Course Project

1. Course Project CE 775 Modeling and Analysis of Environmental Systems

2. Total Maximum Daily Load (TMDL) • Under section 303(d) of the Clean Water Act, states, territories, and authorized tribes are required to develop lists of impaired waters. • Jurisdictions should establish priority rankings for waters and develop TMDLs • A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that load among the various sources of that pollutant.

3. TMDL accounts for point and nonpoint sources • Pollutant sources are characterized as • Point sources that receive a wasteload allocation (WLA) • Point sources include all sources subject to regulation under the National Pollutant Discharge Elimination System (NPDES) program, • e.g. wastewater treatment facilities, some stormwater discharges and concentrated animal feeding operations. • Nonpoint sources that receive a load allocation (LA). • Nonpoint sources include all remaining sources of the pollutant as well as anthropogenic and natural background sources.

4. TMDL Calculation • Account for seasonal variations in water quality • Include a margin of safety (MOS) to account for uncertainty in predicting how well pollutant reductions will result in meeting water quality standards. TMDL = ΣWLA + ΣLA + MOS • where WLA is the sum of wasteload allocations (point sources), LA is the sum of load allocations (nonpoint sources and background), and MOS is the margin of safety.

5. TMDL Definitions • Waterbody/pollutant combination is each pollutant causing a waterbody to be impaired or threatened • ATMDL is developed for each waterbody/pollutant combination. • For example, if one waterbody is impaired or threatened by three pollutants, then three TMDLs will be developed for the waterbody. • States may bundle multiple TMDLs on a watershed scale. • The word TMDL is used to describe a document that addresses waterbody/pollutants combinations (i.e., several TMDLs exist in one TMDL document).

6. TMDL Goals • The goal of developing a TMDL is to create an implementation plan or a watershed plan designed to meet water quality standards and restore impaired waterbodies. • Many states include in their TMDL analyses implementation plans.

7. Required Components of TMDL Development • Problem Definition • Endpoint Identification • Source Analysis • Linkage Analysis • Seasonal Variation • Margin of Safety • Pollutant Load Allocation • Public Participation • Implementation and Reasonable Assurance

8. Upper Oyster Creek • Brazos River Basin • Southwest of Houston • Upper Oyster Creek, Segment 1245 • 54 miles long • Includes Jones Creek, Oyster Creek, Flat Bank Creek, a diversion canal, Steep Bank Creek

9. Upper Oyster Creek • The specific uses are contact recreation, intermediate aquatic life use, and domestic water supply. • Dissolved oxygen concentrations do not attain intermediate aquatic life use. • 24-hour average DO concentration > 4.0 mg/L • 24-hour absolute minimum DO concentration > 3.0 mg/L • When 63F < temperature < 73F • 24-hour average DO concentration > 5.0 mg/L • 24-hour absolute minimum DO concentration > 4.0 mg/L • Affected by municipal and industrial wastewater discharges • Stormwater runoff from agricultural, industrial, and urban areas

10. 9 Point Sources

11. Linkage Analysis – Water Quality Modeling • QUAL2K predicts water quality in river and stream systems • Represents channel in a one dimensional, longitudinal approach • Assumes vertical and lateral complete mixing • Non-uniform steady flow hydraulics • Water quality variables are simulated on a 24-hourtime scale • Excel workbook interface uses Visual Basics for Applications (VBA) macros • Numerical functions are implemented in Fortran 90