1001 39TH ST 2016-01-01 MF Import

._ _ � DAVID L. NELSON AND ASSOCIATES, INC. Consulting Enginecring Geology November 27, 1991 Project No. 10591 Page 7 many variables involved, the above values should be considered general guidelines. Unsupported permanent cut slopes in medium dense native or compacted structural fill soils sheuld be no steeper than 2H to 1V. Once specif.ic plans are developed, more definiti•� information can be procided. Permanent fill embankments are expected to stan�l at various slopes depending on the material and comp.�.ction =ffozt used. For structural fill, that is fill comprised or cl�an imported or on site soils with a relative compaction in excess �f 90$ (AST[d D- 1557) , embankment slopes should be no steeper than 2H: 1V, and properly protected from erosion. We do not recommend placing additional fill on the steep slopes unless the entire embankment is reconstructed as structural fill . Dewatering & Drainage Depen3ing on excavation configuration and ground water conditions at the time of construction, temporary dewatering may be n�cessary. Typically, cui- off drains are used to intercept gro:indwater before it emerges into the excavation. The cut off drain consists of a trench f.illed with pea gravel that intercepts the ground water flow. A perforated pipe is placed near the bottom of the pea gravel and is routt3 to a suitable discharge point. The actual need and design of the cut off drain should be based on conditions observed in the field at the time of construction. Drain installation significantly below the water table will be very difficult without the use of a well point dewatering system. This should be addressed based on ground water conditions found at the time of construction. We suggesi: that a geotechnical consultant be on-site during drain development and construction. Wall and footing drains should be constructed as outliiied in the RETAINING WALL section of this report. Erosion potential should be considered moderate to severe for stripped areas with 15� or steepez grades . Erosion potential for areas in which the existing low ground cover is left intact, and surface water is controlled, is expected to be unaffected by the j proposed development. Construction phase erosion control could include, hut not necessarily be limited to, the use of hay bales, geotext-iie barriers (silt fences) , and controlled surface grading. Roofs and pavements will reduce the surface area available for natural infiltration within the site. This will in turn increase surface runoff . We recommend that roof drains, catch basins or other devices used to collect surface runoff be directed by tight line into the storm drain or other suitable system. Runoff . �