The growth of single cracks in stressed pipeline steel under simulated field conditions has been studied. This allowed simulations to be performed on these as well as stress corrosion crack colonies using a simple superposition model for fatigue and SCC, based on linear elastic fracture mechanics. A simple crack interaction model was implemented to account for the shielding effect of neighboring cracks based on available solutions for pairs of surface cracks. Crack coalescence was considered using a simple proximity model. In general, the resulting model gave reasonable predictions of the growth behavior of a representative colony of shallow cracks.