Combined performance of pumping and tracer tests: A case study

Abstract

A combined pumping and tracer test was conducted at a highly fractured aquifer system. The hydrogeologic units underlying the test site are reclamation soil, weathered rock layer, and fractured layer. The fractured layer is the main aquifer for this site. Prior to pumping and tracer tests, slug tests were conducted at four test wells. The test data revealed existence of a low permeability zone near well OB-1. Generally the estimated hydraulic conductivities are in the order of 10−4 cm/sec. A pumping test with a discharge rate of 57 m3/d was performed for 1,230 min. The pumping test data analysis yielded coherent hydraulic conductivity values with those of the slug tests. However, the separate analysis for each monitoring well based on conventional analytical solutions with highly strict boundary conditions and homogeneity assumption cannot efficiently show the potential existence of the low permeability zone. During the pumping test, when the water levels of the pumping and monitoring wells are stabilized, a convergent radial tracer test was conducted. From the observed tracer concentration, a longitudinal dispersivity of 0.3 m was obtained, which is well consistent with the values in the prominent literature considering the test scale. This study excellently demonstrated a method completing a combined pumping and tracer test at one time.