93-100990COMMMTY DEVELOPMENT
TECHNICAL REVIEW COMMITTEE
DATE:
PROJECT PLANNER:
PLEASE RESPOND BY:
TYPE OF PERMIT(S) REQUIRED:
FILE NUMBER:
PROJECT NAME:
PROJECT ADDRESS:
PROJECT DESCRIPTION:
APPLICANT:
PROJECT BACKGROUND:
SEPA:
May 13, 1993 s (�
Stephen Clifton, 661-4109
May 27, 1993
SEPA review for geologically hazardous areas.
Building permit application BLD 93-0300 on hold
during SEPA review.
SEP 93-0008
Stitt SEPA for New Single Family Residence
29038 15th Place South,
Lot 26, Plat of Marlbrook North
Build new 5516 square foot single family residence
on a lot containing slopes in excess of 40 percent.
Mr. Richard Stitt
839-4328
New Single family residence proposed for site area
containing slopes in excess of 40 percent. SEPA
review required. Geotechnicial report provided
5/12/93.
Required due to slopes in excess of 40 percent.
CC �C-�n
JG Li c FF^'�f
dOF w 33530 1ST WAY SOUTH • FEDERAL WAY, WASHINGTON 88003
DEPARTMENT OF COMMUNITY DEVELOPMENT
June 24, 1993
Delbert Conrad
28913 15th Place South
Federal Way, WA 98003
RE: PROPOSED FENCING: MARLBROOK NORTH DIVISION
Dear Mr. Conrad:
You have asked if a fence can be constructed adjacent to the easterly boundary of Tract A" of
the plat of Marlbrook North, for purposes of homeowners' security. This letter summarizes our
telephone discussion of yesterday. Attached is a copy of the plat for your reference.
As discussed, "Tract A" was created as an open space area and for the private ownership of the
owners of Lots 22 through 32, who share in an equal and undivided interest and maintenance
responsibility for the tract. Accordingly, these homeowners owners have the authority to
construct a fence in the location you propose, providing such a structure is not prohibited by any
recorded agreements, easements, etc.
As can be seen on the plat map, several easements have been located over Tract A (see page
3 of the drawings). Three of these easements are dedicated for purposes of drainage and are
therefore under the control of the City of Federal Way. My discussion with Ron Garrow of the
Public Works Department concluded that the fence you propose would be permitted, if access
gates are provided across the drainage easements, and unobstructed access to these gates is
available to the City on a permanent basis. Further, the City would request that if the
homeowners execute an agreement for the common ownership and maintenance of the fence, the
agreement also reserves to the City permanent access privileges for maintenance of the drainage
easements.
It is the responsibility of the property owners to locate these easements in the field and to
provide the gates. If you have any questions about implementing this requirement, please
contact Ron Garrow, 661-4137.
The remaining easements are reserved for utilities, and recorded under various King County
Auditor's File Numbers, as identified on the plat. As discussed, you should contact King
County Records Division to obtain copies of these easements so as to verify that the proposed
fencing would not violate any recorded conditions. In addition, you may want to contact the
individual utility companies to verify your understanding of the agreements, and to secure verbal
approval of your proposal.
Delbert Conrad
June 24, 1993
Page 2 of 2
Finally, no building permit for the fence will be required, providing fence height does not
exceed 6 feet or incorporate barbed wire.
Please contact me at 661-4019 if you have any further questions at this time.
Sincerely,
Lori Michaelson Schill
Associate Planner
attach: Plat of Marlbrook North
S-S, T-21N, R-4E
c: Brent McFall, City Manager
Kathy McClung, Land Use Administrator
Cary Roe, Surface Water Manager
Ron Garrow, Senior Development Engineer
requires all governmental
Purpose of Checklist: ter 43.21-C RCW, decisions. An
Act (SEPA), Chap making scant
ental Policy acts of a proposal before probable sigxaii
The State Environm onmental imp d for all proposals with P xs to provide
agencies to consider the envir must be prepare u ose of this checklist
ental impact statement (E ) The f our proposal (and to reduce or
Of the environment.
en'viranm acts on the quality identify impacts from Y
adverse imp u and the agency and to help the agency decide whether an El
information to help the proposal, if it can be done)
avoid impacts from
is required.
for Applicants:proposal-
Instructions
ormation about our of your
eck asks you to des crfhe same basic a ental imp with the
to determine whether the the ueesstions briefly,
�� environmental checkhst Answer the q
Governmental agencies use this re preparation of an ELS • You can.
Governor scant, requiring P p description y
proposal are sign�f' own, or give the best most
most precise information 'known, of our knowledge. In
and carefully, to the best Y or project
plans
quest, answer
accurately Yens from your own observations . P
you must answer each q wer, or if a question does not
. you really do not know the any complete answers to the
cases, you should be able to answer the qua 1� not apply."
cos ,� or does
without the need prop
hire ate „day not kno later,
apply to your p p delay
questions now may avoid unnecessa�' shoreline, and landmark
�latiom, such as zoning, ental agencies
overamental reb l f you have problems,
the governor
Some questions ask about g if you can. Y
Answer these questions
designations. aver a
can assist you. even i£ you Plan to
do them help
of your proposal, ormation that will
questions apply to all parts Attach any additional inf
The checklist q different parcels of laud. enc to which you submit this checklist
The ag y related to
period of time or vn environmental effects. orInation reasonably
describe your proposal or its veers or provide additional inf
may ask you to explain your ans act.
determining
if there may be significant adverse imP
Checklist for Non -project Proposals:
h questions may be answered "does
Use of even thong q art D) -
ro ect proposals, Actions (P
t for non-p J supplemental Sheet for Non -project
Complete this checditi complete the licaut,
addition, "ant
not apply.it
'' ' '
t to the words "pro fCi`r _. tic area-,
the references in the checklist t� 1, fec�ted. geogr�p
� roposer, aad •,�.1
actions, �� ro osal, P ~
For non -project
prop
erty or site should be read as p P � 1�
respectively-
A.
1.
2.
3.
4.
S.
6.
7.
S.
BAC
KCROUND
Name of proposed
Project, if applicable:
ST1 � T Firs for ti'c�
Name of applicant:
" fGKAR-P R . S,,, ,i
.EPALTJATfOX Folt
AGENCY USE ONLI,
Address and Phone n
txmber
n.
�, NoN Gar ,4vF apt cant and contact persO
Date checkUst Prepared.- A'0'6) S j 1-- 4- 3: ,g �� L �`�Yi V"/ 9 e o 0
P1�I— 21-$ r1�3 3
Ageltcy requegl g checklist:
C �F
��A��Inr�
Proposed timing or schedule �inclu
Do you c c"PEE- --rz V p Rim ding Phasing,
hsg, rf alUcable):
have any plate 4
connected with this for future addition,
is
Pro osal? yeS explain.
expansion or further acti
N d prop
� laxn vity related
to or
List any environmental info prepared 3' directly related trmation you
a o this Proposal. about that has been pre are
nr a rn N 0 iv r- P d
' or will be
2
3
9. Do you know whether applications are pending for governmental approvals of other
proposals directly affecting the property covered by your proposal? If yes, explain.
DO POT {-N O Ny
10. List any government approvals or permits that will be needed for your proposal, if known.
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11. Give brief, complete description of your proposal, including the proposed uses and the size
of the project and site. There are several questions later in this checklist that ask you to
describe certain aspects of your proposal. You do not need to repeat those answers on this
page.
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12. Location 'of the proposal. Give sufficient information for a person to understand the
precise location of your proposed project, including a street address, if any, and section,
township, and range, if known. If a proposal would occur over a range of area, provide
the range or boundaries of the site(s). Provide a legal description, site plan, vicinity map,
and topographic map, if reasonably available. While you should submit any plans required
by the agency, you are not required to duplicate maps or detailed plans submitted with any
permit applications related to this checklist.
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B. ENVIRONMENTAL ELEMENTS
1. EARTH
4
a. General description of the site (circle one): Flat; rolling; .hilly, steep slopes, mountainous,
other.
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b. What is the steepest slope on the site (approximate percent slope)?
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C. What general types of soils are found on the site (for example, clay, sand, gravel, peat,
mulch)? If you know the classification of agricultural soils, specify them and note any
prime farmland.
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Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe.
No
e. Describe the purpose, type, and approximate quantities of any filling or grading proposed.
Indicate source of fill.
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r I N A L 13Prc- (G r I (-L- w I T H+ +0 '� D S T-v psip I L_ I S o vFL� e- l=
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f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe.
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g. About what percent of the site will be covered with impervious surfaces after project
construction (for example, asphalt or buildings)?
11 170
h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any.
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5
2. AIR
a. What types of emissions to the air would result from the proposal (i.e., dust, automobile,
odors, industrial wood smoke) during construction and when the project is completed? If
any, generally describe and give approximate quantities if known.
T-fl, i c A L- 01✓ 51 N G L-C F,N ^4 1 `1 R- F-,5 l 'P EN c F- .
b. Are there any off -site sources of emissions or odor that may affect your proposal? If so,
generally describe.
No
C. Proposed measures to reduce or control emissions or other impacts to air, if any.
p o N o T y- N a vi oF:.- N FiF--D F4 i- ArJ `C .
3. WATER
a. Surface.
1) Is there any surface water body on or in the immediate vicinity of the site (including year-
round and seasonal streams, saltwater, lakes, ponds, wetlands)? If yes, describe type and
provide names. If appropriate, state what stream or river it flows into.
No
2) Will the project require any work over, in, or adjacent to (within 200 feet) the described
waters? If yes, please describe and attach available plans.
3) Estimate the amount of fill and dredge material that would be placed in or removed from
surface water or wetlands and indicate the area of the site that would be affected. Indicate
the source of fill material.
POP-5 N O'T- ATPi-`f
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4) Will the proposal require surface water withdrawals or diversions? Give general
description, purpose, and approximate quantities if known.
N0
5) Does the proposal He within a 100=year floodplain? If so, note location on the site plan.
rAj 0
6) Does the proposal involve any discharges of waste materials to surface waters? If so,
describe the type of waste and anticipated volume of discharge.
Na
b. Ground.
1) Will ground water be withdrawn, or wail water be discharged to rAoundwater? Give
general description, purpose, and approximate quantities if known.
/'10
2) Describe waste material that will be discharged into the ground from septic tanks or other
sources, if any (for example: Domestic sewage; industrial, containing the following
chemicals...; agricultural; etc.). Describe the general size of the system, the number of
such systems, the number of houses to be served (if applicable), or the number of animals
or humans the system(s) are expected to serve.
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C. Water Runoff (including storm water).
1) Describe the source of runoff (including storm water) and method of collection and
disposal, if any (include quantities, if known). Where will this water flow? Will this water
flow into other waters? If so, describe.
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2) Could waste materials enter ground or surface waters? If so, generally describe.
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d. Proposed measures to reduce or control surface, ground, and runoff water impacts, if any.
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4. PLANTS
a. Check or circle types of vegetation found on the site.
V deciduous tree aide a le aspen ❑then
V evergreen tree fir cedar pine, other
shrubs
_grass
pasture
crop or grain
wet soil plants: cattail, buttercup, bulrush, skunk cabbage, other
water plant: water lily, eelgrass, milfoil, other
mother types of vegetation w 11-F bi-^(?,S) F::'t��t45
b. What kind and amount of vegetation will be removed or altered?
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c. List threatened or endangered species known to be on or near the site.
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d. Proposed landscaping, use of native plants, or other measures to preserve or enhance
vegetation on the site, if any.
M A-T i v EL P L{t t4-r S S H f- V 3 5) A /v i` v.t N.
5. ANIMALS
a. Circle any birds and animals which have been observed on or near the site or are known
to be on or near the site.
F:?
birds: hawk, heron, eagle, on birds other:
mammals: deer, bear, elk, beaver, other:
fish: bass, salmon, trout, herring, shellfish, other:
b. List any threatened or endangered species known to be on or near the site.
P-o N F—
c. Is the site part of a migration route? If so, explain.
No
d. Proposed measures to preserve or enhance wildlife, if any.
Do F-,; 5 H o r APP'-I
6. ENERGY AND NATURAL RESOURCES
a. What kinds of energy (electric, natural gas, oil, wood stove, solar) will be used to meet the
completed project's energy needs? Describe whether it will be used for heating,
manufacturing, etc.
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Vvaop 5 I OVE-
b. Would your project affect the potential use of solar energy by adjacent properties? If so,
generally describe.
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C. What kinds of energy conservation features are included in the plans of this proposal? List
other proposed measures to reduce or control energy impacts, if any.
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7. ENVIRONMENTAL HEALTH
a. Are there any environmental health hazards, including exposure to toxic chemicals, risk of
fire and explosion, spill, or hazardous waste, that could occur as a result of this proposal?
If so, describe.
No
1) Describe special emergency services that might be required.
N 0" F
2) Proposed measures to reduce or control environmental health hazards, if any.
b. Noise.
1) What types of noise exist in the area which may affect your project (for example: traffic,
equipment operation, other)?
jvo I S e5` -"` F(c-AL- OF- AF -F✓A
2) What types and levels of noise would be created by or associated with the project on a
short-term or long-term basis (for example: traffic, construction operation, other)?
Indicate what hours noise would come from the site.
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3) Proposed measures to reduce or control noise impacts, if any.
- 114ONF- Ali F-1_.9!rD
8. LAND AND SHORELINE USE
10
a. What is the current use of the site and adjacent properties?
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Av,�rAcF-N-r _ PR0PF-R--r1F-5 R.ESIvF-N IrlAL-
b. Has the site been used for agriculture? If so, describe.
No
C. Describe any structures on the site.
/\l O N F
d. Will any structures be demolished? If so, what?
DoC-5 NaY APF"
e. What is the current zoning classification of the site?
12, E5 f P F—Wr lA L—
f. What is the current comprehensive plan designation of the site?
PO N o -' V-" O LAJ
g. If applicable, what is the current shoreline master program designation of the site?
PoFS Nvi Appi-y
h. Has any part of the site been classified as an "environmentally sensitive" area? If so,
specify.
`fa5) SM)AVI- A1L1rA r-X.D 0% 5 1-Z,PE-
L Approximately how many people would reside or work in the completed project?
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11
j. Approximately how many people would the completed project displace?
�VaN�
k. Proposed measures to avoid or reduce displacement impacts, if any.
PaF-S N o-r- AFP,,—Y
1. Proposed measures to ensure the proposal is compatible with existing and projected land
uses and plans, if any.
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9. HOUSING
a. Approximately how many units would be provided, if any? Indicate whether high, middle,
or low-income housing.
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b. Approximately how many units, if any, would be eliminated? Indicate whether high,
middle, or low-income housing.
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C. Proposed measures to reduce or control housing impacts, if any.
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10. AESTHETICS
a. What is the tallest height of .any proposed structure(s), not including antennas; what is the
principal exterior building material(s) proposed?
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b. What views in the immediate vicinity would be altered or obstructed?
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12
C. Proposed measures to reduce or control aesthetic impacts, if any.
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11. LIGHT AND GLARE
a. What type of light or glare will the proposal produce? What time of day would it mainly
occur?
IV o " E-r
b. Could light or glare from the finished project be a safety hazard or interfere with views?
/`f
C. What existing off -site sources of light or glare may affect your proposal?
r►oNF
d. Proposed measures to reduce or control light and glare impacts, if any.
DOr s N pT Ar 1'PL-if
12. RECREATION
a. What designated and informal recreational opportunities are in the immediate vicinity?
tieN1_
b. Would the proposed displace any existing recreational uses? If so, describe.
P o GS N n T A P FL*i
C. Proposed measures to reduce or control impacts on recreation, including recreation
opportunities to be provided by the project or applicant, if any.
P 0 G 5 /*J 0 T A F1 Pi,—Y
13
13. HISTORIC AND CULTURAL PRESERVATION
a. Are there any places or objects listed on, or proposed for, nation, state, or local
preservation registers known to be on or next to the site? If so, generally describe.
p0
b. Generally describe any landmarks or evidence of historic, archaeological, scientific, or
cultural importance known to be on or next to the site.
/N 0 "'1 F-
c. Proposed measures to reduce or control impacts, if any.
Pv i:-5 n! aT H1'PL- `f
14. TRANSPORTATION
a. Identify public streets and highways serving the site, and describe proposed access to the
existing street system. Show on site plans, if any.
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b. Is the site currently served by public transit? If not, what is the approximate distance to
the nearest transit stop?
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c. How many parking spaces would the completed project have? How many would the project
eliminate?
pOE S N o7- APP I Y
d. Will the proposal require any new roads or streets, or improvements to existing roads or
streets, not including driveways? If so, generally describe (indicate whether public or
private).
N 0
14
e. Will the project use (or occur in the immediate vicinity of) water, rail,' or air
transportation? If so, generally describe.
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f. How many vehicular trips per day would be generated by the completed project? If
known, indicate when peak volumes would occur.
YAF- I G S ) ,Z ro 4-
g. Proposed measures to reduce or control transportation impacts, if any.
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15. PUBLIC SERVICES
a. Would the project result in an increased need for public services (for example: fire
protection, police protection, health care, schools, other)? If so, generally describe.
No
b. Proposed measures to reduce or control direct impacts on public services, if any.
Par-5 -t°T APPL-�
16. UTILITIES
a. Circle utilities currently available at the site: electricity atural gas water, refus�se cep
telephone sanitary sewer septic system, other.
b. Describe the utilities that are proposed for the project, the utility providing the service, and
the general construction activities on the site or in the immediate vicinity which might be
needed.
N 0 h1 Tz..
15
C. SM-NATURE
The above answeis are true and complete to the best of my knowledge. I understand that the lead
agency is relying on them to make its decision.
SIGNATURE: �J
DATE SUBX1ITTED: P (�- z ' i `13
ALTINAY AND ASSOCIATES INC.
Consulting Engineers
5241 South Graham Street*Seattle*Washington 98118-2918
(206) 723-9349
Established: 1976
ENGINEERING REPORT
for
The Richard Stitt Property
29038-15th Place South
Federal Way Building Permit Application BLD 93-0300
SAP
&to f 3— o3co
,OMMUNITY DEVELOPM,
MAY i ? 1993
V
Altinay and Associates Inc. Richard Stitt
INTRODUCTION
This report was prepared upon the written request of
the property owner, Mr. Richard Stitt. It summarizes the
results of an engineering study conducted for this project
and the recommendations to assist the owner and his
professionals, who may be involved, for the safe development
of the site.
In addition, this report provides information and
specific recommendatios as outlined in the Federal Way City
Code Division 4. Geologically Hazardous Areas Development.
APPLICABILITY
In our judgment, specific site conditions that the
Federal Way City Code could apply to are as shown in the
following table. Details are discussed hereinafter as
appropriate.
Specific Site Condition.
Geologic Hazard Area
Flood Prone Area
Riparian Corridor
Wetlands
Habitat Conservation Area
Abandoned Landfills
Rea,ulations apply
YES
NO
NO
NO
NO
NO
Since the development site contains a very steep slope,
it is classified as in a geologic hazard area, consequently,
regulated by the City Code.
5/7/93 page 1
F1
Altinay and Associates Inc.
GENERAL INFORMATION AND DATA
PROJECT NO.:
PROJECT:
SITE ADDRESS:
DESCRIPTION:
SECTION:
OWNER:
VICINITY MAP:
SITE TOPOGRAPHY:
SLOPES:
Richard Stitt
Building Permit Application BLD 93-0300
Single Family Residence
29038-15th Place South in Federal Way
Lot 26 of Marlbrook North
Mr. and Mrs. Richard Stitt
29849-6th Avenue South
Federal Way 98003
(206) 839-4328
See Appendix A-1
Available w/2 ft contours
See grading and earthwork
GROUND COVER: Wooded area with thick underbrush.
SPRINGS, SEEPS: None observed
EROSION: None observed
PROJECT DESCRIPTION
This project consists of a single family residence with
an attached garage and available utilities.
We understand that the client's application has been
placed on hold and will remain on hold until this report is
submitted to the building official of the City.
SITE DESCRIPTION
The site is located in the southwest quadrant of the
15th Place South Cul-de-sac. The westerly half of the lot is
a native growth protection area. A single family unit is on
5/7/93 page 2
Altinay and Associates Inc. Richard Stitt
the north and the south side of the building site which is
the easterly half of Lot 26. All were created from a King
County Short Plat.
FIELD INVESTIGATIONS
On April 8, 1993, general site conditions, including
the adjacent properties, were visually examined during the
first meeting with the owner. On April 28, 1993, surface and
subsurface conditions were examined. Three test holes were
excavated by a back hoe. Soils were sampled and classified.
Three test pit locations and the soil logs are given in
the appendix A-2 and A-3, respectively.
Visual examination of the site, its contours, slopes,
trees and ground cover indicated that a steep slope of over
40% within a gentle slope area could not be a natural slope,
but man-made. Therefore, it was necessary to examine and
verify the subsurface conditions. Back hoe test pits were
the best approach to directly see site stratigraphy and
identify each type of soil. By doing so, presence of the
fill was observed and documented.
SURFACE CONDITIONS
It appears that the steep slope that exists within and
down hill from the footprint of the house, was the result
of dumping and pushing surplus excavated material downhill
and spreading it. The fill is NOT a density controlled,
engineered fill. It is very soft, loose and wet, therefore,
unsuitable to support building loads, but stable in place if
not disturbed.
Depth of Fill:
It is 5' deep along the apparent upper edge of the
steep drop, but abruptly decreases to 12 inches or less
toward the cul-de-sac. See A-2 for the estimated limits of
the existing fill.
5/7/93 page 3
Altinay and Associates Inc. Richard Stitt
In our opinion, it is not absolutely necessary to
remove the fill. During excavation for footings, unsuitable
material that exists on top of the footing trenches, will
automatically be removed. Elsewhere, the loose fill may be
left in place, so long as it is not allowed to support
building loads or driveway. It should not cause any harm to
the environment.
SUBSURFACE CONDITIONS
Under the area overlain by the fill mass and elsewhere
in the property, soils are natural, undisturbed and
suitable to support building loads. A high degree of
stability is expected throughout the property.
Please see Soil Logs in the appendix A-3.
CONCLUSIONS AND RECOMMENDATIONS
1. Feasibility
It is feasible to construct a single family residence
at the location indicated on the plans if our
recommendations given in this report are followed.
It appears that this location is the most suitable
location for a residence and closely meets all the code
requirements, such as setbacks.
2. Slope Stability, landslide hazard and sloughing
a) There are no impermeable soils, interbedded with
permeable, granular soils in lenses or, impermeable material
overlain with permeable soils that could be classified as
slide -prone.
No faulty ground, soil creep or cracks could be
detected.
5/7/93 page 4
Altinay and Associates Inc. Richard Stitt
b) The existing stratum is of coarse granular
material with low to no plasticity. Capillary rise of ground
water, water table, is unlikely to occur within or near the
project.
The cul-de-sac is a fully improved street with
curb and gutters and other drainage items. No surface runoff
from the street enters the Stitt property. In addition, the
roadway prism in the street right-of-way allows very little
or no water to travel under the pavement and enter the
project site.
Except for the wet mass of fill, the natural,
undisturbed soils are in relatively dry condition.
c) The subject property is on a 35-40 percent
slope. This declivity is usually known to be critical slope
for a material with high silt content and moisture as
described in paragraphs a) and b) above. Site soils are all
granular with high internal friction to resist shearing.
d) Ground cover, vegetation, is another factor
that directly or indirectly reduces water content of the
soils and help increase stability.
Based on all four factors identified above, we conclude
that no geologically hazardous area conditions exist and the
undisturbed soils on the slope are in a balance with
vegetation, underlying geology and surface/subsurface water
environment and in stable condition.
3. Uncontrolled Fill
On the plot plan (A-2), three slope rates are
indicated. The only area with steeper than 40% slope is a
small portion of the man-made fill and shown as 50%.
The approximate limits of the fill are indicated on the
same attachment, A-2.
5/7/93 page 5
Altinay and Associates Inc.
Richard Stitt
The fill material we identified is brown silty sand,
sandy clay with very little scattered gravel. It contains
organic material with no debri in it and appears to be
relatively clean. It can be left in place as is, but should
be stabilized by reducing the moisture content. This could
be accomplished if the fill material is compacted using
heavy equipment, medium size dozer should do the job.
4. Earthwork
The upper layer material of undisturbed site soils and
the entire fill material should not be used for backfilling,
instead, imported select material should be used. Clean,
granular material is recommended.
The top layer of the site soils, identified as brown
sandy material, possesses many roots and is not suitable for
structural backfilling. It should be replaced with clean
material that contains no organics (roots, etc.) as shown
in Appendix.
Re -using the lower layer material and compacting it
properly at a point near its optimum moisture content would
not be difficult to achieve.
Compaction Requirements
a. Site soils:
Material should be placed in no more than 8 inches
thick loose layers and compacted to 90% of its maximum
density determined per ASTM Test Method D 698.
It is likely that some additional suitable backfill
material can be borrowed from the area behind the existing
garage.
5/7/93 page 6
Altinay and Associates Inc. Richard Stitt
b. Import material:
Suppliers in the Federal Way area are likely to have
suitable material of many different gradations. We would
recommend that medium coarse to coarse grade be preferred.
It may be placed in 18 inches thick layers and density test
requirements may be waived. Otherwise, granular material
with some fines should be placed and tested as specified in
the paragraph a. above.
Import material should be approved by the engineer.
5. Impact of seismic vibrations on the project
The damage resulting from earthquakes may be
influenced in a number of ways by the characteristics of the
soils. We believe that all engineers in the geotechnical
field would agree that the loose, sandy deposits may become
liquefied, thus unstable due to vibration. However, the
existing soils in this project area are not loose and sandy
units and consequently not subject to liquefaction.
In other words, earthquake vibrations can cause some
structural damage to the future building as well as the
adjoining residences, but the underlying soils should remain
stable.
6. Foundations
I. Type:
The proposed residential structure and the necessary
retaining walls, as planned, may be supported on
conventional continuous footings, basement walls and
retaining walls, as necessary. No special foundation, such
as piling, should be needed since the existing site soils
offer excellent support.
According to the building plans available to us, some
of the walls need to be higher than 4 feet and therefore,
5/7/93 page 7
Altinay and Associates Inc. Richard Stitt
should be designed properly to resist lateral loads and
support building loads.
Square footings shown on the plans should be tied in to
the building foundations or anchored in to the ground.
II. Allowable foundation pressure:
Basic allowable foundation pressure should be 2000 psf
per foot of depth below the top of inorganic material, sandy
gravel.
This value is for footings having a minimum width of 12
inches and a minimum depth of 12 inches into the gravelly
layer. An increase of 20% is allowed for each additional
foot of width and / or depth to a maximum value of 2500 psf
( UBC Section 29).
Estimated total settlement should be less than 0.5 inch
and differential settlement less than 0.25 inch.
Earth Pressure due to backfill
Attached Table I, (A-4) may be used for designing walls
higher than 4 feet. Or, an equivalent fluid pressure of 30
pcf should be utilized.
Coefficient of Friction
Frictional resistance should be calculated by using a
coefficient of 0.35 between concrete and the site soils. If
more resistance against lateral forces is required, concrete
anchors may be used as shown in Appendix A-5. Anchors
provide better resistance against lateral pressures,
especially for higher walls.
5/7/93 page 8
Altinay and Associates Inc. Richard Stitt
6. Drainage
Our calculations indicate that the increase in peak
runoff rate will be negligible and this project .may be
exempted from on -site runoff control, such as
retention/detention facilities.
Runoff from down spouts still must be controlled to
eliminate undesirable puddles and grooving near the house
and along the slopes.
There is enough room near the natural growth protection
area to install a dispersal trench. Please see A-2.
The dispersal trench recommended for the project
satisfies two principal requirements:
I. Runoff will be discharged at natural location.
II. Concentrated flow will be converted to sheet flow.
7. Erosion and sedimentation control
Each year tons of sediment are washed from construction
sites into drainage ways and underground conduits, then into
lakes and Puget Sound, causing destruction of nature and
costly repairs and cleanups. When the construction starts,
this project will be no exception, however, these conditions
can be controlled, if our recommendations are followed.
I. Temporary: Temporary siltation control should be
provided by a) installing a silt fence at the location shown
in Appendix A-2 and covering the metal grate of the inlet in
the cul-de-sac with filtering fabric,
5/7/93 page 9
Altinay and Associates Inc. Richard Stitt
b) constructing a rock entrance to keep the
street and its drainage system clean.
II. Permanent: Permanent erosion and siltation control
should be provided by compacting loose soils and re -
vegetating bare spots with ground cover or landscaping.
Wet weather considerations
Constructing this project in the rainy season should
not cause or have adverse impact, such as environmental harm
or safety issues on the slopes, if all the erosion control
facilities recommended in this report are installed and
maintained.
Construction Monitoring
We recommend that we be permitted to observe the
excavation work and identify the unsuitable fill material.
EAVIRLs 712/
5/7/93 page 10
Altinay and Associates Inc.
APPENDIX
Vicinity Map
A-1
Plot Plan
A-2
Soil logs
A-3
Table I
A-4
Anchors
A-5
Richard Stitt
5/7/93 page 11
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