  Plasmonic devices with feature sizes of a few nanometers exhibit effects
which can be described by the nonlocal hydrodynamic Drude model. We demonstrate
how to exploit contour integral methods for computing eigenfrequencies and
resonant states of such systems. We propose an approach for deriving the modal
expansion of relevant physical observables. We use the methods to perform a
modal analysis for a metal nanowire. All complex eigenfrequencies in a large
frequency range and the corresponding resonant states are computed. We identify
those resonant states which are relevant for the extinction cross section of
the nanowire.
