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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