Massachusetts Estuaries Project Information

Massachusetts Estuaries Project

The Massachusetts Estuaries project was established in 2001 with the goal of developing nitrogen TMDLs for 89 embayments in Massachusetts. Originally this work was scheduled to be complete by 2010, but delays in completion of studies and budget shortfalls have slowed progress on the effort.

The MEP represents fulfilment of one of the goals of the Buzzards Bay CCMP to identify embayment specific nitrogen loading limits based on sound science. The 1991 CCMP recommended embayment specific modelling and use of parcel level data (and the BBNEP used a parcel level nitrogen loading analysis for the 1991 Buttermilk Bay overlay district), however GIS parcel coverages were not readily available for most towns in the early 1990s, embayment specific modeling was quite challenging in the early 1990s, and site specific water quality data to evaluate water quality modeling was completely lacking. Consequently the BBNEP adopted a simple tiered system of recommended loadings based on the empirical response between nitrogen loading and various ecosystem measures like eelgrass cover.

The MEP approach is based on nitrogen loading model that links embayment specific circulation modeling to land use loading estimates to predict total nitrogen concentrations in the estuary. The MEP runs these water quality models with different loading scenarios that would achieve a nitrogen concentration of around 0.4 ppm Total Nitrogen, if the water quality goal is to restore or protect eelgrass, and 0.5 ppm, if the goal is only to protect or restore benthic habitat like shellfish beds. The water quality and loading software used by the MEP were proprietary customizations of the SMS, WMS, RMS software packages produced by BOSS International. These software packages allow the user to import GIS shapefiles, bathymetric data, and site-specific tidal elevation data to model the embayment's circulation patterns, and to predict concentrations of compounds that act conservatively with mixing (e.g. salinity).

Conceptually, the nitrogen loading methodologies used by the MEP are quite similar to that of the BBNEP's and Cape Cod Commission's approach during the 1990s, and these loading models use similar assumptions. However, MEP updated the values of some of the most important based on their review of new studies and information. Most notably, the MEP uses a considerably lower estimate of loading from lawn fertilization, slightly lower per capita nitrogen contributions from septic systems, higher loadings for cranberry bogs, but lower for other agriculture like corn fields, and higher loading for natural landscapes. The MEP's parcel loading spreadsheets are also more comprehensive in that every Assessor's office parcel area is also assigned an area for impervious, lawn, natural landscapes, and so forth, although because these are based on fixed assumptions or percentages, they are not site specific, and generally equivalent to multiply the number of residential units in a watershed by presumed lawn, roof, and other area types. These parcel areas are multiplied times loading coefficients.

To approximate this loading methodology in a simplified form, the Buzzards Bay NEP's GIS and parcel analysis spreadsheets have been updated to use all MEP loading coefficients, except septic system system loadings, which we still based on numbers of residential units and assumed annual occupancy (this could be approximated by Mass GIS land use, US Census GIS information, town parcel data, and so forth). In contrast, MEP uses parcel data and parcel specific water use records to predict seasonal changes in occupancy, which has its own set of confounding factors (e.g. residential summer water use often doubles in summer because of lawn watering and pool use). To use the BBNEP's spreadsheets, go to our Interactive Loading Spreadsheets page.

Septic Loading Issues

Because most watershed nitrogen loads are dominated by septic systems, the most important element of any nitrogen loading model is to correctly estimate the number of septic systems in the watershed, and beyond that, estimating the number of individuals using those septic systems. The Buzzards Bay NEP's approach was simply to assume per capita wastewater discharge to groundwater was 2.7 kg (5.94 lb). To calculate annual loadings the BBNEP would then use US census statistics and GIS coverages to get average occupancy for the watershed being studied. One disadvantage of this process was that it failed to capture high summer seasonal use which occurred in some Cape Cod coastal areas.

The MEP took a very different approach to the problem by examining annual water use based on municipal water records. The advantage of this process is that it better captured seasonal increased occupancy. The disadvantage of this approach was that it was confounded by the fact that water use during the summer may double at at any particular residence because of lawn and garden irrigation, and consumption for filling pools.

Another issue that arises with water use data is that an assumed wastewater concentration must be adopted. Actual septic system loading is calculated by flow times concentration. In reviewing household wastewater studies, the BBNEP recognized that wastewater nitrogen concentrations from residences with similar occupancies can vary dramatically with water use. That is to say, wastewater nitrogen concentrations will be much higher in homes constructed with low flow devices (toilets and showers) or where water conservation is practiced.

The annual per capita loading rate adopted by the BBNEP (2.7 kg) was based on a review of studies of human waste and wastewater. The value adopted was also comparable to the assumed 35 ppm and 56 gpd per capita discharge assumed by the Cape Cod Commission in their loading models in the 1990s. Today per capita water use discharge to septic systems is generally assumed to be much less than 56 gpd and groundwater effluent concentrations assumed to be higher than 35 ppm. In the MEP loading models, wastewater concentrations are assumed much lower (26.25 ppm), but septic discharge to ground water much higher perhaps 70 or 80 gallons per day for loadings per capita loadings comparable to BBNEP assumed loadings of 2.7 Kg per year.

DEP's Massachusetts Estuaries Project Links

Background Documents

Overview of Program
Oceancscience.net web site (primary host)
Overview of Program
DEP site

Overview of Program
UMass Dartmouth SMAST web site

DEP Fact Sheet
Covers TMDL issues

DEP's list of estuaries
Schedule subject to change

MEP 2001 Pilot Project documents
Has the original planned schedule.

Multi-town collaboration
DEP web page with links

Nitrogen Management Tools
A Cape Cod Commission Report

Restoring Estuaries
A DEP Links page

BB Estuary Reports

West Falmouth Harbor
Completed

Phinneys Harbor / Back River complex
Completed

Wareham River Estuary Complex
Anticipated Jan. 2009

New Bedford Inner Harbor
Anticipated Nov. 2008

Slocums and Little River Complex
Anticipated Nov. 2008

Comments about this page should be directed to Joe Costa.

Our program was established in 1985 after Congress designated Buzzards Bay an "estuary of national significance." We joined the NEP in 1987. Our mission is to protect and restore water quality and living resources in Buzzards Bay and its surrounding watershed through the implementation of the Buzzards Bay Comprehensive Conservation and Management Plan. Click to read more.

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