HomeMy WebLinkAboutSR_ERC_Staff_Report_Lang_Deck_v2DEPARTMENT OF COMMUNITY
AND ECONOMIC DEVELOPMENT
SR_ERC Staff Report Lang Deck_v2
ENVIRONMENTAL REVIEW COMMITTEE REPORT
ERC Meeting Date: February 6, 2023
Project File Number: PR21-000462
Project Name: Lang Back Yard Deck Variances
Land Use File Number: LUA22-000145, V-A, RUV, ERC
Project Manager: Brittany Gillia, Associate Planner
Owner/Applicant/Contact: Karen Lang Crane, 212 S 20th Pl, Renton, WA 98055
Project Location: 212 S 20th Pl
Project Summary: The applicant is requesting SEPA Environmental Review, a Reasonable Use
Variance, and a Variance from setback regulations in order to retroactively permit
a 405-sq. ft. deck addition with an attached 135-sq. ft. aluminum drainage grate
on the rear of an existing single-family home at 212 S 20th Pl (APN 8860500070)
as documented in Warning of Violation (WOV): CODE20-000309 (Exhibit 2). The
existing two-story home is approximately 1,910 sq. ft. in size and was constructed
in 2000. The site is located in the R-6 zoning district and Residential Medium
Density Comprehensive Plan Designation. The entire parcel is mapped with High
Erosion Hazards and High Landslide Hazards and there is a protected slope on the
north edge of the site that begins at the toe of an ecology block wall and extends
approximately 18 feet to the north and descends approximately 20 feet
downward. On the opposite edge of the same ecology block retaining wall a
sensitive slope extends under the deck with a vertical rise of approximately 7 to
9 feet. A small area on the south end of the subject property is mapped with
Moderate Coalmine Hazards.
The applicant is requesting a Reasonable Use Variance from the 15-foot structure
setback from protected slopes required by RMC 4-3-050 G.2 in order to allow the
proposed deck to remain as constructed as close as 3’8” and as far as 5’9” from
the top of the slope. The applicant is also requesting an Administrative Variance
from development regulations to vary from the side yard setbacks which require
a combined 15-feet with not less than 5-feet on either side and rear yard setback
of 25 feet to allow the deck to remain as constructed and extend to both side yard
property lines and within 7.5 feet of the rear yard property line. The single-family
project is not categorically exempt from Environmental Review as it is
encroaching into the setback of a protected slope and requires a variance from
the critical areas regulations. No trees or vegetation would be removed as a part
of the project. The applicant submitted a geotechnical report and drainage
evaluation with the application.
Exist. Bldg. Area SF: 1,910 sf Proposed New Deck Area (footprint):
Proposed New Deck Area (net):
540 sf
405 sf
Site Area: 5,011 sf (0.12
acres)
Total Building Area GSF: 1,910 sf
STAFF
RECOMMENDATION:
Staff Recommends that the Environmental Review Committee issue a
Determination of Non-Significance (DNS).
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City of Renton Department of Community & Economic Development
Lang Back Yard Deck Variances
Staff Report to the Environmental Review Committee
LUA22-000145, V-A, RUV, ERC
Report of February 6, 2023 Page 2 of 4
SR_ERC Staff Report Lang Deck_v2
Project Location Map
ENVIRONMENTAL REVIEW
In compliance with RCW 43.21C.240, the following environmental (SEPA) review addresses only those project impacts
that are not adequately addressed under existing development standards and environmental regulations.
A. Environmental Threshold Recommendation
Based on analysis of probable impacts from the proposal, staff recommends that the Responsible Officials:
Issue a DNS with a 14-day appeal period
B. Exhibits
Exhibit 1: Environmental Review Committee (ERC) Report
Exhibit 2: Warning of Violation: CODE20-000309
Exhibit 3: Site Plan
Exhibit 4: Geotechnical Report, prepared by Geo Group Northwest dated October 26, 2022
Exhibit 5: Drainage Evaluation, prepared by Geo Group Northwest dated March 25, 2022
Exhibit 6: Conceptual Drainage Plan, prepared by Geo Group Northwest dated March 25, 2022
Exhibit 7: Public Comment #1 (from Duwamish Tribe dated August 1, 2022)
Exhibit 8: Public Comment #2 (from Mary Hobson dated August 4, 2022)
C. Environmental Impacts
The Proposal was circulated and reviewed by various City Departments and Divisions to determine whether the
applicant has adequately identified and addressed environmental impacts anticipated to occur in conjunction with
the proposed development. Staff reviewers have identified that the proposal is likely to have the following probable
impacts:
1. Earth
Impacts: A geotechnical report (Exhibit 4) and drainage evaluation (Exhibit 5) prepared by GEO Group
Northwest was submitted by the applicant to address the presence of steep slopes, erosion hazards and
landslide hazards along the north edge of the project site. The reports include an analysis of the project
and its potential impacts on the protected slope, erosion hazards and landslide hazards. The deck has
been constructed without a permit as seen in Warning of Violation (WOV): CODE20-000309 (Exhibit 2)
and the applicant is requesting retroactive permission to retain the deck in its current position.
According to the geotechnical report, the highest elevation and lowest elevations at the site are
approximately 188 feet at the south property line, and 164 feet at the north property line , respectively.
The gentle to moderate slope at the site is separated from the steeply sloping area by an approximately
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
City of Renton Department of Community & Economic Development
Lang Back Yard Deck Variances
Staff Report to the Environmental Review Committee
LUA22-000145, V-A, RUV, ERC
Report of February 6, 2023 Page 3 of 4
SR_ERC Staff Report Lang Deck_v2
4-foot tall ecology block wall that rests along the crest of the steep slope. The site and adjacent vicinity is
underlain by shallow bedrock known as the Renton Formation which is composed of arkosic sandstone,
mudstone, and shale. Two (2) hand borings were completed at the site and dense to very dense soils were
found approximately 2-7 feet below ground surface. The project engineer states that their findings on site
are consistent with the local geographic mapping (Renton Formation). Pursuant to RMC 4-3-050 G.2,
structures shall be set back 15-feet from the top of protected slopes. The top of the protected slope begins
at the base of an ecoblock retaining wall and extends north 18’ over the property line and descends 20’
down, ending in the neighboring property. The current home and existing deck were constructed in 2000
and are located at least 15 feet away from the top of the protected slope. The new deck development
extends to both side lot lines and is within 7.5 feet of the rear yard property line. The distance between
the deck and top of the protected slope fluctuates between 3-5 feet.
In accordance with the procedures described in the 2018 International Building Code (IBC), the project
engineers conclude that the subject site should be classified as Site Class C (Very Dense Soil & Soft Rock).
A factor of safety (FS) value indicates the safety against slope failure. An FS value slightly above 1.0
indicates a slope with minimal stability, and the project engineer states than an FS value of at least 1.5
indicates a sufficiently stable condition for the slope under permanent static conditions and an FS value
of at least 1.2 is considered sufficiently stable for a short-term dynamic condition such as seismic activity.
The factor of safety (FS) was calculated for the site without the deck loads (2.63 static, 1.84 seismic) and
with deck loads (2.39 static, 1.75 seismic) and in both instances demonstrate FS values that meet the
minimum criteria for acceptable slope stability. Geo Group Northwest states the existing vegetation and
dense to very dense soil and shallow bedrock conditions present at the hazard area to be mitigating
factors regarding slope stability and potential landsliding of the hazard area at the site.
A public comment (Exhibit 8) was received regarding concerns of the slope stability due to the additional
load caused by the proposed development. Slope stability analysis from Geo Group Northwest provide
factors of safety greater than 2.39 for rotational landsliding in static conditions and greater than 1.74 in
seismic conditions. Due to these findings, the project engineers state that the mapped landslide hazard
area and sensitive and protected slopes are stable at this time and the risk of impacting the geotechnical
hazards with construction of the proposed deck is negligible. Based on the analysis and conclusions of
the geotechnical report and drainage reports, staff finds no additional mitigation necessary.
Mitigation Measures: None recommended
Nexus: N/A
2. Water
a. Storm Water
Impacts: According to the drainage evaluation prepared by Geo Group Northwest (Exhibit 5) submitted
with the project application, the current stormwater management system for the existing residence
consists of five (5) roof downspout which are tightlined below the ground surface. Upon a site exploration
by Geo Group Northwest, there was no evidence of rutting, channelizing, or concentrating flows found
that demonstrate the existing stormwater management infrastructure adversely affects the retaining wall
and critical areas on or adjacent to the site. In the professional opinion of Geo Group Northwest, the
proposed 135 square foot aluminum drainage grating is acceptable to accommodate the 405 square feet
of new deck area, provided the drainage grating be tightlined via gravity flow to the existing downspouts.
The report specifies that drainage should not be allowed to drain directly below the grating in the retaining
wall backfill area. The drainage control plan (Exhibit 6) demonstrates the applicant’s proposed design
which meets the recommendations of the geotechnical report. Based on the analysis and conclusions of
the drainage report staff finds no additional mitigation necessary.
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2
City of Renton Department of Community & Economic Development
Lang Back Yard Deck Variances
Staff Report to the Environmental Review Committee
LUA22-000145, V-A, RUV, ERC
Report of February 6, 2023 Page 4 of 4
SR_ERC Staff Report Lang Deck_v2
Mitigation Measures: None recommended
Nexus: N/A
3. Historic and Cultural Preservation
Impacts: An agency public comment from the Duwamish Tribe (Exhibit 7) was received for the project.
The comment requests that if the foundation depth goes below fill, that an Inadvertent Discovery Plan
(IDP) be put in place. The deck is being retroactively permitted and no new footings or additional
foundation is proposed, therefore staff is not recommending mitigation.
Mitigation Measures: None recommended
Nexus: N/A
D. Comments of Reviewing Departments
The proposal has been circulated to City Department and Division Reviewers. Where applicable, their comments
have been incorporated into the text of this report and/or “Advisory Notes to Applicant.”
✓ Copies of all Review Comments are contained in the Official File and may be attached to this report.
The Environmental Determination decision will become final if the decision is not appealed within the 14 -day
appeal period (RCW 43.21.C.075(3); WAC 197-11-680).
Environmental Determination Appeal Process: Appeals of the environmental determination must be filed in
writing on or before 5:00 p.m. on February 20, 2023. Appeals must be submitted electronically to the City Clerk
at cityclerk@rentonwa.gov or delivered to City Hall 1st floor Lobby Hub Monday through Friday. The appeal fee,
normally due at the time an appeal is submitted, will be collected at a future date if your appeal is submitted
electronically. The appeal submitted in person may be paid on the first floor in our Finance Department. Appeals
to the Hearing Examiner are governed by RMC 4-8-110 and additional information regarding the appeal process
may be obtained from the City Clerk’s Office, cityclerk@rentonwa.gov.
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CITY OF RENTON
DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT
STAFF REPORT TO THE ENVIRONMENTAL REVIEW COMMITTEE
EXHIBITS
Project Name:
Lang Back Yard Deck Variances
Land Use File Number:
LUA22-000145, V-A, RUV, ERC
Date of Meeting
February 6, 2023
Staff Contact
Brittany Gillia
Associate Planner
Project Contact/Applicant
Karen Lang Crane
212 S 20th Pl, Renton, WA
98055
Project Location
212 S 20th Pl
The following exhibits are included with the ERC Report:
Exhibit 1: Environmental Review Committee (ERC) Report
Exhibit 2: Warning of Violation: CODE20-000309
Exhibit 3: Site Plan
Exhibit 4: Geotechnical Report, prepared by Geo Group Northwest dated October 26, 2022
Exhibit 5: Drainage Evaluation, prepared by Geo Group Northwest dated March 25, 2022
Exhibit 6: Conceptual Drainage Plan, prepared by Geo Group Northwest dated March 25, 2022
Exhibit 7: Public Comment #1 (from Duwamish Tribe dated August 1, 2022)
Exhibit 8: Public Comment #2 (from Mary Hobson dated August 4, 2022)
DocuSign Envelope ID: 9BB52EEA-073E-450F-BED8-2B13DFF227B2