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Coquille River Subbasin

TMDL Title: Coquille River Subbasin TMDL's and WQMP
Water Quality Limited Parameters: Bacteria (water contact recreation and shellfish harvesting), Dissolved Oxygen, pH, Chlorophyll-a, Temperature
Pollutants: Biochemical Oxygen Demand (BODs), e. coli, fecal coliform, Heat, Organic Matter, Sediment Oxygen Demand, Total Phosphorous, Total Organic Carbon
Status: In process of completing a new TMDL and WQMP

Project Summary

DEQ is working to address water quality impairments within the Coquille River Subbasin through the TMDL process. The Coquille River Subbasin TMDLs addresses impairments of dissolved oxygen, temperature, pH, chlorophyll-a and bacteria within the Subbasin. DEQ is working to finalize modeling and narrative drafts and expects to release the TMDLs by year's end of 2021. The new Coquille River Subbasin TMDLs will augment the existing 2001 Upper South Fork Coquille Watershed Temperature TMDL and replace the 1996 Coquille River TMDL. 

The water quality standard and pollutant addressed by the TMDL is location dependent:

​​Bacteria, total organic carbon (TOC), organic matter that may contribute to sediment oxygen demand (SOD), total phosphorus (TP) and solar radiation inputs are the main pollution concerns for the Coquille River and estuary. These parameters are being addressed within the Coquille River Subbasin through the bacteria, dissolved oxygen and temperature TMDLs for the lower Coquille River and Estuary from river mile 0 up to river mile 35.8, downstream from the confluence of North and South Fork Coquille Rivers.

Primary Areas of Concern

Temperature: Applies to two subwatersheds, the middle mainstem Coquille River and lower mainstem Coquille River and estuary and all the lower tributaries that flow into them. The Temperature TMDL is being developed in a manner consistent with addressing known anthropogenic, background, and unidentified heat load sources, applying surrogate measures (site potential shade) and implicit margin of safety within the modeling.

Bacteria: Applies to two subwatersheds that have a higher proportion of urban and agricultural land uses (the middle mainstem Coquille River and lower mainstem Coquille River and estuary).  Bacteria planning targets also apply to four other small tributaries within the Coquille River mainstem (Ferry Cr. Bear cr., Lampa Cr. And Cunningham Cr.)  that are 303(d) (impaired waterbody) listed and have similar problems.

Dissolved oxygen: Applies to two subwatersheds, the middle mainstem Coquille River and lower mainstem Coquille River and estuary and all the lower tributaries that flow into them. The dissolved oxygen TMDL addresses the pollutants of total organic carbon, organic matter that may contribute to sediment oxygen demand, total phosphorus and solar radiation inputs which limits the oxygen carry capacity of waterbodies. An estimated temperature reduction of 2.1 oC combined with reducing phosphorus loads by 20% for the North Fork and 30% for the South Fork and a targeted 30% reduction of bottom deposits of organic matter will improve river conditions enough for the DO criteria to be met consistently.​

River Miles

  • Total number of Coquille River Miles Listed for Temperature Impairments: 40.3 miles; 5 Temp. TMDLs

  • Total number of Coquille River Miles Listed for Bacteria Impairments: 67.4 miles; 8 Bacteria TMDLs

  • Total number of Coquille River Miles listed for Dissolved Oxygen Impairments: 48.2 miles; 13 dissolved oxygen TMDLs


​Bacteria, total organic carbon (TOC), organic matter that may contribute to sediment oxygen demand (SOD), total phosphorus (TP) and solar radiation inputs are the main pollution concerns for the North Fork Coquille River. These parameters are being addressed within the Coquille River Subbasin through the bacteria, dissolved oxygen and temperature TMDLs for the North Fork Coquille River from the confluence with the South Fork Coquille River up to river mile 52.3.​

Primary areas of concern

Temperature: Applies to eight subwatersheds that includes the North and East Fork Coquille River mainstems and sections of Woodward, Moon, Alder, Elk and Middle Creek tributaries. The Temperature TMDL is being developed in a manner consistent with addressing known anthropogenic, background, and unidentified heat load sources, applying surrogate measures (site potential shade) and implicit margin of safety within the modeling.

Bacteria: Applies to the North Fork Coquille River subwatershed, river mile 0 to 19 that has a higher proportion of rural urban and agricultural land uses. The North Fork Coquille experiences higher bacteria concentrations than any of the other major tributaries of the Coquille River Subbasin, and so the highest peak flow nonpoint source load reductions are needed to meet shellfish harvesting criteria in the lower Coquille River.

Dissolved oxygen: Applies to two reaches within the North Fork Coquille River subwatershed, river mile 0 to 27.9. The dissolved oxygen TMDL addresses the pollutants of total organic carbon, organic matter that may contribute to sediment oxygen demand, total phosphorus and solar radiation inputs which limits the oxygen carry capacity of waterbodies. Based on regression modeling, if temperature is reduced 3oC, the mean of the measured DO concentrations will increase 0.6-0.7 mg/L and no more than 10% of individual measurements will be less than 8.0 mg/L.

River miles

  • Total number of North Fork Coquille River miles listed for temperature impairments: 123.8 miles; 8 Temperature TMDLs

  • Total number of North Fork Coquille River miles listed for bacteria Impairments: 38 miles; 2 Bacteria TMDLs

  • Total number of North Fork Coquille River miles listed for dissolved oxygen Impairments: 27.9 miles; 2 dissolved oxygen TMDLs

​​​The Oregon Coquille River Watershed Total Maximum Daily Load Mapping Tool​ is designed to help those working to improve vegetated buffers or riparian areas along the Coquille River. The tool allows users to identify high-priority riparian sites and helps ensure enhancements are made in areas where they will improve water quality. The tool shows users the amount of light and heat the sun delivers under existing riparian conditions and how much light and heat an improved riparian area could block. Many manmade and natural factors influence stream temperature. Reducing shade by removing riparian vegetation is just one activity that can contribute to stream warming. Elevated stream temperatures have been shown to limit aquatic life and salmonid and trout rearing and migration.
 
This tool also provides fish distribution information for multiple fish species and those using the tool can find areas where the potential to improve both water quality and fish habitat is high. Coquille River coho salmon are identified as threatened under the Endangered Species Act. The recovery plan for these fish emphasizes the importance of healthy riparian areas because they provide shade and maintain cool water temperatures for fish. Although riparian plantings take a long time to mature, this tool allows users to preview the potential for improving stream shade over time and provides a unique opportunity to track progress toward improving water quality in the Coquille River.  ​
Supporting Assessment Reports
​​​​​​The Coquille TMDL Low Impact Development Implementation Tool was developed to assist in the implementation of both the Coquille TMDL and Coastal Nonpoint Management Area post construction runoff requirements. The tool provides design storm sizing for LID Best Management Practices (BMPs) specific to the four Western Oregon coastal communities located within the Coquille Watershed: Bandon, Coquille, Myrtle Point, and Powers. The Tool builds upon the Low Impact Development in the Western Oregon Low Impact Development template and incorporates an approach similar to the City of Eugene’s Simplified Approach for Stormwater Management (SIM). The modified SIMs calculator considers coastal hydrological patterns (design storm sizing), soils permeability, and BMP runoff reduction values to produce a coastal specific stormwater output for selected BMP design sizing. The tool provides stakeholders with an implementation-ready tool to plan, develop, design, and implement LID projects within their jurisdictions.
 
The tool incorporates two different design storms: 24-hour design storm to protect water quality on-site and downstream based on the 95th percentile storm and the NOAA ESA west coast region design storm (facilities designed to accept and fully treat 50% of cumulative rainfall from a 2-year, 24-hour storm). DEQ has provided design storm analysis for up to three urban areas: one each for Bandon and Powers and a separate for the combined area of Coquille and Myrtle Point. The tool also incorporates a range of Coquille watershed soil permeability rates and provides a permeability rate drop down box for developers to match their site to soil type. However, due to the variability of soil survey information, onsite soil infiltration testing is recommended for all engineered BMPs. This Tool supports implementation of the Coquille Sub-basin TMDL and Coastal Nonpoint Management Area stormwater runoff requirements by allowing community planners and developers to design and implement size appropriate BMPs to manage the runoff from storms that have a potential to impact water quality within the Coquille watershed.
 
 
If you experience difficulties using the LID Tool, contact Bryan Duggan, South Coast Basin Coordinator.
 

LID Tool Supporting Documents

In order to develop a TMDL that addresses dissolved oxygen listings, models were developed by DEQ for the Coquille River and Estuary, South Fork, Middle Fork, and North Fork Coquille River. The Dissolved Oxygen TMDL focuses on reductions of 20% in Total Organic Carbon (TOC) to meet water quality criteria for DO in all main Coquille waterbodies. Organic matter suspended in the water column may be quantified by TOC concentrations. According to the DEQ water quality models, during the fall and early winter spawning seasons, TOC loading concentrations in the Coquille River and its tributaries increases. A portion of the organic matter that enters during the fall and winter rainfall events may settle and contribute to dissolved oxygen deficits in the lower reaches of the Coquille River during spawning times. While the DEQ modeling shows correlations during the fall between TOC loading and DO deficits, the modeling does not identify the sources of organic matter.

In order to control the TOC load, it is critical to track the TOC load to specific land uses. The Coquille River Watershed TOC Loading Estimation spreadsheet model was designed to address this need and support planning level decision making by calculating average annual TOC loading for the Coquille River Subbasin and its major tributaries. Using the available monitoring data, landuse, literature review values and long-term precipitation data from 1981 to 2010, the spreadsheet model was used to calculate an annual TOC load from runoff, groundwater (baseflow), and sediment associated TOC. The annual loads were then disaggregated to monthly using monthly precipitation to allow for calculating loads during the Fall and Non-Fall periods.  The spreadsheet model calculates annual and monthly organic matter loads by land use source categories for each of the 35 HUC12 Coquille subwatersheds and aggregates by watershed. Basic functions of the loading tool are described in the supporting documents along with illustrations of how to calculate BMP reductions using real world watershed examples.

For requesting data, models or other information used in this TMDL, please complete a Public Records Request.​


Other TMDLs in the South Coast Basin

Chetco, Coos, and Sixes Rivers Subbasins

southcoastmap.PNG

Contacts

Coquille Basin Coordinators:

Basin Coordinator List

Gene Foster 
Watershed Management Manager
503-229-5325