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� CITY of <br />LINO LAS <br />1 0/24/94 <br />Standards for Facility Design <br />severe hardship on any new construction and as long as <br />the flood elevation storm is checked and used, if applicable. <br />Flood Evaluation Storms <br />2. The first Flood Elevation Storm (FES): 100 -year return <br />period, 24 -hour duration, Type II distribution with wet soil <br />conditions (AMC -3). <br />3. The second FES: 100 -year return period, 10-day runoff <br />event using a Type C mass curve as identified in SCS <br />Natural Engineering Handbook, Section 4, Hydrology <br />(NEH -4). <br />Rainfall <br />Rainfall amounts for hydrologic analysis shall be based on <br />Hershfield, D.M., 1961, Rainfall Frequency Atlas of the United <br />States for Durations of 30 Minutes to 24 Hours and Return Periods <br />from 1 to 100 Years, Technical Publication No. 40 (TP -40) and /or <br />SCS Minnesota Hydrology Guide. <br />Hydrology for Landlocked Areas <br />' Available storage volume of landlocked areas shall be established <br />by estimating the water surface elevation resulting form a 100 - <br />year /10 -day runoff (7.2 inches) and saturated_ -or- frozen soil <br />conditions (CN =100). <br />Hydrology - Minor Facilities (I.e., Storm Sewer, Ditches, <br />Culverts) <br />City Projects <br />Rational Method shall be the preferred methodology to calculate <br />peak flow rates for the design of minor systems that do not require <br />hydrograph routings. <br />If a minor system requires the use of a hydrograph method for <br />routing purposes, only methods preapproved by the City will be <br />accepted. If the method is not currently approved by the city, <br />documentation of the methodology used shall be submitted with <br />the calculations. Hydrograph methods currently approved by the <br />Local Water Management Plan <br />Users Manual <br />SEH NO: LINOL9402.00 <br />Page 14 <br />