15 ATTACHMENT 9 - Laserfiche WebLink

Project No. 9929.G Geotechnical Investigation/Vineyard Avenue, Pleasanton 8 August 2003 28. Surface drainage atop the slopes should be designed by the project Civil Engineer and maintained by the property/home owner such that no ponding of water occurs behind the top slopes or that no surface water flows over the top. 29. Drainage benches should be provided for all cut and fill slopes over 30 feet in vertical height and should be placed at the mid point of the slope. Cut or fill slopes inclined at 3:1 do not require benches. The benches are recommended to be a minimum of 6 feet wide and be provided with lined v-ditches that grade to a controlled discharge point. Caution must be exercised to ensure that the uphill lip of the v-ditch is slightly lower than the adjoining ground surface, and the soil is compacted, to prevent infiltration of surface water beneath the ditch which may result in slope failure. It is important that the v-ditch and discharge drains are periodically inspected and maintained to clean any debris or obstructions from allowing proper flow of water. Due to the large surface area of the adjoining slope to the west, significant amounts of surface water due to rain will sheet flow onto the property. It is recommended that a concrete lined v-ditch or deep earth swale be constructed at the toe of the slope and/or at the uphill property line to intercept surface water from entering the building pads. 30. All finished grades should provide a positive gradient away from all foundations to an adequate discharge point in order to provide rapid removal of surface water runoff. No ponding of water should be allowed on the pad or adjacent to the foundations. Surface drainage must be provided as designed by the project Civil Engineer and maintained by the property owners in perpetuity. Ponding of water on the building pad will have an adverse effect on the unsupported exposed slopes by virtue of seepage. Therefore, the pads should be graded in a manner that surface flow is to the street or to a controlled discharge system. 31. Ponded water will cause swelling and/or loss of soil strength and may also seep under structures. Should surface water be allowed to seep under the structures, foundation movement resulting in structural damage and/or standing water within the crawlspace or under the slab will occur. This may cause dampness to the floor which may result in mildew, staining, and/or warping of floor coverings. All compacted, finished grades should be sloped at a minimum 2% TERRASEARCH, ins Page 19 of 53