> AND a couple bottles of that hand sanitizer to make yourself feel better about handling your sandwich.
I make it a habit to never handle that fiberglass rod by the bottom section.
Dip Sanitary first, storm last. Tends to clean up the rod at least a little.
Dip manholes and drainage structures before surveying them. Sketch the connections, account for the flow from site entry to site exit.
Both ends of pipes will always be the same diameter. The occasions that this is not true are so rare that you will be forgiven for making that mistake.
Here is what we use,
Dual-prism Offset
In a conventional survey, use this measurement method to coordinate a point that cannot be observed directly with a pole in a plumb position.
To measure a point using the dual-prism offset method:
As shown in the following diagram, space two prisms (A and B) apart on the range pole. The distance BC is known.
Take two measurements (tap Measure).
Trimble Survey Controller calculates the obscured position (C) and stores it as a raw HA VA SD observation.
BC can be as long as needed to reach the bottom.
Or use Seco PN5198-162, Sewer invert bar for the bottom of your rod
Hi Guys
We use a Leica DISTO D8 with the Adaptor LSA360 mounted on a spider.
The D8 gives you a distance plus delta H and delta V (must have a tilt sensor inside?)
One leg of the spider is fixed and is set up on a levelled point on the MH. The spider can then be levelled using the pill bubble and the other two adjustable legs.
It has been engineering so that the point of measurement is 300mm above the fixed leg.
You can see the red dot on the il. of the pipe you are measuring.
It has been very successful.
Can you provide a picture of this setup? I'm particularly interested in the "spider" component. Thank you!
If you use a level rod, never carry it on your shoulder, especially with the bottom of the rod over your back.
I have a Pipe Mic II, and I've used it on maybe 50 manholes.?ÿ I think its most valuable feature is the ability to measure the pipe size.?ÿ Lots of manholes around here are over 20' deep, and eyeballing those pipe sizes doesn't work very well.?ÿ But I find the Pipe Mic cumbersome to use, and even with a rod bubble attached I don't think I'm coming any closer than 0.05' of an accurate depth measurement.?ÿ So lately I've gone back to using just the fiberglass rod and a carpenter's inclinometer where needed.
Absolutely agree with the Pipe Mic II, just don't forget to add 1' for the vertical offset if you are using it.?ÿ It makes accurate invert readings possible in bell shaped ends where the reading rod alone has no chance of reaching.?ÿ I never trust the tilt of a rod.?ÿ I made an adjustable straight edge out of 1" square aluminum tubing to lay across the manhole rim to ensure an accurate measurement.?ÿ I also empty my pockets, carry a pail, spotlight, gardening knee pad, and a container of disinfecting hand wipes.?ÿ I also bought a cheap collapsible selfie stick for my cell phone if I need to take some photo/video down in the structure (haven't dropped it yet, fingers crossed).
One thing nobody has mentioned is safety glasses.?ÿ I knew a guy from another company who got splashed in the face while measuring inverts.?ÿ He got sick and ended up in the hospital for a few months with some weird infection.?ÿ My crew had to measure a manhole one time that was just shy of 50' deep.?ÿ It was a 48" interceptor line; fastest flowing line I have ever seen.?ÿ We ended up using an anvil tied to a rope.?ÿ Drop the anvil down until you feel it hit the bottom and mark the rope.?ÿ We had to due this several times, due to the swift current.?ÿ Then pull it up and stretch it out to measure the length.?ÿ It sounded like a river when you opened that lid. I am not sure of how accurate this method is, but my theory is, prove me wrong.?ÿ It must have worked because the project was completed.
Need to do some sewer manhole investigation. Can you guys suggest some techniques to get the invert elevations of sewer, drainage & water manholes? I saw a couple over the weekend and some are 2-3 m deep. I also need to get the inverts of pipes leading to each manhole.
Some difficulties I see are :
1. Not enough light to see details even with a strong flashlight.
2. I have the idea of getting a sturdy 3 meter 1" water pipe & dropping it to the invert & measuring what is above the rim & do some plus/minus to get actual depth. First I was toying with the idea of sticking a rod with prism & measuring the prism point but I guess it would take a bit longer doing this method. Add to that the traffic concerns as some manholes are located middle/side of the roads so a quick open, measure & close process would be in order.
3. How do you get the inverts of the pipes without really going under? Physically going down some of these manholes is impossible without any railings.
Suggestions would be welcomed.
Buy a Pipe-MIC II.
I have a Pipe Mic II, and I've used it on maybe 50 manholes.?ÿ I think its most valuable feature is the ability to measure the pipe size.?ÿ Lots of manholes around here are over 20' deep, and eyeballing those pipe sizes doesn't work very well.?ÿ But I find the Pipe Mic cumbersome to use, and even with a rod bubble attached I don't think I'm coming any closer than 0.05' of an accurate depth measurement.?ÿ So lately I've gone back to using just the fiberglass rod and a carpenter's inclinometer where needed.
I only report invert elevations to the nearest 0.1"
>Both ends of pipes will always be the same diameter.?ÿ
Nope - not ALWAYS!
We used to measure manhole depths with the aforementioned 25' Fibreglas rod.
We would tape a 4' lath to the bottom so that 2' extended beyond the bottom of the rod.
We could throw away the?ÿlath when all the work was done.
Another suggestion by my boss at the time was to cover the bottom of the rod with a condom.
I told him "If you can get City Stores to stock condoms I'll order some for us."
That will keep them wondering what we were doing over in the Survey Division.
>Both ends of pipes will always be the same diameter.?ÿ
Nope - not ALWAYS!
YOU know that, and I know that, but I'm not going to let a field crewman believe that. The number of instances where the diameters are actually different is much, much,?ÿ much smaller than the number that will be reported as such if you allow it.
?ÿ
Those heavy duty ones have a 5-6" tall rib in the shape of an X on the bottom of the lid.?ÿ They weigh about double what a normal lid weighs and I've heard that they hurt like hell when they fall on your foot as you're struggling to wrestle them open or closed.
Great tips. Speaking of tips, those heavy lids will chop the tips of your digits clean off.
Be careful.
Indeed they will.?ÿ I have a colleague who lost the tip of a finger during a manhole lid mishap.?ÿ He was wearing thick gloves and at least a quarter inch of his finger was pulled out of the glove.
3. How do you get the inverts of the pipes without really going under? Physically going down some of these manholes is impossible without any railings.
Yeah, don't ever do that. I don't know about safety requirements in countries other than the U.S., but here I would hope no one would ever be asked to climb in to a manhole without first having undergone confined space safety training.
I just had a comprehensive safety class this week for a project I'm working, and they mentioned the same thing about confined spaces, and cited a recent (thankfully not fatal) accident this company had with a veteran guy who did everything right but still had massive injuries from a fall that required a four hour rescue. The 911 call was answered by police, who couldn't do anything other than summon the local fire department, who couldn't do anything because they were not equipped for confined spaces, then had to contact the three fire departments in Indianapolis that are equipped to do confined space rescues.?ÿ The four hours started once those departments arrived. Somewhere else on this forum there was a recent link to a year old story about three fatalities and a near fatality as a result of people climbing down a manhole.
I've measured tons of structures over the years. I was never asked to climb down in one until I moved to Indiana about 15 years ago. I declined when asked. The only other time I declined a work request was when I was surveying inside the Astrodome and was asked about going on the catwalk spanning the dome. I don't do confined spaces and I don't do heights.
1: NEVER go in a manhole.
2: I use a 25 foot level rod - but don't forget to lick the end off before you put it back in the sock.
3: dip sheets: I've run across a few.
?ÿ
...- but don't forget to lick the end off before you put it back in the sock.
3: dip sh(i)ts: I've run across a few.
?ÿ
Funny!
Pipe Mic is a good one to add to a tool kit.?ÿ And an extendable camera pole. For simple dips have been experimenting with long rods and tilt functions on GNSS heads (especially happy with the new non-compass based).?ÿ
For documenting have been trying all manner of inverting scanners, image based SLAM types systems, DotProduct, and now waiting to hear how one outfit is doing with their inverted BLK360 tests. trying to avoid going down in MH's altogether...
Yes!?ÿ Keep us posted on this front.
We've duct taped a 90?ø angle iron to the bottom of a beater 25' rod. It's handy for sliding (close) to the ie of pipes in offset manholes. We take a reading against the rod with plumb bob string stretched between the edges of the rim. Still not as accurate as a Pipe-Mic though.
Does anybody else use a hidden point for measuring inverts or is it just us? Easily get most data that is needed within 2-3m(depending on how many extensions you have) This way we get a coordinate for where the pipe ties in not just the elevation.?ÿWe used to either tape em or use the "sewer rod" but different results for different crews.
Normally we'll measure the inverts, top of?ÿpipes and inside of the barrel as it's bitten us in the past not having the info. It can be a little time consuming so might not be the best if it's in the middle of an intersection.
