MORGAN HILL (KPIX 5) – Flanked by members of Congress and local leaders, the Santa Clara Valley Water District broke ground on a 10-year, $575 million project that will reduce the risk of flooding and help its largest reservoir withstand a major earthquake.

“We saw the floods just a couple of years ago. And in fact, we don’t need a cataclysmic event for those floods to happen again. We just need a topping over,” said San Jose City Councilmember Raul Peralez, referring to the devastating 2017 floods which inundated neighborhoods in San Jose.

There is little risk of flooding currently. Anderson Reservoir, which overlooks Morgan Hill, has been depleted by the drought and further emptied in anticipation of the start of construction.

Groundbreaking on the Anderson Reservoir rebuilding project near Morgan Hill on July 7, 2021. (CBS)

Groundbreaking on the Anderson Reservoir rebuilding project near Morgan Hill on July 7, 2021. (CBS)

The challenge for the water district four years ago was the agency was not able to drain the reservoir faster enough and make room for the next round of rain. Instead, the reservoir filled to capacity and cascaded uncontrollably over the spillway, flooding communities downstream.

Phase one of the retrofit project will include burrowing a new tunnel that will enlarge the reservoir’s drainage capacity. The second phase involves a major retrofit of the dam, which federal regulators fear could collapse in the event of a major earthquake.

Anderson Reservoir near Morgan Hill on July 7, 2021. (CBS)

Anderson Reservoir near Morgan Hill on July 7, 2021. (CBS)

“If this dam were completely full and we were to have a 7.2 or higher earthquake, it would basically sink about 50 feet and that would send a wall of water to flood not only Morgan Hill but an area from Monterey all the way up to Palo Alto,” said Morgan Hill Mayor Rich Constantine.

The water district expects construction to take roughly a decade – the reservoir’s much-need capacity lost in the interim.

“Anderson has more water than all the other reservoirs in Santa Clara County put together. So, we need it. And we’re not going to be able to use it again until it’s fixed. So, this is a very important day,” said Rep. Zoe Lofgren (D-San Jose).