EE was working in the bottom of the pit, bolting up fabricated parts for the pit Dewatering system pumps. EE was lifting up a 10' HDPE ""T"" to bolt it to a valve. As EE was lifting the ""T"", it shifted to EE's left side. EE felt some discomfort on EE's left shoulder down to EE's elbow. EE was given restrictions for muscle strain.