Virginia Administrative Code › Title 9 - ENVIRONMENT › Agency 25 - STATE WATER CONTROL BOARD › Chapter 790 - VIRGINIA POLLUTANT DISCHARGE ELIMINATION SYSTEM (VPDES) PERMIT REGULATION › Part III - Manual of Practice for Sewerage Systems and Treatment Works › Article 6 - Biological Treatment › Section 9VAC25-790-720 - Sewage stabilization ponds and aerated lagoons

Current through Register Vol. 40, No. 24, July 15, 2024
A. General design. Basins with surface areas
					 many times larger than conventional biological reactors, that utilize
					 relatively low (less than 500 mg/l) levels of biomass, are typically referred
					 to as stabilization ponds (if unaerated) but are referred to as facultative
					 lagoons if aerated. This section provides criteria for achieving final effluent
					 levels of 45 mg/l BOD5 and 45 mg/l, or higher suspended
					 solids, as permitted limits applicable to the geographic allowance for sections
					 of Virginia. This level of treatment has been established in accordance with
					 the federal requirements for secondary treatment equivalency as achievable
					 through the use of stabilization ponds and facultative lagoons. The design
					 information contained herein pertaining to features other than biological
					 treatment performance criteria shall apply to the construction of earthen
					 basins used in the treatment of sewage.
Stabilization ponds or facultative lagoons may be
						designed to achieve a higher degree of treatment or used as a biological
						treatment phase in conjunction with other unit processes. Proposed design
						parameters to achieve other than 45 mg/l BOD5 effluent
						limits shall be thoroughly reviewed with the area engineer during the
						preliminary engineering conference. Necessary features for protecting public
						health and welfare and preventing potential violations of water quality
						standards shall be addressed in the design report.
1. The engineering design report shall
					 contain pertinent information on location, geology, soil conditions, area for
					 expansion, and any other factors that may affect the feasibility and
					 acceptability of waste stabilization ponds or aerated lagoons used for sewage
					 treatment. Specifically, the report shall contain the following supplementary
					 field survey data.
a. The location and
					 direction of all residences, commercial development, recreation areas and
					 potable water supplies within one-half mile of the proposed pond or lagoon
					 site. If practicable, ponds and lagoons should be located so that local
					 prevailing winds will be in the direction of uninhabited areas.
b. Borings or other necessary geophysical
					 analyses required to determine surface and subsurface characteristics of the
					 immediate area and their effect on the construction and operation of ponds or
					 lagoons located on the site.
c.
					 Data demonstrating anticipated permeability at the elevation of the proposed
					 pond or lagoon bottom.
d. A
					 description, including maps showing elevations and contours, of the site and
					 adjacent areas suitable for expansion.
e. A closure plan shall be submitted to the
					 department prior to issuance of an operating permit.