Following heavy rainfalls, the combined sewer facilities beneath MLK Boulevard surcharged and the four-lane street became an open channel for excess flows. The City of Chattanooga hired CTI to perform an analysis of alternatives to eliminate surcharging in a seven-block area. The optimum solution was found to be construction of underground detention facilities providing 300,000 gallons of storm water storage.

Despite the numerous obstacles, the project was successfully completed on time and within the construction estimate.

Challenges

• Gas and electric lines, sewer junction boxes, BellSouth’s main fiberoptic duct bank, as well as the 110-year-old combined sewers inhabited the “nether region” of the busy boulevard, and some of these components were not recorded on any drawings of the project area.
• During design, it was discovered that gas and underground electrical services to former businesses in the area were still active. CTI coordinated the abandonment of gas and underground electrical services and adjusted the culvert design to avoid BellSouth’s fiberoptic duct bank.
• The schedule was compressed due to the upcoming conversion of the street from one-way traffic to two-way traffic. The street was closed completely for only 9 days to install the precast concrete box culvert. At least two lanes of traffic were kept open at all other times.
• Chattanooga’s annual Riverbend Festival “Bessie Smith Strut” down MLK Boulevard also took place in mid-construction; however, the festival was not adversely impacted.
• Two buried sanitary sewer junction boxes that were not shown in the historical records were unearthed during construction operations. Both boxes were incorporated into the sewer replacement.

Project Elements

• 300,000 gallons of underground storm water storage.
• Installation of 1,240 linear feet of pipe, 10 catch basins, 6 manholes, and 378 linear feet of 12x8-foot culvert.
• Streetscape with stamped concrete and lighting.
• Replacement of the combined sewer (new 24-inch and 42-inch PVC) on two blocks of Douglas Street, from 8th Street to 10th Street
• Construction of streetscape components for the north block of M.L. King Boulevard between Houston Street and Mabel Street, including:
  • Installation or adjustment of storm drainage structures
  • Asphalt repair