ARCHIVED REPORTS_2022 [REV] RCSI W/CHANGES

Home Browse Search

2-7 Forward Composting Facility SWT Engineering Report of Composting Site Information - August 2019January 2022 z:\projects\allied waste\forward\resource recovery facility\5 yr permit rvw 2019-2020\rcsi 2019\text\sec 2.doc 2.1.4 Grading and Drainage Plan The RRF/Compost Facility was upgraded in 2014 to meet the requirements of WDR Order No. R5-2014-0006 and WDR Order No. 2020-0012-DWQ . grading and drainage plan (Figure 6) shows the proposed2014 stormwater grading plan for of the RRF/Compost Facility. The grading plan is the same for all of the po tential composting options. A one percent minimum grade is provided at all points in the C ompost Facility site. The composting windrows and heaps are arranged normal to the site slope to allow free drainage and minimize any ponding. The composting pad will be constructed of compacted native soils. These soils are silt and clay and when compacted will provide a composting pad of relatively low-permeability soils. During periods of wet weather, the Compost F acility may suspend composting operations to prevent damage to the composting pad. Alternatively, economics may a llow construction of a gravel surfaced or asphalt paved composting pad to allow continuous operations. During periods of extreme wet weather, the Compost F acility may choose to not accept wastes. The site is sloped to drain surface water to perimeter ditches designed to conve y storm water from a 25-year, 10-minute duration storm event (0.368 inches) assuming all the water that falls o n the C ompost Facility site runs off. The ditches will carry the runoff water to a sedimentation (lined compost retention) basin, which is designed sized to hold the net average annual rainfall during months where rainfall exceeds evaporation (5.67 inches) assuming all the water that falls on the site composting runs off. This exceeds contain the 25-year, 24 -hour rainfall event (2.84 inches), with adequate freeboard. In accordance with WDR Order No. R5-2014-0006 and WDR Order No. 2020 -0012-DWQ, the compost pond is lined with a geosynthetic clay liner (GCL) overlain with a 60-mil HDPE geomembrane and contains a pan lysimeter . The location of the compost sedimenretentation basin is shown on Figure 2. All surface water runoff from the Compost Facility will be collected and stored in the sedimentation (compost retention) basin and evaporated. If necessary, cCollected runoff that meets water quality criteria for stormwater discharge may be discharged to the South Fork ormay be used to add water to the initial compost mixture to provide the desired initial moisture content, or evaporated. If necessary, collected runoff which does not meet the water quality criteria for stormwater discharge will be either pumped to a leachate evaporation impoundment or will be collected and removed for off -site disposal. 2.1.5 Pad Composition and Dimensions As detailed in the Lewis Engineering le tter, dated December 14, 2014, compost operations at the facility occur on a compacted pad that has a permeability no greater than the 1 x 10 -5 cm/sec regulatory requirement. The Compost Facility pad will be constructed of low permeability compacted nativ e soil. It is anticipated that the compacted native soil will provide adequate protection of groundwater. The compost pad area is utilized (i.e., the amount of area) based on the selected composting method and materials. The green and wood waste grinding area is approximately 1.56 acres. The material sorting area is approximately 1.07 acres, and the windrow areas are approximately 14.8 acres, and the ASP composting area is approximately 3 acres . The windrow curing and product screening area, and final product storage area is approximately 2.97 acres. The remaining acreage is for equipment and vehicle access roads, and the detention pond.