BLD20120428 Critical Area Notice of Decision.pdfIty 0 , Mon S
Critical Area Notice of Decisiol
Applicant: Property Owner:
Critical Area File Permit Number:
Site Location: I I Parcel Number:
Project Description:
❑ 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.
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. >4 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, _µ4_ The proposal is consistent with the general purposes of this title and the public interest;
4, >4_ Any alterations permitted to the critical area are mitigated in accordance with ECDC
23.40.110, Mitigation requirements.
5. 1
_74_ 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. —)d— The proposal is consistent with other applicable regulations and standards.
F -I 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.
AFavorable 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.
E] Conditions, Critical Area specific condition(s) have been applied to the permit number referenced
above, See referenced permit number for specific condition(s).
gn
Reviewer �Slmnaturk, 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
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TERRA A.SS00ATES, enc.
Consultants in Geotechnical Engineering, Geology
and
Environmental Eartli Sciences
Mr, Lance Horton
9115 Park Road
Edmonds, Washington 98020
Subject: Landslide/Erosion Hazard Evaluation
Deck Replacement
9115 Park Road
Edmonds, Washington
Dear Mr. Horton:
July 20, 2012
Project No. T-6747
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As requested, on July 17, 2012 a representative of Terra Associates, Inc. met with you at the subject site. The
purpose of our meeting was to complete a geologic reconnaissance of the property and assess the landslide hazard
as defined by the City of Edmonds Municipal Code (EMC) relative to replacement of an existing deck.
The residence is a two-story wood -framed structure located on the north side of Park Road. The deck in question
is attached to the north side of the residence. The deck is typical wood -framed construction with two levels
providing floor level access from the lower and upper levels of the residence. The deck dimensions are
approximately 10' x 12'. Below the deck grade descends to the north with grade transition accommodated by
four terraced walls, each about three feet in height. At the base of the terraced walls the grade is level forming a
landing area that extends about 10 to 15 feet to the north. On the north side of the landing there is a three- to four -
foot tall rockery that accommodates a grade transition to a relative level naturally vegetated area. This area
extends to the crest of a steeper north facing ravine slope. The ravine contains a drainage referred to as Shell
Creek.
Review of the U.S.G.S. Geologic Map of the Edmonds East and Part of the Edmonds I17est Quadrangles by James
P. Minard, 1983 indicates soils in the site vicinity consist of glacial till (Qvt) transitioning to Advance outwash
(Qva) in the Shell Creek drainage. Glacial till consists of a highly consolidated soil matrix composed of silt, sand,
and gravel along with cobble and boulder inclusions. The Advance outwash underlies the till and is typically
composed of relatively clean gravel and sand. Because of their high degree of consolidation both formations
exhibit high shear strength and low compressibility and are inherently stable in steep sloping terrain.
12525 Willows Road, Suite 101, Kirkland, Washington 98034
Phone (425) 821-7777 m Fax (425) 821-4334
Mr. Lance Horton
July 20, 2012
The USDA Natural Resources Conservation Service (NRSC formerly Soil Conservation Service) maps the soils
in the site vicinity as Aldenvood gravelly sandy loath, 15 to 25 percent slopes. The NRSC erosion hazard
classification is indicated as moderate.
Section 23.80.020 of the EMC defines erosion and landslide hazard areas as follows:
A. Erosion Hazard Areas. Erosion hazard areas are at least those areas identified by the U.S. Department of
Agriculture's Natural Resources Conservation Service as having a "moderate to severe," "severe," or "very
severe" rill and inter -rill erosion hazard. Erosion hazard areas are also those areas impacted by shoreland
and/or stream bank erosion. Within the City of Edmonds erosion hazard areas include:
I. Those areas of the City of Edmonds containing soils that may experience severe to very severe erosion hazard.
This group of soils includes, but is not limited to, the following when they occur on slopes of 15 percent or
greater:
a. Alderwood soils (15 to 25 percent slopes).
b. Alderwood/Everett series (25 to 70 percent slopes).
c. Everett series (15 to 25 percent slopes).
2. Any area with slopes of 15 percent or greater and impermeable soils interbedded with granular soils and springs
or groundwater seepage.
3. Areas with significant visible evidence of groundwater seepage, and which also include existing landslide
deposits regardless of slope.
B. Landslide Hazard Areas. Landslide hazard areas are areas potentially subject to landslides based on a
combination of geologic, topographic, and hydrologic factors. They include areas susceptible because of any
combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Within the
City of Edmonds landslide hazard areas specifically include:
1. Areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence and
Iandslide hazard area as identified in the 1979 report of Robert Lowe Associates and amended by the 1985
report of GeoEngineers, Inc.
2. Any area with a slope of 40 percent or steeper and with a vertical relief of 10 or more feet except areas
composed of consolidated rock. A slope is delineated by establishing its toe and top (as defined in Figure 1 in
subsection (13)(1) of this section) and is measured by averaging the inclination over at least 10 feet of vertical
relief or 25 feet of horizontal distance. Benches, steps and variations in gradient shall be incorporated into a
larger slope if they do not meet criteria defining toe and/or top depicted in Figure 1 in subsection (13)(1) of this
section (see also Figure 2 at the end of this subsection). If the toe or top of a slope is located off of a subject
property, then the location of the toe or top shall be delineated 200 horizontal feet from the property boundary
or at its natural location, whichever is closer to the subject parcel (see Figure 2 at the end of this subsection).
3. Any area potentially unstable as a result of rapid stream incision or stream bank erosion.
4. Any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by debris flow or
deposition of stream -transported sediments.
Project No. T-6747
Page No. 2
Mr. Lance Horton
July 20, 2012
Based on these definitions the ravine slope north of the property would be classified as an erosion and landslide
hazard area.
During our site reconnaissance, we did not observe any evidence of recent or past slope instability or erosion.
Both the terraced area below the deck and the native area north of the property are landscaped and naturally
vegetated and well protected from erosion.
The new deck is located in the same footprint of the previous deck. There was some minor ground disturbance
below the deck when a new support beam was installed. This ground disturbance had no impact on stability and
did not present an erosion risk. Based on our observations and document review, in our opinion, replacement of
the deck as planned has absolutely no adverse impacts to the landslide hazard or erosion hazard areas as defined
by the EMC.
We trust the information presented is sufficient for your current needs. If you have any questions or require
additional information, please call.
Sincerely yours,;
TERRA ASS6;(1lkTVS, YNQF - /
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Project No, T-6747
Page No. 3