24106 102ND PL W.PDFiiiiiiiiii
240
24106 102ND PL W
ADDRESS:
TAX ACCOUNT/PARCEL NUMBER:
BUILDING PERMIT (NEW STRUCTURE):
COVENANTS (RECORDED) FOR:
CRITICAL AREAS:- DETERMINATION: 0 Conditional Waiver Study Required 0 Waiver
A
DISCRETIONARY PERMIT #'S:
DRAINAGE PLAN DATED:
PARKING AGREEMENTS DATED:
EASEMENT(S) RECORDED FOR:
PERMITS (OTHER):
PLANNING DATA CHECKLIST DATED:
SCALED PLOT PLAN DATED:
SEWER LID FEE $:
SHORT PLAT FILE:
SIDE SEWER AS BUILT DATED:
SIDE SEWER PERMIT(S) #:
GEOTECH REPORT DATED:
STREET USE / ENCROACHMENT PERMIT #:
WATER METER TAP CARD DATED:
OTHER
LID
LOT: BLOCK:
LATEMP\DSrs\Fornis\Street File Checklist.doc
PLANNING DATA
SINGLE FAMILY RESIDENTIAL
11 STREET :F:IL:E:]l
Name: � ��,o V�-
Date: g-
SiteAddress: Q-qlo� 10a -4
-18-6?
Plan Check #:
Project Description: I Lx,
Reduced Site Plan Provided: NO)
Zoning:
Map Page: -3
Corner Lot: (YES
Flag Lot: (YES / 00
Critical Areas Determination #: C DC)9-00 Ll
12T-Study Required
11 Waiver
SEPA Determination:
R-Exempt
Needed (for over 500 cubic yards of grading)
0 Fee El Checklist 0 APO List with notarized form
Requirect
Street:
Side: -7 1/
1 Side: -c-
Rear: eo -
Actual Setbacks
Street: I
Side:
Side:
Rear:
El Detached Structures:
11 Rockeries:
El Fences/Trellises:
El Bay Windows/Projecting Modulation:
El Stairs/Deck:
Height
Datum Point:
Datum Elevation: V 0
Maximum Height Allowed: (,)-a
Actual Height: 9,"7'5�' -755'
Parking Required:
Parking Provided:
Lot Area: A9,
Maximum Lot Coverage: 35% Proposed: Ile -
Lot Coverage Calculations:
ADU Created: (YES / NO)
Subdivision:
Legal Nonconforming Land Use Determination Issued: (YES
Comments
Plan Review By: Manning Data Form 04-11-06.doc
9
0
CONFORMED COPY
200907090785 1 PG
0710912009 4:23�m
, N2.00
SNOHOMISH COUNT ASHINGTON
Return Recorded instrument To: a.,-ry
S 10 �� P, 6 Ic
City of Edmonds Developmem SeFvieeq gepa"ment Pia""itig Bi-
121 5 th Avenue North, Edmonds WA 98020
ACCESSORY DWELLING UNIT STATEMENT
Property Address: 24106 102 nd pl W, Edmonds Washington
Assessor's Parcel Number: 00555000003800
Legal Description: RJCHMOND PARK HOMES NO 2 BLK 000 D-00 - TR38
Grantor(s): Property Owner Kent and Janyce Short
Grantee: City of Edmonds
Related Permit Numbers: BLD-2009-0336
I. have read the requirements for accessory dwelling units contained in Chapter 20,21 of the
Edmonds Community Development Code (ECDC) and understand that an accessory dwelling unit
as',defliked in ECDC Section 21.05.015 is prohibited until an Accessory Dwelling Unit Permit is
approved.
I a.1sou.nderstand that an Accessory Dwelling Unit Permit cannot be approved unless all the
c iter a
rR 4 -.in Chapter 20.21 are met, and all the necessary items are submitted, including an affidavit
of%bccupancy and a covenant to be filed with the Snohomish County regarding the regulations
imposed on Accessory Dwelling Units.
OWNER/GRANTOR(S): Kent and Janyce Short
SIGNATURE:
V
DATEIi this day of T(A� �, 2009
.0q
On this day personally appeared before me7 �Ilhorlt,lt`o� me known to be the individual described
therein and who executed the within and foregoing instrument, and acknowledged that he signed the
same as, reeiv
��0 94untary act and deed, for the use and purposes therein mentioned. Notary's pressure
eal - "4
s $rQ* 'el"
Dated:
.0
Signature of Notary Public:
Pul C)
Residing At:
..7 . ......... My Appointment Expires:
OF W
/111111k
- THIS. -DOCUMENT MUST BE RECORDED WITH THE SNOHOMISH COUNTY AUDITOR -
E
CITY OF EDMONDS
1215 1h Avenue North, Edmonds WA 98020
Phone: 425.771.0220 - Fax: 425.771.0221 - Web: www.ci.edmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT - PLANNING DIVISION
C %3
. lg9
CRITICAL AREAS RECONNAISSANCE REPORT
Site Location: 24106 102 d Place West Tax Acct. Number: 00555000003800
Determination: STUDY REQUIRED Determination #: CRA-2008-0045
Applicant: Mark Lowe / Chermak Const. Owner: Kent Short
CRITICAL AREAS DETERMINATION: STUDY REOUIRED (CRA-2008-0045)
During review and inspection of the subject site, it was found that the site may contain (or be adjacent to) critical
areas, including a Geologically Hazardous Area (Landslide Hazard Area), pursuant to Chapter 23.40 of the
Edmonds Community Development Code (ECDC).
Geologically hazardous areas include areas susceptible to erosion, land sliding, earthquake, or other geological
events. They pose a threat to the health and safety of citizens when incompatible development is sited in areas of
significant hazard. Such incompatible development may not only place itself at risk, but also may increase the
hazard to surrounding development and use.
The LiDAR map (attached) indicates that there is a steep slope (approximately 52%) adjacent to the western edge of
the property. The site is relatively flat and has a rolling slope of approximately 10%. See map for approximate top
of slope. Projects proposed further than 65' from the top or toe of the slope (50' buffer + 15' setback from the
critical area) will not require a geotechnical report to address critical areas issues (of course, other departments may
require a report to address their codes, depending on the scope of work proposed).
ALLOWED ACTIVITIES
Certain activities are allowed in or near critical area buffers as specified in ECDC 23.40.20. If you have any
questions about whether your proposed development qualifies as an allowed activity, please contact a Planner for
more information.
EXEMPT DEVELOPMENT PROPOSALS *
Certain development proposals may be exempt from Critical Areas Requirements (ECDC 23.40.230). If you think
that a specific development proposal may be exempt, contact a Planner for more information.
Page I of 2
GENERAL CRITICAL AREAS REPORT REOUIREMENTS
Critical Areas Reports identify, classify and delineate any areas on or adjacent to the subject property that may
qualify as critical areas. They also assess these areas and identify any potential impacts resulting from your specific
development proposal. If a specific development proposal results in an alteration to a critical area the critical areas
report will also contain a mitigation plan. You have the option of completing the portion of the study that classifies
and delineates the critical areas and waiting until you have a specific development proposal to complete the study.
You may also choose submit the entire study with your specific development application.
Please review the minimum report requirements for all types of Critical Areas which are listed in ECDC
23.40.09O.D. There are additional report requirements for different types of critical areas (see below).
Note that it is important for the report to be prepared by a qualified professional as defined in the ordinance.
There are options on how to complete a critical areas study and an approved list of consultants that you may
choose from. You may contact the Planning Division for more information.
0 General Mitigation Requirements for all Critical Areas are discussed in ECDC 23.40.110 through 23.40.140.
STUDY REQUIREMENT — LANDSLIDE HAZARD AREA
It appears that this property contains or is adoacent to a Landslide Hazard Area.
• A Landslide Hazard Area is any area with a slope of forty percent (40%) or steeper and with a vertical relief of
ten (10) or more feet (except areas composed of consolidated bedrock).
• Landslide Hazard Areas are further defined and illustrated in ECDC 23.80.020.B.
• In addition to the general requirements for Critical Areas reports referenced above, specific Critical Area report
requirements for Landslide Hazard Areas are provided in ECDC 23.80.050.
DEVELOPMENT PROPOSALS ASSOCIATED WITH LANDSLIDE HAZARD AREAS
Development is restricted within a Landslide Hazard Area and its buffer.
• Projects that will intrude into these areas will require a report by a licensed Geotechnical Engineer.
• The criteria that are applied depend on the amount that the buffer is reduced.
• The buffer can be reduced to a minimum of ten (10) feet (with an additional 15' building setback per ECDC
23.40.280) if a report is prepared that meets the standards listed in ECDC 23.80.050). The alteration must also
meet the requirements listed ECDC 23.80.060.
• In addition, proposals to reduce the buffer to less than ten (10) feet must comply with the design standards
listed in ECDC 23.80.070.A.3.
Gina Coccia, Associate Planner June 17, 2009
Name, Title Signature Date
Cited sections of the Edmonds Community Development Code (ECDQ can befound on the City ofEdmonds
website at www.ci.edmonds.wa'.us.
Page 2 of 2
E;Q
CONFORMED COPY
00907090785 1 PG
710912009 4:23 12.00
NOHOMISH COUNTr �IASHINGTON
Return Recorded Instrument To: d_17-), dj
. a-/,, & C 4) 00;r
City of Edmonds Dewlap Nonni
121 5'h Avenue North, Edmonds WA 98020
ACCESSORY DWELLING UNIT STATEMENT
Property Address: 24106 102n, pl W, Edmonds Washington
Assessor's Parcel Number: 00555000003800
Legal Description:
RICHMOND PARK HOMES NO 2 BLK 000 D-00 - TR 38
Grantor(s): Property Owner Kent and Janyce Short
Grantee: City of Edmonds
Related Permit Numbers: BLD-2009-0336
I have read the requirements for accessory dwelling units contained in Chapter 20.21 of the
Edmonds Community Development Code (ECDC) and understand that an accessory dwelling unit
as defined in ECDC Section 21.05.015 is prohibited until an Accessory Dwelling Unit Permit is
approved.
I also understand that an Accessory Dwelling Unit Permit cannot be approved unless all the
criteria in Chapter 20.21 are met, and all the necessary items are submitted, including an affidavit
of occupancy and a covenant to be filed with the Snohomish County regarding the regulations
imposed on Accessory Dwelling Units.
OWNER/GRANTOR(S): Kent and Janyce Shor
SIGNATURE:
V
DATE� this day of TO-( 2009
-01
On this day personally appeared before me� �",&r"t,'to� me known to be the individual described
therein and who executed the within and foregoing instrument, and acknowledged that he signed the
same as ��0beeiv/94untary act and deed, for the use and purposes therein mentioned. Notary's pressure
seal �jl* 6nQdV�z//
IN
;0/1. 12- - D
S� Co -'0 Dated:
Z: --o
,\ol A R Y
!Sgnature of Notary Public:
S
PUB%-\c Residing At:
Az
X ....... My Appointment Expires: -bq -2i))Q
0 F W
- THIS DOCUMENT MUST BE RECORDED WITH THE SNOHOMISH COUNTY AUDITOR -
FIGURF C.2.2.A TYPICAL TRENCH INFILARATION SYSTENll
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or occurs awfAq ftpermitted pro)ect.
THE TOPOGRAPHY INFORMATION NA5.-OATHERED FROM
THE 5NOHOM15H rOUNTY "615" DATA INFORMATION STORED
ON THE 5NOHOM15H COUNTY 'Sno5rope" V�EB 51TE
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VICMTY MAP
N.T.S. f
SITE NOTE5:
1. ALL EX6,AVATION 5TOCK, PILES TO BE
COVERED NITHIN 24 HOURS
2. NEA ADDITION TO CONNECT TO EX15TIN6
UTILITIES, AND STORM DRAIN LINES
SEE NOTE FOR DRYNELL
5. RE-6RADE BACK TO THE OR16INAL CONTOURS
AFTER CONSTRUCTION 15 COMPLETE
4. ALL EXCAVATION SURPLUS TO BE HAULED OFF TO
AN APPROVED LANDFILL SITE.
Kent 4 Janyce Short
24106 102nd. Flo( e Nest
Edmonds, NA. 15020
LOT GOVERAOE (EXISTING BUILT IN 1156)
LOT SIZE = 10,214 e �.
EXIST. STRUGTURE = 163'� 5.f.
EXIST. DRIVES � REAR AGGE55= 1340 S.F.
EXIST. FRONT NALK= 100 S.F.
EXIST. REAR GONG. STAIRS= 100 S.F.
NEN5TRUGTURE = 32-'�
NEN NALKS = ' 2-5 5.f. 3(0
TOTAL IMPERVIOUS = �� 5.f. 2�qs
TOTAL =53%
PARCEL NO.
00555000005800
EXISTING
APPR GY ENUNEERINC3
A_19
-7111-110
L55AL
RIGHMONP PARK HOMES NO 2 BILK 000 0-00 - TR 55
IN SNOHOMISH COUNT"(
51 TE PLAN
Sr,ALE : I" = 10'-0" 0 5 10 20
C�ODES
TH15 DE516N 15 IN ACCORDANCE V41TH THE FOLLOVqIN(5 CODES AS
AMENDED BY THE NA5111N&TON STATE BUILDIN6 CODE:
2006 1 Rr,
200(b UNIFORM MECHANICAL CODE
2006 UNIFORM PLUMBIN6 CODE
NA5HIN6TON STATE ENER6Y CODE, NAC 51-11 M5EC)
NA5HINGTON STATE VENTILATION $
INDOOR AIR OUALITY CODE. NA 51-15 (VIAO)
ENERG)"' GODE SUM�IARY'
HEATIN6 SYSTEM TYPE
ELEG.
OPTION
IV
HVAC AFUE
MED.
MAX. 6LAZIN6 % UNLIMITED
DOOR U-VALUE
0.20 (R-5)
CEILIN65
N1 ATTICS
R-35
VAULTED
R-30
NALL5
ABOVE 6RADE
R-21
BELON 6RADE
INT. R-21
I EXT. R-10
FLOOR
R-50
SLAB ON 6RADE
R-10
FROM 2006 I/GE6 CHAPTER 6
LU�IBER STRENGTHS
FRAMIN& MEMBER TYPE
FB
FV
E
JOISTS AND RAFTERS:
HEM -FIR #2
b5o
150
1,300.000
BEAMS AND HEADERS:
4" NOMINAL DOU6-FIR #2
b" NOMINAL DOUC7-FIR #1
b15
1000
IbO
IbO
1'(000'000
1.700,000
LAMINATED STRAND LUMBER (L5L)
1,700
2250
400
400
1,300,000
1,500,000
1.3 E
1.5 E
PARALLEL STRAND LUMBER:
2qOO
210
2,000,000
PARALLAM (P5L)
GLU-LAMINATED TIMBERS:
24F-V4
2400
IcIO
IbOOOOO
POSTS:
4" OR 6' NOM. DOU(5-FIR #1
2X STUDS HF 11STUD"
1200
1 1 5 1
e)5
-15 1
1'(000'000
1,400,000
APA RATED 5HEATHIN&
EXP05URE
SPAN RATIN6
ROOF
NALL
FLOOR (T46)
EXTERIOR
EXTERIOR
EXTERIOR
32/16
24/0
4e)/24
LOADING � DEFLEGTION
TYFE OF
CON15TRUCTION
LOADIN(S (FSF)
DEFLECTION
LIVE
LOAD
DEAD
LOAD
TOTAL
LOAD
LIVE
LOAD
TOTAL
LOAD
Roar= (comp.)
25
10
35
L/240
L/150
CEILIN(5 (ATTIC, ABOVE)
[a
5
15
L/240
L/240
FLOOR
40
10
50
L14bO
L/360
r-LOOR (1/41 CEILIN&)
40
15
55
L/450
1-1560
PECK (SPACED NOOP)
60
10
-70
L/450
1-1560
EXTERIOR NALL
-
10
10
INTERIOR ViALL
10
10
Zone Corner W rlagA:�_
SLI—backs jRs2eguired Actual
.d
Front
Sidea)le�7'
Rear
Other
A� ROVED BY, ANNING
pt, BE S U175
JUN 29 2009
BUILDING DEPARTMENT
CITY OF EDMONDS
A � V 14 WO
R FESUB
JUN 2 9 2009
BUILDING DEPARPAENT
CITY OF EDMONDS
R
I)TREET FILE
CkdEdmoftds Building Depafted
APPROVED PLAN
GEOTECHNICAL ENGINEERING STUDY
PROPOSED ADDITION To THE SHORT RESIDENCE
24106 - 102N" PLACE WEST
EDMONDS, WA
G-2897
Prepared For
Kent and Janyce Short
24106 - 102nd Place West
Edmonds, WA 98020
June 24, 2009
0
GEO GROUP NORTHWEST, INC.
13240 NE 20th Street, Suite 10
Bellevue, Washington 98005
Phone: (425) 649-8757
JUN 29 2009
"U"Dwe oePA8TX16,yr
STREET FILE CITY OF EDMONDS
roup Northwest, Ine,
June 24, 2009
Kent and Janyce Short
24106 - 102nd Place West
Edmonds, WA 98020
GeotechnicafEngineers, Geologists
& Envimnmental Scientists
Subjects Geotechnical Engineering Study
Proposed Addition. to the Short. Residence
24106 - 102' Place West
Edmonds, WA
Ref: City of.Edmonds, "Determination Regarding Critical Areas Checklist:
CRA20090045," dated June 17, 2009.
Dear Mr. and Mrs. Short:
G-2897
The purpose of this report is to provide an assessment -of the geologic hazard(s) associated with a
steep slope located on the adjacent property West of your lot and to provide geotechnical design
recommendations for the proposed house addition.
The scope of work for this study consisted of reviewing the -geologic map for the project site
area, a site visit on June 23, 2009, reconnaissance of the site, and adjacent slope, the drilling of
two shallow hand auger borings in the vicinity of the proposed addition to -evaluate the
subsurface soil conditions, and reviewing the, plans for the�proposed addition.
Site and Project Description
The project site is located on the west side of 102 d Place West, approximately as illustrated on
the Vicinity Map, Plate 1. The site consists of a residential lot that measures 85' wide by 120.17'
long, The lot is surrounded by residentially developed properties. Topographically, theleastern
portion of the lot (east of the house) is relatively levei. The middle portion of the lot slopes
moderately down to the west next to the house and transitions to the western yard area that
gradually slopes down to the west. A steep slope, approximately 18 to 20 feet tall, is located on
the adjacent property west of the subject site. The slope is vegetated with -small fiT trees and
13240 NE 20th Street, Suite 10 - Bellevue, Washington 98005
Phone 425/649-8757 - Fax 425/649-8758
4
June 24, 2009 G-2897
Geotechnical Engineering Study Page 2
Proposed Addition to Short Residence
some brush. The top of the steep slope is located on the adjacent property, just beyond a wood
fence that defines the west property line of the subject lot. The slope has a gradient dabout 52
percent based on the LiDAR topographic map provided by the City (Plate 2 of Illustrations).
The existing house was constructed around 1956. The house is one-story with a daylight
basement. The house footprint is approximately 1,200 sf not including an open carport attached
at the south end of the house. An existing concrete pad and a wood deck extend off the west side
of the house. The yard area west of the house is a garden area. The existing house is connected
to the sanitary sewer. City storm water drains are not available for the lot. Roof water down
spouts discharge to splash blocks on the east side of the house and into subsurface concrete tile
pipes on the west side.
The proposed addition will be a two-story wood framed structure constructed on the west side of
the existing house. The lower level will extend the daylight basement and have 14'by 18'(252
sf) of new living space. The upper level (Nook) will come off the main floor of the house and
have 8'by 18'(144 st) of new living space. About 212 square feet of impervious deck will be
constructed around the Nook (above the remaining portion of the lower level addition). New
stairs will be added at the north end of the lower level addition. A plan view of the proposed
addition is illustrated on the Site Plan, Plate 3.
Relative to the steep slope, the west side of the existing house is setback about 63 to 64 feet from
the west property line (top of steep slope) and the proposed 18'wide lower addition will be
located some 48 to 49 feet from the west property line.
According to the Edmonds Community Development Code (ECDC) the adjacent steep slope is
designated as a critical area with geologic hazards, including a landslide hazard. A geotechnical
engineering report (also referred to as a 'critical areas report') is required as part of the submittal
process for the building permit.
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
ASSESSMENT OF GEOLOGIC CHARACTERISTICS
Geology and Site Soils
G-2897
Page 3
I
According to the area geologic map , the project site is mapped as Glacial Till (Qvt) of the Fraser
Glaciation Period. Glacial Till is described as consisting of a poorly sorted, nonstratified
lodgement till that is an extremely compact mixture of clay, silt, sand, pebbles, and cobbles
deposited as ground moraine under the glacier in the upland areas. West of the site the soils are,.
mapped as Advance Outwash (Qva). Advance Outwash underlies the till and consists of mostly
clean, pebbly sand with increasing gravel content higher in the section. The Advance Outwash
was deposited by meltwater flowing from the advancing front of the glacier.
Two shallow hand auger borings were drilled in the area of the proposed addition west of the
house to evaluate the site soils. The soils encountered consisted of 2 to 10 inches of topsoil
underlain by brown gravelly sand to the total depth of the borings (10 to 16 inches - gravel
refusal). The gravelly sand is very dense, based on probing, and the gravels are subrounded. The
gravelly sand is consistent with the Advance Outwash deposit described above. Glacial Till was
not encountered in the borings.
Soils along the west property line, above the top of the slope, were probed with a 1/2-inch steel
rod and found to be loose to a depth of 3 to 3.5 feet and dense below that depth.
Hydrology
The Advance Outwash sand has a moderately high permeability rate and water readily infiltrates
into the deposit. According to the geologic map the Advance Outwash deposit extends some
1,600 feet west of the site. No expressions of water seepage were observed on the slope.
Minard, J. P., 1976, "Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles,
Washington," Department of Interior, U.S. Geological Survey, Map MF- 1541, 1:24,000.
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
SLOPE STABILITY EVALUATION
G-2897
Page 4
The project site is not located in a known active landslide area. The dense Advance Outwash
deposits are generally stable in the absence of water seepage. No groundwater seepage or springs
were observed. The topography of the slope indicates that historically there has not been incising
into the slope as a result of water runoff or springs. We did not observe evidence of current or
recent slope instability, such as soil tension cracks, scarps, slumps, or slides, on the subject and
adjacent properties. Vegetation on the slope consists of some brush and fir trees. In general, the
trunks of the trees are straight. It is our opinion that the slope is stable.
SITE VULNERABILITY EVALUATION
The slope appears to be stable and the risk is low of a deep seated slide occurring, based on our site
reconnaissance observations, the geology, and hydrology. Based on discussions with Mr. Short, he
is not aware of any slides or other instability occurring on the slope in the 25 years he has lived on
the property. We do not anticipate naturally caused slides to occur on the slope and do not
anticipate the top of the slope to retreat.
Concentrated storm water runoff should be avoided on the slope. Based on our plan review of the
proposed addition, storm water was to be discharged to a dry well located in the west yard area. To
mitigate against a potential concentration of storm water above the slope we recommend the storm
water be discharged to a infiltration trench located between the addition and slope.
EROSION HAZARD EVALUATION
The hazard of water erosion is low based on the geology and site conditions.
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
DISCUSSION AND RECOMMENDATIONS
G-2897
Page 5
Based on the site conditions, it is our professional opinion that the proposed addition will have no
impact on the stability of the steep slope, will not increase the potential for slides, and will not
increase the potential for erosion. We conclude that the proposed addition will avoid impacts to
the geologic hazard area and no geological hazards will result from the proposed development
either on the subject site or on the adjacent properties.
Based on the plans for the addition, the addition will be supported on a spread footing foundation
consisting of strip footings. Excavation is anticipated for the foundation and the infiltration
trench. No other site grading is planned.
Storm Water Infiltration
A City storm water drainage system is not available at the site. The site soils consist of gravelly
sand and the discharge of storm water into an infiltration trench is recommended. We recommend
the infiltration trench be located a minimum of 10 feet west (down -gradient) of the addition, and a
minimum of 25 feet from the west property line. The infiltration trench should be installed
parallel to the slope of the ground (which is generally parallel to the west property line). The
perforated pipe in the trench should be installed level to allow water to be dispersed over the length
of the trench. Water can be input into both ends of the trench if desired. We recommend
constructing the trench as illustrated on Plate 4 (Fig. C.2.2.A, January 2009, King County Surface
Water Design Manual, Appendix Q. Based on the medium sand site soil, the trench length should
be 30 feet per 1,000 square foot of impervious surface area. For the proposed addition (252 sf
impervious surface area) we recommend a minimum trench length of 10 feet. The trench length
should be increased appropriately if additional water will be input into the trench.
TO prevent potential back -flow of the roof system into the footing drain system, the footing drain
should not discharge into the roof drain infiltration trench. We do not anticipate that the footing
drains will generate much water, if any, based on the site soils. We recommend the footing
drain(s) be discharged to either a small drywell or a infiltration trench located such that it is not
down -gradient (down -slope) of the roof infiltration trench. The drywell can be a few feet in
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
G-2897
Page 6
diameter and deep enough so the footing drain discharge line can gravity drain (1/2percent
gradient). If the soils consist of the gravelly sand, the footing drain discharge line can consist of
perforated pipe. The discharge point should be a minimum of 10 feet from the structure.
Minimum Buffer and Building Setback
Based on our findings and conclusions, it is our professional opinion that the non -disturbance
buffer can be reduced to 10 feet from the top of the slope for the purpose of constructing the
addition and infiltration of storm water.
Foundation Recommendations
It is our professional opinion that the proposed addition can be supported on a conventional spread
footing foundation. The plans specify 12-inch wide strip footings for the foundation, however we
recommend the strip footings be a minimum of 16-inches wide and the stem wall be a minimum of
8-inches wide, unless the smaller footing and stem wall width is approved by a structural engineer
or is shown to meet the minimum building code requirements. Footings should be supported on
dense, undisturbed soil to minimize settlement. If loose soil is present, the loose soil should be
compacted (if less than I 0-inches thick) or be removed and replaced with compacted fill meeting
the compaction specifications for structural fill. The footing width should be increased to 16-
inches if the foundation is supported on compacted soil or structural fill.
The following spread footing foundation design criteria is applicable for footings supported as
described above:
0 Allowable bearing pressure, including all dead and live loads:
Minimum depth to bottom of perimeter footing below
adjacent final exterior grade:
Minimum depth to bottom of interior footings
below top of floor slab:
0 Minimum width of strip wall footings:
GEO Group Northwest, Inc.
= 2,000 psf
= 24 inches
= 12 inches
= 16 inches
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
0 Minimum lateral dimension of column footings:
Estimated post -construction settlement:
0. Across building width:
G-2897
Page 7
= 24 inches
= less than 1/2 inch
= less than 1/2 inch
A one-third increase in the above allowable bearing pressures can be used when considering short-
term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the
foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the
buried portions of the foundations. For the latter, the foundations must be poured "neat" against
compacted soil. Our recommended parameters are as follows:
Passive Pressure (Lateral Resistance) = 350 pef equivalent fluid weight
Coefficient of Friction (Friction Factor) 0.35
Structural Fill Specifications
Structural fill is defined as fill soil that supports building foundation loads, floor slabs, patios,
porches, retaining walls, sidewalks, and pavements. In general, during wet weather the structural
fill material should be a free draining, granular material, containing no more than 5 percent fines
(silt and clay -size particles passing the No. 200 mesh sieve), be free of organic and other
deleterious substances, and have a maximum size of 3-inches. The sandy site soil should be
useable as structural fill.
Structural fill material should be placed and compacted at or near the material's optimum moisture
content and in lifts that are I 0-inches thick or less. Below foundation footings, concrete slab
floors, patios, walkways, or other structural elements, structural fill should be compacted to a
minimum of 95 percent of the material's maximum dry density, as determined by ASTM Test
Designation D- 15 5 7 (Modified Proctor).
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
Slab -on -Grade Floors
G-2897
Page 8
To mitigate settlement of the floor slab, should loose subgrade soil be encountered we recommend
removing the loose material down to the underlying dense undisturbed soil and replacing it with
structural fill. If loose soil is greater than 2 feet in thickness we recommend the geotechnical
engineer evaluate the site conditions and provide recommendations.
For dry storage and living space, slab -on -grade floors should be placed on a capillary break to
prevent wicking of moisture through the slab. The capillary break should consist of a minimum
four (4) inch layer of gravel or crushed rock containing no more than five (5) percent fines passing
the No. 4 (1/4-inch) sieve. A 5/8-inch crushed rock with no minus fraction is typically an
acceptable material for use as a capillary break (pea -gravel is not recommended).
To reduce water vapor transmission through the slab we recommend installing a I 0-mil reinforced
vapor barrier, such as MoistO' by Fortifiber Corporation, between the capillary break and
concrete floor slab. Two to four inches of sand may be placed over the membrane for protection
during construction (optional).
Footing Drains
We understand the lower level interior floor elevation will be lower than the surrounding finished
grade. Subsurface footing drains should be installed at the base of the footing to prevent moisture
intrusion into the lower level. A water -proof coating should also be applied to the foundation
footing and stem wall.
The footing drain should consist of a four (4) inch minimum diameter, perforated, rigid drain pipe
laid at the bottom of the footing. The drain line should be bedded in clean drain rock and the drain
rock protected with geotextile. filter fabric, such as Mirafi 140N, or equivalent, as shown on the
Footing Drain Detail, Plate 5.
Roof and other drain lines should not be connected to the footing drain system. Footing drains
should be tight -lined to a separate discharge point, such as a small drywell or infiltration trench
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
G-2897
Page 9
located down -gradient of the structure. Installation of clean -outs is recommended to allow periodic
maintenance.
Erosion Control and Mitigation Recommendations
The construction of the addition and infiltration trench should cause minimal site disturbance. No
mitigation measures are recommended. It is our opinion that it is not necessary to install erosion
and sedimentation control measures, such as a silt fence down -gradient from the site disturbance
area, provided the site work is performed and completed in the dry summer months. The existing
garden area will provide filtration and runoff control.
REPORT PREPARATION
The services described in this report were prepared by Mr. William Chang, RE, senior
geotechnical engineer and principal of GEO Group Northwest, and by Mr. Wade Lassey, a licenced
engineering geologist. Mr. Chang has 30 years of experience as a geotechnical engineer and Mr.
Lassey has been practicing 19 years as an engineering geologist.
LIMITATIONS
This report has been prepared for the specific application to the subject project. The findings and
recommendations stated herein are based on our field observations, our experience, and judgement.
The recommendations contained herein are our professional opinion. No warranty is expressed or
implied. It is understood that constructing on, below, or above a steep slope has inherent risk and
the property owner assumes the risk.
In the event that soil conditions vary during site work, GEO Group Northwest, Inc. should be
notified and the recommendations herein re-evaluated, and where necessary, be revised. GEO
Group Northwest, Inc. should be retained to review the final design plans to confirm the validity of
the recommendations contained in this report if there are significant changes to the project as
described herein.
GEO Group Northwest, Inc.
June 24, 2009
Geotechnical Engineering Study
Proposed Addition to Short Residence
Please contact us if you have any questions.
Sincerely,
GEO Group Northwest, Inc.
Wade J. Lassey
Engineering Geologist
William Chang, P.E.
Principal
Attachments:
Plate I -
Vicinity Map
Plate 2 -
Topographic Map
Plate 3 -
Site Plan
Plate 4 -
Infiltration Trench
Plate 5 -
Footing Drain Detail
cc: Mr. Mark Lowe, Chermak Construction, Inc.
GEO Group Northwest, Inc.
G-2897
Page 10
ILLUSTRATIONS
GEO Group Northwest, Inc.
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C.2.2 FULL INFILTRATION
IFIGURE C.2.2.A TYPICAL TRENCH INFILTRATION SYSTEM
6"
6"
12"
roof
drain
NTS 4" rigid or 6" flexible i
perforated pipe
.................................................
17—
.................................................
infiltration trench sump w/solid lid
o.� roof drain
PLAN VIEW
NTS
overflow
—J�r
4" rigid or 6" flexible splash block
perforated pipe
F, 7r 5.0 rn�
washedrock in 11
1 112"-3/4" I'min
--------- ---------------------
fine mesh CB sump w/solid lid
varies Scmen
filter fabric
-compacted backfill
4 rigid or 6" flexible
24" V
perforated pipe
V V washedrock
12 V
1 1/2"-3/4"
V
J
SECTION A
NTS
INFILTRATION TRENCH
PLATE4
2009 Surface Water Design Manual — Appendix C
('45
1/9/2009
.4
Foundation
Wall
Slope to drain
0 0
0 00 0 0 0 0 0 0
0 0 0 0 o COMPACTED 0
ONSITE BACKFILL
0 0 0 o MA TERIA L WA TER PROOFING
0 (IF USABLE) 0
0 Co 4=0
0 0 0 0 0
0 0 0 0
0 0 RAB
0
0 0 0 0 0 000
CAPILL4RYBREAK 00
GEOTEXTILE
FILTER FABRIC FOOTING 0 0 0 0 0 0 0 0
(Miraft 140 N, or Dense Undislurbed Soil
equivalent) FOOTING DRAIN: or,51ructural Fill
WASHED DRAIN RO(,-'K Alinimum 4-inch diameter rigid
perforaled PVC pipe with positive
gradient to discharge point.
NOT TO SCALE
NOTES:
1.) Do not replace rigid PVC pipe with flexible corrugated plastic pipe.
2.) Perforated PVC pipe should be tight jointed and laid with perforations down,
with positive gradient to discharge.
3.) Do not connect roof downspout drains into the footing drain I ine system.
4.) Interior backfill below slab -on -grade floor should be compacted to 95%
of the materials maximum dry density.
FOOTING DRAIN DETAIL
Group Northwest, Inc. SHORT RESIDENCE
Geotechnical Engineers, Geologists. &
Environmental Scientists 24106 - 102ND PL. W.
EDMONDS, WASHINGTON
SCALE NONE DATE 6/24/09 1 MADE WJL I C11KD WC JOB NO. G-2897 PLATE 5
.10