Los Angeles County Supervisor Hilda Solis is resurfacing the idea of building a rail line along the Los Angeles River, east of Downtown LA.

She sent a letter Wednesday afternoon to Metro’s Board of Directors urging its members to look at “all feasible build alternatives” for the West Santa Ana Branch rail line. That line is slated to run roughly 20 miles between Downtown LA and the Gateway Cities in southeast LA County, offering passengers a transfer-free ride from Union Station to the Orange County border.

Metro aims to open the West Santa Ana Branch line by 2028, but the agency has yet to determine exactly where the Downtown LA portion of the line will run. The agency’s Board of Directors is set to decide today which Downtown LA route options will be carried into the line’s environmental review process.

Metro staffers have discounted the alignment along the river. But Solis says it should be on the table. It’s the only option that would potentially lead to the line being built as heavy rail.

It would open the door to revolutionizing transportation connections between Orange County and LA.

As Streetsblog argued earlier this month, if that alignment were built as heavy rail, the West Santa Ana Branch could potentially be built as an extension of Metro’s Red and Purple subway lines. The Red and Purple lines run through North Hollywood, Hollywood, Los Feliz, Koreatown, MacArthur Park, and Downtown, and the Purple Line is being extended now from Koreatown to the Westside, through Mid City, Fairfax, Century City, Beverly Hills, Westwood, and Brentwood.

If those lines were to connect to the West Santa Ana Branch, it would open the door to revolutionizing transportation connections between Orange County and LA, should OC leaders ever choose to build rail north from Santa Ana to Artesia.

I am calling upon my @metrolosangeles colleagues to stand with the #LittleTokyo & #ArtsDistrict communities and eliminate Alternative F & replace it with Alternative H as a one-seat ride to Union Station with a connection/transfer point to the Blue Line. #WSAB #SELA



Read more pic.twitter.com/RcNxePUVaQ — Hilda Solis (@HildaSolis) May 23, 2018

As Solis’ letter highlights, an alignment along the river would eliminate the need to build several miles of costly new train tunnels under Downtown Los Angeles. It would also spare Little Tokyo, where work on the Regional Connector is underway and where part of the Gold Line Eastside extension was built, from another decade of construction.

Studying this particular alignment would help the Metro board fully understand “additional options for a one-seat ride into Union Station,” the letter says.

But Metro staffers have rejected that option. Instead, they are recommending that board study three light rail options: two that run through Little Tokyo and terminate at different spots in or near Union Station and another that would end in the Downtown LA “transit core,” likely close to either Seventh Street/Metro Center or the Pershing Square subway stations.

After multiple Metro directors inquired about building the line as an extension of the Red and Purple lines, Metro staff released a report that flatly dismissed the concept, saying it would cost too much: $12 to $18 billion.

Staffers said those figures were “based on recent Metro projects,” but Streetsblog called them “bogus.” There isn’t a transportation project in Los Angeles County that can be compared cost-wise to a heavy-rail version of the West Santa Ana Branch.

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To date, all heavy rail Metro projects have been built as costly underground subways.

Subways are a type of heavy rail, but heavy rail trains can also be built above ground. They can carry a high volume of passengers, and generally require tracks that are fully separated from cross-traffic like cars and pedestrians. That makes them faster and more reliable than light rail lines, which tend to have lots of grade-level intersection crossings.

Most of the West Santa Ana Branch will be built along an existing railroad right-of-way. In that sense, it’s similar to the most recent extension of the Bay Area’s heavy rail BART system, where more than 5 miles of track were built for less than $1 billion over the past three years.

“Building a train on an existing ROW does not cost more than a whole new tunnel and tracks through Downtown,” Streetsblog wrote.

Still, the alignment that Solis is pushing for would be costly if it were built as heavy rail. It would likely require more grade separation than light rail due to the presence of the third rail.

But, as Streetsblog wrote, it “has the potential to be a win-win-win for Metro riders, and for the communities the WSAB would serve.” Metro supervisors will have to decide whether it’s worth it.