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8.A. - Page 37 <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 />s) The outfall for the bio -retention basins shall release the discharge near the <br />base of the seasonal creek and shall not be allowed to flow over the top of <br />the creek banks. <br />t) Cut-off plugs consisting of controlled density fill about 2 feet wide and <br />keyed into the native soils shall be installed at 25- to 50 -foot intervals along <br />all pipeline trenches and at the beginning, midpoints, and ends of the culvert <br />and all 36 -inch -diameter detention pipes. Specific recommendations for the <br />cut-off plugs shall be presented in the design -level geotechnical report. <br />u) All proposed structures shall be designed in accordance with the seismic <br />design criteria of the 2010 California Building Code (CBC) or other recent <br />applicable building code. <br />v) Cut areas in serpentinite and exposed fill slopes composed of serpentinite <br />rock shall be capped with asbestos -free soil. <br />21 <br />