Square Wet Wells - Good Idea or Bad Idea?

[yogibear1]

Our system (in west central Florida) has over 650 wastewater pump stations. Most of the stations use submersible non-clog pumps passing a 3 inch sphere. The majority of wet wells in use are predominantly round precast concrete with an anti-corrosion liner or coating.

Our Pump station Advisory Team has been kicking around the idea of square/or squarish wet wells (made of precast concrete and coated/lined) and has asked me to get some feedback from other users, particularly large municipal users. On the plus side is more volume per foot of depth, some benefits with the top slab and hatch arrangement, and more room for a stilling well (for the level transducer).

On the negative side the squared interior corners can accumulate grease, so we would specify that the interior corners would have generous fillets and that the bottom would also have fillets between the sides and base to direct sediment toward the pumps.

All of our precast is very heavy and designed for anti-flotation since we have a high ambient ground water level.

We would like to hear from you. What do you use and why?
One would assume pre-cast plants that make round wet wells can also make square wet wells any comments on this?

 

[dicksewerrat]

You better check the cost of the square ones. and you said cleaning out square is much more expensive. Fillets are just a bigger square corner. Have you and your team ever actually cleaned out or been on site while a square well was cleaned? don't bother with square. the operational cost will be much higher than a round one.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[stanier]

Pumping Stations by Sanks covers this subject.

The square sections will cost more. Fillets will be required. Submersible mixers may also be needed.

You dont say if you have submersible pumps but this is assumed. The larger stations in Sydney have rectangular wet wells and dry mounted subnmersible pumps in a dry well. This makes for hydraulic smoothness and helps with maintenance access.

That said there are also large circular stations here but these generally have submersible pumps.