He said "rigorous" scientific samples of the water were carried out regularly by independent testers who answered to the Auckland City Council, and these showed the development was not contributing to sediment in the water.
Manager of Auckland Council's regulatory compliance Steve Pearce said the inspections carried out at the development site have found they are operating "to a high standard".
The site has resource consent to discharge sediment into the receiving environment. This consent requires the site has numerous erosion and sediment control (ESC) devices to control the amount of stormwater runoff and sediment discharge.
The site is tested every week. Council takes samples once a fortnight during normal weather conditions, and the company does its own additional tests on weeks that council does not.
"Furthermore, if a weather event occurs an automated alarm is triggered and an independent expert is required to inspect the site and take water samples from the ESC devices to confirm discharge levels are acceptable," Pearce said.
"During recent extreme weather events, the streams in the catchment above the development became a dirty yellow colour. Natural slips which occurred following extreme rainfall contributed to this."
The group of protesters, called the Evan C. Williams Removal Committee, displayed large photographs outside Te Papa yesterday of sediment going into the harbour.
Group leader Geoff Reid alleged Williams' Weiti Bay property development was causing "enormous plumes" of dirt and sediment to pour down streams and into the harbour, colouring the formerly clear water and suffocating marine life.
A video on Facebook of sediment in the reserve has already been viewed more than 37,000 times and shared more than 700 times.
Williams said the sediment shown in the protest group's videos and photos was naturally occurring and a different colour to construction sediment, which is a light-coloured clay and easy to spot, he said.
Williams said there had been some incidents where silt and sediment from his development spilled into the water, but these were of a low level.
The protesters handed a letter to the museum's board demanding Williams' immediate removal from his position.
Reid, who has lived next to the marine reserve in north Auckland for most of his life, said he believed Williams was "ignoring our community's pleas to stop the destruction of the local environment".
Williams has spent $3 million on measures to prevents silt spilling into the water, and long-term protection of the streams would likely cost $6m.
He was "really disappointed" the group hadn't accepted his company's commitment to the environment and the "high standards" they were complying with.
Reid said the group's protest "isn't just a one-off".
"we're not going away. We're committed to seeing change."
Williams has planted four to five million trees through his projects and has committed to planting 2.5 million on the Weiti Bay property.
