WATER STORAGE ASSESSMENT AND RELATED IMPROVEMENTSGreat Falls, Montana
About the ProjectThe City of Great Falls maintains several water storage facilities located within its distribution system. In 2012, the City retained AE2S to conduct detailed assessments for five steel storage facilities.
The Seasonal Clearwell at the Water Treatment Plant (WTP) site (2 million-gallon ground storage), the surge tank at the 33rd Street Pump Station (30,000-gallon pump station storage), the Gore Hill Water Tower (500,000-gallon elevated tank), the Skyline Water Tower (750,000-gallon elevated tank), and the Ella Avenue Water Tower (750,000-gallon elevated tank).
Date: 2017 – 2018
Client: City of Great Falls
- Steel Storage Assessments
- Final Design, Bidding, and Construction Phase Services
- Construction Sequencing Strategies
- Temporary Distribution System Operating Strategies
- Coating Application Specifications and Enforcement
- Electrical and SCADA Improvements
- Hydraulic Modeling
On-Site Field Evaluation Findings
Based on the on-site field assessments (including live float down inspections), the Seasonal Clearwell was recommended for demolition to coincide with major improvements slated at the WTP, and the Gore Hill Water Tower (500,000-gallon) and the 33rd Street Surge Tank were also identified for demolition and replacement.
The Skyline Water Tower and the Ella Avenue Water Tower were recommended for complete reconditioning consisting of structural improvements, safety improvements, and sandblasting and re-coating of the interior and exterior surfaces.
Demolition, Reconditioning, and ReplacementDesign of the 33rd Street Surge Tank replacement and reconditioning of the Skyline Water Tower and Ella Avenue Water Tower was initiated in the fall of 2013. The project was bid as three separate contracts in April 2014, and favorable bids were received.
Refurbishment of the Ella Avenue Water Tower was completed in October 2014. Refurbishment of the Skyline Water Tower was completed during the 2015 construction season. The 33rd Street Surge Tank was replaced in late 2014, which was bid as a glass-fused-to-steel tank to prevent corrosion of the tank and extend the service life.
Undertaking the reconditioning of the water towers was viewed as a risky endeavor by the City, based on past experiences. However, clear specifications defining contractor qualifications and performance requirements, coupled with competent inspection services, mitigated the risk and resulted in a successful project.
The high performance coating system was inspected prior to the expiration of the two-year warranty period, and only minor touch-up work was required. The coating systems are anticipated to last 20-25 years.
Electrical Design ImprovementsThe City of Great Falls enlisted AE2S to complete the final design of electrical improvements at the Gore Hill Pump Station. The pump station consists of three split case horizontal booster pumps, ranging from 75-200 horsepower, with an approximate capacity of four million gallons per day (MGD).
The electrical design consisted of complete replacement of service feeders, main switchgear, installation of an automatic transfer switch, 16-inch water main extensions, and eternal emergency backup power connections.
In addition, AE2S designed the replacement of existing constant speed across the line starters with all new variable frequency drives to improve electrical efficiency and process performance. Due to water system demands, timing of the construction of new electrical gear was critical to the project.
AE2S worked in cooperation with the City to develop critical path scheduling to minimize water service impacts. In addition, AE2S Instrumentation and Controls staff performed onsite controls systems startup of all new systems to provide a seamless startup for the City of Great Falls.
Due to these efforts, the total shutdown time for the Project was less than 30 mins, over the course of the six-month project.