As COVID Variants Surge, Tracking Where They're Spreading In Mass. Remains A Challenge Chelsea public works employees Alex Arroyo (left) and Tony Rosa collect wastewater samples so they can be tested for COVID-19 variants Craig LeMoult / GBH News On a street corner in Chelsea last week, public works employees opened a manhole cover and pulled up a container hanging underground by a rope. Inside, a device had been pumping up samples of the wastewater flowing below every 15 minutes for the past 24 hours. They sucked up some of the cloudy wastewater with what looked like a turkey baster and transfered 50 milliliters into each of 3 test tubes.