HomeMy WebLinkAboutMeadowlake Village Memory Care Building - Drainage ReportMeadowlake Village: Memory Care Building
Drainage Report
Meridian, Idaho
Prepared for
LRS Architects
720 NW Davis, Suite 300
Portland, OR 97209
Prepared by
SPF Water Engineering, LLC
300 East Mallard, Suite 350
Boise, Idaho 83706
(208)383-4140
10/31/2011
d9�9p�, Of \�Pyoz
SPF WATER
�„ ENGINEERING
Table of Contents
1. Project Overview.............................................................
2. Existing Conditions..........................................................
2.1. Site Geology........................................................
2.2. Groundwater.......................................................
3. Proposed Conditions.......................................................
4. Stormwater Analysis and Sizing ......................................
4.1. Methodology........................................................
4.2. Peak Flows..........................................................
4.3. Infiltration/Percolation Facility Volumes ..............
4.4. Sand/Grease Traps .............................................
5. Summary .........................................................................
ndices
Appendix A
Basin Map
Appendix B
Runoff, Seepage Bed, and Sand/Grease Trap Calculations
Appendix C
Soils Report
SPF Water Engineering, LLC Page ii Meadowlake Village- Memory Care
926.0020 Drainage Report
1. PROJECT OVERVIEW
The Meadowlake Village development is located south of East Franklin Road and east of
Eagle Road within the City of Meridian Idaho. The proposed Memory Care Hospital site is
located within the Meadowlake Village community and is bounded by Arbor Lane to the
south and west and by an existing paved service road to the north and east. The project
site is approximately 1.6 acres in size and will include the construction of a new 30,165 SF
Memory Care facility. The existing and proposed storm water design utilizes subsurface
infiltration facilities for the disposal of storm water. All streets and drainage facilities within
and surrounding the project site are private. All stormwater calculations were performed
in accordance with ACHD requirements as outlined in ACHD Policy Manual Section 8000.
2. EXISTING CONDITIONS
The proposed building site is covered with irrigated grass turf and generally has graded
slopes of less than 2% with one exception; slopes along the southeast portion of the site
approach 20% where the previously graded building pad transitions to the constructed
service driveway. With the exception of previously constructed utility improvements, this
previously constructed building pad is void of any significant natural or constructed
features. Currently, storm water runoff that falls on the site infiltrates into the soil, or
drains into one of the existing storm drain facilities located on and near the site.
A number of storm drainage facilities for this site were constructed with the initial Grand
Lodge construction in approximately 2005. Based on our review of the record drawings it
is appears that these facilities were located and sized (based on —2004 requirements) to
serve the development based on the initial master plan. Additional drainage
improvements are proposed with this development based on plan modifications and the
current stormwater requirements.
2.1. Site Geology
The Geotechnical report prepared by Materials Testing and Inspection dated August 22,
(in Appendix D) generally describes the site to have approximately 2 -feet of lean clay with
silt and gravel fill materials extending to a depth of approximately 2 feet bgs. Below these
surficial soils a layer of weakly cemented silty sand extends to a depth of approximately 7
feet bgs. This layer of silty sand is underlain by a thick layer of poorly graded sand and
gravel that extended to the bottom of the excavated test pits. These poorly graded sands
and gravels located approximately 7 feet bgs are well suited for the subsurface disposal of
stormwater with recommended design infiltration rates of 8 inches/hour.
2.2. Groundwater
Groundwater was not encountered in test pits excavated to a maximum depth of 16.4 feet
bgs. The Geotechnical Report states that IDWR well drillers reports within % mile of the
project site indicate that groundwater levels are typically 20 to 40 feet bgs. The
Geotechnical Report estimates that groundwater levels are greater than 15 feet bgs
throughout the year.
SPF Water Engineering, LLC Page 1 Meadowlake Village- MemoryCare
926.0020 Drainage Report
3. PROPOSED CONDITIONS
The proposed site will consist of a new 30,165 SF Memory Care facility to be built on a
previously constructed building pad site within the Meadowlake Village campus. Minor
street improvements to add off-street parking spaces will be included in the construction.
The building and surface improvements will be collected in drainage inlets and will be
conveyed to existing and proposed subsurface seepage beds located on the site.
There are 4 existing seepage beds which were constructed with the initial development to
serve the project site and the adjacent tributary areas. These existing drainage basins are
identified as Basins A, B, C and D. Based on current storm drainage requirements,
additional stormwater facilities will be required to accommodate the impervious area
added by this building construction. Two additional subsurface seepage beds (Seepage
Beds D-2 and E) are proposed to provide additional storage and subsurface disposal area
for the fully developed site.
4. STORMWATER ANALYSIS AND SIZING
On-site storm water will be conveyed on paved surfaces or in landscape/drainage swales
to existing and proposed drainage inlets. From the point of collection at the drainage
inlets the water will be conveyed via a piped conduit system to a sand and grease trap for
water quality treatment. The sand and grease traps discharge to existing and proposed
subsurface infiltration facilities (seepage beds) for the ultimate disposal of the collected
storm water. Stormwater conveyance and infiltration facilities have been sized to
accommodate the 100 -year storm event. Calculations are provided in Appendix B.
4.1. Methodology
The proposed site was broken into separate drainage basins representing surface runoff
entering each catch basin. The Rational Method was used to determine the peak flow
leaving each basin. The Rational Method calculates runoff from the following equation:
Q = C`I*A
where Q = Runoff (cfs)
C = runoff coefficient based on land use
I = Rainfall Intensity (in/hr)
A = Area (acres)
4.2. Peak Flows
Peak flows were calculated using the Rational Method. The Method assumes that the
peak flow will occur when the runoff from the most hydrologically distant point on the site
reaches the point of interest (time of concentration). The Rational Method uses a Rainfall
Intensity, Duration, and Frequency graph to determine the rainfall intensity to use. The
rainfall intensities decrease as the storm duration increases, therefore the peak runoff flow
will occur when the intensities are the highest and the duration is the shortest. The
standard storm duration of 10 -minutes was used to determine the peak 100 -year storm
flows. Calculations for each basin's runoff can be seen in Appendix B.
SPF Water Engineering, LLC Page 2 Meadowlake Village- Memory Care
926,0020 Drainage Report
4.3. Infiltration/Percolation Facility Volumes
Four existing subsurface seepage beds (Basins A through D) currently serve the project
site and the adjacent tributary areas. With these improvements one existing seepage bed
(Seepage Bed C) will be extended and two new seepage beds (Seepage Beds D-2 and E)
will be added to provide the necessary subsurface storage and disposal capacity for the
fully developed site.
Basin E was added to reduce the drainage area tributary to existing Basin A. With the
additional impervious roof area, existing Basin A had insufficient storage volume for the
100 -year storm event. With the addition of Basin E, the existing seepage bed serving
basin A has capacity to manage 100% of the total 100 -year runoff volume with
approximately 17% excess capacity for sedimentation.
Existing Basin B was found to have adequate storage capacity to accommodate the
additional tributary runoff from the new building site. The additional contribution from the
new proposed building is minimal and calculations indicate that this existing seepage bed
has sufficient volume to hold the 100 -year runoff volume with over 25% excess capacity
for sedimentation.
As constructed, the seepage bed for Basin C is undersized to fully store and dispose of
the 100 -year run-off volume for the basin. The existing seepage bed facility offers 884
cubic feet of available storage or approximately 54% of the 1,634 cubic foot, 100 -year
runoff volume for the basin. As a result, this seepage bed will be expanded to a total
length of 42 feet with these improvements to provide the necessary storage volume for the
100 -year event, including 25% excess capacity for sedimentation.
An additional seepage bed (Seepage Bed D-2) has been added to existing Basin D to
accommodate the additional impervious roof area for the proposed building. The existing
seepage bed (Seepage Bed D-1) and drainage inlet will remain undisturbed. An
additional drain inlet will be located adjacent to the existing inlet and will drain through a
sand and grease trap to a new seepage bed located at the southeast corner of the site.
The new seepage bed (Seepage Bed D-2) provides capacity in the overall basin for 125%
of the 100 -year runoff volume.
As previously mentioned, Basin E was added to reduce the total tributary area of Basin A.
As designed, Seepage Bed E provides capacity for 125% of the 100 -year runoff volume.
The required seepage bed storage volumes (Vr) were calculated by subtracting the
volume of water infiltrated in the seepage bed(s) during the storm event from the total
runoff volume. This volume (Vr) was then increased by 25% to allow for sedimentation.
The drainage facilities have been designed to drain within a 24 hr period based on an
infiltration rate of 8 in/hr per the geotechnical report. Storm drainage runoff and seepage
bed sizing calculations are located in Appendix B.
4.4. Sand/Grease Traps
Sand and grease traps are required to be installed upstream of the infiltration/percolation
facilities to remove the majority of the oil, pollutants, and sediments. Sand and grease
traps shall be designed to limit the velocity through the throat of the baffles to 0.50 ft/s or
less. Using the width of the vault, maximum allowable velocity, and calculated peak flows,
SPF Water Engineering, LLC Page 3 Meadowlake Village- Memory Care
926.0020 Drainage Report
the required distance between the baffles can be calculated. For this project all on-site
flows including the 100 -year peak flows are proposed to be routed through existing or new
sand and grease traps. The calculations indicate that peak flows through the sand and
grease traps will not exceed the maximum allowable rate of 0.50 ft/second. Calculations
are provided in Appendix B.
One additional inlet is proposed for existing Basin A to drain a minor low point where
ponding currently occurs. This new inlet is proposed to be connected to an existing inlet
which drains directly into Seepage Bed A. The existing inlet is located in a grassy
landscape area and does not have a downstream sand and grease trap prior to
discharging to the seepage bed. The proposed inlet will be located adjacent to the
existing service driveway in a landscape area. This service drive is intended for
emergency access and is closed by bollards in both directions. As a result, the runoff
does not have the pollutants typically contained in street runoff. As a result, a sand and
grease trap is not proposed for this additional inlet.
5. SUMMARY
The storm drain system and facilities for the Meadowlake Village Memory Care building
are designed to meet current City of Meridian discharge and water quality requirements.
The facilities were designed to handle the 100 -year storm event using the Rational
Method.
SPF Water Engineering, LLC Page 4 Meadowlake Village- Memory Care
926.0020 Drainage Report
Appendix A
Basin Map
BASIN CALCULATIONS
BASIN A:
LANDSCAPE= 21,571 SF
PAVEMENT/ROOF= 36,535 SF
TOTAL= 58,106
BASIN B:
LANDSCAPE=9;634 SF
PAVEMENT/ROOF= 8,225 SF
TOTAL= 17,859
BASIN Ci
LANDSCAPE=5,111 SF
PAVEMENT/ROOF= 17,017 SF
TOTAL= 22,128
BASIN D:
LANDSCAPE= 10,914 SF
PAVEMENT/ROOF= 19,016 SF
TOTAL= 29,930
BASIN E:
LANDSCAPE=8,950 SF
PAVEMENT/ROOF= 20,678 SF
TOTAL= 29,628
NOTES:
E
1. REFER TO MEADOW LAKE VILLAGE RETIREMENT RESORT
DRAINAGE REPORT AND RECORD DRAWINGS PREPARED BY
BRIGGS ENGINEERING, FOR DRAINAGE BASIN CALCULATIONS
OUTSIDE OF THE BASINS SHOWN ON THIS PLAN.
BASIN
7
GRAND
LODGE
ASSISTED
LIVING
1 SPF WAENGINEETER
NG
300 East Mallard Drive, Suite 350
Boise, Idaho 83706
Tel (208) 383-4140 Fax (208) 383.4156
MEADOWLAKE VILLAGE -MEMORY CARE
100'
Br. '0" DRAINAGE BASIN MAP
Appendix B
Runoff, Seepage Bed, and Sand&Grease Trap Calculations
Basin 'A' See age Bed Calculation
Projecftocation Meadowlake Village Memory Care
Using Zone "Ae OF Curve Predevelopment Rate (if any): 0 cfs max
___ -_ —_-__.--
jReturn Period? 100 Void Volume: (v„°;d) 40%
— -- ~ 58,106 : --
Area Pipe Size(diameter m): 12
Drainage Area aces :Area in Acres
Pipe Area (ftp). (AP) 0.79
Runoff Coefficient (c )I 0.67 Number of Pipes 1
Percolation Rate inches/Hr 8 Flniltration Ca__ type Base
'----i0. u ace
.1Ttridth (ft) .
i.—•-th—•
(ft+)�----90-'Area 900 — Of Seepage Bed (Infiltration Area)
Leng�--
:Depth(fl)��--�10nclu ing - ree oard
Comnute Volume
Storm Duration
I Q Runoff Vol
Percolation Vol PreDev. Vol
VR Required Vol
Min Hr
in/hr cfs ft,
ft, ft3
ft3
10 0.17
3.11 2.79 1,672
100 0
1,572
60 1
1.15 3,709
600
109
Enter Total Design Vol.
3 f 09
Size Seepage Bed
Width Depth
ft ft
:d for 25% Sediment
to Drain
Relevant Equations
Q=CIA
Q= Flow Rate (cfs)
C= Runoff Coeffcien
1= Rain Intensity
A= Drainage Area
W0
VR Required Volume AG = Width X Depth
AN Net x -Sectional Area AN = [AG-API[Vvoid IAP
Aa Gross Sectional Area WxD
AP Pipe x -Section
Vv°;a Void Volume
Runoff Coefficient (c) for G
DA 11
DA3
21571 36535
c1 I c2 c3
0,21 0.95
Weighted (c) Value: 0.67
Yes
V: 3!0l
>mbined Areas /= 7 3U4Z
oma
Total Area v I �Ox �'4
Ex. s �� e
58106 SF
1.33 Acres
ok-
-7 cis
10/31/2011
Basin 'B' Seepa a Bed Calculation
Project/Location I Meadowlake Village Memory Care
Using Zone "A" OF Curve Predevelopment Rate (if any): 0 cfs max
Re -turn Period?100 Void Vo(ume: (V,°;d) 407,
_... 9 ( ) Area in A' -Pipe _ —.—
Area �" n 7 859 Srze(diameter in): 12
Drainage Area acres ' _ –
°fB5 Pipe Area (ft'): (AR) 0.79
Runoff Coefficient (c), 0.55 Number of Pipes 1
Percolation Rate Inches/Hr 8 Infiltration Calculation type Base
.Wiath7ttj . 10. urface
jlerigt4(ft) —25 Are a 250 Of Seepage Bed (infiltration Area)
_..—.J
:Depth (ft) - 10-, Including 1- ree pard
•COMDute Volume
Storm Duration II
Q
Runoff Vol
Percolation Vol PreDev. Vol
VR Required Vol
Min Hr
in/hr cfs
ft,
ft3 ft3
ft
10 1 0.17
3.11 0.70
417
28 0
389
60 1 1
1.15 1 0.26
926
167 0
758
5 10
Time to Drain
Enter Total Design Vol.
759
Size Seepage Bed
Width Depth
Ac
AR AN
ft ft
ft
ft k
Width Yes
10 10
1 100
1 0.79 !
Length
Required Storage Volume(ft)
759 25% Sed. 949
Width Depth (with t foot freeboard)
Adj. Length
Adjusted for 25% Sediment
5 10
Time to Drain
5.7
Fours_
References:
Relevant Equations
VR
Required Volume
AG = Width X Depth
Q=CIA
AN
Net x -Sectional Area
AN = [A(3-ApJ1VV01Dj+AP
Q= Flow Rate (cfs)
Ac
Gross Sectional Area WxD
C= Runoff Coefficien
AR
Pipe x -Section
I= Rain Intensity
Vv°id
Void Volume
A= Drainage Area
Runoff Coefficient (c) for C
DA 1DA 2 DA 3
9634 8275
c1 c2 F'3-
0.21 0.95
Weighted (c) Value: 0.55
2M
)mbined Areas V, = -7 J ���
Total Area ' /
LL 17859SF Eats+n� Y1�=
0.41 Acres
QPKto a O.?C' GFS
10/31/2011
Basin 'C' See a e Bed Calculation
Project/Location I Meadowlake Village Memory Care
Using Zone "A" OF Curve an
if Rate Predevelo ment Y))= - 0 cfs max
P (
Return Period? 100 Vold Volume: (V a,d) 40%
— --- - Pi � n 22,128 Pipe S¢e(diameter m): 12
Drainage Area(aces):A,eamncres z
•--• D,5( Pipe Area (AP) 0.79
Runoff Coefficient c 0.78 Number of Pipes 1
Percolation Rate ( )Inches�Hr 8 Infiltration Calculation type Base
�706.7t7: 1 u7ace
iLe
—.ngth---
(ftT-----42Area 420 +— Of Seepage Bed (Infiltration Area)
— • • �
:Depth—(ft") • —1 --Including l- ree oard
COmDute Volume
Storm Duration
I Q
Runoff Vol
Percolation Vol
PreDev- Vol
VR Required Vol
Min Hr
in/hr cfs
ft3
ft3
ft3
ft3
10 0.17 1
3.11 1 CL2J3
I736
47
0
690
60 1 1
1.15 1 0:45
1.634
28
0
4- ,. l
Width I Depth I AG AP AN
ft ft ft ft, W Width Yes
for 25% Sediment
Relevant Equations
VR
Required Volume
Q=CIAAN
Net x -Sectional Area
Q= Flow Rate (cfs)
AG
Gross Sectional Area wxD
C= Runoff Coefficien
AP
Pipe x -Section
1= Rain Intensity
VVW
Void Volume
A= Drainage Area
Runoff Coefficient (c) for C
DA DA2 DA3
5111 17017
c1 c2 1 a3
0.21 0,96
Weighted (c) Value: 0.78
Az—
= Width X Depth
_ (AG-APj[Vvoio)+Ap
V,, 13 S`i
)mbined Areas ,
Total Area '�4 o a
22128 SF
0.51 Acres 47x
�fai v;1ok-
6e- t�kcr+c(ed 17r�1 2OI ro '7a�`�
4-2
/'\ �kto f• Z3 10131/2011
Pro
Basin 'd' Seemae Bed Calculation I
on
Drainage Area (acres): Area in Acres
Runoff Coefficient (c)
Percolation Rate Inches/H'
:T1Mj{tj : " f0. urface
jLerigth({t)�_-_ 50Area
�Depth(ft)�10� ncu ing1-
Compute Volume
Predevelopment Rate (if any):
100 Void Volume: (Vmd)
?9,930 Pipe Size(diameter-in):
Pipe Area (ft'): (AP)
0.68 Number of Pipes
8Infiltration Calculation type
500 `-" Of Seepage Bed (Infiltration Area)
N
max
Storm Duration I
I Q
Runoff Vol
Percolation Vol PreDev. Vol
VR Required Vol
Min Hr I
in/hr I cfs
ft3
ft3 ft3
ft,
10 0.17 1
3.11 1 1.45
867
56 0
812
60 1 1 1
1.15 1 0.53
1924
333 0
11591
ti
Time to Drain 6.0
Enter Total Design Vol.
1 591
�Ize Seepage Bed
Width Depth Ac
Ap AN
pass (jYtggk?
ft ft ft
ft ttJ
Width
Yes
10 1 10 1 100
1 0.79 t ,SAO- ::
Length
Required Storage Volume (ft)
1591 25% Sed. 11989
Width Depth with 1 foot freeboard)
Adj. Length
Adjusted for 25% Sediment
10 10
a
=
ti
Time to Drain 6.0
Hours
References:
Relevant Equations
VR
Required Volume
Ac = Width X Depth
Q=CIA
AN
Net x -Sectional Area
AN = [AG-AP][Vvoio]+AR
Q= Flow Rate (cfs)
Ac
Gross Sectional Area WxD
C= Runoff Coefficien
A,
Pipe x -Section
1= Rain Intensity
VV01d
Void Volume V / rS 51
A= Drainage Area
yr _
Runoff Coefficient (c) for C
DA DA2 DA3
114
09 19016
c1I c21 c3
6' .21 0.95
Weighted (c) Value: 0.68
V, 1 a� 4fjS - Sic( °-g L —8c2
:;mbined Areas Ft 3
Total Area
29930 SF f t
0.69 Acres
c
10%al/-1eLI/Cv�e J�
f Yo I T 3
Dlt'73.Gr
a02� Z-7" Vr oL- 10/31/2011
Cf�Pk,� i.45' CFS
Basin 'E' Seepa a Bed Calculation
Project/Location I Meadowlake Village Memory Care
Using Zone "A" OF Curve � redevelopment Rate (if any): 0 cfs max
ri — --
;Return Period?
100 ,Void Volume: (v a,") 400
- — -- - -
Area m fe 29,62E Pipe S¢e(diameter in): 12
,Drainage Area acres -- --
( )'Area in Acres i Pipe Area (ft): (AP) 0.79
Runoff Coefficient (c } _ 0.72 Number of Pipes 1
'Percolation Rate IInches/Hr 8 Infiltration Calculation type Base
:1�ic3th�tf 'I u ace
--
----• Of Seepage Bed (Infiltration Area)
iLengt�(�t)�_-- 53 Area '5
•Depth (ft) • 10.7- nc u ing 1- ree oard
._.�_
Comr)ute Volume
Storm Duration
I Q
Runoff Vol
Percolation Vol PreDev. Vol
VR Required Vol
Min Hr
in/hr cfsft
1 0.794 77.
ft3 ft3
W10
0.17
3.11 1.53
918
59 0
859
60 1
1.15 0.57
2 037
353 0
1 684
Time to Drain 6.0
Hours
Enter Total Desi n Vol.
1 884
Size JeeDaae tsea
Width Depth AG
AP AN
t P =
ft ft ft
ft ft
Width Yes
10 10 100
1 0.794 77.
Length
Required Storage Volume (ft)
1684 25% Sed. 2105
Width Depth with t foot freeboard)
Adj. Length
Adjusted for 25% Sediment
10 10
Time to Drain 6.0
Hours
References:
Relevant Equations
VR
Required Volume
AG = Width X Depth
Q=CIA
AN
Net x -Sectional Area
AN = [AG-AP)[VV01D7*AP
Q= Flow Rate (cfs)
AG
Gross Sectional Area WXD
C= Runoff Coefficien
AP
Pipe x -Section
1= Rain Intensity
VVO1d
Void Volume
A= Drainage Area
Runoff Coefficient (c) for C
DAII2
8950 DA2DA3 0678
c1 c2 c3
0.2 0.951 �J
Weighted (c) Value: 0.72
)mbined Areas r 4
Total Area V - Z5A, T
29628 SF
0.68 Acres r -p= �5'3 )1 11)
v% � L��—
C -(s
10/31/2011
Sand/Grease Trap Velocity Calculation
Meadowlake Village Memory Care
Note: Existing S&G trap dimensions taken from original construction plans prepared by Briggs
Engineering dated 5/25/2005.
Peak
Baffle
Throat
Velocity
Vault
Number of
Area (A)
Velocity
Basin
Flow
Spacing
width
(V) 0.5 f/s
Notes
Size
S&G Traps
sq. ft.
OK
Q-cfs
inch
inch
max.
A
1500 G
1
2.79
17
59
6.97
0.40
=> YES
Existing
B
1000 G
1
0.7
12
48
4.00
0.18
=> YES
Existing
C
1000 G
1
1.23
12
48
4.00
0.31
=> YES
Existing
D1000
G
2
1.45
12
48
8.00
0.18
=> YES
1-1 Existin , D-2 New
E
1000 G
1
1.53
12
48
4.00
0.38
=> YES
New
Note: Existing S&G trap dimensions taken from original construction plans prepared by Briggs
Engineering dated 5/25/2005.
Appendix C
Soils Report
MATERIALS
TESTING &
INSPECTION
❑ Environrnental Services ❑ Geotechnical Engineering ❑ Construction Materials Testing ❑ Special Inspections
GEOTECHNICAL ENGINEERING REPORT
of
Memory Care Building
Meadow Lake Village at Touchmark
4037 Clocktower Lane
Meridian, Idaho
Prepared for:
Touchmark Development & Construction
5150 SW Griffith Drive
Beaverton, Oregon 97005
MTI File Number B110725g
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4746 • Fax (208) 322-6515
mti@mti-id.com • www.mti-id.com
6 MATERIALS
TESTING &
INSPECTION
22 August 2011
Page # I of 2'
\\server\reports\boise 2011 re orts\600-
❑ Environmental Services ❑ Geotechnical Eigineeling ❑ GonawA9r�MyaAl �T +ji{I I�gpoteclr� �PP�` AUAO`
Mr. Joseph A. Billig
Touchmark Development & Construction
5150 SW Griffith Drive
Beaverton, Oregon 97005
(503)646-5186
Re: Geotechnical Engineering Report
Memory Care Building
Meadow Lake Village at Touchmark
4037 Clocktower Drive
Meridian, Idaho
Dear Mr. Billig:
In compliance with your instructions, we have conducted a soils exploration and foundation evaluation for the
above referenced development. Fieldwork for this investigation was conducted on 11 August 2011. Data
have been analyzed to evaluate pertinent geotechnical conditions. Results of this investigation, together with
our recommendations, are to be found in the following report. We have provided three copies for your review
and distribution.
Often questions arise concerning soil conditions because of design and construction details that occur on a
project. MTI would be pleased to continue our role as geotechnical engineers during project implementation.
Additionally, MTI would be pleased in providing materials testing and special inspection services during
construction of this project. If you will advise us of the appropriate time to discuss these engineering
services, we will be pleased to meet with you at your convenience.
MTI appreciates this opportunity to be of service to you and looks forward to working with you in the future.
If you have questions, please call (208) 376-4748.
Respectfully Submitted,
Materials Testing & Inspection, Inc.
Elizabeth Brown, E.I.T.
Staff Engineer
Reviewed by: Kevin L. Schroeder, P.G.
Reviewed by:
General Manager
!'nnvriuhl Li
22 / j
Materials "Testing & Inspection, Inc.
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515
mti@mti-id.com • www,mti-id.com
6 MATERIALS
TESTING &
INSPECTION
22 August 2011
Page # 2 of 25
\\serverUeports\boise\2011 reports\600-
❑ Environmental SerJiceS LI Geotechnical Engineering Ll Con si clr) b"�'�$s i pa�Fl AS{AG
TABLE OF CONTENTS
SoilsSurvey Review......................................................................................................................
VolatileOrganic Scan ................... ................. ...................... ............ .............. ....... .,........ ...............
SITEHYDROLOGY..................................................................................................................................
Groundwater...................................................................................................................................
SoilInfiltration Rates.....................................................................................................................
FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS...........................................................
Foundation Design Recommendations ............. ............................ ..................................................
ut..,.. et.,t_ ,..._r—A,
11
12
13
13
14
14
14
15
15
Backfillof Walls ......... .................. ..................... .................................... ...............
..................................... 16
Excavations...............................................................................................................................................
16
GroundwaterControl.................................................................................................................................
16
GENERALCOMMENTS ........................... ............ ....... ..... ........ ........................................
............................. .._... 17
REFERENCES.........................................................................................._..........................................................
18
APPENDICES......................................................................................................................................................
19
AcronymList.............................................................................................................................................
19
Geotechnical General Notes .......... .................................... ...............................................
................... .... , 20
GeotechnicalInvestigation Test Pit Log.....................................................................................................
21
Plate1: Vicinity Map......................................._..................................................,..........._........................
24
Plate2: Site Map ............ .......... .......... ............. ............. ................ .....................................................
,.,... ... 25
Copyright c 201 I Materials Testing &Inspection, Inc.
2791 South Victory View Way Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515
mti@mti-id.com • www.mti-id.com
I
6 MATERIALS
TESTING &
INSPECTION
22 August 2011
Page# 3of25
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EXECUTIVE SUMMARY
The following is a brief summary of significant geotechnical issues for the proposed development, presented
with conclusions and recommendations. This summary must be read in conjunction with the entire
accompanying report for proper interpretation of the overall investigation.
Subsurface Conditions: The profile below represents a generalized interpretation for the project site. Note
that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles
presented in the logs, which can be found in the Appendix.
The materials encountered during exploration are quite typical for the geologic area mapped as Gravel of
Sunrise Terrace. Surficial materials are predominately lean clay with silt and gravel fill materials. These
materials are brown, dry, and stiff to very stiff. Fine grained sand and 4 inch minus cobbles were noted
throughout this material. Organic materials are often noted to depths of roughly L2 feet.
Silty sands are observed below the surfical fill materials. Silty sands are most often a light brown to reddish
brown and generally exhibit moisture contents of dry to slightly moist. Relative densities are medium dense
to dense with many of these firmer soil horizons containing some degree of calcium carbonate cementation
(hardpan).
In many of the deeper developed soils, poorly graded sandy gravels are encountered. Poorly graded gravels
are most often classified as reddish brown, slightly moist, and vary in relative density from dense to very
dense. Clasts found within the poorly graded gravels are generally granitic in composition with minor basalt
clasts.
Groundwater Conditions: During this field investigation, groundwater was not encountered in test pits
advanced to a maximum depth of 16.4 feet bgs. Soil moistures in the test pits were generally dry to slightly
moist.
In the vicinity of the project site, groundwater levels are controlled in large part by residential and commercial
irrigation activity and leakage from nearby canals. Maximum groundwater elevations likely occur during the
later portion of the irrigation season. During a previous investigation performed in February 2001 at the
Meadow Lake Village Development, no evidence of groundwater was noted within test pits advanced to
depths as great as 14.2 feet bgs. Furthermore, according to USGS monitoring well data within approximately
%2 -mile of the project site, groundwater was measured at a depth of 40.0 feet bgs, which equates to a
groundwater elevation of 2,635 feet above mean sea level (msl). Idaho Department of Water Resources Well
Driller's Reports within %2 -mile of the project site indicate static groundwater levels range between 20 and 40
feet bgs.
Shallow water has been encountered on nearby projects that is a result of leakage from nearby canals and
irrigation activity. However, the native poorly graded gravels were in a relatively dry state which indicates
that water hasn't been at this elevation in the recent past. Based on evidence of this investigation and
background knowledge of the area, MTI estimates groundwater depths greater than approximately 15 feet bgs
throughout the year.
Copyright c 2011 Materials Testing & Inspection, Inc.
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515
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MATERIALS
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❑ Environmental Services ❑Geotechnical Engineering ❑ Gonsyt� Qaµalp rrt>'Gifl� ,p g � Pp�g Qs
Building Foundations: Based on data obtained from the site and test results from various laboratory tests
performed, MTI recommends following guidelines for the net allowable soils bearing capacity:
Soil Bearing Capacity
Footing Depth
ASTM D 1557
dub ade Com action
Net Allowable
Soil Bealrin -Q# aci
Footings must bear on competent, native,
2,500 lbs/ftz
cemented silty sand sediments or compacted
Not Required for
structural fill. Existing lean clay fill materials
Native Soil
I
A /3 increase is allowable
must be completely removed from below
for short-term loading,
foundation elements. Excavation depths ranging
95% for Structural Fill
which is defined by seismic
from 1.8 to 2.8 feet bgs should be anticipated to
events or designed wind
expose proper bearing soils.
seeds.
Footings must bear on competent, native,
undisturbed poorly graded sandy gravel sediments
6,000 lbs/ft'
or compacted structural fill. Existing lean clay
Not Required for
fill materials and silty sand sediments must be
Native Soil
A 1/3 increase is allowable
completelly removed from below foundation
for short-term loading,
elements. Excavation depths ranging from 6.6 to
95% for Structural Fill
which is defined by seismic
8.3 feet bgs should be anticipated to expose
events or designed wind
proper bearing soils.
speeds.
MTI recommends that a qualified geotechnical engineer or engineering technician verify the bearing soil
suitability for each structure at the time of construction.
Footings should be proportioned to meet either the stated soil bearing capacity or the 2009 IBC minimum
requirements. Total settlement should be limited to approximately I inch, and differential settlement should
be limited to approximately '/2 inch. Objectionable soil types encountered at the bottom of footing
excavations should be removed and replaced with structural fill. Excessively loose or soft areas that are
encountered in the footing subgrade will require over -excavation and backfilling with structural fill. To
minimize the effects of slight differential movement that may occur because of variations in character of
supporting soils and seasonal moisture content, MTI recommends continuous footings be suitably reinforced
to make them as rigid as possible. For frost protection, the bottom of external footings should be 30 inches
below finished grade.
Building Floor Slabs: Uncontrolled fill, was encountered in portions of the site. MTI recommends that
these fill soils be excavated to a sufficient depth to expose competent, native soils or to a minimum depth of
11/2 feet below finished subgrade. A qualified soils technician should be present during excavation to identify
these materials.
Copyright a 2011 Materials Testing & Inspection, Inc.
2791 South Victory View Way - Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515.
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22 August 2011
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INTRODUCTION
This report presents results of a geotechnical investigation and analysis in support of data utilized in design of
structures as defined in the 2009 International Building Code (IBC). Information in support of groundwater
and storm water issues pertinent to the practice of Civil Engineering is included. Observations and
recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans or
drawings for the proposed development from those enumerated in this report should be brought to the
attention of the soils engineer to determine whether changes in foundation recommendations are required.
Deviations from noted subsurface conditions, if encountered during construction, should also be brought to
the attention of the soils engineer.
Project Description
The proposed development is in the southeastern portion of the City of Meridian, Ada County, Idaho, and
occupies a portion of the SE'/4NW'/a of Section 16, Township 3 North, Range 1 East, Boise Meridian. This
project will consist of construction of a single story Memory Care building to be developed with
spread/continuous footings and concrete floor slabs. Total settlements are limited to 1 inch. Loads of up to
2,000 pounds per lineal foot for wall footings, and column loads of up to 50,000 pounds were assumed for
settlement calculations. Retaining walls are not anticipated. MTI has not been informed of the proposed
grading plan.
Authorization
Authorization to perform this exploration and analysis was given in the form of a written authorization to
proceed from Mr. Richard M. Wessell of Touchmark Development and Construction to Bradley Tanberg of
Materials Testing and Inspection, hie. (MTI), on 8 August 2011. Said authorization is subject to terms,
conditions, and limitations described in the Consulting Agreement entered into between Touchmark
Development and Construction and MTI. Our scope of services for the proposed development has been
provided in our proposal dated 28 July 2011 and repeated below.
Purpose
The purpose of this Geotechnical Engineering Report is to determine various soil profile components and
their engineering characteristics for use by either design engineers or architects in:
• Preparing or verifying suitability of foundation design and placement
• Preparing site drainage designs
• Indicating issues pertaining to earthwork construction
Copyright D ZQI I Materials Testing & Inspection, Inc.
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2
6 MATERIALS
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Scope of Investigation
The scope of this investigation included review of geologic literature and existing available geotechnical
studies of the area, visual site reconnaissance of the immediate site, subsurface exploration of the site, field
and laboratory testing of materials collected, and engineering analysis and evaluation of foundation materials.
Warranty and Limiting Conditions
MTI warrants that findings and conclusions contained herein have been formulated in accordance with
generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics,
and engineering geology only for the site and project described in this report. These engineering methods
have been developed to provide the client with information regarding apparent or potential engineering
conditions relating to the site within the scope cited above and are necessarily limited to conditions observed
at the time of the site visit and research. Field observations and research reported herein are considered
sufficient in detail and scope to form a reasonable basis for the purposes cited above.
Exclusive Use
This report was prepared for exclusive use of the property owner(s), at the time of the report, and their
retained design consultants ("Client"). Conclusions and recommendations presented in this report are
based on the agreed-upon scope of work outlined in this report together with the Contract for Professional
Services between the Client and Materials Testing and Inspection, Inc. ("Consultant"). Use or misuse of this
report, or reliance upon findings hereof, by parties other than the Client is at their own risk. Neither Client
nor Consultant make representation of warranty to such other parties as to accuracy or completeness of this
report or suitability of its use by such other parties for purposes whatsoever, known or unknown, to Client or
Consultant. Neither Client nor Consultant shall have liability to indemnify or hold harmless third parties for
losses incurred by actual or purported use or misuse of this report. No other warranties are implied or
expressed.
Report Recommendation are Limited and Subiect to Misinterpretation
There is a distinct possibility that conditions may exist that could not be identified within the scope of the
investigation or that were not apparent during our site investigation. Findings of this report are limited to data
collected from noted explorations advanced and do not account for unidentified fill zones, unsuitable soil
types or conditions, and variability in soil moisture and groundwater conditions. To avoid possible
misinterpretations of findings, conclusions, and implications of this report, MTI should be retained to explain
the report contents to other design professionals as well as construction professionals.
Since actual subsurface conditions on the site can only be verified by earthwork, note that construction
recommendations are based on general assumptions from selective observations and selective field
exploratory sampling. Upon commencement of construction, such conditions may be identified that required
corrective actions, and these required corrective actions may impact the project budget. Therefore,
construction recommendations in this report should be considered preliminary, and MTI should be retained to
observe actual subsurface conditions during earthwork construction activities to provide additional
construction recommendations as needed.
Copyright 0 2011 Materials Testing & Inspection, Inc.
2791 South Victory View Way • Boise, ID 837013 • (208) 376-4748 • Fax (208) 322-6515
mti@mti-id.com • www.mti-id.com
MATERIALS
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❑ Geotechnical
n
22 A-Wft-1
91--Ist 2011
Pa'gftz:�_- # 7 of 25
I
Since
t to
ion, do not
eparate the
Rather, provide geotechnical
or authorizecforr their use,
of
tthe completereport to otherldesign pro► the report.
contractors. sessional or
This report is also limited to information available at the time it was prepared. In the evcr=-t additional
information is provided to MTI following publication of our report, it will be forwarded to tt- alie
evaluation in the form received. nt for
Environmental Concerns
Comments in this report concerning either onsite conditions or observations, including soil app4Z:!___Jr arJce
odors, are provided as general information. These comments are not intended to describe, s and
evaluate environmental concerns or situations. Since personnel, skills, procedures, standards, an fy'> or
differ, a geotechnical investigation report is not intended to substitute for a geoenvironmental irrv� equipment
estigation or
a Phase II/VI Environmental Site Assessment. If the potential for petroleum or hazardo�S materials
contamination or other environmental hazards relating to the site exists, MTI must be inforrnect prior to the
commencement of the geotechnical investigation. If environmental services are needed, MTI can
a separate contract, those personnel who are trained to investigate and delineate soil and water ccoriprovrde, via
amination.
SITE DESCRII'TION
Site Access
Access to the site may be gained via Interstate 84 to the Eagle Road exit. Proceed north on Eagle Road
approximately 0.5 mile to its intersection with Franklin Road. From this intersection, proceed east33 mile
0
to Touchmark Way. Follow Touchmark Way to the south east to its intersection with ClocktoOe Drive.
Continue south on Clocktower Drive 310 feet to Arbor Court, The site is located on the east side r Abor
Drive approximately 205 feet south of Clocktower Drive. Presently the site exists as a landscaped area within
the existing Meadow Lake Village Development. The location is depicted on site map plates inclthin
uded i the
Appendix.
Regional Geology
The project site is located within the western Snake River Plain of southwestern Idaho and eastern Oregon,
The plain is a northwest trending rift basin, about 45 miles wide and 200 miles long, that developed about ] 4
million years ago (Ma) and has since been occupied sporadically by large inland lakes. Geologic materials
found within and along the plain's margins reflect volcanic and fluvial/lacustrine sedimentary processes that
have led to an accumulation of approximately 1 to 2 km of interbedded volcanic and sedimentary deposits
within the plain. Along the margins of the plain, streams that drained the highlands to the north and south
provided coarse to fine-grained sediments eroded from granitic and volcanic rocks, respe ctively About 2
million years ago the last of the lakes was drained and since that time fluvial erosion acrd deposition has
dominated the evolution of the landscape.
Copyright ® ?ot 1 Mazcria�s 7atin
r' ---^• S � Inspectioq Inc,
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6 MATERIALS
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�'-- -_.__.._..._....,-�
The project site is underlain by "Gravel of Sunrise Terrace" as mapped by Othberg and Stanford (1993), The
Sunrise terrace is the third terrace above the modem Boise River in the eastern Boise Valley, composed of
sandy pebble and cobble gravel, and is about 115 feet above river level. Quaternary faulting has probably
truncated and tilted this terrace along with older surfaces. The surface of this deposit is mantled with 3-7 feet
of loess containing a weakly to moderately developed duripan. Based on stratigraphic correlation the Sunrise
terrace may be correlative with the Wilder terrace further to the west.
General Site Characteristics
This proposed development consists of approximately I acre of relatively level land with a slight downward
slope along the southeastern project boundary. Throughout the majority of the site, surficial materials consist
of fine-grained clay -silt with gravel fills, Vegetation primarily consists of lawn grasses and other landscaping
plants typical of and to semi -arid environments.
Regional drainage is north toward the Boise River. Storm water drainage for the site is achieved by
percolation through surficial soils. Storm water drainage collection and retention systems are not in place on
the project site and do currently exist within the driveways around the project site.
Regional Site Climatology and Geochemistry
According to the Western Regional Climate Center (WRCC, 2006) the average precipitation for Treasure
Valley is on the order of 10 to 12 inches per year, with an annual snowfall of approximately 20 inches and a
range from 3 to 49 inches. The monthly mean daily temperatures range from 21' F to 95' F with daily
extremes ranging from -25' F to I I I° F. Winds are generally from the northwest or southeast with an annual
average wind speed of approximately 9 miles per hour (mph) with a maximum of 62 mph. Soils and
sediments in the area are primarily derived from siliceous materials and exhibit low electro -chemical potential
for corrosion of metals or concretes. Local aggregates are generally appropriate for Portland cement and lime
cement mixtures. Surface waters, groundwaters, and soils in the region typically have pH levels ranging from
7.2 to 8.2 (USGS 2006).
Geoseismic Setting
Soils on site are classed as Site Class D in accordance with Chapter 16 of the 2009 edition of the IBC.
Structures constructed on this site should be designed per IBC requirements for such a seismic classification.
Our investigation did not reveal hazards resulting from potential earthquake motions including: slope
instability, liquefaction, and surface rupture caused by faulting or lateral spreading, Incidence and anticipated
acceleration of seismic activity in the area is low,
Copyright ° 2011 Materials Testing & Inspection, Inc,
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SOILS EXPLORATION
Exploration and Sampling Procedures
Field exploration conducted to determine engineering characteristics of subsurface materials included a
reconnaissance of the project site and investigation by test pit. Test pit sites were located in the field by
means of visual approximation from on-site features or known locations and are presumed to be accurate to
within a few feet. Upon completion of investigation, each test pit was backfilled with loose excavated
materials. Re -excavation and compaction of these test pit areas are required prior to construction of overlying
structures.
In addition, samples were obtained from representative soil strata encountered. Samples obtained have been
visually classified in the field by professional staff, identified according to test pit number and depth, placed
in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been
described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented
on these logs. MTI recommends that these logs not be used to estimate fill material quantities.
Laboratory Testing Program
Along with our field investigation, a supplemental laboratory testing program was conducted to determine
additional pertinent engineering characteristics of subsurface materials necessary in an analysis of the
anticipated behavior of the proposed structures. Laboratory tests were conducted in accordance with current
applicable American Society for Testing and Materials (ASTM) specifications, and results of these tests are to
be found on the accompanying logs located in the Appendix. The laboratory testing program for this report
included: Atterberg Limits Tests - ASTM D 4318 and Grain Size Analysis - ASTM C 117/C 136.
Soil and Sediment Profile
The profile below represents a generalized interpretation for the project site. Note that on site soils strata,
encountered between test pit locations, may vary from the individual soil profiles presented in the logs, which
can be found in the Appendix.
The materials encountered during exploration are quite typical for the geologic area mapped as Gravel of
Sunrise Terrace. Surficial materials are predominately lean clay with silt and gravel fill materials. These
materials are brown, dry, and stiff to very stiff. Fine grained sand and 4 inch minus cobbles were noted
throughout this material. Organic materials are often noted to depths of roughly 1.2 feet.
Silty sands are observed below the surfical fill materials. Silty sands are most often a light brown to reddish
brown and generally exhibit moisture contents of dry to slightly moist. Relative densities are medium dense
to dense with many of these firmer soil horizons containing some degree of calcium carbonate cementation
(hardpan) -
Copyright® 2011 Materials Testing & Inspection, Inc,
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515
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In many of the deeper developed soils, poorly graded sandy gravels are encountered. Poorly graded gravels
are most often classified as reddish brown, slightly moist, and vary in relative density from dense to very
dense. Clasts found within the poorly graded gravels are generally granitic in composition with minor basalt
clasts.
Soils Survey Review
Review of the United States Department of Agriculture (USDA) Soil Conservation Service, Soil Survey of
Ada County Area, Idaho, 1980, indicates that the site is underlain by the Elijah silt loam. Specific soils
characteristics, as defined by the USDA, are moderately slow permeability above the hardpan and very slow
through fractures in the hardpan, slow runoff, and slight erosion hazard.
Volatile Organic Scan
No environmental concerns were identified prior to commencement of the investigation. Therefore, soils
obtained during on-site activities were not assessed for volatile organic compounds by portable
photoionization detector. Samples obtained during our exploration activities exhibited no odors or
discoloration typically associated with this type contamination. No groundwater was encountered.
SITE HYDROLOGY
Existing surface drainage conditions are defined in the General Site Characteristics section. Information
provided in this section is limited to observations made at the time of the investigation. Either regional or
local ordinances may require information beyond the scope of this report.
Groundwater
During this field investigation, groundwater was not encountered in test pits advanced to a maximum depth of
16.4 feet bgs. Soil moistures in the test pits were generally dry to slightly moist.
In the vicinity of the project site, groundwater levels are controlled in large part by residential and commercial
irrigation activity and leakage from nearby canals. Maximum groundwater elevations likely occur during the
later portion of the irrigation season. During a previous investigation performed in February 2001 at the
Meadow Lake Village Development, no evidence of groundwater was noted within test pits advanced to
depths as great as 14.2 feet bgs. Furthermore, according to USGS monitoring well data within approximately
t/2 -mile of the project site, groundwater was measured at a depth of 40.0 feet bgs, which equates to a
groundwater elevation of 2,635 feet above mean sea level (ms]). Idaho Department of Water Resources Well
Driller's Reports within '/2 -mile of the project site indicate static groundwater levels range between 20 and 40
feet bgs.
Co ri hl ° 201 I Materials Testing & Inspection, Inc.
2791 South Victory View Way • Boise., ID 83709 • (208) 376-4748 Fax (208) 322-6515
mti@rnti-id.com • www.mti-id.com
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❑ Environmental Services ❑ Geotechnical Engineering ❑ Consly�jygp
Shallow water has been encountered on nearby projects that is a result of leakage from nearby canals and
irrigation activity. However, the native poorly graded gravels were in a relatively dry state which indicates
that water hasn't been at this elevation in the recent past. Based on evidence of this investigation and
background knowledge of the area, MTI estimates groundwater depths greater than approximately 15 feet bgs
throughout the year.
Soil Infiltration Rates
Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was not tested in the field.
Given the absence of direct measurements, for this report an estimation of infiltration is presented using
generally recognized values for each soil type and gradation. Of soils comprising the generalized soil profile
for this study, silty sand soils usually display rates of 4 to 8 inches per hour; though calcium carbonate
cementation may reduce this value to near zero. Poorly -graded gravel sediments typically exhibit infiltration
values in excess of 12 inches per hour. Infiltration testing is generally not required within these sediments
because of their free -draining nature.
It is recommended that infiltration facilities constructed on the site be extended into native poorly graded
sandy gravel sediments. Excavation depths of approximately 6.6 to 8.3 feet bgs should be anticipated to
expose these sandy gravel sediments. Because of the high soil permeability, ASTM C 33 filter sand, or
equivalent, should be incorporated into design of infiltration facilities. An infiltration rate of 8 inches per
hour should be used in design.
FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS
Various foundation types have been considered for support of the proposed structure. Two requirements must
be met in the design of foundations. First, the applied bearing stress must be less than the ultimate bearing
capacity of foundation soils to maintain stability. Second, total and differential settlement must not exceed an
amount that will produce an adverse behavior of the superstructure. Allowable settlement is usually exceeded
before bearing capacity considerations become important; thus, allowable bearing pressure is normally
controlled by settlement considerations.
Considering subsurface conditions and the proposed construction, it is recommended that the structure be
founded upon conventional spread footings and continuous wall footings. Total settlements should not
exceed 1 inch if the following design and construction recommendations are observed.
Foundation Design Recommendations
Based on data obtained from the site and test results from various laboratory tests performed, MTI
recommends following guidelines for the net allowable soils bearing capacity:
Copyright ° 2011 Materials Testing & Inspection, Inc.
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Soil Bearing Capacity
Footing Depth
ASTM A 1557
Sub rade Compaction
Net Allowable
Soil Bearing,Capacity
Footings must bear on competent, native,
2,500 lbs/ft2
cemented silty sand sediments or compacted
Not Required for
structural fill. Existing lean clay fill materials
Native Soil
1
A /3 increase is allowable
must be completely removed from below
for short-term loading,
foundation elements.' Excavation depths ranging
95% for Structural Fill
which is defined seismic
from 1.8 to 2.8 feet bgs should be anticipated to
events or designee d wind
expose proper bearing soils.
speeds.
Footings must bear on competent, native,
undisturbed poorly graded sandy gravel sediments
6,000 lbs/ftz
or compacted structural fill. Existing lean clay
Not Required for
fill materials and silty sand sediments must be
Native Soil
A 1/3 increase is allowable
completely removed from below foundation
for short-term loading,
elements. Excavation depths ranging from 6.6 to
95% for Structural Fill
which is defined by seismic
8.3 feet bgs should be anticipated to expose
events or designed wind
proper bearing soils.
speeds.
MTI recommends that a qualified geotechnical engineer or engineering technician verify the bearing soil
suitability for each structure at the time of construction.
Footings should be proportioned to meet either the stated soil bearing capacity or the 2009 IBC minimum
requirements. Total settlement should be limited to approximately 1 inch, and differential settlement should
be limited to approximately %2 inch. Objectionable soil types encountered at the bottom of footing
excavations should be removed and replaced with structural fill. Excessively loose or soft areas that are
encountered in the footing subgrade will require over -excavation and backfilling with structural fill. To
minimize the effects of slight differential movement that may occur because of variations in character of
supporting soils and seasonal moisture content, MTI recommends continuous footings be suitably reinforced
to make them as rigid as possible. For frost protection, the bottom of external footings should be 30 inches
below finished grade,
Floor Slab -on -Grade
subgrade A qualified soils technician should be present during excavation to identify these materials.
Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or
floor -supporting fill. In addition, the remaining subgrade should be treated in accordance with guidelines
presented in the Earthwork section. Areas of excessive yielding should be excavated and backfilled with
structural fill. Fill used to increase the elevation of the floor slab should meet requirements detailed in the
Structural Fill section. Fill materials must be compacted to a minimum 95 percent of maximum density as
determined by ASTM D 1557.
Copyright O 2011 Materials Testing & Inspection, Inc.
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A free -draining granular mat (drainage fill course) should be provided below slabs -on -grade. This should be
a minimum of 4 inches in thickness and properly compacted. The mat should consist of a sand and gravel
mixture, complying with Idaho Standards for Public Works Construction (ISPWC) specifications for'/4-inch
(Type 1) crushed aggregate. A moisture -retarder should be placed beneath floor slabs to minimize potential
ground moisture effects on moisture -sensitive floor coverings. The moisture -retarder should be at least 15 -mil
in thickness and have a permeance of less than 0.01 US perms as determined by ASTM E 96. Placement of
the moisture -retarder will require special consideration with regard to effects on the slab -on -grade. The
granular mat should be compacted to no less than 95 percent of maximum density as determined by ASTM D
1557. Upon request, MTI can provide further consultation regarding installation
CONSTRUCTION CONSIDERATIONS
Recommendations in this report are based upon structural elements of the project being founded on
competent, native, cemented silty sand sediments or compacted structural fill. Structural areas should be
stripped to an elevation that exposes these soil types.
Earthwork
Excessively organic soils, deleterious materials, or disturbed soils generally undergo high volume changes
when subjected to loads, which is detrimental to subgrade behavior in the area of pavements, floor slabs,
structural fills, and foundations. Mature trees, landscaping plants, and thick grasses with associated root
systems were noted at the time of our investigation. It is recommended that organic or disturbed soils, if
encountered, be removed to depths of I foot (minimum), and wasted or stockpiled for later use. Stripping
depths should be adjusted in the field to assure that the entire root zone or disturbed zone or topsoil are
removed prior to placement and compaction of structural fill materials. Exact removal depths should be
determined during grading operations by a qualified geotechnical representative, and should be based upon
subgrade soil type, composition, and firmness or soil stability. If underground storage tanks (USTs),
underground utilities, wells, or septic systems are discovered during construction activities, they must be
decommissioned then removed or abandoned in accordance with governing Federal, State, and local agencies.
Excavations developed as the result of such removal must be backfilled with structural fill materials as
defined in the Structural Fill section.
MTI should oversee subgrade conditions (i.e., moisture content) as well as placement and compaction of new
fill (if required) after native soils are excavated to design grade. Recommendations for structural fill
presented in this report can be used to minimize volume changes and differential settlements that are
detrimental to the behavior of footings, pavements, and floor slabs. Sufficient density tests should be
performed to properly monitor compaction. For structural fill beneath building structures, one in-place
density test per lift for every 5,000 square feet is recommended. In parking and driveway areas, this can be
decreased to one test per lift for every 10,000 square feet.
°.2011 Materials Testing & Inspection, Inc.
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4748 - Fax (208) 322-6515
mti®mti-id.com • www.mti-id.com
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Dry Weather
If construction is to be conducted during dry seasonal conditions, many problems associated with soft soils
may be avoided. However, some rutting of subgrade soils may be induced by shallow groundwater
conditions related to springtime runoff or irrigation activities during late summer through early fall. Solutions
to problems associated with soft subgrade soils are outlined in the Soft Subgrade Soils section. Problems
may also arise because of lack of moisture in native and fill soils at time of placement. This will require the
addition of water to achieve near -optimum moisture levels. Low -cohesion soils exposed in excavations may
become friable, increasing chances of sloughing or caving. Measures to control excessive dust should be
considered as part of the overall health and safety management plan.
Wet Weather
If construction is to be conducted during wet seasonal conditions (commonly from mid-November through
May), problems associated with soft soils must be considered as part of the construction plan. During this
time of year, fine-grained soils such as silts and clays will become unstable with increased moisture content,
and eventually deform or rut. Additionally, constant low temperatures reduce the possibility of drying soils to
near optimum conditions.
Soft Subgrade Soils
Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut
under construction traffic, During periods of wet weather, construction may become very difficult if not
impossible. The following recommendations and options have been included for dealing with soft subgrade
conditions:
• Track -mounted vehicles should be used to strip the subgrade of root matter and other deleterious
debris. Heavy rubber -tired equipment should be prohibited from operating directly on the native
subgrade and areas in which structural fill materials have been placed. Construction traffic should be
restricted to designated roadways that do not cross, or cross on a limited basis, proposed roadway or
parking areas.
• Construction roadways on soft subgrade soils should consist of a minimum 2 -foot thickness of large
cobbles of 4 to 6 inches in diameter with sufficient sand and fines to fill voids. Construction entrances
should consist of a 6 -inch thickness of clean, 2 -inch minimum, angular drain -rock and must be a
minimum of 10 feet wide and 30 to 50 feet long. During the construction process, top dressing of the
entrance may be required for maintenance.
• Scarification and aeration of subgrade soils can be employed to reduce the moisture content of wet
subgrade soils. After stripping is complete, the exposed subgrade should be ripped or disked to a
depth of 1 V2 feet and allowed to air dry for 2 to 4 weeks. Further disking should be performed on a
weekly basis to aid the aeration process.
• Alternative soil stabilization methods include use of geotextiles, lime, and cement stabilization. MTI
is available to provide recommendations and guidelines at your request.
Co -ri hl " 2011 Materials Testing & Inspection, Inc
2791 South Victory View Way • Boise, ID 83709 - (208) 376-4748 - Fax (208) 322-6515
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Frozen Subgrade Soils
Prior to placement of structural fill materials or foundation elements, frozen subgrade soils must either be
allowed to thaw or be stripped to depths that expose non -frozen soils and wasted or stockpiled for later use.
Stockpiled materials must be allowed to thaw and return to near -optimal conditions prior to use as structural
fill,
Structural Fill
Soils recommended for use as structural fill are those classified as GW, GP, SW, and SP in accordance with
the Unified Soil Classification System (USCS) (ASTM D 2487), Use of silty soils (USCS designation of
GM, SM, and ML) as structural fill may be acceptable. However, use of silty soils (GM, SM, and ML) as
structural fill below footings is prohibited. These materials require very high moisture contents for
compaction and require a long time to dry out if natural moisture contents are too high and may also be
susceptible to frost heave under certain conditions. Therefore these materials can be quite difficult to work
with as moisture content, lift thickness, and compactive effort becomes difficult to control. If silty soil is used
for structural fill, lift thicknesses should not exceed 6 inches (loose), and fill material moisture must be
closely monitored at both the working elevation and the elevations of materials already placed. Following
placement, silty soils must be protected from degradation resulting from construction traffic or subsequent
construction.
Recommended granular structural fill materials, those classified as GW, GP, SW, and SP, should consist of a
6 -inch minus select, clean, granular soil with no more than 50 percent oversize (greater than %-inch) material
and no more than 12 percent fines (passing No. 200 sieve). These fill materials should be placed in layers not
to exceed 12 inches in loose thickness. Prior to placement of structural fill materials, surfaces must be
prepared as outlined in the Construction Considerations section. Structural fill material should be moisture -
conditioned to achieve optimum moisture content prior to compaction. For structural fill below footings,
areas of compacted backfill must extend outside the perimeter of the footing for a distance equal to the
thickness of fill between the bottom of foundation and underlying soils, or 5 feet, whichever is less.
Each layer of structural fill must be compacted, as outlined below:
• Below Structures and Rigid Pavements: A minimum of 95 percent of the maximum dry density as
determined by ASTM D 1557.
• Below Flexible Pavements: A minimum of 92 percent of the maximum dry density as determined by
ASTM D 1557 or 95 percent of the maximum dry density as determined by ASTM D 698.
The ASTM D 1557 test method must be used for samples containing up to 40 percent oversize (greater than
a/< -inch) particles. If material contains more than 40 percent but less than 50 percent oversize particles,
compaction of fill must be confirmed by proof rolling each lift with a 10 -ton vibratory roller (or equivalent)
until the maximum density has been achieved. Density testing must be performed after each proof rolling
pass until the in-place density test results indicate a drop (or no increase) in the dry density, defined as the
maximum density or "break over" point. The number of required passes should be used as the requirement on
the remainder of fill placement. Material should contain sufficient fines to fill void spaces, and must not
contain more than 50 percent oversize particles.
Copyright ° 2011 Materials Testing & Inspection, Inc.
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Backfill of Walls
Backfill materials must conform to the requirements of structural fill, as defined in this report. For wall
heights greater than 2.5 feet, the maximum material size should not exceed 4 inches in diameter. Placing
oversized material against rigid surfaces interferes with proper compaction, and can induce excessive point
loads on walls. Backfill shall not commence until the wall has gained sufficient strength to resist placement
and compaction forces. Further, retaining walls above 2.5 feet in height shall be backfilled in a manner that
will limit the potential for damage from compaction methods and/or equipment. It is recommended that only
small hand -operated compaction equipment be used for compaction of backfill within a horizontal distance
equal to the height of the wall, measured from the back face of the wall.
Backfill should be compacted in accordance with the specifications for structural fill, except in those areas
where it is determined that future settlement is not a concern, such as planter areas. In nonstructural areas,
backfill must be compacted to a firm and unyielding condition..
Excavations
Shallow excavations that do not exceed 4 feet in depth may be constructed with side slopes approaching
vertical. Below this depth, it is recommended that slopes be constructed in accordance with Occupational
Safety and Health Administration (OSHA) regulations, section 1926, subpart P. Based on these regulations,
on-site soils are classified as type "C soil, and as such, excavations within these soils should be constructed
at a maximum slope of 1'/z foot horizontal to 1 foot vertical (1'/2H:1 V) for excavations up to 20 feet in height.
Excavations in excess of 20 feet will require additional analysis. Note that these slope angles are considered
During our subsurface exploration, test pit sidewalls generally exhibited little indication of collapse. For deep
excavations, native granular sediments cannot be expected to remain in position. These materials are prone to
failure and may collapse, thereby, undermining upper soils layers. This is especially true when excavations
approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in
accordance with procedures outlined in this report.
Shallow soil cementation (caliche) was observed throughout much of the site and may cause difficulties
during foundation development and utility placement. Cemented soils should be anticipated throughout the
site at depths of 1.8 to 8,3 feet bgs.
Groundwater Control
Groundwater was not encountered during the investigation and is anticipated to be below the depth of most
construction. However, special precautions may be required for control of surface runoff and subsurface
seepage. It is recommended that runoff be directed away from open excavations. Silty soils may become soft
and pump if subjected to excessive traffic during time of surface runoff Ponded water in construction areas
should be drained through methods such as trenching, sloping, crowning grades, nightly smooth drum rolling,
or installing a French drain system. Additionally, temporary or permanent driveway sections should be
constructed if extended wet weather is forecasted.
Copyright C 2011 Materials resting & Inspection, Inc.
2791 South Victory View Way • Boise, ID 83709 - (208) 376-4748 • Fax (208) 322-6515
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GENERAL COMMENTS
When plans and specifications are complete, or if significant changes are made in the character or location of
the proposed development, consultation with MTI should be arranged as supplementary recommendations
may be required. It is recommended that suitability of subgrade soils and compaction of structural fill
materials be verified prior to placement of structural elements. Additionally, monitoring and testing should
be performed to verify that suitable materials are used for structural fill and that proper placement and
compaction techniques are utilized.
c 2011 Materials Testing & Inspection, Inc.
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515
mti@mti-id.com • www,mti-id.com
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REFERENCES
American Society for Testing and Materials (ASTM) (1999), Standard Test Method for Materials Finer than 75-µm (No. 200) Sieve
in Mineral Aggregates by Washing: ASTM C 117 — 95, West Conshohocken, PA: ASTM.
American Society for Testing and Materials (ASTM) (1999). Standard Test Method for Sieve Analysis of Fine and Coarse
Aggregates: ASTM C 136 — 96a. West Conshohocken, PA: ASTM.
American Society for Testing and Materials (ASTM) (2000). Standard Test Methods for Laboratory Compaction Characteristics of
Soil Using Standard Effort D698-00ael. West Conshohocken, PA: ASTM,
American Society for Testing and Materials (ASTM) (2002). Standard Test Methods for Laboratory Compaction Characteristics of
Soil Using Modified Effort D1557-02el. West Conshohocken, PA: ASTM.
American Society for Testing and Materials (ASTM) (2006). Standard Practice for Classification of Soils for Engineering Purposes
(Unified Soil Classification System) D2487-06. West Conshohocken, PA: ASTM.
American Society for Testing and Materials (ASTM) (1999). Standard Test Methods for Liquid Limit, Plastic Limit. and Plasticity
Index of Soils: ASTM D 4318 — 86. West Conshohocken, PA: ASTM.
Collett, R. A, U. S. Department of Agriculture, Soil Conservation Service. (1980). Soil Survey of Ada County Area, Idaho.
Washington, DC: U. S, Government Printing Office.
Desert Research Institute. Western Regional Climate Center. [Online] Available: <http://www.wrec.dri.edu/> (2011).
International Building Code Council (2009). International Building Code, 2009. Country Club Hills, IL: Author.
Local Highway Technical Assistance Council (LHTAC) (2005), Idaho Standards for Public Works Construction, 2005. Boise, ID:
Author.
Othberg, K. L. and Stanford, L. A., Idaho Geologic Society (1992). Geologic Map of the Boise Valley and Adioining Area, Western
Snake River Plan. Idaho. (scale 1:100,000). Boise, Idaho: Joslyn and Morris.
State of Idaho, Department of Health and Welfare, Division of Environmental Quality. (April 2000). Technical Guidance Manual
For Individual and Subsurface Sewage Disposal Systems. Boise, Idaho: Author.
U. S. Department of Agriculture, Natural Resource Conservation Service. Web Soil Survey. [Online] Available:
<http://websoilsurvey.nres.usda.gov/app/> (2011).
U. S. Department of Commerce, National Oceanic and Atmospheric Administration and Desert Research Institute. Western
Regional Climate Center. [Online] Available: <http://www.wrcc.dri.edu/> (2011).
U. S. Dept. of Labor, Occupational Safety and Health Administration. "CFR 29, Part 1926, subpart P: Safety and Health
Regulations for Construction, Excavations. 09861". [Online] Available: <www.osha.gov> (2011).
U. S. Geological Survey. (2006). National Water Information System: Web interface. [Online] Available:
<h9p:J/watcrdqta.usgs.gov/nwis>
Copyright C 2011 Materials Testing & Inspection. hte.
2791 South Victory View Way • Boise, ID 83709 • (208) 376-4748 • Fax (208) 322-6515
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APPENDICES
ACRONYM LIST
AASHTO: American Association of State Highway and Transportation Officials
ACCP: Asphalt Cement Concrete Pavement
ACHD: Ada County Highway District
ASTM: American Society for Testing and Materials
AU: Augersample.
bgs: below ground surface
CB: Carbide bit
CBR: California Bearing Ratio
D: natural dry unit weight, pef
DB: diamond bit
DM: Dames & Moore sampling tube
GS: grab sample
IBC: International Building Code
ISPWC: Idaho Standards for Public Works Construction
ITD: Idaho Transportation Department
LL: Liquid Limit
M: water content
MSL: mean sea level
N: Standard "N' penetration: blows per foot, Standard Penetration Test
NP: nonplastic
PCCP: Portland Cement Concrete Pavement
PERM: vapor permeability
PI: Plasticity Index
PID: photoionization detector
PVC: polyvinyl chloride
Qc: cone penetrometer value, unconfined compressive strength, psi
Qp: Penetrometer value, unconfined compressive strength, tsf
Qu: Unconfined compressive strength, tsf
SPT: Standard Penetration Test (140:pound hammer falling 30 in. on a 2:in, split spoon)
SS: split spoon (13/8:in. inside diameter, 2:in, outside diameter, except where noted)
ST: shelby tube (3: in. outside diameter, except where noted)
USCS: Unified Soil Classification System
USDA: United States Department of Agriculture
UST: underground storage tank
V: vane value, ultimate shearing strength, tsf
WT: apparent groundwater level
Copyright ° 2011 Materials Testing & Inspection, Inc.
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GEOTECHNICAL GENERAL NOTES
LAT1VEDENSITY _AND Cl1N.SIS WCAT
TIdN
Field Test
Coarse -Grained Soils
SPT Blow Counts Fine -Grained Soils
SPT Blow Counts
Very Loose:
<4 Very Soft:
<2
Loose:
4-10 Soft:
2-4
Medium Dense:
10-30 Medium Stiff:
4-8
Dense:
30-50 Stiff:
8-15
Very Dense:
>50 Very Stiff:
15-30
MH. Inorganic, elastic silts; sandy, gravelly or clayey elastic silts
Hard:
>30
Description
Field Test
Dry
Absence of moisture, dusty, dry to touch
Moist
Damp but not visible moisture
Wet
Visible free water, usually soil is below
water table
PARTICLE SIZE
Boulders: >12 in. Coarse -Grained Sand: 5 to 0.6 mm Silts: 0.075 to 0.005 mm
Cobbles: 12 to 3 in. Medium -Grained Sand: 0,6 to 0.2 mm Clays: <0.005 mm
Gravel: 3 in. to 5 mm Fine -Grained Sand: j 0.2 to 0.075 mm
UNIFIED SOIL CLASSIF_ ICA1T STEM
Major Divisions,
Description
Field Test
Weakly
Crumbles or breaks with handling or
GP Poorly -graded gravels; gravel/sand mixtures with little or no fines
slight finger pressure
Moderately
Crumbles or beaks with considerable
SW Wcll-graded sands; gravelly sands with little or no fines
fin er ressure
Strongly
Will not crumble or break with finger
Fine Grained
Soils>50%
passes No.200
sieve
pressure
PARTICLE SIZE
Boulders: >12 in. Coarse -Grained Sand: 5 to 0.6 mm Silts: 0.075 to 0.005 mm
Cobbles: 12 to 3 in. Medium -Grained Sand: 0,6 to 0.2 mm Clays: <0.005 mm
Gravel: 3 in. to 5 mm Fine -Grained Sand: j 0.2 to 0.075 mm
UNIFIED SOIL CLASSIF_ ICA1T STEM
Major Divisions,
Symbgl Sail pescrippons
Coarse -Grained
Soils
<50%
passes No. 200
sieve
Gravel & Gravelly
Soils
<50%
coarse fraction
passes No.4 sieve
GW Well -graded gravels; gravel/sand mixtures with little or no fines
GP Poorly -graded gravels; gravel/sand mixtures with little or no fines
GM Silty gravels; poorly -graded gravel/sand/silt mixtures
GC Clayey gravels; poorly -graded gravel/sand/clay mixtures
Sand & Sandy
Soils
>50%
coarse fraction
passes No.4 sieve
SW Wcll-graded sands; gravelly sands with little or no fines
SP Poorly -graded sands; gravelly sands with little or no fines
SM Silty sands; poorly -graded sand/gravel/silt mixtures
r
SC Clayey sands; poorly -graded sand/gravel/clay mixtures
Fine Grained
Soils>50%
passes No.200
sieve
Silts & Clays
LL < 50
ML Inorganic silts; sandy, gravelly or clayey silts
CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium -plasticity clays
OL Organic, low -plasticity clays and silts
Silts & Clays
LL> 50
MH. Inorganic, elastic silts; sandy, gravelly or clayey elastic silts
CH Fat cla s; hi h- lastici
Y g P ty, inorganic clays
OH Organic, medium to high -plasticity clays and silts
Highly Organic Soils
PT Peat, humus, hydric soils with high organic content
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GEOTECHNICAL INVESTIGATION TEST PIT LOG
Test Pit Log #: TP -1 Date Advanced: 8/11/2011 Logged by: Elizabeth Brown, E.I.T.
Excavated by: Struckman's Backhoe Service Location: See Site Map Plates
Depth to Water Table: Not Encountered Total Depth: 9.0 Feet bgs
Depth
Field Description and
Sample
Sample Depth
QP
Lab
(Feet bgs)
USCS Soil and Sediment Classification
Type
Feet b s
Test ID
Lean Clay Fill (CL -FILL): Brown, dry, very
0.0-1.8
stiff, with silt and fine grained sand
2.0-2.5
Organic materials to 1.2 feet bgs.
Silty Sand (SM): Light brown, dry, medium
1.8-6.6
dense to dense, intermittent weak calcium
GS
2.0-2.4
A
carbonate cementation, fine grained sand.
Poorly Graded Sandy Gravel (GP): Reddish
brown, slightly moist, dense to very dense, fine
6.6-9.0
to medium grained sand, fine to coarse gravel,
5 inch minus cobbles.
Lab Test ID M LL PI I Sieve Anal sis
% 1" #4 1 #10 #40 #100 9200
A 21.9 NP NP 1 100 72 1 65 41 30 21.1
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GEOTECHNICAL INVESTIGATION TEST PIT LOG
Test Pit Log #: TP -2 Date Advanced: 8/11/2011 Logged by: Elizabeth Brown, E.I.T,
Excavated by: Struckman's Backhoe Service Location: See Site Map Plates
Depth to Water Table: Not Encountered Total Depth: 10.6 Feet bgs
Depth
Field Description and
Sample
Sample Depth
Qp
Lab
Feet b s
USCS Soil and Sediment Classification
Type
Feet bgs)
Test ID
Lean Clay Fill (CL -FILL): Brown, dry, very
0.0-2.8
stiff, with silt, fine grained sand, and 4 inch
2.25-2.5
minus cobbles.
Organic materials to 1.2 feet bgs.
Silty Sand (SM): Reddish brown, slightly
moist, medium dense to dense, weak to
2.8-9.3
moderate calcium carbonate cementation, fine
to medium grained sand.
Poorly Graded Sandy Gravel (GP): Reddish
brown, slightly moist, dense to very dense, fine
8.3-10.6
to medium grained sand, fine to coarse gravel,
5 inch minus cobbles.
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GEOTECHNICAL INVESTIGATION TEST PIT LOG
Test Pit Log #: TP -3 Date Advanced: 8/11/2011 Logged by: Elizabeth Brown, E.I.T.
Excavated by: Struckman's Backhoe Service Location: See Site Map Plates
Depth to Water Table: Not Encountered Total Depth: 16.4 Feet bgs
Depth
Field Description and
Sample
Sample Depth
Qp
Lab
Feet b s
USCS Soil and Sediment Classification
T e
Feet b s
Test ID
Lean Clay Fill (CL -FILL): Brown, dry, stiff,
0.0-2.5
with silt, fine grained sand, and 4 inch minus
1.75-2.0
cobbles.
Organic materials to 1.2 feet bgs.
Silty Sand (SM): Light brown, dry to slightly
2.5-6.7
moist, medium dense to dense, weak calcium
carbonate cementation, fine grained sand.
Poorly Graded Sandy Gravel (GP): Light
L.7-16.4
brown to brown, slightly moist, dense to very
dense, fine to medium grained sand, fine to
coarse gravel, 6 inch minus cobbles.
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