As shown in Table.
1, pit 4(30% bentonite) gives the lowest average grounding resistance and also the second lowest in terms of fluctuation of readings over 1 year period.
As aforementioned, a GIM should also be able to minimize the extent of fluctuation of steady state grounding resistance over a long period of application.
Both pit 4 and 5 produced similar amount of fluctuation but the former is chosen as the best ratio as it recorded lowest resistance and lower implementation cost since less bentonite is required for installation.