This paper concerns the advective migration of an aqueous contaminant in a fractured permeable formation. Calculation and analysis refer to fractures in which advection velocity is comparatively small. The slow advective velocity is created by some local cavities or almost vertical orientation of the fractures. It is shown that the advective contaminant transport is characterized by two dimensionless parameters: (1) the ratio between the permeable block and fracture flow rates, termed the mobility number ; (2) the ratio between the longitudinal advection velocity of the permeable block flow and that of the fracture flow, termed the advection velocity ratio .For a sufficiently large domain, continuum parameters can be applied to characterization of the fractured permeable formation. Then the mixing between the permeable block flow and the fracture flow is a mechanism leading to contaminant dispersion. For very small values of the advection velocity ratio, the effective dispersivity is fully determined by the mobility number. Its value decreases with increase of the mobility number. Under such conditions, the equivalent porosity is constant, and its value is identical to that of the permeable blocks. A significant value of the advection velocity ratio increases the equivalent porosity of the fractured permeable formation. With regard to the effective dispersivity of the domain, if the advection velocity ratio is equal to unity then the effective dispersivity vanishes. The larger the deviation of the advection velocity from unity, the larger is the effective dispersivity of the fractured permeable medium.