On-Site Wastewater Treatment and Disposal Systems - Forced ...

4. Crushed stone or gravel placed around the distribution pipes
should be 3/4 to 2-l/2 in. (2 to 6 cm).
5. Filter cloth or equivalent should be used on top of the rock or
gravel to prevent sand from settling into the aggregate, thus
reducing the void capacity.
6. Care should be exercised in assembling the perforated distri-
bution pipes (4 in. [lo cm]) to prevent pipe glues and solvents
from contacting the synthetic liner.
7. The bed surface should be sloped for positive drainage.
8. A relatively porous topsoil, such as loamy sand or sandy loam,
should be used if required to support vegetation to prevent
erosion, or to make the appearance more acceptable.
9. The bed should be located in conformance with local code re-
quirements.
10. Construction techniques described previously for subsurface
disposal systems, where soil permeability may be decreased by
poor construction practices, should be used for ETA systems
(39) (40) (41).
7.3.2.7 Operation and Maintenance
Routine operation and maintenance of an ET or ETA disposal unit consists
only of typical yard maintenance activities such as vegetation trimming.
Pretreatment units and appurtenances require maintenance as described in
Chapter 8. Unscheduled maintenance requirements are rare, and stem
mainly from poor operating practices such as failure to pump out septic
tank solids.
7.3.2.8 Considerations for Multi-Home and Commercial
Wastewaters
ET systems may be applicable to small housing clusters and commer-
cial/institutional establishments, but large area requirements may limit
their practicality. Adjustments in the type of pretreatment used may be
required depending on the wastewater characteristics. For example, a
grease trap is normally required prior to septic tank or aerobic treat-
ment of restaurant wastewater disposed of in an ET system.
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