GMP 135.A  (December 12, 2013), GUIDANCE MEMORADEUM AND POLICY, regarding 12VAC5-610-955, pg. 2 Drip Dispersal

“Procedures:  Designs for drip dispersal require the practice of engineering.  Drip dispersal designs pursuant to Va. Code Section 32.1-163.5 must comply with the emergency regulations; otherwise a professional engineer (PE) can propose drip dispersal in accordance with Va. Code Section 32.1-163.6 and not adhere to the emergency regulations.”

12 VAC5-610  The Sewage Handling and Disposal Regulations is the “Prescriptive Regulation”.  By definition, Drip Dispersal is not a “conventional” system and thus design / review is covered by CHAPTER 613 REGULATIONS FOR ALTERNATIVE ONSITE SEWAGE SYSTEMS as a 163.6 submission.  Engineering criteria for LPD and now drip are in the 610 regulations.  Current application (design) of treatment and dispersal under site and sizing criteria in 613 has evolved from the criteria, the approach in 610 regarding the concepts In ground, Shallow Placed, and Fill systems.  Reference to those sections is is incomplete and at best cumbersome. 

“12VAC5-613-40.E. All plans and specifications for AOSSs shall be properly sealed by a professional engineer licensed in the Commonwealth pursuant to Title 54.1 of the Code of Virginia unless such plans are prepared pursuant to an exemption from the licensing requirements of Title 54.1 of the Code of Virginia. All AOSS designs prepared by a professional engineer shall be reviewed by the department pursuant to § 32.1-163.6 of the Code of Virginia unless otherwise designated in writing by the professional engineer.”

12VAC5-610-955 B.3. “Except as provided by 12 VAC 5-613, drip systems dispersing septic tank effluent shall comply with the requirements of 12 VAC 5-610-594.  Drip systems dispersing of secondary effluent or better require a minimum of six inches cover over the tubing.  Cover maybe achieved by a combination of the installation depth and Group II or Group III cover or other approved materials over the drip field”

The first sentence should be removed.   I suggest replacing with  “Drip systems designed to disperse septic tank effluent require at least 12 inches of soil cover over the soil treatment area”

PE designs under 32.1-163.6 pursuant to the AOSS Regs (613), regarding STE must have an 18” separation to limitation from the point of application and a minimum of 12” cover.   The AOSS regulations are silent as to depth of installation of STE and pretreated effluents.

Gravelless products will be reviewed and listed similar to treatment systems per 613 (the AOSS regulations).  Why not have proprietary drip systems packages that meet the regulations be reviewed and listed?

Interestingly 12 VAC 5-610-950. Absorption area design. E.1., the requirement of 12” of cover has it’s basis in “frost” protection.