In this paper Block World environment with STRIPS representation is proposed to model the problem of loading and unloading containers in small container terminal in Gliwice, Poland. It is assumed that containers are represented by blocks and reachstackers are represented by robot arms. STRIPS planning with complete information is usually hard problem, very often at least NP-complete (e.g. optimal planning in Block World environment is NP-complete). To reduce this complexity a heuristic for sub-goal ordering is introduced.