L
= KA
| |
The minimum "K" values shall be as follows:
|
Street Class
|
Crest Curve
|
Sag Curve
| |
---|---|---|---|
Major collector
|
145
|
100
| |
Minor collector
|
65
|
60
| |
Minor street
|
28
|
35
| |
Intersection (stop conditions)
(Rounded by PC/PT of curb returns)
|
3
|
3
|
Street Class
|
Sight Distance
(feet)
| |
---|---|---|
Major collector
|
350
| |
Minor collector
|
275
| |
Local
|
200
|
Q = CIA
| |||
Where:
| |||
"Q" is the required capacity, in cubic feet
per second, for the collection system at the point of design.
| |||
"A" is the tributary drainage area, in acres,
and shall include areas tributary from outside sources as well as
from within the site itself.
| |||
"C" is the coefficient of runoff applicable
to the drainage area and shall be based on consideration of soil conditions,
average slope of the drainage area and degree of ultimate development
of the area, but in no case shall be less than the following coefficients:
|
Topography
| |||||
---|---|---|---|---|---|
Usage
|
Density
(units per acre)
|
Flat
(0%-10%)
|
Rolling
(10%-20%)
|
Hilly
(Over 20%)
| |
Residential
| |||||
High-density
|
4-6
|
0.50 (0.40)
|
0.55 (0.45)
|
0.60 (0.55)
| |
Medium-density
|
1-4
|
0.45 (0.35)
|
0.50 (0.40)
|
0.55 (0.50)
| |
Low-density
|
Fewer than 1
|
0.40 (0.30)
|
0.45 (0.35)
|
0.50 (0.45)
| |
Impervious surfaces
|
0.90
|
0.90
|
0.90
| ||
Undeveloped woodland
|
0.30 (0.20)
|
0.35 (0.25)
|
0.50 (0.45)
| ||
Pasture and grassed areas
|
0.30 (0.20)
|
0.36 (0.20)
|
0.42 (0.37)
| ||
Cultivated fields
|
0.50 (0.50)
|
0.60 (0.50)
|
0.72 (0.62)
|
The above runoff coefficients assume that clay
soils (sand gravel soils coefficients indicated in parenthesis) are
present. For residential uses, the coefficients assume that paved
areas (parking) have been provided. Any deviation from these factors
would result in an adjustment in "C" values. Determination of nonlisted
uses shall be a subject of special study and approved by the Borough
Engineer.
| |
"I" is the rainfall intensity, in inches per
hour, and shall be determined from the graph entitled "Rainfall Intensity
Duration for Essex and Union Counties," copies of which are on file
with the Borough Clerk and which is made a part hereof. The minimum
time of concentration shall be 10 minutes, which shall be used as
the initial T, for all roadway drainage systems.
|
"R" is the hydraulic radius of the conduit flowing
full.
| ||
"n" is Manning's roughness coefficient, which
shall be as follows:
|
Concrete pipe
|
0.012
| ||
Corrugated metal, 2 2/3 x 1/2 inches corrugations
| |||
Plain or fully coated
Paved invert
Fully paved
|
0.024
0.020
0.012
| ||
3 x 1 inches corrugation
|
0.027
| ||
6 x 2 inches corrugation (field bolted)
|
0.032
| ||
"n" for other materials shall be as recommended
by the Borough Engineer.
| |||
"S" is the slope of the energy gradient, in
feet per foot, and shall generally be considered as being the same
as the slope of the invert of the pipe (S0);
however, such slopes shall be checked against the available hydraulic
gradient whenever the system flows full or where the system discharges
into a body of water.
|
Desirable Minimum Gradients for Concrete
Pipe
| ||
---|---|---|
Diameter
(inches)
|
Slope N=0.012
| |
15 (minimum permissible)
|
.008
| |
18
|
.006
| |
24
|
.005
| |
30
|
.004
| |
36
|
.003
| |
42
|
.002
| |
48
|
.0016
| |
54
|
.0014
| |
60
|
.0012
| |
66
|
.0011
|
Unlined
| |||
Earth, uniform section
|
0.018 - 0.027
| ||
Earth, nonuniform section
|
0.025 - 0.040
| ||
Earth, not maintained
|
0.080 - 0.012
|
Lined
| |||
Concrete
| |||
Finished
|
0.015
| ||
Rough
|
0.25
| ||
Riprap
|
0.35
|
Materials
|
Velocity
(feet per second)
| |
---|---|---|
Fine sand to fine loam
|
2.5 to 3.5
| |
Stiff clay to hardpan
|
3.75 to 6.00
| |
Concrete-lined ditch
|
15
|
Velocities shall be controlled by use of check
dams or baffles where necessary.
|
Facility
|
Maximum Side Slope
| |
---|---|---|
Channel
|
2:1
| |
Ditch
|
4:1
| |
Swale
|
6:1
|
Street Class
|
Minimum Average Maintained Footcandles
|
Uniformity
(average to minimum)
| |
---|---|---|---|
Major collector
|
0.5
|
6:1
| |
Minor collector
|
0.3
|
—
| |
Local
|
0.2
|
—
|