We present a numerical extension to the analytical propagation model introduced in Hein and Spanier (2008) to describe the leptonic population in the galactic disc. The model is used to derive a possible identification of the components that contribute to the leptonic cosmic ray spectrum, as measured by PAMELA, Fermi and HESS, with an emphasis on secondary <i>e</i><sup>+</sup>−<i>e</i><sup>−</sup> production in collisions of cosmic ray particles with ambient interstellar medium (ISM). We find that besides secondaries, an additional source symmetric in <i>e</i><sup>+</sup> and <i>e</i><sup>−</sup> production is needed to explain both the PAMELA anomaly and the Fermi bump, assuming a power-law primary electron spectrum. Our model also allows us to derive constraints for some properties of the ISM.