Dam today

The upper portion of the dam was originally made of wood. Today, it is constructed of concrete. The 400-foot-long underground headrace tunnel was constructed of limestone with lime-sand mortar, creating an irregular, elliptical vault six-feet wide and seven-feet high. It was an impressive feat of engineering for its time. The clearing of the trench without mechanization might have been accomplished by using oxen or horses pulling scrapers. Underground construction of the millrace was necessary as the Old San Antonio Road passed right over the top of the millrace as it emerged from the river ford.