ORD. 345 - Town of Westlake Master Drainage Study 2000TOWN OF WESTLAKE, TEXAS
ORDINANCE NO, 345
AN ORDINANCE OF THE BOARD OF ALDERMEN OF THE TOWN OF
WESTLAKE, TEXAS, APPROVING A MASTER DRAI.NAGE STUDY
PREPARED BY CARTER & BURGESS, JANUARY, 2000.
WHEREAS, a Master Drainage Study for the Tours of Westlake has been
prepared by Carter & Burgess. Two large stream systems flow through Westlake, into
adjacent communities and then to Lake Grapevine. Marshall Branch and its tributaries
can be found within the western half of the Town. The study characterizes the flood
plains for Marshall Branch, Paigebrooke Creek, Tributary MB-3, and Tributary MB-7.
Golf Course Creek, also a tributary of Marshall Branch, drains north into the Town of
Trophy Club through the center of the Town. Located within the eastern side of the
Town, Kirkwood Branch flows east into the Town of Southlake. Tributaries studied
include Higgins Branch and Kirkwood Tributary. The location of these streams can be
found on the Master Drainage Study plan.
NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF
THE TOWN OF WESTLAKE, TEXAS:
SECTION l: That the Board of Aldermen of the Town of Westlake, Texas,
hereby approves a Master Drainage Study prepared by Carter & Burgess in January,
2000.
PASSED AND APPROVED ON THIS 24"" DAY OF JANUARY, 2000.
ATTEST:
Gin
CrCrossw5 , Town ecretary
APPROVED, AS TO FORM:
L.':Stanton Lowry; Town Attorney
Scott Bradley, Mayor
Trent Petty; Town Manag9r'
Town of Westlake
Master Drainage Study
Volume 1
Report, Appendices A & B
Marshall Branch & Tributaries
Paigebrook Creek
Golf Course Creek
Kirkwood Branch
Kirkwood Tributary
Higgins Branch
Jalluary 2000
«� Carters=Burgess
Consultants in Planning, Engineering, Architecture,
Construction Management, and Related Services
3880 Hulen Street
Fort Worth, Texas 78107
817-735-£000
C&B Job NLII lbel' 9818450/0
Town of Westlake
Master Drainage Study
981845010
*,;RNjE of
r0
CC* Cartern Burgess
Consultants in Planning, Engineering, Architecture,
Construction Management, and Related Services
Westlake
Master
Drainage
Study
January 2000
Prepared for the:
Town of
Westlake
Marshall Branch &
Tributaries
Paigebrook Greek
Gulf Course Greek
Kirkwood Branch &
Tributaries
K!,rkwaod Tributary
Hriiggins Branch
3.380 Flue n Street
Rork Yforth, Texas 76107
817_g 3 5-6000
ei'E`vtronfiie itcal@c-I�'.cUCT(
TOWN OF WESTLAKE
!MASTER DRAINAGE STUDY
TABLE OF CONTENTS
VOLUME I - REPORT
EXECUTIVE SUMMARY ........................................... . . .......... 1
1.0 INTRODUCTION....................................................... 3
2.0 NATURAL RESOURCES CONSTRAINTS ...................... . ............ 4
3.0 HYDROLOGY ....................................
3.1 MARSHALL BRANCH WATERSHED ................................. 4
3.1.1 FEMA Effective Conditions ........... . . 4
3.1.2 Existing Conditions ................ . ........................ 4
3.1.3 Ultimate Conditions ........................................ 10
3.2 KIRKWOOD BRANCH WATERSHED ......... . ..................... 12
3.2.1 FEMA Effective Conditions ....................... ............ 12
3.2.3 Ultimate Conditions .......... . ............................. 14
4.0 HYDRAULICS .......... .............................................. 15
4A MARSHALL BRANCH/GOLF COURSE CREEK ....................... 15
4.1.1 FEMA Effective/Corrected Effective Conditions .................. 15
4.1.2 Existing Conditions ................................ . . ...... 16
4.1.3 Marshall Branch Floodplain Reclamation ..................... . . 18
4.2 KIRKWOOD BRANCH ............................................ 19
4.2.1 FEMA Effective Conditions ...... ............................ 19
4.2.2 Existing Conditions ........................................ 19
4.2.3 Flood plain Reclamation - Kirkwood Branch and Higgins Branch .... 23
5.0 REGIONAL DETENTION ANALYSIS ...................................... 24
5.1 MARSHALL BRANCH/GOLF COURSE CREEK ....................... 24
5.2 KIRKWOOD BRANCH ............................................ 26
6.0 MAJOR ROADWAY CROSSINGS ........................................ 28
7.0 MAJOR PERMITTING ISSUES ........................................... 29
7.1 SECTION 404 OF THE CLEAN WATER ACT ......................... 29
7.2 FEMA FLOODPLAIN REGULATIONS .............. . ................ 30
7.3 TNRCC WATER APPROPRIATIONS REGULATIONS .................. 31
7.4 TNRCC DAM SAFETY REGULATIONS .............................. 31
7.5 NPDES PHASE II STORM WATER PERMITTING ..................... 32
&0 COORDINATION WITH ADJOINING JURISDICTIONS .................. . ..... 32
TABLES
1 -
Soil Classifications....................................................... S
2 -
Land Use Master.........................................................7
3 -
Marshall Branch Watershed Existing Conditions Sub -Basin Characteristics ..........
9
4 -
HEC-1 Model Flow Summary - Marshall Branch Watershed ......................
10
5 -
100-Year Flow Comparison - Marshall Branch Watershed . . ............ . ........
11
6 -
Kirkwood Branch Watershed Existing Conditions Sub -Basin Characteristics .........
14
7 -
100-Year Flow Comparison - Kirkwood Branch Watershed ......................
'I 5
8 -
Comparative 100-Year Water Surface Elevations Marshall Branch/Golf Course Creek.
18
9 -
Comparative 100-Year Water Surface Elevations For Kirkwood Branch ............
21
10-
100-year Flow Comparison with Proposed Detention for Marshall Branch ...........
26
11 -
Flow Comparison Westlake Proposed Detention - Kirkwood Branch ...............
28
12 -
Structure Comparisons at Existing and Proposed Road Crossings ................
29
FIGURES
Figure 1 - Vicinity Map
VOLUME 2 -APPENDICES
Appendix A - Water Resources Assessment and Natural Environment Survey, March 1999
Appendix B - Exhibits
Exhibit 1 - Natural Resource Constraints
Exhibit 2 - Marshall Branch Drainage Area Delineation
Exhibit 3 - Kirkwood Branch Drainage Area Delineation
Exhibit 4 - Marshall Branch Soils Map
Exhibit 5 - Kirkwood Branch Soils Map
Exhibit 6 - Marshall Branch Existing Land Use Map
Exhibit 7 -- Kirkwood Branch Existing Land Use Map
Exhibit 8 - Marshall Branch Proposed Land Use Map
Exhibit 9 - Kirkwood Branch Proposed Land Use Map
Exhibit 10 - 100-Year Floodplain Delineations Map
Exhibit 11 - Detailed Floodplain Delineations Map - 200 Scale Sheets 1 thru 11
Exhibit 12 - Proposed Regional Detention Facilities
Appendix C - Hydrologic Models
FEMA Effective NUDALLAS Models
Existing Conditions NEC-1 Models
Ultimate Conditions HEC-1 Models
Existing Conditions/Ultimate Offsite HEC-1 Models
Ultimate Offsite/Existing Offsite HEC-1 Models
Appendix D - Hydraulic Models
FEMA Effective HEC-2 Models
Existing Conditions HEC-RAS Models
EXECUTIVE SUMMARY
A Master Drainage Study for the Town of Westlake has been prepared by Carter & Burgess.
Two large stream systems flow through Westlake, into adjacent communities and then to Lake
Grapevine, Marshall Branch and its tributaries can be found within the western half of the town.
This study characterizes the flood plains for Marshall Branch, Paigebrook Creek, Tributary
MB-3, and Tributary MB-i. Gulf Course Creek, also a tributary of Marshall Branch, drains north
into the Town of Trophy Club through the center of the town. Located within the eastern side of
the town, Kirkwood Branch flows east into the Town of Southlake. Tributaries studied include
Higgins Branch and Kirkwood Tributary. The location of these streams can be found on the
Westlake Master Drainage Study plan.
Extensive development proposed within the town emphasizes the need for accurate modeling of
existing flood plains and the determination of regional detention alternatives. This study
provides the information necessary to update the FEMA Flood Insurance Rate Maps replacing
approximate flood zones with modeled flood plains and water surface elevations. The existing
conditions were modeled using GIS mapping techniques to characterize drainage subareas, soil
types, and land use. Ultimate development conditions were similarly analyzed and options for
regional detention were developed.
Specific findings of the study are:
Existing hydrologic studies are inadequate. Models were updated in HEC--I format to
characterize drainage sub -areas and existing stream characteristics within the Town of
Westlake.
Detailed hydrologic modeling of existing conditions show that Marshall Branch and Kirkwood
Branch 100-year flows are approximately those previously modeled for FEMA. However,
Golf Course Creek has substantially less flow due to the attenuation provided by two large
existing stock tanks. It should be noted that hydraulic models also exist for Marshall Branch
and Golf Course Creek through the Town of Trophy Club that use ultimate flow values.
Detailed hydraulic modeling of flood plains is virtually nonexistent within Westlake. Previous
modeling for FEMA Flood Insurance Rate Maps (FIRM) stops in the middle of Lake Turner
on Marshall Branch and at Dove Road for Kirkwood and Higgins Branch. The remainder of
the FIRM flood zones identified within Westlake are approximate Zone "A" areas and do not
have water surface elevation information.
Previous hydraulic models utilized widely spaced surveyed cross -sections with limited
topographic information between sections. One -foot contour interval mapping prepared for
this study allowed the addition of supplemental cross -sections and more accurate mapping.
Lake Turner 100-year water surface elevations, as mapped by FEMA, do not reflect existing
conditions. They are based on the dam configuration prior to modifications made
subsequent to 1984 to provide an emergency spillway for large event flows.
Detailed existing flood plains have been determined and mapped for this study on all
strearns and tributaries previously mapped by FEMA. The effective HEC-2 hydraulic models
have been updated and converted to the newer HEC-RAS format as part of this study.
98104501.R07 Page 1
In general, the existing conditions flood plain is smaller than the approximate flood zones for
all waterways. The Drainage Master Plan map shows the revised existing flood plains for
Westlake. Within Westlake the revised existing flood plains consist of 510.3 acres. This
total includes 27.1 acres of flood plain added to the Kirkwood Branch system to aid in
detention analysis. The plotted flood plains represent 90.6% of the 563.3 acres in FEMA
mapped flood zones.
® Existing conditions HEC-2 models revise the flood plains throughout Westlake and generally
tie to FEMA models just downstream of State Highway 114. The exception is Golf Course
Creek. The new model uses flow values significantly less than the FEMA model. Therefore,
a Letter of Map Revision may require revisions to the map in the Town of Trophy Club.
Ultimate flow analysis was performed on both the Marshall Branch stream system and the
Kirkwood Branch system. Within both systems, fully developed flows represent an increase
of about 30% over existing flows.
Models were prepared to show the relative difference between a fully developed watershed,
full development in Westlake with existing conditions upstream, and existing conditions in
Westlake with full development in upstream communities. The analyses show that, for both
stream systems, development of communities upstream of Westlake will significantly
increase the downstream flooding potential. Development of upstream communities without
Westlake development would result in increased flows within 5% of the total ultimate flow
value on both major streams. Full development of Westlake will result in local flow increases
but will not substantially increase the overall flood flows where the waterways leave
Westlake.
o Regional detention facilities are proposed to meet Westlake ordinance requirements for
development of Circle T Ranch, the Fidelity Investments site, and other properties within
Westlake. The locations of possible regional detention sites are identified on the Westlake
Master Drainage Study plan. Sites were chosen to take advantage of infrastructure
improvements proposed in the approved Circle T Ranch Master Plan.
Proposed regional detention sites are also located to utilize existing lakes, wetlands and
waterways to the maximum extent. Detention will be provided by modifying existing dams
and by restricting the size of proposed bridge crossings. This reduces the overall cost of
providing detention and utilizes existing environmental features for water quality
enhancement.
Additional detention analyses on Marshall Branch and Kirkwood Branch showed that it is
also possible to provide detention that will mitigate for ultimate development, including that in
upstream communities. However, to accomplish this will require the construction of large
detention facilities, 52 acres and 17 acres respectively, on each waterway. Construction of
these facilities would require property acquisition and substantial environmental permitting.
Construction costs and responsibilities for these sites should be borne principally by the
upstream communities where the flow originates.
88184501.R07 Page 2
1.0 INTRODUCTION
This master drainage study was prepared by Carter & Burgess (C&B) for the Town of
Westlake, Texas. The town is generally located south of State Highway 114 (SH-114),
and west of State Highway 170 and U.S. 377 (Denton Highway). The town is bounded
by the communities of Fort Worth, Trophy Club, Southlake and Keller. The Dentonl
Tarrant County line runs through the center of the town. A vicinity map is included as
Figure 1.
The western half of the town is traversed by Marshall Branch, a tributary of Lake
Grapevine, Golf Course Creek, a tributaryj of Marshall Branch, and by a number of
unnamed tributaries to Marshall Branch. Marshall Branch is identified on FEMA Flood
Insurance Rate Maps(FIRM) as Zone "AE" flood plain and Zone "A° flood hazard area.
The FEMA maps showing Marshall Branch are Firm #655 of Denton County and FIRM
#180 of Tarrant County. The effective detailed study reach of Marshall Branch extends
from Lake Grapevine, through the Town of Trophy Club, to upstream of the Lake Turner
dam, located just within the town limits south of SH-114. The effective flood zones are
plotted on Appendix B, Exhibit No. 10 of this report.
The eastern half of the town comprises a portion of the watershed for Kirkwood Branch,
Higgins Branch, a tributary of Kirkwood Branch, and several unnamed tributaries of
Kirkwood Branch. These streams are identified on FEMA maps as Zone "AE" flood
plains based on previous studies. The FEMA maps showing Marshall Branch are Firm
#660 of Denton County and FIRM #185 of Tarrant County. The effective flood zones are
plotted on Appendix B, Exhibit No. 10 of this report. The Kirkwood Branch watershed,
discharging to Lake Grapevine, represents a total area of approximately 5441 acres of
which 1324 acres (29.3%) are within the Town's Corporate limits. The remainder of the
Kirkwood Branch watershed is within the City of Southlake to the south and east of the
Town of Westlake.
The purpose of this study was to:
Review and revise existing flood plain studies.
Provide data to update and extend detailed flood plains throughout Westlake.
Study the impacts of proposed development within and upstream of the town.
Recommend major crossing structure sizes, proposed channelization, regional
detention facilities and/or other measures to manage storm water within the
community.
A concurrent study has been prepared for Hillwood Development Corporation on the
Circle T Ranch. This study incorporates the flood plain data gathered there and extends
the delineations of flood plains to encompass the entire town. Proposed drainage
improvements and regional detention calculations were developed in cooperation with
that study. The resultant study addresses Town of Westlake flood management criteria.
Calculations for detention requirements are included for a series of design storm
conditions in accordance with town design standards.
This master drainage study shows that the existing FEMA flood hazard areas do not
accurately show the extent of 100-year flood plains within the Town of Westlake. It also
98984501.R07 Page 3
shows that proposed regional detention facilities will adequately mitigate for proposed
development within the town limits including the commercial and major retail areas within
Circle T Ranch.
2.0 NATURAL RESOURCES CONSTRAINTS
A reconnaissance of 'the Town of Westlake was undertaken for the purpose of identifying
major natural resource constraints within stream corridors and likely storm water control
areas. Field biologists from C&B, Inc. conducted a series of site visits focusing on
identifying areas of natural environmental importance and the general jurisdictional limits
of the waters of the United States (U.S.), including wetlands, streams and ponds. This
report, "Water Resources Assessment and Natural Environment Survey', March 1999.
(Appendix A) contains a summary of these findings including the results of a similar
survey conducted on the Circle T Ranch property,
3.0 HYDROLOGY
3A MARSHALL BRANCH WATERSHED
3.1.1 FEMA Effective Conditions
The development of hydrology models in this study began with the
collection of existing models for Marshall Branch and Golf Course Creek,
a tributary of Marshall Branch. The effective hydrology models for these
creeks were not available from the FEMA library, however, a 1992 study
for the Town of Trophy Club provided substantially similar models. The
flow values are comparable to the flows shown on the FEMA effective
HEC-2 model. The models are in NUDALLAS format, a format developed
by, but no longer supported by, the Fort Worth District Corps of
Engineers. The models were developed for Trophy Club. As such, the
upstream areas south of SH-114 are represented as single large drainage
basins. The Trophy Club models are considered the duplicate effective
model and are included in Appendix C for reference.
3.1.2 Existing Conditions
The hydrology analysis developed in this study utilizes the design storm
values from the duplicate effective models as the reference values for
existing conditions model development and analysis. The existing FEMA
effective 100-year flow for Marshall Branch at SH-114 is 11200 cfs and for
Golf Course Creek at SH-114 is 1955-cfs. For this study, the watershed
hydrology is calculated using is the HEC-1 model. The large upstream
sub -basin was subdivided relative to existing drainage areas and
proposed development plans.
In order to calculate the runoff curve numbers required for the hydrologic
analysis of the Marshall Branch and Golf Course Creek watersheds, a
98184501.R07
Page 4
Geographic Information Systems (GIS) model was developed. This
model was comprised of three layers of information. Each layer, called a
coverage, described a basic attribute of the watershed. The layers
described and delineated: 1) watershed sub -basins; 2) hydrologic soil
groups; and 3) existing land use.
To create the modeling parameters separate map "coverages" were
developed. Sub -drainage areas were mapped from topographic data to
the limits needed for further detailed study. Soil hydrologic groups were
mapped from Soil Resource & Conservation Service (SRCS) soil survey
maps for Denton and Tarrant Counties. Tabie a indicates the soil types
present within the Marshall Branch drainage basin and their associated
hydrologic group. Appendix A - Exhibit 4 - Marshall Branch Soils Map
shows the resulting GIS coverages.
98184501.R07 Page 5
Table 1 - Soil Classifications
nton iro '
,
Soil Number
Soil
:
Soil Classification
i 11
Birome Fine Sandy Loam, 1-3% slopes
C
12
Birome Fine Sandy Loam, 3-5% slopes
C
13
Birome-Rayex-Aubrey-Complex 2-15% slopes
i D
24
Callisburg Fine Sandy Loam 3-5% slopes
C
27
(Crockett Fine Sandy Loam, 1-3% slopes
D
39
_
Gowen Clay Loam Occasionally Flooded
i B
46
Justin Fine Sandy Loam, 3-5% slopes
B
58
Mingo Clay Loam, 1-3% slopes
C
60
Navo Clay Loam, 1-3% slopes
D
67
Sanger Clay, 1-3% slopes
D
68
Sanger Clay, 3-5% slopes
D
75
Somervell Gravelly Loam, 1-5% slopes
B
83
Wilson Clay Loam, 0-1 % slopes
D
Tarrarit!Cbunty
Soil Number
Soil
11
12
13 iBirome-Aubrey-Urban
;Birome Fine Sandy Loam, 1-5% slopes I
Birome-Aubrey-Rayex-Complex, 5-15% I
Land Complex, 5-15% slopes
G
D
C
21
Crosstell Fine Sandy Loam, 1-3% slopes
D
22
Crosstell Fine Sandy Loam, 3-6% slopes
D
29
Gasil Fine Sandy Loam, 1-3% slopes
B
30
Gasil Fine Sandy Loam, 3-8% slopes
B
31
Gasil Sandy Clay Loam Graded, 1-5% slopes
B
36
Justin Loam, 1-3% slopes v
B
39
Lindale Clay Loam, 1-3% slopes
C
41
Lott Silty Clay, 1-3% slopes i
C
61
Purves Clay, 0-3% slopes
D
63
Rader Fine Sandy Loam, 0-3% slopes
D
65
Sanger Clay, 1-3% slopes
D
66
71
Sanger Clay, 3-5% slopes
Silstid Loamy Fine Sand, 1-5% slopes
D
A
I 72
Silstid-Urban Land Complex, 1-5% slopes
A
83
Whitesboro Loam, frequently flooded
C
98184501.R07 Page 6
Finally, existing land use maps were reviewed and modified based on
1998 aerial photography and field observations. The resultant areas were
then added to a GIS coverage map of the sub -drainage areas. Exhibit 6
Marshall Branch Existing Laud Use shows the resulting GIS
information. Table 2 shows the land use parameter matrix used in
conjunction with the soils information to generate the sub -basin CN
numbers.
Table 2 - Lama Use Master
Pasture / Range
49
69
79
i 84
Row Crops
67
i 78
85
89
Woods
36
60
73
79
Farmstead
59
74
82
� I
j 86
Parks / Open Space
39
61
74
80
Residential ('/4-acre lots)
61
75
83
87
Residential (%-acre lots)
54
70
80
85
Residential (1-acre lots)
51
68
79
84
Residential (< 2-acre lots)
46
f
65
77
82
Commercial - (65% impervious)
72
72
72
72
Commercial - (75% impervious)
78
78
78
78
Commercial (85% impervious)
89
92
94 I
95
Paved / Streets
98
98
98
98
Gravel Pits _
20
20 I
20
20
Water Bodies
98
98
98
98
ArcView (GIS software) provides the user with the ability to "intersect"
coverages. This process is similar to overlaying vellum sheets. The
resulting intersected coverage is made up of the sub -shapes defined by
all boundaries delineated in all input coverages. Sub -shapes were
created with a precision of 0.001 feet within the GIS model. Further, the
sub -shapes retain the attributes of all input coverages. Sub -shapes have
only one soil type, land use, and watershed attribute. All sub -shapes
within a given watershed sub -basin were individually assigned curve
numbers based on their soil type and their land use utilizing the SRCS
98184501.RQ7 page 7
curve number method described in TR-55 for urban areas. The curve
number for each sub -shape was then multiplied by the sub-shape's area.
The area and area x curve number attributes of all sub -shapes within
each watershed sub -basin were summed. The sum of the area x curve
number was then divided by the sum of the area for each watershed sub -
basin thus providing a weighted average calculation to determine the
overall curve number for each watershed sub -basin. No manual
calculation or summation of individual land use types was performed. All
land uses and soil types within each watershed were considered at one
time.
The existing conditions HEC-1 model was created by combining the
derived drainage area and CN number information with drainage times of
concentration. The time of concentration was calculated for each sub -
basin by measuring overland flow, shallow concentrated flow and channel
routing parameters, as outlined in the SRCS TR-55 manual. Routing data
along each reach of the existing major stream network was calculated
utilizing stream cross -sections with calibrating flow values that were
developed by the existing conditions HEC-RAS hydraulic models.
Table 3 is a tabulation of the individual Marshall Branch and Golf Course
Creek watershed sub -basin characteristics used in the HEC-1 model.
Certain sub -basins are already developed, some with existing local
detention facilities, and therefore are not represented in Table 3. In
particular, the Alliance Gateway Center (Gateway) east of SH-377 is fully
developed with detention ponds provided. The sub -areas for the two
tributaries upstream of SH-377 in Gateway were added to the model with
data directly from the flood study reports for those streams. The areas,
CN#s and reservoir routings are as -built conditions. The same is true for
the tributary from the Tom Thumb (formerly Food Lion) warehouse area
located in the northwest corner of the intersection of SH-170 and SH-377.
Specific hydrographs for each design storm are included in the model to
reflect the present developed condition for each of these areas.
Appendix B, Exhibit 2 shows the existing conditions drainage area
delineations.
The existing conditions HEC-1 model is included in Appendix C. The
existing conditions HEC-1 model includes data for the 5, '10, 50, and 100-
year design storms. These design storms were chosen to coincide with
Town of Westlake requirements for detention of developed flows. A
comparison of 100-year peak flood flows is found in Table 4.
93184501.R07
Page 2
Table 3 - Marshall Branch Watershed Existing Conditions
Sub -Basin Characteristics
I a4rea [3eslgnatlQM
GN number
Tlrne of Basm^area
anCeniraQionkrs�
Marshal! Branch
34
82
1.11
1.856
32
79
0.74
1.254
22
82
0.72
0.358
29
75
0.93
0.230
Nokia PD1
95
0.167
i 0.036
Nokia PD2
19
95
94
0.167
0.29
0.230
0.038
23
84
0.31
0.063
25
84
0.38
0.067
20
84
0.30
0.041
14
85
0.33
0.231
13
81
0.47
0.311
28
65
0.56
0.331
12
78
0.48
0.278
4
84
----
0.65
0.518
64 �
81 —
- 0.19
0.119
27
68
0.84
1.163
18
66
0.38
0.220
10
6
71
81
_
0.46
0.63
0.382
0.349
2
83
0.51
0.268
Golf Course Creek
120
92
0.18
0.300
130
89
0.43
0.460
26
—
68
--
0.40
0.311
21
62 �
_-- 0.28
0.108
16
65
0.39
0.163
8
64
0.42
0.221
__j
98184501.R07 Page 9
Table 4 - HEC-1 Model Flow Summary - Marshall Branch Watershed
Crass .;Section=
FEMA
Existing
[ Cornrnerots
No
frective "
Conditions
Flow iiow'
f -
j
Marshall Branch
22470
11200
11200
Upstream of existing Trophy Club Dr.
23740
I
11200
11330
Downstream of SH-114 North Frontage I
road bridge I
24750
I 11200
11445
I At Lake Turner Dam proposed weir
26410
N/A
8760
Marshall Branch channel
28380
N/A
8820
Downstream of main Street bridge
Golf Course Creek
8842
1955
808
Downstream of Lake 2
9320
N/A
617
Upstream of Lake 2
10990
N/A
_ 590
Upstream of Lake 1
13335
N/A —l—_
793
Upstream of Dove Rd.
The detailed calculation of flow at SH-114 remains substantially the same
as the effective model, ± 1% difference (11200 cfs versus 11330 cfs,
respectively). This is attributable to the present lack of any substantial
new upstream development except for those areas constructed with
detention to mitigate the impacts of peak discharges as indicated above.
For this reason it was determined that the model did not need to extend
downstream into the town of Trophy Club.
A substantial difference in flow values is noted above within the tributary
named Golf Course Creek. The existing large stock tanks within the
Fidelity Investments tract provide significant detention within this small
basin. The FEMA model did not account for attenuation provided by the
two existing lakes. The resultant existing model flood flows, which
incorporated the two lakes, are substantially smaller than those from the
FEMA effective model. Therefore, the newly calculated flow is
significantly smaller than that previously assumed.
3.1.3 Ultimate Conditions
Ultimate conditions HEC-1 models for Marshall Branch and its tributaries
within Westlake were developed using the existing conditions model as
the baseline. Ultimate development was determined from the approved
Zoning Maps for Westlake, Keller, and Fort Worth. Circle T Ranch
development was based on the ranch Master Plan approved by the Town
of Westlake. As noted above, sub -areas within Alliance Gateway and the
9B184601.R07 Page 10
Tom Thumb complex are also developed with existing detention. Many of
the sub -areas upstream of Westlake within the City of Keller have been
developed as well. However, where the approved zoning is denser than
existing development, the zoning was used for this portion of the study.
The UIS coverage maps for existing land use were modified as necessary
and new Arclnfo calculations produced ultimate development CN#s for
each sub -area. Appendix 8 - Exhibit 8 includes a map showing the
ultimate development coverages. Time of concentration calculations for
each sub -area were also modified to account for ultimate conditions. For
comparison purposes and for use in detention analysis, ultimate
conditions models were prepared for three design scenarios utilizing the
existing stream systems:
Full ultimate development of the entire Marshall Branch
watershed.
Existing conditions within the Town of Westlake plus ultimate
conditions within all other portions of the watershed.
Ultimate development of the Town of Westlake plus existing
conditions within all other portions of the watershed.
Table 5 shows the results of these models compared to the existing and
FEMA effective models for key study locations. Note that the ultimate
model analysis is limited to the overall impact of 100-year design storm
flows. Several conclusions are evident in the comparison.
Table 5 - 100-Year Flow Comparison - Marshall Branch Watershed
Location
Existing
Full
Existing
Ultimate
Conditions
Ultimate
Onsite
Onsite
Flows
Development
Ultimate
Existing
Flows
Offsite
Ofrsite
(cfs)
(cfs)
I (cfs)
(cfs)
Marshall Branch
Upstream of State Hwy_114 1
11,328
I 14,221
14,963
10,901
Upstream Town Limit
5,850 I
8,575
8,331
5,720
Golf Course Creek
Upstream of State Hwy. 114
808
926
880
866
The majority of impacts from ultimate development will result from
development upstream of the Town of Westlake. This is not unexpected in
an analysis of this type even though much of the Town of Westlake
98184501.R07 Paoe 11
development involves a large increase in impervious cover. Proposed
commercial, retail and industrial development is generally located along
the existing stream. Increased impervious cover (pavement, buildings,
etc.) generally includes storm sewer and/or improved open channels.
The result is a decrease in the time of concentration. This increases the
peak flow potential but also gets the peak flow into the creek much
sooner. Therefore, as the stream peak flow proceeds downstream
increases are not cumulative because the sub -area peak has already
occurred.
Finally, there are localized flow increases at key locations on Marshall
Branch and on several tributaries within the Town of Westlake. Where
flows are expected to be greater than existing, detention should be a
consideration with future development to attenuate the increases at these
locations.
3.2 KIRKWOOD BRANCH WATERSHED
3.2.1 FEMA Effective Conditions
Hydrologic analysis of the Kirkwood Branch watershed was previously
submitted to the Federal Emergency Management Agency (FEMA) in
NUDALLAS. Correspondence with the FEMA library indicated that the
hydrologic model for Kirkwood Branch was only available on microfiche
and no work maps were available.
3.2.2 Existing Conditions
Review of the model printed from the microfiche revealed that the entire
Kirkwood Branch watershed upstream of SH-114 was modeled as a
single catchment. For the purposes of this study, the resolution of the
effective model was too coarse. Therefore, as part of this study, detailed
hydrologic models were developed in HEC-1 for existing and ultimate
development conditions. HEC-1 was selected for consistency with the
Marshall Branch hydrologic model and because of its ability to be readily
converted to HEC-HMS in the future as HMS becomes the standard
hydrologic model.
Development of the HEC-1 model involved further delineation of the
Kirkwood Branch watershed and its subcatchments. Delineation of the
catchments was completed using one foot contour interval areal
topographic information developed for this study. The watershed and its
sub -areas were digitized and converted to ArcView coverages.
The SRCS method of determining peak runoff and runoff volumes was
selected as the analysis method in HEC-1. This method requires runoff
curve numbers and times of concentration for each catchment within the
watershed. Runoff curve numbers used in this method are calculated
98184501.R07 Page 12
based on the soil type and land use. See Table 1 - Soil Classification,
Section 3.1.2 and Table 2 - Land Use Master, Section 3.1.2 of this report.
The Tarrant and Denton County Soil Surveys were digitized within the
delineated Kirkwood Branch watershed and converted to an ArcView
coverage. Utilizing the soil surveys, the digitized soil groups were labeled
in terms of their hydrologic group, A, B, C, or D. The 1998 1 m Digital
Ortho Quarter Quads provided by the Texas Department of
Transportation were used to determine the existing land uses within the
Kirkwood Branch watershed. Land uses were digitized from the photos
and converted into an ArcView coverage. Ultimate land uses based on
local zoning ordinances were overlain on the existing land use coverages
and an ultimate land use map was generated. This information was also
converted to an ArcView coverage. Based on the soils and land use
coverages ESRI's ArcView Geographic Information System analysis tools
were used to calculate runoff curve numbers in individual catchments.
Times of concentration for each catchment were calculated by assigning
overland travel velocities based on land use within each catchment as
detailed in Table 6. Overall velocities for each catchment were calculated
for existing and ultimate development conditions using ArcView. Using
these velocities and travel distances measured from the topographic
information, times of concentration were calculated.
These input parameters were used in the HEC-1 models to calculate
peak flows for existing and ultimate development conditions. Appendix B
- Exhibit 5 shows the Kirkwood Branch Soils Map. !-Appendix E -
Exhibit 7 shows the Kirkwood Branch Existing Land Use Map. Appendix
8 - Exhibit 9 shows the Kirkwood Branch Proposed Land Use Map.
98184501.R07 Page 13
Table 6 - Kirkwood Branch Watershed Existing Conditions Sub -
Basin Characteristics
3.2.3 Ultimate Conditions
Based on these existing conditions hydrologic and hydraulic models,
several development scenarios were compared. The 100-year storm
peak flows at SH-114 were initially compared for existing and ultimate
development conditions. This comparison determined that peak flows will
increase once the watershed is fully developed. Two alternative
development scenarios were also investigated to determine the percent of
the increase in peak flow that could be attributed to the Town of Westlake
and to other jurisdictions within the Kirkwood Branch watershed. The
following scenarios were considered: 1) the Town fully developed and all
areas outside the corporate limits remain under existing conditions, and 2)
the Town under existing conditions and all areas outside the corporate
limits under ultimate development conditions. The peak flows calculated
under these various scenarios are summarized in Table 7:
98184501.R07
Page 14
Table 7 -100-Year Flow Comparison - Kirkwood Branch Watershed
FEMA '
_xostEng Full Existing
Ultimate j
z * }"
�.,
Effective?
�endit�o�� Ultimate Onsif
RUMS Devertopment .Ultimate
Onsite
Eicis#mg 1
MM i offs tte
Offsite
=._
Kirkwood Branch
i
Upstream of SH-114
—
6800
5,300 6,493 I 6,223
5,604
j Higgins Branch
Upstream of KB Confluence
2750
1871 2442 2442
1871
The flows shown in Table 7 indicate that development in the Kirkwood
Branch watershed will increase peak flows when compared to existing
conditions. The calculated ultimate development peak flow, however, was
within 10% of those calculated in the effective model provided by FEMA.
This slight difference in peak flows is attributed to two primary sources: 1)
HEC-1 calculates runoff and peak flows differently than NUDALLAS, and
2) the watershed contributing runoff to Kirkwood Branch at SH-114 was
previously modeled as a single catchment. The model developed for this
study incorporates multiple catchments and storage routings throughout
the watershed to more accurately characterize the flows at Highway 114.
The flows calculated under the existing/ultimate development scenarios
indicate that approximately 75% of the increase in peak flow will be the
result of development outside of the Town's corporate limits. There are
flow increases at key locations along Kirkwood Branch within the Town of
Westlake. Regional detention needs should be explored. Detention
should be a consideration with future development to attenuate these flow
increases.
4.0 HYDRAULICS
4.1 MARSHALL BRANCH/GOLF COURSE CREEK
4.1.1 FEMA Effective/Corrected Effective Conditions
The FEMA effective zone "AE" and "A" flood plains are shown in
Appendix B, Exhibit 10, as they are located on the Flood Insurance Rate
Maps referenced above. The FEMA effective flood plain and floodway
models were available, in hard copy only, from the FEMA library and are
included in Appendix D. Also, included in the appendix is a duplicate
effective model created to verify the model received from FEMA. All of
these "effective" models are in the HEC-2 format.
98184501A07 Page15
For this master drainage study the analysis for Marshall Branch was
converted to HEC-RAS format. HEC-RAS is the newest format and
replaces HEC-2 with an easier to manage windows format. The corrected
effective models included in Appendix D are the results of importing the
effective models into the new format. At SH-114 and Lake Turner dam,
errors occurred because HEC-2 does not require the bridge table data to
match the cross-section information as HEC-RAS does. Therefore, bridge
deck data had to be shifted to line up with the cross-section. The
corrected model water surface elevations at these two locations do not
provide an exact match to the effective model but are very close. This
was deemed acceptable because the bridge, as modeled in the effective
FEMA model, no longer exists. Additionally, the dam has been modified
since the publication of the effective model.
Since the adoption of the effective HEC-2 model for Marshall Branch,
SH-114 has been rebuilt. Frontage roads were constructed north and
south of the location of future highway improvements. Each frontage road
has a large bridge spanning the Marshall Branch flood plain. Additionally,
improvements were made to the Lake Turner Dam to meet state dam
safety requirements. A 300-foot wide emergency spillway was cut from
the lake around the west end of the dam.
The FIS effective floodway model was also corrected to account for the
dam modifications and the SH-114 frontage road crossings. The
corrected effective floodway model was not further revised for the existing
conditions analysis. The floodway was not extended to include any
upstream portions of Marshall Branch as there is to be no changes to the
FEMA flood zone designation.
The effective HEC-2 model for Golf Course Creek ends just before the
right-of-way for SH-114. For this reason no change to the downstream
model was made. The existing model will tie to the effective model water
surface elevations.
4.1.2 Existing Conditions
Existing conditions models were developed for this study in order to
update and set the existing conditions 100-year floodplain boundaries.
The updates to the original FIS of Marshall Branch include the new
SH114 frontage road crossings, the modification to the spillway system of
Lake Turner, the Main Street bridge crossing (section 286+99) and the
Roanoke Road crossing (section 341+32). One -foot contour interval aerial
topography, prepared for the Circle T Ranch development, was utilized to
generate cross -sections for the entire length of Marshall Branch included
in this study. Additionally, a ground survey was obtained at Lake Turner
dam to ensure accuracy when modeling the spillway modifications.
The existing conditions of Golf Course Creek were modeled similarly in
HEC-RAS format. Several sections downstream of SH-114 were added
98184501.R07 Page 16
from the effective model to verify the tie-in with Trophy Club. Rather than
several bridges, as at Marshall Branch, the two existing frontage roads
cross with a long multiple box culvert. The culvert is not a restriction as it
was designed to carry more flow than the upstream ponds will allow out.
Appendix B, Exhibit 11- Sheets 1-11 shows the existing 100-year
floodplain delineations as well as the cross-section locations and
identifications used in the NEC-RAS model.
Hydraulic models for this study were prepared using the HEC-RAS v.2.2
format because of its ease of operation and improved bridge analysis
algorithms. The models were calculated using HEC-2 conveyance
methodology and compared to the effective HEC-2 output. The models
match downstream in Trophy Club where flow values are not revised.
The existing 100-year flood plains do not overtop the highway bridges.
Water surface elevations over the dam and into Lake Turner are
substantially lower than the effective model elevations. 'This is attributable
to the previous spillway modifications. The existing conditions HEC-RAS
models are included in Appendix D. Table 8 shows the comparison
between the FEMA effective, corrected effective and existing conditions
hydraulic models for Marshall Branch and Golf Course Creek.
98184501.P.07 Page 17
Table 8 - Comparative 100-Year Water Surface Elevations
Marshall Branch/Golf Course Creek
StP�a "Crass Effeettve
Section HEC 2 MQde
Number
CorFected
EffectIVeoof1oas'
t�}EC RA$JVIadeL
i Exrs#ing
HEC i A 111 o E
` ztra t ai€ Eraz-104
22370
590.85
590.82
590.82
1 22470
591.08
591.02
591.02
` 23320
593.82
593.81
23410
594.10
594.10
--
23435
i
593.90
�-
23450
595.84
595.10
23495
594.12
23550
596.17
596.08
23740
I
594.51
23940
!
594.90
24000
I
595,44
24320
598.10
598.08
596.64
24650
593.78 I
598.77
608.01
24750
613.85
613.86
610.84
24970*
613.86
613.86
612.33
25490
612.33
" ;GoFfi Course Greek:
5444
600.55
597.96
5489
600.71
598.08
5607
609.11
598.20
5656
609.36
599.06
6035
609.41
605.34
6165
612.54
609.18
Limit of FEMA's Detailed Study
No corrected effective model was required
4.1.3 Marshall Branch Floodpiain Reclamation
Westlake development regulations limit the extent of flood plain
modification allowable with development. For this reason, this study does
not include extensive establishment of floodways along Marshall Branch
or its tributaries. The only existing floodway established on these streams
is shown on the current FEMA Flood Insurance Rate Maps between the
Lake Turner dam and SH-114. Calculations were made to modify this
floodway to account for dam and roadway reconstruction since the FEMA
models were completed. The modified floodway plan and model will be
included in the proposed Letter of Map Revision (LOMR) for Marshall
Branch. The only other floodplain reclamation areas considered were
88184501.R07
Page 18
those proposed within the approved Master Plan for Circle T Ranch. The
master plan shows modifications to Lake Turner and to the main channel
of Marshall Branch upstream of the Lee Tract,
Lake Turner is to be modified in several ways. Hillwood Development
Corporation proposed to modify the shoreline configuration, primarily in
the upstream channel portion of the lake that is adjacent to the proposed
mall site, and to deepen the lake by removing accumulated siltation. This
is proposed to enhance conveyance of flood waters with minimal
disturbance of the adjacent retail and commercial sites. The lake
reconfiguration will result in a decrease of flood plain storage volumes in
that reach of Marshall Branch. This decrease was offset in the regional
detention analysis described elsewhere in this report.
The other major reclamation area studied is the proposed relocation of
the creek upstream of the Lee Tract. The Circle T Ranch Master Plan
shows the stream to be relocated north and west to parallel State
Highway 170. The "channel" is included in the proposed regional
detention sites within this report. It is also planned as a mitigation site for
loss of waters of the U.S. The proposed cross-section of the relocated
stream consists of a 200-foot bottom with a meandering low flow channel.
4.2 KIRKWOOD BRANCH
4.2.1 FEMA Effective Conditions
The Kirkwood Branch watershed through the Town of Westlake consists
of Kirkwood Branch, an unnamed tributary through the Solana complex,
and Higgins Branch as well as several minor tributaries. Detailed studies
of Kirkwood Branch and Higgins Branch were completed by the Corps of
Engineers. Kirkwood Branch and an unnamed tributary were modified by
LOMR in 1991. Appendix D contains the effective models for Kirkwood
Branch and Higgins Branch. However, the FEMA library was unable to
provide detailed work maps indicating the location of individual cross
sections. Further inspection of the effective models revealed that detailed
study of Kirkwood Branch had only been completed to approximately
4000 feet upstream of Sam School Road. As a result, Kirkwood Branch,
the unnamed tributary through the Solana complex, and Higgins Branch
were re -modeled.
4.2.2 Existing Conditions
One -foot contour interval topographic information provided for this project
was used to determine cross section and lengths between cross sections.
Field visits throughout the watershed were conducted to determine
roughness coefficients along the waterways. Additionally, all bridge and
culvert structures were field inspected to verify dimensions and other
physical characteristics. This base information was entered into a HEC-
RAS model of the Kirkwood Branch watershed.
98184501.R07 Page 19
Peak flows throughout the watershed were calculated for the 5-, 10-, 50-,
and 100-year return period storm events. These peak flow values were
entered as flow profiles in the HEC-RAS model and the water surface
elevations under these storm event conditions were calculated. The
existing conditions 100-year storm floodplain was then plotted on the
topographic map of the watershed. A copy of the existing conditions
HEC-RAS model under existing and ultimate conditions is provided in
Appendix D. Table 9 shows the comparison of the 100-year water
surface elevations for the effective and existing conditions models for
Kirkwood Branch, Kirkwood Branch Trib., and Higgins Branch.
98184501.R07 Page 20
Table 9 - Comparative 100-Year Water Surface Elevations
For Kirkwood Branch
l , �;t!'�rB,S�gFn��t
CCu IcwAlraneM
� ��FS,�e�t�on
t�lu6er t FItAiotlel
16830
�Etftive-F�Ei �
E
-576.49
stiagvl��C RAS
IGlkrcet
16980
576.99
575.81
17180
577.57
576.66 !
17380
17580
577.99
578.56
577.19
577.80
17780
579.05
578.36
17980
579.51
578.91
18080
579.72
579.22
18247
585.02
18347
585.32
18350
582.79
18547
585.41
18575
i
583,42
18747
585.56
18947
585.82
19122
'
584.11
19147
_ 586.24
19347
i 586.65
19547
586.92
19617
587.41
19660
I 585.13
19667
586.86
19717
587.34
19747 i
588.31
19750
584.63
19858
585.34
19947
589.02
20147
589.89
i_ 20297J
590.86
20400
_
590.22
20510
592.93
20695 _
_
_
591.06
21120
591.92
21170
593.84
21385
592.06
21945
595.22
22000
595.31
22130
598.99
22165
597.24
22465
597.70
22645
597.87
22955
600.51
98184501.R07 Page 21
t
1
Se
!�
i
23000
601.10
23290
602.41
23140
603.03
i
23670
_
603.33 I
23740
605.37
24070
606.03
tilt iris 8ra�h
50260
591.92
50495
591.44
640
j 593.87
50820
593.64
51135
594.56
1500
597.73
_
51510
595.71
1900
599.67
1936
599.86
51940
598.08
52010
i 600.25
52170
600.55
Kirkwood'Tra4uta`_ , '�
1000
585.87
j
�_-- ---- 1-.
1060
585.87
1100
585.88
40115
585.50
1150
F 585.90
40190
i
585.49
1348
586.39
40390
585.49
1485
40545
1605
1706
587.79
588.91
- 590.74
586.56
40785
-
589.92 -
1890
591.69
_ 1925
40955
591.98
591.32
41025
592.44
2040
592.58
2125
593.67
41205 1
--1--
593.32
98184501.R07 Page 22
4.2.3 Flood plain Reclamation - Kirkwood Branch and Higgins Branch
This study included a floodway evaluation for Kirkwood Branch and
Higgins Branch. These creeks have a certain amount of development
pressure and also have extensive riparian vegetation and "natural areas".
Therefore, the study investigated the maximum encroachment that might
be allowed while preserving the "natural areas".
Kirkwood Branch
Kirkwood Branch does not have a designated FEMA floodway. Possible
encroachments were developed so that they would not encroach into
delineated wetland area and dense woods. Possible encroachments are
shown in three separate areas of Kirkwood Branch:
Cross Section 321+85 to 309+05
This section of Kirkwood Branch has scattered trees and narrow
channel banks. Encroachments are shown on both banks from
the limit of study to cross section 309+05. Encroachments were
not calculated further downstream so the pond would not be
impacted.
Cross Section 286+80 to 282+30
This section of Kirkwood Branch also has scattered trees along
the creek. Possible encroachments are shown on both banks
downstream of the existing lake and wetlands area to the city
limits of Westlake.
Cross Section 241+95 to 204+00
This section of Kirkwood Branch has dense woods along the
banks. The possible encroachments shown through these
sections are outside of these woods. There are also delineated
wetland areas within this section of proposed floodway.
Encroachments were not taken further downstream due to the
heavily wooded overbank area.
A copy of the proposed floodway HEC-RAS model for Kirkwood Branch is
provided in Appendix D.
Higgins Branch
Higgins Branch does have an existing FEMA floodway delineated from
the confluence with Kirkwood Branch to the end of the FEMA study, near
Randol Mill Road. The banks of this branch and overbank areas are
heavily wooded. The effective floodway was plotted on the new
98164501.R07 Page 23
topographic mapping. It was found to "miss" the creek in several places.
For this reason, a revised floodway was computed.
Encroachment analysis first used the existing FEMA floodway widths.
The proposed encroachments were then widened to limit impacts to the
trees. Aerial photographs and the natural resources map were used to
locate the extent of woods. The floodway width at cross section 502+60
was increased from the FEMA floodway to tie into the proposed floodway
for Kirkwood Branch. The floodway location was further adjusted to meet
the existing creek and to limit future disturbance of environmentally
sensitive areas. No floodway modifications were made south of Dove
Road.
A copy of the proposed floodway HEC-RAS model for Higgins Branch is
also provided in Appendix D.
6.0 REGIONAL DETENTION ANALYSIS
5.1 MARSHALL BRANCH/GOLF COURSE CREEK
The hydrologic analysis outlined in previous chapters indicates a need for
regional detention to mitigate flow increases from ultimate development.
Therefore, an analysis of detention requirements was developed for on the
Marshall Branch watershed within the Town of Westlake, Several alternative
methods and locations were examined for mitigation of development impacts.
The analysis was accomplished in conjunction with a similar study for proposed
development on Circle T Ranch (CTR). Lake Turner, a large lake on Marshall
Branch, is located adjacent to US-114 along the north boundary of CTR and the
Town limits. Since the creek and its tributaries drain to and through Lake Turner
before discharging downstream through the Town of Trophy Club, this was used
as the control point for the detention analysis.
The analysis seeks to locate detention facilities such that peak flows downstream
of Lake Turner do not increase beyond the existing peak flows. The Town of
Westlake has development regulations that require consideration of detention for
the 5-, 10-, 50-, and 100-year design storms. Besides the design storms several
other factors have helped to determine proposed pond locations and sizes. Peak
flows should be managed where the stream flows from one major property to
another. This means that we also had to look at peak flows on Marshall Branch
and Tributary MB-3 where they leave CTR and enter the Lee property, upstream
of the proposed Mall site adjacent to Lake Turner.
Another consideration was the proposed mall site itself. The proposed
development plans call for limiting the rise of Lake Turner to the maximum extent
practicable. This can be accomplished if most detention is located along
Marshall Branch upstream of the mall, thus keeping the developed flow in the
channel as low as possible. Over -detention, detaining more than is required,
may be desirable if it helps to meet the mall reach objectives.
98184501.R07
Page 24
A final, but very important, consideration is whether or not detention is provided
for watershed areas outside of the Town of Westlake ( most of which is the CTR).
The total watershed of Marshall Branch to Lake Turner is 9.54 square miles (sq.
mi.). Of this, 5.39 sq. mi., or 62% of the watershed, is upstream of CTR and
other portions of the town of Westlake. The question is then whether or not the
proposed detention will be watershed based and detain peak flows from all future
development or regionally based and provide detention for CTR and Westlake
development. For this study, regional detention facilities are designed to
compensate only for development within the Town of Westlake. Append& B -
Exhibit 12 shows the proposed location of all detention facilities mentioned in the
following paragraphs.
An existing pored on stream MB-3 was chosen as the detention location on that
stream. The stream requires detention from proposed CTR and Westlake
development as it drains into the Lee property before joining Marshall Branch.
The pond was sized to control all four design storm discharges. Detention on
Paigebrook creek, which drains to the eastern arm of Lake Turner, is projected to
have limited detention needs. The mall constraints dictated maximizing detention
on Marshall Branch and making up the difference on Paigebrook creek. As a
result, detention for the 5- & 10-year storms, only, is proposed on the existing
lake, Dove Pond, just upstream of Lake Turner.
The analysis consisted of locating detention to best attenuate ultimate (fully
developed) flows. Again the aim was to provide over -detention on Marshall
Branch to reduce flows in the proposed Mall reach to the maximum extent
practicable. We also tried to take advantage of the proposed CTR Master Plan.
Detention was first sited on Marshall Branch upstream of a crossing of the
proposed Westlake Parkway. The dry detention facility would encompass the
proposed golf course and the outlet structure would be a restricted size bridge
opening. The backwater created behind the Westlake Parkway bridge provides
the majority of all detention requirements.
Another obvious location for detention is within the proposed channel where
Marshall Branch is to be relocated adjacent to State Highway 170 between the
westernmost crossing of Westlake Parkway and the Lee tract. The creek
channelization is proposed to be overly wide due to considerations related to
Section 404 (wetlands/waters of the U.S.) Permitting. The bottom width of the
channel is proposed to be 200 feet ± with a top width of about 300 feet. Two (2)
roads are proposed to cross the channel, Roanoke Road and Westlake Parkway.
Detention is proposed within the channel section by restricting the bridge
structures at both crossings. This will allow temporary backwater up to 9 feet
deep in the channel.
In this study the efficiency of the combination of ponds described above and
shown on Exhibit 1 was examined. It has been found that the detention
necessary to attenuate the 5-year storm also works on the 10-year storm
because the peak flows are relatively close. Similarly, providing detention for the
100-year storm also attenuates the 50-year storm. The Marshall Branch HEC-1
98184501.R07 Page 25
5.2
models with detention are included in Appendix C. Table 10 shows the study
results.
Marshall Branch �
Upstream of SH-114 1 11,328
i
14,221
10,645
Upstream of Lee Tract ! 5,850
8,575
5,763
Golf Course Creek
Upstream of SH-114
808
926
776
For the 100-year conditions the existing peak flow values are compared to
discharges for the two study conditions at several key locations. The first study
condition assumes that the entire watershed is ultimately developed. The second
condition is one where the entire watershed is ultimately developed except for
non -Westlake areas within the 3.11 sq. mi. in subareas 32 and 34. In other
words, detention is provided for CTR, Westlake and other offsite areas not within
those two subareas.
The results indicate that the proposed ponds are necessary if detention is to
attenuate for the ultimate development of all property with the Town of Westlake.
The Table shows that, with all ponds, the 100-year storm has been adequately
reduced at the key locations; upstream of the Lee Tract and below Lake Turner.
The "Detention/Offsite Existing" condition, however, does not provide detention
for the offsite, upstream, communities of Keller and Fort Worth that make up most
of subareas 32 and 34, It assumes that they will provide detention such that the
peak flows do not exceed existing peaks. Under these conditions, the ponds
located wholly within the proposed Circle T Ranch development are adequate to
fully attenuate ultimate flows for the regulatory design storms. The remaining
detention provided still includes 2.79 sq. mi. of watershed areas outside the
Westlake town limits.
KIRKWOOD BRANCH
Several alternatives were considered as part of the detention analysis for this
Kirkwood Branch and its tributaries. The objective was to detain flows to match
post -development peak flows to pre -development peak flows for the 5-, 10-, 50-,
98184501.R07 Page 26
and 100-year storm events within the Kirkwood Branch watershed upstream of
SH-114. As part of this analysis, the existing and ultimate development
conditions models were used.
From the land use and drainage area maps, it is apparent that, with the exception
of sub -area 15, areas outside of the Town's corporate limits represent a small
fraction of the drainage basin. Therefore a detention alternative was sought that
effectively protects properties within the corporate limits of the Town yet does not
require the Town to detain more runoff that it generates. This hydrologic model
was developed assuming that the Kirkwood Branch watershed is modeled under
ultimate development conditions with the exception of sub -area 15 which remains
under existing development conditions. Sub -area 15 lies within the Town of
Southlake.
The results of this detention analysis indicated that it would be necessary to
provide approximately 57 ac--ft of detention storage in two locations within the
watershed. The first consists of an existing stock tank with a modified outfall
structure located at the junction of sub -areas 18 and 19. This location was
selected in order to reduce peak flows originating from within the town of
Westlake, routed through a short section within the town of Southlake, to pre -
development levels. This detention facility was modeled to provide approximately
40 ac•ft of storage.
A second location was selected at the downstream end of sub -area 8 in another
existing stock tank located upstream of Dove Road. This location was selected
because the stock tank is existing and significant changes in flow are expected to
occur between pre and post development conditions in this sub -area. This
detention facility was modeled to provide approximately 17 ao-ft of storage.
The final HEC-1 models used to calculate the peak flows are included in
Appendix C. Appendix B - Exhibit 92 indicates the location of the two
detention facilities.
Combined, these two detention facilities are capable of detaining peak flows such
that the peak flow calculated at SH-114, under ultimate development conditions
throughout the portions of the watershed within Westlake, does not exceed that
calculated under existing conditions. Table 11 indicates the flow comparisons of
the regulatory storm events. The final HEC-1 model used to calculate the peak
flows is included in Appendix C.
98184501.R07 Page 27
Table 1-1 - Flow Comparison Westlake Proposed Detention -
Kirkwood Branch
f Refurh Iriterval.
Peak Flbw at 'SH 114
Stdrm
.
(years):
Effirrctive-Existing
Ultimate
Detention
FEMA
, Conditions
# Conditions_(1&
Existing)`
,
(cfs�)
f` . leis)
-487
ice)`
'
I 1692
(cfs)
I
1460
10
, 2'14-1 i
2471
2090
50
4257
4815
4230
100
I
WOO
51-00 �
5907
5262
6.0 MAJOR ROADWAY CROSSINGS
The study included an analysis of existing and proposed major road crossings in
Westlake. In general, it was found that existing culverts and bridges are not sufficiently
large enough to convey the '100-year design storm flows. The exceptions are the
bridges and culverts under SH•-114. in all cases SH-114 will convey ultimate 100-year
discharges.
Analyses were made using standard homographs and/or computer programs that
calculate structure sizes for normal flow conditions. Culvert & bridge design are based
on Westlake drainage design criteria with adequate freeboard below proposed road or
bridge low chord elevations. The results of these analyses are shown in Table 12.
W8 501.R01
Page 28
Table 12 - Structure Comparisons at Existing and
Proposed Road Crossings
Crjeek
LocatrommStrud�rre
�xrst T
�, r�S1pa�u
P�opased Strucfure
Marshall Branch
Westlake Parkway Crossing
` None
50' Bridge
West of Roanoke Road
'
Old/New Roanoke Road
5-7'X6' Skewed
100' Bridge with
Crossing
Multiple Box Culverts
80' Bottom width
Westlake Parkway Crossing
None
100' Bridge with
East of Roanoke Road
80' Bottom width
Westlake Parkway Crossing
None
500' Bridge
at Proposed Mall
f
New Road - Trophy Lake Drive
None
300' Bridge
at West Side of Proposed Mail
Paigebrook Creek
Westlake Parkway Crossing i
South of Lake Turner
None
4-10'x10' MBC (min)
350' Bridge proposed
Road Crossing at Dove Road
3-6'x4' Multiple Box
3-12'x8' Multiple Box
Upstream in Tributary
Culverts (MBC)
Culverts (MBC)
i Golf Course Creek
Dove Road Crossing
Upstream in Tributary
2-5'x3' Multiple Box
Culverts (MBC)
2-10'X6' Multiple Box
Culverts (MBC)
Kirkwood Branch
Sam School Road Crossing
7-10'x10' Multiple Box
7-10'x10' Multiple Box
Culverts (MBC)
Culverts (MBC)
Dove Road Crossing
2-36" Corrugated
4-10'x6' Multiple Box
Higgins Branch
Kirkwood Branch
Unnamed Tributary
Dove Road Crossing
Dove Road Crossing
Metal Pipe
4-7'x4' Multiple Box
Culverts (MBC)
2-24" RCP Protruding
from the fill
Culverts (MBC)
4-10'x6' Multiple Box
Culverts (MBC)
2-9'x6' Multiple Box
Culverts (MBC)
7.0 MAJOR PERMITTING ISSUES
The following paragraphs outline permitting and regulatory issues that are important for
development along or across existing flood plains. The information provided is not
intended to be comprehensive but rather informative, Regulations may be modified in
the future, therefore, it is the responsibility of the designer to verify which regulations and
permits are required for the particular project.
7.1 SECTION 404 OF THE CLEAN WATER ACT
Selected land development within the limits of the Town of Westlake may be
subject to regulation under Section 404 of the Clean Water Act. Section 404
98184501.RO7 Page 29
permits are required when there is a discharge of dredged or fill material into
waters of the U.S. Examples of activities that may require a permit include the
construction of roads, buildings, residential areas, utility lines, and other
developments within, crossing, or directly impacting any waters of the U.S..
Permits are also required for the modification of ponds, streambeds or wetlands
for flood control, maintenance or aesthetic reasons.
Section 404 permits are processed and issued by the U.S. Army Corps of
Engineers (USACE) and may be authorized under one of the following permits:
Nationwide General Permits, Regional General Permits, Individual Permits and
Letters of Permission. Nationwide general permits are designed by the Chief of
the USACE to regulate specific activities having minimal impacts with little delay
or paperwork. Regional general permits are similar to the nationwide permits but
are authorized for specific geographical regions. Individual permits cover
projects and activities that have more than minimal impacts to waters of the U.S.
which must be reviewed on an individual project basis, require a public notice
period, and typically require a longer period for processing. Letters of Permission
are a type off individual permit issued through an abbreviated process which
includes coordination with various government agencies, but does not include a
public notice. Generally, development within waters of the U.S. in the Town of
Westlake will most likely require nationwide or individual permits. Ultimately, the
type of permit depends on the amount of impacts to jurisdictional waters.
Waters of the U.S. regulated by Section 404 include rivers, streams (including
perennial, intermittent and ephemeral), bogs, sloughs, lakes, ponds (including
stock tanks connected to other jurisdictional waters) and wetlands. The
jurisdictional limits of these water bodies are determined using the ordinary high
water mark (OHWM). Wetlands are defined by their OHWM and must meet the
three following parameters: 1) Contain hydric soils, 2) Have at least 50% or more
of hydrophytic vegetation and 3) Contain the necessary hydrology, which means
that they must be saturated or inundated at lest 5% of the growing season.
Determination of the jurisdictional status of a wetland, swale, tributary, creek, or
pond is essential in order to know whether or not a permit is necessary for the
proposed activity.
It is the responsibility of the designed to contact the Corps of Engineers for a
deten-nination of impacts to waters of the US and to verify the current regulations
applicable to the proposed activity.
7.2 FEMA FLOODPLAIN REGULATIONS
The Town of Westlake is a participant in the National Flood Insurance Program
(NFIP) administered by the Federal Emergency Management Agency (FEMA).
FEMA has issued Flood Insurance Rate Maps (FIRM) that delineate designated
flood hazard zones. Portions of Westlake are included on Denton County and
Tarrant County FIRMs. The current maps show that most of the town hazard
zones are unstudied. This Master Drainage Study includes detailed modeling of
all the FEMA designated streams. The town may use this data to prepare Letters
96184501.R07 Page 30
of Map Revision (LOMRs) changing the limits and designation of studied
waterways.
Development along and/or within a designated flood 'hazard zone is regulated by
town ordinance and federal regulations. Flood hazard zones may be modified by
map amendment or revision. Project engineers are cautioned to consult the
regulations, City Engineer, and FEMA to determine what the flood zone impacts
may be and whether or not a map revision will be required. Depending on the
type of flood zone on the portion of waterway impacted, determination of
minimum finished floor elevations for proposed structures may be required.
7.3 TNRCC WATER APPROPRIATIONS REGULATIONS
Texas Natural Resource Conservation Commission (TNRCC) is the state agency
which regulates and appropriates surface water on state waters. There are
several existing lakes and ponds within the Town of Westlake which are subject
to regulation by TNRCC. Ponds, smaller than 200 ac ft in volume, that are
constructed and used for agricultural purposes are exempt from most regulatory
constraints. When development occurs, the status of existing ponds changes.
TNRCC requires a Water Appropriation Permit for all non-agricultural
impoundments of state water. Existing ponds of less than 200 ac ft may qualify
for permitting under one of two possible exemptions to allocation of water rights.
Water rights within that portion of the Trinity River Basin that includes the town of
Westlake have all been allocated. New impoundments on state waters must
obtain approval for transfer of rights from one or more current owners of those
rights prior to application for water rights
TNRCC should be contacted for information, instructions and permit application
materials prior to development and/or construction of any permanent
impoundment of surface water within the town limits.
7.4 TNRCC DAM SAFETY REGULATIONS
TNRCC also regulates dams that may be constructed for impoundment,
temporary or permanent, of state waters. Dam safety criteria vary according to
size of impoundment and height of dam. The design storm for dam safety is
measured in terms of some portion of the Probable Maximum Flood, dependent
on the reservoir and structure size. The analysis involves an examination of
flooding levels downstream of the dam in non -breach, barely overtopping, and
breach conditions. In general, any dam which exceeds 6 feet in height is subject
to state regulation even though they are not required to review and approve
every dam. Dam safety calculations and modeling will be reviewed when
submitting an application for a Water Appropriations Permit. If a Water permit is
not required, it is still the designer's responsibility to ensure that the dam in
question complies with the state dam safety criteria.
98184501.R07 _ Page 31
7.5 NPDES PHASE it STORM WATER PERMITTING
On December 8, 1999, EPA released new rules which will require most smaller
cities located in urbanized areas to obtain NPDES permits for their storm water
discharges. Although the Town of Westlake is not listed on EPA's reference list
included with the regulatory release, the town would appear to meet the threshold
criteria required for permitting.
The Phase 11 rules require affected cities to implernent 6 minimum control
measures designed to improve the quality of stormm water runoff within the town.
These 6 control measures include the following:
Public Education and Outreach on Storm Water Impacts
Public Involvement/Participation
Illicit Discharge Detection and Elimination
Construction Site Storm Water Runoff Control
Post -Construction Storm Water Management in New Development and
Redevelopment
Pollution Prevention/Good Housekeeping for Municipal Operations
Permit applications (or General Permit notices of intent) are due to TNRCC (as
the permitting authority for Texas) by March 10, 2003 and may be required
sooner depending on TNRCC's rule implementation schedule. Municipal
programs must be fully implemented within 5 years of permit issuance.
Certain elements of this plan will meet some of the requirements of the NPDES
Phase II regulations. Existing city storm water and flood plain ordinances meet
much of the intent of the new regulation.
Adjacent municipal jurisdictions included on EPA's reference list include Keller,
Denton County and Tarrant County. The City of Fort Worth is included in EPA's
Phase I storm water program.
It should also be noted that the Phase 11 rules remove the so-called ISTEA
exemption that temporarily postponed the need for small cities to obtain NPDES
storm water permits for City -owned or sponsored construction projects.
8.0 COORDINATION WITH ADJOINING JURISDICTIONS
This drainage study has identified issues which impact the town of Westlake that may
result From runoff in upstream jurisdictions. Several waterways studied herein originate or
flow through Fort Worth, Keller, and/or Southlake before entering Westlake.
Development policies in these communities can impact the flooding potential on these
streams. For instance, this study suggests that the greatest impact to Marshall Branch
peak flows under ultimate development conditions is due to increased runoff projected
within the subareas in Keller and Fort Worth.
Similarly, flood management decisions within Westlake can and will impact both Trophy
Club and Southlake. Proposed regional detention facilities will mitigate future impacts. A
98184501.R07 Page 32
positive impact identified in the study for Trophy Club is the significantly reduced
discharges on Golf Club Creek due to the existing lakes on the Fidelity property.
It is in the town's best interest to seek coordination and cooperation with these adjoining
communities particularly in terms of detention requirements to mitigate future
development impacts.
98184501.R07 Page 33
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TOWN OF WESTLAKE Del-orme Atlas Maps,
Carter., IgurgS 023 Tarrant and Denton Counties, Texas 5.0
Conzilanis in Planning, Engineering, Archileclure,
Con Irticlion Monagerneni, and Reloled Services C&B Project No. 981845010
a
APPENDIX A - WATER RESOURCES ASSESSMENT
AND NATURAL ENVIRONMENT SURVEY
Water
Resources
Assessment
and
Natural
Environment
Survey
March 1999
Prepared for:
Water Resources Assessment The Town of
and Natural Environment Survey Westlake
981845011
3880 Hulen Street
CZ Carter= Burgess Fort Worth, Texas 76107
Consultants in Planning, Engineering, Architecture, 817-735-6000
Construction Management, and Related Services Environmental@c-b.com
WATER RESOURCES ASSESSMENT
AND
NATURAL ENVIRONMENT SURVEY
TOWN OF WESTLAKE, TEXAS
Prepared for:
The Town of Westlake, Town Council
3 Village Circle, Suite 207
Westlake, Texas 76262
March 1999
Prepared by:
Carter.= Burgess
Consultants in Planning, Engineering, Archileclure,
Construction Management, and Related Services
3880 Hulen Street
Fort Worth, Texas 76107-7254
(817) 735-6000
C&B Number 981845011
WATER RESOURCES ASSESSMENT
AND
NATURAL ENVIRONMENT SURVEY
TOWN OF WESTLAKE
Westlake, Texas
TABLE OF CONTENTS
PAGE
I. INTRODUCTION....................................................
1
I( METHODOLOGY....................................................
2
III. NATURAL ENVIRONMENTAL RESOURCES .............................
3
IV. JURISDICTIONAL WATERS OF THE U.S.................................
4
V. SOILS DESCRIPTION ...............................................
10
VI. RECOMMENDATIONS ..............................................
10
APPENDICES
APPENDIX A -SITE MAPS
APPENDIX B - PHOTOGRAPHS
APPENDIX C - JURISDICTIONAL WATERS OF THE U.S. MAP
APPENDIX D - MAPS OF NATURAL RESOURCE AREAS
INTRODUCTION
A reconnaissance of the Town of Westlake was undertaken to identify valuable natural
areas and natural resource constraints within the Town of Westlake (Appendix A,
Exhibit 1). Site visits by field biologists from Carter and Burgess, Inc. were comprised of
two major components: identifying quality natural landscape features and determining
the general limits of the jurisdictional waters of the United States. This report contains a
summary of these findings and includes the results of a similar survey conducted on the
property of Circle T Ranch.
The natural resource component of this study identified and assessed the quality of
major landscape features such as native oak woodlands, riparian protected corridors and
significant wetland areas. In the field, observations were made to include any wildlife
habitat such as nesting sites for migratory birds. By determiding-the presence and
quality of such areas, the necessary information is available for the Town to make plans
that integrate preservation into development. In an area where commercial and
residential growth is at an unprecedented high, looking at these aspects will promote the
Town of Westlake as an environmental forerunner. It also will establish a favorable
precedent for surrounding communities to make natural area preservation a priority.
The second component of this study was to determine the general limits of jurisdictional
waters of the United States. Examples of jurisdictional waters include rivers, streams,
lakes and ponds connected to another jurisdictional water or a navigable water (water
used in interstate commerce) and have a definable bed or bank produced by the
presence of water. Wetlands are also considered as jurisdictional and are therefore also
subject to regulation. In general terms, in order to alter a creek, pond or wetland that is
jurisdictional, a permit must be filed and issued from the United States Army Corps of
Engineers (COE). These permits are based upon areas and length of stream impacted.
A more detailed explanation of this topic and the necessary permits is included in the
Master Drainage Study.
The Town of Westlake (Appendix A, Exhibits 2-4) spans both Tarrant and Denton
counties and is located along State Highway 114 (S. H. 114) and east of S. H. 377. Land
use ranges from natural areas, cattle ranching and cultivation to residential and
commercial development.
98184501.R02 Page
METHODOLOGY
Identification of quality natural landscape features included site visits where property
access was allowed. Site visits were used to identify vegetation, locate valuable wildlife
habitat and observe any wildlife present. These visits were supplemented by using
aerial photography to create a map of an overall view of these features.
The general jurisdictional waters determination was conducted by Carter and Burgess,
Inc. A map of jurisdictional waters, with characteristics and locations, has been prepared
to assist in overall planning. Recently, a full delineation of all the jurisdictional waters on
Circle T Ranch property was completed by Carter & Burgess Inc. Therefore, the Circle T
Ranch information in this report includes the detail necessary for site specific planning.
Jurisdictional waters include rivers, strearns (including perennial, intermittent and
ephemeral), bogs, sloughs, lakes, ponds (including stock tanks connected to other
jurisdictional waters), and wetlands. The jurisdictional limits are determined using the
ordinary high water mark (OHWM) for each of these water bodies.
Wetlands are those areas that are inundated or saturated by surface or ground water at
a frequency and duration sufficient to support, and that under normal circumstances do
support, a prevalence of vegetation typically adapted for life in saturated soil conditions
(as defined by the COE and U.S. Environmental Protection Agency ].
Wetlands were delineated using the criteria from the 1987 COE Wetland Delineation
Manual (COE '1987 Manual). Wetlands must contain three parameters under normal
conditions to be identified as jurisdictional. These three criteria include the presence of
(1) hydric soils, (2) hydrophytic vegetation, and (3) wetland hydrology.
Hydric soils have been defined as soils that are saturated, flooded, or ponded long
enough during the growing season to develop anaerobic conditions that favor the growth
and regeneration of hydrophytic vegetation (as defined by the Natural Resources
Conservation Service (NRCS) and amended by the National Technical Committee for
Hydric Soils].
Hydrophytic vegetation is defined as the macrophytic plant life that occurs in areas
where the frequency and duration of inundation or soil saturation produce permanently
or periodically saturated soils of sufficient duration to exert a controlling influence on the
plant species present (COE 1987 Manual). In order to facilitate wetland delineations,
plant species have been categorized according to their wetland indicator status. These
categories consist of obligate wetland plants (OBL), facultative wetland plants (FACW),
facultative plants (FAC), facultative upland plants, and obligate upland plants. In order
for a site to be classified a wetland, 50 percent or greater of the dominant plant species
on the site have to be FAC, FACW, or OBL.
The third and final criteria for a site to be determined a wetland is wetland hydrology. A
site must be periodically inundated or saturated at the soil surface during some portion of
98184501.R02 Page 2
the growing season. The growing season is generally defined in NRCS soil surveys as
xost-free days.
Certain portions within the Town limits were surveyed using a Trimble Global Positioning
System (GPS) to determine the location of bodies of water with sub -meter accuracy.
This was especially useful in mapping Marshall Branch and its many tributaries near
S. H. 377.
III. NATURAL ENVIRONMENTAL RESOURCES
The Town of Westlake is located in the Cross Timbers and Prairies vegetational area of
Texas as described in Manual of the Vascular Plants of Texas (Correll and Johnston,
1979). undisturbed land within this vegetational area will typically contain post oak
(Quercus stellata), blackjack oak (Q. marilandica), mesquite (Prosopis glandulosa),
cedar elm (Ulmus crassifolia), sugar hackberry (Celtis laelfigata), and pecan (Carya
iilinoensis).
The majority of the vegetation of the Town of Westlake has been modified from its
original oak forest system to create suitable areas for pasture, cultivation, commercial
and residential development. Remnant forest stands of post oak, black jack oak, pecan
and elm (Ulmus spp.) are scattered throughout and have been maintained along many of
the waterways and ponds (Appendix B, Photograph 1). The following section of this
report will highlight significant natural resources (Appendix C, Key Map 2) identified in
the survey.
Wetlands
Large low lying areas to the west of Roanoke Road along Marshall Branch encompass a
patchwork of wetlands and small tributaries (Appendix B, Photograph 2; Appendix C,
Sheet 1 and 2). Isolated wetlands and fringe wetlands associated with ponds in this
wetland complex have created a prime environment for observing migratory song birds,
waterfowl, raptors and wildlife. This area offers a unique scrub habitat with protection for
species of song birds and an ample prey base for the raptors nearby. Another distinct
and diverse wetland is located to the north of the pond on the Fidelity Investment tract
along Golf Course Creek (Appendix C, Sheet 13) and the wetland along the
southernmost pond of Kirkwood Branch(Appendix C, Sheet 11) were mapped as fringe
or seep wetlands. A detailed account of wetlands determined through site visits is
included in Section IV of this report.
Hardwood Forests
The most contiguous and established hardwood forests (Appendix B, Photograph 3;
Appendix C, Sheet 13,16 and 17) are contained on the private property of Fidelity
Investments and MacGuire Properties. Dominated by post and blackjack oak, these
tracts contain natural associations of pecan and black walnut (Juglans nigra). This type
of system typically supports a healthy wildlife population because of the many sources of
food from the trees. The size of these forest remnants is significant in reducing the
amount of edge effect and invasive species present in the system.
98184501.Ro2 Page 3
Wooded Stream Corridors
Notable areas with protective stream corridors are present on the southwest edge of
Turner Lake, the southern portion of Dove Road Tributary (Appendix B, Photograph 4;
Appendix C, Sheets 14 - 18), Golf Course Creek, and portions of Kirkwood Branch.
Although some of these creeks have been impacted by livestock operations, restoration
would be minimal due to already present large trees. Wooded stream corridors are
important to reduce the amount of erosion, maintain water quality, and provide
necessary cover for wildlife.
Migratory Bird Nesting Areas and Endangered Species
No endangered or threatened species or their habitat, specific to Tarrant or Denton
counties, was observed within Westlake town limits. A pair of red-tailed hawks (Buteo
}amiaicensis) were observed south of Dove Road, near Dove Road Tributary (Appendix
C, Sheet 18) and appeared to be guarding a territory or possibly a nesting site. Egret
(Bubul'cus ibis) and heron (Ardaa herodias) nesting sites have been noted in the past at
Wetland R (Appendix C, Sheet 6). Although many migratory birds are not protected by
the Threatened and Endangered Species Act, their nesting sites are protected
underneath the Migratory Bird Treaty Act during breeding and nesting season.
IV. JURISDICTIONAL WATERS OF THE U.S.
The Town of Westlake was surveyed to determine the status and characteristics of
waters of the U.S. within the town limits. Creeks, tributaries, ponds and wetlands
considered to be within jurisdictional limits of the U.S. were verified (Appendix A,
Exhibit ,). A map of the waters of the U.S. has been created using existing maps and by
applying information collected with the GPS system (Appendix C). Each body of water
has been labeled with an identifier (A, B, C, etc.) and described in the following text.
Circle T Ranch is addressed separately, as it was contained within its own study.
Marshall Branch (Appendix C, Sheets 1 and 2)
Marshall Branch (Appendix B, Photograph 5) bisects the western portion of the ranch
from north to south with an OHWM ranging from 6 to 50 feet, with an average of 15 feet.
This intermittent creek is joined by seven main tributaries and numerous smaller
tributaries. Perennial pools (Appendix B, Photograph 6) are naturally distributed along
its length, which seem to support a variety of wildlife. Evidence was found of large
snapping turtles (Chelydra serpentine serpentina), red -eared sliders (Trachemys scripta
elegans), fresh -water mussels, beavers (Castor canadensis) and several species of
snakes. An abundance of field mice were observed during field surveys, as well as
many hawks, owls and song birds.
Marshall Branch is open with relatively little tree cover except for a region of large
American elms (Ulmus americans), green ash (Fraxinus pennsylvanica), sugar
hackberry and Bois d'arc (Maclura pomifera) which is located in the portion west of
Roanoke Road to the south (Appendix B, Photographs 7 and 8). The rest of the banks
are open with some small individual cedar elm and sugar hackberry trees. Wetland/
riparian vegetation found on the creek includes black willow (Sa/ix nigra), water willow
98184501.RO2 Page 4
(Justicia americana), rattlebush (Sesbania drummondii), cattails (Typha spp.),
switchgrass (Panicum virgatum), spike-rush (Eleocharis spp.), common cocklebur
(Xanthium strumarium), sumpweed (Iva annua), balloonvine (Cardiospermum
halicacabum), umbrella sedge (Fuirena simptex) and other sedges (Cyperus spp.).
Numerous small tributaries with defined channels and associated wetland plant species
occur along the creek. These have been added to the total area and length of Marshall
Branch. Tributaries that have been added to this category are those that have a length
less than 550 feet and have similar vegetation. Several wetlands are present in the low
areas adjacent to Marshall Branch and its tributaries that are described in the wetland
section of this report.
Marshall Branch (Appendix C, Sheet 3)
The channel in this section was bare of trees although a few black willow saplings are
growing along the tributary channel. There is an additional drainage (a tributary across
S.H. 170) north of Marshall Branch. This tributary to Marshall Branch appears to have
been modified during the construction of S.H. 170. The streambed between S.H. 170
and Marshall Branch has been channelized and is heavily vegetated with cattails. All the
area dominated by hydrophytic vegetation is within the OHWM of the channel and is thus
a water of the U.S. but not a wetland.
Creeks and Tributaries
The main tributaries and creeks discussed in this report empty into Marshall Branch or
Kirkwood Branch. Marshall Branch tributary #3 and Marshall Branch tributary #8
M133 - MB8 are tributaries of Marshall Branch. Dove Road tributary connects with
Marshall Branch at Pond S1 (Turner Lake), which ultimately leads to Grapevine Lake.
Kirkwood Branch lies to the east of the property.
Tributary MB8 (Appendix 8, Photograph 9; Appendix C, Sheet 1) is a large tributary
that enters from the southern property boundary and runs parallel to Marshall Branch
prior to their confluence. This creek has natural meanders along most of its length with a
few portions that seem to have been channelized in the past. The OHWM ranges from
3 to 10 feet with an average of 6 feet. The main channel depth ranges from 1 to 4 feet
with an average of 3 feet. It is sparsely covered with trees along the channelized
portions and cedar elms provide the main canopy along the remainder of the creek. Two
smaller tributaries empty into this creek. The sub -tributary to the southeast has a wide
shallow channel with heavy vegetation such as switchgrass, spike-rush, umbrella
sedges, and various other sedges. Common herbaceous vegetation along the other
tributary and the main branch of M68's earthen channels include switchgrass,
sumpweed and common cocklebur.
Tributary MB7 (Appendix C, Sheet 1) which originates in the southwest corner of the
Circle T Ranch has been channelized and receives water from culverts under S.H. 377
and fields to the north and the south. The streambed alternates between a limestone or
earthen channel, sand deposits, and an approximate 900-foot span where the channel is
similar to wetland fringe. Vegetation along the tributary consists of black willow, spike-
rush, sumpweed, common cocklebur and goldenrod (Solidago spp.).
98184501.R02 Page 5
Tributary MB6 (Appendix C, Sheets 1 and 4) begins east of Roanoke Road below the
wetland seep N1. It flows through Bermuda grass as a small channel until it widens into
the man-made Pond M. The other portion of MB6 that is free -flowing is between
Wetland G and Pond F with a small channel averaging 4 feet across.
Tributary M135 (Appendix B, Photographs 10 and 11; Appendix C, Sheet 2) is almost
identical to MB7. It includes only a small wetland fringe area (approximately 100 feet in
length), where the artificial channel ends to the east. There is a pool/holding area where
MB5 comes from S.H. 377 that includes several medium-sized black willow trees and
cattails (Appendix B, Photograph 12).
Tributary MBSA (Appendix C, Sheet 2) is another channelized tributary. It seems to
receive much less water than MB5 and MB7 and its channel is surrounded by mesquite,
honey locust (Gleditsia triacanthos) and a grove of common persimmon (Diospyros
virginiana) trees. There is no direct connection from a culvert under S.H. 377.
Tributary MBSB (Appendix C, Sheet 2) consists of a very small holding pond (Appendix
B, Photograph 13) with spike-rush, sumpweed, dock (Rumex spp.) and common
cocklebur at its origin. This drains into a small tributary averaging 4 feet at the OHWM
with similar vegetation.
Tributary MB4 (Appendix B, Photograph 14; Appendix C, Sheet 3) flows west to east
from north of S.H. 170 has been completely channelized in the past. Wetland/ stream
vegetation present includes black willow trees at the culverts and cattails, sumpweed,
water willow, common cocklebur and goldenrod growing in the channel or up its banks.
Tributary MB3 (Appendix C, Sheet 5) is east of Roanoke Road in the main grazing land
of Circle T Ranch. Very little woody species were observed and the dominant
herbaceous species consisted of dock and spike -rushes.
Dove Road Tributary (Appendix C, Sheets 6 and 8) is located east of M83 and empties
directly into Ponds T1 and T2. Very little vegetation exists within the cut channel banks.
South of Dove Road, the creek has been modified to be held in two large ponds with a
cement spillway in between. Large cottonwood and American elm trees line the
tributary.
Tributary N2 (Appendix C, Sheet 4) is a small tributary that leads off the property and is
surrounded by bermuda grass. The channel is vegetated with various species of rushes
and sedges, spike -rushes and bushy bluestem (Andropogon glomeratus).
Ponds including stock tanks) and Wetlands
Pond A (Appendix B, Photograph 15; Appendix C, Sheet 1) is located in the
southwest corner of the Circle T Ranch and according to the Department of the Interior's
National Wetlands Inventory (NWI) maps (Appendix A, Exhibit 5), the pond qualifies as
a Palustrine-Unconsolidated Bottom -Permanently Flooded -Excavated (PUBHx) body of
water. This status was verified and vegetation at the pond included common cocklebur,
switchgrass, sumpweed, umbrella sedges and balloonvine.
98184501.R02 Page 6
Ponds 61 and B2 (Appendix B, Photographs 16 and 17; Appendix C, Sheet 9) are
two side by side ponds that have been excavated in the Marshall Branch channel and
are considered to be PUBHx. The ponds have steep banks vegetated with black willow
and rattlebush. Other wetland vegetation includes water willow, spike -rushes, and
balloonvine. Avian species present included a great blue heron.
Wetland C (Appendix B, Photograph 98; Appendix C, Sheet 1) is a shallow wetland
that catches the runoff from a cultivated field. it is bordered by a few large black willow
trees, with the herbaceous material comprised of spike -rushes, balloonvine and dock.
Pond D (Appendix C, Sheet 9) is a series of unclassified small ponds near a lowland
section of Marshall Branch that are bordered by spike -rushes and sumpweed.
Wetland E (Appendix B, Photograph 19; Appendix C, Sheets 9 and 2) is a long
wetland with small associated pockets that is affected by the hydrology of Marshall
Branch, especially from its overflow of a small tributary. No open water area exists, but
wetland vegetation and hydric soils confirm its status. Plants present are bushy blue -
stem, spike-rush, switch grass, soft rush (Juncus spp), and sedges.
Pond F (Appendix B, Photographs 20 and 21; Appendix C, Sheet 9) is an
unclassified body of water, with a manmade berm to the northwest side. It receives water
from M136 and the other ponds upstream. It is surrounded by a wetland fringe of
common cocklebur, sumpweed, switchgrass and spike -rushes. Mallard ducks (Anas
platyrhynchos) and a species of shorebird were seen on a site visit in November 1998,
Wetland G (Appendix B, Photograph 22; Appendix C, Sheet 1) is a seep resulting
from the impoundment of Pond H. Black willow trees are present, as well as spike -
rushes, sedges, common cocklebur and sumpweed.
Pond H (Appendix B, Photograph 23; Appendix C, Sheet ?) is classified as
Palustrine-Unconsolidated Bottom -Permanently Flooded -Impounded (PUBHh) body of
water. It is located directly west of Roanoke Road along MB6. Vegetation present
included large black willows, common cocklebur, cattails and sumpweed. A great blue
heron was observed at this pond.
Wetland I (Appendix C, Sheet 2) is similar in vegetation to Wetland G, but it is not
technically a seep, as it receives its hydrology from a culvert underpass of Roanoke
Road. It also is populated by common dock and the same species as Wetland G.
Wetland J (Appendix C, Sheet 2) is a shallow wetland similar to Wetland C. It receives
water from the cultivated fields to the west. It also had a large black willow tree marked
with a water line at its base.
Wetland K (Appendix B, Photograph 24; Appendix C, Sheet 2) is a large wetland that
receives its hydrology from field runoff and MB5. The vegetation is markedly different
than its surroundings of a few mesquite trees. The vegetation noted at the site included
spike-rush, switch grass, black willow, balloonvine, common cocklebur and sedges.
98184501.RO2 Page 7
Wetland L (Appendix C, Sheet 2) occurs at the confluence of tributaries M135 and
MB5A. A few small sugar hackberry trees were present at the edge of the area with
spike-rush being the dominant vegetative wetland species.
Pond M (Appendix C, Sheet 4) represents the two ponds directly east of Roanoke Road
along MB6 and are classified as a PUBHh. At the time of inspection the larger pond had
been recently cleaned and excavated with a large cottonwood remaining. Spike -rushes
were growing in the smaller pond.
Wetland N (Appendix C, Sheet 4) is a seep wetland on a hillside at the beginning of
MB6. It is surrounded by bushy bluestem and the interior contains spike -rushes, soft
rushes, bristle grass (Setaria sp.), smartweed (Persicaria spp.) and various species of
sedges.
Wetland Q (Appendix C, Sheet 5) is a wetland created from the runoff hydrology above
the area. Vegetation observed at this site included small black willow trees, sumpweed,
common cocklebur, and the same plant species listed for Wetland NI. Bermuda grass is
present as a planted invasive species.
Ponds P and Q (Appendix C, Sheet 5) are located along MB3 and is classified as
PUBHh. These ponds have wetland fringes along their shallow zones.
Wetland R (Appendix C, Sheet 6) seems isolated from the main lake by a small berm.
It is likely that water in the pond is renewed during high water events. Approximately
two-thirds of this pond is vegetated with water willow, rice cutgrass (Leersia oryzoides)
and swamp smartweed as dominant vegetation. Because the pond, including open
water areas, acts as a wetland system; the entire pond area, not just two-thirds of it, is
included as a wetland.
Pond S1 (Appendix C, Sheets 6 and 7) did have approximately 2.5 acres of fringe
vegetation dominated by swamp smartweed, spike-rush, and flatsedge. The fringe area
is technically a wetland and is listed as such in this report.
Waters S2 and S3 (Appendix C, Sheet 6) include the channels to the west of Pond S1.
These are heavily wooded and contain wetland vegetation confined to the channels.
Wetland vegetation in such a channel is likely to be transitory, washed away during
severe storms, so these vegetated areas are waters of the U.S. but not wetlands.
Pond T1 and T2 (Appendix C, Sheet 6) are primarily open water areas, even though
Pond T2 was dry during the site visits. These sections did not have any fringe wetlands
to speak of.
In general, the wetland areas in the eastern region were quite similarly vegetated.
Similar trees occur along the waterways in both the east and west portions of the ranch.
In most areas when the wetland vegetation began mixing with the Bermuda grass, the
wetland ended. Soils tested at the edge of the wetlands were invariably the mapped fine
sandy loam.
98184501.R02 Page 8
Pond U (Appendix C, Sheet 8) is classified as a PUBFx (Palustrine-Unconsolidated
Bottom -Semi -permanently Flooded -excavated) body of water according to the NWI map.
This pond is located at the top of a branch of Dove Road tributary.
Pond V1 and Wetland V2 (Appendix C, Sheet 9) is not wooded along its shores and the
wetland V2 is closely associated with the channel. An overflowing channel played a
large role in maintaining hydrology. Wetland vegetation observed at the site included
celery leaf buttercup (Ranunculus sceleratus), water hyssop (Bacapa spp.), soft rush
(Juncos effusus), and bushy bluestem.
Pond W (Appendix C, Sheet 10) had no fringe wetlands associated with it. The
drainage into this pond maintains a small wetland area before widening into the pond.
This channel also continues on to Pond X and its associated wetlands.
Pond X (Appendix C. Sheet 10) and its associated wetlands (X1, X2 and X3) contained
dominant vegetation species that were OBL or FACW species. Large trees provide
canopy for portions of the ponds and channels.
Pond Y (Appendix C, Sheet 11) and its associated wetlands (Y1 and Y2) included the
following dominant vegetation: soft rush, bushy bluestem, red -top panic grass (Panicum
rigidulum), common persimmon, southern dewberry (Rubes spp.) and Bermuda grass.
The persimmon was found in the tree or sapling vegetation layer. There is a large
wetland seep located to the northeast of this pond.
Stage Coach Road Tributary, found along Roanoke Road (Appendix B, Sheet 12),
ranges from a 4-foot deep winding channel forested with post and blackjack oaks and
sumac to a shallow open wetland channel with an OHWM of 20-feet. Wetland species
present include black willow, goldenrod, dock, bushy bluestem, spike -rushes and
cattails. A sub -tributary enters from Melissa Road with an OHWM that has been
channeled and altered to form two jurisdictional ponds along its length.
The Fidelity Investments tract (Appendix C, Sheet 13), contains large areas of
jurisdictional waters primarily associated with the larger tributary. Two large stock tanks
and two other impoundments are jurisdictional waters. In addition, the stock tank located
on the smaller tributary is jurisdictional. Finally, a small seepage wetland located down
gradient from a non -jurisdictional waters is located south of Dove Road.
A small wetland off Mahoeta Boone Trail and J. T. Ottinger Road is a seep from the pond
to the south. This wetland contains mainly cattails and black willows and is surrounded
by oak woodlands.
Kirkwood Branch and its tributaries (Appendix A, Photograph 25 and Appendix C,
Sheet 16) are characterized by large American elms, cottonwoods, and stream corridors
of post and blackjack oaks. The earthen streambed OHWM ranges from 6 to 25 feet
wide and becomes braided at the increased widths. Herbaceous riparian vegetation
found along the creek includes Chasmanthium spp. and other grasses. Unfortunately,
surveys of this creek were not in detail due to lack of private property access. A main
98184501.RO2 Page 9
tributary of Kirkwood Branch from the north has been channelized in some portions
through the Corporate Plaza off Kirkwood Boulevard. Portions of this tributary have
been left natural and contain black willow, cattails, and bushy bluestem.
Pond Z (Appendix C, Sheet 14) is located to the south of Dove Road in the pathway of
Kirkwood Branch. It is a large pond with a small seep on the northeastern dam wall.
Much of the shoreline is open with other areas of woody and riparian species.
Pond AA (Appendix C, Sheet 15) is a series of ponds constructed in the path of a
tributary to Kirkwood Branch. They are located north of Pond Z and have similar
attributes with varying tree cover and wetland fringe.
Pond AB and associated wetlands (Appendix B, Photograph 26 and Appendix C,
Sheet 17) are located south of S. H. 114 and to the east of Precinct Line Road. The
ponds and wetlands that receive water from hillside seeps have been altered in the past
but remain jurisdictional. Wetland species observed in the area include black willow,
cottonwood, smartweed, spike -rushes, sedges and cattails. In addition to the wetland
species, some prairie species are present on the adjacent uplands.
V. SOILS DESCRIPTION
The general soil types for this area are described as Crosstell-Gasil-Radar on the east
half of Circle T Ranch and Ponder -Sanger -Slidell soils to the west. No hydric soils as
defined by the Tarrant or Denton county Soil Surveys are found within the town limits.
Soil types and definitions presented in Appendix A, Exhibit 6 is a result of surveys
conducted by the U. S. Department of Agriculture, Soil Conservation Service in Tarrant
(1979) and Denton (1975) counties.
VI. RECOMMENDATIONS
Valuable woodlands, stream corridors and jurisdictional waters, including wetland areas
have been identified in the Town of Westlake. Many of these areas are contain quality
ecosystems that justify varying degrees of protection or preservation. Integrating these
areas into future development plans for the town is an attainable goal. Considerations
that need to be made include the quality of the natural area, the value of a particular area
to local wildlife and migratory species and the surrounding area.
The blackjack and post oak woodlands identified through this survey are quality
examples of an ecosystem that is becoming less common in the Dallas/Fort Worth
Metroplex due to complete removal, degradation and fragmentation of the forests. The
size of the woodlands in Westlake is important to maintain the system balance and
reduces the number of invasive species. Preserving these woodlands ensures seed
banks for native species to re -forest other areas in the future. It is also important to
retain the continuity between different woodland patches and stream corridors to offer a
means of protected travel for wildlife.
98184501.R02 Page10
The larger wetland areas described in this report support a large diversity of local and
migratory species. They provide a function of water cleansing as well as being areas of
high diversity. Maintaining these wetlands with ample buffer zones will allow them to
serve as a refuge in a developing area.
Wooded stream corridors identified in this survey help control erosion, maintain water
quality and offer future mitigation opportunities for diversity enhancement. In these
areas, large trees are already present. Riparian quality would benefit from planting native
shrubs and grasses underneath, and native tree species where many of the trees have
been removed.
98184501.R02 Page 11
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C&B Project No. 981845010
Photo #9
Tributary MB8
Photo #10 — View along Tributarj MB5
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C&B Project No. 98184501Q
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TOWN OF WESTLAKE Carter & Burgess, Inc.
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(817) 735 - 6000
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LEGEND
Wetland
Jurisdictional Pond j
T I'%..# Creek
D
N
m �
.......... Town Boundary
L
P
L 8
0
o
U
SHT. NO.
Carter:: Burgess -Jurisdictional Waters of the U. S. DATE ZS199
Town of Westlake DRAWN MBM 12
West Lake, TX DESIGNED
J013 NO. 98184501 CHEC ED PDM Appendix B
JbId40U1\4U4\dgn\VIIt)wIIZ.snt Mar. U5, 1999 Ub:b2:31
LEGEND
Wetland
4" Jurisdictional Pond
I'`r Creek
.............. Town Boundary
.......�-.. Circle T Ranch Bounda
Hardwood Forest
Unique
0 300 600 900
GRAPHIC SCALE IN FEET
I
C�3 Carter =Burgess Jurisdictional Waters of the U. S. aIEh
EEL 6nRGESSS,INC.9 Westlake, Texas
am.v mm
...\95184501\404\dan\9715w113.sht Mar. 05. 1999 08,40:42
LEGEND
Wetland
Jurisdictional Pond
I'`1 Creek
.......... Town Boundary
............ - Circle T Ranch Boundary
Wooded Stream Corridor
: -,z
\'
0 300 600 900
L
T
GRAPHIC SCALE. IN FEE
r
0
O �
U -
� SHT. NO.
Carter :: Burgess DATE �9
g Jurisdictional Waters of the U. S. DRAWN MBM
Conxulmna in Planning, Engmeonng, Archneome,
Conxrrvciion Mnnagem•ni and Reloied Sarvicex n
CARTER 8 BURGESS, INC. Westlake, � T
0880 HULEN BEET DESIGNED
FORT WORTH,TX 76107-7254
(017) 705 - 60M
ICHECKED PDM
IT
0 300 600 900
GRAPHIC 5 A E IN FEET
LEGEND
PI �O Wetland
Jurisdictional Pond
#0%4 Creek
.......... Town Boundary
•- - Circle T Ranch Boundary
Hardwood Forest
Jurisdictional Waters of the U. S.
�i� Carter ::Burgess DATE
Consultant: in Pl—ing, Engineedng, Archiree.-DRAWN
Con -01.n M... g-1 and Related 5-1—
CARTER & BURGESS, INC. Westlake, Texas
3880 HUIEN STREET DESIGNED
FORT WORTH,TX 76107-7254
)817) 735 - 60M
CHECKED-
MA
SHT. NO.
15
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-A ----------
Carter:: Burgess Jurisdictional Wafers of the U. S. DITE 3W9 SHT. NO.
CIC.—It-1, In PI... i,g, E,91—Ing, A,chiv.o— DRAWN MBM
C—An,cfi Mo—g—nt nd Roluf,d 5—i— 18
CARTER & BURGESS, INC. Westlake, Texas
3880 HULEN MEET` DESIGNED
FORT WORTH,
TX 76707-7254
(8171 735 - 6000
PDM
APPENDIX B - EXHIBITS
1) Natural Resource Constraints
2) Marshall Branch Drainage Area Delineation
3) Kirkwood Branch Drainage Area Delineation
4) Marshall Branch Soils Map
5) Kirkwood Branch Soils Map
6) Marshall Branch Existing Land Use Map
7) Kirkwood Branch Existing Land Use Map
8) Marshall Branch Proposed Land Use Map
9) Kirkwood Branch Proposed Land Use Map
10) 100-Year Floodplain Delineations Map
11) Detailed Floodplain Delineations Map - 200 Scale
12) Proposed Regional Detention Facilities
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