How to add stormwater pipe protection?

[AnnieManning]

 Hello brains trust.

I'm helping someone re-landscape their driveway. We're using geogrid and locking gravel. A stormwater pipe that has been installed in an elevated position crosses the driveway. It has already been broken by a truck and a piece of metal plunked on top where the hole is. We don't want to raise the profile of the driveway too high because of the slope, So we're looking for a low profile strong solution to protect this broken stormwater pipe. Two thoughts that have crossed our mind are formwork and cement but that would require really raising the level or some kind of fabricated metal protection design for just this purpose but does such a thing exist. Any suggestions welcome! Thanks.

[Dave-1 · Accepted solution]

Good morning @AnnieManning 

How about some kind of mechanical protection, something along the lines of the Custom Concrete Products 450 x 900 x 40mm Plain Paver Tho would suggest that you also support either side of the pipe with some kind of base product.

How low profile are you thinking of going? The more I look at your pic the more I think it needs to be raised a resonable amount to encompass the geogrid and also whatever mechanical protection you use. You might need to come up with a steeper pipe to rd and then a flatter pipe to house section?

For the effort required into providing a solid top to protect the damaged pipe Id almost be tempted to hire a digger and dig it out and then put it back in a little deeper. If not then a trench about half way down the pipes diameter with a tamped roadbase then bricks layed on top up to level with the pipe, more road based tamped around the pipe and bricks with those concrete pavers over the top may be enough to protect the pipe itself and give you something to have that geogrid  flow over.

Its going to be a hard call whichever way effort wise.

Dave

[AnnieManning]

Dave, really grateful for your insights and suggestions. Excellent ideas. I'll head out and ruminate 

[JacobZ]

Hi @AnnieManning,

Thank you for your question about protecting a stormwater channel under a driveway.

That's a tough one, because whatever you use to protect the pipe will need to be able to support the weight of vehicles going over it in the same way a bridge does. The load needs to be transferred sideways and then down, so it is not applied directly down on to the pipe.

Unfortunately, I don't see a way for this to be possible without raising the height of the driveway by at least 100mm or lowering the level of the pipe by at least 100mm. 

My suggestion, as someone who has a habit of overengineering everything, is to essentially encase the pipe in a steel and concrete frame so the load is transferred sideways and around the pipe.

As you can imagine, this is not a small amount of work, but it is the only way I see of completely protecting the pipe.

If you wanted to do something like this, unless you are very keen, you'd likely need the assistance of a concreting contractor.

I like @Dave-1's idea of using compacted road base around the pipe with concrete pavers over the top. If you were to use this method, I would suggest using the layout of concrete in my above render as an example of where you would need the gravel and road base to go. You could then use some concrete pavers over the top of the compacted base to distribute the load.

Let me know what you think.

Jacob

[AnnieManning]

Thank you so much Jacob. Really helpful. What do you make of Dave's idea re bricks? Budget is a problem for professional concrete help. This morning Im thinking of a hybrid version of suggestions so far... lay bricks on a bed of cement either side of the pipe rising proud of the pipe bu say 30mm and place a  piece of strong steel formwork grid on top as it's drying and lay a further 70mm on top of the pipe and over the bricks and grid. then lay the 2inch geogrid over and integrate with 4inch geogrid surrounding the bricks. Fill with aggregate and top with locking gravel. 

The problem is complicated by 2 factors: the pipe has broken and needs mending (polypipe sleeve? So there's even more need for the covering to be incredibly strong) and the pipe is double the usual size in order to cater for an undeveloped site neighbouring. So the decision remains whether we need to treat the entire pipe - preferable - or at least work in a way that is able to be remedied when the inevitable second break occurs when the neighbouring property trucks roll in. An absentee neighbour makes collaboration extremely difficult. )

[MitchellMc]

Hi @AnnieManning,

Have you contacted your local council to discuss the issue?  This area could be on a council-owned easement outside your property, and the infrastructure is either owned by them or whoever deals with stormwater in your area. If this is outside your property boundaries, the council might be responsible for repairing the pipe and correcting issues.

Mitchell

[AnnieManning]

Thanks Mitchell. As it's urgent we might do a temp fix and put in for an inspection

[MitchellMc]

I'd still recommend contacting the council @AnnieManning. I would suggest that what needs to happen here is that the pipe needs to be dug up and replaced. It needs to be set at a depth suitable for vehicles to cross it without causing damage. Given it has already been damaged, you might find the council deals with it urgently. I certainly wouldn't think they would advise you to complete any remediation work until they have had the opportunity to inspect the damage.

Mitchell