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24953 DRAINAGE TECHNICAL REPORT-RIVERWALK 8TH ~ ~ ~ i: - - - I I • , RECEIVfFD ~ SPOKANE C[}UN7Y ENGINEERS OFFICE _ o~~FICuAL Pueuc DOCtJMEwT ORIG« FE8 0 CONSrRuCnvN RJWs ~ PRI ~I'►~"E I~~~~'~ ~+►~E c~NrY Er~~F~ ~ - di-l- G ~ DA~ ~CCEFTED. ACCEP'fANCE EXP'iR~; PROJECT L.14NE M LES . . + car~~~UMN4 OWUMErrtATM AND CEFrnFIEo Ft F-cORa DRAw4NGS,~AS-BuILTS* AFIE FIEQUMM PR JR TO RELEASE OF INSPECtM ODNID. APPHOAC4A PERMIT REQUIRED1 Oi$) 4W3600 F7 w J r'S TV {.rVN0 1 T1 VCMN ~ `i y ~ y ~A ,q • ' ~ . CID'O~ ~M SPOKANE • COEUR D'ALENE DRAINAGE TECHNICAL REPORT for the RIVERWALK 8TH ADDITION PUD JANUARY 1999 Prepared for: SHOREWOOD HOMES 3901 Schreiber Way Coeur d'Alene, ID 83814 Prepared By: Inland Pacific Engineering Comparry 707 W. 7th Avenue Suite 200 Spokane, WA 99204 (509)458-6840 DRAINAGE REPORT for the Riverwalk 8th Addition PUD Plat Spokane County, Washington .Tanuarv 1999 The design impravements shown in this sct of plans and calculations conform to the applicabie editions of the Spokane County Standards for Road and Sewer Construction and the Spokane County Guidelines for Stormwater ManagemQnt. All design deviations have becn approved by the Spokane County Engineer. I approve these plans (calculations) for construction. This report has been prepared by Susan K. Murphy of Inland Pacific Engineering Company undcr the direction of the undersigned professional engineer whose seal d signature appear hereon. `~►G ~w . ~ . ~ 7"• ~ ~ r 2' i4b~ .r~;';;`G~ r 1 ~ipIr~rc C1124~~M ~r`..~._:~- ~._...r. 1'odd R. Whipple, P.E. Riverwalk 8th Addition PUD Drainage Narrative GENERAL Riverwalk 8th Addition PUD Plat is a 7.86 acre development of 34 single family residential lots located north and east of the intersection of Indiana Avenue and Barker Road, within Spokane County, Washington. The site is currently vacant with field grass, alfalfa and fallow fields as the predominant land cover and vegetation. Single family residential development lies directly to the south and west. A 1" to 400' scale vicinity and location map have been included within the technical section of this document. PURPOSE The purpose of this report is to detennine the extent of storm drainage facilities which will be required to dispose of the increase in stormwater runoff created by the development of the Riverwalk 8th Addition plat. The storm drainage facilities on this project will be designed to dispose of runoff from a ten year design storm, as required by the Spokane County Guidelines for Stormwater Management, though the calculations are also included to verify that the facilities also generally contain the 50-year storm. This development is within the Aquifer Sensitive Area of Spokane County and is subject to'208' requirements. For this project, the 10-year curve from the Spokane, Medical Lake, Reardon, Cheney and Rockford intensity curves was used, as well as the SCS iso-pluvial rainfall curves. Per direction from Spokane County, the SCS curves have been further refined with the NOAA iso-pluvial curves. AIVALYSIS METHODOLOGY Per the Spokane County Guidelines for Stormwater Management, the Rational Method, which is recommended for basins less than ten acres in size, will be used to determine the peak discharges and runoff volumes for all onsite basins. PR4JECT DESCRIPTION This phase of the Riverwalk 8th Addition plat comprises 341ots of the approved 393 lots in the approved preliminary plat and SEPA documents. The Riverwalk 8th Addition subdivision is located in the NE 1/4 of the S W l l4 of Section 8, T. 25 N., R. 45 E., W.M. within Spokane County, Washington. TOPOGRAPHY The existing site naturally drains to the north, sloping gently towazds the Spokane River from Indiana Avenue. Within the plat the natural topography was used as much as possible to route Inland Pacific Engineering Company D 1Riverwalk 8th Addition Plat Drainage Report storm drainage. However, due to the flat slopes and the County's minimum requirements for slope, the roadway profiles have been forced down to facilitate drainage by localizing low spots for pond placement. Due to the flat slopes encountered, no concentrated pre-existing flows were observed nor were there any signs that anything other than sheet flow and ground absorption have occurred on this site. The general slopes within this plat vary from flat to nearly flat with the maximum existing slope at 0.025/ft. Generally, the area within this platted portion of the overall preliminary plat would be characterized as flat. For development purposes as stated the natural sloping was used for design and is maintained as possible throughout the project. SOILS As can be seen from the accompanying soils map from the Spokane County Soils Survey as performed by the SCS, the site consists of one type of soils within the Class B type. This soil type is described as follows. GgA - Garrison gravelly loam, 0 to 5 percent slopes: Soils within this soil type are some what excessively drained soils formed in gravelly glacial outwash material from a variety of igneous rock. Surface runoff is slow, and the hazard of erosion is slight. Spokane County Guidelines for Stormwater Management indicate this to be a Soil Group Type B and pre-approved for drywell installation. Hydrologic Soil Classification - B DRAINA GE NARRA TI VE Uffsite Based upon the general geographic tendencies of this site, no offsite flows aze expected for this phase. Onsite As this plat is within the aquifer sensitive area of Spokane County all onsite drainage will be collected and treated using the "208" runoff inethod as described in the Spokane County Guidelines for Stormwater Management. To facilitate this analysis the Riverwalk 8th Addition plat was divided into 8 permanent sub-basins (A through H). Although there are 8 basins, these basins have been combined where practical to utilize the same pond. Table 1 lists the basins and pond combinations for easy reference. Inland Pacific Engineering Comparry D2 Riverwalk 8th Addition Plat Drainage Report Table No. 1 . , a t C4. . . . . . . . . . ~fL "S. - d~ : : . . . _ , . , . r 1:; . 5 WEIGHTED "C1SiIMMAR.Y Basiuns To#al Total Stireet-Imp. Tatal Weighted Area Acreage Area (Sl) -Impervious "C" - .(SF) ` (CF) :Area r- , x - . 9 . . 4. . . - - (SF/AC} A 32366 0.74 4454 12154/0.28 0.43 B 18794 0.43 3745 8145/0.19 0.48 C 32704 0.75 4477 12177/0.28 0.43 D 25917 0.59 5643 11143/0.26 0.48 E 7372 0.17 3269 3269/0.08 0.50 A F 142465 3.27 17615 47315/1.09 0.40 G 84943 1.95 13418 32118/0.74 0.43 FG 227408 5.22 31033 79433/1.82 0.41 H 26747 0.61 5373 10873/0.25 0.46 "208" Calculations Within each basin the streets are divided into sub-basins by high and low roadway profiles. These facilities capture upstream stormwater runoff from the impervious street surface and direct the runoff into grassy '208' ponds. As shown on the '208' calculation worksheets included, the '208' storage volume provided is adequate to perform '208' treatment for the runoff created by the first half inch of rainfall. Curb Inlets Calculations It is necessary to check the adequacy of the curb inlets provided to divert the runoff from the gutter into the '208' ponds. The curb irilet calculation sheets included show the required lengths of curb openings. For curb inlets greater than 4.0', either multiple curb inlets aze added or the curb inlets are lengthened as required. DRAINAGE CALCULAT'IONS SUMMARY Calculations have been included for Drainage Basin considerations such as Peak Flow, Time of Concentration, "208" sizing, drywell requirements, inlet sizing and curb inlets, as well as culverts Inland Pacific Engineering Comparry D3 Riverwalk 8th Addition Plat Drainage Report and pipe flows, some of which are summarized below with the remaining calculations included in the appendix. Within the calculation section and where it has been determined necessary for clarity, several sketches, as well as details from the plans have been incorporated to demonstrate assumptions and conclusions. BASIN DESCRIPTIONS Basins A through G Within this plat, and due to the general geographic features, several basic assumptions were followed and can be used to describe each basin. First, due to the relative flatness of the plat and project vicinity, minunum road grade is limited to O.OOSft/ft; second, a large tract pond if practical will be used in the open space area; third, all other ponds will be of the lot pond configuration; fourth, that where practical, drywells will be minimized by combining basins and providing piping between ponds. All of these steps have been used in various basins throughout the drainage design of this project. Table No. 2- Pond and 208 Basin Summary " / : . . . ' . A ~ . . e E ° , ~X.,_~L~ . . Riverwalk 8th Addition - BA:SIN,,SUNI~I~IARY t , 208 'Valume 208 '~ulume 208 Area Drywells . , , ~R . ~ _ . . . c - .:Prov, ~ded s e9uired * ~equired fcfl rovided f} P { A A 186 280 560 1- B B B 156 187 375 1- A C C 187 280 560 1- B D D 235 254 508 1- B E E 136 170 340 1- A F FG 734 952 1428 3- B** G FG 559 341 682 H C(RW6) 224 387 774 1- B Type A is a Spokane Standard Drywell - Single Depth, Capacity 0.3 cfs - Type B is a Spokane Standard Drywell - Double Depth, Capacity 1.0 cfs Basins F& G have been combined for the Bowstring Calculation. Pand F is designed to provide `208' treatment to a depth of 8"; all other `208' treatment areas are based on a depth of 6" . Inland Pacific Engineering Company D4 Riverwalk &h Addition Plat Drainage Report Table No. 3- Curb In1et/Catch Basin Surnmary . _ . , . E t . , ~ ~ erwa lkidd~tio n~ ~'iat -..Curb l.' u~ap.ma s . ry . Y ti t ~j . ♦ . ' ' ~~a L+ s $as~n ~z ={~4~`oad ~ ~.p =Curb Im~et ~ 7 ~~~n - i~ . t fH`. a4>st , . Cond•fi~on~ ~l ~oa~ * i' ed i 1 I A A Sump - B B Continuous - C C Sump - D D Sump - E E Continuous - F FG Continuous G FG Continuous - H C(RW6) Continuous - Per Spokane County Guidelines curb drops in a sump condition have a capacity of 4.0 cfs Per WSDOT Hydraulics Manual, Grate Inlet, has a sump capacity of 13.0 cfs NOTE: 4nly curb drop and grate calculations were performed for those cases "On Grade", curb drops and catch basins in sump condition are assumed to handle 4.0 cfs. Inland Pacific Engineering Con;pany DS Riverwalk 8th Addition Plai Drainage Report . , ~ ►e~y ~ ~ ~ I ~ M ~~a 11}..J ^-W~W A ~ M ~ t ~ I Omnat~ IM. ~ p 00 Ary Dr, ~ R "oot Mt Q m` IarGr ft. el a vYU Cnnei 0t, 6~nK Pa. / Orwn ~n0 ~ w R r ~ uernM ~a. YtWhnk. i ~ Yc Mu Ad Q ;:0 2 ~ s tQ r ~ GnOr ~ S ~ i } ~ t . ~ ~ Nel9N M. 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I~ ' . _ ~ ' ~ ~ ` I * 1 11 ~ _ ,f__ i~ . 1• ~ ' Y' ~ . - ,l ~ i{~ 'f t 'it7~~' t~~ ~ ~i~, . ~4 S . NoRr~~url~`~uV I, I;~~j. ; r ~ ~ • ti - . y iy.~~ • ~ Gn [3 n ~ i - ` ~ ,,pr~\_ _ ~ '~r,''.. ~ w ` , i~ ~ ~I ~ . : •M `l ~ el.~~ tti~, 7 \ ~ ~ -Y,_ ~ i -f•w jj ~ t: ~ ~I .y~ v%si. kr . L r 1 S I ~ Weighted Runoff Coefficient Calculation ^ Project: Riverwalk 8th Addition Basin: A IPE Job 96087 ~ Total Area (acres): 0.74 Designer: SKM Imp. Area (acres): 0.28 Date: 04/15 Grass Area (acres): 0.46 Imp. Area "C": 0.90 Grass Area "C": 0.15 - (Imp. Area)(Imp. "C")= 0.2520 ~ (Grass Area)(Grass "C")= 0.0690 0.7400 0.3210 Weighted "C"= 0.3210 0.43 ~ 0.7400 6 ~ r.~ I ` _ I ~ Weighted Runoff Coefficient Calculation ~ Project: Riverwalk 8th Addition Basin: B IPE Job 96087 ^ Total Area (acres): 0.43 Designer: SKM o Imp. Area (acres): 0.19 Date: 04/15 - Grass Area (acres): 0.24 r , Imp. Area "C": 0.90 ' Grass Area "C": 0.15 ~ (Imp. Area)(Imp. "C")= 0.1710 ~ (Grass Area)(Grass "C")= 0.0360 0.4300 0.2070 Weighted "C"= 0.2070 0.48 0.4300 . ~ ; I '_1 Weighted Runoff Coefficient Calculation ~ Project: Riverwalk 8th Addition ~ Basin: C IPE Job 96087 ~ Total Area (acres): 0.75 Designer: SKM Imp. Area (acres): 0.28 Date: 04/15 Grass Area (acres): 0.47 Imp. Area "C": 0.90 Grass Area "C": 0.15 ~ (Imp. Area)(Imp. "C")= 0.2520 _ (Grass Area)(Grass "C")= 0.0705 J 0.7500 0.3225 Weighted "C"= 0.3225 0.43 0.7500 ~ D F- ~ _ Weighted Runoff Coefficient Calculation ~ Project: Riverwalk 8th Addition Basin: D IPE Job 96087 _ Total Area (acres): 0.59 Designer: SKM Imp. Area (acres): 0.26 Date: 04/15 J Grass Area (acres): 0.33 I mp. Area "C": 0.90 Grass Area "C": 0.15 J (Imp. Area)(Imp. "C")= 0.2340 (Grass Area)(Grass "C")= 0.0495 0.5900 0.2835 ~ Weighted "C"= 0.2835 0.48 - 0.5900 ~ a l ~ ~ Weighted Runoff Coefficient Calculation ^ Project: Riverwalk 8th Addition Basin: E IPE Job 96087 Total Area (acres): 0.17 Designer: SKM Imp. Area (acres): 0.08 Date: 04/20 Grass Area (acres): 0.09 Imp. Area "C": 0.90 Grass Area "C": 0.15 ~ (Imp. Area)(Imp. "C")= 0.0720 ~ (Grass Area)(Grass "C")= 0.0135 0.1700 0.0855 Weighted "C"= 0.0855 0.50 ~ 0.1700 o~ ~ fj _S ~ ~ Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: F IPE Job 96087 ~ Total Area (acres): 3.27 Designer: SKM a Imp. Area (acres): 1.09 Date: 05/28 ~ Grass Area (acres): 2.18 - Imp. Area "C": 0.90 Grass Area "C": 0.15 (Imp. Area)(Imp. "C")= 0.9810 - (Grass Area)(Grass "C")= 0.3270 ~ 3.2700 1.3080 Weighted "C"= 1.3080 0.40 3.2700 ~ ~ ~ ~ Weighted Runoff Coefficient Calculation ~ Project: Riverwalk 8th Addition ~ Basin: G IPE Job 96087 Total Area (acres): 1.95 Designer: SKM , _ Imp. Area (acres): 0.74 Date: 05/20. Grass Area (acres): 1.21 ^ Imp. Area "C": 0.90 Grass Area "C": 0.15 , (Imp. Area)(Imp. "C")= 0.6660 e ~ (Grass Area)(Grass "C")= 0.1815 1.9500 0.8475 Weighted "C"= 0.8475 0.43 1.9500 ~ . - ~ . ~ ; . ~ ~ ~ ~ Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition ~-J Basin: FG IPE Job 96087 _ Total Area (acres): 5.22 Designer: SKM Imp. Area (acres): 1.82 Date: 05/28 -Grass Area (acres): 3.40 Imp. Area "C": 0.90 Grass Area "C": 0.15 (Imp. Area)(Imp. "C")= 1.6380 (Grass Area)(Grass "C")= 0.5100 5.2200 2.1480 Weighted "C"= 2.1480 0.41 ~ 5.2200 ~ ~ ~ - ~ ; ~ - Weighted Runoff Coefficient Calculation & Project: Riverwalk 8th Addition . ~ Basin: H ( RuJ (o C.) IPE Job 96087 ~ Total Area (acres): 0.61 Designer: SKM J Imp. Area (acres): 0.25 Date: 05/07 . Grass Area (acres): 0.36 Imp. Area "C": 0.90 _ Grass Area "C": 0.15 ~ (Imp. Area)(Imp. "C")= 0.2250 (Grass Area)(Grass "C")= 0.0540 ~ 0.6100 0.2790 Weighted "C"= 0.2790 0.46 v 0.6100 , - ~ ~ CLJ BOWSTRING METHOD PROJECT: Rivenvalk 8lh Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: A BASIN: A 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0.74 Acres DATE: 04115 Imp. Area 4454 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 5.51 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 10 Area (acres) 0.74 Ct = 0,15 Imperoious Area (sq ft) 4454 L= 60 ft. 'C' Factor 0.43 n= 0.40 '208' Volume Provided 280 S= 0.020 Area * C 0,318 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. intens, Q Devel. Vol.ln Vol.Out Slorage 234 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0 For Z2 5.51 330 3.05 0.97 429 330 99 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3,5 5 300 3.18 1.01 407 300 107 S= 0.012 10 600 224 0.71 508 600 -92 15 900 1.77 0.56 570 900 -330 d= 0.144 ft. 20 1200 1.45 0.46 605 1200 -595 25 1500 1.21 0.39 621 1500 -879 A R Q Tc Tctotal I Qc 30 1e00 1.04 0.33 633 1800 -1167 35 2100 0.91 0.29 641 2100 -1459 0.55 0.01 0.97 2.24 5.51 3.05 0.97 40 2400 0.82 0.26 656 2400 -1744 45 2700 0.74 024 662 2700 -2038 Qpeak for Case 1= 0.97 cfs 50 3000 0.68 0.22 673 3000 -2327 55 3300 0.64 0.20 695 3300 -2605 60 3600 0.61 0.19 721 3600 -2879 CASE 2 65 3900 0.60 0.19 766 3900 -3134 70 4200 0.58 0.18 796 4200 -3404 Case 2 assumes a Time of Concentration less than 5 minutes so that lhe 75 4500 0.56 0.18 822 4500 -3678 peak flow =.90(3.18)(Imp. Area) = 0.29 cfs 80 4800 0.53 0.17 828 4800 -3972 85 5100 0.52 0.17 862 5100 -4238 90 5400 0.50 0.16 877 5400 -4523 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.16 906 5700 -4794 0.97 cfs 100 6000 0,48 0.15 934 6000 -5066 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume = ImpeNious Area x,5 in 112 inlft 186 cu ft 208' Storage Volume Provided 280 cu ft DRYWELL REQUIREMENTS -10 YR. DESIGN STORM Maximum Storage Required by Bowstring 107 cu ft Number and Type of Drywells Required 0 Single 1 Double t--j BOWSTRING METHOD PROJECT: Riverwalk 8th Addiuon PEAK FLOW CALCULATION PROJECT Riverwalk Sth Addition OETENTION BASIN DESIGN BASIN: B BASIN: B 10-Year Design Stortn DESIGNER: S. Murphy Tot. Area 0.43 Acxes DATE: 05l21 Imp. Area 3745 SF C = 0.48 Time Increment (min) 5 CASE 1 Time of Conc, (min) 5.26 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow . 10 Area (acres) 0.43 Ct = 0.15 Impervious Area (sq ft) 3745 L= 60 ft. 'C Factor 0,48 n= 0.40 '208' Volume Provided 175 S= 0.020 Area' C 0.206 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.in Vol.Out Storage 163 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.26 316 3.11 0.64 272 316 -44 72 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.66 264 300 -36 S= 0.008 10 600 2.24 0.46 327 600 -273 15 900 1.77 0.37 368 900 -532 d= 0.133 ft. 20 1200 1.45 0.30 391 1200 -809 25 1500 1.21 0.25 401 1500 -1099 A R Q Tc Tc total I Qc 30 1800 1.04 021 409 1800 -1391 35 2100 0.91 0.19 415 2100 -1685 0.47 0.07 0.64 2.00 5.26 3.11 0.64 40 2400 0.82 0.17 424 2400 -1976 45 2700 0.74 0.15 429 2700 -2271 Qpeak for Case 1= 0.64 cfs 50 3000 0.68 0.14 436 3000 -2564 55 3300 0.64 0.13 450 3300 -2850 60 3600 0.61 0.13 467 3600 -3133 CASE 2 65 3900 0.60 0.12 496 3900 -3404 70 4200 0.58 0.12 516 4200 -3684 Case 2 assumes a Time of Concentration less than 5 minutes so that lhe 75 4500 0.56 0.12 533 4500 -3967 peak flow =.90(3.18)(Imp. Area) = 0.25 cfs 80 4800 0,53 0.11 537 4800 4263 85 5100 0.52 0.11 559 5100 -4541 90 5400 0.50 0.10 568 5400 -4632 So, the Peak flow for the Basin is the greater of the two flaws, 95 5700 0.49 0,10 587 5100 -5113 0.64 cfs 100 6000 0.48 0.10 605 6000 -5395 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in 112 iNft 156 cu ft 208' Storage Volume Provided 187.5 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Borvstring -36 cu ft Number and Type of Drywells Required 0 Single 1 Double BOWSTRING METHOD PROJECT: Rivenxalk 8th Addiuon PEAK FLOW CALCULATION PROJECT Riverwalk Bth Additian DETENTION BASIN DESIGN BASIN: C BASIN: C 10-Year Design Starm DESIGNER: S. Murphy Tot. Area 0.75 Aaes DATE: 05120 Imp. Area 4477 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 5,45 OutBow (cfs) 1 60 ft. Overland Flow Design Year Fiow 10 Area (acxes) 0.75 Ct = 0.15 Impervious Area (sq ft) 4477 L= 60 ft. 'C' Factor 0,43 n= 0.40 '208' Volume Provided 280 S= 0.020 Anea " C 0.323 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol,in Vol.Out Storage 234 ft. Gutter flow (min) (sec) (iNhr) (cfs) (au ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.45 327 3.06 0.99 433 327 106 7-2 = 1 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 1.03 412 300 112 S= 0.012 10 600 224 0.72 514 600 -86 15 900 1.77 0.57 577 900 -323 d= 0.148 ft. 20 1200 1.45 0.47 613 1200 -587 25 1500 1.21 0.39 629 1500 -871 A R Q Tc Tc total I Qc 30 1800 1.04 0.34 641 1800 -1159 35 2100 0.91 029 649 2100 -1451 0,55 0.07 0.99 2.19 5.45 3.06 0.99 40 2400 0.82 0.26 664 2400 -1736 45 2700 0.74 0.24 671 2700 -2029 Qpeak for Case 1= 0.99 cfs 50 3000 0.68 0.22 682 3000 -2318 55 3300 0.64 0.21 704 3300 -2596 60 3600 0.61 0.20 730 3600 -2870 CASE 2 65 3900 0.60 0.19 776 3900 -3124 70 4200 0.58 0.19 806 4200 -3394 Case 2 assumes a Time oi Concentration less lhan 5 minutes so that the 75 4500 0.56 0.18 833 4500 -3667 peak flow =.90(3.18)(Imp. Area) = 0,29 cfs 80 4800 0.53 0.17 839 4800 -3961 85 5100 0.52 0.17 874 5100 -4226 90 5400 0.50 0.16 889 5400 -4511 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.16 918 5700 -4782 0.99 cfs 100 6000 0.48 0.15 946 6000 -5054 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in 112 iNR 187 cu ft 208' Storage Volume Provided 280 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 112 cu ft Number and Type of Drywells Required 0 Single 1 Double ( 1(~ 1 I ) f 1~ j l~~ 4 f IC~ f l~~~ f 1;~ 4 J( 1( I f 1 BOWSTRING METHOD PROJECT; Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk Sth Addition DETENTION BASIN DESIGN BASIN: D BASIN: D 10-Year Design Sto►m DESIGNER: S. Murphy Tot. Area 0.59 Acres DATE: 05120 Imp. Area 5643 SF C = 0.48 Time Incremenl (min) 5 CASE 1 Time of Conc. (min) 5.60 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 10 Area (acres) 0.59 Ct = 0.15 Impervious Area (sq ft) 5643 L= 60 ft. 'C' Factor 0.48 n= 0.40 '208' Volume Provided 254 S= 0.020 Area * C 0.283 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 205 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.60 336 3.02 0.85 385 336 49 7-2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.90 362 300 62 S= 0.008 10 600 2.24 0.63 453 600 -147 15 900 1.77 0.50 508 900 -392 d= 0.148 ft. 20 1200 1.45 0.41 540 1200 -660 25 1500 1.21 0.34 553 1500 -947 A R Q Tc Tc total I Qc 30 1800 1.04 0.29 564 1800 -1236 - 35 2100 0.91 0.26 571 2100 -1529 0.58 0.07 0.85 2.34 5.60 3.02 0.85 40 2400 0.82 0,23 584 2400 -1816 45 2700 0.74 0.21 590 2700 -2110 Qpeak for Case 1= 0.85 cfs ' 50 3000 0.68 0.19 600 3000 -2400 55 3300 0,64 0.18 619 3300 -2681 60 3600 0.61 0.17 642 3600 -2958 CASE 2 65 3900 0,60 0.17 682 3900 -3218 70 4200 0.58 0.16 709 4200 -3491 Case 2 assumes a Time of Cancentraaon less than 5 minutes so that the 75 4500 0.56 0.16 732 4500 -3768 peak flow =.90(3,18)(Imp. Area) = 0.37 cfs 80 4800 0.53 0.15 • 738 4800 -4062 85 5100 0.52 0.15 768 5100 -4332 90 5400 0.50 0.14 781 5400 -4619 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.14 807 5700 -4893 0.85 cfs 100 6000 0.48 0.14 831 6000 -5169 208' DRAINAGE POND CALCULATIONS Required'208' Starage Volume = Imperoious Area x.5 in I 12 inlft 235 cu ft 206' Storage Volume Provided 254 cu ft DRYWELL REQUIREMENTS • 10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 62 cu ft Number and Type of Drywells Required 0 Single 1 Double ) I ~ ( ) f 1 I l ~ ~ ~ ~ ~l { 1 l ~ i 1 ~ ~ I l f 1 I ~ ( 1 f 1 ( I BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Rivenwalk 8th Addition DETENTION BASIN DESIGN BASIN: E BASIN: E 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0.17 , DATE: 05120 Imp, Area 3269 SF C = 0.50 Time Increment (min) 5 CASE 1 Time af Conc. (min) 5.00 OutBow (cfs) 0.3 40 ft. Overland Flow Design Year Flow 10 Area (acres) 0.17 Ct = 0.15 Impervious Area (sq ft) 3269 L= 40 ft. 'C' Factor 0.5 n= 0.40 '208' Volume Provided 170 S= 0.020 Area ` C 0.085 Tc = 2.56 min., by Equation 3-2 af Guidelines . Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 138 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.00 300 3.18 0.27 109 90 19 Z2 = 1 Type B =1,0 n= 0.016 Ralled = 3.5 5 300 3.18 0.27 109 90 19 S= 0.008 10 600 2.24 0.19 134 180 -06 15 900 1.77 0.15 151 270 -119 d= 0.098 ft. 20 1200 1,45 0.12 160 360 -200 25 1500 1.21 0.10 165 450 -285 A R Q Tc Tc total I Qc 30 1800 1.04 0.09 168 540 -372 35 2100 0,91 0.08 170 630 -460 0.24 0.05 0.27 2.07 5.00 3.16 0.27 40 2400 0.82 0.07 174 720 -546 45 2700 0.74 0.06 176 810 -634 Qpeak for Case 1= 0.27 cfs 50 3000 0.68 0.06 179 900 -721 55 3300 0.64 0.05 165 990 -805 60 3600 0.61 0.05 192 1080 -888 CASE 2 65 3900 0.60 0.05 204 1170 -966 70 4200 0.58 0.05 212 1260 -1048 Case 2 assumes a Time of Concentrabon less than 5 minutes so that lhe 75 4500 0.56 0.05 219 1350 -1131 peak flow =.90(3.18)(Imp. Area) = 0.21 cfs 80 4800 0.53 0,05 221 1440 -1219 85 ' 5100 0.52 0.04 230 1530 -1300 90 5400 0.50 0.04 234 1620 -1386 So, the Peak flow for the Basin is the greater of lhe two flows, 95 5700 0.49 0,04 242 1710 -1468 0.27 cfs 100 6000 0.48 0,04 249 1800 -1551 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in I 12 inlfl 136 cu ft 208' Storage Volume Provided 170 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstnng 19 cu ft Number and Type of Orywells Required 1 Single 0 Double 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th AddiGon DETENTION BASIN DESIGN BASIN: F BASIN: F DESIGNER: S. Murphy Tot. Area 3.27 Acres DATE: 06125 Imp. Area 17615 SF C = 0.41 Time Increment (min) 5 CASE 1 Time of Conc. (min) 11.09 Outflow (cfs) 0 120 ft. Ovedand Flow Design Year Flow 50 Area (aaes) 3.27 Ct = 0.15 Impenrious Area (sq ft) 17615 L= 120 ft, 'C' Factor 0.41 n= 0.40 50-year Volume Provided 1834 S= 0.020 Area' C 1.341 Tc = 4.95 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 950 fl. Gutter flow (min) (sec) (in/hr) (cfs) (cu ft) (cu ft) (cu ft) ' Z1= 50.0 11,09 666 3,03 4.06 3622 0 3622 Z2 = 3.5 n= 0.016 5 300 4.58 6.14 2468 0 2468 S= 0.013 10 600 3.20 4.29 3449 0 3449 15 900 2.45 3.28 3700 0 3700 d= 0.243 ft. 20 1200 1.95 2.61 3729 0 3729 25 1500 1,62 2.17 3749 0 3749 A R Q Tc Tc total I Qc 30 1800 1.56 2.09 4238 0 4238 35 2100 1.28 1.72 3992 0 3992 1.51 0.12 4.06 6.14 11.09 3.03 4.06 40 2400 1.19 1.59 4172 0 4172 45 2700 1.08 1.45 4231 0 4237 Qpeak for Case 1= 4.06 cfs ' 50 3000 0.99 1.33 4282 0 4282 55 3300 0,92 1.23 4350 0 4350 60 3600 0.87 1.17 4463 0 4463 CASE 2 65 3900 0.82 1.10 4536 0 4536 70 4200 0.80 1.07 4747 0 4747 Case 2 assumes a Time of Concentration less than 5 minutes so that lhe 75 4500 0.77 1.03 4879 0 4879 peak flow =.90(4,58)(Imp. Area) = 1.67 cfs 80 4800 0.75 1.01 5054 0 5054 85 5100 0.72 0.97 5142 0 5142 90 5400 0.71 0.95 5356 0 5356 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.93 5482 0 5482 4.06 cfs 100 6000 0.67 0.90 5593 0 5593 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impenrious Area x.5 in 112 in/ft 734 cu ft 50 year Volume Provided 1834 cu ft , DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 5142 cu ft Number and Type of Drywells Required 0 Single ERR Double INLAND PACIFIC ENGINEERING t~1 f~~~J I 1 I i I l Ie I 1 E)( 1 i. _J I I~ i, i 1 I 1 BOWSTRING METH00 PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk Sth AddiUon DETENTION BASIN DESIGN BASIN: G BASIN: G 10-Year Design Stonn DESIGNER: S. Murphy Tot. Area 1.95 Acres DATE: 05120 Imp. Area 13418 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.82 Outflow (cfs) 0 60 ft. Overland Flow Design Year Flow 10 , , Area (aaes) 1.95 Ct = 0.15 Impervious Area (sq ft) 13418 L= 60 ft. 'C Factor 0.43 n= 0.40 '208' Volume Provided 341 S= 0.020 Area " C 0.839 Tc = 3.27 min., by Equation 3-2 of Guidelines" Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storege 600 ft. Gutter flow (min) (sec) (inmr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 ForZ2 7.82 469 2.54 2.13 1341 0 1341 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 2.61 1072 0 1072 S= 0.013 10 600 2.24 1.88 1427 0 1427 15 900 1,77 1.48 1573 0 1573 d= 0.191 fl. 20 1200 1.45 1,22 1653 0 1653 25 1500 121 1.01 1684 0 1684 A R Q Tc Tc total I Qc 30 1800 1.04 0.87 1709 0 1709 35 2100 0.91 0,76 1724 0 1724 0.97 0.09 2.13 4.56 7,82 2,54 2.13 40 2400 0.82 0.69 1760 0 1760 45 2700 0.74 0.62 1774 0 1174 Qpeak tor Case 1= 2.13, cfs , . 50 3000 0.68 0.57 1802 0 1802 55 3300 0.64 0.54 1857 0 1857 60 3600 0.61 0.51 1923 0 1923 CASE 2 65 3900 0.60 0.50 2042 0 2042 70 4200 0.58 0.49 2120 0 2120 Case 2 assumes a Time of Concentrafion less than 5 minutes so that the 75 4500 0.56 0.47 2188 0 2188 peak flow =.90(3.18)(Imp. Area) = 0,88 cfs 80 4800 0.53 0.44 2204 0 2204 85 5100 0.52 0.44 2293 0 2293 90 5400 0.50 0.42 2331 0 2331 So, the Peak flow for the Basin is the greater of lhe iwo flows, 95 5700 0.49 0.41 2408 0 2408 2.13 cfs 100 6000 0.48 0.40 2479 0 2479 208' DRAINAGE POND CALCUlATIONS Required'20S' Storage Volume , = Imperoious Area x.5 in 112 iNft 559 cu ft . 208' Storage Volume Provided 341 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM ' Maximum Storage Required by Bowstring 2293 cu ft „ Number and Type of Drywells Required 0 Single ERR Double , ( J ~ ( I ( I I J ( ~ ( ~ ( i 1 I 1 ! J ( I I j [ l [ 1 BOWSTRING METHOD PROJECT: Riverrvalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: FG BASIN: FG 10-Year Oesign Storm DESIGNER: S. Murphy Tot. Area 5.22 Aaes DATE: 06125 Imp. Area 31033 SF C = 0.41 Time Inaement (min) 5 CASE 1 Time of Conc. (min) 10.91 Outflow (cfs) 3 120 ft. Overland Flow . Design Year Flow 10 Area (acres) 5.22 Ct = 0.15 Impervious Area (sq ft) 31033 L= 120 ft. 'C' Factor 0.41 n= 0.40 '208' Volume Provided 2175 S= 0.020 Area * C 2.144 Tc = 4,95 min., by Equation 3-2 af Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 950 ft. Gutter Aow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50,0 ForZ2 10,91 655 2.14 4.58 4016 1964 2052 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 6.81 2736 900 1636 S= 0.013 10 600 2.24 4.79 3854 1800 2054 15 900 1.77 3.79 4253 2700 1553 d= 0.254 ft. 20 1200 1.45 3.10 4415 3600 815 25 1500 1.21 2.59 4461 4500 -39 A R Q Tc Tc total I Qc 30 1800 1.04 2.23 4502 5400 -698 35 2100 0.91 1.95 4523 6300 -1777 1.72 0.13 4.58 5.96 10.91 2.14 4.58 40 2400 0.82 1.75 4603 7200 -2597 45 2700 0.74 1.58 4629 8100 -3471 Qpeak for Case 1= 4.58 cfs 50 3000 0.68 1,46 4690 9000 -4310 55 3300 0.64 1.37 4825 9900 -5075 60 3600 0.61 1,31 4990 10800 -5810 CASE 2 65 3900 0.60 1.28 5294 11700 -6406 70 4200 0.58 1.24 5490 12600 -7110 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 1.20 5660 13500 -7840 peak flow =.90(3.18)(Imp. Area) = 2.04 cfs 80 4800 0.53 1,13 5697 14400 -8703 85 5100 0.52 1.11 5924 15300 -9376 90 5400 0.50 1.07 6017 16200 -10183 So, the Peak 8ow for the Basin is the greater of the two flows, 95 5700 0.49 1.05 6211 17100 -10889 4.58 cfs 100 6000 0.48 1.03 6392 18000 -11608 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in I 12 inlft 1293 cu ft 208' Storage Volume Provided 2175 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 2054 cu ft Number and Type of Drywells Required 0 Single 3 Double BOWSTRING METH00 PROJECT: Riverwalk 8th Addi ion PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN OESIGN BASIN: H~RU1lo~ BASIN: H 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0.61 Acres DATE: 04120 Imp. Area 5373 SF C = 0,46 Time Increment (min) 5 CASE 1 Time of Conc, (min) 7.01 Outflow (cfs) 1 75 ft. Overland Flow Design Year Flow 10 Area (acres) 0.61 Ct = 0.15 Impenrious Area (sq fl) 5373 L= 75 ft. 'C' Factor 0.46 n= 0.40 '208' Volume Provided 387 S= 0.010 Area " C 0.281 Tc = 4.60 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol,ln Vol.Out Storage 225 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0 ForZ2 1.01 421 2,68 0.75 424 421 3 Z2= 1 TypeB=1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.89 359 300 59 S= 0.010 10 600 2.24 0,63 467 600 -133 15 900 1.77 0,50 518 900 -382 d= 0.138 ft. 20 1200 1.45 0.41 546 1200 -654 25 1500 121 0,34 558 1500 -942 A R Q Tc Tc total I ' Qc 30 1800 1.04 0.29 567 1800 -1233 35 2100 0.91 0.26 573 2100 -1527 0.48 0.07 0.75 2.41 7.01 2.68 0.75 40 2400 0.82 0.23 585 2400 -1815 45 2700 0.74 0.21 590 2700 -2110 Qpeak for Case 1= 0.75 cfs 50 3000 0.68 0.19 600 3000 -2400 55 3300 0.64 0.18 618 3300 -2682 60 3600 0.61 0.17 641 3600 -2959 CASE 2 65 3900 0.60 0.17 681 3900 -3219 70 4200 0.58 0.16 707 4200 -3493 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.56 0.16 730 4500 -3770 peak flow =.90(3.18)(Imp. Area) = 0.35 cfs 80 4800 0.53 0.15 735 4800 -4065 85 5100 0.52 0.15 765 5100 -0335 90 5400 0.50 0.14 778 5400 -4622 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.14 803 5700 -4897 0.75 cfs 100 6000 0.48 0.13 827 6000 -5173 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume = Impervious Area x.5 in I 12 inlft 224 cu ft 208' Storage Volume Provided 387 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 59 cu ft Number and Type of Dryweils Required 0 Single 1 Double 50-year STORM BOWSTRING METH00 PROJECT: Rivernralk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk Sth Addition DETENTION BASIN DESIGN BASIN: A BASIN: A DESIGNER: S. Murphy Tot. Area 0.74 Acres DATE: 05123 Imp. Area 4454 SF C = 0.43 Time Inaement (min) 5 CASE 1 Time of Conc. (min) 528 Outilaw (cfs) 1 60 ft. Overland Flow Design Year Flow 50 Area (acres) 0.74 Ct = 0.15 Impervious Area (sq fl) 4454 L= 60 ft. 'C' Faclor 0.43 n= 0.40 50-yearValume Provided 280 S= 0.020 Area' C 0.318 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol.ln Vol.Out Storage 234 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50,0 5.28 317 4.48 1.43 605 317 289 Z2 = 3.5 n= 0.016 5 300 4.58 1.46 586 300 286 S= 0.012 10 600 3.20 1,02 721 600 121 15 900 2.45 0.78 766 900 -114 d= 0.166 ft. 20 1200 1.95 0.62 811 1200 -389 25 1500 1.62 0.52 829 1500 -671 A R Q Tc Tc latal I Qc 30 1800 1.56 0.50 947 1800 -853 35 2100 1.28 0.41 899 2100 -1201 0.74 0.08 1.43 2.01 5.28 4.48 1.43 40 2400 1.19 0.38 946 2400 -1454 45 2700 1.06 0.34 965 2700 -1735 Qpeak for Case 1= 1.43 cfs ' 50 3000 0.99 0.32 979 3000 -2021 55 3300 0.92 0.29 998 3300 -2302 60 3600 0.67 0.28 1026 3600 -2574 CASE 2 65 3900 0.62 0.26 1046 3900 -2854 70 4200 0.60 0.25 1097 4200 -3103 Case 2 assumes a Time of Concentration less lhan 5 minutes so thal lhe 75 4500 0.71 025 1129 4500 -3371 peak flow =.90(4.58)(Imp. Area) = 0.42 cfs 80 4800 0.15 0.24 1171 4800 -3629 85 5100 0.72 023 1193 5100 -3907 90 5400 0.71 023 1244 5400 -4156 So, the Peak flow for the Basin is the greater of the lwo flows, 95 5700 0,69 022 1275 5100 -4425 1.43 cfs 100 6000 0.67 0.21 1302 6000 4698 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in 112 inlft 186 cu ft 50 year Volume Provided 280 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Sforage Required by Bowstring 289 cu ft Number and Type of Drywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING ~ I 1L 1 i 1 l j lml C7::j f° Y"'`jo ,07 I ?~l f~ f 1 i I Z 1I ) I )(____J 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 81h Addition PEAK FLOW CALCULATION PROJECT Rive►walk 8th Addition DETENTION BASIN DESIGN BASIN: B BASIN: B DESIGNER; S. Murphy Tot. Area 0.43 Acres DATE: 05123 Imp. Area 3745 SF C = 0.48 Time Increment (min) 5 CASE 1 Time of Conc. (min) 5,08 Outflow (cfs) 1 60 ft. Overland Fiow Design Year Flow 50 Area (acres) 0.43 Ct = 0.15 Impervious Area (sq ft) 3745 L= 60 ft. 'C' Factor 0.48 n= 0.40 50-year Volume Provided 175 S= 0.020 Area " C 0206 Tc = 3.27 min,, by Equation 3-2 of Guidelines Time Time Inc, Intens, Q Devel, Vol.ln Vol,Oui Storage 163 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 5.08 305 4,55 0.94 364 305 79 Z2 = 3.5 n= 0.016 5 300 4.58 0.95 380 300 60 S= 0.008 10 600 3.20 0.66 465 600 -135 15 900 2.45 0.51 508 900 -392 d= 0.153 ft. 20 1200 1.95 0.40 525 1200 -675 25 1500 1.62 0.33 536 1500 -964 A R Q Tc Tc total I Qc 30 1800 1.56 0.32 613 1800 -1187 35 2100 1.28 0.26 582 2100 -1518 0,63 0.08 0.94 1.81 5.08 4.55 0.94 40 2400 1.19 0.24 612 2400 -1788 45 2700 1.08 0.22 625 2700 -2075 Qpeak for Case 1= 0.94 cfs 50 3000 0.99 0.20 634 3000 -2366 55 3300 0.92 0.19 646 3300 -2654 60 3600 0.87 0.18 665 3600 -2935 CASE 2 65 3900 0.82 0.17 678 3900 -3222 70 4200 0.80 0.17 711 4200 -3489 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.16 732 4500 •3768 peak flow =.90(4.58)(Imp. Area) = 0.35 cfs 80 4800 0.75 0.15 759 4800 -4041 85 5100 0.72 0.15 773 5100 -4327 90 5400 0.71 0.15 807 5400 -4593 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.14 827 5700 -4873 0.94 cfs 100 6000 0.67 0.14 844 6000 -5156 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in I 12 iNft 156 cu ft 50 year Volume Provided 187.5 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 80 cu ft Number and Type of Drywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING ~ ~ i i l I 1 ( 1 S 01 ~ ~ ~ I _n J ( I l ~ 4 1 ~ ( I f ) 50-year STORM BOWSTRING METH00 PROJECT: Rivenvalk.6th Addition PFAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: C BASIN: C DESIGNER: S. Murphy Tot, Area 0.75 Acres DATE: 05123 Imp. Area 4477 SF C = 0.43 Time Inaement (min) 5 CASE 1 Time of Conc. (min) 5.27 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 50 Area (acres) 0.75 Ct = 0.15 Impervious Area (sq ft) 4477 L= 60 ft. 'C' Factor 0.43 n= 0.40 50-year Volume Provided 280 S= 0.020 Area' C 0.323 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol.ln Vol.Out Storage 234 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0 5.27 316 4.49 1.45 613 316 297 Z2 = 3.5 n= 0.016 5 300 4.58 1.48 594 300 294 S= 0.012 10 600 3.20 1.03 730 600 130 15 900 2.45 0.79 796 900 -104 d= 0.167 ft, 20 1200 1.95 0.63 822 1200 -378 25 1500 1.62 0.52 840 1500 -660 A R Q Tc Tc total I Qc 30 1800 1.56 0.50 960 1800 -840 35 2100 1.28 0,41 911 2100 -1189 0.75 0.08 1.45 2.00 5.21 4.49 1.45 40 2400 1.19 0,38 958 2400 -1442 45 2700 1.08 0.35 978 2700 -1722 Qpeak for Case 1= 1.45 cfs 50 3000 0.99 0.32 992 3000 -2008 55 3300 0.92 0.30 1011 3300 -2289 60 3600 0.87 0.28 1040 3600 -2560 CASE 2 65 3900 0.82 0.26 1060 3900 -2840 70 4200 0.80 0.26 1111 4200 -3089 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.25 1144 4500 -3356 peak flaw =.90(4.58)(Imp. Area) = 0.42 cfs 80 4800 0.75 0.24 1187 4800 -3613 85 5100 0,72 0.23 1209 5100 -3891 90 5400 0,71 0.23 1261 5400 -4139 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.22 1292 5700 -4408 1.45 cfs 100 6000 0,67 0.22 1320 6000 -4680 208' ORAINAGE POND CALCULATIONS Required'208' Storage Volume . = Impenrious Area x.5 in 112 iNft 187 cu ft 50 year Volume Provided 280 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STOR Maximum Storage Required by Bowstring 297 cu ft Number and Type of Orywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: D BASIN: D DESIGNER: S. Murphy Tot. Area 0.59 Acxes DATE: 05/23 Imp. Area 5643 SF C = 0.48 Time Increment (min) 5 CASE 1 Time of Cqnc. (min) 5.38 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 50 Area (acres) 0.59 Ct = 0.15 Impervious Area (sq ft) 5643 L= 60 fl. 'C' Factor 0.48 n= 0.40 50-year Volume Provided 254 S= 0.020 Area " C 0,283 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devei. Vol.ln Vol.Out Storage 205 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) - Z1= 50.0 5.38 323 4.45 1.26 545 323 222 Z2 = 3.5 n= 0.016 5 300 4.58 1.30 521 300 221 S= 0.006 10 600 3.20 0.91 643 600 43 15 900 2.45 0.69 701 900 -199 d= 0.171 ft. 20 1200 1.95 0.55 723 1200 -417 25 1500 1.62 0.46 739 1500 -761 A R Q Tc Tc total I Qc 30 1800 1.56 0.44 844 1800 -956 35 2100 1.28 0.36 801 2100 -1299 0.78 0.09 1.26 2.12 5.38 4.45 1.26 40 2400 1.19 0.34 842 2400 -1558 45 2700 1.08 0.31 859 2700 -1841 Qpeak for Case 1= 1.26 cfs ' 50 3000 0.99 0.26 872 3000 -2128 55 3300 0.92 0.26 888 3300 -2412 60 3600 0.87 0.25 914 3600 -2686 CASE 2 65 3900 0.82 0.23 931 3900 -2969 70 4200 0.80 0.23 976 4200 -3224 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.22 1005 4500 -3495 peak flow =.90(4.58)(Imp. Area) = 0,53 cfs 80 4800 0.75 0.21 1043 4800 -3757 85 5100 0.72 0.20 1062 5100 -4038 90 5400 0.71 0.20 1108 5400 -4292 So, lhe Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 OZO 1135 5700 -4565 1.26 cfs 100 6000 0.67 0,19 1159 6000 -4841 208' DRAINAGE POND CALCULATIQNS Required'208' Storage Volume = Impervious Area x.5 in ! 12 iNft 235 cu ft 50 year Volume Provided 254 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 222 cu ft Number and Type of Drywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT; Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk Sth Addition DETENTION BASIN DESIGN BASIN: E BASIN: E DESIGNER: S. Murphy Tot. Area 0.17 Acres DATE: 05123 Imp. Area 3269 SF C = 0.50 Time Increment (min) 5 CASE 1 Time of Conc. (min) 5.00 Outflow (cis) 0.3 40 ft. Overland Flow Design Year Flow 50 Area (acres) 0.17 Ct = 0.15 Impervious Area (sq ft) : 3269 L= 40 ft. 'C' Factor 0.5 n= 0,40 50-year Volume Provided 170 S= 0,020 Area " C 0,085 Tc = 2.56 min., by EquaGon 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 138 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 5.00 300 4.58 0.39 156 90 66 Z2 = 1 n= 0,016 5 300 4.58 0.39 156 90 66 S= 0.008 10 600 3.20 0.27 191 180 11 15 900 2.45 0.21 209 270 1 -61 d= 0.112 ft. 20 1200 1.95 0.17 216 360 -144 25 1500 1.62 0.14 221 450 -229 A R Q Tc Tc total I Qc 30 1800 1.56 0.13 252 540 •288 35 2100 1.28 0.11 240 630 -390 0.32 0.06 0.39 1.90 5.00 4.58 0.39 40 2400 1.19 0.10 252 720 468 45 2700 1.08 0.09 257 810 -553 Qpeak for Case 1= 0.39 cfs 50 3000 0.99 0.08 261 900 -639 55 3300• 0.92 0.08 266 990 -724 60 3600 0.87 0.07 274 1080 -806 CASE 2 65 3900 0.82 0.07 279 1170 -891 70 4200 0.80 0.07 293 1260 -967 Case 2 assumes a Time of Concentration less than 5 minutes so that the 15 4500 0.77 0.07 301 1350 -1049 peak flow =.90(4.58)(Imp. Area) = 0.31 cfs 80 4800 0.75 0.06 313 1440 -1127 85 5100 0.72 0.06 318 1530 -1212 90 5400 0.71 0.06 332 1620 -1288 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.06 340 1710 -1370 0.39 cfs 100 6000 0.67 0.06 348 1800 -1452 208' DRAINAGE POND CALCULATIONS ' Required'208' Storage Volume = Impervious Area x.5 in I 12 inlft 136 cu ft 50 year Volume Provided 170 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 66 cu ft Number and Type of Drywells Required 1 Single 0 Double INLAND PACIFIC ENGINEERING ~ ( l I 1 I l ~ 1 4 1 { 1 C~3 ~ 1 l 01 ~ ~ ( ~ ~ 1 l ) ( ~ ~ 1 1 1 BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: F BASIN: F 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 3.27 Acres DATE: 06125 Imp. Area 17615 SF C = 0.41 Time Increment (min) 5 CASE 1 Time of Conc. (min) 11.72 Outflow (cfs) 0 120 ft. Overiand Flow Design Year Flow 10 Area (acres) 3.27 Ct = 0.15 Impervious Area (sq ft) 17615 L= 120 ft. 'C' Factor 0.41 n= 0.40 '208' Volume Provided 1834 S= 0.020 Area' C 1.341 Tc = 4.95 min., by Equation 3-2 of Guidelines Time Time Inc, Intens. Q Devel. Vol,ln Vol.Out Storage 950 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 11.72 703 2.05 2.75 2591 0 2591 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 4.26 1714 0 1114 S= 0,013 10 600 2.24 3.00 2415 0 2415 15 900 1.77 2.37 2703 0 2703 d= 0.210 ft. 20 1200 1.45 1.94 2198 0 2798 25 1500 1.21 1.62 2821 0 2821 A R Q Tc Tc total • I Qc 30 1800 1.04 1.39 2843 0 2843 35 2100 0.91 1.22 2854 0 2854 1.18 0.10 2.75 6.77 11.72 2.05 2.75 40 2400 0.82 1.10 2901 0 2901 45 2700 0.74 0.99 2916 0 2916 Qpeak for Case 1= 2.75 cfs 50 3000 0.68 0,91 2953 0 2953 55 3300 0.64 0.86 3037 0 3037 60 3600 0.61 0.82 3140 0 3140 CASE 2 65 3900 0.60 0.80 3330 0 3330 70 4200 0.58 0.78 3452 0 3452 Case 2 assumes a Time of ConcenVation less than 5 minutes so thal the 75 4500 0.56 0.75 3558 0 3558 peak flow =.90(3.18)(Imp. Area) = 1.16 cis 80 4800 0.53 0.71 3581 0 3581 85 5100 0.52 0.70 3722 0 3722 90 5400 0.50 0.67 3780 0 3180 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.66 3902 0 3902 2.75 cfs 100 6000 0.48 0.64 4015 0 4015 208' ORAINAGE POND CALCULATIONS • Required'208' Storage Volume ' = Imperoious Area x.5 in ! 12 in/ft 734 cu ft 208' Storage Volume Provided 1834 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 3722 cu ft Number and Type of Drywells Required 0 Single ERR Doub►e 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Adtlition DETENTION BASIN DESIGN BASIN: G BASIN: G DESIGNER: S. Murphy Tot. Area 1.95 Acres DATE: 06/25 Imp. Area 13418 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.40 Outflow (cfs) 0 60 ft. Overiand Flow Design Year Flow 50 Area (acres) 1.95 Ct = 0.15 Impervious Area (sq ft) 13418 L= 60 ft. 'C Factor 0.43 n= 0.40 50-year Volume Provided 341 S= 0.020 Area * C 0.839 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol.ln Vol.Out Storage 600 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 7,40 444 3.75 3.15 1872 0 1872 Z2 = 3.5 n= 0.016 5 300 4.58 3,84 1544 0 1544 S= 0.013 10 600 3.20 2,68 2015 0 2015 15 900 2.45 2.05 2159 0 2159 d= 0,221 ft. 20 1200 1.95 1,64 2209 0 2209 25 1500 1.62 1.36 2243 0 2243 A R Q Tc Tc total I Qc 30 1800 1.56 1.31 2552 0 2552 35 2100 1.28 1.07 2416 0 2416 1.30 0.11 3.15 4.13 7.40 3.75 3.15 40 2400 1.19 0.99 2535 0 2535 45 2700 1.06 0.91 2582 0 2582 Qpeak for Case 1= 3.15 cfs 50 3000 0.99 0.83 2616 0 2616 55 3300 0.92 0.77 2662 0 2662 60 3600 0.87 0.73 2736 0 2736 CASE 2 65 3900 0.82 0.69 2785 0 2785 70 4200 0.80 0.67 2919 0 2919 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.65 3003 0 3003 peak flow =.90(4.58)(Imp. Area) = 1.27 cfs 80 4800 0.15 0.63 3114 0 3114 85 5100 0.72 0.60 3170 0 3170 90 5400 0,71 0.60 3305 0 3305 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.58 3385 0 3385 3.15 cfs 100 6000 0.67 0.56 3456 0 3456 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume = Impervious Area x.5 in ! 12 inlft 559 cu ft 50 year Volume Provided 341 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 3170 cu ft Number and Type of Drywells Required 0 Single ERR Double INlANO PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: FG BASIN; FG OESIGNER: S. Murphy Tot. Area 5.22 Acres DATE: 06125 imp. Area 31033 SF C = 0.41 Time Inaement (min) 5 CASE 1 Time of Conc. (min) 10.36 Outflow (cfs) 3 120 ft. Overland Flow Design Year Flow 50 Area (acres) 5,22 - Ct = 0.15 Impervious Area (sq ft) 31033 L= 120 ft, 'C' Factor 0.41 n= 0.40 50-year Volume Provided 2175 S= 0.020 Area ` C 2.140 Tc = 4.95 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Voi.Out Storage 950 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu fl) (cu ft) Z1 = 50.0 10.36 622 3.14 6.13 5605 1865 3740 Z2 = 3,5 n= 0,016 5 300 4.58 9.80 3940 900 3040 S= 0.013 10 600 320 6.85 5506 1800 3106 15 900 2.45 5.24 5828 2700 3128 d= 0.293 ft. 20 1200 1.95 4.17 5890 3600 2290 25 1500 1,62 3.47 5934 4500 1434 A R Q Tc Tc total I Qc 30 1800 1.56 3.34 6716 5400 1316 35 2100 1.28 2.74 6332 6300 32 2.30 0.15 6.73 5,41 10,36 3,14 6,73 40 2400 1.19 2.54 6623 7200 -517 45 2700 1.08 2.31 6729 8100 -1371 Qpeak for Case 1= 6,73 cfs 50 3000 0.99 2.12 6804 9000 -2196 55 3300 0.92 1.97 6914 9900 -2986 60 3600 0.87 1.86 7097 10800 -3703 CASE 2 65 3900 0.82 1.75 7215 11700 -4485 70 4200 0.80 1.71 1553 12600 -5047 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 1.65 7164 13500 -5736 peak flow =,90(4.58)(Imp. Area) = 2.94 cfs 80 4800 0.75 1.61 8044 14400 -6356 85 5100 0.72 1.54 8185 15300 -7115 90 5400 0.71 1.52 8527 16200 -7673 So, the Peak flow for the Basin is lhe greater of the two flows, 95 5700 0.69 1.48 8730 17100 -8370 6.73 cfs ' 100 6000 0.67 1.43 8907 18000 -9093 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume = ImpeNious Area x.5 in I 12 in/ft 1293 cu ft 50 year Volume Provided 2175 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STOR Maximum Storage Required by Bowstring 3740 cu ft Number and Type o( Drywells Required 0 Single 3 Double INLAND PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: H BASIN: HDESIGNER: S. Murphy Tot. Area 0.61 Acres DATE: 04120 Imp. Area 5373 SF C = 0.46 Time Increment (min) 5 CASE 1 Time of Conc. (min) 6.78 Outflow (cfs) 1 75 ft. Overland Flow Design Year Flow 50 Area (acres) 0.61 Ct = 0.15 Impervious Area (sq ft) 5373 L= 75 ft. 'C' Factor 0.46 n= 0.40 50-year Volume Provided 387 S= 0.010 Area " C 0.281 Tc = 4.60 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 225 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu fl) (cu ft) (cu fl) Z1 = 50,0 6.78 407 3.97 1.11 607 407 200 Z2 = 1 n= 0.016 5 300 4.58 1.29 517 300 217 S= 0.010 10 600 3.20 0.90 663 600 63 15 900 2.45 0.69 714 900 -186 d= 0.160 ft. 20 1200 1.95 0.55 732 1200 -468 25 1500 1.62 0.45 745 1500 -755 A R Q Tc Tc total I Qc 30 1800 1.56 0.44 848 1800 -952 35 2100 1.28 0.36 804 2100 -1296 O.fiS 0.08 1,11 2.19 6.78 3.97 1.11 40 2400 1.19 0.33 844 2400 -1556 45 2700 1,08 0.30 860 2700 -1840 Qpeak for Case 1= 1.11 cfs 50 3000 0.99 0.28 872 3000 -2126 55 3300 0.92 0.26 888 3300 -2412 60 3600 0.81 0.24 913 3600 -2687 CASE 2 65 3900 0.82 0.23 929 3900 -2971 70 4200 0.80 0.22 974 4200 -3226 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.22 1002 4500 -3498 peak flow =.90(4.58)(Imp, Area) = 0.51 cfs 80 4800 0.75 0.21 1039 4800 -3761 85 5100 0.72 0.20 1058 5100 4042 90 5400 0.71 0.20 1103 5400 -4297 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0,69 0.19 1130 5700 4570 1.11 cfs 100 6000 0,67 0.19 1154 6000 4846 208' DRAINAGE PONO CALCULATIONS Required'208' Storage Volume = Imperoious Area x.5 in ! 12 iNft 224 cu ft 50 year Volume Provided 387 cu ft ORYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 217 cu ft Number and Type of Drywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING f 1 I l~~ I 1~ 1~ I„~ ~~6~ ~C~ (J I, 1~~ I 1 l n I f► I l I~ l 1 208' Pond Calculations Project: Riverwalk 8th Addition Date: 25-Jun-97 Designer: S. Murphy . Upstream Carryover Accumul. Pond '208' '208' Curb Drop Imper. Storage Storage Storage Typel Storage Carryover Sub-Basin Station R/L Area Req't Req't Req't Size Providetl Downstream A 18+20 L 4454 185.6 185.6 28 x20 280.0 B 13+20 L 3745 156.0 156.0 Odd 187.5 C 18+20 R 4477 186.5 186.5 28x20 280.0 D 12+40 L 5643 235.1 235.1 Odd 254.0 E 10+53 R 3269 136.2 136.2 Odd 170.0 F 20+24 R 17615 734.0 734.0 Odd 1834.0 G 20+00 L 13418 559.1 559.1 Odd 341.0 ` Calculated per Figure 18 of Guidelines Calculated per Figure 16 of Guidelines A 4 foot curb drop with a 6" gutter has a capacity of 4.0 cfs in sump condition. ~ C~7 l ) I 1( J I1( 1 I~ ( 1( ~ I } I l I ~ l 1~ I[ 1 RIVERWALK 8TH ADDITION CURB INLET CALCULATIONS • Curb Inlet Depression = 2 in. Standard Curb Inlet Length = 4 ft. Upstream Gutter Roughnes Reciprocal Depth Length Curb Orop Impervious Peak Flow' Slope Coeff. Cross slope of Flow Required Basin Station RIL Area c.f.s. S n Z Zln d* QalLa** QI(QalLa) Remarks A 18+20 L 4454 0.97 Sump condition' B 18+20 L 3745 0.64 0.0080 0.0160 50 3125 0.13 0.088 7,29 Need 2- 4' curb inlets C 18+20 R 4477 0.99 0.0117 0.0160 50 3125 0.14 0.096 10.29 Sump condition*** D 12+37 L 5643 0.85 Sump condition"" E 10+53 R 3269 0.27 0.0087 0.0160 50 3125 0.09 0.062 4.32 Need 1- 5' curb inlet F 20+35 L 17615 2.75 0.0087 0.0160 50 3125 0.22 0.149 18.43 Need 3- 6' curb inlets G 20+35 R 13418 2.13 0.0087 0.0160 50 3125 0.20 0.136 15.71 Need 4- 4' curb inlets C-RW6 10+55 L 5373 0.65 0.0100 0.0160 50 3125 0.12 0.085 7.66 Need 2- 4' curb inlets Calculated per Figure 18 of Guidelines Calculated per Figure 16 of Guidelines A 4 foot curb drop with a 6" gutter has a capacity of 4.0 cfs in sump condition. ~ ~ INLAND PA►CIFIC ENGIhJEERING, INC. ~ i ~ ~ i - , I ' . . I . iC ~ f ~ 1 +OFF1C1AL PUBLIC DCCtAWAr SPOKANE COtJNTY ENG9NEEFrS OFFUE ~ OR G NA~ j pfl'? 1~-~'~ , . . j " FiL; i ~wini^i ~ U COUNTY ENGRiM i, ~ ~ ~ SPOKANE ~ COEUR D"ALENE DRAINAGE TECHNICAL REPORT for the RIVERWALK 8TH ADDITION PUD JUNE 1997 Prepared for: PACIFIC PROPERTIES 14410 Bel-Red Road Bellevue, WA 98007 Prepared By: Inland Pacific Engineering Company 707 W. 7th Avenue Suite 200 Spokane, WA 99204 (509)458-6840 DRAINAGE REPORT for the Riverwalk 8th Addition PUD Plat Spokane County, Washington June1997 Prepared for: PACIFIC PROPERTIES 14410 Bel-Red Road Bellewe, WA 98007 Prepared by: Inland Pacific Engineering Company 707 W. 7th Avenue Suite 200 Spokane, WA 99204 (509)458-6840 _ : . The-design umprove14enf.s shawn in this set Qf plans and calculations : conform ta the applicable;editions.ofthe Spokane Gounty Standards for Road:-$nd Sewer Construction and th,e Sgokane Co-unfiy Guideliaes for Stormw$ter Managemen#. AIl desYga deviations ~ . have:been app' ove&by:the',~Spokane County Engineer. I approve these~Wans (calcnlati4ns) fo ' r -Consh•ucort. This report has been prepared by Susan K. Murphy of Inland Pacific Engineering Company under the direction of the undersigned professional engineer whos seal and signature appear hereon. O~ ~►1 ti ~t . . ~ SfGN~ - EXPIRES 9/24/ ~ Todd R. VVhipple, P.E. . Riverwalk 8th Addition PUD Drainage Narrative GENERAL Riverwalk 8th Addition PUD Plat is a 7.86 acre development of 34 single family residentiallots located north and east of the intersection of Indiana Avenue and Barker Road, within Spokane County, Washington. The site is currently vacant with field grass, alfalfa and fallow fields as the predominant land cover and vegetation. Single family residential development lies d'uectly to the south and west. A 1" to 400' scale vicinity and location map have been included within the technical section of this document. PURPOSE The purpose of this report is to determine the extent of storm drainage facilities which will be required to dispose of the increase in stormwater runoff created by the development of the Riverwalk 8th Addition plat. The storm drainage facilities on this project will be designed to dispose of runoff from a ten year design storm, as required by the Spokane County Guidelines for Stormwater Management, though the calculations are also included to verify that the facilities also generally contain the 50-year storm. This development is within the Aquifer Sensitive Area of Spokane County and is subject to '208' requirements. For this project, the 10-year curve from the Spokane, Medical Lake, Reardon, Cheney and Rockford intensity curves was used, as well as the SCS iso-pluvial rainfall curves. Per direction from Spokane County, the SCS curves have been further refined with the NOAA iso-pluvial curves. . ANALYSIS METHODOLOGY Per the Spokane County Guidelines for Stormwater Management, the Rational Method, which is recommended for basins less than ten acres in size, will be used to determine the peak discharges - and runoff volumes for all onsite basins. PROJECT DESCAIPTION This phase of the Riverwalk 8th Addition plat comprises 341ots of the approved 3931ots in the approved preliminary plat and SEPA documents. The Riverwalk 8th Addition subdivision is located in the NE 1/4 of the S W 1/4 of Section 8, T. 25 N., R. 45 E., W.M. within Spokane County, Washington. TOPOGRAPHY The existing site naturally drains to the north, sloping gently towards the Spokane River from Indiana Avenue. Within the plat the natural topography was used as much as possible to route Inland Pacific Engineering Company D1 Riverwalk 8th Addition Plat Drainage Report stonn drainage. However, due to the flat slopes and the County's rninimum requirements for slope, the roadway profiles have been forced down to facilitate drainage by localizing low spots for pond placement. Due to the flat slopes encountered, no concentrated pre-existing flows were observed nor were there any signs that anything other t,han sheet flow and ground absorption have occurred on this site. The general slopes within this plat vary from flat to nearly flat with the maximum existing slope at 0.025/ft. Generally, the area within this platted portion of the overall preliminary plat would be characterized as flat. For development purposes as stated the natural sloping was used for design and is maintained as possible throughout the project. sorr.s As can be seen from the accompanying soils map from the Spokane County Soils Survey as perfonned by the SCS, the site consists of one type of soils within the Class B type. This soil type is described as follows. GgA - Garrison gravelly loam, 0 to 5 percent slopes: Soils within this soil type are some what excessively drained soils formed in gravelly glacial outwash material from a variety of igneous rock. Surface runoff is slow, and the hazard of erosion is slight. Spokane County Guidelines for Stormwater ManaQe~ment indicate this to be a Soil Group Type B and pre-approved for drywell installation. Hydrologic Soil Classification - B DRAINAGE NARRATIVE Offsite Based upon the general geographic tendencies of this site, no offsite flows are expected for this phase. - Onsite As this plat is within the aquifer sensitive area of Spokane County all onsite drainage will be collected and treated using the "208" runoff method as described in the Spokane County Guidelines for Stormwater Management. To facilitate this analysis the Riverwalk 8th Addition plat was divided into 8 permanent sub-basins (A through H). Although there are 8 basins, these basins have been combined where practical to utilize the same pond. Table 1 lists the basins and pond combinations for easy reference. Inland Paciftc Engineering Companry D2 Riverwalk 8th Addition Plat Drainage Repon Table No. 1 WEIGHTED "C"" SUMMARY Basins Totai Total Street Imp. Total Weighted Area Acreage Area (SF) Impervious "C" I (SF) Area (SF/AC) , A 32366 0.74 4454 12154/0.28 0.43 B 18794 0.43 3745 8145/0.19 0.48 C 32704 0.75 4477 12177/0.28 0.43 D 25917 0.59 5643 11143/0.26 0.48 E 7372 0.17 3269 3269/0.08 0.50 F 142465 3.27 17615 47315/1.09 0.40 " G 84943 1.95 13418 32118/0.74 0.43 FG 227408 5.22 31033 79433/1.82 0.41 H 26747 0.61 5373 10873/0.25 0.46 "208" Calculations Within each basin the streets are divided into sub-basins by high and low roadway profiles. These facilities capture upstream stormwater runoff from the impervious street surface and direct the runoff into grassy '208' ponds. As shown on the '208' calculation worksheets included, the '208' storage volume provided is adequate to perform '208' treatment for the runoff created by the first half inch of rainfall. Curb Inlets Calculations It is necessary to check the adequacy of the curb inlets provided to divert the runoff from the gutter into the '208' ponds. The curb inlet calculation sheets included show the required lengths of curb openings. For curb inlets greater than 4.0', either multiple curb inlets are added or the curb inlets are lengthened as required. DRAINAGE CALCULATIONS SUMMARY Calculations have been included for Drainage Basin considerations such as Peak Flow, Time of Concentration, "208" sizing, drywell requirements, inlet sizing and curb inlets, as well as culverts Inland Pacifrc Engineering Company D3 Riverwalk 8th Addition Plat Drainage Report and pipe flows, some of which are summarized below with the remaining calculations included in the appendix. Within the calculation section and where it has been determined necessary for clarity, several sketches, as well as details from the plans have been incorporated to demonstrate assumptions and conclusions. BASIN DESCRIPTIDNS Basins A through G Within this plat, and due to the general geographic features, several basic assumptions were followed and can be used to describe each basin. First, due to the relative flatness of the plat and project vicinity, minimum road grade is limited to O.OOSftIft; second, a large tract pond if practical will be used in the open space area; third, all other ponds will be of the lot pond configuration; fourth, that where practical, drywells will be minimized by combining basins and providing piping between ponds. All of these steps have been used in various basins throughout the drainage design of this project. Table No. 2- Pond and 208 Basin Summary Riverwalk 8th Addition - BASIN SIJMMARY Basin . Pond 208 Valume 208 Area 20$ .Area Drywells Required (cf) Required {sf} Providecl (sf) Required * A A 186 372 560 1- B B B 156 312 375 1- A C C 187 374 560 1- B D D 235 470 508 1- B E E 136 272 340 1- A F FG 734 1468 3668 3- B** G FG 559 1118 H C(RWb) 224 448 774 1- B Type A is a Spokane Standard Drywell - Single Depth, Capacity 0.3 cfs - Type B is a Spokane Standard Drywell - Doubte Depth, Capacity 1.0 cfs Basins F& G have been combined for the Bowstring Calculation. Inland Pacifcc Engineering Comparry D4 Riverwalk 8th Addition Plat Drainage Report Table No. 3- Curb Inlet/Catch Basin Summary ~ ~;Itivervyalk~8th Addi~ion Plati Curb Inlet and Catch Basiris Summary .u. c re i Curb.inlet _ Catch BasYn , .t _ r Condition Condition} A A Sump - B B Continuous - C C Sump - D D Sump - E E Continuous - F FG Continuous G FG Continuous - H C(RW6) Continuous - Per Spokane County Guidelines curb drops in a sump condition have a capacity of 4.0 cfs Per WSDOT Hydraulics Manual, Grate Inlet, has a sump capacity of 13.0 cfs NOTE: Qaly curb drop and grate calculations were performed for those cases "On Grade", curb drops and catch basins in sump condition are assumed to handle 4.0 cfs. Inlanri Paciftc Engineering Company DS Riverwalk 8th Additinn Plat Drainage Repon . . a ~ ~ o P a~ pewrea/ Rr as..... ~ V ~ r- ~ r Nar~n ~N r 11sw~ Aw. ~ ~ d ~ . Sare~ Ara ~ LIWW* ~ f a a, ~ ~i yc dwea A.e ~ MtlN~ s ~pp. ~ ~ d Aw. ~ ~~.'v~• ~ ~ o VIN'"n sre.e A... 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F~~' ' Y' t 1+ ~ .1•~t . ~...n f~, r ~ T"^ A~< , r ~ , - ' r~'~, ; ~ !h , ~ Q• o- , o~tt~ N l r;1 ~ yv~ t - •w y" ~ ~x~; r . f . ~ ~i ti f . ~ l 1 't :.r - ~~.'"i.t~ M.~i ! ~ ~ 1~ 1', `~c!""~' lp i 1~ ''i. ~rt. ` ` f'''+ t l . t `j~.~ J:' iI . ~y ~ ~ ~ ~M ~ ~ • Y 7/ ♦ Il,:w~ ~~a i . S; ~r .[4~~'t ,':~r,~~,'~' ~~rJ~ 5J'. ~ti 1~ ~r~ii~ ~i'`, ~.~!i~!'~:'!d { ~ . . ~ _ 'Y~ ~ ~1 r~ ` , ra~~•ll' ~ . J +4:~~~.;:.. ti • 4~ i~~ ~1 . Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: A IPE Job 96087 Total Area (acres): 0.74 Designer: SKM Imp. Area (acres): 0.28 Date: 04/15 , ~ Grass Area (acres): 0.46 ~ Imp. Area "C": 0.90 ~ Grass Area "C": 0.15 ~ ~ (Imp. Area)(Imp. "C")= 0.2520 (Grass Area)(Grass "C")= 0.0690 ~ 0.7400 0.3210 - Weighted "C"= 0.3210 0.43 ~ 0.7400 . ~ ~ ~ Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: B - IPE Job 96087 . ~ Total Area (acres): 0.43 Designer: SKM _ Imp. Area (acres): 0.19 Date: 04/15. Grass Area (acres): 0.24 Imp. Area "C": 0.90 Grass Area "C": 0.15 . ~ (Imp. Area)(Imp. "C")= 0.1710 (Grass Area)(Grass "C")= 0.0360 ~ 0.4300 0.2070 Weighted "C"= 0.2070 0.48 0.4300 ~ ~ . I ~l ._J ~ J ~ i ~ Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: C- IPE Job 96087 Total Area (acres): 0.75 Designer: SKM Imp. Area (acres): 0.28 Date: 04/15 Grass Area (acres): 0.47 Imp. Area "C": 0.90 Grass Area "C": 0.15 (Imp. Area)(Imp. "C")= 0.2520 ~ (Grass Area)(Grass "C")= 0.0705 ~ 0.7500 0.3225 Weighted "C"= 0.3225 0.43 0.7500 o, a B w~ ~ ~J Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition ~ Basin: D IPE Job 96087 Total Area (acres): 0.59 Designer: SKM Imp. Area (acres): 0.26 Date: 04/15 ~ Grass Area (acres): 0.33 ~ Imp. Area "C": 0.90 Grass Area "C": 0.15 ~ (Imp. Area)(Imp. "C")= 0.2340 ' (Grass Area)(Grass "C")= 0.0495 0.5900 0.2835 ~ : ~ Weighted "C"= 0.2835 0.48 B 0.5900 ~ ~ o ~`n ~ Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: E IPE Job 96087 ~ Total Area (acres): 0.17 Designer: SKM , Imp. Area (acres): 0.08 Date: 04/20 Grass Area (acres): 0.09 Imp. Area "C": 0.90 J Grass Area "C": 0.15 . (Imp. Area)(Imp. "C")= 0.0720 (Grass Area)(Grass "C")= 0.0135 ~--0.1700 0.0855 ~ ~ Weighted "C"= 0.0855 0.50 0.1700 ~ - ~ i~ Weighted Runoff Coefficient Calculation ~ Project: Riverwalk 8th Addition Basin: F ~ IPE Job 96087 Total Area (acres): 3.27 Designer: SKM Imp. Area (acres): 1.09 Date: 05128 Grass Area (acres): 2.18 Imp. Area "C": 0.90 , Grass Area "C": 0.15 ~ (Imp. Area)(Imp. "C")= 0.9810 ^ (Grass Area)(Grass "C")= 0.3270 ~ 3.2700 1.3080 ~ Weighted "C"= 1.3080 0.40 E 3.2700 s ~ ~ ~ I L-J ~ Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: G IPE Job 96087 Total Area (acres): _ 1.95 Designer: SKM ~ Imp. Area (acres): 0.74 Date: 05/20 Grass Area (acres): 1.21 Imp. Area "C": 0.90 ~ Grass Area "C": 0.15 l , ~ (Imp. Area)(Imp. "C")= 0.6660 (Grass Area)(Grass "C")= 0.1815 _ a 1.9500 0.8475 w Weighted "C"= 0.8475 0.43 1.9500 ~ ~ ~ ~ L ) i Weighted Runoff Coefficient Calculation Project: Riverwalk 8th Addition Basin: FG IPE Job 96087 Total Area (acres): 5.22 Designer: SKM Imp. Area (acres): 1.82 Date: 05/28 ~ Grass Area (acres): 3.40 ~ Imp. Area "C": 0.90 , Grass Area "C": 0.15 (Imp. Area)(Imp. "C")= 1.6380 ~ (Grass Area)(Grass "C")= 0.5100 ^ 5.2200 2.1480 Weighted "C"= 2.1480 0.41 5.2200 ~ ~ ~ Weighted Runoff Coefficient Calculation ^ Project: Riverwalk 8th Addition Basin: H CRWloC.~ IPE Job 96087 Total Area (acres): 0.61 Designer: SKM ~ Imp. Area (acres): 0.25 Date: 05/07 Grass Area (acres): 0.36 Imp. Area "C": 0.90 Grass Area "C": 0.15 ~ ~ ~ (Imp. Area)(Imp. "C")= 0.2250 ~ (Grass Area)(Grass "C")= 0.0540 ~ 0.6100 0.2790 Weig hted "C"= 0.2790 0.46 0.6100 ~ ~ ~ ~ i ~ I J , I F-7, BOWSTRING METHOD PROJECT: Riverwalk 8ih Addition PEAK FLOW CALCUlATION PROJECT Riverwalk Sth Addition DETENTION BASIN DESIGN BASIN: A BASIN; A 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0,74 Acres DATE: 04115 Imp, Area 4454 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 5.51 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 10 , Area (acres) 0.74 Ct = 0.15 Imperoious Area (sq ft) 4454 L= 60 ft. 'C' Factor 0.43 n= 0.40 '208' Volume Provided 280 S= 0.020 Area' C 0.318 Tc = 3.27 min., by Equation 3-2 of Guidelines ' Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 234 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cw ft) (cu ft) Z1= 50.0 For Z2 5.51 330 3.05 0.97 429 330 99 Z2 = 3.5 Type B =1,0 n= 0.016 Rolled = 3.5 5 300 3.18 1.01 407 300 107 S= 0.012 10 600 2.24 0.71 508 600 -92 15 900 1.77 0.56 570 900 -330 d= 0.144 ft. 20 1200 1.45 0.46 605 1200 -595 25 1500 1.21 0.39 621 1500 -879 A R Q Tc Tc total I Qc 30 1800 1.04 0.33 633 1800 -1167 35 2100 0,91 0.29 641 2100 -1459 • 0.55 0.07 0.97 2.24 5.51 3.05 0.97 40 2400 0.62 0.26 656 2400 -1744. 45 2700 0.74 0.24 662 2700 -2038 Qpeak for Case 1= 0.97 cfs 50 3000 0.68 0,22 673 3000 -2327 55 3300 0.64 0.20 695 3300 -2605 60 3600 0.61 0.19 721 3600 -2879 CASE 2 65 3900 0.60 0.19 766 3900 -3134 70 4200 0.58 0.18 796 4200 -3404 Case 2 assumes a Time of Concentration less lhan 5 minutes so that the 75 4500 0.56 0.18 822 4500 -3678 peak ilow =.90(3.18)(Imp. Area) = 0.29 cfs 80 4800 0,53 0.17 828 4800 -3972 85 5100 0.52 0.17 862 5100 -4238 90 5400 0.50 0.16 877 5400 -4523 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.16 906 5700 -0794 0.97 cfs 100 6000 0.48 0.15 934 6000 -5066 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in ! 12 iNfl 186 cu ft . 208' Storage Volume Provided 280 cu ft DRYWELL REQUIREMENTS -10 YR. DESIGN STORM Maximum Storage Required by Bowstring 107 cu ft Number and Type of Drywells Required 0 Single , 1 Double . e I ~ i I f l ! ? f j [ i f - ~ ~ ~ f 1 f ~ ~ I f ~ ( ~ ~ -"[,7 BOWSTRING METHOD PROJECT: Riverwalk Bth Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: B BASIN: B 10-Year Design Stortn DESIGNER: S. Murphy Tot. Area 0.43 Acres DATE: 05121 Imp. Area 3745 SF C = 0.48 Time Incxement (min) 5 CASE 1 Time af Conc. (min) 526 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 10 . Area (aaes) 0.43 Ct = 0.15 Impenrious Area (sq fl) 3745 L= 60 ft. 'C' Factor 0.48 n= 0.40 '208' Volume Provided 175 S= 0,020 Area' C 0Z06 Tc = 3,27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel, Vol,ln Vol.Out Storage 163 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.26 316 3.11 0.64 272 316 -44 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.66 264 300 -36 S= 0.008 10 600 2.24 0.46 327 600 -273 15 900 1.77 0.37 368 900 -532 d= 0.133 ft. 20 1200 1.45 0.30 391 1200 -809 25 1500 1.21 0.25 401 1500 -1099 A R Q Tc Tc total I Qc 30 1800 1.04 0.21 409 1800 -1391 35 2100 0.91 0.19 415 2100 -1685 0.47 0.07 0.64 2.00 526 3.11 0.64 40 2400 0.82 0.17 424 2400 -1976 45 2700 0.74 0.15 429 2700 -2271 Qpeak for Case 1= 4.64 cfs 50 3000 0.68 0,14 436 3000 -2564 55 3300 0.64 0.13 450 3300 -2850 60 3600 0,61 0.13 467 3600 -3133 CASE 2 65 3900 0,60 0.12 496 3900 -3404 70 4200 0.58 0.12 516 4200 -3684 Case 2 assumes a Time of Concentration less than 5 minutes so thai the 75 4500 0,56 0.12 533 4500 -3967 peak flow =,90(3.18)(Imp. Area) = 0.25 cfs 80 4800 0,53 0,11 537 4800 -4263 85 5100 0.52 0.11 559 5100 -4541 90 5400 0.50 0.10 566 5400 -4832 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0,10 587 5700 -5113 0.64 cfs 100 6000 0,48 0,10 605 6000 -5395 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impenrious Area x,5 in / 12 iNft 156 cu ft 208' Storage Volume Provided 187.5 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring -36 cu ft Number and Type of Drywells Required 0 Single 1 Dauble I L ~ U ~7 BOWSTRING METHOD PROJECT: Riverwalk 6th Addition PEAK FLOW CALCULATION PROJECT Rive►waik 8th Addition DETENTION BASIN DESIGN BASIN: C BASIN: C 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0.75 Acres DATE: 05120 Imp. Area 4477 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 5.45 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 10 . Area (acres) 0.75 Ct = 0.15 Impervious Area (sq ft) 4477 L= 60 ft. 'C Factor 0.43 n= 0.40 '208' Volume Provided 280 S= 0.020 Area' C 0.323 Tc = 3.21 min., by Equation 3-2 of Guidelines Time Time Inc, Intens. Q Devel. Val.ln Val.Out Storage 234 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 5.45 327 3.06 0.99 433 327 106 Z2 = 1 Type B =1.0 ' n= 0,016 Rolled = 3.5 5 300 3.18 1.03 412 300 112 S= 0.012 10 600 2.24 0.72 514 600 -86 15 900 1.77 0.57 577 900 -323 d= 0.148 ft. 20 1200 1,45 0.47 613 1200 -587 25 1500 1.21 0,39 629 1540 -871 • A R Q Tc Tc total I Qc 30 1800 1.04 0.34 641 1800 -1159 35 2100 0.91 0.29 649 2100 -1451 - 0.55 0.07 0.99 2.19 5.45 3.06 0.99 40 2400 0.82 0.26 664 2400 -1736 45 2700 0.74 0.24 671 2700 -2029 Qpeak for Case 1= 0.99 cfs 50 3000 0.68 0.22 682 3000 -2318 55 3300 0.64 0,21 704 3300 -2596 60 3600 0.61 0.20 730 3600 -2870 CASE 2 65 3900 0.60 0.19 776 3900 -3124 70 4200 0.58 0.19 806 4200 -3394 Case 2 assumes a Time of Concentra6on less than 5 minutes so that the 75 4500 0.56 0.16 833 4500 -3667 peak flow =.90(3.18)(Imp. Area) = 029 cfs 80 4800 0.53 0.17 839 4800 -3961 85 5100 0.52 0.17 874 5100 -0226 90 5400 0.50 0.16 889 5400 -4511 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0.16 918 5700 -4782 0.99 cfs 100 6000 0.48 0.15 946 6000 -5054 208' ORAINAGE POND CALCULATIONS Required'208' Storage Volume = Impenriaus Area x.5 in /12 iNft 187 cu ft , . , 208' Storage Volume Provided 260 cu ft DRYUVELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bovustring 112 cu fl Number and Type of Drywells Required 0 Single 1 Double ~ I; ~ i I ~ i I! 1 I J(~1 {1 ~f ~ 1 I ! J ~ i I 1 f I I I BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addibon DETENTION BASIN DESIGN BASIN: D BASIN: D10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0.59 Aaes DATE: 05/20 Imp. Area 5643 SF c = 0.48 Time Inaement (min) 5 CASE t Time of Conc. (min) 5.60 OutFlow (cfs) 1 60 ft. Overland Flow Design Year Flow 10 • Area (acres) 0.59 Ci = 0.15 Impervious Area (sq ft) 5643 L= 60 ft. 'C Factor 0.48 n= 0.40 '208' Volume Provided 254 S= 0.020 Area " C 0.283 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 205 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 ForZ2 5.60 336 3.02 0.85 385 336 49 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.90 362 300 62 S= 0.008 10 600 224 0.63 453 600 -147 15 900 1.77 0.50 508 900 -392 d= 0.148 ft. 20 1200 1.45 0.41 540 1200 -660 25 1500 1.21 0.34 553 1500 -947 A R Q Tc Tc total I Qc 30 1800 1.04 0.29 564 1800 -1236 35 2100 0.91 0.26 571 2100 -1529 0.58 0.07 0.85 2,34 5.60 3.02 0.85 40 2400 0.82 0.23 584 2400 -1816 45 2700 0.74 0.21 590 2700 -2110 Qpeak for Case 1= 0.85 cfs 50 3000 0,66 0.19 600 .3000 -2400 55 3300 0.64 0.18 619 3300 -2681 60 3600 0.61 0.17 642 3600 -2958 CASE 2 65 3900 0.60 0.17 682 3900 -3218 . •70 4200 0.58 0.16 709 4200 -3491 Case 2 assumes a Time of ConcentraGon fess than 5 minutes so that the 75 4500 0.56 0.16 732 4500 -3768 peak flow =.90(3.18)(Imp. Area) = 0.37 cfs 80 4800 0.53 0.15 • 738 4800 -4062 85 5100 0.52 0.15 768 5100 -4332 90 5400 0.50 0.14 781 5400 -4619 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0,49 0.14 807 5700 -4893 0.85 cfs 100 6000 0.48 0.14 831 6000 -5169 208' DRAINAGE POND CALCULATIONS Required '208' Storage Volume = Impervious Area x.5 in ! 12 iNft 235 cxi ft 208' Storage Valume Provided 254 cu ft DRYWELL REQUIREMENTS, 10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 62 cu ft Number and Type of Drywells Required 0 Single 1 Double L--J 1 L--j BOWSTRING METHOD PROJECT: RiverHralk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: E BASIN: E 10-Year Design Storm DESIGNER: S. Murphy Tot. Mea 0,17 DATE: 05120 Imp. Area 3269 SF C = 0.50 Time Increment (min) 5 CASE 1 Time of Conc, (min) 5.00 Outflow (cfs) 0.3 40 ft. Overland Flow Design Year Flow 10 , Area (aaes) 0.17 Ct = 0.15 Impervious Area (sq ft) 3269 L= 40 ft. 'C' Factor 0.5 n= 0.40 '208' Volume Provided 170 S= 0.020 Area' C 0.085 Tc = 2.56 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol,Out Storage 138 ft, Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (au ft) (cu ft) Z1= 50.0 For Z2 5.00 300 3.18 0.27 109 90 19 Z2= 1 TypeB=1.0 n= 0.016 Rolled = 3.5 5 300 3.18 027 109 90 19 S= 0.008 10 600 2.24 0.19 134 160 -46 15 900 1.77 0.15 151 270 -119 d= 0,098 ft. . 20 1200 1.45 0.12 160 360 -200 25 1500 1.21 0.10 165 450 -285 A R Q Tc Tc total I Qc 30 1800 1.04 0.09 168 540 -372 35 2100 0.91 0.08 170 630 -460 024 0.05 0.27 2.07 5.00 3.18 027 40 2400 0.82 0,07 174 720 -546 45 2700 0.74 0.06 176 810 -634 Qpeak for Case 1= 0,27 cfs 50 3000 0.68 0.06 179 900 -721 55 3300 0.64 0,05 185 990 -805 60 3600 0.61 0.05 192 1080 -888 CASE 2 65 3900 0.60 0.05 204 1170 -966 70 4200 0.56 0.05 212 1260 -1048 Case 2 assumes a Time of Concentration less than 5 minutes so lhat the 75 4500 0.56 0.05 219 1350 -1131 peak flow =.90(3.18)(Imp. Area) = 0.21 cfs 80 4800 0.53 0.05 221 1440 -1219 85 5100 0.52 0.04 230 1530 -1300 90 5400 0.50 0.04 234 1620 -1386 So, the Peak flow for the Basin is the greater of the two flaws, 95 5700 0.49 0.04 • 242 1710 -1468 0.27 cfs 100 6000 0.48 0.04 249 1800 -1551 208' DRAINAGE POND CALCULATIONS Required'208' Slorage Volume . = Impervious Area x.5 in I 12 iNft 136 cu ft . 208' Storage Volume Provided 170 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 19 cu ft Number and Type of Drywells Required 1 Single , , . 0 Double f 1 ~ J~__ I f 1 i. ! l 1 I ~ C~ ~ 1~_ J I i i I I I E I 50-year STORM 80WSTRING METHOD PROJECT: Rivenvalk 8lh Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8lh Addition DETENTION BASIN DESIGN BASIN: F BASIN: F DESIGNER; S. Murphy Tot. Area 3.27 Acres DATE: 06125 Imp. Area 17615 SF ' C = 0.41 Tme Increment (min) 5 CASE 1 Time of Conc. (min) 11.09 Outflow (cfs) 0 120 ft, Ove~and Flow Design Year Flow 50 Area (acres) 3.27 Ct = 0.15 Impervious Area (sq ft) 17615 L= 120 ft. 'C' Factor 0.41 n= 0.40 50-year Volume Provided 1834 S= 0.020 Area " C 1.341 Tc = 4.95 min,, by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 950 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = , 50.0 , Z2 = 3.5 11.09 666 3.03 4,06 3622 0 3622 n= 0.016 5 300 4.58 6.14 2468 0 2468 S= 0.013 ' 10 600 320 4.29 3449 0 3449 15 900 2.45 3.28 3700 0 3700 d= 0.243 ft. 20 1200 1.95 2.61 3729 0 3729 25 1500 1.62 2.17 3749 0 3749 A R Q Tc Tc total I Qc 30 1800 1.56 2.09 4238 0 4238 35 2100 1,28 1.72 3992 0 3992 1.57 0.12 4.06 6.14 11.09 3.03 4.06 40 2400 1.19 1.59 4172 0 4172 45 2700 1,08 1.45 4237 0 4237 Qpeak for Case 1= 4.06 cfs 50 3000 0,99 1.33 4282 0 4282 55 3300 0.92 1.23 4350 0 4350 60 3600 0.87 1.17 4463 0 4463 CASE 2 65 3900 0.82 1.10 4536 0 4536 70 4200 0.80 1.07 4747 0 4747 Case 2 assumes a Time of ConcentraGon less than 5 minutes so that the 75 4500 0.77 1.03 4879 0 4879 peak flow =.90(4.58)(Imp. Area) = 1.67 cfs 80 4800 0.75 1.01 5054 0 5054 85 5100 0.12 0.97 5142 0 5142 90 5400 0.71 0.95 5356 0 5356 So, the Peak flow for the Basin is the greater o( the two flows, 95 5700 0,69 0.93 5462 0 5482 4.06 cfs 100 6000 0,67 0.90 5593 0 5593 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in 112 iNft 734 cu ft 50 year Volume Provided 1834 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 5142 cu ft Number and Type of Drywells Required 0 Single ERR Double INLAND PACIFIC ENGINEERING BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk Sth Addilion •DETENTION BASIN DESIGN BASIN: G BASIN: G 10-Year Design Storm DESIGNER: S. Murphy Tot, Area 1.95 Acres DATE: 05/20 Imp. Area 13418 SF C = 0.43 Time Inaement (min) 5 CASE 1 Time of Conc. (min) 7.82 Outflow (cfs) 0 60 ft. Overland Flow ' Design Year Flow 10 , , Area (aaes) 1.95 Ct = 0.15 Impervious Area (sq ft) 13418 L= 60 ft. 'C' Factor 0.43 n= 0.40 '208' Volume Provided 341 S= 0.020 Area' C 0.839 Tc = 3.27 min., by Equation 3-2 af Guidelines" Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 600 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (ai ft) Z1= 50.0 For Z2 7.82 469 2.54 2.13 1341 0 1341 ZZ = 3.5 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 2.67 1072 0 1072 S= 0.013 10 600 2.24 1,88 1427 0 1427 15 900 1.77 1.48 1573 0 1573 • d= 0.191 R. 20 1200 1.45 1.22 1653 0 1653 25 1500 1,21 1.01 1684 0 1684 A R Q Tc Tc total I Qc 30 1800 1.04 0.87 1709 0 1709 35 2100 0.91 0.76 1724 0 1124 0.97 0.09 2.13 4.56 7,82 2,54 2.13 40 2400 0.82 0.69 1160 0 1760 45 2700 0.74 0.62 1774 0 1774 Qpeak for Case 1= 2.13 cfs 50 3000 0.68 0.57 1802 0 1802 55 3300 0.64 0.54 1857 0 1857 60 3600 0.61 0.51 1923 0 1923 CASE 2 65 3900 0.60 0.50 2042 0 2042 10 4200 0.58 0.49 2120 0 2120 Case 2 assumes a Time of Concentration less than 5 minutes so that thA' 75 4500 0.56 0,47 2188 0 2188 peak flow =,90(3.18)(Imp. Area) = 0.88 cfs 80 4800 0,53 0,44 2204 0 2204 85 5100 0,52 0.44 2293 0 2293 90 5400 0.50 0.42 2331 0 2331 So, the Peak flow for the Basin is the greater of the two flows, 95 5100 0.49 0.41 2408 0 2408 2•13 cfs 100 6000 0.48 0.40 2479 0 2479 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume = Impervious Area x,5 in ! 12 iNft 559 cu ft ' 208' Storage Valume Provided 341 cu ft DRYUVELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 2293 cu ft „ Number and Type of Drywells Required 0 Single ' ERR Double r-71 1`1 77 t---j r"~ BOWSTRING METHOD PROJECT: Riverwalk 8lh Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addilion DETENTION BASIN DESIGN BASIN: FG BASIN: FG 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 5.22 Acres „ DATE: 06l25 Imp. Area 31033 SF C = 0.41 Time Increment (min) 5 CASE 1 Time of Conc. (min) 10.91 Outflow (cfs) 3 120 ft. Overland Flow Design Year Flow 10 Area (acres) 5.22 Ct = 0,15 Impenrious Area (sq ft) 31033 L= 120 fl. 'C Factor 0.41 n= 0.40 '208' Volume Provided 2175 S= 0.020 • Area' C 2,140 Tc = 4.95 min., by Equabon 3-2 of Guidelines Time Time inc. Intens. Q Devel. Vol.ln Vol.Out Storage 950 ft. Gutter flow (min) (sec) (inmr) (cfs) (cw ft) (cu ft) (cu ft) Z1= 50.0 For Z2 10.91 655 2.14 4,58 4016 1964 2052 Z2 = 3.5 Type B =1.0 n= 0.016 Rolled = 3,5 5 300 3.18 6,81 2736 900 1836 ' S= 0.013 10 600 2.24 4,79 3854 1800 2054 15 900 1.77 3.79 4253 2700 1553 d= 0.254 ft. 20 1200 1.45 3.10 4415 3600 815 25 1500 1.21 2.59 4461 4500 -39 A R Q Tc Tc total I Qc 30 1800 1.04 2,23 4502 5400 -898 35 2100 0.91 1,95 4523 6300 -1777 1,72 0.13 4.58 5.96 10.91 2.14 4.58 40 2400 0.82 1.75 4603 7200 -2597 45 2700 0.74 1.58 4629 8100 -3471 Qpeak for Case 1= 4.58 cfs 50 3000 0.68 1.46 4690 9000 -4310 55 3300 0,64 1.37 4825 9900 -5075 60 3600 0.61 1.31 4990 10800 -5810 CASE 2 65 3900 0.60 128 5294 11700 -6406 70 4200 0.58 1.24 5490 12600 -1110 Case 2 assumes a Time of Concentratian less than 5 minutes so that the 75 4500 0.56 1.20 5660 13500 -7840 peak flow =.90(3,18)(Imp. Area) = 2.04 cfs 80 4800 0.53 1.13 5697 14400 -8703 85 5100 0.52 1.11 5924 15300 -9376 ' 90 5400 0.50 1.07 6017 16200 -10183 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 1.05 6211 17100 -10889 4.58 cfs 100 6000 0.48 1.03 6392 18000 -11608 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Imperoious Area x.5 in I 12 inlft 1293 cu ft 208' Starage Volume Provided 2175 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Msximum Storage Required by Bowstring 2054 cu ft Number and Type of Drywells Required 0 Singie 3 Double ~jj T:7 BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: H (,PUOlo-L) BASIN: H 10-Year Design Storm DESIGNER: S. Murphy Tot. Area 0.61 Acres DATE: 04120 Imp. Area 5373 SF C = 0.46 Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.01 Outflow (cfs) 1 75 ft. Overland Flow • ' Design Year Flow 10 , Area (acres) 0,61 Ct = 0.15 Impervious Area (sq ft) 5373 L= 75 ft. 'C' Factor 0.46 n= 0.40 '208' Volume Provided 387 S= 0.010 Area' C 0281 Tc = 4.60 min,, by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol,ln Vol.Out Storage 225 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 For Z2 7,01 421 2.68 0.75 424 421 3 Z2 = 1 Type B =1.0 n= 0.016 Rolled = 3.5 5 300 3.18 0.89 359 300 59 S= 0.010 10 600 2.24 0.63 467 600 -133 15 900 1.77 0.50 518 900 -382 d= 0.138 ft. 20 1200 1.45 0.41 546 1200 -654 25 1500 1.21 0.34 558 1500 -942 A R Q Tc Tc total I Qc 30 1800 1.04 0,29 561 1800 -1233 35 2100 0.91 0.26 513 2100 -1527 0.48 0.07 0.75 2.41 7.01 2,68 0.75 40 2400 0.82 0,23 585 2400 -1815 45 2700 0.74 021 590 2700 -2110 Qpeak for Case 1= 0.75 cfs " 50 3000 0.68 0.19 600 3000 -2400 55 3300 0.64 0.18 618 3300 -2682 60 3600 0.61 0,17 641 3600 -2959 CASE 2 65 3900 0.60 0,17 681 3900 -3219 70 4200 0.58 0,16 707 4200 -3493 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0,56 0,16 730 4500 -3770 peak flow =.90(3.18)(Imp. Area) = 0.35 cfs 80 4800 0.53 0.15 735 4800 4065 85 5100 0.52 0.15 765 5100 -4335 90 5400 0.50 0.14 778 5400 -4622 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.49 0,14 803 5700 -4897 0.75 cfs 100 6000 0.48 0.13 827 6000 -5173 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume . = Impervious Area x.5 in /12 inlft 224 cu ft ' 208' Storage Volume Provided 387 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 59 cu ft Number and Type of Drywells Required 0 Single 1 Double ci-i ~ 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwaik 8th Addition DETENTION BASIN DESIGN BASIN; A BASIN; A DESIGNER: S. Murphy Tot. Area 0.74 Acres DATE: 04I15 Imp. Area 4454 SF C = 0.43 Time Increment (min) • 5 CASE 1 Time of Conc. (min) 5.28 Outflow (cfs) 1 60 ft. Overland Flow Design Year Flow 50 , Area (acres) 0.74 Ct = 0.15 Imperoious Area (sq ft) 4454 L= 60 ft. 'C' Factor 0.43 n= 0.40 50-year Volume Provided 280 S= 0,020 Area' C 0.318 Tc = 3.27 min., by EquaGon 3-2 of Guidelines ' Time Time Inc. Intens. Q Devel. Vol.ln Vol,Out Storage 234 ft, Gutter flow „ (min) (sec) {iNhr} (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 5.28 317 4.48 1.43 605 317 289 Z2 = 3.5 n= 0.016 5 300 4.58 1.46 586 300 286 S= 0.012 10 600 3.20 1.02 721 600 121 15 900 2.45 0.78 786 900 -114 d= 0.166 ft. 20 1200 1.95 0.62 811 1200 -389 25 1500 1.62 0.52 829 1500 -671 A R Q Tc Tc tatal I Qc 30 1800 1.56 0.50 947 1800 -853 35 2100 1.26 0.41 899 2100 -1201 0.74 0.08 1.43 2.01 5.28 4.48 1.43 40 2400 1.19 0.38 946 2400 -1454 45 2700 1.08 0.34 965 2700 -1735 Qpeak for Case 1= 1.43 cfs 50 3000 0.99 0.32 979 3000 -2021 55 3300 0.92 0.29 998 3300 -2302 ' 60 3600 0.87 0.28 1026 3600 -2574 CASE 2 65 3900 0.82 0.26 1046 3900 -2854 10 4200 0.80 0.25 1097 4200 -3103 Case 2 assumes a Time of Concentration less than 5 minutes sa that the 75 4500 0.77 0.25 1129 4500 -3371 peak flow =.90(4,58)(Imp, Area) = 0.42 cfs 80 4800 0.75 0.24 1111 4800 -3629 85 5100 0.72 0.23 1193 5100 -3901 90 5400 0.71 0.23 1244 5400 -4156 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.22 1275 5700 -4425 1.43 cfs 100 6000 0.67 0.21 1302 6000 -4698 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume . = Impervious Area x.5 in I 12 iNft 186 cu ft 50 year Volume Provided 280 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STOR Maximum Storage Required by Bowstring 289 au ft Number and Type of Drywells Required 0 Single 1 Dauble INLAND PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addibon DETENTION BASIN DESIGN BASIN: B BASIN; B DESIGNER: S. Murphy Tat. Area 0.43 Acres DATE: 05f21 Imp. Area 3745 SF C = 0.48 Time increment (min) 5 CASE 1 „ Time of Conc. (min) 5.08 OutFlow (cfs) 1 60 ft. Overland Flow Design Year Flow 50 . Area (acres) 0.43 Ct = 0.15 Impervious Area (sq ft) 3745 L= 60 ft. 'C' Factor 0.48 n= 0.40 50-year Volume Provided 175 S= 0.020 Area ` C 0.206 Tc = 3,27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 163 ft. Gutter flow (min) (sec) (inmr) (cfs) (cu ft) (cu ft) (cu ft) ' Z1= 50.0 5.08 305 4.55 0.94 384 305 79 Z2 = 3.5 n= 0.016 5 300 4.58 0.95 380 300 80 S= 0.008 10 600 3.20 0.66 465 600 -135 15 900 2.45 0.51 508 900 -392 d= 0.153 ft. 20 1200 1.95 0.40 525 1100 -675 25 1500 1.62 0.33 536 1500 -964 A R Q Tc Tc total I Qc 30 1800 1.56 0.32 613 1800 -1187 35 2100 1.28 0.26 582 2100 -1518 0.63 0,08 0.94 1.81 5.08 4.55 0.94 40 2400 1.19 0.24 612 2400 -1768 45 2700 1.08 0.22 625 2700 •2075 Qpeak for Case 1= 0.94 cfs . 50 3000 0.99 0.20 634 3000 -2366 55 3300 0.92 0.19 646 3300 -2654 60 3600 0.87 0.18 665 3600 -2935 CASE 2 65 3900 0.82 0.17 678 3900 -3222 70 4200 0.80 0.17 711 4200 -3489 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0.16 732 4500 -3768 peak flow =.90(4.58)(Imp. Area) = 0.35 cfs 80 4800 0.75 0.15 759 4800 -4041 85 5100 0.72 0.15 773 5100 -4327 90 5400 0.71 0,15 807 5400 -4593 So, the Peak flow for the Basin is the greater of the lwo flows, 95 5700 0.69 0.14 827 5700 4873 0.94 cfs 100 6000 0.67 0.14 844 6000 -5156 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume • = Impervious Area x.5 in ! 12 iNft 156 cu ft 50 year Volume Provided 187.5 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STOR Maximum Storage Required by Bowstring 80 cu ft Number and Type of Orywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING . o . . _ , . . , , . _ . . ,a o 50-year STORM BOWSTRING METHOD PROJECT; Riverwalk Sth Addition PEAK FLOW CALCULATION PROJECT Rivennalk 8th Addition DETENTION BASIN DESIGN BASIN: C BASIN; C DESIGNER: S. Murphy Tot. Area 0.75 Acxes DATE: 05120 Imp. Area 4477 SF C = 0.43 Time Increment (min) 5 CASE 1 ' Time of Conc. (min) 5.27 = OutBow (cfs) 1 60 ft. Overland Flow Design Year Flow 50 , Area (aaes) 0.75 Ct = 0.15 Impervious Area (sq ft) 4477 L= 60 ft. 'C' Factor 0.43 n= 0.40 50-year Volume Provided 280 S= 0.020 Area' C 0.323 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Oui Storage 234 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 5.27 316 4.49 1.45 613 316 297 Z2 = 3.5 n= 0,016 5 300 4.58 1.48 594 300 294 S= 0,012 10 600 3.20 1.03 730 600 130 15 900 2.45 0,79 796 900 -104 d= 0.167 ft. 20 1200 1.95 0.63 822 1200 -378 25 1500 1.62 0.52 840 1500 -660 A R Q Tc Tc total I Qc 30 1800 1.56 0.50 960 1800 -840 35 2100 1.28 0.41 911 2100 -1189 0.75 0.08 1.45 2.00 5.27 4.49 1.45 40 2400 1.19 0.36 958 2400 -1442 45 2700 1.08 0.35 978 2700 -1722 , Qpeak for Case 1= 1.45 cfs 50 3000 0.99 0,32 992 3000 -2008 55 3300 0.92 0.30 1011 3300 -2289 60 3600 0.87 0.28 1040 3600 -2560 CASE 2 65 3900 0.82 0.26 1060 3900 -2840 70 4200 0,80 026 1111 4200 -3469 Case 2 assumes a Time of Concentration less lhan 5 minutes so that the 75 4500 0.77 0.25 1144 4500 -3356 peak flow =.90(4.58)(Imp. Area) = 0.42 cfs 80 4800 0.75 0.24 . 1187 4800 -3613 85 5100 0.72 0.23 1209 5100 -3891 90 5400 0.71 0.23 1261 5400 -4139 So, the Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.22 1292 5700 -4408 1.45 cfs 100 6000 0.67 0.22 1320 6000 -4680 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume . = Impervious Area x.5 in ! 12 iNft 187 ar ft , 50 year Volume Pravided 280 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STOR Maximum Storage Required by Bowstring 297 cu ft Number and Type of Drywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING C7 (7) F---7 t-7 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Rivervualk 8th AddiGon DETENTION BASIN DESIGN BASIN: D BASIN: D DESIGNER: S. Murphy Tot. Area 0.59 Aaes DATE: 05I07 Imp. Area 5643 SF C = 0.48 Time Inaement (min) 5 CASE 1 Time of Conc, (min) 5.38 Oufflow (cfs) 1 60 ft. Overland Flow Design Year Flow 50 , Area (acxes) 0.59 Ct = 0,15 Impenrious Area (sq ft) 5643 L= 60 ft. 'C' Faclor 0.48 n= 0.40 50-yearVolume Provided 254 S= 0.020 Area' C 0.283 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 205 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 5.38 323 4.45 1,26 545 323 222 Z2 = 3.5 n= 0.016 5 300 4.58 1,30 521 300 221 S= 0.008 10 600 3.20 0.91 643 600 43 15 900 2.45 0,69 701 900 -199 d= 0.171 ft. 20 1200 1.95 0,55 723 1200 477 25 1500 1.62 0.46 739 1500 -761 A R Q Tc Tc total I Qc 30 1800 1.56 0,44 844 1800 -956 35 2100 1.28 0.36 801 2100 -1299 0.78 0.09 1.26 2.12 5.36 4.45 1.26 40 2400 1.19 0.34 842 2400 -1558 45 2700 1.08 0.31 859 2700 -1841 Qpeak for Case 1= 1.26 cfs 50 3000 0,99 0.28 872 3000 -2128 55 3300 0.92 0.26 888 3300. -2412 60 3600 0.87 0.25 914 3600 -2686 CASE 2 65 3900 0.82 023 931 3900 -2969 70 4200 0.80 0.23 976 4200 -3224 Case 2 assumes a Time of Concentration less lhan 5 minutes so that the 15 4500 0.77 022 1005 4500 -3495 peak flow =.90(4.58)(Imp. Area) = 0.53 cfs , , . 80 4800 0.75 0.21 1043 4800 -3757 85 5100 0.72 0.20 1062 5100 -4038 90 5400 0.71 020 1108 5400 -4292 So, lhe Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.20 1135 5700 4565 1.26 cfs 100 6000 0.67 0.19 1159 6000 -4641 208' DRAINAGE POND CAICULATIONS . Required '208'Storage Volume . = Impervious Area x,5 in ! 12 iNft 235 cu ft . 50 year Volume Provided 254 au ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STOR •Maximum Storage Required by Bowslring 222 cu ft Number and Type of Drywelis Required 0 Single 1 Double INLAND PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT: Rivenaralk 8th Addition PEAK FLOW CALCULATION PROJECT Rivenroalk 8fh Addition DETENTION BASIN DESIGN BASIN: E BASIN: E DESIGNER: S. Murphy Tot. Area 0.17 Acres DATE: 05120 Imp. Area 3269 SF C = 0,50 Time Increment (min) 5 CASE 1 Time of Conc, (min) 5.00 Outflow (cfs) 0.3 ' 40 ft. Overland Flow Design Year Flow 50 , Area (acres) 0,17 Ct = 0.15 Imperoious Area (sq ft) 3269 L= 40 ft. 'C Factor 0.5 n= 0.40 50-year Volume Provided 170 S= 0,020 Area' C 0.085 Tc = 2.56 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Starage 138 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 5.00 300 4.58 0.39 156 90 66 72 = 1 n= 0.016 5 300 4.58 0.39 156 90 68 S= 0.008 10 600 3.20 0.27 191 180 11 . , 15 900 2.45 0.21 209 270 -61 d= 0.112 ft. 20 1200 1.95 0.17 216 360 -144 ' 25 1500 1.62 0.14 221 450 -229 A R Q Tc Tc total I Qc 30 1800 1.56 0.13 252 540 -288 35 2100 1.28 0.11 240 630 -390 0.32 0.06 0.39 1.90 5.00 4,58 0.39 40 2400 1.19 0.10 252 720 -468 45 2700 1.08 0.09 257 810 -553 Qpeak for Case 1= 0.39 cfs 50 3000 0.99 0,08 261 900 -639 . 55 3300 0.92 0.08 266 990 -724 60 3600 0.87 0.07 274 1080 -806 CASE 2 65 3900 0.82 0.07 279 1170 -891 70 4200 0.80 0.07 293 1260 -967 Case 2 assumes a Time of Concentration less than 5 minutes so that lhe 75 4500 0.77 0,07 301 1350 -1049 peak Flow =.90(4.58)(Imp, Area) = 0.31 cfs 80 4800 0.75 0.06 313 1440 -1127 85 5100 0.72 0.06 318 1530 -1212 • • 90 5400 0.71 0.06 332 1620 -1288 So, lhe Peak flow for the Basin is the greater of the two flows, 95 5700 0.69 0.06 340 1710 -1370 0.39 cfs 100 6000 0.67 0.06 348 1800 -1452 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume ; = Impervious Area x.5 in 112 iNft 136 cu ft , 50 year Volume Provided 170 cu ft ORYWELL REQUIREMENTS -10 YEAR DESIGN STOR , Maximum Storage Required by Bowstring 66 cu ft Number and Type of Drywells Required 1 Single 0 Double INLAND PACIFIC EN6INEERING o. ..m. . , o , p f BOWSTRING METH00 PROJECT: Riverwalk 8lh Addition PEAK FLOW CALCULATION PROJECT Riverrvalk 8th Additian DETENTION BASIN DESIGN BASIN: F BASIN: F 10-Year Design Storm DESIGNER: S. Murphy Tol. Area 3.27 Acres OATE: 06125 Imp. Area 17615 SF C = 0.41 Time Increment (min) 5 CASE 1 Time of Conc. (min) 11.72 Outflow (cfs) 0 120 ft. Overland Flow Design Year Flow 10 Area (acres) 327 Ct = 0.15 Impervious Area (sq ft) 17615 L= 120 ft. 'C' Factor 0.41 n= 0.40 '208' Volume Provided 1834 S= 0.020 Area' C 1.341 Tc = 4.95 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Starage 950 ft. Gutter flow , (min) (sec) (inmr) (cfs) (cu R) (cu ft) (cu fl) Z1= 50.0 For Z2 11.72 103 2.05 2,15 2591 0 2591 Z2 = 3.5 Type B =1.0 , n= 0.016 Rolled = 3.5 5 300 3.18 4,26 1714 0 1714 S= 0.013 10 600 2.24 3.00 2415 0 2415 15 900 1,77 2,37 2703 0 2703 d= 0.210 ft. 20 1200 1.45 1.94 2798 0 2798 25 1500 1.21 1.62 2821 0 2821 A R Q Tc Tc total I Qc 30 1800 1.04 1.39 2843 0 2643 35 2100 0.91 122 2854 0 2654 1.18 0.10 2.75 6.77 11.72 2.05 2,15 40 2400 0.82 1.10 2901 0 2901 45 2700 0.74 0.99 2916 0 2916 Qpeak for Case 1= 2.75 cfs 50 3000 0.68 0.91 2953 0 2953 55 3300 0.64 0.86 3037 0 3037 60 3600 0.61 0.82 3140 0 3140 CASE 2 65 3900 0.60 0.80 3330 0 3330 70 4200 0.58 0.78 3452 0 3452 Case 2 assumes a Time of Concentration less lhan 5 minutes so that the 75 4500 0.56 0.75 3558 0 3558 peak flow =.90(3.18)(Imp. Area) = 1.16 cfs 84 4800 0.53 0.71 3581 0 3581 85 5100 0.52 0.70 3722 0 3722 • 90 5400 0.50 0.61 3780 0 3760 So, the Peak flow for the Basin is the greater of the lwo flows, 95 5700 0.49 0.66 3902 0 3902 2.75 cfs 100 6000 0.48 0.64 4015 0 4015 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Impervious Area x.5 in ! 12 iNft 734 ar ft 208' Storage Volume Provided 1834 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 3722 cu fl Number and Type of Drywells Required 0 Single ERR Double 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8lh Addition DETENTION BASIN DESIGN BASIN: G BASIN: G DESIGNER: S. Murphy Tot. Area 1,95 Acres DATE: 06125 Imp. Area 13418 SF C = 0.43 Time Increment (min) 5 CASE 1 Time of Conc. (min) 7.40 OuMow (cfs) 0 60 ft. Overland Flow Design Year Flow 50 Area (acres) 1.95 Ct = 0.15 Impervious Area (sq ft) 13418 L= 60 ft. 'C' Factar 0.43 n= 0.44 50-year Volume Provided 341 S= 0.020 Area * C 0.839 Tc = 3.27 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.in Vol.Out Storage 600 ft. Gutter flow (min) (sec) (inmr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 7.40 444 3.75 3.15 1872 0 1672 Z2 = 3.5 n= 0.016 5 300 4.58 3.84 1544 0 1544 S= 0.013 10 600 3.20 2.68 2015 0 2015 15 900 2.45 2.05 2159 0 2159 d= 0.221 ft. 20 1200 1.95 1.64 2209 0 2209 25 1500 1.62 1.36 2243 0 2243 A R Q Tc Tc total I Qc 30 1800 1.56 1.31 2552 0 2552 35 2100 1.28 1.07 2416 0 2416 1.30 0.11 3.15 4.13 7.40 3.75 3.15 40 2400 1.19 0.99 2535 0 2535 45 2700 1.08 0.91 2582 0 2582 Qpeak for Case 1= 3.15 cfs 50 3000 0.99 0.83 2616 0 2616 55 3300 0.92 0.77 2662 0 2662 60 3600 0.87 0.73 2736 0 2136 CASE 2 65 3900 0.82 0.69 2785 0 2785 70 4200 0.80 0.67 2919 0 2919 Case 2 assumes a Time of Concentration less than 5 minutes sa that the 75 4500 0.77 0.65 3003 0 3003 peak flow =.90(4.58)(Imp. Area) = 1.27 cfs 80 4800 0.75 0.63 3114 0 3114 85 5100 0.72 0.60 3170 0 3170 90 5400 0.71 0.60 3305 0 3305 So, the Peak flaw for the Basin is the greater of the two flows, 95 5700 0.69 0.58 3385 0 3385 3.15 cfs 100 6000 0.67 0.56 3456 0 3456 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume = Imperoious Area x.5 in ! 12 iNft 559 cu ft 50 year Volume Provided 341 cu ft DRYWELL REQUIREMENTS - 50 YEAR DESIGN STORM Maximum Storage Required by Bowstring 3170 cu ft Number and Type of Drywells Required 0 Single ERR Double INLANO PACIFIC ENGINEERIN6 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk Bth Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN; FG BASIN: FG DESIGNER: S. Murphy Tot. Area 5.22 Acres DATE: 06125 Imp. Area 31033 SF C = 0.41 Time Increment (min) 5 CASE 1 Time of Conc, (min) 10.36 Outflow (cfs) 3 120 ft, Overland Flow Design Year Flow 50 Area (acres) 5.22 Ct = 0.15 Impervious Area (sq ft) 31033 L= 120 fl. 'C' Factor 0.41 n= 0.40 50-year Volume Provided 2175 S= 0.020 Area' C 2.140 Tc = 4.95 min., by Equation 3-2 of Guidelines Tme Time Inc. Intens. Q Devel. Vol.ln Vol.Out Storage 950 ft. Gutter flow (min) (sec) (iNhr) (cfs) (cu ft) (cu ft) (cu ft) Z1= 50.0 10.36 622 3.14 6.73 5605 1865 3740 Z2 = 3.5 n= 0.016 5 300 4.58 9.80 3940 900 3040 S= 0.013 10 600 3.20 6.85 5506 1800 3706 15 900 2.45 5.24 5828 2700 3128 d= 0,293 ft. 20 1200 1.95 4.17 5890 3600 2290 25 1500 1.62 3.47 5934 4500 1434 A R Q Tc Tc total I Qc 30 1800 1.56 3.34 6716 5400 1316 35 2100 1.28 2.74 6332 6300 32 2,30 0.15 6.73 5.41 10.36 3.14 6.73 40 2400 1.19 2,54 6623 7200 -577 45 2700 1.08 2.31 6729 8100 -1371 Qpeak for Case 1= 6.73 cfs 50 3000 0.99 2.12 6804 9000 -2196 55 3300 0.92 1.97 6914 9900 -2986 60 3600 0.87 1.86 7097 10800 -3703 CASE 2 65 3900 0.82 1.75 1215 11700 -4465 • . . 70 4200 0.80 1.71 7553 12600 -5047 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 1.65 7764 13500 -5736 peak flow =.90(4.58)(Imp. Area) 2.94 cfs 80 4800 0.75 1.61 8044 14400 -6356 85 5100 0.72 1.54 8185 15300 -7115 90 5400 0.71 1.52 8527 16200 -7673 So, lhe Peak flow for the Basin is the greater of the two 8ows, 95 5700 0.69 1,48 8730 17100 -8370 6.73 cfs 100 6000 0.67 1.43 8907 18000 -9093 208' DRAINAGE POND CALCULATIONS Required'208' Storage Volume . = Impervious Area x.5 in I 12 iNft 1293 cu ft 50 year Volume Provided 2175 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STOR Maximum Storage Required by Bowstring 3740 cu ft Number and Type of Drywells Required 0 Single 3 Double INLAND PACIFIC ENGINEERING 50-year STORM BOWSTRING METHOD PROJECT: Riverwalk 8th Addition PEAK FLOW CALCULATION PROJECT Riverwalk 8th Addition DETENTION BASIN DESIGN BASIN: H BASIN: H( DESIGNER: S. Murphy Tot. Area 0.61 Acres DATE: 04120 Imp. Area 5373 SF C = 0.46 • Time Increment (min) 5 CASE 1 Time of Conc. (min) 6.78 Outflow (cfs) 1 75 ft, Overiand Flow Design Year Flow 50 . , . Area (acres) 0.61 Ct = 0.15 Impervious Area (sq ft) 5373 L= 75 ft. 'C' Factar 0.46 n= 0.40 50-year Volume Provided 387 S= 0.010 Area' C 0281 Tc = 4.60 min., by Equation 3-2 of Guidelines Time Time Inc. Intens. Q Devel. Vol.ln Vol.Out Starage 225 ft. Gutter flow (min) (sec) (inlhr) (cfs) (cu ft) (cu ft) (cu ft) Z1 = 50.0 6.78 407 3.97 1.11 607 407 200 Z2 = 1 n= 0.016 5 300 4.58 1,29 517 300 217 S= 0,010 10 600 3,20 0.90 663 600 63 15 900 2.45 0.69 714 900 -166 d= 0.160 ft. 20 1200 1.95 0.55 732 1200 -468 25 1500 1.62 0.45 745 1500 -755 A R Q Tc Tc total I Qc 30 1800 1.56 0.44 848 1800 -952 35 2100 1.28 • 0.36 804 2100 -1296 0.65 0.08 1.11 2.19 6.78 3.97 1.11 40 2400 1.19 0.33 844 2400 -1556 45 2700 1.08 0.30 860 2700 -1840 Qpeak for Case 1= 1.11 cfs 50 3000 0.99 0.28 872 3000 -2128 55 3300 0.92 0.26 888 3300 -2412 60 3600 0.87 0.24 913 3600 -2667 CASE 2 65 3900 0.82 0.23 929 3900 -2971 70 4200 0.80 0.22 974 4200 -3226 Case 2 assumes a Time of Concentration less than 5 minutes so that the 75 4500 0.77 0,22 1002 4500 -3498 peak flow =.90(4.58)(Imp. Area) = 0.51 cfs 80 4800 0.75 021 1039 4800 -3761 85 5100 0.72 0.20 1058 5100 -4042 90 5400 0.71 0.20 1103 5400 -4297 So, the Peak flow for the Basin is the greater of the two flows, 95 5100 0.69 0,19 1130 5700 -4570 1•11 cfs 100 6000 0.67 0.19 1154 6000 -4846 208' DRAINAGE POND CALCULATIONS Required '208'Storage Volume , = Impervious Area x.5 in 112 iNft , 224 cu ft 50 year Volume Provided 387 cu ft DRYWELL REQUIREMENTS -10 YEAR DESIGN STORM Maximum Storage Required by Bowstring 217 cu ft Number and Type of Drywells Required 0 Single 1 Double INLAND PACIFIC ENGINEERING 208' Pond Calculations Project: Riverwalk 8th Addition Date: 25-Jun-97 Designer: S. Murphy Upstream Carryover Accumul. Pond '208' '208' Curb Drop Imper. Storage Storage Storage Typel Storage Carryover Sub-Basin Station R!L Area Req't Req't Req't Size Provided Downstream A 18+20 L 4454 185.6 185.6 28 x20 280.0 6 13+20 L 3745 156.0 156.0 Odd 187.5 C 18+20 R 4477 186.5 186.5 28x20 260.0 D 12+40 L 5643 235.1 235.1 Odd 254.0 E 10+53 R 3269 136,2 136.2 Odd 170.0 F 20+24 R 17615 734.0 734.0 Odd 1834.0 G 20+00 L 13418 559.1 559.1 Odd 341.0 * Calculated per Figure 18 of Guidelines Calculated per Figure 16 of Guidelines ~ A 4 foot curb drop with a 6" gutter has a capacity of 4.0 cfs in sump cond'rtion. F----) ~ .c') ~ ~ ~ . ~ I I r"! . ~ ~ ) i ) ( t i ~ i ) i ~ ( , ) ~ ~ E RIVERWALK 8TH ADDITION CURB INLET CALCULATIONS Curb Inlet Depression = 2 in. Standard Curb Inlet Length = 4 ft. Upstream Gutter Roughnes Reciprocal Depth Length Curb Drop Impen►ious Peak Flow Slope Caeff. Cross slope of Flow Required Basin Station RIL Area c.f.s. S n Z Zln d' QalLa*" QI(QalLa) Remarks A 18+20 L 4454 0.97 Sump condition"'* B 18+20 L 3745 0.64 0.0080 0.0160 50 3125 0.13 0.088 7.29 Need 2- 4' curb inlets C 18+20 R 4477 0.99 0.0117 0.0160 50 3125 0.14 0.096 10.29 Sump condition"* D 12+37 L 5643 0.85 Sump condi6on"' E 10+53 R 3269 0.27 0.0087 0.0160 50 3125 0.09 0.062 4,32 Need 1- 5' curb inlet F 20+35 L 17615 2.75 0.0087 0.0160 50 3125 0.22 0.149 18.43 Need 3- 6' curb inlets G 20+35 R 13418 2.13 0.0087 0.0160 50 3125 0.20 0.136 15.71 Need 4- 4' curb inlets C-RW6 10+55 L 5373 0.65 0.0100 0.0160 50 3125 0.12 0.085 7.68 Need 2- 4' curb inlets Calculated per Figure 18 of Guidelines Calculated per Figure 16 of Guidelines A 4 foot curb drop with a 6" gutter has a capacity of 4.0 cfs in sump condition. v ,y~ v ~ INLAND PACIFIC ENGINEERING, INC. March 19, 1997 f IPE W . O. #96087 Spokane County Public Works Engineering Division 1026 W. Broadway Avenue Spokane, Washington 99260-0170 Atm: Bill Johns, P.E. RE: Riverwalk 8th Addition (P1414 -G) Clarification of Street and Storm Drainage Plans submittal timing Dear Bill: The above referenced project is in the design stage in our office, and clarification of an issue regarding the acceptance of Indiana Avenue to the east plat boundary of the Riverwalk plat has become necessary. We have been informed by Paul Lennemann of your office that the street and storm drainage plans will not be accepted for submittal until Indiana Avenue has been accepted into the County road system. Our client, Pacific Properties, should not be punished for what has become an ongoing problem regarding the record drawings for Indiana Avenue. Riverwalk 6`h Addition is in the final stages of platting, extending Indiana Avenue to the east plat boundary, providing Pacific Properties with an access onto Indiana Avenue. If Riverwalk 41h and 5`h Additions have been reviewed and accepted without Indiana Avenue's acceptance, what would make 81 Addition's position any different? Pacific Properties has been cooperative in working out the Barker Road improvements and the I-90 traffic signal as part of Riverwalk 71h Addition, and should not be penalized for a punch list on an adjacent project that does not affect his access. ~ a~a , I Your consideration in this matter would be greatly appreciated. Should you have any questions, please contact me at 458-6840. ~ Sincerely, Inl d Paci ngineering Company ~ . Todd R. Whipple, P. E. , TRW/sm cc: file, Pacific Properties ( Dotumtnt1960871bjahnt ~ . A 22 k+"7 r 37 I~ Riverwalk 1 st < ~3 ✓ ng90, qE BAL~Diwi! r LN 55083.9052 95005514 NEW RESIDENCE/GARAGE - GAS _ 018907 E BALDWIN LN 55083.9052 y~ 95006331 SEWER CONNECTION - RIVERWALK (95 S-746) i bi piss E~ :~:AL ~DM p LN 55083.9052 95005521 NS RESIDENCE/GARAGE - GAS 018911 E BALDWIN LN 55083.9052 95006333 SEWER CONNECTION - RIVERWALK (95 S-748) /0 : 2~33~109IMPT71N LN 55083.9052 95010187 S'~IDENCE W/GARAGE - NATURAL GAS 018923 E BALDWIlN LN 55083.9052 95010188 R CONNECTION - RIVERWALK (95S-1156) LN 55083.9052 001536 ,V016IDENCE/ATTACHED GARAGE - FORCED- AIR GAS 018925 E BALDWIN LN 55083.9052 96001541 SEWER CONNECTION - RIVERWALK 1ST (96S-189) ~0160liN~~ 9TT W Y LN 55083.9052 96001364 .~dSIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001605 N HARMONY LN 55083.9052 96001379 SEWER CONNECTION - RIVERWALK (96S-149) J 01020 ~ fA ' ~ ~ ~O ~ `Y LN 55083.9052 96007752 MOWNECE/ATTACHED GARAGE - FORCED AIIZ GAS 001620 N HA.RMONY LN 55083.9052 96007760 SEWER CONNECTION - RIVERWALK 1 ST (96S-1008) v VtMv TONY LN 55083.9052 001404 IW. SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001621 N HARMONY LN 55083.9052 96001410 SEWER CONNECTION - RIVERWALK 1 ST (96S-157) 01 ~,►200 US= MA ►'~~OO` ~►YO I PdLN 55083.9052 96003656 'S` "IDENCE/ATTACHED GARAGE - NAT'LJRAL GAS 001624 N HARMONY LN 55083.9052 96003672 SEWER CONNECTION - RIVERWALK 1 ST (96S-495) a0nt~2~~I~ . ~ : ►ulc0 ~~~►Y~4 LN 55083.9052 96001.586 IMSxIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001625 N HARMONY LN 55083.9052 96001610 SEWER CONNECTION - RIVERWALK 1ST (96S-196) LN 55083.9052 U 96001384 - SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001703 N HARMONY LN 55083.9052 96001388 SEWER CONNECTION - RIVERWALK 1ST (96S-151) ~0 A0?ON91,0'+►~j OONY LN 55083.9052 96001424 01TESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001707 N HARMONY LN 55083.9052 96001434 SEWER CONNECTION - RIVERWALK 1ST (96S-165) ~ OOWI[Owk ~okm W0 ~ 'Y LN 55083.9052 95005486 i NEW RESIDENCE/GARAGE - GAS 001710 N HARMONY LN 55083.9052 95006330 _ SE R CONNECTION (95S-745)RIVERWALK ( 0.0~3 . ' ►~~"O y LN 55083.9052 \ ,5014172 qWSIDENCE/ATTACHED GARAGE - MNATURAL GAS 001713 N HAR.MONY LN 55083.9052 95010185 SEWER CONNECTION - RIVERWALK (95S-1154) 100~1 ~ ~ ~~~T -r~~;•us0~,.~ LN 55083.9052 95005516 "~'EW RESIDENCE/GARAGE - GAS 001716 N HARMONY LN 55083.9052 95006329 SEVVER CONNECTION - (95S-744) RIVERWALK ~O.O~lir7 ~I►-~'~ O_,;!1 LN 55083.9052 95010181 ~.$.ESIDENCE W/GARAGE - NATURAL GAS 001719 N HARMONY LN 55083.9052 95010184 SEWER CONNECTION - RIVERWALK (95S-1153) JOAMMIMM-0- _~1MI MR Wo LN 55083.9052 94010381 Wl SIDENCE 001722 N HARMONY LN 55083.9052 94012296 %DR)?ff S R ONNECTION (94S-1382) LN 55083.9052 950007 -►7 AIlZ CONDITIONER 04WA m Ps- ~~~I~~O P ~Y~a LN 55083.9052 95010174 NIDS ENCE/ATTACHED GARAGE - NATURAL GAS 001723 N HARMONY LN 55083.9052 95010186 SEWER CONNECTION - RIVERWALK (95S-1155) ~f OWR' N- ARMO ~°YA" LN 55083.9052 96001512 ~`SIDENCE/ATTACHED GAR.AGE - FORCED AIR GAS 001726 N HARMONY LN 55083.9052 6001525 WER CONNECTION - RIVERWALK 1 ST (96S-185) 00 1 ` '1 i tOr,~ LN 55083.9052 95008628 SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001805 N HARMONY LN 55083.9052 95008921 SEWER CONNECTION - RIVERWALK 1ST (95S-1018) 000- ~Ti~PRI~~ O~Y~ LN 55083.9052 95008630 SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001813 N HARMONY LN 55083.9052 95008920 SEWER COTINECTION - RIVERWALK 1ST (95S-1017) 001813 N HARMONY LN 55083.9052 96003749 J AIR CONDITIONER 00 ~ maxARMONY " LN 55083.9052 96000015 .MSIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001822 N HARMONY LN 55083.9052 96000094 SEWER CONNECTION - RIVERWALK 1 ST (96S-9) ~OOW&ONW M (~i ►T~`~ LN 55083.9052 95009804 I SIDENCE W/GARAGE - NATURAL GAS 001823 N HARMONY LN 55083.9052 95009963 SEWER CONNECTION - RIVERWALK 1ST (95S-1131) 001900 N HARMONY LN 55083.9052 95002973 INSTALL SIGNS FOR SUBDIVISIONS ~0 Q~1~1~ 00!111, C~~~iDLL~►AN LN 55083.9052 95010464 kTESIDENCE W/GAR.A.GE - GAS 001725 N MCMILLAN LN 55083.9052 95010530 R CONNECTION - RIVERWALK 1ST (95S-1182) ~ r C►I M`'° LN 55083.9052 ° 9 010468 I&SIDENCE W/GARAGE - GAS 001726 N MCMILLAN LN 55083.9052 95010531 SEWER COrNECTION - RIVERWALK 1ST (955-1183) A w"m me ► AN LN 55083.9052 96002347 SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001729 N MCMILLAN LN 55083.9052 96002357 R CONNECTION - RIVERWALK (96S-309) ,Q,~ ► 'C '~AN LN 55083.9052 5006413 ~tESIDENCE W/GARAGE - NATURAL GAS 001731 N MCMILLAN LN 55083.9052 95006634 SEWER CONNECTION - RIVERWALK 1 ST (95 S-786) v / i 10l MM i W6 , C , oWL~AN LN 55083.9052 96000413 AESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001732 N MCMII.,LAN LN 55083.9052 96000416 SEWER CONNECTION - RIVERWALK (96S-33) ' 00jlj9fM• , , I~~~~ WW~ LN 55083.9052 95006483 AESIDENCE W/GAR.AGE - NATUR.AL GAS 001736 N MCMR„LAN LN 55083.9052 95006636 SEWER CONNECTION - RIVERWALK 1 ST (95S-787) ~0j 1~ R, WC , V AN ` LN 55083.9052 96004157 f,ESIDENCE/ATTACBED GARAGE - FORCED AIR GAS 001737 N MCIVBLLAN LN 55083.9052 96004179 SEWER CONNECTION - RIVERWALK 1 ST (96S-565) ~ 00l: wn,N,~.~ LN 55083.9052 ~ 95006412 AESIDENCE W/GARAGE - NATURAL GAS 001738 N MCMII,LAN LN 55083.9052 95006517 SEWER CONNECTION - RIVERWALK 1ST ADD -(95S-774 001738 N MCMILLAN LN 55083.9052 96003363 ADDITION ONTO EXISTING GARAGE , . . 0 C A, , i ~+L~►,~A~T LN 55083.9052 95006506 R SIDENCE W/GA.RAGE - NATURAL GAS 001104 N MCN.QLLAN LN 55083.9052 95006639 SEWER CONNECTION - RIVERWALK 1ST (95S-790) 001~8~t.~0~T~C ~~►~N~ LN 55083.9052 95007393 ASIDENCE W/GARAGE - NATURAL GAS 001810 N MCNiILLAN LN 55083.9052 95007395 SEWER CONNECTION - RIVERWALK 1 ST (95S-847) 001891EM1MI~ ~1V.II~M ► LN 55083.9052 96001533 AESIDENCE/ATTAC]HED GARAGE - FORCED AIR GAS 001815 N MCMILLAN LN 55083.9052 96001534 SEWER CONNECTION - RIVERWALK 1 ST (96S-186) 00 o►, L= L LN 55083.9052 96000135 JASIDENCE/ATTACHED GARAGE - FORCED AIR GAS 001816 N MCMILLAN LN 55083.9052 96000137 SEWER CONNECTION - RIVERWALK (96S-14) 001816 N MCMILLAN LN 55083.905 96002849 S G POOL & HEATER O6@JWNI.► ~ "v CI~~ M-A1to- LN 55083.905 95010483 AESIDENCE W/GARAGE - GAS 001821 N MCMILLAN LN 55083.905 95010529 SEWER CONNECTION - RIVERWALK 1ST (95S-1181) lo:.M :~2~?~N M*bi ~+L~~~X~~ LN 55083.905 96000125 ISIDENCE/ATTACHED GARAGE - NATUR.AL GAS 001822 N MCMILLAN LN 55083.9052 96000136 SEWER CONNECTION - RIVERWALK (96S-13) Riverwalk 2nd ~ WO► ~ ~AWN`A AVE 55083.9000 96010647 =SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019110 E INDIANA AVE 55083.9000 97001028 SEWER COrNECTION - RIVERWALK 2ND (97 S-90) MIIlf►1iE D ~:1 ~ A AVE 55083.9000 96004463 NRESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019117 E IlNDIANA AVE 55083.9000 96006913 SEWER CONNECTION - RIVERWALK 2ND (96S-892) AVE 55083.9000 96006809 ' SIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019122 E INDIANA AVE 55083.9000 96007137 SEWER CONNECTION - RIVERWALK 2ND (96S-917) OMMIN r► lb'TANA AVE 55083.9000 96004474 OPESIDENCE/ATTACHED GAR.AGE - FORCED AIR GAS 019125 E INDIANA AVE 55083.9000 96006914 SEWER COrdNECTION - RIVERWALK 2ND (96S-893) no128 mm, MD M, A AVE 55083.9000 96004461 IfESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019128 E INDIANA AVE 55083.9000 96006912 SEWER CONNECTION - RIVERWALK 2ND (96S-891) 002020 N MICHIELLI LN 55083.9000 0'`0j1i IM] S~'~-AI,w►'~C~O M P'r V E R LN 55083.9000 96007415 &ESIDENCEATTACBED GARAGE - FORCED AIR GAS 001852 N SALMON RIVER LN 55083.9000 96007428 SEWER COTTNECTION - RIVERWALK 2ND (96S-964) 00 ~~2~Tf•~T i~ ,•:~RIVER LN 55083.9052 96007879 'RESIDENCE W/GARAGE - NATURAL GAS 001902 N SNAxE RIVER LN 55083.9052 96008817 SEWER COr1NECTION - RIVERWALK 2ND (96S-1154) t4~ Riverwalk 3rd AVE 55083.9000 ~ 9601647 ATTACHE~D GARAGE - FORCED AIR GAS M SID.~NCE/ 019110 E INDIANA AVE 55083.9000 97001028 SEWER CONNECTION - RIVERWALK 2ND (97 S-90) 019117 E INDIANA AVE 55083.9000 96004463 RESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019117 E IlvDIANA AVE 55083.9000 96006913 , SEWER CONNECTION - RIVERWALK 2ND (96S-892) - 019122 E 1NDIANA AVE 55083.9000 ' ~ 96006809 RESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019122 E INDIANA AVE 55083.9000 96007137 . SEWER COr1NECTION - RIVERWALK 2ND (96S-917) 019125 E INDIANA AVE 55083.9000 96004474 RESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019125 E INDIANA AVE 55083.9000 96006914 SEWER CONNECTION - RIVERWALK 2ND (96S-893) 019128 E INDIANA AVE 55083.9000 96004461 RESIDENCE/ATTACHED GARAGE - FORCED AIR GAS 019128 E INDIANA AVE 55083.9000 96006912 SEWER CONNECTION - RIVERWALK 2ND (96S-891) 002020 N MICHIELLI LN 55083.9000 001852 N SALMON RIVER LN 55083.9000 96007415 RESIDENCE/ATTACHED GAR.AGE - FORCED AIR GAS ~ ~ e ~ ~ 001852 N SALMON RIVER LN 55083.9000 96007428 SEWER CONNECTION - RIVERWALK 2ND (96S-964) 001902 N SNAKE RIVER LN 55083.9052 96007879 RESIDENCE W/GARAGE - NATURAL GAS 001902 N SNAKE RIVER LN 55083.9052 ~ 96008817 ' ~ S I R CONNECTION - RIVERWALK 2ND (96S- 154) , 01827 NRtqff LN 55083.0000 Z~ t ' 004671 Sd`A`", r2~10~ RESIDENCE/ATTACHED GAR.AGE - NAT'IJRAL GAS 001827 N MICHIELLI LN 55083.0000 96005168 SEWER CONNECTION - RIVERWALK 3RD (96S-669) 0 W,,U • ! CHIELLI LN 55083.0000 96004713 RESIDENCE/ATTACHED GARAGE - NAT'LTRAL GAS 001903 N MICHIELLI LN 55083.0000 96005169 3d SEWER CONNECTION - RIVERWALK 3RD (96S-670) 0 0 1 ff0~~'4 ll~ U CHM LLI LN 55083.0000 96004682 RESIDENCE/ATTACHED GARAGE - NATUR.AL GAS 001904 N MICHIELLI LN 55083.0000 96005170 SEWER CONNECTION - RIVERWALK 3RD (96S-671) OWNT N MICHIELLI LN 55083.0000 96004685 RESIDENCE/ATTACHED GARAGE - NATURAI, GAS 001,907 N MICHIELLI LN 55083.0000 96005172 SEWER CONNECTION - RIVERWALK 3RD (96S-672) C,~2~ N MICHIELLI LN 55083.0000 96007376 RESIDENCE W/GARAGE - GAS (MODEL HOME) 001922 N MICHIELLI LN 55083.0000 96007379 SEWER COr1NECTION - RIVERWALK STH (96S-950) " +t~,~.,. 14'" " t , fi 1611 P~• ~ ~ March 27, 1997 Todd Whipple, P.E. Inland Pacific Engineering 707 West 7th Avenue, Suite 200 Spokane, WA 99204 SUBJECT: P1414G - Riverwalk 8th Addition Plan Submittal (IPE letter dated March 19, 1997) Gentlemen: We have considered your request, and have reviewed our files for the various phases of the Riverwalk project. It appears that access to Riverwalk 8th is, by any routing plan, available only by traveling some distance on Indiana Avenue. At our last site visit on March 26, 1997, Indiana has not yet been paved from the east boundary of Riverwalk 2nd, through Riverwalk 6th, to the access point for Riverwalk 8th. We would also like to note that the plat approval for Riverwalk 7th was granted in spite of the lack of approved plans for the Barker Road improvements. Those improvements became necessary due to the lot threshold which IPE had indicated would require those improvements. The plan acceptance of Riverwalk 7th was not affected by the acceptance of Indiana, as the primary access to most of the Riverwalk 7th lots is expected to occur from Mission Avenue. The County has been working with IPE since at least the Spring of 1996 on developing the construction documentation for those phases of Riverwalk which constructed Indiana, and the supporting drainage facilities, up to the westerly boundary of Riverwalk 6th (phases 1, 2, and 3). This was all so that following phases which access lndiana could have plans submitted and plats approved. The first submittal of the Record Drawings and supporting documents for phase 1 was Todd Whipple, P.E. P1414G - Plan Submittal March 27, 1997 Page 2 of 3 received in November 1996, and comments were returned in December 1996. To date, the actions necessary to address the various comments noted in our review of IPE's submittals for phases 1, 2, and 3 have not yet been completed. We are enclosing a list which summarizes generally the actions necessary to address the different categories of the comments provided. Please refer to the actual comments (previously provided) for the specific items of concern. As you will recall, the plans for Riverwalk 4th and Sth also were not to be submitted until the County had accepted the construction and established Indiana for maintenance. This position was taken so that the Sponsor did not get placed in the position of having to maintain and plow what would be the major access into and through this large subdivision until the roads were finally _ established as County-maintained roads. This is similar to the situation in the Westwood d velopment, with which you are familiar. It is unfortunate that this position had to be taken on 6'r-ec&.k e*O~G those projects, but it was the only option available to the County tq(eniic)e some achon toward the acceptance of Indiana. As the Sponsor demonstrated progress on the acceptance of Indiana, the County relaxed that position to accepting the plans for review, and then construction, with plat approval of those phases to be granted when Indiana had been established. At our last meeting with the Sponsor of phases 1, 2, and 3(on February 24, 1997), we had indicated the County Engineer would be willing to grant Final Approval for Riverwalk 4th and ~ Sth. 1~h~s'"~llowe-~ve , w~as cont~inge ~ ~t upon cont~in~ued pxto,g~rtess towratd.,iti e accep.ta.inceUan~°ddK /~l E&t~ab~l[i:'s?hn1~r~~t o; ndiana. ,We are conccrned that progress may be stagnating. This will havc an AC21,effect on the plat approvals for Riverwalk 4th and Sth. There are many items which can, and should be completed prior to the actual submittal of the Record Drawings and supporting documents. Among these items are any plan changes which are Todd Whipple, P.E. P1414G - Plan Submittal March 27, 1997 !c~" Page 3 of 3 ~ contemplated4zshould be treated in a fashion analogous to a Design Deviation Request in the project design process. If plan changes are necessary to account for field conditions, then the justification for those changes, to include all supporting calculations, will need to be submitted, and then receive the County Engineer's approval, prior to submitting the Record Drawings. This is necessary so that (1) the processing of the Record Drawings is not delayed by the processing of the plan changes, and (2) so that Record Drawings are not returned due to plan changes which the County Engineer will not approve. This will also minimize the potential to re-record any additional easements which may result from the proposed plan change. In light of the above, we do not feel that it would be prudent ' to allow plan submittals for additional projects which can be expected to have their primary access from Indiana, until Indiana has been accepted, and established by the County for maintenance. This includes Riverwalk 9th, as well as Riverwalk 8th. Please let us know, in writing, when the Record Drawings and supporting documents for Riverwalk 1st, 2nd and 3rd will be submitted; we would also like to know when to expect any Todd Whipple, P.E. P1414G - Plan Submittal March 27, 1997 Page 4 of 3 Plan Change Requests which may be needed. I would appreciate your response by April 4, 1997. If you have any questions, please contact Ed Parry, either by letter, or by telephone at 456-3600. Sincerely, W il l iam A. Johns, P. E. Spokane County Engineer 1 dwar . Parr P. E. PMJ , eview Engineer cc: Project file: P1414, P1414A, P1414B, P1414C, P1414D, P1414E, P1414F, P1414G, P1414H Spokane County Public Works Director: Dennis Scott, P.E. Spokane County Engineer's Office: Bill Hemmings, P.E., Ed Parry, P.E., Dean Franz, P.E. Sponsors: Riverwalk lst, 2nd, 3rd, 4th, Sth: Ed Dean/Mark Hancock, Dean Housley Company, 16720 N.E. 116[h Street, Redmond, WA 98052 • Riverwalk 8th: Mike Miller, P.E./Doug Birch, Pacific Proper[ies Incorporated, 14410 Bel-reci Road, Bellewe, WA 98007 Riverwalk 9th: Mike Klicka, P.O. Box 1455, Hayden Lake, TD 83855