4107 OLIVE ST 2018-01-02 MF Import

DAVID L. NELSON AND ASSOCIATES, INC. lConsulting Engineming Geology July 13, 1990 Pro}act No. 9490 Page 9 pressures. Otherwise, a reduction of passive pressure will be required. Specific reductions in passive pressure could be developed once the downalope geometry and building designs ere known. An appropriate factor of safety rr should be applied to the above base friction value to resist sliding. (I The above values assume the presence of the soils encountered in our explorations, and a free -draining material behind the subgrade wall. These values do not take into account hydrostatic pressures, sloping ground behind the wall, or surcharges due to equipment or adjacent structural loads. These values further assume the use of an effective drain system along the backside of the wall. We suggest the use of a free -draining sand and fine gravel backfill along the backside of the wall to reduce pressures on walls and to reduce potential for moisture problems. We suggest any basement or retaining wall areas utilize the recommendations as shown on the enclosed Subdrain a Backf ill Scheme enclosed. The drainage blanket should extend to within about two (2) feet of finished exterior grade and have a minimum thickness of 12 inches. The remaining two feet should be backfilled with low permeability on - site soils. A perforated drain pipe should be embedded in the drainage blanket along the base of the wall. The pipe should be set such that a positive drainage gradient is established and access to an outlet provided. The use of ADS flexible type drain pipe is not recommended for greater than 4 foot embedment depths or where excavation and replacement type maintenance are not desired. Rockeries Rockeries could be used on site but they should be considered on a case -by - case basis. 'They will not be suitable for all potential cuts on site. Rockeries provide erosion protection for existing stable soil conditions; they are not considered retaining structures. They should not be considered for retaining the existing fill or on the steeper portions of the site. Potential rockery cuts should be reviewed by a geotechnical consultant to determine if the soils at the rockery location are compatible with rockery construction. Constructton of rockeries is an art and should be accomplished by an