The wetted area is given by:
A w = (2 h prime(L 2+ W 2+2 h prime))/(sinβ)+ A 2
(5)
The time required for the basin to empty is given by:
T = (V)/(R × A w)
(6)
where R = percolation rate in gal/ft2/day.
The factor of safety is given by:
FS = 7/(T)
(7)
50' x 80' basin (bottom dimensions), 10' deep with 2:1 side slopes( = 26.6°), and an absorption rate of 20 gal/ft²/day.
A2 = (50)(80) = 4,000 ft 2
L 1 = L 2+(2 h)/(tanβ) = 80+(2(10))/(tan 26.6^circ) = 120'
W 1 = W 2+(2 h)/(tanβ) 50+(2(10))/(tan 26.6circ) = 90prime
A1 = (90)(120) = 10,800 ft 2