LA, Philadelphia engineers conduct hydraulic steel structure inspection at Sepulveda Dam

VAN NUYS, California – Engineers with the U.S. Army Corps of Engineers Los Angeles and Philadelphia districts performed a periodic hydraulic steel structure inspection of Sepulveda Dam March 22-23 in Van Nuys.

The dam on the Los Angeles River is a massive concrete structure, easily visible from two major freeways and has been used as a location for numerous films. To perform the inspection, structural engineers Robert Lawrence and Joseph Cervantes, both of Philadelphia, ventured deep into its cavernous rooms of hydraulic equipment with the LA District team.

Seven submersible spillway crests – drum, gates and vertical lift gates – were visually inspected, said Gabby Bernaldino, LA District civil engineer.

“The crest gates are designed to float on water in a chamber, located inside the spillway crest,” she said. “They operate automatically and rise as the reservoir water surface elevation rises. The gates are set for fully automatic operations, but (they) can also be operated in semi-automatic or emergency manual mode.”

The purpose of the inspection was to detect any potential damage, deterioration or signs of distress within the structure and to identify any maintenance repair requirements.

Inspections are done in accordance with the Corps’ regulations to ensure the dam’s critical internal infrastructure – structural elements that could render it inoperable – is fit for service. The inspections are best done when there’s no water present, as per engineering regulations. During the inspection, the LA River at Van Nuys was very shallow.

“The inspection procedure was designed to detect damage, deterioration or signs of distress to avert any premature failure of the structure and to identify any future maintenance or repair requirements,” Bernaldino said.

Prior to the inspection, LA District personnel received confined space training. Before anyone entered the structure, heavy steel plates and matching gaskets on top of the dam were removed from deep ventilation shafts that descend to a tunnel spanning the length of the dam. Ventilation hoses like those used by firefighters were inserted to remove any toxic gas buildup, and then the air quality was checked. Once the safety protocol was completed, Corps’ personnel went inside.

Entry to Sepulveda Dam’s interior is a boxy, castle-like concrete cube at the top. Once inside, a series of long stairwells lead to the seven spillway gates and the tunnel at the very bottom. Now 80 years old, the dam contains a mixture of vintage and modern equipment. Time-yellowed schematics used during construction hang on walls, along with an ancient intercom system, while modern LED lighting provides illumination. At some points, daylight can be seen through heavy grates above the Los Angeles River.

The Corps acquired more than 2,100 acres of land for construction, operations and maintenance of the Sepulveda Dam, which was built in response to historic flooding of Los Angeles in 1938. The dam was completed in December 1941 and dedicated in 1942. It marks the beginning of the channelized LA River. Together with Hansen and Lopez dams, Sepulveda is vital for flood-risk management for portions of the San Fernando Valley and areas contiguous to the LA River.

The primary purpose of the dam and reservoir is flood-risk management, but the project also is authorized for recreation.

Of the total acreage, the Corps reserves 313 acres of land for dam operations, and more than 1,500 acres have been leased to the City of Los Angeles for recreational purposes.

The Sepulveda Basin is a popular recreation area with a model plane airport, softball fields and a Japanese garden. It is home to a variety of species and is an important nesting area for birds.