HomeMy WebLinkAboutLUA16-000464_MiscPRELIMINARY TECHNICAL INFORMATION REPORT
for
Stewart Short Plat
2216 High Ave NE
Renton, WA 98056
April 7, 2016
Encompass Engineering Job No. 15671
Prepared For
Sandjay LLC
3933 Lake Washington Blvd NE, Ste. #100
Kirkland, WA 98033
Western Washington DMsion Eastern Washington Division
165 NE Juniper St., Ste 201, Issaquah, WA 98027 108 East 200 Street, Cle Elum, WA 98922
Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419
www.EncornpassES.net
TABLE OF CONTENTS
SECTION 1 -PROJECT OVERVIEW ........................................................................................ 11
FIGURE 1 .................................................................................................................................. 1
TIR Worksheet ..................................................................................................................... 1
FIGURE 2 .................................................................................................................................. 7
Site Location ........................................................................................................................ 7
FIGURE 3 .................................................................................................................................. 8
Drainage Basins, Sub-Basins & Site Characteristics ............................................................. 8
SECTION 2 -CONDITIONS AND REQUIREMENT SUMMARY ...................•....................•••••... 11
SECTION 3 -OFFSITE ANALYSIS ...................................•••...............................................•.... 14
SECTION 4 -FLOW CONTROL & WATER QUALITY ANALYSIS .....................•••................... 23
SECTION 5 -CONVEYANCE SYSTEM ANALYSIS & DESIGN ....•.................................•.•.•.... 23
SECTION 6 -SPECIAL REPORTS & STUDIES ...........................................••.......................••• 23
SECTION 7 -OTHER PERMITS ...........................•••.............•..•••.......................•••.................... 24
SECTION 8-TESC ANALYSIS & DESIGN .................................•••.......................................... 24
SECTION 9 -BOND QUANTITIES, FAC. SUMMARY & DEC. OF COVENANT ....................... 26
SECTION 10 -OPERATIONS & MAINTENANCE MANUAL. .•..............................................••• 26
APPENDIX A-GEOTECHNICAL REPORT .................•...............•..•••••••••....................•.••......•. 28
APPENDIX B -ARBORIST REPORT ............................................................••......................... 49
APPENDIX C -KCRTS ANALYSIS .........................•.............•.••........................••..................... 63
l'lgure 1
KING COUNTY, WASH!KGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER
Project Owner Sandjay LLC
Phone-------------
Address 3933 Lake Washington Blvd NE
Ste, #100, Kirkland, WA 98033
Project Engineer Barry Constant, PE
Company Encompass Engineering & Surveying
Phone 425-392-0250
Part 3 TYPE OF PERMIT APPLICATION
!El Landuse.~
Subdivison ~ UPD
D Building Services
M/F / Commerical / SFR
!El Clearing and Grading
D Right-of-Way Use
D Other
Parts PLAN AND REPORT INFORMATION
Technical Information Report
Type of Drainage Review @' Targeted
(circle): Large Site
Date (include revision
dates):
Date of Final:
Part 6 ADJUSTMENT APPROVALS
I
Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Name Stewart Short Plat
ODES Permit# ----------
Location Township _23'-N ____ _
Range __ 5E ____ _
Section 5 -~-----
Site Address 2216 High Ave NE
Renton, WA 98056
Part4 OTHER REVIEWS AND PERMITS
D DFWHPA D Shoreline
D COE404 Management
D DOE Dam Safety D Structural
RockeryNault/ __ D FEMA Floodplain D ESA Section 7 D COE Wetlands
D Other
Site Improvement Plan (Engr. Plans)
Type (circle one): ~/ Modified /
a Site
Date (include revision
dates):
Date of Final:
Type (circle one): ~ Complex I Preapplication / Experimental / Blanket
Description: (include conditions in TIR Section 2)
Date of Aooroval:
2009 Surface Water Design Manual 1/9/2009
KING COUNTY, WASHINGTON, SGRFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part? MONITORING REQUIREMENTS
Monitoring Required: Yes,® Describe:
Start Date: NIA
Completion Date:
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan: Green River Valley
Special District Overlays: _"'..,,,_ tic,._ A ____________________ _
Drainage Basin: East Lake Washington -Renton
Stormwater Requirements: -----------------------
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
D River/Stream ----------
0 Lake
D Wetlands __________ _
D Closed Depression --------
0 Floodplain __________ _
D Other ___________ _
Part 10 SOILS
l!J Steep Slope ---------
0 Erosion Hazard --------
0 Landslide Hazard--------
0 Coal Mine Hazard--------
0 Seismic Hazard --------
0 Habitat Protection--------0 __________ _
Soil Type Slopes Erosion Potential
InC 5 to 15 eercent Low to Moderate
InC >40 percent High
D High Groundwater Table (within 5 feet) D Sole Source Aquifer
D Other D Seeps/Springs
D Additional Sheets Attached
2009 Surface Water Design Manual
2
1/9/2009
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE LIMITATION/ SITE CONSTRAINT
l]I Core 2 Offsjte Anal)!sis
~ Sensitive/Critical Areas Wellhead Protection Area { zone 2}
~ SEPA
D Other
D
D Additional Sheets Attached
Part 12 TIR SUMMARY SHEET lnrovide one TIR Summarv Sheet =r Threshold Dischame Areal
Threshold Discharge Area:
TDA-1 /name or descriotionl
Core Requirements (all 8 apply)
Discharoe at Natural Location Number of Natural Discharae Locations: 2
Offsite Analysis Level: ( 1 D 2 I 3 dated: -
Flow Control Level: ~
1
2 / 3 or Exemption Number
lincL facilitv summarv sheetl Small Site MPs
Conveyance System Spill containment located at: Contractor Shed
Erosion and Sediment Control ESC Site Supervisor: TBD Contact Phone:
After Hours Phone:
Maintenance and Operation Responsibility: (Private) I Public
If Private, Maintenance Loa Reauired: Yes /No'l
Financial Guarantees and Provided: C Yes)/ No -
Liabilitv -By Owner
Water Quality Type: C Basig / Sens. Lake / Enhanced Basicm I Bog
(include facility summary sheet) or Exemptionl\Jo.
Landscape Manaaement Plan: Yes Kl'Jo)
Soecial Reauirements las annlicablel
Area Specific Drainage Type: CDA / SDO I MDP I BP I LMP / Shared Fae. I None
Reauirements Name: N/A
Floodplain/Floodway Delineation Type: Major I Minor / Exemption / None
100-year Base Flood Elevation (or range): NU!.
Datum:
Flood Protection Facilities Describe:
N/A
Source Control Describe landuse: NIA (comm./industrial landuse) Describe any structural controls:
2009 Surface Water Design Manual 1/9/2009
3
KING COUNTY, WASHIKGTON, SCRFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE LIMITATION/ SITE CONSTRAINT
IBJ Core 2 -Offsite Anall(sis
IBJ Sensitive/Critical Areas Wellhead Protection Area {zone 2}
IBJ SEPA
D Other
D
D Additional Sheets Attached
Part 12 TIR SUMMARY SHEET lorovide one TIR Summarv Sheet =r Threshold Discha=e Areal
Threshold Discharge Area:
TDA-2 (name or descriotionl
Core Requirements (all 8 apply)
Discharae at Natural Location Number of Natural Discharae Locations: 2
Offsite Analysis Level: ( 17)213 dated: -
Flow Control Level: ( 1 7)2 I 3 or Exemption Number
(incl. facilitv summarv sheet\ Small Site'S"MPs
Conveyance System Spill containment located at: Contractor Shed
Erosion and Sediment Control ESC Site Supervisor: TBD Contact Phone:
After Hours Phone:
Maintenance and Operation Responsibility: (Private)/ Public
If Private, Maintenance Loq Required: Yes (No')
Financial Guarantees and Provided: C!!::JI No -
Liability By Owner
Water Quality Type: ,~ I Sens. Lake / Enhanced Basicm / Bog
(include facility summary sheet) or Exemption o.
Landscaoe Manaqement Plan: Yes /(No )
Special Requirements (as anolicable)
Area Specific Drainage Type: CDA / SDO / MDP /BP/ LMP / Shared Fae./ None
Reouirements Name: NIA
Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): NIA
Datum:
Flood Protection Facilities Describe: NIA
Source Control Describe landuse: NIA
(comm./industrial landuse) Describe any structural controls:
2009 Surface Water Design Maoual 1/9/2009
3
KING COUNTY, WASHl"1GTON, SGRFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Oil Control High-use Site: Yes /(NO )
Treatment BMP: N/A -
Maintenance Agreement: Yes /~
with whom?
Other Drainaae Structures
Describe:
N/A
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION AFTER CONSTRUCTION
[ii Clearing Limits [ii Stabilize Exposed Surfaces
!El Cover Measures Qsl Remove and Restore Temporary ESC Facilities
!El Perimeter Protection 0 Clean and Remove All Silt and Debris, Ensure
0 Traffic Area Stabilization Operation of Permanent Facilities
0 Sediment Retention 0 Flag Limits of SAO and open space
D Surface Water Collection
preservation areas
0 Other 0 Dewatering Control
0 Dust Control
0 Flow Control
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: lndude Facilitv Summarv and Sketch)
Flow Control T voe/Description Water Quality T voe/Description
D Detention 0 Biofiltration
!El Infiltration 4' Dia. Dry Wells 0 Wetpool
0 Regional Facility 0 Media Filtration
0 Shared Facility 0 Oil Control
0 Flow Control 0 Spill Control
BMPs 0 Flow Control BMPs D Other 0 Other
2009 Surface Water Design Manual
4
1/9/2009
KING COUNTY, WASHINGTON, SuRFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
0 Drainage Easement 0 Cast in Place Vault
0 Covenant 0 Retaining Wall
0 Native Growth Protection Covenant 0 Rockery > 4' High
[I Tract 0 Structural on Steep Slope
0 Other D Other
Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a · ii engineer under my supervision, have visited the site. Actual site conditions as observed were
inco or led in · rksheet and the attached Technical Information Report. To the best of my
kno I ge the mfor t, n here is accurate.
2009 Surface Water Design Manual
5
1/9/2009
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Da te: 2/22/2016 Notes: Tax Lot #3344500189
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King County iMa p -100-yr Flood Plain
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as to acc uracy ccmpleteness, umell'less. or rights to the use of such 1nforrnalt<n . T hs d:>cument1s ror I nrended
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writen perrnissio, of King County.
Date : 2/2212016 No~s Ta x Lot #33445 00 189
King C~y
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GIS CENTER
1 Legend
Parcels
FEMA
P'7I preliminary 100-
k'...::.I year floodplain
Site Address: 2216 High Ave NE, Renton WA, 98056
334450-0189 King County Tax Parcel:
I. PROJECT OVERVIEW
This project involves the development ofa 0.51-acre parcel into two single-family lots and one
tract containing a native growth protection area (open space). Currently, the parcel contains an
existing house, rock retaining wall, driveway, concrete walk/patio, and about 24 significant trees.
The site slopes to the east and to the west. Along the eastern edge of the property, the site slopes
eastward with slopes that are greater than 40%. The western portion of the property slopes
toward the west with slopes ranging from approximately 5% to 19%. Per the SCS Soil maps, the
site is underlain with Indianola loamy sand with 5 to 15 percent slopes. This is confirmed in the
attached geotechnical engineering study.
Proposed Drainage Controls
The site storm drainage system has been designed according to the standards set forth by the
2009 King County Surface Water Design Manual (KCSWDM) and as amended by the City of
Renton. This project involves development of this parcel into two single family residential lots.
The total impervious area to be developed inside each new lot is in two parts. The first area is
the house itself which is 3,000 square feet or 6,000 square feet for both lots combined. The
second area is the driveway which is about 400 square feet or 800 square feet for both lots. The
total new impervious area to be added is approximately 3,400 square feet for each lot or 6,800
for both lots combined and represents about 43 percent of impervious coverage per lot.
This project creates more than 5,000 square feet, and the site is larger than 22,000 square feet
therefore, this project qualifies for Full Drainage Review.
It is proposed that full infiltration will be implemented for Flow Control for the house. The
infiltration drywells are over-sized and an overflow swale located between the new lots will
divert any overflow toward the street and away from the steep slope area along the western side
of the site. Any overflow for the proposed drywell located at the southeast comer of the site will
spill onto a rock pad to disperse the flow. Proposed driveway runoff for each lot will be
mitigated through filter strips located along the edge of each driveway.
II. CONDITIONS AND REQUIREMENTS SUMMARY
Conditions and Requirements
Provide Full Infiltration per 2009 KC SWDM Section C.2.2:
• Section C.2.2.2 -Minimum Design Requirements for Full Infiltration.
• Section C.2.2. 1 and C.2.2.4
o Figure C.2.2.C
CORE REQUIREMENTS
Core Requirement #1: Discharge at the natural Location
The site contains two natural discharge locations. For the west discharge location, runoff from
the western portion of the site generally sheet flows across the site to the west and collects in a
channel along the edge of the roadway and flows south toward an existing inlet. For the east
discharge location, runoff from the eastern half of the site sheet flows across the site toward the
east and then across the property to the east until it enters a roadway ditch along Jones Ave NE.
Refer to the Level 1 Downstream Analysis in Section 3 for a complete description of the existing
drainage paths.
Core Requirement #2: Otfsite Analysis
An offsite drainage analysis is provided in Section 3 of this TIR. Level 1 Drainage Analysis has
been prepared and no problems identified.
Core Requirement #3: Flow Control
This project qualifies for Full Drainage Review. The proposed project site will produce more
than 5,000 square feet of new impervious surfaces. Flow control BMPs for infiltration will
provide the required flow control for proposed improvements.
This site has two distinct drainage areas (TDA-l & TDA-2) and various flow control BMP' swill
be used to control the site's runoff. TDA-1 at the west area of the site consists of green space,
new driveway pavement, and new roof area. For TDA-1, storm water run-off tributary to new
driveway pavement will be mitigated through the use of filter strips along the southern edge for
the new driveways. Roof run-off will be conveyed to infiltration drywells to allow for full
infiltration. TDA-2 located at the eastern region of the site will consist mostly of green space
and a new tract will be created for the area of the site containing steep slopes. The new tract
(NGPT "A") will contain open space only and will remain undisturbed.
At TDA-1, storm water run-off tributary to the paved access driveway will be allowed to
infiltrate through the use of pervious pavement. The remainder of the site area will consist of 3
new homes, an existing home, new driveways and an access drive. Mitigation of surface run-off
for this area will be performed through the use of filter strips, infiltration vaults and pervious
concrete pavement. The access driveway will use pervious concrete pavement for storm water
mitigation, roof run-off will be mitigated through the use of infiltration drywells, and driveway
run-off will be mitigated through the use of filter strips.
Core Requirement #4: Conveyance System
Conveyance system analysis and design is provided in Section 5 of the TIR.
Core Requirement #5: Erosion and Sediment Control
A temporary erosion and sediment control (TESC) plan provides BMPs to be implemented
during construction.
Core Requirement #6: Maintenance and Operations
See Section X -Operation and Maintenance Manual
Core Requirement #7: Financial Guarantees and Liability
The owner will arrange for any financial guarantees and liabilities required by the permit.
Core Requirement #8: Water Quality
Refer to section 8 of this TIR for Water Quality Analysis and Design
SPECIAL REQUIREMENTS:
Special Requirement #1: Other Adopted Area-Specific Requirements
Critical Drainage Area -N/ A
Master Drainage Plan -NI A
Basin Plan -This site is located within the May Creek drainage basin
Lake management Plan -N/ A
Shared Facility Drainage Plan -N/ A
Special Requirement #2: Floodplain/Floodway Delineation
The limits of this project do not lie in a I 00-year floodplain
Special Requirement #3: Flood Protection Facilities
This special requirement is required for projects with Class I or 2 streams with an existing flood
protection facility. The site does not contain any streams and is therefore not applicable.
Special Requirement #4: Source controls
This project is a 2-lot single-family residential project and this requirement is not applicable.
Special Requirement #5: Oil Control
This project is not considered high-use in need of oil control.
Ill. OFF-SITE ANALYSIS
Project Overview
This project involves the development ofa 0.51-acre parcel into two single-family lots and one
lot containing open space. Currently, the parcel contains an existing house, rock retaining wall,
driveway, concrete walk/patio, and about 24 significant trees. The site slopes to the east and to
the west. Along the eastern edge of the property, the site slopes eastward with slopes that are
greater than 40%. The western portion of the property slopes toward the west with slopes
ranging from approximately 5% to 19%. Per the SCS Soil maps, the site is underlain with
Indianola loamy sand with 5 to 15 percent slopes. This is confirmed in the attached geotechnical
engineering study.
Downstream Drainage
Existing Conditions West Drainage Basin
Runoff from the western portion of the site generally drains west from the subject site. The run
off drains toward a depression located along the edge of High Avenue NE, the overflow travels
south along the edge of the roadway into a CB located at point (A) and from there the flow
travels through an 8-inch pipe that runs underneath High Avenue NE and into the 1-405 corridor.
There were no apparent downstream drainage problems.
Existing Conditions East Drainage Basin
Runoff from the eastern portion of the site generally drains east from the subject site. The run-off
sheet flows easterly across the site and then down a steeply sloped region along the eastern edge
of the property into the neighboring property along the east. From there, the flow empties into a
ditch located along the western side of Jones Ave NE. The flow travels through a 12" concrete
culvert located beneath the driveway at 2217 Jones Ave NE and into a ditch line toward the north
along Jones Ave NE. The flow is then conveyed through a 12" Corrugated Metal Pipe located
beneath the driveway at 2301 Jones Ave NE and empties into a channel that conveys the storm
flow into a wetland. From that point, the flow travels north through a culvert that runs beneath
NE 24th Street and into a channel located on the north side ofNE 24th Street. The flow continues
to be conveyed north through the channel and empties into a drainage structure located more
than a quarter mile downstream of the subject property and then beneath 1-405 until it eventually
reaches a channel that carries the storm flmv into Lake Washington. There were no apparent
downstream drainage problems.
Developed Conditions
Runoff from the proposed roof area within each new lot will be directed to drywells for full
infiltration of all roof runoff Proposed dri vew ay runoff for each lot will be mitigated through
filter strips along the edge of each dri vev.;a y . Storm water overflow for the infiltration dry wells
shall be directed to a swale located bet"veen the two new lots to convey excess water toward the
street. Storm water overflow for catch ba sin located at the southeast comer of the site will spill
onto a rock pad for dispersion.
Western Drainage Basin
Photo 1: Depression area loc ated o n west side of the subject property
Photo 2 : Downstream flowpath along High Ave NE on west side of subject property
Photo 3: Catch Basin located on west side of High Ave NE
Photo 4 : West side of High Av e SE where storm flow reaches I-405 corridor
t·astern Drainage Basin
Photo 5 : Neighbo ring propeny located just east of the subject property
Photo 6: Ditch along 2217 Jones Ave NE
' Photo 7: 12" concrete dri vewa y culvert at 2217 Jones Ave NE
Photo 8: Concrete culvert outflow location to channel at 2301 Jones Ave NE
Photo 9: Channel located at 230 l Jones Ave NE
.:. ., -,..,,.._ ... -~ -c... -.....
-:--...,,; ......_ ........ _... r.
~ ...... -_ ..
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Photo 10 : Upstream end of culv e,1 fo r driveway located at 2301 Jones Ave NE
. __ .._ ..... ,,._
Photo 11 : Downstream end of culvert for driveway located at 2301 Jones Ave NE
Photo 12: Channel located to the north of the property at 2301 Jones Ave NE
Photo 14 : Culvert end on south side ofNE 24th Street
Photo 15 : Downstrea m c hannel located north of NE 24th St .
IV. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN
Flow Control BMPs
I. This project is a residential two lot short plat. The total impervious area for this project
exceeds 5,000 square feet, and therefore this project qualifies for the Full Drainage Review
process.
• Full Drainage Review is required.
• This project proposes to construct 6,800 square feet of new impervious surfaces. The
improvements are proposed on an individual site/lot that is smaller than 22,000 square
feet with less than 45% of total impervious surface coverage, and the flow control BMPs,
as discussed in Appendix C of the 2009 King County Surface Water Design Manual, are
required.
2. Considering the size of the existing parcel, the topography of the project site, and the
configuration of the proposed improvements, the most feasible flow control approach for the
project site is Full Infiltration. SCS soil maps define this area as consisting oflndianola
loamy sand and a Geotechnical Investigation was performed to confirm that the soils would
support the Full Infiltration design approach. Refer to Section 6 of this TIR for Geotechnical
Investigation Reports.
• Implement Dry Wells for Full Infiltration. The design is based on drywells containing at
least 90 cubic feet per each 1,000 square feet of impervious surfaces served.
• The total impervious surface areas served by Full Infiltration is 6,220 square feet, which
only includes the roof areas for the new homes constructed on the two new lots.
• A total of 6 dry wells, containing 60 cu. ft. each are proposed to service the new lots.
• The infiltration dry wells will be located at least IO feet from the new property lines.
• Filter strips are proposed to mitigate storm water tributary to the proposed driveways.
Water Quality BMPs
Water quality design for Full Infiltration is not required, since the overall pollution generating
impervious area is less than 5,000 square feet.
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Since the storm drain system is private, systems serving regular single family residential facility,
a conveyance system analysis is not required.
VI. SPECIAL REPORTS AND STUDIES
Geotechnical Engineering Report
Arborist Report
VII. OTHER PERMITS
Building permits will be required.
VIII. TESC ANALYSIS AND DESIGN
The potential for erosion within the site will be mitigated by use of erosion control measures
during clearing, grading, and site development activities. Filter fences will be installed along the
downhill perimeter of the site to protect adjacent properties from sediment-laden water. A
rocked construction entrance will be installed at the entrance to the site to protect mud from
entering the paved roadway. Stockpiles and exposed disturbed areas will be covered to protect
from erosion and sediment runoff.
Element I: Mark Clearing Limits.
All clearing, grading, sensitive areas, and buffers will be clearly marked in the field prior to
construction in accordance to the plans and specifications. Prior to beginning land disturbing
activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and
their buffers, and trees that are to be preserved within the construction area. These shall be
clearly marked, both in the field and on the plans, to prevent damage and offsite impacts. Plastic,
metal, or stake wire fence may be used to mark the clearing limits.
Element 2: Establish Construction Access.
Construction access will be provided for the site. Driveway re-alignment should be completed
after all other construction is complete. Stabilize the construction access with rock per the storm
water plans if the driveway is disturbed. Access points shall be stabilized with a pad of quarry
spalls, crushed rock, or equivalent BMP prior to traffic leaving the construction site to minimize
the tracking of sediment onto all roads and accesses.
Element 3: Control Flow Rates.
Flow rates from the construction site are not expected to negatively impact the downstream
corridor. A temporary sediment pond is being proposed as part of this project along with other
proposed sediment retention BMPS described in Element 4. At all times, flow rates shall be
controlled for this project. Natural drainage patterns shall be protected as much as possible
during construction, and concentrated flow should not be permitted. Properties and waterways
downstream from development sites shall be protected from erosion due to increases in the
volume, velocity, and peak flow rate of stormwater runoff from the project site.
Element 4: Install Sediment Controls.
Silt fence should be used to protect all sensitive area slopes. Soils should be covered if not
worked for 7 days during the dry season or 2 days during the wet season. The street should be
swept each night or as required. If the minimum BMPs fail to retain sediment to the sight,
additional BMPs will be used.
Element 5: Stabilize Soils.
Soils shall be covered if not worked for 7 days during the dry season or 2 days during the wet
season. Soil stockpiles will be covered unless worked. Soil stockpiles shall be located away from
drain inlets and surface water discharge locations. Soil stockpiles shall be stabilized and covered
as needed or removed to an approved disposal site. Soils shall be stabilized at the end of the shift
before holidays or weekends if needed based on weather forecast.
Element 6: Protect Slopes.
The site has a steep slope area located along the eastern portion of property. Slope protection is
anticipated. In the event that erosion does occur along the edges of the project, energy dissipater
(flow spreaders) shall be used or the surface water will be routed away from the slopes.
Element 7: Protect Drain Inlets.
There are existing catch basins located downstream of the project. Filter fabric protection shall
be used for sediment control.
Element 8: Stabilize Channels and Outlets.
Existing or proposed channels or drainage outlets are not components of this project, thus
stabilization of these elements are not required.
Element 9: Control Pollutants.
Pollution generated from construction must be controlled at all times. Control of pollutants other
than sediments include the following:
• All pollutants other than sediments shall be handled and disposed of in a manner that
does not cause contamination of stormwater.
• Cover, containment and protection from vandalism shall be provided for all chemicals,
liquid products, petroleum products, and non-inert wastes present on the project site.
• Maintenance and repair of heavy equipment and vehicles involving oil changes, hydraulic
system drain down, solvent and de-greasing cleaning operations, fuel tank drain down
and removal, and other activities which may result in discharge or spillage of pollutants
to the ground or into stormwater runoff must be conducted using spill prevention
measures, such as drip pans. Contaminated surfaces shall be cleaned immediately
following any discharge or spill incident. Emergency repairs may be performed on-site
using temporary plastic placed beneath and, if raining, over the vehicle.
• Wheel wash or tire bath wastewater shall be discharged to a separate on-site treatment
system or to the sanitary sewer, if available.
Element 10: Control De-Watering.
De-watering is not anticipated for the site. In the event that dewatering is necessary, storm shall
be treated such that sediment remains on site. This shall be done by routing the storm water
through a straw filter, silt fence, and/or sediment trap.
Element 11: Maintain BMPs.
BMPs shall be inspected monthly and after every significant storm event, sediment shall be
removed from the BMPs as necessary for them to continue operating at the required performance
level. In the event that a BMPs has been damaged, it shall be replaced immediately.
Element 12: Manage the Project.
Construction activities shall be phased such that the impact to the area will be kept at a
minimum. Coordination will occur with all utility agencies that are affected by this project.
BMPs shall be inspected regularly and after each significant storm event. The Contractor will
provide a Certified Erosion and Sediment Control Specialist. If for any reason a BMPs is not
sufficient for the project, additional BMPs will be installed.
IX. BOND QUANTITIES and DECLARATION of COVENANT
Bond Quantities
Not applicable.
Facility Summaries
Not applicable.
Declaration of Covenant
Declaration of Covenant for maintenance will have to be approved and recorded.
X. OPERATION AND MAINTENANCE MANUAL
Operations and Maintenance Instructions for Basic Infiltration
Your property contains a stormwater management flow control BMP (best management practice)
called "full infiltration," which was installed to mitigate the stormwater quantity and quality
impacts of some or all of the impervious surfaces on your property. Full infiltration is a method
of soaking runoff from impervious area ( such as paved areas and roofs) into the ground. If
properly installed and maintained, full infiltration can manage runoff so that a majority of
precipitation events are absorbed. Infiltration devices, such as gravel filled trenches, drywells,
and ground surface depressions, facilitate this process by putting runoff in direct contact with the
soil and holding the runoff long enough to soak most of it into the ground. To be successful, the
soil condition around the infiltration device must be reliably able to soak water into the ground
for a reasonable number of years.
The infiltration devices used on your property include the following as indicated on the flow
control BMP site plan: D gravel filled trenches, iJ drywells, D ground surface depressions. The
size, placement, and composition of these devices as depicted by the flow control BMP site plan
and design details must be maintained and may not be changed without written approval either
from the King County Water and Land Resources Division or through a future development
permit from King County.
Infiltration devices must be inspected annually and after major storm events to identify and
repair any physical defects. Maintenance and operation of the system should focus on ensuring
the system's viability by preventing sediment-laden flows from entering the device. Excessive
sedimentation will result in a plugged or non-functioning facility. If the infiltration device has a
catch basin, sediment accumulation must be removed on a yearly basis or more frequently if
necessary. Prolonged ponding around or atop a device may indicate a plugged facility. If the
device becomes plugged, it must be replaced. Keeping the areas that drain to infiltration devices
well swept and clean will enhance the longevity of these devices. For roofs, frequent cleaning of
gutters will reduce sediment loads to these devices.
APPENDIX A
GEOTECHNICAL REPORT
GEOSPECTRUM CONSULTANTS, INC .. ·-·-·-~---
·---------~
Geotechnical EnginF.?-ering and Earth Sciences
:--·--···
I
. . --i
March 21, 2016
Mr. Hugh Stewart
c/o Encompass Engineers
165 NE Juniper Street, Suite 201
Issaquah, WA 98027
SUBJECT: GEOTECHNICAL EVALUATION
Proposed 2-Lot Residential Subdivision
2216 High Avenue NE
Renton, Washington
Project No. 16-10201
Dear Hugh,
This report presents the results of our evaluation of your subject lot for the proposed 2-
lot subdivision. Our work was performed in accordance with the conditions of our
proposal dated February 19, 2016. The purpose of our work was to evaluate the site for
new residence structures and the feasibility of onsite infiltration systems.
Our site evaluations were based on a site plan provided by Encompass Engineering
(see Figure 2). The site plan indicates that the existing property will be.subdivided to
create two new residential lots on the western 2/3 of the property and a open space on
the eastern 1/3 of the property. We understand that two new wood-frame residence
structures will be constructed on the new lots.
C -·· -----·-----··-·--·•·-----------
PO. &..,x 276, Issaquah, vVA 98027-0:Z/,' , Phone: (425) 391-4228 Fax (425) 391-4228
i
Stewart March 21, 2016
SCOPE OF WORK
Our scope of work included site reconnaissance, subsurface explorations, laboratory
testing, engineering evaluations and the preparation of this report. The scope of work
included the following specific tasks:
o Reviewed published geologic mapping and USDA soil mapping of the site
vicinity.
o Performed a site reconnaissance to observe the surface conditions at the
site.
o Excavated four test pits to observe and sample the subsurface conditions.
Approximate locations of the test pits are shown on Figure 2 and logs of
the test pits are included in Appendix A.
o Performed laboratory testing including moisture content and grain size
analyses.
o Performed engineering evaluations of the site conditions observed and
encountered in our explorations and results of our laboratory testing.
o Prepared this geotechnical report summarizing our findings, evaluations
and recommendations for development of the new lots.
OBSERVED SITE CONDITIONS
Surface Conditions
The site is located on the east side of High Avenue about 400 feet south of NE 24th
Street (see Figure 1 ). The site vicinity topography shown on Figure 1 indicates the site
to be within a broad ridge that is gently inclined down to the northwest and is bordered
on the east by a broad northwest draining ravine and on the west by a cut slope
associated with 1-405 west of High Avenue.
Most of the property is gently sloped, but the eastern 1/3 of the property is occupied by
the western slope of a local ravine that drains to the north. Based on the topography of
Figure 2, the property has only about 4 feet of elevation difference across the proposed
new lot area but the eastern ravine slope has about 10 to 18 feet of height with
gradients that range from about 10 percent up to about 60 percent. The eastern slope
area with gradients greater than 40 percent is delineated on the site plan of Figure 2.
Project No. 16-102-01 Page2
Stewart March 21, 2016
Vegetation on the site included lawn grass in the front yard and within the fenced rear
yard. The eastern slope also included ivy, blackberries and other underbrush. Trees on
the site included a few fruit trees as well as maple, cedar and fir trees ranging from
about 12 to 24 inches in diameter. We noted a recently cut 42" maple stump and logs
east of the garage and a pile of wood chips west of the garage.
Subsoils
Subsurface conditions were explored by four test pits excavated within the site area.
The approximate locations of the test pits are shown on Figure 2. More detailed
descriptions of the subsurface conditions encountered at each test pit as well as
laboratory test results are presented in Appendix A.
Our observations of the soil samples from the test pits indicated that the subsoils were
generally natural but included some surface fill as encountered at the TP-2 location
near the top of the eastern ravine slope. The natural soils at the test pit locations
included a surface layer of topsoil underlain by medium grained sand with some silt to a
depth of about 2 feet below the natural surface. Deeper natural soils were generally
medium grained sand with fine gravel and minor silt content. The fill and natural soils
were loose to depths of about 3 to 5+ feet becoming medium dense at greater depths
and dense soils were encountered at about 5.5 feet in TP-2. The upper natural soils
were generally dark brown to brown becoming light brown below about 2 feet.
Results of our grain size analyses of soil samples from the test pits (see Figures A-3
and A-4) indicate that the natural soils are predominately medium sand with only about
2 to 11 percent fines and about 3 to 20+ percent gravel.
Surface and Subsurface Water
No surface seepage or springs were observed on the site and no free ground water was
observed in any of the test pits. No red-brown mottling was observed to the maximum
depth of our test pits. The surface fill soils were generally moist to very moist and the
deeper soils generally became less moist. Measured moisture contents of the subsoils
ranged from about 5.8 to 24 percent of dry weight.
Subsurface Variations
Based on our experience, it is our opinion that some variation in the continuity and
depth of subsoil deposits and ground water levels should be anticipated due to natural
deposition variations and previous onsite grading. Due to seasonal moisture changes,
ground water conditions should be expected to change with time. Care should be
exercised when interpolating or extrapolating subsurface soils and ground water
conditions between or beyond our test pits.
Project No. 16-102-01 Page3
Stewart March 21, 2016
SITE EVALUATION
General
Review of published geologic mapping of the site vicinity (see Figure 1) indicates the
site to be in an area mapped as recessional outwash sands (Qys) which were
deposited during the recession of the most recent glaciation (Vashon) that covered the
Puget Sound area about 13,500 to 15,000 years ago. Based on the subsoils observed
in our site explorations in our opinion the site soils are Qys deposits.
Review of USDA soil survey mapping of the site vicinity (see Figure 1) indicates the
site to expose Indianola soils (lnC). The Indianola soils are described as loamy sand
to a depth of 17 inches and sand from 17 to 60 inches. Based on the sand subsoils
encountered in our site explorations per USDA classifications. the subsoils at the site
appear to be consistent with the Indianola classification.
Geologic Hazards Assessment
Landslide: The Renton Sensitive Areas Maps indicate the site is not within a Landslide
Hazard area and the geologic map of Figure 1 indicates no mapped landslides within
the site vicinity but the site does contains steep slopes within the eastern ravine. Our
site observations indicate the proposed lots are currently stable but as with all
development on or near slopes, the owner, must be aware of and accept the risk that
future slope failures may occur and may result in damage to his property and/or
neighboring property. Considering the gentle to very gentle slope gradients of the
upper western portion of the site where the new lots are proposed, it is our opinion that
the potential for future instability of the western lots area is very low to nil but the steep
eastern ravine slope has potential for future shallow slope failures particularly during
strong seismic ground shaking.
The risk of structure damage resulting from a slope failure varies with the distance from
the slope, the slope height and its steepness as well as other factors. We evaluated
the stability of the steep eastern ravine slope by performing stability analyses of that
slope considering both static conditions and the IBC seismic criteria discussed below
under the Seismic hazard evaluations. Results of our evaluation indicated a safety
factor in excess of 1.5 for static conditions but under the IBC seismic loading criteria our
analyses indicated that there is a moderate risk of shallow slope failures and/or ground
displacements near the top of the slope during IBC Design level ground shaking.
In general to minimize risk, structures should be set back from the top of adjacent steep
slopes as far as possible within the constraints of the development plans.
Recommended minimum slope setbacks are intended to place the proposed
development at a distance from the slope where the risk is at a reasonable level
generally considered acceptable by the engineering profession. Considering the results
Project No. 16-102-01 Page4
Stewart March 21, 2016
of our seismic stability analyses, at a setback distance of 15 feet from the top of the
steep slope as shown on Figure 2 (15 foot setback+ O buffer), the static safety factor
exceeds 1.5 and we estimate seismic slope displacements on the order of Y. inch. If
the setback + buffer is increased to a total of 25 feet (15 foot setback + 10 foot buffer),
we estimate seismic slope displacements could be reduced to the order of 1/10 inch or
less. We recommend at least a minimum 15 foot structure setback+ 0 buffer (total of
15 feet) from the top of the eastern steep slope for structures supported on or in the
undisturbed medium dense to dense natural soils at the site.
Erosion: The Renton Sensitive Areas Maps indicate the site is not within a Erosion
Hazard area. We observed that the site is well vegetated we observed no indication of
any seepage or concentrated water flow or current or past erosion on the site
(excluding the base of the ravine). Based on our site observations and explorations it is
our opinion that there is no unusual erosion risk at this site and any erosion potential
resulting from development will be mitigated by our recommended grading procedures
and drainage/erosion control measures and by final re-vegetation/landscaping
incorporated into the proposed development plans.
Coal Mine: The Renton Sensitive Areas Maps indicate the site is not within a Coal Mine
Hazard area.
Seismic: The Puget Sound region is a seismically active area. About 17+ moderate to
large earthquakes (M5 to M7+) have occurred in the Puget Sound and northwestern
Cascades region since 1872 (144 years) including the 2/28/01 M6.8 Nisqually
earthquake and it is our opinion that the proposed structures will very likely experience
significant ground shaking during their useful lives.
Based on a recently published study the site lies only about 1.5 miles south of the
southern limits of the Seattle fault zone and about 18 miles southwest of the estimated
trace of the South Whidbey-Lake Alice fault both of which have postulated maximum
credible magnitudes of 7.0 to 7.5. Another recent study of the Vashon-Tacoma area
presents evidence for the east-west trending Tacoma Fault which is indicated to pass
through the south end of Vashon and the middle of Maury Island about 10 miles
southwest of the site. The study suggests that the Tacoma Fault and the Seattle fault
may be linked by a master thrust fault at depth.
The Seattle fault has been documented to have moved at its west end (Bainbridge
Island) about 1000 to 1100 years ago and evidence of movement at the east end has
also recently been documented. Some experts feel that the recurrence interval
between large events on the Seattle Fault may be on the order of several thousands of
years but our calculations indicate it may be on the order of 1200 to 1400 years. The
activity of the documented Tacoma fault is considered to be on the same order as the
Seattle fault. The recurrence of a maximum credible event on the South Whidbey fault
is not known but some experts have assigned a recurrence of about 3000 years,
Project No. 16-102-01 Page 5
Stewart March 21, 2016
however smaller events will occur more frequently as evidenced by the 5.3 event on
May 2, 1996 which was attributed to that fault.
In addition to Puget Sound seismic sources, a great earthquake event (MS to M9+) has
been postulated for the Cascadia Subduction Zone (CSZ) along the northwest Pacific
coast of Oregon, Washington and Canada. The current risk of a future CSZ event is
not known at this time. Published reports have indicated recurrence intervals for a CSZ
event to range from as little as 100-200 years to as long as 1000+ years and the time of
the last event is reported to have been about 316 years ago.
Considering all of the above, it is our opinion that the proposed structures will very likely
experience significant ground shaking during their useful lives. The 2012 International
Building Code (IBC) adopted by the City of Renton requires that a Maximum
Considered Earthquake Geometric Mean (MCEG) ground motion peak horizontal
ground acceleration (PGA) be used for site liquefaction evaluations but that the IBC
Design Earthquake which is defined as 2/3 of the MCEG ground motions may be used
for consideration in other geotechnical seismic site evaluations for new construction.
The MCEG PGA of the 2012 IBC is based on consideration of both probabilistic ground
motions with a 2475-year recurrence interval and deterministic ground motions based
on a model of known fault locations and characteristics adjusted for site specific soil
conditions. Per section 1803.5.12(2) of the 2012 IBC, we have estimated the MCEG
PGA for this site to be about 0.58g in accordance with Section 11.8.3 of ASCE 7-10.
We estimate the IBC Design Earthquake ground motion PGA for this site to be 0.39g.
Please note that the Design Earthquake ground motion PGA is not intended for
structural analyses. Spectral accelerations per the 2012 IBC should be considered in
structural design. This site is considered to be a Site Class D per the IBC definitions.
Secondary seismic hazards due to earthquake ground shaking include induced slope
failure, liquefaction, lateral spreading and ground settlement. Considering the lack of
shallow ground water at the site, it is our evaluation that the potential for damage to the
structures due to liquefaction and lateral spreading is low. Provided the structures are
founded on medium dense to dense natural soils as recommended, the potential for
significant induced settlement is considered low. The potential for seismically induced
shallow failures of the steep eastern slope is considered moderate but structures that
are properly setback from the slope and supported on medium dense natural soils
should not be significantly affected by slope movements.
Structure Support Considerations
Our explorations indicate that the site is underlain by recessional outwash soils that are
typically loose within the upper 3 to 5+ feet depths. Structures supported on the loose
soils could would experience significant static foundation settlements due to the
compressibility of the loose subsoils. Methods to help control the potential for
excessive foundation settlements at the site could include the following:
Project No. 16-102-01 Page6
Stewart March 21, 2016
o Deepened spread footings with low bearing pressure: Our analyses indicate
that if spread footings are deepened to bear on medium dense to dense natural
soils with foundation bearing pressures limited to 1000 psf or less, static
foundation settlements could be reduced to about 1/3 to 1/2 inch for loads up to 3
kif. The surface of existing soils exposed in the foundation excavation should be
compacted prior to placing concrete.
o Spread footings on a structural fill zone: Our analyses indicate that spread
footing foundations supported on a zone of structural fill with a vertical bearing
pressure of 2000 psf could limit static foundation settlements to about 1/4 to 1/2
inch for loads up to 3 kif. Existing loose soils would be excavated to expose
medium dense soils or to a depth equal to at least 1.5 times the footing width or at
least 3 feet below the footing base, whichever is greater and replaced with
properly compacted structural fill to the minimum foundation depth.
o Driven pile foundations: The structure could be supported on a system of grade
beams over driven pipe piles embedded into dense natural soils at depth. Pipe
pile support is constructed by driving typically 3-inch to 4-inch diameter steel pipe
to refusal into deep bearing soils. Installation is normally accomplished with a
tractor mounted hydraulic hammer system. Representative piles are typically
load tested to verify allowable capacities to limit settlements to Y.. inch or less.
Based on our explorations and our judgment, we expect that pile foundations
might extend to depths of 20 to 30 feet before achieving adequate resistance.
Your final selection of a foundation system should be based on consideration of
damage risk (settlement potential) versus cost.
Preparation of slab-on-grade subgrade areas should include excavation of the surficial
soils in the subgrade area and replacement with structural fill. Existing sand soils could
likely be re-used as structural fill with proper compaction. As a minimum we
recommend that subgrade preparation for a slab-on-grade floor include excavation of
the existing fill, organic and loose soils and replacement with structural fill as required to
provide a minimum of 18 inches of structural fill below the slab subgrade.
Recommendations for foundation design, subgrade preparation and structural fill
placement and compaction are presented below in RECOMMENDATIONS.
Storm Water Infiltration Feasibility
Feasibility of storm water infiltration was evaluated in accordance with the King County
Surface Water Design Manual (KCSWDM) Appendix C -Small Project Drainage
Requirements criteria. Section C.2.2.2, 1 a) of KCSWDM Appendix C states that the
infiltration soils "cannot be comprised of fill materials" and Section C.2.2.2, 1 b) of
KCSWDM Appendix C states that the depth to "the maximum wet season water table or
hardpan must be at least 3 feer. Section C.2.2.2 requires the natural soils for Full
Project No. 16-102-01 Page?
Stewart March 21, 2016
Infiltration must be clean ·coarse sands or cobbles or medium sands" however Section
C.2.3.2 allows Limited Infiltration into "fine sands, loamy sands, sandy loams or loams".
Based on our site explorations and laboratory testing combined with review of soil
mapping and research of other subsurface data, we conclude that the subsoils in the
site vicinity are medium sand with some fine gravel and trace silt which is consistent
with recessional outwash sand (Qys) soils and the mapped Indianola soils. Our
explorations also indicate that the eastern area of the proposed lots is likely mantled by
shallow fill soils up to 1 or 2 feet thick consisting of medium sand similar to native soils.
Based on the grain size analyses results of Figures A-3 and A-4, the onsite natural soils
contain about 89 to 98 percent sand and gravel and about 2 to 11 percent silt and are
classified as medium sand per the USDA system. Ground water was indicated to be
below 6 feet and is likely at the level of the eastern ravine. Therefore full infiltration is
considered feasible per the conditions of Section C.2.2.2 of the 2009 KCSWM.
RECOMMENDATIONS
Recommendations for foundation design, site grading, drainage control including
infiltration systems design, erosion control, plan review and recommended construction
observations are presented below.
Spread Footing Foundations with Low Bearing Pressure
Conventional spread footings founded on the compacted surface of medium dense to
dense natural sand soils with a vertical bearing pressure of 1000 psf or less can be
used for structure support with moderate foundation settlements. Existing fill and loose
soils should be excavated as required to expose undisturbed medium dense to dense
natural soils and the exposed soil surface in the footing excavations should be
compacted in place to a dense condition prior to placing steel and concrete. All
footings should be founded at least 18 inches below the lowest adjacent final grade.
Square footings should be at least 24 inches wide and continuous wall footings should
be at least 18 inches wide. Footings may be designed based on a maximum
allowable vertical bearing pressure of 1000 psf.
Settlement of spread footing foundations supported on a compacted subgrade with
bearing pressure no greater than 1000 psf are expected to be on the order of 1/3 to 1/2
inch for loads up to 3 kif. Differential settlements between adjacent foundations is
expected to be on the order of % inch. Settlements are expected to occur primarily
during construction.
For lateral design, resistance to lateral loads can be assumed to be provided by friction
acting at the base of foundations and by passive earth pressure. A coefficient of friction
of 0.35 may be assumed with the dead load forces in contact with onsite soils. An
Project No. 16-102-01 Page 8
Stewart March 21, 2016
allowable static passive earth pressure of 150 psf per foot of depth may be used for the
sides of footings poured against existing loose soils but may be increased to 250 psf
per foot for footings bearing laterally against properly compacted structural fill.
The bearing values indicated above are for the total dead load plus frequently applied
live loads. If normal code requirements are applied for design, the vertical bearing
pressure and the allowable lateral passive pressures may be increased by 33% for wind
and seismic forces.
Spread Footing Foundations on Structural Fill Zone
Conventional spread footings founded on a properly compacted structural fill zone
could be used to support structural loads up to about 3 kif with estimated static
foundation settlements of about 1/4 to 1/2 inch. All footings should be founded at least
18 inches below the lowest adjacent final grade. Square footings should be at least 24
inches wide and continuous wall footings should be at least 18 inches wide. Footings
may be designed based on an allowable vertical bearing pressure of 2000 psf.
The zone of compacted structural fill should extend vertically to the top of the medium
dense to dense natural soils or to at least 1.5 times the footing width below the bottom
of footing, whichever is greater and should extend horizontally from the edge of footing
at a 1 :1 projection down from the edge of footing (3 foot minimum). The exposed
medium dense natural surface should be compacted in place before placement of the
structural fill to final foundation level.
The structural fill zone should be constructed using approved onsite materials or
imported sand and gravel materials. The compacted structural fill must meet the
following criteria:
o Must be compacted in accordance with our recommendations for structural fill
placement presented below under "Site Grading"
o Must be compacted to at least 95 percent of the maximum dry density as
determined by the ASTM 01557 test method.
Settlement of spread footings supported on a properly constructed zone of structural fill
is expected to be about 1/4 to 1/2 inch. Differential settlements between adjacent
footings is expected to be on the order of about 1/3 inch. Settlements are expected to
occur primarily during construction.
For lateral design, resistance to lateral loads can be assumed to be provided by friction
acting at the base of foundations and by passive earth pressure. A coefficient of friction
of 0.4 may be assumed with the dead load forces in contact with structural fill soils. An
Project No. 16-102-01 Page9
Stewart March 21, 2016
allowable static passive earth pressure of 250 psf per foot of depth may be used for the
sides of footings poured against properly compacted structural fill.
The bearing values indicated above are for the total dead load plus frequently applied
live loads. If normal code requirements are applied for design, the vertical bearing
pressure and the allowable lateral passive pressures may be increased by 33% for wind
and seismic forces.
Driven Pipe Pile Foundations
Properly constructed pipe piles are considered a feasible foundation system alternative
to control both static and seismic structure settlements. This type of support is
constructed by driving 3-inch or 4-inch diameter steel pipe to refusal into the bearing
soils below the upper loose/soft soils. Piles typically penetrate about 5 to 15 feet into
the bearing soils before encountering refusal. Based on our explorations and our
judgment, we expect that pile foundations might extend to depths of 20 to 30 feet
before achieving adequate resistance.
Pile installation should be accomplished with a tractor mounted hydraulic hammer
system with a hammer weight in the range of at least about 850 to 1100 pounds.
Refusal penetration rates for piles will depend on the hammer size and the load testing
results. Refusal penetration rate for a 3-inch pile driven with a tractor-mounted 8501b
hydraulic hammer typically should be in the range of about 10 to 12 seconds per inch.
However minimum pile penetration for lateral load support may govern.
Based on our experience, an allowable vertical downward capacity of 12 kips can
generally be achieved for 3-inch diameter piles and 20 kips can be achieved for 4-inch
diameter piles installed as recommended above (Factor of Safety = 2+) but greater
allowable capacities should be confirmed based on a site specific load test of the
proposed pile and installation criteria. We recommend that all pile load tests and
installation be observed by our office to verify the allowable capacity and refusal criteria
for the production piles. No uplift capacity should be assumed for driven pipe piles.
Load tests should be performed on representative piles prior to production pile
installation to verify the appropriate allowable vertical capacity and refusal criteria. At
least 3% of the piles should be load tested to confirm capacity. Testing should be
accomplished according to the ASTM quick test procedure described in the ASTM D
1143-81 test method for piles under static axial compressive load. Allowable capacity
should be based on test pile settlement of 1/4 inch or less for the design load and a
Factor of Safety of 2.0+ of ultimate capacity.
Capacity may be limited by the structural capacity of the pipe and connections which
should be detenmined by the structural engineer. The pipe which fonms the pile, must
be of structural quality and must be galvanized. Pipe couplers should also be
galvanized or provided with a zinc coating. The pipe pile supports should be capped
Project No. 16-102-01 Page 10
Stewart March 21, 2016
with a grade beam to transfer structural loads to the piles. The pile/grade beam system
should be designed by a qualified structural engineer.
No lateral support should be assumed for the piles. Resistance to lateral loads can be
provided by battered piles (compression only) and by passive earth pressure against
the sides of grade beams. An allowable static passive earth pressure of 150 psf per
foot of depth may be used for the sides of grade beams poured against existing soils.
Site Grading
Site grading is expected to consist primarily of subgrade preparation for construction of
foundations, slabs and pavements. Recommendations for site preparation, temporary
excavations, structural fill and subgrade preparation are presented below.
Site Preparation: Existing fill soils should be stripped from planned structural fill areas.
Debris and trash, plus rocks and rubble over 6 inches in size, should be removed from
the subgrade. Subsoil conditions on the site may vary from those encountered in the
borings. Therefore, the soils engineer should observe the prepared areas prior to
placement of any new fills.
Temporary Excavations: Sloped temporary construction excavations may be used
where planned excavation limits will not undermine the adjacent existing structures or
interfere with other construction. Based on the conditions observed at the site it is our
opinion that temporary excavations which will require workers to enter them can be
made vertically to 3 feet but deeper excavations in un-saturated soils should be sloped
no steeper than 1 :1 (horizontal:vertical). Where there is not enough room for sloped
excavations, shoring should be provided. It should be noted that the contractor is
responsible for maintaining safe construction excavations.
Structural Fill: On site soils may be used for general structural fill (subject to final
approval during construction) provided that the soil moisture content is suitable for
compaction and they do not contain any organics. All imported fill should be clean,
sand and gravel materials free of organic debris and other deleterious material.
Structural fill should be placed in horizontal lifts not exceeding 8 inches in loose depth
and compacted to the required density
General structural fill should be compacted to at least 90 percent of the maximum dry
density as determined by the ASTM 01557 test method unless otherwise specified.
Structural fill within the optional structural fill zone for foundation support should be
compacted to at least 95 percent of the maximum dry density as determined by the
ASTM 01557 test method.
Pavement and Slab Subgrade Preparation: Concrete slabs-on-grade should be
supported on a subgrade consisting of at least 18 inches of general structural fill.
Asphalt pavement sections (AC and base course) should be supported on a subgrade
Project No. 16-102-01 Page 11
Stewart March 21, 2016
consisting of at least 6 inches of crushed gravel over 12 inches of general structural fill
In driveway areas a minimum 8-inch depth of crushed gravel should be provided above
the general structural fill. All topsoil and organic soils in the subgrade areas should be
excavated and replaced with compacted structural fill. The imported crushed gravel fill
should be compacted to at least 95 percent of the maximum dry density as determined
by the ASTM 01557 test method.
Risk of slab cracking can be reduced by placing 2-way reinforcement steel, and greater
excavation and replacement of the existing soils with new structural fill. If interior
concrete slabs are constructed they should be underlain by a polyethylene vapor barrier
of at least 6 mil thickness.
Drainage Control
Surface drainage from the adjoining upslope areas should be controlled and diverted
around the development area in a non-erosive manner. Adequate positive drainage
should be provided away from the structures and on the site in general to prevent water
from ponding and to reduce percolation of water into subsoils. A desirable slope for
surface drainage is 2% in landscaped areas and 1 % in paved areas.
Roof drains should be tightlined into the storm drain system (no splash blocks). Due to
the permeable nature of the natural site soils a perimeter footing drain is considered
optional. If a footing drain is provided, ii should be independent of the roof drain
system and placed adjacent to the base of the continuous exterior foundations. The
footing drain should consist of a four-inch diameter perforated PVC drain pipe placed in
at least one cubic foot of drain gravel per lineal foot along the base of the foundations.
The drain gravel zone around the pipe should be encapsulated with a membrane of
Mirafi 140 filter fabric or equivalent between the drainage zone material and onsite silty
soil backfill.
Design of storm water infiltration systems should be in accordance with Appendix C of
the 2009 KCSWM which has been adopted by the City of Renton. Per Section C.2.2.3
gravel filled trenches for full infiltration into medium sand should be designed based on
a trench length of at least 30 feet per each 1000 square feet of impervious surface. Per
Section C.2.2.4 gravel filled dry wells for limited infiltration into fine sand or loamy sand
should be designed based on a well volume of at least 90 cubic feet per each 1000
square feet of impervious surface.
We recommend that where fill soils are present, the infiltration trenches and dry wells
be deepened as required to penetrate into clean natural sand soils at least 3 feet below
the old topsoil surface. In addition we recommend that all infiltration systems be
located at least 25 feet horizontally from the top of the adjacent eastern ravine slope.
The storm water infiltration systems must also include adequate de-silting to remove
suspended fines from the water. Sill deposition from dirty storm water will reduce the
Project No. 16-102-01 Page 12
Stewart March 21, 2016
infiltration capability of the system. Periodic cleaning of the de-silting system should be
performed to maintain the system capability.
If permeable surface paving is proposed, the existing topsoil/organics and silty soils
overlying the natural sand soils should be removed to expose the clean natural sand
soils or to a depth of at least 18 inches and replaced with properly compacted clean
onsite sand soils or imported free draining structural fill to provide suitable subgrade
support and to allow water passing through the permeable pavement to infiltrate into
the natural sand subsoils.
If there is inadequate available space on the site for infiltration of all onsite storm water
runoff, dispersion BMP methods may be used per Sections C.2.1 and C.2.4 of the 2009
KCSWM with the exception that we do not recommend the use of splash blocks
(C.2.4.2). In addition we recommend that rock pads (C.2.4.3) and gravel filled
dispersion trenches should be located at least 1 O feet in the downslope direction away
from the structures. Final grades around the structures should be sloped to drain away
from the structures and dispersion trenches should be placed so that the dispersed
storm flow will not be directed towards the structures or other neighboring structures.
Erosion Control
Onsite materials are expected to be highly erodible when exposed in slope areas. No
excavated material should be wasted on the slopes. Siltation fences or other suitable
detention devices should be provided around soil stockpiles and around the lower sides
of exposed soil areas during construction to control the transport of eroded material.
The lower edge of the silt fence fabric should have "J" shaped embedment in a trench
extending at least 12 inches below the ground surface. Surface drainage should be
directed away from slopes and exposed soil areas should be planted immediately with
grass and deep rooted plants to help reduce erosion potential.
Cutting and clearing should be avoided on the slope areas. Pruning or cutting back of
trees with a minimum of disturbance to the existing slope vegetation is recommended
as opposed to felling. If felling is required, stumps should be left intact to reduce
disturbance to the shallow soils.
Observations and Testing During Construction
Recommendations presented in this report are based on the assumption that soil
conditions exposed during construction will be observed by our office so that any
necessary design changes or supplemental recommendations may be made. All
footing excavations should be observed prior to placement of steel and concrete to see
that they have penetrated into bearing soils and that excavations are free of loose and
disturbed materials. Proper fill placement and compaction should be verified with field
and laboratory density testing by a qualified testing laboratory. Installation and load
Project No. 16-102-01 Page 13
Stewart March 21, 2016
testing of driven pipe piles should be observed by our office to confirm allowable
capacities. Production pile refusal criteria for all driven pipe piles should be confirmed
by our office. Drainage control and infiltration systems construction should be observed
to verify proper construction.
Plan Review
This report has been prepared to aid in the evaluation of this site and to assist the
owners and their consultants in the design and construction of the project. It is
recommended that this office be provided the opportunity to review the final design
drawings and specifications to determine if the recommendations of this report have
been properly implemented and to make any supplemental design recommendations
which may be required.
CLOSURE
This report was prepared for specific application to the subject site and for the exclusive
use of Hugh Stewart and his representatives. The findings and conclusions of this
report were prepared with the skill and care ordinarily exercised by local members of
the geotechnical profession practicing under similar conditions in the same locality.
We make no other warranty, either express or implied.
Variations may exist in site conditions between those described in this report and actual
conditions encountered during construction. Unanticipated subsurface conditions
commonly occur and cannot be prevented by merely making explorations and
performing reconnaissance. Such unexpected conditions frequently require additional
expenditures to achieve a properly constructed project. If conditions encountered
during construction appear to be different from those indicated in this report, our office
should be notified.
Respectfully submitted,
GEOSPECTRUM CONSULTANTS, INC.
James A. Doolittle
Principal Engineer
Encl: Figures 1 and 2
Appendix A
Dist: 1/Addressee
1/Encompass Engineering via email
Project No. 16-102-01
.,,,~" no -··
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f"i:x:01RES oci2i Z6 ff l
Page 14
Geotechnloat Eng/n,gerfnQ cnc::1 Earth Science#
SITE VICINITY GEOLOGIC MAP
Proposed 2-IDt Residential SUb:!ivision
2216 High Avenue NE
Renton, Washington
Proj. No.16-102 Date 3/16 Figure 1
' !
----
/ ·',t(_,,/
//
_,.//
i , -
......
~ ... g
: '5 0
TP-2
·~·-~·-."I'
' 8. '
',
08?.
\ ' .., ill
-------~t;',.;..._9/.?._:: _____ -;'"
ref: Site Plan, 2216 High Ave. NE,
·-..1·"-:.·;
',._
' /.
/•
/ C
!__
.. ·.·. :--:=:>-
Pre~ by ~anpass. ~?,'=nee~ing & surveying, SITE EXPLORATION PLAN
GEOSPECTRUM CONSULTANTS, INC.
Proposed 2-Lot Residential Sul:division
2216 High Avenue NE
Renton, Washington
Proj. No.16-102 Date 3/16 Figure 2
APPENDIX A
FIELD EXPLORATION
Our field exploration included a site reconnaissance and subsurface exploration
program. During the site reconnaissance, the surface site conditions were
noted, and the locations of the test pits were approximately determined {see
Figure 2).
Test pits were excavated using a Cat 304 trackhoe. Soils were continuously
logged and classified in the field by visual examination, in accordance with the
ASTM Soil Classification system.
Logs of the test pits are presented on the test pit summary sheets A-1 and A-2.
The test pit summaries include descriptions of the soils and pertinent field data.
Soil consistency and moisture conditions indicated on the logs are interpretations
based on the conditions observed in the field. Boundaries between soil strata
indicated on the logs are approximate and actual transitions between strata may
be gradual.
Results of our Grain Size Analyses tests are presented on Figures A-3 and A-4.
TEST PIT NO. 1
Logged by JAD
Date: 3/2/16 Elevation: 275'
Depth Blows Class. Soil Description Consistency Moisture Color W(%) Comments
0 OL Sod/topsoil w/organics loose moist gark -rown
1 -& roots hair to 1-Yz" to ····-···· ···-·· ···--···········--·--······· ··········-··· .......... .....
-~M' Sand, medium, wtth silt very brown
24.0 moist
2-....... . ···-·-· ....................... -----········ ... . ------------· ..
-SP Sand, fine-medium, with some silt moist ~~ht 12.2 own
3-
-loose
4-to
-medium ense
5-·················
-medium
10.0
6 ense
-Maximum depth 6 feet.
7-No ground water observed.
-
TEST PIT NO. 2
Logged by JAD
Date: 3/2/16 Elevation: 279'
Depth Blows Class. Soil Description Consistency Moisture Color W(%) Comments
0 QL . TRPS.Oi!W/r9.9!S to .!''. .. loose moist <1,;irl<.llr~ FILL -
1 -SP Sand, fine-medium ~tt J ....... own
-·······--.. ................ .. -······------···
2-Ole. .. . TORS.OJI ............... .. <1,;irl< llrri
-§~ Sand, medium, with silt brown
14.8
3-......... ............. ~-fine roots __ ...... ... ......... .... . ...... " .......... -------------..
-SP Sand, medium w/fine gravel medium slitiry light ense m IS
brown
5.8
4-
-
5-
-············· ....
6.1 s-dense
-
7-Maximum depth 6 ft.
-No ground water observed.
GEOSPECTRUM CONSULTANTS, INC. Proposed 2-Lot Residential Subdivision
I 2216 High Avenue NE
Geotechnical Engineering and Earth Sciences Renton, Washington
Proj. No. 16-102 I Date 3/16 I Figure A-1
TEST PIT NO. 3
Logged by JAD
Date: 3/2/16 Elevation: 273'
Depth Blows Class. Soil Description Consistency Moisture Color W(%) Comments
0 OL Sod/topsoil w/organics loose moist gark -rown
1 -& roots Y." to 6" to ········· ···----------······· . . . . . . . . . . -. -····-·· ------··········
-~e,t Sand. medium, with silt vei brown
most 13.1
2----·· ........ ........... ........ ... -----·-· ······ ················
-SP Sand, medium moist ~~ht 7.4
& some fine gravel
own
3----················
medium -dense
4-
-
5-'" ...... -..
-more gravel 7.6
6 -Maximum depth 6 feet.
7-No ground water observed.
-
TEST PIT NO. 4
Logged by JAD
Date: 3/2/16 Elevation: 274'
Depth Blows Class. Soil Description Consistency Moisture Color W(%) Comments
0 OL Topsoil w/ roots loose moist gark -rown
1 -········------·-············ ········--... ...... .. ·········----
-§M1 Sand. f~limedium. with silt brown 11.9 me gravel
2-.... .... ·····--···· ....... ·············
-SP Sand, riedium. wifh fine gravel light some s1
3-... .......... . .. brown
-slig/l\lY m IS 7.3
4-
-········· ...•.......... ..... . ········-·-····· ........ ·······
5-SP Sand. fige-med w.ith fine gravel medium moist some silt ense -9.7
5-
-
7-Maximum depth 6 ft.
-No ground water observed.
GEOSPECTRUM CONSULTANTS, INC. Proposed 2-Lot Residential Subdivision
I 2216 High Avenue NE
Geotechnical Engineering and Earth Sciences Renton. Washington
Proj. No. 16-102 I Date 3/16 I Figure A-2
90
80
70
i
~ 60
> ..
ffi 50
lE .. I 40
30
20
10
'
0
1000
Symbol
SIZE OF OPENING IN INCHES US. STANDAIID SIEVE SIZE
1100 6"
'
1 ·
I I
I I
I
I I
I
I • . I
I
I
COBBLES
0
!::::.
'v
s• 111.2• .,,.
• • '
I 1111
II I
l I I
11
' I '
11
111 ! I
1111
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100
40 60 O ., •• ~ 10 20 • 10 200
' ' ' ' I ~: I . 111 \ "· . \
\~ i \
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\
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10 1.0 . 0.1
GRAIN SIZE IN MIUJMETERS
I
. I
l
I
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0.01
I
80
80
70
I 50
so
40
30
20
10
0
0.001
Coarse l'1ne Coars Medlum F"U18
GRAVEL SAND FINE GRAINED
Location Sample ,
TP-l
TP-2
TP-2
Depth " Moisture " Passing #200
2 '-3' 12.2 11 • 3
2'-3' 14. 8 9.5
3'-4' 5.8 2.1
TEST PITS 1 AND 2
GRAIN SIZE ARALYSES RESULTS
GEOSPECTRUM CONSULTANTS, INC.
Proposed 2-!Dt Residential subdivision
2216 High Avenue NE
'· Renton, Washington
Proj. No.16-102 Date 3/16 Figure A-3
l SIZE OF OPENING IN INCHES U.S. STANOA!ID SIEVE SIZE I ' HYDROMETER I
100 :.,...,.,.........,..-,-6!.:'""TI.;;;',...' -r1;,:i'~::..·---r'{•_'-;.'{•:-r'm~r1/lf---r/2
/JTIT40f'r,
60
-''T
1
-'~-0 i
200rf0niT1il-""ilirirrT11""i100
11 1ld I .!1
00 ~!l1-l-l~l4-++-lµ_.j--t+H+f-+-tt'J(t--#H-t++-t-+-tttt-H+tl -t-ittlttttt-i---1ao
00 ~1~,~,,-4-+-~~-m+++-r+-t-;ttt+rt++-~111~,,~~
101U4l-l-~-l--Ul-!4+-1-+--+---H+!+++-f--l~-fttt+ri-+-t--ti1t!t+-t--t---lfftrt-i-t--t---!70
i 11 ~ 50 ll+!-l-l-tt...+--+ltll++-H-t--!tttH+t-t--\itttttt-t-t--tttt1H-t-t--r-tttttt'H"""t"--, 50
; 50 ~· !-!--1--l----lH,;,I · -1+++-+-~l lf++H-+-r-ftttt+-t-t--ittttti"';--t---ttttttt"i'"-t-150
! I I 1. I 1 1 11 !z 40 ll+l-l-l-4...+--+H-11++-H-t--t+t+H+t-i--!f~tt-t-t--tttt1H-t-r-r-mttt'H"""t"-f 40 i 1 111 I 30 H4+.µ..1-++-l*f-H++---+HtiY-t++-ttffiH-t-t--t---ttttii't-t--t---ttttttt-t-t--i30
11 ! I 11 I I I I
20 ll+l44-+-+--~l+++-4-+--t+t+H+t-t---!ftHi:!'A::+-+--tttt1H-t+-r-tttttt't-t""t"-i 20
10 ll+W-l-l-4-!I __µµ.I i++-+--:f--H+l++++-!--iH+hti++-ifi M+++-..--HH-H+f-f--t10
I
foU.ooW.ll.L-L-,ollol.J'l.l.·.i.• .!...l.J-1..low.JL!..J....L.....l..-, • .U.01.J·..U...l..l.-L-::o:-.!.J. ,~1..1-.1...1-..i.::'-o:-:.0~1u.i..w...J.-i..-:o.oo:-:'01
COBBLES
symbol
D
0
GRAIN SIZE IN MIWME'!ERS
Coarse Fine Coars M&dklm Fine
GRAVEL SAND FINE GRAINED
Location Sample I Depth I Moisture I Passing 1200
TP-3 2'-3' 7.4 1 • 9
TP-4 1 '-2' 11. 9 9.8
TEST PITS 3 AND 4
GRAIN SIZE ANALYSES RESULTS
GEOSPECTRUM CONSULTANTS, INC.
Proposed 2-I.Dt Residential subdivision
2216 High Avenue NE
~{;-:',' ~~
~~>)~'Sc-~
Renton, Washington
Proj. No.16-102 Date 3/16 Figure A-4
APPENDIXB
ARBORIST REPORT
AF~
11+15 !',;"E 128ili St Suite 110 Iililtland W.'\ 98034 • (4-25)820-3420 • FAX (425)820-34-37
WV.-"W.americanforestrnanagement.com
Arborist Report
2216 High Ave NE
Renton, WA
February 251", 2016
Table of Contents
1. Introduction .............................................................................................................. 1
2. Description ............................................................................................................... 1
3. Methodology ............................................................................................................ 1
4. Observations ........................................................................................................... 2
5. Discussion ............................................................................................................... 2
6. Tree Retention ......................................................................................................... 3
7. Tree Replacement ................................................................................................... 3
8. Tree Protection Measures .......................................................................... .4
Appendix
Site/Tree Photos -pages 5 -9
Tree Summary Table -attached
Tree Plan Map -attached
American Forest Management 2/25/2016
2216 High Ave NE Arborisl Report
1. Introduction
American Forest Management, Inc. was contacted by Hugh Stewart of Sand jay LLC, and was asked to compile
an 'Arborist Report' for one parcels located within the City of Renton.
The proposed home remodel encompasses the property at 2216 High Ave NE. Our assignment is to prepare a
written report on present tree conditions, which is to be filed with the preliminary permit application.
This report encompasses all of the criteria set forth nnder City of Renton code section 4-4-130. The tree
retention requirement is 300/o of significant trees.
Date of Field Examination: February 1s••, 2016
2. Description
22 significant trees were identified and assessed on the property. These are comprised of a mix of native species
and planted ornamental species. According to City of Renton code, a significant tree is a "tree with a caliper of
at least six inches (6"), or an alder or cottonwood tree with a caliper of at least eight inches (8"). Trees qualified
as dangerous shall not be considered significant. Trees planted within the most recent ten ( I 0) years shall
qualify as significant trees, regardless of the actual caliper."
A numbered aluminwn tag was placed on the lower trnnks of the subject trees. These numbers were used for
this assessment. Tree tag nwnbers correspond with the nwnbers on the Tree Swnmary Tables and copy of the
attached site survey.
There are two neighboring trees with a drip lines that extend over the property line.
3. Methodology
Each tree in this report was visited. Tree diameters were measured by tape. The tree heights were measured
using a Spiegel Relaskop. Each tree was visually examined for defects and vigor. The tree assessment
procedure involves the examination of many factors:
• The crown of the tree is examined for current vigor. This is comprised of inspecting the crown
(foliage, buds and branches) for color, density, form, and annual shoot growth, limb dieback and
disease. The percentage of live crown is estimated for coniferous species only and scored
appropriately.
• The bole or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting
bodies of decay ( conks or mushrooms), seams, insects, bleeding, callus development, broken or dead
tops, structural defects and unnatural leans. Structural defects include crooks, forks with V -shaped
crotches, multiple attaclunents, and excessive sweep.
• The root collar and roots are inspected for the presence of decay, insects and/or damage, as well as if
they have been injured, undermined or exposed, or original grade has been altered.
Based on these factors a determination of condition is made. The four condition categories are described below
based on the species traits assessed:
Excellent -free of structural defects, no disease or pest problems, no root issues, excellent structure/form with
uniform crown or canopy, foliage of normal color and density, above average vigor, it will be wind finn if
isolated, suitable for its location
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
Page 1 American Forest Management 2/2512016
2216 High Ave NE Arborist Report
Fair -minor structural defects not expected to contribute to a fail me in near future, no disease concerns,
moderate pest issues, no significant root issues, asymmetric or wibalanced crovm. 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 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
A 'viable' tree is "A significant tree that a qualified professional has determined to be in good health, with a
low risk a/failure due to stroctural defects, is wind firm if isolated or remains as pari of a grove, and is a
species that is suitable for its location. "Trees considered 'non-viable' are trees that are in poor condition due to
disease, age related decline, have significant decay issues and/or cumulative structural defects, which
exacerbate failure potential.
The attached tree map indicates the 'condition' of the subject trees found at the site.
4. Observations
The subject trees are comprised of a mix of native and planted species. The native tree species are primarily in
along the north and east property lines. Specific tree information can be found on the attached tree table. The
non-viable and neighboring trees are described below.
Tree# 102 is a flowering cherry west of the home. This tree has five co-<lominant stems. Many of the main
stems are dead. The subject tree has poor form and decay in the stems. This tree is in decline and is non-viable.
Tree #108 is a young big leaf maple on the north property line. This tree has severe decay. One of the co-
dominant stems is dead and the main trunk is over 50% decayed. This tree is in poor condition and is non-
viable.
Tree #116 is a red alder east of the current home. The lower trunk of this tree is covered in ivy. This tree has
evidence of decay and a smaller than average cro\.VU. This tree is in poor condition and is non-viable.
Tree# 119 is a bitter cherry in the southeast comer of the property. This tree is almost entirely covered in
English ivy. This tree has a 10% live crown. The subject tree is in poor condition and is non-viable.
Tree# 121 is a mature big leaf maple tree east of the current home. This tree has co-<lominant stems that fork I'
from the ground. One trunk is leaning west towards the home. There is decay in the stem leaning towards the
home. There is reaction wood around the decay, evidence that the decay has been compartmentalized. The most
concerning defect is the v-shaped attaclnnent between the co-dominant stems and the seam between the branch
attachments. This tree is in poor condition and is non-viable.
Neighboring Trees
Tree #201 and #202 are Douglas-fir trees north of the property line. Both trees have full crowns and no notable
defects. The subject trees are in good condition and are viable.
5. Discussion
The extent of drip-lines (farthest reaching branches) for the subject trees can be found on the tree summary
tables at the back of this report. These have also been delineated on a copy of the site survey for viable/healthy
trees proposed for retention. The information plotted on the attached survey plan may need to be transferred to
a final tree retention/protection plan to meet City submittal requirements. The trees that are to be removed shall
be shown "X'd" out on the final plan.
Page 2 American Forest Management 2/25/2016
2216 High Ave NE Arborist Report
The Limits of Disturbance (LOO) measurements can also be found on the tree sunnnary table. This is the
recommended distance of the closest impact (soil excavation) to the trunk face. These should be referenced
when determining tree retention feasibility. The LOO measurements are based on species, age, condition, drip-
line, prior improvements, proposed impacts and the anticipated cumulative impacts to the entire root zone.
Tree Protection fencing shall be located beyond the drip-line edge of retained trees, and only moved back to the
LOO when work is authorized.
The neighboring trees are two mature Douglas-fir trees and need to be protected with tree protection fencing.
Tree #20 I and #202 are on the north perimeter and with tree protection fencing, erected per the attached plan,
no significant impacts are anticipated.
6. Tree Retention
A total of 22 significant trees were identified on the subject property. Six of the significant trees are in poor
condition. These six non-viable trees vvere not included in the tree calculation.
Landmark trees and tree groves were prioritized when selecting trees for retention, per the City of Renton tree
code 4-4-130.
Tree Calculation based on 16 healthy viable significant trees
Viable Trees proposed for removal -12 (75%)
Viable Trees proposed for retention -4 (25%)
Tree Type Removal Retained
Landmark# 1 0
Landmark% 100% 0%
Significant # 11 4
Significant % 73% 27%
Total# 12 4
Total% 75% 25%
7. Tree Replacement
Total
1
100%
15
100%
16
100%
Replacements trees may be required. Consult your city planoer for tree replacement requirements. All
replacement trees are to be planted on site. For planting and maintenance specifications, refer to Section 4-4-
130 of the Renton Tree Ordinances.
Page3 American Forest Management 2/25/2016
2216 High Ave NE Arborist Report
8. Tree Protection Measures
The following guidelines are recommended to ensure that the designated space set aside for the preserved trees
are protected and construction impacts are kept to a minimwn.
• Tree protection barriers shall be initially erected at 5' outside of the drip-line prior to moving any
heavy equipment on site.
• Tree protection fencing shall only be moved where necessary to install improvements, but only as
close as the Limits of Disturbance, as indicated on the attached plan.
• Excavation limits should be laid out in paint on the ground to avoid over excavating.
• Excavations within the drip-lines shall be monitored by a qualified tree professional so necessary
precautions can be taken to decrease impacts to tree parts. A qualified tree professional shall monitor
excavations when work is required and allowed up to the "Limits of Disturbance".
• To establish sub grade for foundations, curbs and pavement sections near the trees, soil should be
removed parallel to the roots and not at 90 degree angles to avoid breaking and tearing roots that lead
back to the trunk within the drip-line. Any roots damaged during these excavations should be exposed
to sound tissue and cut cleanly with a saw. Cutting tools should be sterilized with alcohol.
• Areas excavated within the drip-line of retained trees should be thoroughly irrigated weekly during dry
periods.
• Preparations for fmal landscaping shall be accomplished by hand within the drip-lines of retained trees.
Plantings within the drip lines shall be limited. Large equipment shall be kept outside of the tree
protection zones.
There is no warranty suggested for any of the trees subject to this report. Weather, latent tree comiitions, and
future man-caused activities could cause physiologic changes and deteriorating tree condition. Over time,
deteriorating tree conditions may appear and there may be conditions, which are not now visible which, could
cause tree failure. This report or the vetbal comments made at the site in no way warrant the structural stability
or long tenn condition of any tree, but represent my opinion based on the observations made.
Nearly all trees in any condition standing within reach of improvements or human use areas represent hazards
that could lead to damage or injury.
Please call if you have any questions or I can be of further assistance.
Sincerely,
Kelly Wilkinson
ISA Certified Arborist #PN-7673A
ISA Tree Risk Assessment Qualified
Page4 American Forest Management 2/25/2016
2216 High Ave NE Arborist Report
Photos
Tree #103, #102 and #101 -planted ornamental trees
~
. /
' .....
~,
Page 5 American Forest Manage me nt 2/25/2016
2216 High Ave NE Arborist R eport
Tree #104 -Austrian black
Page 6 American Fo rest Ma nagem ent 2 /25/2016
22 16 High Ave NE Arborist Report
Tree #114-westem red cedar with co-dominant stems
• .. _ • .•• t,. .. . -
Page 7 America n Fo rest Ma nagement 2/25/2016
2216 High Ave NE Arborist Report
Page 8 America n Forest Management 2/25/2016
2216 High Ave NE Arborist Report
Page 9 America n Forest Management 2/25/2016
!
/ t' ; ,....
. ..,
l
i
HOUSE
--Li,.,, r5 or D:ST0 :?.eijN'C.~
--lp~ C 1)._:. ~-
~ ;·((;
/ \ • \
. .::: .··· I . '
,a;~'l-\ ~'; ·.
......
< .:S:
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i
-ti--·-"'=-~~ I YCL
::/ir "'-~
~tr
m .. ;:;:
:::: .... . . . . ttm~
:Hi 11\\.\\ . . . . .. : . : . . ... . . . .
. . ~P.HAli ....... .
,/L %w~ m lilj!J!!!i!Ji!li iii!!iii / *'o\ m :·:·:·:·:·:·=··· .-.·:·=· . ~ -:-:,:,:-:-:,::: •:•:.:-:
. . L.-L..,Cl) :i ' cJ::.;f;~ :·:·:·:·:·:·:·:· :,:,:-:·
4-N h\~~~~:,r0if~~J;;:~}ll :m:w ",~---·-·· .... ,. ,~Y1:l:· ······· <?. •,•. ,' 128.w ~--i~;··-~-~-(~,.i_.;·./-:~·:::::::: ·-:::::: _
\tf1ff~){lJllllllllitli ~-~·
Tree/
. --,;, ·-..---· --
101 Amur maple
102 flowering cherry
103 Magnolia
104 Austrian pine
105 Sitka spruce
106 western red cedar
107 big leaf maple
106 big leaf maple
109 lodgepole pine
110 Douglas-fir
111 Austrian pine
112 big leaf maple
113 big leaf maple
114 western red cedar
115 bitter cherry
116 red alder
117 bitter cherry
118 black cottonwood
119 bitter cherry
120 black cottonwood
121 big leaf maple
122 flowering cherry
201 I Douglas-fir
202 Douglas-fir
Tree Summary Table
For: 2216 Higfi Ave NE
City of Renton
DBH Height
' ' N
.:;, u, ,,
4,3 21 13
o, o, 1.;,,
9,5 14 12
10, 7 26 12
15 32 2
15 57 10
30 86 16
12 68
10 64
16 69
28 95
11 62
15,14,14 64 21
8, 16 42 10
24,7 60 12
9,12,11 49 16 / 12
14 43 15
6,7 54 15 / 10
18, 14 75 19 / 14
6, 10 23
26 68 13 / 14
23, 28 89 22
, 1 , ... ,
10, 10 26 11
27 I 92 I
29 99
s E
113
14
16
24
10
12
16
16
14
7
21
14
11
14/ 12
7
16 / 10
23/ 14
12 / 14
8
22
10/ 8
12 / 10
Drip-Line and Limits of Disturbance measurements from face of trunk
\IV
11 10
14 21
17 9
10 7
12 9
14 12
8
6 8
8 7
9 18
4
11 11
15/ 12 12 / 12
18 9
7 / 10 11 / 10
15 / 14 9114
9 / 14
18 21
15 15
Neighboring Trees
I
American Forest Management, Inc.
Date: 2/19/2016
Inspector: Wilkinson
.
fair viable
poor non-viable
fair viable
fair viable
good viable
good viable
fair viable
poor non-viable
fair viable
good viable
fair viable
fair viable
fair viable
good viable
fair viable
poor non-viable
fair viable
fair viable
poor non-viable
fair viable
poor non-viable
poor non-viable
I good I viable
I good I viable
decay in stems
dead stems, decay, poor form
forks at base and reconnects at 5'
leans south
landmark tree
severe decay, dead co-dominant ster
flat side
ivy covering trunk
ivy covering trunk
ivy
ivv
ivy
severe trunk decay
forks at base, some dead stems
ivy covering trunk, 10% live crown
ivy
decay, black on lower trunk
decay
I
I
Trees on neighboring properties -Drip-line and Limits of Disturbance measurements from property lines
remove
remove
remove
remove
remove
remove
remove
remove
remove
remove
remove
remove
remove
remove
retain
remove
retain
retain
remove
retain
remove
remove
I
I
APPENDIXC
KCRTS ANALYSIS
KCRTS Storm Water Analysis
fi) Land Us.e Summary
Area
TIii Forest 0.36 acresl
Till Pasture 0.00 acres!
TIii Grass 0.00 acres!
Outwash Forest 0.00 acres
Outwash Pasture 0.00 acresi
Outwash Grass. 0.00 acres!
Wetland 0.00 acresi
' Impervious 0.00 acres!
Total
0.36 acres'
Scale Factor : 1.00 Hourly Reduced
lime Series: IPre-Oev-1111-Forest.TSF
Compute Time Series ----------Modify User Input -----------Fi I e for computed Time Series (.TSF]
Pre-Developed Condition
Area
Till Forest 0.16 acres
Till Pasture 0.00 acres
Till Grass 0.00 acres•
Outwash Forest 0.00 acres
Outwash Pasture 0.00 acres
Outwash Grass 0.00 acres
Wetland 0.00 acres
Impervious 0.20 a,:re":
Total ---1
' 0.36 acres1
Scale Factor : 1.00 Hourly Reduced
X
11
1»1
I
I
X
11
Time Series: !Dev-Till-Forest TSF I »j
Compute Time Serles I --------------------··-------------'·
Modify User Input I
.c-..-_-.. -... ---.... ---------F-i-le-,-.,-r--c~;;;~~;ed-Ti~---.,-s~.-r-ie_s_(_-T_S_F] ___ -_-_------~
Developed Condition
KCRTS Storm Water Analysis (continued)
Flow Frequency Analysis
-------------~--------------------~-~~-~-------~--
Time Series File:pre-dev-till-forest.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--------Flow Frequency Analysis-----~
Flow Rate Rank Time of Peak --Peaks -Rank Return Prob
(CFS) (CFS) Period
0.023 2 2/09/01 18: 00 0.029 1 100.00 0.990
0.006 7 l/06/02 4: 00 0.023 2 25.00 0. 960
0.017 4 2/28/03 3: 00 0.018 3 10.00 0.900
0.001 8 3/24/04 20: 00 0.017 4 5.00 0.800
0.010 6 l/05/05 8 :DO 0.015 5 3.00 0.667
0.018 3 1/18/06 20: 00 0.010 6 2.00 0.500
0.015 5 11/24/06 6: 00 0.006 7 1.30 0.231
0.029 1 l/09/08 9 :00 0.001 8 1.10 0. 091
Computed Peaks 0.027 50.00 0.980
Flow Frequency Analysis
------~-----~-------------~---~---------------------
Time Series File:dev-till-forest. tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--------Flow Frequency Analysis-------
Flow Rate Rank Time of Peak --Peaks Rank Return
(CFS)
0.055
0.045
0.063
0.050
0.059
0.059
0. 072
0.105
Computed Peaks
(CFS) Period
6 2/09/01 2: 00 0.105 1 100.00
8 l/05/02 16: 00 0. 072 2 25.00
3 2/27/03 7: 00 0.063 3 10.00
7 8/26/04 2 :00 0.059 4 5.00
4 10/28/04 16: 00 0.059 5 3.00
5 l/18/06 16: 00 0.055 6 2.00
2 10/26/06 0: 00 0.050 7 1. 30
1 l/09/08 6 :00 0.045 8 1.10
0.094 50.00
Developed-Pre-Developed= Runoff(IOO-year event)
0.105 -0.029 = 0.076 cfs < 0.10 cfs Okay
No flow control ( detention) required
Prob
0.990
0. 960
0.900
0.800
0.667
0.500
0.231
0. 091
0.980