HomeMy WebLinkAboutGRD2008-00006 - GRD Engineering / Geo-Tech Reports - 10/26/2022 Mason County Review Checklist
For a Geological Assessment
Instructions:
This checklist is intended to assist Staff in the review of a Geological Assessment. The
Assessment 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
Assessment 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:
0
Permit# 20ZT-�-ow 0 LD Parcel # (ZI oS G7( -- `-1`f 0 a 1
Date(s) of the Document(s)reviewed:
(1) A discussion of geologic conditions in the general vicinity of the
proposed development, with geologic unit designation based
on referenced maps.
OK? Comment:
(2) (a)A discussion of the gro6Ad water conditions at the site,
OK? Y Comment: 'I�Ai 3
(b) A di sion of the estiMated depth 1to water
OK? Comment: IJt) !Zyns,�a
(c) A discussion of the quantity of surface seepage
OK? _Comment: y\0 s a s
(d) Adis ussion of the upslope geomorphology
OK?�Comment: 'per
(e) A discussion of locatio f upland w terbodies and wetla ds.
OK? Comment: no UtOie� o� S alc-e
(3) The a oximate depth to hard or dens oce mpetent soil, e.g. glacial till or outwash sand.
OK? Comment: ?-S C-
(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 dgwnslope movement, etc.).
OK.-1_Comment: aCV1e PregQ,,,�
(5) A discussion of the history of landslide activity in the vicinity, as available in the
referenced maps and records.
OK?�_Comment: A o �\'6
(6) An opinion on whether the proposed development is within the landslide hazard area or
its associated buffer or setback and the potential for landslide activity at the site in light of
the prop sed development.
OK? Comment: _
(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.
OK?_Y Comment: (\o-�- r c JaCt
(8) If the presence of a hazard is deter fined within 300 feet of the proposed development,
then the following are delineated on a geologic map/site map:
(a) the area of the proposed development,
OK? _Comment:_Q7, ya-2-,-A-Y c�
Page 1 of 2 Form Effective June 2008
(b) the boundaries of the landslide hazard area (top, both sides, and toe),
OK?'_Comment: W\ A-
(c) the associated buffers (top, both sides, and toe)
OK?_ Comment:
(d) building or other setbacks (top, both sides, and toe).
OK?_Y Comment: See "� 05k�
(9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the
location and nature of existing and Rroposed development pn the site.
OK?_�Comment: a Gc_CUV O
Are the Document(s) signed and stamped? .
Type and #of License:�rS� �,vc�►.�e� �dly (Q
If not approved, what is the next action/recommendation for further action?
Reviewed by �C on
Time spent in review: J e S
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
07/07/2008 07:24 3603770274 GLEN JURGES ME 01/03
RECEIVED
AUG 2 0 2008
Mason County Department of Community Development-LD - PLANNING
Submittal Checklist For a Geological Assessment
instructions:
This checklist must be submitted with a Geological Assessment and completed, signed, and
stamped by the licensed professional(s)who prepared the Geological Assessment 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_I�(V �`e n ���, _ Parcel# // /
4a✓a 2 Vie�J �� �� ��-� ✓rep✓ ggr�6 �lVo sklee l C 4lKesr
Site Address n P .—�. �``
(1) A discussion of geologic conditions in the general vicinity of the
d e ek• cuss eye,ems(
proposed development, with geologic unit designation based
on referenced maps.
Located on page(s)
(2) (a)A discussion of the ground water ponditions at the site,
Located on page(s) -
(b) A discussion of the estimated depth to water wof et `a"�`kr
Located on page(s) /f ��V4
(c) A discussion of the quantity of§urface seepage
Located on page(s)_
(d) A discussion of the upslope geomorphology
Located on page(s)
(e) A discussion of location of upland water ie and wetlands.
Located on page(s) k • �, �e-Ae e s eh
(3) The approximate depth to hard or dense competent soil, e g glacial till or outwash sand.
Located on page(s) 3 - ' LSE
(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 indica ng downslope movement, etc.).
Located on pages) �!/on• a�( aaLewer �+'� �rcu�`
•
(5) A discussion of the history of landslide activity in the vicinity, as available in the
referenced maps and record d ��
Located on page(s) e ��r��r �� �c.�(r/�Car' �••
(g) An opinion on whether the proposed development is within the landslide hazard area or
its associated buffer or setback and the potential for landslide activity at the site in light of
the proposed development. 5.
Located on page(s)
(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.
Page 1 of 2 Form Effective June 2008
07/07/2008 07:24 3603770274 GLEN TUPGES PAGE 02/03
Located on page(s)
(9) if the presence of a hazard is determined within 300 feet of the proposed development,
then the following are delineated on a geologic map/site map'
(a) the area of the proposed development,
Located on Map(s)
(b) the boundaries of the landslide hazard area(top, both sides, and toe),
Located on Map(s) 'zIL
(c) the associated buffers(to both sides,and toe)
Located on Map(s) ?,I, P/ ..
(d) building or other setbacks(top, both sides. and top)
Located on Map(s) Silt L' a �ka`° -
(9) A site map drawn to scale showing the property boundaries, scale, north arrow, and the
location and nature of existing and proposed de v lopment on the site.
Located on Map(s) N �K�� s
k/Ltt-i- 'W CievPsctl 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 Geological Assessment, dated t`� '1` z ", and entitled 4 ro l rta/ /�s5cs5
vi r1rry 941,/111 f5-, Pluf c i Z 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)
R��sr^
19466 O
s`sIOtiAL�'
8 13 V%
EXPIRES: 06/ 151/v
Disclaimer: Mason County does not certify the quality of the work done in this Geological
Assessment.
Page 2 of 2 Form Effective June 2008
AML GEOTECHNICAL SERVICES, INC.
Retaining Systems, Slope Stability, Stormwater Management
July 31,2008
Mr.Glen Jurges
JURGES ENTERPRISES INC.
2020 Enetai Beach Road
Bremerton,WA 98310
Regarding: Geological Assessment of Fair Harbor Tracts,located at E.Grapeview Loop Road,Grapeview,
WA 98546, and Having the Legal Description, "A Portion of section 5, TWSP 21 North,
Range I West W.M., Mason County Washington," more specifically "Plat of Detroit #2,
Parcels 1 through 23 of BLA#07-82".
Dear Glen:
The following is a discussion of the various geotechnical factors that may impact the proposed
development of the above-referenced property.
GENERAL SITE DECRIPTION
The property actually consists of several parcels, 23 in all; they all begin with the number 1210551,
followed in succession by the numbers 44001,44003,44005, 44006,44010,45006,45010,45011, 54002,
54005, 54009, 55002, 55006,56002,56003, 56005, 56007,56009, 58002,58003, 58004,58006, 59002. It
is situated off the west side of Grapeview Loop road, close to the Fair Harbor Marina and a short distance
north of the small town of Grapeview. The property(including all of the above parcels)has a total area of
approximately 19 acres. The general area in which the property is situated may be described as undulating,
consisting of rolling hills covered by woodland tracts, scattered housing and some pasture land. The
property rises gently towards the west, and is traversed by a gully that becomes wider and deeper towards
the northern end of the property;the side slopes of this gully are heavily wooded and it has been designated
as a jurisdictional wetland because it is subject to seasonal stream flow. The property has been partially
cleared but still contains small tracts of trees and brush, much of which lie within the designated wetland
buffer zone(s). Access at the time of this writing is by way of a gravel driveway from Grapeview Loop
Road at a point close to the Fair Harbor Marina parking lot.
GEOLOGY
Our geological reference has been a map compiled by the Washington State Department of Natural
Resources,Map GM-65,"Geologic Map of the Vaughn 7.5 minute quadrangle,Pierce and Mason counties,
Washington by Robert L. Logan and Timothy J. Walsh, 2007". According to this map the entire property
and its' surroundings lie within a geological unit known as Vashon till(designated Qgt in the map legend.)
This unit is described thus: "Vashon till—Unstratified to moderately stratified,compact,unsorted mixture
of clay, silt, sand, and gravel deposited directly by glacial ice; gray to tan; nearly everywhere in contact
with underlying units; does not drain well as permeability and porosity are low; sand and finer grains in
matrix are very angular; pebble-to boulder-size clasts are commonly striated and faceted, having angular
(or)rounded edges; boulders are generally disseminated and relatively rare; may contain interbeds of sand
and gravel. The surface of this unit is characterized by streamlined drumlins, striations,and flutes that are
generally hundreds to thousands of feet long. Angular to subrounded glacial erratic boulders, consisting
mostly of plutonic or metamorphic rock, are common but disseminated on the surface of this unit. Unit
may be capped by a few feet of unsorted and stained ablation sand and gravel or by unit Qgos. Vashon till
locally crosscuts older sediments, forming angular unconformities. Drag folding and horizontal shearing
may occur at the base of the till,especially in thick deposits. Unit Qgt ranges in thickness from 0 to at least
50 feet".
FIELD INVESTIGATION/OTHER RESEARCH
On Thursday, July 10, 2008 an engineer from this office visited the property and carried out a thorough
visual examination of surface features,soil exposures,and vegetation types. Slope inclinations and
6009 Jon Court SE, Telephone: 360-413-1745
Olympia, WA 98513 Facsimile: 360-491-9740
AML Geotechnical Services, Inc.
Retaining Systems,Slope Stability, Stormwater Management
-2-
stabilities were also evaluated and a number of photographs, some of which are attached to this assessment,
were taken. Adjoining properties were not examined because the owners of the properties to the north and
east denied us access. Because the property lies within 2000 feet of the shoreline of Case Inlet the
Washington State Coastal Zone Atlas was consulted to enable an evaluation of the stability of the slopes in
the area, and to research the history of slide activity(if any)within the property and surrounding areas (a
copy of the Coastal Zone Atlas map of the area is attached to this assessment.)
FINDINGS
The Coastal Zone Atlas shows the entire area within which the property is situated as being stable, i.e. an
area within which there is no history of slide activity. Our observations at the site bear this out;the natural
slopes that we observed exhibit no indications of instability, past or present. The steepest slopes on the
property are those rising to the western property line and the side slopes of the gully referred to in a
previous section. These slopes are inclined at approximately 28—30%,depending on where one measures
them. Although they are inclined at more than 15%,they exhibit none of the other criteria used by Mason
County to define Landslide Hazard Areas(see Ch. 17.01.100,LANDSLIDE HAZARD AREAS, Section A
Classification, Item le of the County code.) All of these slopes are wooded and the vegetation is
comprised of typical upland indigenous species, i.e. a mix of evergreen and deciduous trees with ground
cover consisting of salal, Oregon grape, vine maple, sword fern, and assorted berries. We found no
indications of groundwater seepage or water loving plant species. More than 10 years ago much of the site
was graded by the previous owner, resulting in a relatively level area to the west of the centrally located
gully, and a short steep bank about 10 to 12 feet in height along the western edge of the property. One of
the attached photographs shows this bank, which is now covered by a dense growth of immature alder and
ground covering brush. A ditch along the toe of this slope, some 3 feet in depth, contains a small volume
of water that drains towards the south. The grading operation has resulted in the removal from relatively
large areas of the original native upper soil horizon(s). The soil exposed in these areas wherein the
vegetation (consisting of grass and weeds) is sparse consists of cemented glacial drift. This material is
comprised of pale, yellowish brown silty sand and gravel held in a tightly cemented matrix that greatly
restricts root penetration,hence the sparse growth of grass in many areas.
SOIL CHARACTERISTICS
According to the Soil Survey of the Mason County Area,compiled by the Soil Conservation Service of the
United States Department of Agriculture the dominant soil type in the area is Sinclair shotty loam. As
noted in the previous section the original upper soil horizons have been graded off in the area west of the
gully, leaving only the cemented drift that comprises the substratum. According to the Survey the shotty
material is found only in the upper 10 to 12 inches of the original soil profile, and we did not observe any
soil that could be described as shotty during our inspection. The term "shotty" is not commonly used in
soil mechanics and should be explained here; it refers to a hard, granular pebble-like soil that is about the
size of bird-shot, and is usually not angular. It results from the grinding and erosion processes that
accompany glacial advance or retreat over granitic materials. In any event,the soil that we observed at the
site is a competent material quite capable of supporting single family residences on conventional shallow
foundations, i.e. continuous or spread footings. Because of its' dense and well graded character this soil is
not likely to be prone to the process of liquefaction during even a major seismic event, a process that
requires an initial state of low relative density, a soil that is uniform in terms of grain size distribution, and
a high water table. Foundations may be designed for allowable loads of 2000 lb/ft2• a number sufficiently
conservative to provide an adequate Factor of Safety in the event of seismic activity or sustained high wind.
The water in the bottom of the ditch along the west side of the property is an indication that the cemented
drift is present at relatively shallow depth on the native slopes, resulting in a perched water table at the
interface of the upper,relatively permeable soils that comprise the surface mantle and the underlying very
slowly permeable drift. As long as this water is enabled to drain freely it is unlikely to jeopardize the
stability of the slope.
AML Geotechnical Services, Inc.
Retaining Systems, Slope Stability, Stormwater Management
-3-
CONCLUSIONS&RECOMMENDATIONS
General Comments
Based upon our observations and the results of other research of the area, we can find no geotechnical
reason why the project as we understand it should not be allowed to proceed. We found no indications of
slope instability on the property, and the Coastal Zone Atlas indicates that there is no history of slide
activity within the general area. The property is well drained and we do not anticipate groundwater to be
an issue since the wetland has been delineated and the buffer zones established. The wetland buffer zones
will ensure that no buildings or other facilities are placed too close to the existing slopes. The only issue
that we consider significant is the intention to create a street along the man-made slope that extends along
the west end of the property. The cut necessary to facilitate the construction of this street is likely to be at
least 10 feet high. Given the soil types present the cut is likely to be capable of free standing without
serious risk of failure but in the interests of aesthetic considerations and in order to prevent erosion due to
the elements(wind,rain,freeze-thaw cycles)it should be protected by a rockery. Note that a rockery more
than 4 feet in height will require a separate building permit and any rockery more than 6 feet in height must
be engineered. We have included a typical rockery cross section as an attachment to this assessment,
illustrating drainage,rock type and placement,and permissible proximity to other structures.
In summary,based upon our understanding of the proposed development of this property,and the results of
our inspection of the site,and other research,we believe the project should be allowed to proceed.
END OF ASSESSMENT TEXT
LIMITATIONS
This report has been prepared in accordance with generally accepted engineering principles and practices.
We make no warranty, either expressed or implied. The opinions expressed are based upon the results of
our investigations, and observable conditions at the site. They should not be applied to other, surrounding
properties. If conditions are encountered which appear to differ from those described in this report we
should be immediately notified, so that we may review the situation and, if necessary, modify the
recommendations of this report. In the event that such notice is not forthcoming we retain the right to
disclaim any or all of the recommendations contained herein. This report is for the information of our
client,Mr.Glen Jurges only. Its'reproduction and/or transmittal to any third party by any means,except in
its' entirety, without the written authorization of AML Geotechnical Services, Inc. is prohibited. We
would like to thank you for having given us this opportunity to provide you with geotechnical engineering
services. Please contact us at 360-413-1745 should you have any questions regarding any of the contents
of this report. This study has been carried out in association with Mr. Kurt Groesch, P.E., whose technical
review we gratefully acknowledge.
Yours very sincerely
AML Geotechnical Services,Inc. w. GRQ�s
CEO
Alastair Lumsden,P.Eng. 294664' Kurt W.Groesch,P.E.
President
Sj0'�TAll
EXPIRES: 06/15/ �o
AML Geotechnical Services, Inc.
Retaining Systems,Slope Stability, Stormwater Management
AML Geotechnical Services,Inc.
Retaining Systems,Slope Stability, Stormwater Management
ROCKERY CROSS SECTION DETAIL,TYPICAL
(Not to Scale)
No otter structures,including walks,otter
Rockeries,or parking lots within this zone. ,
W
• � Minimum 8" Thick
— Layer of > 2",
1 �'�=•�ci' 41. < 4" Quarry Spalls,
� •� � or, Alternatively,
�, '��'` •u; Crushed Rock
h <10 ' y
n ° Filter Fabric
Clean Native
Ground
h
MiniBlum c 3 a d •�. .
. , :
12" /��o�o y . T' Min. 6" Pea Gravel
C n
.,. ,rr
I
i
Firm Native
Ground 4•� �..—
GENERAL NOTES
1. Rockeries 4' and over in height require a 4. The long dimension of all rocks shall be placed
building permit. perpendicular to the wall. Each rock should bear
on two rocks in the tier below.
2. Rockeries 6' and over in height require
engineering supervision by special inspector 5. Improved walking surfaces above and adjacent to
(UBC 306b), which at minimum shall consist of rockeries over 30'in height shall be protected by
inspection and written certification of subgrade, a guardrail conforming to UBC 1711.
placement of base course and drainage, and
finished rockery. 6. Rockeries are erosion-control structures, not
retaining wall. Native material must be stable
3. Rock shall be sound and have minimum density and free-standing in cut face.
of 160 pounds per cubic foot.
"L Geotechnical Services, Inc.
Retaining Systems,Slope Stability, Stormwater Management
WASHINGTON STATE COASTAL ZONE ATLAS MAP OF THE AREA
Rv9 �.
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Scale 1:24,000 O� m=
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0 .5 1 MACS (
0 500 1000 1500 Sictres r
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�.1µ -1....•.>•nrrar:��J. lfrre mRif e"r�nnnaea:•eLe[r:r:o.aY eier r+e r, `) /-/r
aopr�ee na�.��u•a.nern.anr.�rrae �--- arbor _ r.
�µ pa 6a5 n. rr.e n°r•r e.+"r(ttsraaim rnl.^errm i 1
�i w.•rw.w • ar.«:mrrcde:am>mr.mm nriu•ny/r.e,rew { \ �• � � �^�.' / i�
�wn.ar u•.e rarranw xr••uuvw�,.rw.o-n«««r e,r !' I �.• �<• ,��
°sxrrtena.nai,n,ran.enm.ws<.nn nwre�. I
aetn s,sr«r aoeYmrrarmeor �7 � ! ,� / .
Approximate Site Location / {•• 5 {' ��
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"L Geotechnical Services, Inc.
Retaining Systems,Slope Stability, Stormwater Management
DETAIL FROM WASHINGTON STATE DEPARTMENT OF
NATURAL RESOUCES MAP OF THE AREA
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om
Approximate Site Location
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ti/ � I i _. !__ _ ,,pp�I� 7 '_ ,I. _- ./ :-�-_ / ^o•f —BeH POINT � 1
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Reference: Washington State Department of Natural Resources Map GM-65,"Geologic Map of the
Vaughn 7.5 minute quadrangle, Pierce and Mason counties, Washington by Robert L. Logan and
Timothy J.Walsh,2007."
"L Geotechnical Services,Inc.
Retaining Systems, Slope Stability, Stormwater Management
i
� Y
View towards the southwest,looking over some of the south end of the property.
"L Geotechnical Services,Inc.
Retaining Systems, Slope Stability, Stormwater Management
j
�M
"tit�1 r� ,}p j r:• ""������>�1��„i�� ���T.'S'[� ��F. j���{.��t 5rkr °'G.�3'"`' �ti�^�.�
�'rf�Y`• },a�s,.,,���+d ti4'+T�a��'� .dl h.Jt F���1�,ltt Y, ���G - y ",rt�l `�'ttSy d.- 't. .,
Gt4r"
aT (t tl
r.
View towards the south,looking over the west side of the property
from the north end of the graded area.
AML Geotechnical Services,Ina
Retaining Systems, Slope Stability,Stormwater Management
s s
View of some of the build-able area,facing towards the southwest
from the northern sector of the property. The tree-line in
the upper foreground is located in the wetland.
AML Geotechnical Services,Inc.
Retaining Systems, Slope Stability,Stormwater Management
Y { 4!1 s 3
F A'4F r' �� ` 6 lRti f�5Y� y! !• t( r 7 '�Jr IVY
01 ar;
I e y
x '� 'f'�•. 1 :: f P �'h F..
� ��' �,r�c y r� ) `� � S s• �`c +l�`?{,i�,,.r a�h f�t,„f`l�A. ��:.
� �E,3.
,... �.• ti .�t`tJ.i t1 .� �./a1 {��,,,r ,Is, "� ��' CL +Cam<� t!
i=
till j 1� j �r�f" 1�Y ub ```•��':
Soil exposed in the graded area of the property. The grass cover is sparse in this area
due to the dense,cemented nature of the soil. Note the gravel content.
AML Geotechnical
RetainingSlope Stability, / l Management