The Jacksonville (Florida) Electric Authority (JEA) is no stranger to undertaking large scale rehabilitation projects to address its sewer infrastructure needs. JEA is a publicly owned electric, water and wastewater utility in northeast Florida. The sewer collection system handles more than 75 million gallons of wastewater every day. The waste collection and treatment system consists of more than 3,800 miles of collection lines, 55,000 manholes, more than 1,300 pumping stations and 11 wastewater treatment plants.
Recently, JEA completed a major upgrade to its Mandarin Water Reclamation Facility. This facility is a regional sewer plant treating an average of 7.5 million gallons daily, with the ability to treat up to 8.75 million gallons per day (mgpd) and also reclaims treated wastewater for irrigation purposes. Some of the equipment and structures at the plant had reached the end of its service life and needed rehabilitation or replacement to keep the facility updated, modernized, reliable and structurally sound. Work included installation of new odor control systems, rehabilitation of existing concrete channel structures, the installation of a 1.6 million-gallon concrete storage tank and expanding the high-level ultraviolet disinfection system to increase the plants reclaimed water output.
These upgrades will allow the plant to send nearly all its treated wastewater to the reclaimed water system for irrigation purposes and not to the St. Johns River for discharge. The entire project took place in two phases beginning in 2016 through completion in 2017.
Rehabilitation of Existing Concrete Channel Structures – Challenges and Scope of Work
Mittauer and Associates, Orange Park, Florida, was the design engineer and John Collins of J. Collins Engineering Associates, Jacksonville, Florida, acted as the engineering project manager. One of the challenges in the design phase was to fully assess the damage to the concrete channel structures. As is typical with treatment plant headworks structures, hydrogen sulfide concentrations are some of the highest in the entire waste collection system and JEA was concerned about concrete deterioration. In addition to deterioration from H2S, the amount of grit moving through the channels was also a known concern adding to the deterioration of the concrete surfaces.
Inspection of the channels was not an option because the majority of them were under roof and under constant flow. Also, the structures had been coated previously but the condition of that coating was unknown. Considering this, the length of time the structures had been in service and concerns about previous coating failure, and the desire for the Mandarin Water Reclamation Facility to undergo a major facility upgrade to extend the service life well into the future, JEA decided to include all the concrete channel surfaces for rehabilitation.
This scope of work was to be performed in Phase 1 of the project and totaled 11,000 sq ft. WPC Industrial Contractors was awarded the contract and Concrete Conservation Inc. (CCI), a Spectrashield applicator since 1993, was awarded a subcontract for installing the lining system in the concrete channels.
Spectrashield was introduced in 1993 and is a product of CCI Spectrum, Inc. Since its introduction Spectrashield has been installed in more than 70,000 structures (more than 7 million square feet) in the United States, Canada, Eastern Europe and Australia through a network of licensed applicators. Spectrashield is a patented multi-layered polymeric lining system designed to stop infiltration and prevent corrosion. By stopping infiltration, Spectrashield has helped municipal utilities reduce O & M costs associated with treating unnecessary groundwater, and with its corrosion protection restores and adds life to aging structures. Spectrashield is cost competitive, an alternative to more traditional cementitious and expoy systems, has a 100-year design life, is a rapid trenchless application that can be installed in manholes, lift station wetwells and wastewater treatment plant structures, and all this adds up to a very low life cycle cost.
As with any large-scale sewer construction project, time is always of concern, particularly in this case with the length of time and cost to bypass 7.5 million gallons of sewage per day. Once the system was on bypass and inspected, many of the concerns were verified.
There was original coating failure in places and concrete deterioration throughout. Using the patented Spectrashield process, a unique multi-layered liner system that has ease of installation and fast curing times, CCI was able to mobilize in and out of the work site based on the Contractors scheduling needs and completed the 11,000 sq ft of Spectrashield lining in January and February 2017.
Rehabilitating these structures resulted in the prevention of future corrosion and infiltration/exfiltration issues. JEA and its customers can feel confident their money was spent wisely and these structures will perform as designed for years to come.