CRA19970236Critical Areas- Checklist
--------------------------------------------------------------
Site Information (soils/topography/hydrology/vegetation) QQ
1. Site Address/Location: D1�2 njo & S _2'?-
2. Property Tax Account Number: qN(j :: �( - M —
3. Approximate Site Size (acres or square feet):
4. Is this site currently developed? yes; X- no.
If yes; how is site developed?
5. Describe the general site topography. Check all that apply.
Flat: less than 5-feet elevation change over entire site.
Rolling: slopes on site generally less than 15% (a vertical rise of 10-feet over a
horizontal distance of 66-feet).
Hilly: slopes present on site of more than 15% and less than 30% ( a vertical rise of
10-feet over a horizontal distance of 33 to 66-feet).
Steep: grades of greater than 30% present on site (a vertical rise of 10-feet over a
horizontal distance of less than 33-feet).
Other (please describe):
6. Site contains areas of year-round standing water:
ND
; Approx. Depth:
7. Site contains areas of seasonal standing water: NO ; Approx. Depth:
What season(s) of the year?
8. Site is in the floodway 1 " 0 floodplain of a water course.
9. Site contains a creek or an area where water flows across the grounds surface? Flows are year-
round? Nu Flows are seasonal? (What time of year? ).
10. Site is primarily: forested X ; meadow ;shrubs ; mixed
urban landscaped (lawn,shrubs etc)
11. Obvious wetland is present on site: �)n
DETERMINATION:
STUDY REQUIRE CONDITIONAL WAIVER
City of Edmonds
Critical Areas Checklist
`4C. t sa'i
The Critical Areas Checklist contained on
this form is to be filled out by any person
preparing a Development Permit
Application for the City of Edmonds prior to
his/her submittal of a development permit to
the City.
The purpose of the Checklist is to enable
City staff to determine whether any potential
Critical Areas are or may be present on the
subject property. The information needed to
complete the Checklist should be easily
available from observations of the site or
data available at City Hall (Critical Areas
inventories, maps, or soil surveys).
An applicant, or his/her representative, must
fill out the checklist, sign and date it, and
submit it to the City. The City will review
the checklist, make a precursory site visit,
and make a determination of the subsequent
steps necessary to complete a development
permit application.
With a signed copy of this fonn, the
applicant should also submit a vicinity map
or plot plan for individual lots of the parcel
with enough detail that City staff can find
and identify the subject parcel(s). In
addition, the applicant shall include other
pertinent information (e.g. site plan,
topography map, etc.) or studies in
conjunction with this Checklist to assist
staff in completing their preliminary
assessment of the site.
I have completed the attached Critical Area Checklist and attest that the answers provided are
factual, to the best of my knowledge (fill out the appropriate column below).
Owner Applicant: Applicant Representative:
Name
Street Address
Sienature
U d&&;
Name
: Oly 2'J" r5�- �5J
Street Address
• PhoneState,
Phone
Date Signature
Date
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CA FILE NO. 61 '-CZ '('
Critical Areas Checklist
--------------------------------------------------------------
Site Information (soils/topography/hydrology/vegetation) / n
1. Site Address/Location: Le-�
2. Property Tax Account Number: i'N%
3. Approximate Site Size (acres or square feet):
4. Is this site currently developed? yes; Y- no.
If yes; how is site developed?
5. Describe the general site topography. Check all that apply.
Flat: less than 5-feet elevation change over entire site.
Rolling: slopes on site generally less than 15% (a vertical rise of 10-feet over a
horizontal distance of 66-feet).
Hilly: slopes present on site of more than 15% and less than 30% ( a vertical rise of
10-feet over a horizontal distance of 33 to 66-feet).
Steep: grades of greater than 30% present on site (a vertical rise of 10-feet over a
horizontal distance of less than 33-feet).
Other (please describe):
6. Site contains areas of year-round standing water: ND ; Approx. Depth:
7. Site contains areas of seasonal standing water: ND ; Approx. Depth:
What season(s) of the year?
8. Site is in the floodway 0 U floodplain of a water course.
9. Site contains a creek or an area where water flows across the grounds surface? Flows are year-
round? No Flows are seasonal? (What time of year? )•
10. Site is primarily: forested X ; meadow ;shrubs : mixed
urban landscaped (lawn,shrubs etc) 15C,
11. Obvious wetland is present on site: �tn
7
"ca_chk.doc; Rev 10/03/97
-- ----- ----- 1 Z OL3-
City of Edmonds
Critical Areas Checklist
`°c. l Sy"
The Critical Areas Checklist contained on
this form is to be filled out by any person
preparing a Development Permit
Application for the City of Edmonds prior to
his/her submittal of a development permit to
the City.
The purpose of the Checklist is to enable
City staff to determine whether any potential
Critical Areas are or may be present on the
subject property. The information needed to
complete the Checklist should be easily
available from observations of the site or
data available at City Hall (Critical Areas
inventories, maps, or soil surveys).
An applicant, or his/her representative, must
fill out the checklist, sign and date it, and
submit it to the City. The City will review
the checklist, make a precursory site visit,
and make a determination of the subsequent
steps necessary to complete a development
permit application.
With a signed copy of this form, the
applicant should also submit a vicinity map
or plot plan for individual lots of the parcel
with enough detail that City staff can find
and identify the subject parcel(s). In
addition, the applicant shall include other
pertinent information (e.g. site plan,
topography map, etc.) or studies in
conjunction with this Checklist to assist
staff in completing their preliminary
assessment of the site.
I have completed the attached Critical Area Checklist and attest that the answers provided are
factual, to the best of my knowledge (fill out the appropriate column below).
Owner �pplicant: Applicant Representative:
Name Name
1.12
Street Address Street Address
A, State, ZIP Phone
Signature
Date Signature
Date
I
Dennis M. Bruce, RE.
M.S.C.E., M.B.A. Geotechnical/Civil Engineer
November 4, 1997
Mr. Dennis V. O'Leary
Chief Financial Officer
Lynnwood Mortgage Corporation
6505 - 218th Street S.W., Suite 9
Mountlake Terrace, Washington 98043
Subject: Geotechnical Evaluation - Lots 2 and 3
Approximately 84th Place and 182nd Place, Edmonds, WA
This engineering report presents the results of a geotechnical evaluation of the
property at approximately 84th Place and 182nd Place, Edmonds, Washington. This
evaluation was necessitated by owner and developer concerns, as well as City of
Edmonds requirements.
REFERENCES:
• Vicinity Map (figure 1)
• Topographic Survey Map by Chadwick and Winters, of Lots 2 and 3
dated October, 1997
• Site photographs (available)
BACKGROUND:
It is understood that Lots 2 and 3 are part of an overall parcel containing Lot No.
1 with existing residence, and Lots 2, 3 and 4 (see Survey map and plot plans). This
investigation deals with Lots 2 and 3 with regard to geotechnical slope issues. It is
understood that property owner wishes to construct a single family residence on Lot 3
and another single family residence on Lot 2. No development or construction has
occurred on either Lot 2 or 3 to date.
Lots 2 and 3 contain a "flatter" portion, as well as a more steeply sloped rear
(southerly portion). The flatter portions of the lots currently consist of lawn grasses,
with a few mature trees. The steeper (southerly) portion of the lots are densely
vegetated with shrubs, bushes and trees (see photographs).
SOILS • FOUNDATIONS • SITE DEVELOPMENT • INSPECTION DRAINAGE • DESIGN & PERMIT • LEGAL
17814 8th Ave. N.W. • Shoreline, Washington 98177 (206) 546-9217 • FAX 546-8442
Mr. Dennis V. O'Leary
Page two
ASSESSMENT:
While not within the scope of this evaluation, this engineer assessed the
existing residence on Lot 1 for any geotechnical distress. No evidence of any
foundation settlements or shifting were observed. Visual assessments of Lots 2 and 3
by this engineer throughout the past year revealed no evidence of any geotechnical
distress: No sliding, no creep, no shifting, nor any significant erosional degradation
was observed on the overall property, including Lots 2 and 3.
In order to augment existing site geotechnical information, soil test pits were
dug (by backhoe) under this engineer's observation on August 9, 1997.
See soil test pit logs (attached).
The findings of the four soil test pits (plotted on the Survey Topographic Map)
were very similar. Namely: dense brown, silty sand to approximately three (3) to four
(4) foot depths. Dense to very dense grayish brown weathered glacial till (hardpan).
No ground water was present in any of the four soil test pits. All test pit walls
remained vertical and stable throughout the excavated time frame (approximately two
hours).
CONCLUSIONS/RECOMMENDATIONS:
Based on the findings of this investigation, and experience with similar sites in
the area, Lots 2 and 3 are geotechnically approved for the proposed single family
residences, subject to the following conditions:
• Standard reinforced continuous and spread footings. Allowable bearing
pressure: 2,000 p.s.f.
• Equivalent fluid pressure of 35 p.c.f. is recommended for any retaining wall
provided the drainage zone is inspected and verified by this engineer.
For retaining wall design, use a friction factor of 0.55 and passive pressure of
350 p.c.f.
• The foundations for the proposed structures may be placed anywhere on Lots
2 and 3, outside of the dashed top -of -bank survey area (see Topographic map).
In other words, there are no geotechnical limitations to the proximity of the
proposed residences and the top -of -slope line. (It is geotechnically
Mr. Dennis V. O'Leary
Page three
possible, but not likely, to properly construct a foundation on the steeper
portions of Lots 2 and 3. This would require uneconomic stabilizing techniques
and methods).
To be clear, the geotechnical set -back distance to the top -of -bank dashed line is
zero. It is understood that political or zoning set -back distances do apply per
City of Edmonds requirements. It is important to restate, however, that no set-
back distance is essential for geotechnical reasons. If desired, exceptions or
variances could be pursued.
Geotechnical inspection by this engineer prior to any foundation concrete
placement.
The proposed structures can be supported on conventional continuous and
spread footings bearing on undisturbed native soils or on structural fill placed above
native soils. See the later sub -section entitled General Earthwork and Structural Fill
for structural fill placement and compaction recommendations. Continuous and
individual spread footings should have minimum widths of eighteen (18) and twenty-
four (24) inches, respectively, and should be bottomed at least eighteen (18) inches
below the lower adjacent finish ground surface.
Depending on the final site grades, some overexcavation may be required
below footings to expose competent native soils. Unless lean concrete is used to fill
the over excavated hole, the width of the overexcavation at the bottom must be at least
as wide as the sum of two times the depth of the overexcavation and the footing width.
For example, an overexcavation extending two feet below the bottom of a three-foot
wide footing must be at least seven feet wide at the base of the excavation.
Footings constructed according to the above recommendations may be
designed for an allowable soil bearing pressure of three thousand (3,000) pounds per
square foot (p.s.f.). A one-third increase in this design bearing pressure may be used
when considering short-term wind or seismic loads. For the above design criteria, it is
anticipated that total post -construction settlement of footings founded on competent,
native soils (or on structural fill up to five (5) feet in thickness) will be about one-half
inch, with differential settlements on the order of one -quarter inch.
Lateral loads due to wind or seismic forces may be resisted by friction between
the foundations and the bearing soils, or by passive earth pressure acting on the
vertical, embedded portions of the foundations. For the latter condition, the
foundations must either be poured directly against undisturbed soil or the backfill
placed around the outside of the foundation must be level structural fill. We
Mr. Dennis V. O'Leary
Page four
recommend the following design values be used for the foundation's resistance to
lateral loading:
Parameter
Coefficient of Friction
Passive Earth Pressure
Where:
Design Value
0.55
350 p.c.f.
(1) p.c.f. is pounds per cubic foot.
(2) Passive earth pressure is computed using the equivalent fluid density.
We recommend that a safety factor of at least 1.5 be used for design of the
foundation's resistance to lateral loading.
SLABS -ON -GRADE:
Slab -on -grade floors may be supported on undisturbed, competent native soils
or on structural fill. The slabs may be supported on the existing soils provided these
soils can be recompacted prior to placement of the free -draining sand or gravel
underneath the slab. This sand and gravel layer should be a minimum of four (4)
inches thick. We also recommend using a vapor barrier such as 6-mil. plastic
membrane beneath the slab with minimum overlaps of 12 inches for sealing purposes.
PERMANENT FOUNDATION AND RETAINING WALLS:
Retaining walls backfilled on one side only should be designed to resist lateral
earth pressures imposed by the soils retained by these structures. The following
recommended design parameters are for walls less than twelve (12) feet in height
which restrain level backfill:
Parameter
Active Earth Pressure"
Passive Earth Pressure
Coefficient of Friction
Soil Unit Weight
Design Value
30 p.c.f.
350 p.c.f.
0.55
125 p.c.f.
Mr. Dennis V. O'Leary
Page five
Where:
(1) p.c.f. is pounds per cubic foot
(2) Active and passive earth pressures are computed using equivalent fluid
densities.
For restrained walls which cannot deflect at least 0.002 times the wall
height, a uniform lateral pressure of one hundred (100 p.s.f. should be
added to the active equivalent fluid pressure).
The values given above are to be used for design of permanent foundation and
retaining walls only. An appropriate safety factor should be applied when designing
the walls. We recommend using a safety factor of at least 1.5 for overturning and
sliding.
The above design values do not include the effects of any hydrostatic pressures
behind the walls and assume that no surcharge slopes or loads will be placed above
the walls. If these conditions exist, then those pressures should be added to the above
lateral pressures. Also, if sloping backfill is desired behind the walls, then we will
need to be given the wall dimensions and slope of the backfill in order to provide the
appropriate design earth pressures.
Heavy construction equipment should not be operated behind retaining and
foundation walls within a distance equal to the height of the wall, unless the walls are
designed for the additional lateral pressures resulting from the equipment. Placement
and compaction of retaining wall backfill should be accomplished with hand -operated
equipment.
Retaining Wall Backfill
Backfill placed within eighteen (18) inches of any retaining or foundation walls
should be free -draining structural fill containing no organics. This backfill should
contain no more than five (5) percent silt or clay particles and have no particles greater
than four (4) inches in diameter. The percentage of particles passing the No. 4 sieve
should be between twenty-five (25) and seventy (70) percent. Due to their high silt
content, if the native soils are used as backfill, a drainage composite, such as Mirafi
and Enkadrain, should be placed against the retaining walls. The drainage
composites should be hydraulically connected to the foundation drain system. the
purpose of these backfill requirements is to assure that the design criteria for the
retaining wall as not exceeded because of a build-up of hydrostatic pressure behind
the wall. The subsection entitled General Earthwork and Structural Fill contains Mr.
Dennis V. O'Leary
Page six
recommendations regarding placement and compaction of structural fill behind
retaining and foundation walls.
EXCAVATION AND SLOPES:
In no case should excavation slopes be greater than the limits specified in local,
state and national government safety regulations. Temporary cuts up to a height of
four (4) feet deep in unsaturated soils may be vertical. For temporary cuts having a
height greater than four (4) feet, the cut should have an inclination no steeper than 1:1
(Horizontal:Vertical) from the top of the slope to the bottom of the excavation. Under
specific recommendations by the geotechnical engineer, excavation cuts
may be modified for site conditions. All permanent cuts into native soils should be
inclined no steeper than 2:1 (H:V). Fill slopes should not exceed 1:1 (H:V). It is
important to note that sands do cave suddenly, and without warning. The contractors
should be made aware of this potential hazard.
Water should not be allowed to flow uncontrolled over the top of any temporary
or permanent slope. All permanently exposed slopes should be seeded with an
appropriate species of vegetation to reduce erosion and improve stability of the
surficial layer of soil.
DRAINAGE CONSIDERATIONS:
Footing drains are recommended at the base of all footings and retaining walls.
These drains should be surrounded by at least six (6) inches of one -inch -minus
washed rock wrapped in non -woven geotextile filter fabric (Mirafi 140N, Supac 4NP, or
similar material). At the highest point, the perforated pipe invert should be at least as
low as the bottom of the footing and it should be sloped for drainage. All roof and
surface water drains must be kept separate from the foundation drain system.
No groundwater was observed in any of the test pits during the field work.
Seepage into the planned excavation is possible, and likely if excavation occurs
during winter months, and if encountered should be drained away from the site by use
of drainage ditches, perforated pipe, French drains, or by pumping from sumps
interconnected by shallow connector trenches at the bottom of the excavation.
The excavation and site should be graded so that surface water is directed off
the site and away from the tops of slopes. Water should not be allowed to stand in any
area where foundations, slabs, or pavements are to be constructed. Any exposed
slopes to be covered with plastic to minimize erosion. Final site grading in areas
adjacent to buildings should be sloped at least two (2) percent away from the building,
except where the area adjacent to the building is paved.
Mr. Dennis V. O'Leary
Page seven
GENERAL EARTHWORK AND STRUCTURAL FILL:
The proposed building and pavement areas should be stripped and cleared of
all surface vegetation, all organic matter, and other deleterious material. The stripped
or removed materials should not be mixed with any materials to be used as structural
fill.
NOTE: Specific clearing limits to be established at pre -construction meeting with City
of Edmonds building officials and inspectors.
Structural fill is defined as any fill placed under the building, behind permanent
retaining or foundation walls, or in other areas where the underlying soils needs to
support loads. This engineer should observe site conditions during and after
excavation prior to placement of any structural fill.
All structural fill should be placed in horizontal lifts with a moisture content at or
near the optimum moisture content. The optimum moisture content is that moisture
content which results in the greatest compacted dry density. The moisture content of
fill soils is very important and must be closely controlled during the filling and
compaction process.
The allowable thickness of the fill lift will depend on the material type,
compaction equipment, and the number of passes made to compact the lift. In no case
should the lifts exceed twelve (12) inches in loose thickness. The following table
presents recommended relative compaction for structural fill:
Location of Fill Placement
Beneath footings, slabs or walkways
Behind retaining walls
Beneath pavements
Minimum Relative
Compaction
95%
90%
95% for upper 12 inches of
subgrade, 90% below that level
Where: Minimum relative compaction is the ratio, expressed in percentages, of
the compacted dry density to the maximum dry density, as determined in
accordance with ASTM Test Designation D-1557-78 (Modified Proctor).
Mr. Dennis V. O'Leary
Page eight
Use of On -Site Soils
If grading activities take place during wet weather, or when the silty, on -site soils
are wet, site preparation costs may be higher because of delays due to rains and the
potential need to import granular fill. The on -site soils are generally silty and thus are
moisture sensitive. Grading operations will be difficult when the moisture content of
these soils exceeds the optimum moisture content.
Moisture sensitive soils will also be susceptible to excessive softening and
"pumping" from construction equipment traffic when the moisture content is greater
than the optimum moisture content.
Ideally, structural fill which is to be placed in wet weather should consist of a
granular soil having no more than five (5) percent silt or clay particles. The percentage
of particles passing the No. 200 sieve should be measured from that portion of the soil
passing the three -quarter -inch sieve.
The use of "some" on -site soils for fill material may be acceptable if the upper
organic materials is segregated and moisture contents are monitored by engineering
inspection.
DRAINAGE CONTROLS:
No drainage problems were evident on Lots 2 and 3. Surface runoff flows
generally westerly (from the flatter portions of the lots). This engineer recommends
compliance with the City of Edmonds standard storm water drainage controls. The
surficial sandy soils are such that it is practical to utilize an infiltration storm water
system.
CONCRETE:
All foundation concrete (footings, stem walls, slabs, any retaining walls,
etc.) shall have a minimum cement content of 5-1/2 sacks per cubic yard of concrete
mix.
INSPECTION:
The recommendations of this report are only valid when key geotechnical
aspects are inspected by this engineer during construction:
• Soil cuts
• Foundation subgrade verification
Mr. Dennis V. O'Leary
Page nine
• Any retaining wall, or rockery placement
• Any fill placement and compaction
• Subsurface drainage installation
SUMMARY:
• The two proposed single family residences (on Lots 2 and 3) are
geotechnically viable when constructed in accordance with the
recommendations herein, compliance with City of Edmonds approved plans
and key geotechnical inspection during construction.
There are no geotechnical constraints limiting the proximity of the proposed
residences to any sloped portion of the property. As a practical measure, this
engineer recommends the residences be situated no further southerly than the
dashed top -of -slope line. If desired, however, it is geotechnically feasible to
construct the residences beyond (more southerly) than the dashed survey line.
GEOTECHNICAL REVIEW OF PLANS:
Prior to the City of Edmonds issuing a building permit, this engineer should
review the specific house plans for compliance with the recommendations of this
geotechnical report.
CLOSURE:
The findings and recommendations of this report were prepared in accordance
with generally accepted professional engineering principles and practice. No other
warranty, either express or implied, is made. The conclusions are based on the results
of the field exploration and interpolation of subsurface conditions between explored
locations. If conditions are encountered during construction that appear to be different
than those described in this report, this engineer should be notified to observe the
situation and review and verify or modify the recommendations.
If there are any questions, do not hesitate to call.
DMB:vIb
l
Dennis M. Bruce, P.E.
Geotechnical/Civil Engineer
ie�