The tentative roadwork schedule that the town engineer had distributed
to everyone was already slipping a little, as the rest of the week
after the catch-basins went in had the guys working elsewhere. Then
they seemed to take the Friday completely off, even though it would have
been a really nice day for work. The guys explained later that they
didn't want to tackle this next piece on a Friday anyway, as their
experience says they'll hit the nastiest surprises right at the end
of a week when the town offices close early and nobody can be reached
for problem resolution. So nothing further moved here until the
[Thumbnail pictures are linked to larger ones.]
Day 3 [a very long one]
|They measured and marked out a fairly large area. As it's hard to see their orange paint in this shot, I've artificially ringed just outside it with red dots. The two big infiltration structures would go in here. I was relieved that all this seemed well clear of where *my* water feed most likely crossed under the road, so they wouldn't have to dance around that.|
The infiltration pit structures were substantially larger than the
catch basins, and got moved up in readiness the same way. They're
designed to get drainage stone backfill put in around them but the
narrow slots don't let it into the inside, and the interior volume can
buffer some amount of water for a while before it seeps away. The total
amount of that volume needed presumably came from engineering calculations.
The developer disagreed with the town engineer's requirement for the two pits, however, insisting that one of the structures would have been more than enough for this application. Who knows, with the elimination of the curbs and water thus theoretically able to run off the sides of the road crown as it came down the hill instead of all piling up at the bottom, maybe he was right.
|No sooner than the infiltration parts got moved away, a delivery of drainage stone arrived and got dumped into the same spot. Two or three truckloads of the same type of two-inch or so gravel as in the old drywell were brought in, I lost count. But it was clear that they'd need quite a bit of it.|
|Excavation began, with the same sub-inch precision that I continually admired this operator's ability to maintain. He really made something of an art and a science of having things go right, because as he put it, with these pieces of equipment things can go *wrong* very quickly if one isn't paying attention.|
|He had his challenges cut out for him that morning, with my FiOS fiber right in the way again [the tiny one that looks parallel to the tree]. My power feed above that and all the neighbor's service drops were also part of his headaches that morning. The expected dirt volume would be much larger than for the catch basins and would mostly be replaced with stone, so he wanted to truck most of it away. But to drop dirt into the dumper, he had to swing the bucket in sideways with about a foot to spare between the truck and the fiber, and then dump the bucket very carefully without pulling the boom and stick up too far.|
At one point he tried to move forward a little to open the bucket more
toward the front of the truck, hoping that the fiber that was by
necessity resting on the hydraulics
would gently slide back ... but it hung up under the bolt heads at the
end of the cylinder, and I watched in horror as he started to put a
nasty pull on the drop. The other people around saw this too and we all
yelled "YO!!" and whether he heard that or not he stopped and backed
off. The cable is really small, and he could barely see it up through
his cab window. So ... crisis averted, and I still had my internet
FiOS drops don't always get flown from the pole; this one hops off mid-cable and just attaches to the main messenger for the trunk, which even though thus slightly deflected nonetheless provides enough tension against the house attachment to hold everything up. Part of that is because the fiber drop cables come in a variety of fixed lengths with preassembled connectors, so some adaptation has to be made to reach end-to-end and not have too much excess coiled up somewhere, and they don't weigh much so it isn't a lot of sideways pull on the trunk. The fact that such a rig had a lot more overall "springiness" to it probably helped save the drop; if it had been held between two hard points it might well have snapped.
|But clearly the truck was a bit too high to safely work with, so they went to an alternate means of removal -- filling the loader bucket and driving that away to somewhere in the main site to dump it. More digger sex. It wasn't actually that much slower than using the truck.|
|A little later on a couple of emergency-responder vehicles came barreling up the road and stopped dead when they saw the digging operations completely blocking passage. They had to turn around and take a different route. I have no idea where they were going as we didn't see them come in the other end of the street, but presumably they did what they needed to do despite this minor hiccup.|
|However, a police supervisor showed up a little later to mildly chide the foreman that they had no idea any of this work was going on -- said he had to notify the police department on any day they were going to block roads, and have a detail present to manage traffic especially in cases where emergency vehicles had to get somewhere and weren't expecting obstructions. This was news to the crew, as they'd thought the "48 hour notice" and everything else they'd put in at town hall constituted sufficient warning, but evidently this wasn't the case and there had been a bunch of miscommunication.|
After everyone was clear on these additional procedural wrinkles they got
back to work, and with this end of the hole down to depth it was time to
start laying in filter cloth. This would go in under the entire drainage
structure, to help prevent silting of its lowest points.
This immediately had me wondering if I should have done the same on my own little drainage pits. I'd planned for some silt accumulation area by placing the bigger rocks at the bottom but expected crap to come from above, not below.
|Another layer of bedding stone was brought over and dumped in. Our police super was still on site, but was replaced a while later with a regular patrolman assigned to this for the rest of the afternoon.|
|Leveling such a bed is for the most part a by-hand operation with a shovel and rake, as large equipment can't really get to the point and a human walking on the surface has a much better idea of what's close to level or not. They never actually checked it *with* a level, but a very slight tilt to something like this totally doesn't matter from a functionality standpoint.|
|They used the "rock drop" trick again to find the center offset, and marked out the 8-foot diameter for placement.|
The first low half was then lowered in and placed. Note that unlike the
catch basins, this structure is open on the bottom to the stone bed as
that's part of the infiltration area. Next came a ring of some sort of
sealant goop, presumably to adhere the sections together -- certainly
not for leakproofing, as this entire thing would inherently be a big
The attachment points for the rigging hooks were short sections of steel cable, which would simply flex out of the way as the next piece came down on top. This removed the inconvenience of having to saw off solid rings or the like.
I backed way off for this next lift to get the wider picture, because
I figured I knew what was
going to happen. This was the heaviest item because the top half of the
infiltration structure is closed, and thus contains the most concrete of
all the parts here. I should *not* have been able to see the top of the
excavator from this viewpoint, but as the operator tried to lift this
thing out on such a long lever arm the entire digger body started to tip
up. He was also very close to the edge of the hole. I thought I heard
him emit a little "whoa!" from inside the cab ... although he's probably
well acquainted with the dynamics of all this.
In general the structure piece was within manageable lifting limits [PDF brochure, 2.2 Mb] of the excavator, but not *quite* when out at full reach like this which derates capacity to about 4500 pounds even with the machine's "heavy lift" feature enabled.
|I highly recommend the above-linked brochure as an instructive read for anyone even mildly interested in equipment like this, as the engineering behind it is rather fascinating. The lift limit table is on page 21. There are many videos kicking around about how to operate these things, including the one where a guy has his 6-year-old son digging a drain or something... I spent a little while doing research, learning fun little facts such as the difference between the ISO and SAE joystick control standards, stuff about hydraulic pump controls and maintenance, and how Cat's automatic "grade control" works. This ain't your daddy's rusty old four-lever backhoe, by any means.|
|He managed to slightly unweight the piece and drag it a little closer, where the boom angle became more reasonable and he was finally able to pick it up to swing into the pit. It was clear that it was still approaching the limits of the excavator, but the machine would have told him if anything was exceeded by simply opening hydraulic relief valves under excess load -- the same thing happens when a part reaches its limit of motion, which a good operator will try to minimize happening anyway.|
|Putting in the top half was a little fiddly because it had to be spun so its main pipe hole would face the other end of the pit, but after a little bit of wrestling the two pieces were perfectly mated.|
|The end of the pit was also covered with filter fabric, and the first of many loads of drainage stone was dumped in. A few more loader trips brought it up to the edge of the pit at the end and in a couple of feet.|
|Digging could then proceed on the other half of the pit, revealing the sides of the catch basins and still carefully avoiding the water main. At this point they gave up on trying to shift dirt offsite, and simply made a big pile on the other side of the excavator where there was room. This meant that each bucket had to be swung around 180 as it came out, but at least this was largely out from under the overhead wires so it went pretty quick.|
|The filter-fabric lining was continued in a couple more strips from the giant roll they had.|
Graveling in at the end of the pit allowed the loader to advance over
the drywell structure just far enough to be able to dump *over* it and
into the middle. That stone then got spread to under where the second
structure had to sit.
Okay, so I've got an excess of stone-dumping shots with dust flying up. They did a lot of this, it was an integral part of the works.
|The next structure piece had gotten staged a little too far under the wires along the side, so it had to be dragged out of place before being lifted for real. I might have thought about unhooking the far-side rig points before doing this, so it wouldn't tip up and dig the front corner into the ground...|
|The second drywell would sit a a fairly generous distance away from the first, leaving enough space in between to contain the design equivalent of four feet of stone around each one. In reality it would all be one big blob of stone under here.|
More wrangling ensued on the upper half; the important thing here was
to line up all the pipe openings facing each other. I'm guessing all
the holes were custom-cut by the supplier for this project, as they
appeared to be cored right through the grid and not originally cast in.
They didn't bother with the gasket goop on this one and the final mating
was a little off, but none of that would affect the function.
At this point they started bringing over over the rest of the stone supply, and it was already clear that it wouldn't be anywhere near enough. The foreman hopped into the dump truck, dropped its load of dirt from the morning right about where he'd parked, and headed off to the local supplier for more stone. Meanwhile the other crew guy worked on spreading what they had.
He brought out the cute mini-excavator, which looked like a toy next
to the big one. This also had a small plow on the front which was used
to good effect to push the bulk of the stone toward the pit, and then
its arm could reach over and spread it past the drywell.
Except that this sprang a hydraulic leak in one of the hoses going to the extra movement axis that tilts the bucket sideways. Fortunately there are a couple of valved disconnect points on the arm just above that, as other implements might not need a hydraulic feed, so the guy could just shut off that part of the system and keep pressure to the rest while tying the extra hoses out of the way. But in the meantime it had spewed a bit of hydraulic oil over everything around it [which smells *nasty* -- similar to brake fluid], and now the bucket was kind of floppy because its side-swing cylinders had no pressure.
|A guy from the hired engineering company showed up to inspect some things, and wanted the crew fellow to break off from his stone-pushing to check some heights. There was apparently concern that the top of the structure was a little too high, not allowing sufficient depth of roadbed above. But the last thing anybody wanted to do was pull those structures up again and try to muck around underneath.|
The foreman arrived back in the midst of this, and in the interest of
high-volume pit-filling backed right in on top of the first drywell
and dropped the load. There was more chatter and I guess the inspection
guy was ultimately okay with what they'd done, because work proceeded
It was already way past the crew's usual stop time and getting later in the day, and they wanted to get this *finished* before the day was out instead of leaving the road unusable overnight.
|They brought in the bobcat [or Cat's equivalent skid-steer] to help push stuff around, and both of them worked together at it for a bit. Then the foreman took the truck off for *another* load of stone.|
|Somehow I'd gotten occupied talking to other people or doing something inside or whatever, and missed the fact that the crew guy had already cut and installed the 8" pipe going between the infiltrators [arrow]. It was almost buried by the time I came back for a look.|
This fellow figures prominently in the next part of the story, as he
was basically working alone for another hour or more. He's a trooper,
a short but sturdy type of guy who's just a bundle of energy and keeps
working, working, working as long as is needed. He's always the man jumping
in and out of the pit, and was also the one cutting the water-main back on
that job and getting totally soaked in the process. If anything when
the boss is offsite he works *harder*, not slacking or anything. I
can totally understand that work ethic -- sometimes it's easier to just
concentrate and get stuff done, rather than have to interact with
other crew. So now that there was enough stone in here to walk around
on, it fell to him to get all the piping installed while the next load
of stone was being fetched.
It was really tempting to jump in and help him now and again, but I figured he knew what he was doing. I did bring him a couple more rocks from my little wall out front to hold down the filter cloth edges.
|And even with all that heavy equipment, sometimes it comes down to simple hand digging for the final touches on something that needs to be cleared. Here he had cut through the filter cloth and was prepping the rubber sleeve coming out of the catch basin to receive a pipe.|
|He put in the first of the two 12-inch pipes, first inserting into the infiltration structure since he could push it way into there, and then back toward the catch basin to insert into its fitting. As the catch basin fitting was so far behind the cloth I couldn't see anything of what he did to attach the pipe, so figured I'd wait for the second one to capture further details.|
|The second pipe had a complication: the hole that the concrete company had cut pointed nowhere near the catch basin. The plastic pipes don't flex enough for an S-bend, so he had to make a new hole aimed at the basin fitting. He took the diamond-grit saw [possibly his favorite tool?] and slit into parts of the web including some rebar if the occasional flying sparks were any indication, and then bashed out the rest with the big sledge.|
|Then he could insert the pipe, and used a clever means of prying it into the rubber fitting far enough to be secure.|
Last step was to tighten a band clamp around the rubber sleeve, and I
watched him shift the pipe back and forth in the process to make sure
he got the deepest seating on it. No idea how long a stainless steel
clamp will really last underground, but it was supposed to go on anyway.
The other end of the pipe just sat loose in its hole. I think the idea is that once water gets out of the catch basins and into the infiltration area, nothing more needs to be leakproof. But I guess that we still want a half-decent seal between the basin and its outflow pipe so less water goes in stray directions too soon.
|With all the pipes laid in, the thing looked just like the design! Funny that. Except that there was probably a lot more drainage stone involved in this than anyone had predicted.|
|The guy covered up the original hole with some of the blocks from the old drywell, which were still kicking around in the fill pile, and laid another bit of filter cloth over the remaining small openings.|
|Conveniently, the foreman returned at this point with their last load of stone, saying he'd had to chase all over the landscape to find a gravel place that was still open as the local one had already closed. They were really coming up against time here.|
|That all got pushed in and spread and seemed to be enough to finish the pit up to the level of the drywell tops. They checked that the steel cover plates were on right; even if all these structures would eventually have access manholes they would get them later after grading was done as otherwise they'd just be in the way. With dirt about to cover everything back up, I made the guess [confirmed by the foreman] that instead of worrying about precise locations now they'd just find them again later with a metal detector.|
|There was still a giant mound of dirt in the road, so one guy worked on loading and hauling three or four truckloads of that away while the other finalized the pit and the stone for regrading.|
|That involved flopping the filter fabric edges over, and eventually laying more over the top of everything to completely encase the drainage structure in a cocoon of the stuff -- top, bottom, and all sides, and all gaps pretty much closed except for the two pipe penetrations from the basins. Minor rips around the edges weren't an issue; there's only so much precision you can have on something like this and it wasn't like a residential air-sealing job that had to be perfect.|
|They left enough of the dirt mound to use as backfill, and while they were rushing to get this done they still worked carefully. It was interesting to watch all this disappear but still think about what was under there now.|
In the last bits of daylight the area got a fairly rough but vehicle-passable
grading job for the overnight, and early the next morning the Hard Working
Fellow went over it a bit better. He thought he was going to have time to
get out the vibrating compactor and roll over it a bit, but got diverted to
something else back at the subdivision and never did. That's okay, the
passage of the loader and various normal vehicles did a sufficient packing
job for now.
That was it for a while; then came another multi-day hiatus. The next phase of the job would involve the Pulverizer, an apparently limited technical resource which the foreman said he was on the wait-list for about a week out so there wasn't much more to be done here. They had plenty to continue working on over in the subdivision anyway.