[Ord. 520, June 1999; Ord. 601, Oct. 2004; Ord. 720, June 2009; Ord. 996, July 2014]
Sediment shall be maintained on site and excess stormwater runoff shall be detained in connection with any new construction, development, redevelopment or land use change occurring within the City of Collegedale in accordance with the requirements set forth in this chapter 5. Notwithstanding the foregoing, exceptions to this requirement are as follows:
(1) 
For stormwater detention, the development of any single-family or two-family lot not a part of a larger development unless the impervious area exceeds ten thousand (10,000) square feet.
(2) 
For stormwater detention, the development of commercial, industrial, high density residential or agricultural property in which the increase in the run off rate does not exceed the pre-development rate of run off.
(3) 
A determination by the city that the excess runoff from the proposed construction, development, redevelopment or land use change will be insufficient to adversely affect the carrying capacity of the receiving body or watercourse. In this connection and should the city's determination of insufficient adverse effect be sought, the developer shall make available to the city such hydraulic or hydrologic computations as will support the requested exception.
[Ord. 520, June 1999; Ord. 996, July 2014]
The peak discharge after full development resulting from the proposed development shall not exceed the corresponding peak discharge rate prior to development during storms of 1-year, 2-year, 5-year, 10-year and 25-year return frequency storm as determined at the property line of the development.
[Ord. 520, June 1999; Ord. 996, July 2014]
There shall be no detrimental effect on the floodway or the flood elevation during a 100-year storm upstream or downstream of the proposed development area as a result of the proposed development.
[Ord. 520, June 1999; Ord. 996, July 2014]
The increased stormwater runoff resulting from proposed development shall be detained by providing for appropriate detention storage as required by this chapter 5. In no case shall the design maximum water elevation of a detention facility be less than one foot (1') below the lowest ground elevation adjacent to, or opening into an existing or future structure or above the elevation of any public street.
[Ord. 520, June 1999; Ord. 996, July 2014]
Designs for detention storage and related appurtenances shall be submitted to the city for approval. Upon submittal of a design the city shall determine as to those control elevations that shall be entered on the final plat or make a determination as to the necessity for deed restrictions on any particular lot in said subdivision. Where a non-subdivided parcel of land is proposed for development, the city shall make a determination as to the need for covenants to maintain responsibility for mandatory drainage facilities. All said facilities shall be designed and constructed in accordance with the City of Collegedale specifications and shall be located in easements dedicated to the public.
[Ord. 520, June 1999; Ord. 996, July 2014]
(1) 
The drainage area used in computation will be the total area tributary to the detention storage outlet.
(2) 
The developer will be required to submit detailed hydrologic and hydraulic calculations to show that the requirements of this chapter 5 will be met. A unit hydrograph method of analysis (SCS) will be used for detailed hydrologic computations. The hydrologic report shall show and state that there is no increase in the stormwater runoff rates as a result of the development.
(3) 
No orifice or flow control opening shall be less than one inch (1") in size.
[Ord. 520, June 1999; Ord. 996, July 2014]
The discharge velocity from detention facilities shall not exceed three feet (3') per second at the property line unless it is determined by the city that greater velocities will not be harmful to the receiving channel. Where the city's determination is requested, the developer shall make available such hydraulic or hydrologic computations as will adequately support the course of action being requested.
[Ord. 520, June 1999; Ord. 996, July 2014]
Emergency spillways shall be provided to permit the safe passage of runoff generated from rainfall events up to the 100-year rainfall event.
[Ord. 520, June 1999; Ord. 996, July 2014]
Detention storage areas shall have adequate capacity to contain the storage volume of tributary stormwater runoff with at least one foot (1') of freeboard above the water surface during the 100-year rainfall event.
[Ord. 520, June 1999; Ord. 996, July 2014]
Stormwater control systems may be planned in coordination by two (2) or more property owners as long as the potential for damage from stormwater is not increased at intervening locations.
[Ord. 520, June 1999; Ord. 996, July 2014]
Stormwater control measures shall be installed prior to undertaking other grading of site and a schedule of construction for this purpose shall be submitted prior to construction in the City of Collegedale.
[Ord. 520, June 1999; Ord. 996, July 2014]
The total drainage area must be used in calculating the allowable release rate. The required storage volume will be based on the project area only, with extraneous flows from upland areas being bypassed or discharged via overflow spillways or other devices. Where storm sewers are required they shall be of such size as will provide sufficient capacity to receive the flow generated by ten-year storm from upland areas. As to the latter and regardless of whether it has occurred in fact, such upland areas shall be deemed to have been fully developed for all purposes of this requirement.
[Ord. 520, June 1999; Ord. 684, Nov. 2007; Ord. 996, July 2014]
The developer shall comply with the State of Tennessee General NPDES Permit for Stormwater Discharges Associated with Construction Activity, the Hamilton County Water Quality Program and provide copies of each to the city prior to starting construction.
[Ord. 520, June 1999; Ord. 684, Nov. 2007; Ord. 996, July 2014]
Land disturbances associated with any new construction, development, redevelopment, or land use change regardless of use shall incorporate into the development plan the following elements as a minimum:
(1) 
Stone construction entrance.
(2) 
Silt fence or other sediment retaining device on the low side of the site.
(3) 
Temporary seeding of disturbed areas remaining open more than two (2) weeks.
(4) 
Removal of soil tracked into the public right-of-way.
(5) 
Permanent seeded.
A copy of the development plan shall be submitted to the city prior to starting construction.