Construction Specifications.
Type of Concrete | Average Strength (pounds per square inch) |
|---|---|
Class P | 6,500 |
Class A | 5,500 |
Class B, B-1 | 5,000 |
Class C, C-1 | 4,500 |
Qp = CIA |
Where: | ||
Qp | = | The peak runoff rate in the cubic feet per second (CFS) |
C | = | The runoff coefficient |
I | = | The average rainfall intensity in inches per hour (in./hr.), occurring at the time of concentration tc (minutes) |
tc | = | The time of concentration in minutes (min.) |
A | = | The size of the drainage area |
Q = 1.486\n AR 2/3 S1/2 |
Where: | ||
n | = | Manning's roughness coefficient |
A | = | Cross-sectional area of flow in square feet |
R | = | Hydraulic radius in feet (R = A/P, where P is equal to the wetted perimeter) |
S | = | Slope of conduit in feet per foot |
The Manning roughness coefficients to be utilized are shown in Exhibit K, set out at the end of this subsection. |
Pipe Diameter (inches) | STM Class Pipe | Minimum Cover (surface to top of pipe) | Pipe Diameter (inches) | ASTM Class Pipe | Minimum Cover (surface to top of pipe) |
|---|---|---|---|---|---|
12 inches | III | 17 inches | 24 inches | III | 15 inches |
IV | 12 inches | IV | 6 inches | ||
V | 7 inches | V | 6 inches | ||
15 inches | III | 16 inches | 30 inches | III | 10 inches |
IV | 11 inches | IV | 6 inches | ||
V | 7 inches | V | 6 inches | ||
18 inches | III | 16 inches | 36 inches & above | III | 6 inches |
IV | 10 inches | IV | 6 inches | ||
V | 6 inches |
Inlet Type | Inlet Size (interior) | Campbell Foundry No. (or Approved Equal) |
|---|---|---|
"A" | 24" x 42" | 3405 |
"B" | 48" x 42" | 2618 |
"D" | 24" x 42" | 2617 |
"E" | 48" x 42" | 3425 |
Pipe Size | Manhole Spacing |
|---|---|
15" or less | 500' |
18" — 36" | 600' |
42" — 60" | 700' |
60"+ | 700'+ |
MINIMUM TOP WIDTHS | |
|---|---|
Height (Feet) | Top Width (Feet) |
0 — 15 | 10 |
15 — 20 | 12 |
20 — 35 | 14 |
SIZE OF STORAGE AREA* | |||
|---|---|---|---|
Elevation | Less than 15 square miles | 15 — 100 square miles | Greater than 100 square miles |
Less than 2 feet below | 40% | 65% | 90% |
Between 2 feet and 4 feet below | 25% | 50% | 75% |
Over 4 feet below | 10% | 25% | 50% |
Notes: |
|---|
* Area contributing floodwaters to the flood hazard area at the site in question. This effective detention storage will be required to provide for drainage of the developed land in accordance with the criteria already established in these regulations. However, the gross storage considered for crediting will not exceed that which would be filled by runoff of a 100-year storm from the site. |
Construction Specifications.
Type of Concrete | Average Strength (pounds per square inch) |
|---|---|
Class P | 6,500 |
Class A | 5,500 |
Class B, B-1 | 5,000 |
Class C, C-1 | 4,500 |
Qp = CIA |
Where: | ||
Qp | = | The peak runoff rate in the cubic feet per second (CFS) |
C | = | The runoff coefficient |
I | = | The average rainfall intensity in inches per hour (in./hr.), occurring at the time of concentration tc (minutes) |
tc | = | The time of concentration in minutes (min.) |
A | = | The size of the drainage area |
Q = 1.486\n AR 2/3 S1/2 |
Where: | ||
n | = | Manning's roughness coefficient |
A | = | Cross-sectional area of flow in square feet |
R | = | Hydraulic radius in feet (R = A/P, where P is equal to the wetted perimeter) |
S | = | Slope of conduit in feet per foot |
The Manning roughness coefficients to be utilized are shown in Exhibit K, set out at the end of this subsection. |
Pipe Diameter (inches) | STM Class Pipe | Minimum Cover (surface to top of pipe) | Pipe Diameter (inches) | ASTM Class Pipe | Minimum Cover (surface to top of pipe) |
|---|---|---|---|---|---|
12 inches | III | 17 inches | 24 inches | III | 15 inches |
IV | 12 inches | IV | 6 inches | ||
V | 7 inches | V | 6 inches | ||
15 inches | III | 16 inches | 30 inches | III | 10 inches |
IV | 11 inches | IV | 6 inches | ||
V | 7 inches | V | 6 inches | ||
18 inches | III | 16 inches | 36 inches & above | III | 6 inches |
IV | 10 inches | IV | 6 inches | ||
V | 6 inches |
Inlet Type | Inlet Size (interior) | Campbell Foundry No. (or Approved Equal) |
|---|---|---|
"A" | 24" x 42" | 3405 |
"B" | 48" x 42" | 2618 |
"D" | 24" x 42" | 2617 |
"E" | 48" x 42" | 3425 |
Pipe Size | Manhole Spacing |
|---|---|
15" or less | 500' |
18" — 36" | 600' |
42" — 60" | 700' |
60"+ | 700'+ |
MINIMUM TOP WIDTHS | |
|---|---|
Height (Feet) | Top Width (Feet) |
0 — 15 | 10 |
15 — 20 | 12 |
20 — 35 | 14 |
SIZE OF STORAGE AREA* | |||
|---|---|---|---|
Elevation | Less than 15 square miles | 15 — 100 square miles | Greater than 100 square miles |
Less than 2 feet below | 40% | 65% | 90% |
Between 2 feet and 4 feet below | 25% | 50% | 75% |
Over 4 feet below | 10% | 25% | 50% |
Notes: |
|---|
* Area contributing floodwaters to the flood hazard area at the site in question. This effective detention storage will be required to provide for drainage of the developed land in accordance with the criteria already established in these regulations. However, the gross storage considered for crediting will not exceed that which would be filled by runoff of a 100-year storm from the site. |