Bay Program officials can’t yet pinpoint the exact amount of sediment and nutrient reductions needed to clean up the Chesapeake.

But they narrowed the range for the ultimate answer.

Recent computer model estimates suggest that the Bay jurisdictions will likely have to slash nitrogen runoff an additional 24 million to 104 million pounds a year. About 285 million pounds now enter the Bay annually. The results suggest a similar level of effort for phosphorus.

Officials generally expect that the level of reductions needed to clean up the Bay will be toward the middle to high end of the range.

If so, that means the region would need to accomplish at least as much — and maybe twice as much — in the next 8 years as in the past 15, during which nitrogen runoff was slashed by a bit more than 50 million pounds a year.

The range of potential nutrient and sediment reductions stem from computer model estimates of what could be achieved from three levels of actions that might be taken on the land, and by wastewater dischargers, throughout the watershed.
The three levels, or “tiers” frame the boundary of what most officials think is feasible by 2010, the Bay cleanup deadline set in the Chesapeake 2000 agreement.

They range from merely continuing existing policies, (Tier 1), to boosting spending to encourage the maximum feasible participation in existing voluntary programs, (Tier 2), to “full implementation” of nutrient control efforts throughout the watershed, something that would likely require not only more spending, but could mean new regulatory programs as well (Tier 3).

“Tier 2 is doing as much as we reasonably can do in a cooperative program,” said Tom Simpson of the University of Maryland’s College of Agriculture and Natural Resources and chair of the Bay Program’s Nutrient Subcommittee. “Tier 3 is as far as we can go without major cultural and behavioral change.”

The results show that Tier 1 would do little more than hold the line on nutrients in the face of population growth expected in the next decade. Tier 2 would achieve a nitrogen reduction of about 60 million pounds from current levels, while Tier 3 would achieve a reduction of about 100 million pounds.

Officials stress that the tiers themselves do not dictate the level of nutrient reductions that will actually be required, or prescribe how those goals would be achieved within individual rivers. Rather, they set a framework so water quality managers can make sure nutrient reduction goals to be set in the coming months will be doable — and affordable.

“Those results kind of define the outer boundaries of the ballpark,” said Mike Bowman of the Virginia Department of Environmental Quality, who chairs the Bay Program’s Tributary Strategy Workgroup, which developed management assumptions behind each tier. “They don’t really design the interior of the ballpark, they don’t tell you where the seats are, they don’t put in the dugouts. Those kinds of details have to be fleshed out.”

Those details will emerge in coming weeks as state and federal officials begin feeding nutrient and sediment reductions associated with various tiers into the Bay Program’s water quality model to see how each affects the Chesapeake and its tidal tributaries.

The Bay Program is in the process of developing a new set of state water quality standards for the Bay and its tidal rivers that are aimed at protecting important species, such as fish and shellfish, and resources, such as underwater grasses.

Attaining those standards will ultimately be the measure of whether the Bay is cleaned up enough to be removed from the EPA’s list of impaired waters. If that goal is not achieved, the Bay region — under a court order issued in 1999 — will have to develop an enforceable cleanup plan known as a Total Maximum Daily Load in 2011.

Using the tiers as a guideline, officials will look at computer model results — river by river — to determine the amount of nutrient reductions needed to meet the proposed standards.

In some places, the standards might be met with nutrient reductions close to a Tier 1 level of effort. In other rivers, actions may need to go almost to Tier 3.

And in some places, it’s possible that even a Tier 3 effort would not attain some of the new standards. In those cases, officials say, some parts of the proposed standards may need to be changed.

For example, the standards call for allowing enough light to penetrate the water to allow underwater grasses — crucial habitat for everything from waterfowl to young crabs — to flourish in shallow water. Generally, it’s hoped that goal would be met at depths of 2 meters and less.

But if the water quality model shows the goal could not be met under Tier 3 nutrient and sediment reductions, the boundary may be scaled back to 1.5 meters, or even 1 meter in some places.

The same process will be played out not only for water clarity, but also other key water quality parameters in the new standards — dissolved oxygen and chlorophyll a (a measure of algae) — for each major river system.

Right now, water quality monitoring data suggest that the proposed standards are not being met in most places, which means significant nutrient and sediment reductions will likely be needed.

“I fully anticipate that most goals will be somewhere between Tier 2 and Tier 3,” Simpson said, “but it will vary depending what river you are on.”

Indeed, because the process is driven by water quality goals, it means the burden may not fall evenly among different rivers. That’s a sharp departure from the original “40 percent” nutrient reduction goal, set in the 1987 Bay Agreement, which called for across-the-board nutrient reductions.

“Nutrient and sediment goals in our river basins have to be driven by what we need to reduce to get water quality criteria attainment,” said Rich Batiuk, associate director for science in the EPA’s Bay Program Office. “We are not striving for equity in the tiered scenarios.”

If results show that certain basins have to do far more than others, officials have suggested that some mechanisms may need to be developed to help equalize the burden. For example, increased financial assistance could be targeted to certain areas. But those details are yet to be worked out.

Batiuk noted that some rivers heavily influence water quality in adjacent waterways. In those instances, it may be possible to shift some burdens from place-to-place. But again, details for allocating actual nutrient and sediment goals for particular rivers have not been decided.

In addition to figuring out how different levels of nutrient reductions will affect the Chesapeake, the Bay Program will use the tiers to determine how much they will affect the pocketbook. It’s expected the cleanup will cost several billion dollars.

Officials will be able to use tier information to gauge not only the level of effort, but the cost-effectiveness of nutrient reductions in various places, and from various sources.

Ultimately, the Bay Program — a state-federal partnership — will agree on nutrient and sediment allocations, or caps, for each of nine major Bay tributaries. It will also make allocations to individual states within each basin.

At that point, it will be up to the states to decide how to achieve nutrient reductions to attain the cap. Although tiers will serve as a reality check for making allocations, officials stress that they will not actually prescribe nutrient reduction strategies.

That will be done state-by-state, with the input of local tributary groups or teams. They will be free to choose whatever nutrient and sediment control practices they wish, as long as they reach the ultimate river goal.

“I don’t see the tiers strongly influencing the tributary strategies that are going to be developed,” Simpson said. “They may inform them a little. But the tributary strategies are going to be what works best locally.”

Nutrient and sediment runoff is considered to be the most important water quality problem facing the Chesapeake. Excess nutrients spur algae blooms that cloud the water, blocking sunlight from reaching underwater grasses, which provide important food and habitat for everything from waterfowl to young blue crabs. When the algae die, they sink and decompose in a process that depletes the water of oxygen.

Sediment also clouds the water before settling to the bottom where it smothers bottom-dwelling species such as oysters and clams.