Here’s what you need to know about Boston-area development this week

Welcome to Critical Mass., a weekly roundup of the most notable development news in the Boston area. This week, a potentially big development in Dorchester starts to advance and another potentially big development on the Eastie-Revere line clears a milestone.

UMass’s building authority finalized a 99-year, $235 million ground lease of the old Bayside Expo Center site in Dorchester with developers Accordia Partners and Ares Management. The pair can now get down to planning what could end up as well over 3 million square feet of new development—easily one of the biggest projects in Boston.

And speaking of easily biggest projects in Boston, thoroughbred racing is officially done at Suffolk Downs on the East Boston-Revere line. What’s next for the 161-acre site is one of the great parlor games in Boston-area development.

Photo courtesy of Greystar

A parking lot at Newbury and Dartmouth streets in Back Bay fetched $40 million. L3 Capital, a Chicago investment firm that specializes in retail projects, won the bidding and will likely redevelop the surface lot. And the slow death of downtown Boston parking norms continues.

Also, Greystar officially opened its Elan Union Market in Watertown: a 282-unit apartment complex at 130 Arsenal Street, where studios start at $1,750 a month and where at least 75 of the units have already been leased. (Its lobby is pictured above.)

Finally, WS Development scored the annual HubWeek ideas fest, which is moving this October from Government Center to the Seaport, where WS Development is spearheading some major projects.