ARCHIVED REPORTS_2002_3 JTD - Laserfiche WebLink

Home Browse Search

• All landfill surface water is routed to one of three sedimentation basins see Drawing 9. The sedimentation basins for the existing Forward Landfill are located in the southwest corner of the site, on either side of the South Branch. The sedimentation basin for the existing Austin Road Landfill is located southwest of the existing Austin Road Landfill. Water collected in the sedimentation ponds is sampled in accordance with the site's Stormwater Pollution Prevention Plan (SWPPP) before it is discharged to the North or South Branches. The erosion control measures incorporated in the site design include the following: • Collection and control of runoff, diverting it away from highly erodible areas. • Construction of intermediate and final landfill slopes with drainage benches at intervals designed to control slope runoff velocities and volumes. • Hydroseeding with fast germinating drought-tolerant grass seed on intermediate surfaces that will be exposed for more than 180 days and all surfaces that are at final grade. Seeded surfaces will be watered until growth is well established. Proposed landfill slopes for the three major areas of the Forward Landfill were • evaluated using the Universal Soil Loss Equation (USLE) (see Drawing 11). The evaluation method determines the potential for soil erosion based on the rainfall and runoff factor, the soil erodibility factor, the topographic factor derived from the slope gradient and length, the cover and management factor, and the support practice factor. The evaluation indicates that the average soil loss will be approximately 1.0 to per acre per near for each area evaluated which is below the two tons per acre per year allowed by the CIWMB. The vegetative layer of the final soil cover will be seeded with native grasses to protect the upper layer of soil, and to minimize erosion. 5.2.6.2 REALIGNMENT OF LITTLE JOHNS CREEK The North Branch of the South Fork of Little Johns Creek is currently located to the south of the existing Austin Road Landfill footprint (see Drawing 2). For the future Forward Landfill, this creek will be realigned to the north and west of the existing Austin Road Landfill footprint. This proposed realignment increases the overall length of the creek by three percent, with a proportionate change in slope, or grade, of the channel. The creek will exit the landfill site at essentially the same • location at which it now exits. The new realigned creek will provide the same Forward Landfill JTD 5-10 L:\Allied\2000.193\Reports\td:Sec-5.0:05/24/02 BRYAN A.STIRRAT&ASSOCIATES