HomeMy WebLinkAbout03332 - Technical Information Report FIELDS TOWN HOMES
1 512/518 Union Avenue NE
Renton, Washington
TECHNICAL INFORMATION REPORT
May 16, 2006
Updated June 26, 2006
Prepared for:
Timberstone Homes, Inc.
Attn: Jim Pitzer
46533 — 284th Avenue SE
Enumclaw, Washington 98022
(253) 632-9159 office
Submitted by:
Offe Engineers, PLLC
Attn: Darrell Offe, P.E.
13932 SE 159th Place
Renton, Washington 98058-7832
(425) 260-3412 office 1) v L. "ii
(425) 988-0292 fax wo • �
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/ 4.4,,G 27460.Q, G 27460 FISTV GN7'
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EXPIRES l,m FP
Project Description
The purpose of this report is to present a preliminary drainage and downstream review
for the proposed Fields 7-unit Town Home project in accordance with the City of Renton
requirements. The project is located at 512/518 Union Avenue NE within the City limits
of Renton.
The Fields Town Home project is a proposal to create 7 multi-family residential units on
the two existing properties comprising of 0.52 acres. The project is currently two
separate tax parcels, 102305-9114 and 102305-9411. The two parcels currently our
occupied with existing residences that serve access from Union Ave. NE, see Figure 1 for
a vicinity map and Fgure 2 of a March 2003 Aerial Photo. Figure 3 shows the proposed
site plan for the short plat.
The parcel is bounded to the West by Union Avenue NE; which is fully-developed with
curb, gutter and sidewalk along the project frontage. To the East, North and South the
project adjoins existing residential use.
Review of Resouroes
Critical Drainage Area Map
• Maplewood Creek/ Cedar River/ Lake Washington Watershed
Flood plain/floodway (FEMA) Maps
• There is no mapped floodplain in the immediate area per the available FEMA
map.
Sensitive Areas �
• Wetlands -There are no known wetlands located on the project.
• Streams and 100 Year Flood Plains-There are no apparent streams or ��
floodplains that go through or abut the project. Downstream of this property,
Maplewood Creek begins on the south side of NE 4�' Street.
• Erosion Hazard Areas-There are no landslide hazard areas for the project. j
• Landslide Hazard Areas-There are designated sensitive slopes on and ,
adjoining the property.
• Seismic Hazard Areas-The area is not mapped as a seismic hazard area.
• Coal Mine Hazard Areas-The property does not appear to be located within II
a designed coalmine hazard area.
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U.S. Department of Agriculture, King County Soils Survey
• The soils have been classified by Cornerstone Geotechnical as Recessional
Outwash. These types of soils are made up of sands and gravels capable of site
infiltration. The Geotechnical report prepared for this project was provided to
the City as part of the preliminary short plat submittal.
Flow Control Application
• The proposed developed would generate an additional 9,400 square feet of new
impervious after January 8, 2001. The project meets the threshold for Small
Project Drainage Review. The proposed dispersion of the storm water runoff
would be through dry-wells for the roof drains and an infiltration trench under
the road way. The site is located with a Zone 2 Aquifer Protection Area.
Infiltration of storm water is proposed as the flow control for this project.
Water Quality Application
• Aquifer Protection would be required for this project based upon notes provided
at the pre-application meeting. The proposed project would not generate an
additional 10,000 square feet of impervious area (as identified under Appendix C,
KC Drainage Manual) therefore water quality protection is not proposed. The
entire project would infiltrate (disperse) into the existing soils.
Landslide Hazard Drainage Area Map
• The site is not located in a landslide hazard drainage area.
Field Inspection
OfFe Engineers has visited the site on several occasions. The most resent visit occurred
the morning of November 2, 2005. The ground slopes from Union Avenue NE towards
the existing home on the East side of the property. Surrounding the project exist multi- ,
family projects. The property does not currentJy discharge into the storm system within
Union Avenue. The site sets about 4 feet below Union Ave. The existing buildings,
home, and driveway appear to infiltrate into the ground. There are no signs of water
ponding on site. Appendix D contains site photos.
Review of the 8 Core Requirements and 5 Special Requirements of the 2005
King County Surfaoe Water Design Manual i
Offe Engineers has reviewed the Core and Special Requirements in Chapter 1 of the
King County Surface Water Design Manual, and addresses each of the requirements as
follows: '
Core Require�nent No. 1 —Discharge at Natu�a/Location
The project currently infiltrates into the soils; the proposed project would do the same.
The entire project will disperse within infiltration trenches and dry wells on-site.
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Core Requirement No. 2—Of�'si[�e Ana/ysis
East Property -The property appears to be an isolated parcel below Union Avenue NE
with no water flowing onto the parcel. The surrounding properties are developed and
contain the storm water within their projects. Union is above this parcel with curb,
gutter and sidewalk. The storm system in Union flows south towards NE 4"' and not on
this property.
Core Re�quirement No. 3—F/ow Contro/
The proposed project will be required to provide control of the proposed houses and
driveways. Infiltration utilizing Appendix C of the KC Drainage Manual will be used to
control the storm water runoff.
Core Re+quirement No. 4—Conveyanoe Sys�em
No conveyance system is being proposed
Core Repuirement No. 5—Erosion and Se+diment Contro/
A Temporary Erosion and Sediment Control Plan implementing the Best Management ,
Practices will be designed as part of the final engineering plans for the project in I
accordance with City of Renton requirements.
Core Requirement No. 6—Maintenance and Operations
The Maintenance and Operations Manual for the Fields Short Plat will be included in the
Final Storm Drainage Report as part of the final engineering design for the project.
Cor�e Repuirement No. 7—Financia/Guarantees and Liabi/ity
The Financial Guarantees and Liabilities will be required prior to the project being
' finalized hy tr��e City oF Renton.
Core Requirement/i�o. 8 — Water Qualrty
The proposed project will not create an additional 10,000 square feet of impervi�
surface; therefore no water quality treatment is being proposed.
Specia/Repuirement No. 1 —Adop[�d Area-Specific Requirements
The project is located within the Cedar River Basin Plan.
Speaa/Repuirement No, Z—F/aadp/ain/F/oadway O�e/ineation
This requirement does not apply.
Specia/Requirement No, 3—F/oor/Prote�ction Faci/ities
This requirement does not apply.
Specia/Repuirement No. 4—Sou�ae Contro/s
This �equirement does not apply.
Specia/Requirement No. 5—Oi/Contro/
This requirement does not apply.
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Appendix A
Drainage Design
Design Criteria
Based upon Figure 1.1.2A of the 2005 King County Drainage Manual, this projects meets
the threshold criteria for Small Project Drainage Review.
The existing property was build out in the late 60's and contains several outbuildings, a
house w/ deck and patio, a large driveway, and detached garage. The existing site
topography shows that there is approximately 6,550 square feet of impervious area.
The proposed development consists of two new buildings (West and East) and a paved
access road to provide access for the residence and emergency vehicles. The proposed
project will generate 15,860 square feet of impervious area.
The new added impervious area would be 9,310 square feet. This is less than 10,Q00
square feet for a single family project and therefore meets the threshold criteria for
Small Project Drainage Review.
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June 25, 2006 PriortoJan, 2001
Fields Town Homes
512 Union Avenue
Renton
Existing Area
Location Description (Existin4) (sq. ft.)
512/518 Union Avenue Houses 960 (impervious-typ.J
outbui/dings/garage 470
compacted driveway 2060
Paved AC Driveway 2220
Sidewa/k/concrete pads 840
Total 6550
Acres 0.15
Proposed Area
Description �Developed� (sq. ft.)
West Bui/ding 3100
East Bui/ding 4880
New access road 7880
Total 15860
Acres 0.36
Added New Impervious 9310 square feet
I I
� S
I �I
1.i.2 DRAI?�IAGE REVIEW T'YPES AND REQUIRE'�4ENTS I
,I I
FIGURE 1.1.2.A FLOW CHART FOR DETERMIIVING TYPE OF DRAINAGE REVIEW REQUIRED I',
- Is the ro'ect a sin !e famil resfden ia!or a ricultural ' II
P 1 9 Y r 9 > .Siv�ALL PR03ECT DRAINAGE R.EVTEW :
. project that resuits in 2,000 sf of new impervio�s " Section 1.1:2.1
su�face and meets one of the fotlowing criteria? fVpte:The ptDjec#may also be sut�lecf to
•The project results in<_10,000 sf of total impervious Targefed 13rainage Review as det�tmined
surface added since 1/8/01 and_<35,000 sf of new '�Q�ayy. �
pervious surface,or for sites zoned as RA, F,or A, n - _;;., _ -
pervious surface<_70,000 sf or 3596 of the sfte, Yes ; � ':
whichever is greater, OR � � '
•The project results in<_4°/fl total impervious surface a }
<_15%new pervfous surface on a singie parcel ske � ��
zoned as RA or F,or a singte/multiple parcet site zoned � -=-,,� #
as A,and all impervious area on the site,except 10,000 sf ' =
of it,will be set back fr�m its natural location of discharge �
from the site at least 100 ft for every 10,000 sf of total
impervious surface?
No
Does the project result in�,000 sf poes the project have the characteristics of one or more of the
of new impervious surface or following categories of projects(see the more detailed
>_35,000 sf of new pervious threshold language on p. 1-14)?
surface, OR is the project a 1. Projects containing or adjacent to a flood,erosion,or steep
redeve/opment project on a parcel stope hazard a�ea; projects within a C�Itical Dralnage Area
�I or combination of parcels in which No or Landslide Hazard Drainage Area; or projects that propose
new pfus replaced impervlous >_7,000 sf(3 ac if the project is in Smalt Project Drainage
surface totals>_5,000 sf and whose Review)of land dlsturbing activity.
valuation of proposed improvements 2, projects proposing to constnrct or modify a drainage
� — (excluding required mitigation and Pipe/ditch that is 12"or larger or receives runoff from a i2"
frontage improvements)is>50%oi
the assessed value of existing or larger drainage pipe/ditch.
improvements? 3. Redevelopment projects proposi�g>_$100,000 in
improvements to an existing high-use site.
Yes No Yes
Reassess whether �;�����p;7g�Ip�=,qG�.����� s ��
drainage review is -Secfion 9"l.2.�i:-�' :�:�- �;�
� required per Section �� '°�� � =��� � _� g ���
1.1.1 (p• 1-9). �� �` ._�:� '�a-�� ��� U �"�
>x,
- -.,�
�
Isthe projectan Urban Planned Development(UPD), �'��,�g�,��p�������r=`=�
OR dces it resuft in>50 acres of new lmpervious No =:_ge�iion°Z �#,2 3�: '
surface within a subbasin or multiple subbasins that � � ;; - �� � .'� � `��r ��
� � � � � � -'�t�,. .�
are hydraulically connected,OR does it have a project � , ,� �,� � �� � ;
' site z50 acres within a c►itical aqulfer recharge area? � x=;, � � `�� � ' '
Yes
�AKGE PR07E�1'I)RATIvACiEr��Et� %;
: :S8C1KsTi�1 '{ ��'`�, ' ' � 's
rs
,e � � � �,�.,� : _,�,2 �gms�.:,# ��+,.
�:'f ���� �, �',tS` }'k`���"-�.a��
a t �`'T � ��� ;� '�_ *c
�z�.,��r;_. :+ z
2005 Surface Water Design Manua] I/24,%2005
1-11
, ,
].1.2 DRAiNAGE REVIE��'TYPES AhD REQUIRE?�1E1v'TS
1.i.2.1 SMALL PR03ECT DRAINAGE REVIEV4'
Small Project Drainagc Review is a simplified drainage review for small residential building,clearing,and
subdivision projects or small agricultura[projects that result in either(a) I 0,000 square feet or Iess of
impen�ious surface added on or after January 8,2001 (the effective date of the ESA 4(d)Rule for Puget
Sound Chinook salmon)or(b) less than 4°io of total impervious surface as specified in this section. The
core and special requirements applied under Full Drainage Review are replaced with simplified smalk
project drainage requirements that can be applied by a non-engineer. These requirements include simple
stormwater dispersion,infiltration,and site design techniques called flow controi Best Management
Practices(BMPs),which provide the necessary mitigation of flow and water quality impacts for small
projects. Also included are simple measures for erosion and sediment control (ESC). This simplified
form of drainage review acknowledges that drainage impacts for many small project proposals can be
effectively mitigated without construction of costly flow control and water quality facilities.
The Small Project Drainage Review process minimizes the time and effort required to design, subinit,
review,and approve drainage facilities for these proposals. In most cases, the requirements can be met w�ith
submittals prepared by contractors,architects,or homeowners without the involvement of a civil engineer.
Note:some projects subject to Smald Project Drainage Review may also require Targeted Drainage
Review if they meet any of the threshold criteria in Section 1.1_2.1(p. 1-14).
Threshold
, '� Small Project Drainage Review is required for any single family residential project or agricultural project
that will result in 2,000 square feet13 or more of new impervious surface,AND that meets one of tl�e
following criteria:
• The project will result in no more than 10,040 square feet13 of total impervious sur3'aee added on or
after January 8,2001 and no more than 35,000 square feetl3 of new pervious surface(for sites zoned
as RA,F,or A,this new perveous surjace threshold may be increased to 70,000 square feet13 or 35°�0
T of the site,whichever is greater),OR
E • The project will result in no more than 4%total impervious surface and 15%new pervious surface
• on a single parcel site zoned as RA or F,or on a single or multiple parcel site zoned as A,AND all
4 impervious surface azea,except 10,000 square feet of it,will be set back from its natural tocation of
discbarge from the site at least 100 feet for every 10,000 square feet of total impervious area.
Note:for the purposes applving this threshold to a proposed single family residential subdivisio»(i.e.,plat
or shorl plat project), the impervious surjace coverage assumed on each created lot shall be 4,000 square
. feet(8,OD0 square feet if the site is zoned as R�4)or the maximum allowed by KCC 21A.12.030, whichever
° is less. A lower impervrous sur}'ace coverage may be assumed for any lot in which the lower impervious
surface coverage is set as the maximum through a declaration of covenant recorded for the lot. Atso, the
', new pervious surface assumed on each created lot shall be the entire lot area, except the assumed
' impervious portion arrd any portron in which native conditions are preserved by a clearing limit per KCC
16.82, a covenant or easernent recorded for the lot, or a tract dedicated by the proposed subdivtsion.
Scope of Requirements
� ff Small Project Drainage Review is required,THEN the proposed project must comply with the
� simpli$ed small project submittal and drainage design requirements detaiied in Small Project Drainuge
Requirements adopted as Appendix C to this manual and available as a separate booklet from DNRP or
r DDES. These requirements inciude simplified B?�4Ps.measures for flo���controt and erosion and sediment
control.
- ` t3 The ihresholds of 2,000, 10,000,35,000,and 70,000 square Seet of impervious or pervious surface shafl be applied b.
lhreshold discharge area and in accordance with tfie definitions of these surfaces in Section 1.1.
"'OO� �urte:c R';iter b��i_e'�1�nua�
SECTION :.1 DRr1I'�IAGE REVIEI�'
Presumption of Compiiance with Core and Speciaf Requirements
The simplified drainage requirements applied under Small Project Drainage Review are considered
sufficient to meet the overall intent of the core and special requirements in Sections 1.2 and 1.3, except
under certain conditions when a proposed project has characteristics that trigger Targeted Drainage
Review(see the threshold for Targeted Drainage Review in Section 1.I.2.2,p. 1-14)and may require the
involvement of a civil engineer. Therefore,any proposed project that is subject to Small Project Drainage
Review as deternvned above and complies with the small project drainage requirements detailed in Appendix
C is presumed to comply with all the core and special requirements in Sections 1.2 and 1.3 exeept those
requirements that would apply to the project if it is subject to Targeted Drainage Review as specified in
Sec;tion 1.1.2.2(p. 1-14).
1.1.2.2 TARGETED DRAINAGE REVIEW
Targeted Drainage Review(TDR)is an abbreviated evaluation by DDES permit review staff of a proposed
project's compliance with selected core and special requirements. Projects subject to this type of drainage
review are typically Small Project Drainage Review proposals or o[l�er small projects that have site-specific
or project-specific drainage concerns that must be addressed by a civil engineer or DDES engineering
review staff. Under Targeted Drainage Review,engineering costs associated with drainage design and
review are kept to a minimum because the review includes only those requirements that would apply to the
particular project.
Threshold
Targeted Drainage Review is required for any proposed project that is subject to drainage review as
determined in Section 1.1.2 (p. 1-9)but is not subject to Full or Large Project Drainage Review as
determined in Sections 1.1.2.3(p. 1-16)and 1.12.4(p. 1-17), AND that has the characteristics of one or
more of the following project categories:
T • TDR Project Category#1:Projects that contain or are adjacent to a jtood hazard area,erosion
M haZard area,or steep slope hazard area as defined in KCC 21A.06;OR projects located within a
� Critical Drainage Area or Landslide Hazard Drainage Area; OR projects that propose 7,000 square
o feet(3 acres if in Small Project Drainage Review)or more of land duturbing activity. Note: ar rhe
; discretion of DDES, this category may also include arry project in Smald Project Drainage Review that
0
has a design or sile-specific issue that must be addressed by a civi!engineer.
• TDR PrOjeCt Category#2:Projects that propose to construct or modify a drainage pipe/ditch that
is 12 inches or more in size/depth or receives surface and storm water runoff from a drainage
� pipeJditch that is 12 inches or more in size/depth.
• TDR Project Category#3:Redevelopment projects that propose S l 00,Q00 or more of
improvements to an existing high-use site.
Scope of Requirements
IF Targeted Drainage Review is required,THEN the applicani must demonstrate that the proposed project
# complies with the selected core and special requirements conesponding to the project category or
categories that best match the proposed project. The project categories and applicable requirements for
� each aze described below and summarized in Table 1.1.2.A(p. i-12},
=; Note:If the proposed project has the characteristics of more than one project category, the requirements
of each applieable category shall apply.
Compliance witt�these requiremenEs requires the submittal of engineering plans and calculations stamped
by a civit engineer,unless deemed unnecessary by DDES. The engineer need onty demonstrate
compliance with those core and special requirements that have been predetermined to be applicable based
on specific project characteristics as detailed below and summarized in Table 1.1.2.A(p. 1-12). The
�;�q;2pp5 2005 Surface Water Design Manual
1-14
�.
SECTiOt� 1.1 DRr1TNAGE REVTEW
_
TABI,E.I«I.2.A REQUi "�iENT5 AI'PLIED UNDER EACH DRAINAGE REVIEW TYPE
Small Project Targeted Full Large Project
Drainage Drainage Drainage Drainage _
Review Review Review Review
Single family Projects that are not subject to Full or All projects that UPDs,OR
residential Large Project Drainage Review,AND result in 2,000 projects that
projects and have characteristics of one or more sf of new result in>_50
agricultura! of the following categories of projects: impervious or acres of new
projects that 1. Projects containing or adjacent to a >_35,000 sf of impervious
result in>_2,000 flood, erosion,or steep slope new pervious within a sub-
sf of new harard area; projects within a surface, but are basin or mu!-
impervious Critical Drairtage A�ea or Landslide not subject to Gple subba-
surface but do Hazard Drainage Area;or projects Small Project sins that are
not exceed the proposing>_7,004 sf of land Drainage hydraulically
total impervious disturbing activity(3 ac if in SmaU Review, OR connected,
surface and Project Drainage Review). redevelopment OR project
new perviaus 2. Projects that construct or modify projects meet- sites>_50
surface a drainage pipe/ditch that is 12"or ing drainage acres within a
thresholds targer or ceceive runoff from a 12" review threshold critical aqui-
specified in or larger drainage pipelditch. #7 in Section fer recharge
Section 1.1.2.1 3.Redev.projects with>_$100,000 in 1.1.1 (p. 1-9). area.
(p. 1-13}. improvements to a high-use siie�'�
Category Category Category
1 2 3
SMALL PROJECT DRAIPtAGE ✓
REQUIREMENTS
CORE REQUIREMENT#1 *Iz) ,
Discharge at Natural Location � � � 'i
CORE REQUIREMENT#2 *(2) ✓lay ✓(s� ✓{s> '
Offsite Analysis
CORE REQUIREMENT#3 *(2) ✓(3) ✓�s� �_ ,
Fiow Control
CORE REQUIREMENT#4 �(2) ✓ ✓ ✓
Conveyance System
CORE REQUIREMENT#5 ✓ ✓ ✓ ✓ �
Erosion&Sedimeni Control
CORE REQUIREMENT#6 *(2) � � � �
Maintenance 8 Operations
CORE REQUIREMENT#7 *(2) ✓(3) ✓(3> ✓{al ✓(3)
Financial Guarantees&Liability
CORE REQUIREMENT�8 Water *12) �C�1 �(3>
Quality
SPECIAL REQUIREMENT#1 ✓(s) ✓(31 ✓(3)
Other Adopted Requirements
SPECIAL REQUIREMENT#2 ✓(�) �(31 �(3)
Fiood Hazard Area Defineation
SPECIAL REQUIREMENT#3 �(3} ✓(3f ✓(3)
Flood Protection Facilities
SPECIAL RE�UIREMENT�i4 ✓(3) ✓(3> ✓(3) �(3) ✓(a)
Source Control
SPECIAL REQUIREMENT#5 ✓(3) ✓�31 ✓t3)
Oil Control
��� Category 3 projects installing oil controls that construct or modify a 12-inch pipe/ditch are also Category 2 projects.
�2} May be applied by DDES based on project or site-specific conditions.
�3� These recui�ements have exemptians or thresholds that may preclude or limit their application to a specific project.
Fields Town Homes
Design
Buildings Proposed Storm Water Propose�d
Treatrnent number
West Building 3100 sq. feet Dry-wel/ 1 per 1000 sq, f� 3
East Building 4880 sq. feet Dry-we// 5
Road
Access Road 7880 sq. feet Infi/tralion Trench 240 f�et
30/in. Feet per 1000 sq, fie+et
Appendix B
Technical Information Worksheet
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City of Renton
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND
PROJECT ENGINEER DESCRIPTION
Project Owner: Timberstone Homes,Inc. Project Name: Fields Town Homes
Address: 46533—284�'Ave. SE
Enumclaw,WA 98022 Location
Phone: (253) 632-9159 attn: 7im Pitrer Township: 23 North
Project Engineer: Darrell Offe, P.E. Range: 5 East
Company: Offe Engineers, PLLC Section: 10
Address/Phone: 13932 SE 159th Plaoe
Renton,WA 98058-7832
425 260-3412
Part 3 TYPE OF PERMIT Part 4 OTHER REVIEWS AND PERMITS
APPLICATION
� Subdivision ❑ DFW HPA � Shoreline Management
❑ Short Subdivision ❑ COE 404 ❑ Rockery
❑ Grading ❑ DOE Dam Safety ❑ Structural Vaults ,
❑ Comme ial • ❑ FEMA Floodplain ❑ Other II
� Other � ❑ COE Wetlands
Part 5 SITE COMMUNITY AND DRAINAGE BASIN
Community
North Renbon
Draina e Basin I
9
Maplewood Creek/ Cedar River/ Lake Washingbon
Part 6 SITE CHARACTERISTICS
❑ River L� Floodplain
❑ Wetlands
❑ Stream
❑ Seeps/Springs
� Critical Stream Reach
❑ High Groundwater Table
❑ Depressions/S1�vales � Groundwater Recharge
❑ Lake '`', Other
❑ Steep Slopes
Part 7 SOILS
Soil Type Slopes Erosion Potential Erosive Velcoties
Reoessional Outwash 0 - 10% No
❑ Additional Sheets Attached
Part 8 DEVELOPMENT LIMITATIONS
REFERENCE LIMITATION/SITE CONSTRAINT
❑ Ch. 4—Downstream Analysis
❑
❑
❑
❑
❑
❑ Additional Sheets Attached
Part 9 ESC REQUIREMENTS
MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION AFTER CONSTRUCTION
❑ Sedimentation Facilities ❑ Stabilize Exposed Surface
� Stabilized Construction Entrance ❑ Remove and Restore Temporary ESC Facilities
❑ Perimeter Runoff Control ❑ Clean and Remove All Silt and Debris I
❑ Clearing and Grading Restrictions ❑ Ensure Operation of Permanent Facilities
❑ Cover Practices ❑ Flag Limits of SAO and open space
Construction Sequence preservation areas I
❑ Other ❑ Other
Part 10 SURFACE WATER SYSTEM
❑ Grass Lined ❑ Tank � Infiltration Method of Analysis
Channel ❑ Vault ❑ Depression ��
❑ Pipe System Compensation/Mitigati
❑ Energy Dissapator ❑ Flow Dispersal on of Eliminated Site
❑ Open Channel � wetland ❑ Waiver Storage
❑ Dry Pond ❑ Stream ❑ Regional �1�
❑ Wet Pond Detention
Brief Description of System Operation: Catch basins within access road discharging into
infiltration trend� under the road. The homes and driveways will discharge into dry
wells located on the individual lots.
Facility Related Site Limitations
Reference Facility Limitation
Part 11 STRUCTURAL ANALYSIS Part 12 EASEMENTS/TRACTS
❑ Cast in Place Vault ❑ Drainage Easement
❑ Retaining Wall ]�Access Easement
❑ Rockery>4' High �� Native Growth Protection Easement
� Structural on Steep Slope ❑ Tract
'�� Other ❑ Other
Part 13 SIGNATURE OF PROFESSIONAL ENGINEER
I or a civil engineer under my supervision has visited the site. Actual site conditions as observed
were incorporated into this worksheet and the attachments. To the best of my knowledge the
information provided here is accurate.
/ 2 � z� 2��
S' ned/Date
Appendix C
Geotechnical Report
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c:\offe engineers�projects\davis group�fields project\level one\tir\storm report.doc �I
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i _ I
Geotechnical Engineering Report
Field Properh•
Renton, ��'ashington
For
Pitzer Homes, Inc.
Cornerstone "e25-'3U- F+ve NE. C102. Woodinviile `J'JA 98072
, Phone: 425-844-1977
Geotechnical� (n�i. Fax: 425-844-1987
Noti'ember 3, 200�
Mr.James M. Pitzer.Jr.
Pitzer Homes, Inc.
�6533 -284`h Avenue SE
Enumcla«, Washineton 980�2
Geotechnical En�ineering Report
Fields Property �
Renton. W'ashinaton
CG File No. 1986
Dear Mr. Pitzer:
I�ITRODL'CTIO`
This report presents the results of our geotechnical en�ineering in�estigation at the proposed four-lot
residential project in Renton, Washington. The site is located at �08 and 51? Union A��enue NE, as
sho��n on the Viciniry �tap in Figure l.
You ha��e requested that we complete this report to e��aluate subsurface conditions and provide
recommendations for site derelopment. For our use in preparing this report, we have been provided �ith
an undated, untitled site plan that sho�tis the proposed locations of the access road, building lots and
eristing strucmres and underground utilities. You have requested that He e��aluate the subsurface soil and
ground ��ater conditions and pro��ide recommendation for de�elopment, including our opinion re�arding
the feasibility of do«nspout storm ��ater infiltration at the site. ,
PROJECT DESCRIPTION
The rectangular-shaped project site consists of a total of four planned sinele-famil�� residences, and a
small access road, as sho�tn in the Site Plan, Figure 2. V4'e ha��e not been pro��ided �ti�ith a gradina plan,
but ��e understand that site grading will include minor cuts and fills. W'e understand that ihe current plan
is to infiltrate storm�tiater from the planned rooftop downspouts. '
_��:�chn��al EnLin�crin��R�purt
�ids Property
'� ��ember 3, 200�
�� � r File No. 1986
. ��•e 2
`C�OPE
i :�.� purpose of this study is to explore and charactenze the subsurface conditions and present
-�.:ommendations for site development. Specifically, our scope of ser�-ices as outlined in our Services
0`_reement,dated September 23.200�,includes the following:
.. Review available geologic maps and existing reports of the area.
�. Explore the subsurface conditions at the site w•ith backhce-excavated test pits.
Provide recommendations for building foundations.
'. Pro��ide recommendations for site preparation and grading.
� Pro�ide general recommendations for site drainage.
f?. I'�- '��..� � ��.�-..._ � ��\,?' _�, .:,,�...._�C. .; _.. �'_ .�... �cl,l. ...�.u ...i ... ..'�i�,....�.�*._
S[TE CO\DITIO\S
Surface Conditions
t he project site is approximately 0.50 acres in size and has maximum dimensions of appro�cimately 230
f�et in the east-w�est direction and 100 feet in the north-south direction. Access to the site is pro��ided by �
t�nion Avenue Iv'E, �t•hich runs along the w•estem edge of the site. Multi-family condominiums and
���rtment complexes border the north, west and east property lines. A proposed layout of the project site i
�� . _� �: _ n'..... _ . . . � I
. ,._ _. , ... �. .. ,�, .. _ �.. � . �� ._ �� , .. .. . . . . _.
� � site. A rockery exists along the w�est boundary south of the ex�st�ng driti-e��ay and is covered in
','sckberry bushes. A retaining w�all exists along the southern property line with the project site seated ��
�.:�proximately 4 to 5 feet below the neighboring property. An existing one-story residence eYists �vithin
?'�e site with associated sheds. The site is primarily vegetated�+-ith a manicured law�n,a garden. and a few
, _� ��.iduo�_: ?ree<.
(;eolog�
�Iost of the Puget Sound Region was affected by past intrusion of continental glaciation. The last period I
of elaciation,the Vashon Stade of the Fraser Glaciation, ended approximately l 1,000 years ago. :�4any of '',
the geomorphic features seen today are a result of scouring and o�•erridmg by glacial ice. During the
Vashon Stade, much of the Puget Sound region was o�-erridden by o�•er 3,000 feet of ice. Soil layers
o��erridden by the ice sheet��ere compacted to a much greater extent than those that were not.
Cornerstone Geotechnical, Inc. I
, .
G�utr�i�ni�al �.n��nr�nn� R�purt
Fields Propert}�
No��ember 3, 200�
CG File No. 1986
Page 3
The geologic unit mapped for this area is shown on the Geologic Map of ihe Renton Ouadrangle, King
County. Washin�ton, by D.R. Mullineaux(USGS 1965). The site is shown to be underlain by glacial till
with recessional outvvash mapped nearby. Glacial till consists of an assortment of sand, silt and gravel
deposited at the leading edge of the advancing glacier. Our site expiorations encountered material that we
have characterized as recessionai outwash. Recessional outwash is the sediment deposited by meltw•ater
streams from the retreating glacier. This sediment rypically consists of sand and gravel, but may contain
layers of silt or clay.
E�plorations
Subsurface conditions were explored at the site on October 2�, 2005, by exca�•ating a total of four test
pits. The test pits were excavated to depths of 7.3 to 8.9 feet below the ground surface. The explorations
were located in the field by an engineer from this firm w�ho also examined the soils and geologic
conditions encountered, and maintained logs of the test pits. The approximate locations of the
explorations are show�n on the Site Plan in Figure 2. The soils w�ere ��isually classified :-, =.r.er.�'
...,��'�'.. .� •._ '. . ? .,..-;�`. � ., ... , �• .. '. .. . � . ,. _ _ ... ._. .. ? : _ .
tiubsurfacc C ondi[ion�
A brief description of thr �uns�n��n� en��untrrr� ;n uur C�piurauun� i� in�iu�ir� ��.i�»�. f-ur a inur�
detailed description of the soils encountered. re��iew the test pit logs in Figures 4 and 5.
Test pits encountered a surficial layer of topsoil approximately 0.5 feet in depth within the site. Below i
the to soil w�e encountered fill material in Test Pit 1 hr h .�
p s t oug 3 from 0 to 1.9 feet in depth. F�ll matenal
ranged from loose to medium dense silry fine to medium sand with gra�•el and roots to fine to medium
sand �•ith gra��el and organics. Buned topsoil was encountered in Test Pits 1 through 3 at depths ranging
from 1.2 to 2.1 feet below surface ele��ation. Below�the fill and topsoil in Test Pits 1 through 3, medium
dense brown silty fine to med�um sand w�as encountered at 1.7 to 4.2 feet in depth. From depths ranging
. from 3.9 to the bottom of the Test Pits 1 through 3 at 7.3 to 8.9 feet, medium dense to dense fine to coarse
sand w-ith gra��el �4�as encountered. We have interpreted this soil to be recessional ouhvash. Within Test
P�t 4, medium dense fine to medium gra�•el w�ith fine to medium sand w�as obser�•ed from 0.2 to 2.0 feet
and dense fine to coarse sand�-ith gra�•el was obsen•ed from ?.0 to the bottom of the test pit at 7.6 feet in
depth,also interpreted as recessional out�a•ash.
Cornerstone GeotechnicaL Inc
�•.. .. ,. . . -.. .. - ' ,n;�
�_l�� �.�-�.u��...i }_ ` :l.l:�: _ �k:
Fields Property ^
No��ember 3. 2005
CG File No. 1986
Page�
H��drologic Conditions
Ground ��•ater seepage ���as not encountered in our test pit explorations, nor w�as there any indication that
significant w•ater exists. The underl}�ing ouht•ash is considered���ell draining. Additional studies could be
done if it is important to verify the depth to the groundw�ater table. How�ecer, we expect the ground water
table to be deeper than our explorations.
GEOLOGIC H aZARDS
Landslide Hazards
The subject site is underlain by dense glacial soils at shallo�v depths. These materials rypically exhibit
�-ery high shear strength and ha��e a high resistance to slope failure. The terrain „-ithin the site is
eenerall�� tlat, po�in� l�ttle n�k of slope failure.
Erosion Hazard
The erosion hazard criteria used for determination of affected areas include soil type, slope gradient,
�c�zetation co��er, and ground water conditions. The erosion potential is related to vegetative co�-er and
*he specific surface soil tr�pes (group classification), which are related to the underlyine geologic units.
C)�er the majoriry of the site, ���e consider the erosion hazard to be slight �vith �•egetati�-e co�-er in place ,
and moderate when stripped of vegetation. Best management practices (B�4Ps) and applicable codes
should be followed during site grading to limit potential for erosion. �'�'e do not expect this site w�ill
require unusual or extreme erosion management methods. There are no���ater bodies adjacent to the site.
Seismic Hazard
It is our opinion, based on our subsurface erplorations, that the Soil Protile in accordance ���ith Table
161�.1.1 of the 2003 International Building Code (IBC) is Soil Class D. V4'e referenced the 2002 map �
from the US Geological Sun-ey (USGS) „�ebsite to obtain �•alues for S, and S,. The USGS website
includes the most updated published data on seismic conditions. The seismic design parameters are:
SS 139.97"o g
S� �7.70°o g
F, 1.0 From Table 1615.1.2(1)of the 2003 IBC
F., 1.32 From Table 161�.1.?(2)of the 2003 IBC
Cornerstone Geotechnical, Inc.
G�uterl�ri,:a� f,n_�in��r�n�Rrp.�rt
Fields Property
November 3, 2005
� CG File No. 1986
Page 5
Site specific ccefficients and adjusted maximum considered earthquake spectrai response acceleration
parameters apply as show�n in Section 1615.1 of the IBC.
Additional seismic considerations include liquefaction potential and amplification of ground motions by
soft soil deposits. The liquefaction potential is highest for loose sand with a high ground w�ater table. The
underlying medium dense to dense sandy soil is considered to have a lo�v potential for liquefaction and
amplification of��ound motion.
CO`CLl-SIOtiS .a\D RECO�i�IE\D.aTlO`S
General
It is our opinion thai the site is compatible w�ith the pianned de�•elopment. The underlying medium dense
to dense, native soils are capable of supporting the planned structures and pavements. We recommend
:hat the foundations for the s�-uctures extend through any topsoil, fill, loose, or disturbed soils, and bear
��:, [[,. �.;�:�.' ,'C:.,..�._ ��n�� ..� �?�n. �. .�:.i�i�: <,,;;,. ,,- t?.. ...._.....:, ..'1 ��'.�..�. .�� �.lc�� .,_�.._
H:.�Cu Uil �}1C SL,�;L1;1�i .��, u::!i+'.. ��h... ,�.: ��:.�:1� ��ii.` �\��l��r:._1��;:�. ;i ._ Va� ��^';,;U,l .,.,.. ,11: ���li� ... ,��
���e appear to be feasible for the infil�ation of storm�ti�ater. How�ever, the placement of a large or deep
;r.nitration system may be timited by a high wintertime ground water table. Ground �vater levels would
ha��e to be evaluated through a wet season to confirm this. Howe��er, it is our opinion that roof
downspout infiltration through shallow-trenches or dry�.�ells is feasible.
Site Preparations and Grading �
The first step of site preparation should be to strip the ��egetation, topsoil. fill or loose soils to erpose
medium dense to �•ery dense native soils in pa�•ement and building areas. This material shoutd be �
remo�•ed from the site, or stockpiled for later use as landscaping fill. The resulting subgrade should be
compacted to a firm, non-yielding condition. Areas obsen�ed to pump or ���ea�•e should be repaired prior '
to placing hard surfaces.
The glacial outwash is considered somewhat moisture sensiti��e. We erpect these soils �ti�ould be more
di�cuh to compact to structural fill specifications in wet weather. We recommend that earthwork be
conducted during the drier months. Additional expenses of���et w�eather or winter construction �ti�ould
include extra excavation and use of imported fill or rock spalls. During wet weather, alternative site
preparation methods may be necessary. These methods may include utilizing a smooth-bucket trackhce
Cornerstone Geotechnical, Inc.
�C��Ic'��1Tli�d� f,Il�iI:�CI i[1L ���l��ft
Fields Property
November 3,2005
CG File No. 1986
Page 6
to complete site stripping and di��erting construction traffic around prepared subgrades. Disturbance to
the prepared subgrade may be minimized b}�placing a blanket of rock spalls or imported sand and gra�-e1
in traffic and road�vay areas. Cutoff drains or ditches can also be helpful in reducing grading costs during
the wet season. These methods can be evaluated at the time of construction.
Structural Fill
General: All fill placed beneath buildings, pa��ements or other settlement sensiti�-e features should be
placed as structural fill. Structural fill,by definition, is placed in accordance v��ith prescribed methods and
standards, and is monitored by an experienced geotechnical professional or soils technician. Field-
monitonng procedures w•ould include the performance of a representati�•e number of in-place density tests
to document the attainment of the desired degree of relati�•e compaction.
�taterials: Imported structural fill should consist of a good quality, free-draining granular soil, free of
organics and other deleterious material, and be w�ell graded to a maximum size of about 3 inches.
Imported, all-��•eather structural fill should contain no more than � percent fines(soil finer than a Standard
U.S.No. 200 sieve),based on that fraction passing the U.S. 3'4-inch sieve.
The use of on-site soil as structural fill�•ill be dependent on moisture content controi. Some drying of the �
native soils may be necessary in order to achieve compaction. During w�arm, sunny days this could be
accomplished by spreading the material in thin lifts and compacting. Some aeration and/or addition of
moisture may also be necessary. We expect that compaction of the nati.-e soils to structural fill
specifications�a�ould be difficult during���et weaiher. �
Fill Placement: Follo�ving subgrade preparation. placement of the structural fill may proceed. Fill
should be placed in 8- to 10-inch-thick uniform lifts, and each lift should be spread e��enly and be
thoroughly compacted prior to placement of subsequent lifts. .All structural fill underlying building areas,
and within a depth of 2 feet below pavement and side�valk subgrade, should be compacted to at least 95
percent of its maximum dry density. Marimum dry density, in this report, refers to that density as i
determined by the ASTM D 1557 compaction test procedure. Fill more than 2 feet beneath s�dewalks and
pa�-ement subgrades should be compacted to at least 90 percent of the maximum dry density. The
moisture content of the soil to be compacted should be within about 2 percent of optimum so that a
readily compactable condition exists. It may be necessan� co o�cr��ca�atc an� remu�e ��et >:.rti�ial �u�l�
Cornerstone Geeterhrica! !nc
li�. .._..,.�.�. � _ _ _ ' _
Fields Propem
November 3. ��
CG F�t; �t, 1�,�
Pa��: -
�I�ernpurar�� and Permanrnt Slopr�
Temporary cut slope stability is a func:;un �>: <n,:t��. ��:,:«�:_. ,u�:. ... ,.:� :.N� ,:r�� ,��r,_,...:r�_ ��; ,���
depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and ti:�
presence of surface or ground w�ater. It is exceedingly difficult under these��ariable conditions to estima�.�
a stable temporary cut slope geometn�. Therefore, it should be the responsibility of the contractor ��
maintain safe slope configurations, since the contractor is continuously at the job site, able to obser�e t}�:�
nature and condition of the cut cl�pe�. and able t� m�nitor the �uhcurface material� and �-
conditions encountere.
�Ve anticipate tempora;z .u?, :�,r :n,ts�..:�:ur. ��: u:�ii.��,. t ��r p;a.:;:::;; pu�����,.,. t.� ���«;;:m�::� �:
temporary cuts in the fill or nati��e soils be no greater than 1 S Horizontal to 1 Vertical (I.�FI '�.
slopes w��th plastic sheeting and d���erting surface runotf away from the top of cut slopes. ��'e do r
recommend ��ertical slopes for cuts deeper than 4 feet, if�t�orker access is nece�
cut slope heights and inclinations conform to local and�VISHA!OSHA standar.
Final slope inclinations for structural fill and the cuts in the nati�-e soils should � . �.; :_ ..... . _,.
Lightly compacted fills or common fills should be no steeper than 3H:1`'. Common fills are defined .
6ll material w�ith some oreanics that are "trackrolled" into place. They �could not meet the compact:�
specification of structural fill. Final slopes should be t:
Con��ent�onal, shallow� spread foundations should be founded on undisturbed, medium dense or better,
native soils, or be supported on structural fill extending to those soils. If the soil at the planned bottom of
footing elevation is not medium dense to ��ery dense, it should be overexca�-ated to expose suitable
bearing soil, and the excavation should be filled with structural fill, or the footing may be overpoured
with extra concrete.
Cornerstone Geotechnical, Inc.
� Fields Property
No�•ember 3. �'
CG �� �� �
P�-
protection and beanng capacity considerations. International Building Code (IBC) guidelines �
minimum foundation widths should be followed for both continuous and isolated spread footing>.
Standing water should not be allowed to accumulate in footing trenches. Al( loosc or di�turhed ;c��'
should be removed from the foundation exca�-ation prior to placing concrete.
For foundations constructed as outlined abo�•e, v��e recommend an allowable desi�n beanne pressure u:
2,000 pounds per square foot (ps fl be used for the footing design. An increase of one-third is allo��e�
���hen using the alternate load combinat�on in Section 1601.3.2 of the �C that includes .�-ind ���
earthquake loads. Potential foundation settlement using the recommended allowable bearing pressure ;�
estimated to be less than 1-inch total and 'ii-inch differential betw•een footings or across a distance ��;�
about 30 feet. Higher soil bearing �•alues may be appropriate for footings founded on the unw•eathere�
oui«��h. an� «;ih ��t�3er !n���ire� The>e hi<�her �a!:te� c,n he de'ern1�•,�u a''er a .*et te�t ,�.' z ,;�ec:t:,
'� =t'
1__..,..�. :�l�u� �:.": ��. .'�> ..:' �:� .i.�'.:li.,. `'�?'�,�:.. .,. . .i��..:u.;::��;1 :1�'.. . ..�_ ._.i� �.r:. ..':�. "�_ i`.. . . . .���.
resistance acting on the below-grade portion of the foundation. For the latter, the foundation must t��
poured "neat" against undisturbed soil or backtilled with clean, free-draining, compacted structural fi::.
Passive resistance may be calculated as a triangular equivalent fluid pressure distnbution. �t :
recommend that an equi��alent fluid density of 225 pounds per cubic foot (pc� be used to calculate th_
allowable lateral passive resistance for the case of a le��el ground surface adjacent to the footing. :�•�
alio�vable ccefficient of friction between footings and soil of 0.40 may be used, and should be applied '��
the �•ertical dead load only. A factor of safery of 2.0 has been applied to the passi�•e pressure to accou, •
fOi Tc'qlttrc�� ^'����RltP,r; ti� �_L-,`.�rL .1,C•c pr.::�_:rc'� Tt`� 4f?C'lnp �ri�l};�;`T„ a�i�: rtit 1.^..�,..�� �? fCi�'n• ,
S8 t c''
Slabs-On-Grad�
Slab-on-grade ar� _ _ �,,. F', .}� .:;: �, :;,�;. . ;t..., _
subsection. Slabs should be supported on medium dense to ��ery• dense nati.•e soils, or on structural �
extending to these soils. 1H'here moisture control is a concem,we recommend that slabs be underlain b�,
inches of free-draining coarse sand or pea gra��e) for use as a capillar. '� , -
G�utc:�h�u�al En�in��nn� K���urt
F�elds Property
No�•ember 3. '0�1�
CG File'`o. 19�6
Pa�_ ��
I)rain:�,r
«'e re��,:;,., _ � :..... .... � .. ..,�: . ....t... .. .. ........ . ..... �. ..���. . ...... . ...... .._.._ :�;�.. _ . .
collected and routed to an appropriate storm water discharge system, described below. Final site grad�
should allow� for drainage aw�ay from any buildings. We suggest that the finished ground surface i�_
sloped at a gradient of 3 percent minimum for a distance of at least 10 feet a��•ay from the buildings. ��
indicated in IBC Section 1803.3. Surface watc- :'� ' : ,� :. "�_ ..: _ ��-... . � ... � - . - . .. .. _
� . .._ ... .._.._ ..._. . . . �...... . .. .�- -- . ,...�: _.: , : :.._ ...._ �.. .,.._.. :.., .�.,.._ .. ....
important. It is good practice to use footing drains installed at least 1 foot belo�t� the planned finishe�'.
floor slab or craw•1 space ele��ation to pro�lde drainage for the craw�l space. At a minimum, the cra��:
space should be sloped to drain to an outlet tied to the drainage system. If drains are omitted around slat�-
on-grade floors \1�;.'� . i�; ._.�. �1�.,.���1 . � �i ,i�.. �i,: �t3t` .}':t�i:�� �� .. ... ... . .. .. i�` t ���ii', ;l'�u'.c
,!'Tc�!;.'�:^ ..�.
'.� „�1. .. � .. .��,�,i. _ ,.,..,.. ::1�, �: �i�t: ,.. ��; -i:,.,;-�l;:i::'C;... t.,iu'..:t�: E'\ C },;fi� ,..... . . ._i;i�..,;�;C�1 f�,,
free-draining material, such as pea gra�•el. Footing drains should discharge into tightlines leading to a:�
appropriate collection and discharge point. Craw•1 spaces should be sloped to drain, and a posit��:
connection should be made into the foundation drainage system. For slabs-on-grade. a drainage pa�;;
should be provided from the capillan hr�ak mat�r�al t�� the ti��r.n�_ �iram ���tcm. Rc�of��rain� :holil�3 n��t
hC �i�I?il�:?�(� Tl� ���a�� (�r it���t!?l�� �r31;1�.
L't1�itICS
Our exE�luranon; in�ii�ate thst ��e::�tic �i�ep ci���at�nn�, ��ill not h� nrcc�e�l to in>tall utii�t�e�. :�nti�ipat«?
ground ���ater is expected to be handled with pumps in the trenches. We also expect that some groun�
�ti�ater seepage may de��elop during and follo«-ing the�ti�etter time� of the ��car. ���e c�p�ct th�� ,ec�a��� ���
t�1���t1� u���.0 he?���� th� u�utc-:ahle ��t,hin th< <�u?«a�h �ic�+��,ii.
Pa��ement
The performance ut rua�3��a� pa��mrnt �� �nti�ail� ;�latr�i tu thr �un�iition� of th� un��rl��n� �ub�ra��
We recommend that the subgrade soils �-ithin the roadH�ays be treated and prepared as described in t:
Site Preparation and Grading subsection of this report. Prior to placing base material, the subgra. .
,., _ , _ _ . . , , �.__ , .. _ .- . � . _ _ _ - . . • .- - ., , -„� _
Cornerstone =__ _- -
�l«�I��tiiliti3! �il� :'.CC:; _ }Z�}�Ut�I
F�elds Property
No��ember 3, ?00�
CG File tio. 1986
Page 10
�vith a piece of hea�y construction equ�pment, such as a fully-loaded dump truck. Any areas ���ith
excessi�e ���eaving or flexing should be o�•erexcavated and recompacted or replaced with a structurai fill
or crushed rock placed and compacted in accordance w-ith recommendations pro��ided in the Structural
Fill subsection of this report.
Iafiltration
V4'e encountered soils in our explorations that meet the description of soi(s suitable for infiltration as
described by the King County manual. Conditions appear to be suitable to meet the requirement for
infiltration using a dryv��ell or trench as defined in the King Counry manual. The lots are smaller than
22,000 square feet w�ith soils that are well suited for downspout infiltration. It is our interpretation that
do�vnspout infiltration should be used for the proposed residences.
Use of do��nspout infiltration in the manual (sections 5.1.1 and C.2.3) includes dryv�•ells, or infiltrat�
trenches w�ith a length dependent upon the square footage of the roof. Based on our explorations, �
recommend that the proposed infiltration system extend th-
Design Manual. An infiltration trench designed as described in Section C.2.3.2 in the King Cour
manual may also be used. If used, the length of these trenches, based on the specification for "medi�_.
sand" outlined in the K�r . r. ,..�.. _,. :. ,..� : �, -. . ....__:.__. _ _, - ' � � ,-„- ,
._. ., , •-- . ._ _ ..,.
� ; , 1� � t:i i � �c; . �i.�:; i� ;
,
�e s oul e retaine to provi e u:;,::,s,:��r, ..::.: .�>i:,:..:.:,,��n ,�;;:�" u..:�r.� ���;;,,�..�::�,:: ;v �un;.,
that the conditions encountered aze consistent with those indicated by the explorations, and to pro��,
recommendations for design changes, should the conditions revealed during the �•ork differ from th��
anticipated. As part of our sen-ices, �e «�ould also e��aluate ��_
in�t�ilati�n acti��itiec c�mn1�-��ith c�ntract nlan� and ��ecificah�-
Cornerstone �.._ =_�- _ ��
Fields Property
November 3, 200�
CG Fil� '�- � ��
n,�,., �
.� t YI i ±�i� i< i I'( �f1 �
V�'e ha�•e prepared this repor. , _ _ _ _-- , _ . . _
project. The data and report should be pro��ided to prospective contractors for their bidding a
estimating purposes. !�_. . .. .. ., _. . _. ., . ,--< ._ : __. _.,_ .__.. .__ ,. � : _. . �._ _ --- : ._ _
of subsurface condit�
The scope of our Nuri. �iur� nut �n�iu4c ��r�i�r� r�i:�t�.i tu wn�tru�u�n -_
recommendations are not intended to direct the contractors' methods, techn�ques, sequences
procedures, ercept as specifically described in our report. for consideration in design. There are possi��
��ariations in subsurface eonditions. VVe recommend that project planning include contingencie, �� !��_�.'
and schedule, should areas be found�vith conditions that��ary from those described in this rer
Within the limitations of scope, schedule and budeet for our �t-ork, ��•e have stri��ed to take ��:� .::�:
�vork has been completed in accordance w•ith generally accepted practices follo�ved in thi�
thi:re��n �t�� prepared. \�, �;her.�ndition�. e�pre;�ed �r im}�lied. >h<,t:;d ht urder�to��
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Cornerstone °hore (425)844-1977 Fields Properry
n Fax:(425)844-logi
, Geotechnical� IIIC. FileNumber Figure
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Site Plan
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LEGEND
G 2� 4�
TP-1
� Number and Approximate
Location of Test Pit
Sca�e�' _�C I
Cornerstone P^��e �a25�au���" Fields Property
Geotechnical, Inc. Fa*,sz5,�s-���-
Re`=rence Site Pl�n based on undated unt�t!ed electron�c site plan , Fila Numbsi Fipure
.� _. .u�.E _ _� ,,,_a��,e ,';a,•9n0'� 1986 2
Unified Soil Classification System
MAJOR DIVISIONS GROUP GROUP NAME
SYMBOL
GRAVEL CLEAN GRAVEL GW WELL-GRADED GRAVEL FINE TO COARSE GRAVEL
COARSE-
GRAINED MORE THAN 5096 OF GP POORLY-GRADED GRAVEL
COARSE FRACTION
SOILS RETAINED ON NO.4 GRAVEL '
siEVE WITH FINES GM si�7�r G�vE�
GC CLAYEY GRAVEL '
MORE THAN 50% '
RETAINED ON SAND CLEAN SAND SW y�/ELL-GRADED SAND.FINE TO COARSE SAND
number 200 SIEVE
SP POORLY-GRADED SAND
h10RE THAN 50%OF
COARSE FRACTION SAND '
PASSES NO.4 SIEVE y�TH FINES SM si�'Y sANo ,
SC CLAYEY SAND I
SILTAND CLAY INORGANIC ML SILT
FINE-
GRAINED UQUID LIMIT CL CLAY
LESS THAN 50%
SOILS ORGANIC OL ORGANIC S�LT. ORGANIC CLAY
MORE THAN 50% SILT AND CLAY INORGANIC
PASSES NO.200 SIEV MH SILT OF HIGH PLASTICITY.ELASTIC SILT
LIQUID LIMIT CH CLAY OF HIGH PLASTICITY,FAT CLAY
50%OR MORE
ORGANIC OH ORGANIC CLAY.ORGANIC SILT I�
HIGHLY ORGANIC SOILS pT PEqT �'i
NOTES. � II
SOIL MOISTURE MODIFIERS
1) Field classification is based on Dry-Absence of moisture, dusty, dry
v�sual examination of soil in general to the touch
accordance with ASTM D 2488-83.
2) Soil classification using laboratory Moist-Damp, but no visible water
tests is based on ASTM D 2487-83. Wet-Visible free water or saturated.
3) Descriptions of soil density or usually soil is obtained from
consistency are based on below water table
interpretation of blowcount data.
visual appearance of soils, and/or
test data.
Cornerstone �no�e �;a2F�a�a-�9-- Unified Soil Classification System
� Geotechnical, Inc. Fax:(425)84A-198:
17025-130th Ave NE C-�02 • ti'��ood�nvi!le '�vA. 98C'2 Figure 3
LOG OF EXPLORATION II
DEPTH USC SOiI DESCRIPTION I
TEST PIT ONE I'
0.0-0.5 SM DARK BROWN TO BLACK SILTY FINE SAND WITH ROOTS (LOOSE. MOIST)
(TOPSOIL)
0.5-0.9 SM GRAY SILTY FINE TO MEDIUM SAND WITH GRAVEL AND ROOTS (LOOSE TO
MEDIUM DENSE,MOIST) FI ILL1
0.9-1.2 SM BROWN SILTY FINE TO MEDIUM SAND WITH GRAVEL AND ROOTS (LOOSE TO '
MEDIUM DENSE,MOIST) F( ILII
12-1.7 SM DARK BROWN TO BLACK SILTY FINE SAND WITH ORGANICS (LOOSE, MOISTj
OPSOiI
1.7-4.6 SM BROWN SILTY FINE TO MED�UM SAND WITH GRAVEL AND ROOTS(MEDIUM DENSE,
MOIST)(WEATHERED OUTWASH)
4.6-6.7 SW BROWN FINE TO COARSE SAND WITH GRAVEI (OENSE, MOIST) (RECESSIONAL I
OUTWASH)
6.7-8.6 SP TANISH BROWN FINE SAND WITH TRACE SIIT (MEDIUM DENSE, MOIST)
(RECESSIONAL OU7WASH) I
8.6-8.9 SW BROWN FINE TO COARSE SAND WITH GRAVEL (DENSE, MOIST) (RECESSIONAL
OUTWASH)
SAMPLES WERE COLLECTED A7 0.7, 1.0,2.4,4.9 AND 8.9 FEET
GROUND WATER SEEPAGE WAS NOT ENCOUNTERED
TEST PIT CAVING WAS NOT ENCOUNTERED
TEST PIT WAS COMPLETED AT 8.9 FEET ON 10/24/05
TEST PIT TWO
0.0-0.4 SM DARK BROWN TO BLACK SILTY FINE SAND WITH ROOTS (LOOSE. MOIST)
(TOPSOIL)
0.4-1.1 SP TANISH BROWN FINE SAND WITH ROOTS (LOOSE TO MEDIUM DENSE, MOIST)
F( ILL)
1.1-1.4 SM BROWN SILTY FINE TO MEDIUM SAND WITH GRAVEL AND ORGANICS (LOOSE TO
MEDIUM DENSE,MOIST) F( ILL)
1.4-1.7 SM DARK BROWN TO BLACK SILTY FINE SAND WITH ROOTS (LOOSE, MOIST)
0(T PSOILI
1.7-4.2 SM BROWN SILTY FINE TO MEDIUM SAND WITH GRAVEL AND ROOTS(MEDIUM DENSE,
MOIST)(WEATHERED OUTWASH)
d.2-6.4 SW BRO�VN FINE TO COARSE SAND WITH GRAVEL (MEDIUM DENSE TO DENSE, DRY)
(RECESSIONAL OUTWASH)
6.4-7.8 SP-SM BROWN FINE TO MEDIUM SAND WITH GRAVEL AND SILT (DENSE, MOIST)
(RECESSIONAL OU7WASH)
SAMP�ES WERE COLLECTED AT 0.8, t.8,2.5,4.5 ANO 6.7 FEET
GROUND WATER SEEPAGE WAS NOT ENCOUNTERED
TEST PIT CAVING WAS NOT ENCOUNTERED
TEST PIT WAS COMPIETED AT 7.8 FEET ON 10/24/05
CORNERSTONE GEOTECHNICAL, INC.
FILE NO 1986
FIGURE 4
TEST PIT THK=�
0.0-0.6 Sht DARrC 3nO�.;N 7G is�.Cri Si�T Y F.NE SA�:D `.'�,-r, ROO�j ��OOjc, ��"OiS-
(TOPSOIL)
0_6-1.9 SP BROWN FINE TO MEDIUM SAND WITH GRAVEL AND ROOTS (MEDIUM D�'
� MOIST) Fi ILLI
1.9-2.1 SM DARK BROWN TO BLACK SIITY F
TO MEDIUM DENSE,MOIST)(TOPSC
2.1-3.9 SM UGHT BROWN SILTY FINE TO MEC
DRY)(VYEATHERED OUTWASH)
3.9-7.1 SP BROWN FINE TO MEDIUM SAND(DENSE.MOIST)(RECESSIONAL OUTWASh
7.1-7.3 SW GRAY FINE TO COARSE SAND WITH GRAVEL (DE�.` - --
OUTWASH)
SAMPLES WERE COLLECTED AT 1.2,2.6,4.2 AND 7�
GROUND WATER SEEPAGE WAS NOT ENCOUNTE=
0.0-0.2
��Jv�c,'.?O.;'�(70PSOIL
0.2-2.0 GP BROWN FINE TO MEDIUh"
OUTWASH)
2.0-7.6 SW GRAY FINE TO COARSE SAND WITH GRAVEL (DENSE, MOIST) (RECESSIC
OUTWASH)
SAMPI.ES WERE COLLECTED AT 1.6.2.4,6.4 AND 7.6 FEET
GROUND WATEf2 SEEPAGE WAS NOT ENCOUNTERED
TEST PIT CAVING WAS NOT ENCOUNTERED
TEST PIT WAS COMPLETED AT 7.6 FEET ON 10/24/05
CORNERSTONE GEOTECHNICAL, INC.
FiLE NO 19$6
FIGURE 5
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-- - eo ec �ica n ineerin e or -
, . , ,, . . , ,. . , , , ,. . . , . . , , ,
' I 1 1 1 . I / I I'I I ' / I .f' 1
6eotechnical Services Are PeMormed tor • �evation,configuration,location,orientation,or weight of the
Specific Purposes, Persons, and Projects ����aosed smx�,�e,
� _._� . �, . , - �; ��t�� �, _•� , ___._ �. :�.-�'���s c` • c��position of the design team,or
;r ������e�ts A y u�ac��.n�a�er�,��een�g stu��y��,����aa��c�a�v���i engi- • project ownership.
neer may not fulfill the needs of a construction contractor or even another
civi!engineec Because e�h gqtechniql engineering study is unique,each As a general rule,ahvays inform your geotechnical engineer of project
geotechnical engineering report is unique,prepared solelyfor the client.No changes�ven minor ones—and request an assessmer�of their impad.
� one except you should rely on your geotechnical engineering report without Geotechnrc�l engir�eers cannof accept respons�bility or/iability lor ptoblerns ,
Ifirst conferting with the geotechniql engmeer who prepared�t Arzd no one thaf oaur berause therr repo7s do not consider de�icpments of which i
i —nof even you—sh�ld apply th� �pert f�r a�;y G��pcs �,: .-�t ��rv,ti_ T��
Pyrpnt iho n�p'ri���a�a, rnf+p('!:1.�,���.
� V � SubsuMace Conditions Can Change
� Read the Full Report A�P;;;?Ch�iCc'@��i'1P= "�fapCrt S bdS?� .. .... ...�I'S,`'d:FX 5t�d d'
5..� ...:S,. _., �"15^..�°.,�C,:f'��D?C2JSp:. �S0'�y _ '`i a y?�:?�"'�:,3 ,�?i T2�`'2 c(J�y ��'2s;.�r�r�ed. t7u.�iDf;P:y�''�geotechnica!engineer-
� engineering repert did not read:t all.Do not rely on an execu�ive sumriary. ing repeRwr�ese adeGuacy m�y have been affected by:the passage of
' De^ot read sp!?c'ed e'��°�t;a-�'y time;by man-made events,such as construction on or adjacent to the site;
�r by natural events,such as f:oods,earthquakes,or groundwater fluctua- �
A 6eoteehnical Engineering Report Is Based on ���ns.Always contact the geotechnical engineer before applying tt�e report (
A Unique Set of Project-Specif�c Factors :�deterrnine if it is still reliable.A minor amount of additional testing or '
,���_� � � � _ �_ � __ � �_ � . . . � ��_ � �c? sYe. �'a:- ��a�ys s ccc!�ereve�c r�a;cr cr��Ie�s.
i "5'��'.e�.@�i35;St'I ,y -c S� ���'3�'..J�.Ij� �;.i�'� '::C':i��
dient's goals,object�ves,antl nsk management preferences the gere�. Most 6eoteehnical Findngs Are Protessional
nature of the sVucture involved,its size,and configuration;the locat�^ �� 0(ll�l0I1S
the structure on the site;and other planned or exi�ting site improvemenis 5"e ex�c�,�_� i�entirizs subsura�e ccnd'ti�ns cnly a;inose poirts where
such as a�ess roads,pzrking lots,and underground utilities.Unless the su;,su�ac�;es�s are conduct�d or samples are taken.Geotechnical engi-
geotechnical engineer who conducted the study specifically indicates oth- neers review field and laboratory data antl then appty their professional
;r.ti se,do not rely on a geotechnipl engineering repoR ttiat was: jutlgment to render an opinion about subsurface contlitiorts throughout the
• ^ot prepared for you, site.Actual subsurface conditions may diffe�—sometimes significar�ly—
• not prepared for your project, from those indicated in your report.Retaining the geotechniql engineer
• not prepared for the specific site explored,or who developed your repoR to pravide construction observation is tt�e
• completed before important project changes were made. most effective method of managing the risks associat�with u�anticipated
���- . _^�
Typical changes that can erode the re!iab:lity of an existing geetech��,
1 e�gineering report include those that affect: A R6pOPt's Reeommendations Are Noi Fnal
• the function of the proposed structure,as when it's changed fr�T� C� �. _ re r ., .-?���������� ��_��Te ;'� _ ������ � ;;�.,
parking garage to ar office building,or from a light industrial plant report. Those rec�mmen.datic,as are not finat,cecause geetechnical engi-
' to a refrigerated warehouse, neers develop them principally from judgment and opinion.Geotechnical
'� engin�rs can finalize their recommendations on�y by observing actual
�
� ___ .
subsurface conditions revealed during consiruction. The geatechnical have led to disappointments,ciaims,and dispute�-To heip reduce the risk � �
engineer who develo�d your report cannot assume responsibrlity or of such outcomes,geotechniqi engineers commonly include a variety of i ,
tiability lor tt►e raporYs recommendations if that engir►�er does not perfomr expianatory provisions in their reports.Sometimes labeled'iimitations' I
' _ �� �r:-^,-._- many of these provisions indicate where geotechnica�engineers'respansi- I�
�it�t��s begfn and end,to help others recognize their own responsibilities I
A 6eotechnical Engineering Report Is Subject to .�,�r!sks. R�ad these provisi�ns c�ose+'y Ask qu?sticns.Your gect�hnia!
Misinterpretation ��_ __�����. ���c� � � ;; � ; ,
,._ ; _=- _ -- = __�s �, _ .-�� ��a'.i�n of geotec���;�ai engineer'3
' rep;;��;as rzs��.���n;,osi�y prc�iems.Lo,�er that risk by having your g?o- Geoenvironmental Concerns Are Not Covered
technipl enginee�confer with appropriate members of th�e design team aft2r The eau`pr�°nt.����ques.a^d personnel used ta�=r�•T ;oe�env,.•or-
submitting the report.Also retain your geotechniat engineer to review perti- r�enta�study���r s��:fi;znt{y fron those used t��_��:�T,a c��'�chnical j
nent elements of ihe design team's pla�s and specifications.Contractors can stutly.Far Lhat reason,a g2otechnical engineering report does not usually i
' also misinterpret a gectechnicai engineering report Reduce that risk by relate any geoenvironmental findings,conclusions,or recommendations;
having your geot�chni�a!engineer part�c'pa'?�n pr?bid and pr?censtru�!ion e.g.,about the likelihood oi encountering underground storage tanks or �
_� ==� a���t;�r.v�-� ��r��' �__•:,±�� •=��!atedcontaminants.Unanticipatedenvironmerdalproblemshaveled �
'.��rrrerous projectlailures.if you have not y�obtained your ewri geoen- �
Do Not Redraw the Engineer�S �OJS :��n�ental information,ask your geotechnical consultant for risk man-
G� e�r- �� e =_ ._�,.-.�� c�r g,��:- � �gs case��r=� z��^�ent gu�da�ce. Do nof,�etyen an envircRTEf1!31(_°L'O,�f�f�pd(E�lC!
..�c�f �.� _.a._ �' � ,;y�� ,. �.,_ 3i�fy'�et3 ' 'V2flt2ff0f5.. �� ��`..�.�
� omissio�u,the f�gs inciuded in a geotechnical engineering report shc..�
� neverbe redravm for inclusion in architectural or other design dra�n-���� 06tain Protessional Assistanee To Deal with Mold
Oniy photographic or e!ectronic reproduction is accep'2ble.but�eceg��� Dir���.�.�. __- �_ .�a�� _� �_• � . - � __�y� :,: ��•,�� _ .
��:_�c�'.. "� �ys _ ..��'er�'�cC „.,,?,��cK. �afz:� � . �.... ._ _'1�_ . ..,� v. . _.. .; :� ... �' � �. . _ .
�r�wing an indoor surfaces.To be eflective,all such strategie5 snould be �
6ive Contractors a Complete Report and ��vised for ttte express purpose of moid prevention,integrated intD a Com- �
6uidance ����hensive plan,and executed with diligent oversight by a professionai i
Sc . ^h`?'S d^�C��y',r'� ...,..., c� , iar.c'j Cc,c`rB `.:y ;c:i"ic�c T�Id prevention consultant.Be��use just a smaii amour�of water or
con�r,�±;�� a�':?for una�ticipated subsurface conditions by limit+ng what moisture can lead to the development of severe moid infeshtions,a num- �
they provi�e for bid prepara'ion.To help prevent cost!y problems,give con- ber of mcid prevention strategies focus on keeping building surfaces dry. '
tractors the complete geatechnical engineering report,butpreface it wi�h a While groundwater,water infi�tration,and similar Issues may have been
clearly written letter of transmittal.In that{etter,advise contractors th�t the addressed as part of the geotechnical engineering sti�dy whose fndings
repo�t was not prepared f�r purpose.s of 6id development and that the are c�nvey�in this repor?.the geotechnica!e-;;;-��r����a�c=�!'��s
r�ort's accuracy is limited;encourage them io confer with the geotect�^i�! a�o;ect is nct a mc!d prevent:on consult��t: none ol the services per-
engineer who prepared the repoR(a modest f�may be required)and/orr'e lormed in connection with the geotechnica/engineer's study
conduct additio�al stutly to obtain the specific types cf inforrnation they were designed or conducted for the purpose ol mold preven- '
need or prefer.A prebid con',erence can also be+�luabie.Be sure contrac- tion. Proper implementation ol the recommendations conveyed �
tors havt sulficient time to perform additionai�tudy.Only then might ye� in this report wil!not oi itsell tre sulficienf to prevent mold lrom
be in a position to give coniractors the best i�`or^�a'ion zvai'zC'??o yc��. growing in or on the structure invo/ved.
whi'e requ�ring the�te at least share s� ��� r_-=�; ����_�;� '.�s
_ T--,�°��� ���� :���� ,�,��s V Rely, on Your ASfE-Member 6eotechncial
Engineer for Additional Assistance
Read Responsi6ility Provisions Closely �:�:-�:-�� � �,�sF�T������F:�:� � ���� -��_�_�9�o,��n���a�
c_ � . : _ _ _ ���es�cr�; � , __� ���,r� j_ �. .�a�.�e i^�t e�g ��e�s t;;a�i��array�?risK rra�agz^��e�t tec�;�:;;ues that can be of �
-�.�_ _, ���-��r,�,� �`a•'��s.�.��::^�� :��_�a�����r�g disci- genuine benef;t for everyone involved with a construction projed.Cor�er
p;ines.This iack of unoerstanding has created wrealist�c expectations that with you ASFE-member geotechnipl engineer ior more information.
ASFE
T�� Iest 1���Ie �� F�rt�
; Teiephone:301;�6�-2733 Facs�m�Ie 3u1i589-2�t7
e-mail:inf�@as!e.org tivu►�w.asfe.or�
CoPY�ght 2004 by ASFE.!rx_OuDlitation,reproQuction.or copyinq o!this daumerrt,in whole a in part.Dy arty means whalsoever,is strictly ArohibiteQ except wrth ASff�S
speciflc wrnten permission.fxcerpGng,quoting.a ocherwise extracring wordiny fiom ttus documem rs permrtted onty wrth the e�255 wntten pertnissian ol ASff,aisd only fa
purposes of scAolarly resea2h ar book rewew Qny members ot ASff may use this Oocument as a complemeni io a as an element of a peotechnica/engirneerinp repo2 Arry aticer
brm,mdrvrduaf,or otfrer errtily t/�at so uses this daumerrt wifhaut Derng an ASFE memDer couJd be cammrtting neg.�;ger,t or m;entional(lraudulent)misrepresentatron.
��uER�E045 G'N