Virginia Law

A. A professional engineer designing a treatment works pursuant to § 32.1-163.6 of the Code of Virginia may deviate from the design criteria in subdivisions 10, 11, and 13 of 12VAC5-613-80 and from the laboratory sampling location specified in 12VAC5-613-100 B through F in accordance with this part.

B. Designs pursuant to this part shall at a minimum be substantiated by:

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

2. Relevant peer-reviewed research; or

3. Regulations or technical guidance from other states or the U.S. Environmental Protection Agency.

C. The soil treatment area shall be adequately sized to accommodate the hydraulic and organic capacity of the underlying soil to be used;

D. Sampling and monitoring pursuant to 12VAC5-613-100 B through F may be accomplished either in situ, immediately beneath the soil treatment area and within 24 inches of the point of effluent application, or within the treatment system at a point identified by the design engineer.

1. The professional engineer shall provide a sampling and monitoring plan to demonstrate that the design complies with the water quality standards in 12VAC5-613-90.

2. For in situ monitoring, the design engineer shall specify locations within the soil treatment area's zone of influence (i.e., mounding) where samples representative of the effluent quality being achieved by the treatment works can be collected. Monitoring wells or lysimeters shall be located at least six inches above any seasonal or permanent water table. Monitoring may be conducted using sampling wells, lysimeters, or other methods approved by the department. Suction lysimeters may not be used for fecal coliform monitoring.

3. The design engineer shall identify an intermediate compliance point (or points) within the treatment system along with corresponding constituent concentrations (e.g., BOD₅, fecal coliforms) for use if in situ monitoring is not desired or if an in situ sample cannot be obtained for any reason. The intermediate compliance point and the corresponding constituent concentrations shall be approved by the department. The AOSS operation permit shall be conditioned upon compliance with the constituent concentrations approved pursuant to this subdivision.

E. The following additional performance requirements shall apply to in situ monitoring:

1. BOD₅ less than or equal to 5 mg/l.

2. Fecal coliforms less than or equal to 2.2 col/100 ml.

F. The frequency of sampling shall be in accordance with 12VAC5-613-100.