Akron Water Pollution Control Station No Feasible Alternative

water quality models. In most cases, the racks no longer overflowed, as
expected.
Another measure that is important when examining sewer separation is the
increase in storm water flows to the receiving waters. With separation, storm
water flows that were originally captured by the racks and sent to the WPCS
would no longer be captured. While separation would almost eliminate overflows
at the racks, there would be a substantial increase in storm flows to the receiving
waters.
The reduction in the overflow volumes, events, and hours of overflow at each
rack were determined. Included is the corresponding storm water flows (totaling
1774.4 MG). Rack overflows were reduced from 779.3 MG to 149.7 MG. Rack
40’s overflow was reduced by 251.4 MG, and secondary bypass at the WPCS
was reduced by 508.6 MG. The overall reduction in overflows and bypass was
1389.6 MG. Overflow events were eliminated at all but six racks (40, 29, 18, the
diversion chamber, 16 and14). In 1994, four major rainfall events triggered the
overflows, even with sewer separation.
Another important consideration with respect to the success of sewer separation
concerns footer drains as well as unidentified direct connections. It is well
recognized that sewer separation results do not measure up to original
expectations because of the impractical and improbable footer drain removal
success. Sewer separation has been implemented many times without
addressing footer drains. This is driven by the cost prohibitiveness of
removing/rerouting footer drains. Consequently peak flows in “separated sewer”
areas remain high and are unsuccessful. The inability to accurately identify and
remove from a sewer system all storm water connections in urban areas also
contributes to the lack of success with sewer separation projects.
Cost estimates performed for system-wide separation found this improvement
would be prohibitively expensive. Implementation of this improvement would
cause lengthy disruptions to traffic and other utilities, along with increased noise
and construction traffic in every combined sewer area of the City. In addition, the
recreational water quality benefit in terms of attainment of water quality standards
from system-wide sewer separation was found by the model to be insignificant,
and the overall biological water quality benefit is not predictable. Based on
insignificant water quality benefits of system-wide separation, the recreational
benefit of partial separation via inflow removal would also be insignificant.
However, inflow removal (defined as partial separation) remained in the
alternative matrix as a cost-effective means to eliminate or reduce the wet
weather volume reaching selected racks.
4.3.2.2. Express Sewers
The Facilities Plan 98 6 in Section 13.2.3.2 and associated supporting documents describes the
methodology and resources used to develop the capital, O&M and present worth costs for
express sewers CSO control. A summary of these resources and methods follows.
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