HomeMy WebLinkAboutGeoTech Evaluation for BLD2017-00944 - BLD Engineering / Geo-tech Reports - 11/4/2017 � • f
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November 4, 2017 Michael Kipp
171 SE Paulcyn Lane
Shelton, Washington 98584
RE: Geotechnical Evaluation Report for Property Located at 181 E Bergeson Road
Parcel 22003-12-90120,Harstine Island, Mason County, Washington
Dear Mr. Kipp,
Envirotech Engineering (Envirotech) has completed this geotechnical evaluation for the above
referenced property. A geotechnical report has been previously prepared for this property by
Geotechnical Testing Laboratory (GTL) on April 28, 2005 with subsequent addendums.
Specifically, we are addressing current site conditions, items not provided by GTL with relation
to County code, and provisions for the proposed home to be constructed as the second phase of
development.
Our geotechnical evaluation included reviewing the aforesaid report and its addendums,
conducting a site visit, completing a Mason County Submittal Checklist, and providing our
conclusions and recommendations regarding the proposed project.
A site visit was completed on October 13, 2017 by Michael Staten with Envirotech. It was
apparent that general conditions provided by GTL have not changed, and new geological hazards
than what was presented by GTL were not present.
Upslope Geomorphology
The upland area of the property and beyond is generally situated on a gentle sloping hillside and
crest of glacial origin.
Upslope Water Bodies
There are no apparent water bodies or wetlands located upslope from the planned development
that would significantly influence the Project.
Envirotech Engineering Geotechnical Evaluation
PO Box 984 Page 1 of 3 181 E Bergeson Road
Belfair,Washington 98528 Parcel 22003-12-90120
Ph.360-275-9374 November 4,2017
Vegetation Buffer and Considerations
For this project, we believe that a detailed clearing and grading plan is not warranted unless
Mason County thresholds are exceeded, and basic vegetation management practices should be
adhered to.
It is our opinion that vegetation should not be removed from slopes exceeding 30% on the
property, and within 10 feet from top of critical slope as delineated by GTL. Any danger tree to
life or property shall be removed immediately. Any tree removed shall maintain stumps,
underbrush and existing grades. Two trees should be planted of same species for every tree
removed.
On-Site and Off-Site Impacts
From a geotechnical position, it is Envirotech's opinion that the subject property and adjacent
properties to the proposed development should not be significantly impacted if all
recommendations in this report and the GTL report are followed. This opinion is based on the
expected site development, existing topography, existing nearby development, land cover, and
adhering to the recommendations presented in this report. Future development or land disturbing
activities on neighboring properties or properties beyond adjacent parcels that are upslope and/or
downslope from the subject property could cause problems to the subject property. For this
reason, future development or land disturbance near the subject property should be evaluated by a
geotechnical engineer.
Structural Mitigation
With respect to landslide alleviation or slope improvements, structural mitigation is not necessary
for this project. This determination is based on the anticipated improvements of the project,
engineering conclusions,and compliance with all recommendations provided in this report.
Site Plan
The site plans prepared by GTL appear sufficient for the geotechnical design of this project. The
planned 30ft x 4011 2"d phase home with associated parking will be located southwest and nearly
adjacent to the existing home. This location is within the constraints of all geotechnical
parameters provided by both GTL and Envirotech.
2"d Phase Development
With the exception of bearing capacity, it is our opinion that all development recommendations
provided in the GTL report is sufficient for the proposed project. Envirotech recommends a
bearing capacity of no more than 1500 psf for the 2nd phase development.
Envirotech Engineering Geotechnical Evaluation
PO Box 984 Page 2 of 3 181 E Bergeson Road
Belfair,Washington 98528 Parcel 22003-12-90120
Ph. 360-275-9374 November 4,2017
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Limitations
Limitations provided by GTL should be acknowledged by the owner and contractor. Envirotech
examined the GTL report for completeness with relation to code, but do not accept their
responsibility. Our scope of services included observing the property for changes since the GTL
report was written, and provide conclusions and recommendations for the development that GTL
did not include in their original work.
Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or require
additional information.
Best Regards,
Envirotech Engineering
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Michael Staten, P.E.
Geotechnical Engineer
Envirotech Engineering Geotechnical Evaluation
PO Box 984 Page 3 of 3 181 E Bergeson Road
Belfair,Washington 98528 Parcel 22003-12-90120
Ph. 360-275-9374 November 4,2017
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.
Applicanl1wner Michael Kipp Parcel# 22003-12-90120
Site Address 181 E Bergeson Road, Harstine Island
(1) (a)A discussion of general geologic conditions in the vicinity of the proposed development,
Located on page(s) 3(GTL)-Geotechnical Testing Laboratory Report
(b) A discussion of specific soil types
Located on page(s) 4(GTL)
(c) A discussion of ground water conditions
Located on page(s) 4(GTL)
(d) A discussion of the upslope geomorphology
Located on page(s) 1 (Envirotech)-Envirotech Engineering Evaluation
(e) A discussion of the location of upland waterbodies and wetlands
Located on page(s) 1 (Envirotech)
(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) 5(GTL)
(2) A site plan which identifies the important development and geologic features.
Located on Map(s) Site Plan(GTL)
(3) Locations and logs of exploratory holes or probes.
Located on Map(s) 3&Well Reports(GTL)
(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) Site Plan (GTL)
(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) 9& Figure 4(GTL)
(6) A description and results of slope stability analyses performed for both static and seismic loading
conditions. Analysis should examine worst case failures. The analysis should include the
Simplified Bishop's Method of Circles. The minimum static safety factor is 1.5, the minimum
seismic safety factor is 1.1. and the quasi-static analysis coeffients should be a value of 0.15.
Located on page(s) 8(GTL)
(7) (a)Appropriate restrictions on placement of drainage features
Located on page(s) 14(GTL)
(b) Appropriate restrictions on placement of septic drain fields
Located on page(s) 14(GTL)
(c) Appropriate restrictions on placement of compacted fills and footings
Located on page(s) 12(GTL)
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) 2(Envirotech)
(e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of
other slopes on the property.
Located on page(s) 8(GTL)
(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) 2(Envirotech)
(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) 10(GTL)
(10) An analysis of both on-site and off-site impacts of the proposed development.
Located on page(s) 2(Envirotech)
(11) Specifications of final development conditions such as, vegetative management, drainage,
erosion control, and buffer widths.
Located on page(s) 8-10(GTL)& 1-2(Envirotech)
(12) Recommendations for the preparation of structural mitigation or details of other proposed
mitigation.
Located on pages) 2(Envirotech)
(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) Site Plan(GTL)
I, Michael C Staten 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 11/4/17 and entitled 181 E Bergeson Road
Parcel 22003-12-90120 meets all the requirements of the Mason
County Resource Ordinance, Landslide Hazard Section, is complete and true, that the assessment
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)
C LY dE S
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SS40A. 1"V.
Page 2 of 2 Form Effective June 2008
Disclaimer: Mason County does not certify the quality of the work done in this Geotechnical Report.