HomeMy WebLinkAbout; Sewer Master Plan Update 2003 Part 1; City of Carlsbad Sewer Master Plan Update 2003; 2003-03-30CITY OF CARLSBAD
SEWER MASTER PLAN UPDATE
Prepared For:
City of Carlsbad
1635 Faraday Avenue
Carlsbad, Califomia 92008
Prepared By:
DUDEK & ASSOCIATES, INC.
605 Third Street
Encinitas, CA 92024
TEL (760) 942-5147
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 Engmeer
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 Laboratoty Supervisor
City of Carisbad
SEWER MASTER PLAN UPDATE
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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
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
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
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
EXISTING WASTEWATER FLOWS
4.1 ENCINA FLOW METERS 4-1
4.2 fflSTORICAL FLOWS 4-2
4.3 AVERAGE DRY WEATHER FLOWS 4-3
4.4 PEAK DRY WEATHER FLOWS 4-5
4.5 INFLOW AND ESfFILTRATION 4-6
4.6 EXISTING UNIT FLOW FACTORS 4-7
4.7 EXISTING FLOWS PER SUB-DRAINAGE BASIN 4-9
City of Carlsbad
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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
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
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 POTENTL\L 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
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 Carlsijad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE iv 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 Enema WPCF Capacity Ovraership 3-18
Table 4-1 Enema WPCF Flow Meters 4-1
Table 4-2 August 2001 Encina Member Agency flow Sununary 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 Svmimary 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 Proj ected Peak Flows at Lift Stations 6-17
Table 7-1 Summary ofV/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 *l-2
Figure 1-3 LFMZ and Sub-Drainage Basin Boundaries *l-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
SEWER MASTER PLAN UPDATE
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LIST OF FIGURES (continued)
Figure 2-5 Dry Weather Unit Hydrographs for Intemal Loads 2-6
Figure 2-6 Historical and Proj ected Ultimate Flows 2-10
Figure 2-7 V/C hiterceptor Peak Wet Weather Flow 2-12
Figure 2-8 South Agua Hedionda Peak Dry Weather Flow 2-13
Figure 2-9 Proj ected Carlsbad PWWF in the Buena Interceptor 2-14
Figure 2-10 Projected Carlsbad PWWF m the Vallecitos Interceptor 2-14
Figure 2-11 Projected Carlsbad PWWF m the Dovrastream 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 Extemal Loads 5-5
Figure 5-2 Dry Weather Unit Hydrographs for Intemal 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 Dovrastream 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 vl 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 centrifligally cast fiberglass reii
CIP Capital Improvement Program
City City ofCarlsbad
DIP Ductile iron pipe
EDU Equivalent Dwelling Unit
EIR Environmental Impact Report
ESD Encinitas Sanitary Division, City c
EWA Encina Wastewater Authority
^s 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
If 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 Cartsbad
SEWER MASTER PLAN UPDATE VII
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ANNOTATION (continued)
RCP Reinforced concrete pipe
SAH South Agua Hedionda
SanGIS San Diego County Geographic Information System
SFDU smgle 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
SEWER MASTER PLAN UPDATE VIII
Dudek & Associates, Inc.
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 comer of
the present village area of the City Carlsbad, were initially constmcted 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 Ihe 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 coimections. 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 constmcted 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-ovmed and operated by six northem San Diego County wastewater agencies as fhe 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 comer of the City is provided by the Leucadia Coimty Water District (LCWD),
and the Vallecitos Water District (VWD) provides service to the Meadowlark area along the eastem City
limit. The Carlsbad service area boundary and adjacent district boundaries are shovra on Figure 1-1.
The elevation of the service area varies from just under 600 feet at the eastem 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 eastem service area boundary, and drain west to the coast and ultimately the
Encina WPCF. These sewage drainage basins are defmed by the existing and plaimed 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.
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SEWER MASTER PLAN UPDATE 1 -1 March 2003
LEGEND
I I SEWER SERVICE AREA BOUNDARY
CITY OF CARLSBAD BOUNDARY
03-2003 CarlsbadlOl.mxd
The northem-most dramage basin in the City is the Vista/Carlsbad (V/C) basm. The V/C basin begins at
fhe northeast Carlsbad boundary and extends west, with an area that extends approximately Vi mile south
of Highway 78 and, further west, to the Buena Vista Lagoon. At fhe Buena Vista Lagoon, the basin turns
south and extends along fhe 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 fhe 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 fhe lagoon before draining to the V/C basin. The SAH basin
is approximately two miles wide at the eastem City boundary, and narrows to about Y2 mile wide at its
westem boundary with fhe V/C basin.
The drainage basin that includes fhe Encinas Canyon area is called fhe Buena/Vallecifos 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 fhe eastern boundary of
the service area adjacent fo the Vallecitos Wafer District, and extends west fo 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 fhe north shore ofthe Batiquifos Lagoon to Interstate 5. At Interstate 5, fhe
basin turns north and follows the coast to fhe Encina WPCF.
1.3 GROWTH MANAGEMENT PLAN
On July 1, 1986, fhe City Coimcil of Carlsbad adopted a Grov^^ Management Plan to help assure
provision of adequate facilifies for fiiture development. Implementation of the Growth Management
Program was envisioned as a three level system, involving 1) a Citywide Facilifies and Improvement
Plan, 2) the preparation of 25 Zone Facilities Plans, and 3) individual projecf approvals. The Citywide
Plan estabhshed 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 disfrict must be provided concurrent
with development.
• WASTEWATER TREATMENT CAPACITY PERFORMANCE STANDARD - Sewer
plant capacify is adequate for af least a five year period.
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LEGEND
l~l SEWER SERVICE AREA BOUNDARY
MAJOR DRAINAGE BASINS
I I VISTA/CARLSBAD
I I NORTH AGUA HEDIONDA
IBB SOUTH AGUA HEDIONDA
I I BUENA/VALLECITOS
I I NORTH BATIQUITOS
FIGURE 1-2
CITY OF CARLSBAD
MAJOR DRAINAGE BASINS
DUDEK
!& ASS(X,b\TES. INC,
03-2003 Carlsbad102,mxd
LEGEND
l~l SEWER SERVICE AREA BOUNDARY
nn LFMZ BOUNDARY
I I SUB BASIN BOUNDARY & DESIGNATIONS
LFMZ'S BY COLOR
1 11 1 1 8 1 1 17
1 |2 LJ 9 1 1 18
1 1 3 1 1 10 1 1 19
1 ^4 1 1 13 1 1 20
1 1 5 1 1 14 1 1 21
1 |6 1 1 15 1 1 22
1 ^7 1 1 16 1 1 24
1 1 25
FIGURE 1-3
CITY OF CARLSBAD
LFMZ AND SUB-DRAINAGE BASIN
BOUNDARIES
!ii ASSOCIATES, KNC.I DUDE
03-2003 Car1sbacJ103.mxd
As part of the Growth Management Plan, the Cify 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 fhe 1992 Master Plan of Sewerage fo 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 fhe following sub-sections.
1.4.1 1987 Master Plan of Sewerage
The 1987 Master Plan of Sewerage was fhe first master plan prepared in accordance with Cify of Carlsbad
Growth Management Plan. In 1987, fhe majority of development in Carlsbad was along fhe coastal strip
and predominantly residential. The population of fhe 1987 study area was esfimated af 39,000, and fhe
ultimate population was projected to be 95,700. Average wastewater flows were projected af a rate of
220 gallons per day per equivalent dwelling unif (EDU). In 1987, the ultimate average flow from the City
ofCarlsbad was projected fo be 13.41 milUon gallons per day (MGD).
1.4.2 1992 Master Plan of Sewerage
The 1992 Master Plan of Sewerage was an update of fhe 1987 Master Plan. By 1992, fhe population of
the study area had increased to 65,000 and the ultimate population projection had increased fo 130,000.
Development was starting to progress inland and the percentage of commercial/mdusfrial development
had increased since fhe last Master Plan. The projected population grov*^ curve first developed in the
1987 Master Plan was revised to increase more rapidly through fhe year 2000, and then flatten out to an
annual growth rate of approximately 1 percent from fhe year 2000 fo 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 fhe 1992 sewer system recommended in this update included capacify upgrades fo
fhe Vista/Carlsbad Interceptor, replacement of the Home Pant Lift Station, and the constmction of gravity
sewers to lift stations in LFMZs 2 and 7. It was also recommended fo 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.
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SEWER MASTER PLAN UPDATE 1-3 March 2003
1.43 1997 Sewer Master Plan Update
In 1994, fhe Cify of Carlsbad adopted a new General Plan. The 1997 Sewer Master Plan Update
incorporated fhe revised 1994 land use and population projections. Because ultimate population
projections were reduced only slightiy from those used in fhe previous Master Plan, an updated capacify
analysis of fhe interceptors was deemed unnecessary. The 1997 Master Plan Update focused on analyses
of the NAH and SAH sewer basins to determine whether excess hydraulic capacify in the NAH
Interceptor could be used fo convey portions of fhe SAH flows. Preliminary sizing, slope and alignment
of fhe SAH Interceptor was performed as part of this update. Also included in fhe update were additional
hydraulic analyses of the V/C Interceptor and a detailed survey of the exisfing lift stations.
1.5 2003 UPDATE SCOPE AND PURPOSE
This report represents an update ofthe Cify of Carlsbad Sewer Master Plan (Master Plan) for the planning
period between 2002 and buildout of the District's service area. In summary, fhe scope includes tasks to
document exisfing facilifies, project ultimate average wastewater flows, estimate existing and ultimate
peak flows, and develop a computer model fo perform an exisfing and ultimate system capacify analysis.
The outcome of these analyses is a recommended long-term Capital Improvement Program (CIP) for
improvement of existing wastewater collection and freatment facilities. An update of the sewer
connection fee is included to finance fhe recommended facilifies, and an out-of-basin sewer study for the
SAH basin is included to determine when fhe 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 fhe sewer collection system. The sewer GIS was used to create a computer model of fhe
interceptor system and produce maps of fhe collection system for this report. The completed sewer GIS
and supporting documentation has been submitfed under a separate cover. Supporting environmental
documentation in compliance with the California Environmental Quality Act (CEQA) for fhe 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 fhe City's recently compiled
Growth Database, which projects the number of addifional single and multi-family units and the number
and size of non-residential buildings at buildout. The capacify analyses are performed with a state-of-the-
art hydraulic model based on fhe newly developed sewer GIS. Major improvements over previous
modeling efforts include: 1) a single integrated model of fhe sewer collection system, 2) an accurate
representation of the Vallecitos and Buena Interceptors (modeled as a combined interceptor in fhe
previous Master Plans), 3) fhe determination of existing peak wet weather flows from available meter
data, and 4) analysis using extended period simulations, which account for travel fime in fhe
determination of peak flow rates.
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SEWER MASTER PLAN UPDATE 1 -4 March 2003
CHAPTER 2
EXECUTIVE SUMMARY
2.1 INTRODUCTION AND SCOPE
The Cify of Carlsbad Sewer Master Plan Update documents the existing sewer collection system and
identifies required fecilities 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 exisfing facihties, projecf ultimate
wastewater flows, estimate exisfing and ultimate peak flows, and develop a computer model to perform
an existing and ultimate system capacity analysis of fhe 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 Geogr^hical 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 siq)porting documentation were submitted fo the City under a separate cover in February 2003.
Si5>porting environmental documentation in compliance vwth the Califomia Enviromnental Quality Act
(CEQA) for fhe projects identified in the Master Plan Update CIP vdll also be subniitted separately at a
later date.
In this Master Plan Update, ultimate sewer flow projections are based on the City's recently compiled
Growdi 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-fhe-
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 exisfing peak wet weatiier 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 die City, wifli the exception of the
souflieasf comer of the City. Wastewater collection in the southeastem area is provided by fhe Vallecitos
Wafer District (VWD) and fhe Leucadia County Water District (LCWD). Carlsbad's Sewer Service Area
extends from the Pacific Coast approximately 5 miles inland, providing wastewater collection, freatment
and disposal service to customers within its 30 square mile service area. Wastewater is conveyed to the
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SEWER MASTER PLAN UPDATE 2-1 March 2003
Encina Wafer Pollution Control Facility (WPCF) for freatinent and disposal through an ocean outfall.
The Encina WPCF is ovmed and operated by flie Encina Wastewater Authority (EWA), a joint powers
authority made vip of six northern San Diego County wastewater agencies.
The City of Carlsbad sewer service area is comprised of five major dramage basins, which extend from
approximately flie eastem service area boundary, and dram west to flie coast and ultimately fo the Encina
WPCF. These sewage drainage basins are defined by flie existing and planned mtercepfors within the
City of Carlsbad. Four of the interceptor systems have been constmcted and are now in use. Most
interceptors convey iqjstream flows from otiier agencies in addition to City of Carlsbad flows. The
existing interceptor systems in order from north to south are hsted below.
• Vista/Carlsbad (V/C) Interceptor - collects City of Vista and Carlsbad flows. Jointly owned by flie
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 flirough die Encinas Canyon: flie Buena Interceptor, ovmed by flie City of Vista's Buena
Satiation Distiict, and die Vallecitos Interceptor. The City of Carlsbad has edacity rights in flie
Buena hiterceptor and die City of Carlsbad, City Vista and flie VWD share capacity ownership in the
Vallecitos Interceptor.
• North Batiquitos (NB) Interceptor - collects only Carlsbad flows in die vpper reaches. The last
approxunately half mile before flie Encina WPCF is joinfly owned by flie City of Carlsbad, flie
LCWD, and flie Encinitas Sanitary Division of tiie City of Encinitas. The combined ovmership
section is sometimes referred fo as the Ponto Interceptor or the Occidental Sewer.
In addition to fhe approximately 30 miles of mterceptor sewers, the City of Carlsbad currently owns,
operates, and maintains approxunately 200 miles of gravity collector system pipehnes and approxunately
5,000 manholes. Eighteen wastewater hft stations are currentiy located within fhe City ofCarlsbad Sewer
Service Area. The Buena Vista and Agua Hedionda Lift Stations, which are part ofthe V/C Interceptor,
are operated and maintained by tiie Encina Wastewater Authority. The remainder of the hft stations are
owned and operated by tiie City of Carlsbad. Exhibit 1 in Appendix A provides an illustration of die
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 northem coastal areas of San Diego County confinue to develop, flie
City of Carlsbad has experienced gradually increasing wastewater volumes. The Enema Wastewater
Authority operates and maintains numerous flow meters throughout die service areas of its six member
agencies. A Centi^ized Flow Metering Program was implemented m 1989 and meter upgrades were last
City of Carisbad Dudek & Associates, I nc.
SEWER MASTER PLAN UPDATE 2-2 March 2003
OCEANSIDE
1VC3
LEGEND
l~1 SEWER SERVICE AREA BOUNDARY
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
FIGURE 2-1
CITY OF CARLSBAD
EXISTING INTERCEPTOR SYSTEM
DUDEK lit ASSOCUTES, LNC.
03-2003 Carlsbad201.mxd
made in 1996. Wastewater flows generated within the City of Carlsbad are metered in the interceptor
pipelines upsfream 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 Southem Califomia 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
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.
City of Carisbad
SEWER MASTER PLAN UPDATE 2-3
Dudek & Associates, Inc.
March 2003
Table 2-1
AUGUST 2001 ENCINA MEMBER AGENCY FLOW SUMMARY
Interceptor
System
Carlsbad
Flows
Other Agency Flows Total
Flow
Interceptor
System
Carlsbad
Flows Agency Flow
Total
Flow
Vista/Carlsbad & NAH 3.89 MGD City of Vista 5.84 MGD 9.73 MGD
Buena 1.06 MGD Buena
Vista (raceway)
1.84 MGD
0.20 MGD 3.10 MGD
Vallecitos 0.97 MGD Vallecitos 4.28 MGD 5.25 MGD
Norlh 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 Uft Station.
Figure 2-3
AUGUST 2001 FLOW SUMMARY BY INTERCEPTOR
Vista/Carlsbad &
NAH
Buena Vallecitos
CARLSBAD INTERCEPTOR SYSTEMS
North Batiquitos
From Figure 2-3, it is apparent that Carlsbad flows comprise a minority ofthe total flows in each ofthe
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.
City of Carlsbad
SEWER MASTER PLAN UPDATE 2-4
Dudek & Associates, Inc.
IVlarch 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 unh 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 ofthe tme 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 intemal flows to the interceptor system model. Peak dry and wet weather flows
were input to the model using hydrographs (diumal 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
1 0
10 15
Time (hours)
2 0 2 5
•V 1 •L 1 • V A 1 "B 2 + V 2
City of Carisbad
SEWER MASTER PLAN UPDATE 2-5
Dudek & Associates, Inc.
March 2003
Figure 2-5
DRY WEATHER UNIT HYDROGRAPHS FOR INTERNAL LOADS
2 .0
1 .8
1 .6
1 .4
1 .2
1 .0
0.8
0.6
0.4
0.2
0.0
0:00 3:00 6:00 9:00 1 2:00 1 5:00
Time of Day (hours)
1 8:00 21 :00 24:00
'Residential 'N on-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 l&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
82 V2 Buena/Racewav External I&I 1.1
437 Carlsbad Internal I&I to Buena 0.5
VA1 Vallecitos External I&I 3.5
Ll Leucadia External I&I 2.1
TOTAL ESTIMATED I&I 17.4
City of Carisbad
SEWER MASTER PLAN UPDATE 2-6
Dudek & Associates, Inc.
March 2003
Hydraulic analyses were performed on fhe existing interceptor system with both dry and wet weather
flows, edacity 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 VCl4 and VCl5 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 VCl5 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 fhe Buena Infercepfor, 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 fo be deficient with respect fo the City's design criteria (pipelines over 12-inch in diameter
should nof 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 doctnnented
in Table 2-3.
Table 2-3
EXISTING PWWF ANALYSIS SUMMARY FOR GRAVITY PIPELINES
Model
ID Reach Length
(ft.)
Diam.
m.) Location/Comments
274-281 VC3 2,830 36 Approach to Buena Vista Lift Station - pipeline flowing 75% full
309-310 veil 896 42 Approach to Agua Hedionda Uft station - localized surcharging
300-307 VCl 3 3,510 42 Downstream of Agua Hedionda Lift Station - pipeline capacity is
exceeded for short periods; two very flat sections (reaches 290
and 288} and one short 20' pipe with neg. slope (reach 287)
290-298 VCU 4,530 42
Downstream of Agua Hedionda Lift Station - pipeline capacity is
exceeded for short periods; two very flat sections (reaches 290
and 288} and one short 20' pipe with neg. slope (reach 287) 283-289 VC15 1,860 42
Downstream of Agua Hedionda Lift Station - pipeline capacity is
exceeded for short periods; two very flat sections (reaches 290
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 Lower Buena, isolated flat sections
377 B8 93 30
Lower Buena, isolated flat sections
The longest sections of pipeline in Table 2-3 are in the Vista/Carlsbad Infercepfor in Reach VC-3, which
is upsfream of the Buena Vista Lift Station, and Reaches VC-13-15, which are downstteam of the Agua
Hedionda Lift Station. These pipeline reaches are planned for fiiture 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 capacify deficiencies are short sections of pipeline in the upsfream and exfreme
downsfream reaches of the Buena Interceptor. These pipelines are flowing full because of isolated
reaches with very flat slopes.
City of Carisbad
SEWER MASTER PLAN UPDATE 2-7
Dudek & Associates, Inc.
March 2003
Table 2-4 summarizes fhe peak flow tributary to fhe 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 POTENTL4JL PEAK FLOWS TO INTERCEPTOR LIFT STATIONS
Lift Station
Lift Station
Firm Capacity
(MGD)
PDWF
to Wet Well
(MGD)
PWWF
to Wet Well
(MGD)
Peak Velocity
In Force Main'^'
(fps)
Buena Vista 21.5 10.2 18.9 6.9
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 — 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 1-5
(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 fhe 1.7 MGD of available pumping capacify
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 tiie PDWF to the Foxes Landing Lift Station, there is
approximately 1.4 MGD of available pumping capacity to convey stormwater flows. The downsfream
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 wafer levels m 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 hft station.
For fhe V/C Interceptor a hydraulic analysis of peak wet weather flows was performed. Results indicate
that fhe Buena Vista Lift Station may be potentially operating near its firm capacify during severe storm
events, and fhe capacify 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
exceedmg fhe 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 fo
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
City of Carisbad
SEWER MASTER PLAN UPDATE 2-8
Dudek & Associates, Inc.
March 2003
peak ultimate flows to identify and size required interceptor capacify improvements. Planned
improvements fo the collection system were also considered to accurately model future flows. Planned
improvements include fhe elimination of nine hft stations, which will accomplished by the construction of
new gravity pipelines. Most of these hft 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 mto 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 fhe eastern portion of the City.
These developments include Kelly Ranch, Viflages 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 wiU have a mixed-land use. The remainder of fiiture
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 fhe westem portions of the City.
Flow generation factors are used in conjunction wifh fhe City's Growth Database to project ultimate
wastewater flows and distribute flows in tiie ultimate system hydraulic analysis. The City's estabhshed
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 fhe Cify 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), fhe 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 fhe City's
Growth Database are as follows:
Single-family dwelling unit - 220 gallons per day
Multiple-family dwellmg unit -160 gallons per day
Non-residential -1,150 gallon per day/10,000 sqft of building area
Based on these unif 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 wifh 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 fo the Encina WPCF from its member agencies, and allocates fhe flow fo
the Carlsbad interceptor systems.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-9 March 2003
Figure 2-6
HISTORICAL AND PROJECTED ULTIMATE FLOWS
Receded flows from Encina meters
2003 Master Plan projections
1996 Ocean Outfall Capacity Reort projections
1992 Master Plan projections
1987 Master Plan projections
1985 1990 1995 2000 2005 2010 2015 2020
Table 2-5
EXISTEVG AND PROJECTED ULTIMATE ADWF TO THE ENCINA WPCF
interceptor
System
Existing Flows (Aug 2001 Projected Ultimate Fiows interceptor
System Carisbad other Agency Fiows Total Carisbad other Agency Flows'^' Total interceptor
System Flows Agency Fiow Flow Fiows Agency Fiow Flow
Vista/
Carisbad 2.55 MGD City of Vista &
Oceanside 5.84 MGD 8.39 MGD 2.83 MGD City of Vista &
Oceanside 9.72 MGD 12.55 MGD
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 0,73 MGD Buena
Vista (raceway)
1.84 MGD
0.20 MGD 2.77 MGD 0.88 MGD Buena
Vista (raceway)
3.31 MGD
0,60 MGD 4.79 MGD
Vallecitos 0.90 MGD Vallecitos 4.28 MGD 5.18 MGD 1.54 MGD Vallecitos 11.04 MGD 12.58 MGD
North
Batiquitos 1.33 MGD Leucadia/
Encinitas 5.14 MGD 6.47 MGD 1,67 MGD Leucadia/
Encinitas 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
City of Carisbad
SEWER MASTER PLAN UPDATE 2-10
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March 2003
From Table 2-5 it is apparent that flows from Carlsbad will increase within all existing mtercepfors except
fhe NAH Interceptor. The majority of the flow increase to fhe 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 fhe capacity of the existing pipelmes during peak flow conditions. The City of Vista is
planning to divert a portion of thefr flow from the Buena Interceptor to the Vallecitos Interceptor in the
fiiture, and the VWD is planning a replacement of fhe Vallecitos Interceptor with increased capacity.
2.6 ULTIMATE SYSTEM EVALUATION
Hydraulic analyses were performed to determine the ability of the mtercepfors to convey projected peak
flows. Analysis of fhe ultimate interceptor system was accomphshed by adding fhe SAH Interceptor to
the existing system model. City of Carlsbad flows were analyzed in the Buena and Vallecitos
Intercepfors and the peak flows compared to exisfing edacity rights. Flow analysis results from the
SewerCAD ultimate system model are presented graphically for each interceptor system and compared to
fhe gravity pipeline capacities. The graphs illusfrate fhe composite peak flow in each pipeline segment
over the course of fhe 24-hour flow simulation. Flows and capacities are schematically illustrated
according to the reach designations shown in Figure 2-1. Where hft stations are included in the
interceptor, the lift station name and firm pumping capacity are indicated on the gr^h.
2.6.1 Vista/Carlsbad Interceptor
Figure 2-7 illustrates results from the PWWF analysis for fhe V/C Interceptor, and makes a comparison
with existing pipeline edacities. 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 fhe length of fhe V/C Interceptor. The other,
more conservative scenario, assigns most of I&I to the upsfream Reach VI, with the remainder at the
confluence with the NAH Interceptor. As stated previously, it is nof known how much I&I is currenfiy
contributed by the NAH Infercepfor. Although the intemal I&I rate in the ultimate system model was
increased by 20 percent over fhe existing I&I rate, it is noted that I&I was not included for fhe SAH
Interceptor. Flows entering the V/C Interceptor at the upsfream 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 downsfream of VCIO, 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 VCIO, which is currently under construction as a 48-inch diameter
pipeline, may flow fiill for short periods during severe storm events.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-11 March 2003
Figure 2-7
V/C INTERCEPTOR PEAK WET WEATHER FLOW
~* Full Pipeline Capacity
Projected PWWF - Internal 1/1 applied at VCl & VCIO
• ' Projected PWWF - Internal 1/1 distributed
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 uhimate 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 upsfream tmnk sewer along El Camino Real and Sunny Creek Road (SAHTIE
and SAHTIG) is also depicted in Figure 2-8. On the basis of this analysis there should be sufficient
City of Carisbad
SEWER MASTER PLAN UPDATE 2-12
Dudek & Associates, Inc.
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
12
11
Q
«1(
ro
Q.
O ro a ro •>
o
• I
1
T SAH I ' Lift ' J
^ ^ • V
.<s-^ .<s-^ ..<^^ .<s^^ # # # # # # # c,^ o,^ c^^ ci^i* cf
Full Pipeline Capacity
75% Full Capcity
Projected Peak Dry Weather Flow
2.6.4 Buena Intercepetor
Figure 2-9 illusfrates the projected uhimate 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.
City of Carisbad
SEWER MASTER PLAN UPDATE 2-13
Dudek & Associates, Inc.
March 2003
_ 6 .0
Q
I 5.5
I 5.0
u.
j£ 4.5 ra
0)
S: 4 .0
1 .0
2 0.5
O
0.0
Figure 2-9
PROJECTED CARLSBAD PWWF IN THE BUENA INTERCEPTOR
•Projected U Itim ate PWWF
•Carlsbad Leased Capacity
•Carlsbad Capacity (smoothed)
~l—I—I—I—\—I—I—I—I—I—r 1—i—I—I—1—I—i—I—I—I—I—^—I—I—I—I—I—I—I—r
B1 Bl 82 B2 B2 B2 B2 B4 B4 B4 B4 B4 B4 B5 B6 B6 B7 B7 B8 BB BB
2.6.5 Vallecitos Interceptor
Figure 2-10 illustrates the projected uhimate 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
Q 5.0
O
s T 4.5
o
LL iS ".0
0)
Q.
X 3.5 o
CD
Q.
5 3.0
T3
<U
ro 2.5
o
_i
o
.£ 2.0 «
Q.
>
ra
O
1 .5
1 .0
5 MGD Leased
Capacity
•Garlsbad Leased Capacity
•P rejected U Itim ate PWWF
J
n—I—I—I—\—I—]—1—1—I—I—I—I—r
V3 V3 V3 V4 V4 V4 V4 V4 V5 V5 V6 V6 V6 V6 V7 V7 V8 V8
City of Carisbad
SEWER MASTER PLAN UPDATE 2-14
Dudek & Associates, Inc.
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 fiill 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
Q O
S
Q-
2-
a.
Full Pipeline Capacity "Car Is bad Peak Wet Weather Flow Carlsbad Leased Capacitvl
2.7 RECOMMENDATIONS
Gravity interceptor replacements for the V/C Interceptor at Reaches VC3, VCl IB, 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 ofthe 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 ("r|") of 0.012, assuming that the future
pipe will be PVC-lined.
City of Carisbad
SEWER MASTER PLAN UPDATE 2-15
Dudek & Associates, Inc.
March 2003
Figure 2-12
V/C INTERCEPTOR CAPACITY WITH RECOMMENDED IMPROVEMENTS
'Design Capacity (75% full) of Recommended Pipeline Replacements
"75% Full Pipeline Capacity - existing
"Projected PWWF - internal I/I applied at VCl & VC1 1
Proiected PWWF - internal I/I distributed
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 uhimate 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
Design Report for Agua Hedionda Lift Station Upgrade, dated March 7, 2000 was prepared for the City.
City of Carisbad
SEWER MASTER PLAN UPDATE 2-16
Dudek & Associates, Inc.
March 2003
Design Report for Agua Hedionda Lift Station Upgrade, dated March 7, 2000 was prepared for fhe City.
The recommendations from that report include replacement of the existing hft station with fhe exception
of the emergency generator building.
Most of the Soufli 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 edacity 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 constioicted in tiie fixture ahgnment of Cannon Road. A gravity
sewer wifl be constructed with the forcemain that wiU connect with a gravity hne in Faraday Road and
convey flows from the Faraday Business Park and to the SAH Lift Station. After completion of these
projects, fhe two Faraday Lift Stations and the Kelly Lift Station wiU be removed
The District shares ownership or leases capacity in several facilities with the City of Vista, fhe 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 Infercepfor, the Buena
Interceptor, fhe Vallecitos Interceptor and the Occidental Sewer. The foUowing discussions provide an
overview of these facilities relative fo projected ultimate wastewater flow conditions.
Vista/Carlsbad Interceptor. The Vista/Carlsbad Infercepfor 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
fhe agreement, Carlsbad has a 43.9% ownership in the downsfream reach of fhe V/C Interceptor (VC15).
Projected flows for Carlsbad are now lower, and fhe percentage of flow for Carlsbad in this reach is now
esfimated at 37.2%. It is recommended that a new agreement be negotiated based on fhe iq)dafed 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 fo lease an additional 0.8 MGD of capacity. It is estimated tiiat
Carlsbad wifl nof requhe any additional capacity in this interceptor to convey projected ultimate flows. It
is noted that the existing Buena Infercepfor does nof have fhe capacity fo convey buildout flows based on
ultimate flow projections for fhe 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 fhe Buena and Raceway Lift
Stations to the Vallecitos Interceptor.
Vallecitos Interceptor. The City of Carlsbad currentiy 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 nof have the capacity to convey buildout flows for the VWD and
fiiture flows from fhe BSD and the City of Vista Raceway Basin. The VWD plans to replace the existing
Vallecitos Interceptor with a larger capacity infercepfor. Based on projected ultimate flows, Carlsbad
could reduce thefr leased capacity fo ^proximately 4.0 MGD.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-17 March 2003
Occidental Sewer. The Occidental Sewer is joinfly 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 requfred to convey the ultimate PWWF. The
LCWD projects that they wifl need to acquire an additional 1.6 MGD of conveyance capacity in tiie
Occidental Sewer in tiiefr most recent Master Plan. It is recommended that the ownership edacities
defmed in the 1972 Occidental Pipelme Agreement be updated based on current flow projections.
2.8 CAPITAL EMPROVEMENT 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 groiq) of projects mcludes improvements fo 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 grotq) consists of interceptor capacity projects,
which were identified from fhe hydraulic analysis performed as part of this Master Plan Update. The last
group of projects are for improvements af tiie Encina Wafer Pollution Confrol Facility, which were also
defined in flie City's 2002-2003 CIP.
Table 2-6 mcludes a planning level estimate of probable constmction costs. Costs should be considered
relative to tiie 2002 Engineering News Record Constmction Cost Index (ENR CCI) of 6538. Cost
estimates for flie Encina WPCF projects and most of the coflector system projects were obtamed from tiie
City's 2002-2003 CIP. It is noted that costs identified for V/C Interceptor capacity improvements
represent fhe total cost, although a portion of these costs wiU be shared by the City of Vista. The costs for
the Encina WPCF projects represent fhe City's pro-rated share for the projects.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 2-18 March 2003
Table 2-6
RECOMMENDED SEWER CAPITAL IMPROVEMENT PROGRAM
Project
ID Description/Location Project
Type Size/Quantity Probable
Co nsf r. Cost
COLLECTOR SYSTEM & REHABILITATION PROJECTS:
1 Avenida Encinas Gravity Sewer - new sewer along north side of
Lanakai Mobil Home Park to reduce odors new gravity sewer 1000' of 8" pipeline $ 175,000
2
North Agua Hedionda Interceptor Rehabilitation - West Segment (Gove
Dr. to Hoover St.) - rehab manholes, new access road, erosion
protection, minor sewer realignment, EIR, construct mitigation site
rehab manholes,
new access road,
sewer realignment
19 manholes
700' of 24" pipeline $ 3,629,000
3 North Agua Hedionda Interceptor Rehabilitation - East Segment (ECR
to Kelly Dr.) - replace/rehabilitate manholes
rehab/replace
manholes 21 manholes $ 620,000
4 North Agua Hedionda Trunk Sewer Replacement (Reach NAHT1A)-
Tamarack Av. from ECR to Calavera Hills Treatment Plant
replace FM with
gravity sewer 5000' of 8" pipeline $ 1,533,000
5 North Batiquitos Interceptor Rehabilitation - MH Rehab & new access
road from ECR west to NB Lift Station
access road &
MH rehab — $ 1,000,000
6 El Camino Sewer - Construct gravity sewer in ECR from Chestnut Av.
To Tamarack Av. new gravity sewer 4200' of 8" pipeline $ 420,000
7 Sewer Lift Stations Repairs/Upgrades - Terramar, Villas and Gateshead
Lift Stations
Lift Station
Upgrades — $ 235,000
8 Remove Forest Lift Station and construct gravity sewer using
microtunelling construction new gravity sewer 1400' of 8" pipeline $ 800,000
9 Home Plant Lift Station - replace pumps, upgrade wehwell, manifold
piping, ventilation system, and reconstruct influent gravity sewer
L.S. Improvements
& gravity sewer 260' of 15" pipeline $ 585,000
10 Remove LCWD La Costa Meadows Lift Station and construct gravity
sewer new gravity sewer 600' of 8" pipeline $ 175,000
11 Remove La Golondrina Lift Station and constmct gravity sewer new gravity sewer 1000'of 8" pipeline $ 150,000
12 Poinsettia Lift Station Odor and Noise Abatement L.S. rehab — $ 221,800
13 Sewer Line Refurbishment/Replacement - replace or refurbish sewer
lines older than 30 years
replace/refurbish
gravity sewers — $ 7,868,000
14 Vista/Carlsbad Interceptor Rehabilitation Reaches VC1 and VC2 - line
pipelines and rehab manholes
line sewers &
rehab manholes
9,430' of 36" pipeline
25 manholes $ 377,000
continued next page
City of Carisbad
Sewer Master Plan Update 2-19
Dudek & Associates, Inc.
March 2003
Table 2- 6 (continued)
Project
ID Description/Location Project
Tvpe Size/Quantity Probable
Constr. Cost
COLLE CTOR SYSTEM & REHABILITATION PROJECTS (continued):
15 Gateshead Lift Station -remove station & construct new gravity sewer L.S. replacement
with gravity sewer 200' of 8" pipeline $ 60.000
16 Vancouver Lift Station -remove station & construct new gravity sewer L.S. replacement
with gravity sewer 300' of 8" pipeline $ 60,000
17 Simsbury Lift Station -remove station & constmct new gravity sewer L.S. replacement
with gravity sewer 500' of 8" pipeline $ 100,000
18 Villas Lift Station -remove station & construct new gravity sewer L.S. replacement
with gravity sewer 2000' of 8" pipeline $ 270,000
19 Woodstock Lift Station -remove station & construct new gravity sewer L.S. replacement
with gravity sewer 400' of 8" pipeline $ 80,000
20 Faraday #14 (Upper) Lift Station - remove station & connect to existing
gravity sewer
L.S. replacement
with gravity sewer — $ 30,000
21 Faraday #10 (Lower) Lift Station - remove station & connect to existing
gravity sewer
L.S. replacement
with gravity sewer — $ 30,000
22 North Batiquitos L.S. Modifications- new gas detectors, ventilation
system, odor control, improved pump access, wiring, & float switch L.S. rehab — $ 500,000
23
Cadsbad Trunk Sewer Reaches VCTIA, 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
25 Sewer Monitoring Program - monitor sewer flows in pipelines and at lift
stations monitor flows ~ $ 600,000
26 Sewer Access Hole Rehabilitation - replace or refurbish manholes older
than 30 years
rehab/replace
manholes -$ 2,800,000
27 Sewer Connection Fee Update prepare report ~ $ 15,000
Collector System & Rehabilitation Projects Subtotal $ 22,789,000
continued next page
City of Carisbad
Sewer Master Plan Update 2-20
Dudek & Associates, Inc.
March 2003
Table 2- 6 (continued)
Project
ID Description/Location Project
Tvoe Size/Quantity Probable
Constr. Co£(t
INTERCEPTOR CAPACITY PROJECTS:
28 Vista/Carlsbad Interceptor Reach VC3 - capacity upgrade upstream of
the Buena Vista Lift Station
interceptor
replacement 3,350' of 42" pipeline $ 2,570,000*
29 Buena Vista Lift Station - capacity increase, control system upgrade,
new back-up generator L.S. rehab Lift Station capacity = 26 MGD $ 735,000*
30 Buena Vista Lift Station Force Main (VC4) - replace existing 16" pipeline
with 24" pipeline to provide dual 24" FMs & increase capacity new force main 3,840' of 24" force main $ 1,244,000*
31 Vista/Carlsbad Interceptor Reach VC11B - upgrade capacity and
constmct new bridge crossing over the Agua Hedionda Lagoon
interceptor replace-
ment & new bridge 915' of 54" pipeline $ 2,900,000*
32 Agua Hedionda Lift Station and Force Main VCl2 - rehab lift station and
constmct new force main
L.S. rehab &
new force main
Lift station capacity = 36 MGD
200' of 36" force main $ 6,250,000*
33 V/C Interceptor Reaches VC13, VC14 & VC15 - Increase interceptor
capacity from the AH Lift Station to Encina WPCF
interceptor
replacement
3510' of 54" pipeline
6,831'of 60" pipeline $ 10,200,000*
34 South Agua Hedionda Lift Station and Force Main - constmct lift station,
force main and gravity sewer in Cannon Rd., remove Kelly Lift Station
New L.S., FM &
gravity sewer
Lift Station capacity = 4.2 MGD
5,380'of 14" force main
2,568' of 12" gravity pipeline
$ 8,827,000
Interceptor Capacity Projects Subtotal $ 32,726,000
ENCINA WATER POLLUTION CONTROL FACILITY PROJECTS:
35 Encina WPCF Building Improvements improve building — $ 1,787,000
36 Capital Acquisitions - Unit 1 acquisitions — $ 3,415,000
37 Capital Planning/Services planning — $ 1,910,000
38 Cogeneration Project - upgrade of the eiectrical generators facility upgrade — $ 581,000
39 Flow Equalization Project - construct tank for peak effluent flows construct tank — $ 8,189,000
40 Phase IV Expansion - Debt Service on Phase IV plant expansion debt service — $ 13,082,000
41 Phase V Expansion - expand plant capacity for buildout conditions TP expansion — $ 11,693,000
42 Phase V Expansion - Interim capacity improvements TP expansion — $ 222,000
43 Plant Rehabilitation machinery rehab — $ 2,909,000
44 Pump Station Interfaces - develop active flow monitoring system report — $ 60,000
45 Technology 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
City of Carisbad
Sewer Master Plan Update 2-21
Dudek & Associates, Inc.
March 2003
CHAPTER 3
EXISTING SYSTEM DESCRIPTION
This chapter summarizes the exisfing wastewater facihties witiiin the City of Carisbad Sewer Service
Area. These facilities include the main sewer interceptors, lift stations, and wastewater freatment and
disposal facilities. Information regarding the existing wastewater collection system facilities was derived
from the District's sewer aflas books, as-buih constmction 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 fhe majority of fhe City, wifh fhe exception of the
southeast comer of the City. Wastewater collection in the southeastem area is provided by the Vallecitos
Water District (VWD) and fhe Leucadia County Wafer Disfrict (LCWD). Carisbad'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 eastem boundaiy.
The proximity of the Pacific Ocean is a major influence on coastal Southern Califomia weather. Early
morning and late evening fog in fall and late spring; dry, warm summers; and cool to moderate winters
are typical of tiie subnopic climate experienced in northem San Diego County. The temperature range
increases with distance mland from the coast, with an average annual temperature in tiie low fo mid 60
degrees Fahrenheh (°F) at the coast and in the inland valleys. The mean temperature range for the City of
Carisbad is typically between 55°F in January fo 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 uhimate development, there will be five major interceptors within the City of Carlsbad Sewer Service
Area. Four of the interceptor systems have been constmcted 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.
City of Carisbad Dudek & Associates, Inc.
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3-1
OCEANSIDE
LEGEND
I I SEWER SERVICE AREA BOUNDARY
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
FIGURE 3-1
CITY OF CARLSBAD
EXISTING INTERCEPTOR SYSTEM
DUDE
l& ASSOCIATES. INC.!
03-2003 Caflsbad301 .mxd
3.2.1 Vista/Carlsbad Interceptor
The Vista/Carlsbad (V/C) Interceptor is jointly owned by the City of Vista and fhe 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 fhe City of Vista and a small
portion ofthe 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 fhe V/C
Interceptor just upsfream 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 constmcted in 1965. Sections of fhe interceptor were replaced wifh
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 currentiy under constmction. For fhe purposes
of this Master Plan, fhe 2001-2002 Vista/Carisbad Sewer Replacement Project is considered to be a part
of the exisfing sewer system and has been included in the exiting system sewer model as currently
designed.
The existing V/C Interceptor includes gravity pipelmes ranging from 30 to 48 inches in diameter, paraflel
18-inch force mains at the Agua Hedionda Lift Station, and parallel 24 and 16-inch diameter force mains
at fhe Buena Vista Lift Station. Most of tiie gravity pipelines are vifrified clay pipe (VCP), ductile iron
pipe (DIP), or reinforced concrete pipe (RCP) witii a PVC liner (T-Lock liner). Approximately 3,500
linear feet of pipeline was constmcted in Jefferson Street and Oak Avenue in 2002 using microtonneling
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 fhe frade name "Hobas" on fhe
constmction 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 tiie NAH Infercepfor.
Ultimately tiie 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 fhe V/C Interceptor Sewer was revised in
Febmary 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 m the Febmary 2002 Agreement witii Vista, is shown in Table 3-1. Figure 3-2 illustrates the
reach designations of the V/C Interceptor.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-2
Table 3-1
Vista/Carlsbad Interceptor Ownership
(from February 2002 Agreement with tiie City of Vista)
Pipe
Size
Full Flow Pipe
Capacity
(MGD)
City of Vista City of Carlsbad
Pipeline Reach Pipe
Size
Full Flow Pipe
Capacity
(MGD)
Average Percent Capacity Average Percent Capacity
(inches)
Full Flow Pipe
Capacity
(MGD)
Flow
(MGD)
Capacity Rights
(MGD)
Flow
(MGD)
Capacity Rights
(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
VCU 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
It is noted that each pipeline "reach", as defmed 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 constmction 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 ("T)") of 0.013 for unlined sections, and a coefficient of
0.012 for fhe PVC-lined RCP and CCFRPM pipe sections (reaches VC5 through VCIO).
The full flow capacity of each pipeline section based on constmction drawing data is illustrated on Figure
3-3. Also shown on the chart are fhe firm capacities of the Buena Vista and Agua Hedionda Lift Stations
as reported by Encina Operations Staff (firm capachy is defined as the capacity of msfalled pump
facilities with the largest unit out of service) and the "average" reach capacifies listed in Table 3-1.
City of Carisbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
3-3
Figure 3-2
VISTA/CARLSBAD INTERCEPTOR
'VC3-36"-''-; •••-<r.- .
•i ijBUENA VISTA U-"'-
' ''''^^•is^:'''"lii^-iJ'''
jj|;^br-4vc5B - 42"-:;^
ENCINA
WPCF
NOR BATIQUITOS
INTERCEPTOR
JALEGEND
j- ' , INTERCEPTOR SY
|j-=J>— GRAVITY
•FORCEMAIN
LIFT STATIONS
City of Carisbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
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3-4
Figure 3-3
FULL PIPE CAPACITY OF THE VISTA/CARLSBAD INTERCEPTOR SYSTEM
Q O
o m a.
CO O
c
O
CO
T3 c re <u
Q.
CL
>.
ro I-
O
o
A K<D A f.^ KI« Kb Kb Kb <b K*^ K*^ K^ K"J> /-"b /-<b Cj ^'b ,-'b r'b ,-1^ r'V r'V r"^ /-"^ /-"^ r"^ r'^
Reach Designation
• Min. reach capacity from V/C Ownerstiip Agreement • Calculated capacity based on construction drawings
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 constmction drawings are less than the reported capacity documented in
Table 3-1. Most notably, there is a very flat 400-ft segment in VCl4 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 VCl5 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 Carisbad
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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 EI 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 upsfream of the Agua Hedionda Lift Station.
The NAH Interceptor was constmcted 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 constmcted
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
constracted, 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 ofthe
five gravity reaches in the 1992 Master Plan. However, several flatter sections exist which restrict the
flow capacity. The HAH Interceptor is illusfrated 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
m3
''•i000^i?B^
LEGEND
INTERCEPTOR SYSTEM
GRAVITY
— FORCEMAIN
SIPHON
• LIFT STATIONS
City of Carisbad
SEWER MASTER PLAN UPDATE
3-6
Dudek & Associates, Inc.
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Figure 3-5
CAPACITY OF THE NORTH AGUA HEDIONDA INTERCEPTOR
a o 5
ro
Q.
O
o
ro
o a. ro O o c
0) a. iii >, •> ro Foxes
Lift Station
Capcity = 3.7 MGD
75% Full Capacity
• Full Flow Capacity
^ # # # # # # # # # # # # # #
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 aligmnent 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, constraction 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 Carisbad
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3-7
Figure 3-6
BUENA AND VALLECITOS INTERCEPTORS
LEGEND
INTERCEPTOR SYSTEM
——GRAVITY
SIPHON
Buena Interceptor
The first interceptor constracted 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 comer of El
Camino Real and Palomar Airport Road, downsfream 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 constracted 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 Carisbad
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3-8
capacity on a temporary basis. Under this agreement, the City of Carlsbad can discharge an addhional
peak flow rate of 0.8 MGD into the Buena Interceptor until a replacement sewer is constracted. The
current ownership and capacity rights based on flow capacities calculated from GIS data are summarized
in Table 3-2 and illusfrated on Figure 3-7.
Table 3-2
CARLSBAD CAPACITY RIGHTS IN THE BUENA INTERCEPTOR
Pipeline
Reach
Min.
size
(in.)
Min.
Slope
Full Flow
Capacity
(MGD)
75% full
Capacity
(MGD)
Carlsbad
Percent
Ownership
Carlsbad Ca oacitv (MGD) Pipeline
Reach
Min.
size
(in.)
Min.
Slope
Full Flow
Capacity
(MGD)
75% full
Capacity
(MGD)
Carlsbad
Percent
Ownership
100% ful!
Caoacitv
With Add'l
0.8 MGD
81 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
86 21 0.56% 7.68 7.00 28.21% 2.17 2.97
37 24 0.25% 7.36 6.71 31.71%, 2.33 3.13
88 30 0.07%, 6.79 6.19 34.88% 2.37 3.17
Figure 3-7
CAPACITY OF THE BUENA INTERCEPTOR
City of Carisbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
3-9
In fhe downsfream reaches of B7 and B8, three isolated pipelines have very flat slopes. Two 30-mch
diameter pipehnes in Reach B8 have a slope of 0.03 percent, and are fafrly short pipelines (less than 200-
feet). The 24-inch pipelme in Reach B7 is neariy 600 feet in length and has a slope of 0.04 percent,
resulting in a capacity of less tiian 3 MGD (indicated by an "X" data pomt marker m Figure 3-4). Both
of the pipelines up- and downsfream have much steeper slopes, and a hydrauhc jump wiU occur near the
upsfream manhole. The upsfream manhole should be inspected for signs of surcharge, since existing
flows m this reach are higher than tiie computed pipelme capacity. Consistent wifh fhe previous Master
Plan, these flat segments are nof considered in the calculation of fhe City of Carisbad leased capacity in
Table 3-2.
Vallecitos Interceptor
The Vallecitos Interceptor was constracted nearly 20 years after the Buena Interceptor by fhe San Marcos
County Wafer District, which is now fhe Vallecitos Water Disfrict (VWD). The City ofCarlsbad, City of
Vista and fhe VWD share capacity ownership in this pipeline. The Vallecitos Infercepfor begins af fhe
end of fhe VaUecifos siphon near tiie intersection of Camino Vida Roble and El Camino Real,
downsfream of fhe discharge of fhe Vallecitos Lift Station. The interceptor then foUows Palomar Airport
Road in the same approximate ahgnment as fhe Buena Interceptor, crossing under Interstate 5 fo fhe
Encina WPCF. The total length of tiie mterceptor is approximately 3.4 miles.
The exisfing interceptor, constiiicted in 1983, consists of gravity pipehnes ranging from 30 to 54 inches in
diameter and includes two siphons near fhe upsfream end. There are no lift stations along the alignment.
The gravity pipehnes are constmcted of VCP wifh fhe exception of fhe downsfream 54-inch secfion,
which is consfructed of DIP. The VaUecifos Interceptor currenfiy serves portions of LFMZs 5, 13, 18
and 20. The ultimate service area will increase to include all of LFMZs 10 and 17, and tiie portion of
LFMZ 6 that is currentiy served from LCWD.
The title of fhe original interagency agreement for the Vallecitos Interceptor is the Palomar Joint Land
Outfall Interceptor Interagency Agreement, which was signed in 1985. Under tiiis agreement, tiie City of
Carlsbad has a 24 percent capacity ownership and can discharge a peak flow rate of 5.0 MGD into fhe
Vallecitos Interceptor. Portions of fhe Vallecitos Interceptor are reported to be in poor condition, and
VWD plans fo replace the pipehne in fhe fUmre. Additionally, fhe City of Vista has plans to discharge a
portion of the fUmre flows from fhe Buena and Raceway Lift Stations to fhe Vallecitos Infercepfor. The
force mains from these two lift stations currently discharge to the Buena Interceptor.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
3-10
OCEANSIDE
FOREST
LIFT STATION'^
HOME PLANT
LIFT STATION^
CHINQUAPIN I .
LIFT STATION'-
SAND SHELL
LIFT STATION
KNOTS LANE
LIFT STATION
LEGEND
SEWER SERVICE AREA BOUNDARY
EXISTING LIFT STATIONS
FORCEMAIN
GRAVITY INTERCEPTOR SEWER
SIPHON
FIGURE 3-10
CITY OF CARLSBAD
EXISTING LIFT STATIONS AND
FORCEMAINS
PUDE
& ASSOCIATES. UNCI
03-2003 CarlsbadSlo.tnxd
OCEANSIDE
VISTA METER
STATION
SHADOWRIDGE
W. R. P.
BUENA LIFT
STATION
VISTA
SAN MARCOS
LCWD BATIQUITOS
FORCEMAIN
GAFNER
FAILSAFE
LEGEND
LCWD SEWER FACILITIES
CITY OF VISTA/BSD SEWER FACILITIES
VALLECITOS SEWER FACILITIES
NOTE: SEWER INTERCEPTORS CONVEYING
CARLSBAD FLOWS ARE NOT SHOWN
FIGURE 3-11
CITY OF CARLSBAD
OTHER AGENCY WASTEWATER
FACILITIES
UDEK
& ASSOCUTHS. 1-\C.
03-2003 Car1sbad311.mxd
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 ofCarlsbad, 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 mms 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 ofthe NB Interceptor was constracted in 1974 and is approximately 1.6 miles
in length. The last 1,000 foot section was originally constracted 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 constracted
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 illusfrated on Figure 3-8.
Figure 3-8
NORTH BATIQUITOS INTERCEPTOR
Vv/c^i'iirrERCEPToR,:'
, V- VALLEcrrbs i BUENA .,
INTERCEPTORS; &i--ie-^->;iiJlX_i
'(;^^=±~:::z:r^:^^:.^ -.-'LEGEND'
INTERCEPTOR SYSTEM^
GRAVITY
FORCEMAIN
'•••f^i-:i^'
s ENCWA
LIFT STATIONS
u vti ,1 „E|Sl"vM..4 it #«l
1 *
yNORTH
^BATIOUrTOS
City of Carisbad
SEWER MASTER PLAN UPDATE
3-11
Dudek & Associates, Inc.
March 2003
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 ftill 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
Q
O
o ro a ro O c
W
a c
"3 o.
a.
>. > ro
O
22
20
18
16 ^75% Full Capacity
Full Flow Capacity
Carlsbad Leased Capacity
NB Lift
Station
Capacity = 3.2 MGD
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 pipehnes, 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 Carisbad
SEWER MASTER PLAN UPDATE
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March 2003
3-12
Forcemains within fhe District are constmcted 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 fhe sewer system GIS. Table 3-3 presents a summary by
pipeline diameters of fhe 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 Total Length of Pipelines Pipeline Total Length of Pipelines
Diameter Gravity Forcemain Diameter Gravity Forcemain
(in) (if) (If) (in) (If) (If)
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
The summary information in Table 3-3 was obtained from the City of Carisbad Sewer System GIS, which
includes pipelines constracted up through 2001. Infonnation in the Sewer System GIS was obtained from
as-buih drawings, constmction drawings, and the City's existing Sewer Atias Book. Information from the
Sewer Atlas Books was used for pipelines for which no design drawings could be located (primarily in
tiie older "village" areas).
3.4 LIFT STATIONS AND FORCEMAINS
Eighteen wastewater lift stations are currently located within fhe City of Carlsbad Sewer Service Area.
The Buena Vista and Agua Hedionda Lift Stations, which are part of fhe V/C Interceptor, are operated
and maintained by fhe Encina Wastewater Authority. The remainder of the lift stations are owned and
operated by fhe City ofCarlsbad. Figure 3-10 illusfrates 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 tiie table, several lift stations are pumping "out of basin". These lift stations may be
eliminated with the constraction of the future South Agua Hedionda Interceptor and/or other additional
collector sewers.
City of Carisbad
SEWER MASTER PLAN UPDATE
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March 2003
3-13
Table 3-4
SUMMARY OF EXISTING LIFT STATIONS
Lift Station Name
Interceptor
System
Discharge
Construction/
Rehabilitation
Date
Pump Infonnation Station Capacity Force
Main
Diam.
Flow
Meter Comments Lift Station Name
Interceptor
System
Discharge
Construction/
Rehabilitation
Date Qty. Motor Design Point (gpm) (MGD)
Force
Main
Diam.
Flow
Meter Comments
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 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 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" Yes operated by Encina; 2 duty &
2 standby pumps
Gateshead NAH 1985 2 3 Hp 40 gpm @ 25' 40 0.06 4" Gorman Rupp package station
Vancouver NAH 1981 2 15 Hp 150 gpm @ 103' 150 0.22 8" Yes S&L package station
Kelly Ranch NAH 2001 2 10 Hp 325 gpm @ 61' 325 0.47 6" 48,000 gal overflow tank
Simsbury'^* NAH 1985 2 50 Hp 382 gpm @ 200' 382 0.55 8" Yes
Villas NAH 1983 2 15 Hp 125 gpm @ 90' 125 0.18 4" Yes Gorman Rupp package station
Woodstock NAH 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 Vallecitos 1995 2 25 Hp 307 gpm @ 144' 307 0.44 6"
Upper Faraday #10'^' Vallecitos 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 LCWD 1981 2 5 Hp 110 gpm @ 45' 110 0.16 4" S&L package station
(1) station Capacity Is ttie duty capacity with one pump out-of-service, except for the Agua Hedionda LS which assumes 2 pumps out-of-servlce
(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 Carisbad
City of Carisbad
SEWER MASTER PLAN UPDATE 3-14
Dudek Associates, Inc
March 2003
The firm capacity of a lift station, as indicated in Table 3-4, is the hydraulic output of fhe installed
pumping units wifh fhe largest pumping unh out-of-service. The "installed" capacity of a lift station is
equal to the hydrauhc output of all installed pumping imifs. The "hydraulic output" of a smgle pump is
defined by the certified pump curve, the losses within fhe forcemain system, and design operation point
for fhe equipment. The hydrauhc output of several pumps working in parallel is defined by the
cumulative hydraulic effect of the pumps, and is nof equal fo fhe mathematical sum of the individual
nameplate pump capacifies. A hydrauhc analysis of both the pump and the forcemain systems is required
to determine fhe hydraulic output of a given hft station. The majority of fhe 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 imder normal operating conditions, only one pump is operating af a tune and fhe
pumps altemate as fhe pumps start and stop. However, if one pump can not keep up or fails fo start, fhe
second pump will operate automatically.
Each of fhe hft stations has standby power capabihty consisting of either installed generators or a
connection for a portable generator. When station alarms occur, a signal is sent fo the Disfrict Confrol
Center by telephone line. The Home Plant, Foxes and North Batiquitos stations are equipped wifh full
telemetry. Odor confrol consisting of air injection on the force main fo prevent production of hydrogen
sulfide is provided at the Lower Faraday Lift Station. At the other stations, the wet weUs are cleaned
periodically.
Many of fhe lift stations have recentiy undergone, or are planned fo undergo, rehabilitation projects fo
improve station operation and reliability. A site vish to each pump station was conducted as part of fhe
1997 Master Plan Update. Appendix B of that report contained a detailed inventory ofthe mechanical
and elecfrical equipment compiled by City staff. Since tiie last master plan the Poinsettia, Kelly Ranch,
Knots Lane, and Sand SheU Lift Stations have been constracted and the Foxes Landing and Chinquapin
Lift Stations have been rehabihtated.
3.5 INTER-AGENCY AGREEMENTS
Wastewater collection systems operate primarily on a gravity flow basis. However, pohtical boundaries
are nof always established fo match natural drainage contours. As a result, some portions of a given
service area may drain in an undesirable direction, away from fhe remainder of the gravity collection
system. Inter-agency agreements can be developed fo aUow the wastewater flows to be conveyed info the
collection system of an adjacent Disfrict or agency.
The City jointly owns capacity in most of the interceptors with upsfream sewering agencies, as described
previously in Secfion 3.2. The joint ownership agreements are summarized in Table 3-5 and included in
Appendbc B. Figure 3-11 illustrates other agency facilities that are within fhe Carlsbad Sewer Service
Area or along ifs boundary.
City of Carisbad Dudek & Associates, Inc.
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Table 3-5
INTER-AGENCY AGREEMENTS FOR SEWER INTERCEPTORS
Interceptor Joint Agency Agreement/Date
Vista/
Carisbad City of Vista Agreement for Ownership, Operation, and Maintenance of
the Vista/Carlsbad Interceptor Sewer- 2/26/02
Buena Buena Sanitation District
Agreement Between the BSD and City of Carisbad 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-Carisbad-Leucadia-Encinitas Agreement in
Regard to Construction of Sewer Pipeline South from the
Encina Water Pollution Control Facility - 8/24/72
In addition to the inter-agency agreements for fhe intercepfors, 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 wiU flow to the Vallecitos Interceptor in the futare, after
addifional off-site gravity conveyance facilities are constracted. Agreements were signed between fhe
City of Carisbad and the LCWD to transfer 111 EDU's of capacity and flow from the LCWD to Carisbad
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 facihties
tributary to the City of Carlsbad system are constracted and connected.
Tract 93-04, also known as Rancho Carrillo Village Q, is a 25 lot subdivision located in the southwest
comer of sub-drainage basin 188. Wastewater collected on the property will also flow to the Vallecitos
Interceptor in fhe futore, after addhional off-site gravity conveyance and lift station facilifies are
constracted. 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 facihties fributary to
Carlsbad are completed. Once these facilities are constracted, fhe LCWD may consider negotiating a
futore agreement with Carlsbad for the detachment of the remaining 68 additional lots served by the
Meadows III Pump Station.
City of Carisbad
SEWER MASTER PLAN UPDATE
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March 2003
3-16
3.6 WASTEWATER TREATMENT AND DISPOSAL
Wastewater generated within tiie City of Carisbad Sewer Service Area is freafed at tiie Encina WPCF.
The Encina WPCF provides fiill secondary freatinent, sludge handling, and disposal tinough a deep ocean
ouffall. The freatment levels meet current Sfafe and Federal requirements for secondary freatment. The
Encina WPCF is owned and operated by fhe Encina Wastewater Autiiority (EWA), a johif powers
authority made up of six northem San Diego County wastewater agencies. The EWA maintains a 10
member Etoard consisting of council members or directors from each ofthe member agencies. The EWA
operates and maintains tiie Enema Wastewater Pollution Confrol Facility (WPCF) (Unh 1) and ocean
ouffall (Unh J) and fhe Buena Vista and Agua Hedionda Lift Stations. Vista and Carlsbad share tiie
operation and maintenance expenses for fhe Buena Vista and Agua Hedionda Lift Stations.
3.6.1 Treatment
EWA's sfate-of-tiie-art freatment facility is designed fo freaf wastewater fo tiie secondary level. Most of
the freatment plant's highly freafed wastewater is discharged into the ocean tiirough an ouffall. Treatment
processes at the Encina WPCF include screening, grit removal, primary clarification, and freatment of
activated sludge. The waste activated sludge is tiiickened and pumped fo anerobic digester for
stabilization. The digested sludge is tiien dewatered and used as a soh amendment. Sludge hauling and
handling is done by private contractors. Digester gas is used fo fuel gas driven blowers and generators to
reduce outside energy dependence.
The capacity of tiie EWA facility has been expanded several times. The current rated liquid capacity is
36.0 MGD while the rated solids handing capacify is 38.0 MGD. The difference in tiie two capacities
represents the equivalent amount of sludge that is disposed back fo the sewer system from fhe
Shadowridge WRP and tiie Gafner WRP. These two plants rely upon tiie Enema WPCF for sludge
digestion, dewatering, and disposal. However, fhe Gaftier WRP has ceased primary and secondary
freatment and no longer discharges sludge fo the plant.
3.6.2 Disposal
Effluent from the EWA plant is discharged to tiie Pacific Ocean through fhe Encina Ocean Ouffall. The
Encina Ocean OutfeU system includes fhe Interim Flow Equalization Facihties, fhe Effluent Pump
Station, and the ouffall. When fhe influent flows exceed the hydraulic capacity of tiie outfall, the excess
flow is diverted fo tiie flow equalization facilities. When the flow rates faU fo within acceptable levels,
tiie stored flow is pumped from tiie basins back fo the outfall. The equalization allows tiie plant fo pass
high flow^s associated with storm events at a flow rate greater tiian fhe hydraulic capacify of fhe
downsfream ouffaU.
City of Carlsbad Dudek & Associates, Inc.
SEWER M/!LSTER PLAN UPDATE March 2003
3-17
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 fhe original 48-inch, 6,600-foot outfall
constmcted in 1965 and tiie 72-inch, 2,300-foot extension constracted in 1973. The ouffall extension
project also added an 800-foot diffuser system to the end of the ouffall. The current capacity of fhe
Encina Ocean Ouffall 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 fhe Revised Basic Agreement, which was last amended in Febmary
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
Cify of Carisbad currentiy has a capacity ownership of 9.24 MGD for both liquid and solids. The ocean
ouffall system is referred to as Unh 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
Encina
Member
Agency
WPCF fUnit n Outfall (Unit Jl Encina
Member
Agency
Treatment Solids Encina
Member
Agency Percentage ADWF Percentage ADWF Percentage ADWF PWWF*
Encina
Member
Agency 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
City of Carisbad
SEWER MASTER PLAN UPDATE
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March 2003
3-18
CHAPTER 4
EXISTING WASTEWATER FLOWS
As population has grown and the northem coastal areas of San Diego County continue fo develop, the
City of Carlsbad has experienced gradually increasing wastewater volumes. This chapter documents
exisfing wastewater flows within the sewer service area. Historical wastewater flows are summarized and
unit flows are developed for residential and commerciaVindusfrial areas. Peaking curves for each
interceptor system and contribufing upsfream agency are developed for dry weather flows. Exisfing
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 Cenfralized Flow Metering Program was implemented in 1989 and
meter upgrades were last made in 1996. Wastewater flows generated within fhe City of Carlsbad are
metered in the interceptor pipelines upstream of fhe Encina WPCF. Because of flow contributions from
upsfream agencies, Carlsbad flows must be determined by subtracting other agency flows from measured
flows at fhe 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:
Carisbad flow = (C3-V1) -H (81 -(82 + V2)) + (C1 -VA 1) -h (C2-L1)
Table 4-1
ENCINA FLOW METERS
Meter
ID. Location Meter
Tvoe
Metered Row Meter
ID. Location Meter
Tvoe Carisbad OtfierAaencies
VI Havmar Drive in Vista ADS 3600* Vista & Oside
BVPS Discharqe of the Buena Vista LS. Ultrasonic Portions of ttie V/C Interceptor Vista &Oside (VI)
C3 VC influent line to the Encina V\PCF ADS 3600* V/C and N/\H Interceptors Vista &0'side(V1)
B2 •scharae of the BSD Buena LS. Maqmeter _ Buena Sanitation District
V2 Downstream of the Vista Raceway LS. ADS 3600* Raceway basin (Vista)
Bl Buena influent line to the Encina V\IPCF ADS 3600* Buena Interceptor BSD&Racewav(B2,V2)
VA1 Downstream of the Vallecitos LS. UltiBsonic Valledtos
Cl Valledtos influent line to thie Endna WPCF ADS 3600* Vallecitos Interceptor
I'™—-' • : ' : ' .-i-—.—~ -
Valledtos (VA1)
L1 Disdiarqe of Batiquitos LS. Ultrasonic
,, , ,, ,—_ . ......v...,vi,,-'r.,IV.
LCWD and ESD
C2 NB influent line to tiie Encina WCF ADS 3600* North Batiquitos Interceptor LCWD and ESD (Ll)
' Axuracy of ttie MoM 3600 meter is vwthin plus or nrinus 5% under ideal flow conditions
City of Cartsbad
SEWER MASTER PLAN UPDATE
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March 2003
4-1
OCEANSIDE
^BVll=
LEGEND
SEWER SERVICE AREA BOUNDARY
« ENCINA FLOWMETERS
SEWER INTERCEPTOR SYSTEM
GRAVITY SEWER
FORCEMAIN
SIPHON
UPSTREAM AGENCY FACILITIES
FIGURE 4-1
CITY OF CARLSBAD
ENCINA FLOW METER LOCATIONS
4i ASStXnATESaNCJ
03-2003 Carisbad401.mxd
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 Southem Califomia 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 fransitioned from mainly agricultaral use to urbanized development.
Figure 4-2
HISTORICAL WASTEWATER FLOWS
7.0
3.5
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 flucmations that cannot be
explained. Overall, there is no sfrong frend of peak flows occurring in any particular month or season.
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Figure 4-3
5-YEAR MONTHLY WASTEWATER FLOWS VS. RAINFALL
Q
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U-
cn m
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3 -
mu
asellne C
If low for 2
Plan
Augu
ry Weatt'
002 Mast
pdate
t 2001
er
er
Jan-97 Jul-97 Jan-98 Jul-98 Jan-99 Jul-99 Jan-00 Jul-00 Jan-01 Jul-01
1 2
o
4 -=
'Monthly rainfall total 'Average monthly wastewater flows Smoothed flow data
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
SystemSMHI
Carlsbad Other Agency Flows Total
Flow
Interceptor
SystemSMHI Flows Agency Flow
Total
Flow
Vista/Carlsbad & NAH 3.89 MGD City of Vista 5.84 MGD 9.73 MGD
Buena 1.06 MGD Buena
Vista (raceway)
1.84 MGD
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 ttian ttie upstream flow metered at the North Batiquitos Lift Station.
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10
9
8
7
6
5
4
3
2
1
Figure 4-4
AUGUST 2001 FLOW SUMMARY BY INTERCEPTOR
• Buena 8 D
• City of Vista
n Vallecitos
• Leucadia/Encinitas
• Carlsbad
• Buena 8 D
• City of Vista
n Vallecitos
• Leucadia/Encinitas
• Carlsbad
• Buena 8 D
• City of Vista
n Vallecitos
• Leucadia/Encinitas
• Carlsbad
• Buena 8 D
• City of Vista
n Vallecitos
• Leucadia/Encinitas
• Carlsbad
•i Vista/Carisbad &
NAH
Buena Vallecitos
CARLSBAD INTERCEPTOR SYSTEMS
North Batiquitos
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 tme 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 downsfream 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
upsfream flows, an error of even 3 percent on the upsfream 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 (Ll)
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 frends 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 moming 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 illusfrates 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
23456789
Average Dry Weather Flow (MGD)
10 11
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4.5 INFLOW AND INFILTRATION
Storm water inflow and infiltration (I&I) is fhe combination of wet weather infilfration and dfrect storm
inflow that estabhshes fhe maximum hydrauhc capacity of wastewater conveyance facihties. Infilfration
enters fhe collection system underground, due fo either a permanently high groundwater table or as a
result of rainfaU percolation and temporary rising of groundwater levels. While the amoxmf of infiltration
from rainfaU events can be estimated from an evaluafion of flow data and rainfaU records, infilfration that
occurs year-round can typically only be defected from pipeline video inspections or manhole inspections.
The presence of excessive amounts of infilfration indicates broken or poorly constmcted pipes, pipe
joints, or manholes.
Inflow in a collection system generally refers fo exfraneous wafer that flows directly info the system as a
result of storm wafer nmoff. The entry points may be at manholes or from ihich connections fo fhe sewer
system, such as roof and yard drains. The rate of inflow depends on fhe amount and intensity of rainfall
and the ground satarafion level.
For fhis Master Plan Update, high intensify rainfall events over fhe past five years were analyzed fo
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 locafion. 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 upsfream agency and interceptor system is calculated by adding
the peak I&I fo fhe PDWF.
Results of the I&I investigation indicate that there are high I&I rates fo fhe Vista/Carisbad (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 m the Vista drainage basin remain
elevated for several months after periods of heavy rainfaU. This is attributed to increased infilfration from
high groimdwater levels. The inflow during periods of high rainfaU is also significant, and is attributed
primarily fo iUich 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 fhe ADWF af fhe upsfream end of the interceptor. An
evaluation of flow data from the Encina C3 meter indicates that approximately 4.5 MGD of addifional
inflow is confribufed 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 fhe NAH Infercepfor, so the origin of the additional
I&I cannot be accurately determined.
The I&I confribution 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 fhe BSD is diverted fo the Shadowridge Wafer Reclamation Plant during high rainfall periods. In
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fhe VaUecifos Infercepfor, almost aU of fhe I&I recorded af the downsfream Encina meter Cl can be
attributed fo Vallecitos. The instantaneous peak I&I from VaUecifos is estimated to be approximately 4.0
MGD, and fhe theoretical PWWF is esfimated to be approximately 2.6 times the ADWF. If is not known
whether there are currently any upsfream pumping limitations that would prevent fhe total flow from
being discharged fo fhe VaUecifos Interceptor. It is noted that VaUecifos was completing ifs Sewer
Master Plan Update af the time of fhe writing this report.
In the North Batiquifos (NB) Interceptor, fhe peak I&I flows measured af fhe downsfream Encina meter
C2 are fj^jically lower than flows measured in fhe upsfream meter Ll, which meters flow from the LCWD
and ESD. Because of the upsfream NB Lift Station, which employs fixed speed pumping equipment, I&I
flow rates for Carlsbad caimot be directly determined from fhe Encina meters. In fhe 1999 LCWD
Wastewater Master Plan, the mstanfaneous peak I&I flowing to the NB Infercepfor was esfimated fo be
approximately 4.2 MGD. Using fhis flow rate, fhe PWWF for Leucadia/Encinitas is estimated to be
approximately 2.5 times fhe ADWF.
4.6 EXISTING UNIT FLOW FACTORS
Flow generafion factors based on exisfing flow conditions were developed fo distribute flow in the
exisfing 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 Cify of Carlsbad wafer
bilhng records, which were assigned an assessor parcel number (APN) by City staff. If is noted that the
flow generafion factors based on exisfing condifions are different than fhe flow factors developed to
projecf 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,
wifh a few commercial estabhshments. There are no residential flows fributary to the hft station. An
analysis of fhe flow generated within this service area was conducted to determine exisfing flow
generation rates for indusfrial business park fype developments.
The total flow fo fhe Faraday Upper Lift Station for August 2001 was determined from pump run-time
records provided by Cify of Carlsbad Public Works Operation staff. Wafer records were obtained and
reviewed fo determine which parcels had active wafer usage from commercial meter accounts.
Corresponding informafion on fhe building area and parcel size was obtained from the City's Growth
Database for parcels wifh active water usage. The unif sewage flow generafion rate for fhe Faraday
service, area based on the building size, was detennined fo be 0.39 gpm per 10,000 square feet of building
area. This retum rate of potable water fo the sewer system from commercial meter accounts was
approximately 94 percent The return rate is considered fo be high and is attributed to fhe fact that
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hrigafion wafer fo fhis area is supplied through separate irrigation meters. Table 4-3 summarizes fhe
results of the Faraday Indusfrial 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 Lof Area with 8/01 wafer usage - 313 Acres
Total Building Area wifh 8/01 wafer usage - 3,990,514 sqft
Average Building size • 48,665 sqfl/lot
Water supphed from commercial meters - 7,377,524 gallons
Total Gallons of Sewage Pumped''' • 6,944,880 gallons
Retum rate to sewer system (excluding irrig) - 94%
Average flow rate of sewage pumped - 156 gpm
Unh Wastewater Flow Rate (parcel based) - 715 gpd/acre
Unit Wastewater Flow Rate (building based) • • 561 Kpd/10,000 sqft
Unif Wastewater Flow Rate (building based) • - 0.39 Rpm/10,000 sqft
Equivilent EDUs'^' • • 2.88 EDUs/10.000 soft
(1) From Faraday Sewage Lift Station flow meter records
(2) Based on 220 gpd/EDU
4.6.2 Residential Unit Flows
To determine the average wastewater flow for residenfial customers, water meter records were obtained
for parcels within fhe sewer service area and sorted based on the wafer meter fype. Meter accounts that
do not conttibute fo sewer flows (irrigation, agriculture, fire protection, and temporary meters) were first
deducted from the data. For commercial, institutional, and multi-family accounts, fhe percentage of
potable wafer entering the sewer system was assumed to be approximately 90 percent. These accoimt
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 retom rate fo fhe sewer system from single-family water meters is affected by fhe lof size and
irrigafion demands, and is highly variable. For fhis reason, water billing data from residential accounts
was nof used directly. Single-family meters and duplex meters were assigned an equivalent dwelling unit
(EDU) of 1 and 2, respectively. To determine fhe flow per residential EDU, the total sewer flow
estimated from non-residential and multi-family wafer accounts was deducted from fhe total sewer flow,
based on fhe August 2001 Encina meter reading. The resulting residential flow component was then
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divided by the total number of EDUs. Using fhis methodology, the average unit flow per residential imif
for fhe existmg Carlsbad sewer system is calculated to be approximately 195 gpd/EDU.
4.7 EXISTING FLOWS PER SUB-DRAINAGE BASIN
Cify of Carlsbad water bUling records linked to the City's parcel base were used to determine fhe exisfing
wastewater flow generation within each sub-drainage basm. Residential wastewater flows were estimated
for each sub-drainage basin based on a unit flow generafion rate of 195 gpd per single-family residenfial
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 esfimated
from water billing data using fhe assumed retum 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.
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Table 4-4
EXISTING WASTEWATER FLOWS PER SUB-DRAINAGE BASIN
Sub-Interceptor No. of Residential Non-Res. Total flow Sub-Interceptor No. of SF Residential Non-Res. Total flow
basin'^' System SF Units Flow'^' (gpm) flow'^ (gpm) (gpm) taasln*^^ System Units Flow'^' (gpm) flow''' (gpm) (gpm)
1A V/C 153 20.72 92.25 112.96 6A NB 498 67.43 45.06 112.49
IB V/C 208 28.16 19.23 47.39 JA* NAH 527 71.36 5.82 77.18
IC V/C 118 15.98 0.00 15.98 78 NAH 448 60.66 15.18 75.84
ID 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
IH V/C 606 82.05 119.35 201.41 138 Vallecitos 0 0.00 113.01 113.01
11 NAH 945 127.95 55.86 183.81 148 NAH 1 0.14 3.28 3.42
1J NAH 949 128.49 19.53 148.02 158* NAH 4 0.54 54.91 55.45
2A V/C 583 78.94 67.97 146.91 188 Vallecitos 951 128.77 28.71 157.48
28* NAH 223 30.19 0.00 30.19 19A N8 414 56.06 4.94 60.99
2C NAH 1,412 191.18 0.57 191.76 198 N8 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
38 V/C 0 0.00 107.96 107.96 19D N8 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 58.03 227.55 208 Buena 291 39.40 1.01 40.41
4B N8 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
58* 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 10.99 218 NB 82 11.10 9.91 21.01
5E Buena 0 0.00 39.19 39.19 210 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
51 Buena 0 0.00 105.15 105.15 24A* NAH 233 31.55 0.00 31.55
5J Buena 0 0.00 12.78 12.78 248* 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 (6.8 MGD) Total Flow
(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.
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