7425 HARDESON RD BASE FILE 2016-01-01 MF Import

� � � � � � ��_l � I� �� �' � � � � � � � � �� GEOTECHNICAL ENGINEERING STUDY Traa; and Associates July 1£�, 2005 E-11860 Page 9 Footinc� excavations should be observed by a representative of ECI, prior to placing forms or rebar, to verify that soil conditions are as anticipated in this report. Slab-on•Grade Floors The slab-on-grade floors for tlie buildings and the bottom of the vault should be supported on a minimum of 12 inches of structural fill. The slab-on-grade floors should be provided with a capillary break consisting of a minimum of 4 inclies of free-draining sand or gravel. In areas where slab moisture is undesirable, a vapor barrier, such as a 6-mil plastic membrane, should be placed beneath the slab. Retaining Wal�s and Stormwater Control Vault The proposed stormwater control vault retaining walis and other retaining walls should be designed to resist tl�e lateral loads imposed by the retained soils and applicable surcharge loads. Walls that are designed to yield can be designed to resist the lateral earth pressures imposed by an equivalent fluid with a unit weight of 35 pcf. If walls are to be restrained at tl�e top from iree movement, tlie equivalent fluid weight should be increased to 50 pcf. These values are based on horizontal backfill conditions. Surcharges due to backfill slopes, hydrostatic pressures, traffic, structural loads, or other surcharge loads are assumed to not act on the wall. If such surcharges are to apply, they should be added to the above design lateral pressure. The passive pressure, allowable bearing capacity, and iriction coefficient previously provided in tho Foundations section are applicable to the retaining waA design. To reduce tlie potential for hydrostatic pressures to build up behind site retaining walls, including the stormwater control vault retaining walls, the walls should be backfilled with a iree-draining material extending at least 18 inches behind the wall. The free draining backfill should consist of eitlier pea gravel or washed rock. A rigid, 4-inch diameter, scl�edule 40 PVC or SDR 35, perforated drain pipe should be placed at the base of the wall and should be surrounded by a minimum of 1 cubic foot per lineal foot with 1-inch washed rock. The drainpipe should be placed with the perforations in the down position, The remainder of the backfill should consist of structural fill. Garth Consullan�s, Inc