Groundwater in the Great Lakes Basin

(Gorman and Halvorsen, 2006). Any system more
complicated than a septic tank with a gravity-fed
drainfield is considered to be alternative, for example,
a mound system. According to a survey of regulators in
the Great Lakes region, nearly all jurisdictions permit
the use of alternative systems, but a significantly
smaller percentage have codes that regulators feel are
adequate standards for alternative systems (Gorman
and Halvorsen, 2006). Alternative OWTS (Figure 2)
use components such as pumps, aerators, filters and
controls which require regular maintenance and are
more prone to failure (Gorman and Halvorsen, 2006).
In the Great Lakes region, where many new homes are
being constructed in sensitive areas, effective programs
for regulating OWTS are more important than ever
(Gorman and Halvorsen, 2006).
The mound system, the most common type of alternative
OWTS in the Great Lakes region, consists of a
septic tank, a pump chamber and a soil absorption
bed. It is used where native soil is thin and/or the
water table close to the surface, thus requiring that the
absorption bed be embedded in a raised mound of sand
(Figure 2). Clarified effluent is pumped from the septic
tank via the pump chamber in controlled pressurized
doses to the soil absorption bed. The sand acts as a
medium for aerobic bacterial digestion and secondary
treatment of effluent. Since this system distributes
water in controlled pressurized doses, there is less
chance for localized clogging. Nonetheless, solids must
be pumped periodically from both the septic tank and
the pump chamber. Additionally, special maintenance
and site preparation are required to ensure that effluent
does not leak at the base of the mound (Wisconsin
Department of Commerce, 1999).
The permitting of alternative systems involves two key
challenges: the added difficulty of assessing the ability
of these designs to perform, and the increased importance
of maintenance (because of the greater use of
pumps, filters and controls than conventional systems)
to ensure proper operation. Since these systems are
located on highly desirable but highly environmentally
sensitive land, the consequences of failure increase.
These challenges are compounded because alternative
OWTS are used in areas less suited to on-site
wastewater treatment and are therefore less capable of
buffering contamination related to failure.
Even trained individuals have difficulty in evaluating
the suitability of an alternative system for a particular
site. Lack of communication at point of sale increases
the likelihood that homeowners acquiring alternative
OWTS will be unfamiliar with the relatively high
level of maintenance required for this type of system
(Gorman and Halvorsen, 2006). Wisconsin is often
cited as having a particularly good OWTS code. Their
approach accommodates alternative technologies but
requires maintenance contracts and connects OWTS
permitting to planning efforts. Wisconsin implements
uniform standards and criteria for the design, installation,
inspection and management of OWTS so that the
system is safe and will protect both public health and
the water. The regulation, which does not dictate the
selection of certain OWTS, instead sets parameters,
options, prohibitions and limitations for the design of
OWTS (Wisconsin Department of Commerce, 2007).
GROUNDWATER CONTAMINATION FROM
SYSTEM FAILURE AND SEPTAGE DISPOSAL
The U.S. Environmental Protection Agency (EPA)
considers OWTS a significant source of groundwater
contamination (Gorman and Halvorsen, 2006). The
close proximity of on-site wastewater systems and
water wells in developed areas, reliance on poor soils
for on-site disposal, relatively shallow water table
depth (less than 15 feet for most of the Great Lakes
Basin) and the general lack of awareness by homeowners
about proper septic tank maintenance pose a
significant threat to public health (Lovato, personal
communication). In fact, septic systems are the
perceived source of non-point groundwater pollution
in 81% of watersheds and represent the number-one
cause of non-point groundwater pollution in Michigan
(Falardeau, 2006). Density of septic systems is correlated
to occurrence of viral waterborne disease (Mark
Borchardt, personal communication). Tracers from
failing septic systems can emerge from groundwater to
surface water within 1 to 2 hours of a flush (Joan Rose,
personal communication).
Other related sources of non-point pollution include land
application of septage from both septic tank pumping
and “porta johns,” municipal sewer infrastructure
breaks and leaks, illicit connections and “pit” latrines
and outhouses. An estimated 120 million gallons of raw
septage are pumped from septic tanks in Michigan
alone each year, and half is applied to land disposal sites
with little or no treatment (Fishbeck et al., 2004). Raw
septage from temporary toilets is also often land-applied
in Great Lakes jurisdictions. Ontario has banned land
application of raw sewage/septage, but not treated
sewage or biosolids (McLeod, 2003). More than half of
the about 300,000 tonnes of Ontario biosolids produced
each year is spread on land (Ontario MOE, 2006). The
Canadian government had originally proposed a ban on
all land application of untreated septage to be in place by
2007 (ECO, 2005; Mason and Joy, 2003). This deadline
has since been pushed aside awaiting the creation of
additional treatment facilities (Kovessy, 2008).
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