N.J. Admin. Code § 7:14A-23.6

Current through Register Vol. 56, No. 21, November 4, 2024

Section 7:14A-23.6 - Sanitary sewer design

(a) Proposed sewerage systems shall connect into downstream sewer lines and pump stations that have adequate conveyance capacity.

(b) Gravity sanitary sewers, including outfalls, shall be designed to carry at least twice the estimated average projected flow when flowing half full. In the case of large interceptor sewer systems, consideration may be given to modified designs. In addition, sanitary sewer conveyance systems shall meet the following requirements:

1. Materials used in sewer construction shall be acceptable to the Department for the purposes and conditions they are intended to serve;

2. Sewers shall be designed with the following minimum hydraulic slopes (grades producing velocities of greater than 10 feet per second are not recommended unless supported by adequate justification acceptable to the Department):

PVC Pipe (Polyvinylchloride)
Pipe diameter (based on Kutter's or Manning's formula with n =	Fall in feet
0.01)	per 100 feet
of sewer
8 inches	0.30
10 inches	0.20
12 inches	0.15
14 inches	0.12
15 inches	0.10
16 inches	0.09
18 inches	0.075
20 inches	0.065
21 inches	0.06
24 inches	0.05
27 inches	0.042
30 inches	0.035
36 inches	0.028

All Other Pipe Material (based on Kutter's or Manning's formula with n =
0.013)
Pipe Diameter	Fall in feet
per 100 feet
of sewer
8 inches	0.40
10 inches	0.29
12 inches	0.22
14 inches	0.17
15 inches	0.16
16 inches	0.14
18 inches	0.12
20 inches	0.10
21 inches	0.095
24 inches	0.080
27 inches	0.067
30 inches	0.058
36 inches	0.046

i. When grades or sizes less than those specified in this paragraph are proposed, justification for the use of such grades shall be provided with the treatment works approval application.

ii. The minimum diameter of sewer extensions shall be eight inches, however, consideration will be given to the use of smaller diameter sewers for lateral connections;

3. Sewers crossing streams and/or located within 10 feet of the stream embankment, or where site conditions so indicate, shall be constructed of steel, reinforced concrete, ductile iron or other suitable material;

4. Sewers conveying sanitary flow, combined sanitary and stormwater flow, or industrial flow shall be separated from water mains by a distance of at least 10 feet horizontally. If such lateral separation is not possible, the pipes shall be in separate trenches with the sewer at least 18 inches below the bottom of the water main, or such other separation as approved by the Department;

i. Where appropriate separation from a water main is not possible, the sewer shall be encased in concrete, or constructed of ductile iron pipe using mechanical or slip-on joints for a distance of at least 10 feet on either side of the crossing. In addition, one full length of sewer pipe should be located so both joints will be as far from the water line as possible. Where a water main crosses under a sewer, adequate structural support for the sewer shall be provided. The Department may also require additional structural support for storm sewers crossing over sewer lines;

5. Any sewer within 100 feet of a water supply well or a below-grade reservoir shall be constructed of steel, reinforced concrete, ductile iron or other suitable material, shall be completely watertight and shall be tested for watertightness after installation;

6. The construction of sewer lines through storm sewer pipes or manholes will not be approved;

7. Sewer lines, including force mains and laterals, shall be constructed at least three feet below the proposed grade (as measured from the top of the pipe to the grade elevation);

8. Sewer pipes, including force mains and laterals, shall be sized to adequately convey the projected contributory flow in accordance with this subchapter. In general, sewer lines that are larger than hydraulically necessary to carry the projected flow and for which the larger size is proposed only for the purpose of achieving the minimum slope requirements specified in this section are not permitted;

9. Sewer lines shall not be approved for the use of storage or detention of sewage unless they are designed as an integral part of an existing combined sewerage system (sanitary/storm) where in-line storage is being proposed as a corrective measure to prevent the discharge of untreated wastewater from the treatment works;

10. New sewerage systems or extensions shall be designed as separate systems, in which all water from roofs, cellars, streets and other areas is excluded; except that separate connections to an existing combined system may be approved when it is demonstrated to the satisfaction of the Department that no other alternative is feasible. In addition, the Department may permit, on a case-by-case basis, the introduction of contaminated stormwater from containment areas into sanitary sewers;

11. To minimize the development of septic conditions, the Department may require special operational and/or maintenance procedures for treatment works if the initial contributory flows to the treatment works will be substantially below the design capacity; and

12. When a smaller sewer joins a larger one, the invert of the larger sewer should be lowered sufficiently, or the smaller pipe raised sufficiently, to maintain the same energy gradient. An approximate method for securing these results is to place the 0.8 depth point of both sewers at the same elevation.

(c) For sewers other than circular in cross section, the submitted data shall include the geometrical shape, dimensions and hydraulic characteristics of the proposed sewer.

(d) Approval for curved sewers will be considered by the Department only under the following circumstances:

1. Areas where curved streets comprise the general layout, or the use of curved sewers would permit substantial savings in cost to avoid deep cuts due to rocks or obstructions;

2. The minimum diameter of the sewer is eight inches and the minimum radius of curvature is 100 feet; and

3. Manhole spacing does not exceed 300 feet.

(e) All sanitary sewers, manholes, and cleanouts shall be tested by an infiltration, exfiltration or pressure test after being flushed and before being placed into use. The maximum rate of infiltration/exfiltration shall not exceed 100 gallons per inch diameter per mile per day.

N.J. Admin. Code § 7:14A-23.6

Amended by R.1997 d.107, effective 5/5/1997.
See: 28 New Jersey Register 380(a), 28 New Jersey Register 2779(a), 28 New Jersey Register 3494(a), 28 New Jersey Register 3858(a), 28 New Jersey Register 4697(a), 28 New Jersey Register 5028(a), 29 New Jersey Register 1704(a).
In (b)3, substituted "and/or located" for "and located".