Virginia Administrative Code
Title 9 - ENVIRONMENT
Agency 25 - STATE WATER CONTROL BOARD
Chapter 790 - SEWAGE COLLECTION AND TREATMENT REGULATIONS
Part III - Manual of Practice for Sewerage Systems and Treatment Works
Article 3 - Sewage Treatment Works
Section 9VAC25-790-450 - Treatment works design
Current through Register Vol. 41, No. 3, September 23, 2024
A. The sewage treatment process consists of a sequential, upstream to downstream, arrangement of unit operations that remove or modify contaminants through several treatment phases, including (i) primary, (ii) secondary, and (iii) tertiary. A conventional or established secondary treatment process will include primary treatment. Advanced wastewater treatment works include all three phases of treatment. Sewage treatment works should be designed to provide waste water treatment for the tributary sewage flows from either the estimated population 10 years hence or a capacity required by applicable state or federal requirements.
B. Location. A sewage treatment works site shall be located as far as practicable from any existing built-up commercial or residential area, which will probably develop within the design life of the treatment works. The treatment works site shall be (i) protected by a buffer zone, (ii) located to avoid flooding, (iii) provided with year-round access, and (iv) provided with ample area for any future expansion. The minimum distance between the locations of effluent discharges from separate treatment works on the same watershed shall be 500 feet.
C. Restrictions. All new primary and secondary sewage treatment unit operations shall provide the minimum buffer zones as shown in Table 2 (found in 9VAC25-790-460) unless they qualify for reduced requirements as provided in this chapter. Buffer zones for advanced treatment (AWT) and natural treatment operations will be established on a case-by-case basis considering the reliability requirements and process design. Buffer zones are areas of controlled or limited use.
D. Flooding. All mechanical and electrical equipment that could be damaged or inactivated by contact with or submergence in water (motors, control equipment, blowers, switch-gear, bearings, etc.) shall be physically located above the 100-year level or otherwise protected against the 100-year flood/wave action damage. All components of the treatment works shall be located above or protected against the 25-year flood/wave action level and remain fully operational. Consideration should be given to designing the treatment works in such a way as to facilitate the removal of vital components during more extreme flood events.
E. Closure. A closure plan shall be submitted to the department in accordance with this chapter.
Statutory Authority
§ 62.1-44.19 of the Code of Virginia.