The Lower Green River Subwatershed “begins at river mile 32 near Auburn and extends 21 miles to river mile 11 in Tukwila.” The three major tributaries of this section are Springbrook Creek, Mullen Slough and Mill Creek.  Beginning in this area and continuing downstream to the mouth, “approximately 80% of the Lower Green River Subwatershed has a levee or revetment on at least one bank in response to periodic flooding.” This area is significantly more developed than the upper watershed, with residential property making up half of the area and commercial a quarter (King County 2005).

From river mile 11 to its mouth in Elliott Bay, the Green River is known as the Duwamish River (also classified as the Duwamish Estuary Subwatershed).  In addition to the primary flow of the Green River, Hamm Creek and Riverton Creek feed into Duwamish Estuary Subwatershed (King County 2005).

The Duwamish Estuary is further subdivided at river mile 5.5.  Upstream of this point, commercial development is still mixed with urban residential (42% and 29% respectively) (King County 2005). Although the upper part of the Duwamish is not a manmade channel, it retains the levees and revetments which stemmed the threat of flooding before the Howard A. Hanson dam was built.

The lower Duwamish has been dredged and filled to support navigation and water-dependent businesses.  This industrialized area is also known as the Duwamish Waterway.  The Green River/Duwamish GRP boundary ends at river mile 6.5, just upriver of this area.  Strategies for the Lower Duwamish Waterway are included in the Central Puget Sound GRP.

Despite seemingly contiguous sections, the reason for Green River/Duwamish having two separate names is due to its pre-industrialized past.  Prior to 1906, the Duwamish River was created by the confluence of the Green, White and Black Rivers.  The Green and White Rivers met upstream and their combined discharge met the Black River in what is now Tukwila.  It was at this confluence that the three rivers’ output created the separately defined entity of the Duwamish River.  The name “Duwamish” is derived from the Native American Lushootseed language, meaning “People of the Inside.” This was a reference to the Duwamish tribe’s settlements along the rivers inland.  The settlement surrounding the confluence of the Black and Green Rivers was called “Inside Place,” from which the Duwamish peoples’ name originated.

In 1906, a debris jam from a flood redirected the White River away from the Green and into the Puyallup River, which subsequently flowed out to Commencement Bay in Tacoma.  Prior to the construction of the Hanson Dam, the Green River was subject to frequent flooding.  It was built for the express purpose of flood control and to provide a water supply source for Tacoma.  The debris jam was replaced with a permanent diversion wall in an early attempt to control flooding, ensuring the river’s altered course permanently remained (King County). Ten years later, the opening of the Lake Washington Ship Canal dropped the level of Lake Washington (the source of the Black River) by 8.8 feet (KCTS). The Black river subsequently dried up and its remaining stream bed/marshland now carries drainage and runoff.  As a result, the confluence of rivers that once made up the Duwamish disappeared, melding it as a singular river with the Green.

The naming designations, however, did not change.  The Duwamish and the Green are now divided based upon the site of the historical confluence with the Black, despite their contemporary physical congruence. In addition to the upstream changes, manmade intervention significantly altered the area around the mouth of the Duwamish.  Starting in 1913, “the Duwamish was transformed from a nine-mile, shallow and meandering river to a five mile engineered waterway” (Boeing).  This also resulted in the creation of Harbor Island, which remains as the dominant feature of the Duwamish Waterway mouth and the epicenter for the Port of Seattle’s maritime shipping operations.  These manmade modifications and the resulting large reduction in river flow further shaped the lower parts of the river.  Prior to these changes, the Duwamish Estuary had around 4,000 acres of tidal marshes and intertidal mudflats.  This habitat has since disappeared and “97% of the estuarine mudflats, marshes, and forested riparian swamps have been filled” (King County 2005). Most of this was replaced by the heavily commercialized area located just north of the planning area.

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Another major impact of the dams on the hydrology of the Green River/Duwamish is the blockage of sediment transport by water flow in the riparian habitat.  According to Ecology’s Green/Duwamish and Central Puget Sound Watershed Salmon Habitat Plan:

“Howard Hanson Dam completely blocks large woody debris and sediment (gravel) from the Upper Green from reaching the Middle Green and beyond.  As a result, there is a gravel deficit because winter flows flush sediments downstream of Howard Hanson Dam with no replenishment from the Upper Green.  This has resulted in channel incision (downcutting) and subsequent armoring (removal of smaller sediments leaving bare rock or large boulders).  Lack of sediment has a significant effect on spawning in the river downstream.”

Water Resource Inventory Area (WRIA):

WRIA 9 completely encompasses the planning area.  Most of the precipitation arrives during the winter months when water demands are the lowest, and only a fraction becomes available for human and economic uses.  During the summer, the snowpack is gone; there is little rain so low stream flows are dependent on groundwater inflow.  This means that groundwater and surface water are least available when water demands are the highest.

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Prevailing winds in the area are generally from the north in July through September, and south in October through June (WRCC). The average wind speed at SeaTac is 6.8 mph.  The lightest winds are usually experienced in September, with the lowest monthly average of 5.4 mph at Boeing Field.  Winds are typically strongest in March, with the highest monthly average of 8.5 mph at SeaTac (WRCC).

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The overall river current is controlled by the natural slope of the river from the foothills and input from both tributary creeks (especially during heavy instances of precipitation) and the dam flood gates.  Water volumes of 1200 cubic feet per second (cfs) are considered average, with usual summer flows dropping below 300 cfs and winter flows near 2500 cfs at the Auburn gauge.  Flood stage for the same gauge is 9000 cfs (USGS). Tidal influences will significantly affect the velocity near the mouth, with changes of 1.2 knots or more near river mile 11.  High tide can slow the river here to a near-standstill, even with high winter flows.

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Road Transportation: Vehicle traffic on roadways pose an oil spill risk in the area.  Commercial trucks can contain hundreds to thousands of gallons of fuel and oil, and almost any kind of hazardous waste or material.  An accident involving a fully loaded tank truck on the various roads and highways that border the river and its tributary creeks could result in a substantial oil spill.  Smaller vehicle accidents pose a similar risk, commensurate to the volume of fuel and oil they carry.  Spills from vehicles onto roadways could cause fuel or oil to flow from ditches or hardened surfaces into streams, creeks, wasteways, or storm water systems ultimately impacting the Duwamish/Green Rivers or other streams in the area.  Highway bridges pose the greatest risk of road spills due to the quantity of vehicles and speed of travel, but accidents are also common on the smaller roads in the upper watershed, particularly during winter weather.

Rail Transportation: The BNSF Railroad operates a rail line that runs parallel to the Green River over the Cascade Mountain Range.  Formerly the Northern Pacific Railway, this line goes from Auburn through Stampede Pass to Yakima.  Train locomotives pose the greatest spill risk in this area, as they typically hold several thousand gallons of diesel fuel plus large quantities of lube and motor oils.  Due to the steep grade of the pass, most of the train cars using this route are empty.  However, each tanker car can contain residual oils in the tens or hundreds of gallons.  Therefore empty unit trains, which consist of 100 or more oil tanker cars, can present a risk to the upper watershed of 10,000 gallons of diesel in external “saddle” tanks on the locomotives, plus 10,000 or more gallons of residual crude oil.  As traffic of fully loaded oil and coal trains along the relatively flat Columbia River rails has increased, use of the Stampede Pass route has also increased in order to return empty cars to eastern Washington and beyond.

The Lower Green River watershed, by contrast, is at risk from fully loaded oil trains.  The area between Auburn and Tukwila is part of a major rail transportation corridor, which stretches between Canada to the north and Oregon to the south, generally alongside Interstate 5.

Trains loaded with crude from the Bakken Formation in South Dakota or the Alberta oil sands in Canada travel west from Spokane, along the Columbia River to Vancouver at the Oregon border before heading north along I-5 to refineries in Anacortes and Blaine.  Trains carrying Albertan oils also cross the Canadian border in Blaine and travel south to Tacoma or beyond.  Each loaded tanker car typically contains 29,000 gallons of crude oil or other petroleum products.  Unit trains carry 100 or more of these tanker cars of crude, plus a buffer car of sand and the locomotives.  Each full unit train poses a spill risk of nearly 3 million gallons of crude oil plus 10,000 gallons of diesel fuel.  Tanker cars of crude can also be transported in smaller numbers, mixed alongside boxcars and tankers of other products.  In September 2014 BNSF reported 8-12 trains carrying one million gallons or more of Bakken crude traversing King County each week (WA Military Dept.).

Just outside the planning area, BNSF operates a rail yard in southern Auburn south of Highway 18 and east of Highway 167.  The yard is located on the historic bed of the White River, which now is located further south and empties into the Puyallup.  Although the surface water has relocated, there is still an underground flow between the subterranean aquifers of the White and Green Rivers estimated at 30 to 60 cfs (approximately 1-10% of the total river volume, depending on season) (WRIA 9 2005).  Therefore, even though it is located in a different watershed, oil spilled at this rail yard could eventually appear on the Green River.

Commuter trains using diesel locomotives run on BNSF tracks between Tacoma and Seattle, including Amtrak and the Sounder.  The Link Light Rail line between SeaTac airport and Seattle is electric and therefore not a potential spill source.

Oil Pipelines: The Olympic Pipeline crosses the Green River in Tukwila and Kent. It also crosses several tributaries, including Mill Creek in Kent, Mill Creek in Renton, and Springbrook Creek in Renton.  This pipeline transports refined petroleum products; mainly diesel, gasoline, and jet fuel.  If the pipeline were to leak or rupture, impact to sensitive resources in the area could be significant due to the volume of product.  Control points previously identified by the Olympic Pipeline Company were visited during the creation of the plan, and many of those sites were selected to be included in this GRP.

Aircraft: Seattle-Tacoma International Airport is located west of the Green River, while Renton Municipal Airport is located east of the upper Duwamish. Auburn Municipal Airport located at 400 23rd Street NE, Auburn, WA, is located approximately 3,000 feet west of the Green River. Boeing Field is also just north of the furthest downstream section of the planning area.  There is always a potential for aircraft failures during inbound and outbound flights that could result in fuel releases to water.

Recreational Boating: Accidents involving recreational watercraft on the Green/Duwamish could result in spills between a few gallons to several dozen gallons of fuel oil.  Accidents could include a vessel grounding, fire, sinking, or explosion.  Bilge discharges and refueling operations could also occur (and are likely most common) and also have the potential to impact sensitive resources on the river.  The majority of motorized boat traffic ends downstream of the planning area, but the Green River is considered a navigable waterway up to the Highway 516 bridge in Kent” (USCG). Recreational vessels in the remainder of the watershed tend to be hand-launched rafts, canoes, or kayaks.

Other Spill Risks: Other potential oil spill risks in the area include road run-off during rain events, on-shore or near shore construction activities where heavy equipment is being operated, and the migration of spilled oil through soil on lands adjacent to the river or along creek/stream banks.

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This section is purposely broad in scope and should not be considered comprehensive.  Some of the sensitive resources described in this section cannot be addressed in Response Strategies and Priorities because it is not possible to conduct effective response activities in these locations.  Additional information from private organizations or federal, state, tribal, and local government agencies should also be sought during spills.

This material is presented with enough detail to give general information about the area during the first phase of a spill response.  During an actual incident, more information about resources at risk will be available from the Environmental Unit in the Planning Section.

Note: specific resource concerns related to areas that already have designated protection strategies may be found in the “Resources At Risk” column of the matrix describing the individual strategies.

The information provided in this section can be used in:

• Assisting the Environmental Unit (EU) and Operations in developing ad hoc response strategies.
• Providing resource-at-risk “context” to responders, clean-up workers, and others during the initial phase of a spill response in the GRP area.
• Briefing responders and incident command staff that may be unfamiliar with sensitive resource concerns in the GRP area.
• Providing background information for personnel involved in media presentations and public outreach during a spill incident.
• Providing information on benthic and water column species or cultural resources present to assist in planning for oils with the potential to sink or submerge.

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Several of the species found in this area have been classified under the Federal Endangered Species Act or by the Washington State Fish and Wildlife commission.

Classification types are:

• Federal Endangered (FE)
• Federal Threatened (FT)
• Federal Candidate (FC)
• State Endangered (SE)
• State Threatened (ST)
• State Sensitive (SS)

Federal and State listed species that may occur within this area include:

Birds:

• marbled murrelet [FT/SE]
• yellow billed cuckoo [FT/SE]

Mammals:

• No listed mammals anticipated in this area.

Fish:

• bull trout [FT]
• chinook salmon (Puget Sound) [FT]
• steelhead (Puget Sound) [FT]

Amphibians/Reptiles:

• Oregon spotted frog [FT/SE]

Critical Habitats:

Critical habitats are the specific areas, occupied by an endangered or threatened species at the time it was listed, that contain the physical or biological features that are essential to the conservation of that species – and that may need special management or protection. Critical habitat may also include areas that were not occupied by the species at the time of listing but are essential to its conservation.

The following species have federally designated critical habitats within this area:

• bull trout
• chinook salmon (Puget Sound)
• steelhead (Puget Sound)

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• Wetlands in this region are freshwater and range from seasonal open marshes to forested swamps along rivers and streams. All wetland types support a diverse array of amphibian, bird, insect, fish, and wildlife species.
• The rivers and streams throughout this region provide spawning and rearing habitat for various salmonid species. The associated riparian scrub and woodlands play a crucial role in supporting wildlife and a large diversity and abundance of passerine bird species as breeding, migrating, and overwintering habitat.
• Side channels and stream mouths are concentration areas for fish and provide feeding and resting areas for a variety of birds.
• Steep forested hill slopes in developed areas along river valley. These areas provide wildlife habitat and migration corridors.
• Lowland lakes serve as foraging areas for wintering waterfowl concentrations. Western grebes, mergansers, cormorants, coots and Canada geese are the most numerous species. These areas also support the breeding activities of freshwater resident species such as mallards, pintail, etc.
• Subsurface Habitats
  • Fine sediments (mud/silt/sand) – Associated with slow/still water flows. May have aquatic vegetation present.
    • Animals associated with these areas tend to be: cold or warm water fishes; birds (dabbling ducks); semi-aquatic mammals (muskrat, beaver, etc.); shellfish (freshwater clams); amphibians and reptiles (frogs, newts, salamanders, turtles, etc.); insects caddis flies, mayflies, dragonflies, and stoneflies). Many other animals also utilize these areas for foraging.
  • Coarse sediments (gravel/cobble) – Associated with moderate water flow. May have aquatic vegetation present.
    • Animals associated with these areas tend to be: cold or warm water fishes; birds (dippers, harlequin ducks); semi-aquatic mammals (muskrat, beaver, etc.); shellfish (freshwater mussels, crayfish); amphibians and reptiles (tailed frogs, torrent salamanders; insects caddis flies, stoneflies). Many other animals also utilize these areas for foraging.
  • Bedrock – Associated with fast water with little or no deposition of loose bed materials. Aquatic vegetation typically not present.
    • Animals associated with these areas tend to be mostly cold-water fishes, birds (dippers, harlequin ducks), and amphibians (torrent salamanders).

Fish:

• All northwest salmonid species, including bull trout [FT], chinook [FT], and steelhead trout [FT] are present and spawning in this river system. Juvenile salmonids use shallow nearshore areas extensively for feeding and rearing.
• Resident fish are present year-round and include various species such as resident cutthroat and rainbow trout, stickleback, sculpin, sucker, and lamprey.

Wildlife:

• Significant waterfowl concentrations are present along the lower Green River and within associated wetlands below the Flaming Geyser Park. Harlequin duck nesting areas located throughout drainage above this park.
• Sensitive nesting species in the region include raptors (bald eagles, osprey, northern goshawks, and peregrine falcons) and great blue herons.
• Resident and migratory songbirds heavily utilize riparian habitats year-round and are susceptible both to oil and to response activities that disturb riparian vegetation
• Winter elk range in upper reaches of the Green River. King county elk habitat includes resident and migratory elk.
• Other small mammals common to the region include semi-aquatic species such as beaver, muskrat, river otter and raccoon. These species are vulnerable to contact with spilled oil because of their habitat preferences.
• Harbor seals and sea lions are common throughout the Duwamish waterway and the lower Green River.

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2. Green River Natural Resource Area: ~300 acres of stormwater retention and managed wetland. Waterfowl concentration area. Salmonid rearing area. Van Dorn’s and Valley Floor Parks are in the same general vicinity.
3. North Green River Park: Riparian vegetation and wetland habitat. Waterfowl concentration area.
4. East Green River Park: Riparian vegetation and wetland habitat. Waterfowl concentration area. Flooded fields provide forage habitat for large numbers of dabbling ducks.
5. Green River Natural Area: ~920-acre area, with ~6 miles of shoreline. Deciduous riparian forest, wetlands, and meadows located along south bank of river.
6. Black Diamond Natural Area: ~650 acres. Deciduous riparian forest, wetlands, and meadows located along both riverbanks.

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During a spill response, after the Unified Command is established, information related to specific archeological concerns will be coordinated through the Environmental Unit.  In order to ensure that tactical response strategies do not inadvertently harm culturally sensitive sites, WDAHP should be consulted before disturbing any soil or sediment during a response action, including submerged soils or sediments.  WDAHP and/or the Tribal governments may assign a person, or provide a list of professional archeologists that can be contracted, to monitor response activities and cleanup operations for the protection of cultural resources at risk.  Due to the sensitive nature of such information, details regarding the location and type of cultural resources present are not included in this document.

Table 6-1: GRD-GRP Cultural Resource Contacts

Discovery of Human Skeletal Remains

Any human remains, burial sites, or burial-related materials that are discovered during a spill response must be treated with respect at all times (photographing human remains is prohibited to all except the appropriate authorities).  Refer to the National Historic Preservation Act Compliance Guidelines (NWACP Section 9403) during an emergency response.

Procedures for the Discovery of Cultural Resources

If any person monitoring work activities or involved in spill response believes that they have encountered cultural resources, all workers must stop immediately and notify the Unified Command and Cultural Resource Specialist.  The area of work stoppage must be adequate to provide for the security, protection, and integrity of the material or artifact(s) discovered.

Prehistoric Cultural Resources (May include, but are not limited to, any of the following items):

• Lithic debitage (stone chips and other tool-making byproducts)
• Flaked or ground stone tools
• Exotic rock, minerals, or quarries
• Concentrations of organically stained sediments, charcoal, or ash
• Fire-modified rock
• Rock alignments or rock structures
• Bone (burned, modified, or in association with other bone, artifacts, or features)
• Shell or shell fragments
• Petroglyphs and pictographs
• Fish weirs, fish traps, and prehistoric water craft
• Culturally modified trees
• Physical locations or features (traditional cultural properties)
• Submerged villages sites or artifacts

Historic cultural material (May include any of the following items over 50 years old):

• Bottles, or other glass
• Cans
• Ceramics
• Milled wood, brick, concrete, metal, or other building material
• Trash dumps
• Homesteads, building remains
• Logging, mining, or railroad features
• Piers, wharves, docks, bridges, dams, or shipwrecks
• Shipwrecks or other submerged historical objects

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Tribal and commercial salmon fisheries and recreational fisheries targeting species such as salmon and steelhead are important to area and local economies.

Fish hatcheries and facilities:

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The Air Operations Branch (Operations Section) will manage all aircraft operations related to a response and will coordinate the establishment of any Flight Restriction Zones as appropriate. Environmental Unit staff will work with the Air Operations Branch Director to resolve any conflicts that arise between flight activities and sensitive resources.

In addition to restrictions associated with wildlife, Tribal authorities may also request notification when overflights are likely to affect culturally sensitive areas within reservations.  See Oil Spill Best Management Practices (NWACP Section 9301) for more information on the use of aircraft and helicopters in open water and shoreline responses.

Wildlife Deterrence: The Wildlife Deterrence Unit within the Wildlife Branch (Operations Section) manages wildlife deterrence operations. These are actions intended to minimize injuries to wildlife by keeping animals away from the oil and cleanup operations. Deterrence activities may include using acoustic or visual deterrent devices, boats, aircraft or other tools. The Wildlife Branch works with state and federal agencies, and the Environmental Unit (Planning Section), to develop deterrence plans as appropriate.

For more information see the Northwest Wildlife Response Plan (NWACP Section 9310) and Northwest Area Wildlife Deterrence Resources (NWACP Section 9311).

Oiled Wildlife: Capturing oiled wildlife may be hazardous to both personnel and the affected animals. Incident personnel should not try to approach or capture oiled wildlife but should report any observations of oiled wildlife to the Wildlife Branch (Operations Section).

For more information see the Northwest Wildlife Response Plan (NWACP Section 9310).

Wildlife Refuges and Wilderness Areas: There are no federally designated wilderness areas or wildlife refuges present in this GRP region.

Aquatic Invasive Species: The waters of this region may contain aquatic invasive species (AIS) – species of plants and/or animals that are not native to an area and that can be harmful to an area’s ecosystem. If so, preventative actions may be required to prevent the spread of these species as a result of spill response activities and the Environmental Unit is able to recommend operational techniques and strategies to assist with this issue.

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