Section 100. Performance requirements; laboratory sampling and monitoring

A. Laboratory sampling is not required for any small AOSS with an installed soil treatment area that is sized for septic tank effluent and complies with the requirements of 12VAC5-610 for septic tank effluent.

B. All effluent samples must be taken at the end of all treatment, prior to the point where the effluent is discharged to the soil treatment area unless changed pursuant to 12VAC5-613-90 or 12VAC5-613-210. The designer shall identify the sampling points. When required, the sampling point for chlorine disinfection shall be at the end of the chlorine contact tank if TRC is to be used to measure compliance.

C. All sampling and monitoring shall be conducted according to procedures approved under 40 CFR Part 136 or alternative methods approved by the U.S. Environmental Protection Agency unless other procedures have been specified in this chapter.

D. The owner of each small AOSS must ensure that an initial grab sample of the effluent from the treatment unit is collected within 180 days of system operation. The sample must be analyzed in accordance with 40 CFR Part 136 or alternative methods approved by the U.S. Environmental Protection Agency within the first 180 days of operation. Thereafter, if the treatment unit has received general approval, a grab sample is required once every five years. Samples shall be analyzed for BOD₅ and, if disinfection is required, fecal coliform. Treatment units utilizing chlorine disinfection may alternatively sample for TRC instead of fecal coliform. Sample results shall be submitted to the local health department by the 15th of the month following the month in which the sample was taken.

E. For small AOSSs that utilize a treatment unit that has not received general approval, in addition to the initial sample required by subsection D of this section, four additional grab samples of the effluent from the treatment unit shall be collected, analyzed, and submitted to the department within the first two years of operation and annually thereafter. The interval for collecting the samples shall not be less than quarterly or more than semiannually. Sample results shall be submitted to the local health department by the 15th of the month following the month in which the sample was taken. After two years of sampling in accordance with this subsection, the owner may submit a request to the department to reduce the sampling frequency to once every five years. The department shall grant such requests if the mean of five or more consecutive samples complies with the applicable performance requirements of this chapter.

F. Sampling and monitoring requirements for AOSS treatment systems with flows greater than 1,000 GPD are contained in Table 3:

Table 3 Sampling and Monitoring for Large AOSSs
PLANT SIZE	>2.0 MGD	>1.0 - to 2.0 MGD	> 100,000 GPD to 1.0 MGD	> 40,000 GPD to 100,000 GPD	>10,000 GPD to 40,000 GPD	>1,000 GPD to 10,000 GPD
Flow	Totalizing, Indicating, & Recording	Totalizing, Indicating, & Recording	Totalizing, Indicating, & Recording	Totalizing, Indicating, & Recording	Measured	Measured or Estimate
BOD5, TSS	24-HC* 1/day	24-HC 5 days/wk	8-HC 3 days/wk	4-HC 1 day/wk	Grab quarterly	Grab 1/yr
Total Nitrogen	24-HC weekly	24-HC weekly	8-HC monthly	4-HC quarterly	Grab quarterly	Grab 1/yr
TRC, End of Contact Tank**	Grab daily	Grab daily	Grab weekly	Grab weekly	Grab weekly	Grab 1/yr
Fecal Coliform***	Grab weekly	Grab weekly	Grab monthly	Grab monthly	Grab quarterly	Grab 1/yr

*HC – hourly, flow weighted composite samples

**if disinfection required and chlorine used

***if disinfection required and a disinfectant other than chlorine used

G. Systems with direct dispersal to ground water as described in 12VAC5-613-90 C shall comply with the following:

1. Small AOSS treatment systems:

a. Shall incorporate a method to remotely monitor the operation of treatment units and processes, including the status of the disinfection unit, and automatically notify the operator and local health department if an alarm condition occurs;

b. Shall be sampled quarterly in accordance with 12VAC5-613-90 C and as defined in the renewable operating permit; and

c. No treatment units or systems shall be deemed generally approved.

2. Large AOSSs must be continuously monitored for the proper operation of all treatment units. If the wastewater treatment works is not manned 24 hours a day, telemetry shall be provided that monitors all critical systems, including turbidity into the disinfection unit and the functionality of the disinfection unit, and notifies the operator and local health department if an alarm condition occurs.

a. Treatment works with a design flow of less than 40,000 GPD shall be sampled at least monthly in accordance with 12VAC5-613-90 C and as defined in the renewable operating permit.

b. Treatment works with a design flow of 40,000 GPD or greater shall be sampled at the frequency specified in Table 3 of this section. Total phosphorus and other limited parameters not listed in Table 3 of this section shall be conducted at a frequency defined in the renewable operating permit. The treatment works must comply with the continuous operability requirements of a Reliability Class I rating as described in 9VAC25-790. Appropriate backup power sources, equipment redundancy, and failsafe modes must be in place.

3. Ground water monitoring is required for all large AOSSs with direct dispersal of effluent to the ground water and such monitoring shall be conducted in accordance with the renewable operating permit.

Historical Notes

Derived from Volume 28, Issue 05, eff. December 7, 2011; Errata, 28:6 VA.R. 641 November 21, 2011.

Statutory Authority

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