Why Wasn't Castlewood Worth a Dam?

Castlewood Dam was a masonry rock-fill dam constructed in 1890 across Cherry Creek approximately 30 miles southeast of Denver, Colorado. The dam contained an uncontrolled overflow spillway passing over the dam at about the middle of the crest length. The dam failed at approximately 12:15 am on August 3, 1933 after a heavy rainfall. The flood resulting from the dam break flowed through downtown Denver. The dam site and remains are now located within the boundaries of Castlewood Canyon State Park in Douglas County, as shown in Figure 1. After the dam was built, its safety was questioned by citizens downstream due to a number of problems with leakage, settlement, and cracking during its first 12 years of operation. Despite these initial problems, Castlewood Dam survived for over 42 years with only minor leakage issues during the last 30 years of its life. Following the failure, a few questions as to its exact cause remained. In this article we explore the cause of failure based on newly found evidence and modern evaluation techniques.