Wall Cracking During Well Installation
Wall Cracking During Well Installation
(OP)
I currently live in a house that is on a well. Last summer the well had to be replaced. During the driving of the new well casing the house moved at about 25ft down and there appeared several cracks in the drywall on the upper level, but also cracks in the masonry foundation wall. The installers stopped, then finished without any subsequent issues.
Here are some basics regarding the house. It is a ranch with a roof that spans between exterior walls. There is an interior bearing wall down the middle of the house, so there are three total (2 exterior and 1 interior). The largest cracks were step cracks on the interior wall, and they were no greater than 1/8".
My bet is that the house settled slightly and instantly. I would like to know if there are any opinions as to what may have caused instantaneous settling. A follow up is whether or not this is something that could cause settling in the future, or if it is most likely a one time thing. There was no previous indication of settling ever happening and the house was built in the 50s.
Here are some basics regarding the house. It is a ranch with a roof that spans between exterior walls. There is an interior bearing wall down the middle of the house, so there are three total (2 exterior and 1 interior). The largest cracks were step cracks on the interior wall, and they were no greater than 1/8".
My bet is that the house settled slightly and instantly. I would like to know if there are any opinions as to what may have caused instantaneous settling. A follow up is whether or not this is something that could cause settling in the future, or if it is most likely a one time thing. There was no previous indication of settling ever happening and the house was built in the 50s.





RE: Wall Cracking During Well Installation
RE: Wall Cracking During Well Installation
Mike Lambert
RE: Wall Cracking During Well Installation
Here are some basic answers to your questions:
1. There is a basement - the CMU walls I refer to are basement walls.
2. I do not know if there was drilling to remove soils. The well was hammered.
3. It's about 20ft from the nearest foundation wall.
4. I don't know the depth of the casing or the depth of the well.
5. Southeast Wisconsin.
6. No idea as to the soils type.
7. There are two decently large pine trees and one red maple within about 30ft of the well.
8. Haven't heard anything from the neighbors regarding problems.
9. They were hammering the well and when it was approximately 25ft down the problems started happening.
10. Haven't noticed outside ground settling outside of the fill mound of dirt shrinking a bit.
11. Do not know depth to ground water.
RE: Wall Cracking During Well Installation
RE: Wall Cracking During Well Installation
Sorry, but there are just too many could be this and could be that items with a situation like this.
Best of luck.
Mike Lambert
RE: Wall Cracking During Well Installation
RE: Wall Cracking During Well Installation
I'm from Wisconsin and have seen problems with soil shrinkage that later showed itself with sudden cracks forming, etc. The trees nearby some times were taking water from clay soils. More severe problems like this are farther north, in the Fox River valley (Green Bay area) and near lake Superior. However, the silty clay final deposition over last stage glacial soils (from wind blown silt) does have some potential for this situation in most of the state. That shallower final layer varies in thickness from 10 feet in south west to only 5 feet or so east. However, to blame the problem on shrinkage is unlikely due to the basement excavation requirement which likely went below that clay. An exception may be present locally. This tree moisture demand has seen itself as the cause many times in south part of Wisconsin.
Other than the above possibility, it would seem that some site condition, such as a looser, disturbed zone in original construction, erosion of soil from under a building due to sump pump removal of water collected there, would be what I would look for. To have this happen so long after construction, I'd tend to look at more recent events, such as the sump pump effect. Have there been any sewer damage situations in the last few years? Could the site have been a former quarry or gravel pit, later filled?
If a local geotech is involved, I'd ask if he/she has had experience with clay shrinkage problems. They don't teach this in class.
A "topog map" of the main floor and basement floor elevations might point you toward the area of most effect from what ever is the cause.
Collapse of cavities in rock is unlikely, but not totally so. That's a common S.W. Wisconsin problem.
RE: Wall Cracking During Well Installation
Thank you for your input.
RE: Wall Cracking During Well Installation
In answer to the question, "Is this an on-going threat?", keeping a record of what is happening helps in those cases. At wall cracks draw a light line across it just over 2 inches long. Place cross marks 2 Inches apart. Record length between marks has well as displacement periodically.
For mapping floor elevations use a garden hose fitted with clear plastic tubes on each end (get the fittings at hardware store). Or use a clear plastic hose to begin with. Fill hose with water and flush out air. Place tubes side by side to be sure water levels are same. Use this form of level to record differences in floor elevation at representative places against a more permanent bench mark elevation. This is useful to see effects of current settlement as well as keeping a record with time.
To see if there are any cavities under floor slab, hammer blows on floor are useful. Even light ones tell a lot. Varying pitch of sound is what you listen for. Cavity has lower pitch.
RE: Wall Cracking During Well Installation
This sudden draw-down create a certain settlement and cracks.
RE: Wall Cracking During Well Installation
RE: Wall Cracking During Well Installation
Last summer was quite dry. I am suspicious of soil drying and shrinkage.
RE: Wall Cracking During Well Installation
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Wall Cracking During Well Installation
If you have time go to the WEB site for Wisconsin Geologic and Natural History.
http://wgnhs.uwex.edu/
Click on Maps. Then scroll through maps and find your county for soil types. I found Waukesah county on second page. These are pedologic soil maps that give a pretty good idea of what is under the area. These are free downloads. Do a "view all maps". The map symbols can then be taken to the profiles in the borders. For instance Miami silt Loam is a common type and more detailed descriptions of these soil series, developed on that wind blown silt (now silty clay) layer can be found by more searches. From these upper 4 feet of descriptions we usually can tell a lot as to what goes on.
RE: Wall Cracking During Well Installation
The new well was installed because the old casing had corroded which they found when they were trying to replace the pump. Basically everything got worse till it was all broken, then they broke it some more. If you can imagine a worst case scenario this was it. At least now the well and pump are both new and work!
RE: Wall Cracking During Well Installation
Richard A. Cornelius, P.E.
WWW.amlinereast.com