Soil turning black

Blacktie.

Hi everybody. I have a black layer on top of some of my back garden lawn and am at a loss to what it could be. It doesn't have any smell and only covers a thin layer on top as far as I can tell.

Would it have anything to do with work we had done on the back garden recently when building a Pergola out from the house? We had to clear some of the grass area and cover it in cement and raise up the cement area right outside the door by a couple of inches. HERE is a pic of what I'm talking about. We've laid tiles down on it now.

About 2 months after this was complete I noticed we started to get some black soil around a manhole we have in our back garden. The manhole appears the be just a storm drain and the foul is buried a bit deeper judging by my neighbor's manhole depth. I can't see any leaks around the manhole so I don't think that's what's causing it and the gulley drain in fron of the pergola drains fine to the manhole. I've also noticed the dog digging around the area a bit but that could be unrelated.

Any ideas what could be causing this? I can't find anything online about it.

Some pics of the black soil are HERE

10-10-20

It appears to be algae. Is the garden prone to dampness or do you have excess run-off from the house and new patio area? You do have moss and that's an indication of some unfavorable soil conditions. There also appears to be a drop into the area of higher grass indicating run-off.

The soil might also be heavily compacted causing any rain to sit on the surface. To fix that you would need to break the sub-soil to allow proper drainage.

Edit: Ah, in the photo of the patio, I can see that you're missing a down-pipe in the middle. Was this re-routed or what? Is this a source of run-off?

Blacktie.

10-10-20 wrote: »

It appears to be algae. Is the garden prone to dampness or do you have excess run-off from the house and new patio area? You do have moss and that's an indication of some unfavorable soil conditions. There also appears to be a drop into the area of higher grass indicating run-off.

The soil might also be heavily compacted causing any rain to sit on the surface. To fix that you would need to break the sub-soil to allow proper drainage.

Edit: Ah, in the photo of the patio, I can see that you're missing a down-pipe in the middle. Was this re-routed or what? Is this a source of run-off?

O interesting so loosening the soil should help. It was wet for a long time in winter alright and yes there is a noticeable slope down toward the house.

Yeah the downpipe was cut short and the water runs down the pergola roof into a gutter that runs to either side and draining down to the floor gully you can see in the photos.

joe123

Have the exact same thing in my lawn. Oily black patches just like in your photo.

I read before that its slime mold and that its not bad for a lawn, but again hard know if that's exactly what it is.

My own lawn suffers from poor growth in some areas, bad drainage and Im seeing leather jackets lately too so probably not an example of a well conditioned lawn!

fryup

burst sewage pipe? any bad smells of late

i'd call in someone before it gets worse

magicbastarder

the OP said there was no smell.

fryup

how about waste pit for sink waste where is that situated?

Blacktie.

fryup wrote: »

how about waste pit for sink waste where is that situated?

Not sure I'd assume it's all going to sewer as my neighbors lines up with mine but is a good bit lower and his waste goes through that one. There's no sewage smell and it appears to just be a layer on top. I think I'll scrape it away and break the the soil. Maybe it will help.

10-10-20

Mix some "sharp sand" into the soil if you break it up. You can get it in a builder's providers, but have a read of this thread:
https://www.boards.ie/vbulletin/showthread.php?t=2054996843