There are sweet, succulent bay scallops here like you’ve never tasted — and premium water quality is the reason why.

As essentials of life on Nantucket, both were the primary motivators for around 30 islanders to brainstorm and write the island’s first-ever harbor management plan in 1993 and a major revision of it in 2007.

People “from away” come to Nantucket for everything they can do in and on the clear, warm harbor waters, and thousands of Nantucketers rely on them for their livelihood.

So protection of this living resource through harbor planning — creating a management plan ensuring harbor health and a sustainable marine economy — came naturally to this island of 15,000. Nantucket embodies the island experience in southern New England, where islanders and people from “America” share, for pleasure or commerce, the harbor.

Vying for a piece of the harbor and its waters are three ferry fleets; fuel, modular home and aggregate barges; cruise ships; two yacht clubs; kayakers; divers; kiteboarders; mega-yachts; charter fishing boats; one massive marina; harbor launch services; mooring companies; several boat yards and more than 1,800 mooring owners. All depend on the harbor in some capacity; all depend on high water quality.

“I think it was just a matter of there was so much change going on in the early 1990s,” said marine superintendent Dave Fronzuto. “The town’s master plans was going on and a lot of planning initiatives were happening and we just felt we needed to do something for the harbor.”

Egged on by the Massachusetts Office of Coastal Zone Management’s (CZM) early 1990s dictum that all 78 harbor communities draft harbor plans, Nantucket began its effort in 1991, joining the 20 or so that currently have plans today.

“They were significant issues and I think they are what drove the demand to have an update of the harbor plan,”

“Nobody does this until there is some sort of crisis that becomes evident,” said Dan Hellin, a research associate with the Urban Harbors Institute, the consulting team from the University of Massachusetts at Boston that helped Nantucket with the 2007 revision. “Communities 20 or 30 years ago didn’t plan, but as soon as development caught up with them, that’s when they said, `we have to do a plan.'”

With water quality as its guiding light, the Nantucket Harbors Plan Advisory Committee worked with the University of Rhode Island and CZM on a plan that led to Nantucket being designated a federal no-discharge zone within three miles of the island, organizing the mooring field into a grid and setting policies on water quality, navigation and harbor safety, commercial and recreational boating, public access, tourism and water-dependent uses on the waterfront.

But in 2004, the harbor’s burgeoning uses and a failed eminent domain taking of the harbor’s only boatyard for public use prompted a revision, completed in 2007 and now being reviewed by CZM. This time around, though, the stakes are higher. A second yacht club now under construction, flagging bay scallop populations, 3,400 boats anchored or docked in the harbor during the summer, 30 ferry trips daily during the season, plus poor circulation and harbor pollutants from a variety of sources are pushing water quality dangerously close to what the authors of a UMass Dartmouth report said is the danger of eutrophication.

Facilitating a year of public meetings to gather local information on environmental conditions, natural and cultural resources, human commercial and recreational activities on the harbor, and then employing Global Positioning System technology to map out the physical characteristics of the harbor, the Urban Harbors Institute began assembling a mock-up of the revised harbors plan, based on input from islanders. This led to policy and goal recommendations that became part of the revised plan now being put into action by the harbor plan implementation committee and the Nantucket board of selectmen.

An offshoot of this revised plan is a series of articles on this year’s town meeting warrant that — with voter cooperation — will establish a development-curbing harbor overlay zoning district for Nantucket’s harbors. The district would be designed to preserve water-dependent uses on waterfronts of Nantucket Harbor and Madaket Harbor on the island’s west end. One article seeks to make permanent a temporary moratorium on docks, wharves and piers in all zoning districts except for the harbor zoning overlay district.

These refinements to the original 1993 plan all go back to something Nantucket values very highly. “They fear that they’re losing their working waterfront to gentrification and they say `what can we do to preserve our working waterfront?’ ” said Urban Harbors Institute Director Jack Wiggin. “The need to dredge could be one issue. Dozens of issues are possible, and those are identified by the people in the municipality.”

–Peter B. Brace is the environmental, growth & development reporter at the Nantucket Independent.