The Indiana Department of Environmental Management (IDEM) is soliciting public comment for the development of its draft 2014 303(d) List of Impaired Waters and the Consolidated Assessment and Listing Methodology (CALM) used to develop it. The 303(d) list will be submitted to the United States Environmental Protection Agency (U.S. EPA) on April 1, 2014. Any person having water quality data to support or refute the listing of a specific waterbody or to add a waterbody to the list will be able to provide that information to IDEM during the public comment period. Comments and suggestions regarding the CALM will also be accepted during this period. IDEM will review and respond to all comments received and will work with U.S. EPA after the comment period ends to finalize the list for U.S. EPA approval.

The draft 303(d) list and the CALM will be also be available April 30, 2014, on IDEM's website at:

The IDEM Office of Water Quality (OWQ) is preparing to update its 303(d) List of Impaired Waters, as required by Section 303(d) of the federal Clean Water Act (CWA) and the Water Quality Planning and Management regulation contained in the Code of Federal Regulations (CFR) at 40 CFR Part 130. Under the CWA, each state is required to assemble all existing and readily available water quality related data and information for use in assessing its waters for compliance with the state's water quality standards (WQS). Water quality criteria are developed to protect uses articulated in Indiana's WQS, including recreational uses, aquatic life use, and the use of some waters as a drinking water resource. The state is then required to prepare and make public a list of those waters not meeting WQS and the methodology used to evaluate the data and determine impairment status. The 303(d) List of Impaired Waters will identify:

A TMDL evaluation is a process that quantifies the amount of a specific pollutant that a waterbody can assimilate and still meet WQS. What constitutes a pollutant is described in Section 502(6) of the CWA and includes materials such as sewage, chemical wastes, biological materials, and wastes from industrial, municipal, and agricultural operations. The definition also encompasses drinking water contaminants that are regulated under Section 1412 of the Safe Drinking Water Act. A TMDL is a written, quantitative assessment that:

As part of IDEM's TMDL process, the public is invited to participate in the plan to develop and implement the TMDL.

On May 8, 2013, IDEM received a partial approval of Indiana's 2010 303(d) list. The U.S. EPA's partial approval is based on issues regarding changes IDEM made to the 303(d) list in response to public comments received prior to IDEM's submission of the 2010 303(d) list to the U.S. EPA. The U.S. EPA's proposed decision identifies the water quality limited segments and associated pollutants to be added to Indiana's 2010 Section 303(d) list. The U.S. EPA published its proposed decision for a 30 day public comment period on June 14, 2013, and reopened the comment period on September 13, 2013, to allow an additional 30 days for the public to comment on the proposed changes. The U.S. EPA's decision document, which explains the rationale for its decision and the specific waterbodies to which it pertains, is available online at: http://www.epa.gov/region5/water/impairedwatersin/index.html

More detailed information regarding IDEM's position on the waterbodies and pollutants in question can be found in IDEM's 2010 303(d) list submittal, which is available online at: http://www.in.gov/idem/nps/3889.htm.

The issues raised by the U.S. EPA in response to IDEM's 2010 303(d) list submittal have yet to be resolved. IDEM did not add the impairments proposed by U.S. EPA in its 2010 decision document to Indiana's 303(d) list submittal for 2012, and these impairments have not been added to the draft 2014 303(d) list published in this notice.

These issues illustrate that any concerns the U.S. EPA may have regarding revisions to a state's assessment methodologies and corresponding changes to its 303(d) list can impose significant delays in approval. For this reason, IDEM has determined that reviewing all public comments together with those provided by the U.S. EPA will allow IDEM to more effectively evaluate all the available information and will allow IDEM to work through any issues and receive timely approval from the U.S. EPA.

To date, IDEM has received no communication from the U.S. EPA regarding the status of its review of IDEM's April 1, 2012 303(d) list submittal. There also has been no communication from the U.S. EPA about the revisions to the 303(d) list that IDEM submitted as an addendum to the Integrated Report on December 28, 2012.

The 303(d) List of Impaired Waters is developed pursuant to Section 303(d) of the federal CWA. This notice serves as a solicitation for any additional water quality related information that may be used to further develop and refine the 2014 303(d) list and satisfies the federal Water Quality Planning and Management regulation at 40 CFR Part 130.

IDEM presented the 2014 Draft 303(d) List of Impaired Waters at the March 12, 2014 Environmental Rules Board meeting, which was held at the Indiana Government Center in Indianapolis. This meeting was open to the public and the public was given an opportunity to discuss the list.

At this time, IDEM solicits the following:

(1) Water quality data or water quality related information to support or refute the listing of a specific waterbody or to add a waterbody to the 303(d) list.

(2) Comments and suggestions regarding the CALM.

Comments may be submitted in one of the following ways:

(1) By mail or common carrier to the following address:

2014 Draft 303(d) List of Impaired Waters

Betsy Rouse, Administrative Assistant

Rules Development Branch

Office of Legal Counsel

Indiana Department of Environmental Management

100 North Senate Avenue

MC 65-41

Indianapolis, IN 46204-2251

(2) By facsimile to (317) 233-5970. Please confirm the timely receipt of your faxed comments by calling the Rules Development Branch at (317) 233-8903.

(3) By electronic mail to brouse@idem.in.gov. To confirm timely delivery of your comments, please request a document receipt when you send the electronic mail. PLEASE NOTE: Electronic mail comments will NOT be considered part of the official written comment period unless they are sent to the address indicated in this notice.

(4) Hand delivered to the receptionist on duty at the thirteenth floor reception desk, Office of Legal Counsel, Indiana Government Center North, 100 North Senate Avenue, Indianapolis, Indiana.

Regardless of the delivery method used, to properly identify each comment with the action it is intended to address, each comment document must clearly specify the LSA document number of the action on which you are commenting.

All comments must be postmarked, faxed, or time stamped not later than July 29, 2014. Hand-delivered comments must be delivered to the appropriate office by 4:45 p.m. on the above-listed deadline date.

Additional information regarding this notice may be obtained from Jody Arthur, Watershed Assessment and Planning Branch, Office of Water Quality, (317) 308-3179 or (800) 451-6027 (in Indiana).

For the development of the 2014 Draft 303(d) List of Impaired Waters, IDEM has followed, to the degree possible, the 305(b) and 303(d) reporting methods outlined in the U.S. EPA "Guidance for 2004 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d), 305(b) and 314 of the Clean Water Act" (U.S. EPA, 2003) and the additional guidance provided in the U.S. EPA memorandums containing information concerning CWA Sections 303(d), 305(b), and 314 integrated reporting and listing decisions for the 2006, 2008, 2010, 2012, and 2014 cycles (U.S. EPA, 2005-2013).

The 303(d) list was developed using IDEM's 305(b) Assessment Database (ADB). Interpretation of the data and listing decisions take into account the U.S. EPA's guidance and IDEM's current (CALM).

One aspect of the U.S. EPA's guidance calls for a comprehensive listing of all monitored or assessed waterbodies in the state based on the state's assessment and listing methodology. Each waterbody assessment unit (AU), which may consist of an entire waterbody or a segment of a larger waterbody, is to be placed in one or more of five categories depending on the degree to which it supports designated uses. The U.S. EPA's guidance encourages states to place a waterbody AU in additional categories as appropriate in order to more clearly illustrate where progress has been made in TMDL development and other restoration efforts. A detailed explanation of the five categories is provided in IDEM's CALM in Attachment 1. The following is a summary of the five categories:

The 303(d) List of Impaired Waters will consist of all impairments listed in Category 5. This category includes waters where the WQS is not attained because the waterbody AU is impaired or threatened by one or more pollutant or pollutants for each of which a TMDL is required. It should be noted that the U.S. EPA's most recent guidance does not change existing rules for listing and delisting waterbody impairments from Category 5. The existing regulations still require states, at the request of the U. S. EPA's Regional Administrator, to demonstrate good cause for not including waterbody impairments on the 303(d) list that were included on previous 303(d) lists (pursuant to 40 C.F.R. 130.7(b)(6)(iv)).

IDEM maintains assessment information for all Indiana waters in its ADB for CWA 305(b) reporting and 303(d) listing purposes and to provide assessment information when requested by the public. Each lake, stream, or reach of stream in the ADB is assigned a unique assessment unit identification (AUID). IDEM's methods for defining representative units of assessment are described in detail in IDEM's CALM (Attachment 1). The sizes of AUs in the ADB vary based on a number of factors. A single AU may or may not represent the entire river or stream to which it is associated. IDEM's methods for defining representative AUs are discussed in detail in the CALM.

Each impairment is listed individually on Indiana's 303(d) list to achieve consistency in how U.S. EPA tracks TMDL development and to facilitate more effective planning by IDEM. Therefore, a single AU may appear on the 303(d) list for one or more impairments.

The geographical extent and location of each AU within a given 12 or 14 digit hydrologic unit code (HUC) are defined for mapping purposes through a process called reach indexing. Reach indexing uses software tools that work with geographical information systems (GIS) applications to delineate for a waterbody one or more units of assessment and to "key" these AU (as defined by IDEM) to the National Hydrography Dataset (NHD)¹. This "key" is called the Reach Index. IDEM developed its first statewide Reach Index in 2002, which facilitates mapping of Indiana's 305(b) assessments and 303(d) listings in GIS applications and incorporation of this information into IDEM's ADB and the U.S. EPA's national databases.

When Indiana created its Reach Index in 2002, the NHD was available only in medium resolution (1:100,000 scale), and, in keeping with the then current methods of indexing, IDEM assigned each waterbody an AUID based on the 14 digit watershed in which it was located. In most cases, each 14 digit watershed was assigned a single AUID regardless of how many individual streams were located in the watershed. Therefore, an assessment of any stream would be applied to all the streams in the watershed regardless of where the sample was located or its relative representativeness to each stream. This problem was not preventable at the time because, while the software tool had the capability to re-index or "split" these watershed-wide AUs into smaller AUs, it had no built-in means for tracking changes in segmentation or the corresponding application of existing assessment information for CWA purposes.

In 2006, IDEM developed an administrative process to support the splitting of AUs into smaller units allowing more accurate application of assessment data and for tracking those changes in the ADB. At that time, changes in segmentation were considered on a case-by-case basis and were generally made either to accommodate a more accurate assessment or to correct an earlier assessment in which the data were inappropriately applied.

When the NHD became available for Indiana at the high resolution (1:24,000 scale), IDEM found that a significantly higher number of first and second order streams² appear at this scale than were visible in its original Reach Index. These small streams and stream networks are an important component of the hydrology in their watersheds and can have significant effects on water quality in larger streams. Therefore, IDEM began revising its Reach Index in 2008 to incorporate the high resolution NHD allowing still more accurate application of assessment data and a more comprehensive picture of water quality conditions throughout Indiana.

IDEM completed the indexing of all high resolution streams in Indiana and the data processing needed to enter the resulting segmentation information into the ADB in early 2014. The next and final phase of this work is to conduct a statewide review of the new high resolution index to correct any errors and to ensure consistency in the application of indexing decision rules that IDEM developed to govern how assessment units are defined. Once this work is complete, re-indexing will be conducted on a very limited basis when needed to support National Pollutant Discharge Elimination System permit development or other OWQ program needs.

All changes in segmentation must be accurately tracked so that 305(b) assessment and 303(d) listing information associated with the original AU is not lost. IDEM's methods for tracking segmentation changes for the purposes of reporting to the U.S. EPA have evolved throughout the course of this project. Despite some administrative changes over time, IDEM has, at the request of the U.S. EPA, consistently retired the original AUID for any AU re-indexed. IDEM also continues to evaluate any existing information in the ADB for all designated uses assessed to ensure that no valuable information is lost and that assessment information is appropriately applied to each resulting new AU.

All AUIDs that have been retired due to segmentation changes during the 2014 cycle are identified in Attachment 2.

Section 303(d) of the CWA requires that states consider all readily available data sources in the preparation of their 303(d) lists and 305(b) assessment process. IDEM reviews data generated and submitted by external parties that is obtained in any of the following three ways:

Although these data are collected by organizations external to IDEM, most of these data sets are submitted to IDEM and housed internally making them easily obtainable through program staff within IDEM. All data received are reviewed for usability in accordance with IDEM's Assessment Branch, Quality Assurance Project Plan (QAPP) (IDEM, 2004).

IDEM has also received a number of water quality data sets from external organizations. IDEM has found that the external data sets shown in Table 1 meet the necessary data quality requirements as outlined in IDEM's QAPP for 305(b) assessment purposes and is currently in the process of evaluating these data. IDEM anticipates incorporating any of the impairments identified as a result of these assessments into its 2016 303(d) list submittal.

Each 303(d) list builds upon the previously approved list. The challenges associated with developing a 303(d) list that accurately conveys the status of impairment of Indiana waters are compounded because, as the list is being developed, it is subject to change as a result of negotiations with the U.S. EPA. Despite this, IDEM continues to make progress in its water quality assessments and remains committed to moving forward in its reporting of results to the public despite the unresolved issues associated with either the 2010 or 2012 303(d) list. Therefore, in order to develop the Indiana's draft 2014 303(d) list, IDEM segregated the impairments still in question from the rest of the 2012 303(d) list and has made revisions based on the most current information available.

The CWA does not clearly define the timeline for TMDL development. However, in response to the 1998 Federal Advisory Committee Act (FACA) committee's recommendations, U.S. EPA has issued guidance for states to develop expeditious schedules of not more than eight to 15 years. In accordance with the CWA, the 303(d) list guides TMDL development. IDEM works with U.S. EPA through every 305(b)/303(d) assessment and listing cycle to determine the number of TMDLs that must be developed in order to keep pace with the number of new impairments identified each cycle and to meet the goal of completing TMDLs for impairments within 15 years of their listings.

This short term (two-year) schedule for TMDL development is currently under development and will be submitted to U.S. EPA with IDEM's submittal of its Integrated Report and 303(d) list in 2014. IDEM will also provide with its submittal a long term TMDL development schedule that will identify a timeline for TMDL development for all impairments identified on the draft 2014 303(d) list.

To develop both schedules, IDEM generally prioritizes TMDL development to address impairments identified on its earliest 303(d) lists. However, because IDEM employs a watershed approach that considers all the known impairments in a given watershed, the resulting TMDL reports commonly include additional impairments identified in subsequent 303(d) lists and impairments newly identified as a result of the additional water quality monitoring conducted for TMDL development.

IDEM focuses its TMDL development on bacteria and impaired biotic communities with nutrient-related sources because these are the types of impairments most commonly identified in Indiana waters. Most of these impairments have been found through TMDL development to be nonpoint source driven and their sources are relatively well understood. Therefore, the resulting TMDLs readily lend themselves to effective management through locally led watershed management planning and implementation efforts.

For the 2014 cycle, IDEM moved a total of 56 impairments previously listed in Category 5 to Category 4A based on TMDL approvals. Of this total, there are 47 impairments that were moved based on TMDLs approved in previous cycles (Attachment 3, Table 3b). These impairments were added back to Category 5 as a result of changes made in segmentation and have since been verified to have originated from reaches with impairments for which a TMDL has been approved. The remaining nine impairments were based on new TMDLs approved for the 2014 cycle (Attachment 3, Table 3c).

TMDLs were also approved for an additional 69 newly identified impairments (Attachment 3, Table 3d). These impairments were found during assessment of data collected for TMDL development and have been added directly to Category 4A. Their addition to Category 4A does not change the number of impairments listed in Category 5. They are included in this notice in order to provide a full accounting of all impairments for which TMDLs have been approved during the 2014 cycle.

To facilitate public review, all impairments moved into Category 4A for the 2014 cycle are identified in Attachment 3, Table 3a and are keyed to the TMDL in which they are addressed. The TMDL reports for approved TMDLs, along with information on their development, can be found online at: http://www.in.gov/idem/nps/2347.htm.

In accordance with IDEM procedure and U.S. EPA policy, impairments may not be removed from the 303(d) list based solely on changes in segmentation. All impairments in an AU that has been re-indexed must be reevaluated to determine their applicability to the resulting new AUs. All impairments that were delisted as a result of changes in segmentation for the 2014 cycle are identified in Attachment 4. For the 2014 cycle, IDEM has removed a total of 802 impairments from Category 5 as a result of changes in segmentation.

This section includes waterbody impairments removed from Category 5 based on more recent data or other information for previously assessed impairments that have become available since IDEM's 2012 303(d) list submittal. The waterbody impairments removed from Indiana's 303(d) list are located primarily in the Great Lakes basin and Ohio River tributaries, which were sampled by IDEM in 2010, and the White River, West Fork basin sampled in 2011. Assessments for the Ohio River were also revised this cycle based on data and information provided by the Ohio River Valley Sanitation Commission (ORSANCO). Detailed information on how IDEM incorporates ORSANCO's data and assessments into the state's 303(d) listing processes is provided in IDEM's CALM.

As a result of these assessments, IDEM has found that water quality standards are now met for a total of 80 previously identified impairments (Attachment 5). These impairments have been removed from Category 5A for the 2014 cycle.

IDEM routinely reviews its 303(d) list for errors and omissions and to ensure consistency with Indiana's WQS and the information IDEM maintains in its ADB. For the 2014 cycle, IDEM has identified a total of 21 impairments that should not be listed in Category 5 for various reasons. These impairments and IDEM's reasons for removing them from Category 5 appear in Attachment 6.

In accordance with IDEM procedure and U.S. EPA policy, impairments may not be removed from the 303(d) list based solely on changes in segmentation. All impairments of an AU that has been re-indexed must be reevaluated to determine their applicability to the resulting new AUs. Attachment 7 identifies all the impairments that were added back to the list under their new AUIDs and includes both impairments for which the applicability of the original assessment have been verified and those still pending reassessment. For the 2014 cycle, IDEM has added a total of 1,196 impairments to Category 5 as a result of changes made in segmentation.

This section includes waterbody impairments added to Category 5 based on more recent data or other information that have become available since IDEM's 2012 303(d) list submittal. For a lake or stream to be listed, IDEM must have sampling data representative of that waterbody and the data collected must support 303(d) listing in accordance with IDEM's CALM. The waterbody impairments added to the 303(d) list on the basis of new or revised assessments are located primarily in the Great Lakes basin and Ohio River tributaries, which were sampled by IDEM in 2010, and the White River, West Fork basin sampled in 2011. Assessments for the Ohio River were also revised this cycle based on data and information provided by the ORSANCO. Based on these assessments, IDEM has added a total of 329 impairments to Category 5 (Attachment 8).

IDEM routinely reviews its 303(d) list for errors and omissions and to ensure consistency with Indiana's WQS and the information IDEM maintains in its ADB. For the 2014 cycle, IDEM has identified a total of 32 impairments that should be added to Category 5 for various reasons. These impairments and IDEM's reasons for adding them to Category 5 appear in Attachment 9.

Table 2 summarizes the proposed removals from and additions to Indiana's 303(d) list and their impacts on the total number of AUs listed by waterbody type and their associated stream miles and lake acres. Table 3 and Table 4 provide a comparison of the 2012 and 2014 303(d) lists in terms of the total number of AUs listed and the total number of impairments listed, respectively. Table 5 summarizes the proposed changes to Indiana's 303(d) list in terms of the types of impairments that appeared on the 303(d) list submitted as an addendum to the 2012 Integrated Report on December 28, 2012, versus those that appear on the 2014 draft 303(d) list. The proposed changes will result in a draft 2014 303(d) List of Impaired Waters containing a total of 3,637 individual impairments compared to 3,039 individual impairments³ for the 2012 303(d) list submitted to the U.S. EPA on December 28, 2012 (AUs with multiple impairments are listed once for each impairment).

Attachment 10 consists of the proposed Category 5A and Category 5B impairments that together comprise the draft 2014 303(d) list of impaired waters for Indiana. The 303(d) list is a subset of Indiana's Consolidated List to be submitted to the U.S. EPA in 2014 as part of Indiana's Integrated Water Quality Monitoring and Assessment Report.

All information used to create the maps in this report was obtained from IDEM databases and Geographical Information Systems Libraries, and the State of Indiana Geographical Information Office.

Indiana Administrative Code (IAC): http://www.in.gov/legislative/iac/title327.html

Indiana Department of Environmental Management (IDEM). 2004. Quality Assurance Project Plan for Indiana Surface Water Quality Monitoring and Total Maximum Daily Load (TMDL) Program. Office of Water Management, Assessment Branch, Environmental Toxicology and Chemistry Section. Indianapolis, IN.

Indiana Department of Environmental Management (IDEM). 2005. Indiana Water Quality Monitoring Strategy (draft). Office of Water Management, Assessment Branch. Indianapolis, IN. B-001-OWQ-A-00-06-0-R3.

U. S. Environmental Protection Agency. 2003. Guidance for 2004 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d) and 305(b) of the Clean Water Act, July 21, 2003. Washington, D.C.: U.S. Environmental Protection Agency.

U. S. Environmental Protection Agency. 2005. Guidance for 2006 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d), 305(b) and 314 of the Clean Water Act, July 29, 2005. Washington, D.C.: U.S. Environmental Protection Agency.

U. S. Environmental Protection Agency. 2006. Information Concerning 2008 Clean Water Act Sections 303(d), 305(b), and 314 Integrated Reporting and Listing Decisions. Washington, D.C.: U.S. Environmental Protection Agency.

U. S. Environmental Protection Agency. 2009. Information Concerning 2010 Clean Water Act Sections 303(d), 305(b), and 314 Integrated Reporting and Listing Decisions. Washington, D.C.: U.S. Environmental Protection Agency.

U. S. Environmental Protection Agency. 2011. Information Concerning 2012 Clean Water Act Sections 303(d), 305(b), and 314 Integrated Reporting and Listing Decisions. March 21, 2011 Memorandum from U.S.EPA Office of Wetlands, Oceans and Watershed to U.S. EPA Regional Water Division Directors and Directors in U.S. EPA's Region 1 Office of Environmental Measurement and Evaluation, Region 2 Division of Environmental Science and Assessment, Region 7 Environmental Sciences Division, and Region 10 Office of Environmental Assessment. Washington, D.C.: U.S. Environmental Protection Agency.

U. S. Environmental Protection Agency. 2013. Information Concerning 2014 Clean Water Act Sections 303(d), 305(b), and 314 Integrated Reporting and Listing Decisions. September 3, 2013 Memorandum from U.S.EPA Office of Wetlands, Oceans and Watershed to U.S. EPA Regional Water Division Directors and the U.S. EPA Region 1 Office of Environmental Measurement and Evaluation. Washington, D.C.: U.S. Environmental Protection Agency.

Section 303(d) of the 1972 Federal Clean Water Act (CWA) requires each state to identify those waters that do not meet the state's water quality standards (WQS) for designated uses. For these impaired waters, states are required to establish total maximum daily loads (TMDLs) to meet the state's WQS. In addition, the U.S. EPA has released guidance recommending that states, territories, and authorized tribes submit an Integrated Water Quality Monitoring and Assessment Report (IR) that will satisfy the CWA requirements for both the Section 305(b) water quality report and Section 303(d) list of impaired waters. Indiana Department of Environmental Management (IDEM) has integrated this guidance into its Consolidated Assessment and Listing Methodology (CALM).

IDEM has developed a water quality monitoring strategy (WQMS) to guide its monitoring activities that are aimed at assessing the quality of Indiana's surface waters. Specific goals of the WQMS include:

To achieve these goals, IDEM has divided the state into major water management basins and employs a rotating basin monitoring strategy that allows IDEM to focus its monitoring resources in a different basin each year. IDEM's 305(b) assessment and 303(d) listing processes also follow this rotating basin approach as well. Prior to 2010, IDEM's WQMS was to use a five year basin rotation approach to monitor for CWA purposes. Using this strategy, one to two basins were monitored each year, which provided a comprehensive statewide data set for assessments every five years (Figure 1) (IDEM, 2005). In 2010, the WQMS was revised to a nine-year basin rotation, which will result in the completion of a comprehensive assessment every nine years going forward and allow the reallocation of resources necessary to meet a broader range of monitoring objectives (Figure 2) (IDEM, 2010).

Lakes and reservoirs in Indiana are monitored for IDEM by the Indiana Clean Lakes Program (CLP) administered by Indiana University's School of Public and Environmental Affairs. This monitoring does not follow the rotating basin due to the unequal distribution of lakes across the Indiana landscape. Using an approach similar to rotating basins, lakes throughout the state are divided into five regions that are defined in a way that maximizes monitoring resources. The following monitoring programs provide water quality data in support of IDEM's CWA programs:

The CWA provides the underpinning for Indiana's WQS, which are articulated in Title 327, Article 2 of the Indiana Administrative Code (IAC) and are designed to ensure that all waters of the state, unless specifically exempted, are safe for full body contact recreation and are protective of aquatic life, wildlife, and human health. These beneficial uses are described in the state's WQS as "designated" uses. IDEM monitors and assesses Indiana's surface waters to determine the extent to which they meet WQS and support their designated uses and to identify, where possible, the sources of impairment for those waters that do not support one or more of these uses.

Use support status is determined for each waterbody using the assessment guidelines provided in the U.S. EPA's documents regarding the 305(b) and 303(d) reporting methods outlined in the U.S. EPA "Guidance for 2004 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d), 305(b) and 314 of the Clean Water Act" (U.S. EPA, 2003) and the additional guidance provided in the U.S. EPA's memorandums containing information concerning CWA Sections 303(d), 305(b), and 314 integrated reporting and listing decisions for the 2006, 2008, 2010, 2012, and 2014 cycles (U.S. EPA, 2005-2013). Available results from six types of monitoring data listed below are integrated to provide an assessment for each stream waterbody for 305(b) reporting and 303(d) listing purposes:

IDEM maintains its CWA Section 305(b) assessment and 303(d) listing information in the Assessment Database (ADB). Each waterbody assessment unit (AU) is assigned a unique identifier in the ADB to which all assessment information for that waterbody is associated. This identifier is called an assessment unit identification (AUID).

In general, each AUID corresponds to the watershed in which it is located as defined by the United State Geological Survey (USGS) hydrologic unit code (HUC) system, which is a hierarchical system that divides and then subdivides the United States into successively smaller geographic areas based on surface hydrologic features or drainages. Under this system, the average size of an 8-digit hydrologic unit area in Indiana, commonly known as a subbasin, is about 448,000 acres (700 square miles). The 12- and 14-digit hydrologic unit areas, or subwatersheds, within an 8-digit hydrologic unit area are much smaller. The 12- and 14-digit hydrologic unit areas in Indiana range in size from less than five acres (less than one hundredth of a square mile) to about 28,000 acres (almost 44 square miles).

The geographical extent and location of each AU within a given 12- or 14-digit HUC are defined for mapping purposes through a process called reach indexing. Reach indexing uses software tools that work with geographical information systems (GIS) applications to delineate for a waterbody one or more units of assessment and to "key" these AU (as defined by IDEM) to the National Hydrography Dataset (NHD)⁴. This "key" is called the Reach Index. IDEM developed its first statewide Reach Index in 2002, which facilitates mapping of Indiana's 305(b) assessments and 303(d) listings in GIS applications and incorporation of this information into IDEM's ADB and the U.S. EPA's national databases.

In these databases, Indiana lakes and reservoirs, including Lake Michigan, are assigned a single AUID with sizes reported in acres. Each lake in IDEM's ADB is presently associated with the 14-digit HUC in which it resides. As time allows, IDEM will begin associating lakes with their 12-digit HUC to better support the Nonpoint Source Section 319 program, which has adopted this scale for watershed management planning and implementation purposes.

Indiana's Lake Michigan shoreline is divided into reaches and assigned an AUID in accordance with the 8-digit HUC in which each shoreline reach is located. The shoreline is measured and reported in miles.

With the exception of the Ohio River whose AUIDs are likewise associated with their 8-digit HUCs, rivers and streams in IDEM's ADB are also divided into reaches with each assigned a unique AUID in accordance with the 12-digit HUC in which it is located. River and stream reaches are measured in miles. Their sizes vary widely, and a single AU may or may not represent the entire river or stream to which it is associated.

In keeping with the then-current methods of indexing when Indiana created its first Reach Index in 2002, IDEM assigned each waterbody an AUID based on the 14-digit watershed in which it was located. In most cases, each 14-digit watershed was assigned a single AUID regardless of how many individual streams were located in the watershed. Therefore, an assessment of any stream would be applied to all the streams in the watershed regardless of where the sample was located or its relative representativeness to each stream. This problem was not preventable at the time because the software tool, though it had the capability to re-index or "split" these watershed-wide AUs into smaller AUs, had no built-in means for tracking changes in segmentation or the corresponding application of existing assessment information for CWA purposes.

In 2006, IDEM developed an administrative process to support the splitting of AUs into smaller units allowing more accurate application of assessment data and tracking of those changes in the ADB. At that time, changes in segmentation were considered on a case-by-case basis and were generally made either to accommodate a more accurate assessment or to correct an earlier assessment in which the data were inappropriately applied. When AUs were split, IDEM reevaluated previous assessments of the original AU along with any recent data that were available at the time of re-indexing. The reassessment process ensured that the original assessment information was properly applied to the resulting new AUs. In most cases, the original assessment was applied to only one or two of the resulting AUs with the remaining not assessed.

When the NHD became available for Indiana at the high resolution (1:24,000 scale), IDEM found that a significantly higher number of first and second order streams⁵ appear at this scale than were visible in its original Reach Index. These small streams and stream networks are an important component of the hydrology in their watersheds and can have significant effects on water quality in larger streams. Therefore, IDEM began revising its Reach Index in 2008 to incorporate the high resolution NHD allowing still more accurate application of assessment data as well as a more comprehensive picture of water quality conditions throughout Indiana.

In early 2014, IDEM completed indexing all high resolution streams in Indiana. All of the resulting segmentation information has been prepared for entry into the ADB, and most of this data entry is now complete. The next and final phase of this work is to conduct a statewide review of the new high resolution index to correct any errors and to ensure consistency in the application of indexing decision rules that IDEM developed to govern how assessment units are defined. Once this work is complete, re-indexing will be conducted on a very limited basis when needed to support National Pollutant Discharge Elimination System permit development or other IDEM Office of Water Quality (OWQ) program needs.

The goal of the high resolution indexing process is to identify all streams and stream reaches that are representative for the purposes of assessment. In practice, this process leads to grouping tributary streams into smaller catchment basins having similar hydrology, land use, and other characteristics such that all tributaries within the catchment basin can be expected to have similar potential impacts. Catchment basins, as defined by the aforementioned factors, are typically very small, which significantly reduces the variability in the water quality expected to be found from one stream or stream reach to another. Given this, all tributaries within a catchment basin are assigned a single AUID. Grouping tributary systems into smaller catchment basins also allows for better characterization of the larger watershed. Assigning unique AUIDs to each catchment basin will more accurately represent the variability within a larger watershed.

Using the catchment basin approach, indexing at high resolution is guided in large part by the hydrology of a system. This is because the mechanisms of large streams and rivers are very different from those of small streams and tributary systems thereby making it logical to separate these into separate AUIDs. However, other factors, such as the following, are also considered when deciding how to define a water quality AU:

Aerial photography is particularly important in determining appropriate segmentation within a watershed because it provides very recent and accurate information about the presence and thickness of riparian buffers, the presence and spatial extent of rural development, and the types of land use practices in the watershed. All of this information can help to determine where differences in water quality might be expected to result from one or more of these factors. Due to the potential impacts these factors can have on stream water quality, they are all considered when determining whether segmentation should occur and where it should occur along the stream reach.

On each AU indexed, IDEM must evaluate any existing information in the ADB for all designated uses assessed to ensure that no valuable information is lost and that assessment information is appropriately applied to the resulting new AU.

This process was particularly complicated in cases where there are two or more previously assessed AUs that were combined through the indexing process. For each new AU entered into the ADB, reports were generated from the database for the original AUs from which the new AU was derived. These reports were then compared to determine, for each designated use, whether there is any existing assessment information for the original AUs and to identify any conflicting assessment information.

In most cases, conflicting information was resolved prior to entering the new AU into the ADB. However, for some AUs, a thorough reevaluation of all existing data for the watershed is necessary to ensure that the assessment information entered is indeed representative of the AU in question. AUs for which questions still remain regarding the representativeness of their assessments are flagged in the ADB for reassessment as time allows. For these AUs, all information from the original AU or AUs has been carried over in the ADB, and any conflicting assessment information has been flagged for later resolution ensuring that no valuable assessment information is lost.

The designated uses outlined in Indiana's WQS and the narrative and numeric criteria to protect them provide the underpinning for IDEM's 305(b) assessment process and 303(d) listing decisions. Water quality assessments are made by compiling existing and readily available data from site-specific chemical (water, sediment, and fish tissue), physical (habitat, flow data), and biological (fish community, macroinvertebrates, and E. coli) monitoring of Indiana's rivers, streams, and lakes and evaluating those data against Indiana's WQS. Waters identified as not meeting one or more of their designated uses are then placed on the Indiana's 303(d) List of Impaired Waters. IDEM's decision-making criteria are a combination of the narrative and numeric criteria stated in Indiana's WQS in IAC 327, Article 2. More detailed information regarding IDEM's WQS-based approach to evaluating fish tissue data and IDEM's use of site-specific water quality criteria in the 305(b) assessment process is also provided in later sections of this document.

Chemical data for toxicants [dissolved metals, polynuclear aromatic hydrocarbons (PAHs), pesticides, ammonia, and free cyanide], conventional water chemistry parameters (dissolved oxygen, pH, temperature, and anions), and bacteria (E. coli) were evaluated for compliance with Indiana's WQS found at 327 IAC 2-1-6 and 327 IAC 2-1.5-8. U.S. EPA 305(b) guidelines were applied to chemical and biological data as indicated in Guidelines for Preparation of the State Water Quality Assessments (305(b) Reports) and Electronic Updates: Supplement (U.S. EPA, 1997).

Table 6 shows the minimum data required for 305(b) assessments. For each AU with sufficient data to make one or more designated use assessments, IDEM applies the 305(b) assessment process described in Table 7. Assessment data are integrated for the purposes of making water quality assessments, meaning that all data for a given waterbody are considered together. In accordance with U.S. EPA policy, IDEM generally treats each type of data as independently applicable.

Indiana's WQS contain provisions for the calculation of site-specific criteria (SSC) for the protection of aquatic life and human health in order to provide: (1) an additional level of protection; or (2) a less stringent criteria in cases where it can be shown that site-specific conditions indicate the criterion contained in Indiana's WQS for the pollutant in question is unnecessarily stringent⁷. SSC are typically developed for the NPDES program on a case-by-case basis to ensure that the specific pollutant or pollutants contained in a permitted discharge do not impair aquatic life or human health use support.

The SSC expressed in Indiana's WQS apply only to the stream or stream reach and the pollutant for which they were calculated. Until now, IDEM has been generally unable to apply SSC in its assessment processes because of the way AU are defined. Few SSC are broadly applicable to the basin in which they are located. Therefore, in order to apply SSC, the AU must match the reach to which the criterion applies both in terms of its location and length.

In most cases, the AU as a whole is larger than the reach to which the SSC applies. Therefore, applying a site-specific criterion to the entire AU would result in the criterion being used to assess the water quality condition for the entire waterbody as opposed to the specific reach to which it applies. In the past, IDEM's policy in these cases has been to give precedence to the ambient water quality criterion expressed in the state's WQS.

IDEM has put the necessary internal processes in place to make the changes in segmentation that are needed to more accurately apply SSC. Such changes require close coordination between IDEM's NPDES, WQS, and 305(b) and 303(d) programs. Given the scientific and regulatory complexities involved, changes in segmentation for these reasons are rare and must necessarily be considered on a case-by-case basis. In the future, IDEM plans to coordinate this work with NPDES permit renewals for those facilities discharging to waters with applicable SSC.

IDEM collaborates with the Ohio River Valley Water Sanitation Commission (ORSANCO) to conduct water quality assessments of the Ohio River reaches that border Indiana. ORSANCO is an interstate water pollution control agency for the Ohio River established through a compact agreement between member states and approved by Congress. Under the terms of the compact, member states cooperate in the control of water pollution in the Ohio River Basin.

ORSANCO monitors the Ohio River on behalf of the compact states under CWA Section 305(b) and produces a water quality assessment report of its water quality condition every two years. Although this report identifies water quality issues on the Ohio River, ORSANCO, unlike its compact states, is not required to develop a 303(d) List of Impaired Waters. Identifying Ohio River impairments on a 303(d) list for the purposes of TMDL development is the responsibility of each compact state.

Every two years, ORSANCO prepares a description of the proposed assessment methodology for review by the 305(b) Work Group, which is made up of the state agency personnel responsible for preparing the Integrated Reports in each state and one or more U.S. EPA representatives responsible for reviewing state reports. When the 305(b) Work Group reaches agreement on the methodology, it is submitted to ORSANCO's Technical Committee for review and approval. Once approved, ORSANCO applies the methodology to the available information to make its preliminary assessments, which are then distributed to the 305(b) Work Group for review. When the 305(b) Work Group reaches agreement on the assessment, each state incorporates the results into its Integrated Report and 303(d) List of Impaired Waters, and ORSANCO completes its 305(b) report for submittal to the U.S. EPA.

ORSANCO's role in completing Ohio River use attainment assessments and developing a biennial report on Ohio River water quality conditions is primarily to facilitate interstate consistency in CWA 305(b) assessments and how impairments are identified on the compact states' 303(d) lists for the purposes of TMDL development. However, such consistency is not always possible given the differences in the compact states' WQS and their CWA Sections 305(b) and 303(d) assessment and listing methodologies. Given these differences, the compact states are not obligated to incorporate any or all of ORSANCO's water quality assessments into their own reports. Specifically, U. S. EPA guidance states that "data and information in an interstate commission 305(b) report should be considered by the states as one source of readily available data and information when they prepare their Integrated Report and make decisions on segments to be placed in Category 5; however, data in a 305(b) Interstate Commission Report should not be automatically entered in a state Integrated Report or 303(d) list without consideration by the state about whether such inclusion is appropriate." (U.S. EPA, 2005)

Appendix A contains a comparison of the relative stringencies of applicable criteria in ORSANCO's Pollution Control Standards (PCS) and Indiana's WQS and the different ways in which these criteria are used to determine the degree to which the Ohio River supports aquatic life use, recreational use, and fish consumption. In order to achieve consistency with other compact states, IDEM generally defers to ORSANCO's methods for evaluating the available data for assessment purposes. And, where there are not significant differences between ORSANCO's criteria and those expressed in Indiana's WQS, IDEM incorporates ORSANCO's assessments directly into its Integrated Report and 303(d) List applying them to the corresponding reaches defined in IDEM's ADB. However, in cases where the water quality criteria ORSANCO uses are less stringent than the water quality criteria expressed in Indiana's WQS or its methods for applying them are significantly inconsistent with IDEM's assessment methodology, or both situations exist, ORSANCO's data are evaluated against IDEM's assessment methodology, and the results are compared to Indiana's WQS to make the assessment. IDEM's methods for applying ORSANCO's assessments or data, or both, for the purposes of Integrated Reporting are described below and summarized in Table 8.

ORSANCO uses both water chemistry results and biological monitoring results to determine the degree to which the Ohio River supports aquatic life. ORSANCO's fish community assessments of the Ohio River use the Ohio River Fish Index (ORFIn), which was developed based on the nationally used Index of Biotic Integrity (IBI) designed to assess smaller streams. The ORFIn has been customized to assess the Ohio River with expected values developed for the different habitats found in this large river system. The ORFIn combines various attributes of the fish community to give a score to the river based on its biology. The total score is compared to an expected score, which varies depending on the habitat type and location. IDEM defers to ORSANCO's assessments based on biological data. IDEM also defers to ORSANCO's approach to evaluating water chemistry data. However, assessments may differ somewhat depending on the parameter in question and whose criterion, ORSANCO's or Indiana's, is more stringent (CALM Appendix A).

Indiana's E. coli criteria are slightly more stringent than ORSANCO's. However, unlike Indiana's WQS, ORSANCO's criteria do not allow exceptions for exceedances that are incidental and attributable solely to E.coli resulting from the discharge of treated wastewater from a wastewater treatment plant. ORSANCO's assessment methodology also directly applies its single sample maximum criterion to individual results, which provides a more robust assessment than Indiana's combined criteria and assessment methodology can. Indiana, therefore, defers to ORSANCO's assessments of recreational use support for the Ohio River.

In addition to assessments of aquatic life use support and recreational use support, ORSANCO also makes assessments of the degree to which the Ohio River supports fish consumption. In applying these assessments to Indiana reaches of the Ohio River, IDEM emphasizes that this information is not intended to be a public health advisory and recommends that the public refer to the most current Indiana Fish Consumption Advisory (FCA) or contact the Indiana State Department of Health (ISDH), or both, with any specific questions or concerns regarding the health risks associated with consuming fish caught from the Ohio River. Important differences between fish consumption use impairments identified as a result of these assessments and the health advisories provided in the FCA are discussed in more detail in the section of this methodology describing Indiana's assessment methodology for fish consumption for other Indiana waters and Lake Michigan.

ORSANCO uses both fish tissue data and water sample results to make its fish consumption use assessments, and its methods for evaluating the data differ somewhat from IDEM's methods for similar assessments on other Indiana waters. Unlike ORSANCO's methodology, IDEM's assessment methodology relies on fish tissue data only and requires only one exceedance of the applicable criterion to assess impairment. IDEM's methods are intended to result in a more conservative estimate of conditions in smaller rivers and streams for which there is commonly less available data.

In contrast, the Ohio River is a large and complex river system, and the ORSANCO monitoring programs that provide data for the assessment of fish consumption use support result in a far more robust data set than those available for similar assessments of other Indiana waters. IDEM's collaboration with ORSANCO allows IDEM to focus its monitoring resources on other waters, and, as a result, IDEM's monitoring on the Ohio River is comparatively quite limited.

For most of the Ohio River, IDEM defers to ORSANCO's assessment methodology for fish consumption use support. For those reaches where IDEM has sampled for fish tissue, results for methylmercury and PCBs in fish tissue are reviewed independently of ORSANCO results using the same methods applied to other waters in the state. Where IDEM's assessment for a given reach differs from ORSANCO's assessment, IDEM defers to ORSANCO's assessment because the latter is typically based upon a more recent and robust data set.

In 2012, ORSANCO's technical committee approved the use of the U.S. EPA guidance issued in 2010 for implementing the national methylmercury water quality criterion in CWA programs and began using this methodology for its 2014 cycle assessments. The criteria ORSANCO applies in its fish consumption assessments are shown in Table 9. ORSANCO's criterion for methylmercury in fish tissue is equivalent to that used by IDEM in its fish consumption assessments on other waters. ORSANCO's assessment methodology does not include a similar criterion for PCBs in fish tissue. Therefore, in cases where IDEM has results for PCBs in fish tissue from Ohio River fish, IDEM evaluates the results using ORSANCO's methods and the criterion applicable to other Indiana waters.

In addition to fish tissue data, ORSANCO's monitoring programs provide results for PCBs, dioxin, and total mercury in the water column. For PCBs and dioxin, ORSANCO's criteria are more stringent than those expressed in Indiana's WQS.

With regard to mercury in the water column, ORSANCO's chronic aquatic life use criterion for total mercury in ambient waters is equivalent to the criterion used by Indiana. ORSANCO applies this criterion in its assessments of fish consumption use support as opposed to aquatic life use support because it considers bioaccumulation of mercury in fish tissue more of a human health concern than a threat to aquatic life. IDEM concurs with ORSANCO's use of water column results for mercury in assessments of fish consumption use based on this rationale and defers to ORSANCO on its fish consumption use assessments for the Ohio River. Unlike ORSANCO, IDEM also applies the chronic criterion for total mercury in its assessments of aquatic life use support on the Ohio River.

For sites where the results for total mercury or PCBs, or both, in water conflict with the fish tissue results for that same contaminant, the fish tissue results are given more weight in the assessment decision. Fish tissue contaminants data are given more weight in the assessment decision because fish tissue levels of these contaminants are an indicator of more direct potential mercury exposure to individuals consuming fish from the Ohio River while their concentrations in the water column are more an indicator of potential bioaccumulation than direct impacts from consumption. IDEM concurs with this approach.

IDEM's lakes assessments have largely been limited to CWA Section 314 assessments of lake trends and trophic state. This has been due to the absence of water quality criteria in the state's WQS. Indiana's WQS contain narrative criteria for all waters of the state. The few designated use assessments made on lakes and reservoirs to date are based primarily on narrative criteria.

On a national scale, the number one impairment of lakes and reservoirs has long been identified as nutrients. For this reason, the U.S. EPA has mandated that states develop and adopt nutrient criteria into their WQS. In 2001, EPA published recommended criteria for both causal (total nitrogen and phosphorus) and response (chlorophyll a and turbidity or water clarity) variables in the Federal Register (66 FR 1671). These criteria were developed for waterbodies in "aggregated" ecoregions based on the work of Omernik and Gallant (1988). The U.S. EPA's ecoregional approach uses lake data from a number of states. The analyses used to derive the criteria applicable to Indiana included only nine Indiana lakes comprised of one natural lake and eight reservoirs. IDEM believes the U.S. EPA's published criteria are not as Indiana-specific as is necessary to ensure accurate assessments of water quality conditions in lakes throughout the state. The U.S. EPA recognizes these concerns and encourages states to modify or refine their criteria to reflect conditions on a smaller geographic scale (U.S. EPA, 2000c).

In 2007, IDEM developed additional criteria for assessing recreational use support in lakes and reservoirs within the context of aesthetics in order to more fully assess the water quality condition of Indiana's lakes and reservoirs. It should be noted that the assessment criteria described here does not replace any assessment criteria currently in place for lakes and reservoirs. The assessment criteria for recreational use support with respect to human health remains unchanged as do those used to determine drinking water and aquatic life use support (Table 6).

These criteria used to determine recreational use support within the context of aesthetics are based on the results of a study conducted by of Limno-Tech, Inc. (LTI). In 2004, IDEM contracted with LTI to recommend potential nutrient water quality criteria for Indiana's lakes based on data collected throughout Indiana over several decades. Under this project, a comprehensive database of lakes data was developed for use in analyzing nutrient relationships for Indiana's lakes. The final report for this study was submitted to IDEM in 2007. A summary of the data and analytical methods used and the resulting recommendations are provided below.

The LTI study used both agency data and volunteer data collected by the Indiana CLP from 321 natural lakes and 113 reservoirs from 1989 to 2005. Of the 13,063 individual samples with water quality data, 70% of the samples were collected under the volunteer monitoring program. In order to have sufficient data for robust analyses, it was important to use volunteer data if its reliability could be verified. The Indiana CLP is funded by IDEM's Section 319 grant program and operates under an IDEM-approved Quality Assurance Project Plan (QAPP) (IDEM, 2004) that documents the data quality of all data collected under the program.

Given the importance of volunteer data to this study, the data were examined to determine if there was a significant difference depending on whether the data were collected by volunteers or the agencies. LTI first plotted raw data values against each other. However, it became apparent that averaged data provided a much better representation of potential relationships. For example, Figure 3 shows the growing season (June to August) average of Secchi depth and chlorophyll a (Chla) values for lakes where at least three different years of Chla samples existed. This analysis shows that volunteer data are indistinguishable from agency data and no bias should exist if all datasets are combined. Similar conclusions were reached when LTI made additional comparisons between Secchi depth and total phosphorus (TP) and between Chla and TP. The absence of bias between volunteer and agency data was also confirmed by evaluating lakes where agency and volunteer data were used to calculate summer medians versus lakes where only agency data were available.

Data from all sources were reviewed for quality assurance and evaluated to identify spatial and temporal patterns. Suitable models for developing criteria were evaluated and statistical analyses were applied to establish the recommended total phosphorus thresholds, which are shown in Table 10.

The associated range of Chla represents the range of concentrations that, based on LTI's analysis of natural lakes and reservoirs in Indiana, can be expected when TP concentrations are at or below 54 ug/L or 51 ug/L, respectively.

Multiple linear regression analyses were conducted on total phosphorus (as a response variable) for each data set (natural lakes and reservoirs) using regression tree analysis (RTA) methods developed by Soranno, et.al, (personal communication). RTA was used to determine appropriate TP thresholds.

Once the TP thresholds were established, median values above and below the threshold for each lake type were calculated for two biological response variables, Secchi depth and Chla. The median values above and below represent the range of expected values for each response variable associated with its corresponding TP threshold. For example, in Figure 4, the median below line represents the median of all Chla concentration values that fall to the left of the calculated TP threshold whereas the median above line represents all of the Chla values that fall to the right of the threshold (that is, correspond to TP "exceedances"). A simplified model of how the median values calculated for a given TP threshold are used to determine recreational use support is provided in the discussion regarding IDEM's assessment methodology for recreational use (Figure 5).

A biological response factor for Chla was then calculated as the median of the biological response above the threshold divided by the median of the biological response below the threshold. The biological response factor for Secchi depth was calculated as the median of the biological response below the threshold divided by the median of the biological response above the threshold. Based on the work of Soranno, et al., a biological response factor of 2 or greater is considered significant and could reasonably be designated as a relevant TP threshold above which action should be taken.

Table 11 shows that the thresholds calculated are very significant for Chla in both reservoirs and natural lakes. The threshold for Secchi depth in reservoirs, while still significant, is not nearly as strong as the threshold for Chla as indicated by their biological response factors (3.6 for Secchi depth vs. 13.2 for Chla). The same holds true for natural lakes (1.9 for Secchi depth and 5.6 for Chla), and the biological response factor for Secchi depth falls below that which is considered significant for the purposes of setting an appropriate TP threshold.

Because the TP thresholds for Chla are much stronger than those for Secchi depth, IDEM's assessment methodology incorporates the TP thresholds developed for Chla. Other reasons for this decision are that Secchi depth measurements are inherently more subjective than Chla measurements, and IDEM does not have survey data regarding aesthetics, which is necessary to adequately translate Secchi depth information into use support status. While there is similarly little analogous information available for Chla, IDEM considers Chla data obtained through laboratory analyses of water samples a more reliable indicator of phosphorus enrichment than Secchi depth for the purposes of 305(b) assessment and 303(d) listing decisions.

In some cases, the Chla data were not consistent with the expectations regarding the TP levels measured for a given lake (for example, low Chla values associated with high TP values or vice versa). For these situations, IDEM's methodology used the TSI score as a surrogate response variable (in addition to Chla) to determine impairment status. The TSI score can be affected by a number of variables in addition to phosphorus (see Table 8). However, the index places additional weight on algal concentration, adding significantly more points where concentrations are high. While the TSI does not provide a direct response variable for TP, it can be a useful indicator in cases where Chla results are mixed.

In addition to providing a surrogate measure for Chla, the TSI score also provides a good measure of overall trophic condition of a given lake. Recognizing the connection between trophic status and nutrient enrichment, the U.S. EPA generally considers hypereutrophic conditions as measured by the TSI indicative of impairment (U.S. EPA, 2000c). IDEM does not believe that the TSI score alone is sufficient information for making designated use assessments because it can be affected by a number of variables in addition to nutrient loading. However, in cases where the Chla results are mixed, IDEM used the most recent TSI score to determine impairment. If the TSI score indicates eutrophic or hypereutrophic conditions, the lake was assessed as impaired. It should be noted that TSI scores were not used in the absence of Chla results. TSI scores were only reviewed in cases where there were sufficient TP and Chla data but those data showed conflicting results.

The benchmarks from the LTI study were used to make assessments for recreational uses (as opposed to other designated uses), specifically within the context of aesthetics. Because IDEM does not have sufficient information regarding the response of aquatic communities to nutrient enrichment, these benchmarks are used to make recreational use support determinations only. These assessments are made within the context of aesthetics as opposed to health risk. Recreational use support assessments for human health are based on pathogen data and are made in the same manner as for rivers and streams when adequate data are available. All impairments identified based on this methodology were assessed as impaired for phosphorus as opposed to nutrients because the LTI study did not include analyses of other nutrient-related parameters.

Figure 5 provides a simplified model of how the median values calculated for a given TP threshold are used to determine recreational use support. A more detailed discussion is provided in following section.

Indiana's CLP samples between 70 and 80 lakes each year in accordance with a rotating sampling strategy similar to the rotating basin strategy employed by IDEM for monitoring streams. However, the basin rotation IDEM employs for Indiana's rivers and streams does not work well for lakes because of their unequal distribution across the Indiana landscape. While some basins contain very few lakes, others contain more than can feasibly be sampled in a given year. Therefore, the Indiana CLP's monitoring rotation for lakes is designed to analyze all public access lakes once every five years. Through this rotation, a given lake is monitored approximately once every five years in July and August. Approximately 80 lakes are sampled each year. About 400 lakes are monitored in a five-year rotation. In general, only public lakes having an accessible boat launching area were sampled. The July through August period is used because this is the time of year when worst case scenarios and stable conditions (warm temperatures, thermal stratification, hypolimnetic anoxia, and algal blooms) are expected.

For purposes of determining recreational use support within the context of aesthetics, the following general rules were applied:

The thresholds shown in Table 10 were applied to all natural lakes and reservoirs for which sufficient data were available. IDEM's methods for applying these criteria are summarized in Table 12 and are illustrated in Figure 6. All waters found to be not supporting of recreational use (aesthetics) were categorized as impaired and placed in Category 5A of Indiana's 303(d) List of Impaired Waters.

Given the robust, Indiana-specific dataset upon which the thresholds recommended in the LTI study were developed, IDEM believes LTI's recommendations to be appropriate for making designated use assessments and will likely provide the basis for rulemaking to establish nutrient criteria for Indiana's lakes in the future. When IDEM finalizes its nutrient criteria and incorporates them into the state's WQS, IDEM will review all lakes assessments made with the present methodology to determine their consistency with the revised WQS.

CWA Section 314 lakes assessments were based on the Indiana Trophic State (or eutrophication) Index, a modified version of the BonHomme Index developed for Indiana lakes in 1972. This multi-metric index combines chemical, physical, and biological data into one overall trophic score for each public lake and reservoir sampled (Table 13). Scores range from zero to 75. Lower values reflect lower concentrations of nutrients (Table 14). This information is useful in evaluating watershed impacts on lakes. Declining or extirpated Cisco populations and the presence of exotic and potentially toxic blue-green algae species were also considered when evaluating lake water quality for aquatic life use. For drinking water reservoirs, taste and odor were also considered as potential indicators of other water quality problems within the waterbody.

The U.S. EPA "generally believes that fish and shellfish consumption advisories1/4based on reach specific information demonstrate impairment of CWA section 101(s) 'fishable' uses" and continues to require that IDEM makes water quality assessments for fish consumption and places waters with fish consumption advisories on its 303(d) list of impaired waters (U.S. EPA, 2000a). However, Indiana's WQS do not contain numeric criteria for the concentration of mercury or polychlorinated biphenyls (PCBs) in fish tissue. IDEM's past and present fish consumption use assessments are a translation of the narrative portion of Indiana's WQS, which states that surface waters "1/4shall be free from substances in concentrations that on the basis of available scientific data are believed to be sufficient to injure, be chronically toxic to, or be carcinogenic, mutagenic, or teratogenic to humans, animals, aquatic life, or plants." (327 IAC 2-1-6 (a)(2) and 327 IAC 2-1.5-8(b)(2)).

IDEM began using fish tissue data directly in its CWA assessments in 2008 to more accurately characterize the extent of impairment. Based on the guidance issued by the U.S. EPA (U.S. EPA, 2010) and approved by ORSANCO's technical committee for use in Ohio River assessments, IDEM has refined its methods for evaluating mercury concentrations in fish tissue for its CWA 305(b) assessment and 303(d) listing processes for the 2012 cycle. These changes and their rationale are discussed in more detail in the following sections. IDEM's methods for evaluating PCB concentrations in fish tissue remain unchanged.

In 2001, the U.S. EPA issued a revised human health-based water quality criterion for methylmercury (U.S. EPA 2001). The new criterion is unique among all U.S. EPA (Clean Water Act 304(a)) water quality criteria in that it identifies an acceptable mercury concentration in fish tissue rather than water. A fish tissue criterion is logical because it is fish that are the main source of methylmercury exposure to both humans and wildlife. Also, a tissue-based criterion eliminates the need for a bioaccumulation factor in the criterion calculation, which can be a significant source of uncertainty. The derivation of the methylmercury water quality criterion is based on the reference dose of 0.1 ug/kg body weight/day, exposure data (for example, the amount of methylmercury ingested, inhaled, or absorbed per day), and data about the target population to be protected. The U.S. EPA criterion (U.S. EPA 2001) is 0.3 mg/kg wet weight methylmercury in fish muscle tissue. Since nearly 100 percent of the mercury in fish muscle is methylmercury, the criterion can reasonably be considered a total mercury criterion.

The U.S. EPA has not issued a human health-based criterion for PCBs in fish tissue, and Indiana's WQS do not contain a numeric concentration criterion for PCBs in the edible portion of fish tissue. However, Indiana has adopted human health WQS to protect the public from adverse impacts due to: (1) exposure through public drinking water supplies withdrawn from surface waters; and (2) nondrinking water exposures such as consumption of fish caught in Indiana lakes, rivers, and streams. Although human consumption of sport fish is not explicitly described in Indiana's WQS, criteria for fish consumption are included as part of the calculation of the human health criteria IDEM plans to propose in the future. The fish consumption values in the human health criterion calculation are intended to ensure that the levels of a carcinogenic chemical in fish are not at levels harmful to people who consume them.

Without a U.S. EPA criterion derived specifically for fish tissue concentration of PCBs, using the U.S. EPA's methodology for deriving ambient water quality criteria for the protection of human health (U.S. EPA 2000b) to calculate a concentration value for PCBs is a reasonable alternative that results in a criterion that is more readily applicable to Sections 305(b) and 303(d) water quality assessments than using FCA grouping levels. IDEM's benchmark criteria for mercury and PCBs in fish tissue are shown in Table 15.

A fish consumption advisory is determined based on the quantity of a chemical in fish, such as milligrams of chemical per kilogram of the edible portion of fish tissue (mg/kg). WQS, on the other hand, are expressed as the quantity of the chemical in water, such as micrograms of a chemical per liter of water (ug/L). The exposure assumptions upon which the human health criteria are based can be used to calculate a maximum safe fish concentration. That fish concentration value can then be directly compared to the values used to issue fish consumption advisories to determine whether the advisory is less or more protective than the WQS.

The levels of fish tissue contaminants that trigger a FCA and the levels of fish tissue contaminants on which the WQS criteria are based are derived using the same contaminant result, reference dose and body weight assumptions. Although EPA derived its recommended screening value for a fish advisory limit for mercury and human health methylmercury criterion from virtually identical methodologies, it is important to clarify the distinctions between the two values. They are consistently derived, but, because the two values differ in purpose and scope, they diverge at the risk management level. Fish advisories are intended to inform the public about how much consumers should limit their intake of individual fish species from certain waterbodies. Alternatively, the human health criterion is used as the basis for nonregulatory and regulatory decisions. The criterion serves as guidance for use in establishing water quality standards, which, in turn, serve as a benchmark for attainment, compliance, and enforcement purposes.

FCAs are intended to provide for the protection of human health over a lifetime of exposure, maximizing benefits of eating fish while minimizing the risk. The calculations used to determine if an FCA should be issued are based on contaminant concentration found in fish, which is treated as a constant while consumption rates are allowed to vary (how much fish can one safely consume and not exceed a particular dose rate). Allowing for different consumption rates makes it possible to safely consume fish that have different levels of contamination. The recommended consumption rate is reduced as fish tissue contaminant concentrations increase. In contrast, WQS criteria calculations start with an assumed level of fish consumption and derive a criterion for a safe level of exposure. Because the consumption rate is held constant, the resulting criterion can be applied consistently to all waters. FCAs are expressed for a given waterbody in terms of certain species within certain size ranges. Very few FCAs apply to all fish in a given waterbody, which limits their utility for water quality assessment purposes.

IDEM's assessment methodology for evaluating fish tissue data is directly applicable to all waters and uses the revised human health-based water quality criterion for methylmercury (U.S. EPA 2001) and a criterion for PCBs derived from the U.S. EPA's (2000b) human health methodology.

While mindful of the differences in purpose and function of the FCA and the 303(d) list, IDEM's methodology maintains as much consistency as possible between the protocols that ISDH, IDEM, and IDNR use to assess data for the FCA and the protocols that IDEM uses to assess data for the determination of impairment. For PCBs, the WQS-based threshold is lower than the FCA threshold for a Group 2 advisory. Therefore, there is a concentration range where there could be a WQS exceedance but still unlimited consumption. However, the threshold for mercury is higher than that which would trigger a Group 2 advisory (Table 16). For mercury, given the existing exposure assumptions upon which the water quality criteria are based, issuance of a FCA does not necessarily indicate an exceedance of WQS.

IDEM's benchmark criteria do not reflect any determination by IDEM of what an appropriate fish consumption rate should be. The consumption rates expressed in Indiana's WQS for human health are 15.0 g/day for waters in the Great Lakes basin (327 IAC 2-1.5-14) and 6.5 g/day for downstate waters (327 IAC 2-1-8.6). For mercury, IDEM defaulted to the U.S. EPA water quality criterion 0.3mg/kg methylmercury wet weight determined at a consumption rate of 17.5 g/day) for mercury in fish tissue and a reference dose of 0.1 ug/kg body weight/day (U.S. EPA, 2001), which corresponds to approximately two meals per month, between a Group 2 (32 g/day) and a Group 3 (7.4 g/day) advisory.

For calculating the criterion for PCB in fish tissue, IDEM used the same consumption rate the U.S. EPA used to calculate its criterion for mercury in fish tissue for the general population, which is 17.5 g/day national consumption rate. The use of a higher consumption rate in the PCB calculation is consistent with that used by the U.S. EPA and results in a more protective criterion than applying the consumption rate expressed for either the Great Lakes basin or downstate waters. The same holds true for mercury. IDEM's decision to use the U.S. EPA's criterion value for mercury in fish tissue was a policy decision based on the fact that the U.S. EPA's criterion is more protective. Calculations for both criteria are provided at the end of this appendix.

IDEM's assessment methodology for evaluating fish tissue data is summarized in Table 17 and reflects a conservative approach intended to both identify waters in which the data indicate impairment for mercury or PCBs, or both, and to provide for the protection of human health.

For PCBs, all samples from a given sampling reach must have results below the benchmark for PCBs in order to be assessed as fully supporting, and all waters with a sample result exceeding the benchmark are classified as impaired. This is a highly conservative approach that considers only the highest sample PCB concentration, which may be one of a number of samples collected at the site.

For the 2008 and 2010 cycles, IDEM used the same approach to evaluate mercury in fish tissues as that used for PCBs. For the 2012 cycle, IDEM refined its assessment methods for mercury based on the U.S. EPA's more recent guidance (U.S. EPA 2010), which provides recommendations on the use of the U.S. EPA's water quality criterion for mercury in fish tissue in CWA 305(b) assessments. It should be noted that the U.S. EPA's 2010 guidance did not change the methylmercury criterion that IDEM uses in these assessments and, also, did not change how it is applied as it still requires only one exceedance of the criterion to trigger an impairment decision. Rather, the guidance provides a new approach to analyzing the data. Instead of individually evaluating each sample result from a given site, IDEM now calculates a single, trophic level, consumption rate–weighted, arithmetic mean result for the site based on all the samples collected during a given sampling event for the purposes of evaluating fishable use support for mercury. The calculation IDEM now uses for the purpose of evaluating methylmercury in fish tissue, which is provided at the end of this appendix, apportions the national default consumption rate of 17.5 g/day across three trophic levels based on the amount and type of fish (by trophic level) that people might be consuming and, as such, more accurately characterizes human exposure and, therefore, fishable use support.

Sport fish are of particular importance to the question of consumption because they comprise the majority of fish taken by anglers. Most sport fish are predator species but also include omnivores such as carp. Therefore, to properly determine the degree to which a waterbody supports fish consumption, an appropriate methodology takes into consideration both the types of fish being caught and how differences in species affect the concentrations of the contaminant in question. Prior to the release of the U.S. EPA's 2010 guidance on the implementation of its water quality criterion for methylmercury in fish tissue, IDEM used the same methods to make fish consumption assessments for both contaminants.

The differences in IDEM's assessment methods for PCBs and mercury are a function of how these contaminants accumulate in the tissues of fish once ingested by them. PCB concentrations in fish are primarily a function of their fat content while mercury concentrations are more a function of their trophic level. Because PCBs accumulate in the fatty tissues of fish, concentrations tend to be higher in more fatty species such as carp and catfish as opposed to species such as bass and sunfish, which are leaner by comparison. In contrast, mercury tends to be higher in predator species because it biomagnifies up the food chain as larger fish consume smaller fish containing mercury.

The method of calculating a trophic level–weighted, arithmetic mean for mercury would not be appropriate for PCBs because trophic levels are less predictive than individual species of PCB concentrations in fish caught at a given site and, thus, less representative of the amount of PCBs a person might consume. Based on the way that PCBs bioaccumulate in fish tissue (by accumulating in their fatty tissue), IDEM continues to use the results of individual samples for the purposes of assessment, and the type of fish species continues to be a factor in assessment. Based on the U.S. EPA's 2010 guidance, the particular species is no longer as relevant for evaluating total mercury concentration (most of which is methylmercury) in fish tissue, which is more a function of trophic level for determining fish consumption use support. For evaluating mercury in fish tissue, IDEM's revised methods use a trophic level, geometric mean to calculate a consumption-weighted, arithmetic mean for the site, which considers consumption levels across all trophic levels and includes all species types.

Given the change in its assessment methodology for mercury in fish tissue, IDEM conducted a statewide reassessment of all IDEM fish tissue data to ensure the accuracy of Indiana's 303(d) list with regard to impairments for mercury in fish tissue that were identified based on the previous method. The data set reviewed for this reassessment was comprised of results from sampling conducted from 1990 through 2011 and is IDEM's longest duration and most complete fish tissue data set to date. IDEM emphasizes that in completing its statewide reassessment, no waterbody impairment previously identified on Indiana's 303(d) list was delisted due to the age of the data available for assessment.

The following describes, in detail, the steps in IDEM's assessment process for assessing the "fishable use" of Indiana waters.

In addition to data quality, the adequacy of a data set for the purposes of making a 305(b) or 303(d) assessment, or both, and listing decisions is measured by the amount of data available and the age of the data, both of which can affect the degree to which the data accurately represents waterbody conditions.

The previous minimum data requirements for fish tissue assessments still apply. One sampling event was considered sufficient for assessment purposes. At a given sampling event, composite samples were made for each species within a given size class collected at the site, which provides one or more species-specific results for assessment. For PCBs, results for each individual sample were compared to the 0.02 mg/kg criterion to make the assessment. For mercury, a consumption-weighted, arithmetic mean was calculated for each sampling event using the results from all the samples collected. The arithmetic mean result for each sampling event was then treated as an individual result and compared to the 0.3 mg/kg criterion. Multiple sampling events within a single year or multiple years for a site were not pooled together for either type of assessment (mercury or PCBs).

U.S. EPA guidance suggests that, while all readily available data should be reviewed, 305(b) assessment decisions should be based on data five or fewer years old. However, IDEM has established 12 years as the appropriate index period for the purposes of evaluating fish tissue data. Given the persistent nature of fish tissue contaminants in the environment, aggregating data over several years minimizes the effects of temporal, spatial, and species level variability on the assessment process. Based on IDEM's sampling strategy, an index period of 12 years ensures two full cycles of fish tissue data for use in evaluating fish consumption use support.

Data collected outside the index period were also evaluated, most often as supporting information where more recent data are available. Where there were not more recent data available, it should be noted that waters were not delisted based on age of data alone. In cases where the original data used to make an impairment decision were outside the current index period, IDEM applied its revised assessment methodology for mercury by taking the approach that if the original data indicated impairment when evaluated based on its consumption-weighted, arithmetic mean, then the lake or stream reach remained assessed as impaired for mercury in fish tissue unless there were more recent results from within the 12-year period of assessment to indicate otherwise.

It should also be noted that a fully supporting assessment for mercury in fish tissue does not preclude the listing of a waterbody for an impairment of its fish consumption use. A waterbody is listed as impaired for fish consumption based on impairment for either mercury or PCBs in fish tissue.

Independent applicability was applied to all results obtained within the index period for assessment. By definition, the index period is the period of time over which the data may reasonably be considered representative of conditions in a given waterbody. A single, older result collected within the index period may well be representative of the variability within the waterbody and was considered equally valid as any other sample collected in the same index period.

Therefore, where there were conflicting results from samples collected within the index period, the waterbody was assessed as impaired regardless of when in the index period the exceeding results were collected and even if the more recent results indicate full support.

The WQS-based assessment thresholds shown in Table 15 were applied to all lakes and streams for which sufficient fish tissue data were available. IDEM's methods for applying these criteria are summarized in Table 17. All waters found to be not supporting due to either mercury or PCBs, or both, were categorized as impaired and placed in Category 5B of the 2014 Indiana 303(d) List of Impaired Waters.

In some cases, fish can be very mobile and difficult to attribute to a discrete portion of a lake or river reach. In determining the appropriate geographical extent to which results can be confidently applied, IDEM followed the general rules described below. Unless otherwise stated, the same general rules were applied to assessments of both PCBs and mercury in fish tissue.

a) Stream Order Considerations

For flowing waters, stream order was the primary factor considered in determining the appropriate distance over which the results should be applied. Stream order is a good indicator of relative stream size, and, to the extent that size affects flow, the size of a given stream has a significant effect on species and sizes of fish that might be caught there.

Generally, in cases where significant differences in stream order exist in a given watershed, results were applied only to the stream on which they were obtained. This is because the fish community found in a third or fourth order stream might reasonably be expected to be very different from the fish communities found in its first and second order tributaries. Likewise, the expectations for the type and sizes of fish found in a fifth order stream would be different from those for a third or fourth order stream. Given this, results obtained from fifth order and greater streams were limited only to the mainstem and were not considered representative of their tributaries. Because of the significant effects that stream order has on the structure of the fish community in a given stream, basing extrapolations primarily on stream order allows us to more reliably apply fish tissue results on a stream-specific basis.

Most of Indiana's larger streams and rivers (third, fourth, and fifth order streams) have been monitored for many years resulting in very robust data sets. On these streams, results were applied to greater lengths where bounding samples upstream and downstream were available.

Results for many of Indiana's smaller streams (first and second order streams) are generally more limited. On these waters, results were applied only to the 12-digit watershed boundary except in cases where additional results from sites in an upstream or downstream watershed supported assessment over a greater distance. In these cases, assessments were limited to mainstem reaches between the sites and were not applied to their tributaries. Results from a mainstem site were also applied to its headwaters if obtained in the same watershed or the watershed immediately downstream.

b) Background Conditions

For PCBs, relative concentrations are used as an indicator of background conditions. Values greater than 1,000 ppb for PCBs were considered suggestive of point sources, most of which are known legacy sources of this contaminant. Values lower than this can be reasonably attributed to atmospheric and biological redistribution of contaminants or low level nonpoint sources and were considered representative of background conditions. Therefore, for PCBs, monitoring results in a smaller watershed were also extrapolated into other streams of similar stream order in that watershed when values were consistently low such as to suggest background conditions. In cases where the sampling site was located in a particularly large or hydrologically complex watershed or far upstream from most or all streams in the watershed, extrapolations were more limited. Extrapolations around sites with very high PCB concentrations suggesting point sources were also limited.

Unlike PCBs, there is no concentration value for mercury that is considered particularly suggestive of point sources. High mercury values in fish tissue are more indicative of localized methylation processes affecting the amount of mercury available for uptake than any sources of contamination. Most mercury in fish tissue is the result of atmospheric deposition, which is diffuse in nature. As a result, background conditions for mercury in fish tissue are very difficult to determine because they are highly dependent on the structure of the fish community, which differs significantly depending on the size of the stream in question. While it may be possible to predict background conditions for a given stream order to guide extrapolations of results for mercury in fish tissue, stream order, itself, remains a more reliable indicator of the extent to which those results may be representative for the purpose of determining use support.

c) Results from Lake Samples

For a given lake or reservoir, all fish tissue data were aggregated unless there was evidence that fish from certain parts of the lake were isolated and may have been exposed to a different level of contamination.

Fish community structure within a lake can clearly influence the fish community structure for some distance in streams flowing from lakes. Given this, results from lakes and reservoirs were applied downstream into adjacent watersheds in cases where there are downstream data to support the assessment. In cases where there were no data available for out-flowing streams, results for lake samples were applied only to the lake from which they were collected.

IDEM emphasizes that the purpose of the 303(d) List of Impaired Waters is not to provide the public with a list of waters that they should or should not swim in or catch and eat fish from. Section 303(d) of the CWA requires that states develop a list identifying impairments to water quality for which a TMDL is required. The 303(d) list is not and was never intended to be a public health advisory. IDEM continues to defer to the Indiana FCA on questions regarding the relative risks of consuming fish caught from Indiana waters and recommends that the public refer to the current FCA or contact the ISDH with any specific questions or concerns in this respect. The current fish consumption advisory can be found online at: http://www.in.gov/isdh/23650.htm and contains more specific information than the 303(d) list does regarding the sizes and species of fish that can be safely consumed and how often.

Because IDEM uses the similar methods in determining unsafe levels of mercury and PCBs that ISDH uses in determining fish consumption advice, the concentrations of these contaminants used to determine impairment correspond closely to the meal frequency recommendations published in the FCA. However, it is important to emphasize that one cannot assume, because a particular waterbody does not appear on the 303(d) list for fish consumption that the fish in that waterbody are safe for consumption of more than one meal per week. Likewise, due to the statewide fish consumption advisory for carp, it should not be assumed that carp greater than 15" in length from waters assessed as fully supporting are safe for consumption of more than one meal per month for the general population or at all by sensitive populations.

At present, adequate translators do not exist for applying concentrations of mercury or PCBs in fish tissue to concentrations in the water column. Toxicants may be present in fish at levels that have no ill effects on aquatic life but, due to bioaccumulation, may make them unsafe to eat. The concentrations shown in Table 15 apply only to fish tissue, not to water. Therefore, it also should not be assumed that if a waterbody is impaired for fish consumption that mercury or PCBs, or both, are present in the water column in amounts harmful to human health.

IDEM's fish consumption use assessments are required by the U.S. EPA and are a translation of the narrative portion of Indiana's water quality standard, which states that surface waters shall be free from substances in concentrations that on the basis of available scientific data are believed to be sufficient to injure, be chronically toxic to, or be carcinogenic, mutagenic, or teratogenic to humans, animals, aquatic life, or plants." (327 IAC 2-1-6 (a)(2) and 327 IAC 2-1.5-8(b)(2)). In addition to resolving the issues associated with using the FCA for assessments, IDEM believes this assessment methodology is consistent with this standard, achieves consistency with the decision making criteria used in developing the FCA, and is consistent with U.S. EPA 305(b) and 303(d) policy guidance.

Biological assessments for streams are based on the sampling and evaluation of either the fish communities or benthic aquatic macroinvertebrate communities, or both. Indices of Biotic Integrity (IBI) for fish and macroinvertebrate IBI (mIBI) assessment scores, or both, were calculated and compared to regionally calibrated models. In evaluating fish communities, streams rating as "fair" or worse are classified as nonsupporting for aquatic life uses. For benthic aquatic macroinvertebrate communities, individual sites are compared to a statewide calibration at the lowest practical level of identification for Indiana. All sites at or above background for the calibration are considered to be supporting aquatic life uses. Those sites rated as moderately or severely impaired in the calibration are considered to be nonsupporting. Waters with identified impairments to one or more biological communities are considered not supporting aquatic life use. The biological thresholds Indiana uses to make use attainment decisions are shown in Table 18 to provide greater context for understanding the range of biological conditions that is considered either fully supporting or impaired.

IDEM's aquatic life use assessments are never based solely on habitat evaluations. However, habitat evaluations are used as supporting information in conjunction with biological data to determine aquatic life use support. Such evaluations, which take into consideration a variety of habitat characteristics as well as stream size, help IDEM to determine the extent to which habitat conditions may be influencing the ability of biological communities to thrive. If habitat is determined to be driving a biological community impairment (IBC) and no other pollutants that might be contributing to the impairment have been identified, the IBC is not considered for inclusion on IDEM's 303(d) List of Impaired Waters (Category 5). In such cases, the waterbody is instead placed in Category 4C for the biological impairment.

IDEM's use support criteria for fish community and macroinvertebrate community data have undergone significant changes since they were first adopted in 1996. Table 19 summarizes the evolution of IDEM's criteria for making assessments with biological data.

The biological criteria that were developed for both fish and macroinvertebrate communities for the 2004 305(b) and 303(d) assessment and listing cycle were calibrated to reference conditions throughout Indiana and applicable to all waters. However, with all of these changes, the resulting criteria were applied only to the basins being assessed at the time. For the 2006 cycle, IDEM began reviewing all aquatic life use support assessments made prior to 2002 to ensure their consistency with the statewide criteria developed in 2004. This review was completed for the 2008 cycle.

Although the fish community criteria developed in 2004 remains in effect today, IDEM revised its assessment methods for evaluating macroinvertebrate data for the 2010 cycle.

The statewide mIBI developed for the 2004 cycle was based on riffle/run samples collected throughout the state from 1990 through 1994. Office of Water Quality used the riffle/run method w from 1996 through 2003, collecting samples at some of the same sites sampled for the original calibration of the index that were randomly selected for follow-up sampling. Beginning in 1998, the Office of Water Quality also collected samples at probabilistic sites chosen for the Watershed Monitoring Program where a suitable riffle/run habitat was present. Unfortunately, less than half of the probabilistic sites sampled during this time had riffle/run type habitats within the allowed distance, which reduced the effectiveness of the riffle/run method as a monitoring tool. This necessitated the development of a macroinvertebrate sampling method which could be used at all probabilistic sites, regardless of habitat.

The new multi-habitat method (mHAB) differs primarily from the riffle/run method in that it samples all habitats available at a stream site using a D-frame net instead of the kick screen used in the riffle/run method. In 2004, 62 sites (a subset selected from all sites previously sampled with the riffle/run method between 1990 and 2003), were re-sampled with the new MHAB method. The idea was to develop an index calibrated, not on the best possible reference conditions, but on a normal distribution of stream conditions based on mIBI scores obtained at previously sampled sites. It was later determined that this was too few samples to develop an efficient statewide index; therefore, these samples were combined with probabilistic samples collected in 2005, 2006, and 2007 (a total of 247 samples) to develop the index currently in use.

Twelve metrics were chosen from a pool of more than 100 possible metrics in the development of the new mIBI. These 12 metrics provided the best correlation to the data and describe a diversity of features that characterize the quality of a stream or river. The scores for each individual metric are totaled and can range from 12 to 60. As with the fish community IBI, mIBI scores less than 36 are considered non-supporting of aquatic life use while those equal to or greater than 36 are supporting of aquatic life use.

IDEM incorporated the mHAB methods into it monitoring programs in 2004 and began using the mIBI scores derived with the mHab methods beginning with the 2010-cycle assessments of aquatic life use support. At this time, IDEM is considering whether a reevaluation of waters previously assessed using the original mIBI is now in order. However, due to the differences in sampling methods used to obtain the data for the original mIBI and the new index now in place, such a reassessment may not be necessary or appropriate.

For the development of its 303(d) List of Impaired Waters, IDEM has followed, to the degree possible, the 305(b) and 303(d) reporting methods outlined in the U.S. EPA's Guidance for 2006 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d), 305(b) and 314 of the Clean Water Act (U.S. EPA, 2005) and the additional guidance provided in the U.S. EPA memorandums containing information concerning Clean Water Act Sections 303(d), 305(b), and 314 integrated reporting and listing decisions for the 2008, 2010, 2012, and 2014 cycle (U.S. EPA, 2006-2013). The 303(d) list was developed using IDEM's 305(b) Assessment Database (ADB). Interpretation of the data and listing decisions take into account IDEM's assessment methodologies and the U.S. EPA's guidance.

Waterbody AUs were classified as monitored if surface water quality data used for assessments were not more than five years old or were still considered representative of current conditions. Data from a given monitoring site are considered representative of the waterbody for that distance upstream and downstream in which there are not significant influences to the waterbody that might cause a change in water quality. Using this same rationale, data may also be extrapolated to some distance into tributaries upstream of a given sampling location. Waterbody AUs with one or more monitoring sites upstream and downstream and those for which reliable assessments can be made based on extrapolation of representative data are classified as monitored. Only monitored waterbodies are considered for 303(d) listing purposes. Any waters identified as "Not Supporting" of one or more designated uses in accordance with the criteria described in previous sections of this methodology are placed on Indiana's 303(d) List of Impaired Waters.

Interpretation of the data through the 305(b) assessment process and the subsequent 303(d) listing decisions are based in large part on U.S. EPA guidance. U.S. EPA guidance calls for a comprehensive listing of all monitored or assessed waterbodies in the state. Prior to 2006, U.S. EPA required that states place each waterbody into only one category. The U.S. EPA now encourages states to place a waterbody AU into additional categories as appropriate in order to more clearly illustrate where progress has been made in TMDL development and other restoration efforts. Given this, IDEM places each waterbody into one of five categories of the Consolidated List depending on the degree to which it supports the designated beneficial use in question. Therefore, because IDEM makes use support assessments for three to four of the beneficial uses designated for each waterbody, a single waterbody may appear in one or more categories of the Consolidated List for different uses.

Because each situation is unique and resources and data sets are sometimes limited, the 303(d) listing process may, at times, require IDEM staff to apply rational professional discretion. Written justification for any waterbody AU assessed in a different manner than indicated in the water quality assessment methodology outlined above will be made available upon request so that stakeholders will understand how each decision was made.

The current 303(d) List of Impaired Waters includes impairments identified on previous 303(d) lists, which still require TMDL development. For an AU to be listed, it must have been assessed using representative data, and the data must support listing. Any data, both internal or from outside sources, that is used for listing decisions must meet IDEM's quality assurance and quality control requirements as outlined in IDEM's surface water quality monitoring Quality Assurance Project Plan.

The U.S. EPA's new guidance does not change existing rules for listing and delisting. The existing regulations require states, at the request of the U.S. EPA's Regional Administrator, to demonstrate good cause for not including impairments on the 303(d) list that were included on previous 303(d) lists (pursuant to 40 CFR Part 130.7(b)(6)(iv)). In general, IDEM will only consider delisting an AU if one of the following is true:

Because the Ohio River is a boundary between states and U.S. EPA Regions, the development of a TMDL for the river will involve more than one state. To date, no TMDLs have been completed for the reaches of the Ohio River that border Indiana. However, ORSANCO is working with Ohio, West Virginia, Kentucky, Illinois, and Indiana (IDEM) to assist U.S. EPA Region 5 complete a bacteria TMDL for the entire river.

The CWA does not clearly define the timeline for TMDL development. However, the U.S. EPA, in response to the Federal Advisory Committee Act (FACA) Committee's recommendations, has issued guidance for states to develop expeditious schedules of not more than eight to 15 years. 40 CFR Part 130.7 also dictates that the 303(d) list specifically include the identification of waters targeted for TMDL development in the next two years. In accordance with the CWA, IDEM uses the 303(d) list to guide TMDL development. Every CWA 305(b)/303(d) assessment and listing cycle, IDEM works with the U.S. EPA to determine the number of TMDLs that must be developed in order to meet the goal of completing TMDLs for impairments within approximately 15 years of their listing. In addition to developing a short term list of TMDL priorities every two years, IDEM also revises its long term schedule for TMDL development to reflect all impairments currently listed in Category 5 of Indiana's Consolidated List, which makes up Indiana's 303(d) List of Impaired Waters.

The TMDL Program has worked typically from the oldest list (1998) forward, taking into account IDEM's rotating basin monitoring schedule. Where there has been special funding from U.S. EPA, the occasion for interstate TMDLs, or an opportunity to participate in a U.S. EPA initiative, the TMDL program has taken advantage and done that project as well. To take advantage of all available resources for TMDL development, IDEM's prioritization of impairments for TMDL development is driven by:

Indiana Administrative Code (IAC): http://www.in.gov/legislative/iac/title327.html

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Indiana Department of Environmental Management. 2005. Surface Water Quality Monitoring Strategy 2006-2010. Indianapolis, IN: Indiana Department of Environmental Management.

Indiana Department of Environmental Management. 2010. Surface Water Quality Monitoring Strategy 2011-2019. Indianapolis, IN: Indiana Department of Environmental Management.

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U.S. Environmental Protection Agency. 2000a. Office of Water Memorandum: Guidance to Promote Consistency in the Use of Fish and Shellfish Tissue Data by States, Territories, Authorized Tribes and EPA Regional Offices in Clean Water Act Section 303(d) Decision-making. Washington, D.C.: U.S. Environmental Protection Agency, Office of Water. WQSP-00-03.

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U.S. Environmental Protection Agency. 2000c. Nutrient Criteria Technical Guidance Manual: Lakes and Reservoirs, First Edition. Washington, D.C.: U.S. Environmental Protection Agency, Office of Water. EPA-822-B00-001.

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U. S. Environmental Protection Agency. 2003. Guidance for 2004 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d) and 305(b) of the Clean Water Act, July 21, 2003. Washington, D.C.: U.S. Environmental Protection Agency.

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The U.S. EPA stipulates that the risk assessment parameters used to categorize fish tissue contaminant data must be at least as protective as those used in the WQS-based fish concentrations. The equation for calculating a fish tissue criterion for PCBs utilizes the guidance provided by the U.S. EPA for calculating screening values for target analytes (http://www.epa.gov/waterscience/fishadvice/volume1/v1ch5.pdf). The U.S. EPA's Office of Water recommends the use of this calculation method because it is the basis for developing current water quality criteria for the protection of human health. The general equation used for calculating Screening Values (SVs) for carcinogens in fish tissue is derived from this guidance and is as follows: