Seems like ground water movement would dictate the placement of the absorption field, as much as the other factors.
Trenching the Absorption Field for the Infiltrators/Chambers
c) five communal septic tanks and absorption fields
(one set each in Heung Yuen Wai, Ha Heung Yuen, Tsung Yuen Ha, Chuk Yuen North, and Chuk Yuen South); and
Cover the absorption field
with hard surfaces, such as concrete or asphalt.
Thus, a location with soil suitable for an absorption field (a place that yields positive results on the "perc test") can be at a significant distance from the house and at a greatly higher elevation; the source of any potential leaching is sited away from the waterfront.
These "secrets" include more general application of trenchless technology, indoor installations, use of pressure sewers as a weapon in the fight against infiltration and inflow, flat-land use, and use as a stopgap measure in fighting waterfront pollution one house at a time--by re-siting absorption fields "up, up, and away" from the water's edge.
The BOD and solids are discharged to a soil absorption field, where they form an anaerobic layer, or "biomat," within the trench.
The pretreatment system allows higher soil loading rates, which prevents hydraulic overloading or reduces the size of the absorption field required.
Tank sizes, absorption fields
, and frequency of pumping are discussed,