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 3 - Sewage Treatment Works › Section 9VAC25-790-450 - Treatment works design

Current through Register Vol. 40, No. 24, July 15, 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.
1. Within buffer zones, neither residential
					 uses, high density human activities, nor activities involving food preparation
					 are to be established within the extent of the buffer zone. The extent of the
					 buffer zone perimeter is measured from the treatment units. Buffer zone
					 requirements for sewage sludge incinerator restrictions shall be established in
					 accordance with applicable state and federal regulations.
2. The department may approve a reduction of
					 up to one half of the listed buffer zone requirements based on one or more of
					 the following factors:
(i) site topography,
(ii) prevailing wind directions,
(iii) existence of natural
					 barriers,
(iv) establishment of an
					 effective windbreak,
(v) type of
					 adjacent development, and
(vi)
					 provision of enclosed units, as described in this chapter.
3. The prevailing wind direction should be
					 determined by on-site data. Local weather station records may be utilized if
					 they are demonstrated to be applicable. Attention should be paid to both
					 moderate and high speed winds since the high velocity winds often have a
					 prevailing direction different from the prevailing direction of moderate
					 winds.
4. A windbreak should be
					 located on both sides of the treatment works normal to a line projected through
					 the treatment works and the area that is to be protected, as close to the
					 treatment works as practicable. An effective windbreak may be comprised of
					 man-made or natural barriers that extend from the ground surface to a height of
					 16 feet. Alternatively, a cultivated tree windbreak may be developed by
					 planting at least four rows of fast-growing evergreen trees (pine family
					 preferred), planted on staggered 10-feet centers. Rows should be spaced no
					 greater than 16 feet apart. The minimum tree height at planting shall be six
					 feet, unless taller trees are required in order to provide a windbreak which
					 will be immediately effective. The variety of tree used should be readily
					 adaptable to the soil and climate at the treatment works site.
5. Reduced buffer distances will be
					 established for enclosed treatment unit operations or processes. Covered units
					 shall be provided with screened intake openings and positive forced draft
					 ventilation and shall have provisions for removal of aerosols and odors from
					 the exhaust.
6. Owners of existing
					 sewage treatment works or those treatment works proposed for upgrading shall
					 take whatever steps possible to provide as much of the required buffer as is
					 reasonably possible under the specific existing conditions at each treatment
					 works site. Wherever a demonstrated nuisance problem does exist, corrective
					 action (wind breaks or odor control measures, for example) shall be
					 undertaken.
7. The required buffer
					 zone shall be maintained by adequate legal instruments such as either
					 ownership, recorded easements, or restrictive zoning throughout the life of the
					 treatment works.
8. The director
					 may consider exceptions to the listed buffer zone requirements in accordance
					 with this chapter.