This document proposes to establish Total Maximum Daily Loads (TMDLs) for nitrogen and phosphorus in Mattawoman Creek (basin number 02-14-01-11). Mattawoman Creek ultimately drains to the Chesapeake Bay, and is a part of the Lower Potomac Tributary Strategy Basin. The river is impaired by the nutrients nitrogen and phosphorus, which cause excessive algal blooms and low dissolved oxygen. Mattawoman Creek was identified first in 1996 as being impaired by nutrients due to signs of eutrophication (expressed as high chlorophyll a levels), suspended sediments, and in 2002 for evidence of impacts to biological communities. The suspended sediments and biological impairments will be addressed at a later date. Excess nutrients in an aquatic system act as a fertilizer - algal growth is promoted, the algae ultimately dies and decomposes, leading to bacterial consumption of dissolved oxygen. The water quality goal of these TMDLs is to reduce high chlorophyll a concentrations (a surrogate for algal blooms), and to maintain the dissolved oxygen criterion at a level whereby the designated uses for Mattawoman Creek will be met. The TMDLs for the nutrients nitrogen and phosphorus were determined using the WASP 5.1 water quality model. Loading caps for total nitrogen and total phosphorus entering Mattawoman Creek are established for low flow and average annual flow conditions.