Water Quality in the Mid-Coast Region

Water Quality Snapshot


Water quality and water quality management in the Mid-Coast region was summarized during Step 2 of the planning process. The entire report on water quality can be accessed here.

  • Water quality affects the extent to which water bodies can support beneficial uses, such as drinking water, industrial, agricultural, and fish and wildlife.

  • Numerous state agencies manage water in the region, including:

    • Oregon Department of Environmental Quality, which establishes water quality standards for Oregon's surface waters​.

    • Oregon Department of Agriculture regulates agricultural practices to prevent water pollution.

    • Oregon Department of Forestry regulates forestry practices to prevent water pollution.

    • Oregon State Parks manages potable water supply in state parks.

    • Oregon Health Authority implements regulations to ensure drinking water standards.

  • Numerous Mid-Coast water bodies are water quality limited for not meeting one or more water quality parameters, such as temperature, or E. coli.​

  • About 4 miles of beaches in the Mid-Coast are listed as water quality limited for enterococcus, which can cause illness from contact recreation, such as swimming.

  • Surface water is the primary source of drinking water for nearly all of the municipal and community water providers in the Mid-Coast.

  • Several water providers in the Mid-Coast use groundwater. Common groundwater contaminants include arsenic, lead, nitrates, and fecal coliform bacteria.

  • Numerous organizations and various private entities conduct some monitor water quality monitoring activities in the Mid-Coast.

Oregon establishes criteria for water quality standards to ensure an adequate quantity of reliably high quality water is available for beneficial uses - recreation, irrigation, industry, wildlife, and fish.

These criteria and standards include:

  • Temperature

  • Biological criteria

  • Sedimentation

  • Turbidity

  • Dissolved oxygen

  • Fecal indicator bacteria

  • Aquatic weeds or algae

  • Chlorophyll a

  • pH

  • Toxic compounds


Graphic credit: Kenneth Buddha Jeans. CC x 4.0.

Whats the Point?
Point and Non-Point Source Pollution

Point source pollution can be traced back to its original source and is regulated by state permitting programs. Examples of point source pollution include confined animal feeding operations, industrial wastewater, municipal wastewater, permitted pesticides, stormwater outfalls, and vessel discharges.

Nonpoint source pollution can come from multiple sources and cannot always be easily pinpointed to a specific location or activity. Examples of nonpoint source pollution include:

  • Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas

  • Oil, grease and toxic chemicals from urban runoff and energy production

  • Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks

  • Salt from irrigation practices and acid drainage from abandoned mines

  • Bacteria and nutrients from livestock, pet wastes, and faulty septic systems

Statewide Water Quality Toxics Assessment Report (2015) can be accessed here.


Sedimentation is a significant risk to drinking water sources. Water with high levels of fine sediment or turbidity requires extensive treatment to reach drinking water standards, and turbidity levels can be associated with bacteria levels. Source water assessments provide a comprehensive review of the risks to drinking water sources for each water provider in the Mid-Coast.

FireShot Capture 073 - Oregon Drinking W
Oregon Drinking Water Protection Program Interactive Map Viewer
FireShot Capture 079 - SLIDO_ Statewide
Statewide Landslide Information Layer for Oregon

Water Quality Standards and Programs in the Mid-Coast

Numerous state and federal statutes implement regulations affecting the management of water quality in Oregon. In addition, other programs with water quality regulations include the Groundwater Quality Protection Rules, Underground Injection Control Rules, NPDES and WPCF Permits Program Rules, Reclaimed Water Program Rules, Hazardous Waste Management Program, Underground Storage Tank Program, Municipal Solid Waste Program, the Oregon Groundwater Quality Protection Act of 1989, and ​Biosolids Program regulateing biosolids through the Oregon Department of Environmental Quality.

Practices Act

Establishes rules and requirements for operating plans, reforestation, water protection, forest chemicals, harvesting and slash treatment, landslide and public safety, air quality, visual and scenic quality, and fish and wildlife habitat protection.

Safe Drinking Water Act

A federal act that sets national standards for drinking water quality, including establishing standards for safe levels of contaminants and testing for contaminants. You can learn more here about the Drinking Water Protection Program.

Total Mean Daily Loads

The maximum amount of a pollutant allowed to enter a waterbody such that the waterbody will meet and continue to meet water quality standards for a particular pollutant.

Coastal Zone Management Act

Requires that land uses in the coastal zone and in adjacent lands which drain into the coastal zone, may affect the quality of coastal waters and habitats, and efforts to control coastal water pollution from land use activities must be improved.

Clean Water Act

Defines the beneficial uses of waterways to establish water quality benchmarks that maintain water quality. The Act makes it unlawful to discharge a pollutant into a waterway without a permit, and requires states to consider the cumulative impacts of point and nonpoint pollutants. Waters not meeting water quality standards are identified  as 303d impaired waters.

Agricultural Water Quality Management Act

Establishes requirements for landowners to prevent and control water pollution from agricultural activities and soil erosion. A Mid-Coast Agricultural Water Quality Management Area Plan guides landowners and others in addressing water quality issues related to agricultural activities.

Onsite Wastewater Treatment Systems

Mandates requirements for the construction, operation, and maintenance of onsite wastewater treatment systems. Septic systems are required to be decommissioned when a sewer system becomes available, or the system is violating current maintenance standards.

National Pollutant Discharge Elimination System

Required if wastewater, stormwater, rain, or snowmelt leaves a site through a point source. An NPDES permit specifies an acceptable level of a pollutant that can be discharged into waterways and may specify best management practices to protect water quality.

Water Quality Monitoring in the Mid-Coast

The Mid-Coast Watersheds Council, Siletz Watershed Council, and the Yaquina Watershed Council collaborate with the Lincoln County SWCD, which periodically conducts much of the water quality monitoring in the Mid-Coast. Also, the Alsea Watershed Study is a paired watershed study that studies the impacts of forest practices on water quality, aquatic habitat, and salmon.

The Oregon Department of Environmental Quality monitors and evaluates water quality via the Ambient Monitoring Network and Oregon Water Quality Index, watershed monitoring (TMDLs), toxics monitoring, biomonitoring, Oregon Beach Monitoring Program, Volunteer Water Quality Monitoring, Groundwater Monitoring, and National Aquatic Resource Surveys. Information about all of these programs can be found here. Water Quality Assessment Information from DEQ can be found here. And a collection of DEQ’s ambient water quality, watershed and groundwater monitoring project reports can be accessed here.

Water Quality Impaired Streams in the Mid-Coast

Oregon’s Section 303(d) lists water quality impaired streams that have been identified for not meeting water quality standards for a specific water quality parameter. TMDLs (or alternate pollution control plans) are required for all water quality-limited streams. TMDLs set specific criteria for pollutant amounts in stream reaches that are water quality limited.

Groundwater Quality

Multiple water providers in the Mid-Coast use groundwater. Some of these water providers have water treatment systems and others do not. According to DEQ, statewide studies of groundwater during the past 20 years have found that nitrate is the most commonly detected groundwater contaminant, followed by pesticides, volatile organic compounds, and bacteria. Private, domestic wells are not required to conduct routine water quality testing or to treat contaminants. Oregon’s Domestic Well Safety Program partners with local health departments and water providers to promote domestic well safety and improve local and state capacity to assess and manage risks associated with private wells.

© 2021 Oregon Mid-Coast Water Planning Partnership