CriticalAreaReport.pdf
1101 Fawcett Avenue, Suite 200
Tacoma, Washington 98402
253.722.2411
December 8, 2016
Reid Middleton
728 134 Street, Suite 200
th
Everett, Washington 98204
Attention: Julian Dodge
Subject: Critical Areas Report
Northstream Culvert Repair
Edmonds, Washington
File No. 0180-030-01
INTRODUCTION
GeoEngineers, Inc. (GeoEngineers) has been supporting Reid Middleton for the Northstream culvert repair
project along Puget Drive in Edmonds, Washington. We conducted a site visit on February 26, 2016 to
evaluate critical areas, habitat features and stormwater conveyance within the project area. We have
prepared this critical areas report to support permitting requirements with the City of Edmonds (City), as
defined in Edmonds Municipal Code (EMC) section 23.90.020.
PROJECT SUMMARY
The goal of this project is to repair a degraded pipe that passes Northstream Creek under Puget Drive. This
36-inch concrete pipe will be repaired by adding a cure-in-place lining to shore up cracks and deformities
that have developed. This requires dewatering the culvert for approximately 2 days. Upstream of the section
to be repaired, Northstream flows through a 30-inch high density polyethylene (HDPE) pipe that crosses
12 Avenue N and 11 Place N. This pipe was installed as an emergency repair following flooding and
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failure of the old storm system. Sections of that old system, which does not currently contact the creek, will
also be abandoned as part of this project.
METHODS
Habitat assessment consisted of evaluating in-stream physical properties regarding potential fish and
wildlife habitat, as well as a general assessment of the surrounding basin. Public-mapped data sources
were reviewed prior to the fieldwork. These sources included:
Reid Middleton | December 8, 2016 Page 2
WDFW SalmonScape (http://apps.wdfw.wa.gov/salmonscape/): SalmonScape maps
hydrography, fish distribution, and passage barriers throughout the state. Some irregularities do
exist between the toggled hydrography layer and the basemapÔs embedded channel lines.
WDNR FPARS (https://fortress.wa.gov/dnr/protectiongis/fpamt/default.aspx): This system shows
the regulated stream-type database used by cities and counties throughout the state. Mapped
drainages are typically either F (fish bearing) or N (non-fish) type, occasionally with a perennial (p)
or seasonal (s) addition. These hydrography layers were created at a coarse spatial scale and are
not regularly updated.
WDFW PHS (http://wdfw.wa.gov/mapping/phs/): This database is similar to SalmonScape;
however, its broader focus displays any state-priority habitat or species, not specifically salmon.
Cutthroat trout distribution is mapped by PHS but not SalmonScape, as well as more detailed
wetland habitat layers.
USFWS NWI (https://www.fws.gov/wetlands/Data/Mapper.html). This system maps wetlands at a
coarse, reconnaissance-level scale using aerial photography.
City of Edmonds GIS mapping (http://www.edmondswa.gov/studies-menu-home.html): The City
provides both PDF and web-based mapping applications, displaying stormwater, critical areas,
watersheds, and other relevant data surrounding the project area.
Google Earth or similar aerial photography: Using aerial photography, especially historical data to
assess how sites have changed, provides a lot of information about site conditions.
Physical stream measurements and observations were taken during the fieldwork using standard stream
assessment equipment: an engineer-scaled stadia rod, rangefinder equipped with inclination (gradient)
measurement capability, camera, and field notebook. Characteristics measured include stream bankfull
width (BFW) (at a variety of locations), channel gradient (where it appeared stable and indicative of the
systemÔs state), sediment composition (particularly noting potential cached material behind the upstream
inlet), and specific habitat features such as large woody debris, deep pools, or side channels/tributary
confluences.
HABITAT ASSESSMENT
The desktop study for this stream was relatively brief, as neither FPARS, SalmonScape, nor PHS map the
channel extending to or beyond Puget Drive. These sources show a Type-N (FPARS) channel extending east
from Puget Sound and terminating at Grandview Street, over 1,000 feet west (downstream) of the project
area. The NWI map does not show any features at or near the project area. The CityÔs mapping application
appears to show the most accurate location of the Northstream channel.
While infrequently mapped and confined within degraded urban corridors, the channel must be presumed
to support or potentially support fish habitat based on its physical characteristics. WAC 222-16-031 defines
a fish bearing channel for western Washington as having two or more feet of defined channel within the
BFW for channels of 16-percent or less gradient.
File No. 0180-030-01
Reid Middleton | December 8, 2016 Page 3
Downstream Conditions
Conditions within and surrounding the channel reflect the urban, highly developed nature of the landscape.
Downstream of the culvert, the channel runs through the backyard of a single-family residence. This reach
varies between 4 and 7 foot BFW and commonly features vertical banks between 1 and 4 feet, often
comprised of large landscape rocks (Photo 1). Small foot bridges span the channel in multiple locations
and constructed vertical drops in the channel between ½ and 1½ feet were commonly noted. The
downstream reach abuts mowed lawns and patio features, lacking mature riparian vegetation. Sediment
conditions within this reach are predominantly sand, with occasional gravel deposits (Photo 2). A
visually-estimated ratio of 75 percent sand to 25 percent gravel was noted.
A small (12-inch-diameter) storm culvert discharges to the channel approximately 5 feet above the
downstream outfall (Photo 3). This feature likely contributes to some of the structural concerns along the
outfall, as water runs alongside and under the lower section of pipe. At the 36-inch pipe outfall (Photo 4),
a small water surface drop (about 8 inches) has developed a plunge pool 9 feet long, 7 feet wide, and about
1-foot maximum depth. This area is the only section of the downstream channel with significant shading
vegetation, with mature cedar (Thuja plicata) and cascara (Rhamnus purshiana) surrounding the outlet.
English ivy (Hedera helix) and a small patch of slough sedge (Carex obnupta) are also present near the
outfall.
Upstream Conditions
The stream is culverted under Puget Drive in a series of culverts including an existing 36-inch-diameter
concrete pipe, then a 30-inch-diameter HDPE pipe from the south side of Puget Drive to 11 Place N, and
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a 30-inch-diameter concrete pipe upstream to the inlet. The length and age of this system almost certainly
produces a total fish passage barrier.
Photo 2.Downstream substrate conditions.
Photo 1. Downstream channel conditions.
File No. 0180-030-01
Reid Middleton | December 8, 2016 Page 4
Photo 4. Downstream outlet.
Photo 3. Storm tributary above downstream outlet.
The culvert inlet east of 12 Avenue N features a metal 36-inch-diameter corrugated metal pipe equipped
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with a vertical overflow entrance and grated trash racks (Photo 5). Minimal small debris was noted racking
on the inlet. These features appeared to be relatively new construction and in good condition.
Upstream channel conditions are much more natural as the stream flows through Maplewood Park. At the
inlet the channel flows through a flat, confided valley approximately 50-feet wide, bordered by Puget Drive
to the north and residential development to the south (Photo 6). The channel features short, shallow banks
and the area outside the channel support wetland conditions. The width of riparian habitat steadily
increases moving upstream.
Photo 5. Upstream culvert inlet.
Photo 6. Upstream channel, just above culvert.
File No. 0180-030-01
Reid Middleton | December 8, 2016 Page 5
The upstream channel averages 2.5 percent-gradient and 6 foot BFW (Photo 7), with areas of dynamic
braiding about 150 feet above the inlet. Substrate in this area includes a more natural sand, gravel, and
cobble mix within the banks (Photo 8); however, large sand and small gravel deposits were noted within
200 feet of the inlet (Photo 9). Some suspected planting efforts were noted near the culvert inlet, featuring
maple (Acer macrophyllum) and cedar, with some volunteer alder (Alnus rubra) noted as well. Creeping
buttercup (Ranunculus repens) forms a generally consistent ground cover above the culvert inlet. Further
upstream, dense salmonberry (Rubus spectabilis) dominates the channel with cedar, hemlock (Tsuga
heterophylla) and alder forming the canopy. Upland plants such as salal (Gaultheria shallon) and sword
fern (Polystitchum munitum) were noted on slopes above the channel corridor. Some non-native species
such as English ivy, Himalayan blackberry (Rubus armeniacus) and holly (Ilex aquifolium) were observed in
sparse, infrequent patches.
Photo 8. Upstream channel with gravel, cobble, sand, and large woody debris
Photo 7. 6-foot wide upstream channel; gravel and sand near culvert
Photo 9. Sand and gravel deposits above the active channel, approximately 200 feet upstream from culvert
File No. 0180-030-01
Reid Middleton | December 8, 2016 Page 6
CRITICAL AREAS REVIEW
The following critical areas were observed at the site: a (potentially) fish-bearing stream and an associated
riverine wetland (upstream of the culvert crossing). While DNR FPARS maps the channel as non-fish bearing
downstream of the project area, the size of the system potentially provides habitat for resident fish. Due to
multiple downstream barriers precluding anadromous fish access to the project area or adjacent reaches
of the system, the City will most likely require a 75-foot buffer for the channel (EMC 23.90.040 D).
A formal wetland delineation and rating effort was not conducted at the site due to the wetland being
outside the project impact area. Work is not proposed above the current Northstream culvert inlet. Required
wetland buffers, depending on the wetland rating habitat score, would likely range between 60 and
165 feet. No impacts are proposed within the wetland upstream of the culvert inlet. To complete the culvert
repair, water will be diverted around the Puget Drive culvert from the manhole connection of the
36-inch-diameter concrete culvert and the 30-inch-diameter HDPE culvert, west of 11 Place N and south
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of Puget DriveÐover 300 feet away from the wetland. Water will be placed back into the channel
downstream of the Puget Drive crossing, right at the outfall plunge pool. Less than 5 feet of the downstream
channel may be dewatered during construction.
There are no species of local importance, priority species, or endangered, threatened, sensitive or
candidate species mapped, known to occur or observed at the project area. There will be no impacts to the
existing condition of the stream channel and its riparian buffer.
File No. 0180-030-01
Reid Middleton | December 8, 2016 Page 7
SUMMARY
The proposed project will repair a degraded culvert that crosses Northstream Creek under Puget Drive. The
creek flows through additional culverts upstream of the culvert remediation area, nullifying impacts from
dewatering to the upstream channel. Following Figure 23.90.000, located at the end of EMC chapter 23.90,
(City of Edmonds Critical Areas Compliance Requirements - FWHCA), this report has described the creek
and shown that the project avoids impacts to the stream and its buffer. There will be no project activities
or potential impacts occurring near the upstream channel and its associated wetland, no wetland
delineation or rating was conducted for this regulated critical area.
Sincerely,
GeoEngineers, Inc.
Adam L. Wright Joseph O. Callaghan, PWS
Staff Biologist Associate Environmental Scientist
ALW:JOC:tln
Attachments:
Figure 1. Vicinity Map
Figure 2. Northstream Creek Map
Appendix A. Preliminary Construction Drawings
One copy submitted
Disclaimer: Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a copy
of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record.
File No. 0180-030-01
SITE
µ
2,00002,000
Feet
Vicinity Map
Notes:
1. The locations of all features shown are approximate.
Northstream Culvert Repair
2. This drawing is for information purposes. It is intended to assist in
showing features discussed in an attached document. GeoEngineers, Inc.
Edmonds, Washington
cannot guarantee the accuracy and content of electronic files. The master
file is stored by GeoEngineers, Inc. and will serve as the official record of
this communication.
Figure 1
Data Source: Mapbox Open Street Map, 2016
Projection: NAD 1983 UTM Zone 10N
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Preliminary Construction Drawings
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8410 154 Avenue NE
th
Redmond, Washington 98052
425.861.6000
December 12, 2016
Reid Middleton, Inc.
728 134 Street, Suite 200
th
Everett, Washington 98204
Attention: Julian Dodge
Subject: Geologic Hazards Assessment
Northstream Culvert Repair
Edmonds, Washington
File No. 0138-030-00
INTRODUCTION
This report presents a summary of our geologic hazards assessment for the Northstream Culvert Repair
project located along Puget Drive in Edmonds, Washington. A vicinity map of the site area is provided as
Figure 1. GeoEngineers, Inc. (GeoEngineers) is providing additional critical areas and permitting support for
the project per the requirements defined in the Edmonds City and Community Development Code (ECDC)
section 23.90.020. The results of those services are summarized in a separate report.
GEOLOGIC HAZARDS
Geologic hazardous areas are defined in Chapter 23.80 of the ECDC in three separate categories:
(1) erosion hazards, (2) landslide hazards, and (3) seismic. A description of each hazard and their relevance
to the project site are discussed in the following sections.
Erosion
Erosion hazards are defined in the regulations as areas with slopes of 15 percent or greater containing
soils which have moderate to very severe rill and inter-rill erosion hazard according to the mapped
description of soil units of the United States Department of Agriculture Soil Conservation Service (SCS)
Soil Classification System. Some of these soils include Alderwood, Alderwood/Everett, and Everett soils.
Both the Alderwood and Alderwood/Everett series are mapped on the property and subject to erosion.
However, based on the Temporary Erosion and Sediment Control (TESC) plans prepared by Reid Middleton
and the limited grading activity required for the storm pipe on 12 Avenue North, in our opinion the erosion
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hazard will be properly mitigated for the project.
Reid Middleton, Inc. | December 12, 2016 Page 2
Landslide Activity
Landslide hazard areas are defined as areas subject to landslides based on a combination of geologic,
topographic, and hydrologic factors. They include areas susceptible with any combination of soil, slope
inclination, structure, hydrology, or other factors. There are several areas and conditions specifically
included in the ECDC:
areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence
and landslide hazard area as identified in the 1979 report by Robert Lowe Associates and
amended by the 1985 report of GeoEngineers, and further discussed in the 2007 report by Landau
Associates;
coastal areas mapped as class u (unstable), uos (unstable old slides), and urs (unstable recent
slides) in the Department of Ecology Washington coastal atlas;
areas designated as quaternary slumps, earthflows, mudflows, or landslides on maps published by
the United States Geological Survey or Washington State Department of Natural Resources.
any slope of 40 percent or steeper than exceed a vertical height of 10 feet over a 25-foot horizontal
distance.
any slope with all three of the following characteristics:
slopes steeper than 15 percent;
hillsides intersecting geologic contacts with a relatively permeable sediment overlying a
relatively impermeable sediment; and
springs or groundwater seepage;
any area potentially unstable as a result of rapid stream incision or steam bank erosion;
any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by
debris flow or deposition of stream-transported sediments; and
any slopes that have been modified by past development activity that still meet the slope criteria.
Steep slopes are present on the sides of the creek, and on both sides of Puget Drive. Geologic maps of the
area indicate subsurface soils consist primarily of advance outwash in the immediate vicinity, and glacial
till to the east. Advance outwash is typically clean sand in the area, with increasing gravel content in higher
elevations.
The advance outwash has been glacially consolidated and is dense to very dense with a high internal friction
angle and low cohesion. Surficial sections of the material are subject to calving when dried and exposed to
weathering, but the soil typically has a maximum stable angle of repose ranging from about 1.25H:1V
(horizontal to vertical) to 1.5H:1V. No recent landslide or erosional features were observed during our
reconnaissance. With the exception of older deciduous trees, the trees are largely vertical along the slope.
We did not observe indications of seepage or recent slope movements in the areas of the proposed
improvements. In our opinion, future slope instability will likely not encompass the proposed new culvert
rehabilitation area provided the construction notes and TESC plans are accomplished as specified on the
plans.
File No. 0138-030-01
SITE
µ
2,00002,000
Feet
Vicinity Map
Notes:
1. The locations of all features shown are approximate.
Northstream Culvert Repair
2. This drawing is for information purposes. It is intended to assist in
showing features discussed in an attached document. GeoEngineers, Inc.
Edmonds, Washington
cannot guarantee the accuracy and content of electronic files. The master
file is stored by GeoEngineers, Inc. and will serve as the official record of
this communication.
Figure 1
Data Source: Mapbox Open Street Map, 2016
Projection: NAD 1983 UTM Zone 10N
AA
PPENDIX
Report Limitations and Guidelines for Use
Reid Middleton, Inc. | December 12, 2016 Page A-1
APPENDIX A
REPORT LIMITATIONS AND GUIDELINES FOR USE
1
This appendix provides information to help you manage your risks with respect to the use of this report.
Read These Provisions Closely
It is important to recognize that the geoscience practices (geotechnical engineering, geology and
environmental science) rely on professional judgment and opinion to a greater extent than other
engineering and natural science disciplines, where more precise and/or readily observable data may exist.
To help clients better understand how this difference pertains to our services, GeoEngineers includes the
following explanatory “limitations” provisions in its reports. Please confer with GeoEngineers if you need to
know more how these “Report Limitations and Guidelines for Use” apply to your project or site.
Geotechnical Services are Performed for Specific Purposes, Persons and Projects
This report has been prepared for City of Edmonds and Reid Middleton for the Northstream Culvert
Rehabilitation Project specifically identified in the report. The information contained herein is not applicable
to other sites or projects.
GeoEngineers structures its services to meet the specific needs of its clients. No party other than the party
to whom this report is addressed may rely on the product of our services unless we agree to such reliance
in advance and in writing. Within the limitations of the agreed scope of services for the Project, and its
schedule and budget, our services have been executed in accordance with our agreement with
Reid Middleton dated February 25, 2016 and generally accepted geotechnical practices in this area at the
time this report was prepared. We do not authorize, and will not be responsible for, the use of this report
for any purposes or projects other than those identified in the report.
A Geotechnical Engineering or Geologic Report is based on a Unique Set of Project-Specific Factors
This report has been prepared for the Northstream Culvert Rehabilitation project. GeoEngineers considered
a number of unique, project-specific factors when establishing the scope of services for this project and
report. Unless GeoEngineers specifically indicates otherwise, it is important not to rely on this report if it
was:
not prepared for you,
not prepared for your project,
not prepared for the specific site explored, or
completed before important project changes were made.
For example, changes that can affect the applicability of this report include those that affect:
the function of the proposed structure;
Developed based on material provided by GBA, GeoProfessional Business Association; www.geoprofessional.org.
1
GeoEngineers, Inc.
File No. 0138-030-01
Reid Middleton, Inc.|December 12, 2016Page A-2
elevation, configuration, location, orientation or weight of the proposed structure;
composition of the design team; or
project ownership.
If changes occur after the date of this report, GeoEngineers cannot be responsible for any consequences
of such changes in relation to this report unless we have been given the opportunity to review our
interpretations and recommendations. Based on that review, we can provide written modifications or
confirmation, as appropriate.
Environmental Concerns are Not Covered
Unless environmental services were specifically included in our scope of services, this report does not
provide any environmental findings, conclusions, or recommendations, including but not limited to, the
likelihood of encountering underground storage tanks or regulated contaminants.
Subsurface Conditions Can Change
This geotechnical or geologic report is based on conditions that existed at the time the study was performed.
The findings and conclusions of this report may be affected by the passage of time, by man-made events
such as construction on or adjacent to the site, new information or technology that becomes available
subsequent to the report date, or by natural events such as floods, earthquakes, slope instability or
groundwater fluctuations. If more than a few months have passed since issuance of our report or work
product, or if any of the described events may have occurred, please contact GeoEngineers before applying
this report for its intended purpose so that we may evaluate whether changed conditions affect the
continued reliability or applicability of our conclusions and recommendations.
Geotechnical and Geologic Findings are Professional Opinions
Our interpretations of subsurface conditions are based on field observations from widely spaced sampling
locations at the site. Site exploration identifies the specific subsurface conditions only at those points where
subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data
and then applied its professional judgment to render an informed opinion about subsurface conditions at
other locations. Actual subsurface conditions may differ, sometimes significantly, from the opinions
presented in this report. Our report, conclusions and interpretations are not a warranty of the actual
subsurface conditions.
Geotechnical Engineering Report Recommendations are Not Final
We have developed the following recommendations based on data gathered from subsurface
investigation(s). These investigations sample just a small percentage of a site to create a snapshot of the
subsurface conditions elsewhere on the site. Such sampling on its own cannot provide a complete and
accurate view of subsurface conditions for the entire site. Therefore, the recommendations included in this
report are preliminary and should not be considered final.
finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers
cannot assume responsibility or liability for the recommendations in this report if we do not perform
construction observation.
GeoEngineers, Inc.
File No. 0138-030-01
Reid Middleton, Inc.|December 12, 2016Page A-3
We recommend that you allow sufficient monitoring, testing and consultation during construction by
GeoEngineers to confirm that the conditions encountered are consistent with those indicated by the
explorations, to provide recommendations for design changes if the conditions revealed during the work
differ from those anticipated, and to evaluate whether earthwork activities are completed in accordance
with our recommendations. Retaining GeoEngineers for construction observation for this project is the most
effective means of managing the risks associated with unanticipated conditions. If another party performs
field observation and confirms our expectations, the other party must take full responsibility for both the
observations and recommendations. Please note, however, that another party would lack our project-
specific knowledge and resources.
A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation
Misinterpretation of this report by members of the design team or by contractors can result in costly
problems. GeoEngineers can help reduce the risks of misinterpretation by conferring with appropriate
members of the design team after
plans and specifications, participating in pre-bid and preconstruction conferences, and providing
construction observation.
Do Not Redraw the Exploration Logs
Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation
of field logs and laboratory data. The logs included in a geotechnical engineering or geologic report should
never be redrawn for inclusion in architectural or other design drawings. Photographic or electronic
reproduction is acceptable, but separating logs from the report can create a risk of misinterpretation.
Give Contractors a Complete Report and Guidance
To help reduce the risk of problems associated with unanticipated subsurface conditions, GeoEngineers
recommends giving contractors the complete geotechnical engineering or geologic report, including these
When providing the report, you should preface it with a clearly
written letter of transmittal that:
advises contractors that the report was not prepared for purposes of bid development and that its
accuracy is limited; and
encourages contractors to confer with GeoEngineers and/or to conduct additional study to obtain
the specific types of information they need or prefer.
Contractors are Responsible for Site Safety on Their Own Construction Projects
s, methods,
schedule or management of the work site. The contractor is solely responsible for job site safety and for
managing construction operations to minimize risks to on-site personnel and adjacent properties.
Information Provided by Others
GeoEngineers has relied upon certain data or information provided or compiled by others in the
performance of our services. Although we use sources that we reasonably believe to be trustworthy,
GeoEngineers cannot warrant or guarantee the accuracy or completeness of information provided or
compiled by others.
GeoEngineers, Inc.
File No. 0138-030-01