The looming threat of a mega-development over the Turnpike has galvanized the Fenway and Back Bay neighborhoods. But be prepared to wait. The excitement could turn to boredom as the approval process drags on for what could easily be a year or two.

The planned development has already garnered an enormous amount of attention. The Globe has editorialized twice against any large development; both it and the Herald are following the story closely in their news pages. A small group of community leaders and politicians that represent the neighborhoods has begun meeting to plot strategy. Meanwhile, a petition written by both neighborhoods' civic groups is circulating, calling for a dramatically scaled back development and community approval of any design. The petition, circulating for only a week, already has close to 1,000 signatures.

Yet the cause of all this activity is still only slightly more than a rumor. No one has seen even preliminary designs for a proposal; even basic information such as size and density is missing.

What is known is that the Turnpike Authority has agreed in principal to lease the air rights for what are known as Parcels 11 and 12 to Millennium Partners, a New-York developer. These two parcels cover about five acres, beginning at Massachusetts Avenue (across from Tower Records) and extending to the Muddy River. The Authority expects Millennium to develop about two-thirds of those parcels.

Any development, when it comes, will be governed by a Memorandum of Understanding executed by the city and the Turnpike Authority earlier this year. To its credit, the agreement recognizes that affected communities have a right to participate in any development and so it creates a citizens advisory committee (CAC) that will review and modify any development proposal.

Unfortunately, the CAC itself is not wholly satisfactory. The CAC consists of 11 members, five of whom are chosen by the Turnpike Authority and six by the Mayor. One presumes that the five selected by the Turnpike Authority (which is, after all, the project's co-developer) will be backers of the development. One also presumes the Mayor's appointees will be more cognizant of community concerns. Still, the structure of the committee means that in controversial decisions there will be, at best, a 6-5 split within the committee.

One is tempted to compare the coming Millennium development to the proposed football stadium in South Boston. In that case, the entire community organized and with virtually one voice fought against the stadium. To the surprise of many, the community won. The lesson for the Fenway and the Back Bay is that concerted action works. The two neighborhoods, historically split apart by the Turnpike itself, now need to unite.

But the stadium analogy doesn't hold completely. The construction of a stadium allowed for a simple yes or no choice. The residents in South Boston chose "no." In the case of Turnpike development, the choices are more complex. Most people would welcome some development over the 'Pike. It's a big, ugly, noisy road and it should be covered over.

It is possible, of course, that what is acceptable to the Fenway and Back Bay is simply unacceptable to the developer, and vice versa. In that case, expect a big fight that will be resolved quickly. (Who wins, of course, is anyone's guess.)

It is more likely, however, that some sort of middle ground will be possible. In that circumstance, the process will be prolonged. The debate will focus on such scintillating issues as height, traffic, parking, materials, shape, density and use — issues that take time and effort to resolve. Under these circumstances, Fenway and the Back Bay will need more than unity. They'll also need stamina.