HomeMy WebLinkAboutOnsite Wastewater Treatment System Design 02.20.2015c.&£tech
HEPWORTH-PAWLAK GEOTECHNICAL
Hepworth-Pawlak Geotechnlcal, Inc.
5020 County Road 154
Glenwood Springs, Colorado 81601
Phone: 970-945-7988
Fax: 970-945-8454
Emafl: hpgeo@hpgeotech.com
ONSITE WASTEWATER TREATMENT SYSTEM DESIGN
PROPOSED BARN
GARFIELD COUNTY PARCEL: 239327300005
12431 STATE HIGHWAY 82
NEAR CARBONDALE
GARFIELD COUNTY, COLORADO
JOB NO. 114 494B
FEBRUARY 20, 2015
PREPARED FOR:
KATHLEEN SULLIVAN
12431 HIGHWAY 82
CARBONDALE, COLORADO 81623
(kbsullivanlO@gmail.com)
TABLE OF CONTENTS
INTRODUCTION ........................................................................................................... -I -
BACKGROUND INFORMATION ................................................................................ -I -
PROPOSED CONSTRUCTION ..................................................................................... -I -
SITE CONDITIONS ....................................................................................................... -2 -
SUBSURFACE CONDITIONS ...................................................................................... -2 -
OWTS ANALYSIS ......................................................................................................... - 2 -
DESIGN RECOMMENDATIONS ................................................................................. - 3 -
SOIL TREATMENT AREA ....................................................................................... -3 -
OWTS COMPONETS ................................................................................................ -4 -
OWTS OPERATION AND MAINTENANCE .............................................................. -6-
0WTS OPERATION .................................................................................................. -6-
0WTS MAINTENANCE ........................................................................................... - 7 -
OWTS CONSTRUCTION OBSERVATION ................................................................. - 7 -
LIMITATIONS ............................................................................................................... - 8 .
FIGURE 1 -OWTS SITE PLAN
FIGURE 2 -SOIL TREATMENT AREA CALCULATION
FIGURE 3 -SOIL TREATMENT AREA PLAN VIEW
FIGURE 4 -SO IL TREA TMENT AREA CROSS SECTION
ATTACHMENTS
APPENDIX A -Valley Precast Tank Detail
APPENDIX B -Logs of Profile Pits and USDA Test Results
Job No. 114 4948
INTRODUCTION
This report provides the results of an onsite wastewater treatment system (OWTS) design
for the proposed barn for the property located at 12431 State Highway 82, near
Carbondale, Garfield County, Colorado. The purpose-of this report was to provide design
details for an OWTS in accordance with the 2014 Garfield County Onsite Wastewater
Treatment System Regulations and the Colorado Department of Public Health and
Environment's Regulation #43. The services were performed in accordance with our
agreement for professional services to Kathleen Sullivan dated December 1, 2014.
BACKGROUND INFORMATION
Hepworth-Pawlak Geotechnical (HP Geotech) previously performed a subsoil study for
foundation design and percolation test at the site, and submitted our findings in a report
dated November 21, 2014, Job No. 114 494A. The field and laboratory information
obtained from that study was utilized in the OWTS design contained in this report.
PROPOSED CONSTRUCTION
The proposed construction on the property will consist of a new barn located southeast of
the existing residence as shown on Figure 1. The OWTS for the barn is to be designed as
for an auxiliary building with no living space. Estimated wastewater flow for the
structure was based on fixture unit flows per Table 6-2 of Regulation #43 of the State of
Colorado. Water will be supplied to the barn by the existing well located north of the
main residence.
If proposed construction is different than that described above, we should be contacted to
re-evaluate our design recommendations.
Job No. 114 494B
-2-
SITE CONDITIONS
The property consists of an approximately 1.68 acre lot. There is currently a three
bedroom residence and barn on the property . The existing barn will be removed to allow
for construction of the new barn . Vegetation consists of lawn grasses and scattered trees.
The Roaring Fork River lies along the southern property boundary. There is an irrigation
ditch and a swale located between the Roaring Fork River channel and the proposed soil
treatment area, see Figure 1. The ditch flows water seasonally.
SUBSURFACE CONDITIONS
\.
The field exploration was conducted by HP Geotech on November 12, 2014. Two
exploratory pits and three percolation test holes were excavated at the approximate
locations shown on Figure 1 to evaluate the subsurface conditions. Logs of the profile
pits from our November 21 , 2014 report are provided as an attachment to this report . The
soils encountered, below about 3Yi feet of fill in Pit I and 5Y2 feet of fill in Pit 2, consisted
of silt and sand overlying slightly silty sandy gravel with cobbles and boulders. A
hydrometer and gradation analysis was performed on a sample of the sand and silt soils
from Pit 2. The results of the hydrometer/gradation analyses are also provided as an
attachment. The soils classified as Sandy Loam per the USDA classification system.
Percolation tests were performed in the three test holes (P-1, P-2 and P-3) on November
12, 2014. Percolation test rates ranged from about 23 to 80 minutes per inch. Percolation
test procedures outlined in Regulation #43 were not utilized and the results were only
used for comparison of the soil profile pit evaluations .
OWTS ANALYSIS
Based on the test pit evaluations, the soil treatment trenches are expected to be located
sand and silt or the underlying silty, sandy gravel soils. The soil treatment area will be
sized for a Long-Term Acceptance Rate (LTAR) of0.35 gallons per square foot per day
based on the variable soil types and relatively slow percolation test results encountered .
Job No. 114 4948
-3-
The system will be designed to consist gravity fed Infiltrator trench soil treatment area
(ST A). A 50 feet horizontal setback is required from the soil treatment area, septic tank
and sewer line to any surface water features.
The sewage will gravity flow to the septic tank for primary treatment then gravity flow to
the soil treatment area for disposal and final treatment.
DESIGN RECOMMENDATIONS
The system has been designed to consist gravity fed Infiltrator trench soil treatment area
(ST A). The design recommendations presented below are based on the proposed
construction, the site and subsurface conditions encountered and our experience in the
area. Locations of the components of the OWTS are shown on Figure 1. The STA is
located about 30 feet from the area we tested and we expect the subsoil conditions will be
generally similar to our profile pits, but we should determine actual subsoil conditions at
the ST A at the time of construction.
If conditions encountered during construction are different than those that are described in
this report please contact us so we can re-evaluate our design recommendations.
SOIL TREATMENT AREA
• The treatment system will consist of one trench with 14 Infiltrator Quick 4 Plus
Standard chambers. The ST A was sized based on an LT AR of 0.35 gallons per
square feet per day.
• Each chamber was allowed 12 square feet of area. No reduction in the ST A was
applied for use of chambers. The total ST A is 168 square feet. Soil treatment
area calculations are shown on Figure 2.
• The base and sidewalls of the trench excavations should be scarified prior to
chamber installation.
• A minimum of 12 inches and a maximum of 24 inches of cover soil should be
placed over the chambers.
Job No. 114 4948
-4-
• Backfill should be graded to deflect surface water away from the absorption area
and should be sloped at l Horizontal to 1 Vertical or flatter.
• Disturbed soil should be re-vegetated as soon as possible with a native grass mix.
No trees, shrubs or other plants with deep roots should be planted on or near the
absorption area as this may damage the system piping.
• Four inch diameter inspection ports should be installed vertically in to the
knockouts provided in the Infiltrator end caps at each end of the trench. The
inspection port piping should be screwed into the top to the chambers and should
not extend down to the ground surface inside the chambers . The inspection ports
should extend at least 8 inches above the finished ground surface or be protected
in a valve box at finished grade .
• A plan view of the absorptio n area is presented as Figure 3 and a cross section of
the absorption area is presented as Figure 4
OWTS COMPONETS
Recommended OWTS components provi ded below are based on our design details and
our experience with the specific component manufacturers. Equivalent components may
be feasible but would need to be approved by us prior to construction .
Septic Tank
• A 500 gallon, two chamber VaUey Precast septic tank is proposed for primary
treatment of sewage. A copy of the tank detail is provided as an attachment to th is
report. An effluen t fil ter should be installed in the outlet tee of the tank .
• The tank must be set level. A gravel road base bedding material may be necessary
to prevent tank damage during placement and act as a leveling course.
• Install tank with 2 feet minimum cover so il for frost protection. Maximum tank
soil cover depth is 4 feet.
• The septic tank lids must extend to finished grade ground surface and should be
made to be easily located .
Job No. 114 4948
-5-
Sewer Pipe
• The sewer line from the barn to the septic tank should not be less than the
diameter of the building drain ~d not less than 4 inches in diameter.
• The sewer pipe should have a rating of SDR35 or stronger.
• Sewer pipe should be sloped at 2% minimum from the barn to the septic tank
except for the last I 0 feet, which should be sloped at 4% maximum (2%
minimum) to help limit disturbance of solids in the tank.
• 36 inches minimum of cover soil should be provided over the sewer pipe. Paved
areas, patios or other areas without vegetative cover may be more susceptible to
frost. We recommend 48 inches of soil cover over the sewer pipe in these areas
and the pipe be insulated on top and sides with 2 inch thick blue foam insulation
board. If adequate soil cover is not possible, we should be contacted for re-
evaluation prior to installation.
• The sewer pipe should be bedded in compacted % inch road base or native soils
provided that the native soils contain no angular rocks or rocks larger than 2Yi
inches in diameter to help prevent settlement of the pipe. Sags could cause
standing effluent to freeze and damage piping.
• Install cleanout pipes within 5 feet of building foundation, where the sewer pipe
bends 90 degrees or more and every 100 feet of sewer pipe.
• All 90 degree bends should be installed using a 90 degree long-sweep or by using
two 45 degree elbows.
• The sewer line location shown on Figure l is considered conceptual. We assume
that there will be only one sewer line exiting the barn. It is the responsibility of
the owner to locate all sewer line exit locations and connections to the septic tank.
Effluent Transport Piping
• The effluent transport pipe should be 4 inch diameter SDR35 sloped at a 2%
minimum to drain to the soil treatment area.
• The effluent transport pipe should be bedded in compacted% inch road base or
native soils provided that the native soils contain no angular rocks or rocks larger
Job No. 114 4948
-6-
than 2!h inches in diameter to help prevent settlement of the pipe. Sags in the
piping could cause standing effluent to freeze and damage the piping .
• A minimum 24 inches of cover soil should be provided over the effluent transport
pipe. Paved areas, patios or other paved area or areas without vegetative cover
may be more susceptible to freezing . We recommend 48 inches of soil cover ove r
the pipe in these areas. If adequate cover soil is not possible the effluent pipe
should be insulated on top and sides with 2 inch th ick foam insulation board, and
we should re-evaluate the proposed soil cover prior to installati on .
• All 90 degree bends should be installed using a 90 degree long-sweep or by us ing
two 45 degree elbows.
OWTS OPERATION AND MAINTENANCE
The OWTS will require periodic inspection and ma intenance to funct ion properly. A
properly designed, installed and maintained system can greatly increase its lifespan. The
level of maintenance will vary depending .on the comp lexity of the system and water use
habits of the residents . We recommend that an OWTS Operation and Maintenance
(O&M} Manual be developed. Depending on the complexity of the system a contract
with an OWTS maintenance provider may be prudent. Below are some basic
recommendations for the O&M .
OWTS OPERATION
• Use of high efficiency water fixtures is recommended to decrease the hydraulic
load on the OWTS system.
• Fix plumbing leaks immediately as this may cause a hydraulic overload of the soil
absorption system .
• Do not irrigate the area on top of or directly upgradient of the soil absorption field
as this may cause a hydraulic over1oad.
• Do not dispose of household was te down household drains as this may clog or
damage OWTS components. Examples of household waste includes : dental floss,
cotton swabs , coffee grounds, paper towels, feminine products and many other
kitchen and bath items.
Job No . 1 t 4 4948
- 7 -
• Use of kitchen garbage disposals is not recommended. If a garbage disposal is
utilized, kitchen wastewater should be screened thoroughly. Many kitchen solids
are not decomposed in the septic tank and may cause increased tank pumping
frequency.
• Do not dispose of household chemicals, greases, oils, paints, hot tub water or
water softener backwash in household drains. A separate drywell, if feasible, may
be necessary for hot tub water or water softener backwash disposal.
• Limit the use of bleach as this may harm useful bacteria in the septic tank and soil
absorption system.
• Liquid dishwasher and clothes washer detergent is recommended for households
served by an OWTS . Clay substances used as fillers in powder detergents may
result in clogging of the soils absorption system .
• The effluent in septic tanks can freeze during extended periods of non-use. We
recommend that a tank heater be installed in this system to help prevent freezing.
OWTS MAINTENANCE
• Inspect the septic tank, effluent filter and soil treatment area at least annually for
problems or signs of failure .
• The effluent filter should be cleaned annually by spray washing solids into the
first chamber of the septic tank.
• Septic tank should be pumped and cleaned every 3 to 5 years depending on use .
Longer pumping intervals may increase the amount of solids that reach the soil
absorption area, which may shorten its life span.
• Pumping of the septic tank should take place when the level of the sludge and
scum layers combined take up 25 to 33% of the capacity of the first chamber of
the tank.
OWTS CONSTRUCTION OBSERVATION
The Garfield County Environmental Health Department requires that the designer provide
an As-Built certification of the OWTS construction. We should be provided with at least
Job N o. 114 4948
-8-
48 hour notice prior to the installer needing the As-Built inspections. Prior to issuance of
our certification letter, we require observation of all system components prior to back.fill.
The number of site visits required for the inspection will depend on the installer's
construction schedule.
LIMITATIONS
We have prepared this design in accordance with generally accepted engineering
principles and practices in this area at this time. We make no warranty either expressed
or implied. The recommendations provided in this report are based on the site conditions,
profile pits, percolation tes t ho les, soil texture analysis, the proposed construction and our
experience in the area . Variations in the subsurface conditions may not become evident
until excavation is performed . If conditions encountered during construction appear
different from those described in this report, we should be notified so that re-evaluation of
the recommendations may be made .
This report has been prepared for the exclusive use by our client for design purposes . We
are not responsible for technical interpretations by others of our information . As the
project evolves, we should provide continued consultation and field services during
construction to review and monitor the implementation of our recommendations, and to
verify that' the recommendations have been appropriately interpreted. Significant design
changes may require add itional analysis or modifications to our design .
It is our opinion that the designed location of the OWTS components does not violate any
setback requirements of the current Garfield County Regulations. Below is a table of
common minimum horizontal setbacks to OWTS components. Refer to the Garfield
County Regulations for a complete list of required setbacks. We recommend the OWTS
components be surveyed by a Professional Colorado Land Surveyor and verified by H-P
Geotech prior to the system permitting.
Job No . 114 494 8
-9 -
Table I -Common Minimum Horizontal Setbacks from OWTS Components
Water Lined Lake, Dry
Wells Supply Occupied Ditch Irrigation Ditch Septic
Line Dwelling or Ditch, or Tank
Lake Stream Gulch
Absorption 100' 25' 20 ' 20' 50' 25 ' 5' Area
Septic 50' 10' 5' Tank 10' 50' 10' -
Building 50' 1 O' O' 10' 50' 10 ' -Sewer
Please contact us for any necessary revisions or discussion after review of this report by
GarfieJd County. If you have any questions, or if we may be of further assistance , please
let us know
Respectfully Submitted,
HEPWORTH -PAWLAK GEOTECHNICAL, INC .
~ c3.£vr> 7 r;&iJ
Jason A. Deem
Project Geologist
Reviewed by:
JAD/ksw
Palomino Design Build, PC -Jack Palomino (1a~kp!t!L1rn11H)55([f~m;:iil.~'.Pllt )
Job No. 114 4948 ~ech
-9-
Table 1 -Common Minimum Horizontal Setbacks from OWTS Components
Water Lined Lake, Dry
Wells Supply Occupied Ditch Irrigation Ditch Septic
Line Dwelling or Ditch, or Tank
Lake Stream Gulch
Absorption 100 ' 25' 20 ' 20' 50' 25 ' 5' Area
Septic 50' 10' 5' 10' 50 ' 10' -Tank
Building 50 ' IO' O' 10' 50' 10' -Sewer
Please contact us for any necessary revisions or discussion after review of this report by
Garfield County. If you have any questions ; or if we may be of further assistance, please
let us know
Respectfully Submitted,
HEPWORTH -PAWLAK GEOTECHNICAL, INC.
Jason A. Deem
Project Geologist
Reviewed by:
David A. Young , P .E.
JAD/ksw
Palomino Design Build, PC -Jack Palomino (jackpalomino55 @gmail.com)
Job No. 11 4 494 8
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PROPOSED SO'L
TREATMENT
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AREA CONSISTING OF ONE ROW
OF 14 INFILTRATOR QUICK
APPROXIMATE SCALE:
1 INCH = 40 FEET
114 4948 ~tech
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12431 STATE HIGHWAY 82
OWTS SITE PLAN FIGURE 1
OWTS ABSORPTION AREA CALCULADONS
In accordance wth the 2014 Garfiek:I county OWTS Regulati>ns and the CObrado Department of Heath and Envioment's
Regulatbn #43 the treatment area was cak:ulated as fobws:
CALCULADON OF OWJS DESIGN FLOW;
Q = F1+F2+F3+F4
WHERE:
Q = DESIGN FLOW BASED ON AXTURE UNITS
Fl= TOILET=
F2 = BATH SINK =
F3 =SHOWER=
F4 = UTIUTY SINK =
Q=
tALCULADON OF OWTS ABSORmON AREA;
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1
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24.8 GALLONS PER DAY
14.7 GALLONS PER DAY
8.4 GALLONS PER DAY
8.4 GALLONS PER DAY
56.3 GALLONS PER DAY -}· -
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I
L MINIUMUM ABSORPTION AREA AGGREGATE :;:; Q + LTAR I
--·~------·-__ I_
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.....
WHERE :
Q= -------LTAR (SOIL TYPE 3) =
MINIMUM SOIL TREATMENT AREA =
SIZE ADJU5rMENT FOR CHAMBERS =-
NUMBER OF TRENCHES =
NUMBER OF CHAMBERS PER TRENCH=
SOIL TREATMENT AREA PER CHAMBER =
ACTIJAL SOIL TREATMENT AREA=
114 494B ~tech
HEPWORTH-PAWUIJ< GEOTECHNICAL
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56.3 GALLONS PER DAY
0.35 GALLONS PER SQUARE FOOT PER DAY
160.9 SQUARE FEET l
1.0 *NO REDUCTION TAKEN
1
14
12 SQUARE FEET
168.0 SQUARE FEET
--:------
12431 STATE HIGHWAY 82 FIGURE2 SOIL TREATMENT AREA CALCULATIONS
411 non-perforated
SDR35 pipe
sloped at 2%
min. down to
trench
4 inch diameter inspection
port installed vertically into
knockouts provided in end
caps. Install vents at each
end of trench. Removable
cap to be placed on top of
pipe. Pipe must stick up at
least 8 inches above finished
grade or be installed at
grade in a valve box.
Fourteen Infiltrator Quick 4
Plus Standard Chambers.
APPROXIMATE SCALE:
1 INCH= 10 FEET
114 4948
Notes:
Infiltrator Quick 4
Plus Standard End
Cap
1.""Chambers should be installed level on a scarified ground surface.
2. All piping should have a rating of SDR35 or stonger.
3. Changes lo this design should not be made without consultation and approval by HP Geolech .
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HEPWORTH-PAWLAK GEOTECHN!CAL
12431 STATE HIGHWAY 82
ABSORPTION AREA PLAN VIEW FIGURE3
114 4948 ~ech
Infiltrator Quick 4 Plus
Standard chamber installed
level with 12" minimum and
18" maximum cover soil.
Cover Soil Graded to
Deflect Surface Water
Scarify ground surface prior
to chamber installation
Notes:
:;:-chambers shou ld be installed level on a scarified ground surface.
2. Care should be taken by the contractor to avoid compaction of the native soils In
the trench areas.
3. Changes to this design should not be made without consultation and approval
by HP Geotech.
12431 STATE HIGHWAY 82 FIGURE4
HEPWORTHPAWLAK GEOTECHNICAL SOIL TREATMENT AREA CROSS SECTION
APPENDIX A
Valley Precast Septic Tank Detail
Job No. J 14 4948
Item#
500T-2CP
DESIGN NOTES
• Design per performance test per
ASTM C1227
• Top surface area 23.4 ftZ • re @ 28 days: concrete = 6,000 PSI
Min.
Installation:
• Tank to be set on 5" min. sand bed
or pea gravel
• Tank to be backfilled uniformly on all
sides in lifts less than 24" and
mechanically compacted
• Excavated material may be used for
ba~kfill, provided large stones are
removed
• Excavation should be dewatered and
tank filled with water prior to being
put in service for installation with
water table less than 2' below grade
• Meets C1644-06 for resillent
connectors
• Inlet and Outlet identified above pipe
• Delivered complete with internal
piping
• PVC or concrete risers available
• Secondary safety screen available
with PVC riser
•see installation guide on our website
ALLOWABLE BURY
(Based on Water Table)
WATER TABLE ALLOWABLE
EARTH FIU
O' • O" 3'-0~
1'. 0" 4'-0"
2' -0" 4'-0"
500 Gallon Top Seam
Two Compartment
----~s,811'----
5
F
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6"
. 5 "
·~. .. ....
----52"----
Digging Specs rnvert
Top
View
20" Clear Access
Butyl Rubber
Sealant
Section
View
Dimensions
7' Long x 7' Wide Inlet Outlet Length Width Height
56" below Inlet invert 56" 53" . ss· 58" 68"
Net caeac!!Y. Net Wei ght
Inlet Side OuUetSlde Total Lid Tank Total
3'-0" 4'-0"
DRY 4'-0" 251 gallons 251 gallons 502 gallons 1,340 lbs
Water&
Wastewater (719) 395-6764
VALLEY •Systems
4,650 lbs 5,990 lbs
28005 Co. Rd. 317
P.O.Box925
Buena Vista, CO 81211
•Products Fax: ~719} 395-3727 0 PRECAST, Inc. •Service Website: www.valleyprecastcom
Email: frontdesk@valleyprecast.com
Job No. J 14 4948
APPENDIXB
Logs of Profile Pits
USDA Gradation Test Results
PIT 1
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WC •13.3
00:101
-200;54
-i +4 .. 70
-..... 20Q 01 10
PIT 2
WC •11 .5
00•100
GRAVEL .. 5 1 SAMPLE TAKEN
SANO a 52 } FROM PERCOLATION
SILT •32 TEST HOLE P 2 AT 21/2
0
5
10
LEGEND :
CLAY•11 J T04FEET 10
FILL; about 6 inches of topsoil overlying silty clayey sand and gravel with cobbles and small boulders, medium
dense, moist, mixed browns.
SAJl.ID AND SILT {SM·ML); slightly gravelly, medium stiff, moist, red.
GRAVEL (GM); with cobbles and small boulders, sandy, silty, dense, moist, reddish brown, subrounded rocks.
2" Diameter hand driven liner sample.
Disturbed bulk sample.
NOTES:
1. Exploratory pits were excavated on November 12, 2014 with a Cat 307 trackhoe.
2. Locations of exploratory pits were measured approximately by pacing from features shown on the site plan
provided.
3. Elevations of exploratory pits were not measured and the logs of exploratory pits are drawn to depth .
4. The exploratory pit locations and elevations should be considered accurate only to the degree Implied by the method
used.
5. The lines between materials shown on the exploratory pit logs represent the approximate boundaries between
material types and transitions may be gradual.
6. No free water was encountered in the pits at the time of excavating. Fluctuation in water level may occur with time.
7. Laboratory Testing Results:
WC = Water Content (%)
DD = Dry Density (pcf)
+4 = Percent retained on the No. 4 sieve
-200 = Percent passing No. 200 sieve
114 494A
Gravel = Percent retained on No. 1 O Sieve
Sand = Percent passing No. 1 O sieve and retained on No. 325 sieve
Silt = Percent passing No. 325 sieve to particle size .002mm
Clay = Percent smaller then particle size .002mm
LOGS OF EXPLORATORY PITS Figure 2
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I HYDROMETERANALYSIS I SIEVEANALYSIS
7 HR TIME READINGS U.S. STANDARD SERIES I
O i~ ~. 15 MIN 60MIN19MIN 4 MIN. 1 MIN #200 #100 #50 #30 #16 #8 #4
CLEAR SQUARE OPENINGS
3/8' 3/4' 1112" 3· 5'6' 8' 100
:
10 90
20 80
:
30 70
40 60
50 50
60 40
70 30
80 20
90 10
100 0
.001 .002 .005 .009 .019 .037 .074 .150 .300 .600 1.18 2.36 4.75 9.5 19.0 37.5 76.2 152 203
12.5 127
DIAMETER OF PARTICLES IN MIWMETERS
CtAYlOSLl
GRAVEL 70 % SAND 20 % SILTANDCLAY 10 %
LIQUID LIMIT % PLASTICllY INDEX %
SAMPLE OF: Slightly Silty Sandy Gravel with Cobbles FROM: Pit 1 at 6 to 7 Feet
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114 494A ~ GRADATION TEST RESULTS Figure 4
HEPWORTH-PAWLAK GEOTECHNICAL