HomeMy WebLinkAboutRS_Drainage_Technical_Information_Report_Meadow_Ave_220307_v1
Western Washington Division Eastern Washington Division
165 NE Juniper St., Ste 201, Issaquah, WA 98027 407 Swiftwater Blvd, Cle Elum, WA 98922
Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419
www.EncompassES.net
PRELIMINARY TECHNICAL INFORMATION REPORT
For
Meadow Ave Short Plat
3804 Meadow Avenue N
Renton, WA 98056
January 29, 2021
Revised March 7, 2022
Prepared by:
Ian Dahl
Encompass Engineering Job No. 20591
Prepared For:
Huy Nguyen
15400 SE 155th Place, Unit 99
Renton, WA 98058
Meadow Ave Short Plat Preliminary Technical Information Report
3/7/2022 P a g e | i
Table of Contents
I. PROJECT OVERVIEW ................................................................................................................ 1
II. CONDITIONS AND REQUIREMENTS SUMMARY ...................................................................... 7
III. OFFSITE ANALYSIS .................................................................................................................. 12
IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT AND WATER QUALITY FACILITY ANALYSIS
AND DESIGN ........................................................................................................................... 19
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ..................................................................... 23
VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 23
VII. OTHER PERMITS ..................................................................................................................... 23
VIII. CSWPP ANALYSIS AND DESIGN .............................................................................................. 23
IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of COVENANT ................... 23
X. OPERATION AND MAINTENANCE MANUAL .......................................................................... 23
List of Figures
Figure 1 – TIR Worksheet
Figure 2 – Vicinity Map
Figure 3 – Soils Map and Legend
Figure 4 – Existing Conditions Map
Figure 5 – Developed Conditions Map
Figure 6 – Drainage Review Flow Chart
Figure 7 – Downstream Map
Appendix A
Geotechnical Engineering Study by Earth Solutions NW dated March 12, 2020
Geotechnical Review Letter by Earth Solutions NW dated March 7, 2022
Appendix B
WWHM Output
Appendix C
Arborist Report/Tree Plan by Layton Tree Consulting, LLC dated February 12, 2020
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner ___________________________
Phone _________________________________
Address _______________________________
_______________________________________
Project Engineer _________________________
Company ______________________________
Phone _________________________________
Project Name _________________________
DPER Permit # ________________________
Location Township ______________
Range ________________
Section ________________
Site Address __________________________
_____________________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Landuse (e.g.,Subdivision / Short Subd. / UPD)
Building (e.g.,M/F / Commercial / SFR)
Clearing and Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline Management
Structural Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review (check one):
Date (include revision dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
____________________________________
__________________
Plan Type (check one):
Date (include revision dates):
Date of Final:
Full
Modified
Simplified
____________________________________
__________________
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Experimental / Blanket
Description: (include conditions in TIR Section 2)
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Approved Adjustment No. ______________________ Date of Approval: ______________________
2016 Surface Water Design Manual 4/24/2016 1
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
_________________________________________
_________________________________________
Re: KCSWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan : ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: ____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
_______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
_____________________________________
Part 10 SOILS
Soil Type
_________________
_________________
_________________
_________________
Slopes
_________________
_________________
_________________
_________________
Erosion Potential
_________________
_________________
_________________
_________________
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
2016 Surface Water Design Manual 4/24/2016 2
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
_____________________________________
LIMITATION / SITE CONSTRAINT
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area)
Threshold Discharge Area:
(name or description)
Core Requirements (all 8 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility summary sheet) Level: 1 / 2 / 3 or Exemption Number ____________
Flow Control BMPs _______________________________
Conveyance System Spill containment located at: _________________________
Erosion and Sediment Control /
Construction Stormwater Pollution Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Maintenance and Operation
Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and
Liability
Provided: Yes / No
Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. ______________________
Landscape Management Plan: Yes / No
Special Requirements (as applicable):
Area Specific Drainage Requirements Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): ______________
Datum:
Flood Protection Facilities Describe:
2016 Surface Water Design Manual 4/24/2016 3
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area)
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control
High-use Site: Yes / No
Treatment BMP: ________________________________
Maintenance Agreement: Yes / No
with whom? ____________________________________
Other Drainage Structures
Describe:
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Protection of Flow Control BMP Facilities
(existing and proposed)
Maintain BMPs / Manage Project
MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure operation of Permanent Facilities, restore
operation of Flow Control BMP Facilities as necessary
Flag limits of SAO and open space preservation areas
Other ______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention
Infiltration
Regional Facility
Shared Facility
Flow Control BMPs
Other
________________
________________
________________
________________
________________
________________
Vegetated Flowpath
Wetpool
Filtration
Oil Control
Spill Control
Flow Control BMPs
Other
________________
________________
________________
________________
________________
________________
________________
2016 Surface Water Design Manual 4/24/2016 4
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Covenant
Tract
Other ___________________________
Cast in Place Vault
Retaining Wall
Rockery > 4’ High
Structural on Steep Slope
Other ______________________________
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate.
Signed/Date
2016 Surface Water Design Manual 4/24/2016 5
Meadow Ave Short Plat Preliminary Technical Information Report
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I. PROJECT OVERVIEW
Project: Meadow Ave Short Plat
Site Address: 3804 Meadow Avenue N, Renton, WA 98056 (See Vicinity Map)
Tax Parcel #: 334270-0570
Zoning District: R-6, Single Family Residential
Site Area: 25,536 SF (0.59 Acres)
Site Location: The site is in the City of Renton within the NW quarter of Section 32,
Township 24 North, Range 5 East, W.M, King County, Washington. The
site is located on the northeast corner of the intersection of Meadow Ave
N and N 38th St.
Figure 2: Vicinity Map
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Pre-developed Site Conditions
The project site is located in the City of Renton on a 25,536 SF (0.59 Acres) lot that is zoned R-6 (single-
family residential). The site is accessed from Meadow Ave N, north of the intersection of N 38th St and
Meadow Ave N. The site is bordered to the north and south by single family residences, to the east by I-
405, and to the west by Meadow Ave N right-of way (ROW).
The site is currently developed with a single-family residence accessed from Meadow Ave N via two gravel
driveways on the western side of the site. The site slopes gently to the northwest at approximately 2%.
The property is located within the May Creek drainage basin. Stormwater runoff currently leaves the site
at a single natural discharge location at the northwest corner, creating one Threshold Discharge Area for
the site. The majority of the site gently slopes at approximately 2%, allowing stormwater to sheet flow
northwest into Meadow Ave. A cleared area on the adjacent parcel 334270-0630 is tributary to the site.
This off-site area sheet flows to the north over approximately 10-15% slopes onto the existing gravel
driveway located in the southern portion of the site. See full downstream analysis in Section III of this
Technical Information Report (TIR).
An Existing Conditions Map is included as Figure 4 at the end of this Section.
Critical Areas
According to the City of Renton online mapping system, there is a High Erosion Hazard Area in the
northeast corner of the project site. There are no required buffers or building setbacks associated with
the erosion hazard area. No other critical areas have been identified on the project site.
Soils
Per the US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS) Web Soil
Survey (WSS) information, the majority of the project site is underlain with Indianola loamy sand, 5 to 15
percent slopes with a small portion of the site in the northeast corner underlain with Norma sandy loam
(See Figure 3 on the following page). Soil explorations detailed in the Geotechnical Engineering Study by
Earth Solutions NW dated March 12, 2020 (Appendix A) encountered primarily medium dense silty sand
and poorly graded sand. These findings are consistent with geologic and soil mapping resources. An in-
situ infiltration test was performed and a design infiltration rate of 5 inches per hour was determined by
the Geotech, which is suitable for stormwater infiltration.
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Figure 3: Soil Map and Legend
Developed Site Conditions
The project proposes the development of three (3) single-family lots within the 25,536 SF (0.59 Acres)
parcel, as well as a 7.5-foot right-of-way dedication with frontage improvements. Lot 1 is 8,230 SF (0.19
AC) and is located in the north portion of the site. Lot 2 is 8,043 SF (0.18 Acres) and is located in the central
portion of the site. Lot 3 is 7,868 SF (0.18 AC) and is located in the southern portion of the site. All three
(3) lots will have driveway access off of Meadow Ave N. Frontage improvements will include the addition
of a 5-foot sidewalk, 8-foot planter strip, as well as curb and gutter along the edge of asphalt roadway.
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The total disturbed area for this project, including the construction of frontage improvements, is 27,320
SF (0.627 AC).
The parcel is zoned R-6, which allows for a maximum building coverage of 40% and a maximum impervious
surface coverage of 55%. The maximum allowable building/impervious surface for each lot is discussed
below:
· Lot 1: The maximum allowable building coverage for Lot 1 is 8,230 SF*0.4 = 3,292 SF, and the
maximum impervious surface coverage is 8,230 SF*0.55 = 4,527 SF. The final site layout of Lot
1 has not been determined at this stage; therefore, this report assumes that the future
impervious surfaces required to construct the residence on Lot 1 will use the maximum
coverages stated above.
· Lot 2: The maximum allowable building coverage for Lot 2 is 8,043 SF*0.4 = 3,217 SF, and the
maximum impervious surface coverage is 8,043 SF*0.55 = 4,424 SF. The final site layout of Lot
2 has not been determined at this stage; therefore, this report assumes that the future
impervious surfaces required to construct the residence on Lot 2 will use the maximum
coverages stated above.
· Lot 3: The maximum allowable building coverage for Lot 2 is 7,868 SF*0.4 = 3,147 SF, and the
maximum impervious surface coverage is 7,868 SF*0.55 = 4,327 SF. The final site layout of Lot
3 has not been determined at this stage; therefore, this report assumes that the future
impervious surfaces required to construct the residence on Lot 3 will use the maximum
coverages stated above.
Stormwater runoff from the proposed development of Lots 1-3 will be managed as follows:
· Lot 1: Stormwater BMP’s satisfying Core Requirement #9 will be used to the maximum extent
feasible to mitigate new runoff created by the proposed single-family residence and other
impervious surfaces on-site. A 30’x9’ gravel filled full infiltration trench is proposed on Lot 1
to the west of the proposed structure to mitigate stormwater from impervious areas. An
emergency overflow to the public storm system from the infiltration trench will be provided.
This report assumes that the maximum impervious surface per zoning (4,527 SF) will be
conveyed to this infiltration trench.
· Lot 2: Stormwater BMP’s satisfying Core Requirement #9 will be used to the maximum extent
feasible to mitigate new runoff created by the proposed single-family residence and other
impervious surfaces on-site. A 30’x9’ gravel filled full infiltration trench is proposed on Lot 2
to the west of the proposed structure to mitigate stormwater from impervious areas. An
emergency overflow to the public storm system from the infiltration trench will be provided.
This report assumes that the maximum impervious surface per zoning (4,424 SF) will be
conveyed to this infiltration trench.
· Lot 3: Stormwater BMP’s satisfying Core Requirement #9 will be used to the maximum extent
feasible to mitigate new runoff created by the proposed single-family residence and other
impervious surfaces on-site. A 30’x9’ gravel filled full infiltration trench is proposed on Lot 3
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to the west of the proposed structure to mitigate stormwater from impervious areas. An
emergency overflow to the public storm system from the infiltration trench will be provided.
This report assumes that the maximum impervious surface per zoning (4,327 SF) will be
conveyed to this infiltration trench.
Please refer to Core Requirement # 9 in Section II and Section IV of this TIR for additional discussion on
stormwater BMPs. A Developed Conditions Map is provided as Figure 5 at this end of this Section.
N 38TH STREET MEADOW AVENUE NEastern Washington Division407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433
Western Washington Division165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250
ncompass
ENGINEERING & SURVEYING
E Know what'sCallbelow.
before you dig.
R NORTHEXISTING CONDITIONS AREAS
PREDEVELOPED MODELED AREA
FIGURE 4 - EXISTING CONDITIONS MAP
Eastern Washington Division407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433
Western Washington Division165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250
ncompass
ENGINEERING & SURVEYING
E Know what'sCallbelow.
before you dig.
R NORTHDEVELOPED CONDITIONS AREAS
MITIGATED MODELED AREAS
FIGURE 5 - DEVELOPED CONDITIONS MAP
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II. CONDITIONS AND REQUIREMENTS SUMMARY
The 2017 City of Renton Surface Water Design Manual (RSWDM) was utilized to determine and address
all core and special requirements. Based on the criteria specified in Figure 1.1.2.A of the RSWDM, the
project falls under Full Drainage Review. Per Section 1.1.2.4 of the RSWDM, the project must meet all nine
(9) core and all six (6) special requirements. See Figure 6 below for more information on how the type of
drainage review was determined.
Figure 6: Drainage Review Flow Chart
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Core Requirements
Core Requirement #1: Discharge at the Natural Location
The proposed development runoff will follow existing drainage patterns toward the Meadow Ave
N storm system or will be fully infiltrated on-site. Refer to the Level 1 Downstream Analysis in
Section III of this TIR for a complete description of the existing drainage paths.
Core Requirement #2: Downstream Analysis
A Level 1 Downstream analysis has been completed for the site and no existing or potential
drainage problems have been identified. This analysis is included in Section III of this TIR.
Core Requirement #3: Flow Control Facilities
Based on the City of Renton’s flow control application map, the project site is located within the
Peak Rate Flow Control Standard (Existing Site Conditions). Flow control facilities are required to
match the developed peak discharge rates to existing site conditions peak discharge rates for 2-,
10- and 100-year return periods.
The proposed stormwater BMPs result in a 0.2289 CFS decrease in the 100-year flow using 15-
minutes time steps. This is below the allowable threshold of a 0.15 CFS maximum increase per
Section 1.2.3.1.B of the RSWDM; therefore, the project meets flow control exemption 2. No
formal flow control facilities are proposed at this time; however, flow control BMPs will be
implemented as described in Core Requirement #9. Please refer to Section IV of this TIR for
additional discussion.
Core Requirement #4: Conveyance System
Conveyance in compliance with the requirements detailed in Section 1.2.4.1 of the City of Renton
2017 SWDM will be provided with final engineering.
Core Requirement #5: Construction Stormwater Pollution Prevention
The limits of construction for the project are less than 1 acre. A temporary erosion and sediment
control (TESC) plan providing details on best management practices (BMPs) to be implemented
during construction is included in the engineering plan set. A Construction Stormwater Pollution
Prevention Plan (CSWPPP) will be provided with final engineering. Please refer to Section VIII of
this TIR for additional discussion.
Core Requirement #6: Maintenance and Operations
An Operation and Maintenance Manual will be provided with final engineering.
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 Facilities
In accordance with Section 1.2.8.1.A of the RSWDM, Basic Water Quality Treatment is not
required for this project as new plus replaced pollution generating impervious surfaces (PGIS)
does not exceed 5,000 SF. The development results in 768 SF of concrete driveway within the
ROW dedication area, 485 of pavement replacement within the existing ROW, and 3,700 SF of on-
site driveway is estimated for the future build-out of Lots 1-3. These quantities total to 4,953 SF
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of PGIS that will be created or replaced as a result of this project; therefore, the project meets
surface area exemption 1.
Core Requirement #9: Flow Control BMPs
Per section 1.2.9.3.1 of the RSWDM, this project is classified as a small subdivision; therefore, it is
subject to the Small Road Improvement and Urban Road Improvement Project BMP Requirements
detailed in Section 1.2.9.3.2 in the RSWDM. Although implementation of individual lot BMPs is
not required until building permit application, BMPs have been considered for the future
improvements on Lots 1-3 based on Section 1.2.9.2 of the RSWDM. See Section IV of this TIR for
further discussion and flow control analysis.
Impervious Surface BMPs
Full Dispersion: Infeasible for Lots 1-3.
· Lots 1-3: The space required for a 100-foot native vegetated flowpath segment is not available
on these sites.
Full Infiltration: Feasible for Lots 1-3.
· Lots 1-3: Soil explorations detailed in the Geotechnical Engineering Study by Earth Solutions
NW dated March 12, 2020 (Appendix A) encountered primarily medium dense silty sand and
poorly graded sand. An in-situ infiltration test was performed and a design infiltration rate of
5 inches per hour was determined which is suitable for stormwater infiltration. Per section
C.2.2.3 of the RSWDM, 30 liner feet of 2’ wide trench per 1,000 SF of tributary impervious
surface can be used to design full infiltration trenches in coarse sands. A 30’x2’ trench has an
infiltration area of 60 SF; therefore, 60 SF of infiltration area is required per 1,000 SF of
tributary impervious surface. For Lots 1-3, three infiltration trenches of 30’x9’ are proposed
which provides an infiltration area of 270 SF each. A 30’x9’ trench has the ability to mitigate
up to (270 SF/60 SF)x1,000 SF= 4500 SF of tributary impervious surface. This allows each
trench to mitigate the entire maximum impervious surface coverage for each lot. As an
additional safety measure, an emergency overflow to the public storm system from the
infiltration trenches will be provided.
As all target impervious surfaces on the project site have been mitigated with flow control
BMPs, no further BMPs have been considered.
Pervious Surface BMPs
Soil Amendment: Feasible for Lots 1-3
· Lots 1-3: All disturbed, pervious areas of the project will meet soil amendment requirements
as detailed in Section C.2.13 of the RSWDM.
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Special Requirements
Special Requirement #1: Other Adopted Area-Specific Requirements
Critical Drainage Area – N/A
Master Drainage Plan – N/A
Basin Plan – N/A
Lake management Plan – N/A
Shared Facility Drainage Plan – N/A
Special Requirement #2: Flood Hazard Area Delineation
The limits of this project do not lie within a delineated FEMA 100-year floodplain.
Special Requirement #3: Flood Protection Facilities
This project does not rely on or propose to modify/construct a new flood protection facility.
Special Requirement #4: Source controls
The project is a single-family residential development; therefore, this requirement is not
applicable.
Special Requirement #5: Oil Control
This project is not considered high-use in need of oil control.
Special Requirement #6: Aquifer Protection Area
The site is not located within an Aquifer Protection Area Zone per the City of Renton Groundwater
Protection Area Map Reference 15-B.
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III. DOWNSTREAM ANALYSIS
A Level 1 Downstream analysis has been conducted per the requirements in Section 1.2.2.1 of the
RSWDM. Please see Tasks 1 through 4 below for a summary of the results.
Task 1: Define and Map the Study Area
The area of analysis extends from the site discharge points along Meadow Ave N and the eastern limit of
the site along the I-405 barrier wall to approximately a quarter-mile downstream where the two discharge
areas converge. A Downstream Map is provided in Figure 7 below.
Figure 7: Downstream Map
Task 2: Review All Available Information on the Study Area
Per King county resources, there have been no significant drainage complaints within a quarter-mile
downstream of the site.
Task 3: Field Inspect the Study Area
A field inspection was performed by Encompass Engineering & Surveying on January 26, 2021. Please refer
to Task 4 for a detailed description of the downstream drainage system and analysis.
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Task 4: Describe the Drainage System
Stormwater runoff currently leaves the site at a single natural discharge location at the northwest corner
creating one Threshold Discharge Area for the site. The majority of the site gently slopes at approximately
2%, allowing stormwater to sheet flow northwest into Meadow Ave. A cleared area on the adjacent parcel
334270-0630 is tributary to the site. This off-site area and sheet flows to the north over approximately
10-15% slopes onto the existing gravel driveway in the southern portion of the site.
Runoff in the southeast portion of the site sheet flows on gravel driveway and grass towards a low point
along the I-405 wall on the eastern side of the site (A). From here, stormwater is assumed to infiltrate
directly into the soil as no outlet exists. This observation is consistent with type A/B outwash soils found
and detailed in the Geotechnical Engineering Study by Earth Solutions NW dated March 12, 2020
(Appendix A). Runoff from the southwestern portion of the site sheets flows towards Meadow Ave N
where it enters the City of Renton (COR) storm system in a Type 1 CB (B) on the edge of asphalt. Runoff
from the northern portion of the site sheet flows to the north and west, eventually entering Meadow
Ave N and entering a Type 1 CB (C) just northwest of the site at the edge of asphalt. The southern of
these two Type 1 CBs (B) outlets to the NW through a 10” DI storm pipe into a Type 2 CB approximately
12 feet away (D). From here, stormwater flows to the north through an 18” Poly storm pipe (E) into
another Type 2 CB (F). This Type 2 CB collects stormwater from the Type 1 CB (C) just northwest of the
site via an 8” DI storm pipe.
Stormwater continues north on Meadow Ave N through a series of Type 2 CBs and 18” Poly storm pipe.
It turns to the west when it reaches the intersection of Meadow Ave N and N 40th St, and runs westward
on N 40th St downhill towards lake Washington. Stormwater continues through a series of Type 2 CBs
and 18” poly pipe, through the intersection of N 40th St and Park Ave N, to the intersection of N 40th St
and Wells Ave N. The Type 2 CB in this location (G) is where the analysis was completed, just over ¼ mile
downstream of the site. Please refer to Figure 7 on the previous page, for the approximate location of
identified drainage features.
If conveyance system nuisance, severe erosion, severe flooding, or wetland hydrology problems are
identified downstream of the site under Core Requirement #2, additional impact analysis and/or
mitigation may be required. As discussed in Task 2, there have been no recent significant drainage
complaints within a quarter-mile downstream of the site. As no existing drainage or conveyance issues
have been recently identified, further impact analysis and mitigation of the downstream stormwater
system is not required. Please refer to the conveyance analysis in Section V of this TIR for additional
discussion and evaluation of the on-site conveyance system capacity. Photographs from the site visit are
included on the pages that follow.
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Element A- Low point on eastern side of site by I-405 Wall
Element B- Type 1 CB on Meadow Ave N collecting runoff from southern site frontage and yard
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Element C- Type 1 CB on Meadow Ave N collecting water from the northern site frontage and yard
Element G- Type 2 CB on N 40th St
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IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN
Part A: Existing Site Hydrology
The 25,536 SF (0.59 AC) site is currently developed with a single-family residence accessed from Meadow
Ave N via two gravel driveways on the west side of the site. The property is located within the May Creek
drainage basin. Stormwater runoff currently leaves the site at a single natural discharge location at the
northwest corner creating one Threshold Discharge Area for the site. The majority of the site gently slopes
at approximately 2%, allowing stormwater to sheet flow northwest into Meadow Ave. A cleared area on
the adjacent parcel 334270-0630 is tributary to the site. This off-site area and sheet flows to the north
over approximately 10-15% slopes onto the existing gravel driveway in the southern portion of the site.
See full downstream analysis in Section III of this Technical Information Report (TIR).
Soil explorations detailed in the Geotechnical Engineering Study by Earth Solutions NW dated March 12,
2020 (Appendix A) encountered primarily medium dense silty sand and poorly graded sand. An in-situ
infiltration test was performed and a design infiltration rate of 5 inches per hour was determined by the
Geotech, which is suitable for stormwater infiltration.
WWHM 2012 was used to model the existing condition within the 27,320 SF (0.627 AC) limits of
disturbance using existing surfaces found on site including rooftop, driveway, lawn and walkways. See the
summary of existing and developed analyses on the following pages, as well as the existing conditions
map provided as Figure 4 for more details.
Part B: Developed Site Hydrology
The project proposes the development of three (3) single-family lots within the 25,536 SF (0.59 Acres)
parcel, as well as a 7.5-foot right-of-way dedication with frontage improvements. Lot 1 is 8,230 SF (0.19
AC) and is located in the north portion of the site. Lot 2 is 8,043SF (0.18 Acres) and is located in the central
portion of the site. Lot 3 is 7,868 SF (0.18 AC) and is located in the southern portion of the site. All three
(3) lots will have driveway access off of Meadow Ave N. Frontage improvements will include the addition
of a 5-foot sidewalk, 8-foot planter strip, as well as curb and gutter along the edge of asphalt roadway.
Stormwater runoff from the proposed development of Lots 1-3 will be managed as follows:
· Lot 1: Stormwater BMP’s satisfying Core Requirement #9 will be used to the maximum extent
feasible to mitigate new runoff created by the proposed single-family residence and other
impervious surfaces on-site. A 30’x9’ gravel filled full infiltration trench is proposed on Lot 1
to the west of the proposed structure to mitigate stormwater from impervious areas. This
report assumes that the maximum impervious surface per zoning (4,527 SF) will be conveyed
to this infiltration trench. Additionally, an emergency overflow to the public storm system
from the infiltration trench will be provided.
· Lot 2: Stormwater BMP’s satisfying Core Requirement #9 will be used to the maximum extent
feasible to mitigate new runoff created by the proposed single-family residence and other
impervious surfaces on-site. A 30’x9’ gravel filled full infiltration trench is proposed on Lot 2
to the west of the proposed structure to mitigate stormwater from impervious areas. This
report assumes that the maximum impervious surface per zoning (4,424 SF) will be conveyed
to this infiltration trench. Additionally, an emergency overflow to the public storm system
from the infiltration trench will be provided.
Meadow Ave Short Plat Preliminary Technical Information Report
3/7/2022 P a g e | 18
· Lot 3: Stormwater BMP’s satisfying Core Requirement #9 will be used to the maximum extent
feasible to mitigate new runoff created by the proposed single-family residence and other
impervious surfaces on-site. A 30’x9’ gravel filled full infiltration trench is proposed on Lot 3
to the west of the proposed structure to mitigate stormwater from impervious areas. This
report assumes that the maximum impervious surface per zoning (4,327 SF) will be conveyed
to this infiltration trench. Additionally, an emergency overflow to the public storm system
from the infiltration trench will be provided.
WWHM 2012 was used to model the proposed condition as follows:
· Lot 1: The modeled limits of disturbance for Lot 1 is 8,230 SF. The maximum impervious
surface per R-6 zoning of 4,527 SF was assumed, with the entirety of this area being conveyed
to the full infiltration trench. Per Table 1.2.9.A in the RSWDM, the area going to full infiltration
can be subtracted from the model. The remaining 3,703 SF of pervious surface on Lot 1 will
meet soil amendment requirement as detailed in Section C.2.13 of the RSWDM; therefore, it
has been modeled as 100% pasture with flat slopes in type A/B soils.
· Lot 2: The modeled limits of disturbance for Lot 2 is 8,043 SF. The maximum impervious
surface per R-6 zoning of 4,424 SF was assumed, with the entirety of this area being conveyed
to the full infiltration trench. Per Table 1.2.9.A in the RSWDM, the area going to full infiltration
can be subtracted from the model. The remaining 3,619 SF of pervious surface on Lot 1 will
meet soil amendment requirement as detailed in Section C.2.13 of the RSWDM; therefore, it
has been modeled as 100% pasture with flat slopes in type A/B soils.
· Lot 3: The modeled limits of disturbance for Lot 3 is 7,868 SF. The maximum impervious
surface per R-6 zoning of 4,327 SF was assumed, with the entirety of this area being conveyed
to the full infiltration trench. Per Table 1.2.9.A in the RSWDM, the area going to full infiltration
can be subtracted from the model. The remaining 3,541 SF of pervious surface on Lot 1 will
meet soil amendment requirement as detailed in Section C.2.13 of the RSWDM; therefore, it
has been modeled as 100% pasture with flat slopes in type A/B soils.
· ROW Dedication & Road Widening: The modeled limits of disturbance for the ROW
dedication area and road widening is 2,995 SF. This will include 838 SF of sidewalk, 768 SF of
driveway entrance as well as 485 SF of asphalt road repair. The remaining 904 SF of pervious
surface will meet soil amendment requirement as detailed in Section C.2.13 of the RSWDM;
therefore, it has been modeled as 100% pasture with moderate slopes in type C soils.
Please refer to Core Requirement #9 in Section II of the TIR for additional discussion. A Developed
Conditions Map is provided as Figure 5. A summary of the existing and developed analyses is provided in
the table on the following page.
Meadow Ave Short Plat Preliminary Technical Information Report
3/7/2022 P a g e | 19
On-site + Off-Site Existing Proposed
Condition Measured Modeled Measured Modeled
Lawn, Mod: 14,050 SF
(0.322 AC)
14,050 SF
(0.322 AC)
11,850
(0.272 AC)
Pasture, Mod: 11,850
(0.272 AC)
Roof, Flat: 1,995 SF
(0.046 AC)
1,995 SF
(0.046 AC)
9,729 SF
(0.223 AC)
Driveway, Flat: 10,122 SF
(0.232 AC)
10,122 SF
(0.232 AC)
4,418 SF
(0.101 AC)
768 SF
(0.018 AC)
Sidewalk, Flat: 719
(0.017 AC)
719
(0.017 AC)
838 SF
(0.019 AC)
838 SF
(0.019 AC)
Road, Flat: 434 SF
(0.010 AC)
434 SF
(0.010 AC)
485 SF
(0.011 AC)
485 SF
(0.011 AC)
Total Area: 27,320 SF
(0.627 AC)
27,320 SF
(0.627 AC)
27,320 SF
(0.627 AC)
13,941 SF
(0.320 AC)
Part C: Performance Standards
Based on the City of Renton’s flow control map, the project site is located within the Peak Rate Flow
Control Standard (Existing Site Conditions). Flow control facilities are required to match the developed
peak discharge rates to existing site conditions peak discharge rates for 2-, 10- and 100-year return
periods. However, as determined in Part D on the following page, the site meets flow control exemption
2 per Section 1.2.3.1.B of the RSWDM, and flow control facilities are not required.
Per section 1.2.9.3.1 of the RSWDM, this project is classified as a small subdivision; therefore, it is
subject to the Small Road Improvement and Urban Road Improvement Project BMP Requirements
detailed in Section 1.2.9.3.2 in the RSWDM.
The site falls within a Basic Water Quality treatment area in accordance with Section 1.2.8.1.A of the
RSWDM, however new plus replaced impervious pollution generating areas within the project site is
under 5,000 SF. Therefore, water quality treatment is not required.
Part D: Flow Control System
As shown in the table below, the proposed stormwater BMPs result in a 0.2289 CFS decrease in the 100-
year flow using 15-minutes time steps. This is below the allowable threshold of a 0.15 CFS maximum
increase per Section 1.2.3.1.B of the RSWDM; therefore, the project meets flow control exemption 2. No
formal flow control facilities are proposed at this time; however, flow control BMPs will be implemented
as described in Core Requirement #9 in Section II of this TIR. Please refer to Appendix B for a copy of the
full WWHM data output.
Meadow Ave Short Plat Preliminary Technical Information Report
3/7/2022 P a g e | 20
Part E: Water Quality System
In accordance with Section 1.2.8.1.A of the RSWDM, Basic Water Quality Treatment is not required for
this project as new plus replaced pollution generating impervious surfaces (PGIS) does not exceed 5,000
SF. The development results in 768 SF of concrete driveway within the ROW dedication area, 485 SF of
pavement replacement within the existing ROW, and 3,700 SF of on-site driveway is estimated for the
future build-out of Lots 1-3. These quantities total to 4,953 SF of PGIS that will be created or replaced as
a result of this project; therefore, the project meets surface area exemption 1.
Meadow Ave Short Plat Preliminary Technical Information Report
3/7/2022 P a g e | 21
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
A conveyance system analysis will be provided with final engineering
VI. SPECIAL REPORTS AND STUDIES
· Geotechnical Engineering Study by Earth Solutions NW dated March 12, 2020
· Arborist Report/Tree Plan by Layton Tree Consulting, LLC dated February 12, 2020
VII. OTHER PERMITS
· Civil Construction Permit
· Final Short Plat
· Building Permits
· Right-of-Way Use Permit
VIII. CSWPP ANALYSIS AND DESIGN
A CSWPPP will be provided with final engineering.
IX. BOND QUANTITIES, FACILITY SUMMARIES AND DECLARATION of
COVENANT
Bond Quantities, Facility Summary and Declaration of Covenant to be provided with Final Engineering.
X. OPERATION AND MAINTENANCE MANUAL
An Operation and Maintenance Manual to be provided with Final Engineering.
Appendix A
Geotechnical Engineering Study by Earth Solutions NW dated March 12, 2020
EarthSolutionsNWLLC
EarthSolutionsNWLLC
15365 N.E. 90th Street, Suite 100 Redmond, WA98052
(425) 449-4704 Fax (425) 449-4711
www.earthsolutionsnw.com
Geotechnical Engineering
Construction Observation/Testing
Environmental Services
GEOTECHNICAL ENGINEERING STUDY
PROPOSED SHORT PLAT
3804 MEADOW AVENUE NORTH
RENTON, WASHINGTON
ES-7126
PREPARED FOR
MR. HUY NGUYEN
March 12, 2020
_________________________
Brian C. Snow, G.I.T.
Staff Geologist
_________________________
Keven D. Hoffmann, P.E.
Senior Project Manager
GEOTECHNICAL ENGINEERING STUDY
PROPOSED SHORT PLAT
3804 MEADOW AVENUE NORTH
RENTON, WASHINGTON
ES-7126
Earth Solutions NW, LLC
15365 Northeast 90th Street, Suite 100
Redmond, Washington 98052
Phone: 425-449-4704 | Fax: 425-449-4711
www.earthsolutionsnw.com
03/16/2020
Geotechnical-Engineering Report
Important Information about This
Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes.
While you cannot eliminate all such risks, you can manage them. The following information is provided to help.
The Geoprofessional Business Association (GBA) has prepared this advisory to help you – assumedly a client representative – interpret and apply this geotechnical-engineering report as effectively as possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface conditions at project sites and development of them that, for decades, have been a principal cause of construction delays, cost overruns, claims, and disputes. If you have questions or want more information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Active engagement in GBA exposes geotechnical engineers to a wide array of risk-confrontation techniques that can be of genuine benefit for everyone involved with a construction project.
Understand the Geotechnical-Engineering Services Provided for this ReportGeotechnical-engineering services typically include the planning, collection, interpretation, and analysis of exploratory data from widely spaced borings and/or test pits. Field data are combined with results from laboratory tests of soil and rock samples obtained from field exploration (if applicable), observations made during site reconnaissance, and historical information to form one or more models of the expected subsurface conditions beneath the site. Local geology and alterations of the site surface and subsurface by previous and proposed construction are also important considerations. Geotechnical engineers apply their engineering training, experience, and judgment to adapt the requirements of the prospective project to the subsurface model(s). Estimates are made of the subsurface conditions that will likely be exposed during construction as well as the expected performance of foundations and other structures being planned and/or affected by construction activities.
The culmination of these geotechnical-engineering services is typically a geotechnical-engineering report providing the data obtained, a discussion of the subsurface model(s), the engineering and geologic engineering assessments and analyses made, and the recommendations developed to satisfy the given requirements of the project. These reports may be titled investigations, explorations, studies, assessments, or evaluations. Regardless of the title used, the geotechnical-engineering report is an engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination, systematic inquiry, or thorough investigation of all site and subsurface conditions.
Geotechnical-Engineering Services are Performed for Specific Purposes, Persons, and Projects, and At Specific TimesGeotechnical engineers structure their services to meet the specific needs, goals, and risk management preferences of their clients. A geotechnical-engineering study conducted for a given civil engineer
will not likely meet the needs of a civil-works constructor or even a
different civil engineer. Because each geotechnical-engineering study
is unique, each geotechnical-engineering report is unique, prepared solely for the client.
Likewise, geotechnical-engineering services are performed for a specific
project and purpose. For example, it is unlikely that a geotechnical-
engineering study for a refrigerated warehouse will be the same as
one prepared for a parking garage; and a few borings drilled during
a preliminary study to evaluate site feasibility will not be adequate to
develop geotechnical design recommendations for the project.
Do not rely on this report if your geotechnical engineer prepared it:
• for a different client;
• for a different project or purpose;
• for a different site (that may or may not include all or a portion of
the original site); or
• before important events occurred at the site or adjacent to it;
e.g., man-made events like construction or environmental
remediation, or natural events like floods, droughts, earthquakes,
or groundwater fluctuations.
Note, too, the reliability of a geotechnical-engineering report can
be affected by the passage of time, because of factors like changed
subsurface conditions; new or modified codes, standards, or
regulations; or new techniques or tools. If you are the least bit uncertain
about the continued reliability of this report, contact your geotechnical
engineer before applying the recommendations in it. A minor amount
of additional testing or analysis after the passage of time – if any is
required at all – could prevent major problems.
Read this Report in Full
Costly problems have occurred because those relying on a geotechnical-
engineering report did not read the report in its entirety. Do not rely on
an executive summary. Do not read selective elements only. Read and refer to the report in full.
You Need to Inform Your Geotechnical Engineer About Change
Your geotechnical engineer considered unique, project-specific factors
when developing the scope of study behind this report and developing
the confirmation-dependent recommendations the report conveys.
Typical changes that could erode the reliability of this report include
those that affect:
• the site’s size or shape;
• the elevation, configuration, location, orientation,
function or weight of the proposed structure and
the desired performance criteria;
• the composition of the design team; or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
or site changes – even minor ones – and request an assessment of their
impact. The geotechnical engineer who prepared this report cannot accept
responsibility or liability for problems that arise because the geotechnical engineer was not informed about developments the engineer otherwise would have considered.
Most of the “Findings” Related in This Report Are Professional Opinions
Before construction begins, geotechnical engineers explore a site’s
subsurface using various sampling and testing procedures. Geotechnical engineers can observe actual subsurface conditions only at those specific locations where sampling and testing is performed. The data derived from
that sampling and testing were reviewed by your geotechnical engineer,
who then applied professional judgement to form opinions about
subsurface conditions throughout the site. Actual sitewide-subsurface
conditions may differ – maybe significantly – from those indicated in
this report. Confront that risk by retaining your geotechnical engineer
to serve on the design team through project completion to obtain
informed guidance quickly, whenever needed.
This Report’s Recommendations Are Confirmation-Dependent
The recommendations included in this report – including any options or
alternatives – are confirmation-dependent. In other words, they are not
final, because the geotechnical engineer who developed them relied heavily
on judgement and opinion to do so. Your geotechnical engineer can finalize
the recommendations only after observing actual subsurface conditions
exposed during construction. If through observation your geotechnical
engineer confirms that the conditions assumed to exist actually do exist,
the recommendations can be relied upon, assuming no other changes have
occurred. The geotechnical engineer who prepared this report cannot assume
responsibility or liability for confirmation-dependent recommendations if you
fail to retain that engineer to perform construction observation.
This Report Could Be Misinterpreted
Other design professionals’ misinterpretation of geotechnical-
engineering reports has resulted in costly problems. Confront that risk
by having your geotechnical engineer serve as a continuing member of
the design team, to:
• confer with other design-team members;
• help develop specifications;
• review pertinent elements of other design professionals’ plans and
specifications; and
• be available whenever geotechnical-engineering guidance is needed.
You should also confront the risk of constructors misinterpreting this report. Do so by retaining your geotechnical engineer to participate in prebid and preconstruction conferences and to perform construction-phase observations.
Give Constructors a Complete Report and GuidanceSome owners and design professionals mistakenly believe they can shift unanticipated-subsurface-conditions liability to constructors by limiting the information they provide for bid preparation. To help prevent the costly, contentious problems this practice has caused, include the complete geotechnical-engineering report, along with any attachments or appendices, with your contract documents, but be certain to note
conspicuously that you’ve included the material for information purposes only. To avoid misunderstanding, you may also want to note that
“informational purposes” means constructors have no right to rely on
the interpretations, opinions, conclusions, or recommendations in the
report. Be certain that constructors know they may learn about specific
project requirements, including options selected from the report, only
from the design drawings and specifications. Remind constructors
that they may perform their own studies if they want to, and be sure to
allow enough time to permit them to do so. Only then might you be in
a position to give constructors the information available to you, while
requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions. Conducting prebid and
preconstruction conferences can also be valuable in this respect.
Read Responsibility Provisions Closely
Some client representatives, design professionals, and constructors do
not realize that geotechnical engineering is far less exact than other
engineering disciplines. This happens in part because soil and rock on
project sites are typically heterogeneous and not manufactured materials
with well-defined engineering properties like steel and concrete. That
lack of understanding has nurtured unrealistic expectations that have
resulted in disappointments, delays, cost overruns, claims, and disputes.
To confront that risk, geotechnical engineers commonly include
explanatory provisions in their reports. Sometimes labeled “limitations,”
many of these provisions indicate where geotechnical engineers’
responsibilities begin and end, to help others recognize their own
responsibilities and risks. Read these provisions closely. Ask questions.
Your geotechnical engineer should respond fully and frankly.
Geoenvironmental Concerns Are Not Covered
The personnel, equipment, and techniques used to perform an
environmental study – e.g., a “phase-one” or “phase-two” environmental
site assessment – differ significantly from those used to perform a
geotechnical-engineering study. For that reason, a geotechnical-engineering
report does not usually provide environmental findings, conclusions, or
recommendations; e.g., about the likelihood of encountering underground
storage tanks or regulated contaminants. Unanticipated subsurface
environmental problems have led to project failures. If you have not
obtained your own environmental information about the project site,
ask your geotechnical consultant for a recommendation on how to find
environmental risk-management guidance.
Obtain Professional Assistance to Deal with Moisture Infiltration and Mold
While your geotechnical engineer may have addressed groundwater,
water infiltration, or similar issues in this report, the engineer’s
services were not designed, conducted, or intended to prevent
migration of moisture – including water vapor – from the soil
through building slabs and walls and into the building interior, where
it can cause mold growth and material-performance deficiencies.
Accordingly, proper implementation of the geotechnical engineer’s recommendations will not of itself be sufficient to prevent moisture infiltration. Confront the risk of moisture infiltration by
including building-envelope or mold specialists on the design team. Geotechnical engineers are not building-envelope or mold specialists.
Copyright 2019 by Geoprofessional Business Association (GBA). Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with GBA’s specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of
GBA, and only for purposes of scholarly research or book review. Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm, individual, or other entity that so uses this document without being a GBA member could be committing negligent or intentional (fraudulent) misrepresentation.
Telephone: 301/565-2733
e-mail: info@geoprofessional.org www.geoprofessional.org
March 12, 2020
ES-7126
Mr. Huy Nguyen
15400 Southeast 155th Place, Unit 99
Renton, Washington 98058
Dear Mr. Nguyen:
Earth Solutions NW, LLC (ESNW), is pleased to present this geotechnical report for the subject
site. While specific site plans were not available at the time of this report, we presume the site
will be developed into a short plat, comprised of several two- to three-story residential structures
and related infrastructure improvements. Based on the results of our study, construction of a
short plat is feasible from a geotechnical standpoint.
Based on the conditions observed during the fieldwork, the subject site is underlain primarily by
medium dense recessional outwash deposits. The proposed structures can be supported on
conventional spread and continuous foundations bearing on undisturbed competent native soil,
recompacted native soil, or new structural fill. We anticipate competent native soil suitable for
support of foundations will be encountered beginning at depths of about two to four feet below
existing grades across the site.
This report provides geotechnical analyses and recommendations for the proposed short plat.
The opportunity to be of service to you is appreciated. If you have any questions regarding the
content of this geotechnical engineering study, please call.
Sincerely,
EARTH SOLUTIONS NW, LLC
Brian C. Snow, G.I.T.
Staff Geologist
15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 •(425) 449-4704 • FAX (425) 449-4711
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
Earth Solutions NW, LLC
Table of Contents
ES-7126
PAGE
INTRODUCTION ................................................................................. 1
General..................................................................................... 1
Project Description ................................................................. 2
SITE CONDITIONS ............................................................................. 2
Surface ..................................................................................... 2
Subsurface .............................................................................. 2
Topsoil and Fill ............................................................. 2
Native Soil ..................................................................... 3
Geologic Setting ........................................................... 3
Groundwater ................................................................. 3
GEOLOGICALLY HAZARDOUS AREAS EVALUATION .................. 3
Erosion Hazard ........................................................................ 4
Landslide Hazard .................................................................... 4
Regulated Slopes .................................................................... 5
Seismic Hazard ....................................................................... 5
Analysis of Proposal .............................................................. 6
DISCUSSION AND RECOMMENDATIONS ....................................... 6
General..................................................................................... 6
Site Preparation and Earthwork ............................................. 6
Temporary Erosion Control ......................................... 6
In-Situ and Imported Soil ............................................. 6
Structural Fill ................................................................ 7
Subgrade Preparation .................................................. 7
Excavations and Slopes .............................................. 7
Foundations ............................................................................ 8
Seismic Design ....................................................................... 9
Slab-on-Grade Floors ............................................................. 9
Retaining Walls ....................................................................... 9
Drainage................................................................................... 10
Infiltration Evaluation ................................................... 10
Utility Support and Trench Backfill ....................................... 11
LIMITATIONS ...................................................................................... 11
Additional Services ................................................................. 11
Earth Solutions NW, LLC
Table of Contents
Continued
ES-7126
GRAPHICS
Plate 1 Vicinity Map
Plate 2 Test Pit Location Plan
Plate 3 Retaining Wall Drainage Detail
Plate 4 Footing Drain Detail
APPENDICES
Appendix A Subsurface Exploration
Test Pit Logs
Appendix B Laboratory Test Results
Earth Solutions NW, LLC
GEOTECHNICAL ENGINEERING STUDY
PROPOSED SHORT PLAT
3804 MEADOW AVENUE NORTH
RENTON, WASHINGTON
ES-7126
INTRODUCTION
General
This geotechnical engineering study (study) was prepared for the proposed short plat to be
constructed on the east side of Meadow Avenue North, nearest the intersection with North 38th
Street, in the Kennydale neighborhood of Renton, Washington. To complete the scope of
services, we performed the following:
Subsurface exploration to characterize the soil and groundwater conditions;
In-situ infiltration testing;
Laboratory testing of representative soil samples collected on site;
Review of on-site geologically hazardous areas;
Engineering analyses and recommendations for the proposed short plat, and;
Preparation of this report.
The following documents and resources were reviewed as part of our report preparation:
Preliminary Geologic Map of Seattle and Vicinity, Washington, compiled by H.H. Waldron
et al., dated 1961;
Web Soil Survey (WSS) online resource, maintained by the Natural Resources
Conservation Service (NRCS) under the United States Department of Agriculture (USDA);
Soil Survey of Snoqualmie Pass Area, Parts of King and Pierce Counties, Washington,
prepared by the United States Department of Agriculture Soil Conservation Service, dated
1990;
Soil Survey of King County Area, Washington, prepared by the United States Department
of Agriculture Soil Conservation Service, dated 1973;
Liquefaction Susceptibility Map 11-5, prepared by the King County Flood Control District,
dated May 2010;
Renton Municipal Code (RMC);
City of Renton Critical Areas Map: Online “COR Maps”, and;
City of Renton Surface Water Design Manual.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 2
Earth Solutions NW, LLC
Project Description
We understand the proposed project will likely consist of constructing a three-lot short plat and
associated improvements. At the time this report was prepared, neither site plans nor building
load values were available for review. However, we anticipate the proposed residential structures
will be two to three stories and constructed using relatively lightly loaded wood framing supported
atop conventional foundation systems. Based on our experience with similar developments, we
estimate wall loads of about 1 to 2 kips per linear foot and slab-on-grade loading of 150 pounds
per square foot (psf) will be incorporated into final designs.
Grade cuts and fills to establish individual-lot subgrade and finish grade elevations are expected
to be less than five feet. Stormwater management will presumably use infiltration to the extent
feasible.
If the above design assumptions are incorrect or change, ESNW should be contacted to review
the recommendations provided in this report. ESNW should review the final designs to verify the
geotechnical recommendations provided in this report have been incorporated into the plans.
SITE CONDITIONS
Surface
The subject site is located northeast of the intersection between North 38th Street and Meadow
Avenue North, in Renton, Washington. The approximate location of the property is illustrated on
Plate 1 (Vicinity Map). The site is comprised of one tax parcel (King County Parcel No. 334270-
0570), totaling about 0.59 acres.
The site is currently developed with a single-family residence and a detached shed structure.
The existing topography is relatively level, with less than two feet of elevation change across the
site. To the east of the sound barrier wall, grades descend sharply to the Interstate 405 corridor.
Subsurface
An ESNW representative observed, logged, and sampled five test pits on February 17, 2020.
The test pits were excavated at accessible locations within the property, using a mini-trackhoe
and operator retained by our firm. The approximate locations of the test pits are depicted on
Plate 2 (Test Pit Location Plan). Please refer to the test pit logs provided in Appendix A for a
more detailed description of subsurface conditions. Representative soil samples collected at the
test pit locations were analyzed in general accordance with Unified Soil Classification System
(USCS) and USDA methods and procedures.
Topsoil and Fill
Topsoil was generally encountered within the upper 6 to 42 inches of existing grades where test
pits were excavated. In some instances, relic topsoil horizons were observed beneath fill soil.
The topsoil was characterized by a dark brown color, the presence of fine organic material, and
small root intrusions. Root zones extended between about four to five feet below the existing
ground surface (bgs).
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 3
Earth Solutions NW, LLC
Fill was observed at test pit locations TP-1, TP-2, TP-3, and TP-4, extending to a maximum depth
of about five feet bgs. The fill soil generally consisted of tan silty sand with minor interbedded
topsoil. In TP-4, rebar, plastic bags, and wood debris was observed.
Native Soil
Underlying the topsoil and fill, the native soil consisted primarily of medium dense silty sand and
poorly graded sand with variable silt and gravel content (USCS: SM, SP, and SP-SM). The native
deposits were primarily observed in a wet condition at the time of our exploration, and weak iron
oxide staining was noted at several locations. The maximum exploration depth was roughly nine
feet bgs.
Geologic Setting
Geologic mapping of the area indicates the site is underlain by younger gravel (Qyg) and younger
sand (Qys) as part of the Vashon recessional outwash series. Recessional outwash was
deposited by glacial meltwater and is readily comprised of silt, clay, sand, and gravel.
The referenced WSS resource identifies Indianola loamy sand (Map Unit Symbol: InC) across
the majority of the site, with Norma sandy loam (Map Unit Symbol: No) mapped along the eastern
edge. The Indianola loamy sands were formed in eskers, kames, and terraces, and the Norma
sandy loams were formed in flood plains.
Based on our field observations, the native soil on site is generally consistent with the geologic
and soil mapping resources outlined in this section.
Groundwater
During the subsurface exploration, perched groundwater seepage was encountered at test pit
locations TP-3 and TP-4 at eight-and-one-half and five-and-one-half feet bgs, respectively.
Groundwater seepage may be encountered within site excavations depending on the time of year
and extent of grading activities. Seepage rates and elevations fluctuate depending on many
factors, including precipitation duration and intensity, the time of year, and soil conditions. In
general, groundwater flow rates are higher during the winter, spring, and early summer months.
GEOLOGICALLY HAZARDOUS AREAS EVALUATION
To evaluate geologically hazardous areas, we reviewed Chapter 4-3 of the City of Renton (City)
Municipal Code (RMC). The RMC provides designation and definition criteria for identifying
specific geologically hazardous areas and developing appropriate site development plans which
will not adversely impact the site or surrounding properties.
According to the referenced City Critical Areas Map, erosion hazards, landslide hazards, and
regulated slopes are all mapped within 50 feet of the subject site. The mapped hazards are
largely associated with the hillslope east of the subject site (outside of the property boundaries)
and bordering Interstate 405. Additionally, a seismic hazard area is mapped within 500 feet of
the subject site.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 4
Earth Solutions NW, LLC
Erosion Hazard
According to RMC 4-3-050G5c, erosion hazard areas can be defined as:
i. Low Erosion Hazard (EL): Areas with soils characterized by the NRCS as having slight or
moderate erosion potential and a slope less than 15 percent.
ii. High Erosion Hazard (EH): Areas with soils characterized by the NRCS as having severe
or very severe erosion potential and a slope greater than 15 percent.
The referenced City Critical Areas Map designates a high erosion hazard on the eastern slope of
the site (bordering Interstate 405). The site soils are predominantly mapped as Indianola loamy
sand (Map Unit Symbol: InC), with Norma sandy loam (Map Unit Symbol: No) along the eastern
edge. The USDA SCS 1973 King County Soils Survey classifies the erosion hazard of Indianola
soils as slight to moderate. The USDA SCS 1990 Snoqualmie Pass Area Soil Survey states
there is no hazard of erosion associated with Norma soils.
In our opinion, given that the site topography is relatively level, the site soils within the proposed
development areas generally exhibit low erosivity potential in a typical construction setting. Best
Management Practices (BMPs), in general accordance with City surface water and stormwater
regulations, should be used for site design and development. At a minimum, silt fencing should
be placed along the entire development envelope, and soil stockpiles should be covered when
not in use. If construction occurs during periods of wet weather, methods to control surface water
runoff will likely be necessary. Construction entrances should be surfaced with quarry spalls to
minimize off-site tracking of silt and soil generated during site construction.
Landslide Hazard
Per RMC 4-3-050G5b, landslide hazard areas can be defined as:
i. Low Landslide Hazard (LL): Areas with slopes less than 15 percent.
ii. Medium Landslide Hazard (LM): Areas with slopes between 15 percent and 40 percent,
underlain by soils that consist largely of sand, gravel, or glacial till.
iii. High Landslide Hazards (LH): Areas with slopes greater than 40 percent and areas with
slopes between 15 percent and 40 percent underlain by soils consisting largely of silt and
clay.
iv. Very High Landslide Hazards (LV): Areas of known mapped or identified landslide
deposits.
The referenced City Critical Areas Map designates a landslide hazard on the eastern slope
bordering Interstate 405. In our opinion, given that the slope is largely vegetated with
blackberries, trees, and other shrubs; has a slope of about 31 percent; and is outside of the
proposed development area, the landslide hazard may be characterized as low to medium.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 5
Earth Solutions NW, LLC
Regulated Slopes
According to RMC 4-3-050G5a, steep slopes may be categorized into two types:
i. Sensitive Slopes: A hillside, or portion thereof (excluding engineering retaining walls),
characterized by:
a. An average slope of 25 percent to less than 40 percent, as identified in the City
Steep Slope Atlas or in a method approved by the City, or;
b. An average slope of 40 percent or greater, with a vertical rise of less than 15 feet,
as identified in the City Steep Slope Atlas or in a method approved by the City;
c. Abutting an average slope of 25 percent to 40 percent, as identified in the City Steep
Slope Atlas or in a method approved by the City.
ii. Protected Slopes: A hillside, or portion thereof, characterized by an average slope of 40
percent or greater grade and having a minimum vertical rise of 15 feet, as identified in the
City Steep Slope Atlas or in a method approved by the City.
The referenced City Critical Areas Map designates portions of the eastern slope both as sensitive
and protected slopes. Because the eastern slope is located outside of and well away from the
anticipated grading and construction activities, it is our opinion that the designations of sensitive
and/or protected slopes on site should not impact the proposed short plat from a geotechnical
standpoint.
Seismic Hazard
Per RMC 4-3-050G5d, seismic hazard areas can be defined as:
i. Low Seismic Hazard (SL): Areas underlain by dense soils or bedrock. These soils
generally have site classifications of A through D, as defined in the 2012 International
Building Code (2012 IBC).
ii. High Seismic Hazard (SH): Areas underlain by soft or loose, saturated soils. These soils
generally have site classifications E or F, as defined in the 2012 IBC.
The referenced City Critical Areas Map designates a seismic hazard area approximately 260 feet
to the east of the subject site. Based on the conditions observed during our subsurface
exploration and the lack of an established, shallow groundwater table, it is our opinion that the
seismic hazard on site is low. The referenced Liquefaction Susceptibility Map identifies low
potential for liquefaction at the subject site.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 6
Earth Solutions NW, LLC
Analysis of Proposal
ESNW should be contacted to review both the preliminary and final project plans to further
evaluate the proposed construction and any potential impacts to geologically hazardous areas.
If more significant grading activities or larger-than-anticipated residential structures are proposed,
ESNW should reevaluate the potential impacts to the adjacent hazard areas.
DISCUSSION AND RECOMMENDATIONS
General
Based on the results of our investigation, construction of the proposed short plat is feasible from
a geotechnical standpoint. The primary geotechnical considerations associated with the
proposed development include site preparation and earthwork, suitability of on-site soil as
structural fill, subgrade preparation, temporary excavations, building foundations, retaining walls,
drainage, and infiltration feasibility.
Site Preparation and Earthwork
Site preparation activities should consist of installing temporary erosion control measures and
performing site stripping within the designated clearing limits. Subsequent earthwork activities
may involve infrastructure and utility installations.
Temporary Erosion Control
Erosion control measures should conform to the standards and requirements of the Washington
State Department of Ecology, King County, and City, where applicable. Please refer to the
Erosion Hazard section of this report for a more detailed discussion on recommended temporary
erosion and sediment control measures during construction.
In-Situ and Imported Soil
The majority of the soils encountered during our subsurface exploration have a moderate to high
sensitivity to moisture and were generally in a wet condition at the time of exploration. The soils
anticipated to be exposed at this site will degrade if exposed to wet weather and construction
traffic. Compaction of the soils to the levels necessary for use as structural fill may be difficult or
impossible during wet weather conditions. Soils encountered during site excavations that are
excessively over the optimum moisture content will likely require aeration or treatment prior to
placement and compaction. Conversely, soils that are substantially below the optimum moisture
content will require moisture conditioning through the addition of water prior to use as structural
fill. An ESNW representative should determine the suitability of in-situ soils for use as structural
fill at the time of construction.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 7
Earth Solutions NW, LLC
Imported soil intended for use as structural fill should be evaluated by ESNW during construction.
The imported soil must be workable to the optimum moisture content, as determined by the
Modified Proctor Method (ASTM D1557), at the time of placement and compaction. During wet
weather conditions, imported soil intended for use as structural fill should consist of a well-graded,
granular soil with a fines content of 5 percent or less (where the fines content is defined as the
percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction).
Structural Fill
Structural fill is defined as compacted soil placed in foundation, slab-on-grade, roadway,
permanent slope, retaining wall, and utility trench backfill areas. Structural fill placed and
compacted during site grading activities should meet the following specifications and guidelines:
Structural fill material Granular soil*
Moisture content At or slightly above optimum**
Relative compaction (minimum) 95 percent (Modified Proctor)
Loose lift thickness (maximum) 12 inches
* The existing soil may not be suitable for use as structural fill unless the soil is at (or slightly above) the optimum
moisture content at the time of placement and compaction
** Soil shall not be placed dry of optimum and should be evaluated by ESNW during construction
With respect to underground utility installations and backfill, local jurisdictions may dictate the soil
type(s) and compaction requirements. Areas of otherwise unsuitable material and debris should
be removed from structural areas and replaced with structural fill.
Subgrade Preparation
Following site stripping, ESNW should observe the subgrade to confirm soil conditions are as
anticipated and to provide supplementary recommendations for subgrade preparation as
necessary. In general, foundation subgrade surfaces should be compacted in situ to a minimum
depth of one foot below the design subgrade elevation. Uniform compaction of the foundation
and slab subgrade areas will establish a relatively consistent subgrade condition below the
foundation and slab elements. Supplementary recommendations for subgrade improvement may
be provided at the time of construction and would likely include further mechanical compaction
or overexcavation and replacement with suitable structural fill.
Excavations and Slopes
Excavation activities on site are likely to expose loose to medium dense native soil beginning at
depths of approximately two to four feet bgs. Based on the soil conditions observed at the
subsurface exploration locations, the following maximum allowable temporary slope inclinations
may be used.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 8
Earth Solutions NW, LLC
The applicable Federal Occupation Safety and Health Administration and Washington Industrial
Safety and Health Act soil classifications are also provided:
Areas exposing groundwater seepage 1.5H:1V (Type C)
Loose soil; fill 1.5H:1V (Type C)
Medium dense to dense native soil 1H:1V (Type B)
Permanent slopes should be planted with vegetation to both enhance stability and minimize
erosion and should maintain a gradient of 2H:1V or flatter. The presence of perched groundwater
may cause localized sloughing of temporary slopes. An ESNW representative should observe
temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed
soil conditions and to provide additional excavation and slope recommendations as necessary.
If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be
necessary to support excavations.
Foundations
The proposed residential structures can be supported on conventional spread and continuous
footings bearing on undisturbed competent native soil, compacted native soil, or new structural
fill. We anticipate competent native soil suitable for support of foundations will be encountered
at a depth of about two to four feet below existing grades. Where loose or unsuitable soil
conditions are encountered at foundation subgrade elevations, compaction of the soils to the
specifications of structural fill or overexcavation and replacement with suitable structural fill will
likely be necessary.
Provided the structure will be supported as described above, the following parameters may be
used for design of the new foundations:
Allowable soil bearing capacity 2,500 psf
Passive earth pressure 300 pcf
Coefficient of friction 0.40
A one-third increase in the allowable soil bearing capacity can be assumed for short-term wind
and seismic loading conditions. The passive earth pressure and coefficient of friction values
include a safety factor of 1.5. With structural loading as expected, total settlement in the range
of one inch is anticipated, with differential settlement of about one-half inch. The majority of the
settlement should occur during construction when dead loads are applied.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 9
Earth Solutions NW, LLC
Seismic Design
The 2015 IBC recognizes the American Society of Civil Engineers (ASCE) for seismic site class
definitions. In accordance with Table 20.3-1 of the ASCE Minimum Design Loads for Buildings
and Other Structures Manual, Site Class D should be used for design. Please refer to the Seismic
Hazard section of this report for an opinion of the site-specific seismic hazard.
Slab-on-Grade Floors
Slab-on-grade floors should be supported on a firm and unyielding subgrade consisting of
competent native soil or at least 12 inches of new structural fill. Unstable or yielding areas of the
subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior
to slab construction.
A capillary break consisting of a minimum of four inches of free-draining crushed rock or gravel
should be placed below the slab. The free-draining material should have a fines content of 5
percent or less defined as the percent passing the number 200 sieve, based on the minus three-
quarters-inch fraction. In areas where slab moisture is undesirable, installation of a vapor barrier
below the slab should be considered. If used, the vapor barrier should consist of a material
specifically designed to function as a vapor barrier and should be installed in accordance with the
manufacturer’s specifications.
Retaining Walls
Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The
following parameters may be used for retaining wall design:
Active earth pressure (unrestrained condition) 35 pcf
At-rest earth pressure (restrained condition) 55 pcf
Traffic surcharge (passenger vehicles) 70 psf (rectangular distribution)
Passive earth pressure 300 pcf
Coefficient of friction 0.40
Seismic surcharge 6H psf*
* Where H equals the retained height (in feet)
The passive earth pressure and coefficient of friction values include a safety factor of 1.5.
Additional surcharge loading from adjacent foundations, sloped backfill, or other loads should
be included in the retaining wall design. Drainage should be provided behind retaining walls
such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic
pressures should be included in the wall design.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 10
Earth Solutions NW, LLC
Retaining walls should be backfilled with free-draining material that extends along the height of
the wall and a distance of at least 18 inches behind the wall. The upper 12 inches of the wall
backfill may consist of a less permeable soil, if desired. A perforated drainpipe should be placed
along the base of the wall and connected to an approved discharge location. A typical retaining
wall drainage detail is provided on Plate 3. If drainage is not provided, hydrostatic pressures
should be included in the wall design.
Drainage
Discrete zones of perched groundwater seepage should be anticipated in site excavations
depending on the time of year grading operations take place. Temporary measures to control
surface water runoff and groundwater during construction would likely involve interceptor
trenches, interceptor swales, and sumps. ESNW should be consulted during preliminary grading
to both identify areas of seepage and provide recommendations to reduce the potential for
seepage-related instability.
Finish grades must be designed to direct surface drain water away from structures and slopes.
Water must not be allowed to pond adjacent to structures or slopes. In our opinion, foundation
drains should be installed along building perimeter footings. A typical foundation drain detail is
provided on Plate 4.
Infiltration Evaluation
In accordance with the 2017 City of Renton Surface Water Design Manual (2017 RSWDM), a
small-scale Pilot Infiltration Test (PIT) was completed at test pit location TP-2. The PIT was
completed by excavating a roughly three-foot by four-foot (infiltration surface) test pit to a depth
of about three and one-half feet bgs and following the prescribed PIT procedure as outlined in
the 2017 RSWDM.
Based on the results of the PIT, the following design parameters are recommended:
Measured infiltration rate 10 inches per hour (iph)
Total correction factor 0.5
Design infiltration rate 5 iph
The correction factor of 0.5 was selected based on the guidelines provided in the 2017 RSWDM.
In our opinion, a correction factor of 0.5 is suitable for the observed conditions at the testing
location. At this time, the design infiltration rate of 5 iph is applicable only at the location of TP-2
and only at the infiltration test depth. ESNW should be contacted to review stormwater
management plans if infiltration is used for design. Supplementary recommendations and/or
testing may be necessary depending on the size, depth, and siting of infiltration facilities.
Mr. Huy Nguyen ES-7126
March 12, 2020 Page 11
Earth Solutions NW, LLC
Utility Support and Trench Backfill
The soils observed at the subsurface exploration locations are generally suitable for support of
utilities. Use of the native soil as structural backfill in the utility trench excavations will depend on
the in-situ moisture content at the time of placement and compaction. If native soil is placed
below the optimum moisture content, settlement will likely occur once wet weather impacts the
trenches. Native soil will be difficult or impossible to use as utility trench backfill during wet
weather conditions. Moisture conditioning or treatment of the soils may be necessary at some
locations prior to use as structural fill. Utility trench backfill should be placed and compacted to
the specifications of structural fill provided in this report or to the applicable requirements of the
presiding jurisdiction.
LIMITATIONS
This study has been prepared for the exclusive use of Mr. Huy Nguyen and his representatives.
The recommendations and conclusions provided in the geotechnical engineering study are
professional opinions consistent with the level of care and skill that is typical of other members in
the profession currently practicing under similar conditions in this area. A warranty is not
expressed or implied. Variations in the soil and groundwater conditions observed at the test
locations may exist and may not become evident until construction. ESNW should reevaluate
the conclusions provided in this geotechnical engineering study if variations are encountered.
Additional Services
ESNW should have an opportunity to review the final design with respect to the geotechnical
recommendations provided in this report. ESNW should also be retained to provided testing and
consultation services during construction.
Drwn. MRS
Checked BCS Date Mar. 2020
Date 03/13/2020 Proj. No. 7126
Plate 1
Earth Solutions NWLLC
Geotechnical Engineering,Construction
EarthSolutionsNWLLC
EarthSolutionsNWLLC Observation/Testing and Environmental Services
Vicinity Map
Meadow Avenue Short Plat
Renton, Washington
Reference:
King County, Washington
OpenStreetMap.org
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.
SITE
Newcastle
Renton
Drwn. MRS
Checked BCS Date Mar. 2020
Date 03/13/2020 Proj. No. 7126
Plate 2
Earth Solutions NWLLC
Geotechnical Engineering,Construction
EarthSolutionsNWLLC
EarthSolutionsNWLLC Observation/Testing and Environmental Services
Test Pit Location Plan
Meadow Avenue Short Plat
Renton, Washington
NORTH
0 30 60 120
Scale in Feet
1"=60'
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-7126, Feb. 2020
Subject Site
Existing Building
Proposed Lot Letter
A
B
C
Sound
Barrier Wall
TP-1
TP-2
TP-3
TP-4
TP-5
TP-1
130
130MEADOW AVENUE N.SR-405A
N. 38TH
STREET
Drwn. MRS
Checked BCS Date Mar. 2020
Date 03/13/2020 Proj. No. 7126
Plate 3
Earth Solutions NWLLCEarthSolutionsNWLLC
EarthSolutionsNWLLC Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
Retaining Wall Drainage Detail
Meadow Avenue Short Plat
Renton, Washington
NOTES:
Free-draining Backfill should consist
of soil having less than 5 percent fines.
Percent passing No. 4 sieve 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-inch
Drain Rock.
LEGEND:
Free-draining Structural Backfill
1-inch Drain Rock
18" Min.
Structural
Fill
Perforated Rigid Drain Pipe
(Surround in Drain Rock)
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Drwn. MRS
Checked BCS Date Mar. 2020
Date 03/13/2020 Proj. No. 7126
Plate 4
Earth Solutions NWLLC
Geotechnical Engineering,Construction
Observation/Testing and Environmental Services
EarthSolutionsNWLLC
EarthSolutionsNWLLC
Footing Drain Detail
Meadow Avenue Short Plat
Renton, Washington
Slope
Perforated Rigid Drain Pipe
(Surround in Drain 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-inch Drain Rock
SCHEMATIC ONLY - NOT TO SCALE
NOT A CONSTRUCTION DRAWING
Earth Solutions NW, LLC
Appendix A
Subsurface Exploration
Test Pit Logs
ES-7126
Subsurface conditions on site were explored on February 17, 2020, by excavating five test pits
using a mini-trackhoe and operator retained by our firm. The approximate locations of the test
pits are illustrated on Plate 2 of this study. The test pit logs are provided in this Appendix. The
test pits were advanced to a maximum depth of about nine feet bgs.
The final logs represent the interpretations of the field logs and the results of laboratory analyses.
The stratification lines on the logs represent the approximate boundaries between soil types. In
actuality, the transitions may be more gradual.
GRAVEL
AND
GRAVELLYSOILS
CLAYEY GRAVELS, GRAVEL - SAND -
CLAY MIXTURES
WELL-GRADED SANDS, GRAVELLYSANDS, LITTLE OR NO FINES
POORLY-GRADED SANDS,GRAVELLY SAND, LITTLE OR NO
FINES
SILTY SANDS, SAND - SILTMIXTURES
CLAYEY SANDS, SAND - CLAYMIXTURES
INORGANIC SILTS AND VERY FINESANDS, ROCK FLOUR, SILTY OR
CLAYEY FINE SANDS OR CLAYEYSILTS WITH SLIGHT PLASTICITY
INORGANIC CLAYS OF LOW TO
MEDIUM PLASTICITY, GRAVELLYCLAYS, SANDY CLAYS, SILTY CLAYS,LEAN CLAYS
ORGANIC SILTS AND ORGANICSILTY CLAYS OF LOW PLASTICITY
INORGANIC SILTS, MICACEOUS OR
DIATOMACEOUS FINE SAND ORSILTY SOILS
INORGANIC CLAYS OF HIGHPLASTICITY
SILTSANDCLAYS
MORE THAN 50%
OF MATERIAL ISLARGER THANNO. 200 SIEVE
SIZE
MORE THAN 50%OF MATERIAL IS
SMALLER THANNO. 200 SIEVESIZE
MORE THAN 50%OF COARSEFRACTION
PASSING ON NO.4 SIEVE
MORE THAN 50%OF COARSEFRACTION
RETAINED ON NO.4 SIEVE
SOIL CLASSIFICATION CHART
(APPRECIABLEAMOUNT OF FINES)
(APPRECIABLE
AMOUNT OF FINES)
(LITTLE OR NO FINES)
FINEGRAINEDSOILS
SAND
AND
SANDY
SOILS
SILTS
AND
CLAYS
ORGANIC CLAYS OF MEDIUM TO
HIGH PLASTICITY, ORGANIC SILTS
PEAT, HUMUS, SWAMP SOILS WITHHIGH ORGANIC CONTENTS
LETTERGRAPH
SYMBOLSMAJOR DIVISIONS
COARSE
GRAINEDSOILS
TYPICAL
DESCRIPTIONS
WELL-GRADED GRAVELS, GRAVEL -SAND MIXTURES, LITTLE OR NO
FINES
POORLY-GRADED GRAVELS,
GRAVEL - SAND MIXTURES, LITTLEOR NO FINES
SILTY GRAVELS, GRAVEL - SAND -
SILT MIXTURES
CLEANGRAVELS
GRAVELS WITH
FINES
CLEAN SANDS
(LITTLE OR NO FINES)
SANDS WITH
FINES
LIQUID LIMITLESS THAN 50
LIQUID LIMITGREATER THAN 50
HIGHLY ORGANIC SOILS
DUAL SYMBOLS are used to indicate borderline soil classifications.
The discussion in the text of this report is necessary for a proper understanding of the nature
of the material presented in the attached logs.
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
Earth Solutions NW LLC
127.5
126.5
123.0
122.0
MC = 16.20%
MC = 18.40%
MC = 2.90%
Fines = 1.40%
MC = 21.90%
SM
TPSL
SP
SM
Brown silty SAND, medium dense, moist (Fill)
Relic TOPSOIL Horizon
Tan poorly graded SAND with gravel, medium dense, moist
[USDA Classification: very gravelly coarse SAND]
Tan silty SAND, medium dense, moist
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
2.5
3.5
7.0
8.0
NOTES Surface Conditions: gravel
GROUND ELEVATION 130 ft
LOGGED BY BCS
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY KDH
DATE STARTED 2/17/20 COMPLETED 2/17/20
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-1
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GENERAL BH / TP / WELL - 7126.GPJ - GINT STD US.GDT - 3/16/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
128.5
127.5
127.0
125.0
120.5
MC = 11.00%
MC = 20.50%Fines = 33.20%
MC = 27.70%
Fines = 8.20%
MC = 19.20%
MC = 14.70%Fines = 5.10%
TPSL
SM
TPSL
SM
SP-SM
Dark brown TOPSOIL, root intrusions to 5' (Fill)
Tan silty SAND, medium dense, moist (Fill)
Relic TOPSOIL Horizon
Tan silty SAND, medium dense, moist
-slight caving to BOH
-infiltration test, [USDA Classification: slightly gravelly very fine sandy LOAM]
Gray poorly graded SAND with silt, medium dense, wet
[USDA Classification: slightly gravelly SAND]
-weak iron oxide staining to 8'
-becomes poorly graded sand with gravel
[USDA Classification: gravelly coarse SAND]
Test pit terminated at 8.5 feet below existing grade. No groundwater encountered duringexcavation. Caving observed from 3.0 feet to BOH.
0.5
1.5
2.0
4.0
8.5
NOTES Depth of Topsoil & Sod 6": grass
GROUND ELEVATION 129 ft
LOGGED BY BCS
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY KDH
DATE STARTED 2/17/20 COMPLETED 2/17/20
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-2
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GENERAL BH / TP / WELL - 7126.GPJ - GINT STD US.GDT - 3/16/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
129.5
127.0
126.0
121.5
MC = 15.20%
MC = 11.40%
Fines = 15.20%
MC = 22.90%
MC = 23.10%
TPSL
SM
TPSL
SM
Dark brown TOPSOIL (Fill)
Brown silty SAND, medium dense, moist (Fill)
Relic TOPSOIL Horizon
-charcoal fragments
Tan silty SAND, medium dense, moist
-weak iron oxide staining
-at 4' [USDA Classification: slightly gravelly loamy SAND]
-becomes gray, light groundwater seepage at 8.5'
Test pit terminated at 8.5 feet below existing grade. Groundwater seepage encountered at8.5 feet during excavation. No caving observed.
0.5
3.0
4.0
8.5
NOTES Depth of Topsoil & Sod 6": grass
GROUND ELEVATION 130 ft
LOGGED BY BCS
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY KDH
DATE STARTED 2/17/20 COMPLETED 2/17/20
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-3
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GENERAL BH / TP / WELL - 7126.GPJ - GINT STD US.GDT - 3/16/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
125.5
121.0
MC = 22.60%
MC = 24.30%
MC = 18.40%
SM
SM
Tan silty SAND, medium dense, moist (Fill)
-becomes brown
-interbedded dark brown TOPSOIL in fill
-rebar, plastic bags, and wood debris
Gray silty SAND, medium dense, moist
-weak iron oxide staining
-light groundwater seepage
Test pit terminated at 9.0 below existing grade. Groundwater seepage encountered at 5.5feet during excavation. Caving observed from 1.5 to 5.0 feet.
4.5
9.0
NOTES Surface Conditions: gravel
GROUND ELEVATION 130 ft
LOGGED BY BCS
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY KDH
DATE STARTED 2/17/20 COMPLETED 2/17/20
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-4
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GENERAL BH / TP / WELL - 7126.GPJ - GINT STD US.GDT - 3/16/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
125.5
124.5
120.0
MC = 10.90%
MC = 6.60%
Fines = 7.80%
MC = 45.40%
TPSL
SM
SP-
SM
Dark brown TOPSOIL
-root intrusions to 4'
Tan silty SAND, medium dense, moist
Gray poorly graded SAND with silt, medium dense, moist
[USDA Classification: gravelly SAND]
-8" tan silty sand lens
-becomes wet
Test pit terminated at 8.0 feet below existing grade. No groundwater encountered during
excavation. No caving observed.
2.5
3.5
8.0
NOTES Depth of Topsoil & Sod 30": grass
GROUND ELEVATION 128 ft
LOGGED BY BCS
EXCAVATION METHOD
TEST PIT SIZE
EXCAVATION CONTRACTOR NW Excavating GROUND WATER LEVELS:
CHECKED BY KDH
DATE STARTED 2/17/20 COMPLETED 2/17/20
AT TIME OF EXCAVATION ---
AT END OF EXCAVATION ---
AFTER EXCAVATION ---SAMPLE TYPENUMBERDEPTH(ft)0
5
PAGE 1 OF 1
TEST PIT NUMBER TP-5
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GENERAL BH / TP / WELL - 7126.GPJ - GINT STD US.GDT - 3/16/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
TESTS
U.S.C.S.MATERIAL DESCRIPTION
GRAPHICLOG
Earth Solutions NW, LLC
Appendix B
Laboratory Test Results
ES-7126
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
3
D100
140
Specimen Identification
1
fine
6 HYDROMETER304
1.4
33.2
8.2
5.1
15.2
101/2
COBBLES
Specimen Identification
4
coarse
20 401.5 8 14
USDA: Tan Very Gravelly Coarse Sand. USCS: SP with Gravel.
USDA: Tan Slightly Gravelly Very Fine Sandy Loam. USCS: SM.
USDA: Gray Slightly Gravelly Sand. USCS: SP-SM.
USDA: Gray Gravelly Coarse Sand. USCS: SP-SM with Gravel.
USDA: Tan Slightly Gravelly Loamy Sand. USCS: SM.
6 60
PERCENT FINER BY WEIGHTD10
0.526
0.174
0.399
0.111
7.406
0.137
0.259
1.314
0.253
GRAIN SIZE DISTRIBUTION
100
36.98
3.06
8.55
LL
TP-01
TP-02
TP-02
TP-02
TP-03
0.2
0.085
0.154
3/4U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
GRAVEL SAND
37.5
9.5
9.5
19
9.5
%Silt
0.19
1.38
0.79
TP-01
TP-02
TP-02
TP-02
TP-03
2 2003
Cc CuClassification
%Clay
16
PID60 D30
coarse SILT OR CLAYfinemedium
GRAIN SIZE IN MILLIMETERS
3/8 50
5.0ft.
3.5ft.
5.0ft.
8.5ft.
4.0ft.
5.00ft.
3.50ft.
5.00ft.
8.50ft.
4.00ft.
PL
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GRAIN SIZE USDA ES-7126 MEADOW AVENUE SHORT PLAT.GPJ GINT US LAB.GDT 3/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0.0010.010.1110100
3
D100
140
Specimen Identification
1
fine
6 HYDROMETER304
7.8
101/2
COBBLES
Specimen Identification
4
coarse
20 401.5 8 14
USDA: Gray Gravelly Sand. USCS: SP-SM.
6 60
PERCENT FINER BY WEIGHTD10
0.2650.664
GRAIN SIZE DISTRIBUTION
100
7.71
LL
TP-05
0.086
3/4U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS
GRAVEL SAND
19
%Silt
1.23
TP-05
2 2003
Cc CuClassification
%Clay
16
PID60 D30
coarse SILT OR CLAYfinemedium
GRAIN SIZE IN MILLIMETERS
3/8 50
4.0ft.
4.00ft.
PL
PROJECT NUMBER ES-7126 PROJECT NAME Meadow Avenue Short Plat
GRAIN SIZE USDA ES-7126 MEADOW AVENUE SHORT PLAT.GPJ GINT US LAB.GDT 3/10/20Earth Solutions NW, LLC
15365 N.E. 90th Street, Suite 100
Redmond, Washington 98052
Telephone: 425-449-4704
Fax: 425-449-4711
Earth Solutions NW, LLC
Report Distribution
ES-7126
EMAIL ONLY Mr. Huy Nguyen
15400 Southeast 155th Place, Unit 99
Renton, Washington 98058
15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711
Earth Solutions NW LLC
Geotechnical Engineering, Construction
Observation/Testing and Environmental Services
March 7, 2022
ES-7126.01
Mr. Huy Nguyen
15400 Southeast 155th Place, Unit 99
Renton, Washington 98058
Subject: Geotechnical Review: Infiltration Trenches
Proposed Short Plat
3804 Meadow Avenue North
Renton, Washington
Reference: Earth Solutions NW, LLC
Geotechnical Engineering Study, ES-7126, dated March 12, 2020
Encompass Engineering & Surveying
Preliminary Short Plat Plans, Drawing No. 20591, dated March 7, 2022
2017 City of Renton Surface Water Design Manual (2017 Renton SWDM)
Greetings, Mr. Nguyen:
As requested by Encompass Engineering & Surveying (Encompass), Earth Solutions NW, LLC
(ESNW) has prepared this letter for the subject project. Based on our understanding of site
conditions and review of COR Maps, a high erosion hazard (EH) area is present along the eastern
margin of the subject site. The City of Renton (City), pursuant to the requirements of the
referenced 2017 Renton SWDM, requires that a geotechnical professional review the referenced
plans because the infiltration trenches are sited within 200 feet of an EH area.
As summarized in the referenced geotechnical report, the site is underlain generally by one-and-
one-half to four-and-one-half feet of fill, with underlying native recessional outwash deposits.
Previous infiltration testing within the recessional outwash (at TP-2, approximately three-and-
one-half feet below grade) resulted in a recommended long-term infiltration rate of 5 in/hr for the
tested location and depth. In our opinion, the previous infiltration testing indicates the native
recessional outwash possesses moderate to high capacity to function as a suitable receptor soil
for infiltration systems.
Mr. Huy Nguyen ES-7126.01
March 7, 2022 Page 2
Earth Solutions NW, LLC
ESNW recommends the infiltration trenches be sited within the well-drained, native recessional
outwash at depth. Topsoil, existing fills, silt-rich soil, or otherwise unsuitable material must be
completed advanced through such that the infiltration trench bottoms are sited entirely within the
native recessional outwash. Over-excavations, as recommended by ESNW at the time of
construction, should be restored using washed drain rock or gravel backfill per City Standard Plan
225.20. Based on our review of the referenced plans, these recommendations have been
incorporated into the infiltration trench designs.
Provided the recommendations outlined in the referenced geotechnical report and this review
letter are incorporated into construction, it is our opinion the infiltration trenches are feasible, from
a geotechnical standpoint, as depicted on the referenced plans. Considering cumulative impacts
from the project and surrounding area under full built-out conditions, it is our opinion the proposed
infiltration trenches will not adversely affect the site and surrounding area.
ESNW should be contacted to observe and document infiltration trench installation.
Supplementary recommendations may be provided at the time of construction based on observed
conditions.
We trust this letter meets your current needs. Please call if you have any questions about this
letter or if we can be of further assistance.
Sincerely,
EARTH SOLUTIONS NW, LLC
Keven D. Hoffmann, P.E.
Associate Principal Engineer
cc: Encompass Engineering & Surveying
Attention: Mr. Costa Philippides, P.E. (Email only)
03/07/2022
Appendix B
WWHM Output
WWHM2012
PROJECT REPORT
20591 WWHM 1/27/2021 6:46:41 PM Page 2
General Model Information
Project Name:20591 WWHM
Site Name:
Site Address:
City:
Report Date:1/27/2021
Gage:Seatac
Data Start:1948/10/01
Data End:2009/09/30
Timestep:15 Minute
Precip Scale:1.000
Version Date:2019/09/13
Version:4.2.17
POC Thresholds
Low Flow Threshold for POC1:50 Percent of the 2 Year
High Flow Threshold for POC1:50 Year
20591 WWHM 1/27/2021 6:46:41 PM Page 3
Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
A B, Lawn, Flat 0.322
Pervious Total 0.322
Impervious Land Use acre
ROADS FLAT 0.01
ROOF TOPS FLAT 0.046
DRIVEWAYS FLAT 0.232
SIDEWALKS FLAT 0.017
Impervious Total 0.305
Basin Total 0.627
Element Flows To:
Surface Interflow Groundwater
20591 WWHM 1/27/2021 6:46:41 PM Page 4
Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
A B, Pasture, Flat 0.272
Pervious Total 0.272
Impervious Land Use acre
ROADS FLAT 0.011
DRIVEWAYS FLAT 0.018
SIDEWALKS FLAT 0.019
Impervious Total 0.048
Basin Total 0.32
Element Flows To:
Surface Interflow Groundwater
20591 WWHM 1/27/2021 6:46:41 PM Page 5
Routing Elements
Predeveloped Routing
20591 WWHM 1/27/2021 6:46:41 PM Page 6
Mitigated Routing
20591 WWHM 1/27/2021 6:46:41 PM Page 7
Analysis Results
POC 1
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #1
Total Pervious Area:0.322
Total Impervious Area:0.305
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.272
Total Impervious Area:0.048
Flow Frequency Method:Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.117712
5 year 0.152554
10 year 0.177699
25 year 0.211909
50 year 0.239222
100 year 0.268153
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.018418
5 year 0.023514
10 year 0.027077
25 year 0.031804
50 year 0.035494
100 year 0.039335
Annual Peaks
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.152 0.024
1950 0.163 0.026
1951 0.104 0.016
1952 0.084 0.013
1953 0.090 0.014
1954 0.098 0.015
1955 0.107 0.017
1956 0.106 0.017
1957 0.120 0.019
1958 0.097 0.015
20591 WWHM 1/27/2021 6:47:13 PM Page 8
1959 0.099 0.016
1960 0.097 0.015
1961 0.102 0.016
1962 0.089 0.014
1963 0.101 0.016
1964 0.097 0.015
1965 0.126 0.019
1966 0.083 0.013
1967 0.149 0.022
1968 0.162 0.025
1969 0.112 0.018
1970 0.108 0.017
1971 0.129 0.020
1972 0.154 0.021
1973 0.081 0.013
1974 0.118 0.019
1975 0.136 0.021
1976 0.092 0.014
1977 0.099 0.016
1978 0.121 0.019
1979 0.166 0.026
1980 0.149 0.024
1981 0.122 0.019
1982 0.171 0.027
1983 0.139 0.022
1984 0.088 0.014
1985 0.121 0.019
1986 0.105 0.017
1987 0.162 0.026
1988 0.099 0.015
1989 0.123 0.019
1990 0.272 0.033
1991 0.183 0.026
1992 0.087 0.014
1993 0.075 0.012
1994 0.082 0.013
1995 0.108 0.017
1996 0.131 0.022
1997 0.119 0.018
1998 0.113 0.018
1999 0.231 0.036
2000 0.115 0.018
2001 0.126 0.020
2002 0.147 0.023
2003 0.116 0.018
2004 0.216 0.034
2005 0.099 0.016
2006 0.094 0.014
2007 0.261 0.041
2008 0.176 0.026
2009 0.150 0.024
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
1 0.2721 0.0411
2 0.2607 0.0363
3 0.2310 0.0340
20591 WWHM 1/27/2021 6:47:14 PM Page 9
4 0.2161 0.0329
5 0.1825 0.0270
6 0.1764 0.0263
7 0.1714 0.0261
8 0.1656 0.0256
9 0.1628 0.0256
10 0.1621 0.0256
11 0.1616 0.0254
12 0.1538 0.0237
13 0.1521 0.0237
14 0.1503 0.0235
15 0.1495 0.0232
16 0.1486 0.0224
17 0.1473 0.0220
18 0.1395 0.0219
19 0.1358 0.0214
20 0.1312 0.0212
21 0.1292 0.0203
22 0.1263 0.0201
23 0.1258 0.0195
24 0.1230 0.0194
25 0.1215 0.0193
26 0.1212 0.0191
27 0.1210 0.0190
28 0.1198 0.0188
29 0.1191 0.0186
30 0.1179 0.0181
31 0.1164 0.0180
32 0.1154 0.0178
33 0.1129 0.0177
34 0.1123 0.0177
35 0.1084 0.0171
36 0.1078 0.0170
37 0.1072 0.0169
38 0.1056 0.0167
39 0.1051 0.0166
40 0.1036 0.0163
41 0.1023 0.0157
42 0.1008 0.0157
43 0.0990 0.0157
44 0.0989 0.0156
45 0.0986 0.0155
46 0.0985 0.0155
47 0.0981 0.0154
48 0.0972 0.0152
49 0.0971 0.0152
50 0.0966 0.0149
51 0.0945 0.0144
52 0.0920 0.0143
53 0.0904 0.0142
54 0.0891 0.0138
55 0.0882 0.0138
56 0.0871 0.0137
57 0.0839 0.0132
58 0.0827 0.0130
59 0.0823 0.0129
60 0.0808 0.0129
61 0.0755 0.0120
Appendix C
Arborist Report/Tree Plan by Layton Tree Consulting, LLC dated February 12, 2020
LAYTON TREE CONSULTING, LLC
It’s all about trees……
PO BOX 572, SNOHOMISH, WA 98291-0572 * 425-220-5711 * bob@laytontreeconsulting.com
ARBORIST REPORT/TREE PLAN
3804 Meadow Avenue N
Renton, WA
Report Prepared by:
Bob Layton
Registered Consulting Arborist #670
Certified Arborist #PN-2714A
February 12, 2020
Arborist Report – 3804 Meadow Ave N
Page 2 Layton Tree Consulting LLC February 12, 2020
Table of Contents
Assignment.................................................................................................................................................... 3
Description .................................................................................................................................................... 3
Methodology ................................................................................................................................................. 3
Judging Condition...................................................................................................................................... 3
Judging Retention Suitability .................................................................................................................... 4
Observations ................................................................................................................................................. 4
Discussion/Recommendations ...................................................................................................................... 5
Tree Density-Tree Replacement ................................................................................................................... 5
Arborist Disclosure Statement ...................................................................................................................... 5
Attachments
Photos, pages 6 - 8
Tree Summary Table
Tree Plan Map
Tree Retention Worksheet
City of Renton – Approved Tree List
Arborist Report – 3804 Meadow Ave N
Page 3 Layton Tree Consulting LLC February 12, 2020
Assignment
Layton Tree Consulting, LLC was contacted by Huy Nguyen, and was asked to compile an Arborist Report
for one parcel in Renton. The subject property is located at 3804 Meadow Avenue N (Parcel 334270-
0570). The purpose of the report is to satisfy City requirements associated with tree retention
regulations and the proposed development of the property.
My assignment is to prepare a written report on present tree conditions, which is to be submitted to the
City with the development application materials.
This report covers all of the criteria set forth under the City of Renton’s tree regulations, Municipal Code
Section 4-4-130 - Tree Retention and Land Clearing Regulations.
Date of Field Examination: February 11, 2020
Description
Two significant trees were identified on the property. A numbered aluminum tag was attached to the lower
trunk of the subject trees. These tag numbers correspond with the numbers on the attached Tree Summary
Table and attached Tree Plan Map.
There are no significant neighboring tree issues associated with this property.
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 or canopy of the tree is examined for current vigor/health by examining the foliage for
appropriate color and density, the vegetative buds for color and size, and the branches for structural form
and annual shoot growth; and the overall presence of limb dieback and/or any disease issues.
The trunk or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting bodies of
decay (conks or mushrooms), seams, insect pests, bleeding or exudation of sap, callus development, broken
or dead tops, structural defects and unnatural leans. Structural defects can include but are not limited to
excessive or unnatural leans, crooks, forks with V-shaped crotches, multiple attachments.
The root collar and exposed surface roots are inspected for the presence of decay, insect damage, as well as
if they have been injured or wounded, undermined or exposed, or the original grade has been altered.
Judging Condition
The three condition categories are described as follows:
Good – free of significant structural defects, no disease concerns, minor pest issues, no significant root
issues, good structure/form with uniform crown or canopy, foliage of normal color and density, average or
normal vigor, will be wind firm if isolated or left as part of a grouping or grove of trees, suitable for its
location
Arborist Report – 3804 Meadow Ave N
Page 4 Layton Tree Consulting LLC February 12, 2020
Fair – minor to moderate structural defects not expected to contribute to a failure in near future, no disease
concerns, moderate pest issues, no significant root issues, asymmetric or unbalanced crown or canopy,
average or normal vigor, foliage of normal color, moderate foliage density, will be wind firm if left as part of
a grouping or grove of trees, cannot be isolated, suitable for its location
Poor – major structural defects expected to cause fail in near future, disease or significant pest concerns,
decline due to old age, significant root issues, asymmetric or unbalanced crown or canopy, sparse or
abnormally small foliage, poor vigor, not suitable for its location
The attached tree conditions map indicates the ‘condition rating’ of the subject trees found at the site. The
attached Tree Summary Table provides specific information on tree sizes and drip-line measurements.
Judging Retention Suitability
Not all trees necessarily warrant retention. The three retention suitability categories as described in
ANSI A300 Part 5 (Standard Practices for the Management of Trees During Site Planning, Site
Development and Construction) are as follows:
Good – trees are in good health condition and structural stability and have the potential for longevity at
the site
Fair – trees are in fair health condition and/or have structural defects that can be mitigated with
treatment. These trees may require more intense management and monitoring, and may have shorter
life-spans than those in the “good” category.
Poor – trees are in poor health condition and have significant defects in structure that cannot be
mitigated with treatment. These trees can be expected to decline regardless of management. The
species or individual tree may possess characteristics that are incompatible or undesirable in landscape
settings or be unsuited for the intended use of the site.
Observations
The subject trees are described as follows:
Tree #1 is a mature English walnut, located in the northeast portion of the property. It is completely
covered with or consumed by English ivy. The ivy has encroached into the top of the tree. An inspection
of the root crown, trunk and branch/stem attachments is not possible. See pictures below. The
majority of tree crown extends south. Vigor appears fairly good. Overall condition is rated as ‘fair-poor’
due to the ivy encroachment.
Tree #2 is a semi-mature to mature Douglas fir. The top has broken out in the past. Vigor is good. The
lower trunk is sound with no outward indicators of any internal decay issues. Condition is rated as fair
to good.
Neighboring Trees
No issues.
Arborist Report – 3804 Meadow Ave N
Page 5 Layton Tree Consulting LLC February 12, 2020
Discussion/Recommendations
Tree locations are shown on the attached map. The driplines of both trees have also been delineated.
The health and stability of both of the subject trees will be compromised by new development. Given
the location of existing trees within the site interior, the retention of either tree would dramatically
impact the buildable portion of the proposed lots. The proposal is to remove the two existing trees and
replace with new trees to meet the minimum tree density requirement. See the attached Tree
Retention Worksheet and section below.
Tree Density-Tree Replacement
The property is proposed for a 3 Lot Short Plat. For detached single-family development, a minimum of
2 significant trees per every 5,000 sq. ft. of lot area is required.
Lot A – 8,781 sq. ft. = 3.51 (4) replacement trees
Lot B – 8,585 sq. ft. = 3.43 (3) replacement trees
Lot C – 8,359 sq. ft. = 3.34 (3) replacement trees
Replacement trees shall be at least 2-inch caliper for deciduous species and 6-feet in height for
evergreen species. The approximate location of replacement trees is shown on the attached Tree Plan
Map. The City’s approved tree list is attached. Replacement tree species shall be chosen from this list.
Arborist Disclosure Statement
Arborists are tree specialists who use their education, knowledge, training and experience to examine
and assess trees, recommend measures to enhance the beauty and health of trees, and attempt to
reduce the risks associated with living near trees. Clients may choose to accept or disregard the
recommendations of the arborist, or to seek additional advice.
Arborists cannot detect every condition that could possibly lead to the structural failure of a tree. Trees
are living organisms that grow, respond to their environment, mature, decline and sometimes fail in
ways we do not fully understand. Conditions are often hidden within trees and below ground.
Arborists cannot guarantee that a tree will be healthy and/or safe under all circumstances, or for a
specified period of time. Likewise, remedial treatments, like any medicine, cannot be guaranteed.
Treatment, pruning and removal of trees may involve considerations beyond the scope of the arborist’s
services such as property boundaries, property ownership, site lines, disputes between neighbors, and
other issues. Arborists cannot take such considerations into account unless complete and accurate
information is disclosed to the arborist. An arborist should then be expected to reasonably rely upon
the completeness and accuracy of the information provided.
Trees can be managed, but they cannot be controlled. To live near trees is to accept some degree of
risk. The only way to eliminate all risk associated with trees is to eliminate all trees.
Arborist Report – 3804 Meadow Ave N
Page 6 Layton Tree Consulting LLC February 12, 2020
Photo Documentation
Tree #1 – compromised by ivy growth
Tree #1 – massive ivy growth into tree canopy
Arborist Report – 3804 Meadow Ave N
Page 7 Layton Tree Consulting LLC February 12, 2020
North property line, Tree #1 on right
Northwest corner of property
Arborist Report – 3804 Meadow Ave N
Page 8 Layton Tree Consulting LLC February 12, 2020
Tree #2, back or east side of property
Tree #1, looking west from back of property
Layton Tree Consulting LLC
For:Huy Nguyen
Site:3804 Meadow Ave N - Renton
Tree Summary Table
Date:
Tree/DBH Height Retention
Tag #Species (inches)(feet)Condition Suitability Comments Proposal
N S E W
1 English walnut 28 58 16 36 20 22 Fair-poor IBF consumed by ivy, heavy lean south Remove
2 Douglas fir 37 106 16 17 16 17 Fair-good IBF old broken top, sound Remove
OFF-SITE TREES
No issues
Drip-Line and Limits of Disturbance measurements from face of trunk
IBF - in building footprint
Drip-Line / Limits of Disturbance
(feet)
2/11/2020
DEPARTMENT OF COMMUNITY
AND ECONOMIC DEVELOPMENT
TREE RETENTION WORKSHEET
Planning Division
1055 South Grady Way-Renton, WA 98057
Phone: 425-430-7200 | www.rentonwa.gov
1.Total number of trees over 6” diameter1, or alder or cottonwood
trees at least 8” in diameter on project site trees
2.Deductions: Certain trees are excluded from the retention calculation:
Trees that are dangerous2 trees
Trees in proposed public streets trees
Trees in proposed private access easements/tracts trees
Trees in critical areas3 and buffers trees
Total number of excluded trees: trees
3.Subtract line 2 from line 1:trees
4.Next, to determine the number of trees that must be retained4, multiply line 3 by:
0.3 in zones RC, R-1, R-4, R-6 or R-8
0.2 in all other residential zones
0.1 in all commercial and industrial zones trees
5.List the number of 6” in diameter, or alder or cottonwood trees
over 8” in diameter that you are proposing5 to retain4:trees
6.Subtract line 5 from line 4 for trees to be replaced:
(if line 6 is zero or less, stop here. No replacement trees are required) trees
7.Multiply line 6 by 12” for number of required replacement inches:inches
8.Proposed size of trees to meet additional planting requirement:
(Minimum 2” caliper trees required for replacement, otherwise enter 0)inches per tree
9.Divide line 7 by line 8 for number of replacement trees6: (If remainder is .5 or greater, round up to the next whole number) trees
1 Measured at 4.5’ above grade. 2 A tree certified, in a written report, as dead, terminally diseased, damaged, or otherwise dangerous to persons or property by a licensed
landscape architect, or certified arborist, and approved by the City. 3 Critical areas, such as wetlands, streams, floodplains and protected slopes, are defined in RMC 4-3-050. 4 Count only those trees to be retained outside of critical areas and buffers. 5 The City may require modification of the tree retention plan to ensure retention of the maximum number of trees per RMC 4-4-130H7a. 6 When the required number of protected trees cannot be retained, replacement trees, with at least a two-inch (2") caliper or an evergreen at least
six feet (6') tall, shall be planted. See RMC 4-4-130.H.1.e.(ii) for prohibited types of replacement trees.
1
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\Tree Retention Worksheet.docx 08/2015
Minimum Tree Density
A minimum tree density shall be maintained on each residentially zoned lot (exempting single-family
dwellings in R-10 and R-14). The tree density may consist of existing trees, replacement trees, or a
combination.
Detached single-family development7: Two (2) significant trees8 for every five thousand (5,000) sq. ft. of lot
area. For example, a lot with 9,600 square feet and a detached single-family house is required to have four (4)
significant trees or their equivalent in caliper inches (one or more trees with a combined diameter of 24”). This
is determined with the following formula:
Multi-family development (attached dwellings): Four (4) significant trees8 for every five thousand (5,000) sq.
ft. of lot area.
Example Tree Density Table:
Lot Lot size Min significant
trees required
New Trees Retained Trees Compliant
1 5,000 2 2 @ 2” caliper 0 Yes
2 10,000 4 0 1 tree (24 caliper
inches)
Yes
3 15,000 6 2 @ 2” caliper 1 Maple – 15
caliper inches
1 Fir – 9 caliper
inches.
Yes
7 Lots developed with detached dwellings in the R-10 and R-14 zoned are exempt from maintaining a minimum number of significant trees onsite,
however they are not exempt from the annual tree removal limits.
8 Or the gross equivalent of caliper inches provided by one (1) or more trees.
2
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APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 1
In the City of Renton there is an overabundance of maple and cherry species. According to the most recent street tree inventory, maples
currently comprise 35% and cherry 24% of all species. To reduce a catastrophic loss of species, experts agree that 10% or less of any species
or cultivar exist within a street tree population. Because of this, planting maple or cherry trees within the right-of-way is discouraged.
SMALL TREES:
30 feet in height or less
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Acer buergeranum / Trident Maple 20 20
yellow
orange
and red
Adaptable to urban environments. Decidiuous: prefers moist, well-drained soils:
tolerates infertile sites. Drought tolerant.
Acer campestre / Hedge Maple 30 30 yellow
Deciduous; prefers moist, rich soils; slow growing tree tolerant of air pollution
and soil compaction; yellow fall color; cultivars available including Queen
Elizabeth maple (‘Evelyn’) with dark green, glossy foliage.
Acer circinatum / Vine Maple 20-25 10
orange
and red
Deciduous; prefers moist, well-drained soils; tolerates seasonal saturation and
varying soil types; drought tolerant once established; bushy shrub or small tree;
most often multi-trunked and does well in small groups; white flowers April-
June.
Acer ginnala 'Flame' / Amur Maple 20 20 red
Deciduous; prefers moist, well-drained soils, but is tolerant of drought; is often
multi-trunked, but can be pruned to a single stem; rounded form; fragrant,
yellowish-white flowers in spring; cultivars are available such as ‘Flame’ and
‘Embers’ with differing fall colors. Select or prune for single stem; can be multi-
trunked.
Acer grandidentatum 'Schmidt' / Rocky Mt.
Glow Maple 25+ 15 intense
Acer griseum / Paperback Maple 25 20 scarlet
Deciduous; prefers moist, well-drained soils, but is moderately drought tolerant;
bronze peeling bark provides year-round visual interest; often multitrunked, but
can be trained to a single stem; slow growing; disease and pest resistant.
Smooth, peeling, cinnamon colored bark.
APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 2
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Acer palmatum / Japanese Maple 20 24
yellow,
orange,
red
Prefers moist, well-drained soils; deciduous; slow to moderate growth rate;
multi-trunked with spreading branches; intolerant of inundation but moderately
drought resistant; vibrant fall colors; many cultivars available including ‘Emperor
I’, ‘Katsura’, and ‘Osakazuki’. Hundreds of varied cultivars. Can be slow growing.
Acer saccharum 'Apollo' 25 10
yellow,
orange Prefers well drained soils, but grows in varying soils; hearty.
Acer platanoides 'Globosum' / Globe
Norway Maple 20 18 yellow
Moist soils preferred, but tolerates drought and seasonal inundation; tolerant of
urban pollution; dense, compact, round form; slow-growing deciduous tree with
brilliant fall color; shallow root system may make mowing under the tree slightly
difficult; good selection for locations under power lines; another cultivar well
suited for such a location is A. platanoides ‘Almira,’ reaching only 20-25 ft.
Rounded top, and compact growth.
Acer truncatum / Purpleblow maple 20-25 20-25
Prefers moist, well-drained soil, but drought tolerant; very cold hardy deciduous
tree; moderate growth rate; yellow flowers in spring; an additional maple
cultivar of interest is 'Pacific sunset'.
Acer truncatum x A. platanoides 'Warren's
Red' / Pacific Sunset 30 25
yellow-
orange/
red
Acer Triflorum - Roughbark maple 25-30 20-25
apricot,
gold
Deciduous; prefers moist soils, but somewhat drought tolerant once established;
rough, knobby trunk provides interest in winter; disease and pest resistant; non-
aggressive roots do not damage sidewalks or driveways.
Amelanchier grandiflora 'Princess Diana' 20 15 bright red Good for limited space.
Amelanchier x grandiflora 'Autumn
Brilliance' Serviceberry 20 15
red or
yellow
Moist to dry, well-drained soils; small tree; drought tolerant; white clustered
flowers in spring; also try 'Princess Diana' for bright red fall color and the slightly
taller 'Robin Hill' (20-30 feet). Reliable bloom.
Amelanchier laevis ' lustre' / Luster
Serviceberry 25 25
red or
yellow
Moist to dry, well-drained soils; small tree; drought tolerant; white clustered
flowers in spring.
APPROVED TREE LIST – Small, Medium, and Large
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Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Arbutus 'Marina' 25 15 evergreen
Good substitute for Pacific Madrone. May exceed 25' height under some site
conditions.
Carpinus caroliniana / American hornbeam 20-30 20-20
Deciduous; prefers moist, rich soils; grows near saturated areas but is only
weakly tolerant of saturation; blooms March-May; slow growing; deep coarse
laterally spreading roots; medium life span; also consider Carpinus japonica
(Japanese hornbeam).
Cercis canadensis / Eastern Redbud 25 30 yellow
Deciduous; prefers moist, rich soils; tolerant of shade; somewhat drought
resistant, but not in full sun; purple-lavender flowers; medium longevity; often
multi-trunked; shallow, fibrous roots become deeper on drier sites; fairly short-
lived; blooms March-May. Blooms before leaves are out.
Cornus kousa 'Chinensis' / Chinese Kousa
Dogwood 20 20
reddish to
scarlet
Prefers moist soils; tolerant of varying soil types; moderate growth rate;
deciduous; white flowers in June and large red fruits that resemble a raspberry
in September; red to maroon fall color; more disease resistant than other
dogwoods; many additional cultivars available. Most resistant to disease of the
dogwoods.
Crataegus crus-galli 'Inermis' / Thornless
Cockspur Hawthorn 25 30
orange to
scarlet Red persistent fruit.
Crataegus x lavalii / Lavalle Hawthorne 28 20
bronze,
coppery
red
Deciduous; prefers moist, well-drained soil, but tolerant of varying soil types;
white flowers in spring; fruit can be a bit messy. Thorns on younger trees.
Crataegus phaenopyrum / Washington
Hawthorn 25 20 scarlet Thorny.
Fraxinus pennsylvanica 'Johnson' /
Leprechaun Ash 18 16 yellow
Prefers moist, well-drained soils; deciduous: slow to moderate growth rate;
tolerant of inundation but moderately drought resistant. A miniature in every
way.
Magnolia x loebneri 20 20 yellow Several cultivars.
Magnolia grandiflora 'Little Gem' 15 10 evergreen Useful where larger varieties are inappropriate.
Magnolia grandiflora 'Victoria' 25 20 evergreen
APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 4
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Malus spp. / Flowering crabapple 15-25 6-15
Selection should be based on disease resistance to apple scab and fireblight.
Tolerant of prolonged soil saturation; short lived; tolerant of drought and
seasonally saturated soils; deciduous; white or faintly pink flowers in spring;
numerous Malus species and cultivars provide a variety of foliage and flower
colors, forms and fruit.
Malus 'Adirondack' 18 8 yellow Red fruit. Excellent scab resistance.
Malus 'Red Barron' 18 8 yellow Good for narrow spaces. Red berries.
Malus 'Golden Raindrops' 18 13 yellow Abundant yellow fruit.
Malus 'Tschonoskii' 28 14 scarlet Sparse green fruit, pyramidal.
Parrotia persica / Persian Parrotia 30 20
yellow-
orange
red
Moist to dry soils; drought tolerant when established, deciduous tree with
moderate growth rate; brilliant fall color; often multi-trunked, but can be
trained to have just one; tolerates urban pollution and soil compaction; surface
roots do not generally cause problems; virtually disease and pest-free.
Pranus 'Frankthrees' / Mt. St. Helens Plum 20 20 Purple foliage.
Prunus 'Newport' / Newport Plum 20 20
reddish to
scarlet Purple red foliage.
Prunus cerasifera 'Krauter Vesuvius' /
Flowering Plum 30 15 Upright growth, darkest foliage of the plums.
Prunus cerasifera 'Thundercloud' / Plum 20 20 Dark purple foliage.
Prunus x hillieri 'Spire' 30 10
orange
red
Prunus 'Snowgoose' / Snow Goose Cherry 20 20 Upright when young, spreading when older.
Prunus serrulata 'Amanogawa' / Flowering
Cherry 20 6 bronze Particularly useful for very narrow planting strips.
Prunus serrulata 'Shirofugen' / Japanese
flowering cherry 25 25
Deciduous flowering tree; moist, well-drained soils; double pink to white blooms
in spring; vigorous grower; additional desirable choices include P. serrulata
‘Snowgoose’, ‘Kwanzan’, and ‘Shirotae’.
Prunus x yedoensis 'Akebono' / Flowering
Cherry 25 25 yellow
APPROVED TREE LIST – Small, Medium, and Large
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Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Quercus Ilex / Holly Oak 20 20
Prefers moist soils, but grows in varying soils; hearty, slow-growing evergreen
tree; light pink flowers May-June; pruning will keep tree small for a hedge,
without pruning may grow considerably larger – not appropriate under utility
lines; tolerates salt water spray. Prune to keep small, leave it alone to grow
large.
Styrax japonica / Japanese Snowbell 25 25 yellow Plentiful, green 1/2 inch seeds.
Styrax obassia / Fragrant Snowbell 30 25
Prefers moist, well-drained soil but tolerates wide variations; fragrant with
flowers; twisting bark. Try other Styrax species.
APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 6
MEDIUM TREES:
30 to 50 feet in height
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Acer campestre 'Evelyn' / Queen Elizabeth
Maple 35 30 yellow More upright branching than the species.
Acer platanoides 'Columnar' / Columnar
Norway maple 40 15 yellow
Deciduous; adapts to varying soils; upright or columnar in form making this
cultivar a better choice for narrow locations; tolerant of drought and seasonal
inundation; tolerates urban pollution and displays brilliant fall color; shallow
rooting necessitates locating at least 4-6 feet from sidewalks and driveways to
prevent heaving of pavement. Good close to buildings.
Acer truncatum x A. platanoides
'Klethsform' / Norwegian Sunset 35 25
yellow-
orange/
red
Acer rubrum 'Bowhall' / Bowhall Maple 40 15
yellow
orange
Acer rubrum 'Karpick' / Karpick Maple 35-40 20
yellow to
orange May work under very high powerlines with arborist's approval.
Acer rubrum 'Scarsen' / Scarlet Sentinel
Maple 40 20
yellow
orange
Acer rubrum / Red Maple 35-50 15-40
Deciduous tree known for fall color; prefer wet or moist soils; fast growing with
roots that may heave sidewalks or interfere with mowing; many cultivars of
varying heights available including: A. rubrum, 'Armstrong', 'Bowhall', 'Karpick',
'Scarsen', and 'Red Sunset'.
Betula jacquemontii / Jacquemontii Birch 40 30 yellow White bark makes for good winter interest.
Carpinus betulus 'Fastigiati' / Pyramidal
European Hornbeam 35 25 yellow
Fagus sylvatica 'Dawyck Purple' / Dawyck
Purple Beech 40 12
Purple foliage.
APPROVED TREE LIST – Small, Medium, and Large
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Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Fraxinus americana 'Autumn Applause' /
Ash 40 25 purple
Deciduous; prefers moist, well-drained soils; dense, wide spreading canopy;
long-lived; purple fall color; moderate growth rate; also try F. Americana
'Junginger'.
Fraxinus oxycarpa 'Raywood' / Raywood
Ash 35 25
reddish
purple
Pyrus calleryana 'Aristocrat' / Pear 40 45 red
Pyrus calleryana 'Chanticleer' / Flowring
Pear 40 15
Deciduous tree that grows well in a variety of soil types; orange to reddish fall
color; white flowers in spring; additional cultivars of interest include P.
calleryana 'Redspire' and 'Aristocrat'.
Pyrus calleryana 'Redspire' / Pear 40 45 red
Pyrus calleryana 'Autumn Blaze' / Pear 30 25 scarlet Vigorous.
Ginko biloba 'Autumn Gold' / Maidenhair
tree 45 35 yellow
Moist soils; deciduous ornamental tree; fast growing and long-lived; tolerant of
urban pollution, summer drought and winter inundation; showy fall color; grows
in soils of varying quality; provides dense canopy; additional cultivars available.
Ginko biloba 'Princeton Sentry' 40 15 yellow Very narrow growth.
Gleditsia triacanthos inermis 'Shademaster'
/ Shademaster Thornless Honeylocust 45 35 yellow
Deciduous; prefers moist, rich soils, but will grow in varying soil types; a
thornless cultivar tolerant of drought and seasonal inundation; adapts to urban
pollution and displays vigorous growth; deciduous tree with showy yellow fall
color; additional cultivars available such as ‘Imperial,’ which grows 30-35 feet,
‘Moraine,’ and ‘Rubylace’. Do not confuse with 'Sunburst'.
Koelreuteria paniculata / Goldenrain Tree 20-35 10-30 yellow
Deciduous; prefers moist well-drained soils, but is tolerant of poor soils; medium
rate of growth and longevity; tolerant of periods of drought and seasonal
inundation; tolerates urban pollution; provides a dense, wide-spreading canopy.
Midsummer blooming.
Oxydendron arboreum / Sourwood 35 12
reddish
purple Consistent and brilliant fall color.
Prunus sargentii 'Columnarus' 35 15
orange to
orange
red The cherry with the best fall color.
APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 8
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Quercus 'Crimschmidt' / Crimson Spire Oak 45 15 Hard to find.
Robinia x ambigua 'Idahoensis' / Pink Idaho
Locust 35 25 yellow Fragrant flowers.
Tilia americana 'Redmond' 35 20 yellow Pyramidal, needs water.
Tilia cordata 'Chancole' / Chancelor Linden 35 20 yellow Pyramidal.
Tilia cordata 'De Groot' / Linden 30-50 20 yellow Compact, suckers less than other Lindens.
Tilia cordata 'Greenspire' / Greenspire
Linden 40 30 yellowish Symmetrical pyramidal form.
Tilia cordata 'Littleleaf' / Littleleaf Linden 30-50 30
Deciduous; prefers moist, well-drained soils, but tolerant of a variety of soil
types; tolerant of wind and urban pollution; fast growing and long-lived;
tolerates summer drought and seasonal inundation; provides a dense canopy; C.
cordata is the hardiest Linden; many forms available including, T. cordata
‘Chancellor’, ‘Corzam’, and ’Greenspire’.
APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 9
LARGE TREES:
50 feet in height or taller
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Acer freemanli / Autumn Blaze Maple 50 40 orange
Abies grandis / Grand Fir 100 40
Evergreen; tolerant of fluctuating water tables and floods; medium rate of
growth; root structure depends on site conditions – shallow in moist areas, deep
taproot in drier conditions.
Acer nigrum 'Green Colunm' / Green
Column Maple 50 20
yellow to
orange Good close to buildings.
Acer platanoides 'Emerald Queen' 50 40 yellow
Deciduous; fast growing with an erect, spreading form; prefers moist soils, but is
tolerant of summer drought and seasonal inundation; tolerates urban pollution;
avoid locating near structures due to shallow, vigorous rooting; additional
cultivars available including A. platanoids ‘Parkway’.
Acer pseudoplatanus / Sycamore maple 40-60 25-40
Deciduous; prefers moist, well-drained soils but is adaptable to may soil types;
tolerates summer drought and seasonal inundation; tolerant of urban pollution
with a moderate growth rate; sturdy, resistant to wind and salt spray; a number
of cultivars are available including: A. pseudoplatanus ‘Atropurpureum,’ ‘
Brilliantissimum,’ ‘Cox’ (Lustre), and ‘Puget Pink’.
Acer saccharum 'Bonfire' 50 40
bright
orange
red Fastest growing sugar maple.
Acer saccharum 'Commemoration' 50 35
orange to
orange-
red Resistant to leaf tatter.
Acer saccharum 'Green Mountain' 45 35
red to
orange
Acer saccharum / Sugar maple 60-75 35
yellow,
orange
Deciduous; prefers moderately moist, well-drained soils; long-lived and tolerant
of urban pollutants; slow to medium growth rate; needs large planting area; a
variety of cultivars available including Acer saccharum ‘Legacy’.
APPROVED TREE LIST – Small, Medium, and Large
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Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Calocedrus decurrens / Incense cedar 75-90 10-20
Evergreen; tolerant of poor soils; drought tolerant after established; tolerant of
wind and urban conditions; narrow growth habit makes this a good choice for
smaller spaces and ideal for screening, fragrant tree; slow growing and long-
lived.
Carpinus betulus / European Hornbeam 40-60 30-40
Deciduous tree: tolerant of urban pollution and poor soils; cultivars available
and suggested include 'Fasigiata' (30-40 ft height) and 'Franz Fontaine' (30-35 ft
height).
Cedrus deodara / Deodar cedar 40-60 20-40
Evergreen; prefers moist, well-drained soils, but drought tolerant when
established; fairly fast growing and long lived; dense, wide spreading canopy;
attractive cultivars available.
Cercidiphyllum japonicum / Katsura Tree 40-60 20-40
apricot,
orange
Deciduous; requires moist soil and does not do well on hot dry sites. Leaves are
heart-shaped.
Cercidiphyllum japonicum / Katsura Tree 40 40
yellow to
orange
Fagus sylvatica / Green Beech 50 40 bronze Silvery-grey bark.
Fraxinus american 'Autumn Purple' /
Autumn Purple White Ash 60-80 50-70
to a dark
purple
Deciduous; prefers moist well-drained soils but tolerates a range of soil types;
Also try 'Rosehill'.
Fraxinus latifolia / Oregon Ash 40-80 30
Deciduous; saturated, ponded or moist soils; flood tolerant; small green-white
flowers; tolerant of poor soils.
Fraxinus pennsylvanica / Green Ash 50 40
Deciduous; prefers moist soils; fast growth rate; salt, seasonal drought and
urban pollution; numerous cultivars including'Patmore' (50-60 ft. height),
'Summit' (to 45 ft. height), and 'Urbanite' (to 50 ft. height).
Fraxinus pennsylvanica 'Patmore' /
Patmore Ash 45 35 yellow Extremely hardy, may be seedless.
Fraxinus pennsylvanica 'Urbanite' / Ash 50 40
deep
bronze
Gleditsia triacanthos inermis 'Skyline' /
Skyline Thornless Honeylocust 60-70 40 yellow
Deciduous; prefers moist soils, but will grow in poor soils; tolerant of drought,
seasonal inundation, and urban pollution; occasionally fruit pods can create
litter during winter months; thornless. Do not confuse with 'Sunburst'.
APPROVED TREE LIST – Small, Medium, and Large
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Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Gymnocladus dioicus espresso / Espresso
Kentucky Coffeetree 50 35 yellow Deciduous; drought and variable soil tolerant; seedless.
Liquidamber styraci fleia / American
sweetgum 60-75 40
Deciduous; prefers moist well-drained soils but tolerant of poor soils; drought
tolerant after established; avoid major roadways and restricted sites. Many
cultivars available.
Liriodendron tulipifera / Tulip Tree 60-80 30-60 yellow
Deciduous; prefers moist, deep, well-drained soils, but tolerates poor soils; fast
growing; needs large growing area, lower growing cultivars available such as
'Columnar'. Fast-growing tree.
Metasequoia glyptostoboides / Dawn
redwood 70-100 25
Deciduous; prefers moist, deep, well-drained soils, but tolerates compacted and
poor soils; long-lived, fast growing conifer; tolerant of seasonal inundation and
drought; can grow in standing water; needles turn russet in the fall; needs large
growing area; lower growing cultivars available such as M. glyptostroboides
‘Gold Rush’ and ‘Sheridan Spire’.
Nothofagus antartica / Southern Beech 50 35 none Rugged twisted branching and petite foliage.
Nyssa sylvatica / Tupelo 70+ 20
apricot to
bright red Handsomely chunky bark.
Picca omorika / Serbian spruce 50-60 20-25
Slow growing; tolerant of varying soils and urban pollution; moderately drought
tolerant once established; elegant evergreen spruce, good for narrow locations;
lower growing cultivars available.
Pseudotsuga menziesii / Douglas fir 75-120 40
Evergreen conifer; moist to dry soils; long-lived with a medium to fast rate of
growth; tolerant of summer drought, winter inundation, and poor soils;
withstands wind and urban pollution; provides a nice canopy, but potential
height will restrict placement.
Quercus coccinea / Scarlet oak 50-60 45
brilliant
scarlet to
red
Deciduous; grows in a variety of soil types; long-lived with a moderate growth
rate; tolerant of summer drought and urban pollution; does not tolerate
saturated soils or shade.
APPROVED TREE LIST – Small, Medium, and Large
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Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Quercus macrocarpa / Burr oak 70-80 30-40
Prefers moist soils, but is adaptable to varying soils; slow growing and long-lived;
rugged looking deciduous tree; tolerant of seasonal drought and inundation;
tolerates urban pollution and city conditions; provides a wide-spreading, dense
canopy.
Quercus phellos / Willow oak 60-70 50
Deciduous; prefers moist, well-drained soils, but grows in a wide range of soils
types; long-lived tree with moderate growth rate and fibrous root system;
tolerant of seasonal drought and inundation, as well as urban pollution; provides
a wide-spreading, dense canopy; small delicate leaves.
Quercus palustris 'Crownright' 80 40 More upright form of Pin Oak.
Quercus robar / English oak 40-60+ 40
Prefers well-drained soil; slow to moderate growth rate; long-lived deciduous
tree; tolerant of seasonal drought and inundation; tolerates urban pollution,
poor soils and constrained root space; susceptible to powdery mildew; many
varieties and cultivars available including: ‘Concordia,’ ‘Fastigiata,’ ‘Foliis
Variegatis, and ’Westminster Globe.’
Quercus rubra / Northern red oak 60-75 50
Prefers moist, well-drained soils, but drought tolerant when established;
tolerates seasonal inundation, urban pollution and salt spray; moderate rate of
growth and longevity; provides a dense, wide-spreading canopy; susceptible to
oak wilt fungus.
Quercus shumardii / Shumard's oak to 70 50
Prefers moist, well-drained soils; deciduous, long-lived tree; tolerant of seasonal
drought and inundation, urban pollution and poor soils.
Taxodium distichum / Bald cypress to 75 40
Deciduous conifer; wet, mucky soils; tolerant of summer drought and seasonal
flooding; will grow in poor soils; slow growing; long-lived with a wide-spreading
canopy; roots do not appear to lift sidewalks as readily as other species; prune
lower branches for sight-lines; cultivars include T. distichum ‘Shawnee Brave’.
Thuja plicata / Western red cedar 200+ 60
Moist to swampy soils; evergreen tree tolerant of seasonal flooding and
saturated soils; a good tree for screening; long-lived; cultivars ‘Pumilio’ and
‘Cuprea’ are shorter versions, ‘Aurea’ and ‘Atrovirens’ have distinctive foliage.
Tilia americana x euchlora 'Redmond' /
Redmond Linden 50 35 yellow
Prefers moist, rich soils, but tolerant of a variety of soils; tolerant of seasonal
drought and inundation, urban pollution and poor soils; deciduous tree
resistant; also try 'Sentry' and 'Boulevard'.
APPROVED TREE LIST – Small, Medium, and Large
H:\CED\Data\Forms-Templates\Self-Help Handouts\Planning\treeslist_march2010.doc P. 13
Botanical name / Common Name
Mature
Height
in Feet
Mature
Spread
in Feet Fall Color Comments
Tilia plalyphyllos / Bigleaf linden 60-80 60
Prefers moist, well-drained soils, but grows in a variety of soil types; deciduous
tree with medium growth rate; long-lived; tolerant of seasonal drought and
inundation; tolerates urban pollutants; provides a wide-spreading, dense
canopy; yellowish-white flowers attract bees.
Tilia tomentosa / Silver Linden 40-75 25-45
Deciduous; prefers moist, well-drained soils, but drought tolerant when
established; urban tolerant. Cultivars include 'sterlay' and 'Green Mountain'.
Ulmus ssp. / Elm hybrids 50-60 35-50 yellow
Deciduous; prefers moist, well-drained soils, but drought tolerant; rapid grower;
a hybrid elm resistant to Dutch elm disease; suggested hybrids include
‘Accolade’, ‘Homestead’ and ‘Pioneer’.
Ulmus 'Homestead' / Homestead Elm 60 35 yellow
Ulmus parvifolia / Lace Bark Elm 50 40
Deciduous; prefers moist, well drained soils but tolerant of soil types and hot dry
conditions. Flaking bark of orange, gray, green and brown color. Several cultivars
including 'Allee' and 'Bosque'.
Ulmus 'Pioneer' / Pioneer Elm 60 50 yellow Resistant to Dutch elm disease.
Umbellularia californica / Oregon myrtle 40-75+ to 50
Prefers moist, well-drained soils; slow growing evergreen tree with aromatic
leaves; tolerates seasonal drought and inundation; tolerant of urban pollution;
provides a wide spreading, dense canopy; resistant to pests and disease; good
for tall hedges or, when trunks are thinned, as a street tree; requires summer
watering until established.