Drainage and grading leads, from the shape of the land

This page is about a list of addresses in your service area. It is also, deliberately, about what the measurement cannot tell you, because a grading contractor who arrives to a job that is not there stops answering the phone.

Slope alone is not the job. Area is.

Two walls can both read −6% and be completely different work. One collects nine square meters from a side yard. The other collects the back half of a hillside.

So contributing area is measured per wall, not per property: sampled at nine points beside the wall and re-sampled at every displaced footprint position, then published with its range and the distribution it came from — never as a bare maximum, and rounded to the precision it actually has.

How the water gets routed

Three steps, and each one is a place where cheaper products cut a corner.

1. Bare ground, or a refusal

The surface is a bare-earth model with the trees and buildings stripped out. Before a single drop is routed, the surface is tested: the median step between adjacent elevations has to clear 0.004 m. Below that, the surface is a coarse source stretched onto a fine grid, and every channel computed from it would be interpolation presented as measurement. The engine declines the address rather than draw on it.

2. Every hollow filled to its spill point

Each closed depression is raised until it overflows, so no water is left with nowhere to go. The depth it raised is kept, not discarded — a real hollow beside a house is exactly the thing worth telling you about.

Skip this step and millimeter-deep pits eat the map. Measured on real ground: 282,572 m² of contributing area in Chicago and 201,312 m² in Pittsburgh drained into interior pits two to four millimeters deep and simply stopped, against largest surviving channels of 1,034 m² and 33,931 m². Water spills over a 2 mm lip; an unconditioned model does not.

3. Water spreads the way water spreads

Modeled flow divides the way overland flow actually behaves — near-single-channel in a steep gully, dispersive across a lawn. The cheap shortcut forces every drop into one channel and manufactures a hard line across ground where flow really spreads.

Buildings act as walls in the model, so water routes around the house rather than through it.

Standing water, as a depth and an extent

The depression fill gives this for free: how deep water gets before it spills, counted within 20 m of the footprint and outside every building. Under 3 cm is measurement noise and is not counted.

The arithmetic was checked against synthetic ground where the answer is known: a bowl cut into a 2% slope fills to its spill point at 0.28 m predicted against 0.289 m measured.

An independent check on the routing

Where a city digs its storm drains is a yardstick nobody here tuned. Pittsburgh Water publishes the location of every inlet it maintains, so the model can be scored against ground somebody else surveyed for their own reasons.

What gets a property onto your list

1. The building the address names was established.
2. It was identified at high confidence — proximity-only answers are excluded from lists entirely.
3. At least 3 m of wall has ground the engine called as falling toward the structure: the direction survived displacing the outline one meter in each of sixteen directions, seventeen positions in all, all agreeing on the sign.

Walls that lean but were not called are reported separately, and they do not qualify anybody.

Pricing

Territory access from $14 per property: 25 for $450, 100 for $1,600, 500 for $7,000, or $35 each held exclusively for twelve months. Separate from the platform plans and not metered against lookups. A refusal is never billed, and a wrong building is replaced free.