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In the Oyster Pond Watershed there are:

  • 211 parcels = 727 acres
  • 166 parcels =  271 acres
  • 225 dwelling units
  • 603 bedrooms
  • 48% seasonal use
  • 24% of land in conservation*
  • 8% of remaining vacant land is developable*
  • Wastewater 28,900-gpd, annual average
  • 160 dwelling units added since 1977

*estimated prior to Headwaters purchase

cover page Final OP Alternative Analysis
cover page

Wright-Pierce's July 30th Presentation

Powerpoint Presentation by Wright-Pierce on October 3, 2013

Falmouth Enterprise Article Feb 26, 2013 - Consultant Suggests Town Examine Goal for Quality of Oyster Pond

MA Surface Water Quality Standards 314 CMR 4.00

RFP for Oyster Pond Comprehensive Wastewater Management Plan (CWMP)

Article 17 - Spring 2011 Town Meeting - Wastewater Management Projects to Implement CWMP

The Scoop on Poop - Know Your Wastewater Options -
A video of the excellent Jan. 4, 2011 meeting at the Waquoit Bay National Estuarine Research Reserve

Nitrogen 101 - A primer on how nitrogen moves from our septic systems to estuaries

EPA Approval Letter of Oyster Pond TMDL for Total Nitrogen – May 5 2008

Final – Oyster Pond Embayment System Total Maximum Daily Loads for Total Nitrogen – Ma EOEA & DEP - Feb 7, 2008

Nutrient Management for Oyster Pond

How Did We Get Here?

The road to devloping a Comprehensive Wastewater Managment Plan for Oyster Pond

…. It was over 25 years in the making

In the mid 1980’s alert Falmouth residents noticed a profound change in our estuaries.

* Mid 80s - Pond Watchers Citizen Monitoring program initiated for Oyster, Litte and Green Ponds.

*1987 -  Town Meeting appropriated $5,000 “to conduct investigations of the physical, chemical, and biological characteristics” of Oyster, Little, and Green Ponds and to prepare a “comprehensive program for restoration, preservation and maintenance”.

* 1989 – Collapsed culvert at Surf Drive replaced with larger one increasing salinity and causing profound changes to the pond

* 1998 – Weir built to control pond salinity

* 2006 – Listed as an impaired water body due to nutrients & pathogens on Mass Clean Water Act 303 (d) list

* 2007 - Final Massachusetts Estuarine Project (MEP) report for Oyster Pond.

* 2008 Total Maximum Daily Loads (TMDLs) for nitrogen approved for Oyster Pond by the EPA and DEP.

* Aug 2010 – Buzzards Bay Coalition & Conservation Law Foundation file suit against EPA for “failing to properly manage sources of nitrogen pollution like septic systems, stormwater, & wastewater treatment plant discharges on Cape Cod including Falmouth and Bourne.”

*Spring 2011 - Falmouth passes a $2.7 million funding package for wastewater treatments and studies that includes $300, 000 for an Oyster Pond CWMP.

* Nov. 2012 Town issues an RFP for Oyster Pond CWMP

* Jan 2013 Wright Pierce is selected to develop the Oyster Pond CWMP.

Oyster Pond Comprehensive Wastewater Management Plan (CWMP)

The Town of Falmouth and the Town appointed Water Quality Management Committee (WQMC) have released the final version of the Alternatives Analysis for Oyster Pond.  This report is part of the Comprehensive Wastewater Management Plan (CWMP) for Oyster Pond.  

The WQMC is a town government committee investigating and pursuing solutions for the poor water quality in Falmouth’s estuaries due to high nutrient levels (nitrogen and phosphorus).  The high nitrogen levels are mainly due to too many septic systems in a watershed.  CWMPs will be developed for all of these water bodies.  The WQMC is exploring using everything from eco-toilets to sewers to inlet widening as treatment options, while tailoring them to fit the unique needs of each waterbody.  Oyster Pond is also suffering from poor water quality as shown by the algal bloom in the summer of 2016.  The bloom in part was due to the high level of nutrients in the pond. 

A CWMP considers all wastewater treatment alternatives and prepares a cost effective analysis of treatment options.   The level of treatment is based on how much nitrogen must be removed to return the water back to good water quality.  This is known as the Total Maximum Daily Load (TMDL) or the maximum amount of nitrogen that can enter a pond and not degrade its water quality.  For Oyster Pond, it was determined that 70% of the nitrogen entering the pond must be removed.

A CWMP includes the following:

  1. Needs Assessment – assesses current and future nitrogen sources
  2. Develop and Screen Alternatives – identifies and evaluates treatment options
  3. Evaluate Alternatives - for feasibility and costs
  4. Identify Recommended Plan – produces a preliminary engineering plan

The report sent out in November was comprised of part 2 (Develop and Screen Alternatives) and part 3 (Evaluate Alternatives) for Oyster Pond.
The majority of this report goes through the due diligence of exploring all treatment alternatives, even though most of them are not feasible for Oyster Pond.  The Draft Alternatives Analysis Report analyzed five potential treatment options.  The Final has narrowed this down to only two.

Proposed Treatment Plan 1 for Oyster Pond. Parcels in yellow would be connected to the sewer system.  A total of 145 dwelling units from 85 parcels would be connected. 

The most important part of the document to focus on is Section 5.5 Focused Review of Plan 1 and Plan 5 on page 5-22.   The conclusions of the report is that there are only two main scenarios for nitrogen treatment in the pond  - sewering (Plan 1) or using advanced Innovative & Alternative (I/A) denitrifying septic systems (plan 5).  I/A septic systems remove far more nitrogen from a septic system than a Title V system.  Title V septic systems are excellent at removing pathogens from entering our waterways, they remove only some of the nitrogen.  Plan 5 is broken down into subcategories of different types of I/A systems depending on how much nitrogen they remove from the septic flow.  Examples of these systems can be found in Appendix F.  It is a review of the pilot project using low emitting nitrogen systems in West Falmouth Harbor.

Proposed Treatment Plan 5 map for Advanced Innovative and Alternative Septic Systems.  A total of 204 dwelling units would be required to upgrade to a denitrifying septic system.  More parcels are included in this plan than in Plan 1.  This is because all of the nutrients from households in Plan 1 would be taken out of the pond's watershed.  In contrast, nitrogen would still be released to the pond under Plan 5.  This requires a greater number of homes to participate to meet the required lower nitrogen levels. 

Even though this part of the CWMP is complete, it will still be years before any of these plans are put in place.  There are still many unanswered questions. Section 6 Next Steps reviews some of the technical questions.  However, there are a lot of political considerations, too.  Will the MA Department of Environmental Protection allow a CWMP based only on I/As?  It's never been done before. I/As need a lot of monitoring to ensure they are functioning properly.  What type of protocol needs to be put in place to make sure homeowners are complying with their septic system monitoring? 

Another big political question is how to equitably pay for I/As if they are required.  Falmouth has paid for 30% percentage of the sewering costs for the Little Pond neighborhood.  How will they do that for I/As?  Buy the systems in bulk from a vendor?

There will be several meetings and discussions over the plan for Oyster Pond. There will likely be a neighborhood meeting this summer to discuss all of this.  

On Wednesday, July 30th, the Town of Falmouth’s Water Quality Management Committee (WQMC) and Wright-Pierce, the town consultant, held a neighborhood meeting to talk about plans for improving Oyster Pond’s water quality.  (See the presentation here).  In response to comments and questions at that meeting, the WQMC has developed an Oyster Pond CWMP Q and A and an Oyster Pond Fact Sheet. Homeowners might also find it useful to read the Weir Conservation Commission Order of Conditions and the Hydrodynamic Study and Weir Design that are referenced in the Q and A and Fact Sheet. These documents are also useful for understanding how the pond functions why the weir was installed.

Alternative Analysis
Wright-Pierce, the consultant retained by the Town, has developed five plans for lowering the current input of nitrogen coming from our backyard septic systems as they are the largest contributor (71%) to the nitrogen load. These plans vary in scope and cost and we urge you to please read the Comprehensive Wastewater Management Plan.  It consists of two parts, the Needs Assessment (see below for more information) and the Alternatives Analysis.  The Alternatives Analysis provides the heart of the plan with proposals and rough cost estimates.

The Alternative Analysis examines methods for reducing the nitrogen flow into Oyster Pond. It looks at non-structural measures as well as structural wastewater collection systems.  It includes an in-depth review of all aspects of a wastewater system from how to collect the wastewater to where it will be treated to how and where the treated effluent will be disposed.   There are six composite plans proposed:

  • Collect wastewater and send it to the Town’s existing wastewater treatment facility on Blacksmith Shop Road.
  • Collect wastewater and send it to the WHOI campus at an upgraded and expanded facility.
  • Collect wastewater and treat it at a new facility in the Oyster Pond watershed area.
  • Require all 165 residences in the Oyster Pond watershed to install enhanced septic systems (known at Innovative Alternative systems or I/A systems ) plus install “mixers” to manage the stratification of the pond.
  • Require Advanced I/A systems at all 165 residences to treat nitrogen to a lower levels than systems mentioned in the above bullet.
  • No Action

These alternatives vary in cost and impacts to homeowners.


Needs Assessment
We are well on our way to finding a solution to removing the excess nitrogen polluting Oyster Pond.  The Draft Needs Assessment for the Oyster Pond Comprehensive Wastewater Management Plan (CWMP) is now available for review.  The Needs Assessment gathers the physical, biological and water quality information on the pond together to evaluate the current condition of the pond.  This is the first part of the larger CWMP that will develop a plan to control nitrogen coming from septic systems, garden fertilizes and stormwater run-off.

Edward Leonard of Wright-Pierce presented a powerpoint on the findings of the Draft Needs Assessment to the Town of Falmouth Water Quality Management Committee on Oct 3, 2013. He also distributed a handout responding to comments from the committee, OPET and the public.

 Highlights of the presentation:

  • W-P says that Phosphorus management is also warranted for OP, not just Nitrogen, as both P and N play a role in water quality of OP. (OPET has been saying this for years).
  • Oyster Pond is a complex and difficult system to model due to its submerged kettleholes.  It is very different from the other south facing estuaries in Falmouth
  • Nitrogen from atmospheric deposition is dropping due to Clean Air Act implementation of pollution controls on cars and smoke stacks.  The calculations in the Massachusetts Estuaries Report (MEP) to determine the nitrogen levels to restore water quality in OP used 1990 data. Levels have dropped considerably since then. Using updated atmospheric N levels would lower the number of parcels needing wastewater treatment.
  • Nitrogen levels are falling in the pond due to less atmospheric N, stormwater improvements, and improved flushing. 
  • W-P suggested a data logger be installed at OP3 at 4m depth to monitor conditions, which are highly variable there.  This location is the "sentinel point" or the area selected to show when Oyster Pond reaches its water quality goal.
  • The next section of the CWMP- Identifying and Screening Treatment Alternatives - will be finished in about 6 months.
  • The entire CWMP will be completed in 2015

A Comprehensive Wastewater Plan for Oyster Pond

Nitrogen and to a lesser degree, phosphorus, are impacting Oyster Pond. Just as nitrogen feeds your garden plants, italso feeds the plants or algae in the pond. The over-abundance of nitrogen is increasing the amount of aquatic vegetation growing in the pond. This growth in vegetation in turn decreases the amount of oxygen available to fish and other aquatic dwellers. Low oxygen stresses fish and other aquatic critters.  The benthic habitat, the bottom of the lake and the sediment layers, is severely stressed with few creatures and little variability. High nitrogen levels also increase the turbidity or cloudiness of the pond. In the 1990s nitrogen caused such an abundance of aquatic vegetation that is was difficult to swim or boat in the pond.  

Much of the CWMP will focus on limiting nitrogen from septic systems as they are the largest source (71%) to the pond.  

The remainder of the CWMP will include:

  • An Evaluation of Treatment Alternatives will look at both traditional and non-traditional technologies and could include tying into the Town’s Wastewater Treatment Plant, installing cluster denitrifying septic systems or using permeable reactive barriers to filter nitrogen from the groundwater before it enters the pond. 
  • Screening and Ranking the Alternatives will examine each treatment alternative for costs, impact on water quality and habitat, reliability, regulatory constraints, and public acceptability. Funding, financing, and possible user charges for the various alternatives are also a key component of the screening process.
  • A Draft CWMP will include preliminary designs for any proposed facilities plus detailed capital, operating, maintenance and administrative costs for the recommended plan. The plan will also include funding and financing the implementation of the recommended plan with projections on the impact to the town, property owners including residential, institutional and commercial.

This article appeared in the Summer 2012 OPET newsletter. Following this is an article on how nutrients, especially nitrogen, impact Oyster Pond.

WQMC—Working on Improving Water Quality for Oyster Pond  by Steve Leighton

Readers of this newsletter may be interested in what is going on at the town level to improve the water quality in Oyster Pond.  Below is an outline.  The first and second parts are a possibly tedious account of the legal background and bureaucratic realities.  The third section tries to explain what may happen in the future in the ‘physical’ world aka your backyard.

Legal background
Falmouth’s  increase in population, their septic systems and the associated nitrogen flowing through the ground water into the ponds has resulted in algal blooms and other problems with normal pond life.   (Title 5 septic systems remove the pathogens, but not the nitrogen.)    The federal Clean Water Act mandates that the states and towns restore the water quality in places like the Falmouth estuaries primarily by reducing the amount of nitrogen entering the ponds.  In fact, total maximum daily loads (TMDL’s) of nitrogen have been set.  (Warning: if you don’t like acronyms then these issues are not for you - sorry, they go with the territory.)    To meet those requirements, the Falmouth Water Quality Management Committee (WQMC) was formed by the town to determine how to remove the excess nitrogen (“meet the TMDLS’s”) in the most equitable and cost effective way for the residents of Falmouth.

Planning process
The WQMC has been meeting for almost a year to carry out specific tasks related to nitrogen reduction spelled out by Town Article 17 passed in the spring of 2011.  One of the tasks is to develop a Comprehensive Water Management Plan (CWMP) for Oyster Pond, as well as for the other Falmouth Estuaries.  The CWMP’s serve several purposes. They are memos of understanding to show the good faith and intent of the town to spend money to clean up the water bodies, they are loan applications so the towns can borrow that money from the state at favorable rates (2% or 0%), and they are “building permits’” so the state can review the technical plans.  The latter gives the town some feedback on the feasibility of its proposed methods for clean up and provides uniform standards for fairness among the towns.

For historical reasons beyond the scope of this article, the Oyster Pond CWMP will be developed a couple of years behind the schedule for some of the other estuaries, but perhaps before some of the others.  This is not bad for us as we may benefit from some of the experiences of the pioneering estuaries and may act as a model for the lagging ones.

pond weeds
Excessive aquatic plant growth in 2000

Here is a regulatory road map to help you understand how regulations in the Clean Water Act filter down to the local level to control the amount of pollutants entering water bodies.

The actual CWMP will be prepared by a consulting engineering firm to be chosen by the town.  The Request for Proposals (RFP) to procure this firm has been drafted by the WQMC and is expected to be issued this summer.  At an OPET meeting earlier this year I as a representative of the WQMC presented some                               
of the ideas that went into the RFP and they were generally approved by the OPET board and others in attendance.  The task of the consultant will be to study the pond and its environment and the nitrogen removal requirements (TMDL’s) and to suggest various methods by which the TMDL’s might be met.  These suggestions will be presented to the surrounding residents for comment and review.  Based on those comments and advice from the WQMC, a preferred method will be described in a CWMP.  The CWMP will then be sent to the selectmen for review and then sent to the Massachusetts Department of Environmental Protection (Mass DEP) for their approval.  This process will take several years and will include Falmouth ballot initiatives to approve the capital expenditures.  Of course, there will also be town wide discussion of funding mechanisms such as betterments, sewer fees and/or tax increases.  It is also possible that financing can replace debt being retired so that there will be “no new taxes”.

Technologies being considered
There are a variety of technologies being studied for the various estuaries but not all can be applied to all of the ponds.  For instance, although there will be a demonstration project to show how much nitrogen can be removed from Little Pond by oyster culture, ironically that method cannot be used in Oyster Pond since its salinity must remain low to provide a spawning ground for the river herring.  Likewise, inlet widening to increase tidal flushing is not feasible for Oyster Pond since it would increase the salinity and change the basic character of the pond.  Permeable reactive barriers (trenches filled with wood chips to convert nitrates into nitrogen gas) will be tried at some of the other estuaries but are less likely to be the solution for Oyster Pond.  Boulders would make excavation difficult and residents and the conservation commission are expected to object to the flora and habitat destruction near the edge of the pond.  An active group is promoting eco-toilets (composting, urine diverting etc.) as an economical solution for some areas.  If anyone is interested in participating in a demonstration project of this technology they will be enthusiastically welcomed by the eco-toilet sub-committee of the WQMC.  In fact there is a $5000 subsidy available to the first several dozen homeowners who sign up.  This study is distinct from the Oyster Pond CWMP development but if enough homeowners were interested it could be a part of the solution for Oyster Pond.  A very unscientific poll of Oyster Pond board members found little interest because of the perceived difficulty of retrofitting these units to existing houses or fears of real estate devaluation.

Having nearly ruled out the technologies above, what remains that might be used?  The sewage from the houses in the Oyster Pond watershed could in principle either be denitrified on site in individual denitrifying septic systems or in cluster systems serving groups of houses or it could be carried off to the central sewage plant on Blacksmith Shop Rd, presumably with some connection to the existing force main that runs under the bike path.  A variety of sewage systems will be evaluated, including traditional, vacuum, low pressure, STEP, STEG, grinder pump etc.  A key question that must be answered is, “Will the town be allowed to send more sewage to the central plant at all?”  The plant has enough internal capacity but there is limited ability to disperse the treated effluent without simply moving the problem from the south coast to West Falmouth Harbor and various fresh water ponds in the vicinity of the plant.  The town is pursuing an ocean outfall permit that would handle the increased volume but it will be several years until we know if that is approved.

This planning and decision process will take years and will involve much public discussion and democratic debate.  The WQMC is dedicated to public outreach to keep all the residents informed and to utilize citizen opinion.  We welcome your ideas and questions. by Steve Leighton

Steve Leighton is the former President of OPET. He stepped down as President when he was appointed to the Water Quality Management Committee (WQMC) by the Board of Selectmen.

How Excess Nutrients Impact Oyster Pond

Oyster Pond is suffering from the impacts of excess nutrients.  Nitrogen and to a lesser degree, phosphorus, are changing Oyster Pond.  Just as nitrogen feeds your garden plants, it also feeds the plants or algae in the pond.  The over-abundance of nitrogen is increasing the amount of aquatic vegetation growing in the pond.  This growth in vegetation in turn decreases the amount of oxygen available to fish and other aquatic dwellers.  It also increases the turbidity or cloudiness of the pond.  In the mid 1980’s the impacts of nitrogen caused such an abundance of macroalgae and aquatic vegetation that is was difficult to swim or boat in the pond, and caused some neighbors to sell their homes.

The impacts of excessive nutrients are most dramatically at the most basic level of the pond and far from our sight.  Excessive nutrients are causing a shift in the pond’s benthic animal communities.  One measure of a water body’s health is to look at the diversity, distribution, and population of these pond bottom dwellers.  The Oyster Pond Massachusetts Estuaries Report (MEP) found few species, only an average of 3 species per sample, compared to 30 species per sample in a nearby healthy estuary.  The numbers of these animals were low and unevenly distributed, all indicators of a stressed, impoverished community and habitat suffering from excessive nutrients.

Summary of conditions
From the Oyster Pond Massuchusetts Estuaries Project Report, 2006.- Click for a larger image - use your BACK button to return to this page.

Too Many Septic Systems
The problem of too much nitrogen entering the estuaries in Falmouth was first recognized in the mid 1980s and the main culprit was indentified as our septic systems. Only 3% of Falmouth is hooked up to the sewer.  The rest of us have individual septic systems.  While Title V septic systems are excellent at removing pathogens from entering our waterways, they remove only some of the nitrogen.  Nitrogen from our wastes, soaps, laundry detergent, and food scraps enters our septic systems and leaches down through the soils into the groundwater.  The groundwater gradually migrates downhill entering Oyster Pond and other estuaries.

Falmouth MA Population growth

When Falmouth’s population was low, salt ponds and estuaries could absorb this extra nitrogen.  But as Falmouth’s population has grown, so too has the number of septic systems leaching nitrogen, increasing the amount and concentration of it in our estuaries.  It is now too high for water bodies to absorb and is known as eutrophication.  The same population growth has occurred around Oyster Pond. 

Since the 1980s, concerned residents of Oyster Pond have been working on trying to mitigate the impacts of this excess nitrogen.  The Pond Watchers were part of this effort to document the condition and amount
of nutrients in the Pond.  In 1985, OPET began its own Water Quality Monitoring Program.

The Role of the Weir
In the late 1980s, the culvert under Surf Drive that connects Oyster Pond to the Lagoon began filling in with debris and partially collapsed.  This severely limited the outflow of the pond, causing the concentration of nitrogen and phosphorous in the pond to rise, causing excessive freshwater algae and aquatic weed growth.  To prevent problems with clogging, the culvert was replaced by one with a much larger diameter.  While it allowed more outflow, this allowed a large influx of salt water to enter the pond at high tide.  Salinity levels jumped from 2-5 parts per thousand (ppt) to 15ppt. 

This caused a rapid change in the habitat of the pond – yellow and white perch populations crashed and barnacles started growing on the Treetops dock.  The pond waters stratified with the heavier salt water sinking to the bottom of the pond while the fresh water from precipitation and groundwater floated on top.  This stratification also caused anoxic conditions at pond bottom as it limited the interchange of oxygen between the two layers.  The influx of salt water also stimulated the saltwater algae to grow and caused the fresh water vegetation to die, further exasperating the severe benthic oxygen depletion. New plant growth in the pond exploded, now thriving on nitrogen-limited conditions.  It was so high that it was difficult to swim or even boat on the pond. 

Click for a larger image - use your BACK button to return to this page.

In 1989, the weir was placed just north of the culvert to again limit salt water inflow and return Oyster Pond to its recent historic lower salinity levels.  The drop in salinity also dampened the impacts of high nitrogen.  This is because saline waters are sensitive to nitrogen.  Salt waters are said to be nitrogen limited -- meaning that the amount of nitrogen can limit or increase impacts to a water body’s habitat.  In contrast, fresh waters are phosphorus limited.  Due to Oyster Pond’s very low salinity – between 1 -2 ppt (compared to Vineyard Sound’s 32ppt), the pond is sensitive to both nitrogen and phosphorus.  With the weir control, the salinity can be temporarily increased to reduce freshwater type growths of aquatic weeds and algae. If nitrogen-limited plants begin to increase to too much density, the salinity can be lowered. Ecosystem plants are remarkably adaptive, but there is a time lag which has given OPET an advantage. In the northern basin, phosphorus’s sources (mosquito creek outflow and stormwater road runoff) and impacts to Oyster Pond are not as well documented as nitrogen and are less well known.

MEP Reports
The Department of Environmental Protection initiated the MEP studies to study the impacts of nutrients on estuaries around the state.  Oyster Pond was one of the earliest ponds studied of the 89 targeted bays.  The goal of the MEP is to set the highest amount of nitrogen a water body can absorb and still maintain a healthy ecosystem.  This is known as the Total Maximum Daily Load (TMDL).  The MEP reports set a TMDL for both the concentration or amount of nitrogen in the water column (expressed as mg/l) and the load or amounts entering ponds (expressed as kg/day or kg/year).  After the TMDLs are set, the results are sent to Mass Department of Environmental Protection (DEP) and the EPA for their approval.  Once the TMDLs are accepted by those authorities, the Town of Falmouth is obligated to meet the TMDLs.  Oyster Pond’s TMDLs were accepted by the EPA in 2008.  The numbers are .55 mg/l for nitrogen concentration and the load is 1.53 kg/day.  The sources of controllable nitrogen include septic systems, stormwater runoff and lawn runoff from fertilizers.  Uncontrollable sources include atmospheric deposition from nitrogen produced by coal burning plants and automobile emissions from the Eastern Seaboard.

Simple Mass Balance for N control
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Septic systems contribute 71% of the controllable load to Oyster Pond.  The remaining sources are from stormwater runoff and fertilizers.  To the right is one scenario for meeting the TMDLs.

Oyster Pond Environmental Trust, Inc.
501(c) 3 non-profit organization
PO Box 496 • Woods Hole, MA 02543-0496