§ 155.035 DESIGN BASIS.

   Storm water drainage systems, roadways and other drainage systems shall be designed to handle stormwater runoff as outlined herein.

(A)   Frequency of rain event.
(1)   Storm sewers, open ditches, driveway, culverts	25-year frequency
(2)   Road culverts	25-year frequency or meet INDOT requirements if necessary
(3)   Protection for buildings	50-year frequency
(B)   Runoff.
(1)   25 acres or less	Rational method Q=CIA
(2)   25 acres or more	S.C.S.-TR-55 or other method approved by the City Engineer
(C)   Overland flow time.	Use chart A
(1)   First pavement inlet	Minimum   - 10 minutes
(2)   First ditch catch basin	Minimum   - 10 minutes
(D)   Rainfall intensity.	Use chart B

 

   (E)   Run-off coefficients.

      Weighted averages shall be used to define run-off coefficient.

Type of area	Run-off coefficient
Business	0.60   -   0.75
Residential - Single family	0.40   -   0.50
Residential - Multi-Family	0.60   -   0.75
Industrial - Light	0.60   -   0.80
Industrial - Heavy	0.70   -   0.90
Parks, Cemeteries	0.25    -    0.40
Playgrounds	0.30   -   0.45
Railroad Yard	0.30   -   0.40
Woodland	0.20   -   0.40
Grassland	0.25   -   0.45
Cropland	0.50   -   0.70
Pavement	0.90
Roofs	0.90
Lawns, Dense soil, Flat, 0-2%	0.20   -   0.25
Lawns, Dense Soil, Avg. 6% or less	0.25   -   0.35
Lawns, Dense Soil, Steep, Over 6%	0.35   -   0.40

 

(Ord. - -, passed - -03; Am. Ord. 16-2020, passed 12-7-20)

Editor’s note:

   Charts A and B can be found in Exhibit “A” attached to Ordinance 16-2020.