About 5,000 barrels of oil spilled from a 22-foot rupture in the Pegasus oil pipeline in late March. The pipeline was moving diluted tar sands oil from Canada.
Exxon said a new pipeline section was installed after the damaged section was removed and sent to a third-party laboratory for metallurgy testing.
Environmental groups say Canadian crude oil is more toxic than conventional oil. Exxon detected signs of benzene in early air quality samples but has since given the all-clear. Drinking water in the area remains free of contamination.
Work continues in an area marshland soiled by the spill.
"In the marsh, the remaining oil continues to be contained and is being cleaned up by work crews using a combination of pumps, backhoes and oleophilic and hydrophobic pads, made from specially designed materials that absorb oil but not water," Exxon said in a statement.
Exxon said it would provide a more accurate assessment of the amount of oil spilled once the pipeline is fully repaired. It gave no indication of a restart or repair completion date.
The accident remains under investigation.