The monitoring results for August are available on our monitoring results tracking spreadsheet. The monitoring results have also been added to our website 2024 sampling season spreadsheet. The results may be accessed from the Water Quality Monitoring Tab at the top of the TRWA website home page and clicking on either the sample bottle picture or link to the data under the Documents heading.
The results again show high levels of nitrate downstream of the Brockton WWTP (Matfield River 0.85 mg/l and Taunton River at Cherry St. in Bridgewater 1.04 mg/l, not as high as last month but double what we would like to see). This suggests that the Brockton WWTP plant may not have attained full operation of its nitrogen removal facilities. It also reflects lower available stream dilution (193 cubic feet per second (cfs) in August vs 351 cfs in June). The Town River below the Bridgewater WWTP had a similarly high nitrate level of 0.78 mg/l.
Total phosphorus (TP) levels are elevated in some locations like last month due to lower dilution, however, the instream levels benefited from low rainfall which contributed less TP containing stormwater to the rivers. TP measured in the Town River at Haywood St below Bridgewater WWTP was high again at 0.166 mg/l because Bridgewater negotiated a 10 year schedule until 5/01/2027 for installation of TP removal facilities. Fortunately the Bridgewater Clean Water Act permit schedule for total nitrogen was only for 5 years (completion required 5/01/2022). These levels of phosphorus are high enough to stimulate algae and weed growth in fresh waters.
The number of bacteria water quality criteria violations was similar to last month. River temperature was cooler which reduces bacteria levels while flow was slightly higher from a small rainstorm a few days prior which tends to increase bacteria levels due to bacteria in stormwater runoff. This follows a similar pattern from last year’s results.
As our sampling moves through September and October we will be watching how river water temperature currently around 20 degrees C and stormwater runoff affect bacteria (and TP) levels. Our data last year and this year indicates that municipalities, commercial properties, state and EPA need to do a better job of stormwater management to keep bacteria levels in our rivers safe. More intense rainfall rates associated with climate change make addressing this problem critical.