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6607-11-01; Avenida Encinas Offsite Storm Drain Hydrology; Avenida Encinas Offsite Storm Drain Hydrology; 1994-07-01
92-1016-5 AVENIDA ENCINAS & OFFSITE STORM DRAIN C.T. 94-01 HYDROLOGY STUDY MARCH 1994 JULY 1994 pi.,-- - .7220 AVEFW/ENCINAS STE 204; CARLSBAD CA 92008 "(619) xV/ PT-I ON _b.we_^A!l V L,-MPF JZL V-foi,/,,! /noj . SECTION 1 STORM DRAIN LINE "A" * A .PO'KTL.jC»Jr __4__ _T_ 6 /P-.Q.... J=t_£*-^ <o.-"£? iO-8 17. t ACS. 333. _2iti±2.50 _M _. J2. J3 1M3. a _________ 31 3,5".... .s;tr_.2:7 ... .-7 r . ftsV»- s. A - 4-..1 ;>r.H O-VS" _..A~7. /O.Q A-? _. ..5,1.. .A_-1 Sr^ tfcC.- .__..3-a.._S-3L A--UL .A-12L. L3 _^ **$- -Tt*-7» . 4.-^- _., !SLl 3.6 ... 6*5:. __A_rQ_H.O ^7. .-1 ^>-JQ Cf-.t^. — Cfj«-f H A ^J^ 7.*?~ 7 *? " A-Oo A~?-t 5:0 ; A -71 ±22. A_£ _^r! 6.5- 9-C, Z2 3,58. __. .!.._ _._o>58_ 9.0 fe-i _..J2?..-3_0-6 SO. 0.5"/ o.'b O.tf 3._sa. j?._s j9^?_._._ J-H- c. i a..e K.-21 J . c 5> 2..,£ o s^d W 3*4 * . .A ^ A ^ A r A . . ..... -A . A <l***~v <5>.^ 11 . _ O-~7 11 or? «' ^-*7 ii <Q~? " ^7 <^-? 0.7 <D,"7 o»-> o,~> o."^ LJMP* "A" -. 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VbfA-*?o * A-y? ] US" ,-— j ' C- / •po<c»y\ Pr-TO pr- (ll&i - P' '^x 68^-^-9.0) } -h oO j<a. pr.(5) ~ 34. &3-3-3 SECTION 3 STORM DRAIN LINES "B" THRU "X" *Tr 15" C.RS /-n&r+^ = ss: 5- <^p ' S\ p-—* Kior A D Tt> THH 7t? VTH-':^ jgr&xxW I L\i-'' T „ ,f M A O — T«=> B-*. t ~P-/ 6 __ I ^—I — — 33.0 ' 3.11 0.3 5-0 V t _ 1 M O S-lor^T-N-TT*-£ c,T^LCrc:'17 T » PCJP d- 9. ? 3-)TO A-P-&A T L P-&CSU 3-3 T 't--^ . II TO K-f (J . == \N . » & A 6^.00- o- 30' L — \ i __ " 16 >4 To - 3- 4 ^.O. CPS ^TTDP-A^ F - / v^"i -- JAJ& ^>i , " • *, /LJ 7V/ — ~ SECTION 4 PIPE HYDRAULICS ********•»*•»***•*****»*•»*******»•*******«****•*»*»»» + ****»•*»******* »»*-i * O'OAY rONSIJLTANTS * * 722C- Avenida Enciuas, Suite 204 * * farlsbadi California, 92009 * * (613) ^31-7700 * * MX {619} 931-R680 * ******************************************************************* ******** ******** *** *** *** |< ( 3S.05'} >| »** Depth { 2. 51'}AAAAAAA * * * *** * * * ** * * ** *** ***j< ( 25.00'} >|**» ************************ r** ***** Trapezoidal Channel Trapezoidal Channel Flowrate ........ 323. 200 CFS Velocity 4,283 fps Depth of Flow 2.513 feet Critical Depth 1.655 feet Freeboard 0.0O0 feet Total Depth 2.513 feet Width at Water Surface .... 35.052 feet Top Width , 35.052 feet. Slope of Channel 0.500 % Left Side Slope 2.000 : 1 Right Side Slope 2.000 -. 1 Base Width 25.000 feet X-Sectional Area 75.454 sq. ft. Wetted Perimeter 36.238 feet ARA{2/3) 123.034 Mannings 'n' 0.040 - PW **********************»*-»**»*****»**»*******»*****•**»»*****»****•»» * --VOAY CONSULTANTS * 7220 nVftuida Encinus.. Suite * Carlsbad, California, 92009 * (619) 931-7700 FAX {619} 931-8680 * * * * ********************************************************** Inside Dianeter ( 84,00 in.} * Water ( 63 { 5. 71 iu.} 30'? ft- } * v_ Circular Channel Section Flowrate 323.200 CFS Velocity 10.320 fps Dianeter of Pipe 84.000 inches Depth of Flow 63.710 inches Depth of Flow 5.3G9 feet Critical Depth 4.725 feet Depth/Diameter (D/d) 0.758 Slope of Pipe 0.300 \ X-Sectional Area 31.317 sq. ft. Wetted Perimeter 14.798 feet AIT(2/3) 51.622 Mannings 'n' 0.013 Hin. Fric. Slope, 84 inch Pipe Flowing Full 0.256 % /L_ TO A******************************************************* *******»•»«• * 0'l>A.Y CONSULTANTS * 7220 Avenic!a Encinas, Suite 204 v * Carlsbad; California, 92005 < * (619) 931-7700 * FAX (619) 931-8680******************************i Inside Diameter ( 84, M0 in• » * * * : * * * * Water * | 1 I 1 * ( 44.1.6 in.) ( 3.680 ft.) I ! * v Circular Channel Section Flowrate 323.200 CFS Velocity 15.763 fps Diameter of Pipe 84,000 inches Depth of Flow . . 44.163 inches Depth of Flow 3.680 feet Critical Depth 4.730 feet Depth/Dianeter (D/d) 0.526 Slope of Pipe 0.865 % X-Sectional Area . ,. 20.503 sq. ft. Wetted Perimeter 11.356 feet ARA(2/3) 30.401 Mannings 'n' 0.013 Min. Fric. Slope. 84 inch Pipe Flowing Full 0.256 % ************************** ****************************»****»****»,••• * rt'DAY CONSULTANTS * * 7220 AvenicU Encinas, Suite 204 * rarisbad. California, 92009 * * 931-7736 * * PAX (619) 931-8680A******************************************************* Inside Diameter { 84 . 00 In . } * * A A A AAAAAA-AAAAAAAA-AAAA * Water * * » * * •( 62 ( 5.246 ft.)* • v 95 in.} Circular Channel Section Flowrate .................. 318.800 CFS Velocity .................. 10.305 fps Diameter of Pipe.. .......... 84.000 inches Depth of Flow...., ......... 62,955 inches Depth of Flow ...... . ....... 5,246 feet Critical Depth ............ 4.712 feet Depth/Diameter (D/d) ..... 0.749 Slope of Pipe .... ......... 8 . 300 \ X-Seotional Area .......... 30,938 sq. ft. Wfitted Perimeter .......... 14.652 feet. ARA (2/3) .................. 50.919 Mannings 'n' ........ ....... 0.013 Min. Fric. Slope, 84 inch Pipe Flowing Full ........ 0.249 % 11*52.35" TO il-t-86.2>l *********** A******************************************************* * 9'DAY CONSULTANTS * * 7220 Avenida Encinas, Suite 204 * * rarlsbad, California, 92009 * * {619} 93J.-770© * * FAX (61S) 931-8680 ******************************************************************** Inside Diameter { 84.QQ In.} * I yv A A A Water * ! 1 I 1 * (63.71 in, } ( 5.309 ft.} I I * v Circular Channel Section Flowrate 323.200 CF3 Velocity . , ... 10.320 fps Diameter of Pipe , 84.000 inches Depth of Flow 63.710 inches Depth of Flow 5.309 feet Critical Depth 4,725 feet Depth/Diaaeter (D/d) 0.758 Slope of Pipe ,., 0.300 % X-Sectional Area 31.317 sq. ft. Wetted Perimeter .. > 14.798 feet ARA{2/3) , 51.622 Mannings 'n' 0.013 Hin. Fric. Slope, 84 inch Pipe Flowing Full 0.256 % A ****************** A A*********************** A*********************** * O'.OAY CONSULTANTS * * 7220 Avftnida Encinas, Suite 204 * * Carlsbad, California, 92009 * * {619} 931-7706 * * FAX (619) 331-8686 *A***************************A************************************** Inside Diameter ( 73.00 in.) LAAAAAAAAAAA Water { 38 ( 3. 07 in.) 172 ft.) * ________ v_ Circular Channel Section Flowrate .................. 266.200 CF3 Velocity .................. 16.548 fps Diameter of Pipe ........... 78.000 inches Depth of Flow .............. 38.068 inches Depth of Flow .............. 3.172 feet Critical Depth ............ 4.365 feet. Depth/Diameter (D/d) ..... ©.488 Slope of Pipe ............. 1.120 % X-Sectional Area ...... .... 36.086 sq. ft. Wetted Peri»eter .......... 10.055 AIT(2/3) .................. 22.005 Mannings 'n' .............. 0.013 Min. Fric, Slope, 78 inch Pipe Flowing Full ....... 0.258 % 3l-i-8£.-'5»l TO ************************«*************»*****»**»*****************.)., n'DAY CONSULTANTS * 7220 Avenida Encinas., Suite 204 Carlsbad,- California, 92009 (619) 931-7700 FAX (619) 931-8680 *it****************************************************************** * * * * * Inside Diameter { 78.00 in. } AAAAAAAAAAAAAAAAAAAAA Water ( 54 ( 4. 46 in . } 38 ft,. * ________ v_ Circular Channel Section Flowrate .................. 239.600 CFS Velocity .................. 9.685 fps Diameter of Pipe ........... 78.060 inches Depth of Tlow .............. 54,457 inches Depth of Flow .............. 4.538 feet Critical Depth ............ 4.149 feet Depth/Diameter (D/d) ..... 0.698 Slope of Pipe ...... ....... 0.300 \ X-Sectional Area .......... 24.739 sq. ft. Wetted Perimeter .......... 12.859 feet AIT (2/3} ........ ........... 38.269 Mannings 'n' .............. 0.013 Min. Fric. Slope, 78 inch Pipe Flowing Full ....... 0.209 % N /A ****************«*********1 * * * * * O'DAT CDHSULTABTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 . FAX (619) 931-8680 * * I************************** Inside Diaaeter { 42.00 in.) AAAA-AAAAAAAAAAAAAAAAA Water { 1.60 in.) 134 ft.) * v_ Circular Channel Section Flowrate' 79.600 CFS Velocity 29.492 fps Diameter of Pipe 42.000 inches Depth of Flow 13.604 inches Depth of Flow 1.134 feet Critical Depth 2.790 feet Depth/Diameter (D/d) 0.324 Slope of Pipe 12.150 % X-Sectional Area 2.699 sq. ft. Wetted Perimeter 4.238 feet ARA{2/3) ; 1.998 Mannings 'n' 0.013 Min. Fric. Slope, 42 inch Pipe Flowing Full 0.626 \ ft*************! O'DAY COMSBLTAMTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 Inside Diaaeter ( 42.00 in.) * * * * 1 Water * | ! I * • ( 22.27 in.) { 1.856 ft.) tr * v Circular Channel Section Flowrate 55.500 CFS Velocity 10.713 fpa Dianeter of Pipe 42.000 inches Depth of Flow. 22.268 inches Depth of Flow 1.856 feet Critical Depth ;. 2.338 feet Depth/Diaaeter (D/d) 0.530 Slope of Pipe 1.000 * X-Sectional Area 5.180 sq. ft. Wetted Perimeter 5.709 feet ARA(2/3) 4.855 Mannings 'n' 0.013 Hin. Fric. Slope, 42 inch Pipe Flowing Full ... 0.304 t \\-C3, lf D ************: * * * * * t******************: O'DAY COMSULTAHTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 {619} 931-7700 FAX (619) 931-8680 Inside Diameter ( 24.00 in.) * * AAAAAAAA.AAAAAAAAAAAAA Water ( 886 in.) 738 ft.) * v_ Circular Channel Section Flowrate 28.800 CFS Velocity 27.339 fps Diameter of Pipe. 24.000 inches Depth of Flow 8.859 inches Depth of Flow 0.738 feet Critical Depth 1.843 feet Depth/Diaaeter (D/d) 0.369 Slope of Pipe 19.200 % X-Sectional Area 1.053 sq. ft. Wetted Perimeter 2.612 feet ARA{2/3) 0.575 Mannings 'n' 0.013 Min. Fric. Slope, 24 inch Pipe Flowing Full 1.620 % ********! r***************************************************** O'DAY CONSULTANTS * 7220 Avenida Encinas, Suite 204 * Carlsbad, California, 92009 * (619) 931-7700 * PAX (619) 931-8680 * Inside Diameter ( 18.00 in.) * * * * Water * I I I I » • ( 1.67 in.) ( 0.139 ft.) * * I * * I*v Circular Channel Section Flowrate 1.200 CFS Velocity 14.653 fps Diameter of Pipe 18.000 inches Depth of Flow 1.667 inches Depth of Flow 0.139 feet Critical Depth 0.409 feet Depth/Diameter (D/d) . 0.093 Slope of Pipe 41.600 % X-Sectional Area 0.082 sq. ft. Wetted Perimeter 0.928 feet ARA{2/3) 0.016 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.013 % A******************************************** 9'.DAY CONSULTANTS * 722ft Avenid.a Encinas, Suite 204 * Carlsbad, California* 92009 * (619) 931-7700 * FAX (619} 931-8680 ******************************************************************** Inside Diameter 18.00 in.} * * * * Water * j I * { 2.89 in.} { 0.241 ft.)* *i I v Circular Channel Section Flowrate 5.000 CFS Velocity 27.305 fps Dianeter of Pipe 18.000 inches ORpth of Flow 2.887 inches Depth of Flow 0.241 feet Critical Depth 0.861 feet Depth/Diameter (D/d) 0.160 Slope of Pipe 72.800 % X-Sectional Area 0.183 sq. ft. Wetted P«ri»eter 1,236 feet ARA(2/3) 0.051 Mannings 'n' 0.013 Min. Fric. Slope,, 18 inch Pipe Flowing Full .,. 0.227 % I **********r**********i * * * * * 0' DAY COHSTJLTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 (A********************! * * * * Inside Diameter { 18-00 in.) AAAAAAAAAAAAAAAAAAAAA Water ( 3 ( 0. 98 in,) 332 ft.) 9 v_ Circular Channel Section Flowrate 1.600 CFS Velocity 5.490 fps Diameter of Pipe 18.000 inches Depth of Flow 3.984 inches Depth of Flow 0.332 feet Critical Depth 0.477 feet Depth/Diameter (D/d) 0.221 Slope of Pipe 2.000 % X-Sectional Area 0.291 sq. ft. Wetted Perimeter 1.469 feet ARA(2/3) 0.099 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.023 % • A************************************* •**•************! 0'DAY CONSULTANTS 7220 ?.venida Encinas, Sui ^arlsbnd, California, 92009 (619) 931-7700 (619} 931-8680 * * * * * VAV lHtQ\ Q'SI—QtOft * ft****************************************** A*********************** Inside Diameter { 18.00 in.} * A - IAAAAAAAAAAA Water ( 9 ( 0. 86 in.} 822 ft.} * v_ Circular Channel Section Flowrate 28.160 CFS Velocity 28.339 f ps Diameter of Pipe 18.000 inches Depth of Flow 9.865 inches Depth of Flow 0.822 feet Critical Depth 1.492 feet Depth/Diameter (D/d) 0.548 Slope of Pipe 21.100 \ X-Sectional Area 0.992 sq. ft. Wetted Perimeter 2.501 feet ARA(2/3) 0.535 Mannings rn' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 7.. 156 % ' ************************************************************* CONSULTANTS * * 7226 Av^uida Encinas. Suite 20! * * farJsbad, California, 92009 * * (619} 931-770© * * Fax {619} 931-8680 * ******************************************************************* Inside Diameter { 18.00 in.) Water 79 in.5 { 0.3SS ft.) * v_ Circular Channel Section Flowrate 5.140 CFS Velocity 13.641 fps Diameter of Pipe 18.000 inches Depth of Flow 4.786 inches Depth of Flow 0.399 feet Critical Depth 0.869 feet Depth/Diameter (D/d) 0.266 Slope of Pipe 10.000 \ X-Sectional Area 0.377 sq. ft. Wetted Perimeter 1.625 feet ARA(2/3) 0.142 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.239 % __ **. .v i-,^.n ********************************************************************* O'DAY CONSULTANTS * * 7220 Avenida Encinas, Suite 204 * * Carlsbad, California, 92009 * * {619} 931-7700 * * FAX (619) 931-8680 *a****************************************************************** Inside Diameter { 18.00 in.) * * * * : « * * *Water * J I I 1 * { 4.80 in.} { 0.400 ft.)* * * *I v Circular Channel Section Flowrate 14.300 CFS Velocity 37.791 f ps Diameter of Pipe 18.000 inches Depth of Flow 4.800 inches Depth of Flow 0.400 feet Critical Depth 1.385 feet Depth/Diaaeter (D/d} 0.267 Slope of Pipe 76.500 % X-Sectional Area 0.378 sq. ft. Wetted Perimeter 1.628 feet ARA(2/3) 0.143 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 1.852 % ft***************************************************-*************** * * 9 'DAY CONSULTANTS * 7220 f^venida Encinas, Suite 204 rarlsbad, California. 92009 * (619) 931-7700 * * FAX (619) 931-8680 *********************************#********•»***********************.» Tnside Diameter { 18.0« in.} AAAAAAAAAAAAAAAAAAAAA A * Water * * * * * ( 13 23 in.} ( 1.102 ft. )* * * * * v_ Circular Channel Section Flowrate 20.900 CFS Velocity 15.020 fps Diameter of Pipe 18.000 inches Depth of Flow 13,225 inches Depth of Flow 1.102 feet Critical Depth 1.472 feet Depth/Dianeter (D/d) ...... 0.735 Slope of Pipe 5.000 % X-Sectional Area 1.392 sq. ft, Wetted P«ri«eter 3.089 feet ARA(2/3) „ . 0.818 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 3.9S9 % /L __ t EV(_V C-&To »*********#**********»****************»**********»»********»******» ~'DAY CONSULTANTS "7220 Avenida Eneinas. Suite Carlsbad, California, 92009 (619) 931-7706 FAX (619) 931-8680 * * *************************** ************:********************** Inside Dianeter { 30.00 in,} * * * Water * * * * * { 22 70 in. } { 1.892 ft.}* * * * * v_ Circular Channel Section Flowrate 41.400 CFS Velocity 10.387 fps Diameter of Pipe 30.000 inches Depth of Flow , 22.705 inches Depth of Flow 1.892 feet Critical Depth 2.156 feet Depth/Diameter (D/J) 0.757 Slope of Pipe 1 - 200 % X-Sectional Area 3.986 sq. ft. Wetted Periaeter 5.276 feet AR/v{2/3) 3.306 Mannings 'n' 0,013 Kin. Fric. Slope, 30 inch Pip« Flowing Full 1.019 % li ._ IS. A I/ ft******************: * O'DAY CONSULTANTS * 7220 Avenida Encinas, Suite 204 * * Carlsbad, California, 92009 * * (619) 931-7700 * * FAX (619) 931-8680 * A****************************************************************** Inside Diameter ( 18.00 in.) { 6 ( 0. 40 in.) 533 ft,) • v_ Circular Channel Section Flowrate 5.400 CPS Velocity 9.585 fps Dianeter of Pipe 18.000 inches Depth of Flow 6.398 inches Depth of Flow 0.533 feet Critical Depth 0.893 feet Depth/Diameter (D/d) 0.355 Slope of Pipe 3.600 \ X-Sectional Area 0.563 sq. ft. Wetted Perineter 1.916 feet AR'v(2/3) 0.249 Mannings 'n' 0.013 Hin. Fric. Slope, 18 inch Pipe Flowing Full 0.264 % L_ ******** I * * * * 0'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680>******************** Inside Diameter ( 18-00 in.) AAAAAAAAAAAAAAAAAAAAA Water ( 6 ( 0. 35 in.) 529 ft.) * v_ Circular Channel Section Flowrate 5.400 CFS Velocity 9.700 fps Diameter of Pipe 18.000 inches Depth of Flow 6.345 inches Depth of Flow 0.529 feet Critical Depth 0.899 feet Depth/Dia»eter (D/d) 0.353 Slope of Pipe 3.720 % X-Sectional Area 0.557 sq. ft. Wetted Perimeter 1.907 feet ARA(2/3) 0.245 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.264 % »I i ME *****»**»***»**: * >*«****************** **********! 0'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 ;***************»**»****************** Inside Diameter ( 18.00 in.} AAAAAAAAAAA/V A A A A A Water ( 6 ( 0- 68 in.) 556 ft.) Circular Channel Section Flowrate 8.600 CFS Velocity 14.421 fps Diameter of Pipe. 18.000 inches Depth of Flow 6.677 inches Depth of Flow 0.556 feet Critical Depth 1.131 feet Depth/Diameter (D/d) 0.371 Slope of Pipe 7.800 % Z-Sectional Area 0.596 sq. ft. Wetted Perimeter 1.965 feet AR"(2/3) 0.269 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.670 \ — ft*********************************************)********************** * * * * O'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 * * * * * Inside Diameter ( 18.00 in.) * ( 11 ( 0. 10 in.) 925 ft.) • v_ Circular Channel Section Flowrate 5.200 CFS Velocity 4.547 fps Diameter of Pipe 18.000 inches Depth of Flow 11.097 inches Depth of Flow 0.925 feet Critical Depth 0.875 feet Depth/Diameter (D/d) 0.616 Slope of Pipe 0.500 % X-Sectional Area 1.143 sq. ft. Wetted Perimeter 2.709 feet ARA(2/3) 0.643 Mannings '11' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.245 % ft*********************** O'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 *************** * * ! * Inside Diameter ( 24.00 in.) X.A A A A* Water { 18 { 1. 67 in.) 556 ft.) * v_ Circular Channel Section Flowrate 15.200 CFS Velocity 5.795 fps Diameter of Pipe 24.000 inches Depth of Flow 18.674 inches Depth of Flow 1.556 feet Critical Depth 1.401 feet Depth/Diameter (D/d) 0.778 Slope of Pipe 0.500 % X-Sectional Area 2.623 sq. ft. Wetted Perimeter 4.321 feet ARA(2/3) 1.880 Mannings 'n' 0.013 Min. Fric. Slope, 24 inch Pipe Flowing Full 0.451 \ r»ir****»************»************<r*********** * * * * * O'DAY CONSULTANTS * 7220 Avenida Encinas, Suite 204 * Carlsbad, California, 92009 * (619) 931-7700 * FAX (619) 931-8680 *I******************** Inside Diameter { 18.00 in.) * A AA AAA4 * LA A A A A Water ( 4 ( 0. 83 in.) 403 ft.) * v_ Circular Channel Section Plowrate 3.700 CFS Velocity 9.696 fps Diameter of Pipe 18.000 inches Depth of Flow 4.831 inches Depth of Flow 0.403 feet Critical Depth 0.733 feet Depth/Diameter (D/d) 0.268 Slope of Pipe 5.000 \ Z-Sectional Area 0.382 sq. ft. Wetted Peri»eter 1.634 feet ARA{2/3) 0.145 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.124 \ •It************************************************** 0'DAY CONSULTANTS 7220 Aveiiida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 Inside Diameter ( 18.00 in.) * * AAAAAAAAAAAAAAAAAAAAA Water * ( 4 ( 0- 75 in.) 396 ft.) * v_ Circular Channel Section Flowrate 3.200 CFS Velocity 8.589 f ps Dianeter of Pipe 18.000 inches Depth of Flow 4.749 inches Depth of Flow 0.396 feet Critical Depth 0.681 feet Depth/Diameter (D/d) 0.264 Slope of Pipe 4.000 % X-Sectional Area 0.373 sq. ft. Wetted Perineter 1.618 feet ARA(2/3) 0.140 Mannings 'n' 0,013 Min. Fric. Slope,- 18 inch Pipe Flowing Full 0.093 % u _ ****************************** * * * * * O'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 ******** * * * * * Inside Dianeter { 18.00 in.) * Water * { 6 ( 0- 55 in.) 545 ft.) * v_ Circular Channel Section Flowrate 4.200 CFS Velocity 7.228 fps Diaaeter of Pipe 18.000 inches Depth of Flow 6.546 inches Depth of Flow 0.545 feet Critical Depth 0.785 feet Depth/Diameter (D/d) 0.364 Slope of Pipe , 2.000 \ X-Sectional Area 0.581 sq. ft. Wetted Perimeter 1.942 feet ARA(2/3) 0.260 Mannings 'n' 0.013 Min. Fric. Slope» 18 inch Pipe Flowing Full 0.160 % ******: * * * * * i*********»******************«****»»***»»» O'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 * * * * r *****!.*****. Inside Diameter ( 18.00 in.) AAAAAAAAAAAAAAAJ Water ( 10 ( 38 in.) 865 ft.) * v_ Circular Channel Section Flowrate 4.700 CFS Velocity 4.447 f PS Dianeter of Pipe 18.000 inchesDepth of Flow 10.385 inches Depth of Flow 0.865 feet Critical Depth 0.835 feet Depth/Diameter (D/tl) 0.577 Slope of Pipe 0.500 % X-Sectional Area 1.056 sq. ft. Wetted Perimeter 2.588 feet ARA(2/3) 0.581 Mannings 'n' 0,013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.200 % U» t********»*************************** * O'DAY CONSULTANTS * * 7220 Avenida Encinas, Suite 204 * * Carlsbad, California, 92009 * * {619} 931-7700 * * FAX (619) 931-8680 * Inside Diaaeter ( 18.00 iu.) * h A A A * water * | I I I * * ( 6.16 in.) ( 0.513 ft.) I I * v Circular Channel Section Flowrate 5.300 CFS Velocity 9.305 fps Diameter of Pipe 18.000 inches Depth of Flow 6.161 inches Depth of Flow 0.513 feet Critical Dftpth 0.883 feet Depth/Dianeter (D/d} 0.342 Slope of Pipe 4.000 % X-Sectional Area 0.535 sq. ft. Wetted Perimeter 1.875 feet ARA{2/3) 0.232 Mannings *n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.254 % A****************************************************************** * * * * 0'DAY CONSULTANTS 7220 Avenida Encinas, Suite 2' Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 204 Inside Diameter { 18.00 in.) * * AAAAAAAAA/VAAAAAAAAAAA Water * ( 4 { 0. 28 in.) 357 ft.) " v_ Circular Channel Section Flowrate 2.600 GPS Velocity 8.092 fps Diameter of Pipe 18.000 inches Depth of Flow 4.278 inches Depth of Flow 0.357 feet Critical Depth 0.612 feet Depth/Diameter (D/d) 0.238 Slope of Pipe 4.000 % X-Sectional Area 0.322 sg. ft. Wetted Perimeter 1.528 feet ARA(2/3) 0.114 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.061 % * it*************************************************' * O'DAY CONSULTANTS * * 7220 Avenida Encinas, Suite 204 * * Carlsbad, California, 92009 * * (619) 931-7700 * * FAX (619) 931-8680 * Inside Diameter { 18.00 in. ) * * * * AAAAAAAAAAAAAAAAAAAAA Water * ( 5 * * * 10 in.) ( 0.425 ft. ) v Circular Channel Section Flowrate 2.600 CFS Velocity 6.319 f ps Dianeter of Pipe 18.000 inches Depth of Flow 5.097 inches Depth of Flow 0.425 feet Critical Depth 0.615 feet Depth/Diameter (D/d) 0.283 Slope of Pipe 2.000 \ X-Sectional Area 0.411 sq. ft. Wetted Perimeter 1.683 feet ARA(2/3) 0.161 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.061 % «O "L—iwfe ^ A******************' * * 0'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 t ****! >***** * * » * * Inside Diameter ( 18.00 in.) AAAAAAAAAAAAAAAAAA.AAA * Water * * { 5 { 0. 72 in.) 477 ft.) * v_ Circular Channel Section Flowrate 2.300 CFS Velocity 4.761 fps Diameter of Pipe 18.000 inches Depth of Flow 5.719 inches Depth of Flow , 0.477 feet Critical Depth 0.572 feet Depth/Diameter (D/d) 0.318 Slope of Pipe 1.000 I X-Sectional Area 0.483 sq. ft. Wetted Perimeter 1.796 feet ARA(2/3} 0.201 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.048 % #*************»*********]r *********** * * * * * ******: 0'DAY CONSULTANTS 7220 Avenida Bncinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 FAX (619) 931-8680 ;***************************: Inside Diameter { 18.00 in.) * A/tAAAAAAAAAAAAA Water * 43 in.) 453 ft.} * v_ Circular Channel Section Flowrate 12.300 CFS Velocity .27.379 fps Diaaeter of Pipe 18.000 inches Depth of Flow 5.430 inches Depth of Flow 0.453 feet Critical Depth 1.328 feet Depth/Dianeter (D/d) 0.302 Slope of Pipe 35.000 \ X-Sectional Area 0.449 sq. ft. Wetted Perineter 1.744 feet ARA{2/3) 0.182 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full , 1.372 % ********* O'DAY CONSULTANTS * 7220 Avenida Encinas, Suite 204 * Carlsbad, California, 92009 * (619) 931-7700 * FAX (619) 931-8680 * r **** Inside Diameter ( 18.00 in.) * » A A A A A A A A A A A A A A A A A A A A A A * Water * | I * I I* ( 3.15 in.) ( 0.263 ft.) I I» v Circular Channel Section Flowrate 5.700 CFS Velocity 27.378 fps Diameter of Pipe 18.000 inches Depth of Flow 3.155 inches Depth of Flow 0.263 feet Critical Depth 0.923 feet Depth/Diameter (D/d) 0.175 Slope of Pipe 65.700 * X-Sectional Area 0.208 sq. ft. Wetted Perimeter , 1.296 feet. ARA(2/3) 0.062 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.294 % A****************' 0'DAY CONSULTANTS 7220 Avenida Encinas, Suite 204 Carlsbad, California, 92009 (619) 931-7700 >** * * ********* * * * * FAX (619) 931-8680 *a****************************************************************** Inside Diameter ( 18.00 in.) * * AAAAAAAAAAAAAAAAAAAAA Water * ( 5 ( 0- 34 in.) 445 ft.) » v_ Circular Channel Section Flowrate 0.900 CFS Velocity 2.051 fps Dianeter of Pipe 18.000 inches Depth of Flow 5.338 inches Depth of Flow 0.445 feet Critical Depth 0.353 feet Depth/Diameter (D/d) 0.297 Slope of Pipe 0.200 % X-Sectional Area 0.439 sg. ft. Wetted Perineter 1.728 feet ARA(2/3) 0.176 Mannings 'n' 0.013 Min. Fric. Slope, 18 inch Pipe Flowing Full 0.007 % SECTION 5 HGL CALCULATIONS n-4 f. Junction losses The hydraulic analysis of junctions requires the evaluation of pressures and momen- tums at various locations inthe junction. Mr. Donald Thompson, Chief Engineer of Design, City of Los Angeles, has evolved a mathematical derivation which has simplified these calculations (see Section VII, Volume 2). The head loss at a junc- tion, h., is computed as follows: h. = AY * hyl - hy2 •where h 1 = upstream velocity head h 2 = downstream velocity head AY = change in hydraulic grade line g. Manhole losses The following head losses at manholes for conduits under pressure are in addition to transition or junction head losses. (1) Manhole shaft on rectangular conduit - head loss negligible. (2) Manhole shaft on circular or arch conduit: hm ' °-05hv2 where h * = downstream velocity head (3) Rectangular structure with manhole shaft joining circular conduits with or without shaped invert For D. ForD, 0b *m 0.12h'v2 kmhv2 where Dj and E>2 are the diameters of the conduits entering and leaving the manhole respectively; k.m is the head loss coefficient whose values are shown In Fig. n-2. For junctions h. Flow separation m Occasionally, such as with relief drains, there is need for the separation of flow. Although a great deal of experimentation has been done on this subject, attempts of experiments to arrive at general solutions have been few. Even less is known in the determination of head losses for flow separations in storm drains. The recommendations of the A8CE Task Committee on Branching Conduits are suitable for general use to determine the head losses. The recommendations, presented in the ASCE Journal of the Hydraulic Division, HY5, May 1973, are based on results of the committee's investigations made on the subject of head losses for dividing flow with special reference to large hydraulic conduits. Of the numerous experiments investigated, all were for pressure flow with the major- ity at low velocities and for various pipe sizes and branch angles. The recom- mended head loss coefficients are shown in Figs, n-3 and U-6. Figures n-4 and II-5 were developed from the committee's recommended head loss coefficients and extrapolation from the experimental data presented. I II. STORM DRAIN SYSTEMS Hydraulic Grad* Lin»-£ontrol Criteria 1. The design of the main-tine underground storm drain system is based on the laws of hy- draulics. After the hydrology is completed and the quantity of flow in each section of the conduit is known, the final conduit sizes are determined. 2. Generally speaking, the storm drain conduit will discharge into a channel or conduit where the hydraulic gradient or water surface is above the soffit of the conduit. This will normally be the point of control for the start of hydraulic computations. Taking count of all the losses, the conduit is sized to keep the hydraulic gradient below the ground surface so that inflow may be accepted from catch basin and laterals. Care must be ex- ercised that the construction slope of the conduit is such that the velocity will be at least 4 fps when the conduit is half-full. This will allow a fair self-cleansing velocity, m ad- dition, steep construction slopes are to be avoided so that velocities are not excessive during part-full flow conditions. If a storm drain is designed to flow full during peak flow conditions, the conduit will be less than full during most of the storm and will flow part full for the entire storm period when the peak flow is lower than the design runoff for the conduit. 3. If part-full flow is supercritical, care must be exercised at transitions, bends, inlets, and other obstructions, that a hydraulic jump is not created. Hydraulic jump may raise the hydraulic grade above the street elevation, where water might discharge through catch basins rather than enter the main-line conduit..— '~^ 4. The^jqllowing head losses for pressure flow conduits are used by the City of Los Angeles. a. Head loss due to friction = LS where Sf» £ length of conduit friction slope (hydraulic grade line) b. Bend loss due to curves = 0.002A £- •where A = angle of curvature in degrees c. Bend loss due to angle point h = 0.0033A-3-a <Jg where A = deflection angle in degrees d. Transition loss — See Fig. H-l. If the rate of contraction or expansion is different for the side walls than for the top and floor slabs, the bend loss is based on the condition which produces the greater loss. e. Sudden expansion or contraction loss Conduits of unequal sizes may have to be joined without the use of transitions, how- ever, a sudden contraction without a transition should be avoided. HEAD I TO BBHP5 - O-OC L-£t-A-Ti C"rv» ot/ruBr Q 333 .a 7.35- I if i -ro 3-33-1 8V 7.4-0 0.10^3) TO 6M-1S.T6,0.48 13.37 c-.o. To o.ttfc) 0.57 15.78 W. i, . 8G I"7J7 w C.o,I7./-7 I"7.SO 10.S--3I . SO c-o. LS> S/-86 C-0, C.-0, O-o. 0-3 64- 18.78 J9.QS" I9.cs- lfe.SC> 04.^6 w. s. 6=^ IO.3I 20.0 DGPr-M S-.315 HC.L. O ft) 78 0.7^56 • -At*. W.S. W.5 C..O. TO c.o. 78 3.8.43 Tc> c.o. T8 4-.SM- 30.7? 0.0-7 Q 0=3 IN\/ EM-H&U 40 o.s S.8O c-o, TO 0.5 TC? O.05& S-80 0.88 \\L" FR.1C-T: H&U UP . 6,0' TO C..O. TO f.tO 16 S5--CO 9 -"70 0-53 ^•"(^SS.94 V/Ar\-j>i /x.JK .' u H > "7^.30 SECTION 6 CURB INLET SIZING C _J_j /Qi I C v* 3 £>'ML-fer ==> >'a 05= => )£> I J!<,J\~}\ = "7 AS - SECTION 7 EXHIBITS O \* LEUCA'DIA RUN'OFF COEFFICIENTS (RATIONAL METHOD) LAND USE Coefficient. C Soil Group (1) A B C D Undeveloped .30 .35 .40 .45 Residential: Rural .30 .35 .40 .-3 Single Family . .40 .45 .50 .55 Multi-Units ' .45 .30 .60 .70 Mobile Homes (2) .45 .50 .53 .65 \ Commercial (2) .70 .75 .80 .33 80% Impervious Industrial (2) .80 .85 .90 .95 90% Impervious NOTES: Cl) Obtain soil group from maps on file with the Department o£ Sanitation • and Flood Control. " • (2) Where actual conditions deviate significantly from the tabulated imperviousness values of 30% or 90%, the values given for coefficient . C/may be revised by multiplying 80% or 90% by the ratio of actual iaperviousness to the tabulated imperviousness. However, in no case shall the final coefficient be less than 0.30. For exaapie: Consider commercial property on D soil group. Actual imperviousness - 50% Tabulated imperviousness = 80% Revised C * °_ X 0.85 = 0.55 APPENDIX IX 440 \ ' */• ..- / / — , - - ..1.7 i A { ! '/i i i //i '/ 1'. ' • • - " - //!/T7T1 ; '• - :-t ; ' . - - 'f(A A // / \ f ' -i i '-•••- ' / f ' < -f 'w_4. i_4-^ : //./ i/ 1 Xi 1 ' / / J ' ^ if' 1 yJI j ,/ •4 i |u_y — ,x x' .^ — -^ : r^ ' ' -f n ft (^ -^ -^ ]S ' *] * JT ^^ ^ ' , y^1-1 — J* i ^ A ' ^^ ' ** ' *" </" " ' ^ ' ' ^*| ' J^>'-r I r-^*^ ! of Wow > 300 & a/ ,Pu/ro//. C •. SO SAN DIEGO COUNTY t DEPARTMENT-OF SPECIAL DISTRICT SERVICES ! DESIGN MANUAL. APPROVED '"' ••' _':^\ _:"'/ '•"- '-•**- f£ UR8AN AREAS OVERLAND TIME OF FLOW CURVES DATE AP°ENDIX X-C V ^.. 800 700 eoa \ S00 \ * Ttrrre of 3000 /000 360 20* \ \ 3~ \ ~ VX NOTE Fc NATURAL 20 | ADO TEN MINUTES TO COMPUTED T»MEI OF CON- j — 5 e/ffcf/rt slooe fine (Set Appendix. X-8) L /tf/'/ffs feet A/ot/rs <?— /o ^S000 - —J000 — /600 • /GO0• 900,800 • 70O • 600 -SOO • MO • •200 -2OO H J20 10 ^-90 A \ \ 240 -40 -30 . — 20 — /£ — /* \-3 a -7 — S — J SAN DIEGO COUNTY . DEPARTMENT OF SPECIAL DISTRICT SERVICES DESIGN MANUAL NOMOGRAPH FOR DETERMINATION OF TIME OF CONCENTRATION {Tc) FOR NATURAL WATERSHEDS HATP 1 rNTENSmrDUR/\TION DESIGN CHART ! i H-I M i ntnrnnTHinnnw* < 'i i 'I I'lMU-t UI-Hin 11 llTI i Equation: I * 7.44 P D ~'64S I «= Intensity Un./Hr.) 6 Hr, Precipitation (In.) Duration (Min.) 10 . 15 20 Minutes 40 50 1 Pi ir.it inn 5 6 Directions for Application: 1) From precipitation Raps determine 6 hr. and 24 hr. amounts for the selected frequency. These maps are printed 1n the County Hydrology Manual (10, 50 and 100 yr. maps Included 1n the Design and Procedure Manual). 2) Adjust 6 hr. precipitation (1f necessary) so • that 1t 1s within the range of 45X to 65X of the 24 hr. precipitation. (Hot nppllcable to Desert) 3) Plot 6 hr. precipitation on the right side of the chart. 4) Draw a line through the point parallel to the plotted lines. 5) This line is the Intensity-duration curve for the location being analyzed. Application Form: 0) Selected Frequency _jOQ_yr. '** %* 2) Adjusted *Pg* 3) tc- 4) I • 24 In. mln. 1n/hr. *Not Applicable to Desert Region Revised l/8f, AlMMiNHTX XI A COUNTY OF SAN DIEGO DEPARTMENT OF SANITATION FLOOD CONTROL 100-YEAR 6-UOUJ* PREC1PITAT10IJ ^20-/ ISOPLUVIALS OF 100-YEAR 6-HOUR or An i;:cn\v U.S. DEPARTMEN NATIONAL OCEANIC AND AT: IPKCMl fTUOIEt ORANCII. OrriCt OF II !flli€^ ISI'JIKKIC AOMINISTKATIOM IIKOLOOV, NATIONAL WEATHER tXMVICC 30 118 |.>t. 30» J51 116" • <>,! I /8S AI'IM-HIUV V! !•' -,'.,•• . t . 'V;'. • r v.v/', V •:• COUNTY OF SAM DIEGO DEPARTMENT OF SANITATION 8- FLOOD CONTROL 30' 15' 33' 100-YEAR 24-HOllR PRECIPITATION "~2(UI$GPLUVIALS 0^ 100 -YEAR 24-HOUR PRECIPITATION IN "EMTHS OF AN INCH U.S. DEPARTMKN NATIONAL. OCKAMC AND AV SPECIAL. iTUDlES BKANCII. Office OK II ••":::. 30' IHI"30'10' Il<.«is,;,l l/Kf,AI'I'I-MHIX XI -II o s* n/^ "> RCSIDENTIAI. STREETONE sioe ONLY SJ ff;:|:^]^£^ ~ " " 14 12 — (0-J 7—p £7 •-: ~.-. : --:=_.._;--.;].j?/ •: :...- :: - ~- j. 7-- - Q3* 7**_ '?*»^- -y.iL;jj^;.;rj. : • 'jj : / —. *S>J^^ ' 'fe- • '-• ;, ". .- / V--" -7: —r.'::'~.~7:'.; :—~~^7 "*-^ — ./ i '" ~~~-'• ••• t- '•" ?C~ •' ' '' ' • - '- ': 0.6- as iir/ —•-? / • •—^ ^..., . - f~ ~ -.---._••--• :- • ~-i..t.--^r * ^~ J — DISCHARGE (C.FS.) EXAMPLE: Giv«m fts 10 S* 2.5% Chart gN««: D«pth * 0.4, Voloa'ty = 4.4 tps. SAN DIEGO COUNTY DEPARTMENT OF SPECIAL DISTRICT SERVICES DESIGN MAMUAt GUTTER AND ROADWAY DISCHARGE-VELOCITY CHART DATE APPENDIX X-D (V\/VP CITY OF CARLSBAD OHTHOPHOTO MAPPING FRASER ENGINEERING. INC.COOPER ENGINEERING ASSOCIATES :" 15 23 296-6 II 11 IIII i3ajrn*!» CITY OF CARLSBAD OHTHOPHOTO MAPPING FRASER ENGINEERING, INC.COOPER ENGINEERING ASSOCIATES 23 i!j} iiiiicl 11} B < «• -4- _L tit 24 23 22 21 20 19 18 17 >~ * / /^^r:\ 3| ^T^QSiiitefe ^-r^£ff-ff fflJ . _ ^^s^^^^'^:^^-^^z=^:i^j^-'^'-'---'•-'-'-'r/f v^^^i^m^^j^i? %^.-M^---^^^%ri^^mm^-s \ l-'"" '--•=-. - {/'''^-^^cf^ff rct;f ste&r^ri---^=^i^ltf,:^^f f w rr n'"y^^^^^4?;ii£3^^(irn"-£T- r 7 /.'- L-i--td^^**:t^^^^a*^^^^fe -r-^-.^ BENCHMARK; REVISOM OESCRIPTIOM WtMCMT PUWS rOfc ~~ STORM DRAIN C.T. 94-01 t •CAMSVmoi «\«,M! lias CMWO 94-503 i /-, •* I . \ * sU - >-. Jr ; fA K STORM DRAIN DATA NO. c' •) £ > <! QEITA OR 'BEARING A- TOW A-1S41-1 2tT47'JZ*srii'irarii'irWin?awns' 21WW 2roa';y RADIUS 687.00' M7.00' — — — — —— —— l£NGTH S4.K1 2Z4.Wiw.rr MS1 M.25' 5.25' ».»' 142.00" 176.001 REMARKS 24' RCP - 13W-D If «CP - 13SO-D ) RECORD FROM: NORTH COUNTY VEKTTC*. CONTROL DATABOOK, Wffl 135 NO. OC 0147ELEVMW 50SS8 US.L -*Sr~lisr- onNORorMW REVISON DESCRIPTION ~SSt~•ssr DTWH VPHOUU. MTE HTW. cnv WPHCMN. Y.fllCtt'y OP CARLSBAD Ippl13 || ENGINEERING OEPMTMENT || A wnovcucNT ruws rot: STORM DRAIN PE MM* EXPffiES lI-i1-« cnfENcSIIS ~oST~ 51^11— l""~ .. sro. 2. STFft R K.K. rtRCKS. mm& fnOETHILSUNO MIRK 3MLDUL f TO Bi DPPRMD Bi miUMV_ ._ . _ PLANS FOR THE IMPROVEMENT OF OFFSITE STORM DRAINcoeuoforDtSUI 4,ikllt£i SOUTHarCMtSBRD OH CARLSBAD »IM>. WfTtteOVUP LfNE OHfONWsr/K£7 menus BKID&E HO a 78 04 ABfTH COUNTr KfffXM. CDHTTm MTA BOOK filfff 135. HO X 0147 ELEVATION<50.5S8 M-S.L. C.M. W.P. 34-SO3 £r<y>f/ti GFIW GAra M>rofzt f?l tt f t A /fff^fV/va N2I'09'?9"H tfS'SS'OI-t ttij'Sff'iru &AOIUS AfC/lffiV6r» ?33J6>' Z4O.J9' l&. 45 ' ifS'/ttAtfiVS wicrco-nx}"" " D pise $£7 fiusn IN HOIKcomer oratiocE ABUTMENT.LOCATION* R890T 4.$*1U£5 SWH0rCKR(.*BmDON CAttSPAP fLVP. NQtrWOVW LIM€ OH POffTiOsrr££r wtrrsss ex/pee HO. wa 04 ff£COKP£f fXt»f: NOKTH COWTr VFrr/ gOOff f>4G£ IAS. NO OC 0147ELEVATION-50.558 MSI. okv*~?--•"•--"" ' '^"' —-.._££_ ^.mauoL — _-S^T ^ST REVISION DESCRIPTION »tn.•o.-nrr TS=T '""MICITY OF CARLSBAD ||«""T'|f<7 ll»>INCim»l OIPAHIlUNTll . 1 PLANS FOR THE IMPROVEMENT OP' OFFSITE STORM DRAIN C.T. it-OI .. liUi c \ ^JJn'Jfv !riCLO K TT INIIWIR MTE C.T. 94-01 11 3J7-^ C.M.W.D. 94-503 STORM DRAIN DATA NO. C 3 C 5 C > •-->_c >< >e.> DELIA OR 8EARWC N 172CW W N 4f 17-W W N WITT* ff N WI5W ff RADIUS i LENGTH 46.7S" 224.001 mW 1S.W REMARKS WRCPf -01 tf RCP (1X0-0) 9f KP (13«KI>W KP (I3M-0) O't&y *i9-tii -no* Si^wJiTF«t>9->11 -KM DESCNEO 8T: _J,<^ WK: AUfc. 18*4 _ PTOJECT UCRLJ^<JT1. ^OB HO.; M-1Q1J EMWNEEIt Of WOM: OATt: aofiCE ma »ct 12014 "AS-BUttT " REVIEWED BV: INSPECTOR 5«E BENCHMARK: APFVOK. jaonnsofm or SOUTH ENIWTO CWU8W SUrC fWK 40 FEET EASTOF CDflEMME Of NMTH KXJWCWUBN) am ON POHTD snm BRUCE NO. amI. ON POHTD IHCOUITYM" ELfWIUK 50SS CM9M0W «W REVISION DESCRIPTION emo tmtMn am CTT VMOWH. Yf II CITY OF CARLSBAD if ^i18 II CN&NEERWC DEPARTMENT || X STORM DRAIN at.N-ot PI UM* EXPIRES 12-J1-W CITY ENGINEER DATE pSR-tfi 1| PWJECTNO. IJDftwiHC NO.J S^«?; Ji C.T. 94-01 II 337-9 SECTION 8 URBAN POLLUTION STUDY TO v\ AC "D"- i /• M COia-TpJA^ c Q.Q ^ te-B =r /51S5Q |l .^^ul^tfg^j^jMitVti,^. •*- Q D»*S.<3 ly ^^ "^T—-0 •n L r=-i ii- 1— irrj T'— i^- ...... ^ J£L " JZL V- FTT-S/ - VA ^ rr p, rr - 37**- eP XX 34 /f f=T 6-s A*******************************A********************************** * O'OAY CONSULTANTS * 7220 rWejiida Encinas, Suite 204 * * CarlsbaJ, California4 32009 * * (619) 931-770© * * FAX (619) 931-8680 *A****************************************************************** Itiside Diameter { 36 -W0 in. } * * * * * * * A A A A A y» A A A AA/V/V/. A A A A A /\ /\ ~ * Wat.er * 1 I I * ( 24.20 in. } ( 2.017 ft.) 1 * ___ v Circular Channel Section Flowrate 37. 4€>0 CFS Velocity 7.401 fps Diameter of Pipe 36.000 inches Depth of Flow 24.202 inches Depth of Flow . 2.017 feet Critical Depth 1,908 feet Depth/Diameter (D/d} 0.672 Slope of Pipe 0.500 % X-Sectional Area 5.053 sq. ft. Wetted Perimeter ., 5.768 feet ARA(2/3) 4.627 Mannings 'n' 0.013 Min. Fric. Slope, 36 inch Pipe Flowing Full 0.314 \ ***************************************************•***»***»*******> * O'DAY CONSULTANTS * * 7220 Avenida Encinas. Suite 204 * * -"arlsbad, California, 3206S * * (619) 931-7700 * * ?AX (619) 931-8680 ******************************************************* ******** ******** *** * ** *** j< / 9.52'} >| *** ***A.AAAAAAA vfater Depth { 0,33*}AAAAAAAA*»* *** * ** *** * »* *** *** ***!< ( 8.00'} >|*************************** ******************** Trapezoidal Channel Trapezoidal Channel Flowrate 37.400 CFS Velocity 11.217 fps Depth of Flow 0.381 feet Critical Depth . -. e. 822 feet Freeboard 0.000 feet Total Depth 0-381 feet Width at Water Surface .... 9.522 feet Top Width 9.522 feet Slope of Channel 4.000 % Left Side Slope 2.000 -. 1 Right Side Slope 2.000 s 1 Base Width 8.000 feet X-Sectional Area 3.335 sq. ft. Wetted Perimeter 9.702 feet ARA(2/3) 1.636 Mannings 'n' 0.013 RUNOFF CURVE NUMBERS FOR HYDROLOGIC SOIL-COVER COMPLEXES (CN) TABLE I-A-1 AMC 2 la - 0.2S Cover . ,. Treatment ,land Use op Practrce3 Water Surfaces (during floods) Urban Commercial- industrial High density residential Medium density residential Low density residential Barren Fallow Straight row Vineyards (see accompanying • '• ' disked annual grass or legume cover Roads (hard surface) (dirt) Row crops ' Straight row Contoured . •- Narrow leaf chaparral • . - Hydro logic Soil Grouos Hydro logic Condition*' A 97 89 75 73 70 78 76 land-use descript 76 Poor 65 Fair 50 Good 33 7** .. 72 Poor 72 Good 67 Poor 70 Good , 65 Poor 71 Fair 55 B 98 50 82 80 78 86 85 ion) 85 78 69 Si 8if 82 81 78 79 75 82 72 C 59 91 88 86 84 "9F 90 90 85 79 7^ 90 87 88 85 84 82 88 81 D i 99 92 90 88 . 87 93 92 92 89 8k 80 92 89 91 89 88 "86 91 86 I-A-5 \n CN •tf» COUNTY OF SAN DIEGO 6O OEPARTHENT OF SANITATION AND 55 FLOOD CONTROL 10 1.5 Precipitation 20 in inches 25 30 35 8.24 Erosion and Sediment Control Handbook 3600 X A, X CjVtf where 7* *» time, hr A, a surface area of basin, ft* (m2) Conversely, the size of orifice needed to dewater a basin within a specified time TIB " 3600 x r x cdg Thus a typical 10,000-ft* (930-ms) basin would need a 0.068-ft2 (0.0063-m1) or 3.6-in- (9-cm-) diameter orifice to dewater a 2-ft (0.6-m) settling zone in 24 hr. Several orifices adding up to 0.068 ft1 (0.0063 tn9) in surface area could be used. - Figure 8.176 presents the same riser with a shield tack-welded over the orifice. The shield greatly reduces clogging of the orifice, but it will somewhat lower the discharge rate through the orifice. Figure 8.17c and d shows a siphon used to dewater a basin to the sediment level. This method, as presented in the SCS Maryland handbook (9), calls for a 4-in- (10-cm-) diameter siphon. With the system shown in Fig. 8.11 c, runoff from small storms and base flow would flow through the siphon with no backing up and storage. In the system of Fig. 8.17d small flows would back up and discharge in a batch fill and drain process. This would allow some settling of the sediment. Neither system would dewater below the siphon. The method shown in Fig. 8.11 e has been frequently observed at California construction sites. It is potentially the worst possible to be employed. Although the basin would dewater rapidly, most runoff would flow straight across the basin and out the multiple holes. Not only would there be no backing up of the water, with associated particle settling, but the straight channel flow through the basin would retuspend previously deposited solids. The discharge from such basins has been found by the authors to contain more sediment than the runoff into the basins. The dewatering hole shown in Pig. 8.17f can dewater the entire basin, includ- ing the sediment zone. However, this system is poor for two reasons. First, any orifice sized to dewater the basin quickly would directly pass low flows associated with the more common storms and provide either no treatment at all or negative treatment. Second, any sediment accumulating near the riser would be quickly washed through the orifice. A number of consultants have suggested the systems shown in Figs. 8.17; and h. The gravel piled around the base of the riser acts as a coarse filter to keep sediment from escaping. These systems have not been monitored to assess their effectiveness. Additionally, the system shown in Fig. 8.17» has been suggested for the dewatering of sediment in large basins. Performance of this system also has not been-verified. In all cases, the dewatering hole must; be sized to prevent smaller storms from draining without any retention time in the basin. Figure 4.2 shows that, within a typical 6-hr storm, for 4 hr the flow rate will be about 60 percent or less of the average rate. If, for example, the basin were designed for a 10-year interval storm that drops 2.6 in (6f mm) in 6 hr, a much Sediment Retention Structures 8.25 more common storm may drop only 0.5 in (13 mm) hv6 hr, The average flow rate of the more common storm through the basiri~mayT>e only 20 percent of the 10- year storm. For 4 of 6 hr of the common storm, the flow rate may be only 12 percent (60 percent of 20 percent) of the average flow rate from the 10-year storm. A dewatering hole sized to dewater a basin quickly (24 hr) would in all likelihood pass the email storm without ponding, and thus without trapping sed- iment, Dewatering holes sized to drain a basin over a longer period, such as 3 to 6 days, will back up the smaller flows and cause siltation of the basin. EXAMPLE 8.1 Given: Basin surface area - 14,400 ft1 (1338m') Basin depth D - 4.2 ft (1.3 m) Q design - 2.64 ft'/sec (0.0748 m'/sec) (i - 0.44 In/hr (12 mm/hr)] Find: Unobstructed orifice size at bottom of steel riser to dewater a fuJ] basin in 24 hr. Solution; A.VSE 14.400(^81) 41,736 294,166 A ' "3600 X T X Ct\ft 3600(24)<0.6)( 1/32.2) I" (133am*(\/2Tni) 2167 1 " l3600(24)(0.6)(V9-81 m/sec2) " 162,388 J - 0.14 ft* (0.013 m') - 20.4 in9 (133 cm1), or five holes of 2.28 In (5.8 cm) diameter Now Find: Depth to which this baain will fill during • smaller storm precipitating 0.5 in (13 mm) in 6 hr. Solution: D hr /13mm-TT— "\ 6hr 0.063 i: \ 0.44 in/hr ,/ (0.0748 mVroc) 0.5 ft%ec 12 0.014 m'/.ec For 4 of 6 hr, Qm - 0.6Q,v( - 0.3 ftVaec (0.0084 roVsec) Now Qoui - Cj X A,\/2gh; therefore, the head of water h which would balance out Qin and Q^, ia fc „ ( s~i \*. / 0-3 y (f lCrfXXA'2*/ \0.6(0.14)(v/6T4)/ ll I1 L 0.6(0.013 m'X V19-6 JH/BBC!) J 0.0084 mVsec 009- — = 0.2 ff. (O.Ofi m) SECTION 9 DESILTATION BASIN STUDY TWIT ^ A a--o»-' acr JO ^^i_^ ^» •'A-tJ •' *'^' v/s^S&IS •.^P* !•-. •i".v*T'V'viSEP-^ • Aii average flow ^ratfa«tlunp«*k flow, is us«l to find the required sorfic* ana of wdizssni t>»«tT»« ^sd traps. The T«t>r^«i fimmlt a jtfll applied, except that an avei«j« pvedpitation. intensity instead of the pnk intensity is used; «„ - C X _ Avenge precipitation intensity i*, is determined by taking the total ninM - for a specified storm return period and duration (e^ 10-year, 6-hr storm) and "Tdwidiujthat total by the number of hours of duration: total 6-hr rain 6 A 6-hr ttom dorttion it soOMtML Sediment basins designed wit Jtona peaJa and being somewhat oversized during th* rest of tha storm. K*~ «• - ..,.„. i "T^/g. M i :V ; i_ TUg ill> >X TN; e M. fc p = '. v- ;•' to ;<:J gS -A A. '5 BKJTi t K» >-*)sJ f f* ^ whet* 4, it the appropriate surface ue& for trtppinj partide* of a certaia 9» and V, is the setdingvekxatyfior that size partide. • I iC A IS.fl-T- va.- Vl &L.S CJ T • •£•«• Emnoa mod S«dimaat Control Hudbook TABLE 8J Sm&e*An*R«iaii«DMiitxdfSei&B>«itTnp*<iidBaini Faiticl* att*. mm ft/we (m/Me) ' daciwp OJ (eovnetaDd) 0.2 (medium wad) 0.1 (fin* wncD 0.05 (coazwiOt) 0.02 (medium lilt) 0.01 (Out lilt) 0.005 (day) 019 (0058) 0067 (0020) O023 (O0070) 0.0062 (0.0019) .0.00096(0.00029) 0.00024 (0.000073)0.00006 (0000018) 6J 173 512 1916 U50.0 5,000.0 20,000.0 (20.7) (58.7) Q.TLO) (635JJ)waou» (16,40401) (65^17J) . .". ';'.- "£'.' • :£-$'-*£{-?i'&-. ^.V**f&£- '"&$&£*' JC- PR.ig-r i t- t- j? ' / a {=£;/«. O.. a. 6.C . C >-! ^- te) ( O. oS 0. OC'j, 3-^5 *^-?':~^ ..;.-,,, w.. •' rr-r- -&$]; ''i$$g&: ^. - o • C O a. -7 0. C Ft/ 1 TV I/,. C|42 . '.; -..^.V'- ','.., F£ : •-—'•'-•'•'•:'.**> ""U.-;; •£•<•*•*•••& -"•'<:*.? !-'•'•• \G - Q-SB x x •3T?'7. AwJ Op A i. a, DgTlaVg.»VM *Jt=O YQ D. 145 AKt ^A rr _ 9, s5"Q j?^ /-,. \nr V/T a**!!;? OF Tug ViW-M v,^ Mfe•": i'.'.—*V".•:—'••.<- '; The general form of th« universal soil Ices equation in -' where A -soil loss, tons/Caere) (year) -- . I Rm rainfall erosion index, in 100 ft - tons/acre X m/hr ;"•'•;- K - soQ erodibflity factor, toes/acre per unit of S . ; LS - slope length and steepness factor, dimeosionless C - vegetative corer factor, dimenaionlesa ''.---, p — titMltHl CTBtTrfl p'^'^T'** flx-tn^ dm»»Bgjonlfff ---'.'- P o &fc 5, "Ibe difierences in peak intensity are reflected in the coefficients of theequ*-. tioos for the rainfall factor. Figure 5JS a * graphical representation of the equa- tions. The equations, also shown on th* curves for ^x*^ individual storm type, -r typ«l O fi-KUp" typeU when p is the 2-year, 6-hr rainfall in inches. (If p is in mfllimeters, the equations become: R - a0219p12, type It R - O.OI34p", type t E - 0.0082SpH 1 IA-). T art Tms -si-re" -Sec" P<H\6IT ^ X. R= • * •"'>'*"-•'i.i.T .*. . .•-.,;. ;5;,^M^__i^sip&ssasa&.-i "P^3?35-;•;•:; '-3'.^ .'~£'-'r*'£$$&• 7- 4< •. C^t.U C I11 *.»x.^,A«. /5"j/, r;-^ •...*-_-< TUG 5o,L c-^,*,,,^ FH,,^ k ,** e«*tt*»r %»K"1 ) Fi^.^s^. TvJg- Sc>' « ^'=°-?-C.T' 3.O */c Of~ fvu^ io'i » 0 °h Fit. S.U --•:-.;.:;;.: -^»i$sS /* f>w ^>. 2. ?.6 .Z^.eri,"»ftlT V "b.f- ^.ovJ<-^'l£L;g.tiA>v . A •>"\:-f:-ri--'.-j-'7- ••=•-". •'•- /•'.-•••=':- .-r.-.>•.-- ••-•: v -;•- -- -: 're-'--. TABLE 5.8 C V«lu« for Soil LOH Equation* CJkctor Soak* NO • Tumpatary wiBnp- 90% ami, animal griini. so mulch Wood fiber mulch. S too/to* (1.7 t/ha), with i^dt Excelsior aat,jutaf LS toaa/acn (3.4 t/ia), tadotd down 4 too/eat (9.0 t/ha), tackad down •Adaoud tan Bad. U. li nxl 20 LO 0.01 05 03 O2 0X5 0 99 90 SO 80 95 P: Tuff CcuT7?n'_-nj^'=> r*/- — /» i-s, ff (— r>v«J — ^ TABLES.? J»FactorsteCoo»ttnctionata«(Ailapt«dfrontRtf. 15) Comp«s»d «nd snootix TnekmUnd ilrac eontour- TndcmtkKl op tnd down dap*t Punchwljtrtw Hough, imftiUr cut LOOM to 12-in (30-cm) depth L3 03 Tmd Buk> «Meud op «ad don tlopt. rrjmd Buka ariwad pmlU to coatta.«in Tip. U tad 8JO. / / 6. t BEST ORIGINAL • ^4 . 2SS ^=^> L-S^ 3 J 4 nu nui tux «ui at* 1 W» Hi UN *M ftlt Ul «J| Ml Ulf »ltUt«MkMl»UTL]a&W*M 3 »Jt M4 lit Ad 1 » M) *-• *•* «M ' *i imunim UC MJW 9M MM MA WJi 1*31 1*?1 «Ji — - --- • J "Mim ami an. "0»" tun nai i>« nta U9 Ml «— U- V" S» UT B7T 1M IM M> .&M •* IM 1* Ut *M MUI MMUl Ui Ml IU» tlM 1LM rtM HJTut nM lur an MM MM MJt rr.wttM MM I4M MJt ftM MM M^ UM ttM MM MM I MM MM IU» tUl MM 1LM IU* »M VJt MM MM Ml* «.« MM MM MM Kit TJ.M mM mM 9t*f MM HIM MU1 ||1M .•• AfcM MM^f* TUI MM MM **• ft" M10 MUt fHM HUtj^ ffgy f^f| ffjt 7m ••• MtM MM MM MM m" TTIH MKM H.Tt fltH M.H Hlf 4M k.4» MM *4M MM* HUT 1MM M119 IMM MM MM MM MM1 «« AM *» MJ» ATC MM MM MM MM fMM «M MM «U* «kM «U» Mil M.TT |M1 MM MM M« W9 tMM JO4 «M «UI **» *U> MM MM; MJI 1«M »« MM MM Ixn Mt» MM MJI «ui m.m MM mm MM nn MM MH MM j ! ' *_j*i CJ6-, Ji Using the USLE Sample SoQ Loss Calculation; Step-byStep Procedure JL Determine the H factor. 2. Based on soQ sample particle size analysis, determine the K value from the nomograph (Fig. 5.6). Repeat if you have more than one soQ sample. 3. Divide the site into sections of uniform slope gradient and length. Assign an ~ LS value to each section (Table 5.5). £ 4- Choose the C value(s) to represent a seasonal average of the effect of mulch ~\- and vegetation (Table 5.6). . : 5. Set tb» P factor bntd oa the final padinf ptactk* applied to tfa* slope* • tT«bto5.7). & Multiply th» five factors tof«tl>*r to obtain ptr atn MS fca*. 7. Multiply aoflloaiperigtbyttoacrean to tod tfa» total vojume of Mftmnpt. If the soil loss prediction show* wcmtre vobaw kxt from tfa* site, eonsidtr and gradient, or (c) incMMBf naidi ippluatioB zato « Ac ~ CX I O3~7 A- O. 105"? TV* j: 33 * ^_«6 2 c~ v• ,,, . ,r *, •'"• ". * ' •'. /x'.*•"> «P'••«VV.\f i -y;;'-. •^- ,*\. x'.J-i'»v.> 15 B.16 Erosion and Sediment Control Handbook TABLE 8.1 Surface Araa Requirements of Ssdimsnt Trsps and Bsslns Particle sl*e, mm 0.5 (cosrse ssnil) 0.2 (medium ssn<l) 0.1 (An* land) 0.05 (come lilt) 0.03 (m.dlum.lll) 0.01 (nn.illt) 0.006 (cUy) Settling velocity, ft/sea (in/«oc) 0.10 (0.088) 0.007 (0.020) 0.023 (0.0070) 0.0062 (0.0010) .0.00086 (0.00020) 0.00024 (0.000073) 0.00006 (0.000018) Surface srea requlrsments, ft' per ftVaes hn' per m'/tte discharge dJscksrgs) 6.3 J7.8 82.2 193.6 1,260.0 6.000.0 20,000.0 (20.7) (88.7) (171.0) (636.0) (4.101.0) (16,404.0) (66,617.0) weight composed of particles in the 0.01- to 0.02-mm range. A surface area 4 times larger would be needed to capture 6 percent more of thla soil. A balance between the cost-effectiveness of a certain basin size and the desire to cRplure fine particles must be achieved. It is desirable to capture the very small soil particles (clays and flue elite) because they cause turbidity and other water quality problems. However, Table 8.1 shows that a basin would have to be very targe to capture particles smaller than 0.02 mm, particularly clay particles 0.005 mm and srnaMar. Because of the high cost of trapping very small particles, the authors recommend 0.02 aa Die design particle else for aedlment basins except In areas with coarse soils, where a larger design particle May be used. The 0.02-mm particle is classified as a medium silt by the AASHTO soil classification system. 8.2d Basin Discharge Rate The peak discharge, calculated by Ilia rational or another approved method, la used to size the basin riser. During any major ttorm, a sediment baaln should fill with water to the top of its riser and then discharge at the rate of inflow to the basin. A sediment Imsln Is not designed with a large water storage volume as la a reservoir. If the inflow exceeds the design pbak flow used to size the riser, the over/tow should discharge down an emergency spillway. S.2e Design Runoff Hate In the equation for surface area of a sediment basin, the discharge rat* Q Is a variable to be chosen by the designer. The above discussion of baain discharge rate shows that the discharge rate is, to a large extent, equal to the inflow. The riser Is sized to handle the peak inflow to the basin. The authors suggest deter- mining the surface area by the outrage runoff ol a 10-year, 6-hrttorm instead "•..:* •'':;.$.. Sediment Itelenlloa Structures 8.17 of the peak How. A substantial savings In size, and therefor* cost, i« obtained, •nd baaln efficiency la not significantly decreased. Consider a baaln designed to capture the 0.02-mro particle at the avenge run- off rat*. The average rainfall per dour 1» 17 percent of the lota) rainfall In a 6-hr •torm (Sec. 4.10'On • site with soils with • moderately lilfh.clay content, under Ideal tettllnf conditions thle basin would retain about 02 percent of the eroded aoll (I.e., 82 percent of the soil, by weight, la composed of 0.02-mm or larger particle*). . If the surface area of thie baaln were Instead designed for the peak flow, It Would be roughly 3 time* larger. According to data from the U.S. Bureau of Reclamation (10), 25 percent of the total rainfall in a 6-hr storm fall* in a K-hr period (Fig. 4.2). Since the rainfall intensity i value is In unit* of inches (or mil- •-limelers) per hour, the peak (low can be calculated by using an f value of 60 percent of the 6-hr total. Since baain eurface area it directly proportional to the discharge rat« (A - I.2(//V.) anil the peak discharge rate In a 0-hr «loim la 2.0 times the average rate (G0% - 2.8 X 11%), the eurface area sited for the peak flow would be about 3 lime* th« surface area sized for the average Row. The battn •Ized for the peak flow would capture, during moat of the itorm eicept the peak, particles with approximately one-third the settling velocity of the detlgn parti- cle. Since the 0.02-mm porllcle eettlee at 0.00006 ft/aee (0.00029 m/sec), particles with • settling velocity of 0.00032 ft/sec (0.000098 m/sec) woul<l then be cap- tured. TJieta are approximately O.Ol-mm particles. Suppose a basin on a site with clayey soils were sired by using the peak runoff rate. For tre purpose of Illustration, euppoee the soil composition were typical of the San Frsncisco Bay Area as in the preceding example (62 percent of par- ticles, by weight, greater than 0.02 mm and 6-percent, by weight, from 0.01 to 0.02 mm). A Luln with a large surface area based on (he peak runoff would cap- ture the 0.01- to 0.02-mm particles a* well as particles greater then 0.02 mm, or 67 percent of the eroded material. The basin efficiency would be increased 8 per- cent (6/62) by tripling the surface area. Thus It is generally much more cost- effective to sfce a basin by using ttie average runoff rather tli»n tlig peak^'and". 'basin efficiency will not be yignlflcantlv |ogBn^'.",--,-.-. 8.2f Settling Depth If • basin la tco shallow, water flowing rapidly through the basin inoy resiiepend settled partlcks and decrease efficiency of capture. A similar problem occurs in grit-settling chamber* at sewage treatment planta, where velocity must be con- trolled to prevent particle reauspenslon. An equation that describes scour in a grit chamber (2) Is:ftlX 1.486'X r"» X *(S, - 1) X304.8 COUNTY OF SAN 01EGO DEPARTMENT OF SANITATION FLOQO CONTROL «»5 PRECIPITATIflH Of 10-YEAR PRECIPITATIOC4 IN \EMTHS OF AH INCH" 10-YEAR 6-HOUI ^•16- IS6PLUVIAI.S j-.. .IP-ivy Yt'F^*» 33' ll'tCIAL (TUDICI DRAMCH, OKFICL' OF I OlIMieniC APMINIITMATION UltOLOOV, MATIONAt WCATIIKII S(XVIC| U.S. DEPARTMEl T OF COMMERCE HATIOHAL OCEANIC AMD A) r? :-.: '••': .'•'M.I. . .• 8.14 Erosion «n«5 Sediment Control Handbook . 0.2 A 6 80.3 0.4 0.8 O.B 1.0' Surlicl MM •d|uumtnt liclor Fig. 8.14 Effect of turbulence on sediment btein efficiency i (3, 7) upon performance, there ii little guidance on reducing turbulence and Increasing efficiency to that predicted for /deal condition*. More research need* to be per- formed on sediment baalni before significant improvement* in detign can be pro- posed. However, tlie following pracClces can Influence turbulence to torn* degree and reduce the surface area adjustment multiplier: • Ileduc* water velocities through the basin. The Ideal surface area to computed by using the equation A - <J/V,. Increasing the surface area increase* the cross-sectional area of the flow through the basin and decrease* the horizontal flow velocity, and thus turbulence. An alternative way to reduce horizontal velocity Is to Increase basin settling depth. This has a small effect on reducing turbulence. • Eliminate unnecessary angles or dogleg* In the flow. When water flow change* direction, random currents that inhibit particle settling are set up. Long, straight basin* are beet. • Reduce the effect of wind-Induced turbulence. Large open water surfaces are effected by wind, which produce* eroas- and cau nlercurrenU that binder set- tling and may resuspend bottom deposits. Using several smaller basins with a total capacity equal to the capacity of one large basin should Improve capture efficiency. Note: Multiple batini mutt bt placed In paralltl, not in seriw. If small basin* were In eerie*, each one would In iiydraulically overloaded and thus would perform poorly. Surf at* Arta formula The basin designer should select a surface area idju*tment factor based on site conditions. A U.S. Environmental Protection Agency publication on erosion con- trol for surface mining (6) proposes a surface area adjuelment factor of 1,2. This ' Sediment Retention Structure*8.15 :''{.' factor I* based an the assumption that (hs basin Is well designed in all key •:'*••' aspect* (shape, outlet location, riser design, etc.) but that turbulence and other P nonfdeal conditions will reduce the basin'* efficiency. The resulting sediment {•f- basin surface area sizing formula become*; ?£. •;;•-.'"• • i. A .125 It *-;J' '( r'. . - * ;;',r where A, I* the appropriate surface area for trapping particles of a certain six* '''? and V. i* the settling velocity for that slxe particle. •;!;, 8.2b Basin Efficiency , '":, The trapping efficiency of a basin is a function of the particle site distribution '/' of the Inflowing *edim«nt. Assuming Ideal settling conditions, all particle* with ).< *l» *nd density equal to or.larger than those of the design particle v/ill be •'' '•! retained In the basin. In addition, some smaller particles will be captured while -; •£•' the basin is dwalerlng and the overflow rate ho* decreased. The additional cap- -.' ,.\' tura> ranges from 2 to 0 percent of the total sediment load. Far our purposes the '•' l'i increase I* not important enough to include In the calculations, particularly since '''.'<• the increase is offset by reduced capture efficiency of the basin when flow exceeds ' •'•; the design value. ' i •:', • Therefore, (d«al basin efficiency correspond* to (lie percent of toll equal to or '•• ':': larger than the design particle size. For example, if a sediment basin on a site is -. . designed to capture the 0.02-mm particle and 64 percent of the particle* on this v" ait* are greater than or equal to 0.02 mm, the maximum efficiency o'f the basin Is 64 percent. Tli« only practical way to increase this efficiency is to increase the surface area ot* the basin. 8.2o Dealgn Particle Size The equation A, - l.ZQ/V, defines the relation between size of particle to be captured end the surface area required for the baaln. By applying this equation with the settling velocities V, of various particle size* from Pig. 8.12, Tabl* 8.1 of surface ares* per unit discharge is derived. From Table 8-1 it I* clear that the surface area required increases very rapidly •• the particle *Us decreases. To capture the 0.02-mm particle, the area must b* 6.6 time* larger than the area required to capture the 0.06-mra particle. To cap- ture the 0.01-nim particle, the basin area must be 4 time* larger than for the 0.02- mm particle iiml 26 time* larger than for the 0.05-mm particle. For particle* •mailer than 0.0'.! mm, the surface area requirement increases dramatically. Where toll* have, a high content of clay or fine silt, increasing the size (and thus cost) of a basin will not bring about a proportional increase in basin effi- ciency. For example, a typical soil in the San Francisco Day Area is 62 percent by weight composed ot particles 0.02 mm and larger, but it 1*9 only 6 percent by r~ •> r MiTiHF P.rllcle tetdlnc velocity curvet. (7) SwTJ^Hr^al^iiiiiv ' •-"^ •^i^-\^"-x- • a* ** -16- *'fll •::^HF TaM«5-1 Standard Sieve Sizes-All Available in 8-io- Dianettr Sirvei; Most Also Available in 12- •ad lS4k. Dtaowton (UA Bonan o/Steadanb and ASTM Designattons) ; FlMMTM* StoWftNOB SlTO (omtatTfofeJ (•»)SimNo. e x H 4 ! 3t 3 24 2 • 1* • ' » .' .'• *-li 1 • --I i i i - ;* 1 ^' * 10L6 88.9 7ai . 63u5 504 44.4 - 38.1 3L7- . .' .- , asA ."";:. 223 : 19.1 • 15.9 12.7 111. 9JS2 7.93 6J5 " 3i . 4 5 6 . 7 ' 8 10 12 14 ; 16 . 18 20 . 25 30 35 40 45 50 60 70 80 100 120 140 170 200 230 270 325 . 400 SJJ6 4.76 • 4.00 3J6 2JBZ 2J38 2.00 ' - " L68 L4I U9 1JO 084o.n OS9 OJSO 0.42 035 . 0297 0.250 0.210 0.1T7 0149 0125 0105 0098 oj>T4 <: 0062 0.053 0044 0.037 Ion a logarithmic scale. Standard procedure uses the percenf passing (also termed per- Cfnt finer or percent mailer) as the ortjinaty plotted on a natural scale of die grain- . • Typical grain-size distribution curves are shown in Fig, 5-4. One of die curves (curve . :,;B) is obtained from die data shown in Fig. 5-3. . .. • . -vibe author has found diat die most reliable and most easily duplicable mediod of #t^':i^i^ifcrining die "sieve analysis on a fine-grained soil is to take an oven-dry quantity of .*•;• ^material, brew it as fine as possible, then wash it on die #200 sieve (see Fig. 5-2).oven- -^ dry"i^ and sieve die rnridue through a stack of sieves. This ensures that little dust will - -: adhere to the larger partides and dtat all die reducible lumps are water-softened so they" rbe reduced to elemental soil particles. This method is used to obtain curve A (data not shown), which is displayed in Fig. 5-4. ' '•.' 3S *%i!Jf^^^ !x .'^iiiuL • ' - •" .-'^Ntf.--^' ".*-•*>/': /""-': - <Vja^5"*?*':*'''-V '. • "' -r- ' *' COUJ CD COBSUS S84VEL tears* • Fine SAND Coarse) Hed i urn Fine SILT and CUY Mesh Oosning - Ins Sieve Sizes Hydrometer Analysis too 90 70 £ 6U ^ t- 4)sUJ aeu* °" HO in 0 76 3 I 1 1 t T » 1 2 1 }" 5 £ * 1$ 16 20 30 40 60 80 fHQJ200] FT IT 11 li UJ«gL~Vi i ' 1 1 — I ft-iJr " ' r T . . — , i t 1 1 I i 1 i (r r Jr i; i tii ii Ji i > 1 r ; 1 ' ' 1 1 J | [ 1 _ }. t J t \ i 1 i t J tt~ t i i ' 1 1 ! 1 t . • i t 1 1 1 i i i i f J i - .-*•I > i - - t ' t t _L L,V, 'VttlV nr T Jr-rJi\1 VV \ iH'\( A ^t 1\i\ iu\^ en '*7^i i\ r '\ri p, iP\i ,* , i i r ri-i- 1" r1 J «Ii!J I fVr»\'x\i i\> i *l\ !.• \\o : oL ^^Vi \ *+ 1 _j i , 1 [ 1 i i \— Jk,,. i t i i VL •« I ' ' S^ ) ^1 tI I \-* ;'W-<^ >,(_t. '^*-~«J^>*» ^ 'j*^ ~~ • «^r)~^~— A**^_ >'** • *** " n~ _. — •_ • '*^»«*— W^ '*^ iin^. ^t i ^ ii - i — a^ a 10 20 30 TO SO 60 70 80 .90 ? 1 — JlflQ 100 50 10.0 5.0 1.0 O.I 0.05 GRAIN SIZE IN MILLIMETERS 0.01 O.OOS 0.001 SAMPLE 0 12-1 O 13-1 C 20-1 A 22-2. CUSSifl CATION AND SYMBOL Siltv sand (SM) Silty sand (SM) Silty sand (SM) S.iltv sand (SM) * •LL Ncn —__ — 'PI Plastic —__ „ *LL - Liquid Limit *P1 - Plasticity Index GRAIN SIZE DISTRIBUTION CURVES BATIQUITOS LAGOON EDUCATTOHAL P?JtK DRAWN BY: ,-v, I CHECKED BY:PROJECT NO: --S1 33J-SIO1 | FIGURE NO; g.^* WOODWARD-CLYDE CONSULTANTS RUNOFF COEFFICIENTS (RATIONAL METHOD) LAND USE Coefficient. C Soil Group (1) A B C D Undeveloped .50 .35 .40 .45 Residential: Rural .50 .55 .40 .-3 Single Family .40 .45 .50 .55 Multi-Units ' .45 .50 .60 .70 Mobile Homes (2) .45 .50 .55 .65 Commercial (2) .70 .75 .80 .35 80% Impervious Industrial (2) .80 .85 .90 .95 90% Inroervious NOTES: (1) Obtain soil group from maps on file with the Department of Sanitation • and Flood Control. (2) Where actual conditions deviate significantly from the tabulated imperviousness values of 30% or 90%, the values given for coefficient C, may be revised by multiplying 80% or 90% by the ratio of actual inperviousness to the tabulated imperviousness. However, in no cass shall the final coefficient be less than 0.50. For example: Consider commercial property on D soil group. Actual imperviousness = 50% Tabulated imperviousness = 80% Revised C » 12. X 0.85 = 0.55 APPENDIX IX oao -4 control practical than construction in areas with low It value*. If a more precis*.' vafae.foT S. is needed, other references (10,20,21) that explain how to calculate''. £ far individual storms and years from local data should bt "i»miltfd1 .; : An "Jsoerodenfmap, prepared by Wischmeier for theUSDA (20) and shown in Fif. JL2, is wed to find tile R value for sites east of the Rocky Mountain* (approximately 104* west longitude). R can b« interpolated for points between the Dae*. Contact local sofl conservation service offices for more detailed infor- mation on R values in areas covered by this map West of the 104th west merid- ian, irrefular topography makes use of a generalized map impractical For the western states, R is calculated by using rainfall data. Results of investigations at •ti- Ertanatmf SoilLot» 30 10 VlS. 8-4 Time distribution data provided by Wendell £ Service, Wett Technical Ser i Type II. Fi$. &3 Distribution of norm types in the western United States. (4) Type n storms occur in Arizona. Colorado, Idaho. M«"U"if, Nevada, New Mexico. Utah, tt>A Wyomingalso. the Runoff and Soil Loss I in the western states coul 2-year, S-hr rainfall data ^pes(I,IA,andn)areu ntion of type I, IA, and E A storm type is distir: Figure 5.4 illustrates the storm*. A type E storm is by a strong peak in rainf: H storms occur in the foi • The eastern parts of V Nevada) • All of Idaho, Montana. Type I and IA storm; that occur in southern <- definite peak ytttflgr to characteristic of storms ington, and the westerr. the rainfall distribution • •>/ •'' . '.'••? .',BEST COUNTY OF SAM DIEGO . DEPARTMENT OF SANITATION I FLOOD CONTROL • • •. •.,"!•?: i. tsEv.v'ayt:•:,.-, 2-YEAR G^OURl PRECIPITATION ^-lO-ISOPLUViALSVOF 2-YEAR G-liOUR PRECIPITATION IN TENTHS OF .AM INCH 33* > Pff fmn4 by U.S. DEPARTMENT OP COMMERCE NATIONAL OCEANIC AND ATMOSPMIRIC ADMINISTRATION IPCCIAL STUDICI BRANCH. OrFICC Of IIVOROLOOV. NAUONAL VCATIIBK SKKVICS i— 1—30.' HO*30 •15 6.14 Erosion and Sediment Control Handbook Solution: for type !A storm area, K - lO.Zp" - 28.7 It. - 1.6(27.8 in) - HA [0.050(701 mm) - 4M| ff, - K. -I H - 28.7 + 41.4 - 70.1 5.2c Soil ErodiliUily Factor K The soil eroitiliility factor K is a measure of (ha susceptibility of soil particles to detachment am) transport by rainfall and rumtlf. Texture is the principal factor affecting K, but structure, organic matter, and permeability also contribute, K value* tange from 0.02 to 0.69. Several methods can be uaeii to estimate a K value for a lite, but • nomograph method using analyses of site soils is tlte most reliable, tf a recent aoil survey for the area lias been published and minimal soil disturbance is anticipated, the K value listed in the survey of the soil series found on the site can be used. ' Nomograph Method " The preferred method for determining K values io the nomograph method. Use of the nomograph requires a particle size analysis to determine the percentages of sand, very Tine sand, silt, and clay. The size tango for each class is listed in Table 6.1. ASTM D-422 (1) is a standard hydrometer analysis for particle size distribution. (Specific parlicla sfeos can ho dasiuuated in I to request for annlyals. More lyjiicully, values are reported for specified stz4 interval*, such a* every 6 or 10 pm. The fee for a particle size analysis is normally only a small fraction of tin total fee for a geotechnical report.) The determination of the K value should be based on the soil exposed during the critical rainfall months. Subsoils exposed during grading will have If values different from the topsoil K value. On large sites, several samples should be token and analyzed separately Io ensure that differences In soil texture are detected. If fill ia imported, this material also should be characterized. The more carefully the site soils are characterized, the more accurate the K values will be. If analysis indicates significant variation in soil credibility, It might be advisable to use different K values for different part* of the site and to focus erosion control efforts on the most susceptible areas. A simpler and more conservative approach is to use the highest value obtained by analysis for all parts of the site, since it may not be possible to know exactly what soil* will be •xpoied or how vailed the molU ar». A nomograph developed by Erickaon of the SCS-Utah office (6), based on the original nomograph provided by Wlschmeier (21), is reproduced in Fig. 6.8. To use the nomograph, enter the triangle with any two of the particle size percent.: total sand and silt; silt and clay; or clay and total sand. Use whoU numbers. Follow (he dashed straight lines to their point of intersection. From that point, follow parallel to the doited curves to the right side of the triangle, where the K values are listed, L . Estimating Soil Lou 5.16 \3 (Example 5-4) Fif. 6.0 Triangular nomofr«ph Tor eitlmiilnf K vain*. (8) 8e» T.lila 6.3 for •cljujt- ments to K value under ctrUin conditions. EXAMPLE 5.4 Qlvon: A soil with tlte following nattiv.U tlx* mttrihution. Cum|xii >>nt Ssnd Vtry fins s«nd Silt CUy Sits, mm 2.D-0.1 0.1-0.06 0.05-0.002 !.*•• than 0.002 Fraction, % 30 10 20 40 Find: Texture and K value. Solution: Entering I'if. 6.1 with 10 percent total sand sml 20 percent silt, tins leilur* Is found to its on tliu border between cluy ami clay luum. |£nt«ring Pig. 6.0 wllli Ilie nuitiu percent! (see bold Untt), His K value Is foumt to be 0.19. Tabls 6.3 descrities adjustment* to the K factor. Adjustment 1 |« a correction (or very l~ v 1 1 1 i - r ORIGINAL B.22 Erosion and Sediment Control Handbook Estimating Soil Loss 5.23 Length Slope I.S Factor incrcoia 100 ft (30.S m) 3:1 0 13 1 10(1 ft (30,6 m) 2:1 17.32 1.9 tOO ft (30.6 m) 1.6:t 2a.os 2.8 TADLB B.6 (7 Values for Sail Ixws Equation* The effect of length I* not at great as the effeot of alope angle: LS increases 30 to 60 percent for each doubling of lunglh. For trample, on a 2:1 slope, 1,8 doubles when /- is quadrupled: Slop* Length I.S Factor Increase 2:1 30 ft (0.1 m) 9.76 1 2:1 GO ft (18.3 m) 13.81 1.4 2:1 120 ft (36.0 ro) 19.42 2 Thus, very long slopes and especially, long, sleep slopes, should not be con- structed. Those that already exist should not be disturbed. Slope length can be shortened by installing midslope diversions. Local build- ing codes often require terraces or drainage ditches at specified Intervals. Chap- ter 70 of the Uniform Building Code specifies a 30-ft (9.1-m) interval. (9) Several .erosion control manuals recommend IB-ft (4.6-m) intervals between terraces. (2, 18). Because these Intervals are defined as vertical risa, tho slope length would be somewhat longer. Decreasing steepness will require use of more land and so must be incorpo- rated early in the project design. To ensure slope stability, a maximum gradient is frequently recommended by (he soils engineer. 5.2e Cover Factor C The cover factor C is defined as the ratio of soil loss from land under specified crop or mulch conditions to the corresponding loss from tilled, bare soil. The C is iio( the same as the runoff coefficient C used in the rational method. In tlio USI<1£, the C factor reduces the soil loss osl imote according to the effec- tiveness of vegetation and mulch at preventing detachment and transport of soil particles. On construction sites, recommended control practices include the seed- ing of grasses and the use of mulches. These measures are often considered "tem- porary"—they are designed to control erosion primarily during the construction period. Permanent landscaping may be added leler, or temporary erosion control plants may be left as a permanent cover. Any product that reduces the amount of soil exposed la raindrop impact will reduce erosion. Table 6.6 lists C factors for various ground covers. The C values for vegetation were obtained from USDA publications (14, 20); those for mulch were obtained from Burgess Kay at the University of California, Davis, who tested .Materials on experimental plots under a rainfall simulator. (II) When the soil surface Is bare, C is 1.0. At Ilia other end of the scale, undis- turbed native vegetation is assigned a value of 0.01; hence the advantage of retaining as much existing vegetation as possible is clear. A C value of 0.1 is used Type of cover Nona Native vegatstltn Jjndiitorbeil) Temporary seeding*: 90% cover, >nmial grasses, nn mulch Wood fiber mulch, X lon/acm f.1.7 I/ha), wlili uedt Excelsior met, jutet Straw mulcht 1.6 tolWucre (3.4 t/ha), tacked down 4 torn/acre (8.0 i/hi), tacked down C factor 1.0 0.01 O.I 06 0.3 02 0.05 Soil li>»» rctliiclinn, Vi fl 09 90 fill 7(1 80 85 | . . 'Ad.pt.d ham IMi. 11, 16. .ml JO tPerilopwupIoz:!. if a complete cover of newly Boeiletl animal grassesIs well established before tho onset of rains. In many area*, eeed and wood fiber mulch are applied hydraulicully thorlly before the rainy season, 'rim early rains cause the seeds to germinate, liul a com- plete grass cover is not established until at least 4 weeks later. During the ger- mination and eerly growth period, the wood fiber mulch provides only marginal protection. A C value of 0.5 is an appropriate overage representing little protec- tion initially anil more thorough protection when the grass is well eatulilishuil. On bare soils mulch can provide immediate reduction in soil loss, and it per- forms better thim temporary seed ings in some cases. Straw mulch is more effec- tive than wood liber mulch; It reduces loss about 80 percent (C value, 0.2) when it Is applied st -lie rate of 3000 Ib/acre (3.4 t/ha) and tacked down. Additional . reduction is ebtjjned with 8000 Ib/acre (90 1/lia) of straw, but Ms rate may not be cost-effective. Wood fiber mulch alone (without seed) provides very little soil loss reduction; it primarily holjij seeds to liccomo established so thai the now grim can provide the erosion control. Other products, such as jute, eicolsior, and pupcr mulling, provide an intermediate love) of protection; the C value equal* approximately 0.3. Test results of various mulch treatments are presented in Chop, ft. 5.2f Erosion Control Practice Factor P The erosion control practice factor r is defined as the ratio of soil loss with u given surface condition to soil loss with up-and-down-bill plowing. Practices that reduce Uio velocity of runolf and the tendency of runolf to (low directly down- slope reduce OIK P factor. In agricultural uses of the USLE. P is used to describe plowing and tillage practices. In construction site applications, P reflects the roughening of the soil surface by tractor treads or by rough grading, ruking, or disking. ^t?$$& i*ii Estimating Soil Loss 0.19 for th« ioit series In * table of phyilcal and chemical properties. A portion of ont of these table* It reproduced M Table 5.4. This method of finding 1C ihould be used only if minimal toll disturbance It anticipated and • titt analysis of aoiltis not available. B.2d Length-Slope Factor LS , ; The »lop« length-gradient factor LS describe* the combined effect of flop* length and elope gradient. It I* the ratio of toll IOM per unit area on a alt* to the cor- responding loat from a 72.6-ft- (22.1-m-) long experimental plot with • 9 percent elope. Table 6.5 lists values of the LS factor for slopes 0.6 to 100 percent and lengths 10 to 1000 ft (3 to 305 m). The valuet are derived from Wiichmeiir't empirical equation (21), which it shown In the table. braabon (10) hat verified the LS values for steep slopes by tiling a rainfoll simulator i Determining LS Since the LS factor hat a considerable effect on predicted erosion (eicept for K, it Is the only factor substantially greater than 1), care in figuring values for the factor I* warranted. In particular, results of the toil (oat calculation will be more accurate If the U8LE It Individually applied to portions of a site with similar tlopet (similar gradient and length) and tumrnlng tin Individual toll lot! Mil- mates. Do not average slope steepness and length for an entire site, If an estimate for complex slopes if desired, ut« ih« method described by Potter and Wischmeier (8) or Fsraelson. (10) Slope gradient can be expressed In either percent or at a ratio of horizontal to vertical height. Table 5.4 lists elope gradlenta both ways. Slope length Is the distance of overland flow to the nearest diversion or chan- nel. For a long slope with several inidslope diversion*, lie* the slope length equal to the distance from the top of the slope to the first bench or the distance between benches, whichever i* greater. To use Table 6.6, start with elope gra- dient and then move across the row to the right until you reach the-column for the appropriate slope length. For example, a 10 percent (lop* that la 100 ft (30.0 m) long has an LS value of 1.37. Diteuaflon ofLS • , ' Slop* gradient and slop* length strongly influence the transport of toil particle* once the particles are dislodged by raindrop impact or by runoff. In flat areas, runoff Is slow and soil particles are not moved far from tb« point of raindrop impact. Thus, LS It small—less than 1.00 for slopes lest than 8 percent with '•ngtfia (ess than 70 ft (21 m). On steep slopes, soil movement increases dramat- , IcaJly, For example, on a 100-ft- (30.6-m-) long elope, doubling the gradient from 3:1 to 1.6:1 triples the LS factor (i.e., triples the soil Iocs): ' ' ' ' I . ' B.aa Erosion and Sediment Control Handbook Length Slop* LS Factor Increase lOti ft (30.6 m) 3:1 IMS 1 100 ft (30.6 m) 2:1 17.82 JOO ft (30.8m) 1.5:1 26.68 2.8 j The effect of length It not at great M the effect of elope angle: LS increase* 30 J to 60 percent for etch doubling of length. For example, on • 2:1 slope, LS doublet ' when//It quadrupled: T' Stop*Length LS Factor Increase til SO ft (9.1 n) t.7,6 1 2:1 60 ft (18.3 ut 13.81 1.4 2tl 120 ft (36.6 ml 19.42 2 Thua. very long slope* and especially, long, steep slopes, should not be con- structed. Those that already exist ihould not be disturbed. Slop* length can b* shortened by Installing mldtlop* dlvtrsiont. Local build- Jug code* often require isnarua or drainage ditches at specified Interval*. Chap. ter 70 of tba Uniform Building Cods specifies a 30-ft (9.1-m) Interval (9) Several 'erosion control manuals recommend 16-ft (4.8-ro) Intervals between terraces. (2, 18). Because these interval* or* defined as vertical rite, the slope length would 'be somewhst longer. Decreasing steepness will require use of more land and so must be Incorpo- rated early In the project design. To ensure slope stability, a maximum gradient I* frequently recommended by the toll* engineer. 6.2e Cover Factor C The cover factor C I* defined aa the ratio of toll loss from land under specified crop or mulch condition* to the corresponding losa from tilled, bar* soil. The C is not the same a* the runoff coefficient C used in the rational method. In the USLE, the C factor reduce* the soil lose estimate according to the effec- tiveness of vegetation end mulch at preventing detachment and transport of toil particle*. On construction *U<«, recommended control practices Include the seed- ing of grasies and the use of mulches. These measure* are often considered "tem- . porary"—they are designed to control erosion primarily during the construction period. Permanent landscaping may be added later, or temporary eroelon control planta may b* left a* a permanent cover. Any product that reduce* the amount of toil exposed to raindrop Impact will reduce erosion. Table 6.6 list* C factor* > for variou* ground cover*. Trw C value* for vegetation were obtained from USDA publication* (14, 20); lhot» for mulch were obtained from Burgess Kay at the University of California, Davis, who tested material* on experimental plot* under a rainfall simulator. (1!) When the soil lurfac* li> tare. C I* 1.0. At the other end of the scale, undis- turbed native vegetation I* tsslgned a value of 0.01; hence the advantage of retaining aa much existing vegetation as possible Is clear. A C value of 0.1 i* ussd . 00m o EX/MBIT vv 133NS 33S 3NITO1VH 00-05+91 'VIS