Page 10 - May-June2018

Chattanooga from page 9 an overall Consent Decree program SSO Reduction
basis as described throughout this A complete database is collected and
feet of pipe to identify areas where section.
unwanted groundwater or stormwater can RDII Removal maintained regarding reported SSOs
infiltrate the sanitary sewer system. From in the system. Wet-weather SSOs are
the SSES, approximately 41,000 linear To quantify the effectiveness trended on a regular basis to review
feet of sewer and service pipeline and the of overall basin rehabilitation, project results. The city reviews the
associated manholes were rehabilitated. monitors are placed at the exit of SSOs reported occurring during pre-
These repairs were completed to help the sewershed and at any entrance SSES and rehabilitation periods to
reduce SSOs in the area. Construction points to the sewershed. To quantify similar rainfall events during post-SSES
was completed in early 2018. The cost to the effectiveness of project-specific and rehabilitation periods and makes
complete was approximately $2.2 million. rehabilitation, monitors are placed representative comparisons as a factor
upstream and downstream of the in evaluating the performance of the
Dobbs Branch 3: This project involved rehabilitation as close as possible constructed rehabilitation. Preliminary
a SSES on approximately 45,000 linear to eliminate as much of the non- results of completed projects indicate
feet of pipe to identify areas where rehabbed sewer as possible. Utilizing a substantial decrease in SSOs at
unwanted groundwater or stormwater can the pre- and post-flow monitoring all project sites and, in some areas,
infiltrate the sanitary sewer system. From data, the city performs an RDII elimination of SSOs.
the results of the SSES, approximately analysis on completed projects.
33,000 linear feet of sewer and service Preliminary results from 2009-2017 of For more information on the City of
pipeline and the associated manholes completed projects shown in the graph Chattanooga’s CD program upgrades, visit the
were rehabilitated. In addition, 800 linear below indicate the city is exceeding its Story Map here: https://earthworx.maps.arcgis.
feet of 78-inch pipe and the pump station Phase II reduction goal. com/apps/MapTour/index.html?appid=39dca8b
wet well were cleaned. These repairs were b743c4ac0896f054700b283ee
completed to help reduce sanitary sewer
overflows in the area. Construction was
completed in early 2018. The cost to
complete was approximately $3.6 million.

Friars Branch Basin Improvements:
This project involved a SSES on
approximately 214,104 linear feet of
pipe to identify areas where unwanted
groundwater or stormwater can infiltrate
the sanitary sewer system. From the
results of the SSES, approximately
24,000 linear feet of sewer and service
pipeline and the associated manholes
were rehabilitated. These repairs were
completed to help reduce SSOs in the
area. Construction was completed in
early 2018. The cost to complete was
approximately $6.6 million.

The city’s rehabilitation program is well
underway. The total linear footage of SSES
and rehabilitation is shown in the figure
above right.

Analysis of Completed Rehab
Effectiveness

The effectiveness of completed
rehabilitation is assessed with data
collected prior to and following
rehabilitation efforts. In particular, the
city reviews completed work and further
evaluates successful projects based on
RDII removal and SSO reductions. The
effectiveness of rehabilitation is analyzed
both on a project-by-project basis and on

10 TPW May/June 2018