Florence Aerial Sewer Crossings

Florence Water & Wastewater Department
Lauderdale County, Alabama

The City of Florence raised concerns about two of their 40 year old 42″ steel aerial sewer lines to EOS. The interceptor sewer in question is one of two main sewer lines for the City of Florence carrying as much as 25 MGD during peak flow events. A testing consultant was hired to measure the thickness of the existing steel pipe with an ultrasonic instrument. These test results indicated that the pipe was at risk for failure. The pipe needed to be repaired or replaced in a timely manner.

Alternatives discussed and analyzed for repairing the existing pipe included interior lining, exterior lining, and welded on patches. Alternative materials considered for replacing the pipe included ductile iron or steel. After evaluating all options with the suppliers, manufacturers, and owner, replacing with steel pipe was selected as the preferred alternative. It was decided that the steel pipe with a high performance coating system would give the owner a lasting solution while also being cost effective. The use of steel pipe also enabled the existing concrete piers to be reused without modifications thus eliminating the need for costly construction in the creek.

The construction of this project was challenging. The contractor was responsible for bypass pumping the entire flows and was not allowed by the permitting authorities to get heavy equipment into the creek. The contractor made use of a small crane mounted on a barge for the lower crossing and a 250 ton crane on the south bank for the upper crossing.