Educate me storm water culverts

[Bill]

TBH’rs- educate me!

Retired in Montana, house is finished. We have a large gravel are in front of the L shaped house and attached 3-car garage.

When graded, the plan was for water to flow to one area, and then down a steep grade we built up.

The good news is it works as designed- the rain water moves under the gravel (clay soil and rocks underneath) away from the building. Re-grading is not an option and frankly water is going where we wanted it to go.

The bad news is once it starts down the grade, it’s eroding the highly clay and rock backfill.

What are my options? What type of collector goes on top? Can it be under the gravel? How big a culvert? I have several sticks of 4” pvc left over from the construction.

Thanks!

Point where water goes viewed from the garage.



Erosion after 3 days of on again off again rain. This area gets around 12” of rain per year.






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[lab man]

It looks like once you get some grass established your problem will be resolved. Get a roll of curlex to keep the soil from eroding until you get the grass growing.

[BrianL]

You need grass or to extend your gravel

[Arrowsmith]

We fought the same fight 2 years ago. I would grade the yard, broadcast expensive Kentucky Bluegrass seed plus fertilizer and it would rain and wash my work away. After two rounds of that I went to Menard's and bought several rolls of excelsior erosion control blankets. I regraded eroded spots, broadcast more seed and fertilizer. Rolled out the mat on top. The mat helps prevent erosion, holds the seed in place, holds in moisture, and acts as a greenhouse effect. First 3 pictures were from June 2019. Last 3 pictures were taken a few minutes ago. We have a lot of elevation changes (slopes) around our house. The excelsior blanket is $40.00 a roll for a 4'x100' roll. I have used 5 or 6 rolls but it's well worth it. It will allow your grass seed to germinate and fill in without getting washed away. I even pulled some of the blanket up after the grass took hold and reused it in other areas.

https://www.menards.com/main/outdoor...4423565122.htm

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[Bill]

Thanks. Is there a way to dig out the trench, lay pipe/ culvert and have a basin on top to channel the water down the slope underground? I’m trying to grow native grass around the house, but fear the water would erode through it and underlying soil.


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[Arrowsmith]

Thanks. Is there a way to dig out the trench, lay pipe/ culvert and have a basin on top to channel the water down the slope underground? I’m trying to grow native grass around the house, but fear the water would erode through it and underlying soil.


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Yes. You can definitely do that. The rip rap beside our driveway is a drainage channel with geotextile fabric under the crushed rock. We could have installed a culvert or as the locals in Iowa say a "tile" under the rock. The rip rap channel has worked well. The first picture is before we installed the geotextile fabric. The second picture is after we installed the fabric and rock. We have a lot of slope so there is no problem with water flow. You could install a pipe under a channel like this if you have sufficient slope. I would go with a 6" to 8" pipe to avoided it getting clogged up.

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[Bill]

How large are these ‘rip rap’ rocks? We excavated a crawl space in fractured Montana ‘granitite gneiss’ and I have a supply of rock in various sizes that I need to do something with.

Would the fabric form a trough down the grade, fill with rocks, put a layer above and the soil above to seed?


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[Drycreek3189]

You said regrading was not an option so I will refrain from saying to NEVER dump all your water in one spot. Oops, I said it
There are several ways to handle this but most of the simple solutions are still gonna have your water dumping in one spot at the bottom. My advice would be to have a couple dirt contractors look at it and suggest some alternative solutions. Good luck !

[Bill]

I said that about regrading since we put down multiple dump trucks if washed gravel. That plus were built on lots of rock, there were several granite areas we gave up trying to jackhammer.

All my gutters downspouts go into 4” pvc which daylight at the bottom, or the other side of the house. No problems there, I wonder why.

Thanks for the comments and suggestions.


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[Briar Friar]

French drains and underground drain pipes clog and are to be avoided...unless your coming straight from the gutter down pipes directly into the pipe and moving the water away. I was grading by hand with a contractor rake yesterday before and during the rain. Moving water over top of the soil is always best with use of a swale. Use a mix of 3-5” and 5-7” stones in the middle and sides of a swale. Use larger stones where the most erosion is happening on the slope. Its gonna be a continual maintenance issue no matter what you do.

IMO...Landscape fabric is a pain and always gets weeds and tears up and looks trashy “when” the soil erodes away around it. My landscaper doesnt like it and neither do I.

Good luck Mr Bill.

[WItoTX]

If you don't need grass there, I would dig 18" down, drain tile a foot down, the bottom 6" with a bed of pea gravel, place drain tile, then fill another 6" with pea gravel before topping it with soil, or with some sort of nice looking stone would be the way I go. That way you don't have to mess with the drain tile getting plugged as often.

Also, whatever you do, it's going to require maintenance. Unless you pour concrete. Then you might be good.

[Bill]

Thanks again.

If I I start under the existing gravel where the water is going now, dug it 18” deep, “lined” the trough with thick plastic, put 6-12” of 3-8 inch rock from the foundation excavation (which fractured surprisingly into rectangular pieces), then some gravel, then plastic above and then 6” of soil.

Maybe the water will flow through the rocks and exit at the bottom?


..... and I thought finishing up the house I could start scouting full-time for elk.


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[Arrowsmith]

How large are these ‘rip rap’ rocks? We excavated a crawl space in fractured Montana ‘granitite gneiss’ and I have a supply of rock in various sizes that I need to do something with.

Would the fabric form a trough down the grade, fill with rocks, put a layer above and the soil above to seed?


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I just saw this.

The rip rap rock I used is approximately 2" to 4" crushed stone. I installed woven geotextile fabric under the rock. The fabric prevents erosion and weed growth. The runoff flows good thru the rock. You will get a little be weed growth in silt especially on the upper end of the flume. I spray any weeds with gysophate. You can use bigger crushed stone or rock chunks. I used stone just big enough hopefully not to be displaced by the water flow. It has worked fine for two years now.

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[bmac]

Thanks again.

If I I start under the existing gravel where the water is going now, dug it 18” deep, “lined” the trough with thick plastic, put 6-12” of 3-8 inch rock from the foundation excavation (which fractured surprisingly into rectangular pieces), then some gravel, then plastic above and then 6” of soil.

Maybe the water will flow through the rocks and exit at the bottom?


..... and I thought finishing up the house I could start scouting full-time for elk.


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As long as you keep it in the rock trough lower then ground on sides you should be good but make sure you have a rock pad on the bottom as well. If the rocks get to high, the water will want to ride the sides of the channel and wash out around it. Seems you are correct path as culverts just speed water up on steep grades and you will end up with a self digging pond at the outfall.


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[Bill]

A friend in Pennsylvania who has had creek/ water/ runoff issues suggested installing a catch basin like this at the edge where the water is collecting, putting some rip rap rock in it to slow any water flow and running 4” non-perf pipe to the bottom.

I could probably cover in some type of cloth under the gravel.




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