UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, DC. 20460

THE ADMINISTRATOR 

Deborah L. Swackhamer, Ph.D. 

Chairwoman 

Science Advisory Board 

1200 Pennsylvania Avenue, NW 

Washington, D.C. 20460 

Dear Dr. Swackhamer: 

Thank you very much for the Science Advisory Board's recommendations on the U.S. Environmental 

Protection Agency's draft document Methods and Approaches for Deriving Numeric Criteria for 

Nitrogen/Phosphorus Pollution in Florida 's Estuaries, Coastal Waters, and Southern Inland Flowing 

Waters. We at the EPA are committed to using sound science as the basis for our actions, and we 

appreciate your thorough review of the methods we plan to use to derive numeric nutrient criteria for 

Florida's waters. Following many of your suggestions, we are currently modifying our methods and 

approaches and have considered our work on these proposed criteria a priority since we first presented 

them to you in December 2010. 

We are pleased to know that the SAB's generally supports our methods and approaches as valid, 

scientifically based methods for developing numeric nutrient criteria. Additionally, we agree with your 

conclusion that a dual nutrient strategy that calls for developing both numeric nitrogen and phosphorus 

criteria is warranted. We also agree with your encouragement that the EPA continue to develop numeric 

nutrient criteria using a combination of our three general approaches: reference conditions, stressorresponse and mechanistic modeling where data and models are available to give greater confidence in 

the resulting criteria values. Further, we plan to explain in more detail the link between nitrogen and 

phosphorus pollution and the assessment endpoints in the different waterbody types. 

With regard to estuaries, we understand your concerns about the time available to develop mechanistic 

models for Florida's estuaries. As we indicated in December, we were well on our way in the 

development of these models, and we are currently conducting calibration and sensitivity analyses on 

them. We are pleased that you support our use of healthy seagrass communities as a biological endpoint 

for Florida estuaries. On the issue of additional measures to determine the health of seagrass and fauna! 

communities to translate Florida's narrative nutrient criterion, the EPA has conducted a thorough 

literature review to evaluate the appropriate assessment endpoints to protect aquatic flora and fauna 

populations from nitrogen and phosphorus pollution. Although we continue to explore additional 

endpoints such as macroalgae, epiphytes, benthic macroinvertebrates, fish, harmful algal blooms and 

coral indices, it is not clear that there are sufficient data available now to support an assessment analysis 

based on these endpoints.

Internet Address (URL) http //www epa gov


Recycled/Recyclable Printed with Vegetable Oil Based Inks on 100% Postconsumer. Process Chlorine Free Recycled Paper
For coastal waters, the EPA appreciates your support of the use of satellite imagery to derive numeric 

nutrient criteria for these waters. The EPA plans to investigate how we can validate satellite data with 

expanded use of field observations beyond the three-nautical-mile limit as the SAB recommended. We 

agree with, and are following up on, your suggestion to cross-calibrate data to ensure that data from 

future sensors can be used if existing platforms are retired. 

For South Florida inland flowing waters, the EPA understands your concerns about the challenges 

associated with deriving numeric nutrient criteria that would be protective within man-made and 

managed Class III canals. Because Florida has designated the uses of these waters no differently than 

other flowing waters within the state, state regulation currently requires these waters to meet the same 

water-quality goals and the same level of protection as other Class III waters across the state. In 

response to your suggestions, the EPA is exploring the use of natural factors for South Florida inland 

flowing waters in the derivation of numeric nutrient criteria. The EPA is also evaluating options to 

characterize aquatic life in canals and other South Florida inland flowing waters, including the use of 

chlorophyll-a and periphyton data as well as the use of multiple lines of evidence. We agree with the 

SAB that nutrients in canals should be managed to ensure the attainment and maintenance of 

downstream water-quality standards. 

Finally, the EPA will be taking into account the SAB's comments on our proposed approach to develop 

downstream protective values to provide assurance that proposed water-quality standards for 

downstream estuaries will be attained and maintained by nutrient inputs from upstream sources. There is 

a distinct difference between establishing a water-quality standard to proactively protect designated uses 

and establishing a total maximum daily load to restore conditions in degraded waterbodies, even though 

the tools to develop each might be very similar. We understand your concerns about the need to 

maintain flexibility for nutrient allocation across tributaries to achieve necessary estuarine load 

reductions. Setting downstream protective values does not preclude any allocation option, including the 

use of trading scenarios, which may be available to the state to implement these water-quality standards. 

Nitrogen and phosphorus pollution poses a significant water-quality problem in our nation's waters, 

including those in Florida. Your considered advice and expert recommendations are greatly appreciated 

and will strengthen the scientific basis and analytical methodologies. We at the EPA rely on our 

partnership with Florida to develop scientifically sound and defensible numeric nutrient criteria for 

estuarine, coastal and South Florida inland flowing waters. 

I thank you once more for your hard work and expertise.
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY


WASHINGTON, D.C. 20460 

PRO

THE ADMINISTRATOR 

Judith L. Meyer, Ph.D. 

Chairwoman 

Nutrient Criteria Review Panel 

Science Advisory Board 

1200 Pennsylvania Avenue, NW 

Washington, D.C. 20460 

Thank you very much for the Science Advisory Board's recommendations on the U.S. Environmental 

Protection Agency's draft document Methods and Approaches for Deriving Numeric Criteria for 

Nitrogen/Phosphorus Pollution in Florida 's Estuaries, Coastal Waters, and Southern Inland Flowing 

Waters. We at the EPA are committed to using sound science as the basis for our actions, and we 

appreciate your thorough review of the methods we plan to use to derive numeric nutrient criteria for 

Florida's waters. Following many of your suggestions, we are currently modifying our methods and 

approaches and have considered our work on these proposed criteria a priority since we first presented 

them to you in December 2010. 

We are pleased to know that the SAB's generally supports our methods and approaches as valid, 

scientifically based methods for developing numeric nutrient criteria. Additionally, we agree with your 

conclusion that a dual nutrient strategy that calls for developing both numeric nitrogen and phosphorus 

criteria is warranted. We also agree with your encouragement that the EPA continue to develop numeric 

nutrient criteria using a combination of our three general approaches: reference conditions, stressorresponse and mechanistic modeling where data and models are available to give greater confidence in 

the resulting criteria values. Further, we plan to explain in more detail the link between nitrogen and 

phosphorus pollution and the assessment endpoints in the different waterbody types. 

With regard to estuaries, we understand your concerns about the time available to develop mechanistic 

models for Florida's estuaries. As we indicated in December, we were well on our way in the 

development of these models, and we are currently conducting calibration and sensitivity analyses on 

them. We are pleased that you support our use of healthy seagrass communities as a biological endpoint 

for Florida estuaries. On the issue of additional measures to determine the health of seagrass and faunal 

communities to translate Florida's narrative nutrient criterion, the EPA has conducted a thorough 

literature review to evaluate the appropriate assessment endpoints to protect aquatic flora and fauna 

populations from nitrogen and phosphorus pollution. Although we continue to explore additional 

endpoints such as macroalgae, epiphytes, benthic macroinvertebrates, fish, harmful algal blooms and 

coral indices, it is not clear that there are sufficient data available now to support an assessment analysis 

based on these endpoints.

Internet Address (URL) . http://www.epa.gov


Recycled/Recyclable Printed with Vegetable Oil Based Inks on 100% Postconsumer. Process Chlorine Free Recycled Paper
For coastal waters, the EPA appreciates your support of the use of satellite imagery to derive numeric 

nutrient criteria for these waters. The EPA plans to investigate how we can validate satellite data with 

expanded use of field observations beyond the three-nautical-mile limit as the SAB recommended. We 

agree with, and are following up on, your suggestion to cross-calibrate data to ensure that data from 

future sensors can be used if existing platforms are retired. 

For South Florida inland flowing waters, the EPA understands your concerns about the challenges 

associated with deriving numeric nutrient criteria that would be protective within man-made and 

managed Class III canals. Because Florida has designated the uses of these waters no differently than 

other flowing waters within the state, state regulation currently requires these waters to meet the same 

water-quality goals and the same level of protection as other Class III waters across the state. In 

response to your suggestions, the EPA is exploring the use of natural factors for South Florida inland 

flowing waters in the derivation of numeric nutrient criteria. The EPA is also evaluating options to 

characterize aquatic life in canals and other South Florida inland flowing waters, including the use of 

chlorophyll-a and periphyton data as well as the use of multiple lines of evidence. We agree with the 

SAB that nutrients in canals should be managed to ensure the attainment and maintenance of 

downstream water-quality standards. 

Finally, the EPA will be taking into account the SAB's comments on our proposed approach to develop 

downstream protective values to provide assurance that proposed water-quality standards for 

downstream estuaries will be attained and maintained by nutrient inputs from upstream sources. There is 

a distinct difference between establishing a water-quality standard to proactively protect designated uses 

and establishing a total maximum daily load to restore conditions in degraded waterbodies, even though 

the tools to develop each might be very similar. We understand your concerns about the need to 

maintain flexibility for nutrient allocation across tributaries to achieve necessary estuarine load 

reductions. Setting downstream protective values does not preclude any allocation option, including the 

use of trading scenarios, which may be available to the state to implement these water-quality standards. 

Nitrogen and phosphorus pollution poses a significant water-quality problem in our nation's waters, 

including those in Florida. Your considered advice and expert recommendations are greatly appreciated 

and will strengthen the scientific basis and analytical methodologies. We at the EPA rely on our 

partnership with Florida to develop scientifically sound and defensible numeric nutrient criteria for 

estuarine, coastal and South Florida inland flowing waters. 

I thank you once more for your hard work and expertise.