A.7 Columbia Slough, OR

A.7.1 Contacts

Jennifer Sutter
Oregon DEQ
2020 SW 4^th Ave, Suite 4000
Portland, OR 97201
503-229-6148
[email protected]

A.7.2 Summary

Environment:	Freshwater slough
Scale:	Full
Contaminants of Concern:	Stormwater discharges, DDT/DDE, dieldrin, dioxins, PCBs, and lead
Source Control Achieved Prior to Remedy Selection?	Source control implemented as part of remedy
Final Remedy:	Source control, hotspot removal (dredging), and MNR

A.7.3 Site Description

The Columbia Slough watershed drains approximately 32,700 acres of land encompassing 31 miles of waterway just south of the Columbia River. In addition to the city of Portland, the watershed includes Fairview Lake and Fairview Creek, and portions of Troutdale, Fairview, Gresham, Maywood Park, Wood Village, and Multnomah County. Over 50 individual sites have been identified and are in various phases of the remedial process. Primary sources of contamination at this site include soil erosion via surface runoff, contaminated groundwater discharges, and direct discharge into the slough from municipal stormwater systems that received stormwater from private, commercial, and industrial facilities.

The watershed once contained a system of side channels, lakes, and wetlands that comprised the floodplain of the Columbia River between the mouths of the Willamette and Sandy Rivers. High water seasonally inundated the floodplain, cutting new channels and depositing sediment. Native Americans used these waterways and the uplands for fishing, hunting, and gathering food.

Over the years, the watershed and waterway have been drastically altered. Beginning in 1918, levees were built and wetlands were drained and filled to provide flood protection and allow for development. The waterway was channelized, and dozens of streams were diverted from natural channels to underground pipes. Today the Columbia Slough comprises a 19-mile main channel that parallels the Columbia River, as well as approximately a dozen additional miles of secondary waterways. Other remaining major surface water features include Fairview Creek, Fairview Lake, and Smith and Bybee Lakes. Floodplain development has resulted in an extensively managed surface water system that includes levees, pumps, and other water control structures in the Middle and Upper Sloughs. The levee system greatly reduced the Columbia River’s connection to its floodplain.

The Slough is currently divided into three sections, based on hydraulic characteristics:

• The Upper Slough starts at the mouth of Fairview Lake on the east and flows west to the mid-dike levee at NE 142nd Avenue. It includes Big Four Corners East & West Sloughs. It receives water from Fairview Lake, Fairview Creek, Wilkes Creek, stormwater outfalls, natural springs, groundwater, and overland flow.
• The Middle Slough extends from the mid-dike levee, near NE 142nd Avenue to the Pen 2 levee, near NE 18th Avenue. It includes a substantial southern arm complex of sloughs and lakes, including Peninsula Drainage Canal, Prison Pond, Mays Lake, Johnson Lake, Whitaker Slough, Whitaker Ponds, and Buffalo Slough. The Middle Slough receives water from the Upper Slough, stormwater outfalls, natural springs, groundwater, and overland flow. Pumps are used to move water from the Upper and Middle Slough to the Columbia River or the Lower Slough.
• The Lower Slough starts at the Pen 2 levee, near NE 18th Avenue, and extends approximately 8.5 miles to the Willamette River. The lowlands of the Lower Slough Watershed are subject to flooding because they are not protected by levees. Water flow and levels in the Lower Slough are affected primarily by the Columbia River and Willamette River and the ocean tides, and to a lesser extent by pumping. During high tide, the Columbia and Willamette Rivers create a backwater effect that complicates flow patterns.

The Columbia Slough Watershed now includes several types of land uses: residential neighborhoods, commercial and industrial development, agriculture, Portland International Airport, interstate highways, railroad corridors, and large open spaces. Much of Portland’s industrial and commercial land is located within the watershed. In addition to industrial development in the area north of Columbia Boulevard and the Rivergate area, land is preserved for industrial uses in the Columbia South Shore area between NE 82nd and NE 185th Avenues north of Sandy Boulevard.

Over time, extensive alteration of the Slough’s watershed, due to industrial and residential development, has had a deleterious effect on the environmental quality of the watershed. As development occurs, the natural topography, hydrology, and vegetation are altered and impervious surfaces such as streets, parking lots, and buildings are placed over much of the land. As a result of urbanization, industrial releases, alteration of water flows, and runoff from agricultural land, the Columbia Slough has polluted water, sediments, and fish.

A.7.4 Remedial Objectives

Concerns for this case study include both ecological and human health risks associated with mercury. The sediment cleanup action objectives’ focus is on achieving compliance with cleanup standards in surface sediments of the bioactive zone (40 mg/kg, Washington State Department of Ecology sediment quality standard). These are defined in the 2007 Cleanup Action Plan.

A.7.5 Remedial Approach

Final selected remedy: Unique aspect of this site is the watershed-based remedial approach developed in the 2005 ROD consisting of source controlThose efforts that are taken to eliminate or reduce, to the extent practicable, the release of COCs from direct and indirect ongoing sources to the aquatic system being evaluated., hot spot cleanup, and natural recovery.

• Source control—implementing actions that address the sources of contamination to reduce contaminant inputs. Addressing the sources of contamination is important because it will prevent recontamination of remediated sediments and allow natural recovery processes to effectively reduce existing contamination in the slough.
• “Hot spot” cleanup—dredging sediments that are contaminated at levels that exceed the general pervasive level of contamination throughout the slough.
• Long-term monitoring—evaluate the effectiveness of the actions taken and identify areas where more focused attention is necessary.

Source Control Actions in Progress:

• Blasen site located at 1601 N. Columbia Boulevard.
• Upland and bank cleanup was initiated at the Pacific Meat site located at 2701 N Newark Street.
• Upland source control remedy is pending at the Wastech site located at 701 Hunt Street.

Cleanup Action Selected:

• A feasibility study was completed and remedial action proposed for the Fuel Processors, Inc. site located at 4150 N Suttle Road.
• Upland source control remedy was selected at the Precision Equipment site located at 8440 N. Kerby Avenue.
• Upland stormwater source control remedy selected for the Portland Willamette site located at 6800 NE 59th Avenue.

Upland Cleanup Completed:

• Surface soil cleanup was completed at the Carco site located at 900 N Columbia Boulevard.
• Metal-contaminated soil was removed at the Macadam Aluminum and Bronze site just west of I-5 and the storm drain system was cleaned and replaced.
• Monitoring at the ICN Pharmaceuticals site located at 6060 NE 112th Avenue was completed and the site was removed from DEQ’s confirmed release list and inventory.

A.7.6 Monitoring

Long-term Monitoring

The Columbia Slough Watershed Long-Term Monitoring Plan (LTMP) describes monitoring that the U.S. Department of Energy, Office of Basic Energy Sciences (BES) will conduct in the Slough Watershed over the next ten years and beyond. This is a dynamic plan, and as technology and monitoring approaches change, the LTMP will also be changed to reflect those changes. The following highlights fiscal year 2010 Columbia Slough long-term monitoring efforts.

Sediment Monitoring

Sediment sampling was conducted by the city in 2006. A report documenting this sampling event is available on the city web page. Data from this sampling event is being combined with data collected in the DEQ sampling, private party cleanup site sampling, MCDD sampling for channel maintenance, and ODOT sampling for bridge construction into a slough sediment database that will be used to determine data gaps and plan remedial measures.

No slough-wide sediment sampling is planned for the next year. In-line sediment sampling in the MS4 in the Marx-Whitaker and/or I-5 to MLK target areas may be conducted.

Initial Water Quality Monitoring

Water quality samples were taken at nine sites throughout the Columbia Slough. Continuous, 15 minute, samples were taken for temperature, pHA measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14., conductivity, and dissolved oxygen. Grab samples were taken bi-monthly and analyzed for the following analytes/parameters:

• Chlorophyll a
• Biological oxygen demand (5 day, BOD-5)
• Conductivity (specific)
• Copper (total and dissolved)
• Flow Direction and velocity
• Dissolved oxygen
• E. coli
• Hardness (total)
• Lead (total and dissolved)
• Mercury
• Nickel (total and dissolved)
• Nitrogen (ammonia, nitrate and total Kjeldah)
• pH
• Phosphorus (total and ortho phosphate)
• Secchi disc
• Temperature
• Total suspended solids
• Zinc (total and dissolved)

Ongoing Water Quality Monitoring

Continuous water quality monitoring of at least three Columbia Slough sites will continue as in past years, and a fourth site will be added again once the Vancouver Avenue bridge restoration is completed. Continuous monitoring measurements include temperature, pH, conductivity, and dissolved oxygen. A water quality report summarizing sample results over the past five years is under development by the city and will be submitted to DEQ in 2011.

The City of Portland is updating its watershed monitoring approach. The city’s new surface water quality monitoring program, Portland Area Watershed Monitoring and Assessment Program (PAWMAP), incorporates the best available science and protocols developed by the national Environmental Monitoring and Assessment Program (EMAP). The PAWMAP program includes spatially-balanced random selection of stream survey sites. Elements to be monitored address all four watershed health goals (hydrology, habitat, water quality, and biological communities), and the effort will be expanded to include systematic monitoring of terrestrial habitat. In addition, the new approach will increase the rigor, accuracy, and cost-efficiency by streamlining efforts and coordinating to fulfill many of the city’s compliance monitoring requirements. The new monitoring program was designed in 2009 and began implementation in the summer of 2010. The first year of monitoring will establish baseline data against which future years’ results can be compared to measure changes in watershed health.

For fiscal year 2011, five perennial sites have been selected in the Columbia Slough. These sites will be monitored quarterly during dry weather and once during wet weather. Grab samples will be collected for the following analytes:

• Alkalinity
• Chlorophyll a
• BOD-5
• Carbon, dissolved organic 
(summer only)
• Carbon, total organic
• Conductivity (specific)
• Copper (total and dissolved)
• Dissolved oxygen
• E. coli
• Hardness (total)
• Physical Habitat Monitoring
• Lead (total and dissolved)
• Mercury, total
• Nitrogen (ammonia, nitrate, nitrite, and total Kjeldahl)
• pH
• Phosphorus (total and ortho-phosphate)
• Temperature
• Turbidity
• Total suspended solids
• Zinc (total and dissolved).

PAWMAP also includes physical habitat monitoring using EMAP National Streams and Rivers Assessment protocols. Each of the five perennial slough sites will be surveyed each year. The surveys will be conducted July through September during dry weather. Physical habitat indicators evaluated through stream surveys include the following:

• Large wood
• Depth refugia zone
• Substrate composition
• Amount of off-channel habitat
• Bank condition
• Stream connectivity
• Bio-Monitoring
• Width and composition of vegetated riparian
• Breaks and barriers
• Plant community composition
• Floodplain condition
• Canopy cover

BES will continue monitoring a variety of species of concern. Some of the species are on the federal Threatened and Endangered list and some are on the State of Oregon list of sensitive species. BES will conduct quarterly fish monitoring at the slough’s confluence with the Willamette River. BES will also monitor birds, amphibians, turtles, and macrophytes at various sites in the slough watershed.

Bio-monitoring is also conducted as part of PAWMAP and includes the following: fish (quarterly) and benthic macroinvertebrates (annually).

Stormwater Monitoring

DEQ and the city plan to develop a contaminant-loading model that will estimate the type and concentration of pollutants associated with stormwater runoff. The results of this study will be used to identify outfalls where source control measures appear to be warranted and to determine when adequate source control measures have been completed.

Costs: DEQ has developed a process through which private parties can get release from liability for sediment cleanup by contributing to a fund managed by DEQ. Payment is based on the site’s likely contribution to sediment contamination. DEQ has accumulated > $2 million via this option and has used it to collect data in two priority areas in the slough using a combination of MIS and discrete sediment sampling. Parties can also opt for release from state natural resource damage claims by contributing to a separate fund to be used for habitat enhancement projects.

RAOs/project objectives achieved?: The completed objectives are noted in the discussion of the remedial approach (Section A.7.5). The city is conducting long term monitoring of environmental conditions including wide spread fish tissue and sediment sampling conducted every 10 years. Baseline samples were collected in 1995, and the first 10-year samples were collected in 2005/2006. DEQ has worked with the city to lay out Watershed Action Plan describing watershed-wide source control efforts. DEQ is working with individual parties to ensure source control is implemented at specific sites.

A.7.7 References

Portland Bureau of Environmental Services Columbia Slough Program. http://www.portlandonline.com/bes/index.cfm?c=49910&.

Columbia Slough Sediment Analysis Report 2006 Sampling. http://www.portlandonline.com/bes/index.cfm?c=49910&a=234746.

The State of the Slough: 2010 Annual Report Columbia Slough Sediment Project. http://www.portlandonline.com/bes/index.cfm?c=49910&a=335382.

Publication Date: August 2014