Septic system feasibility soil testing and observation techniques.

This page describes some soil testing and observation techniques employed by Acorn Onsite, Inc. to determine appropriate septic system design.

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Initial Site Evaluation

Civil Engineer asses the surface conditions

An important first step in the septic system testing process is to have a Civil Engineer assess the visibly apparent condition from the surface. 

Observe Topography

An experienced Civil Engineer will be able to make some preliminary judgement on the generally topography from a walk-around of the project site.

Determine areas for further exploration

Once our Civil Engineer has walked the project site, he will have determined a few areas for further soil exploration.

Soil Profiles

Excavate about eight feet deep for a septic system soil profile in Pleasanton, CA.

Excavate about 8-10 feet depth

Conducting a Soil Profile involves bringing a backhoe or excavator in and excavating to see the in place soil conditions. 

Examining the soil profile for septic system soil characterization in Arnold, California.

Examine the soil conditions

Acorn Onsite, Inc. observe the soil conditions ad create a soil profile log. Our expert staff are skilled in identifying applicable soil features. Some soil characteristics include, texture, structure, color, to name a few.

Civil engineer creating a soil profile log sheet for a recently conducted soil observation.

Create Soil Log

Our expert staff record the soil information. This data is then used to determine leach line trench depth, application rate, length of trench, and other pertinent design details.

Percolation Test

Perc Test

Often refereed to as a perc test, percolation testing is done in some counties to assist in application rate determination. 

Process of a Percolation Test

Typically following a soil profile observation, a percolation test is setup at a depth of 12 to 48 inches, depending upon the soil conditions encountered in the soil profile. The percolation test is setup by auguring 8 to 12 inch diameter holes in the test area. A perforated pipe is placed vertically and surrounded by pea gravel. The hole is then presoaked. It is critical to auger the hole correctly with the appropriate attention toward the gravel/soil interface. Acorn Onsite, Inc. staff are experts in correctly setting up percolation test holes.

Measure percolation rate

Typically the following day of setup, the percolation test is then run. The measurement of the percolation rate involves putting a known height of water in a measuring the drop in 30 minute readings over a 4 hour period. Water is added as needed over the test length.

Groundwater depth determination

In some specific sites it is necessary to determine the depth to groundwater. Whether it is a limiting condition or having the appropriate vertical setback clearance. Techniques for groundwater depth determination vary depending upon the site and soil conditions. Sometime a backhoe is used to observe the depth at the same time as the soil profile. Alternatively, borings can be done to determine the depth to groundwater if it is anticipated beyond the reach of a backhoe.

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Wet Weather Testing

Wet weather testing being setup in Solano County, California.

When is Wet Weather Testing Needed?

On certain sites where groundwater or redoximorphic features indicate a high seasonal water table  wet weather testing may be appropriate.

What is wet weather testing?

Tyipcally, is is a soil profile and/or percolation test conducted during the wet weather season.

Expert Staff Available

Acorn Onsite, Inc. has the expert staff available to answer your questions and run the applicable wet weather testing. Give us a call today at 925-447-5200 or 1-800-832-7711