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2019.0394 Drainge Report Addendum (Accepted) TAHOMA TERRA PHASE II, DIVISION II Yelm, WA ADDENDUM TO STORM DRAINAGE REPORT For Tahoma Terra Divisions 5 & 6 Prepared by: Benjamin E. Enfield, PE KPFF Project No. 414004 May 26, 2020 100P ROF E SSIONA L E N GINEERR EGI S T E R EDTOSATEOFWASHIN G T NBENJA M I N E.A.E N F I ELD Tahoma Terra Phase II, Division II Storm Drainage Report Addendum Yelm, WA KPFF Consulting Engineers May 26, 2020 ATTACHMENTS A. Updated Calculations for Existing Wetpond and Infiltration Pond B. Stormwater Pond Maintenance and Modification Exhibit C. Stormwater Conveyance Analysis SUMMARY This addendum has been prepared to address comment letters received from the City of Yelm dated April 10, 2020 for Tahoma Terra Phase II, Division II (previously known as Tahoma Terra Divisions 5 & 6). This addendum is prepared for the storm report dated May 12, 2014. The proposed concept for water runoff treatment and flow control for this project remains unchanged from the plan identified in the Master Plan documents. Per the May 24, 2016 ‘Letter of Understanding – Tahoma Terra Master Plan Community, Stormwater Requirements & Vesting” referenced in the Hearing Examiner conditions “The remaining development of the 198-lots, which may be phased, will not require any stormwater changes to the existing pond system, unless the as stated monitoring or study of the facility determines it is not meeting the original designed performance requirements.” EXISTING POND BASIN AREAS AND POND SIZES Analysis of the current basin areas for the existing storm ponds in comparison to the basins used in 2006 and 2014 Storm Reports has determined that the currently proposed basins are larger than the basins shown in the previous reports. Table 1: Basin Area to Wetpond “A” and Infiltration Pond (acres) 2006/2014 Report Current Impervious Area 23.20 31.551 Pervious Area 38.54 43.124 Total Basin Area 61.74 74.675 Updated calculations show that the original infiltration pond was designed with enough capacity to handle runoff from the current basin area, but the existing wetpond is slightly undersized. See Attachment A for supplemental stormwater calculations. Increasing the wetpond depth in relation to the original design depth of 3.65’ to a depth 4.75’ will provide the required pond volume as shown in the attached calculations. The ponds have enough existing outer berm height that adjustment to the intermediate berm and spillway elevations can be performed while still maintaining freeboard. The pond modification is proposed in conjunction with recommended maintenance activities. To ensure protection of the pond liner it is proposed to remove sediment from the wetpond to a pond bottom elevation of 342.0’ (1.0’ above the original pond bottom). The modifications proposed to the spillway to provide the required wetpond storage include raising/rebuilding the rip rap spillway from the wetpond to the infiltration pond to an elevation of 346.75’ (2.1’ above original design elevation) and the top of berm between the ponds to an elevation of 347.75’ (1.75’ above original design). See Attachment B for proposed pond maintenance and modifications exhibit. NARRATIVE STORMWATER CONVEYANCE SYSTEM The destination of stormwater generated from this project remains the same as previously identified (the existing ponds located south of Tahoma Boulevard) but the conveyance system Tahoma Terra Phase II, Division II Storm Drainage Report Addendum Yelm, WA KPFF Consulting Engineers May 26, 2020 within Tahoma Terra Phase II, Division II has been reconfigured to divert proposed runoff away from the existing Tahoma Terra Divisions 3 & 4 conveyance systems. The Phase II, Division II (aka Div. 5 & 6) storm conveyance system now conveys the majority of storm runoff south though the current development area directly to the proposed Tahoma Boulevard storm system rather than through the existing Div. 3 &4 system. The proposed conveyance system has been designed with adequate capacity for development. Analysis of the 25-year and 100-year flow events through the system was performed with a conservatively assigned backwater elevation at the crown of the outfall pipe (an elevation above the pond spillway). The analysis showed the HGL was below the minimum required 0.5’ depth below all catch basin rim elevations for the 25- year design storm and below all structure rims for the 100-year design storm. See Attachment C for stormwater conveyance analysis results. Tahoma Terra Phase II, Division II Storm Drainage Report Addendum Yelm, WA KPFF Consulting Engineers May 26, 2020 Attachment A Updated Calculations for Existing Wetpond “A” and Infiltration Pond 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268269 270 271 272 273 274 275 276 310 311 312 313 314 315 316 317 318 319 320 321 322 PARK 308 309 OPEN SPACE OPEN SPACE OPEN SPACE 330 329 201202203204205206207208209 210 211 212 213 214 215 216 217 218 219220221222223224225226227228229 277 278 279 280 281 282 283 284 285 286 287 288 289 290291292293294295296297298299300301 302303304305 306 307 323 324 325 326 327 328331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356357358359360361362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 386 387 388 389 390 391 392 393 394 395 396 397 398 ALLEY 1 PARK 385 OPEN SPACE WELL OS 86 OPEN OPEN OPENOPENOPEN OPENO P E N 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1413121110987654321 ALLEY 1 41 44 43 42 45 73 74 75 76 77 78 79 80 81 82 83 84 85 87 88 89 90 91 92 93 94 95 96 97 98 99100101102103104105106107108109110111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170171172173174175176177178179180 181 182 183 184 185 186 187 188 189 190 191192193194195196197198199200 OPEN OPENOPEN OPEN PARKALLEY 250+00 31+00 32+00 33+00 34+00 35+00 36+00 37+00 38+00 39+0040+0041+0042+0043+0044+0045+0046+0047+0048+0049+00 345342345 34210+0029+00TAHOMA TERRA PH II, DIV II (aka DIV 5&6), PHASE 2 OVERALL BASIN TO EXISTING PONDS DATE: 5/26/2020 EXISTING INFILTRATION POND EXISTING WET POND "A" WELL 1A TAHOMA BLVD TAHOMA TERRA PHASE II, DIVISION II (aka DIV 5 & 6) TAHOMA TERRA DIV 3 & 4 (200 LOTS) PH II, DIV II - PHASE 2 (136 LOTS) PH II, DIV II - PHASE 1 (62 LOTS) BASIN BOUNDARY TO EXISTING STORM PONDS Appended on: Saturday, May 23, 2020 7:52:16 AM LPOOLCOMPUTE [N-Pond] SUMMARY using Puls, 24 hr Storm Event Start of live storage:340 ft Summary Report of all Detention Pond Data Project Precips BASLIST2 [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [2 yr 24 hr] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [25 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] [B-Pond] Using [TYPE1a.rac] As [100 year] [24.0] LSTEND BASLIST [B-Pond] LSTEND Record Id: B-Pond Event Match Q (cfs)Peak Q (cfs)Max Depth (ft)Vol (cf)Vol (acft)Time to Empty (hr) 2 yr 24 hr 11.2451 8.9979 0.2479 4751.1206 0.1091 0.1667 25 year 23.0154 10.9654 2.1441 45334.4748 1.0407 0.1667 100 year 28.0127 11.9872 3.0839 68338.5944 1.5688 0.1667 Event Precip (in) 6-month 1.28 2 yr 24 hr 2.00 25 year 3.50 100 year 4.00 BasinID Event Peak Q (cfs)Peak T (hrs)Peak Vol (ac-cf)Area (ac)Method/Loss Raintype B-Pond 2 yr 24 hr 11.2451 8.00 5.3641 74.675 SBUH TYPE1a.rac B-Pond 25 year 23.0154 8.00 11.8272 74.675 SBUH TYPE1a.rac B-Pond 100 year 28.0127 8.00 14.2295 74.675 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 11.2451 8.00 5.3641 74.675 SBUH TYPE1a.rac B-Pond 2 yr 24 hr 11.2451 8.00 5.3641 74.675 SBUH TYPE1a.rac B-Pond 25 year 23.0154 8.00 11.8272 74.675 SBUH TYPE1a.rac B-Pond 25 year 23.0154 8.00 11.8272 74.675 SBUH TYPE1a.rac B-Pond 100 year 28.0127 8.00 14.2295 74.675 SBUH TYPE1a.rac B-Pond 100 year 28.0127 8.00 14.2295 74.675 SBUH TYPE1a.rac Page 1 of 3 5/23/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html INFILTRATION POND HYDLIST SUMMARY [2 yr 24 hr out] [25 year out] [100 year out] LSTEND STORLIST [N-DETPOND] LSTEND Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 43.124 ac DCIA 31.551 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 30.2372 min DC TC 19.9246 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)43.124 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Dense grasses 0.24 280.00 ft 4.6%0.24 0.00 in 29.4799 min Int Channel Earth-lined (n=0.025)270.00 ft 8.5%0.025 0.7572 min Pervious TC 30.2372 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)31.551 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 2.00 in 0.3714 min Shallow Paved 255.00 ft 1.0%0.01 2.0907 min Int Channel Concrete pipe (n=0.012)2297.00 ft 0.4%0.012 14.2546 min Int Channel Concrete pipe (n=0.012)79.00 ft 0.95%0.012 0.3181 min Int Channel Concrete pipe (n=0.012)63.00 ft 0.51%0.012 0.3462 min Int Channel Concrete pipe (n=0.012)436.00 ft 1.2%0.012 1.5621 min Int Channel Concrete pipe (n=0.012)220.00 ft 1.31%0.012 0.7544 min Int Channel Concrete pipe (n=0.012)103.00 ft 3.17%0.012 0.2271 min Pervious TC 19.9246 min HydID Peak Q (cfs)Peak T (hrs)Peak Vol (ac-ft)Cont Area (ac) 2 yr 24 hr out 8.9979 8.33 5.3641 74.675 25 year out 10.9654 9.50 11.8272 74.675 100 year out 11.9872 9.67 14.2295 74.675 Page 2 of 3 5/23/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Record Id: N-DETPOND DISCHLIST [D-INF] LSTEND Record Id: D-INF Licensed to: Debug License Descrip:Prototype Record Increment 0.10 ft Start El.340.00 ft Max El.347.00 ft Void Ratio 100.00 Length 270.00 ft Width 70.00 ft Length ss1 3.00v:1h Length ss2 3.00v:1h Width ss1 3.00v:1h Width ss2 3.00v:1h Consider wetted surface for infiltration Trap Type Node Infiltration Descrip:Prototype Structure Increment 0.10 ft Start El.340.00 ft Max El.347.00 ft Infiltration rate 20.00 in/hr WP Multiplier 1.00 Page 3 of 3 5/23/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html EXISTING INFILTRATION POND HAS CAPACITY TO INFILTRATE ALL RUNOFF Appended on: Saturday, May 23, 2020 6:57:12 AM B-Pond Event Summary Record Id: B-Pond Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 6.7784 8.00 2.8792 74.675 SBUH 2 yr 24 hr 11.2451 8.00 5.3641 74.675 SBUH 25 year 23.0154 8.00 11.8272 74.675 SBUH 100 year 28.0127 8.00 14.2295 74.675 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 43.124 ac DCIA 31.551 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 30.2372 min DC TC 19.9246 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)43.124 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Dense grasses 0.24 280.00 ft 4.6%0.24 0.00 in 29.4799 min Int Channel Earth-lined (n=0.025)270.00 ft 8.5%0.025 0.7572 min Pervious TC 30.2372 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)31.551 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 2.00 in 0.3714 min Shallow Paved 255.00 ft 1.0%0.01 2.0907 min Int Channel Concrete pipe (n=0.012)2297.00 ft 0.4%0.012 14.2546 min Int Channel Concrete pipe (n=0.012)79.00 ft 0.95%0.012 0.3181 min Int Channel Concrete pipe (n=0.012)63.00 ft 0.51%0.012 0.3462 min Int Channel Concrete pipe (n=0.012)436.00 ft 1.2%0.012 1.5621 min Int Channel Concrete pipe (n=0.012)220.00 ft 1.31%0.012 0.7544 min Int Channel Concrete pipe (n=0.012)103.00 ft 3.17%0.012 0.2271 min Pervious TC 19.9246 min Page 1 of 2 5/23/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html TREATMENT WETPOND Wetpond volume after proposed revisions elev.contour area (ft2) incremental volume (ft3) 342 21,653 343 23,760 22,707 344 25,923 24,842 345 28,143 27,033 346 30,420 29,282 346.75 32,165 23,469 Total Volume =127,332 Required Wetpond Volume (per updated StormShed 6-month storm) = 2.8792 ACFT = 125,418 cu. ft. Original Designed Pond has dead storage volume of 92,548 cu. ft. Proposed Wetpond dead storage volume after maintenenance/modifications = 127,332 cu. ft. See wetpond maintenance/modification exhibit in Attachment B. Tahoma Terra Phase II, Division II Storm Drainage Report Addendum Yelm, WA KPFF Consulting Engineers May 26, 2020 Appendix B Stormwater Pond Maintenance and Modification Exhibit 41DEVELOPMENT REVIEW ENGINEERBY:DATE:APPROVED FOR CONSTRUCTIONAPPROVAL EXPIRES:CALL UNDERGROUND LOCATE TWOWORKING DAYS BEFORE YOU DIG1-800-424-5555R-1318ROADWAY & STORMDRAINAGE DETAILSVERTICAL DATUMNGVD 29PER THURSTONCOUNTY HIGHPRECISION NETWORKHORIZONTAL CONTROL:WASHINGTON STATE PLANE, SOUTHZONE PER TCHPN&THURSTON COUNTY HIGHPRECISION NETWORKA-A ~WETPOND "A" & INFILTRATION PONDSCALE: 1" = 40'C-C~D-D~WETPOND NOTE:WETPOND TO BE UTILIZED AS A TEMPORARY SEDIMENT BASIN. EXCAVATE TO 0.5' BELOW FINAL DESIGN ELEVATION (325.50),(340.50)87653412WETPOND "B"SCALE: 1" = 40'WETPOND "B"91012112B-B~INFILTRATION PONDWETPOND "A"RIP RAP /EMERGENCY SPILLWAYPOND(S) CORNER COORDINATE TABLE592955.6257NORTHING1107337.4940EASTINGBOTTOM RADIUS2.00'1234567891011122.00'2.00'2.00'2.00'2.00'2.00'2.00'5.00'5.00'5.00'5.00'592889.65311107335.5918592881.98661107601.4813592947.95921107603.3835592917.31891107649.2557592916.62081107715.2520593182.60591107718.0656593183.30401107652.0693593540.69851108516.8741593543.66971108522.0868593627.07261108474.5479593624.10141108469.3352C-C~D-D~B-B~A-A~TAHOM A B L V D .TYPE 1 CATCH BASINWITH SOLID COVER.SEE DETAIL ON THISSHEET - LEFT100 LF - 8" PVC @0.1%INV. OUT = 330.06RIP RAP SPILLWAYINV. OUT = 330.16WETPOND "B" RELEASESTRUCTURE DETAILNOT TO SCALESOLID LID8" PVCINV. ELV. = 330.1612" KNOCK OUTWITH 1/2" REBAR@4" O.C.1 11/2007 DLG CDP MRS AS BUILTSD. Re-build spillway toelevation 346.75 and topof berm to elevation347.75'WET POND "A" MAINTENANCE/ADJUSTMENTS:A. REMOVE ALL TREES AND LARGE SHRUBS FROM SEDIMENT POND.B. REMOVE ACCUMULATED SEDIMENT IN BOTTOM OF POND DOWN TO ELEVATION 342.0 (1.0' ABOVEORIGINAL POND DEPTH).C. PERFORM VISUAL INSPECTION AND HAND SHOVEL TESTS TO CONFIRM POND LINER MATERIAL ANDCONDITION. KPFF AND/OR INSIGHT GEOLOGIC TO WALK THE WETPOND AFTER EARLIER STEPS ARECOMPLETE AND INDICATE LOCATIONS TO PERFORM SHOVEL TESTS. D. RAISE/REBUILD SPILLWAY TO INFILTRATION POND "A" TO ELEVATION 346.75' AND TOP OF BERMBETWEEN PONDS TO ELEVATION 347.75' PER DETAIL ON THIS SHEET.E. SUPPLEMENT/RESTORE ROCK PAD AT WETPOND INLET PIPE.E. SUPPLEMENT/RESTORE ROCK PAD ATWETPOND INLET PIPE.A. REMOVE ALL TREES AND LARGESHRUBS FROM POND.B. REMOVE ACCUMULATED SEDIMENT INWETPOND TO AN ELEVATION OF 342.0'(1.0' ABOVE ORIGINAL POND DEPTH).D. RAISE/REBUILD RIP RAP SPILLWAY TOAN ELEVATION OF 346.75' AND TOP OFBERM BETWEEN PONDS TO ANELEVATION OF 347.75'MAY 2020 POND MAINTENANCE RECOMMENDATIONS BY KPFF CONSULTING ENGINEERSEXISTING TOP OF POND = 348'(WETPOND AND INFILTRATIONPOND)D. RAISE BERM TO347.75 (APPROX. 1.75') Tahoma Terra Phase II, Division II Storm Drainage Report Addendum Yelm, WA KPFF Consulting Engineers May 26, 2020 Appendix C Stormwater Conveyance Analysis 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268269 270 271 272 273 274 275 276 310 311 312 313 314 315 316 317 318 319 320 321 322 PARK 308 309 OPEN SPACE OPEN SPACE OPEN SPACE 330 329 201202203204205206207208209 210 211 212 213 214 215 216 217 218 219220221222223224225226227228229 277 278 279 280 281 282 283 284 285 286 287 288 289 290291292293294295296297298299300301 302303304305 306 307 323 324 325 326 327 328331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356357358359360361362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 386 387 388 389 390 391 392 393 394 395 396 397 398 ALLEY 1 PARK 385 OPEN SPACE WELL OS 86 OPEN OPEN OPENOPENOPEN OPENO P E N 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1413121110987654321 ALLEY 1 41 44 43 42 45 73 74 75 76 77 78 79 80 81 82 83 84 85 87 88 89 90 91 92 93 94 95 96 97 98 99100101102103104105106107108109110111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170171172173174175176177178179180 181 182 183 184 185 186 187 188 189 190 191192193194195196197198199200 OPEN OPENOPEN OPEN PARKALLEY 250+00 31+00 32+00 33+00 34+00 35+00 36+00 37+00 38+00 39+0040+0041+0042+0043+0044+0045+0046+0047+0048+0049+00 345342345 34210+0029+002 3 4 522 6 7 10 27 21 30 29 3231 3433 37364646 43 47 49 48 51 19 20 52 53 18 17 54 55 58 57 98 72 73 59 61 60 74 11 63 62 13 15 68 67 16 70 69 71 75 76 78 77 40 39 38 64 23 56 79 83 81 41 10a outfall 12 15 17a19a 21a blvd 22 TAHOMA TERRA PH II, DIV II (aka DIV 5&6), PHASE 2 CONVEYANCE BASIN EXHIBIT DATE: 5/26/2020 CONNECTION TO TAHOMA BOULEVARD STORM CONVEYANCE SYSTEM EXISTING INFILTRATION POND EXISTING WET POND TAHOMA BOULEVARD CB 12 BASIN CB 55 BASIN CB 51 BASIN CB 13 BASIN CB 71 BASIN CB 81 BASIN CB 34 BASIN CB 58 BASIN CB 21A BASIN CB 61 BASIN WELL 1A BASIN DIV 3&4DIV 5&6 Sub-Basin/ Tributary Inlet ## of Roofs tributary to Sub-Basin1Basin Boundary AreaTotal Area2RoadsRoof AreaDriveways(incl. all Lot Impervious)SidewalkLawn/LandscapeTotal Impervious55 17 2.5632.5210.2580.714 0.207 0.083 1.2581.26371273.1743.4680.6041.1340.2300.1811.3202.14951285.3985.3140.7281.1760.3450.2722.7932.52134345.7185.7180.6111.4280.3910.2183.0702.64881242.6062.8580.3531.0080.2070.1491.1411.71761231.1121.7840.2950.9660.0810.0960.3471.43713254.0774.0350.5911.0500.2990.2121.8832.15258112.6382.6380.5560.4620.1270.1581.3351.30221a04.8624.8622.0990.0000.0000.2722.4912.370127638.20831.5725.1273.1922.6911.57818.98412.588sub-totals26570.35564.76911.22111.1304.5773.21934.62230.147Pond Area9.9069.9061.4040008.5021.404Total Area to Ponds = 74.67512.62511.1304.5773.21943.12431.5511. # of roofs tributary to sub-basins based on roof drain connections to storm system. Div 3&4 has 133 lots with roof dry wells.2. Total area = basin boundary area + roof area for lots outside basin but tributary to basin SD - Roof area for lots in basin w/ roof drain connection to another basinBasin Area (Acres)Existing Storm Ponds Sub-Basin Areasto drywell or to another sub-basin. Appended on: Friday, May 22, 2020 9:11:50 AM B-CB 55 Event Summary Record Id: B-CB 55 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.3387 8.00 0.1144 2.521 SBUH 2 yr 24 hr 0.5578 8.00 0.2071 2.521 SBUH 25 year 1.0901 8.00 0.4383 2.521 SBUH 100 year 1.3001 8.00 0.5226 2.521 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 1.258 ac DCIA 1.263 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 26.4383 min DC TC 5.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)1.258 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 195.00 ft 1.5%0.15 2.00 in 23.7246 min Shallow Paved 122.00 ft 1.05%0.01 0.9761 min Int Channel Concrete pipe (n=0.012)280.00 ft 0.4%0.012 1.7376 min Pervious TC 26.4383 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)1.263 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Sheet Smooth Surfaces. 0.011 17.00 ft 2.0%0.011 0.00 in 0.3714 min Shallow Paved 255.00 ft 1.05%0.01 2.0403 min Int Channel Concrete pipe (n=0.012)280.00 ft 0.4%0.012 1.7376 min Pervious TC 4.1493 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:58:56 AM B-CB 71 Event Summary Record Id: B-CB 71 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.5762 8.00 0.193 3.469 SBUH 2 yr 24 hr 0.9491 8.00 0.3391 3.469 SBUH 25 year 1.8146 8.00 0.6841 3.469 SBUH 100 year 2.1394 8.00 0.8068 3.469 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 1.32 ac DCIA 2.149 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 20.4517 min DC TC 5.0251 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)1.32 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 110.00 ft 1.4%0.15 2.00 in 15.4266 min Shallow Paved 135.00 ft 0.51%0.01 1.5499 min Int Channel Concrete pipe (n=0.012)560.00 ft 0.4%0.012 3.4752 min Pervious TC 20.4517 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)2.149 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 135.00 ft 0.51%0.01 1.5499 min Int Channel Concrete pipe (n=0.012)560.00 ft 0.4%0.012 3.4752 min Pervious TC 5.0251 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:56:01 AM B-CB 51 Event Summary Record Id: B-CB 51 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.6723 8.00 0.2288 5.314 SBUH 2 yr 24 hr 1.1084 8.00 0.418 5.314 SBUH 25 year 2.2158 8.00 0.896 5.314 SBUH 100 year 2.6637 8.00 1.0714 5.314 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 2.793 ac DCIA 2.521 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 20.6459 min DC TC 6.1243 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)2.793 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 110.00 ft 1.5%0.15 2.00 in 15.0067 min Shallow Paved 80.00 ft 1.17%0.01 0.6064 min Int Channel Concrete pipe (n=0.012)811.00 ft 0.4%0.012 5.0329 min Pervious TC 20.6459 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)2.521 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 144.00 ft 1.17%0.01 1.0915 min Int Channel Concrete pipe (n=0.012)811.00 ft 0.4%0.012 5.0329 min Pervious TC 6.1243 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:55:27 AM B-CB 34 Event Summary Record Id: B-CB 34 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.6902 8.00 0.2406 5.718 SBUH 2 yr 24 hr 1.1394 8.00 0.4413 5.718 SBUH 25 year 2.2794 8.00 0.9514 5.718 SBUH 100 year 2.743 8.00 1.1391 5.718 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 3.07 ac DCIA 2.648 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 23.2436 min DC TC 8.2146 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)3.07 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 120.00 ft 1.7%0.15 2.00 in 15.3029 min Shallow Paved 215.00 ft 0.56%0.01 2.3556 min Int Channel Concrete pipe (n=0.012)900.00 ft 0.4%0.012 5.5852 min Pervious TC 23.2436 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)2.648 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 240.00 ft 0.56%0.01 2.6295 min Int Channel Concrete pipe (n=0.012)900.00 ft 0.4%0.012 5.5852 min Pervious TC 8.2146 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 1:51:32 PM B-CB 81 Event Summary Record Id: B-CB 81 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.4604 8.00 0.1544 2.858 SBUH 2 yr 24 hr 0.7583 8.00 0.2724 2.858 SBUH 25 year 1.4419 8.00 0.5531 2.858 SBUH 100 year 1.6982 8.00 0.6533 2.858 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 1.141 ac DCIA 1.717 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 27.6955 min DC TC 5.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)1.141 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 170.00 ft 1.0%0.15 2.00 in 25.0015 min Shallow Paved 94.00 ft 1.5%0.01 0.6293 min Shallow Paved 210.00 ft 1.2%0.01 1.5717 min Int Channel Concrete pipe (n=0.012)94.00 ft 0.56%0.012 0.493 min Pervious TC 27.6955 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)1.717 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 175.00 ft 1.2%0.01 1.3098 min Int Channel Concrete pipe (n=0.012)300.00 ft 1.3%0.012 1.0327 min Pervious TC 2.3425 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 11:51:38 AM B-CB 61 Event Summary Record Id: B-CB 61 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.3853 8.00 0.1281 1.784 SBUH 2 yr 24 hr 0.6347 8.00 0.2181 1.784 SBUH 25 year 1.1742 8.00 0.4172 1.784 SBUH 100 year 1.3632 8.00 0.4857 1.784 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 0.347 ac DCIA 1.437 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 17.5883 min DC TC 5.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)0.347 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 102.00 ft 1.5%0.15 2.00 in 14.127 min Shallow Paved 182.00 ft 0.58%0.01 1.9593 min Int Channel Concrete pipe (n=0.012)248.00 ft 0.42%0.012 1.5019 min Pervious TC 17.5883 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)1.437 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 185.00 ft 0.58%0.01 1.9916 min Int Channel Concrete pipe (n=0.012)195.00 ft 1.57%0.012 0.6108 min Int Channel Concrete pipe (n=0.012)248.00 ft 0.42%0.012 1.5019 min Pervious TC 4.1044 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:54:25 AM B-CB 13 Event Summary Record Id: B-CB 13 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.5771 8.00 0.1944 4.035 SBUH 2 yr 24 hr 0.9505 8.00 0.3487 4.035 SBUH 25 year 1.8672 8.00 0.7272 4.035 SBUH 100 year 2.2267 8.00 0.8642 4.035 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 1.883 ac DCIA 2.152 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 18.8187 min DC TC 5.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)1.883 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 105.00 ft 1.5%0.15 2.00 in 14.4585 min Shallow Paved 178.00 ft 0.5%0.01 2.0639 min Int Channel Concrete pipe (n=0.012)404.00 ft 0.54%0.012 2.1578 min Int Channel Concrete pipe (n=0.012)67.00 ft 3.6%0.012 0.1386 min Pervious TC 18.8187 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)2.152 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 178.00 ft 0.5%0.01 2.0639 min Int Channel Concrete pipe (n=0.012)404.00 ft 0.54%0.012 2.1578 min Pervious TC 4.2217 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:58:19 AM B-CB 58 Event Summary Record Id: B-CB 58 Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.3491 8.00 0.118 2.637 SBUH 2 yr 24 hr 0.575 8.00 0.2141 2.637 SBUH 25 year 1.1462 8.00 0.4547 2.637 SBUH 100 year 1.3752 8.00 0.5425 2.637 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 1.335 ac DCIA 1.302 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 18.5884 min DC TC 5.00 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)1.335 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 139.00 ft 1.6%0.15 2.00 in 17.6348 min Shallow Paved 58.00 ft 1.0%0.01 0.4755 min Int Channel Concrete pipe (n=0.012)96.00 ft 5.55%0.012 0.1599 min Int Channel Concrete pipe (n=0.012)79.00 ft 0.95%0.012 0.3181 min Pervious TC 18.5884 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)1.302 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 224.00 ft 0.5%0.01 2.5972 min Int Channel Concrete pipe (n=0.012)316.00 ft 0.95%0.012 1.2725 min Pervious TC 3.8697 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:54:55 AM B-CB 21A Event Summary Record Id: B-CB 21A Licensed to: Debug License Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 0.6317 8.00 0.2148 4.861 SBUH 2 yr 24 hr 1.0414 8.00 0.3908 4.861 SBUH 25 year 2.0369 8.00 0.8322 4.861 SBUH 100 year 2.4313 8.00 0.9937 4.861 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 2.491 ac DCIA 2.37 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 28.7772 min DC TC 6.211 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)2.491 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 270.00 ft 1.9%0.15 2.00 in 28.0025 min Shallow Paved 150.00 ft 2.52%0.01 0.7747 min Pervious TC 28.7772 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)2.37 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 292.00 ft 1.0%0.01 2.394 min Int Channel Concrete pipe (n=0.012)158.00 ft 0.79%0.012 0.6977 min Int Channel Concrete pipe (n=0.012)63.00 ft 0.51%0.012 0.3462 min Int Channel Concrete pipe (n=0.012)103.00 ft 1.86%0.012 0.2964 min Int Channel Concrete pipe (n=0.012)656.00 ft 1.31%0.012 2.2495 min Int Channel Concrete pipe (n=0.012)103.00 ft 3.17%0.012 0.2271 min Pervious TC 6.211 min Page 1 of 1 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html Appended on: Friday, May 22, 2020 8:51:57 AM B-CB 12 Event Summary Record Id: B-CB 12 Event Peak Q (cfs)Peak T (hrs)Hyd Vol (acft)Area (ac)Method 6-month 3.0782 8.00 1.1521 31.572 SBUH 2 yr 24 hr 5.0915 8.00 2.1689 31.572 SBUH 25 year 10.1964 8.00 4.8523 31.572 SBUH 100 year 12.3229 8.00 5.8557 31.572 SBUH All results based on storm duration of 24.0 hours. This is ok if all precipitations are appropriate for the storm duration. If some design event precipitations are for different duration storms, those results are incorrect Design Method SBUH Rainfall type TYPE1a.rac Hyd Intv 10.00 min Peaking Factor 484.00 Storm Duration 24.00 hrs Abstraction Coeff 0.20 Pervious Area 18.984 ac DCIA 12.588 ac Pervious CN 68.00 DC CN 98.00 Pervious TC 38.2518 min DC TC 12.2275 min Pervious CN Calc Description SubArea Sub cn Open spaces, lawns,parks (>75% grass)18.984 ac 68.00 Pervious Composited CN (AMC 2)68.00 Pervious TC Calc Type Description Length Slope Coeff Misc TT Sheet Short prairie grass and lawns. 0.15 206.00 ft 1.3%0.15 2.00 in 26.2497 min Shallow Paved 177.00 ft 0.7%0.01 1.7345 min Int Channel Concrete pipe (n=0.012)528.00 ft 1.49%0.012 1.6977 min Int Channel Concrete pipe (n=0.012)1192.00 ft 0.5%0.012 6.6163 min Int Channel Concrete pipe (n=0.012)108.00 ft 1.83%0.012 0.3133 min Int Channel Concrete pipe (n=0.012)216.00 ft 0.5%0.012 1.1989 min Int Channel Concrete pipe (n=0.012)134.00 ft 1.42%0.012 0.4414 min Pervious TC 38.2518 min DCI - CN Calc Description SubArea Sub cn Impervious surfaces (pavements, roofs, etc)12.588 ac 98.00 DC Composited CN (AMC 2)98.00 DCI - TC Calc Type Description Length Slope Coeff Misc TT Shallow Paved 200.00 ft 0.7%0.01 1.9599 min Int Channel Concrete pipe (n=0.012)528.00 ft 1.49%0.012 1.6977 min Int Channel Concrete pipe (n=0.012)1192.00 ft 0.5%0.012 6.6163 min Int Channel Concrete pipe (n=0.012)108.00 ft 1.83%0.012 0.3133 min Int Channel Concrete pipe (n=0.012)216.00 ft 0.5%0.012 1.1989 min Int Channel Concrete pipe (n=0.012)134.00 ft 1.42%0.012 0.4414 min Pervious TC 12.2275 min Page 1 of 2 5/22/2020file:///C:/Users/bene/Desktop/TT%205&6/Convayance.html OUTFALL TO CB 3 - 25-YR EVENT CB 3 TO CB 55 - 25-YR EVENT CB 51 TO CB 71 - 25-YR EVENT CB 3 TO CB 13 - 25-YR EVENT CB 58 TO CB 81 - 25-YR EVENT OUTFALL TO CB 3 - 100-YR EVENT CB 3 TO CB 55 - 100-YR EVENT CB 51 TO CB 71 - 100-YR EVENT CB 3 TO CB 13 - 100-YR EVENT CB 58 TO CB 81 - 100-YR EVENT