HOW BIGA ?

[LBrown59]

A little confused here.

But here is my novice experience anyway.
When I built my place I went to the county's TxDOT for a permit.
(No charge for residential).
They gave me stakes and flags to mark the location of culvert.
Engineer came, mailed design plans with detail reqs.
Things like width limit, radius of driveway turn-in, etc.
The engineer was cool and advised he only cared about two things.
1. proper size of culvert
2. saftey ends and installed properly.

He advised that the ditch was 2 ft deep, and I must have 18" culvert, with 6" of cover on top. Design spec stated that water must not drain onto road surface.

No problems at all since. Have had 6 concrete mixers over it and 2 were loaded with 10 yards each. Not sure but I was told that is 78,000 pounds total. Never had a problem.

PS. The semi drivers usually tell me they are glad I have 30 foot long culvert.
Some even ask how long it is before they come out.

Where?
Perhaps I can help.

 

[LBrown59]

A little confused here.


The engineer was cool and advised he only cared about two things.
1. proper size of culvert
2. saftey ends and installed properly.

He advised that the ditch was 2 ft deep, and I must have 18" culvert, with 6" of cover on top. Design spec stated that water must not drain onto road surface.


.

I still say basing the diameter of the culvert on the size of the ditch ain't the correct way of doing it.
How do we know the ditch is not to big or to small?
If the ditch is the wrong size and the culvert size is determined from ditch size then the culvert will be the wrong size also.

 

[CharlieTR]

Just a little confused on the terms or can't seem to picture the Schmism's solution in my head. But that's OK, confusion come natural to me. (a lot).

The little I know about the road ditches around here is that they are sized by DOT for drainage needs and built when road is built. I would ask that exact question to your county DOT engineer.

 

[LBrown59]

Just a little confused on the terms or can't seem to picture the Schmism's solution in my head. But that's OK, confusion come natural to me. (a lot).

The little I know about the road ditches around here is that they are sized by DOT for drainage needs and built when road is built. I would ask that exact question to your county DOT engineer.[/quote]

The problem with that is ditches don't stay the way were built. In 40 50 75 years they chang size and shape due to erosion cave ins and cleaning out.
I was showing the guy ftom the state the ditch last summer and the first thing out of his mouth was my god that's way to deep - wonder why it's so darn deep?

Another thing> .They don't change a lot of their drainage ditches and culverts to match changes in topography.

 

[ovrszd]

I still say basing the diameter of the culvert on the size of the ditch ain't the correct way of doing it.
How do we know the ditch is not to big or to small?
If the ditch is the wrong size and the culvert size is determined from ditch size then the culvert will be the wrong size also.

Hold on now Mr Brown, no one said that because it was a 24" ditch, that was the only reason to use an 18" culvert. The engineer wanted the largest culvert he could get into that ditch because of his statement that he didn't want water draining out onto the county roadbed from overflow. In this case the engineer was not going to allow ditch modification. Rightfully so because he is protecting his public roadbed, which is what the taxpayers pay him to do.

In every instance where I install a culvert for a private drive, the first concern is the public roadbed, without exception. I've redesigned private drives because they endangered the public roadbed. Again, that's what the taxpayers are paying for.

First issue, the culvert size is determined by drainage demands.

Second issue, the ditch is modified to fit the culvert size.

Third issue, the driveway is modified to fit the determined culvert and ditch size.

 

[LBrown59]

1*First issue, the culvert size is determined by drainage demands.
2*Second issue, the ditch is modified to fit the culvert size.
3*Third issue, the driveway is modified to fit the determined culvert and ditch size.
***************
1*When my 12'' culvert rusted out the state required an 18'' replacement culvert.
2*No consideration was given to drainage demands.
The ditch was never repaired/corrected to match either volume of water flow/drainage demand or culvert size.
I don't call a 3 to 5 foot deep and wide ditch for an 18'' culvert much of a match.
3* The culvert is already in and is just fine it's the ditch that needs repaired and corrected not the culvert.

First issue, the culvert size is determined by drainage demands.

Second issue, the ditch is modified to fit the culvert size.

Third issue, the driveway is modified to fit the determined culvert and ditch size.

 

[LBrown59]

I Had a 12'' corrugated steel driveway culvert that lasted 30 years before rusting out.
When I replaced it the state specked 15'' corrugated Double wall smooth bore plastic culvert. Don't ask me why.
In 30 years the 12 incher handled the water flow just fine.
Never once did it ever over flow onto the road drive way or yard; not even during the longest hardest down pours.
After 30 years the road ditch had eroded to where it was much much deeper and wider than it was when the steel culvert was installed.
Seems to me requiring a bigger culvert because the ditch had become larger was the wrong approach.
Logic would dictate the proper way of going about things was to repair the ditch first then determine the culvert size based on the size of the repaired ditch.
Upping the size of the culvert as the size of the ditch increase solves nothing but it does compound the problem.

 

[ovrszd]

I Had a 12'' corrugated steel driveway culvert that lasted 30 years before rusting out.
When I replaced it the state specked 15'' corrugated Double wall smooth bore plastic culvert. Don't ask me why.
In 30 years the 12 incher handled the water flow just fine.
Never once did it ever over flow onto the road drive way or yard; not even during the longest hardest down pours.
After 30 years the road ditch had eroded to where it was much much deeper and wider than it was when the steel culvert was installed.
Seems to me requiring a bigger culvert because the ditch had become larger was the wrong approach.
Logic would dictate the proper way of going about things was to repair the ditch first then determine the culvert size based on the size of the repaired ditch.
Upping the size of the culvert as the size of the ditch increase solves nothing but it does compound the problem.

Every governmental organization has different rules concerning culverts. Size, amount of overfill, angle cut of ends, type of culvert, culvert material, etc. In my case we don't allow 12" culverts. They used to. But don't now because there is too much risk of plugging a 12". That rule was changed about ten years ago. So if the life expectancy of a galvanized culvert in your area is 30 years, and your rules changed ten years ago, for the next twenty years your government is going to face discussions with customers as to why they now have to install a bigger culvert???

As I stated above, the first thing to determine is drainage. That is the primary consideration in determining culvert size. In your case it simply sounds like they have changed the minimum culvert size.

Also most organizations want you to use double wall, smooth bore plastic because of the life expectancy. I've been installing culverts since 1989. I don't expect to replace any plastic culvert because of material failure in my lifetime. In my country a galvanized culvert life expectancy is about 15 years if conditions are favorable. I have already replaced several galvanized culverts that I installed since 1989.

One last thing I would add about galvanized culverts. When I started almost twenty years ago I could throw a chain around the middle of an 18", 30 foot long culvert and pick it up with a backhoe without damage. About ten years ago I noticed that I could no longer do that without the culvert buckling and folding in the middle. So I started picking them up with a chain hook at each end. A few years later I had to quit doing that because the metal was so thin the hook would tear thru it. So you can't compare the life span of a 30 year old galvanized culvert to one bought today. They are tremendously different in quality and gauge of metal. That is another reason I use plastic unless it's a big culvert.

 

[LBrown59]

1*there is too much risk of plugging a 12."
2*As I stated above, the first thing to determine is drainage.
3* In your case it simply sounds like they have changed the minimum culvert size.
4*the first thing to determine is drainage.
---->>......>>>
1*When A 12'' corrugated steel culvert never plugged up in 30 years surly a 12'' double wall smooth bore plastic culvert would have been more than enough extra assurance against clogging up.
2*This was determined when the road was built and the ditches installed, however things change a lot in 100 years. In some cases the changes are drastic.
One example is a 24 "culvert buried 15 feet or more under the road bed to handle a small creek only problem is there is no creek there now so no need for a culvert that deep anymore. It don't need to be that big either. Do you need the same size culvert for a small to medium ditch as you do for creeks and runs?
Several years ago the state replaced the old rusted out culvert with a new one.
Instead of installing the replacement to fit / blend in with the present terrain they put the new one right where the old one was.
As a result we now have a huge hole within 3 feet of the edge of the pavement big enough to swallow up a large van or even small trucks that are bigger than pick ups.
To make matters worse the road ditch was filled in leaving a perfect runway dead ending with a drop off right into that hole.
3*With or without considering the culvert nothing has been done about the screwed up ditch.
4*I don't think a ditch that varies back and forth between 3 to 5 foot wide and deep was determined by drainage need or anything else.
The one size fits all mentality is the big problem with government regulation.

 

[ovrszd]

1*there is too much risk of plugging a 12."
2*As I stated above, the first thing to determine is drainage.
3* In your case it simply sounds like they have changed the minimum culvert size.
4*the first thing to determine is drainage.
---->>......>>>
1*When A 12'' corrugated steel culvert never plugged up in 30 years surly a 12'' double wall smooth bore plastic culvert would have been more than enough extra assurance against clogging up.
2*This was determined when the road was built and the ditches installed, however things change a lot in 100 years. In some cases the changes are drastic.
One example is a 24 "culvert buried 15 feet or more under the road bed to handle a small creek only problem is there is no creek there now so no need for a culvert that deep anymore. It don't need to be that big either. Do you need the same size culvert for a small to medium ditch as you do for creeks and runs?
Several years ago the state replaced the old rusted out culvert with a new one.
Instead of installing the replacement to fit / blend in with the present terrain they put the new one right where the old one was.
As a result we now have a huge hole within 3 feet of the edge of the pavement big enough to swallow up a large van or even small trucks that are bigger than pick ups.
To make matters worse the road ditch was filled in leaving a perfect runway dead ending with a drop off right into that hole.
3*With or without considering the culvert nothing has been done about the screwed up ditch.
4*I don't think a ditch that varies back and forth between 3 to 5 foot wide and deep was determined by drainage need or anything else.
The one size fits all mentality is the big problem with government regulation.

Mr Brown, in this case I'm not sure government regulation is the problem. I think maybe the workers that installed these culverts might have contributed to the problem.

As for culvert size, as I said our government changed the rules regarding minimum culvert size. Since I don't figure any of them are reading these posts, I'll say that I have installed some driveway culverts for landowners that are smaller than 15" in areas with minimum drainage and landscaped ditches that they maintain by mowing. I won't tear up someone's well mowed ditch to put in an oversized culvert. I just always make sure the landowner understands that they need to maintain it and keep the ends open.

As for the small culvert in a deep ditch. I have some like that too. Most of mine are caused by land owners not allowing me to go upstream and redesign the ditch. To raise the culvert, you have to raise the bottom of the ditch upstream until it has proper drainage. Our laws give us a 40 foot right of way. I have land owners that will not allow me to get past that 40 foot boundary. I have incidents where I had to haul dirt in with a dump truck because the landowner would not let me on his land to redesign the ditch an use the dirt to fix the road. The same road that the landowner uses to get to town.

As for a hole at the edge of the road. I avoid those at all costs. In one case I installed 120 feet of culvert so I could design a slope on each side gentle enough to mow. Your example sounds like they put in too short of culvert. Again, poor workmanship.

I always involve the landowners on both sides of the road in the decision making process. I always make sure I leave their land in better shape than I found it. I have even spent hours in people's yards with a rake and shovel picking up clods so they can mow. I even rebuild fence that needs moved for a project. But I also have the government side to please in regards to their requirements of culvert size and design. So I'm just the little guy caught in the middle.

 

[schmism]

the reason why culvert sizes change over time is because the amount of water the ditch carries changes over time. usually it carries more... not less..

why?

there is this thing called "time of concentration". its basicly how long it takes the water to flow off the ground and "into" the ditch.

as you devolope more land, convert more land from woods to "cleared property" the water runs off faster. SO

water USED to run into the ditch at a rate of X (cfs) the ditch (and culverts) were designed to carry the water away at X rate.

Now as develompent occures the water runs off quicker.. now you have water entering the ditch at 2X but the ditch can only carry it away at X. then you have issues.... (this is why major subdivsions are required to have retention ponds... a place to collect the water at 2x and allow it out into the "old" ditch at X rate... so durring times of high rainfall, it fills up quick, and slowly drains out)

so the culvert sized was increased and some time in the future they will come out and re-dig the ditches.

again most drainage calcs use a rain fall intenisty # (50 year rain etc) so that number will also change as they re-calc those numbers based on the last 50 or 100 years vs the 50 year number that was used in 1960.

so yes the ditch may have lived there for 80 years, but the engineering behind the size of the ditch changes over time based on a WHOLE lot of things. (not to mention arbitray changes in design specs like min slopes, etc)


as for who do you ask? your local DOT does not maintain all roads/ditches. Those in a city or under "county" maintaince do not fall into the DOT supervision and therefore the DOT engineer is likely to give you 'Thats not my problem" kind of answer ( in other words "Check with the county/city people, i dont have that information")

 

[LBrown59]

So the culvert size was increased and some time in the future they will come out and re-dig the ditches.

The last thing this ditch needs is widened or deepened.
Seems to me it shouldn't take a 60'' deep by 60 '' wide ditch when it only has a 15'' culvert in it; especially when the 15'' culvert is more than enough to handle the volume of water flow.

 

[LBrown59]

----->> 1* As for the small culvert in a deep ditch. I have some like that too. Most of mine are caused by land owners not allowing me to go upstream and redesign the ditch.
......>>> 2* As for a hole at the edge of the road. I avoid those at all costs. In one case I installed 120 feet of culvert so I could design a slope on each side gentle enough to mow. Your example sounds like they put in too short of culvert. Again, poor workmanship.
********

1*What caused this here is erosion of the bottom and cave in of the sides of the ditch several times during the 40 years I've lived here.
Each time the state would just dig out the bottom of the ditch without repairing the caved in sides and each time they would dig a little deeper down.
The result is the ditch is much wider and deeper than it was when I first moved here.
2*This hole is what's left of a run that no longer exist. The run could not be filled in clear to the end due to the state having a culvert running under the road 15 feet below the road surface. Filling in the last few feet of the run would have buried the inlet of the sates culvert under 13 feet of earth and blocked the water flow into it.
As a result we now have a section of the road ditch that is 15 feet deep 25 feet long and 20 feet wide
This is a rather bad situation for traffic as it's only about 3 feet from the edge of the blacktop to the edge of the hole.