Small box culvert construction

[Hank11]

I want to build a small box culvert to allow driving and walking over a swale at the entrance to my shop. I'm thinking about 18" across by 4" high. I'd pour a flat slab 24" X 10 ', then two curbs at 4" high on top of that, then a place a slab on top of the curbs to cap it. In the end, a 4" tall X 18" wide box culvert.

Before anyone suggests it, I don't have enough height to put in a big round culvert. Several smaller round culverts might work but I think would clog easier than a wide box culvert.

Your ideas and suggestion are welcomed.

 

[mike93lx]

Never heard of a box culvert... Interesting. Getting that top slab strong enough to support vehicle traffic feels like it will be difficult

 

[Jim greengo]

Picture?

 

[Lynden]

Most cities have standard plans for low-height, under-sidewalk box culverts which drain onto the street through the curb. These culverts can have either a reinforced concrete top or a galvanized steel plate top. Check for standard plans at your city's public works department. Here are examples I found on the web.

https://www.lbiw.com/media/g1qptpiz/d-307-curb-outlet-w-concrete-slab.pdf (scroll down for detail of culvert with steel plate top)

https://www.lbiw.com/media/f4yjpb4j/d-306-curb-outlet-w-steel-plate.pdf

 

[Firebrick43]

In Asia box culverts seem to be the standard or were at least when I was there 20 years ago. All precast concrete with concrete lids with holes for water ingress

Okinawa had miles of them from the ridge to the sea all which was under your feet. After a monsoon rain it was pretty crazy the noise the running water made. Lots of them in S Korea and Philippines as well.

Big ones were used under raids and we made impromptu scud bunkers in Kuwait with them before the war started in 2003.

I think if I was to pave over a scale I front of my shop door I would to a trench drain system in concrete.

 

[Hank11]

Like this only much, much, much smaller:

 

[Hank11]

The water drains parallel to the front wall of the shop. Actually splits around the corner of the front wall and porch and divides in two. Even in storms the water is not near the building 10-12 feet out.

The culvert would let drainage continue as it is now - the drainage is perfect. I'd like to not have to step in or over water in the swale if its raining and to have a flatter more level surface to back a truck or trailer onto to load and unload once in a while so the trailer is more level and nearer the right height to meet the porch.

 

[strutaeng]

I'm not really visualizing what you are trying to do, but box curverts sounds doable.

A structural type of slab (maybe 2 beams on the sides with slab in the middle is an option also). You just need to provide some sort of support on each end. Like a miniature bridge.

 

[Rusty Wrench]

Elliptical corrugated metal pipe (CMP) is what the civil design guys use when depth/cover is a constraint. Should be bedded in gravel. The size most shallow I remember is 8 inches with various sizes in the other dimension. Contractors supply yards will have a whole catalog of them.
I think your idea will work but elliptical pipe seems easier to me if it fits.

 

[starquestMM]

Easiest is a manufactured trench drain. Firebricks picture doesn't show the top grate

 

[Hank11]

Easiest is a manufactured trench drain. Firebricks picture doesn't show the top grate

No, the drainage happens on the end - not on the top surface.

 

[TonyG109]

Just thinking out loud here and trying to keep the creative juices flowing...

Perhaps you could use a couple of lengths of steel beams across the 18" dimension where the tires would cross the culvert. This should support the weight of a vehicle better than a concrete cap. The rest of the culvert could be concrete to match the height of the beams. Needless to say, properly sized beams would be critical for the anticipated load. Maybe weld the beams together and/or cap them with a plate to spread the load?

I often see beams on CL or FB for somewhat reasonable prices.

 

[Firebrick43]

No, the drainage happens on the end - not on the top surface.

The flow thru from end to end as well as the top if the correct one is installed

 

[merlin1952]

Hank, have you looked in to the black double walled corrugated plastic pipe? It comes in sized from 4” thru about 18” or more and it is rated for vehicles. I have a situation similar to what you are describing and I am planning to use the corrugated pipe.

NuFlo 18 in. x 20 ft. Corrugated HDPE Drainage Pipe at Tractor Supply Co.

 

[Jeepster04]

No reason that wont work and its pretty neat. How thick will the top slab be?

It'll nee to be thick enough to have two mats of steel, one near the bottom and one near the top. I'd at least do 1' centers and use at least #4 bar.