Dry Well question

[MerlinsBeard]

I have noticed in this year that one of my 2 dry wells in the back yard is starting to have water pool during heavy rain. I have noticed over the last couple of years that the ground around the inspection cover has sank into a slight pit and the cover has sunk with it. The standing water typically only lasts while the heavy rain is active and after a little while the standing water disappears.

In contrast, the other dry well has been the same since the house was constructed. Is this something I should be concerned about? Is there any investigation I should try to do? I have a walk out basement so the sump pump practically never runs, but don't want to let this go if it's the start of a new problem. Any suggestions?

 

[Don1357]

You don't say how deep these dry wells are. I think this would be material to any answer.

 

[Shiftless]

It’s probably impossible to say what the current depth is. If it’s filled with stones and the spaces between the stones are being gradually silted in, the effective capacity of the dry well is certainly diminished.
Based on the description, that would be my first guess.

I don’t know how to remedy this situation except to dig it up and start all over again.

 

[larry4406]

How is the water treated that discharges to the drywells?

Are they feed via rain leaders from downspouts? Do you have leaf/gutter guards? Perhaps the drywells have failed due to pluggage from organics.

Were the pits lined with geotech fabric? If not perhaps they have silted in and failed as suggested.

You indicated that the surface of the ground around the drywell in question has settled. Perhaps it is now collecting more water than it did prior. Perhaps restore the grade and original contours and see how it goes.

 

[Bretny]

What's supplying the dry well? Gutters? Sump pump? Kitchen sink?

Most drywells like leachfields have a useable life.

 

[MerlinsBeard]

Unfortunately I was not around when they made the drywells, so I don't know exactly how deep it is, and how it was constructed. House is about 10 years old now, about 1100-1300 square feet based on the floor plan.

The ground looks as if a 4x4' square has settled down a couple inches around the inspection cover. Our house is on public water and sewer, so I believe that the drywells are just for back of the house roof drainage. The front of the house downspouts don't connect to the rear downspouts, but there is a significant slope from the front yard to the backyard. There is a cherry tree and crepe myrtle in the front yard, and pond behind us, so there shouldn't be any foliage concerns as far as I can tell, just normal roof shingle runoff.

I don't know exactly how the drywell was constructed, so I'll have to email the builder and see if I get something.

Would this be something I could dig up and try to fix myself, or should it be left to someone experienced? I'm a little bit handy, but don't have any experience in drainage related issues. The overflow pvc pipe drains in the backyard into the pond, but usually when the rains hard, the pond water level swells past the overflow pvc exit point so I can't tell if water is coming out when there is standing water there at the drywell.

 

[Shiftless]

It sounds like the natural water level in that part of your property is quite high. During rainstorms if the high water mark is near the top of your drywell, of course your drywell won’t provide any place for water to drain. At that point it’s flooded. Is the pond the lowest point on your property? Do you have a basement?

 

[dcg9381]

<pulled - Misunderstood thanks Shiftless>

 

[Shiftless]

dcg:
I think you misunderstood the situation the O.P. was asking about. It’s not a water supply well.

 

[ace10]

Ground water changes. Or you could be facing a gradual failure. Or end of useful life. Who knows?

Heck, on one end my property I had a spring pop up last year. Never had any surface water in that area in the twenty years preceding. Now there are reeds growing and it's kinda mushy all year round.

 

[K'ledgeBldr]

Determine the elevation of the pond at “normal” fill. What is the elevation difference between the pond and the dry wells? What’s the elevation of the pond after a “turd-floater”?

Can you determine the elevation of the discharge line @pond and dry well?

What is the annual rainfall for your area? Are you currently above or below average? As noted previously, ground water levels can change due to rainfall. But, most dry wells would not be largely effected by ground water due to their design.

I’m kinda thinking that a high pond level is back-feeding into the dry well through the discharge line- but that’s clearly depend on elevation change of pond versus dry well.

 

[MerlinsBeard]

Did some trimming over the weekend to try to show slope, though it can be hard over pictures. The standing water appears to be runoff collection from the sloped hill from front to back yard. I don't believe the drywell is overflowing (which is only fed I believe from back roof drainage).

Talked to builder, he said to regrade will fill dirt and reseed, which is ok, but doing that would cover the inspection port. I could attempt to extend the pipe, or dig down and replace it with a longer pvc pipe.