I saw the thread this morning on obtaining an accurate measurement on manholes... but what about storm inlets? Those 2'x4' grates are heavy, fall back in and require (usually) two men to open. What does everyone use? I haven't been able to figure out a reliable system yet.
Funny story about inlets;
When I was much younger and stronger my I-man and I were going through a big topo job we had already shot and getting inverts. I would lift the lids off and take notes and he would hop down to measure. While he was climbing out and putting the lid back I would move on to the next one. I pulled one lid that had a lot of sandy silt around the lid and as the lid came out the silt settled into the inlet forming an apparent dry bottom of about 1.5 feet deep. Along comes Curt and hops in, all the way up to his belly button. Unfortunately I had not seen him coming to warn him as I was busy writing my note about the inlet being full of water.
Not that I have done very many, but usually I just measure down from the top of the grate with a tape measure or laser.
Right. Me too. I try very hard to avoid lifting those square/rectangular grates.
I have never seen a sewer of any kind where on any given measurement 0.04'+/- would make a difference. Any closer will only allow the engineer to add more decimal places. I use a fiberglass tape with a 5/8x24" bar taped to the first 2', everyone new it was the turd tape. 😉
Storm inlets aren't flat like manhole covers, so creativity is called for. I like to tip the grate back, add the dip to my rod height, and take the shot right over the invert. That way you've got both a location and an invert elevation.
Dave
If I can't get lid off I use a thin rod and if there's gunk in the base hopefully I hit the invert and not an obstacle.
I always make note of condition and get RL at top centre of grate.
I let those of interest know the condition of the pit, as a blocked one can have unpleasant outcomes, more so in days of flash flooding that are more norm than occasionally.
As said elsewhere here sewer /storm water inverts are or should never be used to better than ±20-35 mm.
If exceedingly flat is only option, then unless they're 'chasing the wind' that too doesn't really impact on an outcome.
Who ever lays pipes should always check inverts on site and lay grades accordingly IMO.
I did a sewer connection once that was used for design upstream.
The contractor used my inverts and nearby control, set his laser and laid right to the pit.
Hadn't bother to check his gear or the invert he was heading for, and last pipe was lower than my given invert which I was pleased to know was at the correct RL.
Sometimes, when your lucky, you can directly shoot inverts with a reflectorless gun.
:stakeout: :totalstation:
In the Virgin Islands. they're all filled with sediment, so I just note that and move on. It's easy.
😀 Too funny!!
