Manhole Depth Measurement

Franz,

1. A mirror works better than a flashlight. I carry one just for dipping manholes.

2. Redirect traffic with lots of cones. Helps to have a partner.

3. Even if your elev rod is at an angle, you can estimate pretty close, but the Pipe-Mic II is the bomb:
http://www.chrisnik.com/pipe-mic_ii.html

Dave

SURVEY ALL RIM ELEVATIONS , HAVE A SCETCH OF THEM THEN MANUALY GO IN THE FIELD OPEN EACH ONE AND USE A LASER DISTANCE METER TO SHOOT AVERAGE PIT DEPTH AND IF INVERT OF PIPES CAN BE SEEN SHOT THEM TO AND ADD THE INFO TO YOUR SCETCH..

Agree with laser, but they (Leica) doesn't like wet surfaces. Can be a fiddle.
I like a PVC pipe with a piece of tape attached (taped).
I don't like indirect measurement by deduction, but have used your suggested idea.
Slope is accountable for if you know offset at rim which would be constant, then a Excel file would work, or as said estimate is often reliable.
A piece of 2" X 1" or is it other way round(?) to lay across hole. A thing straight piece of wood, something.

Couple things learnt.
Don't have anything in pockets, and don't wear a field bag.
Bending over an open manhole things have a habit of taking advantage of gravity and disappearing!
Also remember what those cesspit's contain. Wear gloves and have an offsider watch around you and be your scribe.
Wash well including your measuring rod and have something to wrap it's business end.
Nothing worse than human crap all over your gear when you throw it in the back of your wagon to come home.

Banging Manholes

Underground utility location is a tremendous source of liability and is taken far too lightly by many if not most surveyors in my estimation.

We used to go in the manhole, measure the size, type and direction of pipes and then using a lath and torpedo level on the pipe measure to the rim with a tape.

That method was unsafe and now out of use in my part of the country for the most part.

The most common method is to measure with a 25 foot fiberglass rod, some folks measure the slope and reduce to vert by either using a builders inclinometer or measuring approx HD and reducing from the hypotenuse.

Strips of flagging are often tied on the bottom of the rod at typical pipe sizes to aid the eye, I tie a bigger knot so I can feel it slip under the pipe opening.

Bell ends can be confusing when determining size.

Pipe type can be difficult without being able to hit the pipe with a hammer.

A signal mirror can help throw a powerful beam of light.

Dye tabs can help determine if structures are connected and which way they are flowing.

Pre field research along with knowledge of the age of the system along with the standards in place at the time the system was built can go a long way in helping to solve it.

Having your partner hit one with a hammer and listening at the other can help determine if they are connected or in extreme cases help you find a structure that is under brush or refuse.

Some shops like to use "dip sheets", blank worksheets with fields to fill in the details. If you go this route be sure to make some on waterproof paper.

Depending on the scheduling of it all I like to walk the site with a competed topo on mylar and draw in the pipes in the field while I measure the inverts this is only really possible on bigger jobs.

Some shops shoot the center of the lid, some the north rim, some like to open the manhole before locating, approximate the center on the surface and shoot that. There are sound arguments for all approaches but I have always preferred the center of the lid.

I like to write my point number on the ground to the north of the structure to give me a check on orientation when I make my sketch, you would be surprised how often sketches get skewed.

A plastic bag with a rubber band on the bottom of the rod does wonders to keep the poop off.

I take off my regular vest and tool belt and carry by tools in a bucket, nothing like the feeling that comes along when you see a field book hit the invert of a flowing sewer manhole and watch the book take off down the line (so I have heard).

I am all for one person crews but prefer to have a helper when getting civil detail.

Great tips. Speaking of tips, those heavy lids will chop the tips of your digits clean off.

Be careful.

Lost Field Books

I take off my regular vest and tool belt and carry by tools in a bucket, nothing like the feeling that comes along when you see a field book hit the invert of a flowing sewer manhole and watch the book take off down the line (so I have heard).
Well mine lodged in the debris below.
It's a sinking feeling like no other. Retreiving or not retrieving wasn't an option.
I wasn't about to redo all previous work.

+1 on the Pipe-Mic. It's the best method I have found for measuring manholes without going inside (which I'm not about to do).

The mirror works very well if you have bright sunlight.

Another trick I have found is to take a digital camera and turn the flash on. Reach inside with the camera and snap a shot. You'll be surprised how much you can see in the picture. At least you know you're not missing any pipes.

Pipe-Mic II. Try it and you'll never go back!

I sure would like to see an affordable digital imagery approach. Maybe like this?

http://www.rapidview.com/panoramo_si.html

Great tips mates, thanks a lot.
Will take a look at the Pipe Mic.

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.

I bought a Pipe Mic II, a few years ago, and I would never go back to getting inverts without it. It also added the 1 foot extension, for those pipes that are recessed.

C Billingsley and I have measured hundreds of structures since I bought the Pipe Mic, and now we have added one to his truck as well. We have a great system down. We use the worksheet available on the ChrisNik website, and it really makes getting the inverts easy.

I have a really bright, hunting spotlight that I use for lighting up a manhole. It works great.

Another trick that a former coworker came up with was using an azimuth compass to get an azimuth reading on each pipe coming in and out of the structure. My former boss said it really helps connect the pipes in the office.

That's very very neat.

I endorse the digital camera comment.
I use one and (always!?) orient camera looking down the hole from the south side with axis of image east West.
Makes easier to check flow directions and other pipe info later.
Occasionally it is useful to give relevant information to those in need of the urgency for maintenance.
Couple incidents were a massive invasion of willow roots, another chockers with nappies and other unsavoury items.
That is often enough to trigger a response from those who need to know.
Otherwise a "you need to check manhole" email often falls on deaf ears.

It's a must have (photos) in data collection.

Jimmy,

That is a good worksheet on the ChrisNik website:
http://www.chrisnik.com/uploads/Pipe_Mic_sample_sheet.pdf

Dave

> I sure would like to see an affordable digital imagery approach. Maybe like this?
>
>> http://www.rapidview.com/panoramo_si.htmlbr >
The approximate price of the PANORAMO SI is 150,000.00 without reporting software, around 180,000.00 with reporting software.

Ouch.

Banging Manholes

Some great ideas here , the best one for me was the flagging tied to the rod at the common pipe sizes ..... I am going to implement this for sure thanks.

Banging Manholes

Another tool I forgot which can be quite handy is the 9' folding level rod for measuring inside the manhole, ie measuring down from the top of can to ie of pipe where direct measurement is impractical due to slope or being obscured by can.

I always just used a telescoping leveling rod to measure from the invert to the manhole rim. A good sketch is appreciated by the computer jocks back in the office. Thankfully I haven't had to do sewer inverts in over a decade. The last batch I had to do was on a military base and the experience left me severely traumatized with PTSD, Post Turd Stress Disorder. Also don't forget to have a can or two of Lysol handy to disinfect the rod before it goes back in the truck.

> Also don't forget to have a can or two of Lysol handy to disinfect the rod before it goes back in the truck.

AND a couple bottles of that hand sanitizer to make yourself feel better about handling your sandwich.