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(007) Nutrients in the Chesapeake Bay- A Regional Alternative to the Traditional TMDL.
Rue, Bill*,1, Muessig, P1, Whitaker, J1, Powell, M1, Spano, T2, 1 EA Engineering, .2 Metropolitan Washington Council of Governments, .
ABSTRACT- In 1998, the Chesapeake Bay and many of its tidal tributaries were listed as "impaired waters" for nutrients which required the development of a Total Maximum Daily Load (TMDL). To avoid the regulatory impacts that a regulatory TMDL might have on the cooperative efforts being used by the tributary strategy programs being implemented by the states within the watershed, the Chesapeake 2000 agreement included formal commitments which require the states to restore the Bay water quality by 2010. The scientific efforts to meet this commitment are enormous and include: (1) the development of four new Bay-specific designated uses; (2) Chesapeake Bay-specific ambient water quality standards for dissolved oxygen, and innovative criteria for water clarity and chlorophyll-a; (3) a series of statistically-based implementation procedures to determine the acceptability of allowable criteria excedences which to not result in impairment of designated uses; and (4) a massive 3-D modeling effort to determine the duration, magnitude and frequency of concentrations in all segments of the Bay, and to calculate the loadings which will be allocated to the various tributaries to the Bay. When finalized, the use designations, criteria, and implementation procedures will need to be adopted into each state's water quality regulations. Notably, it was decided to develop numeric criteria for water clarity and chlorophyll-a, rather than nitrogen and phosphorus which are the constituents which will ultimately have to be reduced from point and non-point sources to achieve compliance. This talk will address the alternative approach to the TMDL, and discuss the approaches to the proposed Bay-specific ambient water quality criteria and implementation procedures.
Key words: TMDL
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