In 1972, the National Pollutant Discharge Elimination System (NPDES) program was established under the authority of the Clean Water Act. 

Phase I of the NPDES stormwater program was established in 1990.  It required NPDES permit coverage for large or medium municipalities that had populations of 100,000 or more.  In North Carolina, there are six Phase I communities. 

The Phase II program extends permit coverage to smaller (< 100,000 pop.) communities and public entities that own or operate a municipal separate storm sewer system (MS4).

Biological Oxygen Demand is a measure of the amount of oxygen needed to help material degrade.

TMDL stands for Total Maximum Daily Load.  It's a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources.

Water quality standards are set by States, Territories, and Tribes. They identify the uses for each water body, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use.

A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and non-point sources. The calculation must include a margin of safety to ensure that the water body can be used for the purposes the State has designated. The calculation must also account for seasonal variation in water quality.

A TMDL provides a detailed water quality assessment that provides the scientific foundation for an implementation plan. An implementation plan outlines the steps necessary to reduce pollutant loads in a certain body of water to restore and maintain human uses or aquatic life. The development of TMDLs and implementation plans are often the best method to improve water quality.

The Clean Water Act, Under Section 303, establishes the water quality standards and TMDL programs.

Section 303(d) of the Clean Water Act (CWA) requires states to develop a list of waters not meeting water quality standards or which have impaired uses. Listed waters must be prioritized, and a management strategy or total maximum daily load (TMDL) must subsequently be developed for all listed waters.

Preparation of a basinwide water quality plan is a five-year process, which is broken down into three phases (Table A-2).   While these plans are prepared by the DWQ, their implementation and the protection of water quality entail the coordinated efforts of many agencies, local governments and stakeholder groups in the state.   The first cycle of plans was completed in 1998, but each plan is updated at five-year intervals.

At the present time, the water quality surrounding Oak Island is sufficiently poor quality that it is listed as part of the Section 303(d) category.  However, Oak Island does not have a requirement to perform TMDL monitoring at this time.  Regardless, the town is doing some voluntary testing of Davis Creek and other areas for preliminary assessment of water quality before island-wide sewer takes shape.  

Benthic macroinvertebrates, or benthos, are organisms that live in and on the bottom substrate of rivers and streams.  They are primarily insect larvae such as Mayflies Stoneflies, and Caddisflies.  They have proven to be a reliable tool for monitoring since they are very sensitive to subtle changes in water quality.  Since they have life cycles of 6-12 months, the effects of short-term pollution (e.g., spill) will generally not be overcome until the next generation develops.