Bazalgette Overengineering

London’s sewage system was a hot 💩 mess in the 1800s. Not only did the city experience several cholera outbreaks, but at one point, the entire city smelled so bad that people named it The Great Stink.

Joseph Bazalgette was selected to lead the construction of London’s new sewerage system in 1859. There were many initial proposals made. Eventually, engineers came up with a final blueprint for the reconstruction.

However, this opportunity, like a full-scale sewage reconstruction, didn’t come often. Bazalgette needed to get it right for generations to come. He said,

And doubled the pipe diameters. Based on the Hagen-Poiseuille equation, the throughput was increased by at least 16x.

This skyrocketed the price and time to complete the construction. Many lawmakers and individuals opposed the project due to its scale and cost, but the plan was eventually ratified.

Not only did he 16x-ed the pipes, but he also used a bleeding-edge technology called Portland cement. It’s a specific type of cement that’s strong in water. Patented in 1824, Portland cement was a relatively new technology that was being actively improved in the 1840s and 1850s.

Nevertheless, Bazalgette was a strong proponent of using Portland cement. His bet eventually proved successful.

Much of Bazalgette’s system is still in use today, more than 150 years later (although there were minor rebuilds). Even though London’s population quadrupled in the 20th century, Bazalgette’s overengineered system was more than enough to handle the load.

According to analysis, if it weren’t for Bazalgette (and had gone with the initial proposed pipe diameters), the sewerage would’ve overflowed in the 1960s.

This is an old story, yet it resembles so many engineering decisions today.

Written 100% by a human being.