[Ord. No. 5.000 § IV, 9-9-1991]
The capacity of a storm drainage system shall provide for the requirements set forth in Section 425.160. Total routing capability for a one percent (1%) storm event is required.
[Ord. No. 5.000 § IV, 9-9-1991]
Enclosed system capacity shall be determined from hydraulic conditions indicating least capacity. Pipe velocities shall not exceed fifteen (15) feet per second at design capacity. Energy dissipation is required at outfall points. Storm sewer capacity shall be determined from Mannings Equation. The minimum pipe size is fifteen-inch diameter. Pipe lines twenty-four (24) inches and larger in diameter may be laid on curved alignments. All pipe laid under paved sections of streets shall be reinforced concrete pipe. All other pipe shall be corrugated galvanized metal or approved equal.
[Ord. No. 5.000 § IV, 9-9-1991]
Points of unflow to an enclosed system shall provide a fifty hundredths (0.50) foot freeboard above the effluent pipe plus head requirements for inlet losses. The minimum fall through a structure shall be twenty hundredths (0.20) feet. The crown of inlet pipes shall be at or above the crown of outlet pipes.
[Ord. No. 5.000 § IV, 9-9-1991]
Curb inlets are required on all streets unless a variance is approved by the City Engineer. The minimum inside length of a curb inlet is five (5) feet, the minimum inside width is three (3) feet. Inlet setback is one (1) feet minimum and two (2) feet maximum. The minimum opening height is fifty hundredths (0.50) feet. The minimum gutter depression is thirty-three hundredths (0.33) feet. Gutter transitions are five (5) feet upstream and sump, and three (3) feet downstream. Flow deflectors may be required by the City Engineer. Inlet capacity shall be determined by the formula:
Q = 0.7 L (a = y)3/2
Where:
Q
=
runoff in cfs
L
=
length of opening
a
=
gutter depression
y
=
depth of flow or by APWA methods. Reduction for partial obstruction is not required.
[Ord. No. 5.000 § IV, 9-9-1991]
Culverts shall be sized in accordance with APWA methods for inlet control or outlet control. Culverts shall be reinforced concrete pipe or reinforced concrete box with entrance and outlet sections or headwalls. Energy dissipation is not required for culverts unless calculations predict a hydraulic jump in the downstream channel.
[Ord. No. 5.000 § IV, 9-9-1991]
Street gutter flow shall be determined using Izzard's Formula. Maximum allowable curb spread shall be ten and fifty hundredths (10.50) feet for streets twenty-eight (28) feet wide and less. For streets over twenty-eight (28) feet wide curb spread shall not exceed elevent and five-tenths (11.5) feet. Curb inlets shall be spaced to control flows to these spreads.
[Ord. No. 5.000 § IV, 9-9-1991]
A. 
Constructed open channels shall be designed to flow requirements set forth previously. The controlled channel shall contain the required design flood with a one-foot freeboard. A freeboard is not required for flood plain channels, but the limits of the flood plain section shall be delineated. Flood plain channels shall be graded to completely drain back to the controlled channel on cessation of the flood.
B. 
The design flow velocity in a controlled open channel shall be determined. The minimum allowable channel liner for velocities up to seven (7) fps is staked sod. The minimum allowable liner for velocities from seven (7) to ten (10) fps is stone rip rap. Minimum thickness of stone liner is twenty (20) inches with minimum rock diameter of ten (10) inches. The minimum allowable liner for velocities from ten (10) to fifteen (15) fps is rock filled revet mattress, nine (9) inches thick. The minimum allowable liner for velocities over fifteen (15) fps is concrete or sound in situ rock.
C. 
Channel side slopes shall not be steeper than 3:1 for turf liners, 2:1 for rock and revet mattress liners, and 1:1 for concrete liners. Liners shall extend to the freeboard top elevation. Channel alignment changes shall be approved by the City Engineer. Liner heights may be required to be higher on the outside of curved sections of channels.
D. 
The use of natural channels is permitted, but the City Engineer may direct improvements or modification. Easement requirements are the same as for constructed channels.
[Ord. No. 5.000 § IV, 9-9-1991]
A. 
Detention basins shall be designed to function automatically, with only occasional cleaning required. The controlled outlet and storage shall handle a four percent (4%) probability flood. Discharge shall be designed to avoid the overloading of downstream systems as defined previously. The City Engineer may impose discharge rates to avoid additional flooding of currently overloaded downstream facilities. This rate shall not be more restrictive than 2.2 cfs per controlled acre for the four percent (4%) event. The facility shall provide for the release of a minimum of eighty percent (80%) of accumulated water within twenty-four (24) hours after the flood event.
B. 
Overflow spillways shall provide capacity to pass the one percent (1%) probability flood event without overflowing detention facility dikes. Overflow spillways discharge into flood channels as described previously.
C. 
Detention facilities shall not be designed to store sediment.
D. 
The City Engineer may require the submittal of elevation-capacity curves, inflow hydrographs, stage-discharge rating curves, and routing curves.