HomeMy WebLinkAboutGEO2010-00018 for BLD2010-00278 - BLD Engineering / Geo-tech Reports - 6/8/2010 MASON COUNTY
DEPARTMENT OF COMMUNITY DEVELOPMENT
Planning Division
P O Box 279, Shelton, WA 98584
11910
(360)427-9670
Geotechnical ReportReview Acceptance Letter
June 08, 2010
MICHAEL LEENHOUTS
3016 NIAGARA ST
BELLINGHAM WA 98226-4216
Case No.: GE02010-00018
Parcel No.: 322365100011
Proiect Description: GEO REPORT SUBMITTED FOR BLD2010-00278
The Geotechnical Report for MICHAEL LEENHOUTS has been received and reviewed by the
Planning Department. The report was prepared by Alan Tahja dated 4/26/2010.
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. 365 if you have questions.
Sincerely,
Z�Z N �
Allan Borden
Land Use Planner
Mason County Planning Department
Comments:
6/8/2010 Page 1 of 1 GE02010-00018
RECEIVED
�&o Zv Io - 6(oc) 18
APR 2 9 2010 FnL -61d W1 D QO 278
426 W. CEDAR ST.
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 Michael & Becky Leenhouts Parcel# 32236-51-00011
Site Address 100 E Pebble Beach Lane,Union, WA 98592
(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 2-3,4& 5
(c) A discussion of ground water conditions
Located on page(s) Page 2
(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 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 2
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) Plan Sheets 1 &2
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) 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 Printout Shts 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 4
(7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) Page 4
(b) Appropriate restrictions on placement of septic drain fields
Located on page(s) Page 1
(c) Appropriate restrictions on placement of compacted fills and footings
Located on page(s) Pages 4& 5
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 and Plan Shts 1 & 2
(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 and Plan Shts 1 &2
(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) Page 5 and E&S Plan Sheet
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) _ Page 5
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and buffer widths.
Located on page(s) Page 5
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on page(s) Page 5
(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
Report, dated 4/26/2010 and entitled Leenhouts 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)
pF WASy
76
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�014 ���STER�� �ww
ssjONAL
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 �� A. 1'
Planning Division y of WAgJ�!
PO Box 279
Shelton, WA 98584
Michael&Becky Leenhouts
3 016 Niagara St 01;'�, CI ST V,
Bellingham, WA 98226-4216 SSIONAL
(360) 739-5537 (cell)
Re; Geotechnical Report
Hazard Area Reduction Request
100 E Pebble Beach Lane
Union, WA 98592
Parcel No.: 32236-51-00011
Case No.s: SWG97-00435,DDR2010-00035
BLD2010-00278
Mason County's geotechnical document review process will determine that the proposed
Michael and Becky Leenhouts residential improvements on their 100 E Pebble Beach Lane
property in Union, Washington, Mason County,will result in encroachment inside the 50-foot
vegetated Hazard Area Buffer required under Resource Ordinance 17.01.100.
Stability analysis of the slopes located on the northwesterly portion of the site between the
existing residential features and State Route 106 at the toe of the steep slope (>40%) is itself
stable and not likely to produce any slope instability as a result of the Leenhouts' proposed
activities. The currently proposed residential remodel and residence addition on the location of
the existing concrete patio are proposed to be inside the 50-foot Hazard Area buffer. With the
exception of an existing garage,the existing property improvements are all already inside the 50-
foot hazard area buffer.
A Hazard Area Buffer reduction down to as little as 5-feet is requested for future residential
development of the Leenhouts' property. This reduction request is equivalent to a request for an
intrusion as great as 45-feet into the hazard area buffer. These requests are predicated on
residential foundations being excavated to such depths that the foundation footings bear on the
natural undisturbed glacial till soil layers underlying the site.
Therefore, on behalf of the Leenhouts, I request that a reduction in the Landslide Hazard Area
buffer required in Section 17.01.100 be reduced to as little as 5-feet for 100 E Pebble Beach
Lane to allow the construction of currently proposed development of the property as promoted in
my site plans and geotechnical report dated 4/26/2010, and building construction plans as
prepared by Tami Selby of SELBY DESIGNS, LTD.
Sincerely,
c�4'
v
A an jA. Tahja,
File:C.TrojecWLeenhoutsIHA Buffer Reduction Rqst 1 of 1 4/26/2010
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Mason County DCD
Planning Division
PO Box 279
Shelton, WA 98584
Michael& Becky Leenhouts
3016 Niagara St
Bellingham, WA 98226-4216
(360) 739-5537
Re; Geotechnical Report
100 E Pebble Beach Lane
Union, WA 98592
Parcel No.: 32236-51-00011
Case No.s: SWG97-00435, DDR2010-00035
BLD2010-00278
INTRODUCTION
I was contacted in mid April this year by Mr. Mike Leenhouts who requested my investigation and
documentation of slope stability and landslide hazard issues relating to the remodeling and addition
to their seasonal residence located approximately 0.1 miles up E Pebble Beach Lane from US
Highway 106, approximately two miles west of Twanoh State Park. The property is identified as
Mason County tax parcel number 32236-51-00011.
I visited the site on April 22°d and 25d'of this year to collect topographic information and verify
measurements and feature locations. Measurements were made using a 4-foot Soil Probe Rod, 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 SoftreeTM Terrain 3-d contour modeling program,
GALENATM Slope Stability Analysis software and Microsoft Office Word 2003. Arial topography
and an elevation datum were developed from Mason County's website GIS mapping.
The site is generally located on the northerly facing hillside located along the south shore of Hood
Canal. The steepest slope in the vicinity of the Leenhouts property was found to be a slope
paralleling Hood Canal on the Leenhouts property approximately 85 feet southeast of Hood Canal's
southerly shoreline. The slope between the level portion of the Leenhouts property and the toe of
slope at the Highway 106 elevation measured approximately 75%over an elevation difference of
approximately 30+feet. E Pebble Beach Lane, a private road, generally defines the Leenhouts'
southeasterly property boundary. A site plan is appended to the end of this report to help visualize
the property's layout and topographic features.
The Leenhouts property includes a recently upgraded(SWG97-00435)onsite septic system,two
residential features and a detached residential garage.
File:C.1Projects1LeenhouWGeo-Rpt 1 of 6 4/26/2010
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
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 or improvement. Mason County classifies properties with a slope
exceeding 40%as a Landslide Hazard Area and are further designated b the County as "critical
� Y tY
areas requiring immediate protection from incompatible land uses.", requiring the preparation of a
geotechnical report. Mason County's Resource Ordinance stipulates "The intent of the Geotechnical
Report is to specify how hazards are to be mitigated when development is proposed within the
landslide hazard area itself or its buffers or setbacks.". This report is intended to show how
development can be mitigated and occur within the landslide area buffer on the Leenhouts' property.
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 property has been logged in the past,but has second growth timber scatter over most of the
property's unimproved areas generally either on the slope between the dwellings and the highway or
between the garage and Pebble Beach Lane. The vegetated areas of the property are covered with
young and medium aged second growth Douglas Fir, Hemlock, Cedar trees and low growing native
vegetation,mainly Salal, Oregon Grape, and Huckleberry plants. The south shore of Hood Canal in
this area is comprised mainly of steep slopes which connect the sea level elevation of Hood Canal
northwest of the Leenhouts property and the relatively level upland area approximately a quarter
mile southeast of Hood Canal,typically at less than a 600 foot sea level elevation. Washington
State's Coastal Atlas indicates the Leenhouts property is located in an area of"Intermediate"
stability,typically stable but susceptible to instability if disturbed.
No wetlands or upland water bodies were found or observed during the property's
reconnaissance/inspection. Surface soils may become saturated through the course of the wet season,
but the static groundwater elevation likely coincides with the tide elevation of Hood Canal.
Inspection of the Geologic Map of Shelton 1:100,000 Quadrangle, Washington' on the following
page finds the property located in an area between Hood Canal to the northwest, and an upland area
southeast of Hood Canal. The map reveals that the site soils are classified as Continental Glacial
Deposits, Fraser Glaciation,Vashon Stade(Qga),which are further described on the following page.
Inspection and soil analysis finds the soil to be classified under the Unified Soil Classification
System(USCS)as a coarse grained soil with a fairly high percentage of fines which gives it a dual
soil classification of GW-SW. Probing areas of the property with a titanium probe rod, inspection of
the cut banks located along Jenn's Way, and inspection of soil log holes excavating for designing a
new septic system drainfield found a fairly uniform soil layer of the loamy sandy gravel to a depth of
50 feet or more underlain by a consolidated glacial till layer. The shallow surface soil(s)displays a
modest amount of cohesion,but most of the soil's strength is derived from its granular texture and
internal friction characteristics of the soil.
1 DNR OFR2003-15 Geologic Map of Shelton 1:100,000 Quadrangle,Washington
File:C:IProjectslLeenhoutslGeo-Rpt 2 of 6 4/26/2010
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Advance outwash,late Wisconsinan (Pleistocene}—Glaciofluvial
sand and gravel and lacustrine clay,silt,and sand deposited during
the advance of glaciers;sandy units commonly thick,well sorted,and
fine grained,with interlayered coarser sand,gravel,and cobbles and
silt rip-up lag deposits at their base;may contain nonglacial sedi-
ments;generally overlain by till.
Fault n '.:,
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2. SITE PLAN WITH IMPORTANT DEVELOPMENT AND GEOLOGIC FEATURES:
The attached site plan shows the location of the slope located between the Leenhouts property and
Highway 106 and the general locations of the existing and proposed dwelling features.
3. LOCATIONS OF LOGS OF EXPLORATORY HOLES OR PROBES:
Soil probe locations are provided on the attached plan sheets along with depths from the ground's
surface to the hardpan layer underlying the site. The slope between the Leenhouts building area and
the Highway 106 elevation is modeled as a hardpan soil layer underlying a moderately firm surface
soil layer approximately 3 to 4 feet thick.
4. AREA OF PROPOSED DEVELOPMENT&BOUNDARIES OF HAZARDS, BUFFERS,
AND SETBACKS:
The attached site plan shows the locations of existing property improvements(single family
residence&detached garage),the location of the existing septic system,the landslide hazard areas
(areas containing slopes greater than 40%) as well as the 50-foot wide landslide hazard area buffers
required around Landslide Hazard Areas by the County. The major proposed development proposed
on the property at this time is the remodeling and addition to the existing residence.
File:C.lProjecWLeenhoutslGeo-Rpt 3 of 6 4/26/2010
f '
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
5. CROSS SECTION WITH PROPOSED GRADE CHANGES:
A cross section view is provided in the attached plan sheets. This same cross section was used in
modeling the site's stability. No grading or grade changes are required or proposed on the property's
steep slope.
6. SLOPE STABILITY ANALYSIS:
The steep slope generally descending from southeast to northwest on the property appear stable in
their present condition. Back analysis of the standing cut banks in the area provided values in what
soil characteristics can be expected from the site's soils and can be used in stability modeling. The
steep hillside is modeled as a cemented glacial till layer beneath a moderately firm surface soil layer
composed of weathered glacial till approximately 3-feet thick.
As indicated earlier in this report, Unified Soil Classification System typing places the soils in a dual
symbol category due to its gravel, sand, silt and clay components. A USCS soil classification of
GW-SW is used for modeling the site's slopes. The soil mechanical properties used in the stability
analysis are based on the shallow soils characterized as having a soil unit weight of 125 lbs/ft, a phi
angle of 42°, and a cohesion character of 2001bs/ft2. The deeper cemented till substrate is modeled
as having a soil density of 130 lbs/ft3,a phi angle of 42°, and a cohesion character of 4001bs/ft
The slope geometry and soil characteristics provide a factor of safety for the site in a static analysis
of 2_3 and a dynamic analysis of 1_8, both of which meet the County's minimum safety
requirements.
7. RECOMMENDED SETBACKS &DRAINAGE:
The existing residence is located southeast of the crest of the northwesterly descending slope on the
property and may be considered safe in its present location. The existing residence is located
approximately 16+feet away from the crest of the steep slope and an existing concrete patio 8-feet
wide extends from the existing house towards the crest of the slope. The dwelling addition is
proposed to be located in the approximate footprint of the existing concrete patio,which will provide
an approximate 8-foot separation between the dwelling and the top of the Hazard Area. This location
may be considered an intrusion of approximately 42'f which stability analysis indicates is a safe
location. A hazard area buffer reduction request accompanies this report which requests an intrusion
of roughly 45-feet be allowed into the hazard area buffer.
Drainage from the present leveled building location sheets to its natural drainage relief generally to
the northwest, Highway 106's drainage ditches, and ultimately to Hood Canal. The dwelling addition
adds no new imperviousness to the property and the existing drainage regime functions adequately.
If remodeling of the dwelling includes the addition of gutters and downspouts,the downspout
discharges should be located as far back from the crest of the steep slope as practicable. Splash
blocks which disperse downspout discharges would be an acceptable stormwater management
feature,but should be located no nearer than 5-feet back from the crest of the steep slope.
File:C:IProjectsUenhoutslGeo-Rpt 4 of 6 4/26/2010
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
8. CLEARING, GRADING,AND VEGETATION MANAGEMENT:
The currently proposed dwelling remodel and addition will require clearing of the area where the
existing patio concrete is,but otherwise no actual site clearing will be required. Trees on the steep
slope may be topped or limbed for view enhancement, but the tree stumps and roots should remain
and the existing vegetation on the slope should be preserved, or may be replaced with landscape
plantings which would provide a root structure for soil stability and erosion resistance.
9. EROSION AND SEDIMENT CONTROL:
Inspection of the Soil Survey of Mason County found the site to be located in an area with an
Alderwood soil type (A,,),which is identified in the County's Critical Resource Ordinance as an
erodible soilsusceptible and to severe erosion when disturbed. As roe located over a
property rtY
potentially erodible soil, Mason County requires the development of an Erosion and Sediment(E&S)
Control Plan. An E&S Plan sheet is included in the appendix which includes minimum E&S
measures which need to be employed when land disturbing activities are undertaken during the
property's development activities. Any silt or mud escaping the Leenhouts property onto
neighboring properties could be identified as a violation of Mason County's Stormwater
Management regulations. All measures necessary to remove mud&turbidity from construction
runoff should be implemented and maintained until the completed construction area has become
permanently stabilized with vegetation or gravel.
Recommended silt fence installation locations are indicated on the Erosion and Sediment(E&S)
Control Plan sheet prepared for the proposed land disturbing activities. A permanent access to the
existingresidence and existing garage already exist and are stable in their resent condition. The
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proposed work is expected to be performed during favorable weather during the dry season of 2010.
10. ON-SITE AND OFF-SITE IMPACTS:
The proposed remodel and addition to the existing residential features on the Leenhouts property are
not expected to result in either any onsite or offsite detrimental impacts.
11. SPECIFICATIONS OF FINAL DEVELOPMENT:
Upon completion of the proposed dwelling improvement(s), any denuded soils should be seeded
with grass and covered with a 3-inch or thicker layer of straw or hay to protect the bare soil from
potential erosion impacts until permanent vegetation is able to perform that function.
12. RECOMMENDATIONS FOR THE PREPARATION OF STRUCTURAL MITIGATION
OR DETAILS OF OTHER PROPOSED MITIGATION:
Modeling of the slopes in the area of the proposed work indicate that the hillsides located on the
Leenhouts property are stable,requiring no structural measures or mitigation. Footings constructed
adjacent(>5' back) from the crest of the steep slope should bear on the undisturbed glacial till layer
underlying the site.
File:C.TrojectslLeenhoutslGeo-Rpt 5 of 6 4/26/2010
r
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
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,the stability analysis printout,and an Erosion and
Sediment Control Plan Sheet.
Summary& Conclusions:
The Leenhouts' property and proposed land disturbing activities,though located in an area
designated in Mason County's Critical Resource Ordinance as a Landslide Hazard, does not contain
any landslide hazard features that cannot be overcome or mitigated. Please feel free to contact me if
there are any questions or concerns regarding this report or my findings.
Sincerely, 1'
�,of WA t
Alan A. Tahja, P.E.
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Attached: Geotechnical Report Checklist �SSIONAL S�'
Hazard Area Reduction Request
Plan Views, Cross Section Sheet and E&S Plan Sheet
GALENATM Stability Analysis Printout
File:C:IProjectslLeenhouts)Geo-Rpt 6 of 6 4/26/2010
Rev# Description Date TAHJA ENGINEERING,INC. SITE PLAN
Alan Tahja,P.E. Michael&Becky Leenhouts Leenhouts
PO Box 235 3016 Niagara A
Hoodsport, WA 98548 Bellingham, WA 98226-4216 1 of 4
Mason Co.Prcl No.: 32236-51-00011 (360)877-9512 (360)739-5537 (cell)
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Alan Tahja,P.E. Michael&Becky Leenhouts Leenhouts
PO Box 235 3016 Niagara St. AM
Hoodsport WA 98548 Bellingham, WA 98226-4216 2 of 4
Mason Co.Prcl No.: 32236-51-00011 (360)877-9512 (360)739-5537 (cell)
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Alan Tahja,P.E. Michael&Becky Leenhouts Leenhouts
PO Box 235 3016 Niagara St.
HoodspoA WA 98548 Bellingham, WA 98226-4216 3 of 4
Mason Co.Prcl No.: 32236-51-00011 (360)877-9512 (360)739-5537 (cell)
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Erosion & Sedime Control:
I.Install silt fences befor commencing land disturbing activitie /
near house&SR 106.
2.Cover un-worked denuded s 'Is with a 3"+thick layer of str or
hay as soon as practical(7 day ' it summer,2 day limit inter). / Z
3.Seeded completed work areas wit rass seed and co v straw
Maintain temporary E&S measures til site beco s rman
s bilized with grass&native vegetatio Its,
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TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Leenhouts X-Section A-A Static Stability Analysis
GALENA v«a.&o,
160
140
A.
120 pF WASFj
Phreatic Surface(saturated surface soils) -
80
-3'Tltick Weathered Surfers Soil Layer., I
784
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Leenhouts Dwelling �`sSIONAL
40
Cemented Glacial Till substrate
i
20-
HWY 106
/s Analysis: 1
Multiple Stability Analysis
0 Method: Bishop Simplified
Surface: Circular
-20 Results
Critical(minimum)
-40 Factor of Safety: 2.26
0 50 100 150 200 250 300
Edited:25 Apr 2010 ProwaW 25 Alx 2010
Proiect: Leenhouts Pebble Beach Residence
Static
F& C:\Documents and Settings\Owner\My Documents\Projects\Leenhouts\Galena Files\Leenhouts Static 1.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) - Weathered Till Surface Soil Layer
Cohesion Phi UnitWeight Ru
200.00 34.0 125.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till Layer
Cohesion Phi UnitWeight Ru
400.00 34.0 130.00 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: 1 - Weathered Till Surface Soil
0.00 120.00 300.00 120.00 Layer
Profile: 2 (10 points) Material beneath: 2 - Cemented Glacial rill Layer
68.50
0.00 27.00 18.00 54.00 19. 00 57.00 20.00
81.10 37.50
85.00 39.00 125.30 46.00 175. 10 56.00
220.30 66.00 265.50 76.00
Slope Surface (8 points) -------------
81. 10 40.00 125.30
0.00 19.00 54.00 20.00 67.50 30. 00
50.00
175.10 60.00 220.30 70.00
265.50 80.00
File:C:IProjectslLeenhouts X-Sec A-A Analysis Printout I of 4
4/2 6/2010
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Phreatic Surface (2 points) ----------------
0.00 100.00 300.00 100.00
Failure Surface ---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 46.00 YL: 19.85 XR: 86.00 YR: 41.11
Centre: XC: 61.03 YC: 39.83 Radius: R: 25.00
Variable Restraints -------------------
Parameter descriptor: XL XR R
Range of variation: 25.00 25.00 15.00
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: 3.81
There were: 1028 successful analyses from a total of 1729 trial circles
701 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 2.26
Circle and Results Summary (Lowest 16actor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 64.57 31.80 51. 68 19. 96 80.32 39.43
17.50 2.261
2 67.80 32.81 53. 95 20.00 84.86 40.85
18.86 2.471
3 68.87 33.75 56.23 21.65 84.86 40.85
17.50 2.530
4 65.14 33.18 51. 68 19. 96 82.59 40.34
18.86 2.531
5 61.21 29.25 44 .86 19.83 78.05 37.75
18.86 2.583
6 65.73 30.84 47.14 19.87 84 .86 40.85
21.59 2.617
7 59.77 28.99 44.86 19.83 75.77 36.08
17.50 2.790
8 63.47 34.68 53. 95 20.00 80.32 39.43
17 .50 2.809
9 62.37 33. 62 49.41 19.91 80.32 39.43
18.86 2.818
10 62. 64 32.09 44 .86 19.83 82.59 40.34
s9 2.856
2111 65.62 34 .61 51.68 19.96 84.86 40.85
20.23 2.873
12 68.14 34.42 53.95 20.00 87.14 41.37
20.23 2.889
13 71.18 32.07 51. 68 19.96 91. 68 42.39
22.95 2. 913 49.41 19.91 7805 37.75
14 61.27 32.79 .
17.50 2.956 34 .76 49.41 19.91 82.59 40.34
15 63.15
20.23 2.959 20.00 82.59 40.34
16 64.29 35.78 53.95
18.86 2.963
File:C:IProjects\Leenhouts X-Sec A-A Analysis Printout 2 of 4
4/26/2010
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Leenhouts X-Section A-A Static Stability Analysis
GALENA v ryon5,01
160
o.1so
140
120
P^ceatic Surface(saturated surface soils) F'p
100 ___.._----------_-------------_..__....__..-.�...
so -3'Thick Weathered Smlace Soil Layer.,
Co
Laenlawta Dwelling
40
Cemented Glacial Till Suhatrate
HWY 106
20 Analysis: 1
Multiple Stability Analysis
0 Method: Bishop Simplified
Surface: Circular
-20 Results
Critical(minimum)
Factor of Safety. 1.84
-40
0 50 100 150 200 250 300
Edted:25 Apr 2010 Prateaaa l 25 Apr 3010
Project Leenhouts Pebble Beach Residence
Dynamic
Ei(a: C\Documents and Settings\Owner%My Documents\Projeas\Leenhouts\Galena Files\Leenhouts Dynamic 1.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) - Weathered Till Surface Soil Layer
Cohesion Phi UnitWeight Ru
200.00 34 .0 125.00 1.10
Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till Layer
Cohesion Phi UnitWeight Ru
400.00 34.0 130.00 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: 1 - Weathered Till Surface Soil Layer
0.00 120.00 300.00 120.00
Profile: 2 (10 points) Material beneath: 2 - Cemented Glacial Till Layer
0.00 18.00 54.00 19.00 57.00 20.00
68.50 27.00 81.10 37.50
85.00 39.00 125.30 46.00 175. 10 56.00
220.30 66.00 265.50 76.00
Slope Surface (8 points) -------------
0.00 19.00 54.00 20.00 67.50 30a00
81. 10 40.00 125.30 50.00
175.10 60.00 220.30 70. 00 265.50 80.ao
File:C:IProjectslLeenhouts X-Sec A-A Analysis Printout 3 of 4 4/26/2010
Oppol-
TAHJA ENGINEERING, Inc.
PO Box 235, Hoodsport, WA 98548
(360) 877-9512
Phreatic Surface (2 points) ---- 0.00 100.00 300.00 100.00
Failure Surface ---------------
Initial circular surface for critical search defined by: XL,XR,R
Intersects: XL: 46.00 YL: 19.85 XR: 86.00 YR: 41.11
Centre: XC: 61.03 YC: 39.83 Radius: R: 25.00
Earthquake Force ----------------
Pseudo-static earthquake (seismic) coefficient: 0.150
Variable Restraints -------------------
Parameter descriptor: XL XR R
Range of variation: 25.00 25.00 15.00
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: 2.54
There were: 1028 successful analyses from a total of 1729 trial circles
701 analyses terminated due to unacceptable geometry
Critical (minimum) Factor of Safety: 1.84
Circle and Results Summary (Lowest 15 Factor of Safety circles)
--------------------------
Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right
Radius FoS
1 64 .57 31.80 51. 68 19. 96 80.32 39.43
17.50 1.844
2 67.80 32.81 53.95 20.00 84.86 40.85
18.86 1. 983
3 65. 14 33.18 51. 68 19.96 82.59 40.34
18.86 1.992
4 68.87 33.75 56.23 21.65 84.86 40.85
17.50 2.022
5 61.21 29.25 44.86 19.83 78.05 37.75
18.86 2.099
6 65.73 30.84 47. 14 19.87 84.86 40.85
21.59 2.113
7 63.47 34 . 68 53.95 20.00 80.32 39.43
17.50 2.115
8 62.37 33. 62 49.41 19. 91 80.32 39.43
18.86 2.143
9 62.57 51.34 53. 95 20.00 93.95 42. 91
32.50 2. 156
10 64.56 50.72 53. 95 20.00 96.23 43.42
32.50 2. 166
11 65.62 34.61 51. 68 19.96 84.86 40.85
20.23 2.167
12 60.58 51.82 53. 95 20.00 91. 68 42.39
32.50 2.172
13 62.39 5o.64 51.68 19.96 93. 95 42.91
32.50 p.Z73
14 63.55 49. 62 53.95 20.00 93. 95 42.91
31.14 2.179
15 61.54 50.20 53.95 20.00 91.68 42.39
31. 14 2.182
File:coiprojectslLeenhouts X--Sec A-A Analysis Printout 4 of 4 4/26/2010
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: 1 wP hjofs
Permit# U �� `V ) Parcel # 7Z36 S
I✓v OZ C
Date(s)of Mlihentto(s) revie l bw 2-0 to
(1) (a)A discu sion of general geologic conditions in the vicinity of the proposed development,
OK?__V Comment:
(b) Adis ssion of specific soil types
OK? Comment:
(c) A discussion of ground.water conditions
OK? V Comment:
(d) A dis ussion of the upslope geomorphology
OK?L Comment:
(e) A discussion of the location of upland waterbodies and wetlands
OK? V Comment:
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
refer ced maps and records
OK? Comment:
(2) A site plan y�hich identifies he import n�pme and geologic features.
OK? ✓ C m m oent: Pte�
(3) Locations d logs of a lorato oles or grebes.
OK?Comment:
(4) The area of the proposed de elopment, the boundaries of the hazard, and associated buffers and
setbacks Pall be delineated (to t s, an toe)on a geologic map of the site.
OK? I Z Comment: l 7/
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorporates the details f ropos� es.
OK? Comment:
(6) A description and results of Alope stability analyses performed for both static and seismic loading
conditions.Analysis should examine worst case failures. The analysis should include the
Simplified B' hop's Method of Circles. The minimum static safety factor is 1.5, the minimum
seismic s ety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
OK? Comment:
(7) (a)Apprc iate restrictions on placement of drainage features
OK?___V Comment:
(b) Appropriate restrictions on placement of septic drain fields
OK? Comment:
(c) Appropriate restrictions on placement of compacted fills and footings
OK? Comment:
(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?__ ,--Comment.-
(e) Recommen ed setbacks from the landslide hazard areas shoreline bluffs and the tops of
other sl es on the property.
OK? Comment:
(8) Recommendations for the prep a on of a detaile clearing and grading pla �ich specifically
identifies vegetation to be removed, a schedule for vegetation removal and replanting, and the
method of vv etation 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�rosion, landslides and harmful constr ction methods
.
OK? ✓ Comment: C� 5
(10) An analysis both on-site and off-site impac s of the proposed development.
OK? Comment:
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion cont and buffer widths.
OK? Comment:
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
OK? Comment:
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location
and nature existing and proposed development on the site.
OK? Comment: - - E�g_"e-
Are the Documents signed and stamped?
Type and #of License: ,/ 1- 36 Z 8 1(
If not approved, what is the next action/recommendation for further action? L
Reviewed by , on
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 Assessment
Page 2 of 2 Form Effective June 2008
Mason County Review Checklist
1` 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: La6w,hiry
Permit#_otlb �6a Parcel # �7-?�6 S�
s
Date(s) of tt�e-Docdrri'e t�s re 'W�
(1) (a)A discu pion of general geologic conditions in the vicinity of the proposed development,
OK?I/Comment:
(b) A disc ssion of specific soil types
OK? Comment:
(c) A disc ssion of ground,water conditions
OK? V Comment: -
(d) A di s ussion of the upslope geomorphology
OK? Comment:
(e) A discussion of the location of upland waterbodies and wetlands
OK? V Comment:
(f) A discussion of history of landslide activity in the activity in the vicinity, as available in the
refergmed maps and records
OK? V Comment:
(2) A site plan�ich identifies he important developmeand geologic features.
OK? ✓ Comment:
(3) Locations d logs of a lorato oles or pcpbes.
OK?Comment: G
(4) The area of the proposed de elopment, the boundaries of the hazard, and associated buffers and
setbacks all be delineated(to , t , s, an toe,)on a geologic map of the site.
OK?__. Comment: tql/
(5) A minimum of one cross section at a scale which adequately depicts the subsurface profile, and
which incorporates the details f ropos� �� es.
OK? IZ Comment:
(6) A description and results of Alope stability analyses performed for both static and seismic loading
conditions.Analysis should examine worst case failures. The analysis should include the
Simplified t3' hop's Method of Circles. The minimum static safety factor is 1.5, the minimum
seismic s ety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
OK? Comment:
(7) (a)AppropFiate restrictions on placement of drainage features
OK?__V Comment:
(b) Appropriate restrictions on placement of septic drain fields
OK? Comment:
(c) Approp late restrictions on placement of compacted fills and footings
OK? Comment:
(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?_'ZComment:
(e) Recommen ed setbacks from the landslide hazard areas shoreline bluffs and the tops of
other sl es on the ro ert
P P Y
OK? Comment: �i s
(8) Recommendations for the prep a on of a detaileb clearing and grading plan Aich 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 osion, landslides and harmful constr ction m hods.
OK? Comment:
(10) An analysis both on-site and off-site impac s of the proposed development.
OK? Comment:
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion conter and buffer widths.
OK? Comment:
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
OK? V Comment:
(13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location
and nature existing and proposed development on the site.
OK? Comment:
Are the Documents signed and stamped?
Type and (�
YP ��f License: .� ��
If not approved, what is the next action/recommendation for further action? g `
� l
Reviewed by on
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 Assessment
Page 2 of 2 Form Effective June 2008
I