Virginia Administrative Code › Title 12 - HEALTH › Agency 5 - DEPARTMENT OF HEALTH › Chapter 610 - SEWAGE HANDLING AND DISPOSAL REGULATIONS › Part V - Design and Construction Criteria › Article 5 - Subsurface Soil Absorption System › Section 12VAC5-610-966 - Pads

Current through Register Vol. 40, No. 24, July 15, 2024
A. A pad is
					 an absorption area wider than three feet but not longer than 100 feet with a
					 level infiltrative surface where the bottom of the pad meets the original soil.
					 The minimum standoff to a limiting feature in accordance with
					 12VAC5-613-80
					 is to be met under the entire infiltrative surface.
B. The minimum effluent quality dispersed to
					 a pad is TL-2 effluent and pad bottom loading rates shall not exceed the values
					 for pads noted in Table 5.5 of
					 12VAC5-610-950.
C. The longest dimension of the basal area of
					 the pad, its length, shall be oriented parallel to the natural surface
					 topographic contours. Minor deviations from surface contours are acceptable as
					 long as the bottom of the pad is level (the entire bottom surface of the pad is
					 at the same elevation, not to exceed 10% of the depth of the pad from the
					 ground surface or plus or minus two inches, whichever is less), and intersects
					 a similar soil horizon across its surface.
D. Pads and trenches may be used together in
					 a single system when the respective pad or trench subsystems follow the
					 respective design criteria found in this chapter and are separated by a minimum
					 of six feet between the sidewall of the pad and the trench. When multiple pads
					 are used on a site, the pads must be separated by the width of the pad as
					 measured perpendicular to the natural surface topographic contour.
E. Pads shall be limited to sites with slopes
					 of 10% or less (less than or equal to 10 feet of rise for every 100 feet of
					 run).
F. All pads must be dosed.
					 Pad systems over 1,000 gallons per day must be pressure dosed. When pads are
					 installed at less than 12 inches from the ground surface, timed dosing shall be
					 used to disperse the effluent.
G.
					 The minimum absorption area for single family residential dwellings shall be
					 400 square feet.
H. Pad
					 construction.
1. Gravel pads shall have a
					 minimum installation depth of 12 inches, unless in Texture Group I or II soils
					 where the installation depth can be reduced to eight inches. On sloping sites,
					 the minimum installation depth is measured on the downhill side of the pad
					 infiltrative surface. The construction of the pad's gravity percolation line
					 and gravel bedding shall follow
					 12VAC5-610-930
					 E with the exception that the bottom of the pad is level and not sloping.
					 Piping shall have a maximum center to center spacing of nine feet.
2. Gravel pads utilizing low pressure
					 distribution shall follow
					 12VAC5-610-940
					 for construction and dosing cycle (volume). Gravel pads using low pressure
					 distribution shall have a minimum installation depth of 12 inches, unless in
					 Texture Group I or II soils where the installation depth can be reduced to
					 eight inches. On sloping sites, the minimum installation depth is measured on
					 the downhill side of the pad infiltrative surface. Piping shall have a maximum
					 center to center spacing of nine feet.
3. Pads utilizing gravelless material as
					 found in
					 12VAC5-610-930
					 F shall follow
					 12VAC5-610-930
					 F and manufacturer instructions on minimum depth of installation, but in no
					 case shall a pad be installed at less than eight inches from the original soil
					 surface. Gravelless material shall have a maximum center to center spacing of
					 nine feet. On sloping sites, the minimum installation depth is measured on the
					 downhill side of the pad infiltrative surface.
4. Designs supported by a division approved
					 manufacturer's design manual may deviate from the maximum slope, depth of
					 installation, separation distance between pads, and timed dosing when the
					 dispersal area is constructed in accordance with the approved manual.