N.J. Admin. Code Tit. 7, ch. 50, subch. 6, app A

PINELANDS SEPTIC DILUTION MODEL

December 1993

The water quality standards of the Pinelands Comprehensive Management Plan allow the use of individual on-site septic systems provided that the design of the system and the size of the parcel on which the system is located will ensure that the concentration of nitrate-nitrogen in the groundwater exiting the parcel or entering a surface water body will not exceed 2 ppm (N.J.A.C. 7:50-6.84(a)4 iii). The model used to calculate the minimum land area necessary to dilute nitrogen from septic systems to concentrations that will comply with the water quality standards was developed by K.W. Brown (An Assessment of the Impact of Septic Leach Fields, Home Lawn Fertilization and Agricultural Activities on Groundwater Quality, 1980). The following formula is used: Data in image

Where:	At	=	total parcel area
Af	=	area of disposal field
F	=	unit conversion factor of 10
Lf	=	flux of nitrate-nitrogen below disposal field
(kg/ha/yr)
C	=	concentration of nitrate-nitrogen (ppm)
Df	=	equivalent depth of percolate below disposal field
(cm/yr)
Do	=	equivalent depth of percolate below open acres
(cm/yr)

In using this model, it is necessary to assume values for factors such as wastewater flow into the system, the concentration of nitrogen in the wastewater and the amount of rainfall diluting the nitrogen. The standard assumptions required for use in the Pinelands Dilution Model are contained in Table 1.

The assumed wastewater flow for non-residential uses must be consistent with the values contained in N.J.A.C. 7:9A-7.4, as amended, except that the number of employees may not be utilized in calculating wastewater flow for office uses. Absent actual monitoring of nitrogen concentration in the wastewater, the residential nitrogen concentration of 39.45 ppm will be utilized. If the applicant establishes wastewater flow based on monitoring of flows pursuant to N.J.A.C. 7:9A-7.4, then water quality monitoring must also be done to establish actual nitrogen concentration in the wastewater. All structures are assumed to contribute to the generation of wastewater unless it is demonstrated that the nature of the building construction precludes human occupancy.

TABLE 1

Parameter	Assumption
1.	Number of persons/dwelling	3.5
2.	Number of persons/age restricted dwelling	2.0
3.	Residential wastewater flow (gallons/capita/day)	75
4.	Plant uptake of nitrogen	4.5% (A soils)
9.0% (B soils)
5.	Infiltrating rainfall	20 inches/year
(50.8 cm/year)
6.	Nitrogen production (grams/capita/day)	11.2 gms
7.	Distribution of nitrogen in wastewater	83% blackwater
17% greywater
8.	Nitrogen concentration in wastewater for	39.45 ppm
residential uses

Notes

N.J. Admin. Code Tit. 7, ch. 50, subch. 6, app A

Amended by R.1994 d.590, effective 12/5/1994.
See: 26 New Jersey Register 165(a), 26 New Jersey Register 4795(a).
Administrative Correction.
See: 27 New Jersey Register 2212(c).