HomeMy WebLinkAboutGEO2009-00005 Shared Bulkhead - GEO General - 2/5/2009 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
(360)427-9670
Geotechnical ReportReview Acceptance Letter
February 05, 2009
STEVE LATHAM
5648 179TH AVE SE
BELLEVUE WA 98006
Case No.: GE02009-00005
Parcel No.: 422055200951
Proiect Description: BULKHEAD (SHARED WITH NEIGHBOR)
The Geotechnical Report for STEVE LATHAM has been received and reviewed by the Planning
Department. The report was prepared by Alan Tahja, Tahja Engineering, Inc. dated 1/30/2009.
Based on the certification provided by the licensed engineer/geologist, the referenced
Geotechnical Report was prepared in general accordance with the requirements in the Mason
County Resource Ordinance, Landslide Hazard Areas 17.01 .100.E.5. Mason County considers
the review valid until such time as scope of project, site conditions, and/or regulations change.
Should the scope of work, site conditions, and/or regulations change after the original review, then
an addendum from the original author of the report may be required to address these changes.
The report would only be re-reviewed if a permit for development were submitted after these
changes occur. Mason County does not certify the quality of the work done in this Geotechnical
Report.
Please contact me at (360) 427-9670, ext. 295 if you have questions.
Sincerely,
Tammi Wright
Land Use Planner
Mason County Planning Department
Comments:
2/5/2009 Page 1 of 1 GE02009-00005
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Mason County DCD
Planning Division
PO Box 279
Shelton, WA 98584
Tracy DeLeo & Charles Smith
61 N Gull PI
Hoodsport, WA 98584
(360) 877-9915
Stephen& Amy Latham
60 N Gull PI
Hoodsport, WA 98548
5648 1791h Ave. SE
Bellevue, WA 98006-5931
Re, Geotechnical Report
60 N Gull PI &
61 N Gull Place, Hoodsport, WA 98548
Parcel No.s: 42205-52-00051 & 00951
Mason County's geotechnical document review process will determine that the proposed
Smith-DeLeo/Latham Lake Cushman Erosion Protection Wall Project construction will result
in development inside a Landslide Hazard Area or inside the required 50-foot Vegetated
Hazard Area Buffer required under Resource Ordinance 17.01.100.
The purpose of the project is to provide stability to the lake shoreline located between the lake
and existing residences.
On behalf of the Smith-DeLeos and Latham families, I request that the proposed shoreline
stabilization wall be allowed to be sighted on the landslide hazard area and inside the hazard
area's buffer as promoted in my site plans and geotechnical report dated 1/30/09.
Sincerely, A
WA
Alan A. Tahja, P.E.
w�
�0 RE 8TER��
�SSIONAL E��1�
File: C:IProjectslSmith-DeLeo/Latham WA Buffer Reduction Rgst 1 of 1 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Mason County DCD
Planning Division
PO Box 279
Shelton, WA 98584
Tracy DeLeo & Charles Smith
61 N Gull P1
Hoodsport, WA 98584
(360) 877-9915
Stephen & Amy Latham
60 N Gull P1
Hoodsport, WA 98548
5648 179th Ave. SE
Bellevue, WA 98006-5931
Re; Geotechnical Report
60 N Gull PI &
61 N Gull Place, Hoodsport, WA 98548
Parcel No.s: 42205-52-00051 & 00951
Mason Co. Case No.s:
INTRODUCTION
I was contacted in late 2008 by Mr. Charles Smith and Tracy DeLeo who requested my
investigation and documentation of slope stability and landslide hazard issues relating to the
permitting and development of their property located at Lake Cushman Development Division
19, Hoodsport, Washington. Mr. Smith and his neighbors, Steve and Amy Latham wish to install
an erosion control retaining wall along the Ordinary High Water(OHW) elevation of Lake
Cushman. Both the Smith-DeLeo and Latham properties have been developed in the past with
single family residences and appurtenant structures, including garages and a stairway and dock
on the Smith-DeLeo property.
The site was visited in October and December of 2008 and in January 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. Property improvements are
located generally on the level portions of the properties, with the hillside descending down to the
lake being vegetated with natural vegetation and fairly young second growth Douglas Firs,
Hemlock, Maple and Alder trees with an understory of Huckleberry, Salal, and Oregon Grape
vegetation.
File: C:I Projects lSmith-DeLeo-LathamlGeo-Rpt 1 of 7 1/30/2009
TAHJA ENGINEERING, Inc.
PO Boa 235, Hoodsport, WA 98548
(360) 877-9512
The westerly boundaries of the two properties is defined by the Lake Cushman shoreline/Marine
Bluff which averages between 90 and 120% between the lake elevation and the developed
residential areas, over an elevation difference of roughly 30 feet. The slope immediately adjacent
to the lake OHW elevation rises at slopes between 230% and vertical over an elevation
difference of approximately 18-feet.
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 west of the Smith-DeLeo and Latham properties categorizes
the properties as being within Landslide Hazard Areas defined in Mason County's Critical
Resource Ordinance, requiring 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 approximately 5 miles west of Hoodsport Washington in the area identified on
the Geologic Map of Shelton 1:100,000 Quadrangle, Washington' on the following page. The
map reveals that the soils surrounding the subject properties are glacial deposits classified as
Continental Glacial (Qgo) soils. The soils are further described as follows:
CONTINENTAL GLACIAL DEPOSIT'S
Fraser (Aatiation, Vashon Stade
Pro<,.4acial and recessional ourivash, late 'Visconsinan (I'Ieisto-
g° cene)—Typically poorly to moderately sorted, rounded gravel and
sand with localized coarser- and finer-grained constituents; lithologi-
cally varied mixture of mostly northern-provenance clasts, especially
containing granitic and metamorphic rocks that identify the unit as
being deposited by the Puget lobe of the Cordilleran glacier; also con-
tains varying amounts of locally derived Crescent Formation basalt,
and in the hlox Chehalis Creek valley, central Cascade Range—
derived andesitic clasts; typically shades of gray where fresh or
brown where stained especially in proglacial and morainal aras- buff
staining near the ground surface; fine sand, silt, and clay constitute
local overbank sediments having relatively poor permeability or del-
taic foreset bedding along north sides of valleys with higher permea-
bility; porous and permeable enough to yield small to moderate quan-
tities of groundwater; very poorly consolidated to loose; moderately
to well-rounded clasts; mostly unweathered ix�-ith rare weathered
reworked clasts; thickness varies and Ls not well known; most com-
monly occupies outwash channels scoured into or through till_
DNR OFR2003-15 Geologic Map of Shelton 1:100,000 Quadrangle, Washington
File: C:IProjectslSmith-DeLeo-LathamlGeo-Rpt 2 of 7 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
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As the portion of the Geologic Map of Shelton 1:100,000 Quadrangle reveals, the Smith-
DeLeo/Latham properties are located in the vicinity of at least three fault lines identified on the
map as (1) a fault line which follows Hood Canal is located approximately 4 miles east of the
project sites, (2) two fault lines intersect north of Dow Mountain approximately 3-1/2 miles
northeast of the project area, and (3) a fault line courses through Lake Cushman from southwest
to northeast through Lake Cushman approximately 3-1/2 miles northwest of the project site. The
presence of these features does not represent a hazard, and standard seismic analysis of the site is
intended to anticipate potential tectonic impacts.
Inspection of the Washington Coastal Atlas and other related landslide hazard mapping found
little information for the project area. The predominantly glacial till and basalt rock substrate
underlying the Lake Cushman area provide a very stable condition in gently sloping areas. The
steep slopes surrounding Lake Cushman may be considered of intermediate stability, susceptible
to erosion and dis-lodging of the shallow surface soils developed on the steep Olympic Mountain
foothillsides. The area immediately surrounding the subject properties has displayed no large
scale instability.
2. SITE PLAN WITH IMPORTANT DEVELOPMENT AND GEOLOGIC FEATURES:
A site plan showing the general topography of the area surrounding the Smith-DeLeo / Latham
property is attached as an appendix. Utilities (water, phone & electricity) are delivered to the
sites from the North Gull Place Cul-de-Sac right of way. Both sites already have existing septic
systems approved at the time of their construction/installation and exhibit no discernable
File: C:IProjectslSmith-DeLeo-LathamlGeo-Rpt 3 of 7 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
problems. No upland water bodies or wetlands other than Lake Cushman were found in the
Smith-DeLeo/ Latham property vicinity. The groundwater elevation was modeled as coinciding
with the Lake Cushman water surface elevation.
3. LOCATIONS OF LOGS OF EXPLORATORY HOLES OR PROBES:
Various areas of the subject properties were inspected by different methods. The steep lake
shoreline bluff provides an easily accessible view of the glacial till substrate materials underlying
the project areas. Additional soil probing along the top of the steep bank and the upland areas of
the properties exhibited a 6 to 30-inch deep layer of weathered till soils overlying a strongly
cemented glacial till substrate.
Modeling of the site employed a moderately cemented weathered till soil layer overlying a
stronger cemented till layer beneath the surface soil layer. The site soils were 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 steep slope bordering the westerly property boundaries 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.
The existing residential structures are located within the 50-foot vegetated buffer required under
Mason County's Critical Resource Ordinance. The currently proposed activities are located
either at the top or toe of the steep shoreline slope. The proposed shoreline erosion control
retaining wall and concrete tie-back deadmen will be sited in the hazard area or inside the 50-
foot vegetated buffer area(s). A request for a reduction of the hazard area buffer to zero-feet will
be prepared for the proposed site improvements.
5. CROSS SECTION WITH PROPOSED GRADE CHANGES:
A cross section view of each of the subject properties is provided in the attached plan sheets as
well as a part of the GALENA Stability Analysis Print-Out. Minor grade changes in the form of
retaining wall backfill and landscape sloping above the retaining walls will be performed.
6. SLOPE STABILITY ANALYSIS:
The steep slope(s) to the west of the Smith-DeLeo / Latham properties displays minor sloughing
of the shallow vegetated soil layer off of the cemented glacial till layer underlying the two
properties. The trees on the steep hillside were found to be growing reasonably straight with no
indications of trunk curvature typically associated with mass landslide movements.
File:C:IProjectslSmith-DeLeo-tathamlGeo-Rpt 4 of 7 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
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 weights of 130 and 131 lbs/ft3, a phi
angle of 38°, and a cohesion character of 200 lbs/ftz for the moderately cemented soils and 500
lbs/ft2 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 1.9 and 1.5 for the Smith-DeLeo site in a static & dynamic
analysis and Factors of Safety of 1.5 and 1.3 for the Latham site in a static condition & dynamic
analysis.
7. RECOMMENDED SETBACKS & DRAINAGE:
Slope stability analysis indicates that the westerly descending slope west of the Smith-DeLeo /
Latham properties is stable in its present geometry and condition and does not represent a
landslide or geological hazard to the existing residential improvements on the subject properties.
Drainage from the present site is generally dispersed and migrates towards the west, 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 proposed shoreline retaining wall is clear of vegetation, requiring no removal
of vegetation for the proposed construction. The contractor and owner have indicated their
intention of hand digging the pile footings planned for the retaining wall. This construction
method will minimize impacts to the existing vegetation on the sites.
Vegetation should be encouraged to grow on the completed slope above the proposed retaining
wall(s). The existing bare slope above the retaining wall location should receive a cover of
geosynthetic filter fabric to keep the natural hillside soils in place and allow the seeping of
groundwater through the gravel backfill mater that will be installed between the completed
retaining wall and the existing hillside slope.
9. EROSION AND SEDIMENT CONTROL:
File:C:WrojectslSmith-DeLeo-Latham lGeo-Rpt 5 of 7 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Inspection of the Soil Survey of Mason County found the site to be located in an area with a
Hoodsport Gravelly Sandy Loam (He) soil type, which is not identified in the County's Critical
Resource Ordinance as a severe erosion hazard, and does not require the development of a site
specific Erosion and Sediment (E&S) Control Plan. The proposed hand digging of the retaining
wall pile footings will minimize the disturbance of the soils in the construction area.
The work is proposed to be accomplished during the lake's low level period in the late Winter
and early Spring before Tacoma City Light raises the lake's water surface elevation for
summertime recreational purposes.
The project properties already have existing stable vehicle accesses off of N Gull Place Court
and already have all weather erosion resistant driving and parking surfaces.
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 west of the existing
building areas 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 existing improvements are safe. The proposed retaining wall/erosion control wall(s) is
proposed to reduce the continual erosion of the lake shoreline resulting from the seasonal raising
and lowering of the lake and the impact of wind and watercraft waves which attack the lake
shoreline upper elevation during the Summer season.
The retaining walls have been designed to provide against toe kick-out, overturning, and
excessive deformation the backfilled wall could develop. The footings for the proposed retaining
wall wide flanged piles are specified to be a minimum of 6-feet deep which will be almost
entirely located within the glacial till hardpan soil layer located at the toe of the existing steep
shoreline slope.
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:
File: C:TrojectslSmith-DeLeo-LathamlGeo-Rpt 6 of 7 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
The Smith-DeLeo /Latham properties, 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 the
Smiths and Lathams are proposing should not result in any adverse impacts to either their or their
neighbors' properties.
Please feel free to contact me if there are any questions or concerns regarding this report or my
findings.
Sincerely,
y� A
Alan A. Tahja, P.E.
Attached: Plan Views & Cross Section Sheet
GALENATM Stability Analysis Printouts (2) ��'yC,�EGIsTER�O
SSIONAL ECG
File: C:IProjectslSmith-DeLeo-LathamlGeo-Rpt 7 of 7 1/30/2009
Rev# DMripdon Date TAHJA ENGINEERING,INC. SITE PLAN
Alan Tahja,P.E. Smith-DeLoo/Latham Smith,C
PO Box 235 60&61 N Gull Place s„
Hoodsport, WA 98548 Hoodsp A WA 98548 1 of 6
Mason Co.pmj No.s: 42205-52-ow51&00951 (360)877-9512 (360)877-9915
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Alan Tahja,P.E. Smith-DeLeo/Latham Smith, C
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PO Box 235 60&61 N Gull Place
Hoodsport, WA 98548 Hoodspo4 WA 98548 5 of 6
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Smith-DeLeo X-Section A-A Static Stability Analysis
GALENA vo ,,am
Cemented Glacial Till
860 Weather Surface Soils
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780 wcaawK Tina layer
aj784
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_-- Analysis: 1
700 Multiple Stability Analysis
Method: Bishop Simplified
Surface: Circular
680
Results
Critical(minimum)
660 Factor of Safety 1.85
0 50 100 150 200 250 300
Edbd 29 Jn 2DOR Prod 2e Jon AOa
Project Smith-DeLeo Stability Model
Static
File: C:1Documents and Settings\OwnerWy DocumentslProjects%Smith ChatfesZmith StalwlityGStatc t.pmf 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) - Cemented Glacial Till
Cohesion Phi UnitWeight Ru
500.00 38.0 131.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Weather Surface Soils
Cohesion Phi UnitWeight Ru
200.00 38.0 130.00 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 (10 points) Material beneath: 1 - Cemented Glacial Till
0.00 699.00 37.10 719.00 66.50 735.00
67.90 735.50 69.20 737.50
76.80 753.50 81.30 755.50 103.80 757.50
112. 10 775.50 295.40 777.50
Profile: 2 (2 points) Material beneath: 2 - Weather Surface Soils
0.00 820.00 300.00 820.00
Slope Surface (10 points)
File:C:IProjectslSmith-DeLeo X-Sec A..A-Analysis Printout I of 4 1/30/2009
0
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
-------------
0.00 700.00 37.10 720.00 66.50 736.00
67.90 738.00 69.20 740.00
76.80 756.00 81.30 758.00 103.80 760.00
112.10 778.00 286.40 780.00
Phreatic Surface (2 points)----------- 0.00 738.00 300.00 738.00
Failure Surface
---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 50.00 YL: 727.02 XR: 125.00 YR: 778.15
Centre: XC: 75.68 YC: 769.92 Radius: R: 50.00
Variable Restraints
-------------------
Parameter descriptor: XL XR R
Range of variation: 70.00 70.00 45.00
Trial positions within range: 10 10 10
-------------------------------------------------------------------------------------
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: 2.40
There were: 512 successful analyses from a total of 1001 trial circles
489 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.85
Circle and Results Summary (Lowest 12 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 50.46 774.37 61.67 733.37 90.00 758.77
42.50 1.848
2 46.78 778.48 61.67 733.37 90.00 758.77
47.50 1.859
3 43.17 782.50 61.67 733.37 90.00 758.77
52.50 1.877
4 54 .26 770.13 61. 67 733.37 90.00 758.77
37.50 1.891
5 39.61 786.47 61.67 733.37 90.00 758.77
57.50 1.896
6 58.24 765.69 61.67 733.37 90.00 758.77
32.50 1. 910
7 36.09 790.40 61.67 733.37 90.00 758.77
62.50 1.915
8 32.60 794.29 61.67 733.37 90.00 758.77
67.50 1.936
9 50.00 792.23 38.33 720.67 121.11 778.10
72.50 1.945
10 51.18 797.23 46. 11 724.90 121.11 778. 10
72.50 1.960
11 62.58 760.85 61.67 733.37 . 90.00 758.77
27.50 1. 967
12 49.11 786.56 30.56 716.47 121.11 778.10
72.50 1.969
File:C.-Wrojectsl Smith-DeLeo X-Sec A-A Analysis Printout 2 of 4 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Smith-DeLeo X-Section A-A Static Stability Analysis
GALENA v-s.01
Cemented Glacial T,9
660 "Affter Sudboe soft
840 4 1=
620
600
Ham L-w
780 W-ha Till Soil Uya
i•
760
S i cemeeedGlaei&lTiu
Duck,Location 4
740 Phmaoc Swf High Lk,Leal
�
== Analysis: 1
700 ----- Multiple Stability Analysis
Method: Bishop Simplified
Surface: Circular
6110
Results
660 Critical(minimum)
Factor of Safety: 1.49
0 50 11 150 200 250 300
Eden:XJM ZW Moo.aee:Y.in WN
Proiect Smith-DeLeo Stability Model
Dynamic
Eft CADocuments and Settings%OwneAMy Doaunentslprojects%SffM Charles\Smith Stabifity%Static t.gmi 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) - Cemented Glacial Till
Cohesion Phi UnitWeight Ru
500.00 38.0 131.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Weather Surface Soils
Cohesion Phi UnitWeight Ru
200.00 38.0 130.00 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 (10 points) Material beneath: 1 - Cemented Glacial Till
0.00 699.00 37.10 719.00 66.50 735.00
67. 90 735.50 69.20 737.50
76.80 753.50 81.30 755.50 103.80 757.50
112. 10 775.50 295.40 777.50
Profile: 2 (2 points) Material beneath: 2 - Weather Surface Soils
0.00 820.00 300.00 820.00
Slope Surface (10 points)
File:C.IProjectslSmith-DeLeo X-Sec A-A Analysis Printout 3 of 4 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
-------------
0.00 700.00 37.10 720.00 66.50 736.00
67.90 738.00 69.20 740.00
76.80 756.00 81.30 758.00 103.80 760.00
112.10 778.00 286.40 780.00
Phreatic Surface (2 points)---------- 0.00 738.00 300.00 738.00
Failure Surface
---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 50.00 YL: 727.02 XR: 125.00 YR: 778.15
Centre: XC: 75.68 YC: 769.92 Radius: R: 50.00
Earthquake Force
----------------
Pseudo-static earthquake (seismic) coefficient: 0.150
Variable Restraints
-------------------
Parameter descriptor: XL XR R
Range of variation: 70.00 70.00 45.00
Trial positions within range: 10 10 10
-------------------------------------------------------------------------------------
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: 1.89
There were: 512 successful analyses from a total of 1001 trial circles
489 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.49
Circle and Results Summary (Lowest 11 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 50.00 792.23 38.33 720.67 121.11 778.10
72.50 1.489
2 49.11 786.56 30.56 716.47 121.11 778.10
72.50 1.492
3 57.46 790.60 38.33 720. 67 128.89 778. 19
72.50 1.511
4 54.11 786.30 38.33 720. 67 121.11 778.10
67 .50 1.517
5 51.18 797.23 46.11 724.90 121.11 778.10
72.50 1.517
6 58.69 796.30 46. 11 724.90 128.89 778. 19
72.50 1.517
7 55.02 791.81 46.11 724.90 121.11 778.10
67.50 1.529
8 50.46 774.37 61.67 733.37 90.00 758.77
42.50 1.529
9 48.64 780.01 22.78 712.28 121.11 778. 10
72.50 1.533
10 40.97 782.46 22.78 712.28 113.33 778.01
72.50 1.536
11 46.78 778.48 61.67 733.37 90.00 758.77
47.50 1 .536
File:C:IProjectslSmith-DeLeo X-Sec A-A Analysis Printout 4 of 4 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Latham X-Section A-A Static Stability Analysis
GALENA v. 5c,
Cemented Glacial Tip
820
Weathered Syrface Till Soil
A.
y� FWA
Eu It—L 1,1 I
780
w-lkdea S760
ur snit
Ce d Glacut rill 784 �CV,
�EGI STF, '
�SSIDNAL
Lk CYdimiin 738 EL Ph—tie Swf—
740
720
Analysis: 1
Multiple Stability Analysis
Method: Bishop Simplified
700 Surface: Circular
Results
Critical(minimum)
680 Factor of Safety. 1.53
0 20 40 60 80 100 120 140 160 180 200
E—d.28 Ln 2006 P xr d:28 J: zoos
Pr ject Latham Stability Analysis
Static
File: C:1Documents and Settings\O.vneAMyDocmwftWfojscts%SmiMCftdes%LaftmStabilit M-aMamGALENAStability-Static.ymf Tahja Engineehng,inc.
Galena 5.01 Analysis Results Licensee: Tahja Engineering, Inc.
DATA: Analysis 1 - Static
Material Properties (2 materials)
-------------------
Material: 1 (Mohr-Coulomb Isotropic) - Cemented Glacial Till
Cohesion Phi UnitWeight Ru
500.00 38.0 131.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Weathered Syrface Till Soil
Cohesion Phi UnitWeight Ru
200.00 38.0 130.00 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: 2 - Weathered Syrface Till Soil
0.00 800.00 200.00 800.00
Profile: 2 (8 points) Material beneath: 1 - Cemented Glacial Till
0.00 699.00 27.00 719.00 44.80 729.00
50.80 733.00 55.80 737.50
62.20 753.50 88.90 776.00 185. 90 789.00
Slope Surface (11 points)
-------------
File:C:IProjectslLatham X-Sec A-A Analysis Printout 1 of 4 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
0.00 700.00 27.00 720.00 44.80 730.00
50.80 734.00 54.90 738.00
55.80 740.00 62.20 756.00 66.80 760.00
78. 90 770.00 88.90 778.00
185.90 790.00
Phreatic Surface (2 points) ------------ 0.00 738.00 200.00 738.00
Failure Surface
---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 40.00 YL: 727.30 XR: 100.00 YR: 779.37
Centre: XC: 50.10 YC: 776.27 Radius: R: 50.00
Variable Restraints
-------------------
Parameter descriptor: XL XR R
Range of variation: 55.00 55.00 35.00
Trial positions within range: 10 10 10
-------------------------------------------------------------------------------------
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: 1.74
There were: 718 successful analyses from a total of 1001 trial circles
283 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.53
Circle and Results Summary (Lowest 13 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 29.02 793.25 49.17 732.91 90.83 778.24
63.61 1.535
2 25.77 796.23 49.17 732.91 90.83 778.24
67.50 1.537
3 32.32 790.21 49.17 732.91 90.83 778.24
59.72 1.537
4 31.50 795.52 43.06 729.02 96.94 779.00
67.50 1.539
5 32.25 798.26 49.17 732.91 96.94 779.00
67.50 1.542
6 35.71 787.10 49.17 732.91 90.83 778.24
55.83 1.544
7 31.86 787.68 43.06 729.02 90.83 778.24
59.72 1.546
8 28.50 790.94 43.06 729.02 90.83 778.24
63.61 1.547
9 34 .69 792.08 43.06 729.02 96.94 779.00
63.61 1.549
10 30.87 792.81 36.94 725.59 96.94 779.00
67.50 1.550
11 35.33 784.32 43.06 729.02 90.83 778.24
55.83 1.551
12 35.38 795.01 49.17 732.91 96. 94 779.00
63.61 1. 553
13 25.23 794.12 43.06 729.02 90.83 778.24
67.50 1.553
File:C.-WrojecWLatham X-Sec A-A Analysis Printout 2 of 4 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Latham X-Section A-A Dynamic Stability Analysis
GALENA vn s m
Cemented Wooer TV
820
WeafMrad S3+hce 7N Soll
800 1�
Ea u.H—Lornion
780
Wvd—d S,rt«Soil
760
c—.d ol..a rdi
740 Lk C..k—.739 El. Plre Surface
720 /
Analysis: 1
Multiple Stability Analysis
Method: Bishop Simplified
700 Surface: Circular
Results
Cnecat(minimum)
680 Factorof Sarety 1.25
0 20 40 60 80 100 120 140 160 180 200
E,Rod:2e Jan 2=1 Hoo—d:28 J n 2M
Project: Latham Stability Analysis
Dynamic
EAL C:1Documents and SethngsXOwnerWly DocumentsWrojec%NSmdh Chanes1La03am StabildyU Vham GALENA Stability-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) - Cemented Glacial Till
Cohesion Phi UnitWeight Ru
500.00 38.0 131.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Weathered Syrface Till Soil
Cohesion Phi UnitWeight Ru
200.00 38.0 130.00 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: 2 - Weathered Syrface Till Soil
0.00 800.00 200.00 800.00
Profile: 2 (8 points) Material beneath: 1 - Cemented Glacial Till
0.00 699.00 27.00 719.00 44.80 729.00
50.80 733.00 55.80 737.50
62.20 753.50 88.90 776.00 185.90 789.00
Slope Surface (11 points)
-------------
File:C:IProjectsQatham X-Sec A-A Analysis Printout 3 of 4 1/30/2009
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
0.00 700.00 27.00 720.00 44.80 730.00
50.80 734 .00 54.90 738.00
55.80 740.00 62.20 756.00 66.80 760.00
78. 90 770.00 88.90 778.00
185.90 790.00
Phreatic Surface (2 points)------------ 0.00 738.00 200.00 738.00
Failure Surface
---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 40.00 YL: 727.30 XR: 100.00 YR: 779.37
Centre: XC: 50.10 YC: 776.27 Radius: R: 50.00
Earthquake Force
----------------
Pseudo-static earthquake (seismic) coefficient: 0.150
Variable Restraints
-------------------
Parameter descriptor: XL XR R
Range of variation: 55.00 55.00 35.00
Trial positions within range: 10 10 10
-------------------------------------------------------------------------------------
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: 1.43
There were: 718 successful analyses from a total of 1001 trial circles
283 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.25
Circle and Results Summary (Lowest 11 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 31.50 795.52 43.06 729.02 96.94 779.00
67.50 1.254
2 32.25 798.26 49.17 732.91 96.94 779.00
67.50 1.256
3 30.87 792.81 36.94 725.59 96. 94 779.00
67.50 1.260
4 25.77 796.23 49.17 732.91 90.83 778.24
67.50 1.264
5 29.02 793.25 49.17 732.91 90.83 778.24
63.61 1.264
6 34.69 792.08 43.06 729.02 96.94 779.00
63.61 1.264
7 30.29 789. 65 30.83 722.15 96. 94 779.00
67.50 1.265
8 32.32 790.21 49.17 732.91 90.83 778.,24
59.72 1.267
9 35.38 795.01 49.17 732.91 96. 94 779.00
63.61 1.268
10 34. 15 789.14 36.94 725.59 96. 94 779.00
63.61 1.270
11 28.50 790. 94 43.06 729.02 90.83 778.24
63.61 1.274
IProjectslLatham X-Sec A-A Analysis Printout 4 of 4 1/30/2009
MASON COUNTY ENVIRONMENTAL CHECKLIST 2
questions later in this checklist that ask you to describe certain aspects of
your proposal. You do not need to repeat those answers on this page.
(Lead agencies may modify this form to include additional specific
information on project description). Shoreline protection is to be
constructed using steel 1-beams and treated lumber along
approximately 100 lineal feet of frontage. Height of the bulkhead to
be a maximum of 14 feet above the existing beach grade at the OHW
elevation of 738 feet Steel 1-beams to be augered in by hand a
minimum of 6 feet(2 feet in width) and filled with concrete. Bulkhead
shall be reinforced by steel tieback cables and concrete anchor
blocks. Entire bulkhead to be backed with filter fabric, gravel, and
topsoil running the length of the bulkhead, then planted with native
vegetation. Minimal vegetation shall be disturbed. Manmade debris
on the beach shall be removed from the site. Materials and
equipment shall be driven to the site.
12. What is the location of the proposal? Give sufficient information for a
person to understand the precise location of your proposed project
including a street address, if any, and section, township, and range, if
known. If a proposal would occur over a range of area, provide the range
or boundaries of the site(s). Provide a legal description, site plan, vicinity
map, and topographic map, if reasonably available. While you should
submit any plans required by the agency, you are not required to duplicate
maps or detailed plans submitted with any permit applications related to
this checklist.
Take SR Hwy 101 to Hoodsport, then turn left on North Lake
Cushman Rd. Turn left on Standstill Drive (Division 19) and follow to
the site.
B. ENVIRONMENTAL ELEMENTS:
1. EARTH:
a. General description of the site (circle one): Flat, rolling, hilly, steep
slopes, mountainous, other.
b. What is the steepest slope on the site (approx. percent slope)? Greater
than 50%.
Mason County Department of Community Development
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 Charles Smith,Tracy DeLeo,Stephen & Amy Latham Parcel# s 42205-52-00051
&42205-52-00951
Site Address 61 & 61 N. Gull Place, Hoodsport,Washington 98548
(1) (a) A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) Pages 1-3
(b) A discussion of specific soil types
Located on page(s) Pages 2,4,5& 6
(c) A discussion of ground water conditions
Located on page(s) Page 4
(d) A discussion of the upslope geomorphology
Located on page(s) Pages 1-3
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s) Page 4
(f) A discussion of history of landslide activity in the 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) Plan Sheets 1 -7
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) Plan Sheet l
(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 Sheet 1
(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 2-5& 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) Page 5 and 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) Pages 3-4
(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 4
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.
Located on page(s) Page 4
(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 5
(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) Pages 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 Sheet 1
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
Report, dated 1/30/09 and entitled Tracy DeLeo, Charles Smith Stephen and Amy Latham
Geotechnical Report meets all the requirements of the Mason County Resource
Ordinance, Landslide Hazard Section, is complete and true, that the report 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)
WA
A T 30784
GIISTER��
`SSI0 L
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.
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: Steve &Amy Latham
Permit# BLD2009-00069 Parcel#42205-52-00951
Date(s) of the Document(s)reviewed: Geotechnical Report 1/30/2009
(1) (a)A discussion of general geologic conditions in the vicinity of the proposed development,
OK? Yes Comment: Pages 2-3
(b) A discussion of specific soil types
OK? Yes Comment: Page 2, 3, 4, 5 & 6
(c) A discussion of ground water conditions
OK? Yes Comment: Page 4
(d) A discussion of the upslope geomorphology
OK? Yes Comment: Pages 2-3
(e) A discussion of the location of upland waterbodies and wetlands
OK? Yes Comment: Page 4
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
referenced maps and records
OK? Yes Comment: Page 3
(2) A site plan which identifies the important development and geologic features.
OK? Yes Comment: Plan Sheets 1-7
(3) Locations and logs of exploratory holes or probes.
OK? Yes Comment: Plan Sheet 1
(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? Yes Comment: Plan Sheet 1
(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? Yes Comment: Plan Sheets 2-5
(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.
OK? Yes Comment: Page 5 & GALENA Stability Analysis Pages 1-3
(7) (a)Appropriate restrictions on placement of drainage features
OK? Yes Comment: Page 5
(b) Appropriate restrictions on placement of septic drain fields
OK? Yes Comment: Pages 3-4
(c) Appropriate restrictions on placement of compacted fills and footings
OK? Yes Comment: Page 6
(d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other
slopes on the property.
Page 1 of 2 Form Effective June 2008
OK? Yes Comment: Page 4
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.
OK? Yes Comment: Page 4
(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? Yes Comment: Page 5
(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? Yes Comment: Page 6
(10) An analysis of both on-site and off-site impacts of the proposed development.
OK? Yes Comment: Page 6
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and buffer widths.
OK? Yes Comment: Page 6
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
OK? Yes Comment: Page 6
(13) A site-map to scale showing the property boundaries, scale, north arrow, and the location
and nature of existing and proposed development on the site.
OK? Yes Comment: Plan Sheet 1
Are the Documents signed and stamped? Yes
Type and #of License: Professional Engineer #30784
If not approved, what is the next action/recommendation for further action?
Reviewed by Tammi Wright Planner on 2/5/09
Time spent in review:
SECOND REVIEW/ UPDATE:
Reviewed by on
Time spent in second review:
THIRD REVIEW/UPDATE:
Reviewed by on
Time spent in third review:
Disclaimer: Mason County does not certify the quality of the work done in this Geological Report.
Page 2 of 2 Form Effective June 2008