some thoughts from Dozer
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Road Update

image roadschematic.jpgAs the road project is finally nearing a point of stability, I’ve been meaning to post an update. Not that this project is really applicable to what most people are doing, but a good review with respect to ‘how things can go wrong’ nevertheless. First off let me say that this project has not been the smoothest, mostly due to trying to get the road in during the rainy season (as anemic as it has been) and the fact that the road is a natural waterway. This, unfortunately, makes the job much tougher.

This road project involves laying in a road from a public road up a slight incline about 200 or so meters and then there is an adjoining road which doglegs off to the left. (double click on the road schematic image to follow along). The upper section (red color) is not being surfaced. The brown section is being surfaced and involves a road joint into the intersecting road section (tan color). The lower section (green) involves an intersection with the existing public asphalt road. The yellow section along the side of the road indicates drainage.

Due to the extreme amount of water runoff on this path it was decided early on to install some kind of drainage on one side. The road is being constructed to slightly angle off to the side with the drainage. Also it was clear that the lower section would need subterranean drainage installed to allow the water to run under the road in an existing gully and waterway.

image roadsurvey.jpgAs The engineer did a suitable job mapping the site and drawing up a suitable site diagram. This was further used to find a suitable contract to due the site preparation and put the road in.

The project at this point has three main players, the engineer (Phim) who did the site survey, the road contractor (Nat) has bid a fixed price to lay in the road and some workers (foreman Jim) I had working on some other stuff (at our house) that coincidentally had about 10 years worth of road experience.

The road was laid in using 20 centimeters of road dirt and about 7 centimeters of road gravel on top. The contractor Nat did a really good job on this portion. The road was well prepared to the level specified by the contractor, a heavy steam roller was used — and everything basically went according to plan for this phase.

We had been discussing drainage with the engineer. For the lower road joint the obvious choice was subterranean drainage rounds. The engineer, Phim and the road contractor, Nat, both suggested subterranean drainage for the upper road joint also, which sounded good. The engineer further suggested constructing a surface drainage gutter out of cinderblock and running it the distance of the public road section that we were doing.

On the day that section of the road was being done (the upper portion) a JCB dug the upper joint road trench and sunk in 60 centimeter reinforced drainage rounds, the same type that would be used on the lower section. The depth of the lower rim of the rounds was about 1 meter.

Now, using the power of hindsight as my guide, let me list all of the problems which eventually were uncovered.

Too many drainage rounds were laid under the road at the upper road joint. If the adjoining road is 8 meters wide (as the tan color road is) only 6 should be used to allow for drainage repositories to be placed on either side for the road (with a meter in width). First we removed two of the 9 that were initially put in, then another time we removed another one. The thought of Nat was that by using a lot of drainage rounds the road entry could be expanded – which it could not unless we cut into existing adjoining land plots.

The engineer and road contractor were recommending apples and oranges. In general if you are going with surface gutter drainage, you wouldn’t put subterranean drainage under the road joint (specifically the upper road joint), you would use a surface gutter system throughout. The surface gutter, if we had used one here, would have been about 40 centimeters wide and about 50 centimeters deep. At the upper road joint we would have gone with either a metal grate as a covering (to allow it to be driven over) or a reinforced concrete plates.

Ultimately the way of doing the gutter the way the engineer recommended would have never really held up under these circumstances. In the examples we had looked at the guttering was done on the sides of a concrete road. Doing a gutter here would have required that poured cement be used though out – probably cost wise the same as the subterranean drainage rounds.

In the end the deep drainage we were doing didn’t hold up and we shifted gears and replaced it with the subterranean drainage. True, part of the problem was trying to put the drainage in during the rainy season and the parts that failed hadn’t been rendered yet. In any event, it became clear that doing anything with deep drainage constructed this way was fighting a losing battle. Total impact on the project was probably about 20k or more which yields the sucked rating on the project overall. Another thing which was worse than I expected, all of the scraped up dirt which was taken off the road was used as fill dirt, some directly adjacent to the road. The amount of dirt erosion during the rain is pretty heavy.

One other thing I noticed is that my road workers that really did seem to have a lot of experience with roads, were slow to advise or point out anything. They had it in their head, but for some reason it didn’t come out until after the fact, like ‘I didn’t think that would work?’. Well, why didn’t you say anything?

I could go on and on. In the end the ultimate cost of the road with the drainage was still lower than some initial ‘rip off’ bids for the road alone without drainage, so that is good. The subterranean drainage is in place and ready for the eventual upgrading of the road. For now it is a matter of waiting to see how everything holds up until after the rainy season. It will for sure need to be maintained, since during a hard rain there is visible erosion. I can see why people really like concrete roads, in some places of high water flow that is the ultimate solution.

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