Geotechnical Engineering Report, McCormick Woods Parcel A, …€¦ · LU19-PLAT PRELIM-02. Infiltration Assessment Page 2 June 26, 2019 McCormick Woods Parcel A, Port Orchard, Washington

Corporate Office 17522 Bothell Way Northeast Bothell, Washington 98011 Phone 425.415.0551 ♦ Fax 425.415.0311

www.riley-group.com

June 26, 2019

Mr. James Tosti Windward Real Estate 805 Kirkland Avenue, Suite 200 Kirkland, Washington 98033

Subject: Infiltration Assessment

McCormick Woods Parcel A McCormick Woods Drive SW & St. Andrews Drive SW

Port Orchard, Washington RGI Project No. 2019-088A

As requested, The Riley Group, Inc. (RGI) is pleased to provide the results of our recent infiltration testing at the proposed McCormick Woods Parcel A residential development Site, located in Port Orchard, Washington (Figure 1). RGI previously completed a geotechnical engineering report for the Site which is summarized in our report:

Geotechnical Engineering Report, McCormick Woods Parcel A, McCormick Woods Drive SW & St. Andrews Drive SW, Port Orchard, Washington, dated May 29, 2019.

The results of infiltration testing in the proposed stormwater pond area at the Parcel A site is summarized in this report.

General

The project site is located on the northeast corner of McCormick Woods Drive SW & St. Andrews Drive SW in Port Orchard, Washington. The approximate location of the site is shown on Figure 1.

The site is currently occupied by a vehicle storage lot in the east-central portion of the property. The remainder of the property is forested.

RGI understands the site is to be developed with a 55 lot residential development. An access road will wind through the site with entrance/exit areas on McCormick Woods Drive SW and St. Andrews Drive SW. A stormwater pond will be located in the northern portion of the site.

Geology Review of the Geologic Map of Surficial Deposits in the Seattle 30’ x 60’ Quadrangle, Washington, by James C. Yount, etc. (1993) indicates that the soil in the project vicinity is mapped as Vashon Till (Qvt), which is a nonsorted, nonstratified mixture of clay, silt, sand, and gravel deposited by the Vashon ice sheet. These descriptions are generally similar to the findings in our field explorations.

lstone

Static Received Stamp

lstone

Text Box

LU19-PLAT PRELIM-02

Infiltration Assessment Page 2 June 26, 2019 McCormick Woods Parcel A, Port Orchard, Washington RGI Project No. 2019-088A

Subsurface Conditions

RGI completed eight test pits (TP-1 through TP-8) at the Site as part of our geotechnical engineering report. Infiltration test pits IT-1 and IT-2 were completed in the area of the proposed stormwater pond during this phase of work. The test pits and infiltration test pits are shown on Figure 2.

Soil conditions documented in the infiltration test pits IT-1 and IT-2 included approximately three feet of reddish brown silty sand underlain by gray sand with some silt to the depths explored. These subsurface conditions were similar to the geotechnical test pits completed in the pond area (IT-3 and IT-4). Test pits IT-3 and IT-4 were completed to depths of 10 and 12.5 feet below grade in the pond area.

Groundwater was not encountered in the test pits completed in the pond area at the time of our explorations.

Infiltration Testing

RGI oversaw the completion of a Pilot Infiltration Tests (PIT), in IT-1 and IT-2 (Figure 2). The infiltration tests were completed at a depth of approximately 6 feet below existing grade in the gray sand unit. The water source for the testing was a water truck. The small scale pilot infiltration test (PIT) was completed per the guidelines in the Washington State Department of Ecology Stormwater Management Manual for Western Washington (SWMMWW).

Infiltration Testing Results

The field measured infiltration rates in IT-1 and IT-2 IT-1 were both 3 inches per hour. We applied the SWMMWW correction factors to the field measured rates to estimate the Ksat design

Ksat design = Ksat initial x (CFv) x (CFt) x (0.9)

Where CFv = Site variability correction factor

CFt = Test method uncertainty

0.9 = Long-term conductivity loss

CFv = 1

CFt = 0.5

Application of the stormwater manual correction factors to the field measured rates yielded recommended long-term design rates as follows:

IT-1/IT-2 (3 inches/hour) x (1) x (0.5) x (0.9) = Ksat design 1.3 inches/hour

USGS, 2014, Bremerton West, WashingtonUSGS, 2017, Burley, Washington

7.5-Minute Quadrangle

Approximate Scale: 1"=1000'

0 500 1000 2000 N

Site Vicinity Map

Figure 1

06/2019

Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311

McCormick Woods Parcel ARGI Project Number:

2019-088ADate Drawn:

Address: McCormick Woods Dr. Southwest & St. Andrews Dr., Port Orchard, Washington 98367

SITE

TP-1

TP-2

TP-3TP-4

TP-5

TP-6

TP-7

TP-8

IT-1

IT-2

N

Geotechnical Exploration Plan

Figure 2

Approximate Scale: 1"=200'

0 100 200 400

= Infiltration test pit by RGI, 06/10/19= Test pit by RGI, 04/30/19= Site boundary

06/2019

Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311

McCormick Woods Parcel ARGI Project Number:

2019-088ADate Drawn:

Address: McCormick Woods Dr. Southwest & St. Andrews Dr., Port Orchard, Washington 98367

Project Name: McCormick Woods

Project Number: 2019-088A

Client: Windward

Test Pit No.: IT-1

Date(s) Excavated: 6/10/2019

Excavation Method: Test Pit

Excavator Type: Tracked Excavator

Groundwater Level: Not Encountered

Test Pit Backfill: Cuttings

Logged By ELW

Bucket Size: 4'

Excavating Contractor: Client Provided

Sampling Method(s)

Location McCormick Woods Drive SW and St. Andrews Drive SW, Port Orchard, WA

Surface Conditions: Mixed Brush/Ferns

Total Depth of Excavation: 6 feet bgs

Approximate Surface Elevation 380

Compaction Method Bucket tamp

US

CS

Sym

bol

TPSL

SM

SP-SM

REMARKS AND OTHER TESTSG

raph

ic L

og

MATERIAL DESCRIPTION

6" topsoil

Reddish brown silty SAND with trace gravel, loose to medium dense, moist

Becomes medium dense

Gray SAND with some silt, medium dense to dense, moist

PIT infiltration test conducted at 6'

PID

Rea

ding

, ppm

Dep

th (

feet

)

0

5

10

Sam

ple

ID

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

380

375

370

Sheet 1 of 1

The Riley Group, Inc. 17522 Bothell Way NE, Bothell, WA 98011


Project Number: 2019-088A

Client: Windward

Test Pit No.: IT-2




Groundwater Level: Not Encountered


Logged By ELW

Bucket Size: 4'

Excavating Contractor: Client Provided

Sampling Method(s)

Location McCormick Woods Drive SW and St. Andrews Drive SW, Port Orchard, WA




Compaction Method Bucket tamp

US

CS

Sym

bol

TPSL

SM

SP-SM

REMARKS AND OTHER TESTSG

raph

ic L

og


6" topsoil

Reddish brown silty SAND with trace gravel, loose to medium dense, moist

Gray SAND with some silt, medium dense to dense, moist

Infiltration test conducted at 6'

PID

Rea

ding

, ppm

Dep

th (

feet

)

0

5

10

Sam

ple

ID

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

380

375

370

Sheet 1 of 1



Project Number: 2019-088

Client: Windward

Test Pit No.: TP-1




Groundwater Level: Seepage at 5'


Logged By ELW

Bucket Size: 4'

Excavating Contractor: Client

Sampling Method(s) Grab

Location McCormick Woods Drive SW and St. Andrews Drive SW




Compaction Method Bucket tampU

SC

S S

ymbo

l

Tpsl

SM

SM

REMARKS AND OTHER TESTS

19% moisture, 19% fines

17% moisture

11% moisture

Gra

phic

Log


8" topsoil

Reddish brown silty SAND with some gravel, loose, moist


Gray silty SAND with trace gravel, dense, moist, (Glacial Till), moderately cemented

Becomes wet

Contains sand lens with light groundwater seepage

Test pit terminated at 7'

Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

411

406

401

396

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-2




Groundwater Level: Not encountered


Logged By ELW

Bucket Size: 4'




Surface Conditions: Ferns/Moss

Total Depth of Excavation: 10.5 feet bgs



SC

S S

ymbo

l

Tpsl

SM

SP

SM


10% moisture

4% moisture

3% moisture

21% moisture

Gra

phic

Log


6" topsoil



Gray SAND with some gravel, medium dense, moist

Increasing in gravel

Tan mottled silty SAND with some gravel, medium dense, moist to wet

Test pit terminated at 10.5'

Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

387

382

377

372

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-3






Logged By ELW

Bucket Size: 4'




Surface Conditions: Ferns/Mixed Brush




SC

S S

ymbo

l

Tpsl

SM

SP-SM


11% moisture

18% moisture

10% moisture

Gra

phic

Log


6" topsoil

Reddish brown silty SAND, loose, moist


Gray SAND with some silt, medium dense, moist


Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

386

381

376

371

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-4






Logged By ELW

Bucket Size: 4'








SC

S S

ymbo

l

Tpsl

SM

SM

SP-SM

SW-SM


11% moisture

7% moisture




6% moisture

7% moisture

Gra

phic

Log


6" topsoil



Tan silty SAND with trace gravel, medium dense, moist, lightly cemented

Gray SAND with some silt and gravel, medium dense to dense, moist

Becomes dense, well cemented

Gray SAND with some silt and trace gravel, medium dense to dense, moist


Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

379

374

369

364

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-5






Logged By ELW

Bucket Size: 4'




Surface Conditions: Ferns/Mixed Brush/Moss




SC

S S

ymbo

l

Tpsl

SM

SM

SP-SM

SP-SM


10% moisture




6% moisture

5% moisture

Gra

phic

Log


6" topsoil

Reddish brown silty SAND with trace gravel, loose, moist


Gray silty SAND with some gravel, dense, moist (Glacial Till)

Moderately cemented

Gray SAND with some silt and trace gravel, dense, moist

Contains silty SAND interbeds

Gray SAND with some silt and gravel, dense, moist


Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

376

371

366

361

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-6






Logged By ELW

Bucket Size: 4'




Surface Conditions: Ferns/Moss




SC

S S

ymbo

l

Tpsl

SM

SP-SM

SP

SP-SM


17% moisture

8% moisture

7% moisture

20% moisture

10% moisture

Gra

phic

Log


6" topsoil


Becomes tan, medium dense

Gray SAND with some silt and trace gravel, medium dense, moist

Lightly cemented

SAND with trace silt, medium dense, moist

Becomes wet

Light groundwater seepage

Gray SAND with some silt, dense, moist to wet, well cemented


Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

380

375

370

365

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-7






Logged By ELW

Bucket Size: 4'




Surface Conditions: Mixed Brush/Ferns/Moss




SC

S S

ymbo

l

Tpsl

SM

SP-SM

SM


6% moisture

9% moisture

Gra

phic

Log


6" topsoil



Gray gravelly SAND with some silt, medium dense, moist

Gray silty SAND with some gravel, very dense, moist (Glacial Till)


Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

408

403

398

393

Sheet 1 of 1




Client: Windward

Test Pit No.: TP-8






Logged By ELW

Bucket Size: 4'








SC

S S

ymbo

l

Tpsl

SM

SP-SM


13% moisture


Gra

phic

Log


6" topsoil



Gray SAND with some silt and gravel, dense, moist

Very dense, well cemented


Dep

th (

feet

)

0

5

10

15

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

413

408

403

398

Sheet 1 of 1




Client: Windward

Key to Logs

US

CS

Sym

bol

REMARKS AND OTHER TESTSGra

phic

Log

MATERIAL DESCRIPTIONDep

th (

feet

)

Sam

ple

Num

ber

Sam

ple

Typ

e

Ele

vatio

n (f

eet)

1 2 3 4 5 6 7 8

COLUMN DESCRIPTIONS

1 Elevation (feet): Elevation (MSL, feet).2 Depth (feet): Depth in feet below the ground surface.3 Sample Type: Type of soil sample collected at the depth interval

shown.4 Sample Number: Sample identification number.

5 USCS Symbol: USCS symbol of the subsurface material.6 Graphic Log: Graphic depiction of the subsurface material

encountered.7 MATERIAL DESCRIPTION: Description of material encountered.

May include consistency, moisture, color, and other descriptivetext.

8 REMARKS AND OTHER TESTS: Comments and observationsregarding drilling or sampling made by driller or field personnel.

FIELD AND LABORATORY TEST ABBREVIATIONS

CHEM: Chemical tests to assess corrosivityCOMP: Compaction testCONS: One-dimensional consolidation testLL: Liquid Limit, percent

PI: Plasticity Index, percentSA: Sieve analysis (percent passing No. 200 Sieve)UC: Unconfined compressive strength test, Qu, in ksfWA: Wash sieve (percent passing No. 200 Sieve)

MATERIAL GRAPHIC SYMBOLS

Silty SAND (SM)

Poorly graded SAND (SP)

Poorly graded SAND with Silt (SP-SM)

Well graded SAND with Silt (SW-SM)

Topsoil

TYPICAL SAMPLER GRAPHIC SYMBOLS

Auger sampler

Bulk Sample

3-inch-OD California w/brass rings

CME Sampler

Grab Sample

2.5-inch-OD ModifiedCalifornia w/ brass liners

Pitcher Sample

2-inch-OD unlined splitspoon (SPT)

Shelby Tube (Thin-walled,fixed head)

OTHER GRAPHIC SYMBOLS

Water level (at time of drilling, ATD)

Water level (after waiting)

Minor change in material properties within astratum

Inferred/gradational contact between strata

? Queried contact between strata

GENERAL NOTES

1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may begradual. Field descriptions may have been modified to reflect results of lab tests.2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representativeof subsurface conditions at other locations or times.

Sheet 1 of 1


Documents

Geotechnical Engineering Report, McCormick Woods Parcel A, …€¦ · LU19-PLAT PRELIM-02. Infiltration Assessment Page 2 June 26, 2019 McCormick Woods Parcel A, Port Orchard, Washington