5010 DOVER ST Geotech Report 2025-07-31

August 22nd 2022 G-5756 Ben Erickson Page 5 resisted by friction between the foundation and the supporting subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter case,the foundations must be poured"neat" against the existing undisturbed soil or be backfilled with compacted structural fill. Our recommended parameters are as follows: -Passive Pressure(Lateral Resistance) 350 pcf, equivalent fluid weight,for structural fill or competent undisturbed native soil -Coefficient of Friction(Friction Factor) 0.35 for structural fill or competent undisturbed native soil. Concrete Slabs-on-Grade Slab-on-grade floors should be constructed on a firm,unyielding subgrade. During preparation of the slab subgrade, any areas of the subgrade that have been disturbed by construction activity should be either re-compacted or excavated and replaced with compacted structural fill. We recommend that structural fill placed below slab-on-grade floors conform to the earthwork and grading recommendations provided in this report. To avoid moisture build-up on the subgrade,the floor slab should be placed on a capillary break, which is in turn placed on the prepared subgrade. The capillary break should consist of a 6"-minimum thickness layer of crushed rock or gravel that contains no more than five percent material finer than a No. 4 sieve. A vapor barrier, such as a 10-mil plastic membrane,should be placed over the capillary break and taped or sealed to minimize water vapor transmission upward through the slab, if post-construction vapor transmission is undesirable. Drainage Water should not be allowed to stand in areas where footings, slabs, or pavements are to be constructed. Final site grades should provide drainage away from the building structure. Footing drains,consisting of a 4-inch minimum diameter,rigid perforated drain pipe, should extend around new perimeter foundations and be installed behind new retaining walls. Footing drains should be bedded in washed drain rock and the rock wrapped with geotextile filter fabric, such as Mirafi 140N,or equivalent,as illustrated Plate 4—Typical Footing Drain. The drain rock should extend above the base of the vertical drain mat.Roof and other drain lines should not be connected to the footing drain system. We recommend installing a sump pump system if the GEO Group Northwest,Inc.