Short answer
Anderson's soils are mostly dense glacial till that drains slowly, with wetter soils in low depressions. In a 120-point sample of city land, the USDA soil survey estimates a seasonal water table within about a foot of the surface at 56% of points and within 3 feet at 69%. These are estimates for mapped soils, and conditions on your lot can differ.
Search for “Anderson Indiana high water table” and you’ll mostly find social media posts and city documents. Here’s what the public soil data actually shows, what it can and can’t tell you, and why it matters so much for basements here.
How the ground was made
Glaciers covered this part of Indiana more than once. When the last ice sheet melted back, it left a blanket of till: clay, silt, sand and stones packed together. Till is dense, and water moves through it slowly. Where meltwater rivers ran, they left sand and gravel outwash, which drains much better. Low, flat spots in the till collected water and fine sediment for thousands of years and became the darkest, wettest soils in the area.
What the soil survey shows inside city limits
We looked up the mapped soil at 120 random points inside the Census boundary of Anderson using the USDA NRCS Soil Data Access service.
| Most common soils | Share of sampled points | What it’s like |
|---|---|---|
| Crosby silt loam | 21% | Somewhat poorly drained, over dense till |
| Cyclone silt loam | 10% | Poorly drained |
| Brookston silty clay loam | 8% | Poorly drained, in depressions |
| Fox silt loam | 6% | Well drained outwash |
| Mahalasville silty clay loam | 5% | Poorly drained |
| Kokomo mucky silt loam | 5% | Very poorly drained |
| Drainage class | Share of sampled points |
|---|---|
| Well drained | 28% |
| Moderately well drained | 12% |
| Somewhat poorly drained | 22% |
| Poorly drained | 26% |
| Very poorly drained | 8% |
Source: USDA NRCS soil survey. Shares of sampled land, not of homes.
The estimated water table
For each mapped soil, the survey estimates the shallowest depth the seasonal saturated zone reaches in a typical year. Across our sample (USDA NRCS soil survey, 120 points):
- 56% of points: estimated seasonal water table within about 1 foot of the surface
- 69% of points: within about 3 feet (USDA NRCS estimates)
A typical basement floor sits 6 to 8 feet below the ground outside. When the saturated zone is within a few feet of the surface, the lower walls and the floor are sitting in wet soil for part of the year. Water under pressure finds the joint where the wall meets the floor and any cracks in the slab.
What these numbers can’t tell you
- They’re estimates for mapped areas. Soil maps are drawn at a scale that can’t show every lot, and fill, grading and old drainage change conditions on individual properties.
- They aren’t measurements. We didn’t find groundwater measurements at a useful neighborhood scale. Wells in the region measure deeper aquifers, not water near basement depth.
- “Very limited” is a building rating. 71% of sampled city land is rated “very limited” for homes with basements (USDA NRCS), mainly because of wetness. That describes how hard the ground is to build on. It doesn’t prove a particular basement leaks.
What it means for your basement
On a lot with a shallow seasonal water table, the usual pattern is water at the floor-wall joint or up through the floor in late winter and spring, and a sump pump that runs for weeks. Surface fixes such as downspouts and grading still matter, because they keep extra water out of ground that’s already full. They won’t lower the water table, though. Collecting water at the footing with interior drain tile and pumping it out with a well-sized sump pump is the fix that addresses water from below.
On the better-drained outwash soils, basements more often stay dry until roof water, grading or an old footing drain fails, so the fix often starts outside. See yard drainage.
Check your own lot
- Open the USDA Web Soil Survey and search your address.
- Draw an area of interest around your lot.
- In “Soil Data Explorer”, look at the drainage class, “Dwellings With Basements” and “Depth to Water Table”.
- Compare that with what you see after heavy rain and in early spring.
Nearby towns vary even more than Anderson’s neighborhoods do. The data and methods page compares Anderson with 12 towns around it.