Virginia Law

Part V. Design and Construction Criteria

Article 1
General Requirements

12VAC5-610-660. General.

Article 1
General Requirements

The criteria contained in this section shall apply to all onsite sewage disposal systems. Deviations from these criteria may be considered by the district or local health department on a case-by-case basis.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.1, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-670. Sewage flows.

Subsurface soil absorption systems shall be designed on the basis of the sewage flows tabulated in Table 5.1.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.2, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-680. Water saving plumbing devices.

Water saving plumbing devices are encouraged to lengthen the life of the subsurface soil absorption system. However, only permanent water saving plumbing devices such as low flush toilets shall be considered in reducing the size of the absorption area. Devices such as inserts in showers are considered temporary.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.3, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-690. Recycle and reuse systems.

Recycle and reuse systems are methods, processes and equipment in which sewage is restored to a condition suitable for reuse. When recycle and reuse systems are utilized in conjunction with toilet wastes only, an approved method of sewage disposal shall be provided to properly dispose of sewage generated via handwashing and other related sanitation activities. All recycle and reuse systems shall provide for an approved method of sewage disposal to handle excess sewage generated within the system. These systems are considered experimental unless they have been previously deemed to be satisfactory in accordance with the provisions of 12VAC5-610-441 and/or as a minimum have been certified by the National Sanitation Foundation as meeting the current Standard 41 as determined by the bureau. Water recycle and reuse systems intended to produce water for other than toilet flush water are considered experimental and shall comply with the provisions of 12VAC5-610-441. All proposals for recycle and reuse systems shall be submitted to the bureau through the district or local health department.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.4, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-700. 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.

Statutory Authority

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

Historical Notes

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

12VAC5-610-710. Reserve absorption area sites.

Separate reserve area or areas meeting the requirements of Part III, Article I of this chapter and equalling 50% of the required absorption area shall be provided where the estimated or measured percolation rate exceeds 45 minutes/inch.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.6, eff. February 5, 1986; amended, eff. May 11, 1988.

Article Art
Icle 2

12VAC5-610-720. General.

Article 2

Building Sewers

Sewers referred to in this section are watertight, smooth bore, rigid conduits which convey sewage from a building drain to a pretreatment unit and are not to be confused with public sewers addressed in the Sewerage Regulations. (See 12VAC5-580-10 et seq.)

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.7, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-730. Minimum size.

Sewers shall have a minimum internal diameter (ID) of three inches. Larger sewers may be required depending on projected flows.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.8, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-740. Slope.

The minimum slope for three- and four-inch sewers is 1-1/4 inches per 10 feet, and for a six-inch sewer is 3/4 inch per 10 feet.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.9, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-750. Materials.

All sewers shall be of cast iron (CI) pipe not less than service weight, schedule 40 plastic pipe, extra strength vitrified clay or other acceptable materials to be evaluated on a case-by-case basis. Bituminous fiber pipe is prohibited. Sewers passing under driveways shall be heavy duty CI or schedule 40 plastic pipe, or other acceptable material to be evaluated on a case-by-case basis.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.10, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-760. Sewer appurtenances.

A. Joints. Sewer joints shall be of the compression type except that plastic pipe may be welded sleeve or chemically fused.

B. Adapters. Joining of pipes of different sizes and/or material shall be accomplished by use of a manufactured adapter specifically designed for that purpose.

C. Bends. The building sewer shall have a straight alignment where possible. When a straight alignment is not possible ells not exceeding 45 degrees shall be used.

D. Cleanouts. Cleanouts shall be brought to the ground surface and shall be provided every 50 feet to 60 feet along the length of the building sewer. Cleanouts shall be brought to the ground surface for access.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.11, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-770. Sewer construction.

A. Location. Sewers passing within 50 feet of a nonpublic drinking water supply well or other nonpublic drinking water supply source shall have special construction and pipe materials to provide adequate protection. Special construction constitutes water pipe meeting AWWA specifications, pressure tested (10 feet of water) in place without leakage prior to backfilling. However, under no circumstances shall a sewer come within 10 feet of a nonpublic drinking water supply source.

B. Above grade installation. Sewers constructed above grade shall be adequately supported and protected against freezing. When plastic pipe is used for above grade installation the pipe must be protected against ultraviolet radiation, i.e. shielded against sunlight.

C. Bedding. All sewers shall be bedded to supply uniform support along the length of the sewer.

D. Backfilling and tamping. Sewer trenches shall be backfilled with suitable material free of large stones and clumps of earth and tamped to prevent movement of the sewer as soon as possible after the installation of the sewer has been approved.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.12, eff. February 5, 1986; amended, eff. May 11, 1988.

Article 3
Pretreatment Systems

12VAC5-610-780. General.

Article 3
Pretreatment Systems

As used in this article, "pretreatment" refers to treatment works designed to prepare sewage for disposal in a soil medium.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.13, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-790. Types.

Three general types of pretreatment systems are described herein. They are as follows:

A. Biological;

B. Physical; and

C. Chemical.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.14, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-800. Aerobic biological systems.

Aerobic biological treatment systems will be considered on a case-by-case basis at the request of the owner. These systems shall meet the applicable criteria contained in 12VAC5-640-360 of the Alternative Discharging Sewage Treatment Regulations for Individual Single Family Dwellings or 12VAC5-580-770 of the Sewerage Regulations (12VAC5-580-10 et seq.) or criteria developed by a testing laboratory or agency approved by the division. Where an activated sludge process is used to produce a secondary effluent, provisions shall be made to protect the drainfield from bulking solids. Use of an aerobic pretreatment system shall not result in the reduction of the absorption area requirements contained in Article 5 (12VAC5-610 900 et seq.) of this chapter.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.15, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-810. Anaerobic biological systems.

Septic tanks are the most commonly used pretreatment systems and under normal circumstances are the most inexpensive units that give acceptable results with a minimum of maintenance.

The preferred material for use in constructing septic tanks is concrete. Other materials may be considered on a case-by-case basis. All materials must be resistant to corrosion, both chemical and electrolytic, and must have sufficient structural strength to contain sewage and resist lateral compressive and bearing loads.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.16, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-815. Septic tank design.

A. Tank capacity. The minimum hydraulic detention time shall be 48 hours based on daily design flow. In no case shall the septic tank capacity be less than 750 gallons. Table 5.2 contains the minimum required septic tank capacities for dwelling units.

B. Tank dimensions. Septic tanks shall be rectangular in plan, cross-section and longitudinal view. The length to liquid depth to width ratio should be approximately equal or greater than 2 to 1 to 1 (2:1:1) and less than or equal to 3 to 1 to 1 (3:1:1). In no case shall the liquid depth be less than four feet or greater than eight feet. A minimum of one foot free board shall be provided. Inlet and outlet structures shall be placed on the longitudinal axis of the tank. Typical tank dimensions are found in Table 5.3.

C. Inlet-outlet structure.

1. General. The inlet and outlet structures shall function as a baffle. The invert of the inlet structure shall be greater than one inch but less than two inches higher than the invert of the outlet structure with the tank installed. The inlet structure shall extend six to eight inches below and eight to 10 inches above the normal liquid level. The outlet structure shall extend below the normal liquid surface to a distance of 35 to 40% of the liquid depth and eight to 10 inches above the normal liquid level. The inlet and outlet structures shall have an open space not less than four inches by four inches in cross-section or four inches in diameter.

2. Materials. All materials used for inlet and outlet structures shall have long term resistance to chemical and electrolytic corrosion. When pipe tees are used as inlet and outlet structures, the material shall be compatible with the material used in the sewer.

D. Top access and watertightness. All septic tanks shall be watertight and shall be provided with a watertight top. As a minimum, access manholes shall be provided over the inlet and outlet structures and shall have a minimum open space of 18 inches by 18 inches. When the septic tank has in excess of 30 inches of soil cover, an access manhole shall be brought to within 18 inches of the ground surface and shall be provided with a tight fitting cover. In wet areas the manhole covers shall be watertight.

E. Construction of septic tanks. The contractor and/or manufacturer shall design and construct the septic tank to withstand the lateral and bearing loads to which the septic tank is expected to be subjected.

F. Placement of septic tanks. The precast septic tank shall be bedded with at least six inches of sand or fine gravel where rock or other undesirable conditions are encountered. The tank shall be placed level. Where excavation is required, the hole shall be sufficiently large to permit placement of the tank. Backfilling the excavation for all septic tanks shall be done in layers with sufficient tamping to avoid settling. Backfill material shall be free of large stones and debris.

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.

12VAC5-610-817. Maintenance.

A. In order to encourage proper maintenance and reduce the likelihood of solids being discharged to an absorption field, all septic tanks constructed after July 1, 2000, shall be designed to allow for routine inspection without being uncovered (i.e., have an inspection port as provided for in subsection B of this section) or have an effluent filter as provided for in subsection C of this section, or be designed for reduced maintenance as provided for in subsection D of this section.

B. Inspection port. An inspection port is a three-inch or larger port pipe or structure which allows access to the septic tank for the purpose of measuring sludge and scum accumulation. The inspection port shall terminate at or above grade and be designed to allow an inspection of sludge buildup in the septic tank. The inspection port shall be constructed of schedule 40 PVC pipe, or its equivalent, and shall be fitted with a watertight threaded cap. The recommended location of the inspection port shall be in or near the manhole cover on the inlet side of the septic tank away from the inlet tee. Other locations may be approved by the district health department on a case-by-case basis.

C. Effluent filters. An effluent filter is a device which has one or more of the following purposes: (i) to manage solids to provide greater service life to a pump or other components of an onsite system; (ii) to manage the total suspended solids (TSS) passed to the absorption field, potentially enhancing absorption field life; or (iii) some other purpose recognized as beneficial by the department.

1. All effluent filters shall be designed to improve the quality of effluent leaving the tank in a manner which is consistent with their purpose.

2. Septic tank outlet filters shall be constructed from a material which resists the corrosive nature of the environment within a septic tank.

3. A tamper proof child resistant at-grade access port shall be provided to assure the filter can be readily maintained as necessary.

D. Reduced maintenance septic tanks. Septic tanks which are sized 30% larger than shown in Table 5.3 and which are baffled such that the first compartment is nominally the volume required in Table 5.3 shall be considered to be a reduced maintenance septic tank.

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.

12VAC5-610-820. Miscellaneous.

A. Multiple septic tanks in series. The required volume for a septic tank may be satisfied by the utilization of two septic tanks in series; however, the first septic tank in series shall equal to 1/2 to 2/3 the required total volume.

B. Physical and/or chemical systems. Physical or chemical systems, or both, utilized as pretreatment for subsurface disposal of sewage shall meet the applicable criteria contained in 12VAC5-580-930 through 12VAC5-580-960 of the Sewerage Regulations.

C. Water stop. A water stop is a method for sealing the annular space around a conduit or pipe, or both, for the purpose of preventing infiltration or exfiltration, or both. Conduits or pipes passing through the walls of a pretreatment unit shall be provided with a water stop.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.17, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-830. (Repealed.)

Historical Notes

Derived from VR355-34-02 §§ 4.18 and 4.19, eff. February 5, 1986; amended, eff. May 11, 1988; repealed, Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

Article 4
Conveyance Systems

12VAC5-610-850. General.

Article 4
Conveyance Systems

For the purpose of this chapter an "effluent conveyance system" is defined as the piping, mechanical equipment and appurtenances utilized to transport effluent from a pretreatment system to a point where the flow is split for distribution to a subsurface soil absorption system.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.20, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-860. Conveyance methods.

Three basic methods utilized to convey effluent are:

1. Gravity;

2. Pumping; and

3. Dosing siphons.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.21, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-870. Gravity effluent mains.

A. Size. Mains transporting effluent by gravity shall have a minimum internal diameter of three inches.

B. Slope. Gravity mains shall have a slope of not less than six inches per 100 feet.

C. Materials. Gravity mains spanning disturbed soil shall meet the material specifications contained in 12VAC5-610-750. The mains shall meet the specifications until placed two feet in undisturbed soil or until termination in a structure. The remaining gravity mains shall have a minimum crush strength of 1500 pounds per foot and may be constructed of cast iron, plastic, vitrified clay or other material resistant to the corrosive action of sewage. All gravity mains shall be watertight, smooth bore, rigid conduits.

D. Appurtenances.

1. Joints. Gravity mains shall have joints of the compression type with the exception of plastic mains which may be welded sleeve or chemically fused.

2. Adapters. Joining of mains of different size and/or material shall be accomplished by use of a manufactured adapter specifically designed for that purpose.

3. Valves. Valves shall be constructed of materials resistant to the corrosive action of sewage. Valves placed below ground level shall be provided with a valve box and a suitable valve stem so that it may be operated from the ground surface.

E. Flow diversion devices. Flow diversion is a technique for increasing the useful life of an absorption area. Flow diversion provides for diversion of flow to two alternate equally sized absorption areas whose sum meets the area requirements in 12VAC5-610-950 B with a rest period of approximately one year for recovery of each absorption area. These devices shall meet the material requirements contained in paragraph D 3 of this section.

F. Construction. Construction standards for gravity effluent mains are the same as those for house sewers and are found in 12VAC5-610-770.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.22, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-880. Pumping.

A. Force mains in general.

1. Velocity. At pumping capacity, a minimum self-scouring velocity of two feet per second shall be maintained. A velocity of eight feet per second should not be exceeded.

2. Air relief valve. Air relief valves shall be placed at high points in the force main, as necessary, to relieve air locking.

3. Bedding. All force mains shall be bedded to supply uniform support along their length.

4. Protection against freezing. Force mains shall be placed deep enough to prevent freezing.

5. Location. Force mains 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 force main come within 10 feet of a nonpublic drinking water source.

6. Materials of construction. All pipe used for force mains shall be of the pressure type with pressure type joints.

7. Anchors. Force mains shall be sufficiently anchored within the pump station and throughout the line length. The number of bends shall be as few as possible. Thrust blocks, restrained joints and/or tie rods shall be provided where restraint is needed.

8. Backfilling and tamping. Force main trenches shall be backfilled and tamped as soon as possible after the installation of the force main has been approved. Material for backfilling shall be free of large stones and debris.

B. Pumping station and pumps in general.

1. Sizing. Pumping station wet wells shall provide at least one quarter (1/4) day storage above the high level alarm set point. Actual volume between high and low level limits is determined on a case-by-case basis depending on the objective of pumping: (i) when low pressure dosing is utilized see 12VAC5-610-940 A for sizing requirements; (ii) when pumping to a gravity distribution box the wet well shall be sized to provide a working volume between 1/4 the daily flow and the daily flow; (iii) when pumping for the purpose of enhancing flow distribution (see 12VAC5-610-930 A) the working volume of the wet well shall be 0.6 of the volume of the percolation piping.

2. Materials. Materials for construction of pumping stations are the same as for septic tanks (see 12VAC5-610-810). All materials and equipment utilized in pumping stations shall be unaffected by the corrosive action of sewage.

3. Access. An access manhole terminating above the ground surface shall be provided. The manhole shall have a minimum width dimension of 24 inches and shall be provided with a shoe box type cover adequately secured.

4. Construction. Pumping stations constructed of precast or poured in place concrete shall conform with the construction requirements contained in 12VAC5-610-815 E. When precast concrete pipe is utilized for a pumping station, the pipe shall be placed on and bonded to a concrete pad at least six inches thick and having a width at least one foot greater than the diameter of the pipe. All pumping stations shall be watertight. All conduits entering or leaving the pumping stations shall be provided with a water stop. The influent pipe shall enter the pumping station at an elevation at least one inch higher than the maximum water level in the wet well (total usable volume).

5. Installation. Placement of pumping stations shall conform to the requirements for placement of septic tanks contained in 12VAC5-610-815 F.

6. Pumps. All pumps utilized shall be of the open face centrifugal, vertical turbine, or suction lift type designed to pump sewage. Pumps utilized for the sole purpose of pumping effluent to a higher elevation shall have a capacity approximately 2.5 times the average daily flow in gallons per minute but not less than five gallons per minute at the system head. Pumps utilized for the purpose of enhancing flow distribution (See 12VAC5-610-930 A) shall have a minimum capacity of 36 gallons per minute at system head per 1200 linear feet of percolation piping. Pumps discharging to a low pressure distribution system shall be sized in accordance with 12VAC5-610-940 A. Dual alternating pumps are required on systems 1800 linear feet or greater in accordance with 12VAC5-610-930 B. Pumps shall be so placed that under normal start conditions it shall be subjected to a positive suction head. When multiple pumps are used, each pump shall have its own separate suction line. Suitable shutoff valves shall be provided on the discharge line and suction line (if provided) for normal pump isolation. A check valve shall be placed in the discharge line between the pump and shutoff valve. When the pump discharge is at a lower elevation than the high liquid level in the pump station, an antisiphon device shall be provided on the pump discharge. Pumps shall be piped so that they can be removed for servicing without having to dewater the wet well.

7. Controls. Each pumping station shall be provided with controls for automatically starting and stopping the pumps. When float type controls are utilized, they shall be placed so as to be unaffected by the flow entering the wet well. Provisions shall be made for automatically alternating the pumps. The electrical motor control center and master disconnect switch shall be placed in a secure location above grade and remote from the pump station. Each motor control center shall be provided with a manual override switch. The control panel shall be located to allow for working access, taking into consideration the finished ground surface elevation.

8. Alarms. A high water alarm with remote sensing and electrical circuitry separate from the motor control center circuitry shall be provided. The alarm shall be audiovisual and shall alarm in an area where it may be easily monitored. When multiple pumps are utilized, an additional audiovisual alarm shall be provided to alarm when a pump motor fails to start on demand.

9. Ventilation. Positive ventilation shall be provided at pumping stations when personnel are required to enter the station for routine maintenance.

a. Wet wells. Ventilation may be either continuous or intermittent. Ventilation, if continuous, shall provide at least 12 complete air changes per hour; if intermittent, at least 30 complete air changes per hour. Such ventilation shall be accomplished by mechanical means.

b. Dry wells. Ventilation may be either continuous or intermittent. Ventilation, if continuous, shall provide at least six complete air changes per hour; if intermittent, at least 30 complete air changes per hour. Such ventilation shall be accomplished by mechanical means.

C. Conveyance pumps and pump stations that move TL-2 effluent or TL-3 effluent to a soil dispersal system shall comply with the following.

1. Subsection A of this section shall apply, except that the minimum velocity in the force main may be reduced to one foot per second.

2. Pump station wet wells shall provide at least one-quarter-day storage above the high level alarm set point. Alternatively, storage may be provided in a treatment tank such as a recirculation tank, but the maximum water level must be one inch below the invert of the pipe from the septic tank.

3. Subdivisions B 2, B 3, B 4, B 5, B 7, B 8, and B 9 of this section shall apply.

4. All pumps utilized shall be of the open face centrifugal, vertical turbine, or suction lift type designed to pump sewage.

a. Pumps utilized for the purpose of enhancing flow distribution (See 12VAC5-610-930 A) shall have a minimum capacity of 36 gallons per minute at system head per 1,200 linear feet of percolation piping.

b. Pumps discharging to a low pressure distribution system shall be sized in accordance with 12VAC5-610-940.

c. Dual alternating pumps are required on systems 1,800 linear feet or greater in accordance with 12VAC5-610-930 B.

d. Submersible pumps shall be placed so that under normal start conditions the pump shall be subjected to a positive suction head.

e. When multiple pumps are used, each pump shall have its own separate suction line. Suitable shutoff valves shall be provided on the discharge line and suction line (if provided) for normal pump isolation. A check valve shall be placed in the discharge line between the pump and shutoff valve. When the pump discharge is at a lower elevation than the high liquid level in the pump station, an anti-siphon device shall be provided on the pump discharge. Pumps shall be piped so that they can be removed for servicing without having to dewater the wet well.

D. Pumps integral to treatment systems are pumps that move wastewater within the treatment unit and are required to achieve the desired effluent quality. Subsections A, B, and C of this section do not apply to these integral pumps.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.23, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000; Volume 39, Issue 4, eff. November 24, 2022.

12VAC5-610-890. Siphons.

A. Use. Intermittent dosing siphons have two major uses:

1. Low pressure dosing of subsurface soil absorption systems (see 12VAC5-610-940); or

2. To provide more uniform distribution of effluent to large or multiple sectioned subsurface soil absorption systems which split the flow 12 or more times or contain 1200 linear feet or more of percolation piping (see 12VAC5-610-930 A and B).

B. Materials. Materials for construction of dosing siphon chambers are the same as for septic tanks (see 12VAC5-610-810).

C. Number and sizing. Dosing siphons discharging to subsurface soil absorption systems shall have an average discharge rate greater than 2.5 times the average daily influent flow in gallons per minute but not less than 70 gallons per minute per 1200 linear feet of percolation lines. Twin alternating siphons are required where the system to be dosed exceeds 1800 linear feet in accordance with 12VAC5-610-930 B. The volume of the dosing chamber shall equal 0.6 the volume of the percolation piping for enhanced flow distribution. Actual dosing chamber volume is determined on a case-by-case basis where low pressure distribution is utilized (see 12VAC5-610-940 A).

D. Access. The siphon chamber shall terminate at or above the ground surface. The top of the chamber shall be removable to an extent to allow access for maintenance, repairs and removal of the siphon components.

E. Construction. Dosing chambers constructed of precast or poured in place concrete shall conform with the construction requirements contained in 12VAC5-610-815 E.

F. Force mains. Force mains used in conjunction with siphons shall meet the applicable criteria contained in 12VAC5-610-880 A.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.24, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

Article 5
Subsurface Soil Absorption System

12VAC5-610-900. General.

Article 5
Subsurface Soil Absorption System

Subsurface soil absorption systems are sewage disposal systems which utilize the soil to further treat and dispose of effluent from a treatment works in a manner that does not result in a point source discharge and does not create a nuisance, health hazard or ground or surface water pollution.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.25, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-910. Scope.

For the purpose of this chapter, a "subsurface soil absorption system" shall refer to that part of a sewage disposal system beginning at the flow splitting device and extending through the absorption area or areas.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.26, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-920. Distribution methods.

The term distribution methods refers to the piping, flow splitting devices, gravel, and other appurtenances beginning at the point of flow splitting and ending at the application of effluent to the soil absorption area. Two basic methods are considered:

A. Gravity; and

B. Pressure.

Statutory Authority

§§ 32.1-12, 32.1-164, and 32.1-164.9 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 1.3, eff. February 5, 1986; amended, eff. May 11, 1988; amended, Virginia Register Volume 16, Issue 16, eff. July 1, 2000; Volume 32, Issue 24, eff. August 25, 2016.

12VAC5-610-930. Gravity distribution.

Gravity distribution is the conveyance of effluent from a distribution box through the percolation lines at less than full flow conditions. Flow to the initial distribution box may be initiated by pump, siphon or gravity.

A. Enhanced flow distribution. Enhanced flow distribution is the initiation of the effluent flow to the distribution box by pump or siphon for the purpose of assuring more uniform flow splitting to the percolation lines. Enhanced flow distribution shall be provided on systems where the flow is split more than 12 times or the system contains more than 1200 linear feet of percolation lines. For the purpose of this chapter, enhanced flow distribution is considered to produce unsaturated soil conditions.

B. System size. Distribution systems containing 1800 or more linear feet of percolation piping shall be split into multiple systems containing a maximum of 1200 linear feet of percolation piping per system.

C. Distribution boxes. The distribution box is a device for splitting flow equally by gravity to points in the system. Improperly installed distribution boxes are a cause for absorption field malfunction.

1. Materials. The preferred material for use in constructing distribution boxes is concrete (3000 psi). Other materials may be considered on a case-by-case basis. All materials must be resistant to both chemical and electrolytic corrosion and must have sufficient structural strength to contain sewage and resist lateral compressive and bearing loads.

2. Design. Each distribution box shall be designed to split the influent flow equally among the multiple effluent ports. All effluent ports shall be at the same elevation and be of the same diameter. The elevation of the effluent ports shall be at a lower elevation than the influent port. The placement of the influent ports shall be such as to prevent short circuiting unless baffling is provided to prevent short circuiting. The minimum inside width of a gravity flow distribution box shall be equal to or greater than 12 inches. The inside bottom shall be at least four inches below the invert of the effluent ports and at least five inches below the invert of the influent port. A minimum of eight inches freeboard above the invert of the effluent piping shall be provided. The distribution box shall be fitted with a watertight, removable lid for access.

3. Installation. The hole for placement of the distribution box shall be excavated to undisturbed soil. The distribution box shall be placed in the excavation and stabilized. The preferred method of stabilizing the distribution box is to bond the distribution box to a four inch poured in place Portland cement concrete pad with dimensions six inches greater than the length and width dimensions of the distribution box. The box shall be permanently leveled and checked by water testing. Conduits passing through the walls of a distribution box shall be provided with a water stop.

D. Lead or header lines. Header or lead lines are watertight, semirigid, or rigid lines that convey effluent from a distribution box to another box or to the percolation piping.

1. Size. The lead or header lines shall have an internal diameter of four inches.

2. Slope. Minimum slope shall be two inches per 100 feet.

3. Materials. The lead or header lines shall have a minimum crush strength of 1500 pounds per foot and may be constructed of cast iron, plastic, vitrified clay, or other material resistant to the corrosive action of sewage.

4. Appurtenances.

a. Joints. Lead or header lines shall have joints of the compressions type with the exception of plastic lead or header lines that may be welded sleeve, chemically fused, or clamped (noncorrosive) flexible sleeve.

b. Adapters. Joining of lead or header lines of different size or material shall be accomplished by use of a manufactured adapter specifically designed for the purpose.

c. Valves. Valves shall be constructed of materials resistant to the corrosive action of sewage. Valves placed below ground level shall be provided with a valve box and a suitable valve stem so that it may be operated from the ground surface.

5. Construction.

a. Bedding. All lead or header lines shall be bedded to supply uniform support and maintain grade and alignment along the length of the lead or header lines. Special care shall be taken when using semirigid pipe.

b. Backfilling and tamping. Lead and header lines shall be backfilled and tamped as soon as possible after the installation of the lead or header lines has been approved. Material for backfilling shall be free of large stones and debris.

6. Termination. Header or lead lines shall extend for a minimum distance of two feet into the absorption trenches.

E. Gravity percolation lines. Gravity percolation lines are perforated or open joint pipes that are utilized to distribute the effluent along the length of the absorption trenches.

1. Size. All gravity percolation lines shall have an internal diameter of four inches.

2. Slope. The slope of the lines shall be uniform and shall not be less than two inches or more than four inches per 100 feet.

3. Design. Effluent shall be split by the distribution system so that all gravity percolation lines installed shall receive an equal volume of the total design effluent load per square foot of trench, i.e., the fraction of the flow received by each percolation line divided by the length of the gravity percolation lines shall be equal for all gravity percolation lines in a system.

4. Length. No individual gravity percolation line shall exceed 100 feet in length.

5. Materials.

a. Clay. Clay tile shall be extra-strength and meet current ASTM standards for clay tile.

b. Perforated plastic drainage tubing. Perforated plastic drainage tubing shall meet ASTM standards. At not greater than 10 feet intervals the pipe shall be plainly marked, embossed, or engraved thereby showing the manufacturer's name or hallmark and showing that the product meets a bearing load of 1,000 lb. per foot. In addition, a painted or other clearly marked line or spot shall be marked at not greater than 10 feet intervals to denote the top of the pipe.

The tubing shall have three holes, 1/2 to 3/4 inch in diameter evenly spaced and placed within an arc of 130 degrees, the center hole being directly opposite the top marking.

Spacing of each set of three holes shall be at four inch intervals along the tube. If there is any break in the continuity of the tubing, an appropriate connection shall be used to join the tubing.

6. Installation.

a. Crushed stone or gravel. Clean gravel or crushed stone having a size range from 1/2 inch to 1-1/2 inches shall be utilized to bed the gravity percolation lines.

Minimum depth of gravel or crushed stone beneath the percolation lines shall be six inches. Clean course silica sand (does not effervesce in presence of dilute hydrochloric acid) may be substituted for the first two inches (soil interface) of the required six inches of gravel beneath the percolation lines. The absorption trench shall be backfilled to a depth of two inches over the gravity percolation lines with the same gravel or crushed stone. Clean sand, gravel, or crushed stone shall be free of fines, clay, and organic materials.

b. Grade boards or stakes. Grade boards or stakes placed in the bottom or sidewalls of the absorption trench shall be utilized to maintain the grade on the gravel for placement of the gravity percolation lines. Grade stakes shall not be placed on centers greater than 10 feet.

c. Placement and alignment. Perforated gravity percolation piping shall be placed so that the center hole is in the horizontal plane and interfaces with the minimum six inches of graded gravel. When open joint piping is utilized the upper half of the top of the 1/4-inch open space shall be covered with tar paper or building paper to block the entrance of fines into the pipe during the backfilling operation. All gravity percolating piping shall be placed in the horizontal center of the absorption trench and shall maintain a straight alignment and uniform grade.

d. Backfilling. After the placement of the gravity percolation piping the absorption trench shall be backfilled evenly with crushed stone or gravel to a depth of two inches over the piping. Untreated building paper or other suitable material shall be placed at the interface of the gravel and soil to prevent migration of fines to the trench bottom. The remainder of the trench shall be backfilled with soil to the ground surface.

F. Gravelless material is a proprietary product specifically manufactured to disperse effluent within the absorption trench of an onsite sewage system without the use of gravel. Gravelless material may include chamber, bundled expanded polystyrene, and multi-pipe systems. The division shall maintain a list of all generally approved gravelless material. Gravelless material on the generally approved list may be used in accordance with Table 5.4 of 12VAC5-610-950.

1. Gravelless material that received general approval as of December 12, 2013, shall retain such status when used in accordance with the requirements of this chapter. After December 12, 2013, the division shall review and evaluate new applications for general approval pursuant to the requirements of this chapter.

a. Any manufacturer of gravelless material may submit an application for general approval to the division using a form provided by the division. A complete application shall include the manufacturer's contact information, product specifications, product approvals in other states or territories, installation manual, and other information deemed necessary by the division to determine compliance with this chapter.

b. The manufacturer of gravelless material shall identify in the application for general approval any recommendation that deviates from the requirements of this chapter. If the recommendation is approved by the division, then the manufacturer shall include the deviation in the gravelless material's installation manual.

2. Gravelless material shall have the following minimum characteristics for general approval:

a. The minimum exterior width shall be at least 90% of the total width of the absorption trench. The exterior width of a chamber system shall be measured at the edge or outer limit of the product's contact with the trench bottom unless the division determines a different measurement is required based on the gravelless material's design. The exterior width of bundled expanded polystyrene and multi-pipe systems shall be measured using the outside diameter of the bundled gravelless material unless the division determines a different measurement is required based on the gravelless material's design. The division shall establish the exterior width of any gravelless material that is not considered a chamber, bundled expanded polystyrene, or multi-pipe system.

b. Gravelless material shall have a minimum height of eight inches to provide a continuous exchange of air through a permeable interface.

c. Gravelless material shall have a permeable interface that shall be located along the trench bottom and trench sidewalls within the absorption trench.

d. Gravelless material shall provide a minimum storage capacity of 1.3 gallons per square foot of trench bottom area.

e. Gravelless material shall pose no greater risk to surface water and groundwater quality than gravel in absorption trenches. Gravelless material shall be constructed to maintain structural integrity such that it does not decay or corrode when exposed to effluent.

f. Gravelless material shall have a minimum load rating of H-10 or H-20 from the American Association of State Highway and Transportation Officials or equivalent when installed in accordance with the manufacturer's specifications and minimum specified depth of cover in nontraffic or traffic areas, respectively.

3. For designs using gravelless material, the absorption trenches shall receive an equal volume of effluent per square foot of trench. Trench bottom area shall be equal to or greater than the minimum area requirements contained in Table 5.4 or Table 5.5 of 12VAC5-610-950. Trench sidewall shall not be included when determining minimum area requirements. When open-bottom gravelless material is utilized, it shall provide a splash plate at the inlet of the trench or other suitable method approved by the manufacturer to reduce effluent velocity.

4. Installation of gravelless material shall comply with this chapter and the approved installation manual unless the department grants a deviation pursuant to 12VAC5-610-660 or the division has granted a deviation identified in the installation manual.

5. Gravelless material shall contain a pressure percolation line along the entire length of the trench when low pressure distribution is utilized pursuant to 12VAC5-610-940 D.

6. When pumping effluent to overcome gravity, any open-bottom gravelless material shall provide a high-flow splash plate at the inlet of the trench or other suitable method approved by the manufacturer to reduce effluent velocity.

7. When enhanced flow distribution is used, open-bottom gravelless material shall contain a percolation pipe that extends a minimum of 10 feet from the trench's intersection with the header line. The percolation pipe shall be installed in accordance with the manufacturer's approved installation manual. The dosing volume shall be a minimum 39 gallons per 100 linear feet of absorption trench.

8. Gravelless material may be substituted for gravel in accordance with this chapter, provided that the certifying licensed professional engineer or onsite soil evaluator approves the substitution. The certifying licensed professional engineer or onsite soil evaluator shall document the substitution and related design changes on the inspection report submitted in accordance with 12VAC5-610-330. A new construction permit pursuant to 12VAC5-610-310 is not required for the substitution.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.28, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000; Volume 32, Issue 24, eff. August 25, 2016; Volume 39, Issue 4, eff. November 24, 2022.

12VAC5-610-940. Low pressure distribution.

Low pressure distribution is the conveyance of effluent through the pressure percolation lines at full flow conditions into the absorption area with the prime motive force being a pump or siphon. Low pressure systems are limited to a working pressure of from one to four feet of head at the distal end of the pressure percolation lines. For the purpose of this chapter low pressure distribution is considered to provide unsaturated soil conditions.

A. Dosing cycle. Systems shall be designed so that the effluent volume applied to the absorption area per dosing cycle is from seven to 10 times the volume of the distribution piping, however, the volume per dosing cycle should not result in a liquid depth in the absorption trench greater than two inches.

B. Manifold lines. Manifold lines are watertight lines that convey effluent from the initial point of flow splitting to the pressure percolation lines.

1. Size. The manifold line shall be sized to provide a minimum velocity of two feet per second and a maximum velocity of eight feet per second.

2. Materials. All pipe used for manifolds shall be of the pressure type with pressure type joints.

3. Bedding. All manifolds shall be bedded to supply uniform support along its length.

4. Backfilling and tamping. Manifold trenches shall be backfilled and tamped as soon as possible after the installation of the manifold has been approved. Material for backfilling shall be free of large stones and debris.

5. Valves. Valves for throttling and check valves to prevent backflow are required wherever necessary. Each valve shall be supplied with a valve box terminating at the surface.

C. Pressure percolation lines. Pressure percolation lines are perforated pipes utilized to distribute the flow evenly along the length of the absorption trench.

1. Size. Pressure percolation lines should normally have a 1-1/4 inch inside diameter.

2. Hole size. Normal hole size shall be 3/16 inch to 1/4 inch.

3. Hole placement. Center to center hole separation shall be between three and five feet.

4. Line length. Maximum line length from manifold should not exceed 50 feet.

5. Percent flow variation. Actual line size, hole size and hole separation shall be determined on a case-by-case basis based on a maximum flow variation of 10% along the length of the pressure percolation lines.

6. Materials and construction. The preferred material is plastic, either PVC or ABS, designed for pressure service. The lines shall have burr free and counter sunk holes (where possible) placed in a straight line along the longitudinal axis of the pipe. Joining of pipes shall be accomplished with manufactured pressure type joints.

7. Installation.

a. Crushed stone or gravel. Clean gravel or crushed stone having a size range from 1/2 inch to 3/4 inch shall be utilized to bed the pressure percolation lines. Minimum depth of gravel or crushed stone beneath the percolation lines shall be 8-1/2 inches. Clean course silica sand (does not effervesce in the presence of dilute hydrochloric acid) may be substituted for the first two inches (soil interface) of the required 8-1/2 inches of gravel beneath the pressure percolation lines. The absorption trench shall be backfilled to a depth of two inches over the pressure percolation lines with the same gravel or crushed stone. Clean sand, gravel or crushed stone shall be free of fines, clay and organic materials.

b. Grade boards or stakes. Grade boards or stakes placed in the bottom or sidewalls of the absorption trench shall be utilized to maintain the gravel level for placement of the pressure percolation lines. Grade stakes shall not be placed on centers greater than 10 feet.

c. Placement and alignment. Pressure percolation lines shall be placed so that the holes face vertically downward. All pressure percolation piping shall be placed at the same elevation, unless throttling valves are utilized, and shall be level. The piping shall be placed in the horizontal center of the trench and shall maintain a straight alignment. Normally the invert of the pressure percolation lines shall be placed 8-1/2 inches above the trench bottom. However, under no circumstance shall the invert of the pressure percolation lines be placed closer than 16-1/2 inches to the seasonal water table as defined in 12VAC5-610-470 D. When the invert of the pressure percolation lines must be placed at an elevation greater than 8-1/2 inches above the trench bottom, landscaping over the absorption area may be required to provide the two inches of gravel and six inches of fill over the pressure percolation lines required in subdivision 7 a of this subsection.

d. Backfilling. After the placement of the pressure percolation piping the absorption trench shall be backfilled evenly with crushed stone or gravel to a depth of two inches over the opening. Untreated building paper or other suitable material shall be placed at the interface of the gravel and soil to prevent migration of fines to the trench bottom. The remainder of the trench shall be backfilled with soil to the ground surface.

8. Appurtenances. The distal (terminal) end of each pressure percolation lines shall be fitted with a vertical riser and threaded cap extending to the ground surface. Systems requiring throttling valves will be supplied with couplings and threaded riser extensions at least four feet long so that the flow may be adjusted in each line.

D. Gravelless material with general approval may be used for low pressure distribution in accordance with the manufacturer's approved installation manual, Table 5.4 of 12VAC5-610-950, and the applicable requirements of this chapter.

Statutory Authority

§§ 32.1-12, 32.1-164, and 32.1-164.9 of the Code of Virginia.

Historical Notes

Derived from VR355-34-02 § 4.29, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000; Volume 32, Issue 24, eff. August 25, 2016.

12VAC5-610-950. Absorption area design.

A. The absorption area is the undisturbed soil medium utilized for absorption of the effluent. The absorption area includes the infiltrative surface in the absorption trench and the soil between and around the trenches when trenches are used.

B. Suitability of soil horizon. The absorption trench bottom shall be placed in the soil horizon or horizons with an average estimated or measured percolation rate less than 120 minutes per inch. Soil horizons are to be identified in accordance with 12VAC5-610-480. The soil horizon must meet the following minimum conditions:

1. It shall have an estimated or measured percolation rate equal to or less than 120 minutes per inch;

2. The soil horizon or horizons shall be of sufficient thickness so that at least 12 inches of absorption trench sidewall is exposed to act as an infiltrative surface; and

3. If no single horizon meets the conditions in subdivision 2 of this subsection, a combination of adjacent horizons may be utilized to provide the required 12-inch sidewall infiltrative surface. However, no horizon utilized shall have an estimated or measured percolation rate greater than 120 minutes/inch.

C. Placement of absorption trenches below soil restrictions. Placement of the soil absorption trench bottom below soil restrictions as defined in 12VAC5-610-490 D, whether or not there is evidence of a perched water table as indicated by free standing water or redoximorphic features, including concentrations, depletions, or stains, nodules, or concretions of iron and manganese, requires a special design based on the following criteria:

1. The soil horizon into which the absorption trench bottom is placed shall be a Texture Group I, II, or III soil or have an estimated or measured percolation rate of less than 91 minutes per inch.

2. The soil horizon shall be a minimum of three feet thick and shall exhibit no characteristics that indicate wetness on restriction of water movement. The absorption trench bottom shall be placed so that at least two feet of the soil horizon separates the trench bottom from the water table or rock. At least one foot of the absorption trench side wall shall penetrate the soil horizon.

3. A lateral ground water movement interceptor (LGMI) shall be placed upslope of the absorption area. The LGMI shall be placed perpendicular to the general slope of the land. The invert of the LGMI shall extend into, but not through, the restriction and shall extend for a distance of 10 feet on both sides of the absorption area (See 12VAC5-610-700 D 3).

4. Pits shall be constructed to facilitate soil evaluations as necessary.

D. Sizing of absorption trench area for septic tank effluent.

1. Required area. The total absorption trench bottom area required shall be based on the average estimated or measured percolation rate for the soil horizon or horizons into which the absorption trench is to be placed. If more than one soil horizon is utilized to meet the sidewall infiltrative surface required in subsection B of this section, the absorption trench bottom area shall be based on the average estimated or measured percolation rate of the "slowest" horizon. The trench bottom area required in square feet per 100 gallons (Ft²/100 Gals) of sewage applied for various soil percolation rates is tabulated in Table 5.4. The area requirements are based on the equation:

log y = 2.00 + 0.008 (x)

where y = Ft²/100 Gals

x = Percolation rate in minutes/inch

Notwithstanding the above, the minimum absorption area for single family residential dwellings shall be 400 square feet.

2. Area reduction. See Table 5.4 for area reduction when gravelless material or low pressure distribution is utilized. A reduction in area shall not be permitted when flow diversion is utilized with low pressure distribution. When gravelless material is utilized, the design width of the trench shall be used to calculate minimum area requirements for absorption trenches.

E. Minimum cross section dimensions for absorption trenches.

1. Depth. The minimum trench sidewall depth as measured from the surface of the mineral soil shall be 12 inches when placed in a landscape with a slope less than 10%. The installation depth shall be measured on the downhill side of the absorption trench. When the installation depth is less than 18 inches, the depth shall be measured from the lowest elevation in the microtopography. All systems shall be provided with at least 12 inches of cover to prevent frost penetration and provide physical protection to the absorption trench; however, this requirement for additional cover shall not apply to systems installed on slopes of 30% or greater. Where additional soil cover must be provided to meet this minimum, it must be added prior to construction of the absorption field, and it must be crowned to provide positive drainage away from the absorption field. The minimum trench depth shall be increased by at least five inches for every 10% increase in slope. Sidewall depth is measured from the ground surface on the downhill side of the trench.

2. Width. All absorption trenches utilized with gravity distribution shall have a width of from 18 inches to 36 inches. All absorption trenches utilized with low pressure distribution shall have a width of eight inches to 24 inches.

F. Lateral separation of absorption trenches. The absorption trenches shall be separated by a center to center distance no less than three times the width of the trench for slopes up to 10%. However, where trench bottoms are two feet or more above rock, pans, and impervious strata, the absorption trenches shall be separated by a center to center distance no less than three times the width of the trench for slopes up to 20%. The minimum horizontal separation distance shall be increased by one foot for every 10% increase in slope. In no case shall the center to center distance be less than 30 inches.

G. Slope of absorption trench bottoms.

1. Gravity distribution. The bottom of each absorption trench shall have a uniform slope not less than two inches or more than four inches per 100 feet.

2. Low pressure distribution. The bottom of each absorption trench shall be uniformly level to prevent ponding of effluent.

H. Placement of absorption trenches in the landscape.

1. The absorption trenches shall be placed on contour.

2. When the ground surface in the area over the absorption trenches is at a higher elevation than any plumbing fixture or fixtures, sewage from the plumbing fixture or fixtures shall be pumped.

I. Lateral ground water movement interceptors. Where subsurface, laterally moving water is expected to adversely affect an absorption system, a lateral ground water movement interceptor (LGMI) shall be placed upslope of the absorption area. The LGMI shall be placed perpendicular to the general slope of the land. The invert of the LGMI shall extend into, but not through, the restriction and shall extend for a distance of 10 feet on either side of the absorption area.

J. Controlled blasting. When rock or rock outcroppings are encountered during construction of absorption trenches the rock may be removed by blasting in a sequential manner from the top to remove the rock. Percolation piping and sewer lines shall be placed so that at least one foot of compacted clay soil lies beneath and on each side of the pipe where the pipe passes through the area blasted. The area blasted shall not be considered as part of the required absorption area.

K. Trenches receiving TL-2 effluent or TL-3 effluent are exempt from the increase in trench depth with slope and the soil cover requirements as found in 12VAC5-610-950 E. The following additional requirements shall apply.

1. Soil dispersal loading rates shall not exceed the values in Table 5.5.

2. The minimum vertical separation to a limiting feature shall be maintained under the entire infiltrative surface in accordance with 12VAC5-613-80.

3. The minimum soil cover, after settling, shall be six inches as measured from the finished ground surface to the uppermost limit of the dispersal media (or gravelless material) utilized in the absorption area. On sloping sites, cover shall be tied back into the existing slope to facilitate stabilization of the slope and maintenance of the site. The soil cover, with amendments as needed, shall be of a quality, character, and fertility suitable to establish a vegetative cover that is uniform and sufficiently mature to survive and inhibit erosion.

4. The minimum installation depth is equal to the sidewall of the dispersal system construction as described in 12VAC5-610-930 F (gravelless), 12VAC5-610-940, and subdivision E 1 of this section. On sloping sites, the minimum installation depth is measured on the downhill side of the absorption trench.

5. When trenches are installed at less than 12 inches from the ground surface, timed dosing shall be used to disperse the effluent.

6. For slopes up to 15% slope, there are not any soil texture group limitations for shallow placed trenches receiving TL-2 effluent or TL-3 effluent. For slopes over 15%, trench systems installed in Texture Group III and IV soils shall have a 12-inch or greater installation depth.

7. Designs supported by division-approved manufacturer design manuals may deviate from subdivisions K 4 and K 5 of this section.

8. Notwithstanding subdivisions K 1 through K 7 of this section, the minimum absorption area for a single-family residential dwelling receiving TL-2 effluent or TL-3 effluent shall be 400 square feet.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.29, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000; Volume 32, Issue 24, eff. August 25, 2016; Volume 39, Issue 4, eff. November 24, 2022.

12VAC5-610-955. Drip dispersal.

A. Drip dispersal applies wastewater in an even and controlled manner over an absorption area. Drip dispersal system components may include treatment components, a flow equalization pump tank, a filtration system, a flow measurement method, supply and return piping, small diameter pipe with emitters, air/vacuum release valves, redistribution control, and electromechanical components or controls.

B. Drip dispersal system tubing shall be color coded and certified by the manufacturer as designed and manufactured for the dispersal of wastewater. All drip dispersal system tubing shall be equipped with emitters approved for use with wastewater. For the application of septic tank effluent, the tubing must have self-cleaning emitters.

1. The minimum linear feet of tubing in the system shall be one-half of the minimum soil absorption area in square feet.

2. All tubing shall be placed on contour.

3. Except as provided by 12VAC5-613, drip systems dispersing septic tank effluent shall comply with the requirements of 12VAC5-610-594.

4. Drip systems dispersing secondary effluent or better require a minimum of six inches of cover over the tubing. Cover may be achieved by a combination of installation depth and Group II or Group III soil cover or other approved material over the drip field.

5. The discharge rate of any two emitters shall not vary by more than 10% in order to ensure that the effluent is uniformly distributed over the entire drip field or zone.

6. The emitters shall be evenly spaced along the length of the drip tubing at not less than six inches or more than 24 inches apart.

7. The system design shall protect the drip emitters and system from the effects of siphoning or backflow through the emitters.

C. Drip dispersal systems shall comply with the following minimum soil absorption area requirements:

1. For the dispersal of septic tank effluent, the minimum soil absorption area for a drip system shall be calculated by multiplying the trench bottom area required for a low pressure distribution system in Table 5.4 of 12VAC5-610-950 by three.

2. For the dispersal of TL-2 effluent or TL-3 effluent, the minimum soil absorption area shall be in accordance with Table 5.5 of 12VAC5-610-950.

3. Air/vacuum release valves shall be located at the high points of the supply and return manifolds to each zone.

D. All drip dispersal systems shall be equipped with devices or methods to restrict effluent from draining by gravity to portions of a zone or laterals lower in elevation. Variable distribution due to gravity drainage shall be 10% or less within a zone.

E. A minimum of six hours of emergency storage above the high water alarm in the pump chamber shall be provided. The equalization volume shall be equal to 18 hours of storage. The equalization volume shall be measured from the pump off level to the high water alarm level. An audio/visual alarm meeting the requirements of 12VAC5-610-880 B 8 shall be provided for the pump chamber.

F. Each drip dispersal zone shall be time-dosed over a 24-hour period. The dose volume and interval shall be set to provide unsaturated flow conditions. Demand dosing is prohibited. Minimum dose volume per zone shall be 3.5 times the liquid capacity of the drip laterals in the zone plus the liquid capacity of the supply and return manifold lines (which drain between doses) accounting for instantaneous loading and drain back.

1. At each dosing cycle, the system design shall only allow a full dose volume to be delivered.

2. For design flows greater than 1,000 gallons per day, a means to take each zone off line separately shall be provided. The system shall have the capability to bypass each zone that is taken out of service such that each subsequent dose is dispersed to the next available zone in sequence.

G. Filtration shall be provided to remove suspended solids and prevent clogging of emitters. The filtration design shall meet the drip tubing manufacturer's particle size requirements for protection of the emitters at a flow rate equal to or greater than the rate of forward flushing. Filter flush water shall be returned to the treatment system at a point where the residuals and volume of the flush water do not negatively impact the effluent quality or exceed the hydraulic design capacity of the treatment system.

H. A means for measuring or estimating total flow dispersed to the soil absorption area and to verify field dosing and field flushing rates shall be provided.

I. The system shall provide forward field flushing to achieve scouring velocity as specified by the drip tubing manufacturer. Field flushing shall occur on a routine schedule to prevent excessive solids accumulation and clogging. Flush water shall be returned to the treatment system at a point where the residuals and volume of the flush water do not negatively impact the effluent quality or exceed the hydraulic design capacity of the treatment system.

J. Electrical components shall be Underwriters Laboratory (UL) listed for the intended purpose. The designer shall provide a description with a schematic diagram of the electrical and control functions in the operation and maintenance manual. The electrical control equipment shall be mounted within a National Electrical Manufacturers Association (NEMA) 4X rated enclosure with a rigid latching door. All switches shall be clearly identified, and all internal wiring shall be factory installed. All wiring shall be installed according to applicable electrical safety codes and the manufacturer's installation schematic.

K. All components in a drip dispersal system shall be rated to withstand contact with wastewater and recommended for this application by the manufacturer. All components shall be protected from freezing.

L. The designer of the drip dispersal system shall verify the dosing rates, the flushing rates, and other parameters critical to the proper operation of the system at the startup inspection. A summary of the startup inspection shall be included in the operation and maintenance manual and shall include, at a minimum, the dosing volume, the forward flow flushing rate, the pressure head of the system, and verification of proper cycling between zones.

Statutory Authority

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

Historical Notes

Derived from Virginia Register Volume 32, Issue 24, eff. August 25, 2016; amended, Virginia Register Volume 39, Issue 4, eff. November 24, 2022.

12VAC5-610-960. Elevated sand mound.

A. An elevated sand mound is a soil absorption system that incorporates low pressure distribution and sand filtration to produce treated sewage prior to absorption in the natural underlying soil. The elevated sand mound utilizes less gross soil area than most other soil absorption systems. Elevated sand mounds differ from pads in that elevated sand mounds are always an aboveground system, may receive septic tank effluent, and always require pressure distribution, and the infiltrative surface follows the natural ground surface and contour of the site.

B. Mound systems receiving septic tank effluent shall be designed and constructed in accordance with the Wisconsin Mound Soil Absorption System Siting, Design and Construction Manual prepared by the Small Scale Waste Management Project, School of Natural Resources, College of Agricultural and Life Sciences, University of Wisconsin-Madison dated January 2000. Drip dispersal or low pressure distribution shall be used.

C. The manual referred to in subsection B of this section shall be used for the designated construction of elevated sand mounds. The following criteria are required for all elevated sand mound systems in addition to the requirements found in the manual.

1. The proposed mound site shall be fenced, roped, or otherwise secured, and marked, to prevent damage by vehicular traffic. Activities on the mound site shall be severely limited in order to protect it to the greatest extent possible.

2. The mound must be constructed during dry weather and soil conditions.

3. Wooded sites shall not be used unless it is shown by the applicant that the wooded site is the only site available, and if the applicant can demonstrate that the site can be properly prepared. If a wooded site is used, trees shall be removed by cutting them off at ground level, leaving the stumps in place. The cut trees shall be removed using methods that do not require driving equipment over the mound site and that do not result in the removal of any soil from the site. Larger basal areas may be required on wooded sites.

4. When the depth to a restriction, shrink-swell soils, or a water table is less than 24 inches, pretreatment sufficient to produce TL-2 effluent or TL-3 effluent may be used to reduce these distances in accordance with 12VAC5-613-80.

5. The minimum absorption area for single family residential dwellings shall be 400 square feet.

D. Elevated sand mounds receiving TL-2 effluent or TL-3 effluent shall adhere to the following additional design criteria.

1. The basal area (interface of fill sand and original soil surface) loading rate shall not exceed the values found in Table 5.5.

2. The minimum sand depth under the dispersal system is six inches.

3. The minimum soil cover, after settling, shall be six inches as measured from the finished ground surface to the uppermost limit of the dispersal media (or gravelless material) utilized in the absorption area. The finished sideslopes cannot exceed 1:4 (rise:run). The soil cover, with amendments as needed, shall be of a quality, character, and fertility suitable to establish a vegetative cover that is uniform and sufficiently mature to survive and inhibit erosion.

4. Vertical separation to limiting features as found in 12VAC5-613-80 shall be maintained under the entire infiltrative surface of the basal area.

5. Designs supported by division approved manufacturer design manuals may deviate from pressure dosing but require dosing to a gravity distribution system at a minimum.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.31, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000; Volume 39, Issue 4, eff. November 24, 2022; Errata, 39:6 VA.R. 985 November 7, 2022.

12VAC5-610-965. Sand-on-sand.

A. Sand-on-sand is a process of modifying a soil absorption system site using fill material which is similar in texture to the original, naturally occurring material. Filling is accomplished in a manner which allows for adequate treatment and disposal of effluent, protection from frost and traffic damage, and does not promote the creation of restrictive horizons. Sand-on-sand systems are considered Type II systems and are used to overcome limitations encountered with certain high water table soils. A detailed description of the siting criteria used for sand-on-sand systems is found in 12VAC5-610-597.

B. Site preparation. All surface vegetation and organic matter, including but not limited to grass, shrubs, trees, leaf litter, branches, limbs, and tree stumps shall be removed. Special consideration shall be given to site preparation to avoid soil compaction and other damage which may create discontinuities and restrictive horizons when the fill material is placed on the site.

C. Fill material. Fill material may be added to such a site and used for residential onsite wastewater disposal for flows up to 1,000 G.P.D. on sites meeting the criteria established in 12VAC5-610-597 provided that:

1. The fill material used is the same texture as the underlying material;

2. The coarse fragment content of the fill material is neither greater than 10% by volume nor noncarbonaceous and inorganic material greater than two mm in size;

3. The fill material is placed in such a manner as to prevent the formation of any restrictive horizons;

4. The fill material covers an area 10 feet greater in all horizontal dimensions than the soil absorption system;

5. The sides of the filled area are sloped at not greater than 1:10 (rise:run);

6. The fill material provides at least six inches of cover over all portions of the system; and

7. The fill material is stabilized to prevent surface erosion.

D. Application rate. All sand-on-sand systems shall be designed on a 30 mpi loading rate and shall use a method of pressure distribution which achieves unsaturated flow conditions.

E. Fill depth. All sand-on-sand systems utilizing gravel trench designs shall have a minimum of 25 inches of fill over the original site.

F. System placement. The drainfield trenches shall be placed so that there is six inches of fill, or more, beneath the trench bottom and six inches of fill over the trenches.

G. The remaining design and construction criteria for sand-on-sand systems are the same as for the design and construction of a similar system in original undisturbed soils.

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.

12VAC5-610-966. Pads.

A. A pad is an absorption area wider than three feet but not longer than 100 feet with a level infiltrative surface where the bottom of the pad meets the original soil. The minimum standoff to a limiting feature in accordance with 12VAC5-613-80 is to be met under the entire infiltrative surface.

B. The minimum effluent quality dispersed to a pad is TL-2 effluent and pad bottom loading rates shall not exceed the values for pads noted in Table 5.5 of 12VAC5-610-950.

C. The longest dimension of the basal area of the pad, its length, shall be oriented parallel to the natural surface topographic contours. Minor deviations from surface contours are acceptable as long as the bottom of the pad is level (the entire bottom surface of the pad is at the same elevation, not to exceed 10% of the depth of the pad from the ground surface or plus or minus two inches, whichever is less), and intersects a similar soil horizon across its surface.

D. Pads and trenches may be used together in a single system when the respective pad or trench subsystems follow the respective design criteria found in this chapter and are separated by a minimum of six feet between the sidewall of the pad and the trench. When multiple pads are used on a site, the pads must be separated by the width of the pad as measured perpendicular to the natural surface topographic contour.

E. Pads shall be limited to sites with slopes of 10% or less (less than or equal to 10 feet of rise for every 100 feet of run).

F. All pads must be dosed. Pad systems over 1,000 gallons per day must be pressure dosed. When pads are installed at less than 12 inches from the ground surface, timed dosing shall be used to disperse the effluent.

G. The minimum absorption area for single family residential dwellings shall be 400 square feet.

H. Pad construction.

1. Gravel pads shall have a minimum installation depth of 12 inches, unless in Texture Group I or II soils where the installation depth can be reduced to eight inches. On sloping sites, the minimum installation depth is measured on the downhill side of the pad infiltrative surface. The construction of the pad's gravity percolation line and gravel bedding shall follow 12VAC5-610-930 E with the exception that the bottom of the pad is level and not sloping. Piping shall have a maximum center to center spacing of nine feet.

2. Gravel pads utilizing low pressure distribution shall follow 12VAC5-610-940 for construction and dosing cycle (volume). Gravel pads using low pressure distribution shall have a minimum installation depth of 12 inches, unless in Texture Group I or II soils where the installation depth can be reduced to eight inches. On sloping sites, the minimum installation depth is measured on the downhill side of the pad infiltrative surface. Piping shall have a maximum center to center spacing of nine feet.

3. Pads utilizing gravelless material as found in 12VAC5-610-930 F shall follow 12VAC5-610-930 F and manufacturer instructions on minimum depth of installation, but in no case shall a pad be installed at less than eight inches from the original soil surface. Gravelless material shall have a maximum center to center spacing of nine feet. On sloping sites, the minimum installation depth is measured on the downhill side of the pad infiltrative surface.

4. Designs supported by a division approved manufacturer's design manual may deviate from the maximum slope, depth of installation, separation distance between pads, and timed dosing when the dispersal area is constructed in accordance with the approved manual.

I. The minimum soil cover, after settling, shall be six inches as measured from the finished ground surface to the uppermost limit of the dispersal media (or gravelless material) utilized in the absorption area. If the cover is mounded above grade, the finished sideslope cannot exceed 1:4 (rise:run). The soil cover, with amendments as needed, shall be of a quality, character, and fertility suitable to establish a vegetative cover that is uniform and sufficiently mature to survive and inhibit erosion.

Statutory Authority

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

Historical Notes

Derived from Virginia Register Volume 39, Issue 4, eff. November 24, 2022.

Article 6
Privies

12VAC5-610-970. General.

Article 6
Privies

A privy is a nonwater carriage device for temporary storage or permanent disposal of human excreta. The privy shall not be used as the receptacle of any water carriage wastes.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.32, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-980. Types.

A. Privies are divided into two categories, those that function as disposal facilities and those that function merely as holding facilities with ultimate disposal of the contents at another facility via pump and haul.

B. Disposal privies.

1. Pit privy.

a. Description. A pit privy consists of a lined earthen pit with a suitable rodent and insect proof structure and pit vent stack. The structure shall be provided with self-closing lid or lids on the seat riser. The pit privy is located exterior to a dwelling.

b. Location. Required separation distances from various structures and topographic features are the same as for subsurface soil absorption systems and may be found in Table 4.2. The bottom of the pit privy shall be at least two feet above the seasonal water table and any rock. Location of pit privies shall also comply with 12VAC5-610-593 1 through 6 and 10.

c. Utilization. The Uniform Statewide Building Code of Virginia normally prohibits the installation of pit privies at new homes. In case of hardship, unsuitable soil conditions or temporary recreational use, a privy can sometimes be constructed after obtaining the approval of the building official with the approval of the department. A sewage disposal system meeting the requirements of 12VAC5-610-250 A and B shall be provided to treat other sewage (wastewater) generated from activities such as laundering, bathing, handwashing, and cooking. Pit privies utilized at existing dwellings should be abandoned within one year of the availability of sanitary sewers. Proper abandonment consists of removing the structure and covering the pit with at least two feet of soil. Pit privies are an acceptable means of sewage disposal at isolated areas such as primitive camping areas, public boat launching areas, recreation areas, state parks and wilderness areas where pressurized water systems are not provided.

2. Incinerator toilets.

a. Description. Incinerator toilets are devices that utilize electrical energy or burning gas to incinerate human excreta deposited directly into them. They function both as toilet and disposal facility and produce an inert ash. Incinerator toilets are located in the interior of a dwelling.

b. Utilization. In addition to the conditions stated in subdivision 1 c of this subsection for pit privies, incinerator toilets shall not be utilized where they are subjected to frequent use and/or peak loading conditions.

c. Certification. All incinerator toilets must be certified by the National Sanitation Foundation as meeting the current Standard 41.

3. Composting toilets.

a. Description. Composting toilets are devices which incorporate an incline plane, baffles or other suitable devices onto which human excreta is deposited for the purpose of allowing aerobic decomposition of the excreta. The decomposing material is allowed to accumulate to form a humus type material. These units serve as both toilet and disposal devices. Composting toilets are located interior to a dwelling.

b. Utilization. In addition to the conditions stated in subdivision 1 c of this subsection for pit privies, all materials removed from a composting privy shall be buried. Compost material shall not be placed in vegetable gardens or on the ground surface.

c. Certification. All composting toilets must be certified by the National Sanitation Foundation as meeting the current Standard 41.

C. Holding privies.

1. General. Due to the nature of these devices, i.e., they require routine pump and haul, special care shall be taken in selecting these devices for use. These devices are satisfactory for use at mass gatherings, transient worker populations, construction sites, recreation areas, etc.

2. Vault privy.

a. Description. A vault privy is similar to a pit privy except that, instead of an earthen pit, a water and corrosion proof containment vessel (vault) is provided. The vault shall be provided with access for periodic removal of the vault contents.

b. Location. Vault privies shall be located to prevent contamination of ground water or surface water. The elevation of the top of the vault or access port shall be placed two feet above the annual flood elevation. Separation distances from structures and topographic features will be determined on a case-by-case basis.

c. Utilization. Vault privies are an acceptable method of holding human excreta where ground water, surface water or other conditions prohibit the installation of other approved sewerage facilities. The conditions contained in subdivision B 1 c of this section shall be met.

3. Portable privies.

a. Description. A portable privy is a type of vault privy that is generally manufactured as a single unit and is easily transported.

b. Location. Location of portable privies should be determined on a case-by-case basis under the supervision of the district or local health department.

c. Utilization. Portable privies are normally used in association with mass gatherings, construction sites, etc., where temporary facilities are required.

d. Numbers required.

(1) When portable privies are used at mass gatherings, one privy per 100 persons shall be provided as a minimum.

(2) When portable privies are used at construction sites or transient worker locations, one privy per 25 persons shall be provided as a minimum.

e. Pumping. The containment vessel of the portable privies shall be pumped as often as necessary to prevent overflow. It is recommended that they be pumped when 2/3 full.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.33, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

Article 7
Storage Facilities Criteria for Pump and Haul of Sewage

12VAC5-610-990. General.

Article 7
Storage Facilities Criteria for Pump and Haul of Sewage

Storage facilities associated with pump and haul operations permitted under 12VAC5-610-420 shall meet the criteria contained herein.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.34, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1000. Location.

The storage facilities shall be accessible by an all weather road of suitable carrying capacity to handle a fully loaded tank truck. Sufficient all weather surface area with appropriate carrying capacity shall be provided for maneuvering the tank truck.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.35, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1010. Design.

A. Capacity. Temporary storage facilities shall have sufficient capacity to store the projected flow for 48 hours.

B. Materials. The materials utilized shall be resistant to the corrosive action of sewage and shall be capable of withstanding the internal and external loads placed upon it.

C. Watertightness. The storage facility shall be watertight.

D. Access. The storage facility shall be easily accessible for the removal of the sewage. An access manhole with minimum dimensions of 18 inches by 18 inches terminating at or above the ground surface shall be provided. The storage facility shall be a closed containment vessel and all access ports shall be provided with removable covers.

E. Venting. Adequate venting shall be provided in all storage facilities.

F. Level Alarm. All facilities shall be provided with an audiovisual alarm to be activated when the storage facility is 3/4 full. Audiovisual alarms shall alarm at two locations, one that is manned 24 hours per day and the other at the site of the storage facility where the storage facility receives sewage on a 24-hour basis. When sewage flow is intermittent only one alarm at the storage facility is required.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.36, eff. February 5, 1986; amended, eff. May 11, 1988.

Article 8
Vehicle Specifications for Sewage Handling

12VAC5-610-1020. General.

Article 8
Vehicle Specifications for Sewage Handling

All vehicles utilized to transport sewage shall be kept in a clean and sanitary condition.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.37, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1030. Vehicle identification.

The name and address of the owner shall be displayed on each side of the vehicle in letters at least four inches high. In addition, the sewage handling permit number shall be displayed immediately beneath the owners name and address and in plain sight.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.38, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1040. Sewage containment vessel (tank).

The tank in which the sewage is to be transported shall be fully enclosed and watertight. All inlets and outlets to the tank shall be secured and made watertight during transit. The tank shall be secured to the truck.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.39, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1050. Pumps.

When a pump is utilized to transfer sewage, the pump shall be watertight and properly valved and/or capped to prevent spillage during transport.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.40, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1060. Valves.

All valves shall be watertight.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.41, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1070. Hoses.

Suction and discharge hoses shall be watertight and provisions shall be made for carrying the hose in a manner to prevent leakage.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.42, eff. February 5, 1986; amended, eff. May 11, 1988.

Article 9
Special Facilities

12VAC5-610-1080. Anaerobic lagooning of septage.

Article 9
Special Facilities

A. General. An anaerobic lagoon for the purpose of this chapter is a nondischarging facility consisting of an open impervious structure, constructed of earth or other material specifically designed for receiving and stabilizing septage and other sewage sludges. Industrial waste sludges and sludges containing toxic material shall not be placed in these lagoons.

B. General site requirements.

1. Engineering, geologic, soil and hydrologic evaluation. Geologic information required by the district or local health department and the division shall include, but not be limited to, soil characteristics, percolation information, maximum ground water table, direction of ground water movement and permeability.

2. Location.

a. Minimum setback distances for topographic features are the same as those for subsurface soil absorption systems and are contained in Table 4.2.

b. Buffer zone. Buffer zone criteria are contained in Appendix I.

c. Flood protection. The anaerobic lagoon and operational components shall be located at an elevation which is not subject to the 100-year flood/wave action or shall otherwise be adequately protected against the 100-year flood/wave action damage. The anaerobic lagoon shall remain fully operational during the 25-year flood/wave action.

d. Surface runoff. Adequate provisions shall be made to divert storm water around the anaerobic lagoon and otherwise protect the lagoon's embankments.

3. Access. An all weather access road shall be provided.

4. Fencing. The facility site to include treatment units and appurtenances shall be fenced with a five foot fence (woven wire plus barbed wire); gates and locks to provide controlled entry into the facility. The fence shall be posted with signs identifying the facility, safety and health dangers and trespass penalties. The fence shall not be constructed closer than 10 feet to the outside edge of any treatment unit or appurtenance.

C. Design requirements (see Figure V-1 for typical sections).

1. Receiving facilities.

a. An impervious pad or sufficient strength to support a loaded tank truck and with drainage to the lagoon shall be provided at the point or points where the contents of the tank truck is offloaded into the lagoon or receiving facilities.

b. The receiving and inlet facilities shall be designed to transport the septage into the lagoon, to distribute the septage as evenly as possible throughout the lagoon and to minimize generation of odors and suspension of solids.

2. Treatment units.

a. Anaerobic lagoons.

(1) Number and capacity. A minimum of two lagoons shall be provided. The combined total capacity of the lagoons shall provide eight months storage based on the average daily discharge into the lagoon.

(2) Operating depth. The normal operating depth shall be from three to five feet.

(3) Lagoon bottom. The lagoon bottom shall be level, constructed of impervious material (10^%686 sm/sec) and be a minimum of two feet above the seasonal water table or at the original ground surface.

(4) Lagoon embankments. Embankments and/or dike walls shall be impervious and structurally stable. They shall be designed to permit access of equipment by appropriate lining or internal barriers necessary for sludge removal in a nuisance free and safe manner, and to minimize risk, supervision, operation and maintenance. Earthen embankments shall be sloped (minimum 1:3) and seeded with proper cover, subject to soil characteristics, to minimize erosion.

(5) Freeboard. A minimum freeboard of two feet above the normal depth shall be provided.

(6) Shape. A uniform shape shall be provided, i.e., round, square, or rectangular with no narrow or elongated portions. The lagoon shall not contain islands, peninsulas or coves unless they are part of the inlet/outlet design.

b. Sludge dewatering. When sludge dewatering units are provided they shall be designed in accordance with 12VAC5-580-700, Sludge Dewatering, Virginia Sewerage Regulations.

3. Supernatant disposal. Normally the lagoon supernatant should be included in the sludge mixed liquor which is disposed of on the land. When a system is designed to provide for separate supplemental supernatant disposal it shall be by subsurface soil absorption system. The minimum subsurface soil absorption system field size shall be based on the anticipated average daily supernatant generation rate and shall meet all applicable criteria contained in Article 1 (12VAC5-610-450 et seq.) of Part III and Article 5 (12VAC5-610-900) of this part. The lagoon outlet shall be designed to minimize the solids content of the supernatant withdrawn for disposal in the subsurface soil absorption system and shall be provided with a means to control the rate and quantity of supernatant withdrawal.

V0110040.JPG, SIZE-38 PICAS, TYPE-DPI

For Anaerobic lagooning of septage, see Virginia Administrative Code print product.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.43, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-1090. Lime stabilization of septage.

A. General. Lime stabilization of septage is a process consisting of the addition of hydrated lime in sufficient quantity usually 50 pounds per 1000 gallons, to raise the pH and hold it at 12 or higher for at least 30 minutes before dewatering or land spreading. The process normally requires mixing during the lime addition process as well as a mixing tank to facilitate the holding and mixing requirement.

B. Mixing equipment.

1. Mixing may be accomplished by recirculation through the pump truck. Mixing through the pump truck is limited to operations where no more than one load at a time is processed. In this case a mixing tank is not required.

2. When a mixing tank is required a minimum capacity of 2000 gallons shall be provided. Mixing tank volume in excess of 2000 gallons may be required on a case-by-case basis. When separate mixing capability is necessary it may be accomplished by either mechanical mixing or air diffusion.

a. Mechanical mixers shall be capable of maintaining the bulk fluid velocity above 26 ft/minute and an impeller Reynolds number greater than 1000.

b. Diffused air requirements range from 150 to 250 CFM/1000 Ft of tank volume for course bubble diffusers. The diffusers shall be mounted such that a spiral roll is established in the mixing tank away from the point of lime addition.

C. pH. Suitable methods of measuring pH values in excess of 12 shall be provided and maintained to measure the pH of the septage-lime mixture.

D. Dewatering. Dewatering is required prior to landfilling lime stabilized septage and may be desirable before land spreading. Criteria for dewatering facilities may be found in 12VAC5-580-700 of the Sewerage Regulations. In addition all filtrate from the dewatering facilities must be:

1. Disposed of in a subsurface soil absorption system; or

2. Collected in an impervious container or earthen basin for ultimate disposal in an approved sewerage system or treatment works or by land spreading.

E. Storage facilities. Regardless of the equipment used to land spread the lime stabilized septage, there will be extended time periods, particularly during winter, when the septage cannot be land applied. Therefore, storage facilities shall be provided. The design and construction of the storage facilities shall adhere to the following criteria:

1. General site requirements. If the storage facilities are to be constructed of manufactured materials, i.e., steel or concrete, the site requirements shall conform to 12VAC5-610-1080 B 2. Where an earthen storage facility is to be provided site requirements shall conform with 12VAC5-610-1080 B 1 and 2.

2. Design requirements.

a. Transfer facilities. When the storage facilities are located adjacent to the mixing facilities described in subsection B of this section the piping shall be arranged in such a manner to eliminate spillage, reduce splashing and facilitate distribution of the septage through the storage unit.

b. Receiving facilities. When the storage facilities are remote from the mixing facilities and require vehicular transport of the lime stabilized septage the receiving facilities shall conform to 12VAC5-610-1080 C 1.

c. Capacity. The storage volume shall be based upon a mass balance which considers as a minimum monthly pumping rates (number of loads pumped per month), number, location and nature of land spreading sites including soil type, crop cover and topography and seasonal application to cropped or pastured land. In no case shall the storage capacity be less than 60 days.

d. Storage facilities. When the storage facility is of a manufactured material (steel, concrete, etc.) it shall be watertight and fitted with appropriate piping and appurtenances to facilitate removal of the stored material. When the storage facility is of earthen construction it shall adhere to the design requirements contained in 12VAC5-610-1080 C 2 a (2), (3), (4), (5), and (6) above. See Appendix P.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.44, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1100. Storage facilities for unstabilized septage.

Unstabilized septage storage facilities shall conform to 12VAC5-610-1090 E above as applicable.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.45, eff. February 5, 1986; amended, eff. May 11, 1988.

Article 10
Sewage Dump Stations

12VAC5-610-1110. General.

Article 10
Sewage Dump Stations

A dump station is a facility for receiving sewage from a recreational vehicle. The dump station shall be connected to an approved sewerage system or treatment works.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.46, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1120. Location.

The relationship of a dump station to structures and topographic features shall be in accordance with Table 4.4 and 12VAC5-610-470 A, C, F, and G. Dump stations shall be at least 50 feet from any habitation or camp site.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.47, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1130. Design.

A dump station shall consist of the following features:

A. A four inch sewer pipe trapped below the frost line and connected to an approved sewerage system.

B. The sewer inlet shall be surrounded by a concrete pad sloped to drain to the sewer inlet. The pad shall have minimum dimensions of 60 inches by 36 inches by six inches thick. The sewer inlet shall be at least six inches below the lip of the pad and located not more than 1/4 the length from one end of the pad. The end of the pad where the sewer inlet is located shall be curbed with a four inch curb.

C. The sewer inlet shall be fitted with a fly tight cover.

D. A water supply properly protected against cross connection and backflow shall be provided to facilitate washdown of the pad area. The water outlet shall be posted with a sign stating "Notice: Unsafe Water Outlet. This water for washdown purposes only".

E. The sewer line shall meet the material and construction specifications contained in Part IV, Article 2 of this chapter.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.48, eff. February 5, 1986; amended, eff. May 11, 1988.

Article 11
Nonpublic Drinking Water Supply Systems Utilized in Conjunction with Onsite Sewage Disposal Systems

12VAC5-610-1140. General.

Article 11
Nonpublic Drinking Water Supply Systems Utilized in Conjunction with Onsite Sewage Disposal Systems

A. Authority for this article is found in § 32.1-164 B 6 of the Code of Virginia. This article pertains only to new construction where a nonpublic water supply, other than a private well, is to be constructed and utilized in conjunction with an onsite sewage disposal system. Approval of the water supply is an integral part of the issuance of an operation permit for a sewage disposal system (see 12VAC5-610-340) and no separate permit is required. An approval of a water supply under this section connotes a water supply meeting the quantity, quality and construction standards of a satisfactory water supply at the time of approval.

B. Quantity.

1. The system shall be capable of supplying water in adequate quantity for its intended usage. Failure to provide adequate capacity may cause intermittent flows and negative pressures which may cause contamination of the system through cross connections or other system deficiencies.

2. The source shall have a capacity to produce 150 gallons per bedroom per day for residential use.

3. The minimum system capacity (source plus storage) should be capable of delivering a sustained flow of five gallons per minute per connection for 10 minutes for ordinary residential use.

C. Quality.

1. Water sources described in this section shall be considered satisfactory if the water sample or samples test negative for coliform organisms. Sources with positive coliform counts, but with less than 100 MPN/100ml shall be provided with a means for continuous disinfection (chlorination).

2. A sample tap shall be provided at or near the water entry point into the system so that samples may be taken directly from the source; this requirement may be met by utilizing the first tap on the line near where the plumbing enters the house (may be a hose bib), provided the tap precedes any water treatment devices.

3. The entire water system including the well shall be disinfected prior to use. After operating the well to remove any remaining disinfectant, a sample of the water from the well shall be collected by the district or local health department for bacteriological examination. The sample may be collected by the owner, or an agent designated by the owner, provided the sample is submitted to a private, certified (by Division of Consolidated Laboratory Services) laboratory for analysis.

4. If tests indicate that the water is unsatisfactory and no other approval source is available, adequate approved methods of water treatment shall be applied. The district or local health department shall be consulted when treatment is necessary.

D. Approval. All water supplies covered by this chapter shall be approved by the district or local health department before being placed into service as a satisfactory water supply.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.49, eff. February 5, 1986; amended, eff. May 11, 1988; Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-1150. (Repealed.)

Historical Notes

Derived from VR355-34-02 § 4.50, eff. February 5, 1986; amended, eff. May 11, 1988; repealed, Virginia Register Volume 16, Issue 16, eff. July 1, 2000.

12VAC5-610-1160. Springs.

A. Sanitary survey. Only springs which are found acceptable following a sanitary survey (12VAC5-610-1150 B) will be considered for use as a source of potable water. The following shall be considered when making the sanitary survey:

1. The spring's source should be an aquifer which is not subject to pollution;

2. The spring should not be subject to flooding;

3. Consideration should be given to fencing an adequate area completely around the spring to prevent contamination by people and/or animals;

4. Consideration should be given to diverting surface water away from the spring; and

5. The distance from other sources of pollution shall be the same as for subsurface soil absorption systems contained in Table 4.4 and 12VAC5-610-810 A.

B. Construction of springs and/or reservoirs.

1. The spring shall be completely enclosed. The walls and cover shall be constructed of durable watertight material.

2. All springs and/or reservoirs shall be accessible for cleaning and maintenance. When access is through the top, the opening shall have a minimum dimension of 24 inches. The opening shall be fitted with a solid, watertight cover which overlaps the framed opening and extends vertically down around the frame at least two inches (shoe box).

3. The top of the cover frame shall be at least two 12 inches above the surrounding ground surface.

4. Overflows shall be screened to prevent entrance of undesirable materials (See 12VAC5-610-1170 C 9).

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.51, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1170. Cisterns.

A. General. Cisterns shall be considered only when no other source of potable water is feasible.

B. Location and protection. The following precautions should be taken with regard to the location and protection of cisterns:

1. The distance from other sources of pollution shall be the same as for subsurface soil absorption systems contained in Table 4.4 and 12VAC5-610-810 A; and

2. Cisterns shall be located in a manner that will not subject them to flooding.

C. Construction.

1. The cistern shall be constructed of watertight, durable, structurally sound material, with a smooth interior surface.

2. When the cistern is filled by rainfall provisions shall be made to bypass, divert or otherwise remove the water that falls at the beginning of a rain.

3. Cisterns shall be accessible for cleaning.

4. Where a manhole cover is used, it shall be watertight and the manhole shall be at least 24 inches in diameter.

5. Where another type of cover is used, it shall be a solid, watertight cover which overlaps the framed opening and extends vertically down around the frame at least two inches.

6. The top of the cover frame shall be at least 12 inches above the surrounding ground surface.

7. All openings into the cistern shall be screened in order to prevent the entrance of insects, rodents and other animals and pollutants.

8. When screens and filters are utilized for filtering roof runoff, they shall be accessible for regular cleaning.

9. Drain and overflow pipes shall not be connected directly to any sewer, soil pipe, house drain or other waste pipe. An air-gap shall be provided on all drains and overflow pipes. Drains and overflow pipes shall be suitably screened.

10. Asphaltic roofing material or painted roofs should not be utilized in conjunction with cisterns because of the potential leaching of toxic materials.

D. Potability. Cisterns cannot be relied upon to provide potable water without adequate treatment. Adequate treatment consists of removal of solids washed from the roof and continuous disinfection.

Statutory Authority

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

Historical Notes

Derived from VR355-34-02 § 4.52, eff. February 5, 1986; amended, eff. May 11, 1988.

12VAC5-610-1170:1. APPENDIX F. Field Guide To Soil Texture Classes.

APPENDIX F.

Field Guide To Soil Texture Classes

Field Guide To Soil Texture Classes (USDA)

Introduction-The purpose of this test is to provide a standard procedure for estimating soil texture in the field. The texture is estimated by the "feel" of moist soil. The texture of a soil cannot be estimated by "feel" if it is either dry or wet.

Definitions

Particle Size Classes

Sand-Sand has a particle size ranging from 0.05 millimeters (mm) to 2.0 millimeters (mm) in diameter. Sand imparts a gritty feel to soil due to the shape of the individual particles.

Silt-Silt has a particle size ranging from 0.002 millimeters (mm) to 0.05 millimeters (mm) in diameter. When moist, silt has a floury feel and does not ribbon when pressed between the thumb and forefinger due to the shape of the individual particles. When placed between the teeth silt has a gritty feeling.

Clay-Clay has a particle size less than 0.002 millimeters (mm) in diameter. Clay exhibits collodial properties, has a negative charge and is flat and platelike in shape. Moist clay is sticky and will ribbon readily when pressed between the thumb and forefinger. When placed between the teeth clay has a smooth slick feeling.

Soil Texture-Soil texture refers to the relative proportions of sand, silt and clay particles in a soil material that has a particle size less than two (2) millimeters (mm) in diameter. Soil texture is an indicator of infiltration capacity, permeability, degree of aeration and drainage as well as other physical characteristics of a soil material.

Soil Texture Classes-The United States Department of Agriculture (USDA) has identified twelve (12) soil texture classes as follows: sand, loamy sand, sandy loam, sandy clay loam, loam, silt loam, silt, silty clay loam, clay, clay loam, sandy clay and silty clay. Each texture class has a distinctive characteristic(s) which can be estimated in the field by trained personnel.

Distinguishing Characteristics-The following characteristics are based on moist soil.

Sand-Sand has a gritty feel, does not stain the fingers and does not form a ball when moist.

Loamy Sand-Loamy sand has a gritty feel, stains the fingers (silt and clay) and forms a weak ball but cannot be handled without breaking.

Sandy Loam-Sandy loam has a gritty feel, forms a ball that can be picked up with the fingers and handled with care without breaking.

Loam-Loam may have a slight gritty feel but does not show a finger print and forms only short ribbons of from 0.25 inch to 0.50 inch in length. Loam will form a ball that can be handled without breaking.

Silt Loam-Silt loam has a floury feel when moist and sticky when wet but will not ribbon and forms a ball that will tolerate some handling. Silt texture has not been found in any Virginia soils.

Sandy Clay Loam-Sandy clay loam has a gritty feel but contains enough clay to form a firm ball and may ribbon to form 0.75 inch to 1 inch long pieces.

Silty Clay Loam-Silty clay loam is sticky when moist and will ribbon from one (1) to two (2) inches. Rubbing silty clay loam with the thumb nail produces a moderate sheen. Silty clay loam produces a distinct finger print.

Clay Loam-Clay loam is sticky when moist. Clay loam forms a thin ribbon of one (1) to two (2) inches in length and produces a slight sheet when rubbed with the thumb nail. Clay loam produces a nondistinct finger print.

Sandy Clay-Sandy clay is plastic, gritty and stocky when moist and both forms a firm ball and produces a thin ribbon to over two (2) inches in length.

Silty Clay-Silty clay is both plastic and sticky when moist and lacks any gritty feeling. Silty clay forms a firm ball and readily ribbons to over two (2) inches in length.

Clay-Clay is both sticky and plastic when moist, produces a thin ribbon over two (2) inches in length, produces a high sheen when rubbed with the thumb nail and forms a strong ball resistant to breaking.

12VAC5-610-1170:2. APPENDIX G. Percolation Test Procedure and Percolation Test Data Forms.

APPENDIX G.

1. Percolation Test Procedure

2. Percolation Test Data Forms

Percolation Test Procedure

Definition-The percolation test is a field procedure conducted in the soil horizon(s) selected for installation of the proposed subsurface soil absorption system for the purpose of observing the rate that clean water will permeate the soil under saturated conditions. The test provides a method for approximating the actual movement of wastewater through the soil which will occur during operation of the subsurface soil absorption system.

Test Holes

1. Test holes shall be located at points and depths selected by and/or approved by the district or local health department.

2. The depth of the test hole shall be placed in the "slowest" portion of the horizon(s) selected for installation of the absorption trenches. (See § 4.03A).

3. The portion of the test hole penetrating the horizon(s) selected for placement of the absorption trenches shall be 7 (±) 2 inches in diameter. Minimum acceptable horizon thickness is twelve (12) inches. The diameter of the test hole above the selected horizon(s) may be as large as necessary to conduct the test and prepare the hole in the selected soil horizon(s).

4. Test holes shall, where possible, be constructed within four (4) to six (6) feet of an existing profile hole.

5. A portion of the material excavated from the test hole should be mounded around the test hole to prevent surface water runoff from entering the hole in the event of rainfall during the period preceding and continuing through the conduct of the test.

6. Where indicated the bottom and sidewalls of the hole shall be scarified with a sharp pointed instrument or knife to remove any smeared soil surfaces. Two inches of clean course sand or clean fine gravel (pea gravel) shall be added to the hole to protect the bottom infiltrative surface from scouring and sedimentation.

Presoaking

1. Swelling Procedure-When shrink-swell soils are suspected the soil surrounding the test hole shall be saturated for at least 24 hours by keeping at least 12 inches of water in the hole for the 24 hour period. An additional three days for swelling may be required during dry periods when cracking has occurred. After completion of the swelling procedure stated above the hole shall be left overnight before proceeding with the measurement procedure.

2. Saturation Procedure-All test holes not subject to the swelling procedure shall be kept saturated with at least 12 inches of water for a 4 hour period on the day preceding the measurement of the percolation rate. Residual water in the hole shall be left to provide overnight soaking.

Measurement of Percolation Rate-All measurements shall be made from a fixed reference point.

1. Test holes with 6 inches or less of water remaining after the overnight soaking period.

a. Carefully fill the hole with water to a depth of 6 inches over the sand/gravel.

b. Record water surface drop every 30 minutes for a 4 hour period.

c. After recording the water surface drop each 30 minutes estimate if, based on the last reading, the hole will go dry add sufficient water to maintain not more than one (1) inch water depth over the sand/gravel at the end of the test period.

d. The drop measured during the last 30 minute period shall be used to compute the percolation rate for the hole tested.

e. In soils where the first 6 inches of water seep away in less than 30 minutes after the overnight saturation period, add an additional 6 inches of water and the time interval between measurements shall be taken as 10 minutes and the test run to completion, i.e. hole goes dry. The drop that occurs during the final 10 minutes is used to calculate the percolation rate.

2. Test hole with more than 6 inches of water remaining after the overnight soaking period. The water depth over the gravel shall be recorded. More than 6 inches of water remaining in the hole after soaking procedure is prima-facie evidence of unsatisfactory for installation of a subsurface soil absorption system.

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12VAC5-610-1170:3. APPENDIX H. Land Disposal Criteria.

APPENDIX H.

Land Disposal Criteria

The following sections are reproduced from the Commonwealth of Virginia Sewerage Regulations, State Department of Health and State Water Control Board February 1977.

25.07 Sludge and Solids Disposal

25.07.01 General

A plan shall be provided for the disposal of sludge and solids from each treatment facility as part of the final engineering documents (cf. Section 2.04.02). Before sludge is disposed of by land application, its short term and long term chemical effects on the land and groundwater must be evaluated. The evaluation program should consider the existing industrial waste surveys and general characteristics of the land to be used as well as other appropriate information. Adequate provisions for residue disposal, air pollution control, soil contamination prevention and groundwater/surface water contamination prevention shall be provided. Sludge shall not be applied to root crops or crops intended for human consumption in the raw form. Disposal of sludge shall be in such a manner as not to cause health hazards, destroy vegetation, create odor and/or vector problems, render the soil unsuitable for future land use or create other nuisances. Land areas proposed for sludge disposal should be remote from inhabited dwellings, water supplies and shellfish areas. Disposal of sludge to open dumps is prohibited. Designs incorporating the use of sludge as a soil conditioner should be forwarded to the Department of Agriculture and Commerce by the Department for appropriate review and comment.

25.07.02 Land Acquisition or Control

When land application constitutes a primary means of sludge disposal for a facility and the facility does not possess sufficient alternate disposal means, the continued availability of the land shall be protected. Such land shall also be protected from improper concurrent uses during utilization periods. The means of such protection for land availability and from improper concurrent uses shall be determined by the Department, the Board and the owner at the preliminary engineering conference.

25.07.03 Sludge Stabilization and Pathogen Reduction Prior to Land Application

Sludge shall be subjected to a treatment process which will stabilize many of the organic materials present in raw sludge. Anaerobic digestion, composing, aerobic digestion, heat treatment, processes or chemical treatment processes such as high lime or chlorine dosages are considered to produce stabilized sludges. For some projects, it may be necessary to achieve additional pathogen reduction beyond that attained by stabilization.

25.07.04 Sludge Composition and Soil Evaluation

The following parameters for sludge and soil composition may be employed to determine the sludge classification and suitability of soils for sludge application. Determination of specific parameters to be run shall be made at the preliminary engineering conference and the results of the analyses shall be included as a portion of the sludge disposal plan required in accordance with Section 25.07.01.

Appendix J contains forms which are recommended for use by the owner of the treatment facility in providing the results of background sludge and soil analyses. A one-quart soil sample shall be taken from the top four inches of soil and retained indefinitely.

After the sludge disposal plans required in accordance with Section 25.07.01 is approved by the Department and the Board, the Department and the Board waive the requirement for the sludge composition analyses and soil evaluation at any new application site for which either of the two following criteria apply:

a. the sludge is applied as a single application not to be repeated for at least five years.

b. the sludge application area is no larger than 10 acres.

This waiver in no way limits the powers of the Board and the Department in the control of any sludge application practice, regardless of frequency of application or size of the application area, for which groundwater contamination, surface runoff, soil toxicity, health hazards or nuisance conditions are considered to be a problem or a potential problem. Additionally, all other requirements contained in Section 25.07 including protection from improper concurrent uses, stabilization, sludge classification, application and disposal methods, soils, application rates, runoff control, sludge transport, etc. shall apply to all sludge application sites, regardless of size. As a further condition of this waiver provisions, the plant owner shall provide advance notification for concurrence to the appropriate Regional Offices of the Department and the Board of any new site(s) for which sludge application is intended. The notification for concurrence may be made by phone call to be confirmed in writing or by letter mailed in time to ensure receipt by the Department and Board prior to utilization of the new site(s). As a minimum, the notification for concurrence shall provide the location and size of the area, owner's name, proposed application rate, percentage of solids and any special or unusual conditions which may exist.

25.07.05 Sludge classification

Prior to land application, sludge shall be evaluated in accordance with Section 25.07.03 and 25.07.04. The sludge shall be classified by its characteristics. For new projects, sludge characteristics may be approximated by data obtained from like treatment facilities receiving flow from similar waste contributors. Pilot studies for sludge characteristics may be required when deemed appropriate by the Department and the Board.

a. Class A-Class A sludge shall be suitable for land application at the approved site in accordance with the approved application conditions indefinitely under proper management. Sludge which is classified as Class A shall be stabilized and shall not contain heavy metals or other undesirable components in quantities that (1) may be harmful to the production of crops, trees or other vegetation; (2) may result in crops or vegetation containing components which may be harmful to the health of animals or humans when consumed; (3) may render the soil unsuitable for future land use and (4) degrade existing groundwater quality. Appendix K presents standards for Class A sludge based on maximum allowable levels of certain heavy metals.

b. Class B-Class B sludge is sludge which is raw, partially stabilized, chemically or bacteriologically contaminated or contains undesirable components which makes it unfit for land application. This shall include unstabilized pumpage from septic tanks. Disposal of Class B sludge may be implemented by (1) conveyance to sewage treatment plant having approved sludge handling facilities, provided that detrimental effects to the plant shall not occur; (2) stabilization of sludge such that it shall meet the requirements of Section 25.07.05a, above; and (3) other methods which will be evaluated on a case by case basis. Raw or partially stabilized sludge shall be mixed with solid waste for disposal in solid waste landfills.

25.07.06 Application and Disposal Methods

Spray application of Class A sludge to the land is acceptable when no transport of aerosols beyond the boundaries of the application area is predicted.

a. Liquid Sludge

Liquid sludge shall generally have a solids content of less than 12 percent. Liquid Class A sludges shall be applied to land by plowing, discing, or direct injection so that the sludges are immediately covered or by spraying or spreading on pasture that has been clipped short, permanent crop land or land that is producing trees or nursery stock. Only application sites especially selected for sludge application and approved by the Department and the Board may be used. Liquid sludges shall not be mixed with solid wastes for disposal in solid waste landfills.

b. Final Dewatered Sludge

Final dewatered sludge is sludge that is dewatered for the purpose of ultimate disposal and is defined as having a solids content usually ranging between 12 percent and 30 percent. Dewatered sludges including those dewatered through the use of centrifuges, vacuum filters and filter presses may be disposed with solid wastes if the ratio of sludge is high enough so as to prevent problems with compaction and extruding of sludges to the surface of the ground. These dewatered sludges may also be disposed in separate trenches at approved solid waste landfill sites or other approved sites. Dewatered Class A sludges may also be applied to the land by plowing or discing into the soil immediately after application or by spraying or spreading on pasture that has been clipped short, permanent crop land or land that is producing trees or nursery stock. Only application sites especially selected for sludge application and approved by the Department and the Board may be used.

c. Dried Sludge

Dried sludge is sludge that has a solids content greater than 30 percent. Dried Class A sludges from treatment processes may be disposed in solid waste landfills or atop the landfills to promote growth of vegetation, landfills selected for sludge disposal or plowing or discing into the ground or by spraying or spreading on pasture that has been clipped short, permanent crop land or land that is producing trees or nursery stock. Only application sites especially selected from sludge application and approved by the Department and the Board may be used.

d. Other Solids

Grit, rages and other debris or screenings from sewage treatment plants shall be stored in covered containers. These solids are classified as Class B, and subsequent disposal shall be by burial at solid waste landfill sites or other sites approved by the Department and the Board.

25.07.07 Soil

Soils shall be well drained. A minimum soil depth of two feet is preferred.

25.07.08 Application Rates

For land application systems, the engineer shall consider sludge composition, soil characteristics, climate, vegetation, cropping practices and other critical factors in determining application rates. Since sludge and site factors vary widely, application rates shall be determined for each specific site. Application rates shall be approved by the Department and the Board.

Nitrogenous substances are usually the limiting factor in determining annual application rates. Unless it can be satisfactorily demonstrated that the nitrogen uptake of crops to be harvested justifies a higher loading rate, the initial design application rate shall not exceed five tons of dry weight solids/acre/year. Guidelines for allowable application rates for specific crops are presented in Appendix K. Additionally, Appendix K presents guidelines on maximum loadings of cadmium, maximum cumulative levels for metals and acceptable soil pH levels. For any site receiving only a single application of sludge not to be repeated for at least five years, the maximum allowable loading rate for the on-time application shall be 15 tons of dry weight solids/acre. The above notwithstanding, at no time shall sludge be applied to a depth greater than 0.5 inches in any single application procedure.

No crops should be removed by harvesting or grazing less than 30 days after the last application of sludge. Pasture should be clipped immediately prior to sludge application.

25.07.09 Groundwater Quality

Land application sites, landfills, sludge lagoons and sludge holding facilities shall be designed and operated so that the utilization of sludge does not result in groundwater quality changes. If the presently existing concentration of any parameter is high in the groundwater than the level allowed for a raw water supply source (reference: Commonwealth of Virginia Waterworks Regulations), then the sludge utilization or disposal technique shall not result in an increase in the concentration of that parameter.

25.07.10 Holding Facilities

a. Emergency Holding

Raw sludges, septic tank sludges, sludges from upset digesters and sludges of similar nature may be stored in emergency holding facilities. Subsequent processing of the supernatant and sludge shall be provided in an approved manner. Such holding facilities should be located remote from human activity. The engineer shall provide a plan for approval by the Department and the Board. The plan shall address sampling, odor control, vector control, potential soil and water pollution, and security.

b. Routine Holding

During periods when application of sludges to agricultural land is not possible due to climatic or other conditions, a holding facility shall be provided. The engineer shall provide a mass balance which determines the amount of sludge storage which is to be provided. The location and protection of the holding facility shall conform to the requirements stated in Section 25.07.01a, above. Holding shall be utilized to enhance runoff prevention.

25.07.11 Incineration

Incineration of sludges and screenings from treatment facilities is an approved method of solids reduction. Such facilities shall meet all requirements for air pollution control. The ash from such processes may be buried or spread on land selected for such purposes and approved by the Department and the Board.

25.07.12 Sludge Lagoons

a. Long Term Storage Lagoons

Long term storage lagooning of stabilized sludges is allowable if provisions are made for ultimate disposal of the sludge in accordance with the requirements of the section. Decant liquid from the lagoon shall be conveyed to a plant by an approved method for treatment in a manner that will not upset the plant's operational efficiency. Adequate provisions shall be made to prevent seepage from the lagoon. Fencing and warning signs shall be required.

b. Ultimate Disposal Lagoons

Lagooning of stabilized sludges as a means of ultimate disposal is allowable if stored in accordance with Section 25.07.12a above and covered with soil upon completion of use to a depth of two feet.

25.07.13 Transport of Sludge

The engineer shall furnish the final engineering documents (Section 2.03) the equipment and materials needed for sludge handling, including nonspill, water-tight vehicles for transport, routes, quantities of sludge and procedures to be used. Transport vehicles should be equipped with tow hooks, and transport routes through heavily populated areas should be avoided.

25.07.14 Land Reclamation

Land reclamation is an accepted practice usually utilizing high application rates of liquid sludge. Class A sludges are acceptable for land reclamation. The sludge utilization program shall be developed between the owner, the Department, the Board, the Division of Mined Land Reclamation (when appropriate) and other agencies as appropriate.

25.07.15 Other Methods

Other methods of sludge and solids disposal, such as preparation and use as a soil conditioner, will be considered on a case by case basis.

25.07.16 Runoff Prevention

An area which has sludge applied by spraying or spreading shall be located a minimum distance of 50 feet from all surface water. Containment and controlled release of runoff from sludge application areas or effective erosion control methods should be practiced as necessary.

12VAC5-610-1170:4. APPENDIX I. Buffer Zones.

APPENDIX I.

Buffer Zones

A. All anaerobic lagoons shall provide the minimum buffer zone as shown below unless they qualify for reduced requirements as provided in (B) below. Buffer zones are areas of controlled or limited use. Within buffer zones residential uses or high density, human activities or activities involving food preparation are prohibited. The extent of the buffer zone perimeter is measured from the perimeter of the lagoon.

B. The Department shall consider reduction of up to one half of the above listed buffer zone requirements based on topography, prevailing wind directions, provision of covered units or the inclusion of an effective wind break in the overall anaerobic lagoon design.

1. The prevailing wind direction should be determined by on-site data. Local weather station records may be utilized if they are demonstrated to be applicable. Attention should be paid to both moderate and high speed winds since the high velocity winds often have a prevailing direction different from the prevailing direction of moderate winds.

2. A windbreak should be located on both sides of the anaerobic lagoon normal to a line projected through the plant and area which is to be protected as close to the plant as practical. An effective windbreak is comprised of manmade or natural barriers which extend from the ground surface to minimum height of 16 feet. A cultivated tree windbreak may be developed by planting at least four rows of fast growing evergreens (pine family preferred) planted on staggered 10 feet centers. Rows should be spaced no greater than 16 feet apart. The variety of tree used should be readily adaptable to the soil and climate at the plant site.

C. The required buffer zone shall be maintained by an adequate legal instrument throughout the life of the anaerobic lagoon.

12VAC5-610-1170:5. APPENDIX J. Sludge Dewatering.

APPENDIX J.

Sludge Dewatering

The following section is reproduced from the Commonwealth of Virginia Sewerage Regulations State Department of Health, State Water Control Board, February 1977

25.05 Sludge Dewatering

25.05.01 General

Drainage from beds and concentrate or filtrate from dewatering units shall be returned to the sewage treatment process at appropriate points preceding disinfection. These organic loads shall be considered in plant design, and alternatives for handling these loads may be considered similar to those for supernatant (See Section 25.01.06d).

25.05.02 Sludge Drying Beds

a. Area

The sludge drying bed area required for dewatering aerobic and anaerobic digested sludge shall not be less than the following:

For other types of sludge treatment, the drying bed area will be evaluated on a case by case basis.

b. Percolation Type

1. Gravel

The lower course of gravel around the underdrains shall be proper graded and should be 12 inches in depth, extending at the underdrains. It is desirable to place this in two or more layers. The top layers of at least three inches shall consist of gravel 1/8 inch to ¼ inch size.

2. Sand

The top course shall consist of at least 12 inches of sand with a uniformity coefficient of less than 4.0 and an effective grain size between 0.3 and 0.75 millimeters.

3. Underdrains

Underdrains shall be clay pipe, concrete drain tile or other underdrain material acceptable to the Department and the Board and shall be at least four inches in diameter and sloped not less than one percent to drain. Underdrains shall be spaced not more than 20 feet apart.

c. Impervious Types

Paved surface beds may be used if supporting data to justify such usage are provided.

d. Walls

Walls shall be watertight and extended 15 to 18 inches above and at least six inches below the surface.

e. Sludge Removal

Not less than two beds shall be provided and they shall be arranged to facilitate sludge removal. Concrete truck tracks should be provided for all percolation type sludge beds. Pairs of tracks for percolation type beds should be on 20-foot centers.

f. Sludge Influent

The sludge pipe to the beds shall terminate at least 12 inches above the surface and be arranged so that it will drain. Concrete splash plates shall be provided at sludge discharge points.

25.05.03 Rotary Vacuum Filtration

a. Where units will not operate on a continuous basis and the plant does not have digesters, aerated storage tanks should be provided for the sludge.

b. A maximum amount of flexibility consistent with reasonable economy should be designed into the system. Design flexibility should include, but not be limited to, the following:

1. sludge and chemical dilution facilities;

2. separate chemical conditioning tanks;

3. variable speed filter pan agitator drives; and

4. effective filter media cleaning facilities.

25.05.04 Centrifugation

a. Where units will not operate on a continuous basis and plant does not have digesters, aerated storage tanks should be provided for the sludge.

b. Successful application of centrifugation of municipal type sludges requires consideration of numerous factors. Therefore, proper scale-up data pertaining to the particular sludge to be dewatered shall be obtained and submitted to the Department and Board for approval.

c. Provisions for addition of coagulants to the sludge before or during introduction of the centrifuge shall be considered.

25.05.05 Pressure Filtration

a. The addition of and mixing of coagulants before filtration shall be considered.

b. Design data shall be collected from laboratory tests and be properly scaled-up to plant size.

c. Adequate storage should be provided for single unit systems for down time and for multiunit systems on one or two shift cycles.

25.05.06 Lagooning

a. Lagooning for dewatering may be used where suitable land is available for this use.

b. The soil shall be reasonably porous, or underdrains shall be provided. The maximum water table level shall be 18 inches below the bottom of the lagoon. The surrounding areas shall be grades to prevent surface water from entering the lagoon. The maximum depth shall be 24 inches or less. There shall be two or more lagoons. Any underdrainage fluids shall be returned to the treatment plant and be treated.

c. Loading rates, buffer zones, odor control and groundwater protection will be addressed in the preliminary engineering conference.

12VAC5-610-1170:6. APPENDIX K. Map of Physiographic Provinces.

APPENDIX K.

Map of Physiographic Provinces

12VAC5-610-1170:7. APPENDIX L. Suggested Scale and Contour Interval for Subdivision Plats.

APPENDIX L.