HomeMy WebLinkAbout136-01 - Ord. Amending County Resource Ordinance ORDINANCE NUMBER 136 - 01
AMENDMENTS TO THE MASON COUNTY RESOURCE ORDINANCE
AN ORDINANCE amending the Mason County Resource Ordinance , Ordinance 77-93 ,
regulations which apply to Geologically Hazardous Areas . This is Section 17 . 01 . 100
Landslide Hazard Areas , under the authority of Chapters 36 . 70 and 36 . 70A RCW .
WHEREAS , the Board of County Commissioners held a public hearing on December 11 ,
2001 , to consider the recommendations of the Planning Commission , the Mason County
Department of Community Development , and citizens on the proposed amendments ;
WHEREAS , the Mason County Planning Commission formulated its recommendations after a
public hearing on November 19 , 2001 , and approved findings of fact ;
WHEREAS , these hearings were duly advertised public hearings ;
WHEREAS , these amendments are intended to comply with the Orders of the Western
Washington Growth Management Hearings Board , Case No . 95 -02 -0073 ;
WHEREAS , the Mason County Board of County Commissioners has approved findings of fact
to support its decision as ATTACHMENT A ;
NOW , THEREFORE , BE IT HEREBY ORDAINED , that the Board of County
Commissioners of Mason County hereby approves and ADOPTS the amendments to the
Mason County Resource Ordinance , as amended , as described by ATTACHMENT B .
DATED this 11 th day of December , 2001 .
Board of County Commissioners
Mason County , Washington
ATTEST :
Herb Baze , Chair
Clerk of the Board
Wesley 19. Johnsoly! Commissioner APPROVED AS TO FORM :
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Ro ert Holter , Commissioner Prosecuting Attorney
Resource Ordinance Sec. 17. 01 . 100 Landslide Hazard Areas ATTACHMENT A
Mason County Planning Commission
November 19 , 2001
FINDINGS OF FACT
1 . PROPOSED ACTION
Under consideration is a proposal to amend the Mason County Resource Ordinance Sec .
17 . 01 . 100 Landslide Hazard Areas , intended to designate, protect, and guide development in
these areas in Mason County . These changes are proposed to update the county regulations and
to address the concerns of the Western Washington Growth Management Hearings Board
(Hearings Board) in case 495 -2 -0073 addressed in their Findings and Order, dated July 13 , 2001 .
2 . PUBLIC PARTICIPATION
A Mason County Planning Commission public hearing was scheduled for November 19, 2001
and comments were received from the commission members and the public . In addition, public
participation was provided through the SEPA review process to agencies and interested parties in
October and November 2001 , other written public comment by the Washington Department of
Natural Resources (DNR) , and public testimony at the hearing .
3 . ENVIRONMENTAL REVIEW
A determination of non-significance (DNS ) was issued by Mason County on October 29, 2001 ;
no agency comments were received in response to this threshold determination and environmental
checklist . After review of the comments received and consideration of the changes proposed
since that issuance, it was determined by the Department of Community Development that no
significant adverse impacts are expected from this action .
4 . GROWTH MANAGEMENT HEARINGS BOARD COMPLIANCE - DISCUSSION
The previous Order of the Growth Management Hearings Board (GMHB), Case 995 -2-0073 ,
dated July13 , 2001 , expressed concern over the use of Best Available Science (BAS ) and public
participation in establishing development review standards for landslide hazard areas . The
discussion of these issues was presented in the staff report for the November 19 , 2001 public
hearing and is summarized below :
1 . Triggering distance for geological assessment or geotechnical report.
The draft landslide hazard areas ordinance text, in the Section E Geotechnical Report, now
includes the triggering distance from the edge of buffer revised from 200 feet to 250 feet, which
same distance recommended by Mason County ' s geotechnical consultant in the 2000 drafts of
this ordinance . The DNR geologist, who was part of an interagency review group , supported this
proposed triggering distance revision to minimize such hazards and also suggested other
ordinance text revisions to improve the clarity and to include additional geological information
submitted to Mason County .
2 . Public participation.
Public input was noted in the text above .
3 . Compliance with Other Resource Ordinance Sections and the Shoreline Master Program.
The current Resource Ordinance Sec , 170010100 , Landslide Hazard Areas , has direct references
to resource protection in shoreline areas , as emphasized in Sec . 17 . 01 . 110 , Fish and Wildlife
Conservation Areas . In the sub -sections regarding proposed development ( Sec . 17 , 01 . 100 . E . 7)
and bank protection and bulkhead projects ( Sec . 17 . 0 1 . 100 . D . 7), a proposal must meet fish and
Resource Ordinance Sec. 1 " 100 Landslide Hazard Areas
and bank protection and bulkhead projects (Sec . 17 , 01 . 100 . D . 7), a proposal must meet fish and
wildlife habitat conservation area regulations and complete a habitat management plan as part of
the development review (as noted in Sec . 17 . 01 . 110 . G. Le bank stabilization) .
5 . GROWTH MANAGEMENT HEARINGS BOARD COMPLIANCE - FINDINGS
A . Mason County finds that these amendments and the provisions of this Section 17 . 01 , 100
of the Resource Ordinance are an important part of the implementation of GMA and county goals
for environmental protection, specifically for landslide hazard areas .
B . Mason County finds that the proposed landslide hazard areas ordinance classifies
landslide hazard areas of the county and regulates proposed development in these geologically
hazardous areas to protect the conditions and values of those critical areas .
C . Mason County finds that the proposed landslide hazard area ordinance standards work
together with other resource standards , including fish and wildlife habitat conservation areas and
the Shoreline Master Program, to provide adequate protection of values , functions , and conditions
of these geologically hazardous areas .
D . Mason County finds that the designation of landslide hazard areas provides a level of
protection from geologic hazards that supports the goals of the Growth Management Act and
incorporates Best Available Science in the development of the ordinance regulations .
E. Mason County finds that all of the issues stated in the Growth Management Hearings
Board Findings and Order of July 13 , 2001 have been addressed in the revisions made and the
public review of the Mason County Resource Ordinance Sec . 17 . 01 . 100 Landslide Hazard Areas .
6 . CONCLUSIONS
The Mason County Board of Commissioners finds that the ordinance revisions for the proposed
changes to the Mason County Resource Ordinance Sec . 17 . 01 . 100 are consistent with the goals of
the Mason County Comprehensive Plan and the goals of the Growth Management Act .
The Mason County Board of Commissioners approves these revisions and hereby adopts this
Findings of Fact for the proposed changes to the Mason County Resource Ordinance Sec .
17 . 01 . 100 Landslide Hazard Areas ,
Chair, Mason County Boar of C nmissioners
Date
17 . 01 . 100 LANDSLIDE HAZARD AREAS ATTACBMIENT S
The purpose of the Landslide Hazard Section is to identify areas that present potential dangers to public
health and safety , to prevent the acceleration of natural geological hazards , to address off site
environmental impacts , and to minimize the risk to the property owner or adjacent property owners
from development activities .
Except for the exceptions listed below , development in or near landslide hazard areas requires a permit
and the professional preparation of a geotechnical report or geological assessment to determine under
what conditions the development may proceed at a reasonable risk . All development applications are
reviewed to determine if they are likely to be in or near a landslide hazard area .
• Landslide hazard areas are described in A .
• The designation of landslide hazard areas is done in B .
• Activities exempt from these requirements are described in C . 1 . and others are listed in section
17 . 01 . 130 of the Resource Ordinance .
• Activities requiring permits are described in C . 2 .
• Standard requirements for certain activities are contained in D .
• When a geotechnical report or geological assessment is required is determined in E 1 and 2 .
• The standards for a geotechnical report and geological assessment are contained in E . 3 , 4, 5 ,
and 6 .
• The general review standard for approval of a permit is in E . 7 .
® Notice of the risks inherent in development in a landslide hazard area is required for the
applicant and future property owners in F .
A . CLASSIFICATION
1 . The following shall be classified as Landslide Hazard Areas :
a . Areas with any indications of earth movement such as debris slides,
earthflows , slumps and rockfalls ( see figure F . 100 ) .
b . Areas with artificial oversteepened or unengineered slopes , i . e . cuts or fills .
c . Areas with slopes containing soft or potentially liquefiable soils .
d . Areas oversteepened or otherwise unstable as a result of stream incision ,
stream bank erosion , and undercutting by wave action .
e . Slopes greater than 15 % ( 8 . 5 degrees ) and having the following :
I . Hillsides intersecting geologic contacts with a relatively permeable
sediment overlying a relatively impermeable sediment or bedrock ( e . g .
sand overlying clay ) ; and
ii . Springs or groundwater seepage .
f . Any area with a slope of forty percent or steeper and with a vertical relief of
ten or more feet except areas composed of consolidated rock. A slope is
delineated by establishing its toe and top and measured by averaging the
inclination over at least ten feet of vertical relief .
2 . The following information may be used as a guide by the County to indicate areas that
have a higher likelihood of meeting the classification criteria above :
a . The areas identified on the Mason County Soil Survey Map as having slopes
greater than 15 % .
b , The areas identified on the Coastal Zone Atlas , Volume 9 , of Mason County ,
Washington as :
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 j
I . Unstable - " U "
ii . Unstable Old Slides - " UOS "
iii . Unstable Recent Slides - " URS "
iv . Intermediate Slopes - 44
1 "
v . Modified Slopes - " M "
c . The areas identified as Class 2 , 3 , 4 , or 5 of the maps : of " Relative Slope
Stability of the Southern Hood Canal Area , Washington " , by M . Smith and R . J .
Carson , Washington State Department of Natural Resources , Division of Earth
Resources , 1977 and " The Geological Map of North Central Mason County ,
Washington " , by R . J . Carson , 1976 , U . S . Geologic Survey OFR 76 - 2 ,
B . DESIGNATION
1 . Lands of Mason County classified as Landslide Hazard Areas are hereby designated ,
under RCW 36 . 70A . 060 and RCW 36 . 70A . 170 , as critical areas requiring immediate
protection from incompatible land uses .
2 . Upon an application for development on either mapped or unmapped lands , the Director
shall determine if a hazard exists on a particular site based on :
a . Information supplied by the applicant in the form of a geotechnical report or
geological assessment ,
b . Actual physical observation of the site ,
c . Existing County Hazard Area maps, or
d . Other means determined to be appropriate .
If the presence of a hazard is determined , the boundaries of the hazard and associated
buffers shall then be delineated (top , both sides , and toe ) on a geologic map of the site .
C . LAND USES
1 . Exempt Uses
a . The growing and harvesting of timber, forest products and associated
management activities in accordance with the Washington Forest Practices Act
of 1974, as amended , and regulations adopted pursuant thereto ; including , but
not limited to , road construction and maintenance ; aerial operations;
applications of fertilizers and pesticides ; helispots ; and other uses specific to
growing and harvesting timber forest products and management activities,
except those Forest Practices designated as " Class IV -General Forest
Practices " under the authority of the " IA
Iashington State Forest Practices Act
Rules and Regulations " , WAC 22216 -030 ;
b . Those activities and uses conducted pursuant to the Washington State Surface
Mining Act , RCW 78 . 44 and its Rules and Regulations , where State law
specifically exempts local authority ;
c . Existing and ongoing agriculture , aquaculture , floriculture , horticulture , general
farming , dairy operating under best management practices ( BMP ) of the
Washington State Department of Ecology ' s Storm Water, Water Quality ,
Hazardous Waste , Wetland , and Solid Waste Program and BMP from the
Departments of Health , Agriculture , Transportation , and State Conservation
District Office .
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 2
2 . Permit Required Uses
Permits are required for all new construction , grading , land clearing , and other uses
subject to Section 17 . 01 . 050 , and any Class IV Conversion Permit pursuant to the
State Forest Practices Act which involves conversion to a Permit Required Use , and are
within a Landslide Hazard Area or its buffer . Permit Required Use may require a
Geotechnical Report , see Section 17 . 01 . 100 . E .
D . DEVELOPMENT STANDARDS
Any land use on Landslide Hazard Areas or their buffers shall conform to the following
standards :
1 . Grading
a . No grading shall be performed in landslide hazard areas prior to obtaining a
grading permit subject to approval , by the Director , based on recommendations
contained in the geotechnical report with slope stability , drainage , erosion
control and grading recommendations .
b . Clearing during grading shall be limited to the area of the approved
development .
c . No fill , dead vegetation ( slash /stumps ) , or other foreign material shall be
placed within a Landslide Hazard Area ; with the exception of engineered
compacted fill for construction of buttresses for landslide stabilization which
shall be in accordance with recommendations specified in a Geotechnical
Report .
2 . Land Clearing
a . Within this section , " Land Clearing " is defined as the cutting or harvesting of
trees or the removing or cutting of vegetation so as to expose the soil and
which is not otherwise exempt from this section .
b . Land Clearing in Landslide Hazard Areas or their buffers is permitted when it is
consistent with the recommendation and plans contained in the Geotechnical
Report and development approval .
c . If there is no Geotechnical Report for the site , land clearing is not permitted :
however removal of danger trees , selected removal for viewing purposes of
trees less than 6 inches dbh (diameter at breast height ) and trimming or pruning
of existing trees and vegetation is allowed with the qualifications cited herein .
Danger trees shall be identified with the recommendation of a member of the
Association of Consulting Foresters of America , an arborist certified by the
International Society of Arboriculture , or with the recommendation of a person
qualified to prepare a geotechnical report if removing trees for slope
stabilization purposes . Removal of trees less than 6 inches dbh shall be limited
to less than 2 percent of the total number of trees of that size or larger in the
hazard area . Removal of multiple trees in a concentrated area , i . e . within a
distance of 25 feet of each other , shall be accompanied by replacement by
deep rooting native shrubs or other vegetation that serve similar moisture and
erosion protective functions to that provided by the removed trees . Trimming
and pruning shall be accomplished in accordance with pruning standards of the
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 3
International Society of Arboriculture , as published in " ANSI A300- 95 " or
subsequent updated versions in order to minimize the potential for long term
damage to the trees .
d . Removal of selected trees and ground cover is allowed without a permit for the
purpose of surveying and geotechnical exploration activities that do not involve
grading , provided that re -vegetation of the disturbed areas occurs immediately
afterward .
e . Land clearing for which a permit has been obtained shall not be allowed during
the wet season , i . e . from November 1 through May 1 , unless special provisions
for wet season erosion and landslide protection have been addressed in the
Geotechnical Report and approved by the Director .
3 . Drainage
a . Surface drainage , including downspouts and runoff from paved or unpaved
surfaces up slope , shall not be directed onto or within 50 feet above or onto
the face of a Landslide Hazard Area or its associated buffer . If drainage must
be discharged from the top of a Landslide Hazard Area to below its toe , it shall
be collected above the top and directed to below the toe by tight line drain and
provided with an energy dissipating device at the toe .
b . Stormwater retention and detention systems , including percolation systems
utilizing buried pipe or french drain , are prohibited unless a licensed civil
engineer certifies appropriate mitigation measures .
c . Erosion shall be controlled as provided in the Mason County Stormwater
Management Ordinance and any geotechnical report or geological assessment
prepared for the site .
4 . Sewage Collection /Treatment Systems
Sewage collection and treatment systems shall be located outside of the Landslide
Hazard Areas and associated buffers , unless an approved geotechnical report specifies
appropriate mitigation measures . See Section 17 . 01 . 100 . E .
5 . Subdivision Design and Lot Size
For the purpose of determining lot sizes under Title 16 of the Mason County Code , and
other county regulatory requirements , the Director shall review available information
and required Geotechnical Reports or Geological Assessments under Section
1 1601 . 100 . E , and make a decision� vl n a case - by-case basis based on the reports . To
avoid impacts to anadromous fisheries and fish habitat, land divisions , (short plats,
subdivisions , and large lot divisions ) shall not be approved unless :
a . No improvements or construction shall be within fish and wildlife habitat
conservation areas , wetlands, or their buffers , provided that necessary water or
wetland crossings or encroachments approved pursuant to other sections of
the Mason County Resource Ordinance or other county regulations may be
permitted for roads and utilities .
b . All lots must have designated building areas on which structures may be safely
located without the requirement for bulkheading , bank protection or other
structures that encroach on fish and wildlife habitat conservation areas ,
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 4
wetlands , or their buffers . Future buildings are to be limited to such designated
areas .
The number , size , or configuration of lots may be changed as a condition of approval to
meet this requirement .
6 . Buffers
a . A 50 foot ( 15 . 25 meter) buffer of vegetation is required around the Landslide
Hazard Area .
b . Upon finding substantial evidence that the proposed development is to be
located near or within a hazardous area , the Director may require a
Geotechnical Report or Geological Assessment pursuant to Section
17 . 01 . 100 . E . Based on the results of the Geotechnical Report or Geological
Assessment, the Director may increase the buffer .
c . An application may be made to reduce the buffer for the purpose of
constructing a single family residence on a lot existing or vested by December
6 , 1996 . Notice of application for the reduction of the buffer shall be made as
provided in Section 15 . 07 . 010 of the Mason County Development Code ( which
specifies how notice is sent to adjacent property owners and posted on the
site ) . The Director shall approve such a reduction only on finding that the
approval is conditioned as necessary to be consistent with the
recommendations contained within the Geotechnical Report or Geological
Assessment (described in Sections 17 . 01 . 100 . E . ) and on finding that impacts
to anadromous fish or their habitat or to fish and wildlife habitat conservations
areas shall be avoided or mitigated as detailed in an approved Habitat
Management Plan (described in Section 17 . 01 . 110 . )
7 . Bulkheads and Bank Protection
Bulkheads and bank protections , along with related fill , constructed for landslide
stabilization measures approved under the Shoreline Master Program or the Fish and
Wildlife Habitat Conservation Area regulations , shall be consistent with
recommendations specified in a Geotechnical Report .
8 . Residential Densities and Floor Area Ratios
The landslide hazard area and its buffer shall be counted in calculating the number of
dwelling units (determined by the size of the site and residential density allowed ) or the
area of non -residential building (determined by the size of the site and the floor area
ratio allowed ) that may be built on the site ; provided that :
a . the development is outside of the landslide hazard area or its buffer , and
b , the development is able to comply with all county regulations without
encroaching on the landslide hazard area or its buffer .
Clustering of residential development away from landslide hazard area and its buffer
may receive a density bonus if performed meeting the design requirements contained in
Chapter 16 . 22 , Mason County Code .
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 5
E . GEOTECHNICAL REPORT
1 . Applicability
Every application for development within a Landslide Hazard Area or its buffer or within
250 feet of the buffer shall meet the standards of Section 17 . 01 . 100 . D and shall
require either a Geological Assessment or a Geotechnical Report , or both , in
accordance with the following guidance :
Category a . Areas with slopes greater than 40 percent ( 21 . 8 degrees ) will require
an Geotechnical Report .
Category b . Areas with any visible signs of earth movement such as debris slides ,
earthflows , slumps and rockfalls , or areas within 200 feet of
previously mapped or recorded landslides will require a Geotechnical
Report .
Category c . Areas within 100 feet of oversteepened or otherwise potentially
unstable slopes as a result of stream incision , stream bank erosion , and
undercutting by wave action will require an Geotechnical Report .
Category d . Areas with slopes between 15 percent ( 8 . 5 degrees ) and 40 percent ( 21 . 8
degrees ) will require a Geological Assessment , and may further require
a Geotechnical Report upon analysis of the following factors by the
Director :
( 1 ) Lot size and use ;
( 2 ) Overall height of slope and maximum planned cut or fill ( requires a
grading plan ) ;
( 3 ) Soil types and history of sliding in the vicinity (from the Geological
Assessment ) ;
( 4 ) Groundwater conditions , including depth to water and quantity of
surface seepage (from the Geological Assessment) ;
( 5 ) Approximate depth to hard or dense competent soil , e . g . glacial till or
outwash sand (from the Geological Assessment) ;
( 6 ) Impervious surfaces and drainage , schemes ( requires
development/grading plan ) ;
( 7 ) Wastewater treatment ( requires on -site sewage disposal system
approval from Mason County Department of Health ) ;
( 8 ) Potential off-site impacts , including adjacent properties , roadways, etc .
( requires environmental statement dependant on scope of project ) .
2 . Waiver of Geotechnical Report
The Director may waive the requirement for the Geotechnical Report for Category c
and d sites upon. a written finding in the Geological Assessment that the potential for
landslide activity is low and that the proposed development would not cause significant
adverse impacts , or that there is adequate geological information available on the area
proposed for development to determine the impacts of the proposed development and
appropriate mitigating measures .
3 . Qualifications of Preparer
The Geologic Assessment shall be prepared at the discretion of the Director by either a
licensed civil engineer with specialized knowledge of geotechnical /geological
engineering or a practicing engineering geologist with special knowledge of the local
conditions . The preparer shall have at least three years of experience in landslide
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001
assessment and shall submit a statement of qualifications with the assessment or
report , unless they have been previously determined to be qualified by Mason County .
The Geotechnical Report shall be prepared at the discretion of the Director by a
licensed civil engineer with specialized knowledge of geotechnical /geological
engineering . The Geotechnical Report may also be prepared by a practicing engineering
geologist with special knowledge of the local conditions , provided the work is
performed under the supervision of a licensed civil engineer who will stamp the report
and attest to the competency of the engineering geologist to perform landslide
evaluations in accordance with the prevailing standard of practice .
4 . Content of the Geological Assessment
A Geological Assessment shall include but not be limited to the following :
( 1 ) A discussion of geologic conditions in the general vicinity of the proposed
development , with geologic unit designation consistent with terminology used
in the Coastal Zone Atlas (Washington Department of Natural Resources , 1980 )
or in applicable U . S . Geologic Survey maps ( e . g . Geological Map of North
Central Mason County , by R . J . Carson , 1976 , U . S . Geologic Survey OFR 76 -2 ) .
Use of Soil Conservation Service soil layer terminology is considered
inappropriate for this assessment .
( 2 ) A discussion of the ground water conditions at the site , including the depth to
water and the quantity of surface seepage .
( 3 ) The approximate depth to hard or dense competent soil , e . g . glacial till or
outwash sand .
( 4 ) A discussion of any geomorphic expression of past slope instability ( presence
of hummocky ground or ground cracks , terraced topography indicative of
landslide block movement , bowed or arched trees indicating downslope
movement , etc . ) .
( 5 ) A discussion of the history of landslide activity in the vicinity , as available in
the Coastal Zone Atlas , the map of " Relative Slope Stability of the Southern
Hood Canal Area , Washington" by M . Smith and R . J . Carson , 1977 ; and the
landslide records on file with the Mason County Department of Community
Development .
( 6 ) An opinion on the potential for landslide activity at the site in light of the
proposed development .
( 7 ) A recommendation by the preparer whether a Geotechnical Report should be
required to further evaluate site conditions and the proposed development of
the subject property .
5 . Content of a Geotechnical Report
A Geotechnical Report shall include but not be limited to the following :
( 1 ) A discussion of general geologic conditions , specific soil types, ground water
conditions and history of landslide activity in the vicinity as required for the
Geologic Assessment described above .
( 2 ) A site plan which identifies the important development and geologic features .
( 3 ) Locations and logs of exploratory holes or probes .
( 4 ) A minimum of one cross section at a scale which adequately depicts the
subsurface profile , and which incorporates the details of proposed grade
changes .
( 5 ) A description and results of slope stability analyses performed for both static
and seismic loading conditions .
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 7
( 6 ) Appropriate restrictions on placement of drainage features, septic drain fields
and compacted fills and footings , including recommended setbacks from
shoreline bluffs and the tops of other slopes on the property .
( 7 ) 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 .
( 8 ) 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 .
( 9 ) An analysis of both on -site and off-site impacts of the proposed development .
( 10 ) Specifications of final development conditions such as , vegetative
management , drainage , erosion control , and buffer widths .
6 . Applicable Standards
Geological Assessments and Geotechnical Reports shall be prepared using terminology ,
descriptions, evaluation methods and mitigation approaches that reflect the current
standard of care for practitioners in the field of geologic hazards . The standard of care
shall be considered to be represented by , but not limited to , Turner , A . K . and Schuster ,
R . L . ( 1996 ; " Landslides , Investigation and Mitigation " , Transportation Research Board
Special Report 247 , National Academy Press , Washington DC . ) for classification ,
analysis and conceptual mitigation of landslides ; Washington Department of Ecology
( 1993 ; " Slope Stabilization and Erosion Control Using Vegetation , A Manual of Practice
For Coastal Property Owners" , Publication No . 93 -30 , Olympia , WA ; and " Vegetation
Management : A Guide For Puget Sound Bluff Property Owners" , Publication No . 93 - 31 ,
Olympia , WA ) for vegetation management and it use in slope stabilization and erosion
protection ; and Washington Department of Ecology ( 1995 ; " Surface Water and
Groundwater on Coastal Bluffs" , Publication No . 95 - 107 , Olympia , WA ) for water and
drainage management and its use in slope stabilization and erosion protection .
7 . Administrative Determination
Any area in which the Geotechnical report or geological assessment indicates the
presence of landslide hazards shall not be subjected to development unless the report
demonstrates conclusively that the hazards can be overcome , and that the
development meets all standards in Section 17 . 01 . 100 . D . Hazards must be overcome
in such a manner as to prevent harm to property and public health and safety , and to
assure no significant adverse environmental impact . Impacts to anadromous fish or
their habitat or to fish and wildlife habitat conservations areas shall be avoided or
mitigated as detailed in an approved Habitat Management Plan , as described in Section
17 . 01 . 110 . The Director may submit either the Geologic Assessment or the Geo -
technical Report to an outside agency with geotechnical expertise or to a geotechnical
consultant for third party peer review prior to issuing a ruling on the project .
F . APPLICANT HOLD HARMLESS STATEMENT
The property owner shall be required to acknowledge in writing the risks inherent in developing
in a geologic hazard area , to accept the responsibility of any adverse affects which may occur
to the subject property or other properties as a result of the development , and to agree to
convey the knowledge of this risk to persons purchasing the site by filing the notice on the
property title .
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 $
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Hopenclature of parts of a landslide ( from Eckel , 1958 ) :
tkbris slide : Incoherent or broken mosses of rock Earthflowi eolluvial materials that move downslope
i�o her debris that move downslone by slid- in a axnner similar to a viscous fluid .
Ina on a surface that underlies the deposit .
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slwo : coherent or twtaet cusses that move doo- msloJe poekfall : rock that his coved grta%rlly by fallfAQ
by rotational slip on surfaces that uMerlle as (Trough the air .
well as penetrate the landslide enposit .
Landslide Hazard Areas - Mason County Resource Ordinance
December 11 , 2001 9