A 16-inch sewer line overwhelmed by excessive storm flows broke and spilled raw sewage into a creek for hours Tuesday morning near Carillo Way and Melrose Drive in Carlsbad.

A customer discovered the leak and notified Vallecitos Water District crews about 9 a.m. Tuesday, said district spokesman Chris Robbins. The area had more than 3 inches of rain on Monday.

Upon arrival crews used sandbags and a portable pump to divert much of the flow into a nearby sewer manhole, Robbins said. All flow was stopped by 1:10 p.m., and repairs were expected to be complete by the end of the workday.

No estimate of the total spill was available, he said. However, crews estimated the sewage was leaking at the rate of 300 gallons per minute when it was discovered.

Contamination signs were posted from the spill site along the unnamed creek to the Batiquitos Lagoon, and to the ocean at the mouth of the lagoon.

Though storm drains and sewer drains are separate, stormwater often enters sewers in various ways during big storms, Robbins said.

philip.diehl@sduniontribune.com

Twitter: @phildiehl