Attorneys for the mining conglomerate Cemex filed their latest appeal in the effort to build a sand-and-gravel mine in Soledad Canyon, just east of the city of Santa Clarita. The mining company purchased the mineral rights to extract 56 million tons of aggregate, a material vital for construction that’s in rich supply there, according to the federal government. Cemex needs a beneficial-use permit from the State Water Resources Control Board to use the Santa Clara River in order to sustain its mining operations. … Opponents of the mine, which include the city, argue that the facility would add hundreds of truckloads daily to an already congested Highway 14, a massive amount of air pollution from mining operations, and impacts to the river, including about 322-acre-feet of water use annually.