HomeMy WebLinkAboutTIR Complete (rev 8-8-2016)
TABLE OF CONTENTS
SECT ION 1 - PROJECT OVERVIEW
FIGURE 1
TIR Worksheet
FIGURE 2
Site Location
FIGURE 3
Drainage Basins, Sub-Basins & Site Characteristics
SECTION 2 - CONDITIONS AND REQUIREMENT SUMMARY
SECTION 3 – OFFSITE ANALYSIS
SECTION 4 – FLOW CONTROL & WATER QUALITY ANALYSIS
SECTION 5 – CONVEYANCE SYSTEM ANALYSIS & DESIGN
SECTION 6 – SPECIAL REPORTS & STUDIES
SECTION 7 – OTHER PERMITS
SECTION 8 – TESC ANALYSIS & DESIGN
SECTION 9 – BOND QUANTITIES, FAC. SUMMARY & DEC. OF COVENANT
SECTION 10 – OPERATIONS & MAINTENANCE MANUAL
APPENDIX A – GEOTECHNICAL REPORT
APPENDIX B – ARBORIST REPORT
APPENDIX C – KCRTS ANALYSIS
Site Address: 2525 Aberdeen Ave NE, Renton WA, 98056
King County Tax Parcel: 334390-2000, 334390-2021
I. PROJECT OVERVIEW
This project involves the development of two existing parcels with a total area of 0.61 acre into
four single-family lots. A boundary line adjustment will be made to the existing two parcels and
the larger of the two adjusted parcels will then be subdivided into three lots for a total of four
lots. The boundary line adjustment and 4-lot short plat will occur concurrently. The first parcel
(#334390-2000) contains an existing home with various retaining walls, driveway, concrete
walk, shed, carports, grass/brus h and about 54 significant trees. The second parcel (#334390-
2021) contains a few small concrete pads, an existing shed and some retaining wall. The
majority of the site slopes downward toward the east property limit at slopes of approximately
2% to 40%. A small portion along the north and west property limits drain toward the north and
northwest at slopes ranging from 17% to 71%. Per the Natural Resources Conservation Service
Soil Survey, the site is underlain with Indianola loamy sand. A geotechnical engineering study
was also performed to verify infiltration and the report has been attached.
King County
Date: 2/24/2016 Notes:
The information included on this map has been compiled by King County staff from a variety of sources and is
subject to change without notice. King County makes no representations or warranties, express or implied,
as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended
for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or
consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse
of the information contained on this map. Any sale of this map or information on this map is prohibited except by
written permission of King County.
Vicinity Map
City of Renton Storm Sewer Atlas
SITE
II. CONDITIONS AND REQUIREMENTS SUMMARY
Conditions and Requirements
Provide Full Infiltration per 2009 KC SWDM Section C.2.2:
Section C.2.2.2 – Minimum Design Requirements for Full Infiltration.
Section C.2.2.1 and C.2.2.4
o Figure C.2.2.C
CORE REQUIREMENTS
Core Requirement #1: Discharge at the natural Location
Runoff generally sheet flows across the site in an easterly direction. Refer to the Level 1
Downstream Analysis in Section 3 for a complete description of the existing drainage path.
Core Requirement #2: Offsite Analysis
An offsite drainage analysis is provided in Section 3 of this TIR. Level 1 Drainage Analysis has
been prepared and no problems identified.
Core Requirement #3: Flow Control
This project qualifies for Full Drainage Review. The proposed project site will produce more
than 5,000 square feet of new impervious surfaces. Flow control BMPs for infiltration will
provide the required flow control for proposed improvements.
This site has two distinct drainage areas (TD1 & TD2) and various flow control BMP’s will be
used to control the site’s runoff. TDA-2 at the northwest area of the site consists of green space
and a portion of the paved access driveway. At TDA-1, storm water run-off tributary to the
paved access driveway will be allowed to infiltrate through the use of two infiltration basins. The
remainder of the site area will consist of 3 new homes, new driveways and an access drive.
Mitigation of surface run -off for these areas will be performed through the use of filter strips for
the driveways and infiltration basins the remaining impervious areas.
Core Requirement #4: Conveyance System
Conveyance system analysis and design is provided in Section 5 of the TIR.
Core Requirement #5: Erosion and Sediment Control
A temporary erosion and sediment control (TESC) plan provides BMPs to be implemented
during construction.
Core Requirement #6: Maintenance and Operations
See Section X – Operation and Maintenance Manual
Core Requirement #7: Financial Guarantees and Liability
The owner will arrange for any financial guarantees and liabilities required by the permit.
Core Requirement #8: Water Quality
Refer to section 8 of this TIR for Water Quality Analysis and Design
SPECIAL REQUIREMENTS:
Special Requirement #1: Other Adopted Area-Specific Requirements
Critical Drainage Area – N/A
Master Drainage Plan – N/A
Basin Plan – This site is located within the May Creek drainage basin
Lake management Plan – N/A
Shared Facility Drainage Plan – N/A
Special Requirement #2: Floodplain/Floodway Delineation
The limits of this project do not lie in a 100 -year floodplain
Special Requirement #3: Flood Protection Facilities
This special requirement is required for projects with Class 1 or 2 streams with an existing flood
protection facility. The site does not cont ain any streams and is therefore not applicable.
Special Requirement #4: Source controls
This project is a 4-lot single-family residential project and this requirement is not applicable.
Special Requirement #5: Oil Control
This project is not considered high-use in need of oil control.
III. OFF-SITE ANALYSIS
Downstream Drainage Analysis
Existing Conditions
Encompass Engineering & Surveying performed a level I downstream analysis for this project on
both TDA’s. There are 2 threshold discharge areas on these parcels. Runoff generally drains in
the northeast direction across both parcels. A small portion of surface run-off drains toward the
north/northwest limits of parcel 3343902021.
Northeast TDA #1 (Approximate Area = 24418.50 sf):
Runoff draining toward the northeast discharge location will sheet flow toward the west ern edge
of Aberdeen Avenue and flow north along the road until it reaches a Catch Basin, located at
point (A), which is approximately 10 feet away from the discharge location. From there, the
flow travels along the closed conveyance system for approximately 30 feet to a second catch
basin located at point (B), located along the edge of Aberdeen Ave. Fr om there, the flow
continues northward until it reaches a manhole at point (C) which is located at the intersection of
Aberdeen Ave and NE 26th Place. The flow then travels westward toward a stormwater
detention facility at point (E) which is located at the western end of NE 26th Place. The flow is
then conveyed westward toward catch basins located at point (F), point (G) and point (H). After
point (H), the flow is conveyed through the closed conveyance system to point (I) which is
located within the east ern end of NE 26th Street. At that point, the flow is directed northward
until it reaches a manhole located at point (J) and then flows into a manhole at point (K). The
flow then travels northwest until it reaches a manhole at point (L) which is located at the
intersection of NE 28th Street and Kennewick Pl NE and which is more than one-quarter mile
downstream of the site’s discharge location. The flow is then conveyed northwest through a
series of storm sewer pipes until it reaches NE 30th Street and then conveyed east/northeast until
it discharges into May Creek which ultimately drains into Lake Washington. There were no
apparent downstream drainage problems or erosion issues identified during the downstream
drainage analysis.
North/Northwest TDA #2 (Approximate Area = 1971.25 sf):
The Runoff discharg ing from the site at the north and northwest property limits are conveyed to a
stormwater detention facility through sheet flow toward NE 26th Place where the stormwater is
collected into a stormwater inlet located at point (E), which is within the south curb-line of NE
26th Place and then conveyed into the stormwater detention facility, which is located at the
western end of NE 26th Place. At this point, the flow has converged with the flow from the
Northeast Discharge Location (TDA-1). Since the 2 threshold discharge areas converge within
¼ mile, it is considered a single discharge location. The combined flow is then conveyed toward
the west . There were no apparent downstream drainage problems or erosion issues identified
during the downstream drainage analysis.
Developed Conditions
Runoff from the proposed roof area within each new lot will be directed to basins for full
infiltration of all roof runoff. Proposed driveway runoff for each lot will be mitigated through
filter strips along the edge of each driveway. The access drive that will connect individual
driveways to Aberdeen Avenue will be constructed of permeable pavement with flow barriers
installed at 5.5 foot intervals to capture runoff and allow for full infiltration. The existing home
on the subject site was built in 1962 and will remain intact after the proposed improvements and
boundary line adjustment. Since the home was constructed prior to the implementation of water
quality and flow control requirements, runoff for the lot containing the existing home is not
required to be mitigated.
Photo 1: Stormwater inlet located near the northeast corner of the subject property
Storm Inlet
Photo 2: Curb Inlet located in South Curb-line of NE 26th Place
Photo 3: Stormwater Detention Facility located at the west end of NE 26th Place
Photo 4: Storm Manhole located in pavement of NE 26th Street
Photo 5: Storm Manholes located in pavement of NE 27th Street
Photo 6: Storm Manholes located in Kennewick Pl NE near intersection of NE 28th Street
IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN
Drainage Design
This project will involve adding approximately 1,186 sq-ft of new impervious surface in the
public R/W, so flow control is not being proposed for the improvements in the public R/W.
Runoff from the new frontage improvements will be routed into the existing CB/pipe storm
system in Aberdeen Avenue NE.
Infiltration BMP’s will be provided for new roof surfaces on the lots and for the access driveway
to allow for full infiltration of the runoff. New driveways for each lot will have a filter strip
located along the downstream edge of each to mitigate storm runoff. KCRTS analysis for the
proposed infiltration basins is shown in Appendix C.
The access driveway contains approximately 3,060 sq-ft of PGIS and approximate area for each
of the three individual driveways is 500 sq-ft each for a total of 4,560 of new PGIS which is
below the 5,000 sq-ft threshold for requirement of water quality treatment. Therefore, w ater
quality treatment will not be needed for this project.
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Since the small infiltration basins will allow for full infiltration up to a 100-year storm event, a
conveyance system analysis is not required as the flow rate through the proposed sewer would be
zero. The onsite conveyance system is only being provided to provide protection against an
infiltration device failure.
VI. SPECIAL REPORTS AND STUDIES
Geotechnical Engineering Report
Arborist Report
VII. OTHER PERMITS
Building permits will be required.
VIII. TESC ANALYSIS AND DESIGN
The potential for erosion within the site will be mitigated by use of erosion control measures
during clearing, grading, and site development activities. Filter fences will be installed along the
downhill perimeter of the site to protect adjacent properties from sediment -laden water. A
rocked construction entrance will be installed at the entrance to the site to protect mud from
entering the paved roadway. Stockpiles and exposed distur bed areas will be covered to protect
from erosion and sediment runoff.
Element 1: Mark Clearing Limits.
All clearing, grading, sensitive areas, and buffers will be clearly marked in the field prior to
construction in accordance to the plans and specifications. Prior to beginning land disturbing
activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and
their buffers, and trees that are to be preserved within the construction area. These shall be
clearly marked, both in the field and on the plans, to prevent damage and offsite impacts. Plastic,
metal, or stake wire fence may be used to mark the clearing limits.
Element 2: Establish Construction Access.
Construction access will be provided for the site. Driveway re-alignment should be completed
after all other construction is complete. Stabilize the construction access with rock per the
stormwater plans if the driveway is disturbed. Access points shall be stabilized with a pad of
quarry spalls, crushed rock, or equiva lent BMP prior to traffic leaving the construction site to
minimize the tracking of sediment onto all roads and accesses.
Element 3: Control Flow Rates.
Flow rates from the construction site are not expected to negatively impact the downstream
corridor. A temporary sediment pond is not being proposed as part of this project, however other
sediment retention BMPS are being proposed as part of Element 4. At all times, flow rates shall
be controlled for this project. Natural drainage patterns shall be protected as much as possible
during construction, and concentrated flow should not be permitted. Properties and waterways
downstream from development sites shall be protected from erosion due to increases in the
volume, velocity, and peak flow rate of stormwater runoff from the project site.
Element 4: Install Sediment Controls.
Silt fence should be used to protect all sensitive area slopes. Soils should be covered if not
worked for 7 days during the dry season or 2 days during the wet season. The street should be
swept each night or as required. If the minimum BMPs fail to retain sediment to the sight,
additional BMPs will be used.
Element 5: Stabilize Soils.
Soils shall be covered if not worked for 7 days during the dry season or 2 days during the wet
season. Soil stockpiles will be covered unless worked. Soil stockpiles shall be located away from
drain inlets and surface water discharge locations. Soil stockpiles shall be stabilized and covered
as needed or removed to an approved disposal site. Soils shall be stabilized at the end of the shift
before holidays or weekends if needed based on weather forecast.
Element 6: Protect Slopes.
The site has a steep even slope to the west property limit. Slope protection is anticipated. In the
event that erosion does occur along the edges of the project, energy dissipater (flow spreaders)
shall be used or the surface water will be routed away from the slopes.
Element 7: Protect Drain Inlets.
There are existing catch basins located downstream of the project. Filter fabric protection shall
be used for sediment control.
Element 8: Stabilize Channels and Outlets.
Existing or proposed channels or drainage outlets are not components of this project, thus
stabilization of these elements are not required.
Element 9: Control Pollutants.
Pollution generated from construction must be controlled at all times. Control of pollutants other
than sediments includes the following:
All pollutants other than sediments shall be handled and disposed of in a manner that
does not cause contamination of stormwater.
Cover, containment and protection from vandalism shall be provided for all chemicals,
liquid products, petroleum products, and non-inert wastes present on the project site.
Maintenance and repair of heavy equipment and vehicles involv ing oil changes, hydraulic
system drain down, solvent and de-greasing cleaning operations, fuel tank drain down
and removal, and other activities which may result in discharge or spillage of pollutants
to the ground or into stormwater runoff must be conducted using spill prevention
measures, such as drip pans. Contaminated surfaces shall be cleaned immediately
following any discharge or spill incident. Emergency repairs may be performed on-site
using temporary plastic placed beneath and, if raining, over the vehicle.
Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment
system or to the sanitary sewer, if available.
Element 10: Control De-Watering.
De-watering is not anticipated for the site. In the event that dewatering is necessary, storm shall
be treated such that sediment remains on site. This shall be done by routing the storm water
through a straw filter, silt fence, and/or sediment trap.
Element 11: Maintain BMPs.
BMPs shall be inspected monthly and after every significant storm event, Sediment shall be
removed from the BMPs as necessary for them to continue operating at the required performance
level. In the event that a BMPs has been damaged, it shall be replaced immediately.
Element 12: Manage the Project.
Co nstruction activities shall be phased such that the impact to the area will be kept at a
minimum. Coordination will occur with all utility agencies that are affected by this project.
BMPs shall be inspected regularly and after each significant storm event. The Contractor will
provide a Certified Erosion and Sediment Control Specialist. If for any reason a BMPs is not
sufficient for the project, additional BMPs will be installed.
IX. BOND QUANTITIES and DECLARATION of COVENANT
Bond Quantities
To be provided in Final Engineering
Facility Summaries
To be provided in Final Engineering.
Declaration of Covenant
Declaration of Covenant for maintenance will have to be approved and recorded.
X. OPERATION AND MAINTENANCE MANUAL
Operations and Maintenance Instructions for Basic Infiltration
Your property contains a stormwater management flow control BMP (best management practice)
called "basic dispersion," which was installed to mitigate the stormwater quantity and quality
impacts of some or all of the impervious surfaces or non-native pervious surfaces on your
property. Basic dispersion is a strategy for utilizing any available capacity of onsite vegetated
areas to retain, absorb, and filter the runoff from developed surfaces. This flow control BMP has
two primary components that must be maintained:
(1) The Infiltration devices from the developed surfaces
Your property contains a stormwater management flow control BMP (best management practice)
called "full infiltration," which was installed to mitigate the stormwater quantity and quality
impacts of some or all of the impervious surfaces on your property. Full infiltration is a method
of soaking runoff from impervious area (such as paved areas and roofs) into the ground. If
properly installed and maintained, full infiltration can manage runoff so that a majority of
precipitation events are absorbed. Infiltration devices, such as gravel filled trenches, drywells,
and ground surface depressions, facilitate this process by putting runoff in direct contact with the
soil and holding the runoff long enough to soak most of it into the ground. To be successful, the
soil condition around the infiltration device must be reliably able to soak water into the ground
for a reasonable number of years.
The infiltration devices used on your property include the following as indicated on the flow
control BMP site plan: gravel filled trenches, drywells, ground surface depressions. The
size, placement, and composition of these devices as depicted by the flow control BMP s ite plan
and design details must be maintained and may not be changed without written approval either
from the King County Water and Land Resources Division or through a future development
permit from King County. Infiltration devices must be inspected annually and after major storm
events to identify and repair any physical defects. Maintenance and operation of the system
should focus on ensuring the system's viability by preventing sediment -laden flows from
entering the device. Excessive sedimentation will result in a plugged or non-functioning facility.
If the infiltration device has a catch basin, sediment accumulation must be removed on a yearly
basis or more frequently if necessary. Prolonged ponding around or atop a device may indicate a
plugged facility. If the device becomes plugged, it must be replaced. Keeping the areas that drain
to infiltration devices well swept and clean will enhance the longevity of these devices. For
roofs, frequent cleaning of gutters will reduce sediment loads to these devices.
APPENDIX A
GEOTECHNICAL REPORT
EarthSolutionsNWLLC
EarthSolutions
NW LLC
Geotechnical Engineering
Geology
Environmental Scientists
Construction Monitoring
1805 - 136th Place N.E., Suite 201 Bellevue, WA98005
(425) 449-4704 Fax (425) 449-4711
www.earthsolutionsnw.com
GEOTECHNICAL ENGINEERING STUDY
PROPOSED SHORT PLAT
2525 ABERDEEN AVENUE NORTHEAST
RENTON, WASHINGTON
ES-4338
Drwn.
Checked Date
Date Proj. No.
Plate
Earth Solutions NWLLC
Geotechnical Engineering,Construction Monitoring
EarthSolutionsNWLLC
EarthSolutions
NW LLC and Environmental Sciences
Vicinity Map
Aberdeen Avenue N.E.
Renton, Washington
MRS
HTW
02/23/2016
Feb. 2016
4338
1
NORTH
NOTE: This plate may contain areas of color. ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black & white reproductions of this plate.
Reference:
King County, Washington
Map 626
By The Thomas Guide
Rand McNally
32nd Edition
SITE
Drwn.
Checked Date
Date Proj. No.
Plate
Earth Solutions NWLLC
Geotechnical Engineering,Construction Monitoring
EarthSolutionsNWLLC
EarthSolutions
NW LLC and Environmental Sciences
Test Pit Location Plan
Aberdeen Avenue N.E.
Renton, Washington
MRS
HTW
02/23/2016
Feb. 2016
4338
2
NORTH
0 20 40 80
Scale in Feet1"=40'
NOTE: This plate may contain areas of color. ESNW cannot be
responsible for any subsequent misinterpretation of the information
resulting from black & white reproductions of this plate.
NOTE: The graphics shown on this plate are not intended for design
purposes or precise scale measurements, but only to illustrate the
approximate test locations relative to the approximate locations of
existing and / or proposed site features. The information illustrated
is largely based on data provided by the client at the time of our
study. ESNW cannot be responsible for subsequent design changes
or interpretation of the data by others.
LEGEND
Approximate Location of
ESNW Test Pit, Proj. No.
ES-4338, Feb. 2016
Subject Site
Existing Building
TP-1
TP-2
TP-3
TP-4
TP-1
300
290
300 290
310
310
300
300
House
Shed
Sheds ABERDEEN AVENUE N.E.
Drwn.
Checked Date
Date Proj. No.
Plate
Earth Solutions NWLLC
Geotechnical Engineering,Construction Monitoring
and Environmental Sciences
EarthSolutionsNWLLC
EarthSolutions
NW LLC
RETAINING WALL DRAINAGE DETAILAberdeen Avenue N.E.
Renton, Washington
MRS
HTW
02/23/2016
Feb. 2016
4338
3
NOTES:
Free Draining Backfill should consist
of soil having less than 5 percent fines.
Percent passing #4 should be 25 to
75 percent.
Sheet Drain may be feasible in lieu
of Free Draining Backfill, per ESNW
recommendations.
Drain Pipe should consist of perforated,
rigid PVC Pipe surrounded with 1"
Drain Rock.
LEGEND:
Free Draining Structural Backfill
1 inch Drain Rock
18" Min.
Structural
Fill
Perforated Drain Pipe
(Surround In Drain Rock)
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Drwn.
Checked Date
Date Proj. No.
Plate
Earth Solutions NWLLC
Geotechnical Engineering,Construction Monitoring
and Environmental Sciences
EarthSolutionsNWLLC
EarthSolutions
NW LLC
FOOTING DRAIN DETAIL
Slope
Perforated Rigid Drain Pipe
(Surround with 1" Rock)
18" (Min.)
NOTES:
Do NOT tie roof downspouts
to Footing Drain.
Surface Seal to consist of
12" of less permeable, suitable
soil. Slope away from building.
LEGEND:
Surface Seal; native soil or
other low permeability material.
1" Drain Rock
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Aberdeen Avenue N.E.
Renton, Washington
MRS
HTW
02/23/2016
Feb. 2016
4338
4
APPENDIX B
ARBORIST REPORT
Arborist Report
2525 Aberdeen Ave NE
Renton, WA
January 27th, 2016
American Forest Management 1/27/2016
Table of Contents
1. Introduction .............................................................................................................. 1
2. Description ............................................................................................................... 1
3. Methodology ............................................................................................................ 1
4. Observations ........................................................................................................... 2
5. Discussion ............................................................................................................... 2
6. Tree Retention ......................................................................................................... 3
7. Tree Replacement .................................................................................................. .3
8. Tree Protection Measures…………………………………………………………………4
Appendix
Site/Tree Photos – pages 5 – 11
Tree Summary Table - attached
Tree Plan Map – attached
2525 Aberdeen Ave NE Arborist Report
Page 1 American Forest Management 1/27/2016
1. Introduction
American Forest Management, Inc. was contacted by Bill Hegger, and was asked to compile an ‘Arborist
Report’ for two parcels located within the City of Renton.
The proposed 4-Lot short plat encompasses the property at 2525 Aberdeen Ave NE. Our assignment is to
prepare a written report on present tree conditions, which is to be filed with the preliminary permit application.
This report encompasses all of the criteria set forth under City of Renton code section 4-4-130. The tree
retention requirement is 30% of significant trees.
Date of Field Examination: January 25th, 2016
2. Description
54 significant trees were identified and assessed on the property. These are comprised of a mix of native species
and planted ornamental species. According to City of Renton code, a significant tree is a “tree with a caliper of
at least six inches (6"), or an alder or cottonwood tree with a caliper of at least eight inches (8"). Trees qualified
as dangerous shall not be considered significant. Trees planted within the most recent ten (10) years shall
qualify as significant trees, regardless of the actual caliper.”
A numbered aluminum tag was placed on the lower trunks of the subject trees by the surveying crew. These
numbers were used for this assessment. Tree tag numbers correspond with the numbers on the Tree Summary
Tables and copy of the attached site survey.
There is one neighboring tree with a drip line that extends over the property line.
3. Methodology
Each tree in this report was visited. Tree diameters were measured by tape. The tree heights were measured
using a Spiegel Relaskop. Each tree was visually examined for defects and vigor. The tree assessment
procedure involves the examination of many factors:
The crown of the tree is examined for current vigor. This is comprised of inspecting the crown
(foliage, buds and branches) for color, density, form, and annual shoot growth, limb dieback and
disease. The percentage of live crown is estimated for coniferous species only and scored
appropriately.
The bole or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting
bodies of decay (conks or mushrooms), seams, insects, bleeding, callus development, broken or dead
tops, structural defects and unnatural leans. Structural defects include crooks, forks with V-shaped
crotches, multiple attachments, and excessive sweep.
The root collar and roots are inspected for the presence of decay, insects and/or damage, as well as if
they have been injured, undermined or exposed, or original grade has been altered.
Based on these factors a determination of viability is made. Trees considered ‘non-viable’ are trees that are in
poor condition due to disease, extensive decay and/or cumulative structural defects, which exacerbate failure
potential. A ‘viable’ tree is a tree found to be in good health, in a sound condition with minimal defects and is
suitable for its location. Also, it will be wind firm if isolated or left as part of a grouping or grove of trees. A
‘borderline’ viable tree is a tree where its viability is in question. These are trees that are beginning to display
symptoms of decline due to age and or species related problems. Borderline trees are not expected to positively
contribute to the landscape for the long-term and are not recommended for retention.
The attached site plan/tree map indicates the viability of the subject trees.
2525 Aberdeen Ave NE Arborist Report
Page 2 American Forest Management 1/27/2016
4. Observations
The subject trees are comprised of a mix of native and planted species. The native tree species are primarily in
the access easement and in Lot 1. Specific tree information can be found on the attached tree table.
Douglas-fir trees
The Douglas-fir trees vary in age and condition. Some of the common defects include broken tops, crooked
trunks and small live crowns. The Douglas-fir trees in Lot 1 are growing very closely together, a few have poor
trunk taper and small crowns as a result of this. Additionally, many of the trees exhibit signs of suppression.
Big leaf maple trees
The big leaf maple trees on the property are in fair to poor condition. Structural defects such as co-dominant
stems with poor attachment, crooks in the trunk and leaning trunks were common. Decay was also observed in a
few of the maple trees.
Pacific madrone trees
The pacific madrone trees on the property are generally in decline. Concerning defects observed included stem
cankers and branch dieback. The pacific madrone trees range from fair to fair-poor condition.
Western red cedar trees
The western red cedars on the property are young and have good vigor. The two western red cedars are both in
good condition and are viable.
Other concerning trees
Tree #115 is a European white birch planted in the center of the property. This tree has an over exposed root
flare. This tree additionally has significant trunk decay. This tree is in poor condition and is non-viable.
Tree #117 is a flowering cherry tree planted in the center of the property. This tree has a co-dominant stem that
forks 5’ from the base of the trunk. The attachment between the two main stems is a weak, v shaped attachment
and there is decay at the area of attachment. This tree is in poor condition and is non-viable.
Tree #118 is a grand fir on the south edge of the property. This tree has moderate dieback in over 30% of the
crown. No concerning defects were observed on the trunk of the tree. This tree is in decline and is in fair to poor
condition. The subject tree is borderline viable.
Tree #122 is a cherry plum in the center of the property. This tree has a large, visible, column of decay in 8 feet
of the lower trunk. This tree is in poor condition and is non-viable.
Neighboring Trees
Tree #201 is a young lodge pole pine north of the property line. This tree has a full crown and good taper. No
concerning defects were observed.
5. Discussion
The grade in most of Lot 1 will be lowered by a few feet to match the grade of the rest of the property. Grade
changes should not occur within the limits of disturbance for trees that will be retained. Lowering the grade near
trees removes and damages roots, which reduces the ability of the tree to absorb water and nutrients and
maintain vigor. Grade changes can also reduce the structural integrity of trees.
Finished landscaping work within the drip-lines of retained trees shall maintain existing grades and not disturb
fine root mass at the ground surface. Finish landscape with beauty bark or new lawn on top of existing grade.
Add no more than 2” to 4” of mulch/beauty bark or 2” of composted soil to establish new lawn.
The extent of drip-lines (farthest reaching branches) for the subject trees can be found on the tree summary
tables at the back of this report. These have also been delineated on a copy of the site survey for viable/healthy
trees proposed for retention. The information plotted on the attached survey plan may need to be transferred to
2525 Aberdeen Ave NE Arborist Report
Page 3 American Forest Management 1/27/2016
a final tree retention/protection plan to meet City submittal requirements. The trees that are to be removed shall
be shown “X’d” out on the final plan.
The Limits of Disturbance (LOD) measurements can also be found on the tree summary table. This is the
recommended distance of the closest impact (soil excavation) to the trunk face. These should be referenced
when determining tree retention feasibility. The LOD measurements are based on species, age, condition, drip-
line, prior improvements, proposed impacts and the anticipated cumulative impacts to the entire root zone.
Tree Protection fencing shall be located beyond the drip-line edge of retained trees, and only moved back to the
LOD when work is authorized.
There are no major conflicts concerning neighboring trees. Tree #201 is on the north perimeter and with tree
protection fencing, no major root damage is expected.
6. Tree Retention
A total of 54 significant trees were identified on the subject property. Five of the significant trees are in poor
condition and three are in fair-poor condition. These eight borderline to non-viable trees were not included in
the tree calculation.
Landmark trees and tree groves were prioritized when selecting trees for retention, per the City of Renton tree
code 4-4-130.
Tree Calculation based on 46, healthy, viable, significant trees
Viable Trees proposed for removal – 28 (61%)
Viable Trees proposed for retention – 18 (39%)
7. Tree Replacement
Replacements trees may be required. Consult your city planner for tree replacement requirements. All
replacement trees are to be planted on site. For planting and maintenance specifications, refer to Section 4-4-
130 of the Renton Tree Ordinances.
Tree Type Removal Retained Total
Landmark # 2 3 5
Landmark % 40% 60% 11%
Significant # 26 15 41
Significant % 63% 37% 89%
Total # 28 18 46
Total % 61% 39% 100%
2525 Aberdeen Ave NE Arborist Report
Page 4 American Forest Management 1/27/2016
8. Tree Protection Measures
The following guidelines are recommended to ensure that the designated space set aside for the preserved trees
are protected and construction impacts are kept to a minimum.
Tree protection barriers shall be initially erected at 5’ outside of the drip-line prior to moving any
heavy equipment on site.
Tree protection fencing shall only be moved where necessary to install improvements, but only as
close as the Limits of Disturbance, as indicated on the attached plan.
Excavation limits should be laid out in paint on the ground to avoid over excavating.
Excavations within the drip-lines shall be monitored by a qualified tree professional so necessary
precautions can be taken to decrease impacts to tree parts. A qualified tree professional shall monitor
excavations when work is required and allowed up to the “Limits of Disturbance”.
To establish sub grade for foundations, curbs and pavement sections near the trees, soil should be
removed parallel to the roots and not at 90 degree angles to avoid breaking and tearing roots that lead
back to the trunk within the drip-line. Any roots damaged during these excavations should be exposed
to sound tissue and cut cleanly with a saw. Cutting tools should be sterilized with alcohol.
Areas excavated within the drip-line of retained trees should be thoroughly irrigated weekly during dry
periods.
Preparations for final landscaping shall be accomplished by hand within the drip-lines of retained trees.
Plantings within the drip lines shall be limited. Large equipment shall be kept outside of the tree
protection zones.
There is no warranty suggested for any of the trees subject to this report. Weather, latent tree conditions, and
future man-caused activities could cause physiologic changes and deteriorating tree condition. Over time,
deteriorating tree conditions may appear and there may be conditions, which are not now visible which, could
cause tree failure. This report or the verbal comments made at the site in no way warrant the structural stability
or long term condition of any tree, but represent my opinion based on the observations made.
Nearly all trees in any condition standing within reach of improvements or human use areas represent hazards
that could lead to damage or injury.
Please call if you have any questions or I can be of further assistance.
Sincerely,
Kelly Wilkinson
ISA Certified Arborist #PN-7673A
ISA Tree Risk Assessment Qualified
2525 Aberdeen Ave NE Arborist Report
Page 5 American Forest Management 1/27/2016
Photos
Tree #103, #102 and #101 – Douglas-fir trees on east side of Lot 4
Tree #110 – pacific madrone with co-dominant stems and stem cankers
2525 Aberdeen Ave NE Arborist Report
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Lot 1
Tree #115, #116 and #117 – ornamental trees planted in Lot 3 and 4
2525 Aberdeen Ave NE Arborist Report
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Tree #115 – European white birch with an over exposed root flare
Tree #117 – flowering cherry with decay and co dominant stems
2525 Aberdeen Ave NE Arborist Report
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View of Lot 1 from the east
Tree #118 – grand fir with moderate limb dieback
2525 Aberdeen Ave NE Arborist Report
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Tree #120 – black oak
Tree #122 – cherry plum with severe decay
2525 Aberdeen Ave NE Arborist Report
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Tree #127 – big leaf maple, co dominant stems with poor attachment
South end of Lot 1
2525 Aberdeen Ave NE Arborist Report
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Tree #146 – pacific madrone with Nattrassia canker
South perimeter of Lot 1 and 2
Tree Summary TableAmerican Forest Management, Inc.For: 2525 Aberdeen Ave NE Date: 1/25/2015City of RentonInspector: WilkinsonTree/DBH HeightTag # Species(inches) (feet)Condition Viability CommentsProposalNSEW101 Douglas-fir31 90 11161122fair viable broken top, landmarkretain102 Douglas-fir23 65 8121810fair viable crooked trunkretain103 Douglas-fir6 22 6565 good viableretain104 western red cedar6 22 6565 good viableremove105 Douglas-fir36 107182022 good viable landmarkremove106 big leaf maple12, 20 619912 poor non-viable one stem dead, the other declining remove107 lodgepole pine8 36 89811fair viableremove108 western red cedar6 286810fair viableremove109 Douglas-fir17 63 111112fair viable diebackremove110 pacific madrone21 4614922fair viable decay, 10% dieback, forks at 5' remove111 pacific madrone13 522fair viable 20% diebackremove112 Douglas-fir6 268910fair viableremove113 Douglas-fir17 8713812fair viableremove114 Douglas-fir16 9114148fair viableremove115 European white birch 9 35 1161012 poor non-viable exposed root flare, decayremove116 honey locust10 39 818128fair viable exposed root flareremove117 flowering cherry16 37 14161212 poor non-viable severe decayremove118 grand fir41 104 182118 fair-poor borderline severe diebackremove119 giant sequoia11, 11 46 8610fair viable forks at 1'retain120 black oak25 76 252127fair viableretain121 honey locust9 29 0fair viable leans Sretain122 cherry plum20 27poor non-viable severe decayremove123 Douglas-fir24 961112good viableretain124 big leaf maple8 34 200024fair viable crooked, leans NWretain125 Douglas-fir14 59 13585fair viable crook at 7'remove126 big leaf maple11 58 731612fair viableremove127 big leaf maple12, 6, 14 61 1816617fair viable forks at 2', poor attachmentremove128 Douglas-fir17 88 91118fair viableremoveDrip-Line and Limits of Disturbance measurements from face of trunkDrip-Line/Limits of Disturbance (feet)Trees on neighboring properties - Drip-line and Limits of Disturbance measurements from property lines
Tree Summary TableAmerican Forest Management, Inc.For: 2525 Aberdeen Ave NE Date: 1/25/2015City of RentonInspector: WilkinsonTree/DBH HeightTag # Species(inches) (feet)Condition Viability CommentsProposalNSEW129 Douglas-fir12 84 858fair viableremove130 Douglas-fir12 85 5517fair viableremove131 Douglas-fir15 86915fair viableremove132 Douglas-fir10 41 812fair viable suppressedremove133 Douglas-fir12 8889fair viableremove134 Douglas-fir6 31 83210fair viable suppressedremove135 Douglas-fir14 90 1073fair viableremove136 Douglas-fir6 42 34122fair viableremove137 Douglas-fir16 92 6515fair viableremove138 Douglas-fir10 51 7628poor non-viable broken top, 30% live crownremove139 Douglas-fir10 76 3743fair viableremove140 Lombardy poplar16 90 6657fair viableremove141 Douglas-fir7 68 7644fair viableremove142 big leaf maple7 47 8693fair viableremove143 Douglas-fir8 62 8015fair viable suppressedretain144 Douglas-fir20 95 7131114fair viableretain145 Douglas-fir9 51 21074fair viableretain146 pacific madrone13 48fair-poor borderline decay, 50% diebackremove147 Lombardy poplar10 58 244fair viableretain148 Lombardy poplar9 62 344fair viableretain149 Douglas-fir8 30 87112 fair-poor borderline broken top, small live crownremove150 Douglas-fir17 95 10111512fair viableretain151 Douglas-fir12 60 41610fair viableretain152 Douglas-fir11 58 717fair viable 10 deg lean Eretain153 western larch6 32 786 good viableretain154 Lombardy poplar37 101 677fair viable landmarkretain201 lodgepole pine9 326good viableDrip-Line and Limits of Disturbance measurements from face of trunkDrip-Line/Limits of Disturbance (feet)Trees on neighboring properties - Drip-line and Limits of Disturbance measurements from property linesNeighboring Tree
APPENDIX C
KCRTS ANALYSIS
Stormwater Design
Per Geotechnical Engineering Study conducted for this project by Earth Solutions NW, March 7,
2016, the underlying soil is poorly graded sand with gravel and is very suitable for infiltrating
stormwater. Per their recommendations, a design infiltration rate of 20 inch/hr should be used (this
includes a factor of safety of greater than 10, a very conservative design rate).
Small Infiltration Basins will be used to infiltrate stormwater the future homes on the lots and for
the private shared driveway, as outlined in section 5.4.7 of the 2009 King County Surface Water
Design Manual (KCSWDM).
Each lot will have a maximum of about 3,000 sq‐ft of impervious surface. The shared driveway will
have about 3,000 sq‐ft of paving. KCRTS was used to design 100‐year infiltration for a 3,000 sq‐ft
impervious area, to conceptually size infiltration for each of the three new lots and the shared
driveway.
KCRTS Input:
Regional Scale Factor per 2009 KCSWDM fig 3.2.2.A ST 1.0
Developed Conditions Impervious Area 3,000 sq‐ft = 0.07 acres
Developed Conditions Pervious Area 0
Using KCRTS:
Developed Conditions Flows (3,000 sq‐ft impervious)
Flow Frequency Analysis
Time Series File:15615d.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.017 6 2/09/01 2:00 0.033 1 100.00 0.990 100yr
0.015 8 1/05/02 16:00 0.026 2 25.00 0.960 25yr
0.020 3 12/08/02 18:00 0.020 3 10.00 0.900 10yr
0.017 7 8/26/04 2:00 0.020 4 5.00 0.800
0.020 4 10/28/04 16:00 0.018 5 3.00 0.667
0.018 5 1/18/06 16:00 0.017 6 2.00 0.500 2yr
0.026 2 10/26/06 0:00 0.017 7 1.30 0.231
0.033 1 1/09/08 6:00 0.015 8 1.10 0.091
Computed Peaks 0.031 50.00 0.980 50yr
The infiltration basins were sized for the 100 year storm.
Infiltration Basin Design
KCRTS Input:
Developed Conditions Flows from above (3,000 sq‐ft impervious)
infiltration rate of 20 in/hr => 3 min/inch (equivalent design infiltration rate)
(2) Infiltration Basins per lot (or joint driveway) See diagram below
(2) 5’ X 5’ bottom infiltration areas
(2) 3’ deep X 4’ diameter precast CB’s w/o bottom
2.5’ of washed gravel below open part of CB’s
Infiltration Basin Routing File for KCRTS
Stage Discharge Storage Perm‐Area
(Ft) (CFS) (Cu‐Ft) (Sq‐Ft)
0.00 0.000 0. 0.
1.00 0.000 17.5 50
2.00 0.000 35 50
3.00 0.000 56.3 50
4.00 0.000 81.4 50
5.00 0.000 106.5 50
6.00 0.000 131.6 50
7.00 0.000 156.7 50
8.00 0.000 181.8 50
0.00 Ft : Base Reservoir Elevation
3.0 Minutes/Inch: Average Perm‐Rate
Using KCRTS to route developed flows though above defined double infiltration basins:
Flow Frequency Analysis
Time Series File:basin3000x2-5x5.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) (ft) Period
0.000 6 2/09/01 3:00 0.000 5.34 1 100.00 0.990 100yr
0.000 8 1/05/02 17:00 0.000 1.05 2 25.00 0.960
0.000 4 2/27/03 8:00 0.000 0.86 3 10.00 0.900
0.000 7 8/26/04 3:00 0.000 0.83 4 5.00 0.800
0.000 3 10/28/04 17:00 0.000 0.73 5 3.00 0.667
0.000 5 1/18/06 14:00 0.000 0.71 6 2.00 0.500
0.000 2 10/26/06 1:00 0.000 0.59 7 1.30 0.231
0.000 1 1/09/08 10:00 0.000 0.51 8 1.10 0.091
Computed Peaks 0.000 3.91 50.00 0.980
Double infiltration basins will fill up to a depth of 2.84’ in a 100
year storm.