There is no statutory language in 32.1-163.6 authorizing VDH to develop any vertical separation distances within the proposed Performance Requirements. Rather, it is incumbent upon VDH to establish effluent and water quality standards that are consistent with the statutory language. It is the role of the engineer designer to develop the vertical separation necessary to meet those standards.
Discussion – Treatment Works
The statutory definition of Treatment Works is very clear:
"Treatment works" means any device or system used in the storage, treatment, disposal or reclamation of sewage or combinations of sewage and industrial wastes, including but not limited to pumping, power and other equipment and appurtenances, septic tanks, and any works, including land, that are or will be (i) an integral part of the treatment process or (ii) used for ultimate disposal of residues or effluents resulting from such treatment.
A treatment works includes any land that is an integral part of the treatment process or used for the ultimate disposal of effluents. For a conventional septic system, the land is both an integral treatment process and the receiving environment for ultimate disposal. For an engineered system, the land may be part of the treatment, but not necessarily as we can design a treatment system that meets the statutory standard prior to any final disposal. So in many cases, the land is only used for ultimate disposal purposes.
In short, the statutory compliance point for an engineered system is the end of the treatment works – but can be, at the discretion of the designer, prior to this point. VDH has no statutory authority to prescribe a compliance point short of the end of the treatment works.
