Gravel road construction / maintenance 3

[AKpatriot]

I live on a remote island in SE Alaska, I serve on a community road committee; we are looking for guidelines and "how to" data to help us specify road improvements.

Our roads are left over logging access roads filled with large rocks and boulders... grading is impossible in the current configuration. I'm not an engineer but spent my 33 year career working with engineers so I have some ideas about how to properly design and maintain things. We have very limited funds; my goal is to repair our roads so that they will be less expensive to maintain thereby leaving dollars in our annual budget to continue road improvements.

Any help will be greatly appreciated by our little community.

Thanks,
Howard

 

[CarlB]

A comprehensive manual can be found at:

http://www.epa.gov/owow/nps/gravelroads/

..lots of pictures

 

[AKpatriot]

CarlB; Thanks for the info... I'll definately follow up on your suggestion... take good care.

h

 

[oldestguy]

I took a look at the link noted above. Most seems OK, but for your situation, some of it looks not something usable.

I note the under-drainage section really is not good for you.

While geotech wrapped drain pipe may work out in your gravel soils, I'd look to minimize frost heave and resulting weak spring conditions by following a few rules I have learned about this.

Keeping your ground water table below the final grade at least 4 feet does wonders. Backfill perforated pipe with clean-coarse sand, similar to concrete sand. Don't use open graded rock since it plugs up.

Any use of under-drains should be placed to cut-off the flow coming towards the subgrade. Drawdown of water table to drains running under the roadway is not usually possible.

People driving fast on gravel roads can cause wash-board surface to develop. Your grading guys should use a deep blade cut when re-shaping the roads, since shallow cuts somehow do not get rid of inherent weaknesses and wash-boarding soon comes back.

When changing road profile, remember the worst frost-susceptible soils are found just below topsoil in what we used to call the B-horizon. You might want to undercut that stuff at least 18 inches, if you can. It's at the change from cut to fill.

Roads with culverts probably will heave up in winter, but culverts won't. To minimize that dip, replace subgade in tapers back away from culvert with non-heaving sand and gravel fill.

 

[BigH]

As usual, oldestguy gives good advice. I'll give this some thought, too, but the first question I have that comes to mind is what regulatory responsibility does the logging companies have to leave the area. Even here in Indonesia, the mines must rehabilitate areas that they have mined - fill in and reforest/vegetate. There are bonds that they must post to show that they can and will do this. Ongoing mines are supposed to rehab at least as much area as they have mined during the course of the year (from memory but there are rules on the rehab). So, any help to be expected?
What is the side road drainage like? Fully developed side ditches? If not, then work to get them dug so, as oldestguy suggests, to lower the water table and promote runoff to minimize ponding up into the road. If you have the topography, can even cut very deep trenches with a small excavator and backfill with rock to draw the water down even more - but then drain these trenches off downhill (thinking you might be in a mountainous area). You may get some plugging depending on the nature of the soil - could wrap the french drains with geotextile (too bad you don't have palm hair!! - I've seen it used before). You could also dig a trench down the centre of the road, backfill with gravel as oldestguy has alluded to - then take it off to the side - this will reduce the mounding that occurs between road edge drains. Just some initial thoughts.

 

[AKpatriot]

Oldestguy & BigH... thanks so much for your input... our main problem here is funding... we have an extremely limited budget and lots of rough roads. There is no funding from the logging companies / operation as the US Forest Service was responsible for building the roads to give successful bidders access to the timber... the history of logging in SE Alaska is a true lesson of why we need Government to stay our of our lives as much as is possible.

You've given me some good ideas and a good reference resource... now if I can convince our road committee to take a longer term view... just maybe we can eliminate some of the reoccuring problems...

Thanks so much!

 

[swazimatt]

are the roads just rough, or do they turn to mud in the wet season?

 

[BigRK]

I have dealt with a lot of that working in the forest industry in the Pacific Northwest. The rock used in your roads is probably pretty low quality in terms of hardness. Most likely something they could dig directly out of a pit with an excavator as opposed to something that needed to be drilled and shot with explosives. You may be able to break a lot of it down in place by simply running a large grid roller or even a D-8 Cat back and forth over it. You won't get anything great but if lucky you will get something small enough to roughly shape up with a grader when done. It helps if you have some volunteer labor to hand roll some of the more stubborn donakers out of the roadway.

More expensive would be to hire someone with a portable jaw/crusher to dig up the rock, run it through the jaw and place it back on the road. The last few years there have been a number of equipment manufacturers that have started to sell small, highly mobile, tracked jaws that do a pretty good jaw of crushing down to about 3" minus or so. It would be fairly expensive though, down here about $10,000 per mile, I imagine it would cost you more up there.

 

[AKpatriot]

swazimatt & BigRK... thanks much for the input. Yes, the roads are rough... and they get muddy during rain/snow season but are not "mud boggs". BigRK described the roads very accurately... mostly, they were initially installed to allow logging access... material mined from rock pits in the general vacinity... some was shot as roads were installed through hilly terrain. The material was laid down over existing forest floor and forest debris... we have numerous large boulders in some of the roads thet prevent any effective grading... and we have numerous reoccuring pot holes. BigRK... I can send you some photos if I have your email... the jaw/crusher is a great idea.

We are currently working on a plan to install a few culverts and try to repair the worst of the pot hole areas before winter snows begin... then work on a mid-range plan for winter snow removal & maintance AND a longer thrm plan for next spring - summer and beyond... the goal is to repair the roads as best as we can with VERY limited funds in such a manner as to reduce maintenance costs thereby allowing us to spend more of our limited budget continually improving the community road system.

Thanks so much for your interest and input...

Howard

 

[BigRK]

Check out the following links, it might give you some ideas:

http://www.fahrindustries.com/Low_Volume_Roads.html

http://www.terex.com/main.php?obj=p...nav=prod&cid=e75ed9c85681b27ffcfe5cadbd68c04e