New Jersey Administrative Code › Title 7 - ENVIRONMENTAL PROTECTION › Chapter 14A - NEW JERSEY POLLUTANT DISCHARGE ELIMINATION SYSTEM › Subchapter 23 - TECHNICAL REQUIREMENTS FOR TREATMENT WORKS APPROVAL APPLICATIONS › Section 7:14A-23.6 - Sanitary sewer design

Current through Register Vol. 56, No. 14, July 15, 2024
(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.