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

water tables (see Chapter 3). Corrective actions include improving
surface drainage by regrading or filling low areas. High water table
conditions may be corrected in some instances by installing drains (see
Section 7.2.6).
Lack of maintenance of the treatment unit preceding
field may also be a cause of occasional failure.
point of infiltration and inflow during wet periods.
pumped and leaks repaired.
the soil absorption
The unit may be a
The unit should be
Continuous Failure: The causes of.continuous failure are more difficult
to determine. However, learning the age of the system when failure
first occurred is very useful in isolating the cause.
If failure occurred within the first year of operation, the cause is
probably due to poor siting, design, or construction. It is useful to
check the performance of neighboring systems installed in similar
soils. If they have similar loading rates and are working well, the
failing system should be checked for proper sizing. A small system can
be enlarged by adding new infiltration areas. In some instances, the
sizing may be adequate but the distribution of the wastewater is poor
due to improper construction. Providing dosing may correct this problem
(see Section 7.2.8). Damage to the soil during construction may also
cause failure, in which case the infiltrative area is less effective.
Reconstruction or an addition is necessary. Alternate systems should be
considered if the site is poor. This includes investigating the fea-
sibility of a cluster or community system if surrounding systems are
experiencing similar problems.
If the system had many years of useful service before failure occurred,
hydraulic overloading or poor maintenance is usually the cause. The
first step is to find out as much about the system as possible. A
sketch of the system showing the size, configuration, and location
should be made. A soil profile description should also be obtained.
These items may be on file at the local regulatory agency but their ac-
curacy should be confirmed by an onsite visit. If the system provided
several years of useful service, evidences of overloading should be
investigated first. Wastewater volume and characteristics (solids,
greases, fats, oil) should be determined. Overloading may be corrected
by repairing plumbing, installing flow reduction fixtures (see Chapter
51, and eliminating any discharges from foundation drains. If the vol-
ume reductions are insufficient for acceptance by the existing infiltra-
tive surface, then additional infiltrative areas must be constructed.
Systems serving commercial buildings may fail because of the'wastewater
characteristics. High solids concentrations or large amounts of fats,
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