Administrative Code

Virginia Administrative Code
5/27/2024

Part III. Location, Design, Construction, Operation and Maintenance Criteria
Article 1
Site Requirements

12VAC5-640-390. General.

All discharging systems shall be located so that the treatment system, the point of discharge, all appurtenances, and the effluent leaving the system are sited in a manner that protects public health and minimizes environmental impacts.

Statutory Authority

§§ 32.1-12, 32.1-163 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-400 § 3.1, eff. July 30, 1992.

12VAC5-640-400. Classifications of discharge points.

The nature of the discharge point will determine what precautions must be taken to protect public health and environmental resources.

1. Where an all weather stream is available, it shall be used rather than discharging to an intermittent stream, dry ditch, or wetland. An all weather stream can readily dilute the effluent at least 10:1 at the seven consecutive day average of a 10-year low flow (7-Q-10) and thereby minimize public health and water quality impacts.

2. An all weather stream is represented by a solid blue line on the most recently published 7.5 minute United States Geologic Survey topographic map and has a 7-Q-10 flow that can provide 10:1 dilution of the effluent. Intermittent streams are represented by a dotted and dashed blue line on the most recently published 7.5 minute United States Geologic Survey topographic map. An all weather stream that provides less than 10:1 dilution of the effluent based on 7-Q-10 flow shall be considered an intermittent stream. Intermittent streams and dry ditches have an assigned stream flow 7-Q-10 of zero.

3. An owner may submit to the division additional hydrologic data, including but not limited to stream records and anecdotal evidence of long time residents, to support that a stream can provide a dilution ratio of 10:1. When in the opinion of the division, the evidence warrants a change, the division may determine that a stream is an all weather stream for the purposes of this chapter. The owner may also request site specific stream flow determinations from the Department of Environmental Quality.

4. Discharges into intermittent streams or dry ditches that do not have the dilution capability cited in subdivision 1 of this section shall be located entirely within the owner's property, or within a recorded easement as described in subdivision 2 of 12VAC5-640-450.

a. The average slope for any intermittent stream or dry ditch discharge receiving effluent from a discharging system shall be a minimum of 2.0% for the first 500 feet from the point of discharge. The intermittent stream or dry ditch shall be protected from erosion by the discharge as needed.

b. In order to prevent ponding, the minimum slope shall not be less than 1.0% at any point.

c. All slope measurements described in subdivisions 1 and 2 of this section shall be made prior to initiating any grading and are intended to reflect naturally occurring swales and drainage ways. Nothing contained herein however, is intended to prohibit a property owner from making minor grading improvements to prevent ponding in areas with minimal slopes. Naturally occurring swales and drainage ways may be extended with an engineered channel on a case-by-case basis, but any engineered channel must tie into the existing natural swale or drainage.

5. Wetlands shall be confirmed by the U.S. Army Corps of Engineers or the Department of Environmental Quality, as appropriate, based on the type of wetland. Confirmation of delineated wetlands shall be provided and include a wetland delineation map, wetland field data sheets, and any other documentation from the U.S. Army Corps of Engineers or the Department of Environmental Quality indicating their approval of the wetland boundary. 7-Q-10 flows cannot be calculated for wetlands and therefore the assigned 7-Q-10 flow value is zero. Discharges to wetlands shall be located entirely within the owner's property, or within a recorded easement as described in subdivision 2 of 12VAC5-640-450.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.2, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-410. Subdivisions.

Discharging systems may be permitted in existing subdivisions in accordance with this chapter.

No discharging system shall be permitted in any subdivision created after July 30, 1992, when a central sewer system is available or may be permitted to serve the subdivision. If the SWCB determines that no central sewage facilities are reasonably available or may be permitted, and each proposed site is eligible for registration under the General Permit, then the locality, in which the proposed subdivision is located, may request that the department review the plan for compliance with this chapter. When subdivisions are proposed utilizing individual discharging systems and dry ditch discharges, the use of easements shall be prohibited for multiple systems discharging to a single dry ditch or intermittent stream unless the owner(s) take necessary action to prevent access by children, animals, or other vectors.

Statutory Authority

§§ 32.1-12, 32.1-163 and 32.1-164 of the Code of Virginia.

Historical Notes

Derived from VR355-34-400 § 3.3, eff. July 30, 1992.

12VAC5-640-420. Setback distances from discharge points and downstream channels for the protection of public health.

A. Discharges proposed within one mile (upstream or up channel) of any public water intake shall not be permitted.

B. Discharges proposed within one mile upstream or up channel of any area explicitly designated for public swimming shall not be permitted.

C. When any river, stream, or other potential discharge area appears to receive significant primary contact use, such as, but not limited to, swimming, water skiing, tubing, or wet-wading, so that the discharge will pose a significant threat to public health, the district health director may require a higher level of treatment and reliability class for the permitted discharge facility.

D. The district health director, in consultation with the local governing authority and the department, may prohibit discharges into specified portions of the river, stream, or other potential discharge area. Prior to taking such action, the health director shall take the following steps:

1. Publish a notice announcing the department's intention to consider areas for restricting the use of discharging systems, establishing the date, time and location or locations of the public meeting or meetings, and soliciting public comment on the proposed area or areas being reviewed;

2. Request the opinion of the local governing body and other appropriate government agencies concerning proposed restrictions to be submitted before the close of the public comment period;

3. Have a public comment period on the proposal of not less than 30 days;

4. Hold at least one public meeting, 30 days or more after publication of the notice specified in subdivision 1 of this subsection; and

5. Evaluate the public comments received and staff evaluations regarding the use of the proposed area or areas for primary contact uses.

When in the best professional opinion of the health director the area or areas under consideration receives, for 30 days or more per year, significant primary contact uses, such that the discharge will pose a significant threat to public health, the director may designate areas where discharge systems are prohibited. Prohibited discharge areas may include areas upstream in the main channel and tributaries, from the area under review, for distances up to one mile if warranted by the evidence. Prohibited discharge areas shall be clearly defined in writing and delineated on a United States Geological Survey 7.5 minute topographic map. The prohibition on discharges, if any are found necessary, shall be effective upon notice after completion of the elements contained in this section.

E. The wastewater treatment system (tankage and components), shall be a minimum of 50 feet from private and public water wells and private cisterns. The discharge point and the channel of treated effluent flow shall be located in accordance with the distances given in Table 3.1 from private and public water wells and cisterns. Where the bottom elevation of a cistern is located above the elevation of the discharge point, the setback distances shall not apply. The setback distances between the water well or cistern and the downstream channel established in Table 3.1 shall apply for 50 feet downstream of the discharge point for all weather streams and 500 feet downstream for intermittent stream or dry ditch discharges. For wetlands where the flow path can be established, generally where the slope is 10% or greater, the setback distances between the water well or the cistern and the "downstream channel" shall apply for 250 feet downstream of the discharge point. For wetlands where the flow path cannot be established, generally where the slope is less than 10%, then the distance shall be measured radially for 250 feet from the point of discharge.

F. Setback distances to other wells not covered in Table 3.1 of this section, such as geothermal and gas wells, will be determined on a case-by-case basis.

G. No discharging system or any portion of the channel carrying the treated effluent flow shall be within 100 feet of a spring. Further, no discharging system shall discharge within 1,500 feet upstream or 100 feet downstream of any spring used for human consumption.

H. Discharging systems are prohibited from discharging directly into sink holes or into dry ditches, intermittent streams, wetlands, streams, or other waterways that flow into sink holes within 1,500 feet from the point of discharge.

I. Dry ditch discharges shall not have limestone outcrops within the dry ditch channel. This provision shall apply for a distance of 50 feet along the channel.

J. Except as noted below, the department will not approve discharging systems except where discharge points will be at least 500 feet apart. The separation distance may be reduced to 250 feet between discharge points in accordance with the following:

1. For discharges to an all weather stream, the distance may be reduced to 250 feet by providing a Reliability Class II facility.

2. For discharges to a dry ditch or intermittent stream, the distance may be reduced to 250 feet by providing a Reliability Class I system that produces a TL-3 effluent and a fecal coliform concentration of 100 col/100 ml or less.

3. No reduction in the distance between discharge points is allowed for discharges to wetlands.

K. No discharge shall be permitted under this chapter which will result in the condemnation of shellfish waters or the continued condemnation of shellfish waters closed only because of inadequate water quality.

TABLE 3.1 SETBACK DISTANCES FROM PRIVATE AND PUBLIC WATER WELLS AND CISTERNS
(All distances are in feet)

Type of Water Supply

Distance from Point of Discharge

Distance from Downstream Channel

Discharge to All Weather Stream

Discharge to Wetland2, Intermittent Stream, or Dry Ditch

Class I1 Well

100

100

100

Class II1 Well

100

100

100

Class IIIA Well

50

50

50

Class IIIB Well

50

50

50

Class IIIC Well

100

50

100

Class IV Well

100

50

100

Cistern

100

50

100

1Class I and II well specifications are found in the Waterworks Regulations (12VAC5-590). All other well specifications may be found in the Private Well Regulations (12VAC5-630).

2The downstream "channel" of a wetland where the flow path can be established shall be a minimum of 25 feet wide and approximately centered on the flow path. Where the flow path cannot be established in a wetland, then the distance shall be measured radially from the point of discharge.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.4, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

Article 2
Design Requirements

12VAC5-640-430. Performance requirements.

Article 2
Design Requirements

A. All systems operated under this chapter shall meet the effluent limitations set forth by the State Water Control Board in the General Permit. All systems operated under this chapter shall maintain the treatment system in accordance with the approved construction permit or as modified by the final construction permit in accordance with the operation permit, "as built" plans, and the operation and maintenance manual.

B. No system shall be approved for use which provides a bypass pipe, or otherwise allows untreated or partially treated effluent to discharge in the event of a system failure.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.5, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-432. Treatment unit and additional system component classifications.

A. Biological treatment units will be classified by the division according to the data available to demonstrate the performance limits and reliability of those treatment units. The division may classify treatment units as generally approved or not generally approved. The type and frequency of testing for each approval class is designed to reflect the certainty with which the system has demonstrated its ability to meet the limits of the General Permit or the performance requirements of this chapter.

1. General approval may be issued by the division for both TL-2 and TL-3 treatment units in accordance with the current policies of the division. Generally approved units shall be listed on the division's website.

2. Nongenerally approved biological treatment unit designs shall be properly supported with design calculations and one or more of the following:

a. Documentation from applicable engineering standards, texts, or other publications;

b. Relevant peer-reviewed research;

c. Technical guidance from other states (may be considered on a case-by-case basis); or

d. Technical guidance from the U.S. Environmental Protection Agency.

Scale drawings of the treatment unit, appropriate design calculations, and control system details shall be provided that demonstrate the ability of the unit to meet the required effluent limits and reliability standards at the proposed design flow.

B. Additional system components for discharging systems will be classified by the division as generally approved or not generally approved.

1. The division shall consider additional system components such as post-filtration, disinfection, dechlorination, and post-aeration to be generally approved if the unit has been tested and approved under a National Sanitation Foundation (NSF) or other recognized protocol for the proposed wastewater use or if the design complies with the design standards in 12VAC5-640-460.

2. Nongenerally approved system component designs shall be properly supported with design calculations and one or more of the following:

a. Documentation from applicable engineering standards, texts, or other publications;

b. Relevant peer-reviewed research;

c. Technical guidance from other states (may be considered on a case-by-case basis); or

d. Technical guidance from the U.S. Environmental Protection Agency.

Scale drawings of the treatment unit, appropriate design calculations, and control system details shall be provided that demonstrate the ability of the unit to meet the required effluent limits and reliability standards at the proposed design flow.

C. Discharging systems that are comprised entirely of generally approved biological treatment units and system components as described in this section are considered generally approved treatment systems.

Statutory Authority

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

Historical Notes

Derived from Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-434. Reliability.

A. Reliability is a measure of the ability of a component or system to perform its designated function without failure or interruption of service. Overflow criteria, such as the allowable period of noncompliant discharge, are utilized solely for the establishment of reliability classification for design purposes and are not to be construed as authorization for, or defense of, an unpermitted discharge to state waters. The reliability classification shall be based on the water quality and public health and welfare consequences of a component or system failure.

B. Reliability Class I is required for dry ditch and intermittent stream discharges with 250 feet of easement available and wetland discharges with 100 feet of easement available.

1. For biological treatment processes, Reliability Class I shall be met by providing one of the following:

a. A passive, backup biological treatment system (e.g., an intermittent sand, peat, or media filter or a constructed wetlands);

b. A generator for the treatment system with automatic transfer switch;

c. A 24-hour holding tank for raw wastewater with telemetry system to immediately notify the operator of system failure; or

d. Any alternative means that limits the discharge of a noncompliant effluent to a maximum of 24 hours.

2. For disinfection, a Reliability Class I design shall ensure that the effluent is continually disinfected by providing electronic or mechanical means of monitoring the process such that failure of disinfection systems may be corrected within 24 hours.

C. Reliability Class II is required for dry ditch and intermittent stream discharges with 500 feet of easement available and wetland discharges with 250 feet of easement available. Reliability Class II is also required for the reduction of the distance between discharge points to 250 feet on an all weather stream.

1. For biological treatment processes, Reliability Class II shall be met by providing:

a. A fixed film biological treatment process such as an intermittent sand filter, recirculating media filter, or a peat filter;

b. A suspended growth biological system followed by post-filtration;

c. Telemetry to relay alarm conditions to the operator; or

d. Any alternative means that limits the discharge of a noncompliant effluent to a maximum of 36 hours.

2. For disinfection, a Reliability Class II design shall ensure that the effluent is continually disinfected by providing electronic or mechanical means of monitoring the process such that failure of disinfection systems may be corrected within 36 hours.

D. Reliability Class III is required for all weather stream discharges with a separation distance between discharge points of 500 feet or greater. For the purposes of this chapter, noncompliant discharges must be limited to a maximum of 48 hours.

Statutory Authority

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

Historical Notes

Derived from Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-440. Special factors affecting system design.

Each type of discharging system has its own unique advantages and disadvantages. These unique characteristics define the situations where a system may be used to advantage. The design of the system must be appropriate for the intended use and the site conditions where the system is to be installed. Subdivisions 1 through 6 of this section contain a list of factors that will require special design consideration. This list should not be considered all encompassing. There may be other design factors that require special consideration. A preliminary engineering conference may be scheduled with the department to discuss such factors prior to submitting designs for department review.

1. When a discharge is proposed to a wetland, dry ditch, or intermittent stream, restricted access to the wetland, dry ditch, or intermittent stream in accordance with 12VAC5-640-450 to protect public health.

2. Intermittent use for the purposes of this chapter constitutes use of the system for less than three consecutive months. Systems serving weekend cottages or other intermittent uses require special design, operation, and maintenance consideration.

3. When a discharging system is proposed to be located in an area subject to infiltration by surface water or shallow groundwater, the department may require additional protection from infiltration, inflow, and flotation, including placement of the system above natural grade.

4. Erosion must be controlled by the owner of the discharging system in accordance with any local erosion control ordinances.

5. All systems shall normally be designed to treat the BOD5 loading rate of 0.4 lbs/day per bedroom and a flow of 150 gallons per day per bedroom for systems up to three bedrooms. Systems serving single family dwellings having more than three bedrooms shall be permitted and designed to treat the anticipated loading rate based on BOD5 and be capable of handling anticipated peak loading and flow rates. All systems shall be designed to operate over the range of anticipated flow and loading rates. When a system is permitted with a design less than the maximum capacity of the dwelling, the owner shall have the construction permit recorded and indexed in the grantor index under the owner's name in the land records of the clerk of the circuit court having jurisdiction over the site of the discharging system.

6. All system designs must include protection of the components from freezing or other adverse weather conditions and ensure that the system will function properly year round.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.6, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-450. Design criteria for the use of intermittent streams, dry ditches, or wetlands.

All owners of systems discharging to an intermittent stream, dry ditch, or wetland shall ensure the following conditions are met:

1. Direct contact between minimally diluted effluent and insects, animals, and humans must be restricted for the life of the system. This will be achieved by reducing the chance of ponding and run-off and limiting access to the effluent. The department shall require fencing, rip-rap, or other barriers to restrict access to effluent discharging to a dry ditch, intermittent stream, or wetland as deemed necessary to protect public health. This determination shall be made by the department on a case-by-case basis.

a. For dry ditch and intermittent stream discharges, the restricted access area shall begin at the point where the effluent is discharged and continue for 500 feet, until the effluent discharges into an all weather stream or is no longer visible during the wet season. The design shall provide justification for the length of the restricted access channel if less than 500 feet.

b. For wetland discharges, the restricted access shall extend for a distance of 250 feet along the flow path of the discharge unless a 10:1 dilution with the wetland can be achieved. If the flow path cannot be established and a 10:1 dilution cannot be obtained, then access shall be restricted for 100 feet radially from the point of discharge. For wetland discharges, the access barrier may be a subsurface discharge point, but in no case shall the discharge point and diffuser be greater than 18 inches below the natural wetland surface.

2. When effluent is discharged to a dry ditch, intermittent stream, or wetland, the owner shall own the land or acquire an easement from the downstream or downgradient land owner to discharge on all land below the point of discharge for the distance shown in Table 3.2. To allow for system construction and repair within the restricted access area, and to facilitate maintenance and monitoring, the easement shall be a minimum of 25 feet wide and approximately centered on the low point of the dry ditch or intermittent stream for the entire length of the restricted access area. For wetlands, the easement shall be measured radially from the point of discharge unless flow direction can be established. In those cases where flow direction can be established, the easement shall be a minimum of 25 feet wide and approximately centered on the discharge path and extend for a distance along the flow path as described in Table 3.2. If the slope across the discharge site is equal to or greater than 10%, the flow direction can be determined by observation. For slopes less than 10%, a site specific study must be conducted to document the direction of flow. All easements must be in perpetuity and shall be recorded by the owner with the clerk of the circuit court having jurisdiction over the property prior to issuance of the construction permit. For the purposes of complying with this chapter, written approval to utilize an easement owned by the Virginia Department of Transportation shall be recorded by the owner with the clerk of the circuit court office having jurisdiction over the property.

3. Each discharging system that discharges to a dry ditch, intermittent stream, or wetland must receive additional treatment beyond that required by the General Permit in order to reduce the increased potential for public health problems which may result when partially treated effluent is not diluted. Such additional treatment shall be capable of producing an effluent with a quality of 10 mg/l of BOD5, 10 mg/l of suspended solids and a fecal coliform level of less than or equal to 100 colonies per 100 ml. Treatment units approved as TL-3 are recognized as having the ability to meet this BOD5 and TSS standard, but have not been tested for compliance with the fecal coliform standard. Therefore, the following reliability classifications in Table 3.2 must be met when designing discharge systems intended to discharge into dry ditches, intermittent streams, or wetlands.

TABLE 3.2
REQUIREMENTS FOR RELIABILITY CLASSIFICATION AND OWNERSHIP OR EASEMENTS DOWNSTREAM FROM SYSTEMS THAT DISCHARGE TO DRY DITCHES, INTERMITTENT STREAMS, OR WETLANDS

Reliability Class

Downstream or Down Channel Distance for Dry Ditches or Intermittent Streams (feet)

Wetlands from Discharge Point along Flow Path or Radially from Discharge Point

No spring below

Spring below

Reliability Class I

250 ft

1,500 ft

100 ft

Reliability Class II

500 ft

1,500 ft

250 ft

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.7, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-460. Design requirements for system components.

A. All discharging systems shall be equipped with a means of disinfecting the effluent which is acceptable to the division and meets the performance requirements of this chapter.

1. All discharging systems utilizing chlorine as a disinfectant shall be equipped with a chlorinator and contact chamber. Dechlorination is to be supplied if required by the General Permit.

a. Chlorinator capacity shall be based on the degree of treatment, flow variations, and other variables in the treatment processes. For disinfection, the capacity shall be adequate to maintain a total chlorine residual between 1.0 mg/l and 3.0 mg/l in the effluent after the required contact period. All chlorinators shall be designed to provide the appropriate dose of chlorine and mix the chlorine with the effluent. All chlorine products used to disinfect effluent from a discharging system shall be approved by the U.S. Environmental Protection Agency for use as a sewage disinfectant; products unapproved for wastewater disinfection are not acceptable. Use of unapproved products shall constitute a violation of this chapter.

b. The chlorine contact chamber shall have a length to width ratio of 20:1 and shall provide a contact time of 30 minutes based on peak hourly flow, or 60 minutes based on peak daily flow. The length to width ratio may be reduced on a case-by-case basis when increased chlorine contact times are utilized.

c. When required by the General Permit, dechlorination capacity shall be adequate to dechlorinate the maximum chlorine residual anticipated and achieve the required General Permit effluent limits for total residual chlorine by providing at least 1-1/2 parts sulfite salt to one part chlorine. Provisions shall be made to thoroughly mix the dechlorinating agent with the contact tank effluent within a period of approximately one minute.

d. To meet Reliability Class I or Class II, all chlorination and dechlorination units shall be alarmed to notify the operator when tablets are not present in the dosing chamber or equipped with duplicate units that automatically switch over to the redundant unit if the primary unit is not operating.

2. Disinfection can be achieved through exposure of microorganisms to a sufficient level of ultraviolet light (UV) irradiation at the germicidal wavelength for an adequate period of time.

a. UV disinfection equipment shall be capable of providing a minimum average calculated dose of 50,000 microwatt-seconds per square centimeter after the UV lamps have been in operation for 7,500 hours or more and at a 65% transmissivity. The dosage may be reduced on a case-by-case basis when sufficient information is provided to demonstrate that the required level of disinfection can be obtained at a lower dose level through test data.

b. UV lamps shall produce 90% or more of their emitted light output at the germicidal wavelength of 253.7 nanometers.

c. UV lamp assemblies shall be so located as to provide convenient access for lamp maintenance and removal.

d. UV lamps should not be viewed in the ambient air without proper eye protection as required by VOSH and other applicable regulations. The system design should prevent exposure of bare skin to UV lamp emission for durations exceeding several minutes.

e. An elapsed time meter shall be provided to indicate the total operating time of the UV lamps.

f. UV systems are sensitive to color and suspended solids. Precautions should be taken to protect the UV system from both color and excessive suspended solids.

g. To meet Reliability Class I or Class II, all UV units shall be equipped with a sensor to detect bulb failure with an alarm or equipped with duplicate units that automatically switchover if the primary unit is not operating.

B. Post-aeration as required by the General Permit shall be provided to ensure that the final effluent complies with the dissolved oxygen effluent limits in the General Permit. Post-aeration may involve diffused aeration or cascade type aeration. All post-aeration designs shall assume a zero dissolved oxygen concentration in the influent wastewater to the post-aeration unit.

1. Effluent post-aeration may be achieved by the introduction of diffused air into the effluent.

a. Diffused aeration basins shall be designed to eliminate short-circuiting and the occurrence of dead spaces. For maximum efficiencies, sufficient detention time shall be provided to allow the air bubbles to rise to the surface of the wastewater prior to discharge from the basin.

b. When the detention time in the aeration basin exceeds 30 minutes, consideration shall be given to the oxygen requirements resulting from biological activity in the aeration unit.

c. Diffused air aeration systems shall be designed utilizing Fick's Law (the rate of molecular diffusion of a dissolved gas in a liquid) in the determination of oxygen requirements. Supporting experimental data shall be included with the submission of any proposal for the use of diffusers that are considered nonconventional. Such proposals will be evaluated on a case-by-case basis by the division.

d. Alternatively, an airflow of one cubic foot per minute at a diffuser submergence of one foot is sufficient to increase the dissolved oxygen of 1000 gallons per day of effluent to greater than five mg/l dissolved oxygen at 25°C.

e. If airflow is to be siphoned off the blower for the biological treatment unit, calculations shall be submitted to verify that there is sufficient air for both uses.

2. Effluent post-aeration may be achieved through a turbulent liquid-air interface established by passing the effluent downstream over either a series of constructed steps that produces a similar opportunity for transfer of dissolved oxygen to the effluent, otherwise known as cascade or step aeration.

a. The following equation shall be used in the design of cascade/step type aerators:

rn = (Cs-Ca)/(Cs-Cb)

where: r

=

Deficit ratio

Cs

=

Dissolved oxygen saturation (mg/l)

Ca

=

Dissolved oxygen concentration above the weir, assumed to be 0.0 mg/l

Cb

=

Dissolved oxygen concentration in the effluent from the last or preceding step

n

=

The number of equal size steps

r

=

1 + (0.11) (ab) (1 + 0.046 T) (h)

where: T

=

Water temperature (°C)

h

=

Height of one step (ft)

a

=

1.0 for effluents (BOD5 of less than 15 mg/l) or
0.8 for effluents (BOD5 of 15 mg/l to 30 mg/l)

b

=

1.0 for free fall and 1.3 for step weirs

b. The equation for determining the number of steps is dependent upon equidistant steps, and if unequal steps are used, transfer efficiencies must be determined for each separate step.

c. The effluent discharge to a cascade type aerator shall be over a sharp weir to provide for a thin sheet of wastewater. Consideration shall be given to prevention of freezing.

d. The final step of the cascade type aerator shall be above normal stream flow elevation and the cascade aerator shall be protected from erosion damage due to storm water drainage or flood/wave action.

e. When pumping is necessary prior to discharge over the cascade aerator, the range of the flow rate to the post-aeration unit must be accounted for in the design.

f. A step aerator with multiple steps each less than or equal to one foot and a total drop of five feet is sufficient to increase the dissolved oxygen in an effluent at 25°C to greater than five mg/l.

C. Post-filtration may be used to ensure compliance with the reliability standards in 12VAC5-640-434 and generally follow the biological treatment unit and are prior to disinfection in the treatment process. For granular media filters, the media depth shall not be less than 30 inches. Sand media for intermittently dosed and recirculated effluent, shall have an effective size of 0.30 mm to 1.0 mm and 0.8 mm to 1.5 mm, respectively. The uniformity coefficient should not exceed 4.0. No more than 2.0% shall be finer than 0.177 mm (80 mesh sieve) and not more than 1.0% shall be finer than 0.149 mm. No more than 2.0% shall be larger than 4.76 mm (4 mesh sieve). Larger granular media up to five mm in effective size may be considered on a case-by-case basis. The filter shall be equipped with an underdrain. The surface of the filter shall be accessible for maintenance. For the purposes of a filtration unit, the maximum surface hydraulic loading rate is 15 gpd/sf.

D. Constructed wetlands that are used as a passive backup biological treatment unit for the purposes of meeting Reliability Class I requirements of 12VAC5-640-434 B shall be lined with a minimum surface area of 100 square feet, a depth of 18 inches, a length to width ratio of about four to one, and shall have subsurface flow. Wastewater shall be disinfected prior to entering the constructed wetlands and sampling ports shall be provided to allow monitoring of the influent to the wetlands. Effluent dechlorination prior to entering the wetlands may be necessary to protect the plants from toxic levels of chlorine.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.8, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

Article 3
Construction Requirements

12VAC5-640-470. General construction requirements.

Article 3
Construction Requirements

A. No portion of any system may be covered or used until inspected, corrections made if necessary, and approved, by the department or unless expressly authorized in writing by department. All applicable sections contained in the Sewage Handling and Disposal Regulations, 12VAC5-610, shall be used to establish design and construction criteria not contained in this chapter.

B. Gravity sewer lines and lines between components of the system shall be schedule 40 pipe and shall have a minimum grade of 1.25 inches per 10 feet for three-inch and four-inch sewer lines. Discharge lines after primary or secondary treatment units shall have a minimum grade of six inches per 100 feet. Where minimum grades cannot be maintained, detailed pump specifications shall be shown on the site plan in accordance with Article 4 (12VAC5-610-598 et seq.) of Part IV of the Sewage Handling and Disposal Regulations.

C. The treatment unit and all piping and appurtenances shall be located in conformance with the approved plans. All changes in location shall be approved by the local department prior to the installation of the system.

D. All pumps and appurtenances to the pump shall be installed according to the plans and specifications approved by the department and referenced in the permit.

E. All wiring shall be approved by the local building official and shall be weather tight and permanent in nature (hard wired).

F. The control panel for the system shall be located within 15 feet of the treatment unit and shall be provided with a manual override switch. Each pumping station shall be provided with controls for automatically starting and stopping the pumps based on water level. When float type controls are utilized they shall be placed so as to be unaffected by the flow entering the wet well.

G. All mechanical treatment units shall be provided with an alarm system on a separate electrical circuit from the remainder of the treatment unit. The alarm shall be both audio and visual and shall be located in an inhabited portion of the dwelling. Examples of alarm conditions to be monitored include aerator failure, blower failure, and high water level.

H. Except for the discharge pipe, and step type post aeration if used for post-aeration, no portion of the discharging system may be located in the 100-year flood plain.

I. The design must allow for sampling to confirm the efficacy of the treatment process. Sampling ports shall be identified on the construction documents and shall meet the following minimum requirements:

1. All discharging systems utilizing chlorine as a disinfectant shall be equipped with a four inch or larger sampling port connected to an approved effluent collection box at the chlorine contact chamber after the 30-minute or 60-minute contact time (i.e., the sampling port shall be located at the outlet end of the chamber).

2. A separate sampling port shall be required after the dechlorination unit.

3. The sampling location is to be identified and a port provided if needed for sampling the final effluent prior to the effluent entering the discharge channel.

4. Other sampling ports may be required on a case-by-case basis due to the system design.

J. All discharging systems shall have a clean out port, accessible from the surface of the ground within 10 feet of the influent invert of the treatment unit.

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

L. Sand filter liners shall be constructed of clay having a permeability of 10-6 cm/sec. or less, a 28 mil vinyl or PVC plastic liner, concrete, or other material approved by the division. A watertight seal shall be provided where underdrain piping exits the filter.

M. The owner of each discharging system shall post a permanent sign at the point of discharge with the following notice:

This pipe carries treated sewage effluent and is not suitable for human consumption. This system is owned by (FULL NAME OF PERMIT HOLDER) and is maintained by (NAME AND PHONE NUMBER OF LICENSED OPERATOR WITH OVERSIGHT OF THE SYSTEM).

The sign shall be posted within three feet of the discharge pipe, shall be plainly visible to the public, and shall be constructed of durable material. All lettering shall be at least one-inch high and shall be clearly legible. The sign shall have black letters on a white background (or be painted in other contrasting colors) and be plainly visible at a distance of 25 feet to a person with normal vision. Failure to maintain this sign shall be grounds for suspending the owner's operation permit.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.9, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-480. (Repealed.)

Historical Notes

Derived from VR355-34-400 § 3.10, eff. July 30, 1992; repealed, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

Article 4
Monitoring, Operation, and Maintenance Requirements

12VAC5-640-490. Monitoring.

Article 4
Monitoring, Operation, and Maintenance Requirements

A. Discharging systems that discharge improperly treated effluent can endanger public health and threaten environmental resources. All discharging systems shall be routinely inspected and the effluent sampled to determine compliance with the effluent limitations set forth by the State Water Control Board in the General Permit and in accordance with 12VAC5-640-430 and 12VAC5-640-510. All testing requirements contained in this chapter are the responsibility of the system owner to have collected, analyzed, and reported to the department.

B. There are two types of testing recognized by this chapter: formal compliance testing and informal (process control) testing. Formal testing is conducted to determine either compliance or noncompliance with the General Permit. Informal testing is conducted to assess the treatment system's performance and to determine when additional formal compliance testing is necessary. Informal testing may support but shall not be the sole basis for revoking the approval of the system pursuant to 12VAC5-640-280.

C. All treatment systems shall undergo startup testing to assess the ability of the system to comply with the established performance requirements.

1. Treatment systems are considered generally approved for the purposes of establishing startup testing requirements only when all treatment components (i.e., biological treatment unit, disinfection, dechlorination, post-aeration, etc.) of the system are considered generally approved as described in 12VAC5-640-432.

2. All new discharging systems shall undergo formal startup compliance testing for parameters limited by the General Permit. The collection, storage, transportation, and analysis of all formal compliance samples shall be in accordance with the requirements of the General Permit.

a. For generally approved systems, the first formal compliance testing event shall occur 45 to 90 days after the system begins discharging. If the formal compliance test data indicate the system is in compliance with the General Permit, then the system will revert to annual formal compliance sampling in accordance with the General Permit. The initial sample may be used to comply with the first annual sampling requirement. If the testing data indicates that any parameter is out of compliance, subsection E of this section shall apply.

b. For nongenerally approved systems, the first formal compliance testing event shall occur 45 to 90 days after the system begins discharging. Three additional formal compliance testing events are to occur quarterly and at least 60 days apart. If the four startup compliance test data indicate the system is in compliance with the General Permit, then the system will revert to annual formal compliance sampling in accordance with the General Permit. If the testing data indicates that any parameter is out of compliance, subsection E of this section shall apply.

3. Informal (process control) testing shall be conducted monthly for at least six consecutive months beginning the second full month after the issuance of the operation permit. After successful startup of the treatment system, informal testing shall be conducted semiannually at a minimum and any time formal testing is conducted. Informal testing shall be in accordance with the approved operation and maintenance manual, which shall include at a minimum the tests listed in Table 3.3. The specific test, sample location, and frequency shall be itemized in the operation and maintenance manual for the treatment system.

D. Both formal and informal routine monitoring is required after a system successfully completes startup testing.

1. After a system successfully completes startup testing, the system formal testing reverts to the General Permit monitoring frequency for the parameters limited by the General Permit. The collection, storage, transportation, and analysis of all formal testing shall be in accordance with the requirements of the General Permit.

2. Informal (process control) testing shall be conducted during routine maintenance visits. The specific test, sample location, and frequency shall be itemized in the operation and maintenance manual for the treatment system. When an operation and maintenance manual is not available, informal testing shall be sufficient to assess the treatment system's performance. Table 3.3 contains the minimum informal testing that must be conducted as appropriate for a given system.

TABLE 3.3
INFORMAL (PROCESS CONTROL) TESTING

Treatment Unit

Informal Tests

Septic tank/trash tank

Sludge depth

Suspended growth biological treatment unit

Dissolved oxygen, settleabilty, pH, odor

Fixed film biological treatment unit

Dissolved oxygen (effluent from unit), pH, odor

Chlorine disinfection/dechlorination

TRC at end of contact tank (>1.0 mg/l),

TRC after dechlorination

Ultraviolet disinfection UV

Turbidity prior to UV

Final effluent

Dissolved oxygen, pH, odor, color

E. The department may require additional formal compliance testing or informal testing, or both, as necessary to protect public health and the environment. Additional testing shall be based on observed problems and shall not be implemented routinely on all discharging systems.

1. Anytime a discharging system is found to be out of compliance with the effluent limitations of the General Permit, follow-up formal compliance testing shall be repeated between 45 and 90 days after the original samples were collected and the results reported to the local health department. Prior to resampling, the operator should attempt to determine the reason for the noncompliance and take corrective actions.

2. Anytime an informal test reveals a potential problem, additional formal or informal testing may be conducted to review the effectiveness of any repairs or adjustments.

3. Anytime the results of two consecutive formal compliance tests as specified in subdivision C 2 or D 1 of this section result in a violation of the effluent limitations of the General Permit, informal testing shall revert to monthly frequency until satisfactory results are obtained for six consecutive months. Nothing in this section shall preclude requiring the collection of samples for formal compliance testing as described in subdivisions C 2 and D 1 of this section to determine compliance with the effluent limitations set forth in the General Permit.

F. The owner of each system is responsible for ensuring that the collection, analysis, and reporting of all effluent sample tests are completed in a timely fashion and in accordance with this section and 12VAC5-640-510. The department shall conduct an annual inspection and may conduct additional inspections at its discretion. Furthermore, the department may conduct or mandate formal or informal testing as deemed appropriate. If a system is in compliance three consecutive years, the department may reduce the department inspection frequency to a three-year cycle. Annual inspections by the department will resume if the department receives evidence that the system is out of compliance. Compliance for the purposes of this section is compliance with the testing, inspection, effluent limits, and reporting requirements of this chapter. Inspection by the department does not substitute for the required operation, maintenance, testing, and reporting requirements in 12VAC5-640-490, 12VAC5-640-500, and 12VAC5-640-510.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.11, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-500. Operation and maintenance requirements.

A. Due to the potential for degrading surface water and groundwater quality or jeopardizing the public health, or both, routine operation and maintenance of discharging systems is required. In order to assure the treatment system is operated, maintained, monitored, and reported properly, the permit holder shall engage a licensed operator as defined in subsection E of this section. Reporting in accordance with 12VAC5-640-490 and 12VAC5-640-510 is sufficient evidence of an ongoing contract. Owners with existing monitoring waivers that allow the owner to collect formal compliance samples as of December 16, 2015, may be extended, but no new waivers shall be issued. In the event the individual fails to collect three or more of any of the required samples in any five-year period, the department will void the waiver and require evidence of an operation and maintenance contract that includes monitoring.

B. It is the owner's responsibility to do the following:

1. Have the system operated and maintained by a licensed operator;

2. Have an operator visit the system at the frequency required by this chapter (at least semiannually);

3. Have an operator collect and analyze any samples required by this chapter;

4. Provide prompt maintenance and repair of the treatment works. If an owner is notified by the operator of a repair or maintenance need pursuant to subdivision C 4 of this section and the discharge does not comply with the effluent requirements of the General Permit, then the owner shall begin pump and haul of the sewage and take other actions as may be directed by the local health department until the treatment works returns to normal function;

5. Keep a copy of the log provided by the operator on the property where the system is located in electronic or hard copy form, make the log available to the department upon request, and make a reasonable effort to transfer the log to any future owner;

6. Follow the O&M manual (where available) and keep a copy of the O&M manual in electronic or hard copy form for the system on the property where the system is located, make the O&M manual available to the department upon request, and make a reasonable effort to transfer the O&M manual to any future owner; and

7. Comply with the VPDES permit requirements contained in 9VAC25-110.

C. The operator has the following responsibilities:

1. Perform all testing required in either Part I A or Part I B (9VAC25-110-80) of the General Permit, as appropriate, and in this chapter, unless the owner maintains a waiver in accordance with subsection A of this section. Note: The treatment works will be sampled during normal discharging operations or normal discharging conditions (i.e., operations that are normal for that facility). The operator should not force a discharge in order to collect a formal sample, but the informal sampling should be used to identify any operational problems;

2. Whenever an operator performs a visit that is required by this chapter, he shall do so in such a manner as to accomplish the various responsibilities and assessments required by this chapter through visual or other observations and through laboratory and field tests that are required by this chapter or that he deems appropriate;

3. When performing activities pursuant to a visit that is required by this chapter, the operator is responsible for the entire system, and where applicable, the operator shall follow the approved O&M manual;

4. Provide a written or electronic notification to the owner within 24 hours whenever the operator becomes aware that maintenance or repair of the owner's treatment works is necessary; and

5. Document the results of each site visit in the log and report in accordance with 12VAC5-640-510. Each operator shall keep an electronic or hard copy log for each system for which he is responsible. The operator shall provide a copy of the log to the owner. In addition, the operator shall make the log available to the department upon request. At a minimum, the operator shall record the following items in the log:

a. Results of all testing and sampling;

b. A copy of the Discharge Monitoring Report required by the General Permit;

c. Maintenance, corrective actions, and repair activities that are performed;

d. Recommendations for repair and replacement of system components;

e. Sludge or solids removal; and

f. The date reports were given to the owner.

D. In localities where a public service authority, sanitary district, or other public utility exists which operates and maintains the systems, permitted under this chapter, the requirements for the operation and maintenance contract may be waived by the division provided the owner of the system subscribes to the service and the utility meets the minimum elements described in 12VAC5-640-490, 12VAC5-640-500, and 12VAC5-640-510.

E. In order to competently evaluate system performance, collect samples, interpret sample results, and repair and maintain discharging systems, an individual must be knowledgeable in sewage treatment processes. All individuals who perform maintenance on discharging systems pursuant to 12VAC5-640-500 are required to hold a valid Class IV or higher wastewater works operator license or an alternative onsite sewage system operator license issued by the Board for Waterworks and Wastewater Works Operators and Onsite Sewage System Professionals.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.12, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-510. Information to be reported electronically.

A. Every owner issued an operation permit for a discharging system is responsible for having the results of all mandated testing and inspections submitted to the department in the form and format acceptable to the department.

B. All formal compliance testing, informal testing, repairs, modifications, alterations, expansions and routine maintenance must be reported.

C. All reports and test results must be submitted by the 15th of the month following the month in which the activity occurred.

D. All reports and test results shall be submitted electronically. When formal testing indicates that a discharge limit established in the General Permit is being exceeded or when informal testing indicates a discharging system may be in violation of the General Permit requirements, the owner shall notify the maintenance provider and the department within 24 hours.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.13, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

12VAC5-640-520. Failure to submit information.

Failure to conduct mandatory monitoring or to report monitoring results as required in 12VAC5-640-490 and 12VAC5-640-510 may result in the revocation of the owner's operation permit. The department shall notify the Department of Environmental Quality of the revocation of the operation permit.

Statutory Authority

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

Historical Notes

Derived from VR355-34-400 § 3.14, eff. July 30, 1992; amended, Virginia Register Volume 32, Issue 6, eff. December 16, 2015.

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