Conceptual design of submerged pipeline in reservoir
Conceptual design of submerged pipeline in reservoir
(OP)
Though this doesn't really count as "offshore" engineering I thought I would post this here anyway.
I'm undertaking a concept design/preliminary costing for a submerged pipeline approx 5mi long in a reservoir. Location is California. The pipeline will be conveying freshwater (non-drinking), peak flows of up to 2400cfs and under pressure (not sure how much pressure yet).
My questions are:
Is PVC or HDPE pipe suitable? Do these pipe types come in rolls, or lengths?
Does the pipe need to be anchored, or just weighed down? If anchored, what method? I assume bottom is mostly mud/silt.
Are there any standards/guidelines for this type of construction?
Any guidance appreciated.
I'm undertaking a concept design/preliminary costing for a submerged pipeline approx 5mi long in a reservoir. Location is California. The pipeline will be conveying freshwater (non-drinking), peak flows of up to 2400cfs and under pressure (not sure how much pressure yet).
My questions are:
Is PVC or HDPE pipe suitable? Do these pipe types come in rolls, or lengths?
Does the pipe need to be anchored, or just weighed down? If anchored, what method? I assume bottom is mostly mud/silt.
Are there any standards/guidelines for this type of construction?
Any guidance appreciated.





RE: Conceptual design of submerged pipeline in reservoir
RE: Conceptual design of submerged pipeline in reservoir
RE: Conceptual design of submerged pipeline in reservoir
Plastic pipe is from manufacturing, experience and/or practical matters also some limited in size. I really can’t imagine how e.g. one could possibly do a demanding underwater job (at least successfully) for a two thousand four hundred cubic feet per second flow quantity with a “pvc” pipeline? Likewise, I’m rough guessing that it might take in parallel something like FIFTEEN OR TWENTY of even the very largest hdpe pipelines available (assuming they were acceptable in all other respects for such installation?) to come close to handling that magnitude of flow volume at reasonable flow velocity for plastic pipes!
That being said, in my opinion some underwater pipe installation and (perhaps more importantly) subsequent trouble-free performance of underwater pipelines is a very rigorous application perhaps/arguably worthy of the very strongest, toughest pipe available. To get a feel for some extreme demands on some large underwater pipelines in even rather shallow water, and in some cases not too long after original design/installation, you might want to read e.g. the ASCE paper, “Marine Outfall Performance II: Stabilization and Case Studies” etc. available at htt
Some closer to home, I am aware of a significant 36” hdpe line that was laid across a rather shallow bay in Florida a few hours from where I live just a very few years ago (reportedly also by an experienced marine contractor). I understand this line, that I think was shorter than your job being a little less than a mile long, was initially required to be trenched, and also was very frequently concrete-weighted. I have heard third-hand this line also somehow encountered some weight slippage, I guess resulting in a sort of bunching up of weights from their original assembled positions. For whatever reasons also (I believe there may have been much time$?-consuming debate as to who/what exactly was responsible), a significant extent of this line also ended up being too shallow. Apparently also there was additionally at some point a realization or fear that the inside diameter of this newly line might not be adequate for (future?) flows (this is also something that should be very carefully considered proably best upfront, as the plastic pipe inside diameter used for such purposes can be quite small for nominal pipe sizes), as I eventually even noticed a budget issue request apparently once contemplated to replace at least some of the new line at http://w
I do not write this to diminish the utility of the specified/suggested pipe nor those who have thus trusted it (no pipe material is invulnerable, and I suspect there are quite probably many more claimed successes than problems with even the plastics); however, I just wanted to make the point that this can be very rough business with some sobering though perhaps some non-obvious realities for even the very strongest/most gouge resistant pipes conventionally used for such purposes. Additionally, I think some of this sort of work is sometimes done with very heavy equipment and rip-rap etc. working/rubbing around the pipes, and in conditions with zero visibility of what is actually going on beneath the surface. Over the years when I have been associated with marine pipeline work, I have even heard from some contractors in many situations that instead of long welded strings of pipe, individual shorter or segmented pipe assemblies can be easier or maybe even critically needed in some areas to get them installed properly where they are intended to go (I suspect examples could include strong winds or currents and/or unstable trenches that fill more rapidly than most lay folks might realize).
Just a couple other comments – while I guess it could be argued that conditions in a “reservoir” might be kinder than say that on the Cape of Good Hope, I don’t know enough of your perhaps inland application to know that there might not be some significant storms, cyclonic or tornado, marine traffic, erosion, or seismic activity to challenge the location and integrity of even your line(s) over many years. According to Al gore and his ilk some of these sorts of events are even increasing and not necessarily "Acts of God"?!!
If you have gotten this far reading this or other references, you might realize also that an ability to dependably repair a broken or damaged marine pipeline in place might also be an admirable consideration for at least some Engineers/Owners in upfront material selection (in this regard, I wonder if it is difficult to get a proper fusion job on a pipeline underwater?) Finally, I’m not even exactly sure how one can safely make an assumption that even some underwater pumped pipelines will always be totally full of water, maybe particularly if when installed they really end up looking some like “Nessie”, instead of a profile view straight line on paper!
While I probably have not addressed all issues in even this very long post, in summary I think this can be a complicated business, that is thus perhaps/arguably not for the faint of heart, pocketbook, nor experience (perhaps this was also sort of the gist of the admittedly much shorter messages of others including Mr. Halloran). [I will also post this response on the "Off Shore" site thread, where I first saw this now dual inquiry.]