Town of Westport Massachusetts Estuaries Project Partnership for the Nitrogen Management of the Westport Rivers Embayment System

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1 Town of Westport Massachusetts Estuaries Project Partnership for the Nitrogen Management of the Westport Rivers Embayment System Project: Data Collection and Modeling Required for Massachusetts Estuaries Project Linked Watershed-Embayment Nitrogen Management Approach for the Westport Rivers Embayment System in Support of Management and Restoration Dr. Brian L. Howes & Roland Samimy DEP/SMAST Massachusetts Estuaries Project Coastal Systems Program School of Marine Science and Technology - UMD Overview: The overall scope of this project is to be performed as a collaborative effort between the Town of Westport (appropriate departments and MEP committee formed by order of Board of Selectman) and the DEP/SMAST Massachusetts Estuaries Project (MEP). SMAST (School for Marine Science and Technology-UMD) serves as the technical and fiscal coordinator for this effort. The overarching project goal is the protection and restoration of the health of the Westport River Embayment System to the Town of Westport through watershedembayment nitrogen management planning. The embayment system covered under this agreement includes Westport Harbor with associated tributary systems such as the east and west branches of the Westport River as well as Horseneck Channel. The specific goals of the project are: to compile, review and synthesize relevant studies related to the nutrient related health of the Town of Westport s embayment including data from the coordinated Westport River Watershed Alliance (WRWA) / Coalition for Buzzards Bay (CBB) water quality monitoring effort to establish the existing nitrogen distribution and long-term baseline; to conduct field data collection, produce field validated Hydrodynamic and Nitrogen Models of the embayment system of concern; to determine quantitative nitrogen targets for the management/restoration of the embayment system to maintain/restore habitat quality to designated water quality standards; to determine potential nitrogen management options on a site specific basis for the embayment system for evaluation by the Town, including both soft solutions (ecological manipulations, tidal manipulation, regulatory options, etc) and hard solutions (wastewater

2 facilities, runoff control, etc); to test an initial what if scenario for the embayment to address the efficacy of nitrogen management options recommended from regional and national experience, by the Town MEP Committee (established) and the Town s engineering consultants (as appropriate); to provide assistance to integrate the nitrogen management feasibility effort with the Town or its selected consultants for selected options to be implemented, e.g. Wastewater Facilities Planning (if needed); to enhance public education as to the health of Westport s coastal embayment system, its future and best practices for its protection and restoration. The project will be conducted over a two year period. The overall project builds on a Westport River wide water quality monitoring program that has established the baseline summer nutrient related water quality for Westport s embayment and adds the core Massachusetts Estuaries Project (MEP) data collection, modeling and synthesis. The minimum three year (summers) baseline water quality monitoring data has been developed by the WRWA and CBB (working with SMAST Coastal Systems Laboratory scientists) and is a prerequisite to the MEP analysis to support the assessment and modeling effort. The Estuaries Project analysis of the Westport River system (estuarine monitoring and assessment, modeling and synthesis) will be under the direction of Dr. Brian L. Howes, Manager of the Coastal Systems Program at SMAST-UMD and Technical Director of the Massachusetts Estuaries Project. The University will serve as the prime contractor for this effort, although technical specialists with proven capabilities and experience within the region will be integrated into the project as required. The project will work with the Westport MEP Committee (established) to evaluate the Town of Westport s embayment system as to its tolerance for watershed nitrogen loading (the target nitrogen levels supportive of healthy habitat quality). The goal of this project is to provide information necessary to support both hard and soft approaches to the management and restoration plans for this embayment system. A quantitative numerical model will be parameterized using site specific information and field validated using both freshwater inflow, measured tidal flows and present salinity and nutrient distributions. The model to be used has been accepted as the necessary approach by DEP and EPA for southeastern Massachusetts embayments. The project tasks will include: data collection focusing on watershed source analysis, nutrient distributions, development of a hydrodynamic model, mapping of eelgrass and wetlands, and survey of benthic indicator species. These parameters, when coupled, provide the data base for synthesis of nitrogen dynamics within the system, enabling construction of an embayment specific Linked Watershed-Embayment Model and a quantitative assessment for this embayment of the Town of Westport. The effort will also include an evaluation of the current and potential ecological health of the system. 2

3 PROJECT TASKS Westport s Embayment Nitrogen Management and Restoration Project will focus on the Westport Rivers Embayment System and its tributary sub-embayments as follows: Westport Rivers Embayment System 1. Westport River (mouth) 2. West Branch of Westport River 3. East Branch of Westport River 4. Horseneck Channel 5. The Let The basic project components are: Nitrogen Related Water Quality Modeling / Hydrodynamic Modeling bathymetric survey data collection on tidal exchange, salinity distributions, validation by velocity (ADCP) quantitative numerical modeling & validation Watershed Nitrogen Loading determination and confirmation of contributing areas data collection on stream flow & nitrogen load (annual) land-use data (from Town Planning & SRPEDD) watershed nitrogen model (present, build-out and best case ) Quantitative Watershed-Embayment Nitrogen Model nitrogen recycling within each embayment system predictive N management model, with validation Habitat Assessment dissolved oxygen (high frequency measurements in targeted areas) macrophyte surveys (eelgrass & macroalgae), with incorporation of historical data benthic infauna community (animal indicators of stress) Synthesis of Modeling and Habitat Assessments determination of nitrogen loading tolerances (i.e. threshold nitrogen loads) projection of embayment health under build-out and best case potential loadings evaluation of soft and hard nitrogen management options (initial screening) Information Transfers presentations and discussions with MEP committee public meetings and workshops reports and data displays The tasks required for fulfilling the data needs and goals of the project are detailed below. 3

4 Task 1: Review of Existing Studies and Water Quality Data. SMAST/MEP will perform a review of all existing studies of Westport s embayment system and watershed, which are provided by the Town or to which SMAST/MEP has independent access. SMAST/MEP will review the water quality data which has been collected by the WRWA and CBB and analyzed by SMAST for: (1) quality of sampling approach, (2) quality and capability of chemical analysis, (3) quality assurance procedures, (4) completeness, (5) availability of actual data, and (6) applicability to the nitrogen modeling, engineering and management effort which is the focus of this project. Task 2: Cumulative Nitrogen Loading Assessment The ecological health of the Westport River Embayment System is the integration of the amount and distribution of nutrient inputs from the surrounding upland watersheds, the rate at which these nutrients are removed by tidal flushing and the physical structure of the embayment. This Task focuses on the rate of nutrient input from the surrounding watershed. The total nitrogen input to the embayment will be determined by the Southeastern Regional Planning and Economic Development District (SRPEDD) using a land-use loading model which is similar in form to traditional approaches by the Cape Cod Commission and the Buzzards Bay Project, but which has been upgraded to include site-specific data and measured nitrogen attenuation. Quantification of the total nitrogen input to the embayment system will be based on a watershed land use analysis to be undertaken by SRPEDD with direct input from the Town of Westport Planning Department. The watershed to the overall Westport River system will be divided into regions a) contributing directly via groundwater to the estuary, b) contributing to freshwater lakes and ponds, c) contributing to fresh and saltwater wetlands, and d) contributing areas to streams and rivers. A full land-use loading model will be applied to each of these sub-watersheds (where they exist) to determine the spatial distribution and amount of nitrogen loading to the estuarine portions the watershed-embayment system. In support of the loading models is data collection on land-use and its validation, physical and biogeochemical data collection on the freshwater lakes and ponds, and the spatial and areal distribution of wetlands. The land-use modeling will rely heavily on GIS approaches, but field data collection will also be required. Lake and pond field data collection of stratification, nutrient and chlorophyll levels is important for determining attenuation rates. GIS work will be conducted among the Town Departments and the MEP Project Team. Task 3. Stream and River Transport of Watershed Nitrogen to the Embayment. As indicated in Task 2, attenuation of watershed nitrogen during surface water transport can significantly reduce the amount of watershed nitrogen entering an estuary. SMAST/MEP will directly measure nitrogen, and phosphorus inputs of each major stream/river discharges in the embayment undergoing the full modeling effort. These direct measurements of watershed freshwater and nutrient inputs will a) serve to validate the watershed delineations, b) validate the land-use models, c) as discussed in tasks described below, help to calibrate the hydrodynamic models applied to estuarine circulation. These direct measurements are also applied to the system nitrogen loading models. The use of river validated models is necessary to minimize uncertainties and provide for effective watershed management decisions. 4

5 Surface water inflow volume and mass transport of nitrogen will be determined using sitespecific flow discharge relationships and continuous records of water levels. Nutrient samples will be collected for inorganic and organic nitrogen concentrations at weekly intervals for a minimum of 14 months. Total nitrogen (not just inorganic forms) is required to accurately determine the input through this pathway. The MEP Technical Team has identified 6 significant surface water inflows to the Westport River Embayment System within the Town of Westport. Field verification of stream discharge prior to instrument deployment will determine the final number of streams to be gauged. Stream gauging and nitrogen load sampling will be conducted in the first year of this collaborative effort. Task 4. Nitrogen Recycling within the Estuarine Complex. In addition to new nitrogen entering the estuary from the surrounding watershed, nitrogen is recycled within the sediments and water column. This recycled nitrogen adds directly to the eutrophication of the estuarine waters in the same fashion as watershed inputs. In some systems under MEP investigation, recycled nitrogen can account for about half to the nitrogen supply to phytoplankton blooms during the warmer summer months. It is during these warmer months that estuarine waters are most sensitive to nitrogen loadings. Failure to account for this recycled nitrogen generally results in significant errors in determination of threshold nitrogen loadings. In addition, since the sites of recycling can be different from the sites of nitrogen entry from the watershed, both recycling and watershed data is needed to determine the best approaches for nitrogen mitigation. The organic rich nature and relatively shallow waters of coastal systems like many of those in southeastern Massachusetts and on Cape Cod result in sediments having a significant role in system biogeochemical cycles. Organic matter deposition to sediments, hence benthic respiration, tends to decrease with increasing depth of overlying waters due to interception by water column heterotrophic processes. The result is that embayment respiration rates are typically many-fold higher than in the adjacent offshore waters. With potential stratification of embayment waters, sediment metabolism plays a major role in bottom water oxygen declines (an ecosystem structuring parameter). In order to determine the contribution of sediment regeneration to nutrient levels within each embayment during the most sensitive summer interval (July-August), sediment samples will be collected and incubated under in situ conditions. Time series measurements of total dissolved nitrogen, nitrate+nitrite, ammonium and ortho-phosphate will be made on each incubated core sample. The rate of oxygen uptake will also be determined in order to (1) allow evaluation of the sensitivity to oxygen depletion of each embayment area under periodic stratification, (2) allow ranking of sediments as to organic matter deposition rates (not possible using organic content), and (3) to parameterize nitrogen models. Assays will be performed on 60 sites distributed among the embayment system. The results allow the spatial pattern and rate of nutrient inputs from the sediments to the water column to be entered into the nutrient model. From our experience, sediment regeneration during the summer is a large and important source of nutrients supporting both phytoplankton and macroalgal blooms in embayments throughout S.E. Massachusetts. 5

6 Task 5. Assessment of Nutrient Related Ecological Health. The nutrient related ecological health of an estuary can be gauged by the nutrient, chlorophyll and oxygen levels of its waters and the plant (eelgrass, macroalgae) and animal communities (fish, shellfish, infauna) which it supports. MEP technical specialists will conduct surveys of these parameters over a two year period. These data will be synthesized into an assessment of the systems present health and will also be used for projections of future conditions based upon the water quality modeling effort (see below). Mapping of eelgrass and macroalgal communities will be conducted during the summer and fall months. MEP (DEP mapping program) has refined these surveys and mapping techniques for recent studies. Macroalgal mapping will focus on distribution and coverage. Macroalgae are a natural part of estuarine systems, but become excessive under nutrient enrichment. Existing data on the system collected over the past decades will be used to assess changes in distribution or community structure. Benthic animals are a key indicator of the health of estuarine systems. Benthic sampling and analysis will be performed primarily by SMAST staff who have more than 30 years of experience in Buzzards Bay and Cape Cod embayments. These water quality and habitat data sets will be synthesized and integrated with the modeling efforts, for both hind and forecasting of habitat quality changes linked to watershed management. Task 6. Hydrodynamic Field Data Collection and Modeling. To ensure the Town of Westport receives a final product that provides the basis for sound engineering and management decisions, the project team uses a well-vetted top echelon water quality modeling approach. A. Tide Data Collection Measurements of tidal elevation will be made at 4-5 locations within the embayment system under consideration. Precise knowledge of tidal elevation time histories at strategic points is required to understand the flushing characteristics throughout the system. As the tide rises in Buzzards Bay, water floods into the embayment system and is distributed through to the upper portions of the embayment. Characteristics of the embayment system, such as depth, and bottom roughness (friction), distort the tidal wave as it travels through the system from inlet to headwaters. Tidal distortion may include a reduction in the range of the tide (damping) and/or a delay in the time of occurrence of low and high tides. The extent of tidal damping through the system affects the volume exchange, and hence the flushing characteristics, between Buzzards Bay and the remote portions of the system. Measurement of the tidal elevation time histories at key locations will provide information to calibrate and verify the two-dimensional numerical model, which will be used to evaluate flushing characteristics and compute residence times. The system forcing tides, or the offshore tides, in Buzzards Bay will be measured using two tide gauges offshore of the embayment. For the embayment system, the two tide gauges will be installed on a pipe anchor in approximately feet water depth. Accurate measurement of the forcing tide is critical, because the forcing tide will provide the basis for evaluating flushing characteristics within the system. Therefore, two gauges will be used to ensure 100% data return. 6

7 The forcing tide measurements will be input directly to the computer model as a forcing boundary condition. Measurement of the tidal response in portions of the embayment quantifies the extent of tidal damping through the connecting channels and coves. Spatially distributed placement of gauges throughout the system will allow for detailed analysis of tidal damping around the embayment. Each gauge will be installed to an existing pier piling or other stable structure such that the recording sensor remains submerged at all tide stages. Exact location of each gage will be determined during a pre-survey site visit. Standard operating procedure is to obtain permission(s) from private land owners prior to tide gage installation on their property (if required). The vertical elevation of each tide gage will be measured relative to the Town s vertical datum. The Project Team assumes that the Town will provide the location and position (both horizontal and vertical) of local benchmarks nearest to each tide gage. The Project Team will provide the instrumentation and labor to survey the gauges into the Town datum. B. Review Available Bathymetric Data and Collection of Additional Data Although NOAA digital bathymetry is typically available for this region, these depth measurements were made in the 1930s. Although it is likely that bathymetric conditions within many areas of the systems have shown negligible change over the past 60-to-70 years, the region adjacent to shallower areas needs to have an updated bathymetric survey for this study. The collection of depth data will be performed while the tide gages are collecting data. The depth measurements will be referenced to the local instantaneous water level; the local water level at all locations within the system will be referenced to the Town s vertical datum using water level measurements recorded by the tide gages (i.e., tide-corrected bathymetry measurements). The bathymetry survey will be performed using a shallow draft boat, capable of traversing the shallow regions of the Westport Rivers system adjacent to the inlet of Westport Harbor as well as throughout the west branch of the Westport River and Horseneck Channel. Bathymetry surveying will also be conducted in the deeper regions of the central basin (Westport Harbor) and the east branch of the Westport River. Bathymetry transects running parallel to each other will be spaced approximately 250 feet apart. Detailed measurements will be obtained at any constriction points in any of the navigational channels and longitudinal transects running the length of the east and west branches of the system will be performed. The bathymetric data will be acquired utilizing a portable bathymetric data acquisition system. A fathometer with depth resolution to 0.10 ft. will be used in conjunction with a differential geographic positioning (DGPS) system. This system records depth as a function of survey location. DGPS offers unparalleled positioning precision for the cost, typically yielding absolute horizontal accuracy to within 2 meters over 95 percent of the time. An integrated survey software package will be used to record depth and DGPS data simultaneously to a laptop computer. In addition to data recording, the survey software is also a powerful data editing and graphics package that allows data to be corrected for tidal deviations before being output to a plotter. Positions will be recorded in Massachusetts State Plane 1983 coordinate system (X-Y) at 7

8 an approximate rate of one value every two seconds. Depending upon boat speed during the survey (estimated at 3-5 knots), position measurements will be made approximately every feet along each survey line. Depth values are recorded continuously (approximately every 0.5 seconds, or every 3 feet along the survey line). In addition to bathymetric data collection, the level of numerical modeling proposed for the more complex systems warrants model validation using tidal current data. Cross-sectional profiles of currents will be measured using an Acoustic Doppler Current Profiler (ADCP) over tidal cycles as appropriate. This will be in association with other parts of the field program. C. Hydrodynamic Model Development The Project Team s technical approach for evaluating estuarine hydrodynamics includes model development and calibration. The Surface Water Modeling System (SMS) will be utilized to model both hydrodynamics and water quality (an overview of the SMS package will be provided upon request). The SMS package provides a user-friendly grid generation program and post-processing software for the RMA-2 model developed by Resource Management Associates (King, 1990). The RMA-2 model is a two-dimensional, depth-averaged finite element model, capable of simulating hydrodynamics in complex river and estuary systems. The model has been standardized by the U.S. Army Corps of Engineers and is widely accepted for a broad range of estuarine applications. Members of the MEP Technical Team from Applied Coastal Research and Engineering (ACRE) have used RMA-2 for numerous hydrodynamic studies in Buzzards Bay and on Cape Cod. To develop the model grid, Applied Coastal will depend primarily on the existing data, as well as new bathymetry data collected as part of this study. Bathymetry data will be converted to the Massachusetts State Plane 1983 coordinate system (X-Y) and a map will be prepared for incorporation into the Town s GIS. A model grid will be developed with knowledge of the system bathymetry, potential regions of nutrient loading, and regions where structural modifications are proposed. The Project Team s modeling approach utilizes a finite element model developed by Resource Management Associates (RMA-2 Model) which solves the full two-dimensional depthaveraged hydrodynamic equations. It allows for variable computation cell sizes to take advantage of limited bathymetric information. This type of model was developed to handle complex flow patterns associated with systems. Output from the model provides complete depth-averaged, twodimensional current velocities for all computational nodes as a function of time within the estuary system. Our modeling approach is a three-part process: Development: Set-up the model for the embayment system. Input shoreline positions, bathymetry data, and specify boundary conditions (i.e., tides measured in Buzzards Bay). Calibration: Ensure model predictions are consistent with natural processes using a thorough comparison to measured field data. Application: Use the calibrated model to evaluate hydrodynamic characteristics and to determine potential improvements to flushing associated with engineering alternatives. 8

9 Flushing rates and residence times are computed easily from the wealth of detailed sitespecific data this model will provide. Both local and system residence times will be computed. Local residence times represent the average time required for a parcel of water in a subembayment to be flushed out of the sub-embayment, and will be computed as the volume of water in each sub-embayment divided by the volume of water entering the sub-embayment over an average tidal cycle (tidal prism). System residence times represent the average time required for a parcel of water to be flushed out of the estuary from the sub-embayment, and will be computed as the volume of water in the estuary divided by the tidal prism of the sub-embayment. The draft and final report will assess the significance of tidal flushing on water quality from both local and system residence time perspectives. Since the flushing analysis will utilize a numerical hydrodynamic model, results can be incorporated into a water quality model to indicate nutrient and/or other constituents (pollutants) impact to the estuarine system. By incorporating the data collected for other portions of this project, the two-dimensional model can provide the basis for a water quality model that incorporates the estuarine hydrodynamics and point and non-point source nutrient inputs. In addition, the hydrodynamic model can be used to evaluate potential improvement of flushing rates as a result of channel dredging and/or other engineering modifications (e.g. alterations to culverts). D. Output The results will be incorporated into the MEP Thresholds Document for the embayment system. The report will include a description of the model development, including model input information, assumptions used, and calibration procedures. Calibration plots will be presented showing the accuracy of the computations with respect to the measured data. Tables of system (and local) residence times will be presented for the embayment system. In addition, the tidal constituents (amplitude and phase) from both the measured and computed data will be presented. Time series plots showing the measured versus model water elevations at various locations will be presented. A discussion of the system tidal versus nontidal (or residual) processes will be presented to provide some context of the overall tidal processes within the study area embayment. Finally, the report will analyze all generated information to describe the hydrodynamics of the system to provide the Town with a concise understanding of the important hydrodynamic features of the Westport River system, and the spatial pattern of tidal exchange rates relates to observed water quality. The model used by the MEP Technical Team, the RMA-2 numerical model, interfaces with a larger user-interface software package called SMS (Surfacewater Modeling System). The SMS package is a user interface, and allows a simpler method of changing model parameters as well as provides effective graphics presentation capabilities to view results. Bathymetric data in the form of a map for each of the study area embayment system will be provided to the Town in a digital format compatible with the ArcView GIS system. Task 7: Water Quality Modeling and Scenario Runs for Each Embayment A. Nitrogen Loading and Water Quality Data 9

10 SMAST/MEP will use the watershed nitrogen loading data developed by SRPEDD (with input from the Town Planning Department) as a data stream for the water quality model. For parameterizing the nitrogen models, the source terms from task 2 will used as best estimates and an assessment of uncertainties in source terms will be presented. More importantly, in a few instances it may be necessary to refine the spatial distribution of nitrogen input to a subembayment. The proper distribution of nitrogen input relative to the spatial distribution of tidal flushing is important for proper conduct of the water quality modeling. This effort will build on the previous work and will not repeat the collection of the land-use base data, which has been conducted by the Town or SRPEDD. The water quality sampling data from on-going efforts (WRWA and CBB) and that collected as part of the present effort will be utilized for parameterizing the models. This data set represents the only long-term data that will be incorporated into the water quality modeling effort. B. Develop and Apply Water Quality Models The Project Team employs a Linked Watershed-Embayment Nitrogen Management Model, the numerical model is validated using both freshwater and nutrient levels. The model is supported by the RMA-2 Model and uses the same boundary fitted grid to match shoreline geometry, and can be run in either two or three dimensional mode depending on the problem. The model simulates the dispersion of both conservative and non-conservative constituents. The water quality model can simulate the nutrient dynamics In the Westport River embayment application, the nitrogen model will be applied to the embayment system as a whole. A nutrient advection/dispersion analysis will be conducted to determine the rate at which nutrients build up and are flushed from the system. The parameter of interest in these applications is biologically available nitrogen. Nitrogen is typically the limiting nutrient for phytoplankton in marine systems, and it is expected that it is the limiting nutrient in these systems. The nitrogen cycle is complex, involving a series of transformations, and thus no one component may be treated as a conservative tracer. Total nitrogen, to a first approximation may be treated as if it behaves conservatively, and by measuring the various nitrogen components and summing them, SMAST/MEP may calculate a mass balance for nitrogen. Where flushing is slower, and anoxic bottom conditions may develop, denitrification can alter this assumption, and this of course will be an issue in some low circulation areas of the embayment systems. The nitrogen sources for each of these systems will be the nitrogen loads calculated from the land uses in the watershed, benthic nitrogen flux, and offshore concentrations. In an ideal system, the water column concentrations should match the concentrations calculated by the model based on flushing characteristics and loads. Any disagreements will focus the need for further refinements of the modeling assumptions, requiring modifications to the loading or flushing calculations, or evaluation of possible additional sinks or sources of nitrogen. This evaluation will help to identify the critical nitrogen loads for each system that will maintain in situ total nitrogen levels below established water quality standards. For example, the threshold for reestablishment of eelgrass is associated with the Massachusetts SA Surface Water Standard. 10

11 The calibration exercise for a pollutant transport or water quality model is an important component of any analysis. The approach and level of effort varies for each project however. Both qualitative and quantitative comparisons to data can be made. In general, the calibration process is an organized procedure to select model coefficients to best match measured data. The calibration should be based on the following two principles (McCutcheon et al., 1990): 1) The simplest model formulation that accurately represents the physical conditions should be used to solve the problem at hand, and 2) The model coefficients and parameters should be uniform in space and time, unless there is strong evidence in the measured data that they should be changed. Sensitivity analysis is used to determine which parameters and coefficients are most important in a model and the range and scale over which changes in those values are important. For a select set of parameters and coefficients, values will be changed by 50 percent or by a factor representative of the range of values observed or expected, and the resulting effects on the model output will be observed. The models will be calibrated to long-term nitrogen levels from the monitoring efforts, then used to assess the impacts from loads resulting from future build-out. A series of model runs will be used to calculate the critical nitrogen loading limits for the embayment system based on the MA/CCC surface water/nitrogen concentration standards described above. Task 8. Nitrogen Loading, Ecological Health and Management Report. A written report (also on CD ROM) will be produced which integrates all of the information and maps within Tasks 1-7, above. The report will provide a description of field sampling and data. More importantly the report will provide the assessment of present system nutrient loading and ecological health as well as the supporting data and discussion. The target nitrogen threshold for the modeled embayment system will be determined and used as the basis for watershed management evaluations and to develop critical management nitrogen loads. Projections of estuarine health under different nitrogen loading rates and distributions and with different tidal flushing possibilities will be discussed based upon the validated water quality model (Task 6). The projections of estuarine health under present conditions and under various nutrient management options will be used to evaluate potential management options for use by the local community for use in land acquisition, land-use planning, wastewater facilities planning, etc. 11

12 Massachusetts Estuaries Project Deliverables The Massachusetts Estuaries Project s overall deliverable is to determine the watershed nitrogen loading targets for guiding nitrogen reductions (or limits) within contributing watersheds to the Town s estuary. Each major sub-embayment to the estuarine system will be assessed. However, it should be noted that the sub-embayments within a system do not operate independently, as nitrogen is transferred between them once it reaches the bay waters. The Massachusetts Estuaries Project (MEP) will incorporate all of the previous data and analysis conducted by the Town of Westport and will work with the Town s consultants relative to nitrogen management planning (as necessary). Summary of deliverables by MEP for Town of Westport: MEP watershed delineation, based upon hydrologic evaluation by SMAST scientists and SRPEDD with confirmation by the USGS; Validation of watershed area and discharge based upon measured stream discharges; Nitrogen loads to the embayment system (and selected sub-embayments) from its associated watershed (includes term for natural attenuation during transport) and nitrogen recycling from the bay bottom; Assessment of current and historical trends in nutrient related health of each subembayment, based upon D.O., benthic animals, macroalgae, eelgrass coverage. Hydrodynamic analysis of the embayment system, including circulation, volumetric exchange and analysis of the potential for enhancement of flushing; Water Quality model (validated) which maps the nitrogen distribution throughout each estuary under: Present conditions Build-out of watershed Increased tidal exchange (if possible) No anthropogenic nitrogen input from watershed 1 additional: nitrogen source relocation, restoration of tidal restricted wetland, or other as appropriate Critical nitrogen target for each sub-embayment for wastewater & land-use planning Implementation guidance (DEP) indicating new (and old) approaches for achieving nitrogen reductions (as needed). To maximize efficiency and to best integrate the Massachusetts Estuaries Project with the site specific needs of the Town of Westport, Project Staff will work with the Town s MEP committee (established). This committee will be critical in bringing forward site-specific issues within the embayment system of interest, to keep key members of the Town informed and to ensure maximum use of existing data and information resources. Bound copies (3) of the final MEP Reports will be submitted to the Town with one unbound original for reproduction. An electronic copy of all final reports will also be provided to the town. In addition to reports, project personnel will provide quarterly updates & presentations to the MEP Committee and 2 public meetings within the total project costs. 12

13 PROJECT MILESTONE SCHEDULE Embayment Yr 0 Yr 0.5 Yr 1 Yr 1.5 Yr 2 Yr 2.5 Westport River Embayment System MEP Stream Data Collection MEP Field Data Collection MEP Threshold Report X X X X X X Time has been included for DEP & EPA review and revisions of final threshold reports, but additional time may be requested by the Agencies or the Town. Note: Stream data is collected on major freshwater inflows.

14 Town of Westport Contact: Roland Samimy, Estuaries Project: Assessment, Synthesis, Modeling & Recommendations These are "not to exceed" cost estimates and may be reduced based upon existing data review. Town of Westport Funds for Match by Estuaries Project* Westport River East Task Description and West Branch 2 year Total Yr 1 1 Compilation and review report on previous studies/data $2,000 $2,000 2 Cummulative Nitrogen Loading Determination $8,000 $8,000 $8,000 3 Stream/River Transport from watershed to estuaries $30,000 $30,000 $24,000 Gauging and nutrient sampling 5 streams, mo. 4 Nitrogen recycling within the embayments, 48 sites total $24,000 $24,000 $10,000 5 Assessment of nutrient related health, Total/Estuary--> $11,000 $11,000 $6,000 Infauna & Eelgrass/Macroalgal Surveys, D.O. Moorings 6 Hydrodyamic field data collection and modeling $20,000 $20,000 $20,000 Bathymetry, Stage, Velocity, Numerical Models (2) 7 Water Quality Models & Scenario Runs (2) $20,000 $20,000 $0 8 Nitrogen Loading, Ecological Health, Management Report $20,000 $20,000 $0 Total Project Cost, to be matched by Estuaries Project (1:1 basis)= $135,000 $70,000 9 Meetings, Outreach Tools To Be Determined Massachusetts Estuaries Project Matches both Town Funds and cost of available data on a 1:1 basis. Existing Town Match, Data from Previous Studies = To be evaluated To be evaluated -$0 Total Town of Westport Cost Share = $135,000 $70,000 14

15 REFERENCES Hargrave, B Coupling carbon flow through some pelagic and benthic communities. Journal Fisheries Research Board of Canada 30: Howes, B.L Sediment metabolism within Massachusetts Bay and Boston Harbor: relating to sediment-watercolumn exchanges of nutrients and oxygen in MWRA Environmental Quality Department Technical Report Series No Massachusetts Water Resources Authority, Boston MA. 68pp. Howes, B.L., D.D. Goehringer, N.P. Millham, D.R. Schlezinger, G.R. Hampson, C.D. Taylor and D.G. Aubrey Nantucket Harbor Study: A quantitative assessment of the environmental health of Nantucket Harbor for the development of a nutrient management plan. Technical Report to the Town of Nantucket, pp Jorgensen, B.B The sulfur cycle of a coastal marine sediment (Limfjorden, Denmark). Limnology Oceanography, 22: King, I.P Program Documentation RMA2 A Two Dimensional Finite Element Model for Flow in Estuaries and Streams. Resource Management Assoc., Lafayette, CA. Klump, J. & C. Martens Benthic nitrogen regeneration. In: Nitrogen in the Marine Environment, (Carpenter & Capone, eds.). Academic Press. McCutcheon, S. C., Z. Dongwei, and S.Bird, Model calibration, validation, and use, Chapter 5 in Technical Guidance Manual for Performing Waste Load Allocations. In: Book III: Estuaries, Part 2: Application of estuarine waste load allocation models, J.J., Martin, R.B. Ambrose, and S. C. McCutcheon (eds.), US Environmental Protection Agency, Office of Water, March Murphy, J., J.P. Reilly A modified single solution method for the determination of phosphate in natural waters. Analytica chemica Acta 27: Scheiner, D Determination of ammonia and Kjeldahl nitrogen by indophenol method. Water Resources 10: