A Total Maximum Daily Load (TMDL) is a regulatory term in the U.S. Clean Water Act, describing a value of the maximum amount of a pollutant that a body of water can receive while still meeting water quality standards. Alternatively, TMDL is an allocation of that water pollutant deemed acceptable to the subject receiving waters. TMDLs have been used extensively by the United States Environmental Protection Agency (EPA) and state environmental agencies in implementing the Clean Water Act by establishing maximum pollution limits for industrial wastewater dischargers. A 13.3 mile long segment of the Meduxnekeag River from above the confluence of the South Branch to the Maine/Canada border was studied by Maine DEP staff to evaluate current water quality and to assess the impact of existing and proposed licensed discharges upon water quality. The water quality model QUAL2E, version 3.22, was used in the evaluation. An empirical total phosphorous (TP) allocation model was developed for the point sources. Several summers of instream monitoring were made under varying conditions of TP treatment by the Houlton treatment plant.