HomeMy WebLinkAbout03176 - Technical Information Report - Geotechnical � � , 13256 Northeast 20th Street,Suite 16
G E O T E C H Bellewe,Washington 98005
CONSULTANTS, INC. (425)'747-5618 FAX(425)747-8561
February 3, 2004
JN 04008
�
Center Cycle
20 Southwest 7th Street, Suite G �""3 � 76
Renton, Washington 98055 j
�
Attention: David Groom I
i
Subject: Transmittal Letter-Geotechnical Engineering Study
Proposed New Center Cycle Building •
39xx Lind Avenue Southwest I
Renton, Washington II
Dear Mr. Groom: �
;
We are pleased to present this geotechnical engineering report for your new Center Cycle building �
to be constructed in Renton. The scope of our services consisted of exploring site surface and '�,
subsurface conditions, and then developing this report to provide recommendations for general
earthwork and design criteria for foundations, retaining walls, and pavements. This work was i
authorized by your acceptance of our proposal, P-6284, dated January 7, 2004.
The attached report contains a discussion of the study and our recommendations. Please contact
us if there are any questions regarding this report, or for further assistance during the design and
construction phases of this project.
Respectfully submitted,
GEOTECH CONSULTANTS, INC.
�«- ���
• Marc R. McGinnis, P.E.
Principal
cc: The Ronhovde Architects-Torjan Ronhovde
MRM: esn
..�_.,r^r�r�.�i"",
- �: 'il � �
. '�d+ '�
�NR 13 20a4
_�!n±���v�sio�,
GEOTECH CONSULTANTS, INC.
.. ,
GEOTECHNICAL ENGINEERING STUDY
Proposed New Center Cycle Building
39xx Lind Avenue Southwest I
Renton Washin ton
, 9
This report presents the findings and recommendations of our geotechnical engineering study for I�
the site of the proposed new Center Cycle building to be constructed in Renton. We were provided
with an undated copy of the Proposed Site Plan developed by The Ronhovde Architects. Based on
this plan, and discussions with Torjan Ronhovde, we anticipate that a one-story retail structure will
be constructed on the north portion of the site. This building will be used for sales and repair of
bicycles. Currently, concrete masonry unit (CMU) construction is being contemplated for the
exterior building walls. Although no final grading information was provided on the site plan, we !
understand that the slab-on-grade floor will be near the existing site grade. Therefore, no cuts or i
fills in excess of a few feet are anticipated. The southem half of the property will be covered with ,
paved parking, which will be accessed both from Lind Avenue Southwest and from the paved
access road near the southeastem comer.
If the scope of the project changes from what we have described above, we should be provided �'
with revised plans in order to determine if modifications to the recommendations and conclusions of �
this report a�e waRanted. �
SlTE CONDITIONS �
SURFACE �
The Vicinity Map, Plate 1, illustrates the general focation of the site. The irregularly shaped lot is I
situated on the southeastern comer of the intersection of Lind Avenue Southwest and Southwest
39th Street. Lind Avenue Southwest abuts the western property line, and a paved access road for
the adjacent cinemas to the east extends along the angled eastem property line. Immediatefy
south of the site is a railroad spur that appears to have been unused for a long time. At the time of
our field work, there was water standing in a depressed portion of this railroad spur, off the
southeastem corner of the site. This depression appears to have been intentionally created to
allow railroad cars to off-load at the low doors along the no[th wall of the adjacent warehouse
building.
Currently undeveloped, the subject lot is covered with low grass and weeds, with Scotch broom and
blackberry vines in the northem tip of the site. The ground surface is relatively flat, and only slightly
above Lind Avenue Southwest and the adjacent paved access road. We observed shallow standing
water at isolated locations on the property, following recent rains.
The development around the site is strictly industnal and commercial in nature. Tilt-up warehouse
and office buildings occupy most of the site vicinity. Immediately to the north is a newer office park,
with a storm detention pond in its southeastem corner, to the east of the subject site. Several
hundred feet to the east is a new multi-screen movie theater.
GEOTECH CONSULTANTS, INC.
� Center Cycle JN 04008
, ' February 3, 2004 Page 2
SUBSURFACE
The subsurface conditions were explored by excavating five test pits at the approximate locations I
shown on the Site Exploration Plan, Plate 2. Our exploration program was based on the proposed I
construction, anticipated subsurface conditions and those encountered during exploration, and the I
scope of work outlined in our proposal.
The test pits were excavated on January 16, 2004 with a rubber-tired backhoe. A geotechnical I�
engineer from our staff observed the excavation process, logged the test pits, and obtained
representative samples of the soil encountered. "Grab" samples of selected subsurface soil were I
collected from the backhoe bucket. The Test Pit Logs are attached to this report as Plates 3
. through 5. . I
Soi!Conditions i
The test pits all encountered generally similar subsurface conditions. The upper 5 to 6 feet li
of soit is fill consisting of slightly silty, gravelly sand that was brought to the property from an I
off-site source. Based on the observed difficulty of excavation throughout this fill, it appears �
to be medium-dense, and to have been compacted in lifts when it was placed.
Underlying the fill was a 12- to 18-inch-thick layer of silt and organic silt that appears to i
have been the original topsoil before the fill was placed. The surface organics were
removed before laying the fill over the topsoil. Beneath the topsoil, we observed 3 to 4 feet '
of loose silt, linderlain by loose to medium-dense, silty sand. These soils are typical of the �
sediments that have been deposited in,the Kent/Renton Valley by flooding and meandering
of rivers and streams following the recession of the glaciers over 10,000 years ago.
The borings and test pits that we have previously completed for geotechnical studies on
numerous projects in the area have encountered similar subsurface conditions.
Groundwafer Conditions
Perched groundwater seepage was observed just above the old topsoil layer in all of the
test pits. This shallow groundwater has resulted from precipifation percolating downward
through the fill until it is stopped, or slowed, by the lower permeability of the silt topsoil. The
fill soils became very moist to wet within a few feet of the perched water layer.
In addition to the shallow, pe�ched seepage, moderate groundwater seepage was observed
below a depth of approximately 10 feet. This seepage level appears to represent the
regional water table that underlies the valley. This water table typically rises and falls
seasonally.
The final logs represent our interpretations of the field logs and laboratory tests. The stratification
lines on the logs represent the approximate boundaries befinreen soil types at the exploration
locations. The actual transition between soil types may be gradual, and subsurface conditions can
vary between exploration locations. The logs provide specific subsurface information only at the
locations tested. The relative densities and moisture descriptions indicated on the test pit logs are
interpretive descriptions based on the conditions observed during excavation.
GEOTECH CONSULTANTS, INC.
:
' Center Cycle JN 04008
' � February 3, 2004 Page 3
The compaction of backfill was not in the scope of our services. Loose soil will therefore be found
in the area of the test pits. If this presents a problem, the backfill will need to be removed and
replaced with structural fill during construction.
CONCLUSIONS AND RECOMMENDATIONS
GENERAL
TH1S SECTlON CONTA/NS A SUMMARY OF OUR STUDY AND FINDfNGS FOR THE PURPOSES OF A
GENERAL OVERVIEW ONLY. MORE SPECIFlC RECOMMENDATIONS AND CONCLUSlONS ARE
CONTAlNED 1N THE REMAINDER OF THlS REPORT. ANY PARTY RELYlNG ON THlS REPORT SHOULD
. READ THE ENTIRE DOCUMENT.
The test pits conducted for this study encountered 4 to 5 feet of moderately compact fill overlying
soft, organic silt and ►oose alluvial soils. Based on the observed conditions, the anticipated
commercial nature of the construction, and our previous experience with similar projects in the
area, it is our opinion that the planned building can be supported on conventional foundations. The
nearby buildings typically have utilized conventional foundations, with post-const►uction settlement
within acceptable limits for commercial and industrial buildings. However, in order to reduce the
poten#ial for excessive post-construction differential settlement for this retail building, we
recommend that the following measures be taken:
1. Keep the foundation subgrade elevations as close to the existing ground surface as
possible, in order to maximize the thickness of compacted fill between the #ootings and
the soft, organic silt and loose ailuvium.
2. Ensure that the fill within 2 feet of the bottoms of all foundations is compacted to a
minimum of 95 percent of the maximum Modified Proctor (ASTM Test D-1557) dry
density. If the earthwo�lc occurs during hot, dry weather, it may be possible to
overexcavate one foot below the footing, recompact the underlying fill to at least 95
percent relative compaction, then replace the one foot of fill with proper compaction. In
its current, overly moist state, it will likely not be possible to achieve 95 percent
compaction on the existing fill soils.
3. Utilize only continuous footings, even to support interior�olumns and walls.
4. Reinforce the continuous footings sufficiently so that they could theoretically span a
minimum distance of 10 feet without support. This creates foundations that are
relatively rigid, similar to grade beams.
By implementing these foundations measures, the potential for excessive differential settlement
should be low. Howevec, as with any commercial buildings in the vicinity that are unde�lain by
alluvial soils, it is possible that slight cosmetic cracking may develop in the CMU walls over time.
This should not present a structural concem.
The floor slab should be underlain by at least 12 inches of structural fill compacted to a minimum
95 percent relative compaction. Floor slabs should also be reinforced with rebar to limit cracking if
differential settlement does occur. Typically, No. 4 rebar at a maximum spacing of 16 inches
running in both directions is sufficient. Additionally, walkways and slabs should be doweled into the
GEOTECH CONSULTANTS. INC.
� Center Cycle JN 04008
, February 3, 2004 Page 4
foundations at doonNays. This allows them to "ramp away" from the doorway if they settle relative
to the building, reducing the potential for a downset and trip hazard at the door threshold.
Based on our observations, and the results of our laboratory tests, the moisture contents of the on-
site fill soils are above the optimum moisture content necessary for the required structural fill
compaction. These fine-grained silty soils are sensitive to moisture, which makes them impossible
to adequately compact when they have moisture contents even 2 to 3 percent above their optimum
moisture content. The reuse of these soils as structural fill to level the site will only be successful
during hot, dry weather. Aeration of each loose lift of soil will be required to dry it before the lift is
compacted. Altematively, the soil could be chemically dried by adding lime, kiln dust, or cement,
provided this is allowed by the responsible building department. Regardless of the method of
drying, the earthwork process will be slowed dramatically. The earthwork contractor must be
prepared to rework areas that do not achieve proper compaction due to high moisture co�tent. The
soft silt and a�luvial soils that underlie the existing fill are totally unsuitable for reuse as structural fill,
including utility trench backfill in structural areas, such as pavements.
The drainage and/or waterproofing recommendations presented in this report are intended only to
prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active
seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from
the surrounding soil, and can even be transmitted from slabs and foundation walls due to the
concrete curing process. Excessive water vapor trapped within structures can result in a variety of
undesirable conditions, including, but not limited to, moisture problems with flooring systems,
excessively moist air within occupied areas, and the growth of molds, fungi, and other biological
organisms that may be harmful to the health of the occupants. The designer or architect must
consider the �tential vapor sources and likely occupant uses, and provide sufficient ventilation,
either passive or mechanical, to prevent a build up of excessive water vapor within the planned
structure.
Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the
recommendations presented in this report are adequately addressed in the design. Such a plan
review would be additional work beyond the current scope of work for this study, and it may include
revisions to our recommendations to accommodate site, develapment, and geotechnical
constraints that become more evident during the review process.
We recommend including this report, in its entirety, in the project contract documents.
SEISMIC CONSIDERATIONS
The site is located within Seismic Zone 3, as illustrated on Figure No. 16-2 of the 1997 Uniform
Building Code (UBC). In accordance with Table 16-J of the 1997 UBC, the site soil profile within
100 feet of the ground surface is best represented by Soil Profile Type SE (Soft Soil). The loose
sands that lie beneath the regional groundwater table are susceptible to seismic liquefaction. The
recommendations presented in this report are intended to prevent a catastrophic failure of the
foundation system in the event of liquefaction during a large earthquake. It is not practical to
prevent structural damage or to ensure that the building is usable after such an earthquake.
However, by preventing catastrophic failure of the foundations due to liquefaction, the safety of the
occupants should be protected. This conforms to the intent of Section 1626.1 of the 1997 UBC,
which requires that the design "safeguards against major structural failures and loss of life."
GEOTECH CONSULTANTS, INC.
� Center Cycle JN 04008
, ' February 3, 2004 Page 5
CONVENTIONAL FOUNDATIONS
The proposed structure can be supported on continuous conventional #ootings bearing at least 2
feet of structural fill that is compacted to at least 95 percent of the maximum Modified Proctor
(ASTM Test D-1557) dry density. In order to minimize the potential for differential settlement, the
base of the footings should be set as close to the existing grade as is possible. This maximizes the
depth of compacted fill between the footings and the old topsoil and loose alluvial soils.
If the earthwork is conducted during hot, dry weather, the existing fill could be excavated and
replaced with adequate compaction beneath footings. Proper compaction of structural fill should
be verified with frequent density testing during fill placement. Prior to placing structural fill beneath
foundations, the excavation should be observed by the geotechnical engineer to document that
adequate bearing soils have been exposed. We recommend that continuous footi�gs have
minimum widths of 16 inches. Additionally, they should be su�ciently reinforced to theoretically be
able to span a minimum distance of 10 feet without support. This will result in a relatively rigid
foundation that is similar to a grade beam, and is intended to reduce the potential for excessive
differential settlement as the underiying soft and loose soils consolidate over time. Footings should
also be bottomed at least 18 inches below the lowest adjacent finish ground surface, but this grade
could be built higher than the existing grade by placing fill around the building to raise the final
ground surface.
An allowable bearing pressure of 2,000 pounds per square foot (ps� is appropriate #or footings
supported as discussed above. A one-third increase in this design bearing pressure may be used
when considering short-term wind or seismic loads. For the above design criteria, it is anticipated
that the total post-construction settlement of footings founded on competent native soil, or on
structural fill up to 5 feet in thickness, will�be one to 2 inches, with differential settlements on the '
order of one-half inch in a distance of 25 feet along a continuous footing with a uniform load.
Lateral loads due to wind or seismic forces may be resisted by friction between the foundation and
the bearing soil, or by passive earth pressure acting on the vertical, embedded portions of the
foundation. For the latter condition, the foundation must be either poured directly against relatively
level, undisturbed soil or be surrounded by level structural fill. We recommend using the following
ultimate values for the foundation's resistance to lateral loading:
� CoefFicient of Friction 0.45
Passive Earth Pressure 300 pcf
Where:(i)pcf is pounds per cubic foot,and(ii)passive earth
pressure is computed using the equivalent fluid denaity.
If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will
not be appropriate. We recommend maintaining a safety factor of at least 1.5 for the foundation's
resistance to lateral loading, when using the above ultimate values.
GEOTECH CONSULTANTS, INC.
• Center Cycle JN 04008
, • February 3, 2004 Page 6
PERMANENT FOUNDATION AND RETA/N/NG WALLS
Tall retaining walls are not anticipated for this project. However, walis backfilled on only one side
should still be designed to resist the lateral earth pressures imposed by the soil they retain. The
following recommended parameters are for walls that restrain level backfill:
Actfve Earth Pressure ' 40 pcf
Passive Earth Pressure 300 pcf
Coefficient of Friction 0.45
Soil Unit Weight 130 pcf
Where: (i) pcf is pounds per cubic foot, and (ii) active and
passive earth pressures are computed using the equivalent fluid
pressures.
'For a restrained wall that cannot deflect at least 0.002 times its
height,a uniform lateral pressure equal to 10 psf times the height
of the wall should be added to the above active equivalent fluid
pressure.
The values given above are to be used to design permanent foundation and retaining walls only.
The passive pressure given is appropriate for the depth of level structural fill placed in front of a
retaining or foundation wall only. The values for friction and passive resistance are ultimate values
and do not include a safety factor. We recommend a safety factor of at least 1.5 for overtuming
and sliding, when using the above values to design the walls. Restrained wall soil parameters
should be utilized for a distance of 1.5 times the wall height from comers or bends in the walls.
This is intended to reduce the amount of cracking that can occur where a wall is restrained by a ,
comer.
The design values given above do not include the effects of any hydrostatic pressures behind the
walls and assume that no surcharges, such as those caused by slopes, vehicles, or adjacent
foundations will be exerted on the walls. If these conditions exist, those pressures should be added
to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need
to be given the wall dimensions and the slope of the backfill in order to provide the app�opriate
design earth pressures.
Heavy construction equipment should not be operated behind retaining and foundation walls within
a distance equal to the height of a wall, unless the walls are designed for the additional lateral
pressures resufting from the equipment. The wall design criteria assume that the backfill wilf be
well-compacted in lifts no.thicker than 12 inches. The compaction of backfill near the walls should
be accomplished with hand-operated equipment to prevent the walls from being overloaded by the
higher soil forces that occur during compaction.
Retainin4 Wal!Bac�ll and Waterproofinq
Backfill placed behind retaining or foundation walls should be coarse, free-draining
structural fill containing no organics. This backfill should contain no more than 5 percent silt
or clay particles and have no gravel greater than 4 inches in diameter. The percentage of
GEOTECH CONSULTANTS, INC.
� Center Cycle JN 04008
. � February 3, 2004 Page 7
particles passing the No. 4 sieve should be between 25 and 70 percent. If the existing
slightly silty fill soil is reused as wall backfill, a minimum 12-inch width of free-draining gravel
should be placed against the backfilled retaining walls. The native soils that underlie the fill
are not acceptable for reuse as retaining wall backfill, due to their low compacted strength.
The later section entitled Drainage Considerations should also be reviewed for
recommendations related to subsurface drainage behind foundation and retaining walls.
The purpose of these backfill requirements is to ensure that the design criteria fo� a
retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the
wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively
impermeable soil or topsoil, or the surface should be paved. The ground surface must also
slope away from backfilled walls to reduce the potential for surface water to percolate into
the backfill. The section entitled General Earthwork and Structural Fill contains
recommendations regarding the placement and compaction of structural filf behind retaining
and foundation walls.
The above recommendations are not intended to waterproof below-grade walls, or to
prevent the formation of mold, mildew or fungi in interior spaces. Over time, the
performance of subsurface drainage systems can degrade, subsurface groundwater flow
pattems can change, and utilities can break or develop leaks. Therefore, waterproofing
should be provided where future seepage through the walls is not acceptable. This typically
includes limiting cold-joints and wall penetrations, and using bentonite panels or j
membranes on the outside of the walls. There are a variery of different waterproofing ,
materials and systems, which should be installed by an experienced contractor familiar with
the anticipated construction and subsurface conditions. Applying a thin coat of asphalt
emulsion to the outside face of a wall i� not considered waterproofing, and will only help to
reduce moisture generated from water vapor or capillary action from seeping through the
concrete. As with any project, adequate ventilation of basement and crawl space areas is
important to prevent a build up of water vapor that is commonly transmitted through
concrete walls from the sunounding soil, even when seepage is not present. This is
appropriate even when waterproofing is applied to the outside of foundation and retaining
walls. We recommend that you contact a specialty consultant if detaifed recommendations
or specifications related to waterproofing design, or minimizing the potential for infestations
of mold and mildew are desired.
SLABS-ON-GRADE
The building floors can be constructed as slabs-on-grade atop the existing structural fill, provided
the subgrade soils are compacted to at least 95 percent of the maximum Modified Proctor dry
density. Additionally, we recommend reinforcing floor slabs and entry walks with rebar to reduce
cracking that could resutt from differential settlement as the underlying soils consolidate.
Additionally, it is prudent to dowel slabs and entry walks into the continuous foundations at
doonivays, preventing a downset from occurring at the door threshold.
All interior slabs-on-grade should be underlain by a capillary break or drainage layer consisting of a
minimum 4-inch thickness of coarse, free-draining structural fill with a gradation similar to that
discussed in Permanent Foundation and Retaining Walls. As noted by the American Concrete
Institute (ACI) in the Guides for Concrete Floor and Slab Structures, proper moisture protection is
desirable immediately below any on-grade slab that will be covered by tile, wood, carpet,
impermeable floor coverings, or any moisture-sensitive equipment or products. ACI also notes that
GEOTECH CONSULTANTS, INC.
. CenterCycle JN 04008
� February 3, 2004 Page 8
vapor retarders, such as 6-mil plastic sheeting, are typically used. A vapor retarder is defined as a
material with a permeance of less than 0.3 US perms per square foot (psfl per hour, as determined
by ASTM E 96. It is possible that concrete admixtures may meet this specification, although the
manufacturers of the admixtures should be consulted. Where plastic sheeting is used under slabs,
joints should overlap by at least 6 inches and be sealed with adhesive tape. The sheeting should
extend to the foundation walls for maximum vapor protection. If no potential for vapor passage
through the slab is desired, a vapor ba►rier should be used. A vapor barrier, as defined by ACI, is a
product with a wate� transmission rate of 0.00 perms per square foot per hour when tested in
accordance with ASTM E 96. Reinforced membranes having sealed overlaps can meet this
requirement.
In the recent past, ACI (Section 4.1.5) recommended that a minimum of 4 inches of well-graded
compactable granular material, such as a 5/8 inch minus crushed rock pavement base, should be
placed over the vapor retarder or barrier for protection of the retarder or barrier and as a "blotter"to
aid in the curing of the concrete slab. Sand was not recommended by ACI for this purpose.
However, the use of material over the vapor retarder is controversial as noted in current ACI
literature because of the potential that the protectioNblotter material can become wet between the
time of its placement and the installation of the slab. If the material is wet prior to slab placement,
which is always possible in the Puget Sound area, it could cause vapor transmission to occur up
through the slab in the future, essentially destroying the purpvse of the vapor barrier/retarder.
Therefore, if there is a potential that the protection/blotter material will become wet before the slab
is installed, ACI now recommends that no protection/blotter material be used. However, ACI then
recommends that, because there is a potential for slab cure due to the loss of the blotter material,
joint spacing in the slab be reduced, a low shrinkage concrete mixture be used, and "other
measures" (s#eei reinforcing, etc.) be used. ASTM E-1643-98 "Standard Practice for Installation of
Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs"
generally agrees with the recent ACI literature.
We recommend that the contractor, the project materials engineer, and the owner discuss these
issues and review recent ACI literature and ASTM E-1643 for installation guidelines and guidance
on the use of the protection/blotter material. Our opinion is that with impervious surfaces that all
'I means should be undertaken to reduce water vapor transmission.
EXCAVATIONS AND SLOPFS
Excavation slopes should not exceed the limits specified in local, state, and national government
safety regulations. No deep excavations are anticipated, with utility trenches likely being the
deepest temporary cuts that will be necessary. Temporary cuts in the upper approximately 4 feet
of the existing fill can be cut at a 1:1 (Horizontal:Vertical) inclination. Near, or below, the level of
perched seepage, the temporary cuts will either need to be flared out to an approximate 1.5:1 (H:�
inclination, or excavation shoring will be needed. Excavations that extend into the wet sands would
require substantial shoring.and excavation dewatering.
The above-recommended temporary slope inclinations are based on what has been successful at
other sites with similar soil conditions. Temporary cuts are those that will remain unsupported for a
relatively short duration to allow for the construction of foundations, retaining walls, or utilities.
Temporary cut slopes should be protected with plastic sheeting during wet weather. It is also
important that surface water be directed away from temporary slope cuts. The cut slopes should
also be backfilled or retained as soon as possible to reduce the potential for instability. Please note
that loose or wet soil can cave suddenly and without warning. Excavation, foundation, and utility
GEOTECH CONSULTANTS, INC.
' Center Cycle JN 04008
• • February 3, 2004 Page 9
contractors should be made especially aware of this potential danger. These recommendations
may need to be modified if the area near the potential cuts has been disturbed in the past by utility
installation, or if settlement-sensitive utilities are located nearby.
DRAINAGE CONSlDERATIONS
Foundation drains should be used where a slab is below the outside grade, or the outside grade
does not slope downward from a building. Drains should also be placed at the base of all earth-
retaining walls. These drains should be surrounded by at least 6 inches of 1-inch-minus, washed
rock and then wrapped in non-woven, geotextile filter fabric (Mirafi 140N, Supac 4NP, or similar
material). At its highest point, a perforated pipe invert should be at least 6 inches below the bottom
of a slab floor or the level of a crawf space, and it should be sloped for drainage. All, roof and
surface water drains must be kept separate from the foundation drain system. A typical drain detail
is attached to this report as Plate 6. For the best long-term performance, perforated PVC pipe is
recommended for all subsurface drains.
Groundwater was observed during our field work. If seepage is encountered in an excavation, it
should be drained from the site by directing it through drainage ditches, perforated pipe, or French
drains, or by pumping it from sumps interconnected by shallow connector trenches at the bottom of
the excavation.
Water should not be allowed to stand in any area where foundations, slabs, or pavements are to be
constructed. Final site grading in areas adjacent to a building should slope away at least 2 percent,
except where the area is paved. Surface drains should be provided where necessary to prevent
ponding of water behind foundation or retaining walls.
PAVEMENT AREAS
The pavement section may be supported on the existing fill soils, provided the subgrade can be
compacted to a 95 percent density. Because the site soils are silty and moisture sensitive, we
recommend that the pavement subgrade be in a stable, non-yielding condition at the time of
paving. Granular structural fill or geotextile fabric may be needed to stabilize soft, wet, or unstable
areas. To evaluate pavement subgrade strength, we recommend that a proof roll be completed
with a loaded dump truck immediately before paving. In most instances where unstable subgrade
conditioc�s are encountered, an additional 12 inches of granular structural fill will stabilize the
subgrade, except for very soft areas where additional fill could be required. The subgrade should
be evaluated by Geotech Consultants, Inc., after the site is stripped and cut to grade.
Recommendations for the compaction of structural fill beneath pavements are given in the section
entitled Genera/ Earthwork and Structural Fill. The performance of site pavements is directly
related to the strength and stability of the unde�lying subgrade.
The pavement for lightly loaded traffic and parking areas should consist of 2 inches of asphalt
concrete (AC) over 4 inches of crushed rock base (CRB) or 3 inches of asphalt-treated base (ATB).
We recommend providing heavily loaded areas with 3 inches of AC over 6 inches of CRB or 4
inches of ATB. Heavily loaded areas are typically main driveways, dumpster sites, or areas with
truck traffic.
GEOTECH CONSULTANTS, INC.
' Center Cycle JN 04008
• February 3, 2004 Page 10
The pavement section recommendations and guidelines presented in this report are based on our
experience in the area and on what has been successful in similar situations. As with any
pavements, some maintenance and repair of limited areas can be expected as the pavement ages.
To provide for a design without the need for any repair would be uneconomical.
GENERAL EARTHWORK AND STRUCTURAL FlLL
All building and pavement areas shoutd be stripped of surface vegetation, topsoil, organic soil, and
other deleterious material. The stripped or �emoved materials should not be mixed with any
materials to be used as structural fill, but they could be used in non-structural areas, such as
landscape beds. .
Structural fill is defined as any fill, including utility backfill, placed under, or close to, a building,
behind permanent retaining or foundation walls, or in other areas where the unde�lying soil needs
to support loads. All structural fill should be placed in horizontal lifts with a moisture content at, or
near, the optimum moisture content. The optimum moisture content is that moisture content that
results in the greatest compacted dry density. The moisture content of fill is very important and
must be closely cont�olled during the filling and compaction process.
The allowable thickness of the fill lift will depend on the material type selected, the compaction ,
equipment used, and the number of passes made to compact the lift. The loose lift thickness i
should not exceed 12 inches. We recommend testing the fill as it is placed. If the fill is not '
sufficiently compacted, it can be recompacted before another lift is placed. This eliminates the
need to remove the fill to achieve the. required compaction. The following table presents
recommended relative compactions for structural fill:
�
Beneath footings, slabs 95%
or walkwa s
Filled slopes and behind 90%
retainin walls
95%for upper 12 inches of
Beneath pavements subgrade; 90% below that
level
Where: Minimum Relative Compactlon is the ratlo,expreased in
percentages, of the compacted dry density to the maximum dry
density, as determined in accordance with ASTM Teat
Designation D 1557-91 (Modified Procto�.
The Genera! section should be reviewed for considerations related to reuse of the on-site soils as
structural fill. Structural fill that will be placed in wet weather should consist of a coarse, granular
soil with a silt or clay content of no more than 5 percent. The percentage of particles passing the
No. 200 sieve should be measured from that portion of soil passing the three-quarter-inch sieve.
GEOTECH CONSULTANTS, INC.
• Center Cycle JN 04008
, � February 3, 2004 Page 11
LIMITATIONS
The analysis, conclusions, and recommendations contained in this report are based on site
conditions as they existed at the time of our exploration and assume that the soil and groundwater
conditions encountered in the test pits are representative of subsurface conditions on the site. If
the subsurface conditions encountered during construction are significantly different from those
observed in our explorations, we should be advised at once so that we can review these conditions
and reconsider our recommendations where necessary. Unanticipated soil conditions are
commonly encountered on construction sites and cannot be fully anticipated by merely taking soil
samples in test pits. Subsurface conditions can also vary befinreen exploration locations. Such
unexpected conditions frequently require making additional expenditures to attain a propeny
constructed project. It is recommended that the owner consider providing a contingency fund to
accommodate such poterrtial extra costs and risks. This is a standard recommendation for all
projects.
This report has been prepared for the exclusive use of Center Cycle, David Groom, and their
representatives, for specific application to this project and site. Our conclusions and
recommendations are professional opinions derived in accordance with cuRent standards of
practice within the scope of our services and within budget and time constraints. No warranty is
expressed or implied. The scope of our services does not include services related to construction
safety precautions, and our recommendations are not intended to direct the contractors methods,
techniques, sequences, or procedures, except as specifically described in our report for
consideration in design. Our services also do not include assessing or minimizing the potential for
biological ha�ds, such as mold, bacteria, mildew and fungi in either the existing or proposed site
development. ,
ADDITIONAL SERVlCES
Geotech Consultants, lnc. should be retained to provide geotechnical consultation, testing, and
observation services during construction. This is to con�rm that subsurface conditions are
consistent with those indicated by our exploration, to evaluate whether earthwork and foundation
construction activities comply with the general intent of the recommendations presented in this
report, and to provide suggestions for design changes in the event subsurface conditions differ
from those anticipated prior to the start of construction. However, our work would not include the
supervision or direction of the actual work of the contractor and its employees or agents. Also, job
and site safety, and dimensional measurements, will be the responsibility of the contractor.
During the construction phase, we will provide geotechnical observation and testing services only
when requested by you or your representatives. We can only document site work that we actually
observe. It is still the responsibility of your contractor or on-site construction team to verify that our
recommendations are being followed, whether we are present at the site or not.
GEOTECH CONSULTANTS, INC.
' Center Cycle JN 04008
• � February 3, 2004 Page 12
The following plates are attached to complete this report:
Plate 1 Vicinity Map
Plate 2 Site Exploration Plan
Plates 3 - 5 Test Pit Logs
Plate 6 Typical Footing Drain Detail
We appreciate the opportunity to be of service on this project_ If you have any questions, or if we
may be of further service, please do not hesitate to contact us.
Respectfully submitted,
GEOTECH CONSULTANTS, INC.
�
�'° �1��'
,�� ��w�s���cr��
��� � `� �� t�A
. �����������1���
���I���.�� 2�31ay
i
` �� QS
Marc R. McGinnis, P.E.
Principal
MRM: esn
� GEOTECH CONSULTANTS, INC.
t
� �
�: '�I c� '7�
�
, �
�
�
-_� J.� a� � .,, _ . .. aa w r-� I
" ...._--- -
�_j _ ,,. . t : _ � ---1- :� -- -----�' t a ,� ,� � �$� w �� N �
. � ---------- ,._._ _ � Q_
b31 �",.' yf � t ,� tr N30U3BV r+'-�-OfiF7T-- , �JI 3S1YI'"YtIZTT—.-_- .3L�Ar WdFi � �
r�•
; � • -. - - C
� :' ;� x U n� �I�H� �X 311d 1� a�H ld � 35 AY Nlifi �
F . W + �e
`. y F W 6 J�� � '� � 11�Mt07Nil�` tl F N�oj ' Z, . � O.
i
,, . 1�3 —
, S n �� i' (�
I u � �
U � 3:
. a � � O a��� �'p� ,ioxes��a ,��{r Sj Nj� � �� N��f� _��'��,�; �+ 3$AY illOf! O C f�
�'� � = cTJ 5 W......._... .. �d o.. c� .
� � C,_' r-�• � 9 cV �or S ap�ts 3S Ad� _H160I
Q (�•_
,Q `�; t, ��'`'./ 8 s¢ �' � ._3 r + ,,,� i "' - is nv Nieot � _ �
,� � w <� � � i �{"��"! '"l 3s� u� 3S AV N N F-
'�,� � s nr s3rror � o i � y� 3S AV H 80I� "1801 w H180t � N "
. �i`��'� S. � x �J O� � � p
� -5.� t'n�6..._ GRANT. AV_�/ (w9i c I �`
�� i S AY IFJ[N 1N 9 '• � --- ��G 3S y' .. Hl OI N; ?., ����
`��:?c. � .. ' 7 l00 , � 6S'�` ���a '1
� � `'�. .. _oo[ e�S-Av � 1MR19 � ;[ ~
< ' -.�.._. �n6 ,,,i .._..... ,_„ .� N � � p�S� i7150I H
. -— ..._. ... _ .:35
� � �
�4..�3L`� _,. S. ..'����-�Y--Es- �_NO !L�__..��_,r �db�' — 8 S -- 35 - AV H15 i . �ltev iusoi �.
„ rf 1 �i���v € s nv" .,.avo3� .�. � 0 � 160I �I --- - d _ V � � �
1-_ � �' ,� �,G bj C
AV 1l N „ �r_ � � n�w� � )� � s� AV tlV039 S.-._' � y�utial�
wo�� \ Y3� , ' _ '_
�S N � �� �-....__ �� ti;�`"� '��z ..� '" � '3 t'`� 3S�tYilllW • J � c�o m
V
BENSON �E " S�` ��%-`s
..S... .._...�� �P 5� ll '�/yj� � 113N
�b C� � �I �, '���v A.. � .
� ��AV' S713M tN)S__ NIb'W :%. GI i ��'�._ ^»(sn� Ns � � � � Q�
.. .
-t _� �. -� �' � � � �
�� \ `1��t ' �".�.""-�...�.. y�... J Cj ���5 � �r
i �� � -- ...��, eg �SWYIIIIMr���°%; s tiv.. 3
� ��
_ s � � F
N AV F— '� ----___.-- F�� S � � � �
u3 � � � �~s � �
� �� �r '`' s � �` I CD
N .� ne c�. �m3�LL�M N � � « N��N `'�� �$m�xi1M�u�s,� � �
Ot. �
__ ��� � - � - � �
NVJOI s nv • sa3 -._� 3 � y � :�� 1 � „ �vP P�S�i�,k����� �,�'�y ��_s_nr�� .sraa�a_��� +..
� � UO 11N5' � y0 ��/ f �r -S' - - 5 ItroON �xnu� �S� s �+ „^.� �V yEne S1
'vl 5 �.:, AY �` ��n'"__'- .�' � } y� N -A 1 df !M �n�e �� �I lH �. r+` � �
�x� S Ay � ��\ siaao� � � � � , onsi _ dnv M�� wJ ,�'"�a � RD S �/N, � ,-; >6' � �
. �i iriin � ��, _ ..- - ._—. _ �_� � .. . j �, __�
.. . � ' yernn_r
- �� OUh �„ --
x� c,> s _.._� _.. t� � ���s � � KS �� �sZ .� s�� y�,�, _ �
-S � w AVB� H��11YHS � � 3�❑ ��� �KE. A�-.�.°.+ s v sie�a'��`�'„� '��,��. � FRWY� � � � W��nll� N �
� 3Ii�v7 l N � � � v x�.,.: �� t/� 1`�0� 'y �+ vf1 . .' � � �
AV N :: ,� ZE� A� - - � �' � V LLEY � � � o � r °°
�. �� PZN ��� s� ..M� � � 'L V
yI��� „�� '� W� � .� � a 17 yA � �?
�$I� �i' � ..�� 4 �(l y � Z � N �f �r tloLv � � /�71.,,1 Yll � 3 F .�w �
F� � �7
d 1`g'1�"��� ._..�ap�E �` � ,!•- -�- 7. -� n1 � N � � `n �, �Z
nsnr� ONII,� .�54` � � -y --� M5�-Ay' 2 31 N � �
{ a Te-. 3 w �r+ ;� � ,
ns nI'�sp�,�.� � a�33°`�;- -��- =S�� �''n °°et � fa"
�"�^d %'� . �'n ns nv A 4N l �o MS oo►e � J
i-i ��,� �3k�� � d � -'�►� ���3$ �' n� � QNI� �.
o�
v� ��,���j����^�� ^ N . G� � I@"Iv...h n�� � r 4 i r n N . Q ��
� �' Z
���— '' - � - �-a � .� e��- 3SN �
. b-- ;r /w
_ __3___—�-- [•J
-,,. ,�ry MS�..,���� � � 4 _�j15.-A 'SrMOHl �MS AV � ON dl1�:-�..,,. �/ - .. - —..---.—� --—- �,—---—�, � -- V C�
. _ _ ��"�:.3 N �
'^b _�.._ �O
s -�_ � v
!en� ��
p!-.; �' ...._ ._____ ,'.�o- ar+a�ava
� •----- 00[. � '� �
' . ,���`av >»` MS A 113MOd `:� �, � t, � �
� 3 .
hr ' \`�,' J NACHES �,V �" ... ��0 � _
,^v�'�t, �'( _AV_.SW- ESQ.. __5. ....---_ _ ..._.---- _--- -� .... � .�i
� MS �{ AV T.. 3lVOSAVO -'.. 3; .
�yy �b -� ,r � � O�K�' ... ... ���7iii �� � _.__.- ���,.. o
outhwest 39th
Street
%'.�. .�.`.`•`
� ��
� ��
! ��
� � `�•
3 � 0 �•
,t 1 Tp_1 ♦
� •� � •
O j � �`�'%
mj Proposed �� `��
c � Buitding � �
♦ 9
m / .
Q I � �� `����'
a � '�� '� �'�
t I � do�
..�
J 1 �
/ ��
� `♦
1 Q � '�
j �,� Proposed Parking '�
TP-5 '�.`
1 • .`
.�
, ��•�
L.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.�.��•���':7��
� NORTH
�
�,.�-
,
�V
(Source: Proposed CenterCyGe Site Plan-Renton; The Ronhovde Architects; undated} Not To Scale
,
G E O T E C H SITE EXPLORATION PLAN
� CONSULTANTS, �Nc. 8245 West Mercer Way
Mercer island, Washington
Job No: ate: a e:
00039 Feb. 2000 2
� � �v °'°' TEST PIT 1
- �`�� o�y�tiefi������ 5
. � ��4 ��or ��a�o �5G
Description
Brown to gray, slightly gravelly, slightly silty SAND, fine- to medium-grained,
FILL moist, medium-dense (FILL)
- becomes very moist
5 0� Black, organic SILT, low plasticiry, very moist, soft
' ' ' '� Gray SILT with occasional lenses of silty sand, non-plastic, very moist, loose
� ;
ML I
10 � Il�li'�I I
— ; sM i; Dark gray to black, silty SAND, fine-grained, wet, loose to medium-dense �
��!,.
* Test Pit was terminated at 12 feet on January 16, 2004. � �
* Slight perched groundwater seepage was observed at apprdximately 5
15 feet and below 10 feet during excavation. '
* Slight caving was observed below 8 feet during excavation.
'��
�� �,{��`i�t TEST PIT 2
�4� �`��fi'`��`�°'a'��'� 5G� �
9 G° �S �S Description �
Thin layer of railroad bailast rock over brown to gray, slightly silty, gravelly SAND,
medium-to fine-grained, moist, medium-dense (FILL)
FILL - becomes very moist .
5 1
M� Dark brown SILT with fine organics, low plasticity, very moist, soft
�� � � � Dark gray SILT with lenses of sifty sand, low plasticity, �ery moist, loose
ML
Z i � ii�
�� ' i Dark gray, silty SAND, fine-grained, wet, loose to medium-dense
� SM �
�I �
� * Test Pit was terminated at 11.5 feet on January 16, 2004.
* Perched groundwater seepage was observed at approximately 4.5 feet
15 and below 10 feet during excavation.
" Slight caving was observed from 4 to 5 feet and below 10 feet
during excavation.
' � TEST PIT LOG
4 � GEOTECH 39xx Lind Avenue Southwest
CONSULTAN'I'S,nvc. Renton, Washington
�
� � Job No: Date: Logged by: Plat+e:
04008 January 2004 MRM 3
� �,� �.�,��`� TEST PIT 3
��, �a����r�a�,ro�� G5
� ��� G° �S°' 4`' Description
Brown, slightly silty, gravelly SAND, medium-to fine-grained, moist, medium-
dense (FILL)
FILL becomes light gray, gravelly SAND, very moist
�
5 M� Brown SILT with fine organics, low plasticity, very moist, soft
+� Dark gray SILT, low plasticity, very moist, loose
* Test Pit was terminated at 6.5 feet on January 16, 2004.
* Perched groundwater seepage was observed at approximately 4.5 feet
10 during excavation.
* Slight caving was observed between 4 and 5 feet during excavation.
15
1 �� ob� TEST PIT 4
,� �� {
�tiY� �o ofiti�fi�abroti� �GS
� G �S � Descnptton
Brown, slightly silty, gravelly SAND, medium-to fine-grained, moist,
FILL medium-dense (FILL)
- becomes very moist'
5 0 Dark brown, organic SILT, low plasticity, very moist, soft
�' ' ''. : Dark gray SILT with lenses of silty sand, non-piastic, very moist, loose
��
IML �
10 � '
! sM ; Dark gray, silty SAND, fine-grained, wet, loose
* Test Pit was terminated at 11.5 feet on January 16, 2004.
'` Perched groundwater seepage was observed at approximately 4 feet
15 and below 10 feet during excavation.
" Slight caving was observed below 10 feet during excavation.
� TEST PIT LOG
� � GEOTECH 39xx Lind Avenue Southwest
CONSULTANTS,�rc. Renton, Washington
�
� • �� ...�,s... Job No: Date: Logged by: Plate: 4
��� 04008 January 2004 MRM
` �,`. �`��,�',��,t TEST PIT 5 �
, ���' �°o�,���aa�,�� �G5
� 9 G �C 4 Description
Brown, slightly silty, gravelly SAND, medium-to fine-grained, moist,
FILL medium-dense (FILL)
- becomes very moist
� � FILL ray, slightly silty, gravelly SAND, medium-to coarse-grained, wet, loose (FILL)
� Dark brown, organic SILT, low plasticity, very moist, soft
'�I~� � Daric ra SILT low lastici ve moist loose
10 * Test Pit was terminated at 8.5 feet on January 16, 2004.
* Moderate perched groundwater seepage was observed from 4 to 6 feet
during excavation.
* Heavy caving was observed from 4 to 6 feet during excavation.
15
i
' - TEST PIT LOG
� GEOTECH 39xx Lind Avenue Southwest
CONSULTANTS,nvc. Renton, Washington
�
� • Job No: Date: Logged by: P/at�e:
04008 January 2004 MRM 5
�
�
Slope backfill away from
foundation. Provide surface
drains where necessary.
Tigh�ine Roof Drain
(Do not connect to footing drain)
Backfill ea
(See text for �
requirements) �
: � Vapor Retarder
Nonwoven Geotextile � or Bamer
Filter Fabric �
Washed Rodc LL' SLAB
(7/8" r�n. size) - I
- a o Q o..Q- •.o-,.4:-.o,.�--.o,.Q- �.o,.�- -.o,.Q
v o v�o�o . .o'°'O000.o•O.opo o•a.0 po.p'p•Q po..•�•opo.0•� �
c o o e o 5 ,?'cQ o•� QOcp o•o �p0cp o•o p0d�o•o ?'d�o•o °c
Oo 00 O Oo `-i �� - o- �oip�.'��.o� •�.op�.°••�.op�e'�a.op�.'�a.ui
OnOnO c0 _ --' t' - �-x-'�. v .. o.'.o . .b��.o ...ti,�.o ., b.�.o ., b.�•o ...
� o 0 0 .s..,a,-.-. - - `� ,i� +'
°p°p° op oG� ,:`�' €�
0 0 0 0 0
6" 171�I1. �,�, ��
oa
Free-Draining Gravel
4" Perforated Hard PVC Pipe (if appropriate}
(Invert at least 6 inches below
slab or crawl space. Slope to
drain to appropriate outfall.
Place holes downward.)
NOTES:
(1) In crawl spac�s, provide an outlet drain to prevent buildup of waterthat
bypasses the perimeter footing drains.
(2) Refer to report text for addfional drainage and waterproofing considerations.
�
TYPICAL FOOTING DRAIN
� G E O T E C H 39�oc Lind Avenue Southwest
CONSULTANTS, iNc. Renton, Washington
o . c e: at�e:
04008 Jan.2004 Not to Scale 6