General Trend of Low E.coli Levels in May Continues in 2017
May is usually a good month for E.coli levels in the Neponset River Watershed because of cooler temperatures and higher than average water levels in the river and streams. This May was no exception to that rule.
Only two points in the watershed had E.coli concentrations above the level that is safe for swimming and fishing. Those points were on Pecunit Brook (PEB008) in Canton and at Pine Tree Brook (PTB047) in Milton. Conversely, 95% of waterbodies sampled were safe for fishing and swimming in terms of E.coli. Both Pine Tree and Pecunit Brook are on our Hot Spot list and we have on-going investigations trying to track down the source of the E.coli contamination. We recently partnered with EPA to conduct pharmaceutical testing in these waterbodies and are awaiting the results of their analyses.
Early Signs of Major Progress in Meadow Brook
Meadow Brook in Norwood has long been the Neponset’s most polluted brook. It’s shown on the map as the yellow dot in the middle of Norwood label MEB001. The brook is severely polluted because the sewers near the brook have an under-drain structure. An under-drain is perforated pipe designed to keep groundwater away from the sewer and drain it into the brook. Unfortunately, as the sewers aged they started to leak and the under-drains began carrying sewage directly to the Brook. The town of Norwood has been investing a lot of money to repair the sewers and disconnect the under-drains in this part of town. We may finally be starting to see the positive impact of all of that investment.
The last time that Meadow Brook had E.coli levels that were deemed safe for fishing and swimming was November 2006, and we suspect that the cold weather may have had something to do with the low E.coli concentration observed that month. This is one of the reasons why we don’t monitor all year round anymore.
To put the change in water quality we saw in May in perspective, the average E.coli level for Meadow Brook over the past 9 years is 2,231 colony forming units (CFU). The amount that Massachusetts deems to be safe for swimming and fishing is 235 CFU. This month the E.coli concentration was 171 CFU.
Kudos to the Norwood DPW for all the progress they have made toward bringing Meadow Brook back to a healthy condition. The E.coli concentrations in Meadow Brook will certainly be something worth tracking this summer. We are very hopeful that this trend will continue and that the brook can begin to recover.
Chris Hirsch, NepRWA Environmental Scientist firstname.lastname@example.org