People in the Seaview neighborhood are wondering why signs have been installed in front of their houses instructing them not to park at the curb on certain Tuesdays this summer.

It's all part of a yearlong experiment scheduled to begin June 20. Seattle Public Utilities is trying to SEE if regularly scheduled street sweeping can reduce the amount of "nonpoint" pollution entering Puget Sound.

Sometimes it's easy to find the source of pollution. It can be as obvious as a pipe coming out of a factory. But the sources of generalized pollution are more difficult to determine. Nonpoint pollution is drops of oil, grease, antifreeze and automatic transmission fluid dripping from parked cars across the city. Dust particles fly from brake pads onto streets as hundreds of passing cars and trucks stop at trafffic signals. Contaminants attach to street dirt and sediment that drains into storm water catch basins.

Seattle Public Utilities set up an experiment area in the Seaview neighborhood, said Jan Sblendorio, project manager. It includes 42nd, California, 44th, 45th and 46th avenues southwest from Southwest Brandon south to Findlay streets. Findlay will be swept but not Brandon Street.

Vacuum-equipped street sweepers will clean one side of each street every Tuesday for a year. So each side of the street will be swept every two weeks.

There was even a comparative test of different kinds of street sweepers to determine which did the best job, Sblendorio said.

Throughout the year-long experiment, the amount of debris they sweep up will be measured and analyzed. The amount of debris left on the street also will be examined.

The experiment area has catch basins at its lowest points. That's where the experiment's effectiveness will be measured so the catch basins' intake grates, down pipes and containers were cleaned before the experiment began.

Sediment from the catch basins will be measured and analyzed every four weeks.

Seattle Public Utilities' street sweeping experiment also will broaden the reach of a study by the University of Washington. Besides looking for street pollution, scientists also will watch catch basins for evidence of mosquito larvae infected by the West Nile virus, Sblendorio said.

For the sake of comparison, a similar size area a few blocks south is being monitored without regular street sweeping.

Seattle Public Utilities is conducting similar tests in Columbia City and the Duwamish basin.

One reason the city chose the Seaview neighborhood is the experiment required a neighborhood where the storm water runoff is in separate pipes from the sewer system. In many places around Seattle, storm water occasionally overflows its pipes and combines with sewer system water and then untreated sewage pours into Puget Sound.

There also had to be curbs and gutters in the test area.

Tim St. Clair can be reached at 932-0300 or tstclair@robinsonnews.com