Administrative Code

Virginia Administrative Code
10/27/2021

Article 1. General Requirements

12VAC5-610-591. Overview.

General Criteria for the Selection of a Wastewater Treatment and Disposal System Based on Site Conditions

Article 1

Site Limitations

The intent of this part is to provide guidance on how to match various treatment and dispersal systems to site-specific conditions in order to construct a safe, proper, and adequate sewage system for the site under consideration. Article 1 (12VAC5-610-591 et seq.) identifies site conditions which limit or prohibit the use of onsite systems. Article 2 (12VAC5-610-594 et seq.) establishes criteria for the use of systems that rely on naturally occurring undisturbed soils to treat and disperse effluent, with or without pretreatment. Article 3 (12VAC5-610-597 et seq.) establishes criteria for the use of systems which rely on fill soils to accomplish treatment prior to dispersal.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-592. Setback distances.

A. Septic tanks, other tanks, and header line setback distances. The minimum separation distances between septic tanks, pump chambers, aerobic pretreatment devices (including sand filters, biofilters, and aerobic treatment units), header lines, and similar devices as determined by the department, and various structures and topographic features are contained in Table 4.1 entitled Minimum Separation Distances for Pretreatment Units, Conveyance Lines, and Header Lines.

B. Manifolds. Manifolds shall not pass closer than 50 feet to any drinking water source unless pressure tested in place at pump shut-off head. Under no circumstances shall a manifold come within 10 feet of a drinking water source.

C. Absorption area. The absorption area is the soil medium beginning at the interface between the soil and the gravel, sand, or other point of effluent application, which is utilized for dispersal of the effluent. The absorption area includes the infiltrative surface in the absorption trench, or the point of effluent application, and the soil between and around the effluent distribution system. Setback distance to various structures and topographic features and an absorption area are contained in Table 4.2.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-593. Physical features.

Physical features, landscape position and soil characteristics affect the ability of soil-based systems to treat and disperse effluent. In order to correctly select and place a sewage system in the environment such that public health and the environment are protected, it is necessary to understand and consider the local hydrologic conditions, the regional geology, and the nature of the soils occurring on the site being evaluated. At a minimum, the following features shall be considered:

1. Marshes and swamps. Placement of subsurface soil absorption systems on or in swamps and marshes is prohibited.

2. Seasonal water table. A vertical separation distance between the point of effluent application and a seasonal water table shall be maintained which reflects the quality of the effluent and the receiving environment. Minimum vertical separation distances may be found in Articles 2 (12VAC5-610-594 et seq.) and 3 (12VAC5-610-597 et seq.) of this part and Tables 4.3 and 4.4.

3. Slope. Subsurface soil absorption trench systems shall not be placed on slopes greater than 50% unless terraced. Criteria for other types of onsite systems are contained in Tables 4.3 and 4.4.

4. Drainage ways. Subsurface soil absorption systems shall not be placed at a position in a drainage way subject to intermittent flooding.

5. Fill material. Placement of subsurface soil absorption systems in fill materials is generally prohibited except in three specific situations. The Wisconsin Mound system is considered a fill system as is the sand-on-sand system. These systems are governed by criteria found in 12VAC5-610-960, 12VAC5-610-965, and Table 4.4. Fill material consisting of colluvial soil derived from sandstone (noncarbonaceous) in the mountainous area may be considered on a case-by-case basis for placement of subsurface soil absorption systems.

6. Sink holes. Placement of a subsurface soil absorption system at the low point of a sink hole is prohibited. For set back distance see Table 4.2.

7. Flood plains. Subsurface soil absorption systems shall not be placed in flood plains subject to annual or more frequent sustained (24 hours) flooding.

8. Alluvial and colluvial deposits. Placement of subsurface soil absorption areas in alluvial and colluvial deposits with shallow depths, extended periods of saturation, or possible flooding is prohibited.

9. Shrink-swell soils. When soils containing horizons with shrink-swell characteristics (see definitions in 12VAC5-610-120) have been identified, they shall be rejected for use for subsurface soil absorption systems.

10. Soil restrictions. Soil restrictions in themselves may form the basis for outright rejection of the site.

11. Free standing water. The presence of free standing water in a profile hole may be grounds for rejection of the site.

Statutory Authority

§§ 32.1-12 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

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