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Mr. Ron Bottoms, City Manager <br />October 1, 2008 <br />Page 22 of 31 <br />k I o t z associates <br />should be generally viewed as a complement to long term solutions dealing with <br />channel capacity and sewer system capacity. <br />Detention may be onsite or offlite, and usually consists of some type of pond with <br />storage that is dry until a storm event. Wet bottom detention (i.e., the pond never <br />complete drains) is also provided in several areas. Onsite detention is located at <br />or near the source of runoff for which control is sought, while offsite detention is <br />commonly a shared, or "regional detention," facility. <br />Onsite detention is commonly built and maintained by the property owner of 2, <br />single parcel of property, while ofEsite or regional detention is often owned and <br />maintained by a government entity which sells or provides storage in the <br />detention system for areas in need of detention storage. Onsite detention facilities <br />can also be located relatively easily underground, though costs for underground <br />detention will be typically much larger than a surface detention facility. <br />IThile onsite detention is primarily used for mitigation of new development, <br />regional detention offers an opportunity to address existing excess runoff and <br />channel flow problems. The regional detention facility can be sized, if adequate <br />space for the regional detention facility can be identified, to reduce downstream <br />impacts of excessive runoff from already developed areas upstream of the <br />detention facility. <br />9 MI MTN I m4- <br />• Ability to mitigate excess runoff at far distance points <br />• Ability to mitigate excess runoff from different points <br />• Ability to achieve economy of scale in construction costs <br />• Ability to transfer construction costs of detention facility to others not <br />involved in the construction process <br />• Possible dual use of the detention pond as an amenity facility <br />• Reduction in the number of locations to be maintained <br />• Need for the pond owner to construct the pond upfront before full construction <br />cost recovery may be possible <br />• Owner will typically be responsible for maintenance of the regional facility <br />• Purchase of storage space by other parties requires proper legal transfers <br />