15A NCAC 02B .0224. HIGH QUALITY WATERS

High Quality Waters (HQW) are a subset of waters with quality higher than the standards and are as described by 15A NCAC 2B .0101(e)(5).  The following procedures shall be implemented in order to implement the requirements of Rule .0201(d) of this Section.

(1)           New or expanded wastewater discharges in High Quality Waters shall comply with the following:

(a)           Discharges from new single family residences shall be prohibited.  Those existing subsurface systems for single family residences which fail and must discharge shall install a septic tank, dual or recirculating sand filters, disinfection and step aeration.

(b)           All new NPDES wastewater discharges (except single family residences) shall be required to provide the treatment described below:

(i)            Oxygen Consuming Wastes:  Effluent limitations shall be as follows: BOD₅= 5 mg/l, NH₃‑N = 2 mg/l and DO = 6 mg/l.  More stringent limitations shall be set, if necessary, to ensure that the cumulative pollutant discharge of oxygen‑consuming wastes shall not cause the DO of the receiving water to drop more than 0.5 mg/l below background levels, and in no case below the standard.  Where background information is not readily available, evaluations shall assume a percent saturation determined by staff to be generally applicable to that hydroenvironment.

(ii)           Total Suspended Solids:  Discharges of total suspended solids (TSS) shall be limited to effluent concentrations of 10 mg/l for trout waters and PNA's, and to 20 mg/l for all other High Quality Waters.

(iii)          Disinfection:  Alternative methods to chlorination shall be required for discharges to trout streams, except that single family residences may use chlorination if other options are not economically feasible.  Domestic discharges are prohibited to SA waters.

(iv)          Emergency Requirements:  Failsafe treatment designs shall be employed, including stand‑by power capability for entire treatment works, dual train design for all treatment components, or equivalent failsafe treatment designs.

(v)           Volume:  The total volume of treated wastewater for all discharges combined shall not exceed 50 percent of the total instream flow under 7Q10 conditions.

(vi)          Nutrients:  Where nutrient overenrichment is projected to be a concern, appropriate effluent limitations shall be set for phosphorus or nitrogen, or both.

(vii)         Toxic substances:  In cases where complex wastes (those containing or potentially containing toxicants) may be present in a discharge, a safety factor shall be applied to any chemical or whole effluent toxicity allocation.  The limit for a specific chemical constituent shall be allocated at one‑half of the normal standard at design conditions.  Whole effluent toxicity shall be allocated to protect for chronic toxicity at an effluent concentration equal to twice that which is acceptable under design conditions.  In all instances there may be no acute toxicity in an effluent concentration of 90 percent.  Ammonia toxicity shall be evaluated according to EPA guidelines promulgated in "Ambient Water Quality Criteria for Ammonia ‑ 1984"; EPA document number 440/5‑85‑001; NITS number PB85‑227114; July 29, 1985 (50 FR 30784) or "Ambient Water Quality Criteria for Ammonia (Saltwater) ‑ 1989"; EPA document number 440/5‑88‑004; NTIS number PB89‑169825.  This material related to ammonia toxicity is hereby incorporated by reference including any subsequent amendments and editions and is available for inspection at the Department of Environment and Natural Resources Library, 512 North Salisbury Street, Raleigh, North Carolina.  Copies may be obtained from the National Technical Information Service, 5285 Port Royal Road, Springfield, Virginia 22161 at a cost of forty‑seven dollars ($47.00).

(c)           All expanded NPDES wastewater discharges in High Quality Waters shall be required to provide the treatment described in Sub-Item (1)(b) of this Rule, except for those existing discharges which expand with no increase in permitted pollutant loading.

(2)           Development activities which require an Erosion and Sedimentation Control Plan in accordance with rules established by the NC Sedimentation Control Commission or local erosion and sedimentation control program approved in accordance with 15A NCAC 4B .0218, and which drain to and are within one mile of High Quality Waters (HQW) shall be required to follow the stormwater management rules as specified in 15A NCAC 2H .1000.  Stormwater management requirements specific to HQW are described in 15A NCAC 2H .1006.

(3)           Listing of Waters Classified HQW with Specific Actions.  Waters classified as HQW with specific actions to protect exceptional water quality are listed as follows:  Thorpe Reservoir [Little Tennessee River Basin, Index No. 2-79-23-(1)] including all of its tributaries shall be managed with respect to wastewater discharges through Item (1) of this Rule.  Item (2) of this Rule shall not be applied in association with this HQW because of the local government implementation of WS-III stormwater management requirements.

If an applicant objects to the requirements to protect high quality waters and believes degradation is necessary to accommodate important social and economic development, the applicant may contest these requirements according to the provisions of G.S. 143‑215.1(e) and 150B‑23.

 

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

Eff. October 1, 1995;

Amended Eff. August 1, 1998; April 1, 1996.