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Gravity networks - underground storage chambers & attenuation tanks

Gravity networks - underground storage chambers & attenuation tanks

Something that is fundamentally missing from civil 3d is attenuation tanks.

Two typical examples used in the UK on the links below.

Whilst there are workarounds using square pipes or structures, these really aren't ideal as we start to use more complex tank sizes and shapes.

It might be something that we get the manufacturers to produce, similar to pkt kerb files.

There are companies in the UK who are very keen to get their products into civil 3d and would be happy to produce the necessary files for their products.  This would also help to bridge the gap between microdrainage and civil 3d.

The same also applies to having filter trenches etc within civil 3d, we need a way to attach them to pipes within drainage models, i.e. if it is a perforated pipe, it will have a trench of x length etc.

Can this be considered please.




I think it would need several solutions;

They would fall into two categories with multiple sub-categories;

Attenuation tanks

  • standard shape tanks - (i.e. square, rectangle) that would have a length x width x depth
  • non-standard shape tanks - that would be built as blocks, i.e. specify the shape, L shape, inverted L shape, T shape etc that could be specified as being x number of x size blocks wide by x number of blocks high etc
  • Combined attenuation and treatment stone - Tanks that contain a combination of stone filter trenches and attenuation tanks.  Like this product. This could be achieved with the option above having tanks either side of a set width filter trench.

Filter trenches

  • standard size filter trench - would be attached to a pipe have a length x width x depth, width of stone on the outside and possibly in between, below and above the pipe
  • non-standard sized filter trench -  more complicated, perhaps using shape options and specifying an area x depth.

Need the USA products such as Stormtech and Cultech, etc..


Need the USA products such as Stormtech and Cultech, etc..

Need Underground Chamber detention modeling capability in Hydrographs by Product.


@fcernst  Absolutely, I think the ability to model tanks in general should come in the core release, then specific country products could come in the specific country kits.


@fcernst  Absolutely, I think the ability to model tanks in general should come in the core release, then specific country products could come in the specific country kits.


I have been using Attenuation tanks in my design (square crate boxes) for years. I created a simple box part in 2011 for use and have been using ever since, I did create another version which enabled different shapes of squares but don't really use this.


Here are some notes and findings.

With these the sizes range from 1m to 60m in width or length in half meter increments. The Xml file for the sizes becomes very large and difficult to manage. We should be able to specify any distance to keep the xml file small, this must be possible as the micro drainage parts use this functionality but I need to test.


The structure is not relative to the surface but the pipe, in Part builder this is simple enough to control however, in IPE this is more difficult.

After many hours of trial and error the only method I found which worked (PK3/4) was the introduction of a Null surface model (containing hidden geometry) and more hidden geometry in the UGStructure part to control the placement point of the base relative to the pipe.


I have since given up on this with IPE since 1) Inventor is not shipped with Civil3d and 2) overly complicated to maintain the part sizes and control the placement relative to the pipe opposed to surface.


I have noted issues in display particularly in sections / long sections possibly as a result of the placement being the pipe. The box in section displays incorrectly, positioned at the ground level (insertion level) in 3d the box section displays correctly.





Hi @MikeEvansUK  this is something we've discussed a good number of times over the years. 


I agree the solution of oversized rectangle / square manholes or rectangle / square pipes does provide a reasonable solution.  I have went down the pipe solution will 10mm null structures at the start and end of the tank.  The size of the pipe is in a range so can be set as any length x width x height and the pipe is relative to the surface in terms of cover.  However the major downside to this is if you have to offset tanks on the pipes when you have to drag it away from the structure and it loses its association / invert levels or if that tanks is split size or level tanks.


Given we are now on r2020 its time we have a proper solution to design challenges.  I.e. attenuation tanks, filter trenches etc.  Especially for abnormal sized filter trenches, i.e. under a treepit or a rain garden.  It needs to be a flexible solution and one that is compliant in BIM.


Thanks for your input.




Wow, I was reading this, and it's really sad that Carlson bought Hyrdocad (and Adesk got SSA, I'm sure they are both comparable) bu I could do what your asking in 2009, and with ease. I would model rain gardens with and without infiltration based on soils, and/or storage with no issue and the company's that make them even supply models for import.


Disappointing that with the release of C3d 2021 this hasn't been addressed yet...

Before I get in over my head, has anyone come up with anything, perhaps adapting the egg shaped pipes in part builder or the box culvert option mentioned above? [I'm wondering about box culverts connected to square manholes at the ends to maintain associations?]

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