After a heavy rain, plant influent flow suddenly increases from 3.0 MGD to 5.0 MGD. Within hours, final effluent TSS rises from 18 mg/L to 45 mg/L. Settleometer results show the SVI remains normal and steady at about 120 mL/g (no signs of bulking). You confirm the clarifier sludge blanket level is rising (from about 2 ft to about 5 ft) and solids are approaching the weirs. Aeration basin DO and pH are normal. Based on these observations, what is the best FIRST operational action to respond to this hydraulic shock load and reduce effluent solids loss?