PVC drainage connection approval memo, Apr 1985

NYC 9/11 Public Portal Document

below optimum moisture before final Pipe zone materials include the material The performance of a flexible conduit backfill operations are begun. If jetting is in the haunching area and the initial does not depend only on the class of used, desired density of the embedment backfill (see Figure 4). They include a embedment materials used, but more materials should be previously obtained number of processed materials plus the importantly, on the density of the material by other methods. Neiter flooding or soil types listed under USCS Soil in the haunching zone. Figure 3 on page 7 jetting should be used I the possibility of Classification System (FHA Bulletin No. shows that a Series 46 Perma-Loc pipe washing away side support exists. 373). These materials are grouped into will perform in Class III material equally as five broad categories according to their well as in a Class I material if adequate suitability for this application, as follows. compaction is achieved. A further Johns-Manville’s position on deflection comparison of Figure 2 and Figure 3 testing is that routine roeasurement of Class I. Angular, ’A" to 114" graded shows that a Series 10 Petma-Loc pipe deflection of installed Perma-Loc may be ■stone, including a number of fill will perform as well as a Series 46 pipe at unnecessary, unecxromical, and an materials that have regional significance the same height of cover when the added construction cost for Perma-Loc such as coral, slag, cinders, crushed appropriate bedding class and PVC pipe installations. This position, stone and crushed shells. compaction are utilized. By using a applies to all routine deflection testing combination of soil class, soil density, and whether performed by the "Go-No Go Class II. Coarse sands and gravels with series classification of Perma-Loc, the Gauge" method for compliance to . maximurn particle size of IVa", including design engineer can achieve the most maximum deflection Imte or by. variously graded sands and gravels economical installation within the , instruments which measure and record containing small percentages of fines,- recommended deflection limits. . actual pipe deflections. When . '■ ■ ' ■ generally granular and noncohesive, -' - recommended inslaiation practices are ■ either wet or dry: Soil type GW, GP, SW Excavation and pipe laying followed, including required compaction and SP are included in this class. As with other pipes, the trench for PVC . in the haunching area, pipe deflection will is excavated with bell holes to give not exceed our reewnmended long-term ■• Class III. Fine sand and-clayey gravels, uniform bearing along the full length of deflection limit of 7.S%. Al this deflection including fine sands, sand-clay mixtures, each pipe section. The ditch should be limit, the PVC sewer pipe will have a ■ and gravel-clay mixtures. Soil types GM, wide enough to allow for proper minimum factor of safety of 4 in structural GC and SM and SC are included in this placement and compaction of the failure. Proof of this position is that more class. selected materials in the haunching . than 500,000,000 feet of PVC sewer pipe area. are performing satisfactorily in the field Class IV. Silt, silty clays, and clays, today. including inorganic clays and silts of Sheeting medium to high plasticity and liquid If unstable-soil conditions or regulations On the other hand, where improper. limits. Soil types MH, ML, CH and CL require the use of sheeting or boxes, they installation practices are known or „ are included in this class. should be used in a manner not to disturb suspected, questionable bedding the embedment material within three pipe materials are employed and/or _ Class V. These materials are not diameters on each side of the installed installation conditions are severe, . recommended for bedding, haunching or pipe. ■deflection testing of these sections of the . ■ initial backfill. , installation should beconsidered Compaction techniques : advisable by the engineer. Flooding or jetting are commonly used methods for obtaining desired densities of granular embedment materials. If ■ flooding is used, the embedment materials should be allowed to dry

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r-' .B NYC-WTC_000165049