HomeMy WebLinkAboutLUA15-000761_Biological Assessment_Tran Stream
7K Environmental
Kate Knox Machata
7K Environmental
4062 NE 87th St.
Seattle, WA 98115
Kris Sorensen
Planning Division,
Community & Economic Development
City of Renton
1055 South Grady Way
Renton, WA 98057
August 31, 2015
(Revised September 17, 2015)
RE: Buffer Enhancement Permit Application for Alyssa and Tony Tran (Parcel number 334210‐
3365)
Dear Mr. Sorensen:
With this letter report, we are requesting critical areas exemption from the City of Renton for proposed
buffer enhancement work in parcel 334210‐3365. Additional materials are attached to meet permit
submittal requirements as indicated on the Exemption from Critical Areas Regulations checklist.
Project Introduction
In August 2015, 7K Environmental was contracted to assist Alyssa and Tony Tran with permit
preparation for buffer enhancement plantings which will also provide visual privacy from adjacent
properties and help to limit trespass in the stream buffer adjacent to their home. This report has been
prepared to describe existing conditions on the site, discuss existing ecological functions in the stream
buffer, and provide details of the proposed stream and buffer enhancement activities along the
unnamed stream that crosses their property. This letter report is designed to serve as the Standard
Stream Study and Biological Assessment per Renton Municipal Code (RMC) 4‐8‐120D.
Project Site Description and Landscape Position
The Tran property (Parcel number 334210‐3365) is located at 2816 Kennewick Place NE in the City of
Renton (see Figure 1 provided by City of Kent). This parcel lies approximately 600 feet east of I‐405 in
the developed urban neighborhood of Kennydale. A small, unnamed tributary of May Creek (See Figure
2) with an average ordinary high water (OHW) width of 2 feet lies near the northern edge of the Tran
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property. No wetlands were observed on the property or adjacent to the property boundary as far as
was visible from the Tran property.
The unnamed tributary has a small watershed (estimated to be about 40 acres in size) upstream from
the subject parcel. Approximately 80 feet upstream from the parcel, the stream is impounded by a 2‐3
foot high concrete dam. A 24‐inch diameter CMP culvert carries water west under NE 29th Street. The
stream conveys water approximately 700 feet north and west to its confluence with May Creek which
joins Lake Washington approximately one mile further north and west. May Creek is known to be a fish
bearing stream with documented presence with possible spawning for fall Chinook and coho salmon and
winter run steelhead. No fish presence has been noted in the unnamed tributary on the Tran property
(SalmonScape 2015).
Site History
The Tran’s purchased the subject parcel in 2011. The existing dilapidated structure was demolished in
2012, and site grading was completed to allow for construction of a new residence under the new single
family residence combination permit number CP12039. Existing uses in the vicinity of the channel prior
the new construction (See Figure 2) included a home with landscaped yard including a swimming pool,
fence, and rock terrace retaining wall which paralleled the channel, approximately 15 feet to the south.
Regulatory Framework
The regulatory framework for work along the stream and in its buffer must consider federal, state and
local level jurisdiction.
Federal Jurisdiction
As a tributary of May Creek which flows to Lake Washington, the unnamed tributary to May Creek on
the Tran property is considered a Water of the United States, and thus will be regulated under Section
404 of the Clean Water Act. The U.S. Army Corps of Engineers (ACOE) regulates work below Ordinary
High Water (OHW). Federal permits may be required for any work that occurs below OHW.
The ACOE Nationwide permit 18 allows for minor discharges as follows:
18. Minor Discharges. Minor discharges of dredged or fill material into all waters of the United
States, provided the activity meets all of the following criteria: (a) The quantity of discharged
material and the volume of area excavated do not exceed 25 cubic yards below the plane of the
ordinary high water mark or the high tide line; (b) The discharge will not cause the loss of more
than 1⁄10‐acre of waters of the United States; and (c) The discharge is not placed for the
purpose of a stream diversion. Notification: The permittee must submit a pre‐construction
notification to the district engineer prior to commencing the activity if: (1) The discharge or the
volume of area excavated exceeds 10 cubic yards below the plane of the ordinary high water
mark or the high tide line, or (2) the discharge is in a special aquatic site, including wetlands.
(See general condition 31.) (Sections 10 and 404).
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If any work in the channel is proposed and is limited to streambank stabilization and has discharge
below 10 cubic yards and does not result in stream diversion, no ACOE pre‐construction notification
should be needed.
State Jurisdiction
The Washington State Department of Ecology regulates water quality under Section 401of the Clean
Water Act. If the project impacts are less than (temporary or permanent impacts) ½ acre of wetland, no
individual 401 review is required. An Hydraulic Project Approval (HPA) would be required for any work
below OHW. Most construction projects or activities in or near state waters are required to obtain an
HPA from Washington Department of Fish and Wildlife (WDFW) which is designed to ensure projects
meet state conservation standards to protect fish life. Larry Fisher is the regional wildlife biologist. An
HPA application can be completed by filling out the online application form located at the website
address http://wdfw.wa.gov/licensing/hpa/.
Local Jurisdiction: City of Renton
Local code provides for protection of critical areas including streams and their buffers. Based on current
2015 code guidance, the unnamed tributary crossing the Tran property is a City of Renton Stream Class 4
(See Figure 3). Class 4 streams have buffer use restrictions for a standard width of 35 feet. Per the
code, these buffer widths assume degraded buffers with no enhancement. Code allows that narrower
buffers may be permitted under restored or improved buffers that restore and protect riparian
functions. This parcel had a previous legal alteration that occurred within the buffer decades ago in the
form of a retaining wall and fence.
Existing Conditions
The stream and its buffer at this property exhibit characteristics of a heavily urbanized its riparian
environment (see Photographs 1‐3). The stream lies at the northern edge of the Tran property. The
Tran property boundary extends a minimum of 5 feet and up to approximately 13 feet north of the
stream. Adjacent land use on the parcel to the north of the channel is a residence with fenced yard. A
line of western red cedar trees parallels the property line. Vegetation in the herb and shrub layer on the
north side of the stream is sparse due to the dense canopy cover formed by the line of cedar trees (see
Photograph1). Many lower branches of the cedars were cleared by the neighbor in late July or early
August 2015 which has opened up the understory to some extent along the western edge of the
properties. Vegetation on the south bank of the stream is currently maintained lawn up to a rock
terrace which effectively stabilizes the slope leading up to the home.
The stream bed lies in swale that is approximately 6 ‐8 feet lower than surrounding topography. A
topographic map showing 2 foot contours in the vicinity of this property is provided in Figure 4. The
stream is approximately 2 feet wide at OHW along the length of the channel on the Tran property
(approximately 80 linear feet). Along much of the stream, the banks were stabilized with reused
concrete riprap that appears to have been placed at least several decades ago. Hollow concrete blocks
were placed more recently along 27 linear feet of the northern bank of the channel. The block is
proposed to be removed and banks will be stabilized with rushes and/or sedges. The stream bed
substrate is composed of a mix of sand and gravel with some silt. Some of the gravel‐sized material is
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chunks of angular broken concrete. Flows are regulated by a dam on private property that is about 100
feet upstream from the Tran property. A culvert at the west edge of the property conveys water under
NE 29th Street and off the property.
Existing Stream Buffer Functions
Intact riparian buffers provide important ecological functions that can be described as supporting
Hydrology, Biogeochemistry, Plant Community and Habitat/Faunal Support systems (following Brinson
et al. 1993, Brinson et al. 1995, and AC Kindig 2003.). Riparian buffers in an urban environment are
commonly degraded from decades of human encroachment and provide ecological functions to varying
degrees. Hydrology functions provided by riparian buffers may include maintenance of water quality to
downstream waters including stream temperature regulation, and regulation of water quantity from
delaying or retaining precipitation and stormwater runoff. Biogeochemistry functions provided by urban
riparian buffers may include regulation of sediment and nutrient inputs to downstream waterways
through streambank stabilization and filtration of runoff from upgradient systems. Riparian buffers may
support diverse native and/or non‐native plant communities. These plant communities may provide
limited habitat opportunities for aquatic species, small birds or mammals, and beneficial insects with life
history strategies that allow survival in narrow corridors within the urban environment. In this urban
corridor, the primary goals for protecting and enhancing riparian buffers are to support cleaner water,
stream temperature regulation, stream bank stabilization, and to a limited degree provide improved
habitat for aquatic species and wildlife that can survive in the urban environment.
Ecological functions provided by the riparian buffer along the unnamed tributary to May Creek are
described under existing conditions in the sections below. The next section describes the proposed
buffer restoration and enhancement activities and assesses potential for improvement in ecological
functions that may result from this work.
Hydrology Functions
Under existing conditions, the stream and its buffer provide minimal to no hydrology functions with
enhance water quality or regulating stormwater runoff. Tree canopy cover occurs only on the northern
bank of the channel. The channel is recessed within the shallow ravine and is partially shaded by these
trees during mid‐summer. These trees also intercept some precipitation to help reduce storm runoff
entering the stream. The channel banks are nearly vertical with riprap lining much of the channel on
both sides. Sediment transport may occur to the stream from bare soil below the cedar canopy. Intact
lawn grass on the southern bank reduces potential for transport of sediment to the stream from
erosion. The existing retaining walls upslope from the stream reduce precipitation runoff from the
upslope urban environment.
Biogeochemistry Functions
Under existing conditions, the stream and its buffer provide low to moderate biogeochemistry
functioning. There is minimal vegetation in contact with the stream during normal flows due to riprap
along steep channel banks. The plant community is maintained lawn to the south and bare herb layer
on the north and thus there is minimal potential for nutrient uptake and transformations in the riparian
buffer.
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Plant Community Functions
The cedar trees paralleling the property line are a native tree species. The rest of the riparian buffer is
dominated by non‐native, predominantly herbaceous species including weeds, lawn grasses, and
horticultural plants. The northern bank has only sparse vegetation in the understory. Under existing
conditions, the stream and its buffer provide low to moderate plant community functions. The cedar
tree canopy to the north of the stream provides a slight potential for insect and litterfall input to the
creek that could support downstream aquatic food web cycling.
Faunal Support/Habitat Functions
Minimal to no native faunal support or habitat functions are provided within the stream or its riparian
buffer under its existing conditions. No fish are known to occur within this small, 2‐foot wide, unnamed
tributary. There is little habitat structure within the channel due to the straight, rip rap lined bank. The
sparse understory plant community and adjacent developed areas limit potential species that could
utilize this habitat. However, ducks and deer have been seen in this riparian corridor (A. Tran, Pers.
Comm. 2015).
Proposed Project
Planting Plan
The proposed planting plan is provided in Figure 5. A row of native plants will be installed along the
north property boundary to provide dual function of designed visual privacy and limiting trespass and
restoring native plant community functions. The row of tall Oregon grape (Mahonia aquifolium) will be
planted at 3‐foot spacing in a row that parallels the property boundary and south of the row of cedar
trees per Figure 5. The proposed planting area occupies approximately 110 square feet in the stream
buffer.
Removal of Concrete Block
Approximately 27 linear feet of vertical concrete block will be removed from the north bank of the
channel. This stream bank in this area will be restored to soft banks and stabilized with native rushes
(Juncus effusus, Juncus acuminatus) and/or native sedges (Carex utriculata, Carex lenticularis var.
lipocarpa).
Construction Sediment and Erosion Control Measures
Construction best management practices will be used during plant installation to prevent discharge of
sediment to the stream. Mulch will be applied at the base each shrub as needed. Fertilizers should not
be used given proximity to the stream. In‐stream work to remove the bank armoring block will be done
using work area isolation to minimize sediment disturbance. A typical for work area isolation is shown
in Figure 6.
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Analysis of Project Effects
The scale of the proposed planting project is very small and thus potential lift for ecosystem functions is
limited. The proposed project will provide minor, incremental positive impact to ecosystem functioning
in the riparian buffer.
Hydrology Functions
Increasing shrub canopy cover in the riparian buffer will provide incremental benefits to regulation of
stream temperatures along this 80 foot long reach of the stream. However, as the proposed planting is
on the north side of the channel, minimal additional shading will be provided. Some of the shrubs may
overhang the channel as they grow larger. Additional vegetation and development of shrub and herb
canopy layers below the tree layer will intercept additional precipitation during storm events. Removal
of the concrete block and restoration of herbaceous vegetation on the stream bank may provide minor
reduction in stream velocity to delay stormwater relative to current condition with the concrete block.
The proposed project will result in minor and incremental increase in hydrology functions in the stream
and its buffer.
Biogeochemistry Functions
Increasing plant cover and diversifying the plant community throughout the riparian buffer will
incrementally improve biogeochemical cycling opportunities in this short reach along the stream.
Restoring the channel bank to soil with native herbaceous vegetation for bank stabilization will provide
minor opportunity for nutrient retention along the channel. Due to the small area and single native
shrub species proposed, minimal changes to biogeochemical functioning in the buffer will be realized
from the proposed project.
Plant Community Functions
The proposed project will incrementally increase the native plant diversity within a portion of the buffer
by developing an understory shrub canopy cover below the cedar trees. This shrub canopy cover may
provide greater shade cover over the stream that could help to regulate stream temperatures.
Installing the row of native plants in the buffer is designed to limit human access to the stream and area
immediately adjacent to the stream. The proposed project will have a minor and incremental increase
in plant community functions in the stream buffer.
Faunal Support/Habitat Functions
Although only a very small incremental increase in native plant diversity is proposed, increased diversity
in native plant community will incrementally increase the opportunities for foraging birds and beneficial
insects. There are limited opportunities for improving faunal support functions due to the heavily urban
environment in the surrounding landscape. Due to the scale of this project there will be little to no
change in faunal support/habitat functions due to the proposed planting project.
Recommended Project Conditions
• No pesticides or fertilizers shall be used north of the fence or rock retaining wall. Grass north of
the rock wall should be left to grow and should not be mowed.
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• If shrubs die, replant in place with the same species or alternate native species from the list in
Appendix A.
Conclusions
In conclusion, the proposed project includes planting shrubs and herbs along approximately 80 linear
feet of riparian buffer for an unnamed tributary of May Creek. Approximately 20 native shrubs [tall
Oregon grape (Mahonia aquifolium)] will be installed in the riparian buffer covering approximately 110
square feet. Bank armoring will be removed from a section of the stream. Sediment and erosion
control measures are proposed to protect water quality in the stream during the installation and
establishment period. The proposed project will provide minor incremental lift in ecosystem functions
along this short reach of stream.
We are happy to discuss the proposed project in further detail. Please contact the homeowner Alyssa
Tran at 206‐307‐1874 and/or Kate Knox Machata at 206‐683‐7229 or via email at
a.kate.knox@gmail.com if additional information is needed.
Sincerely,
Kate Knox Machata, M.S.
Professional Wetland Scientist #2104
7K Environmental
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References
AC Kindig & Company and Cedarock Consultants. 2003. City of Renton Best Available Science Literature
Review and Stream Buffer Recommendations. Prepared for the City of Renton dated February 27, 2003.
Brinson, M.M. 1993. A hydrogeomorphic classification for wetlands. Wetlands Research Program
Technical Report WRP‐DE‐4. Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg,
MS.
Brinson, M. M., Hauer, F. R., Lee, L. C., Nutter, W. L., Rheinhardt, R. D., Smith, R. D., and Whigham, D.
(1995). "A guidebook for application of hydrogeomorphic assessments to riverine wetlands," Technical
Report WRP‐DE‐11, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. NTIS No. AD
A308 365.
Federal Register. 2012. Nationwide Permits, Conditions, Further Information, and Definitions . Vol. 77,
No. 34 Issued Tuesday, February 21, 2012.
King County IMAP. 2015. Accessed online at: www.kingcounty.gov/operations/GIS/Maps/iMAP.aspx
Page 9
FIGURES
Figure 1. Neighborhood detail map prepared by City of Renton for inclusion with permit application.
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Figure 2. 2009 aerial imagery of parcel (Source: King IMap. 2009.)
Figure 3. City of Renton stream class mapping showing Tran property on a class 4 stream. Source:
http://rentonwa.gov/uploadedFiles/Business/EDNSP/projects/wtrclass.pdf
Stream
Tran property
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Figure 4. 2 foot contours in the vicinity of the Tran property. (Contour layer source is City of Renton GIS
Data available at: http://rentonwa.gov/government/default.aspx?id=29887)
LY &TRAN RESIDENCE
2816 KENNEWICK PL NE RENTON WA 98056
Parcel Number:334210-3365
LEGAL DESCRIPTION:
HILLMANS LAKEGARDENOFEDEN #1PARTOFLOT51VOL.11,PG.63
THAT PORTION OF THE __________,___________,SECTION _____TOWNSHIP_____NORTH,RANGE ____EAST,W.M.SW 1/4 SE 1/4 32 24 05
87.61'
82.90'
KENNEWICK PL NE149.33'NE29thST150.00'TREE SITE PLAN
RESIDENCE AREA
39'
35'
4'
13'
17'
7'ROCKTERRACE
FENCE
STREAM
APPX.15'
Tall Oregon Grape
at 3-4 foot spacing
(These dimensions are appx.
measurements on Land Survey.)
Bank Armoring to be
removed
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Figure 6. Typical for work area isolation of the north stream bank during removal of concrete block to
protect water quality. Figure from http://www.catchmentsandcreeks.com.au/docs/IB‐1.pdf
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PHOTOGRAPHS
Photograph 1. Looking east from northwest corner of the Tran property along unnamed stream.
Approximate
Property
Boundary
Proposed
Planting Area
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Photograph 2. Looking east toward dam on neighbor’s property in the background.
Photograph 3. Looking northeast toward neighboring property and fence beyond line of cedar trees.
Concrete riprap has been in place along most of the stream for several decades or more.
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Appendix A
Additional Native shrub species that may be installed if replanting is required in the future
include:
Shrubs
Acer circinatum (vine maple)
Corylus cornuta (Hazelnut)
Holodiscus discolor (Oceanspray)
Lonicera involucrata (Black twinberry)
Mahonia aquifolium (Tall Oregon grape)
Rhododendron macrophyllum (Pacific rhododendron)
Ribes sanguineum (Red flowering currant)
Rosa pisocarpa (Clustered wild rose)
Rosa gymnocarpa (Bald hip rose)
Rubus spectabilis (Salmonberry)
Cornus sericea (Red twig dogwood )
Rubus parviflorus (Thimbleberry)
Vaccinium ovatum (Evergreen huckleberry)
Low shrubs
Gaultheria shallon (Salal)
Arctostaphylos uva‐ursi (Bearberry or Kinnickinnick)
Understory herbaceous species
Polystichum munitum (swordfern)
Fragaria virginiana (wild strawberry)
Stream bank planting herbaceous species
Juncus effusus
Juncus acuminatus
Carex utriculata
Carex lenticularis var.lipocarpa