HomeMy WebLinkAboutDDR2006-00132 BLD2024-01382 - DDR Reports - 11/3/2008 TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Mason County DCD
Planning Division
PO Box 279
Shelton, WA 98584
Mike Straight
PO Box 149
Lilliwaup, WA 98555
(206) 271-6608
Re; Geotechnical Report
345 N. Shar lane, Lilliwaup, WA 98555
Parcel No.: 32309-34-00030
Mason Co. Case No.s: DDR2006-00132
BLD2006-00679 (Garage)
INTRODUCTION
I was contacted in late 2008 by Mr. Mike Straight who requested my investigation and
documentation of slope stability and landslide hazard issues relating to the permitting and
development of his property located at the far end of Shar Lane (a private road),just south of the
plat of Colony Surf, Lilliwaup, Washington.
The site was visited in October of this year to collect topographic information and verify
measurements and feature locations. Measurements were made using a Trimble T5415 total
station, a 4-foot range pole, a Sokkia model No. 8047-55 inclinometer, 100 foot and 300 foot
long fiberglass surveyor's tapes and other field equipment common to surveying. Software
employed in creating a site plan and writing this report included AutoCAD 2006, a Terrain 3-d
contour modeling program, GALENA Slope Stability Analysis software, and Microsoft Office
Word 2003. Areal contours were developed from Mason County's GIS website information.
Contours within the property boundaries were developed from topographic survey information
collected for this project.
The site has even aged second growth timber in the southerly two-thirds of the property. The
northerly third of the property has been cleared in the past and has been used as a recreational
camp site. An Onsite Sewage System (OSS) is being designed generally in the location indicated
on the attached site plan. The northerly third of the property is level, but the level portion of the
property is bounded on the south by a hillside with slopes varying between 40 and 70% with an
average downslope of 60% over an elevation difference of roughly 300 feet. The property is
located in an area where the Olympic Mountain foothill glacial till (Qgt) soils become buried
under non-glacial quaternary sediments (Qls).
Under Mason County's Resource Ordinance, land disturbing activities within 300 feet of a
landslide hazard area(slopes>40% with more than 10 feet of height) requires some level of
technical investigation or special report in the form of either a geotechnical assessment, or a
geotechnical report. The slope to the south of the Straight property categorizes Mr. Straight's
File: C:IProjectslMStraightlGeo-Rpt 1 of 6 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
building plans as being within the County's Critical Resource Ordinance 50-foot hazard area
buffer, so requires the preparation of a geotechnical report based on the owner's plans, site
conditions, and the County's approval of the proposal. The following thirteen elements are
required by Mason County to be addressed in geotechnical reports prepared to comply with
Mason County's Critical Resource Ordinance Sections 17.01.100 through 17.01.104.
1. SURFACE AND GEOLOGIC CONDITIONS:
The site is located immediately south of the Community of Colony Surf Washington in the area
identified on the Geologic Map of Shelton 1:100,000 Quadrangle, Washington' on the following
page. Hood Canal is located approximately a third of a mile east of the Straight property. The
map reveals that the soils surrounding the Straight property are glacial deposits classified as
Continental Glacial (Qgt & Qls) soils. The soils are further described as follows:
'Dill,late N1 isconsinan (Pleistocene)—Unsorted, unstratified, highly
compacted mixture of clay, silt, sand,gravel, and boulders deposited
by glacial ice of the Puget lobe; gray; may contain interbedded strati-
fied sand,silt,and gravel,sand-size fraction is very angular and con-
tains abundant polycrystalline quartz,which distinguishes this unit
from alpine till; cobbles and boulders are commonly striated and(or)
faceted, although unweathered almost everywhere, may contain cob-
bles or small boulders of deeply weathered granitic rock.
Landslide deposits(Holocene}—Poorly sorted mixtures of locally
derived rock and(or) soil emplaced by mass-wasting processes;
deposits vary widely in size, composition, and mode of emplacement,
only the largest landslides are shown; includes rock falls(Schuster
and others, 1992) in the southeast Olympic Peninsula that are proba-
bly seismically induced,and large deep-seated landslides along Hood
Canal (Carson, 1976)and along steep-sided inner gorges of river val-
leys in the southern Olympics; smaller shallow deposits such as
debris flows in steep mountain drainages and rock topples along
coastal bluffs, although numerous and dangerous, are too small to
show at the map scale.
The building area at the top of the hillside overlooking Hood Canal has been leveled in the past,
requiring a very modest volume of cutting, which steepens at the transition from the Olympic
foothill plateau to the Hood Canal sea level elevation at an approximate 40%to 70% slope as
shown on the attached site plan. The hillside slopes are covered with medium aged second
growth fir, hemlock, cedar, and maple trees with a dense understory of Salal, Oregon Grape, and
Huckleberry. The hillside surfaces just south of the leveled area have a moderately dense soil to
a depth between 2 and 3-feet where an underlying glacial till layer is present and the soil
character becomes strongly cemented. Approximately 100-feet downslope from the "upper"
level portion of the property, the surface soil becomes much deeper to a depth estimated at 50-
feet or more. This portion of the slope generally coincides with the steepest portion of the
property with the surface of the moderately cemented soil standing near its natural angle of
1 DNR OFR2003-15 Geologic Map of Shelton 1:100,000 Quadrangle, Washington
File:C:iProjectsWStraightlGeo-Rpt 2 of 6 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
repose. Inspection of the steep hillside areas of the property found little evidence of recent
landslide activity or movement. The access road to the property has been constructed at some
distant past date, and aside from raveling of the upper roadside's cut bank, appears stable in its
present condition. The cut bank developed during road construction was sloped at near a 100%
slope, but through natural weathering and winter freeze thaw cycles, is relaxing to a near 2:1
slope where it should become stable.
As the following portion of the Geologic Map of Shelton 1:100,000 Quadrangle reveals,the
Straight property is located in the vicinity of at least one fault line identified on the following
map as (1) a fault line which follows Hood Canal is located approximately 3/8 ms of a mile east of
the Straight property. The presence of this feature does not represent a hazard, and standard
seismic analysis of the site is intended to anticipate potential tectonic impacts.
Qga Qap 123*00'
47'30'
t `+� traight•• C2apwt OP
roject
_ Location
-
:Vd
F` Q ~� Napo
r .
n � a
.L5
✓ O
Inspection of the Washington Coastal Atlas reveals that the upper(northerly) portion of the
Straight property is situated in an area of"Intermediate" stability, indicating that the slopes are
generally stable, but susceptible to instability when disturbed. The Washington Coastal Atlas
classifies the southerly portion of the Straight property as being in an area classified as an
"Unstable Old Landslide"area.
No land disturbing activities are planned for any of the steep slopes (>40%) on the property.
2. SITE PLAN WITH IMPORTANT DEVELOPMENT AND GEOLOGIC FEATURES:
A site plan showing the general topography of the area surrounding the Straight property is
attached as an appendix. An ecology block wall has been installed at some past date across the
northerly boundary of the property, and a utility cargo container has been placed on the property
as shown on the site plan. Utilities(water, phone & electricity) are available to the site at the
Shar Lane right of way. An Onsite Septic System is being designed for the site in the location
indicated on the site plan. The proposed drainfield (Glendon cell) is the most practical location
on the site and should be considered acceptable as shown on the site plan. No upland water
bodies or wetlands were found in the Straight property vicinity.
File:C:TrojectsW StraightlGeo-Rpt 3 of 6 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
3. LOCATIONS OF LOGS OF EXPLORATORY HOLES OR PROBES:
Various areas of the Straight property were inspected by different methods. The attached site
plan shows the locations of soil log holes excavated in the area of the proposed septic system
drainfield. Soil log holes on the adjacent property were also inspected. The excavations all
showed a moderately dense soil typically 3-feet or less in depth resting on top of a very stiff
cemented glacial till layer. Soil probing with a steel rod found the level area of the property to be
excavated down to the till layer. The road cut slopes in the southerly portion of the property were
easily accessible and revealed a fairly deep (>30') layer of moderately cemented gravelly sand.
Modeling of the site employed a moderately cemented weathered till soil layer in the northerly
area of the Straight property overlying a stronger cemented till layer beneath the surface soil
layer. The southerly portion of the site is modeled as a homogenous soil of moderately cemented
gravelly sand (USCS GP-GC) located above a deep glacial till layer..
4. AREA OF PROPOSED DEVELOPMENT & BOUNDARIES OF HAZARDS,
BUFFERS, AND SETBACKS:
The attached site plan shows the general locations of existing improvements and planned new
construction. The slope to the south of the Straight residence is labeled as hazard areas on the
appended site plan. The hazard area's vegetated buffer (50-feet from hazard areas) is also labeled
on the attached site plan.
A building setback from the crest of the southerly descending slope of 20-feet or more is
recommended to be incorporated into the site's development plans. A request for a reduction of
the hazard area buffer to 20-feet will be prepared for the proposed site development.
5. CROSS SECTION WITH PROPOSED GRADE CHANGES:
A cross section view of the property is provided in the attached plan sheets as well as a part of
the GALENA Stability Analysis Print-Out. No grade changes are proposed for any of the slopes
on or near the Straight property.
6. SLOPE STABILITY ANALYSIS:
The steep slope to the south of the Straight property displays no indications of soil movement or
slope instability. The trees on the steep hillside were found to be growing straight with no
indications of trunk curvature typically associated with moving slopes or surface creep
associated with freeze/thaw cycles.
Unified Soil Classification System typing places the hillside soils in a dual symbol category due
to its fines content falling between 5 and 12%. The coarse element of the soil conforms to a GP
classification, and the fine soils conform to a GC soil category. The soils are best described as a
GP-GC soils characterized as having a saturated soil unit weight of 131 lbs/ft3, a phi angle of
420, and a cohesion character of 2001bs/ft2 for the moderately cemented soils and 5001bs/ft2
File:C:TrojectsW StraightlGeo-Rpt 4 of 6 1 1/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
cohesion for the cemented glacial till soil located at the property's high elevation. The water
table is located beneath the till layers underlying the site, and shouldn't affect the stability of the
hillside slopes.
The slope geometry and soil characteristics provide a factor of safety for the site in a static and a
dynamic analysis that exceeds the County's minimum safety requirements. Analysis of the site
indicates Factors of Safety of J$in a static condition and 1_3 under dynamic conditions for the
hillside south of the Straight property.
7. RECOMMENDED SETBACKS & DRAINAGE:
Slope stability analysis indicates that the southerly descending slope south of the Straight
property is stable in its present geometry and condition and does not represent a landslide or
geological hazard to the proposed residence construction or neighboring properties.
Drainage from the present site is generally dispersed and migrates towards the south, which
should be preserved as the Best Management Practice (BMP) for this site's stormwater runoff.
The site's permeable soils are fairly shallow, generally making infiltration of stormwater runoff
impractical and difficult. Dispersing stormwater into vegetated areas of the yard should be
employed as the primary stormwater Best Management Practice for this site and location. Gutter
downspouts should be discharged onto splash blocks located near the corners of the building(s).
Stormwater runoff from the driveway and parking areas should be dispersed into vegetated strips
paralleling the driveway or parking area. The yard area between the roof downspouts and top of
the steep slope should be maintained with a lawn and/or vegetation of the owner's choosing.
8. CLEARING, GRADING,AND VEGETATION MANAGEMENT:
The location of the planned residence location was cleared at some past historic date. The main
grading on the site will be excavation of building footings, which should bear on the undisturbed
glacial till layer underlying the building location(s).
Vegetation should be encouraged to grow on the unimproved areas of the Straight property.
Removing trees from the southerly descending slope to maintain a view towards Hood Canal
may be allowed, but their stumps and understory vegetation should be left to provide erosion
protection and provide an element of cohesion to the shallow surface soils.
9. EROSION AND SEDIMENT CONTROL:
Inspection of the Soil Survey of Mason County found the site to be located in an area with a
Hoodsport Stoney Sandy Loam (Hg) soil type, which is not identified in the County's Critical
Resource Ordinance as a severe erosion hazard.
The Straight property extends several hundred feet to the south from the planned development
area and will provide adequate silt and erosion protection to neighboring properties.
File: C:Trojects3f StraightlGeo-Rpt 5 of 6 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
The site already has an access to the property Shar Lane and already has an all weather erosion
resistant surface.
10. ON-SITE AND OFF-SITE IMPACTS:
Construction and completion of the proposed improvements are not expected to result in any
adverse on-site or off-site impacts.
11. SPECIFICATIONS OF FINAL DEVELOPMENT:
Encouraging vegetation to grow and act as a stormwater mitigation and bank stability element is
strongly recommended. Promoting vegetation on the steep slopes to the south of the building
area is recommended.
12. RECOMMENDATIONS FOR THE PREPARATION OF STRUCTURAL
MITIGATION OR DETAILS OF OTHER PROPOSED MITIGATION:
Modeling of the slope in the proximity of the residence and amenities indicates that the location
of the proposed improvements are safe. No other structural mitigation or details appear
warranted other than placing footings on the un-disturbed glacial till layer underlying the
proposed residence location and maintaining a 20-foot plus building setback from the crest of the
steep southerly descending downslope.
13. SITE PLAN WITH THE LOCATION OF EXISTING AND PROPOSED
DEVELOPMENT ON THE SITE:
A site plan is attached as an appendix to this report and is hereby made a part of this report along
with the cross section view of the property, and the stability analysis printout.
Summary & Conclusions:
The Straight property, though in the vicinity of slopes identified as hazard areas by Mason
County terminology, is stable in its present condition. Development of the site as Mr. Straight is
proposing should not result in any adverse impacts to either his, or his neighbors' properties.
Please feel free to contact me if there are any questions or concerns regarding this report or my
findings.
Sincerely, ?,
v�OF WASx
R
Alan A. Tahja, P.E.
Attached: Plan ViewsM& Cross Section Sheet NV
�7g4
GALENATM Stability Analysis Printout 0.� ��CIsrER�� '
�`S`sIONAL ttl
File:C:TrojectslMStraight�Geo-Rpt 6 of 6 11/3/2008
Rev# Description Date TAHJA ENGINEERING,INC. SITE PLAN
Alan Tahja,P.E. Mike Straight Straight,M
PO Box 235 PO Box 149
Hoodsport, WA 98548 Lilliwa¢p, WA 98555 1 of4
Mason Co.Prc/No.: 32309-34-00030 (360)877-9512 (206) 271-6608
� o s
Z N
II( o 0 o 0
J s /
,
If I
\\\\,X`�t`\\1\
, I
VOA A\
I
Rev# Description Date TAHJA ENGINEERING,WC. SITE PLAN
Alan Tahja,P.E. Mike Straight Straight;M
PO Box 235 PO Box 149
Mason Co.PrGI No.: 32309-34-00030 (3 od ypoA W2 98548 LAwaup, WA 98555 $"
(206) 271-6608 2 of 4
05
\\ 1X6 1 \,
1 I
009~ our 104014( _ 1
r/ 09/~ our i
/'/ � I
, r
Q+ O ,
0
Ul
r
a
r (au�l pagseQ
la ng eald p1enH \
S � ,
3 � \
4
N Soil Logs;
SL1-SL5 all revealed a hard cemented
SCALE: I"=50' Glacial Till soil located witin 3-feet WAsy
w F 0 10 30 50 of the surrounding ground's surface. �' '� c
gee � 0
� z
S
Property Line(PL) -150' Op
O $�30784
4
Shar Lane Ss ONAL E�
w
utdi 5Exist.Ecology Block Wall a v w, Exist. Colo
d UtititieBlock W wate y
•
low Oli'
So, L Car o-Cog nta--- o
L' ----�J Cergo Container Op �O
<Da h dC rea Eu�e o Exist. Zvi A t 0 Y
fie) r Garage �ro
El
Conjectural .
v Residence Conjectural
ResidenceJ Or
/
SL1
_ -20'Building S c y
\ �m Crest of Slo — ne _ �- N
e
P —
\�\ SL c
GlendonY
Septic _ 00
I -Jr raifitield
ICEM SU II Area —�
Op SL4 Glendon
I�I Septic
Drain
ea
90
Sao �/ ��e•: ��-_ego-- W
I p p'
co
Conjectural g
Note:The cut banks on the upper side of Residence V k �.
SCALE: I"= 100'
N Shar Lane reveal Loamy Gravelly Sand '� b
o zs so env to depths in excess of 30-feet.
S°0 b
W E �� p
ero
Moderately Cemented
Loamy Gravelly Sand
OF OAsy
4111
NALYj
goo �
t
Cross Section Through A - A
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Mike Straight—Shar Lane Stability Analysis
GALENA v.-5ol
700
oo WA
s
;�`'°a G� ��CI S 1 Egrb� w
400 ¢VtD SIOAIAL ET1t'1�
.o-.V,ccn.nwt ou,:w nu
300
Analysis: 1
Multiple Stability Analysis
Pb nw Swfh Metdod: &shop Sun;Wiied
200 ---_.. ---- ------.___ .._.�._._. __...._._ Surface: Circular
Results
Criaesl(minimum)
100
Factor of Safety. 1.76
0 11 200 300 400 500 600 700 e00 900
E&od 3 Nov 70B Pro—W 3 Nov 1tlOB
PPrpiect: Mike Straight Stability Analysis
Dynamic
Eilit C:Oocuments and seangs%ownerwy Documents%Propcts%StraightWikovStability FilesWodel 1 Static.gmf Tahja Engineering,Inc.
Galena 5.01 Analysis Results Licensee: Tahja Engineering, Inc.
DATA: Analysis 1 - Static
Material Properties (2 materials)
-------------------
Material: 1 (Mohr-Coulomb Isotropic) - Moderately Cemented & Weather Till
Cohesion Phi UnitWeight Ru
200.00 42.0 131.00 1. 10
Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till
Cohesion Phi UnitWeight Ru
500.00 42.0 131.00 1.10
Water Properties
----------------
Unit weight of water: 62.400 Unit weight of water/medium above ground: 62.400
Material Profiles (2 profiles)
-----------------
Profile: 1 (2 points) Material beneath: 1 - Moderately Cemented & Weather Till
-10.00 650.00 900.00 650.00
Profile: 2 (6 points) Material beneath: 2 - Cemented Glacial Till
300.00 250.00 700.00 545.00 730.00 555.00
850.00 555.00 855.00 565.00
884 . 30 567.00
Slope Surface (39 points)
-------------
File: C:�ProjectsiMStralghtlGALENAPrintout 1 of 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
0.00 210. 00 51.20 220.00 84 .30 226.00
126. 90 240.00 147.90 250.00
169.70 260. 00 189.20 270.00 208.70 280.00
223.20 290.00 237.80 300.00
256.20 310.00 282.50 310.00 289. 10 320.00
301.70 340.00 314.40 350.00
331. 90 360.00 347.80 370.00 367.00 380.00
385.60 390.00 402.20 400.00
417.80 410.00 436.20 420.00 453.70 430.00
470. 60 440.00 487.50 450.00
503.40 460.00 518.70 470.00 534.00 480.00
559.80 480.00 569.80 494 .00
581.30 500.00 598.00 510.00 620.00 520.00
678. 60 540.00 705.30 550.00
722.30 556.00 845.70 556.00 848.20 566.00
884 .30 570.00
Phreatic Surface (2 points) ---------------- 0.00 200.00 900.00 200.00
Failure Surface
---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 195.00 YL: 272. 97 XR: 720.00 YR: 555. 19
Centre: XC: 380.01 YC: 558.23 Radius: R: 340.00
Variable Restraints
-------------------
Parameter descriptor: XL XR R
Range of variation: 363.00 305.00 289.00
Trial positions within range: 20 20 30
----------------------------------------------------------------------
RESULTS: Analysis 1 - Dynamic
Bishop Simplified Method of Analysis - Circular Failure Surface
---------------------------------------------------------------
Critical Failure Circle Search using Multiple Circle Generation Techniques
Factor of Safety for initial failure circle approximation: 2. 99
There were: 7490 successful analyses from a total of 12001 trial circles
4511 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.76
Negative normal stresses exist on the base of one or more slices - examine slice data
and consult the Galena Users' Guide
Circle and Results Summary (Lowest 5 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 190.29 784.35 242.76 302.70 583.55 501.35
484.50 1.764
2 165.20 760.77 204.55 277.87 567.50 490.78
484.50 1.766
3 195.80 774. 90 242.76 302.70 583.55 501.35
474 .53 1.769
4 170.81 751.21 204.55 277.87 567.50 490.78
474 .53 1.772
5 182.41 773.05 223. 66 290.31 583.55 501.35
484 .50 1.774
File:C:IProjecwM StraightlGALENA Printout 2 of 4 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
GALENA v-soi
700
a00
Yr�ixnnf I3wIJmp Lo.uonn
'jF
500 5�
INWI haJirc F.'+Iwuv
000 Vtya
JlniW,CcrtwnWlGWcwl'Illl
0
0,
300
Analysis: 1
Multiple Stability Analysis
Ylraw: . Method: Bishop Simplified
200 ---- ------._.. .---------�....-- - ---- --..__, Surface: Circular
Results
Critical(minimum)
100 Factor of Safety, 1.31
0 100 200 300 400 500 600 700 aw 900
S*W-3 Nov 2008 Pi-I 3 Nov MW
Protect Mike Straight Stability Analysis
Dynamic
Eta C:Cocuments and Settings%OwnerWy DocumentsProieds%StralghMAike�Stabillty FIIesWodel 1 Static.gmf Tahja Engineering,Inc.
Galena 5.01 Analysis Results Licensee: Tahja
Engineering, Inc.
DATA: Analysis 1 - Dynamic
Material Properties (2 materials)
-------------------
Material: 1 (Mohr-Coulomb Isotropic) - Moderately Cemented & Weather Till
Cohesion Phi UnitWeight Ru
200.00 42.0 131.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till
Cohesion Phi UnitWeight Ru
500.00 42.0 131.00 1.10
Water Properties ----------------
Unit weight of water: 62.400 Unit weight of water/medium above ground: 62.400
Material Profiles (2 profiles)
-----------------
Profile: 1 (2 points) Material beneath: 1 - Moderately Cemented & Weather Till
-10.00 650.00 900.00 650.00
Profile: 2 (6 points) Material beneath: 2 - Cemented Glacial Till
300.00 250.00 700.00 545.00 730.00 555.00
850.00 555.00 855.00 565.00
884.30 567. 00
Slope Surface (39 points)
-------------
0.00 210.00 51.20 220.00 84 .30 226.00
126. 90 240.00 147.90 250.00
File:C:IProjectslMStraightlGALENA Printout 3 of 4 11/3/2008
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
169.70 260.00 189.20 270.00 208.70 280.00
223.20 290.00 237.80 300.00
256.20 310.00 282.50 310.00 289. 10 320.00
301.70 340.00 314.40 350.00
331. 90 360.00 347. 80 370.00 367.00 380.00
385. 60 390.00 402.20 400.00
417.80 410.00 436.20 420.00 453.70 430.00
470. 60 440.00 487.50 450.00
503.40 460.00 518.70 470.00 534 .00 480.00
559.80 480.00 569.80 494 .00
581.30 500.00 598.00 510.00 620.00 520.00
678. 60 540.00 705.30 550.00
722.30 556.00 845.70 556.00 848.20 566.00
884.30 570.00
Phreatic Surface (2 points) ---------------- 0.00 200.00 900. 00 200.00
Failure Surface
---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 195.00 YL: 272. 97 XR: 720.00 YR: 555. 19
Centre: XC: 380.01 YC: 558.23 Radius: R: 340.00
Earthquake Force
----------------
Pseudo-static earthquake (seismic) coefficient: 0.150
Variable Restraints
-------------------
Parameter descriptor: XL XR R
Range of variation: 363.00 305.00 289.00
Trial positions within range: 20 20 30
----------------------------------------------------------------
RESULTS: Analysis 1 - Dynamic
Bishop Simplified Method of Analysis - Circular Failure Surface
---------------------------------------------------------------
Critical Failure Circle Search using Multiple Circle Generation Techniques
Factor of Safety for initial failure circle approximation: 2.27
There were: 7490 successful analyses from a total of 12001 trial circles
4511 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.31
Circle and Results Summary (Lowest 6 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 190.29 784.35 242.76 302.70 583.55 501.35
484.50 1.308
2 165.20 760.77 204.55 277.87 567.50 490.78
484 .50 1.312
3 195.80 774.90 242.76 302.70 583.55 501.35
474.53 1.312
4 182.41 773.05 223. 66 290.31 583.55 501.35
484.50 1.317
5 201.33 765.42 242.76 302.70 583.55 501.35
464 .57 1.317
6 170.81 751.21 204 .55 277.87 567.50 490.78
474.53 1.318
File: C.•"Projects'',MStraightlGALENA Printout 4 of 4 1 1/3/2008
1
1� D -Z-00(o-- 0 OIIL
MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
411 No. Fifth Street//P.O. Box 186, Shelton WA. 98584
360.427.9670 ext. 352
Request for
Administrative reduction in the Required Setbacks ($90.00)
For administrative review, the minimum variance on a yard setback request is 5 feet
from the side lot lines and 10 feet front and rear lot lines or right of way. Request for
further reduction requires standard variance. Setbacks are measured from the furthest
proiection of the structure.
Applicant/Owners: ,
Mailing Address:
City: L n t>>n State: �� , Zip: cT q 5-5 S
Site Address:
Telephone No.: O 7 a
Parcel Number(s): 30 Zoning S
Requested Variance: ron / Rear • Side Yard (please circle all that apply)
� � r
Requested setback variance: f i C� FT.
An illustrated site plan is required:
Your site plan must show the following:north arrow,abutting street or easements,set backs to
all property lines and existing buildings, slopes, surface water,wetlands, critical area, septic,
well and driveway. Show all proposed new development. TO BE KEP
IN
The following circumstances must apply. PARCEL
T THE
Front and or Rear Yard requirements:
r,�e FILE
1) Existing lots of record as of March 5, 2002;
You must meet one of the following. (Please circle all that apply)
2) One of the following exists on the lot:
jasteep slopes, wetlands, or streams present;
soils that restrict building or septic development;
c) lot width at the front yard line of no more than 50 feet;
d) lot size of no more than one-fourth acre;
eX -xisting improvements of buildings, septic systems, and well areas.
3�de yard requirements:
—1) Existing lots of record as of March 5, 2002;
You must meet one of the following. (Please circle all that apply)
2) One of the following exists on the lot:
steep slopes, wetlands, or streams present;
b) soils that restrict building or septic development;
c) lot width at the front yard line of no more than 50 feet;
d lot size of no more than one-half acre;
—� e) isting improvements of buildings, septic systems, and well areas
HAadministativevariance.doc (tw) February 05
these circumstances preclude a reasonable development proposal from
e setback standard for Rural Residential 2.5, 5, 10, or 20 zones.
Q��"-A I r C-A
�et�uJUIL=_ 4nnyiso_ (I A7kE! 1.
Owner/Agent (please indicate)
Signature and date
Official Use Oniy
Approved Jam. (if, Date
Denied Date
Reason for denial:
HAadministativevariance.doc (tw) February 05
WATER LINE GRAVEL ACCESS ROAD 60'EASEMENT
lol—
SOIL LOGS ----- --- I S W
PRIMARY&RESERVE - 1 r43
DRAINFIELD AREA
- - _ ✓ l5 TRANSPORT LINE
- _ o
m OUBLE ENCASED
/IN 10'OF WATER)
-- SEPTIC 1 ems,TANKS
3 BDRM HOME I 'M_�o 51opo— �
50'SETBACK `$ 0.42%Ol.S
FROM TOP OF BANK o QSON*NAMSOF.
APEATHEW)T#_L
BUT PEp11140'iI L
WITH ROOTS
TOP OF BANK TO BOTTOM
c� h 0-3E"+0Lfri
m SOME&W�4 Crr
3
�� +�
WITH ROOTS
TO BOTTOM #
GRAVEL
ACCESS ROAD
- -- O'EASEMENT
SITE PLAN:
FOR: STRAIGHT JOB#:
PARCEL#: 32309-34-00030 DATE: 09 MAY 2005
BY: TJS DESIGN PAGE_ OF
NORTH ARROW: SCALE: 1" = 6'