On July 29th, 4-7 inches of rain throughout central Mercer County, flooding parts of Princeton, Melrose, Lilly Grove, and Athens. Now, the rarity of the event is coming into scope.
At the wastewater treatment facility in Princeton, a continuous record of rain measurements has been ongoing since 1940. Another measurement period between 1900 and 1914 exists, bringing the entire period of records for Princeton to 92 years. The July 29th rainstorm dumped 5.78 inches of rain on the measurement site- an all time record for the site.
"It wasn’t until we came in the next day and saw the ditches washed out and a lot of debris on the roads that I thought wow, we did get a lot of rain last night and then when we got here and saw the measurements, yeah it was a lot of rain," said Princeton Sanitary Board Superintendent Randall Bailey.
According to the National Weather Service, that extreme reading qualifies as a "1 in 500 year" flood event, meaning that a similar event has a 0.2% chance of occurring on any given year. This doesn’t mean Princeton is safe from similar events for 500 years, although incredibly unlikely, a similar rain event could happen at anytime. Instead, take the 500 year event label as an example of just how remarkable and rare the rainstorm was.