The signs are all over the state. In Brunswick, a new and trendy restaurant/cinema/art gallery has opened in a revitalized mill alongside the once filthy Androscoggin River. Cross the bridge into Topsham and you have to play bumper cars with all the construction vehicles bringing people to work on the latest riverside office development. In Skowhegan, city officials and volunteers have been meeting for several years to plan the state's first whitewater kayak run on the fast-moving portion of the Kennebec River that roars just behind downtown. In Gardiner, enhancements for that city's waterfront park include a new boat launch and a boardwalk that can be used by anglers. Newly built trails stretch along the Kennebec river. And in Lewiston and Auburn, old riverside mills are being transformed into office space, restaurants and condominiums.

Thirty plus years after the Clean Water Act was passed, our rivers are now clean enough that Mainers can say the words "economic development" and "rivers" in the same sentence and not be laughed at.

Which is precisely what a group of community activists and lawmakers did Tuesday at a Statehouse press conference. They proposed a $25 million bond to support riverfront community development. And we're definitely not laughing. This is a serious idea that merits serious consideration.

Much of the public's focus on our rivers in the last three decades has been on the ecological restoration of the waterways. We've worked to stop pollution, fix up sewage treatment plants, stem shoreline erosion, restore fish runs. Those efforts have been paid for by lots of federal dollars, matched by private donations and local and state funds.

Now that what's in the rivers is in much better shape, we are turning our attention to what's along those rivers. Shoreland and the historic structures beside our rivers can be a focus for economic revitalization efforts; the benefits of river restoration should not simply be ecological. Yet unlike the ecological restoration of our waterways, there's not a lot of money for those kinds of efforts and, because they often take place on private land, they don't attract the same kinds of charitable funds that restoration efforts do.

But the benefits are there. Just ask the folks in Old Town. That city tore down an abandoned paper plate factory, developed a park along the Penobscot riverfront ... and since then, a business complex and new restaurant have opened on the river and another abandoned mill has been turned into housing for seniors.

Projects funded by the bond would include building renovation, recreational access and even the creation of jobs. Proponents of the bond say it could be applied to rivers large and small throughout the state; that's good. The grants from the bond fund would require matching funds, which is also good because it means grant dollars will be multiplied. Bond proponents have not yet said who should oversee the bond's grants, but the Department of Economic and Community Development is the logical place.

There will be a lot of requests for bonds this session, given that no bonds were passed in the previous legislative session. The riverfront community development bond will have to compete alongside roads and infrastructure repair for the Legislature's go-ahead.

Yet as the Brookings report on the state's economic future said, investment in Maine's quality places is a crucial task if the state is to flourish. And now that we've cleaned them up, our rivers are an asset of enormous potential.