Early settlers around Long Island Sound found the water packed with schools of fish: They marveled at the large numbers of osprey that would dive into the water, emerging moments later with a meal.

Sturgeon, salmon and shad were abundant, while the shores were densely forested. The land above 40th Street in today’s Manhattan — much of which is part of the Sound’s watershed — was so densely wooded that, one settler wrote, it was “useless except for hunting.”

Today, the Sound’s watershed is one of the nation’s most densely populated. The resulting wastes have taken a toll: Excess nutrients, primarily nitrogen, spur algae blooms that ultimately rob the Sound’s water of oxygen, threatening crabs, lobsters and other important species. Likewise, the algae has blotted out sunlight for underwater grasses, causing the beds — and the habitat they provide — to disappear.

In short, much of what ails the Chesapeake Bay — and many other coastal waterways — also ails the Sound. But this year, the Sound got something that the Chesapeake lacks: an enforceable plan to clean up the Sound within the next 14 years.

Connecticut and New York, with assistance from the EPA, drafted a cleanup plan known as a Total Maximum Daily Load. It outlines how the states will reduce their nitrogen flows into the Sound by nearly 60 percent.

The plan allocates specific nitrogen reductions to every wastewater treatment plant, which will be enforced through discharge permits. It also seeks a 10 percent reduction in runoff, mainly from stormwater, and outlines other actions to be taken if necessary.

The path taken by the Sound is sharply different from the one being taken by the Chesapeake, which is trying to avoid a TMDL through programs voluntarily implemented by the states.

In a sense, both could ultimately serve as models for what does — and doesn’t — work in coastal cleanup efforts.

The Clean Water Act requires a TMDL, essentially a pollution budget for a body of water, for any waterway that fails to meet water quality standards. The TMDL requirement was largely ignored for nearly two decades until environmental groups began suing the EPA to force their development.

A TMDL sets the maximum amount of pollution that a waterbody can receive and still attain its standards. That “load” is then allocated among various pollution sources.

For wastewater treatment plants and industries with discharge permits, this can be enforced through permits. For runoff sources, the EPA requires that states show they have adequately funded programs in place to get needed reductions.

Ultimately, if a state fails to implement a TMDL and attain water quality standards, the EPA could step in and enforce the cleanup plan on its own, as well as withhold millions of dollars of grants from the states.

Although many coastal waters around the United States are impaired by nutrient pollution, Long Island Sound is the largest coastal waterbody area to get a TMDL so far.

The Long Island Sound watershed drains an area of more than 16,000 square miles, including almost all of Connecticut, parts of New York Massachusetts, New Hampshire and Vermont — even a tiny bit of Canada.

Altogether, about 200 million pounds of nitrogen enter the Sound each year. Before Colonial settlement, the Sound received only a fraction of that. This increase has caused large areas of the Sound’s bottom to become depleted of oxygen — or hypoxic — during the summer.

As a result, the Sound fails to meet dissolved oxygen water quality standards for Connecticut (which are 6 milligrams of oxygen per liter of water) and New York (5 mg/l). In the 1980s, the EPA established the Long Island Sound Study — the agency’s equivalent to the Chesapeake Bay Program — to work with the states to clean up the Sound.

The states, in the early 1990s, froze the amount of nitrogen entering the Sound, and a few years later implemented low-cost nitrogen controls on selected wastewater treatment plants. The result was a decrease of 7 million pounds of nitrogen a year.

That wasn’t enough to end hypoxic conditions in the Sound. So in the late 1990s, the states and the EPA began working to develop a TMDL aimed at cleaning up the Sound.

The TMDL calls for a phased-in approach to meeting water quality standards. Initial efforts are focused on the “in basin” portion of the watershed — mainly Connecticut and parts of Long Island and New York City. It calls for a 58.5 percent nitrogen reduction from the “in basin” area.

In that area, “point sources” — mainly wastewater treatment plants — are the dominant nitrogen source, accounting for almost three quarters of what enters the Sound. The TMDL directs that 90 percent of the reductions come from point sources, with the remaining 10 percent coming from runoff controls.

The TMDL sets a limit, which is enforceable through permits, for each wastewater treatment plant. “It starts to cut through the generalities and makes it very clear what the ultimate goal is for each community,” said Mark Tedesco, director of the EPA’s Long Island Sound Study. “That’s really important.”

Computer models suggest that still may not be enough to meet dissolved oxygen standards.

If that proves to be the case, nitrogen reductions would be phased in for “out-basin” sources and, if that fails to achieve the water quality standards, the TMDL outlines several other options such as dredging to improve water circulation, relocating outfalls from wastewater treatment plants, growing “seaweed farms” to remove nutrients, or even pumping oxygen into hypoxic areas.

“We never know with certainty what is going to happen, how the system is going to respond and what is ultimately going to be needed,” Tedesco said. “The one thing we don’t think is going to change is the reductions that are needed from the New York and Connecticut portions of the basin.”

The TMDL also notes that computer modeling suggests the New York and Connecticut standards for dissolved oxygen likely were not met, at least under some conditions, even during pre-Colonial time. Therefore, the TMDL notes that the states may adjust dissolved water quality standards downward, to about 3.5 mg/l, for some of the deeper parts of the Sound.

Ultimately, through whatever combination of actions is necessary, the TMDL promises to achieve water quality standards by 2014.

The Chesapeake fails to meet existing water quality standards in both Maryland and Virginia, mainly because of low dissolved-oxygen levels in deep parts of the Bay.

Like Long Island Sound, the dissolved oxygen levels in those areas were probably low even before settlement, but have been made worse in recent decades by huge nutrient increases.

But rather than develop a TMDL, the Bay states are working — with the EPA’s blessing — to clean up the Chesapeake by 2010. Otherwise, the agency would be bound by a court agreement to require an enforceable TMDL in 2011.

Rather than try to meet state water quality standards, the Bay Program is working to establish new criteria that would more realistically reflect the needs of fish and other resources.

In addition to modifying dissolved oxygen criteria, it is working on new criteria for water clarity standards, which would protect grass beds, and chlorophyll, which would regulate algae production. Once developed, the criteria would be adopted as state water quality standards. Attaining those standards will become the Bay’s cleanup goal.

By the end of this year, the Bay Program will determine — tributary by tributary — the amount of nutrient and sediment reductions needed to achieve the revised standards. After that, all six states in the Bay’s 64,000-square-mile watershed will develop strategies to achieve their share of the reductions.

Unlike a TMDL, those plans will not be enforceable.

Although the Bay states have adopted some enforceable elements over the years, such as laws that regulate some animal wastes, most nutrient reductions will rely on voluntary measures driven in large part by programs that share the costs with farmers, or provide grants to wastewater treatment plants for upgrades that achieve certain levels of nitrogen reductions.

With potentially huge reductions needed, officials say they will spur more action through cooperation than through regulation. Right now, about 300 million pounds of nitrogen enters the Bay each year. Preliminary estimates indicate that may need to be cut to 150 million to 200 million pounds to meet the new standards.

“We’re looking at big load reductions,” said Rich Batiuk, associate director for the EPA’s Bay Program Office. “We need innovation and opportunities to try new and different things, and people don’t do that very well within the straitjacket of a regulatory program.”

If the Bay Program’s approach works, it would complete a bigger job than Long Island Sound, and in less time. Its Chesapeake 2000 Agreement calls for a clean Bay by 2010 — when the Sound would still be four years from its goal.

Despite that, some — including the Chesapeake Bay Foundation, the region’s largest environmental group — embrace doing a TMDL now. “The relevant difference,” said David Anderson, a CBF attorney, “is that a TMDL is enforceable.”

The Chesapeake 2000 Agreement is not. If it fails to deliver by 2010, it would force the region to develop a TMDL. But under EPA regulations, the region could get another 15 years to achieve its objective. If that happens, a “clean” Bay could be a quarter century away — not a decade. “That’s our most significant concern,” Anderson said.

The Sound’s TMDL sets sharp reduction goals, and will revisit those goals as time goes on. By contrast, Anderson said, the Bay Program won’t have a new goal until the end of this year, and won’t have tributary strategies to reach the goals for another year.

That leaves little time — eight years — to do more than was done in the last 13 years. “We are going to have to ramp down very quickly in order to clean the Bay by 2010,” Anderson said.

Skepticism is fueled by the Bay Program’s failure to meet its 40 percent reduction by its 2000 goal. That goal was set in its 1987 Bay Agreement. It was later reduced to a 20 percent reduction for nitrogen, but the Bay states only cut nitrogen by 15 percent, according to Bay Program figures.

Recent actions of the states provide some grounds for concern, Anderson said. For example, Virginia’s grant program for wastewater treatment plants was slashed as Gov. Jim Gilmore looked for ways to balance the books and deliver promised tax cuts. Pennsylvania has yet to launch any program to fund nitrogen upgrades at wastewater treatment plants. And although Maryland has a grant program for nitrogen reductions at wastewater treatment plants, it recently wrote a draft permit that allows increased nitrogen discharges at an expanding plant.

Had the Bay Program opted for a TMDL, Anderson said, dischargers would have each been assigned a specific nutrient reduction, and states would have felt greater pressure to fund programs that would help achieve permit limits.

And, as is the case in Long Island, the Bay Program would still be able to revise its water quality standards and update the TMDL in the future, Anderson said. The key difference, he said, is that a TMDL would have placed more pressure to take action faster in the Bay.

That is what has happened in Long Island Sound, said Amanda Waters, a policy analyst for Save the Sound, a Connecticut-based environmental group, which is backing legislation to boost funding for plant upgrades. “It’s really the best effort we’ve made so far in nitrogen reductions,” she said.

In Long Island Sound, both states are responding with major new funding programs to help fund wastewater treatment plant upgrades, which are expected to cost about $1 billion. In New York, according to EPA’s Tedesco, the state has earmarked $200 million to support upgrades at plants in Long Island Sound. In Connecticut, the state is not only establishing a grant program, but is also setting up a trading program that will allow treatment plants to trade nitrogen “credits” and achieve more cost-effective reductions.

Bay Program officials dispute any suggestion that the Chesapeake cleanup has stalled. Its computer models show the states have cut nitrogen from 360 million pounds in 1985 to 300 million in 2000.

“We’re making excellent momentum in some areas, and we are making smaller progress in other areas. I don’t see us stalling,” said Bill Matuszeski, director of the EPA’s Bay Program Office. “The bottom line is performance. Long Island Sound has achieved a 7 million pound reduction. We’ve achieved a 60 million pound reduction. I’ll set that up on a table against anybody else.”

He and others say Long Island Sound is a poor analogy for the Bay. A key difference, they say, is that wastewater treatment plant discharges account for a majority of the nitrogen in the Sound, but only about a fifth of it in the Bay. If all their discharge pipes were corked, the Bay would still not achieve its clean water goals.

Wastewater discharge plant operators fear that, under a TMDL, regulators would ultimately be forced to ratchet down discharges further and further — at greater and greater costs — if reductions from agriculture and other runoff sources fail to materialize. Treatment plant operators say because their permits are easier to enforce than runoff controls, their ratepayers could end up paying huge amounts of money to achieve ever-smaller reductions — and the states would still fail to meet the clean Bay goal.

“The whole process has the potential to put a disproportionate and inequitable burden on the point sources,” said Chris Pomeroy, who represents the Virginia Association of Municipal Wastewater Agencies. “Let’s not fool ourselves. This is not going to get done without the nonpoint sources doing their share. Our ratcheting down disproportionately on point sources will cost increasing amounts of public funds and won’t get us where we need to be.”

Even in Long Island Sound, where point sources dominate, achieving maximum “limit of technology” nitrogen controls was not considered feasible. “What was central to the TMDL, for us anyway, is that it is a cost-effective TMDL,” said Martin Overton, assistant public works director in Norwalk, CN.

Squeezing every pound of possible nitrogen reduction from wastewater treatment plants, Overton said, could easily cost $4 billion — a price tag that “is simply not realistic” — and would still have failed to attain water quality standards.

“Some of us would prefer to go before a judge and argue our case than be forced into wastewater treatment plant expenditures that were not necessarily related to cleaning up the Sound,” he said.

Instead, Overton characterized the TMDL as a compromise which phases in nitrogen reductions, reassesses water quality, and includes state action to adopt less stringent dissolved oxygen water quality standards.

It is the question of lawsuits — and public acceptance — where Bay Program officials feel their approach will ultimately prevail.

TMDLs are increasingly mired in suits around the nation. And officials say a TMDL for a large, complex estuary like the Chesapeake could be the target for litigation that would bog down action for years.

Fueling that concern is uncertainty about new TMDL rules adopted by the EPA last year that were so controversial that Congress blocked the agency from implementing them before this October. Many critics have threatened lawsuits over the regulations.

“Until these things are sorted out, it is dangerous to head down the classic TMDL route with a complicated system,” Matuszeski said. “It’s another good reason for us going the way we are going.”

Although the Bay Program failed to meet its 2000 nutrient goal, Matuszeski said actions so far have helped build public understanding — and involvement — in nutrient reduction efforts. As new water quality criteria go out for public review, he and others feel “stakeholder” involvement will increase and translate into broader cleanup support.

“We are building long-term buy-in and commitment,” said Batiuk, of the Bay Program Office. “We certainly have not gone as far as we would like, but we do have a good track record, and it has been through a cooperative mode. If people want to dig their heels in, they will stop dead everything in its track, regardless of whether you have a TMDL in place or not.”

Public support is particularly important in the Bay, Batiuk said, because most nutrients come from runoff. Controlling runoff is harder to regulate, and requires willing action by farmers and other landowners. “When you have systems — the Rappahannock comes to mind — where less than 10 percent of the load is coming from point sources, you need the buy-in from the agricultural community and others out there,” Batiuk said.

In Long Island Sound, Overton said outreach and education efforts were poor. Some plant operators were caught off guard by the nitrogen allocations, he said, and municipal officials who make local spending decisions were not included in outreach efforts. “My chief elected official, finance director and town council members were not selected for specific mailings,” he said. “For me to go to the boss and say I need $60 million to expand the plant — you need to explain a lot.”

But outreach in Long Island Sound in some ways is daunting, Overton acknowledged. In a point-source dominated watershed, he said, “the stakeholders are everybody. Every time you flush the toilet, it’s you. And how you get the word out to Manhattan, I don’t know.”

As a result, Overton characterized the Long Island Sound TMDL as “a heck of a good start on a very complicated issue.”

Environmentalists tend to agree. Waters, of Save the Sound, said cleaning up — and maintaining — the Sound will ultimately require actions that go beyond those spelled out in the TMDL. “But for now,” she said, “we are happy with this effort.”

And in the coming years, people from around the nation will watch Long Island Sound and the Chesapeake Bay to see which — if either — succeed.

“There are advantages and disadvantages to each approach,” said the EPA’s Tedesco. “And it may be that the right approach for one area is not the right approach for another area.”