16-102953Homes by Landmark
P.O Box 26116
Federal Way, WA 98093
Phone: 253-927-6116
Fax: 253-927-4652
Email: Dilito&omcast.net
April 26, 2016
City of Federal Way
ATTN: Jim Harris, Planner
33325 8" Ave S
Federal Way, WA 98003
Jim,
Thank you for meeting with me at Norpoint Heights plat on 4/21/2016. We would like to
request a deviation from the plans. Page GR-03 there is a detail showing a rock wall on lots 11
and 12 and we would like to replace it with a block wall per the attached block wall detail report
done by Geo Resources dated 9/7/2015.
This block wall would be identical materials as the pond block wall, page PN-01 section
AA.
Before we built the wall we discussed with the only affected neighbor Gary Stark and he
was fine with the wall he requested some minor grading and beauty bark.
As an alternative to this wall we would like to request to remove one block with only 3'
of wall exposed. This would then become just a landscape wall and would help to minimize the
need for a retaining wall and have no engineering requirement with a 2:1 slope above the wall.
Thank you for your consideration in this matter.
Sincerely,
David itowitz
President
Ph 253-896-1011
Fx 253-896-2633
Landmark Homes, Inc.
PO Box 26116
Federal Way, Washington 98093-2116
Attention: Mr. David Litawitz
GeoResources, LLC
5007 Pacific Hwy E., Ste. 16
Fife, Washington 98424
September 7, 2015
Geotechnical Analysis Letter -
Retaining Wall Design
NorPoint Residential Plat
SW 29t' Avenue and Norpoint Blvd.
DocID: Landmark. Norpoint. L2
As requested, we are pleased to present the attached retaining wall design
calculations and cross sections for a gravity wall using pre -cast concrete ecology blocks.
Based on the proposed grading plan prepared by the ESM Consulting Engineers dated
May 2012), the proposed retaining wall will be used for grade separation along the north
property line above the existing concrete retaining wall near the stormwater facilities at the
site. The wall will range from less than 1-foot to a max exposed height of 5 feet, with at
least 1-foot of embedment. We have previously prepared a Geotechnical Report for the
site.
Subsurface Conditions
Our interpretation of the subsurface conditions at the site are based on our site
observations, data review, previous test pit excavations for our report, and our experience
in the area. We also recently observed the cut slopes for the concrete retaining wall. In
general, the site soils consist of a veneer of recessional sand and gravel with variable
amounts of silt, cobbles and boulders, up to approximately 3 feet. Weathered glacial till was
encountered below the recessional soils to depths of 4 to 5 feet below the ground surface.
Undisturbed glacial till was encountered at depth in the cut slope.
The recessional outwash sand with gravel and weathered till soils were in a medium
dense to dense condition. The outwash and weathered glacial till was underlain by dense to
very dense glacial till. No groundwater seepage was observed at the site at the time of our
site visits.
A typical detail for wall construction is provided as Figure 1.
LIMITATIONS
We have prepared this report for Landmark Homes and other members of the
design team for use in evaluating a portion of this project. The data used in preparing this
report and this report should be provided to prospective contractors for their bidding or
estimating purposes only. Our report, analyses, conclusions and interpretations are based on
data from others and limited site reconnaissance, and should not be construed as a warranty
of the subsurface conditions. We did not perform any subsurface explorations for the
preparation of this design, but observed explorations excavated previously by others as
described above.
Variations in subsurface conditions are possible between the explorations and may
Landmark - Norpoint
September 7, 2015
Page 2
also occur with time. A contingency for unanticipated conditions should be included in the
budget and schedule. Sufficient monitoring, testing and consultation should be provided by
our firm during construction to confirm that the conditions encountered are consistent with
those indicated by the explorations, to provide recommendations for design changes should
the conditions revealed during the work differ from those anticipated, and to evaluate whether
earthwork and foundation installation activities comply with contract plans and specifications.
If there are any changes in the loads, grades, locations, configurations or type of
facilities to be constructed, the conclusions and recommendations presented in this report
may not be fully applicable. If such changes are made, we should be given the opportunity to
review our recommendations and provide written modifications or verifications, as
appropriate.
We have appreciated working for you on this project. Please do not hesitate to call
at your earliest convenience if you have any questions or comments.
Respectfully submitted,
GeoResources, LLC
als
Dana C. Biggerstaff, PE
Senior Geotechnical Engineer
BPB:DCB:bpb
DocID: Landmark.Norpoint.L2
Attachments:Appendix "A" Wall Design Calculations
Brad P. Biggerstaff, LEG
Principal
Min. 6 degree batter
FINISH GRADE a
0
6" MIN COVER —//PLACEE
K
ON 6CSTB
OR CONCRETE BASE
GRAVEL BACKFILL FOR WALLS (SECTION
9-03.12(2) OF THE WSDOT STANDARD SPEC),
MIN 1 FOOT WIDTH
GRAVEL BACKFILL FOR DRAIN (SECTION
SEC 9-03.12(4) OF THE WSDOT STANDARD SPEC)
BLOCK WALL DETAIL
NTS
NOTES:
1. CONSTRUCT BLOCK WALL IN ACCORDANCE WITH
MANUFACTURER'S RECOMMENDATIONS.
2. ENGINEER SHALL VERIFY SUBGRADE CONDITIONS FOR
ROCKERIES OVER 4 FEET.
3. NO STRUCTURE SHALL BE LOCATED WITHIN A
HORIZONTAL SETBACK EQUAL TO THE WALL HEIGHT
FROM THE BACK OF THE UPPER BLOCK COURSE.
4. BLOCK BACKFILL SHALL CONSIST OF STRUCTURAL FILL
COMPACTED TO 95% OF MDD PER ASTM D-1557.
SKETCH NO:
SK1
PROJECT NAME: PROJECT NO: BY: DATE:
Landmark. Norpoint Landmark. Norpoint DCB 9/8/2015
CONSTRUCTION FIELD SKETCH:
GeoResources, LLC LANDMARK HOMES
5007 Pacific Hwy. E,•Suite 20 PHONE: 253)896-1011 ECOLOGY BLOCK WALL
Fife, WA 98424 FAX: M3)896-2633 TACOMA, WASHINGTON
G E O'T' E C I --I IV I C.4 L—
gravity wall .36LOCKS.dwg OS Sep 2015 — 4:14 pm
GeoResourFes,Calculation No. GC-001
Project: Landmark.Norpoint Revision No. Rev. 00
Feature: Ecology Block Wall Job No. Landmark. Norpoint
Subject: Retaining Wall Design
Gravity Retaining Wall Calculations
Soil Properties Block Properties
Block Height: h:=24 in
Unit Weight: ry:=125 Zb Block Width: w:=72 in
ft Block Depth: d := 24 in lb
Effective Friction Angle: O.'.-= 36_' Block Weight: ybIo,tisA=145
ft
Soil/Block Base Friction: µ:=0.45 Rows of Blocks: R:=3
(From NAVFAC DM7_.2)-
Wall Properties
Slope Angle Above Wall:
8:=0 ° ;
Wall Batter:
cx:=-6
Wall/Soil interface Friction Angle:
`f'w:=24'0
Total., Wall Height:
Ht:=R• h=6 ft
Embedment Depth:
He:=1 ft
Exposed Height:
H;=Ht=He=5 ft
Earth Pressure Coefficients
Active
Rankine:
cos (13) — V cos (8)2 —cos (0')2 K.R� 0.26
;T
Cos ('3)+ IC -Os — Cos (0')2
Coulomb:
2
KaC :=
cos[x) =0.21
z
2 i sin (0'+ �, } • sin ( '-18) �
cos (a) •cos(�w—a) I1+ cos((pO+6)•cos(aL-0),
Project: Landmark.Norpoint
Feature: Ecology Block Wall
Subject_ Retaining Wall Design
�l
Calculation No. GC-001
Revision No. Rev. 00
Job No. Landmark.Norpoint
Passive
� z
K cos 03) + cos (;�} = cas (¢�) — � 85
PC:- a 2 —
cos(Q)— cos(Q) — Cos(01
Ko:=1-- sin (r5')=0A
Equivalent Fluid Pressures
GIR:-ry•K.R•cos (,Q)•1 ft=32.5 tb
tz
G :�.7.KV0•cos(p}•1 ft =481.5 1b
ft 12
Retaining Wall Calcs:
Calculate Wall Weights
W totat Ht . d -Ibtocks' 1 ft = 1740 lb
Check Bearing Capacity:
At Rest
GaC:='y .Ka,C • cos 1 ft = 24.5. lb
t
(Q}• f f
Go:=ry�Ko•cos 1 t=51.5 lb
ft 2
Allowable Bearing Pressure = qA:=2000 lb
ft2
Wtot�� _ -
Net Bearing Pressure = q — 870 — lb z
d• 1 ft ft
Factor of Safety
.Check Overturning:
— QA = 2.3 > 2.0 OK
FSbeareng :
Available Resisting Moment = A1IA-:=Wtotat ` d j =1740 lb • ft
1
Project: Landmark.Norpoint
Feature: Ecology Block Wall
Subject: Retaining Wall Design
Overturning Moment :
Check Sliding Resistance:
Sliding Force
Calculation No. GC-001
Revision No. Rev. 00
Job No. Landmark.Norpoint
Fl.:= � .H .. y.KQc• 1 ft=482.7 lb
M'A:=F,. Ht =965.4 lb• ft
3
Factor of Safety
= FR:=F1=482.7lb
NIA
FSovertzcrrlbL9 NI =1.8 > 1.5 .'. OK
A
Resistance to Sliding from friction FR:=Wtotai •µ=783 lb
(neglecting passive pressure)
Factor of Safety FSstiaing:= R =1.6 > 1.5 OK
FIR
Passive Pressure was
neglected for sliding, which is
a conservative assumption for
this case
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