N.J. Admin. Code § 19:5-7.8

Current through Register Vol. 56, No. 12, June 17, 2024

Section 19:5-7.8 - Drainage

(a) Each subdivision submitted shall be reviewed by the NJMC to ensure the adequacy of all drainage provisions proposed within said subdivision and that potential adverse drainage conditions on all adjoining property resulting from such development have been addressed appropriately.

(b) Drainage systems shall be designed in accordance with 19:4-8.6.

(c) In addition to the requirements of 19:4-8.6, the following shall apply to drainage systems in proposed ROWs and subdivision drainage easements:

1. All pipeline and open channel drainage systems shall be designed to convey the maximum discharge commensurate with design.

2. Pipes shall be considered "flowing full" at maximum capacity.

3. Minimum design velocity of "flowing full" condition for drainage piping shall be two feet per second, or as otherwise approved on a case-by-case basis by the NJMC.

4. For drainage systems utilizing pipes that are 48-inch pipelines and larger, vertical and horizontal deflections may utilize 100-foot, or greater, radius curves.

5. The spacing between inlets shall not exceed 400 feet or a design inlet flow of six cubic feet per second; whichever condition shall be more stringent. Access manholes shall be spaced at a maximum of 400 feet intervals through ROWs and at pipe junctions where there are no catch basins. However, a recommended spacing length shall be 300 feet to allow for easier access to pipes for inspection and maintenance.

6. "Dish" street intersections shall not be permitted. Sufficient catch basins shall be installed at street intersections and low points in the street to avoid gutter overflow.

7. Reinforced concrete pipe shall be utilized in ROWs and shall have appropriate cover for the design load proposed.

8. Catch basins and manholes shall be constructed in accordance with New Jersey Department of Transportation Standard Specifications for Road and Bridge Construction, 2001 Edition, incorporated herein by reference, as amended and supplemented, which can be obtained from the New Jersey Department of Transportation, 1035 Parkway Avenue, PO Box 600, Trenton, NJ 08625-0600. Castings shall conform to NJDOT Standard Specification for Road and Bridge Construction.

9. Permissible design velocities in open channels shall be as follows:

Excavation Material	Velocity (fps)
Table 5-4
Permissible Design Velocities in Open Channels
Fine sand to firm loam	2.0 to 3.0
Stiff clay to hardpan	3.0 to 5.0
Concrete lined ditch	10 (maximum)

10. Channel and ditch banks shall be protected by use of vegetation and/or rip rap as design velocity dictates.

11. The minimum Manning's roughness coefficient "n," used in the Manning's equation listed in 19:4-8.6(b)4 i, shall be as follows for the calculation of discharge flows in open channels:

Channel Type and Condition	Manning's "n"
Table 5-5
Minimum Manning's Roughness Coefficient "n" Used in the
Calculation of Discharge Flows in Open Channels
Concrete lined ditch--good condition	0.013
Unlined ditch--good condition	0.025
Natural streams and watercourses--fair to	0.030 to 0.150
poor condition

12. If an alternative flow formula is used, discharge coefficients shall be equivalent to the Manning's roughness coefficient "n" specified in (c)11 above.

N.J. Admin. Code § 19:5-7.8

Administrative correction.
See: 36 N.J.R. 1955(a).
Amended by R.2009 d.40, effective 1/20/2009.
See: 40 N.J.R. 4696(a), 41 N.J.R. 624(b).
In (c)5, substituted "400" for "500" twice and inserted the last sentence.