12VAC5-613-10 Definitions   

“Limiting Feature” means a feature of the soil that limits or influences intercepts the vertical movement of water, including seasonal, perched or permanent water tables, fragipans, soil restrictions, pervious or impervious bedrock, slowly permeable horizons, and excessive rock fragments.Should be inclusive and not repeat the list of features in other sectionsl

“Percolation Test” means a standardized qualitative test for measuring water movement through the soil.
   Need a definition

“Project area boundary” means the limits of the three-dimensional space defined when (i)….(ii)…(iii) the lower vertical limit is the vertical separation required by this chapter. a permeability limiting feature or the
permanent water table.  Poorly worded and redundant

“Soil treatment area,” means the physical location in or on the naturally occurring soil medium….the soil treatment area includes subsurface drainfields, drip dispersal fields, treatment pads and elevated sand mounds.  

 “Treatment works,” means a method using a septic tank or septic tanks to treat sewage before the effluent is dispersed to a soil treatment area.  As opposed to a treatment system?

 “Vertical separation” means the vertical distance between the point of effluent application to the soil…and     a limiting feature of the soil treatment area.such as seasonal high ground water, bedrock, or other   restriction. Redundant and exclusive.

12VAC5-613-20 Purpose and Authority

7. Inform and assist owners, applicants, onsite soil evaluators, system designers, and other persons of the
    requirements for obtaining a permit or other authorization for an AOSS.
    There was a time when the Department assisted in the complexities of permitting. The term         inform  is strident and implies your on your own, good luck.

12VAC5-613-40

 G.1. Depth to limiting features, including seasonal per perched water tables, pans, restrictions, or  pervious  
       or impervious bedrock.
       Redundant and inconsistent with the definition.

      2. Slope of the project area.
      4. Landscape and landform
       Combine as 2. Morphometry, including aspect, gradient shape and position.  

3.  Ksat or percolation rate at the appropriate depths proposed installation depth and at depths below in the    
      soil treatment area to demonstrate compliance this chapter. Ksat or percolation rate may be estimated   
      for small AOSSs. Ksat or percolation rate must be measured using an appropriate device or method for   
      large AOSSs.

Test depths should be the determined by the engineer or OSE.  As written this requirement   allows  the regulators to determine the test depth after the fact.  In my opinion “standard engineering practice” does not allow rate and other limiting factor estimates for design purposes.  Estimates cannot be easily defended in a courtroom.  All systems should require testing.

Part II Table 1

Until the percolation test is standardized it’s use as a basis for application rate is inappropriate, should use Ksat which is reproducible. Furthermore allowing estimates of the narrow range of rates is highly presumptive.  I agree with those who question the scientific basis for the difference between TL-2 and TL-3 effluent.  There is no maximum percolation rate, say 120 mpi, mentioned in the regulation.

13.a. What is now determined to be permeability limiting?  Even restrictions have rates.
          (ii) hydraulic gradient sufficient to move the applied effluent off the site should imply that
                the soil treatment area should exceed the “application area”. This is a concept that is  
                often overlooked during site evaluation.

           (iii) standardized water mounding equations must be identified