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87:hT 66� 9Ti80 3J11 X21 <br />NEXTEL ConmuNcaUons, inc. <br />August16,1989 <br />GT6E TZ8 90Z�NOIltYJO"I <br />&91M•13127-0 <br />Page 5 <br />Subarade Verffica8on: Upon completion ot sVipping, excavation, and pre-rolling, all surfaces to <br />recetve structural fill should be prooi-rolled with a heavy compactor under the observatlon of an <br />AGRA representative, to assess the subgrade condNions prior to fill placement. <br />� E ui nt Shaker Foundationa <br />We antldpate that the prefabricated equipment shelter will be placed on shallow concrete footlngs <br />and that beari�ig pressures will be relatively low. Our specific conClusions and reCommendations <br />for equipment sheller foundations are presented below: <br />Subarade Conditions: Foodngs may be constructsd on ellher lhe near-surface, undisturbed, <br />medium dense gravelly s3nd (Fill) or on sUuctural fill bearing pads placed above properly prepared <br />subgrade soils. In tf'�e former case, the naGve subgrade should be compacted to a firm and <br />unyielding condition. In the latter sase, all fill shoidd be compaded to at least 90 percent of the <br />Modified Practor maximum density. <br />Su¢arade Verificat(on: Foofings should never be cast atop sufl, loose, organic, or frozen soils; nor <br />atop suBgrades covered by standing water. We recommend that all footlng excavations be <br />observed by a representalNe of AGRA prior to concrete placement, to confirm the condiGon of <br />bearing soils are the same as those assumed during design. <br />Bearina Pads: Generally, loose or soft soil conditions which may be encountered below footing <br />subgrade levels should etther be recompacted as described in the Site Preparallon sedion of this <br />report oY be overexpvated and replaced with beadng pads of structural fill. These bearing pads <br />should be wide enough to contain a 1 H:1 V slope extendfng from 1 foot outside each edge of the <br />footing down to ihe boltom oithe overexcavaUun. The s�:bgrade ot the overexpvated area should <br />be compacted as ouUined in the Site Preparat/on section of thl's report. All bearing pads should be <br />compacted as described in the Structura! Fill section of lhis reporf <br />�otina Oenths: Forfrost and ernsion protection, all exterior footings should be embedded at least <br />18 inches below exterior finish gr ades. ' <br />Bearinq Caoacitles: We recommend uUlizing a maximwn allowable bea�ing capacity oi 2,000 <br />pounds per square fooi (psF) for eq�ipment building foundaUons supparted on property prepared <br />medfum-dense �ravelly sand (Fill). N higher bearing capaaUes are required. we recommend <br />utifizfng a maximum allowable bearing capacity of 2,500 psf for equlpment building foundatlon <br />supporled on 1 foot of properly compacted bearing pads placed over these fill sdis. <br />Lateral Resistance: Lateral forces on tha foundatlon caused by seismic or transient loading <br />conditions may be resisted hy a combination of passive soil pressure against the side of the <br />ioundatlon and shear fric8on resistancs along the base. M allowabie base iriction value of 0.35 <br />would be appropriate, in our opfnion. M ailowable passive earth pressura of 250 pounds per cubk <br />i,wormrftocwa rrqK++ucaua�woaura Nnawod�l G.nn Nr..W <br />siis #: �ainnc� �v �,ar� va�n• WdzS:Z � 66-9I-e �A9 J,I�S <br />