The City’s own list of ground-problem triggers is mostly about water, and water is the one part of the problem an owner can control. Poway Structural designs and installs drainage fixes for homes and properties across the city. If the water work involves a slope, a wall, or an engineered drain system, we coordinate with licensed engineers as needed.
Six sources on a big lot
The Safety Element (May 2026) names “saturation of incompetent material by periods of prolonged rainfall, over-irrigation, leaky swimming pools or utility pipes and leach line discharge” among the triggers for slope and ground problems. Only the rain is out of your hands. Here is where the rest comes from on a Poway property:
Irrigation. Lawns, orchards, slope plantings, and landscape beds. A drip line or sprinkler zone that runs too long, or a broken line that runs for weeks, can soak a pad or slope.
Pools and spas. A slow leak from a pool shell or its plumbing can add a surprising amount of water to the ground, often right next to a retaining wall or at the top of a slope.
Septic and leach fields. Some rural and large-lot homes are on septic. The leach field is designed to put water into the ground. Where it sits relative to slopes, walls, and the house matters.
Roof water. A large roof sends a lot of water to a few downspouts. If those empty at the foundation or over the edge of a slope, the soil there takes it all.
Hardscape. Big driveways and patios shed water. Where does it go?
Storm runoff. During prolonged rain, water running off the slopes above can cross your lot.
A dry pad, described
Picture the lot from above after a long rain. Ground next to the house falls away from it on all sides. Roof water drops into closed pipe and travels to an outlet at the bottom of the lot, not onto the face of a slope. Sprinkler heads throw water at plants, not stucco, and they run only as long as those plants need. Flat pads have swales or area drains so puddles never sit for long. Each retaining wall has a drain behind it with outlets that actually run. The pool plumbing is tight, and the overflow empties somewhere harmless. The leach field sits as far from slope tops and wall backfill as the septic design allows.
If your lot is missing a piece of that picture, that piece is what we fix.
A site visit, hose in hand
The strip around the house is only the start. On a big lot, we follow each downspout to its end, read the grades with a level, find where every drain outlets (or doesn’t), and look at the irrigation controller and a few heads in action. We check the pool deck and equipment pad and ask where the septic tank and field are. Stains on concrete, white mineral crust on block, soft or washed-out soil, and a patch of grass greener than the rest all point to water. Sometimes the quickest answer is a garden hose: run it into a drain inlet and watch where the water shows up.
After that we line the water up with the damage. A cracked footing corner under a downspout that dumps on the pad edge is rarely a coincidence.
What the water does once it’s in
On clay-rich fill, water can swell expansive clay and soften fill so it compresses. The Safety Element says fill from the Friars and Mission Valley formations is the main material in local fill settlement and expansive soil problems. See fill settlement and expansive clay.
On slopes, water adds weight and reduces strength. See hillside foundations.
Behind retaining walls, water pressure is the main reason walls lean. See retaining wall repair.
Fixes, from simple to involved
The simplest work is shaping soil so it falls away from the house, and pulling planters and sprinkler heads back from the walls. Next come buried lines that collect downspouts and carry the water to a safe spot, plus surface swales and catch basins on flat areas. More involved jobs include subsurface drains where water collects below ground, new drains and outlets behind retaining walls, closed pipe that carries water around or down a slope, and drainage in crawl spaces under raised homes.
Some work sits outside our lane. Pool and plumbing leak testing is specialized, so if we suspect a leak, we’ll recommend a leak detection company and plan around what it finds. Changes to a septic system go through a septic professional and the agency that permits it. We don’t redesign leach fields.
Simple drainage fixes often need no permit. Work that reshapes the ground or changes where water flows across the lot can need a City of Poway grading permit, and we check the City’s current rules against your scope before we start.
Straight answers
We already have a subdrain. Why is the ground still wet?
Old drains clog, their outlets get buried under landscaping, and some were never tied to anything at the far end. We test them before adding more.
Where should downspouts empty on a sloped lot?
Into closed pipe that ends at a safe outlet low on the property, never onto the face of a slope or the top of a wall. A splash block at the foundation just moves the puddle a foot.
How do I know if my pool leaks?
Watch the water level against evaporation over a few days, or hire a leak detection service. Wet soil near the pool when it has not rained is a clue.
Ready when you are
Tell us where water collects, where cracks or wall movement show up, and whether you have a pool or septic system.
Sources
City of Poway General Plan Public Safety Element (May 2026): saturation triggers; Friars and Mission Valley fill. City of Poway Grading Permits page.