Divers helping build the passageway were forced to evacuate yesterday after high tide made it unsafe.
It was not known how long it would take salvors to empty the final tank.
Pockets of lighter oil were still leaking from the Rena but were staying within a 6km radius of the ship.
Of the 88 containers lost at the same time, 58 remained unaccounted for and vessel skippers were urged to take "extreme caution" in Bay of Plenty waters.
Volunteers needed for clean up
While the pumping operation continues, iwi and New Zealand Defence Force personnel will this morning focus clean up efforts on Matakana Island, after reports of more oil arriving on shore.
National On Scene Commander Nick Quinn said it was thought the oiling was due to the release of heavy fuel oil from the stricken Rena several days ago.
Lighter hydraulic oil being released around the bow section of the Rena appeared to be dispersing naturally, he said.
Volunteer clean-ups are scheduled to begin on Papamoa Beach and Te Tumu at 9am and Maketu at 2pm, amid calls from MNZ for those registered to volunteer to turn up.
While about 7,500 people have registered to volunteer to clean up Bay of Plenty, only 160 people showed up yesterday.
Mr Quinn also said reports yesterday of an oil slick south of the East Cape had been confirmed as algal bloom.
"We're conscious that as we head back into another working week that people will be busier, but we'd really appreciate anyone that can spare a few hours to pop down to one of the clean up events and help."