Item 7F - Wastewater Master Plan aid
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Mom. r4 PLAN
An lement o the Southlake Comprehensive Plan
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Adopted by the Southlake City Counci
Ordinance No. 1034A
April ##, 2026
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WAS - -WATER MASTER PLAN
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Comprehensive Plan
City of Southlake City Council
Mayor Shawn McCaskill
Mayor Pro Tern Randy Williams
Deputy Mayor Pro Tern Kathy ey
Councilmember Place 2 Rand bins
Councilmember Place 3 Fra s S li
Councilmember Place 4 in Reyn
Councilmember Place uc Taggart
Planning & Zoning Commissio idor Planning Committee
Chair Daniel Kubiak Kathy Talley - City Council
Vice Chair Mike Forman Randy Robbins - City Council
Commissioner Gina Cannov Austin Reynolds - City Council
Commissioner David Cunni am Frances Scharli - City Council
Commissioner Michael Spr r Daniel Kubiak - Planning & Zoning
Commissioner Stacy co Michael Springer - Planning & Zoning
Commissioner L David Cunningham - Planning & Zoning
Gina Cannova - Planning & Zoning
Mike Forman - Planning & Zoning
Magdalena Battles - Parks Board
Chad Patton - Ex-Officio
City of Southlake Staff
City Manager Alison D. Ortowski
Assistant City Manager James Brandon
Assistant City Manager Stacey Black
Chief Financial Officer Sharen Jackson
Interim Director of Public Works Lauren LaNeave
City Engineer Jeff Ginn
Director of Economic Development & Tourism Daniel Cortez
Director of Planning and Development Services Dennis Killough
Deputy Director of Planning and Development Services Jenny Crosby
Assistant to the Director Ryan Firestone
Senior GIS Analyst Jesus Gabriel
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Southlake's Wastewater Master Plan is the C' s long-r framework for managing,
operating, and reinvesting in the wastewater Coll on s stem as e community approaches
buildout. Like the City's other supporting master p i rves as a practical "knowledge base"
that documents existing conditions, establishes cle rvice expectations, and helps translate
Southlake's Comprehensive Plan vision int lemen le utility policy. The plan emphasizes
reliability, public health protection, regulator o ce, d lifecycle reinvestment shifting the
focus from primarily expanding infrastructure s and strengthening the system the City
already maintains.
The technical foundation for this n i by the Wastewater Modeling Study prepared
by Freese and Nichols, which ev d Sys performance under existing and future flow
conditions and identified e eather stress, inflow and infiltration (1/1), operational
constraints, and capacity itatio a fect levels of service. The modeling results, combined
with local system know e and o rational experience, support a data-driven understanding
of risk and performance. tech al basis helps the City prioritize improvements, focus 1/1
reduction where it preserve e st capacity, and coordinate investments with downstream
interfaces and regional partner
This Wastewater Master Plan is intended to be used as a policy and decision-making guide for day-
to-day utility management and long-term capital planning. It provides direction for establishing
and tracking levels of service, advancing asset management and renewal programs, guiding
development and redevelopment review, sequencing capital projects,and communicating program
priorities to residents and stakeholders. Ultimately, the plan equips the City with a consistent
framework to justify budgets and capital programming, improve transparency and accountability,
and ensure Southlake's wastewater system continues to support community quality of life and
long-term resiliency.
WASTEWATER MASTER PLAN
TABLE OF CONTENTS
PAGE CHAPTER
6 CHAPTER 1: INTRODUCTION
12 CHAPTER 2: WASTEWATER SYSTEM OVERVIEW
20 CHAPTER 3: WASTEWATER FLOWS
24 CHAPTER 4: HYDRAULIC WASTEW R MODEL UPDATE
28 CHAPTER 5: SYSTEM ANALYSI ND P ORMANCE
34 CHAPTER 6: WASTEWATER I STRUCTURE AND ASSET
MANAGEMENT
40 CHAPTER 7: RESILI CE, O AND INFILTRATION
REDUCTION, AN Y EM TEGRITY
44 CHAPTER 8: O , DEVELOPMENT AND SYSTEM
PROTECT
48 CHAPTER O UNITY ENGAGEMENT, PARTNERSHIPS, AND
FUNDING
52 CHAPTER 10: PLAN ADOPTION AND PUBLIC ENGAGEMENT
56 WASTEWATER MASTER PLAN POLICY STATEMENTS SUMMARY
58 GLOSSARY OF TERMS
62 APPENDIX A: FREESE AND NICHOLS WASTEWATER
INFRASTRUCTURE MODELING STUDY - EXECUTIVE SUMMARY
ORDINANCE
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Southlake's Wastewater Master Plan is the City's -ran olicy and planning framework
for managing, operating, and reinvesting in the was ater collec system as the community
approaches buildout. While much of Southlake's hi ric u ' ity focus as necessarily centered on
expanding infrastructure to support growth, the C stewater priorities increasingly reflect
a mature system environment, one where maintainin liability, managing risk, and reinvesting
in aging assets becomes the primary driver -term rformance. This plan provides a clear,
consistent foundation for decision-making th u e ellent service, protects public health,
and aligns infrastructure investments wi com e ctations.
Like the City's other supporting m r pl s, thi ocument functions as a "knowledge base" that
explains how Southlake manages to y and how the City will guide long-term, data-
driven decisions in the years ea e plan is supported by the Wastewater Modeling Study
prepared by Freese & Nic ides technical findings and performance insights under
existing and projected c tions. e ults combined with Southlake's operational knowledge,
prior planning efforts, an going gram experience help the City define service expectations,
identify system constraint d v erabilities, and prioritize improvements in a way that is
transparent, defensible, and a ith adopted policy direction.
BACKGROUND
The wastewater collection system is a critical public utility that protects public health and
environmental quality by safely conveying sanitary flows from homes, businesses, and civic
facilities to downstream treatment. In a built-out or near-built-out community, the wastewater
system's performance is shaped as much by ongoing reinvestment and system integrity as by new
infrastructure. Reliable collection depends on the capacity and condition of pipes, manholes, lift
stations, and force mains, as well as the City's ability to manage wet-weather response and reduce
inflow and infiltration (I/I) that can stress the system during storms. As a result, wastewater planning
is inherently tied to risk management reducing the likelihood of backups, overflows, and service
disruptions while maintaining predictable, cost-effective service over time.
Southlake's wastewater system is a network of local collection infrastructure that also relies on key
downstream interfaces and regional partners. For example, in the City's North Service Area (Denton
Creek Basin), flows are conveyed to a regional lift station and treatment system operated by TRA,
WASTEWATER MASTER PLAN
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iIIustrating how IocaIcoIIection performance an ow apacity work together to define overaII
reliability. This Wastewater Master Pla tabli he ity's planning and policy basis for those
decisions. It documents existing co o su arizes technical analysis, and translates system
needs into implementable directi at pport udgeting, capital programming, maintenance
priorities, and development coor ti hnical foundation for this plan is informed by
the wastewater modeling eff re d by Freese & Nichols, as well as prior plans and studies,
including the City's 2012 W M r Plan, flow monitoring and system evaluation work, and
key program milestones t have s e urrent operating conditions and system understanding.
PLANNING CONTEXT: NE A G B DOUT
As Southlake nears buildout, astewater planning shifts from primarily adding capacity to
strategically sustaining performance. This transition requires a stronger emphasis on stewardship:
reinvesting in aging infrastructure, maintaining reliable service levels during wet-weather conditions,
and managing system risk using data-driven tools. In practical terms, this means prioritizing renewal
and rehabilitation where condition and criticality indicate higher risk, using modeling and monitoring
to understand constraints, and sequencing improvements in a way that balances performance needs
with financial sustainability.
This context also reinforces the importance of preserving available capacity through proactive
system integrity measures. Inflow and infiltration reduction, targeted rehabilitation, and operational
improvements can often extend the effective life and performance of the existing system, reduce
wet-weather stress, and avoid or defer more costly capacity expansions. The Wastewater Master
Plan provides the framework to make those choices consistently linking performance expectations
to measurable levels of service, aligning investments with risk, and ensuring that decisions are
grounded in defensible technical analysis rather than reactive response.
ORDINANCE NO. 1034AADOPTED
PREVIOUS WASTEWATER MASTER PLANS
Southlake has a history of wastewater planning that reflects the City's evolving growth and
infrastructure needs. Previous master plans, most notably the 2012 Wastewater Master Plan, helped
establish baseline system understanding, identify early capacity needs, and guide investment during
periods of active development. Over time, additional technical work such as flow monitoring, system
evaluations, and targeted investigations has supported operational decision-making and helped
the City better understand wet-weather behavior, system constraints, and areas where 1/1 affects
performance.
This Wastewater Master Plan builds on those efforts rather than replacing them. It consolidates
knowledge gained through prior planning and field work, updates the City's technical understanding
using current modeling tools and datasets, and reframes long-range wastewater planning around
buildout stewardship, service reliability, and lifecycle reinvestment. Where prior plans focused
heavily on expansion and growth-driven capital needs, this update emphasizes managing a mature
system through targeted rehabilitation, performance-based pr' itization, and transparent, long-
term investment planning.
SCOPE AND GOALS
This plan addresses Southlake's wastewater colle n s emNanhe policies, practices, and
investments necessary to sustain reliable service ove e scope includes system performance
evaluation, wet-weather response considerations, ide cation of constraints and vulnerabilities,
and alignment of long-term needs with imple le po irection. The plan also establishes how
wastewater decisions should be guided and e supporting day-to-day management
as well as multi-year capital programmin .
The overarching goals of the Wast ter ster n are to:
• Maintain reliable, cost-effec service that protects public health and supports
quality of life.
• Define and track w ewat v f service and use performance information to inform
decisions.
• Advance an asset ma eme pproach that prioritizes renewal and rehabilitation based on
risk and lifecycle needs.
• Reduce 1/1 and improve s stem integrity to preserve capacity and improve wet-weather
reliability
• Coordinate wastewater planning with development, redevelopment, and regional system
interfaces.
• Support financial sustainability through transparent long-range planning and defensible
capital programming.
RELATIONSHIP TO THE STRATEGIC MANAGEMENT SYSTEM
Southlake's Strategic Management System provides the City's framework for turning community
priorities into measurable actions, supported by performance tracking and continuous improvement.
The Wastewater Master Plan supports this approach by establishing a clear basis for wastewater
service expectations, identifying implementation priorities, and linking technical needs to policy
direction and investment decisions. In practice, the plan helps define what success looks like for
wastewater service and provides a structure for monitoring progress over time.
8 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
City of Southlake Strategy Map
The mission of the City of Southlake is to provide municipal services that support
the highest quality of life for our residents,a supportive environment for local
INTEGRITY businesses,and unique and special experiences for visitors.
INNOVATION
TEAMWORK We#W' &t- on Our Focus Areas
EXCELLENCE
ACCOUNTABILITY
Safety& Infrastructure& Partnerships& Performance
Security Development Volunteerism Management&
Service Delivery
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We Serve W�e Provide - _ _ -
- - Promote
LearningOur Financial Stewardship-' -
Growth
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C1 Delivering outstanding F1 Safeguarding the Achievin strong L7 Defining and managing
customer experiences public trust through outco hrough a professional workplace
through innovation, a commitment to con evaluation culture that supports
passion,and a strong thoughtful planning and rsuit of better City values and promotes
culture. responsible,conservative ices that improve a positive employee
C2 Enhancing the sense financial management. usiness operations. experience.
of community by F2 Investing to provide& B2 Co ting with select L2 Fostering positive
proactively creating maintain high quality partn implement employee engagement.
opportunities for public assets. Ace lutions
community partnerships, L3 Attracting,developing&
volunteer involvement, 3 fining an retaining a talented and
and citizen engagement. environment of motivated workforce
future readiness by for lasting world-class
understanding and performance.
acting upon the forces,
trends,and coming
challenges affecting
services.
C=Customer Objectives ncial ves B=Business Objectives L=Learning&Growth Objectives
Because wastewater pe ance i closely tied to reliability, risk management, and lifecycle
reinvestment, the plan sup s str gic management by encouraging proactive, data-informed
decisions rather than reacti t-driven responses. It also helps align wastewater capital
programming and operational lorities with broader City objectives—supporting coordinated
implementation,clearer accountability,and improved communication about why specific investments
are necessary.
RELATIONSHIP TO THE CITIZEN SATISFACTION SURVEY
Citizen satisfaction and community trust are directly influenced by the reliability and predictability
of essential services—especially utilities that residents depend on every day but rarely think
about unless something goes wrong. While wastewater infrastructure is largely unseen, residents
experience its performance through service reliability, backups and overflows, odor concerns,
construction impacts, and the City's responsiveness when concerns arise. The Citizen Satisfaction
Survey provides an important "community lens" for this Wastewater Master Plan because it helps
define what "excellent service" means in practice and highlights the service attributes residents
value most. In 2025, providing sewer service was rated as important by 97% of respondents (very
or somewhat important), reinforcing wastewater as a core expectation for daily quality of life.
The survey also confirms that Southlake's wastewater service is performing strongly and is among
the City's highest-rated services. In 2025, 91% of respondents reported being very or somewhat
satisfied with sewer service, including 77% who indicated they were very satisfied. This broader
context matters because resident confidence in City services remains high overall 89% reported
being very or somewhat satisfied with thejob the City is doing to provide services, and 96% indicated
they receive at least a good value for their tax dollars.
By establishing clear wastewater levels of service, linking reinvestment decisions to risk-based asset
management, and strengthening communication around priorities and impacts, the Wastewater
Master Plan helps the City sustain (and improve) the satisfaction drivers reflected in the survey like
reliability, responsiveness, predictability during construction, and responsible stewardship of public
funds. In this way, the Citizen Satisfaction Survey informs not only what the City invests in, but also
how the City explains and delivers wastewater improvements in a way that maintains trust over
time.
RELATIONSHIP TO THE COMPREHENSIVE PLAN
Southlake's Comprehensive Plan is the community's long- oadmap for growth, investment,
and quality of life. It coordinates policies across land use, bilit rks and open space, economic
development, and public facilities to ensure that
decisions support a cohesive vision over time e
Wastewater Master Plan is one of the Comprehe
Plan's supporting master plans that helps implement t
vision by translating broad community goals i ctica
utility policies, service expectations, and ve
priorities.
In this role, the Wastewater Mas Pla prove s the
technical and policy foundation de inate 1
wastewater decisions with other Cit ities. It supports '%40.
development and redevelo n helps protect
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long-term system mainta ility, a en es that public
investments in infrastru e are a ned with service
expectations and risk red 'on o omes. The plan's SOUTHLAKE
technical findings and perfor insights are derived
from the Wastewater Modeling dy prepared by Freese Comprehensive Plan
& Nichols and are reinforced by prior plans and studies,
including the City's 2012 Wastewater Master Plan and
related flow monitoring and evaluation efforts. Together, these inputs support a defensible, data-
driven approach to wastewater stewardship that helps sustain Southlake's quality of life as the
community approaches buildout.
10 WASTEWATER MASTER PLAN I SOUTHILAKE COMPREHENSIVE PLAN
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Southlake's wastewater collection system is a wide ne rk of pipes, structures, and
pump stations that protects public health and sup s da' qualit f life by reliably conveying
sanitary flows to downstream treatment. Although t e system is underground, it functions
as a coordinated "conveyance chain" moving flow neighborhood-scale lines into larger
interceptors, through lift stations where ne and u ately into regional infrastructure. The
purpose of this chapter is to provide a plain-Ian a er nding of how the system is organized,
how it functions, and where key dependencies a mance and planning priorities.
The City's wastewater system is rall uncle ood through two primary basin contexts, the
Central Basin and the Denton Cre asi identifiers shown on the City's sanitary sewer
mapping (e.g., "S-" basins and asins � •
Because much of the Cen n Iready L ��1% = — 7reb_
developed, the Master PI near- term
emphasis increasingly s toward e Denton
Creek Basin: preserving w eath reliability, o N17
managing inflow and infiltrati lanning for
remaining growth and potentia ptic-to-sewer
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SERVICE AREAS AND BASIN CONTEXT r 1
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Southlake's wastewater system is organized
around basin-based collection patterns that NiBf
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where flows naturally concentrate. City mapping
illustrates multiple basin identifiers across the '
community (including S-01 through S-11 in the
Central Basin context and N-12 through N-19
and related identifiers in the Denton Creek Basin S
context).This basin organization matters because ~ \
it provides a practical planning and operational
structure: it clarifies where flows originate, how Figure 2-1:Southlake Basin Map
12 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
they route through the network, and where performance constraints or wet-weather sensitivity may
be concentrated.
From a planning standpoint, the Central Basin's largely built-out condition means its long-term
strategy is predominantly stewardship, targeted rehabilitation, renewal, and operational efficiency
to sustain levels of service. In contrast, the Denton Creek Basin remains the primary area where
remaining growth, wet-weather response, and potential septic incorporation can more directly
influence system loading and capital timing. This is why the plan places added emphasis on Denton
Creek Basin performance and downstream conveyance dependencies in the chapters that follow.
COLLECTION SYSTEM COMPONENTS AND HOW THEY FUNCTION TOGETHER
Southlake's wastewater collection system functions as an integrated conveyance network moving
wastewater from individual homes and businesses through neighborhood-scale pipes, into larger
trunk and interceptor facilities, and then through lift stations and force mains where topography
requires it. The wastewater system should be understood as a " ain" of connected components.
Each component has a distinct role, but system reliability de ds on how they operate together
especially during wet-weather conditions when inflow and i on (1/1) can rapidly increase flows
and stress available capacity.
Because much of the Central Basin is already built the y-to-da collection "chain" extension
there is primarily sustained through maintenance, r w and targeted rehabilitation with some
septic to sewer growth. In the Denton Creek Basin, same collection components must also
accommodate remaining growth potentia n tr tions, and downstream conveyance
dependencies making system integrity, wet- t fo ance, and risk management a larger
driver of planning and investment decisions.
GRAVITY MAINS
Gravity mains form the backbone o lake's wastewater collection system. These pipes convey
flow using slope and are t h st link in the system—collecting wastewater from local
service lines and routing ward er nk lines and interceptors. In the modeled Denton Creek
Basin system, the waste r netwo is described as primarily a gravity flow system that follows
the major drainage basins, pipe es range from 2 to 27 inches, reflecting the transition from
neighborhood lines to larger c nce corridors.
From a performance perspective, gravity mains are where wet-weather stress often becomes visible
first through surcharging in manholes, localized restrictions, or capacity-limited segments that can
contribute to overflows if downstream constraints are present. The modeling approach evaluates
how lines surcharge and whether that surcharging is driven by downstream restriction or insufficient
local capacity, which supports a more targeted and defensible CIP strategy over time.
TRUNK LINES AND INTERCEPTORS
As wastewater flows consolidate, trunk lines and interceptors serve as the "spine" of the collection
system by carrying flow from multiple neighborhoods and basins toward downstream lift stations
or transfer points. These facilities are especially important during peak wet-weather conditions
because they represent the shared pathways for large drainage areas. Mapping and model results
are used to identify interceptor segments where modeled flows exceed capacity during peak wet-
weather events and where surcharging may occur due to downstream restriction.
LIFT STATIONS
Where gravity conveyance is not practical due to topographic constraints or basin transitions,
lift stations provide the pumping needed to move wastewater to the next stage of the
system. In the Denton Creek Basin model, there are 12 lift stations, and they are described
as necessary due to local topographic constraints or to pump flows across sub-basins.
Lift stations are key reliability points because they concentrate risk: a lift station failure can affect a
larger upstream area than a typical pipe defect, and wet-weather conditions can increase influent
rates and shorten response time.
The modeling study also provides clear design logic for lift station performance: firm pumping
capacity is intended to meet 125% of peak wet-weather design flows, where "firm capacity" assumes
the largest pump is out of service. This helps define how lift station needs are evaluated and how
upgrades are justified when service levels are threatened and provides buffer for both supply and
planning improvements.
Bank Street Circle 10 78.54IW5.42 3,184
Burney Lane Circle 5 19 3.58 526
Coventry Circle 4 7 .47 485
Crown Ridge Circle 5 .63 3.30 420
Dove Estates Circle 5 9.33 1,370
Gateway Circle 8 50. 7.00 2,632
Loch Meadows Circle 12 6.00 5,076
Lonesome Dove Rectangle %,J0T90--W 16.00 28,424
Quail Run Circle 28.27 5.58 1,181
Saddleback Circle 6 28.27 5.15 1,089
Shady Lane Rectangle - 170.00 13.75 25,432
Torian Lane Circ 28.27 10.03 2,121
Fig)nder
: on Creek Basin Lift Stations
FORCE MAINS
Force mains convey wastewate pressure downstream of lift stations. They are a necessary
counterpart to pumping in areas where gravity service cannot be maintained continuously. City
mapping distinguishes force mains from gravity lines, and the CIP mapping also highlights force
main infrastructure and proposed improvements in context.
From a performance standpoint, force mains must be sized to meet pumping capacity while
maintaining appropriate velocities and pressures. The modeling study's criteria recommend force
mains support lift station capacity with velocities that provide scouring (to reduce sediment
deposition) and avoid excessive pressure. While force mains are typically fewer in number than
gravity mains, they often represent higher-consequence assets due to repair complexity and the
service area affected.
MANHOLES AND SYSTEM ACCESS
A wastewater collection system can only be maintained if it is accessible. Manholes provide critical
access for inspection, cleaning, condition assessment, and response activities. Cleanouts provide
localized access points that support maintenance, particularly at the neighborhood scale. The City's
WASTEWATER MASTER PLAN
sanitary sewer mapping and CIP map legend also identify operational appurtenances such as plug
valves and air release assemblies, which support operational control and force main functionality.
Because wet-weather reliability is closely tied to the system's ability to use available storage
without triggering overflows, manhole-related performance criteria also matter. The modeling study
references a wet-weather evaluation approach tied to surcharge levels relative to the manhole rim,
which helps quantify how close the system is operating to overflow conditions during design storms.
METERS AND WHOLESALE CONNECTIONS
In addition to City-owned collection infrastructure, system performance and planning are influenced
by where flows enter the system and how they are measured. The Denton Creek Basin modeling work
notes that the City receives flow from two wholesale meters in the North Service Area, reinforcing
the need to account for metered inflows and external contributors when evaluating capacity and
wet-weather behavior.
REGIONAL/WHOLESALE INTERFACES AND DOWNSTREA EPENDENCIES
Although Southlake owns and operates the local colle n s overall system reliability is
influenced by key regional interfaces and downstrea onveyanc ependencies—particularly in
the Denton Creek Basin context. The Freese & Ni s m eling st dy notes that, in the North
Service Area, all flow is conveyed to the TRA Kirk d Station, which has a firm capacity of
6.05 MGD and transports flow via a 30/24/20-inch fo main to the TRA Denton Creek Regional
Wastewater System (DCRWS) wastewater tr t pla
City mapping also depicts TRA system element e tinction between TRA Central Basin and
TRA Denton Creek Basin features, un ing t Southlake's local decisions ultimately connect
to broader regional system perfor ce.
This downstream dependency is i ant for wo reasons. First, it reinforces why wastewater
planning must address pe ea conditions, not just average daily flow—because wet-
weather peaks are wha ess li ati s, trunk lines, and downstream interfaces. Second, it
elevates the value of I/I uction a targeted rehabilitation as practical strategies to preserve
effective capacity and redu void le peak flow stress before major regional upgrades become
necessary.
SEPTIC PRESENCE AND SERVICE GAPS
Not all properties within Southlake are connected to the municipal wastewater collection system.
Some areas more commonly near the edges of the system footprint and in lower-density or historically
unserved areas continue to rely on private septic systems. From a master planning standpoint, these
service gaps matter because future septic-to-sewer transitions can change both the timing and
location of flow increases and may require localized collection extensions, lift station modifications,
or downstream conveyance considerations.
The Freese & Nichols study frames septic incorporation as a distinct driver category in the CIP,
describing projects that may be triggered as interest is shown and noting they are primarily in
the northern and western portions of the City. In this plan, septic-to-sewer is treated as a flexible,
location-specific pathway that must remain consistent with overall system performance and financial
sustainability goals.
CURRENT OPERATIONAL CONTEXT
Day-to-day wastewater system performance in a mature community depends heavily on proactive
operations and maintenance, rapid response capability,and disciplined reinvestment.While localized
issues can occur anywhere, wet-weather conditions tend to amplify vulnerabilities especially where
1/1 increases system loading and drives surcharge risk. As a result, the City's operational context is
closely connected to the plan's technical foundation: using consistent evaluation tools (modeling
+ monitoring + field verification) to identify recurring drivers of service disruption and to prioritize
improvements based on risk and performance outcomes.
The Freese & Nichols modeling study describes how the wastewater model was developed using
the City's GIS data, force mains for all lift stations, and gravity lines, with as-built information used
to supplement the network where available. It also references historical flow monitoring inputs used
for calibration and notes that RDII insights were used to identify basins for follow-up SSES activities
(as originally flagged in the monitoring analysis). This reinforces a key operating principle for the
Master Plan: combine model-based screening with field confirm n to refine project scope, timing,
and expected outcomes so investments are both strategic an fective.
REGULATORY ENVIRONMENT
Southlake's wastewater collection system operat with a well- •
defined regulatory environment that is designed r ct public •
health, preserve water quality, and ensure utilitie e planned, •
operated, and reinvested in responsibly ov Whi he City's
day-to-day work is focused on maintaining a is such as
preventing backups, minimizing disruptions, a po ng quickly
when issues arise, the regulatory fr rk p ides the baseline
expectations for how the system st p orm d how risks must
be managed. In practical terms, ula everything from •
wet-weather planning assumptions esign s andards to overflow
prevention, recordkeepin in nd the prioritization of
rehabilitation projects th duce e Inerability.
At the state level, Texas es shes re requirements for wastewater collection systems through
the Texas Commission on En ntal Quality (TCEQ). These requirements influence how new
infrastructure is designed and w existing infrastructure is evaluated particularly under wet-
weather conditions. Collection system design criteria (such as acceptable surcharge conditions,
pipe capacity and velocity expectations, lift station reliability assumptions, and wet well sizing)
are intended to ensure that systems convey wastewater safely and predictably. As a result, local
planning must account not only for average daily flows, but also for peak wet-weather conditions
that can cause surcharging and contribute to the risk of sanitary sewer overflows (SSOs). This is
one reason the Wastewater Master Plan places strong emphasis on understanding wet-weather
response, identifying where inflow and infiltration (1/1) is influencing performance, and targeting
improvements that preserve effective capacity and reduce peak system stress.
Regulation also intersects with how wastewater projects are scoped and prioritized. In a near-built-
out community, the most cost-effective compliance strategy is often to prevent avoidable system
stress before it becomes an overflow risk. That means using data-informed approaches such as
flow monitoring, basin screening, and field verification to identify where rehabilitation, repairs, or
targeted 1/1 reduction work can deliver measurable performance improvements. It also means using
design standards and levels-of-service expectations consistently so that capital investments are
WASTEWATER MASTER PLAN
sized appropriately: large enough to protect reliability under defined wet-weather conditions, but
phased in a way that avoids unnecessary overbuilding. In this sense, the regulatory environment
supports a disciplined planning approach that connects technical analysis to clear, defensible
investment decisions.
The regulatory framework also extends to regional coordination and downstream dependencies.
Southlake's wastewater collection system does not operate in isolation; its performance is affected
by key interfaces with regional partners and downstream infrastructure that ultimately receives and
treats the City's conveyed flows. This makes coordination and transparency especially important
when evaluating peak flow conditions, capacity limitations, and improvement timing. A master
plan that documents the basis for flow projections, wet-weather evaluation methods, and system
constraints helps ensure that the City can communicate clearly with partners and stakeholders
about why certain investments are needed and how they support ongoing service reliability and
regulatory compliance.
The regulatory environment reinforces the importance of co uous stewardship. Wastewater
compliance is not achieved through a single project or on e plan, it is maintained through
consistent operations, preventive maintenance, targeted tment, and ongoing updates to
reflect changing conditions. As Southlake continues t atur e wastewater program must
remain focused on protecting levels of service thro asset m ement, reducing I/I where
it drives wet-weather risk, and maintaining a tra ren tanning ramework that ties capital
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programming to measurable performance. Includin i gulatory context in this chapter helps
the reader understand that wastewater planning is no lely about infrastructure it is also about
managing risk and meeting defined public he den mental responsibilities in a way that is
sustainable for the community.
Collection tem n expectations, Establishes baseline criteria for planning
State (TCEQ) wet-we ey lift station assumptions, design storm evaluation, reliability
triter eneral pli standards. expectations, and how projects are scoped and
justified
Federal (Clean Water Prote of wate uality; Reinforces the importance of preventing overflows
Act/ EPA) overarc fram rk that informs and protecting receiving waters through sound
state grog enforcement. utility stewardship.
Regional/Wholesale Downstream Wveyance and Requires coordination on capacity and wet-weather
Interfaces treatment dependencies; coordination peak considerations; underscores the need for
with partner agencies. transparent planning and documented assumptions.
Local Standards and City design standards, development Implements compliance locally through consistent
Policies requirements, O&M practices. design review, reinvestment standards, and
maintenance practices.
Supports data-driven prioritization (flow
Performance and Monitoring, documentation, and monitoring, basin screening, post-project
Accountability continuous improvement verification) and transparent reporting of progress
toward service goals.
A • • (�
Legend
-i pi.- 11L Manholes __Plug Valve Adjacent City Boundary
Cleanouts ........ County Boundary
Lift Stations 7-1 Southlake City Limits
10"and Smaller Lines
Wastewater Line Parcel Boundaries
12"and Larger TRA Denton Creek Basin
Wastewater Line TRA Central Basin
Unknown
Wastewater Transfer
Line
Creek Basin
Force Main TRA Lift Station
TRA Big Bear Creek TRA Force Main
Interceptor
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Wastewater flow is the single most importan put to u rstanding how a collection
system performs because it determines whether pi lift ations, d downstream conveyance
operate within their intended service levels or begin ur rge under stress. This chapter explains
the different types of wastewater flow the City plans how those flows behave over time, and
why wet-weather response is often the facto defin stem risk and investment priorities. It
provides the planning context needed to inter rfo ance findings in later chapters and to
support defensible capital planning decisions.
As Southlake approaches buildou ow anni also becomes more nuanced. Growth-driven
increases still matter, but system or easingly shaped by the "hidden drivers" of wet-
weather behavior such as inflow an ration I/1), rainfall-derived inflow and infiltration (RDII),
and how quickly peak flows ra specific basins. Understanding both typical dry-weather
conditions and peak wet- ther r on allows the City to prioritize improvements that protect
public health, avoid serve isruptio , and make the most cost-effective use of existing capacity.
FLOW TYPES AND PLANNI EPTS
Wastewater flow can be grouped into two primary planning categories: dry weather sanitary flow
and wet-weather response. Dry weather sanitary flow reflects the everyday wastewater generated
by residents, employees, and visitors typically following predictable daily patterns tied to household
routines and commercial activity. This baseline flow is the foundation of system sizing and long-term
demand planning, and it provides the "normal operating condition" that supports routine system
management.
Wet-weather response occurs when rainfall and groundwater conditions introduce additional flow
into the system that is not sanitary wastewater. This is generally described as inflow and infiltration
(1/1) and is often quantified through rainfall-derived inflow and infiltration (RDII) concepts. Inflow
includes direct connections or pathways that quickly route stormwater into the sanitary system (such
as illicit connections, faulty cleanouts, or cross connections), while infiltration is water that enters
through defects and joints in pipes and structures and can persist after rain events. Wet-weather
response is important because it can increase flows rapidly and disproportionately, especially in
mature systems, and it can be the dominant driver of surcharge risk, backups, and overflow potential
during major storm events.
20 WASTEWATER MASTER PLAN I SOUTHLAKECOMPREHENSIVE
WASTEWATER MASTER PLAN
From a planning perspective, a key concept is that wet-weather peaks are not evenly distributed
across the system. They concentrate based on basin characteristics, infrastructure age and condition,
groundwater conditions, and how quickly rainfall translates into inflow pathways. As a result, flow
planning must look beyond systemwide averages and focus on where peak flows occur, how long
they last, and what assets are most sensitive to those peak conditions.
HISTORICAL FLOW TRENDS AND KEY DRIVERS
Historical wastewater flow trends provide context for how the system has evolved and what factors
influence performance over time. In general, long-term flow patterns are shaped by three broad
drivers:
1. Community activity and land use patterns - The mix of residential and commercial activity
affects baseline sanitary flow and peak hour variations.
2. System maturity and condition - As systems age, defects and maintenance needs can
influence infiltration and wet-weather response if not addressed through rehabilitation and
reinvestment
3. Weather and groundwater - Rainfall intensity, antece moisture, and groundwater levels
affect RDII response and can reveal which basins are ost sitive to I/1 during storm events.
In a community nearing buildout, historical trends of sho that w eather variability becomes
a key defining feature of system performance. E w average daily sanitary flow remains
relatively stable, wet-weather peaks can increase or b e more impactful if 1/1 pathways expand,
if rainfall patterns shift, or if localized constrai develo trunk lines, lift stations, or downstream
interfaces. For planning purposes, this reinfor ee track flow behavior over time and to
integrate monitoring and field verification in o ty targets rehabilitation and prioritizes
capital projects.
PLANNING ASSUMPTIONS USE R P CT NS
Future wastewater flow pr ' s based on a combination of land use assumptions and
wastewater generation ra hat sl evelopment patterns into expected sanitary flow. At a
planning level, projectio re typica grounded in:
• Population and emp en (location consistent with the City's land use and growth
framework, recognizing esidential units, commercial activity, and civic uses contribute
differently to wastewater eneration.
• Per-capita and per-employee flow criteria that reflect typical planning standards for sanitary
flow generation.
• Buildout assumptions that account for remaining development potential, redevelopment,
and changes in land use intensity over the planning horizon.
Residential Average Day Per Capita Flow 73 71d
verage Day Per Capita Flow 100
(gpcd)Non-Residential Average Day Per Acre tial Average Day Per AcreFlow (gped) 20 30
Peak Wet Weather to Average Day ather to Average Day
Peaking Factor 4'0 or 4.0
Figure 3-1: Existing Wastewater Design Criteria Figure 3-2: Growth Wastewater Design Criteria
Because wastewater planning must account for both typical operations and stress conditions,
projections are not limited to average daily flows. They also include peaking factors and wet-
weather response assumptions that help the City evaluate how system constraints may emerge
under high-flow conditions. This approach supports more realistic capital planning by focusing on
the conditions that most directly influence risk particularly peak wet-weather periods.
PROJECTED FLOWS (EXISTING VS. BUILDOUT SCENARIOS)
Projected flow analysis compares current conditions to anticipated future conditions to understand
how remaining growth and system transitions may affect performance. From a planning standpoint,
this chapter evaluates wastewater flow under two core future scenarios:
• Buildout without septic incorporation, reflecting the wastewater system as it exists today
with growth accommodated primarily within already-served areas.
• Buildout with septic incorporation, reflecting a potential pathway where some properties
currently relying on septic systems transition to municipal astewater service over time.
Existing 12,368 18,230 1.5 5.07
Buildout Without Septic Users 13,992 24,503 1.62 6.47
Buildout With Septic Users 16,181 24,503 1.84 7.35
Figure 3-3:North Service Area Prod d Wastewater Flows
These scenarios are important because they
change both the total volume of flow and t
geographic pattern of flow increases. I ula -
septic incorporation is not only a"gro "v able .
, it is also a system connectivity v ble _ _ • • •
shift where collection extensions ar e a •
how localized capacity, lif n eration, 0 • • _
and downstream conv ce cted. _
Including both scenario eflects t planning 0 • 0 • •
approach established by . y Sta ent ST1: _
maintaining an investment st g at remains
valid whether septic-to-sewer sitions occur
more gradually, more quickly, or in targeted areas extending service where practical and cost-
effective while preserving flexibility for locations where connection feasibility or cost may point
toward alternative solutions.
IMPLICATIONS OF PEAK WET-WEATHER FLOW ON PERFORMANCE, RISK, AND CIP SIZING
Peak wet-weather flow has outsized influence on wastewater system risk because it is the condition
most likely to trigger surcharging, backups, and overflow potential. In practical terms, a system
can appear to function well under dry weather sanitary flow while still being vulnerable under
design storm conditions if 1/1 is high or if critical conveyance segments and lift stations are already
operating near their effective capacity. This is why the City's wastewater investment strategy must
be grounded in wet-weather performance: it is the best indicator of where reliability is most at risk
and where improvements produce the greatest risk reduction benefit.
Peak wet-weather flow also affects how capital improvements are sized and sequenced. Projects
designed solely around average conditions can underperform during stress events, while projects
WASTEWATER MASTER PLAN
sized around extreme conditions can be costly if not timed appropriately. This plan therefore
emphasizes a balanced approach: using peak wet-weather performance to identify where risk is
unacceptable, pairing capacity upgrades with system integrity measures (particularly 1/1 reduction),
and confirming priority needs through targeted field evaluation before committing to major capital
expansion. The result is a CIP that is more defensible and cost-effective focused on preserving
service levels, minimizing disruptions, and reducing long-term risk as Southlake approaches buildout.
ORDINANCE NO. 1034AADOPTED •
CHAPTER4:
HYDRAULIC WASTEWATER MODE4 UPDATE
A hydraulic wastewater model is one of the m valuable ning tools for a near-built-
out community because it allows the City to evalu Sys beha r, not just individual pipes.
Wastewater performance is rarely defined by one is nstraint; it is typically the result of how
multiple upstream basins, trunk lines, lift stations, an ownstream interfaces respond together
especially during wet-weather conditions.A ca dmo rovides a consistent way to understand
where capacity is being consumed, where su a i reases, and which improvements will
produce the greatest reliability benefit.
This chapter describes the model' fra wor sed to support the Wastewater Master Plan,
including the model platform, dat ur ion basis, and the performance standards used
to evaluate the system. It also expla w RD screening and design-storm testing help translate
monitoring data into action iti nd how the model should be maintained as a "living tool"
that evolves alongside re ilitatio of s, development changes, and updated flow monitoring.
WHY HYDRAULIC MODEL MAT IRS FOR A BUILT-OUT WASTEWATER SYSTEM
In a mature system environme , the key planning question is often not "where do we extend
service," but "where is reliability most at risk and what is the most cost-effective way to reduce
that risk?" Hydraulic modeling supports this by testing how the collection system performs under
both typical and stressed conditions, including peak wet-weather flow that can drive manhole
surcharge, backups, and potential overflows. The model also supports defensible prioritization by
distinguishing between lines that surcharge due to downstream restrictions versus insufficient local
capacity, which is essential for selecting the right type of improvement and avoiding overbuilding.
MODEL PLATFORM, DATA SOURCES, AND STRUCTURE
The City's wastewater model is built using InfoWorks ICM and is structured to reflect the real-world
conveyance chain across the system: gravity mains, interceptors, lift stations, force mains, and key
transfer points. The model includes gravity lines from the City's GIS database and force mains for
all lift stations, with as-built drawings used to add new lines and refine network attributes where
available. When invert elevations were not available from as-builts, inverts were estimated using
accepted engineering approaches (including slope-based assumptions and interpolation between
known upstream/downstream elevations).
WASTEWATER MASTER PLAN
The model's loading and demand inputs are also structured to support planning needs. Wastewater
loads were updated based on available customer/meter information and flow projections so the
model can be used to evaluate existing conditions and future scenarios consistently.
FLOW MONITORING AND CALIBRATION BASIS
Hydraulic modeling is only as useful as its ability to represent observed system behavior. Model
calibration is the process of adjusting parameters until simulated flows, depths, and velocities reflect
what was observed during flow monitoring. The calibration basis used for this plan includes both
dry-weather and wet-weather conditions, which is critical for a system where wet-weather response
can be the defining driver of risk.
Dry-weather calibration was based on the period May 11 through May 17, 2018, while wet-weather
calibration used December 19 through December 21, 2017 a storm window that provides a
representative wet-weather response for RDII evaluation. The monitoring dataset reviewed for
calibration includes rainfall and flow monitoring data from the Ci s prior flow monitoring work and
provides the baseline against which the model's performance hecked.
RDII AND BASIN SCREENING
A key planning value of the modeling and monitori or ' the abi y to screen and rank basins
based on wet-weather sensitivity. RDII (rainfall-deriv f and infiltration) is defined as rainwater
that enters the sanitary system during storm events, basin-level RDII volumes can be used to
prioritize where additional field investigation S wo ' likely to yield the greatest benefit.
The basin screening approach categorizes i in low-to-moderate, high, and excessive
RDII intensity based on a normalize ate al/LF/in). This allows the City to focus limited
investigation resources where w eat r res nse is most pronounced and where system
integrity improvements can reduc ea preserve effective capacity.
SYSTEM DESIGN CRITERI I
The model-based evalua is paire ith design criteria that help translate hydraulic results into
practical improvement reco end ns.
• Gravity trunk lines / inte tors (existing): evaluated at peak wet-weather flow where the
hydraulic grade line (HGL) remains at least 3 feet below the manhole rim, which supports
effective use of system storage and helps attenuate peak wet-weather impacts.
• Future trunk lines / interceptors: aligned with TCEQ requirements, including peak wet-
weather design where the pipe is 7S% full while maintaining minimum and maximum velocity
standards (minimum 2 fps, maximum 8 fps).
• Surcharge-state diagnostics: the model evaluates whether surcharging is driven by
downstream restriction or insufficient capacity using defined surcharged state indicators.
• Lift stations and force mains: firm capacity concepts and criteria are used to evaluate pumping,
wet well storage, and force main velocities and pressures. The study defines firm pumping
capacity as the total available capacity with the largest pump out of service and references
TCEQ wet well sizing requirements. Force main criteria include velocity and pressure limits
and a minimum scouring velocity under single-pump operation.
FREESE City of Southlake CITY OF
°NICHOLS Design Storm Comparison SOUTHLAIfE
3.4
0
2.65in/hr Average Peak Total
Intensity Intensity De pth
2.5 NOAA Atlas 145-year,6-hour 1 0.51 1 2.68 1 3.58
NOAA Atlas 145-year,24hour 1 0.21 1 0.84 4.95
December 19,2017 0.08 1.92 2.02
2.0
r
1.92 in/hr
1.5
c
m
1.0 0.84in/hr
0.5
❑.0
a0 0a 0a 0 oa o g o aa oa 0a 0a a 0 a oa oa aaa oa
o aN 8
ae-0 gaN8
0 .
N eY N cm V V cD rti m m O .- N M V, ID n W Q O
—December 19,2017 —NOAA Atlas
aM—NOAA Atlas 14:5-Yr 6-Hr
Figure 4-1:Desi ompa Tabie
DESIGN STORM SELECTION AND LOS BASIS
To evaluate wet-weather perform e c siste y across PolicK Statement
the system, the plan uses a com "d " as the
basis for testing and comparing sy espo . A design LS2. Use a consistent,
storm establishes the level is OS) condition for systemwide planning basis
wet-weather evaluation ating re table reference for evaluating capacity and
point for identifying con nts, com ring alternatives, and performance
sizing improvements. decisions "
basins across
For this plan, the NOAA Atlas 14 ear, 6-hour design storm
was selected as the wet-weather basis because it aligns with
observed regional storm characteristics and provides a meaningful stress test for collection system
performance. The study provides the corresponding storm depth and intensity characteristics used
for evaluation. Applying this standard consistently across all basins ensures that capacity findings
and wet-weather performance conclusions are directly comparable across different parts of the
system and over successive planning cycles which is the systemwide planning basis that Policy
Statement LS2 establishes as the foundation for sound investment decisions.
MODEL MAINTENANCE AS A "LIVING TOOL"
To remain useful beyond plan adoption, the wastewater model should be maintained as a living
tool that is updated as system conditions change. This includes: incorporating newly constructed
or rehabilitated infrastructure, updating demand allocations as development occurs, refining
assumptions as additional flow monitoring or SSES data becomes available, and using post-project
verification to confirm performance outcomes. The goal is a continuous feedback loop: field data
improves the model, the model improves prioritization, and implemented projects provide new data
to refine future decisions.
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This chapter describes how Southlake's waste er system rforms today and how that
performance is expected to change as the commun' ppr ches bui out. In a near-built-out city,
wastewater planning is less about extending new se d more about sustaining reliability like
reducing the likelihood of backups and overflows, prot g downstream conveyance, and making
reinvestment decisions that are both defens' d co fective. Because wastewater systems
typically appear "fine" in everyday condition th aningful performance insights come
from understanding how the system be aves pe wet-weather periods, when inflow and
infiltration (I/I) can rapidly increase f d sh k operational margin.
The purpose of this chapter is to tr at rformance analysis into clear planning direction.
It explains the performance fr e used to interpret results, summarizes where constraints
occur and why, and identif' y of needs rise to the top whether they are true capacity
limitations, operational c raints, dri wet-weather sensitivity, or areas where additional field
verification is warranted re majo nvestment decisions are made. This chapter also establishes
the baseline levels of servic OS) at will support the plan's asset management approach and
capital programming strategy Sequent chapters.
PERFORMANCE FRAMEWORK AND DEFINITIONS
Wastewater system performance is best understood through a reliability lens: how the system
behaves under both typical conditions and peak stress conditions, and how close it operates to
outcomes that affect customers and public health. The framework used in this plan focuses on
several interrelated indicators that describe risk and system resilience.
One of the most important concepts is surcharging, which occurs when water levels in the system
rise above the top of the pipe and portions of the gravity network begin to pressurize. Surcharging
can be part of normal wet-weather behavior, especially in older systems that rely on available storage
volume within pipes and manholes. However, surcharging also serves as an early warning indicator
because as the hydraulic grade line (HGL) rises closer to the manhole rim, the system has less buffer
and becomes more vulnerable to backups and potential overflows. Defined HGL thresholds provide
a consistent way to interpret whether wet-weather surcharge behavior remains within acceptable
limits or begins approaching a reliability risk condition.
WASTEWATER MASTER PLAN
A second key concept is the relationship between localized constraints and systemwide bottlenecks.
Many wastewater issues are not caused by a single undersized segment; instead, a downstream
restriction can raise the HGL and create surcharging across an entire upstream area. This is why
systemwide evaluation is so valuable: it helps distinguish between problems that require localized
upsizing and problems that require relieving a downstream bottleneck to restore broader system
performance. Lift stations are also central to this framework because they concentrate risk and
can influence large upstream areas. When lift station influent approaches or exceeds firm pumping
capability during peak wet-weather conditions, the system has less margin to respond, and reliability
risk increases quickly.
EXISTING CONDITION PERFORMANCE FINDINGS
Under existing conditions, system constraints tend to appear where multiple stressors overlap: wet-
weather inflows increase quickly, downstream conveyance has limited margin, and certain segments
or facilities serve as shared pathways for large contributing areas. The practical result is that some
locations become repeat "hotspots" during storm conditions no ecessarily because the same pipe
is always the root cause, but because the system in that vic' has less buffering capacity and is
more sensitive to peak wet-weather loading.
A systemwide wet-weather response map is partic y helpful a is stage because it shows
not only where surcharge occurs, but also how wi pre t is and ow it clusters. That pattern
matters. Concentrated surcharge "trees" typically su ownstream bottlenecks that propagate
upstream. Isolated surcharge pockets more en sug localized capacity or condition issues.
This plan uses those patterns as a planning ide es where performance appears most
sensitive and where more detailed field verific 'on be targeted, especially in areas that are
also associated with higher RDII sensit' ' or k operational challenges.
FUTURE/BUILDOUT PERFORMA E FI S
As Southlake approaches ewater performance is influenced by both incremental
increases in sanitary flow how t- ther peaks respond as system loading grows. The plan
evaluates future conditio sing sce rio- ased planning so that long-range decisions remain valid
under different pathways. I e sce io, buildout occurs largely within already served areas. In the
second scenario, buildout inc s tic-to-sewer transitions in targeted areas over time. Including
both scenarios helps the City pla sponsibly without assuming a single outcome especially because
septic incorporation can change where flows enter the system and may influence the timing and
location of infrastructure needs.
What is most important from a performance perspective is not simply that flows increase; it is
how those increases affect peak wet-weather margin at key system control points. Lift stations
are particularly useful performance markers because they integrate upstream system behavior.
When peak wet-weather influent approaches firm pumping capacity, system reliability becomes
more sensitive, and the consequences of operational interruptions increase. Similarly, trunk and
interceptor segments that serve large contributing areas become more critical at buildout because
they have less margin to absorb wet-weather peaks without widespread surcharging.
DOWNSTREAM CAPACITY CONSIDERATIONS
Southlake's wastewater system is connected to regional conveyance and treatment infrastructure,
and those downstream interfaces shape what "reliability" means locally. In practical terms, a local
collection system can only perform as well as its ability to transfer flow downstream under peak
conditions. When downstream conveyance or firm capacity thresholds are approached during wet-
weather peaks, upstream parts of the system have less operating margin. This relationship is why
the plan emphasizes a balanced strategy: addressing localized constraints where they exist, but
also reducing avoidable peak flows systemwide through integrity and 1/1-focused measures that
preserve effective capacity.
This is also where planning discipline matters. Downstream capacity considerations are not simply
a reason to expand infrastructure; they are a reason to invest strategically. In mature systems,
targeted rehabilitation, 1/1 reduction, and operational improvements can often produce meaningful
peak flow reductions and restore performance margin at a lower lifecycle cost than large-scale
expansion especially when confirmed through follow-up engineering evaluation. This chapter uses
downstream dependency as a systemwide lens for prioritization: projects that reduce peak stress at
major conveyance points and lift stations often provide outsized reliability benefits.
PRIORITY DRIVERS
This plan identifies priority areas using a driver-based appr so the City can match the right
solution to the right need. Not every "red spot" on a - ther map requires a large pipe
replacement. Some locations are true capacity limitati that ant upsizing or parallel relief.
Others are driven primarily by downstream restrictio here a to ed bottleneck relief project
can restore performance across a larger upstream a. S others ay be symptoms of system
integrity issues where 1/1 increases wet-weather I o the point that otherwise adequate
infrastructure becomes stressed.
FREESE city au CITY OF
7.0
�7 NI�HQL$ euildout Li on FI mparison W/o Septic SOUTHLAKE
19
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5.36
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0 4.0
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tied abp e10 a�Q `ems
6ac� o��e 0 `° o, r as 'saa� Ire
� L Q roc. owe
■Firm Capacity ■Average Daily Flaw ■Peak Wet Weather Flow
Figure 5-1:Buildout Lift Station Flow Comparison without Septic
30 WASTEWATER MASTER PLAN I SOUTHILAKECOMPREHENSIVE
WASTEWATER MASTER PLAN
FREESE City of Southlake CITY OF
7.0
��<NICHQL$ Buildout Lift Station Flaw Comparison w/Septic SOUTHLAKE
6.20
6.0
5.36
5.0
p 4.0
3
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0. $
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L a G e
v
■Firm Capacity ge Dai w ■Peak Wet Weather Flow
Figure 5-2:B out L" tatio ow Comparison with Septic
For planning purposes, priority ds ar
grouped into practical c s: acity- Policy Statement
driven improvements, ration e .ency
improvements, RDII/I/I- en inte ty needs, Improvereliability � - '
and engineering evaluatio eeds at require performance,
f service
field verification before co �t � to major identifying - '
capital commitments. This stru re supports a adjusting '
more cost-effective capital strategy because it ' ' based resulis documented
encourages sequencing allowing the City to start
with targeted investigations and rehabilitation
where the evidence suggests 1/1 is a significant
driver, while reserving large capacity projects for locations where constraints persist even after
integrity strategies are implemented or where downstream bottlenecks are clearly limiting
performance. This is also the approach that Policy Statement LS3 establishes: improving reliability
over time by routinely evaluating system performance, identifying the recurring drivers of service
disruption, and adjusting maintenance and capital priorities based on documented results rather
than assumption.
LEVELS OF SERVICE (LOS) BASELINE
The performance findings summarized in this chapter establish the baseline levels of service
(LOS) framework for the Wastewater Master Plan. In wastewater planning, LOS is best defined
through outcomes and margins: the system's ability to convey flows reliably under defined wet-
ORDINANCE NO. 1034AADOPTED
weather conditions, the extent and severity of
surcharging, the margin between peak influent PoficV Statement
and firm pumping capability at lift stations, and
the presence (or absence) of conditions that LS1. Define
increase backup and overflow risk. service that guide planning, operations,
reliableinvestment decisions, emphasizing
Establishing this baseline is important for two conveyance, minimized backups/overf lows,
reasons. First, it gives the City a consistent, and ' - ' performance.
transparent way to explain priorities:
improvements are not selected only because
they are "old" or "large," but because they
measurably reduce risk and protect service reliability where performance is most sensitive. Second,
it creates a foundation for asset management once the City understands where the system is most
vulnerable under peak conditions, it can align reinvestment priorities with consequence of failure
and performance outcomes, ensuring renewal and rehabilitation decisions are tied to service results
rather than age or isolated defects. Together, these two functi are what Policy Statement LS1
directs: defining clear wastewater levels of service that guide nning, operations, and investment
decisions with an emphasis on reliable conveyance, m d backups and overflows, and
dependable wet-weather performance.
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CHAPTER 6:
WASTEWATER INFRASTRUCTURE
ASSET MANAGEMENT
As Southlake approaches buildout, the long- succe�7
f the wastewater program
depends less on expanding the system and more ste ardingkLIat the City already owns.
Wastewater infrastructure is largely unseen, but it on the most consequential systems the
City manages because it protects public health and nmental quality every day. In a mature
community, the most common drivers of ser risk a ackups, wet-weather vulnerabilities, lift
station disruptions, and pipe failures that are ly to asset condition, system integrity,
and lifecycle reinvestment rather than growth ne anagement provides the framework to
manage these realities deliberately, tr ent d cost-effectively.
This chapter establishes the foun ion t ke's wastewater asset management approach
as a core implementation strategy ater Master Plan. It describes why reinvestment
becomes the dominant Ion s egy at buildout, the essential components of an asset
management program, an w th it prioritize renewal and rehabilitation using a risk-based
framework. It also expl how as management ties directly to levels of service (LOS), how
it should be coordinated day-t ay operations and capital planning, and how performance
reporting creates a continuo e ck loop that strengthens decisions over time. This chapter is
intended to be practical: it pro s the "why" and the "how" that will support policy statements,
budgeting, and program execution after plan adoption.
ASSET STEWARDSHIP AT BUILDOUT
In a growing community, utility investment is often driven by the need to extend service and
add capacity to support development. As Southlake nears buildout, that equation changes. The
wastewater collection system becomes a long-lived, high-value public asset where the dominant
driver of investment is not expansion, but keeping the existing system reliable, maintainable, and
resilient. Pipes age, lift station equipment reaches the end of its useful life, manholes deteriorate,
and force main appurtenances require replacement. At the same time, wet-weather conditions can
expose vulnerabilities in older infrastructure, particularly where inflow and infiltration (I/I) increase
peak loads and reduce operating margin. In this environment, reinvestment is not optional it is the
primary means of sustaining service and managing risk.
Asset stewardship at buildout means the City must treat wastewater infrastructure as a portfolio
with lifecycle needs. Policy Statement AM1 establishes this as a formal commitment: managing
WASTEWATER MASTER PLAN
the wastewater system as a long-life public
asset by prioritizing preventive maintenance, Policy
renewal, and replacement based on lifecycle
needs rather than reactive repair alone. Planned AM1. Manage
the wastewater system as
renewal typically costs less than emergency " public asset by prioritizing
response and reduces the social and economic preventive maintenance, renewal, -
nd
disruption associated with backups, outages replacement based on lifecycle needs
and repeated repairs. Over time, a disciplined rather than reactive repairalone.
reinvestment strategy protects system value,
improves reliability, and reduces the likelihood of
deferred maintenance compounding into costly,
large-scale rehabilitation needs.
This stewardship focus also supports long-term flexibility. By managing assets intentionally,
especially those that drive systemwide risk such as trunk lines, lift stations, force mains, and key
interceptors,the City improves its ability to adapt to changing co ions(redevelopment, regulatory
updates, evolving wet-weather patterns, and shifting service pectations). In other words, asset
management is not only a maintenance strategy; it is a res' trategy that allows Southlake to
sustain excellent service as the community matures.
ASSET MANAGEMENT PROGRAM COMPONENTS
A wastewater asset management program is most of ive when it is structured as a repeatable
process rather than a one-time assessment core ponents typically include: inventory,
condition assessment, criticality, risk scoring, a r ning all supported by consistent data
management and governance.
Inventory is the foundation.The Cit ould aint a complete, up-to-date inventory of wastewater
assets such as gravity mains, for ai es, cleanouts, lift stations, appurtenances, and
major interceptors linked to geo ra forma ion (GIS) and supporting attributes (age, material,
diameter, depth, service ar, la history, maintenance history). A good inventory allows
the City to understand w it ow wh it is, and how it connects as a system. It also enables
practical coordination wi reets, d 'nage, and other infrastructure work so that renewal projects
can be bundled when it ma sens
Condition assessment establishe ow assets are performing and how deterioration is progressing.
For wastewater systems, condition assessment can range from routine field observations and
maintenance records to targeted investigations such as CCTV inspections of gravity mains, manhole
condition inspections, lift station equipment assessments, force main evaluation strategies, smoke
testing to identify illicit connections and surface inflow pathways, dye testing to confirm suspected
inflow sources and trace connection points, and basin-level investigations tied to wet-weather
performance. Not every asset requires the same intensity of inspection; asset management works
best when condition assessment is targeted based on risk and consequence. The goal is not to
inspect everything every year, but to collect enough reliable information to predict failure likelihood
and identify where renewal will reduce risk most effectively.
Criticality evaluates the consequence of failure. In wastewater systems, criticality is often highest
where a single asset serves a large upstream area, where failure affects critical facilities, where access
is difficult, where repair time is long, or where downstream dependencies create cascading impacts.
Trunk lines, lift stations, major force mains, and key interceptors are common "high criticality" assets
because they can affect broad service areas and can be more disruptive to repair.
ORDINANCE NO. 1034AADOPTED
Risk scoring combines condition and criticality
into a repeatable prioritization tool. A typical PoficV Statement
approach uses a risk matrix (likelihood of failure
x consequence of failure) to assign risk tiers AM2. Establish and -
formal
across the asset portfolio. This creates a common wastewater asset managementprogram
language for decision-making and helps separate that includesand urgent" needs from "important but criticality assessment, and risk-informed
manageable" needs, enabling the City to program renewal planningguide annual budgets
work over time instead of reacting to crises. and - ' - ' ' -
Renewal planning converts risk insights into an
implementable multi-year program. Renewal
planning identifies the right type of intervention (repair, rehabilitation, replacement), the right
timing (near-term vs. planned), and the right delivery strategy (standalone project, bundled project,
coordination with other improvements). Taken together, these components, inventory, condition
assessment, criticality, risk scoring, and renewal planning con e the formal asset management
program that Policy Statement AM2 directs the City to establ' and maintain, ensuring that annual
budgets and multi-year capital programming are guided sistent, documented information
rather than institutional memory or reactive pressure.
RISK-INFORMED PRIORITIZATION FRAMEWORK
A risk-informed framework ensures that the City priori s wastewater reinvestment in a way that
is transparent and aligned with the outcomes is ca bout most—reliability, responsiveness,
and public health protection. Because wastew r i c be immediate and consequential, the
prioritization framework should reflect the spe ensions that matter most in a collection
system. e)
INVENTORYO'
REPORTINGPLANNING
Asset ® A .rz.-t
Data Inspection& Consequence Risk Evaluation Rehab&Replacement Track&Measure
&Mapping Assessment &Impact I I Strateav Results
• Service Reliability • Reduced Overflows Proactive Maintenance
36 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
Public health and environmental protection are central. Assets that can contribute to backups,
overflows, or uncontrolled releases during failure events carry a higher consequence because they
directly affect residents, businesses, and water quality. The City's prioritization framework should
explicitly recognize these risks and treat them as high priority even when failures are infrequent
because the consequences are significant.
Consequence of failure should be evaluated in a practical, location-specific way. High-consequence
assets often include: trunk lines that serve multiple basins, lift stations with large upstream service
areas, force mains that are difficult to isolate or repair, and assets near sensitive receptors.
Consequence can also increase where redundancy is limited, where access is constrained, or where
a failure would disrupt traffic, businesses, or critical facilities.
Reliability and service continuity is the core performance objective. Prioritization should favor
investments that measurably improve the City's ability to sustain service during peak wet-weather
conditions and reduce repeat operational challenges. Reliability-driven prioritization is especially
important where wet-weather flow response creates narrow m ins—because small asset failures
or minor constraints can become large disruptions during sto events.
Operational risk and maintainability is the fourth pillar. me is may not be at the highest
immediate failure risk but may create recurring opera al burden ch as frequent maintenance
needs, difficult access, limited isolation capability, erfo ance se sitivity. Prioritization should
recognize that reducing operational burden can
improve service reliability and free staff resources
for proactive work. Over time, operati -.
efficiency improvements can deliver meaning I
lifecycle savings and reduce the probability th "
minor issues become major failures. - • - •
These four pillars: public hea pr • • " • •
consequence of failure, service re ty, an • • " - -
operational risk are the e nsions • " - •
that Policy Statement M3 a lis as - • • • - • •
the foundation for a istent, ansparent
prioritization framework, 'th r vestment
becoming an increasing foc outhlake approaches buildout. A well-designed framework
translates these concepts into simple scoring system that staff can apply consistently clear
enough to explain to decision-makers and the public, but detailed enough to distinguish between
competing needs. A recommended approach is a tiered system: Risk Tier 1 (highest), Tier 2, and Tier
3 where Tier 1 assets become the focus of near-term action or targeted assessment, Tier 2 assets
are programmed, and Tier 3 assets are monitored and managed through routine maintenance and
long-range planning.
COORDINATION WITH O&M AND CIP
Asset management is most effective when it is integrated with both operations and maintenance
(O&M) and the Capital Improvement Program (CIP). O&M is the City's first line of defense; it provides
the real-time information that reveals where assets are struggling and where failures are likely.
Maintenance records, response history, lift station run-time trends, cleaning frequencies, CCTV
findings, and complaint patterns are all valuable asset management inputs. A mature program treats
O&M data as an "early warning system" that helps direct inspections and refine renewal priorities.
CIP is the long-term reinvestment tool. The role of asset management is to provide the justification
for CIP projects and to ensure they are sequenced logically. Sequencing should follow a simple
principle: confirm needs before committing major capital. In practice, that means using screening
tools (performance patterns, RDII indicators, known constraint locations) to identify candidate
areas, then using targeted field verification (engineering evaluations, SSES work, CCTV, lift station
assessments) to confirm root causes, and then selecting the most appropriate intervention. This
stepwise approach reduces the risk of oversizing solutions or investing in capacity upgrades when
integrity improvements would have achieved the intended benefit at lower cost.
Coordination also improves efficiency by aligning wastewater renewal with other City work. Where
feasible, rehabilitation projects can be coordinated with roadway projects, drainage improvements,
or other utility work to reduce disruption and avoid repeated surface restoration. This is particularly
valuable in built-out areas where construction impacts are more sensitive and community disruption
can be a significant factor in project delivery.
PERFORMANCE REPORTING AND CONTINUOUS IMPROVEMENT
Asset management is not complete unless the City measures omes and uses those outcomes to
improve future decisions. Performance reporting provides a bility: it allows staff and decision-
makers to see whether reinvestment is improving reliab' re g wet-weather vulnerabilities,
and lowering operational burden. It also provides tran rency to ents by demonstrating that
projects are selected for measurable reasons and tha est nts are oducing real improvements.
This plan's levels of service framework is the natural "s card" for wastewater performance. Over
time, the City should track a small set of LOS d me that are meaningful, measurable, and
useful for decision-making. Examples include. e i epeat surcharge hotspots, improved
margin at key lift stations during wet-weath s, duced frequency of localized backups
or service disruptions, reduced RDII .vity targeted basins after rehabilitation, and fewer
reactive repairs in high-criticality a s. T spe .c metrics can evolve as data improves, but the
key is consistency using the same as e to demonstrate progress.
Continuous improvement e porting leads to action. If performance improves after
rehabilitation, the City c efine i rio .zction approach and replicate successful strategies. If
performance does not im ve as ex ted, the City can adjust assumptions, revisit field verification
methods, or refine how so ns a selected. This feedback loop is what turns the model and
monitoring tools into a living p : implemented projects generate new data, new data improves
prioritization, and improved prio ization increases the effectiveness of future investments.
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CHAPTER7:
RESILIENCE, INFLOW
REDUCTION & SYSTEM INTEGRITY
In a near-built-out community, the long-term rforma of a wastewater system is
increasingly defined by what happens during wet- her con diti . Even when the collection
system performs well under normal dry-weather itar low, inflow and infiltration (I/I) can
rapidly increase system loading during storm event king operational margin and elevating
the risk of surcharging, backups, and potentia verflo his makes I/I reduction one of the most
practical and cost-effective "capacity strategi , ble §�ause it preserves the usable capacity
of existing infrastructure and helps protect lev of without immediately resorting to major
expansions.
This chapter establishes Southlak ram ork fo educing I/I and strengthening system integrity
as a foundational resilience strateg ow the City should structure an investigation-to-
rehabilitation program, how c ing and targeted Sanitary Sewer Evaluation Study (SSES)
work can focus resources e t e the greatest benefit, and how private-property outreach
supports long-term re' It also a es s wet-weather preparedness and operational resilience
because even the best int ty prog m must be paired with lift station reliability, monitoring, and
a clear response posture to ag eak events effectively.
WHY 1/1 REDUCTION IS A FOU ATIONAL STRATEGY
Inflow and infiltration reduction is foundational because it addresses the difference between what
the community generates as sanitary flow and what the system is forced to convey during storms. In
many systems, wet-weather peaks not average daily flow drive risk. When avoidable storm-driven
inflows are reduced, the system gains measurable breathing room across multiple components:
trunk lines surcharge less frequently, lift stations regain
capacity margin, and downstream interfaces experience
lower peak stress. This improves reliability in the Policy Statement
conditions that matter most and reduces the likelihood RS1. Advance a sustained inflow
of customer impacts. and infiltration reduction program
Inflow and infiltration reduction also preserves the value areasthrough targeted investigation and
of prior and future investments. A collection system can rehabilitation, focusing on
be upgraded repeatedly and still underperform during with recurring wet-weather impacts
storms if I/I remains high. Conversely, targeted integrity and the greatest risk-reduction
improvements can allow the City to delay or resize 'L_ potential.
WASTEWATER MASTER PLAN
major capital projects because the system is no longer carrying water it shouldn't. From a financial
standpoint, this is cost avoidance with real lifecycle benefit reducing emergency response, repeated
repairs, and premature upsizing driven by peak conditions that are partially preventable. Realizing
that benefit requires a sustained program focused on the areas where recurring wet-weather impacts
are greatest and risk-reduction potential is highest, which is the approach that Policy Statement
RS1 directs the City to advance.
PROGRAM STRUCTURE
A successful 1/1 program is structured as a repeatable cycle, not a one-time project. The key is
sequencing work so the City confirms root causes before committing major capital. The most
effective programs follow a clear progression:
1. Screening and targeting: Use system performance information, wet-weather response
patterns, basin screening indicators, service calls, and repeat maintenance needs to identify
candidate areas. This step helps the City focus effort wher the payoff is highest rather than
trying to "boil the ocean."
2. Field investigation and confirmation: Once a basin o ea is identified, the City confirms
1/1 sources using appropriate tools: targeted C ma le inspections, smoke testing
where appropriate, dye testing for suspected st connecti and lift station wet-weather
trend review. The purpose is to differentiate ee ) true st uctural defects and pathway
issues and (b) capacity constraints that woul even after integrity improvements.
3. Rehabilitation and repair sequencing afte onfirmation does the City implement
rehabilitation—prioritizing repairs that k t-weather response most effectively.
Importantly, the City should resist the to t reat rehab as "everything everywhere."
Sequencing should prioritize t est erage defects first, then reassess wet-weather
response before expanding reh foot 'nt.
4. Post-project verification: A program discipline is verifying outcomes. After
rehab, the City shoul p wet-weather response in the targeted area to baseline
conditions (either t gh it , lift station influent trends, or focused follow-up data).
This ensures the ram is ver g measurable benefit and provides a feedback loop to
refine future targets
SSES STRATEGY AND PRIORI ION APPROACH
Sanitary Sewer Evaluation Study work is most effective when it is basin-based, risk-informed, and
tightly connected to the City's performance findings. A basin-based approach helps the City address
1/1 as a system problem rather than as a series of isolated repairs. It also allows the City to align SSES
priorities with the areas that show the strongest wet-weather sensitivity and the highest potential
risk reduction benefit.
A recommended prioritization structure for SSES is a tiered approach:
• Tier 1: Highest wet-weather sensitivity and highest consequence
Basins that show pronounced wet-weather response and are upstream of high-criticality
assets (major interceptors, key lift stations, regional interface points) should receive first
priority because 1/1 reduction in these areas protects the most consequential parts of the
system.
• Tier 2: Repeat operational issues
Areas with recurring maintenance needs, repeated surcharging patterns, or frequent service
complaints should be addressed next especially when issues cluster around older infrastructure
or known infiltration pathways.
• Tier 3: Opportunistic / coordination-driven
Basins or segments that can be cost-effectively
addressed through coordination with roadway RS2. Use appropriate" "
ld
projects, reconstruction work, or bundled evaluations and
system
rehabilitation programs can be prioritized when assessments to confirm suspected
timing and efficiency align. problem areas and refine project
scope, sequencing, . expected
This approach keeps SSES practical and strategic ensuring outcomes before - capital
the City is investing investigation and rehabilitation
resources where they will reduce risk most, while allowing
the program to scale over time as funding and staffing
capacity allow. It also reflects the discipline that Policy Statement RS2 establishes: using appropriate
field evaluations and system assessments to confirm suspected roblem areas and refine project
scope, sequencing, and expected outcomes before major capit ommitments are made.
PRIVATr_-PROPERTY 1/1 PREVENTION
Long-term 1/1 reduction requires addressing both p c and privy ources. While the City can
rehabilitate pipes, manholes, and lift stations, priv -pro ty issues can reintroduce avoidable
inflow pathways if they are not addressed through e n and, where appropriate, enforcement
tools. An education-first approach is especial) ' porta a community-focused planning context
because residents often do not realize that ce diti on private property can contribute to
wet-weather problems.
Private-property outreach shout o o clear, .
ofic)6 Statement
actionable practices residents can plem t: RS3. Implement
education-
program
• Verify cleanout caps ar se nd secureprivate-propertyprevention,
Missing or damage ea t s can act as including verifyingcleanout
direct inflow poi during e nts, allowing IF caps are present sealed and
stormwater to ente e sanity system. preventing
from connecting to the sanitary
• Prevent stormwater so from connecting to system.
sanitary
Downspouts, yard drains, and sump-type
discharges should never route to sanitary. Even well-intentioned connections can meaningfully
increase wet-weather system loading.
• Protect manhole areas and avoid ponding around structures
Where private landscaping or grading directs stormwater toward manholes or cleanouts,
small drainage corrections can reduce inflow risk.
• Communicate what residents will notice and why it matters
Residents are more likely to participate when outreach ties actions to real outcomes: fewer
backups, fewer disruptions, and lower long-term costs.
Taken together, these outreach practices reflect the approach that Policy Statement RS3 directs
implementing an education-first program on private-property 1/1 prevention that focuses on verifying
cleanout caps are present and sealed and ensuring stormwater sources are not connecting to the
sanitary system.
WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE '
WASTEWATER MASTER PLAN
WET-WEATHER PREPAREDNESS AND OPERATIONAL RESILIENCE
Even with a strong 1/1 program, wet-weather events will remain a defining stress condition for the
system. Operational resilience is therefore a necessary companion strategy focused on keeping
critical assets reliable and ensuring rapid response capability when conditions shift quickly. This
is especially important at lift stations, which often act as system control points and can become
immediate risk drivers during wet-weather peaks.
Operational resilience should include:
• Lift station reliability posture
Preventive maintenance, redundancy awareness, and a clear readiness standard for critical
stations (especially those with large upstream service areas or downstream interface
importance). Reliability planning should include backup power considerations where
appropriate and clear escalation procedures during storm events.
• Monitoring and situational awareness
Using available instrumentation and operational data to i ify abnormal wet-weather inflow
patterns, confirm response trends, and trigger early ac Even simple thresholds (e.g., rapid
rise rates, high wet well levels, repeated alarms) ca p e response time and reduce risk.
• Storm response readiness
Clear roles, response checklists, and a "play ok" f wet-weather conditions—particularly
for known sensitive areas. The goal is not on spond to incidents, but to reduce the
likelihood that conditions escalate to c tomer i cts.
• Integration with the 1/1 program
Operational findings should feed k int n scr ening and SSES targeting. If certain areas
consistently stress the system ri for that is a strong signal to prioritize confirmation
work and integrity improve nts.
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As Southlake's development peak is largely o wastewa fanning must balance two
realities at the same time: the system must remain r ble resilie under peak conditions, and
the City should avoid overbuilding infrastructure t i t yet needed or that could be better
addressed through targeted rehabilitation and integrit easures. Growth and redevelopment still
influence wastewater loading, but in a matur unit e most cost-effective strategy is often
to right-size improvements, time investments de a d need, and ensure new development
does not introduce long-term operatio I or an burdens. This chapter establishes how
Southlake will coordinate wastewate ng development decisions so the system remains
dependable, maintainable, and fin ally twin e.
This chapter also provides the mp tation ridge between technical evaluation and day-to-
day planning practice. It e ctations for capacity demonstration and infrastructure
compatibility, outlines ho e City ul aluate and sequence developer-related improvements,
and identifies opportuniti o simpli the system where Iifecycle benefits exist. Finally, it frames
septic-to-sewer transitions stra ic, feasibility-driven pathway coordinated with performance,
constructabifity, and long-ter tainabifity so that future connections strengthen the system
rather than creating unintended sts or operational complexity.
BUILDOUT READINESS AND RIGHT-SIZING PHILOSOPHY
Buildout readiness means the City has a clear, defensible approach to sustaining wastewater
levels of service as remaining growth occurs and redevelopment continues. In a near-built-out
environment, the City's planning posture should prioritize right-sizing building what is needed,
when it is needed, and in the form that provides the best Iifecycle value. Right-sizing is especially
important in wastewater because oversizing can create new problems (low velocities, sediment
deposition, added maintenance burden) while still failing to address the true drivers of risk (wet-
weather peaks and I/1).
A right-sizing approach starts with a simple principle: use performance evidence to define need.
Where constraints are driven by peak wet-weather conditions,the City should first consider strategies
that preserve effective capacity such as targeted rehabilitation, 1/1 reduction, and operational
improvements before committing to major conveyance expansion. Where true capacity limitations
exist, improvements should be phased so that early actions address the most critical bottlenecks
44 WASTEWATER MASTER PLAN I SOUTHILAKE COMPREHENSIVE PLAN
WASTEWATER MASTER PLAN
and highest-consequence assets first, with later phases PolicK Statement
triggered by measurable thresholds including growth
milestones, verified performance indicators, or confirmed GD1. Plan and - strategic
wet-weather response patterns.This sequencing supports wastewater improvements to
fiscal stewardship and reduces disruption for residents and support long-term buildout
businesses by avoiding "build now just in case" projects conditions while avoiding
and it is the planning and phasing discipline that Policy unnecessary overbuilding, using
Statement GD1 directs: supporting long-term buildout sequencing and • match
conditions while avoiding unnecessary overbuilding by demonstrated •
matching timing and investment to demonstrated need. L,
DEVELOPMENT AND REDEVELOPMENT COORDINATION
Development and redevelopment coordination ensures that new projects connect to the system
responsibly, do not shift undue cost or risk onto existing residents, and remain compatible with
long-term system performance goals. In practice, this means t City should require a consistent
level of wastewater coordination during entitlement, plattin nd construction—especially when
projects occur in areas that are sensitive under wet-we onditions or where downstream
capacity margins are limited.
A coordinated approach generally includes three e tati
• Capacity demonstration and "no adverse impac valuation
Development proposals should demo that nstream collection infrastructure can
accommodate projected wastewater fl s st lished planning assumptions and that
the project will not increase surcharge/ n n a way that degrades levels of service.
This does not mean every proj ires ull system model update; rather, the City should
apply a tiered approach—us' scre ing esholds to determine when a localized analysis
is sufficient and when broa ev arranted based on basin sensitivity, proximity
to known constraints, and the e of proposed change.
• Infrastructure corn ability co ructability
New public or priv wastewa r facilities should be compatible with the City's standards for
materials, access, an ainta' bility. Compatibility includes connection locations, manhole
spacing, pipe sizing tha its appropriate velocities and maintenance needs, lift station
design features (if applica e), and configuration that avoids creating long-term operational
liabilities.
• Required improvements and timing
Where development triggers the need for PolicK Statement
improvements whether localized upgrades,
upsizing, lift station modifications, or access GD2. Require new development
enhancements the City should clearly define and " • " • • demonstrate
what must be constructed, when it must be adequate wastewater c- • -
constructed, and whether it must be completed and • - •
before occupancy. Timing should be consistent and ' •te system impacts
with right-sizing: improvements are required through appropriate u• ' - • "
when they are necessary to maintain LOS and timing, or participation in r" • " •
protect public health, but the City should avoid IL improvements.
requiring unnecessary oversizing that adds long-
term costs without clear performance benefit. This framework reflects the requirement that
Policy Statement GD2 establishes that new development and redevelopment demonstrate
ORDINANCE NO. 1034AADOPTED
adequate wastewater capacity and infrastructure compatibility, and mitigate system impacts
through appropriate upgrades, timing, or participation in required improvements.
SYSTEM SIMPLIFICATION OPPORTUNITIES
As systems mature, complexity can become an invisible cost driver. Lift stations with small service
areas, fragmented force mains, redundant configurations, and hard-to-access infrastructure can
increase maintenance burden and risk over time. System simplification focuses on reducing that
complexity where it is feasible and where it produces measurable lifecycle benefits.
Opportunities for simplification often include:
• Reconfiguration and consolidation of subareas to reduce the number of lift stations,
where gravity alternatives are feasible or where consolidation improves redundancy and
maintainability.
• Lift station reduction or modernization where a fa has high lifecycle cost, limited
redundancy, frequent operational issues, or is
sensitive to wet-weather inflows. In some cases
the best long-term investment may be to elimin " •
a station; in others, it may be to modernize or
reliability and maintainability.
• Operational efficiency projects t duce
response risk (improved access, is
capability, standardized components, in
enhancements), especially wh ities e high
consequence or where repai e i ng.
A simplification strategy should b dence- ased and coordinated with asset management.
Simplification is not purs ly cause fewer assets is better, but because targeted
reconfiguration or conso tion c e operational risk, lower long-term lifecycle cost, and
improve reliability partic during et-weather events. Pursuing those opportunities when they
are supported by engineeri valua n and lifecycle benefit is the approach that Policy Statement
GD3 directs.
SEPTIC-TO-SEWER TRANSITION FRAMEWORK
Septic-to-sewer transitions are a distinct type of "growth" decision because they change system
connectivity and can alter where flows enter the collection network. In Southlake, septic presence
is not simply a gap to be filled universally; it is a strategic planning consideration that should be
evaluated based on feasibility, interest, constructability, performance implications, and long-term
sustainability.
A plan-ready framework for septic-to-sewer should include:
• Maintain a general, feasibility-driven approach
The City should evaluate septic transitions when there is demonstrated interest, when public
health or environmental factors warrant consideration, or when coordinated infrastructure
projects make conversion more feasible. The City should avoid committing to broad, unfunded
conversion assumptions without clear implementation pathways.
46 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
• Evaluate system impacts and infrastructure needs
Each potential conversion area should be evaluated for localized collection needs (extensions,
lift stations,force mains),downstream compatibility,
and wet-weather sensitivity. The goal is to ensure
new connections do not unintentionally create new PolicK Statement
operational vulnerabilities or require premature
major upgrades. Evaluate � •
incentives only when they are
• Use targeted incentives where justified targeted, clearly justified, and
Where a septic transition provides broader substantial enough to influence
homeowner decisions
system or community benefit such as risk
reduction, environmental benefit, or a coordinated alignedremaining fiscally responsible and
long-term
infrastructure opportunity targeted incentives or phased implementation tools may be appropriate, • _
s.
so long as they align with financial sustainability
and demonstrated feasibility. This is the standard that licy Statement ST2 establishes:
evaluating septic-to-sewer incentives only when the re targeted, clearly justified, and
substantial enough to influence homeowner decisio ile remaining fiscally responsible
and aligned with long-term planning priorities.
PROTECTION OF LONG-TERM MAINTAINABILITY
Long-term maintainability is one of the most importa nd most preventable, drivers of lifecycle
cost. Decisions made during development ent, ement width, access routes, manhole
placement, depth, and component selection— n intenance challenges for decades. As
Southlake approaches buildout, protectin mai i i ecomes even more critical because the
City will increasingly rely on proacti wal d efficient operations to sustain service levels
without unnecessary disruption. A intai bility cused approach includes:
• Clear standards for access an ements
Public wastewater i u hould be placed where it can be accessed safely and
consistently for in ction, to ce, and renewal. Easements should provide adequate
width, access rou and co tructability for future rehab work. Where infrastructure is
placed in constraine as, d ign requirements should explicitly address how maintenance
and emergency respon ccur.
• Compatibility with the asset management program
New assets should be incorporated into the City's inventory, tagging, and condition
assessment framework from day one. Standardizing components where feasible (valves,
controls, monitoring equipment, lift station features) simplifies training, reduces spare parts
burden, and improves response consistency.
• Protection from avoidable future conflicts
Development coordination should reduce future conflicts with buildings, trees, walls, and
landscaping that block access or complicate renewal. Preventing future conflicts is often far
less costly than resolving them later, especially in built-out neighborhoods.
This maintainability focus ensures that new development strengthens the overall utility system rather
than adding hidden lifecycle liabilities. It also supports transparency: when the City can explain that
standards protect long-term cost and reliability, development requirements are easier to justify and
easier to apply consistently.
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Wastewater is one of the most essential service e City pro es, yet it is largely "invisible"
when it is working as intended. Residents typically ex ienc astewa r service through outcomes
such as reliability, responsiveness, minimal disruptio r construction, and confidence that the
City is protecting public health and the environment. B use the collection system is underground
and technical by nature, effective implemen depe on more than engineering solutions.
It also requires clear communication, strong to r rship, coordinated relationships with
regional providers, and a sustainable funding y t aligns long-term reinvestment needs
with community expectations.
This chapter establishes how S lak understanding and support for wastewater
priorities, including inflow and infiltr (1/1) pre ention, fats-oils-and-grease (FOG) management,
and the impacts associated w d capital improvements. It also outlines how the City will
coordinate with partners peciall RA d internal departments, to deliver projects efficiently,
and how a long-range fu g frame rk should be structured so that service reliability and levels
of service (LOS) remain sus able Southlake approaches buildout.
COMMUNICATION GOALS FO ASTEWATER
The City's wastewater communication goals should be grounded in what residents and businesses
actually experience and care about: reliability, responsiveness, and predictability. Most community
members do not interact directly with pipes or lift stations, but they do notice service disruptions,
odor concerns, backups, and the inconvenience of construction. The objective of wastewater
communication is therefore to translate technical needs into clear, relatable outcomes explaining
what the City is doing, why it matters, and how those actions protect quality of life.
A strong communication approach emphasizes four consistent themes:
1. Public health and environmental protection-Wastewater service is foundational to community
health and clean waterways.
2. Reliability during wet-weather conditions - Peak wet-weather conditions are where risk
concentrates; proactive work reduces the likelihood of backups and overflows.
48 WASTEWATER MASTER PLAN I SOLITHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
3. Responsible stewardship and cost effectiveness - Planned renewal and targeted integrity
improvements reduce long-term costs and emergency disruptions.
4. Transparency and predictability - Residents benefit from understanding project timing,
neighborhood impacts, and what to expect during construction.
CUSTOMER-FOCUSED OUTREACH STRATEGY
Customer-focused outreach should support two goals at the same time: prevent avoidable
problems and maintain trust during improvements. On prevention, outreach should reinforce simple
behaviors that reduce system stress—particularly 1/1 prevention on private property and responsible
disposal practices that reduce clogs and backups. On construction impacts, outreach should focus
on predictability: clear schedules, notification methods, what residents will see, how access will be
managed, and where to call with concerns.
A cornerstone of Southlake's customer-focused wastewater o ach is the City's Fats, Oils, and
Grease (FOG) Program, which directly addresses one of the common and preventable causes
of sewer backups: grease buildup and blockages. Fats, oils, se are present in most residential
and commercial kitchens and can accumulate in sewer li incr . g the likelihood of backups or
overflows. The City also communicates that conseque can inclu ublic health endangerment,
damage to homes or businesses, and impacts to cre stre s, and nds. This program provides
a clear, practical way to connect "what you do in en" to "how the wastewater system
performs."
Southlake's FOG program is established by Ord n n upported by a FOG Policy Manual that
addresses commercial food service establishm ui ents. For residents, the City emphasizes
best practices such as disposing of gr the sh (after cooling into a container), wiping dishes
before washing, and using sink stra s to duce ildup. For businesses, the program emphasizes
staff training, maintaining a clean G-f , and properly managing greasy wash water so
it goes to an appropriate drain rath n an outdoor drain that flows directly to waterways. The
City also requires grease tr ed at least every 90 days, with more frequent cleaning
as needed, and provides dance the mmon "25% rule" for when cleaning is due. In addition,
the City requires permit liquid w to haulers for grease and grit waste, with registration and
reporting requirements inte d to sure proper disposal tracking.
This FOG framework fits natura alongside the plan's 1/1 prevention messaging. Together, they
create a "customer partnership strategy" that reduces avoidable system stress, improves reliability,
and helps protect public investment in the wastewater system.
PARTNERSHIPS
Wastewater service reliability is strengthened through coordinated partnerships both external
and internal. Externally, Southlake's downstream dependencies and regional interfaces mean the
City benefits from ongoing coordination with partners such as TRA on conveyance assumptions,
operational expectations, and long-range capacity considerations. Clear communication and shared
planning assumptions help ensure systemwide reliability under peak wet-weather conditions and
reduce surprises as conditions change over time.
Internally, partnership is equally important. Wastewater projects frequently intersect with streets,
right-of-way (ROW), drainage, and development activity. Coordinating schedules and scopes can
reduce community disruption and lower lifecycle cost by bundling restoration work and avoiding
repeated construction impacts in the same corridor. This coordination also supports efficient
delivery: projects can be timed with pavement programs, roadway reconstruction, or other utility
improvements where it provides clear benefit.
FUNDING FRAMEWORK PRINCIPLES
A financially sustainable wastewater program must match the reality of a near-built-out system:
reinvestment and renewal become the dominant long-term cost drivers. Funding strategy should
therefore be designed to support predictable, ongoing lifecycle work not just occasional large
projects. The plan's levels of service (LOS) framework provides the "why" for investment; the
funding framework provides the "how."
Funding principles for the Wastewater Master Plan should include:
• Lifecycle alignment: Budgets and reserves should reflect ongoing renewal and rehabilitation
needs, not just reactive repair.
• Reliability protection: Funding should maintain the Cit ability to prevent backups and
overflows, particularly during wet-weather stress con ns.
• Transparency: The City should be able to explain o rat ees support service outcomes
and how capital priorities align with documente eeds.
• Affordability and predictability: Rate st ty _
matters; long-range planning supports smoot
investment profiles and reduces large S. •
• Coordination with development: Where ow
redevelopment drives new nee e Ci ould
apply consistent policies for os esp ibility " •
and timing. -
Together these principles ref he ancially resilient
and transparent approac at is atement FS1
directs aligning budgets, ves, ra an fees, and capital planning with lifecycle needs and long-
term service expectations he utili can sustain reliable performance without financial volatility.
CAPITAL PLANNING AND DE Y STRATEGIES
Capital planning is where the plan becomes executable. The City's capital strategy should reflect the
sequencing logic established earlier:confirm needs,target the right solution,and phase improvements
to protect service levels while avoiding unnecessary overbuilding. This includes a mix of project types
such as rehabilitation, targeted bottleneck relief, lift station reliability improvements, and localized
capacity upgrades prioritized by risk and consequence. Treating this work as a planned, ongoing
obligation integrated into annual budgeting and capital
programming rather than a series of reactive responses, Policy Statement -7
is the reinvestment discipline that Policy Statement FS2
directs, ensuring the system remains dependable without FS2. Treatrenewalreplacement
relying on crisis-driven spending. as _ planned, ongoing obligation
integrated into annual budgeting
Delivery strategies should focus on minimizing disruption and capital programming so
and maximizing lifecycle value. In built-out corridors, the system remains dependable
bundling projects and coordinating restoration can without relying on
materially reduce cost and community impact. The City LL spending.
• WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE PLAN
WASTEWATER MASTER PLAN
should also use a practical "project packaging" approach: group similar rehab projects to improve
contractor efficiency, coordinate lift station upgrades with force main improvements where
needed, and time work to reduce traffic and business disruption when feasible. Clear construction
communication is part of successful delivery, not an afterthought.
GRANTS AND ALTERNATIVE FUNDING
While wastewater reinvestment is typically funded through utility revenues and planned capital
programming, alternative funding can be valuable when it reduces local burden, accelerates high-
benefit projects, or supports innovation. The City should evaluate grants and partnership funding
opportunities where they align with plan priorities particularly for resilience improvements, targeted
rehabilitation, monitoring enhancements, or projects that provide regional benefit.
Alternative tools can also include cost-sharing
partnerships, interlocal coordination where projects
overlap jurisdictions or regional assets, and opportunities PolicV Statement
tied to regulatory compliance or environmental benefit. �3. Pursue grants, partnerships,
The guiding principle is that external funding should id cost-effective delivery
not drive the project list; it should support the prioritie
already established through risk-based planning a
LOS alignment which is precisely the standard long-ter. system performance and
at
ratepayersreduce the burden on
Policy Statement FS3 establishes: pursuing g6_..' while maintaining accountability for
partnerships, and cost-effective delivery strategIL, outcomes.
when they strengthen long-term system p ance
and reduce the burden on ratepayers, while n
accountability for outcomes.
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This chapter documents how the Wastewater Ma r Plan vanced from a drafted policy
framework into an adopted supporting element of hlake's Co rehensive Plan. Southlake's
comprehensive planning process is designed to be spar t, iterative, and community-informed.
Rather than treating adoption as a single vote at the e City uses a sequence of public meetings
to build understanding, gather feedback, and r fine pla ection before formal action is taken. This
approach helps ensure the plan reflects co rio s, aligns with related Comprehensive
Plan elements, and provides clear implem ta e tion for staff and decision-makers.
The adoption process also reinforc ity' ommitment to meaningful public involvement.
Wastewater service is often most icea whe conditions change such as during major storm
events that increase wet-weathe st ocalized repairs that affect access or require
construction,or the rare in tan wh ustomers experience backups, odors,or service disruptions.
Residents form impression s r ility, communication, responsiveness, and confidence in
long-term stewardship. tructure ad ion process provides opportunities to ask questions,
review plan concepts, an vide in t in settings designed for dialogue, not just formal hearings.
Through Corridor Planning mi e work sessions, the SPIN Town Hall Forum/Open House,
Planning and Zoning Commiss iew, and City Council readings, the City is able to incorporate
feedback while keeping the plan grounded in objective data, regulatory requirements, and long-
term infrastructure stewardship.
ROLE OF THE CORRIDOR PLANNING COMMITTEE IN PLAN DEVELOPMENT
As part of the Comprehensive Plan update process, the Corridor Planning Committee provided
early guidance and direction that helped shape the development of the Wastewater Master Plan
(along with the Water and Stormwater plans being updated concurrently). Committee meetings
were structured to build shared understanding, review baseline conditions, and provide policy-
level feedback that staff could translate into clear plan direction. This step is important because the
Committee's role is not to design project solutions, but to help establish priorities, expectations, and
policy choices that guide how the City manages its infrastructure over time.
The City's Comprehensive Planning webpage documents the Committee schedule and topics,
including an initial overview meeting and subsequent plan-focused meetings. The Corridor Planning
Committee meeting on January 13, 2026 (overview of the Stormwater, Water, and Wastewater
plan updates) established shared context for the comprehensive utility planning effort, and the
WASTEWATER MASTER PLAN
February 10, 2026 meeting (Water/Wastewater focus) provided direction that informed refinement
of plan chapters, policy statements, and implementation pathways. Presentation materials from
these meetings are posted online to support ongoing transparency and resident awareness.
COMMUNITY ENGAGEMENT APPROACH AND COMMUNICATION STRATEGY
The City's engagement approach for these plan updates is built around multiple touchpoints, clear
communication, and accessible ways for residents to participate. The Comprehensive Planning
webpage emphasizes that presentation materials are posted online after meetings so residents
can stay informed even if they cannot attend in person. This Wastewater Master Plan also supports
expanding communication beyond meetings by using consistent messages and plain-language
tools that explain service expectations, wet-weather reliability principles, and "what residents can
expect" during planned reinvestment and capital delivery. In particular, the plan's emphasis on inflow
and infiltration (1/1) reduction and system integrity benefits from communication tools that help
residents understand how private-property practices and stormwater connections can influence
wet-weather system stress and long-term cost.
A central engagement milestone forthese plan updates is the Open House/Town Hall Forum on
March 2, 2026 at 5:00 p.m. in the Southlake Town Hall Cou bers. The City's Comprehensive
Planning page notes that this open house is intended t ovide dents an opportunity to share
feedback with staff on the Water, Wastewater, and St water Mast lans. This event is especially
valuable because it is designed for dialogue in a le orm etting than a public hearing, allowing
staff to clarify questions, identify recurring themes, an ment input that can be reflected in final
plan edits before adoption.
FORMAL REVIEW AND ADOPTION SCHED
After incorporating Committee dire n d p is input, the Wastewater Master Plan proceeds
through the City's formal adoptio thw . The icipated schedule for public consideration and
adoption includes:
January - April 2026 F ack Opportunity with City staff
March 2, 2026 — Open se Town Hall Forum (public feedback opportunity)
March 5,2026—Planni nd ing Commission meeting(formal reviewand recommendation
step)
April 7, 2026 — City Council 1st Reading (initial consideration)
April 21, 2026 — City Council 2nd Reading (final adoption consideration)
This stepwise schedule serves two purposes. First, it provides multiple opportunities for public
awareness and feedback prior to final adoption. Second, it supports good governance by ensuring
the plan is reviewed through the City's established boards and commission structure before Council
action. Planning and Zoning Commission review provides an additional public forum to evaluate
the plan's consistency with the Comprehensive Plan framework and its policy direction, while City
Council readings provide the final legislative pathway for adoption.
HOW FEEDBACK IS USED TO REFINE THE PLAN
Public engagement and board/commission review are not symbolic steps; they are intended to
improve the final document. Feedback from the Corridor Planning Committee and SPIN Open
House is used by staff to refine narrative clarity, strengthen communication tools (including 1/1
prevention messaging and "what residents can expect" guidance during construction), confirm that
policy statements are supported by clear rationale in earlier chapters, and ensure implementation
pathways are understandable. Feedback may also identify where additional graphics, maps, or
plain-language explanations are needed to make wastewater system planning concepts accessible
to residents.
The City's approach also emphasizes follow-through. Meeting materials are posted publicly, and the
plan is refined transparently so residents can see that input was received and addressed. Where
feedback reflects localized concerns such as odor issues, backup questions, service reliability
perceptions, construction disruption concerns, or questions about septic-to-sewer transitions
staff use documented information such as system performance findings, operational data, service
request trends, field observations, and technical study results to determine the most appropriate
plan response. Depending on the issue, that response may be improved communication, operational
adjustments, targeted maintenance practices, a standards/design alignment topic, 1/1 investigation
and rehabilitation sequencing, or a capital planning consideration.
DOCUMENTATION AND ADOPTION OUTCOME
Upon adoption, the Wastewater Master Plan becomes an o element supporting the City's
Comprehensive Plan and provides policy direction that 'des:
1. Wastewater service expectations and perforZ
ageme t practices
2. Asset management foundations and develohe Wastewater Infrastructure Asset
Management Plan
3. 1/1 reduction and system integrity progr d' including SSES prioritization principles
and outreach practices
4. Development and redevelo nt c dinat expectations that protect system performance
and long-term maintainabili
5. Long-range funding ning, and partnership strategies supporting lifecycle
reinvestment and r bility
Adoption also establishes ear b is for accountability, what the City committed to do, how
progress will be tracked, and idents can stay informed as implementation proceeds.
AFTER ADOPTION
Once adoption is completed, the Wastewater Master Plan transitions from a planning document into
the City's formal policy framework for wastewater system decision-making and service delivery.
Adoption establishes an official, Council-recognized basis for how the City will define wastewater
service expectations, evaluate system performance, prioritize reinvestment, and communicate
consistently with the community. It also clarifies how model findings, operational data, and asset
information will be used to support decisions and how the City will align wastewater infrastructure
stewardship with the Comprehensive Plan's broader goals for neighborhood stability, resilience,
and quality of life. In practical terms, adoption provides staff with clear direction to apply the plan's
policy statements when evaluating maintenance needs, capital improvement priorities, development
review, and regulatory responsibilities.
Following adoption, the City applies the plan in three primary ways. First, it becomes the guiding
reference for program implementation—supporting consistent customer communication, improved
1/1 prevention and FOG outreach, and clearer expectations for what residents and businesses can
WASTEWATER MASTER PLAN
anticipate during planned infrastructure work. Second, it becomes the organizing framework for
decision support and long-range planning formalizing how the City maintains and uses model
findings, strengthens its asset inventory and condition practices, and advances the Wastewater
Infrastructure Asset Management Plan to prioritize renewal and reinvestment. Third, it becomes the
foundation for sustainable funding and partnerships connecting documented needs (operations,
compliance, renewal, resiliency, and prioritized improvements) to transparent funding discussions
and enabling coordinated delivery with water, stormwater, streets, and redevelopment so the
community experiences fewer repeat disruptions and more predictable, accountable infrastructure
stewardship.
w
tea.. A14
ORDINANCE NO. 1034A I ADOPTED2026
WASTEWATER MASTER PLAN POLICY STATEMENTS
. 7 '�I=: W i
Manage the wastewater system as a long-life public asset by prioritizing
AM1 preventive maintenance, renewal, and replacement based on lifecycle needs
rather than reactive repair alone.
Establish and maintain a formal wastewater asset management program that
AM2 includes asset inventory, condition and criticality assessment, and risk-informed
renewal planning to guide annual budgets and multi-year capital programming.
Prioritize wastewater investments using a consistent, transparent framework
AM3 that considers public health, service reliability, consequences of failure, and
operational risk, with reinvestment becoming an increasing focus as Southlake
approaches buildout.
Define clear wastewater levels of service de planning, operations, and
LS1 investment decisions, emphasizing reli e con nce, minimized backups/
overflows, and dependable wet-weat performan
LS2 Use a consistent, systemwide plann b for evaluating capacity and wet-
weather performance so decisions are parable across basins and over time.
Improve reliability over time outin evaluating system performance,
LS3 identifying recurring drivers of r r ption, and adjusting maintenance
and capital priorities bas on d en d results.
� - . . . . IL
Plan and phasing s tegi ter improvements to support long-term
GD1 buildout conditions w of i unnecessary overbuilding, using sequencing
and timing to e strated need.
Require ne develo en and redevelopment to demonstrate adequate
GD2 wastewater acity a infrastructure compatibility and to mitigate system
impacts throu ap priate upgrades, timing, or participation in required
improvements.
Pursue opportunities to simplify wastewater operations and reduce long-term
GD3 risk and cost such as targeted system reconfiguration or consolidation when
supported by engineering evaluation and lifecycle benefit.
Advance a sustained inflow and infiltration reduction program through targeted
RS1 investigation and rehabilitation, focusing on areas with recurring wet-weather
impacts and the greatest risk-reduction potential.
Use appropriate field evaluations and system assessments to confirm suspected
RS2 problem areas and refine project scope, sequencing, and expected outcomes
before major capital commitments.
Implement an education-first public outreach program on private-property
RS3 1/1 prevention, including verifying cleanout caps are present and sealed and
preventing stormwater sources from connecting to the sanitary system.
WASTEWATER MASTER PLAN
Septic-to-Sewer Transition (ST)
Maintain the City's general approach to septic-to-sewer transition while
ST1 recognizing that conversion cost and physical feasibility vary by location,
extending service where practical and cost-effective - and considering
alternative solutions where connection is not feasible.
Evaluate septic-to-sewer incentives only when they are targeted,clearly justified,
ST2 and substantial enough to influence homeowner decisions while remaining
fiscally responsible and aligned with long-term planning priorities.
FT Me . -MBLVKC_ML1J Jill.
Fund the wastewater utility in a financially resilient and transparent manner by
FS1 aligning budgets, reserves, rates/fees, and capi planning with lifecycle needs
and long-term service expectations.
Treat renewal and replacement as a planne n Wng obligation integrated into
FS2 annual budgeting and capital program so th stem remains dependable
without relying on crisis-driven seen
Pursue grants, partnerships, and co ff ive delivery strategies when they
FS3 strengthen long-term system performa and reduce the burden on ratepayers
while maintaining accountabili outc S.
ORDINANCE
GLOSSARY OF TERMS
AM — Asset Management P&Z — Planning and Zoning Commission
Atlas 14 — NOAA Precipitation Frequency PID — Public Improvement District
Estimates (Rainfall Atlas)
RDII — Rainfall-Derived Inflow and Infiltration
CCTV — Closed-Circuit Television (pipe
inspection) ROW — Right-of-Way
CIP — Capital Improvement Program SCADA — Supervisory Control and Data
Acquisition
CMOM — Capacity, Management, Operation,
and Maintenance (wastewater program SSES — Sanitary Sewer Evaluation Study
framework)
SSO — Sanit Sewer Overflow
DCRWS — Denton Creek Regional Wastewater
System TCEQ — x ommission on Environmental
Quali
ETJ — Extraterritorial Jurisdiction
T — T ity River Authority
FOG — Fats, Oils, and Grease
_SS
otal Suspended Solids (only include if
gpd — gallons per day d; o wise omit)
gpm — gallons per minute D — ariable Frequency Drive
GIS — Geographic Information Sy WMP — Wastewater Master Plan
HGL — Hydraulic Grade Line
1/1 — Inflow and Infiltrati
ICM — Integrated Catchmen de
(InfoWorks ICM platform)
InSAR — Interferometric Synthetic Aperture
Radar (only include if used; otherwise omit)
LOS — Level of Service
MG — million gallons
MGD — million gallons per day
N/A — Not Applicable
NOAA — National Oceanic and Atmospheric
Administration
O&M — Operations and Maintenance
58 WASTEWATER MASTER PLAN SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
Asset (Wastewater) — Any component of the Consequence of Failure — The expected impact
wastewater collection system the City owns if an asset fails, including public health risk,
or is responsible for managing, such as pipes, environmental impact, service disruption, and
manholes, lift stations, force mains, and related repair complexity.
appurtenances.
Critical Bottleneck — A system location (pipe
Asset Criticality — A measure of the segment, junction, lift station, force main, or
consequence of failure for an asset based downstream interface) that limits conveyance
on factors such as the number of customers and can drive upstream surcharge and reliability
affected, proximity to sensitive areas, lack of risk.
redundancy, and difficulty of repair.
Design Storm — A rainfall event selected as a
Asset Management — A structured, risk-based standard basis for evaluating system response
approach to managing infrastructure over and sizing improvements (e.g., a NOAA Atlas 14
its lifecycle, including inventory, condition 5-year, 6-hou torm).
assessment, prioritization, renewal planning,
and performance tracking. Dry Wea ow (DWF) — Wastewater
flow d g p s without rainfall influence,
Average Day Flow (ADF) — Typical daily con ' ing prima of sanitary flow and
wastewater flow under normal conditions, g ndw er infiltr ion unrelated to rain
generally reflecting base sanitary wastewater e is
generation.
irm city (Lift Station) — The pumping
Backflow / Backup (Sewer Backup) — A 'ty ailable when the largest pump is out
condition where wastewater reverses direction e e (used for reliability-based design and
or rises to the point of impacting ups valuation).
plumbing or structures due to dow rea
restriction, surcharge, or lift statio it orce Main — A pressurized pipeline that
conveys wastewater pumped from a lift station
Basin (Wastewater Basin) — e a that to a downstream discharge point.
drains wastewater to a s is col io th
or discharge point, used rganizi system FOG (Fats, Oils, and Grease) — Grease material
planning, monitoring, and p itizati from kitchens and food service operations that
can accumulate in sewer lines, contributing to
Buildout — The condition in whi he blockages and backups.
community's land use and development
potential is largely realized, shifting Gravity Main — A pipeline that conveys
infrastructure needs from expansion to renewal wastewater using gravity and slope rather than
and stewardship. pumping.
Cleanout — A capped pipe access point Hydraulic Model — A computer-based
(often on private property) used to provide simulation of the wastewater system used to
maintenance access to the sanitary service line evaluate flows, depths, velocities, surcharge
or small-diameter collection piping. conditions, and performance under various
scenarios.
Condition Assessment — The process
of evaluating the physical condition and Hydraulic Grade Line (HGL) — The elevation
performance of assets using inspections, to which wastewater would rise in a manhole
maintenance records, CCTV, field observations, or pipe under pressurized conditions; used to
and other data sources. evaluate surcharge and overflow risk.
ORDINANCE NO. 1034A . . • 2026
Infiltration — Groundwater that enters the Rainfall-Derived Inflow and Infiltration (RDII) —
sanitary sewer system through defects, cracks, The portion of wet-weather flow that enters the
joints, or deteriorated structures. sanitary sewer system in response to rainfall,
used to characterize basin sensitivity and
Inflow — Stormwater that enters the sanitary prioritize investigation/rehabilitation.
sewer system directly and quickly during rainfall
through improper connections or openings Rehabilitation — The repair or renewal of an
(e.g., missing cleanout caps, illicit tie-ins). existing asset to restore performance and
extend service life (e.g., lining, point repairs,
Inflow and Infiltration (1/1) — The combined manhole rehabilitation, lift station component
contribution of inflow and infiltration that replacement).
increases wastewater flows above normal
sanitary levels, especially during storms. Renewal / Replacement — Planned
reinvestment in assets to address aging,
Interceptor — A large-diameter pipeline that deterioration, r performance limitations,
collects flow from multiple smaller lines and typically ba on risk and lifecycle strategy.
conveys it toward lift stations, force mains, or
downstream transfer points. Right-Si g anning and designing
impr ments match demonstrated
Level of Service (LOS) — A defined, measurable ne and erform e criteria while avoiding
expectation for system performance and ce y overbuilding and added lifecycle
reliability (often tied to wet-weather behavior, bu
surcharge thresholds, lift station margins, and
operational outcomes). DA monitoring and control system
rack lift station performance, alarms,
Lift Station — A facility that pumps w ter vels, and operational status in real time.
from a lower elevation to a higher e do o
continue conveyance when gravit ow i nitary Sewer Overflow (SSO) — An event
feasible. where wastewater discharges from the sanitary
sewer system to the environment due to system
Manhole — A vertical acce truc t failure, blockage, surcharge, or equipment
connects sewer pipes an rovides ry r issues.
inspection, cleaning, main t nce, a repair.
Sanitary Sewer Evaluation Study (SSES) — A
Peak Wet-Weather Flow (PW The structured program to identify and reduce 1/1
highest flow experienced during or following through basin screening, field investigations,
a rainfall event due to combined sanitary flow defect ranking, targeted rehabilitation, and
and RDII/1/1 response; often drives system post-rehab verification.
stress and sizing.
Surcharge — A condition where wastewater
Peaking Factor — A multiplier used to estimate rises above the pipe crown and pressurizes
peak flow conditions relative to average flow part of the system, often evaluated relative to
(used for planning and design). manhole rim elevation.
Private-Property 1/1 — Inflow or infiltration Septic System — An on-site wastewater
sources located on private property (e.g., treatment system used where properties are
missing cleanout caps, improper storm not connected to the municipal sewer system.
connections) that contribute additional wet-
weather flow to the public system.
. • WASTEWATER MASTER PLAN SOUTHLAKE COMPREHENSIVE PLAN
WASTEWATER MASTER PLAN
Septic-to-Sewer Transition — The process of
converting areas served by septic systems
to municipal wastewater collection service,
typically evaluated based on feasibility,
performance implications, and community
benefit.
Service Area — The geographic area served by
the City's wastewater collection system (may
include multiple basin contexts).
Wet Well — The below-grade holding structure
at a lift station where wastewater collects
before being pumped.
Wet-Weather Response — The change in
system flow and performance during rainfall
events due to RDII/1/1 contributions.
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FREES ND ICHOLS, INC. �EESEANDCHDLS, INC
TEXAS REGISTERED TEXAS REGISTERED
ENGINEERING FIRM ENGINEERING FIRM
F-2144 F-2144
Prepared by:
FREESE AND NICHOLS,INC.
801 Cherry Street,Suite 2800
Fort Worth,Texas 76102
817-735-7300
FNI Project Number: SOL23532
62 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
ivi
North Service Area Wastewater Master Plan Update
r7uic� s
City of South lake CITY OF
SOUTHLAKE
EXECUTIVE SUMMARY
1.0 INTRODUCTION
The City of Southlake (City) contracted with Freese and Nichols, Inc. (FNI) to prepare an update of the
City's Wastewater Master Plan for the North Service Area (Denton Creek Basin).This report presents the
analysis approach, findings, and results of the North Service Area Wastewater Master Plan Update. The
goal of the Wastewater Master Plan is to evaluate and analyze the wastewater collection system to
measure existing (2023) performance, identify deficiencies, and deter ine improvements needed to
meet future conditions. Historical wastewater flows were reviewed stablish trends and project flows
for the system evaluations. Based on the evaluations, a phased ita rovement Plan (CIP) through
Buildout was developed for the system. The recommend provement . I serve as a basis for the
design, construction, and financing of lines and faciliti quired meet the Ci y's future system needs.
2.0 LAND USE ASSUMPTIONS
FNI worked with City staff to develop and distrib th city-wide population and employment
growth as part of the concurrent W er Pla FNI. Population and employment projections from
the U.S.Census Bureau by Cens ock Gr (CBG) re used as a starting point.The City of Southlake's
Future Land Use Plan and informa nown elopments provided by City staff were used to adjust
the population and a roj ns. These projections were then refined for the North Service
Area based on the ice area bo ary a d distributed by flow monitoring basin at the parcel level.The
buildout projections in a two s arias: (1)without the incorporation of existing septic users and (2)
with the incorporation of e septic users. Table ES-1 summarizes the population and employment
projections for the North Service Area.
Table ES-1: North Service Area Population and Employment Projections
Population Employment
Planning Year Population Growth
Existing(2023) 12,368 - 18,230
Buildout Without Septic Users 13,992 13% 24,503 34%
Buildcut With Septic Users 16,181 31% 24,503 34%
ES-1
FREESE
North Service Area Wastewater Master Plan Update
City of Southlake 13 CITY OF
5OUTHLAKE
3.0 WASTEWATER FLOW PROJECTIONS
Projected wastewater flows were estimated based on the projected residential population and
employment growth. Based on the review of historical data presented, the historical overall per capita
flows, the 2018 Wastewater Collection System Flow Monitoring Report, and the need to plan for high
rainfall years, FNI utilized an existing residential average day per capita flow of 73 gallons per capita per
day (gpcd), a non-residential average day per employee production of 20 gallons per employee per day
(gped), and an existing peak wet weather to average day peaking factor of 4.0. It was decided to use a
residential average day per capita flow and non-residential average day r employee production of 100
gpcd and 30 gped, respectively, for growth areas to provide cons ive estimates of growth-related
flows. Based on the population and employment projections wa ater flow design criteria, the
projected buildout wastewater flows were calculated,as s in Table ES-
Table ES-2: North Service Area Pr a astewater Flows
VIA r
Existing 12,368 8, 1.27 5.07
Buildout Without Septic User 992 24,503 1.62 6.47
Buildout With Septic Us 1 81 IL 24,503 1.84 7.35
4.0 EXISTING WASTE S M
The City of Southlak orth 5ery re a ers approximately 13 square miles.Within the service area,
there are approximat 95,119 li r feet of gravity mains and 30,270 linear feet of force mains that
are owned and operated e .All flow in the North Service Area is conveyed to the TRA Kirkwood
Lift Station, which has a firm pacity of 6.05 MGD and transports flow through a 30/24/20-inch force
main to the TRA Denton Creek Regional Wastewater System Wastewater Treatment Plant (DCRWS
WWTP).This lift station is located at the intersection of North White Chapel Boulevard and Sabre Drive.
The wastewater collection system is primarily a gravity flow system that follows the major drainage basins
of the service area. The wastewater lines range from 2 to 27 inches in diameter. There are currently 12
lift stations in the wastewater collection system. These lift stations are required because of local
topographic constraints or to pump flows across sub basins. The City also receives flow from two
wholesale meters in the North Service Area.
ES-2
64 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
North Service Area Wastewater Master Plan Update
r��11CHoLS
City of Southlake rLa 13 CITY OF
SOUTHLAKE
Wastewater Model Development
The hydraulic model of the City's wastewater system includes force mains for all lift stations and all of the
gravity lines from the GIS database. As-built drawings provided by the City were used to add new lines
that have been constructed. If as-built drawings showing the pipe invert elevations were not available,
inverts were calculated either from known inverts using Texas Commission on Environmental Quality
(TCEQ) minimum slope requirements or by straight-line interpolation if upstream and downstream invert
elevations were available. Wastewater loads were updated throughout the model based on the water
billing meter data provided by the City and the wastewater flow projecti ns.
Historical Flow Monitoring Review and Data Evaluati
FNI reviewed the flow monitoring and rainfall data from t 018 Wast er Collection System Flow
Monitoring Report by RJN Group to be used in the calibr n oft astewate odel. Notably,this data
is over five years old and impacts the calibration of the ow conditions have likely changed since
2018, and the Country Lane Lift Station has sin decom ioned.
Rainfall dependent inflow and infiltration (RDII) i e ' d a rainwater that enters the sewer system
during a storm event. An RDII volu a Iculat to assist in ranking the temporary flow monitoring
basins. Flow meter basins with level u the temporary flow monitoring period, Basin N-
13 and Basin N-15, were i ified llow-up Sanitary Sewer Evaluation Study (SSES) activities when
the original flow mon' ng ana wa formed.
Wastewater Mode ibrati
Model calibration is the pro of rectifying parameters within the 1nfoWorks 1CM wastewater model
until the model generates and conveys flow in the same manner as observed during the flow monitoring
period. A properly calibrated model shows that the model produces results that reflect the flow, depth,
and velocity data obtained during flow monitoring. The period of May 11 through May 17, 2018, was
selected for dry weather model calibration, and the date range selected for wet weather calibration was
December 19 through December 21, 2017. All flow meter basins were calibrated within industry
standards.
ES-3
FREESE
North Service Area Wastewater Master Plan Update r, :NICNQLS
City of Southlake SOUTHLAKE
Design Storm Selection
One of the major objectives of this study is to understand how the collection system behaves during wet
weather events. Inflow and infiltration can lead to bottlenecks in the system and wastewater overflows.
To evaluate the system as a whole, a common storm event must be selected as the basis for evaluation
moving forward; this is referred to as a "design storm" and establishes a level of service. The National
Oceanic and Atmospheric Administration (NOAA) Atlas 14 5-year, 6-hour design storm was chosen, as it
corresponds closely with recent weather trends. The total depth of the 5-year, 24-hour design storm is
3.58 inches with a peak intensity of 2.68 inches per hour.
Existing Wastewater System Analysis
FNI used the calibrated hydraulic model to evaluate the exis ' system ake recommendations to
address deficiencies and short-term needs.The calibrati ows w e scaled t atch the total observed
existing flows to account for the growth that occurred a 018 flow monitoring analysis. Most of
the modeled existing pipeline capacity constr ' ccur do ream of the Dove Estates Lift Station,
Burney Lane Lift Station, and Quail Run Lift Sta n a y restrictions. The proposed system
improvements, including these areas d be for projected buildout flow conditions. All lift
stations are shown to meet the p ing c city re 'rement of 125%of peak wet weather flows with
the largest pump out of service un ons.
5.0 FUTURE TE STEM ANALYSIS
Hydraulic analyses were ucte identify projected deficiencies in the City's wastewater collection
system and to establish a CIP einforce the existing system and convey projected wastewater flows.
Various combinations of improvements and modifications were investigated to determine the most
appropriate approach for conveying projected flows. Parameters used in developing the CIP included
accommodating anticipated growth, including that from existing septic users, simplifying system
operations,and providing the capacity to handle peak wet weather flows.
As part of this study, the feasibility of eliminating existing lift stations with gravity sewer improvements
was also considered.The City expressed interest in decommissioning the Coventry Lift Station and Shady
Oaks Lift Station (located in the South Service Area). Alternatives aimed to decommission these lift
stations were explored during CIP development.
ES-4
66 WASTEWATER MASTER PLAN I SOUTHILAKE COMPREHENSIVE
WASTEWATER MASTER PLAN
FREESE
North Service Area Wastewater Master Plan Update
City of Southlake CITY OF
IISOUTHLAKE
The buildout peak flows are projected to slightly exceed the firm capacity of the TRA Kirkwood Lift Station.
With anticipated SSES efforts,the peak flows may be lowered to avoid increasing the capacity of this lift
station and force main. However, these potential capacity issues may need to be addressed as part of
TRA's future planning efforts.
The existing wastewater collection system under projected buildout peak wet weather flow conditions(5-
year,6-hour storm)was evaluated to determine where additional capacity is required.These results show
an increase in projected surcharging and overflows downstream of the Dove Estates Lift Station, Burney
Lane Lift Station, and Quail Run Lift Station. Additional capacity restrictions are shown near the Crown
Ridge Lift Station, Saddleback Lift Station,and Loch Meadows Lift Stati hen flows from existing septic
users are included, triggering capacity recommendations. All lif s except the Burney Lane Lift
Station and Loch Meadows Lift Station are shown to meet the ping ca requirement underfuture
conditions.Capacity improvements at these lift stations a re ired to ad ws from septic users in
the collection system.
6.0 WASTEWATER SYSTEM CA PR MENT PLAN
The goal of the CIP is to address exis ' ienci the system, as well as provide capacity for future
flows in the wastewater collect' syste on co letion of the wastewater model that represents
existing and future loading con capita provement projects were prioritized in order of
importance.Where exi a ne o be upgraded,the recommended improvements are sized to
carry projected bui flows. Th IP is categorized by four drivers: hydraulic capacity, operational
efficiency, engineering e tions d septic user incorporation.
Table ES-3 summarizes the recommendations based on the hydraulic analyses for the buildout CIP. All
project costs shown in this report are based on construction costs representing 2024 conditions and
should be adjusted in the future to reflect the current construction environment. The cost estimates
include material and construction costs, engineering design fees, and general contingency. Additional
expenses related to environmental,geotechnical, land acquisition, change order contingency,operations
and maintenance, and soft costs are not included.These costs also do not include escalation or inflation.
ES-5
FREESE
North Service Area Wastewater Master Plan Update <NICHQLS
City of Southlake r,,a19 CITY OF
SOUTHLAKE
Table ES-3:Wastewater System Capital Improvement Projects Cost Summary
Wastewater Project Drive�mw Cost 'q
Capacity Projects $6,750,300
Operational Efficiency Projects $1,862,100
Engineering Evaluation Projects $1,049,400
Septic User Incorporation Projects $35,652,400
CIP Total $45,314,200
ES-6
68 WASTEWATER MASTER PLAN I SOUTHLAKE COMPREHENSIVE
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