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NPDES Permits in New England

OMSAP  LogoOMSAP Recommendations

July, 2000

Ronald Manfredonia
Associate Director, Water Quality Policy
EPA Region 1, New England
1 Congress Street, Suite 1100 (CAA)
Boston, MA 02114

Arleen O'Donnell
Assistant Commissioner
Massachusetts Department of Environmental Protection
1 Winter St.
Boston, MA 02108

Dear Ron and Arleen,

On behalf of the Outfall Monitoring Science Advisory Panel (OMSAP), I would like to forward several recommendations to the Environmental Protection Agency Region 1 and the Massachusetts Department of Environmental Protection. The following recommendations pertain to the National Pollutant Discharge Elimination System (NPDES) permit requirement that the Massachusetts Water Resources Authority (MWRA) develop a food web model scope of work as well as revisions to thresholds in the MWRA Contingency Plan.


As described on page nine of the MWRA NPDES outfall discharge permit, MWRA has developed and submitted a food web model scope of work to characterize the seasonal abundance of important prey of endangered species in Massachusetts and Cape Cod Bays. MWRA proposes an incremental approach, beginning with an examination of the likelihood that the environmental conditions in the bays will worsen as a result of the outfall relocation.

Recommendation: OMSAP recommends that EPA and MADEP accept MWRA's food web model scope of work statement as final and having fulfilled the permit requirement. Additionally, OMSAP invites concerned parties such as the Barnstable County Science Advisory Panel to submit proposals of modifications to the monitoring program that address their issues of concern. Of course, any revision to the monitoring program must be based on valid scientific considerations.

Recommendation: While the development of a quantitative, predictive food web model would provide information useful for the design of the monitoring program, OMSAP members believe that the development of such a model is not feasible. The development of such a model would require an understanding of the complex physical, chemical, and biological linkages in the bays that is well beyond current capabilities. However, OMSAP believes that careful monitoring and analysis based on a qualitative understanding of the bays ecosystems is critical and, moreover, that review and refinement of the monitoring program must be ongoing.


Several years ago, the Outfall Monitoring Task Force (OMTF) asked that MWRA attempt to develop a zooplankton threshold. MWRA has since made two attempts at developing such a threshold. The first, which is included in the Contingency Plan, is based on the so-called Acartia hypothesis and is aimed at detecting a "shift towards an inshore community". Acartia hudsonica and Acartia tonsa are common in inshore waters, but not offshore. When the Acartia hypothesis was originally developed, it was thought that the limiting growth factor for Acartia is nutrient concentration, so that an increase in Acartia abundance offshore would be indicative of eutrophication. However, further review has shown that Acartia may instead be limited by salinity and temperature. If this is true, then, as the new outfall will not significantly affect salinity in Massachusetts Bay, there is no reason to believe that an increase in Acartia abundance offshore would be a good indicator of an outfall effect. It is important to note that the OMTF did not officially approve the Acartia threshold during the permitting process and, because it was part of the Contingency Plan, it was accepted as part of the permit without full scientific review.

After finding that the Acartia threshold would not be a useful indicator of change, MWRA began to develop an alternative zooplankton threshold aimed at detecting a decline in mean abundance of five species (including Calanus finmarchicus) during the winter and spring. However, baseline monitoring results show dramatic differences in abundances among the sampling regions, suggesting that this approach would not be a sensitive indicator of change.

Recommendation: OMSAP does not support the current narrative zooplankton threshold as it is currently formulated and recommends its deletion from the Contingency Plan. However, OMSAP believes that continued zooplankton monitoring is extremely important and requests that MWRA present a plan to OMSAP in fall 2000 for analyzing zooplankton data using a system-wide approach. Since the Massachusetts and Cape Cod Bays system flows like a "conveyor belt" from north to south, MWRA should develop a method for analyzing the current data spatially and temporally to contrast differences between the northern boundary stations and Cape Cod Bay. If changes in the zooplankton communities in Massachusetts and Cape Cod Bays were, in fact, due to variations in input from the Gulf of Maine, then this should not raise an alarm about the effect of the outfall. On the other hand, changes in Cape Cod Bay that cannot be explained by changes in input from the north would be of greater concern. MWRA may also propose an alternative to this suggested method of analysis.


The current Contingency Plan threshold for the toxic dinoflagellate Alexandrium tamarense states that "the baseline seasonal mean shall not exceed the 95th percentile" in the nearfield. At its March meeting, OMSAP reviewed two sampling programs: those of MWRA and Dr. Don Anderson (Woods Hole Oceanographic Institution). Dr. Anderson's sampling effort is more effective in capturing Alexandrium in the water column. The program concentrates sampling along several transects between April and June, when Alexandrium blooms most commonly occur. The 95th percentile Alexandrium threshold based on the MWRA data is 10 cells per liter, while that based on Anderson's data is 71 cells per liter. Though the MWRA and Anderson datasets differ, both detected the large 1993 bloom.

Dr. Anderson is also currently funded by Sea Grant to determine whether spatial or temporal patterns of baseline shellfish toxicity can be used to develop a pattern-based threshold. This study is based on a 30-year record of paralytic shellfish toxicity constructed and maintained by the MA Division of Marine Fisheries. Preliminary analysis indicates that significant toxicity in northern stations can be used to predict later toxicity at southern stations. This is consistent with the theory that the source area for Alexandrium lies to the north of Massachusetts Bay, with transport to the south by a coastal current. Toxicity occurs during most years in southern Maine and northern Massachusetts, but cells seldom enter Massachusetts Bay in sufficient numbers to bloom substantially and cause toxicity. If Alexandrium cells were stimulated by nutrients from the outfall, then the effects would be expected to be seen "downstream" due to the circulation through Massachusetts Bay. This suggests that post-relocation occurrence of toxicity at the seven southern stations without a prior bloom at the northern stations would be indicative of an outfall effect, since there is no record of toxicity within the bay without a bloom further north. Another potential indicator of an outfall effect may be high toxicity at a southern station and low toxicity at the northern stations.

Recommendation: There is convincing evidence that Alexandrium is extremely variable and patchy in terms of occurrence. It is unclear whether it is more important to document abundances in areas where it is found infrequently or where it has never been found. Given all of these uncertainties, and the fact that there is a better, more integrated measure under development, OMSAP recommends deletion of the current Alexandrium cell count threshold. OMSAP is interested in evaluating the new paralytic shellfish toxicity threshold being developed by WHOI that uses the long-term shellfish monitoring.


The Contingency Plan threshold for floatables states that "floatables shall not exceed five gallons/day in the final collections device." However, the Deer Island Treatment Plant (DITP) design makes it impracticable and somewhat dangerous to sample the final collections device. MWRA has other measurements of plant performance such as sludge and scum removal, and fats, oil, and grease effluent concentrations. These measurements are an indication of plant performance and are made daily in primary treatment, reported in the monthly discharge report, and eventually posted on the Internet. There is also a field program that will net sample over a measured distance to capture floatables during each of the nearfield surveys seventeen times per year. Results of this field information will be summarized in the annual Outfall Monitoring Overview reports.

Recommendation: OMSAP believes that the current measurements of sludge and scum removed by the DITP as well as fats, oils, and grease measurements in the treated effluent adequately address the NPDES permit requirements for aesthetics. OMSAP recommends that MWRA delete the current floatables threshold in the Contingency Plan. OMSAP also recommends that MWRA report the sludge, scum, fats, oil, and grease measurements in the annual Outfall Monitoring Overview; address concerns regarding floatables if there is an adverse DITP event; and "fingerprint" the floatables from the DITP in a special study.


OMSAP strongly believes that there is no value in maintaining thresholds shown to be scientifically invalid (zooplankton and Alexandrium), or impossible to evaluate due to treatment plant design (floatables). Retaining such thresholds would undermine the purpose of the Contingency Plan – to detect changes due to the operation of the outfall. As our knowledge of the ecosystem improves, thresholds may be refined or added. In the meantime, we feel that it would be a disservice to rely on thresholds in which we have no confidence.


Dr. Andrew Solow
Woods Hole Oceanographic Institution
Outfall Monitoring Science Advisory Panel Chair

cc: Cathy Coniaris, NEIWPCC

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