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8D�GT 66, 9i�80 3111 ?lM <br />NEXTEL Communications, Inc. <br />Atgusl 16, 1999 <br />bi6E IZ8 90Z�NDf1tl:)0"I <br />9-91 b}13127-0 <br />Page 8 <br />foot (pcfl, expressed as an equivalent fluld unit weight, may be used for fhat portion of the <br />foundation embedded more than 1 ieet below finished exterio� subgrade elevaUon. 'The aliowable <br />passive earth pressure value incorporates a safery factor of 1.5, whicFi is typical tor transiEnt <br />loading conditlons. <br />Settlements: With the fooling subgrade areas prepared as described above, we would not exped <br />settlements greater than 1 inch. Settlements may be greater ihan this if loose subgrade soils are <br />leR within toodng areas. On the other hand, �rve would expec� less settlement if the actual <br />foundation laads are less than the allowabie maximum soil bearing pressure given above. <br />4,3 Structural Fill <br />The following comments, recommendations, and conduslons regarding the use ofstructural fill are <br />provided for design and construction purposes. <br />Mate�ia :"Structural flil' indudes any fill materials placed underfooGngs, pavements, driveways, <br />and other permanent sVuctures. Typical materials used iorstriictural flll include clean, well-graded <br />sand and gravel (plt-run); clean sand; aushed soil; controlled-densily flll (CDF); lean-mix concrete; <br />and various soil mixtures af sflt, sand, and gravel. Recycled concrete derived fiom crushed parent <br />material is also useful as stn�ctural fill. <br />S�,il Composltion: Soils used for structural fill should not contaln individual parlldes greater than <br />about 6 inches in diameter and should be free of organics, debrls, and other deletazious materials. <br />Glven these prerequisites, the suftability of solls used for �tnictural fill depends p�imarity on the <br />nrain-size distributbn end molsture content of the solls when they are placed. As tlie "fines" <br />content (ii�a: pation passing the U.S. No. 200 Sleve) Increases, soils become more senslUve to <br />small changes In r;oisture content. Sails wntalning more than about 5 percent flnes (by welght) <br />cannot be consistently compacted to a firm, unyielding ccndiHop when the molsture content fs rtwre <br />than about 2 percentage points above optimum. The use'of'dean" soil Is necessary for fill <br />placement durin,g wet-weaHter site wo►ic. Clean sails are defineii as granular soils that have a fines <br />content of less than 5 percent (by welght}, based on the soll tractlor� passfng the U.S. No. 4 Sbve. <br />On-Si ' s: We offer the following evaluation of the on-site soiis in rel:.don to potenlial use as <br />sWetural fill or badcfill for the monopole tower mat foundation excavetkn: <br />• Oroanic Salls Sod, topsoil, and organfc-rich soils are � suitable for use as structurel fili <br />under any circumstances, due to theU high orgen(c content. Consequenqy, these materials <br />can be used only for norrstructural purposes, such as in landsceping areas. <br />Gravefly Sands fFlll): The gravelly sand fiIl overtying the native soils appear suitaWe for <br />reuse as structural fill wlth the condidon that masture cdntents be adjusted to the optimum <br />molsture content. Partides larger than 6 Inches r►�y be encountered and should be <br />sawrnnvuoa.ss wq.n.u�.a�ooa�,3 in n..rNk.w �,..n ►w..,o <br />sriot�: �211M[�3 �Jt+ NLtIV3 t'i�1tl: IVd'LS�Z : 66-9I-B �A8 Jl�S <br />