Page 1 of 18 HIGHLIGHTED EDITS MADE PURSUANT TO OMB COMMENT

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131 [EPA - HQ - OW - 2009 - 0596 ; FRL - XXXX - X]

[RIN 2040 - AF11] Water Quality Standards for the State of Florida’s Lakes and Flowing Waters; Supplemental Notice of Data Availability and Request for Comment AGENCY: Environmental Protection Agency (EPA). ACTION: Supplemental Notice of Data Availability and Request for Comment. SUMMARY: This action is a supplemental notice of data availability and a request for comment related to EPA’s January 26 , 2010 notice of proposed rulemaking (NPRM), proposing numeric nutrient water quality criteria to protect aquatic life in lakes and flowing waters within the State of Florida. In the January 2010 NPRM, EPA proposed to classify Florid a ’s streams into four regions (referred to in the proposed rule as “Nutrient Watershed Regions”) for application of total nitrogen (TN) and total phosphorus (TP) criteria . Streams within each of these regions (Panhandle, Bone Valley , Peninsula and North Ce ntral) reflect similar geographical characteristics including phosphorus - rich soils, nutrient concentrations and nutrient ratios. In this notice, EPA is requesting comment on revised stream region boundaries based on additional information about watershed delineations and phosphorus - rich geological formations in Florida. Based on comments and additional information, th is revised regionalization approach would result in five Nutrient Watershed Regions for Florida’s streams and a clarification of certain wate rshed boundaries for the Bone Valley and Peninsula regions. EPA is also requestingPage 2 of 18

comment on basing the TN and TP criteria for the nutrient watershed regions on a combination of the 75 th and 90 th percentile values (depending on regions) of the benchmark sites outlined in the alternate approach at proposal. EPA is continuing to consider the primary

approach proposed in January 2010 to use the 75 th percentile of sites with healthy

biological conditi on as measured b y the Stream Condition Index (SCI). The January 2010 proposal also proposed application of the Vollenweider equation to ensure that nutrient criteria in streams are protective of downstream lakes and requested comment on alternative approac hes such as the BATHTUB model and whether there should be an allowance for use of other models that are demonstrated to be protective and scientifically

defensible. T oday ’s notice also requests comment on using the BATHTUB model in place of the Vollenweide r equation for deriving both TP and TN criteria to protect downstream lakes , allowing the use of alternative models under certain circumstances, and providing for an alternative approach to protect downstream lakes when limited data are available that woul d use the lake criteria themselves as criteria for upstream waters flowing into the lake . EPA is seeking comment on alternative stream regionalization approaches, use of the benchmark dataset to derive criteria, and derivation of lake downstream protection values discussed in more detail below, and will consider the comments received before finalizing the proposed rule, “Water Quality Standards for the State of Florida’s Lakes and Flo wing Waters . ” This supplemental notice focuses solely on the de lineation o f stream nutrient regions, resulting criteria associated with two approaches (EPA’s SCI - based approach and the alternative benchmark distribution approach), and protection of downstream lakes in Florida. EPA is not soliciting comment on any other provision s of the January 2010 proposal.Page 3 of 18

DATES : Comments must be received on or before [insert date] , 30 day s after publication in the Federal Register . ADDRESSES : Submit your comments, identified by Docket ID No. EPA - HQ - OW 2009 - 0596 , by

one of the following methods: 1. www.regulations.gov : Follow the on - line instructions for submitting comments. 2. Email: ow - docket@epa.gov 3. Mail to: Water Docket, U.S. Environmental Protection Agency , Mail code: 2822T, 1200 Pennsylvania Avenue, NW, Washington, DC 20460 , Attention: Docket ID No. EPA - HQ - OW - 2009 - 0596 . 4. Hand Delivery : EPA Docket Center, EPA West Room 3334, 1301 Constitution Avenue, NW, Washington, DC 20004, Attention Docket ID No. EPA - HQ - OW 2009 - 0596. Such deliveries are onl y accepted during the Docket’s normal hours of operation, and special arrangements should be made for deliveries of boxed information. Instructions : Direct your comments to Docket ID No. EPA - HQ - OW - 2009 - 0596. EPA’s policy is th at all comments received will be included in the public docket without change and may be made available online at www.regulations.gov , including an y personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted b y statute . Do not submit information that you consider to be CBI or otherwisePage 4 of 18

protected through www.regulations.gov or e - mail . The www.regulations.gov Web site is an “anon ym ous access” sy stem, which means EPA will not know your identity or contact information unless you provide it in the body of your comment . If you send an e - mail comment directl y to EPA without going through www.regulations.gov your e - mail address will be automatically captured and included as part of the comment that is placed in the public docket and made av ailable on the Internet . If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD - ROM you submit . If EPA cannot read your comment due to technical diffi culties and cannot contact you for clarification, EPA may not be able to consider your comment . Electronic files should avoid the use of special characters, an y form of encry ption, and be free of any

defects or viruses . For additional information about EPA ’s public docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm . Docket : All documents in the docket are listed in the www.regul ations.gov index . Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted b y statute . Certain other material, such as copy righted material, will be publicly available only

in h ard cop y . Publicly

available docket materials are available either electronically in www.regulations.gov or in hard copy at a docket facility. The Office of Water (OW) Docket Center is open from 8:30 until 4:30 p.m., Monday

through Friday , excluding legal holiday s . The OW Docket Center telephone number is (202) 566 - 2426, and the Docket address is OW Docket, EPA West, Room 3334, 1301 Constitution Avenue, NW, Washington, DC 20004 . The PublicPage 5 of 18

Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holiday s . The telephone number for the Public Reading Room is (202) 566 - 1744 . FOR FURTHER INFORMATION CONTACT : Danielle Salvaterra , U.S. EPA Headquarters, Off

ice of Water, Mailcode: 4305T, 1200 Pennsylvania Avenue, NW, Washington, DC 20460 ; telephone number: 202 - 564 - 1649 ; fax number: 202 - 566 - 9981 ; email address: salvaterra.danielle @epa. gov. SUPPLEMENTARY INFORMATION : This supplementary information section is organized as follows: Table of Contents I. General Information A. What Should IConsider as I Prepare M y Comments for EPA? B. How Can I Get Copies of This Document and Other Related Information? II. Background III. Supplemental Information on Numeric Nutrient Criteria f or the State of Florida’s Lakes and Flowing Waters A. Stream Regionalization and Alternative Approaches to Stream Criteria Derivation B. Downstream Protection of Lakes I. General InformationPage 6 of 18

A . W hat Should I Consider as I Prepare My Comments for EPA? 1. Submitting CBI

. Do not submit this information to EPA through http://www.regulations.gov or e - mail . Clearl y mark the part or all of the information that yo u claim to be CBI . For CBI information in a disk or CD - ROM that you mail to EPA, mark the outside of the disk or CD - ROM as CBI and then identify electronically

within the disk or CD - ROM the specific information that is claimed as CBI . In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket . Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2. 2 . Tips for Preparing Your Comments . When submitting comments, remember to: 1. Id entify

the rulemaking by

docket number and other identifying information (subject heading, Federal Register date , and page number). 2. Follow directions -- The agency may ask you to respond to specific questions or to address a particular issue. 3. Explain why

you agree or disagree; suggest alternatives and substitute language for your requested changes. 4. Describe an y assumptions and provide any technical information and/or data that yo u used. 5. Provide specific examples to illustrate your concerns, and suggest alternatives. 6. Make sure to submit your comments by the comment period deadline identified.

B . How Can I Get Copies of This Document and Other Related Information?Page 7 of 18

1. Docket . EPA has established an official public docket for this action under Docket Id. No. EPA - HQ - OW - 2009 - 0596. The official public docket consists of the document specificall y referenced in this action, any public comment s received, and other information related to this action . Although a part of the official docket, the public docket does not include CBI or other information whose disclosure is restricted b y statute . The official public docket is the collection of materials that is available for public viewing at the OW Docket, EPA West, Room 3334, 1 301 Constitution Ave., NW, Washington, DC 20004 . Th is Docket Facility is open from 8:30 a.m. to 4:30 p.m., Monday through Friday , excluding legal holiday s . The Docket telephone number is 202 - 566 - 1744 . A reasonable fee will be charged for copies. 2. Electronic Access . You may access this Federal Register document electronically through the EPA Internet under the “ Federal Register” listings at http://www.epa.gov/fedrgstr/ . An electronic version of the public docket is available through EPA's electronic public docket and comment sy stem, EPA Dockets . You may use EPA Dockets at http://www.regulat ions.gov to view public comments, access the index listing of the contents of the official public docket, and to access those documents in the public docket that are available electronically . For additional information about EPA's public docket , visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm . Although not all docket materials may be available electronically , you may still access any of the publicl y available docket materials through the Docket Facilit y identified in Section I. B.1 .Page 8 of 18

II. Background On January

26, 2010, EPA proposed “Water Quality Standards for the State of Florida’s Lakes and Flo wing Waters” (75 FR 4173). EPA conducted 13 public hearing sessions in six cities in Florida and held a 90 - day public comment period as part of the proposed rule generating over 22,000 public comments. EPA is reviewing and considering these comments in preparation of the final rule, which is scheduled to be signed b y the EPA Administrator on October 15, 2010. Today ’s notice reflects a review of comments and new information received by the Agency

as part of the public comment process, and requests further comment on possible revisions, additional options, and new information related to specific approaches and issues identified in the January 26, 2010 proposal. EPA is only seeking comment on the items presented in this supplemental notice . EPA is not soliciting comment on any other provisions of the January 2010 proposed rule. III. Supplemental Information on Numeric Nutrient C riteria for the State of Florida’s Lakes and Flowing Waters A. Stream Regionalization and Alternative Approaches to Stream Criteria Derivation EPA proposed classifi cation of Florida’s streams north of Lake Okeechobee by separating watersheds with substanti ally different stream molar ratios of TN to TP into Nutrient Watershed Regions (NWR) . The resulting regions reflect the inherent differences in the natural factors that contribute to nutrient concentrations in streams (e.g., geology , soil composition, and/ or hydrology) . Reliance on a watershed - based classification approach reflects the understanding that upstream water quality affectsPage 9 of 18

downstream water quality . EPA requested public comment on the stream regionalization approach as well as factoring in geolog ical influences from phosphorus - rich soils when classifying stream regions (75 FR 4195 - 96). EPA received public comments and information that suggested refining the proposed stream regions to account for natural variability

in soil nitrogen and phosphorus as well as clarifying the boundaries of the proposed stream regions. Today , EPA is requesting comment on a revised approach to certain stream regions suggested b y FDEP and other commenters. More specifically, EPA is considering additional information on the influence of phosphorus - rich soils and geology in Florida (associated with the Hawthorne Group) for areas in the northern Panhandle region. Based on comments and information received, the Agency is also considering further refinements to the regional bo undaries separating the Peninsula region from the West Central region (referred to in the proposed rule as “Bone Valley”). Based on geological information 1 , EPA is considering dividing the proposed Panhandle region into a Panhandle West (less phosphorus - ri ch) and Panhandle East (more phosphorus - rich) region. In drawing the boundary between the two regions, EPA is continuing to rel y on the watershed approach described in the proposed rule and is considering using the eastern boundary of the Apalachicola Rive r watershed as the dividing line between the two regions. EPA believes that dividing the Panhandle region in this manner may

more accuratel y represent the natural influences on stream TP

1 Scott, T.S., 1988, The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin No. 59; 148 p.; Scott, T.S., K.M. Campbell, F.R. Rupert, J.D. Arthur, T.M. Missimer, J.M. Lloyd, J.W. Yon and J.G. Duncan, 2001, Ge ologic map of the state of Florida: Florida Geological Survey Map Series 146; Scott, T.S., 2001, Text to accompany the geologic map of Florida: Florida Geological Survey Open - File Report 80; 29 p.Page 10 of 18

concentrations and provide finer spatial resolution with respect to T P criteria; however, we request comment on this conclusion. EPA is considering these adjustments in the Panhandle region to account for natural geological influences on stream phosphorus concentrations. EPA considered different approaches to classifying Fl orida’s streams for application of TN criteria, such as the four Nutrient Watershed Regions discussed in the January 2010 proposal and two regions as originall y suggested b y FDEP. However, differences in the resulting TN criteria based on these stream clas sification schemes were minor and the approaches were comparable. Therefore, to assure consistency and clarity

in applicability

decisions and implementation, EPA is also considering using the same revised Panhandle delineation for stream TN criteria as wel l as the TP criteria. This consistency in regionalization for TN and TP provides clarity to the public on which stream criteria appl y at any given location, which can help facilitate the State’s implementation of both stream TN and TP criteria.EPA also re examined the watershed delineations of the West Central and Peninsula regions based on comments and information from FDEP and others. As a result of this review, EPA has gained greater knowledge of the watershed boundaries and is considering refining the b oundary delineations accordingl y. The result for the West Central region would be a modified western boundary that shifts from Florida’s west coast shoreline inland to the east as explained in more detail below. EPA believes that these possible adjustments to the West Central and Peninsula stream region boundaries more accurately

reflect the watershed boundaries; however, we request comment on this conclusion.Page 11 of 18 As a result of the new information and possible adjustments to the proposed stream regionalization approach that are outlined above, EPA is considering five Nutrient Watershed Regions for deriving TP and TN criteria for streams. The five Nutrient Watershed Regions would include a Panhandle West region encompassing Perdido Bay Watershed, Pensacola Bay W atershed, Choctawhatchee Bay Watershed, St. Andrew Bay Watershed, and Apalachicola Bay Watershed. Itwould also include a Panhandle East region encompassing Apalachee Bay Watershed, and Econfina/Steinhatchee Coastal Drainage Area. The West Central ( Bone Va lley) and Peninsula region s would be revised slightly to more accurately

reflect watershed boundaries (e.g., the Sarasota Bay and Charlotte Harbor Watersheds would move from the West Central (Bone Valley) to the Peninsula region). The proposed North Centra l region encompassing the Suwannee River Watershed would remain unchanged. EPA is providing the following information in the docket to illustrate and delineate the revised Nutrient Watershed Regions under consideration: 1. Map of revised TN , T P regions, 2. Map of Hawthorne group overlaid on revised Panhandle regions, 3. GI S shapefile of revised TN , T P regions, 4. Florida geological information on the Hawthorne group (see footnote 1). EPA is also providing additional information in this notice and in the doc ket on the TN and TP criteria that are based on the revised Nutrient Watershed Regions under consideration. Using EPA’s previousl y proposed approach (75 th percentile) and the revised stream regions discussed in this notice, the TN and TP criteria would be: Panhandle West

– 0.84 mg/L and 0.03 mg/L, respectivel y; Panhandle East

– 0.77 mg/L and 0.10 mg/L, respectively ; North Central

– 1.48 mg/L and 0.36 mg/L, respectivel y;Page 12 of 18

West Central

– 1.80 mg/L and 0.73 mg/L, respectively ; and P eninsula

– 1.20 mg/L and 0.10 mg/L, respectivel y. To illustrate the derivation of stream criteria based on the revised regions, EPA has re - organized the same nutrient dataset provided in the proposed rule and is making it available to the public in the docket for this notice. These da ta were organized on the basis of site averages to derive the proposed criteria outlined above. At proposal, EPA also requested comment on the benchmark distribution approach. In response to comments, the Agency is considering using a combination of the 7 5 th and 90 th percentile values (depending on regions) based on benchmark sites , with additional data quality

screens applied, to establish criteria. EPA is considering the 90 th percentile for all regions except the West Central, where the Agency is conside ring the 75 th percentile due to less data available. Using the benchmark distribution approach and the revised stream regions discussed in this notice, the TN and TP criteria would be: Panhandle West

– 0.62 mg/L and 0.04 mg/L, respectivel y; Panhandle East

– 0.97 mg/L and 0.11 mg/L, respectively ; North Central

– 1.90 mg/L and 0.35 mg/L, respectivel y; West Central

– 1.30 mg/L and 0.35 mg/L, respectively ; and Peninsula

– 1.67 mg/L and 0.11 mg/L, respectivel y. Included in the docket for today’s notice is the be nchmark dataset presented at proposal with the additional quality assurance screens applied , that was used to calculate these values . The stream criteria using this approach are calculated on the basis of Waterbody I dentifiers (WBIDs) and the derivation is outlined in more detail in the docket for today ’s notice. EPA requests comment on this approach. EPA is soliciting comment on the refined regionalization approach and criteria described in this supplemental notice. The Agency is specificall y requesting c omment on revised stream criteria using EPA’s previously proposed approach (applied to the revisedPage 13 of 18

regions) as outlined above as well as alternative stream criteria based on utilization of the benchmark distribution approach applied to the revised regions, also outlined above. EPA will evaluate all data and information submitted by the close of the public comment period for this supplemental notice with regard to regionalization and criteria derivation for Florida’s streams . B. Downstream Protection of Lak es In its January

2010 FRN, EPA proposed a phosphorus loading model equation first developed b y Vollenweider2 to relate a lake TP concentration criterion to the concentration necessary in incoming stream s to support the lake criterion. EPA proposed to apply th e equation’s resulting stream concentration as the applicable criterion for all stream segments upstream of the lake if those concentrations were more stringent than the otherwise applicable instream criteria for the stream segments. EPA mathematic al ly derive d this equation, with allowable input of lake - specific characteristics, to calculate values intended to serve as protective criteria necessary to assure attainment and maintenance of the lake numeric nutrient criteria also included in the propos al (75 FR 4198). The proposed Vollenweider model equation requires input of two lake - specific characteristics: the fraction of inflow due to stream flow and the h ydraulic retention time. Because lake - specific input values may not alway s be readil y availab le, EPA provided alternative preset values for percent contribution from stream flow and h ydraulic retention time that could be used in those instances. EPA’s January 2010 proposed rule discussed the flexibility for the State to use site - specific inputs to the Vollenweider

2 Vollenweider, R.A. 1975. Input - output models with special reference to the phosphorus loading concept in limnology. Schweizerische Zeitschrift fur Hydrologie. 37:53 - 84; Vollenweider, R.A. 1976. Advances in differing critical loading levels for phosphorus in lake eutrophication. Mem. Ist. Ital. Idrobid. 33:53 - 83.Page 14 of 18

equation for these two parameters , as long as the State determines that they are appropriate and documents the site - specific values. EPA requested comment on several technical aspects of this equation and its application. In addition, EP A requested comment on the potential to develop a corollary approach for nitrogen . Several commenters suggested the need for protective TN values to protect downstream lakes that are nitrogen - limited (such as man y of the lakes in the phosphorus - rich areas of the State). EPA recognized that more specific information may be readil y available for individual lakes that could allow the use of alternative approaches such as the BATHTUB model 3 and requested comment in the January 2010 proposal on the availability and application of th is model . EPA also requested comment on whether there should be a specific allowance for use of alternative lake - specific models where demonstrated to be protective and scientifically defensible based upon current and readil y available data. EPA received man y comments on this proposed approach for protection of lakes downstream of rivers and streams . Some felt that that the Vollenweider equation was overly simplistic to represent all lakes in Florida and that it does not include the necessary factors to account for phy sical, hydrologic, chemical, and biological processes necessary to determine protective criteria . Comments included a recommendation to use models that can better represent site - specific conditions , such as BATHTUB.

3 Kennedy, R. H., 1995. Application of the BATHTUB Model to Selected Southeastern Reservoirs . Technical Report EL - 95 - 14, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. ; Walker, W. W., 1985. Empirical Methods for Predicting Eutrophication in Impoundments; Report 3, Phase II: Model Refinements . Technical Report E - 81 - 9, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. ; Walker, W. W., 1987 . Empirical Methods for Predicting Eutrophi cation in Impoundments; Report 4, Phase III: Applications Manual. Technical Report E - 81 - 9, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.Page 15 of 18 BATHTUB is designed to apply empirical eutrophication models to morphometricall y complex lakes and reservoirs. The program performs steady - state water and nutrient balance calculations, uses spatially segmented hydraulic network s, and accounts for advectiv e and diffusive transport of nutrients. BATHTUB predicts nutrient related water quality

conditions such as to tal phosphorus, total nitrogen and chloroph yl l a concentrations , transparency , and hy polimnetic oxygen depletion rate s. The model can apply to a variet y of lake sizes , shapes and transport characteristics . A high degree of flexibility is available for specifying model segments as well as multiple influent streams. Because water quality

conditions are calculated using empirically - derived relationships , BATHTUB inherentl y accounts for internal loading of phosphorus from bottom sediments. Additional technical references are available that describe the model and its applications. 4 For the provision of EPA’s proposed rule for deriving criteria for protecti on of downstream lakes (§ 131.43(c)(2)(ii)), EPA is considering requiring the use of BATHTUB rather than a loading model equation based on Vollenweider. The rule would therefore require that the criteria for protection of downstream lakes would be the more stringent of the instream TP and TN criteria value or the concentration of TP and TN derived from application of BATHTUB. The resulting criteria using BATHTUB could be either more or less stringent than the criteria derived using Vollenweider, depending on site - specific lake factors. EPA believes BATHTUB may be more appropriate for 4 Walker, W.W., 1981. Empirical Methods for Predicting Eutrophication in Impoundments; Report 1, Ph ase I: Data Base Development. Technical Report E

– 81

– 9, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.; Walker, W.W., 1982. Empirical Methods for Predicting Eutrophication in Impoundments; Report 2, Phase II: Model Testing. Technical Report E

– 81

– 9, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.; Walker, W.W., 1999. Simplified Procedures for Eutrophication Assessment and Prediction: User Manual ; Instruction Report W - 96 - 2, U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, M.S.Page 16 of 18

downstream protection value calculations than Vollenweider because BATHTUB has the capability to represent a greater number of site - specific variables, which may influence nutrient responses. In addition, BATHTUB can estimate TN concentrations. As noted above, a number of commenters observed that a limitation in EPA’s original proposal was that it only

addressed TP. EPA is also considering additional rule language that would spe cifically authorize FDEP or EPA to use a model other than BATHTUB when either determines that it would be appropriate to use another scientificall y defensible technical model or approach that demonstrates protection of downstream lakes. While BATHTUB is a peer reviewed and versatile model, there are other models that , when appropriatel y calibrated and applied, can offer additional capability to address more complex situations and address an even greater degree of site - specificity . One example of an alternative model that FDEP or EPA might consider using for particularl y complex site - specific conditions is the Water Qualit y Anal ys is Simulation Program (WASP) model . This model allows users to conduct detailed simulations of water qualit y responses to natural and manmade pollutant inputs. WASP is a dy namic compartment - modeling program for aquatic s ys tems, including both the water column and the underl yi ng benthos. WASP allows the user to simulate sy stems in 1, 2, or 3 dimension s , and a variet y of pollutant ty p es. The model can represent time varying processes of advection, dispersion, point and diffuse mass loading , and boundary exchange. WASP also can be linked with hydrodynamic and sediment transport models that can provide flows, depths , velocities, temperat ure, salinity

and sediment fluxes .Page 17 of 18

Additional technical information may be found at http://www.epa.gov/athens/wwqtsc/html/wasp.html . EPA is considering recommending BATHTUB as the method for cal culating the TN and TP downstream protective values in streams that flow into lakes because of its ability to incorporate site - specific factors in estimates, its use of data that may be readily available, and its ease of use and rapid processing time. BATH TUB has been used to model nutrients in lakes and reservoirs throughout the United States. BATHTUB allows for greater site - specificity than the Vollenweider approach, and input of more local information to calculate concentrations of both nitrogen and phos phorus in streams that assure downstream protection of lakes. In certain circumstances, a more complex model such as WASP may

be appropriate, and EPA is considering and requesting comment on adding specific provisions to allow either the Agency or FDEP to use an alternative model such as WASP where greater spatial or temporal detail in model output is called for, or where water quality considerations that fall outside the scope of BATHTUB are to be explicitly

considered. EPA is also requesting comment on i ncluding a provision in this section of the rule that would provide that if data are not readily available to derive a TN or TP downstream protection value using BATHTUB or another scientifically defensible model, the lake criteria values for TN and TP wou ld be used as the downstream protection values where they are more stringent than the instream values. EPA believes that this approach is protective because the allowable concentration of nutrients entering the lake would be equal to criteria that are prot ective of the lake water itself; however, this approach may

result in the application of more stringent criteria in the streamsPage 18 of 18

entering the lake than would be calculated using BATHTUB or another scientifically defensible model if site - specific data were available. EPA is soliciting comment on the approaches to protect downstream lakes described in this supplemental notice. EPA will evaluate all data and information submitted by

the close of the public comment period for this supplemental notice with regard to nutrient criteria to protect downstream lakes in Florida. Dated: July

29, 2010. Peter S. Silva , Assistant Administrator for Water.