  We study pore blockade times for a translocating polymer of length $N$,
driven by a field $E$ across the pore in three dimensions. The polymer performs
Rouse dynamics, i.e., we consider polymer dynamics in the absence of
hydrodynamical interactions. We find that the typical time the pore remains
blocked during a translocation event scales as $\sim N^{(1+2\nu)/(1+\nu)}/E$,
where $\nu\simeq0.588$ is the Flory exponent for the polymer. In line with our
previous work, we show that this scaling behaviour stems from the polymer
dynamics at the immediate vicinity of the pore -- in particular, the memory
effects in the polymer chain tension imbalance across the pore. This result,
along with the numerical results by several other groups, violates the lower
bound $\sim N^{1+\nu}/E$ suggested earlier in the literature. We discuss why
this lower bound is incorrect and show, based on conservation of energy, that
the correct lower bound for the pore-blockade time for field-driven
translocation is given by $\eta N^{2\nu}/E$, where $\eta$ is the viscosity of
the medium surrounding the polymer.
