18-105640 (3)WA
TERRA ASSOCIATES, Inc. co
Consultants in Geotechnical Engineering, Geology
and w1h
Environmental Earth Sciences C7
December 14, 2018
Revised March 29, 2019
Project No. T-7844
Mr. Brian Mattson
Panattoni Development Company
900 SW 16th Street, Suite 330
Renton, Washington 98057
Subject: Infiltration Testing
Tilt 348
1019 South 351st Street
Federal Way, Washington
Dear Mr. Mattson:
As requested, we have completed infiltration testing at the subject property. Our infiltration testing consisted of
one large-scale Pilot Infiltration Test (PIT-1) and three small-scale Pilot Infiltration Tests (PIT-2 through PIT-4)
conducted in general conformance with the procedures outlined in Section 5.2.1 (General Requirements for
infiltration Facilities) of the 2016 King County Surface Water Design Manual.
The tests were performed within the outline of the proposed Infiltration Facility. The locations were based on
sighting from existing structures and GPS coordinates from Google Earth. The approximate locations are shown
on attached Figure 1. The test results are summarized below:
Estimated Design
Approx.
Infiltration Rate
Test
Steady State
Measured Infiltration
Correction
(Isat design = Isat initial x
Test
Elevation
Flow Rate
Rate (Isat initi i)
Factor
FT)
No.
(ft
m
(in/hr
CFTI
(in/hr)
PIT-1
227.5
21.43
19.64
0.21
4.00
PIT-2
223.5
3.00
19.01
0.21
3.99
PIT-3
227
6.00
32.14
0.21
6.75
PIT-4
226.5
3.21
18.82
1 0.21
3.95
ft Feet based on available topography.
gpm Gallons per minute. RESUBMITTED
in/hr Inches per hour.
1 Equation 5-11 2016 King County Surface Water Design Manual.
APR 0 4 2019
Cr1Y OF FEDERAL WAY
COMMUNrrY DEVELOPMENT'
L"
O
12220 113th Avenue NE, Ste. 130, Kirkland, Washington 98034
Phone (425) 821-7777 9 Fax (425) 821-4334
Mr. Brian Mattson
December 14, 2018
Revised March 29, 2019
Based on the results of our test, it is our opinion that the native soils at these locations and depths are suitable for
support of the proposed infiltration facility using a design infiltration rate of 4 inches per hour. Further
excavation of the test locations showed outwash continued to a depth of approximately 15 feet below -grade
(elevation 217 feet). The raw pilot infiltration test data has been included as Figures 2 through 5. The soil logs
for the pilot infiltration tests are attached as Figures 6 through 9.
We trust the information presented is sufficient for your current needs. If you have any questions or require
additional informatiop, please call.
Sincerely N S.
TE
Carol eck
Projec n er
47016
Encl: 1 TEAL EQ \ ion Map
5 — Raw Pilot Infiltration Test Data
Figures 6 through 9 — Soil Test PIT Logs
Project No. T-7844
Page No. ii
Figure 2 - Raw Pilot Infiltration Test Data
Test Number:
PIT-1
Project Name:
Tilt 348
Project Number:
7844
Test Date:
12/10/2018
hole dimensions
10.5' x 10' x 4.5'
Hole area
105 square feet
initial meter reading
1947 gal
time (minutes)
cum vol (gal)
15 2308
30 2610
45 2927
60 3243
75 3592
Falling head test
time (minute) HEAD (Inches)
0 12
1 11.16
2 11
3 10.44
5 10.2
7 9.6
10 9
15 7.68
30 4.8
40
50
60 0
70
80
90
flow rate (gpm) Head (feet)
20.81
20.46
20.08
21.48
22.73
measured infiltration rate using
steady state data
measured infiltration rate using
falling head data
1
1
1 use mean flow rate of last half
hour of test as steady state
infiltration rate
21.43 gpm
2.86 cfm
infiltration rate=steady sate flow
divided by area of pit
0.03 feet per minute
0.33 inches per minute
19.64 inches per hour
96.00 inches per hour
Figure 2 - Raw Pilot Infiltration Test Data
Correction factors
F-testing
0.3
F-geometry
1
F-frequency
1
F-plugging
0.7
factors were otained from the 2016 King County Surface Water Design Manual
corrected steady state Infiltration rate 4.13 inches per hour
corrected falling head infiltration rate 20.16 inches per hour
Figure 3 - Raw Pilot Infiltration Test Data
Test Number:
PIT-2
Project Name:
Tilt 348
Project Number:
7844
Test Date:
3/26/2019
hole dimensions 4' x 4' x 9'
Hole area 16 square feet
initial meter reading 104937 gal
time (minutes) cum vol (gal) flow rate (gpm) Head (feet)
15 104971 3.14 1
30 105007 3.04 1
45
105043
3.15
60
105082
3.19
75
105117
3.14
Falling head test
time (minute)
HEAD (inches)
0 12
1
12
:neasured infiltration rate using
2
12
steady state data
3
11.76
5
11.52
measured infiltration rate using
7
11.4
falling. head data
10
11.16
15
10.8
30
9.96
40
50
60
8.16
70
80
90
use mean flow rate of last half
hour of test as steady state
infiltration rate
3.16 gpm
0.42 cfm
infiltration rate=steady sate flow
divided by area of pit
0.03 feet per minute
0.32 inches per minute
19,01 inches per hour
96.00 :Aches per hour
Figure 3 - Raw Pilot Infiltration Test Data
Correction factors
F-testing
0.3
F-geometry
1
F-frequency
1
IF -plugging
0.7
factors were otained from the 2016 King County Surface Water Design Manual
corrected steady state infiltration rate 3.99 inches per hour
corrected falling head infiltration rate 20.16 inches per hour
Figure 4 - Raw Pilot Infiltration Test Data
Test Number:
PIT-3
Project Name:
Tilt 348
Project Number:
7844
Test Date:
3/26/2019
hole dimensions
4.5' x 4' x 3'
Hole area
18 square feet
initial meter reading
105117 gal
time (minutes) cum vol (gal) flow rate (gpm) Head (feet)
15 105223 5.90 1
30 105307 6.15 1
45
105401
6.05 1
60
105486
5.98 1
75
105569
6.00 1
Falling head test
time (minute)
HEAD ([riches)
0 12
1
11.76
measured infiltration rate using
2
11.52
steady state data
3
11.4
5
11.16
measured infiltration rate using
7
10.8
failing head data
10
10.32
15
9.72
30
8.16
40
50
60
4.8
70
80
90
use mean flow rate of last half
hour of test as steady state
infiltration rate
6.01 gpm
0.80 cfm
Infiltration rate=steady sate flow
divided by area of pit
0.04 feet per minute
0.54 inches per minute
32.14 inches per hour
96.00 inches per hour
Figure 4 - Raw Pilot Infiltration Test Data
Correction factors
IF -testing
0.3
iF-geometry
1
IF -frequency
1
IF -plugging
0.7
factors were otained from the 2016 King County Surface Water Design Manual
corrected steady state infiltration rate 6.75 inches per hour
corrected failing head infiltration rate 20.16 inches per hour
Figure 5 - Raw Pilot Infiltration Test Data
Test Number:
PIT-4
Project Name:
Tilt 348
Project Number:
7844
Test Date:
3/26/2019
hole dimensions
4.5' x 4' x 5.5'
Hole area
18 square feet
initial meter reading
104690 gal
time (minutes) cum vol (gal) flow rate (gpm) Head (feet)
15 104738 3.90 1
30 104783 4.80 1
45
104834
3.70
60
104879
3.65
75
104936
3.21
Falling head test
time (minute)
HEAD (Inches)
0
12
1
12
measured infiltration rate using
2
11.76
steady state data
3
11.52
5
11.04
measured infiltration rate using
7
10.8
failing head data
10
10.56
15
10.08
30
8.4
40
50
60
5.16
70
80
90
use mean flow rate of last half
hour of test as steady state
infiltration rate
3.52 gpm
0.47 cfm
infiltration rate=steady sate flow
divided by area of pit
0.03 feet per minute
0.31 inches per minute
18.82 incises per hour
96.00 inches per hour
Figure 5 - Raw Pilot Infiltration Test Data
Correction factors
F-testing
0.3
F-geometry
1
F-frequency
1
F-plugging
0.7
factors were otained from the 2016 King County Surface Water Design Manual
corrected steady state infiltration rate 3.95 inches per hour
corrected falling head Infiltration rate 20.16 inches per hour
1
2
3
4
5
7
12
13
14
15
16
17
18
19
20
LOG OF PILOT INFILTRATION TEST NO. PIT-1 FIGURE
PROJECT NAME: Tilt 348 PROJ. NO: T -7844 LOGGED BY: BS
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Moderate Vegetation APPROX. ELEV: 230
DATE LOGGED: December 10 2018 DEPTH TO GROUNDWATER: N/A
Description
DEPTH TO CAVING:N/A
FILL: Brown/gray silty SAND with gravel, fine to medium grained sand, fine to coarse gravel, moist,
trace organics.
Tan/gray silty SAND with gravel, fine to medium grained sand, fine to coarse gravel, moist. (SM)
------------------------------------------------------------------------
Tan/gray SAND with gravel and some silt, fine to coarse grained sand, fine to coarse gravel, moist.
Test pit terminated at approximately 15 feet.
No groundwater seepage observed.
No caving observed.
Consistency/ o
Relative Density 2
Medium Dense
Dense
Terra
NOTE: This subsurface information pertains only to this test pit location and should not be -
Associates Inc
interpreted as being indicative of other locations at the site. Consultants in Geotechnical Ingineering
Geology and
Environmental Earth Sciences
LOG OF PILOT INFILTRATION TEST NO. PIT-2 FIGURE
PROJECT NAME: Tilt 348 PROJ. NO: T-7844 LOGGED BY: BS
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Moderate Vegetation APPROX. ELEV: 232
DATE LOGGED, March 26, 2019 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING:N/A
6
., z
a?
t a
a E
N M
0 rn
0
1
2-
7
9
10
11
12
13
14
15
16
17
18
19
20
Description
(8 inches organics)
Tan sandy SILT with gravel, fine sand, fine gravel, moist. (ML)
Consistency/ o
Relative Density
-------------------------------------------------------------------------
Tan transitioning to gray sandy SILT, fine sand, moist. (ML)
Medium Dense
----------------------------------------------------------------------
Gray SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SP)
Dense
Test pit terminated at approximately 15 feet.
No groundwater seepage observed.
No caving observed.
� Terra
NOTE: This subsurface information pertains only to this test pit location and should not be •I Associates Inc.
interpreted as being indicative of other locations at the site. Consultants in Geotechnical Ingineering
Geology and
Environmental Earth Sciences
LOG OF PILOT INFILTRATION TEST NO. PIT-3
FIGURE 8
PROJECT NAME: Tilt 348 PROJ. NO: T-7844 LOGGED BY: BS
LOCATION: Federal Wav, Washington SURFACE CONDITIONS: Moderate Ve- etatiq on� APPROX. ELEV: 230
DATE LOGGED: March 26, 2019 DEPTH TO GROUNDWATER: N/A
6
0 Description
t n
a E
m m
0 , rn
0
(8 inches organics)
I
1 Gray SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SP)
2
3 —{
{ Test pit terminated at approximately 3 feet.
No groundwater seepage observed.
4 No caving observed.
yi
7
8
9
10
11
12
13
14
15
DEPTH TO CAVING:N/A
I
Consistency/ o
Relative Density
Medium Dense
i Terra
NOTE: This subsurface information pertains only to this test pit location and should not be i Associates Inc.
interpreted as being indicative of other locations at the site. Consultants in Geotechnical Ingineering
Geology and
Environmental Earth Sciences
LOG OF PILOT INFILTRATION TEST NO. PIT-4
PROJECT NAME: Tilt 348 PROJ. NO: T-7844
LOGGED BY: BS
FIGURE 9
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Moderate Vegetation APPROX. ELEV: 232
DATE LOGGED: March 26 2019 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING -NIA
6
Z
a�
r a
a E
N M
C rn
0
1
2
3
4
5
6
7
8
10
11
12
13
14
15
Description
Fill: brown/tan silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist, trace
organics, brick and asphalt debris. (SM)
------------------------------------------------------------
Tan/Gray SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SP)
Test pit terminated at approximately 6.5 feet.
No groundwater seepage observed.
No caving observed.
Consistency/ o
Relative Density
Medium Dense
Dense
Terra
NOTE: This subsurface information pertains only to this test pit location and should not be Associates Inc.
interpreted as being indicative of other locations at the site. Consultanis in Geotechnical Nineering
Geology and
EnvironmentM Earth Sciences