These TMDLs address the nutrient, dissolved oxygen and biological oxygen demand impairments in the North Fork St. Lucie River (3194) and C-24 Canal (3218); dissolved oxygen and biological oxygen demand impairments in the C-44 Canal (3218); nutrient and dissolved oxygen impairments in the North St. Lucie Estuary (3194B), C-23 Canal (3200), South Fork St. Lucie River (3210A), Bessey Creek (3211); the nutrient impairments in the St. Lucie River Lower Estuary (3193) and the South St. Lucie Estuary (3210). Impairments in these waters were verified using the methodology established in Chapter 62-303, F.A.C., Identification of Impaired Surface Waters. The WAterSHed (WASH) Model was used to simulate flows from the drainage basins and in stream nutrient values were obtained from measured five- to ten-year annual averages. Percent reductions were specified for the St. Lucie River Lower and Middle Estuary (3193) at Roosevelt Bridge. Loads to the estuary were calculated by multiplying annual average flows by annual average concentrations for the contributing impaired water segments. The final nutrient concentration targets of these waters were established based on a weight of evidence approach which considered targets for the Indian River Lagoon developed to be protective of seagrasses, statewide nutrient concentrations in estuaries, and correlations between nutrients and healthy seagrass beds.