2.0 SYSTEM DESIGN
© Presby Environmental, Inc., Design & Installation Manual, July 2020 Edition
8
Example Using Aquaworx Remediator:
268 ft
2
(Min. SSBA Task 2) / 21.5 ft (Task
4a) = 12.47 ft. 12.47ft – 4.5 ft (Task 4b) =
7.97 / 2 = 3.99 ft SSE on each side. Round
this value up to 4 ft for ease of
construction.
b)
Sloping beds:
For beds on sloping terrain,
the SSE is placed entirely on the down
slope side of the full depth SSBA. No SSEs
are allowed on the up-slope side or ends
of the full depth SSBA.
i.
For site slopes less than 5%: Follow the design procedure outlined in Task 5a except SSE shall be
placed on the downslope side of the full depth SSBA.
ii.
For site slopes equal to or greater than 5%: The minimum SSE for beds on slopes of 5% or more is
2.5 ft. The SSE may fan outward as much as 45 degrees on each side (see illustration in Section 2.3
on page 14) if there is a down slope constraint but can never provide less than a 2.5 ft SSE.
If the full depth SSBA from Task 4c is equal to or larger than the minimum SSBA from Task 2, add a 2.5 ft
SSE to the length of the full depth SSBA on the downslope side. If the full depth SSBA from Task 4c is
smaller than the minimum SSBA from Task 2, divide the minimum SSBA from Task 2 by the full depth SSBA
length on the downslope side of the bed from Task 4 then subtract the full depth SSBA width length from
the side of the bed perpendicular to the downslope edge of the bed. This results in the width of the SSE,
which is a minimum of 6 in thick and is applied to the downslope side of the full depth SSBA. If result is
less than 2.5 ft, increase extension to 2.5 ft minimum.
Design Example #1: Single family residence, two bedrooms, 27 mpi perc rate & single rectangular bed with long
axis parallel with the contour; make bed level.
Task 1: Determine number of EnviroFin Units Needed
EF units required from Table B = 4 units.
Task 2: Determine Minimum System Sand Bed Area SSBA Required
Table B shows a minimum system sand bed area of 134 ft
2
required for this daily flow.
Task 3: Determine Multiple Bed System Layout
N/A using a single bed configuration.
Task 4: Calculate the Full Depth System Sand Bed Area
a)
Full depth SSBA along long axis of EF = (# of EF units -1) x C/L ft + 11 ft).
(4 – 1) x 10.5 +11 = 42.5 ft. The minimum bed length will be 42.5 ft.
b)
Full depth SSBA along short axis of EF units = (# of EF Units – 1) x C/L + 4.5 ft. (1-1) x 0 + 4.5 = 4.5 ft.
c)
Calculate minimum full depth SSBA 42.5 x 4.5 = 191.25 ft
2
.
Task 5: Calculate System Sand Extensions
a)
Level site: The site will accommodate a sand bed length of 42.5 ft. A bed design of 42.5 ft x 4.5 ft
provides 191.25 ft
2
of SSBA, which is larger than the 134 ft
2
required by Task 2. In this case, there will
not be any SSEs.
b)
This is not a sloping site this step not necessary.
