This details a local project to upgrade part of a road from a long-standing
dirt surface to asphalt, including new drainage structures underneath
and some regrading. It was done ancillary to the construction of a new
subdivision nearby, as improvement of its main approach road. The project
also included the
water main tap a few months
before to bring water to the future new houses.
While the abutters (*ahem*) actually didn't mind the dirt road -- if anything it lent a more rural feeling to the area and helped keep traffic speeds a little more in check -- it spent a lot of time being a bumpy mess, especially after all the freeze/thaw cycles in winter. Large potholes would just magically form and grow on a fairly random basis. Oddly, the most impressive effect of this would come when the UPS step-vans drove by a little too fast and emitted some very distinctive booming.
[Thumbnail pictures are linked to larger ones.]
This is why every spring brought the town public-works guys out at least
once with the big grader, when they'd dump a little more fill along the
surface and level it all out. This would last about a week before the
proto-potholes slowly started forming again, like ripples and dunes in
desert sand. This picture is from a few years before the upgrade project,
but it could have been from pretty much any year as it was the same
story every time.
The bigger graders evidently have a feature that can lean the front wheels against the direction of thrust from an angled plow underneath. With quite a few dirt roads still in existence around town, a higher-end model must have been viewed by the DPW as a good investment.
Over many of our objections, the town planning commission voted to approve
the upgrade plan basically because they'd get a paving job for free.
The developer wanted it done and would fund this piece even though
it lay in a different *town* from his subdivision -- as the only vehicle
access it would still pretty much make sense for the potential increase
in traffic. Thus we failed to use disapproval of this as a wedge to impede
the rather unpopular subdivision itself, but it was definitely thought of.
Long story short, we the peasants brought our pitchforks and torches
to a lot of planning hearings over the years, ultimately to no avail.
So it eventually came time to engineer the improvement, and our town asked for a solid, durable design for it. Changing to an impermeable surface would affect all the drainage characteristics, especially for water flowing down the gentle hill, so stormwater management was key. As the nearest land lower than the street was a wetland preserve that already had zero drainage, they weren't going to send it there. The only other choice was sufficient volume of deep soil infiltration to basically just make all the water go away. Including the amount that could be anticipated to come in the typical "hundred year event".
|The plan went through a couple of revisions. The first one had three big infiltration structures and a full set of sidewalks and curbing, until it finally dawned on enough of the players that there simply wasn't enough right-of-way width to put all that in without taking abutter property by eminent domain. They actually didn't want to do that, so the plan got reduced to no sidewalks, no curbs, and a smaller drainage setup which would still meet most of the qualifications for an "accepted street". There aren't any sidewalks in the rest of the local neighborhood area either, so there was no real need to go all-out on this small section.|
One morning the drainage structures got delivered, and then sat there
for another month or so before being used. These weren't from our local
as anyone hereabouts would expect; they came from some different
source and were a casting design I hadn't seen before. All this stuff
had to go in under the road surface, so it was clearly going to be a lot
of digging. And our existing water main was sort of in the way of it
all -- that's the "--W--" line in the plan.
The road going away to the right is the new subdivision road, generously festooned with unfriendly "no trespassing" signs from the developer. Abutter relations were still not exactly what you'd call warm, despite occasional attempts to placate the residents on the corner with small frivolous gifts.
Finally the morning to actually start all this arrived, and equipment
began moving some of the parts to nearer where they'd be installed.
Most medium-heavy equipment has some kind of rigging hook on its business
end, for lifting purposes just like these, where the addition of some
chain and wire bridles makes it into a small mobile crane.
These smaller-diameter bits are catch-basins, where water would go first to drop its sediment and get periodically cleaned out by the town.(*) Thus the bottoms are closed, as these aren't where the infiltration happens.
(*) In theory, anyway; we'll see if it's even on their radar anymore a decade in.
The big excavator moved into place, keeping its boom low to duck under the
various wires across the street. All the wires were the regulation 15 feet
or more up, but this could easily reach higher and hit stuff if the
operator wasn't looking up as well as down.
On Caterpillar's "digger scale" this model is still in the smallish class, compared to the absolutely monster ones used in mining operations.
|Ground was first broken over the "existing drywell" as noted on the plan, with the intent of replacing it with one of the catch basins. Positioning details were all referenced to a set of stakes that they'd surveyed and put in a couple of days before, in lines going off the road into the yards on either side.|
|About two scoops with the bucket pulled up an iron grating and revealed said drywell, which was old and neglected and so plugged up with organic sediment that it was anything but dry. On the original road relatively little water would actually make it into this, so I never saw it actually overflow and puddle. Presumably some of the water could escape out the interstitial stonework cracks once the sediment dropped out, but this thing's days were probably numbered anyway.|
Then the excavator guy spent a while on the phone, after which they
dropped a steel plate back on top of the drywell and covered it back up.
Turned out that they hadn't waited for some sort of 48-hour notification
window related to the "street opening" permit to elapse, and would have
to button up and continue the next Monday instead.
So this was sort of a false start, although a little progress had been made. The catch-basin parts were still lining the side of the road ready to go, so they just put out a few cones around them and left them there rather than try to move them all back to storage.
So things didn't get entirely serious until the next week, but then it all
kicked in for real. The digger's base got placed on the other side of the
drywell location this time, putting the arm right under a fiber drop where
the operator had to be really careful not to swing too high. He would have
had the same problem coming from either side, so it didn't matter. But he
was clearly used to such constraints, and the artistry in his control of
the machine was well-practiced.
I shouldn't really say "base got placed". The excavator is on tracks with easy footpedal control, and one of the stay-low techniques is to dynamically translate the entire thing back and forth to move the bucket over where it's needed. It's like whole-body flow arts on a multi-ton scale.
|The old drywell was turned into so much muddy slop in a matter of minutes, with the blocks that used to be its structure and the old stone bed pulled out and added to the pile. It actually had a respectable amount of drainage bed in two-inch-ish stone underneath and around it, but it was all pretty filthy by now. Probably pushing fifty years old.|
|Once the hole was to depth, a shallow layer of smallish bedding stone was dropped in and leveled over the placement area. This wasn't for drainage, it was just to more easily make a flat bed underneath.|
|To determine the center point of the basin, one guy pulled a tape measure over the alignment stakes, bridged part of the hole with the ladder, and stood on it to lean way out over the hole and drop a couple of orange-painted stones from the right point. Quick and dirty plumb-bob technique, probably not OSHA-approved. From there they could draw out the radius of the basin footprint and swing the paint can around.|
|It looks like a long reach with a heavy weight, but this was well within the excavator's lifting limit and the guy just floated it right over and into the hole.|
|Because of the extra height needed for the basin and its rigging, the arm had to ride high -- right up to his limit, and he bumped the fiber cable upward a couple of times in the process [the really thin one with a slight upward apex over the bucket linkage here]. Fortunately there's a foot or two of leeway in the hang catenary and it was mostly resting on the smooth hydraulic piston, so this was harmless. The guy really knew his limits.|
Next the top half of the basin with its cover went in. There's actually
an O-ring between the halves. Again, these aren't designed to be the
leak point for incoming water, so they get relatively well sealed.
The lift points for the basin piece are simply holes into the sides, into which eyebolts are temporarily placed with friction keeping them in place under lifting tension. The holes are lined with plastic inserts to avoid chipping the concrete.
A little fiddling was needed to put the lid hole at the proper "back center",
at the right location relative to the edge of the road line. They had to
lift the lid up and spin it a little to line it up. The outflow opening
on the side has a big rubber flange, to seal onto whatever pipe runs out.
And the lift holes sit well above the outflow's "invert" level, so they
don't constitute stray leakage points.
Inverts, or the bottom of a pipe's inner surface, are all-important in drainage engineering as that's where the water begins flowing to whatever comes next -- and it had better be all downhill from there.
|The hole then got backfilled in a straightforward way with whatever was handy from the pile without much regard to content type, as it was all just volume. Some of it would get dug up again later anyhow.|
The fill got reasonably leveled, and there wasn't anything left except
a couple of stray bits of junk that had come out. There was some really
old piping around the drywell whose original function nobody could really
guess, and was all full of muck anyways.
Despite the fact that they had just put a big void in the ground, all the dirt from the pile went right back in around it. How, I wondered? Well, there had been a smaller void around the drywell and the new surface did sit just a little higher than before. All of this was temporary, it didn't matter as long as the road stayed nominally usable overnight.
|That finished the first real day, and the next one would be a little more of an adventure as the second basin would have to go in across the street *right* next to the telephone pole at the left. [Upon which there are almost no actual working telephone wires left...] They called in to the local power company to see if they could come out and lend some assistance on it the next day.|
|The power guys showed up bright and early the next morning with two trucks, even though they only needed the one with the pole-handling arm. The idea was to simply hold the pole firmly in place in case the ground it was set into got weakened.|
The claw at the top doesn't actually grip the pole, only wraps around it
as an upper stabilizer. The lifting is done by the nylon choker below,
pulled up by a rope from a winch just under the claw. They put a little
tension on the rope to keep the pole at a predictable height in case
something let loose, and then the two linemen
had to just sit around through the whole digging operation. It was a
nice enough day; I
ventured that it might be a lot easier than wrestling 13.8KV in an
ice storm, but one of the guys said he enjoyed that kind of challenge.
The excavator guy established the edge of his hole and started going down, and although he was pretty close to the pole he managed to leave enough dirt in place on that side that it didn't make any hint of moving. But there was a different surprise, in the form of that thin bit of metal hanging out of the side of the pit.
|They had located the water main fairly easily and were avoiding it, but the bucket suddenly dug into a small pipe running parallel to the main and mangled the crap out of it. Water started coming out one of the broken ends. Oops! But this pipe wasn't running in any logical fashion to feed any of the surrounding houses, and the next challenge was to try and figure out whose water service had just gotten whacked.|
The town water department was called to come evaluate things, and meanwhile
a round of outdoor faucet-checking happened. But everyone around still
had water pressure, so it remained a complete mystery what this pipe was
The guys tried to crimp off the end of the pipe as best they could to temporarily stop the leak, but it kept dribbling a little bit wherever the end happened to be at any moment during subsequent digging.
|They didn't let this little setback hold up the project, though, and went ahead with finishing the hole to depth and bringing in the next load of bedding gravel. Dumping this raised a huge dust cloud -- not exactly "washed stone", huh?|
|Height checking was done with a laser level, using a transit set off to the roadside at a known height and spinning a flat plane of laser light and a ruler-mounted sensor from the bottom of the pit to indicate the exact intersection point of the plane. Typical survey stuff used these days, and obviously makes the whole alignment job easier. The only minor problem that the sensor was supposed to have a nice loud beeper to indicate the detection point, and it was apparently broken leaving only the visual LED indication. The guy at the bottom of the pit couldn't really see that, so they had to talk back and forth to determine where the hit was.|
|Once happy with the bedding height, they started swinging in the next catch-basin pieces. This top half was tilting crazily as it swung over, and I have no idea what was keeping the concrete lid from sliding right off aside from lucky friction. As far as I could see it's just a flat piece, with no alignment ridge to the basin. What if it had slipped off at just the wrong moment and landed on the water main...|
|But the parts made it into the hole without incident and got fitted together. This basin assembly had to go in a little farther off the street centerline, because of having to clear the water main. That's sitting at the lowest horizontal ridge of dirt next to the basin. So while the other basin's lid got its access hole spun away from the road, this one had to be spun toward it to establish proper back-center distance. This time they dropped the temporary steel cover on it *before* starting to dump dirt into the hole...|
Under authorization [and a certain amount of shrugging] from the water
department guys the "mystery pipe" got cut back, crimped and capped off.
Since everyone around still had water there was no point in trying to
find where it came from as long as it wasn't leaking underground.
One problem that plagued parts of this entire project was that the town didn't really have any "as-built" diagrams of what's under this road. The water-main placement was mostly accurate but things like where all the feeds to the houses come off it are a total mystery until one gets dug up for some reason. It was all done fifty-plus years ago with random undocumented updates here and there over the years, which were evidently never officially recorded.
|Backfilling and grading proceeded normally from there on, with a bit of "digger sex" going on as the excavator pushed some spare dirt into the loader bucket to be hauled away. This time there was dirt left over, which made sense as there wasn't a previous drywell void and the grade got restored a little closer to what it had been before.|