Nutrient Practices and Crediting


A variety of practices to reduce nutrient loading to surface waters are approved by the Division. These nutrient reduction practices, which include design criteria and credit calculation methods, are available for use toward compliance with requirements of new or existing development stormwater rules, as well as for generating nutrient reduction credits for trading or offset. They supplement the growing set of stormwater control measures (SCMs) approved by the Division of Energy, Mineral and Land Resources for new development post-construction runoff treatment. Developers can also buy nutrient offset credits from the NC Division of Mitigation Services (DMS) or from private providers approved by the Division of Water Resources (DWR) to meet some of their nutrient reduction requirements.

On this webpage, you can find information regarding the following:

Stormwater Nutrient Accounting Tools

SNAP (Stormwater Nitrogen and Phosphorus) v4.1 is a project-scale tool for modeling nitrogen and phosphorus in stormwater runoff from development sites and nutrient reductions provided by stormwater treatment.  As of October 2018, it is the approved tool for regulatory compliance with stormwater requirements of the Falls and Jordan nutrient strategies, and for alternative riparian buffer mitigation compliance in all watersheds with buffer regulations.  It replaces the Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool version 2.0.  It may also be used across the state for non-regulatory-compliance purposes such as planning, modeling, grant applications, etc.  Most of the Stormwater Control Measures that follow DEMLR’s Minimum Design Criteria, as well as custom SCMs, can be modeled with this tool.

Local programs implementing Falls and Jordan nutrient strategies will need to require use of SNAP v4.1 on all development projects subject to the rules’ nutrient export calculation requirements beginning April 15, 2019.  Local governments are not obliged to accept its use by applicants prior to that date, but may choose an earlier date for mandatory use. Applicable Rules include the Falls Lake nutrient strategy rules for New Development (15A NCAC 02B .0277) and Existing Development (.0278), and in both the Falls and Jordan Lake watersheds for State and Federal Entities (.0281 and .0271) not including NCDOT.  

If you have questions about using SNAP you can post them to the SNAP Users Listserv, or send your questions directly to Trish D’Arconte ( ). To subscribe to the listserv, send an email to with only the word “subscribe” in the subject or body of the email. Make sure to check your Junk Mail box for the subscription confirmation email.

Rules concerning new development in the Neuse and Tar-Pamlico watersheds continue to require the use of older methods. Developments in the Tar-Pamlico watershed should calculate nutrient export and treatment with the Tar-Pamlico Piedmont and Coastal Plain Export Calculation Worksheets .

Developments in the Neuse watershed outside of the Falls Lake watershed should continue to use the calculation method laid out in the Neuse Model Program .

DMS and other providers have received approval from DWR to use the SNAP Tool for generating buffer mitigation credits in accordance with 15A NCAC 02B .0295(o)(9),  as noted in the above approval memo.

Approved Nutrient Reduction Practices

For new development, the Stormwater Permitting Unit (SPU) of the Division of Energy, Mineral and Land Resources (DEMLR) has authority for establishing and revising the set of acceptable SCMs for post-construction stormwater control. SPU partners with the NPS Planning Branch of DWR and stormwater researchers to set and revise nutrient credit assignments for these practices. The currently approved set of new development SCMs, including their nutrient crediting specifications, is captured in DEMLR’s SCM Crediting Document.

For development occurring under Neuse and Tar-Pamlico stormwater rules, in January 2019 DWR authorized the use of an expanded set of SCMs described in Table A-3 of the SCM Crediting Document for rule compliance. The Division’s January 2019 memorandum explains that this interim expansion will be replaced by the full set of practices available in the SNAP tool once readopted Neuse and Tar-Pamlico stormwater rules go into effect.

Nutrient credits may be generated to meet Existing Development Stormwater rule requirements through either retrofitting of existing developed lands using the SCMs and accounting described above or implementation of other approved nutrient reduction practices. Below are documents describing design specifications and nutrient accounting for other types of nutrient reduction practices that are approved by the Division.  (2018 Confidence Evaluation Matrix)

About Nutrient Offsets and Trading

Nutrient offset is a form of trading allowed by the Division of Water Resources under each set of rules governing the four Nutrient Management Strategy watersheds in NC. Other forms of trading are also allowed as provided for within the different strategies’ rules. Effective September 2010, 15A NCAC 02B .0240 addresses procedural requirements for nutrient offsets, including geographic scope, project standards, payment conditions, and other issues.

Developers, wastewater treatment facilities, and others can often meet a portion of their nutrient reduction requirements by purchasing nutrient offset credits. These credits are generated by riparian restoration/enhancement projects constructed elsewhere within the watershed, either by private mitigation providers  or the NC Division of Mitigation Services (DMS). 

The predominant nutrient reduction practice used by those seeking to generate nutrient reduction credits for sale is the restoration and enhancement of riparian forested buffers on agricultural lands. The Division allows the use of forested buffer restoration and enhancement as described in 15A NCAC 02B .0295(n)(2-4) to award a nutrient reduction benefit of 75.7 lbs/yr nitrogen and 4.88 lbs/yr phosphorus. Such projects must meet design criteria.

Other practices are also eligible to generate nutrient reduction credit for sale (e.g., stormwater control measures), but to date, these have not been as cost-effective as buffer restoration.

Developers seeking nutrient offset credits should first consult with their local government permitting authority for routine inquiries. Requests for nutrient offset credits require the submission of a form approved by the local government. Users of the SNAP Tool can generate a generic nutrient offset request form within SNAP. Developers in the Neuse (outside Falls) and Tar-Pamlico watersheds have a different form to use .

For additional questions regarding this topic, please contact DEQ representatives as directed below.


March 2019 Local Government SNAP Training Resources

Materials and presentations for the March 2019 training for local government staff:



For questions regarding nutrient offset credit purchases, please contact your local government permitting representative. Additional inquiries regarding nutrient offset or trading may be directed to: Jim Hawhee, Environmental Program Consultant, 919-707-3675 or

For questions regarding nutrient accounting tools and reduction practices, please contact: Trish D’Arconte, Environmental Program Consultant, 919-707-3678 or

For questions regarding private nutrient mitigation providers please contact: Katie Merritt, Nutrient Offset Banking Coordinator, 919-707-3637 or .

For questions about nutrient credit purchases from the NC Division of Mitigation Service's In-lieu Fee Program, please contact: Kelly Williams, NCDMS In-Lieu Fee Program Coordinator, 919-707-8915 or