ARCHIVED REPORTS_2002_1 - Laserfiche WebLink

Home Browse Search

3.6 DRAINAGE AND EROSION CONTROL 3.6.1 DRAINAGE CONTROL SYSTEM DESIGN The primary function of the Forward Landfill Stage IA drainage control system is to collect and convey storm water in a controlled manner to minimize erosion and infiltration of storm water into the refuse prism. The following sections describe the site hydrology and proposed drainage control features. 3.6.1.1 HYDROLOGY A hydrology study was prepared in August 2001 for the proposed conditions at the entire Forward Landfill site. The study was conducted in accordance with 27 CCR, Section 20365. The objective of the hydrology study was to calculate storm water run-off for sizing and location information for the entire site's storm drain facilities at closure. The Rational Method hydrology utilizing guidelines set forth in the San Joaquin County hydrology manual was used to calculate peak discharge rates for a 24-hour, 1,000-year storm event. A computer program developed by Advanced Engineering Software was used to compute the run-off. The hydrology study map indicating drainage subareas and discharge points and calculations for on site and off-site flows is presented on Figure 1 of Appendix D. A summary of the peak discharge rates are included in the hydrology study calculations included in Appendix D. To size the downdrains for the Stage IA partial closure area the Ci factors (runoff coefficient/rainfall intensity) was determined from the hydrology study. The Stage IA partial closure area was broken into smaller subareas to calculate the flow for each downdrain. The calculations for the downdrain sizing are included in Appendix E. In addition, 100 year flood conditions were also reevaluated to develop a maximum flood elevation along the north and west perimeters of the site directly adjacent to Little Johns Creek. Forward Landfill PFCPCMP 3-11 Z:\PROJECTS\Allied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-sec3.doc:6/16/2008