Leach Field Cover - Infiltrators

[North Jersey]

I attached an elevation for my septic system below.

How much would two feet of cover impact the aerobic activity in my septic bed? The original plans from our engineer called for reducing the orginal grade, leaving only about 8 inches of cover over the infiltrator chambers. We now have a slight basin at the location of the septic bed.

The infiltrator installation instructions mention maximum cover of 48 inches for bed installations and 96 inches for trench installations. Would adding another 16 inches of cover (total of 24 inches) over the bed impede the aerobic activity inside the Infiltrator chambers? The existing 8 inches of cover is quite rocky and not all that rich in organic matter. The grass I planted is growing rather sparsely, and it can't be mowed because of the rocks. I also don't feel all that comfortable moving over a mere 8 inches of cover. My intent is to add only topsoil and densely seed the area.

I appreciate any feedback you can provide.

 

[North Jersey]

I extracted this statement from an Infiltrator Systems information sheet entitled "Cover policy for Infiltrator chambers in conventional septic system applications.":

"During system design it is important to note that any septic system designed and installed deeper than 4 feet may experience performance problems as a result of limited oxygen transfer through the soil.​

That statement seems to imply that installations with under 4 feet of cover won't experience dramatically degraded treament capabilities.

Here's an old diagram from USDA that seems to suggest 2-5' (measured from the bottom of the bed or trench) is acceptable:

 

[Sponsor]

 

[North Jersey]

So, I reached out to Infiltrator, and the tech I spoke with said that 2' of cover is pretty common, and I won't likely significantly ipmact system rformance unless I exceed 4' of cover. If anyone has information to the contrary, please let me know.