As a result of continued growth and development, the City of Glendale, Arizona,needed to upgrade the existing Zone 1 and Zone 2 water booster stations locatedat the Cholla Water Treatment Plant (WTP) to meet increasing water demands. Inaddition, the City needed to investigate improvements to two 10 million gallonstorage reservoirs at the same site for water quality issues related to obtainingadequate chlorine contact time, if prechlorination at the Cholla WTP had to beeliminated for trihalomethane (THM) considerations. HDR Engineering, Inc. wasselected by the City to evaluate potential booster station upgrades and reservoirimprovements, and to design the recommended modifications. The recommendedproject included constructing a new Zone 1B Booster Station, with a tie-in to anexisting 48-inch transmission main, upgrading the existing Zone 1 Booster Station(now referred to as the Zone 1A station) with new pumps and 480 volt power, andadding two new pumps and piping to the Zone 2 Booster Station. The reservoirimprovements included adding a 66-inch diameter outlet structure and baffle wallto the Cholla 2 Reservoir, installing a new 48-inch diameter outlet structure inthe Cholla 1 Reservoir, and installing new 66-inch diameter interconnectingpiping between the two reservoirs and the booster stations. Implementation of therecommended modifications would impact the facilities for delivering water tothree of the City's four pressure zones. Consequently, a detailedconstruction-phasing plan was developed and incorporated into the projectspecifications to ensure that the water supply would not be interrupted duringconstruction of the various improvements. The construction effort was dividedinto four project phases, with interim construction milestones, over a 17-monthperiod to minimize the potential impacts to the storage and delivery system. Theconstruction phasing was also developed to coordinate the work effort at thissite with a treatment plant expansion project and a reservoir constructionproject ongoing concurrently at other locations in the City. Includes figures.
