On 4/10 EE was removing a sump pump from 010 pan conveyor area. EE placed it on a stable surface to remove the coupling from the discharge line. While pushing a 4-ft pipe wrench to loosen the coupling EE felt a pop and some pain in EE's lower left rib cage. EE reported this to EE's supervisor. On 4/12 EE requested to see a doctor. Diagnosis: rib cage intercostal muscle strain.