HomeMy WebLinkAbout2003-11-18; City Council; 17378 Sewer Update1; Sewer Master Plan Update Final ReportSewer Master Plan Update
Final Report
March 2003
3194-01
Prepared for:
City of Carlsbad
1635 Faraday Avenue
Carlsbad, CA 92008
Prepared by:
605 Third Street
Encinitas, CA 92024
760-942-5147
Sewer Master Plan Update - Final ReportMarch 2003
CITY OF CARLSBAD
SEWER MASTER PLAN UPDATE
Prepared For:
City of Carlsbad
1635 Faraday Avenue
Carlsbad, California 92008
Prepared By:
DUDEK & ASSOCIATES, INC.
605 Third Street
Encinitas, CA 92024
TEL (760) 942-5147
March 2003
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE ii March 2003
ACKNOWLEDGMENTS
Dudek & Associates would like to express its sincere appreciation for the assistance and cooperation
provided by the management and staff of the City of Carlsbad and the Encina Wastewater Authority
during the completion and preparation of this Master Plan Update. In particular, the efforts of the
following individuals are acknowledged and greatly appreciated:
• Steven Jantz ...............................................................Project Manager/Associate Engineer
• William Plummer ..............................................................................Deputy City Engineer
• Carrie Loya-Smalley.......................................................................... Senior Civil Engineer
• Terry Smith ....................................................................................... Senior Civil Engineer
• Pat Guevara......................................................................................Public Works Manager
• John “Louie” Montanez ...............................................................Public Works Supervisor
• Karl von Schlieder .................................................................................... GIS Coordinator
• Jim Elder ..........................................................EWA Operations Assistant Superintendent
• Lorren Etienne .................................................................................EWA Project Manager
• Jeff Parks ................................................................................EWA Laboratory Supervisor
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE iii March 2003
TABLE OF CONTENTS
Chapter Description Page
ACKNOWLEDGMENTS...................................................................................................ii
TABLE OF CONTENTS...................................................................................................iii
LIST OF TABLES..............................................................................................................v
LIST OF FIGURES ............................................................................................................v
LIST OF APPENDICES....................................................................................................vi
ANNOTATION.................................................................................................................vi
1 INTRODUCTION
1.1 BACKGROUND.............................................................................................1-1
1.2 SERVICE AREA OVERVIEW.......................................................................1-1
1.3 GROWTH MANAGEMENT PLAN...............................................................1-2
1.4 PREVIOUS MASTER PLANS.......................................................................1-3
1.5 2003 UPDATE SCOPE AND PURPOSE.......................................................1-4
2 SUMMARY OF FINDINGS AND RECOMMENDATIONS
2.1 INTRODUCTION AND SCOPE ...................................................................2-1
2.2 EXISTING SYSTEM OVERVIEW ..........................................................2-1
2.3 EXISTING WASTEWATER FLOWS .....................................................2-2
2.4 EXISTING SYSTEM EVALUATION .....................................................2-5
2.5 ULTIMATE FLOW PROJECTIONS .............................................................2-8
2.6 ULTIMATE SYSTEM EVALUATION ......................................................2-11
2.7 RECOMMENDATIONS ..............................................................................2-15
2.8 CAPITAL IMPROVEMENT PROGRAM ...................................................2-18
3 EXISTING SYSTEM DESCRIPTION
3.1 GENERAL.......................................................................................................3-1
3.2 INTERCEPTOR SYSTEM..............................................................................3-1
3.3 COLLECTOR SYSTEM...............................................................................3-12
3.4 LIFT STATIONS AND FORCEMAINS......................................................3-13
3.5 INTER-AGENCY AGREEMENTS..............................................................3-15
3.6 WASTEWATER TREATMENT AND DISPOSAL.....................................3-17
4 EXISTING WASTEWATER FLOWS
4.1 ENCINA FLOW METERS.............................................................................4-1
4.2 HISTORICAL FLOWS...................................................................................4-2
4.3 AVERAGE DRY WEATHER FLOWS..........................................................4-3
4.4 PEAK DRY WEATHER FLOWS...................................................................4-5
4.5 INFLOW AND INFILTRATION....................................................................4-6
4.6 EXISTING UNIT FLOW FACTORS.............................................................4-7
4.7 EXISTING FLOWS PER SUB-DRAINAGE BASIN....................................4-9
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE iv March 2003
5 EXISTING SYSTEM EVALUATION
5.1 DESIGN CRITERIA.......................................................................................5-1
5.2 EXISTING INTERCEPTOR SYSTEM HYDRAULIC MODEL...................5-2
5.3 CAPACITY ANALYSIS RESULTS ............................................................5-10
6 ULTIMATE SYSTEM FLOW PROJECTIONS AND ANALYSIS
6.1 PLANNED SEWER SYSTEM IMPROVEMENTS.......................................6-1
6.2 CARLSBAD GROWTH DATABASE ...........................................................6-3
6.3 FUTURE FLOW GENERATION FACTORS................................................6-5
6.4 PROJECTED ULTIMATE FLOWS...............................................................6-6
6.5 OTHER AGENCY FLOW PROJECTIONS...................................................6-8
6.6 ULTIMATE INTERCEPTOR SYSTEM HYDRAULIC MODEL.................6-9
6.7 CAPACITY ANALYSIS RESULTS ............................................................6-10
7 RECOMMENDATIONS
7.1 VISTA/CARLSBAD INTERCEPTOR IMPROVEMENTS...........................7-1
7.2 SOUTH AGUA HEDIONDA INTERCEPTOR IMPROVEMENTS.............7-4
7.3 LIFT STATION IMPROVEMENTS ..............................................................7-4
7.4 POTENTIAL FLOWS FROM OTHER AGENCIES .....................................7-5
7.5 JOINT TRANSMISSION SYSTEMS ............................................................7-5
7.6 TREATMENT CAPACITY REQUIREMENTS ...........................................7-6
7.7 OCEAN OUTFALL CAPACITY ..................................................................7-7
7.8 INFLOW AND INFILTRATION STUDY.....................................................7-7
7.9 RECOMMENDED CAPITAL IMPROVEMENT PROGRAM .....................7-8
8 CONNECTION FEE UPDATE
8.1 BACKGROUND.............................................................................................8-1
8.2 GROWTH PROJECTIONS.............................................................................8-2
8.3 CAPITAL COSTS FOR CAPACITY IMPROVEMENTS.............................8-3
8.4 CONNECTION FEE CALCULATIONS........................................................8-3
8.5 SEWER SYSTEM CASH FLOW ANALYSIS ..............................................8-5
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE v March 2003
LIST OF TABLES PAGE NO.
Table 2-1 August 2001 Encina Member Agency Flow Summary.................................................2-4
Table 2-2 Existing System Analysis Peak I&I Rates ....................................................................2-6
Table 2-3 Existing PWWF Analysis Summary for Gravity Pipelines...................................2-7
Table 2-4 Existing Potential Peak Flows to Interceptor Lift Stations....................................2-8
Table 2-5 Existing and Projected Ultimate ADWF to the Encina WPCF....................................2-10
Table 2-6 Capital Improvement Program.....................................................................................2-19
Table 3-1 Vista/Carlsbad Interceptor Ownership...........................................................................3-3
Table 3-2 Carlsbad Capacity Rights in the Buena Interceptor.......................................................3-9
Table 3-3 Conveyance System Summary ....................................................................................3-13
Table 3-4 Summary of Existing Lift Stations ..............................................................................3-14
Table 3-5 Inter-Agency Agreements Summary ...........................................................................3-16
Table 3-6 Encina WPCF Capacity Ownership.............................................................................3-18
Table 4-1 Encina WPCF Flow Meters...........................................................................................4-1
Table 4-2 August 2001 Encina Member Agency flow Summary..................................................4-3
Table 4-3 Faraday Industrial Flow Study Results..........................................................................4-8
Table 4-4 Existing Wastewater Flows Per Sub-Drainage Basin..................................................4-10
Table 5-1 Existing Carlsbad Flow Summary by Interceptor..........................................................5-4
Table 5-2 Existing System Analysis Peak I&I Rates ..................................................................5-10
Table 5-3 Reaches Flowing Full with Existing PWWF.........................................................5-11
Table 5-4 Potential Peak Flows to Interceptor Lift Stations ................................................5-12
Table 6-1 City of Carlsbad Growth Database Summary................................................................6-4
Table 6-2 Carlsbad Wastewater Unit Flow Comparisons..............................................................6-5
Table 6-3 Projected Ultimate Wastewater Flows by Sub-Basin....................................................6-7
Table 6-4 Existing and Projected Ultimate ADWF to the Encina WPCF......................................6-9
Table 6-5 Projected Peak Flows at Lift Stations..........................................................................6-17
Table 7-1 Summary of V/C Interceptor Recommend Improvements ...........................................7-2
Table 7-2 Lift Station Recommended Improvements....................................................................7-4
Table 7-3 Recommended Sewer Capital Improvement Program ..................................................7-9
Table 8-1 Projected Future EDUs within the Sewer Service Area ..............................................8-2
Table 8-2 Capital Improvement Projects for the Connection Fee Update ....................................8-4
Table 8-3 Sewer Connection Fee Calculation ...............................................................................8-5
Table 8-4 Sewer Connection Fee Cash Flow Analysis..................................................................8-6
LIST OF FIGURES
Figure 1-1 Carlsbad Sewer Service Area.......................................................................................*1-1
Figure 1-2 Major Drainage Basins ................................................................................................*1-2
Figure 1-3 LFMZ and Sub-Drainage Basin Boundaries................................................................*1-2
Figure 2-1 Existing Interceptor System.........................................................................................*2-2
Figure 2-2 Historical Wastewater Flows.........................................................................................2-3
Figure 2-3 August 2001 Flow Summary by Interceptor..................................................................2-4
Figure 2-4 Dry Weather Hydrographs for External Loads .......................................................2-5
*= Follows Page No.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE vi March 2003
LIST OF FIGURES (continued)
Figure 2-5 Dry Weather Unit Hydrographs for Internal Loads.......................................................2-6
Figure 2-6 Historical and Projected Ultimate Flows ...............................................................2-10
Figure 2-7 V/C Interceptor Peak Wet Weather Flow....................................................................2-12
Figure 2-8 South Agua Hedionda Peak Dry Weather Flow..........................................................2-13
Figure 2-9 Projected Carlsbad PWWF in the Buena Interceptor...................................................2-14
Figure 2-10 Projected Carlsbad PWWF in the Vallecitos Interceptor.............................................2-14
Figure 2-11 Projected Carlsbad PWWF in the Downstream North Batiquitos Interceptor.............2-15
Figure 2-12 V/C Interceptor Capacity with Recommended Improvements....................................2-16
Figure 3-1 Existing Interceptor System...........................................................................................2-1
Figure 3-2 Vista/Carlsbad Interceptor...........................................................................................*3-3
Figure 3-3 Full Pipe Capacity of the V/C Interceptor .....................................................................3-5
Figure 3-4 North Agua Hedionda Interceptor .................................................................................3-6
Figure 3-5 Capacity of the NAH Interceptor...................................................................................3-7
Figure 3-6 Buena and Vallecitos Interceptors.................................................................................3-8
Figure 3-7 Capacity of the Buena Interceptor .................................................................................3-9
Figure 3-8 North Batiquitos Interceptor........................................................................................3-11
Figure 3-9 Capacity of the North Batiquitos Interceptor...............................................................3-12
Figure 3-10 Lift Stations and Force Mains....................................................................................*3-13
Figure 3-11 Other Agency Wastewater Facilities .........................................................................*3-15
Figure 4-1 Encina Flow Meter Locations......................................................................................*4-1
Figure 4-2 Historical Wastewater Flows.........................................................................................4-2
Figure 4-3 5-Year Monthly Wastewater Flows vs. Rainfall............................................................4-3
Figure 4-4 August 2001 Flow Summary by Interceptor..................................................................4-4
Figure 4-5 Dry Weather Peaking Factor Data.................................................................................4-5
Figure 5-1 Dry Weather Hydrographs for External Loads..............................................................5-5
Figure 5-2 Dry Weather Unit Hydrographs for Internal Loads.......................................................5-6
Figure 5-3 Defect Flow Analysis for the Vista Meter.....................................................................5-7
Figure 5-4 Potential Peak Wet Weather Flows to the V/C Interceptor from Vista .........................5-8
Figure 5-5 Defect Flow Analysis for the C3 Meter.........................................................................5-9
Figure 5-6 NAH Interceptor Hydraulic Analysis Summary..........................................................5-13
Figure 6-1 Future South Agua Hedionda Interceptor Sewer.........................................................*6-2
Figure 6-2 Historical and Projected Ultimate Flows.......................................................................6-6
Figure 6-3 V/C Interceptor Peak Dry Weather Flow.....................................................................6-11
Figure 6-4 V/C Interceptor Peak Wet Weather Flow....................................................................6-12
Figure 6-5 South Agua Hedionda Peak Dry Weather Flow..........................................................6-13
Figure 6-6 Projected Carlsbad PWWF in the Buena Interceptor...................................................6-14
Figure 6-7 Projected Carlsbad PWWF in the Vallecitos Interceptor.............................................6-14
Figure 6-8 Carlsbad PDWF in the Upstream North Batiquitos Interceptor...................................6-15
Figure 6-9 Carlsbad PWWF in the Downstream North Batiquitos Interceptor.............................6-16
Figure 7-1 V/C Interceptor Capacity with Recommended Improvements......................................7-2
Figure 7-2 Upper V/C Interceptor Recommended Improvements ................................................*7-3
Figure 7-3 Lower V/C Interceptor Recommended Improvements................................................*7-3
Figure 7-4 South Agua Hedionda Interceptor Recommended Improvements...............................*7-4
* = Follows Page No.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE vii March 2003
LIST OF APPENDICES
Appendix A Exhibits:
Exhibit 1- Existing Wastewater Collection System
Exhibit 2- Ultimate Wastewater Collection System
Appendix B Ownership/Operation Agreements with other Agencies
Appendix C 24-hour Encina Flow Meter Plots
ANNOTATION
The following abbreviations and acronyms were used in the preparation of this Master Plan:
ADWF Average Dry Weather Flow
APN Assessor Parcel Number
BSD Buena Sanitation Division
CCFRPM centrifugally cast fiberglass reinforced plastic mortar
CIP Capital Improvement Program
City City of Carlsbad
DIP Ductile iron pipe
EDU Equivalent Dwelling Unit
EIR Environmental Impact Report
ESD Encinitas Sanitary Division, City of Encinitas
EWA Encina Wastewater Authority
fps feet per second
GIS Geographical Information System
gpcd gallons per capita per day
gpd gallons per day
gpm gallons per minute
Hp horsepower
hr hour
I&I Inflow and Infiltration
in inches
lf linear feet
LCWD Leucadia County Water District
LFMZ Local Facility Management Zone
mgd million gallons per day
MFDU multi-family dwelling unit
MG million gallons
NAH North Agua Hedionda
NB North Batiquitos
PDWF Peak Dry Weather Flow
PWWF Peak Wet Weather Flow
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE viii March 2003
ANNOTATION (continued)
RCP Reinforced concrete pipe
SAH South Agua Hedionda
SanGIS San Diego County Geographic Information System
SFDU single family dwelling unit
USGS United States Geologic Survey
V/C Vista/Carlsbad
VCP Vitrified clay pipe
VFD Variable frequency drive
VWD Vallecitos Water District
WPCF Water Pollution Control Facility
WRP Water Reclamation Plant
WWTP Waster Water Treatment Plant
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 1-1 March 2003
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
The Carlsbad Sanitary District, formed in 1929, provided the first sewer service to areas now within the
City of Carlsbad. A sewage treatment plant and a system of sewer lines, serving the northwest corner of
the present village area of the City Carlsbad, were initially constructed with the formation of the Sewer
District. Thus, portions of the City’s existing conveyance system date back as far as 1929. The original
treatment plant location was on the south shore of the Buena Vista Lagoon, adjacent to Carlsbad
Boulevard. This is the present location of the Home Plant Lift Station.
The Carlsbad Sanitary District provided sewer service until the City of Carlsbad incorporated in 1952.
When the City of Carlsbad incorporated, there were approximately 600 parcels of property being served
by the Carlsbad Sanitary District. The City of Carlsbad expanded the sewer system and increased the
number of connections. By 1960, it was apparent that a larger treatment facility would be required. To
meet the growing regional needs for sewer service, the City of Carlsbad and the Vista Sanitation District
jointly constructed the Encina Water Pollution Control Facility (WPCF), located just south of Palomar
Airport Road and west of Interstate 5. When the WPCF was put into operation in 1965, wastewater flows
to the old Carlsbad Sanitary District plant were diverted to the new treatment facility. The Encina WPCF
is now jointly-owned and operated by six northern San Diego County wastewater agencies as the Encina
Wastewater Authority (EWA).
1.2 SERVICE AREA OVERVIEW
The City of Carlsbad wastewater service area covers approximately 70 percent of the City limits. Sewer
service to the southeast corner of the City is provided by the Leucadia County Water District (LCWD),
and the Vallecitos Water District (VWD) provides service to the Meadowlark area along the eastern City
limit. The Carlsbad service area boundary and adjacent district boundaries are shown on Figure 1-1.
The elevation of the service area varies from just under 600 feet at the eastern boundary to sea level along
the coast and lagoon shores. The service area is comprised of five major drainage basins, which extend
from approximately the eastern service area boundary, and drain west to the coast and ultimately the
Encina WPCF. These sewage drainage basins are defined by the existing and planned interceptors within
the City of Carlsbad. In addition to the gravity interceptors, a number of lift stations are required to
convey wastewater flows to the Encina WPCF. The major drainage basins are shown on Figure 1-2.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 1-2 March 2003
The northern-most drainage basin in the City is the Vista/Carlsbad (V/C) basin. The V/C basin begins at
the northeast Carlsbad boundary and extends west, with an area that extends approximately ½ mile south
of Highway 78 and, further west, to the Buena Vista Lagoon. At the Buena Vista Lagoon, the basin turns
south and extends along the coast. The basin includes areas west of Interstate 5 from the Buena Vista
Lagoon to the Encina WPCF.
Adjacent to the V/C basin to the south is the North Agua Hedionda (NAH) drainage basin. This basin
drains to the north shore of the Agua Hedionda Lagoon and then into the V/C basin.
The next drainage basin to the south is the South Agua Hedionda (SAH) basin. This basin generally
follows the Agua Hedionda Creek from the City of Vista boundary to the Agua Hedionda Lagoon, and
then continues west along the south side of the lagoon before draining to the V/C basin. The SAH basin
is approximately two miles wide at the eastern City boundary, and narrows to about ½ mile wide at its
western boundary with the V/C basin.
The drainage basin that includes the Encinas Canyon area is called the Buena/Vallecitos basin, since it is
served by two separate interceptors. This basin contains a portion of the Batiquitos Lagoon drainage area,
which is also referred to as the North La Costa area. The drainage area begins at the eastern boundary of
the service area adjacent to the Vallecitos Water District, and extends west to the Encina WPCF.
The most southerly sewer drainage basin is the North Batiquitos basin. This basin begins at El Camino
Real and extends west along the north shore of the Batiquitos Lagoon to Interstate 5. At Interstate 5, the
basin turns north and follows the coast to the Encina WPCF.
1.3 GROWTH MANAGEMENT PLAN
On July 1, 1986, the City Council of Carlsbad adopted a Growth Management Plan to help assure
provision of adequate facilities for future development. Implementation of the Growth Management
Program was envisioned as a three level system, involving 1) a Citywide Facilities and Improvement
Plan, 2) the preparation of 25 Zone Facilities Plans, and 3) individual project approvals. The Citywide
Plan established the following standards for sewer collection and wastewater treatment:
• SEWER COLLECTION SYSTEM PERFORMANCE STANDARD – Trunk line capacity to
meet demands as determined by the appropriate sewer district must be provided concurrent
with development.
• WASTEWATER TREATMENT CAPACITY PERFORMANCE STANDARD – Sewer
plant capacity is adequate for at least a five year period.
EL
ALGALANE
T A M A R A C K
LA
ROAD
D R IV E
A V E N U E
MARRON
V I L L A G E
AIRPORT
R O A D
CAMINO
R O A D
BOULE VARD
POI N SE T TI ACARLSBADCARLSBAD
COSTA
R
EAL
BOULEVARDC AN N O N ROAD
B OU LEVAR DPALOMAR
AVIARAPARK
WAY
C OLL E G E
OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE
5
5
03-2003 Carlsbad102.mxd
FIGURE 1-2
CITY OF CARLSBAD
MAJOR DRAINAGE BASINS
LEGEND
SEWER SERVICE AREA BOUNDARY
MAJOR DRAINAGE BASINS
VISTA/CARLSBAD
NORTH AGUA HEDIONDA
SOUTH AGUA HEDIONDA
BUENA/VALLECITOS
NORTH BATIQUITOS
1"=4000'
8
9
1I
1E
15B1J
5B
14A
18B
16
5I
2C 15A
3B
25
1H
13A
4A
7C1D
19A 19C
7B
19D
5F
1G
22B
2A
19B
5G
1F
6A
5D
7A
20A
1B
17B
1A
3A
4B
17A
5E
13B 5H
18A
5K
10C
20B
5A
10A
5J
24A
20C 21B
14A
5C
2B
14B
10B
21A 6B
20D
1C
22A
3C
24B
20E
21C
OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE
5
5
EL
ALGALANE
T A M A R A C K
LA
ROAD
D R IV E
A V E N U E
MARRON
V I L L A G E
AIRPORT
R O A D
CAMINO
R O A D
BOULE VARD
POI N SE T TI ACARLSBADCARLSBAD
COSTA
R
EAL
BOULEVARDC AN N O N ROAD
B OU LEVAR DPALOMAR
AVIARAPARK
WAY
C OLL E G E
03-2003 Carlsbad103.mxd
FIGURE 1-3
CITY OF CARLSBAD
LFMZ AND SUB-DRAINAGE BASIN
BOUNDARIES
1"=4000'
LEGEND
SEWER SERVICE AREA BOUNDARY
LFMZ BOUNDARY
SUB BASIN BOUNDARY & DESIGNATIONS
LFMZ'S BY COLOR
1
2
3
4
5
6
7
8
9
10
13
14
15
16
17
18
19
20
21
22
24
25
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 1-3 March 2003
As part of the Growth Management Plan, the City of Carlsbad was partitioned into 25 separate planning
areas. These planning areas are identified as Local Facility Management Zones (LFMZs). The City of
Carlsbad Sewer Service Area includes all or portions of LFMZs 1-10, 13-22, 24 and 25.
Some of these planning areas fall into more than one sewer drainage basin. The LFMZs were sub-divided
in the 1992 Master Plan of Sewerage to project flows for specific sewer drainage basins. These sub-
zones, referred to as sub-drainage basins or sub-basins, have been revised in this Master Plan Update to
more accurately allocate and distribute existing and future flows to the sewer interceptors. The LFMZs
and current sub-basin designations used throughout this report are illustrated on Figure 1-3.
1.4 PREVIOUS MASTER PLANS
Summaries of the three most recent Sewer Master Plans are provided in the following sub-sections.
1.4.1 1987 Master Plan of Sewerage
The 1987 Master Plan of Sewerage was the first master plan prepared in accordance with City of Carlsbad
Growth Management Plan. In 1987, the majority of development in Carlsbad was along the coastal strip
and predominantly residential. The population of the 1987 study area was estimated at 39,000, and the
ultimate population was projected to be 95,700. Average wastewater flows were projected at a rate of
220 gallons per day per equivalent dwelling unit (EDU). In 1987, the ultimate average flow from the City
of Carlsbad was projected to be 13.41 million gallons per day (MGD).
1.4.2 1992 Master Plan of Sewerage
The 1992 Master Plan of Sewerage was an update of the 1987 Master Plan. By 1992, the population of
the study area had increased to 65,000 and the ultimate population projection had increased to 130,000.
Development was starting to progress inland and the percentage of commercial/industrial development
had increased since the last Master Plan. The projected population growth curve first developed in the
1987 Master Plan was revised to increase more rapidly through the year 2000, and then flatten out to an
annual growth rate of approximately 1 percent from the year 2000 to buildout. In 1992, the ultimate
average flow projection was increased slightly from the 1987 projection to an estimated flow of 13.84
MGD.
Major improvements to the 1992 sewer system recommended in this update included capacity upgrades to
the Vista/Carlsbad Interceptor, replacement of the Home Pant Lift Station, and the construction of gravity
sewers to lift stations in LFMZs 2 and 7. It was also recommended to divert wastewater flows from the
Palomar Oaks Business Park area, located north of Palomar Airport Road and east of El Camino Real,
from the South Agua Hedionda Drainage Basin into the Buena Interceptor.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 1-4 March 2003
1.4.3 1997 Sewer Master Plan Update
In 1994, the City of Carlsbad adopted a new General Plan. The 1997 Sewer Master Plan Update
incorporated the revised 1994 land use and population projections. Because ultimate population
projections were reduced only slightly from those used in the previous Master Plan, an updated capacity
analysis of the interceptors was deemed unnecessary. The 1997 Master Plan Update focused on analyses
of the NAH and SAH sewer basins to determine whether excess hydraulic capacity in the NAH
Interceptor could be used to convey portions of the SAH flows. Preliminary sizing, slope and alignment
of the SAH Interceptor was performed as part of this update. Also included in the update were additional
hydraulic analyses of the V/C Interceptor and a detailed survey of the existing lift stations.
1.5 2003 UPDATE SCOPE AND PURPOSE
This report represents an update of the City of Carlsbad Sewer Master Plan (Master Plan) for the planning
period between 2002 and buildout of the District’s service area. In summary, the scope includes tasks to
document existing facilities, project ultimate average wastewater flows, estimate existing and ultimate
peak flows, and develop a computer model to perform an existing and ultimate system capacity analysis.
The outcome of these analyses is a recommended long-term Capital Improvement Program (CIP) for
improvement of existing wastewater collection and treatment facilities. An update of the sewer
connection fee is included to finance the recommended facilities, and an out-of-basin sewer study for the
SAH basin is included to determine when the future SAH Interceptor may be required.
A major task included in the Master Plan scope is the development of a Geographical Information System
(GIS) for the sewer collection system. The sewer GIS was used to create a computer model of the
interceptor system and produce maps of the collection system for this report. The completed sewer GIS
and supporting documentation has been submitted under a separate cover. Supporting environmental
documentation in compliance with the California Environmental Quality Act (CEQA) for the projects
identified in the CIP will also be submitted in a separate document.
In this Master Plan Update, ultimate sewer flow projections are based on the City’s recently compiled
Growth Database, which projects the number of additional single and multi-family units and the number
and size of non-residential buildings at buildout. The capacity analyses are performed with a state-of-the-
art hydraulic model based on the newly developed sewer GIS. Major improvements over previous
modeling efforts include: 1) a single integrated model of the sewer collection system, 2) an accurate
representation of the Vallecitos and Buena Interceptors (modeled as a combined interceptor in the
previous Master Plans), 3) the determination of existing peak wet weather flows from available meter
data, and 4) analysis using extended period simulations, which account for travel time in the
determination of peak flow rates.
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-1 March 2003
CHAPTER 2
EXECUTIVE SUMMARY
2.1 INTRODUCTION AND SCOPE
The City of Carlsbad Sewer Master Plan Update documents the existing sewer collection system and
identifies required facilities for the buildout of the District’s service area, anticipated to occur by the year
2020. The scope for this update includes tasks to document existing facilities, project ultimate
wastewater flows, estimate existing and ultimate peak flows, and develop a computer model to perform
an existing and ultimate system capacity analysis of the interceptor system. The outcome of the analysis
is a recommended long-term Capital Improvement Program (CIP). An update of the sewer connection
fee is included to finance the recommended facilities.
A major task included in the Master Plan Update scope is the development of a Geographical Information
System (GIS) for the sewer collection system. The sewer GIS was used to create a computer model of the
interceptor system and produce maps of the collection system for this report. The completed sewer GIS
and supporting documentation were submitted to the City under a separate cover in February 2003.
Supporting environmental documentation in compliance with the California Environmental Quality Act
(CEQA) for the projects identified in the Master Plan Update CIP will also be submitted separately at a
later date.
In this Master Plan Update, ultimate sewer flow projections are based on the City’s recently compiled
Growth Database, which projects the number of additional single and multi-family units and the number
and size of non-residential buildings at buildout. The capacity analyses are performed with a state-of-the-
art hydraulic model based on the newly developed sewer GIS. Major improvements over previous
modeling efforts include: 1) a single integrated model of the sewer collection system, 2) an accurate
representation of the Vallecitos and Buena Interceptors (modeled as a combined interceptor in the
previous Master Plans), 3) the determination of existing peak wet weather flows from available meter
data, and 4) analysis using extended period simulations, which account for travel time in the
determination of peak flow rates.
2.2 EXISTING SYSTEM OVERVIEW
The City of Carlsbad Sewer Service Area includes the majority of the City, with the exception of the
southeast corner of the City. Wastewater collection in the southeastern area is provided by the Vallecitos
Water District (VWD) and the Leucadia County Water District (LCWD). Carlsbad’s Sewer Service Area
extends from the Pacific Coast approximately 5 miles inland, providing wastewater collection, treatment
and disposal service to customers within its 30 square mile service area. Wastewater is conveyed to the
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-2 March 2003
Encina Water Pollution Control Facility (WPCF) for treatment and disposal through an ocean outfall.
The Encina WPCF is owned and operated by the Encina Wastewater Authority (EWA), a joint powers
authority made up of six northern San Diego County wastewater agencies.
The City of Carlsbad sewer service area is comprised of five major drainage basins, which extend from
approximately the eastern service area boundary, and drain west to the coast and ultimately to the Encina
WPCF. These sewage drainage basins are defined by the existing and planned interceptors within the
City of Carlsbad. Four of the interceptor systems have been constructed and are now in use. Most
interceptors convey upstream flows from other agencies in addition to City of Carlsbad flows. The
existing interceptor systems in order from north to south are listed below.
· Vista/Carlsbad (V/C) Interceptor - collects City of Vista and Carlsbad flows. Jointly owned by the
City of Vista and the City of Carlsbad
· North Agua Hedionda (NAH) Interceptor - conveys only City of Carlsbad wastewater.
· Buena/Vallecitos Interceptor system – consists of two separate interceptors sharing a common
alignment through the Encinas Canyon: the Buena Interceptor, owned by the City of Vista’s Buena
Satiation District, and the Vallecitos Interceptor. The City of Carlsbad has capacity rights in the
Buena Interceptor and the City of Carlsbad, City Vista and the VWD share capacity ownership in the
Vallecitos Interceptor.
· North Batiquitos (NB) Interceptor - collects only Carlsbad flows in the upper reaches. The last
approximately half mile before the Encina WPCF is jointly owned by the City of Carlsbad, the
LCWD, and the Encinitas Sanitary Division of the City of Encinitas. The combined ownership
section is sometimes referred to as the Ponto Interceptor or the Occidental Sewer.
In addition to the approximately 30 miles of interceptor sewers, the City of Carlsbad currently owns,
operates, and maintains approximately 200 miles of gravity collector system pipelines and approximately
5,000 manholes. Eighteen wastewater lift stations are currently located within the City of Carlsbad Sewer
Service Area. The Buena Vista and Agua Hedionda Lift Stations, which are part of the V/C Interceptor,
are operated and maintained by the Encina Wastewater Authority. The remainder of the lift stations are
owned and operated by the City of Carlsbad. Exhibit 1 in Appendix A provides an illustration of the
existing wastewater collection and conveyance system and Figure 2-1 illustrates the interceptor reach
designations used throughout this Master Plan Update.
2.3 EXISTING WASTEWATER FLOWS
As population has grown and the northern coastal areas of San Diego County continue to develop, the
City of Carlsbad has experienced gradually increasing wastewater volumes. The Encina Wastewater
Authority operates and maintains numerous flow meters throughout the service areas of its six member
agencies. A Centralized Flow Metering Program was implemented in 1989 and meter upgrades were last
EL
ALGA
L A N E
T A M A R A C K
LA
ROAD
D R I V E
A V E N U E
MARRON
V IL L A G E
AIRPORT
R O A D
CAMINO
R O A D
BO U L EVA R D
PO IN S ETT IACARLSBADCARLSBAD
COSTA
RE
AL
BOULEVARDC ANNON ROAD
BO ULEVARD
PALOMAR
AVI
ARAPARK
W
AY
COLL EGE
5
5
OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE
B4
V4
B 2
VC1
V 6
V3
B6
V5VC4VC14
NB4
B 7
VC3
V 7
B 8
NB8B1VC10
VC13V C2
NAH3NAH5
NB6N A H 2
NB3NB7VC6
N B 2 NB1VC15NBT3BVC11NB9VC5BNAHT1BNAH1VC9
N A H 7
NB10VC5AVC7
VC8
NAH4VC12
NB5
B5
V 8
NAH6
VISTA/CARLSBAD
NORTH AGUA
HEDIONDA
BUENA
VALLECITOS
NORTH BATIQUITOS
03-2003 Carlsbad201.mxd
FIGURE 2-1
CITY OF CARLSBAD
EXISTING INTERCEPTOR SYSTEM
LEGEND
SEWER SERVICE AREA BOUNDARY
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
1"=4000'
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-3 March 2003
made in 1996. Wastewater flows generated within the City of Carlsbad are metered in the interceptor
pipelines upstream of the Encina WPCF. Because of flow contributions from upstream agencies,
Carlsbad flows must be determined by subtracting other agency flows from measured flows at the WPCF.
Carlsbad average annual wastewater flows, as calculated from Encina meter data, are summarized for the
past 15 years on Figure 2-2. As shown on the chart, wastewater flows decreased significantly after 1989.
This was typical of most Southern California sewage agencies, and can be attributed to conservation
measures implemented during drought conditions. Some of the conservation measures were temporary
but many, such as the installation of low-flow bathroom fixtures, have had a lasting effect. Flow meters
were replaced at the beginning of 1996, and the improved accuracy may have contributed to the flow
decrease observed after 1995. It is only over the past four years that wastewater flows have surpassed
flows generated in the late 1980’s. The higher flows are a result of steady increases population, as land
use within the service areas has transitioned from mainly agricultural use to urbanized development.
Figure 2-2
HISTORICAL WASTEWATER FLOWS
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
For this Master Plan Update, EWA meter data for August 2001 was used to determine the existing
average dry weather flow (ADWF). The month of August was selected because it was the most recent
month during the dry season in which all meters appeared to be operating properly and complete flow
data could be obtained. Table 2-1 summarizes the average flow for Carlsbad and the other EWA
agencies for August 2001. This information is illustrated graphically by interceptor system on Figure 2-3.
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SEWER MASTER PLAN UPDATE 2-4 March 2003
Table 2-1
AUGUST 2001 ENCINA MEMBER AGENCY FLOW SUMMARY
Interceptor Carlsbad Other Agency Flows Total
System Flows Agency Flow Flow
Vista/Carlsbad & NAH 3.89 MGD City of Vista 5.84 MGD 9.73 MGD
Buena 1.84 MGDBuena1.06 MGD Vista (raceway)0.20 MGD 3.10 MGD
Vallecitos 0.97 MGD Vallecitos 4.28 MGD 5.25 MGD
North Batiquitos*0.56 MGD Leucadia/Encinitas 5.14 MGD 5.70 MGD
Totals 6.48 MGD 17.30 MGD 23.78 MGD
* Metered flow at EWPCF is .28 MGD less than the upstream flow metered at the North Batiquitos Lift Station.
Figure 2-3
AUGUST 2001 FLOW SUMMARY BY INTERCEPTOR
0
1
2
3
4
5
6
7
8
9
10
Vista/Carlsbad &
NAH
Buena Vallecitos North Batiquitos
Buena SD
City of Vista
Vallecitos
Leucadia/Encinitas
Carlsbad
CARLSBAD INTERCEPTOR SYSTEMS
From Figure 2-3, it is apparent that Carlsbad flows comprise a minority of the total flows in each of the
interceptors. This is especially true in the North Batiquitos Interceptor, for which the Carlsbad flow
proportion is less than 10 percent of the total flow measured at the Encina WPCF. Because Carlsbad
flows are calculated by subtracting upstream and downstream flow meter readings, the resultant flows are
dependent on the accuracy of the meters. If the Carlsbad flow contribution is very small relative to the
upstream flows, an error of 5 percent on the upstream and downstream readings (the rated accuracy of the
gravity flow meters under ideal flow conditions) can have a large effect on the calculated flow for
Carlsbad.
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-5 March 2003
Flow generation factors based on existing flow conditions were developed to distribute flow in the
existing system hydraulic computer model. Sewer flow factors were derived from August 2001 Encina
flow meter data, parcel information contained in the City’s Growth Database, and City of Carlsbad water
billing records, which were assigned an assessor parcel number (APN) by City staff. The average unit
flow per residential unit for the existing Carlsbad sewer system is calculated to be approximately 195
gpd/EDU. It is noted that the flow generation factors based on existing conditions are different than the
flow factors developed to project future flows.
2.4 EXISTING SYSTEM EVALUATION
A new model of the Carlsbad interceptor system was developed from GIS data collected as apart of this
Master Plan Update. The evaluation method employs the use of the SewerCAD hydraulic modeling
software, which performs hydraulic calculations based on standard open channel flow algorithms and
Manning’s equation. SewerCAD performs extended period simulations (EPS) to route wastewater flows
through the conveyance system using a unit hydrograph or diurnal curve. The result of this analysis
technique is a more accurate depiction of the true peaking factor within the subject collection system.
Information from City of Carlsbad water billing records was associated with the City’s parcel base, and
then used to distribute internal flows to the interceptor system model. Peak dry and wet weather flows
were input to the model using hydrographs (diurnal curves) developed from 24-hour metering data. The
peaking curves developed for upstream agency flows are illustrated on Figure 2-4 and the unit
hydrographs applied to Carlsbad flows are shown on Figure 2-5. It is noted that a total flow rate of 6.8
MGD for City of Carlsbad flows was used in the existing system analysis, which is slightly higher than
the actual totals calculated based on the August 2001 Encina meter records. A higher flow was used for
the North Batiquitos Interceptor based on flow meter data from the North Batiquitos Lift Station.
Figure 2-4
DRY WEATHER HYDROGRAPHS FOR EXTERNAL LOADS
0
1
2
3
4
5
6
7
8
9
10
0 5 10 15 20 25
Time (hours)
V1 L1 VA1 B2+V2
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SEWER MASTER PLAN UPDATE 2-6 March 2003
Figure 2-5
DRY WEATHER UNIT HYDROGRAPHS FOR INTERNAL LOADS
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 24:00
Time of Day (hours)
Residential Non-Residential
To evaluate the operation of the existing system during peak flow periods, wet weather flows were
analyzed and compared to dry weather flows. Flow metering data from five storm events was reviewed
and a single storm was selected to determine inflow and infiltration rates (I&I) in the system. The storm
event selected for analysis occurred on November 24, 2001. The total rainfall amount for this storm was
1.29 inches with a peak intensity of 0.55 inches/hour. The rainfall occurred during an off-peak flow
period and lasted for approximately 4 hours. Peak wet weather flow curves were developed based on
observed inflow rates from November 24, 2001 meter data, assuming that the storm event occurred during
the daily peak flow period. Table 2-2 summarizes the I&I applied in the existing system wet weather
hydraulic analysis based on this flow analysis.
Table 2-2
EXISTING SYSTEM ANALYSIS PEAK I&I RATES
Model ID Description Flow Rate
(MGD)
V1 City of Vista External Inflow 2.6
272 City of Vista External Infiltration 3.0
VC_IntWx Carlsbad Internal I&I to V/C 4.7
B2_V2 Buena/Raceway External I&I 1.1
437 Carlsbad Internal I&I to Buena 0.5
VA1 Vallecitos External I&I 3.5
L1 Leucadia External I&I 2.1
TOTAL ESTIMATED I&I 17.4
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SEWER MASTER PLAN UPDATE 2-7 March 2003
Hydraulic analyses were performed on the existing interceptor system with both dry and wet weather
flows. Capacity analysis of open channel systems is generally based on the consideration of the depth of
flow as compared to the diameter of the pipe (D/d). The capacity analysis under dry weather flow
conditions indicates that two flat pipeline reaches in VC14 and VC15 are flowing full. There is a very flat
400-ft segment in VC14 with a slope of less than 0.01 percent that is calculated to have a capacity of 5.5
MGD, and a 20-foot segment in VC15 was found to have a slightly negative slope. The pipelines in these
two sections currently operate under pressure flow conditions. There are a few isolated locations where
flows exceed the 75 percent full criteria in the Buena Interceptor, also due to short sections of very flat
pipeline.
Based on analysis of the existing collection system with wet weather flows, several gravity pipelines were
determined to be deficient with respect to the City’s design criteria (pipelines over 12-inch in diameter
should not flow more than 75 percent full with peak wet weather flows). It is noted that the peak wet
weather event modeled is conservatively based on potential flows and I&I rates that could occur, and is
not based on actual recorded flows. The potentially deficient pipeline reaches identified during the
existing system analyses are located within four separate areas of the interceptor system, as documented
in Table 2-3.
Table 2-3
EXISTING PWWF ANALYSIS SUMMARY FOR GRAVITY PIPELINES
The longest sections of pipeline in Table 2-3 are in the Vista/Carlsbad Interceptor in Reach VC-3, which
is upstream of the Buena Vista Lift Station, and Reaches VC-13-15, which are downstream of the Agua
Hedionda Lift Station. These pipeline reaches are planned for future capacity upgrades, and the
replacement pipelines are sized based on ultimate flows in the next chapter of this report. The other two
areas with existing capacity deficiencies are short sections of pipeline in the upstream and extreme
downstream reaches of the Buena Interceptor. These pipelines are flowing full because of isolated
reaches with very flat slopes.
Model Length Diam.
ID (ft.)(ft.)
274-281 VC3 2,830 36 Approach to Buena Vista Lift Station - pipeline flowing 75% full
309-310 VC11 896 42 Approach to Agua Hedionda Lift station - localized surcharging
300-307 VC13 3,510 42 Downstream of Agua Hedionda Lift Station - pipeline capacity is
290-298 VC14 4,530 42 exceeded for short periods; two very flat sections (reaches 290
283-289 VC15 1,860 42 and 288) and one short 20' pipe with neg. slope (reach 287)
194 B4 594 18 Upper Buena, localized surcharging in very flat reach
1 B7 596 24 Lower Buena, localized surcharging in very flat reach
392 B8 208 30
377 B8 93 30
Location/CommentsReach
Lower Buena, isolated flat sections
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SEWER MASTER PLAN UPDATE 2-8 March 2003
Table 2-4 summarizes the peak flow tributary to the lift stations and the peak forcemain velocities
exhibited based on existing flows. Estimates of peak wet weather flows are provided for the V/C
Interceptor, but only peak dry weather flows are calculated for the NAH and NB Interceptors due to a
lack of wet weather flow monitoring data.
Table 2-4
EXISTING POTENTIAL PEAK FLOWS TO INTERCEPTOR LIFT STATIONS
Lift Station PDWF PWWF Peak Velocity
Lift Station Firm Capacity to Wet Well to Wet Well in Force Main(1)
(MGD)(MGD)(MGD)(fps)
Buena Vista 21.5 10.2 18.9 6.9 (2)
Agua Hedionda 23.0 15.3 24.2 10.6
Foxes Landing 3.7 2.24 ---(3)4.4
North Batiquitos 3.2 1.47 ---(3)2.6
(1) Velocity is based on the peak influent flow to the station for variable speed pumps. For the NB Lift
Station (fixed speed), the velocity is based on the output of a single pump.
(2) Peak velocity in the parallel 16" & 24" section. Velocity is 9.3 fps in the short, single 24" section
and 10.5 fps in the parallel 16" section in the bridge over I-5
(3) Metering data to determine wet weather flows is not available for this system
From the data in Table 2-4, it can be concluded that the North Batiquitos Lift Station has sufficient
capacity for current wet weather flow conditions based on the 1.7 MGD of available pumping capacity
under dry weather conditions. It is less clear if there is sufficient capacity for wet weather flows at the
Foxes Landing Lift Station. Based on the PDWF to the Foxes Landing Lift Station, there is
approximately 1.4 MGD of available pumping capacity to convey stormwater flows. The downstream
reaches of the AH Interceptor are along the north shore of the Agua Hedionda Lagoon, and are potential
sources of I&I to the interceptor system with rising water levels in the lagoon. Wet weather flow data is
needed to estimate the existing I&I to this system, and to determine if there is sufficient available capacity
at the lift station.
For the V/C Interceptor a hydraulic analysis of peak wet weather flows was performed. Results indicate
that the Buena Vista Lift Station may be potentially operating near its firm capacity during severe storm
events, and the capacity of the Agua Hedionda Lift Station could potentially be exceeded for brief
periods. Velocities in the Agua Hedionda forcemain and portions of the Buena Vista forcemain are also
exceeding the recommended maximum velocity of 8.0 fps during peak wet weather flow conditions.
2.5 ULTIMATE FLOW PROJECTIONS
Future flow projections are used to determine required upgrades to the existing collection system to
adequately serve Carlsbad’s wastewater conveyance needs under buildout conditions. The existing
interceptor system, with the addition of the South Agua Hedionda Interceptor, is analyzed with projected
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SEWER MASTER PLAN UPDATE 2-9 March 2003
peak ultimate flows to identify and size required interceptor capacity improvements. Planned
improvements to the collection system were also considered to accurately model future flows. Planned
improvements include the elimination of nine lift stations, which will accomplished by the construction of
new gravity pipelines. Most of these lift stations are currently pumping out-of-basin. The proposed
ultimate collection system is illustrated on Exhibit B in Appendix A.
Build-out projections for the City of Carlsbad have been recently updated and compiled into a Growth
Database, which is maintained by the City. Over half of the projected growth in the City of Carlsbad
Sewer Service Area is associated with known, planned developments in the eastern portion of the City.
These developments include Kelly Ranch, Villages of La Costa, Calavera Hills, Mandana Properties, and
Robertson Ranch, which are primarily residential developments, and the Carlsbad Oaks North and
Faraday Business Parks, and Bressi Ranch, which will have a mixed-land use. The remainder of future
growth in the City of Carlsbad is projected to include smaller, non-specific developments and general
“infill” of established neighborhoods and commercial areas located in the western portions of the City.
Flow generation factors are used in conjunction with the City’s Growth Database to project ultimate
wastewater flows and distribute flows in the ultimate system hydraulic analysis. The City’s established
planning value for wastewater flow is 220 gpd/EDU. Flow factors typically used for design in sewer
systems throughout San Diego County range between approximately 208 gpd/EDU in the City of
Encinitas, to approximately 265 gpd/EDU in the City of Chula Vista. Based on these comparisons and the
calculated unit flow rate for current conditions (195 gpd/EDU), the previously established flow generation
rate of 220 gpd/EDU is considered to be appropriately conservative for flow projections for this Master
Plan Update. The unit flow factors developed to project ultimate wastewater flows from data in the City’s
Growth Database are as follows:
Single-family dwelling unit - 220 gallons per day
Multiple-family dwelling unit - 160 gallons per day
Non-residential - 1,150 gallon per day/10,000 sqft of building area
Based on these unit flow factors, the ADWF flow for the ultimate sewer system is projected to be
approximately 9.9 MGD. This value represents an increase of approximately 3.1 MGD, or 45 percent,
over existing wastewater flows. Figure 2-6 presents historical flows and the projected ultimate flow, and
makes a comparison with previous flow projections. Ultimate flow projections from other agencies that
discharge to the Carlsbad sewer system were obtained from recent planning documents. Table 2-5 lists
the total projected ultimate flow to the Encina WPCF from its member agencies, and allocates the flow to
the Carlsbad interceptor systems.
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SEWER MASTER PLAN UPDATE 2-10 March 2003
Figure 2-6
HISTORICAL AND PROJECTED ULTIMATE FLOWS
9.87
2003 Ultimate
Flow Projection
13.84
13.41
3
4
5
6
7
8
9
10
11
12
13
14
15
1985 1990 1995 2000 2005 2010 2015 2020
Recoded flows from Encina meters
2003 Master Plan projections
1996 Ocean Outfall Capacity Reort projections1992 Master Plan projections
1987 Master Plan projections
Table 2-5
EXISTING AND PROJECTED ULTIMATE ADWF TO THE ENCINA WPCF
Carlsbad Total Carlsbad Total
Flows Agency Flow Flow Flows Agency Flow Flow
City of Vista &City of Vista &
Oceanside Oceanside
North Agua
Hedionda 1.30 MGD ------1.30 MGD 1.07 MGD ------1.07 MGD
South Agua
Hedionda ------------1.87 MGD ------1.87 MGD
Buena 1.84 MGD Buena 3.31 MGD
Vista (raceway)0.20 MGD Vista (raceway)0.60 MGD
Vallecitos 0.90 MGD Vallecitos 4.28 MGD 5.18 MGD 1.54 MGD Vallecitos 11.04 MGD 12.58 MGD
1.33 MGD 5.14 MGD 6.47 MGD 1.67 MGD 8.01 MGD 9.68 MGD
Totals: 6.81 MGD 17.3 MGD 24.1 MGD 9.87 MGD 32.7 MGD 42.5 MGD
(1) Other agency ultimate flow projections obtained from their most recent master planing documents
Interceptor
System
Existing Flows (Aug 2001)Projected Ultimate Flows
Other Agency Flows Other Agency Flows(1)
9.72 MGD 12.55 MGD
Buena 0.73 MGD 2.77 MGD 0.88 MGD 4.79 MGD
2.55 MGD 5.84 MGD 8.39 MGD
North
Batiquitos
Leucadia/
Encinitas
Leucadia/
Encinitas
Vista/
Carlsbad 2.83 MGD
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-11 March 2003
From Table 2-5 it is apparent that flows from Carlsbad will increase within all existing interceptors except
the NAH Interceptor. The majority of the flow increase to the V/C Interceptor is projected to be
generated by the City of Vista. The ultimate flows apportioned to the Buena and Vallecitos Interceptors
will exceed the capacity of the existing pipelines during peak flow conditions. The City of Vista is
planning to divert a portion of their flow from the Buena Interceptor to the Vallecitos Interceptor in the
future, and the VWD is planning a replacement of the Vallecitos Interceptor with increased capacity.
2.6 ULTIMATE SYSTEM EVALUATION
Hydraulic analyses were performed to determine the ability of the interceptors to convey projected peak
flows. Analysis of the ultimate interceptor system was accomplished by adding the SAH Interceptor to
the existing system model. City of Carlsbad flows were analyzed in the Buena and Vallecitos
Interceptors and the peak flows compared to existing capacity rights. Flow analysis results from the
SewerCAD ultimate system model are presented graphically for each interceptor system and compared to
the gravity pipeline capacities. The graphs illustrate the composite peak flow in each pipeline segment
over the course of the 24-hour flow simulation. Flows and capacities are schematically illustrated
according to the reach designations shown in Figure 2-1. Where lift stations are included in the
interceptor, the lift station name and firm pumping capacity are indicated on the graph.
2.6.1 Vista/Carlsbad Interceptor
Figure 2-7 illustrates results from the PWWF analysis for the V/C Interceptor, and makes a comparison
with existing pipeline capacities. For this analysis, a peak I&I rate of 6.1 MGD was added to City of
Vista projected peak dry weather flows. The I&I attributed to Carlsbad, 5.6 MGD, was distributed two
different ways. One flow scenario distributes the I&I along the length of the V/C Interceptor. The other,
more conservative scenario, assigns most of I&I to the upstream Reach V1, with the remainder at the
confluence with the NAH Interceptor. As stated previously, it is not known how much I&I is currently
contributed by the NAH Interceptor. Although the internal I&I rate in the ultimate system model was
increased by 20 percent over the existing I&I rate, it is noted that I&I was not included for the SAH
Interceptor. Flows entering the V/C Interceptor at the upstream end of Reach VC14 are therefore based
on the projected peak dry weather flow from the SAH Interceptor.
From Figure 2-7, it is apparent that the reaches downstream of VC10, Reach VC3, and the Buena Vista
and Agua Hedionda Lift Stations are not adequately sized to convey the projected PWWF. In addition,
analysis results indicate that Reach VC10, which is currently under construction as a 48-inch diameter
pipeline, may flow full for short periods during severe storm events.
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-12 March 2003
Figure 2-7
V/C INTERCEPTOR PEAK WET WEATHER FLOW
0
5
10
15
20
25
30
35
40
45
50
55
60
VC15VC15VC15VC14VC14VC14VC13VC13VC13AH LSVC11VC10VC10VC10VC8VC6VC5BVC5ABV LSVC3VC3VC3VC2VC2VC2VC1VC1VC1VC1VC1Full Pipeline CapacityProjected PWWF - Internal I/I applied at VC1 & VC10
Projected PWWF - Internal I/I distributed
Buena
Vista
Lift Station
Agua Hedionda
Lift Station
2.6.2 North Agua Hedionda Interceptor
The projected ultimate ADWF for the NAH Interceptor is approximately 1.07 mgd, which is less that the
existing ADWF of 1.3 MGD. The capacity of the NAH Interceptor was determined to be sufficient to
convey existing flows, with the exception of several short reaches. Therefore, additional analysis of this
interceptor system was not performed with ultimate system flows.
2.6.3 South Agua Hedionda Interceptor
The projected ultimate PDWF and design capacity of the SAH Interceptor are illustrated on Figure 2.8.
Peak dry weather analysis was performed for the SAH Interceptor since there is no data to estimate peak
wet weather flows. The upstream trunk sewer along El Camino Real and Sunny Creek Road (SAHT1E
and SAHT1G) is also depicted in Figure 2-8. On the basis of this analysis there should be sufficient
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-13 March 2003
capacity in the gravity interceptor system to convey peak wet weather flows. The PDWF through the
SAH Lift Station is projected to be approximately 3.0 MGD, but the lift station capacity will need to be
greater to convey stormwater flows.
Figure 2-8
SOUTH AGUA HEDIONDA PEAK DRY WEATHER FLOW
0
1
2
3
4
5
6
7
8
9
10
11
12
SAH4SAH4SAH4SAH4SAH4SAH LSSAH LSSAH1SAH1SAH1SAHT1GSAHT1GSAHT1GSAHT1GSAHT1ESAHT1ESAHT1ESAHT1ESAHT1EGravity Pipeline Capacity/Peak Flow (MGD) Full Pipeline Capacity Projected Peak Dry Weather Flow
75% Full Capcity
SAH
Lift
Station
2.6.4 Buena Intercepetor
Figure 2-9 illustrates the projected ultimate PWWF generated by the City of Carlsbad in the Buena
Interceptor, and makes a comparison with existing capacity rights. As shown on the chart, the current
leased capacity is projected to be sufficient to convey ultimate flows.
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-14 March 2003
5 MGD Leased
Capacity
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
V3 V3 V3 V4 V4 V4 V4 V4 V5 V5 V6 V6 V6 V6 V7 V7 V8 V8Gravity Pipeline Leased Capacity/Peak Flow (MGD)Carlsbad Leased Capacity
Projected Ultimate PWWF
Figure 2-9
PROJECTED CARLSBAD PWWF IN THE BUENA INTERCEPTOR
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
B1 B1 B2 B2 B2 B2 B2 B4 B4 B4 B4 B4 B4 B5 B6 B6 B7 B7 B8 B8 B8Gravity Pipeline Leased Capacity/Peak Flow (MGD)Series2
Projected Ultimate PWWF
Carlsbad Leased Capacity
Carlsbad Capacity (smoothed)
2.6.5 Vallecitos Interceptor
Figure 2-10 illustrates the projected ultimate PWWF generated by Carlsbad in the Vallecitos Interceptor,
and makes a comparison with the existing capacity rights of 5.0 MGD. Although flows to this interceptor
are projected to increase by approximately 70 percent, the current leased capacity is projected to be
sufficient to convey ultimate flows, as shown on the graph.
Figure 2-10
PROJECTED CARLSBAD PWWF IN THE VALLECITOS INTERCEPTOR
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-15 March 2003
2.6.6 North Batiquitos Interceptor
The upstream portion of the North Batiquitos Interceptor conveys only City of Carlsbad flows. This
portion of the Interceptor was analyzed with the projected PDWF and compared to the design capacity of
the gravity pipelines. There is ample capacity in the upstream gravity pipelines to convey the projected
ultimate flows. The North Batiquitos Interceptor downstream of the lift station was analyzed with both
fixed-speed pumps in operation. City of Carlsbad flows in this portion of the Interceptor are shown on
Figure 2-11, together with the full gravity pipeline capacities and leased capacity in the Occidental Sewer.
Based on this analysis, the existing leased capacity is projected to be approximately 4.0 MGD in excess of
what is required to convey projected peak ultimate flows.
Figure 2-11
CARLSBAD PWWF IN THE DOWNSTREAM NORTH BATIQUITOS INTERCEPTOR
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
NB6 NB6 NB7 NB7 NB7 NB7 NB8 NB8 NB8 NB9 NB9
Full Pipeline Capacity Carlsbad Peak Wet Weather Flow Carlsbad Leased Capacity
2.7 RECOMMENDATIONS
Gravity interceptor replacements for the V/C Interceptor at Reaches VC3, VC11B, and VC13-15 are
recommended to increase the capacity based on projected peak flows. The projected PWWF in the V/C
Interceptor is shown on Figure 2-12, together with the capacity of the existing pipeline reaches and the
recommended pipeline capacities. The design capacity of the new pipelines is calculated based on the
average slope of the existing reach and a Manning’s coefficient (“h”) of 0.012, assuming that the future
pipe will be PVC-lined.
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-16 March 2003
.
Figure 2-12
V/C INTERCEPTOR CAPACITY WITH RECOMMENDED IMPROVEMENTS
15
20
25
30
35
40
45
50
55
VC15VC15VC15VC14VC14VC14VC13VC13VC13AH LSVC11VC10VC10VC10VC8VC6VC5BVC5ABV LSVC3VC3VC3VC2VC2VC2VC1VC1VC1VC1VC1Gravity Pipeline Capacity/Peak flow (MGD)Design Capacity (75% full) of Recommended Pipeline Replacements
75% Full Pipeline Capacity - existing
Projected PWWF - internal I/I applied at VC1 & VC11
Projected PWWF - internal I/I distributed
Buena
Vista
Lift
Station
Agua
Hedionda
Lift Station
36"
54"
54
54"
In addition to the gravity pipeline replacement projects, capacity improvements are recommended for the
Buena Vista Lift Station and force main and the Agua Hedionda Lift Station and force main. Pumping
units were last replaced at the Buena Vista Lift Station in 1994. The reported firm capacity of the lift
station is 14,000 gpm, and the projected ultimate PWWF at the station is approximately 18,000 gpm. The
capacity of the Buena Vista Lift Station has never been confirmed due to existing downstream capacity
limitations. Because of the long length of the force main (approximately 4,000 feet) and high pipeline
velocities with projected ultimate flows, it may be possible to obtain the required increase in station
capacity with the existing pumps and a larger forcemain. It is recommended that a new 24-inch diameter
force main replace the 16-inch main and parallel the existing 24-inch main for its entire length. In
addition to increasing the station capacity, the new parallel force main will reduce peak velocities and
increase reliability
It is recommended that the capacity of the Agua Hedionda Lift Station be increased to a minimum of 33
MGD (23,000 gpm), which is the projected PWWF through the station. A larger force main will be
required at the station. There are several deficiencies with the existing Agua Hedionda Lift station,
including an undersized wet well, lack of full operational redundancy, insufficient space around the
pumping units, and problems related to the age and general condition of the station. A Preliminary
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-17 March 2003
Design Report for Agua Hedionda Lift Station Upgrade, dated March 7, 2000 was prepared for the City.
The recommendations from that report include replacement of the existing lift station with the exception
of the emergency generator building.
Most of the South Agua Hedionda Interceptor has been constructed. The remaining portions of the SAH
Interceptor yet to be installed are the SAH Lift Station and forcemain. The recommended capacity of the
SAH Lift Station is 4.2 MGD (2,900 gpm). The recommended 14-inch diameter force main will have an
approximate length of 5,380 feet and be constructed in the future alignment of Cannon Road. A gravity
sewer will be constructed with the forcemain that will connect with a gravity line in Faraday Road and
convey flows from the Faraday Business Park and to the SAH Lift Station. After completion of these
projects, the two Faraday Lift Stations and the Kelly Lift Station will be removed.
The District shares ownership or leases capacity in several facilities with the City of Vista, the Buena
Sanitation District, the Vallecitos Water District, the Leucadia County Water District and Encinitas
Sanitary Division of the City of Encinitas. These facilities include the V/C Interceptor, the Buena
Interceptor, the Vallecitos Interceptor and the Occidental Sewer. The following discussions provide an
overview of these facilities relative to projected ultimate wastewater flow conditions.
Vista/Carlsbad Interceptor. The Vista/Carlsbad Interceptor ownership percentages and capacity rights
from the 2001 draft agreement with the City of Vista are provided in Table 3-1 of this report. Based on
the agreement, Carlsbad has a 43.9% ownership in the downstream reach of the V/C Interceptor (VC15).
Projected flows for Carlsbad are now lower, and the percentage of flow for Carlsbad in this reach is now
estimated at 37.2%. It is recommended that a new agreement be negotiated based on the updated flow
projections in this Master Plan Update.
Buena Interceptor. The City of Carlsbad leases capacity in the Buena Interceptor. The existing lease
agreement was last modified in 1987 to lease an additional 0.8 MGD of capacity. It is estimated that
Carlsbad will not require any additional capacity in this interceptor to convey projected ultimate flows. It
is noted that the existing Buena Interceptor does not have the capacity to convey buildout flows based on
ultimate flow projections for the BSD and the City of Vista Raceway Basin. The City of Vista includes a
project in their 2001 Master Plan to construct a new force main from the Buena and Raceway Lift
Stations to the Vallecitos Interceptor.
Vallecitos Interceptor. The City of Carlsbad currently leases 5.0 MGD of capacity in the Vallecitos
Interceptor. City of Carlsbad ultimate peak flows in this interceptor are projected to be less than 3.5
MGD. The existing interceptor does not have the capacity to convey buildout flows for the VWD and
future flows from the BSD and the City of Vista Raceway Basin. The VWD plans to replace the existing
Vallecitos Interceptor with a larger capacity interceptor. Based on projected ultimate flows, Carlsbad
could reduce their leased capacity to approximately 4.0 MGD.
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City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-18 March 2003
Occidental Sewer. The Occidental Sewer is jointly owned by the City of Carlsbad, the ESD and the
LCWD. Carlsbad’s current ownership capacity, which is estimated to be approximately 8.5 MGD, is
projected to be approximately 4.0 MGD in excess of what is required to convey the ultimate PWWF. The
LCWD projects that they will need to acquire an additional 1.6 MGD of conveyance capacity in the
Occidental Sewer in their most recent Master Plan. It is recommended that the ownership capacities
defined in the 1972 Occidental Pipeline Agreement be updated based on current flow projections.
2.8 CAPITAL IMPROVEMENT PROGRAM
Improvement projects identified for the Capital Improvement Program (CIP) are summarized in Table 2-
6. The projects are arranged into three groups. The first group of projects includes improvements to the
sewer collector system and rehabilitation projects. These projects were updated from the City’s 2002-
2003 CIP based on discussions with City staff. The next group consists of interceptor capacity projects,
which were identified from the hydraulic analysis performed as part of this Master Plan Update. The last
group of projects are for improvements at the Encina Water Pollution Control Facility, which were also
defined in the City’s 2002-2003 CIP.
Table 2-6 includes a planning level estimate of probable construction costs. Costs should be considered
relative to the 2002 Engineering News Record Construction Cost Index (ENR CCI) of 6538. Cost
estimates for the Encina WPCF projects and most of the collector system projects were obtained from the
City’s 2002-2003 CIP. It is noted that costs identified for V/C Interceptor capacity improvements
represent the total cost, although a portion of these costs will be shared by the City of Vista. The costs for
the Encina WPCF projects represent the City’s pro-rated share for the projects.
Project ProbableType Constr. Cost COLLECTOR SYSTEM & REHABILITATION PROJECTS:1Avenida Encinas Gravity Sewer - new sewer along north side of Lanakai Mobil Home Park to reduce odorsnew gravity sewer 1000' of 8" pipeline 175,000$ 2North Agua Hedionda Interceptor Rehabilitation - West Segment (Cove Dr. to Hoover St.) - rehab manholes, new access road, erosion protection, minor sewer realignment, EIR, construct mitigation siterehab manholes, new access road, sewer realignment19 manholes 700' of 24" pipeline3,629,000$ 3North Agua Hedionda Interceptor Rehabilitation - East Segment (ECR to Kelly Dr.) - replace/rehabilitate manholesrehab/replace manholes21 manholes 620,000$ 4North Agua Hedionda Trunk Sewer Replacement (Reach NAHT1A)- Tamarack Av. from ECR to Calavera Hills Treatment Plantreplace FM with gravity sewer5000' of 8" pipeline 1,533,000$ 5North Batiquitos Interceptor Rehabilitation - MH Rehab & new access road from ECR west to NB Lift Stationaccess road & MH rehab--- 1,000,000$ 6El Camino Sewer - Construct gravity sewer in ECR from Chestnut Av. To Tamarack Av.new gravity sewer 4200' of 8" pipeline 420,000$ 7Sewer Lift Stations Repairs/Upgrades - Terramar, Villas and Gateshead Lift StationsLift Station Upgrades--- 235,000$ 8Remove Forest Lift Station and construct gravity sewer using microtunelling constructionnew gravity sewer 1400' of 8" pipeline 800,000$ 9Home Plant Lift Station - replace pumps, upgrade wetwell, manifold piping, ventilation system, and reconstruct influent gravity sewer L.S. Improvements & gravity sewer260' of 15" pipeline 585,000$ 10Remove LCWD La Costa Meadows Lift Station and construct gravity sewernew gravity sewer 600' of 8" pipeline 175,000$ 11 Remove La Golondrina Lift Station and construct gravity sewer new gravity sewer 1000' of 8" pipeline 150,000$ 12 Poinsettia Lift Station Odor and Noise Abatement L.S. rehab --- 221,800$ 13Sewer Line Refurbishment/Replacement - replace or refurbish sewer lines older than 30 yearsreplace/refurbish gravity sewers--- 7,868,000$ 14Vista/Carlsbad Interceptor Rehabilitation Reaches VC1 and VC2 - line pipelines and rehab manholesline sewers & rehab manholes9,430' of 36" pipeline 25 manholes377,000$ Table 2- 6Size/QuantityDescription/LocationRECOMMENDED SEWER CAPITAL IMPROVEMENT PROGRAMProject IDcontinued next pageCity of Carlsbad Sewer Master Plan Update 2-19Dudek & Associates, Inc.March 2003
Project ProbableType Constr. Cost COLLECTOR SYSTEM & REHABILITATION PROJECTS (continued):15 Gateshead Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer200' of 8" pipeline 60,000$ 16 Vancouver Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer300' of 8" pipeline 60,000$ 17 Simsbury Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer500' of 8" pipeline 100,000$ 18 Villas Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer2000' of 8" pipeline 270,000$ 19 Woodstock Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer400' of 8" pipeline 80,000$ 20Faraday #14 (Upper) Lift Station - remove station & connect to existing gravity sewerL.S. replacement with gravity sewer--- 30,000$ 21Faraday #10 (Lower) Lift Station - remove station & connect to existing gravity sewerL.S. replacement with gravity sewer--- 30,000$ 22North Batiquitos L.S. Modifications- new gas detectors, ventilation system, odor control, improved pump access, wiring, & float switchL.S. rehab --- 500,000$ 23Carlsbad Trunk Sewer Reaches VCT1A, VCT1B, VCT1C - Convey flows from Vancouver and Simsbury Lift Station service areas through LFMZ25 to the V/C Interceptor (see related projects 16 & 17)new gravity sewer 2000' of 8" pipeline 150,000$ 24 Master Plan Update - update of sewer MP and CEQA approval prepare reports -- 305,000$ 25Sewer Monitoring Program - monitor sewer flows in pipelines and at lift stationsmonitor flows -- 600,000$ 26Sewer Access Hole Rehabilitation - replace or refurbish manholes older than 30 yearsrehab/replace manholes-- 2,800,000$ 27 Sewer Connection Fee Update prepare report -- 15,000$ Collector System & Rehabilitation Projects Subtotal 22,789,000$ Size/QuantityTable 2- 6 (continued)Project IDcontinued next pageDescription/LocationCity of Carlsbad Sewer Master Plan Update 2-20Dudek & Associates, Inc.March 2003
Project ProbableType Constr. Cost INTERCEPTOR CAPACITY PROJECTS:28Vista/Carlsbad Interceptor Reach VC3 - capacity upgrade upstream of the Buena Vista Lift Stationinterceptor replacement3,350' of 42" pipeline 2,570,000*$ 29Buena Vista Lift Station - capacity increase, control system upgrade, new back-up generator L.S. rehab Lift Station capacity = 26 MGD 735,000*$ 30Buena Vista Lift Station Force Main (VC4) - replace existing 16" pipeline with 24" pipeline to provide dual 24" FMs & increase capacitynew force main 3,840' of 24" force main 1,244,000*$ 31Vista/Carlsbad Interceptor Reach VC11B - upgrade capacity and construct new bridge crossing over the Agua Hedionda Lagooninterceptor replace- ment & new bridge915' of 54" pipeline 2,900,000*$ 32Agua Hedionda Lift Station and Force Main VC12 - rehab lift station and construct new force mainL.S. rehab & new force mainLift station capacity = 36 MGD 200' of 36" force main6,250,000*$ 33V/C Interceptor Reaches VC13, VC14 & VC15 - Increase interceptor capacity from the AH Lift Station to Encina WPCFinterceptor replacement3510' of 54" pipeline 6,831' of 60" pipeline10,200,000*$ 34South Agua Hedionda Lift Station and Force Main - construct lift station, force main and gravity sewer in Cannon Rd., remove Kelly Lift Station New L.S., FM & gravity sewerLift Station capacity = 4.2 MGD 5,380' of 14" force main 2,568' of 12" gravity pipeline8,827,000$ 32,726,000$ ENCINA WATER POLLUTION CONTROL FACILITY PROJECTS:35Encina WPCF Building Improvements improve building --- 1,787,000$ 36Capital Acquisitions - Unit 1 acquisitions --- 3,415,000$ 37Capital Planning/Services planning --- 1,910,000$ 38Cogeneration Project - upgrade of the electrical generators facility upgrade --- 581,000$ 39Flow Equalization Project - construct tank for peak effluent flows construct tank --- 8,189,000$ 40Phase IV Expansion - Debt Service on Phase IV plant expansion debt service --- 13,082,000$ 41Phase V Expansion - expand plant capacity for buildout conditions TP expansion --- 11,693,000$ 42Phase V Expansion - Interim capacity improvements TP expansion --- 222,000$ 43Plant Rehabilitation machinery rehab --- 2,909,000$ 44Pump Station Interfaces - develop active flow monitoring system report --- 60,000$ 45Technology Master Plan report --- 1,161,000$ Encina WPCF Projects Subtotal 45,009,000$ CAPITAL IMPROVEMENT PROJECT TOTAL = 100,524,000$ * Costs for V/C Interceptor capacity improvememnts includes Vista's share of Interceptor Capacity Projects SubtotalProject IDTable 2- 6 (continued)Description/Location Size/QuantityCity of Carlsbad Sewer Master Plan Update 2-21Dudek & Associates, Inc.March 2003
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-1
CHAPTER 3
EXISTING SYSTEM DESCRIPTION
This chapter summarizes the existing wastewater facilities within the City of Carlsbad Sewer Service
Area. These facilities include the main sewer interceptors, lift stations, and wastewater treatment and
disposal facilities. Information regarding the existing wastewater collection system facilities was derived
from the District’s sewer atlas books, as-built construction drawings, previous reports and studies, and
City Engineering and Public Works staff input. Capacity calculations for the gravity interceptors are
based on the sewer system GIS and were generated using the SewerCAD hydraulic model.
3.1 GENERAL
The City of Carlsbad Sewer Service Area includes the majority of the City, with the exception of the
southeast corner of the City. Wastewater collection in the southeastern area is provided by the Vallecitos
Water District (VWD) and the Leucadia County Water District (LCWD). Carlsbad’s Sewer Service Area
extends from the Pacific Coast approximately 5 miles inland, providing wastewater collection, treatment
and disposal service to customers within its 30 square mile service area. The service area is characterized
by gently rolling to highly dissected mesa-like hills, commonly topped by remnants of marine terraces.
Elevations range from sea level along the coast to over 600 feet along the eastern boundary.
The proximity of the Pacific Ocean is a major influence on coastal Southern California weather. Early
morning and late evening fog in fall and late spring; dry, warm summers; and cool to moderate winters
are typical of the subtropic climate experienced in northern San Diego County. The temperature range
increases with distance inland from the coast, with an average annual temperature in the low to mid 60
degrees Fahrenheit (°F) at the coast and in the inland valleys. The mean temperature range for the City of
Carlsbad is typically between 55°F in January to approximately 70°F in August. The average annual
precipitation is 10.7 inches and most of the rainfall occurs between November and March.
3.2 INTERCEPTOR SYSTEM
At ultimate development, there will be five major interceptors within the City of Carlsbad Sewer Service
Area. Four of the interceptor systems have been constructed and are now in use. The alignments and
reach designations of the existing interceptor sewers are shown on Figure 3-1 and also on the figures
included in the following sub-sections for each individual interceptor system. The naming convention for
the interceptor reaches was developed in previous master plans.
EL
ALGA
L A N E
T A M A R A C K
LA
ROAD
D R I V E
A V E N U E
MARRON
V IL L A G E
AIRPORT
R O A D
CAMINO
R O A D
BO U L EVA R D
PO IN S ETT IACARLSBADCARLSBAD
COSTA
RE
AL
BOULEVARDC ANNON ROAD
BO ULEVARD
PALOMAR
AVI
ARAPARK
W
AY
COLL EGE
5
5
OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE
B4
V4
B 2
VC1
V 6
V3
B6
V5VC4VC14
NB4
B 7
VC3
V 7
B 8
NB8B1VC10
VC13V C2
NAH3NAH5
NB6N A H 2
NB3NB7VC6
N B 2 NB1VC15NBT3BVC11NB9VC5BNAHT1BNAH1VC9
N A H 7
NB10VC5AVC7
VC8
NAH4VC12
NB5
B5
V 8
NAH6
VISTA/CARLSBAD
NORTH AGUA
HEDIONDA
BUENA
VALLECITOS
NORTH BATIQUITOS
03-2003 Carlsbad301.mxd
FIGURE 3-1
CITY OF CARLSBAD
EXISTING INTERCEPTOR SYSTEM
LEGEND
SEWER SERVICE AREA BOUNDARY
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
1"=4000'
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-2
3.2.1 Vista/Carlsbad Interceptor
The Vista/Carlsbad (V/C) Interceptor is jointly owned by the City of Vista and the City of Carlsbad. The
V/C Interceptor is approximately eight miles long, and extends from the Vista meter station just west of
College Boulevard and Highway 78 to the Encina WPCF. Flow from the City of Vista and a small
portion of the City of Oceanside is metered at the upstream reach. The Buena Vista Lift Station and Agua
Hedionda Lift Station, both of which are maintained and operated by the Encina Wastewater Authority,
are a part of the interceptor system. Flow from the North Agua Hedionda Interceptor enters the V/C
Interceptor just upstream of the Agua Hedionda Lift Station. In addition, flow from a portion of the
existing South Agua Hedionda Interceptor enters the V/C Interceptor at Cannon Road, just downstream of
the Agua Hedionda Lift Station.
The V/C Interceptor was originally constructed in 1965. Sections of the interceptor were replaced with
larger diameter pipelines in 1979 and 1987, and the replacement of a two-mile section of 24- and 36-inch
diameter pipeline through the downtown Carlsbad area is currently under construction. For the purposes
of this Master Plan, the 2001-2002 Vista/Carlsbad Sewer Replacement Project is considered to be a part
of the existing sewer system and has been included in the exiting system sewer model as currently
designed.
The existing V/C Interceptor includes gravity pipelines ranging from 30 to 48 inches in diameter, parallel
18-inch force mains at the Agua Hedionda Lift Station, and parallel 24 and 16-inch diameter force mains
at the Buena Vista Lift Station. Most of the gravity pipelines are vitrified clay pipe (VCP), ductile iron
pipe (DIP), or reinforced concrete pipe (RCP) with a PVC liner (T-Lock liner). Approximately 3,500
linear feet of pipeline was constructed in Jefferson Street and Oak Avenue in 2002 using microtunneling
technology to install 42-inch diameter sections of centrifugally cast fiberglass reinforced plastic mortar
(CCFRPM) pipe. The pipe material for this section is listed by the trade name “Hobas” on the
construction drawings. The existing V/C Interceptor serves all or portions of the Local Facility
Management Zones (LFMZ) 1, 2, 3, 13, and 22, and also collects flow from the NAH Interceptor.
Ultimately the V/C Interceptor will serve LFMZ 25 and portions of LFMZ 7, and collect flows from the
future South Agua Hedionda (SAH) Interceptor.
The agreement for Ownership, Operation, and Maintenance of the V/C Interceptor Sewer was revised in
February 2002 and is provided in Appendix B. Carlsbad’s ownership rights in the interceptor are based
on the full flow pipeline capacity and increase in the direction of flow, reaching approximately 50 percent
ownership in the downstream reaches. The V/C Interceptor ownership, based on build-out conditions as
defined in the February 2002 Agreement with Vista, is shown in Table 3-1. Figure 3-2 illustrates the
reach designations of the V/C Interceptor.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-3
Table 3-1
Vista/Carlsbad Interceptor Ownership
(from February 2002 Agreement with the City of Vista)
It is noted that each pipeline “reach”, as defined in the Vista/Carlsbad interceptor ownership documented
in Table 3-1, actually consists of multiple pipeline reaches which may have varying capacities. As part of
the development of the City of Carlsbad GIS, physical information on the V/C Interceptor was obtained
from as-built drawings and construction plans. Slopes for each gravity pipeline were calculated from the
length between manholes and the pipeline inverts. The full pipe capacity was calculated from the sewer
hydraulic model based on a Manning’s coefficient (“η”) of 0.013 for unlined sections, and a coefficient of
0.012 for the PVC-lined RCP and CCFRPM pipe sections (reaches VC5 through VC10).
The full flow capacity of each pipeline section based on construction drawing data is illustrated on Figure
3-3. Also shown on the chart are the firm capacities of the Buena Vista and Agua Hedionda Lift Stations
as reported by Encina Operations Staff (firm capacity is defined as the capacity of installed pump
facilities with the largest unit out of service) and the “average” reach capacities listed in Table 3-1.
Average Percent Capacity Average Percent Capacity
Flow Capacity Rights Flow Capacity Rights
(inches) (MGD) (MGD) (MGD) (MGD) (MGD)
VC1 36 30.0 10.38 100.0% 30.0 0.00 0.0% 0.0
VC2 42 34.0 10.38 93.4% 31.8 0.73 6.6% 2.2
VC3 36 19.5 10.38 89.6% 17.5 1.20 10.4% 2.0
Buean Vista
Lift Station -- 23.1 10.38 89.6% 20.7 1.20 10.4% 2.4
VC4-FM 24 23.1 10.38 89.6% 20.7 1.20 10.4% 2.4
VC5 42 31.5 10.38 89.6% 28.2 1.20 10.4% 3.3
VC6 42 31.5 10.38 81.9% 25.8 2.29 18.1% 5.7
VC7 42 31.5 10.38 79.4% 25.0 2.69 20.6% 6.5
VC8 42 31.5 10.38 79.4% 25.0 2.69 20.6% 6.5
VC9 48 28.5 10.38 75.5% 21.5 3.37 24.5% 7.0
VC10 48 28.5 10.38 74.7% 21.3 3.51 25.3% 7.2
VC11 42 20.5 10.38 69.1% 14.2 4.65 30.9% 6.3
Agua Hedionda
Lift Station -- 23.0 10.38 69.1% 15.9 4.65 30.9% 7.1
VC12-FM 2-18 23.0 10.38 69.1% 15.9 4.65 30.9% 7.1
VC13 42 20.5 10.38 69.1% 14.1 4.65 30.9% 6.4
VC14 42 20.5 10.38 56.1% 11.5 8.11 43.9% 9.0
VC15 42 22.8 10.38 56.1% 12.8 8.13 43.9% 10.0
VC16 54 67.4 10.38 50.2% 33.8 10.28 49.8% 33.6
City of Vista City of Carlsbad
Pipeline Reach Pipe
Size
Full Flow Pipe
Capacity
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-4
Figure 3-2
VISTA/CARLSBAD INTERCEPTOR
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-5
Figure 3-3
FULL PIPE CAPACITY OF THE VISTA/CARLSBAD INTERCEPTOR SYSTEM
0
5
10
15
20
25
30
35
40
45
50
55
60
VC15VC15VC15VC14VC14VC14VC13VC13VC13AH LSVC11VC10VC10VC10VC8VC6VC5BVC5ABV LSVC3VC3VC3VC2VC2VC2VC1VC1VC1VC1VC1Reach DesignationFull Flow Gravity Pipe and Lift Station Capacity (MGD)Min. reach capacity from V/C Ownership Agreement Calculated capacity based on construction drawings
Buena
Vista
Lift Station
Capacity = 21.5 MGD
Agua Hedionda
Lift Station
Capacity = 23 MGD
It is noted that portions of the upstream reaches of the V/C Interceptor have very steep slopes, and the
pipeline capacities at several locations are nearly 100 MGD, which is off the scale of the chart. As can be
seen from Figure 3-2, there are several areas where the capacity of individual pipelines in the V/C
Interceptor as calculated from the construction drawings are less than the reported capacity documented in
Table 3-1. Most notably, there is a very flat 400-ft segment in VC14 with a slope of less than 0.01
percent that is calculated to have a capacity of 5.5 MGD, and a 20-foot segment in VC15 was found to
have a slightly negative slope. The pipelines in these two sections currently operate under pressure flow
conditions. It is also noted that the capacity of the Buena Vista Lift Station as reported in Table 3-1 is
based on the operation of all four pumps.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-6
3.2.2 North Agua Hedionda Interceptor
The North Agua Hedionda (NAH) Interceptor is entirely owned by the City of Carlsbad and conveys only
City of Carlsbad wastewater. Beginning at El Camino Real, the interceptor flows westerly along the
north shore of the Agua Hedionda Lagoon to just east of Interstate 5. The Foxes Landing Lift Station lifts
the wastewater under Interstate 5. The lift station force main discharges into a short gravity interceptor,
which flows to the V/C Interceptor upstream of the Agua Hedionda Lift Station.
The NAH Interceptor was constructed in 1966. The hydraulic profile of the interceptor is very flat, and
most of the reaches have a slope of less than 0.15 percent. Most of the gravity pipelines are constructed
of VCP and the interceptor includes one siphon. The gravity pipelines range in size from 10 to 24 inches
in diameter. This interceptor currently serves portions of LFMZs 1, 2, 5, 14, 15 and 24, and all of LFMZs
7 and 8. When the SAH Interceptor and gravity pipelines to the V/C Interceptor through LFMZ 25 are
constructed, the NAH Interceptor will serve only portions of LFMZs 1, 2, 7 and 14.
The full pipe capacity of the NAH Interceptor was reported to be between 4.6 and 6.8 MGD in each of the
five gravity reaches in the 1992 Master Plan. However, several flatter sections exist which restrict the
flow capacity. The HAH Interceptor is illustrated on Figure 3-4 and the full flow and 75 percent full
(D/d) pipeline capacities based on available GIS data is shown on Figure 3-5. The firm capacity of the
Foxes Lift Station is indicated in red.
Figure 3-4
NORTH AGUA HEDIONDA INTERCEPTOR
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-7
Figure 3-5
CAPACITY OF THE NORTH AGUA HEDIONDA INTERCEPTOR
0
1
2
3
4
5
6
7
8
9
10
NAH7NAH7NAH7Foxes LSNAH5NAH5NAH5NAH5NAH5NAH5NAH5NAH3NAH3NAH3NAH3NAH3NAH2NAH2NAH2NAH2NAH2NAH1NAH1Gravity Pipeline Capcity/Lift Station Firm Capacity (MGD)75% Full Capacity
Full Flow Capacity
Foxes
Lift Station
Capcity = 3.7 MGD
3.2.3 Buena and Vallecitos Interceptors
Two major interceptors follow the Encinas Canyon to the Encina WPCF, the Buena Interceptor and the
Vallecitos Interceptor. Both of these interceptors are owned and maintained by other agencies, and the
City of Carlsbad has capacity rights based on separate interagency agreements. The interceptors share a
single alignment for much of their length, and cross over each other at three separate locations. In the
previous Master Plans, the Buena and Vallecitos Interceptors were evaluated as a single interceptor with
an equivalent pipeline diameter. In this Master Plan Update, the interceptors are analyzed separately.
With the help of City Staff, construction drawings were reviewed for each collector system pipeline that
connects to the interceptor systems to determine if flows are currently being discharged to the Vallecitos
or Buena Interceptor.
The Buena and the Vallecitos Interceptors are both shown on Figure 3-6. The reach designations
assigned to each interceptor were modified from the combined reach designations assigned in the
previous Master Plans.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-8
Figure 3-6
BUENA AND VALLECITOS INTERCEPTORS
Buena Interceptor
The first interceptor constructed through the Encinas canyon was the Buena Interceptor, built in 1964.
This interceptor was owned by the Buena Sanitation District, which is now a part of the City of Vista.
The City of Carlsbad leases capacity in this pipeline. The Buena Interceptor begins at the corner of El
Camino Real and Palomar Airport Road, downstream of the discharge of the Buena Lift Station and the
City of Vista’s Raceway Lift Station. The interceptor flows through the City of Carlsbad’s industrial park
and then parallels Palomar Airport Road, crossing under Interstate 5 and continuing to the Encina WPCF.
The total length of the interceptor is approximately 4.2 miles.
Minor realignments were made to the Buena Interceptor in 1992. The existing interceptor consists of
gravity pipelines ranging from 15 to 30 inches in diameter. There are no lift stations or siphons along the
alignment. Most of the gravity pipelines are constructed of VCP or reinforced concrete pipe (RCP). The
Buena Interceptor currently serves portions of LFMZs 3, 4, 5 and 20. The ultimate service area is
anticipated to remain the same.
The original agreement for the lease of capacity by Carlsbad in the Buena Interceptor was prepared in
1966, and the agreement was replaced with a new agreement in 1981. The 1981 agreement defines
Carlsbad’s ownership rights in the interceptor, which increase in the direction of flow and approach 35
percent ownership in the downstream reaches. In 1987, a third agreement was drafted to lease additional
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-9
capacity on a temporary basis. Under this agreement, the City of Carlsbad can discharge an additional
peak flow rate of 0.8 MGD into the Buena Interceptor until a replacement sewer is constructed. The
current ownership and capacity rights based on flow capacities calculated from GIS data are summarized
in Table 3-2 and illustrated on Figure 3-7.
Table 3-2
CARLSBAD CAPACITY RIGHTS IN THE BUENA INTERCEPTOR
Pipeline Min. Min. Full Flow 75% full Carlsbad
Reach size Slope Capacity Capacity Percent 100% full With Add'l
(in.) (MGD) (MGD) Ownership Capacity 0.8 MGD
B1 15 2.60% 6.73 6.14 17.65% 1.19 1.99
B2 18 0.96% 6.65 6.07 18.84% 1.25 2.05
B4 18 0.58% 5.17 4.72 18.84% 0.97 1.77
B5 21 0.48% 7.10 6.47 21.13% 1.50 2.30
B6 21 0.56% 7.68 7.00 28.21% 2.17 2.97
B7 24 0.25% 7.36 6.71 31.71% 2.33 3.13
B8 30 0.07% 6.79 6.19 34.88% 2.37 3.17
Carlsbad Capacity (MGD)
Figure 3-7
CAPACITY OF THE BUENA INTERCEPTOR
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
B8 B8 B8 B7 B7 B6 B6 B5 B4 B4 B4 B4 B4 B4 B2 B2 B2 B2 B2 B1 B1Pipe Capcity (MGD)Series4Full Flow Capcity75% Full CapcityCarlsbad Leased CapacityCalrsbad Capacity (smoothed)
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-10
In the downstream reaches of B7 and B8, three isolated pipelines have very flat slopes. Two 30-inch
diameter pipelines in Reach B8 have a slope of 0.03 percent, and are fairly short pipelines (less than 200-
feet). The 24-inch pipeline in Reach B7 is nearly 600 feet in length and has a slope of 0.04 percent,
resulting in a capacity of less than 3 MGD (indicated by an “X” data point marker in Figure 3-4). Both
of the pipelines up- and downstream have much steeper slopes, and a hydraulic jump will occur near the
upstream manhole. The upstream manhole should be inspected for signs of surcharge, since existing
flows in this reach are higher than the computed pipeline capacity. Consistent with the previous Master
Plan, these flat segments are not considered in the calculation of the City of Carlsbad leased capacity in
Table 3-2.
Vallecitos Interceptor
The Vallecitos Interceptor was constructed nearly 20 years after the Buena Interceptor by the San Marcos
County Water District, which is now the Vallecitos Water District (VWD). The City of Carlsbad, City of
Vista and the VWD share capacity ownership in this pipeline. The Vallecitos Interceptor begins at the
end of the Vallecitos siphon near the intersection of Camino Vida Roble and El Camino Real,
downstream of the discharge of the Vallecitos Lift Station. The interceptor then follows Palomar Airport
Road in the same approximate alignment as the Buena Interceptor, crossing under Interstate 5 to the
Encina WPCF. The total length of the interceptor is approximately 3.4 miles.
The existing interceptor, constructed in 1983, consists of gravity pipelines ranging from 30 to 54 inches in
diameter and includes two siphons near the upstream end. There are no lift stations along the alignment.
The gravity pipelines are constructed of VCP with the exception of the downstream 54-inch section,
which is constructed of DIP. The Vallecitos Interceptor currently serves portions of LFMZs 5, 13, 18
and 20. The ultimate service area will increase to include all of LFMZs 10 and 17, and the portion of
LFMZ 6 that is currently served from LCWD.
The title of the original interagency agreement for the Vallecitos Interceptor is the Palomar Joint Land
Outfall Interceptor Interagency Agreement, which was signed in 1985. Under this agreement, the City of
Carlsbad has a 24 percent capacity ownership and can discharge a peak flow rate of 5.0 MGD into the
Vallecitos Interceptor. Portions of the Vallecitos Interceptor are reported to be in poor condition, and
VWD plans to replace the pipeline in the future. Additionally, the City of Vista has plans to discharge a
portion of the future flows from the Buena and Raceway Lift Stations to the Vallecitos Interceptor. The
force mains from these two lift stations currently discharge to the Buena Interceptor.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-11
3.2.3 North Batiquitos Interceptor
The North Batiquitos (NB) Interceptor collects only City of Carlsbad flows in the upper reaches. The last
2,415 feet into the Encina WPCF is jointly owned by the City of Carlsbad, the LCWD, and the Encinitas
Sanitary Division of the City of Encinitas. This downstream section is sometimes referred to as the Ponto
Interceptor, and it was originally termed the Occidental Sewer. The NB Interceptor begins on the north
shore of the Batiquitos Lagoon near El Camino Real. The interceptor flows west along the north shore of
the lagoon to the NB Lift Station. The NB Lift Station pumps City of Carlsbad flows up and across
Interstate 5. West of Interstate 5 the interceptor turns north and collects flow the LCWD and ESD. The
NB Interceptor then continues in a northerly direction along the railroad easement to the Encina WPCF.
The jointly-owned portion of the NB Interceptor was constructed in 1974 and is approximately 1.6 miles
in length. The last 1,000 foot section was originally constructed as a 24-inch diameter siphon, but was
replaced with a 48-inch diameter gravity sewer as part of the Encina WPCF Phase III expansion. The
interceptor south of Avenida Encinas, which conveys only City of Carlsbad flows, is approximately 5.9
miles in length. The gravity pipelines range in size from 8 to 48 inches in diameter, and are constructed
of VCP. The NB Interceptor currently serves all of LFMZs 9 and 19, most of LFMZ 21, and portions of
LFMZs 4, 6, 20 and 22. The ultimate service area is anticipated to remain the same. The North
Batiquitos Interceptor is illustrated on Figure 3-8. Figure 3-8
NORTH BATIQUITOS INTERCEPTOR
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-12
Ownership of the Ponto (Occidental) section of the NB Interceptor is stipulated in the Occidental-
Carlsbad-Leucadia-Encinitas Agreement of 1972. Capacity is identified as: 40.0 percent Carlsbad, 40.3
percent Leucadia and 19.7 percent ESD. Based on a full flow capacity of 21.3 MGD for the 39-inch
pipeline, the peak flow capacity for Carlsbad is approximately 8.5 MGD. Costs for operation and
maintenance of the Occidental Sewer are stipulated to be shared in the same percentages, with Carlsbad
named as the agency responsible for management of maintenance Capacities of the gravity pipelines
based on GIS data are shown on Figure 3-9.
Figure 3-9
CAPACITY OF THE NORTH BATIQUITOS INTERCEPTOR
0
2
4
6
8
10
12
14
16
18
20
22
NB9NB9NB8NB8NB8NB7NB7NB7NB7NB6NB6NB LSNB4NB4NB4NB4NB4NB4NB3NB3NB2NB2NB2NB1NB1NB1Gravity Pipeline/Firm Lift Station Capacity (MGD)75% Full Capacity
Full Flow Capacity
Carlsbad Leased Capacity
NB Lift
Station
Capacity = 3.2 MGD
Occidental
Sewer
3.3 COLLECTOR SYSTEM
In addition to the approximately 30 miles of interceptor sewers, the City of Carlsbad currently owns,
operates and maintains approximately 207 miles of wastewater conveyance pipelines, including gravity
flow conduits and forcemains. The collector system also includes approximately 5,000 manholes.
Collector system pipelines range in size from 3 to 27 inches in diameter. Gravity pipe materials used
throughout the system include polyvinyl chloride (PVC), vitrified clay (VCP), and ductile Iron (DIP).
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-13
Forcemains within the District are constructed of ductile iron (DIP), cast iron (CIP), PVC, and Asbestos
Cement (AC) pipe materials. Exhibit 1 in Appendix A provides an illustration of the existing wastewater
collection and conveyance system included in the sewer system GIS. Table 3-3 presents a summary by
pipeline diameters of the City of Carlsbad conveyance facilities, which excludes the interceptor sewers
discussed in the previous section.
Table 3-3
CARLSBAD CONVEYANCE SYSTEM SUMMARY
(Excluding Interceptor Sewers)
Pipeline Pipeline
Diameter Gravity Forcemain Diameter Gravity Forcemain
(in) (lf) (lf)(in) (lf) (lf)
3 144 423 15 8,845 ---
4 3,438 2,107 16 --- ---
6 62,849 7,640 18 4,555 ---
8 851,986 5,654 20 2,050 ---
10 76,621 3,161 21 1,194 ---
12 45,222 3,623 24 5,570 ---
14 --- 2,966 27 2,096 ---
TOTALS: Gravity - 1,064,570 Force Mains - 25,574
Total Length of PipelinesTotal Length of Pipelines
The summary information in Table 3-3 was obtained from the City of Carlsbad Sewer System GIS, which
includes pipelines constructed up through 2001. Information in the Sewer System GIS was obtained from
as-built drawings, construction drawings, and the City’s existing Sewer Atlas Book. Information from the
Sewer Atlas Books was used for pipelines for which no design drawings could be located (primarily in
the older “village” areas).
3.4 LIFT STATIONS AND FORCEMAINS
Eighteen wastewater lift stations are currently located within the City of Carlsbad Sewer Service Area.
The Buena Vista and Agua Hedionda Lift Stations, which are part of the V/C Interceptor, are operated
and maintained by the Encina Wastewater Authority. The remainder of the lift stations are owned and
operated by the City of Carlsbad. Figure 3-10 illustrates the lift station locations and associated forcemain
alignments, and Table 3-4 provides a summary of lift station capacities and features. Table 3-4 is
organized according to the downstream interceptor system to which each lift station currently discharges.
As noted on the table, several lift stations are pumping “out of basin”. These lift stations may be
eliminated with the construction of the future South Agua Hedionda Interceptor and/or other additional
collector sewers.
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BO U LEVAR DPALOMAR
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OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE
FOREST
LIFT STATION SIMSBURY
LIFT STATION
WOODSTOCK
LIFT STATION
VILLAS
LIFT STATION
GATESHED
LIFT STATION
VANCOUVER
LIFT STATION
FARADAY NO. 2
LIFT STATION FARADAY
LIFT STATIONTERRAMAR
LIFT STATION
KNOTS LANE
LIFT STATION
HOME PLANT
LIFT STATION
BUENA VISTA
LIFT STATION
AGUA HEDIONDA
LIFT STATION
FOX'S LANDING
LIFT STATION
NORTH BATIQUITOS
LIFT STATION
CHINQUAPIN
LIFT STATION
POINSETTIA
LIFT STATION
LA GOLONDRINA
LIFT STATION
KELLY RANCH
LIFT STATION
SAND SHELL
LIFT STATION
03-2003 Carlsbad310.mxd
FIGURE 3-10
CITY OF CARLSBAD
EXISTING LIFT STATIONS AND
FORCEMAINS
LEGEND
SEWER SERVICE AREA BOUNDARY
EXISTING LIFT STATIONS
FORCEMAIN
GRAVITY INTERCEPTOR SEWER
SIPHON
1"=4000'
InterceptorSystem CommentsDischarge Qty. Motor Design Point (gpm) (MGD) Terramar V/C 1972 2 3 Hp 100 gpm @ 25' 100 0.14 8" Yes Chinquapin V/C 1959/2001 2 7.5 Hp 360 gpm @ 50' 360 0.52 6" Yes Forest (2)V/C 1950/2001 2 7.5 Hp 360 gpm @ 43' 360 0.52 6" gravity line is in design Home Plant V/C 1963/1991 3 20Hp - 1 VFD 800 gpm @ 70' 800 1.15 10" Yes Buena Vista V/C 1975/1994 4 300 Hp - VFD 6000 gpm @ 142'14,900 (4)21.50 16&24" Yes operated by Encina Agua Hedionda V/C 1976/1988 4 100 Hp - VFD 8000 gpm 16,000 23.04 2-18" Yesoperated by Encina; 2 duty & 2 standby pumps Gateshead (2)NAH (3)1985 2 3 Hp 40 gpm @ 25' 40 0.06 4"Gorman Rupp package station Vancouver (2)NAH (3)1981 2 15 Hp 150 gpm @ 103' 150 0.22 8" Yes S&L package station Kelly Ranch (2)NAH (3)2001 2 10 Hp 325 gpm @ 61' 325 0.47 6" 48,000 gal overflow tank Simsbury (2)NAH (3)1985 2 50 Hp 382 gpm @ 200' 382 0.55 8" Yes Villas (2)NAH (3)1983 2 15 Hp 125 gpm @ 90' 125 0.18 4" YesGorman Rupp package station Woodstock (2)NAH (3)1983 2 2 Hp 50 gpm @ 25' 50 0.07 3"Gorman Rupp package station Foxes NAH 2001 3 38.7 Hp- VFD 1500 gpm @ 61' 2,600 3.74 12" Yes Lower Faraday #14 (2)Vallecitos (3)1995 2 25 Hp 307 gpm @ 144' 307 0.44 6" Upper Faraday #10 (2)Vallecitos (3)1991 2 25 Hp 1000 gpm @ 55' 1,000 1.44 14" Yes Poinsettia Vallecitos 2000 3 125 Hp 850 gpm @ 247' 1,230 1.77 12" Yes Batiquitos NB 1997 3 100 Hp 1210 gpm @ 164' 2,250 3.24 2-14" Yes 172,300 gal overflow tank Knots Lane NB 1999 2 10 Hp 355 gpm @ 44' 355 0.51 6" Yes Sand Shell NB 2002 2 10 Hp 6" Yes La Golondrina (2)LCWD (3)1981 2 5 Hp 110 gpm @ 45' 110 0.16 4" S&L package station(1) Station Capacity is the duty capacity with one pump out-of-service, except for the Agua Hedionda LS which assumes 2 pumps out-of-service (2) Temporary lift station to be eliminated with the construction of a future gravity pipeline(3) Lift station currently discharges out-of-basin(4) Lift station can't operate in excess of 15.8 MGD (11,000 gpm) w/o written authorization from CarlsbadStation Capacity (1)Table 3-4SUMMARY OF EXISTING LIFT STATIONSFlow MeterLift Station NameConstruction/ Rehabilitation DatePump InformationForce Main Diam.City of CarlsbadSEWER MASTER PLAN UPDATE3-14Dudek Associates, IncMarch 2003
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
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The firm capacity of a lift station, as indicated in Table 3-4, is the hydraulic output of the installed
pumping units with the largest pumping unit out-of-service. The “installed” capacity of a lift station is
equal to the hydraulic output of all installed pumping units. The “hydraulic output” of a single pump is
defined by the certified pump curve, the losses within the forcemain system, and design operation point
for the equipment. The hydraulic output of several pumps working in parallel is defined by the
cumulative hydraulic effect of the pumps, and is not equal to the mathematical sum of the individual
nameplate pump capacities. A hydraulic analysis of both the pump and the forcemain systems is required
to determine the hydraulic output of a given lift station. The majority of the Carlsbad lift stations consist
of two pumping units designed in an alternating lead/lag configuration, but operated in a duty/standby
mode. This means that under normal operating conditions, only one pump is operating at a time and the
pumps alternate as the pumps start and stop. However, if one pump can not keep up or fails to start, the
second pump will operate automatically.
Each of the lift stations has standby power capability consisting of either installed generators or a
connection for a portable generator. When station alarms occur, a signal is sent to the District Control
Center by telephone line. The Home Plant, Foxes and North Batiquitos stations are equipped with full
telemetry. Odor control consisting of air injection on the force main to prevent production of hydrogen
sulfide is provided at the Lower Faraday Lift Station. At the other stations, the wet wells are cleaned
periodically.
Many of the lift stations have recently undergone, or are planned to undergo, rehabilitation projects to
improve station operation and reliability. A site visit to each pump station was conducted as part of the
1997 Master Plan Update. Appendix B of that report contained a detailed inventory of the mechanical
and electrical equipment compiled by City staff. Since the last master plan the Poinsettia, Kelly Ranch,
Knots Lane, and Sand Shell Lift Stations have been constructed and the Foxes Landing and Chinquapin
Lift Stations have been rehabilitated.
3.5 INTER-AGENCY AGREEMENTS
Wastewater collection systems operate primarily on a gravity flow basis. However, political boundaries
are not always established to match natural drainage contours. As a result, some portions of a given
service area may drain in an undesirable direction, away from the remainder of the gravity collection
system. Inter-agency agreements can be developed to allow the wastewater flows to be conveyed into the
collection system of an adjacent District or agency.
The City jointly owns capacity in most of the interceptors with upstream sewering agencies, as described
previously in Section 3.2. The joint ownership agreements are summarized in Table 3-5 and included in
Appendix B. Figure 3-11 illustrates other agency facilities that are within the Carlsbad Sewer Service
Area or along its boundary.
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OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE VISTA METER
STATION
SHADOWRIDGE
W. R. P.
BUENA LIFT
STATION
RACEWAY LIFT
STATION
MEADOWS I
LIFT STATION MEADOWLARK
W. R. P.
MEADOWS III
LIFT STATION
VALLECITOS
PEROXIDE
STATION
GAFNER
FAILSAFE
BUENA
FORCEMAIN
MEADOWLARK
FAILSAFE
LCWD BATIQUITOS
FORCEMAIN
VALLECITOS
GRAVITY LINE
MEADOWLARK
FAILSAFE
OUTFALL
03-2003 Carlsbad311.mxd
FIGURE 3-11
CITY OF CARLSBAD
OTHER AGENCY WASTEWATER
FACILITIES
LEGEND
LCWD SEWER FACILITIES
CITY OF VISTA/BSD SEWER FACILITIES
VALLECITOS SEWER FACILITIES
1"=4000'
City of Carlsbad Dudek & Associates, Inc.
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Table 3-5
INTER-AGENCY AGREEMENTS FOR SEWER INTERCEPTORS
In addition to the inter-agency agreements for the interceptors, the City of Carlsbad has agreements with
LCWD to provide sewer service to isolated areas of La Costa located along the Sewer Service Area
boundary. Tract 73-29, also known as Carrillo Estates Unit No. 2, is a 111 lot subdivision that comprises
sub-drainage basin 6B. Wastewater from this development is currently pumped by the La Golondrina Lift
Station to the LCWD Meadows I Pump Station (shown on Figure 3-11). The topography of the property
is such that wastewater collected on the property will flow to the Vallecitos Interceptor in the future, after
additional off-site gravity conveyance facilities are constructed. Agreements were signed between the
City of Carlsbad and the LCWD to transfer 111 EDU’s of capacity and flow from the LCWD to Carlsbad
on EWA flow and EDU reports, until such time as the wastewater service by the LCWD is terminated.
This agreement has been in effect since 1981 and shall not expire until wastewater collection facilities
tributary to the City of Carlsbad system are constructed and connected.
Tract 93-04, also known as Rancho Carrillo Village Q, is a 25 lot subdivision located in the southwest
corner of sub-drainage basin 18B. Wastewater collected on the property will also flow to the Vallecitos
Interceptor in the future, after additional off-site gravity conveyance and lift station facilities are
constructed. The City of Carlsbad and the developer requested a temporary connection to the wet well of
the LCWD Meadows III Pump Station, which is located just south of the Carlsbad Sewer Service Area
boundary, as shown on Figure 3-11. A Reimbursement Agreement for Temporary Wastewater Collection
was approved in October 1998. The agreement will remain in force until off-site facilities tributary to
Carlsbad are completed. Once these facilities are constructed, the LCWD may consider negotiating a
future agreement with Carlsbad for the detachment of the remaining 68 additional lots served by the
Meadows III Pump Station.
Interceptor Joint Agency Agreement/Date
Vista/
Carlsbad City of Vista Agreement for Ownership, Operation, and Maintenance of
the Vista/Carlsbad Interceptor Sewer- 2/26/02
Agreement Between the BSD and City of Carlsbad for the
Lease of Capacity in the Encina Outfall - 12/15/81
Agreement between the BSD and City of Carlsbad for the
Lease of Additional Capacity in the Encina Outfall - 1987
Vallecitos San Marcos Water District
City of Vista
Palomar Joint Land Outfall Interceptor Interagency
Agreement - 1/8/95
North
Batiquitos
Leucadia County Water District
Encinitas Sanitary District
Occidental-Carlsbad-Leucadia-Encinitas Agreement in
Regard to Construction of Sewer Pipeline South from the
Encina Water Pollution Control Facility - 8/24/72
Buena Sanitation DistrictBuena
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3.6 WASTEWATER TREATMENT AND DISPOSAL
Wastewater generated within the City of Carlsbad Sewer Service Area is treated at the Encina WPCF.
The Encina WPCF provides full secondary treatment, sludge handling, and disposal through a deep ocean
outfall. The treatment levels meet current State and Federal requirements for secondary treatment. The
Encina WPCF is owned and operated by the Encina Wastewater Authority (EWA), a joint powers
authority made up of six northern San Diego County wastewater agencies. The EWA maintains a 10
member Board consisting of council members or directors from each of the member agencies. The EWA
operates and maintains the Encina Wastewater Pollution Control Facility (WPCF) (Unit 1) and ocean
outfall (Unit J) and the Buena Vista and Agua Hedionda Lift Stations. Vista and Carlsbad share the
operation and maintenance expenses for the Buena Vista and Agua Hedionda Lift Stations.
3.6.1 Treatment
EWA’s state-of-the-art treatment facility is designed to treat wastewater to the secondary level. Most of
the treatment plant’s highly treated wastewater is discharged into the ocean through an outfall. Treatment
processes at the Encina WPCF include screening, grit removal, primary clarification, and treatment of
activated sludge. The waste activated sludge is thickened and pumped to anerobic digester for
stabilization. The digested sludge is then dewatered and used as a soil amendment. Sludge hauling and
handling is done by private contractors. Digester gas is used to fuel gas driven blowers and generators to
reduce outside energy dependence.
The capacity of the EWA facility has been expanded several times. The current rated liquid capacity is
36.0 MGD while the rated solids handing capacity is 38.0 MGD. The difference in the two capacities
represents the equivalent amount of sludge that is disposed back to the sewer system from the
Shadowridge WRP and the Gafner WRP. These two plants rely upon the Encina WPCF for sludge
digestion, dewatering, and disposal. However, the Gafner WRP has ceased primary and secondary
treatment and no longer discharges sludge to the plant.
3.6.2 Disposal
Effluent from the EWA plant is discharged to the Pacific Ocean through the Encina Ocean Outfall. The
Encina Ocean Outfall system includes the Interim Flow Equalization Facilities, the Effluent Pump
Station, and the outfall. When the influent flows exceed the hydraulic capacity of the outfall, the excess
flow is diverted to the flow equalization facilities. When the flow rates fall to within acceptable levels,
the stored flow is pumped from the basins back to the outfall. The equalization allows the plant to pass
high flows associated with storm events at a flow rate greater than the hydraulic capacity of the
downstream outfall.
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SEWER MASTER PLAN UPDATE March 2003
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The Encina outfall extends along the ocean floor to a point 1.5 miles off shore, at a depth of over 150 feet.
The outfall pipeline consists of two individual sections, including the original 48-inch, 6,600-foot outfall
constructed in 1965 and the 72-inch, 2,300-foot extension constructed in 1973. The outfall extension
project also added an 800-foot diffuser system to the end of the outfall. The current capacity of the
Encina Ocean Outfall is estimated to be approximately 75 MGD. This wet weather flow capacity takes
into account the flow equalization facilities.
3.6.3 Ownership
Each EWA member agency has capacity rights to the Encina WPCF and the ocean outfall system.
Capacity rights are documented in the Revised Basic Agreement, which was last amended in February
2000. A copy of this agreement is included in Appendix B. In the basic agreement, treatment facilities
are referred to as Unit I, and the ownership is broken down into liquid and solids handling portions. The
City of Carlsbad currently has a capacity ownership of 9.24 MGD for both liquid and solids. The ocean
outfall system is referred to as Unit J. Carlsbad’s capacity right for Unit J is 25.54 MGD. Table 3-6
provides a summary of the current EWA ownership.
Table 3-6
ENCINA WPCF CAPACITY OWNERSHIP
Percentage ADWF Percentage ADWF Percentage ADWF PWWF*
MGD MGD MGD MGD
Carlsbad 25.67% 9.24 24.32% 9.24 24.32% 9.24 25.51
City of Vista 22.36% 8.05 21.18% 8.05 21.18% 8.05 22.21
Vallecitos 20.94% 7.54 19.84% 7.54 19.84% 7.54 20.81
Leucadia 19.75% 7.11 20.68% 7.86 20.68% 7.86 21.69
Buena 6.28% 2.26 9.24% 3.51 9.24% 3.51 9.69
Encinitas 5.00% 1.80 4.74% 1.80 4.74% 1.80 4.97
Totals 100% 36.0 100% 38.0 100% 38.0 104.9
* Peak wet weather flows are based on a peaking factor of 2.76 times the ADWF
Encina
Member
Agency
WPCF (Unit I)Outfall (Unit J)
Treatment Solids
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CHAPTER 4
EXISTING WASTEWATER FLOWS
As population has grown and the northern coastal areas of San Diego County continue to develop, the
City of Carlsbad has experienced gradually increasing wastewater volumes. This chapter documents
existing wastewater flows within the sewer service area. Historical wastewater flows are summarized and
unit flows are developed for residential and commercial/industrial areas. Peaking curves for each
interceptor system and contributing upstream agency are developed for dry weather flows. Existing
defect flows from rainfall-induced inflow and infiltration are quantified based on historical events.
4.1 ENCINA FLOW METERS
The Encina Wastewater Authority operates and maintains numerous flow meters throughout the service
areas of its six member agencies. A Centralized Flow Metering Program was implemented in 1989 and
meter upgrades were last made in 1996. Wastewater flows generated within the City of Carlsbad are
metered in the interceptor pipelines upstream of the Encina WPCF. Because of flow contributions from
upstream agencies, Carlsbad flows must be determined by subtracting other agency flows from measured
flows at the WPCF. Figure 4-1 illustrates the locations of the Encina meters that are used to calculate
Carlsbad flows. Details of each meter are provided in Table 4-1. The total flow from Carlsbad is
calculated from the following formula:
Carlsbad flow = (C3-V1) + (B1-(B2 + V2)) + (C1-VA1) + (C2-L1)
Table 4-1
ENCINA FLOW METERS
Meter Meter
ID. Type Carlsbad Other Agencies
V1 Haymar Drive in Vista ADS 3600* --- Vista & O'side
BVPS Discharge of the Buena Vista L.S. Ultrasonic Portions of the V/C Interceptor Vista & O'side (V1)
C3 VC influent line to the Encina WPCF ADS 3600* V/C and NAH Interceptors Vista & O'side (V1)
B2 Discharge of the BSD Buena L.S. Magmeter --- Buena Sanitation District
V2 Downstream of the Vista Raceway L.S. ADS 3600* --- Raceway basin (Vista)
B1 Buena influent line to the Encina WPCF ADS 3600* Buena Interceptor BSD & Raceway (B2, V2)
VA1 Downstream of the Vallecitos L.S. Ultrasonic --- Vallecitos
C1 Vallecitos influent line to the Encina WPCF ADS 3600* Vallecitos Interceptor Vallecitos (VA1)
L1 Discharge of Batiquitos L.S. Ultrasonic --- LCWD and ESD
C2 NB influent line to the Encina WPCF ADS 3600* North Batiquitos Interceptor LCWD and ESD (L1)
* Accuracy of the Model 3600 meter is within plus or minus 5% under ideal flow conditions
Location Metered Flow
EL
ALGA
L A N E
T A M A R A C K
LA
ROAD
D R IV E
A V E N U E
MARRON
V IL L A G E
AIRPORT
R O A D
CAMINO
R O A D
BOU LE VA RD
P O INS ET T I ACARLSBADCARLSBAD
COSTA
R
EAL
BOULEVARDCA N N O N ROAD
BO U LEVAR DPALOMAR
AVIARAPARKW
AY
C O L L EGE
5
5
OCEANSIDE
VISTA
SAN MARCOS
OCEANSIDE
C2
C1
B1
C3
L1
V2
B2
V1
VA1
BV1
03-2003 Carlsbad401.mxd
FIGURE 4-1
CITY OF CARLSBAD
ENCINA FLOW METER LOCATIONS
LEGEND
SEWER SERVICE AREA BOUNDARY
ENCINA FLOW METERS
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
UPSTREAM AGENCY FACILITIES
1"=4000'
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4.2 HISTORICAL FLOWS
Carlsbad average annual wastewater flows, as calculated from Encina meter data, are summarized for the
past 15 years on Figure 4-2. As shown on the chart, wastewater flows decreased significantly after 1989.
This was typical of most Southern California sewage agencies, and can be attributed to conservation
measures implemented during drought conditions. Some of the conservation measures were temporary
but many, such as the installation of low-flow bathroom fixtures, have had a lasting effect. Flow meters
were replaced at the beginning of 1996, and the improved accuracy may have contributed to the flow
decrease observed after 1995. It is only over the past four years that wastewater flows have surpassed
flows generated in the late 1980’s. The higher flows are a result of steady increases population, as land
use within the service areas has transitioned from mainly agricultural use to urbanized development.
Figure 4-2
HISTORICAL WASTEWATER FLOWS
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Monthly wastewater flows for the past five years are shown on Figure 4-3, along with monthly rainfall
totals. From this graph there appears to be slightly higher monthly flows during months where the total
rainfall exceeds about four inches. However, there are also several large flow fluctuations that cannot be
explained. Overall, there is no strong trend of peak flows occurring in any particular month or season.
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Figure 4-3
5-YEAR MONTHLY WASTEWATER FLOWS VS. RAINFALL
2
3
4
5
6
7
8
Jan-97 Jul-97 Jan-98 Jul-98 Jan-99 Jul-99 Jan-00 Jul-00 Jan-01 Jul-01
0
2
4
6
8
10
12
Monthly rainfall total Average monthly wastewater flows Smoothed flow data
Baseline Dry Weather
Flow for 2002 Master
Plan Update
August 2001
4.3 AVERAGE DRY WEATHER FLOWS
For this Master Plan Update, EWA meter data for August 2001 was used to determine the existing
average dry weather flow (ADWF). The month of August was selected because it was the most recent
month during the dry season in which the meters appeared to be operating properly and complete flow
data could be obtained. Table 4-2 summarizes the average flow for Carlsbad and the other EWA
agencies for August 2001. This information is illustrated graphically by interceptor system on Figure 4-4.
Table 4-2
AUGUST 2001 ENCINA MEMBER AGENCY FLOW SUMMARY
Interceptor Carlsbad Other Agency Flows Total
System Flows Agency Flow Flow
Vista/Carlsbad & NAH 3.89 MGD City of Vista 5.84 MGD 9.73 MGD
Buena 1.84 MGD Buena 1.06 MGD Vista (raceway)0.20 MGD 3.10 MGD
Vallecitos 0.97 MGD Vallecitos 4.28 MGD 5.25 MGD
North Batiquitos* 0.56 MGD Leucadia/Encinitas 5.14 MGD 5.70 MGD
Totals 6.48 MGD 17.30 MGD 23.78 MGD
* Metered flow at EWPCF is .28 MGD less than the upstream flow metered at the North Batiquitos Lift Station.
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Figure 4-4
AUGUST 2001 FLOW SUMMARY BY INTERCEPTOR
0
1
2
3
4
5
6
7
8
9
10
Vista/Carlsbad &
NAH
Buena Vallecitos North Batiquitos
Buena SD
City of Vista
Vallecitos
Leucadia/Encinitas
Carlsbad
CARLSBAD INTERCEPTOR SYSTEMS
From Figure 4-4, it is apparent that Carlsbad flows comprise a minority of the total flows in each of the
interceptors. This is especially true in the North Batiquitos Interceptor, for which the Carlsbad flow
proportion is less than 10 percent of the total flow measured at the Encina WPCF. Because Carlsbad
flows are calculated by subtracting upstream and downstream flow meter readings, the resultant flows are
dependent on the accuracy of the meters. If the Carlsbad flow contribution is very small relative to the
upstream flows, an error of even 3 percent on the upstream and downstream readings can have a large
effect on the calculated flow for Carlsbad.
In the North Batiquitos Interceptor, most of the flow generated within Carlsbad is pumped at the North
Batiquitos Lift Station. Further downstream Carlsbad flows join with the flows from LCWD and ESD.
The City’s flow meter at the North Batiquitos Lift Station recorded an average daily flow rate of 0.84
MGD during August 2001, which is 0.28 MGD more than the average flow rate calculated for Carlsbad in
the entire NB Interceptor based on the Encina meters (C2-L1). Carlsbad flows are approximately 10
percent of the total flow from LCWD and ESD. Consequently, the flow calculated for Carlsbad based on
the Encina meters can vary by as much as 70 percent even if the accuracy of the LCWD/ESD meter (L1)
and the meter at the Encina WPCF (C2) are both within +/- 5 percent. The higher flow rate recorded at
the North Batiquitos Lift Station was incorporated in the flow calculations for the NB Interceptor because
it is more conservative and likely more accurate. The total existing ADWF for Carlsbad is therefore
estimated to be 6.8 MGD for this Master Plan Update.
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4.4 PEAK DRY WEATHER FLOWS
Flow meter data from the Encina WPCF meters is recorded in 15-minute intervals. To determine the
existing peak dry weather flow (PDWF), the daily flow for all days in August 2001 was plotted for each
of the Encina meters listed in Table 4-1. The 24-hour flow charts are provided in Appendix C. Flow
data from the meters indicates distinct and repeatable peaking trends for weekends and weekdays.
During weekdays, peak flows were recorded between 8:00 and 10:00 AM, with a second, usually lower
peak at around 9:00 PM. During weekends, the peak morning flows occurred approximately two to three
hours later than the weekday flows. Weekend peak flows were higher than the weekday peaks at all
meter locations. A lag time for peak flows was also apparent at the downstream meters when compared
to upstream meters.
Figure 4-5 illustrates the ratio of peak flows to average flows obtained from the August 2001 Encina
meter data, which is provided for informational purposes. Also shown on the chart is a composite
peaking flow curve derived from the meter data. As is typical of most sewer systems, the peaking factor
is higher as the service area decreases.
Figure 4-5
DRY WEATHER PEAKING FACTOR DATA
Based on Encina Flow Meters for August 2001
y = 2.3536x-0.1843
R2 = 0.817
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
01234567891011
Average Dry Weather Flow (MGD)
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4.5 INFLOW AND INFILTRATION
Storm water inflow and infiltration (I&I) is the combination of wet weather infiltration and direct storm
inflow that establishes the maximum hydraulic capacity of wastewater conveyance facilities. Infiltration
enters the collection system underground, due to either a permanently high groundwater table or as a
result of rainfall percolation and temporary rising of groundwater levels. While the amount of infiltration
from rainfall events can be estimated from an evaluation of flow data and rainfall records, infiltration that
occurs year-round can typically only be detected from pipeline video inspections or manhole inspections.
The presence of excessive amounts of infiltration indicates broken or poorly constructed pipes, pipe
joints, or manholes.
Inflow in a collection system generally refers to extraneous water that flows directly into the system as a
result of storm water runoff. The entry points may be at manholes or from illicit connections to the sewer
system, such as roof and yard drains. The rate of inflow depends on the amount and intensity of rainfall
and the ground saturation level.
For this Master Plan Update, high intensity rainfall events over the past five years were analyzed to
determine the peak I&I. Flow data from select rainfall events were plotted together with the August
2001 24-hour average flow curves developed at each Encina meter location. Estimates of the maximum
instantaneous I&I were then made from these plots, which are included in Appendix C. The theoretical
peak wet weather flow (PWWF) for each upstream agency and interceptor system is calculated by adding
the peak I&I to the PDWF.
Results of the I&I investigation indicate that there are high I&I rates to the Vista/Carlsbad (V/C)
Interceptor. Based on the I&I analysis documented in the City of Vista Infrastructure Review Summary &
Wastewater Master Plan Update, dated July 2001, wastewater flows in the Vista drainage basin remain
elevated for several months after periods of heavy rainfall. This is attributed to increased infiltration from
high groundwater levels. The inflow during periods of high rainfall is also significant, and is attributed
primarily to illicit storm drain connections. The combined peak I&I for City of Vista flows to the V/C
Interceptor is estimated at approximately 7 MGD in the 2001 Vista Wastewater Master Plan Update. This
results in a PWWF that is nearly 2.9 times the ADWF at the upstream end of the interceptor. An
evaluation of flow data from the Encina C3 meter indicates that approximately 4.5 MGD of additional
inflow is contributed by Carlsbad from the V/C and North Agua Hedionda (NAH) Interceptors (refer to
Section 5.2.4). There are no operating flow meters on the NAH Interceptor, so the origin of the additional
I&I cannot be accurately determined.
The I&I contribution from upstream agencies and Carlsbad was estimated in the same manner for the
Buena, Vallecitos and North Batiquitos Interceptors. In the Buena Interceptor, a portion of peak flows
from the BSD is diverted to the Shadowridge Water Reclamation Plant during high rainfall periods. In
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the Vallecitos Interceptor, almost all of the I&I recorded at the downstream Encina meter C1 can be
attributed to Vallecitos. The instantaneous peak I&I from Vallecitos is estimated to be approximately 4.0
MGD, and the theoretical PWWF is estimated to be approximately 2.6 times the ADWF. It is not known
whether there are currently any upstream pumping limitations that would prevent the total flow from
being discharged to the Vallecitos Interceptor. It is noted that Vallecitos was completing its Sewer
Master Plan Update at the time of the writing this report.
In the North Batiquitos (NB) Interceptor, the peak I&I flows measured at the downstream Encina meter
C2 are typically lower than flows measured in the upstream meter L1, which meters flow from the LCWD
and ESD. Because of the upstream NB Lift Station, which employs fixed speed pumping equipment, I&I
flow rates for Carlsbad cannot be directly determined from the Encina meters. In the 1999 LCWD
Wastewater Master Plan, the instantaneous peak I&I flowing to the NB Interceptor was estimated to be
approximately 4.2 MGD. Using this flow rate, the PWWF for Leucadia/Encinitas is estimated to be
approximately 2.5 times the ADWF.
4.6 EXISTING UNIT FLOW FACTORS
Flow generation factors based on existing flow conditions were developed to distribute flow in the
existing system hydraulic computer model. Sewer flow factors were derived from August 2001 Encina
flow meter data, parcel information contained in the City’s Growth Database, and City of Carlsbad water
billing records, which were assigned an assessor parcel number (APN) by City staff. It is noted that the
flow generation factors based on existing conditions are different than the flow factors developed to
project future flows, which are discussed in Chapter 6 of this report.
4.6.1 Faraday Industrial Unit Flow Study
The service area for the Faraday Upper Lift Station consists primarily of office and light industrial uses,
with a few commercial establishments. There are no residential flows tributary to the lift station. An
analysis of the flow generated within this service area was conducted to determine existing flow
generation rates for industrial business park type developments.
The total flow to the Faraday Upper Lift Station for August 2001 was determined from pump run-time
records provided by City of Carlsbad Public Works Operation staff. Water records were obtained and
reviewed to determine which parcels had active water usage from commercial meter accounts.
Corresponding information on the building area and parcel size was obtained from the City’s Growth
Database for parcels with active water usage. The unit sewage flow generation rate for the Faraday
service, area based on the building size, was determined to be 0.39 gpm per 10,000 square feet of building
area. This return rate of potable water to the sewer system from commercial meter accounts was
approximately 94 percent. The return rate is considered to be high and is attributed to the fact that
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irrigation water to this area is supplied through separate irrigation meters. Table 4-3 summarizes the
results of the Faraday Industrial Flow Study.
Table 4-3
FARADAY INDUSTRIAL FLOW STUDY RESULTS
Total Lots in Faraday Lift Station Service Area - 104 Lots
Total Lots with 8/01 water usage - 82 Lots
Total Lot Area with 8/01 water usage - 313 Acres
Total Building Area with 8/01 water usage -
Average Building size -
Water supplied from commercial meters -
Total Gallons of Sewage Pumped(1)-
Return rate to sewer system (excluding irrig) - 94%
Average flow rate of sewage pumped - 156 gpm
Unit Wastewater Flow Rate (parcel based) -
Unit Wastewater Flow Rate (building based) -
Unit Wastewater Flow Rate (building based) -
Equivilent EDUs(2)-
(1) From Faraday Sewage Lift Station flow meter records
(2) Based on 220 gpd/EDU
0.39 gpm/10,000 sqft
2.88 EDUs/10,000 sqft
3,990,514 sqft
48,665 sqft/lot
7,377,524 gallons
6,944,880 gallons
715 gpd/acre
561 gpd/10,000 sqft
4.6.2 Residential Unit Flows
To determine the average wastewater flow for residential customers, water meter records were obtained
for parcels within the sewer service area and sorted based on the water meter type. Meter accounts that
do not contribute to sewer flows (irrigation, agriculture, fire protection, and temporary meters) were first
deducted from the data. For commercial, institutional, and multi-family accounts, the percentage of
potable water entering the sewer system was assumed to be approximately 90 percent. These account
types include newer meters similar to the accounts analyzed in the Faraday study (94 percent return rate),
as well as older commercial meters that included some components of irrigation demand.
The return rate to the sewer system from single-family water meters is affected by the lot size and
irrigation demands, and is highly variable. For this reason, water billing data from residential accounts
was not used directly. Single-family meters and duplex meters were assigned an equivalent dwelling unit
(EDU) of 1 and 2, respectively. To determine the flow per residential EDU, the total sewer flow
estimated from non-residential and multi-family water accounts was deducted from the total sewer flow,
based on the August 2001 Encina meter reading. The resulting residential flow component was then
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divided by the total number of EDUs. Using this methodology, the average unit flow per residential unit
for the existing Carlsbad sewer system is calculated to be approximately 195 gpd/EDU.
4.7 EXISTING FLOWS PER SUB-DRAINAGE BASIN
City of Carlsbad water billing records linked to the City’s parcel base were used to determine the existing
wastewater flow generation within each sub-drainage basin. Residential wastewater flows were estimated
for each sub-drainage basin based on a unit flow generation rate of 195 gpd per single-family residential
meter account (1 EDU), and 390 gpd per duplex meter account (2 EDUs). Wastewater flows from multi-
family and non-residential parcels (multi-family, commercial and institutional meters) were estimated
from water billing data using the assumed return rate to the sewer system of 90 percent. The estimated
flows and EDU count for each sub-drainage basin are provided in Table 4-4. Sub-basin boundaries are
illustrated on Exhibit 1 provided in Appendix A.
1A V/C 153 20.72 92.25 112.96 6A NB 498 67.43 45.06 112.49 1B V/C 208 28.16 19.23 47.39 7A* NAH 527 71.36 5.82 77.18 1C V/C 118 15.98 0.00 15.98 7B NAH 448 60.66 15.18 75.84 1D V/C 428 57.95 81.35 139.30 7C* NAH 383 51.86 0.00 51.86 1E V/C 1,302 176.29 174.07 350.36 8* NAH 133 18.01 0.00 18.01 1F V/C 560 75.82 104.41 180.24 9 NB 513 69.46 107.69 177.15 1G V/C 266 36.02 229.72 265.74 13A* V/C 0 0.00 4.38 4.38 1H V/C 606 82.05 119.35 201.41 13B Vallecitos 0 0.00 113.01 113.01 1I NAH 945 127.95 55.86 183.81 14B NAH 1 0.14 3.28 3.42 1J NAH 949 128.49 19.53 148.02 15B* NAH 4 0.54 54.91 55.45 2A V/C 583 78.94 67.97 146.91 18B Vallecitos 951 128.77 28.71 157.48 2B* NAH 223 30.19 0.00 30.19 19A NB 414 56.06 4.94 60.99 2C NAH 1,412 191.18 0.57 191.76 19B NB 176 23.83 99.23 123.06 3A V/C 244 33.04 145.86 178.90 19C NB 400 54.16 6.15 60.31 3B V/C 0 0.00 107.96 107.96 19D NB 447 60.52 0.98 61.51 3C Buena 0 0.00 41.24 41.24 20A Vallecitos 556 75.28 4.05 79.33 4A Buena 1,252 169.52 58.03 227.55 20B Buena 291 39.40 1.01 40.41 4B NB 857 116.04 12.42 128.46 20C NB 221 29.92 0.00 29.92 5A* NAH 0 0.00 4.91 4.91 20D NB 92 12.46 0.00 12.46 5B* Vallecitos 2 0.27 152.12 152.39 20E NB 2 0.27 0.00 0.27 5C Buena 0 0.00 23.44 23.44 21A NB 138 18.69 1.95 20.63 5D* NAH 0 0.00 10.99 10.99 21B NB 82 11.10 9.91 21.01 5E Buena 0 0.00 39.19 39.19 21C Vallecitos 0 0.00 36.88 36.88 5F Buena 0 0.00 14.13 14.13 22A V/C 0 0.00 18.99 18.99 5G Vallecitos 0 0.00 39.28 39.28 22B NB 137 18.55 94.29 112.84 5I Buena 0 0.00 105.15 105.15 24A* NAH 233 31.55 0.00 31.55 5J Buena 0 0.00 12.78 12.78 24B* NAH 1 0.14 20.44 20.57 5K Vallecitos 5 0.68 42.69 43.37 Totals: 16,761 SF Units 2,269 gpm Res. flow 2,451 gpm Non-Res. flow 4,721 gpm(1) An asterisk denotes sub-basins that are currently discharging out-of-basin.(2) Residential flow based on an average unit flow rate of 195 gallons per day per single family unit. (3) Non-residential flow based on an assumed 90% return rate from commercial, institutional, and mult-family water billing records.Non-Res. flow(3)(gpm)Interceptor SystemInterceptor SystemSub-basin(1)No. of SF UnitsSub-basin(1)Residential Flow(2)(gpm)(6.8 MGD) Total FlowTable 4-4EXISTING WASTEWATER FLOWS PER SUB-DRAINAGE BASINNo. of SF UnitsResidential Flow(2) (gpm)Non-Res. flow(3)(gpm)Total flow (gpm)Total flow (gpm)City of CarlsbadSewer Master Plan Update 4-10Dudek & Associates, Inc.March 2003
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SEWER MASTER PLAN UPDATE March 2003
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CHAPTER 5
EXISTING SYSTEM EVALUATION
The level of sewer service that is provided to a community is the result of the implementation of
improvements that are “designed” in accordance with accepted criteria. The performance of a wastewater
collection system and its components are evaluated based on comparisons with established and verified design
criteria. This chapter describes the criteria, methodology and analyses used in the evaluation of interceptor
facilities relative to 2001 conditions. The evaluation method employs the use of the SewerCAD hydraulic
modeling software, which performs hydraulic calculations based on standard open channel flow algorithms
and Manning’s equation. SewerCAD performs extended period simulations (EPS) to route wastewater flows
through the conveyance system using a unit hydrograph or diurnal curve. The result of this analysis
technique is a more accurate depiction of the true peaking factor within the subject collection system. A
summary of the performance of the existing system under both dry and wet weather conditions is provided.
5.1 DESIGN CRITERIA
Design criteria provide the standards against which the existing system is evaluated. These criteria are also
the basis for planning of new facilities to improve existing service or to handle future wastewater flows. Most
of the design criteria presented in this Master Plan Update conform to existing City of Carlsbad design
standards and planning criteria. The most significant deviation from past standards and practices of the City
occurs in the areas of wastewater flow projection methodology, discussed in Chapter 6 of this report, and
peaking factor identification. Peaking factors used in the hydraulic analysis are based on historical dry and
wet weather peak flows observed from metering data, as previously presented in Chapter 4.
5.1.1 Depth of Flow
Evaluation of gravity pipelines makes use of Manning’s Equation for computation of a pipeline’s capacity.
The capacity of each gravity sewer is based on the relative depth of flow within the respective pipeline reach.
Sewer interceptors are not typically designed to flow full, as unoccupied space at the top of the pipe is
required for conveyance of sewage gasses and to provide contingent capacity for wet weather inflow and
infiltration. Interceptor sizing is typically based on the pipeline flowing 75 percent full at the PWWF if the
pipe is larger than 12-inches in diameter (D/d = 0.75). If the pipeline is 12-inches in diameter or smaller, a
D/d factor of 0.50 is used.
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5.1.2 Pipeline Friction Factor
Friction factors for pipelines vary with the material and the age of the pipe. For analysis purposes, the
pipeline friction factor assumes that the pipeline has been in service for some period of time, and that some
fouling, deposits, and deterioration may have occurred. A roughness factor as indicated by a Mannings’
coefficient (“η”) of 0.013 is typically used to evaluate existing interceptors and for projection of future sizing
needs. Previous studies have shown that this value typically accounts for most pipe roughness, joints, and
fouling that occur after several years of operation. At the direction of City staff, a Manning’s coefficient of
0.012 was used in the evaluation of the PVC-lined RCP and CCFRPM pipeline sections of the V/C
Interceptor installed in 2002 (reaches VC5 through VC11A).
5.1.3 Lift Stations
In the design of sewer lift stations, it is required that spare pumping units be included for mechanical
reliability. A wastewater facility must be capable of conveying peak wet weather flows with the largest
operating unit out of service. Lift stations are typically equipped with a minimum of two pumps and have a
secondary or emergency power source, consisting of either installed generators or a connection for a portable
generator. Forcemains are evaluated based on maintenance of a minimum or maximum allowable flow
velocity, varying between 2.5 and 8.0 fps. Velocities less than 2.5 fps can result in deposition in the
forcemain, while velocities greater than 8.0 fps can damage the pipeline through excessive abrasion.
5.2 EXISTING INTERCEPTOR SYSTEM HYDRAULIC MODEL
A new model of the Carlsbad interceptor system was developed from GIS data collected as apart of this
Master Plan Update. The magnitude of external flows from agencies that contribute to the system and internal
flow generation was determined from flow metering data. Information from City of Carlsbad water billing
records was associated with the City’s parcel base, and then used to distribute internal flows along the
interceptor system. Peak dry and wet weather flows were input to the model using hydrographs (diurnal
curves) developed from 24-hour metering data.
5.2.1 Physical Data Input
The existing Carlsbad interceptor model includes gravity pipelines, siphons, lift stations, and force mains
comprising the V/C, NAH, Buena, Vallecitos and NB Interceptors, as shown on Exhibit 1, provided in
Appendix A. Manhole locations, invert elevations, pipeline diameters, pipeline lengths, and other pertinent
information were obtained directly from the sewer system GIS, developed as a part of this Master Plan
Update, using a graphical interface and standard CADD/GIS software. The model consists of 374 pipeline
segments totaling over 24 miles of pipeline. Pipeline diameters range from 8 to 54 inches. The interceptor
reach naming convention established in the previous Master Plans has been maintained for this analysis.
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In creating a model, there are often basic assumptions that are made to properly represent the system. Siphons
in the Carlsbad interceptor system are typically double or triple barreled sections that may have different pipe
sizes. The SewerCAD model requires that siphons be simplified by representing the section as a single pipe.
An equivalent pipeline diameter was input for siphons based on the combined area of the pipes.
Pump curves, wet well dimensions and forcemains for the Buena Vista, North Agua Hedionda, Foxes
Landing, Home Plant, and North Batiquitos Lift Stations are included in the model. Pumping units at lift
stations can have either fixed speed or variable frequency drive (VFD) motors. Each of the lift stations
modeled, with the exception of the North Batiquitos Lift Station, have VFD pumping units. With variable
speed drives, the rate of flow coming into the station is essentially the same as the rate of flow out of the
station. Lift stations with VFDs were modeled as a single design point pump. The North Batiquitos Lift
Station has two duty pumps with fixed speed drives. Individual pumps and control settings were modeled for
this lift station.
5.2.2 Internal Flow Distribution
Flow generation within Carlsbad is allocated and distributed to the interceptor system in accordance with the
total flow generated within each sub-drainage basin. Sub-basin boundaries are illustrated on Exhibit 1
provided in Appendix A. City of Carlsbad water billing records and the City’s parcel base were used to
determine the existing wastewater flow generation within each sub-drainage basin. Residential wastewater
flows were estimated based on a unit flow rate of 195 gpd per single-family residential meter account, and
390 gpd per duplex meter account (refer to Section 4.6 of this report). Wastewater flows from multi-family
and non-residential parcels (commercial and institutional meter accounts) were estimated from water billing
data using an assumed return rate to the sewer system of 90 percent. This return rate assumes that outdoor
irrigation water for multi-family, commercial and institutional properties is delivered from separate irrigation
meters. The estimated flows and EDU count per sub-drainage basin were previously provided in Table 4-4
The wastewater flows allocated to each sub-drainage basin were considered tributary to the pipeline
interceptors at the corresponding discharge location of the trunk or collector sewers within that sub-basin. For
sub-basins with multiple connection points to interceptor pipelines, flow was typically input at the upstream
connection (a conservative evaluation approach). Table 5-1 summarizes the distribution of average flow
within the system used for this analysis. The hydraulic analysis was performed by peaking the average flows,
as discussed in the following section.
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Table 5-1
EXISTING CARLSBAD FLOW SUMMARY BY INTERCEPTOR
It is noted that the total flow rate of 6.8 MGD is slightly higher than the actual totals calculated for Carlsbad
based on the August 2001 Encina meter records (refer to Table 4-3). The higher flow total is a result of using
higher flows for the North Batiquitos Interceptor in the existing system analysis based on flow meter data
from the North Batiquitos Lift Station. In addition, the distribution of flows using a universal flow rate of 195
gpd/SFDU resulted in an almost exact match with Encina meters in the Carlsbad/NAH interceptor system, but
lower flows in the Buena and Vallecitos Interceptors. Higher peaking factors were therefore applied to the
Buena and Vallecitos systems in the model to more closely match recorded peak flows. It is noted that future
flow projections are based on a more conservative unit flow rate of 220 gpd/SFDU, as discussed later in
Chapter 6 of this report.
5.2.3 Dry Weather Hydrographs
One of the primary differences between the analyses performed in the previous Master Plans and this Master
Plan Update is the use of unit hydrographs or “diurnal curves” as opposed to fixed peaking factors for the
determination of peak dry weather flows. Hydrographs are developed to account for the varying rate of
wastewater production throughout a typical day. The term “diurnal” is indicative of the shape of the curve,
which typically exhibits peak flow periods twice in a 24-hour period. The use of diurnal curves when
accounting for the wastewater production of each contributor allows for a more accurate representation of
flow variations and accounts for the routing of wastewater through the collection system on a temporal basis.
Dry weather hydrographs were developed for each upstream contributing agency and for the internally
generated Carlsbad flows based on flow meter data collected and reviewed from Encina meters. From the
Com/Ind/Inst/MF Total
No. of Flow
(2)Flow(3)Flow
Units (MGD) (MGD) (MGD)
Vista/Carlsbad 4,468 0.87 1.68 2.55
North Agua Hedionda 5,259 1.03 0.28 1.30
Buena 1,543 0.30 0.42 0.73
Vallecitos 1,514 0.30 0.60 0.90
North Batiquitos 3,977 0.78 0.55 1.33
Totals: 16,761 3.3 3.5 6.8
(1) Includes townhomes and condos that receive an individual water bill
(2) Flow per SFDU is based on the overall calculated rate of 195 gpd/SFDU
(3) Sewer flow is estimated at 90% of the average water demand from 2001 billing
records for multi-family, commercial and institutional accounts.
Interceptor System Single Family DU (1)
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graphs in Appendix C, it is clear that the shapes of the unit hydrographs for each basin are similar. However,
each basin exhibits its own unique peaking factor based on the combination of land uses that comprise the
basin. Hydrographs for the existing system model were based on flow data from Sunday, August 26. As
discussed previously in Chapter 4, weekend peaks were observed to be higher than weekday peaks, and the
highest peak flows in most interceptors during August 2001 occurred on August 26. The dry weather
hydrographs generated from the model at the downstream interceptor reaches were then compared to
hydrographs from meters near the Encina WPCF to assure that the model accurately reflected the collection
system flows.
Wastewater flows tributary to the Carlsbad system from other agencies are termed “external loads”. At each
major connection to the Carlsbad system, flow meters are installed for billing purposes. The 24-hour flow
data from each of these meters was analyzed and used to determine the existing dry weather flow entering the
system. Figure 5-1 illustrates the dry weather hydrographs developed for external loads to the Carlsbad
system. The hydrographs represent City of Vista flows to the V/C Interceptor (V1), Buena and Raceway Lift
Station flows to the Buena Interceptor (B2 + V2), Vallecitos flows to the Vallecitos Interceptor (VA1), and
Leucadia and Encinitas flows to the NB Interceptor (L1). Dry weather peaking factors for the upstream
agency flows based on these graphs range from 1.63 for the City of Vista to 1.85 from the Buena and
Raceway lift stations.
Figure 5-1
DRY WEATHER HYDROGRAPHS FOR EXTERNAL LOADS
0
1
2
3
4
5
6
7
8
9
10
0 5 10 15 20 25
TimeHourly Average Flow (mgd)V1 L1 VA1 B2+V2
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The diurnal curves developed for internal loads to each of the interceptors were normalized into “unit” diurnal
curves. Two separate curves were developed based on the flow type. The diurnal pattern for the Carlsbad
single family residential flows was developed by consideration of each of the measured flows within the
system. The “non-residential” flow pattern was based on previously developed curves for the Southern
California region. Figure 5-2 illustrates the diurnal patterns applied to average Carlsbad flows generated
within each sub-drainage basin.
Figure 5-2
DRY WEATHER UNIT HYDROGRAPHS FOR INTERNAL LOADS
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 24:00
Time of Day (hours)
Residential Non-Residential
5.2.4 Wet Weather Flows
To understand the operations of the existing system during peak flow periods, wet weather flows (from inflow
and infiltration) are added to the dry weather flows. This section discusses the methods used to model wet
weather flow events. Long term flow metering data was reviewed to determine the wet weather response of
each interceptor system. Five storm events were reviewed and a single storm was selected to represent wet
weather flows in the system. The largest event occurred on February 22 and 23, 1998. This single event had
a rainfall total of over 2.2 inches. Several million dollars of damages occurred in the surrounding area
according to the National Weather Service. Because of the extreme nature of this event and the questionable
nature of meter and rain gauge operations, this event was not considered for further analysis.
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The storm event selected for the wet weather analysis occurred on November 24, 2001. The total rainfall
amount for this storm was 1.29 inches with a peak intensity of 0.55 inches/hour. The rainfall occurred during
an off-peak flow period and lasted for approximately 4 hours. The fact that it occurred off-peak allowed more
accurate flow measurement of flows entering the system. Because this rainfall event was not preceded by
other storms, it provides a good representation of the inflow component of flow. The inflow component of
rainfall induced I&I produces the highest peak flows in a system. However, storm water induced infiltration
can also increase peak flows. This is evident in the flows from the City of Vista to the Vista/Carlsbad (V/C)
Interceptor.
To illustrate the use of hydrographs for wet weather events, the development of flow curves for the City of
Vista based on Encina flow meter V1 is presented. The inflow component of I&I, or the “defect” flow, was
derived by comparing the peak flow rate of the wet weather event to the average dry weather flow. This flow
curve comparison is presented on Figure 5-3. From Figure 5-3, it is apparent that there was an additional 2.6
MGD of wastewater flow as the result of the peak intensity of the storm (0.55 inches of rainfall per hour).
Figure 5-3
I&I FLOW ANALYSIS FOR THE VISTA METER (V1) ON 11/24/01
0.55 iph
2.60 mgd
0
2
4
6
8
10
12
14
16
048121620
Hour
0.0
0.5
1.0
1.5
2.0
Rainfall 11/24/01 ADWF Estimated I&I
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The City of Vista has exhibited long-term flow response from increased infiltration due to high ground water
levels following major storm events. Based on flow data documented in the July 2001 City of Vista
Wastewater Master Plan Update, an additional base infiltration load of approximately 3.0 MGD has been
experienced for extended periods after storm events due to high ground water levels and pipeline defects.
This infiltration rate was added to the calculated peak inflow rate of 2.6 MGD. The total defect flow
representing peak I&I rates assigned to the Vista system is therefore 5.6 MGD.
With an average dry weather peak flow rate of just over 9.0 MGD, the predicted peak wet weather flow rate
for the existing City of Vista system tributary to the V/C Interceptor is approximately 14.6 MGD (9.0 MGD
+ 5.6 MGD). Using a “fixed pattern”, as illustrated on Figure 5-4, assures that the peak of the sanitary flow
and the defect flows are additive. The peak flow response is what would be predicted if the same rainfall
amount and intensity of the November 24, 2001 storm event occurred coincidental with the peak dry weather
flow during a period of elevated ground groundwater levels (due to a previous storm or series of storms).
Figure 5-4
POTENTIAL PEAK WET WEATHER FLOWS TO THE V/C INTERCEPTOR FROM VISTA
9.0 mgd
14.6 mgd
0
2
4
6
8
10
12
14
16
0 4 8 12 16 20
Hour
ADWF V1_Inflow V1_Infiltration V1_Total
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The City of Carlsbad system also contributes I&I to the V/C Interceptor. The combined flow from Vista and
Carlsbad tributary to the V/C and NAH Interceptors is measured at the C3 Encina meter, which is just
upstream of the Encina WPCF. The effects of the November 24, 2001 storm event at this site are shown on
Figure 5-5.
Figure 5-5
I&I FLOW ANALYSIS FOR THE V/C METER AT ENCINA (C3) ON 11/24/01
0.55
7.298
0
2
4
6
8
10
12
14
16
18
20
048121620
Hour
0.0
0.5
1.0
1.5
2.0
Rainfall 11/24/01 ADWF Defect
As shown on Figure 5-5, the total peak defect flow on November 24, 2001 was approximately 7.3 MGD.
The contribution from Vista for this event was previously calculated to be approximately 2.6 MGD. The
increase in defect flow from the City of Carlsbad to the V/C and NAH Interceptors is therefore calculated to
be approximately 4.7 MGD. Without detailed flow studies and additional monitoring it cannot be accurately
determined where the storm water is entering the system. The internal stormwater inflow for Carlsbad was
distributed evenly in the model along the entire length of the V/C Interceptor. This assumes a bias towards
wet weather flow contributions occurring in the V/C Interceptor rather than the NAH Interceptor. It is noted
that the flow meter at Foxes Lift Station on the NAH Interceptor is not currently operational. This meter is
recommended to be repaired to provide a long-term historical record of wet and dry weather conditions for
this interceptor.
Peak wet weather flow curves were developed based on observed inflow rates from November 24, 2001 meter
data for the Buena, Vallecitos and North Batiquitos Interceptors in a similar manner. For the Vallecitos and
NB Interceptors, the measured I&I during wet weather flow events from upstream sewering agencies was
higher than defect flows recorded at downstream meters at Encina. For these interceptors, I&I was therefore
attributed to the Vallecitos and Leucadia/Encinitas systems, respectively. In the Buena Interceptor, the peak
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I&I rate was calculated from the upstream agency and a measurable amount of inflow was determined to be
generated within Carlsbad. The internal defect flow for this interceptor was applied to the upstream end of
the interceptor in the hydraulic model. Table 5-2 summarizes the I&I applied in the existing system wet
weather analysis.
Table 5-2
EXISTING SYSTEM ANALYSIS PEAK I&I RATES
Model ID Description
Flow Rate
(MGD)
V1 City of Vista External Inflow 2.6
272 City of Vista External Infiltration 3.0
VC_IntWx Carlsbad Internal I&I to V/C 4.7
B2_V2 Buena/Raceway External I&I 1.1
437 Carlsbad Internal I&I to Buena 0.5
VA1 Vallecitos External I&I 3.5
L1 Leucadia External I&I 2.1
TOTAL ESTIMATED I&I 17.4
5.3 CAPACITY ANALYSIS RESULTS
This section discusses the results of the hydraulic analyses conducted with respect to the existing system,
which includes improvements to the V/C Interceptor that are currently under construction. An understanding
of the hydraulic condition of the existing system is necessary to identify existing system deficiencies, and to
help prioritize recommended system improvements resulting from the ultimate system analysis. The capacity
of the interceptor system was evaluated under both dry and wet weather flow scenarios.
5.3.1 Gravity Pipelines
Capacity analysis of open channel systems is generally based on the consideration of the depth of flow as
compared to the diameter of the pipe (D/d). For the interceptor system, this depth to diameter ratio is
constrained to not exceed 0.75 for peak dry weather conditions. It is also considered undesirable to operate
the system at depths over 90 percent of the diameter under peak wet weather conditions. Exceptions to these
guidelines are allowed when considering siphons or other known areas of pressure flow.
The capacity analysis under dry weather flow conditions indicates that two flat pipeline reaches in VC14 and
VC15 are flowing full (refer to Section 3.2.1). There are a few isolated locations where flows exceed the 75
percent full criteria in the Buena Interceptor, also due to short sections of very flat pipeline. These areas are
minor and are not considered to be worthy of further discussion.
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Based on analysis of the existing collection system with wet weather flows, several gravity pipelines were
determined to be deficient with respect to the design criteria established in Section 5.1 of this Master Plan
Update. It is noted that the peak wet weather event modeled is conservatively based on potential flows and
I&I rates that could occur, and is not based on actual recorded flows. The potentially deficient pipeline
reaches identified during the existing system analyses are located within four separate areas of the interceptor
system, as documented in Table 5-3.
Table 5-3
EXISTING PWWF ANALYSIS SUMMARY FOR GRAVITY PIPELINES
The longest sections of pipeline in this table are in the Vista/Carlsbad Interceptor in Reach VC-3, which is
upstream of the Buena Vista Lift Station, and Reaches VC-13-15, which are downstream of the Agua
Hedionda Lift Station. These pipeline reaches are planned for future capacity upgrades, and the replacement
pipelines are sized based on ultimate flows in the next chapter of this report. The other two areas with
existing capacity deficiencies are short sections of pipeline in the upstream and extreme downstream reaches
of the Buena Interceptor. These pipelines are flowing full as a result of isolated pipelines with very flat slopes
(refer to Figure 3-4).
5.3.2 Lift Stations
Lift station facilities within the sewer interceptor system were evaluated by comparing the peak influent
wastewater volume to the lift station’s “firm” pumping capacity, as documented previously in Table 3-4. The
influent wastewater volume of the pump station is defined by the wastewater flowing in the pipeline(s) just
upstream of each lift station in the hydraulic model. As discussed in Chapter 3, lift stations are generally
designed to maintain a “firm” capacity equal to or greater than the projected peak design flow at a specific
point in time.
Model Length Diam.
ID (ft.) (ft.)
274-281 VC3 2,830 36 Approach to Buena Vista Lift Station - pipeline flowing 75% full
309-310 VC11 896 42 Approach to Agua Hedionda Lift station - localized surcharging
300-307 VC13 3,510 42 Downstream of Agua Hedionda Lift Station - pipeline capacity is
290-298 VC14 4,530 42 exceeded for short periods; two very flat sections (reaches 290
283-289 VC15 1,860 42 and 288) and one short 20' pipe with neg. slope (reach 287)
194 B4 594 18 Upper Buena, localized surcharging in very flat reach
1 B7 596 24 Lower Buena, localized surcharging in very flat reach
392 B8 208 30
377 B8 93 30
Location/CommentsReach
Lower Buena, isolated flat sections
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Table 5-4 summarizes the peak flow tributary to the lift stations and the peak forcemain velocities exhibited
based on those flows. Estimates of peak wet weather flows are provided for the V/C Interceptor, but only
peak dry weather flows are calculated for the NAH and NB Interceptors due to a lack of wet weather flow
monitoring data.
Table 5-4
POTENTIAL PEAK FLOWS TO INTERCEPTOR LIFT STATIONS
Lift Station PDWF PWWF Peak Velocity
Lift Station Firm Capacity to Wet Well to Wet Well in Force Main(1)
(MGD) (MGD) (MGD) (fps)
Buena Vista 21.5 10.2 18.9 6.9 (2)
Agua Hedionda 23.0 15.3 24.2 10.6
Foxes Landing 3.7 2.24 ---(3)4.4
North Batiquitos 3.2 1.47 ---(3)2.6
(1) Velocity is based on the peak influent flow to the station for variable speed pumps. For the NB Lift
Station (fixed speed), the velocity is based on the output of a single pump.
(2) Peak velocity in the parallel 16" & 24" section. Velocity is 9.3 fps in the short, single 24" section
and 10.5 fps in the parallel 16" section in the bridge over I-5
(3) Metering data to determine wet weather flows is not available for this system
Based on the data in Table 5-4, there is approximately 1.7 MGD of available pumping capacity at the North
Batiquitos Lift Station to convey stormwater flows. In the hydraulic model simulation, only one fixed-speed
pump operates at the North Batiquitos Lift Station at a discharge rate of approximately 1,200 gpm (1.7
MGD). System operators have stated that a second pump has never needed to operate at the North Batiquitos
Lift Station in response to peak flows during a storm. It can therefore be concluded that the North Batiquitos
Lift Station has sufficient capacity for current wet weather flow conditions.
Based on the PDWF to the Foxes Landing Lift Station, there is approximately 1.4 MGD of available pumping
capacity to convey stormwater flows. The downstream reaches of the AH Interceptor are along the north
shore of the Agua Hedionda Lagoon, and are potential sources of I&I to the interceptor system with rising
water levels in the lagoon. Wet weather flow data is needed to estimate the existing I&I rate to this system,
and to determine if there is sufficient available capacity at the lift station to convey peak wet weather flows.
For the V/C Interceptor a hydraulic analysis of peak wet weather flows was performed. Results indicate that
the Buena Vista Lift Station may be potentially operating near its firm capacity during severe storm events,
and the capacity of the Agua Hedionda Lift Station could potentially be exceeded for brief periods. Velocities
in the Agua Hedionda forcemain and portions of the Buena Vista forcemain are also exceeding the
recommended maximum velocity of 8.0 fps during peak wet weather flow conditions.
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5.3.3 North Agua Hedionda Interceptor
The North Agua Hedionda Interceptor currently conveys flows that will ultimately discharge to the South
Agua Hedionda Interceptor (Sub-basins 5A, 5D, 7C, 8, 15B, 24A and 24B) and the Vista/Carlsbad Interceptor
(Sub-basins 2B and 7A). Consequently, ultimate flows for this interceptor are projected to be considerably
less than existing flows. A capacity analysis of this interceptor was therefore performed with existing flows
to determine the available capacity and estimate the number of future EDUs that the North Agua Hedionda
Interceptor can serve.
Encina meter data indicates that there is a significant volume of I&I generated by Carlsbad (internal defect
flows) within the V/C and NAH Interceptor systems. The amount of I&I attributed to each interceptor is
unknown because the flow meter at the Foxes Lift Station is not operational. Additionally, wet weather flow
monitoring studies performed in 2001 did not provide information on I&I rates due to a lack of significant
rainfall during the monitoring period. In the hydraulic model, the measured internal defect flows are allocated
to the upstream end of the V/C Interceptor and the capacity analysis for the North Agua Interceptor is
performed with peak dry weather flows. Figure 5-6 summarizes the results of this analysis.
Figure 5-6
NAH INTERCEPTOR HYDRAULIC ANALYSIS SUMMARY
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
NAH7NAH7NAH7Foxes LSNAH5NAH5NAH5NAH5NAH5NAH5NAH5NAH3NAH3NAH3NAH3NAH3NAH2NAH2NAH2NAH2NAH2NAH1NAH1Pipe Capacity/Flow (MGD)75% Full Capcity Full Pipe Capacity Existing PDWF
Foxes
Lift
Station
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The chart in Figure 5-6 illustrates the maximum flow rate in each reach of the interceptor over the 24-hour
hydraulic simulation, and provides a comparison with pipeline and lift station capacities. The peak dry
weather flow line represents a composite flow from the analysis results, as the peak flow in each reach may
occur at different time steps in the simulation. As can be seen on Figure 5-6, there are four isolated reaches of
pipeline in the NAH Interceptor that have significantly reduced capacities. These reaches are 24-inch
diameter pipelines with slopes of 0.03 percent or less, and lengths that vary between 126 and 283 feet.
Analysis results indicate that these reaches may be currently surcharging for very brief periods with peak dry
weather flows. If the isolated pipelines are allowed to surcharge for brief periods, the available capacity in
the NAH Interceptor system is limited by the capacity of the Foxes Lift Station, and not the gravity pipelines.
There is currently no way to accurately estimate peak storm water flows in the NAH Interceptor system.
Considering the proximity of the gravity sewers to the lagoon, however, there is a significant potential for
high I&I rates. To estimate the PWWF, a peaking factor of 3.0 was initially applied to the ADWF in this
system. With a peaking factor of 3.0 applied to the ADWF of 1.3 MGD in the NAH service area, the
resulting estimate of PWWF is 3.9 MGD. This flow is higher than current capacity of the Foxes Lift Station.
It is concluded that the amount of additional capacity is this system cannot be estimated without additional
wet weather flow data.
5.3.4 Inter-Agency Pipeline Flows
Peak wastewater flows in gravity pipelines that are jointly-owned with other sewer agencies are compared to
design flows and Carlsbad capacity rights as defined in existing agreements.
Occidental Sewer. The Occidental Sewer is jointly-owned by the City of Carlsbad, the ESD, and the LCWD.
The capacity of the 39-inch diameter gravity pipeline flowing 75 percent full is approximately 19.2 MGD.
Hydraulic analysis results indicate a potential PWWF of 12.5 MGD in this pipeline. Carlsbad owns a total of
40.0 percent of the available capacity, or approximately 8.5 MGD. Peak dry weather flows from Carlsbad are
effected by of the operation of the upstream North Batiquitos Lift Station, and are currently estimated at 2.3
MGD. This value is based on one pump operating at the NB Lift Station. Existing I&I from Carlsbad to the
NB Interceptor has not been sufficient enough to cause a second pump to operate, and therefore is not
effecting peak flows in the Occidental Sewer. The City of Carlsbad is therefore using less than 30% its
allocated capacity in the Occidental Sewer.
Vallecitos Interceptor. Hydraulic analysis results indicate that the PWWF in the Vallecitos Interceptor is
12.7 MGD. The capacity of the interceptor is listed as 20.85 MGD in the 1985 agreement with the VWD
(formerly the San Marcos County Water District), which is based on the pipeline flowing full. Carlsbad has
capacity rights of 5.0 MGD based on peak flow rates to the Vallecitos Interceptor. The PDWF from Carlsbad
in the Vallecitos Interceptor is estimated at slightly less than 2.0 MGD based on Encina meter data and the
peaking curves on Figure 5-2. The estimated defect flows resulting from I&I on November 24, 2001 were
higher at the upstream end of the interceptor (meter VA1) than at the downstream end (meter C1). Therefore,
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I&I in the Vallecitos Interceptor is attributed to flows from Vallecitos in the hydraulic analysis, and it can be
concluded that storm water inflow to this interceptor from the Carlsbad service area is minimal. It is
estimated that Carlsbad is currently using less than half of its leased flow capacity in the Vallecitos
Interceptor.
Buena Interceptor In the existing system model, the total PWWF in the Buena Interceptor at the
downstream reach was calculated to be 4.7 MGD. Most of the gravity reaches in this interceptor have a full
flow capacity between 6.0 and 7.0 MGD. However, there are several shallow sloped pipelines that the model
indicates are surcharging (conveying flows higher than the full pipe capacity) during peak wet weather flow
conditions. Analysis results indicated that two of these pipelines may be surcharging briefly under PDWF
conditions as well. PWWF from the City of Carlsbad is estimated to be approximately 2.2 MGD, which
includes an allocation of 0.5 MGD for the peak I&I rate (refer to Section 5.2.4 and Table 5-2). It is estimated
that Carlsbad has less than 0.5 MGD of available capacity in this pipeline based on existing capacity rights. It
is noted that the discharge rate to the Buena Interceptor from the BSD Buena Lift Station can be highly
variable. The Buena Lift Station shares a common wet well with the influent lift station to the Shadowridge
WWTP. During peak flow periods and periods of high rainfall, a portion of the flow from the Buena drainage
basin is diverted to Shadowridge WWTP to prevent surcharging of the Buena Interceptor.
5.3.5 Flows to the Encina WPCF and Outfall
Evaluation of Carlsbad’s use of the Encina wastewater treatment facility is based on the average dry weather
flow for treatment plant capacity and the peak wet weather flow for capacity in the ocean outfall. As
summarized in Chapter 4 of this report, the existing wastewater flow for Carlsbad, based on meter records for
August 2001, is approximately 6.5 MGD. A slightly higher flow rate of 6.8 MGD was used for the existing
system hydraulic analysis. Compared to existing capacity rights of 9.24 MGD for treatment and solids
handling, the City of Carlsbad is currently using less than 74 percent of its capacity ownership in the Encina
WPCF.
The Encina Ocean Outfall has a maximum instantaneous capacity of 104.9 MGD, considering the capacity
enhancement of constructed flow equalization facilities. Carlsbad’s capacity rights in the outfall are 25.51
MGD, which is based on a peaking factor of 2.76 times the ADWF. Peak flow rates from Carlsbad cannot be
determined from flow meter data since Carlsbad flows are subtracted from other agency flows. Resultant
peak flows from Carlsbad at Encina are likewise not available from the hydraulic analysis. Based on the
peaking factor curve presented on Figure 4-5, the PDWF from Carlsbad is estimated to be 1.7 times the
ADWF, or approximately 11.5 MGD. Approximately 5.2 MGD of I&I was attributed to Carlsbad and added
to Carlsbad flows in the wet weather hydraulic analysis. The estimate of PWWF from Carlsbad to Encina is,
therefore, 16.7 MGD, which is approximately 2.5 times the ADWF. It is therefore estimated that the City of
Carlsbad is currently using approximately 65 percent of its capacity ownership in the Encina Ocean Outfall.
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CHAPTER 6
ULTIMATE SYSTEM FLOW PROJECTIONS AND ANALYSIS
Future flow projections are used to determine required upgrades to the existing collection system to
adequately serve Carlsbad’s wastewater conveyance needs under “buildout” conditions. The existing
interceptor system, with the addition of the South Agua Hedionda Interceptor and incorporation of
planned improvements to the collection system, was analyzed with projected peak ultimate flows to
identify and size required improvements. For this Master Plan Update, a flow projection methodology
consistent with the Carlsbad Growth Database was developed. Ultimate wastewater flows were computed
based on the projected number of single family units, multi-family units, and non-residential building area
tributary to the wastewater collection system and the established unit flow factors. Results of the analysis
are summarized and deficiencies identified. Recommended improvements to the sewer interceptor
system to convey ultimate flows are presented in Chapter 7 of this report.
6.1 PLANNED SEWER SYSTEM IMPROVEMENTS
The City of Carlsbad ultimate sewer system will include the four existing interceptors and the future
South Agua Hedionda (SAH) Interceptor. The assignment of ultimate flows to the interceptor system is
made with the assumption of several future changes to the collection system, which were dicussed and
verifed with City Staff. Exhibit 2, provided in Appendix A, illustrates the proposed ultimate sewer
interceptor system that was analyzed in this Master Plan Update. This map also identifies the interceptor
system to which each sub-drainage basin will ultimately discharge.
6.1.1 South Aqua Hedionda Interceptor
The SAH Interceptor will serve areas south and east of the Agua Hedionda Lagoon, and connect with the
V/C Interceptor between reaches VC13 and VC14. The interceptor will convey City of Carlsbad flows
only. Previous planning studies for the SAH Interceptor included flow contributions from the City of
Vista Raceway Basin and the City of Oceanside’s Leisure Area and Lake Lift Station. The City of Vista
has recently confirmed that they are no longer interested in discharging flows to the SAH Interceptor.
The conveyance of flows from Oceanside are no longer feasible because the eastern portion of Sub-basin
15A, which was previously planned for development and included a sewer extension east to Oceanside,
has now been designated as open space. The SAH Interceptor will serve Sub-basins 5A, 5B, 5D, 7C, 8,
13A, 14A, 15A, 15B, 16, 18A, 24A, and 24B. A new lift station and an approximate one-mile long
forcemain will be included in the SAH Interceptor system.
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Figure 6-1 illustrates the alignment and reach designations of the SAH Interceptor. The eastern portion of
the SAH Interceptor, along Sunny Creek Road and El Camino Real south of Cannon Road, has already
been constructed. This portion of the interceptor is currently tributary to the NAH Interceptor. Another
portion of the interceptor in Cannon Road, west of El Camino Real, has also been constructed, and the
Kelly Ranch Lift Station now lifts flow from that pipeline into the NAH Interceptor. The remaining
portions of the SAH Interceptor, yet to be constructed, include the SAH Lift Station and forcemain. A
new gravity sewer will connect with the gravity line from the Faraday Business Park and discharge to the
SAH Lift Station. When the SAH Interceptor is complete, the Kelly Ranch Lift Station and both Faraday
Lift Stations will be abandoned.
6.1.2 Collector System Improvements
An expansion of the existing collector system will be required to connect future developments with
existing pipelines and interceptors. The size and alignment of these future collection pipelines are not
analyzed in this Master Plan Update. However, the discharge locations to the interceptors are identified
for the hydraulic analysis of the ultimate interceptor system. The assumed general alignments of these
major future collection sewers, future lift stations, and forcemains are shown on Exhibit 2.
A new lift station will be required to convey flows from Sub-basins 16 and 18A to the SAH Interceptor.
Flows from several sub-basins are currently being pumped “out-of-basin”, and future gravity sewers are
planned that will eliminate some existing lift stations. The lift stations planned for elimination include:
• Vancouver Lift Station - A gravity pipeline through LFMZ 25 will convey flows from Sub-basin
2B to the V/C Interceptor. Flows are currently pumped to the NAH Interceptor.
• Simsbury Lift Station - A gravity pipeline through LFMZ 25 will connect with a future gravity
pipeline from the Vancouver Lift Station and convey flows from Sub-basin 7A to the V/C
Interceptor. Flows are currently pumped to the NAH Interceptor.
• Villas Lift Station - A gravity pipeline will extend north from the existing lift station in a future
easement and connect with the future gravity line from the Simsbury Lift Station through LFMZ
25 to the V/C Interceptor. Flows from the Villas Lift Station, which serves several apartment
complexes, are currently pumped to the NAH Interceptor.
• Woodstock Lift Station - Flows from the approximately 20 single family residences served from
the Woodstock Lift Station will be conveyed by gravity through the future Calavera Hills
development in Sub-basin 7C to the SAH Interceptor. Flows are currently pumped to the NAH
Interceptor.
S A H 3 SAHT2BSAH3C
SAHT1E
S A H T 2 C
S
A
H
T
3
B
SAHT1G
S A H T 3 A
S A H 1
SAH4
SAH LIFT
STATION
SOUTH AGUA
HEDIONDA
03-2003 Carlsbad601.mxd
LEGEND
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
FIGURE 6-1
CITY OF CARLSBAD
FUTURE SOUTH AGUA HEDIONDA
INTERCEPTOR SEWER
1"=2000'
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
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• Gateshead Lift Station - Flows from the approximately 25 single family residences served from
the Gateshead Lift Station will be conveyed by gravity through the future Robertson Ranch
development in Sub-basin 14A to the SAH Interceptor. Flows are currently pumped to the NAH
Interceptor.
• Faraday Lift Stations No. 1 and 2 - A gravity pipeline will extend from Faraday Lift Station No.
2 to the SAH Interceptor, and discharge just upstream of the future SAH Lift station. Most of this
pipeline has already been constructed. Flows from Sub-basin 5B are currently pumped to the
Vallecitos Interceptor.
• Kelly Ranch Lift Station – This temporary lift station will be replaced by the SAH Lift Station.
Flows from Sub-basin 8 are currently pumped to the NAH Interceptor.
• La Golondrina Lift Station - The Golondrina Lift Station currently pumps City of Carlsbad flows
in Sub-basin 6B to the LCWD. A future gravity pipeline will convey flows from the Golondrina
service area to the Poinsettia Lift Station and Vallecitos Interceptor. This pipeline is also planned
to collect flows from a small area in the southwest corner of Sub-basin 18B, which currently
discharges to the LCWD.
• Forest Lift Station – A gravity pipeline constructed using a micro-tunneling construction process
will convey flows from Sub-basin 1C to the V/C Interceptor upstream of the Buena Vista Lift
Station. Flows are currently pumped to the V/C interceptor downstream of the Buena Vista Lift
Station.
6.2 CARLSBAD GROWTH DATABASE
Build-out projections for the City of Carlsbad have been recently updated and compiled into a Growth
Database, which is maintained by the City. Growth projections are based on current development plans
and results of the 2000 Census. The City of Carlsbad Growth Database is parcel-based and includes
information on existing land use, as well as growth potential. Growth data provided in the database
consists of the number of projected single family units, multi-family units, and the estimated building area
for non-residential land use at build-out. The building area in the database is generally assumed at 25
percent of the parcel size, unless more detailed planning information was available
Over half of the projected growth in the City of Carlsbad sewer service area is associated with known,
planned developments in the eastern portion of the City. These developments include Kelly Ranch,
Villages of La Costa, Calavera Hills, Mandana Properties, and Robertson Ranch, which are primarily
residential developments, the Carlsbad Oaks North and Faraday Business Parks, and Bressi Ranch, which
will have a mixed-land use. Development information for these large planned projects is typically
lumped onto a single existing parcel in the Growth Database, even if the project boundary encompasses
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SEWER MASTER PLAN UPDATE March 2003
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several existing parcels or drainage sub-basins. Layout maps in various development stages were
provided by the City for most of these projects and used to distribute the projected sewer flow to
appropriate sub-basins. The remainder of future growth in the City of Carlsbad is projected to include
smaller, non-specific developments and general “infill” of established neighborhoods and commercial
areas located in the western portions of the City.
The Growth Database was originally provided by the City of Carlsbad at the start of the Master Plan
Update project. During the course of the project, several updates to the projected future growth were
provided by the City and incorporated into a modified database. The growth potential data in the City of
Carlsbad Growth Database used for this Maser Plan Update is summarized by Local Facility Management
Zone (LFMZ) in Table 6-1. The growth update indicates a slightly lower number of residential units and
more commercial/industrial area than what was projected in the last Master Plan Update. In Table 6-1,
the shaded rows identify LFMZs that are not within the City of Carlsbad sewer system boundary or
sphere of influence.
Table 6-1
CITY OF CARLSBAD GROWTH DATABASE SUMMARY
LFMZ Non-Residential
No. SFDU MFDU Bldg Area (sqft)
1 430 0 0 Downtown area; Unit counts from 5/15/02 LFMZ 1 update
2 25 146 39,656 3 second dwelling units counted as MFU
3 13 0 193,251
4 0 0 50,000
5 0 0 4,137,974 Includes Faraday Business Park and airport
6 185 0 89,988 Future church assumed at 9,100 sqft (25% coverage)
7 345 436 32,670 Calavera unit counts from 7/15/02 update; Future elem.school
8 186 544 6,000 Kelly Ranch
9 41 0 428,100
10 750 320 0 Villages of La Costa; Future elementary school
11 1,266 275 622,972 Villages of La Costa
12 55 0 20,000 Future church assumed at 20,000 sqft
13 0 18 1,482,142 24 room hotel expansion assumed at 1 hotel uni =.75 MFU
14 711 411 229,166 Unit counts from Robertson Ranch update; Future High School
15 807 158 303,798 Sycamore Creek; 8 second dwelling units counted as MFU
16 0 0 1,921,000 Carlsbad Oaks North BP; Building area from 8/01/02 update
17 523 100 2,511,000 Bressi Ranch; 40,000 sqft for private school & daycare/church
18 308 0 2,262,817 140 condos counted as SFU
19 218 78 69,520 61 condos counted as SFU; 78 timeshares counted as MFU
20 687 24 73,450
21 185 210 0
22 168 286 53,280 149 condos counted as SFU
23 0 264 507,000 includes assisted living project (non-res & MFUs)
24 32 0 0
25 130 0 0
Totals:7,065 3,270 15,033,784 shaded rows indicate areas outside of the sewer service area
No. of Res. Units Comments
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SEWER MASTER PLAN UPDATE March 2003
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6.3 FUTURE FLOW GENERATION FACTORS
Flow generation factors are used, in conjunction with the City’s Growth Database, to project ultimate
wastewater flows and distribute flows in the ultimate system hydraulic analysis. Unit flow generation
rates were developed and presented in Chapter 4 of this report based on 2001 flow data. These unit flow
factors were used to distribute flow in the existing system model. For design and planning purposes, a
more conservative approach to flow generation is used. The unit flow factors developed to project
ultimate wastewater flows from data in the City’s Growth Database are listed in Table 6-2, which also
provides a comparison of flow generation factors used in previous planning documents.
Table 6-2
CARLSBAD WASTEWATER UNIT FLOW COMPARISONS Existing System
(Based on 2001 meter data and/or water billing records)
Single Family DU 195 gpd/DU 220 gpd/DU 209 gpd/DU 220 gpd/DU
Multi-Family DU 220 gpd/DU 209 gpd/DU 160 gpd/DU
Faraday 715 gpd/acre
Business Park 561 gpd/10,000 sqft
Restaurants 6,500 gpd/10,000 sqft
1000 gpd/acre
918 gpd/10,000 sqft*1,150 gpd/10,000 sqft
Commercial 1,230 gpd/10,000 sqft
Industrial 750 gpd/10,000 sqft
* Conversion from flow per acre to flow per building area based on an assumed building coverage of 25% of the parcel size.
Non-residential
Land Use
Category
1997 Master Plan
Update
2002 Master Plan
for Future Flows1991 Master Plan
The City’s established planning value for wastewater flow is 220 gpd/EDU. Flow factors typically used
for design in sewer systems throughout San Diego County range between approximately 208 gpd/EDU in
the City of Encinitas, to approximately 265 gpd/EDU in the City of Chula Vista. The City of San Diego
Water & Sewer Design Guide recommends the use of 90 gallons per capita day (gpcd). Based on an
average of approximately 2.5 to 2.6 persons per household, a flow factor between 225 and 235 gpd/EDU
would be recommended using the City of San Diego’s design criteria. Based on these comparisons and
the calculated unit flow rate for current conditions, the previously established flow generation rate of 220
gpd/EDU is considered to be appropriate for flow projections for this Master Plan Update.
The Carlsbad Growth Database projects the number of future multi-family units to be constructed.
According to City Staff, multi-family units are defined as apartment units or low-income housing units.
A lower flow factor for multi-family units was developed based on a research of water billing records and
a comparison of unit flows used by other agencies. The multi-family unit flow factor was also applied to
hotel units, timeshares, second housing units constructed on existing residential parcels, and housing
densities in excess of 12 units per acre on development plans.
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SEWER MASTER PLAN UPDATE March 2003
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The non-residential land use flow factor is applied to building area projections in the Growth Database.
This broad category includes commercial, industrial, medical and office buildings. The composite unit
factor is based on an assumed mix of the land use types and is appropriate (and probably somewhat
conservative) for flow projections of the overall sewer system. Projections made using this factor may
not be representative of smaller areas with a single land use type. Flow projections for future schools
were based on EDU conversions documented in the Carlsbad Municipal Code (Table 13.10.020c).
6.4 PROJECTED ULTIMATE FLOWS
Flow projections for future developments were made by applying the unit flow factors, documented in
Section 6.3 of this report, to the future build-out data in the Growth Database. Parcels with identified
future growth were then apportioned to sub-drainage basins using GIS techniques. Future flows were
added to the existing flows in each sub-basin to obtain ultimate flows. Upon review of the flow data it
was determined that a few of the newer residential areas in the collection system had existing sewer flows
(based on water meter records) but were also included in the Growth Database. The future flow for these
parcels was subsequently deleted from the Growth Database used for this project.
The ADWF flow for the ultimate sewer system is projected to be approximately 9.9 MGD. This value
represents an increase of approximately 3.0 MGD, or 45 percent, over existing wastewater flows. Figure
6-2 presents historical flows and the projected ultimate flow, and makes a comparison with previous flow
projections. Table 6-3 lists the existing and projected future flows by sub-drainage basin.
Figure 6-2
HISTORICAL AND PROJECTED ULTIMATE FLOWS
9.87
2003 Ultimate
Flow Projection
13.84
13.41
3
4
5
6
7
8
9
10
11
12
13
14
15
1985 1990 1995 2000 2005 2010 2015 2020Average Annual Wastewater Flow (MGD)Recoded flows from Encina meters
2003 Master Plan projections
1996 Ocean Outfall Capacity Reort projections
1992 Master Plan projections
1987 Master Plan projections
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SEWER MASTER PLAN UPDATE March 2003
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Table 6-3
PROJECTED ULTIMATE WASTEWATER FLOWS BY SUB-BASIN
SF Units Flow (gpm) SF Units MF units Bldg sqft Flow (gpm) SF Units Flow (gpm)
1A V/C 153 113.0 16 0 0 2.4 169 115.4
1B V/C 208 47.4 0 0 0 0.0 208 47.4
1C V/C 118 16.0 0 0 0 0.0 118 16.0
1D V/C 428 139.3 37 0 0 5.7 465 144.9
1E V/C 1,302 350.4 42 0 0 6.4 1,344 356.8
1F V/C 560 180.2 6 0 0 0.9 566 181.2
1G V/C 266 265.7 14 0 0 2.1 280 267.9
1H V/C 606 201.4 69 0 0 10.5 675 211.9
1I NAH 945 183.8 172 0 0 26.3 1,117 210.1
1J NAH 949 148.0 74 70 0 19.1 1,023 167.1
2A V/C 583 146.9 0 143 39,656 19.1 583 166.0
2B V/C 223 30.2 0 0 0 0.0 223 30.2
2C NAH 1,412 191.8 25 3 0 4.2 1,437 195.9
3A V/C 244 178.9 13 0 0 2.0 257 180.9
3B V/C 0 108.0 0 0 165,351 13.2 0 121.2
3C Buena 0 41.2 0 0 27,900 2.2 0 43.5
4A Buena 1,252 227.5 0 0 50,000 4.0 1,252 231.5
4B NB 857 128.5 0 0 0 0.0 857 128.5
5A SAH 0 4.9 0 0 407,703 32.6 0 37.5
5B SAH 2 152.4 0 0 718,609 57.5 2 209.9
5C Buena 0 23.4 0 0 399,641 32.0 0 55.4
5D SAH 0 11.0 0 0 59,864 4.8 0 15.8
5E Buena 0 39.2 0 0 238,273 19.1 0 58.2
5F Buena 0 14.1 0 0 0 0.0 0 14.1
5G Vallecitos 0 39.3 0 0 770,099 61.6 0 100.9
5H Vallecitos 0 0.0 0 0 365,905 29.3 0 29.3
5I Buena 0 105.2 0 0 429,580 34.4 0 139.5
5J Buena 0 12.8 0 0 96,754 7.7 0 20.5
5K Vallecitos 5 43.4 0 0 651,536 52.1 5 95.5
6A NB 498 112.5 0 0 14,715 1.2 498 113.7
6B(1)Vallecitos 0 0.0 111 0 0 17.0 111 17.0
7A V/C 527 77.2 103 0 21,780 17.5 630 94.7
7B NAH 448 75.8 0 117 10,890 13.9 448 89.7
7C SAH 383 51.9 242 319 23,913 74.3 625 126.2
8 SAH 133 18.0 161 474 6,000 77.7 294 95.8
9 NB 513 177.2 41 0 428,100 40.5 554 217.7
10A Vallecitos 0 0.0 207 0 23,913 33.5 207 33.5
10B Vallecitos 0 0.0 164 0 0 25.1 164 25.1
10C Vallecitos 0 0.0 118 0 0 18.0 118 18.0
13A SAH 0 4.4 0 0 1,330,600 106.4 0 110.8
13B Vallecitos 0 113.0 0 0 151,542 12.1 0 125.1
14A SAH 0 0.0 530 78 388,310 120.7 530 120.7
14B NAH 1 3.4 181 333 23,872 66.6 182 70.0
Existing Units/Flow Ultimate SystemSub-
basin
Interceptor
System
Projected Future Units and Flow
Continued next page
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SEWER MASTER PLAN UPDATE March 2003
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Table 6-3 (Continued)
SF Units Flow (gpm) SF Units MF units Bldg sqft Flow (gpm) SF Units Flow (gpm)
15A SAH 0 0.0 46 100 0 18.1 46 18.1
15B SAH 4 55.5 589 80 303,798 123.2 593 178.6
16 SAH 0 0.0 0 0 1,921,000 153.7 0 153.7
17A Vallecitos 0 0.0 383 100 2,471,000 267.3 383 267.3
17B Vallecitos 0 0.0 140 0 40,000 24.6 140 24.6
18A SAH 0 0.0 0 0 2,221,000 177.7 0 177.7
18B Vallecitos 951 157.5 148 0 41,817 26.0 1,099 183.4
19A NB 414 61.0 11 0 0 1.7 425 62.7
19B NB 176 123.1 61 78 69,520 23.5 237 146.6
19C NB 400 60.3 121 0 0 18.5 521 78.8
19D NB 447 61.5 25 0 0 3.8 472 65.3
20A Vallecitos 556 79.3 215 0 0 32.8 771 112.2
20B Buena 291 40.4 50 0 13,450 8.7 341 49.1
20C NB 221 29.9 239 24 0 39.2 460 69.1
20D NB 92 12.5 78 0 60,000 16.7 170 29.2
20E NB 2 0.3 104 0 0 15.9 106 16.2
21A NB 138 20.6 62 53 0 15.4 200 36.0
21B NB 82 21.0 123 157 0 36.2 205 57.2
21C Vallecitos 0 36.9 0 0 0 0.0 0 36.9
22A V/C 0 19.0 0 0 0 0.0 0 19.0
22B NB 137 112.8 168 0 40,780 28.9 305 141.8
24A SAH 233 31.5 0 0 0 0.0 233 31.5
24B SAH 1 20.6 32 0 0 4.9 33 25.5
25 V/C 0 0.0 130 0 0 19.9 130 19.9
16,761 4,721 gpm 5,051 2,129 14,026,871 2,130 gpm 21,812 6,851 gpm
6.80 MGD 3.07 MGD 9.87 MGD
(1) Flows from this sub-basin currently discharge to Leucadia County Water District
(2) Flow projections are based on the following unit flows: 220 gpd per single family unit, 160 gpd per multi-family unit,
and 1,150 gpd/10,000 sqft of building area for non-residential flows.
Totals:
Sub-
basin
Interceptor
System
Existing Units/Flow Projected Future Units and Flow Ultimate System
6.5 OTHER AGENCY FLOW PROJECTIONS
Ultimate flow projections from other agencies that discharge to the Carlsbad sewer system were obtained
from recent planning documents. Table 6-4 lists the total projected ultimate flow to the Encina WPCF
from its member agencies, and allocates the flow to the Carlsbad interceptor systems. Flows from other
agencies are allocated to the same interceptor system to which existing flows are currently discharged.
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Table 6-4
EXISTING AND PROJECTED ULTIMATE ADWF TO THE ENCINA WPCF
Carlsbad Total Carlsbad Total
Flows Agency Flow Flow Flows Agency Flow Flow
City of Vista & City of Vista &
Oceanside Oceanside
North Agua
Hedionda 1.30 MGD --- --- 1.30 MGD 1.07 MGD --- --- 1.07 MGD
South Agua
Hedionda --- --- --- --- 1.87 MGD --- --- 1.87 MGD
Buena 1.84 MGD Buena 3.31 MGD
Vista (raceway)0.20 MGD Vista (raceway)0.60 MGD
Vallecitos 0.90 MGD Vallecitos 4.28 MGD 5.18 MGD 1.54 MGD Vallecitos 11.04 MGD 12.58 MGD
1.33 MGD 5.14 MGD 6.47 MGD 1.67 MGD 8.01 MGD 9.68 MGD
Totals: 6.81 MGD 17.3 MGD 24.1 MGD 9.87 MGD 32.7 MGD 42.5 MGD
(1) Other agency ultimate flow projections obtained from their most recent master planing documents
Interceptor
System
Existing Flows (Aug 2001) Projected Ultimate Flows
Other Agency Flows Other Agency Flows
(1)
9.72 MGD 12.55 MGD
Buena 0.73 MGD 2.77 MGD 0.88 MGD 4.79 MGD
2.55 MGD 5.84 MGD 8.39 MGD
North
Batiquitos
Leucadia/
Encinitas
Leucadia/
Encinitas
Vista/
Carlsbad 2.83 MGD
From Table 6-4 it is apparent that flows from Carlsbad will increase within all existing interceptors except
the NAH Interceptor. The majority of the flow increase to the V/C Interceptor is projected to be
generated by the City of Vista. The downstream reaches of this intercepetor convey Carlsbad flows from
the NAH and SAH Intercepetors, which are not included in the flow to the V/C Interceptor in Table 6-4.
In the ultimate system, it is projected that reaches VC14 and VA15 will convey an additional 3.9 MGD of
flow from the City of Vista and an additional 1.9 MGD from the City of Carlsbad.
The ultimate flows apportioned to the Buena and Vallecitos Interceptors will exceed the capacity of the
existing pipelines during peak flow conditions. The City of Vista is planning to divert a portion of their
flow from the Buena Interceptor to the Vallecitos Interceptor in the future, and the VWD is planning a
replacement of the Vallecitos Interceptor with increased capacity. Since the City of Carlsbad leases flow
capacity in the Buena Interceptor and has a minority capacity ownership in the Vallecitos Interceptor, an
ultimate hydraulic analysis accounting for upstream agency flows will not be performed on these
Interceptors. Projected peak flows from Carlsbad are instead summarized and compared to existing
capacity agreements.
6.6 ULTIMATE INTERCEPTOR SYSTEM HYDRAULIC MODEL
Analysis of the ultimate interceptor system was accomplished by adding the SAH Interceptor to the
existing system model. Physical data for the SAH Interceptor was obtained from the existing system GIS
for portions that have already been constructed, and available design drawings. The SAH Lift Station was
evaluated assuming variable frequency drive pumping units. Interceptor discharge locations for sub-
basins were re-assigned, as appropriate, to reflect planned changes to the ultimate system. The projected
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SEWER MASTER PLAN UPDATE March 2003
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ADWF based on build-out of the sub-basins (Table 6-3) was then input to the model for internal flows.
External flows from other agencies were evaluated for the V/C and NB Interceptors (Table 6-4).
Hydraulic analyses were performed to determine the ability of the interceptors to convey projected peak
flows. To calculate the PDWF, the dry weather peaking curves developed for the City of Vista and
Leucadia/Encinitas based on existing flows (Figure 5-1) were “scaled up” to reflect the higher base loads
in the ultimate system. The unit peaking curves for residential and non-residential flows within Carlsbad
(Figure 5-2) were applied to the projected ultimate average flows in each sub-basin.
PWWF analyses were performed on the V/C and NB Interceptor systems. The internal and external
defect flows, based on existing wet weather meter data, were increased by 20 percent in the ultimate
system to account for aging of the pipelines and increased inflow from a larger collection system.
Internal defect flows for the NAH, SAH, and Vallecitos Interceptors, and the NB Interceptor upstream of
the NB Lift Station could not be determined from existing meter data. The NAH, SAH, and upstream NB
Interceptor systems were analyzed with peak dry weather flows, and evaluated based on gravity sewers
flowing 75 percent full.
City of Carlsbad flows were analyzed in the Buena and Vallecitos Interceptors and the peak flows
compared to existing capacity rights. For the Buena Interceptor, the internal I&I calculated for the
existing system was increased by 20 percent. This same defect flow was assumed for the Vallecitos
Interceptor in the ultimate analysis, which is considered a valid assumption as this pipeline ages since
both interceptors share a common alignment over most of the their length.
6.7 CAPACITY ANALYSIS RESULTS
Flow analysis results from the SewerCAD ultimate system model are presented graphically for each
interceptor system and compared to the gravity pipeline capacities. The graphs illustrate the composite
peak flow in each pipeline segment over the course of the 24-hour flow simulation. Flows and capacities
are schematically illustrated according to the reach designations shown in Figure 3-1. Where lift stations
are included in the interceptor, the lift station name and firm pumping capacity are indicated on the graph.
6.7.1 Vista/Carlsbad Interceptor
Figure 6-3 illustrates the projected ultimate PDWF in the V/C Interceptor, and provides a comparison
with the pipeline design capacity (d/D = 75%). At the upstream end of Reach VC1, the City of Vista and
Oceanside contribute a collective projected peak flow of approximately 15.2 MGD. Between the Buena
Vista and Agua Hedionda Lift stations, the V/C Interceptor collects flow from the Home Plant Lift
Station and the NAH Interceptor. Flow from the SAH Interceptor is added downstream of the Agua
Hedionda Lift Station at Reach VC14. From this graph it is apparent the reaches downstream of VC10
will need to be upsized based on future peak dry weather flows.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-11
Figure 6-3
V/C INTERCEPTOR WITH PROJECTED PEAK DRY WEATHER FLOWS
0
5
10
15
20
25
30
35
40
45
50
55
60
VC15VC15VC15VC14VC14VC14VC13VC13VC13AH LSVC11VC10VC10VC10VC8VC6VC5BVC5ABV LSVC3VC3VC3VC2VC2VC2VC1VC1VC1VC1VC1Gravity Pipeline Capacity/ Peak Flow (MGD)75% Full Capacity Projected Peak Dry Weather Flow
Buena
Vista
L. S.
Agua
Hedionda
Lift Station
While the flow information presented on Figure 6-3 is informative, historical I&I rates to the V/C
Interceptor are very high, and replacement sewers must be designed based on the projected PWWF.
Figure 6-4 illustrates results from the PWWF analysis, and makes a comparison with existing pipeline
capacities. For this analysis, a peak I&I rate of 6.1 MGD was added to City of Vista projected peak dry
weather flows. The I&I attributed to Carlsbad, 5.6 MGD, was distributed two different ways. One flow
scenario distributes the I&I along the length of the V/C Interceptor. The other, more conservative
scenario, assigns most of I&I to the upstream Reach V1, with the remainder at the confluence with the
NAH Interceptor. As stated previously, it is not known how much I&I is currently contributed by the
NAH Interceptor. Although the internal I&I rate in the ultimate system model was increased by 20
percent over the existing I&I rate, it is noted that I&I was not included for the SAH Interceptor. Flows
entering the V/C Interceptor at the upstream end of Reach VC14 are therefore based on the projected peak
dry weather flow from the SAH Interceptor.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-12
Figure 6-4
V/C INTERCEPTOR PEAK WET WEATHER FLOW
0
5
10
15
20
25
30
35
40
45
50
55
60
VC15VC15VC15VC14VC14VC14VC13VC13VC13AH LSVC11VC10VC10VC10VC8VC6VC5BVC5ABV LSVC3VC3VC3VC2VC2VC2VC1VC1VC1VC1VC1Full Pipeline CapacityProjected PWWF - Internal I/I applied at VC1 & VC10Projected PWWF - Internal I/I distributed
Buena
Vista
Lift Station
Agua Hedionda
Lift Station
From Figure 6-4, it is apparent that the reaches downstream of VC10, Reach VC3, and the Buena Vista
and Agua Hedionda Lift Stations are not adequately sized to convey the projected PWWF. In addition,
analysis results indicate that Reach VC10, which is currently under construction as a 48-inch diameter
pipeline, may flow full during severe storm events.
6.1.1 North Agua Hedionda Interceptor
The projected ultimate ADWF for the NAH Interceptor is approximately 1.07 mgd, which is less that the
existing ADWF of 1.3 MGD. The capacity of the NAH Interceptor was determined to be sufficient to
convey existing flows, with the exception of several short reaches. Therefore, additional analysis of this
interceptor system was not performed with ultimate system flows. A discussion of the capacity of the
NAH Interceptor is provided in Section 5.3.3 of this report.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-13
6.1.2 South Agua Hedionda interceptor
The projected ultimate PDWF and design capacity of the SAH Interceptor are illustrated on Figure 6.5.
The upstream sewer along El Camino Real and Sunny Creek Road (SAHT1E and SAHT1G) is also
depicted in Figure 6-5, since this portion of the SAH Interceptor system will convey the most flow. As
shown on the graph, there is projected to be ample capacity in the gravity interceptor system. The PDWF
through the SAH Lift Station is projected to be approximately 3.0 MGD. The lift station capacity will
need to be greater to convey peak wet weather flows.
Figure 6-5
SOUTH AGUA HEDIONDA PEAK DRY WEATHER FLOW
0
1
2
3
4
5
6
7
8
9
10
11
12
SAH4SAH4SAH4SAH4SAH4SAH LSSAH LSSAH1SAH1SAH1SAHT1GSAHT1GSAHT1GSAHT1GSAHT1ESAHT1ESAHT1ESAHT1ESAHT1EGravity Pipeline Capacity/Peak Flow (MGD) Full Pipeline Capacity Projected Peak Dry Weather Flow
75% Full Capcity
SAH
Lift
Station
6.1.3 Buena Interceptor
The sub-drainage basins served by the Buena Interceptor in the ultimate system are planned to be the
same as those served in the existing system. Flows to this interceptor are projected to increase by
approximately 20 percent. As discussed in Section 5.2.2 of this report, the existing flow in Table 6-4 for
the Buena Interceptor is lower than current metered flows. Flows used in the ultimate system analysis for
the Buena Interceptor are based on future flows added to the existing meter flows, and result in a total
ADWF of approximately 1.2 MGD. Figure 6-6 illustrates the projected ultimate PWWF generated by
Carlsbad in the Buena Interceptor, and makes a comparison with existing capacity rights. As shown on
the chart, the current leased capacity is projected to be sufficient to convey ultimate flows.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-14
Figure 6-6
PROJECTED CARLSBAD PWWF IN THE BUENA INTERCEPTOR
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
B1 B1 B2 B2 B2 B2 B2 B4 B4 B4 B4 B4 B4 B5 B6 B6 B7 B7 B8 B8 B8Gravity Pipeline Leased Capacity/Peak Flow (MGD)Series2
Projected U ltim ate PW W F
Carlsbad Leased Capacity
Carlsbad Capacity (smoothed)
6.1.4 Vallecitos Interceptor
Figure 6-7 illustrates the projected ultimate PWWF generated by Carlsbad in the Vallecitos Interceptor,
and makes a comparison with the existing capacity rights of 5.0 MGD. Although flows to this interceptor
are projected to increase by approximately 70 percent, the current leased capacity is projected to be
sufficient to convey ultimate flows, as shown on the graph.
Figure 6-7
PROJECTED CARLSBAD PWWF IN THE VALLECITOS INTERCEPTOR
5 M GD Leased
Capacity
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
V3 V3 V3 V4 V4 V4 V4 V4 V5 V5 V6 V6 V6 V6 V7 V7 V8 V8Gravity Pipeline Leased Capacity/Peak Flow (MGD)Carlsbad Leased Capacity
Projected Ultimate PWWF
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-15
6.1.5 North Batiquitos Interceptor
The upstream portion of the North Batiquitos Interceptor conveys only City of Carlsbad flows. This
portion of the Interceptor was analyzed with the projected PDWF and compared to the design capacity of
the gravity pipelines, as illustrated in Figure 6-8. As indicated on the graph, there is ample capacity in the
upstream gravity pipelines to convey the projected ultimate flows. Flow to the North Batiquitos Lift
Station consists of flow from the main interceptor and the northern trunk line, Reach NBT3B. The
PDWF to the lift station is projected to be 2.1 MGD (1,500 gpm).
Figure 6-8
CARLSBAD PDWF IN THE UPSTREAM NORTH BATIQUITOS INTERCEPTOR
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
NB1 NB1 NB1 NB2 NB2 NB2 NB3 NB3 NB4 NB4 NB4 NB4 NB4 NB4
75% Full Capacity Peak Dry Weather Flow
The North Batiquitos Lift Station consists of two duty pumps with fixed speed drives. During peak flow
periods one pumping unit is projected to operate continuously, with the second pump cycling on and off.
The North Batiquitos Interceptor downstream of the lift station was analyzed with both pumps in
operation. City of Carlsbad flows in this portion of the Interceptor are shown on Figure 6-9, together with
the full gravity pipeline capacities and leased capacity in the Occidental Sewer. Based on this analysis,
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-16
the existing leased capacity is projected to be approximately 4.0 MGD in excess of what is required to
convey projected peak ultimate flows.
Figure 6-9
CARLSBAD PWWF IN THE DOWNSTREAM NORTH BATIQUITOS INTERCEPTOR
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
NB6 NB6 NB7 NB7 NB7 NB7 NB8 NB8 NB8 NB9 NB9
Full Pipeline Capacity Carlsbad Peak Wet Weather Flow Carlsbad Leased Capacity
6.7.7 Lift Stations
The projected ultimate PWWF through each of the lift stations included in the sewer interceptor system is
shown in Table 6-5. Also provided in this table is a comparison with existing lift station capacities and
the velocity in the lift station force mains based on the projected peak flow. For interceptor systems
without existing wet weather data (gravity pipelines analyzed based on the PDWF), the PWWF at the lift
station is estimated based on the general wet weather peaking factors used in the previous Master Plan.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-17
Table 6-5
PROJECTED PEAK FLOWS AT LIFT STATIONS
Interceptor
System
16"&24" 9.5
24" 12.8
2-16" 14.4
Agua Hedionda V/C 16,000 23.04 21.2 2-18" 14.4
Foxes NAH 2,600 3.74 1.9 2.6
(3)12" 5.1
South Agua Hedionda SAH --- --- 3.0 4.2
(3)14" 6.1
North Batiquitos NB 2,250 3.24 2.1 2.9
(3)14" 4.7
(1) Existing duty capacity with one pump out-of-service
(2) Projected PWWF flow varies depending on the distribution assumptions of I&I in the Carlsbad system.
(3) ExistIng wet weather data not available. PWWF assumed at 1.4 x the PDWF
31-33 (2)
Lift Station Name
26.0V/C 14,000 20.16 16.2 Buena Vista
Station Capacity (1)
(gpm) (MGD)
Max. Ult.
Velocity in
FM (fps)
Projected Ultimate Flow
PDWF (MGD)PWWF
(MGD)
Force
Main
Diam.
For the remaining lift stations in the sewer collection system, only the service area of the Simsbury lift
Station is expected to increase significantly. Although the Simsbury Lift Station is ultimately planned to
be abandoned once a gravity line is constructed to the V/C interceptor through LFMZ 25, it may first
serve future development in the west portion of Sub-basin 7A. Based on the City’s Growth Database, an
additional 103 EDUs are planned, with a corresponding projected flow increase of approximately 16 gpm.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 1 March 2003
CHAPTER 7
RECOMMENDATIONS
Wastewater flow generated within the City of Carlsbad is projected to increase by approximately 45 percent
over existing flows, to a projected ultimate flow of approximately 9.9 MGD by the year 2020 (shown
previously on Figure 6-2). This chapter summarizes recommended improvements to the existing sewer
interceptor system required to adequately convey, pump, treat and dispose of the projected ultimate
wastewater volumes. Joint agency agreements, capacity agreements with the Encina WPCF, potential future
flows from other agencies, and inflow and infiltration are also discussed relative to buildout conditions. A
recommended Capital Improvement Program is provided at the end of the chapter with an opinion of probable
construction costs for each recommended project.
7.1 VISTA/CARLSBAD INTERCEPTOR IMPROVEMENTS
The V/C Interceptor Sewer collects wastewater from the City of Vista and the northern and downtown areas
of the City of Carlsbad. The V/C Interceptor also collects flow from the NAH Interceptor, and will collect
future flows from the SAH Interceptor. Approximately 2.5 miles of gravity pipeline in the V/C Interceptor
are currently being replaced to increase capacity between the Buena Vista Lift Station force main and the
Agua Hedionda Lagoon crossing (Reaches VC5-VC11A), For the purposes of this Master Plan Update, this
current replacement project is considered a part of the existing V/C Interceptor.
Additional replacement projects are recommended to increase the capacity of the interceptor based on
projected peak flows. The projected PWWF in the V/C Interceptor is shown on Figure 7-1, together with the
capacity of the existing pipeline reaches and the recommended pipeline capacities. The design capacity of the
new pipelines is calculated based on the average slope of the existing reach and a Manning’s coefficient (“η”)
of 0.012, assuming that the future pipe will be PVC-lined. The recommended projects are summarized in
Table 7-1, together with an opinion of the probable construction cost, and discussed in the following sections.
It is noted that the ultimate PWWF in the V/C Interceptor projected in this Master Plan Update is slightly
higher than the peak flows projected in the 1992 Master Plan Update. While the projected ultimate ADWF to
the V/C Interceptor from the City of Carlsbad is approximately 40 percent less than the flow projected in
1997, peak flows in the V/C Interceptor are higher as a result of the I&I investigation performed in this
Master Plan Update. Peak flows from the ultimate PWWF analysis in the downstream reach of the V/C
Interceptor (City of Vista and Carlsbad flows) are projected to be approximately 2.4 times the ADWF. The
analysis performed in the 1992 Master Plan used a standard peaking equation, which resulted in a peak flow
that was 2.0 times the ADWF in the downstream reaches of the V/C Interceptor.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 2 March 2003
Figure 7-1
V/C INTERCEPTOR CAPACITY WITH RECOMMENDED IMPROVEMENTS
15
20
25
30
35
40
45
50
55
VC15VC15VC15VC14VC14VC14VC13VC13VC13AH LSVC11VC10VC10VC10VC8VC6VC5BVC5ABV LSVC3VC3VC3VC2VC2VC2VC1VC1VC1VC1VC1Gravity Pipeline Capacity/Peak flow (MGD)Design Capacity (75% full) of Recommended Pipeline Replacements
75% Full Pipeline Capacity - existing
Projected PWWF - internal I/I applied at VC1 & VC11
Projected PW W F - internal I/I distributed
Buena
Vista
Lift
Station
Agua
Hedionda
Lift Station
36"
54"
54
54"
Table 7-1
SUMMARY OF V/C INTERCEPTOR RECOMMEND IMPROVEMENTS
Projected Probable
Ult.Full Unit Construction
PWWF Capacity Cost
(2)Cost(3)
(MGD) (feet) (ft/ft) (in.) (MGD) (in.)(MGD) (MGD)($/lin. ft.)
VC3 26.0 3,350 0.0020 36 20.7 42 28.5 31.6 568.20$ 2,570,000$
BVLS(5)26.0 -- -- -- -- -- -- -- -- 735,132$
VC4-FM 26.0 3,840 NA 16"&24" -- 24 26.0 -- 240.00$ 1,244,000$
VC11B(4)33.0 915 0.0008 42 18.4 54 35.6 39.0 730.50$ 2,900,000$
AHLS(5)33.0 -- -- -- -- -- -- -- --
VC12-FM 33.0 200 NA 2-18" -- 36 33.0 -- 360.00$
VC13 33.0 3,510 0.0010 42 20.5 54 39.8 43.7 730.50$
VC14 36.6 5,059 0.0009 42 19.6 54 37.8 41.4 730.50$
VC15 36.6 1,772 0.0009 42 19.6 54 37.8 41.4 730.50$
(1) Required diameter with the existing slope to convey the design capacity with the pipeline flowing 75% full
(2) Unit construction costs for gravity pipelines based on recent cost data from the 2001-2002 V/C Sewer Replacement
Project. Force main unit costs are based on $10/diameter inch.
(3) Opinion of probable construction costs are order of magnitude planning costs. Costs exclude engineering, administrative,
environmental and legal costs and include a 35% construction contingency.
(4) Replacement of this reach will include a new bridge crossing over the Agua Hedionda Logon. The cost includes an
estimated cost for the bridge of $1,744,000 (developed by W. Koo & Assoc. in the April 2001 Design Report)
(5) Lift station costs include both capacity increase and rehabilitation costs, as defined in the City's current CIP. AH Lift
Station upgrade based on Krieger & Stewart 2000 Preliminary Design Report, which includes replacement of the FM.
Existing Pipe Replacement Pipe
Reach
ID Length Avg.
Slope Diam.Diam(1)Design
Capacity
Full
Capacity
6,250,000$
10,200,000$
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 3 March 2003
7.1.1 Upper V/C Interceptor Recommended Improvements
Figure 7-2 illustrates the recommended capacity improvements to the upper V/C Interceptor. Recommended
pipeline diameters are shown for the replacement pipelines. In addition to the gravity pipeline replacement
recommended for Reach VC3, capacity improvements are recommended for the Buena Vista Lift Station and
force main. Pumping units were last replaced at the Buena Vista Lift Station in 1994. The reported firm
capacity of the lift station is 14,000 gpm, and the projected ultimate PWWF at the station is approximately
18,000 gpm. The capacity of the Buena Vista Lift Station has never been confirmed due to existing
downstream capacity limitations. Because of the long length of the force main (approximately 4,000 feet) and
high pipeline velocities with projected ultimate flows, it may be possible to obtain the required increase in
station capacity with the existing pumps and a larger forcemain.
The existing Buena Vista Lift Station force main (Reach VC4) consists of parallel pipelines (24- and 16-inch
diameter) for most of its length. It is recommended that a new 24-inch diameter force main replace the 16-
inch force main and parallel the existing 24-inch force main for its entire length. In addition to increasing the
station capacity, the new parallel force main will reduce peak velocities and increase reliability.
7.1.2 Lower V/C Interceptor Recommended Improvements
Figure 7-3 illustrates the recommended capacity improvements to the lower V/C Interceptor. It is
recommended that Reach VC11B and Reaches VC13 through VC15 be replaced with a 54-inch diameter
pipeline. This pipe size assumes that the existing flat sections in Reach VC15 can be eliminated in the new
design, and the pipeline slope for Reaches VC14 and VC15 will be a minimum of 0.09 percent. If the
pipeline will have a slope of less than 0.09 percent, a 60-inch diameter pipeline will be required for Reaches
VC14 and VC15 to satisfy City design criteria.
It is recommended that the capacity of the Agua Hedionda Lift Station be increased to a minimum of 33 MGD
(23,000 gpm), which is the projected PWWF through the station. A new 36-inch diameter force main is also
recommended to replace the existing parallel 18-inch diameter force mains (Reach VC12). There are several
deficiencies with the existing Agua Hedionda Lift station, including an undersized wet well, lack of full
operational redundancy, insufficient space around the pumping units, and problems related to the age and
general condition of the station. A Preliminary Design Report for Agua Hedionda Lift Station Upgrade, dated
March 7, 2000 was prepared for the City. Recommendations from the report include replacement of the
existing lift station with the exception of the emergency generator building. The recommended project
includes five new pumping units for a firm pumping capacity of 30 MGD, and a new headworks, wet well,
control building, 2.5 MG emergency storage basin, and 36-inch diameter force main. As the result of this
Master Plan Update analysis, the design flow through this station should be increased from 30 MGD to at
least 33 MGD.
VC 4 - 24"VC3 - 36"
VC2 - 42"VC1 - 36"VC5A - 36"VC5B - 42"VC6 -
4
2"
V C 7 - 4 2 "V C 8 - 4 2 "V
C9
-
4
2
"
VC3
NEW DIAMETER: 42"
CITY OF OCEANSIDE
C A R L S B A D
V IL L A G E D R IV E
MARRON
ROAD
EL CAMI
NO REALVC4 (FORCEMAIN)
PARALLEL DIAMETER = 24"
UPGRADED BUENA VISTA
LIFT STATION
CAPACITY = 18,000 GPM
03-2003 Carlsbad702.mxd
LEGEND
SEWER SERVICE AREA BOUNDARY
INTERCEPTOR SEWER
RECOMMENDED PROJECT
RECOMMENDED FORCEMAIN PROJECT
GRAVITY SEWER
1"=2000'
VC1 - 24"REACH DESIGNATION &
EXISTING DIAMETER
FIGURE 7-2
UPPER V/C INTERCEPTOR
RECOMMENDED IMPROVEMENTS
5
B4 - 18"
V4 - 30"
V 6 - 30"
B 6 - 2 1 "
NAH3 - 24"
NAH5 - 24"
NA H 2 - 24"
B 7 - 2 4 "NAHT1B - 12"NAH1 - 21"B5 - 21"
B8 - 3 0 "
N AH7 - 18"
NAH6 - 16"
NAH4 - 16"NB9 - 39V 8 - 5 4 "V 7 - 3 6 "V5 - 30"VC1
1
A
- 4
8"VC14 -
42"VC1
0 - 4
8"VC13
-
42"VC15 -
42"VC11B -
42
"
VC12 - 18"
VC12 (FORCEMAIN)
NEW DIAMETER = 36"
VC11B
NEW DIAMETER: 54"
VC13
NEW DIAMETER: 54"
VC14
NEW DIAMETER: 54"
VC15
NEW DIAMETER: 54"CARLSBADREAL
EL CAMINOTAMARACK A V E N U E
BOULEVARDPALOMAR AIRPORT ROAD BOULEVAR DCOLLEGE
C A N N O N
ROAD
UPGRADED/RELOCATED
AGUA HEDIONDA
LIFT STATION
ENCINA
WPCF
03-2003 Carlsbad703.mxd
LEGEND
SEWER SERVICE AREA BOUNDARY
INTERCEPTOR SEWER
RECOMMENDED PROJECT
RECOMMENDED FORCEMAIN PROJECT
GRAVITY SEWER
FORCEMAIN
1"=2000'
FIGURE 7-3
LOWER V/C INTERCEPTOR
RECOMMENDED IMPROVEMENTS
V8 - 42"
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 4 March 2003
7.2 SOUTH AGUA HEDIONDA INTERCEPTOR IMPROVEMENTS
Most of the South Agua Hedionda Interceptor has been constructed. The remaining portions of the SAH
Interceptor yet to be installed are the SAH Lift Station and forcemain. The force main will have an
approximate length of 5,380 feet and be constructed in the future alignment of Cannon Road. A gravity sewer
will be constructed with the forcemain that will connect with a gravity line in Faraday Road and convey flows
from the Faraday Business Park and to the SAH Lift Station. After completion of these projects, the two
Faraday Lift Stations and the Kelly Lift Station will be removed. The recommended sizes for the remaining
the SAH Interceptor projects are illustrated on Figure 7-4.
7.3 LIFT STATION IMPROVEMENTS
A capacity analysis of the lift stations included in the major interceptor systems was performed and
documented in Section 6.7.7 of this report. Capacity improvements based on projected ultimate peak flows
are recommended for the Buena and Agua Hedionda Lift Stations.
A detailed survey of the lift stations with respect to the condition, code compliance, standby power and
capacity was performed as part of the 1997 Master Plan Update. A summary of the pertinent recommended
improvements is provided in Table 7-2. For each station, the installation of gas detectors to monitor for
hydrogen sulfide and other combustible gases was recommended. This is a requirement of existing codes
included in Title 8 of the California Code of Regulations and the National Fire Protection Association Article
820. Continuously operating ventilation fans and airflow switches were also recommended for code
compliance. It was recommended that an alarm be added for ventilation fan failure. Each of the station wet
wells was found to have a mercury float that needs to be modified/changed to meet the requirement of a Class
1, Division 1 section of the National Electrical Code.
Table 7-2
LIFT STATION RECOMMENDED IMPROVEMENTS
Terramar 1972 X X X X X
Chinquapin 1959/2001 X X X
Home Plant 1963/1991 X X X X
Gateshead 1985 X X X X
Vancouver 1981 X X X X X
Simsbury 1985 X X X X
Villas 1983 X X X
Woodstock 1983 X X X X
North Batiquitos 1997 X X
La Golondrina 1981 X X X X X X
Lift Station Name
Construction/
Rehabilitation
Date
RECOMMENDED IMPROVEMENT
Gas
Detectors
Float Switch
Modifications
Ventilation
Modifications Alarms
Standby
Generator
Connector
Wiring
Repairs
NAH3 - 24"
NAH5 - 24"
N AH2 - 2 4"NAHT1B - 12"NAH1 - 21"N AH7 - 1 8"
NAH6 - 16"
NAH4 - 16"VC1
1
A
- 4
8
"VC13 -
42"VC11B -
4
2"
VC12 - 18"SAHT2B - 10"SAH4A - 15"
SAHT1E - 18"
S
A
H
T3
B - 1
2"
S A H T 2 C - 12 "SAHT1G - 24"
S A H T 3 A - 1 2 "SA H 1 - 2 1 "
SA H 4 B - 2 4 "
SAHT1E - 24"SAH T2C - 15"SAH3 (FORCEMAIN)
DIAMETER = 14"SAHT3C
DIAMETER = 12"
REAL
EL CAMINO
T A M A R A C K A V E N U E
BOULEVARDB OU LEV AR DC OLLE G E
CA N N O N
ROAD
C H E S T N U T A V E
TAMARACK AVENUESAH LIFT STATION
CAPACITY = 2900 GPM
03-2003 Carlsbad704.mxd
LEGEND
SEWER SERVICE AREA BOUNDARY
INTERCEPTOR SEWER
RECOMMENDED PROJECT
RECOMMENDED FORCEMAIN PROJECT
GRAVITY SEWER
FORCEMAIN
SIPHON
1"=2000'
FIGURE 7-4
SOUTH AGUA HEDIONDA INTERCEPTOR
RECOMMENDED IMPROVEMENTS
SAH1 - 21"REACH DESIGNATION &
EXISTING DIAMETER
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 5 March 2003
7.4 POTENTIAL FLOWS FROM OTHER AGENCIES
Currently, interceptors owned or jointly owned by Carlsbad convey flows from the City of Vista, the City of
Oceanside (through the City of Vista connection), the LCWD, and the Encinitas Sanitary Division of the City
of Encinitas (through the LCWD connection). Future opportunities to convey additional flows were
evaluated in this Master Plan Update. The City of Oceanside had previously expressed a desire to convey
flows from their Leisure and Lake Lift Stations into an eastward extension of the SAH Interceptor. The trunk
sewer extension, previously identified as SAHT2A in the 1992 Master Plan, was located in an area that is now
designated as open space. City staff have stated that it is highly unlikely that this trunk sewer would ever be
constructed, and these additional flows from Oceanside were not included in the ultimate flow projections.
Also, the City of Vista no longer desires to convey flows by gravity from the Raceway Lift Station service
area to a separate eastward extension of the SAH Interceptor. As a result of this and additional environmental
constraints, the previously planned trunk sewer, identified as Reaches SAHT1A-1D in the 1992 Master Plan,
will no longer be constructed. Wastewater flows from Sub-basins 18A and 16 will now be pumped and
discharge to a downstream location on the SAH Interceptor.
In the far southeast corner of the City of Carlsbad service area, one possible future annexation may occur that
would affect wastewater flows. Wastewater from Carlsbad Tract 93-04 (28 units) currently flows to the
LCWD Meadows III Pump Station. Wastewater from these units will flow by gravity into the Vallecitos
Interceptor once a gravity pipeline is constructed. When the gravity system is in place, the LCWD may want
to de-annex 68 units within its boundary, which would allow the Meadows III Pump Station to be abandoned.
There is projected to be ample capacity in the Vallecitos Interceptor for these additional flows.
7.5 JOINT TRANSMISSION SYSTEMS
The District shares ownership or leases capacity in several facilities with the City of Vista, the Buena
Sanitation District, the Vallecitos Water District, the Leucadia County Water District and Encinitas Sanitary
Division of the City of Encinitas. These facilities include the V/C Interceptor, the Buena Interceptor, the
Vallecitos Interceptor and the Occidental Sewer. The following discussions provide an overview of these
facilities relative to projected ultimate wastewater flow conditions.
Vista/Carlsbad Interceptor. The Vista/Carlsbad Interceptor ownership percentages and capacity rights from
the 2001 draft agreement with the City of Vista are provided in Table 3-1 of this report. Based on the
agreement, Carlsbad has a 43.9% ownership in the downstream reach of the V/C Interceptor (VC15).
Projected flows for Carlsbad are now lower, and the percentage of flow for Carlsbad in this reach is now
estimated at 37.2%. It is recommended that a new agreement be negotiated based on the updated flow
projections in this Master Plan Update.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 6 March 2003
Buena Interceptor. The City of Carlsbad leases capacity in the Buena Interceptor. The existing lease
agreement was last modified in 1987 to lease an additional 0.8 MGD of capacity. It is estimated that Carlsbad
will not require any additional capacity in this interceptor to convey projected ultimate flows. It is noted that
the existing Buena Interceptor does not have the capacity to convey buildout flows based on ultimate flow
projections for the BSD and the City of Vista Raceway Basin. The City of Vista includes a project in their
2001 Master Plan to construct a new force main from the Buena and Raceway Lift Stations to the Vallecitos
Interceptor.
Vallecitos Interceptor. The City of Carlsbad currently leases 5.0 MGD of capacity in the Vallecitos
Interceptor. City of Carlsbad ultimate peak flows in this interceptor are projected to be less than 3.5 MGD.
The existing interceptor does not have the capacity to convey buildout flows for the VWD and future flows
from the BSD and the City of Vista Raceway Basin. The VWD plans to replace the existing Vallecitos
Interceptor with a larger capacity interceptor. Based on projected ultimate flows, Carlsbad could reduce their
leased capacity to approximately 4.0 MGD.
Occidental Sewer. The Occidental Sewer is jointly owned by the City of Carlsbad, the ESD and the LCWD.
Carlsbad’s current ownership capacity, which is estimated to be approximately 8.5 MGD, is projected to be
approximately 4.0 MGD in excess of what is required to convey the ultimate PWWF. The LCWD projects
that they will need to acquire an additional 1.6 MGD of conveyance capacity in the Occidental Sewer in their
most recent Master Plan. It is recommended that the ownership capacities defined in the 1972 Occidental
Pipeline Agreement be updated based on current flow projections.
7.6 TREATMENT CAPACITY REQUIREMENTS
Wastewater generated within the City of Carlsbad service area is collected and conveyed to the Encina Water
Pollution Control Facility (WPCF) for treatment and subsequent disposal. Carlsbad currently owns a total
treatment capacity of 9.24 MGD in the Encina WPCF, and has requested additional capacity to total 10.26
MGD in the planned Encina WPCF Phase V expansion. Existing ADWF generation is approximately 6.8
mgd. Based on projected wastewater production increases, the City of Carlsbad is projected to generate an
average dry weather volume of approximately 9.87 MGD at buildout, which is anticipated to occur by the
year 2020.
The requested treatment capacity is approximately 0.4 MGD, or 4 percent greater than the projected ultimate
flows. However, should the “per capita” water usage of customers decrease or increase in the future, the
projected treatment capacity surplus would likewise be reduced or increase. As a policy matter, the Board of
Directors needs to establish the standard for redundancy that it believes prudent for treatment capacity at the
EWA. The established redundancy standard will influence the final decision regarding the City’s
participation in future expansion projects at the EWA facility.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 7 March 2003
7.7 OCEAN OUTFALL CAPACITY
Wastewater tributary to the Encina WPCF is treated to secondary standards and discharged to the Pacific
Ocean through the Encina Ocean Outfall. Capacity rights in the outfall are based on the PWWF. This outfall
facility has an estimated capacity of 104.9 MGD. The District owns 24.32 percent of the available capacity,
or 25.51 MGD. Because flows to the Encina WPCF from the City of Carlsbad are determined by subtracting
upstream agency flows, the peak flow contribution from Carlsbad cannot be easily determined from meter
records. In the ultimate system hydraulic model, approximately 6.9 MGD of peak I/I generated within
Carlsbad was included in the model. This flow rate is based on historical flow data from storm events and an
assumed I/I increase of twenty percent to account for aging of the pipelines and expansion of the collection
system. By removing all flow from upstream agencies in the model, the ultimate PWWF to the Encina WPCF
from the City of Carlsbad is estimated to be approximately 25.0 MGD. The projected PWWF is
approximately 2.5 times the ADWF and is just under the City of Carlsbad’s existing outfall capacity rights.
Therefore no change is recommended to Carlsbad’s proportion of the outfall capacity.
7.8 INFLOW AND INFILTRATION STUDY
Flow increases in the V/C Interceptor during storm events are very high due to I&I from both Vista and
Carlsbad, which can be observed from existing flow records (see Appendix C). Instantaneous storm water
flows originating in the Carlsbad portion of the V/C Interceptor can be estimated from subtracting Vista Meter
flows from flows at the Encina WPCF. However, there is no further data to determine the primary locations
of the storm water ingress. Pipelines along the Buena Vista Lagoon, the low-lying downtown area, and
pipelines in the NAH Interceptor along the Agua Hedionda lagoon are considered likely sources. A detailed
I&I study is recommended to locate the I&I sources, estimate the volume increase due to prolonged storm
water induced infiltration, and recommend improvements to reduce the flows. In the absence of such detailed
information, the I/I rate used in the ultimate system hydraulic analysis was calculated based on the following
procedure:
• I/I rates were determined from recorded EWA meter data from the storm event on November 24, 2001, in
which 1.3 inches of rain fell in 4 hours.
• The measured I/I was added to the PDWF, so that peak storm flows coincide with the peak daily flow
throughout the interceptor system.
• An additional infiltration rate of 3.0 MGD was added to the upstream reach of the V/C Interceptor. This
flow rate is based on an analysis of Vista meter records, and accounts for the increase in infiltration that
would occur in the Vista system if several severe storms had preceded the November 2001 storm.
• Existing I/I flows as determined from the Encina meters were increased by 20 percent in the ultimate
system analysis to account for aging of the pipelines.
It is noted that a much more severe storm in the future could potentially result in higher peak flows than what
are assumed for this analysis. Conversely, an aggressive program to identify and reduce the volume of I&I
could result in reduced peak flows in the future.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 8 March 2003
7.9 RECOMMENDED CAPITAL IMPROVEMENT PROGRAM
Improvement projects identified for the Capital Improvement Program (CIP) are summarized in Table 7-3.
The projects are arranged into three groups. The first group of projects includes improvements to the sewer
collector system and rehabilitation projects. These projects were updated from the City’s 2002-2003 CIP
based on discussions with City staff. The next group consists of interceptor capacity projects, which were
identified from the hydraulic analysis performed as part of this Master Plan Update. The last group of
projects are for improvements at the Encina Water Pollution Control Facility, which were also defined in the
City’s 2002-2003 CIP.
Table 7-3 includes a planning level estimate of probable construction costs. Costs should be considered
relative to the 2002 Engineering News Record Construction Cost Index (ENR CCI) of 6538. Cost estimates
for the Encina WPCF projects and most of the collector system projects were obtained from the City’s 2002-
2003 CIP. It is noted that costs identified for V/C Interceptor capacity improvements represent the total cost,
although a portion of these costs will be shared by the City of Vista. The costs for the Encina WPCF projects
represent the City’s pro-rated share for the projects.
Project ProbableType Constr. Cost COLLECTOR SYSTEM & REHABILITATION PROJECTS:1Avenida Encinas Gravity Sewer - new sewer along north side of Lanakai Mobil Home Park to reduce odorsnew gravity sewer 1000' of 8" pipeline 175,000$ 2North Agua Hedionda Interceptor Rehabilitation - West Segment (Cove Dr. to Hoover St.) - rehab manholes, new access road, erosion protection, minor sewer realignment, EIR, construct mitigation siterehab manholes, new access road, sewer realignment19 manholes 700' of 24" pipeline3,629,000$ 3North Agua Hedionda Interceptor Rehabilitation - East Segment (ECR to Kelly Dr.) - replace/rehabilitate manholesrehab/replace manholes21 manholes 620,000$ 4North Agua Hedionda Trunk Sewer Replacement (Reach NAHT1A)- Tamarack Av. from ECR to Calavera Hills Treatment Plantreplace FM with gravity sewer5000' of 8" pipeline 1,533,000$ 5North Batiquitos Interceptor Rehabilitation - MH Rehab & new access road from ECR west to NB Lift Stationaccess road & MH rehab--- 1,000,000$ 6El Camino Sewer - Construct gravity sewer in ECR from Chestnut Av. To Tamarack Av.new gravity sewer 4200' of 8" pipeline 420,000$ 7Sewer Lift Stations Repairs/Upgrades - Terramar, Villas and Gateshead Lift StationsLift Station Upgrades--- 235,000$ 8Remove Forest Lift Station and construct gravity sewer using microtunelling constructionnew gravity sewer 1400' of 8" pipeline 800,000$ 9Home Plant Lift Station - replace pumps, upgrade wetwell, manifold piping, ventilation system, and reconstruct influent gravity sewer L.S. Improvements & gravity sewer260' of 15" pipeline 585,000$ 10Remove LCWD La Costa Meadows Lift Station and construct gravity sewernew gravity sewer 600' of 8" pipeline 175,000$ 11 Remove La Golondrina Lift Station and construct gravity sewer new gravity sewer 1000' of 8" pipeline 150,000$ 12 Poinsettia Lift Station Odor and Noise Abatement L.S. rehab --- 221,800$ 13Sewer Line Refurbishment/Replacement - replace or refurbish sewer lines older than 30 yearsreplace/refurbish gravity sewers--- 7,868,000$ 14Vista/Carlsbad Interceptor Rehabilitation Reaches VC1 and VC2 - line pipelines and rehab manholesline sewers & rehab manholes9,430' of 36" pipeline 25 manholes377,000$ Project IDcontinued next pageTable 7- 3Size/QuantityDescription/LocationRECOMMENDED SEWER CAPITAL IMPROVEMENT PROGRAMCity of Carlsbad Sewer Master Plan Update 7-9Dudek & Associates, Inc.March 2003
Project ProbableType Constr. Cost COLLECTOR SYSTEM & REHABILITATION PROJECTS (continued):15 Gateshead Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer200' of 8" pipeline 60,000$ 16 Vancouver Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer300' of 8" pipeline 60,000$ 17 Simsbury Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer500' of 8" pipeline 100,000$ 18 Villas Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer2000' of 8" pipeline 270,000$ 19 Woodstock Lift Station -remove station & construct new gravity sewerL.S. replacement with gravity sewer400' of 8" pipeline 80,000$ 20Faraday #14 (Upper) Lift Station - remove station & connect to existing gravity sewerL.S. replacement with gravity sewer--- 30,000$ 21Faraday #10 (Lower) Lift Station - remove station & connect to existing gravity sewerL.S. replacement with gravity sewer--- 30,000$ 22North Batiquitos L.S. Modifications- new gas detectors, ventilation system, odor control, improved pump access, wiring, & float switchL.S. rehab --- 500,000$ 23Carlsbad Trunk Sewer Reaches VCT1A, VCT1B, VCT1C - Convey flows from Vancouver and Simsbury Lift Station service areas through LFMZ25 to the V/C Interceptor (see related projects 16 & 17)new gravity sewer 2000' of 8" pipeline 150,000$ 24 Master Plan Update - update of sewer MP and CEQA approval prepare reports -- 305,000$ 25Sewer Monitoring Program - monitor sewer flows in pipelines and at lift stationsmonitor flows -- 600,000$ 26Sewer Access Hole Rehabilitation - replace or refurbish manholes older than 30 yearsrehab/replace manholes-- 2,800,000$ 27 Sewer Connection Fee Update prepare report -- 15,000$ Collector System & Rehabilitation Projects Subtotal 22,789,000$ Project IDcontinued next pageDescription/Location Size/QuantityTable 7- 3 (continued)City of Carlsbad Sewer Master Plan Update 7-10Dudek & Associates, Inc.March 2003
Project ProbableType Constr. Cost INTERCEPTOR CAPACITY PROJECTS:28Vista/Carlsbad Interceptor Reach VC3 - capacity upgrade upstream of the Buena Vista Lift Stationinterceptor replacement3,350' of 42" pipeline 2,570,000*$ 29Buena Vista Lift Station - capacity increase, control system upgrade, new back-up generator L.S. rehab Lift Station capacity = 26 MGD 735,000*$ 30Buena Vista Lift Station Force Main (VC4) - replace existing 16" pipeline with 24" pipeline to provide dual 24" FMs & increase capacitynew force main 3,840' of 24" force main 1,244,000*$ 31Vista/Carlsbad Interceptor Reach VC11B - upgrade capacity and construct new bridge crossing over the Agua Hedionda Lagooninterceptor replace- ment & new bridge915' of 54" pipeline 2,900,000*$ 32Agua Hedionda Lift Station and Force Main VC12 - rehab lift station and construct new force mainL.S. rehab & new force mainLift station capacity = 36 MGD 200' of 36" force main6,250,000*$ 33V/C Interceptor Reaches VC13, VC14 & VC15 - Increase interceptor capacity from the AH Lift Station to Encina WPCFinterceptor replacement3510' of 54" pipeline 6,831' of 60" pipeline10,200,000*$ 34South Agua Hedionda Lift Station and Force Main - construct lift station, force main and gravity sewer in Cannon Rd., remove Kelly Lift Station New L.S., FM & gravity sewerLift Station capacity = 4.2 MGD 5,380' of 14" force main 2,568' of 12" gravity pipeline8,827,000$ 32,726,000$ ENCINA WATER POLLUTION CONTROL FACILITY PROJECTS:35Encina WPCF Building Improvements improve building --- 1,787,000$ 36Capital Acquisitions - Unit 1 acquisitions --- 3,415,000$ 37Capital Planning/Services planning --- 1,910,000$ 38Cogeneration Project - upgrade of the electrical generators facility upgrade --- 581,000$ 39Flow Equalization Project - construct tank for peak effluent flows construct tank --- 8,189,000$ 40Phase IV Expansion - Debt Service on Phase IV plant expansion debt service --- 13,082,000$ 41Phase V Expansion - expand plant capacity for buildout conditions TP expansion --- 11,693,000$ 42Phase V Expansion - Interim capacity improvements TP expansion --- 222,000$ 43Plant Rehabilitation machinery rehab --- 2,909,000$ 44Pump Station Interfaces - develop active flow monitoring system report --- 60,000$ 45Technology Master Plan report --- 1,161,000$ Encina WPCF Projects Subtotal 45,009,000$ CAPITAL IMPROVEMENT PROJECT TOTAL = 100,524,000$ * Costs for V/C Interceptor capacity improvememnts includes Vista's share of Interceptor Capacity Projects SubtotalProject IDTable 7- 3 (continued)Description/Location Size/QuantityCity of Carlsbad Sewer Master Plan Update 7-11Dudek & Associates, Inc.March 2003
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-1 July 2003
CHAPTER 8
SEWER CONNECTION FEE UPDATE
The City of Carlsbad has historically charged connection fees to provide sewer service to its new
customers. The fees pay for the planning, design and construction of capacity improvements and/or new
facilities required for the conveyance and treatment of sewage. Under California State law, connection
fees must be based on relevant capital costs. This chapter provides an updated basis for sewer connection
fees based on growth projections and capital improvement projects identified to serve future development.
A cash flow analysis is performed with the updated connection fee from a starting date of October 1, 2003
through buildout, which is projected to occur by 2020.
8.1 BACKGROUND
Sewer connection fees are used to generate revenue to construct sewer infrastructure needed to support
new development. Assembly Bill 1600 was incorporated into the California Government Code under
Title 7, Division 1, Chapter 5: “Fees for Development Projects”, effective 1989. Chapter 5 states that any
fee imposed by a local agency must show that the fee will be used only for purposes related to the service
for which the fee is assessed. The law requires that the City of Carlsbad: 1) identify the purpose of the
fee, 2) identify the use for which the fee is to be put, 3) show a relationship between the fee’s use and the
type of development project on which the fee is imposed, and 4) show a relationship between the need for
the facility and the type of development project on which the fee is imposed. This chapter provides the
basis for connection fees needed to satisfy California law.
The current sewer connection fee was developed in 1990 as part of the “Capacity Fee Update to the 1987
Master Plan of Sewerage”. The fee is based on the Equivalent Dwelling Unit (EDU) method. An EDU is
a unit of measure for the sewage generated from particular buildings, structures or uses. One EDU is
equal to an approximation of the amount of sewage generated by an average single-family residence. The
City uses a formula to determine the EDU’s for other residential, commercial and industrial users. The
sewer connection fee is adjusted annually, effective July 1st, according to the Engineering News Record
Los Angeles Construction Cost Index. The 2002-2003 sewer connection fee is $2,060 per EDU.
In the City of Carlsbad, many sewer projects are paid for by Sewer Benefit Area (SBA) Fees. These
developer-paid fees provide direct funding for specific projects. The sewer benefit area fee program was
originally approved by the City Council on January 15, 1991. The SBA fee is collected with the issuance
of building permits within defined sewer benefit areas. Some developments are conditioned to construct
specific facilities prior to or concurrent with the issuance of building permits. In these cases,
reimbursement is given for actual costs through the SBA fee. A SBA fee program has been established
to pay for portions of the South Agua Hedionda (SAH) Interceptor. The SAH Interceptor system is
therefore considered to be “developer funded”. This project and other projects constructed with SBA fees
are not included in the connection fee calculations.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-2 July 2003
8.2 GROWTH PROJECTIONS
The total number of future users must be estimated to calculate connection fees. The City of Carlsbad
Growth Database is used in this Master Plan Update to determine the number of future users and project
the ultimate sewer flow for the capacity analysis (documented in Chapter 6, Section 6.3). Parcels in the
Growth Database are assigned to one of 25 Local Facility Management Zones (LFMZ), illustrated
previously on Figure 1-3. For the connection fee update, an updated version of the Growth Database is
used to determine the number of future users. In the updated Growth Database, future users are based on
development that is projected to occur after October 1, 2003.
Growth data in the updated Growth Database consists of the number of projected residential units and the
estimated building area for commercial and industrial parcels at build-out. Sewer connection fees are
currently assessed based on Equivalent Dwelling Units (EDUs). By definition, one EDU will generate
the equivalent amount of sewage as an average single-family residence, which is estimated to be 220
gallons per day (gpd). EDU conversions for other types of development are defined in Table 13.10.020-c
of the Carlsbad Municipal Code. For commercial developments, the gross floor area of the building in
square feet (sqft) is divided by 1,800 to obtain the number of EDUs. This is equivalent to a sewage
generation rate of 1,225 gpd per 10,000 sqft of building area or 5.6 EDUs/10,000 sqft. For industrial
developments the building area is divided by 5,000, which is equivalent to a sewage generation rate of
440 gpd per 10,000 sqft of building area, or 2 EDUs/10,000 sqft. The projected future EDUs within the
City of Carlsbad Sewer Service Area after October 1, 2003 are summarized in Table 8-1.
Table 8-1
PROJECTED FUTURE EDUs WITHIN THE SEWER SERVICE AREA
Residential Residential
Units Commercial Industrial Units Commercial Industrial
1 689 1,016,581 0 1,254 15 550 275,000 0 703
2 140 39,656 0 162 16 0 0 1,413,522 283
3 12 128,551 20,000 87 17 598 268,000 2,170,000 1,181
4 40 0 0 40 18 0 30,000 2,196,000 456
5 0 0 2,496,687 499 19 84 223,637 0 208
7 705 30,000 0 722 20 497 70,750 0 536
8 256 6,000 0 259 21 392 0 0 392
9 1 411,500 0 230 22 222 84,780 0 269
10 489 0 0 489 24 30 0 0 30
13 0 1,109,692 200,000 656 25 130 0 0 130
14 960 0 0 960
Totals:
* Non-residential EDU conversions are: commercial = building area/1800, industrial = building area/5000
Building Area (sqft)
12,190,356 sqft of building area5,795 residential units
EDUs*LFMZ
Future Development
EDUs* LFMZ
Future Development
9,547 EDUs
Building Area (sqft)
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-3 July 2003
8.3 CAPITAL COSTS FOR CAPACITY IMPROVEMENTS
The purpose of the sewer connection fee is to pay for growth related capacity improvements. All of the
wastewater generated within the City of Carlsbad Sewer Service Area is treated at the Encina WPCF.
The connection fee therefore recovers the cost of capital improvements and expansions to the sewer
interceptor system and the Encina Water Pollution Control Facility (WPCF).
The basis of improvement projects for the connection fee is the Capital Improvement Program (CIP)
previously identified in Table 7-1 of this Master Plan Update. The CIP recommends improvements to the
sewer interceptor system and the Encina WPCF that will be needed to support the build-out population of
the Sewer Service Area, including replacement of existing facilities and maintenance–related projects.
However, only the capacity-related projects identified to accommodate future growth are included in the
connection fee calculations. In the City of Carlsbad, developers provide direct funding for many specific
projects through Sewer Area Benefit Fees. These projects, which include construction of the South Agua
Hedionda Interceptor, pump station and force main, are not included in the sewer connection fees.
The capacity related capital improvement projects required for future development and an estimate of
probable costs are summarized in Table 8-2 for the connection fee update. Also shown in this table is the
proposed project phasing. Project costs reflect future planned expenditures based on the City of Carlsbad
2003-2004 Capital Improvement Program, which exclude funds appropriated for the 2002-2003 fiscal
year. Projected costs for projects that are currently active will therefore differ from the CIP costs
included in Table 7-1, which are based on the 2002-2003 CIP.
Project costs listed in Table 8-2 for improvements to the Vista/Carlsbad Interceptor (project numbers 28-
33) reflect only the City of Carlsbad’s cost share. Carlsbad’s cost share is based on the capacity rights
defined in Exhibit B of the February 8, 2000 Revised Joint Sewage System Agreement with the City of
Vista (provided in Table 3-1 of this Master Plan Update). Costs for projects 28 through 30 are based on a
10.4 percent ownership, projects 31 and 32 are based on a 30.9 percent ownership, and project 33 is based
on a 43.9 percent ownership. Encina WPCF project costs are based on the City of Carlsbad’s current
capacity ownership of the Encina WPCF, as documented in the February 2000 Revised Basic Agreement.
The total cost of projects to be funded from connection fees is estimated at approximately $31,297,000.
8.4 CONNECTION FEE CALCULATIONS
A cost per EDU for sewer service can be determined from the CIP costs and the projected number of
future users, which has been estimated from available planning data. Because the actual number of units
eventually constructed may vary, the estimate of future sewer EDUs is reduced by 10 percent in the
calculation of sewer connection fees. This unit reduction is considered a “safety factor” to ensure that the
necessary fees will be collected even if the Sewer Service Area is not completely buildout as planned.
YEAR 1 2003-2004 YEAR 2 2004-2005 YEAR 3 2005-2006 YEAR 4 2006-2007 YEAR 5 2007-2008 YEAR 6-10 2009-2013 BUILDOUT 2014-2020 24Master Plan Update and CEQA approval for CIP prepare report 305,000 $ 305,000$ 25Sewer Monitoring Program - monitor flows in pipelines and at lift stationsmonitor flows 340,000 $ 20,000 $ 20,000$ 20,000$ 20,000$ 20,000$ 100,000$ 140,000$ 27 Sewer Connection Fee Update prepare report 15,000 $ 15,000$ 28Vista/Carlsbad Interceptor Reach VC3 - capacity upgrade upstream of the Buena Vista Lift Stationinterceptor replacement267,000*$ 267,000$ 29Buena Vista Lift Station - capacity increase, control system upgrade, new back-up generator L.S. rehab 233,000*$ 233,000 $ 30Buena Vista Lift Station Force Main, VC4 - replace 16" pipeline with 24" pipeline to provide dual 24" force mains & increase capacitynew force main 129,000*$ 129,000$ 31Vista/Carlsbad Interceptor Reach VC11B - upgrade capacity & construct new bridge crossing over the Agua Hedionda Lagooninterceptor replacement & new bridge896,000*$ 896,000$ 32Agua Hedionda Lift Station and Force Main, VC12 - rehab lift station, increase capacity and construct new force mainL.S. rehab & new force main1,931,000*$ 348,000$ 1,583,000$ 33V/C Interceptor Reaches VC13, VC14 & VC15 - Increase interceptor capacity from the AH Lift Station to the Encina WPCFinterceptor replacement4,478,000*$ 224,000$ 2,060,000$ 2,194,000$ 40Encina Phase IV Expansion - debt service on Phase IV plant expansiondebt service 11,203,800 $ 936,300 $ 939,600$ 936,400$ 933,900$ 935,500$ 4,665,500$ 1,856,600$ 41Encina Phase V Expansion - expand plant capacity for buildout conditionsTP expansion 11,499,000 $ 11,499,000$ TOTALS: 31,296,800$ $1,189,300 $13,030,600 $4,866,400 $3,147,900 $955,500 $6,110,500 $1,996,600* Cost for V/C Interceptor projects is the City of Carlsbad's share based on capacity rights defined in Exhibit B of the 2/8/2000 Revised Joint Sewage System AgreementTable 8-2CAPITAL IMPROVEMENT PROJECTS FOR THE SEWER CONNECTION FEE UPDATECIP NO.MASTER PLAN PROJECT DESCRIPTION/LOCATIONPROJECT TYPE ESTIMATED COST FUTURE YEAR BUDGET AMOUNTSCity of CarlsbadSEWER MASTER PLAN UPDATE 8-4Dudek & Associates, Inc.July 2003
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-5 July 2003
The calculations for the updated connection fee are shown in Table 8-3. The “Total Cost” in Table 8-3 is
the capital budget minus the available cash balance in the sewer connection fee account. City Staff have
projected the available cash balance on October 1, 2003 to be $23,330,674. The new connection fee is
calculated to be $927 per EDU.
Table 8-3
SEWER CONNECTION FEE CALCULATION
Capital
Budget
Available
Cash
Balance
Total Cost
Future
EDUs
less 10%
Cost Per
EDU
$31,296,800 $23,330,674 $7,966,126 8,592 $927
8.5 SEWER SYSTEM CASH FLOW ANALYSIS
A cash flow table can be constructed using the sewer connection fee calculated in Table 8-3, yearly
buildout projections provided in the City of Carlsbad Growth Database, and project phasing estimates.
Table 8-4 provides a sewer cash flow table using the calculated connection fee over a seventeen-year
period, starting in October 1, 2003 and ending at 2020, which is the projected buildout year for the City.
At the end of the chosen time period the cumulative balance is $0, because the connection fees are based
on a budget that includes the available cash balance. It is noted that all values used in the cash flow tables
are in current dollars.
City of Carlsbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-6 July 2003
Table 8-4
SEWER CONNECTION FEE CASH FLOW ANALYSIS
Fiscal
Year
New
EDUs
Connection
Fee Revenue CIP Costs Balance
Cumulative
Balance
Available cash balance projected for 10/1/03 = 23,330,674$
2003 442 $927 409,803$ 1,189,300$ (779,497)$ 22,551,177$
2004 878 $927 814,043$ 13,030,600$ (12,216,557)$ 10,334,620$
2005 784 $927 726,890$ 4,866,400$ (4,139,510)$ 6,195,111$
2006 860 $927 797,354$ 3,147,900$ (2,350,546)$ 3,844,565$
2007 630 $927 584,108$ 955,500$ (371,392)$ 3,473,173$
2008 782 $927 725,036$ 1,222,100$ (497,064)$ 2,976,109$
2009 682 $927 632,321$ 1,222,100$ (589,779)$ 2,386,330$
2010 599 $927 555,367$ 1,222,100$ (666,733)$ 1,719,597$
2011 543 $927 503,446$ 1,222,100$ (718,654)$ 1,000,942$
2012 491 $927 455,234$ 1,222,100$ (766,866)$ 234,076$
2013 425 $927 394,041$ 249,575$ 144,466$ 378,542$
2014 361 $927 334,703$ 249,575$ 85,128$ 463,671$
2015 243 $927 225,299$ 249,575$ (24,276)$ 439,395$
2016 188 $927 174,305$ 249,575$ (75,270)$ 364,125$
2017 163 $927 151,126$ 249,575$ (98,449)$ 265,677$
2018 157 $927 145,564$ 249,575$ (104,011)$ 161,665$
2019 218 $927 202,120$ 249,575$ (47,455)$ 114,210$
2020 146 $927 135,365$ 249,575$ (114,210)$ $0
Totals: 8,592 7,966,126$ 31,296,800$ (23,330,674)$