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0 •.. DRAINAGE 1 .:: EROSION CONTROL <br />U <br />3.6.1 DRAINAGE CONTROL SYSTEM DESIGN <br />The primary function of the Forward Landfill Stage IA drainage control system <br />is to collect and convey storm water in a controlled manner to minimize <br />erosion and infiltration of storm water into the refuse prism. The following <br />sections describe the site hydrology and proposed drainage control features. <br />3.6.1.1 HYDROLOGY <br />A hydrology study was prepared in August 2001 for the proposed conditions <br />at the entire Forward Landfill site. The study was conducted in accordance <br />with 27 CCR, Section 20365. The objective of the hydrology study was to <br />calculate storm water run-off for sizing and location information for the entire <br />site's storm drain facilities at closure. <br />The Rational Method hydrology utilizing guidelines set forth in the San <br />Joaquin County hydrology manual was used to calculate peak discharge <br />rates for a 24-hour, 1,000 -year storm event. A computer program developed <br />by Advanced Engineering Software was used to compute the run-off. The <br />hydrology study map indicating drainage subareas and discharge points and <br />calculations for on site and off-site flows is presented on Figure 1 of Appendix <br />D. A summary of the peak discharge rates are included in the hydrology <br />study calculations included in Appendix D. To size the downdrains for the <br />Stage IA partial closure area the Ci factors (runoff coefficient/rainfall intensity) <br />was determined from the hydrology study. The Stage IA partial closure area <br />was broken into smaller subareas to calculate the flow for each downdrain. <br />The calculations for the downdrain sizing 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 <br />directly adjacent to Little Johns Creek. <br />Forward Landfill PFCPCMP 3-11 <br />Z:\PROJECTS\Al lied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-sec3.doc: 6/16/2008 <br />