Arkansas’ Water Quality Limited Waterbodies - 303(d) List

Water Division

Sarah Clem, ADEQ Branch Manager- (501) 682-0660

• Introduction
• Methodology
• Table 1 - Assessment Guidance
• Table 2 - Water Quality Limited Waterbodies (303d) Prioritized and Targeted for TMDL for FY 99-00

Introduction

Section 303(d) of the Clean Water Act requires that States identify waters which do not meet or are not expected to meet applicable water quality standards. These water bodies are compiled into a list known as the 303(d) list. The regulation (40 CFR 130.7) requires that each 303(d) list be prioritized and identify waters targeted for Total Maximum Daily Load (TMDL) development in the next two years. The list is due every even numbered year on the first of April.

As a result of several lawsuits concerning past 303(d)/TMDL processes, EPA has issued numerous administrative interpretations, administrative procedures, policies and guidance (some still in draft form) from both headquarters and regional offices for preparation of the 1998, 303(d) list. These documents serve primarily to stimulate questions about how this "new" process relates to existing and future programs.

Methodology

Development of the 303(d) list is a byproduct of the preparation of the "Water Quality Inventory Report" which is another requirement of the Clean Water Act. It is required by Section 305(b). Both of these required documents were developed using extensive data from the fixed-station, ambient water quality monitoring network operated by the Arkansas Department of Environmental Quality. This network currently includes 133 stations that are sampled monthly and an additional 103 stations that were sampled quarterly. More than 30 parameters are analyzed each time these stations are sampled. Additionally, 32 sites on the Buffalo River and its tributaries have been sampled periodically for the last several years and provide excellent assessment data for certain parameters. Data from special projects such as the Illinois River and Tributaries Project and TMDL investigations on six small watersheds were used in this assessment. In addition, letters requesting information and data concerning impaired waters within the State were sent to the United States Geological Service, the Soil and Water Conservation Commission, the Arkansas Game and Fish Commission, the Ozark and Ouachita National Forest, and the Arkansas Water Resources Center. Only limited data was submitted by these agencies.

The support or non-support of designated uses was assessed by comparing monitor data with specific water quality criteria protective of those uses. The guidelines used for making monitored assessments were modified from the EPA guidance document for the 1998 State Water Quality Assessment. The guidance used is shown in Table 1. The criteria used in the guidance were from the ecoregion-based Water Quality Standards of Arkansas, EPA's Quality Criteria for Water and the Safe Drinking Water Act Standards.

A significant modification was made from the EPA guidance and from previous assessments. The modification includes the elimination of the "partially supporting" category. Since this category was ambiguous, we have chosen to eliminate the category. This results in a definitive assessment of either "supporting" or "non-supporting". However, there remained a need for a category of waters for which data indicate that the quality may be of some concern, but which there is no quantitative criteria to measure against, e.g. nutrients, storm flow turbidity or suspended solids. Also, in many instances there is substantial uncertainty about the magnitude or frequency of exceeding a criteria which would result in nonsupport. We therefore established a category for waters of concern. This category is basically equivalent to the category of "partial support" as we used it in previous reports. That category was used when the "support" or "non-support" could not be accurately determined for reasons listed above. The waters of concern category provides a "flag" for waters which will be closely scrutinized in future assessments or in special assessment projects to determine subsequent listing of these waters as "support" or "non-support".

Generally, only the current data was used to monitor a specific river reach on which the data was generated. Other reaches within the segment where no monitoring data exists were placed in the unassessed category. In some cases, professional judgment, personal knowledge, historical data and/or current data from adjacent stream reaches allowed for determination of an evaluated assessment of some stream reaches.

Table 1 - Assessment Guidance

Table 2 - Water Quality Limited Waterbodies (303d) Prioritized and Targeted for TMDL for FY 99-00 (PDF File)

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