Colfax north flat project passes heavy water test

The April 9 heavy rainfall turned out to be a test for the new street drain system which was installed last summer on Cedar Street. Public Works Director Matt Hammer said the new surface drain system worked well to get the surface runoff water from the streets into the North Fork of the Palouse River.

During the heavy runoff, the 9th Street drain into the North Fork of the Palouse River had to be shut because river water flow reached a height where the river threatened to back flow into the North Flat.

Hammer said the city had one pump working to move water from the streets over the dike and into the river. When they had to shut down the 9th Street drain, the auxiliary pump was unable to keep up, and one garage in the neighborhood was flooded.

A second pump was added to the scene.

Hammer said the big plus for the new street drains on Cedar was the ability of the newly surfaced street to move water to the drains.

Street drains for 8th, 9th and 10th streets continued to collect and move water to the river.

City crews blocked off Clay Street which became flooded and a barrier stayed up through the night. Hammer said city crews worked early April 10 to clear the drains and then opened the street.

Water height in the North Fork April 10 reached up the sidewall of the flood control channel which was roaring.

Water flow meters from the U.S.G.S. gauge at Potlatch showed the North Fork of the Palouse soared from around 2,000 cubic feet per second Monday, April 8, to 6,300 cfs after the deluge hit Tuesday, April 9. The meter actually peaked out in the early morning Wednesday, April 10.

Water flow at Colfax would have been higher because tributaries such as Silver Creek at Elberton and Clear Creek at Glenwood increase the volume.

The Palouse River gauge at Hooper, which includes drainage from Pullman and Moscow, actually topped 11,000 cfs on April 9. The river was running at 9,370 Thursday, April 11, morning. Previous maximum flow for that date was 3,980 in 1969.