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Revision d3- Page 5 0( 30 mining progresses across the permit azea. The pumps will discharge the groundwater into a settlement pond that will be located near the northwest corner of the site. Once the groundwater enters the settlement pond, it will percolate and recharge back into the water table or discharge to the Canning Factory Ditch located on the north side of G Road. (4) Mining for sand and gravel will lag slightly behind the overburden highwall. The height of the sand and gravel highwall will be approximately 400-ft long and 12-ft tall. As the sand and gravel material is removed, it will be conveyed or trucked out of the pit for further processing. If the sand and gtavel highwall is located within 100-ft of the north, south or west Permit boundary areas, all mining below the water table shall occur at a 3:1 max slope to minimize the potential of a landslide large enough to damage offsite stmctures. (5) Once the area has been mined for the sand and gravel, overburden material removed in front of the active sand and gravel highwall area (and imported inert fill material) will be placed. The backfilling operations will lag behind the active sand and gravel highwall area . The backfill will be placed such that adequate compaction of the fill material can take place. The may be accomplished by backfilling the area in lifts, or by placing the fill on a gradual slope such that equipment have safe access to place and compact the fill material. Backfill materials will not be placed underwater. (6) Site reclamation in accordance with the reclamation plan section. (b) Earrhmoving Initial earthmoving on the project site will be performed to ensure all drainage will be contained within the project site. This will require a surface drainage Swale to be installed along the southern edge of the project site to contain surface flows within the project area. The drainage Swale will slope towards a new retention pond, which will be excavated near [he west property line. Another drainage Swale will be cut along the north and northwestern portion of the project site to collect runoff' from within the project site and divert it to the new retention pond. The new retention pond, located along the west property line, will be sized to retain the 100-year storm event, as specified in the May 1996 edition of the Srormwarer Management Manua! jor the City ojGrondJuncrion and Mesa County. The pond will have a storage volume ofapproximately 109,000 cubic feet, and will be approximately 600 ft long by 50 ft wide, and 6 ft deep. The project will also require the construction of a settlement pond near the northwest comer of the site. The settlement pond will be a maximum of one acre in size, with 3H:1 V side slopes. The overburden removed from the pond area will be stockpiled around the pond perimeter. Earthmoving for the sand and gravel mining operations will consist of excavating the overburden soils, mining the sand and gravel, and backfilling the excavated areas using overburden soil and imported site materials. The typical sequence of operations is discussed in part (a) above. (c) Al/water diversion and impoundment's The project site is currently hydraulically isolated from upgradient and adjacent property surface Flows. An irrigation ditch located on the adjacent property to the east collects upgradient runoff and diverts it to the south. An existing catch basin located at the southeast comer of 23 Road and G Road collects stotmwater runoff from the south half of G Road. Once the flows enter the catch basin, it is routed through a culvert pipe under G Road and dump into the Canning Factory Ditch located along [he north side of G Road.