Large size wet-tap connection to force main

[kcalderwood]

I am currently in preliminary design for a new treated effluent discharge pipeline. The new pipeline will likely be in the 42" to 48" diameter, and the downstream terminus will be a connection to an existing 96" RCP outfall pipeline force main, operated by a joint powers agency. The force main owner agency would like the connection to be a 45-degree horizontal wye type connection.<br>
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I would prefer to make the connection without shutting down the 96" outfall pipeline. Does anyone know if a wet-tap type connection can be made at a 45-degree angle, at this size? I anticipate that we will have to spec some kind of custom tapping sleeve or concrete connection collar, but I'm not even sure that tapping equipment exists that can do what I want.<br>
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Thanks for your help.

 

[Zee]

Comming from a "hands on" contractors background, I don't know of any type system to "wet tap" an RCP line of that size. <br>
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How much flow has it now? Can it be baffled or bypassed any at all? <br>
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If there is a way I would like to know but I suggest you speak with a local qualified contractor.

 

[kcalderwood]

Thanks for the reply. I've been looking around since I made this post last month, and haven't been able to find any way to do a wet tap. <br>
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Our current thinking is to build a concrete pressure structure around the existing 96" RCP, and cast an angled flanged spool fitting into the top. Then at low-flow periods when the force main operates as a gravity line, cut into the RCP from inside the spool. If the work takes longer than one low-flow window, we can blind flange the spool fitting and come back the next day.<br>
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Now I've got to figure out how to keep pieces of the RCP from dropping into the 96" and possibly damaging the outfall works downstream.

 

[Zee]

Your plan sounds like a winner to me.<br>
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How large pieces are acceptable? Wouldn't a good cut (by pros) make it clean for pulling out the tie in section?.. Followed by dowling 96" in the building of the junction structure?

 

[kcalderwood]

You're right. I'm pretty sure that if we have a qualified contractor, we're unlikely to have problems. I've just never written a spec for this type of work before, and want to make sure I get it tight.<br>
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Thanks again for your input.

 

[Zee]

Where is the project located?<br>