§ SR-15. Design criteria., Article IV. Drainage Plans, Chapter SR. Subdivision Regulations, Appendix, Code of Ordinances, Brookhaven

Collection system. The stormwater collection system shall be designed in accordance with the rational method:

	Q	=	A i R
Where
	Q	=	Discharge in cubic feet per second
	A	=	Tributary drainage area in acres
	i	=	Coefficient of runoff of the drainage area. Calculations of "i" shall be shown on the design sheet.
	R	=	Rainfall intensity in inches per hour as determined by:

	Where
		t	=	Time of concentration in minutes

(1)

Pipes, conduits or ditches shall be designed by the use of Mannings formula:

Where
	V	=	Velocity in feet per second
	R	=	Hydraulic radius in feet
	n	=	Coefficient of roughness where:
	n	=	0.13 for reinforced concrete pipes 24 inches or smaller in diameter
	n	=	0.15 for reinforced concrete pipes 18 inches or smaller in diameter
	n	=	To be determined and approved for special conduits and ditches. Maximum velocity shall be 10.0 feet per second.
	S	=	Slope of the pipe in feet/feet to be used as hydraulic gradient of pipe flow except where the system will be surcharged when the recharge basin is full. Design gradient in this case may be assumed as the lowest inlet invert to the water surface at 80% storage volume where no overflow is provided. In case of outfall in tidal water, use the maximum tide elevation.

(2)

Manholes shall be a maximum distance apart of 350 feet.

(3)

Pipe alignment and location. Storm sewer pipe shall be in a straight line between manholes and shall be placed between the center line of the road and the curbline.

(4)

Valley gutters. Valley gutters will be permitted at T-intersections where they will be parallel to the center line of the through road and shall be installed only after design approval by the Town Engineer. In general, the crown of the intersecting road shall be gradually eliminated starting from a point about 30 feet back from the flow line of the through street. At other than T-intersections, valley gutters will be permitted only when warranted by limited traffic use as approved by the Engineer.

(5)

Gutter flow. Surface drainage in gutters shall be limited to that flow which will not exceed five inches in depth at the curb based on the individual conditions of road grade, runoff factor, rainfall intensity and tributary area and inlet capacity.

(6)

Catch basins. Not more than two catch basins shall be interconnected before being connected to a manhole.

(7)

Brooks, ditches and stream beds. Where existing brooks, water-bearing ditches and dry stream beds giving evidence of seasonal runoff use are encountered, such area shall be maintained for drainage purposes or other adequate means of providing for such drainage and shall be installed at the developer's expense, after approval by the Engineer.

(a)

A right-of-way or drainage easement of sufficient minimum width to include a twelve-foot access strip in addition to the width of the ditch, brook or stream bed as measured from bank top to bank top shall be offered to the Town for drainage purposes. Such right-of-way or drainage easement shall be shown on the drainage plan and on the final plan with property bearings and distances indicated.

(8)

Drainage structures on state or county land. Drainage structures which are located on state highway rights-of-way shall be approved by the appropriate highway engineer's office, and a letter of approval from that office shall be filed with the Town Planning Board. Where county highways are involved, the Planning Board will obtain the approval from the county pursuant to § 239-k of the General Municipal Law.

Editor's Note: General Municipal Law § 239-k was repealed L.1998, c.451, § 2, effective 7-1-1998. See now General Municipal Law § 239-f.