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I ~~ <br />~} <br />thickness of the completed lifts be measured to verify that the required gravel sections have been <br />construced. <br />Drainaee: For adequate performance of any roadway, positive surface drainage must be provided and <br />maintained. This includes periodic cleaning and regazding of the drainage ditches along the edges of [he <br />roadway. In addition, the roadway surface should be graded on a periodic basis to ensure that sufficient <br />crown or super elevations are maintained so that the roadway surface adequately drains into the ditches. <br />We recommend that the roadway be constmcted with a minimum crown or super elevation of 2 percent. <br />The collection and diversion of surface drainage away from [he roadway area is extremely important to <br />satisfactory performance of the roadway. The design of surface drainage features should be carefully <br />considered to remove all water from the roadway surface and embankment areas. In addition, the <br />maintenance of all drainage structures and. roadway surface should be conduced periodically to ensure <br />proper performance. Subsurface drainage ai the site may contribute to roadway distress. Groundwater at <br />the site is capable of entering the subgrade soils and base course and causes them to lose strength. <br />Foundation Recommendations: Based on the subsurface conditions encountered in the test holes, the <br />results of the field and laboraton' investigations and the proposed structures, we believe an economically <br />feasible and safe type of foundation system is straight-shaft skin friction end bearing piers drilled into the <br />underlying cla}'stone bedrock. Foundation movement should be e~thin tolerable limits if the following <br />design and construction precautions aze observed. <br />1) A minimum pier diameter of 12 inches, a minimum bedrock penetration of 5 feet and a <br />minimum pier length of 20 feet are recommended. <br />2) The piers should be designed using an allowable skin friction value of 3,000 psf for the portion of <br />the pier drilled in the bedrock. A drill rig of sufficient size, type and operating condition should <br />be used so that the bottom of the piers can be cleaned out properly and the minimum length and <br />bedrock penetration requirements can be met. if the bottom of the piers are properly cleaned and <br />approved by an engineer from this office, then an allowable end bearing pressure of 30,000 psf <br />may be used in the design. <br />3) The piers should be reinforced their fu]] length with a[ least one #5 reinforcing rod for each 16 <br />inches of pier perimeter. <br />4) The piers should be properly cleaned and dewatered prior to steel and concrete placement. <br />S) A 4-inch void should be provided beneath grade beams to prevent the swelling soils from <br />exerting uplift forces on the grade booms and to concentrate pier loadings. Avoid should also be <br />provided beneath necessary pier caps. <br />6) This office should be retained by the client to observe the pier drilling operations. <br />Sob Number: 03.3838 NWCC, Inc. Page 4 <br />