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Virginia Administrative Code
Title 9. Environment
Agency 25. State Water Control Board
Chapter 790. Sewage Collection and Treatment Regulations
7/10/2020

9VAC25-790-70. Reliability Classification.

The department shall establish the reliability classification following discussion with the owner for inclusion in the engineer's design of the sewerage system or works. Reliability is a measurement of the ability of a component or system to perform its designated function without failure or interruption of service. Overflow criteria, such as a period of 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 will be a major consideration for discussion at the preliminary engineering conference described in this chapter. Pump stations associated with, but physically removed from, the actual treatment works may have a different classification than the treatment works itself. The reliability classification shall be based on the water quality and public health and welfare consequences of a component or system failure. Guidelines for classifying sewerage systems and treatment works are as follows:

1. Reliability Class I. Sewerage systems or treatment works whose location, or discharge, or potential discharge (i) is sufficiently close to residences, public water supply, shellfish, or recreation waters; (ii) has a volume or character; or (iii) for which minimal dilution of 10 to 1, receiving water volume to discharge volume, based on permit flow values is not provided year round, such that permanent or unacceptable damage could occur to the receiving waters or public health and welfare if normal operations were interrupted.

2. Reliability Class II. Sewerage systems or treatment works whose location or discharge, or potential discharge, due to its volume or character, would not permanently or unacceptably damage or affect the receiving waters or public health and welfare during periods of short-term operations interruptions, but could be damaging if continued interruption of normal operation were to exceed 24 hours.

3. Reliability Class III. Sewerage systems or treatment works not otherwise classified as Reliability Class I or Class II.

Unless designated as applying to a particular reliability class, all requirements specified in this chapter and standards contained in this chapter apply equally to all reliability classes.

Statutory Authority

§ 62.1-44.19 of the Code of Virginia.

Historical Notes

Former 12VAC5-581-120 derived from Volume 18, Issue 10, eff. February 27, 2002; amended and adopted as 9VAC25-790-70, Virginia Register Volume 20, Issue 09, eff. February 12, 2004.

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