HomeMy WebLinkAboutC_Proposed Mit Plan Final #2_20191112.pdf Proposed Compensatory Mitigation Plan, FINAL
Apron R Infrastructure Maintenance and Repair Project
Project #LY16160400 The Boeing Company | 11/12/2019 Page 1
Proposed Compensatory Mitigation Plan
Apron R Infrastructure Maintenance and Repair Project (NWS-2017-37)
The Boeing Company
Renton, Washington (Lake Washington)
November 12, 2019
Wood Environment & Infrastructure Solutions, Inc. and WSP
1. Project Description
The Boeing Company (Boeing) is proposing to conduct the Apron R Infrastructure Maintenance and
Repair Project at the Renton, Washington plant located at the southernmost end of Lake Washington
between Rainier Avenue North and Interstate 405 (Township 23N, Range 5E, Sections 7 and 8) (Figure 1).
Apron R is located on the south shore of Lake Washington, north of Buildings 4-41, 4-20, 4-81, 4-82, and
4-83 (Figure 2).
The proposed Apron R Infrastructure Maintenance and Repair Project has been divided into three areas,
described in detail below, to refer to specific portions of the apron in order to describe the project
elements (Figure 2).
Area 1 – West Apron Improvements,
Area 2 – East Apron Improvements, and
Area 3 – Central Apron Improvements.
Project details are provided in the Joint Aquatic Resources Permit Application (JARPA; Wood, 2019) and
the Draft Biological Evaluation (Wood and BergerABAM, 2019).
2. Existing Conditions of Aquatic Resources
The Boeing Renton facility is located on the south shoreline of Lake Washington (Figures 1 and 2). Much
of the facility adjacent to the Lake Washington shoreline is located on what was formerly lakebed that was
exposed with the lowering of the lake level with the construction of the Hiram M. Chittenden locks in
1912. The surrounding topography is flat and highly developed. Properties on both sides of the proposed
project site, as well as the project site, are paved and populated with buildings used for airplane
manufacturing, maintenance, and storage; offices; and vehicle parking. Utilities to the project site and
surrounding properties are provided by the City of Renton and include water, sewer, and electric and the
belowground and aboveground infrastructure to support these services. Within the project area, Boeing
maintains underground utility distribution to buildings and other Boeing facilities.
A vegetation and habitat survey of the site was conducted on October 20, 2016 to assess habitat
conditions and vegetative cover along the entire length (~2,600 feet) of the proposed Apron R project site
along the south Lake Washington shoreline.
Approximately 1,500 feet of the 2,600 feet of the proposed project area along the south Lake Washington
shoreline consists of a pile-supported concrete deck, concrete bulkhead, sheet-pile bulkhead, and riprap
bulkhead. Approximately 350 feet of invasive plant species occur along the top of the riprap bulkhead.
Two concrete ramps are also present along a portion of the concrete bulkhead (Figure 2). The remaining
1,100 feet of shoreline is occupied by a Washington State Department of Natural Resources (DNR)
shoreline habitat mitigation area. The DNR constructed the shoreline habitat mitigation between 2013
and 2015. Mitigation elements included regrading the existing shoreline, replacing existing nearshore
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substrate with sand and pea gravel, incorporating artificial log jams, and removing invasive plant species
and replanting with native vegetation.
Other than the DNR shoreline mitigation area, vegetation along the remainder of the shoreline along the
proposed project site is sparse. There are two vegetated areas at the top of riprapped embankments
consisting primarily of invasive species. Riparian vegetation was limited primarily to large patches of
Himalayan blackberry (Rubus armeniacus) and smaller patches of Japanese knotweed (Polygonum
cuspidatum), English ivy (Hedera helix), and a number of unidentified grass and weed species. Himalayan
blackberry, Japanese knotweed, and English ivy are listed as noxious weeds by King County (King County,
2017). With the exception of the DNR shoreline mitigation area, no trees with trunks greater than or equal
to 10 inches in diameter at breast height (DBH) are located within 100 feet of the project area. Several
small trees are located among the invasive species discussed above and include a single alder tree (Alnus
rubra) and vine maple (Acer circinatum).
The south Lake Washington shoreline adjacent to the Apron R project site as it currently exists provides
no access or refugia restrictions for juvenile salmonids, although the nearshore habitat is highly degraded
from past development and currently has overwater structures, concrete ramps, vertical bulkheads, and in
areas colonized by invasive species.
The area under overwater structures and adjacent to vertical bulkheads provides low-functioning aquatic
habitat and is not a preferred habitat of juvenile salmonids. Additionally, piles supporting the pier and the
shading provided by the pier may also provide refuge for salmonid predators (e.g., smallmouth bass
[Micropterus dolomieu]). Invasive plant species growing along the existing shoreline do not provide
shading or detrital inputs, or insect fall to the lake and provide little value to aquatic species. Although
accessible as refugia for juvenile salmonids, existing environmental conditions are unlikely to provide
optimal refugia habitat for juvenile salmonids.
3. Avoidance and Minimization of Aquatic Resource Impacts
During the alternative analysis process (BergerABAM, 2019), the project was designed to avoid and
minimize impacts to Lake Washington and to meet the requirements of a Nationwide 39 Permit. The
overall project will not expand the footprint of the apron within Lake Washington; in-water work for the
proposed project will be conducted within established U.S. Army Corps of Engineers work windows with
no requested extensions; the proposed project contains the minimum number of permanent and
temporary impacts to Lake Washington and is the least impactful of Boeings existing operations.
The remaining repair work conducted on the Apron will occur on the landward side of the existing
bulkhead and will not result in additional in-water work.
4. Unavoidable Aquatic Resources Impact Acreage
The project will not expand the footprint of the apron within Lake Washington. The placement of fill
material in the lake (within the footprint of the existing pile-supported structure) to support the replaced
apron will result in a loss of approximately 5,226 square feet of waters of the United States. This action
impacts an area that is currently covered by the pile-supported structure and west ramp. This area is
shaded, low function, and degraded aquatic habitat.
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Example Table 1
Expected Impacts to Aquatic Resources
Resource
Identifier Activity
Permanently Impacted
Waters of the U.S.
(sq ft)
Temporarily Impacted
Waters of the U.S.
(sq ft)
Lake Washington –
In-Water
Temporary fill between permanent
and temporary sheet-pile walls 0 4,895
Lake Washington –
In-Water
Structural fill behind
NW Corner Structural Wall 5,110 0
Lake Washington –
In-Water
Outfall 012A
92 0
Lake Washington –
In-Water
Outfall 014A
111 0
Lake Washington –
In-Water
Outfall 002A – Pipe Bedding
366 0
Lake Washington –
In-Water
Outfall 004A – Pipe Bedding
0 327
Lake Washington –
In-Water
Outfall 004A – Pipe Bedding
67 0
Totals 5,746 5,222
5. Impacted Aquatic Resource Functions
With the exception of the DNR shoreline mitigation site, the riparian zone along the project site is sparsely
vegetated and includes a number of invasive species, including Himalayan blackberry, Japanese knotweed,
and English ivy (Amec Foster Wheeler and BergerABAM, 2017). Invasive species do not provide shading or
detrital inputs, or insect fall to the lake and provide little value to aquatic species. The primary ecological
functions provided by riparian vegetation along the project site include:
Nesting and foraging habitat for birds and small mammals,
Input of terrestrial insects from overhanging vegetation,
Input of allochthonous organic matter (via leaf fall),
Limited erosion control, and
Very limited habitat complexity.
The existing riparian vegetation provides very little, if any, shading to the south Lake Washington
shoreline adjacent to the project site because of the dominance of small shrubs and the lack of large
trees. With the exception of the DNR shoreline mitigation area, the remainder of the shoreline along the
project site consists of bulkhead, so that habitat complexity is minimal. Because of extensive commercial
development along the south Lake Washington shoreline in the project area (Renton Municipal Airport to
the west of Boeing and a hotel complex to the east), there is minimal transition between riparian and
upland habitats.
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The area under overwater structures provides low-functioning aquatic habitat and is not a preferred
habitat of juvenile salmonids. Additionally, piles supporting the pier and the shading provided by the pier
may also provide refuge for salmonid predators (e.g., smallmouth bass).
6. Mitigation Site Selection Rationale
There are three mechanisms for providing compensatory mitigation for the unavoidable impacts to Lake
Washington: mitigation banks, in-lieu fee program, and permittee-responsible mitigation. There are no
mitigation banks for loss of aquatic habitat near the site and rather than contributing to the in-lieu fee
program, the permittee-responsible mitigation is being conducted on the site to enhance existing habitat.
7. Mitigation Work Plan and Description of Aquatic Functions
Provided at Mitigation Site
Mitigation at the site consists of the following elements as shown on Figure 3:
Removing the central ramp structure, including in-water piles supporting the central ramp.
Cutting 353 in-water piles (waterward of the west ramp) 2 to 5 feet below the mudline.
Removing invasive species in Areas 1 and 3 and improving soil conditions, re-planting those areas
with native vegetation, and finishing planting beds with wood chips to retain moisture for plants
and help suppress growth of weedy vegetation.
Placing large, woody debris on the DNR mitigation site within the locations where re-planting will
occur. Actual placement will be identified and approved during construction.
Tree replacement will occur within the DNR mitigation area. Replacement of trees will increase
from 5 to 8.
The overall goal of the riparian plantings is to increase shoreline habitat functions by providing riparian
shade during the day, blocking artificial light sources at night, and increasing organic matter input to the
lake. A temporary irrigation system will be installed and operated for a sufficient time period to establish
plants and seed material and to provide for sufficient growth of vegetative cover to prevent soil erosion
(Attachment 1).
The area under overwater structures and adjacent to vertical bulkheads provides low-functioning aquatic
habitat and is not a preferred habitat of juvenile salmonids. Additionally, piles supporting the pier and the
shading provided by the pier may also provide refuge for salmonid predators (e.g., smallmouth bass).
Removing the central ramp, its supporting piles, and cutting the west ramp in-water piles below the
mudline provides a net positive impact to habitat.
Removal of the central ramp structure as well as the in-water piles (waterward of the west ramp) will be
conducted during a winter fish window. The central ramp will be removed with water- and land-based
equipment. A temporary floating debris curtain will be placed around the ramp prior to demolition to
capture and contain all debris. Sediment curtains will be placed in the lake around the work area to
minimize turbidity. Concrete saws will be used to cut the ramp into manageable pieces for removal.
Barges, cranes, and excavators will be used to remove concrete. Once the concrete is removed, piles
supporting the concrete will be cut 2 to 5 feet below the mudline (approximately 155 piles). All material
will be disposed of at approved off-site locations. Removal of the central ramp will remove approximately
4,002 square feet of overwater coverage. The central ramp removal mitigation measure will take place
during the Year 2 (or Year 3) winter fish window (See JARPA Sheet 3).
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8. Site Protection Instrument
There are currently no site protection instruments in place.
9. Maintenance Plan
The native planting areas on Boeing property will be maintained for the first 5 years post-construction as
described below. Planting on the DNR mitigation site will be maintained by DNR. The landscape plans are
included as Attachment 1. Planting will be completed post-construction during the season most suitable
for plant thriving after invasive species removal has been completed.
During the first year, 100% plant survival is required. Failed or dying plants must be replaced with plants
that are equal or greater in size and must be the same species. Deviations in plant sizes and species must
have prior approval prior to procuring plants. Water plants a minimum of 1 inch of water weekly between
June 15 through September 15. At a minimum watering will be required during the first 3 years. At the
end of year 3, the plants will be assessed to determine if additional years of watering are required. All
other maintenance will be performed twice every year (start of the growing season and end of the
growing season) at a minimum for the length of monitoring period. Visual inspections of the site will be
performed to determine if additional maintenance is required and to access the condition of the planted
areas.
Plant Maintenance and Weed Control shall be performed within the following constraints:
Fertilizers shall not be applied to bare soils that may allow runoff into bodies of water. Fertilizers
shall be directly applied to the planting pit. No mechanical devices shall be used to apply the
fertilizer. Herbicides, pesticides (if approved for use), and fertilizer shall not be applied to areas
inundated with water.
Use of herbicides or pesticides, if required, must be approved by state and local agencies. All work
shall be performed by hand wherever possible. If toxic substances are used, they shall not be
allowed to enter the Cedar River or Lake Washington.
Weed control in all areas shall be conducted as follows: At least 3 calendar days prior to
beginning weed control activities, walk through the site with the landscape architect and confirm
the identity, location, type, and approximate number of specified weeds. Remove specified weeds
and receive approval. As much as practicable, ensure that weed seeds or reproducing plant parts
such as vines, runners, or rhizomes don’t remain or become disbursed during control activities.
- As soon as practicable, place weeds and related materials in an approved container and
transport to an approved off-site disposal facility according to applicable laws and
regulations. During transport, ensure that materials are fully enclosed at all times to prevent
escape.
- Keep the site weed free, including weeds that were not initially present in the walk through.
- Unless otherwise approved in writing, use only hand or light mechanical weed control
methods. Hand methods include the use of hand tools. Light mechanical methods include the
use of hand carried, motorized machinery.
- Remove all of plant including roots.
Inside sensitive areas, obtain approval before using wheeled or tracked construction equipment.
Maintain a 3-inch-thick mulch around individual plantings.
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10. Performance Standards
10.1 Year 1
Plant survival during the first year would be the responsibility of the landscape contractor and would be
ensured through correct installation procedures, ongoing maintenance, and replanting, if needed. Growth
during the first year would be minimal as plants are becoming established. Specific performance
standards for the first year include:
100% survival of plants; and
Not more than 10% coverage by non-native invasive species.
10.2 Years 2, 3, and 5
Following the first year of monitoring, performance of vegetation would be measured in plant survival and
percent.
Some plant mortality is expected during years 2, 3, and 5. Planted vegetation is expected to perform well.
Plants will receive supplemental watering and routine maintenance to maintain plants vigor. With proper
growing conditions and maintenance, it is assumed that 80% of the plants will survive and be present
during monitoring years 2, 3, and 5.
Specific performance standards for years 3 and 5 should include:
100% survival for year 2 for container plants and 80% for live stakes;
80% plant survival for years 3 and 5; and
Not more than 10% coverage by non-native invasive species in any year.
11. Monitoring Requirements
Vegetation within revegetated areas will be monitored for a total of 5 years to assess the performance of
the restoration. During the monitoring period, plant survival and establishment will be documented and
compared to performance standards specified below. Monitoring would begin by providing as-built plans
immediately following completion of the installation. Subsequent monitoring will occur at the end of each
growing season (late August – September) in years 1, 2, 3, and 5 following construction. A memorandum
summarizing existing conditions at the time of each monitoring event and compliance with specified
performance standards for each monitoring year will be submitted to the appropriate agency for review
and approval within 90 days of each monitoring event.
Prior to the first monitoring event, the location of four permanent sampling plots (two each bank) will be
selected in representative areas of the riparian buffer plantings zones. The size, location, and shape of
sample plots will be determined using the as-built plans and will encompass approximately 100 square
feet. The locations of the sampling plots will be recorded on the as-built plans. The center of each sample
plot will be marked with rebar and a tall white polyvinyl chloride (PVC) pipe during the first monitoring
event to enable relocation during subsequent monitoring events. During each monitoring event at the
identified locations, plant species observed within the site will be identified and recorded to confirm
percent survival. Overall development of the planted communities will be documented through
photographs taken during 5 monitoring years. Photo points will be established during year 1 monitoring
and identified on the as-built plan. These photos points will be used for the duration of the project.
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Plant survival and growth will be assessed throughout the entirety of the restored area during the first
year of monitoring. During the first monitoring event, all individual plantings will be identified as living or
dead. Dead plants will be flagged in the field for replacement, and their species noted. Site-wide plant
survival will be calculated by subtracting the total number of dead plantings observed during the
monitoring event from the total number of plants installed as listed in the as-built plans.
During the 5-year monitoring period, non-native invasive species such as Scot's broom (Cytisus scoparius),
Himalayan and evergreen blackberry (Rubus laciniatus), reed canarygrass (Phalaris arundinacea), purple
loosestrife (Lythrum salicaria), English holly (Ilex aquifolium), Japanese knotweed, giant knotweed
(Polygonum sachalinense), and English ivy shall be removed and disposed of off-site at an approved
facility. In addition to the plants listed above, other non-native and invasive plants will be managed and
removed should they establish.
12. Long-Term Management Plan
After the 5-year maintenance described above, Boeing will continue with regular vegetation maintenance
of the site as part of the general landscape maintenance performed at the Boeing facility. Landscape
crews will be proficient in maintaining sensitive landscape areas. Additionally, signs will be installed to
clearly identify these areas as critical habitat.
13. References
Amec Foster Wheeler and BergerABAM. 2017. Standard Lake Study Narrative and Habitat Data Report,
Apron R Infrastructure Maintenance and Repair Project, Renton, Washington. Prepared for The Boeing
Company, Renton, Washington. Revised November 2017, Version 2.
BergerABAM. 2019. 404(b)(1) Alternatives Analysis: 2019. Boeing Apron R Infrastructure Improvements,
Renton, Washington. Submitted to The Boeing Company, Renton, Washington. January 17, 2019.
King County. 2017. King County Noxious Weed List. King County, Seattle, Washington, http://
www.kingcounty.gov/services/environment/animals-and-plants/noxious-weeds/laws/list.aspx
(accessed March 2, 2017).
Wood Environment & Infrastructure Solutions, Inc. 2019. Joint Aquatic Resources Permit Application:
Boeing Apron R Infrastructure Maintenance and Repair Project (NWS-2017-37). Prepared for The
Boeing Company, Renton, Washington. Revised March 2019.
Wood Environment & Infrastructure Solutions, Inc., and BergerABAM. 2019. Draft Biological Evaluation,
Apron R Infrastructure Maintenance and Repair Project, Renton, Washington. Project #LY16160400.
Prepared for The Boeing Company, Renton, Washington. Revised March 2019.
Figures
Source: BergerABAM
By: CJW Project: LY16160400
Date: 03/06/19
Figure 1
VICINITY MAP
Boeing Apron R Infrastructure Maintenance and Repair Project
Renton, Washington
Source: BergerABAMBy: CJW Project: LY16160400Date: 03/06/19Figure 2PROJECT AREA PLANBoeing Apron R Infrastructure Maintenance and Repair ProjectRenton, Washington
MITIGATION MEMO
MITIGATION PLAN
BOEING
3
FIGURE
LY16160400
PROJECT NO.
AS SHOWN
SCALE
OCTOBER 2019
DATE
DRAWN BY: PM CHECKED BY: JKHCLIENT PROJECT
TITLE
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Wood Environment &
Infrastructure Solutions, Inc.
3500 188th Street SW, Suite 610
Lynnwood, Washington 98037
Attachment 1 – Landscape Design Plans
(note that this attachment is provided
as a separate pdf file due to its large size)