3121 8TH ST AB 2016-01-01 MF Import

June 1. 2008 Duplcx Building L&A Joh No. ftA055 Pagc 1 �1 Wc recommend that a minimum 4-inch-thick layer, compacted, 7/8-inch crushed rock base (CR33), be used for the driveway. Thc crushed rock base should be topped with a 3-inch-thick Class B asphalt conereie (AC) surface eourse or a 4-ineh conerete reinforeecl pavement with a layer of welded wire fabric at mid-depth. DRAINAGG CONTROL Onsite Stormwatcr Disposal The sitc is underlain by very-dcnse Gesh till soils al shallow depth. The Iresh till soils arc of extremcly low pemicability and onsite disposal of stormwater on site by infiltration or dispersion would be impractical. Also, thc site is (lanked by a steep slope on its east side. Onsite stormwater disposal may cause increase of concentrated groundwater seepage out of this steep slope. Groundwater emerging out this slope under high seepage pressure in the wet winter months may cause erosion in and above the seepage, which could dest�bilize the slope. Thereforc, storm runofi' collcctcd ovcr roofs and driveway should be tightlined to discharge into a nenrby storm sewer. I3uilding �ootprint �xcavation Duilding footprint excavation for the proposed duplex building, if encountering groundwatcr seepage, shoald have bottom of crcavation sloped and ditches excavated along bases of the cut banks to direct collected ground��ater into sump pits lrom �vhich wa[er can be puntped out. A layer of 2-inch crushed rock should bc placed ovcr footing bearing subgrade soils, as rcquired, to protect the soils from disturbance by construction traffia This crushed rock base should be built to a few inclies above groundwat�r lcvel, but not less than 6 inches thick. The crush rock basc sliould be compacted in 12-incli lifts to a non-yielding statc �vith a vibratory mechanical compactor. LIU & ?.SSOCIAT�S, INC.