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8.A. - Page 46 <br />c) All drilled pier foundations shall be designed for soil creep <br />pressures. <br />d) Permanent drainage measures shall be installed on all lots to <br />intercept surface water infiltration and migrating subsurface water <br />and thus reduce the likelihood of soils becoming wet and unstable. <br />e) Drilled pier foundations shall be used for houses on sloping lots. <br />f) Detailed foundation explorations shall be performed for each lot <br />during the design -level geotechnical investigation to collect site- <br />specific data regarding slope creep, expansive soils, and serpentinite <br />rock. <br />g) Garage slabs on grade, driveways, walkways, sidewalks, and pavers <br />shall have sufficient reinforcement and be supported on a layer of <br />non -expansive fill. <br />h) All residences, retaining walls, and bio -retention basins shall be <br />supported on drilled, cast -in-place, straight -shaft friction piers or <br />similar construction. Consideration shall be given on a case-by-case <br />basis to the need for extra steel reinforcement of the piers and grade <br />beams, voids beneath grade beams to mitigate uplift distress to the <br />structures, perimeter subdrains and moisture barriers, and <br />construction precautions for concrete over -pours at the tops of the <br />drilled piers. <br />i) Proper detailing of construction and control joints for concrete slabs <br />shall be considered in the final design of sidewalks and patios in <br />areas of expansive soils. For example, a construction joint with rebar <br />dowels may be provided when concrete slabs on grade meet the <br />proposed perimeter foundation for the residence to minimize vertical <br />offset from soil expansion or shrinkage. <br />j) A detailed creek bank evaluation shall be performed during the final <br />geotechnical investigation once grading and improvement plans are <br />available. <br />k) The design -level geotechnical investigation for Lot 13 and all lots <br />along the downhill side of Laurel Way shall evaluate the potential <br />for creek bank erosion or landsliding, and provide mitigation <br />measures as appropriate. <br />1) All proposed structures and improvements shall be set an appropriate <br />distance from the top of the existing creek banks as determined by <br />the City and per the requirements of Zoning Ordinance <br />Section 32.12. <br />m) Consideration shall be given to biotechnical creek bank stabilization <br />methods and limiting surface water runoff into the creek. <br />n) Install a subdrain system of perforated pipe and permeable drain <br />rock or gravel as needed to mitigate potential springs that could <br />occur during the winter. Subdrains shall be installed where seepage <br />till <br />