Milford and Castor Bay beaches contaminated with sewage following heavy rainstorm

Milford Bay.
Milford Bay. Photo credit: Getty

Two Auckland beaches have been classified as unsafe for swimming after the week's heavy rainfall caused sewage to flow into the sea.

According to Auckland Council's SafeSwim site, both Milford and Castor Bay have warnings to avoid swimming due to wastewater overflow detected by sensors in the network.

Both alerts were issued at 1pm on Tuesday afternoon.

Watercare wastewater operations controller Sifa Pole told Newshub the overflow occurred in the local waterway.

“The sensors at pump stations in Castor Bay and Milford operated as they are designed to do- and went off when the heavy rainstorm occurred which caused substantial flooding across parts of the North Shore," he said.

"The sensors also automatically alerted the Safeswim programme.

"The deluge of stormwater engulfed the wastewater system and a wet weather overflow occurred, into the local waterway, which flows out to sea."

"These engineered overflows are designed to prevent wastewater from backing up and overflowing on private property."

Nearby beaches Mairangi Bay, Narrowneck, Waiake Bay and Long Bay all also have temporary no swim warnings in place, although SafeSwim does not specify the cause of poor water quality.