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Home My WebLink About6608; STATE STREET DRAINAGE IMPROVEMENTS; STATE STREET HYDROLOGY AND DRAINAGE IMPROVEMENTS TECHNICAL MEMORANDUM; 2019-10-23Northwest Quadrant Drainage Program - State Street Drainage Design, Page 1 October 23, 2019 Introduction Frequent surface ponding on both sides of State Street between Grand Avenue and Carlsbad Village Drive has been observed and reported by local residents and City of Carlsbad staff. The ponding is a result of the localized low points in the street, dips in the aggregate concrete gutter, as well as the installation of pop-out seating for some of the local restaurants. The location of the site is shown in Figure 1 – Vicinity Map. Figure 1 – Vicinity Map (N.T.S.) Tech nical Memorandum TO: Danny Zimny FROM: Scott Cartwright DATE: October 23, 2019 SUBJECT: State Street Hydrology & Drainage Improvements n 811,,rn " II' Site Location >,,my nd -y 0 t E w i • .. Lavun• o, ~\ • ,.<-... ►'" 1--% 'l, .s;. 'E . 0 ... .. " • ► y.o«' 1;, ... ~, ... '1-~ • ~► ~ r,\'t('o ~ <s;. Northwest Quadrant Drainage Program - State Street Drainage Design, Page 2 October 23, 2019 The purpose of this technical memorandum is to analyze these drainage issues and provide design backup for proposed improvements, with specific objectives as follows: • Document the tributary drainage area associated with the project site; • Develop hydrologic parameters and calculate 2, 10, and 100-year flow rates for existing conditions per the City of Carlsbad Engineering Standards and the San Diego County Hydrology Manual; • Design a shallow pipe system with grate inlets to convey nuisance ponding south towards the existing stormdrain system within Carlsbad Village Dr. This hydraulic analysis assumes that downstream facilities are functioning in accordance with City standards. No downstream hydrology or hydraulics are included in this current effort. Existing Conditions This area consists of businesses and local restaurants that discharge runoff into State Street. Most of the runoff from State St. will flow south towards Carlsbad Village Dr. to existing inlets to the east and west of State Street. Proposed Conditions The project proposes to install a 10” PVC main storm drain along State Street. A total of five grate inlets will be installed at localized low points along the street for the purposes of draining nuisance flooding. Both the inlets and the storm drain system are only designed to convey nuisance flooding and not designed to capture and convey the 10yr peak flow underground per Carlsbad Design Standards (Drainage and Storm Drain Standards 5.1.B). Surface improvements will also be proposed as part of this project to establish a defined flow path along the gutter line and prevent localized ponding. The existing curb and AC gutter will be removed and replaced with a modified concrete curb and gutter. The crown of the street will remain the same, but the gutter line will be graded to establish a consistent slope along the street to facilitate proper drainage. Northwest Quadrant Drainage Program - State Street Drainage Design, Page 3 October 23, 2019 Methodology Hydrology Existing hydrologic parameters have been developed using the Rational Method procedures according to 2003 County of San Diego Hydrology Manual (SDCHM), as adapted within Volume 1, Chapter 5 of the City of Carlsbad Engineering Standards. Calculations have been performed utilizing these parameters within a standard excel spreadsheet. • Federal Emergency Management Agency (FEMA) Panels have been reviewed for the site. Neither the site, nor surrounding area is located within a floodplain. The FIRMette for the site can be found in Attachment A. • Soils information to develop loss rates has been taken from the San Diego Geographic Information Source (SANGIS). The underlying hydrologic soils for this project is type-B; Refer to the soils maps and SANGIS descriptions in Attachment B. • 6-hour precipitation Rainfall Isopluvial maps for the 2-year, 10-year, & 100-year events are located in Attachment B. • Impervious area estimates were made from public domain aerial photography. These estimates were correlated with C values from Table 3-1 in the SDCHM and it was determined that C value is 0.84 for Commercial land-use with type-B soils. • The project site is relatively small and a conservative total time of concentration (Tc) was assumed to be 5 minutes. • The drainage area (A) was determined based on available topographic information from SANGIS and project specific topographic survey. A site inspection was conducted to verify the potential presence of physical drainage features capable of impacting flow paths, but too insignificant to be identified as part of an area-wide aerial topographic survey. The drainage area delineation can be found on the Hydrology Exhibit in Attachment C. Storm Drain Hydraulic Bentley Flow Master was used to determine the full flow capacity of the proposed 10” PVC storm drain line. This program uses the manning’s equation to determine full flow pipe capacity by inputting the following: roughness coefficient, slope, pipe diameter, & normal depth. Inlet Sizing The grate inlets are being located and designed to drain nuisance flooding at localized low points throughout the street. Flow that is not able to discharge into an inlet will bypass to downstream structures in the same manner as the existing condition. The inlet capacity calculations have been performed based on the San Diego County Hydraulic Design Manual, which can be found in Attachment D. Northwest Quadrant Drainage Program - State Street, Page 4 October 23, 2019 Results and Conclusions Hydrology Results The summary of peak flow rates for the 2, 10, and 100-year event are summarized in Table 1 below. The calculations themselves can be reviewed in Attachment C. TABLE 1- HYDROLOGY SUMMARY – EXISTING Drainage Area Area (ac) C Q2 (CFS) Q10 (CFS) Q100 (CFS) Site 10 – State Street 2.48 0.84 6.6 8.8 13.7 Storm Drain Hydraulics: The results of the Flow Master analysis show that the proposed 10” PVC main storm drain with a minimum of 0.5% slope can adequately convey 2.0cfs. Inlet Hydraulics: Each 18” X 18” grate inlet will have an inlet capacity of 2.4cfs. Five grate inlets will be installed on State Street; The project wide inlet capacity is 12cfs. The proposed storm drain improvements are designed to prevent localized nuisance flooding and they are not sized to convey the 10-year storm event underground per City of Carlsbad standards. Northwest Quadrant Drainage Program - State Street October 23, 2019 Attachment A - FIRMette USGS The National Map: Orthoimagery. Data refreshed April, 2019. National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250Feet Ü117°21'15.24"W 33°9'51.26"N 117°20'37.78"W 33°9'21.14"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOODHAZARD AREAS Without Base Flood Elevation (BFE)Zone A, V, A99With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone X Future Conditions 1% AnnualChance Flood Hazard Zone XArea with Reduced Flood Risk due toLevee. See Notes.Zone XArea with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm SewerLevee, Dike, or Floodwall Cross Sections with 1% Annual Chance17.5 Water Surface ElevationCoastal Transect Coastal Transect BaselineProfile BaselineHydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of StudyJurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 5/9/2019 at 1:19:13 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time. This map image is void if the one or more of the following mapelements do not appear: basemap imagery, flood zone labels,legend, scale bar, map creation date, community identifiers,FIRM panel number, and FIRM effective date. Map images forunmapped and unmodernized areas cannot be used forregulatory purposes. Legend OTHER AREAS OFFLOOD HAZARD OTHER AREAS GENERALSTRUCTURES OTHERFEATURES MAP PANELS 8 1:6,000 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1111111 0-- - -513- L] □ . 121 Northwest Quadrant Drainage Program - State Street October 23, 2019 Attachment B – Soils Exhibit & Excerpts from SDCHM !( Site 10 NORTHWEST QUADRANT 2019 Hydrologic Soil Type Exhibit °0 100 20050Feet7/12/2019 JN H:\PDATA\172862 State Street Drainage Design\GIS\Soil Type Exhibit.mxd <USER NAME>Source: Legend !(Site Location Drainage Area Soils_w_hydSoilTypeSoil Type A B C D State St. South of GrandStreet Name:Site Description: Site 10 Area Ac: 2.48 Michael Baker INTERNATIONAL San Diego County Hydrology Manual Date: June 2003 Table 3-1 Section: Page: RUNOFF COEFFICIENTS FOR URBAN AREAS Land Use Runoff Coefficient "C" Soil Type NRCS Elements Coun Elements %IMPER. A B Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 Low Density Residential (LDR) Residential, 1.0 DU/ A or less 10 0.27 0.32 Low Density Residential (LDR) Residential, 2.0 DU/A or less 20 0.34 0.38 Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 Medium Density Residential (MDR) Residential, 4.3 DU/A or less 30 0.41 0.45 Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 Medium Density Residential (MDR) Residential, 10.9 DU/A or less 45 0.52 0.54 Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 Commercial/lndustrial (N. Com) Neighborhood Commercial 80 0.76 0.77 Commercial/lndustrial (G. Com) General Commercial 85 0.80 0.80 Commercial/lndustrial (O.P. Com) Office Professional/Commercial 90 0.83 i 0.84 i Commercial/lndustrial (Limited I.) Limited Industrial 90 0.83 0.84 Commercial/lndustrial General I. General Industrial 95 0.87 0.87 C 0.30 0.36 0.42 0.45 0.48 0.54 0.57 0.60 0.69 0.78 0.78 0.81 0.84 0.84 0.87 3 6 of26 D 0.35 0.41 0.46 0.49 0.52 0.57 0.60 0.63 0.71 0.79 0.79 0.82 0.85 0.85 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 PROJECT LOCATION2YR P6 = 1.3 IN33°00' 32°30' b "' ~ .. ~.0,~ M ex i c ---·· -:~ ----(--------~------.. --.... -._,J _________ _,: ------r--[() (0 n -····-·-· ~ () __ ... -•-g :::J '< f I' .----\_____ 82°45' ·-. 32°30' County of San Diego Hydrology Manual • Go Rainfall Isopluvials 2 Year Rainfall Event -6 Hours lsopluvial (inches) DPW -C:GIS O.fHl'Wl9T'fo/F';;/;;ic~tru, ~11Clmom,i11it.JflS!:rrvil:: ... N THIS MAP IS PROVIDEDWITl·IOLJTWARRANTYOFAN'fl<INO, EITI-IER EXPRESS 4 g~:~6~~~~~B~F.Tl~:s's.'~~~. ~~~~~~l~:~~IES s C.Op>fright SeinGIS. All Right:e R-«! Tllis products may contain lnloonallon from Iha SNIIOAG Reglonal E ==or~~bereproducedwllhoutlhe Tllisproductmaycootalnl!lfom>atlonwhk:hhasbeeoraproducedllloffll penniBalongrantedb)'ThornasBrolhersMape 3 O 3 Miles ~- PROJECT LOCATION10YR P6 = 1.7 INRiverside County 0 "' co r,, co , :/:: ~i:;f .·. '. ':;:>::\ :; .. r >~.~\\'\I ~ti?:-,...:,:.:~$-.. \. : · .. ~,>··.>-~~j{::<\:: ··· ... ': \:· .... ·.··• .......... \ .. :.:::.;:~;::.-::: ....... >\ . j, \ .~.\\ \ ·: \ ~_/ ~ 33•15~-------i"-----':~~761:;;;,,~¥.~4~~~-----++------i-----!---~~,J,;;*------,,;~L~~-l::~::.:: liI~:: (>···:: ~::·:::.::~:.]· 0 () (I) ~ -:, . . ··:::···• ..... ··········· ··········• .... ···· ..... . ·····-... ·············· .. ) .\ .. ... 5:~·)... ..... ~ 3•00· ...... ·· ... -· 3 "O CD -, ~ 0 0 C: ::, '< 32•4s• -------f-__:__:___ _____ -f~~~~8t~;;~~;J:~:-:_______,~=~~A-__,..._,:~,..,!__-1--_ _,__:::.._.-.,~\__--______,,,-:__---1,.L.:j_j_J____(i·.>c--•.. ~ .. ~ .. ~ •. -cc •• ~ ••• ~ •• ~ r2•4s• • ' ~ j· 32°30' r,, ~ _.q.• ... !/ /LJ ......... ·::>········· . MeX .\ 32•30• County of San Diego Hydrology Manual • Go Rainfall Isopluvials 10 Year Rainfall Event -6 Hours lsopluvial (inches) DPW -C:GIS O.fHl'Wl9T'fo/F';;/;;ic~tru, ~11Clmom,i11it.JflS!:rrvil:: ... N THIS MAP IS PROVIDEDWITl·IOLJTWARRANTYOFAN'fl<INO, EITI-IER EXPRESS 4 g~:~6~~~~~B~F.Tl~:s's.'~~~. ~~~~~~l~:~~IES s C.Op>fright SeinGIS. All Right:e R-«! Tllis products may contain lnloonallon from Iha SNIIOAG Reglonal E ==or~~bereproducedwllhoutlhe Tllisproductmaycootalnl!lfom>atlonwhk:hhasbeeoraproducedllloffll penniBalongrantedb)'ThornasBrolhersMape 3 O 3 Miles ~- PROJECT LOCATION100YR P6 = 2.6 IN32°30' ~-~~a=---___c----'-'.-:-·MeXiC g c'o 32°30' County of San Diego Hydrology Manual . • Rainfall Isopluvials 100 Year Rainfall Event -6 Hours lsopluvial (inches) DPW *GIS 0.pamr.,,,.,,()(P/;bi;cll'~ G,,;,,,;r-'f}f,k!m,m,,"'°'15:>tvi<;l>J N THIS MAP IS PROVIOEDWITl-lOLJTWARRANTYOFAN'fl<INO, EITI-IER EXPRESS 4 g~:~~~~~~~~UF.Tl~:s's_'~~~. ~~~~~~1~:_~~IES Co1¥19h1SanGIS.AIIRlghtsR8NIVed Tllis products may contain inl0fmallon from Iha SNIIDAG Reglonal E ==or~~bereproducedwtthoutlhe TllisproductrneyC<JnlaininfOlffllrtionwhichhe,bi,en"'P'Qduc,ed'Mlh pe,missiongrant!ldtr,lhorre!IBrottv,rsMapll s 3 O 3 Miles ~- Northwest Quadrant Drainage Program - State Street October 23, 2019 Attachment C – Hydrology Summary Calculations State Street Drainage Improvements - Hydrology Summary Table P6 (in)I (in/hr)Q2 (cfs) P6 (in)I (in/hr)Q10 (cfs) P6 (in)I (in/hr)Q100 (cfs) 10 2.48 0.84 5.0 1.2 3.16 6.6 1.6 4.22 8.8 2.5 6.59 13.7 County of San Diego Hydrology Manual (June 2003) Q=CIA Q = Flow Rate (cfs) C = Runoff Coefficient is Office/Commercial Per Table 3-1 of the San Diego County Hydrology Manual I = Intensity (in/hr) A = Area (acres) 10 Year2 YearOn-Site Drainage Subarea Area (ac)C Tc (min)100 YearI I I 1~~~~ !(Site 10 NORTHWEST QUADRANT 2019 Drainage Area Exhibit °0 100 20050 Feet7/11/2019 JN \\CARLCA1FS1.bkr.mbakercorp.com\HROOT\PDATA\172862 State Street Drainage Design\GIS\172862 State Street Drainage Design.mxd <USER NAME>Source: Legend Drainage Area !(Site Location Ex. Stormdrain State St. South of GrandStreet Name:Site Description: Site 10 Area Ac: 2.48 Michael Baker INTERNATIONAL Northwest Quadrant Drainage Program - State Street October 23, 2019 Attachment D – Hydraulics & Inlet Sizing Worksheet for 10" PVC @ 0.5% Project Description Ma n ning Form ula Friction M ethod DischargeSolve For In p u t D a ta 0.01 0Roughness Coefficient ft/ft0.005Channel Slope in10.0Normal Depth in10.0Diameter Res ults cfs2.01Discharge ft²0.5Flow Area ft2.6Wetted Perimeter in2.5Hydraulic Radius ft0.00Top W idth in7.6Critical Depth %100.0Percent Full ft/ft0.006Critical Slope ft/s3.69Velocity ft0.21Velocity Head ft1.05Specific Energy (N /A )Froude Num ber cfs2.17Maximum Discharge cfs2.01Discharge Full ft/ft0.005Slope Full CriticalFlow Type GV F Input Data in0.0Downstream Depth ft0.0Length 0Number Of Steps Pa g e 1 of 227 Siem on Com pany Drive Suite 200 W W atertown, CT 06795 USA +1-203-755-1666 10/23/2019 Fl o wM aster [1 0.0 2 .0 0 .0 1 ]Bentley Systems, Inc. Haestad Methods Solution CenterFlowM aster.fm 8 Worksheet for 10" PVC @ 0.5% GVF Output Data in0.0Upstream Depth Profile Description ft0.00Profile Headloss %0.0Average End Depth Over Rise %100.0Normal Depth Over Rise ft/sInfinityDownstream Velocity ft/sInfinityUpstream Velocity in10.0Normal Depth in7.6Critical Depth ft/ft0.005Channel Slope ft/ft0.006Critical Slope Pa g e 2 of 227 Siem on Com pany Drive Suite 200 W W atertown, CT 06795 USA +1-203-755-1666 10/23/2019 Fl o wM aster [1 0.0 2 .0 0 .0 1 ]Bentley Systems, Inc. Haestad Methods Solution CenterFlowM aster.fm 8 Inlet Capacity Page 1 of 1 State Street - Typical Proposed Grated Inlet in Sag FHWA HEC-22 and San Diego County Drainage Design Manual 18" x 18" grated inlet Weir Orifice Q = inlet capacity of the grated inlet (cfs)Q = inlet capacity of the grated inlet (cfs) Cw = weir coefficient = 3.0 Co = orifice coefficient = 0.67 Pe = effective grate perimeter (ft) w/ 50% clogging factor Ae = effective grate area (ft2) w/ 50% clogging factor d = flow depth approaching inlet (ft)g = gravitational acceleration (ft2/s) d = flow depth above inlet (ft) Pe =2.25 ft (3 sides) Cw =3.0 Ae =1.13 ft2 d = 0.5 ft Co =0.67 g =32.2 ft2/s Q = 2.4 cfs d =0.5 ft Q = 4.3 cfs The weir equation governs (Q = 2.4 cfs). Q10 for entire project site is 8.8 cfs. 2 3 dPCQew2 1 )2(gdACQeo