The document describes a unique treatment scenario at the Tempe Water Treatment Plant caused by a historic September monsoon that dropped 3.29 inches of rain. The large rainfall caused acidic runoff which lowered the pH and alkalinity of the raw water source. To address this, plant operators performed lime shock feeding and adjusted lime dosing to carefully raise the pH within regulatory limits. They also implemented a split alum feeding to optimize chemical dosing and precipitation given the low alkalinity and high turbidity of the raw water during this event. Proper calculation and testing of alkalinity and chemical feeding was crucial to effectively manage the water's acidity without overdosing.