HPWA’s continued proactive efforts for the future of Little Herring and Great Herring Ponds
By Josh Adelson and Don Williams
Accordion SampThe study is a detailed examination of the health of both Little Herring and Great Herring Ponds. It is based on results from 1) a series of monthly tests from April to October 2021 including pollutants, dissolved oxygen, phytoplankton, clarity and others, 2) a study of the ability of 16 pond sediment cores taken from GHP and LHP to release phosphorus pollutant from that sediment both with and without dissolved oxygen present, 3) an extensive examination of Plymouth septic/cesspool records of residences near the ponds to estimate pollution due to these sources, 4) a runoff study to assess how much pollution is due to runoff, and 5) ingress and egress stream flow rates to determine how much phosphorus pollutant is derived from LHP, Carters River and GHP. Once completed and published, the Water Quality Plan will identify the major sources of pollution and suggest ways to mitigate them in both ponds.le Description
The study is being conducted by the Coastal Systems Program from the School for Marine Science and Technology at UMass-Dartmouth (SMAST). The study scope was developed collaboratively by HPWA, SMAST, the Plymouth Department of Marine and Environmental Affairs (DMEA), and TMDL Solutions LLC (TMDL). In addition, HPWA has provided historical pond data. SMAST has been evaluating water quality samples for HPWA for 7 years and has also performed a detailed runoff analysis of GHP. They were also engaged to conduct a similar Water Quality Plan study for Savery Pond in Plymouth that is nearing completion.
The consultants have been taking monthly samples since April and will continue to sample until October.
The last sampling will be in October 2021. SMAST will evaluate data from the multiple testing and research sources. They will document their findings for both ponds, including the pollutant sources and recommended mitigation strategies, in a Water Quality Plan report. Initial drafts of this will be reviewed by experts from the participating entities (HPWA, DMEA, TMDL) to ensure rigor and clarity. This review process should begin in April 2022. We expect the final report to be available to watershed residents and the general public in the summer of 2022. At that time, we will allow time for ample comment and questions by watershed residents.
Hopefully, by that time, we will have had several meetings with watershed residents and made preliminary decisions about how to correct the phosphorus pollution problem. We will then have to weigh carefully the expense, impacts on flora and fauna in the pond and reliability of the various possible treatments.
In April 2021, two divers collected sediment samples in both ponds. In GHP, at a depth of about 30 feet, the divers observed healthy plants at this depth and noted that the water was in a healthy state of oxygenation. They reported that both GHP and LHP are healthier than many of the other ponds that they have sampled. Of course, this does not protect us from the cyanobacteria blooms in summer, but it is nonetheless encouraging.
There are several possible causes for cyanobacteria blooms. Before 2020, GHP would have algae blooms that resulted from an excess of phosphorus in the water. In 2021, the pond water was much warmer, favoring cyanobacteria growth. Rainstorms were more severe causing more runoff and increasing the phosphorus load. Too much of any “good” thing is never good. Massachusetts has outlawed phosphorus in dish detergents, laundry detergents and in consumer fertilizers but there is still a lot of phosphorus left in the soil and in the pond sediments from the cranberry bogs that used to surround LHP and GHP. We cannot control the extremes in weather; our only recourse is to investigate ways to reduce the amount of phosphorus finding its way into our waterways. But first, before choosing an effective method to reduce phosphorus, the phosphorus source must be known. The Water Quality Plan will do that and suggest ways to reduce or eliminate the phosphorus.
It depends on what the recommendations are! Expense, suitability for the environment and reliability must all be considered. Using the Savery Pond Watershed example, they began their process a year ahead of GHP/LHP and they have just submitted the final suggested changes to the consultants. If we will need a grant to conduct a large-scale remediation, it is unlikely that anything can be done before the spring of 2023. If this can be expedited without denying ample review, it will be done but not at the expense of scientific rigor or resident input.
There are many different types of remedies, each with its own advantages and disadvantages. In parallel to conducting the study, HPWA will review our alternatives, with input from residents. It is premature to speculate on what the recommended changes might be at this time, but they might include earthen dams to prevent cranberry bog water containing phosphorus from reaching our waterways, chemically binding waterway phosphorus, better control of water withdrawals by area wells, and reduction of runoff (a previous study has identified the major runoff sites on GHP that could be remediated; 3 have already been done).
Cyanobacteria sadly is becoming a widespread problem and a Google search will quickly reveal different approaches, including chemical treatments, being tried. They are dependent on pond size, source of water, sources and variability of ground water and many other factors. The study will provide the best solutions based on the most current technology, applicable to the causes of pollution found for our ponds.
HPWA is driving this initiative but to act, we will need funding (the size of GHP assures that it almost any solution will be expensive) and of course approvals from the DMEA and other agencies. The Water Quality Plan Study will give HPWA a highly credible plan to tell a grantor what the problem is and how to fix it. We are hopeful that this, along with the reputation and cooperative relationships that HPWA has built over the years, will position us favorably for both grant money and approvals.
We will continue to post updates when we have them on our website at The Herring Ponds Watershed Association (where you can also sign up for our email newsletter) and our Facebook page at https://www.facebook.com/HerringPondWatershedAssociation. In addition, here are credible sites that have no commercial agenda: The Massachusetts DEP has an informational page on cyanobacteria blooms at https://www.mass.gov/guides/cyanobacterial-harmful-algal-blooms-cyanohabs-water. In addition they maintain a list of current affected bodies of water at https://www.mass.gov/alerts/harmful-cyanobacterial-bloom-advisories-in-massachusetts. CDC page https://www.cdc.gov/habs/materials/factsheet-cyanobacterial-habs.html In addition, you can contact me, and if I don’t know the answers to your questions, I will find them out for you.