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7.3 Inlet Hydraulics The procedures and basi.= data used to define .thl~ capacities of the standard inlets under various flow conditions werE! obtained from the USDCM, Volume 1, Section on "Storm Inlets", for curb opening inlets. The procedure ,=onsists of defining the amount and depth of flow in the gutter and determining the th.!oretical flow interception by the inlet. To account for eff,ects which decrease the capacity of the various types of inlets, such as debris plugging, pavement overlaying, and variations in design assumptions, the theoretical capacity calculated for the inlets is reduced to the allowed ,=apacity by the factors presented below for the standard inlets. ]U.LOWABLBIIILE~ CAPACIT'!t' L Pe:i:'centaqe of Inlet Type ~lI1eoretical .... .cape.cit. Allowed coridi ti.on Type R Sump or 5' Length 88 Continuous Grade 10' Length 92 15' Length 95 Sump or Grated Type 13 50 Continuous Grade Continuous Grade Combination Type 3 66 Sum Grated Type C 50 Sum Combination Type 3 65 Allowable standard inlet capacities for the illi1:ial storm have been developed and are pr'esented in Figures 7-5 , 7-6 , and 7-7 for continuous grade and Figure 7-8 for sump conditions. These figures include the rE!duction factors in the abe,ve table. The allowable inlet capac:ity is compatible with the allowable street capacity (see Section 8). The values shown were calculated on the basis of the maximum flow allowed in the stre.!t gutter (or roadside ditch for Type C). I'or the gutter flow amounts less than the maximum, the allowable inlet capacity must be proportionately reduced. 7.3.1 Continuous ~i:'ade Condition For the continuous grade condition, the cap'3.city of the inlet is dependent upon many faGtors including gutter slope, depth of flow in the gutter, height and length of curb openinq, street cross slope, and the amount of depression at the inle1:. In addition, all of the gutter flow l.i.ll not be intercepted and some flow will 7-2 II I II I I I I I I I I I I I I I I I I