The most recent meeting of the Potomac Watershed Roundtable was in Warrenton, VA at Lord Fairfax Community College and had a series of speakers on the Chesapeake Bay strict pollution diet, the Total Maximum Daily Load (TMDL) mandated by the EPA to the six Chesapeake Bay Watershed states and the District of the Columbia. The TMDLs were assigned by the EPA to each segment of the Chesapeake Bay Watershed. For the TMDL, the Chesapeake Bay’s tidal waters have been divided into 92 tidal water segments. There are 35 segments controlled by Virginia and another five Maryland owned segments that include Virginia drainage areas. The different water segments are determined by their varying degrees of salinity, recalling that the Chesapeake Bay Watershed is an estuary. Finally, the TMDLs address only pollution from excess nitrogen, phosphorus and sediment. No action has been taken on other pollutants that might be present in the Chesapeake Bay and its tributaries.
On November 29th 2010 Virginia, submitted the final version of the Virginia Chesapeake Bay Watershed Implementation Plan (WIP) to the U.S. Environmental Protection Agency and December 29th the EPA accepted the revised version of Virginia’s WIP and issued the “final” TMDL, but with “enhanced oversight.” (Doesn’t that sound like fun.) The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution. It is possible that they have been spending a wee bit too much time looking at computer output and missed the big picture.
Mike Rolband, President of Wetland Studies and Solutions, Inc. had an interesting presentation pointing out poor model behavior, mistakes and injustices of the current TMDL, what EPA has called the strict pollution diet, but really is an excess nutrient diet. When Mike showed the group his slides, several aspects of the Chesapeake Bay Watershed, the EPA’s models, the mandated TMDLs became very clear for me. First of all, the level of excess nutrients in each of the major tributaries to the Chesapeake Bay is fairly well known and well predicted and calibrated by the models. Second, this is indeed a diet, the Chesapeake Bay is overwhelmed with excess nutrients and sediment, and like an obese person, less nutrients will improve the situation. Thirdly, land use and population density matter, but generally the higher the population the more total nutrients are released. Waste water treatment plants and urban runoff and septic contribute a larger load of nitrogen than the agricultural sector. Finally, the EPA mandated TMDL and the approved WIPs to implement them require a percentage reduction in nutrient load from each sector.
This turns out to be vastly inequitable. Eliminating the agricultural sector, Northern Virginia with 46% of the watershed population is required to obtain a total nitrogen load for the waste water treatment plants, urban and septic of 2.52 pounds of nitrogen/person/year while the James River Basin is only required to obtain 6.38 pounds of nitrogen/person/year and the state target average is 4.43 pounds of nitrogen/person/year. This is the equivalent of mandating a diet for everyone in Virginia to lose 1/3 of their body weight. This might be just fine and actually beneficial for the 300 pound people who will be forced to lose 100 pounds, but it is lethal for the 150 pound Potomac Watershed that will have to loose 50 pounds each. We in northern Virginia are trapped in some Kafka version of a diet where slow death by starvation (stopping population growth and potentially reducing population) may be the unintended consequences of the EPA mandated pollution diet.