Shallow-placed systems are systems which utilize a natural, undisturbed soil
horizon to treat and disperse effluent where the infiltrative surface is placed
at a depth of less than 18 inches from the original soil surface. Also see
Table 4.3. Shallow-placed systems may use the system designs similar to
in-ground systems; however, when shallow-placed systems are installed at less
than 12 inches from the ground surface, timed dosing shall be used to disperse
B. Septic effluent
prohibited. Septic tank effluent is prohibited for use in shallow-placed
systems because of the increased likelihood for human and vector contact with
Soil criteria when
utilizing secondary effluent. Secondary or better effluent may be utilized in
an shallow-placed system when all of the criteria in this subsection are met.
Also see Table 4.3.
1. Soil texture. In order
to assure effluent dispersal under adverse conditions while maintaining
adequate treatment capacity, shallow-placed systems installed shallower than 12
inches, which utilize absorption trenches, are limited to Texture Group I and
II soils. Any soil texture group may be utilized for absorption trench systems
installed between 12 and 18 inches.
2. Limiting features. A minimum of 12 inches
of soil is required beneath the trench bottom or infiltrative surface before
encountering soils with a seasonal or permanent water table. Additionally, to
assure adequate hydraulic dispersal capacity, bedrock and impervious strata may
not occur within 18 inches of the trench bottom.
3. Separation distances. Table 4.2 contains
the minimum setback distances between an absorption field and various
structures or topographic features.
Admin. Code §
Virginia Register Volume 16, Issue 16, eff. July 1, 2000. Systems Using Fill
§§ 32.1-12 and 32.1-164 of the Code of