culvert for seasonal ditch

[bigballer]

i need to spend alot of time clearing deadfall in my woods but given all the other projects i had to get done this summer didn't really get to it. i figured if i could access the woods in the winter i could spend alot of time out there the only problem is the only way for me access is via the pasture which is the spillway for my seasonal ditch. i decided to cut a swale with my boxblade to keep the water in a semi tight path but in the winter it's still too soft out there to run my tractor. so to get around that i decided if i added a culvert to my open ditch i could get into the woods via the upper part of the property and actually be somewhat productive over the next 5 months.. this would also give my better half yearround access to the roundpen for her horse training - added bonus. So this was todays project.

i picked up a 13' stick of 12" double-wall ads pipe - $5.75/ft.

kinda a steep slope (about and 15" drop over the 13', the ditch was open for the most part but i did have to clear some blackberry vines.. gotta love the NW..


after a dry run i discovered the i would need to do some grading around on the woods side of the road, pretty steep looking:


minimum coverage for this pipe is 12" and to start with i am looking at 15" but will probably end up with 18"-20" since i'll build up the road a bit..

 

[bigballer]

i had some leftover bags of sand from another project so decided to use them as weights to keep the pipe in place during backfill..


after created a "bed" for the pipe to lay in i decided to lay down a couple inches of this wet sand in the bed so i could make sure the corrugations all filled up on the bottom.


starting to backfill. i dug another ditch on the other side of my property and this fill was what came out of the trench, i think they call it glacial till around here, it seems to pack pretty tight.. there were a few rocks in it but i pulled out the bigger ones, figured a few small ones here and there were probably ok. i didn't have a pneumatic compactor so i used a hand tamp.


i wanted to buy a flange but they wanted $200 so i decide to use Eddie Walkers method (as seen on TBN - thanks Eddie!) i did make a modification and cut the bag and and spread some of the mix on the floor of the ditch a couple feet in front of the opening, i also packed this around the first for corrugations on the sides and underneath... goal is to try to keep the water flowing into the pipe, not around it.

 

[bigballer]

i had some leftover basalt riprap from my rockery project last year, i knew i would find a good use for it.. about 3ft in front of the inlet i made a break to slow the water a bit before it hits the pipe.. i ended up using one bag of readymix on each side then placed some of the riprap set in another bag of readymix and wetting with each course.. not sure how it will hold but seemed like a good idea. the bags of sand are temporary, just to place to some pressure on the riprap while the concrete sets up..



outlet in progress. for those interested i laid the backfill in 6" layers tamping each time as tight as possible, probably 4" lift when packed.


here is a preview of the road, my 3500lb tractor didn't have any problems getting over it.. tomorrow will put down more backfill and build up the riprap on both sides.. i also have another frenchdrain the daylights at the outlet (you can see in the pic just before this one on the left)..

 

[EddieWalker]

Looks good. I'm glad you like the cement bag method of building a headwall. It's not something that I thought up, but a pretty simple, inexpensive solution to stop water from eroding around the culvert.

I'm curious how you managed to get a 13ft long culvert? I can only find them in 20 and 24 ft lengths, but sure could use a few in that length for my trails.

Eddie

 

[bigballer]

the place i got this sells minimum 20' lengths except for the 12" pipe (13' and 20'). The guy there said they have a strong demand for the smaller length for exactly the reason you mention - trails, small crossings.. etc..

 

[Greyfields]

We use those concrete bags in storm drain trenches where infiltration into the backfill will cause a "straw" effect. They make great pipe anchores as well on steep slopes.

As with all CPE pipes, the strength of the pipe lies in the backfill. Looks like you did a very nice job.

 

[KennethBrown]

Only problem I see is you need to dress up the outlet just like you did the inlet. I didn't think it was necc and mine washed out. The water will swirl when it comes out of the pipe and eat away at the edges.

 

[KennethBrown]

I forgot to mention- Greta job and even better pictures.

 

[Onthesauk]

Local Co-op sells a grass seed called Partners, developed for the NW. A lot of the loggers use it on skid roads when their done to hold everything in place. Has some deep rooted fescue in it that works well for holding soil in place. Might be worth broadcasting over the whole project when you're done. But looks good!

 

[bigballer]

i appreciate the feedback, i think i'll shore up the sides of the ditch with some of that grass if i can find it here in snohomish county.. i forgot to mention this was still in progress, i ended up setting more of the basalt on the outlet and built up the french drain outlet as well. i'll post some finished picstures tomorrow. the pipe has a pretty good slope (close to an inch per foot) so when the water starts flowing i'll better be able to determine how much pooling i'll get at the outlet. the ditch drops another 8" just below the outlet so i'm hoping it'll be ok. i also topped the drive path with about 5" of 5/8 minus (alot of fines) so when that sets up it should keep the surface water from infiltrating the backfill.

on a side note my neighbor is setting over 150' of this same pipe tomorrow, i'm going to help him backfill and cover.. i will mention to him building up the headwall as he gets alot of my water in his ditch and now that i've done alot of work on my drainage, i think he's going to have to move even more water this winter.. according to the weather man, we're in for rain over the next week so i finished this just in the nick of time. ;-)