S-17-0017_Swan_Lake_Trail_14_MP0.73_&_MP0.96_-_Project_Soil_Investigation20170421.pdf

Page 1 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

Project Soil Investigation Swan Lake Trail #14 MP0.73 and MP0.96

Project Name: Swan Lake Trail #14 MP 0.73 Structure Installation

USDA Soil Survey Data

The USDA NRCS Web Soil Survey classifies crossing site as Pk-Peat and Muck. The soil map unit north is Neuske silt loam, 15 to 35 percent slopes from a parent material of silty till. The map unit south is TtD—Torboy sandy loam, 5 to 25 percent slopes and this component is on edges of terraces. The TtD parent material consists of volcanic ash and glacial outwash. Field investigation more closely matched the 1979 USDA SCS Soil Survey general soil profile of the top 20 inches being organic peat underlain by 16 inches of white marl underlain by fine and coarse sand and lenses of ash.

Map Unit: Pk—Borosaprists

The Borosaprists component makes up 100 percent of the map unit. Slopes are 0 to 2 percent. This component is on depressions. The parent material consists of organic material. Depth to a root restrictive layer is greater than 60 inches. The natural drainage class is very poorly drained. Water movement in the most restrictive layer is moderately high. Available water to a depth of 60 inches (or restricted depth) is very high. Shrink-swell potential is low. This soil is not flooded. It is frequently ponded. A seasonal zone of water saturation is at 0 inches during January, February, March. Organic matter content in the surface horizon is about 65 percent.

The soil is highly restrictive for trails due to depth to saturated zone, organic matter content, and ponding. Chemically, the soil reaction is classified between 3.6-7.3 pH except for the white marl layer which runs strongly alkaline at pH8.5-9.0. It is highly corrosive to uncoated steel. There is a high probability of moderate frost action. Based on my correlation with survey date, the expected long-term settlement of a spread footing would be between 25-80% of organic layer thickness or 4-14 inches for the crossing site.

Engineering Properties–North Ferry Area, Washington Map unit symbol and soil name Pct. of map unit

Hydrolo gic group Depth USDA texture Classification Pct Fragments Percentage passing sieve number— Liqui d limit

Plasticit y index

Unified AASHTO >10 inches

3-10 inches

4 10 40 200

In L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H

Pk—Borosaprists Borosaprists 100 B/D 0-12 Muck PT A-8 0- 0- 0 0- 0- 0 100-100

-100 100-100

-100 85-95-1

80-90-1

Page 2 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

12-60 Muck PT A-8 0- 0- 0 0- 0- 0 100-100 -100

100-100 -100

85-95-1

80-90-1

60-70 Silt loam, silty clay loam, sandy loam

CL, CL-

ML, SC,

SC-SM

A-4, A-6 0- 0- 0 0- 0- 0 85-93-1

75-88-1

60-78-

40-65-

20-30 -40

5-10-15

Particle Size and Coarse Fragments–North Ferry Area, Washington Map symbol and soil name Horizon Depth Sand Silt Clay Total fragments Fragments 2-74 mm Fragments 75-249 mm Fragments

250-599 mm Fragments >=600 mm

In L-RV-H Pct

L-RV-H

Pct

L-RV-H Pct RV Pct RV Pct RV Pct RV Pct RV Pct

Pk—Borosaprists Borosaprists H1 0-12 -15- -60- 10-25- 35 — — — — —

H2 12-60 -15- -60- 10-25- 35 — — — — —

H3 60-70 -63- -19- 10-18- 35 11 11 — — —

Physical Soil Properties–North Ferry Area, Washington Map symbol and soil name Depth Sand Silt Clay Moist bulk density

Saturated hydraulic conductivity Available water capacity

Linear extensibility

Organi c matter

Erosion factors Wind erodibilit y group

Wind erodibility index Kw Kf T In Pct Pct Pct g/cc micro m/sec In/In Pct Pct Pk—

Borosaprists

Borosaprists 0-12 -15- -60- 10-25- 35 0.10-0.20- 0.30

4.00-9.00-14.00 0.30-0.45-0.6

— 40.0-65.0- 90.0

2 2 134

12-60 -15- -60- 10-25- 35 0.10-0.20- 0.30

4.00-9.00-14.00 0.30-0.45-0.6

— 30.0-45.0- 60.0

60-70 -63- -19- 10-18- 35 1.30-1.53- 1.75

1.40-8.00-14.00 0.10-0.15-0.2

3.0- 4.5- 5.9 3.0- 5.5- 8.0

.17 .17

Soil Features–North Ferry Area, Washington and soil name

Restrictive Layer Subsidence Potential for frost action

Risk of corrosion Kind Depth to top Thickness Hardness Initial Total Uncoated steel Concrete

Low-RV- High

Range Low- High

Low- High

Page 3 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

In In In In Pk—Borosaprists Borosaprists — — 4-10 16-51 High High Moderate

Field Soil Investigation

A Williamson Drive Probe was used at Sta 0+13 north edge of water and 0+50 center of crossing until gravity drop refusal at

7.5 and 6.9 feet respectively. The Sta 0+50 probe location had approximately 1.4 foot of water above organic soil. Hammer drop blows were recorded for every 0.5 of ½” pipe travel. Of note was the top 1.5 feet of material was low resistance on top of a couple foot layer of higher resistance material before a couple feet of blow count reversal on top of couple feet of increased resistance before gravity drop refusal around 6-8 foot depth. A 2.5 foot test pit was dug at Sta0+13 north edge of water revealing 1.5 feet of dark organic soil on top of white marl (organic clayey material).

Page 4 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

‐1.5, SPT 10, min 5

‐2.5, SPT 5, min 2

‐3, SPT 17, min 12

‐4.25, SPT 22, min 15‐4.25, SPT 10, min 5

‐5.25, SPT 11, min 6

‐7.6, SPT 86

‐6.9, SPT 35, min 16 (Premature refusal after Williamson correlated to STP)

‐8

‐7

‐6

‐5

‐4

‐3

‐2

‐1

0 10 13 14 20 25 30 35 40 43 50 55 57 59 61 63 67 70 71.5 74 80 85 90

El ev at io n (ft

Distance (ft)

Swan Lake Tr#14 MP 0.75 Proposed Crossing Profile (north on left)

Ground Surface Water Surface Peat Bottom? Resistive Layer Blow Count Reversal Gravity Refusal

Page 5 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

General Soil Analysis and Results

The blow counts were plotted relative to the water surface and ground surface(Sta 0+50 lowered 1.4ft) and corrected to a Standard Penetration Test. Due to the strong correlation between blow count patterns, a third plot was made by lowering Sta0+50 1.1ft. This shifted it about half of the smallest measuring unit of 0.5ft from the ground surface plot. This is reasonable due to potential variations in organic soil settlement and measuring unit size.

For Sandy soil, blow counts were not corrected for depth. Estimated correction factor would increase 1.4-2.5 times blow count (lower # at 7ft depth). Blow counts were not adjusted down 1/3 for water table elevation.

The blow counts were used to help classify the probable soil material. The internal friction angle for medium dense sand was estimated from tables using a blow count of 10. Soil bearing pressures were estimated for sand layer using internal friction angle of 34degrees and no cohesion and compared to a clay layer using friction angle zero and cohesion based on blow counts. All assumptions were for a 1 foot circular footing to represent a helical pile. A factor of safety of 2 selected to account for acceptable risk to minor structure.

Later, calculations were made using Chance Helical Pile Technical Design Manual. Also upon consultation with Jon Berry, Regional Office Geotechnical Engineer, the blowcounts were reduced after a sensitivity analysis. This was due to Jon thinking the numbers at the high end of range were higher than typically seen. Also the increase in blow counts after blow count reversal occurred at 4ft below ground which is the same location as the first pipe joint. So there may have been part of the blow count increase from the pipe joint pushing its way through the upper soil. Nevertheless after speaking with Ian Romain, P.E., an authorized Chance Distributor, he thought that 10 or 12-inch SS5 piles would be more than adequate for the boardwalk.

INITIAL ANALYSIS

Depth Below Top of Ground

(FT)

SPT Blow Counts /Foot (Range)

Probable Material Estimated Bearing (PSF) w/ FS=2

Secondary Material Estimated Bearing (PSF) w/ FS=2

0-1.5 2 (1-5) Soft organic 300

1.5-3.5 17 (10-22) Medium-Stiff marl(clay)

3.5-5 11 (10-15) Loose-Medium sand/silt/ash 2700 Medium clay 3700

5-7 25 (15-35) Medium-Dense sand/silt/ash

Rock Refusal at Sta0+13

6300 Hard clay 7400-9300

REVISED ANALYSIS

Page 6 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

Depth Below Top of Ground (FT)

SPT Blow Counts /Foot (Range)

Intern.

Fric.

Angle Φ

Cohesion C

Probable Material Estimated Bearing (PSF) w/ FS=2

Secondary Material

Estimated Bearing (PSF) w/ FS=2

0-1.5 2 (1-5) - - Soft organic (high risk for settlement)

1.5-3.5 10 (10-22) - 1200 psf Medium-Stiff marl(clay) 3700

3.5-5 8 (10-15) 30◦ 1000 psf Loose sand/silt/ash 1500 Medium clay 3000

5-7 13 (15-35) 32◦ 1600 psf Medium sand/silt/ash

Rock Refusal at Sta0+13

4700 Stiff clay 4800

Helical Pile Soil Analysis

The Helical Pier Foundation Systems Manual by Chance was used for estimating bearing capacity per pile. The major concerns to check for with final pile selection are:

1. Uppermost helix at least 5ft or 5xDiam below soil surface (top of peat)

2. At least 3 feet below seasonal variation in soil properties

3. At least 3xDiam into competent soil (STP Blow Count>4).

4. Spaced laterally 3-5 Diam.

5. Saddle 1 ft above surveyed water line for ice protection

Project Name: Swan Lake Trail #14 MP 0.96 Structure Installation

USDA Soil Survey Data

The USDA NRCS Web Soil Survey classifies crossing with the map unit TtD—Torboy sandy loam, 5 to 25 percent slopes and this component is on edges of terraces. The TtD parent material consists of volcanic ash and glacial outwash. However, due to the resolution of the mapping and field observation of nearly saturated soil at surface, the confidence with this mapping unit is only moderate.

Map Unit: TtD—Torboy sandy loam, 5 to 25 percent slopes

Page 7 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

Slopes are 5 to 25 percent. This component is on edges of terraces. The parent material consists ofvolcanic ash and glacial outwash.

Depth to a root restrictive layer is greater than 60 inches. The natural drainage class is well drained. Water movement in the most restrictive layer is high. Available water to a depth of 60 inches (or restricted depth) is low. Shrink-swell potential is low. This soil is not flooded. It is not ponded. There is no zone of water saturation within a depth of 72 inches. (This is different than observation of saturation in the field). Organic matter content in the surface horizon is about 2 percent. This soil does not meet hydric criteria.

The soil is NOT restrictive for trails. Chemically, the soil reaction is classified between 6.1-7.3 pH; much less reactive than MP0.73. It is moderately corrosive to uncoated steel. There is a moderate frost action and low corrosion potential.

The decision was made by Recreation to install helical pile at this site as well.

Overall, it is expected that conditions at site MP 0.96 will demonstrate characteristics somewhere between the TtD and PkB classifications. Therefore, it is recommended to remove and replace organic material with unclassified borrow from TtD to bring bottom of sill elevation back up to existing grade and reduce season saturation of timber.

Engineering Properties–North Ferry Area, Washington Map unit symbol and soil name Pct. of map unit

Hydrolo gic group Depth USDA texture Classification Pct Fragments Percentage passing sieve number— Liqui d limit

Plasticit y index

Unified AASHTO >10 inches

3-10 inches

4 10 40 200

In L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H

TtD—Torboy sandy loam, 5 to 25 percent slopes

Torboy 100 A 0-6 Ashy sandy loam SM A-2 0- 0- 0 0- 0- 0 85-93-1

80-85-

50-55-

25-30-

15-20 -25

NP-3 -5

6-17 Ashy sandy loam, gravelly sandy loam, fine sandy loam

SM A-2, A-4 0- 0- 0 0- 5- 10 70-85-1

65-83-1

50-63-

25-38-

15-20 -25

NP-3 -5

17-24 Gravelly loamy sand, gravelly sand

SM, SP,

SP-SM

A-1 0- 0- 0 0- 5- 10 60-73-

55-65-

25-38-

0-10- 20 — NP

24-60 Very gravelly sand, gravelly loamy sand, gravelly fine sand

SM, SP,

SP-SM

A-1 0- 0- 0 10-15-

60-68-

40-53-

35-43-

0-10- 20 — NP

Page 8 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017

Particle Size and Coarse Fragments–North Ferry Area, Washington

Map symbol and soil name

Horizon Depth Sand Silt Clay Total fragments Fragments 2-74 mm

Fragments 75-249 mm

Fragments 250-599 mm

Fragments >=600 mm

In L-RV-H Pct

L-RV-H

Pct

L-RV-H Pct RV Pct RV Pct RV Pct RV Pct RV Pct

TtD—Torboy sandy loam, 5 to 25 percent l

Torboy H1 0-6 -68- -26- 4- 6- 8 10 10 — — —

H2 6-17 -68- -24- 5- 9- 12 22 19 3 — —

H3 17-24 -79- -16- 0- 5- 10 28 25 3 — —

H4 24-60 -95- - 1- 0- 4- 8 34 25 9 — —

Physical Soil Properties–North Ferry Area, Washington and soil name Depth Sand Silt Clay Moist bulk density

Saturated hydraulic conductivity Available water capacity

Linear extensibility

Organi c matter

Erosion factors Wind erodibilit y group

Wind erodibility index Kw Kf T In Pct Pct Pct g/cc micro m/sec In/In Pct Pct TtD—Torboy sandy loam, to 25 percent l

Torboy 0-6 -68- -26- 4- 6- 8 1.10-1.20- 1.30

14.00-28.00-42.

0.11-0.12-0.1

0.0- 1.5- 2.9 1.0- 1.5- 2.0

.24 .24 5 2 134

6-17 -68- -24- 5- 9- 12 1.25-1.35- 1.45

14.00-28.00-42.

0.11-0.12-0.1

0.0- 1.5- 2.9 0.5- 0.8- 1.0

.15 .28

17-24 -79- -16- 0- 5- 10 1.40-1.50- 1.60

42.00-92.00-14 1.00

0.05-0.06-0.0

0.0- 1.5- 2.9 0.5- 0.8- 1.0

.10 .24

24-60 -95- - 1- 0- 4- 8 1.40-1.50- 1.60

141.00-300.00- 705.00

0.04-0.05-0.0

0.0- 1.5- 2.9 0.0- 0.3- 0.5

.02 .05

Soil Features–North Ferry Area, Washington Restrictive Layer Subsidence Risk of corrosion

Page 9 of 9 (2016) Swan Lake Trail 14 MP0.73 & MP0.96 ‐ Project Soil Investigation.docx 3/15/2017 and soil name

Kind Depth to top

Thickness Hardness Initial Total Potential for frost action

Uncoated steel Concrete

Low-RV- High

Range Low- High

Low- High

In In In In Torboy — — — — Moderate Low Low