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~ ~ Page 50 Ord. 81- Page 3 New and Infill 4R, 5R, 6R, OF, l-C, 1 Acre 2-C, 3-C, 4-C, 5-C, IN, and multi-family thru industrial portions of MU SECTION 5. Design Criteria and Performance Standards. It shall be the duty of an applicant for a bUilding permit or subdivision of land to provide a storm water management system as provided herein, A. Design Criteria - Unless otherwise provided, the Engineering Regula- tions, Construction Specifications, Design Standards, and amendments adopted by the City Council, Lakewood, Colorado, shall govern the design of improve- ments with respect to managing storm water runoff. B. Storm Water Runoff Release Rate - Any person meeting the application provisions of this ordinance as specified in Section 4 shall control the release rate of storm water runoff so that runoff after development shall not exceed the runoff from the same parcel of land in its natural state for the 5 and 100-year storm respectively. C. Determination of Detention Volume. The volume of required water detention shall be calculated on the basis of runoff from the 5- and lOO-year return frequency storms. Such calculations should be made in accordance with a method of analysis in the Urban Storm Drainage Criteria Manual published by the Denver Regional Council of Governments unless specified otherwise by the Director. D. Compensating Detention. In the event that orderly and reasonable development of an area requires that the detention of storm water be located elsewhere, compensating detention (the detention of an equal volume of storm water) may be provided at an alternative location if approved by the Director. E. Partial and Full Exemption - When it can be demonstrated by the applicant to the Director that a higher storm water release rate will not be contrary to the purpose and intent of this ordinance and where such proposed release rate will not exceed the safe storm water drainage capacity in the downstream portion of the watershed, the release rate may be increased or de- creased as deemed appropriate by the Director. When determining the safe storm water drainage capacity in the downstream portion of the watershed, it shall be assumed that all undeveloped land in the tributary watershed would be granted the same exemption as the applicant. If the safe storm water drainage capacity is exceeded under these conditions, the applicant's release rate will be decreased so that the safe stormwater drainage capacity is not exceeded, F. Emergency Excess Storm Water Passage - An excess storm water passage shall be provided for all storm water detention areas. Such passage shall have the capacity to convey through the proposed development the excess storm water from the tributary watershed. The capacity of such storm water passage shall be constructed in a manner to transport the peak rate of runoff from the IOO-year frequency storm assuming all storm sewers are inoperative, all up- stream areaS are fully developed, and that antecedent rain fall has saturated the tributary water shed.