CANOD.pdfCity of Edmonds
Z,ritical Area Notice of Decision
Applicant:
Property Owner:
Critical Area File
Permit Number:
(36P
Site Location:V�-
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Number:
I Parcel Num
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Project Description:
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F-I 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.
;g -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. X 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.
Fj 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 23.40,160 and
the provisions of the City of Edmonds critical area regulations. See attached findings of
noncompliance.
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.
❑ Conditions. Critical Area specific condition(s) have been applied to the permit number referenced
above, See referenced permit number for specific condition(s).
Reviewer V
Signature U
// "'' Z
S
Date
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
1161
February 21, 2012
HWA Project No. 2012-000-21 Task 4
Mr. David. Clobes
7425 Olympic View Drive
Edmonds, Washington 98026
Subject: GEOTECHNICAL REPORT
Deck Construction
7425 Olympic View Drive
Edmonds, Washington
Dear Mr. Clobes;
This report addresses the applicable requirements of the EC-DCwith -regard to the removal
(demolition) or salvaging a portion of a new deck which we -understand was constructed within
the western portion of your property located at 7425 Olympic View Drive (See Figure 1) without
a permit review or approval by the City of Edmonds. Cornmunications from the City of
Edmonds indicate that the deck was constructed within the minimum required setback from a
Landslide Hazard Area, within an Erosion Hazard Area, and extends into the 25 -foot setback
from the western property line. The purpose of this report is to investigate whether the new deck
was founded on suitable bearing soils, and conclude to what degree the existing deck (or
_proposed modified version thereof) or its removal, will impact local slope stability and the
potential for site erosion consistent with the requirci-rients of the ECDC. Our work included a
site reconnaissance, limited subsurface exploration, code review, and writing this report.
PRINIOUS WORK
In 2003, HWA prepared a geotechnical report for you entitled "Geotechnical Report -Proposed
Extension to Residence: 7425 Olynipic Viei,t, DrNe, Edmonds, Washington, 98026 " for the
purpose of designing and permitting an extension to tfie existing residential structure. At the
time of this current study, the extension has not been constructed. The geologic information
contained in our previous report was used supplement our location specific assessment.
PR0i-r,,c,f DESCRIPTION
Currently, an elevated wooden deck is attached to the noi-thwestern side of the residential
Structure, The deck is approximately 28 feet long and extendsouttwards from the residence to
the northwest about 17.5 feet, as shown. on Ficytire 2, Deck floor elevations apparently match
2 Dr� ve
those of your upper floor. The deck structure issupportedl. by 2 13 � 3001 rows of three, St6k' SE I W
6 --inch by 6 -inch, wooden posts spaced. approximately7to 8 feeth
apait, Within the holheH, WA 9802A�YWO
rows, the posts are spaced 12 to 13 feet apartIN ear the grotind. posts are set on
Tel� 4)".TM MM'
F< 4211'774.27M
February 21, 2012
HWA Project No. 2012-000-21 Task 4
12 -inch diameter cast -in place concrete piers and are secured by bolts into steel brackets that
were embedded in the concrete at the time they were cast (See Photo 1). The concrete piers
extend into the ground to slightly varying depths and rest on individual 4 -foot by 4 -foot concrete
footings. As it is currently situated, the deck extends 10 feet into the setback buffer area for the
western property line. In addition, the deck is situated within the minimum required set back for
an Erosion and Landslide hazard area, as defined in ECDC Section 23.80.070.A. I a.
SITE DESCRIPTION AND OBSERVATIONS
The lot has approximate dimensions of 160 feet by 90 feet and is located on the northeast side of
the intersection of Olympic View Drive and Homeview Drive (Figure 2). Residential lots border
the north and east sides of the property. A steep slope area is located along the north property
line. The ground surface slopes southwards at about 56% declination, but is locally as steep as
109% near the northeast property line. The top of the slope is at about El. 330 feet which is
about 26 feet above the lower floor elevation (El. 304 feet). There are no signs of previous
slope instability, or evidence of slope creep that might be inferred from trees with bent trunks.
Slope vegetation consists mainly of ivy with several large coniferous trees. No slope vegetation
that is typically indicative of seepage or very moist conditions was noted. A rockery is located
about 10 feet from the northern side of the house to provide a private deck. The deck is at El.
313 feet and the rockery is about 7 feet high. The rockery shows no signs of instability, or
seepage through the wall.
SUBSURFACE EXPLORATIONS
The soil conditions supporting the new deck foundations were explored by means of one hand
auger boring (designated HH -5) and supplemented with hand probing utilizing a 6 -foot long, 1/2 -
inch diameter, steel rod. It should be noted that the soil and ground water conditions described
are only for the specific dates and locations reported and, therefore, are not necessarily
representative of other locations and times. It is anticipated that water conditions will vary
depending on seasonal precipitation, local subsurface conditions and other factors.
SUBSURFACE CONDITIONS
According to the geologic map by Minard, J.P (1983), "Geologic Map of the Edmonds East and
Part of the Edmonds West Quadrangles ", the slope consists of advance outwash comprising
mostly clean, pebbly, sand with fine-grained sand and silt common in the lower part of the unit.
Glacial till is present at the top of the slope. Undisturbed advance outwash is typically dense to
very dense. Slopes in glacial outwash, typically slough to the angle of repose of the sand of
around 30° to 330. When slope instability occurs in glacial outwash, it is mainly confined to
loose surficial layers, but deep-seated slides can occur near the contact with less permeable
glacial silts and clay near the base of the deposit. Within the area of the new deck, soil
conditions explored are as follows:
HH -5
0-0.33 feet: Dense crushed rock (Crushed rock -Fill).
Report 2 HWA GeoSciences Inc.
February 21, 2012
HWA Project No. 2012-000-21 Task 4
0.33-1.25 feet: Medium dense, brown gravelly, silty fine -medium SAND (Fill).
1.25 — 5.0 feet: loose to Medium dense, brown to brownish gray, gravelly, silty fine -medium
SAND (Fill).
5.0-5.5 feet: Medium dense, olive gray, coarse to medium SAND with silt (Weathered Outwash).
5.5 to 6.0 feet: Dense, gray, fine -medium SAND (Advance Outwash).
Auger boring terminated at 6.0 feet due to refusal on dense soils.
No indication of seepage was observed while conducting this hand boring.
PB -1
Hand probing adjacent to the northernmost deck footing situated along the row nearest the
existing residence indicated that dense soils are present a somewhat shallower depth than what
was found at the location of HH -5. Our hand probe met with refusal at an approximate depth of
4.0 feet below the existing grade.
We expect that the pocket of loose material encountered at HH -5 thins to the north (as inferred
from P13-1) and is likely dumped material from the original house construction.
PROJECT CONSIDERATIONS
We understand that currently you are considering two alternatives with regard to the disposition
of the deck:
1) Remove the deck which requires a demolition permit from the City of Edmonds, or;
2) Reduce the footprint of the deck so it no longer encroaches into the property line buffer
and obtain a building permit post -construction.
Deck Removal
Removal of the deck and restoration of the disturbed area should be conducted in accordance
with the minimum performance standards described in ECDC Section 23.40.240.0 which states
that:
a. The hazard shall be reduced to a level equal to, or less than, the predevelopment hazard,-
b.
azard;b. Any risk of personal injury resulting from the alteration shall be eliminated or
minimized; and
c. The hazard area and buffers shall be replanted with native vegetation sufficient to
minimize the hazard.
Currently, the deck foundations are situated within a relatively level side yard located along the
western side of the existing residential structure (See Figure 2 and Figure 3). The alteration of
the site ground surface to construct the deck required the installation of 6 cast -in-place concrete
piers and associated below grade footing slabs. These would be the only portions of the deck
structure for which demolition/removal would require additional disturbance of the potentially
Report 3 HWA GeoSciences Inc.
February 21, 2012
HWA Project No. 2012-000-21 Task 4
critical area. Clearly, the above ground portions of the foundation system should be removed to
eliminate the potential nuisance created by projecting concrete piers. However, in our opinion
the excavation and removal of the entire subsurface portions of the deck foundation system will
not serve to reduce the potential hazard. Indeed, additional subsurface disturbance in this area
can only serve to increase the potential for erosion. Therefore, we recommend that the concrete
piers be demolished in-place to a depth of at least 6 -inches below grade and then restoration of
the ground surface should consist of placement of a layer of crushed rock to match local grade.
In this way, we believe the hazard is reduced to a level equal to the predevelopment hazard and
that the finished ground surface is protected from erosion.
Deck Reduction
We understand that consideration is being given to submit a request for approval for a
development permit for a deck of reduced size to eliminate encroachment into the western
property line setback buffer. This would involve reducing the existing deck width by 10 feet
retaining only a strip 7.5 feet wide (about 0.5 feet beyond the innermost line of piers) and the
demolition of the remaining structure.
Construction of the deck is considered an alteration within an erosion and landslide hazard buffer
area by the ECDC. In accordance with ECDC Section 23.80.060, alterations of geologically
hazardous areas or associated buffers may only occur for activities that.
1. Will not increase the threat of the geological hazard to adjacent properties beyond
predevelopment conditions;
2. Will not adversely impact other critical areas;
3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to
or less than predevelopment conditions; and
4. Are certified as safe as designed and under anticipated conditions by a qualified engineer
or geologist, licensed in the state of Washington.
In addition, in accordance with ECDC Section 23.80.070.A.2, alterations of an erosion hazard or
landslide hazard area and/or buffer may only occur for activities for which a hazards analysis is
submitted and certifies that:
a. The development ,ill not increase suuface water discharge or sedimentation to
adjacent properties beyond predevelopment conditions;
b. The development will not decrease slope stability on adjacent properties; and
c. Such alterations will not adversely impact other critical areas,-
Report
reas;
Report 4 HWA GeoSciences Inc.
February 21, 2012
HWA Project No. 2012-000-21 Task 4
The geologic map, our past site experience and our current explorations show that the project
area is underlain by advance outwash. The excavations to accommodate the deck foundation
appear to have been extended through fill soils down to dense native advance outwash soils.
These soils consist of dense, granular, well drained, sand that are typically not subject to global
or deep rotational failure. The most significant risk posed by development in this portion of the
site is likely a temporary increased potential for erosion during construction. This potential
hazard appears to have been mitigated by post construction regrading and replacement of the
crushed rock surface covering. The deck itself has been installed in an area that did not require
modification of the steep portion of the existing hill slope and does not extend any closer into the
geologically sensitive area than the existing residential structure. In our opinion, the deck, in its
reduced configuration will have a minimal impact on site slopes or adjacent properties and will
not increase the hazard level associated with occurrences of shallow landslides, as foundation
loads have been transferred down to deeper competent native (advance outwash) soils below the
shallow existing fill. We conclude that the constructed improvements will not impair local
stability to any significant degree and should be permitted as allowed under the provisions
specified in ECDC Sections 23.80.060 and 23.80.070.A.2.
Abandoned footing piers should be demolished and the surface areas restored as described in the
previous report section.
CONDITIONS AND LIMITATIONS
We have prepared this letter report for use by David Clobes and his designated agents for use in
permitting the demolition of, or obtaining a permit (post construction) for the construction of a
deck of reduced size along the west side of the existing single-family residence on the property.
Experience has shown that soil and ground water conditions can vary significantly over small
distances. Inconsistent conditions can occur between explorations and may not be detected by a
geotechnical study of this nature. If, during future site operations, subsurface conditions are
encountered which vary appreciably from those described herein, HWA should be notified for
review of the recommendations of this letter report, and revision of such if necessary.
The scope of work did not include environmental assessments or evaluations regarding the
presence or absence of wetlands or hazardous substances in the soil, surface water, or ground
water at this site. HWA does not practice or consult in the field of safety engineering, and
construction safety considerations are the responsibility of the Contractor or property owner.
Report 5 HWA GeoSciences Inc.
February 21, 2012
HWA Project No. 2012-000-21 Task 4
We appreciate the opportunity to be of service. If you have any questions or concerns, please do
not hesitate to contact us.
Sincerely,
HWA GEOSCIENCES INC.
Steven E. Greene, L.G., L.E.G.
Senior Engineering Geologist
Attachinents:
Figure I Site Location and Vicinity map
Figure 2 Site Exploration Plan
Figure 3 Photograph of existing Deck and Foundation Configuration
Report 6 HWA GeoSciences Inc.
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