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Home My WebLink AboutCT 97-13; CARLSBAD OAKS NORTH; TEMPORARY DESILTING BASIN CALCULATIONS;Temporary Desilting Basin Calculations Carlsbad Oaks North J.N. 961005/5 Prepared By: O'DA Y CONSULT ANTS, INC. 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92008 SECTION 1 2 3 4 5 DESILTING BASIN CALCULATIONS DESCRIPTION Surface Area Calculations Explanation Soil Loss Calculations Explanation Dewatering Calculation Explanation Basin Sizing, Soil Loss, & Outlet Works Calculation Spreadsheets Exhibits SECTION 1 Surface Area Calculations According to the Fact Sheet for Water Quality Order 99-08-D WQ issued by the State Water Resources Control Board (SWRCB), sediment basins shall, at a minimum, be designed and maintained as follows: Option 1: Pursuant to local ordinance for sediment basin design and maintenance, provided that the design efficiency is as protective or more protective of water quality than Option 3. OR Option 2: Sediment basin(s), as measured from the bottom of the basin to the principal outlet. shall have at least a capacity equivalent to 3,600 cubic feet of storage per acre draining into the sediment basin. The length of the basin shall be more than twice the width of the basin. The length is determined by measuring the distance between the inlet and the outlet; and the depth must not be less than three feet nor greater than five feet for safety reasons anq for maximum efficiency. OR Option 3: Sediment basin(s) shall be designed using the standard equation: As= l.2QNs Where: As is the minimum surface area for trapping soil particles of a certain size; Vs is the settling velocity of the design particle size chosen; and Q=CxlxA where Q is the discharge rate measured in cubic feet per second; C is the runoff coefficient; I is the precipitation intensity for the 10-year, 6-hour rain event and A is the area draining into the sediment basin in acres. The design particle size shall be the smallest soil grain size determined by wet sieve analysis, or the fine silt sized (0.01 mm) particle, and the Vs used shall be 100 percent of the calculated settling velocity. The length is determined by measuring the distance between the inlet and the outlet; the length shall be more than twice the dimension as the width; the depth shall not be less than three feet nor greater than five feet for safety reasons and for maximum efficiency (two feet of storage, two feet of capacity). The basin(s) shall be located on the site where it can be maintained on a year- round basis and shall be maintained on a schedule to retain the two feet of capacity; OR Option 4: The use of an equivalent surface area design or equation, provided that the design efficiency is as protective or more protective of water quality than Option 3. Sediment basins for Carlsbad Oaks were designed to satisfy the requirements of Option L using the following parameters: Appendix 11-A-4 of the San Diego County Hydrology Manual gives the precipitation for a 10-year, 6-hour storm as 1.9 inches for this project. (See Exhibit "N') P = 1.9 inches/6 hours I = 0.32 avg. inches/hour (per Goldman et al., p. 8.16) Appendix IX of the San Diego County Hydrology Manual gives the runoff coefficients for this project as C=0.35 to C=0.45. (See Exhibit "B") Table 8.1 of the Erosion and Sediment Control Handbook (See Exhibit "C") gives the settling velocity for a 0.01 mm sized particle as Vs= 0.00024 feet/second. The San Diego County Soils Interpretation Study gives the soil classification for this project as "B", "C", and "D". (See Exhibit "D") FOR BASIN CALCULATION SUMMARY SPREADSHEET SEE SECTION 4 ( SECTION2 SOIL LOSS CALCULATIONS CHAPTER 5 OF THE EROSION AND SEDIMENT CONTROL HANDBOOK DISCUSSES CALCULATING SOIL LOSS WITH THE UNIVERSAL SOIL LOSS EQUATION IJ.2& Tile EquaUoa n.,-.1r-o1t11elUUftlNINillaa..--11: A•RXKXLSXCXP when A • loi1 lou, tona/(aa-.) (yNr) RAINFALL INDEX '"R" R • ralnJ'LII eroaloa 1.ncla., la 100 ft • t.ona/llCl'I X la/hr K • IOI trodiblUtj factor, V>U/eue pw unit o1 R La • .i.,. -ct.II• ~ fact«, dlmen■lon,_ CL r111bdft-,..__,.., dcdw P • .... ooatnl pniatlee r.cw, r!h •• fr:- RAINFALL EROSION INDEX ''R" IS BASED ON THE GEOGRAPHICAL 0TypelA Im Typej al Type 11 Fis. 5.3 Diitribution of atorrn type. in the .11ttt.m Unii.d Stata (4) 'Type Il stoma occur ill Ari&OGa, Colorado, ldaho, Moatana, Nevad,t. N-Mexico, Utu, and Wyominc ~- IU2 100 600 ·-··-----------+---+---+---+ i 500 --t· · I i 400 --·-+-· j: ~-t= 100 ·-+·-. ----··--1-·- 25 50 75 ,______ 10~ The differences in peak Intensity are reflected ID the codllclents ol the equa- tiona for the ralnlaU fanor. Fisur• U Is a 1raphbl repreeentation ol the equa- tlom. The eq11.1tlona, -1,o shown on the curv• for each mdivldual storm type, are: R • ?:rp11 type II R • 16.55.P" type I R • 10.2pil type IA "P" FOR THIS EQUATION IS THE PRECIPITATION FOR A 2-YEAR, 6-HOUR STORM EVENT. APPENDIX II-A-2 FROM THE SAN DIEGO COUNTY HYDROLOGY MANUAL GIVES P = 1.4 (SEE EXHIBIT "E") R = l 6.55*P/\2.2 = 16.55*1.4/\2.2 = 34.7 SOIL FACTOR "K" FROM THE SOILS REPORT, THE SITE CONSISTS OF 50% SAND AND 50% CLAY (t AND SILT. ASSUMING HALF OF THE 50% IS CLAY, THE OTHER HALF SILT K = 0.24 (SEE TABLE BELOW) PSRCBNT CLAY IOI (( LENGTH SLOPE AND STEEPNESS FACTOR "LS" SLOPE LENGTH AND STEEPNESS FACTOR "LS" IS CALCULATED USING TABLE 5.5 OF THE EROSION AN SEDIMENT CONTROL HANDBOOK, (SEE EXHIBIT "F") FOR BASIN CALCULATION SUMMARY SEE SECTION 4 VEGETATION COVER FACTOR "C" THE COVER FACTOR TABLE LISTED BELOW IS USED FOR AREA UNDER CONSTRUCTION OR CULTIVATION. TO BE CONSERVATIVE THE HIGHEST VALUE IS ASSUMED. C=l.O TA■LII U C v.,.. e. a.At--...11ae• If-. ~ ,,.....u-C-,U.turt.i) T-11 •,....U.,.. ••-.-uaa...-ao...&ldl W ... lbw -..W.." "-/_,. (l.'J t/11&), wit.la ....tt ------.Jutet S-..... t 1.a-i-,a., tJlla). t.Mlra4 ...... ''-'-(9.0 t/1,a), ~ ..... -~-...._, .. , ...... ,,.. .......... ,,,. EROSION CONTROL PRACTICE FACTOR "P,, s..a .... c .... ,..._._,. u • Ul .. cu .. u Ill cu ,. u IO oa • THE P VALUES LISTED BELOW ARE GIVEN FOR AREAS UNDER CONSTRUCTION OR CULTIVATION. TO BE CONSERVATIVE, THE HIGHEST VALUE WAS ASSUMED. P= 1.3 Sud-ooad.ldaa ~ and IIJDOOUl Tnckw.lbd aJoac coat.our• ~ up ud down ll<>pet PundMdauaw ~uncuJa,cut LooM lo 12-ID (3Ckm) d.pU. u l.S u o..t u a.a SECTION 5.31, PAGES 5.27 TO 5.28 LISTS A STEP BY STEP PROCEDURE FOR USING THE UNIVERSAL SOIL LOSS EQUATION (SEE EXHIBIT "G") FOR SOIL LOSS CALCULATION SUMMARY SPREADSHEET SEE SECTION 4 SECTION3 j_ ------11: -·-----------------·---------·---.. . ---~---~-----·----------~~ CO:Oot.t,') =-.-tt..~---------····· ... ·- .... -·-·. -· -~t--·-· ··-··--------------·-· ·--~----___________ -2(_ 11+'-f: -------···--· ---------· -· ... -· . _ ·--· .... J.--·----------·-----------~--/4.~.(o OlA'.:J5~74J ___ ==-____ ,N 2 __________________ _ ; ~ • ·-----·---------·-··---------------------... -rr-... ----· ---- ... r.. . --..... ·--. -. ., .•...••....... -·-··--·. ··---·•---·-··· --·--·-·---- w LPv 0 E9C-FN<.. '-t _:_._-4J.-------------t--------------------- ------------·--------------------- --------·---··----------------------·------.--------------- ' ----------4-•" ....... ----··--... ---. -----··------···· ------·------···- SECTION 4 ( ,asin A -Lot 20 Oesiltation Basin Calculations Oavg = C X iavg X A C= 0.45 iavg = P6/6 hr. Pa= 1.9 in. (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in./hr Pad A= 1.89 ac. Slope A= 0.28 ac. Total A= 2.17 ac. Oavg = 0.308979 cfs Vs= 0.00024 ft/sec min. As = actual As= 1545 sf 2619 sf ~oil Loss Calculations A = R X K X LS X C X p R =16.55(p)2-2 p = 1.4 R = 34.70 in . (per 2yr.-6 hr. lsopluvial) Standpipe Calculations Q=CxlxA Tc= 5 min. (see Desilting Basin Tributary Area Exhibit) I = 7.64 in./hr. Q = 7.2 cfs h= ft. Case 1 Case 2 Q = CPh312 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 2.40074 ft A= 1.34 ft2 d= 0.76 ft d= 1.31 ft 24" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use % Area Length** Slope/ Grade Slope 13.1% 45 2:1 Pad 86.9% 300 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS= 1.81 A= 15.07 tn/yr/ac -oil Loss = 32.7 tn/yr = 594 ,cf LS*** 12 0.28 Basin Dewaterinq Calculations Ao = As(2H) 112 3600(T)Cct(g) 112 H= 2 ft T= 40 hr Cd= 0.6 g= 32.2 ft/sec Ao = 0.010684 ft" = 1.54 in2 'lasin B -Lot 21 Desiltation Basin Calculations Oavg = C X iavg X A C = 0.45 iavg = P6/6 hr. Pe= 1.9 in . (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in./hr Pad A = 3.11 ac. Slope A= 0.77 ac. Total A= 3.88 ac. Oav9 = 0.552695 cfs Vs = 0.00024 ft/sec min. As = 2763 sf actual As= 4075 sf Soil Loss Calculations . = R X K X LS X C X p R =16.55(p)22 p = 1.4 R = 34.70 in. (per 2yr.-6 hr. lsopluvial) Standpipe Calculations Q=CxlxA Tc= 5 min. (see Desilting Basin Tributary Area Exhibit) I = 7 .64 in./hr. Q = 14.8 cfs h= ft. Case 1 Case 2 Q = CPh312 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 4.939174 ft A= 2.75 ft2 d= 1.57 ft d= 1.87 ft 24" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use %Area Length** Slope/ Grade Slope 19.9% 40 1.5: 1 Pad 80.1% 350 2% .. ** = See Des1ltmg Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS= 3.60 A= 29.95 tn/yr/ac Soil Loss= 116.2 tn/yr = 2112 ,cf LS*** 16.88 0.29 Basin Oewatering Calculations H= T= Cd= g= As(2H)112 3600(T)Cd(g) 112 2 ft 40 hr 0.6 32.2 ft/sec Ao= 0.016623 ft" = 2.39 in2 "1asin C -Fill Area Lot 22 Oesiltation Basin Calculations Standpipe Calculations Oavg = C X iavg X A Q=CxlxA C= 0.45 Tc= 5 min. (see Desilting Basin Tributary Area Exhibit) iavg = P6/6 hr. I = 7 .64 in./hr. P5 = 1.9 in. (per 10 yr.-6 hr. lsopluvial) Q = 15.1 cfs iavg = 0.32 in./hr h = 1 ft. Pad A= 3.14 ac. Slope A= 0.81 ac. Case 1 Case 2 Total A= 3.94 ac. Q = CPh312 Q = CA(2gh) 112 Oavg = 0.561691 cfs C= 3.0 C= 0.67 P= 5.019569 ft A= 2.80 ft2 d= 1.60 ft d= 1.89 ft Vs = 0.00024 ft/sec 24" pipe min. As = 2808 sf actual As = 4459 sf Soil Loss Calculations ..... = R X K X LS X C X p R =16.55(p)22 p = 1.4 in . (per 2yr.-6 hr. lsopluvial) R = 34 .70 K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use %Area Length** Slope/ Grade Slope 20.4% 50 1.5: 1 Pad 79.6% 430 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS= 4.10 A = 34.18 tn/yr/ac Soil Loss= 134.7 tn/yr = 2449 cf LS*** 18.87 0.31 Basin Oewatering Calculations H= T= Cd = g= As(2H)112 3600(T)Cd(g) 112 2 40 0.6 32.2 ft hr Ao: 0.018190 ftL = 2.62 in2 'lasin D-Lot 23 Oesiltation Basin Calculations Oavg = C X iavg X A C= 0.45 iavg = Psf6 hr. Ps = 1.9 in. (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in ./hr Pad A= 3.81 ac. Slope A= 0.30 ac. Total A= 4.11 ac. Oavg =· 0.585675 cfs Vs= 0.00024 ft/sec min. As= actual As= 2928 sf 2930 sf Soil Loss Calculations . = R X K X LS X C X p R =16.55(p)2 2 p = 1.4 R = 34.70 in. (per 2yr.-6 hr. lsopluvial) Standpipe Calculations Q=CxlxA Tc = 5 min. (see Desilting Basin Tributary Area Exhibit) I = 7 .64 in./hr. Q = 15.7 cfs h= ft. Case 1 Case 2 Q = CPh312 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 5.233905 ft A= 2.92 ft2 d= 1.67 ft d= 1.93 ft 24" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use % Area Length** Slope/ Grade Slope 7.3% 55 2:1 Pad 92.7% 300 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg . LS = 1.22 A = 10.19 tn/yr/ac Soil Loss = 41. 9 tn/yr = 762 cf LS*** 13.21 0.28 Basin Dewaterinq Calculations H= T= Cd= g= As(2H)112 3600(T)Cig) 112 2 ft 40 hr 0.6 32.2 ft/sec A0 = 0.011952 ft' = 1.72 in2 { "1asin E -Lot 24 (WEST) Desiltation Basin Calculations Oavg = C X iavg X A C= 0.45 iavg = P6/6 hr. Ps = 1.9 in . (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in./hr Pad A= 2.00 ac. Slope A= 0.00 ac. Total A= 2.00 ac. Oavg = 0.285 cfs Vs = 0.00024 ft/sec min. As= actual As= 1425 sf 2355 sf Soil Loss Calculations . ' = R X K X LS X C X p R =16.55(p)2-2 p = 1.4 R = 34.70 in. (per 2yr.-6 hr. lsopluvial) Standpipe Calculations Q=CxlxA Tc= 5 min. (see Desilting Basin Tributary Area Exhibit) I = 7 .64 in./hr. Q = 7.6 cfs h= ft. Case 1 Case 2 Q = CPh 312 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 2.546913 ft A= 1.42 ft2 d= 0.81 ft d= 1.35 ft 18" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use %Area Length** Slope/ Grade Slope 0.0% 0 2:1 Pad 100.0% 230 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS = 0.26 A = 2.17 tn/yr/ac Soil Loss= = 4.3 79 . tn/yr cf LS*** 0 0.26 Basin Dewatering Calculations As(2H)112 3600(T)Cd(g) 112 H= 2 ft T= 40 hr Cd= 0.6 g= 32 .2 ft/sec A0 = 0.009607 ftL = 1.38 in2 ( ~asin F -Lot 24 (NORTH) Desiltation Basin Calculations Oavg = C X iavg X A C= 0.45 iavg = P6/6 hr. P5 = 1.9 in . (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in./hr Pad A= 5.83 ac. Slope A= 0.00 ac. Total A= 5.83 ac. Oav9 = 0.830775 cfs As = 1.2QNs Vs = 0.00024 ft/sec min. As= 4154 sf actual As= 4655 sf Soil Loss Calculations .. = R X K X LS X C X p R =16.55(p)2-2 p = 1.4 in. (per 2yr.-6 hr. lsopluvial) R = 34 .70 Standpipe Calculations Q=CxlxA Tc= 7.4 min. (see Oesilting Basin Tributary Area Exhibit) I = 5.93 in./hr. Q = 17.3 cfs h = 1 ft. Case 1 Case 2 Q = CPh3I2 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 5.765458 ft A= 3.21 ft2 d= 1.84 ft d= 2.02 ft 24" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use %Area Length** Slope/ Grade Slope 0.0% 0 2:1 Pad 100.0% 730 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS = 0.36 A= 3.00 tn/yr/ac SoilLoss= 17.5 tn/yr = 318 cf LS*** 0 0.36 Basin Dewatering Calculations As(2H)112 3600(T)Cd(g) 112 H= 2 ft T= 40 hr Cd= 0.6 g= 32.2 ft/sec Ac,= 0.018989 ft" = 2.73 in2 ~asin G -Lot 24 (SOUTH) Oesiltation Basin Calculations Oavg = C X iavg X A C= 0.45 iavg = Ps/6 hr. Ps = 1.9 in. (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in./hr Pad A= 12.44 ac. Slope A= 0.00 ac. Total A= 12.44 ac. Oavg = 1. 7727 cfs As= 1.2QNs Vs= 0.00024 ft/sec min. As = actual As= 8864 sf 9080 sf Soil Loss Calculations , \ = R X K X LS X C X p R =16.55(p)22 p = 1.4 in. (per 2yr.-6 hr. lsopluvial) R = 34.70 Standpipe Calculations Q=CxlxA Tc = 10 min. (see Desilting Basin Tributary Area Exhibit) I = 4.89 in./hr. Q = 30.4 cfs h= ft. Case 1 Case 2 Q = CPh312 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 10.13071 ft A= 5.65 ft2 d= 3.23 ft d= 2.68 ft 42" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use % Area Length** Slope/ Grade Slope 0.0% 0 2:1 Pad 100.0% 1350 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS = 0.43 A= 3.58 tn/yr/ac Soil Loss = 44.5 tn/yr = 810 cf LS*** 0 0.43 Basin Dewatering Calculations As(2H)112 3600(T)Cig) 112 H= 2 ft T= 40 hr Cd= 0.6 g= 32.2 ft/sec A0 = 0.037040 ftL = 5.33 in2 ..,_asin H -Lot 25 Desiltation Basin Calculations Oavg = C X iavg X A C= 0.45 iavg = P6/6 hr. Ps = 1.9 in . (per 10 yr.-6 hr. lsopluvial) iavg = 0.32 in./hr Pad A= 6.41 ac. Slope A= 1.37 ac. Total A= 7.78 ac. Oavg = 1. 10865 cfs Vs= 0.00024 ft/sec min. As = actual As= 5543 sf 5655 sf Soil Loss Calculations .. = R X K X LS X C X p R =16.55(p)22 p = 1.4 R = 34.70 in . (per 2yr.-6 hr. lsopluvial) Standpipe Calculations Q=CxlxA Tc= 5 min. (see Desilting Basin Tributary Area Exhibit) I = 7.64 in./hr. Q = 29.7 cfs h= ft. Case 1 Case 2 Q = CPh312 Q = CA(2gh) 112 C= 3.0 C= 0.67 P= 9.90749 ft A= 5.52 ft2 d= 3.16 ft d= 2.65 ft 36" pipe K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use %Area Length** Slope/ Grade Slope 17.6% 85 2:1 Pad 82.4% 550 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS= 3.17 A = 26.42 tn/yr/ac Soil Loss = 205.6 tn/yr = 3738 cf LS*** 16.43 0.34 Basin Dewaterinq Calculations As(2H) 112 3600(T)Cig) 112 H= 2 ft T= 40 hr Cd= 0.6 g= 32.2 ft/sec Ao: 0.023069 ftL = 3.32 in2 • ~asin I -Lot 26 Oesiltation Basin Calculations Standpipe Calculations Oavg = C X iavg X A Q=CxlxA C= 0.45 Tc = 5 min . (see Desilting Basin Tributary Area Exhibit) iavg = P6/6 hr. I = 7.64 in./hr. Pe= 1.9 in. (per 10 yr.-6 hr. lsopluvial) Q = 15.5 cfs iavg = 0.32 in./hr h= ft. Pad A= 3.55 ac. Slope A= 0.52 ac. Case 1 Case 2 Total A= 4.07 ac. Q = CPh312 Q = CA(2gh) 112 Oavg = 0.579975 cfs C= 3.0 C= 0.67 P= 5.182967 ft A= 2.89 ft2 d= 1.65 ft d= 1.92 ft Vs= 0.00024 ft/sec 24" pipe min. As = 2900 sf actual As= 3655 sf Soil Loss Calculations . ' = R X K X LS X C X p R =16.55(p)22 p = 1.4 in . (per 2yr.-6 hr. lsopluvial) R = 34.70 K = 0.24 (CIE2, CmE2, & CnG2 soils -per Table 5-2) C = 1.0 (Bare areas -per Table 5-5) P= 1.0 (Packed & Smooth -per Table 5-6) Area Use %Area Length** Slope/ Grade Slope 12.8% 55 2:1 Pad 87.2% 440 2% ** = See Desilting Basin Tributary Area Exhibit *** = Per Figure 5-5 Avg. LS = 1.97 A= 16.38 tn/yr/ac Soil Loss= 66.7 tn/yr 1212 cf LS*** 13.21 0.32 Basin Dewatering Calculations H= T= Cd= g= As(2H) 112 3600(T)Cd(g) 112 2 ft 40 hr 0.6 32.2 ft/sec Ao= 0.014910 ft' = 2.15 in2 MODIFIED TYPE 'F' TYPE 'F' CATCH BASIN CAPACITY ( I I .... w w LL. z § X 0 al LL., 0 .... ::c C> w ::c t /<, ,12 II 10 9 8 1 6 5 4 3 •• ~(70; QI,'/, TiP t )Q.t/ .... 0 0 LL. 400 300 200 100 80 .6 .5 CHART I EXAMPLE 5'• 2' Bo• Q: 75 cfs 0/B : 15 eta/ft. HW HW Inlet o feet./ ( I) 1.75 3.5 (2) 1.90 3.B (3) 2.05 4.1 (2) (3) 30" to 75• 90• and ts• o• (extensions of sides) To use scole (2) or (3). project horizontally to scale (1), then use stroi9ht inclined lina through D and 0 scales, or reverse as Illustrated. ./ ( I ) (2) (3) /.: 8 9 1 8 6 7 6 5 5 4 4 3 3 2 2 1.5 1.5 1.0 1.0 .8 .9 .7 .8 .7 .6 .6 .5 .5 .4 .4 .30 .35 HEADWATER DEPTH FOR soxr curVERfs~ 1' ~ WITH i'N[: -;t·· ..... -~, \,) ..-, .... -· ;J"""C.Q.NT. KOL o ,·.,z_ 10 8 7 6 5 4 3 2 1.5 1.0 .9 .1 .6 .5 .4 .35 .:. OUTLET PIPES ( ( ( O'Day Consultants Inc . 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92008 Tel: (760) 931-7700 Fax: (760) Inside Diameter 24 .00 in.) * * * * * * * AAAAAAAAAAAAAAAAAAAAA * Water * * * * * * * * * * -- Circular Channel Section Flowrate ................. . 15.700 Velocity ................. . 12 .641 Pipe Diameter ............ . 24.000 Depth of Flow ............ . 10.020 Depth of Flow ............ . 0 .835 Critical Depth ........... . 1.430 Depth/Diameter (D/d) 0.418 Slope of Pipe ............ . 2.600 X-Sectional Area 1.242 Wetted Perimeter ......... . 2 .810 AR"(2/3) ................. . 0.721 Mannings 'n' ............. . 0.011 Min. Frie . Slope, 24 inch Pipe Flowing Full ..... . 0 .345 931-8680 Lo, -;:: 10.02 in.) 0.835 ft .) I I V -- CFS fps inches inches feet feet % sq . ft. feet % 23 O'Day Consultants Inc. 2710 Loker Avenue West, Suite Carlsbad, CA 92008 Tel: (760) 931-7700 Fax: (760) * * Inside Diameter 24.00 in.) * * * * * 100 931-8680 -AAAAAAAAAAAAAAAAAAAAA A * Water * * * * * * * * * * Circular Channel Section Flowrate ................. . 7.600 Velocity ................. . 7.331 Pipe Diameter ............ . 24 .000 Depth of Flow ............ . 8.758 Depth of Flow ............ . 0.730 Critical Depth ........... . 0.985 Depth/Diameter (D/d) 0.365 Slope of Pipe ............ . 1.000 X-Sectional Area 1.037 Wetted Perimeter ......... . 2.594 AR" (2/3) ................. . 0 .563 Mannings 'n' ............. . 0.011 Min. Frie. Slope, 24 inch Pipe Flowing Full ..... . 0.081 8.76 in .) 0.730 ft.) CFS fps I I V inches inches feet feet % sq. ft. feet % O'Day Consultants Inc. 2710 Loker Avenue West, Suite Carlsbad, CA 92008 Tel: (760) 931-7700 Fax: (760) Inside Diameter 18.00 in.) * * * * * * * * Water * * * * * * * * * * Circular Channel Section Flowrate ................. . 17.300 Velocity ................. . 11. 325 Pipe Diameter ............ . 18 .000 Depth of Flow ............ . 14.518 Depth of Flow ............ . 1.210 Critical Depth ........... . Greater than Depth/Diameter (D/d) 0.807 Slope of Pipe ............ . 2.000 X-Sectional Area 1.527 Wetted Perimeter ......... . 3.346 ARA (2/3) ................. . 0.905 Mannings 'n' ............. . 0.011 Min. Frie. Slope, 18 inch Pipe Flowing Full ..... . 1.941 100 931-8680 Lor :;:- 14.52 in.) 1.210 ft .) I I V CFS fps inches inches feet Pipe Diameter % sq . ft. feet % ( O'Day Consultants Inc . 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92008 Tel: (760) 931-7700 Fax: (760) 931-8680 * * Inside Diameter 24.00 in.) * * * * * -AAAAAAAAAAAAAAAAAAAAA A * Water * * * * * * * * * * Circular Channel Section Flowrate ................. . 30.400 Velocity ................. . 30 .902 Pipe Diameter ............ . 24 .000 Depth of Flow ............ . 8.424 Depth of Flow ............ . 0.702 Critical Depth ........... . 1.867 Depth/Diameter (D/d) 0.351 Slope of Pipe ............ . 18 .500 X-Sectional Area ......... . 0.984 Wetted Perimeter ......... . 2.536 AR"(2/3) ................. . 0.523 Mannings 'n ' ............. . 0.011 Min. Frie. Slope, 24 inch Pipe Flowing Full ..... . 1.293 8 . 42 in.) 0.702 ft.) CFS fps I I V inches inches feet feet % sq. ft. feet % LOT z. '1 ( Sou TH) ( O'Day Consultants Inc. 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92008 Tel: (760 ) 931-7700 Fax: (760) 931 -8680 Inside Diameter 24.00 in.) * * * * * * * A AAAAAAAAAAA AAAAA AAAA * Water * * * * * * * * * * -- Circular Channel Section Flowrate ................. . 29.700 Velocity ................. . 22.089 Pipe Diameter ............ . 24 .000 Depth of Flow ............ . 10 .639 Depth of Flow ............ . 0.887 Critical Depth ........... . 1.862 Depth/Diameter (D/d) 0.443 Sl ope of Pi pe ............ . 7 .500 X-Sectional Area ......... . 1 .345 Wetted Perimeter ......... . 2 .914 ARA (2/3) ................. . 0 .803 Mannings ' n ' ............. . 0 .011 Min. Frie. Slope, 24 inch Pipe Flowing Full ..... . 1 .234 ,; 10.64 0.887 I I V -- CFS fps inches inches feet feet % sq . ft. feet % zs in.) ft .) O'Day Consultants Inc. 2710 Loker Avenue West, Suite 100 Carlsbad, CA 92008 Te 1 : ( 7 6 0) 9 3 1 -7 7 0 0 Fax : ( 7 6 0) 9 3 1 -8 6 8 0 * * Inside Diameter 24.00 in.) * * * * * -AAAAAAAAAAAAAAAAAAAAA A * Water * * * * * * * * * * Circular Channel Section Flowrate ................. . 15.500 Velocity ................. . 12 .598 Pipe Diameter ............ . 24.000 Depth of Flow ............ . 9.949 Depth of Flow ............ . 0.829 Critical Depth ........... . 1. 424 Depth/Diameter (D/d) 0.415 Slope of Pipe ............ . 2.600 X-Sectional Area ......... . 1.231 Wetted Perimeter ......... . 2.798 ARA (2/3) ................. . 0.712 Mannings 'n' ............. . 0 .0ll Min . Frie. Slope, 24 inch Pipe Flowing Full ..... . 0.336 9 . 95 in .) 0. 829 ft.) CFS fps I I V inches inches feet feet % sq . ft. feet % LoT ZG SECTIONS j ; I .. . -~-- l \ -r-i ! +.· ' ' H1i ·+ . i I '~-j. I.:_ i. I I County of San Diego Hydrology Manual • Rain/all Jsopluvials 2 Year R.aiafall Eveut -6 Hours ll;opluvial (inches) P= I. 7' 1N., E>oHt6'IT /f-/' i ' A f : , i 1 • ,7--;-'""T77Tf: --• ~ --1 l : , ,...,,-,--r,-; n r T'-Trr ··R=r-rT1 0 I ci-,i :1:-!• I ·Jt~ !'! ,·-i ,·rl;-·:-i 11·1,:-rl.0-;--r l'i-:-: . g l t • ·'+ L-i-~i-~_;:_ , '1 ,--·•-+J·;··_:_~:-1-~f•"4i ~:_;J-_ i=p:r -; _ _ ~ ; :: 1 ! '-.. -;:-, i i i .-, j-~ ~J-l -=l +~+!--:: ·1--;- Qr~\ll('Je -·"'-' :.r· I ' . ' •-,-;~=] .Co411ty ., 1 !~·~4-.,_"'-;...·,· _______ !_i~-·-l' --~ I . ' _..,.,,J ; i :' .-f l<o•i , . ; . :_ ' : ' ;_~_:( {,_ '••' -j ·(_ , ! •rt.,•/, -~Y; ; I ~ r ' ' l" ·, -, ••• ... ; ,.~, ,··· ' I ~7:::-Ctlri:'f.i$.Etf.;tt±:1~~:'l=i:i~t±-N~r:t~!::rf1d-~+t.:~af1r1$;:$~1:tt:tr.::l:$.i:::=l-1-:,:::::-Tr· I • '1 ••• ,'j; ••-~_.•f _.•°J..,/0 •-.,y--'i::; •-t-: ! • • ·t :..:~"!-·;•···· .t ti·;" I rrr • ' _'.l,··,.:-;--r'J .~;1 ,_···-'_~·: .,v ,.•· , 1.1-'·, L!•, • ~-f .. /·r . -~l-:~ :-:-::-- .... ·······.! i ;~-~.: ---r- . ! :-1-., --.. , ... ., .. County of San Diego Hydrology Manual • Rain/all Jsopluvials . . , .... ___________________ _ ., i ··t· '' ii-I '. ·! ! ! ~---, I --Ii r r i i I '' ·t-··-~-1-. • i '.' Jj".:-_ -h -·r·r-· ; ; ; ;"" r-,- 1- \0f-: -----r--.. . :-i • I • 10 Year Rainfall Event -6 Hours bopluvilll (lnclwa) P=-/, ? /A/. N , ... ....,.IS~ .. ,ltOUT~Ol'-...-0..UltftllMl'Rlia + C:wl~ICl.UDMl.anNOT LMlialO.lMfN'UiO~ Ol'~NG ..... PQIA..-.c&A,M~ ~...-..--...... ,._....,_ ... _... ....... ._ .. IMGloG....,_. E ~_.=-.. -:_-•...----"-..,... __ .._._ ____ _ ,.__..,...,._ ..... ~ s 3 0 3 Miles ,..., .J . .!.l ... : l l . i I ... / • ·: r ... I ;-.... . f ·: ~ ~-: ... '. l • I • •-i --·· i I I I • ! '. .• ; l :o · -~ c;,' •? ! ' . ;-. ··1 • l •·!,. Ljl= f-· I '• I ~ .. I I -l rt--J-"";-+'I"' +1' +"' -+"' -+.;. ..+-+-1"'-11!l-1=l-1=t7..ifLl--~ll:O:~ •_:_: • i ! .'. I-~·: I I -i .1•M•• . . -. -, I .. i.... County of San Diego Hydrology Manual , • Rainfall Isopluvials 100 Year .Raiofall Event -6 Houn !l 3 Miles I RU~OFF COEFFICIENTS (RATIONAL METHOD) L...\i.'lD USE Undeveloped Residential: !lural Single Family Multi-Units Mobile Homes (2) Commercial (2) 30\ Impervious Industri al (2) 90\ Impervious :--:OTES: Coefficient. C Soil Group (1) A 8 C D . 30 . 35 . 40 . -l-5 . 30 -,. . ~::, . 4-0 . _., . 40 .45 . so . ~:> .45 . 50 . 60 . ;o . 45 . 50 . 55_ .65 . 70 . 75 . 80 .35 .80 .85 .90 .95 (l) Obtain soil group from maps on file witn the Department of Sanitat .:.1.m and Flood Control . (2) Wh ere actual conditions deviate significantly from the tabulated imperviousness values of 80% OT 90%, the values given for coefficien~ C, may be revised by multiplying 80% or 90% by the ratio of actual imperviousness to the tabulated imperviousness. However, i n no case sh a ll the final coefficient be less than 0.50 . For example : Cons .:.Jer ccmrnercial property on O soil group . Actual imperviousness = 50% Tabulated imperviousness = 80 ~.; Revised C = ~ X 0.85 = 0.5., 8.16 Erosion and Sediment Control Handbook TABLE 8.1 Surface Area Requirement. of Sediment Trapa and Basins Particle size, inm 0.5 (coarse aand) 0.2 (medium aand) 0.1 (line 11and) 0.05 (coane silt) 0.0~ (medium silt) 0.01 (finlt'l!lilt) 0.006 (clay) Settlin1 velocity, ft/sec (m/sec) 0.19 (0.058) 0.067 (0.020) 0.023 (0.0070) 0.0062 (0.0019) o.0009& co.ooo:m • 0.00024 (0.000073) 0.00006 (0.000018) SUJface area requirements., rt2 per f\3/aec (m1 per m3/aec discharge dilchaqe) 8.3 17.9 52.2 193.6 1,250.0 5,000.0 20,000.0 (20.7) (58. 7) (171.0) (635.0) (4,101.0) (16,404.0) (65,617.0) eight composed of particles in the 0.01-to 0.02-mm range. A surface area 4 .:imea larger would be needed to capture 5 percent more of this soil. A balance between the cost-effectiveness of a certain basin size and the d~ire to capture fine particles muat be achieved. It is desirable to captW'e the very small soil particles (claya and fine silts) because they cause tuzbidity and other water quality problems. However, Table 8.1 shows that a basin would have to be very large to capture particlea smaller than 0.02 mm, particularly clay pBl'ticlea 0.005 mm and smaller. Because of the high coat of trapping very small particles, the au~hors recommend 0.02 as the design plll'ticle size for sediment basins except in areas with coarse soila, where a larger design particle may be used. The 0.02-mm particle is classified aa a medium silt by the AASHTO soil classification system. 8.2d Basin Discharge Rate The peak discharge, calculated by the rational or another approved method, is used to size the basin riser. Owing any major storm, a sediment basin should fill with water to the top of its riser and then discharge at the rate of inflow to the basin. A sediment basin is not designed with a large water storage volume as is a reservoir. If the inflow exceeds the design peak flow used to size the riser, the overflow should discharge down an emergency spillway. 8.2e Design Runoff Rate In the equation for surface area of a sediment basin, the discharge rate Q is a variable to be chosen by the designer. The above discussion of basin discharge ·a shows that the discharge rate is, to a large extent, equal to the inilow. The . ,ser is sized to handle the peak inflow to the basin. The authors suggest deter- mining the surface area by the average runoff nf a IO-year, 6-hr sto,:m instead I I Sediment Retention Struct, of the peak flow. A substaI and basin efficiency is not s Consider a basin designe off rate. The average rainfal storm (Sec. 4.lf). On·a site, ideal settling conditiona thi soil (i.e., 62 percent of the particles). If the surface area of th would be roughly 3 times Reclamation (10), 25 perce1 period (Fig. 4.2). Since the limeters) per hour, the pel percent of the 6-hr total Si discharge rate (A =-1.2Q/1 times the average rate (50~ flow would be about 3 times sized for the peak flow woul particles with approximate cle. Since the 0.02-mm part with a settling velocity of tured. These are approxim1 Suppose a basin on a sit. rate. For the purpose of ill of the San Francisco Bay J tides, by weight, greater tl 0.02 mm). A basin with a ls ture the 0.01-to 0.02-mm I 67 percent of the eroded m, cent (5/62) by tripling the effective to size a basin b} basin emd~n~;; ·_~H(~~~-~: 8.2f Settling Depth If a basin is too shallow, w settled particles and decre grit-settling chambers at s trolled to prevent particle grit chamber (2) is: V :.cou.r l.· .. _/ t ! ' I • . • ; V ) ·.·,' . --·· . '\ '•' ·~ ..., ... -,, ___ .. , ~·..: \ c.E 6.5 LS . (10) Slope LS valuea for followui, alope .1en&tha l, ft·fm) LS valuea for followiuc llope Janitba l, ft (m) ~adiant 10 20 30 .(() 50 60 70 80 90 100 ·i 150 200 250 300 S50 400 .so 500 600 700 800 900 1000 #, % (3.0) (6.1) (9.1) (12.2) (15.2) (18.3) (21.3) (2'-4) (27.4) (30.5) i (46) (61) (76) (91) (107) (122) (137) (152) (183) (213) (2") (274) (305) i 0.5 0.06 0.07 0.07 0.08 0.08 0.09 0.09 0.09 ·0.09 0.10 ) 0.10 0.11 0.11 0.12 0.12 0.13 0.13 0.13 0.1' 0.14 0.14 0.15 0.15 l 0.08 0.09 0.10 0.10 0.11 0.11 0.12 0.12 0.12 0.12 0.1' 0.1' 0.15 0.16 0.16 0.16 0.11 0.17 0.18 0.18 0.19 0.19 0.20 0.18 0.19 0.19 0.20 , 0.23 0.25 0.32: 2-··· 0.10 0.12 0.14 0.15 0.16 0.17 i 0.26 0.28 0.29 0.30 0.33 0-3-' 0.36 0.37 0.39 0.40 3 0.14 0.18 0.20 0.22 0.23 0.25 0.26 0.27 0.28 0.29 1 .0.32 0.35 0.38 0.40 0.'2 0.-'3 0."5 0..6 0..9 0.51 0.64 0.55 0.57 4 0.16 0.21 0.25 0.28 0.30 0.33 0.35 0.87 0.38 0.40 ' o.~7 0.53 0.58 0.62 0.66 0.70 0.73 0.76 0.82 0.87 0.92 0.96 1.00 J 5 0.17 0.24 • 0.29 0.34 0.38 0.41 0.45 o.~ 0.51 0.53 ' 0.66 0.76 0.85 0.93 1.00 1.07 1.19 1.20 1.31 1.42 1.51 1.60 1.69 Ef 0.21 0.30 0.37 0.43 o.~ 0.52 0.66 0.60 0.64 0.67 1• 0.82 0.95 1.06 1.16 L26 1.3" U3 1.50 1.66 1.78 1.90 • 2.02 2.13 I 7 0.26 0.37 0.46 0.52 0.58 0.64 0.69 0.7' 0.78 0.82 1.01 1.17 1.30 U,1 L54 1.65 1.75 1.84 2.02 2.18 2.33 2.47 2.61 8 0.31 o.-u 0.54 0.63 0.70 0.77 0.83 0.89 0.9" 0.99 i,' L21 UD 1.57 L72 1.85 1.98 2.10 2.22 2.43 2.62 2.80 2.97 3.13 9 0.37 0.52 0.64 0.74 0.83 0.91 0.98 1.05 1.11 1.17 I . U4 1.66 1.85 2.03 2.19 2.35 U9 2.62 2.87 3.10 3.32 3.52 3.71 ~ 10 0.43 0.61 0.75 0.87 0.97 1.06 1.15 1.22 1.30 1.37 1.68 1.94 2.16 2.37 2.66 2.7' 2.90 3.06 3.35 3.62 3.87 4.11 4.33 11 0.50 0.71 0.86 1.00 1.12 1.22 1.32 1.41 1.50 1.58 .. 1.93 2.23 2.50 2.7' 2.95 3.16 3.35 3.63 3.87 4.18 4.47 4.74 4.99 12.5 0.61 0.86 1.05 1.22 1.36 1.49 1.61 1.72 1.82 1.92 2.35 2.72 3.04 3.33 3.59 3.84 '-08 4.30 4.71 5.08 5.43 5.76 6.08 15 0.81 1.14 1.40 1.62 1.81 1.98 2.14 2.29 2.43 2.56 ·i· 3.13 3.62 4.06 4.43 4.79 6.12 6.43 6,72 6.27 6.77 7.24 7.68 8.09 16.7 0.96 1.36 1.67 1.92 2.15 2.36 2.54 • 2.72 2.88 3.<K 3.72 4.30 4..81 5.zt 6.61J 6.08 6.46 6.80 7.46 8.04 8.60 9.12 9.62 20 1.29 1.82 2.23 2.58 2.88 3,16 3.41 3.65 3.87 4.08 5.00 . 5.77 U5 7.06 7.63 8.16 8.66 9.12 9.99 10.79 11.64 12.24 12.90 ; 22 1.51 2.13 2.61 3.02 3.37 3.69 3.99 '-27 4.63 t.77 .. 5.M 6.75 7.54 8.28 8.92 9.54 10.12 10.67 ll.68 12.62 13.49 14.31 15.08 25 1.86 2.63 3.23 3.73 4.16 4.56 ·'-93 5.27 U9 5.89 ' 7.21 8.3a 9.31 10.20 11.02 ll.78 11'9 13.17 14.43 15.58 16.66 17.67 18.63 30 2.51 3.66 4.36 6.03 5.62 6.16 6.65 7.11 7.64 7.95 l 9.74 11.26 12.67 13.77 l'-88 16.91 16.87 17.78 19.'8 21.04 22.49 23.86 25.15 33.3 2.98 4.22 5.17 5.96 6.67 7.30 7.89 U3 8.95 9.43 11.55 13.3" 1'.91 16.33 17.6' 18.86 20.00 21.09 23.10 2'.95 26.67 28.29 29.82 35 3.23 4.57 5.60 6.46 7.23 7.92 8.55 9.1' 9.70 10.22 { 12.52 1U6 16.16 17.70 19.12 20.44 21.68 22.86 25.IW 27.04 28.91 30.67 32.32 40 4.00 6.66 6.93 8.00 8.96 9.80 10.59 11.32 12.00 12.65 15.50 17.89 20.01 21.91 23.67 25.30 26.84 28.29 30.99 33.'8 35.79 37.96 .40.01 45 4.81 6.80 8.33 9.61 10.76 ll.77 12.72 13.60 1U2 15.20 18.62 21.60 24.03 26Jl3 28.-U 30.40 32.24 33.99 37.23 40..22 '2.99 46.60 '8.07 50 5.64 7.97 9.76 11.27 12.60 13.81 14.91 15,94 16.91 17.82 r 2L83 25.21 28.18 30.87 33.34 35.66 37.81 39.85 43.66 47.16 50.41 63.47 56.36 55 6.48 9.16 11~ 12.96 U.'8 lli.87 17.U Ul.32 19."3 20 . .S 25.09 28.97 32.39 36.'8 38.32 40.97 48.'6 '5.80 60.18 64.20 67.94 61.45 64.78 57 6.82 9.64 11.80 13.63 15.24 16.69 18.03 19.28 20.45 2L55 26.40 30.~ 3'.08 37.33 40.32 ~.10 '6.72 '8.19 52.79 57.02 60.96 64.66 68.15 60 7.32 10.35 12.68 U.64 16.37 17.93 19.37 20.71 21.96 23.15 28.35 32.74 36.60 40.10 ~.31 46.:)0 49.11 61.77 66.71 61..25 65.48 69.45 73.21 66.7 8.44 11.93 14.61 16.88 18.87 20.67 22.32 23.87 25.31 26.68 f 32.68 37.7' "2.19 '6.22 49.92 63.37 56.60 69.66 66.36 70.60 75.'7 80.05 84.38 12.70 2L99 23.75 25.39 26.93 28.39 I 85.17 89.78 70 8.98 15.55 17.96 20.08 j. 3'.77 40.15 44.89 48.17 63.11 66.78 60.23 63.48 69.54 76.12 80.30 75 9.78 13.83 16.9' 19.56 21.87 23.96 25.87 27.66 29.34 30.92 37.87 "1. 73 48.89 63.56 57.85 61.85 65.60 69.15 75.75 81.82 87..46 92.77 97.79 . 80 10.55 14.93 18.28 21.ll 23.60 25.85 27.93 29.85 3L66 33.38 40.88 47.20 62.77 57.81 62." 66.76 70.80. 74.63 81.76 88.31 9'.41 100.13 105.55 85 U .30 15.98 19.58 22.61 25.27 27.69 29.90 3L97 33.91 35.7, '3.78 50.66 56.61 61.91 66.87 71.~ 75.82 79.92 87.55 94.67 101.09 107.23 113.03 I 90 12.02 17.00 20.82 24.04 26.88 29.44 31.80 34..00 36.06 38.01 I 46.55 63.76 60.10 66M 71.11 76.02 80.63 84.99 93.11 100.57 107.51 114.03 120.20 95 12.71 17.97 22.01 25.41 28.41 31.12 33.62 35.94 38.12 40.18 49.21 66.82 63.53 69.59 76.17 80.36 85.23 89.84 98.'2 106.30 11_3.64 120.64 127 .06 100 13.36 18.89 23.14 26.72 29.87 32.72 35.34 37.78 40.08 42.24 51.7' 59.7' 66.79 73.17 79.03 84.49 89.61 94.46 103.'8 111.77 119.48 126.73 133.59 tlai:.d from ( 65.41 X s2 4.56 X • ) ( I )"' LS • topocrapbic factor + + 0.066 -Sa + 10,000 J 1• + 10,000 72.6 I • alope laDcih, ft (m X O.ao48) I • alope ltlepual, m • •~t dlpendent upo11 alope ateepneai (0.2 for alopea < l"• 0.3 Coulope11 to H, c><H/6'/T r \ M Car alopee 3.5 to 4.6%, ud ,E 0.5for a1opo1 > 6'1i) Sample Soll Loss Calculation; Step-by-Step Procedu,.. 1. Determine the R ractor. 2. Bued on soil sample particle alze analy1ts: determine the K value from the nomo1raph (Fi1. 5.6). Repeat if you have more than one 1011 sample. 3. Divide the aite into aectlona of uniform slope 1radient and length. ·Aasign an LS value to each section (Table 6.6). 4. Choose the C value(a) to represent a seasonal average of the effect or mulch and vegetation (Tabla 5.6). 5. Set the P factor based on the final gradin1 practice applied to the slopes (Table 5.7). 8. Multiply the five ractora to1atber to obtain per acre aoil lo.._ 7. Multiply soil Ion per acre by the acreage to find the total volu~e of sediment. Ir the aoil loss prediction shows excessive volume loat from the ■ite, consider '. (a) workin1 only a portion of the site at one time, (b} alterin1 the slope length and gradient, or (c) increasing mulch application rate or seeding. ( r-