HomeMy WebLinkAboutTechnical Report 7 - Sewer StudyMaria Miller
May 28, 2024
Page 2
The proposed land use changes will reduce the amount of single family dwelling units and
increase the amount of multi-family dwelling units within Village 7; however, the proposed
changes would result in no net change to the residential dwelling unit count of 1,456
presented in the Otay Ranch General Development Plan for Village 7. To implement the
proposed land use changes, amendments to the Chula Vista General Plan, Otay Ranch
General Development Plan, and the Village 7 SPA Plan are necessary.
Sewage from Village 7 flows to two sewer basins. Sewage from the northern portion of the
project, which includes Parcels R-1, R-2, R-5 and P-1, is conveyed to the Poggi Canyon Sewer
Basin under permanent sewer conditions. Wastewater collected within this basin is conveyed
to sewer lines in Birch Road and La Media Road that ultimately discharge to the existing
Poggi Canyon Interceptor in Olympic Parkway. Parcels R-6, R-7, S-1 and S-3 are currently
served by an interim sewer line that flows north to the Poggi Canyon Interceptor until such
time that the Wolf Canyon Trunk Sewer is available. In the future, these parcels will
abandon the interim northern connection and use the permanent Wolf Canyon Trunk Sewer.
Parcels R-3, R-4, and R-8 will sewer by gravity to the south. The offsite sewer facilities
necessary to convey flows from the site to the Salt Creek Interceptor have not been
constructed. Thus, the development of Parcels R-3, R-4, and R-8 will require either
construction of a temporary sewer line south to Village 8 West or the construction of the Wolf
Canyon Trunk Sewer. Sewage within Village 8 West is conveyed south to the existing Salt
Creek Interceptor.
Purpose
The purpose of this memorandum is to provide an evaluation of the affect that the current
proposed development plan will have on sewer facility planning for the area. Since the
proposed SPA Amendment only affects parcels within the Wolf Canyon /Salt Creek Basin and
does not propose interim service from Poggi Canyon facilities, this study focuses on the
impact this SPA Amendment will have on facilities within the Wolf Canyon/Salt Creek Basin.
Attachment 1 includes a sewer basin map of Village 7 for reference (Exhibit A).
Maria Miller
May 28, 2024
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Village 7 SPA Amendment Summary
A summary of proposed changes to the Village 7 land use plan is provided as follows:
• Rename the western portion of Parcel R-3 into a separate Parcel R-8. Parcel R-8 will
be located adjacent to La Media Road.
• Assign 43 units to Parcel R-3 and change the land use designation in Parcel R-3 from
Single Family to Residential Multi-Family.
• Assign 121 units to Parcel R-4 and change the land use designation in Parcel R-4 from
Single Family to Residential Multi-Family.
• Assign 123 units to Parcel R-8 and change the land use designation (based on Parcel
R-3 land use designation) in Parcel R-8 from Single Family to Residential Multi-
Family.
Proposed Land Use Plan
The project does not propose changes to the backbone street alignments for Village 7 but does
involve adjustments to the land use and residential unit count of Parcels R-3 and R-4, and
the addition of Parcel R-8. A land use plan and site utilization table for the proposed changes
are included in Attachment 2 for reference.
Projected Sewer Flows
Parcels R-3 and R-4 have not been developed and were previously planned for single family
residential development. Table 1 provides a comparison of projected sewer flows based on
the previous and current land use plans for Parcels R-3, R-4, and the addition of Parcel R-8.
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May 28, 2024
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TABLE 1
OTAY RANCH VILLAGE 7
PARCELS R-3, R-4, AND R-8 PROJECTED SEWER FLOWS
Land Use Proposed
Units
Generation
Factor
Average Flow,
gallons per day (gpd)
Previous Land Use Plan
R-3: SF Residential 273 units1 265 gpd/unit 72,345
R-4: SF Residential 59 units1 265 gpd/unit 15,635
Subtotal Previous Land Use Plan 87,980
Current Land Use Plan
R-3: MF Residential2 43 units 182 gpd/unit 7,826
R-4: MF Residential 121 units 182 gpd/unit 22,022
R-8: MF Residential2 123 units 182 gpd/unit 22,386
Subtotal Current Land Use Plan 52,234
Decreased Sewer Flow 35,746
Decreased Sewer Equivalent Dwelling Units (EDUs) 3 155
1 Based on Site Utilization Plan presented in the Village 7 SPA Plan adopted October 12, 2004.
2 Parcel R-3 split into two parcels: Parcels R-3 and R-8.
3 Based on sewer generation factor of 230 gpd/EDU.
Impact on Previous Planning Studies
The November 2010 Overview of Sewer Service for the Village 8 West (November 2010 Sewer
Study) project planned for sewer flows from the Village 7 project. These flows were planned
to flow south through Village 8 West to the Salt Creek Interceptor on a temporary basis and
to the Wolf Canyon Trunk Sewer in Main Street in the ultimate condition. Attachment 3
includes a list of Village 7 parcels in the Wolf Canyon/Salt Creek Basin, and their
corresponding sewer flow projections, that were planned to flow south through Village 8 West
in the November 2010 Sewer Study; Village 7 parcels that had been accounted for are R-3,
R-6, R-7, MU-1 (Mixed Use), TS-1 (Town Square), CPF-2b (Community Purpose Facility),
CPF-3, CP-4, S-1, and S-3 (School). The previous site plan used to estimate sewer flows for
Village 7 in the November 2010 Sewer Study is included at the end of Attachment 3 for
reference.
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May 28, 2024
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The sewer analysis presented in the November 2010 Sewer Study was updated in May 2018
(May 2018 Sewer Study) to include minor land use changes to Village 8 West and to reflect
pipeline slopes that had been established through final engineering plans. Additionally, as
part of the May 2018 Sewer Study, through final engineering efforts for Village 8 West, the
original onsite concept of constructing a temporary deep sewer to convey flows south through
Village 8 West on an interim basis was revised to reflect a permanent gravity sewer to the
south to collect offsite sewer flows from La Media Road/La Media Parkway to the north and
from Main Street to the east. The sewer analysis presented in the May 2018 Sewer Study
was updated in May 2019 (May 2019 Sewer Study) to include minor land use changes to
Village 8 West.
In all three Village 8 West Sewer Studies (November 2010 Sewer Study, May 2018 Sewer
Study, and May 2019 Sewer Study), the sewer generation for Village 7 was estimated using
the City of Chula Vista’s previous sewer generation factors. Table 2 provides a comparison
of projected sewer flows for Village 7 using A) previous land use plan and sewer generation
factors, and B) current land use plan and sewer generation factors.
As previously mentioned, the previous land use plan for Village 7 accounted for Parcels R-3,
R-6, R-7, MU-1, TS-1, CPF-2b, CPF-3, CP-4, S-1, and S-3 within the Wolf Canyon/Salt Creek
Basin per Attachment 3. This sewer evaluation for the proposed Village 7 SPA Amendment
accounts for Parcels R-3, R-4, R-6, R-7, R-8, CPF-2b, S-1, S-3 within the Wolf Canyon/Salt
Creek Basin per Attachment 2. The Site Utilization Table in Attachment 2 includes “Future
Development Areas” that are not accounted for in this Village 7 sewer system evaluation, as
these future areas have not been approved for development and will require a separate SPA
Amendment.
As shown in Table 2, the flows from the proposed SPA Plan Amendment are more than offset
by the reduction in flows as a result of the revised land use plan and current City sewer
generation factors. Thus, the calculations to determine sewer line sizing through Village 8
West in the May 2019 Village 8 West Sewer Study (most recent sewer study) remain valid.
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May 28, 2024
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TABLE 2
OTAY RANCH VILLAGE 7
PROJECTED SEWER FLOWS (SPA AMENDMENT)
Land Use Proposed
Units
Generation
Factor
Average Flow,
gallons per day (gpd)
Previous Land Use Plan and Sewer Generation Factors1
SF Residential 290 units 265 gpd/unit 76,850
MF Residential 306 units 199 gpd/unit 60,894
Elementary School 800 students 15 gpd/students 12,000
High School 2,400 students 20 gpd/student 48,000
Commercial/
Community Purpose Facility 7.9 ac 2,500 gpd/ac 19,750
Subtotal 217,494
Current Land Use Plan and Sewer Generation Factors2
MF Residential 603 units 182 gpd/unit 109,746
Elementary School 800 students 12 gpd/student 9,600
High School 2,400 students 13 gpd/student 31,200
Community Purpose Facility 1.0 ac 1,401 gpd/ac 1,401
Subtotal 151,947
1. Includes Parcels R-3, R-6, R-7, MU-1, TS-1, CPF-2b, CPF-3, CP-4, S-1, and S-3. See Attachment 3 for
old land use plan.
2. Includes Parcels R-3, R-4, R-6, R-7, R-8, CPF-2b, S-1, S-3. See Attachment 2 for current land use plan.
The “Future Development Areas” shown in the Site Utilization Table in Attachment 2 are not accounted
for because these future areas have not been approved for development and will require a separate SPA
Amendment.
Maria Miller
May 28, 2024
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Salt Creek Interceptor Technical Sewer Study. A sewer study for the Salt Creek
Interceptor, dated October 2010, was prepared by PBS&J to address the capacity of the
interceptor sewer due to increased intensity in development within Otay Ranch than what
had previously been evaluated. The October 2010 Salt Creek Interceptor Technical Sewer
Study (October 2010 PBS&J Study) included projected sewer flows from Village 7 and
concluded that certain sections of the Salt Creek Interceptor may require upgrades at
ultimate buildout, but these sections are located upstream of Village 8 West and thus, Village
7 as well. The flows for Village 7 in the October 2010 PBS&J Study were based on previous
City sewer generation factors such that the flows from the proposed SPA Plan Amendment
will be more than offset based on revised flows as a result of current, lower sewer generation
factors. Thus, the findings of the October 2010 PBS&J Study remain valid, and the proposed
Village 7 SPA Amendment will not trigger any upgrades to the Salt Creek Interceptor.
FF:ah
ATTACHMENT 1
EXHIBIT A
VILLAGE 7 SEWER BASIN MAP
ATTACHMENT 2
CURRENT
SITE UTILIZATION PLAN
AND
LAND USE SUMMARY TABLE
INTRODUCTION
SPA PLAN
Village 7 Site Utilization Plan
Exhibit 1.6
INTRODUCTION
SPA PLAN
Village 7 Land Use Districts
Exhibit PC-1
Village Seven Site Utilization Table
RESIDENTIAL USE
Neighborhood Land Use LU District Acres DU du/ac
R-1
Single-Family
Detached SF4 53.1 346 6.5
R-2
Single-Family
Detached SF4, RM1 51 375 7.4
Sub-total single-family: 721
R-3 Multi-Family RM1 2.4 43 17.9
R-4 Multi-Family RM2 3.1 121 39
R-5 Multi-Family RM1 14.5 132 9.1
R-6 Multi-Family RM2 12.3 193 15.7
R-7 Multi-Family RM2 7.9 123 15.6
R-8 Multi-Family RM1 8.3 123 14.8
Sub-total multi-family: 735
Total Residential 152.6 ac. 1,456 9.5
NON-RESIDENTIAL USE
Neighborhood Land Use LU District Acres
P-1 Public Park P 7.6
CPF-1 Private Park CPF 1.1
CPF-2a Private Park CPF 0.9
CPF-2b CPF CPF 1.0 *Area included in R-3
S-1 High School S 53.9
S-3 Elem. School S 11.5
OS Open Space OS 42.6
Total Non-Residential 118.6 ac.
FUTURE DEVELOPMENT AREA - CONCEPTUAL USES
(REQUIRES A SPA AMENDMENT TO OBTAIN DEVELOPMENT APPROVAL)
Neighborhood Land Use LU District Acres
R-9 Residential Undesignated 42
MU Mixed-Use Undesignated 3.7
OS Open Space Undesignated 3
TS-1 Town Square Undesignated 1.9
CPF-3 CPF Undesignated 1.1
Total Future Development 51.7 ac.
VILLAGE TOTAL 321.9 ac.
ATTACHMENT 3
PREVIOUS
LAND USE SUMMARY TABLE
AND
SEWER GENERATION ESTIMATES
(NOVEMBER 2010 SEWER STUDY)