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HomeMy WebLinkAbout; Ridgecrest Dr Storm Drain Rehabilitation Hydrology; Ridgecrest Dr Storm Drain Rehabilitation Hydrology; 2007-06-0111 2QQ7 Harris & Associates Program Managers Construction Managers Civil Engineers City of Carlsbad Ridgecrest Drive Storm Drain Rehabilitation HYDROLOGY STUDY June 2007 Harris & Associates Program Managers City of Carlsbad r *..*,• uT»-J * T\ • cu T* • n i. •.•!•* x: Construction ManagersRidgecrest Dnve Storm Dram Rehabilitation Civil Engineers HYDROLOGY STUDY This limited hydrology study was completed as part of the City of Carlsbad's Ridgecrest Drive Storm Drain Rehabilitation Project. The study was completed to determine the hydraulic design requirements for the replacement of the existing storm drain inlet adjacent to 3010 Ridge Crest Drive. This inlet will be replace as part of the rehabilitation project. The hydrology study used maps and information provided by the City of Carlsbad and information obtained from the San Diego County Hydrology Manual. Topographical and land area calculations were based on aerial topographic maps and photos provided by the City. Rainfall information was obtained from the San Diego County Hydrology Isopluvial maps for 100-year storm events. EXISTING CONDITIONS The existing storm drain inlet on Ridgecrest Drive is a modified grate and curb inlet. The inlet opening is 30-inches wide with a grate that is 40-inches wide by 36-inches deep. The inlet is approximately 6'-6" deep. STUDY DESIGN PARAMETERS 100-Year Storm Event 6-hour precipitation - 2.8 inches 24-hour precipitation -5.1 inches Soil type "D" Land Use - Low Density Residential RESULTS Hydrology calculations were completed using the rational method per County of San Diego Hydrology Manual and are attached to this submittal. 100-year flow at NODE 110 (Storm Drain Inlet): 9.3 cubic feet per second (cfs) Inlet size required: 8" curb face 2" depression H/h=1.67 From nomograph (attached), minimum length opening required is 5.8' Use 7' Type-B Inlet (no grate). Ms. Sheri Howard Page 2 of 2 City of Carlsbad Ridgecrest Drive Storm Drain Rehabilitation June 8, 2007 The existing 18" CMP will be fitted with a liner resulting in the reduction of the storm drain diameter. The final pipe diameter will be approximately 16-inches. Based on the calculation completed for a 16-inch storm drain pipe the required depth (v) at the inlet will be 32-inches. The existing inlet box is approximately 78-inches deep and therefore has sufficient depth for this configuration. Harris & Associates 7.5 San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2005 Version Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 05/03/07 Ridgecrest Drive Storm Drain Rehabilitation City of Carlsbad 5/3/2007 Prepared by Bob Sutherlin File: Ridgecrest (100-year Storm Event) Hydrology Study Control Information ** Program License Serial Number 6032 Rational hydrology study storm event year is 100.0 English (in-lb) input data Units used Map data precipitation entered: 6 hour, precipitation(inches) = 2.800 24 hour precipitation(inches) = 5.100 P6/P24 = 54.9% San Diego hydrology manual 'C' values used Process from Point/Station 100.000 to Point/Station 105.000 **** INITIAL AREA EVALUATION **** Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 0.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 1.000 [LOW DENSITY RESIDENTIAL ] (2.0 DU/A or Less ) Impervious value, Ai = 0.200 Sub-Area C Value = 0.460 Initial subarea total flow distance = 122.600(Ft.) Highest elevation = 320.000(Ft.) Lowest elevation = 317.500(Ft.) Elevation difference = 2.500(Ft.) Slope = 2.039 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 85.00 (Ft) for the top area slope value of 2.04 %, in a development type of 2.0 DU/A or Less In Accordance With Figure 3-3 Initial Area Time of Concentration = 8.38 minutes TC = [1.8*{1.1-C)*distance(Ft.)A.5)/(% slopeA (1/3)] TC = [1.8*(1.1-0.4600)* ( 85.000A.5)/( 2.039A(1/3)]= 8.38 The initial area total distance of 122.60 (Ft.) entered leaves a remaining distance of 37.60 (Ft.) Using Figure 3-4, the travel time for this distance is 0.57 minutes for a distance of 37.60 (Ft.) and a slope of 2.04 % with an elevation difference of 0.77(Ft.) from the end of the top area Tt = [11.9*length(Mi)A3)/(elevation change(Ft.))]A.385 *60(min/hr) 0.571 Minutes Tt=[(11.9*0.0071A3)/ ( 0.77)]A.385= 0.57 Total initial area Ti = 8.38 minutes from Figure 3-3 formula plus 0.57 minutes from the Figure 3-4 formula = 8.95 minutes Rainfall intensity (I) = 5.069(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.460 Subarea runoff = 0.396(CFS) Total initial stream area = 0.170(Ac.) Process from Point/Station 105.000 to Point/Station 110.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** Top of street segment elevation = 317.500(Ft.) End of street segment elevation = 305.000(Ft.) Length of street segment = 659.800(Ft.) Height of curb above gutter flowline = 6.0(In.) Width of half street (curb to crown) = 16.000(Ft.) Distance from crown to crossfall grade break = 0.500(Ft.) Slope from gutter to grade break (v/hz) = 0.020 Slope from grade break to crown (v/hz) = 0.020 Street flow is on [2] side(s) of the street Distance from curb to property line = 9.000(Ft.) Slope from curb to property line (v/hz) = 0.020 Gutter width = 2.000(Ft.) Gutter hike from flowline = 2.000(In.) Manning's N in gutter = 0.0150 Manning's N from gutter to grade break = 0.0150 Manning's N from grade break to crown = 0.0150 Estimated mean flow rate at midpoint of street = 4.954(CFS) Depth of flow = 0.298(Ft.), Average velocity = 2.878(Ft/s) Streetflow hydraulics at midpoint of street travel: Halfstreet flow width = 8.567(Ft.) Flow velocity = 2.88(Ft/s) Travel time = 3.82 min. TC = 12.77 min. Adding area flow to street Decimal fraction soil group A = 0.000 Decimal fraction soil group B = 0.000 Decimal fraction soil group C = 0.000 Decimal fraction soil group D = 1.000 [LOW DENSITY RESIDENTIAL ] (2.0 DU/A or Less ) Impervious value, Ai = 0.200 Sub-Area C Value = 0.460 Rainfall intensity = 4.030(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.460 CA = 2.318 Subarea runoff = 8.947(CFS) for 4.870(Ac.) Total runoff = 9.343(CFS) Total area = 5.040(Ac. Street flow at end of street = 9.343(CFS) Half street flow at end of street = 4.672(CFS) Depth of flow = 0.353(Ft.), Average velocity = 3.325(Ft/s) Flow width (from curb towards crown)= 11.306(Ft.) End of computations, total study area = 5.040 (Ac.) BEST ORIGl ( I. 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S>.'^c«. ^*a|p£ >^^\ f f*^ N E THfS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANT ABILITY AND FITNESS FOR A PARTICULAR PURPOSE.Copyright SanGIS. All Rights Reserved. This products may contain information from the SANDAG Regional Information System which cannot be reproduced without the written permission of SANDAG. This product may contain information which has been reproduced with permission granted by Thomas Brothers Maps. 3 Miles ... I I f 1 , . County ! f'*--''t 1.'T*. 1 IF . »— i County of San Diego Hydrology Manual Rainfall Isopluvials 100 Year Rainfall Event - 6 Hours Isopluvial (inches) CIS N THIS MAP IS PROVIDED WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING. BUT NOT LIMITED TO. THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Copyright SanGIS. All Rights Reserved. This products may contain information from the SANDAG Regional Information System which cannot be reproduced without thewritten permission of SANDAG. This product may contain information which has been reproduced with permission granted by Thomas Brothers Maps. 303 Miles