Administrative Code

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Virginia Administrative Code
Title 9. Environment
Agency 25. State Water Control Board
Chapter 401. Sewage Treatment in the Dulles Area Watershed

9VAC25-401-30. Sewage treatment plant restrictions and requirements.

A. The number of sewage treatment plants discharging effluent to surface waters identified in 9VAC25-401-20 shall be no more than two, one to be under the authority of the Town of Leesburg and one under the authority of Loudoun County. The discharge from the treatment plants shall be in the Broad Run and Goose Creek Watersheds, a minimum of 10 stream miles upstream from the Fairfax County Water Authority water supply intake on the Potomac River.

B. The following maximum effluent limitations shall apply for the sewage treatment plants prescribed in subsection A of this section:


Monthly Average


10.0 mg/l


1.0 mg/l


1.0 mg/l

Total Phosphorus

0.1 mg/l


0.5 NTU

E. coli

less than 2 per 100 ml

The above parameters and all other pollutants shall also be monitored and limited as necessary in accordance with the VPDES Permit Regulation.

The owners of the sewage treatment plants are responsible for knowing nitrate concentrations in the vicinity of Fairfax County Water Authority's intake on the Potomac River. Should nitrate concentrations at the intake reach 5 mg/l, the owners shall evaluate measures they can take to minimize impacts their discharge has on the nitrate concentrations and implement those measures deemed feasible and effective.

C. Requirements for sewage treatment plants in subsection A of this section.

1. The design shall be such that expansions and maintenance of any unit can be accomplished without bypassing wastes to the receiving waters and without degrading treatment.

2. The mechanical and fluid system design shall be such that a single failure of a component or unit shall not interrupt plant operations that are required to meet the final effluent requirements in subsection B of this section.

3. There shall be one independent source of outside power supply and one on-site power supply. Both the off-site and on-site electrical distributions shall be such that the failure of any one given component (mechanical or electrical) in the distribution system shall not cause an interruption of electrical service to parts of the plant that are essential to meet the effluent requirements.

4. The treatment plants shall be staffed 24 hours a day, seven days a week.

D. Design requirements for pumping stations for sewage treatment plants in subsection A of this section. Pumping stations on all sewage collection systems that are connected to the plants identified in subsection A of this section shall meet the Reliability Classification 1 requirements as described in the Virginia Sewage Collection and Treatment Regulations (9VAC25-790), and shall have retention basins with a minimum of one-day capacity. A waiver from the retention basin requirement may be obtained from the Department of Environmental Quality if the owner of the pump station can demonstrate that a sewer system tributary to the pump station meets the infiltration or inflow criteria established by the Sewage Collection and Treatment Regulations, and any other such information that the department may require.

Statutory Authority

§ 62.1-44.15 of the Code of Virginia.

Historical Notes

Derived from Virginia Register Volume 20, Issue 25, eff. September 22, 2004; amended, Virginia Register Volume 36, Issue 12, eff. March 4, 2020.

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