7200 HARDESON RD 2016-01-01 MF Import

r-� CNA Architecture Group 12 April 1991 W-7352 Page 12 Surface runoff from planned graded slopes west of the buildings should be diverted from building areas. We recommend that an adequate catchment or ditch be placed at the base of slope to channel silt and runoff from the slope away from the building and pavement areas. 5.7 Pavement Design Parking, driveway and all paved areas should be designed and constructed in accordance with the following recommendations. Pavement subgrades should be prepared as previously described with the upper two feet for parking and three feet for truck access and driveways subgrades compacted to a minimum of 95 percent modified Proctor (ASTM:D-1557). This will require removal and recompaction of existing soils. Assuming that the roads are founded upon a subgrade of properiy compacted structural �,,F'A fill, during dry conditions, we recommend the compacted fitl subgrade soils be overlayed �M� � with 6 and 18 inches of clean, free-draining sand and gravel for parking and driveway �„� 2 areas respectfully. If subgrades are prepared as previously recommended, a paved G,s� section consisting of a minimum of 2 or 3 inches of Class B asphaltic concrete over 4 or 6 inches of crushed rock base course for parking and driveway areas respectfully, may be considered adequate. It should be understood, however, that a minimum 3 inch thickness of asphaltic concrete is now recommended by the Asphalt Institute even for car parking areas. We are available to provide alternative pavement sections if desired. It should be noted that some reduction of pavement section thickness is possible with the use of a geotextile fabric separation between the subgrade and the base rock. The need for such an application is best addressed in the field at the time of construction. Depending on the subgrade conditions at the time of construction, the subbase of sand and gravel may need to be thickened. Also, if pavement subgrade preparation is performed during wet conditions, we would recommend pavement design to include at least one additional foot of pit-run or the use of an asphalt treated base (ATB). _ y.- � , ay;`'i.