HomeMy WebLinkAboutGEO2011-00055 - BLD Engineering / Geo-tech Reports - 7/1/2011 • Cc�20 �i - 00
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N?_10 Submittal Checklist For a Geotechnical Report
Instructions:
This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the
licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to
the Mason County Resource Ordinance. If an item found to be not applicable, the report should explain
the basis for the conclusion.
Applicant/Owner Robert& Emilia Dunn Parcel# 32232-54-00018
Site Address E 150 E Madrona Beach Lane, Union,Washington 98592
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) Pages 1-3 TAHJA ENINEERING Inc. Geo-Rpt
(b) A discussion of specific soil types
Located on page(s) Pages 2-3& 5&6 .
(c) A discussion of ground water conditions
Located on page(s) Page 5
(d) A discussion of the upslope geomorphology
Located on page(s) Page 2
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s) Page 2
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
referenced maps and records
Located on page(s) Page 3
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) Geo-Rat Plan Sheets 1 &2
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Geo-Rat Plan Sheet 2
(4) The area of the proposed development, the boundaries of the hazard, and associated buffers and
setbacks shall be delineated (top, both sides, and toe) on a geologic map of the site.
Located on Map(s) Plan Sheets 1 & 2
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorporates the details of proposed grade changes.
Located on Map(s) Plan Sheet 3&GALENA Stability Analysis pages 1 &3
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditions. Analysis should examine worst case failures. The analysis should include the
Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5, the minimum
seismic safety factor is 1.1. and the quasi-static analysis coefficients should be a value of 0.15.
Located on page(s) Pages 4-5.& GALENA Stability Analysis Printout pages 2&4.
(7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) Page 5
(b) Appropriate restrictions on placement of septic drain fields
Located on page(s) Page 3
(c) Appropriate restrictions on placement of compacted fills and footings
Located on page(s) Page 6
Page 1 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Located on page(s) Page 5
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.
Located on page(s) Page 5
(8) Recommendations for the preparation of a detailed clearing and grading plan which specifically
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method of vegetation removal.
Located on page(s) Page 6
(9) Recommendations for the preparation of a detailed temporary erosion control plan which
identifies the specific mitigating measures to be implemented during construction to protect the
slope from erosion, landslides and harmful construction methods.
Located on page(s) Page 6
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) Page 6
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and buffer widths.
Located on page(s) Page 6
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s) Page 6
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location
and nature of existing and proposed development on the site.
Located on Map(s) Plan Sheets 1 &2
I, Alan A.Tahia,P.E. hereby certify under penalty of perjury
that I am a civil engineer licensed in the State of Washington with specialized knowledge of
geotechnical/geological engineering or a geologist or engineering geologist licensed in the State of
Washington with special knowledge of the local conditions. I also certify that the Geotechnical
Reports, dated 6/28/2011 ,and entitled Robert& Emilia Dunn Geotechnical Report meets all the
requirements of the Mason County Resource Ordinance, Landslide Hazard Section, are complete and
true, that the reports demonstrates conclusively that the risks posed by the landslide hazard can be
mitigated through the included geotechnical design recommendations, and that all hazards are mitigated
in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp)
°F A
0'4' �EGISTS
�`S`SIONAL
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
TAHJA ENGINEERING, Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
Mason County DCD
Planning Division
PO Box 279
Shelton, WA 98584
Robert&Emilia Dunn
PO Box 514
Union, WA 98592-0514
(360) 898-5575
Re; Geotechnical Report Hazard Area
Reduction Request
150 E Madrona Beach Lane
Union, WA 98592
Parcel No.: 32232-54-00018
Mason County's geotechnical document review process will determine that the proposed Dunn
property improvements are located inside a Hazard Area's 50-foot vegetated buffers identified
on the geotechnical report's site plans.
Stability analysis of the property's slopes indicates that they are stable and the proposed
property improvements will be safe. A hazard area buffer reduction down to as little as 5-feet
back from the crest of the steep slope on the property is supported by the geotechnical report
prepared for the proposed property improvements. This reduction request results in as much as
a 45-foot development intrusion into the standard hazard area buffer.
On behalf of the Dunns, I request that a reduction in the Landslide Hazard Area buffer required
in Section 17.01.100 be reduced down to as little as a 5-foot setback.
lv AA
Sincerely,
w�
BOA GISTS w
Alan A. Tahja, P.E. �SSioNAL
File:C.IProjectslDunnWA Buller Reduction Rqst 1 of 1 6/28/2011
TAHJA ENGINEERING,Inc. 84—D
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
Mason County DCD
Planning Division
PO Box 279
Shelton, WA 98584
Robert&Emilia Dunn
PO Box 514
Union, WA 98592-0514
(360) 898-5575
Re; Geotechnical Report
150 E Madrona Beach Lane
Union, WA 98592
Parcel No.: 32232-54-00018
Mason Co. Case No.s;
INTRODUCTION
I was contacted in April 2011 by Mr. Robert Dunn who requested my investigation and
reporting of the above referenced property for the permitting of a carport-storage building.
The property is located in the Madrona Beach Community located on the south shore of
Hood Canal approximately 3/4 of a mile east of Union Washington. The property is described
as the Madrona Inc. Tr. 18 & T.L. and is identified as Mason County tax parcel number
42318-51-00120.
The site was visited in June of this year to collect topographic information needed to prepare
this report and develop drawings to assist in placing the structure in compliance with
regulatory requirements.
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 AutoCADTM 2006, a SoftreeTM Terrain 3-d contour modeling
program, GALENATM Slope Stability Analysis software and MicrosoftTM Office Word 2003.
The proposed structure location is near the crest of a natural steep bank that descends to a cut
bank excavated during the construction of Madrona Beach Lane in the 1950s. This hillside
begins with a modest slope(<40%)which descends to the top of the cut slope which stands
as tall as 10-feet at its tallest cut. The elevation difference between the top of the slope/cut is
approximately 20 feet. With slopes on or within 300 feet of the property exceeding 40%with
a height of 10 feet or more, Mason County requires a geotechnical report to be developed to
address stability issues relating to the property's development. 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(MCRO) Sections 17.01.100
through 17.01.104.
File:C:IProjects0unn1Geo-Rpt 1 of 7 6/28/201 1
TAHJA ENGINEERING,Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
1. SURFACE AND GEOLOGIC CONDITIONS:
The property fronts on Hood Canal on its north end and is bounded on its south boundary by
E Madrona Beach Lane. E Madrona Beach Lane bisects the Dunn property roughly near the
center of the property as shown on the attached site plans.This raises a question whether the
property is considered to have one front-yard setback dimension or three. The property has
already been developed with a single family residence, and a bulk head constructed along the
Hood Canal shoreline. The Mean High High Water(MHHW)is represented by the water
ward face of the existing concrete bulkhead(s). Most or all of the properties in the Madrona
Beach Tracts are bulk headed.
The property has been cleared in the past during development of the property with the
existing residence. The properties on the waterside of Madrona Beach Lane are rigorously
developed with residences and amenities. The area south of Madrona Beach Lane's route
along the waterfront is relatively natural. Mr. Dunn wishes to install a carport structure on the
southerly portion of his property generally in the location shown on the attached site plans.
The upslope geomorphology of the property may be described as hilly.No wetlands or
upland water bodies were found in the Dunn property vicinity. The southerly third of the
property where Mr. Dunn proposes to install the structure has scant vegetation, particularly in
the area surrounding the proposed structure location. The hillside between the proposed
structure location and the lower portion of E Madrona Beach Lane is vegetated,mainly with
low growing vegetation including salal, oregon grape, and scotch bloom. The few trees in
this area are all growing straight and vertical with no indication of instability.
Inspection of the Geologic Map of Shelton 1:100,000 Quadrangle, Washington', finds the
property located in an area between Hood Canal to the north,and an upland plateau at an
elevation of a couple hundred feet above the Hood Canal sea level elevation. A portion of the
Shelton Quadrangle map reveals the site soils are classified as Qa p,Alpine Glacial Deposits
described as follows:
Alpine outwash,pre—late Wisconsinan(Pleistocene)—Stratified
sand, gravel, and cobbles; in the Quinault basin, clasts consist of
sandstone and less-abundant basalt from the Olympic Mountains core
and peripheral rocks; in streams draining the southern and southeast-
ern Olympics,clasts consist primarily of Crescent Formation basalt
with less-abundant Olympic-core sandstone;may include peat, silt,
and clay, and may be capped by weathered loess;clasts are generally
more rounded than those in till and lack facets and striations; poorly
to moderately sorted; gray to subtle yellow with wispy orange weath-
ering.
As a portion of the Geologic Map of Shelton 1:100,000 Quadrangle on the following page
reveals, the Dunn property is located in the vicinity of several fault lines identified on the
following map as (1) the terminus of two faults emanating from the north and terminating
approximately 9 miles to the northwest of the Dunn property on the north side of Dow
'DNR OFR2003-15 Geologic Map of Shelton 1:100,000 Quadrangle,Washington
File:C.IProjectslDunnlGeo-Rpt 2 of 7 6/28/201 1
TAHJA ENGINEERING,Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
Mountain(2) a fault line runs southwest to northeast through Lake Cushman approximately
11 miles east and north of the Dunn site,and(3)a fault line which follows Hood Canal is
located approximately 4 miles east and north of the Dunn site. The presence of these features
does not represent an unusual hazard. Standard seismic analysis and designs are intended to
anticipate potential tectonic impacts.
Further inspection and soil analysis finds the soil to be classified under the Unified Soil
Classification System(USCS) as a GP-GC soil division. Probing of various locations
throughout the property and inspection of the road cut paralleling the Hood Canal shoreline
revealed a shallow surface horizon of soil generally 1 to 3 feet in depth or less resting atop of
a more densely compacted substrate layer. The substrate layer is composed of multiple layers
of various alpine outwash soils with enough silt and clay to give it a loosely cemented
character. The road cuts along E Madrona Beach Lane are vertical in some locations,
testifying to the stable and cemented character of the substrate soil layers.
Investigation of Washington's interactive geological mapping and Washington State's Dept.
of Ecology's Coastal Atlas found no areas in the Dunn property vicinity identified as
anything but stable.
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2. SITE PLAN WITH IMPORTANT DEVELOPMENT AND GEOLOGIC
FEATURES:
The residence is served with a community sewage system,so no septic drainfield is located
on the property. The attached site plans shows the location of the existing improvements
including an existing waterfront residence and a shoreline concrete bulkhead. Because of the
character of the loosely cemented alluvial soils,the steep slopes shown on the property are
very stable and do not represent a landslide hazard or threat to the Dunn property or
improvements. The proposed structure location shown on the attached site plans is safe in the
File: C Trojects0unnlGeo-Rpt 3 of 7 6/28/2011
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
site's current conditions and the proposed structure location. The available building area
shown on the attached site plan represents as little as a 110'+ separation between the MHHW
(bulkhead) and a conjectural building located just south of the recommended 5-ft geological
setback promoted by this report.
3. LOCATIONS OF LOGS OF EXPLORATORY HOLES OR PROBES:
Soil exploration was performed with a hand driven 4-foot steel rod,and by investigation of
the cut slopes created by construction of E Madrona Beach Lane. Penetration of the surface
soil horizon met moderate resistance,but the soil character turned to a hardpan character,
usually within 2 to 3 feet of the ground's surface. Soil probe locations and depths are
indicated on the attached site plan.
4. AREA OF PROPOSED DEVELOPMENT& BOUNDARIES OF HAZARDS,
BUFFERS,AND SETBACKS:
The near vertical cut bank north of the proposed structure location and an area surrounding
the road cuts is identified on the attached site plans as a hazard area due to its height
exceeding 10-feet and a slope exceeding 40%. A 50' hazard area boundary as well as a
recommended 5' building setback from the crest of the steep slope are shown on the attached
site plans. The conjectural structure location depicted on the site plans is shown 5-ft inside
the property's westerly boundary, and 15-ft north of the property's southerly boundary. The
entire structure is proposed inside the hazard area's 50-ft hazard area's buffer.Nearly all of
Dunn property is located inside the hazard area 50-ft buffer areas. Mason County allows
development on a hazard area or within its associated buffer provided stability issues can or
have been mitigated. Mitigation acceptable to the County is a geotechnical report supporting
the proposed property's development,which shows that the property can be developed safely
in terms of geologic stability. Current standard building setbacks(25' front&20' side-yard)
are shown on the attached site plans. A building setback variance down to 5-ft from the
property's westerly(side)boundary and 10' from the property's south(front)boundary are
being applied for. An Administrative Variance request has been prepared to seek these
building setback reductions. A hazard area buffer reduction request is also being prepared to
allow a structure foundation to be as close as 5-ft back from the crest of the descending slope
located immediately above the road cut banks.
5. CROSS SECTION WITH PROPOSED GRADE CHANGES:
A cross section view is provided in the attached plan sheets. The cross section used in the
stability analysis is slightly edited to represent a worse case scenario for the hillside above E
Madrona Beach Lane in the site's stability analysis model.
6. SLOPE STABILITY ANALYSIS:
The steep slopes on or near the Dunn' property in their present condition contain no obvious
recent mass landslides or stability problem indicators. Trees in the neighborhood are growing
vertically showing no signs of soil movement. The leveled building area in the northerly area
of the property is based on the moderately dense cemented alluvial soil materials and has no
discernable irregularities, settlements, fissures, or evidence of consolidation problems.
File:C.lProjectslDunnlGeo-Rpt 4 of 7 6/28/2011
TAHJA ENGINEERING, Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
The stability model is portrayed with two soil layers, a shallow(<3') surface layer of
weathered alluvial soil, and a deeper soil strata which is modeled as a weakly cemented
alluvial soil. Both soils are composed of generally the same soil components,but the surface
soil layer is modeled with a lower cohesion than ascribed to the substrate soil. Both soils are
modeled with saturated soil conditions(phreatic surface modeled above the ground's
surface). Groundwater at the site is assumed to coincide with the sea level elevations of Hood
Canal. Potable water is likely much deeper.
Unified Soil Classification System typing places the soils in a dual symbol category due to its
fines content falling above 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 soil characterized with the shallow soil layer having a soil unit weight of 120
lbs/ft3, the substrate soil is modeled as having a soil unit weight of 123 lbs/ft3. Both soil
layers are modeled with a phi angle of 34°. The shallow soil is modeled with a cohesion
value of 100 lbs/ft, and the till layer is modeled with a cohesion character of 200 lbs/ft2. A
phreatic surface is assumed above the ground's surface to mimic saturated surface soil
conditions.
The slope geometry and soil characteristics provide a minimum factor of safety for the site in
a static condition of 2.69 and a minimum dynamic factor of safety of 2.65. Both values
exceed the County's minimum safety requirements.
7. RECOMMENDED SETBACKS &DRAINAGE:
The slope stability analysis indicates that the slope present on the Dunn property is stable in
its present geometry and conditions and does not represent a landslide or geological hazard to
the proposed Dunn property improvements. A minimum 5-foot building setback from the
crest of the steep slope is recommended. A hazard area reduction request down to as little as
5-feet accompanies this report.
Drainage from the present site sheets to its natural drainage direction generally to the north
and eventually towards Hood Canal. The area between the proposed structure area and the
crest of the slope should be adequate to disperse and filter stormwater runoff from the
proposed development area,provided as much of this area as practical is maintained with a
vegetation covering. Delivery of concentrated stormwater flows to a slope is not allowed
under the requirements of the County's Resource Ordinance, so the Best Management
Practice(BMP) for this site is the dispersion of collected stormwater as close to its source as
possible. Installing splash blocks at the corners of the proposed structure and sloping the
ground away from the structure's foundation for a minimum of 5 feet should perform
acceptably.
Driveway and parking area runoff should be directed to the edges of the driveway and
parking areas for dispersion into grassed or vegetated areas of the property. The shallow soil
depth to the cemented alluvial soil layer precludes any effective retention of stormwater
runoff on the property itself.
File:C.1Projects0unMGeo-Rpt 5 of 7 6/28/2011
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
8. CLEARING, GRADING, AND VEGETATION MANAGEMENT:
General site grading and preparation for proposed improvements on the property has already
been accomplished, and little, if any, additional clearing or grading will be necessary to
proceed with the proposed development. No formal vegetation plan appears needed for the
proposed property development.No structural fills are anticipated for the proposed
development.
9. EROSION AND SEDIMENT CONTROL:
Inspection of the Soil Survey of Mason County found the site to be located in an area with
Alderwood(Gravelly Sandy Loam(GSL) A,&Ad) soil type(s),which are identified in the
County's Critical Resource Ordinance as susceptible to severe erosion when disturbed. A
formal site specific Erosion and Sediment Control(ESC Plan)accompanies this report.
Nearly all stormwater runoff will exit the Dunn property over the north end of the property.
Runoff from the proposed property improvements will have little if any impact on the hillside
or the properties located between the development location and Hood Canal. The proposed
improvements will not alter the existing stormwater runoff regime since the proposed
development area is already maintained as a graveled parking area and driveway. Access to
the site already exists off of E Madrona Beach Lane (a private development road)and is
stable in its present condition.
10. ON-SITE AND OFF-SITE IMPACTS:
The completed improvements to the Dunn property will not result in any adverse on-site or
off-site impacts.
11. SPECIFICATIONS OF FINAL DEVELOPMENT:
No specific requirements appear needed for the property's proposed improvements,provided
the structure's location does not intrude into the building department property ine setbacks or
the 5-ft hazard setback recommended in this report. Structure foundations should be founded
on the more compacted soil layer underlying the site. A formal vegetation management plan
does not appear warranted for the proposed site's development.
12. RECOMMENDATIONS FOR THE PREPARATION OF STRUCTURAL
MITIGATION OR DETAILS OF OTHER PROPOSED MITIGATION:
Modeling of the northerly descending slope indicates that the location of the existing and
proposed property improvements are or will be safe. No structural measures or mitigation
measures appear needed.
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.
File:C.Trojeds1DunMGeo-Rpt 6 of 7 6/28/201 1
TAHJA ENGINEERING, Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
Summary&Conclusions:
The Dunn property does not contain any jeopardizing landslide hazard features,nor is it
within a distance from any identified hazards which would raise a concern. No adverse
impacts are anticipated from development completion.
Please feel free to contact me if there are any questions or concerns regarding this report or
my findings.
A�
Sincerely, Alan A. Tahja, P.E. �784
w
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Attached: Geotechnical Report Checklist
IONAL St�C3ti�
Hazard Area Reduction Request
2 Plan Views& 1 Cross Section View
GALENATM Stability Analysis Printout
Erosion and Sediment Control(ESC) Plan
File:C:IProjects Dunn IGeo-Rpt 7 of 7 6/28/2011
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Rev# Description Date TAHJA ENGINEERING,INC. CROSS SECTION A—A p4 m
Alan Tabja,P.E. Robert&Emilia Dunn Dunn
PO Box 235 150 E Madrona Beach Lane $„
Hoodsport, WA 98548 Union, WA 98592-0514 3 of3
Mason Co.Prcl No.: 32232-54-00018 (360)877-9512 (360) 898-5575
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Dunn X-Section A-A Static Stability Analysis
GALENA v--5.02
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Analysis: 1
Multiple Stability Analysis
Method: Bishop Simplified
-20 Surface: Circular
Results
-40 Critical(minimum)
Factor of Safety: 2.69
0 s0 100 150 200 250
Edf d:28 Jun 2011 Pnf sud:28 Jun 2011
Protect: Dunn-Madrona Beach Stability Analysis
Static
8& C:\Documents and Settings\OwnerlMy Documents\Galena Files\Models\Dunn Analysis t.gmf Tahja Engineering,Inc.
Galena 5.02 Analysis Results Licensee: Tahja Engineering, Inc.
DATA: Analysis 1 - Static
Material Properties (2 materials) -------------------
Material: 1 (Mohr-Coulomb Isotropic) - Weathered Surface Soil Layer
Cohesion Phi UnitWeight Ru
100.00 34 .0 120.00 1.10
Material: 2 (Mohr-Coulomb Cu increases with depth) - Cemented Alluvial Substrate
Cohesion Phi PI UnitWeight Ru
123.00 34.0 0 123.00 1.10
Water Properties ----------------
Unit weight of water: 12.00 Unit weight of water/medium above ground: 62.40
Material Profiles (2 profiles) -----------------
Profile: 1 (2 points) Material beneath: 1 - Weathered Surface Soil Layer
0.00 80.00 250.00 80.00
Profile: 2 (10 points) Material beneath: 2 - Cemented Alluvial Substrate
0.00 43.00 57.10 41.00 85.40 37.00
120.00 33.00 125.40 17.00
129.00 15.00 164.30 12.00 192.40 11.00
194 .00 6.00 225.70 3.00
Slope Surface (10 points) -------------
0.00 46.00 57.10 44.00 85.40 40.00
121.00 36.00 125.40 20.00
129. 60 16.00 164.30 14.00 192.40 14.00
197.00 8.00 225.70 4.00
File:C:• ProjectsOunnl X-Sec A-A Analysis Printout I of 4 6/28/201 1
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Phreatic Surface (2 points) ------ 0.00 85.00 250.00 85.00
Failure Surface ---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 100.00 YL: 38.36 XR: 130.00 YR: 15. 98
Centre: XC: 121. 92 YC: 36.44 Radius: R: 22.00
External Forces (1 force) ---------------
Force Force X-Pos'n Angle
1 2000.0 115.00 270.0
Variable Restraints -------------------
Parameter descriptor: XL XR R
Range of variation: 40.00 17.00 25.00
Trial positions within range: 12 12 12
-------------------------------------------------------------------------------------
RESULTS: Analysis 1 - Static
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: 12.03
There were: 881 successful analyses from a total of 1729 trial circles
848 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 2. 69
Circle and Results Summary (Lowest 14 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 126.06 28.80 120.00 36.11 126.14 19.30
9.50 2. 689
2 128.64 28.11 120.00 36.11 129.23 16.35
11.77 3.491
3 127.85 27.34 120.00 36.11 130.77 15. 93
11.77 3.512
4 129. 69 29.43 120.00 36.11 127.68 17.83
11.77 3. 946
5 125.77 29.44 116.36 36.52 127. 68 17.83
11.77 4 .047
6 130.25 30.33 120.00 36.11 126.14 19.30
11.77 4.282
7 128.39 31.65 120.00 36.11 124 .59 22. 94
9.50 4 .413
8 123.55 27. 98 112.73 36. 93 130.77 15. 93
14 .05 5.094
9 127.86 28.45 116.36 36.52 133.86 15.75
14.05 5.286
10 128.71 29.83 116.36 36.52 130.77 15. 93
14 .05 5.384
11 122. 61 30.53 112.73 36. 93 126.14 19.30
11.77 5.400
12 128.44 29.34 116.36 36.52 132.32 15.84
14 .05 5.421
13 126.79 31.05 116.36 36.52 126.14 19.30
11.77 5.475
14 124 .75 29. 67 112.73 36. 93 129.23 16.35
14.05 5.555
File: C:IProjectslDunnl X-Sec A-A Analysis Printout 2 of 4 6/28/2011
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Dunn X-Section A-A Dynamic Stability Analysis
GALENA V-502
120
o�
100
80
60 0 'A
moo
4 9j�
ti
20
:iooa Canal
Analysis: 1
Multiple Stability Analysis
Method: Bishop Simplified
-20 Surface: Circular
Results
-40 Critical(minimum)
Factor of Safely: 2.65
0 s0 100 150 200 250
EQrW 28JW2D11 P.oessee1 213 Ju 2011
Protect: Dunn-Madrona Beach Stability Analysis
Dynamic
E$l:: C:Cocuments and Settings\Owner\My Documents\Galena FilesUAodels\Dunn Analysis 1.gmf Tahja Engineering,Inc.
Galena 5.02 Analysis Results Licensee: Tahja Engineering, Inc.
DATA: Analysis 1 - Dynamic
Material Properties (2 materials) -------------------
Material: 1 (Mohr-Coulomb Isotropic) - Weathered Surface Soil Layer
Cohesion Phi UnitWeight Ru
100.00 34 .0 120.00 1.10
Material: 2 (Mohr-Coulomb Cu increases with depth) - Cemented Alluvial Substrate
Cohesion Phi PI UnitWeight Ru
123.00 34 .0 0 123.00 1.10
Water Properties ----------------
Unit weight of water: 12.00 Unit weight of water/medium above ground: 62.40
Material Profiles (2 profiles) -----------------
Profile: 1 (2 points) Material beneath: 1 - Weathered Surface Soil Layer
0.00 80.00 250.00 80.00
Profile: 2 (10 points) Material beneath: 2 - Cemented Alluvial Substrate
0.00 43.00 57. 10 41.00 85.40 37.00
120.00 33.00 125.40 17.00
129.00 15.00 164 .30 12.00 192.40 11.00
194 .00 6.00 225.70 3.00
Slope Surface (10 points) -------------
0.00 46.00 57.10 44.00 85.40 40.00
121.00 36.00 125.40 20.00
129. 60 16.00 164.30 14.00 192.40 14.00
197.00 8.00 225.70 4.00
File: C:IProjectsDDunnl X-Sec A-A Analysis Printout 3 of 4 6/28/2011
TAHJA ENGINEERING, Inc.
PO Box 235,Hoodsport, WA 98548
(360) 877-9512
Phreatic Surface (2 points) ------ 0.00 85.00 250.00 85.00
Failure Surface ---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 100.00 YL: 38.36 XR: 130.00 YR: 15.98
Centre: XC: 121.92 YC: 36.44 Radius: R: 22.00
Earthquake Force ----------------
Pseudo-static earthquake (seismic) coefficient: 0.150
External Forces (1 force) ---------------
Force Force X-Pos'n Angle
1 2000.0 115.00 270.0
Variable Restraints -------------------
Parameter descriptor: XL XR R
Range of variation: 40.00 17.00 25.00
Trial positions within range: 12 12 12
-------------------------------------------------------------------------------------
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: 8.86
There were: 881 successful analyses from a total of 1729 trial circles
848 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 2.65 71
Circle and Results Summary (Lowest 14 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 126.06 28.80 120.00 36.11 126. 14 19.30
9.50 2.645
2 128.64 28.11 120.00 36.11 129.23 16.35
11.77 3.390
3 127.85 27.34 120.00 36. 11 130.77 15.93
11.77 3.420
4 129.69 29.43 120.00 36.11 127.68 17.83
11.77 3.823
5 125.77 29.44 116.36 36.52 127. 68 17.83
11.77 3.876
6 130.25 30.33 120.00 36.11 126.14 19.30
11.77 4.140
7 128.39 31.65 120.00 36.11 124.59 22.94
9.50 4.272
8 123.55 27.98 112.73 36.93 130.77 15.93
14.05 4.789
9 127.86 28.45 116.36 36.52 133.86 15.75
14.05 4.990
10 122.61 30.53 112.73 36.93 126.14 19.30
11.77 5.026
11 128.71 29.83 116.36 36.52 130.77 15.93
14 .05 5.063
12 128.44 29.34 116.36 36.52 132.32 15.84
14 .05 5.107
13 126.79 31.05 116.36 36.52 126.14 19.30
11.77 5.129
14 124.75 29.67 112.73 36.93 129.23 16.35
14 .05 5.130
File:C.IProjectslDunnl X-SecA-A Analysis Printout 4 of 4 6/28/2011
HOOD
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HAZARD ARE (ha) 1 a
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6.67' �O y
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0
Stabilized Construction Entrance
Silt Fence Installation(BMP C223) e
T BMP C105 �\ Pjwer t' °
� Location-Install&maintain until
�' of eAsx Vole until disturbed construction area has
become permanently stabilized with
vegetation,compacted gravel,or a
sA' pavement surface.
e,
Off' �ECISTEgF'20784 � '� 2�
�SSIONAL E��l mat°� / °-e
SCALE: I"=30'
0 10 20 10 / \\
GE0610//
Mason County Review Checklist
for a Geotechnical Report
• Instructions:
This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report is reviewed
for completeness with respect to the Resource Ordinance. If an item is found to be not applicable, the Report should
explain the basis for the conclusion. The Report is also reviewed for clarity and consistency. If the drawings,
discussion, or recommendations are not understandable, they should be clarified. If they do not appear internally
consistent or consistent with the application or observations on site, this needs to be corrected or explained'. If
resolution is not achieved with the author, staff should refer the case to the Planning Manager or Director.
Applicant's Name: 71)4nn
Permit#: l7esl -, Parcel : ' aO/g
Date(s) of the Document(s) reviewed:
1. (a) A discu Oon of general geologic conditions in the vicinity of the proposed development,
OK? Comment:
(b) A discussion of specific soil types
OK? '.-- Comment:
(c) A discussipof ground water conditions
OK? Comment:
(d) A discus of the upslope geomorphology
OK? Comment:
(e) A discussion of the location of upland waterbodies and wetlands
OK? t"', Comment:
(f) A discussion f history of landslide activity in the vicinity, as available in the referenced maps and records
OK? Comment:
2. A site plan that identifies the important development and geologic features.
OK? Comment:
3. Locations and logs of exploratory holes or probes.
OK? Comment:
4. The area of the proposed development, the boundaries of the hazard, and associated buffers and setbacks shall
be delineated (top, both sides, and toe) on a geologic map of the site.
OK? Comment:
5. A minimum of one cross section at a scale which adequately depicts the subsurface profile, and which
incorporates the details of proposed grade changes.
OK? Comment.
6. A description and results of slope stability analyses performed for both static and seismic loading conditions.
Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of
Circles. The minimum static safety factor is 1.5, the minimum seismic safety factor is 1.1 and the quasi-static
analysis coeffients should be a value of 0.15.
OK? Comment:
7. (a) Appropriate restrictions on placement of drainage features
OK? ��Comment:
(b) Appropriate restrictions on placement of septic drain fields
OK? ✓ Comment:
(c) Appropriate r rictions on placement of compacted fills and footings.
OK? Comment:
Page 1 of 2 Form Effective June 2008
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK? '--- Comment:
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes.
OK? ✓ Comment: •
8. Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies
vegetation to be removed, a schedule for vegetation removal and replanting, and the method of vegetation
removal.
OK? ` Comment:
9. Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific
mitigating measures to be implemented during construction to protect the slope from erosion, landslides and
harmful construction methods.
OK? ✓ Comment:
10. An analysis of both on-site and off-site impacts of the proposed"ee\ nt.
OK? Comment:
11. Specifications of final development conditions such as, vegetative management, drainage, erosion control, and
buffer widths.
OK? ✓Comment:
12. Recommendations for the preparation of structural mitigation or details of other proposed mitigagon.
OK? ✓Comment:
13. A site map drawn to scale showing the property boundaries, scale, north arrow, and the location And nature of
existing and proposed development on the site.
OK? ✓ Comment:
Are the Documents signed and stamped?� By whom?
License#: 30727 License type:
FIRST REVIEW pproved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by / on 7 �y Time spent in review: Z •-�
SECOND REVIEW/UPDATE ❑ Approved ❑ Need more info.
Reviewed by , on . Time spent in second review:
THIRD REVIEW/ UPDATE ❑ Approved ❑ Need more info.
Reviewed by , on . Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
Page 2 of 2 Form Effective June 2008