If you are referring to "Erodibility Index", then that value sounds a bit extreme. Zero to 8, is suitable for row crops; 8-24 needs cover and terracing. The highest value I have seen is in the 80's, sugar clay in Oklahoma.
It is the kind of soil you don´t like to encountere behind your foudation.
I dont really know if it is possible that a soil can reach that EI but ASTM d 4829 indicate that soil heaving and EI higher than 130 has a very high potential to swell.
Probably you are dealing with a clay having a high content of kaolinite minerals, son, a special foundation design is requiered see USACE Foundation is Expansive soils, mat desing by the Building Research Advisory Board, or PTI postensined Institute, where is you project located?
An EI of 230 is very very high, the highest I have seen is about 200. Take a very careful look at what you want to do with this stuff. That much expansion can put a lot of pressure on a foundation.
Thanks for all your answers. In our area, EI's of 150 are common. I didn't realize you could get such a high EI! We are planning on using at least 4' of non-expansive import below bottom of post-tension foundation.
