CARY - Excess grease and debris contributed to two sanitary sewer spills earlier this month that caused 4,880 gallons of untreated waste to flow into local tributaries.

Cary officials said the first spill, which happened on Feb. 5, sent 2,491 gallons of untreated waste into an unnamed tributary of Walnut Creek. Town crews cleared the blockage but were unable to flush the creek at the time due to heavy rains that swelled the creek.

The second incident occurred Feb. 6. Debris blocked a sewer line near the 400-block of St. Andrews Lane. That spill caused 2,389 gallons of waste to overflow from a manhole. About half of the sewage - 1,194 gallons - reached an unnamed tributary of MacGregor Lake.

Town crews flushed the affected area and pumped the flushing water back into Cary's collection system.

No fish were believed to be killed in either incident, officials said.

To decrease such incidents, the town launched a full-time, safe disposal option for residential waste cooking oils.

Cary residents can collect their cooking oils, fats and greases in a sealable container and contact the town to schedule a pickup when at least half gallon has been saved.

The program is aimed to reduce sewer blockage and overflows, accidental spills and disposals in landfills.

Since 2006, fats, oils and greases contributed to more than 20,000 gallons of untreated wastewater discharged into Cary area streams, creeks and lakes.