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Home My WebLink About6608; Northwest Quadrant Drainage Improvements; Northwest Quadrant Storm Drain Project Crest; 2008-03-01NORTHWEST QUADRANT STORM DRAIN PROJECT CREST DRIVE CITY OF CARLSBAD HYDROLOGY ANALYSIS Prepared by: Harris & Associates 750 B street, Suite 1800 San Diego, CA 92101 (619) 236-1778 MARCH 2008 NORTHWEST QUADRANT STORM DRAIN PROJECT CREST DRIVE CITY OF CARLSBAD HYDROLOGY ANALYSIS Prepared under the supervision of: Robert Sutherlin Jr. Project Manager R.C.E 38819 IVIARCH 2008 Table of Contents A. Purpose 1 B. Existing Drainage Facilities I C. Hydrology Analysis I D. Proposed Improvements 1 Appendices o 100-year Hydrology Enclosure o Hydrology Map m m m A. Purpose The purpose of the Northwest Quadrant project is to improve drainage at three locations with the city of Carlsbad. This report focuses on the improvements needed for Crest Drive. The project limit is on Crest Drive from Buena Vista Avenue north approximately 1750' to a high point in the roadway profile. In accordance with our scope of services, we have performed a hydrologic analysis to address drainage issues and provide recommendations for a possible storm drain. B. Existing Drainage Facilities Crest Drive is located several miles east of Highway 5 along Buena Vista Avenue. The street has been maintained in a rural type condition without any sidewalks and only rolled curb and gutter on the eastern roadway edge. The existing drainage facilities along Crest Drive handle mainly nuisance flows. Existing facilities consist of several individual 15" x 15" grates located in fi-ont of residences along the western side of the street with small 6" PVC outiet pipes that have been installed to drain eastward across the street and outlet down a natural slope. The largest of these inlets is a 24" x 24" grate located at a sump approximately 825' north of Buena Vista Avenue (shown on the map near node 4). Flow from this sump inlet is piped beneath the roadway and into a gunite ditch that flows down the hillside and then north in a second PCC ditch, ultimately draining to Monroe Street. The PCC ditch is on private property and is not maintained by the city. C Hydrology Analysis (Refer to the Hydrology Map) The project area watershed is encompasses 8 V2 lots that front Crest Drive. These lots total about 3.9 acres and during a 100-year storm event will generate approximately 6.4 cubic feet per second (CFS) runoff Assumptions made are type "D" soil and single family development for 2.9 dwelling units/acre. D. Proposed Improvements h is proposed to construct a second inlet on the east side of the roadway at the sump to capture runoff on this side of the street. The two sump inlets will be connected, with the outlet pipe being directed south along Crest Drive. The proposed storm drain will eliminate flow from being directed into the existing ditch from this area. The outiet pipe will flow south until it nears Buena Vista Avenue, where it will be turned eastward down the slope and connect to the existing 42" storm drain system in Monroe Street to the east. As per city's direction, no hydraulics will be performed on the existing system in Monroe Street as the storm flows reach this system anyway via the existing ditch. 100-year Hydrology San Diego County Rational Hydrology Program CIVILCADD/CIVILDESIGN Engineering Software,(c)1991-2005 Version 7.5 Rational method hydrology program based on San Diego County Flood Control Division 2003 hydrology manual Rational Hydrology Study Date: 01/23/08 NW Quadrant Storm Drainage Project Crest Hydrology "NWCREST" 1/22/08 ********* 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) = 2.500 24 hour precipitation{inches) = 4.300 P6/P24 = 58.1% San Diego hydrology manual 'C values used +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 1.000 to Point/Station 2.000 **** 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 ] (2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.490 Initial subarea total flow distance = 180.000(Ft.) Highest elevation = 198.000(Ft.) Lowest elevation = 196.000(Ft.) Elevation difference = 2.000(Ft.) Slope = 1.111 % INITIAL AREA TIME OF CONCENTRATION CALCULATIONS: The maximum overland flow distance is 70.00 (Ft) for the top area slope value of 1.11 %, in a development type of 2.9 DU/A or Less In Accordance With Table 3-2 Initial Area Time of Concentration = 10.00 minutes (for slope value of 1.00 %) Rainfall intensity (I) = 4.212(In/Hr) for a 100.0 year storm Effective runoff coefficient used for area (Q=KCIA) is C = 0.490 Subarea runoff = 0.433(CFS) Total initial stream area = 0.210(Ac.) Process from Point/Station 2.000 to Point/Station 3.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** Top of street segment elevation = 196.000(Ft.) End of street segment elevation = 194.000(Ft.) Length of street segment = 215.000(Ft.) Height of curb above gutter flowline = 6.0(In.) Width of half street {curb to crown) = 12.500(Ft.) Distance from crown to crossfall grade break = 0.500(Ft.) Slope from gutter to grade break (v/hz) = 0.010 Slope from grade break to crown (v/hz) = 0.010 Street flow is on [2] side(s) of the street Distance from curb to property line = 10.000(Ft.) Slope from curb to property line (v/hz) = 0.010 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 = 1.207(CFS) Depth of flow = 0.222{Ft.), Average velocity = 1.391(Ft/s) Streetflow hydraulics at midpoint of street travel: Halfstreet flow width = 7.579(Ft.) Flow velocity = 1.39(Ft/s) Travel time = 2.58 min. TC = 12.58 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 ] (2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.490 Rainfall intensity = 3.633{In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.490 CA = 0.505 Subarea runoff = 1.400(CFS) for 0.820(Ac.) Total runoff = 1.834(CFS) Total area = 1.030(Ac.) Street flow at end of street = 1.834(CFS) Half street flow at end of street = 0.917(CFS) Depth of flow = 0.243(Ft.), Average velocity = 1.495(Ft/s) Flow width (from curb towards crown)= 9.661(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 3.000 to Point/Station 4.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** Top of street segment elevation = 194.000(Ft.) End of street segment elevation = 189.000(Ft.) Length of street segment = 222.000(Ft.) Height of curb above gutter flowline = 6.0(In.) Width of half street (curb to crown) = 12.500(Ft.) Distance from crown to crossfall grade break = 0.500(Ft.) Slope from gutter to grade break (v/hz) = 0.010 Slope from grade break to crown (v/hz) = 0.010 Street flow is on [2] side(s) of the street Distance from curb to property line = 10.000(Ft.) Slope from curb to property line (v/hz) = 0.010 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 = 2.605(CFS) Depth of flow = 0.239(Ft.), Average velocity = 2.287(Ft/s) Streetflow hydraulics at midpoint of street travel: Halfstreet flow width = 9.197{Ft.) Flow velocity = 2.29(Ft/s) Travel time = 1.62 min. TC = 14.19 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 ] (2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.490 Rainfall intensity = 3.361(In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.490 CA = 0.965 Subarea runoff = 1.410(CFS) for 0.940(Ac.) Total runoff = 3.244(CFS) Total area = 1.970{Ac.) Street flow at end of street = 3.244(CFS) Half street flow at end of street = 1.622(CFS) Depth of flow = 0.250(Ft.), Average velocity = 2.385(Ft/s) Flow width (from curb towards crown)= 10.329(Ft.) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 5.000 to Point/Station 4 000 **** SUBAREA FLOW ADDITION **** 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 ] {2.9 DU/A or Less ) Impervious value, Ai = 0.250 Sub-Area C Value = 0.490 Time of concentration = 14.19 min. Rainfall intensity = 3.361{In/Hr) for a 100.0 year storm Effective runoff coefficient used for total area (Q=KCIA) is C = 0.4 90 CA = 1.901 Subarea runoff = 3.145(CFS) for 1.910{Ac.) Total runoff = 6.389{CFS) Total area = 3.880(Ac.) End of computations, total study area = 3.880 (Ac.) LEGEND 7.97 STORM DRAIN INLET NODE NUMBER AREA (ACRES) STUDY AREA DRAINAGE BOUNDARY FLOW PATH EXISTING STORM DRAIN PIPE GRAPHIC SCALE ( IN FEBT ) 1 Inch - 80 1 CITY OF CARLSBAD NORTHWEST QUADRANT STORM DRAINAGE CREST DRIVE STORM DRAIN HYDROLOGY MAP DATS: 1-30-08 SCAlt: r-BO' 062-0340.04 SHEET 1 OF 1 SHEETS