Using Modern Pigging Technology to Keep Your Force Main Clean The South Omaha Industrial Area Project

The South Omaha Industrial Area (SOIA) Project is an early action project undertaken by the City of Omaha, Nebraska, as part of their Long Term Combined Sewer Overflow (CSO) Control Plan to significantly improve water quality by reducing the pollutants in sewer overflows caused by meat packing waste mixing with stormwater. The upstream collection system serves Omaha’s meat packing district which contributes almost 65% of the sanitary waste loading at the City’s Missouri River Wastewater Treatment Plant (MRWWTP). The wastewater consists of high levels of BOD, fats, oils, and grease that travel to three possible overflow points during wet weather. To eliminate the potential for overflows, the City embarked upon a program to separate meat packing waste from the upstream combined sewers and deliver flows via a new 65,859 m3/day (17.4 mgd) lift station through dual 458 mm(18 inch) force mains and a 610 mm (24 inch) gravity sewer to new, dedicated industrial treatment facilities at the MRWWTP. Due to the unique nature of the grease within the waste, special considerations were taken with the design to allow for ease of cleaning of the force mains.Research conducted into technologies for keeping the lift station and force mains cleaned included a literature review, field visits to existing installations and meetings with contractors specializing in cleaning with pigging equipment. Features were adopted into the lift station and force main design to accommodate regular cleaning using polyurethane foam swabs and pigs. A single, stainless steel launcher was installed at the lift station operating level to allow for insertion of pigs into either force main while maintaining full pumping operations. Additionally, a retrieval chamber was included at the end of the force main prior to entrance to the gravity sewer. Special tracking equipment, inserted into the swabs and pigs and tracked from above at grade level, is used to track the location of the pig as it passes through to the downstream system. Regular use of the pigging equipment by City staff was incorporated into the contracting documents.