Since 2008, we have collected water samples from Great and Little Herring Pond several times a year. When we started out, we were trained by Environmental Management (Kim Michaelis) of the Town of Plymouth. We collected water samples from several sites on Great Herring Pond, all about 50 ft from shore at storm drain discharge Locations.The following year, we added sites on Little Herring Pond and Carter's River. Samples were collected when there had been no rain for at least two days. They were immediately delivered to Envirotech Laboratory in Sandwich for analysis. The laboratory tested for parameters typically used to analyze drinking water, as can be seen from the data (side bar). Sample locations are marked on the two maps available on the water sampling map page.
Our sampling has evolved since. Details of our procedures can be found in our approved quality assurance project plan (QAPP). Our water sampling was supported between 2009 and 2012 by a three year grant from Massachusetts Environmental Trust and by the Town of Plymouth as well as our association members. It continues to be supported partially by the Town.
At present we collect water samples at 9 locations on Great and Little Herring Pond, and on Carter’s River, as marked on the two maps. Two of these locations are away from shore at the deepest points of Great Herring Pond, where samples are drawn from near the pond bottom as well as from the surface. The other locations sample surface water only. They are identical to locations used in the earlier tests. One sampling location is in the middle of Little Herring Pond. Two additional locations are at the beginning and end of Carter's River, the stream connecting the two ponds.
During each sampling event, we also collect a duplicate sample, as required by EPA procedures, to assure analysis integrity.
The laboratory analysis has also changed. At present, the laboratory analyzes for e-coli, total phosphorus, nitrates, nitrites, Kjeldahl (organic) nitrogen and total nitrogen, pH, electrical conductance, turbidity.
Results
Early partial results can be summarized as follows: e. coli counts are generally very low – we do not see any problems from septic systems, bird or other animal pollution. Nutrients (phosphorus) are low in winter, increase dramatically in Spring to very worrisome levels, cause serious algae blooms in summer and early fall, which are obvious from the reduction of water transparency, and then begin to decrease. The cause of the spring peak is of great interest, it may be, at least partially, due to human activities. It is, after all, the time when fertilizer is spread, but this is purely speculative. Nitrogen is fairly low. pH is neutral to slightly acidic.
