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R E II 3 111C
November 28, 2016
Slavik Miniaylo
7316-164`' Street SW
Edmonds, WA 98026
Re: Design Plans and Responses to Plan Review Comments by the
City of Edmonds Titled: 'Miniaylo retaining walls (May 26, 2016)"
Plan Check: BLD2016-0532 at
7316 -164th Street SW, Edmonds, WA
Transmitted electronically to: nwstonecraft@yahoo.com
Our Reference: J 111- 01-16
Dear Slavik:
I
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Adams Resource Consultants (ARC) provides this letter with the attached design plans in response
to the above referenced comments from the City of Edmonds (City). Our efforts are in support of
improvements needed adjacent to the geologically hazardous (steep slope) area, including
rebuilding of the existing unpermitted retaining walls at the above referenced project referred to as
Miniaylo residence. In summary our design recommendations now include: 1) removal and
replacement of the upper retaining wall that is currently leaning and has experienced settlement
over time, 2) lowering the patio area on the west end of the project to limit the maximum wall
height to less than 4 feet and 3) constructing a rock fill buttress adjacent to the existing wall on the
east end of the project area. These recommended changes to the wall areas are depicted on the
attached three drawings.
We have provided our observations and opinions concerning a newly constructed (Lower) wall in a
previous letter titled: "REVISED Geotechnical Assessment for New Retaining Wall at 7316-
164th Street SW' — reference J 111-01-16," dated April 21, 2016. This lower wall is 4 feet
high and was constructed without permit. Our scope of work and efforts were to
investigate the current conditions in support of permitting that structure. We made several
recommendations in our assessment and with the exception of placing survey monitoring
points; all our recommendations have been met concerning that wall. Based on our
observations and preliminary slope stability calculations the lower wall was constructed to
our recommendations and does not adversely impact the stability of the steeper slopes
below to the north.
Miniaylo - New Retaining Wall J-111-01-16
November 28, 2016
We also understand that the Owner wishes to improve other exiting walls in the same area
and we have provided design plans for that work with this letter. It is important to note
that, provided our design is implemented and recommendations followed, all the walls
north of the residence meet or exceed a calculated factor of safety of 1.5. With the
exception of that shown in this design we assume no other fill or debris will be placed on
the slope or elsewhere on this site. We have also assumed all drain systems will extend by
hard line to the base of the steep slope to the north of this project.
In direct response to the comments from the City that addresses our assessment as
previously described we provide the following:
City Comment 1 (a): Clarify the applicability of the letter from Cornerstone
Geotechnical, Inc. in support of the current permit application. The letter from
Cornerstone Geotechnical regards the garden area/concrete planters to the immediate
west of the residence driveway that were part of an `Order to Correct Violation', `Notice
of Civil Violation', Hearing Examiner decision under case number `V-03-173', and
ultimately permitted under permit BLD2004-1037. The approval was for that area alone
with a noted condition that "Any future development will be required to demonstrate
compliance with the Critical Areas Variance criteria in effect at that time." The letter
from Cornerstone dated after the Hearing Examiner decision is bound to that condition
and does not appear to mention the presence of retaining walls of the height or
configuration of those depicted in the provided photographs.
Our letter (April 21, 2016) noted that as part of our assessment we have reviewed several
documents. The documents reviewed included but were not limited to the three items
listed in our letter. It is our professional opinion that the letter from Cornerstone (2005) is
significant in that it supports several key factors that assist with the general stability,
performance and foundation conditions at the site.
Specifically the letter from Cornerstone indicates that "The area along the northeast to
north side of the existing residence is now landscaped with a low block wall (emphasis
added by ARC), grass and shrubs. A low berm has also been place in this area to direct
surface water away from the top of the slope."
We have not observed any other low block wall in this general area north of the residence
near the low berm. Considering this, we believe the above stated reference concerns the
block walls we are asked to evaluate. Thus, we can assume from this description that the
settlement we have observed in the block walls north of the residence has occurred after
the written observations by Cornerstone (2005) or within the last 10 or so years without
noticeable disturbance of the steep slopes to the north and/or west. This is applicable to
our efforts because it is a valuable piece of information regarding the integrity of the steep
slope and native soil in that area.
Miniaylo - New Retaining Wall
November 28, 2016
J-111-01-16
Further in the letter by Cornerstone (2005) they address a functioning drainage system in
the garden areas south of the project site. This is important in terms of our assessment
because we can be assured that little or no water from the garden areas west of the
residence impacts (now or in the future) the stability of the walls in question or the steep
slope north and/or west of the walls.
City Comment 2 (b): Clarify the applicability of the Plan Map titled: "Site Plan for
House Construction," by Partners Architectural, dated June 10, 1999 in support of the
current application. A City of Edmonds record of it could not be found along the
previously submitted documents. The latest `Plan Map' received, reviewed, and
approved as part of the permitted work for the house construction under permits
BLD 1999-023 1 /BLD2000-0325 was prepared on 11-2-98 and dated by the Eric Koch,
architect for `Partners Architectural' on 11-9-98. It was received by the City of Edmonds
as part of a complete permit resubmittal on 11-19-98 and reviewed and approved
approximately two weeks later. That `Plan Map', and the others submitted for review
prior, do not appear to indicate the presence of retaining walls of the height or
configuration of those depicted in the provided photographs.
We will delete our reference to the old site map. We are now providing a new site map
showing the location of the subject retaining walls and our proposed repairs.
City Comment 3 (c): Clarify the omission of Chapter 19.10 ECDC in the referenced
applicable codes regarding permitted activities allowed in a geologically hazardous area.
Chapter 19.10 ECDC is referenced in Chapter 23.80 ECDC and provides the required
procedures related to the issuance of permits within designated earth subsidence and
landslide hazard areas of the city. The current permit application and the submitted
documentation do not meet the requirements of Chapter 19.10 ECDC.
We have reviewed the code and requirements referenced above and believe we have
addressed these adequately for the existing conditions, features and proposed activities that
will occur near the geologically hazardous area. The following conclusions and
recommendations meet or exceed the City's requirements based on: a) our observations of
the geologic strata exposed on the steep slopes, b) hand auger explorations in the lawn
area north of the lower wall, c) observations of conditions exposed in exploration test pits
extending beneath the exiting upper wall, and d) our slope stability calculations. Exceptions
to the requirements in the City Code Section 19.10.030 are described below;
(1) We have combined the North Edmonds Subsidence and Landslide Hazard
Map, Vicinity Map and topography into one submittal, Figure 1.
Miniaylo - New Retaining Wall
November 28, 2016
J-111-01 -16
(2) We have not included any survey topography with this design in
consideration of the small area of change to existing grades.
(3) Our Civil site plans are included in this submittal.
(4) There is no tree cutting or clearing required for this project.
(5) This letter combined with our letter dated (April 21, 2016) comprise the
necessary Geotechnical reporting for this project.
(6) Declarations, if required, will be supplied by the Owner.
(7) No architectural or structural plans are needed for this project.
(8) The owner is directed to complete this project using mostly hand tools and
thus no bonds, covenants or contractor insurance are needed for completion
of this project.
CONCLUSIONS AND RECOMMENDATIONS
In our opinion the attached design meets or exceeds the above stated requirements for retaining
walls. We have based this opinion on geologic and engineering observations provided by the
above mentioned documents, our own observations and stability calculations. Please be aware that
our previous recommendations (April 21, 2016) still apply and we consider those to be crucial to
the overall success for completing this project.
We conclude that, provided the majority of the work is completed "by -hand", including excavation
and placement of rock during the dryer (non -rainy season) months of 2017, the project can proceed
as shown on the plans. We also recommend the following:
1. Complete the entire project according to our recommendations and to the satisfaction of
the City in one "construction season,"
ARC be retained to conduct a pre -construction meeting and provide appropriate
professional observations to document construction progress, and
3. Survey monitoring points are set before beginning construction.
Miniaylo - New Retaining Wall
November 28, 2016
LIMITATIONS
J-111-01-16
Subsurface conditions interpreted from observed soil materials and seepage conditions
encountered formed the basis for developing the recommendations in this report. The nature and
extent of conditions may change over time, often vary between observation locations and
differences may not become evident until after the start of site work. If significant variations then
appear evident, we should be consulted to re-evaluate the conclusions and recommendations in this
report. It should be noted that groundwater seepage and any fluctuations in the level of the
groundwater are dependent on seasonal variations in rainfall, temperature, and other climatic
factors.
Our work for this project was performed, and this report prepared, in accordance with our original
contract with you, executed on April 13, 2016, including any approved changes. We have
completed this work in accordance with generally accepted professional practices for the nature
and conditions of the work done in the same, or in similar localities, at the time the work was
performed. This report is intended for the exclusive use of you and your contractors and/or
consultants for specific application to the referenced property. We make no other warranty,
express or implied.
Miniaylo - New Retaining Wall
November 28, 2016
1-111-01-16
If we may provide any additional information or clarification about this report, please do not
hesitate to contact Wayne by cell at 425.466.2891 or by message at 425.788.3244.
Sincerely,
ADAMS Resource Consultants Company
WAYNE C. ADAMS, PE, PENG, EG
President/CEO
ADAMS Resource Consultants
wayne@Ada nisRes ogrce.coin
ARTHUR ). FLEMING, PE
Associate Engineer
ADAMS Resource Consultants
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Miniaylo - New Retaining Wall J-111-01-16
November 28, 2016
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Slavik Miniaylo
7316-164"' Street SW
Edmonds, WA 98026
Re: REVISED Geotechnical Assessment for New Retaining Wall at
7316 -164th Street SW
Edmonds, Washington
Transmitted electronically to: nwstonecraft@yahoo.com
Our Reference: J 111- 01-16
Dear Slavik:
Adams Resource Consultants (ARC) is pleased to provide this brief letter report addressing the need to
apply for a permit to allow the newly constructed (March, 2016) concrete block retaining wall (Figures 1
through 3) at your above listed residence. As part of our assessment we have reviewed the following:
1) Letter dated January 7, 2005 from Cornerstone Geotechnical, Inc, to Clay Enterprises.
2) Plan Map titled: "Site Plan for House Construction," by Partners Architectural, dated June 10,
1999.
3) Applicable City of Edmonds codes: a) Chapter 23.40 Environmentally Critical Areas General
Provisions, b) Chapter 23.80 Geologically Hazardous Areas and c) Retaining Wall Permit Submittal
Requirements #1362.
In summary, based on our site observations and the previously listed information, the site area in question
that contains a newly constructed cement block wall is located in a Critical (steep (>40 percent) slope and
landslide hazard) Area. It is our professional opinion that this wall does not create a hazard to
neighboring properties, the older block wall above (south) nor to the slope beyond the lawn (north). The
construction of the new wall improves the slope and planting area by removing an older (degraded) wall.
We provide the details of our observations, opinions and recommendations below for your review and
submittal to the City in support of a permit to build and maintain the block wall.
BACKGROUND
)EVELOPMENT SERVICES
Miniaylo - New Retaining Wall J-111-01-16
April 21, 2016
We understand from our conversations that two older block walls were overgrown and leaning prior to
new re -construction. The lower block wall was replaced with the new wall (subject of this letter report).
We understand the new wall was completed by excavating to a firm and stable base and provided with a
3/4 -inch crushed rock leveling surface about 8 inches thick. The blocks were placed with interlocking pegs
at a slight facing batter. A footing drain was placed along the front foot of the wall. Filter fabric and 1
inch diameter drain rock was placed behind the wall to create a blanket drain approximately 12 inches
wide that extends from the top of the wall to the foot. The upper (older) leaning wall was left in place as
shown in Figures 1through 3. We noted that during a site visit in the past a geotechnical engineer noted
(2005) the condition of the two walls and indicated that these walls complied with their
recommendations.
GENERAL OBSERVATIONS
We used a hand auger and shovel to investigate the soil in front and behind the new wall. Our
explorations extended to less than or equal to 4 feet deep and confirmed that the soil conditions
associated with the new wall was as described. We also found determined that soil material behind the
new wall consisted of between 1 and 1.5 feet of loose topsoil and sandy fill that overlies at least 2 to 3
feet of native sand. We did not observe any indications of significant movement, settlement, wet or soft
areas along the wall foundation. The blocks appear level and the wall in good condition.
OVERALL SLOPE STABILITY
We observed soil conditions north and below the wall area where the slope exposes native sand, Figure 2.
This slope extends down at an angle of between 45 and 50 degrees to a creek that flows to the west
within and near the north property line. We did not observe any indications of groundwater seepage,
slope movement or creep in this hillside north and below the block wall. It does not appear that past
movement of the two block walls is related to a larger slope stability issue or landsliding.
CONCLUSIONS AND RECOMMENDATIONS
In our opinion the observed movement of the old wall is an indication of settlement from construction on
loose fill soil materials. The lawn to the north and slope below do not exhibit any signs of landsliding and
though this region has been mapped as containing old landslide features, the slopes described and noted
on Figure 3 seem to be at equilibrium and have not moved for a very long time.
In order to be assured that this area continues to perform well we recommend the following as a
condition of permit:
1. All watering should be kept to a minimum. Planting should include draught resistance vegetation.
No vegetation should be removed from the area between the new wall and the previously
mentioned creek without advice from both a geotechnical and vegetation specialist RECEIVED
I
Miniaylo - New Retaining Wall
April 21, 2016
)-111-01-16
2. With the exception of completing drain rock placement behind the new wall, no additional
construction should take place in the area without the advice of a geotechnical specialist.
3. Surface survey monitoring points should be placed at several locations along the new wall and
north edge of the lawn. These monitoring points should be tied back to nearby fixed (stable)
reference points, such as the house foundation corners or established monuments in the street.
Readings should be taken twice yearly or more often if movement is observed (before and after
the rainy season) by a licensed surveyor or engineer. The readings should be tracked by a
geotechnical specialist.
4. All retaining walls should be no more than a maximum height of 4 feet without specific
engineering design recommendations and engineering construction observations/approval. (The
existing block walls were designed by others for a maximum height of 48 inches.)
5. All new drainage lines from the wall area should be located. Drains should extend down to
positive discharge at the creek on our client's property.
In addition to the recommendations previously provided we also suggest that the owner consider
extending two geotechnical boreholes in the lawn area in front (north) of the new wall. These boreholes
would extend to elevations of the stream to the north and should be fitted with standpipe piezometers so
that the engineer can monitor both groundwater levels and any slope movement. If these boreholes are
completed as described we would recommend that data from the boreholes be collected and tracked in
the same way during the same time frame as the surface survey readings.
In our opinion if the walls noted in Figure 3 are built according to our recommendations, the construction
will improve site conditions and stability.
LIMITATIONS
Subsurface conditions interpreted from observed soil materials and seepage conditions encountered
formed the basis for developing the recommendations in this report. The nature and extent of conditions
may change over time, often vary between observation locations and differences may not become
evident until after the start of site work. If significant variations then appear evident, we should be
consulted to re-evaluate the conclusions and recommendations in this report. It should be noted that
groundwater seepage and any fluctuations in the level of the groundwater are dependent on seasonal
variations in rainfall, temperature, and other climatic factors.
Our work for this project was performed, and this report prepared, in accordance with our original
contract with you, executed on April 13, 2016, including any approved changes. We have completed this
work in accordance with generally accepted professional practices for the nature and conditions of the
work done in the same, or in similar localities, at the time the work was performed. This report is
intended for the exclusive use of you and your contractors and/or consultants for specific application to
the referenced property. We make no other warranty, express or implied.
Miniaylo - New Retaining Wall
April 21, 2016
)-111-01-16
If we may provide any additional information or clarification about this report, please do not hesitate to
contact Wayne by cell at 425.466.2891 or by message at 425.788.3244.
Sincerely,
ADAMS Resource Consultants Company
WAYNE C. ADAMS, PE, PENG, EG
President/CEO
ADAMS Resource Consultants
wa ��etfre,corn
ARTHUR]. FLEMING, PE
Associate Engineer
ADAMS Resource Consultants
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April 21, 2016
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Note: All locationsanddlmensionsshown are approximate.
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