FROM GMP 116, Virginia Department of Health .  It appears the agency is removing benefits to the commonwealth for advantages to a manufacturer.  Consumers do not benefit when the septic field is subject to premature failure.  smaller size septic fields are prone to shorter lifespans.

VDH recognizes that installation of gravelless systems at manufacturer’s recommended specifications may provide benefits to consumers, provided the absorption area is adequate to assure the long-term treatment and dispersal of septic tank effluent or other treated effluents.

Sizing a drainfield smaller than specified in the Regulations may not result in adverse effects to public health or groundwater because this does not change the fundamental processes by which septic effluent trenches function. Such sizing may, however, reduce the operational life of the soil absorption system (i.e. shorten the time to failure). As long as the overall absorption area is maintained “in reserve,” replacing the clogged trenches becomes a matter of long-term operation and management and not one of public health or environmental protection.