PERMFILE121056 - Laserfiche WebLink

Home Browse Search

required for maintenance or under upset conditions. Impoundment design, operation, maintenance, and reclamation information is provided in Exhibit 8w. While it has not been necessary to utilize the basin for this purpose, it is occasionally used to collect and retain minor quantities of Prepazation Plant wash-down water. As an incised and closed basin (ie: no outlet) the only inputs are thickener overflow, wash-down water from the Preparation Plant, or minor incident precipitation, which aze subsequently pumped back into the system by a portable floating pump installation. Water level in the sump is monitored and managed as part of the ongoing plant operations. SMALL AREA EXEMPTIONS AND ALTERNATIVE SEDIMENT CONTROLS The CDMG has approved several Small Area Exemptions (SAE'S) and Alternative Sediment Controls (ABC's) within the permit area. Effective drainage and sedimentation control in these areas will be achieved by a variety of methods, including gravel or asphalt surfacing, vegetative filters, installation of fabric filter fences, rock check dams, gravel filters or berms. Rockdust Tank A SAE for sedimentation control has been granted for the rockdust tank and truck access/unloading azea. The total disturbance will be approximately 0.5 acres. Of the total, 0.3 acres will be surfaced with pit run gravel, which acts as an infiltration screen for any overland flow associated with the rockdust tank and access/unloading area. Estimated peak flow from the area for the 10-year, 24-hour event is 0.04 acre-feet. Runoff from the topsoil pile is controlled by a berm/swale/rock filter system. in addition to the infiltration screen, flow from the tank and unloading azea is conveyed by means of swales and berms to a gravel filter. These measures, in conjunction with existing vegetation, aze effective in controlling runoff from the azea, as observed during previous inspections. Fish Creek Dewaterine Site . At the dewatering site, drainage and sediment will be controlled by the use of ABC's including filter fences, gravel filters, and existing vegetation. In reference to the 0.5 acre topsoil stockpile located to the southwest of the pond, a berm will be established around the stockpile to direct runoff from the stockpile to the two grave] filters by the stockpile. This will effectively treat the estimated 0.02 AF of runoff from the 10-yeaz, 24-hour event until temporary vegetation is established on the stockpile. Once this occurs, the berm and filters can be removed. The runoff from the 0.2 acre stockpile adjacent to the transformer will drain to the low area of negative drainage northeast of the stockpile where adequate vegetation exists to provide filtering and treatment of the water. The small area exemption is shown on Map 26, Fish Creek Borehole Area Facilities and Access Road. The collection TR 05-47 2.05-79.1 Revised - Mazch 2005