Allen Hazen (August 28, 1869 – July 26, 1930) was an American civil engineer and an expert in hydraulics, flood control, water purification and sewage treatment.

Hazen was born in 1869 on his family farm located near the Connecticut River close to the small town of Norwich, Vermont.

In 1905, the two engineers published an influential book, which contained solutions to the Hazen-Williams equation for pipes of widely varying diameters.

[5][6] In 1908, Hazen was appointed by President Theodore Roosevelt to a panel of expert engineers to inspect the construction progress on the Panama Canal with President-elect William H. Taft.

Hazen specifically reported on the soundness of the Gatun Dam (an integral structure in the canal system), which he said was constructed of the proper materials and not in any danger of failure.

[7] Late in his career, Hazen concentrated on ways to statistically describe the recurrence interval of flood flows in rivers.

Hazen’s early work at the Lawrence Experiment Station established some of the basic parameters for the design of slow sand filters.

As a conservative engineer, Hazen recommended that the City install slow sand filters to remove both turbidity and harmful bacteria from its water supply.

[2] At the age of 24, Hazen was charged with the responsibility for sewage collection and disposal for the 1893 Chicago World’s Fair and Columbian Exposition.

[10][13] In 1897, Allen Hazen opened up a single person practice in New York City and for a couple of years, shared the same address as one of his professional colleagues, George W. Fuller at 220 Broadway.