CANOD.pdfCity of Edmonds
Critical Area Notice of Decision
Applicant:
Property Owner:
Critical Area File #:
Permit Number:
Site Location:
Parcel Number:
'? 7 C) 5' 2 q Ck',)
Project Description:(P"J/
(TI
E] Conditional Waiver. No critical area report is required for the project described above.
1. There will be no alteration of a Critical Area or its required buffer.
2. The proposal is an allowed activity pursuant to ECDC 23.40.220, 23,50,220, and/or
23.80.040.
3. The proposal is exempt pursuant to ECDC 23,40,230.
F -I Erosion Hazard. Project is within erosion hazard area. Applicant must prepare an erosion and
sediment control plan in compliance with ECDC 18.30.
Critical Area Report Required. The proposed project is within a critical area and/or a critical area
buffer and a critical area report is required. A critical area report has been submitted and evaluated
for compliance with the following criteria pursuant to ECDC 23.40.160:
1 The proposal minimizes the impact on critical areas in accordance with ECDC 23.40,120,
Mitigation sequencing;
2. The proposal does not pose an unreasonable threat to the public health, safety, or welfare
on or off the development proposal site;
3. The proposal is consistent with the general purposes of this title and the public interest;
4. Any alterations permitted to the critical area are mitigated in accordance with ECDC
23,40.110, Mitigation requirements.
5. The proposal protects the critical area functions and values consistent with the best
available science and results in no net loss of critical functions and values; and
6, The proposal is consistent with other applicable regulations and standards.
E] Unfavorable Critical Area Decision. The proposed project is not exempt or does not adequately
mitigate its impacts on critical areas and/or does not comply with the criteria in ECDC 23.40. t60 and
the provisions of the City of Edmonds critical area regulations. See attached findings of
noncompliance,
Zr' Favorable Critical Area Decision. The proposed project as described above and as shown on the
attached site plan meets or is exempt from the criteria in ECDC 23,40.160, Review Criteria, and
complies with the applicable provisions of the City of Edmonds critical area regulations. Any
subsequent changes to the proposal shall void this decision pending re -review of the proposal,
F1 Conditions, Critical Area specific condition(s) have been applied to the permit number referenced
above. See referenced pert -nit number for specific condition(s),
Reviewer
A,
Signature
I /cC
) I ( '
0
Dateu
Appeals: Any decision to approve, condition, or deny a development proposal or other activity based on the
requirements of critical area regulations may be appealed according to, and as part of, the appeal procedure, if any,
for the permit or approval involved.
Revised 12/16/2010
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EOSPECTRUM CONSULTANTS., iNCE
Engineering
y cyncl Ecirth Sc-,,iences
Mr. Greg Jacobsen
c/o Krannitz Gehl Architects
765 NE Northlake Way
Seattle, WA 98105
SUBJECT: GEOLOGICALLY HAZARDOUS AREAS EVALUATI*1�
Dear Greg,
RECEIVM�
MAY 0 1 2014
DEV�,'-aOPMENT SEMMES Uff
0 N OF EDMONDS
ilvifl
This report presents our geotechnical evaluations and recommendations for
construction of the subject proposed residence. Our services are provided in
-Rccordance with the scope and conditions of our proposal dated October 2, 2013.
Review of Edmonds ECA Inventory mapping indicates that the site lies in an erosion
hazard area and the west slope is considered to be a landslide hazard but the site is
not indicated to be within a seismic hazard area.
We have not been provided any structural load information, but based on our
experience we expect that bearing wall loads will be on the order of I to 3 kips per foot
and column loads are expected to range from about 10 to 20 kips. If actual structural
loads exceed the above values by more than 25%, this office should be notified.
F, 0. Bc-o,- 276-, kscyqcicit i, W/k 98CX, 74)2. 76 (42�) 397-4-228 Fcy,%,'- (4,25) 39
Jacobsen December 4, 2013
COPE OF WORK
Our work has included site reconnaissance, subsurface explorations, engineering
evaluations and the preparation of this report. The scope of work included the following
specific tasks:
o Review of published geologic mapping and Edmonds ECA Inventory Maps
of geologically hazardous Areas maps for the site vicinity.
o Performed a site reconnaissance to observe conditions on the site which
is adjacent to a bluff slope within the BNR right-of-way.
o Performed hand auger borings to explore the subsoil conditions at the
new residence site. Approximate locations of the borings are shown on
Figure 2 and logs of the borings are included in Appendix A.
o Performed engineering evaluations of the surface and subsurface
conditions observed and developed geotechnical recommendations for
foundation design and construction including slope buffer and setback
plus geotechnical recommendations general site development.
o Prepared this geotechnical report summarizing our findings and
geotechnical recommendations for site development including slope
buffer and setback, foundation design and construction, subgrade
preparation, erosion control and drainage control.
Surface Conditions
Our site observations and explorations were made on 11/13/13. The property is
located at the north end of Hanna Park Road and extends from about 100 feet east of
Hanna Park Road to the Burlington Northern Railroad ROW on the west.
Topographically the site is located in a nearly flat terrace area above the northwesterly
facing coastal bluff which drops down to the railroad tracks as shown in Figure 2. The
proposed residence will be located within the upper terrace area approximately where
the existing house is currently located and will be bordered on the north and south by
neighboring residential property within the terrace area and on the west by the very
steep coastal bluff slope as shown in Figure 2.
The proposed building site area is on the upper terrace is currently occupied by the
existing residence and is well vegetated with lawns, thick shrubbery particularly along
the property lines and a few trees as shown on Figure 2.
Project No. 13®133-01 Page 2
Jacobsen December 4, 2013
Our observations of the existing bluff slope indicates that it is well vegetated with thick
shrubbery along the top of the slope except within about the southern 40 to 50 feet
which did not have shrubbery but did have scattered grass and blackberries. Based on
the topography of Figures 2 and 4 the bluff slope is about 25 to 28 feet in vertical height
and is very steep with slope angles ranging from about 50 to 55 degrees based on our
field measurements.
We observe evidence of previous shallow sliding of the bluff slope at three locations
within the southern slope. The heavy shrubbery to the north was 4 to 5 feet in height
and obscured any view of the top of slope in that area.
We noted the tile -covered patio slab near the center of the west side of the existing
house had severe settlement and cracking that appeared to increase towards the north
side of the patio. We also noted two conduits in the house wall immediately north of
the patio but could not determine if they were roof down spouts (no rain at the time of
our observations).
Subsoil Conditions
We drilled four hand auger borings at the approximate locations shown on Figure 2.
Detailed logs of the our borings are presented in Appendix A.
Subsoils encountered in our explorations included a variable depth of fill and weathered
natural soils overlying stiff to very stiff and dense to very dense natural soils.
Loose/soft fill and weathered soil thickness ranged from about 1 to 3.5+ feet thick at
our borings locations. Fill soils were encountered to depths of about 2+ feet at the HA-
2 boring location and included topsoil and silty fine sand with clay. The natural soils
encountered included silty fine sand with gravel, silty sand with clay, clayey sand,
sandy silt and clayey silt which became dense to very dense and stiff to hard at depths
of about 1 to 3 feet below the natural ground surface (below any existing fill soils).
Ground Water Conditions
No ground water was observed in any of the borings to the maximum auger depth of
4.5 feet but the subsoils at all boring locations were field classified as moist to very
moist and the soils at HA -2 were classified as very moist to wet.
Measured moisture contents of the soil samples typically ranged from about 10 to 26
percent.
Project No. 13-133-01 Page 3
Jacobsen
Site Geology
December 4, 2013
Review of published geologic mapping (Figure 1) indicates that the surface soils in the
site vicinity (Qw) are older deposits of the Whidbey Formation, pre -dating the Fraser
glaciation that ended about 13,500 to 15,000 years ago. The Whidbey formation
deposits were glacially consolidated during the Fraser Glaciation. The Whidbey
formation is described as interglacial sediments which are typically bedded, compact,
medium to coarse-grained sands, however the onsite soils encountered were generally
finer grained with fine sand, silt and clay but were dense to very dense and stiff to very
stiff, consistent with glacially consolidated deposits.
Geologic Hazards
Review of Edmonds ECA Inventory mapping indicates that geologic hazards mapped
within 200 feet of the site are limited to erosion hazard and landslide hazard. The site
is not indicated to be within a seismic hazard area.
Landslide Hazard Assessment
The existing bluff slope that borders the west side of the site is considered to meet the
criteria for Landslide Hazard Areas presented in 23.80.020 B of the Edmonds code
based upon its height and very steep inclination.
Our review of the geologic map of Figure 1 indicated no major landslides mapped within
the area included on Figure 1 (more than 1 mile radius around the site). Based on our
surface observations, combined with our shallow explorations and review of the
geologic map of Figure 1, the bluff is composed of dense to very dense and stiff to very
stiff /hard glacially consolidated soils. Our observations of the existing bluff slope
surface and the area above the slope revealed no evidence of deep seated instability of
the slope although we did observe evidence of past shallow slide scars within the
southern portion of the slope.
As with all hillside development, you the owner must be aware of and accept the risk
that future slope failures may occur and may result in damage to your property and/or
neighboring property. In our opinion, the bluff slope is stable with regard to gross or
deep seated stability of the glacially consolidated deposits. However considering the
very steep slope inclination and the observed shallow slide scars, in our opinion there is
a moderate to high risk of future shallow skin failures or sloughing of the bluff slope face
over time. In general shallow slope failures are most likely to occur during the winter
and spring months due to increased soil moisture conditions and during earthquake
shaking due to the additional dynamic loads on the slope.
Project No. 13-133-01 Page 4
Jacobsen December 4, 2013
The risk of structure damage resulting from a shallow slope failure varies with the
distance from the slope. In general to minimize risk, structures should be set back from
the top of adjacent steep slopes as far as practical within the constraints of the
development plans. As a minimum we recommend an average buffer of 20 feet plus a
15 foot setback from the buffer to the structure. Our recommended buffer and setback
lines are shown on Figure 4. Due to variations in the location of the top of slope our
recommended buffer varies from about 17 to 23 feet but averages about 20 feet. For
design the buffer line should be assumed to be 17 feet from the western property line
shown in Figure 4 and the building setback line should be 15 feet east of the buffer or
32 feet from the western property line. Provided that the structure is located behind
our recommended minimum buffer and setback and supported on undisturbed
dense/stiff natural soils, future shallow skin failures and sloughing of the bluff slope
should have no impact on the proposed structure.
In our opinion provided that the recommendations of this report are incorporated into
the design and construction procedures, the proposed residence will not adversely
impact the subject property or adjacent properties and will not adversely impact other
geologic hazard areas.
Erosion Hazard Assessment
The USDA soil mapping of the site area indicates the onsite soils to be Alderwood-
Urban land complex, 2 to 8 percent slopes. Per the criteria for Erosion Hazard Areas
presented in 23.80.020 A of the Edmonds code, the upper site is not considered an
erosion hazard area due to the very minor surface gradients which are much less than
15 percent plus the fact that we did not observe any visible evidence of ground water
seepage on the site. However the bluff slope is considered to be an erosion hazard per
the criteria due to the very steep gradients of the bluff.
Currently the property is generally well vegetated and we observed no indication of
seepage or ongoing erosion areas on the upper site. However, the existing site survey
of Figures 2 and 4 indicates that there is a discharge line from the yard drain catch
basin near the southwest corner of the house that discharges on the bluff slope about
10 feet above the toe of the steep slope.
Based on our site explorations the subsoils are generally silt -clay -sand mixtures and are
considered to have a moderate erosion potential if exposed to concentrated water flow
in graded or disturbed areas. We recommend that the current drain line discharging on
the slope be closed and the discharge be tightlined to the storm drain system (or as a
minimum, the existing pipe should be extended down to the ditch line at the toe of slope
- if allowed). We have provided recommendations for drainage control and erosion
control during and after construction to prevent uncontrolled water flow over the site and
bluff slope surfaces. In our opinion, erosion risk should be low if our recommendations
are followed.
Project No. 13-133-01 Page 5
Jacobsen
Seismic Considerations
December 4, 2013
Although the site is not mapped as a seismic hazard area, the Puget Sound region is a
seismically active area and you should be aware of the potential for seismic shaking
and associated secondary effects. About 17+ moderate to large earthquakes (M5 to
M7+) have occurred in the Puget Sound and northern Cascades region since 1872 (141
years) including the 2/28/01 M6.8 Nisqually earthquake and it is our opinion that the
proposed structure will very likely experience significant ground shaking during its
useful life.
The site lies only about 5 miles southwest of the mapped fault zone of the South
Whidbey Island fault which also has a postulated maximum credible earthquake
magnitude of 7.0 to 7.5. The recurrence intervals of large earthquakes on the South
Whidbey fault (SWF) is not known but recent data indicates that a earthquake on the
order of M6.5 to 7.0 occurred on the SWF about 3000 years ago and smaller events
occur more frequently as evidenced by the 5.3 event on May 2, 1996 which was
attributed to that fault.
Based on a recently published study by the USGS, the site is also located about 18
miles north of the inferred east -west trending Seattle fault zone which passes through
Seattle and trends along the 1-90 corridor. The Seattle fault has a postulated maximum
credible earthquake magnitude on the order of 7.0. The Seattle fault has been
documented to have moved at its west end (Bainbridge Island) about 1000 to 1100
years ago and evidence of movement at the east end has also recently been
documented. Some experts feel that the recurrence interval between large events on
the Seattle Fault may be on the order of several thousands of years but our calculations
indicate it may be on the order of 1200 to 1400 years.
Another recent study (2004) of the Vashon-Tacoma area presents evidence for the
east -west trending Tacoma Fault which is indicated to pass through the south end of
Vashon and the middle of Maury Island about 32 miles south of the site. The study
suggests that the Tacoma Fault and the Seattle fault may be linked at depth.
In addition to Puget Sound seismic sources, a great earthquake event (M8 to M9+) has
been postulated for the Cascadia Subduction Zone (CSZ) along the northwest Pacific
coast of Oregon, Washington and Canada. The current risk of a future CSZ event is
not known at this time. Published reports have indicated recurrence intervals for a CSZ
event to range from as little as 100-200 years to as long as 1000+ years and the time of
the last event is reported to have been in January 1700, nearly 314 years ago.
Considering all of the above, it is our opinion that the proposed residence will very likely
experience significant ground shaking during its useful life. The 2012 International
Building Code (IBC) adopted requires that a Maximum Considered Earthquake
Geometric Mean (MCEG) peak horizontal ground acceleration (PGA) be used for site
liquefaction evaluations. The PGA of the 2012 IBC is based on consideration of both
Project No. 13-133-01 Page 6
Jacobsen December 4, 2013
the Washington coast or from a local earthquake in the Puget Sound region.
Tsunamis risk at your site is somewhat reduced by its location within Puget Sound
which provides some protection from Pacific Ocean tsunamis waves and by the 30+
foot high shoreline which would provide protection from smaller tsunami wave heights.
A tsunamis resulting from a local earthquake could come ashore within minutes of the
earthquake that generates it. We recommend that when a future large earthquake
occurs that you evacuate the subject residence immediately and go to higher ground at
least 100 feet above the beach level and remain there until authorities determine that
there is no tsunamis hazard.
6mfflimamaA MI
In our opinion, the existing fill and loose/soft weathered soils are not suitable for
foundation support. Therefore the new foundations must extend through the fill and
weathered soils into the underlying natural bearing soils encountered at depths of about
1 to 3.5+ feet below ground at our boring locations. We recommend that foundations
for the proposed residence be extended through the existing loose/soft fill soils to bear
within the underlying very dense/stiff/hard natural soils and that the foundations are
located behind the recommended buffer + setback shown in Figure 4.
As an alternative to deep spread footings to penetrate fill and unsuitable soils
foundation loads may be transferred from the recommended minimum foundation
depths to the recommended bearing soils by a monolith of lean concrete.
Recommendations for spread footings optionally supported on a lean concrete monolith
are presented in the RECOMMENDATIONS section of this report.
The observed settlement and cracking of the west side patio slab of the existing house
was likely due to poor subgrade fill and poor drainage design. Our recommendations
fM r subgrade preparation and site drainage should be followed in design and
construction of the proposed new residence.
It should be noted that fill and weathered soil thickness will vary across the site and
may be greater than encountered at the boring locations. Much of the subsoils were
very moist to wet and would require drying back to a suitable moisture content for use
in compacted fills. Ground water may be encountered depending upon the time of year
and de -watering may be required for foundation construction excavations if ground
water levels are above the bearing soils.
Project No. 13-133-01 Page 8
ffl•�
1014OXII,
The following presents our recommendations for design and construction of
foundations, site grading, site drainage, erosion control and observations and testing
during construction.
901�1=Wwo
Conventional spread footings founded on undisturbed dense/stiff natural soils should
provide good support for the proposed residence. Footings should be at least 18
inches wide and all footings should be behind the recommended buffer + setback
shM wn in Figure 4. Footings should also be setback beyond a 1:1 (h:v) projection from
adjacent lower footings. Footing design may be based on
Based on the subsoil conditions encountered at our boring locations footing
embedment depths are expected to range from about 3.5 to 4. feet below the existing
s u rfa ce. As an alternative to deep spread footings to penetrate fill and unsuitable
soils, foundation loads may be transferred from the recommended minimum foundation
depths to the recommended bearing soil embedment by a monolith of lean concrete
having a minimum compressive strength of 1,000_psi,, The width of an un -reinforced
lean concrete monolith should be at least as wide as the footing or at least one-third of
the monolith height, whichever is greater. Reinforced monoliths should be designed by
a structural engineer. A suitable width trench should be excavated with a smooth
edged excavator bucket (no teeth) to expose and clean the very stiff/hard bearing soil
surface (no personnel in the trench) under observation by our office and backfilled as
soon as possible (at least the same day) with the lean concrete to the footing elevation.
Settlement of the structure is expected to be within tolerable limits for this type of
construction. For example, the estimated settlement of a 18 inch wide continuous
footing carrying a load of 3 kips/ft. is on the order of 1/2 inch. Maximum differential
settlement within the proposed structure is expected to be on the order of 1/4 inch.
Settlements are expected to occur primarily during construction.
Resistance to lateral loads can be assumed to be provided by friction acting at the base
of foundations and by passive earth pressure. A coefficient of friction of 0.4 may be
assume with the dead load forces in contact with on-site soils. An allowable static
passive earth pressure of 150 psf per foot of depth may be used for the sides of
footings poured against undisturbed weathered soils or properly compacted fill.
The vertical and lateral bearing values indicated above are for the total dead load plus
frequently applied live loads. For short duration dynamic loading caused by seismic or
wind forces, the vertical bearing values may be increased by 50 percent and allowable
lateral passive pressures may be increased by 33 percent.
Project No. 13-133-01 Page 0
IMMOMMOR
Site grading is expected to be limited primarily to excavation for construction of
foundations and subgrade preparation for slabs and driveway. Footing excavations are
expected to be about 2 to 4 feet deep. Excavation and fill placement within slab and
pavement subgrade areas is expected to be about 1 to 2 feet.
Site Pr���afio�n: Existing vegetation, debris, existing fill and/or loose or soft soils
should be stripped from the areas that are to be graded. During rough grading, excess
soils should be hauled off site and no material should be placed on the slope. Soils
containing more than 1% by weight of organics may be used in planter areas, N
should not be used for fill beneath slab or pavement areas. Stumps, debris and trash
should be removed from the site. Subsoil conditions on the site may vary from those
encountered in our explorations. Therefore, the soils engineer should observe the
prepared areas prior to placement of any -new fills.
Tempora Excavations: Based on the subsurface conditions encountered in out
borings, it is our opinion that temporary excavations in natural soils above the ground
water may be made vertically to depths of 4 feet. Deeper temporary excavations that
personnel will enter should be made at slope gradients no steeper than 1:1
(horizontal:vertical). Excavations that extend below the ground water table should be
de -watered and should be made no steeper than 1.5:1 (h:v). It should be noted that the
contractor is responsible for safety and maintenance of construction slopes.
Structural Fill: In our experience the onsite soils will be moisture sensitive with regard to
compactability for structural fill and the existing silt soils are considered to be generally
too wet for adequate compaction, particularly the silt/clay soils. Excavated sand and
gravel soils are considered technically suitable for general structural fill provided that
they can be dried back adequately for compaction. If moisture contents are too high at
the time of grading, adequate compaction may be very difficult to impossible requiring
the use of clean sand and gravel import material with less than about 10 percent fines
for adequate compaction.
General structural fill should be placed in horizontal lifts not exceeding 8 inches in loose
thickness and compacted to at least 90% of the maximum dry density as determined by
the ASTM D1557 test method. Loose and disturbed soils, form -work and debris should
bM removed prior to placing structural fill or backfill.
Project No. 13-133.-01 Page '10
Jacobsen
Erosion Control
December 4, 2013
Onsite materials are expected to be moderately erodible when exposed to concentrated
water flow therefore drainage should be controlled to prevent concentrated flows.
Exposed soils and stockpiles should be covered during heavy rainfall and no soil should
be placed on the bluff slope or within the slope buffer. Siltation fences or other suitable
detention devices should be provided around soil stockpiles and around the lower sides
of exposed soil areas during construction to control the transport of eroded material.
The lower edge of the silt fence fabric should have "J" shaped embedment in a trench
extending at least 12 inches below the ground surface.
We recommend that the current drain line discharging on the slope be closed and the
discharge be tightlined to the storm drain system (or as a minimum, the existing pipe
should be extended down to the ditch line at the toe of slope - if allowed).
Exposed final graded soil areas should be covered with a non-erosive surface covering
or planted immediately with grass and deep rooted plants to provided permanent
erosion control. In addition we recommend that the exposed soil surfaces of the site be
temporarily covered with straw mulch or other suitable erosion resistant material during
the wet season (11/1 through 3/31) if final erosion control measures are not completed
before 11/1.
Observations and Testing During Construction
Recommendations presented in this report are based on the assumption that soil and
foundation conditions exposed during construction will be observed by our office so that
any necessary design changes or supplements may be made. Footing excavations
should be observed to verify bearing soils plus recommended minimum embedment
and slope setbacks. All subsurface drain systems should be observed by our office to
verify proper construction. Proper pavement and slab subgrade preparation and
structural fill placement and compaction should be observed by our office and verified
with field and laboratory density testing by a qualified testing laboratory.
Project No. 13-133-01 Page 12
Jacobsen December 4, 2013
CLOSURE
This report was prepared for specific application to this project and for the exclusive use
of Mr. Greg Jacobsen and his representatives. The findings and conclusions of this
report were prepared in accordance with the skill and care ordinarily exercised by local
members of the geotechnical profession currently practicing under similar conditions.
We make no other warranty, either express or implied.
Variations may exist in site conditions between those described in this report and actual
conditions encountered during construction. Based on our experience, it is our opinion
that some variation in the continuity and depth of subsoil deposits and ground water
levels should be anticipated due to natural deposition variations and site grading. Due
to seasonal moisture changes, ground water conditions should be expected to change
with time. Care should be exercised when interpolating or extrapolating subsurface
soils and ground water conditions between or beyond our borings.
Unanticipated subsurface conditions commonly occur and cannot be prevented by
merely making explorations and performing reconnaissance. Such unexpected
conditions frequently require additional expenditures to achieve a properly constructed
project. If conditions encountered appear to be different from those indicated in this
report, our office should be notified.
Respectfully submitted,
GEOSPECTRUM CONSULTANTS, INC.
i�t
James A. Doolittl
Principal Engineer
Encl: Figures 1 through 4 I -IJ
Appendix A
Dist: 2/Addressee
Project No. 13-133-01 Page 13
ref: "Geologic Map of the Edmonds East and Part
of the Edmonds West Quadrangles,
Washington", USGS MF -1541, by James Po
Minard, 1983, Scale: 1"= 2000' SITE VICINITY GEOLOGIC MAP
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Edmonds, Washington
Proj. No. 13-133 Date 12/13 Figure 3
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Proj. No. 13-1331 ®ate 12/13 1 Figure 4
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Our field exploration included a site reconnaissance and subsurface exploration
program. During the site reconnaissance, the surface site conditions were noted, and
the locations of the hand auger borings were approximately determined.
The hand auger borings were approximately located using existing structures as a
reference. Elevations at the exploration locations were estimated based on the
topographic mapping included on Figure 2.
The borings were advanced using hand excavation tools. Soils were continuously
logged and classified in the field by visual examination, in accordance with the ASTM
Soil Classification system.
Penetration tests were performed in HA -1 using a 1/2 -inch diameter penetrometer and
a 27.5 -pound driving hammer falling 24 inches. Recorded blows for 12 -inches of
penetration are shown on the HA -1 boring summary.
Logs of the hand auger borings are presented on the boring summary sheets A-1 and
A-2. The hand auger boring summaries include descriptions of the soils and pertinent
field data. Soil consistency and moisture conditions indicated on the logs are
interpretations based on the conditions observed in the field. Boundaries between soil
strata indicated on the logs are approximate and actual transitions between strata may
be gradual.
Logged by JAD
Date: 11/13/13
Depth Blows Class. Soil Description
0 OL Sod & topsoil
SM Silty Sand, fine / , ed to ,parse
1 & graveY, Tine to
10 "
2
3
4 � 75
5 Maximum depth 4.5 feet.
No ground water observed.
6
Logged by
JAD
Date: 11/13/13
Depth Blows Class.
Soil Description
0
OL
topsoil
1
Rt /
Silty fine Sand w/clay
2
3
ML
Clayey w�isand and gravel
-SC....
-Clayey Sated-'VbVeny........
4
Maximum depth 4.1 ft.
5
No ground water observed.
6
7
Consistency Moisture Color
loose moist
dk brc
pd -
Town
Elevation: 47.5'
W(%) Comments
12.1
T edium OwraY-
wn
ense 10.0
very
ha d
Elevation: 43.5'
Consistency Moisture Color W(%) Comments
very
"TI o st
wet
soft
-------- .... dense-tb... -Very
�_ProposedHanna
Park '• •
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Logged by JAD
Date: 11/13/13
Depth Blows Class. Soil Description
OL topsoil
1 SM Silty Sand, fine w/ ravel
W/trace ctgay
2-
............
ML Sandv Silt ve fine w/trace
3-
4-
5-
45 Maximum depth 3 feet.
No ground water observed.
6-
7-1
Logged by JAD
Date: 11/13/13
Depth Blows Class. Soil Description
OL topsoil
1 ML Sandy Silt, very fine w/clay
2
3 w/ ravel
4
5 Maximum depth 3 ft.
No ground water observed.
6
Elevation: 43.5'
Consistency
Moisture
Color W(%) Comments
loose
moistIbrow
o
Drown
firm
most
dense to
v. ense
most
Light
own
.............
bei%m 19.5
stiff
moist
gran
15.2
... l0t...... 15.3
very stiff
e -brn
22.3
Elevation: 44'
Consistency
Moisture
Color W(%) Comments
loose
moistark
o
grown
firm
most
brown
----------
...................
mo7st
.............
bei%m 19.5
stiff
.......
... l0t...... 15.3
Proposed Residence Replacement
741 Hanna Park Road
GEOSPECTRUM CONSULTANTS, INC.,
Engineering ofi,70 Ecyrtti
April 9, 2013
Mr. Greg Jacobsen
c/o Krannitz Gehl Architects
765 NE Northlake Way
Seattle, WA 98105
SUBJECT: GEOTECHr
• ed
osed Residence Replacement
741 Hanna Park Road
Edmonds, Washington
Project No. 13-133-01
We understand that you propose to a construct a partial basement under your new
residence. This addendum supplements our previous report dated 12/4/13 with regard
to our evaluations and recommendations for design of basement retaining walls. Our
work was performed in accordance with the scope and conditions of our proposal dated
October 2, 2013.
Static design of basement walls structurally braced against movement should' be based
on an equivalent fluid density of 60 pcf. This pressure assumes that the wall supports a
horizontal backfill of properly compacted free -draining granular material and that there
is no water pressure behind the wall. Uniform lateral pressure due to a uniform vertical
Surcharge behind a braced wall should be computed using a coefficient of 0,45 times
the uniform vertical surcharge load.
Cantilevered retaining walls as referred to in this report are walls which yield or move
outward during and after backfilling. Actual wall movements will depend on the wall
B'c"ix 276, txT/-1, W/A (4-25) 3511-422-85
Jacobsen
March 20, 2014
This addendum was prepared for specific application to the subject site and for the
exclusive use of Mr. Greg Jacobsen and his representatives. The recommendations
presented herein are based on the assumption that soil conditions exposed during
construction will be observed by our office so that any necessary design changes or
supplements may be made.
Our work was performed with the skill and care ordinarily exercised by local members of
the geotechnical profession practicing under similar conditions in the same locality.
We make no other warranty, either express or implied.
Respectfully submitted,
•SPECTRUM I�SULTANTS, INC.
'
DoolittleJames A.
Principal•
Dist: 1/Addressee via email
EXPIRES�1r91
M --
Project No. 13-133-01 Page 3
e3eotechniccyl En
Mr. Greg Jacobsen
c/o Krannitz Gehl Architects
765 NE Northlake Way
Seattle, WA 98105
SUBJECT: SUPPLEMENTAL EVALUATIONS
Proposed West Yard Grading and Hot Tub
741 Hanna Park Road
Edmonds, Washington
Project No. 13-133-01
In accordance with a request from Bryan Krannitz, this is to confirm our evaluations and
recommendations regarding the subject minor west yard grading and siting of the
proposed hot tub as shown on the attached Figures 1 and 2. We have previously
prepared a geotechnical evaluation report dated December 4, 2013 for your new
residence.
The existing bluff slope that borders the west side of the site is considered to be a
Landslide Hazard Area based upon its height and very steep inclination per the criteria
presented in 23.80.020 B of the Edmonds code.
southernBased upon our previous site observations and shallow explorations and review of tht;
geologic map, the bluff is composed of very den'se/hard glacially consolidated soils.
Our previous observations of the existing bluff slope surface and the area above the
slope revealed no evidence of deep seated instability of the slope on the site or on the
adjacent properties but we did observe evidence of previous of shallow instability in the
portion of •t^
T1^ previously recommended a variable slope buffer that ranged from about- •
23 feet ' from the top of slope due to variations in the top of slope location but averaged
about 20 feet plus a normal 15 foot setback for siting your new residence per the
development standards of section 23.80-070 of the Edmonds code.
P 0. Box 276, Isso.quah, WA 98027-02,76 - Phone: .1425) 391-4228 Fay: (,12 ) 391 2
April 25, 2014
The proposed west yard grading is shown in Figure 1 and will occur within the steep
slope buffer. Based on the sketch of Figure 1, the grading will be limited to a thin cut
between elevation 43 and 44 to create a maximum net grade reduction of about 1 foot.
In our opinion the proposed grading shown in Figure 1 will not adversely impact the
critical area and will not increase the threat of geological hazard to adjacent properties
beyond pre -development conditions provided that our supplemental recommendations
presented below are followed.
We recommend that the proposed cut grading within the buffer be performed per the
following conditions:
o Grading within the buffer should be performed only during the dry season
between 6/1 and 9/1.
A properly constructed siltation fence or other suitable erosion control barrier
shoulN be constructed around the north, west and southern perimeters of the
graded area before grading is started.
o The graded area should be re -vegetated immediately such that the disturbed
surface is fully vegetated and stabilized by 11/1.
largrorswron
The proposed location of the hot tub as shown on Figure 2 extends about 3 feet into the
previously recommended buffer + setback, Although the roof limits of the outdoor
room at the northwest corner of the house shown in Figure 2 also extend into the
setM ack we understand that the roof is structurally supported east of our previously
recommended buffer + setback.
Considering the light load and small size of the proposed hot tub structure we support a
3 foot buffer reduction (14 feet east of the west property line) + 15 foot setback for siting
of the hot tub provided that it is founded on the dense/very dense natural soils. We
also note that the actual top of slope at the hot tub location is approximately 3+ feei
west of the west property line indicating the buffer +setback from the top of slope
location nearest the tub will still be 32+ feet (the minimum previously recommended).
In our opinion the reduced buffer for the hot tub location shown will not adversely
impact the critical area and will riot increase the threat of geological hazard to adjacent
properties beyond pre -development conditions.
Project No. 13-133-01 Page 2
Jacobsen
This letter was prepared with the skill and care ordinarily exercised by local members of
the geotechnical profession practicing under similar conditions in the same locality.
We make no other warranty, either express or implied.
Variations may exist in site conditions between those described in our previous report
and actual conditions encountered during construction. Unanticipated subsurface
conditions commonly occur and cannot be prevented by performing reconnaissance or
explorations. Such unexpected conditions frequently require additional expenditures to
achieve a properly constructed project. If conditions encountered during construction
appear to be different from those indicated in our previous report, our office should be
notified.
Sincerely,
GEOSPECTRUM CONSULTANTS,
James A. Doolittle
Principa
•• -
..l Engineer
Attachment:
. --
Attachment: Figures 1 and 2
dist: 1/Addressee
Project No. 13-133®01
COMBINED STEEP SLOPE BUFFER
AND BUILDING SETBACK PER GEOTECH
REPORT
ORDINARY 5ETBACK
MAX EAVE PROJECTION INTO
STRUCTURE SETBACK
25'-0" 30" EAVE EXCLUSION FROM
HEIGHT RECTANGLE
EXISTING LANDSCAPING
SHRUBBERY
'44
B ' EXISTING RESIDENCE A
43.97 (TO BE DEMOLISHED) 78' 45 N62
�PR-0 NGL -FA' Auro col
ELLIN6
N IF TIAL BA M
tp O r t �1AIjJ2�jcELfLEv
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i411-
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AT GRADE ISe� ! - —
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w
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I42.86' RECT
ADJACENT PROPERTY
is 40
STRUCTURE FOOTPRINT
BUILDING SETBACK
GFR rFfTfF/]H RFGl1RT
ref: Portion of Site Plan transmitted 4/22/14,
by Krannitz Gehl Architects
Proposed Hot Tub Buffer + Setback
Proposed Residence Replacement
GEOSPECTRUM CONSULTANTS, INC.741 Hanna Park Road
is i4'":.:: v.., \"..••..
x: ..{•:
i<
Edmonds, Washington
s
Goat®chn/cca/ Eng/no®i/nc� and Ear/h_ Sc/®nc®s
Proj. No13-133 Date 4/14 Figure 2
Proposed Grading Area
ref® Partial Site Plan transmitted 4/22/14,
by Krannitz Gehl Architects
Proposed West Yard Grading
Proposed Residence Replacement
GEOSPECTRUM CONSULTANTS, INC.741 Hanna Park Road
Edmonds, sr i
Washn
ori•
Washington
qq 4
?iX'
�®ot®chnlco/ Eng/na®r/ng and Eorth Sc/®nccs
Proj. No13-133 ®ate 4/14 Figure 1
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F'67
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• J' i fAL. Y' 1' 1 '•
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ON
7
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ref® Partial Site Plan transmitted 4/22/14,
by Krannitz Gehl Architects
Proposed West Yard Grading
Proposed Residence Replacement
GEOSPECTRUM CONSULTANTS, INC.741 Hanna Park Road
Edmonds, sr i
Washn
ori•
Washington
qq 4
?iX'
�®ot®chnlco/ Eng/na®r/ng and Eorth Sc/®nccs
Proj. No13-133 ®ate 4/14 Figure 1
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