HomeMy WebLinkAboutSWP272330(6) ' ,n employed owrad mm,"any
TECHNICAL MEMORANDUM
' Date: Initially Issued 11/14/06, Reissued 1/30/07
To: Allen Quynn and Ronald Straka, P.E.
' From: Brendan Fisher, PE, LEG and Robert Plum, PE
Subject: Conceptual Recommendations for Erosion Mitigatio 40663 w�
th
' 3209 NE 4 Street, Renton, WA �or�����.
Attachments: Figures 1-6 Site Visit Photographs
wl
Construction Cost Estimate (Addendum 11/16/06) Expi�z�s:_12-3 -0
' SUMMARY
Kleinfelder visited 3209 NE 4th AVE on November 13, 2006 to assess an unstable slope
south of the MacDonald's restaurant. In our opinion, erosion of the slope occurred
' because of heavy rains on November 6, 2006. The slope repair should consist of filling
in the erosional gully. The parking stalls north of the unstable slope should remain
flagged off until the repair is complete.
' INTRODUCTION
During the rainstorm that occurred November 6 2006, the Seattle area recorded record
rainfall. The Seattle-Tacoma airport reported 3.29 inches of rain that day. This intense
rainfall caused the storm systems in Monroe Avenue NE and NE 4th Street in Renton,
WA to reach capacity and ponding was observed south of NE 4th on Monroe Ave NE at
' a low point on the west side of the street. Reportedly, ponding exceeded the top of the
curb and back of the sidewalk and flowed onto the adjacent property; 3209 NE 4th
' Street. Water flowed on the southern boundary of 3209 NE 4th Street and then south
over an approximately 50-foot high 1.5.1 (H- V) or slightly shallower gravel pit slope and
down into the gravel pit below. The quarry, which is not currently in operation, is called
the Balch Pit and owned by LaPianta LLC.
The floodwaters that flowed down the pit slope caused the slope to erode resulting in an
8 to 15-feet deep erosional gully. A six-foot wide zone of the MacDonald's property slid
' down into the pit. Power conduits and irrigation lines that were buried a few feet below
the ground surface were exposed at the slope crest. The MacDonald's has parking
' 77590/SEA7M010.doc Page 1 of 5 January 30,2007
Copyright 2007 Kleinfelder, Inc.
stalls approximately 10-feet from the top of the erosional gully. The stalls have been
' flagged off based on safety concerns.
According the City of Renton, a similar storm event in February 1996 caused similar
' erosion. A topographic map provided by the City of Renton showed that the erosional
gully formed in 1996 was in essentially the same location as the gully that formed during
tthe November 6th storm. It is unclear how the previous erosional gully was mitigated.
KLEINFELDER'S SCOPE OF SERVICES
' Kleinfelder was requested via email from Ronald Straka of the City of Renton Surface
Water Utility Engineering to visit the site and to provide opinion regarding the cause of
' the erosion. Mr.,Straka requested that we author this technical memorandum providing
a conceptual design and material specifications for the slope repair.
' Mr. Brendan Fisher of Kleinfelder visited the site with Allen Quynn and Ronald Straka of
the City of Renton on November 13, 2006 to view the eroded area from above and
' behind the MacDonald's restaurant. Mr. Fisher returned later that day and met with
Mark Hancock of Segale Properties who granted Mr. Fisher access to the quarry.
' PROBLEM DEFINITION
' The slope adjacent to the southern boundary of the MacDonald's restaurant is underlain
by glacial till consisting of silt, sand, and gravel that is heavily overconsolidated. Figure
1 is a picture taken looking west at the quarry slope and erosional gully from Monroe
Street.
' As discussed above, the subject slope was heavily eroded during the rain event on
November 6, 2006. Water entered the southern portion of the MacDonald's property
from Monroe Street. Figure 2 is a picture taken from Monroe Street looking west. The
erosion undermined a chain link fence between the MacDonald's property and the Balch
Pit. The parking stalls adjacent the erosional scarp have been flagged off because of
safety concerns. Figure 3 is a picture of the eroded area taken from behind the
MacDonald's parking lot. Figure 4 shows the parking stalls that have been flagged off
' because of the unstable slope.
The erosional gully extends down the 50-foot slope south of the MacDonald's restaurant
' and at the top of the feature, the soil has formed a near vertical scarp that appears
unstable and will likely ravel with time; eventually seeking equilibrium at a 1.5:1 (H:V) or
' shallower slope. We noted ground cracking about 3 feet north of the scarp suggesting
77590/SEA71VI010.doc Page 2 of 5 January 30,2007
Copyright 2007 Kleinfelder, Inc.
that the scarp is not stable. Given the close proximity to the MacDonald's parking lot,
' this suggests that a portion of the parking lot will be undermined if the slope is not
mitigated. At the base of the gully, there is an area of saturated soil debris that was
generated from the slope erosion. Figure 5 is a photograph taken from the base of the
quarry looking north at the gully. Figure 6 is a similar picture with a geologist in the
erosional gully for scale.
' Based on estimated heights of the erosional gully sidewalls and gully width we estimate
9 9 Y 9 Y
' that approximately 400 to 500 cubic yards of material was washed down to the base of
the quarry. Figure 7 shows a cross-section of the erosional gully.
tGEOTECHNICAL RECOMMENDATIONS
Water that ponds along Monroe Street in the future should be rerouted so that it does
' not enter the MacDonald's property. This may be accomplished temporarily by placing
sandbags on the eastern edge of the MacDonald's property or on the sidewalk adjacent
' Monroe Street. A more permanent solution may be to construct a concrete curve on the
eastern edge of the MacDonald's property. A civil engineer should be consulted to
estimate the height of the curb required for a given storm event.
The erosional gully should be filled in with engineered fill and quarry spalls forming a
' slope no steeper than 2:1 (H: V). As added protection, the City may consider armoring
the completed slope with riprap. The riprap would not be necessary if water can be
' diverted away from the slope during future storm events. The reconstructed slope
should be seeded to enhance erosion control if the City does not choose to armor the
slope with riprap.
t The parking lot behind MacDonald's is susceptible to erosion and being undermined
until the slope is repaired. Therefore, the parking spaces that are currently flagged
should remain blocked off until the reconstruction is completed.
CONCEPTUAL DESIGN
Figure 8 is a sketch of the reconstructed slope. Conceptually, reconstruction of the
' slope should include the following:
1. The wet soil debris at the base of the slope should be removed.
' 2. To facilitate filling in the gully, a construction ramp should be built at the base of
the slope. Materials for the ramp may consist of select borrow material or
77590/SEA71VI010.doc Page 3 of 5 January 30,2007
Copyright 2007 Kleinfelder, Inc.
' within he quarry that is not saturated and can be compacted
existing soli from wlt t q ry p
' well enough to support the heavy equipment.
3. The gully should be filled by placing 12-inch lifts of select granular material
' conforming to WSDOT Standard Specifications Section 9-03.14(2). The select
granular fill (borrow) should be benched into the firm glacial till and compacted to
about 92 percent dry density as determined by ASTM D-1557.
' 4. Near the crest of the slope, the eroded area may be too narrow for larger
construction equipment. Quarry spalls conforming to WSDOT Standard
' Specifications Section 9-13.6 could then be placed in the gully from above in 12
to 18 inch lifts and compacted using a small vibratory compactor.
5. Once the slope is brought up to the elevation approaching the MacDonald's
parking lot, the electrical conduits and irrigation lines could be repaired.
' 6. The finished 2:1 slope may be armored with riprap conforming to WSDOT
Standard Specifications Section 9-13.7(1) or seeded to help prevent subsequent
erosion and raveling of the newly constructed slope.
' LIMITATIONS
' Recommendations contained in this memo are based on a limited field reconnaissance
and our understanding of the proposed project without the benefit of subsurface
' exploration or laboratory testing. The investigation was performed using a mutually
agreed upon scope of services, which included two site visits and discussions with the
City or Renton staff. It is our opinion that this study was a cost-effective method to
' evaluate the subject site and for the purpose of providing a conceptual design.
' If geologic conditions are encountered during construction at this site that are different
from those described in this memo, our firm should be immediately notified so that we
may make any necessary revisions to our recommendations.
The scope of our services does not include services related to construction safety
1 precautions and our recommendations are not intended to direct the contractor's
methods, techniques, sequences, or procedures.
This report has been prepared for use in project planning for the City of Renton in
accordance with the generally accepted standards of practice at the time the memo was
' written. No warranty, express or implied, is made.
' 77590/SEA71VI010.doc Page 4 of 5 January 30,2007
Copyright 2007 Kleinfelder, Inc.
1
1
CLOSURE
1 We appreciate the opportunity to provide geotechnical engineering services to the City
of Renton Maintenance Services Division. If you have any questions or require
clarification, please contact Brendan Fisher at 425.562.4200 (office) or 425.283.9203
(cell).
1
1
1
1
i
1
1
1
1
1
' 77590/SEA71VI010.doc Page 5 of 5 January 30,2007
Copyright 2007 Kleinfelder, Inc.
1
r
� Pt
4
wr
t X
0
UI�
�4wr'V
Notes:
Picture from Monroe Street looking west at the quarry north slope.
The MacDonald's restaurant is to the right of the picture.
' KLEINFELDER Eroded Quarry Slope FIGURE
' Slope Erosion 1
PROJECT NO. 77590 November, 2006 3209 NE 4t" Street, Renton WA
t
--------------- ..............
y
Notes:
' Looking west towards the MacDonald's Property. Water reportedly
entered the property just to the north of the property boundary fence.
' 111 KLEINFELDER Erosion Looking North FIGURE
' Slope Erosion 2
PROJECT NO. 77590 November, 2006 3209 NE 4th Street, Renton WA
i
7
p�
i }
t
't
F
e
� t
Notes:
' Erosional feature measures about 6-ft by 3-ft at the top of the slope
on the south side of the MacDonald's property. The gray pipes are
' probably utility conduits. The white pipe and wire is for the
irrigation system.
' ]kn KLEINFELDER Erosional Scarp FIGURE
Slope Erosion 3
PROJECT NO. 77590 November,2006 3209 NE 4th Street, Renton WA
' •� ^yet. .. . -'. -
Ar
1 '
ei
y
7
a
n .
c
0
'till
• , • Flagged Off Area
Slope Erosion
PROJECT • 77590
November 2007*11 1 3209 NE 411 Street, Renton WA
1
1
1
r
i �F
h ty
�� ♦ 1 iY
t
1
1
Aw
1
Notes:
1 Looking North at the quarry slope.
1 FIGURE
1
Ilk" KLEINFELDER Eroded Quarry n e Slope Erosion 5
3209 NE 41h Street, Renton WA
PROJECT NO. 77590 November, 2006
•r .� r '.r.,
h
Notes:
' Gully side walls range in height to about 15 feet on the west side of
the erosional feature.
' �� KLEINFELDER Eroded Quarry Slope FIGURE
Slope Erosion s
PROJECT NO. 77590 November, 2006 3209 NE 4t" Street, Renton WA
u
O �
W W r�CjU1L.6r
0 0
F--
W
W
A vt yf vtr
�r�A
uj
a
W C�
To ies
Z B a
W s
m
o F C, YL
w w
w _
2
cn
t
Z
w
cc w Z _
a m a ,
// L G Q.SOTad xi t.f-o
S�b��r �o►trt.o� �
OS W SrAt4OA-L4 5POe� 5
�W.
LLJ v3 a CQvrr9r.�r<N 3pi4l
� �` c,, C'�t� , ri?�� �.��R,�A 5i�cr�an( �-t� .�L�) Of►rzQn1��. _ _
uj
C�
Z L' t.tF
W p _
J w
W
a co v
Page 1 of 1
Jamie Warren - Re: NE 4th and Monroe Cost Estimate
From: Bob Plum
To: Allen Quynn; Brendan Fisher
' Date: 11/16/2006 2:51:21 PM
Subject: Re: NE 4th and Monroe Cost Estimate
CC: Brendan Fisher
Allen:
' Our cost estimate is based on
. Unit prices for larger projects from WSDOT, we increased all unit prices by 25% to account for the small
' volumes.
. Based on a unit price sheet from WSDOT, quarry spalls are less expensive than placing and compacting
select fill. Thus we have assumed that virtually all of the backfill will be quarry spalls assuming the
' aesthetic is not a problem (Can't really see slope anyway).
Place 2 feet of quarry spalls over lower portion of slope below failure to protect the slope from future
water damage
. The debris from the slide will be excavated and hauled off the site. There would be a saving if the
material was just spread around, seeded and left on site.
. We assumed some nominal excavation to remove debris, vegetation, and soils to form a uniform,
' benched surface to place the quarry spalls on. We assumed that this excavated material would also be
removed from the site.
. A nominal cost to repair the fence.
. We include no costs associated with paving repair or repair of expose pipes.
In general, the most effeciant construction might be for a large excavator to work from the bottom of the slope
and up to slope to clear away debris and exisitng slopes to form the uniform, benched surface to Place the
' quarry spalls on. The quarry spalls could then be dumped from the top and/or placed from the bottom.
Based on visual approximations, a rough cost estimate is:
' General Mobilization and Misc. $ 7,500
Slope excavation and Benching 125 cy x $20/cy= $ 2,500
Removal of Slide Debris at toe 400 cy x $20/cy= $ 8,000
' Quarry Spalls 700 cy x $15/cy =$10,500
Fence Repair $1,500
Trackhoe (guesstimate) 24 hrs x $250/hr= 6 000
1 Rough Estimate $36,000
Bob Plum
' Principal Professional
Kleinfelder
' Office Phone: 425-562-4200
Cell Phone: 425-417-2241
Fax: 425-562-4201
file://C:\Documents and Settings\JWarren\Local Settings\Temp\GW)00002.HTM 1/30/2007