| (a) Non-conforming technology. An integrated facultative
lagoon is a non-conforming technology and is subject to the requirements
of §217.7(b)(2) of this title (relating to Types of Plans and
Specifications Approvals).
(b) Integrated Facultative Lagoon Design.
(1) The length-to-width ratio of an integrated facultative
lagoon must be 3.0 to 1.0.
(2) A pit must not be less than 0.25 acre in total
surface area.
(3) The outer lagoon area must not be less than 10
times the surface area of the pit.
(4) A pit must have adequate volume to contain:
(A) 0.1 cubic foot per capita per year of sludge storage
for a minimum of 20 years; and
(B) two days of design flow above the sludge storage
area.
(5) The up-flow velocity in the pit must be less than
2.0 feet per day at design flow.
(6) If an integrated facultative lagoon has more than
one pit, influent flow must be split proportional to the pit volumes.
(7) An inlet must be located in the pit portion of
a lagoon.
(8) An outlet must be at a depth of 1.0 foot from
the lagoon surface.
(9) An integrated facultative lagoon must meet the
buffer zone requirements specified in §309.13 of this title
(relating to Unsuitable Site Characteristics).
(10) Depth.
(A) A pit must be at least 15 feet deep during normal
operating conditions, measured from the water surface to the influent
inlet point.
(B) An integrated facultative lagoon must have berms
around the pit.
(C) The berm height must be at least 5.0 feet or one-half
the depth of the outer lagoon, whichever is greater.
(D) The distance from the water surface elevation
during normal operating conditions to the top of the berm around
a pit must be at least 5.0 feet.
(11) Organic Loading. The organic loading into a pit
must not exceed 300 pounds of five-day biochemical oxygen demand
per acre of total lagoon area per day.
(12) Odor Control.
(A) An inlet to a pit must be 3.0 feet above the bottom
of the lagoon and the influent flow must be directed downward.
(B) An integrated facultative lagoon must be capable
of recirculating at least 50% of the design flow from an outlet of
the downstream lagoon.
(C) Oxygenated water from a downstream stabilization
lagoon must be recirculated to the surface of the integrated facultative
lagoon.
(D) An integrated facultative lagoon must prevent
siphoning of lagoon contents through a submerged inlet.
(13) Removal Efficiency.
(A) The design of an integrated facultative lagoon
must not be based on more than 60% organic removal efficiency in
the pit.
(B) The design of an integrated facultative lagoon
must not be based on a subsequent organic removal efficiency of more
than 50% in the outer portion of the integrated facultative lagoon.
(C) The design organic removal efficiency for the
entire integrated facultative lagoon must not exceed 80%.
(14) Detention Time. An integrated facultative lagoon
must provide a minimum of 21 days hydraulic retention time at design
flow.
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