Section 700. Site preparation and alteration

A. Preservation of soil structure. The preservation of the original structure of the soil in the area selected for placement of the absorption trenches is essential to maintaining the percolative capacity of the soil.

1. Prohibition on construction. Subsurface soil absorption systems shall not be constructed in Texture Group III and IV soils during periods of wet weather when the soil is sufficiently wet at the depth of installation to exceed its plastic limit. For the purpose of this chapter, the plastic limit of a soil shall be considered to have been exceeded when the soil can be rolled between the palms of the hands to produce threads 1/8 inch in diameter without breaking apart and crumbling.

2. Soil compaction. Special caution shall be taken in allowing wheeled and tracked vehicles to traverse the area selected for placement of the absorption systems before, during and after construction of the trenches, especially during wet weather. Precaution is especially important where Texture Group III and IV soils are involved. Alteration of soil structure by movement of vehicles may be grounds for rejection of the site and/or system or revocation of the permit.

3. Soil smearing. Excavating equipment utilized to construct the absorption system shall be so designed as not to compress or smear the sidewalks or bottom of the system. Excessive smearing of the usable absorption trench sidewalls or bottom during construction may result in irreversible damage to the soil infiltrative surface and may be grounds for rejection of the site and/or system.

B. Removal of vegetation. Vegetation such as maple, cottonwood, willows and other plant species with extremely hydrophilic (water loving) root systems shall be removed for a minimum of 10 feet from the actual absorption areas. Other trees should be removed from the absorption area.

C. Grading.

1. Pregrading. The proposed site for the subsurface soil absorption system shall not be graded until the district or local health department has completed the site evaluation contained in Article 1 (12VAC5-610-450 et seq.) of Part III of this chapter.

2. Interim grading. Interim grading means site grading during or immediately preceding the construction of the absorption system. Any such grading shall be done in accordance with the conditions contained in the construction permit. The district or local health department may require notification upon completion of the interim grading but before actual installation of the absorption system.

3. Final grading. Final grading of the absorption area site for diversion of surface water (e.g., crowning) for the purpose of eliminating surface water from flowing or ponding on the site, preparation for seeding, etc. shall be accomplished to avoid damaging the absorption area. Prior to grading, the distribution box, pretreatment unit and absorption area shall be clearly staked.

D. Drainage.

1. Surface water. The area surrounding the absorption area shall be graded to divert surface water from the absorption area site. The absorption area site shall also be graded to eliminate the ponding of water.

2. Roof drains, basement sump discharges (nonsewage), floor drains, footing drains, etc., are prohibited from being connected to the sewage disposal system and shall be directed away from the absorption area site in a manner to preclude water flow into, through or over the site. Discharge of sewage into a basement sump collecting water from floor drains, storm water, etc., is prohibited.

3. Lateral ground water movement interceptors (LGMI, e.g., French drains) may be required to divert ground water movement away from the absorption area site. The LGMI shall be placed perpendicular to the general slope of the land and generally parallel to the absorption trenches. A tight drain from the LGMI shall be constructed to discharge into a natural or manmade drainage way.

E. Protection of subsurface soil absorption system.

1. No structures shall be placed over the subsurface soil absorption system. Driveways or parking lots shall not be constructed on the subsurface soil absorption system unless the invert of the lead or header lines or top of the gravel in the absorption trenches is deeper than 30 inches below the ground surface and the driveway or parking lot is paved with portland cement or bituminous concrete to prevent compaction of the trench bottom. Driveways and parking lots shall not be constructed over the distribution box unless adequate structural and access provisions are provided.

2. Where all or part of a subsurface soil absorption system is proposed to be installed on property other than the owners, an easement in perpetuity shall be recorded with the clerk of the court prior to issuance of a construction permit (see 12VAC5-610-280). The easement shall be of sufficient area to permit access, construction, required reserve area (see 12VAC5-610-710), and maintenance of the system.

3. Where the sewer line from the building to the pretreatment unit or the conveyance line is to be placed underneath a state road or in a Virginia Department of Transportation right-of-way, the requirement for a recorded easement in perpetuity can be waived for that portion of the system located underneath the road or in the right-of-way. In its place, the applicant shall obtain the appropriate permit or permits from the Department of Transportation to construct the sewer or conveyance line in its right-of-way. The construction permit for the sewage disposal system shall not be issued until the applicant provides the local health department with a copy of the permit issued by the Department of Transportation. Under no circumstances shall the pretreatment unit, the distribution box, or the soil absorption portion of the system be installed in the Department of Transportation right-of-way.

F. Preplacement and post-placement of utilities. Subsurface soil absorption systems shall not be placed in an underground utility easement. No buried public or private utility service (e.g., water lines, electrical lines, gas lines, etc.) shall traverse the subsurface soil absorption system area nor shall the buried service be closer than 10 feet to the system.

Historical Notes

Derived from VR355-34-02 § 4.5, eff. February 5, 1986; amended, eff. May 11, 1988; Volume 16, Issue 16, eff. July 1, 2000.

Statutory Authority

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