A Special Investigation of Soils (SIS) is also a scope that TDEC may require.  TDEC Rule 0400-48-01-.04(d) identifies slopes of more than 30% as unsuitable unless soil conditions will prevent lateral movement of sewage effluent to the ground surface.  Slopes of greater than 50% are considered unsuitable and not eligible for consideration.  The Divisions’ policy SSD-011-8 allows for investigations to depth, presence and orientation of restrictive layers.  Observations should be made to 6 feet with soil pits.  TDEC will require a SIS if the site meets these conditions:

1. High or Extra High Intensity Soil Map delineates slopes of greater than 30% but less than 50%. Soil map notes will show which soil units are eligible for the investigation.

A Special Investigation of Soils (SIS) will require soil pits to be evaluated.  These maps will be on a map scale of 1 inch equals 100 feet.  To complete this map, we will need the following:

1. All lot corners marked and numbered or grid staked.
2. A numbered line stake shall be visible from any point on the lot.
3. Heavy vegetation removed if it interferes with soil mapping. Cleared areas to be mowed shall be maintained until soil map is completed.
4. Wooded lines cleared for line of sight on lot lines and shall be maintained until soil map is completed.
5. House site or structure to be marked and or flagged.
6. Exisiting High or Extra High Intensity Soil Map
7. Soil Pits

Our deliverable will show the soil series that are located on the lot in accordance with TDEC’s Regulations to Govern Subsurface Sewage Disposal and the Soils Handbook and also the depth to the restrictive horizon which is typically rock. This SIS does not guarantee approval of the TDEC septic permit.