HomeMy WebLinkAboutSWP272850 (5)Geotechnical Report
Park Place North Storm Sewer
Renton, Washington
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GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS
At Shannon & Wilson, our mission is to be a progressive, well -
managed professional consulting firm in the fields of engineering
and applied earth sciences. Our goal is to perform our services
with the highest degree of professionalism with due consideration
to the best interests of the public, our clients, and our employees.
June 6, 2005
Submitted To:
Roth Hill Engineering Partners, LLC
Attn: Mr. Erik Waligorski, P.E.
2600 116th Avenue NE, Suite 100
Bellevue, Washington 98004
By:
Shannon & Wilson, Inc.
400 N 34`h Street, Suite 100
Seattle, Washington 98103
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TABLE OF CONTENTS
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Page
1.0 INTRODUCTION.................................................................................................................. l
2.0 SITE AND PROJECT DESCRIPTION.................................................................................1
3.0 SUBSURFACE EXPLORATION PROGRAM....................................................................2
4.0 GEOTECHNICAL LABORATORY TESTING...................................................................2
5.0 GEOLOGY AND SUBSURFACE CONDITIONS...............................................................3
6.0 SLOPE STABILITY..............................................................................................................4
6.1
Slope Stability Observations......................................................................................4
6.2
Slope Stability Analyses.............................................................................................4
7.0 ENGINEERING CONCLUSIONS AND RECOMMENDATIONS....................................5
7.1
General.......................................................................................................................5
7.2
High -density Polyethylene (HDPE) Pipe Preparation...............................................5
7.2.1 Trench Excavations......................................................................................6
7.2.2 Surface Water and Groundwater Control....................................................7
7.2.3 Pipe Bedding and Initial Backfill.................................................................7
7.2.4 Subsequent Backfill and Compaction..........................................................8
7.3
Wet Weather Conditions............................................................................................9
7.4
Erosion Control........................................................................................................10
7.5
Construction Monitoring..........................................................................................10
8.0 LIMITATIONS....................................................................................................................11
9.0 REFERENCES.....................................................................................................................13
LIST OF FIGURES
Figure No.
1 Vicinity Map
2 Site and Exploration Plan
3 Generalized Subsurface Profile A -A'
4 Typical Tightline Anchoring Details (2 sheets)
5 Typical Pipe Trench Section Excavating Dry
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TABLE OF CONTENTS (cont.) SHANNON 6WILSON, INC.
LIST OF APPENDICES
Appendix
A Subsurface Explorations
B Geotechnical Laboratory Testing
C Important Information About Your Geotechnical Report
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GEOTECHNICAL REPORT
PARK PLACE NORTH STORM SEWER
RENTON, WASHINGTON
1 1.0 INTRODUCTION
This report presents the results of subsurface explorations, laboratory testing, and geotechnical
' engineering studies for a portion of the proposed Park Place North storm system project in
Renton, Washington. The purpose of our geotechnical studies was to evaluate the subsurface
conditions along the portion of the alignment that traverses the slope between an extension of
Park Place North and the Belle Vista apartment complex, located down slope, and to provide
recommendations for design of project elements associated with extending the pipeline down the
steep slope. Our work was accomplished in general accordance with our scope of services
outlined in the subconsultant agreement, dated April 22, 2005.
2.0 SITE AND PROJECT DESCRIPTION
The project is located near the top of a west -facing slope overlooking the southern end of Lake
Washington, as shown in the Vicinity Map, Figure 1. The overall project involves extending an
existing stormwater main southward, across the slope along Park Place North and then westward
down a steep slope to connect with an existing storm system serving an apartment complex. We
understand that the proposed pipeline will consist of a 12-inch-diameter, continuously fuse -
welded, high -density polyethylene (HDPE) pipe.
The portion of the proposed stormwater main that is aligned north -south extends along Park
Place North and then along an existing utility easement that extends southward from the end of
' Park Place North. The utility easement lies along a narrow bench located on the upper portion of
the overall slope. An existing sanitary sewer lies along the bench, parallel to the proposed
alignment of the stormwater main. Several residences are located at the top of the slope east of
the bench, upslope of the proposed storm system, and along Park Place North.
Approximately 75 feet south of the end of the street pavement, the proposed storm line turns to
the west and extends down a steep slope approximately 60 feet high that has an overall
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inclination of about 32 degrees from the horizontal. The steep slope is wooded with small trees
and brush. At the base of the steep slope, the ground flattens to a gentle slope and extends to a
landscaped area and paved parking at the east edge of the Belle Vista Apartments. The steep
slope portion of the site is shown in the Site and Exploration Plan, Figure 2.
3.0 SUBSURFACE EXPLORATION PROGRAM
To evaluate soil conditions at the top of the steep slope near the location where a manhole would
be needed, a boring was drilled to a depth of about 30 feet. The boring was drilled using a track -
mounted rig under subcontract to Shannon & Wilson. To evaluate the thickness of colluvium on
the steep slope, hand -boring probes were conducted using portable, hand -operated equipment.
During the hand boring work, slope measurements were obtained to help construct a slope
profile and to locate the borings. The locations of the borings are shown in Figure 2. The logs of
the borings are presented in Appendix A.
In addition to performing subsurface explorations at the site, we reviewed readily available
information from previous subsurface investigations in the vicinity of the site to help understand
subsurface conditions at the site. We reviewed a Shannon & Wilson report for a geotechnical
study previously conducted east of the site. We also reviewed the logs of wells in the vicinity of
the site available on the website of the Washington State Department of Ecology. We reviewed
a geotechnical report by another consultant for the apartment development down slope of the
site, and we conducted a geologic reconnaissance of the slope in the vicinity of the proposed
pipeline and the wooded slope south of the site to look for evidence of past slope instability or
erosion and for visual clues about subsurface conditions.
4.0 GEOTECHNICAL LABORATORY TESTING
Laboratory tests were performed on selected samples retrieved from the borings to determine
basic index and engineering properties of the soils present at the site. All geotechnical laboratory
testing was performed in our laboratory in Seattle. The testing program included visual
classifications, water content, and grain size analyses. All laboratory testing was performed in
general accordance with the American Society for Testing and Materials (ASTM) standard test
procedures. A brief description of the test procedures is included in Appendix B.
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5.0 GEOLOGY AND SUBSURFACE CONDITIONS
The Puget Lowland has been glaciated as many as six times, the most recent between about
15,000 and 13,000 years ago in the central part of the lowland. The topography and near -surface
geology in the vicinity of the site is largely the product of the last glaciation (Vashon Stade of the
Fraser glaciation). Sediments deposited during or prior to the advance of the Vashon ice sheet
have been overridden by as much 3,000 feet of ice and have been compacted to a very dense or
hard state. Published geologic maps indicate that the hillside upon which the project is located is
underlain by pre-Vashon sand and gravel outwash overlain by Vashon till. Soil exposures in 30-
to 40-foot-high cuts in the hillside approximately 1,000 feet south of the storm sewer alignment
reveal a surficial layer of till approximately 15 feet thick overlying outwash sand and gravel.
These soil conditions are similar to those that underlie the site, based on the subsurface
explorations performed at the site.
Most of the steep slope portion of the alignment is underlain by very dense, gravelly, silty sand
to silty, sandy gravel (till and till -like soils), as shown in the Generalized Subsurface Profile,
Figure 3. The lowermost 15 vertical feet of the slope appears to be underlain by very dense,
slightly silty to silty, fine to medium sand. The very dense soils are overlain by a relatively thin
layer of less dense soils. The steep slope has a layer of less dense colluvial soils approximately 1
to 3 feet thick. Colluvium is the loosened rind of soil mantling most steep slopes, which has
moved down slope from the force of gravity. This layer consists of soils similar to the
underlying soils from which they were derived.
The bench at the top of the steep slope, which the proposed pipeline will descend, is underlain by
fill. The fill was likely placed from a combination of past site grading associated with the
residential development to the east and north, and with the installation of existing utilities along
the bench. The fill encountered in boring B-1 and hand borings HB-1 and HB-2 generally
consists of loose to medium dense, gravelly, silty sand with scattered to numerous organics.
Although not encountered, the fill may contain cobbles, boulders, and wood or other debris.
No seepage or vegetation indicative of perennial seepage was observed on the slope during our
reconnaissance; however, wet conditions were encountered in the lowermost hand boring, HB-7.
The sand layer encountered in that boring is interpreted to be wet; however, because of the wet
weather in the days preceding our hand boring work, the wet soils observed may only reflect
surficial wet conditions and not that the entire sand layer is wet. The fill that underlies the bench
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at the top of the steep slope and the thin layer of colluvium that mantles the steep slope are likely
to be wet during periods of heavy precipitation.
6.0 SLOPE STABILITY
Information obtained from the subsurface investigation, laboratory tests, field observations, and
measurements was used to evaluate the stability of the slope at the project site. Preliminary
slope stability analyses were performed. These stability analyses included estimating the
engineering properties of the slope materials, identifying the approximate locations of the failure
surfaces, and analyzing factors -of -safety (stability factors) for slope stability.
6.1 Slope Stability Observations
While on site to conduct subsurface explorations, we performed a reconnaissance of the site and
vicinity to look for evidence of past landsliding or conditions indicative of marginal instability.
In general, only minor bowing of scattered trees was observed on the slope, an indication that
creep is not a significant process on the slope. Evidence of past landsliding on the slope was not
observed in the vicinity of the alignment except near the base of the slope. What appeared to be
scars of small slumps or set downs were observed at several locations along the lowermost
portion of the slope, less than about 10 to 20 vertical feet above the parking areas along the
eastern side of the Belle Vista Apartments.
Approximately 1,000 feet south of the alignment, extremely steep soil exposures approximately
30 to 40 feet high were observed. These slopes are likely.to be remnant cut slopes from a sand
and gravel pit that once operated at this location. The slopes were estimated to be as steep as
70 degrees. Till overlying sand outwash was observed exposed on these bare faces, geology
similar to that underlying the proposed alignment. No indications of instability were observed.
6.2 Slope Stability Analyses
Stability analyses were conducted using the computer program PCSTABL5MJsi. This program
requires specifying the slope geometry, soil strength parameters, groundwater conditions, and
instructions about critical slide plane searches. The analyses included performing a search for
the most critical failure surface using the Modified Janbu method to determine the stability of the
existing slope. The effect of earthquakes was evaluated by calculating the factor -of -safety using
the pseudo -static method. In the pseudo -static method, the earthquake inertial forces are
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included in the analyses by assuming that an equivalent static horizontal force approximates
them. This horizontal force is equal to the weight of the assumed sliding mass of soil multiplied
by a pseudo -static coefficient. Based on studies by Makdisi and Seed (1978), the appropriate
pseudo -static seismic coefficient is equal to about one-half of the peak ground acceleration
(PGA). A pseudo -static coefficient equal to 0.15g was used in the slope stability analyses.
The stability program calculates the factor -of -safety against failure along either a specified slide
plane or multiple potential slide planes. A factor -of -safety of 1.0 is generally considered
marginally stable. Higher values indicate greater stability, and lower values indicate instability
or sliding. Generally, a factor -of -safety against sliding under static conditions of at least 1.3 is
desirable. A factor -of -safety of at least 1.1 under seismic loading conditions is a generally
acceptable value. The results of our study indicate that a small amount of sliding may occur
under seismic conditions. However, the analysis indicates that the movement would be surficial
in nature (limited to the upper 1 to 3 feet on the steepest portion of the slope) and would not
directly impact the at -grade pipeline at its currently proposed location.
7.0 ENGINEERING CONCLUSIONS AND RECOMMENDATIONS
7.1 General
Based on the results of the subsurface explorations and our engineering analyses, we developed
geotechnical recommendations to assist in the design of the proposed project. Based on our
current understanding of the project, this report assumes that the pipeline for the majority of the
alignment will be installed atgrade, with the exception of top and bottom of slope. The portion
of the pipeline at the top and bottom of the slope transition to belowgrade and will be installed by
trenching. Based on our slope stability analysis, it in our opinion that the slope could support the
proposed stormwater pipeline and remain stable.
The subsequent sections of this report present our conclusions and recommendations regarding
on -grade pipeline, conventional trench excavations, pipe bedding and backfill, erosion control,
and wet weather considerations.
7.2 High -density Polyethylene (HDPE) Pipe Preparation
It is our opinion that because the proposed pipeline extends across steep terrain, it should consist
of durable plastic pipe, such as HDPE pipe. The joints should also be durable and able to carry
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axial loads and accommodate flexural deformation of the pipe. Welded or through -bolted,
flanged joints are examples of suitable joints. The majority of the proposed pipe route will
involve at -grade bearing of the pipe with no soil cover. This type of pipe support requires only
removal of vegetation, debris, and any hard, sharp objects. The pipe should be graded to prevent
sediment accumulation in the pipe that could eventually block or reduce its capacity. The pipe
should be installed with an anchor system to prevent the line from being pulled part by soil creep
or other gravitational effects and to allow regular inspection. Figure 4 (2 sheets) illustrates an
example of a tightline anchoring system. The following sections present recommendations that
are applicable to the top and bottom of slope portions of the proposed pipeline where belowgrade
pipe installation occurs.
7.2.1 Trench Excavations
We anticipate that the fill and near -surface native soils observed in soil borings at the top
and bottom of slope can be excavated using conventional excavating equipment such as rubber -
tired backhoes or tracked hydraulic excavators. Excavation in such soils should not require
unusual equipment or procedures. Excavation through underlying, very dense, till -like soil,
however, may be more difficult, and the use of ripper teeth may facilitate excavation. In
a ihon� comb es na d possibly boulders would be encountered in this glacial soil and the
Contractor should anticipate their presence.
Unshored temporary excavation slopes may be used where planned excavation limits will
not undermine existing structures or extend beyond construction limits. The sides of the
excavation should be sloped back as needed to provide a safe, stable slope. Consistent with
conventional construction practice, temporary excavation slopes should be made the
responsibility of the Contractor, since the Contractor is able to observe the nature and conditions
of the subsurface materials encountered, including groundwater, and has the responsibility for
methods, sequence, and schedule of construction. For planning purposes, and for excavations
less than about 10 feet deep, we recommend temporary excavation slopes in the near -surface
loose soils be no steeper than 1.5 Horizontal to 1 Vertical (1.5H:1V) and those in underlying
dense to very dense soils be no steeper than 1H:IV. Where less competent soils or seepage
zones are encountered, flatter slopes may be required.
Temporary shoring may be required for the trench excavation to protect existing utilities
and structures and/or provided a work environment that compiles with applicable safety
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regulations. If instability is detected, slopes should be flattened or shored. For temporary shored
excavations, construction practice in the Seattle area generally includes: trench boxes,
interlocking steel sheet piles, a combination of soldier piles and horizontal lagging, and/or steel
plates and internal bracing walers, although other methods of trench support are possible. For
relatively shallow excavations (e.g., less than about 10 feet), a trench box is likely the most
economical shoring system; however, it should be understood that a "standard" trench box does
not usually provide adequate support of the trench excavation slope, but instead only provides
safety for workers in the trench. Because the trench box typically is placed after excavation, a
significant amount of soil deformation commonly takes place alongside the excavation limits.
Ground movements can be severe, especially in the presence of groundwater and in near -surface
or loose soils. The Contractor should be held responsible for all damages related to ground
movements. Regardless of the construction method used, all excavation work should be
accomplished in compliance with applicable local, state, and federal safety regulations.
7.2.2 Surface Water and Groundwater Control
Temporary dewatering may be required for excavations made at the bottom of the slope.
Based on the conditions we observed at the ground surface and in the explorations, it is our
opinion th at groom er m ows��o— uld be re ative y sma , an excavations could be kept dry
using sumps. If excessive and continual seepage is encountered during construction, a temporary
interceptor trench located upslope from the trench excavation could be effective. All surface
water should be diverted away from open excavations.
7.2.3 Pipe Bedding and Initial Backfill
Normal pipe bedding procedures should generally prove satisfactory along the proposed
stormwater drainage alignment. For conventional pipe installation, i.e., pipe that is not pile
supported, disturbance of subgrade soils at the bottom of the trench excavation because of
construction equipment and activities will affect support of the proposed pipe. It is anticipated
that much of the soil exposed at the bottom of the excavations will be moisture sensitive and
easily disturbed. The Contractor should take all necessary steps to protect the subgrade from
becoming disturbed.
The recommended typical pipe trench section for bedding and backfilling conventional
pipelines in the dry are shown in Figure 5. Based on the soils encountered in the borings, the
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native soils are moisture sensitive and may become unstable in wet conditions. If these soils
become unstable during excavation, they should be overexcavated and replaced with the
recommended pipe bedding material. Bedding material for flexible pipe (HDPE) should be
clean, granular materials meeting the gradation requirements specified in Section 9-03.12(3) of
the 2004 Washington State Department of Transportation (WSDOT) Standard Specifications or
equivalent. Bedding should be. at least 4 inches thick below the invert of the pipe and extend up
the haunches of the pipe to the 120 degree arc line of the pipe (a height above the invert equal to
0.25 times the outside diameter). Initial backfill material should meet the gradation requirements
for granular bedding material. The bedding and initial backfill materials should be placed in
loose lifts of 4 to 6 inches and carefully worked under and around the pipe by means of
shoveling, vibration, trench tamping equipment, or other approved procedures. The bedding and
initial backfill should be compacted to at least 92 percent of its maximum dry density (as
determined by ASTM test designation: D 1557). Heavy mechanical compaction equipment
should not be used over the pipe until the bedding material and initial backfill are at least 1 foot
above the crown of the pipe.
7.2.4 Subsequent Backfill and Compaction
All subsequent trench backfill where settlements are to be minimized should be structural
fill. In general, we anticipate that most of the on -site soils to be excavated should be suitable for
reuse as structural fill during dry weather provided it is free of organics, cobbles and boulders,
debris, rubbish, and other deleterious material. Either selectively stockpiled, carefully
segregated, on -site fill materials or imported structural fill may be used. If it is necessary to
import structural fill, the imported material should meet the gradation requirements of Bank Run
Gravel for Trench Backfill (WSDOT/American Public Works Association [APWA] 9-03.10) or
an approved substitution. The Wet Weather Considerations section of this report presents
recommendations for materials and construction procedures for wet weather or wet conditions,
no matter what time of year.
We recommend that subsequent backfill be placed and compacted in lifts with a
maximum loose thickness of 10 inches for heavy equipment compactors or 6 inches for hand -
operated mechanical compactors. Trench backfill should be compacted to a dense and
unyielding condition, and to at least 90 percent of the maximum dry density as determined by
ASTM Designation: D 1557 (Modified Proctor) in nonstructural areas where post -construction
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settlements are tolerable. Backfill in areas underlying paved surfaces where settlements are not
desirable should be compacted to at least 95 percent.
7.3 Wet Weather Conditions
Wet weather generally begins about mid -October and continues through about May, although
rainy periods may occur at any time of year. Some of the soil at the site contains sufficient silts
and 'fines to produce an unstable mixture when wet. Such soils are susceptible to changes in
water content, and they tend to become unstable and difficult or impossible to compact if their
moisture content significantly exceeds the optimum. If earthwork at the site continues into the
wet season, or if wet conditions are encountered, we recommend the following:
The ground surface in and surrounding the construction area should be sloped as much as
possible to promote runoff of precipitation away from work areas and to prevent ponding
of water.
2. Work areas or slopes should be covered with plastic. The use of sloping, ditching, sumps,
dewatering, and other measures should be employed as necessary to permit proper
completion of the work.
3. Earthwork should be accomplished in small sections to minimize exposure to wet
conditions. That is, each section should be small enough so that the removal of unsuitable
soils and placement and compaction of clean structural fill can be accomplished on the
same day. The size of construction equipment may have to be limited to prevent soil
disturbance. It may be necessary to excavate soils with a backhoe, or equivalent, located so
that equipment does not traffic over the excavated area. Thus, subgrade disturbance caused
by equipment traffic will be minimized.
4. Fill material should consist of clean, well -graded sand and gravel soil, of which not more
than 5 percent fines, by dry weight, passes the No. 200 mesh sieve, based on wet -sieving
the fraction passing the 3/4-inch mesh sieve. The gravel content should range from between
20 to 60 percent retained on a No. 4 mesh sieve. The fines should be nonplastic.
5. No soil should be left uncompacted and exposed to moisture. A smooth -drum vibratory
roller, or equivalent, should roll the surface to seal out as much water as possible.
6. In -place soils or fill soils that become wet and unstable and/or too wet to suitably compact
should be removed and replaced with clean, granular soil (see part 4).
Grading and earthwork should not be accomplished during periods of heavy, continuous
rainfall.
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7.4 Erosion Control
The Contractor should employ proper erosion control measures during construction, especially if
construction takes place during wet weather. Covering work areas, soil stockpiles, or slopes with
plastic; sloping; ditching; sumps; and other measures should be employed as necessary to permit
proper completion of the work. Bales of straw and/or geotextile silt fences should be
appropriately located to control soil movement and erosion.
We recommend that areas disturbed by construction activities should be hydroseeded and
covered with an erosion -control blanket. Following hydroseeding, the slope face should be
covered with an erosion -control blanket. An erosion -control blanket is recommended to (a)
protect the bare soil face against erosion until vegetation is established; (b) reduce runoff
velocity for increased water absorption by the soil, thus promoting long-term survival of the
vegetation cover; and (c) reinforce the root system of the vegetative cover. We recommend
using a permanent erosion -control, turf -reinforcement mat consisting of UV -stabilized synthetic
fibers and filaments processed into a permanent, high strength, three-dimensional matrix.
The placement of the erosion -control blanket should begin at the top of the slope (slope having a
bare soil face) by anchoring the blanket in a 12-inch-deep by 12-inch-wide trench. The trench
should be backfilled and compacted after stapling the blanket to the slope face. The blanket
should then be rolled down the slope. We recommend that the staples have a minimum length of
12 inches. Stapling the adjacent rolls of the blanket should be done in accordance with the
manufacturer's recommendations. Periodic maintenance of the erosion control blanket should be
anticipated until vegetation is well established.
7.5 Construction Monitoring
We recommend that geotechnical monitoring, testing, and consulting be provided by a
geotechnical engineer or the geotechnical engineer's representative during construction to
confirm that the conditions encountered are consistent with those indicated by our explorations
Such activities would include observation and evaluation of structural fill placement and
compaction, erosion -control measures, and other geotechnically related earthwork activities.
The geotechnical engineer should also evaluate whether earthwork activities comply with the
contract plans and specifications. If conditions encountered during construction differ from
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those anticipated, the design may need to be revised to accommodate the conditions actually
encountered.
8.0 LIMITATIONS
This report was prepared for the exclusive use of Roth Hill Engineering Partners and the City of
Renton for specific application to this project. It should be made available to potential
contractors and/or Contractor for information on factual data but not as a warranty of subsurface
conditions, such as those interpreted from the exploration logs and discussions of subsurface
conditions included in this report.
The analyses, conclusions, and recommendations contained in this report are based on site
conditions as they presently exist and on the site and project descriptions as presented herein.
We should be notified if differences are identified. We assume that the exploratory test borings
and retrieved samples are representative of the subsurface conditions throughout the site; i.e., the
subsurface conditions everywhere are not significantly different from those disclosed by the
explorations. If, during construction, subsurface conditions different from those described in this
report are observed or appear to be present during construction, we should be advised at once so
that we can review these conditions and reconsider our recommendations, where necessary. If
conditions have changed due to natural causes or construction operations at or adjacent to the
site, it is recommended that this report be reviewed to determine the applicability of the
conclusions and recommendations, considering the changed conditions and time lapse.
Within the limitations of the scope, schedule, and budget, the analyses, conclusions, and
recommendations presented in this report were prepared in accordance with generally accepted
professional geotechnical engineering principles and practice in this area at the time this report
was prepared. We make no other warranty, either express or implied. These conclusions and
recommendations were based on our understanding of the project as described in this report and
on site conditions as observed at the time of the exploration.
Unanticipated soil conditions are commonly encountered and cannot be fully determined by a
field reconnaissance or merely by taking soil samples or completing test borings. Such
unexpected conditions frequently require that additional expenditures be made to attain a
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properly constructed project. Therefore, some contingency fund is recommended to
accommodate such potential extra costs.
The scope of our services for this project did not include any environmental assessment or
evaluation regarding the presence or absence of wetlands or hazardous or toxic materials in the
soil, surface water, groundwater, or air, on or below or around the site, or for the evaluation or
disposal of contaminated soils or groundwater, should any be encountered. However, we will be
glad to provide such services on request.
Shannon & Wilson has prepared and included in Appendix C, "Important Information About
Your Geotechnical Report," to assist you and others in understanding the use and limitations of
our reports.
SHANNON & W SON, INC.
1
Theodo"fin,
pkins, E.G.
Senioral Engineering Geologist
JXM:TWH:TMG/twh
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EXPIRES: 9129I v 5
Thomas M. Gurtowski, P.E.
Vice President
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9.0 REFERENCES
American Society for Testing and Materials (ASTM), 2004, Annual book of standards,
Construction, v. 4.08, Soil and rock (I): D 420 — D 5779: West Conshohocken, Pa.
Makdisi, F.I., and Seed, H.B., 1978, Simplified procedure for estimating 'dam and embankment
earthquake -induced deformations: Journal of Geotechnical Engineering, v. 104, no. GT7,
p. 849-867.
Purdue University, 1988, PCSTABLSM/si A computer program for slope stability calculations,
with STEDwin, version 2.7: Annapolis Engineering Software.
Washington State Department of Transportation (WSDOT) and American Public Works
Association (APWA), 2004, Standard specifications for road, bridge, and municipal
construction (M41-10): Washington State Department of Transportation and American
Public Works Association.
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�, , ti� 1 I 1 . • �� ."a.
A CQlean
3 Prnofnt f ,
\
NZ K' nydale
ey del I J =i � wi'.:�' • fib' • —J �` \
PROJECT0.
rrQ f,
LOCATION
NEI
Arm
t a B I' �. • F75
`1 �J Footbr"dg."
or
:,, UldrtB 0 ! �� _, • CER
EP • .0 9L9 i
' H 6E
1— - Swdr 4 Pk ,
bs
AP
0 1/2 1
Scale in Miles
NOTE
Map adapted from 1:25,000 USGS
topographic map of Bellevue South, WA;
quadrangle, dated 1983.
File: J:%211U0326-001121-1-20326-001 Fig 2.dwg Date: 06-02-2005 Author. SAC
NOTES
1. Base map taken from electronic file, "Copy of
Renton Storm (base).dwg, Surveying and Steep
Slope Design," prepared by Roth Hill
Engineering Partners, LLC, dated 5-25-05.
2. Boring locations were measured from existing
site features and stationing stakes, and should
be considered approximate.
0 20 40
Scale in Feet
LEGEND
B-1
Boring Designation and
Approximate Location
HB-1
Hand Boring Designation
and Approximate Location
A JLGeneralized
Subsurface Profile
(See Figure 3)
In" M AW M so
File: J:1211\20326-001\21-1-20326-001 Fig 3.dwg Date: 06-03-2005 Author. SAC
A
West
180
160
120
100
:M M Ow .o " " =a M
1+80 1+60 1+40
1+20 1+00 0+80
Stationing
LEGEND
0 20 40
B-1 - — Boring Designation
(Prof. 15' N.) Projected Distance and Direction
15 Standard Pentetration Test Blows/Feet
Scale in Feet
5ov— Standard Pentetration Test Blows/Inches Driven
Horizontal = Vertical
Approximate Geologic Contact
NOTES
— Bottom of Boring 1.
The subsurface conditions indicated on the profile are
05-11-05 Date of Completion
generalized from materials observed in the borings.
Variations between the profile and actual conditions
HB-1 — Probe Designation
may exist.
7
Approximate Geologic Contact 2.
Profile constructed from topographic survey provided
by Roth Hill Engineering Partners, LLC, dated 5-25-05,
Bottom of Probe
and from measurements obtained in the field.
Loose, slightly gravelly to
gravelly, silty SAND;
0+60 0+40
A'
East
R-1
180
0+20
160
120
100
1
t
11
f]
e�
Discharge to
Catch Basin
TYPICAL PLAN VIEW
Not to Scale
1
lnchor Post
Transition from
Below Grade to
At -Grade
on M O 'M Is INN M. in M an
IW •00 M 'M M
File: J:\21IX20326-001121-1-20326-001 Fig 4.dwg Date: 06-02-2005 Author. SAC
Ground Surface
Existing 12-In. Diameter
Concrete Outfall Pipe
HDPE Pipe
12-In. Diameter
20-Ft. Max.
(TYP.)
H
Chance Chain Shackle
3/8-In. Diameter
Galvanized Steel Cable
Band Clamp (TYP.)
TYPICAL CROSS SECTION
Not to Scale
NOTES
1. Place anchors below each pipe joint
and not more than 20 feet apart.
2. Design ground anchors for the
anticipated axial load, but not less
than 5000 lb.
3. Contractor may propose an
alternate anchor system for
approval by the engineer.
Chance Anchor (TYP.)
I
1
Existing Ground Surface
Restored Surface
Granular Bedding al�o a 120° as
O O
(See text) Q n 0 n n a �)O a
II
6 Do _ 16 Excavation SubgradeIfl, J�
Not to Scale
NOTES
1. Granular bedding and initial backfill material should
meet the requirements of WSDOT Section 9-03.12(3).
Gravel backfill for pipe zone bedding.
2. Subsequent backfill should consist of select trench
excavation material or imported granular material that
meets the requirements (WSDOT/APWA 9-03-10).
Bank run gravel for trench backfill.
SHANNON &WILSON, INC.
APPENDIX A
SUBSURFACE EXPLORATIONS
1
I
11
21-1-20326-001
SHANNON &WILSON, INC.
APPENDIX A
SUBSURFACE EXPLORATIONS
TABLE OF CONTENTS
Page
A.1 INTRODUCTION.......................................................................................................... A-1
A.2 SOIL CLASSIFICATION.............................................................................................. A-1
A.3 SOIL BORINGS............................................................................................................. A-1
A.3.1 Drilling Procedures.....................................................:..................................... A-2
A.3.2 Soil Sampling................................................................................................... A-2
LIST OF FIGURES
Figure No.
A-1
Soil Classification and Log Key (2 sheets)
A-2
Log of Boring B-1
A-3
Log of Hand Boring HB-I
A-4
Log of Hand Boring HB-2
A-5
Log of Hand Boring HB-3
A-6
Log of Hand Boring HB-4
A-7
Log of Hand Boring HB-5
A-8
Log of Hand Boring HB-6
A-9
Log of Hand Boring HB-7
21-1-20326-001-RI -AA/wp/LKD
A-i
21-1-20326-001
SHANNON 6WILSON, INC.
APPENDIX A
SUBSURFACE EXPLORATIONS
A.1 INTRODUCTION
The subsurface exploration program for the Park Place North stormwater project consisted of
drilling and sampling one boring and seven hand boring probes. The approximate exploration
' locations are shown in the Site and Exploration Plan (Figure 2) in the main text of the report.
The approximate locations of the subsurface explorations were determined by measuring from
existing site features and stationing stakes present in the field. Elevations shown on the boring
logs were estimated by plotting the exploration locations on a topographic plan provided by Roth
Hill Engineering Partners, LLC, and are approximate. All the boring locations and elevations
should be considered accurate to the degree implied by the method used.
A.2 SOIL CLASSIFICATION
An engineer from Shannon & Wilson, Inc. was present throughout the current field exploration
period to observe the drilling and sampling operations, retrieve representative soil samples for
subsequent laboratory testing, and to prepare descriptive field logs of the explorations. Soils
were classified in general accordance with the American Society for Testing and Materials
(ASTM) Designation: D 2488-93, Standard Recommended Practice for Description of Soils
(Visual -Manual Procedure). The Unified Soil Classification System (USCS), as described in
Figure A-1, was used to classify the soils encountered in the soil borings. The current boring
logs in this report represent our interpretation of the contents of the field logs.
A.3 SOIL BORINGS
' The subsurface explorations performed for this project consisted of drilling and sampling one
boring using a track -mounted drill rig and advancing seven hand boring probes using portable,
'. hand -operated equipment. The track -mounted boring is designated B-1 and was drilled to a
depth of 31 feet. The hand borings are designated HB-1 through HB-7 and were advanced to
depths ranging between 1.3 and 4.5 feet. The track -mounted boring was performed on May 11,
2005; the hand borings were advanced on May 10 and 18, 2005. The exploration logs are
presented in Figures A-2 through A-9.
21-1-20326-001-R 1-AA/wp/LKD
A-1
21-1-20326-001
SHANNON 6WILSON, INC.
An exploration log is a written record of the subsurface conditions encountered. It graphically
illustrates the soils and geologic materials encountered in the boring and the USCS symbol of
each soil layer. It also includes the natural water content, if measured, and blow counts. Other
information shown on the boring logs includes groundwater observations made during drilling,
approximate ground surface elevation, and types and depths of sampling.
A.3.1 Drilling Procedures
Holt Drilling, a division of Boart Longyear, of Fife, Washington, drilled boring B-1,
under subcontract to Shannon & Wilson, Inc., using a track -mounted drill rig. Drilling was
accomplished using a hollow -stem auger (HSA). HSA drilling consists of advancing
' continuous -flight augers to remove soil from the borehole. Soil samples are taken at the bottom
of the boring by removing the center rod and lowering a split -spoon sampler through the hollow
stem. Upon completion of drilling and sampling, the boring was abandoned in accordance with
Washington State requirements. The spoils generated during drilling were drummed and
removed from the site for disposal.
A two -person crew from Shannon & Wilson, Inc. performed hand borings HB-1 through
HB-7 with portable, hand -operated equipment. The hand borings were used more as probes to
evaluate the thickness of less dense colluvium overlying very dense soils than as borings to .
1 obtained subsurface soil samples. Hand borings HB-1 through HB-4 were advanced with a hand
auger and a split -spoon sampler. Hand borings HB-5 through HB-7 were advanced without
auguring using a split -spoon sampler driven to refusal. The hand borings were terminated at
shallow depths because of the very dense and gravelly nature of the soils.
A.3.2 Soil Sampling
Representative soil samples in boring B-1 were obtained in conjunction with the Standard
Penetration Test (SPT). SPTs were performed in general accordance with ASTM Designation:
D 1686, Standard Method for Penetration Testing and Split -Barrel Sampling of Soils. SPTs were
generally performed at 2.6-foot intervals down to 30 feet, and then at 6-foot intervals. The SPT
consists of driving a 2-inch outside -diameter (O.D.), split -spoon sampler a distance of 18 inches
' into the bottom of the borehole with a 140-pound hammer falling 30 inches. The number of
blows required for the last 12 inches of penetration is termed the Standard Penetration Resistance
(N-value). This value is an empirical parameter that provides a means for evaluating the relative
density, or compactness, of granular soils and the consistency, or stiffness, of cohesive soils.
1
21-1-20326-001-R I-AA/wp/LKD 21-1-203 26-001
11 A-2
SHANNON &WILSON, INC.
These values are plotted at the appropriate depths on the boring logs included in this appendix.
Generally, whenever 50 or more blows were required to cause 6 inches or less of penetration, the
test was terminated, and the number of blows and the corresponding penetration was recorded.
The N-values are plotted on the boring logs.
To evaluate the relative density of soils encountered in the hand borings, Porter
Penetration Tests (PPTs) were performed. The PPT is a modification of the SPT. The PPT
consists of driving a 1.5-inch O.D., split -spoon sampler a total distance of 18 inches into the
bottom of the boring with a 45-pound hammer falling 18 inches. The number of blows required
to drive the sampler for each of the last two 6-inch increments are approximately equivalent to an
SPT value.
Hand borings HB-5 through HB-7 were sampled using a modified PPT in that PPT
N-values were recorded for each 6-inch increment while continuously driving the sampler. The
sampler was emptied of accumulated soil for only the last sample increment to obtain a
representative sample of the very dense soils underlying the layer of colluvium.
The penetration resistance values were recorded by our field representative and are
plotted on the boring logs. The SPT N-value and the equivalent PPT N-value are empirical
parameters that provide a means of evaluating the relative density or compactness of
cohesionless (granular) soils and the relative consistency (stiffness) of cohesive soils. The
terminology used to describe the relative density or consistency of the soil is presented in
Figure A-1.
The split -spoon sampler used during the penetration testing recovers a relatively
disturbed soil sample, which is useful for identification and classification purposes. The samples
were classified and recorded on field logs by our representative. The samples obtained from our
borings were evaluated for potential contamination based on visual appearance and odor and
then sealed in jars and returned to our laboratory for testing.
21-1-20326-001-R 1-AA/wp/LKD
I A-3
21-1-20326-001
11
I
Shannon & Wilson, Inc. (S&W), uses a soil
classification system modified from the Unified
Soil Classification System (USCS). Elements of
the USCS and other definitions are provided on
this and the following page. Soil descriptions
are based on visual -manual procedures (ASTM
D 2488-93) unless otherwise noted.
S&W CLASSIFICATION
OF SOIL CONSTITUENTS
• MAJOR constituents compose more than 50
percent, by weight, of the soil. Major
consituents are capitalized (i.e., SAND).
• Minor constituents compose 12 to 50 percent
of the soil and precede the major constituents
(i.e., silty SAND). Minor constituents
preceded by "slightly" compose 5 to 12
percent of the soil (i.e., slightly silty SAND).
• Trace constituents compose 0 to 5 percent of
the soil (i.e., slightly silty SAND, trace of
gravel).
MOISTURE CONTENT DEFINITIONS
Dry Absence of moisture, dusty, dry
to the touch
Moist Damp but no visible water
Wet Visible free water, from below
water table
ABBREVIATIONS
ATD
At Time of Drilling
Elev.
Elevation
ft
feet
FeO
Iron Oxide
MgO
Magnesium Oxide
HSA
Hollow Stem Auger
ID
Inside Diameter
in
inches
Ibs
pounds
Mon.
Monument cover
N
Blows for last two 6-inch increments
NA
Not applicable or not available
NP
Non plastic
OD
Outside diameter
OVA
Organic vapor analyzer
PID
Photo -ionization detector
ppm
parts per million
PVC
Polyvinyl Chloride
SS
Split spoon sampler
SPT
Standard penetration test
USC
Unified soil classification
WLI
Water level indicator
GRAIN SIZE DEFINITION
DESCRIPTION
SIEVE NUMBER AND/OR SIZE
FINES
< #200 (0.08 mm)
SAND*
- Fine
#200 to #40 (0.08 to 0.4 mm)
- Medium
#40 to #10 (0.4 to 2 mm)
- Coarse
#10 to #4 (2 to 5 mm)
GRAVEL*
- Fine
#4 to 3/4 inch (5 to 19 mm)
- Coarse
3/4 to 3 inches (19 to 76 mm)
COBBLES
3 to 12 inches (76 to 305 mm)
BOULDERS
> 12 inches (305 mm)
Unless otherwise noted, sand and gravel, when
present, range from fine to coarse in grain size.
RELATIVE DENSITY / CONSISTENCY
COARSE -GRAINED SOILS
FINE-GRAINED SOILS
N, SPT,
RELATIVE
N, SPT,
RELATIVE
BLOWS/FT.
DENSITY
BLOWS/FT.
CONSISTENCY
Under 2
Very soft
0-4 Very loose
4 - 10
Loose
2-4
Soft
10 - 30
Medium dense
4-8
Medium stiff
30 - 50
Dense
8 - 15
Stiff
Over 50
Very dense
15 - 30
Very stiff
Over 30
Hard
WELL AND OTHER SYMBOLS
®
Bent. Cement Grout
;• Surface Cement
Seal
®
Bentonite Grout
= Asphalt or Cap
Bentonite Chips
�'� Slough
Silica Sand
® Bedrock
EMPVC
Screen
Al
Vibrating Wire
E
1
UNIFIED SOILCLASSIFICATION SYSTEM (USCS)
(From "St D. 2487=98 & 2488 93)
MAJOR DIVISIONS
GROUP/GRAPHIC
SYMBOL
TYPICAL DESCRIPTION
GW
•''
Well- raded ravels, ravels,
gravelq/sand rf�ixture0ittle or no fines
Clean Gravels
'
Gp
��
Poorly graded gravels, gravel -sand
Gravels
(less than 5%
fines)
mixtures, little or no fines
(more than 50%
of coarse
fraction retained
on No. 4 sieve)
Gravels with
GM
Silty gravels, gravel -sand -silt mixtures
Fines
GC
Clayey gravels, gravel -sand -clay
COARSE-
(more than 12%
fines)
GRAINED
mixtures
SOILS
SW
Well -graded sands, gravelly sands,
(more than 50%
retained on No.
200 sieve)
Clean Sands
little or no fines
(less than 5%
fines)
SP
Poorly graded sand, gravelly sands,
Sands
little or no fines
(50% or more of
coarse fraction
passes the No. 4
Sands with
SM
Silty sands, sand -silt mixtures
sieve)
Fines
(more than 12%
fines)
Sc
Clayey sands, sand -clay mixtures
Inorganic silts of low to medium
MILplasticity,
rock flour, sandy silts,
gravelly silts, or clayey silts with slight
Inorganic
plasticity
Silts and Clays
Inorganic clays of low to medium
(liquid limit less
CL
plasticity, gravelly clays, sandy clays,
silty clays, lean clays
than 50)
Organic
g
OL
=—
Organic silts and organic silty clays of
low
FINE-GRAINED
SOILS
=—
— —
plasticity
(50% or more
passes the No.
Inorganic silts, micaceous or
200 sieve)
MH
diatomaceous fine sands or silty soils,
elastic silt
Inorganic
CH
Inorganic clays or medium to high
fat or fat
Silts and Clays
(liquid limit 50 or
plasticity, sandy clay, gravelly
clay
more)
Organic
OH
�
Organic clays of medium to high
�
plasticity, organic silts
ORGHLY-
ANIC
Primarily organic matter, dark in
PT
Peat, humus, swamp soils with high
SOILS
color, and organic odor
organic content (see ASTM D 4427)
NOTE: No. 4 size = 5 mm; No. 200 size = 0.075 mm
NOTES
1. Dual symbols (symbols separated by a hyphen, i.e., SP-SM, slightly
silty fine SAND) are used for soils with between 5% and 12% fines
or when the liquid limit and plasticity index values plot in the CL-ML
area of the plasticity chart.
2. Borderline symbols (symbols separated by a slash, i.e., CL/ML, silty
CLAY/clayey SILT, GW/SW, sandy GRAVEUgravelly SAND)
indicate that the soil may fall into one of two possible basic groups.
11
1
1
1
SOIL DESCRIPTION
- li
Standard Penetration Resistance
5 r
(140 lb. weight, 30-inch drop)
U)
�
o
Blows per foot
Surface Elevation: Approx. 176.0 Ft.
0 20 40 60
Loose, brown, slightly gravelly to gravelly, silty
SAND; moist to wet; scattered to abundant
roots, wood, charcoal, and organics;
tI
iron -oxide staining; (Fill) SM.
- Layer of clean to slightly silty, fine to
9 Y tY,
`
2�
5
-------
•
medium sand from 5 to 5.5 feet.
8.0
sI
71
Very dense, gray -brown to brown, silty,
gravelly SAND to gravelly, silty SAND; moist;
:.: '.:.
10
- - ----------- - - ----
scattered cobbles inferred from drill action;
4
65
iron -oxide staining, slightly silty at 15 feet;
s=,
0
50/6"
(Till -like) SM.
6I
15
2
63
:..
7
v y
<
<74
•
19'0
2
Very dense, gray -brown, silty, sandy GRAVEL
to silty, gravelly SAND; moist; iron -oxide
50/4"
stained locally, weathered gravels; scattered
cobbles inferred from drill action; (Till -like)
GM/SM.
25
- - 0 - -- - -- - - - ----- -- -
s=
50/4"
3 .0
toZ
30
--t♦—-- -- -- 50/6"
BOTTOM OF BORIN
COMPLETED 5/11/200
35
- - ----- - -- -
Note: Samples S-2, S-4, S-8, and S-9 had a
40
faint hydrocarbon odor.
45
- --- ---- -- ----- = -----
0 20 40 60
LEGEND
' Sample Not Recovered 0 % Water Content
I Standard Penetration Test Plastic Limit 1--0 Liquid Limit
Natural Water Content
>J_
z Park Place N. Storm Sewer
n NOTES Renton, Washington
i 1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
the transition may be gradual. LOG OF BORING B-1
v 3. The discussion in the text of this report is necessary for a proper understanding of the
nature of the subsurface materials.
Y
4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
J
5. Refer to KEY for explanation of symbols, codes and definitions.
y
designation is based lab testing. SHANNON & WILSON, INC. FIG. A-2
6. USCS on visual -manual classification and selected Geotechnical and Environmental Consultants
2
i
I
1
1
t
Ll
r
11
SOIL DESCRIPTION
o
-0 L
Porter Penetration Resistance
Y
o-
�
(40 lb weight, 18" drop)
a
M
(D � o
Blows per 6 inches
Surface Elevation: Approx. 177 Ft.
0 20 40 60
Loose to medium dense, dark brown to brown,
gravelly, silty SAND; moist to wet; numerous
organics and charcoal; (Fill) SM.
m
0 2
a
- --
m
i'
v
0
d
4.5
21
z 4
BOTTOM OF BORING
COMPLETED 5/10/2005
6---
------- - -- -- - - - ---
8
10
- -- - - - ... - - - - - --
12
-- — ----- --
14
----- --- ------ -- -
16
n
18
--- -
— --- -- ----
LEGEND 0 20 40 60
• % Water Content
Grab Sample Plastic Limit 1 Liquid Limit
I Porter Penetration Test Sample Natural Water Content
i
Park Place N. Storm Sewer
L NOTES Renton, Washington
6 1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
the transition may be gradual. LOG OF HAND BORING HB-1
j 3. The discussion in the text of this report is necessary for a proper understanding of the
J nature of the subsurface materials.
e 4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
0 5. Refer to KEY for explanation of symbols, codes and definitions.
6. USCS designation is based on visual -manual classification and selected lab testing. SHANNON & WILSON, INC. FIG. A-3
Geotechnical and Environmental Consultants
i
SOIL DESCRIPTION
o
U)
-o
Porter Penetration Resistance
a
E
CL
a
(40 lb weight, 18" drop)
n
)
Blows per 6 inches
Surface Elevation: Approx. 170 Ft.
Q
0 20 40 60
Loose to medium dense, brown, slightly
m
gravelly, silty SAND to silty SAND, trace of
1 G
clay; moist; abundant organics; (Colluvium)
SM.
o
v 2
- - ---- -- - - __-_-.- - --- . - - - — -
N
a
O
3.5
2
c
z
Dense, brown, silghtly gravelly, silty SAND,
trace of clay; moist; iron -oxide staining;
4.0
4
----------- - ---- ---------------50/4'
scattered organics; Till SM.
BOTTOM OF BORING
COMPLETED 5/10/2005
6
- —-----=-- --- - ---- -----
10
- -- --...--.
12
=---
-- --- ----- - ..... - -
14
- - .. -= - ----------- -
16
- ---- - -- - -- -
I,
i
I
18
-- — -------- --- --- -- - ---
LEGEND 0 20 40 60
• % Water Content
' ® Grab Sample Plastic Limit id Limit
I Porter Penetration Test Sample Natural Water Content
i
Park Place N. Storm Sewer
NOTES Renton, Washington
1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
the transition may be gradual. LOG OF HAND BORING HB-2
i 3. The discussion in the text of this report is necessary for a proper understanding of the
I ature of the subsurface materials.
4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
5. Refer to KEY for explanation of symbols, codes and definitions.
SHANNON 8c WILSON, INC.
6. USCS designation is based on visual -manual Gassification and selected lab testing. FIG. A-4
Geotechnical and Environmental Consultants
�
SOIL DESCRIPTION
o
rn
o
Porter Penetration Resistance
a
E
0
o n
(40 lb weight, 18" drop)
Blows per 6 inches
Surface Elevation: Approx. 146 Ft.
O
0 20 40 60
Loose, gray -brown, silty, gravelly SAND, trace
of clay; wet; numerous roots and organics;
0.8
r
IT
iron -oxide stained; Colluvium SM/GM.
1.7
z
0
50/5"
Very dense, gray -brown, gravelly, silty SAND;
moist; iron -oxide stained; Till SM.
0 2
-
BOTTOM OF BORING
COMPLETED 5/10/2005
4
-- ---
----- - - --- -- - - - - -
6
=---
--- —----=--- ---- -- - - ----
8
-- -- - . ......
10
12
14
- - -- - -----?---------------------------------- ----
16
-- - --
t
1
18
0 20 40 60
LEGEND
4 Ground Water Level ATD • %Water Content
® Grab Sample Plastic Limit 1--0 I Liquid Limit
Z Porter Penetration Test Sample Natural Water Content
>J_
Z
Q
Park Place N. Storm Sewer
NOTES Renton, Washington
t. The boring was performed using drilling methods.
y 2. The stratification lines represent the approximate boundaries types, between soil tand
y the transition may be gradual. LOG OF HAND BORING HB-3
j 3. The discussion in the text of this report is necessary for a proper understanding of the
nature of the subsurface materials.
z 4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
Y
n 5. Refer to KEY for explanation of symbols, codes and definitions.
z 6. USCS designation is based on visual -manual classification and selected lab testing. SHANNON & WILSON, INC. FIG. A-5
Geotechnical and Environmental Consultants
a
1
1
SOIL DESCRIPTION
o
o
Porter Penetration Resistance
a
o @
(40 lb weight, 18" drop)
>1
U
- o
♦ Blows per 6 inches
Surface Elevation: Approx. 126 Ft.
0 20 40 60
Loose, brown, silty SAND; wet; abundnat
2
organics; (Colluvium) SM.
1.0
,�
o
Medium dense to very dense, brown, slightly
silty to silty, fine to medium SAND, trace of
gravel; wet; abundant roots and organics near
a 2
---- _.
top; iron -oxide staining decreasing with depth;
(Outwash) SM/SP-SM.
4
- -- - - - -- - ti -- ..-.. ---- - - -- -
4.5
2 z
50/3"
BOTTOM OF BORING
COMPLETED 5/10/2005
6
- ----- --- - - --....-.-..-- - --
8
- .. .. - - --- -
10
- _... _ _-.. _---- --------- .:...
12
14
- - --- ---- - - - - ----------- - - -
i
16
J
18
.. ..
--- ---- ----- - — --- — - -
LEGEND 0 20 40 60
• % Water Content
2 Ground Water Level ATD
Grab Sample Plastic Limit 1 -0 Liquid Limit
9 I Porter Penetration Test Sample Natural Water Content
J
Park Place N. Storm Sewer
NOTES Renton, Washington
S 1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
the transition may be gradual. LOG OF HAND BORING HB-4
D 3. The discussion in the text of this report is necessary for a proper understanding of the
J nature of the subsurface materials.
4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
Y
a 5. Refer to KEY for explanation of symbols, codes and definitions.
Geotechnical and Environmental Consultants
i 6. USCS designation is based on visual manual classifiption and selected lab testing. SHANNON & MLSON, INC. FIG. A-6
L
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SOIL DESCRIPTION
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�5_
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A Blows per 6 inches
Surface Elevation: Approx. 165 Ft.
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0 20 40 60
Loose, brown to gray -brown, silty, gravelly
SAND; moist; (Colluvium) SM.
2
---A----
2.5
0
Dense to very dense, gray -brown, gravelly,
silty SAND; moist; iron -oxide staining; (Till)
3.3
0
Z-
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4
BOTTOM OF BORING
COMPLETED 5/18/2005
6
— -- ----------
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10
12
------ -
14
- --------
16
18
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LEGEND 0 20 40 60
0 %Water Content
T Porter Penetration Test Sample Plastic Limit 1 0 Liquid Limit
Natural Water Content
Park Place N. Storm Sewer
L NOTES Renton, Washington
1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
the transition may be gradual.
LOG OF HAND BORING HB-5
.9
D 3. The discussion in the text of this report is necessary for a proper understanding of the
nature of the subsurface materials.
4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
D
n 5. Refer to KEY for explanation of symbols, codes and definitions.
n SHANNON & WILS(?N, INC. I FIG. z 6. USCS designation is based on visual -manual classification and selected lab testing. Geotechnical and Environmental Consultants
I
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o
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Penetration Resistance
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o
A Blows per 6 inches
Surface Elevation: Approx. 154 Ft.
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0 20 40 60
Loose to medium dense, brown to gray -brown,
o
gravelly, silty SAND; moist; (Colluvium) SM.
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v
Very dense, gray -brown, gravelly, silty SAND;
moist; Till SM.
1.3
°
Z 2
BOTTOM OF BORING
COMPLETED 5/18/2005
4
- -- - - - - - -- ----- - - - - - -- -- ---
6
------ ----------=--------
8
10
__.. ------- !_. -- - - - -- -
12
14
i
16
18
----- - ----- -— - ----
LEGEND 0 20 40 60
• % Water Content
Z Porter Penetration Test Sample Plastic Limit Liquid Limit
Natural Water Content
z
Park Place N. Storm Sewer
L NOTES Renton, Washington
6 1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
v the transition may be gradual. LOG OF HAND BORING HB-6
j 3. The discussion in the text of this report is necessary for a proper understanding of the
nature of the subsurface materials.
e 4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
0 5. Refer to KEY for explanation of symbols, codes and definitions.
D 6. USCS designation is based on visual -manual classification and selected lab testing. SHANNON & WILSON INC.
Geotechnical and Environmental Consultants
i s s. FIG. A-8
71
1
SOIL DESCRIPTION
5
a
-0
Porter Penetration Resistance
.c
0.
� :-' t
(40 lb weight, 18" drop)
a)>
a)
Blows per 6 inches
Surface Elevation: Approx. 136 Ft.
m
0 20 40 60
Loose to medium dense, brown to gray -brown,
o
silty, gravelly SAND; moist; (Colluvium) SM.
1'0
t=
W
Very dense, gray -brown, silty, gravelly SAND;
moist; Till SM.
1.3
0
z 2
BOTTOM OF BORING
COMPLETED 5/18/2005
4
--- - ---
6
--- - --- ---- — ---- - -
8-
-
10
- - -' -- _ -- --
12
14
-- --- - --+
16
18
-- -------- — --- --- ._:_...--.— ----
LEGEND 0 20 40 60
• % Water Content
I Porter Penetration Test Sample
Plastic Limit 1-0 Liquid Limit
Natural Water Content
Park Place N. Storm Sewer
L NOTES Renton, Washington
1. The boring was performed using drilling methods.
2. The stratification lines represent the approximate boundaries between soil types, and
the transition may be gradual. LOG OF HAND BORING HB-7
i 3. The discussion in the text of this report is necessary for a proper understanding of the
nature of the subsurface materials.
4. Groundwater level, if indicated above, is for the date specified and may vary. June 2005 21-1-20326-001
0 5. Refer to KEY for explanation of symbols, codes and definitions.
6. USCS designation is based on visual -manual classification and selected lab testing. SHANNON & WILSON, INC. T FIG. A-9
Geotechnical and Environmental Consultants
i
C
SHANNON 6WILSON, INC.
APPENDIX B
GEOTECHNICAL LABORATORY TESTING
21-1-20326-001
SHANNON &WILSON, INC.
APPENDIX B
GEOTECHNICAL LABORATORY TESTING
TABLE OF CONTENTS
Page
B.l INTRODUCTION...........................................................................................................B-1
B.2 VISUAL CLASSIFICATION..........................................................................................B-1
B.3 WATER CONTENT DETERMINATIONS....................................................................B-1
BAGRAIN SIZE DISTRIBUTION......................................................................................B-1
B.5 REFERENCE...................................................................................................................B-2
FIGURE
Figure No.
B-1 Grain Size Distribution (B-1)
21-1-20326-001-R 1-AB.doc/wp/LKD 21-1-203 26-001
B-1
SHANNON 6WILSON, INC.
APPENDIX B
GEOTECHNICAL LABORATORY TESTING
B.1 INTRODUCTION
This appendix contains descriptions of the procedures and the results of geotechnical laboratory
tests completed on the soil samples obtained from the recent explorations for the Park Place
North storm,sewer project. The samples were tested to determine basic index properties and
engineering characteristics of the site soils. Laboratory testing on recent soil samples was
completed at Shannon & Wilson's laboratory in Seattle.
B.2 VISUAL CLASSIFICATION
Soil samples obtained from the recent explorations were visually classified in the laboratory
using a system based on the American Society for Testing and Materials (ASTM) Designation:
D 2487, Standard Test Method for Classification of Soil for Engineering Purposes, and ASTM
Designation: D 2488, Standard Recommended Practice for Description of Soils (Visual -Manual
Procedure). This visual classification allows for convenient and consistent comparison of soils
from widespread geographic areas.
The sample classifications have been incorporated into the soil descriptions on the exploration
logs presented in Appendix A.
B.3 WATER CONTENT DETERMINATIONS
Water content determinations were performed in general accordance with ASTM Designation:
D 2216, Standard Method of Laboratory Determination of Water (Moisture) Content of Soil,
Rock, and Soil -Aggregate Mixtures, on all of the recently retrieved geotechnical soil samples.
Water content is plotted on the log of boring B-1 presented in Appendix A as Figure A-2. Water
content was not measured for the samples collected from the shallow hand borings.
BA GRAIN SIZE DISTRIBUTION
Grain size analyses were completed on a selected sample to determine its grain size distribution.
The test was performed in general accordance with ASTM Designation: D 422, Standard
Method for Particle -Size Analysis of Soils. The grain size analysis consisted only of the
21-1-20326-001-R 1-AB.dochvp/LKD
Ni
21-1-20326-001
SHANNON &WILSON, INC.
coarse -grained fraction of the sample, and the grain size distribution was obtained by sieving
(sieve analysis).
The grain size distribution was used to assist in classifying soil and to provide correlations with
soil properties. The results of the grain size analysis are plotted on the grain size distribution
curve presented in Figure B-1. Along with the grain size distribution is a tabulated summary
containing the sample description and the natural water content.
B.5 REFERENCE
American Society for Testing and Materials (ASTM), 2004, Annual book of standards,
Construction, v. 4.08, Soil and rock, (I): D 420 — D 5779: West Conshohocken, Pa.,
American Society for Testing and Materials.
21-1-20326-001-RI-AB.doc/wp/LKD
21-1-20326-001
100
90
80
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M N
SIEVE ANALYSIS I HYDROMETER ANALYSIS
SIZE OF MESH OPENING IN INCHES NO. OF MESH OPENINGS PER INCH, U.S. STANDARD GRAIN SIZE IN MILLIMETERS
N O O y OpD f0 O C� N
o O O o O S O O O O
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O O O
GRAIN SIZE IN MILLIMETERS
COBBLES
COARSE I FINE
COARSE MEDIUM FINE
FINES' SILT OR SLAY
GRAVEL
SAND
BORING AND
SAMPLE NO.
DEPTH
(feet)
U.S.C.S.
SYMBOL
SAMPLE
DESCRIPTION
FINES
%
NAT.
W.C. %
LL
%
PL
%
PI
%
Park Place N. Storm Sewer
Renton, Washington
• B-1, S-3
7.5
SM
Light brown, gravelly, silty SAND
28.6
8.6
GRAIN SIZE DISTRIBUTION •
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June 2005 21-1-20326-001
W SHANNON & WILSON, INC. FIG. B-1
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SHANNON 6WILSON, INC.
APPENDIX C
IMPORTANT INFORMATION ABOUT
YOUR GEOTECHNICAL REPORT
21-1-20326-001
' SHANNON & WILSON, INC. Attachment to and part of Report 21-1-20326-001
- Geotechnical and Environmental Consultants
- Date: June 6, 2005
To: Roth Hill Engineering Partners, LLC
Mr. Erik Walgorski, P.E.
IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL/ENVIRONMENTAL
REPORT
CONSULTING SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND FOR SPECIFIC CLIENTS.
Consultants prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for
a construction contractor or even another civil engineer. Unless indicated otherwise, your consultant prepared your report expressly for you
and expressly for the purposes you indicated. No one other than you should apply this report for its intended purpose without first
conferring with the consultant. No party should apply this report for any purpose other than that originally contemplated without first
conferring with the consultant.
THE CONSULTANTS REPORT IS BASED ON PROJECT -SPECIFIC FACTORS.
A geotechnical/environmental report is based on a subsurface exploration plan designed to consider a unique set of project -specific factors.
Depending on the project, these may include: the general nature of the structure and property involved; its size and configuration; its
historical use and practice; the location of the structure on the site and its orientation; other improvements such as access roads, parking lots,
and underground utilities; and the additional risk created by scope -of -service limitations imposed by the client. To help avoid costly
problems, ask the consultant to evaluate how any factors that change subsequent to the date of the report may affect the recommendations.
'Unless your consultant indicates otherwise, your report should not be used: (1) when the nature of the proposed project is changed (for
example, if an office building will be erected instead of a parking garage, or if a refrigerated warehouse will be built instead of an
unrefrigerated one, or chemicals are discovered on or.near the site); (2) when the size, elevation, or configuration of the proposed project is
'altered; (3) when the location or orientation of the proposed project is modified; (4) when there is a change of ownership; or (5) for
application to an adjacent site. Consultants cannot accept responsibility for problems that may occur if they are not consulted after factors
which were considered in the development of the report have changed.
SUBSURFACE CONDITIONS CAN CHANGE.
Subsurface conditions may be affected as a result of natural processes or human activity. Because a geotechnical/environmental report is
'based on conditions that existed at the time of subsurface exploration, construction decisions should not be based on a report whose
adequacy may have been affected by time. Ask the consultant to advise if additional tests are desirable before construction starts; for
example, groundwater conditions commonly vary seasonally.
'Construction operations at or adjacent to the site and natural events such as floods, earthquakes, or groundwater fluctuations may also affect
subsurface conditions and, thus, the continuing adequacy of a geotechnical/environmental report. The consultant should be kept apprised of
any such events, and should be consulted to determine if additional tests are necessary.
MOST RECOMMENDATIONS ARE PROFESSIONAL JUDGMENTS.
Site exploration and testing identifies actual surface and subsurface conditions only at those points where samples are taken. The data were
extrapolated by your consultant, who then applied judgment to render an opinion about overall subsurface conditions. The actual interface
between materials may be far more gradual or abrupt than your report indicates. Actual conditions in areas not sampled may differ from
those predicted in your report. While nothing can be done to prevent such situations, you and your consultant can work together to help
reduce their impacts. Retaining your consultant to observe subsurface construction operations can be particularly beneficial in this respect.
Page 1 of 1/2005
A REPORT'S CONCLUSIONS ARE PRELIMINARY.
The conclusions contained in your consultant's report are preliminary because they must be based on the assumption that conditions revealed
through selective exploratory sampling are indicative of actual conditions throughout a site. Actual subsurface conditions can be discerned
only during earthwork; therefore, you should retain your consultant to observe actual conditions and to provide conclusions. Only the
consultant who prepared the report is fully familiar with the background information needed to determine whether or not the report's
recommendations based on those conclusions are valid and whether or not the contractor is abiding by applicable recommendations. The
consultant who developed your report cannot assume responsibility or liability for the adequacy of the report's recommendations if another
party is retained to observe construction.
THE CONSULTANTS REPORT IS SUBJECT TO MISINTERPRETATION.
Costly problems can occur when other design professionals develop their plans based on misinterpretation of a geotechnical/environmental
report. To help avoid these problems, the consultant should be retained to work with other project design professionals to explain relevant
geotechnical, geological, hydrogeological, and environmental findings, and to review the adequacy of their plans and specifications relative
to these issues.
BORING LOGS AND/OR MONITORING WELL DATA SHOULD NOT BE SEPARATED FROM THE REPORT.
Final boring logs developed by the consultant are based upon interpretation of field logs (assembled by site personnel), field test results, and
laboratory and/or office evaluation of field samples and data. Only final boring logs and data are customarily included in
geotechnical/environmental reports. These final logs should not, under any circumstances, be redrawn for inclusion in architectural or other
design drawings, because drafters may commit errors or omissions in the transfer process.
To reduce the likelihood of boring log or monitoring well misinterpretation, contractors should be given ready access to the complete
geotechnical engineering/environmental report prepared or authorized for their use. If access is provided only to the report prepared for
you, you should advise contractors of the report's limitations, assuming that a contractor was not one of the specific persons for whom the
report was prepared, and that developing construction cost estimates was not one of the specific purposes for which it was prepared. While
a contractor may gain important knowledge from a report prepared for another party, the contractor should discuss the report with your
consultant and perform the additional or alternative work believed necessary to obtain the data specifically appropriate for construction cost
estimating purposes. Some clients hold the mistaken impression that simply disclaiming responsibility for the accuracy of subsurface
information always insulates them from attendant liability. Providing the best available information to contractors helps prevent costly
construction problems and the adversarial attitudes that aggravate them to a disproportionate scale.
READ RESPONSIBILITY CLAUSES CLOSELY.
Because geotechnical/environmental engineering is based extensively on judgment and opinion, it is far less exact than other design
disciplines. This situation has resulted in wholly unwarranted claims being lodged against consultants. To help prevent this problem,
consultants have developed a number of clauses for use in their contracts, reports and other documents. These responsibility clauses are not
exculpatory clauses designed to transfer the consultant's liabilities to other parties; rather, they are defmitive clauses that identify where the
consultant's responsibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take
appropriate action. Some of these definitive clauses are likely to appear in your report, and you are encouraged to read them closely. Your
consultant will be pleased to give full and frank answers to your questions.
The preceding paragraphs are based on information provided by the
ASFE/Association of Engineering Firms Practicing in the Geosciences, Silver Spring, Maryland
Page 2 of 2 1/2005 1
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City of Renton
Park Place N. Storm Project
Steep Slope Analysis and Design
May 2006
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Prepared by:
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Roth Hill Engineering Partners, LLC
2600 1 16th Avenue NE # 100
R o t h H i 11 Bellevue, Washington 98004
' Tel 425.869.9448
Fax 425.869.1 190
May 9, 2006 800.835.0292
City of Renton
' Renton City Hall — 51h Floor
1055 South Grady Way
Renton, WA 98055
' Attn: Daniel Carey, P.E.
RE: Park Place N. Storm Sewer Project
' Steep Slope Analysis and Design
Design Report
' Dear Mr. Carey:
This letter with attached figures and appendices comprises the revised design report submittal and updates the
original letter report which was dated August 22, 2005. This revised report has been prepared as the result of
' the City's decision to relocate the steep slope pipe alignment thereby modifying the original design location.
The referenced figures are bound at the back of the report. Following the figures are four Appendices:
' • Appendix A, Technical Memorandum from Shannon & Wilson, dated June 21, 2005.
• Appendix B, Letter Report from S&W, dated April 20, 2006.
• Appendix C,Thermal Expansion Calculations, dated June 22, 2005.
• Appendix D, Specifications and Opinion of Probable Construction Cost (May 2006)
The internal organization of this letter report is based on a presentation of various technical issues by topics as
' foe"'oWte'chnical Investigation
Shannon & Wilson, Inc. prepared a geotechnical investigation for this project titled Geotechnical Report, Park
Place North Storm Sewer Proiect, dated June 6, 2005. This report was previously sent to the City. Therefore, a
copy of the report is not included herein nor are its findings recapitulated.
' Review of the S&W report raised some questions regarding its recommendations. To respond to these
questions, S&W prepared a Technical Memorandum dated June 21, 2005. This document is attached as
Appendix A.
tAs a result of the relocated pipe alignment, S&W conducted a site visit on April 12, 2006 in order to assess the
observable ground conditions relative to those along the original alignment. Their findings were presented in a
letter report addressed to Roth Hill dated April 20, 2006. This report is attached as Appendix B. In S&W's
' opinion, the conclusions and recommendations from their earlier investigation are applicable to the revised
alignment.
' Slope Stability Analysis
The slope stability analysis by S&W indicates that the upper manhole and pipe down the steep slope are stable
under static conditions. This is shown on the first page of figures included in their Memorandum in Appendix A.
1
F:\0015\00013\DESIGN\Reports\Letter Report _050906_sks.dx
' Daniel Carey
May 9, 2006
Page 2
1
The FS values (safety factors as calculated by the Modified Janbu Method) are in the range of 1.54 to 1.57 as
' shown on the figure.
The S&W Technical Memorandum further states that the proposed manhole (catch basin) at the top of the hill
would be only marginally stable under seismic conditions. In their opinion, the upper manhole is inadequate to
' support the steep slope pipe under seismic conditions. This is shown on the second figure in the Memorandum
where the FS values are given as being 1.06 and 1.07.
Pipe Anchor System
Due to the marginal stability of the slope under seismic conditions, S&W proposed that the pipeline on the slope
be supported by an anchor system at the top of the slope as described in their original June 5 report.
One initial concern with their anchor system design was whether it would permit the above -grade portion of the
pipe to be 'snaked'. According to their Technical Memorandum, their design allows for the pipe to be laid on a
curve. In a conference call with them on June 16, 2005 they stated that the 3/8-inch diameter galvanized steel
' cables are flexible.
In response the June 241h, 2005 draft of this report, the City raised the question as to whether the clamps and
' galvanized steel cables installed down the full length of the pipe would interfere with the thermal
expansion/contraction features to be incorporated into the pipe's design (as discussed below). We discussed
this with S&W and they agreed that their anchor detail could be modified so that there would be only two pipe
clamps. One clamp would be at the top of the pipeline where it emerges from below grade and a second clamp
' would be located 5 feet down slope from the first clamp. The two pipe clamps would be connected by the 3/8-
inch diameter galvanized steel cable as shown in their original report.
As a point of clarification, S&W's original pipe anchor design indicated a connection to a concrete outfall pipe
pictorially shown at the top of the slope. In the Technical Memorandum (Appendix A), this is acknowledged as
an error on their part.
Based on S&W's geotechnical report, their Technical Memorandum, and our subsequent communications with
them, we recommend that the pipe be anchored to the top of the slope per their original report except that only
two pipe clamps (5 feet apart and interconnected with galvanized steel cable) should be installed as described
above.
m Pipe Plan and Profile
The pipe plan and profile section in the August 22, 2005 version of this report was based on the originally
proposed pipe alignment. For this revision, Figure 1A, Revised Schematic Plan View, has been added to reflect
the new pipe alignment. The following two paragraphs, with their corresponding Figure references, have been
' retained and , in our opinion, are also applicable to the new alignment shown on Figure 1A.
For our analysis, we have schematically laid out a steep slope pipe route with proposed catch basins as shown
on Figure 1, Schematic Plan View. Figure 1 is based on the topographic survey performed by Roth Hill. The
' intent of the pipe alignment is to traverse the slope as perpendicularly to the contours as possible. A `snaked'
alignment is shown (and discussed in more detail below). The exact location of the upstream and downstream
catch basins is subject to adjustment as are the invert elevations of the pipes at the catch basins.
' On Figure 2, Straight Slope Profile, is presented a profile view based on plan view alignment shown in Figure 1
assuming that the pipe is installed at a constant slope between the catch basins at the top and bottom of the
steep slope. Depending upon the exact locations of the manhole and the inverts of the pipe, it appears that
1
F:\0015\00013\DESIGN\Reports\Letter Report_050906_sks.doc
1
' Daniel Carey
May 9, 2006
Page 3
1
much of the pipe would, in fact, be buried with only a relatively small length 'daylighting' above grade. In order to
' maximize the lineal footage of pipe installed above grade, it will apparently be necessary to use prefabricated
bends at the top and bottom of the slope. Figure 3, Slope Profile with Vertical Bends, shows a schematic
representation of this profile.
Thermal Expansion Analysis
HDPE pipe installed on the surface will be subject to ambient temperature fluctuations and direct sunlight.
HDPE pipe that is produced with a minimum 2% concentration of carbon black is well protected from ultraviolet
degradation.
A characteristic of HDPE pipe as compared to other pipe materials is its relatively high coefficient of thermal
' expansion. This means that it lengthens and contracts as the temperature rises and falls. Fortunately, the
forces generated by thermal stresses are relatively low for HDPE because its modulus of elasticity is low and it is
capable of stress relaxation. Nevertheless, this must be taken into account during design and is the reason for
'snaking' the pipe along the ground surface. By installing the pipe in a slightly snaked pattern, thermal
' expansion/contraction can be controlled through control of the lateral deflection. As the pipe warms, the "S"
configuration becomes slightly greater. As the pipe cools, the pipeline becomes straighter.
t In Appendix C is an analysis that calculates the amount of lateral deflection that may be expected for the pipeline
layout shown on Figure 1. This is calculated as 20.4 inches (see Condition 2) and corresponds to a bending
radius of the pipe equal to 71.5 feet. To account for both pipe expansion and contraction we want one-half of
this radius to be greater than the minimum bending radius of the pipe (30 feet). As shown, one-half of 71.8 feet
t equals 35.8 feet which is greater than the 30-foot bending radius of 12-inch HDPE pipe. Therefore, pipe
expansion and contraction will take up the thermal stresses as desired. (A bending radius of 30 feet implies the
maximum bending of the pipe without kinking the pipe wall but not necessarily affecting the integrity of the pipe).
' It should be noted that the calculations in Appendix C are very conservative and the actual deflections and strain
characteristics may be significantly less for a number of reasons including:
1. Friction forces imposed by the terrain
2. The weight of the pipe (but fluid weight is expected to be minimal, especially in extreme temperature
conditions)
3. Temperature variations are not instantaneous
These factors allow for stress relaxation during the temperature fluctuation process.
The revised pipe alignment, as shown in Figure 1A, represents an overall increase in the total lineal footage
installed above grade from 93 feet, as assumed in Appendix C calculations, to approximately 110 feet. The
calculations in Appendix C have not been revised to reflect this change. See On -Slope Pipe Anchors below.
Rather than relying solely on the snaked pipe for mitigating the effects of thermal expansion, the installation of a
'slip joint' is also proposed to be installed at the bottom of the slope. This has been incorporated by the City into
the design shown on the Figure 1A alignment. With the slip joint, the horizontal deflection of the snake pipe can
be reduced from 2 feet to 1.5 feet (+/-) in order to facilitate ease of construction.
On -Slope Pipe Anchors
The S&W Technical Memorandum (Appendix A) recommends anchors on the above -grade portion of the pipe to
restrain against lateral loads. We expect the lateral loads from both static and dynamic hydraulic forces to be
negligible. The above -grade portion of the pipe will be subject to little, if any, hydraulic static pressure which is
FA0015\00013\DESIGN\Reports\Letter Report_050906_sks.doc
Daniel Carey
May 9, 2006
Page 4
the predominant cause of thrust at bends in a pressure pipe situation such as a water main.
The velocity head pressure is also minimal even assuming that it acts in full laterally (i.e., perpendicularly to the
side wall of the pipe, which will not be the case). Manning's equation predicts a velocity of approximately 30 fps
using the anticipated 100-year event flow of 4.3 cfs as provided by the City for this situation. This translates into
the equivalent of 6 psi of pressure for a perpendicularly acting flow. For the same pressure conditions, a 90-
degree bend will experience more thrust than a 45-degree bend. Given the slight degree of bending for the
proposed "S" configuration, we believe the magnitude of the dynamic lateral forces due to velocity will be
negligible as stated above.
For thermal expansion purposes, the Condition 2 analysis in Appendix C proposes two (2) intermediate pin
anchors located as shown on Figure 1. The buried ends of the steep slope pipe constitute anchors at the top
and bottom of the slopes. Pipe anchors will causes the build up of strain in the pipe wall. It is recommended that
the strain be limited to less than 5%. As shown in Appendix C, the minimum anchor spacing using a maximum
allowable strain of 0.05 in/in is 16.1 feet for this application. The spacing shown on Figure 1 exceeds this
minimum threshold as does the spacing for the revised pipe alignment pictured on Figure 1A..
According to the S&W Technical Memorandum, the pin anchors shown on a past Roth Hill project are sufficient
for this purpose. Accordingly, the design for the pin anchors is presented on Figure 4, Type 2 Pipe Anchor
Detail. Note that the pin anchors are to be installed such that the pipe can slip or move axially. In other words,
they are to provide lateral restraint only.
The revised alignment (Figure 1 A) incorporates a buried prefabricated horizontal elbow at the top of the slope.
In our opinion an anchor is not required for this fitting.
Pipe End Connections
The proposed pipe would be anchored at the top of the slope as proposed by Shannon & Wilson. Two pin
anchors would be installed on the steep slope as described in the previous section. We also propose to anchor
the steep slope pipe to the upstream catch basin per Figure 5, Connection Detail. This detail, which was
developed with the assistance of the City, is intended to provide structural support at the upstream catch basin
during construction.
Flanqed Fitting Connections
We originally envisioned that the bends (fittings) required at the top and bottom of the slope (where the pipe
transitions from below grade to above ground and vice versa) would have butt -fused joints. At the July 28tn
2005 meeting in our office, you pointed out that using flanged fittings may offer ease of construction benefits.
We subsequently contacted Performance Pipe to verify that the use of flange fittings would be both feasible and
provide adequate structural integrity. Our subsequent discussion with the technical department at Performance
Pipe verified both of these considerations. We, therefore, believe that the flanged -end fittings are acceptable. A
flanged fitting connection has been incorporated by the City into the design for the revised pipe alignment (Figure
1 A).
Energy Dissipation
As part of our investigation, we examined possible ways of dissipating the energy (or velocity) at the bottom of
the steep -slope pipe. Research of available reference materials and on the Web revealed surprisingly little
information for an application similar to this project. Energy dissipation is usually of concern when flow is
released from a pipe or other conveyance system into the natural environment. The concern, of course, is with
erosion of natural stream channels.
F:\0015\00013\DESIGN\Reports\Letter Report_050906_sks.doc
' Daniel Carey
May 9, 2006
Page 5
1
' We considered two basic approaches. One was to use some type of a vault, with or without baffles, similar to a
detention vault. We identified two concerns with this:
1. The bigger concern is that the vault, even when not equipped with orifice plate restrictors, would still act
' as detention vault and have the affect of restricting the conveyance (hydraulic throughput) capacity of the
system in terms the cfs.
2. A lesser concern was that a vault would not fit the proposed pipe alignment so that inlet and outlet pipes
' would penetrate the sides of the vault perpendicularly.
With these considerations in mind, we believe that the energy dissipater, if any, should be a simple catch basin
with a submerged inlet. This is the second basic approach considered. In the next section is described the
' hydraulic modeling we performed in this approach.
Hydraulic Analysis
In order to better evaluate the hydraulic elements of the steep slope pipe, we used the MOUSE modeling
hydraulic simulation software program from DHI. Four conditions were simulated using a flow of 4.3 cfs. These
simulations were based on the Figure 1 alignment. In our opinion, the modeling results would not differ
' significantly for the revised alignment (Figure 1A). The presentation capabilities of the MOUSE program are
limited but color copies of the graphical output are presented as follows:
• Figure 6, City Design — Unsubmerged Inlet CB, shows the City's design without a submerged inlet catch
' basin at the bottom of the slope.
• Figure 7, City Design — Submerged Inlet CB, pictures the same design with a submerged inlet catch
basin.
' Figure 8, Roth Hill — Unsubmerged Inlet CB, illustrates the Roth Hill schematic (based on Figures 1 and
3) without a submerged inlet catch basin.
• Figure 9, Roth Hill — Submerged Inlet CB, shows the same design with the submerged inlet.
' Note: Figures 6 and 7 are based on the data sent to us from the City by mail transmittal dated May 5, 2005.
Besides showing the impacts of having or not having a submerged inlet catch basin at the bottom of the slope,
the 'City design' is based on a straight slope pipe down the hill whereas the 'Roth Hill' schematic shows the
effects of incorporating vertical pipe bends into the profile.
In terms of distinguishing between the four scenarios, the model results as presented in Figures 6 — 9 do not
reveal any striking information. The submerged inlet catch basin has the expected effect of causing the
hydraulic grade line to rise above the crown of the pipe, i.e. causing the pipe to become slightly pressurized. The
pressure head is approximately 5 feet which is the equivalent of approximately 2 psi. Where submerged, we
anticipate the actual depth of submergence is in reality confined to the bottom of the pipe. (The MOUSE program
' 'connects the dots' between calculation points). Also, in the area of submergence, the velocity in the full pipe will
be correspondingly reduced thereby lowering potential dynamic forces.
We believe that it would be best to submerge the inlet of the down -slope catch basin as shown on Figures 7 and
9 in order to confine the energy dissipation in the upstream pipe under higher flow conditions. With a submerged
inlet, the effects of erosion in the concrete structure should also be mitigated. In general, we expect HDPE to
have better scour -resistant characteristics than concrete. We have shown the depth of submergence to be
approximately 4 feet. We do not consider this to be critical and believe there is no reason to make this depth
greater or lesser as desired.
F:\0015\00013\DESIGN\Reports\Letter Report_050906_sks.doc
' Daniel Carey
May 9, 2006
Page 6
Finally, we believe the pipe should be designed with vertical bends in order to maximize the amount of above -
grade pipe on the slope and reduce the amount of trenching which will result in less disturbance of the soils on
this slope. Figure 9, therefore, schematically represents our recommendations.
Specifications and Opinion of Probable Construction Cost
These were provided under separate cover in August 2005. For this revised report, we have updated this
information and included it in Appendix D. The Engineering News Record Construction Cost Index for Seattle
has increased 3.1 % between August 2005 and April 2006. The costs have been increased and rounded up to
reflect this general price increase. HDPE pipe is recommended for the steep slope construction and should be
Performance Series 4100, DR 17 or approved equal. This pipe has good ultraviolet -resistant characteristics.
The pipe joints are heat -fused and, therefore, will not pull apart (i.e. they act as rigid joints).
Summary of Recommendations
The recommendations in this report are summarized below:
1. Install HDPE pipe above -ground per Figure 1A with an "S"-shaped configuration in order to mitigate the
effects of thermal expansion and contraction.
2. Install the pipe with vertical bends to maximize the lineal footage on the ground surface (similar to Figure
3).
3. Use a submerged inlet catch basin at the bottom of the slope for energy dissipation resulting in a
hydraulic profile similar to Figure 9.
4. Install a pipe anchoring system at the top of the slope as recommended by Shannon & Wilson modified
as described in this report.
5. Install 2 pin anchors on the steep slope at the approximate locations shown on Figure 1A. Pin anchor
design to be per Figure 4.
6. Connect the HDPE pipe to the uphill catch basin as shown on Figure 5. Due to the revised pipe
alignment, the distance from the catch basin at the top of the slope has increased so that the minimum
2' spool shown on Figure 5 is no longer applicable. Also, install a slip joint at the bottom of the slope as
recommended in the August 22, 2005 report and shown on Figure 1A.
7. A new anchor is not required at the proposed horizontal bend shown in the revised pipe alignment.
Conclusion
If you have any questions or comments, please give Erik Waligorski or me a call. We look forward to the
successful completion of this project.
ISincerely,
ROTH HILL ENGINEERING PARTNERS, LLC
Scott K. Slifer, P.E.
cc: Erik Waligorski, P.E., Roth Hill
SKS:sks
EXPiRE3
F:\0015\00013\DESIGN\Reports\Letter Report 050906_sks.doc
9055
9056
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/RIM-176:'35.-
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CURB
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SCALE IN FEET
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CURB - FIGURE 1
CITY OF RENTON
SCHEMATIC PLAN VIEW PARK PLACE N STORM
SYSTEM PROJECT
STEEP SLOPE DESIGN
Roth Hill Engineering Partners, LLC
w 2600 1167h Avenue NE #100
R o t h H i l 1 Bellevue, 48gtm 98004
Te1425.869.949.944
V Fax 425.869.1190
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9056
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/
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`----�-- -��V
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lIX IE=170.42 N (APP
IE=170.32 S g-----
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RIM=105.31/
IE-102.30/12"ADS(NE)
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EX.C91
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IE=102.41 6
IE-102.61 6
IE=102.36 12
SCHEMATIC PLAN VIEW
(REVISED, MAY 2006)
12"W
- 35'ELB0 W __-------
Pa 'STRAIGHT' TRANSVERSE ROUTE
IF PIPE BURIED (CONST.
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(O\Cxu
RBSCALE IN FEET
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CURB FIGURE 1A
CITY OF RENTON Roth Hill Engineering Partners, LLC
PARK PLACE N STORM 26M 116th Avenue NE#100
Bellevue, Washington 98004
SYSTEM PROJECT
O _t/ ' Te1425.8fi9.9448
STEEP SLOPE DESIGN V Fax 425 869 1190
180
180
160
160
140
140
120
120
100
100It
1 "=20' H
1 "=10' V
FIGURE 2 - STRAIGHT SLOPE PROFILE
/o.
5
,F
o /
20.1 LF
SL=0.1490
7.8LF
SL
0.0216
O
O D
A 12in.
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o
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Op
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-
180
180
160
160
140
140
120
120
100
100
1 "=20' H
1 "=1 0' V
FIGURE 3 - SLOPE PROFILE WITH VERTICAL BENDS
42.1 L
SL=0.118,
PREFAB
BEND
106.3 LF
SLOPE VARIES
/
20.1 LF
SL=0.1490
�
7.8LF
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0.0216
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END
0
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A 12in.
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Z
ANVIL FIG. TYPE 212 PIPE
CLAMP WITH GALVANIZED
FINISH OR EQUAL
12" HDPE PIPE
COLLAR (2" PIPE)
WELDED TO PIPE
STAKES
PLATE (SEE
DETAIL THIS
SHEET)
1 1/z"x 6' PIN
PILES EACH
SIDE OF PIPE
MATERIAL TO BE ASTM
FLATTEN TO POINT A 36 GALVANIZED AFTER
FABRICATION PER ASTM
A 153
TYPE 2 PIPE ANCHOR DETAIL
Elm
IVI/-1 I LI\I hiL I V OL. HJ 1IVI H JO
1 /4" PLATE GALVANIZED AFTER
FABRICATION PER ASTM A 123
PLATE DETAIL
NOTE:12" HDPE SHALL
BE FREE TO MOVE
AXIALLY THROUGH
THE PIPE CLAMP
FIGURE 4
CITY OF RENTON Rath Hill Engineering Partners, LLc
TYPE 2 PIPE ANCHOR DETAIL PARK PLACE N STORM 26N 1161h Avenue NE#100
"Ts SYSTEM PROJECT R o _t h /H i l I aTm 425.89a9446g1o^9
STEEP SLOPE DESIGN V Fu 425 869 1190
NON —SHRINK GROUT
MIN. 2' SPOOL
HDPE FLANGE ADAPTOR
BOLTED FLANGED CONNECTION
TO FLANGE ADAPTOR ASS'Y
BOLT (TYP)
12" HDPE PIPE--, J n
BUTT —FUSED
JOINT
HDPE FLANGE —
ADAPTOR
COMPACTED SOIL
SUPPORT UNDER
ASSEMBLY
BACKUP RING
CONNECTION DETAIL
NTS
BUTT —FUSED —"
JOINT
FABRICATED 16" GALV. -
STEEL FLANGE (23 1 /2"
O.D., 21 1 /4" BOLT
CIRCLE DIA.) w/14" DIA.
CENTER OPENING
CITY OF RENTON
PARK PLACE N STORM
SYSTEM PROJECT
STEEP SLOPE DESIGN
4
a MANHOLE WALL
6 x EVENLY SPACED
kqo�GALV. BOLTS W/ NUTS
& WASHERS AS REQ'D
(3/4" DIA.)
�-- HDPE FLANGE ADAPTOR
W
17 1 /2" DIA. CORE DRILL
THRU MH WALL
ti
FIGURE 5
Roth Hill Engineering Partners, LLC
2600 1161h Avenue NE #100
R o t h H i l l Bellevue. Washington 96004
/ Te1425.669.9446
Y Fax 425,869.1190
WATER LEVEL BRANCHES - 15-6-2005 01:16:02 City Steep Storm.PRF
Discharge 4.720 1 4.490 1 4.300 14,300 4.300 cfs
[feet] cjZ�,A C,lj
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
105.0
100.0
,,,, i,
, i,,,,, i, i,,, i,,,,,,,,,,,,,,,,,,,,, i i i,, I i I i „ i i,
i i I iI I I,,, I I I I i
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0.0
20.0 40.0 60.0 80.0 100.0
120.0 140.0
160.0 180.0
200.0 220.0 240.0 260.0 280.0 300.0 320.0
1:0
[feet]
0)
Ground Lev.
(M
O
Opp
C)
o
C,,)
0
0
(0
0
[m]
r`
Invert lev. `r'
o
0
0
CD
0
0
0
0
o
CD [m]CD
Length
100.00
32.81
38.00
125.00
32.81
[m]
Diameter
1.00
1.00
1.00
1.00
1.00
[m]
Slope o/oo
17.00
0.00
68.42
488.00
15.24
0
y
{Q -n
3�
0 > A
a
2
CD
a
WATER LEVEL BRANCHES - 15-6-2005 01:16:10 City Steep Storm Dissipator.PRF
Discharge 4.720 1 4.490 1 4.300 4.300 4.300 cfs
[feet] (:jb Gprb
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
100.0
17-T-f T TIT
r r T 1 i -I -T TT --FT f 1 TT-1 T TTf T T-FT-1 TTr r- T T TT ! T11 T T. i - --r T TT I err
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r TTT rT r-'--T--•Tf I (TT-r T--1 T,-r I rr
0.0
20.0 40.0 60.0 80.0 100.0
120.0
140.0 160.0
180.0 200.0
220.0 240.0 260.0
280.0 300.0 320.0
1:0
[feet]
Ground Lev.
�
"'
o
°°. o
N
0
0
0
o
[m]
Invert lev.
0
o
0
0
0
0
0
0
0
(D
[m]
Length
100.00
32.81
38.00
125.00
32.81
[m]
Diameter
1.00
1.00
1.00
1.00
1.00
[m]
Slope o/oo
17.00
0.00
173.68
488.00
15.24
WATER LEVEL BRANCHES - 15-6-2005 01:16:09 RH Steep Storm.PRF
Discharge 4.720 4.490 4.300 4.300 4.300 4.300 cfs
G�� �,�� �,0� [feet]
180.0
175.0
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
105.0
100.0
rn
Ground Lev.
0
0
Invert lev. "'
0
0
Length
Diameter
Slope o/oo
20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0
1:0
v coo = o
0 0
I i _i Tr
320.0 340.0
[feet]
[m]
0 0 0 0
c? rn o r o
0 0 0 0 LO
100.00 32.81 32.81 32.81 106.30 42.10
1.00 1.00 1.00 1.00 1.00 1.00
17.00 15.24 91.44 3.35 554.00 118.76
[m]
[m]
[m]
WATER LEVEL BRANCHES - 15-6-2005 01:16:24 RH Steep Storm Dissipator.PRF
Discharge 4.720 4.490 4.300 4.300 4.300 4.300 cfs
P 'o^ N
G0
[feet] G�� � G��o G�;o
180.0
175.0
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
105.0
100.0
0.0
20.0 40.0 60.0 80.0 100.0
120.0
140.0
Ground Lev.
C°
0
LO
0
0
Invert lev.
"'
o
a'
0
0
0
Length
100.00
32.81
32.81
Diameter
1.00
1.00
1.00
Slope o/oo
17.00
15.24
91.44
160.0
180.0
200.0
1:0
c
�i
o
O
O
r
0
0
32.81
1.00
3.51
r
220.0 240.0 260.0 280.0 300.0 320.0 340.0
[feet]
0
[m]
co
O
LO [m]
co
106.30 42.10 [m]
1.00 1.00 [m]
591.58 118.76
x
K I c
0 c e'n
W c cc
CD
to
CD
n
APPENDIX A
Technical Memorandum
Shannon & Wilson, Inc.
June 21, 2005
=III SHANNON 6WILSONsILNC.
TECHNICAL MEMORANDUM
TO: Scott Slifer, Roth Hill Engineering Partners
FROM: Thomas Gurtowski, P.E.
DATE: June 21, 2005
Shannon & Wilson, Inc.
400 N. 34Ih St., Suite 100
P.O. Box 300303
Seattle, WA 98103
206.632.8020 Fax: 206*695.6777
RE: RESPONSE TO COMMENTS, GEOTECHNICAL REPORT,
PARK PLACE NORTH STORM SEWER
This technical memorandum addresses additional geotechnical consideration in light of the City
of Renton's (City's) review comments regarding Shannon & Wilson's recent geotechnical report
for Park Place North Storm Sewer Project. This memorandum is a follow up to the phone
conversation between Shannon & Wilson and Roth Hill Engineering (Roth) on June 16, 2005.
(1) The results of the stability analyses that we performed for the project are enclosed. Based on
the slope geometry and soil parameters that we used in our analyses, the looser surficial layer of
soil on the steep slope and the thicker layer of fill at the top of the slope at the location of the
proposed manhole would be marginally stable under seismic loading. Because of their marginal
stability, the fill soils at the top of the slope would not provide sufficient passive resistance to
counter the load of pipe if it were solely support by the manhole, in our opinion. We therefore
recommend that the pipeline on the slope be support by anchors at the top of the slope, as
discussed in our report.
(2) The anchors shown on Figure 4 in our report are helical anchors; however, Manta Ray
anchors would also be suitable for supporting the pipe on the slope. The concrete to HDPE
connection shown on the anchor detail in Figure 4 was inadvertent and not the reason for
recommending anchors. We understand because of thermal expansion, the City and Roth plan to
snake the pipeline down the slope. The anchors and cable stays detailed in our report would not
preclude snaking the pipe down the slope, in our opinion. However, additional anchors should
be provided at locations of bends to restrain the pipeline against lateral loads. These additional
21-1-20326-001
Mr. Scott Slifer
June 21, 2005
Page 2
anchors would not need to be helical or Manta Ray anchors, but could be straight, nail -type
anchors, such as the type shown in the Gephart details recently provide to us by the City.
TWH:JXM:TMG/twh
Enclosures: Park Place North Storm Sewer Renton, Washington (2 sheets)
21-1-20326-001
125
100
75
50
25
Park Place North Storm Sewer Renton, Washington
c:\program files\stedwin\parkpl-9.pl2 Run By: kh 5/31/2005 02:09PM
# FS
Soil
Soil
Total
Saturated
Friction
Piez.
a 1.54
Desc.
Type
Unit Wt.
Unit Wt.
Angle Surfac
b 1.54
No.
(pcf)
(pet)
(deg)
No.
c 1.55
Fill
1
110.0
110.0
30.0
W1
d 1.55
Sand
2
130.0
130.0
40.0
W 1
e 1.561
Gravel
3
130.0
130.0
40.0
W1
f 1.56 1
g 1.57
h 1.57
i 1.57
i 1.57
Sand
4
130.0
130.0
40.0
W1
4
1
r^.
3
-----------------------------------------------------------------
4
25 50 75 100 125 150
PCSTABL5M/si FSmin=1.54
Safety Factors Are Calculated By The Modified Janbu Method
9 .I k
175
125
100
75
50
25
Park Place North Storm Sewer Renton, Washington
c:lprogram files\stedwin\parkpl-8.pl2 Run By: kh 5/31/2005 02:08PM
# FS
Soil
Soil
Total
Saturated
Friction
Piez.
Load Value
a 1.06
Desc.
Type
Unit Wt
Unit Wt.
Angle Surface
Horiz Eqk 0.150 g
b 1.06
No.
(pcf)
(pcf)
(deg)
No.
c 1.06
Fill
1
110.0
110.0
30.0
W1
d 1.06
Sand
2
130.0
130.0
40.0
W1
e 1.071
Gravel
3
130.0
130.0
40.0
W1
f 1.07 1
g 1.07
h 1.07
i 1.07
i 1.07
Sand
4
130.0
130.0
40.0
W1
4
2
3
1
3
- iii
-- _ 4
4
25 50 75 100 125
PCSTABL5M/si . FSmin=1.06
Safety Factors Are Calculated By The Modified Janbu Method
150 175
APPENDIX B
Letter Report
Shannon & Wilson, Inc.
April 20, 2006
® SHANNON 6WILSON, INC.
GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS
IApril 20, 2006
Mr. Erik Waligorski
Roth Hill Engineering
2600 116`h Avenue NE, Suite 100
Bellevue, WA 98004
REC IV p
2006
30THHILL ENGNR. PARTNERS, LLC
BELLEVUE.WA
ALASKA
COLORADO
FLORIDA
MISSOURI
OREGON
WASHING LOU
' RE: CONCLUSIONS AND RECOMMENDATIONS FOR REVISED ALIGNMENT,
PROPOSED PARK PLACE NORTH STORM SEWER EXTENSION,
RENTON, WASHINGTON
' Dear Mr. Waligorski:
We understand that the steep slope portion of the alignment for the proposed Park Place North
Storm Sewer project has been modified since we issued our geotechnical report for the project
on June 6, 2005. It is our understanding that the revised alignment will be approximately
' 30 feet south of the previous alignment at the top of the slope and about 15 feet south at the
bottom of the slope.
For our evaluation of the original alignment, we drilled a boring to a depth of 31 feet at the top
of the slope using a track -mounted drill rig and advanced seven shallow borings on the hillside
to depths between 1.3 and 4.5 feet using hand -operated equipment. Based on these borings, the
ground is underlain at shallow depths by very dense, glacially overridden, sandy gravel to
gravelly sand with some silt. At the top of the slope, fill overlies these soils to a depth of about
8 feet. Using information about the subsurface derived from those borings, we performed
stability analyses and concluded that the fill soils at'the top of the slope would not provide
sufficient passive resistance to the proposed manhole at the top of the slope to support the load
of the pipe under seismic loading. We therefore recommended that the pipeline be supported
by anchors at the top of the slope.
To evaluate whether our conclusions and recommendations for the previous alignment were
still applicable to the revised alignment, we performed a site visit to assess the observable
ground conditions relative to those along the original alignment. Mr. Ted Hopkins of Shannon
& Wilson visited the site on April 12, 2006, and met with Dan Carey, project manager with the
City of Renton. Mr. Carey provided plans for the revised portion of the alignment. In addition
to evaluating ground conditions along the revised alignment, Mr. Hopkins performed a brief
reconnaissance of the slope north and south of this alignment to look for evidence of recent
400 NORTH 34TH STREET • SUITE 100
P.O. BOX 300303 21-1-20326-002
SEATTLE, WASHINGTON 98103
206.632.8020 FAX 206.695.6777
TDD: 1.800.833.6388
www.shannonwilson.com
Mr. Erik Waligorski
SHANNON 6WILSON, INC.
' Roth Hill Engineering.
April 20, 2006
Page 2
' instability that may have occurred since our 2005 evaluation. It should be mentioned that
heavy precipitation this last winter caused numerous landslides throughout the Puget Sound
region.
No evidence of landsliding that took place since our evaluation in 2005 was observed on the
slope in the vicinity of the proposed alignment. Except for the scars of shallow sloughing near
the base of the slope, no evidence of past landslides was observed along the previous and
revised alignments. Based on our observations during our recent site visit, the ground
conditions along the revised alignment are likely to be similar to those encountered in our
subsurface explorations conducted for the previous alignment. Therefore, in our opinion, the
conclusions and recommendations that we provided for the previous alignment are applicable
to the revised alignment.
If you have any questions about conclusions regarding this revised alignment, please contact
me at 206-695-6801 or Ted Hopkins at 206-695-6887.
Sincerely,
SHANNON & WILSON, INC.
Thomas M. Gurtowski, P.E.
Vice President
TWH:TMG/twh
21-1-20326-002-L1 /wp/LKD 21-1-203 26-002
APPENDIX C
Thermal Expansion Calculations
June 22, 2005
' Renton Park Place N. Storm Project
Steep Slope Analysis and Design
' Thermal Expansion Calculations
SKS; 6/22/05
' References:
1. Above Ground Applications for Polyethylene Pipe published by the Plastics Pipe
Institute, Inc., 2000
' 2. Performance Pipe Engineering Manual; Book 2, Chapter 5 published by
Performance Pipe, Inc., 2003
3. Systems Design published by Phillips Driscopipe, 1996
Condition 1 - Lateral Deflection Without Intermediate Anchors
Install pipe in a long arc above grade with the length based on our schematic drawing.
' Calculate the Lateral Deflection
AY = L {Q•AT/2}112, where
AY = the lateral deflection in inches
' L = length between anchor points, or approx. 93 feet or 1116 inches
v = coefficient of expansion/contraction, or 0.0001 in./in./ OF.
AT = temperature change, assume this is 60 OF
' Therefore:
AY = 61.3 inches
' Calculate the Radius for this AY
' R = {4(AY)2 + L2}/ 8AY, where R and L are as per above.
Therefore,
' R = 2,570 inches or 214 feet
' Compare to Pipe Bending Radius
To account for both pipe contraction and expansion, we want 0.5R to be >_ than the
' bending radius of 12-inch HDPE pipe. The bending radius of 12-inch HDPE pipe is
approximately 30 feet.
Therefore,
0.5-R = 107 feet >30 feet and is acceptable
1
' Condition 2 - Lateral Deflection Snaking the Pipe With Intermediate Anchors
This is the originally intended concept and is as shown on our schematic drawing.
Check Minimum Allowable Spacing Between Anchors
L = {D (96-Q-AT)'12} / E'110" , where
L = the minimum allowable spacing between anchors in inches
' D = outside diameter of the pipe, or 12.75 inches
a = coefficient of expansion/contraction, or 0.0001 in./in./'F.
AT = 60°F. = temperature change
' Callow = 0.05 in./in. = maximum permissible strain in the pipe wall (conservative)
Therefore:
L = 193.5 inches or 16.1 feet
If we install 2 pin anchors and, including the end constraints where the pipe transitions
from above -grade to below -grade and vice versa, the 93 feet of pipe would be divided
into 3 segments. This would be 93/3 equals 31 feet which is > 16.1 feet.
' Calculate the Lateral Deflection
From above:
' AY = L {a -AT / 2)1/2 , except now L = 31 feet or 372 inches.
' Therefore,
AY = 20.4 inches
' Calculate the Radius for this AY
R = {4(AY)2 + L2)/ 8AY, where R and L are as per above.
Therefore,
' R = 858 inches or 71.5 feet
Compare to Pipe Bending Radius
' To account for both pipe contraction and expansion, we want 0.5R to be >_ than the
bending radius of 12-inch HDPE pipe. The bending radius of 12-inch HDPE pipe is
approximately 30 feet.
Therefore,
' 0.5•111 = 35.8 feet >30 feet and is acceptable
a
2
APPENDIX D
Specifications and Opinion of Probable Construction Cost
May 2006
City of Renton
Park Place N. Storm Project
Specifications and Opinion of Probable Construction Cost
May 2006
Section references are to 2004 WSDOT Standard Specifications.
7=04.2 Materials (Supplement)
12-inch diameter storm sewer pipe and 18-inch diameter slip joint pipe shall be HDPE,
DR 17, Series 4100 as manufactured by Performance Pipe or approved equal.
Fabricated vertical and horizontal bends shall conform to the above requirements for
HDPE pipe and to the requirements shown on the Drawings.
The top slope anchors, as shown on the Drawings, shall be 1.5-inch diameter, single
' helix Chance SS5 C150-0002 anchors or approved equal. Five foot extensions as
required in the field to achieve the specified pullout strength shall be Chance C150-008
or approved equal. Chance chain shackles shall be C150-0040 or approved equal.
Steel cable shall be 3/8-inch diameter, galvanized, and flexible. Pipe clamps shall be
galvanized. Contractor shall submit cut sheets and/or details for review and approval
prior to construction.
' Type 2 pipe anchors, as shown on the Drawings, to provide lateral pipe restraint for the
above -grade storm sewer pipe, shall consist of Grinnell Type 212 pipe clamps or
approved equal, manufactured of carbon steel with galvanized finish; '/4-inch thick ASTM
A 36 steel plates, fabricated per ASTM A 123 and galvanized; and six-foot long, 1.5-inch
diameter ASTM A 36 pin piles, fabricated per ASTM A 153 and galvanized.
7-04.3 Construction Requirements (Supplement)
Install above -grade HDPE storm sewer pipe, HDPE slip joint, and anchors as shown on
the Drawings. Minimize disturbance to the steep slope during installation.
Top slope anchors shall be installed by workers experienced with the installation of the
' specified components manufactured by A.B. Chance Co. Anchors shall be installed until
a 5,000 pound pullout load is obtained for each anchor. Install the two Chance anchors
at a slight batter as required to avoid physical conflict between the helixes.
' Type 2 Pipe Anchors shall be installed so that the 12-inch diameter storm sewer pipe is
free to move axially through the pipe clamps as shown on the Drawings.
' 7-04.5 Payment (Supplement)
"HDPE Storm Sewer Pipe on Steep Slope, 12-inch Diameter", per linear foot. The unit
' contract price per linear foot shall be full payment for all work required to complete the
installation of the pipe, including fittings and connections to the upstream catch basin.
FA0015\00013\DESIGN\Specs\Specs and cost estimate_sks_050406.doc
Measurement shall include the portion of the storm sewer pipe installed inside the larger
diameter slip joint pipe.
Opinion of Probable Construction Cost $105/If
"HDPE Slip Joint Storm Sewer Pipe, 18-inch Diameter", per linear foot. The unit contract
price per linear foot shall be full payment for all work to complete the installation,
including trench excavation and backfill and connection to the downstream catch basin.
Payment for the portion of the 12-inch HDPE storm sewer pipe sleeved inside the slip
joint pipe shall be under the bid item for the 12-inch pipe.
Opinion of Probable Construction Cost $80/If
"Top Slope Anchor with Pipe Cables", per lump sum. The lump sum price for Top Slope
Anchor with Pipe Cables shall be full payment for all work specified and shall include
furnishing and installing the Chance anchors and appurtenances including all clamps
and pipe cables, complete.
Opinion of Probable Construction Cost $6200 lump sum
"Type 2 Pipe Anchors", per each. The unit contract price per each shall be full payment
for all costs necessary to furnish and install the anchors, complete.
Opinion of Probable Construction Cost $580/ea
7-05.3 Construction Requirements (Supplement)
Connections of the HDPE storms sewer pipe to the catch basins shall be as shown on
the Drawings. Contractor shall take all measures necessary to support the above -grade
portion of the storm sewer pipe until the connections to the catch basins have been
made, the buried portions of the pipe have been backfilled, and all anchors have been
installed.
7-05.5 Payment (Supplement)
"Catch Basin, Type 2, 48-inch Diameter with Submerged Inlet", per lump sum. The lump
sum contract price for installing the "Catch Basin, Type 2. 48-inch Diameter with
Submerged Inlet' shall be full payment for performing all work as shown on the
Drawings and as specified, complete.
Alternatively: state that the submerged inlet catch basin shall be paid as one of the other
catch basins and included in the per each measurement.
Opinion of Probable Construction Cost $2800/lump sum
F:\0015\00013\DESIGN\Specs\Specs and cost estimate_sks_050406.doc
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City of Renton
Park Place N. Storm Project
Steep Slope Analysis and Design
August 2005
PIKE
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Roth Hill Engineering Partners, LLC
RothHill
August 22, 2005
City of Renton
Renton City Hall — 51h Floor
1055 South Grady Way
Renton, WA 98055
Attn: Daniel Carey, P.E.
RE: Park Place N. Storm Sewer Project
Steep Slope Analysis and Design
Design Report
Dear Mr. Carey,
2600 1 16th Avenue NE # 100
Bellevue, Washington 98004
Tel 425.869.9448
Fax 425.869.1 190
800.835.0292
This letter with attached figures and appendices comprises the design report submittal and updates the draft
report which was dated June 24, 2005. The referenced figures are bound at the back of the report. Following
the figures are Appendix A, a Technical Memorandum from Shannon & Wilson dated June 21, 2005, and
Appendix B, titled Thermal Expansion Calculations and dated June 22, 2005. The internal organization of this
letter report is based on a presentation of various technical issues by topics as follows.
Geotechnical Investigation
Shannon & Wilson, Inc. prepared a geotechnical investigation for this project titled Geotechnical Report, Park
Place North Storm Sewer Project, dated June 6, 2005. This report was previously sent to the City. Therefore, :a
copy of the report is not included herein nor are its findings recapitulated.
Review of the S&W report raised some questions regarding its recommendations. To respond to these
questions, S&W has prepared a Technical Memorandum dated June 21, 2005. This document is attached as
Appendix A.
Slope Stability Analysis
The slope stability analysis by S&W indicates that the upper manhole and pipe down the steep slope are stable
under static conditions. This is shown on the first page of figures included in their Memorandum in Appendix A.
The FS values (safety factors as calculated by the Modified Janbu Method) are in the range of 1.54 to 1.57 as
shown on the figure.
The S&W Technical Memorandum further states that the proposed manhole (catch basin) at the top of the hill
would be only marginally stable under seismic conditions. In their opinion, the upper manhole is inadequate to
support the steep slope pipe under seismic conditions. This is shown on the second figure in the Memorandum
where the FS values are given as being 1.06 and 1.07.
Pipe Anchor System
Due to the marginal stability of the slope under seismic conditions, S&W proposed that the pipeline on the slope
be supported by an anchor system at the top of the slope as described in their original June 5 report.
One initial concern with their anchor system design was whether it would permit the above -grade portion of the
F:\0015\00013\DESIGN\Reports\Letter Report_081905_sks.doc
' Daniel Carey
August 22, 2005
Page 2
pipe to be 'snaked'. According to their Technical Memorandum, their design allows for the pipe to be laid on a
curve. In a conference call with them on June 16, they stated that the 3/8-inch diameter galvanized steel cables
are flexible.
In response the June 24th, 2005 draft of this report, the City raised the question as to whether the clamps and
galvanized steel cables installed down the full length of the pipe would interfere with the thermal
expansion/contraction features to be incorporated into the pipe's design (as discussed below). We discussed
this with S&W and they agreed that their anchor detail could be modified so that there would be only two pipe
clamps. One clamp would be at the top of the pipeline where it emerges from below grade and a second clamp
would be located 5 feet down slope from the first clamp. The two pipe clamps would be connected by the 3/8-
inch diameter galvanized steel cable as shown in their original report.
As a point of clarification, S&W's original pipe anchor design indicated a connection to a concrete outfall pipe .
pictorially shown at the top of the slope. In the Technical Memorandum (Appendix A), this is acknowledged as.
an error on their part.
Based on S&W's geotechnical report, their Technical Memorandum, and our subsequent communications with
them, we recommend that the pipe be anchored to the top of the slope per their original report except that only
two pipe clamps (5 feet apart and interconnected with galvanized steel cable) should be installed as described
above.
Pioe Plan and Profile
For our analysis, we have schematically laid out a steep slope pipe route with proposed catch basins as shown
on Figure 1, Schematic Plan View. Figure 1 is based on the topographic survey performed by Roth Hill. The
intent of the pipe alignment is to traverse the slope as perpendicularly to the contours as possible. A'snaked'
' alignment is shown (and discussed in more detail below). The exact location of the upstream and downstream
catch basins is subject to adjustment as are the invert elevations of the pipes at the catch basins.
On Figure 2, Straight Slope Profile, is presented a profile view based on plan view alignment shown in Figure 1
' assuming that the pipe is installed at a constant slope between the catch basins at the top and bottom of the
steep slope. Depending upon the exact locations of the manhole and the inverts of the pipe, it appears that
much of the pipe would, in fact, be buried with only a relatively small length 'daylighting' above grade. In order to
' maximize the lineal footager of pipe installed above grade, it will apparently be necessary to use prefabricated
bends at the top and bottom of the slope. Figure 3, Slope Profile with Vertical Bends, shows a schematic
representation of this profile.
Thermal Expansion Analysis
HDPE pipe installed on the surface will be subject to ambient temperature fluctuations and direct sunlight.
HDPE pipe that is produced with a minimum 2% concentration of carbon black is well protected from ultraviolet
degradation.
A characteristic of HDPE pipe as compared to other pipe materials is its relatively high coefficient of thermal
' expansion. This means that it lengthens and contracts as the temperature rises and falls. Fortunately, the
forces generated by thermal stresses are relatively low for HDPE because its modulus of elasticity is low and it is
capable of stress relaxation. Nevertheless, this must be taken into account during design and is the reason for
'snaking' the pipe along the ground surface. By installing the pipe in a slightly snaked pattern, thermal
expansion/contraction can be controlled through control of the lateral deflection. As the pipe warms, the "S"
configuration becomes slightly greater. As the pipe cools, the pipeline becomes straighter.
FA0015\00013\DESIGMReports\Letter Report_081905_sks.doc
Daniel Carey
August 22, 2005
Page 3
1
In Appendix B is an analysis that calculates the amount of lateral deflection that may be expected for the pipeline
' layout shown on Figure 1. This is calculated as 20.4 inches (see Condition 2) and corresponds to a bending
radius of the pipe equal to 71.5 feet. To account for both pipe expansion and contraction we want one-half of
this radius to be greater than the minimum bending radius of the pipe (30 feet). As shown, one-half of 71.8 feet
equals 35.8 feet which is greater than the 30-foot bending radius of 12-inch HDPE pipe. Therefore, pipe
' expansion and contraction will take up the thermal stresses as desired. (A bending radius of 30 feet implies the
maximum bending of the pipe without kinking the pipe wall but not necessarily affecting the integrity of the pipe).
' It should be noted that the calculations in Appendix B are very conservative and the actual deflections and strain
characteristics may be significantly less for a number of reasons including:
1. Friction forces imposed by the terrain
' 2. The weight of the pipe (but fluid weight is expected to be minimal, especially in extreme temperature
conditions) -
3. Temperature variations are not instantaneous
' These factors allow for stress relaxation during the temperature fluctuation process.
Rather than relying solely on the snaked pipe for mitigating the effects of thermal expansion, the installation of a
' 'slip joint' is also proposed to be installed at the bottom of the slope. This design will be provided by the City.
With the slip joint, the horizontal deflection of the snake pipe shown on Figure 1 can be reduced from 2 feet to
1.5 feet (+/-) in order to facilitate ease of construction.
' On -Slope Pipe Anchors
The S&W Technical Memorandum (Appendix A) recommends anchors on the above -grade portion of the pipe to
' restrain against lateral loads. We expect the lateral loads from both static and dynamic hydraulic forces to be
negligible. The above -grade portion of the pipe will be subject to little, if any, hydraulic static pressure which is
the predominant cause of thrust at bends in a pressure pipe situation such as a water main.
The velocity head pressure is also minimal even assuming that it acts in full laterally (i.e., perpendicularly to the
side wall of the pipe, which will not be the case). Manning's equation predicts a velocity of approximately 30 fps
using the anticipated 100-year event flow of 4.3 cfs as provided by the City for this situation. This translates into
the equivalent of 6 psi of pressure for a perpendicularly acting flow. For the same pressure conditions, a:90-
degree bend will experience more thrust than a 45-degree bend. Given the slight degree of bending for the
proposed "S" configuration, we believe the magnitude of the dynamic lateral forces due to velocity will be
negligible as stated above.
For thermal expansion purposes, the Condition 2 analysis in Appendix B proposes two (2) intermediate pin
anchors located as shown on Figure 1. The buried ends of the steep slope pipe constitute anchors at the top
and bottom of the slopes. Pipe anchors will causes the build up of strain in the pipe wall. It is recommended that
the strain be limited to less than 5%. As shown in Appendix B, the minimum anchor spacing using a maximum
allowable strain of 0.05 in/in is 16.1 feet for this application. The spacing shown on Figure 1 exceeds this
minimum threshold.
According to the S&W Technical Memorandum, the pin anchors shown on a past Roth Hill project are sufficient
for this purpose. Accordingly, the design for the pin anchors is presented on Figure 4, Type 2 Pipe Anchor
' Detail. Note that the pin anchors are to be installed such that the pipe can slip or move axially. -In other words,
they are to provide lateral restraint only.
F:\0015\00013\DESIGN\Reports\Letter Report_081905_sks.doc
' Daniel Carey
August 22, 2005
Page 4
Pipe End Connections
The proposed pipe would be anchored at the top of the slope as proposed by Shannon & Wilson. Two pin
anchors would be installed on the steep slope as described in the previous section. We also propose to anchor
the steep slope pipe to the upstream catch basin per Figure 5, Connection Detail. This detail, which was
' developed with the assistance of the City, is intended to provide structural support at the upstream catch basin
during construction.
Flanged Fitting Connections
We originally envisioned that the bends (fittings) required at the top and bottom of the slope (where the pipe
transitions from below grade to above ground and vice versa) would have butt -fused joints. At the July 28th
' meeting in our office, you pointed out that using flanged fittings may offer ease of construction benefits. We
subsequently contacted Performance Pipe to verify that the use of flange fittings would be both feasible and
provide adequate structural integrity. Our subsequent discussion with the technical department at Performance
' Pipe verified both of these considerations. We, therefore, believe that the flanged -end fittings are acceptable.
Energy Dissipation
' As part of our investigation, we examined possible ways of dissipating the energy (or velocity) at the bottom of
the steep -slope pipe. Research of available reference materials and on the Web revealed surprisingly little
information for an application similar to this project. Energy dissipation is usually of concern when flow is
' released from a pipe or other conveyance system into the natural environment. The concern, of course, is with
erosion of natural stream channels.
We considered two basic approaches. One was to use some type of a vault, with or without baffles, similar to a
detention vault. We identified two concerns with this:
1. The bigger concern is that the vault, even when not equipped with orifice plate restrictors, would still act
as detention vault and have the affect of restricting the conveyance (hydraulic throughput) capacity of the
' system in terms the cfs.
2. A lesser concern was that a vault would not fit the proposed pipe alignment so that inlet and outlet pipes
would penetrate the sides of the vault perpendicularly.
' With these considerations in mind, we believe that the energy dissipater, if any, should be a simple catch basin
with a submerged inlet. This is the second basic approach considered. In the next section is described the
hydraulic modeling we performed in this approach.
' Hydraulic Analysis
' In order to better evaluate the hydraulic elements of the steep slope pipe, we used the MOUSE modeling
hydraulic simulation software program from DHI. Four conditions were simulated using a flow of 4.3 cfs. The
presentation capabilities of the MOUSE program are limited but color copies of the graphical output are
presented as follows:
Figure 6, City Design — Unsubmerged Inlet CB, shows the City's design without a submerged inlet catch
basin at the bottom of the slope.
Figure 7, City Design — Submerged Inlet CB, pictures the same design with a submerged inlet catch
basin.
Figure 8, Roth Hill — Unsubmerged Inlet CB, illustrates the Roth Hill schematic (based on Figures 1 and
3) without a submerged inlet catch basin.
F:\0015\00013\DESIGN\Reports\Letter Report_081905_sks.doc
' Daniel Carey
August 22, 2005
Page 5
• Figure 9, Roth Hill — Submerged Inlet CB, shows the same design with the submerged inlet.
' Note: Figures 6 and 7 are based on the data sent to us from the City by mail transmittal dated May 5, 2005.
Besides showing the impacts of having or not having a submerged inlet catch basin at the bottom of the slope,
' the 'City design' is based on a straight slope pipe down the hill whereas the 'Roth Hill' schematic shows the
effects of incorporating vertical pipe bends into the profile.
' In terms of distinguishing between the four scenarios, the model results as presented in Figures 6 — 9 does not
reveal any striking information. The submerged inlet catch basin has the expected effect of causing the
hydraulic grade line to rise above the crown of the pipe, i.e. causing the pipe to become slightly pressurized. The
pressure head is approximately 5 feet which is the equivalent of approximately 2 psi. Where submerged, we
' anticipate the actual depth of submergence is in reality confined to the bottom of the pipe. (The MOUSE program
`connects the dots' between calculation points). Also, in the area of submergence, the velocity in the full pipe will
be correspondingly reduced thereby lowering potential dynamic forces.
We believe that it would be best to submerge the inlet of the down -slope catch basin as shown on Figures 7 and
9 in order to confine the energy dissipation in the upstream pipe under higher flow conditions. With a submerged
inlet, the effects of erosion in the concrete structure should also be mitigated. In general, we expect HDPE to
have better scour -resistant characteristics than concrete. We have shown the depth of submergence to be
approximately 4 feet. We do not consider this to be critical and believe there is no reason to make this depth
greater or lesser as desired.
' Finally, we believe the pipe should be designed with vertical bends in order to maximize the amount of above -
grade pipe on the slope and reduce the amount of trenching which will result in less disturbance of the soils on
this slope. Figure 9, therefore, schematically represents our recommendations.
' Design Specifications and Details
As discussed with you at the July 28th meeting in our office, we will provide design specifications and details to
' you as a separate submittal and, therefore, these items are not included with this report. The specifications and
details will be supplied to you in Word and DWG format where possible or, where not possible, as PDF files.
' Specifications will be based on WSDOT format as described below.
Bid Items and Opinion of Probable Construction Cost
' As with the specifications and details, we will also provide a cost estimate under separate cover.
We would anticipate the bid items and associated opinion of probable construction cost to be along the lines of
' the following:
1. HDPE Storm Sewer Pipe on Steep Slope, 12-Inch Diameter, per LF
2. HDPE Slip Joint Storm Sewer Pipe, XX-inch Diameter, per LF
' 3. Top Slope Anchor with Pipe Cables, per LS
4. Type 2 Pipe Anchors, per EA
5. Catch Basin Type 2, 48-inch Diameter with Submerged Inlet, per LS
' These bid items would be referenced to WSDOT standard specifications. For example, storm sewer pipe would
be a modification to WSDOT Section 7-04. The pipe anchors also may be described as Section 7-04
modifications. The catch basin would be a Section 7-05 supplement or could be simply paid for on a per EA
F:\0015\00013\DESIGN\Reports\Letter Report_081905_sks.doc
1
' Daniel Carey
August 22, 2005
Page 6
basis with the other catch basins.
The HDPE pipe should be Performance Series 4100, DR 17 or approved equal. This pipe has good ultraviolet -
resistant characteristics. The pipe joints are heat -fused and, therefore, will not pull apart (i.e. they act as rigid
joints).
Summary of Recommendations
The recommendations in this report are summarized below:
1. Install HDPE pipe above -ground per Figure 1 with an "S"-shaped configuration in order to mitigate the
effects of thermal expansion and contraction.
2. Install the pipe with vertical bends to maximize the lineal footage on the ground surface (similar to Figure
3).
3. Use a submerged inlet catch basin at the bottom of the slope for energy dissipation resulting in a
hydraulic profile similar to Figure 9.
4. Install a pipe anchoring system at the top of the slope as recommended by Shannon & Wilson modified
as described in this report.
5. Install 2 pin anchors on the steep slope at the approximate locations shown on Figure 1. Pin anchor
design to be per Figure 4.
6. Connect the HDPE pipe to the uphill catch basin as shown on Figure 5. Also, install a slip joint at the
bottom of the slope.
I
Conclusion
If you have any questions or comments, please give me a call. We look forward to the successful completion of
this project.
Sincerely,
ROTH HILL ENGINEERING PARTNERS, LLC
�2� \
Scott K. Slifer, P.E.
cc: Erik Waligorski, P.E., Roth Hill
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F:\0015\000130ESIGMReports\letter Report081905 sks.doc
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CURB
SCHEMATIC PLAN VIEW
CITY OF RENTON
PARK PLACE N STORM
SYSTEM PROJECT
STEEP SLOPE DESIGN
FIGURE 1
Roth Hill Engineering Partners, LLC
26001161h Avenue NE #100
Bellevue, Washington 96004
RothHill
/ Te1425.669.9448
V Fax 425,869.1190
180
180
160
160
140
140
Al
zz//
,
120
120MA
1?in
100100
1 "=20' H
1 "=1 0' V
FIGURE 2 - STRAIGHT SLOPE PROFILE
42.1 L
SL=0.118j
180
180
160
160///
/
6
140
140
120
120
[j�:27.8LF
100
100
1 "=20' H
1 "=10' V
FIGURE 3 - SLOPE PROFILE WITH VERTICAL BENDS
42.1 L
SL=0.118j
�
PREFAB
BEND
106.3 LF
SLOPE VARIE
20.1 LF
SL=0.1490
�
SL
0.0216
PREFAB
END
0
O D
A 12in.
o,
O 11.5
F
�
N
. o SL=O
0100
�
�j
' O
O
� O
�
00
j
p
�O
z
> �
Z
z
-
ANVIL FIG. TYPE 212 PIPE
CLAMP WITH GALVANIZED
FINISH OR EQUAL
12" HDPE PIPE
COLLAR (2" PIPE)
WELDED TO PIPE
STAKES
PLATE (SEE
DETAIL THIS
SHEET)
�-11/2"x 6' PINS
PILES EACH
SIDE OF PIPE
MATERIAL TO BE ASTM
FLATTEN TO POINT A 36 GALVANIZED AFTER
FABRICATION PER ASTM
A 153
TYPE 2 PIPE ANCHOR DETAIL
NTS
TYPE 2 PIPE ANCHOR DETAIL
Ell
IVI/ ILI\I/ L- IlJ UL /'�J IIVI f-\ JV
1 /4" PLATE GALVANIZED AFTER
FABRICATION PER ASTM A 123
PLATE DETAIL
CITY OF RENTON
PARK PLACE N STORM
SYSTEM PROJECT
STEEP SLOPE DESIGN
NOTE:12" HDPE SHALL
BE FREE TO MOVE
AXIALLY THROUGH
THE PIPE CLAMP
FIGURE 4
Roth Hill Engineering Partners, LLC
i� 2600 1181h Avenue NE #100
R o_ t h / H i I I Te 425.869.9448"' 98004
V Fu 425.869.1190
NON -SHRINK GROUT
MIN. 2' SPOOL
HDPE FLANGE ADAPTOR
BOLTED FLANGED CONNECTION
TO FLANGE ADAPTOR ASS'Y
BOLT (TYP)
12" HDPE PIPE _n� n
BUTT -FUSED —
JOINT
HDPE FLANGE -
ADAPTOR
COMPACTED SOIL
SUPPORT UNDER
ASSEMBLY
BACKUP RING
BUTT -FUSED -v
JOINT
FABRICATED 16" GALV. -
STEEL FLANGE (23 1 /2"
O.D., 21 1 /4" BOLT
CIRCLE DIA.) w/14" DIA.
CENTER OPENING
CITY OF RENTON
CONNECTION DETAIL PARK PLACE N STORM
NTs SYSTEM PROJECT
STEEP SLOPE DESIGN
4
a MANHOLE WALL
6 x EVENLY SPACED
4_. ,-"� GALV. BOLTS W/ NUTS
& WASHERS AS REQ'D
(3/4" DIA.)
,--HDPE FLANGE ADAPTOR
17 1 /2" DIA. CORE DRILL
THRU MH WALL
FIGURE 5
Roth Hill Engineering Partners, LLC
i� 26001161h Are NE#100
R o t h H i l l Tel 425.969.9448g� 98004
Fate 425.869.1190
WATER LEVEL BRANCHES - 15-6-2005 01:16:02 City Steep Storm.PRF
Discharge 4.720 4.490 4.300 4.300 4.300 cfs
10 25
[feet] � c5V GGGG��
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
105.0
100.0
Ground Lev. cli
0
T
0
Invert lev. "'
0
0
Length
Diameter
Slope o/oo
20.0 40.0 60.0 80.0 100.0
120.0 140.0
160.0 180.0
200.0 220.0 240.0 260.0 280.0 300.0
1:0
M
0
coo
0
U
0
0
�
6
C
O
0
0
0
0
(D
320.0
[feet]
[m]
100.00
32.81
38.00
125.00
32.81
1.00
1.00
1.00
1.00
1.00
17.00
0.00
68.42
488.00
15.24
[m]
[m]
[m]
v
m
y
fQ
7 7 T
M � 1
03 M
W C O1
Q
3
M
to
a
WATER LEVEL BRANCHES - 15-6-2005 01:16:09 RH Steep Storm.PRF
Discharge 4.720 4.490 4.300 4.300 4.300 4.300 cfs
� �
[feet] G�G0G0� G0"o 0e�a 0��a Gem
180.0
175.0
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
105.0
100.0
0.0
Ground Lev.
rn
rli
0
Invert lev.
O
`?
0
0
Length
Diameter
Slope o/oo
20.0 40.0 60.0 80.0 100.0
120.0
140.0
160.0
180.0
200.0
220.0 240.0 260.0 280.0 300.0
320.0
340.0
1:0
[feet]
r�
0
cfl
o
00
p
C)
0
0
o
cfl
[m]
0
O
O
p
0
0
o
0
v
0
co
o
cfl
[m]
100.00
32.81
32.81
32.81
106.30
42.10
[m]
1.00
1.00
1.00
1.00
1.00
1.00
[m]
17.00
15.24
91.44
3.35
554.00
118.76
WATER LEVEL BRANCHES - 15-6-2005 01:16:24 RH Steep Storm Dissipator.PRF
Discharge 4.720 4.490 4.300 4.300 4.300 4.300 cfs
1 to roP ,Q'� a'o anti .p`y
[feet] G� G� G� G0 ��� �e� Ge
180.0
175.0
170.0
165.0
160.0
155.0
150.0
145.0
140.0
135.0
130.0
125.0
120.0
115.0
110.0
105.0
100.0
0.0
20.0 40.0 60.0 80.0 100.0
120.0
140.0
160.0
180.0
200.0
220.0 240.0 260.0 280.0 300.0
320.0
340.0
1:0
[feet]
Ground Lev.
M
C°
CD
cp
CN
0
-
0
LO
0
co
0
M
o
co
[m]
Invert lev.
0
OM
O
O
�
O
O
0
0
0
0
0
`n
[m]
Length
100.00
32.81
32.81
32.81
106.30
42.10
[m]
Diameter
1.00
1.00
1.00
1.00
1.00
1.00
[m]
Slope o/oo
17.00
15.24
91.44
3.51
591.58
118.76
APPENDIX A
Technical Memorandum
Shannon & Wilson, Inc.
June 21, 2005
SHANNON 6W�I_SON, INC. Shannonl& Wilson, Inc.
P St., Suite 100
- 6EOTECNNICAL AND ENVIRONMENTAL CONSULTANTS 400 N. 34
P.O. Box 300303
Seattle, WA 98103
1 ' TECHNICAL MEMORANDUM 206.632.8020 Fax: 206*695*6777
TO: Scott Slifer, Roth Hill Engineering Partners
FROM: Thomas Gurtowski, P.E.
DATE: June 21, 2005
RE: RESPONSE TO COMMENTS, GEOTECHNICAL REPORT,
PARK PLACE NORTH STORM SEWER
This technical memorandum addresses additional geotechnical consideration in light of the City
of Renton's (City's) review comments regarding Shannon & Wilson's recent geotechnical report
for Park Place North Storm Sewer Project. This memorandum is a follow up to the phone
conversation between Shannon & Wilson and Roth Hill Engineering (Roth) on June 16, 2005.
(1) The results of the stability analyses that we performed for the project are enclosed. Based on
the slope geometry and soil parameters that we used in our analyses, the looser surficial layer of
' soil on the steep slope and the thicker layer of fill at the top of the slope at the location of the
proposed manhole would be marginally stable under seismic loading. Because of their marginal
stability, the fill soils at the top of the slope would not provide sufficient passive resistance to
counter the load of pipe if it were solely support by the manhole, in our opinion. We therefore
' recommend that the pipeline on the slope be support by anchors at the top of the slope, as
discussed in our report.
' (2) The anchors shown on Figure 4 in our report are helical anchors; however, Manta Ray
anchors would also be suitable for supporting the pipe on the slope. The concrete to HDPE
' connection shown on the anchor detail in Figure 4 was inadvertent and not the reason for
1
recommending anchors. We understand because of thermal expansion, the City and Roth plan to
snake the pipeline down the slope. The anchors and cable stays detailed in our report would not
preclude snaking the pipe down the slope, in our opinion. However, additional anchors should
L be provided at locations of bends to restrain the pipeline against lateral loads. These additional
21-1-20326-001
Mr. Scott Slifer
June 21, 2005
Page 2
anchors would not need to be helical or Manta Ray anchors, but could be straight, nail -type
anchors, such as the type shown in the Gephart details recently provide to us by the City.
TWH:JXM:TMG/twh
Enclosures: Park Place North Storm Sewer Renton, Washington (2 sheets)
21-1-20326-001
125
100
75
50
25
0
Park Place North Storm Sewer Renton, Washington
c:\program files\stedwin\parkpl-9.pl2 Run By: kh 5/31/2005 02:09PM
# FS
Soil
Soil Total
Saturated Friction Piez.
a 1.54
Desc.
Type Unit Wt.
Unit Wt.
Angle Surface
b 1.54
No. (pcf)
(pcf)
(deg) No.
c 1.55
Fill
1 110.0
110.0
30.0 W1
d 1.55
Sand
2 130.0
130.0
40.0 W1
e 1.56
Gravel
3 130.0
130.0
40.0 W1
f 1.56
Sand
4 130.0
130.0
40.0 W1
g 1.57
h 1.57
i 1.57
j 1.57
a
9
1
2
2
3
3
................ inn
_ — 4
4
4
0
25 50 75 100 125
PCSTABLSM/si FSmin=1.54
Safety Factors Are Calculated By The Modified Janbu Method
150 175
125
100
75
50
25
Park Place North Storm Sewer Renton, Washington
Oprogram files\stedwin\parkpl-8.pl2 Run By: kh 5/31/2005 02:08PM
# FS
Soil
Soil
Total
Saturated
Friction
Piez. Load Value
a 1.06
Desc.
Type
Unit Wt
Unit Wt.
Angle Surface Horiz Eqk 0.150 g
b 1.06
No.
(pcf)
(pcf)
(deg)
No.
c 1.06
Fill
1
110.0
110.0
30.0
W1
d 1.06
Sand
2
130.0
130.0
40.0
W1
e 1.07
Gravel
3
130.0
130.0
40.0
W1
f 1.07
g 1.07
h 1.07
i 1.07
j 1.07
Sand
4
130.0
130.0
40.0
W1
4
0L
0
"W.
3
•-wi
--------------------
25 50 75 100 125
PCSTABL5MLsi. FSmin=1.06
Safety Factors Are Calculated By The Modified Janbu Method
150 175
APPENDIX B
Thermal Expansion Calculations
June 22, 2005
Renton Park Place N. Storm Project
Steep Slope Analysis and Design
Thermal Expansion Calculations
SKS; 6/22/05
References:
1. Above Ground Applications for Polyethylene Pipe published by the Plastics Pipe
Institute, Inc., 2000
2. Performance Pipe Engineering Manual; Book 2, Chapter 5 published by
Performance Pipe, Inc., 2003
3. Systems Design published by Phillips Driscopipe, 1996
Condition 1 - Lateral Deflection Without Intermediate Anchors
Install pipe in a long arc above grade with the length based on our schematic drawing.
Calculate the Lateral Deflection
AY = L {a-AT/2}'/2, where
AY = the lateral deflection in inches
' L = length between anchor points, or approx. 93 feet or 1116 inches
a = coefficient of expansion/contraction, or 0.0001 in./in./ OF.
AT = temperature change, assume this is 60 OF
' Therefore:
AY = 61.3 inches
Calculate the Radius for this AY
R = {4(AY)2 + L2}/ 8AY, where R and L are as per above.
Therefore,
R = 2,570 inches or 214 feet
Compare to Pipe Bending Radius
To account for both pipe contraction and expansion, we want 0.5R to be >_ than the
bending radius of 12-inch HDPE pipe. The bending radius of 12-inch HDPE pipe is
approximately 30 feet.
Therefore,
0.5-R = 107 feet >30 feet and is acceptable
1
Condition 2 - Lateral Deflection Snaking the Pipe With Intermediate Anchors
This is the originally intended concept and is as shown on our schematic drawing.
Check Minimum Allowable Spacing Between Anchors
L = {D (96•a•AT)112) / Callow, where
L = the minimum allowable spacing between anchors in inches
D = outside diameter of the pipe, or 12.75 inches
or = coefficient of expansion/contraction, or 0.0001 in./in./'F.
AT = 60°F. = temperature change
Callow = 0.05 in./in. = maximum permissible strain in the pipe wall (conservative)
Therefore:
L = 193.5 inches or 16.1 feet
' If we install 2 pin anchors and, including the end constraints where the pipe transitions
from above -grade to below -grade and vice versa, the 93 feet of pipe would be divided
into 3 segments. This would be 93/3 equals 31 feet which is > 16.1 feet.
Calculate the Lateral Deflection
From above:
' AY = L {Q•AT / 2)1/2 , except now L = 31 feet or 372 inches.
' Therefore,
AY = 20.4 inches
' Calculate the Radius for this AY
' R = {4(AY)2 + L2)/ 8AY, where R and L are as per above.
Therefore,
' R = 858 inches or 71.5 feet
Compare to Pipe Bending Radius
1 To account for both pipe contraction and expansion, we want 0.5R to be >_ than the
bending radius of 12-inch HDPE pipe. The bending radius of 12-inch HDPE pipe is
' approximately 30 feet.
Therefore,
' 0.5-R = 35.8 feet >30 feet and is acceptable
2