Season High Water Table - Florida 1

[rdeaza]

Greeting all,
I need some help to identify the season high water table for a septic design I am working on.

What is the best way to get this information.

This is for a single family lot in naples Florida.

Thanks in advance for any help provided.

 

[bimr]

Geotechnical investigation?

 

[jgailla]

You can go the USDA soil survey for a start.

http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm

The regulating agency will probably require a geotechnical report stating the seasonal high water table, but some may accept the soil survey data.
Throughout Florida, except for the northwest, you will probably need to elevate your septic field above grade. The groundwater is usually too shallow to allow for an underground system.

 

[Ron]

Under Florida law, you generally need 48 inches of separation between the high groundwater and the bottom of the septic drain field pipes. As jgailla notes, many places in Florida do not have this separation capability. It depends on your location; however, the location you noted is not one that I would expect would have that separation. This would require an elevated drain field, with pumping from the tank to the drain field.

To get the high groundwater level for the area, you will either need an engineer to give that to you or also as jgailla notes, you might get by with the generalized soil data from the USDA. That will depend on what the health department in your county requires. Usually the building department or the health department in your county can give tell you what is acceptable for their application.

 

[rdeaza]

Thank you all for the help. 24" inches will be needed from the season high water table to the bottom of the drain field and I need to hire a Geo Engineer to do a Geo technical Investigation.

Thanks.

 

[beej67]

Don't trust the "web soil survey" website to properly answer this question.

When you hire your geotech, make sure to specify that he needs to give you a SHWT determination, not just a determination of where the groundwater is currently. Groundwater elevations in FL fluctuate, and the high fluctuations leave staining in the core sample from organics floating on the top edge of the water. It's this stain depth that he needs to determine. He will give you the results in terms of depth, not elevation, so if you need to determine an elevation instead of just a depth you'll also need to have a surveyor shoot the pit locations.

If you're in a swampy area that is inundated during the wet season, an ecologist can give you a similar analysis by looking at vegetative indicators for how high it gets above the ground.

FL is a very unique place to do engineering in the states.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Drew08]

You might have luck with the USGS groundwater monitoring sites:

http://maps.waterdata.usgs.gov/mapper/index.html

Look for a site screened in the surficial aquifer. There are a bunch in the Naples region. It would probably be best to find 3 or 4 that surround your property and take an average of those. Some basic statistical manipulation of the daily data, and adjustment for the site elevation may be needed.

 

[rdeaza]

Thanks Beej67 and Drew08. I've had luck before with the USGS data. In this case there are not wells near the site and a Geo Investigation will be needed. I have fellow Engineer with the right equipment that will get me the SHWT.

Thanks all for the help.

 

[msquared48]

If you removed all the gators and boas from Florida, the water level would lower three feet.

Mike McCann, PE, SE (WA)

 

[Spartan5]

In Michigan, we would expose the soil profile and look for the presence of redoximorphic features (mottling). The transition from the presence of these features to the absence of them represented the approximate location of the seasonal high water table.

Here is some quick information:

http://nesoil.com/images/redox.htm

http://nesoil.com/properties/eshwt.htm

 

[boo1]

64E-6.001 General.
Where the existing elevation of the bottom surface of the drainfield is less than 24 inches above the wet season high
water table, the bottom of the drainfield shall be maintained at the existing separation or a minimum of 12 inches above the wet season high water table, whichever is greater.

Where the bottom of the drainfield is less than 12 inches above the wet season high water table, the drainfield shall be
brought into full compliance with all new system standards, as long as it is the intent of the applicant to proceed with the addition to the residence.