Permeable Pavers in University Place, WA — Infiltration Tested Against Chambers Creek Outwash.

A permeable interlocking concrete pavement system moves water through the joints into an open-graded reservoir base and, ideally, into the native soil below. That last step is the one that is not automatic. If the native soil will not take the water, the system is a very expensive puddle. University Place sits on Chambers Creek glacial outwash — sand and gravel that drains on its own. It is the friendliest substrate anywhere in our service area, and it is the one most often taken for granted.

Because the outwash drains, standing water is rarely the problem here. Migration is. Loose sandy subgrade moves under load if the base is not confined, and marine air off the Sound keeps every surface damp year-round. So we test infiltration before we design, and the design follows the answer. Where the soil accepts water, the reservoir infiltrates directly. Where it will not — which is common on the tighter ground in and around University Place — the reservoir is sized to store the design storm and release it through a perforated underdrain, so the system still performs and still counts. That distinction also drives whether the project earns impervious-surface credit under Pierce County stormwater rules, which is the reason most Chambers Bay homeowners come to us about permeable in the first place. Designed correctly, it also neutralizes lateral spread and joint washout in sandy subgrade, not ponding.