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<br />':'1 <br /> <br /> <br />. <br />.. <br /> <br />il <br /> <br />I <br />il <br /> <br />II <br /> <br />I <br /> <br />I <br /> <br />I. <br />I <br /> <br />I <br /> <br />Section l2.0-Stormwater Quality Enhancement. For information and <br />design guidelines related to the construction of detention ponds <br />that promote stormwater quality control, the reader is referred to <br />the Urban Storm Drainage Criteria Manual (USDCM), Volume 3, "Best <br />Management Practices". <br /> <br />;~~:t;J5~~~;,,'ll1lJ~lnl~lrrJ~~Jtf~. . <br /> <br />Whenever a detention pond uses an embankment to contain water, the <br />embankment shall be protected from catastrophic failure' due to <br />overtopping. Overtopping can occur when the pond outlets become <br />obstructed or when a larger than lOO-year storm occurs. Failure <br />protection for the embankment may be provided in the form of a <br />buried heavy riprap layer on the entire downstream face of the <br />embankment or a separate emergency spillway having a minimum <br />capacity equal to the lOO-year historical storm event for the <br />basin. Detention facilities in major drainage channels shall have <br />a spillway capacity equal to the lOO-year peak discharge associated <br />with fully developed conditions. Structures shall not be permitted <br />in the path of the emergency spillway or overflow. The invert of <br />the emergency spillway should be set equal to or above the lOO-year <br />water surface elevation. <br /> <br />t~',"~fI[~~~'~f:\~J~"~r~~Jji,,,j~,~,,"... . <br />" .,~, ~ ""-,', ''', ,.,:- - ': ,- <br />All open space detention ponds shall' "be re-vegetated by either <br />irrigated sod or natural dryland grasses in accordance the manual <br />"Guidelines for Development and Maintenance of Natural Vegetation" <br />by Donald H. Godi & Associates, Inc., July 23, 1984, available <br />through the Public Works Department. <br /> <br />ii$j_'l!f'""_~ <br />0~~~c ,-- : '0 :.~~{: . ~~;.: _'" ", -A .'~_ -.'i)i!i ,,_:~,,>! :B:%~ ",; ,-~, ' -\~~ Ie: ~f"': J <br /> <br />To assure that the detention facility performs as designed, <br />maintenance access shall be provided, and shown on the Final Plat. <br />For subdivisions or regional detention ponds, the detention <br />facility is usually dedicated to the City for operation and <br />maintenance. For privately maintained facilities such as P.U.D.'s <br />and commercial or industrial sites, an easement should be granted <br />: to the City to allow access and to assure that the facility <br />'continues to function as intended. The City Public Works <br />Department has standard easement agreement forms for this purpose. <br /> <br />11.6 Design Standards for parking Lot Detention <br /> <br />The requirements for parking lot detention are presented below. <br /> <br />11 -7 <br />