The board of California’s largest urban water supplier voted on Tuesday to spend $141.6 million for a large share of preliminary planning work for the state’s proposed water tunnel in the Sacramento-San Joaquin River Delta.

With the decision, the Metropolitan Water District of Southern California will continue covering nearly half of the preconstruction costs for the proposed 45-mile tunnel beneath the delta, which Gov. Gavin Newsom says the state needs to protect the water supply in the face of climate change and earthquake risks.

“This is about planning for the next 100 years,” said Adán Ortega, Jr., chair of the MWD board.

The MWD’s 38-member board decided to approve the additional spending after a heated debate. Supporters including business advocates and local water officials said the project will ensure the reliability of supplies to protect Southern California’s economy. Opponents including environmental advocates and Delta residents argued the project would harm the environment and push threatened fish species to the brink while failing to deliver the promised water-supply benefits.

The Metropolitan Water District’s board has yet to decide whether to participate in the project, which the state has estimated will cost $20.1 billion. That decision is not expected until 2027.

This is a breaking story and will be updated.