Rock Island, Illinois: what the ground under the city is like
Rock Island sits in Rock Island County, on wisconsinan till plain. The soil mapped here is predominantly classified moderately well drained — and that classification, not the rainfall total, is what decides how a basement behaves.
47% of the mapped soil area around Rock Island is wet enough that the USDA describes it as needing artificial drainage.
Linear extensibility 4.6% — moderate.
Shallowest annual water table around 60 cm (2.0 ft).
Values are for Rock Island County, which is what the soil survey resolves to. Full county report · soil map for a specific address.
The ground under Rock Island
Wisconsinan till plain. Dense basal till (stony clay) under a thin loess cap
The classic American basement belt. Below the topsoil sits dense till that water barely penetrates, so infiltrating water travels sideways along it until it meets the first vertical obstruction — typically a basement wall.
When it shows up here
| Water | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ground movement | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
Water peaks with the March–April thaw, when frozen ground stops absorbing and meltwater plus spring rain arrive together. If a basement here leaks once a year, that is when.
Climate pattern for this physiographic region, not a forecast for your house and not from the soil survey. It answers a question homeowners actually ask: when does this show up.
What repairs cost in Illinois
| Reference job | Modelled range |
|---|---|
| Interior drain along two walls + sump pump | $5,450–$11,700 |
| Exterior excavation of one 40 ft wall | $4,100–$11,650 |
| Underpinning on 10 piers | $16,200–$34,550 |
Regional factor for IL: ×1.08. Full cost breakdown for Illinois · run your own dimensions.
ZIP codes in Rock Island
61201, 61204, 61299
Soil does not stop at a city boundary, and neither does this data — every ZIP code above resolves to the same county soil survey. For the individual survey polygons around one address, use the soil map.
Other places in Rock Island County
Questions about Rock Island
Is the soil the same everywhere in Rock Island?
No. These values describe Rock Island County as a whole, which is the unit the soil survey publishes. Within a city, map units change over a few hundred metres — the soil map draws the actual polygons around a point and is the honest answer for one address.
Which contractor should I call in Rock Island?
We do not rank or recommend individual firms and we are not one. What this page is for is knowing which kind of work the ground here points to before anyone quotes you, and which claim to check. If you want quotes, the form below passes your request to the named networks.
Does this replace an inspection?
No. It tells you what the ground is; an inspection tells you what your building is doing on it. The useful order is: read this, print the brief for your county, then have someone look.
Get quotes in Rock Island
We pass what you enter to the contractor networks listed below. You choose whether to hire anyone.
Page data updated