steven c. devin, p.e., g.e. · embankment fill below the surficial silt along the ... dark gray...

Steven C. Devin, P.E., G.E. Civil and Geotechnical Engineering Services P.O. Box 1782 Quincy, California 95971 (530) 251 7087 [email protected] December 6, 2013 Larry Sullivan Manager Quincy Community Services District 900 Spanish Creek Road Quincy, California 95971 Subject: Quincy Wastewater Treatment Plant “Emergency Effluent” Pond – Berm Integrity Evaluation;

Re: Repair of Existing Leak. Dear Mr. Sullivan:

This letter summarizes the investigation, design, and repair work performed to stop, under normal operating conditions, the leak located below the E-pond berm that parallels Spanish Creek. This work consisted of (1) exploratory trenching and logging of materials encountered; (2) laboratory testing and analyses; (3) seepage analyses for existing and post-construction conditions based upon the logs and the results of laboratory testing; (4) design and construction of a cutoff structure; and (5) preparation of as-built drawings.

A site location map, site plan, and subsurface profile are shown on Plate 1. The cutoff trench sidewall stratigraphy and a typical cutoff trench detail are shown on Plate 2.

Subsurface Exploration

Test Pit TP-1

An exploratory trench was excavated along the toe of the berm inside the E-pond in the vicinity of the location of a known leak on October 10, 2013. The trench was excavated by Tom Vaglavello of Sierra Concrete, Inc. using a Komatsu PC 138 excavator with a 24 inch bucket. I was on-site to direct the excavation, log the trench, and obtain samples for laboratory testing. A log of this excavation, designated test pit TP-1 is included in Appendix A.

The trench footprint extended along the berm from approximately 20 feet upstream (i.e. relative to Spanish Creek) to 50 feet downstream of the opening in the fence which is located on the opposite crest of the berm. This opening provides access to the leak outlet along the streambank below the berm. The test pit log for TP-1 pertains to the portion of the trench approximately 20 feet upstream of the fence opening as shown on Plate 1. This test pit was excavated to a total depth of 12.0 feet. The remainder of the exploratory trench was excavated to a depth of 8 to 10 feet to confirm the extent of an elastic silt layer encountered in the first portion of the trench.

No free groundwater was observed during the excavation.

A thin layer of silt with numerous roots, approximately 6 inches thick, was encountered at the ground surface. A portion of the trench was excavated through the toe of the berm resulting in about a one foot thick exposure of the embankment fill below the surficial silt along the trench wall nearest to the creek. This material consisted of gravelly sand with silt extending to a depth of 1.5 feet. Below the embankment fill, dry, thinly bedded, dark yellowish-brown silty fine sand layers were encountered to a depth of 2.6 feet where an abrupt transition to a dry, light-gray, clean, poorly-graded sand with gravel stratum that extended to a depth of 4.5 feet. This layer is highly permeable and thickens from 2 feet at TP-1 to 4 or 5 feet as the trench was excavated further downstream (see Plate 2). Below the clean sand and gravel a 3 foot thick layer of moist, soft to medium stiff, dark yellowish-orange and dark gray mottled sandy silt with clay and a trace of organics overlies elastic silts having a high organic content.

Steven C. Devin, P.E., G.E. Civil and Geotechnical Engineering Services

2

The visible organics in the elastic silt include very fine root hairs which yield a pinhole porosity when completely decomposed. The tubular micro-pores created by this decomposition do not appear to be highly interconnected. The upper one foot of elastic silt is moist to wet, soft, and very dark gray in color. The elastic silt then becomes wet, soft, and greenish black with a very high organic content resulting in its classification as an organic elastic silt. The proportion of organics then decreases below a depth of approximately 10.5 feet with the elastic silt becoming dark gray extending to the bottom of the excavation at 12.0 feet.

Test Pit TP-2

A second test pit, designated TP-2, was excavated per my instructions by Frank Porter of the QCSD on November 8, 2013 using a John Deere 310K backhoe and subsequently logged by me on November 11, 2013. This test pit was excavated to a total depth of 9.7 feet with sidewalls stepped and laid back to allow safe entry. Field vane shear tests were performed at 6 inch intervals from the bottom of the test pit (i.e. 9.7 feet) to a total depth of 12.3 feet using a Geonor Inspection Vane Tester Model H-60. A manual push static cone penetration test sounding, designated as CPT-1, was made from the existing ground surface near the edge of the test pit and is included as part of the log for test pit TP-2 included in Appendix A. The locations of test pit TP-2 and the sounding CPT-1 are shown on Plate 1.

The stratigraphy encountered in TP-2 was very similar to that previously described for TP-1. The most important finding was that the clean, poorly-graded sand with gravel layer decreased in thickness from 1.9 feet to 1.6 feet along the east wall of the test pit. Additional thinning appears to occur further to the southwest.

Laboratory Testing and Analyses

Classification Tests

Laboratory tests were conducted on selected samples obtained from the test pits. Tests included (1) grain size analyses performed in accordance with ASTM D-422 on samples S-1 and S-2 obtained from depths of 2.0 and 3.0 feet, respectively in TP-1; (2) Atterberg limits determined in accordance with ASTM D-4318 on samples S-4, S-5, and S-6 obtained from depths of 8.0, 8.5, and 11.3 feet in TP-1; (3) natural water contents determined in accordance with ASTM D-2216 on samples S-3, S-4, S-5, ST-1@ 9.1ft, ST-1@ 9.6ft, and S-6, at depths of 5.0, 8.0, 8.5, 9.1, 9.6, and 11.3 feet, respectively in TP-1; and (4) dry unit weights of samples S-5, ST-1, and S-6 from depths of 8.5, 9.3, and 11.3 feet respectively in TP-1 and S-1 from a depth of 8.2 feet in TP-2. The test results are included on each test pit log. A plot of each grain size distribution curve is included in Appendix A along with a plasticity chart for samples tested in accordance with ASTM D-4318.

Samples were classified using the Unified Soil Classification System (USCS) in accordance with ASTM D-2487 and ASTM D-2488. USCS Group Symbols for each layer are shown in parentheses in the Soil Legend on Plate 1 and are also provided on the logs.

Hydraulic Conductivity Estimates

The hydraulic conductivities of the silty fine sand identified between 1.5 and 2.6 feet in TP-1 and the poorly-graded sand with gravel between 2.6 and 4.5 feet were estimated from the particle size distribution data obtained from the grain size analyses using the Kozeny-Carman formula. The estimated saturated hydraulic conductivities were 4.47x10-3 cm/sec (12.67 feet/day) and 2.28x10-1 cm/sec (646.3 feet/day) respectively. It is important to note that the poorly-graded sand with gravel only has 1.2 percent by weight passing the No. 200 sieve size (0.074 mm) which separates sand and larger material from the silt and clay particle sizes. Particles which are smaller than 0.074 millimeters generally cannot be seen with the naked eye. Hence, this material is considered “clean” which is significant for its behavior as a hydraulic conduit under the berm from the E-pond to the streambank.

Seepage Analyses

Seepage analyses were performed using the stratigraphy indentified in the test pits; the estimated hydraulic conductivities of the highly permeable layers using the Kozeny-Carman formula; and the estimated hydraulic properties of the other soils encountered based upon typical values. Both existing and post-construction conditions were analyzed assuming the following scenarios: (1) the pond water surface elevation (WSEL) reaching 3403.68


3

feet which is the elevation of the edge of water that QCSD had marked as the threshold for the start of leakage; (2) a WSEL of 3404.75 feet at the toe of the berm which is the highest WSEL ever observed by QCSD staff; and (3) a WSEL of 3407.75 feet which would put the water surface about 1.25 feet below the crest of the berm. The first scenario was only considered for existing conditions while the third scenario was only considered as a post-construction scenario. The water surface elevation in Spanish Creek was assumed to be 3393.13 feet in this location for all analyses.

The computed flownet for each analysis is included in Appendix B.

Existing Conditions

Seepage analyses of the existing conditions were performed in order to develop confidence in the hydraulic model (i.e. the stratigraphy and estimated hydraulic conductivities) by replicating the observed leakage rate. The QCSD has reported that leakage rates as high as 5 to 10 gallons per minute (gpm) had been measured.

The seepage analyses are performed in two dimensions and represent conditions for a one foot thick cross section (i.e. out of the plane of the two dimensional cross section) when applied to three dimensions. Thus computing seepage rates is complicated by varying thicknesses of soils as one proceeds upstream or downstream along Spanish Creek. In lieu of performing many analyses and summing them up one analysis was performed and the total leakage rate computed assuming contributing widths of 10, 20, and 30 feet. The cutoff trench wall stratigraphy shown on Plate 2 provides the basis for the range of contributing widths analyzed. A summary of estimated leakage rates for scenarios 1 and 2 using this approach is provided in Table 1. Table 1 - Computed Leakage Rates - Existing Conditions

Estimated Leakage Rate (gpm) Contributing Width along Berm (feet) Pond WSEL 3403.68 Pond WSEL 3404.75

Per lineal foot 0.1819 0.3850

10 1.82 3.85

20 3.64 7.70

30 5.46 11.55

While a much more detailed subsurface exploration would be required to define the horizontal and vertical extent of the permeable materials contributing to the leak, the computed values presented in Table 1 compare very favorably with measured leak rates and therefore provide a high degree of confidence in the hydraulic model.

Remediation

A 10± foot deep lean concrete cutoff wall constructed along the toe of the berm was proposed to repair the leak. The constructed wall was 18 to 24 inches thick and extended a minimum of 2 feet into the elastic silt layers. Seepage analyses were performed for a pond WSEL 3404.75 feet at the toe of the berm and for pond WSEL 3407.75 feet which would overtop the cutoff.

The cutoff wall lowers the seepage face on the bank of Spanish Creek below the highly permeable sand and gravel layer and therefore eliminates leakage when the pond water surface elevation is at or below the toe of the berm. When the pond water surface rises above the toe and “overtops” the cutoff, leakage will occur but at a slower rate than if the cutoff was absent. The computed unit width leakage rate was 0.1745 gpm per lineal foot when the pond WSEL reaches 3407.75 feet. This is approximately the same rate as computed for the start of leakage without the cutoff.


4

Cutoff Wall – Design and Construction

The cutoff wall was constructed along the toe of the berm for a total length of 162 feet with 62 feet extending upstream of the fence opening and 100 feet extending downstream as shown in the site plan on Plate 1.

The total cutoff wall depth varied from 10 to 12 feet while the thickness varied between 18 and 36 inches. A typical detail of the as-built cutoff wall is shown in Section A-A on Plate 2.

The wall was constructed by excavating a trench and backfilling with a lean concrete mix having a maximum ⅜ inch aggregate size and 2 sacks of cement per cubic yard. The mix had a water cement ratio of 0.50 and included a water-reducer admixture. Portions of the cutoff trench that had not been excavated for exploratory purposes and then loosely backfilled were excavated to a width of 18 inches when the sidewalls were stable. Wood forms were used to limit the wall width to 24 to 36 inches in the unstable shallow cohesionless soils. Trench widths and depths were increased such that they terminated in native material in locations that had previously been excavated.

Conclusions

Based upon the conditions encountered in the exploratory excavations and observations of trenching during construction, together with the seepage analyses described above, I believe that the seepage caused by the continuity between the pond and the leak outlet location has been largely eliminated in the vicinity of the cutoff wall. Discharge from the leak outlet should not occur for pond water surface elevations lower than the toe of the berm. However, prolonged high water in the pond at or below the toe may result in some leakage if the cutoff wall is laterally bypassed upstream or downstream of the wall. Normal seepage (i.e. percolation), which is occurs slowly and generally does not result in a spring, would continue.

The QCSD has indicated that the pond water surface elevation has never been observed higher than the toe of the berm. However, if higher water levels were to occur the leak would once again become active but at a reduced rate. Additional remedial work along the face of the berm would be required if this becomes an issue.

Professional Statement Recommendations presented within this report are based upon the physical properties of soils encountered in the exploratory test pits and/or borings. If during the course of final design or construction, subsurface conditions are encountered which differ significantly from those detailed within this report, or if substantial changes are made to the site operational or development plan, Steven C. Devin, P.E., G.E. should be contacted immediately in order to evaluate the applicability of this report to the changed conditions. Such an evaluation may result in changes to the recommendations or conclusions made herein. The intent of this report was to assess cause of observed leakage from the E-pond and develop an interim repair. Although a site reconnaissance was made for the purposes described, the potential presence of soil or groundwater contamination was not investigated and no analytical laboratory testing was performed in this regard. This report has been prepared for the exclusive use of the Quincy Community Services District and their retained design professionals in accordance with generally accepted geotechnical engineering practice common to the local area. No other warranty is made, express or implied.

Please do not hesitate to contact me with any questions or to discuss any of my findings.

Sincerely, Steven C. Devin Attachments

Administrator

Devin_CA_Geotech_2013_Signed


A

Appendix A

Test Pit Logs and

Laboratory Test results

3404

3402

3400

3398

3396

3394

3392

0

2

4

6

8

10

12

S-1

S-2

S-3

S-4

S-5

ST-1

S-6

Light brown SILT with Organics (fine roots), dry0.5

Light brown Gravelly SAND with Silt, dry(EMBANKMENT FILL)

1.5Dark yellowish brown, Silty fine SAND,

dry, thinly beddedVery Loose to Loose

-3" = 100.0% -3/4" = 100.0% -No.4 = 100.0% -No.10 = 100.0% -No.40 = 98.1% -No.200 =20.3% Kozeny-Carman Est Ksat = 4.47x10-3 cm/s

2.6Light gray, poorly-graded SAND with Gravel,

dry,Loose

Subangular Gravel with shapes estimated as60% Regular; 20% Flat; 15% Elongated;

and 5% Flat and Elongated

-3" = 100.0% -3/4" = 86.5% -No.4 = 59.5% -No.10 = 43.7% -No.40 = 8.8% -No.200 =1.2% Kozeny-Carman Est Ksat = 2.28x10-1 cm/s

4.5Dark yellowish orange and dark gray, mottled,Sandy SILT with Clay, trace Organics, moist,

Soft to Medium Stiff7.5

Very dark gray Elastic SILT,moist to wet,

Soft8.5

Greenish black, Organic Elastic SILT,wet,Soft

10.5Very dark gray Elastic SILT,

moist to wet,Soft

Test Pit terminated at 12.0 ft.

ML

GP-SP

SM

SP

ML

MH

OH

MH

50.3

65.2

74.1

2.70

40.6

54.3

89.067.70.260

52.40.26052.40.180 0.50

42.40.225

Steven C. Devin, G.E. PROJECT: Quincy CSD Emergency Effluent Pond PROJECT NO.: G2013-12

Civil and Geotechnical CLIENT: Quincy Community Services District

Engineering Services LOCATION: Pond-side toe of berm opposite leak (i.e. opening in fence)

P.O. Box 1782, Quincy, California 95971 CONTRACTOR: Tom Vaglavello ELEVATION: 3404`

TEST PIT - TP-1EXCAVATION EQUIP: Komatsu PC 138 LOGGED BY: S DevinDEPTH TO - WATER: No GW Observed DATE: 10-09-2013

Specific gravity is assumed

Dep

th (f

t)__

____

____

_

Ele

vatio

n (ft

)34

04`

Gra

phic

Sam

ple

No. Description

USC

S

Dry

Uni

t Wei

ght (

pcf)

Spe

cific

Gra

vity

(Gs)

Est

. SP

T N

60

TEST RESULTS

12 24 36 48 60 72 84Water Content -Plastic Limit Liquid LimitCPT qc (tsf) -

0.25 0.5 0.75 1 1.25 1.5 1.75Pocket Pen. qu (tsf)Torvane su (tsf)Corrected s(FV) (tsf)Uncorrected su (FV) (tsf)

This

info

rmat

ion

pert

ains

onl

y to

this

test

pit

or b

orin

g an

d sh

ould

not

be

inte

rpre

ted

as b

eing

indi

citiv

e of

the

site

.

PAGE 1 of 1

3404

3402

3400

3398

3396

3394

3392

0

2

4

6

8

10

12

S-1

Yellowish brown, Silty fine SAND, dry,Medium Dense

1.5Light gray, poorly-graded SAND with Gravel, dry

Loose to Medium Dense

3.1Light yellow brown, fine SAND, occasional traceSilt and Clay, dry to moist, continuous 0.1' thick

layer of organics (wood, etc) at bottom ofstratum

Loose to Medium Dense

4.8Orange brown, mottled, Sandy SILT with Clay,

trace organics (fine root hairs), moist,pinhole porosity

Medium Stiff

7.8Very dark gray Elastic SILT

Soft8.2

Greenish black, Organic Elastic SILT with veryfine root hairs, wet

Soft

Bottom of Excavation@ 9.7 ft.Push hand held field vane from this depth

11.5

Test Pit terminated at 12.3 ft.

SM

SP-SM

SP

ML

MH

OH

MH

62.9

9

18

18

13

8

8

4

3

2

3

2

3

6

36

70

70

51

32.5

33.5

16.5

11

9

10

8

10

25

75.00.25

0.23

0.380.56

0.73 1.12

0.36 1.00

0.13 1.04

0.05 1.20

Steven C. Devin, G.E. PROJECT: Quincy CSD Emergency Effluent Pond PROJECT NO.: G2013-12

Civil and Geotechnical CLIENT: Quincy Community Services District

Engineering Services LOCATION: Pond floor 34' SE of toe of berm opposite leak (i.e. opening in fence)

P.O. Box 1782, Quincy, California 95971 CONTRACTOR: Frank Potter (QCSD staff) ELEVATION: 3404`

TEST PIT - TP-2EXCAVATION EQUIP: John Deere 310K LOGGED BY: S DevinDEPTH TO - WATER: No GW Observed DATE: 11-11-2013

Plotted Static Cone Penetration Test (CPT) Data from nearby CPT-1Projected area is 1.5 cm2 with a 60° cone tip which is isolated from side frictionField Vane: 20mm x 40mm, Area Ratio = 16.9%Approx. vane rod friction correction = 0.44 tsf per foot depth; Apply additional correction of 0.78 to obtain long term su(FV)

Dep

th (f

t)__

____

____

_

Ele

vatio

n (ft

)34

04`

Gra

phic

Sam

ple

No. Description

USC

S

Dry

Uni

t Wei

ght (

pcf)

Spe

cific

Gra

vity

(Gs)

Est

. SP

T N

60

TEST RESULTS

12 24 36 48 60 72 84Water Content -Plastic Limit Liquid LimitCPT qc (tsf) -

0.25 0.5 0.75 1 1.25 1.5 1.75Pocket Pen. qu (tsf)Torvane su (tsf)Corrected s(FV) (tsf)Uncorrected su (FV) (tsf)

This

info

rmat

ion

pert

ains

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y to

this

test

pit

or b

orin

g an

d sh

ould

not

be

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rpre

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as b

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indi

citiv

e of

the

site

.

PAGE 1 of 1

Tested By: S Devin

LL PL D85 D60 D50 D30 D15 D10 Cc Cu

Material Description USCS AASHTO

Project No. Client: Remarks:Project:

Source of Sample: TP-1 Depth: 2.0 Sample Number: S-1Source of Sample: TP-1 Depth: 3.0 Sample Number: S-2

Figure

0.2389 0.1612 0.1371 0.092817.5945 4.8975 2.7990 1.0147 0.5601 0.4539 0.46 10.79

Silty SANDPoorly graded SAND with Gravel

G2013-12 Quincy Community Services District

PE

RC

EN

T FI

NE

R

0

10

20

30

40

50

60

70

80

90

100

GRAIN SIZE - mm.

0.0010.010.1110100

% +3"Coarse

% GravelFine Coarse Medium

% SandFine Silt

% FinesClay

0.0 0.0 0.0 0.0 1.9 77.8 20.30.0 13.5 27.0 15.8 34.9 7.6 1.2

6 in

.

3 in

.

2 in

.1½

in.

1 in

.¾

in.

½ in

.3/

8 in

.

#4 #10

#20

#30

#40

#60

#100

#140

#200

Particle Size Distribution Summary

Quincy CSD Emergency Effluent Pond

Tested By: S Devin

Client:Project:

Project No.: Figure

Quincy Community Services DistrictQuincy CSD Emergency Effluent Pond

G2013-12

SYMBOL SOURCE

NATURAL

USCSSAMPLE DEPTH WATER PLASTIC LIQUID PLASTICITYNO. CONTENT LIMIT LIMIT INDEX

(%) (%) (%) (%)

SOIL DATA

PLA

STI

CIT

Y IN

DE

X

0

10

20

30

40

50

60

LIQUID LIMIT0 10 20 30 40 50 60 70 80 90 100 110

CL-ML

CL or OL

CH or OH

ML or OL MH or OH

Dashed line indicates the approximateupper limit boundary for natural soils

4

7

Atterberg Limits Summary

TP-1 S-4 8.0 54.3 35 54 19 MH

TP-1 S-5 8.5 89.0 56 89 33 OH

TP-1 S-6 11.3 42.4 32 51 19

GREGG DRILLING AND TESTING, INC. and GREGG IN SITU, INC. ENVIRONMENTAL AND GEOTECHNICAL INVESTIGATION SERVICES

UNIFIED SOIL CLASSIFICATION SYSTEM

MAJOR DIVISIONS GROUP

SYMBOLS TYPICAL NAMES

FIELD INDENTIFICATION PROCEDURES (excluding particles larger than 3 inches and

basing fractions on estimated weights) INFORMATION REQUIRED FOR DESCRIBING SOILS

1 2 3 4 5 6

GW Well-graded gravels, gravel-sand mixtures, little or no fines

Wide range in grain sizes and substantial amounts of all intermediate particle sizes

(Cle

an

Gra

vels

Li

ttle

or

no fi

nes)

GP Poorly graded gravels or gravel-sand mixtures, little or no fines

Predominatly one size or a range of sizes with some intermediate sizes missing

GM Silty gravels, gravel-sand-silt mixtures Nonplastic fines or fines with low plasticity (for identification procedures see ML below)

Gra

vels

M

ore

than

hal

f of c

oars

e fra

ctio

n is

larg

er th

an N

o. 4

si

eve

size

.

(Gra

vels

with

Fi

nes

Appr

ecia

ble

amou

nt o

f fin

es)

GC Clayey gravels, gravel-sand-clay mixtures Plastic fines (for identification see CL below)

SW Well-graded sands, gravelly sands, little or no fines

Wide range in grain sizes and substantial amounts of all intermediate sizes missing

Cle

an

Sand

s (L

ittle

or

no

fines

)

SP Poorly graded sands or gravelly sands, little or no fines

Predominantly one size or a range of sizes with some intermediate sizes missing

SM Silty sands, sand-silt mixtures Nonplastic fines or fines with low plasticity (for identification

Coa

rse-

grai

ned

Soils

M

ore

than

hal

f of m

ater

ial i

s la

rger

than

N

o. 2

00 s

ieve

siz

e.

Sand

s M

ore

than

hal

f of

coar

se fr

actio

n is

sm

alle

r tha

n N

o. 4

sie

ve

size

(For

vis

ual c

lass

ifica

tion,

the

¼-in

. siz

e m

ay b

e us

ed a

s eq

uiva

lent

to th

e N

o. 4

sie

ve)

Sand

s w

ith

Fine

s (A

ppre

ciab

le

amou

nt o

f fin

es)

SC Clayey sands, sand-clay mixtures Plastic fines (for identification procedures see CL below)

Identification Procedures on Fraction smaller than No. 40 Sieve Size

For undisturbed soils add information on stratification, degree of compactness, cementation, moisture conditions, and drainage characteristics. Give typical name: Indicate approximate percentage of sand and gravel, maximum size, angularity, surface condition, and hardness of the coarse grains; local or geologic name and other pertinent descriptive information, and symbol in parentheses. Example: Silty sand gravelly; about 20% hard, angular gravel particles 1/2in. maximum size; rounded and subangular sand grains, coarse to fine; about 15% non plastic fines with low dry strength; well compacted and moist in place; alluvial sand (SM).

Dry Strength (Crushing

Characteristics)

Dilatancy (Reaction to

Shaking)

Toughness (Consistency

near PL)

ML Inorganic silts and very fine sands, rock flour, silty or clayey fine sands or clayey silts with slight plasticity

None to slight Quick to slow None

CL Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays

Medium to high None to very slow Medium

Silts

and

Cla

ys

Li

quid

lim

it is

less

th

an 5

0.

OL Organic silts and organic silty clays of low plasticity Slight to medium Slow Slight

MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts

Slight to medium Slow to none Slight to medium

CH Inorganic clays of high plasticity, fat clays High to very high None High

Fine

-gra

ined

Soi

ls

Mor

e th

an h

alf o

f mat

eria

l is

smal

ler t

han

No.

200

sie

ve s

ize.

Th

e N

o. 2

00 s

ieve

siz

e is

abo

ut th

e sm

alle

st p

artic

le v

isib

le to

the

nake

d ey

e.

Soils

and

Cla

ys

Li

quid

lim

it is

gr

eate

r tha

n 50

.

OH Organic clays and silts of medium to high plasticity Medium to high None to very slow Slight to

medium

Highly Organic Soils Pt Peat and other highly organic soils Readily identified by color, odor, spongy feel and frequently by fibrous texture

For undisturbed soils add information on structure, stratification, consistency in undisturbed and remolded states, moisture and drainage conditions. Give typical name, indicate degree and character or plasticity, amount and maximum size of coarse grains, color in wet conditions, odor (if any), local or geologic name, and other pertinent descriptive information, and symbol in parentheses. Example: Clayey silt, brown; slightly plastic; small percentage of fine sand; numerous vertical root holes; firm and dry and place; loess (ML).


P.O. Box 1782 Quincy, California 95971 (530) 283 2553

Steven C Devin

Stamp

Steven C. Devin, P.E., G.E. Exploration Report Terminology Civil and Geotechnical Engineering Services

Exploration Report Standard Practice and Terminology

Exploration Report

The exploration report consisting of test pit or boring logs has been prepared by the Engineer from both field and laboratory data. Differences between field logs and exploration reports may exist.

It is common practice in the soil and foundation engineering profession that field logs and laboratory data sheets not be included in engineering reports, because they do not represent the Engineer’s final opinions as to appropriate descriptions for conditions encountered in the exploration and testing work. The field logs will be retained in my office for review, and I would welcome the opportunity to explain any changes that have been and typically are made in the preparation of my final reports. Results of laboratory testing are generally shown on the test pit or boring logs or are described in the text of the report as appropriate.

Drilling and Sampling Symbols

Abbreviation or Symbol

Description Abbreviation or Symbol

Description

SS

Split Spoon - 1.375” I.D., 2” O.D. (ASTM D1586)

RX (e.g. NX or HQ)

Rock core with diamond bit – H, N, B, A sizes as noted

MC California Modified Sampler (MC) – 2.42” I.D., 3” O.D. (ASTM D3050)

RQD Rock Quality Designation

ST Thin Walled Shelby Tube - 3” O.D. - undisturbed

WOH Weight of 140 lb hammer

GS Grab Sample WOR Weight of drilling rods HSA Hollow Stem Auger P Hydraulic advance – pressure as noted CS Casing - Size as noted PL Plastic limit SPT N value Standard Penetration Test Field

Blows per foot of 140 lb hammer falling 30” on split spoon sampler (ASTM D1586)

LL Liquid limit

NMC Penetration Test Field Blows per foot of 140 lb hammer falling 30” on Modified California sampler (ASTM D3050)

PI Plasticity Index

SPTField N* Estimated SPT Field N from MC sampler (SPTField N* = 0.56· NMC)

w Natural water content

(N1)60 SPT N corrected to 1 atmosphere overburden and 60% hammer energy

WL Wire-Line

USCS Unified Soil Classification System UCS Uniaxial Compressive Strength (psi, psf, or MPa as noted)

Groundwater Level

Water levels indicated on the test pit or boring logs are the levels measured in the excavation or boring at the times indicated. In pervious soils such as sands and gravels, the indicated elevations are considered reliable groundwater levels. In impervious soils such as silts and clays, the accurate determination of groundwater elevations may not be possible, even after several days of observations; additional evidence of groundwater elevations must be sought.

1

Steven C. Devin, P.E., G.E. Exploration Report Terminology Civil and Geotechnical Engineering Services Gradation Description & Terminology

Particle Size Classification Size Range Boulders Over 12 inches (300 mm) Cobbles 3 inches to 12 inches (75 mm to 300 mm) Gravel No. 4 sieve to 3 inches (4.75 mm to 75 mm) Sand No. 200 to No. 4 (0.074 mm to 4.75 mm) Silt 0.002 mm to No. 200 (0.002 mm to 0.074 mm) Clay Smaller than 0.002 mm

Field Descriptive Term of Components Present Percent of Dry Weight Trace 1 to 9 Little 10 to 19 Some 20 to 34 Adjective (e.g. silty) 35 to 49

Note: The terminology of ASTM D 2488 may be used in lieu of the above

Consistency of Cohesive Soils

Unconfined compressive strength, qu (psf)

Field SPT N value (blows/ft) Consistency

Less than 250 0 to 2 Very soft 250 to 500 3 to 4 Soft 500 to 1,000 5 to 8 Medium stiff 1,000 to 2,000 9 to 16 Stiff 2,000 to 4,000 17 to 32 Very stiff Greater than 4,000 Greater than 32 Hard

Relative Density of Granular Soils

Field SPT N value (blows/ft) Relative Density 0 to 3 Very loose 4 to 9 Loose 10 to 29 Medium dense 30 to 49 Dense 50 to 80 Very dense Greater than 80 or 50 for less than 6” advancement Refusal

Rock Quality Designation (Deere, et al, 1967)

RQD (%) Rock Description

0-25 Very Poor

25-50 Poor

50-75 Fair

75-90 Good

>90 Excellent

2


Uniaxial Compressive Strength of Rock (ISRM, 1981)

Grade Description Field Identification Approx. Range of Uniaxial Compressive Strength (MPa)

R0 Extremely Weak Rock

Indented by thumbnail <0.25-1.0

R1 Very Weak Rock Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife.

1.0-5.0

R2 Weak rock Can be peeled by a pocket knife with difficulty, shallow indentations made by firm blows with point of geological hammer.

5.0-25

R3 Medium Strong Rock

Cannot be scraped or peeled with a pocket knife, specimen can be fractured with single firm blow of geological hammer.

25-50

R4 Strong Rock Specimen requires more than one blow of geological hammer to fracture it.

50-100

R5 Very Strong Rock Specimen requires many blows of geological hammer to fracture it.

100-250

R6 Extremely strong rock

Specimen can only be chipped with geological hammer. >250

Bedding, foliation, or flow texture descriptors (USBR, 1989)

Descriptors Thickness/spacing Massive Greater than 10 ft (3 m)

Very thickly, bedded, foliated, or banded

3 to 10 ft (1 to 3 m)

Thickly 1 to 3 ft (300 mm to 1 m) Moderately 0.3 to 1 ft (100 to 300 mm)

Thinly 0.1 to 0.3 ft (30 to 100 mm)

Very thinly 0.03 [3/8 in] to 0.1 ft (10 to 30 mm)

Laminated (intensely foliated or banded)

Less than 0.03 ft [3/8 in] (<10 mm)

3

Steven C. Devin, P.E., G.E. Exploration Report Terminology Civil and Geotechnical Engineering Services Bedrock Void Terminology (USBR, 1989)

Pit (pitted) Pinhole to 0.03 ft [d in] (<1 to 10 mm) openings.

Vug (vuggy) Small opening (usually lined with crystals) ranging in diameter from 0.03 ft [d in] to 0.33 ft [4 in] (10 to 100 mm).

Cavity An opening larger than 0.33 ft [4 in] (100 mm), size descriptions are required, and adjectives such as small, or large, may be used, if defined.

Honeycombed Individual pits or vugs are so numerous that they are separated only by thin walls; this term is used to describe a cell-like form.

Vesicle (vesicular) Small openings in volcanic rocks of variable shape formed by entrapped gas bubbles during solidification.

Intact igneous and metamorphic rock grain size descriptors (USBR 1989)

Descriptor Average crystal diameter Very coarse-grained or pegmatitic > 10 mm (3/8 in)

Coarse-grained 5-10 mm (3/16 - 3/8 in)

Medium-grained 1-5 mm (1/32 - 3/16 in) Fine-grained 0.1-1 mm (0.04 - 1/32 in) Aphanitic (cannot be seen with <0.1 mm (<0.04 in) the unaided eye

Types of Discontinuities (USBR, 1989) Fracture - A term used to describe any natural break in geologic material, excluding shears and shear zones. Examples of the most common fractures are defined as follows:

Joint - A fracture which is relatively planar along which there has been little or no obvious displacement parallel to the plane. In many cases, a slight amount of separation normal to the joint surface has occurred. A series of joints with similar orientation form a joint set. Joints may be open, healed, or filled; and surfaces may be striated due to minor movement. Fractures which are parallel to bedding are termed bedding joints or bedding plane joints. Those fractures parallel to metamorphic foliation are called foliation joints.

Bedding plane separation - A separation along bedding planes after exposure due to stress relief or slaking.

Random fracture - A fracture which does not belong to a joint set, often with rough, highly irregular, and non-planar surfaces along which there has been no obvious displacement.

Shear - A structural break where differential movement has occurred along a surface or zone of failure; characterized by polished surfaces, striations, slickensides, gouge, breccia, mylonite, or any combination of these. Often direction of movement, amount of displacement, and continuity may not be known because of limited exposures or observations.

Fault - A shear with significant continuity which can be correlated between observation locations; foundation areas, or regions; or is a segment of a fault or fault zone reported in the literature. The designation of a fault or fault zone is a site-specific determination.

Shear/fault zone - A band of parallel or sub-parallel fault or shear planes. The zone may consist of gouge, breccia, or many fault or shear planes with fractured and crushed rock between the shears or faults, or any combination. In the literature, many fault zones are simply referred to as faults.

4

Steven C. Devin, P.E., G.E. Exploration Report Terminology Civil and Geotechnical Engineering Services Shear/fault gouge - Pulverized (silty, clayey, or clay-size) material derived from crushing or grinding of rock by shearing, or the subsequent decomposition or alteration. Gouge may be soft, uncemented, indurated (hard), cemented, or mineralized.

Shear/fault breccia - Cemented or uncemented, predominantly angular (may be platy, rounded, or contorted) and commonly slickensided rock fragments resulting from the crushing or shattering of geologic materials during shear displacement. Breccia may range from sand-size to large bouldersize fragments, usually within a matrix of fault gouge. Breccia may consist solely of mineral grains.

Shear/fault-disturbed zone - An associated zone of fractures and/or folds adjacent to a shear or shear zone where the country rock has been subjected to only minor cataclastic action and may be mineralized. If adjacent to a fault or fault zone, the term is fault-disturbed zone. Occurrence, orientation, and areal extent of these zones depend upon depth of burial (pressure and temperature) during shearing, brittleness of materials, and the in-situ stresses. Methods for the Quantitative Description of Discontinuities (ISRM, 1981)

Term Description Grade

I Fresh No visible sign of rock material weathering: perhaps slight discoloration on major discontinuity surfaces.

II Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be discolored by weathering and may be somewhat weaker externally than in its fresh condition.

Slightly Weathered

Moderately Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework or as corestones.

III Weathered

Highly More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework or as corestones. Weathered

IV

Completely All rock material is decomposed and/or disintegrated to a soil. The original mass structure is still largely intact.

V Weathered

Residual Soil

All rock material is converted to soil. The mass structure and material fabric are destroyed. There is a large change in volume, but the soil has not been significantly transported.

VI

Rock Mass Fracture Spacing Terminology (USBR, 1989)

Joint or fracture spacing descriptor True spacing

Extremely widely spaced Greater than 10 feet (ft) (<3 m) Very widely spaced 3 to 10 ft (1 to 3 m) Widely spaced 1 to 3 ft (300 mm to 1 m) Moderately spaced 0.3 to 1 ft (100 to 300 mm) Closely spaced 0.1 to 0.3 ft (30 to 100 mm) Very closely spaced Less than 0.1 ft (<30 mm)

Rock Mass Fracture Roughness Terminology (USBR, 1989)

Descriptor Criteria Stepped Near-normal steps and ridges occur on the fracture surface. Rough Large, angular asperities can be seen. Moderately rough Asperities are clearly visible and fracture surface feels abrasive. Slightly rough Small asperities on the fracture surface are visible and can be felt. Smooth No asperities, smooth to the touch. Polished Extremely smooth and shiny.

5


6

Rock Mass Fracture Density (USBR, 1989)

Descriptor Criteria (excludes mechanical breaks)

Un-fractured No observed fractures.

Very slightly fractured Core recovered mostly in lengths greater than 3 feet (1 m).

Slightly to very slightly fractured1

Slightly fractured Core recovered mostly in lengths from 1 to 3 feet (300 to 1,000 mm)

with few scattered lengths less than1 foot (300 mm) or greater than 3 feet (1,000 mm).

Moderately to slightly fractured1

Moderately fractured Core recovered mostly in lengths from 0.33 to 1.0 foot (100 to 300

mm) from 0.33 to 1.0 foot (100 to 300 mm) with most lengths about 0.67 foot (200 mm).

Intensely to moderately fractured1

Intensely fractured Lengths average from 0.1 to 0.33 foot (30 to 100 mm) with

fragmented intervals. Core recovered mostly in lengths less than 0.33 foot (100 mm).

Very intensely to intensely fractured1

Very intensely fractured Core recovered mostly as chips and fragments with a few scattered

short core lengths. 1Combinations of fracture densities are permissible where equal distribution of both fracture density characteristics are present over a significant core interval or exposure, or where characteristics are "in between" the descriptor definitions. Rock Mass Fracture Openness Terminology (USBR, 1989)

Descriptor Openness Tight No visible separation Slightly open Less than 0.003 ft [1/32 inch (in)] (<1 mm) Moderately open 0.003 to 0.01 ft [1/32 in to 1/8 in] (1 to 3 mm) Open 0.01 to 0.03 ft [1/8 to 3/8 in] (3 to 10 mm) Moderately wide 0.03 ft [3/8 in] to 0.1 ft (10 to 30 mm) Wide Greater than 0.1 ft (>30 mm) (record actual openness)


B

Appendix B

Seepage Analyses Flownets

X-Sec_@_Leak_Seepage_Existing_Dense_Mesh.slimQuincy CSD E-Pond Seepage and Stability

25 50 75 100 125 150 175 200 225 250 275

3370

Material Name Color Model KS (ft/s) K2/K1K1 Angle(deg)

Alpha (1/ft) N

Gravelly SAND with Silt (FILL)Van

Genuchten3.28084e‐006 0.4 ‐2 2.07264 13.1

SILT with Organics (ML)Van

Genuchten4.10105e‐006 0.2 0 0.6096 1.41

Silty fine SAND (SM)Van

Genuchten0.000147 0.2 0 0.48768 1.37

Poorly‐graded SAND with Gravel (SP)Van

Genuchten0.00748031 0.2 0 4.60248 7.35

Fine to medium SAND with Silt (SM)Van

Genuchten0.000131234 0.5 0 3.77952 2.28

Sandy SILT with ClayVan

Genuchten2.37861e‐006 1 0 0.57912 1.31

Elastic SILT (MH)Van

Genuchten1.80446e‐007 1 0 0.1524 1.09

Organic Elastic SILT (OH)Van

Genuchten3.1168e‐008 1 0 0.0463296 1.17

3500

3450

3400

3350

0 50 100 150 200 250 300

Quincy CSD E-Pond Seepage and Stability

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X-Sec_@_Leak_Seepage_Existing_3404-75.slimQuincy CSD E-Pond Seepage and Stability


Alpha (1/ft) N


Genuchten3.28084e‐006 0.4 ‐2 2.07264 13.1


Genuchten4.10105e‐006 0.2 0 0.6096 1.41


Genuchten0.000147 0.2 0 0.48768 1.37


Genuchten0.00748031 0.2 0 4.60248 7.35


Genuchten0.000131234 0.5 0 3.77952 2.28


Genuchten2.37861e‐006 1 0 0.57912 1.31


Genuchten1.80446e‐007 1 0 0.1524 1.09


Genuchten3.1168e‐008 1 0 0.0463296 1.17

25 50 75 100 125 150 175 200 225 250 275

3370

355

3500

3450

3400

3350

0 50 100 150 200 250 300


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X-Sec_@_Leak_Seepage_CUTOFF3_WSEL_3404-75.slimQuincy CSD E-Pond Seepage and StabilityCutoff Wall with Pond WSEL 3407.75Spanish Creek WSEL 3393.13

25 50 75 100 125 150 175 200 225 250 275

3370


Alpha (1/ft) N


Genuchten3.28084e‐006 0.4 ‐2 2.07264 13.1


Genuchten4.10105e‐006 0.2 0 0.6096 1.41


Genuchten0.000147 0.2 0 0.48768 1.37


Genuchten0.00748031 0.2 0 4.60248 7.35


Genuchten0.000131234 0.5 0 3.77952 2.28


Genuchten2.37861e‐006 1 0 0.57912 1.31


Genuchten1.80446e‐007 1 0 0.1524 1.09


Genuchten3.1168e‐008 1 0 0.0463296 1.17

3500

3450

3400

3350

0 50 100 150 200 250 300


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X-Sec_@_Leak_Seepage_CUTOFF3_WSEL_3407-75.slimQuincy CSD E-Pond Seepage and StabilityCutoff Wall with Pond WSEL 3407.75Spanish Creek WSEL 3393.13


Soil Type Alpha (1/ft) N


Genuchten3.28084e‐006 0.4 ‐2 2.07264 13.1


Genuchten4.10105e‐006 0.2 0 0.6096 1.41


Genuchten0.000147 0.2 0 0.48768 1.37


Genuchten0.00748031 0.2 0 4.60248 7.35


Genuchten0.000131234 0.5 0 3.77952 2.28


Genuchten2.37861e‐006 1 0 0.57912 1.31


Genuchten1.80446e‐007 1 0 0.1524 1.09


Genuchten3.1168e‐008 1 0 0.0463296 1.17

Lean Concrete Simple 1e‐014 1 0 General

3500

3450

3400

3350

0 50 100 150 200 250 300


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steven c. devin, p.e., g.e. · embankment fill below the surficial silt along the ... dark gray...

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