9909 2ND AVE W 2018-08-01 - Laserfiche WebLink

December 13,2006 Project No.T-6001 To guard against hydrostatic pressure development, drainage must be installed behind the wall. A typical wall drainage detail is shown on Figure 3. With wall backit placed and compacted as recommended and drainage properly ins:ailed, '.:nrestrained walls can be designed for an active earth pressure equivalen: :o a fluid weighing 35 pcf. For restrained walls, an additional rj uniform lateral pressure of 100 psf should be included. These values assume a horizontal backfill condition and ■ that no other surcharge loading, such as traffic, sloping embankments, or adjacent buildings, will act on the wall. If such conditions exist, then the imposed loading must be included in the wall design. Friction at the base of the wall foundation and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 5.4 of this report. 5.7 Stormwater Detention Vaults We recommend constructing stormwater detention vault footings to bear on the site's native,dense to very dense till-like soils. We recommend placing vault wall backfill as structural fill as described in Section 5.2 of this report. A summary of the recommended geotec-rtical vault design parameters follows: • Allowable Bearing Capacity (FS=3): 6,000 psf(bearing on dense till-like soils) • Allowable Base Friction Coefficient (FS = 1.5): 0.35 • At-Rest Lateral Earth Pressure (drained): 35 pcf(equiv. fluid) + I00 psf(uniform) • Allowable Passive Earth Pressure (FS= 1.5): 350 pcf(equiv. fluid) • Seismic Lateral Earth Pressure: 8H psf(uniform) We recommend providing drainage for the detention vault walls consisting of placing composite drainage panels with full coverage against the walls. The panels should extend to the invert of the wall drain consisting of a perforated, four-inch diameter PVC pipe enveloped in washed drain rock or pea gravel placed around the vault's perimeter. The perforated drain pipe should be placed with its invert no higher than the vault's dead storage elevation, 5.8 Drainage Surface Final exterior grades should promote free and positive drainage away from the building areas. We recommend providing a gradient of at least three percent for a minimum distance of ten feet from the building perimeter, except in paved locations. In paved locations, a minimum gradient of one percent should be provided, unless provisions are included for collection and disposal of surface water adjacent to the structure. Page No. 8