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f <br /> � 10 percent. 'Ihese moisture content test results indicate that the site soils would have to be <br /> � moiswrecondidoned by drying or aaating in order to achieve adequate compaction. lbis can <br /> be disruptive to other activities on a relatively small site and is a time-consuming process unless <br /> weather conditions aze ideal. <br /> IFOUNDATION SUPPORT <br /> IShallow spread footings ahould be founded on undisturbed, medium dense to very deose <br /> nadve till or compacted skucwral fill, We recommend that isolated column and co�inuoua walt <br /> footings have minimum widt6a of 3 fcet and 18 inches, respectively, 'Ihe bace of extaior <br /> ( footings should be founded u least 18 inches below the lowest adjacent grade for frost protxtion. <br /> Interior footings may be founded 12 inches below the bottom of the floor slab. <br /> + We reoommend a maximum allowable soil beazing pressure of 3,G00 psf(pounds per square <br /> � foot) for footings founded on medium dense weathered till or compacted structural fi1L It is <br /> 1 critical that site preparation and structural fill placement in azeas beneath strnctures be completed <br /> + in conformance with our rxommendadons in order to limit foundation seWements. We <br /> recommeud a maximum allowable soil bearing pressure of 6,000 psf for design of footings <br /> � foundad on the dense to very dease unweatherod glacial till. 'Ibe allowable beariag pressures <br /> presented above apply to the total of dead and long-cerm live loads and may be increased by one- <br /> � third when considering earthquake or wind loads. <br /> We estimate that postconstruction seWements of footings founded on the deose to very <br /> dense glacial till will be less than 1/4 inch. 'lt�e settlement of footings founded on structural fill <br /> � or medium dense weathered till may range from 1/2 to 1 inch, depending on actual toundation <br /> loads and the thicimess of fill and/or weathered till that underlies the footings. Maximum dif- <br /> � ferential s�tlements b�ween adjacent compazably loaded colamns should be less than 1/2 inch <br /> where there is a gradual h�ansition from column footings supported on fill/weathered till and <br /> � footings supported on unweathered till. We estimate that the differential settlement between <br /> exterior column footings or along continuous footings will be negligible between footings <br /> supported on dense to very dense glacial till and less than 1/2 inch in 40 to 50 feet where footings <br /> Ibear on swctural fill or weathered till. <br /> Loose or disturbed soits not removed from the footing excavations prior to placing concrete <br /> { will result in increased settlement. Due to the silt content of the till soils, the subgrade soils are <br /> � susceptible to disturbance if allowed to become wet. It may be necessary to pour a lean concrete <br /> "mud mat" or place a layer of crushed rock in the bottom of the footings to protect the footing i <br /> � subgrade from disturbance if footings are constructed during wet weather, We recommend that ( <br /> all footing excavations be obse�ved by a representative from our firm immediately prior to mud <br /> ( mat or steel and concrece placement to confirm that the bearing surface has been preparad in a <br /> � manner consistent with our recommendations and that the subsurface conditions aze as eacpected. <br /> l � <br /> � <br /> � <br /> ( ' <br /> G e o E n y i n e c r • 9 Fk No.32l6-002-R0 1/0 203 71 � <br />