Travelling over RPA's -temporary roadways?

[Chris at eden]

Cheers, I am waiting to hear back from them. Do you know the sort of costs?

 

Not sure mate. I usually point the client in the right direction, and let them sort it directly rather than paying me an arrangement fee.

[Chris at eden]

Cheers, I am waiting to hear back from them. Do you know the sort of costs?

 

p.s. those loads and specifications were given to me directly by Gavin via email so they should be pretty accurate. The below text is the email he sent just for future reference. I find it useful to refer to.

 

Hi Chris

 

As discussed please see info below regarding Cellweb depths.

 

75mm - Pedestrian and cyclepaths

100mm – Cars and light vans (up to approx. 6 tonne GVW)

150mm – Fire engines, Deliver vans etc (up to approx. 30 tonne GVW)

200mm – HGV / Construction traffic (approx. 30 – 60 tonne GVW)

 

Hope this helps – I must stress these figures are approximate – other site factors have to be taken into consideration to assess properly the build up required. I have attached a questionnaire which you can send us if required, and our engineering department can produce this.

 

If you need any further help please don’t hesitate to contact me.

 

Cheers

[benedmonds]

Not sure mate. I usually point the client in the right direction, and let them sort it directly rather than paying me an arrangement fee.

 

Cheers, for that. When there are multiple ways of doing things do you just recommend the best (easiest to prove) irrespective of cost. I am sure 100mm hardwood roadway over a layer of wood chip would be effective but because the roadway suppliers have not done the research like cell web it is difficult to back up the specification...

[ReubenHayes]

Hi there, what is happening to the access after construction?

 

Although there is no problem with cellweb and would go with it, I'm just wondering about the costs to purchase and then removing it after? If it is purely just for construction and then removed after, have you thought about a bridge?

 

Vehicle bridges

 

I have been on a development site where they bridged over the RPA. They were developing a very large golf course and hotel so had a lot of big vehicle movement. The bridge worked really well and after they just removed it so no other traffic would go into the RPA.

[Chris at eden]

Cheers, for that. When there are multiple ways of doing things do you just recommend the best (easiest to prove) irrespective of cost. I am sure 100mm hardwood roadway over a layer of wood chip would be effective but because the roadway suppliers have not done the research like cell web it is difficult to back up the specification...

 

 

I would discuss the options. A the end of the day you could build an elevated concrete slab on plies to cross but I couldn't design that. It would need an engineer.

 

If its light weight traffic I am happy to specify the temp protection as interlocking boards (or ply) and woodchip. Anything bigger I always caveat saying to check the spec with a competent person. I'm not an engineer so I am very careful in what I recommend when it comes to structures.

 

Same with Cellweb roads. I spec footpaths and cycle ways but as soon as you start driving vehicles, I write the spec and then state that they must confirm with an engineer or the supplier and refer back to me if further guidance is required in relation to tree protection.

 

May seem like a bit of a cop-out but my profession is trees, not structures. I see my role as making sure the structures don't damage the trees, not the design of the structures. As long as you offer to consult, I think that is acceptable.

 

Hope that makes sense

[benedmonds]

I would discuss the options.

If its light weight traffic I am happy to specify the temp protection as interlocking boards (or ply) and woodchip.

 

Which is fine as that is mentioned in the BS

 

Anything bigger I always caveat saying to check the spec with a competent person. I'm not an engineer so I am very careful in what I recommend when it comes to structures.

 

That is the issue... Who is the competent person? An engineer will tell you that the structure will withstand the load but not what that load will do to the soil and roots. What we need is some evidence based research to justify any advice we give.

 

Cellweb provides that data so can be specified. Presumably and engineer could work out what surface area is needed to spread a load.. But a soil scientist would need to specify how that compacts a soil. The arb should have figures to say if that reduction in air space is acceptable to the root environment. I have never seen those figures..

[Roz]

To make that evaluation you would need to know the CBR (California bearing ratio) of the soil in situ along with the soil bulk density - with the technical data from Cellweb the impact can be determined.

 

There is going to be some compaction but providing the compaction does not exceed the worst case scenario for root penetration there shouldn't be any issues. Clearly if its a temporary road then before and after bulk density readings can be taken - determining the bulk density of soil is fairly easy if you liked science experiments at school. So in theory using Cellwebs knowledge of their product along with the information about the site you provide for them to draw up a spec you can work out the exact compaction that occurs from the temporary road.

[benedmonds]

To make that evaluation you would need to know the CBR (California bearing ratio) of the soil in situ along with the soil bulk density - with the technical data from Cellweb the impact can be determined.

 

So in theory using Cellwebs knowledge of their product along with the information about the site you provide for them to draw up a spec you can work out the exact compaction that occurs from the temporary road.

 

But what about other products/ali and wooden roadways. Much simpler to install, cheaper (probably still not heard back from cellweb) and I bet as effective..

 

What bulk density impedes root growth? I remember seeing a figure once.. I think when looking at capping dumps..

[Philip Anderson]

But what about other products/ali and wooden roadways. Much simpler to install, cheaper (probably still not heard back from cellweb) and I bet as effective..

 

What bulk density impedes root growth? I remember seeing a figure once.. I think when looking at capping dumps..

 

We were on a school site recently where access to deliver and site a mobile classroom was required over TPO beech trees ,PVC heavy duty ground boards were used interlocking bedded on sharp sand in undulations to make reasonably level.

20 ton excavator + arctic accessed site plus other construction vehicles ,it depends on how much weight how many movements and how long access is required.

[Roz]

A majority of research comes from the agricultural world - not surprising - and clearly there is a vast diversity within the sand, silt & clay classification hence there isn't one table to reference, every site would need to be tested but a rough guide for root impedance Sand >1.80 g/cm3 Silt > 1.65g/cm3 and Clay > 1.47 g/cm3.

 

In relation to the alternatives to a cellular system boards on a geotextile & sand/Woodchips even when secured at the sides is high maintenance due to the roller & squeezing effect of continuous vehicle passes....in my experience I have to say metal/heavy duty PVC track way while pricey is easy to install clean & tidy. If as above you require temp infilling of depressions avoid using building sand due to salt content although if temp may not be too much of an issue..BUT as TPO trees need a proper job