Hydraulic conductivity using borehole infiltration calculation procedures per ASTM D6391-11

[bighouse]

We are performing field permeability testing roughly following Method B of ASTM D6391-11. I am trying to decide between Method B Calculation Procedure 1 and Calculation Procedure 2 (Sect 9.4, p. 12). I have run through the example provided in Fig 5 using both procedures and am getting a more conservative result using Procedure 2. However, I am more inclined to use Procedure 1 for ease of calculation; the built in curve fitting tools on excel are not able to fit the data with an equation of the form specified in the ASTM (Eq 11, p. 12). Would anyone we able to provide me with some insight regarding the differences between the two calculation procedures and which is generally more accepted or widely used? Thanks in advance for all of your help.