HomeMy WebLinkAboutSWP272206(5) RECEIVED
FEB 2 8 1995
S y R DESIGN CO.
' LIMITED GEOTECHNICAL ENGINEERING REPORT
NELSON PLACE STORM SYSTEM REPLACEMENT
RENTON, WASHINGTON
' Submitted To:
' SVR Design Co.
911 Western Avenue, Suite 302 OPUNAL-".
Seattle, Washington 98104
�oT MAP,�-
FILE COF
' Submitted By:
AGRA Earth & Environmental, Inc.
11335 NE 122nd Way, Suite 100
' Kirkland, Washington 98034-6918
' February 1995
File #1 1-0971 2-00
AGRA
' Earth & Environmental
' , AGRA AGRA Earth&
Earth &' Environmental Environmental, Inc.11335 NE 122nd Way
Suite 100
Kirkland,Washington
U.S.A. 98034-6918
' 22 February 1995 Tel (206)820-4669
1 1-0971 2-00 Fax(206)821-3914
' SVR Design Co.
911 Western Avenue, Suite 302
Seattle, Washington 98104
' Attention: Mr. Tom Von Schrader
Subject: Limited Geotechnical Engineering Evaluation
Nelson Place Storm System Replacement
Renton, Washington
Dear Tom:
As requested by you, AGRA Earth & Environmental, Inc. (formerly RZA AGRA) is pleased to
submit this report describing the results of our recent limited geotechnical engineering
' evaluation for the proposed Nelson Place storm system replacement project. The purpose of
this study was to interpret general surface and subsurface site conditions, from which we
could formulate conclusions and recommendations concerning the excavation and backfilling
' of storm drain trenches. As described in our proposal memorandum dated 3 June 1994, our
scope of services consisted of a surface reconnaissance, a limited subsurface exploration,
geotechnical analyses, laboratory testing, and report preparation. We received your written
' authorization for our services on 30 June 1994. This report has been prepared for the
exclusive use of SVR Design Co., the City of Renton, and their agents, for specific application
to this project in accordance with generally accepted geotechnical engineering practice.
' PROJECT DESCRIPTION
' The project site is located at the intersection of Rainier Avenue N., Nelson Place NW, and NW
Third Place in Renton, Washington, as shown on the attached Location Map (Figure 1).
Currently, a storm drain extends from Rainier Avenue N. to NW Third Place along a northwest
trending alignment that traverses several private properties. We understand that this storm
drain will be rerouted northward along Rainier Avenue N. and then westward along NW Third
Place. These existing and proposed alignments are shown on the attached Site and
' Exploration Plan (Figure 2). The new pipe will reportedly have a maximum invert depth of
about 12 feet below grade.
Engineering& Environmental Services
SVR Design Co. 1 1-0971 2-00
22 February 1995 Page 2
It should be emphasized that the conclusions and recommendations contained in this report
' are based on our understanding of the currently proposed utilization of the project site, as
derived from verbal information and plans supplied to us. Consequently, if any changes are
made in the project, we may need to modify our conclusions and recommendations to reflect
those changes.
EXPLORATORY METHODS
We evaluated surface and subsurface conditions at the project site on 15 July 1994. Our
subsurface exploration program consisted of advancing two soil borings (designated B-1 and
B-2) at the project site, to depths of about 1 6'/2 and 21 '/2 feet below existing grade. The
' approximate locations of these borings are shown on Figure 2, and their locations and depths
are summarized in Table 1 , below.
The specific number, locations, and depths of our borings were selected in relation to the
proposed storm drain alignment, under the constraints of budget and site access. We
' determined the approximate location of each exploration by measuring from existing site
features, and we subsequently scaled these locations onto a sketch prepared by our field
representative. As such, the boring locations shown on Figure 2 should be considered
accurate only to the degree permitted by our layout sketch and implied by our measuring
methods.
' It should be emphasized that our explorations reveal subsurface conditions only at discrete
locations across the project site and that actual conditions may vary between these
exploration locations. Furthermore, the nature and extent of any such variations would not
' become evident until construction activities have begun. If significant variations are observed
at that time, we may need to modify the conclusions and recommendations contained in this
report to reflect actual site conditions.
TABLE 1
GENERAL LOCATIONS AND APPROXIMATE DEPTHS OF EXPLORATIONS
Exploration Location Termination Depth
(feet)
B-1 South Shoulder of NW Third Place 16'/z
B-2 East Shoulder of Nelson Place NW 21 '/2
' WAGRA
Earth & Environmental
SVR Design Co. 1 1-0971 2-00
22 February 1995 Page 3
Borings
Both soil borings were advanced with a hollow-stem auger, using a truck-mounted drill rig
operated by an independent firm working under subcontract to AGRA. A geotechnical
engineer from our firm continuously observed the borings, logged the subsurface conditions,
' and obtained representative soil samples. All soil samples were classified in the field, placed
in watertight containers, and transported to our laboratory for further visual classification and
testing. After each boring was completed, the borehole was backfilled with a mixture of soil
' cuttings and bentonite chips, and the surface was patched with concrete or asphalt.
During the drilling process, soil samples were obtained from our borings at 2.5- to 5-foot
' depth intervals by means of the Standard Penetration Test procedure (ASTM:D-1586). This
test and sampling method consists of driving a standard 2-inch (outside diameter) steel
split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling
' a distance of 30 inches. The number of blows required to drive the sampler through each of
the three 6-inch intervals is recorded, and the total number of blows struck during the final
12 inches is considered the Standard Penetration Resistance, or "blow count." If a total of
50 blows is struck within one 6-inch interval, the driving is ceased and the blow count is
recorded as 50 blows for the actual number of inches of penetration. The resulting Standard
Penetration Resistance values provide a measure of the relative density of granular soils and
the relative consistency of cohesive soils.
The attached boring logs describe the various types of soils and materials encountered in our
borings, based primarily on interpretations made in the field and supported by our subsequent
laboratory examination of selected soil samples. These logs also indicate the approximate
' depth of the contacts between different soil types, although these contacts may be
gradational or undulating. Where a change in soil type occurred between sampling intervals,
we inferred the depth of the contact. In addition, our logs indicate the depth of any
' groundwater observed in our boreholes, as well as any laboratory tests performed on the soil
samples.
' SITE CONDITIONS
The following sections present our observations, measurements, and interpretations
concerning surface, soil, and groundwater conditions at the project site. Descriptive logs of
our explorations and graphic results of our laboratory tests are-attached to this report.
Surface Conditions
The project site is situated in a lowland region characterized by dense commercial
development and flat to gently rolling terrain. Lake Washington lies approximately 3/4 mile
north, and the Cedar River lies approximately '/4 mile east. Surface grades are fairly flat and
' level across the site, and asphalt pavement covers the proposed storm drain alignment.
* AG RA
Earth & Environmental
' SVR Design Co. 1 1-0971 2-00
22 February 1995 Page 4
Soil Conditions
Our exploratory borings disclosed somewhat variable soil conditions at the project site. Boring
B-1 , which was advanced at the southern shoulder of NW Third Place, encountered 4 inches
of asphalt mantling about 4 feet of medium-dense, cobbly, sandy gravel fill over 10'/2 feet of
loose to medium-dense, moist to wet, silty, fine sand with some organics. At a depth of 15
feet, boring B-1 disclosed stiff, saturated, sandy silt extending to the termination depth of
16'/2 feet. Boring B-2, which was advanced at the eastern shoulder of Nelson Place NW,
disclosed 4 inches of asphalt mantling '/z foot of sandy gravel fill over 6'/2 feet of very loose
to loose, moist, silty, fine sand. We observed a 2-foot-thick layer of very soft peat at a depth
' of 7'/2 feet, underlain by 9 feet of very loose to loose, wet to saturated, silty, fine sand
interbedded with soft silts. At a depth of 18'/z feet, boring B-2 revealed dense, saturated,
silty sand extending to the termination depth of 21 '/2 feet. Table 2, below, summarizes the
' approximate thicknesses and depths of soil layers disclosed by our borings.
TABLE 2
APPROXIMATE THICKNESSES AND DEPTHS OF SOIL LAYERS
Exploration Thickness of Thickness of Depth to Stiff Depth to
' Asphalt and Sandy Very Loose to Sandy Silt Dense Silty
Gravel Fill Loose, Silty, (feet) Sand
(feet) Fine Sand (feet)
(feet)
B-1 4'/2 10'/z 15 N/E
B-2 1 17'/z * N/E 18
N/E = not encountered within depth of exploration
' * Includes 2 feet of very soft peat at depth of 7'/z feet
To further characterize soil conditions at the project site, we conducted laboratory tests on
' selected samples obtained from our explorations. The results of these tests can be
summarized as follows:
' • A grain size analysis performed on a sample of the upper, very loose to loose,
silty, fine sand yielded a fines content of 32 percent, a sand content of 67
percent, and a gravel content of 1 percent, with a moisture content of 13
percent.
• A grain size analysis performed on a sample of the upper, sandy gravel sand fill
' yielded a fines content of 5 percent, a sand content of 27 percent, and a gravel
content of 68 percent, with a moisture content of 3 percent.
* AGRA
��_�� Earth & Environmental
' SVR Design Co. 1 1-0971 2-00
22 February 1995 Page 5
An Atterberg limit determination performed on a sample of the deep, stiff,
' sandy silt yielded a very low plasticity and a moisture content of 19 percent.
Groundwater Conditions
' We observed groundwater at a depth of about 14 to 15'/z feet below existing grade in both
borings at the time of drilling. It should be realized, however, that high groundwater levels
will likely occur during the winter and spring or after periods of heavy rainfall, and perched
groundwater could form atop the sandy silt or peat horizons. Furthermore, local groundwater
levels could fluctuate due to site utilization, construction activities, and other factors.
' CONCLUSIONS AND RECOMMENDATIONS
Current plans call for installation of a new storm drain pipe along Rainier Avenue N. and NW
' Third Place, with an invert depth of about 10 feet. Our geotechnical conclusions and
recommendations are as follows:
' • Excavation Methods: Based on our explorations, we anticipate that the storm
drain trenches can be readily excavated with a conventional backhoe or
trackhoe. Nonetheless, the excavation contractor should realize that differing
' soil conditions and unexpected underground obstructions might be encountered
along the alignment.
• Shoring and Slopes: Due to the presence of very loose and very soft near-
surface soils, severe sidewall caving could occur in the trenches. As such, the
contractor should be prepared to install trench boxes or shoring systems
appropriate for OSHA Type C soil conditions. If open cuts can be used, we
recommend that the slope inclinations be no steeper than 1 '/z H:1 V
(Horizontal:Vertical).
• Groundwater: It should be noted that perched groundwater or generally higher
groundwater levels could be encountered in the trenches, especially during the
' winter and spring or after extended periods of heavy rainfall. If high
groundwater levels are encountered during construction, localized dewatering
systems, such as pumped sumpholes, might be required. We recommend that
large-scale dewatering systems such as well points not be used, due to the risk
of incurring settlements in adjacent areas.
• Trench Bottoms: We anticipate that the trench bottoms will primarily comprise
very loose to loose, silty, fine sands. In our opinion, compaction of the trench
' bottom should not be attempted, due to the high fines and moisture contents
of these soils. Compactive efforts applied to silty soils would merely cause
disturbance rather than an increase in density.
(DAGRA
<:, Earth & Environmental
SVR Design Co. 1 1-0971 2-00
22 February 1995 Page 6
• Peat Laver: Boring B-2 encountered a 2-foot-thick layer of very soft peat at a
' depth of about 7'/2 feet. If these peats are exposed in the trench bottom, we
recommend that they be overexcavated and replaced with small quarry spalls,
washed rock, or controlled-density fill (CDF).
• Reuse of Sandy Gravels: In our opinion, the cobbly, sandy gravels disclosed in
the upper 4'/2 feet of boring B-1 will provide the most favorable source for
' trench backfill. Due to their low fines content, these soils could be used under
a relatively wide range of weather conditions.
' • Reuse of Silty Fine Sands: The thick deposit of very loose to loose, silty, fine
sands encountered by both borings appears marginally suitable for use as
trench backfill. The wetter portions of these soils will likely require some
' aeration and drying before placement.
• Reuse of Peat: Under no circumstances should the peat soils be reused as
' trench backfill. Furthermore, the contractor should exercise care when
excavating these pests, to avoid contaminating other soils.
' • Backfill Compaction: We recommend that all trench backfill be placed in
horizontal lifts not exceeding 12 inches in loose thickness and then be
' compacted to a uniform density by means of a vibratory roller or hoepack.
Using the modified Proctor maximum dry density (ASTM:D-1557) as a
standard, we recommend that trench backfill be compacted to the following
densities:
Backfill Depth Minimum Compaction
1 Upper 2 feet 95 percent
Below 2 feet 90 percent
' • Backfill Observation and Testing: An AGRA representative should be retained
to periodically observe the backfilling operation and perform a series of in-situ
density tests.
CLOSURE
The conclusions and recommendations presented in this report are based, in part, on the
explorations accomplished for this study. If variations in subsurface conditions are
encountered during earthwork, we may need to modify this report. Because the future
performance and integrity of the backfill depend largely on proper construction procedures,
monitoring by experienced geotechnical personnel should be considered an integral part of the
construction process. We are available to provide geotechnical monitoring and soil testing
1
I AGRA
_, Earth & Environmental
1
SVR Design Co. 1 1-0971 2-00
22 February 1995 Page 7
services during the excavation and backfilling phases of the project. If variations in the
' subgrade conditions are observed at that time, we would be able to provide additional
geotechnical recommendations to minimize delays as the project develops.
We appreciate the opportunity to be of service to you on this project. Should you have any
questions regarding this report or any aspects of the project, please do not hesitate to call.
' Respectfully submitted,
AGRA Earth & EnvironmentAl;
r
Vi
s M. Bri bine, P.E.
or Project Engineer
MEN
1 CT71-
�0 N
hurt D. Merriman,cpfe9
' Associate s �CC
`S h7A3� ;
EXPIRES 11 /20/np�
Enclosures: Figure 1 - Location Map
Figure 2 Site & Exploration Plan
Boring Logs B-1 and B-2
' Grain Size Distribution Graph
' JMB/KDM/lad
* AGRA
Earth & Environmental
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RZA-AGRA 71 NELSON PLACE STORM SYSTE
Wo• 1109 2 RAINIER AVENUE N. & NW. THIRD PLA
ENGINEERING 8 ENVIRONMENTAL SERVICES DESIGNI�JI�B RENTON, WASHINGTB.
11335 N.E. 122nd Way DRAWN
Suite 100 -- LOCATION MAP
Kirkland, Washington DATE JULJUL 19 }4 ,-...
98034-6918 SCALE N-T-S- FIGURE 1
w
U
Q
J
d
2
2 - STORY F-
BUILDING w
AUTO REPAIR m
t SHOP cr
F-
N"C SON p� — - Z
tq cF 1101 - �
T `-APPROXIMATE ALIGNMENT OF B'1
yWFST EXISTING STORM DRAIN
,
B-2 APPROXIMATE ALIGNMENT OF
PROPOSED STORM DRAIN
1
AUTO SALES LOT
Boom
RAINIER AVENUEnow
NORTH
N
LEGEND
B-2
1 BORING NUMBER AND APPROXIMATE
LOCATION
NELSON PLACE STORM SYSTEM
RZA-AGRA w.o. 1109712 RAINIER AVENUE N. & NW. THIRD PLACE
ENGINEERING BENVIRONMENTALSERVICES DESIGN JMB RENTON, WASHINGTON
11335 N.E. 122nd Way DRAWN DMW
Suite 100 SITE & EXPLORATION PLAN
' Kirkland, Washington DATE JUL 1994
BASED ON PLANS BY CITY OF RENTON, DATED 26 MAR. 62. 98034-8819 SCALE NT FIGURE 2
Nelson Race Storm
PROJECT: S stem Repair w-0. 11-09712-00 BORING NO. B- I
' l
STANDARDPENETRATION RESISTANCE
S011L DESCRIPTION W Page I 1
Blows per foot
' A .. Approximate ground surface elevation: Unknown
0 10 20 30 40 5oTESTING
4 Inches asphalt over medium dense,damp,
grayish brown,cobbly,sandy GRAVEL(Fill) ----------..........- .............................
----------....................................... ................................
-----------------------------------------------------------------------------............................. AFFt\
S-7
.....................i................................ -------
...............----------
-------------------------------------------Loose to medium dense,moist to wet,brown,
-
slity,fine SAND with trace roots S-2-
-------- --------------- -------------...................4...........--------..........
................
Becomes gray with rust mottling ..................... ..............................................................................
S-3
- --------------- ----------------- ....................................................
- 10 -
S-4
.................
------ ----------
Becomes wet to saturated
-----------------------..........
..............................................................................................
ATD T ...........
.....................
- 15 ----------------------------------------
Stiff,saturated,brownish gray,sandy SILT S-5—
T
- - --------- ...... --------- ------ .. ..............-----------
Boring terminated at approximately .............. .
76.5 feet ........... ...............................----------- ...............--- - --------
...........---------------------------------------------------------------
---- --------............
20 -
.....................
.....................................
--- -----------
------------------------------ .........................................
................................................---------------------------------
----------
..........--------.....................
------------------ ...........................
25
.........................................................................---------------------
.........................................................................----------------------
................................-------....................................................
.....................................................
........... ...........
30 0 10 20 30 40 50
LEGEND MOISTURE CONTENT
2-inch OD split-spoon sample Grain size analysis Plastic limit Natural Liquid limit -
RZA AGRA, Inc
Engineering&Environmental Services
Groundwater level
ATD at time of drilling 11335NE 122nd Way,Sulte 100
Kirkland,Washington 98034-6918
Drilling started: 15 July 1994 Drilling completed: 15 July 7 994 Logged by: MAW
Nelson Place Storm
PROJECT: System Repair W.O. 17-09772-00 BORING NO. B-2
PENETRATION RESISTANCE Page 1
SOIL DESCRIPTION STANDARD of I
ABlows per foot
Approximate ground surface elevation:Unknown 0 10 20 30 40 5cTESTING
0
4 Inches asphalt over 6 Inches sandy GRAVEL(R11)
-----------I--------------------.......... ...................I...........
------ --------- ................ ..........................................
Very loose to loose,moist,brown,silty,fine
............... ..........................................................................
SAND with some sandy silt Interbeds S-7
------------------------------................................. ..........
S-2
.......... ----------
...........................................
............. .....................
----------- ----------------------
Very soft,wet,dark brown,sandy silty PEAT with ............................ ........................................
some interbedded sandy SILT S-3
......................................................................----------------------..........
-------------------------------------------
- 10
Very loose to loose,wet to saturated,blue-gray
to brown,s1lty,fine SAND Interbedded with very S-4
-----------------------.................................
soft to soft,wet to saturated,blue-gray to
brown,sandy SILT ......---------------------------......................................................
--------------------------------------------------------------................................
....................-----------------------..................................
15
S-5 ATD
............................................................ ....................
..........................................................-----------
7.......... ......................-----------
-------------------------------------------
........... -----------
20 - Dense,saturated,rusty brown,silty SAND with
somegravel S-6 ................................-------------------........ ---------------------
- - --------................................ .......................
Boring terminated at approximately
21.5 feet ......................................................................................................
------- ...................................................................................
25
----------------.............................................-----------
--------------------............... .........................................
......................t.......... . ..............................................-----------
...... ......................................... ....................
30 -
D 10 20 30 40 50
LEGEND MOISTURE CONTENT
0 A
sample Grain
limit Natural Liquid limit
2-inch OD split-spoon sa Grain size analysis RZA AGRA, Inc
Engineering&Environmental Services
Groundwater level
ATD at time of drilling 11335 NE 122nd Way,Suite 100
Kirkland,Washington 98034-6918
Drilling started: 15 July 1994 Drilling completed: 15 July 1994 Logged by: MAW
G A N SIZE DIS R BUTI ON
SIZE OF OPEN NO IN INCHES U.S.STANDARD SIEVE SIZE HYDFK�R
36" 12" 6" 3" 1 1/2" 3/4" 3/8" 4 10 20 40 60 100 200
' 100 _ __
90
t 80 1
F—
' :r 70 4
60
m 1
W 50 `
Z \
Z 40 \
W
U
W 30
IL
20
10
0
1000.00 100.00 10.00 1.00 0.10 0.01 0.00
GRAIN SIZE IN MILLIMETERS
Coarse Fine Coarse Medium Fine Silt Clay
BQVLDER5 CODDLES GRAVEL SAND FINE RAIN D
tExploration Sample Depth Moisture Fines Soil Description
Fi B-1 S-1 3% 5% Sandy GRAVEL, some silt
—�—�—� B-2 S-1 13% 32% Silty SAND
Project: Nelson Place Storm System Repair
RZA AGRA, Inc.
Work Order: 11-9712-00 L^%k Engineering & Environmental Services
' Date: 7-18-94 11335 N.E. 122nd Way
Suite 100
Kirkland, Washington 98034-6918
t