5117 23RD AVE W 2016-01-01 MF Import

G.eotechnical Engineering Report 51 17 23rd Ave W January 2, 2009 RMI File No. 50909 Pagc G Site Drainagc Surfr.ce Drainage: Water should not be allowcd to stand in any area where footings are to be consiructed. Final site grades sliould allow for drainage away from the buildings. We suggest that t'ie finished ground he sloped at a minimum gradient of 3 percent. Existing drainage from the house should be replaced with rigid PVC and taken to the base of the slope. It should discharge through a diffuser on a rock mattress. Subsurface Drainage: It is good practice to use footing drains around all of the structures where moisture control is important. Footing drains should be installed at least I foot below the planned finished footing elevation. The drains sliould consist of 4-inch-diameter, rigid, perforeted PVC �ipe that is surrounded by free-draining matcrial, such as pea gravel and wrapped in a non-woven filter fabric such as Mirafi 140NSL. We recommend that the free-draining material consist of an 18-inch-wide zone of clean (less than 3 pereent fines), granular material piaced along the back of the wall. Pea gravel is an acceptable drain material or a drainage composite may be used. The free-draining material should extend up rhe wall to 1 foot below the finished surface. The top foo! of soil should consist of impermeable soil placed over plastic shecting or building p�per to minimize surface water or fines migration into the footing drain. Footing drains should disch irge into tightlines leading to an approved discharge location such as the base of the slope. Retaining Walls You propose to replaoe the existing wooden retaining wall wi[h a reicforced concrete wall aporoximately 50 fcet long and approsimately G fcet I�igh. We suggest that you consider limiting the wall height to 6 feet and if unsuitable soil is 1'ound at footing clevation either have the contractor overexcavate to the medium dense or better native soil and backfill with crushed rock or rock spalls to the level at which the footing will rest or support this section of the wall on pin piles both vertical and raked. If a 9016. minimum jack hammer is used to drivc the nominal 2" diametcr piles to less than 1" penetration per minutc the design load of each pile may be taken as 2 tons. This will keep the cost down. Do note that he will h�ve to compact soil on the outside of thc retaining wall to not less than 2 feet from the top of the w�ll. RMI ASSOCIATES LLC (� I I�