PROJECT BACKGROUND

In the summer of 2020, Parker Water & Sanitation District (PWSD) began pre-construction efforts on the South Water Reclamation Facility Advanced Water Treatment (AWT) Filter Rehabilitation and Disinfection Improvements project. The goal of this Construction Manager at Risk (CMAR) project was to rehabilitate and upgrade existing infrastructure within PWSD’s South Water Reclamation Facility (SWRF), rated at two million gallons per day (MGD). Constructed in the 1980s, the plant required maintenance to renovate its aging infrastructure and equipment. The facility improvements were scheduled to take place while the plant continued to operate at maximum capacity. 

 

The most critical repairs were related to the AWT filters, which provide the plant’s tertiary treatment process. The scope of work included the selective demo and full rehabilitation of four steel AWT filter units. Each of the tanks had been previously lined with an unknown protective coating material that was failing. The previous coating had started to flake off in and around the edges of the steel basins, exposing the substrate to harmful wastewater corrosives. To prevent this from reoccurring, PWSD needed a quick, effective coatings solution that had proven edge retention. Edge retention is defined as the epoxy’s ability to retain its film thickness around sharp edges and transitions such as those observed in steel structures. While most coatings can exhibit sagging and a reduction in film thickness on edges that lead to accelerated corrosion rates, Warren Environmental’s (Warren) 301-14 formula resists this tendency. 

​

With 26 years of proven performance in the rehabilitation of various wastewater assets, Warren’s 100% solids, high build epoxy system was selected as the best value solution. A&W Coatings, master applicator of Warren’s epoxy, was contracted to complete the scope of relining the steel filters. The Warren + A&W team brought several benefits to the owner and the CMAR, including Warren epoxy’s quick cure time and single coat formula to save time in the schedule. 

​

SCOPE OF WORK

The AWT filter tanks were initially specified for a composite system with epoxy and fiberglass. The consulting engineer, Madero Engineers (MADERO), analyzed the specified system and prepared a report in which Warren’s system was capable of sustaining a high level of corrosion protection for the structures and providing similar levels of structural enhancement to the specified system. In addition, Warren epoxy’s rigorous testing and proven history of long-term performance demonstrated the product’s excellent edge retention—a key requirement for the relining project to succeed. With the project team’s review and approval of MADERO’s report, A&W’s Colorado-based crew first mobilized to the site to begin the coatings scope of work in March 2021. Our crew was tasked with removing the existing lining material, performing surface preparation, and re-lining each of the AWT filter units.  

​

A&W began the surface preparation stage with traditional, dry abrasive blasting to achieve the proper surface profile and cleanliness (SSPC SP-5) for each filter tank. Due to ongoing work in the AWT building and continued function at the plant’s full capacity during construction, 100% containment was not inherently possible. With greater than desired levels of dust escaping the designed containment system, our crew problem-solved by pivoting to wet abrasive blasting with a rust inhibitor for the remainder of the project—solving the issues out of our own volition without additional cost to the owner. This eliminated dust concerns for other trades working near A&W crew members in the AWT building and allowed the plant to function without further issues.  

 

With surface preparation complete, A&W’s crew lined the interior of each filter tank with 125 mils of Warren’s 301-14 high performance epoxy and the exterior of each tank with 50 mils of 301-14. The epoxy’s thickness was tested following application for quality assurance in accordance with NACE SPO188-99 and ASTM D4541-17. Our crew completed the work within four different mobilizations, each of which was three weeks long with approximately five to six weeks in between, allowing for the CMAR’s schedule to be expedited.  

​

PROJECT CHALLENGES

One of the largest challenges to overcome was the result of the dust containment system design. The system was designed to allow the plant to continue operating at full capacity and require the least amount of demo but was not able to contain 100% of the dust generated by blasting, requiring A&W to alter the design. The modifications included reducing two blast nozzles to one and changing the blast method to wet abrasive blasting while accounting for the extra time to implement these changes. Reassessing the best method of setup to prevent dust from escaping the containment made it easier and safer for A&W and other trades working in the facility, without incurring additional costs to the owner. 

​

A&W brought schedule and application flexibility to the project. The CMAR had a limited amount of time to bypass, as the plant was at maximum capacity. With a portion of incoming flow diverted, the plant could not be operated at partial capacity for long. This sense of urgency required clear coordination with the CMAR and PWSD to ensure the schedule could be maintained. Our crew completed the work swiftly with their minimal construction footprint, allowing them to get in and out efficiently. A&W completed each filter in two to three weeks, beating the best competing applicator’s proposed schedule of at least four to six weeks per filter, saving between eight and twelve weeks on the total project schedule and $150,000. 

​