Part 2. What we have seen since the outfall was relocated. MWRA response to exceedances.
In summer, the effluent discharged at the Massachusetts Bay outfall is trapped beneath the thermocline
October 1999 Ammonium concentration (NH4 + uM) Boston nearfield Cape Ann October 2000
Ongoing Monitoring Data reported to MWRA Threshold Exceeded? NO YES Annual Monitoring Report Nov 15 Notify: DITP Regulatory agencies OMSAP Public (web and libraries) 5 days Threshold Level Caution Warning Adjust operations if needed Review supporting data Collect additional data if needed < 90 days Evaluate MWRA contribution w OMSAP and regulators Plan/schedule to address MWRA impacts Report every 30 days to regulators, public on evaluations, action and follow-up Adverse impact? YES NO Quarterly Wastewater Performance Reports Evaluations, actions and follow-up
Contingency Plan threshold exceedances for 2000 Chlorine too high in treatment plant on 12/15/00. Control equipment installed. pH too low in treatment plant on 12/7/00. Artifact of sampling procedure. High chlorophyll in autumn 2000. A regional event. Low DO saturation in bottom waters in October 2000. Recognition of natural phenomena in revising the threshold.