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chen and associates
CONSULTING GEOTECHNICAL ENGINEERS
96 SOUTH ZUNI STREET•DENVER.COLORADO 80223•30317447105
December 31 , 1981
Subject: Additional Subsoil Investigation
and Percolation Tests,
Proposed Cheyenne Gasline
Compressor Station, Rockport,
Colorado.
Job No. 23, 126A
Colorado Interstate Gas Company
• P. 0. Box 1087
Colorado Springs, Colorado 80944
Attention: Mr. Rick Flint •
Gentlemen:
As requested, we performed an additional subsoil investigation and
percolation tests at the Cheyenne Gasline Compressor Station site located
3 miles north of Rockport, Colorado. We previously conducted a soil and
foundation investigation for the proposed compressor station and reported
_our findings under Job No. 23, 126, dated November 2, 1981 . This investigation
was conducted under our offer to perform work for Colorado Interstate
Gas Company, dated December 14, 1981 .
Subsoil Conditions: Two exploratory borings were drilled at the
south end of the compressor building and in the area of the auxiliary
building.
The subsoil conditions encountered in the Holes 7 and 8 in the
building area were similar to those encountered in the six borings
previously drilled. Beneath a thin layer of topsoil , our borings encountered
4 to 9 feet of gravelly sand overlying sandy clay which extended to a
depth of 12 to 15 feet below the ground surface. Beneath the natural
overburden soils, claystone ,bedrock was encountered to the maximum depth
investigated, 50 feet.
The clean to silty sands contain scattered gravels and are medium
dense, slightly moist and light brown in color. The sandy clay encountered
is stiff to very stiff, moist and light brown. The claystone bedrock
encountered is medium hard to hard, moist and light brown.
OFFICES: CASPER • COLORADO SPRINGS • GLENWOOD SPRINGS • SALT LAKE CITY
P..O5 82-
81\0'2-
Colorado Interstate Gas Company
December 31 , 1981
Page 2
No free water was encountered in the test holes at the time of
drilling.
The subsoil conditions encountered in Holes 7 and 8 are similar to
those encountered in Holes 1 through 6, except that the sands contain
less gravel and the clay layer is thicker. Based on the subsoil conditions,
the same foundation recommendations as presented in our original report
should be used for the auxiliary building.
Percolation Tests: Two profile holes 10 feet deep and three
percolation holes approximately 3 feet deep were drilled in the percolation
field area. Locations of the test holes are shown on Fig. 1 . Logs of
the holes are shown on Fig. 2.
The profile holes drilled in the percolation field encountered 2i
to 4i feet of clean to silty sands overlying a 2 to 2i foot layer of
clay. Beneath the clay, clean sands were encountered to a depth of 10
feet. The percolation holes also encountered clean to silty sands. The
bottom 6 inches of Percolation Hole 1 encountered sandy clay.
Percolation tests were run in the percolation holes after saturating
the holes with water for 24 hours. The percolation tests were performed
in accordance with guidelines published in the U.S. Department of Health,
_ Education and Welfare, Manual of Septic Tank Practice Publication No. 526.
Average percolation rates of 120, 40 and 40 minutes per inch were obtained
for the three holes. The low percolation rate obtained in Percolation
Hole 1 was probably due to the 6-inch layer of clay encountered at the
bottom of the hole. The test results are presented on Table I . We
recommend the use of a percolation rate of 40 minutes per inch for
design of the fields. The field should also be located away from the
area of Percolation Hole 1 .
If there are any questions concerning this information or if we can
be of further servi ,. contact us.
J•° ‘sTE.,-. °os� Sincerely,
�7"." ,. • v ..
.
*: 14486 CHEN AND ASSOCIATES, INC.
(4cti /
RJT/Jah ( 0F Cd\°C��� ichard� Tocher
Rev. By: DHA / ;�
Enclosures y (/
cc: Colorado Interstate Gas Co.
Aurora, Colo.
r--I
Future Compressors x
I I
Hole 1, 4 Hole 2I
I
I i i X
Hole 3t •Hole 4 600'
Compressor
Building Hole 5 Hole 6
x
,mole 7
1 °A 2 ...„_----r Auxiliary Building
•2 • dole 8 x
a•3 Parking
1
Ln
w
5
J ` Access Road ____x _x-_-_r---r
tn
. M
U3
A Profile Hole
• Percolation Test Hole
• Test Hole
N
. Rockport
Colorado
3 miles
Scale: 1" = 150'
Note: Holes 1 through 6 previously
drilled on October 7, 1981
for Job No. 23,126.
22,126A
LOCATION OF EXPLORATORY HOLES Fig. 1
Hole 7 Hole 8 Profile 1 Profile 2
^ N
1 •.6.6.
5 150/3 , 47/12
- ✓/
.1
10 15/19 25/12
136/2 149/12
15
20 150/11 I 50/8
-
- 150/7 I 45/12
25
150/7 , 50/9
- 30.
35
50/%Z 175/2
I 50/6 ,53/_,
40
' /2
- 45
1 50/2
- 50
Percolation Percolation Dercol&tion
-ofile 2 Hole 1 Hole 2 Hole 3
.'r -I . 'f.-•' 0 -
=J 5
/
/ -
10 -
15
20
r,
-
• 25 -
- n
r,
- 30
35
40
43
50
TOGS OF E11OR I3P'i HOLES Fla.
LEGEND:
I '
,v Topsoil
[/I Clay (CL) sandy, stiff to very stiff, moist, light brown.
Sand (SP) clean, scattered gravel, medium dense, slightly moist, light brown.
pl Sand (SM) silty, scattered gravel, medium dense, slightly moist, light brown.
IIIClaystone Bedrock, medium hard to hard, moist, light brown.
b Undisturbed drive sample. The symbol 50/3 indicates that 50 blows of a 140
pound hammer falling 30 inches were required to drive the sampler 3 inches.
III Standard Split Spoon Sample.
NOTES:
1. Test holes were drilled on December 10, 1981 with a 4-inch diameter continuous
flight power auger.
2. Locations of test holes were approximately determined by pacing from features
shown on the site plan provided.
3. Elevations of test holes were not determined and logs of test holes are drawn
to depth.
4. No free water was encountered in the test holes at the time of drilling.
23,126A LEGEND AND NOTES Fig. 3
•
TABLE I
1.
PERC0LATIC�Ii TEST RESULTS
Job No. 23, 126A
WATER DEPTH WATER DEPTH
HOLE HOLE .LENGTH OF AT START AT END DROP IN AVERAGE
NO. DEPTH INTERVAL OF INTERVAL OF INTERVAL WATER LEVEL PERCOLATION RAT;
(In. ) (Min. ) (Inches) (Inches) (Inches) (Min /Inch)
Perc 1 39 10 22 22 0
10 22 21 7/8 1/8
10 21 7/8 21 3/4 1/8
30 21 3/4 31 3/8 3/8
30 21 3/8 21 3/8
30 21 20 3/4 1/4
30 20 3/4 20 1/2 1/4
30 20 1/2 20 1/4 1/4
30 20 1/4 20 1/4
30 20 19 3/4 1/4 120
Perc 2 39 10 20 18 2
10 18 16 7/8 1 1/8
10 16 7/8 15 1/2 1 3/8
10 15 1/2 14 3/4 3/4
30 14 3/4 . 12 3/4 2
30 12 3/4 11 1/4 1 1/2
30 11 1/4 9 5/8 1 5/8
30 9 5/8 8 1/4 1 3/8
30 8 1/4 7 1/2 3/4
30 7 1/2 6 1/2 1
30 6 1/2 5 3/4 3/4
30 5 3/4 5 3/4
I I 30 5 4 1/4 3/4 40
4: • Perc 3 37 10 18 17 1
11 10 17 16 1/4 3/4
10 16 1/4 15 3/4 1/2
10 15 3/4 15 1/8 5/8
30 15 1/8 13 5/8 1 1/2
30 - 13 5/8 12 1 5/8
30 12 10 3/4 1 1/4
30 10 3/4 . 9 3/4 1
30 9 3/4 8 7/8 7/8
'� 30 8 7/8 7 7/8 1
30 . 7 7/8 7 1/8 3/4
30 7 1/8 6 3/8 3/4
30 6 3/8 5 5/8 3/4 40
• • ` chen and associates, inc. ''`�-
= CONSULTING ENGINEERS `s.c%,`
SOIL L FOUNDATION
ENGINEERING
96 SOUTH ZUNI STREET • DENVER, COLORADO 80223 • 303/744-7105
SOIL AND FOUNDATION INVESTIGATION
PROPOSED CAYENNE GAS LINE COMPRESSOR STATION
ROC PORT, COLORADO
1
PREPARED FOR:
COLORADO INTERSTATE GAS COMPANY
P.O. BOX 1087
COLORADO SPRINGS, COLORADO 80944
JOB NO. 23,126 NOVEMBER 2, 1981
OFFICES: COLORADO SPRINGS, COLORADO / GLENWOOD SPRINGS, COLORADO / CASPER, WYOMING
I-\ TABLE OF CDNIENTS
CONCLUSIONS 1
SCOPE OF STUDY 2
PROPOSED CONSTRUCTION 2
SITE CONDITIONS 3
SUBSOIL CONDITIONS 3
GEOPHYSICAL SURVEYS •
G4
FOUNEATION RECOMMENDATIONS 6
FLOOR SLABS 8
SURFACE DRAINAGE 8
LIMITATIONS 9
FIG. 1 - LOCATION OF EXPLORATORY HOLES
FIG. 2 - LOGS OF EXPLORATORY HOLES
FIGS. 3 AND 4 - SWELL-CONSOLIDATION TEST RESULTS
FIGS. 5 THROUGH 7 - GRADATION TEST RESULTS
FIG. 8 - CHEYENNE COMPRESSOR STATION MOVEOUT SEISMIC REFRACTION SURVEY
FIG. 9 - CHEYENNE COMPRESSOR STATION DOM HOLE GEOPHYSICAL SURVEY
TABLE I - SUMMARY OF LABJRATORY TEST RESULTS
TABLE II - SUMMARY OF ELASTIC PROPERTIES
L
CONCLUSIONS
(1) The general subsoil conditions at the site consist of a thin layer
of topsoil overlying 15 to 17.5 feet of dense sand and gravel and
stiff clay overburden soils. Claystone and sandstone bedrock was -
encountered at depths ranging from 15.5 to 18 feet below the
ground surface and extended to the maximum depth investigated, 40
feet.
(2) Buildings and compressor foundations constructed on the site
should be founded on spread footings bearing on the sands and
gravels. The footings should be designed for a maximum alowable
bearing pressure of 4,000 psf.
(3) Elastic properties of the subsurface materials for use in dynamic
analysis were determined by geophysical methods, are discussed in
the text and presented on Table II.
(4) Soil related design precautions and construction details are
discussed in the text of the report.
-2-
SCOPE OF STUDY
This report presents the results of a soil and foundation
investigation for a proposed gas line compressor station to be located ,
adjacent to the existing CIG Cheyenne compressor station, approximately
3 miles north of Rockport, Colorado. The report presents a discussion
of subsurface conditions and recommendations for foundation type and
allowable bearing pressures and other soil related design and
construction details. Geophysical surveys were performed at the site
to determine elastic properties of the subsurface materials for use in
dynamic analysis of foundations.
The investigation was conducted in accordance with the Colorado
- - Interstate Gas Company engineering service contract, dated October 13,
1981, Contract Number 656.
��.•'' We understand Southewest Research Inc. will perform studies on the
dynamic behavior of the soil and structure systems and design the
foundation.
PROPOSED CONSTRUCTION
The proposed construction consists of a compressor station with an
ultimate capacity of 30,000 horsepower. Present plans call for the
installation of either two Cooper reciprocal compressors, weighing
approximatly 220,000 pounds each and requiring a foundation 27 feet
long by 18 feet wide, or two Solar Centaur gas turbine centrifugal
compressor packages, each weighing approximately 30,000 pounds.
Associated gas lines will lead into and out of the compressor station.
The building will be a one-story structure with no basement.
-3-
If loadings or conditions are significantly different from those
described above, we should be notified to re-evaluate the recommend-
ations contained in this report.
SITE CONDITIONS
At the time of our field investigation, the proposed site of the
compressor station was a vacant field. An existing compressor station
is located approximately 200 yards to the west of the site. The area
is slightly sloping down to the south with an elevation difference of
approximately 4 feet across the building area. Vegetation consists of
natural grasses. A small natural drainage is located approximately 200
feet to the west of the site and drains down to the south. U.S.
Highway 85 is located approximatly 300 feet to the -east of the site.
SUBSOIL CONDITIONS
The subsoil conditions at the site were investigated by drilling
six exploratory borings at the locations shown on Fig. 1. Logs of the
exploratory borings are shown on Fig. 2. The subsoils encountered in
the exploratory borings were somewhat erratic in both type and depth.
Beneath a thin layer of topsoil, our test borings encountered natural
silty sands and gravel extending from depths ranging from 9 to 17 feet
below the ground surface. A layer of clay 4 to 8 feet in thickness
underlying the sands and gravels was encountered in Test Holes 1
through 4. Sandstone and clays tone bedrock was encoutered at depths
ranging from 15.5 to 18 feet below the ground surface and extended to
the maximum depth investigated, 40 feet.
The silty sand and gravels encountered are medium dense to dense,
-4-
slightly moist to moist and brown in color. The clay layers
encountered are stiff to very stiff, moist and light brown in color.
The sandstone-claystone bedrock encoutered is medium hard to very hard,.
moist and light brown in color.
A summary of laboratory test results is presented on Table I. The
results of swell-consolidation tests, Figs. 3 and 4, indicate the sand
clay and claystone will consolidate noderatley upon loading and
possesses a nil to low swell potential. Gradation test results on
samples obtained from 1-1/2 inch standard penetration tests of the
silty sand and gravel are shown on Figs. 5 through 7. Gravel coarser
than 1-1/2 inches occurs in this stratum but could not be sanpled with
the standard spoon.
No free water was encountered in the test holes at the time of
drilling or when checked several days after drilling.
GEOPHYSICAL SURVEYS
Geophysical surveys were used to obtain dynamic properties of the
foundation materials. Two types of survey were utilized. The first
survey consisted of a standard refraction profile and the second
• consisted of a downhole survey. Both methods measured compressional
and shear wave velocities.
The surface refraction survey consisted of six geophones laid out
at 20 foot intervals. Vertically oriented geophones were used to
detect coressional wave arrivals and horizontally oriented goephones
were used to detect horizontally polarized shear wave arrivals. Energy
for the compressional wave survey was generated by an 8 pound sledge
S.
harmer impacted vertically on a steel plate. Energy for the shear wave
-5-
arrivals was generated by impacting the sledge hammer sideways on
the end of a thick plank held in place by a vehicle (known as the
Ota-Shinea Method). Shear wave arrivals were checked for reversals
which should occur when the impact direction is reversed. The various -
arrivals were recorded on a Nimbus ES-6 seismograph.
The downhole survey utilized the same energy sources for
compressional and shear wave generation. The impact point was located
near the bore hole and the energy was recorded at 2-foot intervals in
the bore hole using a 3 component geophone. Arrival times were
corrected to vertical.
The refraction data were analyzed using a combination of the
Gardner delay time and generalized reciprocal methods. These methods
eliminate the effects of dip and topography of the refractor, allowing
C\� a better determination of velocity. Shear and compressional wave
velocities for the refractor were calculated using the generalized
recriprocal method to obtain what is called a "moveout" plot which is
shown on Fig. 8. Velocities are equal to twice the slope of the line.
Dynamic properties are calculated using compressional and shear wave -
velocities and assumed densities using the formulas shown with the
results on Table II.
The values calculated appear to be reasonable considering the
variability of the subsoil conditions and the materials encountered.
We have suggested the use of the following values for dynamic
analysis:
SOIL TYPE WEIGHT WET YOUNGS MODULUS SHEAR MODULUS POISSONS RATIO
Sand and
gravel 125pcf 1X105psi 4.2X104psi 0.23
Claystone 119pcf 3.5X105psi 1.3X105psi 0.32
-6-
FOUNDATION RECOMMENDATIONS
Considering the subsurface conditions encountered in our borings
and the nature of the proposed construction, we reconuend that the
compressors and buildings constructed on the site be founded on spread
footings placed on the undisturbed natural silty sands and gravel.
Design Details: The following design details should be observed:
(1) Footings placed on undisturbed natural soils below any topsoil may
be desinged for a maximum allowable soil bearing pressure of 4,000
psf.
(2) Dynamically loaded footings should be designed to provide the
proper mass ratio for frequency and amplitude of the supported
machine.
(3) Spread footings placed on granular soils should have a minimum
footing dimension of not less than 18 inches for walls and 2 feet
for columns.
(4) Exterior footings should be provided with adequate soil cover
above their bearing elevation for frost protection. Placement of
foundations 3 feet below the exterior grade is considered adequate
soil cover in this area.
(5) Lateral resistance of spread footing foundations placed on the
undisturbed natural soils at the site will be a combination of
passive earth pressure against the side of the footings and
sliding resistance of footings on the foundation materials.
Passive pressure against the sides of the footing can be
calculated using an equivalent fluid pressure of 200 psf per foot
of depth. Sliding friction at the bottom of the footings can be
-7-
�-• taken as 0.4 times the vertical dead load. Compacted fill placed
against the sides of the footing to resist lateral load-s should be
an on-site granular material approved by the soil engineer. Fill
should be placed and compacted to at least 98% of the maximum
standard Proctor density.
(6) Continuous foundation walls should be reinforced top and bottom to
span an unsupported length of at least" 10 feet.
(7) Based on experience, we estimate the total settlement of footings
designed and constructed as discussed in this section should not
exceed approximately 1 inch with differential settlement across
the building area of less than 3/4 inch.
Construction Details: The following information should be included in
the project specifications and implemented at the tine of
construction:
(1) Areas of loose or soft material encountered within the foundation
excavation should be removed and footings extended to adequate
natural bearing material.
(2) All footing areas should be compacted with a vibratory plate
compactor prior to placement of concrete.
(3) Care should be taken when excavating the foundations to avoid
disturbing the supporting materials. Hand excavation or the use
of a backhoe may be required in excavating the last few inches.
(4) A representative of the soil engineer should observe all footing
excavations prior to concrete placement in order to evaluate the
supporting capacities of the foundation materials.
-8-
FLOOR SLABS
The natural on-site soils, exclusive of topsoil, are suitable to
support light to moderately loa6P slab-on-grade construction. Floor
slabs should be separated from all bearing walls and columns with an
expansion joint which allows unrestrained vertical movement.
Canpressors should be separated from the floor slabs. Floor slabs
should be provided with control joints to reduce damage due to
shrinkage cracking and the slab should be adequately reinforced. 4a
suggest that joints be provided on the order of 15 feet on center.
Floor slabs can be placed on the natural granular soils without the
usual gravel layer.
Fill placed beneath floor slabs should be a granular material
approved by the soil engineer. Fill should be placed and compacted to
at least 95% of the maximum standard Proctor density, within 2% of the
e
optimum moisture content. Any fill required beneath the compressor
pads should be as cohesive as possible and should be compacted to 100%
standard Proctor density. In fill areas, natural soils should be
scarified to a depth of 6 inches and compacted to 95% standard Proctor
density prior to placement of fill.
SURFACE DRAINAGE
The following drainage precautions should be observed during
construction and maintained at all times after the facility has been
completed:
(1) Excessive wetting or drying of the foundation excavations and
under slab areas should be avoided during construction.
(2) Exterior backfill should be moistened and compacted to at least
-9-
90% of the maximum standard Proctor density.
(3) The ground surface surrounding the exterior of the building should
be sloped to drain away from the foundation in all directions. We
recommend a minimum slope of 6 inches in the first 10 feet.
(4) Roof downspouts and drains should discharge well beyond the limits
of all backfill.
ll.
LIMITATIONS
This report has been prepared in accordance with generally
accepted soil and foundation engineering practices in this area for use
by the client for design purposes. The conclusions and recoi&aiendations
submitted in this report are based upon the data obtained from the
exploratory borings drilled at the locations indicated on the
exploratory hole plan. The nature and extent of variations between the
exploratory holes may not become evident until excavation is performed.
if during construction, soil, bedrock and water conditions appear to be
different from those described herein, this office should be advised at
once so that re-evaluation of the recommendations may be made. W
recommend on-site observation of excavations and foundation bearing
J
strata by a soil engineer.
CHEN AND ASSOCIATES, INC.
•
(_ r.
Richard J. Tocher•
•
Reviewed By /
Richard C. Hepworth, P.E.
•
RJT/ram
cc: Ford, Bacon and Davis
Iii(lliw.iv 815
Rockport,
Colorado
3 miles
Approximate Scale: 1" = 100'
600'
ro
c
a°
• Seismic Line
Hole 2 Hole 4
O 0 0 nolc 6
n ter Line
C_on pr_e:;:;or m 600 Lo BOI1Cllllk"lr}:
ldinq 0 0 ®Hole 5 JCC
Hole 1 Hole 3 w
To Existing El. = 5896.14
Compressor Top of 3/8" Behar
Sation
NOTE: Downhole Geophysical Survey Run
in Hole 1.
'3,126 LOCATION OF EXPLORATORY HOOFS Fig. 1
cncn anu associates, inc.
Moisture Content= 28.6 percent
Dry Unit Weight= 96.1 pcf
Sample of: Sandy clay
From. Hole 1 at depth 14'
Expansion under constant
0 - pre:urc upon wet-zing.
O O 1
-r
C12
rn
v
2
3
0.1 1.0 10 100
APPLIED PRESSURE — ksf
Moisture Content = 18.2 percent
Dry Unit Weight = 102.7 pct
Sample of Sandy clay
From Hole 4 at depth 13'
Additional co-rip sior
under constant pros e dte tc
0
etting.
O 1
m
to
0
2
8
3
0.1 1.0 10 100
APPLIED PRESSURE — ksf
3
SWELL-CONSOLIDATION TEST RESULTS Fig
23,126
chen and associates, inc.
Moisture Content= 29.2 percent
1- Dry Unit Weight= 90.3 pcf
Sample of: Claystone
From: Hole 6 at depth 19'
0
Expansion under constant
94 1 pressure upon we4tiai .
0
c9
o 1
0.1 1.0 10 100
APPLIED PRESSURE — ksf
3,126 4
SWELL-CONSOLIDATION TEST RESULTS Fig.
chen and associates, inc.
�'' HYDROMETER ANALYSIS SIEVE ANALYSIS
' _• I IML HEADINGS U.S.STANDARD SERIES I CLEAR SQUARE OPENINGS
i, 24 1111 7 HR '10
45 MIN 15 MIN -60 MIN 19 MIN 4 MIN 1 MIN '200 '100 '50'40'30 '16 I'8 '4 'V '6" 1'5" 3" 5"6' 8"
iW 1 0
I _
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001 • 002 005 009 019 037 074 149 297 I 590 1 19 238 4 76 9 52 19 1 38 1 76 2 12/ 200
042 2 0 152
I DIAMETER OF PARTICLE IN MILLIMETERS
SAND GRAVEL
CLAY TO SILT FINE , MEDIUM COARSE FINE COARSE COBBLES
GRAVEL 53 % SAND 35 % SILT AND CLAY 12 %
%
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF Silty gravel and sand FROM Hole 1 at depth 4'
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U S STANDARD SERIES I CLEAR SOUARE OPENINGS
24 HH 7HR
'10
.15 MIN 15 MIN 60 MIN 19 MIN 4 MIN 1 MIN '200 '100 '50 '40'30 '16 I 8 '4 R'• , 1'b" 3" 5"6' 0
100 1
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1
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0, _1 I I I I 1 S I 1 1 1 11 11 1 1, 1 I 111 I I 1 i ! ]I1] l I 1 1 1 1 111 I 100
001 .002 .005 .009 .019 .037 .074 149 297 I .590 119 1238 4.76 9.52 191 38.1 76.2 127 200
042 2 0 152
IDIAMETER OF PARTICLE IN MILLIMETERS I
SAND GRAVEL
CLAY TO SILT FINE I MEDIUM COARSE FINE I
COARSE COBBLES
GRAVEL 33 % SAND 56 % SILT AND CLAY 11 %
LIQUID LIMIT PLASTICITY INDEX %
SAMPLE OF Silty sand and gravel FROM Hole 2 at depth 4'
3,126 GRADATION TEST RESULTS Fig 5
i:A .'-I')
•
clien and associates, inc.
HYDROMETER ANALYSIS SIEVE ANALYSIS
{ TIME READINGS U.S STANDARD SERIES I CLEAR SQUARE OPENINGS
/41111 /I Iii -
4',MIN I5 MIN GO MIN 19 MIN 4 MIN 1 MIN -200 •100 •50 '40'30 •16 •II 8 •4 k" ar 1'Y' 3" 5"6' 8"
IW 1
V 0
-
'J0 I ' l 10
i
1
1 y t
80 1 • I 1 20
1
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001 002 005 009 019 US/ 11/4 149 20/ 590 119 2 38 4/G 9 52 19 I 39 I /5 2 12/ /0U
042 2 0 152
IDIAMETER OF PARTICLE IN MILLIMETERS
SAND GRAVEL CLAY TO SILT COBBLESFINE I MEDIUM (COARSE FINE I COARSE
GRAVEL 16 % SAND 74 % SILT AND CLAY 10 %
• LIQUID LIMIT % PLASTICITY INDEX %
SAMPLE OF Gravelly Sand FROM Hole 4 at depth 8'
O
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U S STANDARD SERIES I CLEAR SQUARE OPENINGS
24 Hi 7 HR
•1
45 LAIN 15 MIN 60 MIN 19 MIN 4 MIN 1 MIN '700 '100 •50 '40'30 '16 �II '4 I"" 'I ''.'"/•,*
__ I I I 0
1 I II
90 1 1 10
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042 2 0 152
IDIAMETER OF PARTICLE IN MILLIMETERS I
CLAY TO SILT SAND GRAVEL •FINE I MEDIUM (COARSE FINE I COARSE COBBLES
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LIQUID LIMIT g° PLASTICITY INDEX %
SAMPLE OF Silty sand and gravel FROM Hole 5 at depth 4'
6
23,126
GRADATION TEST RESULTS Fig.
I.A :' 14
chen and associates, inc.
HYDROMETER ANALYSIS SIEVE ANALYSIS
Al- I IME READINGS U S.STANDARD SERIES I CLEAR SQUARE OPENINGS
24HR 7HR _
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042 20 152
DIAMETER OF PARTICLE IN MILLIMETERS
CLAY TO SILT SAND GRAVEL
FINE I MEDIUM 'COARSE FINE I COARSE COBBLES
GRAVEL 34 % SAND 50 % SILT AND CLAY 16
%
%
LIQUID LIMIT PLASTICITY INDEX
SAMPLE OF Silty sand and gravel FROM Hole 6 at depth 5'
O ,
HYDROMETER ANALYSIS SIEVE ANALYSIS
7.
TIME READINGS U S STANDARD SERIES I CLEAR SQUARE OPENINGS
24 HF1 7HR
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100
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SAMPLE OF FROM
23,126 GRADATION TEST RESULTS Fig. 7
•
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- Vs Shear wave_velocity of refractor
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CHEYENNE COMPRESSOR STATION
MOVEOUT SEISMIC REFEE1L:i•w
SURVEY
chen and associates, inc.
CONSULTING ENGINEERS
Ny 96 S. ZUNI • DENVER, CO. OO2Z3
23,126b4r Nov. 1181 Fig. 8
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CONSULTING ENGINEERS
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Noise Impact Analysis
/
of
Proposed Addition to
The Cheyenne Compressor Station
Engineering Dynamics , Inc.
December 1981
1 1
•
Prepared By:
J Barthell, Engineer
• Approved By: _
oward N. McGregor, P.E
RECEIVED
WJLJI`r1UU I ITEP.STA;E CAS CO.
LARD DEPARL!ENT
0E0211981
&eferrad te:
•
engineering dynamics
I. Introduction
The Colorado Interstate Gas Company is proposing the installation
of additional gas compressors at the existing CIG Cheyenne Compressor
Station, located in Weld County, Colorado, adjacent to Highway 85 .
Initially, two additional compressors are to be installed in a
separate building located approximately 1200 feet north of the exis-
ting compressor building, which is equipped with four compressors .
Future plans indicate the installation of as many as six additional
compressors such that the total number of compressors at the site
would be twelve.
There are two significant sources of noise at the station, heat
exchanger fan noise and engine noise. Engine noise may be further
separated into exhaust noise and engine noise.
Engineering-Dynamics performed a theoretical analysis of the
noise impact of the existing facility in January, 1978. The acoustic
power levels of each of the noise sources were included in the
report submitted to Colorado Interstate Gas Company. The data is
reiterated in this report for reference. The noise contours were
calculated assuming two additional compressors are installed; and
' for the case when eight additional compressors are installed.
The noise contour of most interest is the 70 dB(A) contour because
it is the limit set by Weld County as the maximum allowable level
at the station property line.
I _
engineering dynamics
II. Source Acoustic Power or Sound Pressure Level Data
A. Engine Noise GMVH
The following measurements were obtained at a distance of 1 m
horizontally from the engine and 1. 5 m vertically above the floor.
The measurements may be considered free-field due to the closeness
of microphone to the engine and the fact that the room was acous-
tically treated. The levels are probably slightly on the high
side especially at the lower frequencies.
Freq-Hz Lp
31 92
63 94
125 94
250 90
500 90
1K 87
2K 84
• 4K 77
8K 70
' B. Engine Exhaust Noise
Freq-Hz LW(re 10-12w)
31 131
63 123
125 125
engineering cync nics, inc
250 113 •
500 106
1K 107
2K 108
4K 102
8K 86
C. Intake Noise
Estimated intake noise levels with C-B inline silencer installed.
Microphone located 3 ft from inlet.
Freq-Hz LP _
31 88
63 93
125 99
250 97
500 , 98
1K 94
2K 94
4K 93
8K 90
D. Intake Silencer Performance
Freq-Hz Insertion Loss-dB
63 2
125 3
engineering cyncmics, inc
250 5
500 14 -
a
1K 19
2K 19 .
4K 21
8K 22
E. Exhaust Silencer Performance-Maxim M41
Freq-Hz Insertion Loss-dB
31 15•
63 32
125 35
250 31
500 25
1K 22
2K 23 '
4K 25
8K 29
F. Heat Exchanger Fan Units 1 through 4
Freq-Hz dB (A) LW (re 10-12)
63 89 102
125 87 100
250 87 100
500 83 96
engineering cyncmics, Inc
1K 80 93
2K 78 91
4K 72 85
A 85 98
G. Heat Exchanger Fan Units 5 through 8 _
Freq-Hz dB (A) L. (re 10-12)
63 90 103
125 87 100
250 88 101
500 84 97
1K 81 94
2K 79 92
4K 76 89
8K 73 86
A . 86 99
engineering cync�rics, inc
III . Power Level Computations
A. Engine Noise - 4 Engines
Compressor
Freq-Hz Lw Building External
Attenuation Lw
31 76 10 66
63 78 15 63
125 78 20 58
250 76 25 51
500 76 35 41
1K 71 40 31
2K 68 40 28
4K 61 40 21
8K 54 40 14
B. Engine Exhaust 4 Engines
Freq-Hz Ijw re 10
Silencer
Freq-Hz Lw Attn Lw
31 137 15 122
63 129 32 97
125 131 35 96
250 119 31 88
500 112 25 87
1K 113 22 91
2K 114 23 91
engineering cyncrmics, Inc
4K 108 25 83
` 8K 92 29 63
C. Heat Exchange Fans 1-4, 4 Units
Freq-Hz LW(re 10-12)
63 108
125 106
250 106
500 102
1K 99
2K 97
4K 94
8K 91
D. Heat Exchanger Fans 5-8, 4 Units
Freq-Hz LW (re 10-12)
63 • 109
125 106
250 107
500 103
1K 100
2K 98
4K 95
8K 92
engineering cyncmics, Inc
E. Intake Noise, 4 Units
Silenced
Freq-Hz Lw Attn L
' 31 66 2 64
63 71 2 69
125 77 3 74
250 75 5 70
500 76 14 62
1K 72 19 53
2K 72 19 53
4K 71 21 50
8K 68 22 46
F. Total Station Power Level
Freq Source
Hz Engine Exhaust Intake Fan 1-4 Fan 5-8 Total
31 66 122 64 100* (E) 100* (E) 122
i
63 63 97 69 108 109 112
125 58 96 74 106 106 109
250 51 88 70 106 107 110
550 41 87 62 102 103 106
1K 31 91 53 99 100 103
2K 28 91 53 97 98 101
4K 21 83 50 94 95 98
8K 14 63 46 91 92 95
A 110
*Estimate no data available from mfg.
engineering cyncmics, inc
The total station power level for the existing facility Cfour
c compressors) is calculated to be 110 dB(A) . The total acoustic power
level will increase 3 dB for every doubling of the number of sources
of equal acoustic power. Conversely, the total acoustic power level
will decrease by 3 dB each time the number of sources of equal acous-
tic power level is halved. Since the acoustic power levels of the
equipment to be installed are assumed to be equal to the equipment
at the existing facility, the total acoustic power level of the
equipment installed can be extrapolated from data of the existing
facility. The total acoustic power for the installation of two
compressors will be 107 dB(A) and the acoustic power for eight T
compressors is 113 dB(A) . The octave band power levels for two ,
four and eight compressors are shown below.
Total Station Power Level
Frequency
(Hz) 2 Compressors 4 Compressors 8 Compressors
31 119 122 125
63 109 112 115
125 106 109 112
250 107 110 113
500 103 106 109
1000 100 103 106
2000 98 101 104
4000 95 98 101
8000 92 95 98
A 107 110 113
engneerinci dynamins
•
G. Sound Pressure Level Contours
Sound pressure level contours for the installation of two
additional compressors are shown in Figure #1. Figure #2 shows
the combined effect of installing the two compressors shown in Figure
#1 and six additional compressors which could be installed in the
future.
engneerinc dynamics
IV. Conclusions
The installation of two additional compressors at the existing
facility will not effect the 60 and 70 dB(A) noise contours which
enclose the existing compressor station. Both the 60 and 70 dB(A)
contours of the proposed compressor station lie within the property
boundary of the compressor site.
The 55 dB(A) contour, shown in Figure #1 , is comprised of noise
contributed from both compressor stations . This contour extends
beyond the property line at the north boundary of the site.
The installation of eight additional compressors at the new
compressor site does not effect the 60 and 70 dB(A) noise contours
of the existing station. The 60 and 70 dB(A) noise contours of the
proposed station lie within the property boundary of the compressor
site. The 55 dB(A) contour encompasses a larger area than the contour
shown in Figure #1 and extends beyond the property boundary at the
site.
enaineerinca dynamics
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