Unusual driveway - I bet nobody's been asked this before!

[Chancerph]

Hi

I am about to install a new access drive or track through a woodland (SSSI) to my house, which is required to have minimal impact on the environment. I have a few questions which I am sure someone can help me with, and I welcome any other comments on the unusual design.

The idea is to construct the track using a sub base of compacted chalk over a geo-textile membrane, with 2600x250x150 untreated hardwood railway sleepers laid flat and bedded on 20mm pea shingle. The sleepers will be spaced 150mm apart, with 20mm pea shingle in between. The sleepers will form the surface along with the pea shingle in the gaps. More sleepers will be laid as shallow kerbs. The bell mouth area adjoining the road is to be surfaced with bound washed gravel with 2 or 3 rows of granite setts and then a strip of tarmac joining the tarmac carriageway. The track is about 80m long. The construction is to be done with extreme care and minimal disruption to the adjacent woodland.

The track will have normal domestic use, apart from next year when I am planning to rebuild my house, so there will be some heavy traffic coming and going for a time.

Some of my concerns are:
1.Will chalk be suitable for the sub-base and what thickness should it be?
2.Is 20mm pea shingle the right choice?
3.Will the sleepers get slippery?
4.Will the surface stay flat, or will it be like driving over a cattle grid?
5.Is 2.6m wide enough for occasional hgvs?
6.How do I find the right contractor for the job?

Thanks in advance

[Tony McC]

1: Yes but less than ideal. Thickness depends on CBR of existing ground, but I'd guess you're going to need somewhere around 300-450mm in two layers.

2: Probably not: spacing too wide; aggregate too deep and too loose.

3: Oh yes!

4: Cattle grid effect, without a doubt

5: No - 3m would be my recommended minimum

6: Try BALI

[Chancerph]

Thanks for that Tony - not very encouraging though.

Can anybody suggest a better way, but still low impact?

[Tony McC]

Self-binding gravel and/or cell matrix/geogrid. These are popular options for no-dig or minimal impact projects.

You could keep the sleepers as an edge restraint, but I'd be loath to use them as a running surface.

[dig dug dan]

you could of course cover each sleeper with chicken mesh to stop it being so slippery.

[Dave_L]

Brown Tarmac! :p

[lutonlagerlout]

why not do as the ancient romans do and have an aggregate road?
start with the big stuff at the bottome (reclaimed hardcore/crushed concrete) say 200mm ,then 100 mm MOT stone,then 40/50 mm of self binding gravel with sleepers for edge restraints,needs to be cambered in the middle for run off
fair bit of earth to move around though
cheers LLL

[bobhughes]

If it were me I wouldn't lay the pretty drive until after the building work. The thought of the damage a 3 axle concrete mixer could do makes me cringe.

Bob