I am in agreement with VOWRA’s comments.  Please consider the following support and additional comments.

12VAC5-613-30. Applicability and scope.

K. Spray irrigation systems …

Spray systems for single family homes <1000 GPD are provided for by GMP 74 under a general permit from DEQ to VDH.  To me they are alternative systems.

12VAC5-613-40. Relationship to other regulations. D.

This section should state that Table 5.4 applies to all effluents >60 Mg/L BOD as stated in 12VAC5-613-80 Part II Performance Requirements Item 11 D.

12VAC5-613-80 Part II Performance Requirements 7.

This prohibition is the result of recommendations of many out-of-state pre-treatment manufacturers who sat on an advisory panel for development of the proposed regs.  There is no technical reason for the prohibition.  The prohibition would cause economic harm to many citizens of the Commonwealth of Virginia.  Many facilities such as schools, churches, existing hamlets / communities, businesses, and small subdivisions may not be able to afford to be built if this prohibition stands. 

The design of future large flow projects would in many cases require pretreatment due to soil and site limitations.  Nutrient discharge requirements, such as required in the Chesapeake Bay Overlay, as well as those evaluated per GMP 72, would further limit large flow systems dispersing septic tank effluent.  The current VDH regulation and policy, in addition to the proposed “replacement” regulations for alternative systems, contain appropriate criteria to ascertain a given projects suitability for septic tank effluent.

The Regulations as currently proposed may be interpreted to allow large systems to be constructed with conventional gravity dispersal of septic effluent. 

Designed properly, large systems with pressure distribution are sustainable and they have a positive environmental impact and can be cost effective. 

The previous proposed VDH mass drainfield regs (2002) Specifically stated “Uniform distribution. All mass sewage disposal systems shall be designed to provide uniform distribution. Mass sewage disposal systems shall not use a distribution box.”

“Uniform Distribution” should be specified to be throughout the entire soil treatment area.  With all large flow systems requiring equal dispersal by definition they would then be subject to the requirements of these replacement regs.

11 a.

I take it this means that in the case of gravity distribution, which includes distribution boxes, pressure manifolds and “enhanced flow” when effluent is deposited in one end of the trench that the designer is to reduce the loading rates provided in Table 1.

Gravity distribution of pretreated effluent is an inappropriate practice, counter to the intent of these regulations.

Virtually all research involving the application of pretreated effluent into the soil involves controlled application, whether onto columns or in situ with low pressure distribution or drip dispersal.  Elimination or the decrease of soil interfaced clogging coupled with microbial reductions results in enhanced performance.  Typical conclusions are that increased loading rates and reduced separations to limitations are possible.  Many states allow one of the two only.  These regs allow for both.

In many states even distribution by drip dispersal or low pressure distribution is required for all pretreated effluent to enhance residence times of effluent in the soil for final treatment.

Gravity dispersal of pretreated effluent to conventional trench type systems is an inappropriate practice for several reasons.  It is anticipated that pretreated effluent will not form a traditional biomat at the trench bottom interface, and effluent will readily flow deeper into the soil column.  The result is deeper microorganism and nutrient penetration (pass through) into the soil column, particularly in the case of compromised effluent quality. 

Further, with out the protection of the soil by the anaerobic biomat there will likely be the translocation of fines deeper in the soil column that will cause soil clogging.  Additionally, the biological polysaccharide “gluing” agents, developed over time, that are an important component of soil structure are washed away, destroying the structure and likely fluidizing the soil with time.

When the hydraulic conductivity of the soil is exceeded the pores are full and the effluent moves down the trench.  This condition is similar to an anaerobic trench except that the anaerobic biomat protects the soil column clogging at the soil interface.  When circumstances are such that pretreated effluent “creeps” down the trench, the entire soil column, not just the surface is clogged, and likely anaerobic and physical compromised as described above.  Significant renovation through resting is unlikely.  

Over all system size may reduced slightly in some states (such as Virginia) when utilizing pressure distribution with anaerobic effluent. 

Typically pressure distribution is often required in extremely coarse or clayey soils and in shallow (<18”) installation depths.

The only appropriate application of gravity dispersed pretreated effluent to conventional trenches is in the remediation of clogged anaerobic trenches.

Proper application of pressure distribution should be required in all trench systems utilizing pretreated effluent, Group One soils (sands), large flow anaerobic systems, and anaerobic systems with infiltrative surfaces installed less than 18” below natural ground surface. 

12VAC5-610 (Sewage Handling and Disposal Regulations) requires that infiltrative surfaces <12” require time dosing.

11d.

The 60 mg/l is generally accepted wastewater strength where a trench may develop a clogging mat.  Wastewater strengths less than 60 mg/l should be required to utilize pressure distribution.

The reg provides for TL-2, TL-1, and STE effluent.  Granted there is a big spread in wastewater strength between TL-1 (30 mg/L) and STE (150 – 300 Mg/l).  Constructed wetland and lagoon design may provide quality less than 60 mg/l and have a value as a nutrient BMP.

With the lack of guidance, direction, in assigning loading rates (maximums are only provided for TL-1 & TL-2) based on wastewater quality this opens up a real gray area.  Consider the outlet “T” aerators, some with inoculants; will they be able to utilized?  At what loading rate, under what justification?