Total Maximum Daily Loads of Nitrogen and Phosphorus and Biochemical Oxygen Demand for Breton Bay in St. Mary's County, Maryland. Final Report.

摘要

This document proposes to establish Total Maximum Daily Loads (TMDLs) for nitrogen, phosphorus and biochemical oxygen demand (BOD) in Breton Bay (basin number 02-14-01-04). Breton Bay ultimately drains to the Chesapeake Bay, and is a part of the Lower Potomac Tributary Strategy Basin. Breton Bay is impaired by nutrients (nitrogen, phosphorus) and BOD, causing occasional algal blooms and low dissolved oxygen. Breton Bay was first identified in 1996 as impaired by nutrients due to signs of eutrophication (expressed as high chlorophyll a levels), suspended sediments, and evidence of impacts to biological communities. The suspended sediments and biological impairments will be addressed at a later date. The water quality goal of these TMDLs is to reduce high chlorophyll a concentrations, and to maintain the dissolved oxygen criterion at a level whereby the designated uses for Breton Bay will be met. The TMDLs were determined using the Water Quality Analysis Simulation Program version 5.1 (WASP 5.1) water quality model. Loading caps for total nitrogen, total phosphorus and BOD entering Breton Bay are established for low flow and average annual flow conditions.