ADPH – PUBLIC HEALTH AREA VIII TRAINING FOR PROFESSIONAL ENGINEERS And Associated Onsite System Professionals

1. Steven E. Speaks
P.E./P.L.S.
President
Larry E. Speaks & Associates, Inc.
535 Herron Street, Montgomery, AL 36104

2. • Bed- an infiltrative surface, square or rectangular in shape, with
no internal trench walls
• Limited Site Conditions- ie. setbacks, slope, walls, embankments,
limited area, vertical separation/restrictive layer
• Treatment is used

3. Gravel Field Standard Construction Specifications
(8)
As an alternative trench system, a bed may be utilized for conventional
systems in Group I, II, and III soils that are not to be modified in accordance
with Rule 420-3-1-.94 Controlled Fill System. All sewage subject to this
paragraph shall be pretreated to a minimum of the secondary standard.
(a) The total bottom area for all beds shall be computed as follows:
1. The bed length shall be computed by dividing the design flow by
the hydraulic linear loading rate in Column 2 of Appendix A,
Table 18, and rounded up to the next whole foot.
2. Bed width shall be computed by dividing hydraulic linear
loading rate in Column 2 of Appendix A, Table 18 by the
application rate in Column 4 of Appendix A, Table 18, and rounded
up to the next whole foot.

4. Gravel Field Standard Construction Specifications (Continued)
3. This shall be the area required for the bed regardless of the
configuration.
(b) For Texture Group 4A soils, it is recommended that the bed be configured
using the dimensions as calculated from this rule paragraph (8)(a)1 and 2. The
bed shall be constructed in accordance with the bed requirements of Converse
and Tyler’s Wisconsin Mound Manual with two exceptions:
1. The configuration (not area) may be varied if the lot requires it and
is approved by the LHD.
2. Low Pressure Pipe (LPP) and time dosing are required for all beds
regardless of the configuration, unless another method of distribution is
approved in a Product Permit or a Performance Permit.

5. For conventional systems on lots in Texture Group 1, 2, 3, and 4A soils and that
are not to be modified in accordance with Rule 420-3-1-.85 Gravel Field Standard
Construction Specifications paragraph (8)

6. (Continued)
PERC RATE
LINEAR LOADING RATE
min/inch
gal/d/ft
SOIL GROUP
U.S.D.A. Textures
BED/PAD LOADING
RATE
gpd/sq.ft.
5
10
15
10
10
10
Group I
Sand, Loamy Sandy
2.27
2.27
2.27
20
25
30
9
8
7
Group II
Sandy Loam, Loam
1.80
1.80
1.80
35
40
45
50
55
60
6
5.8
5.6
5.4
5.2
5
Group III
Sandy Clay Loam, Silty
Loam, Silty Clay Loam,
Clay Loam
1.21
1.21
1.21
0.71
0.71
0.71
65
70
75
80
85
90
4
4
3.5
3.5
3
3
Group IVa
Sandy Clay, Silty Clay, Clay
0.36
0.36
0.36
0.28
0.28
0.28
Group IVb
High Shrink-Swell Clay,
Poorly Structured Soil
0.28
0.28
0.28
0.28
0.28
0.28
95
100
105
110
115
120
NOT
SUITABLE

7. (Continued)
Daily Design Flow
Length =
Length =
Linear Loading Rate
450
Linear Loading Rate
Width =
Width =
Bed/Pad Loading Rate
5
5
.71
= 90
= 8
EXAMPLE:
3 Bedroom dwelling with a perc rate of 60 min/in.
*ROUND UP LENGTH AND WIDTH TO THE NEAREST WHOLE NUMBER.
The area calculated here is required. The configuration is recommended
see Rule420-3-1-.85 Gravel Field Standard Construction Specifications.

28. Reduced setbacks from 25’ to 15’ from drainage ways and embankments,
cuts or retaining walls, per Table 5.
Maximization of disposal area by utilizing different dimensions without
trench separation. Eliminates waste of square footage in conventional 3’
wide trench designs.
Reduction in the required REDF. Area required equivalent in square
footage as required for primary EDF.
Gives ability to maximize small areas of good soils.
Reduced minimum vertical separation distance from >50% rock
(weathered rock) from 18” to 12”.

29. (Continued)
Areas with difficult accessibility may design beds with EZ-Flow bundled
instead of gravel (reduction for EZ-Flow cannot be taken).
Greater flexibility on bed design with width/length to save trees and work
around other limited areas.
Given a conventional design for the primary EDF, treatment and bed
disposal can be specified for REDF.
Given good soil conditions, you can utilize 24” of gravel in beds to handle
occasional large volume of effluent (parties, holidays, gatherings, etc.).

30. Initial cost and periodic maintenance required for treatment atu’s.
Longer area required for placement of tanks.