HomeMy WebLinkAboutSWP272327(1) i I
GURUDWARA SINGH SABHA OF WASHINGTON
WETLAND DELINEATION AND MITIGATION REPORT
Prepared For:
GURUDWARA SINGH SABHA OF WASHINGTON
Renton, Washington
Prepared By:
TALASAEA CONSULTANTS
Woodinville, Washington M4Y B
1996
OV C17Y�FRFN .01V
April24, 1996
Table Of Contents
Page
1.0 INTRODUCTION I
2.0 GENERAL PROPERTY DESCRIPTION AND LAND USE 1
3.0 METHODOLOGY 1
3.1 Background Data Reviewed 2
3.2 Field Investigation 2
4.0 RESULTS 3
4.1 Analysis of Existing Information 3
4.2 Analysis of Field Conditions 3
5.0 WETLAND FUNCTIONS AND VALUES 5
6.0 PROPOSED PROJECT 6
6.1 Description 6
6.2 Development Impacts on Wetlands 6
7.0 WETLAND MITIGATION/RESTORATION 6
7.1 Goals and Objectives 6
7.2 Construction Management 7
7.3 Monitoring Methodology S
7.4 Success Criteria R
7.5 Maintenance (M) and Contingency (C) 9
7.6 Performance Bond 9
7.7 As-Built Plan 9
List Of Tables
Table 1. Wetland Functional Value Ratings 5
References
List Of Figures
Figure 1: Vicinity Map
Figure 2: Location Niap
Figure 3: National Wetlands Inventory Map
Figure 4: Soils Map
Figure 5: Wetland Map
Figure 6: Wetland Mitigation Map
List of Drawings
Drawing WI.O: Conceptual Wetland Mitigation/Restoration Plan
1 1
GURUDWARA SINGH SABHA OF WASHINGTON
WETLAND DELINEATION AND MITIGATION REPORT
April24, 1996
1.0 INTRODUCTION
This report is the result of a wetland inventory and delineation on an approximately
6.2-acre site located in the City of Renton, Washington (Figure 1). The site is
proposed for construction of a new Sikh Temple.
The purpose of this report is to: 1) describe the wetlands identified and delineated on
the property, 2) identify wetland impacts from previous un-permitted activity on the
site, as well as impacts from the proposed development, 3) describe measures
which will be implemented to mitigate wetland impacts from the proposed develop,
and 4) describe measures which will be taken to restore wetlands previously
impacted during the un-permitted on-site activities. Information in this report will be
utilized by the City of Renton, the Corps of Engineers, and any other concerned
agencies to evaluate impacts to wetlands on the project site.
2.0 GENERAL PROPERTY DESCRIPTION AND LAND USE
The site is located in the City of Renton in King County, Washington (Section 31.
Township 23N, Range 5E, W.M.). It consists of the existing Gurudwara Singh Sabha
facilities at 5212 Talbot Road, and adjoining open space areas area to the east
(Figure 2).
The site is bordered by a single family residential development to the north,
undeveloped forested land to the east, and a single family residence to the south.
The majority of the property, with the exception of the far eastern section, has been
cleared and graded in the past. Topographically, the property slopes down
moderately toward Talbot Road. The site is situated at the base of the steep , west-
facing forested side slope of the Kent Valley. A portion of the property extends up
the forested slope.
3.0 METHODOLOGY
The wetland analysis of the subject property involved a two-part effort. The first part
consisted of a preliminary assessment of the site (and its immediate surroundings)
using published information about local environmental conditions. This information
included: 1) wetland and soil maps from resource agencies, 2) wetland map from the
City of Renton, and 3) any relevant studies completed or on-going in the vicinity of
the project site. The second part involved a field survey in which direct observations
and measurements of soils, hydrology and vegetation were made to determine
whether wetlands were present, the types and functional values of these wetlands,
and the extent of the boundaries (see Field Investigation section below).
1
r
5
Z MONROE
�o
s
WOODINVILLE
BOTHELL N
0
N
REDMOND
T:FC E BE:LLEVUE
I
BARE M E
PRESTON�
ISSAQUAH
�
:•;a>:•;:•:...s : RENT N
4' Troje Site
• KENT
rss
DES;:M,OINES
516
• AUBURN
18 Ij
TAC MA i
D614-' DRAWN
FIGURE 1: Vicinity Map AO
®TALASAEA Gurudwara Singh Sabha SCALE FlCU /DWG NO
CONSULTANTS Renton, Washington wh j
Re ura&EnNrcnmenWPla ning 4-16-96 -f-
�xneao.aawH.aea
REMfO
M s SE 125TN ]I
slr 3 s7 Cl 176TI - 5T si
SN v4` 41ST ST ST
I S _ 3 LT
bg
¢ u.ru Is smnl u 1eoTM-si •sT SE 180T
1 _ SE=<182N0SE
� 5T
8 LL1I� I 'sa9M P � ]B3R0 e2b w
FI 31 ~�SE n PL _ N m
Project Site N ee IBM SE y SE 184TH" 3T
]B47H
SE PL 86TH ST SE 186TH E
f
s[m1M
o
S 18TTH 5i SE 189M Q =q 1 SE 188TH
s INN ST I -- � c 1 a> ST e iET sn CT
x sr u1e9M 4r,
SE
S_ 190TH_ST 1- 9oiH ST Q --
p ! IMN 5 SE- Y SF:90M vt
C
1 zxD S7S�Ssam—!�„, — _ SE _ = 192ND`--- ST
sH 194TH ST
S 396M ST SE]9ST1 = Si 197H ST
5 e,
S' 198TH ST Nr 98� BPN l > + .' 1 ` - SE Sr ism 51 yE
199TH
s m 2ooTH ST <I .I �I 6 - �1•• $ - SE ST 200TH ST =
SE
Q;M
rm I ��I I t Y yd � '" yr � •",',`,k s° zmsx"
S '202ND ST C 'e � a w s-
-�..".-_ . tt
i <I 5 20p� S y o` 203RD 1.5T x.• a $ o 0 o PAc Rf: � SE 203RD•Y.
K'' I '^ '� '' SE _ 20 - ST ST
& 6
.. s 1 xwM m 1T°°
s 20 i I -5 205TX P 7osx <$i ; n . _ .r'4t p n v.SESE Si
6�j ST JE5
T61" ---- rPAWR$ 2 fiN PL IARE 2fiIT N ST" 5[YS)M F CEM[N i06M Si F rn�;l _
5 ' 208 zom 2E $ SE g Y 208TH e,EEI�y{,,,n
S 209TH 'S 209 T F _ STN
ST Fig' �-
��K
L__��•• F S" .m 2E a � xUeTN
8 210'lH ST -
�} a PL� � � °E SE 211M 5T � 's Aa` Ex K SE 210TN'W^ PlN
S 212TH ST:ci $<� 6E 212ni ST x '>+^'G SE IIITM < PE ^
'Fr> b d M T SE ;. 222N ST : SE> E 213i Si . 4 n
5 214T s 219xR v + '`y >q 2 X 3 PL W°E„a °e x�n sus.: *� 1B5M =ST x Y xss,v s
p =n.
8
5 216TH SE 216TH ST
ST � \ 70.30DY,� LxE 27 T
---- 2 EN 5T a`
Source: The Thomas Guide, 1995 r
North
FIGURE 2: Location Map DESILTI ADINWN
®TALASAEA Genton, ra Singh Sabha �+ 2 °NQ
CONSULTANTS Renton, Washington 1"=2D00'
DATE
lt.'r &F.vironm<nwPhnning 4-16-96 2
lsex s�o.a a..2>.•ala.r -
w""i..nscw.a::CrpwT! ➢FRSFD
�PPq Mx•'1,)O.F.FPp YI•TSvr
i
3.1 Background Data Reviewed
Background information was reviewed prior to field investigations and included the
following:
• National Wetlands Inventory Map (Renton, Quad), U.S. Fish and Wildlife Service,
1988
• King County Soil Conservation Service, Soil Survey, 1973
• City of Renton Critical Areas Inventory Map, 1991
• Terra Associates, Inc., Wetland Evaluation on South 2.5 acres, Sept. 1994
3.2 Field Investigation
A preliminary wetland delineation was conducted on the northern portion of the site
in May 1995. Following un-permitted clearing and grading activities during the
summer of 1995, a stop work order was placed on the site by the City of Renton and
the Corps of Engineers. Several site visits were then conducted to assess impacts
to wetlands from the un-permitted activity. A,second delineation was conducted on
the entire site on February 13, 1996. The routine on-site determination method was
used to delineate the wetlands using the procedures outlined in both the Federal
Manual for Identifying and Delineating Jurisdictional Wetlands (1989) and the Corps
of Engineers Wetland Delineation Manual (1987).
Plant species were identified according to the taxonomy of Hitchcock and Cronquist
(1973), and the wetland status of plant species was assigned according to the
National List of Plant Species that Occur in wetlands, published'by the U.S. Fish and
Wildlife Service classification system (Reed; 1988, 1993). Wetland classes were
determined on the basis of Cowardin's system of wetland classification.
Vegetation was considered hydrophytic if greater than 50% of the dominant plant
species had a wetland indicator status of facultative or wetter (i.e., facultative,
facultative wetland, or obligate wetland). Soil on the site was considered hydric if
one or more of the following characteristics were present:
• organic soils or soils with an organic surface layer,
• matrix chroma just below the A-horizon (or 10 inches, whichever is less) of 1 or
less in unmottled soils, or 2 or less if mottles were present, or
gleying immediately below the A-horizon.
Indicators of wetland hydrology may include, but are not necessarily limited to:
drainage patterns, drift lines, sediment deposition, watermarks, stream gauge data
and predicted flood elevations, historic records, aisual observation of saturated soils,
and visual observation of inundation.
An evaluation of the vegetation, soils and hydrology was made at various locations
along the interface of wetland and upland. Wetland boundary points were then
determined from this information. Wetland boundaries were marked with flagging
and surveyed.
2
4.0 RESULTS
4.1 Analysis of Existing Information
National Wetland Inventory (NWI) maps,developed by the US Fish and Wildlife
Service (USFWS) do not indicate that any wetlands are located on the project site
(Figure 3). The City of Renton Critical Areas Inventory map also does not indicate
that any wetlands occur on the site. Since these maps are only general inventories
based largely on aerial photographs, and because wetland areas change over time,
actual field investigation was necessary to ensure that any wetlands were identified.
The Natural Resources Conservation Service (MRCS; formerly the SCS) has
mapped the majority of the site as Alderwood gravelly sandy loam, 6 to 15 percent
slopes (AgC) (Figure 4). A small portion of the site, along its eastern edge, is
mapped as Alderwood gravelly sandy loam, 15 to 30 percent slopes (AgD). The
Alderwood series is made up of moderately well drained soils that are not classified
as hydric by the NRCS, but hydric soils may be found within this series as mapped or
un-mapped inclusions.
4.2 Analysis of Field Conditions
Four wetland areas (Wetlands A, B, D, and XNJwere identified and delineated on
the project site (Figure 5). Each of these wetland areas is described below.
Wetland A
This wetland (approx. 29,500 sf on-site) is located at the base of the forested hillside
in the eastern portion of the site. Hydrologically, this wetland is supported by
groundwater seepage from the base of the steep slope. Much of this water is
collected in an excavated ditch along the toe of the slope in the southeastern portion
of the site (Figure 5). Approximately 11,200 sf of this wetland was cleared and filled
during the summer of 1995 (Figure 6). As part of the requirements of the City of
Renton, the original wetland area will be restored. This proposed restoration is
shown on the enclosed Drawing 1.0.
Vegetation in the undisturbed portion of the wetland is forested and is dominated by
red alder (Alnus rubra), western red cedar (Thuja plicata), vine maple (Acer
circinatum), salmonberry (Rubus spectabilis), skunk cabbage (Lysichitum
americanum), slough sedge (Carex obnupta), and lady fern (Athyrium filix-femina).
Soil borings taken in the wetland generally revealed a black (10YR 211) silt that was
often high in organic matter. At the time of the February 1996 field investigations,
soils were generally saturated to the surface throughout the wetland.
Wetland A is rated as a Category 11 wetland according to the City of Renton's
Wetland Ordinance. Category II wetlands require a 50-foot buffer.
Wetland B
Wetland B (13,019 sf on-site) is associated with a small drainage which flows from
east to west near the site's northern property boundary. Most of the vegetation
3
,
ty,r •30 IBH
nn • 16 2
PEMA
UBHrPEMC
1 I Po ... .;Y:....:
;KM
MC (17 ' -ro ect Site •� .. . . ....
:444
\ -.�
PEM PFOC 1 . . r
^1 Cx
A air.: I I �}t •t
w
PFOC
1
EIAC '.. EKCI R3UBH •�I' •. h:-
PfdC
6)•PEl1C '. i�• � _
�__- - • • , e • •PAE•
rt ?EMC
' Drive•i I :�.I �1�//�--�\,\lU}'t\ �•:, ' . 455( ��\ —•.: _ t
o
'Trle&ter� Ell:
,,,I •' ',.d
-PEMG _ ------ "• c 'I PL 2•A0 I �'
24 flik .
z .. I. .�' 1 �_ �: .'� '.:• Sty Ps C
PAlN
pubm wee
t ( ] ..•..-. PEMA •'\
Source: United States Department of the Interior,
Fish & Wildlife Service, Renton Quadrangle 1988
North
i
5FSIC•1 DRAW
FIGURE 3: National Wetlands Inventory Map O'
1�C Ifi1TALASAEA Gurudwara Singh Sabha SCATS FIGURE/DWCNO
CONSULTANTS Renton, Washington 1�'�2000' 4
Resource&Esvironmentd Planning 4-16-96 J
IfOX Id DM AW1l.Yv1
ED
v..c.,aww•.w:,• n REY6
y peq ul•1fH.fe Qu1 ul-1Nf
\ - p 1203 A C zy AgB •
PY I g y
Sk
Ur I o IAgC„
r { a0 i i .•.tom 'r AmC .Y�:
TY • I 1. ..
t _ InC 1 AB o •
x So - I AgD Am8 t �•',.,
___
Y 1 ; 3 Am8 I
I
AgC^w;r":�•
Ur I a. 7• j I o .0.�9 Am C"• a. :r
PY
NB B I Ur co
W. AgC• Y 1 2 ABl�c t 94
' roject ite B
g
N I ..•sr TaWaler• �L •�
WO a O I a„ nk• . '
Ur PY I as '- . AgC - .•
Os 1 mB
Sa So
I
AgC C.
Ma . ii l ABI
NAYCS
. 8 Ng _• 1 - 4515- ..
v � _
•• F ABC4
Pu °"O AmC •t `• No�•
N. AkF AgC AgB
I
At
OS __ 0 . • . . ,• , 9
NB Pc• C n ••Ag8 •1:.. .•1 •5 t pF l A,
® a
.. .. rWo AC
SO I
ABB tro t' i 11
AM 11
Uri yr Os AMC s : ••• p,�
$ •.. Wo O AMC e+
p r
r
I Ur
~ ••-qgD AgC •.� •ol '•••• 9�0
i ABC I Tu
Am
' • S•ry '• Amc A6 _ 1
Ur AMC, • o
AgO,/ •ABC Sk
AMC .-
_ Y. `•AMC
..
: 7 I
Source: United States Department of Agriculture, I
Soil Conservation Service, King County 1973
Soil Legend - j
AgC Alderwood gravelly sandy loam,6-15 % slopes North t
AgD Alderwood gravelly sandy loam, 15-30 % slopes
DESIGN I DRAWN
FIGURE 4: Soils Map
®TALASAEA Gurudwara Singh Sabha nciFF mvc a
CONSULTANTS Renton, Washington 1�'a2000'
Rtaoartt[.Fsvironmenlal Plann(ng 4-16-96 �T
1%Mlerod Wll:aUr
r..i,..5end+V�Iw]3 REVISED .
W OM MI•]]H•Fe f••q MI•]NI
�1
I SUM IT P RK RBv-�T.o4
,
/-UPLAND AREA \ \ ,
—
WETLAND B
Y
_i '� --- ---
WET;
13019 50 FT CLEARING LIMIT
�P
C.aG ACRES Y
¢w � � A ul �'I'� i WETLAND D—, '`I- .WETLAND-A, L
366.60 F4 L 24,506 Ed FT (o-dte) 1 I 1
OG I �^{}, ( ` 0.01 ACRES 1 I I _ p.67.AC RCS. •I' N
IEkCx19TIN6
f 1 \ I A ZEUILDIYGE l I A
.ti.526E
OA
in
le-
21
kir
l i I F
F _ _= .:aTERo 1 '.^ II VI ` f I ;� 1 I 1 A\vI
�I 1 I1 �vi 1
I I � I � .
p I
040
5 3l 3rl '6MP) _
So 1 BVILCING I JI
ni.1
3
1
RIM 139�3 G� I tp./ 1 .r
C 7 /
Y
> �I 2/ « 1E e 149 2s�
RIM 151 l
J35 Oy 1-12 �P'VG BRVG \ F W_h90T OUSE !
r =Y
cLo r;:.TER - �. A�', � "— - - --N�—'- 1 1 � 1 1 ti 1 1 ,r, •i V F A • • 1• y. �� I II� .�"�. ' . . , -
( W.ETLA[IldFT- /iY.1 . 11\ -
�� \�- 'E I I 1 �, 1 1 \ \ !�. •1� t 1 tt4f2 Bd FT• A\ 1( I
RIMg148.52' ( I , ` 1 \I .� i 1 0.21 hCR68 M .l `. •\; '•"'I .
I � 1 1
_ I I IE E=I4294' I I I I 1 � ` , 6 � ` / O I ' I' \ -
- I }
o1Tc BENCH MARK I l/� i IE N=143.7� I �_ � b �' �• _ '� I 1 I�I. •DITGK - 1
IN,PONE.R POLEKE I I /:FSC n \ \ 1 I l: `` ` 1 i 1 \... __\ ; ,-.♦ 1 ; - . . l• . �� I i( I .1 .I 1 1'i�Nl I� �I. . . 1
cL=13,.b, I \ \ I 1 11 11 1 ry1.1 .\t.-�` ( .� '`,{b-1— P�'I `I II4 1, \• ifbj
I
j I I I �b• -
_I,1
NAVEL DRfVE � / / \r~--�,�-t���—i'— •�_I _._ _•_:�'—
24
6s_-F I�
LEGEND WETLAND MAP
5GALE I' = 60'
i i EXISTING WETLANDS
— — — — PROPERTY LINE I \ �11 Ia I FIGURE 5: WETLAND MAP oesen �0
I "LETALASAEA URUDWARA SINGH SABHA
CONSULTANTS
0 50 60 12,- RENTONFWASHINGTONPesou & En. n6e1 Ple ng
r REVISED
SUMMIT PARK 1 /
WETLAND E
- - —
II 0.30 AQ.E$ �\ _
I _ � / -o - UPLAND AREA
� N \ _ —
yy
F— WETLAND A
29,500 SO FT
//I 1 6)0. ACRES L -- - ._�i. , ��/ �i frY i ' /i / -fir•
p BUFFER BOUNDARY _
(PROJECT L;MITS)
U5
¢w WE-'. LAND D--
m _.-- -.. .—� it r-/
1
i j-�DIN6 ij //f BUFFER ��BOUNDARY�-�-
-I (PROJECT LIMITS)
1 A k
L
___— -
� 1 - - - - WETLAND X/Yt�
I
G.:3 ACRES I I
1 1 _ 1 1 1
1j 1
=I:E - - - - -- - - - - -;- - - -
L<'A'„PFa
W
LEGEND l WETLAND MITIGATION MAP
----
SCALE: bv'
1W IMPACTED WETLANDS 5,956 sf.
1
LED-__ �T7
C
CREATED WETLAND 11,300 sf. =5, ,RA„,,,
v� I FIGURE 6: WETLAND MITIGATION �AO
RESTORED WETLAND 11,200 sf. TALASAEA AREA CALCULATIONS '-ALE
so eo 120
CONSULTANTS GURUDWARA SINGH SABHA
WETLAND BUFFER fteeouree i Cnviranment.1 Plennin. AiE
L✓ ,�.,_ � ,,.... ..,..,_,-,,..-..._�..-... ,_„ RENTON, WASHINGTON
— - - — PROPERTY LINE =V1S
i
within this wetland and its southern buffer were cleared (but not filled) during the
summer of 1995. At the time of the February 1996 field investigations, vegetation
within the drainageway consisted largely of rush (Juncus sp.) and watercress
(Rorippa nasturtium-aquaticum).
The northwest corner of the wetland includes a single large (34" dbh) weeping willow
(Salix babylonica), as well as a red alder tree;lady fern, Himalayan blackberry
(Rubus discolor), and bittersweet nightshade (Solarium dulcamara). The drainage
channel in this portion of the wetland appears to have been relocated toward the
south. The original channel is located immediately south of the north property line,
and is still visible. This channel relocation may have occurred during construction of
the housing project north of the subject site.
Wetland B is rated as a Category III wetland according to the City of Renton's
Wetland Ordinance. Category III wetlands require a 25-foot buffer.
Wetland D
Wetland D is a very small (356 so, hydrologically isolated, shallow topographic
depression. Vegetation in the wetland consists of a palustrine emergent patch of
creeping buttercup (Ranunculus repens) and velvet grass (Holcus lanatus). The
wetland is entirely surrounded by Himalayan blackberry which was mowed in the
summer of 1995.
Wetland D would be rated as a Category III wetland according to the City of Renton's
Wetland Ordinance. However, this wetland would not be regulated by the City since
it is an isolated wetland less than 5,000 sf.
Welland X/Y
Wetland X/Y (12,412 so consists primarily of a palustrine emergent wetland
interspersed with scrub/shrub vegetation. The wetland is located in the southeast
portion of the site and appears to have been disturbed in the past. Wetland X/Y is
separated from the larger Wetland A by a low berm. Hydrologically, Wetland X/Y is
supported by groundwater seepage from the toe of the slope. Drainage from this
wetland flows in a southwesterly direction before exiting the site at a small ditch
paralleling the south property line along a gravel drive.
Vegetation in the wetland includes Himalayan blackberry, soft rush (Juncus effusus),
reed canarygrass (Phalaris arundinacea), sedges (Carex sp.), creeping buttercup,
and red alder saplings. Soil borings taken in the wetland revealed variable hydric
soils that had been disturbed in places. At the time of the February 1996 field
investigations, soils were saturated to the surface.
Wetland X/Y is rated as a Category III wetland according to the City of Renton's
Wetland Ordinance. Category III wetlands require a 25-foot buffer.
4
5.0 WETLAND FUNCTIONS AND VALUES
Wetlands in general provide many valuable ecological and social functions, including
stormwater storage, water quality protection, groundwater recharge and discharge,
and wildlife habitat. A wetland functional value assessment was conducted for each
wetland on the project site (TABLE 1). +
TABLE 1. Wetland Functional Value Ratings
FUNCTION: WATER QUALITY IMPROVEMENT
Wetland Rating Comments
A Moderate Moderate flow through wetland; high vegetation density; no
proximity to pollutants
B Low/ Relatively rapid flow through wetland; moderate vegetation
Moderate density in drainage channel; no proximity to pollutants
D Low Limited by very small size; no proximity to pollutants
X/Y Low/ Slow flow through wetland; moderate herbaceous'vegetation
Moderate density; no proximity to pollutants
FUNCTION: FLOOD/STORMWATER CONTROL
Wetland' Rating Comments 11
A Moderate Located hi h in watershed; limited ability for stormwater storage
B Low Small size; limited ability for stormwater storage
D Low Very small size; isolated
X/Y Low/ Relatively small size; moderate stormwater storage capability
Moderate
FUNCTION: GROUNDWATER EXCHANGE _
Wetland Rating Comments
A Moderate/ Presence of seeps indicating groundwater discharge
High
B Low/ Functions primarily as drainage pathway for water discharging
Moderate from seeps associated with Wetland A
D Low Limited by very small size _
XN Low/ Relatively small size; some limited groundwater recharge possible
Moderate 1 _
FUNCTION: NATURAL BIOLOGICAL SUPPORT WILDLIFE HABITAT
Wetland Rating Comments
A Moderate/ Relatively high plant species and structural diversity (forested);
High permanent soil saturation associated with seeps; habitat features
resent
B Low/ Relatively small size; moderate plant species and structural
Moderate diversity (prior to disturbance); disturbed buffers
D Low Very small size; low plant species and structural diversity
XN Low Relatively small size; moderate plant species diversity; low
structural diversity; disturbed condition
5
FUNCTION: CULTURAL/RECREATIONAL VALUE
Wetland Rating Comments
A Moderate Wetland of value primarily as a component of surrounding open
space; little passive or active recreation opportunities
B Low/ Functions primarily as an open space buffer between the projcct
Moderate site and the residential devolo ment to the north
D Low Very small size
x/y Low Little passive or active recreation opportunities; relatively low
aesthetic value due to disturbed condition.
6.0 PROPOSED PROJECT
6.1 Description
The proposed project consists of the construction of a new Sikh Temple facility with
associated parking and landscaping areas (Drawing 1.0).
6.2 Development Impacts on Wetlands
The proposed project requires the filling of 5,600 sf of Wetland X/Y, as well as the
very small (356 sf) Wetland D. Only the impact to Wetland X/Y, however, would be
regulated by the City of Renton, since Wetland D is less than 5,000 sf and is
hydrologically isolated.
In addition, approximately 11,200 sf of Wetland A was previously impacted by un-
permitted clearing and grading activities during the summer of 1995. Clearing
activity during the summer of 1995 also impacted a large portion of the buffer of
Wetland B. Impacts to Wetlands A, B, and D were approved by the Corps of
Engineers in an "after the fact" Nationwide Permit#26 (dated December 11, 1995).
As long as total wetland impacts on the site are below 1 acre, no additional permits
would be required from the Corps. Furthermore, all previous impacts to Wetlands A
and B and their buffers will be restored during the mitigation process (see Section 7
below).
7.0 WETLAND MITIGATION/RESTORATION
A conceptual mitigation/restoration plan isincluded with this report as Drawing 1.
Mitigation for the 5,600 sf of wetland impact to Wetland X/Y will occur as
approximately 11,300 sf(minimum 2:1 replacement-to-loss ratio) of wetland creation
north of Wetland X/Y. This wetland creation area will be integrated into the restored
wetland area and the existing wetlands to create a single wetland system. A 50-foot
buffer will be provided to the created and restored wetland system.
7.1 Goals and Objectives
Goal l:
Replace wetland acreage and functions lost to filling of approximately 5,600 sf of
Category III emergent wetland.
6
Objectives:
1. Create approximately 11,30,0 square feet of emergent and scrub-shrub wetland
(minimum 2:1 replacement-to-loss ratio).
2. Integrate the created wetland with the restored and existing wetlands on the site
. .to create a single contiguous wetland system.
3. Provide wetland hydrology appropriate for each wetland vegetation cover type
created.
4. Create a mitigation wetland area that has greater plant species and structural
diversity than the wetland to be filled.
5. Incorporate habitat features (e.g. snags, down logs, and nesting and roosting
boxes) into the created wetland and its buffer.
Goal 2:
Restore the approximately 11,200 square feet of previously filled forested wetland.
Objectives:
1. Excavate the approximately 11,200 square feet of previously filled wetland area
to its original grade (or slightly lower) to enhance natural drainage retention.
2. Plant the restored wetland area and its buffer with native plant species which are
both conducive to the establishment of a forested community and beneficial to
wildlife.
3. Incorporate habitat features (e.g. snags, down logs, and nesting and roosting
boxes) into the restored wetland and its buffer.
4. Integrate the restored wetland with the created and existing wetlands on the site
to create a single contiguous wetland system.
Goal 3:
Restore/enhance the 25-foot buffer strip associated with the wetland/stream
(Wetland B) along the north property line.
Obiectives..
1. Replant the buffer area with native plant species which are both conducive to
the establishment of a forested community and beneficial to wildlife.
2. Incorporate habitat features (e.g. snags, down logs, and nesting and roosting
boxes) into the restored buffer.
3. Provide a visual screen between the proposed development and the residential
development located to the north of the site.
7.2 Construction Management
Prior to commencement of any work by contractors in the mitigation or restoration
area, the clearing and construction limits will be staked, grade staking will be
completed, and fencing will be installed around all existing vegetation to be saved. A
pre-construction meeting will be held at the construction site to review and discuss all
aspects of the project with the selected contractor.
Talasaea will supervise plan implementation during construction to ensure that
objectives and specifications of the mitigation plan are met. Any necessary
modifications to the design that occur as a result of unforeseen site conditions will be
jointly approved by the City of Renton and Talasaea prior to their implementation.
7
7.3 Monitoring Methodology
As required by the City of Renton, the monitoring program will be conducted for a
period of five years, with reports submitted to the City according to the following
schedule: {
• quarterly for the first year following construction
• annually (at the end of the growing season) for the second through fifth years
Permanent vegetation sampling points will be established at selected locations to
incorporate all of the representative plant communities. The same monitoring points
will be re-visited each year with a record kept of all plant species found. Vegetation
will be recorded on the basis of relative percent cover of the dominant species within
the vegetative strata. An approximately 10-f6ot-radius sampling plot will be used. All
monitoring will be conducted by a qualified biologist from Talasaea Consultants.
Photo-points will be established from which photographs will be taken throughout the
monitoring period. These photographs will document general appearance and
progress in plant community establishment in the mitigation and restoration areas.
Review of the photos over time will provide a semi-quantitative representation of
success of the planting plan.
Monitoring and photo-point locations will be shown on the "as-built" plans, which will
be submitted with the first monitoring report. '
Wi/dli e
Birds, mammals, reptiles, amphibians and invertebrates which are readily
observable (either by direct or indirect means) will be identified and recorded in the
wetland and buffer areas. Direct observations include actual sightings, while indirect
observations include tracks, scat, nests, song, or other indicative signs. The kinds
and locations of the habitat with greatest use by each species will be noted, as will
any breeding or nesting activities.
7.4 Success Criteria
Success of plant establishment within the mitigation and restoration areas will be
evaluated on the basis of both percent survival and percent cover. For woody
planted species, success will be based on a survival rate of 90% for each monitoring
event. Success for herbaceous species will be based on at least an 80% cover of
desirable plant species by the end of the 5-year monitoring period.
Exotic and invasive plant species will be maintained at levels below 20% total cover.
These species include Scot's broom, Himalayan and evergreen blackberry, reed
canarygrass, purple loosestrife, morning glory, Japanese knotweed, and creeping
nightshade. Removal of these species will occur immediately following the
monitoring event in which they surpass the 20% maximum coverage. Removal will
occur by hand whenever possible. No chemical treatment will be employed without
prior approval by the City.
8
7.5 Maintenance(M),and Contingency (C).
Established performance standards for the project will be compared to the
monitoring results in order to judge the success of the mitigation and restoration
project. Contingency will include many of the items listed below and would be
implemented if these performance standards are not met. Maintenance and
remedial action on the site will be implemented immediately upon completion of the
monitoring event (unless otherwise specifically indicated below).
• replace dead plants with the same species or a substitute species that meets
the goals and objectives of the plan (C)
• re-plant areas after reason for failure has been identified (e.g., moisture
regime, poor plant stock, disease, shade/sun conditions, wildlife damage.
etc.) (C)
• line wetland areas with impermeable material where hydrology is deemed to
be insufficient to support the desired wetland plant community. Where
appropriate, liners may be installed immediately upon completion of grading
to increase probability of wetland success (C)
• irrigate with a temporary system for, at least one full growing season following
plant installation (M)
• minor excavation, as needed, to correct alterations of surface drainage
patterns (C)
• remove/control weedy or exotic invasive plants (e.g., Scot's broom, reed
canarygrass, Himalayan blackberry, purple loosestrife, etc.) by manual or
chemical means approved by the City of Renton. Use of herbicides or
pesticides within the mitigation area would only be implemented if other
measures failed or were considered unlikely to be successful; and would
require prior agency approval (C & M)
• clean-up trash and other debris on a bi-yearly basis (M)
• clear or repair trash racks, culverts, etc. on a bi-yearly basis (M)
• selectively prune woody plants to meet the plan's goals and objectives (e.g.,
thinning and removal of dead or diseased portions of trees/shrubs) (M)
7.6 Performance Bond
A performance bond will be posted with the City;by the property owner for 1.5 times
the cost of replacement of plantings and the 5-year monitoring plan to assure the
success of the mitigation and restoration plan. The bond may be released in parti,.!
amounts at the sole discretion of the City in proportion to work successfully
completed over the 5-year monitoring period as the applicant demonstrates
performance for implementing the conditions of the plan.
7.7 As-Built Plan
Following completion of construction activities, a revised set of"as-built" plans for the
wetland mitigation and restoration area will be provided to the City of Renton. The
plans will identify and describe any City-approved changes in grading, planting or
other constructed features in relation to the original approved plan. The plans will
also show photo-point locations and vegetation sampling points.
9
References
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979- Classification of
Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife
Service, Department of the Interior. FWSOBS-70/31.
Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation
Manual. Technical Report Y-87-1, US Army Engineer Waterways Experiment
Station, Vicksburg, Miss.
Federal Interagency Committee for Wetland Delineation. 1989. Federal Manual for
Identifying and Delineating Jurisdictional Wetlands. U.S. Army Corps of Engineers,
U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S.D.A.
Soil Conversation Service, Washington, D.C.
Hitchcock, C.L., and A. Cronquist. 1973. Flora of the.Pacific Northwest. University
of Washington Press. 730 pp.
Munsell Color. 1988. Munsell Soil Color Charts. Kollmorgen Instruments Corp.,
Baltimore, Maryland.
Reed, P.B. Jr. 1988. National List of Plant Species that Occur in Wetlands:
Northwest (Region 9). USF&WS Biol. Report 88.
Reed, P.B. Jr. 1993. Supplement to: National List of Plant Species that Occur in
Wetlands: Northwest (Region 9). USF&WS Biol. Report 88.
Renton, City of. 1991. Critical Areas Inventory Map.
Terra Associates Inc. September 2, 1994. Wetland Evaluation.
U.S. Department of Agriculture, Soil Conservation Service. June, 1991. Hydric Soils
of the United States.
U.S. Department of Agriculture, Soil Conservation Service, King County Area Soil
Survey. 1973.
U.S. Fish and Wildlife Service. 1988. National Wetlands Inventory Map, Renton
Quadrangle.
Washington State Department of Natural Resources. 1994. Endangered,
Threatened and Sensitive Vascular Plants of Washington.
GEOSPECTRUM CONSULTANTS, d .. . .
z
Geotec/-ir'�lccr/ Er�gir�eerir�g crr�d E.ort/-� Sc%c-�r >
April 10, 1996 2�2
-r�F AEM,oN
Mr. Bill Williams DEC 1 0 1996
Church Constructors, Inc,
1530 North Canyon BUILDING DIVISION
Redmond, OR 97756
Subject: GEOTECHNICAL' EVALUATION` "
Proposed Gurudwara Singh Saba Church
5212 Talbot Road South
Renton, Washington
Project No. 96-121-01
Dear Bill,
This report presents the results of our geotechnical investigation„,performed at the
site of the proposed new Gurudwara Singh Saba Church to be located on the
subject property. The purpose of the investigation was to provide geotechnical
engineering evaluations of the site and geotechnical recommendations including
design of foundations and site grading. Our work was performed in accordance
with the scope and conditions of our proposal dated March 14, 1996.
A site development plan and a site topography map were provided to us and were
used as references for our investigation (see,Figure 2). Based on our discussions
with David Ralph of Washington Design Services, the proposed church will range
from one to two-stories above a daylight basement. Finishedi floor grade of the
structure is indicated to be about 160.0 feet. Plan dimensions of the proposed
church are 116 by 106 feet and a 49 by 27 foot portico will extend from the west
side over the access drive. A large portion of the remainder of the property will be
graded and paved for a new access drive from Talbot Road and new parking areas
to the north, east and south of the church.
Grading for site development will include excavation up to 20+ feet below existing
grade for the church,structure and possible excavation of up to 12 feet south of the
building for lower level access apd parking., , The eastern parking areas will,be
terraced with cut/fill grading and separated by retaining walls, slopes or rockeries
on the order of 6 to 8 feet in height.
Based on discussions with the Greg Thesenvitz of SEGA Engineers, bearing wall
loads are expected to be in the range of about 2 to 3 klf and maximum column
loads are expected to be in the range of about 50 to 75 kips. If actual structural
loads exceed the above values by more than 25%, this office should be notified.
Issaquah, WA 98027 C;;'i r,
L
Church Constructors April 10, 1996
SCOPE OF WORK
Our geotechnical evaluation included subsurface exploration, engineering
evaluations and the preparation of this report. The scope of work included the
following specific tasks:
o Observed the excavation of ten test pits to depths ranging from 3 to 11
feet below the ground. Approximate locations of the test pits are shown
on Figure 2..
o Continuously logged the subsurface conditions, as encountered in the
test pits at the time of excavation. Logs of the test pits are presented
on the summary sheets of Appendix A.
o Performed geotechnical engineering evaluations of the site and
developed geotechnical recommendations for foundation design and
site grading.
o Prepared this geotechnical report summarizing our 'findings and
recommendations.
OBSERVED SITE CONDITIONS
At the time of our field investigation the property was occupied by the existing
structures shown on Figure 2 including two church buildings and a residential
building to the north.. Topography in the general site vicinity is gently sloped down
to the west. The referenced topography map provided to us indicates the maximum
elevation difference across the site to be on the order of about 62 feet with an
average gradient of about 12.4 percent.
We noted apparent shallow fill deposits in the northeaster quadrant of the site as
well as localized fill deposits encountered in test pits 1, 5 and 10 which ranged from
about 3 to 4 feet thick as approximately shown on Figure 2. In addition we
observed that the surface soils were generally very moist over most of the site and
some area were especially loose/soft and wet as indicated on Figure 2. Vegetation
on the site consisted primarily of grass and blackberries.
Subsoils
Our evaluation of the subsurface conditions was based on our observations of the
exploratory test pits and surface observations. Subsoils encountered in the test pits
were generally found to be natural glacial till soils with localized areas of fill soils.
The natural soils generally included a topsoil layer of dark brown silty sand with
organics and roots which typically ranged from about 6 to 12 inches thick. The
natural soils were generally, loose to medium dense to depths'of about 1 to 2 feet
below the natural surface. However,`probing of the surface soils indicates that the
thickness of loose/soft/wet soils ranges up to 2+ feet in localized areas and in
particular at the southeast corner of the proposed parking area loose/soft/wet soils
extended to depths of 2 to 3+ feet. The underlying weathered soils were typically
brown to gray brown or gray and red-brown silty fine sand with gravel. Deeper
Project No. 96-121-01 Page 2
Church Constructors April 10, 1996
natural soils were medium dense to very dense to the depths of the test pits and in
test pits 2 and 3 the soils became cemented at depths of 4 to 5 feet.
i
Fill soils were encountered in Test Pits 1, 5 and to depths of about 3 to 4 + feet
(probing of test pit 5 indicated fill extended to 4+ feet). The fill soils were classified
as silty sand with gravel and cobbles and at test pit 1 the fill contained concrete,
plastic, wood, AC pavement and brick debris. Surface topography also indicates a
probable thin fill layer in the area north and east of the proposed church site (see
Figure 2).
Ground Water
Surface water flows in drainages along the north property boundary and in a ditch
in the center of the property. Wet surface conditions were observed at the
southeast corner of the proposed parking area and at localized areas in the north
half of the site.
No ground water surface was observed in any of the test pits and no seepage was
observed except for a minor seep at 5 feet in test pit 4. However the soils were
generally classified as very moist to wet and measured moisture contents were
generally high, ranging from about 12.5 to 27.2 percent. Most of the soils had
moisture contents between 17 and 22 percent. Test pit 6 was the highest with
moisture contents of 26.6 and 27.2 percent.
Subsurface Variations
Based on our experience, it is our opinion that some variation in the continuity and
depth of subsoil deposits and ground water levels should be anticipated due to
natural deposition variations and previous onsite structures and grading. Due to
seasonal moisture changes, ground water conditions should be expected to change
with time. Care should be exercised when interpolating or extrapolating subsurface
soils and ground water conditions between or beyond our test pits.
SITE EVALUATIONS
General
The referenced .geologic map of Figure 1 indicates the site to expose glacial till
(Qgt) soils. Based on the soils observed on the site and review of the referenced
map, it is our opinion that the natural subsoils underlying the site are glacial till
deposits. The referenced map describes the Qgt soils as compact, unsorted
mixtures of sand, silt, clay and gravel soils deposited during the advance of the
Vashon glaciation, the last glacial advance into the Puget Sound area,
approximately 13,000 to 16,000 years ago.
Based on the results of our field investigations combined with our own experience
and judgment, it is our gpinipn that the geotecftnical site conditions are suitable for
the proposed development provided our recommendations are followed.
Project No. 96-121-01 Page 3
Church Constructors April 10, 1996
Structure Support Considerations
Conventional spread footings. are considered appropriate for support of the
proposed structures at this site. Foundations should penetrate through any existing
fill, topsoil and medium dense soils to bear on undisturbed dense to very dense
natural soils. Bearing soils were generally encountered at depths of about 1 to 4
feet below the natural soils surface.
The excavation for the proposed new church basement will range from near 0 at the
southwest corner to 20+ feet at the northeast corner of the structure. We expect
that dense to very dense natural glacial till soils suitable for foundation support will
be exposed over most of the basement grade except at the southwest corner and in
the area of the portico structure west of the main building. Bearing soils in those
areas are expected to be within about 3 to 4 feet of the natural soil surface.
Site Grading 'Considerations
The excavation for the proposed basement will range up to 20+ feet and difficult
digging should be expected in the unweathered glacial till soils below depths of
about 7 to 8 feet. Based on the test pit explorations we expect only minor and/or
localize seepage into the excavation which could be controlled with conventional
sumps and pumps. Some over-excavation for foundations and structural fill
placement for slab support may be required at the southwest corner where final
grades are near existing grade.
Site grading for the proposed new parking areas is expected to .include a possible
excavation of up to 12 feet south of the new church for lower level access and cut
and fill grading to the east creating parking terraces with elevation differences on
the order of 6 to 8 feet. Pavement sections (AC and base course) may be
supported directly on medium dense natural soils which are expected to be about 1
to 2 feet below the existing surface in most 'cut areas. In fill areas or areas where
medium dense natural soils are not exposed at the subgrade level, site preparation
should include stripping of existing loose/soft/wet natural soils and fill and
placement of structural fill to final subgrade elevation. We expect that stripping will
generally average about 1 to 2 feet but some existing soft/wet areas of the site will
require greater stripping (see Figure 2) in particular the southeast corner of the site
where stripping depth may be 3+ feet. We understand that the existing center
drainage ditch will be replaced with a pipe and the ditch backfilled. The ditch
backfill should be.properly compacted structural fill for support of, pavements.
Excavated onsite granular soils cleaned of all debris and organics are considered
technically suitable for use in structural fill for pavement support but based on our
experience glacial till soils are quite moisture sensitive with regard to grading and
compaction characteristics. Measured moisture contents indicate that the onsite
soils are currently too wet to obtain adequate compaction. In our experience the
onsite soils will be very difficult to compact unless they are dried out during warm,
low humidity weather. Site grading should be scheduled during the late summer
months if possible. Wet weather grading may require the use of imported granular
fill soils which are more easily compacted at higher moisture levets. In addition the
onsite soils are not considered suitable for backfill within the drainage zone of the
basement wall or other retaining walls.
Project No. 96-121-01 Page 4
Church Constructors April 10, 1996
Seismic Considerations
The Puget Sound region is a seismically active'area. About 14+"moderate to large
earthquakes (M5 to M7+) have occurred in the Puget Sound and northwestern
Cascades region since 1872 (124 years). The larger recorded seismic events have
included the magnitude 7+ north Cascades earthquake of 1872, the magnitude 7.3
Vancouver Island earthquake of 1946, the magnitude 7.1 Olympia earthquake of
1949, the magnitude 8.1 Queen Charlotte Island earthquake of 1949 and the
magnitude 6.5 Seattle earthquake of 1965.
State published documents indicate ground motion intensities in the Puget Sound
area have ranged up to VIl and VIII on the Modified Mercalli Scale. Intensity VIII is
indicated to be sufficient to cause "considerable damage in ordinary substantial
buildings".
In addition to Puget Sound seismic sources, a great earthquake event (M8 to M9 +)
has been postulated for the Cascadia Subduction Zone (CSZ) along the northwest
Pacific coast of Oregon, Washington and Canada. The current risk of a future CSZ
event is not known at this time. Published reports have indicated recurrence
intervals for a CSZ event to range from as little as 100-200 years to as long as
1000+ years and the time of the last event is reported to have been about 300
years ago.
Considering the above, it is our opinion that the proposed church development will
very likely experience significant ground shaking during its useful life.
Secondary seismic hazards due to earthquake ground shaking include induced
slope failure, liquefaction, lateral spreading and ground settlement. The site lies
on a gentle slope composed of glacial till and older glacially consolidated sediments.
Considering the nature of the glacial materials and the gentle slope gradient, the
potential for an earthquake induced failure of the natural slope is considered to be
low.
Liquefaction is a phenomenon in which typically loose or medium dense saturated
sands temporarily lose strength during earthquake shaking due to
settlement/densification and lack of adequate drainage. Based on the dense to
very dense consistency of the glacial till soils and the lack of ground water observed
during our explorations, in our opinion the potential for liquefaction at this site is
very low to nil.
RECOMMENDATIONS
The following subsections present our recommendations for design of foundations,
retaining walls, site grading, drainage control and erosion control. Also included
are recommendations for plan review and observations and testing during
construction.
Project No. 96-121-01 Page 5
Church Constructors April 10, 1996
Spread Footing Foundations
Conventional spread footings founded on undisturbed dense natural soils should
provide good support for the proposed structure. Suitable bearing soils were
encountered at depths ranging from about 1 to 3.5 feet below the existing natural
ground surface at the test pit locations. All footings should be founded at least 18
inches below the lowest adjacent final grade. Where the natural bearing soils
slope, the footing excavation should be stepped to maintain a horizontal bearing
surface.
Continuous wall footings should be at least 18 inches wide. Square footings for
column support should be at least 24 inches wide. Footings may be designed
based on an allowable bearing pressure of 2000 psf.
As an alternative to deep footings to penetrate fill or unsuitable soils, foundation
loads may be transferred from the minimum foundation depths to the recommended
bearing soils by a monolith of lean concrete having a minimum compressive
strength of 1000 psi. The width of the lean concrete monolith should be at least as
wide as the footing or at least one-half of the monolith height, whichever is greater.
The estimated settlement of a 18-inch wide continuous footing carrying a load of 3
kips per foot is on the order of 1/4 to 1/2 inch. The estimated settlement of a 73-
inch wide isolated square footing carrying a load of 75 kips is on the order of 1/2
inch. Our settlement estimates assume that foundations are supported on
undisturbed dense to very dense natural bearing soils and that all loose/disturbed
material is removed from the bearing surface prior to concrete pour. Maximum
differential settlement within the proposed addition is expected to be 1/2 inch or
less. Settlements are expected to occur primarily during construction.
Resistance to lateral loads can be assumed to.,be provided by friction acting at the
base of foundations and by passive earth pressure. A coefficient of friction of 0.4
may be assume with the dead load forces in contact with on-site soils. An allowable
static passive earth pressure of 250 psf per foot of depth may be used for the sides
of footings poured against undisturbed dense natural soils or properly compacted
structural fill.
The vertical and lateral bearing values indicated above are for the total dead load
plus frequently applied live loads. For short duration dynamic loading caused by
seismic or wind forces, the vertical bearing values may be increased by 50 percent
and allowable lateral passive pressures may be increased by 33 percent.
Retaining Walls
Cantilevered retaining walls as referred to in this report are walls which yield or
move outward during and after backfilling. Actual wall movements will depend on
the wall design and method of backfilling and can range from 0.1% to 0.3% of the
wall height. Design pressures for cantilevered walls given below assume that the
top of the wall will deflect at least 0.2% of the wall height.
Static design of permanent cantilevered retaining walls which support a horizontal
surface of properly compacted clean free-draining granular material may be based
on an equivalent fluid density of 35 pcf. This pressure assumes that there is no
water pressure behind the wall. A uniform lateral pressure due to backfill surcharge
Project No. 96-121-01 Page 6
Church Constructors April 10, 1996
should be computed using a coefficient of 0.25 times the uniform vertical surcharge
load.
Static design of walls structurally braced against movement should be based on an
equivalent fluid density of 60 pcf. This pressure assumes that the wall supports a
horizontal backfill of properly compacted free-draining granular material and that
there is no water pressure behind the wall. Uniform lateral pressure due to a
uniform vertical surcharge behind a braced wall should be computed using a
coefficient of 0.45 times the uniform vertical surcharge load.
Seismic design of retaining walls should include a dynamic soil loading based on a
0.17g 100-year recurrence ground motion level. Dynamic soil pressure should be
assumed to have an inverted triangular distribution. The dynamic soil pressure at
the top of the wall should be at least 16H (psf) where H is the height of the wall
above the footing base. The dynamic soil pressure should diminish linearly to zero
at the base of the wall. Combined static plus dynamic soil pressure should be used
for seismic design of the walls.
Care should be exercised in compacting backfill against retaining walls. Heavy
equipment should not approach retaining walls close enough to intrude within a 1:1
line drawn upward from the bottom of the wall. Backfill close to walls should be
placed and compacted with hand-operated equipment. Recommendations for
placement and compaction of structural fill are presented under "Site Grading".
Design wall pressures given above assume no water pressure behind the walls. We
recommend that a drainage zone be provided behind all retaining walls and a
adequate drain system be provided at the base of all retaining walls. As a minimum,
the drainage zone should be at least 3 feet thick or 1/2 the wall height, whichever is
less. Backfill within the drainage zone should be a clean sand/gravel mixture with
less than 5 percent fines based on the sand fraction. A membrane of Mirafi 140
filter fabric or equivalent should be provided between the drainage zone material
and onsite silty soil backfill. Wall drains should consist of a four-inch diameter
perforated PVC drain pipe placed in at least one cubic foot of drain gravel per lineal
foot along the base of the wall. Drain gravel should be washed material with
particle sizes in the range of 3/4 to 1-1/2 inches. The drainage zone backfill should
be capped with paving or 12 inches of silty soils„to reduce surface-water infiltration.
Conventional spread footing foundations founded on undisturbed dense to very
dense natural soils may be used for support of retaining walls. Design of wall
foundations should be in accordance with the recommendations presented under
"Spread Footings"
Site Grading
Site grading is expected to consist primarily of excavation for the new basement
area and removal of existing fill, placement of fill to establish final grades for the
parking areas and backfill for retaining walls, footings and utility trenches.
Excavation of the on-site glacial till materials is expected to be difficult at depths
greater than about 7 or 8 feet. Onsite granular soils are generally considered
suitable for use in compacted fills but in our experience these soils are quite
moisture sensitive with regard to grading and compaction characteristics and are
currently too wet for adequate compaction. Grading should be scheduled for the
late summer months if possible. Wet weather grading may require the use of
Project No. 96-121-01 Page 7
Church Constructors April 10, 1996
imported granular fill soils which are more easily compacted at higher moisture
levels. Recommendations for site preparation, temporary excavations, structural fill,
subgrade preparation, site drainage and trench backfill are presented below.
Site Preparation: Existing vegetation, debris, and soft or loose soils should be
stripped from the areas that are to be graded. Fill soils should be stripped as
required for foundation and subgrade support. During rough grading, excess soils
may be stockpiled for later use. Stripping in the parking lot area is expected to
average about 1 to 2 feet but may be 3+ feet in existing wet/soft areas. Soils
containing more than 1% by weight of organics may be used in planter areas, but
should not be used for fill beneath building or pavement areas. Stumps, debris and
trash, plus rocks and rubble over 6 inches in size, should be removed from the site.
Subsoil conditions on the site may vary from those encountered in the borings.
Therefore, the soils engineer should observe the prepared areas prior to placement
of any new fills.
Tem on rarvExcavations: Sloped temporary construction excavations may be used
where planned excavation limits will not undermine existing structures or interfere
with other construction. Where there is not enough room for sloped excavations,
shoring should be provided,
Based on the subsurface conditions encountered in the test pits, it is our opinion
that sloped temporary excavations may be made vertically to depths of 4 feet or
less. Excavations up to 10 feet in height should be no steeper than 3/4:1
(horizontal:vertical) and excavations greater than 10 feet should be sloped no
steeper than 1:1. It should be noted that the contractor is responsible for safety
and maintenance of construction slopes.
Any sandy soils exposed in cut slopes should be kept moist, but not saturated, to
retard ravelling and sloughing. Surface drainage should be directed away from the
top edge of the cut slope. Surcharge loads should not be allowed within 5 feet of
the top of the slope or within a 1:1 (horizontal ; vertical) plane gxtending up from the
toe of excavation, whichever is greater.
Structural Fill: Provided that soil moisture can be reduced and maintained near
optimum, excavated onsite soils may be used for structural fill. However these soils
are expected to be moisture sensitive and are currently too wet for practical
compaction. Therefore imported granular fill soils should be used if moisture
conditions cannot be adequately controlled. Loose soils, formwork and debris
should be removed prior to placing fill or backfill. Imported free-draining granular
soils should be used for backfill of retaining walls, and should be capped with
pavement or 12 inches of onsite silty soils to reduce surface water infiltration.
Onsite soils or imported granular fill should be placed in horizontal lifts not
exceeding 8 inches in loose thickness and compacted to at least 90 percent of the
maximum dry density as determined by the ASTM D1557-91 test method.
Imported granular fill should consist of clean, well-graded sand and gravel materials
free of organic debris and other deleterious material. Imported material for wall
drainage zone backfill should be a clean sand/gravel mixture with less than 5
percent fines based on the sand fraction.
Slab Support: Slabs-on-gracje should be supported on undisturbed medium dense to
dense natural soils or on properly compacted structural fill. At the southwest corner
Project No. 96-121-01 Page 8
Church Constructors April 10, 1996
of the basement area, fill or loose/soft natural soils will likely be exposed at slab
level. Where unsuitable ,soils exist at slab level, subgrade preparation should
include excavation down to medium dense to dense natural soils and placement of
structural fill to final subgrade elevation. Subgrade fill should be placed in
accordance with the recommendations for structural fill except that the top 6 inches
of the subgrade fill should be compacted to at least 95 percent of the ASTM D1557-
91 maximum dry density. It should be noted that where the proposed slabs cross
the fill/natural contact line, there will be a high risk of cracking. Risk of cracking
can be reduced by placing construction joints at the contact and by proper steel
reinforcement of the slab.
Interior concrete slabs should be underlain by a capillary break consisting of a
polyethylene vapor barrier of at least 6 mil thickness. If a vapor barrier is used it
should be covered with 2 inches of clean sand to reduce punctures and aid in
concrete curing.
Pavement Supports Asphalt pavement sections (AC and base) should be supported
on undisturbed medium dense to dense natural soils or on properly compacted
structural fill. Pavement subgrade areas should be stripped as recommended under
"Site Preparation". Where unsuitable soils exist at subgrade level, subgrade
preparation should include excavation down to medium dense to dense natural soils
and placement of structural fill to final subgrade elevation. Subgrade fill should be
placed in accordance with the recommendations for structural fill except that the top
6 inches of the subgrade fill should be compacted to at least 95 percent of the
ASTM D1557-91 maximum dry density.
Permanent Sloe Design: Permanent cut slopes should be no steeper than 1 .5:1
(horizontal:vertical). All fill slopes should be made no steeper than 2:1 (h:v). All
vegetation, debris, slopewash and weathered soils should be removed from
proposed fill slope areas prior to fill placement (see "Site Preparation"). Where
existing slope gradients exceed 20 percent, the new structural fill should be placed
on horizontal benches cut into the natural slope. Minimum bench width should be 8
feet. All ;fill should be placed and compacted in accordance with the
recommendations for "Structural Fill".
Rockery Construction: Rockeries should be considered maintenance items that will
require periodic inspection and repair. They should be located so that they can be
reached by a contractor if repairs are necessary.
The rockery keyway should be excavated to expose dense/hard natural soils. The
competency of the foundation subgrade and stability of the exposed slope face
should be verified by the geotechnical engingeer prior to placing rock.
Rocks placed in the lower half of an 8 foot rockery should be 3000 to 4000 lb. rock,
or larger. Rocks placed above this level may gradually decrease in size with
increasing height but should be no smaller than 750 lbs. The long dimension of the
rocks should be oriented into the slope for maximum stability.
Where rockeries support fill soils (limited to '6 feet in height), we recommend that
the minimum rock dimension (into the face) be at least 2 feet or 1/2 the rockery
height above the level of the base of that rock whichever is larger. This would
require 2 to 3 foot long (2000 to 4000 lb.) rock at the base for support of a 4 to 5
foot fill height.
Project No. 96-121-01 Page 9
Church Constructors April 10, 1996
Rocks should be placed to avoid continuous joint planes in the vertical or lateral
directions. Each rock should bear on two or more rocks below it, with good flat-to-
flat contact. The rockery face should be battared into the slope at a gradient of
1 h:5v or flatter.
A minimum 18-inch wide layer of well graded gravel drain material should be
provided for the full height behind the rockery with a perforated drain pipe at the
base. Drain pipes should consist of 4-inch minimum diameter, perforated or slotted
ridgid plastic PVC pipe laid with a positive gradient to a controlled, non-erosive
discharge into the storm drain system. Drain pipes should be placed below the
lowest rock and should be bedded on and surrounded by the gravel drain material.
Special care should be exercised in compacting fill behind, rockeries. Heavy
equipment should be kept beyond a 1.5:1 (h:v)' line drawn upward from the bottom
of the rockery. Backfill close to rockeries should be placed and compacted with
hand-operated equipment as the rockery is constructed. Recommendations for
placement and compaction of structural fill are presented under "Structural Fill" .
Utility Trenches: Buried utility conduits should be bedded and backfilled around the
conduit in accordance with the project specifications. Bedding material should
extend from six inches below the pipe to six inches above the pipe. Where conduit
underlies pavement or slabs-on-grade, the remaining backfill above the pipe should
be placed and compacted in accordance with the recommendations for structural
fill. If imported granular fill is used for trench backfill it should be capped with 12
inches of onsite soils.
Drainage Control
Surface drainage from the adjoining upslope areas should be controlled and
diverted around the development area in a non-erosive manner. Adequate positive
drainage should be provided away from the structure and on the site in general to
prevent water from ponding and to reduce percolation of water into subsoils.
Granular backfill should be capped with paving or 6 inches of onsite silty soils. A
desirable slope for surface drainage is 2% In landscaped areas and 1% in paved
areas.
Roof drains should be tightlined into the storm drain system or other appropriate
discharge point (no discharge on the ground surface). A permanent perimeter
drain, independent of the roof drain system, should be placed adjacent to the base
of the continuous exterior foundations. The drain should consist of a four-inch
diameter perforated PVC drain pipe placed in at least one cubic foot of a well
graded sand and gravel filter material per lineal foot along the base of the
foundations. At least one interior drain should be provided beneath the basement
floor connecting to the perimeter drain on the downslope side at the lowest point.
If conditions exposed during construction warrant, an interceptor subdrain system
may be required to intercept ground water migration form the upslope areas
particularly in the southeast site area. The subdrain should be placed along the
upper side of the developed area but down slope from any surface drainage control
berm and should consist of a filter fabric lined trench filled with clean sand or drain
rock with a perforated PVC drain pipe at the base. The drain trench should be at
least 18" wide, and at least 3 feet deep and should penetrate at least one foot into
the dense to very dense natural glacial till soils. Six inches of native clay soil cover
Project No. 96-121-01 Page 10
Church Constructors April 10, 1996
should be placed over the drain to reduce surface water infiltration. Discharge from
the subdrain should be conducted via tightline to the storm drain system.
Erosion Control
Onsite silty sand materials are expected to be highly erodible when exposed to
concentrated flows. Siltation fences or other, detention devices should be provided
around soil stockpiles and exposed soil areas during construction to control the
transport of eroded material. Exposed final graded soil areas should be paved or
planted immediately with grass and deep rooted plants to help reduce erosion
potential.
Plan Review
This report has been prepared to aid in the evaluation of this site and to assist the
architect, structural and civil engineers in the design and construction of the project.
It is recommended that this office be provided the opportunity to review the final
design drawings and -specifications to determine if the recommendations of this
report have been properly implemented and to make any supplemental design
recommendations which may be required.
Observations and Testing During Construction
Foundation recommendations given in this report are based on the assumption that
all foundations will be placed on undisturbed dense to very dense natural glacial till
soils. All footing excavations should be observed prior to placement of steel and
concrete to see that footings are founded on satisfactory bearing materials and that
excavations are free of loose and disturbed materials. All structural fill and
subgrade areas should be observed by a representative of this office after stripping
and prior to placing fill. Proper fill placement and compaction should be verified
with field and laboratory density testing by this office.
Project No. 96-121-01 Page 11
Church Constructors April 10, 1996
CLOSURE
This report was prepared for specific application to the subject site and for the
exclusive use of Church Constructors, Inc. and; their representatives. The findings
and conclusions of this report were prepared with the skill and care ordinarily
exercised by local members of the geotechnical profession practicing under similar
conditions in the same locality. We make no other warranty, either express or
implied.
Variations may exist in site conditions between those described in this report and
actual conditions encountered during construction. Unanticipated subsurface
conditions commonly occur and cannot be prevented by merely making explorations
and performing reconnaissance. Such unexpected conditions frequently require
additional expenditures to achieve a properly constructed project. If conditions
encountered during construction appear to 'be different from those indicated in this
report, our office should be notified.
Respectfully submitted,
GEOSPECTTRUM CONSULTANTS, INC.�IdAA&
James A. Doo
Principal Engineer tw
co w I�T�
Encl: Figures 1 and 2 0 j 01
Appendix A
Dist: 1/Addressee
3/Washington Design ServicesGF,R�crr, 0
1/SEGA Engineering SroNAL �
1/Gurudwara Singh Saba Church
EXPIRES 3J19/ q
i
Project No. 96-121-01 Page 12
II II .. •��1.i� •AF�i 51G srI�t1�42fm» #„ x �� ,\
I '•a ln �� aA'• 11 V_
6• `aA —
�
',•p r _`e�'�Rvxlpi 1 F�y(�r
+p
a
dI'NF>`.
NITA
Ed
ICI •;' ye���. � ��� �I�
ff'4
.�►A� ? 1^a t Ev I
�'I `/�r7w�L��'G?�� a �� •• �'���
��I it �•'4• �% � —__ __ r
d� 11 .�,ia —�,✓—e_' 1 ---- --- I-
• CONSULTANTS,
... r . Church
i.-
1 a.3o mxs yyp2 9 p e
34•NI1iLOW "�� L31
L1h A nL46 L17 `7�16� I p"^ �� _ T• A. , .v�_ FWD PEBAP 6 CAP -
tl Rf I .gyp YP I m i06E 006 5.
LS L21 Q L22 W L2 [\ -L33^.'-L40� v_
2
f f I � `� o c' Laa Lzs♦ L26 L21 . -28 - 3< ♦ 'i
10 C 1 ¢ p O Ti7 6� L2g 3t ♦ z ,. o" N66'I
X
�' TP-6: `�( >• 4� 191 �Y43 '� 163 � � e` 15 3e'
e thin £117 ? 26 62 n .� / Cm 1♦ l
xaa.E
6NE0 \ \ 1 t IS ape t]> 'o� ji .m j 1 �6!�W♦»
` '�t."E o. L]960
D 1f'ALG XB`� C 3
%ISTSN TP-3 .ncwrr w^ HOUND 33 'yL_'L32 6'� r r 1 r 4♦
I. 1 1 .kl O oa4 ac�Ns 12'NICE ♦ DER r .'
11 ILDIN 0 ,4
TP- 1�� ', 2'HIGH
1 g RiN• 2' P O/�ir'\'�/�PE f//')
? thin f111
r
\.
r'B I� ' �,...d ° � I n I /� � 'a•�__ _ �-�x5:_r.;�.,_ _J�yF.�J Nefi•',.�L f r /// .�` DI N)
Proi!fosed
Y /
Approximate rv^vt.
Qa+inq'Limi s 1.
9. NOI I BUILDING 0 D>$111? l - 21 i ti
,0 of u' EXISTING F 0 1 1, =�. ® R[I� 17O.g9 _ IX
I BaU w n ,; BUILDING \ IS NE-16].13 '•:'
aY tiryr +f � e ( \f SIE96N.ti61
WELL to
6t s D 1 ® 6 ` MUSE N
7
8 j IE NE•149 25 y
IE N- et 0}, 1 ♦ V
a NYC e'PYC _ r a 1 m
2 IBI �`. tq 1.'� , S K -L52 , L53 w"r I ] 1 w /soft h 1 1 t r
I •4 GB I N66'26 Ae'N 200 O1 _.j l - L I 1•
RINA4e 52 i f '] i f �` I DITM-
TE
-TE:N 142 5], o l 1 i - ., ,\ > L4 it4 \ f
1 I IS f4.143.f] L6] L66
\ m
ref: Topographic Survey dated 2-22-96 `��, c .I> } -� wi\ \' TP-9
f�,11? 'O '_ Rim looseY-
by Sadler, Barnard 8 Associates, Inc -12 skfft loose/soft 1
Reduced Scale: 1°=50`
Parking, Building Siting Plan, rev. 3/96 GMYEL ORSNE- < - - 1 'I 21 by Church Constructors, Inc. EPI
_ NU•26ve N '4sz.04 ! 1 �.YY,k ,I�� -
SITE EXPLORATION PLAN
GFOSPECTRUM CONSULTANTS, INC. Proposed Rtn3dw"ra Singh Saba Church
5212 'Talbot Road south
Renton, Washington
Proj. No.96-721 Date 4/96 Figure 2
APPENDIX A
FIELD EXPLORATION
Our field exploration included a site reconnaissance and subsurface exploration
program. During the site reconnaissance, the surface site conditions were noted,
and the locations of the test pits were approximately determined.
The test pits were approximately located using existing features as a guide. The
approximate locations of the test pits are shown on Figure 2. Test Pit elevations
were based on the topographic map provided to us.
Test pits were advanced using a tractor-mounted backhoe. Soils were continuously
logged and classified in the field by visual examination, in accordance with the
ASTM Soil Classification system.
Logs of the test pits are presented on the test pit summary sheets A-1 through A-5.
The test pit summaries include descriptions of the soils and pertinent field data.
Soil consistency and moisture conditions indicated on the logs are interpretations
based on the conditions observed in the field. Boundaries between soil strata
indicated on the logs are approximate and actual transitions between strata may be
gradual.
TEST PIT NO.
Logged By JAD
Date 3/27196 Elev. 169'
Depth W
(ft0,)Blows USCS Soil Description (40)
Sm Silty an w occ. av loose moist dark brn FILL
1 cone. AWs e3'x3' to
2 & plastic sheets & pipe medium
3 dense
4 Silty fine �n� very cedbrn
5 w ra a clay
6 — —
ense moist r� r o 9.9
7
8 b 44 2 NeRse 9.0
9 Iocc.H lfd t? 13 moist
10 � occ. ou er o ft.
11 5.7
12
13 Maximum depth 11 feet.
14 No seepage or ground water encountered.
15
TEST P,IT NO. 2
Logged By JAD
Date 3/27/96 Elev. 176'
0
SM Silt Sind witty orav I 6" edium moist dark brn
1 y & coDbfes to i0 Tense ottled
2 to 94MUr
3 to dense very & gray
4 Silty fine Sand w/occ. gravel dense moist 7.7
5
6 cemented (digs hard) very moist Bros n
7 very difficult digging dense15.6
6
9 Maximum depth 7.5 feet.
10 No seepage or ground water encc untered.
11
12
13
14 .
15
TEST PIT LOGS
GEOSPECTRUM CON$ULTANTS, INC. Gurudwara Singh Saba Church
5212 Talbot Road South
WX
=111 "' ;. Renton, Washington
Goctcchnlco/Enp/noorinp and Eorfh Sc/ancas
Proj. No96-121 I Date 4196 Figure A-1
TEST PIT NO. 3
Logged By JAD
Date 3/27/95 Elev. 171 '
Depth W
(ft.) Blows USCS Soil Description (4b)
0 SM Silty fine Sand medium moist
1 ra - rn
2 wlocc. gravel to 6" dense v olyst re rn
�o gray 20.7
3 Ve wet light-brn
5 cemented (digs hard) dde se moist gray-brn
6 very difficult digging hard
12.5
7
8
9 Maximum depth 7 feet.
1 No seepage or ground water enc untered.
11
12
13
14
15
TEST PIT NO. 4
Logged By JAD
Date 3/27/96 Elev. 163'
0 SM Silty fine Sand r�eae Siem vary eff
rn
with occ. gravel to 4" {n tst Wr
3 dense o gray 20.6
4
6 very moist I{obrn 12.5
6 dense 8a�nod n
7 red-brn
8
9
9 Maximum depth 8 feet.
10—
11 Minor seepage at about 5 feet.
12
13
14
15
TEST PIT LOGS
GuruGEOSPECTRUM CONSULTANTS, INC. 5212 T Singh Saba Church
212 Tallbobo t Road South
q = � Renton, Washington
Gccccnnlcol Enp/noorinp and Eorfn So/onc ar
Proj. No. 96-12 Date 4/96 Figure A-2
TEST PIT NO. 5
Logged By JAD
Date 3/27/96 Elev. 148'
Depth W
(ft.) Blows USCS Soil,,Description (4b)
SM Silty fine Sand (&sod) loose moist dark FILL
to to brown
medium very light
dense moist hrown
2 loose dark 18.6
3 brown
4
5 Maximum depth 3 feet
No ground water encountered.
6
7
Logged By
JAD TEST PIT NO. 6
Date 3/27/96 Elev. 189'
Topsoil/Organics w/roots loose very ark
rown 27.2
SM Silty fine Sand moist o
t w/occ. gravel to 6" to Rn
2 & occ. cobbles to 9" m.dense wet gray &
dense red-brn
with clay tory 26.6
3 dense
4
5 Maximum depth 3.5 ft.
No seepage or ground water enc untered.
6-
7 —
TEST PIT LOGS
GuruGEOSPECTRUM CONSULTANTS, INC. 5212 T Singh Saba Church
212 Tallbobo t Road South
Renton, Washington
Gaotachn/col EnpinaarinD and Eorfh Sc/anc as
Proj. No.96-121 Date 4/96 Figure A-3
The South Pierce County DISPATCH • PO Box 248 • Eatonville, WA 98328
Dispatch classified order/invoice DATE
Taken by
up to 20 words for $6 each week Additional words at 250 per word per week One time $1
billing charge
For the following
Statement To: classified ad which
ran In the Dispatch as
Aoaress. ------ Indicated please remit:
City Zip
Phone
INDEX (Circle One)
Animal Services Garage Sales Misc. Repairs
Announcements Help Wanted Mobile Homes Services
Autos Income Tax Personals Swap
Business Opportunities Landscape Materials Pets Trailers
Daycare Livestock Plants, Garden Wanted
Firewood Lost & Found Real Estate Work Wanted
For Sale Lots, Acerage Rentals
Free Logging Equipment Rentals Wanted
NEW INDEX
NUMBER OF WEEKS PUB DATES
i
TEST PIT NO. 7
Logged By JAD
Date 3/27/96 Elev. 203'
Depth W
(ft.) Blows USCS Soil Description t%>
e SM Topsoil/Organics w/roots hose very dc. brn 8
1 Silty fine Sand m.dense moist brown
w/occ gravel to 6" dense a gn
2 toy —
ray & 2
3 derryise �icn
4
5 Maximum depth 3.5 feet.
No seepage or ground water enc untered.
6
7
TEST PIT NO.
8
Logged eyy JAD
Date 3/27/96 Elev. 20E
Topsoil w/sod loose moist dk brn
t SM Silty fine Sand m dense gray-brn 176
w/occ. gravel to 6" dense RA&r
2
very ra
dense rMn
3
4
5 Maximum depth 3 ft.
No seepage or ground water enc untered.
6
7
TEST PIT LOGS
GEOSPECTRUM CONSULTANTS, INC. Gurudwara Singh Saba Church
5212 Talbot Road South
nl
"'r y '" Renton Washington
Gco/ochn/co/Enp/noa�lnp and Eorth Sc/ancos
Proj. No 96-121 Date 4/96 Figure A-4
TEST PIT NO. 9
Logged By JAD
Date 3/27/96 Elev. 192'
Depth W
(g.)Blows USCS Soil Description N
0 &I Topsoil/Organics w/roots Dose very dark
1 Silty fine Sand/Sandy Silt soft moist brown
to
1.9
2 wet
3 Silty fine Sand w/occ. gravel ense gray & 0.0
dense red-
brow
4
5 Maximum depth 3.5 feet.
No seepage or ground water enc untered.
6 -
7 —
Logged Byy JAD
TEST PIT NO, 10
Date 3/27/96 Elev. 167'
0 SM Silty Sand with gravel medium moist brown FILL
dense
12.2
2 -
3 —
Silty
fine Sand w4occ. gravel loose veryy dark
w/occ.roa s mto�ium To st brown
4 Zsia wet 22.6
5
— it
dense 9'ar- n
7 Maximum depth 6 ft.
No seepage or ground water encountered.
TEST PIT LOGS
GEOSPECTRUM CONSULTANTS, INC. Gurudwara Singh Saba Church
5212 Talbot Road South
NINE Renton, Washington
Gcotachn/ce/Enp/near/np and Eo?h Sc/wnc oa
Proj. No.96-121 Date 4/96 Figure A-5