Working with a contractor who didn’t follow the septic design with respect to cover of the drainfield. The design calls for 4″ Loam and Seed, while the actual installation used mulch (pretty deep, at least where I put my boot in; at least 8″). The contract and design call for the 4″ of loam, so that is what I will be asking the contractor to correct.

Apart from the need to comply with the contract terms, I’d like to be informed and present the contractor with the reason that the loam is called for instead of mulch. This property is in Maine, and by my reading Maine subsurface wastewater disposal rules allow for mulch cover, but only with the explicit consent of the designer. I spoke with the septic designer regarding this situation, and he was unequivocal regarding the loam requirement, but wasn’t able to provide details about the performance difference between loam and mulch cover.

Can anyone point me to a resource that might help educate me on this aspect of septic design/performance?