Flats East Bank Combined Sewer Outfall

In August of 2008 Independence Excavating was awarded the contract to install two new combined sewer outfalls, a new pump station, various storm and sanitary sewer improvements and remediation work on a 25 acre parcel in the Flats area of Cleveland. The project was being performed by a developer but funded by several sources including Clean Ohio, various grants and loans from local and federal government agencies and partial funding by the North East Ohio Regional Sewer District.

The overall goal was simple; remediate a former industrial area, install new infrastructure and prepare the site for building a new mixed use development that includes an office building, hotel, retail stores, a grocery store and a waterfront park. The NEORSD funded a portion of the new infrastructure since it needed to be completed to meet EPA standards for combined sewer outfalls the discharge into a common waterway.

The concrete construction of the pump station consisted of a 7’ thick base mat foundation which supported the 35’ below grade cast in place structure and the 22’ above grade masonry building. The below grade portion of the building was 48’ in diameter x 42’ deep. The foundation walls stepped vertically from 36” to 20” thick. EFCO’s Redi Radius form system was utilized on the project for the tall radius walls. The below grade structure was divided into two sections by a 12” thick concrete wall which separated the wet and dry well areas of the pump station. There are many structural slabs and formed concrete stairs throughout the station which vertically segregate the dry well section.

Several thousand feet of 14” and 10” force main were installed to service the new pump station.

Several thousand feet of 14” and 10” force main were installed to service the new pump station.

The work included installing a 65’ diameter cofferdam that was excavated to a depth of 38’ to allow for the construction of a new 8 million gallon per day pump station. The cofferdam was installed only 25’ from an existing overhead Rapid Transit Authority bridge and 20’ from an active Conrail freight track. These tracks had a major impact on the design and construction of the pump station. Crane access had to be limited to not encroach on either track since one had overhead catenary lines and the other carried freight at speed.

While the pump station was being constructed nearly all of the existing utilities were removed and replaced to accommodate the future construction and the re-configuration of the combined sewers to meet the EPA requirements. Much of the work such as the excavation and backfill activities were funded by the various government agencies due because of the contamination present on the site. Over 4,700 LF of various size storm and sanitary sewers were installed along with 100 LF of box culvert, 7 cast in place vaults, new outfall and several regulators. Several thousand feet of 14” and 10” force main were also installed to service the new pump station.

The Results

During the construction the groundwater that we encountered had to be tested and treated before being discharged into the sanitary sewer. The excavated soils also had to be stockpiled, tested, categorized and removed. Contaminates that were encountered included petroleum in the form of gas and diesel, coal tar and benzene. All water pumped from excavations had to be pumped through a series of frac tanks, weir tanks, particulate bag filters and carbon filter media to remove all of the suspended solids, liquids and benzene prior to discharge. Millions of gallons were treated on-site as part of the project. The soils were carefully excavated and segregated based on the type of contamination, they were protected and contained until the proper method and type of disposal was identified by the analytical testing. Independence Excavating supplied 40 hour OSHA trained personnel to perform the remediation work and we contracted with various specialty companies to perform the treatment and disposal of the solids and liquids removed from the site. Once the utilities were started various bentonite collars were installed to prevent the migration of water in the utility trenches from one are to another.


Cleveland, Ohio


Independence Excavating installed two new combined sewer outfalls, a new pump station, various storm and sanitary sewer improvements and completed remediation work

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