Overnight rains, Bengaluru's heaviest in August in a century, has the city's Varthur Lake spewing foam and froth like never before. On Wednesday, the foam caused by toxic chemicals and untreated sewage in the lake rose to over 10 feet along the tall fence erected to keep the stinking cocktail of pollutants from spilling on to road in Varthur Kodi locality of east Bengaluru.