Happy 2023 to all our members! We are embarking on an exciting, challenging phase for the Herring Ponds Watershed Association (HPWA) where we can improve the water quality of both Great Herring Pond (GHP) and Little Herring Pond (LHP). We thank our members for their support in this endeavor and the Board of Directors for their foresight and dedication to water quality.

Background

Great Herring Pond has been considered “impaired” by Massachusetts because of reduced clarity and high phosphorus pollutant levels. Most years, the result of high phosphorus levels has been summer green algae blooms that are “inconvenient” but not the potentially toxic cyanobacteria. This all changed in 2020 when a toxic cyanobacteria bloom was observed that shut down Great Herring Pond for two summer months. In 2021, a shorter, two-week cyanobacteria bloom occurred and although no cyanobacteria bloom occurred in 2022, the phosphorus problem still exists and needs to be addressed.

Although phosphorus is the culprit in both algae and cyanobacteria blooms, higher temperatures and reduced pond flushing rates due to summer drought favor the cyanobacteria. Rainfall patterns and warming trends will result in more frequent cyanobacteria blooms if nothing is done to reduce phosphorus levels in our ponds.

Partnership with the Town of Plymouth

David Gould (Director) and Kim Tower of the Plymouth Department of Marine and Environmental Affairs (DMEA) have subsidized our water sampling, secured grants for studying and remediating runoff into GHP, helped maintain testing equipment and provided a wealth of knowledge to guide HPWA’s water quality efforts.  HPWA has generously donated funds (again, thanks to all of you!) for purchase of conservation land in our watershed, helped new watershed association startups in Plymouth, and assisted the DMEA in identifying and characterizing cyanobacteria blooms in other Plymouth ponds. Because of this relationship, Plymouth agreed to fund $70,000 of the $80,000 cost of a Water Quality Plan for HPWA to enable it to identify the cause(s) of the phosphorus pollution and suggest ways to remediate it.

Through your generosity, we were able to raise the HPWA $10,000 share in only two weeks! Samples for the Water Quality Plan (WQP) were taken in 2021 and we received the draft of the study from the consultant in August of 2022. Thank you!

A Bit of Pond Chemistry

The main pollutant in the freshwater ponds of southeast Massachusetts is phosphorus. It is an ingredient (second number on the bag) of fertilizer, but, like so many things, too much of it is harmful. In general, the main source of pond phosphorus identified in the WQP is septic systems, followed in order by atmospheric deposition on the pond surface, and then runoff. In some ponds, summer bottom sediments can be a significant source. GHP and LHP have differing sources of phosphorus. Septic systems are the primary source of phosphorus to LHP, but flow from LHP is the primary source of phosphorus to GHP, followed closely by septic system sources. Bottom sediments provide phosphorus only in GHP, only in summer and only account for 12% of its total. Identification of the sources of the phosphorus and where and how it enters the water was the first goal of the WQP so that effective prevention methods can be implemented.

Water Quality Plan Draft Review

Besides myself, the HPWA Board of Directors (BOD) chose a Review Committee consisting of Jack Kedian, Geri Williams, Paul Denoncourt, Tom O’Brien, Jerry Levine, Brian Harrington, Lee Pulis and Jim Smith to examine the draft and devise questions in order to ensure that the course of action would be optimized for workability, affordability and timing. After receiving the draft in August 2022, The Review Committee met 7 times and reduced the 125-page Draft Water Quality Plan to 2 pages of planned next steps involving long-, interim-, and short-term approaches. On December 16, the Review Committee met with consultant Ed Eichner and Kim and David to decide the next steps.

Water Quality Plan Conclusions

The WQP identified septic as the major source of phosphorus in LHP and GHP. Of great interest was that the largest single share of GHP phosphorus comes from LHP. LHP is not troubled by cyanobacteria blooms because it is rapidly flushed. Although it is large, it is shallow and is supplied by a substantial watershed, contributing large amounts of groundwater. However, it transfers most of its phosphorus to GHP. So GHP management options could address LHP septics and/or treat the LHP water in the stream between the two ponds. GHP could also be treated but LHP phosphorus needs to be addressed regardless. The study states that if the amount of phosphorus in GHP can be reduced to 50 kg in April, cyanobacteria blooms might be eliminated in the summer.

The WQP draft provided long-, interim-, and short-term suggestions for improving watershed water quality. Long-term, sewering 128 to 178 Ponds of Plymouth homes (LHP) and 116 to 168 homes northwest of GHP provide the best guarantee of improved water quality. Realistically, it will be expensive and require a lot of time to provide sewer to our watershed.

Accordingly, short-term and interim-term solutions were proposed. These included Permeable Reactive Barriers (PRBs) that could remove phosphorus from Carters River before it enters GHP, treatment of old bogs and GHP deep holes with alum, modification of runoff storm drainage, reduction of LHP runoff. and use of floating islands where plants take up pond phosphorus. Meanwhile, a monitoring program that includes flow measurements, must be initiated. Grant money may be available for some of these options.

Way Forward

Plymouth DMEA and Ed Eichner of TMDL Solutions are currently working to develop a workable, fundable, doable, permittable program forward. Ed Eichner will be making a Zoom presentation on Tuesday, January 24 at 6:00 PM to answer questions and to explain the findings of the Water Quality Plan. Our mutual goal is not to just come up with a way forward, but to devise the best possible, workable way forward. Please plan to attend and ask your questions.

The Zoom meeting link is https://us02web.zoom.us/j/85084874259