz said the Expo Line Board was, in essence, trying to avoid grade separating the line in those areas in order to save money and that the only way those crossings passed muster with the policy was because the EIR envisioned the streets being widened.

Parks said that he changed his mind and wanted to vote because he understood the grade crossing policy would become a major issue and that he supports the policy and completion of the Expo Line from downtown to Santa Monica.

More than three hours of public testimony preceded the vote. Opinions ran the gamut from those saying that mass transit was badly needed on the Westside and that the Expo Line was well designed to those who said the train would badly impact their neighborhoods and should be built correctly the first time around.

Expo Line officials say that the cost of putting the tracks under Overland and Westwood would be an additional $224 million. Bridging over the two streets — which would likely create aesthetic concerns for neighbors — would cost $66 million. No source of money has yet been found for those upgrades; the line is currently going to be paid for with $925 million from the Measure R sales tax increase voters approved in 2008 and about $600 million in state and local funds.