2000 TOWER ST ARTS AND SCIENCES BLDG 2018-01-02 MF Import

Iflexible tubing for footing drainpipes. The nerimeter drains should be sloped to drain 'oy gravity, if practicable, to a suitable discharge point, preferably a storm drain. We recommend that th, cleanouts be ' covered, and be placed in flush mounted utility boxes. Water collected in roof downspot.t lines must not be routed to the footing drain lines. BELOW -GRADE WALLS AND RETAINING WALLS The following recommendations should be used for the design of below -grade walls that are intended to act as retaining walls and for other retaining structures that are used to achieve grade changes. Design Parameters Lateral earth pressures for design of below -grade wal and retaining structures should be evaluated using an equivalent fluid density of 35 pcf provided that the walls will not be restrained against rotation when backfill is placed. If the walls will be restrained from rotation, we recommend using an equivalent fluid density of 55 pcf. Walls arc assumed to be restrained if top movement during backfilling is less than H/1000, where H is the wall height. These lateral soil pressures assume that the ground surface Schind the wall is horizontal I•o: unrestrained walls with backfill sloping up at 2H:1 V, the design lateral earth pressure should he increased to 55 pcf, while restrained wars with a 2H:1V sloping backfill should be designed using an equivalent fluid density of 75 pcf. These lateral soil pressures do not include the effects of surcharges such as floor loads, traffic loads or other surface loading. Surcharge effects should be included as appropriate. Below -grade walls for buildings should also include seismic earth pressures. Seismic earth pressures should be determined using a rectangulardistribution of 811 in psf, where H is the wall height. If vehicles can approach the tops of exterior walls to wi:ain 1/2 the height of the wall, a traffic surcharge should be added to the wall pressure. For car parking areas, the traffic surcharge can be approximated by the equivalent weight of an additional 1 foot of soil backfill (about 125 pso behind the wall. For delivery truck parking areas and access driveway areas, the traffic surcharge can be approximated by the equivalent weight of an additional 2 feet (250 pso of soil backfill behind the wall. Positive drainage should be provided behind below -grade walls and retaining structures as discussed below. These recommendations are based on the assumption that any retaining walls at this project will be provided with adequate drainage. The values for soil bearing, frictional resistance and passive resistance presented above for foundation design ate applicable to retaining wall design. Walls located in level ground areas should be founded at a depth of 18 inches below the adjacent grade. Wall Drainage To reduce the potential for hydrostatic water pressure buildup behind the retaining walls, we recommend that the walls be provided with adequate drainage, as shown in Figure 3. Wall drainage can be achieved by using free draining wall drainage material with perforated pipes to discharge the collected water. Wall drainage material may consist of washed 3/8-inch to No. 8 pea gravel or a mixture of about 30 to 40 percent clean medium to coarse sand and 60 to 70 percent fine gravel, with negligible fine U G e o H n g i n c c r 5 14 File No. 5836-002-001040204