Full pipe flow drainage network

[xeste]

Hi everyone,
i have been commissioned to design a drainage network for a production facility in the Oil&Gas industry.
The point is that the system has to be kept flooded in order to prevent fire hazards due to the potentially flammable fluids (no siphons can be used).
Another problem is the little head available due to a foundation plate placed 1 m under the surface to be drained (i considered an available head of nearly 0,50 m over a 190 x 40 sqm area).
Anyway i'd like to ask you a couple of things:

1) Do you know a book or any reference regarding the design of full flow drainage network, especially for the oil & gas industry?

2) Is there any problem regarding the usage of the EPA's software SWMM to analyze the network even if it's not open-flow?

 

[cvg]

first of all, is this a stormwater drain system/. or is this just plumbing drainage for buildings?
suggest that oil/water separators be used in either case. They make units with large storage volumes that can hold spills. If ou have a spill, then you need to prevent that from entering the storm drain system if at all possible.
you could use SWMMM, but why would you want to?

 

[xeste]

Thanks for the quick reply.
It's a system conceived to drain the water from an open paved area (stormwater, firewater and washwater).
There are various machines and oil tanks so the water is potentially contaminated, but it's not my concern, at least for now, since i've to design just the drainage network, not the treatment system (anyway the final receipt of the network is a first flush basin).
I was thinking of using SWMM in order to evaluate the stormwater runoff and analyze the network.
Maybe there are simpler way to do this but since there isn't so much head available i prefer to be accurate if i can.
Anyway my major concern is to know more about design of full flow drainage networks.

 

[cvg]

well, the drainage network and treatment system are combined, so you will need to incorporate them into the drainage system somehow. as far as maintaining full flow, that will be difficult to do without pressurizing your system. I have not purposely ever designed a storm drain system to always be full. I have designed some that were always full and that requires tailwater on the outfall which is high enough to flood the entire drainage pipe. If there is not a tailwater pond, then you would need an inverted siphon or use valves to shutoff the flow into and out of the storm drain pipes. I have used valves to prevent fuel spills from flowing into a storm drainage system, but that required manual controls to shut the valves. The fuel that made it into the drain still had to be captured and contained in a separator structure which could be pumped out later. We used a Stormceptor which could capture over 3,000 gallons of spill (jet-A, or other hydrocarbon).

 

[beej67]

SWMM will absolutely do what you want it to, and do it well. I used XP-SWMM quite a bit in Florida, where pipes are quite often designed to be "always wet." The problem with SWMM is it's bulky, and you really need to know it well because a small error or omission in your inputs could turn into a big deal. For instance, don't forget to specify an initial ponding elevation at every node. Another option very popular in Florida is ICPR, but I don't have enough familiarity with it to know whether it would work well for a pipe system, or only a connected pond system. (hence the acronym "Interconnected Pond Routing")

If it's overseas in an area with loose regulatory requirements, I think I'd probably design the whole thing to be deep and flat with a single bubble-up at your first flush pond. Any spill would get caught in the inlet itself, and a large enough spill would simply populate down to lower inlets one by one. Spills could be cleaned with a vac truck at each inlet.

Another idea, if you have the space and the fall, is do a conventional dry stormwater conveyance system that discharges to a two stage containment pond. Connect the stages with a permanently wet pipe, to act like a large oil separator. That way, any spill would be collected in a known location for treatment.

My experience with stormwater conveyance in industrial facilities is relatively limited, and here in the states it's usually governed by local regulations tied to land development instead of national ones tied to specific industrial demands. I have done some first flush ponds for containment here, though, and those are interesting work. Check your hydrology - you don't want contaminants to skip out of the pond when a big storm comes.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com