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Home My WebLink AboutCD 2019-0016; ST. ELIZABETH SETON CATHOLIC CHURCH - NEW RECTORY; HYDROLOGY / DRAINAGE STUDY; 2022-11-15 Snipes-Dye associates HYDROLOGY/DRAINAGE STUDY For St. Elizabeth Seton Catholic Church New Rectory Applicant/Developer: St. Elizabeth Ann Catholic Church 6628 Santa Isabel Street Carlsbad, CA 92009 Snipes-Dye Associates 8348 Center Drive, Suite G La Mesa, CA 91942-2910 619/697-9234 Job CA1591 Dated: March 8, 2021 Revised: May 20, 2021 DECLARATION OF RESPONSIBLE CHARGE I, HEREBY DECLARE THAT I AM THE CIVIL ENGINEER OF WORK FOR THIS PROJECT, THAT I HAVE EXERCISED RESPONSIBLE CHARGE OVER THE DESIGN OF THE PROJECT AS DEFINED IN SECTION 6703 OF THE BUSINESS AND PROFESSIONS CODE, AND THAT THE DESIGN IS CONSISTENT WITH CURRENT STANDARDS. I UNDERSTAND THAT THE CHECK OF PROJECT DRAWINGS AND SPECIFICATIONS BY THE CITY OF CARLSBAD IS CONFINED TO A REVIEW ONLY AND DOES NOT RELIEVE ME, AS ENGINEER OF WORK, OF MY RESPONSIBILITY FOR PROJECT DESIGN. MATTHEW P. KURTZ Date R.C.E. 79546 EXP. 09-30-2022 11-15-2022 546 TABLE OF CONTENTS Page Project Information 1 Pre-development Calculations 4 Post-development Calculations 10 Drainage Maps 14 Appendix 17 PRELIMINARY HYDROLOGY FOR St. Elizabeth Seton Catholic Church New Rectory The project is located at 6628 Santa Isabel Street, Carlsbad, CA 92009, with Acessor’s Parcel No. 215-330-01, in Carlsbad, California. The project proposes the addition of a new one-story building with an attached two car garage, concrete sidewalk, landscape areas, a 16’ access DG access road and the removal and replacement of a portion of an A.C. pavement parking lot. PRE-DEVELOPMENT CONDITIONS: The existing site consists of a fully developed Catholic Church with a church sanctuary building, conference center building, two parking lots and a concrete courtyard and is known as St. Elizabeth Seton Catholic Church. The site is landscaped with trees, shrubs and grass. The site is bounded by El Fuerte Street to the East, Alga Road to the north and Santa Isabel Street to the south and west. The 5.04 acre site topography slopes downward westerly toward Santa Isabel Street. Current site storm water drainage runoff flows generally in the southwesterly directions to an existing curb inlet located along Santa Isabel Street. The existing curb inlet is connected to a public underground storm drain system which ultimately discharges to San Marcos Creek approximately 1.5 miles southwesterly of the project site. The easterly portion of the site drainage runoff flows to catch basins connected to a private underground drainage system discharging to the existing curb inlet. The westerly portion of the site sheet flows to a curb outlet along Santa Isabel Street. The runoff then flows, southeasterly approximately 75 feet, within the gutter to the existing curb inlet conveying with the drainage runoff from the easterly portion of the site. The drainage runoff from the westerly parking lot flows through a small grass swale prior to discharging through the existing curb outlet. The drainage runoff from the easterly parking lot flows through a vegetated bio-swale prior to discharging into a catch basin connected to the private underground storm drain system. Runoff from the existing sanctuary and a portion of the conference center building roofs flow through adjacent landscaped areas prior to entering the private underground storm drain system. POST-DEVELOPMENT CONDITIONS: The proposed development consists of the construction of a one-story building with an attached two car garage, concrete sidewalks, landscape areas, a 16-foot decomposed granite access road and the removal and replacement of a portion of an A.C. paved parking lot. The proposed development will drain in a similar manner as the existing conditions, and consists of 3 drainage basins. Drainage basin A, will drain in a general south direction into a proposed private catch basin that discharges into an existing private 18” RCP storm drain line which connects into a public 24” RCP storm drain line at a location southwest of the site and ultimately discharges to San Marcos Creek. Drainage basin B1 consists of an area of approximately 0.01 acre and sheet flows in a general south direction until reaching an existing concrete ribbon gutter which discharges into an existing landscape area at a location southwest of the site. Lastly, drainage basin C1, consists of a new Page 1 of 21 decomposed granite SDG&E access road and the removal and replacement of an existing concrete sidewalk, which drains in a general northwest direction until reaching its discharge location at the northwestern corner of the site. This flow travels west along the northern parking lot and is collected by an existing trench drain, located northwest of the site, and discharges into a private 12” PVC storm drain line which ultimately discharges into the same public 24” RCP storm drain previously mentioned. The following table is a summary of the 100-year peak discharges for the pre- and post- development conditions: CONCLUSION: · The increase of 0.16 cfs is negligible as it will not impact any downstream and adjacent properties due to the construction of the proposed development. Page 2 of 21 PRE-DEVELOPMENT DRAINAGE CALCULATIONS Page 4 of 21 St. Elizabeth Seton Rectory - Basin A Pre-Development Coefficient ( C ) 0.90 778 SF 0.02 AC 0.35 3,618 SF 0.08 AC 18% Revised C ==0.45 P 6 =2.8 inches = 4.03 Feet = 59 Feet = 6.8 % = 4.8 Minutes T = Total Time of Concentration = 5.0 Minutes = 8.50 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.10 Acres Q = CIA = 0.38 ft 3 /sec Figure 3-4 Nomograph for Determination of Time of Concentration Basin A: Q 100 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Pervious- Soil D Soil Group D for Undisturbed Natural Terrain in Table 3-1 0.90(% IMP) + Cp(1 - % IMP) % IMP = Percent of impervious surface = Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 RAINFALL INTENSITY (I): ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration 100 Year-6 Hour Precipitation (See attached isopluvial map) T C= [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Equation 3.1.2 Estimating Runoff Factor for Area PRE-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) RUNOFF FACTOR (C): Land Use Impervious Surface Area CA1591 Pre-Development - Basin A Prepared by: Snipes-Dye Associates Page 5 of 21 St Elizabeth Seton Rectory - Basin B1 Pre-Development Coefficient ( C ) 0.90 401 SF 0.01 AC 0.35 0 SF 0.00 AC 100% Revised C ==0.90 P 6 =2.8 inches = 1.46 Feet = 37 Feet = 3.9 % = 1.4 Minutes T = Total Time of Concentration = 5.0 Minutes = 7.38 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.01 Acres Q = CIA = 0.06 ft 3/sec PRE-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin B1: Q100 RUNOFF FACTOR (C): Land Use Area Impervious Surface Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration TC = [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration CA1591 Pre-Development - Basin B1 Prepared by: Snipes-Dye Associates Page 6 of 21 St. Elizabeth Seton Rectory - Basin B2 Pre-Development Coefficient ( C ) 0.90 968 SF 0.02 AC 0.35 0 SF 0.00 AC 100% Revised C ==0.90 P 6 =2.8 inches = 2.44 Feet = 65 Feet = 3.8 % = 1.9 Minutes T = Total Time of Concentration = 5.0 Minutes = 8.50 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.02 Acres Q = CIA = 0.17 ft 3 /sec PRE-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin B2: Q 100 RUNOFF FACTOR (C): Land Use Area Impervious Surface Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration T C= [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration CA1591 Pre-Development - Basin B2 Prepared by: Snipes-Dye Associates Page 7 of 21 St. Elizabeth Seton Rectory - Basin C1 Pre-Development Coefficient ( C ) 0.90 107 SF 0.00 AC 0.35 1,568 SF 0.04 AC 6% Revised C ==0.39 P 6 =2.8 inches = 3.65 Feet = 51 Feet = 7.2 % = 4.8 Minutes T = Total Time of Concentration = 5.0 Minutes = 8.50 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.04 Acres Q = CIA = 0.13 ft 3/sec PRE-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin C1: Q100 RUNOFF FACTOR (C): Land Use Area Impervious Surface Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration TC = [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration CA1591 Pre-Development - Basin C1 Prepared by: Snipes-Dye Associates Page 8 of 21 St. Elizabeth Seton Rectory - Basin C2 Pre-Development Coefficient ( C ) 0.90 309 SF 0.01 AC 0.35 0 SF 0.00 AC 100% Revised C ==0.90 P 6 =2.8 inches = 1.67 Feet = 70 Feet = 2.4 % = 2.3 Minutes T = Total Time of Concentration = 5.0 Minutes = 8.50 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.01 Acres Q = CIA = 0.05 ft 3/sec PRE-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin C2: Q100 RUNOFF FACTOR (C): Land Use Area Impervious Surface Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration TC = [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration CA1591 Pre-Development - Basin C2 Prepared by: Snipes-Dye Associates Page 9 of 21 POST-DEVELOPMENT DRAINAGE CALCULATIONS Page 10 of 21 St Elizabeth Seton Rectory - Basin A Post-Development Coefficient ( C ) 0.90 3,984 SF 0.09 AC 0.35 602 SF 0.01 AC 87% Revised C ==0.83 P 6 =2.8 inches = 2.38 Feet = 74 Feet = 3.2 % = 2.9 Minutes T = Total Time of Concentration = 5.0 Minutes = 7.38 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.11 Acres Q = CIA = 0.64 ft 3/sec Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration TC = [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): POST-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin A: Q 100 RUNOFF FACTOR (C): Land Use Area Impervious Surface CA1591 Post-Development - Basin A Prepared by: Snipes-Dye Associates Page 11 of 21 St Elizabeth Seton Rectory - Basin B1 Post-Development Coefficient ( C ) 0.90 401 SF 0.01 AC 0.35 0 SF 0.00 AC 100% Revised C ==0.90 P 6 =2.8 inches = 1.46 Feet = 37 Feet = 3.9 % = 1.4 Minutes T = Total Time of Concentration = 5.0 Minutes = 7.38 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.01 Acres Q = CIA = 0.06 ft 3/sec Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration TC = [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): POST-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin B1: Q100 RUNOFF FACTOR (C): Land Use Area Impervious Surface CA1591 Post-Development - Basin B1 Prepared by: Snipes-Dye Associates Page 12 of 21 St Elizabeth Seton Rectory - Basin C1 Post-Development Coefficient ( C ) 0.90 1,410 SF 0.03 AC 0.35 574 SF 0.01 AC 71% Revised C ==0.74 P 6 =2.8 inches = 3.42 Feet = 72 Feet = 4.8 % = 3.3 Minutes T = Total Time of Concentration = 5.0 Minutes = 7.38 Inches/Hour PEAK DISCHARGES (Q): A = Area of the basin = 0.05 Acres Q = CIA = 0.25 ft 3/sec POST-DEVELOPMENT PEAK 100-YEAR DISCHARGE (Q) Basin C1: Q100 RUNOFF FACTOR (C): Land Use Area Impervious Surface Pervious- Soil D % IMP = Percent of impervious surface = Soil Group D for Undisturbed Natural Terrain in Table 3-1 Equation 3.1.2 Estimating Runoff Factor for Area 0.90(% IMP) + Cp(1 - % IMP) RAINFALL INTENSITY (I): 100 Year-6 Hour Precipitation (See attached isopluvial map) ∆Ε = Change in elevation along the Effective Slope D= Water Course Distance S= Slope = (∆E/D) X 100% Tc = Initial Time of Concentration TC = [1.8(1.1-C)(D^1/2)]/[S^(1/3)] = Intensity = Intensity-Duration-Design Chart County of San Diego- Hydrology Manual, Figure 3-1 FAA Rational Formula - County of San Diego Hydrology Manual Figure 3-3 Figure 3-4 Nomograph for Determination of Time of Concentration CA1591 Post-Development - Basin C1 Prepared by: Snipes-Dye Associates Page 13 of 21 DRAINAGE MAPS Page 14 of 21 8348 CENTER DRIVE, SUITE G, LA MESA, CA 91942-2910 (619) 697-9234, FAX (619) 460-2033SNIPES-DYE ASSOCIATES SDSD SD SD SD SD SD SDSD8348 CENTER DRIVE, SUITE G, LA MESA, CA 91942-2910 (619) 697-9234, FAX (619) 460-2033SNIPES-DYE ASSOCIATES APPENDIX Page 16 of 21 Page 17 of 21 SITE P6 = 2.8 Page 18 of 21 Page 19 of 21 Page 20 of 21 Page 21 of 21