1. Installation of Storm Sewer Facilities. When a public storm sewer is accessible, the developer shall install storm sewer facilities. Where no outlets are available within a reasonable distance, adequate provision shall be made for disposal of stormwater. Design of all storm sewers shall be based upon a 10-year reoccurrence interval. Minimum pipe size shall be 15 inches except for intake cross runs which shall be 12-inch minimum diameter. For storms greater than the 10-year, the 100-year storm shall be used for design of overland flow drainage. The developer may consider detention facilities as recommended by the developer’s engineer, and approved by the City Engineer, and in conformance with the stormwater management plan of the City. When stormwater detention or retention is deemed to be necessary for any development, the following guidelines shall be followed:
A. Where possible, underground detention should be considered to mitigate the visual impacts and maintenance difficulties involved with aboveground systems.
B. Aboveground systems may either be for detention or retention.
C. Retention systems shall incorporate landscaping and design so that the area acts as a water feature or amenity and not simply as stormwater detention.
D. Detention shall be landscaped and equipped to provide for useable space rather than vacant ground. Sidewalks, benches, picnic areas, etc., should be used.
E. Landscaping shall follow existing site plan requirements. Planting rates for trees and shrubs may be at one-third the site plan rate.
F. All retention and detention facilities shall be properly maintained in function and appearance.
G. Where possible, retention or detention facilities shall be incorporated into green space, park, or trail facilities to provide for more useable and enjoyable space.
H. Where possible, regional detention should be incorporated. Large detention areas are typically preferable to numerous smaller areas.
I. Concrete flumes shall be used.
J. The bottom of any detention facility must be a minimum of two feet above the seasonal high groundwater table.
2. Sump Pumps and Footing Drains. Sump pumps and footing drains shall be required in all plats approved after the effective date hereof, in all construction where the foundation is in excess of 42 inches in depth. The sump pumps and footing drains shall be installed pursuant to the standard specifications for streets and utility improvements as adopted by the City. Footing drains may gravity flow to the storm sewer line or to a drainage channel subject to approval by the City Engineer. If a foundation is to be less than 42 inches in depth, the construction is only required to have footing drains as long as the footing drains gravity flow to the storm sewer line or to a drainage channel subject to approval by the City Engineer. If the footing drains do not gravity flow to the sewer line or a drainage course, the construction is required to have a sump pump.
3. Compliance With Standard Specifications. All storm sewer design and construction shall be done in accordance with the City standard specifications.