A gravel-filled hole is a dry well, and it works only when the soil underneath it can absorb water faster than the hole collects it. On ground that drains, a properly sized one solves a wet spot. On ground that sheds, it is a bucket that fills up and stays full.

Whether a soakaway empties here

The soil survey maps most of Ogden as built-up ground and does not rate its shed-versus-drain split, which is itself the finding: what is under a given lot here is a question rather than a published answer. What it does give is a slowest infiltration rate of 0.4 inches an hour and a shallowest seasonal water table 29.9 inches down. Test before you dig a soakaway on that basis, because fill behaves nothing like the soil it replaced.

The reasoning behind that

A dry well is storage plus infiltration. The stone holds a volume of water temporarily; the soil at the sides and base is what empties it. If infiltration is slow, the storage fills on the first storm and has not emptied by the second.

Sizing follows from that. The volume has to hold the runoff you are directing into it long enough for the surrounding soil to absorb it, which means it is set by the infiltration rate and the area draining to it — not by how big a hole is convenient to dig.

Two details decide how long it lasts. Fabric between the stone and the soil keeps silt out of the voids. An inspection point lets you see whether it is emptying, which is the only way to know it is still working.

A dry well also has to sit well away from foundations and above the seasonal water table. Below the table, it is already full before the first drop of rain arrives.

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