HomeMy WebLinkAboutAttachment 8S - Sewer StudyCity of Chula Vista
PRELIMINARY SEWER STUDY
For:
Nirvana Business Park
DR21-0024
821 Main Street
Chula Vista, CA 91911
APN: 644-050-13, 644-050-14 & 644-050-80
Project Permit # DR21-0024
Prepared By:
3-4-2022
Gregory W. Lang, P.E. RCE 68075 EXP: 06-30-23
Pasco Laret Suiter & Associates, Inc.
535 N. Highway 101, Suite A
Solana Beach, CA 92075
Prepared for:
VWP-OP Nirvana Owner, LLC
2390 E. Camelback Rd. Ste. 305
Phoenix, AZ 85016
March 4, 2022
PLSA Job No. 3668
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Nirvana Business Park
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Table of Contents
Section 1 - Introduction .................................................................................................................... 1
Section 2 – Project Description ........................................................................................................ 1
2.1 Project Location ...................................................................................................................... 1
2.2 Proposed Project ..................................................................................................................... 2
2.3 Study Area .............................................................................................................................. 2
2.4 Sewage Generation Rates ....................................................................................................... 8
Section 3 – Sanitary Sewer Analysis ................................................................................................ 9
3.1 Model Methodology ............................................................................................................... 9
2.2 Hydraulic Analysis Results .................................................................................................. 10
Section 4 – Conclusions ................................................................................................................. 10
Section 5 – Appendices .................................................................................................................. 12
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Figure Index
Figure 2-1 Project Site ...................................................................................................................... 1
Figure 2-2 Proposed Site Layout ...................................................................................................... 3
Figure 2-3 Sanitary System Sewer Map and Study Area ................................................................. 4
Figure 2-4 Sanitary System Node Map ........................................................................................ 5-6
Figure 2-5 Sanitary Sewer Exhibit ................................................................................................... 7
Figure 3-1 Sanitary Sewer Study Summary (Hydraulic Model Results) ....................................... 11
Table Index
Table 2-1 Sewer Generation Rates based on Lot Area ..................................................................... 8
Table 2-2 Sewer Generation Rates based on Building Square Footage ........................................... 8
Preliminary Sewer Study March 2022
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Section 1 – Introduction
This report provides background data, analysis, and a summary of results as part of a preliminary
sanitary sewer system study for the proposed Nirvana Business Park project. The purpose of this
study is to ascertain the potential impact of the proposed project on the existing sanitary sewer
system and to verify that sufficient capacity exists within the existing sewer facilities. The design
for this sewer study was completed in accordance with the design criteria listed in the City of Chula
Vista’s Subdivision Manual (Revised 03-13-2012), the City of Chula Vista Wastewater Collection
Master Plan (May 2014), and the Sewer System Management Plan (April 2021).
Section 2 – Project Description
2.1 Project Location:
The proposed Nirvana Business Park project is comprised of 13.31 acres, located at 821 Main Street
in the City of Chula Vista, San Diego County, California (APN 644-050-13, 14 and a portion of
644-050-80). The property is defined as Parcel 1 and 2 of Parcel Map 21587 and a portion of Lot
2, Sec 20, T18S, R1E San Bernadino Meridian of ROS 16999. The site is bounded on the north by
automobile salvage yards, on the west by commercial buildings, on the south by Main Street, and
on the east by the Otay Ranch Village 3 development. The entire project site is currently
undeveloped. See Figure 2.1 for vicinity map.
Figure 2-1
Vicinity Map
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2.2 Proposed Project:
The proposed project at 821 Main Street will construct four buildings as follows:
• Building 1 – a 59,044 square-foot warehouse with office and mezzanine
• Building 2 – a 44,592 square-foot warehouse with office and mezzanine
• Building 3 – a 140,802 square-foot, 3-story self-storage building
• Building 4 – a 50,030 warehouse with office and mezzanine
Total building square footage = 294,468 square-feet
The site is General Plan designated IL – Limited Industrial and Zoned (ILP) Limited Industrial. The
proposed light industrial uses include primarily warehouse and manufacturing, assembly, storage, and
warehouse distribution. The self-storage facility will feature interior and exterior accessible storage
spaces, with surface loading and elevators for upper floors.
Hours of operation for the business park are planned to be Monday through Friday 6:00 a.m. to 6:00 p.m.
and Saturday 6:00 a.m. to noon. The self-storage facilities will have 24/7 access.
Please refer to Figure 2-2 on the following page for schematic site layout.
2.3 Study Area:
The project’s study area, shown in Figure 2-3, generally encompasses existing parcels abutting
Energy Way and Nirvana Avenue as well as along Main Street between Heritage Road and Nirvana
Avenue. The primary zoning in the area consists of limited industrial (IL) per the city’s 2005
General Plan. In accordance with the requirements specified in the preliminary permit review
submittal comments, the proposed project is required to prepare a sewer system study with
manhole-to-manhole calculations performed from the upstream sewer system reach on Energy Way
downstream to the connection to the existing 10-inch sewer in Main Street, south of Nirvana
Avenue. Please refer to Figure 2-4 for Sanitary System Node Map.
The proposed project will connect to an existing 8-inch PVC gravity sewer located west of the
project site in Nirvana Avenue (see Figure 2-5).
The 8-inch sewer main in Nirvana Avenue flows southwesterly and connects to an existing 10-inch
sewer main in Main Street at an existing manhole located in the intersection of Nirvana Avenue
and Main Street. There is no additional sanitary sewer flow from the east along Main Street at this
manhole location. The existing 10-inch sanitary sewer main flows westerly in Main Street
approximately 5,800 lineal feet to the intersection of I-805 and Main Street and then an additional
2,100 lineal feet to the intersection of Otay Valley Road and Main Street. Please refer to the City
of Chula Vista’s CV Mapper website for GIS wastewater systems.
The existing 8-inch sewer mains in both Energy Way and Nirvana Avenue and the existing 10-inch
sewer main in Main Street were all constructed in during the 1970s and are generally comprised of
PVC pipe. The systems were installed under Work Order No. EY026 (Drawing No. 75-105D
through Drawing No. 75-111D). The existing branch connecting sewers along Main Street and
west of Brandywine Avenue are generally comprised of vitrified clay pipe (VCP).
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2.4 Sewer Generation Rates:
Preliminary sewer generation rates for the proposed development are based on the planning
requirements provided in the City of Chula Vista Subdivision Design Manual and the City of Chula
Vista Wastewater Collection System Master Plan, May 2014. The Wastewater Master Plan
methodology calculates sanitary flows based on the current or planned parcel zoning, lot area, and
duty factor demands obtained from Table 3-2 of the Wastewater Master Plan. The Average Dry
Weather Flow (ADWF) was calculated for the proposed site as shown in Table 2-1 below. As a
comparison, an alternative method for calculating the ADWF is provided in Table 2-2 on the
following page. The alternative method utilizes a combination of duty factor demands and known
building square footage. Proposed building areas were previously provided in Section 2.2.
Table 2-1
Sewer Generation Rates based on Lot Area
Net Acreage = 13.31 ac
Duty Factor = 712 gpd/ac
AVERAGE DRY WEATHER FLOW = Net Acreage (ac) * Duty Factor (gpd/ac)
= 13.31 ac * 712 gpd/ac
= 9,477 gpd
Table 2-2
Sewer Generation Rates based on Building Square Footage
Building Square Footage = 294,468 sf
Duty Factor = 80 gpd/1000 sf
ADWF = Building Square Footage (sf) * Duty Factor
(gpd/1000 sf)
= 294,468 sf * 80 gpd/1000 sf
AVERAGE DRY WEATHER FLOW = 23,557 gpd
Based on the above methods of calculating the ADWF, the more conservative ADWF of 23,557
gpd will be utilized as the basis of determining equivalent population and sanitary flows from the
proposed site during sewer modeling in Section 3 of this report.
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Section 3 – Sanitary Sewer Analysis
This section of the study report discusses the hydraulic analysis of the existing sewer system with
new flows from the proposed Nirvana Business Park project.
3.1 Model Methodology:
A Microsoft Excel spreadsheet was utilized to perform the hydraulic analysis of the existing
sanitary sewer with the Study Area. Each reach or “Line” of the existing sanitary sewer system
includes the upstream and downstream manhole designations, invert elevations, length, and
diameter of the sewer. Sewer lengths and inverts were obtained from GIS sewer manhole and
sewer main shape files used on the City of Chula Vista GIS website, and from as-built sewer data
also obtained by the City of Chula Vista.
The Average Dry Weather Flow (ADWF) was calculated for each reach by the product of the
cumulative sanitary flow rate. Peak Wet Weather Flow (PWWF) was calculated for each reach by
multiplying the ADWF by the calculated Peaking Factor for Wet Weather Flow. In accordance
with the direction received from the City of San Diego Public Utilities Department, the peaking
factor used was 1.85, found from Chapter 3.3.6 of the City of Chula Vista Wastewater Collection
System Master Plan (May 2014). The pipe capacity was calculated utilizing Manning’s Equation
and a Manning’s “n” value of 0.013.
The ratio of actual depth to pipe diameter (d/D) was calculated by using an Excel algorithm to
select the appropriate d/D (to the nearest 0.1 increment) based on the corresponding ratio of
calculated ADWF to full pipe flow (Q/Qfull).
Existing wastewater flows for reach DD between manholes were found from Appendix 2 of the
City of Chula Vista Wastewater Collection System Master Plan, May 2014. The Average Dry
Weather Flow (ADWF), the Peak Wet Weather Flow (PWWF), and the Peak Wet Weather Flow
d/D were input into the Microsoft Excel Spreadsheet.
The downstream system has been studied to the point in the system where the projected peak wet
weather flow from the proposed development is less than 10% of the total flow, in accordance with
Section 1.7.1 of the City of San Diego Sewer Design Guide (2013).
3.2 Hydraulic Analysis Results:
The results of the hydraulic analysis model are shown in the Sanitary Sewer Study Summary
provided in Figure 3-1 at the end of this section. The results are summarized as follows:
1. The d/D ratios for existing peak flows along the 8-inch diameter Energy Way and Nirvana
Avenue sanitary sewer, from just upstream of the project’s point of connection (Line A
through N) range from 0.04 to 0.24. Normal depth along the stretch of sewer ranges from
0.03 to 0.16.
2. The d/D ratios for proposed peak flows along the 8-inch diameter Nirvana Avenue and
Main Street sanitary sewer, from just downstream of the project’s point of connection (Line
O through Z) range from 0.20 to 0.41. Normal depth along the stretch of sewer ranges
from 0.13 to 0.34.
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Section 4 – Conclusions
The analysis demonstrates that while there is an increase in the planned flow in the existing sewer
main in Nirvana Avenue with the proposed project, the projected peak wet weather flows in the
analyzed, existing sewer mains do not exceed a d/D of 0.7 as required per Table 4-1 of the City of
Chula Vista Wastewater Collection System Master Plan (May 2014) and per Page 36 of the City
of Chula Vista Sewer System Management Plan (April 2021).
Therefore, it is our opinion that the existing sewer infrastructure located in Nirvana Avenue and
Main Street have sufficient capacity to convey the anticipated sewer flows from the proposed
project per the criteria listed in the city’s Wastewater Master Plan. Furthermore, the project should
not be required to upsize the existing sewer mains in Nirvana Avenue since an impact to the existing
sewer infrastructure does not occur in the area analyzed.
DATE: 3/4/2022
BY: PLSA PREPARED BY: MM
JOB NO. REFER TO FIGURE 2-4
MANNING N : 0.013
gpd gpd mgd cfs
A 5085 5084 Energy Way 7.43 Industrial 712 5,290 N/A N/A N/A N/A N/A 5,290 1.85 9,787 0.010 0.02 8 225 1.67 0.03 0.04 0.06 1.29
B 5084 5083 Energy Way 13.68 Industrial 712 9,740 N/A N/A N/A N/A N/A 15,030 1.85 27,806 0.028 0.04 8 400 0.63 0.06 0.09 0.14 1.36
C 5083 5082 Energy Way 11.79 Industrial 712 8,394 N/A N/A N/A N/A N/A 23,425 1.85 43,336 0.043 0.07 8 380 3.32 0.05 0.07 0.11 2.69
D 5082 5081 Energy Way 5.30 Industrial 712 3,774 N/A N/A N/A N/A N/A 27,198 1.85 50,317 0.050 0.08 8 300 0.40 0.08 0.14 0.21 1.39
E 5081 5078 Energy Way 9.45 Industrial 712 6,728 N/A N/A N/A N/A N/A 33,927 1.85 62,765 0.063 0.10 8 300 0.40 0.09 0.16 0.24 1.50
F 5078 5077 Energy Way 8.89 Industrial 712 6,330 N/A N/A N/A N/A N/A 40,256 1.85 74,474 0.074 0.12 8 300 0.67 0.09 0.15 0.23 1.89
G 5077 5076 Energy Way 5.19 Industrial 712 3,695 N/A N/A N/A N/A N/A 43,952 1.85 81,311 0.081 0.13 8 248 3.23 0.07 0.11 0.16 3.34
H 5074 5073 Energy Way 2.42 Industrial 712 1,723 N/A N/A N/A N/A N/A 1,723 1.85 3,188 0.003 0.00 8 191 1.33 0.02 0.03 0.04 0.89
I 5072 5073 Private Road 11.94 Industrial 712 8,501 N/A N/A N/A N/A N/A 8,501 1.85 15,727 0.016 0.02 6 568 2.00 0.04 0.06 0.12 1.82
J 5073 5075 Energy Way 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 10,224 1.85 18,915 0.019 0.03 8 24 2.48 0.03 0.05 0.08 1.90
K 5075 5076 Energy Way 1.66 Industrial 712 1,182 N/A N/A N/A N/A N/A 55,358 1.85 102,412 0.102 0.16 8 282 2.48 0.08 0.13 0.19 3.25
L 5076 5102 Nirvana Ave 3.00 Industrial 712 2,136 N/A N/A N/A N/A N/A 57,494 1.85 106,364 0.106 0.16 8 240 3.75 0.07 0.11 0.17 3.74
M 5102 5120 Nirvana Ave 7.07 Industrial 712 5,034 N/A N/A N/A N/A N/A 62,528 1.85 115,677 0.116 0.18 8 320 6.72 0.07 0.11 0.16 4.82
N 5120 5140 Nirvana Ave 3.77 Industrial 712 2,684 N/A N/A N/A N/A N/A 65,212 1.85 120,642 0.121 0.19 8 320 6.72 0.07 0.11 0.16 4.82
13.31 Industrial 712 9,477 294,468 80 N/A N/A 23,557 23,557 1.85 43,581 0.044 0.07 Project Nirvana
O 5140 5145 Nirvana Ave 0.92 Industrial 712 655 N/A N/A N/A N/A N/A 89,425 1.85 165,435 0.165 0.26 8 300 4.17 0.08 0.14 0.21 4.48
P 5145 5146 Nirvana Ave 3.25 Industrial 712 2,314 N/A N/A N/A N/A N/A 91,739 1.85 169,716 0.170 0.26 8 300 4.17 0.09 0.15 0.22 4.60
Q 5146 5151 Nirvana Ave 1.05 Industrial 712 748 N/A N/A N/A N/A N/A 92,486 1.85 171,099 0.171 0.26 8 181 1.40 0.11 0.19 0.29 3.12
R 5151 5158 Nirvana Ave 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 92,486 1.85 171,099 0.171 0.26 8 112 0.50 0.14 0.25 0.38 2.15
S 5158 5152 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 92,486 1.85 171,099 0.171 0.26 10 254 0.25 0.15 0.28 0.33 1.64
T 5152 5147 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 92,486 1.85 171,099 0.171 0.26 10 317 0.25 0.15 0.28 0.33 1.64
U 5147 5148 Main Street 63.74 Industrial 712 45,383 N/A N/A N/A N/A N/A 137,869 1.85 255,058 0.255 0.39 10 317 0.25 0.18 0.34 0.41 1.83
V 5148 7279 Main Street 1.81 Industrial 712 1,289 N/A N/A N/A N/A N/A 139,158 1.85 257,442 0.257 0.40 10 317 0.25 0.18 0.34 0.41 1.83
W 7279 7281 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 139,158 1.85 257,442 0.257 0.40 10 317 0.25 0.18 0.34 0.41 1.83
X 7281 7284 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 139,158 1.85 257,442 0.257 0.40 10 317 0.25 0.18 0.34 0.41 1.83
Y 7284 7291 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 139,158 1.85 257,442 0.257 0.40 10 317 0.25 0.18 0.34 0.41 1.83
Z 7291 7283 Main Street 8.51 Industrial 712 6,059 N/A N/A N/A N/A N/A 145,217 1.85 268,651 0.269 0.42 10 317 0.25 0.18 0.35 0.42 1.86
AA 7283 7282 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 145,217 1.85 268,651 0.269 0.42 10 305 0.25 0.18 0.35 0.42 1.86
BB 16681 7280 Main Street 29.00 Industrial 712 20,648 N/A N/A N/A N/A N/A 165,865 1.85 306,850 0.307 0.47 10 450 0.25 0.20 0.38 0.46 1.94
CC 7280 7278 Main Street 0.00 Industrial 712 0 N/A N/A N/A N/A N/A 165,865 1.85 306,850 0.307 0.47 10 449 0.33 0.18 0.35 0.42 2.13
DD 7278 7277 Main Street N/A N/A N/A N/A N/A 288,042 2.00 576,629 0.577 0.89 10 384 0.33 0.24 0.52 0.62 0.523 PDWF provided from Appendix 2(5)
Notes
(1) Per 2005 General Plan, code designation IL
(2) Per Table 3-3: Landuse Zoning Designations of the City of Chula Vista Wastewater Collection System Master Plan May 2014
(3) Per Table 3-2: Wastewater Duty Factors of the City of Chula Vista Wastewater Collection System Master Plan May 2014
(4) Wet Weather Peaking Factor from Chapter 3.3.6 of the City of Chula Vista Wastewater Collection System Master Plan May 2014
(5) Appendix 2 of City of Chula Vista Wastewater Master Plan (May 2014)
(6) Uses the more conservative value of ADWF calculated from in-line area and building square footage
Remarks
Pipe
Length
(ft)
Design
Slope (%)
Hydraulic
Radius Rh
(ft)
Normal
Depth dn
(ft)
PWWF
dn/D
Velocity
(ft/sec)
From
MH To MH
In-Line Area
Served
In-Line Area
(Acres) Land Use
(1)
Cum. Total
Avg. Dry
Weather Flow
(ADWF)(6)
Duty Factor
(gpd/ac)(2)
Avg. Dry
Weather
Flow (gpd)
Duty Factor
(gpd/DU)(3)
PIPE
REACH
Duty Factor
(gpd/1000
sf)(3)
Building
Square
Footage (sf)
Avg. Dry
Weather
Flow (gpd)
Wet
Weather
Peaking
Factor(4)
Dwelling
Units
Peak Wet Weather Flow
(PWWF)Line Size
D (in)
NIRVANA BUSINESS PARK
FIGURE 3-1
PWWF
dn/D
Project Nirvana
SANITARY SEWER STUDY SUMMARY
3668
ASSUMED IN-LINE AREA = DEVELOPABLE LOT AREA
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Section 5 – Appendices
1. City of Chula Vista Wastewater Collection System Master Plan, 2014 – Wastewater Duty
Factors and Landuse Zoning Designations (Table 3-2 and Table 3-3, pages 3-9 and 3-10)
2. City of Chula Vista Wastewater Collection System Master Plan, 2014 – Pipeline Design
Criteria (Table 4-1, page 4-1)
3. City of Chula Vista Sewer System Management Plan, April 2021 –Design Criteria (page
36)
4. City of San Diego Sewer Design Guide, 2013 – Chapter 1.7.1 Required Capacity
Downstream of New Gravity Sewers (page 1-13)