Big Bend Dam takes its name from the unique bend in the Missouri River seven miles upstream from the dam. Construction of the dam began in 1959 and the embankment was completed in July 1963. Big Bend dam is 95 feet (29 m) high and 10,570 feet (3,220 m) in length. Power generation began at the facility in 1964 and the entire complex was completed by 1966. The hydroelectric plant generates 493,300 kilowatts of electricity at maximum capacity, with an annual production of 969 million kilowatt hours, and meets peak-hour demand for power within the Missouri River Basin.
Build a flexible virtually maintenance free oil containment system on the tailrace deck of the Big Bend Dam that offered 24/7 continuous protection against catastrophic oil spills and would prevent any hydrocarbons from being discharged into the river.
SorbWeb Plus with SAM was selected as the secondary oil containment system most appropriate for this project. SorbWeb™Plus is passive oil containment system that incorporates two special smart layers. The system incorporates two unique geotextiles which allow water to pass through freely. One layer is designed to manage chronic leaks while the other is designed to seal on contact with oil preventing any hydrocarbons from escaping the oil containment. Perhaps its most attractive attributes are the flexibility and maintenance free continuous protection it offers making it the ideal solution for this project.
Scope of Work
Main Unit Transformer Oil Containment Design
Big Bend has four (4) three-phase transformers located on the tailrace deck. The transformers are enclosed in concrete walls on three sides, with the downstream side open. The upstream wall is the powerhouse while the other two are firewalls. Each of the main unit transformers contains 14,530-gallons of oil and weighs 382,500-pounds.
A curb was placed on the downstream side of the powerhouse to provide enough containment to hold all of the transformer oil and a 25-year 24-hour (4.25”) storm event.
Flexible oil containment
SorbWeb Plus with SAM passive oil containment system was installed in the lower section of each transformer vault. This passive system will allow storm water to flow through while containing any hydrocarbons.
The special oil absorbing mat “SAM” was placed within the containment and it will be used to help collect small chronic leaks of the existing transformer to protect the life of the SorbWeb™Plus passive system.
Fire quenching stone was then placed on top of the SorbWeb™Plus system to help extinguish puddle fires. In the event of a catastrophic oil failure, the passive SorbWeb™Plus system will solidify creating a water-tight barrier inside the vault. This will prevent any hydrocarbons from reaching the drain and being discharged into the river.
Oil containment around a transformer
Station Service Transformer and Delta Feeder Transformer Oil Containment
Big Bend also has two (2) station service transformers and one (1) delta feeder transformer located on the tailrace deck. The station service transformers are located against the powerhouse wall with the other three sides open to the atmosphere. Each of the station service transformers contains 1,080-gallons of oil and weighs 24,000-pounds.
The delta feeder transformer is located against the powerhouse wall with the other three sides open to the atmosphere. The delta feeder transformer contains 483-gallons of oil and weighs 12,027-pounds. Delta feeder transformer containment was combined with station service transformer 1.
SAM Oil Absorbent layer
Once again curbs were installed around the station service transformers. Station service transformer 2 has its own containment area while station service transformer 1 containment was combined with the delta feeder transformer. The curbing was sized to contain all the oil in each transformer within the containment area plus a 25-year 24-hour (4.25”) storm event. The passive SorbWeb™Plus system was installed both at the station service transformers as well as the Delta Feeder’s.
In the event of a catastrophic oil failure, the passive SorbWeb™Plus system will solidify creating a water-tight barrier inside the containment area. This will prevent any hydrocarbons from reaching the drain and being discharged into the river.