Between September 6th and 9th our old bridge was torn out and replaced by a spiffy new culvert. I had fun watching and helping.
This is what we started with. Rotting. Collapsing. Bits in the stream beneath. Not a good look. It was probably built ~1973 by the Freemans, who built the house we live in. It was build of found items. I beams, heavy wooden sleepers, railway iron, you name it.
Conrad made short work of it with a 14 ton digger. He is very skilled with that heavy equipment, and made it look easy.
With the deck off we could see just what a shocking state it was in. And we’d been driving over it (veeery slowly, and veeery carefully) for 18 months. We could really see how the high-water in June washed out under the west side of the bridge, there was really nothing left supporting that side (which explained why it was sinking day after day). It was also much more clear how very non-parallel the main support beams had become.
With that done it was time to put in the diversion. The consent had originally called for pumps to divert the stream, the problem was that all the big-bore pumps are still busy down in Christchurch (all the EQ aftermath). Conrad brought in a pair of pumps the week before, and they were not up to the task, so plan ‘B’ was to divert the flow with a small culvert.
The one risk in doing this is knowing where the pipes are. 15m to the east in the main gas main for Wellington. We weren’t sure exact where the water main lay, though. GWRC came out and marked it- turns out it only runs less than 3m from the western edge of the bridge. So, the culvert went down the east side.
The broken down bridge structure came out next. All that mess had made it into a veritable eel motel. I ended up on eel-patrol, standing next to the site watching the waters. When I spotted movement I would stop the digger, leap in, and rescue an eel (and once a fish I mistook for an eel). In the end was saved 6 eels, 2 largish, 3 medium, and a little finger-thick one. Nice to see them doing well, as they are on their way to being threatened. We should start feeding them.
Once the old bridge was out they prepped the site (sculpting the approaches, a layer of drainage metal underneath), and the culverts went in. Each culvert weighed 7.2 tons, so they needed a grunty Hi-Ab truck to lift them into place, since the 14 ton digger would have had trouble.
At the end of the day they had the culverts in place, and temporarily back-filled so Tam could drive across and up to the house. The cattle grid was also supposed to go in that day, but in a snafu typical of this whole project the cattle grid had somehow been left in New Plymouth. They promised it would be in the next day.
The next day was spent making the concrete-sack filled abutments. The Hessian bags were filled with concrete mix (dry), and stacked in place and secured with rebar. Natural moisture (and rain) helped set them all up in a few days. I spent the day helping. Mixing, filling and stacking 200 x 35 kg bags is a goodly amount of work. I ended up in the part of the work chain where I hauled the newly-filled bags down to the work site where Conrad stacked them. He had brought in some extra hands for that day’s work. With most of the bags in place we opened up the stream at the end of the day, and let it flow back along its natural path.
Then it was time to get the cattle grid in. They ended up sending up a much nicer cattle-stop than the one specified on the plan. I’m not complaining. Made of cast concrete, each piece weighs 2.1 tons. I mentioned how massively over-engineered this whole thing is, right?
When they were done Conrad sculpted everything into place. It all looks lovely. The spray-grass (hydro-seed) people should come soon, to cover the areas that got churned up and re-graded. While they were here, I had Conrad re-grade our washboard drive, and put 20 tons of fresh basecourse down on it.
Now we just wait for the fencer (should be next week) and then we are back in business, with a 1000% better bridge. Highway grade. 13 tons per axel. What hilarious overkill.