1318 37TH ST 2018-01-02 MF Import

James Pirie March 18, 1997 JN 97072 Page 8 All permanent cuts into native soil should be inclined no steeper than 2:1 (H:V). Fill slopes also should not be constricted with an inclination greater than 2:1 (H:V). To reduce the potential for shallow sloughing, fill must be compacted to the face of these slopes. This could be accomplished by overbuilding the compacted fill and then trimming it back to its final inclination. Water should not be allowed to flow uncontrolled over the top of any temporary or permanent slope. Also, all permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve the stability of the: surficial layer of soil. Drainage Considerations We recommend the use of footing drains at the base of footings, where (1) crawi spaces or basements will be below a structure, (2) a slab is below the outside grade, or (3) the outside grade does not slope downward from a building. Drains should also be placed at the base of all backfilled, earth -retaining walls. These drains should be surrounded by at least 6 inches of 1-inch- minus, washed rock and then wrapped in non -woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a perforated pipe invert should be at least as low as the bottom of the footing, and it should be sloped for drainage. Drainage should also be provided inside the footprint of a structure, where (1) a crawl space will slope or be lower than the surrounding ground surface, (2) an excavation encounters significant seepage, or (3) an excavation for a building will be close to the expected high groundwater elevations. We can provide recommendations for interior drains, should they become necessary, during excavation and foundation construction. All roof and surface water drains must be kept separate from the foundation drain system. A typical drain detail is attached to this report as Plate 7. For the best long-term performance, perforated PVC pipe is recommended for all subsurface drains. No groundwater was observed during our field work. If seepage is encountered in an excavation, it should be drained from the site by directing it through drainage ditches, perforated pipe, or French drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of the excavation. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be constructed. Final site grading in areas adjacent to buildings should slope away at least 2 percent, except where the area is paved. Water from roof, storm water, and foundation drains should not be discharged onto slopes; it should be tightlined to a suitable outfall located away from any slopes. Pavement Areas All pavement sections may be supported on competent, nature soil or structural fill, provided these soils are in a stable, non -yielding condition at the time of paving. Structural fill or fabric may be needed to stabilize soft, wet, or unstable areas. We recommend using Supac 5NP, manufactured by Phillips Petroleum Company, or a non -woven fabric with equivalent strength and permeability characteristics. In most instances where unstable subgrade conditions are encountered, 12 inches of granular, structural fill will stabilize the subgrade, except for very soft areas where additional fill GEOTECH CONSULTANTS, INC.