- Programs & Services
- Division of Environment
- Watershed Planning, Monitoring & Assessment
- Total Maximum Daily Loads (TMDLs)
- The Basics of TMDLs
- Establishing Total Maximum Daily Loads
Establishing Total Maximum Daily Loads
Total Maximum Daily Loads (TMDLs) are viewed as the quantitative objectives and strategies needed to achieve water quality standards. The water quality standards, themselves, constitute the goals of water quality adequate to fully support designated uses of streams, lakes, and wetlands. The process of developing TMDLs determines:
- The pollutants causing water quality impairments,
- The degree of deviation away from applicable water quality standards,
- The levels of pollution reduction or pollutant loading needed to attain achievement of water quality standards,
- Corrective actions, including load allocations, to be implemented among point and non- point sources in the watershed affecting the water quality limited water body and,
- The monitoring and evaluation strategies needed to assess the impact of corrective actions in achieving TMDLs and water quality standards, including,
- Provisions for future revision of TMDLs based on those evaluations.
In Kansas, TMDL development will follow the process described in the EPA's Guidance for Water Quality-Based Decisions: The TMDL Process as well as the seven TMDL components suggested in the recommendations of the Federal Advisory Committee on the TMDL Program in its final report, issued July 1998. The TMDL process involves:
- Selection of the pollutant to consider, identifying the problem and defining the goal for improved water quality
- Determination of the assimilative capacity of the water body to receive that pollutant without violation of the applicable water quality standard and the current deviations exceeding that assimilative capacity.
- Estimation of the type, location and magnitude of pollutant sources contributing loads to the waterbody.
- Estimation of the linked relationship between those pollutant sources and their relative impact on the ambient water quality of the water body, including the anticipated response in water quality conditions upon load modifications arising from the contributing sources.
- Allocation of permissible loads among point, non-point and background sources of contributed pollutant reaching the waterbody. Assignment of responsibility for implementing corrective actions among point sources and non-point sources. Establishment of a margin of safety to safeguard the quality of the environment against uncertain relationships between pollutant contributions and ambient water quality.
- Follow-up monitoring to assess the level of implementation along the water body and within the watershed and to evaluate the impact of that implementation on the water quality condition of the impaired waterbody.
- A feedback mechanism which allows TMDLs and their implementation to iterate toward progressive improvement in water quality, as determined though compliance with water quality standards, over time and in response to evaluated information on the effective impact of corrective actions on water quality.
More specifically, each TMDL Kansas submits to EPA will contain the following components:
A. Problem Identification. The pollutant causing the impairment and the designated uses which are impaired will be identified. The rationale for listing the stream segment, watershed or lake on the Section 303(d) list will be described.
B. Current Situation and Desired Objective. The desired outcome of this TMDL process will be expressed, using the current situation as the reference condition of impairment. Deviations from the water quality standards will be documented. From the Kansas perspective, outcomes will be expressed in terms of the minimum frequency (how often), magnitude (how much) and duration (how long) of future deviations above the applicable water quality standard.
In the case of TMDLs involving numeric criteria and empirical stream or lake chemistry monitoring data, Kansas will develop load duration analyses which will describe the idealized desired loadings across the spectrum of flow conditions. Such analyses will be developed using the long term flow historic duration of a stream and converting that cumulative frequency distribution of daily flows into loads by applying the appropriate numeric criteria to the flows and making the appropriate conversions.
The resulting curve relates the load distribution over time and flow conditions which would attain and maintain water quality standards. Empirical data from the stream chemistry monitoring network can overlay this curve by determining the flow conditions when the individual sample was taken, the sample data's relative position is determined by the % exceedance of that flow over the long term, converting the sampled concentration by applying the flow and conversion values. Points plotting above the curve represent deviations from the water quality standard and the permissible loading function, those plotting below the curve represent compliance with standards and represent adequate quality support for the appropriate designated use. Similar analysis can be done for certain lakes, using cumulative frequency distributions of their volume or elevation.
Comparative analysis such as this allows the state to assess the frequency of deviations (how many samples lie above the curve vs. those that plot below); magnitude (how far the deviations plot away from the curve); and duration (potentially how long the deviation is present). The issue of duration can be viewed in terms of the flow conditions under which violations of the standards arise. In this analysis, loads which plot above the curve in the flow regime defined as being exceeded 85-99% of the time are likely indicative of point source influences on the water quality. Those plotting above the curve over the range of 10-70% exceedance likely reflect non-point contributions. Some combination of the two source categories lies in the transition zone of 70-85% exceedance. Those plotting above the curve at exceedances less than 10% or more than 99% reflect extreme hydrologic conditions of flood or drought.
This analysis allows a triage approach to identifying the likely significance of various sources along the waterbody or within the watershed and their contributions to the impaired condition seen within the water quality of the waterbody. Similar analysis is then conducted on a seasonal basis, using three seasons: winter low flow: November-March; spring runoff: April-June; and summer/fall baseflow: July-October. Each analysis serves to identify the critical time periods when water quality conditions deteriorate. Through this analysis, the circumstances and contributing factors of each deviation may be isolated and analyzed as part of the remaining components of the TMDL.
For impairments involving narrative criteria or biomonitoring data, surrogate indicators will be developed to define the TMDL objective. Such indicators include biotic index values, trophic state indices, number of acres covered by macrophytes, etc. Use of time trends in those surrogates will document the current conditions and will be used to define the quantitative outcome desired from establishing the TMDL and making progress toward reducing pollution and impairment in the identified waterbody.
For those waterbodies listed as a result of simulation model results indicating probable violation of water quality standards and impaired uses, the results of the modeling will be used along with sensitivity analysis to adequately define the conditions leading to impairment and the impact of intervening corrective actions toward improving those conditions.
In all situations, the TMDL will state its objective in meeting the appropriate water quality standard by quantifying the degree of pollution reduction expected over time on a mass, volume or % basis. Interim objectives or milestones will also be defined for midpoints in the implementation process. In some situations, such interim objectives will look for progress in moving the condition of an impaired waterbody from a condition of non-support to one of partial support en route to the ultimate objective of full support of that water's designated uses.
C. Source Assessment. Each pollutant source contributing to the deviation from the water quality standards will be identified and their relative contribution to the impaired situation determined/ Based on the flow-load analysis, judgments can be made on the degree point and non-point sources are contributing to the current condition. The number of sources, their geographic location along the segment or within the watershed, the type of source, the magnitude of their potential pollutant loading and their degree of influence on water quality will be identified.
For point sources, the assessment will include the type of wastewater and treatment they use, the volume of their discharged effluent, degree of compliance with existing permits, the limits in place on current permits, the expiration date of those existing permits, their potential for future growth and the expected flow conditions which they are expected to protect. Situations where the point source impacts will accumulate in a watershed setting or in a downstream manner will also be described.
For non-point sources, information will be gathered on the land uses within the watershed, the underlying topographic and soil features, likely contributing areas producing runoff,% of impervious area within the watershed producing stormwater discharges, stream-aquifer interactions, existing management practices in place and the limits of those practices to influence hydrologic extremes, and types of water use present along the streams and lakes, including diversions of that water.
This component will also present any documented information on the background levels of pollutants emanating from natural sources or sources lying outside the effective area under TMDL development. Levels of spatial or temporal uncertainty in the flow and water quality conditions of the impaired water body and its watershed will be expressed as part of the background assessment.
D. Load Allocation. In this context, allocation has the dual meaning of allocation actual allowable pollutant loadings among point and non-point sources as well as the more significant role of assigning appropriate responsibility of pollution reduction to sources and activities influencing the water quality of the impaired stream or lake. This component will lay the groundwork for implementation action to correct or improve the source impacts on water quality. A hierarchy of relative contributions among the sources will be established so that initial efforts will focus on those sources with greater influences. Considerations will be made of future alterations in those sources, seasonal variations and defined flow conditions. A margin of safety will be declared as part of the TMDL objective to provide safeguards to the waterbody from the uncertainty inherent in the impacts of point and non-point sources. The margin of safety will likely vary by pollutant.
E. Implementation. This component will describe the actions to be taken to control and manage point and non-point source contributions to pollutant loadings. Typically, a ten year period of implementation actions will be anticipated after TMDL approval. In the case of point sources (municipal, industrial and livestock), allocations of wasteloads will be made through renewed NPDES permits. The state will strive to place all NPDES permits along a segment, string of segments, within a watershed and eventually throughout each basin on the same schedule. For those point sources needing improvements, a compliance schedule will be developed. Use of the Kansas Water Pollution Control Revolving Loan Fund for upgrading wastewater facilities will continue to assign additional priority points to those scheduled projects discharging into a stream listed under Section 303(d) and subject to the conditions of a TMDL. Permits will reflect TMDL objectives by placing water quality based limitations on effluent discharges. In some cases, individual permits will assign the individual allocation of a wastewater load to a discharger, reflecting the distribution of wasteload allocations among the group of point sources sharing a common waterbody.
The principal mechanism of implementation for non-point sources will be targeted technical assistance, educational outreach and financial resources directed toward placing best management practices in critical contributing areas of watersheds influencing the water quality of listed streams and lakes. The key strategy will be to reduce pollutant loadings from these areas to the maximum extent practicable. Most of these efforts will rely on voluntary, incentive based approaches, consistent with current practice of the Kansas Water Plan, KDHE's Watershed Management Section and the Watershed Restoration and Protection Strategy (WRAPS) activities and federal programs, such as Environmental Quality Improvement Program (EQIP). Reasonable assurances can be made to implement this strategy with the use of the Kansas Water Plan and its supporting programs, its Annual Implementation Plan to set short term priorities for those programs, the $16 million annually available from the State Water Plan Fund and the development of Unified Watershed Assessments (UWAs; described in the Water Quality Management Plan section) to funnel federal funds such as Section 319 grants and EQIP into priority subbasins and watersheds. TMDLs will supplement efforts to improve quality in the priority watersheds identified through the UWA process, by directing resources to priority locations within those watersheds.
The Kansas Water Plan supports water quality protection efforts through directing and funding a number of programs such as non-point source pollution technical assistance, non-point pollution control cost sharing, local environmental protection planning, water resource cost-share, wetland and riparian protection, subbasin water resource management, water quality buffer initiatives, biological monitoring, stream gaging, research evaluations and basin assessments. With the call by the Kansas Water Authority to significantly increase the percentage of stream miles and lake acres which fully support their designated uses by the year 2010, implementation of TMDLs, particularly related to non-point source activities, will work toward achieving that Water Plan goal as well as the goals of the surface water quality standards.
Three mechanisms exist within state authority to address pollution sources, particularly those of a non-point nature.
- Critical Water Quality Management Areas. Watersheds may be designated as critical water quality management areas because of pollutant sources which cause or may reasonably be expected to cause, damage to resources of the state; public nuisance or health hazards; destruction of fishery habitat; excessive deposition of sediments on river bottoms, lakes or reservoirs; additional risk to threatened or endangered fish or wildlife or violation of water quality standards. The Department of Health and Environment evaluates all the pollutant sources and the extent by which they contribute to pollution problems within a proposed area and determines the technical and economic feasibility of simultaneous control of all pollutant sources. A proposed management plan is set forth with an implementation schedule for control of each source, an analysis of the costs and benefits of the plan and the boundaries of the proposed area. Considerable public input is solicited in the pre-designation phase, and the preparation of the management plan as well as formal public hearings on the proposed designation of the area.
- Pesticide Management Area. The Kansas Department of Agriculture is empowered to develop pesticide management areas when notified by EPA or KDHE that a pesticide poses a serious threat to the public health, safety and welfare or to the natural resources of the state. Such areas are developed upon examination of precipitation, topography, soils and depths to ground water and are designated as permitted, modified or prohibited in the use of certain types of pesticides. The Department uses a technical advisory committee in establishing the boundaries and management plan for the proposed area. Designation of the proposed area and its management plan is subject to public notice and comment through public hearings.
- Source Water Protection Planning. Under the guise of the federal Safe Drinking Water Act, the Department of Health and Environment is to stimulate, provide assistance and coordinate the development of state and local source water assessments to protect public water supplies. Such assessment planning delineates local public water supplies, inventories pollutant sources, analyzes the susceptibility of the pollutant risks and informs the public on the present conditions, risks and risk reduction plans associated with their water supplies. The program is coordinated with the State Wellhead Protection Program assessing the protection of ground water supplies. In many situations, developed plans are implemented through actual protective measures in the source water contributing areas falling under local jurisdiction of zoning and ordinances to reduce pollutant threats.
F. Follow-up Monitoring. Follow-up monitoring will be conducted in order to further reduce the uncertainty in environmental impacts of pollutant source contributions and alteration encountered in establishing the objectives and implementation of TMDLs and to determine the effectiveness of implementing actions on improving water quality. Monitoring is conducted on numerous fronts. Implementation monitoring tracks the degree to which corrective or management practices have been put in place for point and non-point sources along the segment or within the watershed. Non-point measures might include acres of land treatment implemented over time, increases in riparian area adjacent to streams, number of agricultural producers participating in cost-share programs and participation in outreach education events focused upon non-point source reductions. Point source monitoring would include compliance monitoring relative to existing and future NPDES permits, episodes of combined sewer overflows, status of scheduled upgrades in treatment facilities, episodes of emergency bypass through treatment works, maintenance schedules and upkeep for treatment facilities and ongoing training for treatment works operators.
Resource monitoring assesses the improvement in water quality conditions in the identified impaired waterbody. Baselines need to be established documenting current conditions. Generally, water quality data taken over a ten-year period will serve as the benchmark by which implementation of TMDLs will improve upon. Data will be examined in summarized form and as to trends over time. The ambient stream chemistry network will be generally maintained, with possible suggestions to expand spatial and temporal coverage in terms of additional sites and frequency of collection. Biomonitoring will continue to play a chief role in representing the integrated impacts of activities on water quality as registered by the supported biota of a stream or lake. The measure of success will be reductions in the frequency, magnitude and duration of violations of the water quality standards over the next decade.
Occasionally, synoptic surveys may be conducted to further evaluate loadings in a watershed setting above historic monitoring points, confirming load contributions from tributary areas within the watershed. Low flow intensive surveys will document impacts of effluent discharges on receiving waters. Stormwater monitoring may be recommended to further evaluate the contributions of urbanized areas on non-point loadings. Some follow up modeling may also be conducted, using BASINS, QUAL-2K, EUTROMOD, CNET, BATHTUB, AnnAGNPS, GWLF etc, to verify previous results, leading to implementation decisions and to further discern locations and conditions needing treatment in order to achieve the TMDL objectives.
The utilization of modeling applications to assist in TMDL development and follow up monitoring are anticipated to become more frequently utilized to predict watershed and loading conditions in selected watersheds.
The purpose of these monitoring efforts is to continue to guide implementation actions toward those opportunities creating the greatest, timely benefits in improving water quality. Monitoring should look toward trends of improvement and the meeting of interim milestones established within the period of TMDL implementation. In all cases, follow up monitoring will incorporate appropriate quality assurance/quality control protocols to assure the reliability of the data used for verification, increased scrutiny and evaluation of management practices.
G. Feedback Mechanism. As stated previously, Kansas intends to use a decade of implementation and monitoring after TMDL establishment to maximize the opportunity of placing resources on pollutant sources at the basin scale. This timeframe also increases the likelihood to discern the signal of positive influence amidst the variable noise associated with flow and water quality data, particularly in non-point source situations. There will be interim objectives incorporated within the TMDL implementation schedule to assess the direction of corrective actions at the midpoint of implementation and make appropriate adjustments. All implementation actions are available for review and adjustment within the timeframe of trying to accomplish the objectives of the TMDLs. NPDES permits are renewed at least every five years. Best Management Practices are subject to availability of funding and administrative policies and will reflect revised directions provided by the Kansas Water Plan and its Annual Implementation Plan.