The Clover Valley Foundation and the Sierra Club have sued the city. They allege Rockin’s approval of 588 homes in the area violates California’s Environmental Quality Act. The development, they contend, would involve excessive removal of trees, improper treatment of prehistoric sites, and air and water pollution. Also, opponents of the plan say they have enough signatures to force the issue to a city vote and potentially overturn it. Backers of the development say developers have already made concessions to their plans, cutting back on the number of planned homes. The City Council is expected to hear the issue at its meeting on Oct. 9.