Groundwater Construction Claims Debate 2

[CivilCon99]

A geotechnical investigations was conducted prior to a bridge replacement project. Two soil borings were completed to bedrock on each side of the stream. The borings only showed free water and no 24hr reading was conducted (due to drilling in the roadway). The free water in the borings showed 5 feet less than normal stream elevation and below the new abutment foundations. During construction of the new abutments adjacent to the river, the contractor encountered water at or above stream elevation. The contractor is seeking a site differing condition claim stating the geotech logs showed free water deeper than their foundations and that they did not plan for enclosed cofferdams and heavy dewatering during construction.
1.) Is the free water in the borings strong enough data for a differing site conditions claim?
2.) Regardless of the geotech report findings, shouldn’t the contractor have to expect water at least at stream level during excavation adjacent to the river and bid/build accordingly?

 

[dik]

I'm not a geotekkie, but my experience is that the groundwater level outside a stream/river is slightly higher than the water level. What was the water level at the time the geotech report was prepared? Was the water high or low? Could it be an unrelated watertable to the stream/river? The contractor might have expected this, but the Contract likely doesn't include for this. The geotech report may have been in error; I don't know what info was provided to the Contractor.

Depending on the jurisdiction, this claim is likely a legitimate Extra to Contract.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[1503-44]

1) Agree with Dik. Its a typical extra payment justification.

2) Groundwater levels adjacent to a stream may be higher, or lower. You have to recognise that water levels can be dynamic, especially throughout the yearly seasons. The classic illustrations usually show a stream water level lower than the groundwater level, which signifies the stream is draining the local groundwater. However when a stream is charging groundwater, stream surfaces are higher than groundwater levels. Higher stream levels are typical during spring rainy and snow melt season when surface runoff is greater and groundwater supplies are being recharged. Lower stream levels are typical during summer when rainfall is usually less and water runoff is reduces by evaporation by higher temperatures. That will tend to drain the groundwater whenever stream levels are lower than groundwater levels.

Water levels may also vary considerably along a stream's course. Some areas may be recharging groundwater, others draining it. That is typical of a changing topography. A stream level 5 ft higher than groundwater indicates that the stream is charging the groundwater at that point in the river. 5ft difference at average stream flow levels is relatively large, so it indicates the stream could be permanently recharging groundwater

It could be reasonable to assume a yearly average condition existed, where groundwater might be approximately equal to stream water levels, with stream typically higher during wetter and spring seasons and somewhst lower in summer, but boring logs were provided showing definitive conditions, making any such assumptions unnecessary. Actually your case would have been better served, if boring logs were not provided.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[dik]

I've never encountered it lower... but it may be possible.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[TigerGuy]

What is the soil type? If you are in sand, I would expect the water level to be very close to stream surface. If you are in clay, who knows, but it is going to change with time.

The geo report should explain that the water level is likely to change, and the construction crews should be prepared to address those changes. The contract is not always written to include those factors. If these factors are not in the contract, it's an extra payment for the extra work.

 

[1503-44]

Dik, please see

https://books.gw-project.org/ground.../chapter/groundwater-connection-with-streams/

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."