4812 HARBOR LN 2018-01-02 MF Import

December 3,1"8 Project No. T41" With wall backfill placed and compacted as recommended and drainage properly irWalled, we recommend designing unrestrained walls with a horizontal backslope for an active earth pressure equivalent to a fluid weighing 35 pef. For a 2:1 backslope, an active earth pressure equivalent to a fluid weighing 50 pcf shouid be used. For restrained walls, an additional uniform lateral pressure of 100 psf should be added These values assume that effective wall drainage is in place and that no other surcharge loading, such as traffic or adjacent buildings, will act on the wall. If such conditions will exist, then the imposed loading roust be included in the wall design. Friction at the base of the foundation footings and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in the t'�unc;ations section of this report. TINIFIT-7 Surface Final exterior grades should promote free and positive drainage away from the building area. We recommend providing a gradient of at least three percent for a minimum dista.rce of ten fee- from the building perimeter, except in paved locations. In paved locations, a minimum gradient of one percent should be provided unless pro%isions arc included for collection and disposal of surface water adjacent to the structure. Surface water must not be allowed to flow uncontrolled over the crest of the road shoulder or onto the slope faces along the west half of the property. Surface water should be directed away from the slopes to a point of collection and controlled discharge. Subsurface In addition to installing drainage behind all below grade walls, we recommend installing a continuous drain along the outside lower edge of the perimeter building foundations. The drains should consist of a four -inch diameter perforated PVC pipe that is backtilled with one-half inch minus drain rock. The drain rock should extend six inches above and to the side of the pipe. The drainpipe invert should be equivalent to the bottom of the footing. Subsurface drains must be laid with a gradient sufficient to promote positive flow to a controlled point of approved discharge. The foundation drains and roof downspouts should be tightlined separately to discharge at an approved location. 5.0 ADDITIONAL SERVICES Terra Associates, Inc. should review the final design and specifications in order to verify that earthwork and foundation recommendations ha, been properly interpreted and implemented in project design. We should also provide geotechnical services during construction in order to observe compliance with the design concepts, specifications, and recommendations. This will also allow for design changes if subsurface conditions differ from those anticipated prior to the start of construction. Page No. 7