Wentzville Water System Master Plan + Improvements

Wentzville is located in western St. Charles County, Missouri, and is the fastest-growing city in Missouri, for two consecutive decades. The City of Wentzville’s existing water system was nearing capacity with a rapidly growing community and associated water demands. The existing distribution system capacity was struggling to keep up with peak-hour demands while maintaining adequate system pressure. The City also needed to diversify its water source to improve reliability since the water supply for the entire community was primarily dependent upon the uninterrupted operation of a long single-feed transmission main from its wholesale potable water supplier.

With the exception of a single emergency well supply, Wentzville purchases all of its potable water from a nearby water utility. The majority of the supply connections are located near the southeast portion of the distribution system, with the majority of Wentzville’s growth occurring on the north and west sides of the community. The significant distance between the supply and continued community growth placed significant strain on the capacity of the existing distribution system requiring significant improvements to continue to support the community’s growth.

The City of Wentzville retained HR Green to perform a water system study and build a hydraulic model of their system. The plan included a complete review and evaluation of the authority’s water supply and distribution system for areas of concern, functionality, useful remaining life, water loss, and the necessity for improvements.

HR Green built the water model utilizing the Watergems software package. Information from the City’s four supply connections, single well site, and pump information was added to the model and calibrated with known pressures in the system to represent the operation of the City’s current four pressure zones. The hydraulic model was used to evaluate system performance during a current average day and maximum day demand conditions as well as a projected future growth average day and maximum day demand condition. Steady-state and extended-period simulations were utilized.

Upon completion of the model, it was utilized to identify problems and deficiencies in the water system. A 10-year implementation plan was developed to address the deficiencies in the system. The final report entailed details of the existing facility flow, system pressures, other operational issues, alternatives for improvements, costs for all alternatives, and recommendations based on sound engineering judgment.

Following completion of the master planning, the City of Wentzville retained HR Green to proceed with the design and construction of a new deep bedrock aquifer well and well house to contain the well along with associated chemical storage and feed facilities including ammonium sulfate, polyphosphate, sodium hypochlorite, and sodium hydroxide. In addition to the new water supply facilities, the project also included a new 2-million-gallon spheroid elevated water storage tank and booster pumps allowing full utilization of the storage tank to shave high-demand periods while minimizing costly distribution system improvements.

The new well supply provided a new lower-cost potable water supply closer to the growing northern and western portions of the distribution system, allowing more time for the City to implement costlier upgrades to their distribution system piping. The new supply and storage tank eliminated immediate concerns with lower system pressures during peak hour demands, while the booster pumps provided the City even more operational flexibility to peak shave peak hour demands while maintaining higher system pressures.