By Bill Forry

Unless you live near that forlorn stretch of River Street near Lower Mills, you probably haven't noticed the rapid progress at the old Berger building, the former Baker Chocolate warehouse that will soon be home to the neighborhood's newest supermarket. Real soon, too, as it turns out.

Vince Droser, project manager for developer Trinity Financial, says to expect an opening in late July, if all goes as planned. That includes paving work along River Street, new street signals and staff training inside the new store.

The arrival of Shaw's in Lower Mills is cause for celebration for many in that area, who've suffered through years of sub-par conditions at the Star Market at 90 River Street. And yet, there is reason to be concerned, too, that the new store will bring with it a new set of problems.

Many of us have been, quite wisely, avoiding that side of the village lately, unless you enjoy sitting in long lines of traffic. Some have unfairly placed blame for the tie-ups at the feet of the soon-to-be finished Shaw's, when in fact the real problem has been the closing of the Roper Bridge over the Neponset. The ongoing detour of the Adams Street bridge has caused a serious ripple effect into Adams Corner and Mattapan.

There is some reason to worry, however, that Dorchester's first and only Shaw's will make an already bad situation worse come late summer. The intersection of River and Washington streets is already gridlocked on many evenings as people attempt to get into the 'burbs via Central Avenue. And for some unknown reason, the city continues to allow parking along River near the key detour route, which leads to an unavoidable bottleneck. With another year of bridge work still to come, it's unlikely to get any better for a while.

The big question now is this: Will it get any worse?

Reporter readers will recall that it was concern about traffic overwhelming Lower Mills' village that torpedoed a 1997 proposal by Stop & Shop, which wanted to build an even bigger store in the neighborhood. The corporate giants proceeded to have a three-year legal war that went to Shaw's in the end &emdash; but it was the community that ended up the real losers: Stop & Shop continues to sit on three very prominent River Street sites, including the old Knights of Columbus building, which stick out like a sore thumb next to the Shaw's parking lot.

And by refusing to sell the K of C property to Shaw's (which Trinity had hoped to acquire to give commuters more breathing room to park and maneuver on the Shaw's site) obstructionist Stop & Shop execs may well be pouring grease on the traffic fire along River.

Trinity Financial and Shaw's has coordinated with the Boston Transportation Department to re-signalize the Washington-River intersection, but there could be real trouble down at Central Avenue, where even regular police details haven't been able to solve the back-ups. Hopefully Shaw's will get proactive, too, and be prepared to put extra resources into making the transition a smooth one.

One good sign: Shaw's executive Paul Gannon, who steered the development of the River Street project for the chain, is a Fields Corner native, whose family remains vigilant civic activists in Dorchester. The neighborhood will be watching closely to see how Gannon and his staff handle this one.