New Jersey Administrative Code
Title 5 - COMMUNITY AFFAIRS
Chapter 21 - RESIDENTIAL SITE IMPROVEMENT STANDARDS
Subchapter 7 - STORMWATER MANAGEMENT
Section 5:21-7.4 - Inlets, catch basins, manholes, and outlets

Universal Citation: NJ Admin Code 5:21-7.4

Current through Register Vol. 56, No. 18, September 16, 2024

(a) Design engineers shall design inlets, catch basins, and manholes in accordance with the NJ DOT Standard Specifications for Road and Bridge Construction, November 2001 as supplemented. For Type A inlets, they should use a frame and single grate. Type B inlets require a frame, grate, and curb-type inlet with back piece. Type E inlets require a frame and double grate.

(b) Design engineers shall use one of the following grate types for stormwater inlets:

1. The NJDOT bicycle-safe grate, as described in the NJDOT Bicycle Compatible Roadways and Bikeways Planning Design Guidelines (April 1996).

2. If there is no bicycle traffic, a grate where each individual clear space in that grate has an area of no more than seven square inches or is no greater than 0.5 inches across the smallest dimension.

3. Another grate design may be used provided that:
i. There will be no bicycle traffic and

ii. Runoff discharging through the inlet is routed through a trash rack that complies with 5:21-7.8(d)1 ii.

(c) Whenever a curb-opening inlet is used, the clear space in that curb opening (or each individual clear space if the curb opening has two or more clear spaces) shall have an area of no more than seven square inches, or be no greater than two inches across the smallest dimension.

1. Exception: Compliance with the above dimensional requirements for curb openings shall not be required provided that runoff discharging through the inlet is routed through a trash rack that complies with 5:21-7.8(d)1 ii.

(d) Inlet spacing depends on the inlet capacity. Maximum gutter line flow is 400 feet. The maximum capacity of a curb inlet shall be six cubic feet per second. Area inlets in parking lots should be limited to three cubic feet per second.

(e) Manholes shall be precast concrete or concrete block coated with two coats of portland cement mortar outside the manhole. Masonry brick may be used to make vertical adjustment to rims, as long as the adjustments are 12 inches or less. In acidic soils, all manholes shall have two coats of black bitumastic waterproofing applied per manufacturer's instruction.

(f) If precast manhole barrels and cones are used, they shall conform to ASTM Specification C478, with round rubber gasketed joints, conforming to ASTM Specification C923. Both ASTM Specifications are incorporated herein by reference. Maximum absorption shall be eight percent in accordance with ASTM Specification C478, method A.

(g) If precast manholes and inlets are used, the top riser section shall terminate less than one foot below the finished grade, and the manhole cover or inlet grate shall be flush with the finished grade.

(h) Manhole frames and covers shall be of cast iron, conforming to ASTM Specification A48, Class 30, incorporated herein by reference, and be suitable for H-20 loading capacity. Manhole covers in remote locations may have a locking device.

(i) Outlet grates, fences, and other safety features for stormwater management facilities shall conform with DEP Stormwater Management Rules, N.J.A.C. 7:8. Safety requirements for detention basins and other stormwater facilities are incorporated in 5:21-7.8(d)6.

(j) The channel should be, insofar as possible, a smooth continuation of the pipe. The pipe may be laid through the manhole and the top half removed by saw cut. The completed channel should be U-shaped. The channel height shall be three-fourths of the diameter of the pipe.

(k) The bench should provide good footing for a workman and a place where minor tools and equipment can be laid. It must have a slope of four to eight percent.

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