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Will the Yard Sink After a Pool Is Filled In?

Posted
Updated
ByAaron Baker

A little, and that is normal. Fill settles over time, and even well compacted fill over a broken shell can keep settling for years. Placing and compacting the fill in thin lifts keeps that settlement small enough for turf, gravel, plants and pavers. It is not small enough for a footing. That is why a partial removal stays landscape only, and why a spot you plan to build on needs the whole shell out and engineered, tested fill.

Why a filled pool settles

Loose fill has air in it. Over time, its own weight, irrigation water and rain press it down and close those gaps. The broken concrete in the bottom of a partially removed shell has spaces between the pieces, and finer material above can work down into them.

A pool filled all at once with dumped dirt and no compaction settles the most. That is the usual cause of a badly sunken yard.

Water makes it worse. If nobody broke drainage holes through the floor, the old shell holds water like a bathtub, and the fill inside stays wet and soft.

How compaction and drainage keep settlement small

We place fill 6 to 9 inches at a time and compact each layer before the next one goes in. Thin lifts are what let the compactor reach the whole depth of each layer. The top is leveled with AB so it matches the rest of the yard.

Before any fill goes in, we break drainage holes all the way through the pool and spa floors so water drains into the ground below. The City of Tucson requires positive drainage through the shell on every filled pool. Pima County’s inspection calls for a 4 inch hole at the lowest point of the pool. We photograph every hole before fill, so the record exists whether or not the inspector asks for it.

Why a partial removal stays landscape only

In a partial removal the lower shell stays in the ground. That is fine under turf, pavers, gravel, gardens and light hardscape. If a low spot shows up in turf or gravel, you top it off. If a few pavers drop, they get lifted and reset.

A structure is different. An addition, a casita, a garage, a ramada, a driveway or a patio slab cannot absorb settlement the way turf can, and a footing that crosses the edge of the old shell sits on two kinds of ground. Oro Valley’s permit page states the rule plainly: if the area stays landscape or open space, the shell may remain below grade with drainage holes through the bottom. If it will support a structure, it may not.

If you plan to build on the spot

The shell comes out entirely. The hole is filled with approved engineered fill placed in lifts, with compaction testing by an independent geotechnical firm as the fill comes up, and the job ends with a stamped letter from the engineer. Oro Valley requires a geotechnical report from a licensed engineer whenever the area will support a structure. We hold every build-over job to that standard no matter where the property is.

Tell us before we start. A partial removal cannot be turned into buildable ground later without digging it all back out.

If your yard already sank

Small low spots in turf or gravel over an old fill can be topped off and regraded. Pavers can be lifted, rebased and reset. If the settlement is large, if water ponds in the same spot, or if a slab near the old pool is cracking, have it evaluated before you add anything on top.

That goes double for an old fill with no permit on record, which is common in Pima County. We can bring in a geotechnical firm to assess the fill and coordinate a permit with the jurisdiction. Our pool removal page covers partial and full removal and what each one leaves you with.

Get a written quote

Call (520) 222-8503 and tell us what you plan to do with the space. To see what your pool costs you each year until it comes out, use the TerraSpec, the pool removal cost calculator.

Sources

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