Wednesday, August 27, 2014

New Stadium Irrigation Intake Screen

A couple of weeks ago, the Stadium began experiencing issues with water supply to the pump station wet well.  Essentially, the flow of water coming into the pump station did not equal the flow going out.  This caused the pump station to low wet well fault.  We assumed that the intake screen was clogged; thus, we called in a local diver to inspect the screen.  Upon inspection, we found that the original barrel screen mesh was very small and the pipe decreased in diameter at the connection of the barrel screen to the intake pipe.  The intake pipe is a 24" pipe and the diameter of the attachment point was only 10".  This meant that the intake pipe was never functioning properly to match the flow demand of the pump station.  Having the restriction point also meant the there was decreased flow and increased velocity.

Why did it work for the last 16 years?

The irrigation supply lake for the Stadium is very small and not very deep.  Because of the size limitations, the water always has a considerable amount of turbulence as the lake draws down and then fills back up (especially in the summer).  Increased turbulence means that there are always addition screen clogging particles floating in the lake. Over time, the lake became more shallow, and the intake screen became closer to the bottom of the lake.  What was once 2' of clearance between the screen and the bottom of the lake, was now only 6"! Combine the lack of clearance, increased water velocity due to the 10" attachment point and the aforementioned problem with turbulence in the water, the system was most likely stirring up the bottom and causing sediment to clog the intake screen.

We called in Logan Diving and Salvage to dredge the bottom around the intake pipe and to remove and replace the screen.  They specialize in underwater construction.  This was just a day at the office for these guys.

Old Screen Coming Out of Irrigation Pond

Old Screen

Inside Old Screen (showing attachment point restriction)

New Screen with Pipe Extension Prior to Installation