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SFPUC June 10, 2020 Page 11 • After each UV lamp break, the concrete floor is scrubbed and debris is removed to ensure that any mercury residue is removed to the maximum extent practicable. Any mercury- contaminated materials are packaged, labeled waste, and stored in the facility's hazardous waste locker for subsequent off-site disposal. Monitoring Monitoring recommendations described here are meant to optimize staff time and the quality of the data staff collect during and following a UV lamp break. Downstream Water Monitoring Water samples should be collected at the Alameda facility downstream over the period that water leaving the Tesla Facility during a UV lamp break passes (consisting of 5 samples: during the expected arrival time+/- 10 minutes and 20 minutes). The expected arrival time can be estimated as: Time delay(hrs) = 1711/Flowrate(million gallons per day, or MGD) Based on the typical range of flowrates (range of 140-290 MGD; average of 220 MGD), the travel time will be 6-12 hours. Results should be compared to the Safe Drinking Water Act's primary Maximum Contaminant Level of 2 pg/L for inorganic mercury [40 CFR 141.62(b)], although the instantaneous peak based on turbulent dispersion should be less than 0.6 ug/L. Ambient Air Measurements Worker should deploy the Jerome mercury vapor analyzer following each spill event to assess the level of elemental mercury vapor in the UV Building. The unit's detection limit of 0.5 ug/m3 is well below the OSHA limit of 25 ug/m3 and the SOP action levels of 3-10 ug/m3. The unit should be deployed to confirm that ambient air mercury concentrations are below industrial thresholds in the SOP. The Jerome analyzer should continue to be recalibrated annually. Visual Monitoring While cleaning UV lamp covers and the UV Building floor following a UV lamp break, workers should look closely for evidence of mercury droplets adsorbed to surfaces, taking notes on, and photographs of any identified mercury droplets, as described in the SOP. During maintenance of the pipeline downstream of the UV Building, workers should look closely for evidence of mercury on the pipeline walls and low points. Water Samples Water"grab" samples should be collected and analyzed for total mercury following each UV lamp break at the following locations, labeled consistently with these names: • Reactor drain (the drainage water from the closed-off reactor section) • Trench (standing water in the grated floor trench,upstream of the 4-inch weir) • Pond inlet(discharges from the below-grade culvert into Grit Pond#1