Discussion of "Estimating Storage Coefficient and Transmissivity from Slug Test Data" by Prabhata K. Swamee and Sushil K. Singh

The authors have proposed an approximation for the well function tabulated by Cooper et al. (1967) for their slug test solution. They then have applied a least-squares error method to estimate the aquifer parameters for two data sets. However, this slug test solution is physically and mathematically wrong (Chapuis 1998) and thus should no longer be used by engineers. The Cooper et al. (1967) solution is in error by a factor of 5-10 for T values and by a factor of 200-50,000 for S values (Chapuis 2009). Similarly, the solution for pulse tests (Bredehoeft and Papadopulos 1980) is in error by a factor 100 for T and a factor 10 super(4)-10 super(8) for S (Chapuis and Cazaux 2002). As a result, the standard D4104 (ASTM 2006b) for slug tests was not renewed in 2002 by ASTM, and the interpretation method of standard D4631 for pulse tests (ASTM 2006a) is likely to be modified.