DRAINAGE CALCULATIONS

Transcription

1 DRAINAGE CALCULATIONS NW 8 th Street and NW 8 th Terrace Roadway and Drainage Improvements City of Miami Project B And NW 14 th Court Roadway and Drainage Improvements City of Miami Project B Miami-Dade County, Florida Prepared for CITY OF MIAMI DEPARTMENT OF CAPITAL IMPROVEMENTS Prepared by 201 Alhambra Circle, Suite 900 Miami, FL Francisco J. Alonso, P.E. FL. No Alhambra Circle, Suite 900 Coral Gables, Florida Date

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3 CITY OF MIAMI CAPITAL IMPROVEMENTS PROGRAM Prepared by: F. Alonso NW 8th STREET DRAINAGE IMPROVEMENTS WATER QUALITY CALCULATIONS Volumetric Retention Treatment Required: Impervious Area= 1.65 ac. Basin1: 0.82 Ac Pervious Area= 0.43 ac. Basin5: 1.26 Ac Total Area= 2.08 ac. SFWMD CRITERIA: a) First inch of runoff from the developed project: ( 1 In x = D.A. Ac. x 1 Ft/12 In ) = Ac.-Ft. b) 2.5 inches times the percentage of imperviousness: Percent Impervious = 79% ( 2.5 In x % Impervious) = 1.98 in. to be treated Volume required to be treated = ( in. to be treated x D.A. Ac x 1 Ft/12 In ) = Ac.-Ft. DERM CRITERIA: t 1" = 2940 x F x C ( F ) WHERE: t 1" = time to generate 1" of runoff, in minutes F = 5 Frequency in years, DCPW Manual, Part II, Section D4-Water Control, Table I Cwtd = 0.76 weighted runoff coefficient ( from the rational formula ) Tc = 10 time of concentration, in minutes CONTRIBUTING AREA AND ROUGHNESS COEFFICIENT CRITERIA. Pervious Areas = 0.43 Ac., C PERV = 0.2 Imperv. Areas = 1.65 Ac., C IMP = 0.9 C =(A IMP x C IMP + A PERV x C PERV )/A T = 0.76 t 1" = 13.9 MIN. TOTAL TIME OF CONCENTRATION (T T ) : T T = t 1" + T C = MIN. STORM INTENSITY ( Dade County Rainfall Intensity-Duration-Frequency Curves) i = = 4.90 IN/HR x F T T ( F ) RUNOFF FLOW Q 1" = C x I x A T = 7.70 CFS FOR THE 1 st INCH OF RUNOFF TOTAL RUNOFF VOLUME TO BE TREATED V 1" (FOR 1 INCH): V 1" = 60 Q 1" T T = 11,053 CF = Ac.-Ft. Volume Treatment Required= ac-ft ac-in

4 Volume Provided by exfiltraton trench System (following SFWMD Exfiltration Trench Equation Derivation): EXFILTRATION TRENCH BASIN Volume Storage in Exfiltraton Trench: WE= 5.00 (Lowest Ground Elev. or Control Weir Elev., ft., NGVD) GW= 2.10 (DERM October Average Groundwater Level, ft., NGVD) WDTH= 4 (Exfiltraton Trench width, ft.) TOP EL.= 3.50 (Exfiltraton Trench Top Elev., ft., NGVD) BOT. EL.= (Exfiltraton Trench Botom Elev., ft., NGVD) d= 2.00 (Exfiltraton Trench Pipe diameter, ft.) INV. EL.= 0.00 (Exfiltraton Trench Pipe Invert Elev., ft., NGVD) D u = D s = H 2 = 1.4 ft ft ft. K 15-avg.= 2.46E-04 cfs/ft 2 -ft From SFWMD Volume IV, pg. F-10, Exfiltration Length Formula L= V K(H 2 W + 2H 2 Du - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 184 ft If Ds > Du, more conservative formula L= V K(2H 2 D u - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 211 ft L provided = 240 ft Factor of Safety= 1.14

5 CITY OF MIAMI CAPITAL IMPROVEMENTS PROGRAM Prepared by: F. Alonso NW 8th TERRACE DRAINAGE IMPROVEMENTS WATER QUALITY CALCULATIONS Volumetric Retention Treatment Required: Basin 6: 0.83 Ac Impervious Area= 1.70 ac. Basin 2: 1.16 Ac Pervious Area= 0.29 ac. Total Area= 1.99 ac. SFWMD CRITERIA: a) First inch of runoff from the developed project: ( 1 In x = D.A. Ac. x 1 Ft/12 In ) = Ac.-Ft. b) 2.5 inches times the percentage of imperviousness: Percent Impervious = 85% ( 2.5 In x % Impervious) = 2.14 in. to be treated Volume required to be treated = ( in. to be treated x D.A. Ac x 1 Ft/12 In ) = Ac.-Ft. DERM CRITERIA: t 1" = 2940 x F x C ( F ) WHERE: t 1" = time to generate 1" of runoff, in minutes F = 5 Frequency in years, DCPW Manual, Part II, Section D4-Water Control, Table I Cwtd = 0.80 weighted runoff coefficient ( from the rational formula ) Tc = 10 time of concentration, in minutes CONTRIBUTING AREA AND ROUGHNESS COEFFICIENT CRITERIA. Pervious Areas = 0.29 Ac., C PERV = 0.2 Imperv. Areas = 1.70 Ac., C IMP = 0.9 C =(A IMP x C IMP + A PERV x C PERV )/A T = 0.80 t 1" = 13.0 MIN. TOTAL TIME OF CONCENTRATION (T T ) : T T = t 1" + T C = MIN. STORM INTENSITY ( Dade County Rainfall Intensity-Duration-Frequency Curves) i = = 4.97 IN/HR x F T T ( F ) RUNOFF FLOW Q 1" = C x I x A T = 7.89 CFS FOR THE 1 st INCH OF RUNOFF TOTAL RUNOFF VOLUME TO BE TREATED V 1" (FOR 1 INCH): V 1" = 60 Q 1" T T = 10,877 CF = Ac.-Ft. Volume Treatment Required= ac-ft ac-in

6 Volume Provided by exfiltraton trench System (following SFWMD Exfiltration Trench Equation Derivation): EXFILTRATION TRENCH BASIN Volume Storage in Exfiltraton Trench: WE= 5.00 (Lowest Ground Elev. or Control Weir Elev., ft., NGVD) GW= 2.10 (DERM October Average Groundwater Level, ft., NGVD) WDTH= 4 (Exfiltraton Trench width, ft.) TOP EL.= 3.50 (Exfiltraton Trench Top Elev., ft., NGVD) BOT. EL.= (Exfiltraton Trench Botom Elev., ft., NGVD) d= 2.00 (Exfiltraton Trench Pipe diameter, ft.) INV. EL.= 0.00 (Exfiltraton Trench Pipe Invert Elev., ft., NGVD) D u = D s = H 2 = 1.4 ft ft ft. K 15-avg.= 2.25E-04 cfs/ft 2 -ft From SFWMD Volume IV, pg. F-10, Exfiltration Length Formula L= V K(H 2 W + 2H 2 Du - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 207 ft If Ds > Du, more conservative formula L= V K(2H 2 D u - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 237 ft L provided = 303 ft Factor of Safety= 1.28

7 CITY OF MIAMI CAPITAL IMPROVEMENTS PROGRAM Prepared by: F. Alonso NW 14th COURT DRAINAGE IMPROVEMENTS-SOUTH WATER QUALITY CALCULATIONS Volumetric Retention Treatment Required: Basin 7: 1.26 Ac Impervious Area= 1.07 ac. Pervious Area= 0.19 ac. Total Area= 1.26 ac. SFWMD CRITERIA: a) First inch of runoff from the developed project: ( 1 In x = D.A. Ac. x 1 Ft/12 In ) = Ac.-Ft. b) 2.5 inches times the percentage of imperviousness: Percent Impervious = 85% ( 2.5 In x % Impervious) = 2.12 in. to be treated Volume required to be treated = ( in. to be treated x D.A. Ac x 1 Ft/12 In ) = Ac.-Ft. DERM CRITERIA: t 1" = 2940 x F x C ( F ) WHERE: t 1" = time to generate 1" of runoff, in minutes F = 5 Frequency in years, DCPW Manual, Part II, Section D4-Water Control, Table I Cwtd = 0.79 weighted runoff coefficient ( from the rational formula ) Tc = 10 time of concentration, in minutes CONTRIBUTING AREA AND ROUGHNESS COEFFICIENT CRITERIA. Pervious Areas = 0.19 Ac., C PERV = 0.2 Imperv. Areas = 1.07 Ac., C IMP = 0.9 C =(A IMP x C IMP + A PERV x C PERV )/A T = 0.79 t 1" = 13.0 MIN. TOTAL TIME OF CONCENTRATION (T T ) : T T = t 1" + T C = MIN. STORM INTENSITY ( Dade County Rainfall Intensity-Duration-Frequency Curves) i = = 4.96 IN/HR x F T T ( F ) RUNOFF FLOW Q 1" = C x I x A T = 4.97 CFS FOR THE 1 st INCH OF RUNOFF TOTAL RUNOFF VOLUME TO BE TREATED V 1" (FOR 1 INCH): V 1" = 60 Q 1" T T = 6,871 CF = Ac.-Ft. Volume Treatment Required= ac-ft ac-in

8 Volume Provided by exfiltraton trench System (following SFWMD Exfiltration Trench Equation Derivation): EXFILTRATION TRENCH BASIN Volume Storage in Exfiltraton Trench: WE= 6.20 (Lowest Ground Elev. or Control Weir Elev., ft., NGVD) GW= 2.10 (DERM October Average Groundwater Level, ft., NGVD) WDTH= 4 (Exfiltraton Trench width, ft.) TOP EL.= 4.70 (Exfiltraton Trench Top Elev., ft., NGVD) BOT. EL.= (Exfiltraton Trench Botom Elev., ft., NGVD) d= 2.00 (Exfiltraton Trench Pipe diameter, ft.) INV. EL.= 1.00 (Exfiltraton Trench Pipe Invert Elev., ft., NGVD) D u = D s = H 2 = 2.6 ft ft ft. K 15-avg.= 1.65E-04 cfs/ft 2 -ft From SFWMD Volume IV, pg. F-10, Exfiltration Length Formula L= V K(H 2 W + 2H 2 Du - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 126 ft If Ds > Du, more conservative formula L= V K(2H 2 D u - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 144 ft L provided = 191 ft Factor of Safety= 1.33

9 CITY OF MIAMI CAPITAL IMPROVEMENTS PROGRAM Prepared by: F. Alonso NW 14th COURT DRAINAGE IMPROVEMENTS-NORTH WATER QUALITY CALCULATIONS Volumetric Retention Treatment Required: Basin 8: 1.50 Ac Impervious Area= 1.28 ac. Pervious Area= 0.22 ac. Total Area= 1.50 ac. SFWMD CRITERIA: a) First inch of runoff from the developed project: ( 1 In x = D.A. Ac. x 1 Ft/12 In ) = Ac.-Ft. b) 2.5 inches times the percentage of imperviousness: Percent Impervious = 85% ( 2.5 In x % Impervious) = 2.13 in. to be treated Volume required to be treated = ( in. to be treated x D.A. Ac x 1 Ft/12 In ) = Ac.-Ft. DERM CRITERIA: t 1" = 2940 x F x C ( F ) WHERE: t 1" = time to generate 1" of runoff, in minutes F = 5 Frequency in years, DCPW Manual, Part II, Section D4-Water Control, Table I Cwtd = 0.80 weighted runoff coefficient ( from the rational formula ) Tc = 10 time of concentration, in minutes CONTRIBUTING AREA AND ROUGHNESS COEFFICIENT CRITERIA. Pervious Areas = 0.22 Ac., C PERV = 0.2 Imperv. Areas = 1.28 Ac., C IMP = 0.9 C =(A IMP x C IMP + A PERV x C PERV )/A T = 0.80 t 1" = 13.0 MIN. TOTAL TIME OF CONCENTRATION (T T ) : T T = t 1" + T C = MIN. STORM INTENSITY ( Dade County Rainfall Intensity-Duration-Frequency Curves) i = = 4.97 IN/HR x F T T ( F ) RUNOFF FLOW Q 1" = C x I x A T = 5.94 CFS FOR THE 1 st INCH OF RUNOFF TOTAL RUNOFF VOLUME TO BE TREATED V 1" (FOR 1 INCH): V 1" = 60 Q 1" T T = 8,195 CF = Ac.-Ft. Volume Treatment Required= ac-ft. 3.2 ac-in

10 Volume Provided by exfiltraton trench System (following SFWMD Exfiltration Trench Equation Derivation): EXFILTRATION TRENCH BASIN Volume Storage in Exfiltraton Trench: WE= 8.50 (Lowest Ground Elev. or Control Weir Elev., ft., NGVD) GW= 2.10 (DERM October Average Groundwater Level, ft., NGVD) WDTH= 4 (Exfiltraton Trench width, ft.) TOP EL.= 7.00 (Exfiltraton Trench Top Elev., ft., NGVD) BOT. EL.= (Exfiltraton Trench Botom Elev., ft., NGVD) d= 2.00 (Exfiltraton Trench Pipe diameter, ft.) INV. EL.= 1.00 (Exfiltraton Trench Pipe Invert Elev., ft., NGVD) D u = D s = H 2 = 4.9 ft ft ft. K 15-avg.= 4.54E-04 cfs/ft 2 -ft From SFWMD Volume IV, pg. F-10, Exfiltration Length Formula L= V K(H 2 W + 2H 2 Du - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 39 ft If Ds > Du, more conservative formula L= V K(2H 2 D u - D 2 u + 2H 2 D s ) + (1.39 x 10-4 )WD u L required = 46 ft L provided = 75 ft Factor of Safety= 1.65

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