The carrier is charcoal. It contains a consortium of efficient bacteria (10 to power 8-9 CFU/g). The soil was contaminated 7 years ago. The soil is clay loam, pH 8.2, low N, P and organic matter content.
At that level it is completely dependent upon the bacteria. If the bacteria are aerobic it is doubtful that you will get treatment at that level of contamination. You might look into an alternative:
www.obio.com
Look at the Piranha mix. We have successfully used their product to treat crude oil in the 5-10% loading range on soil; I have never found another product that would approach that level. it also has the added benefit of a single application and no further tilling.
From literature I found that the optimum weight of the carrier based inoculum is 2% from soil weight in a pot experiment and the frequency of application was once for 150 days and the degradation% of TPH was satisfactory.