HomeMy WebLinkAbout; Sewer Master Plan Update 2003 Part 2; City of Carlsbad Sewer Master Plan Update 2003; 2003-03-30CHAPTER 5
EXISTING SYSTEM EVALUATION
The level of sewer service that is provided to a community is the result of the implementation of
improvements that are "designed" in accordance with accepted criteria. The performance of a wastewater
collection system and its components are evaluated based on comparisons with established and verified design
criteria. This chapter describes the criteria, methodology and analyses used in the evaluation of interceptor
facilities relative to 2001 conditions. The evaluation method employs the use of the SewerCAD hydraulic
modeling software, which performs hydraulic calculations based on standard open channel flow algorithms
and Manning's equation. SewerCAD performs extended period simulations (EPS) to route wastewater flows
through the conveyance system using a unit hydrograph or diumal curve. The result of this analysis
technique is a more accurate depiction of the true peaking factor within the subject collection system. A
summary of the performance ofthe existing system under both dry and wet weather conditions is provided.
5.1 DESIGN CRITERIA
Design criteria provide the standards against which the existing system is evaluated. These criteria are also
the basis for planning of new facilities to improve existing service or to handle future wastewater flows. Most
of the design criteria presented in this Master Plan Update conform to existing City of Carlsbad design
standards and planning criteria. The most significant deviation from past standards and practices ofthe City
occurs in the areas of wastewater flow projection methodology, discussed in Chapter 6 of this report, and
peaking factor identification. Peaking factors used in the hydraulic analysis are based on historical dry and
wet weather peak flows observed from metering data, as previously presented in Chapter 4.
5.1.1 Depth of Flow
Evaluation of gravity pipelines makes use of Manning's Equation for computation of a pipeline's capacity.
The capacity of each gravity sewer is based on the relative depth of flow within the respective pipeline reach.
Sewer interceptors are not typically designed to flow full, as unoccupied space at the top of the pipe is
required for conveyance of sewage gasses and to provide contingent capacity for wet weather inflow and
infiltration. Interceptor sizing is typically based on the pipeline flowing 75 percent full at the PWWF if the
pipe is larger than 12-inches in diameter (D/d = 0.75). If the pipeline is 12-mches m diameter or smaller, a
D/d factor of 0.50 is used.
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5.1.2 Pipeline Friction Factor
Friction factors for pipelines vary with the material and the age of the pipe. For analysis purposes, the
pipeline friction factor assumes that the pipeline has been in service for some period of time, and that some
fouling, deposits, and deterioration may have occurred. A roughness factor as indicated by a Maimings'
coefficient ("TI") of 0.013 is tj^ically used to evaluate existing interceptors and for projection of future sizing
needs. Previous studies have shown tiiat this value typically accounts for most pipe roughness, joints, and
fouling that occur after several years of operation. At the direction of City staff, a Manning's coefficient of
0.012 was used in the evaluation of the PVC-lined RCP and CCFRPM pipeline sections of fhe V/C
Interceptor installed in 2002 (reaches VC5 through VCl lA).
5.1.3 Lift Stations
In the design of sewer lift stations, it is required that spare pumping units be included for mechanical
reliability. A wastewater facility must be capable of conveying peak wet weather flows with the largest
operating unit out of service. Lift stations are typically equipped with a minimum of two pumps and have a
secondary or emergency power source, consisting of either installed generators or a connection for a portable
generator. Forcemains are evaluated based on maintenance of a minimum or maximum allowable flow
velocity, varying between 2.5 and 8.0 l^s. Velocities less than 2.5 ^s can resuh in deposition in the
forcemain, while velocities greater than 8.0 fjps can damage the pipeline through excessive abrasion.
5.2 EXISTING INTERCEPTOR SYSTEM HYDRAULIC MODEL
A new model of the Carlsbad interceptor system was developed from GIS data collected as apart of this
Master Plan Update. The magnitude of extemal flows from agencies that contribute to the system and intemal
flow generation was determined from flow metering data. Information from City of Carlsbad water billing
records was associated with the City's parcel base, and then used to distribute intemal flows along the
interceptor system. Peak dry and wet weather flows were input to the model using hydrographs (diumal
curves) developed from 24-hour metering data.
5.2.1 Physical Data Input
The existing Carlsbad interceptor model includes gravity pipelines, siphons, lift stations, and force mains
comprising the V/C, NAH, Buena, Vallecitos and NB Interceptors, as shown on Exhibit 1, provided in
Appendix A. Manhole locations, invert elevations, pipeline diameters, pipeline lengths, and other pertinent
information were obtained directly from the sewer system GIS, developed as a part of this Master Plan
Update, using a graphical interface and standard CADD/GIS software. The model consists of 374 pipeline
segments totaling over 24 miles of pipeline. Pipeline diameters range from 8 to 54 inches. The interceptor
reach naming convention established in the previous Master Plans has been maintained for this analysis.
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In creating a model, there are often basic assumptions that are made to properly represent the system. Siphons
in Ihe Carlsbad interceptor system are typically double or triple barreled sections that may have different pipe
sizes. The SewerCAD model requires that siphons be simplified by representing the section as a single pipe.
An equivalent pipeline diameter was input for siphons based on the combined area of the pipes.
Pump curves, wet well dimensions and forcemains for the Buena Vista, North Agua Hedionda, Foxes
Landing, Home Plant, and North Batiquitos Lift Stations are included in the model. Pumping units at lift
stations can have either fixed speed or variable frequency drive (VFD) motors. Each ofthe lift stations
modeled, with the exception of the North Batiquitos Lift Station, have VFD pumping units. With variable
speed drives, the rate of flow coming into the station is essentially the same as the rate of flow out of the
station. Lift stations with VFDs were modeled as a single design point pump. The North Batiquitos Lift
Station has two duty pumps with fixed speed drives. Individual pumps and control settings were modeled for
this lift station.
5.2.2 Internal Flow Distribution
Flow generation within Carlsbad is allocated and distributed to the interceptor system in accordance with the
total flow generated within each sub-drainage basin. Sub-basin boundaries are illustrated on Exhibit 1
provided in Appendix A. City of Carlsbad water billing records and the City's parcel base were used to
determine tiie existing wastewater flow generation within each sub-drainage basin. Residential wastewater
flows were estunated based on a unit flow rate of 195 gpd per single-family residential meter account, and
390 gpd per duplex meter account (refer to Section 4.6 of this report). Wastewater flows from multi-family
and non-residential parcels (commercial and institutional meter accounts) were estimated from water billing
data using an assumed retum rate to the sewer system of 90 percent. This retum rate assimies that outdoor
irrigation water for multi-family, commercial and institutional properties is delivered from separate irrigation
meters. The estimated flows and EDU count per sub-drainage basin were previously provided in Table 4-4
The wastewater flows allocated to each sub-drainage basin were considered tributary to the pipeline
interceptors at the corresponding discharge location of the trunk or collector sewers within that sub-basin. For
sub-basins with multiple connection points to interceptor pipelines, flow was typically input at the upstream
connection (a conservative evaluation approach). Table 5-1 summarizes the distribution of average flow
within the system used for this analysis. The hydraulic analysis was performed by peaking the average flows,
as discussed in the following section.
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Table 5-1
EXISTING CARLSBAD FLOW SUMMARY BY INTERCEPTOR
Interceptor System Sinqle Fa milv DU Com/lnd/lnst/WIF Total Interceptor System
No. of Flow'^'' Flow*^' Flow
Units (MGD) fMGD) rMGD)
Vista/Carlsbad 4,468 0.87 1.68 2.55
North Agua Hedionda 5,259 1.03 0.28 1.30
Buena 1,543 0.30 0.42 0.73
Vallecitos 1,514 0.30 0.60 0.90
North Batiauitos 3,977 0.78 0.55 1.33
Totals: 16,761 3.3 3.5 6.8
(1) Includes townhomes and condos that receive an Individual water bill
(2) Flow per SFDU is based on the overall calculated rate of 195 gpd/SFDU
(3) Sewer flow Is estimated at 90% ofthe average water demand from 2001 billing
records for multi-family, commercial and Institutional accounts.
It is noted tiiat the total flow rate of 6.8 MGD is slightiy higher than the actual totals calculated for Carlsbad
based on the August 2001 Encina meter records (refer to Table 4-3). The higher flow total is a result of using
higher flows for the North Batiquitos Interceptor in the existing system analysis based on flow meter data
from the North Batiquitos Lift Station. In addition, the distribution of flows using a universal flow rate of 195
gpd/SFDU resulted in an almost exact match with Encina meters in the Carlsbad/NAH interceptor system, but
lower flows in the Buena and Vallecitos Interceptors. Higher peaking factors were therefore applied to the
Buena and Vallecitos systems in the model to more closely match recorded peak flows. It is noted that future
flow projections are based on a more conservative unit flow rate of 220 gpd/SFDU, .as discussed later in
Chapter 6 of this report.
5.2.3 Dry Weather Hydrographs
One of tiie primary differences between the analyses perfonned in the previous Master Plans and this Master
Plan Update is the use of unit hydrographs or "diumal curves" as opposed to fixed peaking factors for the
determination of peak dry weather flows. Hydrographs are developed to account for the varying rate of
wastewater production throughout a typical day. The term "diumal" is indicative ofthe shape ofthe curve,
which typically exhibits peak flow periods twice in a 24-hour period. The use of diumal curves when
accounting for the wastewater production of each contributor allows for a more accurate representation of
flow variations and accounts for the routing of wastewater through the collection system on a temporal basis.
Dry weatiier hydrographs were developed for each upstream contributing agency and for tiie intemally
generated Carlsbad flows based on flow meter data collected and reviewed from Encina meters. From the
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graphs in Appendix C, it is clear that the shapes of the unit hydrographs for each basin are similar. However,
each basin exhibits its own unique peaking factor based on the combination of land uses that comprise the
basin. Hydrographs for the existing system model were based on flow data from Sunday, August 26. As
discussed previously in Chapter 4, weekend peaks were observed to be higher than weekday peaks, and the
highest peak flows in most interceptors during August 2001 occurred on August 26. The dry weather
hydrographs generated from the model at the downstream interceptor reaches were then compared to
hydrographs from meters near the Encina WPCF to assure that the model accurately reflected the collection
system flows.
Wastewater flows tributary to the Carlsbad system from other agencies are termed "extemal loads". At each
major connection to the Carlsbad system, flow meters are installed for billing purposes. The 24-hour flow data
from each of these meters was analyzed and used to determine the existing dry weather flow entering the
system. Figure 5-1 illustrates the dry weather hydrographs developed for extemal loads to tiie Carlsbad system.
The hydrographs represent City of Vista flows to the V/C Interceptor (VI), Buena and Raceway Lift Station
flows to the Buena Interceptor (B2 + V2), Vallecitos flows to the Vallecitos Interceptor (VAl), and Leucadia
and Encinitas flows to the NB Interceptor (Ll). Dry weather peaking factors for the upstream agency flows
based on these'graphs range from 1.63 for tiie City of Vista to 1.85 from tiie Buena and Raceway lift stations.
Figure 5-1
DRY WEATHER HYDROGRAPHS FOR EXTERNAL LOADS
a> E
5 o
U-
<
o X
Tim e
•V1 -L1 •VAI •B2 + V2
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The diumal curves developed for intemal loads to each of the interceptors were normalized into "unit" diumal
curves. Two separate curves were developed based on the flow type. The diumal pattem for the Carlsbad
single family residential flows was developed by consideration of each of the measured flows within the
system. The "non-residential" flow pattem was based on previously developed curves for the Southem
Califomia region. Figure 5-2 illustrates the diumal pattems applied to average Carlsbad flows generated
within each sub-drainage basin.
Figure 5-2
DRY WEATHER UNIT HYDROGRAPHS FOR INTERNAL LOADS
0:00 3:00 6:00 9:00 12:00 15:00
Time of Day (hours)
18:00 21:00 24:00
'Residential 'Non-Residential
5.2.4 Wet Weather Flows
To understand the operations of the existing system during peak flow periods, wet weather flows (from inflow
and infiltration) are added to the dry weather flows. This section discusses the methods used to model wet
weather flow events. Long term flow metering data was reviewed to determine the wet weather response of
each interceptor system. Five storm events were reviewed and a single storm was selected to represent wet
weather flows in the system. The largest event occurred on Febmary 22 and 23, 1998. This single event had
a rainfall total of over 2.2 inches. Several million dollars of damages occurred in the surrounding area
according to the National Weather Service. Because of the extreme nature of this event and the questionable
nature of meter and rain gauge operations, this event was not considered for further analysis.
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The storm event selected for the wet weather analysis occurred on November 24, 2001. The total rainfall
amount for this storm was 1.29 inches with a peak intensity of 0.55 inches/hour. The rainfall occurred during
an off-peak flow period and lasted for approximately 4 hours. The fact that it occurred off-peak allowed more
accurate flow measurement of flows entering tiie system. Because this rainfall event was not preceded by other
storms, it provides a good representation of the inflow component of flow. The inflow component of rainfall
induced l&I produces the highest peak flows in a system. However, storm water induced infiltration can also
increase peak flows. This is evident in the flows from the City of Vista to the Vista/Carlsbad (V/C)
Interceptor.
To illustrate the use of hydrographs for wet weather events, the development of flow curves for the City of
Vista based on Encina flow meter V1 is presented. The inflow component of l&I, or the "defect" flow, was
derived by comparing the peak flow rate of the wet weather event to the average dry weather flow. This flow
curve comparison is presented on Figure 5-3. From Figure 5-3, it is apparent that there was an additional 2.6
MGD of wastewater flow as the result of the peak intensity of the storm (0.55 inches of rainfall per hour).
Figure 5-3
I.&I FLOW ANALYSIS FOR THE VISTA METER (VI) ON 11/24/01
12
Hour
16 20
1=] Rainfall "11/24/01 "ADWF "Estimated I&I
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The City of Vista has exhibited long-term flow response from increased infiltration due to high ground water
levels following major storm events. Based on flow data documented in the July 2001 City of Vista
Wastewater Master Plan Update, an additional base infiltration load of approximately 3.0 MGD has been
experienced for extended periods after storm events due to high ground water levels and pipeline defects. This
infiltration rate was added to the calculated peak inflow rate of 2.6 MGD. The total defect flow representing
peak I&I rates assigned to the Vista system is therefore 5.6 MGD.
With an average dry weather peak flow rate of just over 9.0 MGD, the predicted peak wet weather flow rate
for the existing City of Vista system tributary to tiie V/C Interceptor is approximately 14.6 MGD (9.0 MGD
+ 5.6 MGD). Using a "fixed pattem", as illustrated on Figure 5-4, assures that the peak of the sanitary flow
and the defect flows are additive. The peak flow response is what would be predicted if the same rainfall
amount and intensity ofthe November 24, 2001 storm event occuned coincidental with the peak dry weather
flow during a period of elevated ground groundwater levels (due to a previous storm or series of storms).
Figure 5-4
POTENTIAL PEAK WET WEATHER FLOWS TO THE V/C INTERCEPTOR FROM VISTA
"ADWF 1 Inflow "V1 Infiltration •VI Total
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The City of Carlsbad system also contributes l&I to the V/C Interceptor. The combined flow from Vista and
Carlsbad tributary to the V/C and NAH Interceptors is measured at the C3 Encina meter, which is just
upstream ofthe Encina WPCF. The effects of the November 24, 2001 storm event at this site are shown on
Figure 5-5.
Figure 5-5
I&I FLOW ANALYSIS FOR THE V/C METER AT ENCINA (C3) ON 11/24/01
12
Hour
16 20
Rainfall '11/24/01 "ADWF "Defect
As shown on Figure 5-5, tiie total peak defect flow on November 24,2001 was approximately 7.3 MGD. The
contribution from Vista for this event was previously calculated to be approximately 2.6 MGD. The increase
in defect flow from the City of Carlsbad to the V/C and NAH Interceptors is therefore calculated to be
approximately 4.7 MGD. Without detailed flow studies and additional monitoring it cannot be accurately
determined where the storm water is entering the system. The intemal stormwater inflow for Carlsbad was
distributed evenly in the model along the entire length ofthe V/C Interceptor. This assumes a bias towards
wet weather flow contributions occurring in the V/C Interceptor rather than the NAH Interceptor. It is noted
that the flow meter at Foxes Lift Station on the NAH Interceptor is not currently operational. This meter is
recommended to be repaired to provide a long-term historical record of wet and dry weather conditions for this
interceptor.
Peak wet weather flow curves were developed based on observed inflow rates from November 24, 2001 meter
data for the Buena, Vallecitos and North Batiquitos Interceptors in a similar manner. For the Vallecitos and
NB Interceptors, the measured I&I during wet weather flow events from upstream sewering agencies was
higher than defect flows recorded at downstream meters at Encina. For these interceptors, I&I was therefore
attributed to the Vallecitos and Leucadia/Encinitas systems, respectively. In the Buena Interceptor, the peak
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I&I rate was calculated from the upstream agency and a measurable amount of inflow was determined to be
generated within Carlsbad. The intemal defect flow for this interceptor was applied to the upstream end of
the interceptor in the hydraulic model. Table 5-2 summarizes the I&I applied in the existing system wet
weather analysis.
Table 5-2
EXISTING SYSTEM ANALYSIS PEAK I&I RATES
Model ID Description Flow Rate
(MGDI
V1 City of Vista External Inflow 2.6
272 City of Vista External Infiltration 3.0
VC IntWx Carisbad Internal l&I to V/C 4.7
B2 V2 Buena/Raceway External I&I 1.1
437 Carlsbad Internal l&l to Buena 0.5
VA1 Vallecitos External I&I 3.5
L1 Leucadia External l&I 2.1
TOTAL ESTIMATED I&I 17.4
5.3 CAPACITY ANALYSIS RESULTS
This section discusses the results of the hydrauhc analyses conducted with respect to the existing system,
which includes improvements to the V/C Interceptor that are currently under constmction. An understanding
ofthe hydraulic condition of the existing system is necessary to identify existing system deficiencies, and to
help prioritize recommended system improvements resulting from the ultimate system analysis. The capacity
ofthe interceptor system was evaluated under both dry and wet weather flow scenarios.
5.3.1 Gravity Pipelines
Capacity analysis of open channel systems is generally based on the consideration of the depth of flow as
compared to the diameter of the pipe (D/d). For the interceptor system, this depth to diameter ratio is
constrained to not exceed 0.75 for peak dry weather conditions. It is also considered undesirable to operate
the system at depths over 90 percent of the diameter under peak wet weather conditions. Exceptions to these
guidelines are allowed when considering siphons or other known areas of pressure flow.
The capacity analysis under dry weather flow conditions indicates that two flat pipeline reaches in VC 14 and
VCl5 are flowing full (refer to Section 3.2.1). There are a few isolated locations where flows exceed the 75
percent full criteria in the Buena Interceptor, also due to short sections of very flat pipeline. These areas are
minor and are not considered to be worthy of further discussion.
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Based on analysis of the existing collection system with wet weather flows, several gravity pipelines were
determined to be deficient with respect to the design criteria established in Section 5.1 of this Master Plan
Update. It is noted that the peak wet weather event modeled is conservatively based on potential flows and
I&I rates that could occur, and is not based on actual recorded flows. The potentially deficient pipeline
reaches identified during the existing system analyses are located within four separate areas of the interceptor
system, as documented in Table 5-3.
Table 5-3
EXISTING PWWF ANALYSIS SUMMARY FOR GRAVITY PIPELINES
Model
ID Reach Length
(ft.)
Diam.
(ft.) 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 Lift 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 fiat sections (reaches 290
and 288) and one short 20' pipe with neg. slope (reach 287)
290-298 VC14 4,530 42
Downstream of Agua Hedionda Lift Station - pipeline capacity is
exceeded for short periods; two very fiat 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 fiat 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 fiat reach
392 BB 208 30 Lower Buena, isolated fiat sections
377 88 93 30
Lower Buena, isolated fiat sections
The longest sections of pipeline m this table are in the Vista/Carlsbad Interceptor in Reach VC-3, which is
upstream of the Buena Vista Lift Station, and Reaches VC-13-15, which are downstream of the Agua
Hedionda Lift Station. These pipeline reaches are planned for future capacity upgrades, and the replacement
pipelines are sized based on ultimate flows in the next chapter of this report. The other two areas with
existing capacity deficiencies are short sections of pipeline in the upstream and extreme downstream reaches
of the Buena Interceptor. These pipelines are flowing fiill as a result of isolated pipelines with very flat slopes
(refer to Figure 3-4).
5.3.2 Lift Stations
Lift station facilities within the sewer interceptor system were evaluated by comparing the peak influent
wastewater volume to the lift station's "firm" pumping capacity, as documented previously in Table 3-4. The
influent wastewater volume of the pump station is defmed by the wastewater flowing in the pipeline(s) just
upstream of each lift station in the hydraulic model. As discussed in Chapter 3, lift stations are generally
designed to maintain a "firm" capacity equal to or greater than the projected peak design flow at a specific
point in time.
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Table 5-4 summarizes the peak flow tributary to the lift stations and the peak forcemain velocities exhibited
based on those flows. Estimates of peak wet weather flows are provided for the V/C Interceptor, but only
peak dry weather flows are calculated for the NAH and NB Interceptors due to a lack of wet weather flow
monitoring data.
Table 5-4
POTENTIAL PEAK FLOWS TO INTERCEPTOR LIFT STATIONS
Lift Station
Lift Station
Firm Capacity
(MGD)
PDWF
to Wet Well
(MOD)
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 —(3) 2.6
(1) Velocity is based on the peak influent flow to the station for variable speed pumps. For the NB Lift
Station (fixed speed), the velocity is based on the output of a single pump.
(2) Peak velocity in the parallel 16" & 24" section. Velocity is 9.3 fps in the short, single 24" section
and 10.5 fps In the parallel 16" section In the bridge over 1-5
(3) Metering data to determine wet weather flows is not available for this system
Based on the data in Table 5-4, there is approximately 1.7 MGD of available pumping capacity at the North
Batiquitos Lift Station to convey stormwater flows. In the hydraulic model simulation, only one fixed-speed
pump operates at the North Batiquitos Lift Station at a discharge rate of approximately 1,200 gpm (1.7
MGD). System operators have stated that a second pump has never needed to operate at the North Batiquitos
Lift Station in response to peak flows during a storm. It can therefore be concluded that the North Batiquitos
Lift Station has sufficient capacity for current wet weather flow conditions.
Based on the PDWF to the Foxes Landing Lift Station, there is approximately 1.4 MGD of available pumping
capacity to convey stormwater flows. The downstream reaches of the AH Interceptor are along the north
shore of the Agua Hedionda Lagoon, and are potential sources of I&I to the interceptor system with rising
water levels in the lagoon. Wet weather flow data is needed to estimate the existing I&I rate to this system,
and to determine if there is sufficient available capacify at the lift station to convey peak wet weather flows.
For the V/C Interceptor a hydraulic analysis of peak wet weather flows was performed. Results indicate that
the Buena Vista Lift Station may be potentially operating near its firm capacify during severe storm events,
and the 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 exceeding the
recommended maximum velocify of 8.0 fps during peak wet weather flow conditions.
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5.3.3 North Agua Hedionda Interceptor
The North Agua Hedionda Interceptor cunently conveys flows that will ultimately discharge to the South Agua
Hedionda Interceptor (Sub-basins 5A, 5D, 7C, 8, 15B, 24A and 24B) and the Vista/Carlsbad Interceptor (Sub-
basins 2B and 7A). Consequently, ultimate flows for this interceptor are projected to be considerably less than
existing flows. A capacify analysis of this interceptor was therefore performed with existing flows to
determine the available capacify and estimate the number of fiiture EDUs that the North Agua Hedionda
Interceptor can serve.
Encina meter data indicates that there is a significant volume of I&I generated by Carlsbad (intemal defect
flows) within the V/C and NAH Interceptor systems. The amount of I&I attributed to each interceptor is
unknown because the flow meter at the Foxes Lift Station is not operational. Additionally, wet weather flow
monitoring studies performed in 2001 did not provide information on I&I rates due to a lack of significant
rainfall during the monitoring period. In the hydraulic model, the measured intemal defect flows are allocated
to the upstream end of the V/C Interceptor and the capacify analysis for the North Agua Interceptor is
performed with peak dry weather flows. Figure 5-6 summarizes the results of this analysis.
Figure 5-6
NAH INTERCEPTOR HYDRAULIC ANALYSIS SUMMARY
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0 ^
i ft fl
\ i : \ 1 ^ • r : ] 1 I : 1 ' /r " t A r 7
/ iJA V
>
-LJ
Lift
Station
-
-1 I \
I
5 _o u.
>.4.5
(0
Q.
to
O
a>
K 2.5
4.0
3.5
3.0 -1
2.0
1.5
1.0
0.5
0.0
^ ^ ^^^^ ^^f^ ^^r^ ^
<<°
75% Full Capcity Full Pipe Capacity •Existing PDWF
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The chart in Figure 5-6 illustrates the maximum flow rate in each reach of the interceptor over the 24-hour
hydrauUc simulation, and provides a comparison with pipeline and lift station capacities. The peak dry
weather flow Ime represents a composite flow from the analysis results, as the peak flow in each reach may
occur at different time steps in the simulation. As can be seen on Figure 5-6, there are foxir isolated reaches of
pipeline in the NAH Interceptor tiiat have significantly reduced capacities. These reaches are 24-mch
diameter pipelines with slopes of 0.03 percent or less, and lengths that vary between 126 and 283 feet.
Analysis results indicate that these reaches may be currently surchargiog for very brief periods with peak dry
weather flows. If the isolated pipelines are allowed to surcharge for brief periods, the available capacify in
the NAH Interceptor system is limited by the capacify of the Foxes Lift Station, and not the gravity pipelines.
There is currently no way to accurately estimate peak storm water flows in the NAH Interceptor system.
Considering the proximity of the gravity sewers to the lagoon, however, there is a significant potential for
high I&I rates. To estimate the PWWF, a peaking factor of 3.0 was initially applied to the ADWT in tiiis
system. With a peaking factor of 3.0 applied to the ADWF of 1.3 MGD in the NAH service area, the
resuhing estimate of PWWF is 3.9 MGD. This flow is higher than current capacity of the Foxes Lift Station.
It is concluded that the amount of additional capacity is this system cannot be estimated without additional
wet weather flow data.
5.3.4 Inter-Agency Pipeline Flows
Peak wastewater flows in gravity pipelmes that are jointly-owned with other sewer agencies are compared to
design flows and Carlsbad capacity rights as defined in existing agreements.
Occidental Sewer. The Occidental Sewer is jointly-owned by the City of Carlsbad, the ESD, and the LCWD.
The capacity of the 39-inch diameter gravity pipeline flowiug 75 percent full is approximately 19.2 MGD.
Hydraulic analysis results indicate a potential PWWF of 12.5 MGD in this pipeline. Carlsbad owns a total of
40.0 percent of the available capacity, or approximately 8.5 MGD. Peak dry weather flows from Carlsbad are
effected by of the operation of the upsfream North Batiquitos Lift Station, and are currentiy estimated at 2.3
MGD. This value is based on one pump operating at the NB Lift Station. Existing I&I from Carlsbad to the
NB Interceptor has not been sufficient enough to cause a second ptmip to operate, and therefore is not
effecting peak flows in the Occidental Sewer. The City of Carlsbad is therefore using less than 30% its
allocated capacity in the Occidental Sewer.
Vallecitos Intercevtor. HydrauUc analysis results indicate that the PWWF in the Vallecitos Interceptor is
12.7 MGD. The capacity of tiie interceptor is listed as 20.85 MGD in tiie 1985 agreement witii the VWD
(formerly the San Marcos County Water District), which is based on the pipeline flowing full. Carlsbad has
capacity rights of 5.0 MGD based on peak flow rates to the Vallecitos Interceptor. The PDWF from Carlsbad
in the Vallecitos Interceptor is estimated at slightiy less than 2.0 MGD based on Encina meter data and the
peaking curves on Figure 5-2. The estimated defect flows resuhing from I&I on November 24,2001 were
higher at the upsfream end of the interceptor (meter VAl) than at the downsfream end (meter Cl). Therefore,
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
5-14
I&I in the Vallecitos Interceptor is attributed to flows from Vallecitos in the hydraulic analysis, and it can be
concluded that storm water inflow to this interceptor from tiie Carlsbad service area is minimal. It is
estimated that Carlsbad is currentiy using less than half of its leased flow capacity in the Vallecitos
Interceptor.
Buena Interceptor In the existing system model, the total PWWF in tiie Buena Interceptor at the
downstream reach was calculated to be 4.7 MGD. Most ofthe gravity reaches in tiiis interceptor have a full
flow capacify between 6.0 and 7.0 MGD. However, there are several shallow sloped pipelines that the model
indicates are surcharging (conveying flows higher than the full pipe capacify) during peak wet weather flow
conditions. Analysis results mdicated that two of these pipelines may be surcharging briefly under PDWF
conditions as well. PWWF from tiie City of Carlsbad is estimated to be approximately 2.2 MGD, which
includes an allocation of 0.5 MGD for the peak I&I rate (refer to Section 5.2.4 and Table 5-2). It is estimated
that Carlsbad has less than 0.5 MGD of available capacity in this pipeline based on existing capacity rights. It
is noted that the discharge rate to the Buena Interceptor from the BSD Buena Lift Station can be highly
variable. The Buena Lift Station shares a common wet well with the influent lift station to the Shadowridge
WWTP. During peak flow periods and periods of high rainfall, a portion of the flow from the Buena drainage
basin is diverted to Shadowridge WWTP to prevent surcharging of tiie Buena Interceptor.
5.3.5 Flows to the Encina WPCF and Outfall
Evaluation of Carlsbad's use of the Encina wastewater treatment facility is based on the average dry weather
flow for treatment plant capacity and the peak wet weather flow for capacity in the ocean outfall. As
summarized in Chapter 4 of this report, the existing wastewater flow for Carlsbad, based on meter records for
August 2001, is approximately 6.5 MGD. A slightly higher flow rate of 6.8 MGD was used for the existing
system hydraulic analysis. Compared to existing capacity rights of 9.24 MGD for treatment and solids
handling, the City of Carlsbad is currently using less than 74 percent of its capacity ownership in the Encina
WPCF.
The Encina Ocean Outfall has a maximum instantaneous capacify of 104.9 MGD, considering the capacity
enhancement of constmcted flow equalization facilities. Carlsbad's capacity rights in the outfall are 25.51
MGD, which is based on a peaking factor of 2.76 times the ADWF. Peak flow rates from Carlsbad cannot be
determined from flow meter data since Carlsbad flows are subtracted from other agency flows. Resultant
peak flows from Carlsbad at Encina are likewise not available from the hydraulic analysis. Based on the
peaking factor curve presented on Figure 4-5, the PDWF from Carlsbad is estimated to be 1.7 times the
ADWF, or approximately 11.5 MGD. Approximately 5.2 MGD of I&I was attributed to Carlsbad and added
to Carlsbad flows in the wet weather hydraulic analysis. The estimate of PWWF from Carlsbad to Encina is,
therefore, 16.7 MGD, which is approximately 2.5 times the ADWF. It is therefore estimated that the Cify of
Carlsbad is currently using approximately 65 percent of its capacity ownership in the Encina Ocean Outfall.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
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CHAPTER 6
ULTIMATE SYSTEM FLOW PROJECTIONS AND ANALYSIS
Future flow projections are used to determine required upgrades to the existmg collection system to
adequately serve Carlsbad's wastewater conveyance needs under "buildout" conditions. The existing
interceptor system, with the addition of the South Agua Hedionda Interceptor and incorporation of
planned improvements to the collection system, was analyzed with projected peak ultimate flows to
identify and size required improvements. For this Master Plan Update, a flow projection methodology
consistent with the Carlsbad Grow^th Database was developed. Ultimate wastewater flows were computed
based on the projected number of single family units, multi-family units, and non-residential building area
tributary to the wastewater collection system and the established unit flow factors. Results of the analysis
are summarized and deficiencies identified. Recommended improvements to the sewer interceptor
system to convey ultimate flows are presented in Chapter 7 of this report.
6.1 PLANNED SEWER SYSTEM IMPROVEMENTS
The Cify of Carlsbad ultimate sewer system will include the four existing interceptors and the future
South Agua Hedionda (SAH) Interceptor. The assignment of ultimate flows to the interceptor system is
made with the assumption of several future changes to the collection system, which were dicussed and
verifed with Cify Staff. Exhibit 2, provided in Appendix A, illusfrates the proposed ultimate sewer
interceptor system that was analyzed in this Master Plan Update. This map also identifies the interceptor
system to which each sub-drainage basin will ultimately discharge.
6.1.1 South Aqua Hedionda Interceptor
The SAH Interceptor will serve areas south and east of the Agua Hedionda Lagoon, and coimect with the
V/C Interceptor between reaches VCl3 and VCl4. The interceptor will convey Cify of Carlsbad flows
only. Previous planning studies for the SAH Interceptor included flow contributions from the Cify of
Vista Raceway Basin and the Cify of Oceanside's Leisure Area and Lake Lift Station. The Cify of Vista
has recently confirmed that they are no longer interested in discharging flows to the SAH Interceptor.
The conveyance of flows from Oceanside are no longer feasible because the eastem portion of Sub-basin
15A, which was previously planned for development and included a sewer extension east to Oceanside,
has now been designated as open space. The SAH Interceptor will serve Sub-basins 5A, 5B, 5D, 7C, 8,
13A, 14A, 15A, 15B, 16, 18A, 24A, and 24B. A new Uft station and an approximate one-mile long
forcemain will be included in the SAH Interceptor system.
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Figure 6-1 illusfrates the alignment and reach designations of the SAH Interceptor. The eastem portion of
the SAH Interceptor, along Sunny Creek Road and El Camino Real south of Cannon Road, has already
been constmcted. This portion of the interceptor is currentiy tributary to the NAH Interceptor. Another
portion of the interceptor in Cannon Road, west of El Camino Real, has also been constmcted, and the
Kelly Ranch Lift Station now lifts flow from tiiat pipeline into the NAH Interceptor. The remaining
portions of the SAH Interceptor, yet to be constincted, include the SAH Lift Station and forcemain. A
new gravity sewer will connect with the gravify line from the Faraday Business Park and discharge to the
SAH Lift Station. When the SAH Interceptor is complete, the Kelly Ranch Lift Station and both Faraday
Lift Stations will be abandoned.
6.1.2 Collector System Improvements
An expansion of the existing collector system will be required to connect future developments with
existing pipelines and interceptors. The size and alignment of these future collection pipelines are not
analyzed in this Master Plan Update. However, the discharge locations to the interceptors are identified
for the hydraulic analysis of the ultimate interceptor system. The assumed general alignments of these
major future collection sewers, future lift stations, and forcemains are shown on Exhibit 2.
A new lift station will be required to convey flows from Sub-basins 16 and 18A to the SAH Interceptor.
Flows from several sub-basins are currently being pumped "out-of-basin", and fiiture gravify sewers are
planned that will eliminate some existing lift stations. The lift stations planned for elimination include:
• Vancouver Lift Station - A gravify pipeline through LFMZ 25 will convey flows from Sub-basin
2B to the V/C Interceptor. Flows are currentiy pumped to the NAH Interceptor.
• Simsbury Lift Station - A gravify pipeline through LFMZ 25 will connect with a future gravify
pipeline from the Vancouver Lift Station and convey flows from Sub-basin 7A to the V/C
Interceptor. Flows are currently pumped to the NAH Interceptor.
• Villas Lift Station - A gravify pipeline will extend north from the existing lift station in a future
easement and connect with the future gravity line from the Simsbury Lift Station through LFMZ
25 to the V/C Interceptor. Flows from the Villas Lift Station, which serves several apartment
complexes, are currentiy pumped to the NAH Interceptor.
• Woodstock Lift Station - Flows from the approximately 20 single family residences served from
the Woodstock Lift Station will be conveyed by gravify through the future Calavera Hills
development in Sub-basin 7C to the SAH Interceptor. Flows are currently pumped to the NAH
Interceptor.
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1 1
AGUA
HEDIONDA
3AH LIFT
STATION
SAH3C
SAH4
SOUTH AGUA
HEDIONDA
1"=2000'
LEGEND
SEWER INTERCEPTOR SYSTEM
— GRAVITY SEWER
^— FORCEMAIN
— SIPHON
FIGURE 6-1
CITY OF CARLSBAD
FUTURE SOUTH AGUA HEDIONDA
INTERCEPTOR SEWER |Si ASSOCUTES. INC.
03-2003 Cartsbadeoi mxd
• Gateshead Lift Station - Flows from tiie approximately 25 single family residences served from
the Gateshead Lift Station wiU be conveyed by gravify tiirough the future Robertson Ranch
development in Sub-basin I4A to tiie SAH Interceptor. Flows are currently pumped to the NAH
Interceptor.
• Faradav Lift Stations No. 1 and 2 - A gravify pipeline will extend from Faraday Lift Station No.
2 to the SAH Interceptor, and discharge just upsfream of the future SAH Lift station. Most of this
pipeline has aheady been constmcted. Flows from Sub-basin 5B are currently pvunped to the
Vallecitos Interceptor.
• Kelly Ranch Lift Station - This temporary lift station will be replaced by the SAH Lift Station.
Flows from Sub-basin 8 are currently pumped to the NAH Interceptor.
• La Golondrina Lift Station - The Golondrina Lift Station cunently pumps Cify of Carlsbad flows
in Sub-basin 6B to tiie LCWD. A future gravify pipeline will convey flows from tiie Golondrina
service area to the Poinsettia Lift Station and Vallecitos Interceptor. This pipeline is also planned
to coUect flows from a smaU area in the southwest comer of Sub-basin ISB, which currently
discharges to the LCWD.
• Forest Lift Station - A gravify pipelme constmcted using a micro-tunneling constraction process
will convey flows from Sub-basin IC to the V/C Interceptor upsfream of tiie Buena Vista Lift
Station. Flows are currentiy pumped to the V/C mterceptor downstream of the Buena Vista Lift
Station.
6.2 CARLSBAD GROWTH DATABASE
Build-out projections for the Cify of Carlsbad have been recently updated and compiled into a Growtii
Database, which is maintained by the Cify. Growth projections are based on current development plans
and results of the 2000 Census. The City of Carlsbad Growth Database is parcel-based and includes
information on existing land use, as weU as growth potential. Growth data provided in the database
consists ofthe number of projected single family units, multi-family imits, and the estimated building area
for non-residential land use at build-out. The building area in tiie database is generally assumed at 25
percent of the parcel size, imless more detailed planning mformation was available
Over half of the projected growth m the City of Carlsbad sewer service area is associated with known,
planned developments in the eastem portion of the City. These developments include Kelly Ranch,
Villages of La Costa, Calavera HiUs, Mandana Properties, and Robertson Ranch, which are primarily
residential developments, the Carlsbad Oaks North and Faraday Busmess Parks, and Bressi Ranch, which
will have a mixed-land use. Development information for these large planned projects is typically
lumped onto a single existing parcel in the Growth Database, even if the project boundary encompasses
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SEWER MASTER PLAN UPDATE March 2003
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several existing parcels or drainage sub-basins. Layout maps in various development stages were
provided by the City for most of these projects and used to distribute the projected sewer flow to
appropriate sub-basins. The remainder of 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 the westem portions of the City.
The Growtii Database was originally provided by the City of Carlsbad at the start of the Master Plan
Update project. During the course of the project, several updates to the projected future growth were
provided by the City and incorporated into a modified database. The growth potential data in the City of
Carlsbad Growth Database used for this Maser Plan Update is summarized by Local Facility Management
Zone (LFMZ) in Table 6-1. The growth update indicates a slightly lower number of residential units and
more commercial/industrial area than what was projected in the last Master Plan Update. In Table 6-1,
the shaded rows identify LFMZs that are not within the Cify of Carlsbad sewer system boundaty or
sphere of influence.
Table 6-1
CITY OF CARLSBAD GROWTH DATABASE SUMMARY
LFMZ
No.
No. of Res. Units Non-Residential
Bldg Area (sqft) Comments LFMZ
No. SFDU MFDU
Non-Residential
Bldg Area (sqft) Comments
1 430 0 0 Downtown area; Unit counts from 5/15/02 LFMZ 1 update
2 25 146 39,656 3 second dwelling units counted as MFU
3 13 0 193,251
4 0 0 50,000
5 0 0 4,137,974 Includes Faraday Business Park and airport
6 185 0 89,988 Future church assumed at 9,100 sqft (25% coverage)
7 345 436 32,670 Calavera unit counts from 7/15/02 update; Future elem.sctiool
8 186 544 6,000 Kelly Ranch
9 41 0 428,100
10 750 320 0 villages of La Costa; Future elementary school
11 1,266 275 622;972 Villages of L.a Costa
12: 55; 0 20,000 Future church assumed af 20,000 sqft
13 0 18 1,482,142 24 room hotel expansion assumed at 1 hotel uni =.75 MFU
14 711 411 229,166 Unit counts from Robertson Ranch update; Future High School
15 807 158 303,798 Sycamore Creek; 8 second dwelling units counted as MFU
16 0 0 1,921,000 Carisbad Oaks North BP; Building area from 8/01/02 update
17 523 100 2,511,000 Bressi Ranch; 40,000 sqft for private school & daycare/church
18 308 0 2,262,817 140 condos counted as SFU
19 218 78 69,520 61 condos counted as SFU; 78 timeshares counted as MFU
20 687 24 73,450
21 185 210 0
22^_^ 168 286 53,280 149 condos counted as SFU
23 0 264 507,000 includes assisted living projecl (non-res & MFUs)
24 32 0
25 130 0 0
Totals 7,065 3,270 15,033,784 shaded rows indicate areas outside of the sewer service area
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6.3 FUTURE FLOW GENERATION FACTORS
Flow generation factors are used, in conjunction with the Cify's Growtii Database, to project ultimate
wastewater flows and distribute flows in the ultimate system hydraulic analysis. Unit flow generation
rates were developed and presented in Chapter 4 of this report based on 2001 flow data. These unit flow
factors were used to distribute flow in the existing system model. For design and planning purposes, a
more conservative approach to flow generation is used. The unit flow factors developed to project
ultimate wastewater flows from data in the Cify's Growth Database are listed in Table 6-2, which also
provides a comparison of flow generation factors used in previous planning documents.
Table 6-2
CARLSBAD WASTEWATER UNIT FLOW COMPARISONS
Land Use
Category
Existing System
(Based on 2001 meter data
artd/or water bilHrtg records)
1991 Master Plan 1997 Master Plan
Update
2002 Master Plan
for Future Flows
Single Family DU 195gpd/DU 220 gpd/DU 209 gpd/DU 220 gpd/DU
Multi-Family DU 220 gpd/DU 209 gpd/DU 160 gpd/DU
Faraday
Business Park
715 gpd/acre
561 gpd/10,000 sqft
Restaurants 6,500 gpd/10,000 sqft
Non-residential 1000 gpd/acre
918 gpd/10,000 sqft* 1,150 gpd/10,000 sqft
Commercial 1,230 gpd/10,000 sqft
Industrial 750 gpd/10,000 sqft
* Conversion from flow per acre to flow per building area based on an assumed building coverage of 25% of the parcel size.
The Cify's established planning value for wastewater flow is 220 gpd/EDU. Flow factors typically used
for design in sewer systems throughout San Diego Counfy range between approximately 208 gpd/EDU in
the Cify of Encinitas, to approximately 265 gpd/EDU in the Cify of Chula Vista. The Cify of San Diego
Water & Sewer Design Guide recommends the use of 90 gallons per capita day (gpcd). Based on an
average of approximately 2.5 to 2.6 persons per household, a flow factor between 225 and 235 gpd/EDU
would be recommended using the City of San Diego's design criteria. Based on these comparisons and
the calculated unit flow rate for current conditions, the previously established flow generation rate of 220
gpd/EDU is considered to be appropriate for flow projections for this Master Plan Update.
The Carlsbad Growth Database projects the number of fiiture multi-family units to be constmcted.
According to City Staff, muhi-family units are defined as apartment units or low-income housing units.
A lower flow factor for multi-family units was developed based on a research of water billmg records and
a comparison of unit flows used by other agencies. The multi-family unit flow factor was also applied to
hotel imits, timeshares, second housing units constmcted on existing residential parcels, and housing
densities in excess of 12 units per acre on development plans.
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SEWER MASTER PLAN UPDATE
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March 2003
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The non-residential land use flow factor is applied to building area projections in the Growth Database.
This broad category includes commercial, industrial, medical and office buildings. The composite unit
factor is based on an assumed mix of the land use types and is appropriate (and probably somewhat
conservative) for flow projections of the overall sewer system. Projections made using this factor may
not be representative of smaller areas with a single land use type. Flow projections for fiiture schools
were based on EDU conversions documented in the Carlsbad Municipal Code (Table 13.10.020c).
6.4 PROJECTED ULTIMATE FLOWS
Flow projections for fiihire developments were made by applying the unit flow factors, documented in
Section 6.3 of this report, to the future build-out data in the Growth Database. Parcels with identified
fiiture growth were then apportioned to sub-drainage basins using GIS techniques. Future flows were
added to the existing flows in each sub-basin to obtain ultimate flows. Upon review of the flow data it
was determined that a few of the newer residential areas in the collection system had existing sewer flows
(based on water meter records) but were also included in the Growth Database. The fiiture flow for these
parcels was subsequently deleted from the Growth Database used for this project.
The ADWF flow for the ultimate sewer system is projected to be approximately 9.9 MGD. This value
represents an increase of approximately 3.0 MGD, or 45 percent, over existing wastewater flows. Figure
6-2 presents historical flows and the projected ultimate flow, and makes a comparison with previous flow
projections. Table 6-3 lists the existing and projected fiiture flows by sub-drainage basin.
Figure 6-2
HISTORICAL AND PROJECTED ULTIMATE FLOWS
- 2003 Master Plan projections
1996 Ocean Outfall Capacity Reort projections
1992 Master Plan projections
1987 Master Plan projections
1985 1 990 1995 2000 2005 2010 2015 2020
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Table 6-3
PROJECTED ULTIMATE WASTEWATER FLOWS BY SUB-BASIN
Sub-
basin
Interceptor
System
Existing Units/Flow Projected Future Units and Flow Ultimate System Sub-
basin
Interceptor
System SFUnits Flow (gpm) SF Units MF units Bldg sqft Flow (gpm) SFUnits Flow (gpm)
IA V/C 153 113.0 16 0 0 2.4 169 115.4
IB V/C 208 47.4 0 0 0 0.0 208 47.4
IC v/c 118 16.0 0 0 0 0.0 118 16.0
1D v/c 428 139.3 37 0 0 5.7 465 144.9
1E v/c 1,302 350.4 42 0 0 6.4 1,344 356.8
IF v/c 560 180.2 6 0 0 0.9 566 181.2
1G v/c 266 265.7 14 0 0 2.1 280 267.9
1H v/c 606 201.4 69 0 0 10.5 675 211.9
11 NAH 945 183.8 172 0 0 26.3 1,117 210.1
1J NAH 949 148.0 74 70 0 19.1 1,023 167.1
2A V/C 583 146.9 0 143 39,656 19.1 583 166.0
2B V/C 223 30.2 0 0 0 0.0 223 30.2
2C NAH 1,412 191.8 25 3 0 4.2 1,437 195.9
3A V/C 244 178.9 13 0 0 2.0 257 180.9
38 V/C 0 108.0 0 0 165,351 13.2 0 121.2
3C Buena 0 41.2 0 0 27,900 2.2 0 43.5
4A Buena 1,252 227.5 0 0 50,000 4.0 1,252 231.5
4B NB 857 128.5 0 0 0 0.0 857 128.5
5A SAH 0 4.9 0 0 407,703 32.6 0 37.5
5B SAH 2 152.4 0 0 718,609 57.5 2 209.9
5C Buena 0 23.4 0 0 399,641 32.0 0 55.4
5D SAH 0 11.0 0 0 59,864 4.8 0 15.8
5E Buena 0 39.2 0 0 238,273 19.1 0 58.2
5F Buena 0 14.1 0 0 0 0.0 0 14.1
5G Vallecitos 0 39.3 0 0 770,099 61.6 0 100.9
5H Vallecitos 0 0.0 0 0 365,905 29.3 0 29.3
51 Buena 0 105.2 0 0 429,580 34.4 0 139.5
5J Buena 0 12.8 0 0 96,754 7.7 0 20.5
5K Vallecitos 5 43.4 0 0 651,536 52.1 5 95.5
6A NB 498 112.5 0 0 14,715 1.2 498 113.7
68*^' Vallecitos 0 0.0 111 0 0 17.0 111 17.0
7A V/C 527 77.2 103 0 21,780 17.5 630 94.7
78 NAH 448 75.8 0 117 10,890 13.9 448 89.7
7C SAH 383 51.9 242 319 23,913 74.3 625 126.2
8 SAH 133 18.0 161 474 6,000 77.7 294 95.8
9 NB 513 177.2 41 0 428,100 40.5 554 217.7
10A Vallecitos 0 0.0 207 0 23,913 33.5 207 33.5
108 Vallecitos 0 0.0 164 0 0 25.1 164 25.1
IOC Vallecitos 0 0.0 118 0 0 18.0 118 18.0
13A SAH 0 4.4 0 0 1,330,600 106.4 0 110.8
138 Vallecitos 0 113.0 0 0 151,542 12.1 0 125.1
14A SAH 0 0.0 530 78 388,310 120.7 530 120.7
148 NAH 1 3.4 181 333 23,872 66.6 182 70.0
Continued next page
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Dudek & Associates, Inc.
March 2003
Table 6-3 (Continued)
Sub-Interceptor Existing Units/Flow Pro, ected Future Units and Flow Ultimate System
basin System SF Units Flow (gpm) SF Units MF units Bldg sqft Flow (gpm) SF Units Flow (gpm)
15A SAH 0 0.0 46 100 0 18.1 46 18.1
15B SAH 4 55.5 589 80 303,798 123.2 593 178.6
16 SAH 0 0.0 0 0 1,921,000 153.7 0 153.7
17A Vallecitos 0 0.0 383 100 2,471,000 267.3 383 267.3
178 Vallecitos 0 0.0 140 0 40,000 24.6 140 24.6
18A SAH 0 0.0 0 0 2,221,000 177.7 0 177.7
188 Vallecitos 951 157.5 148 0 41,817 26.0 1,099 183.4
19A NB 414 61.0 11 0 0 1.7 425 62.7
198 NB 176 123.1 61 78 69,520 23.5 237 146.6
19C NB 400 60.3 121 0 0 18.5 521 78.8
19D NB 447 61.5 25 0 0 3.8 472 65.3
20A Vallecitos 556 79.3 215 0 0 32.8 771 112.2
208 Buena 291 40.4 50 0 13,450 8.7 341 49.1
20C NB 221 29.9 239 24 0 39.2 460 69.1
20D NB 92 12.5 78 0 60,000 16.7 170 29.2
20E NB 2 0.3 104 0 0 15.9 106 16.2
21A NB 138 20.6 62 53 0 15.4 200 36.0
218 NB 82 21.0 123 157 0 36.2 205 57.2
21C Vallecitos 0 36.9 0 0 0 0.0 0 36.9
22A V/C 0 19.0 0 0 0 0.0 0 19.0
228 NB 137 112.8 168 0 40,780 28.9 305 141.8
24A SAH 233 31.5 0 0 0 0.0 233 31.5
248 SAH 1 20.6 32 0 0 4.9 33 25.5
25 V/C 0 0.0 130 0 0 19.9 130 19.9
Totals: 16,761 4,721 gpm 5,051 2,129 14,026,871 2,130 gpm 21,812 6,851 gpm
6.80 MGD 3.07 MGD 9.87 MGD
(1) Flows from this sub-basin cun-ently discharge to Leucadia County Water District
(2) Flow projections are based on the following unit flows: 220 gpd per single family unit, 160 gpd per multi-family unit,
and 1,150 gpd/10,000 sqft of building area for non-residential flows.
6.5 OTHER AGENCY FLOW PROJECTIONS
Ultimate flow projections from other agencies that discharge to the Carlsbad sewer system were obtained
from recent planning documents. Table 6-4 lists the total projected ultimate flow to the Encina WPCF
from its member agencies, and allocates the flow to the Carlsbad interceptor systems. Flows from other
agencies are allocated to the same interceptor system to which existing flows are currently discharged.
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Table 6-4
EXISTING AND PROJECTED ULTIMATE ADWF TO THE ENCINA WPCF
Interceptor
System
Existing Flows (Aug 2001) Projected Ultimate Flows Interceptor
System Carlsbad
Flows
Ottier Agency Flows Total
Flow
Cartsbad
Flows
Other Agency Flows'' Total
Ftow
Interceptor
System Carlsbad
Flows Agency Flow
Total
Flow
Cartsbad
Flows Agency Flow
Total
Ftow
Vista/
Carlsbad 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 ttieir most recent master planing documents
From Table 6-4 it is apparent that flows from Carlsbad will increase within all existing interceptors except
the NAH Interceptor. The majorify of the flow increase to the V/C Interceptor is projected to be
generated by the Cify of Vista. The downstream reaches of this intercepetor convey Carlsbad flows from
the NAH and SAH Intercepetors, which are not included in the flow to the V/C Interceptor in Table 6-4.
In the ultimate system, it is projected that reaches VCl4 and VAl5 will convey an additional 3.9 MGD of
flow from the Cify of Vista and an additional 1.9 MGD from the Cify of Carlsbad.
The ultimate flows apportioned to the Buena and Vallecitos Interceptors will exceed the capacify of the
existing pipelines during peak flow conditions. The Cify of Vista is planning to divert a portion of their
flow from the Buena Interceptor to the Vallecitos Interceptor in the fiiture, and the VWD is planning a
replacement of the Vallecitos Interceptor with increased capacify. Since the Cify of Carlsbad leases flow
capacity in the Buena Interceptor and has a minority capacity ownership in the VaUecitos Interceptor, an
ultunate hydraulic analysis accounting for upstream agency flows will not be performed on these
Interceptors. Projected peak flows from Carlsbad are instead summarized and compared to existing
capacity agreements.
6.6 ULTIMATE INTERCEPTOR SYSTEM HYDRAULIC MODEL
Analysis of the ultimate interceptor system was accomplished by adding the SAH Interceptor to the
existing system model. Physical data for the SAH Interceptor was obtained from the existing system GIS
for portions that have already been constmcted, and available design drawings. The SAH Lift Station was
evaluated assuming variable frequency drive pumping units. Interceptor discharge locations for sub-
basins were re-assigned, as appropriate, to reflect planned changes to the ultimate system. The projected
City of Carisbad
SEWER MASTER PLAN UPDATE
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March 2003
6-9
ADWF based on build-out of the sub-basins (Table 6-3) was then input to the model for intemal flows.
Extemal flows from other agencies were evaluated for the V/C and NB Interceptors (Table 6-4).
Hydraulic analyses were performed to determine the ability of the interceptors to convey projected peak
flows. To calculate the PDWF, the dry weather peaking curves developed for the City of Vista and
Leucadia/Encinitas based on existing flows (Figure 5-1) were "scaled up" to reflect the higher base loads
in the ultimate system. The unit peaking curves for residential and non-residential flows within Carlsbad
(Figure 5-2) were applied to the projected ultimate average flows in each sub-basin.
PWWF analyses were performed on the V/C and NB Interceptor systems. The intemal and extemal
defect flows, based on existing wet weather meter data, were increased by 20 percent in the ultimate
system to account for aging of the pipelines and increased inflow from a larger collection system.
Intemal defect flows for the NAH, SAH, and Vallecitos Interceptors, and the NB Interceptor upstream of
the NB Lift Station could not be determined from existing meter data. The NAH, SAH, and upstream NB
Interceptor systems were analyzed with peak dry weather flows, and evaluated based on gravity sewers
flowing 75 percent full.
City of Carlsbad flows were analyzed in the Buena and Vallecitos Interceptors and the peak flows
compared to existing capacify rights. For the Buena Interceptor, the intemal I&I calculated for the
existing system was increased by 20 percent. This same defect flow was assumed for the Vallecitos
Interceptor in the ultimate analysis, which is considered a valid assumption as this pipeline ages since
both interceptors share a common alignment over most of the their length.
6.7 CAPACITY ANALYSIS RESULTS
Flow analysis results from the SewerCAD uhimate system model are presented graphically for each
interceptor system and compared to the gravity pipeline capacities. The graphs illustrate the composite
peak flow in each pipeline segment over the course of the 24-hour flow simulation. Flows and capacities
are schematically illustrated according to the reach designations shown in Figure 3-1. Where lift stations
are included in the interceptor, the lift station name and firm pumping capacify are indicated on the graph.
6.7.1 Vista/Carlsbad Interceptor
Figure 6-3 illustrates the projected ultimate PDWF in the V/C Interceptor, and provides a comparison
with the pipeline design capacity (d/D = 75%). At the upstream end of Reach VCl, the Cify of Vista and
Oceanside contribute a collective projected peak flow of approximately 15.2 MGD. Between the Buena
Vista and Agua Hedionda Lift stations, the V/C Interceptor collects flow from the Home Plant Lift
Station and the NAH Interceptor. Flow from the SAH Interceptor is added downstream of the Agua
Hedionda Lift Station at Reach VCl4. From this graph it is apparent the reaches downsfream of VCIO
will need to be upsized based on fiiture peak dry weather flows.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE March 2003
6-10
Figure 6-3
V/C INTERCEPTOR WITH PROJECTED PEAK DRY WEATHER FLOWS
•<3 Ktx <b <b <b ^C, \ O (.fo <S? ^ <b f'b r'y r'l (-> (-N f ^
- 75% Full Capacity •Projected Peak Dry Weather Flow
While the flow information presented on Figure 6-3 is informative, historical I&I rates to the V/C
Interceptor are very high, and replacement sewers must be designed based on the projected PWWF.
Figure 6-4 illustrates results from the PWWF analysis, and makes a comparison with existing pipeline
capacities. For this analysis, a peak I&I rate of 6.1 MGD was added to Cify of Vista projected peak dry
weather flows. The I&I attributed to Carlsbad, 5.6 MGD, was disfributed two different ways. One flow
scenario distributes the I&I along the length of the V/C Interceptor. The other, more conservative
scenario, assigns most of I&I to the upstream Reach V1, with the remainder at the confluence with the
NAH Interceptor. As stated previously, it is not known how much I&I is currentiy confributed by the
NAH Interceptor. Although the intemal I&I rate in the ultimate system model was increased by 20
percent over the existing I&I rate, it is noted that I&I was not included for the SAH Interceptor. Flows
entering the V/C Interceptor at the upsfream end of Reach VCl 4 are therefore based on the projected peak
dry weather flow from the SAH Interceptor.
City of Carisbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
6-11
Figure 6-4
V/C INTERCEPTOR PEAK WET WEATHER FLOW
~* Full Pipeline Capacity
Projected PWWF - Internal I/I applied at VCl & VC10
' ' Proiected PWWF - Internal I/I distributed
From Figure 6-4, it is apparent that the reaches downstream 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 conshuction as a 48-inch diameter
pipeline, may flow full during severe storm events.
6.1.1 North Agua Hedionda Interceptor
The projected ultimate ADWF for the NAH Interceptor is approximately 1.07 mgd, which is less that the
existing ADWF of 1.3 MGD. The capacify of the NAH Interceptor was determined to be sufficient to
convey existing flows, with the exception of several short reaches. Therefore, additional analysis of this
interceptor system was not performed with ultimate system flows. A discussion of the capacify of the
NAH Interceptor is provided in Section 5.3.3 of this report.
City of Cartsbad
SEWER MASTER PLAN UPDATE
6-12
Dudek & Associates, Inc.
March 2003
6.1.2 South Agua Hedionda interceptor
The projected ultimate PDWF and design capacify of the SAH Interceptor are tilustrated on Figure 6.5.
The upstream sewer along El Camino Real and Sunny Creek Road (SAHTIE and SAHTIG) is also
depicted in Figure 6-5, since this portion of the SAH Interceptor system will convey the most flow. As
shown on the graph, there is projected to be ample capacify in the gravify interceptor system. The PDWF
through the SAH Lift Station is projected to be approximately 3.0 MGD. The lift station capacity will
need to be greater to convey peak wet weather flows.
Figure 6-5
SOUTH AGUA HEDIONDA PEAK DRY WEATHER FLOW
12
1 1 s
W 10
I ' u. 8 ra a>
9: 7 >«
ra D
Q. ro
O 5 a c
Q.
£ 3
> 2
ra
I
SAH
Lift
station
I
—I—I—i—i—r
^ ^
c,^ cT <b^
ij^ \>^" oN" oS'"' ^ ^ x5^" <^ -<>^ -C^ <^ .<^^ <S-^ ^S^"" .v<5^ .^S-^ .v<^ .^-"^ .is^
<r =r # # #
Full Pipeline Capacity
75% Full Capcity
Projected Peak Dry Weather Flow
6.1.3 Buena Interceptor
The sub-drainage basins served by the Buena Interceptor in the ultimate system are planned to be the
same as those served in the existing system. Flows to this interceptor are projected to increase by
approximately 20 percent. As discussed in Section 5.2.2 of this report, the existing flow in Table 6-4 for
the Buena Interceptor is lower than current metered flows. Flows used in the ultimate system analysis for
the Buena Interceptor are based on fiiture flows added to the existing meter flows, and result in a total
ADWF of approximately 1.2 MGD. Figure 6-6 illustrates the projected ultimate PWWF generated by
Carlsbad in the Buena Interceptor, and makes a comparison with existing capacify rights. As shown on
the chart, the current leased capacify is projected to be sufficient to convey ultimate flows.
City of Cartsbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
6-13
6 .0
Figure 6-6
PROJECTED CARLSBAD PWWF IN THE BUENA INTERCEPTOR
81 Bl B2 B2 B2 82 B2 B4 84 B4 B4 B4 B4 B5 B6 B7 B7 B8 B8 BS
6.1.4 Vallecitos Interceptor
Figure 6-7 illustrates the projected ultimate PWWF generated by Carlsbad in the Vallecitos Interceptor,
and makes a comparison with the existing capacify rights of 5.0 MGD. Although flows to this interceptor
are projected to increase by approximately 70 percent, the current leased capacity is projected to be
sufficient to convey ultimate flows, as shown on the graph.
Figure 6-7
PROJECTED CARLSBAD PWWF IN THE VALLECITOS INTERCEPTOR
Q 5.0
O 5
5 4.5 o u.
•iS 4 0 o a.
1- 3.5
u
ro
Q.
5 3.0
•o
CO ra 2 .5 0) _i
0) .S 2.0
u
Q.
>
ro
O
1 .5
1 .0
5 M GD Leased
C a p a c ity
•Carlsbad Leased Capacity
•Projected U itim ate PWWF
J
V3 V3 V3 V4 V4 V4 V4 V4 V5 V5 V6 V6 V6 V6 V7 V7 V8 V8
City of Cartsbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
6-14
6.1.5 North Batiquitos Interceptor
The upstream portion of the North Batiquitos Interceptor conveys only Cify of Carlsbad flows. This
portion ofthe Interceptor was analyzed with the projected PDWF and compared to the design capacify of
the gravify pipelines, as illustrated in Figure 6-8. As indicated on the graph, there is ample capacity in the
upsfream gravity pipelines to convey the projected ultimate flows. Flow to the North Batiquitos Lift
Station consists of flow from the main interceptor and the northern trunk line, Reach NBT3B. The
PDWF to the lift station is projected to be 2.1 MGD (1,500 gpm).
Figure 6-8
CARLSBAD PDWF IN THE UPSTREAM NORTH BATIQUITOS INTERCEPTOR
ra a.
t
ra 9)
IL
o ra a ra o
<D C
~
CL
> re I-
O
NB4
The North Batiquitos Lift Station consists of two duty pumps with fixed speed drives. During peak flow
periods one pumping unit is projected to operate continuously, with the second pump cycling on and off
The North Batiquitos Interceptor downsfream of the lift station was analyzed with both pumps in
operation. City of Carlsbad flows in this portion of the Interceptor are shown on Figure 6-9, together with
the fiill gravity pipeline capacities and leased capacity in the Occidental Sewer. Based on this analysis.
City of Carisbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
6-15
the existing leased capacify is projected to be approximately 4.0 MGD in excess of what is required to
convey projected peak ultimate flows.
Figure 6-9
CARLSBAD PWWF IN THE DOWNSTREAM NORTH BATIQUITOS INTERCEPTOR
Q
ro Q:
o
ro o a.
o ro a re
O
4) C
ai a
'£
>
C3
NB9 NB9
Full Pipeline Capacity Carlsbad Peak Wet Weather Flow Carlsbad Leased Capacity
6.7.7 Lift Stations
The projected ultimate PWWF through each of the lift stations included in the sewer interceptor system is
shown in Table 6-5. Also provided in this table is a comparison with existing lift station capacities and
the velocity in the lift station force mains based on the projected peak flow. For interceptor systems
without existing wet weather data (gravify pipelines analyzed based on the PDWF), the PWWF at the lift
station is estimated based on the general wet weather peaking factors used in the previous Master Plan.
City of Cartsbad
SEWER MASTER PLAN UPDATE
6-16
Dudek & Associates, Inc.
March 2003
Table 6-5
PROJECTED PEAK FLOWS AT LIFT STATIONS
Lift Station Name
Interceptor
Systern
Station Capacity' Projected Ultimate Flow Force
Main
Diam.
Max. UIL
Velocity in
FM (fps)
Lift Station Name
Interceptor
Systern (gpm) (MGD) PDWF (MGD) PWWF
(MGD)
Force
Main
Diam.
Max. UIL
Velocity in
FM (fps)
Buena Vista V/C 14,000 20.16 16.2 26.0
16"&24" 9.5
Buena Vista V/C 14,000 20.16 16.2 26.0 24" 12.8 Buena Vista V/C 14,000 20.16 16.2 26.0
2-16" 144
Agua Hedionda V/C 16,000 23.04 21.2 31-33'^' 2-18" 144
Foxes NAH 2,600 3.74 1.9 2.6 12" 5.1
South Agua Hedionda SAH — — 3.0 4.2 14" 6.1
North Batiquitos NB 2,250 3.24 2.1 2.9 14" 4.7
(1) Existing duty capacity with one pump out-of-service
(2) Projected PWWF flow varies depending on the distribution assumptions of l&I In the Carisbad system.
(3) Existing wet weather data not available. PWWF assumed at 1.4 x the PDWF
For the remaining lift stations in the sewer collection system, only the service area of the Simsbury lift
Station is expected to increase significantiy. Although the Simsbury Lift Station is ultimately planned to
be abandoned once a gravify line is constmcted to the V/C interceptor through LFMZ 25, it may first
serve future development in the west portion of Sub-basin 7A. Based on the Cify's Growth Database, an
additional 103 EDUs are planned, with a corresponding projected flow increase of approximately 16 gpm.
City of Carisbad
SEWER MASTER PLAN UPDATE
Dudek & Associates, Inc.
March 2003
6-17
CHAPTER 7
RECOMMENDATIONS
Wastewater flow generated within the Cify of Carlsbad is projected to increase by approximately 45 percent
over existing flows, to a projected ultimate flow of approximately 9.9 MGD by tiie year 2020 (shown
previously on Figure 6-2). This chapter summarizes recommended improvements to the existing sewer
interceptor system required to adequately convey, pump, freat and dispose of the projected ultunate
wastewater volumes. Jomt agency agreements, capacify agreements with the Encina WPCF, potential fiiture
flows from other agencies, and inflow and infiltration are also discussed relative to buildout conditions. A
recommended Capital Improvement Program is provided at tiie end of the chapter with an opinion of probable
constmction costs for each recommended project.
7.1 VISTA/CARLSBAD INTERCEPTOR IMPROVEMENTS
The V/C Interceptor Sewer collects wastewater from the Cify of Vista and the northem and downtown areas
ofthe Cify ofCarlsbad. The V/C Interceptor also coUects flow from tiie NAH Interceptor, and wiU coUect
future flows from the SAH Interceptor. Approximately 2.5 miles of gravify pipeline m the V/C Interceptor
are currently being replaced to increase capacify between the Buena Vista Lift Station force main and the
Agua Hedionda Lagoon crossing (Reaches VC5-VC11 A), For the purposes of this Master Plan Update, this
current replacement project is considered a part of the existing V/C Interceptor.
Additional replacement projects are recommended to increase the capacify of the interceptor based on
projected peak flows. The projected PWWF in the V/C Interceptor is shown on Figure 7-1, together with the
capacify of the existing pipelme reaches and the recommended pipeline capacities. The design capacify ofthe
new pipelines is calculated based on the average slope of the existing reach and a Manning's coefficient ("ri")
of 0.012, assuming that the fiiture pipe will be PVC-lined. The recommended projects are summarized in
Table 7-1, together with an opinion of the probable constraction cost, and discussed in the foUowing sections.
It is noted that the ultimate PWWF in the V/C Interceptor projected in this Master Plan Update is slightly
higher than the peak flows projected in the 1992 Master Plan Update. While the projected ultimate ADWF to
the V/C Interceptor from the Cify of Carlsbad is approximately 40 percent less than the flow projected in
1997, peak flows in the V/C Interceptor are higher as a result of tiie I&I mvestigation performed in this
Master Plan Update. Peak flows from the ultunate PWWF analysis in the downsfream reach of the V/C
Interceptor (Cify of Vista and Carlsbad flows) are projected to be approximately 2.4 times the ADWF. The
analysis performed in the 1992 Master Plan used a standard peaking equation, which resulted in a peak flow
that was 2.0 times the ADWF in the downsfream reaches ofthe V/C Interceptor.
City of Carisbad Dudek & Associates, inc.
SEWER MASTER PLAN UPDATE 7-1 March 2003
1 5
Figure 7-1
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 VC1 & VC1 1
" Proiected PWWF - internal I/I distributed
Table 7-1
SUMMARY OF V/C INTERCEPTOR RECOMMEND IMPROVEMENTS
Reach
ID
Projected
Ult.
PWWF
(MGD)
Existing Pipe Replacement Pipe
Unit
Cost>"
($/lin. ft.)
Probable
Construction
Cost'"
Reach
ID
Projected
Ult.
PWWF
(MGD)
Length
(feet)
Avg.
Slope
(ft/ft)
Diam.
(in.)
Full
Capacity
(MGD)
Diam'^'
(In.)
Design
Capacity
(MGD)
Full
Capacity
(MGD)
Unit
Cost>"
($/lin. ft.)
Probable
Construction
Cost'"
VC3 26.0 3,350 0.0020 36 20.7 42 28.5 31.6 $568.20 $ 2,570,000
BVLS'^' 26.0 --~ ~ ----$ 735,132
VC4-FM 26.0 3,840 NA 16"&24" 24 26.0 ~ $240.00 $ 1,244,000
VCl IB*"' 33.0 915 0.0008 42 18.4 54 35.6 39.0 $730.50 $ 2,900,000
AHLS'*' 33.0 ~ -~ ~ -~ --$ 6,250,000 VC12-FM 33.0 200 NA 2-18" ~ 36 33.0 ~ $360.00 $ 6,250,000
VCl 3 33.0 3,510 0.0010 42 20.5 54 39.8 43.7 $730.50
$10,200,000 VCU 36.6 5,059 0.0009 42 19.6 54 37.8 41.4 $730.50 $10,200,000
VCl 5 36.6 1,772 0.0009 42 19.6 54 37.8 41.4 $730.50
$10,200,000
(1) Required diameter with fhe existing slope to convey the design capacity with the pipeline flowing 75% full
(2) Unit construction costs for gravity pipelines based on recent cost data from the 2001-2002 V/C Sewer Replacement
Project. Force main unit costs are based on $10/diameter inch.
(3) Opinion of probable constmction costs are order of magnitude planning costs. Costs exclude engineering, administrative,
environmental and legal costs and include a 35% construction contingency.
(4) Replacement of this reach will include a new bridge crossing over the Agua Hedionda Logon. The cost includes an
estimated cost for the bridge of $1,744,000 (developed by W. Koo & Assoc. in the April 2001 Design Report)
(5) Lift station costs include both capacity increase and rehabilitation costs, as defined in the City's current CIP. AH Lift
Station upgrade based on Krieger & Stewart 2000 Preliminary Design Report, which includes replacement of the FM.
City of Cartsbad
SEWER MASTER PLAN UPDATE 7-2
Dudek & Associates, Inc.
March 2003
7.1.1 Upper V/C Interceptor Recommended Improvements
Figure 7-2 illustrates the recommended capacify improvements to the upper V/C Interceptor. Recommended
pipeline diameters are shown for the replacement pipelines. In addition to the gravify pipeline replacement
recommended for Reach VC3, capacify improvements are recommended for the Buena Vista Lift Station and
force main. Pumping units were last replaced at the Buena Vista Lift Station in 1994. The reported firm
capacify of tiie lift station is 14,000 gpm, and the projected uhimate PWWF at the station is approximately
18,000 gpm. The capacify of the Buena Vista Lift Station has never been confirmed due to existing
downsfream capacify limitations. Because of tiie 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 capacify with the existing pumps and a larger forcemain.
The existing Buena Vista Lift Station force main (Reach VC4) consists of parallel pipelines (24- and 16-inch
diameter) for most of its lengtii. It is recommended that a new 24-inch diameter force main replace the 16-
inch force main and parallel the existmg 24-inch force main for its entire length. In addition to increasing the
station capacity, the new parallel force main wUl reduce peak velocities and increase reliabilify.
7.1.2 Lower V/C Interceptor Recommended Improvements
Figure 7-3 illusfrates the recommended capacify improvements to the lower V/C Interceptor. It is
recommended that Reach VCl IB and Reaches VCl3 through VCl5 be replaced with a 54-inch diameter
pipeline. This pipe size assumes that the existing flat sections in Reach VCl5 can be eluninated in the new
design, and the pipeline slope for Reaches VC14 and VC15 wiU be a minimum of 0.09 percent. If the
pipeline wUl have a slope of less tiian 0.09 percent, a 60-inch diameter pipeline wiU be required for Reaches
VC14 and VCl5 to satisfy City design criteria.
It is recommended tiiat the capacify of the Agua Hedionda Lift Station be increased to a minunum of 33 MGD
(23,000 gpm), which is the projected PWWF through the station. A new 36-inch diameter force main is also
recommended to replace the existing paraUel 18-inch diameter force mains (Reach VCl2). There are several
deficiencies with the existing Agua Hedionda Lift station, including an imdersized wet weU, lack of fiiU
operational redundancy, insufficient space around the pumping units, and problems related to the age and
general condition ofthe station. A Preliminary Design Reportfor Agua Hedionda Lift Station Upgrade, dated
March 7, 2000 was prepared for the Cify. Recommendations from the report include replacement ofthe
existing lift station with the exception of the emergency generator buUding. The recommended project
includes five new pumpmg units for a firm pumping capacity of 30 MGD, and a new headworks, wet well,
confrol bmlding, 2.5 MG emergency storage basin, and 36-inch diameter force main. As tiie resuh of tiiis
Master Plan Update analysis, the design flow tiirough this station should be increased from 30 MGD to at
least 33 MGD.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 3 March 2003
CITY OF OCEANSIDE
UPGRADED BUENA VISTAl |VC3
LIFT STATION
CAPACITY = 18,000 GPM
_J SEWER SERVICE AREA BOUNDARY
INTERCEPTOR SEWER
— RECOMMENDED PROJECT
— RECOMMENDED FORCEMAIN PROJECT
GRAVITY SEWER
kir.. . REACH DESIGNATION &
'-^^ ' EXISTING DIAMETER
FIGURE 7-2
UPPER V/C INTERCEPTOR
RECOMMENDED IMPROVEMENTS DUDEK & ASSOCIATES. LNC.
03-2003 Cai1sbail702.mxd
I NAH4 - iel
AGUA
24-:
UPGRADED/RELOCATED'
AGUA HEDIONDA
LIFT STATION
012-181
HEDIONDA
LAGOON
«OAO
1"=2000'
LEGEND
^3 SEWER SERVICE AREA BOUNDARY
INTERCEPTOR SEWER
RECOMMENDED PROJECT
RECOMMENDED FORCEMAIN PROJECT
— GRAVITY SEWER
^— FORCEMAIN
PALOMAR AIRPORT ROAD
V8 - 42-1 VC15
NEW DIAMETER: S4"|
ENCIN/i
WPCF
CO-""
FIGURE 7-3
LOWER V/C INTERCEPTOR
RECOMMENDED IMPROVEMENTS DUDEK & ASSOCUTES, INC. I
03-2003 Cailsba(1703.m)cd
7.2 SOUTH AGUA HEDIONDA INTERCEPTOR IMPROVEMENTS
Most of the South Agua Hedionda Interceptor has been constmcted. The remaining portions of the SAH
Interceptor yet to be installed are the SAH Lift Station and forcemain. The force main will have an
approximate length of5,380 feet and be constmcted m the future alignment of Caimon Road. A gravity sewer
will be constmcted with the forcemain that will connect with a gravity line in Faraday Road and convey flows
from the Faraday Busmess Park and to the SAH Lift Station. After completion of these projects, the two
Faraday Lift Stations and the Kelly Lift Station will be removed. The recommended sizes for the remaining
the SAH Interceptor projects are illustrated on Figure 7-4.
7.3 LIFT STATION IMPROVEMENTS
A capacity analysis of the lift stations included in the major interceptor systems was performed and
documented in Section 6.7.7 of this report. Capacity improvements based on projected ultimate peak flows
are recommended for the Buena and Agua Hedionda Lift Stations.
A detailed survey of the lift stations with respect to the condition, code compliance, standby power and
capacity was performed as part of the 1997 Master Plan Update. A summary of the pertinent recommended
improvements is provided in Table 7-2. For each station, the installation of gas detectors to monitor for
hydrogen sulfide and other combustible gases was recommended. This is a requirement of existing codes
included in Titie 8 of the Califomia Code of Regulations and the National Fire Protection Association Article
820. Continuously operating ventilation fans and airflow switches were also recommended for code
compliance. It was recommended that an alarm be added for ventilation fan failure. Each of the station wet
wells was found to have a mercury float that needs to be modified/changed to meet the requirement of a Class
1, Division 1 section of the National Elecfrical Code.
Table 7-2
LIFT STATION RECOMMENDED IMPROVEMENTS
Construction/ RECOMMENDED IMPROVEMENT
Lift Station Name Rehabilitation Gas Ventilation Alarms
stanaoy
Generator
Connector
Wiring Float Switch
Date Detectors Modifications Alarms
stanaoy
Generator
Connector Repairs Modifications
Terramar 1972 X x x x X
Chinquapin 1959/2001 X x X
Home Plant 1963/1991 X x X X
Gateshead 1985 X x X X
Vancouver 1981 X X x X X
Simsbury 1985 X x X X
Villas 1983 X x X
Woodstock 1983 X X X X
North Batiquitos 1997 x X
La Golondrina 1981 x x x x X X
City of Carisbad
SEWER MASTER PLAN UPDATE 7-4
Dudek & Associates, Inc.
March 2003
1"=2000'
LEGEND
^2 SEWER SERVICE AREA BOUNDARY
INTERCEPTOR SEWER
RECOMMENDED PROJECT
RECOMMENDED FORCEMAIN PROJECT
FIGURE 7-4
SOUTH AGUA HEDIONDA INTERCEPTOR
RECOMMENDED IMPROVEMENTS .JiSSOOATES, INCl
03-2003 Car1sbad704.mxd
7.4 POTENTLU:. FLOWS FROM OTHER AGENCIES
Currently, interceptors owned or joinfly owned by Carlsbad convey flows from the City of Vista, fhe City of
Oceanside (through tiie City of Vista connection), tiie LCWD, and the Encinitas Sanitary Division of the City
of Encinitas (through the LCWD connection). Future opportunities to convey additional flows were
evaluated in this Master Plan Update. The City of Oceanside had previously expressed a desire to convey
flows from their Leisure and Lake Lift Stations into an eastward extension ofthe SAH Interceptor. The trunk
sewer extension, previously identified as SAHT2A in tiie 1992 Master Plan, was located in an area that is now
designated as open space. City staff have stated that it is highly unlUcely that tiiis truak sewer would ever be
constracted, and these additional flows from Oceanside were not included in the ultimate flow projections.
Also, the City of Vista no longer desires to convey flows by gravity from the Raceway Lift Station service
area to a separate eastward extension of the SAH Interceptor. As a resuh of this and additional environmental
consfraints, the previously planned trahk sewer, identified as Reaches SAHTIA-ID m the 1992 Master Plan,
wiU no longer be constracted. Wastewater flows from Sub-basins 18A and 16 wiU now be pvunped and
discharge to a downsfream location on the SAH Interceptor.
In the far southeast comer of the City ofCarlsbad service area, one possible future aimexation may occur that
would affect wastewater flows. Wastewater from Carlsbad Tract 93-04 (28 units) currently flows to the
LCWD Meadows HI Pump Station. Wastewater from these units will flow by gravity into the Vallecitos
Interceptor once a gravity pipeline is constmcted. When tiie gravity system is in place, tiie LCWD may want
to de-annex 68 units within its boundary, which wou ld aUow the Meadows III Pump Station to be abandoned.
There is projected to be ample capacity in the Vallecitos Interceptor for these additional flows.
7.5 JOINT TRANSMISSION SYSTEMS
The District shares ownership or leases capacity in several facilities with the City of Vista, the Buena
Sanitation District, the Vallecitos Water Disfrict, the Leucadia County Water District and Encmitas Sanitary
Division of the City of Encinitas. These facUities include the V/C Interceptor, the Buena Interceptor, the
Vallecitos Interceptor and the Occidental Sewer. The following discussions provide an overview of these
facilities relative to projected ultimate wastewater flow conditions.
Vista/Carlsbad Interceptor. The Vista/Carlsbad Interceptor ownership percentages and capacity rights from
the 2001 draft agreement with the City of Vista are provided in Table 3-1 of this report. Based on the
agreement, Carlsbad has a 43.9% ownership in the downsfream reach of the V/C Interceptor (VCl5).
Projected flows for Carlsbad are now lower, and ttie percentage of flow for Carlsbad in this reach is now
estimated at 37.2%. It is recommended that a new agreement be negotiated based on the updated flow
projections in this Master Plan Update.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 5 March 2003
Buena Interceptor. The City of Carisbad leases capacity in tiie Buena Interceptor. The existing lease
agreement was last modified in 1987 to lease an additional 0.8 MGD of capacity. It is estimated tiiat Carisbad
wiU not require any additional capacity in this interceptor to convey projected ultimate flows. It is noted that
the existing Buena Interceptor does not have the capacity to convey bmldout flows based on ultimate flow
projections for the BSD and the City of Vista Raceway Basin. The City of Vista mcludes a project in tiien
2001 Master Plan to constmct a new force main from the Buena and Raceway Lift Stations to the Vallecitos
Interceptor.
Vallecitos Interceptor. The City of Carlsbad cuirently leases 5.0 MGD of capacity in the Vallecitos
Interceptor. City ofCarlsbad ultunate peak flows in this interceptor are projected to be less than 3.5 MGD.
The existing interceptor does not have tiie capacity to convey buildout flows forthe VWD and future flows
from the BSD and the City of Vista Raceway Basin. The VWD plans to replace tiie existmg VaUecitos
Interceptor with a larger capacity interceptor. Based on projected ultunate flows, Carlsbad could reduce their
leased capacity to approxunately 4.0 MGD.
Occidental Sewer. The Occidental Sewer is jointly owned by tiie City of Carlsbad, the ESD and tiie LCWD.
Carlsbad's current ownership capacity, which is estimated to be approximately 8.5 MGD, is projected to be
approxunately 4.0 MGD m excess of what is required to convey tiie ultunate PWWF. The LCWD projects
that they wiU need to acquire an additional 1.6 MGD of conveyance capacity in tiie Occidental Sewer in then
most recent Master Plan. It is recommended tiiat ttie ownership capacities defmed in tiie 1972 Occidental
Pipeline Agreement be updated based on current flow projections.
7.6 TREATMENT CAPACITY REQUIREMENTS
Wastewater generated witiiin the City of Carlsbad service area is coUected and conveyed to tiie Encina Water
Pollution Confrol FacUity (WPCF) for freatment and subsequent disposal. Carisbad currently owns a total
freatinent capacity of 9.24 MGD in the Encina WPCF, and has requested additional capacity to total 10.26
MGD in tiie planned Encina WPCF Phase V expansion. Existing ADWF generation is approximately 6.8
mgd. Based on projected wastewater production increases, the City of Carlsbad is projected to generate an
average dry weather volume of approximately 9.87 MGD at buildout, which is anticipated to occur by the
year 2020.
The requested treatment capacity is approximately 0.4 MGD, or 4 percent greater than the projected ultimate
flows. However, should the "per capita" water usage of customers decrease or increase m the fiiture, the
projected freatment capacity surplus would likewise be reduced or increase. As a policy matter, the Board of
Directors needs to establish the standard for redundancy that it believes pmdent for treatment capacity at the
EWA. The estabUshed redundancy standard wUl influence the final decision regarding the City's
participation in fiiture expansion projects at the EWA facUity.
City of Carisbad Dudek & Associates, I nc.
SEWER MASTER PLAN UPDATE 7- 6 March 2003
7.7 OCEAN OUTFALL CAPACITY
Wastewater tiibutary to the Encina WPCF is freated to secondary standards and discharged to the Pacific
Ocean through tiie Encina Ocean OutfaU. Capacity rights in the outfaU are based on tiie PWWF. This outfall
facility has an estimated capacity of 104.9 MGD. The District owns 24.32 percent of tiie available capacity,
or 25.51 MGD. Because flows to the Encina WPCF from tiie City of Carisbad are determined by subfracting
upsfream agency flows, tiie peak flow contribution from Carlsbad cannot be easily determined from meter
records. In the ultimate system hydrauUc model, approximately 6.9 MGD of peak I/I generated withm
Carlsbad was included in tiie model. This flow rate is based on historical flow data from storm events and an
assumed I/I mcrease of twenty percent to account for aging ofthe pipelines and expansion ofthe collection
system. By removing aU flow from upsfream agencies m the model, the ultunate PWWF to the Encina WPCF
from the City of Carisbad is estimated to be approximately 25.0 MGD. The projected PWWF is
approximately 2.5 tunes the ADWF and is just under tiie City of Carlsbad's existing outfaU capacity rights.
Therefore no change is recommended to Carlsbad's proportion of the outfall capacity.
7.8 INFLOW AND INFILTRATION STUDY
Flow increases in the V/C Interceptor during storm events are very high due to I&I from both Vista and
Carlsbad, which can be observed from existing flow records (see Appendix C). Instantaneous storm water
flows origmating in tiie Carlsbad portion ofthe V/C Interceptor can be estimated from subfracting Vista Meter
flows from flows at the Encina WPCF. However, there is no fiirther data to detemiine the primary locations
of the storm water ingress. Pipelines along the Buena Vista Lagoon, the low-lying downtown area, and
pipelines in the NAH Interceptor along tiie Agua Hedionda lagoon are considered lUcely sources. A detailed
I&I study is recommended to locate the I&I sources, estimate the volume increase due to prolonged storm
water induced infiltration, and recommend improvements to reduce the flows. In the absence of such detailed
information, the I/I rate used in the ultimate system hydraulic analysis was calculated based on the foUowing
procedure:
• l/l rates were determined from recorded EWA meter data from the storm event on November 24,2001, in
which 1.3 inches of rain fell in 4 hours.
• The measured l/l was added to the PDWF, so that peak storm flows coincide witii tiie peak daily flow
throughout the interceptor system.
• An additional infiltration rate of 3.0 MGD was added to tiie upsfream reach ofthe V/C Interceptor. This
flow rate is based on an analysis of Vista meter records, and accounts for the increase in infiltration that
would occur in the Vista system if several severe storms had preceded the November 2001 storm.
• Existing I/I flows as determined from the Enema meters were mcreased by 20 percent in the ultimate
system analysis to account for aging of the pipelines.
It is noted tiiat a much more severe storm in the future could potentially result m higher peak flows than what
are assumed for this analysis. Conversely, an aggressive program to identify and reduce the volume of I&I
could result m reduced peak flows in the fiiture.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 7 March 2003
7.9 RECOMMENDED CAPITAL IMPROVEMENT PROGRAM
Improvement projects identified for tiie Capital Improvement Program (CIP) are summarized in Table 7-3.
The projects are arranged mto three groups. The first group of projects includes improvements to the sewer
collector system and rehabilitation projects. These projects were updated from the City's 2002-2003 CIP
based on discussions with City staff. The next group consists of mterceptor capacity projects, which were
identified from the hydraulic analysis performed as part of tiiis Master Plan Update. The last group of
projects are for improvements at the Encina Water Pollution Confrol Facility, which were also defined in the
City's 2002-2003 CIP.
Table 7-3 includes a planning level estimate of probable constraction costs. Costs should be considered
relative to tiie 2002 Engineering News Record Constiiiction Cost Index (ENR CCI) of6538. Cost estimates
for the Encina WPCF projects and most of the collector system projects were obtained from tiie City's 2002-
2003 CIP. It is noted that costs identified for V/C Interceptor capacity improvements represent tiie total cost,
although a portion of these costs will be shared by tiie City of Vista. The costs for tiie Encina WPCF projects
represent the City's pro-rated share for the projects.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 7- 8 March 2003
Table 7- 3
RECOMMENDED SEWER CAPITAL IMPROVEMENT PROGRAM
'''^IcT^* 1 Description/Location Project
Type Size/Quantity Probable
Constr. 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 (Cove
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 wetwell, manifold
piping, ventilation system, and reconstnjct 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 construct gravity sewer new gravity sewer 1000' of 8" pipeline $ 150,000
12 Poinsettia Lift Station Odor and Noise Abatement L.S. rehab — $ 221,800
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 VCl 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 7-9
Dudek & Associates, Inc.
March 2003
Table 7- 3 (continued)
Project
ID Description/Location Project
Type Size/Quantity Probable
Cotistr. Cost
COLLECTOR 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
Carlsbad Trunk Sewer Reaches VCTIA, VCTIB, VCTIC - 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 Cartsbad
Sewer Master Plan Update 7-10
Dudek & Associates, Inc.
March 2003
Table 7- 3 (continued)
Project
ID Description/Location Project
Tvoe Size/Quantity Probable
Constr. Cost
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 VCl 2 - 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 - construct lift station,
force main and gravity sewer in Cannon Rd., remove Kelly Lift Station
NewLS., 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 electrical 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 Cartsbad
Sewer Master Plan Update 7-11
Dudek & Associates, Inc.
March 2003
CHAPTER 8
SEWER CONNECTION FEE UPDATE
The City of Carlsbad has historically charged connection fees to provide sewer service to its new
customers. The fees pay for the planning, design and constraction of capacity improvements and/or new
facilities required for the conveyance and freatment of sewage. Under Califomia State law, connection
fees must be based on relevant capital costs. This chapter provides an updated basis for sewer coimection
fees based on growth projections and capital improvement projects identified to serve future development.
A cash flow analysis is performed with the updated connection fee from a starting date of October 1,2003
through buildout, which is projected to occur by 2020.
8.1 BACKGROUND
Sewer connection fees are used to generate revenue to constmct sewer infrastmcture needed to support
new development. Assembly Bill 1600 was incorporated into the Califomia Govemment Code imder
Title 7, Division 1, Chapter 5: "Fees for Development Projects", effective 1989. Chapter 5 states that any
fee imposed by a local agency must show that the fee wiU be used only for purposes related to the service
for which the fee is assessed. The law requires that the City of Carlsbad: 1) identify the purpose of the
fee, 2) identify the use for which the fee is to be put, 3) show a relationship between the fee's use and the
type of development project on which the fee is imposed, and 4) show a relationship between the need for
the facility and the type of development project on which the fee is imposed. This chapter provides the
basis for coimection fees needed to satisfy Califomia law.
The current sewer connection fee was developed in 1990 as part of the "Capacity Fee Update to the 1987
Master Plan of Sewerage". The fee is based on the Equivalent Dwelling Unit (EDU) method. An EDU is
a imit of measure for the sewage generated from particular buildmgs, stmctures or uses. One EDU is
equal to an approximation of the amount of sewage generated by an average single-family residence. The
City uses a formula to determine the EDU's for other residential, commercial and industrial users. The
sewer connection fee is adjusted annuaUy, effective July 1*', according to the Engineering News Record
Los Angeles Constmction Cost Index. The 2002-2003 sewer connection fee is $2,060 per EDU.
In the Cify of Carlsbad, many sewer projects are paid for by Sewer Benefit Area (SBA) Fees. These
developer-paid fees provide direct funding for specific projects. The sewer benefit area fee program was
originally approved by the Cify Council on January 15, 1991. The SBA fee is collected with the issuance
of building permits within defined sewer benefit areas. Some developments are conditioned to constmct
specific facUities prior to or concurrent with the issuance of building permits. In these cases,
reimbursement is given for actual costs through the SBA fee. A SBA fee program has been established
to pay for portions of the South Agua Hedionda (SAH) Interceptor. The SAH Interceptor system is
therefore considered to be "developer funded". This project and other projects constmcted with SBA fees
are not included in the coimection fee calculations.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-1 July 2003
8.2 GROWTH PROJECTIONS
The total number of fiiture users must be estimated to calculate connection fees. The City of Carlsbad
Growth Database is used in this Master Plan Update to detemiine the number of fiiture users and project
the ultimate sewer flow for the capacify analysis (documented in Chapter 6, Section 6.3). Parcels in the
Growth Database are assigned to one of 25 Local Facilify Management Zones (LFMZ), illustrated
previously on Figure 1-3. For the connection fee update, an updated version of the Growth Database is
used to determine the number of fiiture users. In the updated Growth Database, fiiture users are based on
development that is projected to occur after October 1, 2003.
Growth data in the updated Growth Database consists of the number of projected residential units and the
estimated building area for commercial and indusfrial parcels at build-out. Sewer connection fees are
currently assessed based on Equivalent Dwelling Units (EDUs). By definition, one EDU will generate
the equivalent amount of sewage as an average single-family residence, which is estimated to be 220
gallons per day (gpd). EDU conversions for other types of development are defined in Table 13.10.020-c
of the Carlsbad Mimicipal Code. For commercial developments, the gross floor area of the buUding in
square feet (sqft) is divided by 1,800 to obtain the number of EDUs. This is equivalent to a sewage
generation rate of 1,225 gpd per 10,000 sqft of building area or 5.6 EDUs/10,000 sqft. For industrial
developments the building area is divided by 5,000, which is equivalent to a sewage generation rate of
440 gpd per 10,000 sqft of building area, or 2 EDUs/10,000 sqft. The projected fiiture EDUs within the
City of Carlsbad Sewer Service Area after October 1, 2003 are summarized in Table 8-1.
Table 8-1
PROJECTED FUTURE EDUs WITHIN THE SEWER SERVICE AREA
Future Development Future Development
LFMZ Residential Building Area (sqft) EDUs* LFMZ Residential Building Area (sqft) EDUs*
Units Commercial Industrial Units Commercial Industrial
1 689 1,016,581 0 1,254 15 550 275,000 0 703
2 140 39,656 0 162 16 0 0 1,413,522 283
3 12 128,551 20,000 87 17 598 268,000 2,170,000 1,181
4 40 0 0 40 18 0 30,000 2,196,000 456
5 0 0 2,496,687 499 19 84 223,637 0 208
7 705 30,000 0 722 20 497 70,750 0 536
8 256 6,000 0 259 21 392 0 0 392
9 1 411,500 0 230 22 222 84,780 0 269
10 489 0 0 489 24 30 0 0 30
13 0 1,109,692 200,000 656 25 130 0 0 130
14 960 0 0 960
Totals: 5,795 residential units 12,190,356 sqft of building area 9,547 EDUs
* Non-residential EDU conversions are: commercial = building area/1800, industrial = building area/5000
City of Cartsbad
SEWER MASTER PLAN UPDATE 8-2
Dudek & Associates, Inc.
July 2003
8.3 CAPITAL COSTS FOR CAPACITY IMPROVEMENTS
The purpose of the sewer connection fee is to pay for growth related capacify improvements. All of the
wastewater generated within tiie Cify of Carlsbad Sewer Service Area is freated at the Encina WPCF.
The connection fee therefore recovers the cost of capital improvements and expansions to the sewer
interceptor system and the Encina Water Pollution Confrol Facilify (WPCF).
The basis of improvement projects for the connection fee is the Capital Improvement Program (CIP)
previously identified in Table 7-1 of this Master Plan Update. The CIP recommends improvements to the
sewer interceptor system and the Enema WPCF that wUl be needed to support the build-out population of
the Sewer Service Area, including replacement of existing facilities and maintenance-related projects.
However, only the capacify-related projects identified to accommodate fiiture growth are included in the
connection fee calculations. In the Cify of Carlsbad, developers provide direct fimding for many specific
projects through Sewer Area Benefit Fees. These projects, which include constmction of tiie Soutii Agua
Hedionda Interceptor, pump station and force mam, are not included in the sewer connection fees.
The capacify related capital improvement projects required for fiiture development and an estimate of
probable costs are summarized m Table 8-2 for the connection fee update. Also shown in this table is the
proposed project phasing. Project costs reflect future plaimed expenditures based on the Cify of Carlsbad
2003-2004 Capital Improvement Program, which exclude fiinds appropriated for the 2002-2003 fiscal
year. Projected costs for projects that are currently active wUl therefore differ from the CIP costs
mcluded in Table 7-1, which are based on the 2002-2003 CIP.
Project costs Usted m Table 8-2 for improvements to tiie Vista/Carlsbad Interceptor (project numbers 28-
33) reflect only the Cify of Carlsbad's cost share. Carlsbad's cost share is based on the capacify rights
defined in Exhibit B of the Febmary 8, 2000 Revised Joint Sewage System Agreement with the Cify of
Vista (provided in Table 3-1 of this Master Plan Update). Costs for projects 28 through 30 are based on a
10.4 percent ownership, projects 31 and 32 are based on a 30.9 percent ownership, and project 33 is based
on a 43.9 percent ownership. Encina WPCF project costs are based on the Cify of Carlsbad's current
capacify ownership of tiie Enema WPCF, as documented in the Febmary 2000 Revised Basic Agreement.
The total cost of projects to be funded from coimection fees is estimated at approximately $31,297,000.
8.4 CONNECTION FEE CALCULATIONS
A cost per EDU for sewer service can be determmed from the CIP costs and the projected number of
fiiture users, which has been estimated from available planning data. Because the actual number of imits
eventually constracted may vary, the estimate of fiiture sewer EDUs is reduced by 10 percent in the
calculation of sewer connection fees. This unit reduction is considered a "safety factor" to ensure that the
necessary fees wiU be coUected even if the Sewer Service Area is not completely buildout as planned.
City of Carisbad Dudek & Associates, Inc.
SEWER MASTER PLAN UPDATE 8-3 July 2003
Table 8-2
CAPITAL IMPROVEMENT PROJECTS FOR THE SEWER CONNECTION FEE UPDATE
-
CIP
NO.
MASTER PLAN PROJECT
DESCRIPTION/LOCATION
PROJECT
TYPE
ESTIMATED
COST
FUTURE YEAR BUDGET AMOUNTS -
CIP
NO.
MASTER PLAN PROJECT
DESCRIPTION/LOCATION
PROJECT
TYPE
ESTIMATED
COST YEAR1
2003-2004
YEAR 2
2004-2005
YEAR 3
2005-2006
YEAR 4
2006-2007
YEARS
2007-2008
YEAR 6-10
200^-2013
BUILDOUT
2014-2020
24 Master Plan Update and CEQA approval for
CIP prepare report $ 305,000 $ 305,000
25 Sewer Monitoring Program - monitor flows in
pipelines and at lift stations monitor flows $ 340,000 $ 20,000 $ 20,000 $ 20,000 $ 20,000 $ 20,000 $ 100,000 $ 140,000
27 Sewer Connecfion Fee Update prepare report $ 15,000 $ 15,000
28
Vista/Carlsbad Interceptor Reach VC3 -
capacity upgrade upstream of the Buena
Vista Lift Station
interceptor
replacement $ 267,000* $ 267,000
29
Buena Vista Lift Station - capacity increase,
control system upgrade, new back-up
generator
L.S. rehab $ 233,000* $ 233,000
30
Buena Vista Lift Station Force Main, VC4 -
replace 16" pipeline with 24" pipeline to
provide dual 24" force mains & increase
capacity
new force main $ 129,000* $ 129,000
31
Vista/Carlsbad Interceptor Reach VC11B -
upgrade capacity & construct new bridge
crossing over the Agua Hedionda Lagoon
interceptor
replacement &
new bridge
$ 896,000* $ 896,000
32
Agua Hedionda Lift Station and Force Main,
VC12 - rehab lift station, increase capacity
and construct new force main
L.S. rehab &
new force main $ 1,931,000* $ 348,000 $1,583,000
33
V/C Interceptor Reaches VC13, VC14 &
VC15 - Increase interceptor capacity from
the AH Lift Station to the Encina WPCF
interceptor
replacement $ 4,478,000* $ 224,000 $2,060,000 $2,194,000
40 Encina Phase IV Expansion - debt service
on Phase IV plant expansion debt service $ 11,203,800 $ 936,300 $ 939,600 $ 936,400 $ 933,900 $ 935,500 $ 4,665,500 $ 1,856,600
41 Encina Phase V Expansion - expand plant
capacity for buildout conditions TP expansion $ 11,499,000 $11,499,000
TOTALS: $ 31,296,800 $1,189,300 $13,030,600 $4,866,400 $3,147,900 $955,500 $6,110,500 $1,996,600
' Cost for v/c Interceptor projects Is the City of Carlsbad's share based on capacity rights defined in Exhibit B of the 2/8/2000 Revised Joint Sewage System Agreement
City of Carisbad
SEWER MASTER PLAN UPDATE 8-4
Dudek & Associates, Inc.
July 2003
The calculations for the updated connection fee are shown in Table 8-3. The "Total Cost" in Table 8-3 is
the capital budget mmus the available cash balance in the sewer connection fee account. City Staff have
projected the avaUable cash balance on October 1, 2003 to be $23,330,674. The new connection fee is
calculated to be $927 per EDU.
Table 8-3
SEWER CONNECTION FEE CALCULATION
Capital
Budget
Available
Cash
Balance
Total Cost
Future
EDUs
less 10%
Cost Per
EDU
$31,296,800 $23,330,674 $7,966,126 8,592 $927
8.5 SEWER SYSTEM CASH FLOW ANALYSIS
A cash flow table can be constracted using the sewer connection fee calculated in Table 8-3, yearly
buildout projections provided in the City of Carlsbad Growth Database, and project phasing estimates.
Table 8-4 provides a sewer cash flow table using the calculated connection fee over a seventeen-year
period, starting in October 1, 2003 and ending at 2020, which is the projected buildout year for the City.
At the end of the chosen time period the cumulative balance is $0, because the connection fees are based
on a budget that includes the available cash balance. It is noted that all values used in the cash flow tables
are in current dollars.
City of Carisbad
SEWER MASTER PLAN UPDATE 8-5
Dudek & Associates, Inc.
July 2003
Table 8-4
SEWER CONNECTION FEE CASH FLOW ANALYSIS
Fiscal New Connection Cumulative
Year EDUs Fee vri" l>OSX5 Balance
Available cash balance projected for 10/1/03 = $ 23,330,674
2003 442 $927 $ 409,803 $ 1,189,300 $ (779,497) $ 22,551,177
2004 878 $927 $ 814,043 $ 13,030,600 $(12,216,557) $ 10,334,620
2005 784 $927 $ 726,890 $ 4,866,400 $ (4,139,510) $ 6,195,111
2006 860 $927 $ 797,354 $ 3,147,900 $ (2,350,546) $ 3,844,565
2007 630 $927 $ 584,108 $ 955,500 $ (371,392) $ 3,473,173
2008 782 $927 $ 725,036 $ 1,222,100 $ (497,064) $ 2,976,109
2009 682 $927 $ 632,321 $ 1,222,100 $ (589,779) $ 2,386,330
2010 599 $927 $ 555,367 $ 1,222,100 $ (666,733) $ 1,719,597
2011 543 $927 $ 503,446 $ 1,222,100 $ (718,654) $ 1,000,942
2012 491 $927 S 455,234 $ 1,222,100 $ (766,866) $ 234,076
2013 425 $927 $ 394,041 $ 249,575 $ 144,466 $ 378,542
2014 361 $927 $ 334,703 $ 249,575 $ 85,128 $ 463,671
2015 243 $927 $ 225,299 $ 249,575 $ (24,276) $ 439,395
2016 188 $927 $ 174,305 $ 249,575 $ (75,270) $ 364,125
2017 163 $927 $ 151,126 $ 249,575 $ (98,449) $ 265,677
2018 157 $927 $ 145,564 $ 249,575 $ (104,011) $ 161,665
2019 218 $927 $ 202,120 $ 249,575 $ (47,455) $ 114,210
2020 146 $927 $ 135,365 $ 249,575 $ (114,210) $0
Totals: 8,592 $ 7,966,126 $31,296,800 $ (23.330,674)
City of Carisbad
SEWER MASTER PLAN UPDATE 8-6
Dudek & Associates, Inc.
July 2003