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3.6.1.1 HYDROLOGY <br /> A hydrology study was prepared in August 2001 for the proposed conditions at <br /> the entire Forward Landfill site. The study was conducted in accordance with 27 <br /> CCR, Section 20365. The objective of the hydrology study was to calculate <br /> storm water run-off for sizing and location information for the entire site's storm <br /> drain facilities at closure. <br /> The Rational Method hydrology utilizing guidelines set forth in the San Joaquin <br /> County hydrology manual was used to calculate peak discharge rates for a 24- <br /> hour, 1,000-year storm event. A computer program developed by Advanced <br /> Engineering Software was used to compute the run-off. The hydrology study <br /> map indicating drainage subareas and discharge points and calculations for on <br /> site and off-site flows is presented on Figure 1 of Appendix D. A summary of the <br /> peak discharge rates are included in the hydrology study calculations included in <br /> Appendix D. To size the downdrains for the Stage IA partial closure area the Ci <br /> factors (runoff coefficient/rainfall intensity) was determined from the hydrology <br /> study. The Stage IA partial closure area was broken into smaller subareas to <br /> calculate the flow for each downdrain. The calculations for the downdrain sizing <br /> are included in Appendix E. <br /> In addition, 100 year flood conditions were also reevaluated to develop a <br /> maximum flood elevation along the north and west perimeters of the site directly <br /> adjacent to Little Johns Creek. <br /> 3.6.1.2 PROPOSED FINAL DRAINAGE CONTROL SYSTEM <br /> The proposed final drainage control system for the Forward Landfill Stage IA is <br /> shown on Drawing Sheets 3, 4, 5, 6 and 7. Runoff is directed to the natural <br /> drainage course. <br /> The proposed final drainage control system for Stage IA will include exterior <br /> slope AC downdrains, and topdeck drainage berms, deck inlets, bench drains <br /> and inlets. Runoff is directed to the natural drainage course. Stage IA drainage <br /> improvements will also include placement of additional soils along the perimeter <br /> road to increase the elevation of the road above historic and potential flood <br /> ® levels. Drainage details are presented in Drawing Sheets D-1, D-2, and D-3. <br /> Forward Landfill PFCPCMP 3-11 <br /> ):\Allied\Forward\2005.0051 Partial Closure\Partial Closure Plan\FL-sec3.doc:6/15/2005 <br />