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Technical
Information Report
City of Renton
February 19, 20003
Prepared for:
_ Cambridge Homes, Inc.
1800 NE 44t'' Street
Renton, WA 980
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Prepared By: ��,� `�� �s ER�O �ww� ��
' Jennifer A. Steig, P.E. �SSf�NAL E��`�,�°�
EXPIRES 09,�09/04
PCE Job No. CHAF-0009
City of Renton Development Services Division
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND Part 2 PROJECT LOCATION AND
PROJECT ENGINEER DESCRIPTION
Project Owner: Cambridqe Homes, Inc. Project Name: Elsa Ridqe Short Plat
Address: 1800 NE 44th Street Location:
Renton,WashinQton 98056 Township: 24 North
Phone: f425)271 - 2225 Range: 5 East
Project Engineer: Jennifer Steiq SE 1/4 Section: 32
Company: Peterson Consultinq Enqineers
Phone/Address: (425)827-5874
4030 Lk Washinqton Blvd Suite 200
Kirkland.Wa. 98033
- 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
❑ Commercial ❑ FEMA Floodplain ❑ Other
❑ Other: ❑ COE Wetlands
Part 5 SITE COMMUNITY AND DRAINAGE BASIN
Community:
Newcastle Community Planning Area
Drainage Basin:
Cedar River Basin and May Creek/East Lake Washington Sub-basins
Part 6 SITE CHARACTERISTICS
❑ River ❑ Floodplain
❑ Stream ❑ Wetlands
- ❑ Critical Stream Reach ❑ Seeps/Springs
❑ Depressions/Swales ❑ High Groundwater Table
❑ Lake ❑ Groundwater Recharge
� Steep Slopes ❑ Other
Part 7 SOILS
Soil Type Slopes Erosion Potential Erosive Velocities
� EvC 5 %to 15% Sliqht to Moderate Slow to Moderate
❑ Additional Sheets Attached �,
Part 8 DEVELOPMENT LIMITATIONS '�
REFERENCE LIMITATION/SITE CONSTRAINT
❑
❑
❑
❑
- ❑
❑ 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
� Clearing and Grading Restrictions � Ensure Operation of Permanent Facilities
� Cover Practices � Flag Limits of SAO and open space
� Construction Sequence preservation areas
❑ Other ❑ Other �
iPart 10 SURFACE WATER SYSTEM
❑ Grass Lined ❑ Tank � Infiltration Method of Analysis
Channel 1998 KCRTS
❑ Vault ❑ Depression
� Pipe System
❑ Energy Dissipator ❑ Flow Dispersal
❑ Open Channef
❑ Wetland ❑ Waiver
❑ Dry Pond
. ❑ Stream ❑ Regional
❑ Wet Pond Detention
Brief Description of System Operation: Runoff from the roof areas will be conveyed via
tiahtline to an infiltartion trench. The infiltration trenches are sized per the requirements
set forth in paqes 5-6 to 5-8 of the 1998 KCSWDM
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
R
Part 13 SIGNATURE OF PROFESSIONAL ENGINEER
I or a civil engineer under my supervision my supervision have 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.
,
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� Signed/Date
TABLE OF CONTENTS
SECTION 1: PROJECT OVERVIEW......................................................................................1
FIGURE1: VICINITY MAP..............................................................................................................2
FIGURE2: BASIN MAP ..................................................................................................................3
FIGURE3: SOILS MAP ...................................................................................................................4
FIGURE4: SI'I'E MAP .....................................................................................................................5
SECTION 2: CONDITIONS AND REQUIREMENTS SUMMARY ....................................6
SECTION 3: OFF-SITE ANALYSIS......................................................................................11
SECTION 4: FLOW CONTROL Al\D WATER QUALITY FACILITY ANALYSIS AND
DESIGN...............................................................................................................12
FIGURE 5: EXISTING CONDITIONS MAP.......................................................................................13
FIGURE 6: DEVELOPED CONDI'I'IONS MAP...................................................................................14
SECTION 5: CONVEYANCE SYSTEM ANALYSIS AI�1D DESIGN.................................17
SECTION 6: SPECIAL REPORTS AND STUDIES.............................................................21
SECTION7: OTHER PERMITS............................................................................................22
SECTION 8: ESC ANALYSIS AND DESIGN.......................................................................23
SECTION 9: BOND QUANTITIES,FACILITY SUMMARIES, AND DECLARATION
OFCOVENANT.................................................................................................24
SECTION 10: OPERATIONS AND MAINTENAI�TCE MANUAL.......................................25
APPENDIX A
Geotechnical Engineering Study prepared by Geotech Consultants Inc. dated Septemher 9, 2002
APPENDIX B
Preliminary TIR including Level 1 Downstream Drainage Analysis
APPENDIX C
Bond Quantities Worksheet
Peterson Consulting Engi��ee�•s Page i
Techrzical I1�forrnation Report for Elsa Ridge Febrr�ail� 18, 2003
SECTION l: PROJECT OVERVIE�'�'
The proposed project (E1sa Ridge) is the subdivision of 1.43 acres into 6 single-family
residences. The site is located within the City of Renton at 3785 Lincoln Avenue NE, see
Figure l: Vicinity Map. Vlore generally, the site is located within the I�Tortheast quarter of
Section 32, Township 24 North, and Range 5 East of the Willamette Meridian. The site is
surrounded by a single-family residence on the north, a vacant single-family lot on the west,
Lincoln Place NE on the south, and Lincoln Avenue VE on the east.
Existing Site Conditions:
The site is currently developed as a single-family residence with detached garage that gains
access from Lincoln Avenue NE. On-site vegetation consists mainly of grass, shrubs, and
trees. The westerly third of the site is made up of steep slopes over 40 percent, while the
remainder of the site slopes slightlyto the east and �.��est from a �entle rid«e l�cated just �a;t
nfrl, a����+:.,r, l��„cr�. c<�_ F'I�T111"E' �' RA�I❑ ��I3�.
��_ i� l� -- - _ -.. .:'� '� �_. . .. _�. _.... �t'= __.._ _..�-� ��, ��- \ � -- 1L.-
Map see Figure 3: SCS Soils Map. Everett soils are classified as outwash soils per pag�
25 of the 1998 KCSWDM. These soil � � , - -
Ul1 l:iu(J�ii ,J1L:, �:31tii�liv;:
The developed site will include 6 single-family lots, approximately 901ineal feet of shared
driveway and associated utilities, see Figure 4: Site Map. There will be no direct vehicular
access from Lincoln Avenue NE for any of the lots. Runoff from the new impervious surfaces
will be collected and conveyed to individual lot infiltration trenches or discharged into the
existing tightline storm drainage system on the east side of Lincoln Avenue NE.
Steep slopes setbacks are in accordance with the geotechnical report prepared by Geotech
Consultants Inc. dated September 9,2002. A 10-foot non-disturbance buffer and a 35-foot
foundation setback will be imposed from the crest of the steep slope. It also states that the
foundation setback can be reduced to 30 feet if the new residences on lots 2 and 6 extend their
foundations down to a depth of at least 7 feet below the lowest surrounding grade. Please see
the Geotechnical Engineering Study in Appendix A for more information and details.
Peterson Consulting Enginee�•s Page 1
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DWN. BY.• DATE.• JOB NO.
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ELSA RIDGE
SEC. 32, TWP. 24 N., RGE. 5 E., W M.
DWN. BY.� DATE.• JOB NO.
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Blvd. N.E..Suite 200 RSG 7/3/02 CAMB—G001
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Technical lnformation Report for Elsa Ridge February 18, 1003
SECTION 2: CONDITIONS AND REQUIREMENTS
SUMMARY
King County Surface Water Design Manual Core Requirements:
1. Discharge at the Natural Location
Discharge from the site will be at the natural location. The runoff from the new
residences will be infiltrated on site while the runoff from Tract A and the frontage
streets will be collected and conveyed to the existing closed pipe conveyance systems.
2. Off-Site Analvsis
A Level 1 Downstream Analysis & Conceptual Drainage Report was previously
submitted and is provided in Appendix B.
3. Flow Control
Infiltration trenches are being used in order to meet the flow control requirement for
the new residences.
The new on-site impervious area from Tract A and the frontage roads are exempt from
flow control per page 1-27 of the 1998 KCSWDM. No. 1 —Impervious Surface
Exemption, states that".....a project is exempt if less than S,000 square feet of new
impervious surface will be added and the project is not within a Landslide Drainage
Hazard Area." See Section 4 for detailed documentation.
4. Convevance System
The proposed conveyance system will collect runoff and discharge it to the existing
conveyance system in Lincoln Avenue NE or Lincoln Place NE. Refer to Section 5 of
this report for more information.
5. Erosion and Sediment Control
A Temporary Erosion and Sedimentation Control Plan is provided with this design
submittal in accordance with the City of Renton Standards. Refer to the Section 8 of
this report for more information.
Peter�son Cortstiltiiig E�zgi�reers Pagc 6 ���
Technical Informatlon Report for•Elsa Ridge Februa�y 18, 2003
King County Surface Water Design Manual Special Requirements:
1. Other Adopted Requirements
The site is not located within any Critical Drainage Area, Master Drainage Plan, Basin
Plan, Lake Management Plan,or Shared Facility Drainage Plan. Therefore, this site is
not subject to any specific adopted requirements.
2. Floodplain/Floodwav Delineation
The project does not contain nor is it located next to a stream, lake or wetland per the
King County sensitive area maps. Therefore, no flood plain or floodway delineation is
necessary.
3. Flood Protection Facilities
The project is not anticipated to be located within a floodplain or a floodway area;
therefore, no flood protection facilities are required.
4. Source Control
The proposed project does not meet the threshold for source control requirements.
5. Oil Control
The proposed project does not meet the threshold for oil control requirements.
Hearing Examiners Conditions / Requirements:
1. The applicant shall comply with the conditions imposed by the ERC.
The project complies with all ERC conditions. Detailed responses to the ERC conditions
follow below.
2. The applicant shall obtain demolition pernuts and complete all necessary inspection and
approvals for all existing structures not located on what would become new lot 3. The
satisfaction of this requirement shall be subject to the review and approval of the
Development Services Division prior to the recording of the short plat.
A demolition perrnit�vill be obtained for removal of all structures outside of the new Lot
3.
Peterson Consulting Engineers Page 7
Tech�iical Infonnation Report for Elsa Ridge February 18, 2003
3. The applicant shall place "No Parking" signage near the 20-foot wide private drive serving
the development. The satisfaction of this requirement shall be subject to the Development
Services Division prior to recording of the short plat.
"No Parking"signs have been shown on the Civil Engineering Plans near the 20 foot
private drive.
4. Proposed lots 1 to 4 shall be limited to sharing an access easement roadway that runs east
to west and intersects with Lincoln Avenue NE between proposed lots 1 and 4.
Lots 1 to 4 shall gain access via the proposed access easement; none will have direct
vehicular access from Lincoln Avenue NE.
5. Proposed lots 5 and 6 shall share a driveway that provides access to Lincoln Place NE.
Lots S and 6 shall gain access via shared driveway from Lincoln Place NE.
6. There shall be no other access to the public streets other than that provided by the
respective shared access methods outlined above.
So Noted. �
7. All access limitations and restrictions shall be shown on the face of the plat. �'I
Access restrictions will be indicated on the final plat map.
Environmental Review Committee Mitigation Measures / Conditions:
1. The applicant shall be required to adhere to all recommendations contained within the
September 9, 2002 Geotechnical Report prepared by Geotech Consultants, Inc. with
regard to all earthwork activities, slope setbacks and foundation design. In addition, the
applicant shall include the 45-foot building setback line from the top of the ravine on the
face of the final short plat.
The project is designed in accordance with the geotechnical report.
Peterson Consulting Engineers Page 8
Technical Info�mation Report for Elsa Ridge Februaty 18, 2003
2. Temporary erosion control measures shall be maintained to the satisfactian of the
representative of the Development Services Division for the duration of the project's
construction.
A temporary erosion control plan ("TESC') has been designed and shall be used durifag ,
the construction process.
3. The applicant shall install a silt fence along the down slope perimeter of the area that is to
be disturbed. The silt fence shall be in place before clearing and grading is initiated and
shall be constructed in conformance with the specifications presented in the 1998 King
County Surface Water Design Manual. This will be required during the construction of
both off-site and on-site improvements as well as building construction.
Silt fence has been shown on the TESC plan, and will be installed prior to clearing and
grading.
4. Shallow drainage swales shall be constructed to intercept surface water flow and route the
flow away from the construction area to a stabilized discharge point. Vegetation growth
shall be established in the ditch by seeding or placing sod. Depending on site grades, it
may be necessary to line the ditch with rock to protect the ditch from erosion and to reduce
flow rates. The design and construction of drainage swales shall conform to the
specifications presented in the 1998 KCSWDM. Temporary pipe systems can also be used
to convey storm water across the site. This will be required during the construction of both
off-site and on-site improvements as well as building construction. This mitigation
measure shall be placed on the face of the final short plat prior to recording.
Drainage swales are shown on the TESC plan, and shall be used to intercept flows
perpetuated from the site during construction. The ditch on Lincoln Place NE will be rock
lined near the outfall of the new storm drain outfall.
5. The project contractor shall perform daily review and maintenance of all erosion and
, sedimentation control measures at the site during the construction of both on-site and off-
site improvements as well as building construction. This mitigation measure shall be
placed on the face of the final short plat prior to recording.
So noted.
6. Weekly reports on the status and condition of the erosion control plan ���ith any
recommendations of change or revision to maintenance schedules or installation shall be
Peterso�t Consultir:g Engineer•s Page 9
submitted by the project engineer of record to the Public Works inspector.
Weekly reports will be provided as required.
7. Certification of the proper removal of the erosion control facilities shall be required prior
to the recording of the fmal plat.
So noted.
8. This project shall be subject to the 1998 King County Surface Water Design Manual.
So noted. �
9. The applicant shall pay the appropriate Fire Mitigation Fee based on a rate of�488.00 per
new single-family lot prior to the recording of the final short plat.
All fire mitigation fees required by the Ciry of Renton will be paid by the applicant prior
to recorcling the final short plat.
10. The applicant shall pay the appropriate Traffic Mitigation Fee based on $75.00 per each
new average daily trip associated with the project prior to the recording of the final short
plat.
, All traffic mitigation fees required by the City of Renton will be paid by the applicant
prior to recording the final short plat.
1 l. The applicant shall pay the appropriate Parks Mitigation Fee based on $530.76 per new
single-family lot prior to the recording of the final short plat.
All park naitigation fees required by the City� of Renton will be paid by the ccpplicant prior
to recording tl�e final short plat.
Perersori Cof�sc�lting Engineers Pa�e 10
Technical h2formation Report for Elsa Ridge Februa�y 18, 2003
SECTION 3: OFF-SITE ANALYSIS
A Level 1 Off-Site Drainage Analysis was submitted with the preliminary plat and is provided
in its entirety in Appendix B.
Peterson Consulting Engineers Page 11
Technical Info�mation Report for Elsa Ridge February 18,
SECTION 4: FLOW CONTROL AND WATER QUALITY
FACILITY ANALYSIS AND DESIGN
Existing Site Hydrology:
The westerly third of the site is made up of steep slopes over 40 percent, while the remainder
of the site slopes slightly to the east and west from a gentle ridge located just east of the
existing house, see Figure 5: Existing Conditions Map.
The soils on the site are Everett gravelly sandy loam, as classified by the SCS Soil Survey
Map see Figure 4: SCS Soils Map. Everett soils are classified as outwash soils per page 3-25
of the 1998 KCSWDM. These soils are also confirmed by page 2 of the Geotechnical
Engineering Study found in Appendix A.
Developed Site Hydrology:
The developed site will include 6 single-family lots, approximately 90 lineal feet of shared
driveway and associated utilities, see Figure 6: Developed Conditions Map. There will be
no direct vehicular access from Lincoln Avenue NE for any of the lots. Runoff from the new
impervious surfaces will be collected and conveyed to individual lot infiltration trenches or
discharged into the existing tightline storm drainage system on the east side of Lincoln
Avenue NE.
Peterson Consarlti�:g Engineers Page 1''
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FIGURE 6
Technical Information Report for Elsa Ridge February 18. 2003
Updated April 1, 2003
A. "New Residence - Roof Area" Flow Control
Per the flow chart on page 5-4 of the 1998 KCSWDM, if the lots are less than 22,000 sf and
are underlain by medium sandy soils then downspout infiltration systems must be used as flow
control for the new residences. The geotech report in Appendix D by Geotech Consultants
Inc. confirms these soil conditions, therefore the roof areas will be infiltrated using downspout
infiltration trenches. Per page 5-5 of the 1998 KCSWDM, for every 1,000 sf of roof area, soil
consisting of inedium sand requires 30 LF of infiltration trench, a detail of the trench is
provided on the engineering plans. The runoff from the remainder of the site will be collected
and contained as described below.
"New Residence - Roof Areas" Water Quality
The pollution generating impervious surface from the new residences are less than the 5,000
sf thre�hold; therefore per page 1-50,No. 1 Surface Area Exemption, of the 1998 KCSWDM
water quality treatment is not required for the roof areas.
B. "Tract A" Flow Control
The new impervious surface in'�'ract A and along the frontage of Lincoln Avenue NE is 4,495 i
square feet, less than the 5,000 square feet(s� threshold(see description for Core
Requirement#3, on page 6, of this report), therefore flow control (detention) is not required '
for Tract A. The runoff from Tract A and the off-site frontage improvements east of the
property will be collected in a tightline system and discharged into the existing conveyance
system on the east side of Lincoln Avenue NE. Note, the roof areas from the new residences
and lawn areas are not included in the KCRTS calculations because they are being infiltrated
using downspout infiltration trenches. �
"Tract A" Water Quality
Since the impervious surface in Tract A is less than the 5,000 sf threshold, per page 1-50, No.
1 Surface Area Exemption, of the 1998 KCSWDM water quality treatment is not required for
Tract A.
Peterson Consultrng Engineers Pnge 16
Tech�tical Injormation Report for Elsa Ridge February 18, 2003
Updated April 1, 2003
C. Lincoln Place Improvements - Flow Control
The new impervious surface tributary to the ditch on the south side of Lincoln Place NE is
2,815 square feet, well below the 5,000 square feet (s fl threshold (see description for Core
Requirement#3, on page 6 of this report), therefore flow control (detention) is not required
for the driveway azea. The 100-year developed flow from the area tributary to the ditch in
Lincoln Place is 0.03 cfs, therefore a rock pad will be used to disperse the flow from the
driveway area into the existing ditch on the south side of Lincoln Place NE see KCRTS output
in Section 5. Note, the roof areas from the new residences and lawn areas are not included in
the KCRTS calculations because they are being infiltrated using downspout infiltration
trenches.
Lincoln Place Improvements - VVater Quality
Since the new impervious surface (reference Area Table on following page) tributary to the
ditch on the south side of Lincoln Place NE is less than the 5,000 sf threshold; per page 1-50,
No. 1 Surface Area Exemption, of the 1998 KCSWDM water quality treatment is not required
for the driveway to lot 6.
Peterson Consulting Engineers Pagc 17
Technical Informc�tion Report fo�•Elsa Ridge February 18, 2003
SECTION 5: CONVEYANCE SYSTEM ANALYSIS AND
DESIGN
The conveyance system analysis and design has been completed. See below for more
information.
A. Conveyance Analysis For "Tract A" Runoff
The flow from the developed area of"Tract A"will be collected and conveyed into the
existing conveyance system in Lincoln Avenue NE. Therefore, a conveyance analysis was
completed to see if the conveyance system could convey the 100-year developed flow from
Tract A. A 15-minute time series was created for this area using KCRTS, see Area Table
below. It was found that the 100-year developed flow from this area is approximately 0.05
cfs, see KCRTS output below.
The size and slope of the existing storm system adjacent to the site was used to determine the
maximum capacity of the storm line using the F1owMaster computer program. The capacity
of the existing conveyance system in Lincoln Avenue NE was found to be 34.38 cfs, see
FlowMaster output below for the capacity analysis of the existing storm system. Therefore,
during the 100-year storm event the runoff from the site is only contributing approximately
0.2% of the total capacity for the existing storm system. Therefore, there should be sufficient
capacity in the existing storm system on the east side of Lincoln Avenue NE.
Area Table
Total Area on site = 1.43 acres
Area to Lincoln Avenue Conveyance System = 0.10 acres
Impervious Road: Offsite = 0.07 acres
Impervious Road: On-site = 0.03 acres
KCRTS Input
Scale Factor: Sea-Tac 1.0
Soil Type: Outwash
Areas (from above): Impervious (On-site + Off-site) =0.10 acres
,
Peterson Consulting Ertgineers Page 17
Technical Information Repor•t for Elsa Ridge February 18, 2003
KCRTS Output
Flow Frequency Analysis
Time Series File:tracta.tsf
Project Location:Sea-Tac ,
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob I
(CFS) (CFS) Period
0. 024 7 2/09/O1 2:00 0.047 1 100.00 0 . 990
0. 021 8 1/05/02 16:00 0.036 2 25.00 0. 960
0.029 3 12/08/02 18:00 0.029 3 10.00 0.900
0.025 6 8/26/04 2 :OD 0.029 4 5.00 0. 800
0.029 4 10/28/04 16:00 0.026 5 3.00 0 .667 j
0.026 5 1/18/06 16:00 0.025 6 2.00 0.500 ,
0. 036 2 10/26/06 0:00 0.024 7 1.30 0.231 '
0. 047 1 1/09/08 6:00 0.021 8 1.10 0.091 I
Computed Peaks 0.044 50.00 0. 980
F1owMaster Output
The pipe on the east side of Lincoln Avenue NE is an 18" diameter pipe. The slope of
this pipe was analyzed by F1owMaster, see slope table below.
Pipe Run No. Upstream Downstream pipe Length Pipe Slope
�r Invert Invert
1 134.58 115.89 294 ft 6.34°/a
FlowMaster Output (Existing Storm System Capacity)
Solve for. Full Flow Capacity Manning's Formula �
� ; __ .__ . �_ _ . _ ._ _ _.___ ._, ___._. _
�, ' Mannings Coefficient �I.Q1C� - Flow Area: . 1.8 ft�
..._
Wetted Perimeter 4.71 ft
' Slope: 0.063400 fklft �
�..._
� ropw�dtn g.�o rt
j Depth: 1.50 ik Critical Depth , _1.�Q ft - ' •
� ' Percent Fuil:' �100.0%�
Diameter: 18 �� Critical Slope:; ��0.060712 ft/ft
;. I , __.___.. .
� p`' Discharge: 34.38 cfs ! Velocity 19.46 ftls
. ; ...__.
� _ �� � � . Velocity Head;���� � 5.88 ft
;. � Specific Energy�:: 7.38 ft
_ Froude Num6er; � "�'Q.O�
� � i N1aNimum Discharga:__._ ._.---3�.99 eFs
,. , _
, ._ _r_ _. .
�- . . � ' r: ; Discharge Full ; 34.36 cfs
` � � � Slape Fuil ; � 0.�634D0 ftlft
, , __ _--__ _
Fla�Type:, N!A
,_:.. __.__.:_ _ __._._,_ ____. _ __._.�_� �__�_.____---•.___.. _ ___ _ ____.._._ _ ... . � .._ __
Solue Report...�' Close Help
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Pete�son Conszrlti�tg Ef�gineers Pa,�e 18
Technical Information Report for Elsa Ridge Februaiy I8, 2003
B. Conveyance Analysis For "Lot 6 Driveway" Runoff
The flow from the developed area of the "Driveway Access to Lot 6"will be conveyed into
the existing ditch on the south side of Lincoln Place NE. Therefore, a conveyance analysis
was completed to see if the open ditch could convey the 100-year developed flow from the
Driveway area. A 15-minute time series was created for this area using KCRTS, see Area
Table below. It was found that the 100-year developed flow from this area is approximately
0.03 cfs, see KCRTS output below.
The size and slope of the existing ditch was used to determine the maximum capacity using
the F1owMaster computer program. The capacity of the existing ditch in Lincoln Place NE
was found to be 25.91 cfs, see F1owMaster output below for the capacity analysis of the
existing storm system. Therefore, during the 100-year storm event the runoff from the site is
I only contributing approximately 0.1% of the total capacity for the existing ditch. Therefore,
there should be suff'icient capacity in the existing storm system on the east side of Lincoln
Avenue NE.
Area Table
Total Area on site = 1.43 acres
Area to Lincoln Place Ditch = 0.07 acres
Impervious Road: Offsite = 0.06 acres
Impervious Road: On-site = 0.01 acres
KCRTS Input
Scale Factor: Sea-Tac 1.0
Soil Type: Outwash
Areas (from above): Impervious (On-site + Off-site) =0.07 acres
Petersorz Corist�lti�ig E�rgi���eers Pcige 19
1_me Series �-�ie:lot6driveway.t�
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Fio�.v Frequency Ar:air__
Flow Rate Rank Time of Peak - - Peaks - - Rank Retu�__ _ _��
(CFS) (CFS) Period
0. 017 6 2/09/O1 2 :00 0.033 1 100.00 0. 9��
� 0.015 8 1/05/02 16:00 0.026 2 25. 00 O .G
0.020 3 12/08/02 18 :00 0.020 3 10. 00 0.9
0 .017 7 8/26/04 2 :00 0.020 4 5.00 0. 8
0.020 4 10/28/04 16 :00 0.018 5 3 . 00 O. E
0. 018 5 1/18/06 16:00 0.017 6 2.00 0.5
0.026 2 10/26/06 0:00 0.017 7 1.30 0.23i
0.033 1 1/09/08 6:00 0 .015 8 1. 10 0.091
Computed Peaks 0.031 50. 00 0 .980
FlowMaster Outaut
FlowMaster Output (Existing Storm System Capacity)
� - � - � � . � . x
5olve tor: pischarge Manning's Formula •�'
� . _. _. . .—----___ . _... _
Mannings Coeificient: 0.030 € Fiow Area ✓ 2.D ft�
Wetted Perimeter � �A.47 ft
51ope: 0.2000Qq ft/ft TopWidth:`� ��� � 4.00 ft
', , _..__ .
' Depth: ?.00 ft CnticalDepth�v' � 1.60 ft
: _.�.___�. __.
Critical Slope:; 0.016399 ftift
Left Side Slope: 2�0 H:V �
_.___ . _ .
; � Velocity 1 Z.95 fk/s
Right Side Slope: 2.00 H:V ; Velocity Head�' 2.61 ft
, , ; _._ .. .
Discharge: 25.91 cfs Speciiic Energy� 3.61 ft
� - Fraude Number. 3.23
Flow Type. Supercritical
___.__. _ __ __ _ .. __�_ _.__._.___ .._.�_ _ . ._ _
5olae Report...� Close Help � I
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_ _ _ _ . .. __ _ _ _ _ __.. _.......__ . __ __.__.. ______
Peterson Consirlting Engineers Page 20
Technical Infoi•mation Report for Elsa Ridge ' February 18, 2003
SECTION 6: SPECIAL REPORTS AND STUDIES
A Geotechnical Engineering Study has been prepared by Geotech Consultants Inc dated
September 9, 2002 and can be found in Appendix A.
I
Peterson Coiui�ltifa,;E�zgi�2eers Page 21 ;
Techr:ical lrtfo�mation Report for Elsa Ridge February I8, 1003
SECTION 7: OTHER PERMITS
No other permits are anticipated.
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Peterson Consulting Erigineers Page 22 �
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Technical Information Report for Elsa Ridge February l8, 2003
SECTION 8: ESC ANALYSIS AND DESIGN
A Temporary Erosion and Sediment Control (TESC) plan has been created for the site. Please
reference the engineering plans for more information. The TESC plan is in accordance with
the K ing C ounty S urface W ater D esign M anual. S ome o f t he Best Management Practices
(BMP's) used for the site include filter fence, catch basin protection and a rock-lined
construction entrance. For more detailed information regarding these BMP's see below.
Filter Fabric Fence will be used as perimeter protection, which will reduce the amount of
sediment transported off the site.
A Rock Lined Construction E�:trance will reduce the amount of sediment transported off the
site by construction vehicles and reduce the azeas disturbed by vehicle traffic.
ClearinQ Limits have been delineated on the construction plans for the purpose of preventing
disturbance of those areas of the project that are not designated for clearing and or grading.
The Construction Senuence has been shown on the construction plans to aid the contractor in
applying the erosion control measures at the appropriate stages during construction.
Pete�son Consaclting Engineers Page 23
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SECTION 9: BOND QUANTITIES, FACILITY SUM111_-�Rl ES,
.a'�TP DECL.-�R.�TI()\T (�F C'n�'E\':�'�T
f il_ �3���11�� �7'.I��illl:ll�� ;' l�?��:��!���_ I��l� ` �:�,:: R���_C` :� ,�1��`V�l��C�l l:l .����,,�:1��'.'ti �_ .
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Peterson Consc�lting Engineers Page 24
Tecfznical Information Repart fo��Elsa Ridge Febr-z�my 18, 2003
SECTION 10: OPERATIONS AND MAINTENANCE MANLTAL
The operations and maintenance manual for Elsa Ridge is contained in the next few pages.
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Peterson Consultirtg Engirzeers Page 25
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITTES
NO. 5-CATCH BASINS
Maintenance Defect Conditions When Mainte�ance is Needed Results Expected When
( Component Maintenance is pertormed
Generai Trash&Debris Trash or debris of more than 1/2 cubic foot which is No Trash or debris located
(Includes Sediment) located immediately in front of the catch basin immediately in front of catch
opening or is blocking capacity of the basin by basin opening.
more than 10°�
Trash or debns(in the basin)that exceeds 1/3 the No trash or debris in the catch
depth from the bottom of basin to invert the lowest basin.
pipe into or out of the basin.
Trash or debris in any inlet or outlet pipe blocking Inlet and outlet pipes free of
more than 1/3 of its height. trash or debris.
Dead animals or vegetation that could generate No dead animals or vegetation
odors that could cause complaints or dangerous present within the catch basin.
gases(e.g.,methane).
Deposits of garbage exceeding 1 cubic foot in No condition present which
�olume would attract or support the
breeding of insects or rodenLs.
Structure Damage to Comer of frame extends more than 3/4 inch past Frame is even with curb.
Frame and/or Top Slab curb face into the street(If applicabie).
Top slab has holes larger than 2 square inches or Top slab is free of holes and
cracks wider than 1/4 inch(intent is to make sure cracks.
� all material is running into basin).
Frame not sitting flush on top slab,i.e.,separation Frame is sitting flush on top
of more than 3/4 inch of the frame from the top slab.
slab.
Cracks in Basin Walls/ Cracks wider than 1/2 inch and longer than 3 feet, Basin replaced or repaired to
Bottom any evidence of soil particles entering catch basin design standards.
through cradcs,or maintenance person judges that
structure is unsound.
Cracks wider than 1/2 inch and longerthan 1 foot No cracks more than 1/4 inch
at the joint of any inleb outlet pipe or any evidence wide at the joint of inleVouUet
oi soil paRicles entering catch basin through pipe.
cracks.
SedimenU Basin has settled more than 1 inch or has rotated Basin replaced or repaired to
Misalignment more than 2 inches out of alignment design standards.
I
1998 Surface Water Design Manual 9/1/98
A-5
APPENDIX A MAIN'I'ENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAI'�AGE F.ACILITTES
NO. 5-CATCH BASINS (CONTINUED�
Maintenance Defect Conditions When Maintenance is Needed Resufts Expected When
Component Maintenance is pertormed
�,...
Fire Hazard Presence of chemicals such as natural gas,al and No flarnmable chemicals
gasoline. present.
Vegetation Vegetation growing across and blocking more than No vegetation blocking opening
10%oi the basin opening. to basin.
Vegetation growing in inleUouUet pipe joints that is No vegetation or root growth
more than six inches tall and less than six inches present. I
apart. !
Pollution Nonflammable chemicals of more than 1/2 cubic foot No pollution present other than II,
per three feet of basin Iength. surface film.
Catch Basin Cover Cover Not in Place' Cover is missing or only partially in place.Any open Catch basin cover is closed
catch basin requires maintenance.
Locking Mechanism Mechanism cannot be opened by on maintenance Mechanism opens with proper
Not Working person with proper tools.Botts into frame have less tools. ',
than 1/2 inch of thread.
Cover Difficult to One maintenance person cannot remove lid after Cover can be�emoved by one
Remove applying 801bs.of lift;intent is keep cover from maintenance person. '
sealing off access to maintenance.
Ladder Ladder Rungs Ladder is unsafe due to missing rungs,misalignment, Ladder meets design standards
Unsafe rust,cracks,or sharp edges. and allows maintenance person
safe access.
Metal Grates Grate with opening wider than 7/8 inch. Grate opening meets design
(If Applicable) standards.
Trash and Debris Trash and debris that is blocking more than 20%o( Grate free of trash and debris. �
grate surface.
Damaged or Grate missing or broken member(s)of the grate. Grate is in place and meets I
Missing. design standards. ',
NO. 6 DEBRIS BARRIERS E.G. TRASH RACKS II
� � )
Maintenance Defect Condition When Maintenance is Needed Resutts Expected When
Components Maintenance is Performed.
General Trash and Debris Trash or debris that is plugging more than 20%of Barrier clear to receive capaciry
the openings in the barrier. tlow. ',
Metal Damaged/Missing Bars are bent out of shape more than 3 inches. Bars in place with no bends more I
Bars. than 3/4 inch.
Bars are missing or entire barrier missing. Bars in place according to
design. I
Bars are loose and rust is causing 50%deterioration Repair or replace barrier to
to any part of barrier. design standards.
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9/1/98 1998 Surface Water Desion Manual
A-6 �
APPENDIX A MAINTENANCE STANDARDS FOR PRIVATELY MAIh*CAII�fED DRAINAGE FACILITIES
NO. 7- ENERGY DISSIPATERS
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
, Components Maintenance is Performed.
Extemal:
Rock Pad Missing or Moved Only one layer of rock exists above native soil in Replace rocks to design
Rock area five square faet or larger,or any exposure of standards.
native soil.
Dispersion Trench Pipe Plugged with Accumutated sediment that exceeds 20%of the Pipe cleaned/flushed so that it '
Sediment design depth. matches design.
Not Discharging Vsual evidence of water discharging at Trench musi be redesigned or
Water Prope�ly concentrated points along trench(normal condition rebuilt to standards.
is a"sheet flo�N'of water along trench). Intent is to
prevent erosion damage.
Perforations Over 1/2 of perforations in pipe are plugged with Clean or replace perforated pipe. ,
Plugged. debris and sediment. I
Water Flows Out Maintenance person observes water flowing out Facil'dy must be rebuilt or �
Top of"Distributo�' during any storm less than the design storm or its redesigned to standards.
Catch Basin. causing or appears likety to oause damage.
Receiving Area Water in receiving area is causing or has potential No danger of landslides.
Over-Saturated of causing landsfide problems.
Intemal:
Manhole/Chamber Wom or Damaged SWcture dissipating flow deteriorates to 1/2 or Replace structure to design
Post.Baffles,Side original size or any concentrated wom spot standards.
of Chamber exceeding one square foot which would make
structure unsound.
Other Defects See"Catch Basins'Standard No.5 See"Catch Basins"Standard No.
5
1998 Surface Water Design Manual 9/1/98
A-7
APPENDIX A MAINT'ENANCE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 10-CONVEYANCE SYSTEMS(PIPES & DITCHES)
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
` Component Maintenance is Pertormed
Pipes Sediment 8 Debris Accumulated sediment that exceeds 20%of the Pipe cleaned of all sedirnent I
diameter oi the pipe. and debris.
Vegetation Vegetation that reduces free movement of water All vegetation removed so water
through pipes. fiows freely through pipes. ,
Damaged Protecti�e coating is damaged;rust is causing Pipe repaired or replaced. '
more than 50%deterioration to any part of pipe. ',
Any dent that decreases the cross section area of Pipe repaired or replaced.
pipe by more than 20%.
Open Ditches Trash 8�Debris Trash and debris exceeds 1 cubic faot per 1,000 Trash and debris deared from
square feet of ditch and slopes. ditches.
Sediment Accumulated sediment that exceeds 20%of the Ditch cleaned/flushed of all
design deptfi. sediment and debris so that it
matches design.
Vegeta6on Vegetation that reduces free movement of water Water flows freely through
through ditches. ditches.
Erosion Damage to See"Ponds"Standard No.1 See"Ponds"Standard No. 1
Slopes
Rock Lining Out of Maintenance person can see native soil beneath Replace rocks to design
Place or Missing(If the rock lining. standards.
Applicable).
Catch Basins See"Catch Basins:Standard No.5 See"Catch Basins°Standard
No.5
Debris Barriers See"Debris Barriers"Standard No.6 See"Debris 8arriers'Standard
(e.g.,Trash Rack) No.fi
N0. 11 -CROUNDS (LANDSCAPING)
Maintenance Defect Conditions When Maintenance is Needed Results Expected When
Component Maintenance is Performed
Genera! Weeds Weeds growing in more than 20'/a of the landscaped Weeds present in less than 5%
(Nonpoisonous) area{trees and shrubs only). of the landscaped area.
Safety Hazard Any presence of poison ivy or other poisonous No poisonous vegetation
vegetation. present in landscaped area.
Trash or Litter Paper,cans,botties,totaling more than 1 cubic foot Area clear of litter.
within a landscaped area(trees and shrubs only)of
1,Q00 square feet.
Trees and Shrubs Damaged Limbs or parts of trees or shrubs that are split or Trees and shrubs with less than
broken whicfi affect more than 25%of the total 5%of total foliage with split or
foliage of the tree or shrub. broken limbs.
Trees or shrubs that have been blown down or Tree or shrub in place free of
knocked over. injury.
Trees or shrubs which are not adequately supported Tree or shrub in place and ,
or are leaning over,causing exposure of the roots. adequately supported;remove ,
any dead or diseased trees.
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1998 Surface VVater Design R9anual 9/1/9S
A-9
APPENDIX A MAIIv'TENAI�CE STANDARDS FOR PRIVATELY MAINTAINED DRAINAGE FACILITIES
NO. 12-ACCESS ROADS/EASEMENTS
Maintenance Defect Condition When Maintenance is Needed Results Expected When
Component Maintenance is Pertormed �
�
General Trash and Debris Trash and debris exceeds 1 cubic foot per l,000 Roadway free of debris which
square feet i.e.,trash and debris would fill up could damage tires.
one standards size garbage can.
Blocked Roadway Debris which could damage vehicle tires(glass Roadway free of debris which
or metai), could damage tires.
Any obstruction which reduces clearance above Roadway overhead Gear to 14 feet
road surface to less than 14 feet. high.
Any obstruction restricting the access to a 10 to Obstruction removed to allow at
12 foot width for a distance of more than 12 feet least a 12 foot access.
or any point restricting access to less than a 10
foot widih.
Road Surface Settlement, Pothoies, When any surface defect exceeds 6 inches in Road surface unifoRnly smooth
Mush Spots,Ruts depth and 6 square feet in area.In general,any with no evidence of settlement,
surface defect which hinders or prevents potholes,mush spots,or ruts.
maintenance access.
Vegetation in Road Weeds growing in the road surface that are Road surface free of weeds taller
Surface more than 6 inches tall and less ihan 6 inches than 2 inches.
tall and less than 6 inches apart within a 400-
square foot area.
Modular Grid Build-up of sediment mildly contaminated with Removal of sediment and disposal
Pavement petroleum hydrocarbons. in keeping with Health Department
recommendations for mildly
contaminated soits o�catch basin
sediments.
Shoulders and Erosion Damage Erosion within 1 foot of the roadway more than 8 Shoulder free of erosion and ��'
Ditches inches wide and 6 inches deep. matching the surrounding road. _
Weeds and Brush Weeds and brush exceed 18 inches in height or Weeds and brush cut to 2 inches
hinder maintenance access. in height or cleared in such a way
as to allow maintenance access.
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9/1/98 1998 Surface Water Desi�n Manual
A-10
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G E O T E C H 13?56 Northeast 20th Street, Suite 16
Bellevue,Washington 98005
CONSULTANTS, INC. (425)747-5618 FAX(425)747-8561
September 9, 2002
J N 02326
Cambridge Homes
1800 Northeast 44th Street
Renton, Washington 98056
Attention: Dale Huffman
Subject: Transmittal Letter— Geotechnical Engineering Study
Proposed Elsa Ridge Subdivision
3785 Lincoln Avenue Northeast
Renton, Washington
Dear Mr. Huffman:
We are pleased to present this geotechnical engineering report for the proposed Elsa Ridge I
Subdivision in Renton, Washington. The scope of our services consisted of exploring site surface
and subsurface conditions, and then developing this report to provide recommendations for general
earthwork, design criteria for foundations and retaining walls, and slope setbacks. This work was
authorized by your acceptance of our proposal, P-5860, dated August 14, 2002.
The attached report contains a discussion of the study and our recommendations. Please contact
us if there are any questions regarding this report, or for further assistance during the design and
construction phases of this project.
Respectfully submitted,
GEOTECH CONSULTANTS, INC.
�� � � ���
Kristopher T. Hauck
Geotechnical Engineer
cc: Peterson Consulting Engineers — Jennifer Steig, P.E.
via facsimile: (425J 822-7216
KTH/MRM: alt
GEOTECH CONSULTANTS, INC.
GEOTECHNICAL ENGINEERING STUDY
Proposed Elsa Ridge Subdivision '
3785 Lincoln Avenue Northeast
Renton, Washington
This report presents the findings and recommendations of our geotechnical engineering study for
the site of the proposed Elsa Ridge Subdivision to be located at 3785 Lincoln Avenue Northeast in
Renton, Washington.
We were provided with site plans and a topographic map. Peterson Consulting Engineers
developed these plans, which are dated July 5, 2002. Based on these plans, we understand that
the property will be divided into six different residential lots, with the existing residence remaining
on one of the lots. The existing garage located on the northern portion of the site will be removed.
The development of plans for the individual homes is still in the planning stage, thus detailed plans
for the houses and site grading were not available at the time of this report. We understand that
each lot is to contain an infiltration trench for disposal of storm water.
If the scope of the project changes from what we have described above, we should be provided
with revised plans in order to determine if modifications to the recommendations and conclusions of
this report are warranted.
SlTE CONDITIONS
SURFACE
The Vicinity Map, Plate 1, illustrates the general location of the site. The site is located on the west
side of Lincoln Avenue Northeast in Renton. The prope�ty is generally rectangular in shape, with
approximately 210 feet of frontage along Lincoln Avenue Northeast and a depth of approximately
296 feet in the east-west direction.
An existing residence (#3758) is located in the center of the site. This house contains a basement
with an approximate finished floor elevation of 129 feet and a main fl�or elevation of approximately
136 feet. A gravel driveway extends into the site from the northeast corner of the property, and
extends west to the north side of the existing residence. A detached garage is located northwest of
the house. This structure appears to be supported on small concrete blocks/pads.
The eastern two-thirds of the site is generally landscaped with grass and medium-sized deciduous
and coniferous trees. This portion of the property is relatively flat, with only 1 to 2 feet of fall from
east to west. The ground around the existing residence is a few feet higher in elevation than the
surrounding grade. The western one-third of the site is steeply sloped at an inclination of
approximately 65 to 75 percent. This west-facing slope has a height of approximately 50 to 55 feet.
There were no visible indications of recent slope instability such as tension cracks, areas of
disturbed vegetation, or slide scarps. However, some of the westernmost trees do exhibit a slight
lean, possibly resulting from downslope creep of the near-surface soils. The steep slope appears
to end near the west property line.
The properties to the north and south are developed with single-family residences that are set back
from the common property lines more than 10 feet. The lot to the south contains an existing gravel
driveway that runs parallel to the property line and is approximately 10 feet away at its closest
point.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 2
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SUBSURFACE
The subsurface conditions were explored by excavating five test pits at the approximate locations �I
shown on the Site Exploration Plan, Plate 2. Our exploration program was based on the proposed '
construction, anticipated subsurface conditions and those encountered during exploration, and the
scope of work outlined in our proposal.
The test pits were excavated on August 27, 2002 with a rubber-tired backhoe. A geotechnical
engineer from our staff observed the excavation process, logged the test pits, and obtained
representative samples of the soil encountered. "Grab" samples of selected subsurface soil were
collected from the backhoe bucket. The Test Pit Logs are attached to this report as Plates 3
through 5.
Soil Conditions
The test pits generally encountered approximately 2 to 3 feet of loose, medium- to fine-
grained sand overlying medium-dense, medium-grained sand. These sands are generally
well-graded with very little fines after approximately 3 feet in depth. One test pit (Test Pit 1),
located directly south of the existing residence, encountered approximately 3 feet of loose
fill overlying the native soil. These findings confirm the soils mapped by the U.S. Soil
Conservation Service (SCS) are Everett gravelly, sandy loam. The maximum explored
depth of the test pits was 13 feet from the existing grade. •
No obstructions were revealed by our explorations. However, debris, buried utilities, and old
foundation and slab elements are commonly encountered on sites that have had previous
development.
Groundwater Conditions
No groundwater seepage and no indications of wet soils were observed during our
explorations. The test pits were left open for only a short time period and were conducted
following a relatively dry summer. However, based on the permeability of the encountered
soils, we do not anticipate that significant groundwater will be encountered within the depth
of the explorations.
The final logs represent our interpretations of the field logs and laboratory tests. The stratification
lines on the logs represent the approximate boundaries between soil types at the exploration
locations. The actual transition between soil types may be gradual, and subsurface conditions can
vary between exploration locations. The logs provide specific subsurface information only at the
locations tested. The relative densities and moisture descriptions indicated on the test pit logs are
interpretive descriptions based on the conditions observed during excavation.
The compaction of backfill was not in the scope of our services. Loose soil will therefore be found
in the area of the test pits. If this presents a problem, the backfill will need to be removed and
replaced with structural fill during construction.
GEOTECH CONSULTANTS. INC.
Cambridge Homes JN 02326
September 9, 2002 Page 3
CONCLUSIONS AND RECOMMENDATIONS
GENERAL
THIS SECTION CONTAINS A SUMMARY OF OUR STUDY AND FlNDINGS FOR THE PURPOSES OF A
GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSlONS ARE
CONTAINED!N THE REMAINDER OF THlS REPORT. ANY PARTY RELYING ON THI S REPORT SHOULD
READ THE ENTlRE DOCUMENT.
The test pits conducted for this study encountered medium-dense, medium-grained sands at
depths of approximately 3 to 4 feet below the existing grade. Based on our findings and
engineering analysis, it is our opinion that the proposed building can be supported by conventional
continuous and spread footings bearing directly on the medium-dense native soil.
Of primary concern for development of the site is the protection of the planned structures from
future instability on the steep slope located on the western one-third of the site. Typically, slopes
comprised of sands such as this will experience periodic shallow instability as the near-surface soils
loosen over time due to weathering. Deep instability is not anticipated. In order to evaluate an
appropriate slope setback for the planned structures, we perFormed a slope stability analysis using
the PCSTALB6 program developed by Purdue University. We analyzed the slope's stability under
both static and earthquake conditions. Based on these analyses, we recommend that the
structures be located no less than 45 feet from the crest of the steep slope. This sl�pe setback
consists of a 10-foot undisturbed buffer at the top of the slope, and a 35-foot foundation setback
from the buffer. Appendix A contains the results of our slope stability analysis. In our opinion, the
slope setback for the houses could be reduced to 40 feet if the western houses utilize a basement
that extends to at least 7 feet below the lowest surrounding grade.
No grading or clearing should occur within the recommended 10-foot buffer zone. Non-critical
elements, such as patios and sheds, could be located within the foundation setback zone. In
addition to these setbacks, any hardscape/tandscape elements, such as brick patios, should not be
sloped to drain to the slope.
Based on our explorations and laboratory analyses, it is our opinion that infiltration is feasible at this
site. We understand that each lot will control its own surface water with infiltration trenches. The
test pits generally found medium-grained sand at approximately 3 to 4 feet from the existing grade.
Since the sites are less than 22,000 square feet, and medium-grained sands were encountered,
the infiltration trenches can be designed using the values given in Section 5.1.1 of the King County
Surface Water Design Manual (KCSWDM). However, some overexcavation to reach the medium
sands may be necessary, especially on Lots 3 and 6, due to the presence of some fill soil at the
surface surrounding the existing residence. Therefore, the elevation of the infiltration trench may
need to be lowered in these areas. If the trenches are located over 45 feet from the steep slope,
their operation should not adversely affect slope stability.
The reuse of these soils as structural fill will likely only be successful during hot, dry weather. On
previous projects utilizing similar sand soils as fill, they have required repeated compaction and
wetting to obtain adequate compaction for structural fill. Imported granular fill will be needed
wherever it is not possible to adequately compact the on-site soils.
The erosion control measures needed during the site development will depend heavily on the
weather conditions that are encountered. We recommend that a wire-backed silt fence and highly-
visible construction fence be erected at the edge of the undisturbed buffer prior to beginning
GEOTECH CONSULTANTS, INC
Cambridge Homes JN 02326
September 9, 2002 Page 4
substantial site clearing activities. Rocked construction roads should be extended into the site to
reduce the amount of mud and soil carried off the property by trucics and equipment. Wherever
possible, these roads should follow the alignment of planned pavements. Cut slopes and soil
stockpiles should be covered with plastic during both wet and dry weather. This prevents erosion
and keeps the sands from drying out during hot weather. Following rough grading, it may be
necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping
or an impervious surface. Additional erosion control measures may need to be implemented to
address the conditions encountered during site work.
Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the
recommendations presented in this report are adequately addressed in the design. Such a plan
review would be additional work beyond the current scope of work for this study, and it may include
revisions to our recommendations to accommodate site, development, and geotechnical j
constraints that become more evident during the review process.
We recommend including this report, in its entirety, in the project contract documents. This report
should also be provided to any future property owners so they will be aware of our findings and
recornmendations.
SE/SMIC CONSIDERATIONS
The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1997 Uniform 'i
Building Code (UBC). In accordance with Table 16-J of the 1997 UBC, the site soil profile within �
100 feet of the ground su�face is best represented by Soil Profile Type So (Stiff Soil). The site soils
are not susceptible to seismic liquefaction because of their medium-dense nature and the absence
of near-surface groundwater.
CONVENTIONAL FOUNDATlONS
The proposed structures can be supported on conventional continuous and spread footings bearing
on undisturbed, medium-dense native sand. See the section entitled Genera/ Earthwork and
Struct�ra! Fil! for recommendations regarding the placement and compaction of structural fill
beneath structures. Adequate compaction of structural fill should be verified with frequent density
testing during fill placement. Prior to placing structural fill beneath foundations, the excavation
should be observed by the geotechnical engineer to document that adequate bearing soils have
been exposed. We recommend that continuous and individual spread footings have minimum
widths of 12 and 16 inches, respectively. Footings should also be bottomed at least 18 inches
below the lowest adjacent finish ground surface. The local building codes should be reviewed to
determine if different footing widths or embedment depths are required. Footing subgrades must
be cfeaned of loose or disturbed soil prior to pouring concrete. Depending upon site and
equipment constraints, this may require removing the disturbed soil by hand.
Depending on the final site grades, overexcavation may be required below the footings to expose
competent native soil. Unless lean concrete is used to fill an overexcavated hole, the
overexcavation must be at least as wide at the bottom as the sum of the depth of the
overexcavation and the footing width. For example, an overexcavation extending 2 feet below the
bottom of a 2-foot-wide footing must be at least 4 feet wide at the base of the excavation. If lean
concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing.
GEOTECH CONSULTANTS, INC
Cambridge Homes JN 02326
` September 9, 2002 Page 5
An allowable bearing pressure of 2,500 pounds per square foot (psfl is appropriate for footings
supported on competent native soil. A one-third increase in this design bearing pressure may be
used when considering short-term wind or seismic loads. For the above design criteria, it is i
anticipated that the total post-construction settlement of footings founded on competent native soil,
� or on structural fill up to 5 feet in thickness, will be about one-half inch, with differential settlements
on the order of one-half inch in a distance of 50 feet along a continuous footing with a uniform load.
Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and
the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the
foundation. For the latter condition, the foundation must be either poured directly against relatively
level, undisturbed soil or be surrounded by level structural fill. We recommend using the following
ultimate values for the foundation's resistance to lateral loading:
� , . .
�
Coefficient of Fnction 0.45
Passive Earth Pressure 300 pcf
Where:(i)pcf is pounds per cubic foot,and(ii)passive earth
Epressure is computed using the equivalent fluid density.
If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will
not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's
resistance to lateral loading, when using the above ultimate values.
PERMANENT FOUNDATION AND RETAIN/NG WALLS
� Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures
imposed by the soil they retain. The following recommended parameters are for walls that restrain
level backfill:
. . . , .
Active Earth Pressure � � 35 pcf
Passive Earth Pressure 300 pcf
Coefficient of Friction 0.45
Soil Unit Weight 130 pcf
Where: (i) pcf is pounds per cubic foot, and (ii) active and
passive earth pressures are computed using the equivalent fluid
pressures.
' For a restrained wall that cannot deflect at least 0.002 times its
height,a uniform lateral pressure equal to 10 psf times the height
of the wall should be added to the above active equivalent fluid
pressure.
GEOTECH CONSULTANTS, INC
Cambrrdge Homes J N 02326
September 9, 2002 Page 6
The values given above are to be used to design permanent foundation and retaining walls only.
The passive pressure given is appropriate for the depth of level structural fill placed in front of a
retaining or foundation wall only. The values for friction and passive resistance are ultimate vafues
and do not include a safety factor. We recommend a safety factor of at least 1.5 for overturning
and sliding, when using the above values to design the walls. Restrained wall soil parameters
should be utilized for a distance of 1.5 times the wall height from corners or bends in the walls.
This is intended to reduce the amount of cracking that can occur where a wall is restrained by a
corner.
The design values given above do not include the effects of any hydrostatic pressures behind the
walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent
foundations will be exerted on the walls. If these conditions exist, those pressures should be added
to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need
to be given the wall dimensions and the slope of the backfill in order to provide the appropriate
' design earth pressures.
Heavy construction equipment should not be operated behind retaining and foundation walls within
' a distance equal to the height of a wall, unless the walls are designed for the additional lateral
' pressures resulting from the equipment. The wall design criteria assume that the backfill will be
well compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should
be accomplished with hand-operated equipment to prevent the walls from being overloaded by the
higher soil forces that occur during compacti�-�
Retainin_q Wal!Backfill and Waterproofing
Backfill placed behind retaining or foundation walls should be coarse, free-draining
� structural fill containing no organics. This backfill should contain no more than 5 percent silt
or clay particles and have no gravel greater than 4 inches in diameter. The percentage of
particles passing the No. 4 sieve should be between 25 and 70 percent. If the native sand
is used as backfill, a minimum �12-inch width of free-draining gravel should be placed
�, against the backfilled retaining walls. The drainage composites should be hydraulically
connected to the foundation drain system. Free-draining backfill or gravel should be used
for the entire width of the backfill where seepage is encountered. For increased protection,
� drainage composites should be placed along cut slope faces, and the walls should be
backfilled entirely with free-draining soil.
The purpose of these backfill requirements is to ensure that the design criteria for a
retaining wall are not exceeded because of a buifd-up of hydrostatic pressure behind the
wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively
► impermeable soil or topsoil, or the surface should be paved. The ground surFace must also
� slope away from backfilled walls to reduce the potential for surFace water to percolate into
_ the backfill. The section entitled Genera/ Earthwork and Structura/ FiN contains
recommendations regarding the placement and compaction of structural fill behind retaining
and foundation walls.
The above recommendations are not intended to waterproof below-grade walls. Over time,
the performance of subsurface drainage systems can degrade, subsurface groundwater
flow patterns can change, and utilities can break or develop leaks. Therefore, waterproofing
should be provided where future seepage through the walls is not acceptable. This typically
includes limiting cold-joints and wall penetrations, and using bentonite panels or
membranes on the outside of the walls. Waterproofing systems should be installed by an
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 7
experienced contractor familiar with the anticipated construction and subsurFace conditions.
Applying a thin coat of asphalt emulsion to the outside face of a wall is not considered
waterproofing, and will only help to reduce moisture generated from water vapor or capillary
action from seeping through the concrete. As with any project, adequate ventilation of
� basement and crawl space areas is important to prevent a build up of water vapor that is
commonly transmitted through concrete walls from the surrounding soil, even when
seepage is not present. This is appropriate even when waterproofing is applied to the
outside of foundation and retaining wa►Is.
SLABS-ON-GRADE
The building floors may be constructed as slabs-on-grade atop non-organic native soils. The
subgrade soil must be in a firm, non-yielding condition at the time of slab construction or underslab
fill placement. Any soft areas encountered should be excavated and replaced with select, imported
structural fill.
All slabs-on-grade should be underlain by a capillary break or drainage layer consisting of
' minimum 4-inch thickness of coarse, free-draining structural fill with a gradation similar to th
discussed in Permanent Foundation and Retaining Walls. As noted by the American Concrete
Institute (ACI) in the Guides for Concrefe Floor and Slab Structures, proper moisture protection is
' desirable immediately below any on-grade slab that will be covered by tile, wood, carpet,
impermeable floor coverings, or any moisture-sensitive equipment or products. ACI also notes th�+
vapor retarders, such as 6-mil plastic sheeting, are typically used. A vapor retarder is defined as =
material with a permeance of less than 0.3 US perms per square foot (psfl per hour, as determine;
by ASTM E 96. It is possible that concrete admixtures may meet this specification, although the
manufacturers of the admixtures should be consulted. Where plastic sheeting is used under slabs.
joints should overlap by at least 6 inches and be sealed with adhesive tape. The sheeting should
extend to the foundation walls for maximum vapor protection. If no potential for vapor passage
through the slab is desired, a vapor barrier should be used. A vapor barrier, as defined by ACI, is a
product with a water transmission rate of 0.00 perms per square foot per hour when tested in
accordance with ASTM E 96. Reinforced membranes having sealed overlaps can meet this
- requirement.
In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well-graded ,
compactable granular material, such as a 5/8-inch-minus crushed rock pavement base, be placed
over the vapor retarder or barrier to protect them during slab construction and to act as a "blotter"
for more even curing of the concrete slab. However, more current literature indicates that long-
term vapor problems could result where the protection/blotter material becomes wet before the slab
placement occurs. This is especially an issue in areas with wet climates, such as the Puget Sound.
Therefore, if there is a potential that the protection/blotter material will become wet before the slab
is installed, ACI now recommends that no protectionlblotter material be used. However, they then
recommend that the joint spacing in the slab be reduced, a low shrinkage concrete mixture be
used, and "other measures" (steel reinforcing, etc.) be utilized to reduce the potential for irregular
slab curing and excessive shrinkage cracking due to uneven curing.
We recommend that the contractor, architect, structural engineer, and the owner discuss these
issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance
on the use of the protection/blotter material.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 8
EXCAVATIONS AND SLOPES
Excavation slopes should not exceed the limits specified in local, state, and national government
safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in
unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be
made near property boundaries, or existing utilities and structures. Based upon Washington
Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as
� Type B. Therefore, temporary cut slopes greater than 4 feet in height cannot be excavated at an
inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the
bottom of a cut.
The above-recommended temporary slope inclination is based on what has been successful at
other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a
relatively short duration to allow for the construction of foundations, retaining wal)s, or utilities.
Temporary cut slopes should be protected with plastic sheeting during wet weather. The cut slopes
should also be backfilled or retained as soon as possible to reduce the potential for instability.
Please note that sand can cave suddenly and without warning. Excavation, foundation, and utility
contractors should be made especially aware of this potential danger.
All permanent cuts into native soil and slopes constructed of compacted fill should be inclined no
steeper than 2.5:1 (H:�. To reduce the potential for shallow sloughing, fill must be compacted to
� the face of these slopes. This can be accomplished by overbuilding the compacted �fill and then
trimming it back to its final inclination. Adequate compaction of the slope face is important for long-
term stability and is necessary to prevent excessive settlement of patios, slabs, foundations, or
other improvements that may be placed near the edge of the slope.
Water should not be concentrated to flow uncontrolled over the top of any temporary or permanent
slope. All permanently exposed slopes should be seeded with an appropriate species of vegetation
to reduce erosion and improve the stability of the surficial layer of soil. Any disturbance to the
existing steep slope outside of the building limits may reduce the stability of the slope. Damage to
the existing vegetation and ground should be minimized, and any disturbed areas should be
revegetated as soon as possible. Soil from the excavation should not be placed on the slope, and
this may require the off-site disposal of any surplus soil.
DRA/NAGE CONSIDERATIONS
Foundation drains should be used along the perimeter of all foundations and basement walls.
Drains should also be placed at the base of all earth-retaining walls. These drains should be
surrounded by at least 6 inches of 1-inch-minus, washed rock and then wrapped in non-woven,
geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material). At its highest point, a
perForated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a
crawl space, and it should be sloped for drainage. All roof and surface water drains must be kept
separate from the foundation drain system. A typical drain detail is attached to this report as Plate
9. For the best long-term performance, perforated PVC pipe is recommended for all subsurface
drains.
As a minimum, a vapor retarder, as defined in the Slabs-On-Grade section should be provided in
� any crawl space area to limit the transmission of water vapor from the underlying soils. Also, an
outlet drain is recommended for all crawl spaces to prevent a build up of any water that may
bypass the footing drains.
GEOTECH CONSULTANTS, WC.
Cambridge Homes JN 02326
September 9, 2002 Page 9
No groundwater was observed during our fieldwork. If seepage is encountered in an excavation, it
should be drained from the site by directing it through drainage ditches, perforated pipe, or French ,
drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of '
the excavation.
The excavations should be graded so that surface water is directed away from the tops of slopes. 'I
Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be '
� constructed. Final site grading in areas adjacent to the residences should slope away at least 2
percent, except where the area is paved. Surface drains should be provided where necessary to
prevent ponding of water behind foundation or retaining walls. Water from roof, storm water, and
foundation drains should not be discharged onto slopes.
GENERAL EARTHWORK AND STRUCTURAL F1LL
All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and
other deleterious material. The stripped or removed materials should not be mixed with any
materials to be used as structural fill, but they could be used in non-structural areas, such as
landscape beds.
Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building,
behind permanent retaining or foundation walls, or in other areas where the underlying soil needs
to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or
� near, the optimum moisture content. The optimum moisture content is that moisture content that
results in the greatest compacted dry density. The moisture content of fill is very important and
must be closely controlled during the filling and compaction process.
The allowable thickness of the fill lift will depend on the material type selected, the compaction
equipment used, and the number of passes made to compact the lift. The loose lift thickness
should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not
sufficiently compacted, it can be recompacted before another lift is placed. This eliminates the
need to remove the fill to achieve the required compaction. The following table presents
recommended relative compactions for structural fill:
� � �
, � , �
Beneath footings, slabs 95%
or walkwa s
Filled slopes and behind 90%
retainin walls
95%for upper 12 inches of
Beneath pavements subgrade; 90% below that
level
_ Where: Minimum Relative Compaction is the ratio, expressed in
percentages, of the compacted dry density to the maximum dry
density, as determined in accordance with ASTM Test
Designation D 1557-91 (Modified Proctor).
Structural fill that will be placed in wet weather should consist of a coarse, granular soil with a silt or
clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve
should be measured from that portion of soil passing the three-quarter-inch sieve.
GEOTECH CONSULTANTS, INC
Cambridge Homes JN 02326
September 9, 2002 Page 10
LIM/TAT/ONS
The analyses, conclusions, and recommendations contained in this report are based on site
conditions as they existed at the time of our exploration and assume that the soil and groundwater
conditions encountered in the test pits are representative of subsurface conditions on the site. If
the subsurface conditions encountered during construction are significantly different from those
observed in our explorations, we should be advised at once so that we can review these conditions
and reconsider our recommendations where necessary. Unanticipated soil conditions are
commonly encountered on construction sites and cannot be fully anticipated by merely taking soil
samples in test pits. Subsurface conditions can also vary between exploration locations. Such
unexpected conditions frequently require making additional expenditures to attain a properly
� constructed project. It is recommended that the owner consider providing a contingency fund to
accommodate such potential extra costs and risks. This is a standard recommendation for all
projects.
The recommendations presented in this report are directed toward the protection of onfy the
proposed residences from damage due to slope movement. Predicting the future behavior of steep
slopes and the potential effects of development on their stability is an inexact and imperfect
science that is currently based mostly on the past behavior of slopes with similar characteristics.
Landslides and soil movement can occur on steep slopes before, during, or after the development
of property. The property owners must ultimately accept the possibility that some slope movement
could occur, resulting in possible loss of ground or damage to the facilities west of the proposed
residences.
This report has been prepared for the exclusive use of Cambridge Homes and its representatives
for specific application to this project and site. Our recommendations and conclusions are based
on observed site materials, selective laboratory testing, and engineering analyses. Our
conclusions and recommendations are professional opinions derived in accordance with current
standards of practice within the scope of our services and within budget and time constraints. No
warranty is expressed or implied. The scope of our services does not include services related to
construction safety precautions, and our recommendations are not intended to direct the
contractor's methods, techniques, sequences, or procedures, except as specifically described in
our report for consideration in design.
ADDIT/ONAL SERV/CES
In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide
geotechnical consultation, testing, and observation services during construction. This is to confirm
that subsurface conditions are consistent with those indicated by our exploration, to evaluate
whether earthwork and foundation construction activities comply with the general intent of the
recommendations presented 'in this report, and to provide suggestions for design changes in the
event subsurface conditions differ from those anticipated prior to the start of construction.
However, our work would not include the supervision or direction of the actual work of the
contractor and its employees or agents. Also, job and site safety, and dimensional measurements,
will be the responsibility of the contractor.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 11
The following plates are attached to complete this report:
Piate 1 Vicinity Map
Plate 2 Site Exploration Plan
Plates 3 - 5 Test Pit Logs
Plate 6 - 8 Grain Size Analysis
Plate 9 Typical Footing Drain
Appendix A Slope Stability Analysis
We appreciate the opportunity to be of service on this project. If you have any questions, or if we
may be of further service, please do not hesitate to contact us.
Respectfully submitted,
GEOTECH CONSULTANTS, INC. �
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Kristopher T. Hauck
Geotechnical Engineer
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VICINITY MAP
� GEOTECH 3785 Lincoln Avenue Northeast
CONSUI,TAN'I'S,nvc. Renton, Washington
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� .��—,�_ Job No: Date: Plate:
02326 Sept. 2�02 �
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' SITE EXPLORATION PLAN
� GEOTECH 3785 Lincoln Avenue Northeast
CONSLJLTANTS,nvc. Renton, Washington
' �
�� �--�� Job No: Date: Plate:
' 02326 Sept. 2002 No Scale 2
T
_ I
��lo���"ti a�� y TEST PIT 1
9� ��p� `��� �5G Description
To ���
Brown SAND, occasional gravei, medium-grained, damp to moist, loose (FILL)
FI LL
o ��
m=14.0'/ Red-brown, silty SAND, fine-to medium-grained, abundant roots, moist, loose
5 � snn-
SP an-gray, gravelly SAND, medium-grained, moist, medium-dense
m=5.9%
* Test Pit was terminated at 8 feet on August 27, 2002.
10 * No groundwater seepage was observed during excavation.
* Slight caving was observed from 0 to 4 feet during excavation.
15
� � �� TEST PIT 2
� � �
�4� �'����`�aaro�'� g�� .
9 (',° � � Description
To soil
1 SM Tan-brown, slightly silry SAND, occasional gravel, damp to moist, loose
SP
i
Tan-gray SAND, occasional gravel, medium-grained, moist, medium-dense
5
; SP
10
SP Gray, slightly silty SAND, medium-grained, moist, medium-dense to dense
SM
" Test Pit was terminated at 13 feet on August 27, 2002.
15 " No groundwater seepage was observed during excavation.
* Slight caving was observed between � and 4 feet during excavation.
� ' TEST PIT LOGS
' � GEOTECH 3785 Lincoln Avenue Northeast
I � CONSLTLTAI`'TS,nvc. Renton, Washington
� � Job No: Date: Logged by: Plate:
��� 02326 Sept.2002 KTH 3
�,r�lo���rti a�e 5 TEST PIT 3
9�4 ��p� `��� �5G Description
To soi�
Tan-brown, gravelly SAND, medium-grained, damp to moist, loose
SP
Tan-gray SAND, occasional gravel, medium-grained, moist, medium-dense
5
becomes medium-dense to dense, without gravel
SP
10
" Test Pit was terminated at 11 feet on August 27, 2002.
* No groundwater seepage was observed during excavation.
" Slight caving was observed from 0 to 4 feet during excavation.
15
�,� ,���,��+�� TEST PIT 4
4� ������b'��� �
�' CP �Co- �S5 Description
Old To soil
SP Tan-brown, slight(y silty SAND, occasional gravel, fine-grained, damp, loose
SM
Tan-gray, gravelly SAND, medium-grained, moist, medium-dense
5
SP
. - becomes medium-to coarse-grained, without gravel
10 * Test Pit was terminated at 9 feet on August 27, 2002.
* No groundwater seepage was observed during excavation.
" No caving was observed during excavation.
15
� ' TEST PIT LOGS
� GEOTECH 3785 Lincoln Avenue Northeast
I � CONSUI,TA*I'TS,nvc. Renton, Washington
__�� Job No: Date: Logged by: Plate:
02326 Sept. 2002 KTH 4
1 �� `\
I ���o,��e�,�o-tie�e G5 TEST PIT 5
� G° �� �}5 Description
Crushed rodc 5/8'-
� sM ; Red-brown, silty SAND, fine-grained, moist to damp, loose
' Gray-tan, gravelly SAND, medium- to coarse-grained, moist, medium-dense
Im=3.0%
5 sP - beoomes medium-dense to dense
�
10 " Test Pit was terminated at 9 feet on August 27, 2002.
� ' No groundwater seepage was observed during excavation.
* No caving was observed during excavation.
�
15
�
�
�
�
�
�
�
�
�
� ' TEST PIT LOGS
� GEOTECH 3785 Lincoln Avenue Northeast
I � CONSULTANTS,nvc. Renton, Washington
' � � Job No: Date: Logged by: Plate:
--�� 02326 Sept.2002 KTH 5
I Sample Data:
Test Pit/Boring: 1 Pan#: 17N
Sample: 1 Tare: 0
IDepth: 4' Wet Weight: 551.6
Dry WeigM: 483.7
Wash Data: %Ma'tsture: 14.0
IDry WeigM(before wash): 483.7 91'8f11S
Dry WeigM(after wash): 401 9�8fT1S
I' wasned soii weignt: 82.7 grams
Soil Retained in pan 0.3 g('8ms
I ve =; +ewe - e� ' ;' vc
inches or Alo.: mrr►. j9raans} Percent Retairied Passe�d
>E�h � !Total ' ;:.:Ea�h_' � >Totat �otal :.
____1_U2 � 38.10 � OA� 0.0� 0.0� OA� __ 100_0
I ----h____-----+---------�----------+-----------F------------�--- .
3/4 � 19.05 � 0.0� 0.0� 0.01 0.0� 100.0
----------------�--------y---------;---------y----------;------------y----------
318 � 9.53 � 43.2� 43.2� 8.9� 8.9� 91.1
��-���'r�����r������������'����'��►'--������'.w'---�-��-a��'�����-�.w---�--�r
I � � i � i i
4 ; 4.75 ; 27.4; 70.6; 5.7; 14.6; 85.4
_���_������_��M�����������������_�����_����Mr�r�������___�������__�
10 ; 2.00 ; 26.6; 97.2; 5.5; 20.1; 79.9
--_��'___'___r��-»-�_T_'�__-_'r_-__�-"'T�______'�r��____--__r_�___-__--
40 � 0.43 � 107.7� 204.9� 22.2� __42.3� 57.7
I -------------�---------+---------F---------+-----------F---- --+--------
_____ 100_ � 0.15 173.0 377.9� 35.7 78.0 22.0
----;---------�---------t------_--.�.----------f------------�;----------
Z00 � 0.08 � 23.7� 4Q1.6� 4.9� 82.9� 17.1
������r__������L��������i�M�������L����������i����������L������������.L�����������
I <200 ; 0.00 ; 83.0; 484.6; 17.1; 100.0; '
7otat '. : :484.6 `'��fl.Z «-fl:2
_ _ __ _ _ _. _ _ ..__ .. __
i
sieve oper,irrg�rnm.) '
100.00 1 D.DO 1.00 0.10 0.01
� 100
100.0 100.0 � � I � � �
91.1 � - 80
85.4
79.9� 70 �
�
60 u
m
' 57J 50 «
( I i � �
� I � 30 a
22.0� 20
� 17.1 � 10
i . , � i � o !
�
' GRAIN SIZE AI�TALYSIS
� GEOTECH 3785 Lincoln Avenue Northeast
CONSULTANI'S,nvc. Renton, Washington
Job No: Date: Plate:
02326 Sept. 20�2 6
I Sample Data:
Test Pit/Boting: 1 Pan#: 13N
samp�e: 2 Tare: 0
IDepth: 7' Wet Weight: 554.1
Dry WeigM: 523
Wash Data: %Moisture: 5.s
IDry Weight(before wash): 523 gramS
Dry Weight(atter wash): 491.3 grdms
I Washed Soil Weight: 31.7 gfBfTls
Sal Retained in pan 0.1 grams
- �exe ig _ rcen
lnChes or No. rtm. (gnmsj Percent I�efaineti Passed
. Each � Toial i Each � To�al 'Total <
_�_1 1/2 ____� 38.10 1 0.0� 0.0� 0.0� 0.0� 100.0
f----------+--------F---------+----------�-----------�----------- .
314 � 19.05 � Q.O� O.D� 0.0� O.Q� 10Q.0
-------------;----------y--------�j---------1------------;------------;------------
3/8 � 9.53 ; 27.4� 27.4� 5.3� 5.3� 94.7
��������M�����F���������i.�������MM�������i�����w����4����������i����������
4 ; 4.75 ; 31.0; 58.4; 6.0; 11.2; 88.8
_�_�__�������*��������.�.�����r»����«».r.�__���__�__r�__����_..�������������
10 ; 2.00 ; 23.6; 82.0; 4.5; 15.8; 84.2
-'���__�'___�____--_r_�._ ___r_'w_�-r___-------r_-_______"_r_'--_-��-
______40____ � 0.43 � 157.7� 239.7� 30.3� 46.1� 53.9
--�----------�----------h-----+-----------F----------+-----------
_____ 100 � 0.15 � 228.9� 468.6� 44.0� 90.0� 1 Q.0
---------F----------1---------t----------;------------t-----------}----------
200 � 0.08 � 20.0� 488.6� 3.8� 93.9� 6.1
_��_�_--�__'___�____��_���������__a�__--_"'_.i__��____��_____�_�_--_i.��_____
<200 ; 0.00 ; 31.8; 520.4; 6.1� 1Q0.0; �
_
Total ' S20.4 99.5 ' -0.5
i, Sieve Opening(rrm)
100.00 10.00 1.00 0.10 0.01
100
100.0 100.0 ' � � �
94.7 ' � ,
88.8 842 �
I �� d I
`� y i
1 I A
�.9 i � C
I � �
i y
� a
20 �
� � I , 10 �
I � 10A s� , i i I � i
I
' � � GRAIN SIZE ANALYSIS
� GEOTECH 3785 Lincoln Avenue Northeast
� � CONSLILTAN'I'S,nvc. Renton, Washington
�_� Job No: Date: Plate:
� 02326 Sept. 2002 7
Sample Data:
Test PitlBoring: 5 Pan#: 14N
Sample: 1 Tare: 0
oe�cr,: 3' w�t w�gnt: 551
�ry wei9rn: 534.7
Wash Data: %Masture: 3.0
Dry Weight(before wash): 534.7 grams
orywei�nt�anervrasn�: 516.2 grams
� wasned soii weiynt: 18.5 grams
Soil Retained in pan 0.1 g�ams
I � `:: _: - 8_ _ ' ' >' «
inches or tafo: :t�rri. �grar:es} `: Percent Retai[�ed Passed
i Ea�h : t !'Total -Eash ': � Tota! ; '.�ntal
11/2 � 38.10 � 0.0� 0.0� 0.0� 0.0� 100.0
I ---------------f----------+----------F---------+----------F------------+-----------
3/4 � 19.05 � 14.5� 14.5� 2.7� 2.7� 97.3
----------------;---------i----------;---------y-----------L------------1-----------
3/8 � 9.53 ; 57.6� 72.1� 10.8f 13.5� 86.5
I ----- ----- �~_------+----------�--------+----------�------------�------------
� 4 ; 4.75 ; 52.5; 124.6; 9.8; 23.3; 76.7
' �_ __N_�'-____rt.��"-__.r�'__'__..'._�----__�--t_�_��__'_�.._'__'_.-.-_
10 ; 2.00 ; 35.9; 160.5; 6.7; 30.1; 69.9
'�_"�___-_"_r______"���"_'-r_""---�-T-_-_�r--�r�'�__-'_��-r�_�'_"-_
I 40 � 0.43 � 199.8� 360.3� 37.4 67.5� _�32_5
---------------F--------+----------h-------+----------F------------�----
100 � 0.15 � 149.3� 509.6� 28.0� 95.4� 4.6
_��___________j__________l___��___j__�_�___J__�_��__�i_�___�___�.�__���___
200 � 0.08 � 5.7� 515.3� 1.1� 96.5� 3.5
����� �� L��������i.������� L _�������i��������� 6 �� �����J� ���
I <200 ; 0.00 ; 18.6; 533.9; 3.5; 100.0; �
'Total. I fi33.9 �9.3 ' ;Q:'1
_ ____ _ _ .::. _ _ __...._ _ ___....... __ ..
ISieve Opening(mm.)
100.00 10.00 1.00 0.10 0.01
I 100
100.0 97.3 � � �
90
� �
86.5 � 80
I 76.7 70 �
d
�.9' 60 u�i
i i � a
I � �
� � i
32.5 � a �
i I �
I 1 I 20 I
i I ��
� i i , 4.6 3.5' I � I
I
� � GRAIN SIZE ANALYSIS
�, �` GEOTECH 3785 Lincoln Avenue Northeast
� � CONSLJLTAN'I'S,nvc. Renton, Washington
� Job No: ate: P ate:
I 02326 Sept. 2002 8
r--- —
I
I Slope backfill away from
foundation. Provide surFace
I drains where necessary.
�
I Tightline Roof Drain
(Do not connect to footing drain)
Backfill �a
I (See text for � ;
requirements) e �
I � Vapor Retarder
Nonwoven Geotextile ; �; ' or Barrier
Filter Fabric Q
I Washed Rock �'�- g�qg
. .
(7/8" mm. s¢e)
p O .p O".p..0' •D.'a� D.'�� �.-a� •D..p".p .a
o �Q�o p �e�p o.;'�'o p c.;'°�p o.�.o.0 p c.�'°c��•c��
o c c u e c �..0 c o �J°�o.o-•°"CQ o�o;,�'cF o o ;P°cp o•o e°C
I o0o O OoOoO� cc�.'•a.cp� a.op� °.o,Q�,Qo:a,o��o°e o,��
��O�O °Q°O .��.o . b n.o . .•p�_.o .•o'�.o . 'o.�.o . •o � O .
0 0 o c . �•
�o��� o�o�o . !I, i i
„ °o°o° o°c° �
6 min. o 0 0 �� �
I ao
Free-Draining Gravel
I (if appropriate}
4" Perforated Hard PVC Pipe
(Invert at least 6 inches below
slab or crawl space. Slope to
� drain to appropriate outfall.
Place holes downward.)
�
I NOTES:
(1) In crawl spaces, provide an outlet drain to prevent buildup of water that
bypasses the perimeter footing drains.
� (2) Refer to report text #or additional drainage and waterproofing considerations.
� � FODTING DRAIN DETAIL
� GEOTECH 3785 Lincoln Avenue Northeast
� CONSULTANTS,INC. Renton, Washington
0 0: Date: ca e: Plate:
— 02326 Sept. 2002 N�t to Scale 9
APPENDIX A - SLOPE STABILI TY�t IVALYSIS
Proposed Elsa Ridge Subdivision
3785 Lincoln Avenue Northeast
Renton, Washington
GEOTECH CONSULTANTS, INC.
Profile.out
*�` PCSTABL6 �"
by
Purdue University
modified by
Peter J. Bosscher
University of Wisconsin-Madison
--Slope Stability Analysis-- �
Simplified Janbu, Simplified Bishop
or Spencer's Method of Slices
PROBLEM DESCRIPTION
BOUNDARY COORDINATES
3 Top Boundaries
3 Total Boundaries
Boundary X-Left Y-Left X-Right Y-Right Soil Type
No. (ft) (ft) (ft) (ft) Below Bnd
1 0.00 50.00 50.00 50.00 1
2 50.00 50.00 115.00 100.00 1
3 115.00 100.00 180.00 100.00 1
ISOTROPIC SOIL PARAMETERS
1 Type(s) of Soil
Soil Tofal Saturated Cohesion Friction Pore Pressure Piez.
Type Unit 11Vt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pc� (pcfl (psfl (deg) Param. (psfl No.
Page i
- -�
Prof�le.ouL
1 110.0 115.0 0.� 35.0 0.00 0.0 0 I
A Critical Failure Surface Searching Method, Using A Random
Technique For Generating Circular Surfaces, Has Been Specified.
900 Trial Surfaces Have Been Generated.
30 Surtaces Initiate From Each Of 30 Paints Equally Spaced
Along The Ground Su�face Between X= 35.00 ft.
and X= 90.00 ft.
Each Surface Terminates Between X= 16Q.00 ft.
and X= 165.00 ft.
Unless Further Limitations Were Imposed, The Minimum Elevation
At Which A Surface Extends Is Y= 0.00 ft.
5.00 ft. Line Segments Define Each Trial Failure Surface.
Following Are Displayed The Ten Most Critical Of The Trial
Failure Surfaces Examined. They Are Ordered - Most Criticai
First.
* * Safefy Factors Are Calculated By The Modified Bishop Method * "
Failure Surface Specified By 26 Coordinate Points
Point X-Surf Y-Surt
No. (�) (�)
1 50.17 50.13
2 54.91 51.75
3 59.63 53.39
4 64.33 55.08
5 69.03 56.80
6 73.71 58.55
7 78.38 60.34
8 83.04 62.16
9 87.68 64.02
Paae 2
Profile.out ',
10 92.31 65.91 ,
11 96.92 67.84
12 101.52 69.80
13 106.10 71.80
14 110.67 73.83
15 115.23 75.90
16 119.76 77.99
17 124.29 80.13
18 128.79 82.29 �
19 133.28 84.49
20 137.76 86.73
21 142.21 89.00 ,
22 146.65 91.30 ��
23 151.07 93.63
24 155.48 96.00
25 159.86 98.40
26 162.75 100.00
Circle Center At X= -163.0 ; Y= 683.5 and Radius, 668.3
*" 1.573 **' i
Failure Surface Specified By 26 Coorclinate Points
Point X-Surf Y-Surf
No. (�) (�)
1 50.17 50.13
2 54.94 51.66
3 59.68 53.22
4 64.42 54.83
5 69.14 56.48
6 73.84 58.17
7 78.53 59.91
8 83.21 6t.68
9 87.86 63.50
10 92.51 65.36
11 97.13 67.26
12 101.74 69.20
13 106.33 71.18
14 110.90 73.21
15 115.45 75.27
16 119.99 77.38
17 124.51 79.52
18 129.00 81.71
19 133.48 83.93
20 137.94 86.20
21 142.38 88.50
22 146.79 90.85
Faa2 3
Safery Factors
112.50---- ------ -- - - - --
1.57
�-- _ _ ___-__------_ ---._ _ _.......__.
1.58
��/ �-� 1.80
i
90.00 / //� � 1.81
%`� ///i
i /��
i � ! 1.82
i /
i ! / -%
�/` ���' �j� 1.82
67.50 ��i��i' �� / 1.82
/%� �'-� ��/�
i /�i'� 1.63
.;i �' �
i r '
,i'�� 1.85
�
�
_ _..... ------
1.B5
45.00
22.5
_.-''.__'_.'_ '_-T_ - �',
0 22.50 45.00 67.50 90.00 112.50 135.00 157.50 180.00
Profile.ou�
*'` PCSTABL6 �`
by
Purdue University
modified by
Peter J. Bosscher
University of Wisconsin-Madison
—Slope Stability Analysis--
Simplified Janbu, Simplified Bishop
or Spencer s Method of Slices
PROBLEM DESCRIPTION
�
BOUNDARY COORDINATES
3 Top Boundaries
3 Total Boundaries
Boundary X-Left Y-Left X-Right Y-Right Soil Type
No. (ft) (ft) (ft) (ft) Below Bnd
1 0.00 50.00 50.00 50.00 1
2 50.00 50.00 115.00 100.00 1
3 115.00 100.OQ 180.00 100.00 1
ISOTROPIC SOIL PARAMETERS
1 Type(s) of Soil
Soif Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pc� (pc� (psf} (deg) Param. (ps� No.
Profile.out
1 110.0 115.0 0.0 35.0 0.00 0.0 0
A Horizontal Earthquake Loading Coefficient
Of0.150 Has Been Assigned
A Vertical Earthquake Loading Coefficient
Of0.000 Has Been Assigned
Cavitation Pressure = 0.0 psf
A Critical Failure Surface Searching Method, Using A Random
Technique For Generating Circular Surfaces, Has Been Specified.
900 Trial Surfaces Have Been Generated.
30 Surtaces Initiate From Each Of 30 Points Equalfy Spaced
Along The Ground Surface Between X= 35.00 ft.
and X= 90.00 ft.
Each Surface Terminates Between X= 160.00 ft.
and X= 165.00 ft.
Unless Further Limitations Were Imposed, The Minimum Elevation
At Which A Surface Extends Is Y = 0.00 ft.
5.00 ft. Line Segments Define Each Trial Failure Surface.
Following Are Displayed The Ten Most Critical Of The Trial
Failure Surfaces Examined. They Are Ordered - Most Critical
First.
"* Safety Factors Are Calculated By The Modified Bishop Method "*
Failure Surface Specified By 26 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
?age �
Profile.out
1 50.17 50.13
2 54.91 51.75 I
3 59.63 53.39 �
4 64.33 55.08
5 69.03 56.80
6 73.71 58.55
7 78.38 60.34
8 83.04 62.16
9 87.68 64.02
10 92_31 65_91 I
11 96.92 67.84
12 101.52 69.80
13 106.10 71.80
14 110.67 73.83
15 115.23 75.90
16 119.76 77.99
17 124.29 80.13
18 128.79 82.29
19 133.28 84.49
20 137.76 86.73
21 142.21 89.00
22 146.65 91.30
23 151.07 93.63
24 155.48 96.00 .
25 159.86 98.40
26 162.75 100.00
Circle Center At X= -163.0 ; Y = 683.5 and Radius, 668.3
**` 1.104 "*''
Failure Surface Specified By 26 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
1 50.17 50.13
2 54.94 51.66
3 59.68 53.22
4 64.42 54.83
5 69.14 56.48
6 73.84 58.17
7 78.53 59.91
8 83.21 61.68
9 87.86 63.50
10 92.51 65.36
11 97.13 67.26
12 101.74 69.20
Safery Factors
112.50 -- --------
1.10
1.11
,
% ./=� 1.12
/'' / /
90.00 � �!�� � 1.13
/i//
�/�%
i� �� / �.�3
� /
� � i
%� ,G o' / 1.13
67.50 ,i�"��� �' / 1.13
' �
/ .,,�-%��-//
%/ i/�� .'-- � 1.13
� � .,,. - �
:� � � i
i i' 1.14 '
f
-_ _ _.__ _-.__..- --___---- ."
i
1.15
45.00
1.?.5
0- - _____- -—r--�._. _-- ---
0 22.50 45.00 67.50 90.00 112.50 135.00 157.50 180.00
�
�
�
A
�
W
a
a
�
E L SA RID GE
Preliminary Technical
Information Report
City of Renton
Revised: September 12, 20(
Prepared for:
` Cambridge Homes
1800 NE 44t� Street
Renton, WA 98056
�R ��
��~��'�F WA J��
!
�
Q
Prepared By: �' � `'
� � �
, �
Robert Stewart � �,�
36 2�
�.n�,���1 TER�G`t��'� ,Ly U
Sf ONAL E� ���
Reviewed By: C�
- Jennifer A. Steig, P.E. EXPIRES 09/09/04
PCE Job No. CAMB-0001
City of Renton Development Services Division
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Rar�� ;PRC�J�GT Q�ilN�ft AN� Par� � PRCJ��CT�.QC�T1�N,4�D
PR�3.3EC�#'�#�1���E�f� �}ESCR I PT11��V
Project Owner: Cambridqe Homes, Inc. Project Name: Elsa Ridqe Short Plat
Address: 1800 NE 44th Street Location:
Renton, Washinqton 98056 Township: 24 North
Phone: (425) 271 - 2225
Range: 5 East
Project Engineer: Jennifer Steiq SE 1/4 Section: 32
Company: Peterson Consulting Engineers
Phone/Address: (425) 827-5874
4030 Lk Washinqton Blvd Suite 200
Kirkland. Wa. 98033
:;::F��3 '#''�P�f3F PEFtNI►T` :i
.. .. > Pa�t�# C7THER REVIEWS AN�PERf�aTS ; ;
.��f�U�}�T���:' ' < ' <: <
❑ Subdivision ❑ DFW HPA ❑ Shoreline Management
� Short Subdivision ❑ COE 404 � Rockery
� Grading ❑ DOE Dam Safety ❑ Structural Vaults
❑ Commercial ❑ FEMA Floodplain ❑ Other
❑ Other. ❑ COE Wetlands
P��'€5 SI'1'ECO�MUNITY:ANQ DR�1fi�AGE B�ASIN ' ' >
Community:
Newcastle Community Planning Area
Drainage Basin:
Cedar River Basin and Ma�Creek/East Lake Washington Sub-basins
G
P�G SiTE Cl-#1�#�R��'�R���'IC� < < ;
❑ River ❑ Floodplain
❑ Stream ❑ Wetlands
❑ Critical Stream Reach ❑ Seeps/Springs
❑ Depressions/Swales ❑ High Groundwater Table
❑ Lake ❑ Groundwater Recharge
� Steep Slopes ❑ Other
-
::> :: ,:
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Soil Type Slopes Erosion Potential Erosive Velocities
� EvC 5 %to 15°� Sliqht to Moderate Slow to Moderate
❑ Additional Sheets Attached
:.;:.:.;:.;::.�::..::..:.:..;::.;:;:.:;�..:...:... ..;-;:;.:;:..<:.:::.;::.;::.;::.;:.;:.;:;.;:.:::.;..:;�:.;.:::.:.:;.;:.:;::;:.:;.;:.:;.;:.;:.;::.;:.>;::.;::.;:.;: ...........
::>:::..:.....: ::.:::.::.::.:::::....:: :.::.::::.�.:::..:::::::.;.::.::.:..::.::::::,:.:,:::.::::.:;::>::>::::::>::::::>::::<::::;::::.>:;:>::;:;::;.
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�....�.�t��31�1�F.�.�.._�:��`r.....::;;:.::,.:..:>:::.:::::::::::::.............�:..:.. . ... ..._ . ..... .. .. :�.>:;::�:>:<:::>::::»>:::
REFERENCE LIMITATION/SITE CONSTRAINT
_ ❑
❑
❑
❑
❑
❑ Additional Sheets Attached
___.. .. . ... __ ___._._ _ __ __..... ___.... . __... _. ....... .... .. ._._ ......__ ___...__. .. . _.......
_._.. ._ .__._. ._ ..._. _ _ _ _.._ _......_ __ .__....... . . ___.........._ _ __. ._...__ __
__._ _ _.....__. __ _ __._ _.......... ... . ._.. ......__. __.. ... .... ....... .. ._....____._ .._.....
___. _....... . ... . __ ...__. __ _ . . ......... _ ......... ..___._ .......... . ...... . ...._... .___.... .._._.........
_. ..... __...._... _ _ ._ _... . ..._.... ._........ ......... .... . .......... . . __...... ......._.......... . _____...._
_._..._..... .. . _____ ..___ ___ _ _ __ __.. __._.._._. ...._ _.. ..._.....
_ _ _ _ _ _ __..._.. __.. . ........... ....... . ....._ ........ . __... .........
Pa�� :;���f�Q�tR�NI�NT� ;:::
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
� Clearing and Grading Restrictions � Ensure Operation of Pecmanent Facilities
; � Cover Practices � Flag Limits of SAO and open space
1 � Construdion Sequence preservation areas
❑ Other ❑ �her
r
l��r� 14 SL3R�A�E�AT�R SYSTEE�11 < ` �
❑ Grass Lined ❑ Tank � Infiitration Method of Anatysis
Channel 1998 KCRTS
❑ Vauft ❑ Depression
� Pipe System
❑ Energy Dissipator ❑ Flow Dispersal
❑ Open Channel � W��and
❑ Waiver
❑ Dry Pond � Stream ❑ Regional
❑ Wet Pond Detention
Brief Description of System Operation: Runoff from the roof areas will be conveyed via
tiahtline to an infiltartion trench. The infiltration trenches are sized per the requirements
set forth in papes 5-6 to 5-8 of the 1998 KCSWDM
Facility Related Site Limitations
Reference Facility Limitation
; , ::::>:
Par�.11 STE2U�'�i�RALA�IALYSIS , Part 12 EAS�MEtJTSItE�Ae'��
❑ Cast in Place Vautt ' ❑ Drainage Easement
❑ Retaining Wall ❑ Access Easement
❑ Rockery>4' High ❑ Native Growth Protection Easement
❑ Stnactural on Steep Slope � Tract
❑ Other ❑ Other
P�[t ��<SIG�#i4�'€3RE CjF�'R�F�SSIO?�JAL��CtNEEI�!
,
I or a civil engineer under my supervision my supervision have 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.
1
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'� ' ' 'I�,1�,-�' � �C,�1% � I 1 G�'�
; i ned/Date
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TABLE OF CONTENTS
SECTION 1 - PROJECT OVERVIEW.......................................................................................1
FIGURE1: VICI1vITY MAP...............................................................................................................2
FIGURE 2: EXISTING CONDITIONS MAP..........................................................................................3
FIGURE3: BASIIV MAP...................................................................................................................4
FIGURE 4: DEVELOPED CONDITIONS MAP .....................................................................................5
SECTION 2 - CONDITIONS AND REQUIREMENTS SUMMARY......................................6
SECTION 3 - OFF-SITE ANALYSIS..........................................................................................8
TASK 1: STUDY AREA DEFIlVITION&MAPS......................................................................8
TASK2: RESOURCE REVIEW.................................................................................................8
FIGURE5: SCS SOILS MAP.........................................................................................................10
TASK 3: FIELD ]NSPECTION.................................................................................................11
TASK 4: DR.AINAGE SYSTEM DESCRIPTION AND PROBLEM SCREENING...............11
SECTION 4-FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND
' DESIGN...............................................................................................................12
SECTION 5-CONVEYANCE SYSTEM ANALYSIS AND DESIGN.................................18
SECTION 6-SPECIAL REPORTS AND STUDIES .............................................................18
SECTION 7-OTHER PERMITS.............................................................................................18
SECTION 8-ESC ANALYSIS AND DESIGN .......................................................................18
SECTION 9-BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION
OFCOVENANT.................................................................................................18
SECTION 10-OPERATIONS AND MAINTENANCE MANUAL......................................18
Pete�son Consulting Engineers Page i
APPENDIX A
Sensitive area maps (printed from KC website)
KC Community Planning Map
Basin Map (printed from KC website}
EvC Soils Description
King County Drainage Complaint List
APPENDIX B
Basin Reconnaissance Summary Report for Lake Washington Sub-basin
APPENDIX C
King County Level I Downstream Flow Map
King County Level I Table (East Basin)
King County Level I Table (West Basin)
APPENDIX D
Geotech Report prepared by Geotech Consultants Inc. dated September 9, 2002
Peterson Consulting Engineers Page ii
______ _ _ __ �
Preliminary Technical Information Report for Elsa Ridge Revised September 12, 2002
SECTION 1 - PROJECT OVERVIEW I
The proposed project (Elsa Ridge) is the subdivision of 1.43 acres into 6 single-family
residences. The site is located within the City of Renton at 3785 Lincoln Avenue NE, see
Figure 1 —Vicinity Map. More generally, the site is located within the Northeast quarter of
Section 32, Township 24 North, and Range 5 East of the Willamette Meridian. The site is
surrounded by a single-family residence on the north, a vacant single-family lot on the west,
Lincoln Place NE on the south, and Lincoln Avenue NE on the east.
Existing Site Conditions:
The site is currently developed as a single-family residence with detached garage. On-site
vegetation consisting of grass, shrubs, and trees, see Figure 2: Eaosting Conditions Map. '�
The site is split into two drainage basins (east and west). The east basin slopes easterly at '
approximately 11% and the west basin slopes westerly at approximately 11% until reaching
the top of the steep slope area, see Figure 3: Basin Map. Access to the site is from Lincoln
Avenue NE.
Developed Site Conditions:
The developed site will contain 6 single-family lots and approximately 901ineal feet of shared
driveway with associated utilities, see Figure 4: Developed Conditions Map. Lots 1, 4, and
5, will gain access from Lincoln Avenue NE, Lots 2 and 3 from the shared driveway, and Lot
6 from Lincoln Place NE. No runoff from Tract A or the new residences will be directed
towards the steep slope area. Runoff from the new roof areas will be collected and conveyed
to individual infiltration trenches, while runoff from Tract A will be collected and discharged
into the existing tightline storm drainage system on the east side of Lincoln Avenue NE.
The steep slopes setbacks are per the report prepared by Geotech Consultants Inc. dated
September 9, 2002. A 10-foot non-disturbance buffer and a 35-foot foundation setback will
be imposed from the crest of the steep slope. It also states that the foundation setback can be
reduced to 30 feet if the new residences on lots 2 and 6 extend their foundations down to a
depth of at least 7 feet below the lowest surrounding grade. Please see the Geotech Report in
Appendix D for more information and details.
Peterson Consulting Engineers Page 1
Technical lnfo»nation Report for Elsa Ridge January 14, 2003
Figure 1: Vicinity Map
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GO� � ON—SITE ROAD = 0.03 AG EX. DITCH AREA TO� � ��,x i� I i
� TOTAL LAWN = 0.94 AC. L1 � � ,
` / D���r� \ � -I � ( 4030 Lake Was6ington
AREA TO DI TCH = 0.07 AC. l
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FIGURE 4
Preliminary Technical lnformation Report for Elsa Ridge Revisect September 12, 2002
SECTION 2 - CONDITIONS AND REQUIREMENTS
SUMMARY
King County Surface Water Design Manual Core Requirements:
1. Discharge at the Natural Location
Discharge from the site will be at the natural location. The runoff from the new
residences will be infiltrated on site while the runoff from Tract A and the driveway to
lot 6 will be collected and conveyed to the existing tightline storm drainage system on
Lincoln Avenue NE.
2. Off-Site AnalYsis
A Level 1 Downstream Analysis & Conceptual Drainage Report have been completed.
Refer to Section 3 of this report for more information.
3. Flow Control
Infiltration trenches are being used in order to meet the flow control requirement for
the new residences.
The new on-site impervious area from Tract A and the driveway to lot 6 are exempt
from flow control per page 1-27 of the 1998 KCSWDM. No. 1 —Impervious Surface
Exemption, states that ".....a project is exempt if less than S,000 square feet of new
impervious surface will be added and the project is not within a Landslide Drainage
Hazard Area." The total new impervious surface for tract A and the driveway to lot 6
is 1,600 sf and the site is not located in a landslide hazard drainage area per KC
Sensitive Area Maps. Therefore, flow control for Tract A or the driveway access to lot
6 is not required. Refer to Section 4 of this report for more information.
4. Conveyance Svstem
The proposed conveyance system will collect runoff and discharge it to the existing
conveyance system in Lincoln Avenue NE. Refer to Section 5 of this report for more
information.
5. Erosion and Sediment Control I�
A temporary Erosion and sediment control plan will be completed and designed in
accordance with the City of Renton Standards after preliminary review. Refer to the
Section 8 of this report for more information.
^', .r , �. C�, �. .�: r� ' ���'�_� - -- -- ------ ' . �I
Pt��li�r�i�zn��� 7'ccliraicnll?�t%���m�itio�t Re»��rr tor ELsc. Rid;c� Rcl�ise�f ScP?_°rrib�r i' �04�
King County Surface Water Desig❑ 1lanual Special Requirements:
1. Other Adopted Requirements
The site 1s not located wlthin any Critical Draina�c Area, ��9a;ter Drain�a�c Pt�ln, Basin
Plan, Lake Management Plan, or Shared Facility DrainaQe I'lan. 1-h��ero��c. thi� �ite i�
not subject to any specific adopted req. �
2. Floodplain/Floodway Delineation
The project does not contain nor is it iocateu neht to a �tream, �ai:z or ����tian� p�,
sensitive area maps. Therefore, no flood plain or floodway delineation is necessar
3. Flood Protection Facilitie
The project is not anticipated to be located wrtil:
therefore,no flood protection facilitie�s are required
4. Source Control
The proposed project does not meet the threshold for source control requiremen
5. Oil Control
The proposed project does not meet the threshold for oil control requirement
Peterson Constdting Enginee�s Page 7
Preliminary Technical Information Report for Elsa Ridge Revised September 12, 2002
SECTION 3 - OFF-SITE ANALYSIS
TASK 1: STUDY AREA DEFINITION & MAPS
The 1.43-acre site is located at 3785 Lincoln Avenue NE, in the City of Renton, Washington.
More generally, the site is located within the Northeast quarter of Section 32, Township 24
North, and Range 5 East of the Willamette Meridian, see Figure 1: Vicinity Map.
The site is located within two Sub-Basins of the Cedar River Drainage Basin as defined in the
King County Basin Reconnaissance Program Summary Volume II. The east section of the site
is in the East Lake Washington Sub-Basin and the west section is in the May Creek Sub-
Basin.
UPSTREAM DRAINAGE ANALYSIS
Upstream area tributary to the site consists of the western half of Lincoln Avenue NE and the
first 50 feet of Lincoln Place NE, see Figure 2—Existing Conditions Map.
TASK 2: RESOURCE REVIEW �
Support documentation for the following items may be found in the Appendix. '
Community Plan
The site is located in the Newcastle Community Planning Area (see KC Community Planning
Map in Appendix A).
Adopted Basin Plan / Basin Reconnaissance Summary Report
The site is located in both the East Lake Washington and May Creek Sub-Basin, of the Cedar
River Drainage Basin (see Basin Map in Appendix A and the Lake Washington Basin
Reconnaissance Report in Appendix B). Note however, the May Creek Basin Report is not
included in Volume II of the 1987 Basin Reconnaissance Reports, therefore, is not included in
the Appendix of this report.
'
Peterson Consulting Engif�ee�s Page 8
Preliminary Technical Information Report for Elsa Ridge Revised September 12, 2002
Critical Drainage Area
The site is not located in any of the Critical Drainage Areas as identified in the 1998 King
County Surface Water Design Manual.
Sensitive Area Folio
The King County Sensitive Area maps revealed that the site is located within an erosion
hazard area. The maps did not show the site located within any coalmine, stream / 100-year
floodplains, wetlands, or seismic hazard azeas. However the site is adjacent to a landslide
hazard drainage area (see Sensitive Area Maps in Appendix A).
SCS Soil Survey
The soils on the site, per the SCS Soils mapping, are EvC-Everett Gravelly Sandy Loam, see
Figure 4: SCS Soils Map, and EvC Soils Description in Appendix A. This soil type is also
confirmed on page 2 of the Geotech Report in Appendix D.
VVetlands Inventory
There are no classified wetlands on or near the site per the KC website.
Drainage Complaints
The drainage complaints list from King County Drainage Services can be found in Appendix
A. None of the complaints on the list appeared to be in the downstream flowpath of our site.
� �
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Peterson Consulting Engineers Page 9
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S MAP
EL SA RIDGE
SEC. 32, TWP. 24 N., RGE. 5 E., W M.
Q DWN. BY.• DATE.• JOB NO.
ETERSON 4030 Lake Washington
� ^ Blvd. N.E.,Suite 200 RSG 7/3/02 CAMB-0001
C O NS U LT!NG Kirkland, WA 98033
Z� Tel(425)827-5874 CHKD. BY.' SCALE.•
, .� Fax t425)822-7216 JAS FIGURE 5
Prelirnilzaiy Technical Inforrnation Report for Elsa Ridge Revised September 12, 2002
TASK 3: FIELD INSPECTION
A site visit was made on April 4, 2002, during a cloudy overcast day. The site is currently
developed as a single-family residence with detached garage. On-site vegetation consists of
grass, shrubs, and trees. Access to the site is from Lincoln Avenue NE, see Figure 1:
Vicinity Map. The field investigation confirms that the site is split into two drainage basins
(east and west). The east basin slopes easterly at approximately 11% and the west basin
slopes westerly at approximately 11%until reaching the top of a steep slope area where slopes
are greater than 40%, see Figure 2: Existing Conditions Map.
No visible drainage problems were observed on-site at the time of the field investigation.
TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM
SCREENING
Please reference KC Level 1 Tables and Downstream Flow Map in Appendix "C".
East Basin
Runoff sheet flows off the site in the northerly direction (point AA). Runoff enters a pipe
system (point AC —AE) and then discharges into a ditch (point AF). Runoff continues in the
ditch until entering a concrete pipe (point AG), which conveys the runoff beneath NE 40`h
Street. Runoff is then discharged back into the ditch (point AI�, and flows down gradient
where it enters a PVC pipe (point An. Runoff is conveyed under a driveway for
approximately 10 feet where it is then discharged into the ditch once again (point AJ). Runoff
continues to flow in this ditch, entering and exiting driveway culverts for the remainder of the
downstream analysis (point AK—AN).
West Basin
Runoff sheet flows off the site (point BA), and enters a wet area located west of the site(point
BB). The KC sensitive area maps web site and the KC Sensitive Area Map Folio from
December of 1990 did not indicate any inventoried wetlands in this area. Runoff leaves this
wet area and continues in the northerly direction in a ditch on the east side of Jones Avenue
NE (point BC). Runoff is discharged into a ditch (point BD) and flows in the easterly
direction until entering a culvert(point BE). Runoff is then conveyed under a road via a
culvert and then discharged into May Creek (point BF).
Pete�son Consulting Engineers Page 11
Preliminary Technical Information Report for Elsa Ridge Revised September 12, 2002
SECTION 4 - FLOW CONTROL AND WATER QUALITY
FACILITY ANALYSIS AND DESIGN
Existing Site Hydrology:
The site contains two basins, the east basin slopes easterly at approximately 11% and the west
basin slopes westerly at approximately 11% until reaching the top of a steep slope area where
on-site slopes are greater than 40%, please reference Figure 2: Ezisting Conditions Map,
and Figure 3: Basin Map.
The soils on the site are Everett gravelly sandy loam, as classified by the SCS Soil Survey
Map see Figure 5: SCS Soils Map. Everett soils are classified as outwash soils per page 3-25
of the 1998 KCSWDM. These soils are also confirmed by page 2 of the Geotech Report
found in Appendix D.
Developed Site Hydrology:
The developed site will contain 6 single-family lots and approximately 901ineal feet of shared
driveway with associated utilities, see Figure 4: Developed Conditions Map. Lots 1, 4, and �
5, will gain access from Lincoln Avenue NE, Lots 2 and 3 from the shared driveway, and Lot
6 from Lincoln place NE. No runoff from Tract A or the new residences will be directed
towards the steep slope area. Runoff from the new roof areas will be collected and conveyed
to individual infiltration trenches, and the new lawn areas will be naturally infiltrated. Runoff
from Tract A will be collected and discharged into the existing tightline storm drainage
system on the east side of Lincoln Avenue NE and the runoff from the driveway to access lot
6 will be collected and discharged into the existing ditch on the south side of Lincoln Place
NE.
Peterson Consulting Engineers Page 12
Preliminary Technical Information Report for Elsa Ridge Reviseci September 12, 2001
A. "1�'ew Residence/Roof Area" Flow Control
Per the flow chart on page 5-4 of the 1998 KCSWDM, if the lots are less than 22,000 sf and
contain medium sandy soils then downspout infiltration systems must be used as flow control
for the new residences. The geotech report in Appendix D by Geotech Consultants Inc.
confirms these soil conditions, therefore the roof areas will be infiltrated using downspout
infiltration h-enches. Per page 5-5 of the 1998 KCSWDM, for every 1,000 sf of roof area, soil
consisting of inedium sand requires 30 LF of infiltration trench. Please reference the civil
plans for more details. The runoff from the remainder of the site will be collected and
contained as described below.
"New Residence/Roof Areas" Water Quality
The pollution generating impervious surface from the new residences aze less than the 5,000
sf threshold; therefore per page 1-50, No. 1 Surface Area Exemption, of the 1998 KCSWDM
water quality treatment is not required for the roof areas.
B. "Tract A" Flow Control
The impervious surface in Tract A is less than the 5,000 square feet (s� threshold (see
description for Core Requirement #3, on page 6, of this report), therefore flow control
(detention) is not required for Tract A. The runoff from Tract A and the off-site frontage
improvements east of the property will be collected in a tightline system and discharged into
the existing conveyance system on the east side of Lincoln Avenue NE. Note, the roof areas
from the new residences and lawn areas are not included in the KCRTS calculations because
they are being infiltrated using downspout infiltration trenches.
"Tract A" Water Quality
The impervious surface in Tract A is less than the 5,000 sf threshold, therefore per page 1-50,
No. 1 Surface Area Exemption, of the 1998 KCSWDM water quality treatment is not required
for Tract A.
Petersorz Cof�rsa�lti�ig Engineers Page 13
Preliniir�cu-t� Tech�iicczl l�ij`orntatio�� R��noi7 jor�Elsa Rid�c° Rei�isc�ct Septeniber !', ?00'
"Tract A" Runoff Flo�vs
The 100-year flo�v from the developed site of Tract A is approximately 0.05 cfs, see KCRTS
output below. The capacity of the existing conveyance system in Lincoln Avenue NE is 9.06
cfs. This was found by taking the size, and slope of the existing storm system adjacent to the
site and having F1owMaster solve for "full flow capacit�', see F1owMaster below for the
capacity analysis of the existing storm system. During the 100-year storm event the runoff
from the site is only contributing approximately 0.6% of the total capacity for the existing
storm system. Therefore, there should be sufficient capacity in the existing storm system on
the east side of Lincoln Avenue NE.
Area Table
Total Area on site = 1.43 acres
Area of Residences = 0.32 acres (infiltrate on-
site)
Area to Lincoln Place Ditch = 0.07 acres
Total Lawn = 0.94 acres (infiltrate on-
site)
Area to Conveyance System = 0.10 acres
Impervious Road: Offsite = 0.07 acres ,
Impervious Road: On-site = 0.03 acres I
KCRTS Analysis
KCRTS Input
Scale Factor: Sea-Tac 1.0
Soil Type: Outwash
Areas (from above}: Impervious (On-site+ Off-site) = 0.10 acres
Pervious Lawn = 0 acres
Peterson Consulting Engineers Page 14 I'I
Preliminary Technical Information Report for Elsa Ridge Revised September 12, 2002
KCRTS Output
Flow Frequency Analysis
Time Series File:tracta.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
0.024 7 2/09/O1 2 :00 0.047 1 100.00 0.990
0.021 8 1/05/02 16:00 0.036 2 25.00 fl_960
0.029 3 12/08/02 18:00 0.029 3 10.00 0.900
0. 025 6 8/26/04 2:00 0.029 4 5.00 0.800
0.029 4 10/28/04 16:00 0.026 5 3 .00 0.667
0. 026 5 1/18/06 16:00 0.025 6 2.00 6.500
0.036 2 10/26/06 0:00 0.024 7 1.30 0.231
0. 047 1 1/09/08 6:00 0.021 8 1.10 0.091
Computed Peaks 0.044 50.00 0.980
FlowMaster Analysis
The pipe on the east side of Lincoln Avenue NE is an 18" diameter pipe. The slope of this
pipe was analyzed by F1owMaster, see slope table below.
Pipe Run No. Upstream Invert Downstream Invert Pipe Length Pipe Slope
1 134.58 115.89 294 ft 6.34%
F1owMaster Output (Existing Storm System Capacity)
Solv�for, • ' . Mannir�g's FarmWla � �
. '�.. - ' ' ,
, „_, _.. - - : .- �_�
Mannings Coefficient: 0.012 w Flaw Ar�a:, 1.$ fh�
Wekkad Perimeker: d.}1 ft
�' Slope: 0.006340 ftlfk = .. ` Tap�Jidth;(i� O,OO ft �
Depth: 1.50 -__ ft Critical Depth: 7.16 ft
, ; , Percent FuIL• 100.0 i
. . Diameter: 1 S �n Critical Slope:r— 0.�07058 fklik
-_- .
Discharge: 9.06 cfs Velocity:�-5.�3 ftls '
, -._
_.
. °' - .- Ve(ociky N ead:,, 0.41 ft.
_' Speci�ic Ener�y:� 1.91 ft
:'; :�� ' '_. FroudeNumber.� 0.00 .
' Maximum Discharge: 9.75 cfs
Discharge Full: 9.Q6'c(s
S lope Full:� 0.006340 ftlit
. : . ; . . _
: . _ Flow Type:� . N�,4 F
Peterson Const�lting Engineers Page 15
Preliminary Technical lnformation Report for Elsa Ridge Revised September 12, 2002
G "Driveway to Lot 6" Flow Control
The new impervious surface tributary to the ditch on the south side of Lincoln Place NE is
less than the 5,000 square feet (s fl threshold(see description for Core Requirement#3, on
page 6 of this report),therefore flow control (detention) is not required for the driveway area,
reference Area Table below. The 100-year developed flow from the area tributary to the ditch
in Lincoln Place is 0.03 cfs, therefore a rock pad will be used to disperse the flow from the
driveway area into the existing ditch on the south side of Lincoln Place NE see KCRTS output
below for developed flows. Note, the roof areas from the new residences and lawn areas are
not included in the KCRTS calculations because they are being infiltrated using downspout
infiltration trenches.
"Driveway to Lot 6" Water Quality
The new impervious surface (reference Area Table below) tributary to the ditch on the south
side of Lincoln Place NE is less than the 5,000 sf threshold; therefore per page 1-50, No. 1
Surface Area Exemption, of the 1998 KCSWDM water quality treatment is not required for
the driveway to lot 6.
"Driveway to Lot 6" Runoff Flows
The 100-year developed flow to the ditch in Lincoln Place is 0.03 cfs (from KCRTS Output
below), therefore a rock pad will be used to disperse the flow from the driveway area into the
existing ditch on the south side of Lincoln Place NE see KCRTS output below for developed
flows.
Peterson Consulting Engineers Page 16 '
Preliminary Technical Information Report for Elsa Ridge Revised September 12, 2002
Area Table
Total Area on site = 1.43 acres
Area of Residences = 0.32 acres (infiltrate on-site)
Area to Conveyance System = 0.10 acres
Total Lawn = 0.94 acres (infiltrate on-site)
Area to Lincoln Place Ditch = 0.07 acres
Impervious Road: Offsite = 0.06 acres
Impervious Road: On-site = 0.01 acres
KCRTS Analysis
KCRTS Input
Scale Factor: Sea-Tac 1.0
Soii Type: Outwash
Areas (from above): Impervious (On-site+Off-site) =0.07 acres
KCRTS Output
Flow Frequency Analysis
Time Series File:lot6driveway.tsf
Project Location:Sea-Tac
� ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- ,
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob '
(CFS) (CFS) Period
0.017 6 2/09/O1 2 :00 0.033 1 100.00 0.990 ',
0.015 S 1/05/02 16:00 0.026 2 25.00 0.960 I
0.020 3 12/08/02 18:00 0.020 3 10.00 0.900 '�
0.017 7 8/26/04 2:00 0.020 4 5.00 0 .800 �
I 0.020 4 10/28/04 16:00 0.018 5 3.00 0.667 �I
0. 018 5 1/18/06 16:00 0.017 6 2.00 0.500 I
0. 026 2 10/26/06 0:00 0.017 7 1.30 0.231
0. 033 1 1/09/08 6:00 0. 015 8 1.10 0.091
Computed Peaks 0.031 50 .00 0. 980
�
� Peter-son Consulting Engineers Page 17
II
Preli»tinary Technical Information Report for Elsa Ridge Revised September 12, 2002
SECTION 5 - CONVEYANCE SYSTEM ANALYSIS AND
DESIGN
The conveyance system analysis and design will be completed after the preliminary review.
SECTION 6 - SPECIAL REPORTS AND STUDIES
A geotechnical report has been prepared by Geotech Consultants Inc dated September 9, 2002.
SECTION 7 - OTHER PERMITS
The expected permits associated with this project are as follows:
• City of Renton Clearing and Grading
• City of Renton Building Permits (New Residences)
SECTION 8 - ESC ANALYSIS AND DESIGN
A Temporary Erosion and Sediment Control plan will be completed after preliminary review
and will be in accordance with the City of Renton standards.
�
SECTION 9 - BOND QUANTITIES, FACILITY SUMMARIES,
AND DECLARATION OF COVENANT
Bond quantities and declaration of covenants will be completed and submitted with the final
set of construction plans.
SECTION 10 - OPERATIONS AND MAINTENANCE MANUAL
The operations and maintenance manual will be completed after preliminary review and will
be in accordance with the City of Renton standards.
Peterson Consulting Engineers Page 18
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gravelly coarse sand to very gravelly loamy sand, the presence of a consolidated substratum at a depth
Depth to the IIC horizon ranges from 18 to 36 of 7 to 20 feet. This substratum is the same mate-
inches. rial as that in the Aldertiaood soils.
Some areas are up to 5 percent included Alderwood Some areas are up to 5 percent included Norma,
soils, on the more rolling and undulating parts of Seattle, and Tuk�aila soils, all of which are poorly
the landscape; some are about 5 percent the deep, drained. i
sandy Indianola soils; and some are up to 25 percent Runoff is slow to medium, and the erosion hazard I
Neilton very gravelly loamy sands. Also included is slight to moderate. '
in mapping are areas where consolidated glacial till, hlost of the acreage is used for timber. Capabil-
which characteristically underiies Alderwood soils, ity unit VIs-1; woodland group 3f3.
is at a depth of 5 to 15 feet.
Permeability is rapid. The effective rooting
depth is 60 inches or more. Available water capac- Indianola Series I
ity is low. Runoff is S101r, and the erosion hazard �I
is slight. The Indianola series is made up of somewhat !
This soil is used for timber and pasture and for excessively drained soils that formed under conifers I
urban development. Capability unit IVs-1; woodland �n sandy, recessional, stratified glacial drift.
group 3f3. These undulating, rolling, and hummocky soils are on
terraces. Slopes are 0 to 30 percent. The annual '
Everett gravelly sandv loam, S to 15 percent precipitation is 30 to 55 inches, and the mean
slopes (EvC) .--This soil is rolling. Areas are annual air temperature is about 50° F. The frost-
irregular in shape, tiave a convex surface, and range free season is 150 to 21Q days. Elevation ranges
from 25 acres to more than 200 acres in size. Run- from about sea Ievel to 1,000 feet. ,
off is slow to medium, and the erosion hazard is In a representative profile, the upper 30 inches '
slight to moderate. is brown, dark yellowish-bro��rn, and light olive-
Soils included with this soil in mapping make up bro�,m loamy fine sand. This is underlain by olive ,
no more than 25 percent of the total acreage. Some sand that extends to a depth of 60 inches or more
areas are up to 5 percent Alderwood soils, which (pl. I, right) .
overlie consolidated glacial till; some are up to Indianola soils are used for timber and for urban
20 percent Neilton very gravelly loamy sand; and development.
some are about 15 percent included areas of Everett
soils where slopes are more gentle than 5 percent Indianola loamy fine sand, 4 to 15 percent slopes
and where they are steeper than 15 percent. (InC) .--This undulating and rolling soil has convex
This Everett soil is used for timber and pasture slopes. It is near the edges of upland terraces.
and for urban development. Capability unit VIs-1; :lreas range from 5 to more than 100 acres in size.
woodland group 3f3. Representative profile of Indianola loar.iy fine
sand, 4 to 15 percent slopes, in forest, 1,000 feet
Everett graveliy sandy loam, 15 to 30 percent LJt'St and 900 feet south of the northeast corner of
slopes (EvD) .--This soil occurs as long, narrow sec. 32, T. 25 N., R. 6 E. :
areas, mostiy along drainageways or on short slopes
between terrace benches. It is similar to Everett 01--3/4 inch to 0, leaf litter.
gravelly sandy loam, 0 to 5 percent slopes, but in 621ir--0 to 6 inches, brown (lOYR d/3) loamy fine
most places is stonier and more gravelly. sand, brown (lOYR 5/3) dry; massive; soft,
Soils included ti�•ith this soil in mapping make up very friable, nonsticky, nonplastic; many
no more than 30 percent of the total acreage. Some roots; slightly acid; clear, smooth boundary.
areas are up to 10 percent Alder�:ood soils, which 4 to 3 inches thick.
overlie consolidated glacial till; some are up to 5 B22ir--6 to 15 inches, dark yellowish-bro�.m (lOYR
percent the deep, sandy Indianola soils; some are 4/4) loamy fine sand, broti�rn (lOYR S/3) dry;
up to 10 percent Heilton very gravelly loamy sand; massive; soft, very friable, nonsticky, nor.-
and some are about 15 percent included areas of plastic; common roots; slightly acid; clear,
Everett soils where slopes are less than 15 percent. smooth boundary. 6 to 15 inclles thick.
Runoff is mediurn to rapid, and the erosion hazard C1--15 to 30 inches, light olive-brown (2.5Y 5/4)
is moderate to seve:e. loamy fine sand, yellowish brown (lOYR 6/4)
�1ost of the acreage is usecl for timber. Capa- dry; massive; soft, very friable, nonsticky,
�ility unit VIe-1; l.00dland group 3f?. nonplastic; common roots; sligfitly acid;
gradual, smootlt boundary. 1? to 17 inches
�verett-Alder�.•ood p�avelly sandy loams, 6 to I� thick.
percent slopes (E��C) .--This mapping unit is about C2--30 to 60 inches, olive (SY" 5/=1) sancl, li�ht
caual parts f:verett and :1lcler�.00d soils. Tlie soils brownish gray (2.5Y 6/Z) Sry; singie grain;
are rolling. Slopes are dor.?inantly 6 to 10 percent, loose, nonsticky, tiotiplastic; few roots;
but range from gentle to steep. i�lost areas are sli�htiy acid. �lany feet th.ick.
irre wlar in shape and range from 15 to 100 acres
or more in size. In areas classified as E:verett 7'tiere is a thin, very dark hro�.•n :11 horizon at
�,'_ls, field esamination ana geolo�ic maps indicate the surface in some places. 'Che 6 hori =on ranges
lo
r"�I-IY. 4.ct�r��� ,�•�aor�� n�. w�nu �I
Oanpii(nt lYW ' .
Numb�r Ca0• fyp�of Probl��tt Ilddn�s o/�ropl�m Comn�d Tbro�P�y•
�12-0392 C �FNG 11211 SE 73RD PL- �ROSION 626U2
8�1-OJ28 C FLDG i1205 SE 77TH PL s2aD2
85-0428 C VIOLATE SE 11055 7�ND ST SEE CLP.R%C 6/92-G xE5-0(33i G25G?
65-083� G S1LT5 5117 RI�LE`/LANE SFE 85-G428�ST V�,C NOTFYD 6?.6D2
8b-�JE3"o C; DRNG 7818 1 i1 PL SE SEE 8G-0294 62EOZ
5E-023� C CITCHES 7600 111TF'PL SE MAIfJTENANCE G2�,r�
97-0SS: C FI.DG 6.'Oi LK1lJASH BLVC WA7ER FR�A4 RO.GUWAY b?GD2
87-G5E0 SR WALL 6701 LKl'dASH E3t��D VJ,o.tL�'OT C011N7Y hS41NTAIN�D 62602
b�-0507 t; OR,y3 790a S1GiN A1�c SE SE�.PAGE�Ati RrSIDENTHL CONST 626D2
87-1oZE C FLDG SE t t03G 76TH ST KEhNYD�.LE C�Ef.R!nG OF L4ND 626D2
90-02?5 C �LDG 5121 RIPLEY LN N S70RM �Zr,pp
60-07;9 G FLDG b121 RIH��Y'_N N BACKUP FROM PIAES/90-225,�077 625D2
90-0754 C EFOSION 7200 LK WA BIVD SE CONST WlTH NO EROS��N COPlTkOL 90-0225 828D2
SU-i 120 Cl. DRNGFLDG EE 11204 767H ST MEf+SO TO PA DATED MAY 5. 1892 626D2
81-0408 C ORNG 79�� 1 SGTH AVE SE WATER BYPASSING CATCH Bl�SIN 6�6D2
9i-0r«47 C 'EROSION . 7GJ0 LK WASH BLVD SE DURiNG CCINSTRL'CTIQN OF AP?5 g26p2
91-�'136 C DRAlNAGE COA�CREEK DRAINAGE REQUIREMFhT �gpz
84-040� C DRNG I-405 h GYPSY CREEK GYPSY CREEK 628D3
84-1�OS C FtDG I 405 GYPSY CRE�K ORNGI�GYPSY CREEK 62603
romocatnt Type .
Nump�r God• Typs o�Fropt�m ACdr�ra G ProbE.m � Co�nR�ntt Tbro�v�ps
72-OOY7 C DRNG 11453 SE 87TH ST 828E3
BifJU28 G FLDG 8656 118TH AVE SE 626E3
82-0346 C FLOC 6659 118TH AVE SE�ftE NT b2EE3
b2-�3456 C 8428 116TH AVc SE HYDf�AUIlCS�TUDY REQUEST 826E3
85-�714 C FLpG 8443 1;6TH AVE SE HAS�MENTAND FRON7 YARD V�'ATE� 626E3
9a-1588 C DRNG E409 �16TH AVE SE FI�I�Nu DRAIN WAY-SENSITIVE AF.Ek 826E3
92-C361 SR PROPAOSN SE 8"Tl-IST&125STAV SE FftOPER?YOFFER 62EE3
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RECONNAISSANCE REPORT NO. 28
LAKE WASHINGTON.BASIN
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1
JUNE 1957
Naturai Resources and Parks Division
and Surface Water Mana�ement Division
K�n� Countv. �L'ashin�?on
TABLE OF CONTENTS
I. SUMMARY i
II. INTRODUCTION 1
III. FINDINGS IN LAKE WASHINGTON BASIN 2
A. Overview 2
B. Effects of Urbanization 7
C. Specific Problems 9
1. Threat of damaae to property from landslides
and erosion processes 9
2. Threat of damage to property from flooding 9
3. Loss of fish habitat 10
IV. RECOMMENDATIONS 11
A. Miti�ate current and prevent future threat of damage
from mass-wastina and other forms of erosion 11
B. hlitiQate current and prevent future loss of fish habitat 1=
V. MAP 15
:�.PPE:�lDICES:
APPENDIX A: Estimated Costs A-1
APPENDIX B: Capital Improvement Project Rankin� (for East B-'_
Lake Washinb on and West Lake Washin�on)
;aPPFti`DI\ C� Detailed Findin�s and Recommendatior.s t '
I. SUhII�iARY
Lake Washington Basin combines the East and West Lake Washington Basins, w•hich to�ether
consist of the catchments of many small streams that flow directly into Lake Washington.
Most of the combined basin lies within the incorporated areas of Seattle and other cities
surrounding the lake. The reconnaissance, therefore, focused on five smali, somew•hat iso(ated
geographic areas on County-administered land. For purposes of the study, these have been
named Sheridan, Bnm Mawr, Kenmore, Finn Hill, and Hazelwood.
The Lake Washington Basin has been almost completely urbanized. Expansive areas of
impervious surface and severely altered stream systems have produced substantial increases in
surface water runoEf and attendant problems -- floodin�, erosion, sedimentation, landslides,
and loss of habitat. Even the Hazelwood unit in the southeast quadrant of Lake Washin�ton,
the least developed unit studied, shows severe signs of siream erosion caused by housing
developments upstream.
There were several specific problems found during reconnaissance. There is a threat of
damage to property from eroa�on, inctuding landslides and ot6er forms of mass-vvastin� This
is demonstrated by debris slides at the edge of the plateau above Tributary 0228, the more
shailow slides on the fakeshore cliffs and ravine of Tributarv 0464A, and the severe hillside
erosion along Tributaries 0224 and 0227. There is a threat of damage to properiy from
ftooding due to the deterioratioa of some cutverts. In additioq there has been damage to
ELsh habitat where streams have been placed in culverts, where there are barriers to fish
migration, where the natural features of streams have been destroyed, and where water qualiry
is poor.
Recommendations in the Lake Washina on Basin inciude 1) mitigating current and
prev�enting future erosion, using a combination of rea latory measures (such as stiffening
requirements for permits and property transfers and implementing joint jurisdictional basin
planning) and structural measures (such as increasin� R/D capacities where needed, reroutin�
surface runoff around sensitive areas, and emp[oyino instream erosion control).
Recommendations also include 2) mirigating current and preventing future loss of habitat with
planning and rea latory measures (such as developing water quality standards and treatment
strategies and developing consistent o idelines for protecting wetlands and streams) and
structural measures (including the elimination of barriers and the use of two-ce11 R/D ponds).
II. INTRODUCTION: History and GoaLs of the Progfam
In 1985 the King County Council approved funding for the Ptanning Division (now called the
Natural Resources and Parks Division), in coordination w�ith the Surface Water Managemenc
Division, to conduct a reconnaissance of 29 major drainage basins located in King County.
The effort began with an initial investigation of three basins --Evans, Soos, and Hylebos
Creeks -- in order to determine existing and potential surface water problems and to
recommend action to mitigate and prevent these problems. These initial investi�ations used
available data and new field observations to examine �eolow, hydrology, and habitat
conditions in each basin.
Findings from these three basins led the King County Council to adopt Resolution 6018 in
�pril 1986, calling for reconnaissance to be completed on the remaining 26 basins. The
Basin Reconnaissance Progam, which was subsequently established, is now an important
element of surface water management. The goals of the pro�ram are to provide useful data
with re�ard to 1) critical probiems needing immediate solutions, 2) basin characteristics for
use in the preparation of detailed basin mana�ement plans, and 3) capital costs associated
with the earlv resolution of draina�e problems.
P:L��'B 1
Lake W'ashino on Basin
(Continued)
Creek Basin, and on the west by the Lyon Creek Basin and the city of Lake Forest
Park;
The Finn Hilf area, at the northeastem corner of Lake Washington between Kenmore
and Juanita, is bounded on the north bv the Sammamish River Basin and on the east
and south approximately bv 3-�th Avenue NE from Northeast 145th Street to Juanita
Point.
The Hazelwood area, in the southeast quadrant of Lake Washino on east of Mercer
Island, is bounded on the northeast by the Coal Creek Basin, on the southeast by the
hlay Creek Basin, on the south b� May Creek and Renton, and on the west by Lake
Washino on. Only a small part of the shoreline is administered by Kin� County; the rest
is within Bellevue or Renton.
The total drainage area for Lake Washino on is approximately 603 square miles (not
inciuding the Lake Sammamish Basin's 97.7 miles). While this basin is large, the actual
area studied during reconnaissance is much smaller and includes only the geographic areas
listed above. A total of 13 streams were included in the studv. The total land area for
eacfi geographic unit, together with the len�ths of major tributaries, is as follows:
Unit uare Miles Maj• Tribs Len�th
Sheridan .5 0043 0.4
Brvn Mawr 2.9 0464D 135 mi.
Kenmore 2.2 0056 2.00 mi.
Finn Hill 6.3 02?7 1.00 mi.
0223 2.00 mi.
Hazelwood 2.1 0231 1.30 mi.
These five geo�raphic units are distributed over four Kino County Community Plannino
Areas:
The Shoreline Communitv Plannina Area. which contains ihe Sheridan area, is a mature
suburban communiry, with approximately 90 percent of its usable land already developed.
Sin�le-family residences dominate this area, but the number of multi-family units is stowly
increasing. The Sheridan area contains some of the hiohest densities in the ptann;ng
area: 4-6 single-family units per acre and up to 48 units per gross acre in multi-storied
apartment structures in planned unit developments. These maximum densities are loca[ed
in the south-central portion of the area along Bothell Way (State Road [SR] 5?2).
Community-scale retail business is aiso located along Bothell Way in the same vicinity.
Zonin� changes are likelv to occur as new multi-family units are considered in single-
familv zones. Concunent changes in commercial and business categories should also be
anticipated. These changes, however, are likely to occur along Bothell Wav and not in
the interior of the Sheridan area, which is an established single-Eamily neighborhood.
The ceneral character of the area is therefore unlikely to be �reatly affected.
The Vorthshore Communitv Plannin� Area, which contains the Kenmore and Finn Hill
areas. borders on portions of the cities of Bothell, Kirkland, and Redmond. Woodinvitle,
thouQh unincorporated. is a si�nificant population and commercial center. and much of
tne recent ;:ewth ef rhe Nonhshore Communit�� P!anning Area has been concentrared
P�L��'B >
Lake Washina on Basin
(Continued�
somewhat to 133,000. The estimated fio re for the year 2000 is 135,000. There are
dense concentrations of people in White Center and the North Hili neighborhoods.
Existing development in the Highline Plan Area is substantial and generally not subject to
drastic reorderin�. Future zonino chan�es wilt reinforce and improve existing residential
neighborhoods and business centers.
Geatogic and geomorphic featutes. The deep, elongated trough occupied by Lake
Washinb on w•as carved mostly by glacial ice into unconsolidated glacial and nonglacial
sediments. Those sediments reach thicknesses of more than 3,000 feet north of Mercer
Island, but are thinner where they are lapped onto the bedrock of the Newcastle anticline
to the south. The North Seattte and Intertake drift plains (west and east of the trou�h,
mero ng to the north) are similar in topography and stratiD aphy: drumlinoid piateaus
surfaced with tili overlying proglacial sands and gravels and lacustrine siit exposed mai�ly
in bluEfs alon� the lake. Toward Renton, these materials are plastered over sandstones,
siltstones, and votcanic rocks of the Puget Group and folded into a ridoe perpendicular
to the trough.
The topography, which determines current drainaoe patterns, was shaped by southward ice
movements. Streams tend to flow north or south between drumlins. In the Kenmore
and Bryn Mawr areas, at the northern and southern ends of the lake, respectively, slopes
are relatively gentle, and till mantles the surface to the lake shore. The laroer streams
in these units flow directly toward the lake, and older sediments are exposed mainly in
deep ravines. Alono the eastern and western sides of the trough (where the Shendan,
Finn Hill, and Hazelwood areas are located) major streams rise on the plateau and flow
parallel to the lake. Trough sideslopes, eroded by the sides of the glacier lobe, are
steeper and generallv expose the gravels, sands, and sitts under till. The creeks in thCse
areas are mosth- srr�all and fed hv �eFa�e, e�ceo� where the�� have captured the flrnt :��(
plateau stream�
The difference� 1 _ ...... �,:t-, _ ..:� _ _ ._.:��_,.. � . . � . . , .. _. '
produce differences in the intensity of geomorphic processes. In oeneral, the steep, hi�;' '
lzkeshore hluffs have the hi�hest levefs of �oundw�ater seepa_e, lar,dslidinQ. and actual
west-facing hillsides of Hazelw�ood and Finn Hill, and the bfuffs west of Renton Airpo„
in Bryn Mawr. In these areas, there is �oundwater seepage in exposed sandv lavers
perched over silt or till. This seepaoe contributes to mass movement -- mostly shallow
debris slides in Sheridan and Hazelwood, commonly in artificial cuts but includin� lar�e:
slumps in Bnrvn Mawr and Finn Hill and one lar�e, active slump northeast of the ?�1a��
Creek interchan�e in Hazelwood. Most streams are short and ephemeral and have noc
eroded far into the bluffs. But in Finn Hill, o eater seepa�e has formed ]arger streams:
these have cut eastward, expandin� their catchment areas and increasin� their erosive
potential. Likew�ise, one stream in Hazelwood has carved a deep ravine into the ed�e of
the plateau. These large ravines are quite sensitive to further slope and channel erosion.
«'here slope aspect is parallel to the direction of ice f7ow, there is relativelv impermeable
. till at che surface, so that more of the precipitation runs off into numerous smaller
streams. The IarRest of these have cut throu�h the till and into erodible sediments
beloµ•, formin� ra��ines w�here slidin� and channel erosion are murh more active. Tni� is
P:LWB 5
Lake Washington Basin
(Continued)
flows into Tributary 0281. Drainage from subcatchments 13 and 19 is diffuse, flowing
into Lake Washino on at many points. There were few probfems associated with surface
runoff in these subcatchments. Tributarv 0231, however, has experienced severe channel
erosion due to a combination of increased peak flows from new developments in the area
and the highly erosive nature of the soils alono the channel.
Finn Hill area. Finn HiU is the most complex unit in the Lake Washin�on system.
There are seven streams that drain a flat, developing plateau. The �radients of these
streams increase to a maximum of 8-12 percent as they approach Lake Washinaton.
Most of the runoff in this basin oria nates as impervious runoff or seepa�e out of
hillsides. There are severa! wetlands located in the Finn Hill area. Three are identified
in the Sensitive Areas Map Folio (SANIF) -- one atong the shore near In�lewood
Country Club, another in Big Finn Hill County Park, and the third near Northeast 141st
Street and 34th Avenue NE. Durin� the reconnaissance, 10 other w-etland sites were
discovered, seven oE them on the Tributary 0223 svstem_ The hydrolo�ic response to
storms in the basin is typically fast, except for Tributary 0?3S, which is buffered from
high peak flows by the many wetlands.
Kenmore area. F7ow in the Kenmore area oria nates as runoff from urban areas. The
major tributarv in the basin, 0056, has been channelized over most of its length. The
headwaters of this stream are loca[ed in Snohomish County near a major housino
development. Althou�h the gradients in the basin are typically lower than those in the
other areas, the hydrolo�c response to storms is still fast due to the lack of vegetation
a(ong Tributary 0056, the large amount of runoff Erom impervious surfaces, and the small
size of the basin.
Habitat charaderisrics. Habitat diversity in all stream systems of the Lake �Vashington
Basin has been sio ificantly reduced by urbanization: Long reaches have been
channelized or placed in culverts, reducing spawning and rearing areas. Numerous
barriers, such as culverts, weirs, dams, and artificial cascades prevent access to upper
stream reaches or entry to entire streams. In many streams, urban runoff causes
erosion and �avel movement. This fills pools, deposits silt in rifftes, and generallv
causes unstable stream conditions. Headwater areas have lost wetlaads and npa-ian
vegetation.
The most usable habitat exists in the Finn Hill area where manv streams descend r: :�.
the uplands through deeply incised ravines ro Lake Washington. Vegecation in the
ravines has generally been left undisturbed, and wide riparian corridors eaist all the wa�
to the lake shore. Through these reaches, �adients produce pool-nffle charactenstics
w-ell-suited to fish use. Woody debris is abundant but often unstable because of hieh
flows. Debris jams are common and produce ephemeral barriers to fish movement. I-
Tributarv Q228, however, canditions for fish use are exceilent. Lower reaches of th�
stream have 000d pool-riff�e sequences and relatively clean, stable �ravels, as w•eil a�
lar,e, deep pools. Woody debris is common and stable; vegetation for stream cove:
abundant. Benthic invertebrates are common and diverse, indicatinD a stabie, balanced
stream svstem. Ortly in this svstem w�ere spaw•ning and rearin� salmonids observed.
Even so, a 6-foot-hi;h a�eir at river mile .45 forms an impassable barrier and prevents
uostream mi�ration of anadmmous fish. Resident cutthroat trout occupy the upper
reaches, particularly in the Finn Hill Park area.
P:L��B �
Lake LVashin�ton Ba�i�
(Continued)
Development in the Finn HiU area began at the turn of the century along the lakeshor�
As development continued inland, new drainage systems w�ere constructed and connected
to existino ones downstream. 'The process created a complex drainage system with mar..
sections inadequately sized to handle the added flows. Low divides betw•een manv of th
subcatchments have compounded the problem and made it easy to divert storrnµacer ir�
streams other than those to which the water would naturallv flow. This cross-
ditching resulted in one of the more severe problems noted in this basin durir.
reconnaissance. F7ow from appror.imately 75 acres of subcatchment 1? was di�
subcatchment 13 when a new development was constructed near the ridge line be�wt:
the two subcatchments. The increased flows to subcatchment 13 caused stream erosi
and sediment deposition in Lake Washinb on. Some of the worst erosion discovered
the basin during reconnaissance occurs in the Finn Hill area on Tributary 0229A. L-
addition to the hvdrolo�ic and �eo[oa c problems in Finn Hill, habitat has been lost on
Tributaries 0322 and 0228 throu�h the elimination of riparian corridors and w•etlands.
The Kenmore area has been almost fully deveioped. Its major tributary (0056) has bee
channelized over its entire leno h. The tributary receives runoff from Snohomish �- -�
and direct runoff from 61st Avenue NE (a major arterial). The most severe
channelization and piping occur alona the major arterial where the road has been
constructed up the ravine. The crowding of the stream between the road and th�
walls has resulted in erosion of the shoulder and slopes. Tributary 0056 is also piped
for approximately 60o feet from 61st Avenue IYE and Nonheast 130th Street to a
condominium complex located on Lake Washinb on. This eliminates fish habitat and
restricts access to upstream mi;rants.
These and other problems are discussed in a eater detail in the section on specific
problems (befow) and in Appendix C.
G SpeciEc Problems Identifed
The discussion outlining the eEfects of urbanization in the basin identified man� of the
problems found in the five geographic areas studied during reconnaissance. The
followino discussion b ves further details of those problems and provides examples with
regard to erosion, surface water issues, and habitat loss in the Lake Washin;ton Basin.
1. T3ere is a threat of damage to property from landslides and other erosion processes
active in the basin. Specific problems include:
a. Mass movement, which oocurs at all srales in the basin. Slumping takes place in
the olacially oversteepened trough sideslopes, usually aided by seepape of
e oundwater over perching layers. Slides have occurred in the lakeshore sfopes
of Finn Hill and Hazelwood; an ancient slump is mapped west of Kenmore.
Most impressive oE all are three prehistoric landslides, all now tyin� below L.ake
Wahsin�ton and probably triggered by �eat earthquakes. One other landslide is
located west of the Finn Hill area. Their existence demonstrates the ultimate
instability of most steep slopes in this region.
b. High rates of mass-wasting in the laiger ravines. Examples include the walls of
the I.akend�e ravine. on Tnbutaries 046�1D and E (in Bryn Maw•r), and mam of
the ravines in Finn Hili. hto�•ement ean occur far uphill, as in the two dehris
P:L��'B 9
L..�nc ��d�n:n�ti;n b�i5in
(Continued)
landxapin� works produce barriers of assorted kinds. Specific eaamples of
barriers incfuded:
1) Drop barriers in the form of culverts, weirs and falls occurred in the
following locations:
a) Tributary 02?3 (RM .45), where a concrete spillw�ay is a complete
barrier to upstream migration.
b) Tributarv 0464D (RM .29), where a 3-foot drop from the culvert co
the stream surface is a comptete barrier.
c) Tributary 0227 (RM .13), where an impoundment dam 20-feet hioh and
60-feet wide is a comptete barrier.
d) Tributary 0056 (RM .OS), where mndominium development has
landscaped the stream with pools and w•eirs but provided no fish
passage.
2) Ftow barrieis, formed by culverts without baffles or with steep a ades, have
formed at the following locations:
a) Tributarv 0223 (RM .OS), where the culvert under Holmes Point Road
lacks baffles for fish passage.
b) Tributary 0056 (RM .10), where a box culvert under Bothell Way may
be a velocity barrier at hiph flow.
4) Habitat has aLso been damaged or destroyed because of poor water quality,
usually the result of direct entry of road runoff into stream systems. The w�orst
cases of poor water quality found were in places where roads w•ere constructed
near stream corridors. This runoff contains greases, oils, gasoline, anti-freeze,
and other road-related pollutants. Such problems were apparent in the
Kenmore area where Tributarv 0056 receives direct runoff from 61st Avenue NE
and in Bryn Mawr, which is completely urbanized.
III. RECONIIv�NDATIONS FOR ACTION
The folIowing recommendations propose both regulatory and structural remedies for the
exteasive problems identified and discussed in the previous section. Su;oescions for interlocal
cooperation are ineiuded, where appropriate.
A Mirigate current damage from ma.�-wa.sting and other forms of erosion and prevent
further problems
1. Adopt and implement planning and icgulatory measures to protert seasitive areas in
the Lake �'Vashinjton Basin:
� King County should closety regulate undeveloped areas within I�dslide hazard
zones ['r.at are not alread�• dedicated open �pzce (parks. sc:heo! pr�^ert�, etc.)
P:L��'B 11
Lake Washin�ton Basin
(Continued)
B. Mitigate destruction to ftsh habitat and prevent further damage.
1 Develop and implement pianning and regulatory measares to protect ELsh habitat.
a Fstablish appropriate interioral ag+eements among pubGc entities durin� the basin
planning process. Examples include Snohomish County, Lake Forest Park, Brier,
and Bothell in the Kenmore area; Juanita, Kirkland, and Bothell in the Finn
Hill area; and Bellewe and Renton in the Hazelwood area. Because of the
potential effects to Lake Washinb on water quality, Metro should also be
included in these discussions.
b. Fstablish bilateral ageements between King County and Saohomi.sh Couaty and
betw�een King County and the rrarious cities to develop consistent, comprehensive
guidelines and rewlations for protection and enhancement of wetlands and
stream systems throughout the basin.
c. The King County PubGc Works Department should give immediate coasideration
to the devetopment of water quality standards and treatment strategies for urban
stormwater runoff that enters Lake Washin�on.
d Develop a citizea information and participation program to educate the public on
how to become invotved with water-resource issues. This is critical to nonpoint
control in the Lake Washine on Basin.
e. Minem'n� and preveat loss of habitat features:
1) Fstablish o eenbelts or obtain conservation easements for those criticai
stream corridors and wetlands that remain in the basin. Of particular
interest are the headwater areas of streams 0223 and 0233.
2) Cooperate with the Washine on State Departments of Fisheries and Game
to detect hydraulic code violations throughout the suburban area, particu(arly
in the Finn Hill area where homeowner landscaping causes the toss of
quality habitat.
3) Consult with WashinD on State Departments of Fisheries and Game pnor to
designing capital improvement projects in order to work out details prior to
desio.
2 Design and implement srivctutal solurions in order to restore and protect fish habitat
in Iake Wa.shington Basin.
a. Eliminate drop barriers. Construct dow�nstream weirs or pool-and-weir fi�h
ladders as required. Barners such as the large dam on Tributary 0227 should
be carefully evaluated prior to any removal or conscruction. (In this case, no
action is recommended Eor the dam.)
b. Eliminate flow bartiers Install baffles at 10-foot intervals throuoh culverts.
Several tvpes of structures are possible, e.,.. slot weirs, angfe weirs, and off�:
baffles.
P:L�4B 13
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LAKE WASHINGTON BASIN ����`� , w �
�9
(South Section) '
r \
� Basin Boundary So�rh pr ��'
-�--�-� Subcatchment Boundary vd �
Kenn al
� Collection Point a�����'r Coleman Pt ���D "�z----- ���v
._� �4 Stream 900 "� � c4
`� �;; - 3 sE
o4oau Tributary Number g �` 1'4���
•6404 Proposed Project , � l`� � \J(
� ,,��, ; .? '` \'
� J au,r �'��� I �
, - � ��\� o :. $ 3 - �.��� i
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n_` ` � Alle n �,�� � lo �� � � { _�. 4
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t �� \\l'�''� /� "�<.640� F ' �i�`� ,
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�� i i . . � ,%'�.r.r _ . l . . .
Projccl CoIIcc1. Eslimated C�tils
Numhcr 1'oint I'rojcct Ucsc:ription Prohlcm AddresscJ an�1 (:ommcntti
1G02' !0 Inslall a stan�iar�i control structure at Will miti6ale hi6h peak flows discharging $13G,00O
Wc�lanJ the outlet to Wetland 1G02 (rated #2) to to '1'rib. 0228. (Ucpends on lan�i
1(>02 incrcasc detcnlion. '1'his wctland will arc�uisi�ion cos�s.
require furthcr biological evaluation Project shoul� hc
bcforc K/U �icsign and construction. analyzed a� timc of
basin planning.)
1�iO3 I?,13 Ins�all piping syst�m neccssary to dircct Streambcd erosion in Trib. 0229A located $2S?,(�0
flows (which had been piped from sub- in suhcatchment 13. (Project is indepen-
catchment 12 to l3) back into collcction dently justifiahle.)
p�. 12.
I(iO4 10 Rc�lace existing un�eisized cross PlooJing on upstream side of culvert, which $25,000
culvcrt �t Juanita Drivc. will worsen as devclopment in arca con- (Project is incJcpcn-
tinucs. dcnUy juslifiahlc.)
1605 5 Install 4OU' of ti6htline. ]Iillside erosion and high s�:diment load in �75,000
"Trif�. 0224. (Projcct is in�lcpun-
dently juslifi�ihlc.)
f':I.Wl3.n1'n /1_2
APPENDIX B
CAPITAL IMPROVEMENT PROJECT RANKING
' LAKE WASHINGTON BASIN
(West Lake Washina on Projects)
Prior to the Lake Washin�ton Basin fie(d reconnaissance, one project had been identified for the
West Lake Washin;ton portion of the basin and rated using the CIP selection criteria developed by
the Surface Water Management (SWM) and Naturat Resources and Parks Divisions. Following the
reconnaissance, four projects remain proposed for the West Lake Washington portion of the basin.
They include four new, previously unidentified and unrated projects. These displace the previously
__ seiected project, w�hich w•as eliminated based on the consensus of the reconnaissance team.
The previous SWM capital improvement project list for the West Lake Washino on portion of the
Lake Washinoton Basin had an estimated cost of 5300,000. The revised list increases that cost to
an estimated S301.000.
The following table summarizes the scores and costs for the CIPs proposed for the basin. These
projects were rated accordin� to previously established SWM Pro�am Citizen Advisory Committee
cntena. The projects ranked below are those for which the first rating question, Element 1:
"GO/NO GO," could be ans��ered affirmatively. These projects can be considered now for mer;in�
into the•"live" CIP list.
RANK PROJECT NO. RATING COST
' 1 6405 75 S 72,000
2 6=303 60 56,000
3 6�02 4-� I31,000
4 6�04 32 42.000
TOTAL S 301,000
� I
P L`.�'G.:�PB B-1
-- - � -
n['1'L'NUIX C
1)L:'1'nII,L:U I�INUIN(iS ANll RL?COMMLNUA'I'1ONS
I.i1KG WnSI1INC;'I'UN L3i�SIN
— .._----- ---- - --- ---. . ..
All �I��ins hsted here are located on final display maps in
ihe oflices ot Suriace Waler Managemenl, Buildirig and �and
_ l)evetc��menl_ and Basin Planning.
1'�ih. �� C��Ilcrt. Existing �lnticip�lcd
Itcm` Rivcr Milc I'oint__ c'a�c�oi I'rop. Proj. Con�ii�ians �nd 1'rohlcros Conditions �nJ Prohlcros Rccommcndations
I UOS�, I�;l Ilahitat Condominium devclopment has Same �s existing conclitions. Require dcvclopmcnt to rrovielc fish
Ic�1 .US landscapcd slrc�m l�ut pro- p�s.�:ific facililics.
vi�cd no Cish passaFc
throu�h pon�ls.
2 Uc)5�> l;l Ilsibitat I3o� culvcrt undcr I3othcll S�imc �s cxisting conditions. Construct fish-}�a�.��gc f�cility at
R�1 .IO Way is a drop barricr to downstrenm cnd of hox culvcrt.
upstrcam migranls.
t U�IS�� L•:I Ilahitat Stream reccives rond n�n- As upstrcam dcvclopmcnt in- Isolatc Storm drains from crceks, if
It�1 .Sc> off from numcrous catch- crcascs, watcr quality pos.siblc. Usc vc�ctated sw,ilcs and
hasins. problems will bccomc morc two-ccll R/D pon�s to fil�cr runoff.
scvcre.
-1 l)c)5�; Li l I lahita� Crcek has bcen forced into Same as existing conelilions. ndd hahit�t stnic(ures lo ch�mncl,
IZh1 ..�tO roa�sidc dilch wilh ro�d- rcve�ct�►tc hanks lo rrovidc �ro-
way cons�n�clion. IlaUit�t tcctivc scrccn.
divcrsity lost. I�ish use
dcclining.
5 (l�)5�, I•:? Ilahita� Wctlan� fills ocrurrin� in L.o�.s of wctlands will rcducc L'slablish � cooperitivc hnsin
II�,��I��uicrti hcaJwatcr arcas of strcatn proJuctivily an� plannin� agrccmcnt wilh Snohomish
Snohomish County (city of summcr flows, incrcasing County an� city of L3ricr for
[3ricr). �caks �nd volumcs of winter protcction of wc�l�nas and strc.ims.
flows to Kin� County.
I' I \', Is \I'c C-I
I . ' � I
'I rih. l ('ollc�t. L'•xisting Anticipatcd
licm Itivcr Milu Point Calc�ory Prop. Proj. Conditions anJ Prohlems ('ondilions nnd Prohlems Rccommcndations
Ic) t)222 L3 llabi�at Ilistoric cncroachmcnt on Loss of wctlands may occur in Prescrve thcsc headwater arcas from
IlcaJw;uc�;s wetland. Some fill contin- this hcaclwater area. encroaching dcvclopment. Removc
uing on perimctcr. Portion fill; cnhancc � portion for emcrgcnt
of weUand is bog. manh hahitat. 1'roblcm was rcferred
to [3uil�in6 .ind l.��nd Uevelopmeni for
act ion.
I I U32�1 L?S C;c;ology Gullying of ravine slopes There will be some inrrcase - Rcpair tightline.
RM .IU-.SO below strcct cn�s (61st in [lows as construction - 1toulc �irainagc on north sidc along
PI. NC and G2nd Ave. NC), proceeds on Ihe plateau. bcnrh above the slream (county ro.iJ
culvert outfall (ItM 0.45), Main problem, though, is poor �nd sewer right-o(-way) to �hc wcst,
and hroken tighUinc dcsign and/or failure of or tightlinc to the stream in ��
(RM 035). San�y slopcs drainagc stivctures. s:ifc, noncrosivc manncr.
arc naturally scnsilivc - '1'i6htlinc culvcrt at RM A5.
to channel erosion �nd
sliding. Sc�imenlation
in R/U pond at valley
ntouth.
I? O?2a L'S Ilydrolorry Privatcly ownccl instrcam No future prohlcros antici- Nonc.
Rh1 .IO scdimcnt pon� cxisls at patcd.
this rivcr mile. I'ond
was found lo bc ncarly
fillcd with scdimcnt. This
sedimcnt .ucumulation
appcars ro he a n�tur�l
procezs and nol a result of I
increased peak flows from
upstream developments.
13 O?2�3 LS Ily�irolo�,ry 1G05 Sevcrc hillsidc crosion Conlinucd hillside crosion "I�i�h�linc �raina�c to botlom of hill ;
ItM .d5 ��i (;cology causcd by s�n•facc runoff until mili�ating mcasures and provi�c a�icyu;uc cncrfiy di�.�ipa• ',
from NC 1S4th SI. Jis- are Iaken. tion. i
charFing at lhe lop of a
stccp slopc. '
��:�.w�3.,���c' C-3
r ` � �
r �
I'rih. .Cc (:ollect. Exisling AnticipateJ
Itcn� I:ivcr Milc 1'c>int ('atc�ory Prop. Prc�j. Conditions an�i Prohlcros Con�itions ��nd Prohlcros Rccommenciations
1') I)�?7;\ 1:7 Gcology Somc channel erosion along Probably due to runoff from Control diu:harfic o( runoff from cdge
I:M .?5-.-�0 small tributary channcls. homcs along ed�;c of platcau. of �latcau, cspcci�lly from any
Some deposition abovc new Soils and slopes arc very future sourccs. May bc ncces.k�ry to
housing dcvelorment. sensitive to erosion. Could tighUinc some of thc cxisting
hccome a major prohlcm for sourccs on the steepcst slopcs to the
the downhill devclopmcnt, holtom of hill in � s:►fe, noncrosivc
cspccially since it is m�nncr.
locate�i al the Cocus of
a thcaler-shapcd vallcy.
?O O_'.?713 L•;7 Ily�rolobry 'I'ightline has scparatcd, Slopcs will continue to be Repair tightline in such a way that
ItM ,Ucl-.�5 & G�olobry allowing water to ero�ie u;verely eroded until the segmenls oC culvert can't bccome
stecp hillslope and cause pipe is fixed. 'I'his problem scparatcd, or replace line with
gullying in small Iribu- may be the major sourec oF flexihle pipa (1'roUlem rcfcrred to
tary channcl. Ucposition sedimcnt filling thc pond on King County Drainabe Invesligation
in Trib. 0227 at Ft�lmcs 'I'rib. 0227. ana Roads Maintenance scctions.)
Yt. Ur. (Problcm was first identificd in 1986.)
?( U22fi L�) l labitat Conerete culvert under No change. S�me as exisling Install baffles in culvert. I3ack-
RM .US Ilolmes Pt. Dr. is a partial conditions. [lood to eliminate drop.
migration Uarrier due to
vclocity and outfall drop.
I':I.�1'l;.��I'(' ('-5
a
�
'I'ril�. �1� Collcct. L'aisling Anticipatcd
Itcm Itiv�r Milc Point C�itc�ory Prop. Proj. Con�iitions an�i Problcros Conditions and Problcros Recommcn�ations
27 O22� L10 Ilydrolobry 1G02 Project proposcd hy County Plateau area is developing. An�lyze Projcrt at time of hasin
1tM 1,•IS Surface Water Managemcnt 'I'his loc�tion is c�ccllcnt planning to �ctermine if projcct is
to acquire wctland and for addressing increased neces.s��ry. Conduct Ihorough biologi-
constnict control stn,clurc pcak flows. cal an�ilysis to �lctcrminc cffccts at
to increase storage that timc.
c�pacity.
��t c��2,�t L•'ll 1[ydrolo�,ry Road embankmcnt is eroding Continued eml�ankmcnt crosion Inst.�ll riprap on ero�ing arca.
IZM 1.55 into Trib. 0?28 �t tl�is of N� 133th St. Problem referrcd to King County roa�
loc�tion. Most of shoulder maintcn�nce section of !'ublic Works. I
has been lost.
2') (122�3 Lll liydrology Storm-drainage infiltr�tion Continued flooding and suU- Install unclerbround v��ult in place of
RM 2.40 ficld is failing due to Uasin erosion until mitigat- Jrain ficld and Jis�harge lo ncarby
impen+ious soils. This is ing measures are takcn. drainage swalc. Problem rcfcrrcd to
causing frequent flooding Drainage Invcstigalion Section oC
�nd failure of road sub- Surface Water Managcmcnt.
basc of 149t1� PI.
:�0 (122')i1 L13 Gcolo�,ry Channel downcutting, bank- Recent roadside ditching • lncrease It/U facililics norlh of NC;
ItM .OU- and lower-slope erosion; has expanded thc drainage 120th S�.
,40 deposition �t thc mouth. arca, so downstrc��m problcros - Considcr inchanncl chcck dams in
I��ndsliding on ravinc m�y increase. Impervious middlc reach (state properly).
slopes. surface area may incre�se - Consider redirecting flow lrom arca
greatly upstream, causing west o[ 7(th PI. NE back to the
accclerating erosion in the southwcst (tighllinc along NE llSlh
ravine. St. and �hrou�h small ravine).
I':I.W 13.;1I'(' C-7
_
i
�
I ril�. �� ('olicrt. [_'xisling llnlicipatc�
Ii�n� Itivcr Milc Point ('alc�;ory Nrop. I'roj. Condi�ions �,nd Prohlems Condilions an� Prohlems Recommen�ations
�5 (1?`tl Lilh Gcolofiy �lrtive, major clowncutting L'•rosion seems lo he a rc- -As.sure �roper func�ioning of
ltti1 .3O-.�i5 �� IlyJrology in Ihc ravinc (I2M .40-.bS), sponsc lo incrcase in hi�;h uPstrcam IZ/D facilitics
undcrcutting lowcr stopcs; flows c�uscd by devclopmcnt (cspccially at SE bOth Sl.).
bank crosion upstrcam upstream. l�urthcr incrcases -Rcyuirc onsitc 12/D if/whcn thc two
(RM .GS-.RS). Valley is in impervious surfaces up- larrc parcels along llGlh Ave. S[:
cut into crodible s��nds stream could abbr�vate arc developed. Any runoff from
and gravcls. Channcl erosion. '1'wo R/D (acililics homcs in I��kc Ileights (east of
crosion is undcrcutting upstrcam at SC 60th St. may vallcy) should hc routed around to '
hillslo�cs in places. have already improved Ihc the north; prohibit uncontrolled
►Icavy dcposition in R/D situalion but lhc s��nds ancl dix:hargc onto hillslopcs.
pond (RM .40); dcposition �ravels arc very susccptible -In thc ravinc, reinforce thc small
also around �focks at mouth. to �rosion. bridge (i2M .GS) so th�t �owncuttinfi
Problcm may be affcctcd �an migratc no fur�hcr ups�rcam.
hy prescncc of scwcr line Considcr ins�allation of nc�ck dams
in ravinc. or gabion weirs in gully. Mainlain
natural vcgctation in lhc corri�ior.
3�, U?�il L17 Ilydrology Cxisting R/D facility is No changc. Nonc.
ItM 1.14 detaining water nearly to
capacity. Providing good
detention for tributary.
-1O O1�i-lU WG Ilydrolo�y l�irgc c�uantities of sedi- Problcm will continuc until t'roblcm rcfcrrcd to draina�c
1tM .UO ment accumulating in lower �roundcovcr is recstablishe�. invcs�igation scction o[ S��rfacc
rc.uhcs. Ncw construction Watcr Managemcnt.
u�strcam no1 rontrolling
crosion into crc�k.
i>:i,wi; ni�c� c-�
"Crih. �1; Collcct. Cxisling Anlicipnlc�
Itcm Itivcr h1ilc I'oint C.itc�ory Prop. Proj. Con�itions and Problcros Con�itions �ind Problcros Rccommcn�iations
Q� Q�th-1U WS Ilydrolo6ry G403 Bottom 8' scction of cul- Roadhcd crosion will continuc Replacc bottom seclion of pipc,
1tM .�>4 vcrt cros.sing S 11Sth St. until miti�ating mcasures install gabions to stabilirc failing
has failcd, causing road- are employed. hank, and romove �ehris from ups►rcam
Ued erosion. Upstream end end. �,
is hlocke�f with dcbris,
rausing watcr ro pond to
a depth of 4-6'.
�13 O•I(�aL{ WS Ilydrology G402 A small wctlanJ cxisls on All of the flows generated by Acquire weUand and constnict a
12M .')�i the upstream side of Renlon subcatchment 4 could be control structure in the culvert '
Avc., probahly a result dctaincd by a detention crossing Rcnton Ave.
of thc high fill bcrm used pond at this location.
for thc road.
44 -- W8,9 Geology Runoff from roads, street Gullying will continue as Route flows (especially from culvert
(hillsi�cs) ends, etc., is eroding in- long as flows are routed NC of Uimmit Jr. ILS.) around thc
to the I�illside along onto the slope. Sediment arca, or tightline to bottom of hill.
sevcral pathways, mostly may affcct homes downhill.
within King Counly park
land.
��S U-1�i41� W�4 I[ydrology G304 Small dcpression lorated Lo�:ation is ideal (or Install st�ndard control structure on
ItM 1.32 at corner of 85�h Ave S detention. Wi�h suitable on upstream side of cro�.s-culvert
, anJ Bowling St. control stnicture, detention to detain flows in depression.
cun protcct downstream
reaches.
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OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE
SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT#Z
Basin: Cedar River/i.ake Washin t�n Subbasin Name: East C,ake Washin ton Subbasin Number: East Basin
Symbol Drainage Drainage $lope Distance Existing Potenfial C3bservations of fieid.
Component Type, Compvnent - frpm site Probt�ms PrabEern� ` inspector, resource
Nam�, and Size DEscri tion dischar e ', reviewer, or resident
see map Type:sh�et flow;swafe, drainaga basin,vagetatfon, ;. . °h Y.mf=1,32Q constrictlons,under�apacity,:pUncfing; ' tnbutary area,likelihood of problem,
stredm,channel,pipe,pond; Gover,depth,typ�vf sgtlSlflVe: . ft, overtopp�ng,f�oodi�g;{�abi�at 4F organiSm qy�CilOW;pathways,potential irr�pacts
,.
Size:diameter,surfac�area are8,vo1Uf11e ;: i destructiokf;scoU�ing,bar�{�skau�h�ng;: ` '
' < " ... ' sedlmentatlon,incision otk►+�t ero�[�ff;> '
_.,. >...._
AA Sheet flow Grass area on site +/-8% 0 Sli ht erosion Sli ht erosion No defined ditch
AB Concentrated flow Roadside ed e +/-6% 10 Debris Debris No defined ditch
AC 12" corrugated Leaves roadside edge, +/-3% 250 Debris Debris Pipe mostly filled with debris
PVC i e enters i e s stem
AD Pipe system Pipe system +/-3% 300 Slight Slight No visible problems
sediments sediments
AE 18" corrugated Leaves pipe system, +/-3% 504 Slight erosion Slight erosion No visible problems
PVC i e enters stream channel
AF Ditch Sft deep; 2ft wide; +/-6% 580 Slight erosion Slight erosion Channel has capacity
2:1 side slo es
AG 2.Sft concrete i e Under NE 40 Street +/-3% 590 Debris Debris No visible roblems
AH Ditch 6ft deep; 2ft wide; +/-8% 600 Slight erosion Slight erosion Channel has capacity
2:1 side slo es
AI 2.Sft corrugated Under road to +/-2% 840 Debris Debris No visible problems
vc i e a artments
AJ Ditch 3ft—Sft deep; 3ft wide; +/-3% 850 Slight erosion Slight erosion Channel has capacity
3:1 side slo es
AK Culvert Under driveway to +/-0.5% 1,950 Debris Debris No visible problems
church
AL Ditch 2ft deep; 2ft wide; +/-2% 2,100 Slight erosion Slight erosion Channel has capacity
3:1 side slo es
AM Culvert Under NE 43� Place +/-0.5% 2,110 Debris Debris Sediments at inlet
AN Ditch 2ft deep; 3ft wide; +/-1% 2,140 Slight erosion Slight erosion Over grown vegetation
4:1 side slo es
9R-4�in1304
I
OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE
SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT#2
Basin: Cedar River/Lake Washington Subbasin Name: May Creek Subbasin Number: West Basin
—
'' �ymbol Drainage Drainage �ampanent Slape , �i5t8r�ce' �xis��Ein+g ; Potential C,lbservations of fi�ld
Corr►ponent Type, Description from �ite' 1�Cbblerrl� �robiems ' inspector, resaurce
Nam�, and Size ' di5ch�� e reviewer, or resident '
see map 7ype:sheet f1ow,swale, drainage basin,vegetatian,cover� q�6 y.'m1=1,32Kf' ' const(ictlons,unda[�apacity,ponding, ' trikautary ar�a,iikeiihoad of prob3em,
stream,�hannel,pipe potld, depth,type of sensitave aK@a,, 'ft. 'oyertoppitlg,ftaoding,habit�t,or organism 'overflow pathways,potential itYtpacts '
Size:diameter surface atea xol�me = ' desfruct[on,sco�ring,bank sloughing, >
' ;:: ` 'sed(mentatinn,[nGslon ather erosion
BA Sheet flow Over stee slo es +/-40% 0 Stee slo es Stee slo es Brush, ferns, ve small trees
BB Wet Area Skunk cabba e & brush +/_1% 150 None visible None visible No visible roblems
BC Channel flow Roadside ditch +/-1°/a 400 Debris Debris No visible roblems
BD Channel flow Small stream +/-2% S00 Sli ht erosion Sli ht erosion No visible roblems
BE Culvert Under +/-0.5% 805 Debris Debris No visible roblems
BF Channel flow Ma Creek +/-1% 830 Sli ht erosion Sli ht erosion No visible roblems
9R-4\inR04
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� G E O T E C H 13256 Northeast 20th Stree[,Suite 16
Bellevue,Washington 98005
CONSLJI.TANTS, INC. (425)747-5618 FAX(425)747-8561
September 9, 2002
JN 02326
Cambridge Homes
1800 Northeast 44th Street
Renton, Washington 98056
Attention: Dale Huffman
Subject: Transmittal Letter— Geotechnicai Engineering Study
Proposed Elsa Ridge Subdivision
3785 Lincoln Avenue No�theast
Renton, Washington
Dear Mr. Huffman:
We are pleased to present this geotechnical engineering report for the proposed Elsa Ridge
Subdivision in Renton, Washington. The scope of our services consisted of exploring site surface
and subsurface conditions, and then developing this report to provide recommendations for general
earthwork, design criteria for foundations and retaining walls, and slope setbacks. This work was
. authorized by your acceptance of our proposal, P-5860, dated August 14, 2002.
The attached report contains a discussion of the study and our recommendations. Please contact
� us if there are any questions regarding this repo�t, or for further assistance during the design and
� construction phases of this project.
Respectfully submitted,
GEOTECH CONSULTANTS, INC.
�� � T ���
Kristopher T. Hauck
Geotechnical Engineer
cc: Peterson Consu(ting Engineers —Jennifer Steig, P.E.
via facsimile: (425) 822-7216
KTH/MRM: alt
r_GnTcru rnnici n -cniTc in�r
: GEOTECHNICAL ENGINEERING STUDY
Proposed Elsa Ridge Subdivision
3785 Lincoln Avenue Northeast
Renton, Washington
This report presents the findings and recommendations of our geotechnical engineering study for
the site of the proposed Elsa Ridge Subdivision to be located at 3785 Lincoln Avenue Northeast in
Renton, Washington.
We were provided with site plans and a topographic map. Peterson Consulting Engineers
developed these plans, which are dated July 5, 2002. Based on these plans, we understand that
the property will be divided into six different residential lots, with the existing residence remaining
on one of the lots. The existing garage located on the northern portion of the site will be removed.
The development of plans for the individual homes is still in the planning stage, thus detailed plans
for the houses and site grading were not available at the time of this report. We understand that
each lot is to contain an infiltration trench for disposal of storm water.
If the scope of the project changes from what we have described above, we should be provided
with revised plans in order to determine if modifications to the recornmendations and conclusions of ,
this report are warranted.
- S/TE COND1TlONS I
SURFACE
The Vicinity Map, Plate 1, illustrates the general location of the site. The site is located on the west
side of Lincoln Avenue Northeast in Renton. The property is generally rectangular in shape, with
� approximately 210 feet of frontage a�ong Lincoln Avenue Northeast and a depth of approximately
296 feet in the east-west direction.
An existing residence (#3758) is located in the center of the site. This house contains a basement
with an approximate finished floor elevation of 129 feet and a main floor elevation of approximately
136 feet. A gravel driveway extends into the site from the northeast corner of the property, and
extends west to the north side of the existing residence. A detached garage is �ocated northwest of
the house. This structure appears to be supported on srnall concrete blocks/pads.
The eastern two-thirds of the site is generally landscaped with grass and medium-sized deciduous
and coniferous trees. This portion of the property is relatively flat, with only 1 to 2 feet of fall from
east to west. The ground around the existing residence is a few feet higher in elevation than the
surrounding grade. The western one-third of the site is steeply sloped at an inclination of
approximately 65 to 75 percent. This west-facing slope has a height of approximately 50 to 55 feet.
There were no visible indications of recent slope instability such as tension cracks, areas of
disturbed vegetation, or slide scarps. However, some of the westernrnost trees do exhibit a slight
lean, possibly resulting from downslope creep of the near-surface soils. The steep slope appears
to end near the west property line.
The properties to the north and south are developed with single-family residences that are set back
from the common property lines more than 1 Q feet. The lot to the south contains an existing gravel
driveway that runs parallel to the property line and is approximately 10 feet away at its closest
point.
G=CTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
. September 9, 2002 Page 2
: SUBSURFACE
The subsurface conditions were explored by excavating five test pits at the approximate locations
shown on the Site Explaration Plan, Plate 2. Our exploration program was based on the proposed
construction, anticipated subsurface conditions and those encountered during exploration, and the
scope of work outlined in our proposal.
The test pits were excavated on August 27, 2002 with a rubber-tired backhoe. A geotechnical
engineer from our staff observed the excavation process, logged the test pits, and obtained
representative samples of the soil encountered. "Grab" samples of selected subsurface soil were
collected from the backhoe bucket. The Test Pit Logs are attached to this report as Plates 3
through 5.
Soil Conditions
The test pits generally encountered approximately 2 to 3 feet of loose, medium- to fine-
grained sand overlying medium-dense, medium-grained sand. These sands are generally
well-graded with very little fines after approximately 3 feet in depth. One test pit (Test Pit 1),
located directly south of the existing residence, encountered approximately 3 feet of loose
fill overlying the native soil. These findings confirm the soils mapped by the U.S. Soil
Conservation Service (SCS) are Everett gravelly, sandy loam. The maximum explored
depth of the test pits was 13 feet from the existing grade. �
No obstructions were revealed by our explorations. However, debris, buried utilities, and olc
� foundation and slab elements are commonly encountered on sites that have had previous
: development.
Groundwafer Conditions
No groundwater seepage and no indications of wet soils were observed during our
explorations. The test pits were left open for only a short time period and were conducted
following a relatively dry surnmer. However, based on the permeability of the encountered
soils, we do not anticipate that significant groundwater will be encountered within the depth
of the explorations.
The final logs represent our interpretations of the field logs and laboratory tests. The stratification
lines on the logs represent the approximate boundaries between soil types at the exploration
locations. The actual transition between soil types may be gradual, and subsurface conditions can
vary between exploration locations. The logs provide specific subsurface information only at the
locations tested. The relative densities and moisture descriptions indicated on the test pit logs are
interpretive descriptions based on the conditions observed during excavation.
The compaction of backfill was not in the scope of our services. Loose soil will therefore be found
in the area of the test pits. If this presents a problem, the backfill will need to be removed and
replaced with structural fill during construction.
GEOTECH CONSULTANTS. INC.
Cambridge Homes JN 02326
- September 9, 2002 Page 3
� CONCLUSIONS AND RECOMMENDATIONS
GENERAL
THlS SECTION CONTAINS A SUMMARY OF OUR STUDY AND Fl1VDINGS FOR THE PURPOSES OF A
GENERAL OVERVIEW ONLY. MORE SPECIFIC RECOMMENDATIONS AND CONCLUSlONS ARE
CONTAINED IN THE REMAlNDER OF THlS REPORT. ANY PARTY RELYING ON THlS REPORT SHOULD
READ THE ENTIRE DOCUMEIVT.
The test pits conducted for this study encountered medium-dense, medium-grained sands at
depths of approximately 3 to 4 feet below the existing grade. Based on our findings and
engineering analysis, it is our opinion that the proposed building can be supported by conventional
continuous and spread footings bearing directly on the medium-dense native soil.
Of primary concern for development of the site is the protection of the planned structures from
future instability on the steep slope located on the westem one-third of the site. Typically, slopes
comprised of sands such as this will experience periodic shallow instability as the near-surface soils
loosen over time due to weathering. Deep instability is not anticipated. In order to evaluate an
appropriate slope setback for the planned structures, we perFormed a slope stability anaiysis using
the PCSTAL66 program developed by Purdue University. We analyzed the slope's stability under
both static and earthquake conditions. Based on these analyses, we recommend that the '
structures be located no less than 45 feet from the crest of the steep slope. This sl.ope setback I
. consists of a 10-foot undisturbed buffer at the top of the slope, and a 35-foot foundation setback i,
from the buffer. Appendix A contains the results of our sfope stability analysis. In our opinion, the
slope setback for the houses could be reduced to 40 feet if the western houses utilize a basement
' that extends to at least 7 feet below the lowest surrounding grade.
No grading or clearing should occur within the recommended 10-foot buffer zone. Non-critical
elements, such as patios and sheds, could be located within the foundation setback zone. In
addition to these setbacks, any hardscapellandscape elements, such as brick patios, should not be
sloped to drain to the slope.
Based on our explorations and laboratory analyses, it is our opinion that infiltration is feasible at this
site. We understand that each lot will control its own surface water with infiltration trenches. The
test pits generally found medium-grained sand at approximately 3 to 4 feet from the existing grade.
Since the sites are less than 22,000 square feet, and medium-grained sands were encountered,
the infiltration trenches can be designed using the values given in Section 5.1.1 of the King County
SurFace Water Design Manual (KCSWDM). However, some overexcavation to reach the medium
sands may be necessary, especially on Lots 3 and 6, due to the presence of some fill soil at the
surface surrounding the existing residence. Therefore, the elevation of the infiltration trench may
need to be lowered in these areas. 1f the trenches are located over 45 feet from the steep slope,
their operation should not adversely affect slope stability.
The reuse of these soils as structural fill will likely only be successful during hot, dry weather. On
previous projects utilizing similar sand soils as fill, they have required repeated compaction and
wetting to obtain adequate compaction for structural fill. Imported granufar fifl will be needed
wherever it is not possible to adequately compact the on-site soils.
The erosion control measures needed during the site development wilE depend heavily on the
weather conditions that are encountered. We recommend that a wire-backed silt fence and highly-
visible construction fence be erected at the edge of the undisturbed buffer prior to beginning
�
G�OTECH COhSULTANTS, INC
Cambridge Homes JN 02326
� September 9, 2002 Page 4
� substantial site clearing activities, Rocked construction roads should be extended into the site to
reduce the amount of mud and soil carried off the property by trucks and equipment. Wherever
possible, these roads should follow the alignment of planned pavements. Cut slopes and soil
stockpiles should be covered with plastic during both wet and dry weather. This prevents erosion
and keeps the sands from drying out during hot weather. Following rough grading, it may be
necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping
or an impervious surFace. Additional erosion control measures may need to be implemented to
address the conditions encountered during site work.
Geotech Consultants, Inc. shoufd be a�lowed to review the final development plans to verify that the
recommendations presented in this report are adequately addressed in the design. Such a plan
review would be additional work beyond the current scope of work for this study, and it may include
revisions to our recommendations to accommodate site, development, and geotechnical
constraints that become more evident during the review process.
We recommend including this report, in its entirety, in the project contract documents. This report
should also be provided to any future property owners so they will be aware of our findings and
recommendations.
SE/SMlC CO1VS/DERATIONS
The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1997 Uniform
Building Code (UBC). In accordance with Table 16-J of the 1997 UBC, the site soil profile within
100 feet of the ground surface is best represented by Soil Profile Type So (Stiff Soil). The site soils
: are not susceptible to seismic liquefaction because of their medium-dense nature and the absence
of near-surface groundwater.
CONVENTIONAL FOUNDATIONS
The proposed structures can be supported on conventional continuous and spread footings bearing
on undisturbed, medium-dense native sand. See the section entitled General Earthwork and
Structural Fill for recommendations regarding the placement and compaction of structural fill
beneath structures. Adequate compaction of structural fill should be verified with frequent density
testing during fill placement. Prior to placing structural fill beneath f�undations, the excavation
should be observed by the geotechnical engineer to document that adequate bearing soils have
been exposed. We recommend that continuous and individual spread footings have minimum
widths of 12 and 16 inches, respectively. Footings should also be bottomed at least 18 inches
below the lowest adjacent finish ground surface. The local building codes should be reviewed to
determine if different footing widths or embedment depths are required. Footing subgrades must
be cleaned of loose or disturbed soil prior to pouring concrete. Depenciing upon site and
equipment constraints, this may require removing the disturbed soil by hand.
Depending on the final site grades, overexcavation may be required below the footings to expose
competent native soil. Unless lean concrete is used to fill an overexcavated hole, the
overexcavation must be at least as wide at the bottom as the sum of the depth of the
overexcavation and the footing width. For example, an overexcavation e�ending 2 feet below the
bottom of a 2-foot-wide footing must be at least 4 feet wide at the base of the excavation. If fean
concrete is used, the overexcavation need only extend 6 inches beyond the edges of the footing.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 5
An ailowabie bearing pressure of 2,500 pounds per square foot (psfl is appropriate for footings
supported on competent native soil. A one-third increase in this design bearing pressure may be
used when considering short-term wind or seismic loads. For the above design criteria, it is
anticipated that the total post-construction settlement of footings founded on competent native soil,
or on structural fil( up to 5 feet in thickness, will be about one-half inch, with differentiaf settlements
on the order of one-half inch in a distance of 50 feet along a continuous footing with a uniform load.
Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and
the bearing soil, or by passive earth pressure acting on the vertica(, embedded portions of the
foundation. For the latter condition, the foundation must be either poured directly against relatively
level, undisturbed soil or be surrounded by level structuraf fill. We recommend using the following
ultimate values for the foundation's resistance to lateral loading:
,
Coefficient of Friction 0.45
Passive Earth Pressure 300 pcf
Where: (1)pcf is pounds per cubic foot,and(ii) passive earth
pressure is computed using the equivalent fluid density.
If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will
nat be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's
resistance to lateral loading, when using the above ultimate �alues.
PERMANENT FOUNDATION AIVD RETA/N1NG WALLS
Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures
imposed by the soil they retain. The following recommended parameters are for walls that restrain
level backfill:
� .
Active Earth Pressure � 35 pcf
; Passive Earth Pressure 300 pcf
Coefficient of Friction 0.45
�� Soil Unit Weight 130 pcf
Where: (i) pcf is pounds per cubic foot, and (ii) active and
passive earth pressures are computed using the equivalent fluid
pressures.
' For a restrained wall that cannot deflect at least 0.002 times its
height,a uniform lateral pressure equal to 10 psf times the height
of the wall should be added to the above active equivalent fluid
pressure.
G=OTECH CQNSULTANTS. INC.
Cambridge Homes JN 02326
September 9, 2002 Page 6
� The values given above are to be used to design permanent foundation and retaining walls only.
The passive pressure given is appropriate for the depth of level structural fill placed in front of a
retaining or foundation wall only. The values for friction and passive resistance are ultimate values
and do not include a safety factor. We recommend a safety factor of at least 1.5 for overturning
and sliding, when using the above values to design the walls. Restrained wall soil pararneters
should be utilized for a distance of 1.5 times the wafl height from corners or bends in the walls.
This is intended to reduce the amount of cracking that can occur where a wall is restrained by a
corner.
The design values given above do not include the effects of any hydrostatic pressures behind the
walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent
foundations will be exerted on the walls. If these conditions exist, those pressures should be added
to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need
to be given the wall dimensions and the slope of the backfill in order to provide the appropriate
design earth pressures.
Heavy construction equipment should not be operated behind retaining and foundation walls within
a distance equaf to the height of a wall, unless the walls are designed for the additional lateral
pressures resulting from the equipment. The wall design criteria assurne that the backfill will be
well compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should
be accomplished with hand-operated equipment to prevent the walls from being overloaded by the
higher soil forces that occur during compaction. •
Retainin_q Wa11 Backfill and Waterproofinq
, Backfill placed behind retaining or foundation walls should be coarse, free-draining
structural fill containing no organics. This backfill should contain no more than 5 percent silt
or clay particles and have no gravel greater than 4 inches in diameter. The percentage of ,
� particles passing the No. 4 sieve should be between 25 and 70 percent. If the native sand
is used as backfill, a minimum ,12-inch width of free-draining gravel should be placed
against the backfilled retaining walls. The drainage composites should be hydraulically
connected to the foundation drain system. Free-draining backfill or gravel should be used
for the entire width of the back�ll where seepage is encountered. For increased protection,
drainage composites should be placed along cut slope faces, and the walls should be
backfilled entirefy with free-draining soil.
The purpose of these backfill requirements is to ensure that the design criteria for a
retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the
wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively
impermeable soif or topsoil, or the surface should be paved. The ground surface must also
slope away from backfilled walls to reduce the potential for surface water to percolate into
the backfill. The section entitled General Earthwork and Sfructural Fill contains
recommendations regarding the placement and compaction of structural fill behind retaining
and foundation walls.
The above recommendations are not intended to waterproof below-grade walls. Over time,
the performance of subsurface drainage systems can degrade, subsurface groundwater
flow patterns can change, and utilities can break or develop leaks. Therefore, waterproofing
should be provided where future seepage through the walls is not acceptable. This typically
includes limiting cold-joints and wall penetrations, and using bentonite paneks or
membranes on the outside of the walls. Waterproofing systems should be installed by an
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 7
: experienced contractor familiar with the anticipated construction and subsurFace conditions.
Applying a thin coat of asphalt emulsion to the outside face of a wall is not considered
waterproofing, and will only help to reduce moisture generated from water vapor or capillary
action from seeping through the concrete. As with any project, adequate ventilation of
basement and crawl space areas is important to prevent a build up of water vapor that is
commonfy transmitted through concrete walls from the surrounding soil, even when
seepage is not present. This is appropriate even when waterproofing is applied to the
outside of foundation and retaining walls. �,
SLABS-ON-GRADE ,
The building floors may be constructed as slabs-on-grade atop non-organic native soils. The
subgrade soil must be in a firm, non-yielding condition at the time of slab construction or underslab �
fill placement. Any soft areas encountered should be excavated and replaced with select, imported
structural fill. ,
All slabs-on-grade should be underlain by a capillary break or drainage layer consisting of a II'
minimum 4-inch thickness of coarse, free-draining structural fill with a gradation similar to that '
discussed in Permanent Foundation and Retaining Walls. As noted by the American Concrete
Institute (ACI) in the Guides for Concrete Floor and Slab Strucfures, proper moisture protection is �
desirable immediately below any on-grade slab that will be covered by tile, wood, carpet,
impermeable floor coverings, or any moisture-sensitive equipment or products. ACI also notes that '
vapor refarders, such as 6-mil plastic sheeting, are typically used. A vapor retarder is defined as a
material with a permeance of less than 0.3 US perms per square foot (psfl per hour, as determined
by ASTM E 96. It is possible that concrete admixtures may rneet this specification, although the
manufacturers of the admixtures should be consulted. Where plastic sheeting is used under slabs,
joints should overlap by at least 6 inches and be sealed with adhesive tape. The sheeting should
extend to the foundation walls for maximum vapor protection. If no potential for vapor passage
through the slab is desired, a vapor barr�er should be used. A vapor barrier, as defined by ACI, is a
product with a water transmission rate of 0.00 perms per square foot per hour when tested in
accordance with ASTM E 96. Reinforced membranes having sealed overlaps can meet this
requirement.
In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well-graded
compactable granular material, such as a 5/8-inch-minus crushed rock pavement base, be placed
over the vapor retarder or barrier to protect them during sfab construction and to act as a "blotter"
for more even curing of the concrete slab. However, more current literature indicates that long-
term vapor problems could result where the protection/blotter material becomes wet before the slab
piacement occurs. This is especially an issue in areas with wet climates, such as the Puget Sound.
Therefore, if there is a potential that the protection/blotter material will become wet before the slab
is installed, ACI now recommends that no protectionlblotter material be used, However, they then
recommend that the joint spacing in the slab be reduced, a Iow shrinkage concrete mixture be
used, and "other measures" (steel reinforcing, etc.) be utilized to reduce the potential for irregular
slab curing and excessive shrinkage cracking due to uneven curing.
We recommend that the contractor, architect, structural engineer, and the owner discuss these
issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance
on the use of the protection/blotter material.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 8
EXCAVATIONS AND SLOPES
Excavation slopes should not exceed the limits specified in local, state, and national government
safety regulations. Temporary cuts to a depth of about 4 feet may be attempted verticaNy in
unsaturated soil, if there are no indications of slope instability. However, vertical cuts should not be
made near property boundaries, or existing utilities and structures. Based upon Washington
Administrative Code (WAC) 296, Part N, the soil at the subject site would generally be classified as
Type B. Therefore, temporary cut slopes greater than 4 feet in height cannot be excavated at an
inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the
bottom of a cut.
The above-recommended temporary slope inclination is based on what has been successful at
other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a
relatively short duration to allow for the construction of foundations, retaining walls, or utilities.
Temporary cut slopes should be protected with plastic sheeting during wet weather. The cut slopes
should also be backfi{led or retained as soon as possible to reduce the potential for instability.
Please note that sand can cave suddenly and without warning. Excavation, foundation, and utility
contractors should be made especially aware of this potential danger.
All permanent cuts into native soil and slopes constructed of compacted fiil should be incfined no
steeper than 2.5:1 (H:V). To reduce the potential for shallow sloughing, fill must be compacted to
the face of these slopes. This can be accomplished by overbuilding the compacted •fill and then
. trimming it back to its final inclination. Adequate compaction of the slope face is important for long-
term stability and is necessary to prevent excessive settlement of patios, slabs, foundations, or
other improvements that may be placed near the edge of the slope.
� Water should not be concentrated to flow uncontrolled over the top of any temporary or permanent
slope. AII permanently exposed slopes should be seeded with an appropriate species of vegetation
to reduce erosion and improve the stability of the surficial layer of soil. Any disturbance to the
existing steep slope outside of the building limits may reduce the stability of the slope. Damage to
the existing vegetation and ground should be minimized, and any disturbed areas should be
revegetated as soon as possible. Soil from the excavation should not be placed on the slope, and
this may require the off-site disposal of any surplus soil.
DRAlNAGE CONS/DERATIONS
Foundation drains should be used along the perimeter of all foundations and basement walls.
Drains should also be placed at the base of all earth-retaining walls. These drains should be
surrounded by at least 6 inches of 1-inch-minus, washed rock and then wrapped in non-woven, �I
geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar material}, At its highest point, a
perforated pipe invert should be at least 6 inches below the bottom of a slab floor or the level of a
crawl space, and it should be sloped for drainage. All roof and surface water drains must be kept
separate from the foundation drain system. A typical drain detail is attached to this report as Plate
9. For the best long-term performance, perForated PVC pipe is recommended for all subsurface
drains.
As a minimum, a vapor retarder, as defined in the Slabs-On-Grade section should be provided in
any crawl space area to limit the transmission of water vapor from the underlying soils. Also, an
outlet drain is recommended for all crawl spaces to prevent a build up of any water that may
bypass the footing drains.
GEOTECH CONSULTANTS. INC.
Cambridge Homes JN 02326
September 9, 2002 Page 9
: No groundwater was observed during our fieldwork. If seepage is encountered in an excavation, it
should be drained from the site by directing it through drainage ditches, perforated pipe, or French
drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of
the excavation.
The excavations should be graded so that surface water is directed away from the tops of slopes.
Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be
constructed. Final site grading in areas adjacent to t�e residences should slope away at least 2
percent, except where the area is paved. SurFace drains should be provided where necessary to
prevent ponding of water behind foundation or retaining walls. Water fr�m roof, storm water, and
foundation drains should not be discharged onto slopes.
GENERAL EARTHWORK AND STRUCTURAL FILL
All building and pavement areas should be stripped of surface vegetation, topsoil, organic soil, and
other deleterious material. The stripped or removed rnaterials should not be mixed with any
materials to be used as structural fill, but they could be used in non-structural areas, such as
landscape beds.
Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building,
behind permanent retaining or foundation walls, or in other areas where the underlying soil needs
- to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or
near, the optimum moisture content. The optimum moisture content is that moisture content that
�_ results in the greatest compacted dry density. The moisture content of fill is very important and
must be closely controlled during the filling and compaction process.
The allowabfe thickness of the fill lift will depend on the material type selected, the compaction
equipment used, and the number of passes made to compact the lift. The loose lift thickness
should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not
sufficiently compacted, it can be recompacted before another lift is placed. This eliminates the
need to remove the fill to achieve the required compaction. The following table presents
recommended relative compactions for structural fill:
� i � .
� • � �
Beneatn footings slabs 95%
or walkwa s
Filled slopes and behind 90%
retainin walls
95% for upper 12 inches of
Beneath pavements subgrade; 90% below that
level
Where: Minimum Relative Compaction is the ratio, expressed in
percentages, of the compacted dry density to the maximum dry
density, as determined in accordance with ASTM Test
Designation D 1557-91 (Modified Proctor).
Structural fill that will be pfaced in wet weather should consist of a coarse, granular soil with a silt or
clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve
should be measured from that portion of soil passing the three-quarter-inch sieve.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 10
: L!MlTATIONS
The analyses, conclusions, and recommendations contained in this report are based on site
conditions as they existed at the time of our exploration and assume that the soil and groundwater
conditions encountered in the test pits are representative of subsurface conditions on the site. If
the subsurface conditions encountered during construction are significantly different from those
observed in our explorations, we should be advised at once so that we can review these conditions
and reconsider our recommendations where necessary. Unanticipated soil conditions are
commonly encountered on construction sites and cannot be fully anticipated by merely taking soil
samples in test pits. SubsurFace conditions can also vary between exploration locations. Such
unexpected conditions frequently require making additional expenditures to attain a prope�ly
constructed project. It is recommended that the owner consider providing a contingency fund to
accommodate such potential extra costs and risks. This is a standard recommendation for all
projects.
The recornrnendations presented in this report are directed toward the protection of onl the
Y
proposed residences from damage due to slope movement. Predicting the future behavior of steep
slopes and the potential effects of development on their stability is an inexact and imperfect
science that is currently based mostly on the past bshavior of slopes with similar characteristics.
Landslides and soil movement can occur on steep slopes before, during, or after the development
of property. The property owners must ultimately accept the possibility that some slope movement
could occur, resulting in possible loss of ground or damage to the facilities west of the proposed
residences.
This report has been prepared for the exclusive use of Cambridge Homes and its representatives
for specific application to this project and site. Our recommendations and conclusions are based
on observed site materials, selective laboratory testing, and engineering ana{yses. Our
conclusions and recommendations are professional opinions derived in accordance with current
standards of practice within the scope of our services and within budget and time constraints. No
warranty is expressed or implied. The scope of our services does not include services related to
construction safety precautions, and our recommendations are not intended to direct the
contractor's methods, techniques, sequences, or procedures, except as specifically described in
our report for consideration in design.
ADD1T101VAL SERVICES
In addition to reviewing the final plans, Geotech Consultants, Inc. should be retained to provide
geotechnical consultation, testing, and observation services during construction. This is to confirm
that subsurface conditions are consistent with those indicated by our exploration, to evaluate
whether earthwork and foundation construction activities comply with the general intent of the
recomrnendations presented in this report, and to provide suggestions for design changes in the
event subsurface conditions differ from those anticipated prior to the start of construction.
However, our work would not include the supervision or direction of the actual work of the
contractor and its employees or agents. Also, job and site safety, and dimensional measurements,
will be the responsibility of the contractor.
GEOTECH CONSULTANTS, INC.
Cambridge Homes JN 02326
September 9, 2002 Page 11
� The following plates are attached to compiete this report:
Plate 1 Vicinity Map
Plate 2 Site Exploration Plan
Plates 3 - 5 Test Pit Logs
Plate 6 - 8 Grain Size Analysis
Plate 9 Typical Footing Drain
Appendix A Slope Stability Analysis
We appreciate the opportunity to be of service on this project. If you have any questions, or if we
may be of further service, please do not hesitate to contact us.
Respectfully submitted,
GEOTECH CONSULTANTS, INC. �
� �� � T= �'�
�
Kristopher T. Hauck
Geotechnical Engir
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' VICINITY MAP
� GEOTECH 3785 Lincoln Avenue Northeast
CONSULTANTS,INC. Renton, Washington
�
�-��.-,� Job No: Date: Plate: �
02326 Sept. 2002
' N
�
� �
�.._.._.._.._.._.._.._.._.._.._.._.._.._.._.._.. .._.._.._.._.._.._.._..
� �
� Lot 2 �� Lot 1
� �
I n
e�
a�
I � TP-3� �
�� O
1 Z
, � Lot 3 existing Lo�4 =
house �
I Q
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� TP-1� c
' I J
� Lot 6 Lof 5
1
� ; ,�-z°
I
I
I
' SITE EXPLORATION PLAN
� GEOTECH 3785 Lincoln Avenue Northeast
�
co�suLT�rrrs,mc. Renton, Washington
� �
� "�� Job No: Dare: Plafe:
02326 Sept. 2002 No Scale 2
I
���lo���fiti�o-�� 5 TEST P17 1
9� ��p� `��,�' Q�G Description
ro soil
Brown SAND, occasional gravel, medium-grained, damp to moist, loose (FILL)
FILL
a ��
- 5 m- �4.°�� ; SM Red-brown, silty SAND, fine-to medium-grained, abundant roots, moist, loose
(: .
an-gray, gravelly SAND, medium-grained, moist, medium-dense
m =5.9% ,: SP `.
" Test Pit was terminated at 8 feet on August 27, 2002.
�p ' No groundwater seepage was observed during excavation.
" Slight caving was observed from 0 to 4 feet during excavation.
15
�,� ��,��,��1� TEST P IT 2 �I,
��,�r �o ,��,e�aa�ti� ��5
� 9 �,° � t} Description
-ra Soa
;� SM
' Tan-brown, slightly silty SAND, occasional gravel, damp to moist, loose
� SP
' Tan-gray SAND, occasional gravel, medium-grained, moist, medium-dense
5
' SP
�,
10
�SP ' Gray, slightly silty SAND, medium-grained, moist, medium-dense to dense
� SM
� ;
'` Test Pit was terminated at 13 feet on August 27, 2002.
�� ° * No gro�ndwrater seepage was observed during excava�oor�.
* Slight caving was observed between 0 and 4 feet during excavation.
' TEST PIT LOGS
� GEOTECH 3785 Lincoln Avenue Northeast
CONSULTANTS,IIvc. Renton, Washington
�
, �� Job No: Dafe: Logged by: Plate:
02326 Sept.2002 KTH 3
��.����� TEST PIT 3
�4� �° r���o-o,�� gG5
9 �p �. � Description
o ���
. ' ' an-brown, gravelly SAND, medium-grained, damp to moist, loose
SP
`Tan-gray SAND, occasional gravel, medium-grained, moist, medium-dense
5
' becomes medium-dense to dense, without gravel
.: SP
� 10
* Test Pit was terminated at 11 feet on August 27, 2002.
* No groundwater seepage was observed during excavation.
' Slight caving was observed from 0 to 4 feet during excavation.
�� 15
;
�
� �,� �,�<fi��� TEST PIT 4
9��� ��p��,�o-��e�5� Description
Old To soil
' SP ;'Tan-brown, slightly silty SAND, occasional gravel, fine-grained, damp, loose
SM
Tan-gray, gravelly SAND, medium-grained, moist, medium-dense °
' S v
_ ' SP
. - becomes medium-to coarse-grained, without gravel
10 * Test Pit was terminated at 9 feet on August 27, 2002. I�
* No groundwater seepage was observed during excavation. �
* No caving was observed during excavation.
��Y
� ' TEST PIT LOGS
� GEOTECH 3785 Lincoln Avenue Northeast
CONSULT.ANTS,nvc. Renton, Washington
�
� Job No: Date: Logged by: plate:
02326 Sept. 2002 KTH 4
��`.��c�'��,ti�a�<� � TEST PIT 5
�, o ti ti G
� �Ga� �� �}5 Description
Crushed rock 518'-
. sM ; Red-brown, silty SAND, fine-grained, moist to damp, loose
3 Gray-tan, gravelly SAND, medium- to coarse-grained, moist, medium-dense
— m=3.0'� i .
5 ' SP : becomes medium-dense to dense
�,,-
10 " Test Pit was terminated at 9 feet on August 27, 2002.
" No groundwater seepage was observed during excavation.
� ' No caving was observed during excavation.
15
� .
i
' TEST PIT LOGS
� GEOTECH 3785 Lincoln Avenue Northeast
CONSUI,TANTS,INC. Renton, Washington
�
Job No: Date: Logged by: Plate:
�� 02326 Sept. 20�2 KTH 5
Sample Data:
Test Pit/Boring: 1 Pan#: 17N
Sample: 1 Tare: 0
Depth: 4' WE4 Weight: 551.6
Dry Weight: 483.7
Wash Data: %Moisture: 14.0
ory w�9nt�berore vrasn�: 483.7 grams
�ry wei9rrt�attervrasr,�: 401 grams
wast�ed sa�w�ynt: 82.7 grams
- Sal Retained in pan 0.3 grams
ve< > eewe - ei Ec
1r�es or No. <. mrn. �9eams) Percenf Retairsed Passed :
E�h .; 'Total :.. .:. :'Eaek� # ' Tota! .: <Total
� 11/Z � 38.10 � 0.0� 0.0� 0.0� 0.0� 100.0
��------------F---------+---------�----------+-----------�------------+----------
3/4 � 19.05 � 0.0� O.Of 0.0� d.0� 100.0 �
---------------L--_____�J._____----L___--__�1.__-------;------------.�__-------
3/8 � 9.53 ; 43.2� 43.2� 8.9� 8.9� 91.1
����������������F���������.i������������������.���������4�N»������.4.r��������
4 ; 4.75 ; 27.4; 70.6; 5.7; 14.6; 85.4
, �w���������r����'���ti.�-����������'���'�rt.������������-�-�'-���'������'�
10 ; 2.00 ; 26.6; 97.2; 5.5; 20.1; 79.9
'_��_"��"��r��_�-�'__'.r"-��__-r---___--_'.T.�_'�'__�_r'���'_--"'r__--'__-_'-
40 � 0.43 � 107.7� 2D4.9� 22.2� 42.3� 57.7
______--------F---------+----------F----------+---------_�_--____--�-----------
____�100 _ � 0.15 � 173.0� 377.9� 35.7� 78.0� 22.0
� _.L_�������« 1������__��� �l_��___��_�
������������ , L������� 1 1������M� �
200 � 0.08 � 23.7� 401.6� 4.9� 82.9� 17.1
--------------�-----------�-----------�----------i------------�----------y-_-------
�200 ; 0.00 ; 83.0; 484.6� 17.1; 100.0; �
:
:::..�a�t ;: ;:':..48�S :::.....�OD 2 ;.: ..: .�_2
I
Sieve Opening(mm.)
100.00 10.00 1.0� 0.10 0.01
100
1100.0 100.0 �
91.1 80
85.4
79.9 �� �
d
'� 60 �
5/.7 50 �
_
i � �
30 a
22.0 20
17.1 10
� , i I � I I� I I i ; � 0
�
' GRAIN SIZE ANALYSIS
� � GEOTECH 3785 Lincoln Avenue Northeast
CONSULTAN7'S,nvc. Renton, Washington
�
Job No: Date: Plate:
���� 02326 Sept. 2002 fi
� Sampie Data:
Test PitlBoring: 1 Pan#: 13N
Sample: 2 Tare: 0
� p�: 7' Wet WeigM: 554.1
Dry WeigM: 523
Wash Data: %Moisture: 5.s
I �ry weignt(berore virasn): 523 g ra ms
Dry Weight(afterwash): 491.3 grams
I ' wasr,�d sou w�yrrt: 31.7 grams
Sa1 Retai�ed in pan 0.1 gfAtT15
I � - �. � , r �
tnches ar Nc:. mm. >'(9rarnsl Pevicent Reiained Passed
<Eacfi ; Tofal > EaEfi � Tot� ' 7otal '
1112 � 38.10 � 0.0� 0.0� O.Q� 0.0� 100.0
-------------h-----------�---------F-____----�----------h----------�------------
3/4 � 19.05 � 0.0� 0.0� 0.0� 0.0� 100.0
'��� ��L��������1�������{...�������y�����M���1�������1������'
3/8 � 9.53 � 27.4 f 27.4� 5.3� 5.3� 94.7
���������������M������.i.�������4��������.L���r«���4��w�������i���r�'���
4 ; 4.75 ; 31.0; 58.4; 6.0; 11.2; 88.8
_ _____�'__�'___�r«��_���.M-__�����'��M.�.___��__'_�»'__�___-_��__�_____
10 ; 2.00 ; 23.6; 82.0; 4.5; 15.8; 84.2
'��_'��"___r��'��'_T�_'�_�«r�_�_T_���__'-r���__'__�.�_-��_�--
_____ 40 � 0.43 � 157.7� 239.7� 30.3� 46.1� 53.9 .
------F--------+----------�---------+-----------�------------+-----------
_____ 100 � 0.15 � 228.9� 468.6� 44.0� 90.0� 10.0
------�---------'i'-'-----�-�-.���s-----------�------�------�--�--------
200 � 0.08 � 20.0� 488.6� 3.8� 93.9� fi.1
����������������L�����M���i��������i����������1����������L����������_1���������»
<200 ; 0.00 ; 31.8; 520.4; 6.1; 100.0;
_ _ _ _
' Totat ' '`'�.;4 99.5 0'.5
� � Sieve Opening(mm.)
100.00 10.00 1.00 0.10 0.01
, 100
100.0 100.0 I 90
" 94.7
88.8 84.2 � BO
7Q .o
! � d
j � � � ,
' � � ' 50 � i
53.9 �
- � a,
v
�
ai
;
3p a
20
� 10
` I � i � i 10.0 6.1 I � I � �
I
�
� GRAIN SIZE ANALYSIS
� GEOTECH 3785 Lincoln Avenue Northeast
CONS'LJLTAN'IS,nvc. Renton, Washington
�
� , �_� Job No: Date: Plate:
02326 Sept. 2002 7
Sample Data:
Test PiUBoring: 5 Pan#: 14N
Sample: 1 Tare: 0
Depth: 3' Wet Weight: 551
Dry Weight: 534.7
Wash Data: %Moisture: 3.0
Dry Weight(before wash): 534.7 91'3R15
Dry Weight(afterv+rash): 516.2 9f8fT15
Washed Sal Weight: 18.5 grams
Sal Retained in pan 0.1 grams
ve =' ve - ; :: e�g. F�
inches ar hlo. tim ;:�grarm} : Percent Reiaineti Passed :
. . : �eh>:> � ;7'oE�l �aeh'<> t ;;ToEal >, . ...:iotal ,:::
_____1_112 � 38.10 � OA� 0.0� Q.O� 0.0� 100.0
--------}----------+----------�----------+-----------�-----------+----------- .
_�__314 � 19.05 � 14.5� 14.5� 2.7� 2.7� 97.3
-----;---------y----------;-----------�----------L---�_w_�'-----__--
3/8 ; 9.53 � 57.6� 72.11 10.8� 13.5! 86.5
--------------•---------r---------_�_-------�------------�------------�--------
----
4 ; 4.75 ; 52.5; 124.6; 9.8; 23.3; 76.7
________'��'_�_t_�__�___'_.�_'____--__r_�_�-_"�_____'_�__r'���_��_'_.Y�_�_______ I
10 ; 2.00 ; 35.9; 160.5; 6.7; 30.1; 69.9
_'_-____�__�_rr�'_�___T_'����__r_��'�_.r___�_-__^r-�����_��_r_______'__�
- 40 � 0.43 � 199.8� 360.3� 37.4� 67.5� 32.5
----_--_--_--F--------+---------�----------+----------F---------�-----------
� ___y 100_�- � 0.15 � 149.3� 509.6� 28.0� 95.4� 4.6
�---------;�--_--_---�-----------;----------L------------J-----------
200 f 0.08 � 5.7� 515.3� 1.1� 96.5� 3.5
-- -�-------_i_--------�---------�------------L----------'�---------
<200 ; 0.00 ; 18.6; 533.9; 3.5; 100.0;
Ta�t >:' ;> >;:.533 9 ;. ..J9:9 :<: �.'t:
1
Sieve Opening(mm.)
100.00 10.00 1.00 0.10 0.01
� 10Q
100.0 97.3 gp
86.5 � i 80
76.7 70 �
69.9 °'
� GO N
�
� a
_ � � �
d
32.5 � a
20
f ` ; 10
� i I II ) � �4.6 3.5 � �0
� � GRAIN SIZE ANALYSIS
� GEOTECH 3785 Lincoln Avenue Northeast
co�vs�.,T�rrs,nvc. Renton, Washington
Job No: ate: Plate:
02326 Sept. 2002 8
Slope backfili away from
foundation. Provide surface
drai�s where necessary.
Tightline Roof Drain
(Do not connect to footing drain)
BaCkfiil ' ia
(See text for I� !,'
requirements) e � :
� ' Vapor Retarder
Nonwoven Geotextile � or Barrier
: �>. ::
Filter Fabric � '
Washed Rock ' � ' g�qg ,
(7/8" min. size) - _
� ,� � p c� p o'".p�,.0'- p,.C�" p,.a' ".p .a." p,.A
O O O v •o�Q o 'a-�� o. •�'�• o.�•�.opo �.�.O�po ,<
�o�o�a�o� c� c ?< :��.: �i �-� �?� �j G o ��D o : �O�o . �p'o . �1 0'0 :
O O O O C _; ;: 'a� p ��� • q o�'�� �•• p o�•
o � o oa oa �
0 o v o 0 o a.cp a.np� a.op a.op� a.ep a.e�
OnOoO cOoO ; _ .'o ...y'��.o . .•o��.o .•o��.'o ...•o��.b . .�o'�.o .
� o 0 0 0 .:.:� ;:: ": .:. .��. ..:: ', o .
aOoOo O°C° '� 1 �
0 0 0
_: .;.;. -,..�..:. . :�..;. ..-.;� . :�:.�,:,:
� . . . . ... ..
C�� 17�II1. �O Oa O O� I li�,
00
Free-Draining Gravel
(if appropriate}
4" Perforated Hard PVC Pipe
(Invert at least 6 inches below
slab or crawl space. Slope to
drain to appropriate autfall.
Place holes downward.}
NOTES:
(1) i� crawl spaces, provide an ou#let drain to prevent buildup of wa�er tha�
bypasses the perimeter footing drains.
(2) Refer to report text #or additional drainage and waterproofing considerations.
� FUOTING DRAIN DETAIL
� GEOTECH 3785 Lincoln Avenue Northeast
CONSULTAIV'I5,ING Renton, Washington
0 0: Date: ca e: Plate:
— 02326 Sept. 2002 Not to Scale 9
��
� '~�
APPENDIX A - SLOPE STABILITY aIVALYS/S
Proposed Elsa Ridge Subdivision
3785 Lincoln Avenue Northeast
Renton, Washington
i
GEOTECH CONSULTANTS, IIVC.
• Profile.out
**PCSTABL6 '*
by
Purdue University
modified by
Peter J. Bosscher
University of Wisconsin-Madison
I
--Sfope Stability Analysis--
Simplified Janbu, Simplified Bishop
or Spencer's Method of Slices
PROBLEM DESCRIPTION
� '
BOUNDARY COORDINATES
3 Top Boundaries
3 Total Boundaries
Boundary X-Left Y-Left X Right Y-Right Soil Type
No. (ft} (ft) (ft) (ft) Below Bnd
1 0.00 50.00 50.00 50.00 1
2 50.00 50.00 115.00 10Q.00 1
3 115.00 100.00 180.OQ 100.00 1
ISOTROPIC SOIL PARAMETERS
1 Type(s) 4f Sail
Soil Totaf Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. lntercepf Angle Pressure Constant Surface
No. (pcf) (pcf} (psfl (deg) Param. (psf} No.
Page 1
Profile.out
1 110.0 115.0 0.0 35.0 D.00 0.0 0
A Critical Failure Surface Searching Method, Using A Random
Technique For Generating Circular Surfaces, Has Been Specified.
' 900 Trial Surfaces Have Been Generated.
30 Surfaces Initiate From Each Of 30 Points Equally Spaced
Along The Ground Surface Between X= 35.00 ft.
and X= 90.00 ft.
Each Surface Terminates Between X= 160.00 ft.
and X= 165.00 ft.
Unless Fu�ther Limitations Were Imposed, The Minimum Efevation
At Which A Surface Extends Is Y= Q.00 ft.
5.00 ft. Line Segments Define Each Trial Failure Surface.
L
Fol{owing Are Displayed The Ten Most Critical Of The Trial
Failure Surfaces Examined. They Are Ordered - Most Criticai
First.
** Safety Factors Are Calculateci By The Modified Bishop Mefhod "'`
Failure Surface Specified By 26 Coordinate Points
Point X-Surf Y-Surt I
No. (ft) (ft)
1 50.17 50.13
2 54.91 51.75
3 59.63 53.39
4 64.33 55.08
5 69.03 56.80
6 73.71 58.55
7 78.38 60.34
8 83.04 62.16
9 87.68 64.02
Page 2
• Profile.out
10 92.31 65.91
� 11 96.92 67.84 I
12 101.52 69.80 '
13 106.10 71.80
14 110.67 73.83
15 115.23 75.90
16 119.76 77.99
17 124.29 80.13
18 128.79 82.29
19 133.28 84.49 '
20 137.76 86.73
21 142.21 89.00 j
� 22 146.65 91.30
23 151.07 93.63
24 155.48 96.00
25 159.86 98.40
26 162.75 100.00 I
Circle Center At X= -163.0 ; Y= 683.5 and Radius, 668.3 ''�
""'' 1.573 *"'`
. Failure Surtace Specified By 26 Coortiinate Points
Point X-Surf Y-Surf
� No. (ft) (ft)
1 50.17 50.13
2 54.94 51,66
� 3 59.68 53.22
4 64.42 54.83
5 69.14 56.48
6 73.84 58.17
7 78.53 59.91
8 83.21 61.68
9 87.86 63.50
10 92.51 65.36
11 97.13 67.26
12 101.74 69.20
13 106.33 71.18
14 110.90 73.21
15 115.45 75.27
16 119.99 77.38
17 124.51 79.52
18 129.00 81.71
19 133.48 83.93
20 137.94 86.20
21 142.38 88.50
22 146.79 90.85
Page 3
Safe Factors '
�
112.5 ----- -
1.57
/�—.__—__
1.58
,�! 1.80
/ �
90.0 � '///'/��� 1.61
f � 1.82
i, � •�/
� ����j// 1.82
i' �
�.�
67.5 � �/��� � 1.82
/ //�i
��.i��i'� 1.63
� � � i
i i� � 1.65
�
i
_--...__ _- -------. _ _ ....— —�.
1.85
45.0
22.5
---------.—_
'_ '_T_.__'-...�-'"-_T_' '.�_ _.T._'_.__"_T.. .
0 22.50 45.00 67.50 90.00 112.50 135.00 157.50 180.00
• Profile.out
'`'` PCSTABL6**
by
Purdue University
modified by
Peter J. Bosscher
University of Wisconsin-Madison
--Slope Stability Analysis— II�
Simplified Janbu, Simplified Bishop
or Spencer s Method of Slices
PROBLEM DESCRIPTION
�
' BOUNDARY COORDINATES
� 3 Top Boundaries
3 Total Boundaries
Boundary X-Left Y-Left X-Right Y-Righf Soil Type
No, (ft) (ft) (ft) (ft) Below Bnd
1 0.00 50.00 50.00 50.Q0 1
Z 50.OQ 50.00 115.00 100.00 1
3 115.OQ 10a.00 180.00 100.00 1
ISOTROPiC SOIL PARAMETERS
1 Type(s} of Soil
Soil Total Saturated Cohesion Friction Pore Pressure Piez.
Type Unit Wt. Unit Wt. Intercept Angle Pressure Constant Surface
No. (pc� (pcfl (ps� (deg) Param. (psf} No.
Page 1
- Profile.out
• 1 110.0 115.0 0.0 35.0 0.00 0.0 0
A Horizontal Earthquake Loading Coefficient
Of0.150 Has Been Assigned
A Vertical Earthquake Loading Coefficient
Of0.000 Has Been Assigned
Cavitation Pressure = 0.0 psf
A Critical Failure Surface Searching Method, Using A Random I�,
Technique For Generating Circular Surfaces, Has Been Specified.
900 Trial Surfaces Have Been Generated.
30 Surtaces Initiate From Each Of 30 Points Equafly Spaced
Along The Ground Surface Between X= 35.00 ft. ',
and X= 90.00 ft. '
Each Surface Terminates Between X= 160.00 ft.
and X= 165.00 ft.
Un�ess Further Limitations Were Imposed, The Minimum Elevation
At Which A Surface Extends Is Y= 0.00 ft.
5.00 ft. Line Segments Define Each Trial Failure Surface.
Following Are Displayed The Ten Most Critical Of The Trial
Failure Surfaces Examined. They Are Ordered - Most Critical
First.
`* Safety Factors Are Calculated By The Modified Bishop Method "`
Failure Surface Specified By 26 Coordinate Points
Point X-Surf Y-Surf
No. (ft) (ft)
Page 2
Profile.out
1 50.17 50.13
2 54.91 51.75
3 59.63 53.39
4 64.33 55.08 '
5 69.03 56.80
6 73.71 58.55
7 78.38 60.34
8 83.04 62.16
9 87.68 64.02
10 92.31 65.91
11 96.92 67.84
12 101.52 69.80
13 106.'!0 71.80
14 110.67 73.83
15 115.23 75.90
7 6 119.76 77.99
17 124.29 80.13
18 't 28.79 82.29
19 '133.28 84.49
20 137.76 86.73
21 142.21 89.00
22 146.65 91.30
23 151.07 93.63
24 155.48 96.00 .
25 159.86 98.40
26 162.75 100.00
Circle Center At X= -163.0 ; Y= 683.5 and Radius, 668.3
'`*" 1.104 '`*"'
Failure SurFace Specified By 26 Coordinate Points
Point X-Surt Y-Surt
No. (ft) (ft)
1 50.17 50,13
2 54.94 51.66
3 59.68 53.22
4 64.42 54,83
5 69.14 56.48
6 73.84 58.17
7 78.53 59.91
8 8321 61.68
9 87.86 63.50
10 92.51 65.36
11 97.13 67.26
12 101.74 6920
Page 3
Safety Factors
112.5 — -- —
1.10
1.11
./ � 1.12
/ /
90.0 /�//�/� 1.13
�'/ �� 1.13
� /
� "/// 1.13
/ /
67.5 f�,ij/�� 1.13
�/ / J�
/ /� �j� �.�3
! �
/i� 1.14
... �
�
------ ——�--- 1.15
45.0
22.5
0 22.50 45.00 67.50 90.00 112.50 135.00 157.50 180.00
I
�
�
�
A
�
W
�
�
�
I
►
Site Improvement Bond Quantity Worksheet
King County Department of Development&Environmental Services
900 Oakesdale Avenue Southwest
Renton,Washington 98055-1219
Project Name: Elsa Ridge Date: 19-Feb-03
�ocation: City of Renton, Washington Project No.: Camb-0001
Activity No.:
Note: Alf prices include labor, equipment, materials, overhead and
Clearing greater than or equal to 5,000 board feet of timber? profit. Prices are from RS Means data adjusted for the Seattle area
or from local sources if not included in the RS Means database.
yes X no
If yes,
Forest Practice Permit Number:
(RCW 76.09)
I
Page 1 of 9 j
I
i
Unit prices updated: 02/12/02
Version: 04/22/02
camb0l BQ Sheet.xls Report Date: 2/19/2003
r
Site Improvement Bond Quantity Worksheet
Unit #of
Reference# P�ice Unit Quantity Applications Cost
EROSION/SEDIMENT CONTROL
Backfill & compaction-embankment $ 5.62 CY
Check dams,4" minus rock SWDM 5.4.6.3 $ 67.51 Each 4 1 270
Crushed surfacing 1 1/4" minus WSDOT 9-03.9 3) $ 85.45 CY
Ditching $ 8.08 CY
Excavation-bulk $ 1.50 CY
Fence, silt SWDM 5.4.3.1 $ 1.38 LF 220 1 304
Fence,Temporary (NGPE) $ 1.38 LF
Hydroseeding SWDM 5.4.2.4 $ 0.59 SY 4000 1 2360
Jute Mesh SWDM 5.4.2.2 $ 1.45 SY
Mulch, by hand, straw, 3"deep SWDM 5.4.2.1 $ 2.01 SY 4000 1 8040
Mulch, by machine, straw, 2"deep SWDM 5.4.2.1 $ 0.53 SY
Piping,temporary, CPP, 6" $ 10.70 LF
Piping,temporary, CPP, 8" $ 16.10 LF
Piping, temporary, CPP, 12" $ 20.70 LF
Plastic covering,6mm thick, sandbagged SWDM 5.4.2.3 $ 2.30 SY
Rip Rap, machine placed; slopes WSDOT 9-13.1(2) $ 39.08 CY
Rock Construction Entrance, 50'x15'x1' SWDM 5.4.4.1 $ 1,464.34 Each 1 1 1464
Rock Construction Entrance, 100'x15'x1' SWDM 5.4.4.1 $ 2,928.68 Each
Sediment pond riser assembly SWDM 5.4.52 $ 1,949.38 Each
Sediment trap, 5' high berm SWDM 5.4.5.1 $ 17.91 LF j
Sed.trap,5'high,riprapped spillway berm section SWDM 5.4.5.1 $ 68.54 LF '
Seeding, by hand SWDM 5.4.2.4 $ 0.51 SY '
Sodding, 1"deep, level ground SWDM 5.4.2.5 $ 6.03 SY I
Sodding, 1"deep,sloped ground SWDM 5.4.2.5 $ 7.45 SY
TESC Supervisor $ 74.75 HR 4 1 299
Water truck, dust control SWDM 5.4.7 $ 97.75 HR
WRITE-IN-ITEMS **** (see page 9) I
Each '
I
ESC SUBTOTAL: $ 12,736.98
30%CONTINGENCY 8�MOBILIZATION: $ 3,821.09
ESC TOTAL: $ 16,558.07
COLUMN: A �
Page 2 of 9
Unit prices updated: 02/12/02
Version: 04/22/02
camb0l BQ Sheet.xls Report Date: 2/19/2003
F � . „
.. ..'%"SS,.. ..r'��N:�:. .x d`'...•� y'
Site Improvement Bond Quantity Worksheet
Existing Future Public Private Quantity Completed
Right-of-Way Road Improvements Improvements (Bond Reduction)"
&Draina e Facilities Quant.
Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost
GENERALITEMS
Backfill&Compaction-embankment $ 5.62 CY
Backfill&Compaction-trench $ 8.53 CY
Clear/Remove Brush,by hand $ 0.36 SY �
Clearing/Grubbing/Tree Removal $ 8,876.16 Acre 0.5 4,438.08
Excavation-bulk $ 1.50 CY
Excavation-Trench $ 4.06 CY
Fencing,cedar,6'high $ 18.55 LF
Fencing,chain link,vinyl coated, 6'high $ 13.44 LF
Fencing,chain link,gate,vinyl coated, 20' $ 1,271.81 Each
Fencing,split rail,3'high $ 12.12 LF
Fill&compact-common barrow $ 22.57 CY
Fill&compact-gravel base $ 25.48 CY
Fill&compact-screened topsoil $ 37.85 CY
Gabion, 12"deep,stone filled mesh $ 54.31 SY
Gabion, 18"deep,stone filled mesh $ 74.85 SY
Gabion,36"deep,stone filled mesh $ 132.48 SY
Grading,fine,by hand $ 2.02 SY 118 238.36
Grading,fine,with grader $ 0.95 SY
Monuments,3'long $ 135.13 Each
Sensitive Areas Sign $ 2.88 Each 3 8.64
Sodding, 1"deep,sloped ground $ 7.46 SY
Surveying,line&grade $ 788.26 Da
Surveying,lot location/lines $ 1,556.64 Acre 0.5 778.32
Traffc control crew(2 flaggers) $ 85.18 HR
Trail,4"chipped wood $ 7.59 SY
Trail,4"crushed cinder $ 8.33 SY
Trail,4"top course $ 8.19 SY
Wall,retainin ,concrete $ 44.16 SF
Wall,rockery $ 9.49 SF
Page 3 of 9 SUBTOTAL 238.36 5,225.04
Unit prices updated: 02/12/02
'KCC 27A authorizes only one bond reduction. VersiOn: 4l22/02
carnb0l B(�Sheet.xls Report Date: 2/19/2003
Site Improvement Bond Quantity Worksheet
Existing Future Public Private Bond Reduction"
Right-of-way Road Improvements Improvements
8�Draina e Facilities Quant.
Unit Price Unit Quant. Cost Quank Cost Quant. Cost Complete Cost
ROADIMPROVEMENT
AC Grinding,4'wide machine< 1000sy $ 23.00 SY
AC Grindin ,4'wide machine 1000-2000s $ 5.75 SY
AC Grinding,4'wide machine>2000sy $ 1.38 SY
AC Removal/Disposal/Repair $ 41.14 SY 145 5,965.30
Barricade,type I $ 30.03 LF
Barricade,type Ilf(Permanent) $ 45.05 LF
Curb&Gutter,rolled $ 13.27 LF
Curb&Gutter,vertical $ 9.69 LF 211 2,044.59
Curb and Gutter,demolition and disposal $ 13.58 LF
Curb,extruded asphalt $ 2.44 LF
Curb,extruded concrete $ 2.56 LF
Sawcut,asphalt,3"depth $ 1.85 LF 566 1,047.10
Sawcut,concrete,per 1"depth $ 1.69 LF
Sealant,asphalt $ 0.99 LF 566 560.34
Shoulder,AC, (see AC road unit price) $ - SY
Shoulder,gravel,4"thick $ 7.53 SY
Sidewalk,4"thick $ 30.52 SY
Sidewalk,4"thick,demolition and disposal $ 27.73 SY
Sidewalk,5"thick $ 34.94 SY 118 4,122.92
Sidewatk,5"thick,demolition and disposal $ 34.65 SY
Sign,handicap $ 85.28 EaCh
Striping,per stall $ 5.82 Each
Striping,thermoplastic,(for crosswalk) $ 2.38 SF
Striping,4"reflectorized line $ 0.25 LF
Page 4 of 9 SUBTOTAL 13,740.25
Unit prices updated: 02/12/02
'KCC 27A authorizes only one bond reduction. Version: 4/22/02
camb0l BQ Sheet.xls Report Date:2/19/2003
Site Improvement Bona c�uantity Worksheet �'
Existing Future Public Private 8ond Reduction*
Right-of-way Road Improvements Improvements
8�Drafnage Facilities Quant ;
Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost I
ROAD SURFACING (4"Rock=2.5base&1.5"top course) For'93 KCRS(6.5"Rock=5"base&1.5"top course) I
For KCRS'93, (additional 2.5"base)add: $ 3.60 SY I,
AC Overlay, 1.5"AC $ 7.39 SY �
AC Overlay,2"AC $ 8.75 SY 412 3,605.00 271 2,371.25
AC Road,2",4"rock, First 2500 SY $ 17.24 SY
AC Road,2",4"rock,Qty.over 2500SY $ 13.36 SY
AC Road,3",4"rock, First 2500 SY $ 19.69 SY
AC Road,3",4"rock,Qty.over 2500 SY $ 15.81 SY
AC Road, 5", First 2500 SY $ 14.57 SY
AC Road, 5",Qty.Over 2500 SY $ 13.94 SY
AC Road,6", First 2500 SY $ 16.76 SY
AC Road,6",Qty.Over 2500 SY $ 16.12 SY
Asphalt Treated Base,4"thick $ 9.21 SY 412 3,794.52 271 2,495.91
Gravel Road,4"rock, First 2500 SY $ 11.41 SY
Gravel Road,4"rock,Qty.over 2500 SY $ 7.53 SY
PCC Road,5",no base,over 2500 SY $ 21.51 SY
PCC Road, 6",no base,over 2500 SY $ 21.87 SY
Thickened Edge $ 6.89 LF 50 344.50
Page 5 of 9 SUBTOTAL 7,744.02 4,867.16
Unit prices updated: 02/12/02
'KCC 27A authorizes only one bond reduction. Vefsion: 4/22/02
r,�mb01 RQ Sheet.xls Report Date: 2/19/2003
Site Improvement Bond C�uantity Worksheet
Existing Future Public Private Bond Reduction'
Right-of-way Road Improvements Improvements
8 Drainage Facilities Quant
Unit Price Unit Quant. Cost Quant Cost Quant. Cost Complete Cost �
II
DRAINAGE (CPP=Corrugated PlastiC Pipe,N12 or Equivalent) For Culvert prices, Average of 4'cover was assumed.Assume perforated PVC is same price as solid pi e. i
Access Road,R/D $ 16.74 SY
Bollards-fixed $ 240.74 Each
Bollards-removable $ 452.34 Each
'(CBs include frame and lid)
CB Type I $ 1,257.64 Each 5 6,288.20 1 1,257.64
CB Type IL $ 1,433.59 Each
CB T e II,48"diameter $ 2,033.57 Each
for additional depth over 4' $ 436.52 FT
CB Type il, 54"diameter $ 2,192.54 Each
for additional depth over 4' $ 486.53 FT
CB Type II,60"diameter $ 2,351.52 Each
for additional depth over 4' $ 536.54 FT
CB Type II,72"diameter $ 3,212.64 Each
for additional depth over 4' $ 692.21 FT
Through-curb Inlet Framework(Add) $ 366.09 Each
Cleanout,PVC,4" $ 130.55 Each
Cleanout,PVC,6" $ 174.90 Each 20 3,498.00
Cleanout,PVC,8" $ 224.19 Each
Culvert, PVC,4" $ 8.64 LF
Culvert,PVC,6" $ 12.60 LF
Culvert,PVC, 8" $ 13.33 LF
Culvert,PVC, 12" $ 21.77 LF
Culvert,CMP,8" $ 17.25 LF
Culvert,CMP, 12" $ 26.45 LF
Culvert,CMP, 15" $ 32.73 LF
Culvert,CMP, 18" $ 37.74 LF
Culvert,CMP,24" $ 53.33 LF
Culvert,CMP,30" $ 71.45 LF
Culvert,CMP,36" $ 112.11 LF
Culvert,CMP,48" $ 140.83 LF
Culvert,CMP,60" $ 235.45 LF
Culvert,CMP,72" $ 302.58 LF
Page 6 of 9 SUBTOTAL 6,288.20 4,755.64
Unit prices updated: 02/12/02
`KCC 27A authorizes only one bond reduction. Version: 4/22/02
camb01 E3Q Sheet.xls Report Date: 2/19/2003
Site Improvement Bond Quantity Worksheet
Existing Future Public Private Bond Reduction•
Right-of-way Road Improvements Improvements
DRAINAGE CONTINUED &Drainage Facilities Quant.
Unit Price Unit Quant. Cost Quant. Cost Quant. Cost Complete Cost
Culvert,Concrete,8" $ 21.02 LF
Culvert,Concrete, 12" $ 30.05 LF
Culvert,Concrete, 15" $ 37.34 LF
Culvert,Concrete, 18" $ 44.51 LF
Culvert,Concrete,24" $ 61.07 LF
Culvert,Concrete,30" $ 104.18 LF
Culvert,Concrete,36" $ 137.63 LF
Culvert,Concrete,42" $ 158.42 LF
Culvert,Concrete,48" $ 175.94 LF
Culvert,CPP,6" $ 10.70 LF 125 1337.5
Culvert,CPP,8" $ 16.10 LF 60 966
Culvert,CPP, 12" $ 20.70 LF 97 2007.9
Culvert,CPP, 15" $ 23.00 LF
Culvert,CPP, 18" $ 27.60 LF
Culvert,CPP,24" $ 36.80 LF
Culvert,CPP,30" $ 48.30 LF
Culvert,CPP,36" $ 55.20 LF '
Ditching $ 8.08 CY I
Flow Dispersal Trench 1,436 base+) $ 25.99 LF
French Drain (3'depth) $ 22.60 LF
Geotextile,laid in trench,polypropylene $ 2.40 SY
Infiltration pond testing $ 74.75 HR
Mid-tank Access Riser,48"dia, 6'deep $ 1,605.40 Each
Pond Overflow Spillway $ 14.01 SY
Restrictor/Oil Separator, 12" $ 1,045.19 Each
Restrictor/Oil Separator, 15" $ 1,095.56 Each
Restrictor/Oil Separator, 18" $ 1,146.16 Each
Riprap,placed $ 39.08 CY
Tank End Reducer(36"diameter) $ 1,000.50 Each
Trash Rack, 12" $ 211.97 Each
Trash Rack, 15" $ 237.27 Each
Trash Rack, 18" $ 268.89 Each
Trash Rack,21" $ 306.84 Each
Page 7 of 9 SUBTOTAL 2973.9 1337.5
Unit prices updated: 02/12/02
'KCC 27A authorizes only one bond reduction. Version: 4/22/02
camb0l E3Q Sheet.xls Report Date:2/19/2003
Site Improvement Bond C,�uantity Worksheet
Existing Future Public Private Bond Reduction•
Right-of-way Road Improvements Improvements
&Drainage Facilities Quant.
Unit Price Unit Quant Price Quant. Cost Quant. Cost Com lete Cost
PARKING LOT SURFACING
2"AC,2"top course rock&4"borrow $ 15.84 SY
2"AC, 1.5" top course& 2.5"base course $ 17.24 SY
4"select borrow $ 4.55 SY
1.5"top course rock&2.5"base course $ 11.41 SY
WRITE-1N-ITEMS
Private Infiltration Trenches $ 2,500.00 EA. 6 15,000.00
Large Snadfilter Vault LS
Keystone Wall SF
EA.
EA.
EA.
LF
SF
LF
LF
SUBTOTAL 15,000.00
SUBTOTAL(SUM ALL PAGES): 30,984.73 31,185.34
30%CONTINGENCY&MOBILIZATION: 9,295.42 9,355.60
GRANDTOTAL: 40,280.15 40,540.94
COLUMN: B C D E
Page 8 of 9
Unit prices updated: 02/12/02
"KCC 27A authorizes only one bond reduction. Version: 4/22/02
camb0l BQ Sheet.xis Report D'ate: 2/19/2003
Site Improvement Bond Quantity Worksheet ,
Original bond computations prepared by:
Name: Jennifer Steig �ate: 19-Feb-03
PE Registration Number: 32236 Tel.#: (425)827-5874
F�rm Name: Peterson Consulting Engineers
address: 4030 Lake Washington Blvd. NE, Suite 200, Kirkland Wa. 98033 Project No: Camb-0001
ROAD IMPROVEMENTS&DRAINAGE FACILITIES FINANCIAL GUARANTEE REQUIREMENTS
PERFORMANCE BOND' PUBLIC ROAD&DRAINAGE
AMOUNT BOND'AMOUNT MAINTENANCE/DEFECT BOND"
REQUIRED AT RECORDING OR
Stabilization/Erosion Sediment Control (ESC) (A) $ 16,558.1 TEMPORARY OCCUPANCY*"
Existing Right-of-Way Improvements (B) $ 40,280.1
Future Public Road Improvements& Drainage Facilities (C) $ -
Private Improvements (D) $ 40,540.9
Calculated Quantity Completed (E) $ -
Total Right-of Way and/or Site Restoration Bond*/** (A+g) $ 56,838.2
(First$7,500 of bond*shall be cash.)
Performance Bond"Amount (A+g+C+D) = TOTAL (T) $ 97,379.2 T x 0.30 $ 29,213.7 OR
inimum on amount is .
Reduced Performance Bond'Total*" (T-E) $ 97,379.2
Use larger o x o or( - (g+C)x
Maintenance/Defect Bond*Total 0.25= $ 10,070.0
NAME OF PERSON PREPARING BOND'REDUCTION: Date:
'NOTE: The word"bond"as used in this document means any financial guarantee acceptable to King County.
**NOTE: KCC 27A authorizes right of way and site restoration bonds to be combined when both are required.
The restoration requirement shall include the total cost for all TESC as a minimum,not a maximum. In addition,corrective work,both on-and off-site needs to be included.
Quantities shall reflect worse case scenarios not just minimum requirements. For example,if a salmonid stream may be damaged,some estimated costs for restoration
needs to be reflected in this amount. The 30%contingency and mobilization costs are computed in this quantity.
'**NOTE: Per KCC 27A,total bond amounts remaining after reduction shall not be less than 30%of the original amount(T)or as revised by major design changes.
SURETY BOND RIDER NOTE: If a bond rider is used,minimum additional performance bond shall be $ 40,540.9 (C+D)-E
REQUIRED BOND*AMOUNTS ARE SUBJECT TO REVIEW AND MODIFICATION BY DDES
Page 9 of 9 Unit prices updated: 02/12/02
Version: 4/22/02
camb01 BQ Sheet.xls Report Date: 2/19/2003