Controlling nutrients in the Bay watershed is like going down an ascending escalator — it seems to take two steps forward to get one step ahead.

The nutrient goal in the 1987 Bay Agreement — reduce the amount of nitrogen and phosphorus reaching the Bay 40 percent from 1985 levels by the turn of the century — seems straightforward enough.

But getting that reduction, it appears, actually means cutting nutrient pollution by far more than 40 percent.

Confused?

Then take a look at figures from the Maryland tributary strategy, the most detailed plan so far that shows how to reach the 40 percent reduction goal.

Maryland’s “base load” for nitrogen in 1985 was 76.44 million pounds. A 40 percent reduction in the “controllable” portion of the base load — the portion that can be affected through traditional water quality programs — would cut that to 53.62 million pounds.

Since 1985, nutrient control efforts have cut the annual nitrogen load to about 63.3 million pounds per year.

So the state only needs to cut another 9.58 million pounds to meet its goal, right?

Wrong.

The state’s strategy calls for reducing nitrogen by another 19 million pounds by the turn of the century.

Instead of cutting a total of about 23 million pounds to reach its goal, which straight math would suggest, Maryland plans to reduce nitrogen by more than 30 million pounds a year. The story for phosphorus is pretty much the same.

What is going on here?

In a word: Growth.

The reason is twofold, and both relate to population. More people means more sewage that must be treated to remove nutrients before the wastes can be discharged.

More people also means more development. As land is cleared for homes, roads and shopping centers, the amount of runoff into waterways can increase.

What is true for Maryland is true for other Bay jurisdictions. Like the person descending an ascending escalator, the Bay jurisdictions must work harder and harder to keep pace with growth and meet the nutrient reduction goals.

The whole Bay Program goal for nitrogen is a 74 million pound reduction. But to keep pace with growth, another 31 million pounds must be removed to get the goal.

“In other words, for every two pounds of nitrogen removed, one pound returns as a result of population growth and must also be removed,” said a recent report by the EPA’s Chesapeake Bay Program Office. “The strategies are designed to accommodate this impact, but its extent underlines the need to emphasize nutrient removal from treatment plants and adequate management of the effects of development on the streams and rivers of the Bay.”

The report, “Achieving the Chesapeake Bay Nutrient Goals: A Synthesis of the Tributary Strategies for the Bay’s Ten Watersheds,” shows that some progress has been made in each state to reduce nitrogen loads. But if no additional actions were take between now and 2000, nitrogen loads from Pennsylvania, Virginia and the District of Columbia would exceed 1985 levels. Loads from Maryland would increase, but not to 1985 levels, mainly because Maryland has achieved the greatest reduction so far.

The 1987 Bay Agreement called for reducing nutrients 40 percent from the 1985 baseline level to improve the Bay’s water quality. Too many nutrients spur the growth of algae blooms that block sunlight needed for important Bay grasses and deplete the water of oxygen needed by many species.

But in 1992, the Executive Council — the top policy-making body for the Bay cleanup — called for “capping” the amount of nutrients entering the Bay at the reduced level once it is achieved.

As a result, what started out as a 40 percent reduction from 1985, ended up as a 60 percent cap of 1985 loads. And the two are not the same.

“The goal to reduce 1985 loads by 40 percent includes controlling 100 percent of loads between 1985 and 2000 attributable to growth,” said Bill Matuszeski, director of the EPA’s Chesapeake Bay Program Office. “In other words, you don’t get any relief because you’ve grown between 1985 and 2000.”

To meet the cap, specific limits for nitrogen and phosphorus were set for each of the Bay’s major tributaries. The states then began developing tributary strategies for each of those rivers to show how they would reach the goal.

The difficulty in getting those reductions is illustrated by the fact that none of the tributary strategies being developed are truly “complete” in illustrating both what has to be done to reach the goal, and how it is to be done.

Maryland has a detailed guide as to how to reach its goal, but is still working on ways to pay for it. Costs have been estimated in the hundreds of millions of dollars.

Pennsylvania has developed a plan that falls short of its nutrient reduction goal, but it is largely funded. Officials are trying to determine how to meet the rest of the reduction goal.

The District of Columbia has a plan which surpasses its reduction goal — upgrading the massive Blue Plains wastewater treatment plant — but it requires the completion of negotiations with the federal government over funding and other issues before it can go ahead.

And Virginia is still developing its plan plan for the Potomac River, which is expected to be completed next year.

Part of the problem in making the numbers add up is that the goal is a moving target. No one knows exactly how many people will be in the watershed come 2000.

“There’s an awful lot of projecting going on there,” said Bob Summers, head of the Watershed Management Program in the Maryland Department of the Environment’s Chesapeake Bay and Watershed Management Administration. “But there’s no other way to get the numbers because nobody really knows how that is all going to work out.”

The projections are based on things like how much sewage treatment capacity will be needed in the next six years and how much development will take place. Assumptions are made in all the estimates, Summers said. For example, engineers tend to estimate waste water treatment capacity on the high side so they will not be caught short.

On the other hand, no one really knows where all the new homes to accommodate population growth will be built. Runoff from subdivisions tends to have slightly less nutrients per acre than from farms, but much more than forests. If most of the new development in the next six years comes out of farms, some nutrient estimates being used may turn out to be a little too high. But if that development comes out of forests, they may be much too low.

And then there’s the matter of farm animals. Their numbers have grown rapidly in recent years and they are major sources of nutrient pollution. But unlike people, Summers said, no one projects the populations of chickens and cows into the future.

“Given all the assumptions about growth in the tributary strategies, the exact reductions certainly are not real hard numbers,” Summers said. “As implementation proceeds, we will monitor our progress and make the necessary adjustments. The bottom line is, there is an increase in loading due to growth that will have to be controlled in order to maintain the loading cap.”

Copies of “Achieving the Chesapeake Bay Nutrient Goals: A Synthesis of Tributary Strategies for the Bay’s Ten Watersheds,” are available from EPA’s Chesapeake Bay Program Office, 1-800-YOUR-BAY.