The U.S. Environmental Protection Agency (EPA) has established a plan to reduce harmful levels of nutrients in the Appoquinimink River and its tributaries in New Castle County, Delaware.
The plan establishes "pollution budgets," known as Total Maximum Daily Loads (TMDLs), that set the maximum amount of a specific pollutants that can be introduced into the river and its tributaries.
"This plan is a critical milestone in reducing nutrient impairments and restoring the environmental health of the Appoquinimink River and its tributaries," said Donald S. Welsh, EPA's mid-Atlantic regional administrator.
High nutrient levels in waterways are generally attributed to several sources that include stormwater runoff from farms and fertilized lawns, and discharges from municipal and industrial treatment facilities. All plants and animals need small amounts of nutrients, such as nitrigen and phosphorus, to grow and reproduce. However, an excess of nutrients can lead to eutrophication, a condition in which prolonged blooms of algae rob light and oxygen from other organisms.
When a water body does not meet its water quality standards for a particular pollutant, the federal Clean Water Act requires the state to include the water body on its list of impaired waters. Delaware has listed sections of the Appoquinimink and its tributaries as impaired due to high nutrient concentrations and/or low dissolved oxygen levels.
Once the water body is impaired, a TMDL must be developed to set the maximum amount of a specific pollutants that an estuary, lake or river can receive. After that load amount is calculated, all sources of that pollutant in the watershed are required to reduce their contributions of the contaminant to specified levels.
EPA has established TMDLs for the Appoquinimink River basin to address those stream segments impaired as a result of excess nutrients and low dissolved oxygen. To address nutrient impairments, TMDLs have been established for total nitrogen and total phosphorus in order to attain and maintain applicable water quality standards.
The Appoquinimink River watershed drains approximately 47 square miles in New Castle County. It is primarily an agricultural area, but also includes urban areas of Middletown, Odessa, and Townsend. The Appoquinimink River system consists of three main tributaries, the Appoquinimink River main stem, Deep Creek, and Drawyer Creek. There are several shallow, man-made small lakes and ponds in the watershed (Wiggins Mill Pond, Noxontown Lake, Silver Lake, and Shallcross Lake).
More background information and a copy of the TMDL are available on the EPA website at www.epa.gov/reg3wapd/tmdl/de_tmdl/index.htm#appo .