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To establish maximum and minimum design groundwater table

To establish maximum and minimum design groundwater table

(OP)
Hello,

In a project I have groundwater monitoring (standpipe piezometers) data for 4 months, along with geotechnical recommendations the client requirement is "to establish maximum and minimum design groundwater table with a 1% probability of exceedance in any given year (ie. 1 in 100 year return period)".

Could anyone help on this.

Rgds

Ashok

RE: To establish maximum and minimum design groundwater table

What is your location?

RE: To establish maximum and minimum design groundwater table

Short answer is very difficult to impossible to determine. If you are in clay or plastic silt, your open standpipe piezos are pretty much worthless. Response time is too long. If you are in sand, how often has data been collected?

Another question is, are there any creeks/rivers nearby? If so, then is your site hydrologically connected to the river?

We exclude this kind of language from our scopes when requested. All you can really do is provide a reasonable design groundwater elevation.

Mike Lambert

RE: To establish maximum and minimum design groundwater table

(OP)
Hi Ron,
the location in Oman.

Hi Mike,
the groundwater level is about 8m below ground level, the underlying strata is Gravel/ Conglomerate to 6m depth, followed by Shale/ Mudstone to 30m. Groundwater recorded on daily basis, there is fluctuation due to recent rains and now average depth is about 7m. The site is located in a shallow river/ wadi (not active, only surface runoff after the rain) basin.

Does this require a detail analysis or any simple calculations.

RE: To establish maximum and minimum design groundwater table

So your current water measurements show the water 1m into the shale/mudstone? If so, it sounds like there is either no groundwater and you are just seeing surface water in the piezos or there is groundwater in the shale/mudstone and it is taking a very long time to fill the piezos.

The question is what is the historical information on groundwater in the area? You can't predict 100 years + of groundwater behavior from 4 months of data. A very experienced groundwater hydrologist with lots of experience in the area might be able to make a guess.

Mike Lambert

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