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I I I I I I I I I I I I I I I I I I I 3.9 StxmD SeIer Io1ets A storm __ inlet is an operrlng into a storm systen for the ent:rmx:e of SIIIface storm runoff. There are three types of:inlets: aJrb opening, grated, am canbinatian:inlets. In acW.tioo, :inlets my be further rl,.=ifi"C! as being 00 a cart:inuous grade or in a SIIIIp. 'I1E term "cootinucus grade" refers to an inlet s) lor,.h,t! that the grade of the street has a cmtinuous alop jB5t the inlet and therefore, pooding does oocur at the inlet. 'I1E SIIIIp caxli.tian erlsts \deleyer water is restr:icted to the. inlet area ,-,... the inlet is located at a low lXlint. A SlIIIp cmditian can oocur at a change in grade of the street fmn positive to negative or due to the crown slope of a cross street Iohen the :ln1et is located at 8Il intersection . Canbinatioo curb/grate :inlets or curb opening :inlets Slall be un 1i '""" at all points 10here ponding or SlIIIp cmlitioos exist in street or 10here the street capoci.ty is exceeded. 'I1E allowable inlet caJBCity will be determined using the reduction factors listed in Table 1.6. These n!duction factors carzpensate for debris plugging, IBVaJEnt overlaying, variations in design assunptions or other factors which decrease inlet caJBCities. Adequate details of the ptopaged stozm __ systan, :including plan and profile, details of inlets, nnnhol.es am other aJljllrtenaOCeS shall be incluled in the overall drainage plan SJ!Jnitted for approval. 3.10 QUverts A allvert is defined as a caxluit for the free ~ of surface dra:i1Bge \later m1er highway, raiJ.rood, canal or other E!IIIOOnknent. Culverts my be coostructed with DBllY shapes and mteria1s. Reinforced car:rete pipe (10') is available in roond, elliptical or arch cross sections, in sizes ranging frail 12 inches to Ire inches in dianeter. 'I1E pipe my also be cast-in-p1ace although this CCI1StruC:tiOOllEthod is mt generally used for storm sewers. Corrugated rretal pipe (GlP) allverts are available in round or arch cross sections. Sections of corrugated DEtal can also be bolted together to form several other cross sectiooal shapes, socii as elliptical am pmr shapes fornrl.ng stru:tural plate pipe (SW). Corrugated also cane in varioos diJlEnsions, which effect the hydraulics of the pipe flcM. Reinforced CDOCTete box all verts can be ccn.stm:t.ed with generally any rectangular cross sectioo, the only limitations being the physical site c;onst.raints and the stru:tural requiraJEnts. Precast box culverts are also available in several standard diJIensions. QU vert caJBCities shall be at least equal to the caplcities of all verts designed in accordance with the procedures oot1ined in the fureau of Public Roods, Hydraulic Fngineering Circulars No. 's 5 and 10. Culverts my be of any shape and cmstru::tial as required by existing topograIiric features; provided, Ixlwever, the size, shape, location am type of construction of allverts shall be &Jbject to approval. Culvert installations Slall be designed with an €llEI"gency overflow for the mjor storm on all streets other than mjor arterials. Culverts m1er oajor arterials shall have sufficient mJBCity to p3SS all of the runoff frail the mjor storm ccnsi.dering 20 percent of the inlet plugged. In deternIining the 8IIIllIl1t of eoergen:y overflcM required, the capacity credits in Table 1. 7 shall apply. 'I1E appropriate lIIDUlIt of €llEI"gency overflow alto streets shall be taken into account when analyzing storm runoff am allowable street caracities for the oajor storm. 10