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 9VAC25-790-470 - Treatment works details

Current through Register Vol. 40, No. 24, July 15, 2024
A.
					 Equipment. The specifications should be so written that the installation and
					 essential items of mechanical equipment will be certified by a representative
					 of the manufacturer. The specifications shall require that the equipment
					 manufacturers provide to the owner one complete set of operational
					 instructions, equipment and maintenance manuals, and emergency procedures for
					 each essential mechanical and electrical equipment item. The manuals shall
					 contain drawings of equipment and a numbered parts list keyed to a list of
					 components.
B. Instrumentation.
					 Insofar as possible, all indicating, recording, and totalizing flow meters
					 shall be identical so that repair components and charts are interchangeable.
					 Recording equipment for dissolved oxygen, temperature, pH, and other operating
					 data, along with flow metering equipment, shall be located in areas free from
					 high humidity, extreme temperatures, and corrosive gases. Instrumentation
					 requirements for each treatment works shall be decided on a case-by-case basis.
Facilities for measuring the volume of sewage flows shall
						be provided at all treatment works. Treatment works having a capacity of equal
						to or less than 40,000 gallons per day shall be equipped with a primary
						metering device such as a Parshall flume with separate float well and staff
						gauge, weir box with plate and staff gauge, or other approved devices, as a
						minimum unless nonfluid contact measuring devices are provided. All treatment
						works having a capacity of greater than 40,000 gallons per day shall be
						equipped with indication, recording, and totalizing equipment. The recording
						scale shall be sufficient to accurately record and depict the flow measured.
						Flows passed through the treatment works and flows passed through controlled
						diversions shall be measured in a manner that will allow them to be
						distinguished and separately reported.
C. Component isolation. Properly located and
					 arranged diversion piping or structures shall be provided so that any component
					 of the treatment works process can be independently operated in accordance with
					 the reliability classification, or removed from service independently for
					 inspection, maintenance, and repairs. Adequate access and removal space shall
					 be provided around all components to provide for proper maintenance or removal
					 and replacement without interfering with the operation of other equipment. Due
					 consideration shall be given to the need for lifting and handling equipment
					 available to aid in the maintenance and replacement of all components. In
					 addition, the placement of structures and other devices, such as pad-eyes and
					 hooks to aid handling of heavy or large components, should be considered in the
					 preliminary design. These criteria for adequate access and handling equipment
					 do not apply to the removal or replacement of large tanks, basins, channels, or
					 wells. Lines feeding chemicals or process air to basins, wet wells, and tanks
					 shall be designed to enable repair or replacement without drainage of the
					 basins, wet wells, or tanks.
D.
					 Maintenance provisions. The design of a treatment works should facilitate
					 access for both routine maintenance and equipment failure response.
1. Provisions should be made for flushing,
					 with water or air, all scum lines, sludge lines, lime feed and lime sludge
					 lines, and all other lines that are subject to clogging. All piping subject to
					 accumulation of solids over a long period of time should be arranged in a
					 manner to facilitate mechanical cleaning if possible. The design shall be such
					 that flushing and mechanical cleaning can be accomplished without causing
					 violation of effluent limitations or without cross-connections to the potable
					 water system.
2. Provisions should
					 be made for dewatering each unit. Drain lines should discharge to points within
					 the system such that maximum treatment of the contents of the drained unit is
					 provided. Due consideration shall be given to the possible need for hydrostatic
					 pressure relief devices. Where practicable, all piping shall be sloped or have
					 drains (drain plug or valve) at the low points to permit complete draining.
					 Piping shall not be installed with isolated pockets that cannot be
					 drained.
3. Concrete, metals,
					 control and operating equipment, and safety devices shall, insofar as
					 practical, be designed to protect against corrosion, moisture and heat induced
					 damage.
4. Positive identification
					 of the content of a piping system shall be by lettered legend giving the name
					 of the contents. Arrows should be used to indicate direction of flow. Legends
					 shall be applied close to valves and adjacent to changes in direction, branches
					 and where pipes pass through walls or floors, and at frequent intervals on
					 straight pipe runs. The lettering shall be of such color, size, and location to
					 be clearly visible and readable.
5.
					 A complete outfit of tools and accessories for the treatment works operator's
					 use, such as wrenches, valve keys, rakes, shovels, etc., and such spare parts
					 as may be needed, shall be specified as either contractor or owner furnished. A
					 portable pump is desirable. Readily accessible storage space and work bench
					 facilities shall be specified. Consideration shall be given to provision of a
					 garage area that would also provide space for large equipment maintenance and
					 repair.
6. Concrete, paved, or
					 gravel walkways shall be provided for access to all units. Where possible,
					 steep slopes and narrow stairways shall be avoided to increase access for
					 maintenance. Surface water shall not be permitted to drain into any units.
					 Provision should be made for erosion protection and landscaping, particularly
					 when a treatment works must be located near residential areas.