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HomeMy WebLinkAboutCDP 2022-0008; MARTIN RESIDENCE; FINAL HYDROLOGY STUDY FOR MARTIN RESIDENCE; 2024-05-01 FINAL HYDROLOGY STUDY FOR MARTIN RESIDNECE – BUENA VISTA CIRCLE CDP 2022-0008 GR 2023-0033 DWG 544-4A CITY OF CARLSBAD, CA LAND DEVELOPMENT ENGINEERING PREPARED FOR: PAMELA KAYE SULLIVAN MARTIN 3301 LINCOLN STREET CARLSBAD, CA 92008 PREPARED BY: PASCO LARET SUITER & ASSOCIATES, INC. 1911 SAN DIEGO AVENUE, SUITE 100 SAN DIEGO, CA 92110 PH: (858) 259-8212 Prepared: December 2021 Final: May 2024 __________________________________________________ Bryan A. Knapp, PE #86542 DATE ---------------------5/22/24 No. 86542 l(p_ OJ/Jl/2 TABLE OF CONTENTS SECTION Executive Summary 1.0 Introduction 1.1 Existing Conditions 1.2 Proposed Project 1.3 Conclusions 1.4 References 1.5 Methodology 2.0 Introduction 2.1 County of San Diego Criteria 2.2 Runoff Coefficient Determination 2.3 Hydrology & Hydraulic Model Output 3.0 Pre-Developed Hydrologic Calculations (100-Year Event) 3.1 Post-Developed Hydrologic Calculations (100-Year Event) 3.2 Pre-Developed vs. Post-Developed Peak Flows (100-Year Event) 3.3 Static Volume Analysis 3.4 Hydromodification Analysis 3.5 Storm Water Pollutant Control 3.6 Appendix 4.0 Isopluvial Maps Intensity Duration Design Charts Runoff Coefficients Hydrologic Soil Group - USDA Web Soil Survey Pre-Development Hydrology Node Map Post-Development Hydrology Node Map PLSA 3628-02 Page 1 of 17 1.0 EXECUTIVE SUMMARY 1.1 Introduction This Final Hydrology Study for the proposed development at the vacant lot along Buena Vista Circle, APN: 155-221-05-00 known as the Martin Residence, has been prepared to analyze the hydrologic and hydraulic characteristics of the existing and proposed project site. This report intends to present both the methodology and the calculations used for determining the runoff from the project site in both the pre-developed (existing) conditions and the post-developed (proposed) conditions produced by the 100-year, 6- hour storm. 1.2 Existing Conditions The subject property is located along Buena Vista Circle, south of the Buena Vista Lagoon, in the City of Carlsbad. The site is bound by existing single-family developments to the west, south, and east, as well as Buena Vista Lagoon to the north. The existing site consists of minor landscaping, open space consisting of mostly dirt and grass, and a concrete drainage ditch towards the middle of the site. The project site is located in the Buena Vista Creek Hydrologic Area, and, more specifically, the El Salto Hydrologic Sub-Area (904.21) of the Carlsbad watershed. After review of the site edge conditions, existing topography, and adjacent developments, it was determined that there is no additional offsite runon entering the site from the neighboring properties. The southern-most portion of the site is sloped towards Buena Vista Circle, which then drains north-to-south towards a local low point in the street just south of 2411 Buena Vista Circle. Currently, an inlet exists at the low point of Buena Vista Circle at an existing concrete headwall structure, which then feeds an existing public 12” reinforced concrete pipe sloped at 1.0% as shown on DWG 805-1 that conveys drainage to the lagoon. The 12” drainage pipe is located within a 6’ public drainage easement as shown on Map 2492. The subject property has an approximate gross area of 0.616 acres and is approximately 1.45% impervious in the existing condition. The area that will be analyzed will be the 0.326 acres of developable land past the 100-foot wetland setback in the rear of the property. The existing site can be categorized into two (2) major drainage basins, with two (2) primary discharge locations leaving the property. Drainage basin EX-1 consists of almost the entirety of the project site and primarily drains from the northeast corner of the property to the southwest, discharging to the Buena Vista Lagoon by surface and sheet flow methods before then continuing to the Pacific Ocean. Drainage Basin EX-2 discharges out to the southern property boundary and onto Buena Vista Circle, continuing downstream to the existing inlet, concrete headwall structure, and 12” drainage pipe as described above. Per the Web Soil Survey application available through the United States Department of Agriculture, the basin is generally categorized to have type B hydrologic soils. Based on PLSA 3628-02 Page 2 of 17 the existing impervious area and land use type, a pre-development weighted runoff coefficient of 0.25 was calculated for the subject property using the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration was calculated for the 100-year, 6- hour storm event for the onsite drainage basin. Table 1 below summarizes the results of the Rational Method calculations. EXISTING DRAINAGE FLOWS DRAINAGE AREA DRAINAGE AREA (ACRES) Q100 (CFS) I100 (IN/HR) EX-1 0.294 0.25 3.34 EX-2 0.029 0.03 3.57 TOTAL 0.323 0.28 - Table 1. Existing Condition Peak Drainage Flow Rates Refer to pre-development hydrology calculations included in Section 3.1 of this report for a detailed analysis of the existing drainage basin, as well as a pre-development hydrology node map included in the appendix of this report for pre-development drainage basin delineation and discharge locations. 1.3 Proposed Project The proposed project includes the demolition of all existing onsite improvements and the construction of a single-family residence along with an accessory dwelling unit. The project proposes a private driveway to provide vehicular access to the proposed garage. The proposed pad elevation for the proposed structure is 45.3. Site grading, drainage, and utility improvements typical of this type of single-family residential development will also be constructed as can be seen on the Grading Plans prepared by Pasco, Laret, Suiter & Associates, DWG 544-4A. In the proposed condition the subject property can be categorized into one (1) major drainage basin with one (1) primary discharge locations leaving the property, similar to the existing condition. The total disturbed area making up the portion of the property included in this analysis is 14,207 square feet, and is approximately 70.6% impervious in the proposed condition. Basins PR-1 makes up the majority of the site and is 11,935 square feet. Basin PR-1 is the westerly portion of the disturbed area of the site situated east of the wetland setback. Runoff from basin PR-1 will be directed from impervious surfaces to landscaped swales and area drains to be routed to a biofiltration BMP situated at the corner of the wetland set back and the southerly property line. Once runoff is PLSA 3628-02 Page 3 of 17 treated in the BMP it is released through a flow spread down the existing slope leading to Buena Vista Lagoon similar to existing conditions. Basin PR-2 is made up the remaining frontage of the property. Runoff from the frontage of the property will sheet flow down to a proposed 20-foot diameter tree well within property limits along Buena Vista Circle. Analyzing the extended drainage basin that reaches Buean Vista Circle it was determined there is a 100-yr strom flow rate of 5.32 cfs in the Buena Vista Circle. The project propoes a mountable curb to aid in defing the flow line in Buena Vista Circle and to keep the 100-yr storm with in the right of way. The right of way in front of the project site will be graded at two (2) percent to further prevent runoff from draining outside of the right of way. The 5.32 cfs in the Buena Vista Circle was modeled using Hydraflow Express and Buena Vista Circle’s typical road section. The result showing the 100-yr storm containined within the right of way can be seen in Appendix A. Based on the proposed impervious area and land use type, a post-development weighted runoff coefficient of 0.71 was calculated for the subject property using the methodology described in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided therein. Note, pursuant to the Regional Water Resources Control Board MS4 Permit, pool and jacuzzi areas to be considered impervious area for storm water determination purposes. These areas have been excluded from the total impervious area used for hydrology purposes in determining the site runoff coefficient. Using the Rational Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time of concentration were calculated for the 100-year, 6- hour storm event for the onsite drainage basin. Table 2 below summarizes the results of the Rational Method calculations in the post-developed condition. PROPOSED DRAINAGE FLOWS DRAINAGE AREA DRAINAGE AREA (ACRES) UNMIT. Q100 (CFS) I100 (IN/HR) MIT. Q100 (CFS) PR-1 0.274 1.26 6.59 0.01 PR-2 0.049 0.23 6.59 0.11 TOTAL 0.323 1.49 - 0.12 Table 2. Proposed Condition Peak Drainage Flow Rates Refer to post-development hydrology calculations included in Section 3.2 of this report for a detailed analysis of the proposed drainage basin, as well as a post-development hydrology node map included in the appendix of this report for post-development drainage basin delineation and discharge locations. In an effort to comply with the City of Carlsbad storm water standards, the proposed site has incorporated LID design techniques to optimize the site layout. Runoff from PLSA 3628-02 Page 4 of 17 proposed roofs and new or removed and replaced hardscape areas will be directed to landscaped areas to disperse drainage to pervious surfaces. The landscaped areas will assist to remove sediment and particulate-bound pollutants from storm water. In addition, partial infiltration and evapotranspiration in self-treating yard landscaped areas will assist in slowing runoff discharges and in reducing volume generated during storm events. Proposed surface drainage swales will assist in removing sediment and particulate-bound pollutants from storm water and will assist in decreasing peak runoff velocities by increasing the site’s overall time of concentration. 1.4 Conclusions Based upon the analysis included in this report, there is an increase of ~1.49 cfs in unmitigated peak runoff as a result of the proposed development due to the 994 square feet of increased hardscape in the proposed condition as compared to the existing site. Similar to the existing condition, the majority of the site will discharge in the rear of the property to Buena Vista Lagoon, while a portion of the project site will drain to the front out to Buena Vista Circle. The project will not create a diversion of water and it is not anticipated for runoff produced from the proposed development to have an adverse effect on the downstream watershed. While the proposed project creates additional hardscape, the project also increases the time of concentration to the ultimate discharge point in the Buena Vista Lagoon. Proposed permanent storm water treatment and detention facilities will serve to mitigate peak flows generated in the proposed condition to below pre- project rates. Table 3 below summarizes the results of the detained peak flow conditions. COMPAIRSON DRAINAGE FLOW DRAINAGE AREA DRAINAGE AREA (ACRES) Q100 (CFS) I100 (IN/HR) EX-1 0.294 0.28 - PR-1 (DET) 0.274 0.01 - Table 3. Proposed Condition Peak Drainage Flow Rates (Detained Condition) Basin PR-2 is not included in the table but the difference between basin PR-2 and basin EX-2 is less than 0.1 cfs when flows are mitigated by tree well, see calculations page 13. Basin PR-2 also proposes a HMP sized tree well that will provide 262 cubic feet of storage, which exceeds the required 252 cubic feet of storage due to proposed impervious improvements. Refer to the projects Storm Water Quality Management Plan (SWQMP) included under a separate cover for pollutant control and hydromodification calculations. Also refer to section 3.4 and Appendix B of this report for detailed detention calculations. PLSA 3628-02 Page 5 of 17 1.5 References “San Diego County Hydrology Manual”, revised June 2003, County of San Diego, Department of Public Works, Flood Control Section. “San Diego County Hydraulic Design Manual”, revised September 2014, County of San Diego, Department of Public Works, Flood Control Section “City of Carlsbad Engineering Standards, Volume 5: Carlsbad BMP Design Manual (Post Construction Treatment BMPs)”, revised February 2016 “Low Impact Development Handbook – Stormwater Management Strategies”, revised July 2014, County of San Diego, Department of Public Works Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov. Accessed September 2, 2020 PLSA 3628-02 Page 6 of 17 2.0 METHODOLOGY 2.1 Introduction The hydrologic model used to perform the hydrologic analysis presented in this report utilizes the Rational Method (RM) equation, Q=CIA. The RM formula estimates the peak rate of runoff based on the variables of area, runoff coefficient, and rainfall intensity. The rainfall intensity (I) is equal to: I = 7.44 x P6 x D-0.645 Where: I = Intensity (in/hr) P6 = 6-hour precipitation (inches) D = duration (minutes – use Tc) Using the Time of Concentration (Tc), which is the time required for a given element of water that originates at the most remote point of the basin being analyzed to reach the point at which the runoff from the basin is being analyzed. The RM equation determines the storm water runoff rate (Q) for a given basin in terms of flow (typically in cubic feet per second (cfs) but sometimes as gallons per minute (gpm)). The RM equation is as follows: Q = CIA Where: Q = flow (in cfs) C = runoff coefficient, ratio of rainfall that produces storm water runoff (runoff vs. infiltration/evaporation/absorption/etc) I = average rainfall intensity for a duration equal to the Tc for the area, in inches per hour. A = drainage area contributing to the basin in acres. The RM equation assumes that the storm event being analyzed delivers precipitation to the entire basin uniformly, and therefore the peak discharge rate will occur when a PLSA 3628-02 Page 7 of 17 raindrop that falls at the most remote portion of the basin arrives at the point of analysis. The RM also assumes that the fraction of rainfall that becomes runoff or the runoff coefficient C is not affected by the storm intensity, I, or the precipitation zone number. 2.2 County of San Diego Criteria As defined by the County Hydrology Manual dated June 2003, the rational method is the preferred equation for determining the hydrologic characteristics of basins up to approximately one square mile in size. The County of San Diego has developed its own tables, nomographs, and methodologies for analyzing storm water runoff for areas within the county. The County has also developed precipitation isopluvial contour maps that show even lines of rainfall anticipated from a given storm event (i.e. 100-year, 6-hour storm). One of the variables of the RM equation is the runoff coefficient, C. The runoff coefficient is dependent only upon land use and soil type and the County of San Diego has developed a table of Runoff Coefficients for Urban Areas to be applied to basin located within the County of San Diego. The table categorizes the land use, the associated development density (dwelling units per acre) and the percentage of impervious area. Each of the categories listed has an associated runoff coefficient, C, for each soil type class. The County has also illustrated in detail the methodology for determining the time of concentration, in particular the initial time of concentration. The County has adopted the Federal Aviation Agency’s (FAA) overland time of flow equation. This equation essentially limits the flow path length for the initial time of concentration to lengths under 100 feet, and is dependent on land use and slope. The time of concentration minimum is 5 minutes for purposes of calculating rainfall intensity per the County of San Diego Hydrology Manual requirements. 2.3 Runoff Coefficient Determination As stated in section 2.2, the runoff coefficient is dependent only upon land use and soil type and the County of San Diego has developed a table of Runoff Coefficients for Urban Areas to be applied to basin located within the County of San Diego. The table, included in the Appendix of this report, categorizes the land use, the associated development density (dwelling units per acre) and the percentage of impervious area. For this study, a weighted runoff coefficient was used for both the pre-project and post- developed site in accordance with the equation provided in Section 3.1.2 of the County of PLSA 3628-02 Page 8 of 17 San Diego Hydrology Manual. The weighted runoff coefficient is a function of the total impervious and pervious surface areas in the existing and proposed conditions. PLSA 3628-02 Page 9 of 17 3.0 HYDROLOGY MODEL OUTPUT 3.1 Pre-Developed Hydrologic Model Output (100-Year Event) Pre-Development: Q = CIA *Rational Method Equation P100 = 2.5 *100-Year, 6-Hour Rainfall Precipitation Existing Area – Overall Drainage Basin Total Area = 14,091 sf  0.323 Acres Impervious Area = 100 sf  0.002 Acres Pervious Area = 13,091 sf  0.301 Acres Cn, Weighted Runoff Coefficient - 0.25, Cn value for natural ground, Type B soils * Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 - 0.9, C value for developed / impervious surface * Per SDHDM Section 3.1.2 Cn = 0.9 x 100 sf + 0.25 x 13,091 sf = 0.25 14,091 sf Basin EX-1 Total Area = 12,803 sf  0.294 Acres Cn = 0.25 Ti = 12.5 mins *Per SDCHM Table 3-2, Initial TC Tt = (11.9*((123/5280)^3)/1.4)= 0.029 hours *Per SDCHM Figure 3-4, in hours Tt= 0.029 *60 = 1.78 mins Tc = Ti + Tt Tc = 12.5 + 1.78 = 14.28 mins I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 14.28-0.645 ≈ 3.34 in/hr Q100 = 0.25 x 3.34 in/hr x 0.294 Ac = 0.25 cfs PLSA 3628-02 Page 10 of 17 Basin EX-2 Total Area = 1,288 sf  0.029 Acres Ti = 12.5 mins *Per SDCHM Table 3-2, Initial TC Tt = (11.9*((32/5280)^3)/0.9)= 0.007 hours *Per SDCHM Figure 3-4, in hours Tt= 0.007 *60 = 0.45 mins Tc = Ti + Tt Tc = 12.5 + 0.45 = 12.95 mins I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 12.95-0.645 ≈ 3.57 in/hr Q100 = 0.25 x 3.57 in/hr x 0.029 Ac = 0.03 cfs PLSA 3628-02 Page 11 of 17 3.2 Post-Developed Hydrologic Model Output (100-Year Event) Post-Development (without considering HMP/BMP treatment): Q = CIA *Rational Method Equation P100 = 2.5 *100-Year, 6-Hour Rainfall Precipitation Disturbed Area – Overall Drainage Basin Total Area = 14,091 sf  0.323 Acres Impervious Area = 10,094 sf  0.232 Acres Pervious Area = 3,997 sf  0.091 Acres Cn, Weighted Runoff Coefficient - 0.25, Cn value for natural ground, Type B soils * Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2 - 0.9, C value for developed / impervious surface * Per SDHDM Section 3.1.2 Cn = 0.9 x 10,094 sf + 0.25 x 3,997 sf = 0.71 14,091 sf Basin PR-1 Total Area = 11,721 sf  0.269 Acres Cn = 0.71 Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 5-0.645 ≈ 6.59 in/hr Q100 = 0.70 x 6.59 in/hr x 0.274 Ac = 1.26 cfs PLSA 3628-02 Page 12 of 17 Basin PR-2 Total Area = 2,370 sf  0.054 Acres Cn = 0.71 Ti = 6.7 Min *Per SDCHM Table 3-2, Initial TC Tc = Ti I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 6.7-0.645 ≈ 5.45 in/hr Q100 = 0.71 x 5.45 in/hr x 0.05 Ac = 0.19 cf 3.3 Pre-Developed vs. Post-Developed Peak Flows (100-Year Event) Total Pre-Development (Discharge Leaving Site) Basin EX-1 Q100 = 0.25 cfs *Discharging from the site across the westerly property line Basin EX-2 Q100 = 0.03 cfs *Discharging from the site at the mid southeast corner to Buena Vista Circle Total Q100 = 0.28 cfs Total Post-Development (Discharge Leaving Site) Basin PR-1 Q100 = 1.26 cfs *Discharging evenly through the BMP in the corner where the wetland setback meets the southerly property line Basin PR-2 Q100 = 0.19 cfs *Discharging to Buena Vista Circle Total Q100 = 1.45 cfs Pre-Development vs. Post-Development (Discharge Leaving Site): Pre-Development Post-Development Delta Q100 = 0.28 cfs Q100 = 1.45 cfs 1.17 cfs increase *Total overall site runoff increased in proposed condition from pre-development site. Refer to the following section, Section 3.4, of this report for a discussion of detention PLSA 3628-02 Page 13 of 17 system proposed to mitigate site to existing conditions. Also refer to the Appendix of this report for existing and proposed condition hydrology node maps showing discharge locations from the subject property. 3.4 Detention Analysis The onsite biofiltration basin provides pollutant control as well as mitigation of the 100- year, 6-hour storm event peak flow rate. A routing analysis was performed for the proposed biofiltration facility in the rear of the property to confirm peak flow will be detained and slowly released to match existing conditions. HydroCAD-10 has the ability to route the 100-year, 6-hour storm event inflow hydrograph (generated and modeled using RatHydro, which is a Rational Method Design Storm Hydrograph software that creates a hydrograph using the results of the Rational Method calculations) through each biofiltration facility. Based on the BMP cross-sectional geometry, stage-storage and outlet structure data, HydroCAD-10 has the ability to perform a dynamic / routing analysis and calculate the detained peak flow rate as well as detained time to peak. The results of this analysis can be found in Appendix B of the report. The biofiltration basin consists of a total area of approximately 900 square feet, 3 inches of mulch, 18-inches of engineered soil, 4-inches of 3/8” gravel and 8-inches of 3/4” gravel. Runoff will be biofiltered through the engineered soil and gravel layers, then collected in a series of small PVC perforated drainpipes and directed to a catch basin located in a corner of the biofiltration basin. Once in the catch basin, runoff will be mitigated via a small 0.425-inch low-flow orifice to comply with hydromodification requirements. In larger, high-intensity storm events, runoff not filtered through the engineered soil and gravel layers will be conveyed via an overflow outlet structure consisting of a 36-inch by 36-inch grate located on top of the catch basin. Runoff entering the outlet structure will be conveyed directly to a proposed spread flower PVC outlet pipe and will discharge evenly down the slope towards Buena Vista Lagoon. COMPAIRSON DRAINAGE FLOW DRAINAGE AREA DRAINAGE AREA (ACRES) Q100 (CFS) I100 (IN/HR) EX-1 0.294 0.29 3.88 PR-1 (Unmit) 0.274 1.26 6.59 PR-1 (DET) 0.274 0.01 - EX-2 0.029 0.03 3.88 PR-2 (Unmit) 0.049 0.19 6.59 PR-2 (DET) 0.049 0.12 3.64 Table 4. Detained Condition Peak Drainage Flow Rates PLSA 3628-02 Page 14 of 17 Table 4 above lists a summary of the results of the detention analysis as compared to the pre-project and post-project unmitigated peak flows. Based on the results of the HydroCAD-10 analysis, it was determined that the biofiltration basin facility provides mitigation for the 100-year, 6-hour storm event peak flow rate by detaining the proposed condition to 0.01 cfs, which is below the existing condition Q100 of 0.25 cfs leaving the property to the west via sheet flow methods. The tree well BMP mitigates the proposed flows for PR-2 down to 0.12 cfs which less than 0.1 cfs greater than existing. The tree well detains a higher volume than existing conditions and the difference in peak flows can be considered negligible refer to section 3.4.1 and 3.4.2 for mitigated flow and detention calcs for the proposed tree well. For additional information, refer to Appendix A of this Hydrology Report for the pre- and-post-developed project hydrologic node maps. Lastly, refer to Appendix B of this report for the HydroCAD-10 detailed output, which shows the dynamic routing of the 100-year, 6-hour storm event through the biofiltration basins and the resulting mitigated peak discharge leaving the subject property. 3.4.1 Tree Well Mitigated Flow FLOW RATE (CFS) TREE WELL AREA (SF) PONDING DEPTH (FT) SURFACE VOL. (CF) LAG TIME (SEC) LAG TIME (MIN) 0.19 161 0.5 80.5 424 7.06 Total Area = 2,156 sf  0.049 Acres Cn = 0.71 Ti = 6.7 Min *Per SDCHM Table 3-2, Initial TC Tc = Tt + Lag Time Tc = 6.7 + 7.06 = 13.06 mins I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation I = 7.44 x 2.5 x 12.53-0.645 ≈ 3.55 in/hr Q100 = 0.71 x 3.55 in/hr x 0.049 Ac = 0.12 cfs The mitigated flow for PR-2 generated by the routing of storm water to the tree well BMP is 0.12 cfs. The difference in peak flows generated in pre and post is less than 0.1 cfs which can be considered negligible. PLSA 3628-02 Page 15 of 17 3.4.1 Tree Well Detention Analysis (Static) The proposed tree well BMP basin provides pollutant control as well as mitigation of the 100-year, 6-hour storm event peak flow rate for the proposed portion of the project discharging to Buena Vista Circle. The 100-year, 6-hour storm event detention analysis was performed in accordance with Chapter 6 of the San Diego County Hydrology Manual. The results of the analysis provide a static detention requirement by comparing the total volume produced by the 100-year, 6-hour storm in the existing and developed conditions. The total volume can be calculated after producing a hydrograph for each event (pre- and post-developed) with the results of the Rational Method analysis. Calculations and results of this analysis can be shown below. This method is considered to be conservative, as it does not take into account the routing characteristics of the tree well. Pre-Development: 100-Year Event (Basin EX-2) Volume = C*P6*A *Equation 6-1 of SDCHM Volume = 0.25 * (2.5 in * 1 ft / 12 in) * 1,288 sf = 67.1 CF Post-Development: 100-Year Event (Basin PR-2) Volume = C*P6*A *Equation 6-1 of SDCHM Volume = 0.71 * (2.5 in * 1 ft / 12 in) * 2,156 sf = 318.9 CF Required Detention Volume = Total Post-Development – Total Pre-Development = Prop. Basin PR-2 – Pre Basin EX-2 = 318.9 CF – 67.1 CF = 252 CF  252 CF of static storage required for drainage basin PR-2 to mitigate to pre-development conditions BMP Stage Storage - Tree Well Elevation Tree Well Area (sq-ft) Void ratio of layer Stage Volume (cu-ft) Total Volume (cu-ft) 0 160 0 0 0 0.5 160 0.4 32 32 1 160 0.4 32 64 1.5 160 0.4 32 96 2 160 0.4 32 128 2.5 160 0.4 32 160 3 160 0.4 32 192 3.5 160 0.4 32 224 4 160 0.4 32 256 4.17 160 1 27.2 283.2 I PLSA 3628-02 Page 16 of 17 The difference in Q100 for basins EX-2 and PR-2 is very minimal, approximately 0.18 cfs. The proposed 20-foot diameter HMP sized Tree Well will provide 283.2 CF of storage at ponding depth, meeting the 252 CF storage requirements for POC-2 discharging along the frontage of the property and providing sufficient storage volume to detain the post-developed project to pre-project conditions. The proposed Tree Well was sized for HMP, which significantly increases the storage for the proposed Tree Well. 3.5 Hydromodification Analysis Refer to the project Storm Water Quality Management Plan (SWQMP) prepared by Pasco, Laret, Suiter & Associates under separate cover for discussion of hydromodification management strategy and compliance to satisfy the requirements of the MS4 Permit. 3.6 Storm Water Pollutant Control To meet the requirements of the MS4 Permit, the HMP biofiltration facility is designed to treat onsite storm water pollutants contained in the volume of runoff from a 24-hour, 85th percentile storm event by slowly infiltrating runoff through an engineered soil layer. Refer to the project Storm Water Quality Management Plan (SWQMP) prepared by Pasco, Laret, Suiter & Associates under separate cover for discussion of pollutant control. PLSA 3628-02 Page 17 of 17 4.0 APPENDIX SITE LOCATION IL__·-----_--_I .L SITE LOCATION I I I I I . . . . . . . . • . -) . ,-. ' ' . : . . . ,, .,,. . . -... ·, "~ ~ ~ . I I I I I · . --- . . -~ . . . . . . . . ,=' ·- --. . . . . . . . ' ~ e,a\H'1'Y 0 ~i.NDIEc;o • I -······_--___JI DPW ~GIS [lep:I.J""iJ7ient Di P11Mc Works Grn,r,..•pfll/,; /11furrr,.itiw1 &rv,t r.i-:; Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil SurveyNational Cooperative Soil Survey 12/2/2021Page 1 of 4 36 6 9 8 3 0 36 6 9 8 4 0 36 6 9 8 5 0 36 6 9 8 6 0 36 6 9 8 7 0 36 6 9 8 8 0 36 6 9 8 9 0 36 6 9 9 0 0 36 6 9 8 3 0 36 6 9 8 4 0 36 6 9 8 5 0 36 6 9 8 6 0 36 6 9 8 7 0 36 6 9 8 8 0 36 6 9 8 9 0 36 6 9 9 0 0 467180 467190 467200 467210 467220 467230 467240 467250 467260 467270 467280 467290 467180 467190 467200 467210 467220 467230 467240 467250 467260 467270 467280 467290 33° 10' 2'' N 11 7 ° 2 1 ' 7 ' ' W 33° 10' 2'' N 11 7 ° 2 1 ' 2 ' ' W 33° 10' 0'' N 11 7 ° 2 1 ' 7 ' ' W 33° 10' 0'' N 11 7 ° 2 1 ' 2 ' ' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 25 50 100 150Feet 0 5 10 20 30Meters Map Scale: 1:560 if printed on A landscape (11" x 8.5") sheet. Soil Map may not be valid at this scale. USDA = MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation ServiceWeb Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: San Diego County Area, CaliforniaSurvey Area Data: Version 16, Sep 13, 2021 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jan 24, 2020—Feb 12, 2020 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil SurveyNational Cooperative Soil Survey 12/2/2021Page 2 of 4USDA = □ D D D D D D D D ,,..,,,. ,,..,,,. □ ■ ■ □ □ ,,..._., t-+-t ~ tllWI ,..,,. ~ • Hydrologic Soil Group Map unit symbol Map unit name Rating Acres in AOI Percent of AOI LG-W Lagoon water 0.7 42.9% MlC Marina loamy coarse sand, 2 to 9 percent slopes B 0.2 12.7% TeF Terrace escarpments 0.7 44.5% Totals for Area of Interest 1.6 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil SurveyNational Cooperative Soil Survey 12/2/2021Page 3 of 4USDA = Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—San Diego County Area, California Natural Resources Conservation Service Web Soil SurveyNational Cooperative Soil Survey 12/2/2021Page 4 of 4~ San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26 Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use Runoff Coefficient “C” Soil Type NRCS Elements County Elements % IMPER. A B C D Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35 Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 0.42 0.46 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49 Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 0.48 0.52 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 0.57 0.60 Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63 High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71 High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79 Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79 Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82 Commercial/Industrial (O.P. Com) Office Professional/Commercial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (Limited I.) Limited Industrial 90 0.83 0.84 0.84 0.85 Commercial/Industrial (General I.) General Industrial 95 0.87 0.87 0.87 0.87 *The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area is located in Cleveland National Forest). DU/A = dwelling units per acre NRCS = National Resources Conservation Service 3-6 San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 12 of 26 Note that the Initial Time of Concentration should be reflective of the general land-use at the upstream end of a drainage basin. A single lot with an area of two or less acres does not have a significant effect where the drainage basin area is 20 to 600 acres. Table 3-2 provides limits of the length (Maximum Length (LM)) of sheet flow to be used in hydrology studies. Initial Ti values based on average C values for the Land Use Element are also included. These values can be used in planning and design applications as described below. Exceptions may be approved by the “Regulating Agency” when submitted with a detailed study. Table 3-2 MAXIMUM OVERLAND FLOW LENGTH (LM) & INITIAL TIME OF CONCENTRATION (Ti) .5% 1% 2% 3% 5% 10% Element* DU/ Acre LM Ti LM Ti LM Ti LM Ti LM Ti LM Ti Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9 LDR 1 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4 LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8 LDR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0 100 5.6 MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3 MDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8 MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5 MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3 HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5 HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4 100 2.7 N. Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7 G. Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4 O.P./Com 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 Limited I. 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2 General I. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3 100 1.9 *See Table 3-1 for more detailed description 3-12 48"TD 40"TD 18"TD 18"TD 18"TD 18"TD 12"TD16"TD SW X X XXXXXXXXXXXXXXXX XXXXXX XXXXX XXXXX XXXX OEOE OE OE RF = 53.2RF = 53.9 VEGE VEGE CO N C 44 44 44 44 43 43 4 3 43 43 43 43 43 42 42 42 42 42 41 41 41 40 40 40 39 39 39 38 38 38 37 37 37 36 36 36 35 35 35 34 34 34 33 33 33 32 32 32 31 31 31 30 30 30 29 29 29 28 28 28 27 27 27 26 26 26 25 25 25 24 24 24 23 23 23 22 22 22 21 21 21 20 20 20 19 19 19 18 18 18 17 17 17 16 16 16 15 15 15 14 14 14 13 1 3 13 12 12 12 11 11 1110 10 10 10 9 9 9 9 9 8 8 8 8 8 8 8 8 8 7 AS P H X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 42.4 42.5 43.3 43.6 43.9 42.5 42.3 42.5 42.5 42.6 42.8 42.8 42.8 43.3 43.2 43.2 43.3 43.6 43.6 43.6 43.7 43.7 43.5 43.7 44.3 43.9 42.742.4 43.4 43.8 43.9 44.3 42.9 TC= 4 3 . 7 3 TC= 4 3 . 5 8 TC=4 3 . 4 1 TC=43 . 2 1 TC= 4 3 . 6 2 TC= 4 3 . 4 7 TC=4 3 . 3 0 TC=43 . 1 0 BU E N A V I S T A CIR C L E BUE N A V I S T A L A G O O N L=109.92' D=10°09'28" NODE EX-1.1(44.3 HP) L=123.0' NODE EX-1.3 (41.9 FG) Q100= 0.25 CFS BASIN EX-2 AREA = 1,288 SF (0.029 AC) Cn = 0.25 BASIN EX-1 AREA = 12,803 SF (0.294 AC) Cn = 0.25 NODE EX-2.1(44.2 HP) NODE EX-2.3 (43.1 FG) Q100= 0.03 CFS TOTAL AREA AREA = 14,091 SF (0.323 AC) Cn = 0.25 L=7 0 . 0 ' NODE EX-2.2(44.2 HP) L= 3 2 . 0 ' GRAPHIC SCALE: 1" = 10' 0 10'20'30' J:\ACTIVE JOBS\3628 MARTIN BUENA VISTA CIR-CARLSBAD\CIVIL\REPORTS\HYDROLOGY\Appendix MARTIN RESIDENCE LEGEND SUBJECT PROPERTY / SUBDIVISION BOUNDARY EXISTING RIGHT-OF-WAY / ADJACENT LOT LINE CENTERLINE OF ROAD EXISITING CONTOUR PROPOSED FLOW DIRECTION PROPOSED IMPERVIOUS AREA EXISTING MAJOR DRAINAGE BASINPR-1 EXISTING MAJOR DRAINAGE BASIN PR -2 100 EXISTING HYDROLOGY EXHIBIT PRE-DEVELOPMENT HYDROLOGY NODE MAP BASIN EX-1 - AREA CALCULATIONS BASIN EX-1 TOTAL AREA 12,803 SF (0.294 AC) Cn = 0.25 TIME OF CONCENTRATION = 14.28 MINUTES (PER SDCHM) Q100 = 0.25 CFS BASIN EX-2 - AREA CALCULATIONSTOTAL BASIN - AREA CALCULATIONS TOTAL BASIN AREA 14,091 SF (0.323 AC) BASIN IMPERVIOUS AREA 100 SF (0.002 AC)BASIN PERVIOUS AREA 13,091 SF (0.324 AC) % IMPERVIOUS 0.7% Cn 0.25 BASIN EX-2 TOTAL AREA = 1,288 SF (0.029 AC) Cn = 0.25 TIME OF CONCENTRATION = 12.95 MINUTES (PER SDCHM) Q100 = 0.03 CFS SCALE: 1" = 10' I \ \ I __ ,j ' --- ...... \ \. ) ...... \ \ / ( \ ,.-\ \ \ I I -- N0DEEX-1.2 (43.3 FG) 43.BFG ' ~ ...._ ) ' -.._/ I I I n......, __ / / \ I I II I . I (; I I I I / I /// ~ \ V /" _ , • ~ / ' - 1/ I I I I I I J /. ---............ I ;" I I I I I I I I I I I I I I I I I I I , ~ I ( I I f , I I I I SW X X XXXXXXXXXXXXXXXX XXXXXX XXXXX XXXXX XXXX OEOE OE OE X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 48"TD 40"TD 18"TD 18"TD 18"TD 18"TD 12"TD16"TD RF=53.2 RF = 53.9 VEGE VEGE CON C 44 44 44 44 43 43 4 3 43 43 43 43 43 42 42 42 42 42 41 41 41 40 40 40 39 39 39 38 38 38 37 37 37 36 36 36 35 35 35 34 34 34 33 33 33 32 32 32 31 31 31 30 30 30 29 29 29 28 28 28 27 27 27 26 26 26 25 25 25 24 24 24 23 23 23 22 22 22 21 21 21 20 20 20 19 19 19 18 18 18 17 17 17 16 16 16 15 15 15 14 14 14 13 13 13 12 12 12 11 11 11 10 10 10 10 9 9 9 9 9 8 8 8 8 8 8 8 8 8 7 ASP H 42.4 42.5 43.3 43.6 43.9 42.5 42.3 42.5 42.5 42.6 42.8 42.8 42.8 43.3 43.2 43.2 43.3 43.6 43.6 43.6 43.7 43.7 43.5 43.7 44.3 43.9 42.742.4 43.4 43.8 43.9 44.3 42.9 EOP= 4 3 . 5 8 EOP=4 3 . 4 1 EOP=4 3 . 2 1 EOP= 4 3 . 7 0 EOP= 4 3 . 6 2 EOP= 4 3 . 4 7 EOP=4 3 . 3 0 EOP=43 . 1 0 45.3 TW(42.7 BW) NODE PR-2.2Q100=0.19 CFS (UNMIT)Q100=0.12 CFS (MIT) LANDSCAPE DRAINAGE SWALE 45.8 TW(43.7 BW) 45.0 TW43.5 TW @ FG42.2 BW @ FG40.75 BOT BMP 45.3 TW (42.2 BW) 45.8 FS / HP 46.8 TW (42.8 BW) 45.3 TW(42.8 BW) IE OUT 41.5 44.9 FG BASIN BF-1 Q100 IN = 1.26 CFS Q100 OUT = 0.01 CFS 43.5 IE IE OUT 42.2 20-FTDIAMETERTREE WELL NODE PR-2.145.0 HP BU E N A V I S T A CIR C L E BUE N A V I S T A L A G O O N BMP 1 FG = 43.5 AREA = 960 SF L=109.92' D=10°09'28" BASIN PR-1 11,721 (0.269 AC) Cn = 0.71 BASIN PR-2 2,370 SF (0.054 AC) Cn = 0.71 45.0 TG43.9 IE 46.4 TG 43.8 IE 45.6 TG 44.5 IE 45.6 TG44.7 IE 45.0 TG 44.0 IE 45.6 TG 44.6 IE45.2 TG44.4 IE 45.2 TG44.1 IE 45.2 TG 44.6 IE 45.1 TG42.7 IE 45.1 TG 43.0 IE 45.2 TG 44.6 IE 45.5 HP 44.9 TG 43.8 IE 43.8 IE 43.6 IE 45.3 HP 45.3 FG 44.9 TG 44.0 IE 45.3 FG 44.9 TG 43.9 IE GRAPHIC SCALE: 1" = 10' 0 10'20'30' J:\ACTIVE JOBS\3628 MARTIN BUENA VISTA CIR-CARLSBAD\CIVIL\REPORTS\HYDROLOGY\Appendix PROPOSED HYDROLOGY EXHIBIT MARTIN RESIDENCE POST-DEVELOPMENT HYDROLOGY NODE MAP SCALE: 1' = 10' LEGEND SUBJECT PROPERTY / SUBDIVISION BOUNDARY EXISTING RIGHT-OF-WAY / ADJACENT LOT LINE CENTERLINE OF ROAD EXISITING CONTOUR PROPOSED FLOW DIRECTION PROPOSED IMPERVIOUS AREA BASIN PR-1 - AREA CALCULATIONS BASIN PR-1 TOTAL AREA = 11,721 SF (0.269 AC) Cn = 0.71 TIME OF CONCENTRATION = 5.0 MINUTES (PER SDCHM) Q100 (UNMIT)= 1.26 CFSQ100 (MIT)= 0.01 CFS PROPOSED MAJOR DRAINAGE BASIN PR-1 PROPOSED MAJOR DRAINAGE BASIN PR -2 TOTAL DISTRURED AREA - BASIN CALCULATIONS TOTAL SITE AREA 14,091 SF (0.323 AC) BASIN IMPERVIOUS AREA 10,094 SF (0.232 AC) BASIN PERVIOUS AREA 3,997 SF (0.091 AC) % IMPERVIOUS 71.4% Cn 0.71 100 BASIN PR-2 - AREA CALCULATIONS BASIN PR-1 TOTAL AREA = 2,370 SF (0.054 AC) Cn = 0.71 TIME OF CONCENTRATION = 6.7 MINUTES (PER SDCHM) Q100 = 0.19 CFS I \ \ I __ ,j ' ...... \ \. ...... \ ) I ( \ ,- ---------- I I I I I /' ) ' -- -...... ...._ IL-..,-I---L....,-+--c=!e-alrG--:'!cc.f-JL..,{,l I-' --• - \. ' \. /----r , / ------ ' I _J_ __ 7\ ;-;:--I I '-I / \ I ' / I ' \ / \ ,__/, \ I r ',, \ I / ,~ I / '\ \ / '-,l v _______ _ as .c.---c- • :--.. ·-. ,-·· •. ',." , . •• . .-.-· '·-·'· 0 /===ilf/ •... ;. :· '. ,.-· ·-. - -- ~ ...._ ) ' ...._,,- I I I / I 0 .0 0 n --< - Channel Report Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Tuesday, May 21 2024 BUENA VISTA CIRCLE Q100 FLOW User-defined Invert Elev (ft) = 0.60 Slope (%)= 0.80 N-Value = 0.015 Calculations Compute by:Known Q Known Q (cfs) = 5.32 (Sta, El, n)-(Sta, El, n)... ( 0.00, 1.00)-(10.00, 0.80, 0.015)-(22.00, 0.92, 0.015)-(34.00, 0.80, 0.015)-(38.00, 0.60, 0.015)-(42.00, 0.80, 0.015) Highlighted Depth (ft)= 0.31 Q (cfs)= 5.320 Area (sqft)= 3.19 Velocity (ft/s)= 1.67 Wetted Perim (ft) = 35.51 Crit Depth, Yc (ft) = 0.31 Top Width (ft)= 35.50 EGL (ft)= 0.35 -5 0 5 10 15 20 25 30 35 40 45 50 Elev (ft)Depth (ft)Section 0.00 -0.60 0.50 -0.10 1.00 0.40 1.50 0.90 2.00 1.40 Sta (ft) PLSA 3628-01 Page 15 of 15 APPENDIX B 1L Inflow to BMP-1 3P BMP-1 Routing Diagram for 3628 Prepared by Pasco Laret Suiter & Assoc, Printed 10/4/2023 HydroCAD® 10.20-3c s/n 10097 © 2023 HydroCAD Software Solutions LLC Subcat Reach Pond Link ---[> 0 D 6 [j .------___J 3628 Printed 10/4/2023Prepared by Pasco Laret Suiter & Assoc Page 2HydroCAD® 10.20-3c s/n 10097 © 2023 HydroCAD Software Solutions LLC Summary for Link 1L: Inflow to BMP-1 Inflow = 1.26 cfs @ 4.08 hrs, Volume= 0.032 af Primary = 1.26 cfs @ 4.08 hrs, Volume= 0.032 af, Atten= 0%, Lag= 0.0 min Routed to Pond 3P : BMP-1 Primary outflow = Inflow, Time Span= 0.00-96.00 hrs, dt= 0.01 hrs DISCHARGE Imported from RatHydro adj.csv Link 1L: Inflow to BMP-1 Inflow Primary Hydrograph Time (hours) 95908580757065605550454035302520151050 Fl o w ( c f s ) 1 0 DISCHARGE Imported from RatHydro adj.csv 1.26 cfs 1.26 cfs D 3628 Printed 10/4/2023Prepared by Pasco Laret Suiter & Assoc Page 3HydroCAD® 10.20-3c s/n 10097 © 2023 HydroCAD Software Solutions LLC Summary for Pond 3P: BMP-1 Inflow = 1.26 cfs @ 4.08 hrs, Volume= 0.032 af Outflow = 0.01 cfs @ 4.91 hrs, Volume= 0.030 af, Atten= 99%, Lag= 49.7 min Primary = 0.01 cfs @ 4.91 hrs, Volume= 0.030 af Routing by Dyn-Stor-Ind method, Time Span= 0.00-96.00 hrs, dt= 0.01 hrs Peak Elev= 44.32' @ 4.91 hrs Surf.Area= 900 sf Storage= 1,364 cf Plug-Flow detention time= 1,544.0 min calculated for 0.030 af (93% of inflow) Center-of-Mass det. time= 1,539.9 min ( 1,766.7 - 226.8 ) Volume Invert Avail.Storage Storage Description #1 41.00' 2,430 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Voids Inc.Store Cum.Store Wet.Area (feet)(sq-ft) (%) (cubic-feet) (cubic-feet)(sq-ft) 41.00 900 0.0 0 0 900 42.00 900 40.0 360 360 1,006 43.50 900 20.0 270 630 1,166 45.50 900 100.0 1,800 2,430 1,379 Device Routing Invert Outlet Devices #1 Primary 42.20'6.000" Round Culvert L= 17.0' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 42.20' / 42.03' S= 0.0100 '/' Cc= 0.900 n= 0.013, Flow Area= 0.20 sf #2 Primary 41.25'4.000" Round Culvert L= 17.0' RCP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 41.25' / 41.08' S= 0.0100 '/' Cc= 0.900 n= 0.013, Flow Area= 0.09 sf #3 Device 2 41.25'0.425" Vert. Orifice C= 0.600 Limited to weir flow at low heads #4 Device 1 44.50'36.000" x 36.000" Horiz. Grate C= 0.600 in 36.000" x 36.000" Grate (100% open area) Limited to weir flow at low heads #5 Device 3 41.00'5.000 in/hr Infiltration through soil media over Surface area below 43.50' Primary OutFlow Max=0.01 cfs @ 4.91 hrs HW=44.32' (Free Discharge) 1=Culvert (Passes 0.00 cfs of 1.25 cfs potential flow) 4=Grate ( Controls 0.00 cfs) 2=Culvert (Passes 0.01 cfs of 0.61 cfs potential flow) 3=Orifice (Orifice Controls 0.01 cfs @ 8.41 fps) 5=Infiltration through soil media (Passes 0.01 cfs of 0.10 cfs potential flow) t~ t_ t_ 3628 Printed 10/4/2023Prepared by Pasco Laret Suiter & Assoc Page 4HydroCAD® 10.20-3c s/n 10097 © 2023 HydroCAD Software Solutions LLC Pond 3P: BMP-1 Inflow Primary Hydrograph Time (hours) 95908580757065605550454035302520151050 Fl o w ( c f s ) 1 0 Peak Elev=44.32' Storage=1,364 cf 1.26 cfs 0.01 cfs D