TMDL Water Quality
Total Maximum Daily Load (TMDL) and Water Quality
Benton County is regulated by the State of Oregon’s Total Maximum Daily Load requirements for the Upper Willamette Mainstem, which is a 303(d) listed waterbody. Benton County has been categorized a Designated Management Agency (DMA) which means the County has legal authority over a sector or source that contributes pollutants to the system. The Benton County TMDL Implementation Plan focuses on general applications that will benefit the Upper Willamette River Subbasin which will in turn benefit the mainstem of the Willamette River.
Current TMDLs within Benton County that require pollutant load reduction strategies include bacteria, mercury, and temperature. Benton County has developed strategies to address all TMDLs where Benton County has authority to regulate land uses, while encourage positive actions countywide. In addition, the long term Benton County Riparian and Wetlands Project started in 2009, to primarily address the temperature issues in addition to supporting local comprehensive plan goals for natural stream and riparian resources including stream associated wetlands.
Water quality standards set limits for pollutants that impact the chemical, physical, and biological integrity goals. Streams including the Willamette River, Marys River, Long Tom River, Muddy Creek and many other seasonal and year-round flowing streams do not meet water quality standards in Benton County. TMDLs are used to address both point and non-point source pollution to ensure that water bodies such as rivers, lakes, and streams remain clean and healthy.
Here’s a breakdown of the two main sources of pollution addressed by TMDLs:
Point Sources
- Definition: Point sources are distinct and identifiable sources of pollution that discharge pollutants directly into water bodies through pipes, ditches, or other conveyances.
- Examples: Industrial facilities, sewage treatment plants, and wastewater discharge from urban areas.
- Regulation: Point sources are typically regulated through permits issued under the National Pollutant Discharge Elimination System (NPDES). These permits set limits on the amount and type of pollutants that can be discharged.
Non-Point Sources
- Definition: Non-point sources are diffuse and often harder to pinpoint. They contribute pollutants to water bodies through runoff over land or through atmospheric deposition.
- Examples: Agricultural runoff (pesticides and fertilizers), urban stormwater runoff, and soil erosion.
- Management: Non-point source pollution is managed through best management practices (BMPs), such as riparian buffers, controlled use of fertilizers, and improved land use practices. It’s more challenging to regulate compared to point sources due to its diffuse nature.
Additional Resources
Water Quality Plan
Water Quality Implementation Plan Adopted 2008
2018 Benton County TMDL Implementation Plan Five Year Review (2013-2018)
2023 Five Year Plan Report
Benton County Annual TMDL Reports
2016
2017
2018
2019
2021
2022
2023
2024
By addressing both point and non-point sources, TMDLs aim to improve water quality comprehensively, ensuring that water bodies meet their designated uses such as recreation, drinking water, and habitat for aquatic life.
