HomeMy WebLinkAboutSDP 2023-0025; GRAND HOPE MEDICAL OFFICE; SEWER STUDY; 2024-01-01City of Carlsbad
SEWER STUDY
For:
Grand Hope
Prepared By:
Bryan Knapp, PE 86542
Pasco Laret Suiter & Associates, Inc.
1911 San Diego Avenue, Suite 100
San Diego, CA 92110
Prepared for:
Chosen Wise Properties, LLC
3144 El Camino Real #104
Carlsbad, CA 92008
January 2024
PASCO LARET SUITER
& ASSOCIATES
CIVIL ENGINEERING+ LAND PLANNING+ LAND SURVEYING
SEWER STUDY JANUARY 2024
GRAND HOPE
TABLE OF CONTENTS
Introduction ………………….…………………..……………………………………….. 1
Vicinity Map…………………………...………….……………………………………… 2
Design Criteria ………………………………..……………………………………..…… 2
On-Site Sewer Flow Projections………………………………………………………….. 3
Off-Site Sewer Flow Projections…………………………………………………………..3
Proposed Sewer Impact Calculations……………………………………………………...4
Discussion………………………………………………………………………..……….. 5
Conclusion………………………………………..………………………………………. 5
Appendix
1)……………..……………………..Sewer Study Map for Grand Hope
2)……………..…………………….. Sewer Study Design Criteria
3)……………..…………………….. As-Built Plans
SEWER STUDY JANUARY 2024
GRAND HOPE 1
INTRODUCTION
This report has been prepared to analyze the sewer capacity for the Grand Hope medical
office building project located at 2879 Hope Avenue, Carlsbad CA. This sewer study
estimates the preliminary sewer flow rates generated by the proposed project and presents
the hydraulic calculations for the proposed sewer facilities.
The 0.16± acre project site is bound by Hope Avenue to the north, Grand Avenue to the
south east and two apartment complexes to the southwest and northwest. The existing
site is currently part of the VB- Village Barrio zone. This allows for residential and
mixed use residential, retail and office uses. The Master Plan land use is part of FC –
Freeway Commercial. The project proposes 7,868 SF of medical office space with
subterranean parking and lobby/common areas on a 0.16 acre lot.
The site has an existing 6” lateral that services the dental office building and connects to
the existing 8” main on Hope Avenue. This existing lateral will be removed and a new 6”
PVC sewer lateral is proposed and will be connected to the existing 8” VCP sewer main
in Hope Avenue. The existing public sewer system within Hope Avenue is an 8” VCP,
main and, per best available record information, was constructed at a slope of 0.62% as
shown on DWG 118-9.
SEWER STUDY JANUARY 2024
GRAND HOPE 2
VICINITY MAP
DESIGN CRITERIA
The design for this sewer study was completed in accordance with the design criteria
listed in the City of Carlsbad’s Engineering Standards Volume 1 – Chapter 6 (2022
Edition) and the City of Carlsbad’s Sewer Master Plan (June, 2019). All gravity sewers
have been designed to convey peak daily flow. Per the City of Carlsbad Sewer Master
Plan (CCSMP), all sewers have been designed to convey this flow when flowing half full.
Per Table 4-1 of the CCSMP, Manning’s Equation with an “n” value of 0.013 was used
to size all gravity sewers. All sewers were designed to maintain a minimum velocity of 2
feet per second (ft/sec) at design capacity, or a minimum slope of 1%, per the design
manual. All sewer lines in this study are within public streets. All proposed locations for
the sewer lateral will have less than 15’ of cover.
j
VICINITY MAP t
NOT TO SCALE I
SEWER STUDY JANUARY 2024
GRAND HOPE 3
ON-SITE SEWER FLOW PROJECTIONS AND METHODOLOGY
The proposed on-site sewer flows have been estimated in Million Gallons per Day
(MGD) as well as cubic feet per second (CFS) based on the proposed square footage of
the medical office building for the project site. The on-site sewer flow rate has been
estimated based on criteria as outlined in Chapter 6 of the City of Carlsbad’s Engineering
Standards Volume 1 and section 3.2.3 of the City of Carlsbad’s Sewer Master Plan
(CCSMP). The project proposes 7,868 SF of medical office space on 0.16 acres. Per
Chapter 6.1A of the Eng. Std. Vol. 1, a peaking factor of 2.5 has been applied to convert
Average Daily Flows (ADF) to Peak Daily Flow (PDF).
OFF SITE SEWER FLOW PROJECTIONS AND METHODOLOGY
The existing sewer system has been analyzed using the project’s projected sewer flows
along with existing sewer flows from the surrounding properties. The existing sewer
generation rates for the public sewer mains were calculated by determining the total
amount of EDU’s contributing to the sewer system. The existing flow criteria was
determined from the total EDU’s discharging to the public sewer system spanning from
Grand Avenue to Jefferson Street as shown in Appendix 1. From the City of Carlsbad
Utility Engineer there are 97 EDU’s not including the Carlsbad Village Loft contribution
to the system. Carlsbad Village Loft contribution was determined referencing Carlsbad
Village Lofts (Mixed Use) (RP 16-05 / MS 16-06, February 2019). 156 EDU’s were also
added to the system for the future Hope Avenue Apartments, per the Hope Avenue
Apartment Sewer Study. As mentioned in the previous section, the proposed flow rates
and increase in demand generated by the proposed project were estimated based on the
building’s square footage. This proposed flow rate was added to the existing public
sewer system for the pipe runs adjacent to the subject property (Grand Avenue, Hope
Avenue, Home Avenue and Jefferson Street). The results can be seen in the following
section.
SEWER STUDY JANUARY 2024
GRAND HOPE 4
PROPOSED SEWER IMPACT CALCULATIONS
Proposed Development:
Commercial Healthcare medical office sq ft = 7,868 sq ft (0.17 ac)
Units Conversion:
Unit Flow: 1 EDU/1,800 sf building space
Proposed building = 7,868 sq ft = 4.4 EDU
ADF = Average Daily Flow: 1 EDU = 200 gpd
Peaking factor = 2.5 *Per Eng. Std. Volume 1 – Chapter 6.1.A
Flow Rates:
ADF = EDU x (200 gpd/EDU)
*Per Eng. Std. Volume 1 – Chapter 6.1.A
ADF = 4.4 EDU * 200 gpd/EDU
= 880 gpd
Peak Daily Flow = PDF
PDF = ADF * 2.5
*Per Eng. Std. Volume 1 – Chapter 6.1.A
PDF = 880 gpd * 2.5
= 2,200 gpd = 0.003 cfs
SEWER STUDY JANUARY 2024
GRAND HOPE 5
DISCUSSION
The existing 0.16± acre property is currently zoned in the Village barrio which generates
a planned peak daily flow (design flow) of 0.002 cubic feet per second (cfs) (1,138 gpd)
of sewer runoff using the criteria and methodology listed in Chapter 6.1 of the City of
Carlsbad’s Engineering Standards Volume 1 and Sections 3.2.3 and Table 4-1 of the
CCSMP (June, 2019). This flow, when routed through the existing 8-inch sewer main in
Hope and Home Avenue, as well as the 8 inch main in Jefferson Street have a ratio of
depth of flow to pipe diameter (dn/D) that do not exceed the 0.50 ratio for depth of flow
to pipe diameter (dn/D) for all the subsequent runs downstream of the subject property.
CONCLUSION
This analysis, as shown on the enclosed exhibit, demonstrates that the projected peak
daily flows in the analyzed, existing sewer mains do not exceed a dn/D of 0.5 as required
per City of Carlsbad’s Engineering Standards Volume 1 – Chapter 6.5.
Therefore, it is our opinion that the existing sewer infrastructure located in Hope Avenue
and the subsequent downstream runs have sufficient capacity to convey the anticipated
sewer flows from the proposed project per the criteria listed in the City of Carlsbad’s
Engineering Standards Volume 1 – Chapter 6 and in the city’s Sewer Master Plan (June,
2019). Furthermore, the project should not be required to upsize the existing sewer mains
in Hope Avenue since an impact to the existing sewer infrastructure does not occur in the
area analyzed.
SEWER STUDY JANUARY 2024
GRAND HOPE
APPENDIX 1
PASCO LARET SUITER
& ASSOC IATES
GIV I F\J(_: MFFRll'IG + I Af'J [) Pl ANN 'IG -I 4 \JI") :'.IJR1/FY1f\G
S3S N Coast Highway I 01 Ste A Solana Hesch, CA 9'.'-07S
ph 858.259.8212 fx 8~8.2~9.48 l 2 J plsaengineering.com
' ' ,
'
/
/ .,;, ,,(, ,,
,.,,,,·"· ..
I' _,,." ,,, ." . ,, ' ,,.
\ . :i(' ,.✓ ~~ ~ . . ,..,,
•" ' ;)ff~o ,,._,, --~
:" \ {.<\ '. '.~~
.
GRAND HOPE MEDICAL BUILDING SEWER STUDY
JOB NO. 4037 DATE: 11/7/2023
BY: PLSA
Existing Conditions
FROM TO ADD. EDU IN LINE CUMM FLOW PEAK DESIGN FLOW LINE DESIGN dn(FT)
LINE M.H. M.H. UPSTREAM EDU EDU's RATE PEAK SIZE SLOPE n= dn/D VELOCITY
MANHOLE G.P.D. FACTOR M.G.D. CFS (INCHES) (%) 0.013 (fps)
Future Hope Avenue
Apartments 0 1 156 0 156 31200 2.5 0.078 0.121 6 2.00 0.13 0.26 2.9
The Lofts 0 1A 53 0 53 10600 2.50 0.027 0.041 6 2.00 0.08 0.15 2.1
Grand Ave 1 2 53 97 306 61200 2.50 0.153 0.237 6 1.80 0.19 0.38 3.4
Hope Ave 2 3 53 97 306 61200 2.50 0.153 0.237 8 0.62 0.22 0.33 2.2
Home Ave 3 4A 53 97 306 61200 2.50 0.153 0.237 8 0.96 0.20 0.30 2.6
Home Ave 4A 4B 53 97 306 61200 2.50 0.153 0.237 8 1.00 0.20 0.30 2.7
Jefferson St 4B 5 53 97 306 61200 2.50 0.153 0.237 8 0.58 0.23 0.34 2.2
GRAND HOPE MEDICAL BUILDING SEWER STUDY
JOB NO. 4037 DATE: 11/7/2023
BY: PLSA
Proposed Condition
FROM TO ADD. EDU IN LINE CUMM FLOW PEAK DESIGN FLOW LINE DESIGN dn(FT)
LINE M.H. M.H. UPSTREAM EDU EDU's RATE PEAK SIZE SLOPE n= dn/D VELOCITY
MANHOLE G.P.D. FACTOR M.G.D. CFS (INCHES) (%) 0.013 (fps)
Futue Hope Avenue
Apartments 0 1 156 0 156 31200 2.50 0.078 0.121 6 2.00 0.13 0.26 2.9
The Lofts 0 1 53 0 53 10600 2.50 0.027 0.041 6 2.00 0.08 0.15 2.1
Grand Ave 1 2 53 97 306 61200 2.50 0.153 0.237 6 1.80 0.19 0.38 3.4
Hope Ave 2 3 53 102 311 62200 2.50 0.156 0.241 8 0.62 0.23 0.34 2.3
Home Ave 3 4A 53 102 311 62200 2.50 0.156 0.241 8 0.96 0.20 0.30 2.6
Home Ave 4A 4B 53 102 311 62200 2.50 0.156 0.241 8 1.00 0.20 0.30 2.7
Jefferson St 4B 5 53 102 311 62200 2.50 0.156 0.241 8 0.58 0.23 0.34 2.2
SEWER STUDY JANUARY 2024
GRAND HOPE
APPENDIX 2
Volume 1 6/30/23
Page 41 of 54
CHAPTER 6 – DESIGN CRITERIA FOR SEWER FACILITIES
Prior to preparation of improvement plans, Engineer of Work shall submit a preliminary layout
of the sewer system for review and approval by the City Engineer. Basis of design shall be
demonstrated for the development type and density and corresponding sewer flow generation
factors and the following design criteria.
6.1 SEWER FLOW GENERATION FACTORS
A. Flow Rate Generation – The values in the latest adopted Sewer Master Plan shall govern:
1) An Equivalent Dwelling Unit (EDU) = 200 gal/day, Average Daily Flow (ADF)
2) For ADF less than 100,000 gal/day, a peaking factor (PF) of 2.5 multiplied times the
ADF shall be used to determine Peak Daily Flow (PDF). PDF = ADF x 2.5
a) Residential: Single Family Residence = 1 EDU
b) Residential: Multi-Family Residence = 0.8 EDU
c) Commercial Property: 1 EDU/1,800 square feet of building space
i) To convert raw land to square feet of building space, assume 30%
coverage. This could vary significantly dependent development
constraints.
ii) To convert improved pads to square feet of building space, assume 40%
of coverage.
d) Industrial Property:
i) 1 EDU/5,000 square feet of warehouse space
ii) 1 EDU/1,800 square feet of office space
iii) To convert raw land to square feet of building space, assume 30%
coverage. This could vary significantly dependent issues such as
environmental restrictions.
iv) To convert improved pads to square feet of building space, assume 40%
of coverage.
v) Assume 60% of building space is warehouse, and 40% is office space.
6.2 SEWER MAIN DEPTH AND SIZE
A. Sewer main depth and size shall be as shown below unless approved by the City Engineer.
B. Minimum depth, finish grade to top of pipe: 6 feet
C. Maximum depth, finish grade to top of pipe: 15 feet
D. Design calculations shall be submitted as a basis for pipe size and bedding design.
(Manning "n" for PVC = 0.011).
E. Minimum pipe diameter of sewer main shall be 8 inches. A 6-inch sewer main may be
allowed on cul-de-sac streets with a maximum of 10 units.
Volume 1 6/30/23
Page 42 of 54
F. A decrease in the pipe diameter in the downstream direction of flow will not be allowed
without hydraulic calculations and prior approval of the City Engineer.
G. All sewer laterals and gravity sewer main invert elevations shall be shown in profile on the
improvement plans. Show stationing of manholes and laterals, invert elevations at
manholes and lateral connections, and the distance, pipe size, pipe type, standard
dimension ratio and pipe slope of sewer main segments.
H. All sewer mains 15" and greater pipe diameters shall require special design subject to City
Engineer approval.
6.3 SEWER LATERALS
A. Use 4" minimum diameter pipe for each sewer lateral to single-family residences.
B. Use 6" minimum diameter pipe for sewer laterals for all other development types and sized
for the drainage fixture units in accordance with the latest adopted California Plumbing
Code or for the proposed industrial use water demand.
C. Sewer lateral depth at the property line shall be 5 feet (top of pipe to finish grade @ top of
curb).
D. Sewer laterals shall be constructed in accordance with the Carlsbad Standard Drawings.
The minimum horizontal distance from water services, fire hydrants, driveways, light
standards, electrical utilities, etc. is 10 feet. Special approval is required for horizontal
clearance less than specified herein.
1) Install at a right angle or radial to the main.
2) Laterals shall not be located in driveways.
3) No connections shall be permitted on laterals other than as allowed by the Standard
Drawings.
4) Location of property cleanout: See Standard Drawing No. S-7.
5) If the lowest sanitary sewer fixture in a building structure is lower than 2-feet above
the nearest upstream manhole cover, then the owner must provide a backwater
valve on the sewer lateral to prevent sewage backflow into the structure. The valve
must be installed in a valve box for accessibility and be visible from the public right-
of-way. The property owner shall be responsible for the installation and maintenance
of the backwater valve. The backwater valve shall be shown on the precise grading
and improvement plans.
6) Install sewer laterals using wye fittings, or manholes as required, sized and located
as shown on the Approved Plans.
7) Laterals shall be bedded, backfilled and compacted in the same manner as the
sewer main they are connected to.
--
Sewer Master Plan Update City of Carlsbad
4-10 | June 2019
4.2 Design Criteria
The City of Carlsbad General Engineering Standards, Volume I, Chapter 6, Design
Criteria for Gravity Sewer Lines and Appurtenances, provides design guidelines for the
design of sewer gravity mains, lift stations, and forcemains. New sewer improvement
plans must be reviewed and approved by the City Engineer.
4.2.1 Engineering Standards Design Criteria
The design criteria from City’s Engineering Standards are shown in Table 4-1. Criteria to
be reconsidered in this Master Plan update, highlighted in Table 4-1, include sewer
generation rates, as lower water demands per capita due to voluntary and mandated
water conservation measures are also reflected in lower wastewater flows.
Table 4-1. Sewer Design Criteria
Parameter Engineering Standard Criteria (Volume 1, Chapter 6) Recommended Revised Criteria
Sewer Generation Rate
Residential, Single Family 220 gpd/EDU 200 gpd/EDU
Residential, Multi- Family 176 gpd (80 percent of 220 gpd/EDU) 160 gpd (80 percent of 200 gpd/EDU)
Commercial, Industrial or Institutional
Flow projections for future schools, resort hotels, and certain industrial uses are based on EDU conversions documented in the Carlsbad Municipal Code (Table 13.10.020c).
No change
Peak Daily Flow Factor 2.5 x Average Daily Flow No change
d/D Ratio for Gravity Mains
For sewer mains ≤ 12-inch 0.50 at peak hour dry weather flows No change
For sewer mains > 12-inch 0.75 at peak hour dry weather flows No change
For all sewer mains 0.90 at peak hour wet weather flows No change
Manning's Roughness Coefficient
For PVC-lined pipes in the V/C 0.012 No change
For all other pipes 0.013 No change
Velocity for Gravity Mains
Minimum allowable velocity 2 feet per second No change
Maximum allowable velocity 12 feet per second No change
Velocity for Force Mains
Minimum allowable velocity 2.5 feet per second No change
Maximum allowable velocity 8 feet per second No change
Notes:
d/D=depth-to-diameter ratio; EDU=equivalent dwelling unit; V/C=Vista/Carlsbad
SEWER STUDY JANUARY 2024
GRAND HOPE
APPENDIX 3