little cover for pvc storm sewer pipe in grass area? 2

[PG35]

I have a situation where I only have 12" of cover for a pcv pipe to catchbasin connection? The pipe is in a grassed area that would not expect any vehical loading.

Is there a problem associated with having storm pipes above the frost line? It's done all the time right?

Another problem I am facing is that I am forced to connect to a catchbasin directly below the frame. Can this connection physically be made?

Thanks.

 

[onyeuko]

The cover is too lean as such you should try to protect it by engrooving i.e providing a cover with another pipe preferably(metal. If the location is in such a place that it is exposed to the risk of congelling due to frost, lag the pipe before engrooving it , then build another frost protection for the engrooving pipe with a material that has a high insulating property. Try as much as possible to provide the system with good drainage like by providing a rest bed of sand and gravel.
As to your second question, I do not understand it as such can not profer an answer to it. Good luck
Teddy

 

[cvg]

as long as you have posative drainage in the pipe, freezing of the pipe should not be a problem. Encapsulate the basin and pipe with non frost susceptible backfill

you will probably need to modify the structure to allow the connection below the frame.

 

[dicksewerrat]

Of course, each spring you will have a small lake there. the spring run off will freeze inside the pipe if the ground is frozen and you get snowmelt.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[tsgrue]

.
I'm in the southeast - surface water freezing is usually only a few days per year (if that), so I can't comment on the freezing issues.

If you have heavy traffic loading (emphasis on weight much more than cycles), then the cover might be a concern. In the situation you described, 12 inches should be more than enough. (You could probably drive a loaded pickup over that in decent soils and not have a problem - depending on the pipe, bed and backfill construction method/care).

I rarely see these small pipes and low-head inlets work well - often failing within a year after installation - but it does depend on the watershed. The problem I see is inlet/pipe clogging. If this system is in an "ultra-urban" area (near 100% paved/impervious surface) with no trash, debris, or sediment, then the system might work okay.

I don't use anything less than a 15" diameter pipe for stormwater conveyance and only that if all inlets have fully grated covers. Otherwise, 18" diameter is the minimum I use. The one exception to this is roof drains - to which I might connect 8" or 12" diameter pipes. Have you checked out other installations in similar areas to assess how well those are functioning? This is not about the clean water hydraulics - this is about the clogging. The hydraulic analysis may very well show that everything is fine with a 4" diamater pipe, but that is not reality in most cases - larger pipes are needed to address clogging. The 4" diamater might might need to be an 18" diameter pipe to prevent clogging failure.

Connecting just below the grate should be no problem physically, but the resultant low forcing head at the inlet would likely be a problem.
.

tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation

http://hhwq.blogspot.com

 

[DarthSoilsGuy]

almost every drain pipe we design in my Vermont town is above the frost line.

The town storm sewer system at the street is above the frost line. Most of the work we mess around with are urban rehabilitation projects where you can't adjust the grades much. it makes it a real b###h to get below the frost line, drain, and tie-in.

if you want a little extra security, you can squeek some blueboard over the tiny trench.

2nd question: it depends...

 

[civilperson]

If the basin that you are connecting to is deeper, (you are attaching just below the grate), then why not bury the storm pipe deeper and match 0.8 x crown elevation?

 

[rconner]

It appears there may be some concerns voiced by others on this thread (re loading etc.) I would only add a wonder also if twelve inches of cover, in a "grassy" area, is enough to dependably prevent a quite lightweight, smooth (at least on the outsides?), and sizeable? pipe (that might at times be empty?) from moving/floating?