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8.A. - Page 39 <br />barriers, and construction precautions for concrete over -pours at the tops of <br />the drilled piers. <br />i) Proper detailing of construction and control joints for concrete slabs shall be <br />considered in the final design of sidewalks and patios in areas of expansive <br />soils. For example, a construction joint with rebar dowels may be provided <br />when concrete slabs on grade meet the proposed perimeter foundation for <br />the residence to minimize vertical 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 along the <br />downhill side of Laurel Way shall evaluate the potential for creek bank <br />erosion or landsliding, and provide mitigation 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 the City <br />and per the requirements of Zoning Ordinance 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 rock or <br />gravel as needed to mitigate potential springs that could occur during the <br />winter. Subdrains shall be installed where seepage is observed, and a <br />conceptual subdrain plan shall be prepared once grading plans have been <br />finalized. <br />o) A geotechnical engineer shall be on site during or just following heavy <br />rainstorms to evaluate and map the locations of springs on the site, and <br />provide recommendations for mitigating the adverse impacts of springs or <br />seeps, if necessary. <br />p) The shallow landslide area on Lots 14 and 15 shall be completely removed <br />down to bedrock, and the grade rebuilt with a keyed and benched <br />engineered buttress fill containing subdrains. <br />q) Further evaluation of the questionable landslide near the bottom of Lots 3 <br />and 4 shall be performed during the design -level geotechnical investigations <br />for Lots 1 through 4 to provide detailed recommendations for keyways, <br />benching, and subdrains. The design -level geotechnical investigation shall <br />determine whether mitigation is needed to reduce the potential for damage <br />to the planned site improvements and the potential for adversely affecting <br />neighboring properties. <br />r) The bottom of the bio -retention basins on Lots 5, 7, 8, 9, and 10 shall be <br />lined with HDPE liner to limit water infiltration into the native soils below <br />the permeable filter soils. A subdrain shall be installed above the HDPE <br />liner to intercept the excess water and direct it to a suitable discharge point. <br />The specific recommendations for the HDPE liner system and subdrains <br />shall be presented in the design -level geotechnical report. <br />23 <br />