Measures of nitrates and fecal bacteria can indicate untreated septic discharge in surface and ground water. The plots below show these measures for West Acton, and indicate no septic contamination of the environment.
Fecal Bacteria
Fecal coliform is a class of bacteria that includes E. coli and other bacteria from human and animal waste. It has been monitored in Acton for many years. The average fecal coliform count for West Acton, 72, is lower than Acton’s average, which is 82. The plot below shows fecal coliform counts in West Acton (testing site FP-5C), as well as average counts for Acton. Much of the fecal coliform originates from wildlife, such as geese and beavers.
As a point of reference, the one-day limit for NARA park (Class A water) is 235 E-coli per 100 mL, while the limit for Fort Pond Brook (Class B water) is 409 E-coli per 100 ml. For comparison, NARA park has exceeded 235 E-coli per 100 mL in 9 of the last recorded 11 years, according to Acton Health Department records.
Nitrates
The Acton Health Department measured nitrate levels at monitoring wells from 2009 to 2013. In West Acton (site Massachusetts Ave/Fort Pond Brook), nitrate levels were found to be low, as shown below.
As a point of reference, the maximum nitrate level for drinking water is 10 ppm. Nitrate levels in West Acton stream water are consistently below 5 ppm.
Phosphates
The CWRMP, Phase I, lists the sources of phosphates as sewers, fertilizers, and storm water, with no mention of septic systems. Unfortunately, no phosphate testing in West Acton stream or ground water has been performed in recent decades.
