BPA Project Number:  2003-011-00
CR-336227: Steigerwald Construction
Performance/Budget Period: October 1, 2019 – September 30, 2022

Technical Contact/Project Lead:  Catherine Corbett
Lower Columbia Estuary Partnership
811 SW Naito Parkway, Suite 410
Portland, Oregon 97204
Phone: (503) 226-1565 Ext. 240
Fax: (503) 226-1580
corbett@estuarypartnership.org

Contracting Contact: Tom Argent
Lower Columbia Estuary Partnership
811 SW Naito Parkway, Suite 410
Portland, Oregon 97204
Phone: (503) 226-1565 Ext. 242
Fax: (503) 226-1580
targent@estuarypartnership.org

BPA Project Manager:  Anne Creason
Bonneville Power Administration
905 NE 11th Avenue
Portland, Oregon 97208
Phone: (503) 230-3859
amcreason@bpa.gov

Background
There are three contracts associated with this Project:  
1) Direct implementation- for restoration projects identified, designed, constructed and monitored for effectiveness by Estuary Partnership staff and for those projects where Estuary Partnership act as subcontractors to partners on hydrodynamic and ecological functions modeling and effectiveness monitoring,
2) Coordination - as part of the National Estuary Program (NEP), an important role of the Estuary Partnership is to identify gaps and provide support to partners for ecosystem restoration of the lower Columbia River, specifically in this Project by providing project evaluation, ranking and funding recommendations to BPA; providing technical assistance funding to partners for assessing restoration project feasibility and preliminary engineering designs; providing funding to partners for full engineering designs, permitting, construction and effectiveness monitoring for their restoration projects; providing data and other information to partners to ensure best available science in restoration design and evaluation; and hosting networking and coordination events.
3) Steigerwald construction (capital) – multi-year construction of a large restoration project at the Steigerwald Lake National Wildlife Refuge in Camas/ Washougal, Washington.
This contract focuses on this last item.

The Lower Columbia Estuary Partnership’s (Estuary Partnership) 2011 Comprehensive Conservation and Management Plan (Management Plan) calls for 25,000 acres of habitat to be restored and/or protected by 2025 in the lower Columbia River and estuary. This goal was updated in 2016 to: 1) no new net loss of native habitats as of 2009 (2009 baseline represents 50% loss, or 114,050 acres, since 1870 [see Marcoe and Pilson 2017]), 2) recover 30% by river reach of historic extent for priority habitats by 2030 (restore 10,382 acres) and 3) recover 40% of historic extent for priority habitats by river reach by 2050 (restore 22,480 acres). Since 2000, the Estuary Partnership has been implementing the Lower Columbia River Ecosystem Restoration Program (Program) to restore lower Columbia River ecosystem structure and function, with funding from Bonneville Power Administration (BPA), National Oceanic and Atmospheric Administration (NOAA), and the U.S. Environmental Protection Agency. Since this times, Estuary Partnership-funded projects have restored or protected over 4,182 acres and opened over 82 miles of stream habitat. When combined with partner projects (e.g., CREST, CLT, WDFW), the region has accomplished 236 projects representing 28,387 acres restored or protected. The geographic scope of the Program is within the study area of the Estuary Partnership, and encompasses the lower 146 river miles of the Columbia River from Bonneville Dam to the Pacific Ocean. The overall Program includes toxic contaminant reduction and species recovery efforts, representing the umbrella program for the lower river. NPCC/BPA funding under this Project focuses on a subset of actions addressing BPA’s Columbia River Ecosystem Restoration Program (CEERP) goal of improving habitat opportunity, capacity and realized function for aquatic organisms, specifically salmonids. Funding of this Project provides direct funding for multiple restoration actions under CEERP annually and provides leverage for the Estuary Partnership to expand restoration efforts beyond CEERP for a comprehensive, integrated and collaborative ecosystem based restoration program.    

Under this contract, the Estuary Partnership will focus on constructing the Steigerwald Floodplain Restoration Project, a large floodplain connectivity and flood risk reduction project at a 965-acre area of historic Columbia River floodplain located on the mainstem lower Columbia River. The project is located within the Steigerwald Lake National Wildlife Refuge (Refuge). The project will restore floodplain access for five species of salmonids and two species of lamprey, increasing available floodplain habitat by 14% in a portion of the Columbia River where floodplain restoration opportunities are limited, yet floodplains are a documented benefit to local and upriver salmonids. This is the largest restoration project in the lower river and fills a critical gap in existing habitat between the Columbia Gorge and lower 46 miles of the estuary proper. The project will remove significant portions of private and public land from flooding, which will reduce annual costs. Additionally, the project will elevate State Route 14 to remove flood risk of a major east-west highway. Finally, the project will reconfigure and expand the trail system, increasing recreation and community engagement opportunities at the Refuge.

Major project elements include: 1) removing 2.2 miles of existing levee; 2) constructing two new setback levees to allow Columbia River access to the floodplain and improve flood protection; 3) restoring Gibbons Creek and reconnecting its historic alluvial fan through the removal of diversion structures and an elevated channel to improve habitat and reduce flooding; 4) improving State Route 14 (SR 14) to reduce flooding; 5) excavating four new channels to further reconnect the Columbia River to its adjacent floodplain; 6) grading to create vast areas of new wetlands; 7) planting to restore riparian habitat and engage youth and adult community members; and 8) expanding  the trail network to improve recreation opportunities. NPCC/BPA funding supports the majority of these components but the Estuary Partnership has secured Washington Ecology’s Floodplains by Design and USFWS FLAP grants to support critical aspects (and continues to seek additional leverage).

Historically, the project site was a dynamic portion of the Columbia River floodplain with regular seasonal inundation. The site had two streams (Gibbons and Lawton creeks), expansive emergent wetlands, and was dominated by bottomland hardwood forests and willow bottoms. The floodplain drained to the west, and Gibbons Creek connected to the Columbia River at the current location of the Port’s pump station. Large floods inundated the entire floodplain. The hydrology of the site floodplain has been directly impacted by dam construction along the mainstem Columbia River. The following actions have also impacted the site:

Levee and Diversion Structure. In 1966, a levee was constructed around the site which severed its surface hydrologic connection to the Columbia River. Additionally, the US Army Corps of Engineers (USACE) diverted Gibbons Creek into a confined, elevated channel that spans the site’s wetland complex, which further severed hydrologic connectivity. The Columbia River no longer accesses this portion of its floodplain due to these modifications, and Gibbons Creek only flows into the site’s wetlands when the capacity of its elevated channel is exceeded, which occurs when flow exceeds 70 cubic feet per second (cfs). Gibbons Creek overflows must then be pumped into the Columbia River by the Port. Juvenile salmonids are stranded during Gibbons Creek diversion structure overflows, which occur frequently during winter storms.

Transportation Corridors. Construction of the BNSF Railroad and SR 14, which form the northern boundary of the site, resulted in the placement of new fill and culverts, which restricted the migration of Lawton and Gibbons creek channels, both of which had large alluvial fans.

Commercial and Agricultural Development. The Port and City have developed significant infrastructure at the western end of the site, which permanently impacted wetland, floodplain, and riparian habitats. Agricultural development included removal of the site’s riparian forest, fencing of pastures, and construction of farm roads.

While the existing levee system protects the site from exterior Columbia River floods well above the 1,000-year flood stage, it has severed the site’s connection to the Columbia River and created recurring interior flooding issues. The primary input to the interior drainage system is Gibbons Creek, which has a drainage area of 8 sq. miles and 10- and 100-year discharges of 670 cfs and 1,140 cfs, respectively. Like most streams in the western portion of the Columbia River Gorge (CRG), Gibbons Creek is a high gradient, “flashy” creek that has a high sediment load. The higher elevations of its watershed receive approximately 100 inches of rain annually, often in high-intensity storms and sometimes as rain-on-snow events. In 1992, to help reduce interior flood risk and operating & maintaining (O&M) costs, the USACE constructed a diversion structure and an elevated channel on Gibbons Creek to route a portion of its flow over the site and discharge it directly into the Columbia River. The combined impact of this Gibbons Creek infrastructure and the 5.5-mile levee system on interior flood risk is summarized below.

Public and Private Infrastructure. The Port’s 430-acre Industrial Park (Figure 2) provides the local community with approximately 1,000 jobs and an annual payroll of over $30 million. The City’s Waste Water Treatment Plant (WWTP) serves a population of 15,000. Due to the configuration of the existing levee system, 135 acres of the Port’s Industrial Park and the City’s WWTP are located within the Federal Emergency Management Agency (FEMA) Special Flood Hazard Area (100-year flood zone), which is delineated at elevation 22.4 ft (NAVD88). The Port operates and maintains its pump station solely to manage this flood risk, pumping an average of 10,600 acre-feet of water per year out of the levee system, at a cost of $100,000 annually in electrical costs alone, a significant financial burden.

Based on Port records, Gibbons Creek flooded the site to an elevation of 21 ft in 1996, inundating 63 acres of Port and City infrastructure, including a portion of the City’s WWTP. The 1996 flood also inundated several sites in the Port’s Industrial Park that are listed in Ecology’s Facility/Site Database. Gibbons Creek’s estimated discharge during the 1996 flood was approximately 1,000 cubic feet per second (cfs) indicating that a discharge event near (or in excess of) the 50-year recurrence frequency is enough to threaten Port and City infrastructure. However, FEMA’s 100-year flood zone is calculated assuming operation of the pump station’s three 200-horsepower pumps simultaneously, which have a combined maximum capacity of 200 cfs. Should one of the pumps fail, the calculated level of interior flood protection drops to approximately a 10-year event, significantly increasing flood risk to Port and City infrastructure.

Additionally, in 2012, the USACE updated the Gibbons Creek discharge estimates and resulting interior flood elevations. The updated hydrology increased the site’s 100-year flood stage by 3 ft (a 20% increase). Because the pump system was designed using the outdated 100-year discharge estimate, the current FEMA base flood map likely underestimates flood risk. In other words, the base flood elevation is likely higher than 22.4 ft. Climate change research predicts that Gibbons Creek’s 100-year discharge will increase to 1,370 cfs by the year 2080. Approximately $5,600,000 in capital improvements will also be required to dredge the interior drainage network and upgrade the pump station should the Steigerwald Floodplain Restoration Project not be implemented.

Due to impacts on salmonids and lamprey, the National Marine Fisheries Service (NMFS) and Washington Department of Fish and Wildlife (WDFW) are not currently issuing the regulatory approvals required to dredge Gibbons Creek. As stated in a USFWS letter submitted to Washington State Department of Transportation (WSDOT) on March 22, 2016, the Refuge currently has no way to “effectively dredge the diversion and comply with NMFS regulations,” so their ability to continue dredging Gibbons Creek is uncertain. Without dredging, Gibbons Creek bedload will accumulate and bury much of the diversion structure, causing sediment accumulation upstream through the channel, severely limiting hydraulic capacity of the bridge.

SR 14 and Private Residences. Historically, Gibbons Creek entered Steigerwald National Wildlife Refuge (Refuge) through a 1,500-foot-wide alluvial fan, which provided a large area for Gibbons Creek to process its sediment load (primarily gravel and small cobble). In 1992, the USACE constructed a diversion structure and elevated channel to reduce interior flood risk and O&M costs associated with Gibbons Creek flood waters. It replaced the 1,500 ft wide alluvial fan with a lower gradient, manufactured channel that has a 22-inch wide inlet and a maximum capacity of 70 cfs (as compared to Gibbons Creek’s 2-year discharge of 320 cfs). During storm events, the diversion structure’s 22” wide inlet can clog with debris within minutes, which exacerbates flooding conditions. This infrastructure failed to significantly reduce flood risk to Port and City infrastructure, and it also increased flood risk to SR 14 and upstream residences. In fact, much of the mobile home community located along Gibbons Creek’s west bank flooded in 1996. This increased risk is primarily caused by the stream’s sediment load, the majority of which is deposited within the site where the channel gradient transitions from steep CRG topography to relatively flat floodplain. The elevated flood risk to Port, City, SR 14 and residential infrastructure exists despite USFWS regularly dredging the diversion structure and removing debris from its inlet. Since 1992, USFWS has dredged more than 12,000 cubic yards (CY) of sediment from the diversion structure. During the 1996 flood, the USFWS removed approximately 5,000 CY.

Work Efforts for October 1, 2019 to September 30, 2022
Task 1: Project Initiation
•    Mobilization; Spill Prevention Control and Countermeasure (SPCC) & Erosion and Sediment Control (ESC) plans; fence removal
•    Surveying; clearing and grubbing
•    Fish Salvage; Dewatering and temporary diversion
Mobilization will include costs associated with moving equipment and materials onsite, project administration, staffing, and initiation of project activities. This activity includes the development of the permit required Spill Prevention Control & Countermeasure Plan (SPCC) and the Erosion and Sediment Control (ESC) plan. Fence removal along with clearing and grubbing are required to provide site access and surveying is critical to the success of the sites’ geomorphic design elements and natural features.  Fish Salvage, dewatering and temporary diversion of Gibbons Creek will occur prior to performing the SR 14 Bridge Scour and prior to removal of the Gibbons Creek diversion structures and elevated channel. These critical activities will be performed during permit-approved work windows and in compliance with State-mandated procedures and guidelines.
Schedule: Fall 2019 – Summer 2022.
Outcomes:
•    Develop SPCC and ESC plans.
•    Prepare the site for construction activities.
•    Protect Endangered Species Act listed aquatic species.

Task 2: Construct "Living Shoreline" Along Setback Levees
•    Construct wind-wave overbuild
•    Seed, plant and maintain wind-wave overbuild
The wind-wave overbuild (a living shoreline) encompasses approximately seven acres of the project site. These linear features will be constructed along the toe of, and parallel to, the waterward extent of the eastern and western setback levees. The combined length of these features will be approximately 4,000 ft having an average width of 80 ft. The design team performed wind-wave modelling to assess potential wave-based erosive forces due to the length of the “fetch” that could occur within the site during flood stages. Wind waves were simulated across the site using wind data from the nearby Troutdale Airport along with the projected site bathymetry generated as part of the hydrodynamic modeling for the site. Wave heights, total water levels, and wave overtopping were assessed along the setback levees. Wind waves at the site are typically less than 1.5 ft, but modeled extreme conditions suggest a potential wave height of 2.6 ft and 3.8 ft for the 10- and 100-year wind respectively, in combination with a 100-year water level of 34.4 ft NAVD. The report also concluded that erosion control measures could include a traditional approach, a more environmentally-sensitive approach, or a combination of the two. The traditional approach would be to place rock/rip-rap to armor the toe of the setback levees whereas the proposed wind wave overbuild, or “living shoreline,” will place earth fill at a gentle 20:1 slope, which would then be seeded and planted. The wind wave overbuild is cost-effective as it is less expensive to install and will require far less maintenance over time.  

The wind-wave overbuild will be seeded with a riparian seed mix and densely planted (approximately 14,000 plants) with a variety of native trees and shrubs. The selected plant species will exhibit a tolerance to a range of hydrologic conditions and as such, will remain resilient in the face of projected rising sea levels. Plants will have the ability to slowly adjust and migrate up or downslope, following the changing hydrology, as they find the particular niche where they will be most robust. The planted vegetation will require initial maintenance during the establishment period, but over time, the root systems will knit together to provide a highly stable and erosion resistant soil profile. The wind-wave overbuild will reduce wave runup heights, dissipate wave energy, and prevent erosion. The wind-wave overbuild will provide a transitional ecotone between the floodplain and the adjacent forested upland. Ecotones are often richer in species diversity than either of the adjacent communities, which further promotes the habitat goals designated for this project.
Schedule: Spring 2021 – Fall 2021/Winter 2022.
Outcomes:
•    Create 7 acres of complex habitat in a location where none currently exists, and where a hardened toe would typically be a requirement.
•    Create stable, erosion resistant, and resilient “living shoreline” that will self-adjust to climate induced changes in site hydrology for the 50 year+ lifetime of the project.  
•    Provide a cost-effective approach to stabilization.

Task 3: Alluvial Fan Restoration (Stage 0 Restoration; Hyporheic Exchange)
•    Demo and remove Gibbons Cr. diversion structure and elevated channel
•    Grade upper portion of alluvial fan
•    Place large wood debris (LWD)
•    Construct SR 14 Bridge Scour Protection
•    Maintain vegetation (spray, mow, interplant)

Demolish and Remove Gibbons Creek Diversion Structure and Elevated Channel.  The project will remove the Gibbons Creek diversion structure, elevated channel, and fish ladder. This work is required as part of the Stage 0 restoration of the Gibbons Creek corridor within the project site. The diversion structure consists of a large concrete overflow weir (concrete apron, concrete walls, steel grating, railings, and screens) and a concrete sluice gate immediately downstream of the overflow weir. The Gibbons Creek elevated channel runs atop a berm constructed of earthen fill. The berm is approximately 3,000 ft in length, 80 ft wide at its base and 25 ft wide along the top. Gibbons Creek is confined to an 8 - 10 ft wide channel with a parallel gravel road. The channel is largely devoid of habitat, with only herbaceous vegetation (primarily reed canary grass (Phalaris arundinaceae) along its banks, and with no structural (wood/rock/gravel) complexity. A fish ladder is located at the point where Gibbons Creek discharges to the Columbia River.  The removal of the berm will require the removal of approximately 70,000 CY of earthen fill. The berm will be removed down to match existing grade and this fill will be used for constructing the adjacent west setback levee.

The diversion structure’s sluice gate has a 22-inch width opening and was designed to allow maximum flows of 70 cfs into the elevated channel. When this capacity is exceeded, the diversion structure’s lateral weir will overflow, and discharge into the remnant Gibbons Creek channel (to the west). Eventually this flow reaches the Port’s pump station at the west end of the Refuge where it must be pumped through the levee. This results in significant pumping costs (up to $100,000 or more per year in electrical costs alone) and increased interior flood risk. During storm events, bedload and debris from Gibbons Creek are regularly deposited within the diversion structure. The sediment and debris then cause even modest flows (less than 70 cfs) to spill into the lateral overflow and remnant Gibbons Creek channel. The deposition raises water elevations and thus increasing flood risk to SR 14 and the mobile home community, immediately upstream. USFWS resources are diverted to remove the accumulated debris and sediment. An average of 280 cubic yards (CY) of material per year was removed between 1997 and 2011. Peak sediment removal occurred in 1995 (2,700 CY) and 1996 (5,000 CY). These deposits also increase backwater flooding of SR 14.

Annual removal of sediment and debris requires permitting and typically must be done under extreme circumstances during fall and winter storm periods. During these times of the year, salmon may be spawning, or their eggs may be incubating in stream gravels and are therefore most vulnerable to in-channel disturbance. Additionally, the channel cannot be dewatered during winter and spring, therefore juvenile lamprey, which burrow into stream substrate, cannot be effectively salvaged prior to dredging. USFWS staff have safely removed as many as 147 juvenile lamprey when the work area is dewatered during summer and fall dredging. These overflows also result in the “take” of Endangered Species Act (ESA)- listed salmonids since the fish that are discharged with flood waters are often left stranded as these flood waters disperse overland; or, fish that do reach the pump station may be killed as they are entrained in the pumps. It is also relevant that the fish ladder was poorly designed.  It is perched two to three feet above the Columbia River during low Columbia River stages, which typically coincide with upstream migrations of lamprey and Chinook and Coho salmon; and, it includes hydraulic drops that exceed 1 foot, which does not meet current adult or juvenile fish passage criteria.

The proposed efforts will eliminate any flood risk to the Port and City since the realigned Gibbons Creek will flow entirely within the extent of the new setback levee system. This will also eliminate the take of ESA-listed species since fish will no longer be stranded, floodwaters will no longer be pumped, and there will be no need for maintenance dredging. Debris and sediment that discharge during typical storm events will be processed within the Gibbons Creek alluvial fan and floodplain, replicating its historic condition. Because Gibbons Creek will be re-connected directly to the Columbia River, there will be no obstructions or impediments to fish movements during migration and spawning. The Stage 0 restoration design of Gibbons Creek will maximize geomorphic and biologic processes with the intent of creating a self-sustaining, self-adjusting, and durable solution  
Schedule: Fall 2021 – Winter 2022.
Outcomes:
•    Reduce flooding/flood risk to Port and City infrastructure including private residences, the Industrial Park, SR 14, and the WWTP.
•    Reduce the Port’s annual O&M costs by up to $117,000 and eliminate the need for approximately $5,600,000 in upcoming capital improvements.
•    Eliminate the taking of ESA-listed species due to overflows of the diversion structure.
•    Restore unobstructed fish passage into and out of the site for all life stages at the full range of hydrologic conditions.

Grading Upper Portion of Alluvial Fan. Gibbons Creek, which carries a high bedload, historically entered the floodplains along the Columbia River via an alluvial fan. This alluvial fan provided a large area for energy to dissipate and to process its load of sediment and gravel. As noted, the USACE constructed a diversion structure and elevated channel, effectively separating Gibbons Creek from its former alluvial fan. An integral part of this overall project, and the Stage 0 restoration effort, is the reconnection of Gibbon Creek to its historic alluvial fan and floodplain. This reconnection will facilitate restoration of the alluvial fan’s sediment processes and will not impede sediment transport through the SR 14 bridge.  The Estuary Partnership will grade the upper portion of the alluvial fan to ensure that Gibbons Creek fluvial flows follow site contours to the east of, and away from, the west setback levee. Gibbons Creek will ultimately connect to the newly created channel near the center of the project site. A total area of approximately 11 acres will be regraded to ensure that Gibbons Creek flows will not affect the west setback levee. The grading along the western edge will abut the living shoreline/wind-wave overbuild, which will additionally protect the west setback levee. To further stabilize this regraded area, the Estuary Partnership will replant with a riparian mix of native trees (300 per ac) and shrubs (1330 per ac).
Schedule: Summer 2021

Outcomes:
•    Eliminate risk of erosion along the base of the west setback levee.
•    Enable redirection of Gibbons Creek as part of the Stage 0 restoration.

Large Wood Placement. The Estuary Partnership will place 21 wood habitat structures within the upper portion of the regraded alluvial fan. These structures will consist of a single embedded nurse log, which will be pinned with a single pier log. Nurse logs will be 15 to 25 ft in length, and 10-24 in. in diameter. This wood placement is part of a larger effort that will place over 1,750 pieces of large wood that is integral to the Stage 0 restoration effort. The goal is to increase wood densities to those typically found in streams and wetlands. The active alluvial fan is an ideal place to install LWD. The embedded large wood will interact with changing flows and foster dynamic creation of habitat over time. Wood habitat structures that encourage scour of deep pools provide shaded, cold water refugia for overwintering salmonids and other beneficial aquatic species. These structures also will serve as passive beaver dam analogue structures to encourage beaver dam construction. These structures will encourage development of multiple small thread channels leaving the alluvial fan toe, which may well provide cold-water seeps, and could therefore be a valuable rearing and refuge area for juvenile salmonids during summer months or periods of low flow. The placement of large wood within the upper portion of the alluvial fan may also increase hyporheic flow by creating ponding, sinuosity and multiple channels. The substrate within this portion of the fan is highly porous, consisting of coarse textured alluvium, which will allow for increased hyporheic exchange between surface water and ground water.
Schedule: Fall 2021.
Outcomes:
•    Reduce thermal barriers to salmonids by increasing habitat complexity and encouraging hyporheic exchange.
•    Contribute to development of complex, anastomosing flow patterns.
•    Encourage beaver re-introducing by providing beaver dam analogue structures and cover.
•    Provide substrate and organic food source to support the macro-detrital food web.

SR 14 Bridge Scour. A bridge scour analysis was performed following the Bonneville Power Administration (BPA) HIP III Handbook, HEC -23, and the methodology outlined in the Federal Highway Administration’s, Evaluating Scour at Bridges, 5th Edition, April 2012. Based on these studies, the Estuary Partnership will undertake a variety of measures to prevent future bridge scour and to ensure that Gibbons Creek bedload can pass freely beneath the bridge to be processed downstream within the reconnected alluvial fan.  The Estuary Partnership will excavate the channel to increase the cross-sectional area and place rip-rap to harden and protect this critical infrastructure. Rip-rap will be placed to a thickness of 2.5 ft. throughout, to include the area beneath the bridge, and for a distance of 20 ft. upstream and 20 ft. downstream of the bridge. The upper edge of rip-rap will be keyed/blended into the upper bank slopes and roadway embankment and covered with native material. The streambed will be top dressed in a 4” thick layer of river sediment/cobble to immediately restore the bed to a more natural condition. All rip-rap will be angular rock, having a D-50 of 12”.

Gibbons Creek will be restored for a distance of 700 ft upstream of the bridge. The majority of this restoration will create a natural meandering form that will include a series of constructed riffles, gravel bars, and embedded logs designed to increase floodplain storage and create fish habitat. At the bridge, the existing straight channel alignment will be maintained for a distance of 150 ft upstream and 200 ft downstream. This channel geometry is designed to facilitate sediment transport through and downstream of the SR 14 crossing, to be deposited in the alluvial fan. Creek embankments will be replanted following construction to further stabilize and maintain the stream alignment. The Gibbons Creek channel design and analysis of the SR 14 scour was based off peak flows that were increased by roughly 20 percent to account for projected changes in flood magnitude due to climate change as well as anticipated residential development within the upstream Gibbons Creek watershed, which includes an area of approximately 8 square miles. This increase is based on studies conducted by the Climate Impacts Group at the University of Washington (CIG 2013). The lowering of the bed elevation beneath the SR 14 bridge will increase the bridge’s conveyance capacity by approximately 35 percent, i.e., from approximately 1,300 cfs to over 1,760 cfs. Under existing conditions, Gibbons Creek’s 100-year discharge overtops the bridge. After construction, the bridge will have sufficient capacity to pass the 500-year discharge event. Additionally, the bridge’s restored capacity, in combination with the west setback levee’s floodwall, will protect adjacent residences from Gibbons Creek discharges in excess of the 500-year event.
Schedule: Summer 2020.
Outcomes:
•    Increase the bridge hydraulic capacity by 35%, from approximately 1,300 cfs to over 1,760 cfs.
•    Provide sufficient capacity to pass the 500-year discharge event.  
•    Reduce flood risk for residences located upstream of the SR 14 bridge, also in excess of the 500-year event.
•    Increase fluvial flow to convey sediment downstream for processing/deposition within the alluvial fan.

Vegetation Maintenance. The Estuary Partnership is seeking additional (outside) grant funding to maintain previously planted areas, primarily a 53-acre portion of the alluvial fan, which is also an area designated as a “reed canary grass management zone”. This 53-acre portion of the alluvial fan is dominated by a monoculture of reed canary grass, which has been mowed and treated with herbicide (Summer 2019) and will be seeded (Fall 2019) with a native floodplain seed mix and planted (early winter 2020) with a “Willow Scrub” mix of trees and shrubs. The area will be planted at a density of 300 trees and 1619 shrubs per acre. Because this area is heavily impacted by invasive reed canary grass, it will require significant effort to ensure the success of the willow scrub plantings. The Estuary Partnership will provide mowing and herbicide treatment during the year following planting. In the summer and fall 2020, the Estuary Partnership will mow and spot/band spray to release plantings from competition. Because the site will be heavily planted, all mowing will be performed with hand tools, and herbicide treatments will be performed by individuals using backpack sprayers. In addition to the technical maintenance planned, the site is an active site for the Estuary Partnership’s on-going student and community plantings. For over a decade, we have taken thousands of students and community volunteers to the site to remove invasive plants and plant thousands of trees. We will continue to use this site for on-going student and volunteer planting and plant maintenance projects for many years.

Establishing a riparian plant community within the alluvial fan is critically important since plants adjacent to surface waters provide many important ecological functions including soil stabilization, flow resistance, velocity reduction and provision of cover, shade, and energy input. Vegetation inputs (above and below ground detritus) are critical to a healthy macroinvertbrate population which in turn provides food for higher order organisms, including ESA-listed species. In addition, vegetation complexity and diversity are highly correlated with animal species diversity.
Schedule: Summer 2020.  
Outcomes:
•    Replace a monoculture of invasive reed canary grass with native riparian plant species.
•    Encourage plant biodiversity that restores the historic community lost due to agricultural development.

Task 4: Construction and Contract Management
The overall project is complex with many overlapping activities which will require field oversight and administration to ensure compliance with contract drawings and specifications. Since there are a variety of critical timing restrictions for in-water work/fish passage, detailed project schedules must be developed and strictly followed to meet these deadlines. In addition, the overall project is being performed within a National Wildlife Refuge and in accordance with a variety of Local, State and Federal permits that authorize various regulated activities within environmentally-sensitive areas. These authorizations include both general and special conditions which will be strictly enforced as part of the construction oversight.  

Project Initiation (Task 1) requires the development of Spill Prevention Control and Countermeasure (SPCC) and Soil Erosion and Sediment Control (ESC) plans. Each of these plans must be enforced in the field for the duration of the project. The project team will attend weekly meetings, perform daily field inspections, assist with contract administration, and interface with contractors and engineers to manage issues that may arise during construction. This work will be performed for the duration of the contract period.
Schedule: Fall 2019 – Summer 2022.
Outcomes:
•    Provide expert management to support of the success of the overall project.
•    Enforce SPCC and ESC plans.

Additional benefits of the project
Education Benefits. The project will increase public engagement with the site through student and volunteer planting events. During these events, students and community members learn about the project and Refuge while planting native trees and shrubs. These plantings are a critical part of the project and help achieve many of its goals, including improving water temperatures and food web dynamics. The Estuary Partnership has an established, highly successful and sought-after education and volunteer program that provides applied learning and engages people in restoring natural areas. The Estuary Partnership has partnered with the community to re-establish riparian habitats at the Refuge since 2009.

Recreation Benefits. The Refuge’s existing trail network extends south from the SR 14 parking area along Gibbons Creek’s elevated channel, before turning east along the top of the levee system. The project will remove the elevated channel and trail as well as 2.2 miles of the existing levee/trail. It also will expose the SR 14 parking area to Columbia River floods. Consequently, the project will reconfigure the Refuge trail system and relocate the parking lot. The project team has been coordinating with the Refuge, Port, City, Gorge Refuge Stewards, Friends of the Columbia Gorge, and others to solicit feedback regarding trail design. The reconstructed trail network will have similar widths and surfacing; however, instead of hiking along gravel roads through monotypic habitat, the new trail will meander along the Columbia River, weaving back and forth from the interior of the Refuge to the river through a restored native forest. The project will also increase the number of parking spaces at the Refuge’s relocated parking lot by 50% and increase the length of the Refuge’s trail system by 1.0 miles. The connection to the Port’s trail system (to the west of the project site) will be maintained.