TMDL Alternative - 4b Plan

Impaired waters with enforceable pollution control programs in place that are expected to solve pollution problems (i.e., meet water quality standards) are commonly referred to as “Category 4b” waters because they are moved from Category 5 (303(d) list - impaired and needs TMDL) of the State’s Integrated Report to Category 4b (impaired but TMDL not required). While 4b Plans are not TMDLs, they must have many of the same features, and there must be some legal or financial assurance that they will be implemented.

A 4b Plan allows DWR and EPA to formally recognize actions that, from a local perspective, provide a more appropriate and effective response to impairment than TMDL development. DWR has developed guidance (North Carolina’s Division of Water Resources Category 4b Demonstration Guidance) for communities interested in developing a plan to address impaired waters. The guidance describes the elements required to qualify for Category 4b. EPA has also provided guidance in RECOMMENDED STRUCTURE FOR CATEGORY 4B DEMONSTRATIONS.

In short, the following six elements are required for 4b Plans: 1. Identification of segment and statement of problem causing the impairment; 2. Description of pollution controls and how they will achieve water quality standards; 3. An estimate or projection of the time when WQS will be met; 4. Schedule for implementing pollution controls; 5. Monitoring plan to track effectiveness of pollution controls; and  6. Commitment to revise pollution controls, as necessary.

  
Communities interested in pursuing this option should review the guidance document and plan to meet with DWR’s Modeling and Assessment Branch prior to development. Some communities may find that they are already meeting most if not all of the required elements.

Once developed, North Carolina will periodically evaluate 4b Plans to determine if the plan continues to be implemented as described and continues to meet the requirements to be considered a 4b Plan. This review will take place every two years during development of the biannual Integrated Report.
 

View approved TMDL alternatives