Why does nobody talk about how suction depth actually drops off in brackish water?

I was reading an old Army Corps of Engineers report from 1997 last night while waiting for a tow and saw a chart showing a 15% loss in effective suction when salinity drops below 5 parts per thousand. Nobody at our yard ever mentioned this, and I've been running jobs on the Mississippi River delta for 3 years now. Has anyone else noticed their production numbers tanking in low-salinity zones, or is this just me finding excuses for a bad week?

3 comments

3 Comments

amy_martin4d ago

...so my buddy runs a dredge crew down in Plaquemines Parish, and he called me one night a couple months back cussing up a storm about his numbers being way off. He's been doing this for like 15 years, knows his gear inside and out, but that week his suction depth was just dropping like a rock. Took him forever to figure it out, he had his guys checking hoses and pumps and everything. Turned out they'd moved to a new spot on the river where the incoming tide was mixing with freshwater from a spillway, and the salinity had dropped to almost nothing. Once he realized it was the water itself, he just adjusted his pump speed a little and backed off on the suction head, and things smoothed out. I don't think it's you making excuses at all, that 15% loss the report mentioned sounds exactly like what he saw on his gauges. It's wild how something that small in the water can mess with a whole operation.

stella224d ago

That's a great real-world example, and it mirrors what my crew saw when we were pumping out a brackish pond last fall.

brian_taylor154d ago

You ever seen a guy spend four hours cussing at a hydraulic pump that wasn't the problem? My buddy runs a little one-man operation on the Gulf Coast, and last spring he pulled into a spot where the water looked clear but felt wrong. He had his whole rig torn apart checking seals and impellers, even called a mechanic from two towns over who charged him a weekend rate. Turned out he was pumping in a zone where a small creek dumped freshwater into the saltwater canal, and his gauges showed suction dropping by a solid 10%. He said once he just throttled down and ran his pump slower, the numbers came back to normal. Made him feel like an idiot for not checking the salinity first.