Tentative plans to extend service on Metro's Red and Purple Lines to the Arts District may be under threat, according to an announcement from the Arts District BID.

In advance of the Purple Line extension to Beverly Hills, Metro is planning improvements to the Division 20 rail yard, which flanks the L.A. River. The proposed upgrades include the widening of an existing portal to the southeast of Union Station, as well as the construction of a new turnback facility that will allow subway trains to run more frequently.

However, both the Arts District BID and a newly minted group known as "Save 6th Street Station," have argued that the design of the proposed turnback facility may eliminate the possibility of extending passenger service to a new station at 6th Street.

Metro has previously considered up to two infill stations within the Division 20 yard, with potential locations at 1st and 6th Streets.

Both sites find would serve a community on the cusp of rapid growth, with a variety of large residential developments either planned or underway.

The proposed 1st Street station would directly connect to One Santa Fe, a quarter-mile long mixed-use complex which opened along the perimeter of the rail yard in 2014. The Michael Maltzan-designed building neighbors both the Southern California Institute of Architecture and a $215-million development now rising at 950 E. 3rd Street.

The potential 6th Street stop would abut the rebuilt Sixth Street Viaduct, and sit immediately north of a Bjarke Ingels-designed development which was announced earlier this month.

The Division 20 upgrade will be discussed at the Historic Cultural Neighborhood Council's Urban Design and Land Use Committee this Wednesday from 7 to 9 pm at room 160 in SCI-Arc.