3321 52ND PL SW 2016-01-01 MF Import

c � � Geotechnical Engineering Investigation Schwab Residence ' July 13, 2001 NGA File No. 329401 Page 8 excavation. Also, water should not be allo�..� :� pond in the setback area or tlow onto the face of the slope. It should be understood that the closer site soil disturba�ice and development are to the slope, the more risk there is of affecting slope stability. Care should be taken to minimize disturbance to the slope and setback surficial soils and vegetative cover both during and after conswction. From a geotechnical standpoint, selective pruning and thinning of vegetation in these azeas should be acceptable. Cutting and pruning of trees located on the slope can be performed if allowed by the City, but certain precautions should be tzken. [f tree cutting is allowed by the ciry, we recommend that the trees be cut ro orjust below ground level and that the root bundle/stump be left in place. Pruned materials and debris should be removed from the area and not allowed to remain on the slope. Placement of soil, sod, clippings, or other matter on the slope is not recommended. Disturbed areas should be promptly replanted with suitable vegetation to reduce erosion. Of great importance to [he long-tertn stability of the slope is the control of surface and near- surface water, and erosion protection. We recommend that all drains, including foundat�on, roof, and yard drains, be directed away from the top of slope and routed into a permanent discharge system. Surface drainage over the slope should not be pertnitted. Site Drainage Surface Drainage: The finished ground surface should be graded such that storm water is directed to an appropriate stortn water c�llection system. Water should not be allowed to stand in any area where footings, slabs, or pavements are to be constructed. Final site gades should allow for drainage away from the residence and the steep slope. We suggest tha�t the finished ground be sloped at a minimum gradient of 3 percent for a distance of at least ll? feet away from the improvements. Subsurface Drainage: We recommend the use of footing drains around the residence and behind the basement wall. Footing drains should be installed at least 1 foot below planned finished floor slab. The drains should consist of minimum 4-inch-diameter, rigid, slotted or perforated, PVC pipe surrounded by free-draining material wrapped in a filter fabric. We recommend that the free-draining material consist of an 18-inch-wide zone of clean (less than 3 percent fines), granular material placed along the back of the wall. Pea gravel is an acceptable drain material or NELSON GEOTECHN/CAL ASSOC/ATES, /NC. � �