Muddy Waters May Result as DWP Flushes Tons of Silt From Valley Pipelines

Clouded water may occasionally appear in San Fernando Valley faucets in coming months because of a city project to remove accumulated silt from pipelines, a city water official said Friday.

The project started last September and is designed to flush tons of sediment deposited over decades in the city’s water mains, said Hoover Ng, a sanitary engineer with the Los Angeles Department of Water and Power. Much of the sediment was carried into pipelines from the Los Angeles Aqueduct system, which was not thoroughly filtered for many years, Ng said.

Sediment also enters pipes when reservoirs are drained below normal depths, as has happened in drought years and after the 1971 Sylmar earthquake, Ng said.

Engineers from DWP have been purging the silt from pipes one neighborhood at a time, he said. Valves are adjusted to isolate a particular pipeline and tributaries, then hydrants are opened. The turbulence created by the sudden demand for water flushes silt from the bottoms of the pipes, Ng said.

The 730 miles of pipeline in the northern third of the Valley have been flushed, Ng said.

Water officials received complaints from several residents who were startled recently when muddy-brown water poured from their faucets, he said.

Ng said there is no health hazard from the suspended material, which primarily is sand and clay and contains no toxic compounds. Running a faucet for two minutes should clear discoloration.

The flushing project, at a cost of $500,000 a year, will follow the course of the city’s water mains, proceeding south across the Valley through this year and across the rest of the city over the next five years, Ng said.

The next neighborhood that can expect cloudy water and sporadic drops in water pressure will be a section of Reseda bounded by Roscoe and Victory boulevards, and Louise and Tampa avenues, Ng said.