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

1. Fred Vengrouskie
Alabama Department of Public Health
Onsite Program Evaluator
Soil & Onsite Sewage Branch
Division of Community Environmental Protection

3. 420-3-1-.67 Lot Modification and Controlled Fill Systems
(1) In the event that, due to site conditions and/or
characteristics of a given lot, a Conventional OSS cannot be
used in accordance with the preceding requirements of
these Rules, the LHD may consider approval of plans for
the installation of a Controlled Fill OSS or certain Lot
Modifications. Controlled Fill designs may be considered
only on sites where the fill selection, placement, natural
ground surface preparation and the entire Controlled Fill
construction process will be performed under the direct
supervision of, and certified by, a professional engineer.

4. (a) Site Evaluation - Prior to placing the fill,
the site shall be evaluated in accordance with
the Site Evaluation Criteria of the Onsite
Rules.
(b) Design Calculations – The engineer must
submit the design calculations for the
designed systems size and specifications.

5. 420-3-1-.71 Site Limitation Determination (SLD)
Site evaluations may be preformed using:
*
percolation test*
soil morphology
unified method*
soil mapping
Testing methods approved for Professional Engineers

6. Example: To design a basic controlled fill
septic system for a 5 bedroom house on a
building site that has a 60 MPI perc rate and a
restriction of ASHES at a 24” depth
First determine the design flow:
Design Flow = Number of bedrooms X 150
gallons per bedroom(Table 1)
Design Flow = 5 X 150 = 750 gallons

7. Design Flow
for dwellings

10. Number of bedrooms
X
“Square Feet per Bedroom” in
Table 3 and Table 3a
that corresponds to the measured or
assigned percolation rate

11. The linear amount of 36” wide gravel field line is
determined by multiplying the number of
bedrooms by the square feet per bedroom for the
Soil Texture Group/Perc Rate from Table 3 and
then dividing by 3.
Amount of field line = 5 X 300 ft2 = 1500 ft2
Linear feet(36” wide) = 1500/3 = 500 linear ft

12. Square
feet per
bedroom
Linear feet per
bedroom(36”)

13. Determine the Minimum Vertical Separation
For a 60 MPI perc rate the Minimum Vertical
Separation (MVS) is currently 24”(Table 15).
Note: The MVS for a 31 to 60 rate is currently
proposed to changed to 18”

16. Controlled Fill Systems or Mound designs for
sites with any limiting zone which will require
trench bottoms to be located at 0 to 6 inches
above the natural ground surface shall, as a
minimum, have 6 inches of fill material below
the trench bottoms.
* Does not apply to Drip

17. Trench Profile
Fill
12”
6”
Natural
Ground
Restriction
Ex: Restrictive Zone 24” ASHES @ 60 min/in
24”

20. Absorption Area
Reduced Absorption Area
Distribution Area
Reduced Distribution Area
Basal Area

22. Styrofoam aggregate
Multi-pipe
Chambers

24. The amount of EDF pipe as required in Table
3 or Table 3a (DA)
Required separation distances (5 feet from
sidewall to sidewall) between the EDF
trenches and the distance (5 feet) from the
trench ends or outer sidewalls to the
beginning of the Controlled Fill bed
side/endslope (AA)
Fill height and slope (3:1 or greater)

27. MVS changes from 24” to 12”
A 30” high system is reduced to 0”
because of the MVS break for secondary
treatment
No requirement to keep the field lines 6”
above the natural ground surface for drip.
The system requires much less
landscaping and drainage work

29. Required total area sq. ft.(DA) =
750gal/.2 = 3750 ft2 = 1875 linear ft of
tube/2 - 1000’ zones
No fill required with tubing installed at
a 6 to 12 inch depth but effluent must
be treated to secondary standards

30. Using LPP will reduce the controlled
fill system footprint
Provides equal distribution of effluent

32. Required total area ft2(DA) = 750gal/.4
= 1875 ft2
Absorption Area(AA) = (19+4) x (100+4)
= 23 x 104 = 2392 ft2
Basal Area(BA)
=(23+(2(3)(2.5))) x (104+(2(3)(2.5)))
=(23+15)x(104 +15)
= 38 x 119 = 4522 ft2

34. MVS changes from 24” to 12”
A 30” mound is reduced to 18” because
of the MVS break for secondary
treatment
Requires less landscaping and drainage
Smaller mound footprint

36. Required total area sq. ft.(DA) = 750gal/.6
= 1234 ft2
Absorption Area(AA) = (13 + 4) x (100 + 4)
= 17 x 104 = 1768 ft2
Basal Area(BA)=(13+ 2(3)(1.5))x(104+2(3)(1.5))
= (13 +9) x (104 +9)
= 22 x 113 = 2486 ft2*
*Smallest footprint allowed in current rules