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10/24/94 <br />CITY OF <br />LINO LAS <br />Standards for Facility Design <br />City include: USDA SCS, TR -55, TR -20 and EPA SWMVI <br />methodology. <br />The minor drainage system shall be analyzed and designed using <br />a 10 -year frequency rainfall, and shall be evaluated for the 100 -year <br />frequency rainfall. A local Intensity Duration Frequency Curve <br />shall be used to determine the peak flow rates for the 10 -year <br />event. Full pipe flow analysis shall .be used unless special <br />conditions can be demonstrated to consider pressure flow. <br />County or State Projects <br />Culvert crossings or storm sewer system in County or State right - <br />of -way may have a design frequency which differs from the 10- <br />year. Each agency shall be contacted to determine the appropriate <br />design frequency. <br />Hydraulics <br />Culverts <br />Culverts shall be analyzed using methodology consistent with <br />Federal Highway Administration Hydraulics Design of Highway <br />Culverts - Hydraulic Design Series 5. <br />Anti- seepage collars shall be used on culverts under public streets <br />when there is: <br />• Water and ponding structures with a pool depth of <br />2 feet and a two -day duration, <br />• 250 -acre watershed or more, <br />• Design head of 10 feet or more. <br />The collars shall be installed so as to increase the creep distance or <br />seepage line along conduit by 15 percent. <br />1 -Year and 10 -Year Storm Outlet Structure <br />Outlet structures intended to control peak discharge rates to those <br />rates shown in the plan should evaluate the impacts of discharge <br />Local Water Management Plan <br />Users Manual <br />SEH NO: LINOL9402.00 <br />Page 15 <br />