Comment 1. SMC 25.09.110. Peat Settlement Prone Areas
Transcript of Comment 1. SMC 25.09.110. Peat Settlement Prone Areas
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3131 Elliott Avenue, Suite 600
Seattle, Washington 98121
Tel 206.324.9530
October 3, 2017
Mr. Tom Croonquist
University Village Partnership
2623 University Village Street, Suite 7
Seattle, WA 98105
Re: Response to SDCI Correction Notice #2
University Village Master Use Permit
Seattle, Washington
SDCI Project No. 3025629
17817‐23
Dear Tom:
This letter provides our geotechnical response to the attached Correction Notice #2 (CN2) from SDCI
geotechnical reviewer Dean Griswold, dated August 18, 2017. We understand the Dean did not review
the latest plan set when he created CN2; therefore, many of the comments in Correction Notice #1
(CN1) that were addressed in the submitted drawings are repeated in CN2. This letter supplements our
February 27, 2017 report and our May 3, 2017 letter response to CN1. The purpose of this letter is to
present new information. Therefore, we do not repeat items discussed in our prior documents.
CN2 has two comments. Portions of the comments will be reflected in the revised drawings. Our
responses to portions of the comments are shown below following the comment number and heading.
Comment 1. SMC 25.09.110. Peat Settlement Prone Areas Drawing updates will be performed by SWW. Here we present updated groundwater elevation data and
discuss construction for the West Garage (Building 1).
Groundwater Data
We collected updated groundwater data to support a design annual high groundwater level that can be
expected near the West Garage at University Village. Our previous estimate for this was elevation
29 feet NAVD 88, based on historical water level measurements and observations in monitoring wells
and borehole explorations that extended below the peat into a lower aquifer that had a higher water
head than anticipated in the near surface soils.
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S H U G A R T
W A S S E
W I C K W I R E
architecture & interiors
605 Western Avenue, Su i te 200 Seatt le , WA 98104 P : 206.264 .7744 sww-ai .com
Job No. 1523 1 of 2
Date: October 6, 2017
To: Dean Griswold, SDCI
c/o Andy Paroline
University Village Master Use Permit
SDCI Correction Notice Response Summary
Re: Correction Notice #2 ECA LIQFAC, ECA PEAT, ECA LANDFL
August 18, 2017
Project #3025629
Item Description
General note: we understand that the previous ECA review may not have been looking at
most current plans due to a mix-up on the SDCI documents server. We, with Hart Crowser,
have made every effort to understand and respond to ECA concerns. Please get in touch
directly if further discussion can resolve concerns before issuing another correction notice.
1. SMC 25.09.110. Peat Settlement Prone Areas (repeated and revised item). On the cross-
sections for the proposed buildings and the site development area, show the line of annual
high groundwater level, which is determined by the geotechnical engineering report. The
cross-sections need to show the development above annual high groundwater level. Only
foundation elements, and utility connections may be below groundwater level. SDCI noted
that many plan sheets include cross-sections that include an item "AHGL." This term
might not be familiar to people who are using the plan set. If this abbreviation is to identify
the Annual High Ground Water Level, please spell out this item on the cross-
sections. This applies to cross sections on Sheets 50, 59, 61, 66, 67, 69, 74, 75, 77, 82, 83,
85, 90, 91, 91, 93, 98, 99, and 101.The methane-mitigation measures should be shown in
concept on the plans. These measures need to be above the annual high groundwater level.
Add a note to the plans with the requirement that groundwater collection systems are
prohibited in peat settlement-prone areas. The Environmentally Critical Areas Regulations
includes the provision that in Category II Peat Settlement Prone Areas, some of the Peat
Hazard Area requirements may be waived if the applicant demonstrates that the project has
been designed to avoid adverse impacts to nearby areas due to peat settlement. See SMC
25.09.110.I. If you want to pursue waiver of some of the requirements of the Peat Hazard
Area Development Areas, please identify those items and update the plans accordingly.
A. Please see attached response letter from the geotechnical engineer. Section
drawings have been revised to clarify annual high groundwater level in relation to the
building foundations. As described in the engineer’s response letter and plans, and as
verbally supported by the Engineer’s discussion with ECA reviewer, we are seeking a
partial waiver for subsection D. See revised detail/notes provided on section sheets
(typically Ax-301).
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605 Western Avenue, Su i te 200 Seatt le , WA 98104 P : 206.264 .7744 sww-ai .com
Job No. 1523 2 of 2
2. SMC 25.09.110. Foundations (repeated item). Show deep foundation systems, in concept, on
the plans. The deep foundation systems are needed to mitigate potential settlement
associated with the peat soil unit and other weak subgrade soils.
A. These sheets were included with the previous CN response but (we believe) not seen
by the reviewer due to the SDCI portal mix-up. Conceptual structural foundations are
shown on sheets S1.0 and S2.0 for buildings 1, 2 and 6. Deep foundations for the
remaining buildings are largely identical to building 6.
Additional clarifications:
1. In CN1 and CN2 response, Building 1 (West Garage) was split into buildings 1 and 2 to facilitate
construction sequencing. Buildings 2-6 have been re-numbered 3-7.
Please get in touch if any further clarification is needed.
Thank you,
Chris Ford, Senior Associate
Shugart Wasse Wickwire
Please contact our office regarding any errors or omissions.
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University Village Partnership 17817‐23
October 3, 2017 Page 2
Since our response to CN1, we have drilled and installed four additional monitoring wells near the West
Garage site, as shown on Figure 1. Groundwater monitoring instrumentation was installed in three
shallow wells on site and one deep well in July 2017. The shallow monitoring wells (HC‐1‐17MW,
HC‐3‐17MW, and HC‐4‐17MW) were outfitted with pressure transducers to capture fluctuation of the
water table near the ground surface over time. The deeper well (HC‐3‐17) was instrumented with two
vibrating wire piezometers (VWPs) at depths of 25 and 75 feet below ground surface to monitor the
deeper groundwater in the dense sandy layer below the peat. Groundwater monitoring results are
shown on Figure 2.
Data collected from the instrumentation on site indicate two distinct groundwater sources: 1) a
near‐surface aquifer above and within the peat layer and 2) a deeper, more confined aquifer in the
dense sands that has a higher pressure head than the near‐surface aquifer. The range in near surface
groundwater is from elevation 25.7 to 27.2 feet NAVD 88 in August and September 2017. Data from the
shallow monitoring wells should be used for the annual high groundwater elevation, because the deeper
water conditions are not representative of near‐surface groundwater conditions. The highest measured
elevations from the shallow monitoring wells are listed in Table 1. Additional data will be collected
during the wet season to determine the design annual high groundwater level. Although the presented
data were collected in the dry season, we expect that the design annual high groundwater level can be
lowered from our prior estimate of elevation 29 feet.
Table 1 - High Groundwater Elevation Measurements (West Garage)
Monitoring Well/Boring ID
Ground Surface Elev. (feet)a
Groundwater Elev. (feet)a
Date Recorded
HC-1-17MW 28 27.26 9/10/2017
HC-2-17MWb 28.5 27.1 8/11/2017
HC-3-17MW 28.5 26.77 8/16/2017
HC-4-17MW 27.7 26.83 9/10/2017
Notes: a. All elevations are based on the NAVD 88 datum. b. Not outfitted with pressure transducer, measured with discreet manual readings.
We understand the West Garage will have a finished floor elevation of 28 feet. This is raised 15 inches above
the finish floor elevation for the adjacent Restoration Hardware Building. We expect that this will allow for a
capillary break layer with drains to be installed below the West Garage, similar to what was used for the
Restoration Hardware Building. The installation of this system will not significantly lower the seasonally low
water table, because the new groundwater data show that the water level is seasonally more than 1 foot
below the elevation 28 feet West Garage finish floor. Because the water table is not considerably lowered,
this system should not significantly increase settlement of the peat. Therefore, we recommend a waiver of
the prohibition of subslab drainage for this peat settlement‐prone area at the West Garage site.
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MW-2
HC-105
HC-109
HC-108
HC-110
HC-106
HC-107
HC10-1
HC10-2
HC15-101
HC15-102
HC-3-17MW
HC-1-17MW
HC-2-17MW
HC-1-17
HC-3-17
HC-4-17
HC-2-17
(27')
(26.5')
(25.5')
(27')
HC-4-17MW
N
0 40 80
Scale in Feet
Figure
17817-23 10/17
University Village - MUP
Seattle, Washington
1
Site and Exploration Plan - West Garage (Building 1)
File: L:\N
otebooks\1781727_U
Village W
est G
arage E
xploration_D
esign\C
AD
\1781727-002 (S
Plan).dw
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D
ate: 09-26-2017 A
uthor: ericlindquist
Explorations by Hart Crowser
HC-111
Explorations by others
Monitoring Well, Dames &
Moore, 1993
MW-1
Boring, 2017
Monitoring Well, 2017
Average Low Groundwater Elevation
Boring, 2015
Boring, 2010
Boring, 1994
HC10-1
HC-15-1
LEGEND
Proposed Building
Abandoned Landfill Buffer
HC-1-17
HC-1-17MW
25
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A
ve
nu
e N
E
A A'
Cross Section Location
and Designation
C
C'
B
B'
A
A'
NE 49th Street (Private)
Source: Basemap prepared from AutoCAD survey file
"X-49 UV-SVY.dwg," created by Bush, Roed & Hitchings.
Building 1
West Garage
(27')
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Gro
un
dw
ater Elevatio
ns in
Mo
nito
ring
Wells
(West G
arage/Building 1)
University V
illage - MU
P S
eattle, Washington
17
81
7-2
3
2 Fig
ure
10
/2/1
7
0
1
2
3
4
5
6
24
25
26
27
28
29
30
8/11/2017 8/18/2017 8/25/2017 9/1/2017 9/8/2017 9/15/2017 9/22/2017
Da
ily P
rec
ipit
ati
on
(in
)
Gro
un
dw
ate
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leva
tio
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ft)
Precipitation HC-1-17MW HC-1-17MW - Manual HC-2-17MW - Manual HC-3-17MW HC-3-17MW - Manual HC-4-17MW HC-4-17MW - Manual HC-3-17 VWP#1 (25ft) HC-3-17 VWP#2 (75ft)
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City of SeattleDepartment of Construction and InspectionsEngineering Services
ANDY PAROLINE3617 SW Charlestown StSeattle, WA 98126
Re: Project# 3025629
Correction Notice #2
Review Type ECA LIQFAC, ECA PEAT, ECALANDFL
Date August 18, 2017
Project Address 4500 25th Ave NE Contact Phone (206) 719-0339
Contact Email [email protected]
Contact Fax
SDCI Reviewer Dean Griswold Address Seattle Department ofConstruction andInspections700 5th Ave Suite 2000PO Box 34019Seattle, WA 98124-4019
Reviewer Phone (206) 233-7862
Reviewer Fax
Reviewer Email [email protected]
Owner UNIVERSITY VILLAGE LP
Applicant Instructions
How to Respond to a SDCI Correction NoticePlease see the attached flyer to learn " ".If the 3-step process outlined in the aforementioned document is not followed, it is likely thatthere will be a delay in permit issuance and there is a potential for penalty fees.
Codes Reviewed
This project has been reviewed for conformance with one or more of the following codes: GradingCode; Environmentally Critical Areas Regulations (ECA).
Corrections
1 SMC 25.09.110. Peat Settlement Prone Areas Repeated and Revised Item On the cross-sections for the proposed buildings and the site development area, show the line ofannual high groundwater level, which is determined by the geotechnical engineering report. Thecross-sections need to show the development above annual high groundwater level. Onlyfoundation elements, and utility connections may be below groundwater level.
Project# 3025629, Correction Notice# 2Page 1 of 2
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SDCI noted that many plan sheets include cross-sections that include an item "AHGL." This termmight not be familiar to people who are using the plan set. If this abbreviation is to identify theAnnual High Ground Water Level, please spell out this item on the cross-sections. This applies tocross sections on Sheets 50, 59, 61, 66, 67, 69, 74, 75, 77, 82, 83, 85, 90, 91, 91, 93, 98, 99,and 101. The methane-mitigation measures should be shown in concept on the plans. These measuresneed to be above the annual high groundwater level. Add a note to the plans with the requirement that groundwater collection systems are prohibitedin peat settlement-prone areas. The Environmentally Critical Areas Regulations includes the provision that in Category II PeatSettlement Prone Areas, some of the Peat Hazard Area requirements may be waived if theapplicant demonstrates that the project has been designed to avoid adverse impacts to nearbyareas due to peat settlement. See SMC 25.09.110.I. If you want to pursue waiver of some of therequirements of the Peat Hazard Area Development Areas, please identify those items and updatethe plans accordingly.
2 SMC 25.09.110. Foundations Repeated Item Show deep foundation systems, in concept, on the plans. The deep foundation systems areneeded to mitigate potential settlement associated with the peat soil unit and other weaksubgrade soils.
Project# 3025629, Correction Notice# 2Page 2 of 2