2022-05-06_REVISION - M1998105 (3)

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management practices by directing and controlling surface water runoff that enters the disturbed areas. More information on sediment and surface water control is provided below. 6.1 . Surface Water Handling There are three drainage basins that collect all stormwater runoff on and around the Delta Paving site. These can be seen in Maps C-1, C-2, and F-1 The first is approximately 63 acres and includes the areas in the east of the site that contain the reclaimed lake, currently disturbed area, irrigated fields, and part of the vegetated area in the north. This basin is isolated from offsite surface water, and all water within this area drains to the existing lake in the center of the site. Water collected in the lake is then pumped to the permitted outfall location in the Relief Ditch. The pump allows for the water discharge rate to be controlled preventing erosion of the drainage ditch. The second drainage basin is approximately 29 acres encompassing the southern portion of the permit area and the connected fields to the south. All water within this area drains to the northwest of the fields where it eventually infiltrates into the native soil. The third drainage basin is approximately 40 acres of irrigated fields and vegetated banks in the west of the permit area. Water within this basin drains to the northwest where it can infiltrate into the soil. The surface drainage patterns will not be affected in these two basins until Phase 2 and 3 of mining. 6.1.1. Mining During all phases of mining, and for each drainage basin, surface water runoff will drain to the active mining pit. For Drainage Basin 1, some runoff will collect in the reclaimed lake. Map C-2 shows the anticipated drainage patterns during mining. The site road will be graded to drain into the pit area. Grading of the site to drain internally ensures that no sediment laden water flows enter the river or any other natural waterways. There is more than enough storage within the pits to contain the 5-year and 100-yr storm events. Water collected within the pit will be routed to the pit dewatering pump to be pumped to the existing lake, which acts as a sediment pond. Process water from the processing area will drain to the existing lake. This sediment pond will allow for suspended solids to settle so clean water can be discharged to the permitted discharge location in the Relief Ditch. As the water is being discharged into the drainage canal via a pump, the discharge rate can be controlled to prevent erosion of the ditch. 6.1.2. Post Reclamation The drainage patterns during mining will be retained following reclamation of the site. Any surface water runoff will collect in the reclaimed ponds where it can either infiltrate into the groundwater aquifer or evaporate. There is enough storage capacity above the anticipated lake level and the top of the lake to store the 5-year and 100-year storm events. More on those calculations is provided below. Delta Paving Gravel Pit April 2022 G-3 Lewicki&Associates