Welcome to the forum, Git1Fiddle.

Congratulations on the new pond! Sit tight, some experts on calculations like this are sure to be on their way soon. Few initial thoughts:

A 1.5 acre pond with a watershed of 7 acres and precipitation of around 40" annually [right?] to me seems as though it won't be flowing through most of the year, but that's my WAG.

An overflow pipe is a routine aspect of the job. IMO a qualified contractor shouldn't consider implementing a overflow pipe as a challenge - at least if he's confident in his abilities and has relevant experience. As we know it's always wise to seek a few contractor's opinions/quotes/ideas prior to making any commitments, and I recommend you do that here. A good place to start is to contact your NRCS and request some pond builder/engineer recommendations. Sometimes they're reluctant to provide that information, but it's worth a try.

Again, welcome to the forum. I'm sure some experienced guys will be along soon to guide you capably.

Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau

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