§ 3.10. Stormwater Collection/Conveyance Systems.

a.

System Design Requirements. Drainage improvements shall accommodate runoff from the entire upstream drainage area, and shall be designed to prevent overloading the capacity of the downstream drainage system. The City may require the phasing of development, the use of control methods such as retention or detention, and/or the construction of off-site drainage improvements in order to mitigate the impact of the proposed development. No stormwater collection system shall be constructed within the City unless it is designed in accordance with the City of Waxahachie's Design Manual for the Design of Storm Drainage Systems by a registered professional engineer and approved by the Public Works Director and City Council. All developed areas shall have concrete curb and gutter drainage systems unless the development has an average lot size of at least twenty thousand (20,000) square feet. These lower density developments can utilize drainage ditch systems or swales according to Subsection (b) [sic] below. All plans submitted to the Public Works Director for approval shall include a layout of the system together with supporting calculations for the design of the system. In addition to any others, the plans shall conform to the City of Waxahachie's Design Manual for the Design of Storm Drainage Systems and the C & D Manual, and shall conform to the following standards and minimums:

1.

All drainage systems must be designed in accordance with the C & D Manual. The developer shall be required to construct off-site drainage improvements (upstream, downstream, or possibly both) in accordance with the C & D Manual if such improvements are necessary to protect other properties from flooding or other negative impact resulting from construction of the proposed development.

2.

Run-off conveyed in roadway drainage ditches shall be confined to the ditch. The flow velocity in the ditch shall not exceed six (6) feet per second, and the ditch side slopes shall not exceed three (3) feet horizontal to one foot vertical (3:1). The center of the ditch shall be at least ten (10) feet from the road edge.

3.

No cross-street (i.e., perpendicular to traffic flow) flow of run-off shall be permitted unless approved by the Public Works Director. When such drainage is allowed, it must be across a concrete street (i.e., valley gutter) and as approved by the Public Works Director.

4.

For drainage in creeks or streams, or if the natural condition is altered by the developer, for any excavated channels, if the flow is greater than six (6) feet per second or the slope exceeds three (3) to one (3:1), limestone or similar acceptable rock, a reinforced concrete pilot channel or a concrete channel lining shall be required by the City to prevent erosion. Location and type of construction of the open channel must be approved by the Public Works Director. These drainage facilities must be within a common space or within an easement to ensure protection of the area and access for maintenance.

5.

If the flow is less than six (6) feet per second and if the slope does not exceed three (3) to one (3:1), the creek or excavated channel may be platted as part of the individual lots. The owners of these lots will be responsible for maintenance. Sufficient access shall be provided to provide for protection of these areas and for maintenance purposes.

6.

For erosion and sedimentation control, the City uses the "Storm Water Quality Best Management Practices for Construction Activities in North Central Texas," a copy of which is filed in the City Manager's (or designee's) office. It is the developer's responsibility to be familiar with, and to comply with, these standards as well as any other policies the City may enact regarding erosion, sedimentation control, non-point source pollution, and other similar issues during construction of the development.