Anyway, you may be entirely right, but the hill rises 350 ft in less than a mile, and we're very close to the local apex. It just seems unlikely to me, but I could be wrong.
That said, I read that in the town itself you can hit water 5 feet down in some places.
Are there any wells close to you? You can get the depth to water from them.
FWIW - Mauna Kea State Park (at about 6,500 feet, up in the saddle) gets its water from a perpetual spring located at about 10,000 feet up the side of Mauna Kea. The spring is fed by perched water.
There is perched water at high elevations all over the island.