Hillsborough County, Florida, Pre- and Post-Rehabilitation Effectiveness Project for Wastewater Assessment Project Using Electrical Resistance Testing

In May 2024 Hillsborough County, Florida's Water Resources Department (Tampa, Florida) contracted with Electro Scan Inc. (Sacramento, California) to complete a comprehensive condition assessment program of approximately 33,500 linear feet (LF), or 6.3 miles of wastewater collection system, with 25,822 LF or 89 sewer mains having pre- and post-rehabilitation assessed using electrical resistance testing. In contrast to most repair projects, the Hillsborough County Infrastructure Maintenance Division, Water Resources Department, wished to quantify the effectiveness of its repair & rehabilitation efforts in an area prone to repeated sanitary sewer overflows (SSOs) resulting from wet weather infiltration. Several factors contributed to the County's decision to conduct a comprehensive inspection of pre- and post-rehabilitation efforts, including: 1. Lack of quality control and quality assurance testing on previous repairs and rehabilitation. 2. Continued high rates of infiltration experienced during wet weather and king tide events. 3. Limited knowledge of engineering firms to pinpoint repair locations and recommend correct mitigation strategies. 4. Absence of finding substantive defects using traditional Closed-Circuit Television (CCTV) visual inspection data utilizing Pipeline Assessment Certification Program (PACP) standard coding. 5. The desire to compare and contrast the rehabilitation effectiveness of multiple repair methods, including Cured-In-Place Pipe (CIPP) lining and Chemical Grouting. 6. Significant capital expenditures in piping structures that appear to have little or no reduction in infiltration. Eighty-nine (89) sewer mains were surveyed before and after rehabilitation. Pipe diameters ranged from 8 to 12 inches, with either sewer mains lined with Cured-In Place Pipe (CIPP) trenchless rehabilitation or Chemical Grout used to seal service laterals or joints. While 11 percent of 2,967.4 LF of sewer mains registered 100% reduction in flow, 14 percent or 3,778.4 LF registered greater defect flow after rehabilitation, than before rehabilitation. Overall, estimated defect flow reductions, after rehabilitation, were 55%, indicating major infiltration still exists. Major conclusions from the four-year study indicate that: 1. CCTV and/or AI-CCTV should not be used as a basis for either rehabilitation selection or rehabilitation effectiveness. 2. Quality Assurance (QA) testing must be undertaken immediately following repairs or rehabilitation. 3. Engineering consulting firms must be more engaged in field work standards & procedures. 4. Electrical resistance testing is a valuable tool to quantify pre- and post-rehabilitation effectiveness to help address wet weather and tidal infiltration. Representing the nation's first multi-year study of pre- and post-rehabilitation effectiveness using multiple repair and rehabilitation studies, this paper shares how electrical resistance technology allows municipal sewer and stormwater utilities to conduct quality control and quality assurance testing on a timely basis. Often representing multi-year capital expenditure projects, that may include several professional consulting engineering firms and field contractors spanning many years, the ability to provide unambiguous and unbiased testing results, before and after repairs, rehabilitation, or remediation projects, ensures municipal and private water systems to achieve benefits promised by product suppliers, consultants, contractors, and vendors. Detail comparison of Focused Electrode Leak Location (FELL) and Closed-Circuit Television (CCTV) inspections conducted BEFORE and AFTER REHABILITATION will provide an eye-opening narrative of the strengths, weaknesses, opportunities, and threats (SWOT) of continuing a CCTV ONLY acceptance of repairs. Poor repair methods, lack of professional oversight, and collateral damage to underground assets that caused twenty percent (20%) of pipe defects to be greater AFTER REHABILITATION THAN BEFORE REHABILITATION, truly underscores the importance of this sessions. Comparison of an earlier project that compared CCTV and FELL inspections, calibrated with a multi-year flow meter used to help consulting engineers quantify defect flow reductions AFTER REHABILITATION, will also be presented. LESSONS LEARNED Attendees will benefit from the following lessons learned, including: 1. Developing and administrating a QA/QC Program for All Pipe Repairs, Rehabilitation, and Replacement Projects. 2. Specifying standard operating procedures (SOPs) to hold consulting engineers and contractors to minimum level of performances. 3. Testing approaches for a variety of pipe rehabilitation methods, including but not limited to the testing of Cured-In-Place Pipe, Chemical Grouting, and Point Repairs. 4. Suggested warranty terms and conditions.