North Carolina Administrative Code › Title 15A - Environmental Quality › Chapter 18 - ENVIRONMENTAL HEALTH › Subchapter A - SANITATION › Section .1900 - SEWAGE TREATMENT AND DISPOSAL SYSTEMS › Section 18A .1970 - ADVANCED WASTEWATER PRETREATMENT SYSTEM

Current through Register Vol. 39, No. 2, July 15, 2024
(a) ADVANCED
				  PRE-TREATMENT SYSTEM PERFORMANCE STANDARDS: A wastewater system with a design
				  flow of up to 3000 gallons per day approved pursuant to
				  15A NCAC
				  18A .1957(c) or
				  18A .1969 that includes an
				  advanced pretreatment component shall be designed to meet one of the effluent
				  quality standards specified in Table VII prior to dispersal of the effluent to
				  the soil and shall comply with the requirements of this Rule.
Table VII (Effluent Quality Standards for Advanced
					 Pretreatment Systems)
Parameter
NSF-40
TS-I
TS-II
Carbonaceous Biochemical Oxygen Demand
								(CBOD)
25 (mg/l)*
15 (mg/l)
10 (mg/l)
Total Suspended Solids (TSS)
30 (mg/l)
15 (mg/l)
10 (mg/l)
Total Ammonia Nitrogen (NH3)
10 (mg/1), or at least 80% removal of NH3 if
								influent TKN exceeds 50 mg/l
10 (mg/l)
Total Nitrogen (TN) (TN is Total Kjeldahl Nitrogen
								plus Nitrate+Nitrite Nitrogen)
20 mg/l or 60% removal
Fecal Coliform
10,000 (colonies/100 ml)
1,000 (colonies/100 ml)
*mg/l is milligrams per liter
System performance monitoring, site and system compliance
					 criteria pursuant to these standards are delineated in Paragraphs (n) and (o)
					 of this Rule. These standards or modifications to these standards may be
					 proposed to be complied with by the designer of systems with a design flow of
					 over 3000 gallons per day or Industrial Process Wastewater Systems and approved
					 by the State pursuant to Rules .1938(e) or .1938(f) of this Section,
					 respectively, when documentation is provided that the performance criteria of
					 Rule .1946 of this Section and
					 15A NCAC
					 02L will be met.
(b) Design influent quality shall not exceed
				  the criteria specified in Table VIII, unless the system is designed and
				  approved by the State to handle higher strength wastewater on a product or
				  project-specific basis.
Table VIII (Influent Quality Standards for Advanced
					 Pretreatment Systems)
Parameter
Influent Not to Exceed (mg/l)*
Biochemical Oxygen Demand (BOD)
350
Total Suspended Solids (TSS)
200
Total Kjeldahl Nitrogen (TKN)
100
Fats, Grease and Oil (FOG)
30
*mg/l is milligrams per liter
Maximum influent characteristics in Table VIII are based
					 upon septic tank pretreatment. The product's RWTS, Experimental, Controlled
					 Demonstration, Innovative or Accepted System approval, as applicable, may
					 include alternate or additional influent limitations, such as for systems
					 designed to handle untreated wastewater and special limitations for TS-I and
					 TS-II systems to achieve the proper amount of nitrification.
(c) The site shall be initially evaluated and
				  classified in accordance with the rules of this Section or as otherwise
				  specified in a system-specific approval issued pursuant to
				  15A NCAC
				  18A .1969. A ground absorption system
				  receiving effluent from an advanced wastewater pretreatment system may be used
				  on sites classified as SUITABLE or PROVISIONALLY SUITABLE for conventional,
				  modified, alternative, or E & I or accepted systems in accordance with this
				  Section. Modifications to siting and system design criteria pursuant to
				  Paragraphs (d), (e), (f), (g), (h), (i), and (j) of this Rule shall be
				  acceptable, as applicable.
(d)
				  NSF-40 SYSTEMS SITING AND SIZING REQUIREMENTS: For systems approved to achieve
				  at least NSF-40 standards and designed for no more than 1500 gallons per day,
				  the following siting and sizing factors apply when designing the soil
				  absorption system:
(1) Trench or bed bottom
				  separation distances are as specified in this Subparagraph. In Table IX, "SWC"
				  means "Soil Wetness Condition," and "USC" means an "UNSUITABLE Soil/Fill
				  Condition," other than a SWC.
Table IX: Vertical Separation Requirements for
								NSF-40 Systems (LESS THAN equal to) 1500 gallons per day
Soil/System Criteria
Rule* Reference
Depth from Surface** to UNSUITABLE Soil/Fill
								Condition
Minimum Vertical Trench/Bed Bottom Separation
								Requirement
Gravity Distribution
Pressure Dispersal
Gravity Distribution
Pressure Dispersal
Depth to USC
Depth to SWC
Depth to USC
Depth to SWC
Soil Group I
Rules .1955, .1956, and
.1957(a)
24- inches
24-inches
12-inches
12-inches
12-inches
12-inches
Soil Groups II-IV
Rules .1955, .1956, and
.1957(a)
24-inches
24-inches
12-inches
12-inches
12-inches
12-inches
New Fill
Rule .1957(b)(1)
18-inches to USC, and 12-inches to SWC
18-inches to USC, and 12-inches to SWC
18-inches
18-inches
18-inches
12-inches
Existing Fill (£480 gpd only)
Rule .1957(b)(2)
36-inches of Group I Fill/Soils
24-inches of Group I Fill/Soils
36-inches
36-inches
18-inches
18-inches
*Except as allowed in this Rule, all other requirements of
					 the Rules referenced remain applicable
**Minimum depth of soil/fill required at site to permit
					 system. Depth shall be measured from the naturally occurring soil surface or
					 Existing Fill surface, as applicable
(2) The total drainfield trench length or bed
				  system bottom area, as required for a ground absorption system receiving septic
				  tank effluent, is reduced by 25 percent in soils which are Groups I or II with
				  SUITABLE structure and clay mineralogy. No other reductions in linear footage
				  of nitrification trench, square footage of trench bottom area or system area
				  shall be applied when a PPBPS or innovative trenches or accepted systems are
				  used for the absorption field, except where based on an adjusted design daily
				  flow rate granted in accordance with
				  15A NCAC
				  18A .1949(c). Bed systems
				  remain restricted to a design flow of 600 gallons per day or less;
				  and
(3) The minimum horizontal
				  setback requirements of
				  15A NCAC
				  18A .1950,
				  18A .1951 and
				  18A .1956(6)(g), as applicable,
				  shall be met, except as follows:
Table X
Minimum horizontal setbacks for ground absorption
								systems
Where NSF-40 Pretreatment System are used for (LESS
								THAN equal to) 1500 gallons per day
Land Feature or Component
NSF-40 (feet)
Streams classified as WS-1, except for
								saprolite
70
Waters classified as S.A., from mean high water
								mark
70
Other coastal waters from mean high water
								mark
35
Any other stream, canal, marsh or other surface
								waters, from normal pool elevation
35
Any Class I or Class II reservoir from normal pool
								elevation
70
Any permanent storm water retention pond from flood
								pool elevation
35
Any other lake or pond from normal pool or mean
								high water elevation
35
The Provisions of Subparagraphs (1), (2) and (3) of this
					 Paragraph are also applicable to systems approved as meeting TS-I or TS-II
					 standards pursuant to
					 15A NCAC
					 18A .1969, unless otherwise restricted
					 elsewhere in this Rule.