HomeMy WebLinkAbout2.0 Supplemental Application InfoDrainage Report
(An analysis of existing conditions)
High Mesa Compressor Station
May 23,2014
Prepared for:
Summit Midstream Partners
2128 Railroad Avenue
Suite 106
Rifle, CO 81650
Prepared
+[,ysTStI.
T4[Horizon Court, Suite 110
Grand ]unction, CO 81506
Phone: (970) 241.-4722
Fax (970) 24L-8841,
Job No. 1215-009
11216
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TABLE OF CONTENTS ....................I
I. Introduction........... .........1
A. Background........... .......................1
B. Project Location... ........................1
C. Project Description ............... .......1
D. Previous Investigations.......... .......................2
II. Drainage System Description............... ..........2
A. Existing Drainage Conditions ......................2
B. Offsite Tributary Area......... ........2
C. Proposed Drainage System Description................ ........2
D. Drainage Facility Maintenance............... ........................2
III. DRAINAGE ANALYSIS AND DESIGN CRITERIA ....................3
A. Regulations ......... .......................3
4B. Hydrologic and Hydraulic Criteria..... ........J
C. Calculation Methodology ..........3
D. Input and Results ................ ........................4
IV. CONCLUSIONS .........4
FIGURES
General Location Mup . ...... ... 1
High Mesa Compressor Station Drainage Basin Mrp . ...........2
APPENDIX
Hydrology and Hydraulic Calculations (model output) ............. A
NRCS Web Soil Survey ......... B
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Introduction
A. Background
River City Consultants, Inc. prepared tl'ris Drainage Report for Summit
Midstream Partners of Rifle Colorado. The purpose of this Drainage Report
is to fulfil1 the Garfield County permitting requirements that have surfaced
through Summit Midstream Partners due diligence with the County to ensure
the High Mesa Compressor Station is properly permitted. Accordingly no
new construction is being proposed. The intent of this report is to anaTyze and
quanti{y existing drainage facilities within the High Mesa Compressor Station
Facility.
B. Project Location
The project is approximately 3.75 miles directly south of Parachute Colorado
on High Mesa. The project is southeast of I-70 and the Colorado River,
northeast of Pete and Bill Creek, southwest of Dry Creek, and approximately
2.25 miles north of the Garfield and Mesa County border. The project is
wholly within Parcel # 240936100048, which is owned by Encana Oil & Gas
(USA),Inc.. Primary access to the site is from County Road 304 and private
access roads.
In more legal terms, it is located in East 7z NorthwestVa and Southwest %
Northeast % Section 36, Township 7 South, Range 96 West of tl-re 6th Principal
Meridian, Garfield County, Colorado.
C. Project Description
The purpose of this report is to analyze the existing drainage facilities at the
existing High Mesa Compressor Station. No new construction or surface
disturbance is proposed as part of this project. No lots are being proposed as
part of this project.
The cover conditions at the project site currently consist of gravel, concrete,
metal roofs, and dirt slopes. The existing grades on the project site vary from
less than L percent to 1.5H:1V.
According to the NRCS web site, the upper layer of soil present at the project
site consists of Ildefonso stony loam (7.0%; HSG=A), Potts loam (2.1,%;
HSG=C), and Potts-Ildefonso complex (90.9%; HSG:C). These soil types have
hydrologic soil classifications of A and C. The predominate hydrologic soil
group rating is C, which is also more concervative (i.e., more runoff
predicted), thus all calculations were preformed assuming C type soils.
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D. Previous Investigations
The only previous investigation known to exist for this area is the High Mesa
Compressor Station Expansion Project Final Drainage Report by River City
Consultants, March of.201'1.. This report was completed for Encana Oil & Gas
(USA), Inc., who was the owner of the Compressor Station at that time. The
facility has since been sold/leased to Summit Midstream Partners.
II. Drainage System Description
A. Existing Drainage Conditions
The site drains to Pete and Bill Creek, which in turn ultimately drains to the
Colorado River. Pete and Bill Creek is a seasonal creek and receives runoff
from tl're southern portion of High Mesa.
Existing cover conditions with the major basin are primarily undeveloped.
The development within the basin almost completely consists of dirt/ gravel
roads and pad areas. The predominant drainage pattern is characterizedby
overland flow sloping to the northwest. Grades range from relatively flat on
the pads to 2H1V on cut/fill slopes. Man-made and natural charurels and
other nafural feafures collect and concentrate surface runoff. Occasionally
roads cross the slope also concentrating and diverting runoff. Flow from the
site and areas up-basin from the site drain to Pete and Bill Creek and
ultimately to the Colorado River.
The Site currently contains various improvements/ development. These
include gravel roads, associated shoulders and ditches, various pad areas,
equipmen! pipelines, buildings, and associated facilities. Sage, juniper, and
grasses are the predominate vegetation on areas adjacent to the site and
woulcl be classified as in fair condition.
B. Offsite Tributary Area
Diversion ditches are located upskeam of and adjacent to the site to divert
off-site flows around the site. Accordingly this site does not receive off-site
flow.
C. Drainage System Description
The existing drainage system consists of earthen ditches, culverts, sediment
basins, and detention ponds. Access to and through the site shall be by the
proposed gravel surface roads as shown on the drawings.
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D. Drainage Facility Maintenance
Maintenance will be performed by Summit Midstleam Parhrers. Sediment
basins will be cleaned when sediment reaches the culvert invert. Ditch check
dams wilI be cleaned when sediment build up is one half the height of the
dam or 12 inches, wl-richever is less. Sediment shall be removed from culverts
when the depth of sedimentislh of the pipe diameter or four inches,
whichever is less. Any channel erosion shall be addressed as soon as possible
after it is noted. Channel erosion should be addressed with a long term
solution which can include, but is not limited to: channel reshaping and
lining, slope drains, or channel reshaping and re-routing.
It is advisable to inspect drainage facilities following any major storms or at a
frequency no less than once a month and that inspections be documented by
the person conduction the inspection. Any issues or deficiencies noted during
the inspection should be corrected immediately.
III. DRAINAGE ANALYSIS
A.Regulations
The policy, design criteria, design consh'aints, rnethods of analysis,
recomnendations, and conclusions presented in this report are in
conformance with standard engineering practice and Article VII Standards
Section 7-204 Stormwater Runoff of Garfield County Land Use and
Development Code, Effective July 15,2013 last amended December 1,6,2013.
Hydrologic and Hydraulic Criteria
No drainage constraints were noted for this project. The hydrologic design
criteria presented in this report are in conJormance with standard engineering
practice. Other manuals and publications were also reviewed to determine
conformity with accepted design practices and applicability to the project.
These include the National Engineering Handbook, the Civil Engineering
Reference Manual, and the Certified Professional in Storm Water Quality
(CPSWQ) Study Guide.
Calculation Methodology
Hydrology and hydraulic calculations were performed using Autodesk Storm
and Sanitary Analysis2013. The following model
engines/methods/equations were used: USEPA SWWM (hydrology), SCS
Curve Number (in{iltration method), hydrodynamic (hydraulic routing/lir*),
and Hazen-Williams (hydraulic link).
B.
C.
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D. Input and Results
The model input and results are as follows:
r A composite SCS Curve Number was derived based on cover
conditions within each basin (see attached model printout for specifics)
. The model consists of 5 basins, 9links (ditches and culverts), and L
storage node (sediment basin/detention pond).
. The faclltty was analyzed using a SCS Type II 24hour storm. Total
rainfall values used were: 100 year = 2.6 inches; 50 year : 2.4 inches;25
year:2.2inches;10 year = 1.8 inches;5 year = 1.6 inches; and Zyear =
1.2 inches. RainJall values were derived from the rainfall designer
within Autodesk Storm and Sanitary Analysis.
. Basin sizes ranged from 0.9 acres to 0.1 acres.
. Model continuity for runoff (hydrology) was 0.0% and less than 0.5%
for routing (hydraulic). These values are fully within the acceptable
range.
IV. CONCLUSIONS AND RECOMMENDATIONS
The policy, design criteria, design constraints, methods of analysis,
recorunendations, and conclusions presented in this report are in
con-formance with standard engineering practice and Article VII Standards
Section 7-207 Stormwater Runoff of Garfield County Unified Land Use
Resolution of 2008, as amendedT-19.
The High Mesa Compressor Station existing drainage system is capable of
effectively conveying stormwater runoff from an SCS Type II2year 24huur
storm.
Tl're on-site visit that was conducted as part of this report identified the
following high priority maintenance items:
. Slope erosion on the north end of the internal bench. The Compressor
Station is situated on pads set at different elevations. Stormwater
currently flows from the upper pad to the southwest end, is
concenh'ated and flows down the bench to the lower pad. The bench is
approximately a 2H:1V earthen slope and the stormwater flowing
down this slope has eroded a charrrel down the bench.
o Slope erosion on south end of internal bench. The erosion situation
here is the same as described above, but is located on the south end of
the bench.
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o Culvert plugged with sediment. The south culvert is an 8 inch
diameter steel pipe. This culvert collects stormwater from the upper
bench and eastern portion of the lower berrch. The sedimer-rt transport
from the two erosion issues noted above have lead to sediment being
deposited within the culvert to the point where it is now plugged. The
stormwater now flows across the access load, which is causing
additional erosion and sediment deposition.
These higl-r priority items have been discussed with and communicated in
writing to Summit Midstream Partners. The recommended solution to this
issue is the installation of 8" HDPE pipe slope drains and armoring/energy
dissipation within tl're channel at the toe of the bench. It is recommended the
8" culvert be replaced with 15" Class V RCP. This larger pipe will be much
easier to clean and will increase capacity (see low priority recommendations
below). The Sumrnit Midstrearn Parhrers Operations Group has put this
work on it's project list and will complete said work as soon as possible.
Lower priority recorunendations/ maintenance items identified are:
Lower sediment basin/detention pond cleaning. Any erosion within
the site ultimately transports sediment to the lower basin. As such, this
basin has received signification sediment. Removing sediment from
this basin and creating a retention area of 2 or mole feet below the
outlet pipe would increase water quality capture volume (i.e.,
treatment in the form of retention for the first flush). Increasing the
pond volume would also help retard released flows thus helping to
reduce downstream peak flow values.
Replacement of the south S" steel culvert with 15" Class V RCP.
Upsizing this pipe would facilitate easier clealing and increase
capacity from the 2year storm to the 100 year storm.
These lower priority recommendations and maintenance items are not
immediately needed, but if or when done will ber-refit and add to the
longevity of the facility.
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High Mesa Compressor Station
Existing Hydrology and Hydraulic Model
2 Yr 24 Hr {Minor) Storm
Subbasins
MJK 05.27.14
Elem€n
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Curve
Number
Slopt
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lmperviou!
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Ru nol
{inch€s
Pea
Runol
lc{s
Deptl
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Roughnes
ldavs hh:mm:ss
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0_3 91.5(1.000(94_0r 10.0t 25.0(0.100(0.015r 0.100(0.100(GarCo:7_2C o.ool o.ooo(0.526(0.6i 0.2 0 01:03:31
813 on-slk 01 1 25.C 0.100(0.015r 0_100(0.100(GarCo;1.2C 0.001 0.000(0.641 o.or 0 00:s9:31
814 on-sit€0241 89 0.(0_100t 0.100(GarCo:1.2(0.0t 0.000(o.4e2ol o.6sl o.1r O 01r0O:11
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Hish Mesa Compressor Station
Existing Hydrology and Hydraulic Model
2Yr24 Hr(Minor)Storm
Junctions
MJI( 05.27.14
5t
Elevatio,
lft
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lft
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HG
Time o
Peel
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Tota
Flooder Tinr
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5926 9t 1.5(0.001 6000.0r 71 5l 0001 0g',t0(0.0(\927 At 011 00(131 59)6 9:00'0 l2rol O m:Ool 0.0(
5952.31 5953 3i o ool 5o00.ot 46.61 10(40(o2 o 2'5952.51 o.2 o0(o7l 5952.3:0.0!0 00:ot 00(
5943 801 5944 8a 10t 0.001 6000.0(55.2(101 40{0.2 0.001 5943-9i 0.1 0.0 0 00:0.0(
41 5945.at 5947 8t 1fr o ml 50m.0{52.1 4.001 0.081 o-0I10(0.1:0.0t 0.8 0 011 om 0.0(0.0(
5940 645919 6l 10t 0 001 5000.0{59 3r 10(.0(o4/01(5939 8(01{0.0(000 O,C
5935.2t 5936 7 E 0.001 6000.0(63.2 10(10.001 0.91 0.001 593 o.2:0.0c 1.271 593 0-o O 00:O(
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High Mesa Compressor station
ExistinE Hydrolory and HydEUlic Model
2 Yr24 Hr (Minor)storm
Ml(05.27.14
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Hish Mesa Compressor Station
Existins Hydrolosy and Hydraulic lilodel
2 Yr 24 Hr (N4inor) Storm
MtK 05 27.14
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High Mesa Compressor Station
Existing Hydrology and Hydraulic Model
5 Yr 24 Hr (Mino.) Storm
subbasins
MJK 05-27.14
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Elemen
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(acres)
Weighrec
Curv€
Number
Averagr
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lnfiltratior
linche5
Tota
(inches
Peal
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(cfs
Tim€
Concentratior
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High Mesa Compressor Station
Existing Hydrology and Hydraolic Model
2Yr24 Hr (Minor) Storm
Junctions
M1K05.27.14
SI
Elevatior
lft
Ground/Rin
(Max
(ft
Ground/Rin
Offse
{ft
lnitia
Elevrtior
tft'
Surcharg(
Elevatior
(ftl
Surchargr
Deptl
tft'tftl
Minimun
lcfsl (cfs
HGI
Elevatior
HGI
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Deptl
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Minimun
tft
HGI
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Deptl
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Floodinl
ldays hh:mm
Tota
{ac'inchesl
Tot€
Tim,
{mlnutei
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5952_3',5953.3'1.0c 46.61 10(4At 0.3r 0.3r 5952.61 0.21 0.0(0.711 0.0:0 11:51 o 0o:ool o or 0.0(
5943.8(5944.8(1.0c 0.0(55.2(10(0.381 o.o(5943.9r 0.1r 0.0(o.8t o0(
5947.8!1.0(o.o(52 1.0(40(0.1 o1:0.1;0.0(o.Bl 5945,891 o.oi 11 o.ml o.o(
5940.54 1.0c 0.0(6000-0(59 4.0(oTal o2t o.2 00(o_7:5939.61 0.0 0.001 o o(
5936.7i 1.5C 0.0(6000.0(63 10.ool 1431 O0r 0.21 0.0(1_2:5935.21 0.ool 0.0{
5931.2.1.5(o0(5000.0(62.7 1 10 0(161 0.0(5937 41 17 o-21 0.01 593s.8:0.0:011 0.01 11.0(
5941.21 1.0{0.001 6000.0(51_7 1.0(6 o0l 0.s 5947.41 o 1!0.0r 0.8:5947 _3t 0.0 0 11151 0 00r00 0.0
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Hlgh Mesa Compressorstation
Sisting Hydrolog and Hydraulic Model
5Yr24 Hr (Mjnor)storm
Channek
M)K05.27.74
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High Mesa Compressor Station
Existinc Hydrolosyand Hydraulic Model
5 Yr 24 Hr {Minor) Storm
Pipes
MJ( 05.27.14
Elemen
It
[engtl
(ft
tntet
lnvert
Elevation
Averag{
slop(
l%,
PiPt
Diamete
or Heigh
Manning'!
Roushnes:
Enhanc€Exit/Ben(Additiona
losse
lnitia
FIov
(cfs
Peal
Flos
{crsl
Time o
Peal
Occutrenc(
Ma
Flo!
Trave
(min
Desigr
Capacitl
(cfsl
Design Flos
Ratk
Ma)
Flow D€pth/
Total Deptt
Ratk
Tota
Surchargec
Ma)
Flov
Deptl
(tt
Froudi
Numbe
Reporter
Conditior
(ft
tink 1(22.11 5926_9'5.9501 8.04(0.013(1.000(0.500i 0.000(0.001 1.2!A 12:01 5.1,0.0;3.11 0.41 0.6t 0.0(o_4(Calcr
5935.7:5935.2t 2.330r 8.04(0.024(1.000(0.500t 0.00001 0.001 1 4l 0 12:0t 5.4 0.0(1.0(1.41 o.71
ink 14 9)'5952.3;5943.8t 92.410{8.04t 0.013(1.000(o.soool o.ooool o.ool 0.3{0 11:58 3.61 0.0r 11.6;0.0:0.331 o or o)t calculate(
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High Mesa Compressor Station
Existing Hydrology and Hydraulic Model'lvlodified culved to 15"
5 Yr 24 Hr (Mioor) sto.m
subbasins
MJK05.27.14
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Elemen
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High Mesa Compressor Staton
Existins Hydrology and Hydraulic Model
2Yr24 Hr(Minor)Storm
Junctions
MJKOs.27.14
5t
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{ft
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High Mesa compre$or Station
&istingHydrolo$andHyd.aulicModet-ModifledCulvedto15"
5Yr24 Hr (Minor)stom
Channels
M)K 05.27.14
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High Mesa Compressor Station
Existing Hydroloeyand Hydraulic Model - Modified Culvert to 15"
5 Yr 24 Hr (Minor) Storm
Pipes
MJK 05.27.t4
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HiBh Mesa Compressor Station
Existing Hydrology and Hydraulic [4odel
50Yr 24 H. (Major) Storm
subbasins
MJK 05.27.14
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EIemen
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Hish Mesa Compressor station
Existing Hydrolory and Hydraulic Model
2 Yr24 Hr (Minor) Storm
Junctions
MJK05.27.14
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High Mesa compressor station
Existing Hydrolog and Hydraulic Model
s0Yr 24 Hr (Major) Storm
MiK05.27.14
You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
Hi8h Mesa Compressor Station
Existing Hydrologyand Hydraulic Model
50 Yr 24 Hr (Major) Storm
Pipes
M)K05.27.74
Elemen
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High Mesa Compressor Stat;on
Existing Hydrologyand Hydraulic Model
100 Yr 24 Hr (lvlajor) Storm
Subbasins
MJK 05.27.14
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High Mesa Compressor Station
Exhting Hydrolory and Hydraulic Model
2 Yr24 Hr (Minod Storm
lunctions
vtiK 05.27.14
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593s.2r 5936-1t 1.5(0 ool 6000.0(63.2 1.t 3.t o.o(s935.1 a4:0.0(1.O1 5935 3a o.oi 0m 0.0(0-0(
5935-11 5911 _2)1.5(o ool 5000 0(52 1.0(3.0(3 s1l O.O(5936.81 1.0{0.0(4.4)5935 8i o.o:011 0 00:o(0.0(o-0(
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Hlgh Mesa compressor station
Existing Hydrolory.nd Hydraulic Model
lmYr 24 Hr (Malo4 storm
channels
Ml(05.27.14
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HiAh Mesa Compressor Station
Existing Hydrolosy and Hydraulic Model
100 Yr 24 Hr (Major) Storm
MJK 05.27.14
Elemen
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{ft]
Outle
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Hydrologic Soil Group-Rifle Area, Colorado, Parts of Garrleld and lvlesa Counties
(High lvlesa ComPressor Station)
3
3
-s
vasN $
Ea
B*
I
'i
R3
a
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&
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h
&
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Map prcj#n: Wb l4ecbr offi @diBt6: WGs84 &lgetE: W Zore 12N WGSa4
USDA Natural Resources
- Conseryation Seruice
Web Soil Survey
National Cooperalive Soil Survey
5t13t2014
Page 1 of 4
3
h
s
75319 E3BO E32h
Hydrologic Soil Group-Rifle Area, Colorado, parts of Garfield and [resa Counties
(High Mesa Compressor Station)
MAP LEGEND MAP INFORMATION
The soil surveys that comprise your AOI were mapped at 1:24,000
Waming: Soil Map may not be valid at this scale.
Enlargenrent of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheel for map
measurements,
Source of Map: Natural Resour€s Conseruation Seruice
WebSoilSurveyURL: http://Websoilsuruey.nrcs.usda.gov
Coordinate Sysiem: Web Mercator (EPSG:3857)
l\,4aps from the Web Soil Suruey are based on the Web Mercator
projection, which preseryes direction and shape but distorts
distane and area. A prcjection that preserues area, such as the
Albers equal-area @nic prcjection, should be used if more accurate
calculations of distance oa area are required.
This product is generated from the USDA-NRCS certifled data as of
the version dale(s) listed below.
Soil SurveyArea: Rifle Area, Colorado, Parts of Garfield and Mesa
Counties
Suruey Area Data: Version 7, Dec23, 2013
Soil map units are labeled (as space allows) formap scales '1:50,0OO
or largef,
Date(s) aerial images were photographed: Jun 22, 201o-Sep 3,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
ofmap unit boundades may be evidenl.
Area of lnterest (AOl)
[J Area of lnteresl (AOl)
Soils
Soil Rating Polygons
EA
E A/D
EIB
W B/D
Ec
E c/D
WtD
E Nol rated or not available
Soil Rating Lines
^aA
4 B/D
, , Not raled or not available
Soil Rating Poinls
lA
E A/D
EB
Il B/D
Ec
E CiD
ID
E Nol rated or nol available
water Features
Slreams and Canals
Transponation
{-H Rells
14 lnteEtate Highways
N USRoutes
Major Roads
Local Roads
Background
I Aerial Photography
LSD.\:,Natural Resources
Conseryation Seruice
Web SoilSuruey
National Cooperative Soil Suruey
5113t2014
Page 2 at 4
Hydrologic soil Group-Rifle Area, colorado, Parts of Gadield and Mesa counties High Mesa ComPressor Stalion
Hydrologic Soil Group- Summary by Map Unit - Rifle Area, Colorado, Parts of Gar-field and Mesa Counties (CO683)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
34 lldefonso stony loam, 25
to 45 percent slopes
A 0.6 7.O%
56 Potts loam, 6 to 12
percent slopes
C o.2 2.1%
58 Potts-lldefonso comPlex,
1 2 to 25 percent
slopes
C 7.4 90.8%
Totals for Area of lnterest 8.2 100.0%
Hydrologic Soil GrouP
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
aisigned to one of four groups according to the rate of water infiltration when the
soils-are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, BiD, and c/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission'
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of modLrately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soits that have a high water table, soils that have a claypan or clay layer
at or near the surface, and soils that are shallow over nearly impervious material'
These soils have a very slow rate of water transmission'
lf a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
USDA Natural Resources
-
Conservation Service
Web Soil SurveY
National Cooperative Soil SurveY
5t1312014
Page 3 of4
3 K Factor, Whole Soil-Rifle Area, Colorado, Parts of Garfield and [,4esa Counties
(High lilesa ComPressor Station)
-3
t.-t.
'\,
a
R
$
-J1te 59N
7531$
B
7511S T3BO 7532rc 753310 El39
lbp kle: 1:1,860 if ptuted on A hrdape (11" x 8.5") sltrL
.l{etecN 6 25 50 1oo 150
I *-.
l\ o so 1oo 2oo 3oo
,\ Map prcjdon: !!bbMecbr Coffi @dimt6: WGS84 ftgeb: UTil Zore 12N W(g
7! 359
I
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51i3t2014
Page 1 ol 3UsDA Natural Resources: Conseryation Seryice
Web Soil Survey
National Cooperative Soil Survey
'r.
i
i5:150 75:1:0
.-,-.", [ ]., I -*- .t
'i.te.
.,.
K Factor, \ ,hole Soil-Rifle Area, Colorado, Paris of Garfield and lvlesa Counties
(High Mesa Compressor Station)
Area ot lnterest (AOll
t] Area or lnreresl (Ao0
Soils
Soil Rating Polygons
E .02
W .os
[f .10
fl .is
tl .11
E .20
E .24
trl .2a
tl 32
E37
E .43
@l .4e
E .ss
E .64
E Nol raled orhotavailabte
Soil Rating Lines
F02,i, .os
,. .20
MAP LEGEND
r..t .32
Streams and Canals
Transponation
Rails
d InteEtate H\ghways
M UsRoutes
Majo. Roads
Local Roads
BackgDund
MAP INFORMATION
The soil suryeys that comprise your AOI were mapped at
1:24,0A0.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can Guse
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
s€le.
Please rely on the bar s6le on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Seruice
Web Soil Suruey URL: http:/ ilebsoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Suryey are based on the Web Mer€tor
projection, which preserves directlon and shape but distorts
distance and area. A prcjection that preserues area, such as the
Albem equal-area conic prcjection, should be used if more
accurate calculations oI distance or area are required,
This product is generated from the USDA-NRCS certified data as
ofthe version date(s) listed below.
Soil Survey Area: Rifle Area, Colorado, Parls of Garfield and
Mesa Counties
Suryey Area Data: Version 7, Dec23,2013
Soil map units are labeled (as space allows) for map scales
'1:50,000 oI larger.
Date(s) aerial images were photographed: Jun 22, 20'1G-Sep
3,2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minorshifiing
of map unit boundaries may be evident.
.. Notraiedo.nolavailab," f AedatPhotogEphy
Soil Rating Points
I .o2
I .0s
E .10
E .ls
a .17
E .20
E .24
E .28
ll .32
E .37
tr .13
r '4s
r .5s
I .64
E Not rated or nol available
Water Features
usD,\ NaturalResourcesil conseruation Seryice
Web Soil Survey
Nalional Cooperative Soil Suruey
511312014
Page 2 of 3
K Factor, Whole Soil-Rifle Area, Colorado, Parts of Garfleld and Mesa Counties High Mesa Compressor Slation
K Factor, Whole Soil
Description
Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by
water. Factor K is one of sixfactors used in the Universal Soil Loss Equation (USLE)
and the Revised Universal Soil Loss Equation (RUSLE) to predict the average
annual rate of soil loss by sheet and rill erosion in tons per acre per year. The
estimates are based primarily on percentage of silt, sand, and organic matter and
on soil structure and saturated hydraulic conductivity (Ksat). Values of K range from
0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible
the soil is to sheet and rill erosion by water.
"Erosion factor Kw (whole soil)" indicates the erodibility of the whole soil. The
estimates are modified by the presence of rock fragments.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-breakRule: Higher
Layer Options (Horizon Aggregation Method): Surface Layer (Not applicable)
K Factor, Whole Soil- Summary by Map Unit - Rifle Area, Colorado, Parts of Garfield and Mesa Counties (CO683)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
lldefonso stony loam, 25
to 45 percent slopes
.17 0.6 7.OYo
56 Potts loam, 6 to 12
percent slopes
.J /0.2 2.1Yo
58 Potts-lldefonso complex,
12 to 25 percent
slopes
7.4 90.8%
Totals for Area of lnterest 8.2 100.00/.
USDA Natural Resources
-
Conservation Service
Web Soil SurveY
National Cooperative Soil Survey
5t1312014
F'age 3 of 3
ction 36 \\l_
,''v
\or{heost Corner ol Sect on
s3q'1a'03'w
2694.57
)i---..
, th. .orlhr6t ond ndtheosi quoild ot Seciioh J6, Ionnsh,p 7 Solth.
r Principol Meridion, Count/ ol Gorfi.ld. Slot. ol Colorodo. soid porc.l brin9
th. nniheost cornd or soid Secti@ J6 nheocc the t€st quoiler cor.* beors soulh
o distonce ol 2694.5, le.i, iith oil b.oilnqs h€r.in ldotiv. th.reto:
ftenc. S 53!501" w o distonc. ol 5299-75 f.et lo lh. Point of B€ginning:
ft.n.. tuth rO1J57' Eo51 o dktonc. ol 260.1a r.ct;
Th..c. hih 77a858'w.s! o distonc. or 180,42 l..ti
Ihenq. tuth a820rJ'west o dGlonc. or 67.71 f€.li
Jhe.ce hih 763047'w.sl o dist@c. or 1S.00 re€t:
ie^ce Nqlh 71i240- Sest o disionc. ol 196,6a leel:
lh.nc. Nqth l7a5'16" we.t o disloic. ot 82,44 r.el:
ftenc. Ndlh 21!550'tosl. distonc. ol 164.20 l.cl:
Thenc. Ndlh 7719'57" Eost . dislonc. ol 167.91 reel;
s.nc. bth 55'454a" Elsr o distonce ., a1.66 le.t;
ft.nc. Ndlh 6717'00" Eost o dstonc. ol 26!.0l le€t 1o $. Point oi B.linning.
I IN FEET
'
2.
5.MrCH lS ONED BY tNcaNA OL ANo C,
ESI S EE 6IH PRINCIPAL MERIO]N, (
c@srsrs ot rLoE
,- GRANO RIER GAIHERINC LLC _ HIGH M€sA COMPRESSOR SIIE - SHEETS l-J TI
sHOffi HEFEON ARE BASED ON ilI LINI BEMEN flE NSBEASI CORNEN O' STC
CORNER OI SAIO s'CIION 36, ELEVAIIilS SHOM HEREON ARE EASEO UPON NAW IRNER OI SAIO s'CIION 36, ELEVAIIilS SHOM HEREON ARE EASEO UPON NAW I
NO PffiINC AREAS ARE LOCATEO ON sA'ET C2 ANO NO BUILDINCS ME PURPOITY
11.
frE
FACiLINES 8E fl SIE
rs 24' x 36'.
Proposed Contour
Existing Contour
Proposed Edge of Rood
Existing Edge of Rood
Project Sile Boundory
Proposed Droinoge
Proposed Pipeline Corridor
Proposed Bui,din g/EquiPmeni
Proposed Grovel Surfoce
GENERAL ELEVATION ME14
(lo D.monikol€ uo{mum stuclu.. H.igh0
High Meso Compressor Stotion
Site Plon
SHEET NO, 2 OF 2 SHEEIS
ACOU1TIC) &
NOI9E CONTKOL
ENGINEEKING
t'X Oimi"", 113b1 Mead,owqlen, Suite l, I'oueNon, TX77O92
CO Office:16bO NorLhwesLern Rd, Lan7fionl, CO BASO1
CO ?hone:3O3'b34-9455 l^X ?hone: 2b1-496-9b76
Subject:
Submitted to:
High Mesa Compressor Station (Garfield County, Colorado): Results of a
Sound Survey during Operation of the Station
summit Midstream Partners, LLC and Grand River Gathering, LLC
2100 McKinney Ave., Suite 1250
Dallas, TX75201
H&K Report No. 3001
Date of Report: April '1 5,2014
H&K Job No. 4611
Submitted by: Paul D. Kiteck, Senior Consultant with Hoover & Keith lnc. ("H&K")
REPORT SUMMARY
This report presents the results of a sound survey performed March 12, 2014 at the High Mesa
Compressor Station (abbreviated as "station" in the report). The purpose of the sound survey
was to quanlfy the Station sound level at the Station leased property boundary during operation
and compare the sound contribution of the Station to applicable sound level requirement by
Garfield County. The following table summarizes the measured daytime A-wt. sound levels at the
closest leased property boundaries during Station and estimated Station sound levels if the
Station was operated at full load.
,d Est'd A-Wt. Sound Level at the Leased Boundaries Station
Meas.
Pos.
Description ofthe Sound Measurement Location Meas'd A-Wt.
Sound Level
(90% Load)
Est'd Sound
Level of Station
at Full Load
Pos. 1 NE Leased Property Boundary: 861 feet NNE of Station 42.1 dBA 42.6 dBA*
Pos. 2 West Leased Property Boundary: 1,111 feet west of Station 43.4 dBA 43.9 dBAx
Meas'
Since the Station was operated at 90% offull load during the sound survey, 0.5 dB was added to
the measured A-wt. sound levels to estimate the Station sound level if operated at full capacity.
ln summary, the results of the sound survey and subsequent data calculation indicate that the
Station sound levels are below the sound level limits specified by Garfield County for this type of
facility (i.e., 50 dBA at the leased property boundary for the Station).
-Page i-
Summit Midstream - High Mesa Compressor Station
Results ot 2014 Sound Survey during Operation of the Station
Hoover & Keith lnc.
H&K Job No. 461 1
H&K Report No. 3001 (Dale:04115114)
't.0
2.0
3.0
4.0
TABLE OF CONTENTS
Paqe
INTRODUCTION.............. ..........1
SITE/FACILITY DESCRIPTION ....................'1
couNTY souND LEVEL REQU|REMENT............... ......................1-2
MEASUREMENT LOCATIONS, CONDITIONS AN D MEASUREMENT METHODOLOGY........2
4.1 Sound Measurement Positions and Conditions during the Sound Survey......'.....-..........2
4.2 Data Acquisition and Sound Measurement Equipment --..........2
MEASUREMENT RESULTS, OBSERVATIONS AND FINAL COMMENT. .........,...3
STATION SOUND LEVEL AT FULL LOAD, SUMMARY AND FINAL COMMENT .........,......3-4
5.0
6.0
@D!.X: SITE/FACILITY DRAWINGS, SUMMARY OF THE MEASUREMENT
RESULTS AND ANY SUBSEQUENT SOUND DATA CALCULATIONS........... ...... 5-1 1
Figure 1: Area Layout around the Station showing the Leased Property Boundary and the
Chosen Sound Measurement Positions at the Property Boundary .'.........6
Figure 2: Photo showing the Station/Equipment from the North/NE Side of Station ....................7
Table A: Measured A-Wt. Sound Levels and Unweighted O.B. SPLs at the Chosen/Reported
Sound Measurement Positions during Station Operation.... .......'..'..........'.8
Table B: MeteorologicalConditions during the Sound Survey......... .... ....................8
Summary of Typical Metrics for Regulating Environmental Noise and Acoustical Terminology
related to the Report ....'....... 9-11
-Page ii-
Summit Midstream - High Mesa Compressor Station
Results ol 2014 Sound Survey during Operation of the Station
Hoover & Keith lnc.
H&K Job No. 46'11
H&K Report No. 3001 (Dale:04115114)
1.0 INTRODUCTION
ln this report, Hoover & Keith lnc. ("H&K") presents the results of a sound survey performed on
March 12,2014 during operation of the High Mesa Compressor Station (abbreviated as
"Station"), which is owned and operated by Grand River Gathering, LLC ('GRG"), a company of
Summit Midstream Partners, LLC. The purpose of the sound survey was to quantify the
Station sound level at the Station leased property boundary during operation and compare the
sound contribution of the Statlon to applicable sound level requirement by Garfield County. For
the reader's information, a summary of applicable acoustical terminology in this report and typical
metrics used to measure and regulate environmental noise is provided at the end of the repoft
(Appendix, pp.9-11).
SITE/FACI LITY DESCRIPTION
Figure 1 (Appendix, p. 6) provides an area layout around the Station showing the leased
property line/boundary of the Station (property owned by EnCana Oil & Gas), chosen sound
measurement positions near the closest leased property boundaries and other areas of interest.
The Station is located in Garfield County, Colorado, off County Road 300 (area referred to as
"High Mesa"), and is approximately 3 miles south of Parachute, CO. The land immediately
around the Station is primarily utilized as industrial activities (e.9., natural gas operations). The
closest residences (i.e., closest "residential/agricultural/rural" zoned properties) are located west,
northwest and southwest of the Station, between 4,200 feet to 5,500 feet from the Station.
The Station consist of seven (7) CAT Model 3516 unenclosed skid-mounted engine-driven
reciprocating compressor units [i.e., Units #1-#7; each rated at 1,340 horsepower ("HP")] and a
CAT Model 3616 engine-driven reciprocating compressor unit (i.e., Unit #8; rated at 4,493 HP)
located inside a building (i.e., "Unit #8 Compressor Building"). Consequently, the total Station HP
capacity is 13,873 HP (i.e., 7x|,340HP + 4,493 HP ='13,873 HP). For reference, Figure 2
(Appendix, p. 7) provides a photo showing the Station equipment (i.e., compressor units and
Unit #8 Compressor Building) from the NNE Side of the Station.
COUNTY SOUND LEVEL REQUIREMENT
We understand that Garfield County's position, as related to a conditional use permit ("CUP") for
this facility, requires that the sound decibel limit should be measured at the High Mesa Station
property line (i.e., leased property boundary) and should meet the residentialdecibel limit
pursuant to the COGCC regulations (i.e., 50 dBA). This is based on the COGCC Aesthetic and
Noise Control Regulations Section 802.c (1), which states the following:
"Noise levels from oil and gas facilities located on surface properly owned, leased, or
otherwise controlled by the operator shall be measured at three hundred and fifty (350)
feet or at the property line, whichever is greater."
2.0
3.0
-Page .1-
Summit Midstream - High Mesa Compressor Station
Results of 2Q14 Sound Survey during Operation of the Station
Hoover & Keilh lnc.
H&K Job No. 461 1
H&K Report No. 3001 (Dale.04115114)
MEASUREMENT LOCATIONS. CONDITIONS AND MEASUREMENT METHODOLOGY
sound Measurement Positions and conditions during the Sound survey
4.0
4.1
Consequently, to verify the current Station sound level contribution at the property boundary'
sound tests during Station operation were conducted at the closest leased property boundaries
(i.e,, NE boundary and west boundary). ln our opinion, the Station sound level at other more
distant property boundaries should be equal to or less than the measured Station sound level at
these closest leased property boundaries.
The sound survey was performed by Paul Kiteck of H&K during the daytime of March 12,2014'
During the time frame of the sound survey, the temperature was 30 to 40o F; the sky was clear
and the wind was blowing from the NE/ENE. During the sound survey, seven (7) of the eight (8)
compressor units were operating (i.e., only Unit #1 was not operating). The 7 units could only be
operated for a limited time frame due to pipeline conditions, noting that typically only 3 or 4 units
are operated at this site. Consequently, the total horsepower at the Station operating during the
sound survey was approximately 12,533 HP (i.e., 6x1,340 HP + 4,493 HP = 12,533 HP), which is
approximately 90% of the totalstation HP capacity [i.e., 100x(12,533i13,873 = 90%)]'
Two (2) locations were chosen for measuring the sound level at the closest leased property
boundariesoftheStation(i.e.,Meas.Pos. 1&Meas.Pos.2). Thefollowingprovidesa
description of the reported sound measurement positions during the sound survey'
Pos. 1: Northeast ("NE") leased Siation property boundary, approximately 861 feet NNE of the
Station site center, which is considered the closest leased property boundary; and
Pos. 2: West leased station property boundary, approximately 1,111 feet west of the station site
center, which is considered the closest leased property boundary on the West Side'
Data Acquisition and Measurement Equipment
At each sound measurement location, the A-wt. sound level and unweighted octave-band ("O.8'")
sound pressure levels ("SPLs") were measured at 4 to 5 feet above ground. Sound
measurements were taken during times when the wind was less than five (5) mph, if feasible, and
during a time frame of minimum environmental noise sources not associated with the Station
operation. The sound measurement system consisted of a Larson-Davis ("LD") Model 2900 Real
TimeAnalyzer/SlM (a Type I SLM perANS| Standard 51'4 & S1.11) with a condenser
microphone covered by a windscreen, and the analyzeriSLM was calibrated with a LD Model
CA2SO microphone calibrator that was calibrated within one (1) year of the testing date.
4.2
-Page 2-
Summit Midstream - High Mesa Compressor Station
Results ot 2014 Sound Survey during Operation of the Station
Hoover & Keith lnc.
H&K Job No. 461 1
H&K Report No. 3001 (Dale:04115114)
5.0
5.'l
MEASUREMENT RESULTS AND OBSERVATIONS
Measurement Results and Observations
Table A (Appendix, p. 8) shows the measured A-wt. sound levels and unweighted O.B' SPLs at
the reported sound measurement positions during operation of the Station along with the
arithmetic average of the measured A-wt. sound levels if more than one (1) sample of the sound
level was measured. Table A also includes a summary of the Station operating conditions during
the sound survey. Meteorological conditions that occurred during the sound survey are
summarized in Table B (Appendix, p. 8).
The following Table 1 summarizes the measured A-wt. sound level at the closest leased property
boundaries during Station operation, noting that the measured A-wt. sound levels were primarily
the result of noise contributed by the Station. As mentioned previously, the Station sound level at
other more distant property boundaries should be equal to or less than the measured Station
sound levelat Meas. Pos. 1 and Meas. Pos. 2(i.e., closest leased property boundaries).
Meas.
Pos.
Description of the Sound Measurement Location Meas'd A-Wt.
Sound Level
Pos.1 NE leased property boundary; approx. 861 feet NNE of Station site center 42.1 dBA
Pos. 2 West leased property boundary; approx. 1 ,'l 1 1 feet west of S1q@! JIg J949I 43.4 dBA
faOte t: Summary of the Meas'd A-Wt. Sound Levels at the Closest Leased Property Boundaries
It is our opinion that the measured sound data adequately quantifies the existing sound levels
contributed by the Station for the meteorological conditions that occurred during the sound
survey. At Pos. 1 and Pos. 2, the noise generated by the Station was the primary noise that
contributed to the measured A-wt. sound levels. At Pos. 2, there was also some audible distant
vehicle traffic noise, which did not significantly contribute to the measured A-wt. sound levels.
STATION SOUND LEVEL AT FULL LOAD. SUMMARY AND FINAL COMMENT
Since the Station was only operated at 90% of full capacity during the sound survey, 0.5 dB was
added to the measured Station sound contribution at the leased property boundary [i.e', 10.log
(1/0.90) = 0.5 dBl to represent the maximum sound level of the Station if all Station compressor
units were operated at full capacityl.
The following Table 2 summarizes the estimated maximum sound level of the Station at the
closest leased property boundaries if the Station was operated at full load (i.e., operation of all
Station compressor units).
I Use of 1 0-log [(100/(per cent operating load of station) = resulting dB], added to the measured sound levels during
actual per cent load of station, is an industry standard/method for estimated station sound levels at full capacity, but
assumes similar type of equipment at the station (e.g., mostly engine-driven compressor units), which is the case for
this compressor station.
-Page 3-
6.0
Surnmit Midstream - High Mesa Compressor Station
Results of 2014 Sound Survey during Operation of the Station
Hoover & Keith Inc.
H&K Job No. 461 1
H&K Report No. 3001 (Date.04115114)
ln conclusion, the results of the sound survey and subsequent data calculations indicate that the
sound level of the High Mesa Compressor Station is equal to or lower than the sound level
limits specified by Garfield County for this type of facility (i.e., A-wt. sound level of 50 dBA).
Est'd A-Wt. Level of
Station at Full Load (A-
Description of the Sound Measurement Location
NE leased property boundary; 861 feet NryE rlqlglg! j1!e
; 1,111 feet west of Station site
iable 2: Est'd Sound Level of the Station at Closest Leased Boundaries if the Station was operated at
Full Capacity (i.e., all Compressor Units at the Station operating)
-Page 4-
Hoover & Keilh lnc.
Summit Midstream - High Mesa Compressor Station H&K Job No' 4611
Results of 2014 Sound Survey during Operation of the Station H&K Report No. 3001 (Date: 04115114)
APPENDIX
> FIGURE 1: AREA LAYOUT AROUND THE STATION
SHOWING THE STATION LEASED
PROPERTY BOUNDARY, OTHER AREAS
OF INTEREST AND CHOSEN SOUND
MEASUREMENT POSITION NEAR THE
CLOSEST LEASED PROPERTY
BOUNDARIES
> FIGURE 2: PHOTO SHOWING THE STATION FROM
VIEWPOINT OF THE NORTH.NORTHEAST
SIDE OF THE STATION
> SUMMARY OF THE MEASURED SITE SOUND DATA
AND ANY SUBSEQUENT DATA CALGUATIONS
> SUMMARY OF TYPICAL METRICS FOR REGULATING
ENVIRONMENTAL NOISE AND ACOUSTICAL
TERMINOLOGY RELATED TO THE REPORT
-Page 5-
Summit Midstream - High Mesa Compressor Station
Results of 2014 Sound Survey during Operation of the Station
ENCANA
I\,IESA WATER
FACILITY
FENCELINE
ALONG WEST
SIDE OF
PROPERTY
UNDERGROUND
PIPELINE
Hoover & Keith lnc.
H&K Job No. 461 1
H&K Report No. 3001 (Date.04115114)
1 (CLOSEST PROPERTY
LINE ON NORTH SIDE
OF COMPRESSOR
STATION)
PROPERTY LINE OF ENCANA
(.LEASED PROPERTY)
LEGEND
Q - vensunrvrNT PosrroN
APPROXIMATE SCALE IN FEET
0 400 800 1600
High Mesa Station: Area Layout showing the Station, Leased Property Boundary (i.e.,
EnCana Property Boundary) and Chosen Sound Measurement Positions at the Closest
Leased Property Boundaries (Note: existing topography not shown on this Figure).
AV
\UV
-t
I
I
Figure 1:
-Page 6-
2
(CLOSEST
LINE ON WEST SIDE
OF COMPRESSOR
STATION)
\
Summit Midstream - High Mesa Compressor Station
Results ot 2014 Sound Survey during Operation of the Station
Hoover & Keith lnc.
H&K Job No. 461 1
H&K Report No. 3001 (Date:04115114)
High Mesa Station: Photo showing the Station Equipment Layout (i.e., Compressor Units
& Unit #8 Compressor Building) from Viewpoint of the North/NE Side of the Station.
-Page 7-
,a
Figure 2:
Hoover & Keilh lnc.
Summit Midstream - High Mesa Compressor Station H&K Job No 4611
Results of 2014 Sound Survey during Operation of the Station H&K Report No. 3001 (Date.04115114)
Table A: High Mesa Compressor Station: Meas'd A-Wt. Sound Levels and Unweighted Octave Band ("O.B.") SPLs
at the Closest Leased Property Boundaries as Measured during Daytime of March '12, 2014 with Seven (7)
of the Eight (8) Compressor Units Operating, which is approximately Full HP Capacity of the Station.
Operatinq Conditions of ihe Station (i.e., Compressor Units):
> Units #2, #3,#4,#5,#6  operating (each consisting of unenclosed CAT 3516 skid-mounted engine-driven compressor unit);
> Unit #B operating at approx. full load (CAT 3616 engine-driven compressor unit in a building; engine speed typically 975 rpm);
> Unit#j (CAT 3Si6 skid-mounted engine-driven compressor unit) not operating (i.e., only unit not available during survey).
Measurement Set Time
of Test
Unweiohted Sound Pressure Level ("SPL") in dB per O.B. Freq (Hz)A.Wt,
Level
Comments & Observations
Pos.Description/Location 63 125 250 500 1 000 2000 4000 8000
1 \E "leased" property line;
rpprox. 861 ft. NNE from
:he Station site center
10:00 AM
10:40 AM
10:50 AM
70
ot
70
61
61
OJ
52
52
53
39
37
39
JI
35
JO
34
35
34
30
32
31
23
24
23
21
21
21
42.0
42.0
42.7
Station noise was dominant noise
source during sound tests. Tests
conducted during "low" wind speed
\veraqe SPLs & A-Wt. Sound Level 69 62 52 38 36 35 31 23 21 42.1 and min. noise at the water facility.
2 try'est "leased" property line;
ipprox. 1,1 1 1 ft. west of site
11:30 A|\4
1 1:45 AI/
63
64
59
60
53
51
42
39
39
J6
3t
ao
34
34
30
23
JU
21
43.8
43.1
Station noise was dominant noise
source during sound tests. Some
{verage SPLS & A-Wt. Sound Level 63 59 52 40 39 38 34 27 26 43.4 noise of distant traffic audible.
Measurement Set Temp.
('F)
R.H.
(%l
Wind
Direction
Wind
Speed
Peak
Wind
Sky Conditions
Pos.Date/Time of Testing
1&2 10:00 AM to 12:00 PM (3112114)30-40 35-45 NE/ENE 3-6mph 6-8mph Clear with periods of gusting wind
Table B: High Mesa Compressor Station: Meteorological Conditions during Sound Survey on March 12,2014.
-Page 8-
Hoover & Keilh lnc.
Summit Midstream - High Mesa Compressor Station H&K Job No. 4611
Results of 2014 Sound Survey during Operation of the Station H&K Report No. 3001 (Date. 04115114)
SUMMARY OF TYPICAL METRICS FOR REGULATING ENVIRONMENTAL NOISE AND
ACOUSTICAL TERMINOLOGY RELATED TO THE REPORT
(1) Decibel (dB): A unit for expressing the relative power level difference between acoustical or
electrical signals. lt is ten times the common logarithm of the ratio of two related quantities that
are proportional to power. When adding dB or dBA values, the values must be added
logarithmically. For example, the logarithmic addition of 35 dB plus 35 dB is 38 dB.
(2) A-Weiqhted Sound Level (dBA): The A-wt. sound level is a single-figure sound rating, expressed
in decibels (Re 20 pPa), which correlates to the human perception of the loudness of sound. The
dBA level is commonly used to measure industrial and environmental noise since it is easy to
measure and provides a reasonable indication of the human annoyance value of the noise. The
dBA measurement is not a good descriptor of a noise consisting of strong low-frequency
components or for a noise with tonal components. The A-weighted curve approximates the
response of the average ear at sound levels of 20 to 50 decibels. The following are the relative
response of A-weighted filter per octave band frequency, and a graph/curve is provided below
that shows a graphical representation of the A-wt. filter response per frequency (in Hz).
31.5
Hz
63
Hz
125
Hz
250
Hz
s00
Hz
1,000
Hz
2,000
Hz
4,000
Hz
8,000
Hz
16,000
Hz
-39.4 dB -26.2d8 -16.1 dB -8.6 dB -3.2 dB 0dB +1.2 dB +'1.0 dB 1.1 dB -6.6 dB
RELATIVE RESPONSElas
l0
-10
-20
-30
-40
t6 31.5 63 125 250 s00 1000 2000 4000 8000 16,000
FREQUENCY, HZ
9-B,C \$
B/./
,/
/
/
/
^/
-50
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Summit Midstream - High Mesa Compressor Station
Results of 2014 Sound Survey during Operation of the Station
Hoover & Keith lnc.
H&K Job No. 461 1
H&K Report No. 3001 (DaIe.04l15l14)
(4)
(5)
(6)
(7)
(3) C-Weiqhted Sound Level (dBC): The C-wt. sound level is a single-figure sound rating, expressed
in decibels (Re 20 pPa), which correlates to the human perception of the loudness of sound in
excess of 85 decibels. The dBC level is commonly used to measure industrial and environmental
nolse since it is easy to measure and provides a reasonable indication of the overall sound. The
difference between C and A-weighted sound levels provides an indication of the amount of lower
frequency sound energy. The following are the relative response of C-weighted filter per octave
band frequency, and a graph/curve is provided that shows a graphical representation of the C-wt.
filter response per frequency (in Hz), and the graph/curve above in Definition (2) shows a
graphical representation of the C-wt. filter response per frequency (in Hz).
31.5
Hz
53
Hz
12s
Hz
250
Hz
500
Hz
1,000
Hz
2,000
Hz
4,000
Hz
8,000
Hz
1 6,000
Hz
-3.2 dB 1.0 dB -0.2 dB 0dB 0dB 0dB -0.2 dB -0.8 dB -3.0 dB -8.5 dB
Backqround or Ambient Noise: The total noise produced by all other sources of a given
environment in the vicinity of a specific source of interest, and includes any Residual Noise.
Human Perception of Chanqe in Sound Level
Sound Pressure Level (Lp or SPL): Ten times the common logarithm to the base 10 of the ratio of
the mean square sound pressure to the square of a reference pressure. Therefore, the sound
pressure level is equal to 20 times the common logarithm of the ratio of the sound pressure to a
reference pressure (20 micropascals or 0.0002 microbar).
Octave Band Sound Pressure Level (SPL): Sound is typically measured in frequency ranges
(e.g., high-pitched sound, low-pitched sound, etc.)that provides more meaningful sound data
regarding the sound character of the noise. When measuring two noise sources for comparison,
it is betterto measure the spectrum of each noise, such as in octave band SPL frequency
ranges. Then, the relative loudness of two sounds can be compared frequency range by
frequency range. As an illustration, 2 noise sources can have the same dBA rating and yet
sound completely different. For example, a high-pitched sound at a frequency of 2000 Hz could
have the same dBA rating as a much louder low-frequency sound at 50 Hz.
Davtime Sound Level (Lo) & Niqhttime Sound Level (L"): Lo is the equivalent A-weighted sound
level, in decibels, for a 15 hour time period, between 07:00 to 22:00 Hours (7:00 a.m. to 10:00
p.m.). Ln is the equivalent A-weighted sound level, in decibels, for a t hour time period, between
22:001o 07:00 Hours (10:00 p.m. to 7:00 a.m.).
(8)
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Summit Midstream - High Mesa Compressor Station
Results of 2014 Sound Survey during Operation of the Station
Hoover & Keilh lnc.
H&K Job No. 4611
H&K Report No. 300'1 (Dale:04115114)
(e)Equivalent Sound Level (L"q): The equivalent sound level (L"q) can be considered an average
sound level measured during a period of time, including any fluctuating sound levels during that
period. ln this report, the Leq is equal to the level of a steady (in time) A-weighted sound level that
would be equivalent to the sampled A-weighted sound level on an energy basis for a specified
measurement interval. The concept of the measuring L"q has been used broadly to relate
individual and communrty reaction to aircraft and other environmental noises.
(10) Dav-Niqht Averaqe Sound Level (Lon): The Lon is an energy average of the measured daytime L"q
(Lo) and the measured nighttime Luq (Ln) plus 10 dB. The 10-dB adjustment to the Ln is intended
to compensate for nighttime sensitivity. As such, the Lon is not a true measure of the sound level
but represents a skewed average that correlates generally with past sound surveys which
attempted to relate environmental sound levels with physiological reaction and physiological
effects. For a steady sound source that operates continuously over a24-hour period and
controls the environmental sound level, an Lon is approximately 6.4 dB above the measured Luq.
Consequently, an Lon of 55 dBA corresponds to an L"q of 48.6 dBA. lf both the Lo and Ln are
measured, then the Lon is calculated using the following formula:
Lon = 10 1"g,, (; l o/d/ro + 11 gt'"-'ol''o
)
(11) L-PercentSound Levels:The Lpercent levels (e.9., Lso, Lso & Lro)refertotheA-weighted sound
levels that are exceeded for 90, 50 and 10 percent of the time, respectively, during a sound
measurement period. For example, the S0-percentile exceeded sound level is designated to as
Lso and is sometimes described as the median sound level. The range between the Lroand Leo
values usually provides a good indication of the variability of the sound levels during the period of
measurement.
(12) Sound Level Meter (SLM): An instrument used to measure sound pressure level, sound level,
octave-band SPL, or peak sound pressure level, separately or in any combinations thereof. The
measured weighted SPL (i.e., A-Wt. Sound Level or dBA) is obtained by the use of a SLM having
a standard frequency-filter for attenuating part of the sound spectrum.
(13) Sound Power Level (L* or PWL): Ten times the common logarithm of the ratio of the total
acoustic power radiated by a sound source to a reference power. A reference power of a
picowatt or 10-12 watt is conventionally used.
(14) Tone:A tone is a sound sensation-having pitch, which is a listener's perception of the
frequency (for example, the higher the frequency, the higher the pitch). For a measured
sound spectrum, a tone is represented as a "peak" in the spectrum curve. Noise that
contains significant tones is considered a tonal type of noise.
End of Report
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