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shallow depth to very hazd bedrock materials, we do not believe that steel H-piles driven into the bedrock <br />materials will be feasible for this project. <br />The drilled pier foundation movements should be within tolerable limits of the following design and <br />construction precautions aze observed. <br />1) The portion of the piers drilled into the competent bedrock materials should be designed using an <br />allowable end beazing pressure of 40,000 psf and an allowable skin friction value of 4,000 psf for <br />the portion of the pier penetrating the bedrock materials. The piers should also be designed [o <br />resist lateral loads assuming a modulus of horizomal subgradc reaction of 50 tcf in the overburden <br />soils and a modulus of horizontal subgrade reaction of 300 tcf in the bedrock materials. <br />2) The piers should have a minimum pier length of 20 feet and a minimum bedrock penetration of 6 <br />feet or 3 pier diameters, whichever is greater. <br />3) A minimum pier diameter of 16 inches is recommended to facilitate proper cleaning and <br />inspection of the piers. <br />4) The piers should be reinforced thew full length with one #5 reinforcing rod for each 16 inches of <br />pier perimeter. <br />5) The piers should be properly cleaned, dewatered and inspected prior to steel and concrete <br />placement. <br />6) The presence of groundwater the [es[ holes indicates that the use of casing and dewatering <br />equipment may be required to reduce water infiltration and accumulation. The requirement for <br />casing can sometimes be reduced by placing concrete immediately upon cleaning and inspection <br />of the pier hole. The concrete should not be placed in more than 3 inches of water, unless the <br />tremie or pump method is used [o place the concrete. <br />7) The pier-drilling contractor should mobilize equipment of sufficient size, type and operating <br />condition to adequately clean the bottom of the piers, handle the temporazy casing, and to achieve <br />the minimum bedrock penetrations and pier lengths. <br />8) A 4-inch void should be provided beneath grade beams to prevent the swellings soil from exerting <br />uplift forces on the grade beams and to concentrate pier loadings. Avoid should also be provided <br />beneath necessary pier caps. <br />9) The client must retain this office to observe the pier drilling operations. <br />10) Fill materials placed in the area of foundation construction should be constructed of materials free <br />of cobbles, boulders and deleterious materials. <br />Job Number: 07-7442 NWCC, Iuc. Page 5 <br />