
2018 Indiana Design and Installation Manual
22
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4.0 Sloped Subsurface Bed Design and Installation
4.0.7 ROWS REQUIRED:
All bed systems shall have a minimum of two rows of modules.
4.0.8 ROW LENGTH:
Rows will have a maximum of 100 ft in length unless pressure dosed per 410 IAC 6-8.3 (74)
(r) or ISDH Rule 410 6-10.1 (82) (r).
4.0.9 EQUAL LENGTH:
Rows must be of equal length in order to provide equal distribution.
4.0.10 DISPERSAL AREA:
Dispersal area requirements are located in
IAC 6-8.3 (58) or ISDH Rule 410 6-10.1
(62).
4.0.11 MINIMUM SLOPE REQUIREMENTS:
Maintain a 3:1 slope or gentler for all slopes off the application area.
4.0.12 SUBSURFACE DRAINS:
If subsurface drains are utilized they must remain 10 feet from the edge of the
system sand perimeter.
4.0.13 SIZING GSF SYSTEMS:
TABLE 5: GSF SLOPED SUBSURFACE BED SIZING CHART
Soil
Loading
Rate
(gpd/sf)
Minimum Basal Area
Required (Square Feet)
A42
Modules
per Room
B43
Modules
per Room
Bedrooms per House
3
4
5
1.2
252
335
419
6
6
0.75
402
536
670
8
7
0.6
503
670
838
9
8
0.5
603
804
1005
11
9
0.3
1005
1340
1675
12
10
0.25
1206
1608
2010
13
11
Notes:
The Minimum Basal Areas have been adjusted to reflect a 33% reduction in absorption field area.
Any jetted bath tub with a capacity greater than 125 gallons will be treated as an extra bedroom for the system sizing requirements per Rule
410 IAC 6-8.3.
4.0.14 SYSTEM LENGTH AND WIDTH:
Best engineering practices should be used when construction the bed
systems. Rule IAC 6-8.3 (79) (2) and ISDH Rule 410 6-10.1 (87) (2) states the dimensions of the bed shall be as
long and narrow as the site allows.
4.0.15 BED DESIGN
: For all slopes greater than 0.5%, Eljen recommends moving the upper most lateral a distance
of 1.5’ to 2’ (for A42 and B43 respectively) from the upper edge of the basal area while maintaining a minimum of
6 inches between the module and the upper edge of the basal area. For sloping sites greater than 0.5%, you shall
have a distance between laterals of 3’ for A42 and 4’ for B43’s.
4.0.16 SAND EXTENSION:
For subsurface bed systems on slopes between 0.5% and 10%, a minimum of 4 feet
of INDOT SPEC 23 sand extending from the edge of the furthest downslope GSF module is required. For slopes
between 10% to 15%, a minimum of 6 feet of INDOT SPEC 23 sand extending from the edge of the furthest
downslope GSF module is required. If the design calls for less sand than prescribed above, add a downslope sand
extension to meet the minimum 4 or 6-foot sand requirements from the edge of the furthest downslope GSF module.
Содержание GSF A42
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