Amplification to the Final Environmental Impact Statement New River and Phoenix City Streams Flood Control Project, Maricopa County, Arizona

摘要

This amplification report addresses a point of concern raised by the Arizona State Historic Preservation Officer regarding the effect of the proposed project on Cave Creek Dam. Cave Creek Dam, a historic concrete arch dam, is within the reservoir area of the authorized Cave Buttes Dam, which is a major component of the New River and Phoenix City Streams Flood Control Project. It was determined that modifications to Cave Creek Dam sufficient to make it meet the Corps Dam safety standards would be prohibitively expensive and would alter the physical appearance of the dam. The recommended plan allows the dam to be overtopped, but creates a stilling pool no more than 10 feet lower than the floodwater being impounded by the historic dam. This pool minimizes the physical stresses on the dam, provides stability during floods, and absorbs the erosive energy of floodwater overtopping the dam, thus preventing the dangerous undermining of the dam's foundation.