Point Sources

Point sources data for the Columbia and Willamette Rivers were collected from the Discharge Monitoring Reports (DMR) provided by Oregon Department of Environmental Quality (DEQ) and Washington Department of Ecology (WADOE). The Clean Water Act requires that any discharge “pollutants” through a point source into a water body in the United States should  have a National Pollution Discharge Elimination System (NPDES) permit.  The NPDES permit may define minimum or maximum limits of discharge constituents and may require periodic monitoring and reporting of the discharge.  This reporting is submitted to the local branches of the EPA (Permit Compliance System) and DEQ/WADOE in the form of a Discharge Monitoring Report (DMR).

Oregon

In 1995, a QUAL2E model employed in Tetra Tech Inc.'s Willamette River Basin Water Quality Study utilized steady state point source inputs.  This differs from the CE-QUAL-W2 Version 3 model, which allows for dynamic point source inputs.  This dynamic ability is a significant improvement when considering point sources can have high variability in discharge rates and constituents that are not seasonally related.

The QUAL2E model used the point sources shown in Table 1 for the Lower Willamette River.  The flow and water quality parameters were determined from the DMRs.

Several of these point sources have changed ownership or name or have stopped discharging since 1995 when Tetra Tech collected the data as shown in Table 2.
 

In the case of Union oil, Chevron USA, Lone Star NW, Ross Island Sand & Gravel, and Caffall Bros. (Table 11), no quantitative discharge data were available in order to characterize discharge flows or water quality.  The Tetra Tech point source labeled Chiloquin is an error.  The City of Chiloquin in located in Kalamath County in Southern Oregon on the Williamson River, RM 11.5.

Table 3 identifies the point sources to the Willamette and Columbia Rivers from Oregon that were used in the CE-QUAL-W2 model. Most of the point sources from the Tetra Tech work were included, except the following: Kinder Morgan (Port of Portland #2); Koppers Industries, Inc; Linnton Plywood Association; and Ash Grove Cement Co. because their flows were either zero or negligible.  Additional dischargers into the Willamette River that were considered "major" dischargers by DEQ and that had discharge data were also considered.  In some cases a company had more than one discharge on the same property or more than one property with a discharge.  The locations of these point sources are shown in Figure 1.  Data from the point sources was found to be limited.  Many water quality constituents, such as nutrients, were not monitored in the point sources.  Data was collected on a monthly basis or less frequent.
 

Storm and Combination Sewers

Other point sources in the Willamette Basin include the storm sewer and combined sewer outlets in Portland and upstream districts.  The locations of these outlets were acquired from the individual districts.  Most of the data however is not in a digital format.  The contributing land surface area to each outlet is typically less understood.  The City of Portland provided AutoCAD drawings for each of their Storm and Combined Sewers, as well as aerial photos of the outlets.  Even though the City of Portland has a computer model of their sanitary and storm water system using the EPA Storm Water Management Model (SWMM), little data exists for flow rates from each of these discharges.

One study underway by the City of Portland examines the Swan Island area.  A rational method analysis was performed on a storm sewer collection system on Swan Island with water quality measured by the City of Portland, BES at selected manholes.  The study estimated flow into the Willamette River and associated water quality for a few winter storms.  The study is ongoing and with an expanded scope could provide valuable data for winter modeling.

The City of West Linn utilized the EPA SWMM model to evaluate all existing major basins in West Linn for 10 and 25 year storm events.  This model was constructed to provide a Drainage System Capacity Evaluation component to the City of West Linn Master Storm Drain plan.  Woodward Clyde Consultants, Inc. performed this study in 1996. Assumptions used to generate this model included:

1. The maximum 24-hour rainfall in the city is derived from the applicable regional NOAA Atlas
2. The standard 10 year return frequency 24-hour maximum rainfall in the city is 3.3 inches.
    The distribution of rainfall within the 24-hour period is based on the SCS Type 1A rainfall distribution.

Table 4.  West Linn Storm Water Management Model Results

Due to the lack of consistent water quality and flow data and the focus on summer low-water conditions in the Lower Willamette River, stormwater and CSO inflows were not considered as point sources in the model.

Washington

In Washington, the State Department of Ecology was contacted and a list identified for all major  point sources contributing to the Columbia River in the model domain.  The locations of these sites are shown in Figure 2.  Some of the point sources identified discharged into tributaries of the Columbia River downstream of where gaging stations were used to characterize the tributary flows. These sites (11) were neglected from inclusion in the model since their flow was not significant and would not have much influence on water quality in the Lower Willamette.  The neglected sites are noted as "squares" in Figure 52 and point sources considered in the model are shown as "triangles".  There were 47 point sources considered in the model, and these are listed in Table 15.  Some of these point sources were combined if they discharged to the same model segment.  Similar to the point sources identified in Oregon, the extent of the data was found to be limited.  Many water quality constituents, such as nutrients, were not monitored.  Data were collected on a monthly basis or less frequent.

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