SHOULD ALEXANDRIA'S waterfront be a national historic park? A deputy assistant secretary in the Interior Department recently said "No." We think he's right. Though Alexandria has many historic structures, the waterfront itself has few noteworthy old features left to be preserved. Nor should Interior take charge of the shoreline, as some local factions want, primarily to block development. Alexandria is distinctive as a city and a port - not as a park. The waterfront can best reflect that spirit if it is revived as an attractive place for public activity, combining small-scale commerce, recreation and the arts.

Federal agencies will have to play a part. The long, tangled dispute over land titles, involving the federal government, the city and private developers, needs to be resolved. (The Interior official predicted a settlement next fall, but nobody should bet on that.) Moreover, the government indisputably owns some shoreline properties that ought to be included in any overall waterfront plan.

The big problem is settling on a plan. Interior has suggested a local-state-federal study group. City Council member Robert S. Calhoun advocates a somewhat different joint approach. Before any such venture has much promise, though, local leaders will have to end, or at least tone down, their own disagreements. The council seems to want to try - or, more accurately, try again. Recently it declared its intention to work out a plan by June. That's not much time in which to end years of contention and produce something fairly specific that has broad support. If the council can come through, though, the prospects for the waterfront will be greatly enhanced.