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8.A. - Page 43 <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 />is observed, and a conceptual subdrain plan shall be prepared once <br />grading plans have been finalized. <br />o) A geotechnical engineer shall be on site during or just following <br />heavy rainstorms to evaluate and map the locations of springs on the <br />site, and provide recommendations for mitigating the adverse <br />impacts of springs or seeps, if necessary. <br />p) The shallow landslide area on Lots 14 and 15 shall be completely <br />removed down to bedrock, and the grade rebuilt with a keyed and <br />benched engineered buttress fill containing subdrains. <br />q) Further evaluation of the questionable landslide near the bottom of <br />Lots 3 and 4 shall be performed during the design -level geotechnical <br />investigations for Lots I through 4 to provide detailed <br />recommendations for keyways, benching, and subdrains. The design - <br />level geotechnical investigation shall determine whether mitigation <br />is needed to reduce the potential for damage to the planned site <br />improvements and the potential for adversely affecting neighboring <br />properties. <br />r) The bottom of the bio -retention basins on Lots 5, 7, S, 9, and 10 shall <br />be lined with HDPE liner to limit water infiltration into the native <br />soils below the permeable filter soils. A subdrain shall be installed <br />above the HDPE liner to intercept the excess water and direct it to a <br />suitable discharge point. The specific recommendations for the <br />HDPE liner system and subdrains shall be presented in the design - <br />level geotechnical report. <br />27 <br />