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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.

Basin Summary Report - Supplement to the Statewide Water Quality Toxics Assessment (2015)
Department of Environmental Quality, DEQ15-LAB-0065-TR
(Note: The following information is excerpted from the full report.)

In 2013, DEQ laboratory staff collected seasonal (April, September and November) water samples at 18 locations across the Mid Coast Basin. The sampling locations represented a range of watershed sizes and land uses as well as both freshwater and estuarine environments. Samples collected at the sampling location farthest upstream in the Siuslaw River watershed at Siuslaw Falls contained the greatest number of unique chemicals. The laboratory analyzed samples collected in the Mid Coast Basin for more than 500 unique chemicals. Of these, 49 chemicals were detected at least once.

To capture seasonal use patterns and hydrologic differences, collection of water samples took place three times during the year. In general, spring and summer samples contained the greatest number of unique chemicals.

In general, based on the sampling conducted in this study flame retardants, legacy pesticides and thallium are a concern in the upper Siuslaw River watershed. Additionally, the consistent detection of BHC compounds along the coast as well as coastal ammonia exceedances is also of concern and may warrant additional investigation. 

Priority metals

This group includes all metals for which Oregon has existing water quality criteria. These metals occur naturally and may also be enriched by human activities. Because of this, detections of these metals are common in water. Water samples contained nine different metals with the greatest number, six, found at the Cummins Creek site. Iron exceeded the DEQ aquatic life criterion (1000 μg/L) at two sampling locations, Lake Creek at Sumich Rd during summer sampling and Siuslaw River at Siuslaw Falls during the summer and fall sampling events. The inorganic arsenic level at the Alsea River Port Docks site exceeded water quality criterion (1.0 μg/L) for the protection of human health for saltwater during summer sampling. No freshwater locations exceeded the inorganic arsenic criterion. Thallium, a rarely detected compound across the state, exceeded the applicable water quality criterion (0.043 μg/L) at the Siuslaw River sampling location at Siuslaw Falls Park during spring sampling.

Current use pesticides

Four current use pesticides, all herbicides, were detected in the basin. No site had detections of more than one herbicide. Diuron, a commonly used commercial and agricultural herbicide, was the most common with detections at three sites, Schooner Creek, Yaquina River at Trapp Rd and Marker #47. All 27 diuron detections occurred during summer sampling. Atrazine was detected at the Wolf Creek site during spring sampling. Fluridone, an herbicide used for aquatic weed control, occurred in the spring sample at the Panther Creek site and trifluralin was detected during the spring at the Suislaw River at Siuslaw Falls site. The levels of these herbicides did not exceed any applicable EPA benchmark or DEQ criteria for the protection of aquatic life.

Legacy pesticides

Detections of legacy pesticides occurred at four sites in the Mid-Coast Basin. The Siuslaw River at Siuslaw Falls had the greatest number of unique chemicals in this group, eight. Of which, five (aldrin, dieldrin, heptachlor, heptachlor epoxide and hexachlorobenzene) exceeded their applicable Oregon DEQ criteria for the protection human health. All detections at the Siuslaw River at Siuslaw Falls site occurred during the spring with the exception of endosulfan sulfate, which occurred during the summer and fall. Detections of BHC-alpha occurred at one freshwater site, Siletz River at Moonshine Park, during summer sampling. Samples from the two estuary sites, Alsea River at Port Docks and Siuslaw River at Florence, contained detectable levels of BHC-alpha and beta. These compounds also were found in other estuaries along the Oregon coast and may be transported via the air. Because of their chemical nature, legacy pesticides tend to persist in sediments and bio-accumulate in the food chain making them a concern in the environment.

Combustion by-products (including dioxins and furans)

Detections of combustion by-products occurred at three sites in the Mid Coast Basin. These detections occurred during the summer and fall. Combustion by-products are associated with incomplete combustion of organic matter from automobiles, fossil fuels burning, woodstoves and cigarette smoke. They may also be the result of stormwater run-off. All six compounds detected in the basin occurred in 28 samples from the Yaquina River at Trapp Rd site. Of the six compounds detected at this site, all six were present during the summer sampling, but only two, phenanthrene and fluoranthene, were present during fall. Two compounds, benzo(b)fluoranthene and chrysene, exceeded Oregon DEQ Table 40 water quality criteria at the Yaquina River site, both during the summer sampling. The only detection of anthracene, statewide, occurred at the Yaquina River site below the applicable water quality criterion. Three combustion by-products were detected in the estuarine site, Alsea River at Port Docks. One compound, benzo(b)fluoranthene, exceeded its applicable water quality criterion at this site during the fall sampling. No detectable concentrations of dioxins and furans occurred in any samples in the Mid-Coast Basin.

Flame retardants

The most common group of chemicals detected in the basin was flame retardants with 14 compounds detected. Two sites in the Siuslaw River, at Siuslaw Falls Park (10 compounds) and at the Florence Boat Docks (9 compounds), accounted for a majority of these detections. Additional compounds were detected at Yachats River at RM 0.9 (1 compound), Wolf Creek at mouth (1 compound) and Alsea River at Mill Creek (2 compounds). Due to laboratory capacity, analysis for this group of chemicals only took place once, therefore, seasonality of these compounds cannot be discussed. There are no federal or state criteria developed for this chemical group, however, concern over these chemicals in humans and the environment prompted a ban on their manufacture and use. Similar to PCBs in structure, these chemicals tend to bio-accumulate in the food chain and are most often associated with sediments in the aquatic environment.

Plant and animal sterols

The laboratory measured four plant and animal sterols in the Mid-Coast Basin. All four of these sterols occur naturally in the environment but may also be enriched by humans and human activities. None of the 29 sterols detected currently have a screening value. The predominant source of the two plant sterols analyzed, beta-sitosterol and stigmastanol, is terrestrial plants. Other sources of these sterols may be industrial processes (wood pulping, food oils) and modern pharmaceutical supplements. Beta-sitosterol and stigmastanol were detected at all locations in the Mid Coast Basin. Levels varied across the basin with the lowest values detected at the Alsea River at Port Docks (beta-sitosterol) and Siletz River at Moonshine Park (stigmastanol) sites and the highest values detected at the Alsea River at Mill Creek (beta-sitosterol) and Yachats River (stigmastanol) sites. The laboratory also measured two animal sterols, cholesterol and coprostanol (both 100 percent detection). Measured levels varied across the basin with the lowest levels detected at the Cummins Creek (cholesterol) and Siletz River at Moonshine Park (coprostanol) sites and the highest levels detected at the Lake Creek at Deaddog Hole (cholesterol) and Schooner Creek (coprostanol) sites. Coprostanol is specific to fecal matter from humans and higher mammals (i.e., cattle and birds) as it is formed during digestion from cholesterol. The ratio of coprostanol to cholesterol may be used to evaluate contamination by human sewage. A ratio less than one indicates a biogenic source (i.e., livestock, higher animals) and greater than one a sewage or human source. Ratios measured at all sites in this study were less than one, potentially indicating a biogenic source of coprostanol.

Consumer product constituents including pharmaceuticals

The lab analyzed water samples for 28 consumer product constituents including pharmaceuticals. Five compounds in this group were detected across three sites. Three pharmaceuticals, carbamazapine (anti-convulsant), sulfamethoxazole (antihistamine) and venlafaxine (mood enhancer), were detected in Schooner Creek. Carbamazapine and venlafaxine were detected during the summer sampling while sulfamethoxazole was detected during all three sampling events. This location receives discharge from a major wastewater facility. The insect repellant, DEET, was detected at one site, Siletz River at Moonshine Park, during the summer sampling. In addition, the plasticizer, bis(2-ethylhexyl)adipate, was detected in Wolf Creek during the spring sampling. This compound is used in common personal care products such as nail polish and cosmetics as well as in aircraft hydraulic fluids. Water quality criteria or benchmarks do not exist for these compounds.

Industrial chemicals, ammonia and PCBs

Ammonia is a naturally occurring compound commonly found in waste products. It is included as an industrial compound because of its use in fertilizers and dyes. It may be extremely toxic to aquatic organisms. Detectable levels of ammonia occurred in samples from 14 of 18 sites. Most of these detections were measured during the summer with occasional detections in the spring and fall. No samples exceeded current aquatic life water quality criteria. No samples contained detectable levels of any other industrial chemicals or PCBs.

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.

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