1802 Failure of Puentes II Dam

ABSTRACT ONLY - Since the mid-1600s, four dams have been constructed at the site of Puentes Dam, located in southeast Spain, about 8 miles west of the City of Lorca. The first dam (Puentes I) was intended to be about 80 feet tall, and was destroyed during construction in 1648 by a flood just after the foundation was completed. A second dam (Puentes II) was constructed in 1791 and was about 165 feet tall. The gravity dam consisted of rubble masonry and ashlar facing, with a pile foundation and downstream apron. Beginning in March of 1802, extreme rains fell in the region and the water level in the reservoir rose nearly 140 feet during March and April. On April 30, 1802 at 2:30pm, a large volume of reddish water was reported leaking from the downstream toe and within one hour a loud 'explosive'• sound was noted. Seepage through the foundation had undermined the gravity dam and released a 35-foot-high wall of water towards the City of Lorca. Six-hundred and eight people lost their lives, 809 houses were destroyed, and 229 country dwellings were washed away. Approximately thirty factories, eight mills, and nine hotels were also destroyed. The effects on the local economy and agriculture were catastrophic.
This paper presents a case history with multiple lessons learned over centuries of improvements in dam safety technology. One key lesson to be learned relates to the dangers of extrapolating experience from small dams to large dams - specifically as it relates to seepage through alluvial foundations. We will also discuss the design of Puentes II Dam in the context of the design criteria at the time, and how the lessons learned from this failure informed the design and construction of numerous other dams in Europe for the next several decades, including two subsequent dams designed and constructed at the Puentes Dam Site.