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24,00^ 5.B. CONCRETE BASE: Concrete hapw, for manhole construction shall be
<br />of size and depth as shown on the plans. Concrete used for this purpose shall.
<br />consist of one part Portland cement, two parts of clean pharp sand and four
<br />parts of gr•ded coarse aggregate. Material used for this purpose shall be
<br />sub.jec: to .,.e approval of the Engineer. Base shall be poured on undisturb .d
<br />earth prior to setting the precast manhole. section-. Precast concreL bole
<br />bases shall he considered equal.
<br />24,^00.5.(-. WALLS: Material to he used in a walls of manholes shall be as
<br />specified in Section 24,000.2. All external surfaces of concrete block man-
<br />holes if permitted shall be plastered with 1 1/2 inch coat of Portland cement
<br />c• -tar. Mortar shall contain one part of cement to three parts of suitable
<br />"~aster sand. Lime or mortar mix shall be used in amount necessary to make a
<br />aklitable mixture for plastering purposes, but not to exceed 15% by volume of
<br />cement. Mortar used for laying concrete bin,:., shall consist )f one part Port-
<br />land cement to two parts of sand to which lime or morrr,r mix may be addr' not
<br />to exceed fifteen percent. (15%) by volume o!-mer.i..
<br />24,0oo.5.U. MANHOLE STEPS: Manhole steps .;ha!t ` ';;e type as specified
<br />in Section 2Z_,6 00.?.1. Spacing shall be as sh wn o:i the detailed manhole
<br />plat.,, but no' greater than 16 inches in vertical eli-nment.
<br />24,00o.5.E. ACING: M�;vH_OLB RINGS & COVERS: The frame or ring casting shall
<br />he set to the designation elevation in a full mortar bed.
<br />24,000.5.F. DROP MANHOLE INLETS: Encased drop inlets shall be constr,
<br />required on the plans and in accordance with the atan�iard Drop Tnl:.
<br />Plate.
<br />24,000.6. BACKFILLINC, CLEANTNG UP & M. I".1�ING"ES:
<br />24,fi00.6.A. BACKFILLINC PROCEDURE AT PTP' 7.0NE: All trenches and excavations
<br />sb-it he backtil led ,mm.diately after F laid therein. For backfill up
<br />to d tevr•I of one foot over the top of only selected materials free
<br />r-r.k. boulders, de"iia or other hi, id r i t substances, be
<br />-sed. ,'he backfilling shall ho placed completel the pipe han.,ches in
<br />uniform leyerr, not exceedin„ 4 inches in depth. '.aver shall t-e placed,
<br />then c�refuily and uniformly tair i to eliminate ,Ossibility of lateral
<br />displacement end to proviae unif, -art tel► under the pie, haunches.
<br />The backfill ..,iterial %hall h- easary, tamped in 4 inch layers
<br />And c oroughl%? ,ompacted ,ins' le of the pipe to pr^vide solid
<br />backing ags'nst the external
<br />Till" instRl.lat'„R
<br />.' backtii
<br />oiyl 'oride pint
<br />4.;,ill h.... in accor-
<br />ce .,t'
<br />�.i.4. D-2321
<br />Riven
<br />t'..:nmpacting the
<br />..•k!ili Trb.._
<br />iai around the
<br />pipe t, at least 95 p-rceut >f
<br />maximum density to
<br />a di9tn,- - of
<br />c..• foot h4 v
<br />the top i4 the pipe.
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<br />24,000.4S.P. 4ACKFiLL PR0CFrWRE ABOVI� ,0IPF. ZONE: ,'Type "s") Fr.-,, -dare Where
<br />%Pttiemrnt ;q RI1nWah,P. .succeeding laver:+ of backfill may contain coarser
<br />materials xnd a°ialI he Free from 1•ircrs nt rock, concrete or clay lump mare
<br />24,0VO-1'
<br />2/A4/45S4h
<br />Copertght 1494
<br />So- troo, R.^vene. An'•rlik
<br />i Assnciates, Inc
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