HILO, Hawai'i — Heavy rains continued yesterday on the Big Island, prompting the National Weather Service to issue a flood watch at 3 p.m. and police to close Kamehameha Avenue in Hilo at about 5:30 p.m.

The weather service issued the flood watch because of heavy rains over the windward side of the island extending from Laupahoehoe to Pahoa, but there were no reports of damage as of last night.

Several other Hilo streets were closed because of flooding, including the inbound lane of Bayfront Highway and a portion of Pauahi Street, Hawai'i County Civil Defense said.

Ka'u Highway was closed at the 58-mile marker because of flooding. Mauna Kea Access Road was closed because of snow.

Heavy rain over the weekend forced the release of about 650,000 gallons of partially treated sewage into the ocean near Hilo Bay, and more than 58,000 gallons of raw sewage into Wailoa River as runoff poured into the Hilo sewer system and overwhelmed it, county officials said.

The state Health Department's Clean Water Branch said the 58,000-gallon sewage spill was the largest in Hilo they are aware of that was caused by rainfall, according to Health Department spokeswoman Janice Okubo.

Health officials are warning residents to stay out of brown water that may be contaminated by runoff or sewage.

Parts of Hilo received nearly 29 inches of rainfall from Friday night to Monday morning, flooding roads and causing serious damage to some homes, particularly in the Waiakea Uka area.

Bert Saito, county wastewater division chief, said the flows into the system have subsided, and the system stopped releasing partially treated sewage at about 5:30 p.m. Monday.

Rainwater overwhelmed the Pua Wastewater Pump Station Saturday, triggering the 58,000-gallon raw sewage spill between 7:40 p.m. and 8:45 p.m. into the Wailoa River, which feeds into Hilo Bay inside the breakwater. County officials posted warning signs, and have been working with the Health Department to monitor the river and the shoreline.

The spill was necessary to prevent sewage from backing up into homes or overflowing from manholes, Saito said.

Another 1,000 gallons of raw sewage overflowed at the Pauka'a Wastewater Pump Station from Sunday night to Monday morning. Most of the spill was contained on county property, but some spilled into an adjoining property.

The partially treated discharges into the ocean from the Puhi Bay outfall were from Saturday afternoon to Monday afternoon. About 250,000 gallons were released Monday, county officials said.

Saito said county crews made checks during the flooding to try to determine where the rainwater was leaking into the system so that changes can be made later to curb the problem. Flows at times were five to 10 times normal volume, Saito said.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.