15A NCAC 02B .0733 TAR-PAMLICO Nutrient Strategy: New and expanding wastewAter discharger requirements

The following is the management strategy for new and expanding wastewater dischargers in the Tar-Pamlico River basin:

(1) Purpose. The purpose of this Rule is to establish minimum nutrient control requirements for new and expanding point source discharges in the Tar-Pamlico River Basin in order to maintain or restore water quality in the Pamlico Estuary and protect its designated uses.

(2) Applicability. This Rule applies to all discharges from wastewater treatment facilities in the Tar-Pamlico River Basin that receive nitrogen- or phosphorus-bearing wastewater and are required to obtain individual NPDES permits. This Rule applies to Tar-Pamlico Basin Association member facilities on or after June 1, 2025. This Rule applies to other facilities upon this Rule's effective date.

(3) Definitions. The terms used in this Rule, in regard to point source dischargers, treatment facilities, wastewater flows or discharges, or like matters, shall be as defined in Rule .0701 of this Section and as follows:

(a) "Existing" means that which obtained an NPDES permit on or before December 8, 1994.

(b) "Expanding" means that which increases beyond its permitted flow as defined in Item (4) of this Rule.

(4) "Permitted flow" means the maximum monthly average flow authorized in a facility's NPDES permit as of December 8, 1994.

(5) This Item specifies nutrient controls for new facilities.

(a) Proposed new wastewater dischargers shall evaluate all practical alternatives to surface water discharge pursuant to 15A NCAC 02H .0105(c)(2) prior to submitting an application to discharge.

(b) The technology-based nitrogen and phosphorus discharge limits for a new facility shall not exceed:

(i) For facilities treating municipal or domestic wastewater, the mass load equivalent to a concentration of 3.5 mg/L TN and 0.5 mg/L TP at the monthly average flow limit in the facility's NPDES permit; and

(ii) For facilities treating industrial wastewater, the mass load equivalent to the best available technology economically achievable, calculated at the monthly average flow limit in the facility's NPDES permit.

(c) Proposed new dischargers submitting an application shall acquire nutrient allocation from existing dischargers or nutrient offset credits pursuant to Rule .0703 of this Section for the mass load dictated by this Item. The allocation and offset credits shall be sufficient for any partial calendar year in which the permit becomes effective plus 10 subsequent years of discharge at the proposed design flow rate in accordance with 15A NCAC 02H .0112(c).

(d) The Director shall not issue a permit authorizing discharge from a new facility unless the applicant has satisfied the requirements of Sub-Items (a), (c), and (e) of this Item. If a facility's permit contains tiered flow limits for expansion, the Director shall not authorize an increased discharge unless the applicant has satisfied the requirements of Sub-Items (a), (c), and (e) of this Item.

(e) Subsequent applications for permit renewal shall demonstrate that the facility has sufficient nitrogen allocation or offset credits to meet its effluent nutrient limitations for any partial calendar year in which the permit becomes effective plus 10 subsequent years of discharge at the proposed design flow rate in accordance with 15A NCAC 02H .0112(c).

(f) The Director shall establish more stringent limits for nitrogen or phosphorus upon finding that such limits are necessary to protect water quality standards in localized areas.

(6) This Item specifies nutrient controls for expanding facilities.

(a) Expanding facilities shall evaluate all practical alternatives to surface water discharge pursuant to 15A NCAC 02H .0105(c)(2) prior to submitting an application to discharge.

(b) The nitrogen and phosphorus discharge limits for an expanding facility shall not exceed the greater of loads equivalent to its active allocation and offset credit, or the following technology-based mass limits:

(i) For facilities treating municipal or domestic wastewater, the mass equivalent to a concentration of 3.5 mg/L TN and 0.5 mg/L TP at the monthly average flow limit in the NPDES permit; and

(c) Facilities submitting application for increased discharge or, where an existing permit contains tiered flow limits, for authorization to discharge at an increased flow, shall acquire or demonstrate contractual agreement to acquire, prior to authorization to discharge at the increased flow, nutrient allocation from existing dischargers or nutrient offset credits pursuant to Rule .0703 of this Section for the proposed discharge above 0.5 million gallons per day (MGD). The allocation and offset credits shall be sufficient to meet its effluent nutrient limitations for any partial calendar year in which the permit becomes effective plus 10 subsequent years of discharge at the proposed design flow rate in accordance with 15A NCAC 02H .0112(c).

(d) The Director shall not issue a permit authorizing increased discharge from an existing facility unless the applicant has satisfied the requirements of Sub-Items (a), (c), and (e) of this Item. If a facility's permit contains tiered flow limits for expansion, the Director shall not authorize discharge at an increased flow unless the applicant has satisfied the requirements of Sub-Items (a), (c), and (e) of this Item.

(f) The Director shall modify an expanding facility's permit to establish more stringent limits for nitrogen or phosphorus upon finding that such limits are necessary to protect water quality standards in localized areas.

(g) Existing wastewater dischargers expanding to greater than 0.5 MGD design capacity may petition the Director for an exemption from Sub-Items (a) through (c) and (e) of this Item upon meeting and maintaining all of the following conditions:

(i) The facility has reduced its annual average TN and TP loading by 30 percent from its annual average 1991 TN and TP loading. Industrial facilities may alternatively demonstrate that nitrogen and phosphorus are not part of the waste stream above background levels.

(ii) The expansion does not result in annual average TN or TP loading greater than 70 percent of the 1991 annual average TN or TP load. Permit limits shall be established to ensure that the 70 percent load is not exceeded.

History Note: Authority G.S. 143‑214.1; 143-215.1; 143-215.3(a)(1); 143-215.8B; 143B-282;

Eff. April 1, 1997;

Recodified from 15A NCAC 02B .0229 Eff. April 1, 2020;

Readopted Eff. April 1, 2020.