Rhode Island Code of Regulations › Title 250 - Department of Environmental Management › Chapter 150 - Water Resources › Subchapter 10 - Wastewater And Storm Water › Part 6 - Rules Establishing Minimum Standards Relating to Location, Design, Construction and Maintenance of Onsite Wastewater Treatment Systems › Section 250-RICR-150-10-6.36 - Pressurized Drainfields

Current through June 14, 2024
A. General design
				  parameters for all pressurized drainfields
1.
				  All pressurized drainfields shall include timed-dosing, with the use of a
				  control panel containing elapsed time meters and cycle counters for the pump(s)
				  and alarm(s).
2. Setback to
				  foundation and tanks: The minimum setback distance from the pressurized
				  drainfield to any foundation shall be eight feet (8'), provided that the
				  elevation of the basement slab in the dwelling is above the design seasonal
				  high groundwater table (SHWT) depth and that there are no drains associated
				  with the foundation. The minimum setback distance from the pressurized
				  drainfield to any tank equal or larger than one thousand (1,000) gallon
				  capacity shall be four feet (4').
3. Setback to structures impeding groundwater
				  flow: The interior face of any structural or landscape retaining wall that may
				  interfere with ground water flow, down-gradient from the pressurized
				  drainfield, must be located at least twenty five feet (25') from the
				  pressurized drainfield.
4. All
				  setbacks and all other regulatory requirements contained in the Department
				  Rules, that are not mentioned in §§
											6.36,
				  6.37, and
				  6.38 of this Part, shall be
				  met.
5. Designs greater than nine
				  hundred (900) gallons per day: Where design flows exceed nine hundred (900)
				  gallons per day, the Department may require additional technical studies to
				  ensure that the soil will accept and transmit effluent at the proposed loading
				  rate without excessive mounding of ground water; seepage outbreak, such as at
				  nearby cut slopes, toe slopes or property boundaries; adverse effects on the
				  operation of the pressurized drainfield; or adverse effects on nearby ground
				  water and surface water resources. The Department shall reserve the right to
				  require additional supporting engineering calculations for the use of
				  pressurized drainfields on design flows greater than two thousand (2,000)
				  gallons per day. The Department may require increased setbacks depending on the
				  site specific conditions. In addition, commercial systems with high strength
				  waste shall incorporate added treatment components to ensure treatment limits
				  herein for BOD5, TSS and FOG are achieved prior to using a pressurized
				  drainfield.
6. Pressurized
				  drainfields must be designed by a Class II or III Licensed OWTS Designer unless
				  the Department determines otherwise. No designer or installer shall undertake
				  the design or installation of a pressurized drainfield pursuant to Regulations
				  unless he/she has received appropriate training by a vendor, professional
				  organization, or institution recognized by the Department for this purpose. Any
				  licensed designer or installer must document to the Department that applicable
				  training has been completed. Class I designers can submit designs to the
				  Department for low pressure pipe (LPP) that follow septic tank effluent only.
				  Class I designers must document to the Department completion of training
				  regarding pressurized dosing (selecting a pump for pressurized systems) that
				  has been conducted by a professional organization, or institution recognized by
				  the Department for this purpose.
7.
				  Residual head: Designs should account for a minimum of two feet (2') of head
				  (pressure) at the distal end of each distribution lateral.
8. Design maintenance notes: Designers should
				  provide adequate notes on their plans to facilitate proper maintenance of all
				  system components.
9. Drainfields
				  at different elevations and zoned drainfields: Site conditions may not
				  facilitate installing drainfield trenches or zones at the same elevation. In
				  these situations, gate valves can be used to provide uniform wastewater
				  distribution. Alternately, orifice plates may be used to help equalize flow to
				  trenches that are not at the same elevation. Ball valves shall not be
				  considered a suitable means for flow control. Access ports must be installed at
				  the locations of all valves, lateral ends and orifice plates. Careful attention
				  should be given to drainback when placing trenches or zones at different
				  elevations since uneven drainback may overload zones or trenches. Types of
				  drainfields that can be placed at different elevations shall conform with the
				  Rules.
10. Sequencing valves:
				  Access ports or manholes shall be required for sequencing valves and shall be
				  sufficiently sized to facilitate maintenance.