REVIEWED PLN RESUB7 BLD2020-0733+Geotechnical_Report+1.28.2022_12.27.36_PM+2648527RESUB
Feb 08 2022
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
BLD2020-0733
UALITY
FIELD REPORT
Project Name: Pichner Limited Slo e Evaluation
Report Date: 1/26/2022
Site address: 8120 Talbot Rd, Edmonds, WA 98026
QG Project Number: G22-019
Client: Chris Pichner
Arrival Time: 9:30ain
Consultation Performed: Slope Consultation
Report #: QG22-019-001
Report Status: PASS
Report Remarks:
Quality Geo NW (QG) licensed engineering geologist arrived on site as requested by the client for
consultation on the subject property. We understand that removal of previously installed block
walls, across the backyard slope, is required of the client. Additionally, the city permitting
authority requires QG to address the updated site plan for removing walls, wet season work
requirements, and the updated planting plan for restoration. Additionally, QG must address code
items ECDC 23.80,060 and 23.80.070.
QG was provided an updated site plan, drafted by McDonough's Law Office on 01/13/2022. We
reviewed the proposed removal of walls on site. Currently, it is proposed that all 5 walls be
removed in their entirety, and that surfaces be regraded to resemble their original condition. In
combination with other plans (addressed herein) we consider the removal to be an acceptable path
forward.
Additionally, QG reviewed the proposed replanting and mitigation plan provided by Land Services
NW. The plan specifically details the following:
" The project will mitigate for the unavoidable impacts to 1,452 square feet of
riparian habitat through the removal of invasive species such as English ivy and
Himalayan blackberry and replanting of 3,812 square feet with a robust combination of
groundcover, shrubs and trees. These plants will lead to an improvement of functions and
diversity over the existing conditions. A net gain or positive impact is expected in
landscape roughness, habitat screening, food source, nutrient uptake and aesthetics and
overall habitat resilience... "
QG concurs that their removal, followed by regrading surfaces to near -original condition and
revegetation per the planting plan is acceptable. We understand the new plantings were completed
by the property owner for an estimated cost of $600, saving the cost of subcontracted labor and
their markup. Maintaining new plantings, and preventing exposed soils with complete ground
cover, will remain the responsibility of the property owner throughout the existence of the
property, as is typically the responsibility of any property owner in a sloped area.
Quality Geo NW, PLLC
Serving All of Washington & Oregon J Geotechnical Investigations & Engineering Consultation
Phone: 360 878 97051 Web: qualttygeonw.com I Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513
Site Reconnaissance:
The walls have been completely removed from the site, and the surface regraded to resemble
previous natural slope grade. The removal has occurred during a persistent dry period of weather.
No measurable rainfall has impacted the site during demolition. Replanting appears to have been
completed, with new tree starters and vegetation cover having seeded and planted, with mulch over
the majority of exposed surface soils.
While on site, we conducted a supplementary site surface explorations for a geologic hazard
assessment and site feasibility characterization. Approximate relevant property dimensions and
slope topography were documented and mapped at representative intervals as access allowed. Soil
conditions were evaluated through local exposures. Salient slope features and existing vegetation
were documented to assess general site stability and we searched for possible signs of local
instability of an erosional or subsurface nature currently or in the past.
QG performed general site reconnaissance to consider any indications of localized surface
degradation or large-scale slope instability. No indications of deep-seated displacement were
observed to cross within the slope or near to the residence. Topography was generally consistent
and lacking: significantly oversteepened areas, channelized runout zones, tension cracks, or
hummocky zones. No obvious evidence of rotational or translational failures or major toppling
hazards was observed on the slopes in the proximity of the home. No significant failure features
were observed on adjacent slope areas visible from the subject property during the visit. Review
of available LiDAR imagery did not reveal any obvious historic or recent movement.
Critical Area Ordinance:
The local Critical Area Ordinance (CAO) requires specific conditions be addressed and excepted
by the geotechnical professional. These items were also previously addressed in our first report,
dated 1/15/2021. The following relevant items were specifically requested by the city permitting
authority:
23.80.060 Development standards — General requirements.
A. Alterations of geologically hazardous areas or associated buffers may only occur for
activities that:
4. Are certified as safe as designed and under anticipated conditions by a qualified
engineer or geologist, licensed in the state of Washington... "
So long as the recommendations within this letter, our original report, and the updated planting
plan are followed, QG does not consider the site to be a geohazard and considers the proposed wall
removal & surface restoration as acceptable.
23.80.070 Development standards — Specific hazards.
Quality Geo NW, PLLC
Serving All of Washington & Oregon I Geotechnical Investigations & Engineering Consultation
Phone: 360 878 97051 Web; quahtygeonw.com I Mail; 4631 Whitman Ln SE, Ste D, Lacey, WA 98513
A. Erosion and Landslide Hazard Areas. Activities on sites containing erosion or landslide
hazards shall meet the requirements of ECDC 23.80.060, Development standards —
General requirements, and the specific following requirements:
1. Minimum Building Setback... "
No new dwellings or structures are proposed, and original surface grades are to proposed tobe
restored; therefore no setbacks will be encroached.
11 ... 3. Alterations. Alterations of an erosion or landslide hazard area, minimum
building setback and/or buffer may only occur for activities for which a hazards analysis
is submitted and certifies that:
a. The alteration will not increase surface water discharge or sedimentation to adjacent
properties beyond predevelopment conditions;
b. The alteration will not decrease slope stability on adjacent properties; and
c. Such alterations will not adversely impact other critical areas; ... "
So long as the recommendations within this report are followed, QG does not anticipate any
impacts on the slope, and surface stabilization is expected to exceed it's original status.
" ... 4. Design Standards within Erosion and Landslide Hazard Areas. Development
within an erosion or landslide hazard area andlor buffer shall be designed to meet the
following basic requirements unless it can be demonstrated that an alternative design that
deviates from one or more of these standards provides greater long-term slope stability
while meeting all otherprovisions of'this title. The requirementfor long-term slope stability
shall exclude designs that require regular and periodic maintenance to maintain their level
offunction. The basic development design standards are:
a. The proposed development shall not decrease the factor of safety for landslide
occurrences... "
The proposed improvements are expected to increase the overall surface stability.
... 7. Point Discharges. Point discharges from surface water facilities and roof
drains onto or upstream from an erosion or landslide hazard area shall be prohibited
except as follows:
a. Conveyed via continuous storm pipe downslope to a point where there are no erosion
hazard areas downstream from the discharge; ... "
Drainage Concerns are addressed below, as well as our original report, and within the updated
planting plan.
Erosion Controls & Wet Weather Work:
Walls have been removed, and planting plan completed at this time. Work was completed during
consistently dry weather, successfully avoiding most erosional concerns, While no further work is
anticipated, if additional restoration or work is to be done in the future for upkeep, we recommend
the following be considered by the property owner at such time:
Quality Geo NW, PLLC
Serving All of Washington & Oregon I Geotechnical Investigations & Engineering Consultation
Phone: 360 878 97051 Web; qualitygeonw.com I Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513
Erosion is one of the most common driving forces leading to slope instability. In addition to the
above commentary, the following general recommendations should be implemented in general to
reduce long-term erosion potential of the slope below the project site and maintain slope stability:
• Minimize the volume and velocity of water that travels toward and down the slope face (via
proper choice of site development features including stormwater controls discussed above).
• Avoid the following contributions to accelerating slope erosion and mass wasting from human
activity:
✓ Adding side -cast such as dumping landscape debris or fallen trees on or above the slopes.
✓ Using heavy construction equipment on or near steep slopes.
✓ Excavating near adjacent steep slopes toe or on slope face.
✓ Placing excavated soil or adding structural weight near the steep slope crest.
• Prior to construction, a silt fence and/or a continuous line of straw bales should be placed on
the slopeward edge of the construction area. Heavy construction equipment, construction
materials, or native and imported soils should not be placed behind the erosion control devices.
Suitable temporary erosion and sediment control measures should be implemented at the
construction site during and immediately after ground disturbance occurs. Temporary areas
bare of vegetation should be protected from erosion via a blanket of straw or rolled erosion
control product (RECP) during prolonged breaIcs in site work and prior to reseeding or
revegetation.
• At the end of the project, all bare surfaces and areas of disturbed vegetation should be replanted
and maintained until fully reestablished. Concentrated surface water should not be allowed to
traverse the slope during or after the construction phase of the project. Roof downspouts and
footing drains should be routed into closed separate pipes which outfall into appropriate
drainages. Outlets for these pipes should be protected from erosion through the use of rip -rap
(quarry spalls) or some other energy dissipating device, Similarly, concentrated drainages
should be captured in closed pipe systems and routed down slope to appropriate outfalls.
• Clearing of existing vegetation outside the proposed improvement area on and adjacent to the
existing slopes should be avoided except as approved by a qualified professional. This provides
additional stability to the loose topsoil and minimizes the effects of down -slope water
movement. This is excepting removal of problem, dead, or dying, trees if posing a direct hazard
to site installations or adjacent roadways.
• Grading or excavation of soils during construction should be accompanied by grass reseeding
and re -vegetation as the project is completed.
Quality Geo NW, PLLC
Serving All of Washington & Oregon I Geotechnical Investigations & Engineering Consultation
Phone: 360 878 97051 Web: qualitygeonw.coin j Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513
l,dl LL I 1 1
.- r,�,EO
Closing. -
We trust this letter satisfies your project needs currently and thank you for the opportunity to be
of service. QG wishes you the best while completing the project,
Approved by:
Luke Preston McCann, L.E.G.
Principal Licensed Engineering Geologist
Quality Geo NW, PLLC
Serving All of Washington & Oregon I Geotechnical Investigations & Engineering Consultation
Phone: 360 878 97051 Web: qualitygeonw.com I Mail: 4631 Whitman Ln SE, Ste D, Lacey, WA 98513
BLD2020-0733
QUALITY
TIL I "ti'1'E D f :1:()'1`]•:1'll \' I1'.1I. 1•: \ 1:I N ]:1:2ING .$ CON6ULTING
6/ 18/2020
Chris Pichner
8120 Talbot Rd
Edmonds, WA 98026
Subject: Pichner Critical Slope Consultation
8120 Talbot Rd, Edmonds, WA 98206
QG Project No.: QG20-018
Dear Mr. Pichner:
RECEIVED
Jul 17 2020
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
At your request, Quality Geo, PLLC (QG) has completed a limited evaluation of the existing
terraced landscaping walls within your property. We understand the general quality of the slope
improvements is in question. Further information has been requested by the City of Edmonds to
inform if it is acceptable for the slope to remain in its current condition, and if there will need to
be any further protections.
LITERATURE REVIEW
The Washington Geologic Information Portal (WGIP) maintained by the Department of Natural
Resources Division of Geology and Earth Resources provides 1:24,000-scale geologic mapping of
the region. The subject site is mapped as Quaternary Glacial Till (Qgt), typically comprising
unsorted, sub -angular and highly compacted clay, silt, sand, and gravel deposited directly by
glacier ice, varying in thickness from discontinuous layers less than 1-inch thick to more than 30
feet. Soil is grey where fresh, and yellowish brown where oxidized. Outwash clay, sand, silt, and
gravel may be included, as well as erratic boulders.
According to the regional -scale interactive map, no deep-seated landslides are known to exist
within the site or adjacent vicinity. Available LiDAR imagery of the site did not reveal any
obvious or prominent landslide features within the site or immediate vicinity.
Detailed photo records of the construction process for the walls were provided to QG. Photos
indicate adequate and standard construction practices for landscape walls were followed, including
keying in (embedment) of the wall base, compaction of subgrade, installation of a face drain behind
the wall, and compaction of imported backfill soils resembling a crushed 5/8" top course material.
Quality Geo, PLLC
Geotechnical Engineering & Consulting
Phone: 360-764-8485 1 Web: quality-geo.com I Mail: 420 Golf Club Rd SE, Ste 201, Lacey, WA 98503
Pichner Critical Slope Consultation
6/18/2020
SITE INVESTIGA TION METHODOLOGY
Quality Geo, PLLC
Project # QG20-018
On 6/16/2020, a QG senior geologist visited the site to perform visual reconnaissance of surface
and topographic features. Salient slope features and existing vegetation were observed to assess
general site and wall condition. This included looking for signs of recent or past erosion or
subsurface instability. The wall area was observed and photographed from within the site. Direct
observations of soils where exposed by localized surface erosion or outcropping, were used to
classify stratigraphy and interpret site geology. Inferences from observations are described herein.
A site map is included in Appendix A. Site photos are included in Appendix B.
SURFACE OBSERVATION
QG performed general site reconnaissance to observe and document any indications of localized
surface degradation or slope instability. The subject walls exist along the southern half of the
property and descend to the south towards the adjacent creek. Existing slopes were measured at an
average 30 degree inclination (where not artificially benched). The existing home and foundation
exposures were assessed and did not show any signs of undermining, cracking or displacement.
No indications of historic shallow or deep-seated movement were observed along the slopes.
Topography was generally consistent, lacking features such as: significantly oversteepened native
slopes, apparent scarps, channelized runout zones, or hummocky zones. No obvious evidence of
rotational or translational failures or toppling hazards was observed. No significant failure features
were observed on adjacent slope areas visible from the subject property during the visit. No
massive downslope accumulation, or tension cracks were observed. No significant areas of
scouring from natural stormwater channelization were observed.
The wall and slope faces were generally cleared of vegetatation, with mostly exposed soils. Where
soils were exposed, they appeared to resemble a silty sand with gravel more closely resembling
glacial outwash deposits. Most established trees appeared to grow generally straight, with few
tilted or arched tree trunks present. Drainage tightlines were seen to emanate from the base of
walls, daylighting along the face of the slope and bases of adjacent walls. Scouring from erosion
was seen near these tightline exposures and along the base of some wall sections.
The condition of the landscape walls was assessed during our visit. Blocks measured 6 inches tall
each, utilizing a lip -and -lug style interlocking, with no geogrid reinforcement, and each wall was
a different height, typically tapering at the ends. The blocks appeared to be in good condition, with
no signs of tilting, loose blocks, or irregular change in batter. Most walls did not exceed 4 feet in
height, except for the lower most wall to the south and the upper most wall to the northewast
(identified in Appendix A). These two walls were directly measured to be a maximum of 5.5 tall
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Pichner Critical Slope Consultation Quality Geo, PLLC
6/18/2020 Project # QG20-018
feet from base to top, tapering at the ends. QG understands any wall exceeding 4 feet in height is
required to have an engineered design.
DISCUSSION & RECOMMENDATIONS
The findings of QG's limited reconnaissance at the subject site do not indicate that any excessively
prohibitive conditions exist for the current level of slope development. In consideration of the
available information, and our direct observations, at this time QG does not consider the site to
be within an active landslide hazard area, or erosional hazard area. Based on the information
herein, QG provides the following development and site -specific recommendations to be followed
to minimize the inherent risks of slope side restoration.
Considering the generally satisfactory condition of the walls, free draining nature of native soils,
and lack of evidence regarding any soil movement or degradation of the site, QG does not expect
that the walls will need to be removed. The walls generally serve more of a decorative purpose,
rather than acting as any structural support, due to their limited scale and height. Overall, the
terracing is anticipated to improve slope conditions by reducing erosion and stabilizing the soil
surfaces. However, some changes and improvements will need to be made in order to protect the
existing slope safety factors, and comply with industry standard wall construction.
In order to avoid the need for an engineered wall design, QG recommends the two walls over 4
feet in height be altered such that their maximum height (measured from the bottom of the base
block to the top of the wall) does not exceed 4 feet. This can easily be achieved by removing 3
block courses from the top of the two walls followed by regrading and compaction of the soils
behind the wall. Any new or remaining walls over 4 feet in height will need an engineered design
and must incorporate geogrid reinforcement within backfill soils. Any new permanent graded
slopes be inclined no greater than 3H:1 V at a minimum so as to catch natural topography at the
top and toe of the new incline, while existing adjacent grades may remain at their existing
inclination.
While the walls do have face drains and tightline outfalls installed, these thightlines only serve to
release stormwater in front of other walls, and have contributed to erosion along the bases of walls.
An ideal solution would have all upland stormwater catchments tightlines extend to transport their
water all the way down and away from the walls and slopes, outfalling in an approved existing
drainage conveyance, or a suitable catch basin for redistribution. The existing creek did not exhibit
any sighs of concern related to erosive forces impacting the site. With the city's approval,
establishing an outfall with an energy reducing quarry spall pad over geofabric, within the side of
the creek, is considered an adequate solution from a critical slope protection perspective and is not
anticipated to input enough water to negatively affect the creek.
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Pichner Critical Slope Consultation
6/18/2020
Quality Geo, PLLC
Project # QG20-018
Additionally, all exposed surfaces will need to be stabilized. This can include the installation of
either mulch/bark, fabric and decorative rockery, or revegetation with fast growing and deep
rooting plants, in any combination. According to "Vegetation Management: A Guide for Puget
Sound Bluff Property Owners" (Manashe, 1993) the following types of vegetation provide good
to excellent erosion control:
Common Name
Botanical Name
Deciduous/Evergreen
Mature Height (ft)
Bi leaf Maple
Acer macro h llum
Deciduous
60
Douglas Fir
Pseudotsu a menziesii
Evergreen
200+
Evergreen
Vaccinium ovatum
Evergreen
To 8
Oceanspray
Holodiscus discolor
Deciduous
10+
Oregon Grape
Mahonia spp.
Evergreen
To 6
Pacific Madrone
Arbutus menziesii
Evergreen
70
Red huckleberry
Vaccinium parvifolium
Deciduous
To 12
Rose
Rose spp.
Deciduous
2-10
Salal
Gaultheria shallon
Evergreen
To 4
Sahnonberry
Rubus s ectabilis
Deciduous
To 12
Serviceberry
Amelanchier alnifolia
Deciduous
12+
Snowberry
Symphoricarpos albus
Deciduous
3+
Vine Maple
Acer cricinatum
Deciduous
10+
Willow
Salix spp.
Deciduous
10+
CLOSING REMARKS:
We trust this letter satisfies your project needs currently and greatly thank you for the opportunity
to be of service. QG wishes you the best while completing the project.
Respectfully Submitted,
Quality Geo, PLLC
9110629
Oed oo 6/18/2020
LUKE PRE OW MCCANNI
Luke Preston McCann, L.G.
Principal Geologist
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Pichner Critical Slope Consultation
6/18/2020
LIMITATIONS
Quality Geo, PLLC
Project # QG20-018
Upon acceptance and use of this report, and its interpretations and recommendations, the owner
shall agree to indemnify and hold harmless QG, including its owners, employees and
subcontractors, from any adverse effects resulting from development and occupation of the subject
site. Ultimately, it is the owner's choice to develop and live in such an area of possible geohazards
(which exist in perpetuity across the earth in one form or another), and therefore the future
consequences, both anticipated and unknown, are solely the responsibility of the owner. By using
this report for development of the subject property, the owner must accept and understand that it
is not possible to fully anticipate all inherent risks of development. The recommendations provided
above are intended to reduce (but may not eliminate) such risks.
This report does not represent a construction specification or plan and shall not be used or
referenced as such. The information included in this report should be considered supplemental to
the requirements contained in the project plans & specifications and should be read in conjunction
with the above referenced information. The selected recommendations presented in this report are
intended to inform only the specific corresponding subjects. All other requirements of the above -
mentioned items remain valid, unless otherwise specified.
Recommendations contained in this report are based on our understanding of the proposed
development and construction activities, field observations and explorations, and laboratory test
results. It is possible that soil and groundwater conditions could vary and differ between or beyond
the points explored. If soil or groundwater conditions are encountered during construction that
differ from those described herein, or If the scope of the proposed construction changes from that
described in this report, QG should be notified immediately in order to review and provide
supplemental recommendations.
The findings of this study are limited by the level of scope applied. We have prepared this report
in substantial accordance with the generally accepted geotechnical engineering practice as it exists
in the subject region. No warranty, expressed or implied, is made. The recommendations provided
in this report assume that an adequate program of tests and observations will be conducted by a
WABO approved special inspection firm during the construction phase in order to evaluate
compliance with our recommendations.
This report may be used only by the Client and their design consultants and only for the purposes
stated within a reasonable time from its issuance, but in no event later than 18 months from the
date of the report. It is the Client's responsibility to ensure that the Designer, Contractor,
Subcontractors, etc. are made aware of this report in its entirety. Note that if another firm assumes
Geotechnical Engineer of Record responsibilities they need to review this report and either concur
with the findings, conclusions, and recommendations or provide alternate findings, conclusions
and recommendation.
Land or facility use, on- and off -site conditions, regulations, or other factors may change over time,
and additional work may be required. Based on the intended use of the report, QG may recommend
that additional work be performed and that an updated report be issued. Non-compliance with any
of these requirements by the Client or anyone else will release QG from any liability resulting
from the use of this report. The Client, the design consultants, and any unauthorized party, agree
to defend, indemnify, and hold harmless QG from any claim or liability associated with such
unauthorized use or non-compliance. We recommend that QG be given the opportunity to review
the final project plans and specifications to evaluate if our recommendations have been properly
interpreted. We assume no responsibility for misinterpretation of our recommendations.
5
Pichner Critical Slope Consultation
6/18/2020
Appendix A. Site Map
Quality Geo, PLLC
Project # QG20-018
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Quality Geo,
PLLC
Site Map
Pichner Critical Slope
source: Client provided survey
Scale & Locations are approx.
Not for Construction
. 1
Figure 1
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Pichner Critical Slope Consultation
6/18/2020
Appendix B. Site Photos
Photo 1. Typical landscape wall and slope conditions.
Photo 2. Erosion from daylighting drainage
7
Quality Geo, PLLC
Project # QG20-018