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Guest
Column: Mishawaka counting on several steps to improve sewers
South Bend Tribune -
7/31
Mishawaka is one
of the 105 communities in Indiana with combined sewers. There are
more than 1,100 combined sewer communities nationwide. Combined
sewer systems are found in older communities and tend to be
concentrated in the Midwest and East.
Prior to the
1950s, sewers in Mishawaka and South Bend carried sanitary and
industrial wastes directly to the river without treatment. The
same was true for many cities. These sewers were built large
enough so that when it rained, stormwater could be conveyed to the
river in the same pipes. A 1930 study by the State Department of
Health described the St. Joseph River as grossly polluted. It
estimated that in Mishawaka and South Bend, the sewage of 125,000
people discharged into the river. Additionally, the wastewater
discharged by industries was equivalent in strength to 25,000
people.
The study
recommended that treatment works should be built and placed in
operation early in 1932. The Depression and World War II delayed
action until the late 1940s. By 1952 Mishawaka had built large
interceptor sewers to intercept these waste streams before they
reached the river and a wastewater plant to provide treatment to
these redirected sewage flows.
Although the
construction of wastewater treatment plants stopped the continuous
flow of sewage to our rivers, during wet weather these new
treatment plants could not handle the combined flow of sewage and
stormwater during large rainstorms. When the treatment plants and
sewers reached their capacity in wet weather, excess stormwater
and dilute wastewater carried in combined sewers were discharged
to the river at various points known as combined sewer overflows (CSOs).
Without these CSO relief points, sewers would back up and flood
basements and streets during heavy rainstorms.
Communities are
now prohibited from building new combined sewers. All new sewer
construction must be separated. One set of pipes carries sanitary
wastewater to the treatment plant and another set of pipes carries
stormwater to the river. However, the legacy of combined sewers
remains in the older core area of many cities.
Solving the
problem is complex and costly. The answer may not be to separate
all remaining combined sewers. Some communities with separated
sewer systems are still affected by stormwater getting into the
sanitary sewers and suffer sanitary sewer overflows during wet
weather. Since 1990 Mishawaka has reduced the volume of CSO
discharge to the river by 70 percent through a combination of
sewer separation in older areas and upgrading of the wastewater
treatment plant. However, federal and state regulations demand
that more be done to control CSOs.
In 2000,
Mishawaka was required by the state to submit a long term control
plan (LTCP) for further reduction of combined sewer overflows. All
of the state's 105 CSO communities will be required to develop
LTCPs. Mishawaka's plan recommends increasing the capacity of the
interceptor sewers and improvements at the wastewater treatment
plant to include innovative high-rate treatment options for wet
weather flows. The first-phase upgrade of the wastewater plant
will cost $33 million. Improvements to the sewer system will add
millions more. There is no federal or state grant money to help
communities pay for these improvements.
An expanded plant
would meet the requirement for further CSO control and provide
capacity for growth. Mishawaka's plan will provide treatment for
storms up to 0.8 inches. Larger storms would still result in
overflows, but the first flush of concentrated storm flow would be
treated. Ninety percent of all storms in Mishawaka are less than
0.8 inches. Sewer separation projects will continue to be a part
of the CSO reduction equation where they are cost effective
elements of larger improvement projects.
Reducing the CSO
problem will require a combination of control measures. In
Mishawaka there is no single solution. Separating all remaining
combined sewers to eliminate CSOs completely would be too costly.
It is estimated that total sewer separation in Mishawaka would
cost $50,000 per acre. To separate the 3,300 acres of remaining
combined sewer area would cost $165 million. Also, stormwater is
not pollution free and can contain high levels of bacteria and
pollutants. The EPA is beginning to regulate storm sewer systems
that may lead to control requirements similar to those now imposed
on CSO discharges. Bringing as much stormwater as possible to the
treatment plant is an effective way to avoid future costs if storm
sewer outfalls require treatment.
Mishawaka is in
the forefront in Indiana in facing the challenge of CSO control.
Protecting water quality is a priority as the river becomes a
focal point for the downtown. A blend of control measures will
ensure cost effective CSO reduction. It may take generations for
communities to completely solve the CSO problem but we have come a
long way since the 1920s.
Karl R.
Kopec is wastewater division manager for Mishawaka Utilities. He
lives in Granger.
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