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Gaarde Street - Phase I Stormwater Plan - 1999 STORMWATER PLAN GAARDE STREET - PHASE I CITY OF TIGARD f Prepared by: ///CENTURY WEST ENC/NEERlNG CORPORATION 825 NE Multnomah, Suite 425 Portland, Oregon 97232 (503) 231-6078 DRAFT SEPTEMBER, 1999 STORMWATER PLAN GAARDE STREET - PHASE I CITY OF TIGARD Prepared by: CENTURY WEST ENGINEERING CORPORATION 825 NE Multnomah, Suite 425 Portland, Oregon 97232 (503) 231-6078 w DRAFT SEPTEMBER, 1999 W TABLE OF CONTENTS rr Site Location Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 BasinMap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 +,r Project Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Existing Stormwater System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Proposed Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Water Quantity Analysis and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Hydrologic Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Water Quantity System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Water Quality Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 +r Conveyance System Analysis and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 �r Appendices Appendix A Water Quantity/Quality Control Plan Appendix B Soils Information and Peak Flow Modeling Appendix C Pipe Flow Characteristics Appendix D Summary of 2-10 year Design Storm Modeling r Tables 2a, 2b, 2c, 3a, 3b, and 3c W do aw wr wr sw CHIMNE RIpG f Sw KATHERlN —\V F N v, W KATHERINE to L4 SW SCOTT N SW LY 00' Lp ,. N LA SW SW ANN o V) 3 —' cn U) w SOK W E BNISH m iw N N o SW N SW W A ? Z vii �2 F NLA N 40 Sly N = p SW MARIE y N .�� CARMAN N rrr SW SW CARM 0 N SW WALNUT p im w L i SW ALBERTA Io N PRO S M 3 LOCA ON � N SW JAMES (A _) 9 `L y N n D SW MARION 5 N �O�P irr n N < N SW BENCHVIEW err SW ROSE VISTA 0 Of n� 3 10 Q N SW GAARDE ow 3 +Iwo DESIGNED BY:RCW CHECKED BY: RCW LOCATION MAP DATE: GAARDE STREET IMPROVEMENTS `�IE E(V T IN F2 o pW E S T 09/08/99 DRAWN BY: DAP SCALE: NO SCALE 1444 NWc.tt<<my FIGURE: PHASE I Benl, OR 97701 541-388-3500th—•541-388-5061 fsx 1 FILE: 40084003.01.7H3.DWG CITY OF TIGARD ow WALNUT BASIN 190 191 218 219 220 2900 2700 "WEST" _ "EAST" - - - - - - - - - - - - SW WALNUT STREET 300 1300 1400 I N 1 3000 1900 1800 3300 3400 Ly I 3 Z ! 2000 1500 i t � _ L ! a -0 t Z c Li 4 2100 1501 1502 I Q `1 cn m 3101 wW - __- ----- - -- o LEGEND: C� TAX LOT NUMBER 2000 1100 N i 1700 i 3100 1000 i 900 i Y PLAN SCALE: 1"=100' DESIGNED BY: RCW SCALE : 1"=100' GAARDE STREET FIGURE DRAWN BY : DAP DATE 9/3/99 /�C E N T U R Y WEST IMPROVEMENTS CITY OF TIGARD ENGINEERING CORPORATION CHECKED BY : RCW FILE 7GX3.DWG 825 NE Multnomah Suite 425 PHASE Portland, Oregon 97232 BASIN MAP PROJECT NO.: 40084003.01 503-131-6078 phone • 503-231-6482 fax TIGARD, OREGON ow Project Overview Existing Stormwater System The Gaarde Avenue - Phase I Project includes the extension of approximately 600 feet of improvements south from SW Walnut Street through undeveloped property connecting into the northerly border of Quail Hollow Subdivision. In addition approximately 700 feet of SW Walnut Street between SW 132nd and SW 129th will be widened to meet future needs. The improvements are located in the upper reaches of the Fanno Creek drainage basin. The topography generally slopes from south to north at approximately a 4% grade. Walnut Street has a westerly subbasin which eventually discharges north via a 24-inch pipe to the extension of SW 132nd Avenue which eventually empties into a tributary of Fanno Creek. The water is collected in ditches on each side of SW Walnut or a combination of pipes and catch basins where newer improvements have been completed. The easterly subbasin on Walnut Street collects water in ditches on each side of the street and transports it to a drainage swale with pipes beneath the road approximately 600 feet further to the east. See Appendix A for a map of the existing system. Proposed Improvements Proposed Improvements for the project include: • Widening SW Walnut Street from SW 132nd Avenue to SW 129th Avenue (approx. 700 feet) in sections from 22-feet wide to a minimum width of 44- feet wide to include two travel lanes, center turn lane and two bicycle lanes. The westerly 200 foot section begins at SW 132nd with a transition from the existing width to the final width of 56-feet which also includes a dedicated right turn lane at the SW Gaarde intersection. The easterly 100 section begins at SW 129th with a transition from the existing width to the final width of 44-feet at the east side of the SW Gaarde intersection. The middle 400 foot section, completed to future standards will not require additional modifications in the future when the entire street is rebuilt. Construction of the extension of SW Gaarde Street through undeveloped property to meet the northerly extension of Quail Hollow Subdivision (approx. 600 feet). The new improvements will include a section which varies in width from 48- feet at the intersection with Walnut to 40-feet at the southerly extension. • Install curbs along the entire length of SW Gaarde Street and along the section of SW Walnut which will not be rebuilt in the future on each side of the intersection to control and direct stormwater run-off north. ++rir Install a stormwater system that will collect, convey, and detain stormwater for release through two separate discharge points. Stormwater will be released from this new system at a rate no greater than the predeveloped amount prior it to construction of the additional impervious area. rrr �//CENTURY WEST 3 ENG1NEfR1NG C.ORPORA710N #4008400201 r irr Install water quality manholes at strategic locations to provide collection of solids for flows generated by the additional area using a 25-year design storm. • Utilize passive flow-through stormwater filter system to improve water quality of the additional runoff contributed in that area by the widened street section. dw Upon completion of the proposed project the total increase in impervious paved area where stormwater will be collected (curbed areas) will increase by approximately 1 .25 acres. This includes the new curbed areas along the length of the project. rrr Water Quantity Analysis and Design Hydrologic Analysis Basin hydrology was modeled with the King County Hydrology Computer Program. The SBUH/SCS method for computing runoff hydrograph was used to determine the peak flow for each of the two subbasins within the project limits. The basins are shown in Figure 1 and do include: Gaarde Street and Walnut Street ( East and West). There is a total of approximately 1 .25 acres of additional impervious curbed area resulting from this road improvement project. Existing and future peak flows were calculated for each subbasin in this report. Current off- site surface drainage patterns were assumed to continue following construction of improvements. Discharge flow rates within the existing and proposed Gaarde Street drainage system are assumed to remain constant when the new street and storm drainage improvements are completed. Additional surface runoff generated by the increased impervious area will be retained in oversized pipes with orifices that regulate release rates equal to the predeveloped 25 year design flow prior to construction of the improvements. Surface runoff generated within terrain south of the connection with Quail Hollow Subdivision is retained within the new development according to the latest plans and therefore no additional capacity will be provided in this section. A. Basin Parameters Soil maps in the Soil Survey of Washington County, Oregon, were used to determine the soil type and hydrologic soil group for the project (Appendix B). The 25-year design storm of 24-hour duration based upon the standard SCS Type 1 A rainfall distribution of 3.90 inches was used (Chapter 3, USA Design Requirements). irr The pervious and impervious areas were combined to compute peak flow. These areas were based on field observations and estimated utilizing AutoCAD and Softdesk computer programs. The areas are tabulated in Table 1 . ;�/CENTURY WEST 4 ENC/NEER/NC CORPORATION #4008400201 B. Time of Concentration Time of Concentration is the travel time of stormwater from the hydraulically most remote point in the sub-basin to the sub-basin outlet. In a typical watershed, the time of concentration is generally the sum of travel time through three segments: sheet flow, shallow concentrated flow, and open channel flow. Time of concentration r influences the shape and peak of the runoff hydrograph. Urbanization usually decreases the time of concentration, thereby increasing peak discharge. TABLE 1 +rri PERVIOUS AND IMPERVIOUS AREA ESTIMATE Basin Subbasin Pervious (Acre) Impervious (Acrel: CN = 85 CN 9$ West Existing 0.16 0.35 wr West Proposed 0.06 0.45 Walnut East Existing 0.30 0.13 East Proposed 0.15 0.28 err Existing 3.54 0 Gaarde Proposed 2.76 0.78 Both sheet and shallow flows were recognized in this project. The method described in Chapter 3, SCS TR-55, Second Edition was applied to estimate the time of concentration. Flows greater than 300 foot in length utilized shallow concentrated flow over the remaining length. The worksheets are attached in Appendix B. The time of concentration or travel for sheet flow was calculated using the following equation: R 0.007 (nL ) T = a.f o.4 i p2 R where: T, = time of concentration (hr) or time of travel if combined with shallow flow n = Manning's roughness coefficient which is listed in Table 3-1, SCS TR-55, Second Edition L = flow length(ft) P2 = the design storm 24-hour precipitation (in) s = watercourse slope (ft/ft). +rr dw ///CENTURY WEST C yy ENGINEERING CORPORATION J #4008400201 Ow rr The time of concentration or travel for shallow flow was calculated using the following equation: Tc = L / 3600 V TC =time of concentration (hr) or time of travel if combined with sheet flow L = flow length (ft) V = average velocity r Existing pipes along Walnut were not utilized in the analysis. All flows were assumed to remain on the surface with sheet flow utilized during the initial 300 foot section in all applications and shallow concentrated flow for the remaining distance. Time of concentrations were generally in the 2 to 4 minute range using these assumptions. Inclusion of pipe flows versus shallow concentrated flow through the subbasins would not significantly alter the time of concentration results as the initial sheet flow accounted for a majority of time period. The change in the post development versus predevelopment time of concentration was due to the change in the street grades and the assumption of paved versus unpaved surface for the shallow concentrated flows where applicable. The intensities of the 25-year, 24-hour storms were based on Chapter 3 of the USA design manual. Water Quantity System Design .r The peak flows for the 2- through 25-year storms were determined using SCS Type 1 A, 24- hour duration storm computer program. As identified in the USA Water Quality Standards, the on-site detention facilities shall be designed to capture stormwater runoff after development based upon a 2-through 25-year, 24 hour duration storm event. Stormwater quantity on-site detention facilities shall be designed such that the peak release rates will not exceed predevelopment rates for each of the storm events. The peak flows and total detention volume for the 25- year event are tabulated in Table 2 for the combined Gaarde/Walnut subbasins. The proposed method to detain these volumes is to install an oversized in-line collection pipe along Gaarde Street and Walnut Street. The largest amount to detain is within the Gaarde Street section where (1240 cubic feet or 9,275 gallons ) requires 175 feet of 36-inch pipe to maintain the total predevelopment release rates. An approved water quality manhole with a sump will be installed at the downstream end of each pipe. Discharge through this manhole will be controlled through an orifice which regulates the flow into the downstream piped system ( including the new system on Walnut Street) Within Walnut Street ( West Subbasin), the amount to detain will also include contributions from the above mentioned Gaarde system. A composite hydrograph was prepared using both subbasin to determine detention requirement in this area. The total future flows were tempered by the upstream detention requirements within the new Gaarde section. Therefore the detention volume was less than the amount require for Gaarde. A peak storage of 300 ;CENTURY WEST 6 ENGINEERING CORPORATION #4008400201 ■rr r cubic feet or 2250 gallons of runoff will maintain predeveloped discharge rates. A single 36- inch pipe at least 50 long will provide the necessary capacity. The East Subbasin of Walnut Street will require a peak detention volume of 162 cubic feet within a single 24-inch pipe at least 55 feet long. See Appendix B for calculations of time of concentration, peak flow outputs, and the detention storage output of the computer program for the Gaarde subbasin and the combined Gaarde-Walnut contributions. err See Appendix D for summary of all flows for the 2 year through 10 year design storms. TABLE 2 PEAK FLOWS AND DETENTION VOLUMES FROM 25-YEAR STORM : d= 3.90 inches Existing Proposed betention Improvements Improvements Basin Subbasin Volume T� (minute) Q (cfs) TC (minute) Q'(cfs) (ft3) West 2.6 0.44 3.0 0.54 300 Walnut East 1 .7 0.38 1.8 0.44 162 n/a 5.3 2.32 4.6 2.62 1,240 Gaarde ■r irr ,H ///CENTURY WEST 7 ENOlNEERlNO CORPORATION r #4008400201 �r TABLE 3 PEAK FLOWS AND DETENTION VOLUMES FROM 25-YEAR STORM FOR COMBINING GAARDE AND WALNUT SYSTEMS Existing Proposed petentian :I Improvements I,mpraVements Basin Subbasin Volume +rr T� (minute) Q (cfs) T, {minute) Q (cfs> (ft3l West (3) 2.64(' (3) 2.73(2) 420 Walnut/ Gaarde 1. The combined system collects runoff from existing conditions on Walnut and Gaarde. 2. The combined system for proposed improvements reflects detention of runoff on Gaarde to predeveloped conditions which in turn empties into the Walnut Street West subbasin. 3. Time of Concentration for combined system was based upon overlay of the two hydrographs ( Gaarde and Walnut - West ) for the existing and future conditions. Program does not identify the composite value. �r Water Quality Analysis +� According to Section 3.11.5.c of the USA design manual, activities which create new impervious surfaces are required to construct or fund permanent water quality facilities to reduce contaminants entering the storm and surface water system. The facilities shall be + ► designed for a dry weather storm event totaling 0.36 inches of precipitation falling in 4 hours and to remove 65 percent of the total phosphorous from the runoff from 100 percent of the newly constructed impervious surfaces. Flows above this event are not expected to be treated. For the proposed street improvements, a cumulative water quality credit for phosphorus removal of all catch basins and sumped manholes is 15 percent. The remaining 50 percent removal will be difficult to attain within each of the subbasins due to the build out err of single family dwellings along the street. As noted earlier, there are two separate locations within the street currently collecting flows for eventual discharge into the Fanno Creek system. Installation of a passive flow-through stormwater filter system ( e.g. StormFi/ter by Stormwater Management ) with an upstream solids collection manhole will occur in the Gaarde Street system following the attenuation of +�+ postdevelopment flows with in-line storage, providing treatment to meet water quality parameters. The maximum flow requiring treatment based upon the amount of newly arr �///CENTURY WEST 8 �v ENO/NEER/NG COR/'ORAT/ON #4008400201 ■r W constructed impervious area within Gaarde is equal to 0.20 cfs and is shown in Table 4. Approximately 70 percent of the new impervious area will be located within the Gaarde section of the alignment. The facility will be sized to treat up to150% of the 4 hour design flow ( 0.30 cfs) in the area to increase overall water quality since treatment was not economically feasible within the short section of Walnut. The additional stormwater collected within Walnut Street will be detained in oversized pipes at each of the subbasin locations prior to release through an orifice specifically sized to maintain predevelopment flow rates following completion of the improvements. +rr TABLE 4 SUMMARY OF WATER QUALITY TREATMENT FLOWS d = 0.36" rainfall rrr 4 hrExisting 4 he. - Proposed Basin Subbasin Improvements Improvements Q4 cfs) Q (cfs} Gaarde n/a 0.05 0.20 ----- ----- 0.30 (2) err 1. Final Design treatment requirements to increase overall water quality for entire to Gaarde/Walnut Street improvements = 0.30 cfs. N Conveyance System Analysis and Design as Flow rates based upon a given pipe slope for the 25-year storm event are shown in Table 5. fig TABLE 5 PROPOSED PIPE FLOW CHARACTERISTICS �r Pipe Diameter 25»yr Storm Capacity Slope Velocity (mat,} (in),' (cfs) (cfs) (ft/fit) Mannin 's:>n PVC 12 2.64 3.28—F-0.005 —r-0.010 4.17 PVC 18 2.64 9.65 0.005 0.010 5.46 See Appendix C for detailed calculations of pipe capacities. ��CENTURY WEST 9 ENG/NEER/NG CORPORAT/ON rr #4008400201 im REFERENCES .r City of Tigard: Public Improvement Design Standards. July 15, 1998 rrr Washington County: Uniform Road Improvement Design Standards. Amended through 1997 King County, Washington: Surface Water Design Manual. January 1990. USDA Soil Conservation Service, Engineering Division: Urban Hydrology for Small Watersheds, Technical Release 55. June 1986. Unified Sewerage Agency (USA): Construction Standards. 1991 USDA Soil Conservation Service: Soil Survey of Washington County, Oregon. July 1982. wr w �r +r �r ; CENTURY WEST ENGINEERING CORPORATION 10 #4008400201 rr wr err APPENDIX A WATER QUANTITY/QUALITY CONTROL PLAN wo WATER QUANTITY 190 191 218 219 220 2900 2700 SW WALNUT STREET DISCHARGE To ' EXISTING DITCH EXIST. 24"0 PIPE I _ 300 1300 i 50' 90' I24"0 DETENTION I 36"0 DETENTION � __ __� SEE DETAIL A 1400 I 3000 N 1900 1800 3300 3400 175' t1500 36"0 1 W 2000 ; Z W O I WOf Q _z W 2100 1501 1502 0 a 3101 1700 Q LEGEND: U) (n \ SSWCGE WALRNUTINTO STREET PROPOSED STORM DRAIN 1100 _._- PIPING I PROPOSED MANHOLE z ', BYPASS MANHOLE I EXISTING STORM DRAIN - 3100 TAX LOT NUMBER 2000 MANHOLE W/ 1000 0 ORIFICE PRECAST "STORM FILTER" Ld INOTES: UNIT 8'x12' LONG 1. PROPOSED/EXISTING INLETS NOT -- SHOWN. 2. IN—LINE DETENTION REQUIREMENTS 9000 (PRE)=0.05 cfs ARE SHOWN BETWEEN SELECT I Q4HR(POST)=0.20 cfs MANHOLES. 36"0 DETENTION L=175' _ _�_ .__ _�m.� DETAIL A PLAN N.T.S. SCALE: 1"=100' IDESIGNED BY: RCW SCALE : 1"=100' /� GAARDE STREET FIGURE C _MEERRY WEST WATER QUANTITY/QUALITY DRAWN BY : DAP DATE 9/3/99 ` ENGINEERING CORPORATION IMPROVEMENTS I CHECKED BY : RCW FILE 7GX4.DWG 825 NE Multnomah Suite 425 PHASE Portland, Oregon 97232 CONTROL PLAN PROJECT NO.: 40084003.01 503-231-6078 phone • 503-231-6482 fax TIGARD, OREGON .�wiitiwu�ci ivi.�ii�rcii►ciii. r►vuu�w � uo� . ui -r See fi EV, OWN Product Information Our Full Line of Products Stormwater Management offers the StormFilter TMin three different configurations: Cast-In-Place units for treating flows larger than 1.0 cfs,Precast units for treating flows less than 1 cfs, and Linear units for treating small flows. The Precast StormFilterTM M Flow Spreader Tralrie Bearing Lid 4. Inlet ! �- ea♦ 4�. Ode Radial E1 Filler Carlridgo Undardraia ANY mialteld Adjasleait Nutlet Vetoa e0 No matter which option you choose,the Stormwater Management StonnFilterTM as offers the following benefits: e It is recognized as a Best Management Practice (BMP) and meets various ow regulatory agency requirements for removing stormwater pollutants. Offers a variety of media to remove site specific pollutants. e Is suitable for streets and highways; transit facilities; residential, retail and commercial developments; business and industrial sites; and maintenance facilities. e Is uniquely effective for constrained sites and treatment of high stormwater flows. e Requires simple, predictable and inexpensive maintenance. e Uses less than 10%n of land compared to ponds and swales. e High treatment efficiency —removes up to 90% of all solids, 85% of oils and greases and 91% of solubilized heavy metals. e Independent 3 year study has average first flush removal rates of: TSS 98%; Soluble Metals 93%. e High treatment capability —can treat flows from 0.13 to 8.0 cfs and greater. a Saves up to 10 times the cost of traditional stormwater treatment methods. ,,, http://www.stormwatenngt.conVproducts.html 1/28/99 ++rrri �r it APPENDIX B SOILS INFORMATION and PEAK FLOW MODELING lw ow to 10 4 � r � ate?'`.: � "^ .,;,•-v vxK��- •,. a �yy`C 'fit ',t sw [ ./� ' 30 1:+� _ .ray ?�,y,�y _S, •y. r. �,i�F, �• or nt Ma- 1a� � +#' •y1•r '� �g Jr.. f.z �L'�� a t yu:,.Y' � ^� _ •��-`t't..*� f:,a, ` • a,F d. "!P t ��4q�rTti• .+rY1 ��`!'� i'.�, i'' .�r� �,'•�`•;.,-� .1scK /. x$3 .42 � �' 1a.0 rr 1y � ._j� '; � " ��eS'-�f, I k��n"`P' 9rF•"`s' s :� LI','t'1 5.�+.��ls� .��V; ��g 14 : w FPII.� mike -%TAr �d��'i�,�.7 Y�'S� 1'�k . r •.��� �' '7,�y..y m�•y'� ,� 4 SJ /^„t♦ # •�. .3 } '� ,� `. �, .•^� 'y°' erg /•,t` .{�-KC d •f .� �e i Wit•: �"•�•y � f � ���m,t..r++�j �' :.� ,� �' ? .•-�'+.. ��:�►�n. a..� .t•" a � 'sal .F%- :.4:• i � � d/��r /•f/ STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN Table III-1.3 SCS Western Washington Runoff Curve Numbers (Published by SCS in 1982) Runoff curve numbers for selected agricultural, suburban and urban land use for Type IA rainfall distribution, 24-hour storm duration. LAND USE DESCRIPTION CURVE NUMBERS BY HYDROLOGIC SOIL GROUP A B C D Cultivated land(1) : -winter condition 86 91 94 95 Mountain open areas: low growing brush & grasslands 74 82 89 92 Meadow or pasture: 65 78 85 89 Wood or forest land: undisturbed 42 64 76 81 Wood or forest land: young second growth or brush 55 72 81 86 Orchard: with cover crop 81 88 92 94. Open spaces, lawns, parks, golf courses, cemeteries, landscaping. irr Good condition: grass cover on k75% of the 68 80 86 90 area Fair condition: grass cover on 50-758 of 77 85 90 92 the area Gravel roads & parking lots: 76 85 89 91 Dirt roads & parking lots: 72 82 87 89 dr Impervious surfaces, pavement, roofs etc. 98 98 98 98 Open water bodies: lakes, wetlands, ponds etc. 100 100 100 100 Single family residential(2) : Dwelling Unit/Gross Acre %Impervious(3) Separate curve number 1.0 DU/GA 15 shall be selected for 1.5 DU/GA 20 pervious & impervious 2.0 DU/GA 25 portions of the site 2.5 DU/GA 30 or basin 3.0 DU/GA 34 3.5 DU/GA 38 4.0 DU/GA 42 4.5 DU/GA 46 5.0 DU/GA 48 5.5 DU/GA 50 6.0 DU/GA 52 6.5 DU/GA 54 7.0 DU/GA 56 r PUD's, condos, apartments, %impervious commercial businesses & must be industrial areas computed do (1) For a more detailed description of agricultural land use curve numbers refer 40 to National Engineering Handbook, Sec. 4, Hydrology, Chapter 9, August 1972- (2) Assumes roof and driveway runoff is directed into street/storm system. (3) The remaining pervious areas (lawn) are considered to be in good condition for these curve numbers. two III-1-12 FEBRUARY, 1992 r rir r Sheet flow where 'Sheet flow is flow over plane surfaces. It usually Tt = travel time (hr), occurs in the headwater of streams. With-sheet flow, n = Manning's roughness coefficient (table 3-1), the friction value(Manning's n) is an effective L = flow length(ft), irr roughness coefficient that includes the effect of P2 = 2-year, 24-hour rainfall (in), and raindrop impact; drag over the plane surface; s = slope of hydraulic grade line (land slope, obstacles such as fitter, crop ridges, and rocks; and ft/ft). erosion and transportation of sediment. These n values are for very shallow flow depths of about 0.1 This simplified form of the Manning's kinematic foot or so. Table 3-1 gives Manning's n values for solution is based on the following: (1) shallow steady sheet flow for various surface conditions. uniform flow, (2) constant intensity of rainfall excess 71 (that part of a rain available for runoff), (3) rainfall For sheet flow of less than.300 feet, use Manning's duration of 24 hours, and (4) minor effect of kinematic solution(Overton and Meadows 1976) to infiltration on travel time_ Rainfall depth can be compute Tt: obtained from appendix B. _ 0.007 (nL0•8 (Eq. 3-31 TC (p2o.5 SOA Shallow concentrated flow - After a maximum of 300 feet, sheet flow usually becomes shallow concentrated flow. The average so velocity for this flow can be determined from figure Table 3-1.—Roughness coefficients (Manning's n) for 3-1, in which average velocity is a function of sheet flow watercourse slope and type of channel. For slopes less than 0.005 ft/ft, use equations given in appendix Surface description n' F for figure 3-1. Tillage can affect the direction of shallow concentrated flow. Flow may not always be directly down the watershed slope if tillage runs ft Smooth surfaces(concrete, asphalt, gravel, or across the slope. bare soil) ................................... 0.011 After determining average velocity in figure 3-1, use Fallow(no residue).......................... 0.05 equation 3-1 to estimate travel time for the shaLow Cultivated soils: concentrated flow segment. Residue cover X20% ...................... 0.06 im Residue cover >20% ...................... 0.17 Open channels Grass: Short grass prairie ............. ............ 0.15 Open channels are assumed to begin where surveyed Nr Dense grasses'........................ .... 024 cross section information has been obtained, where Bermudagrass............................. 0.41 channels are visible on aerial photographs, or where blue lines (indicating stre:a ms) appear on United iftRange (natural) ............... .......... .... 0.13 States Geological Survey (USGS) quadrangle sheets. Woods:, Manning's equation or water surface profile Light underbrush.. .. .... .................. 0.40 information can be used to estimate average flow Dense underbrush ... ...................... 0.80 velocity. Average flow velocity is usually determined for bank-full elevation. 'The n values are it composite of information compiled by Engm2n (1986). 'Includes species such as weeping lovegrass, bluegrass, buffalo grass,blue grama grass, and native grass mixtures. aWhen selecting n,consider cover to a height of about 0.1 R This is the only part of tF.e plant cover that will obstruct sheet flow. rr (210-VI-TR-55, Second Ed., June 1986) 3-3 Worksheet 3: Time of concentration (Tc) or travel time (Tt) Project > ?r,t>,' - c-: ~ By Date (o fa;jSS Location 4f1A2Qc 15%• Checked Date Circle one: Developed resen Circle one: Tc Tt through subarea NOTES: Space for as many as two segments per flow type can be used for each worksheet. Include a map, schematic, or description of flow segments. +rr Sheet flow (Applicable to Tc only) Segment ID M 1. Surface description (table 3-1) 5(A�- 2Mcz /3/�rtE Sort, 2. Manning's roughness coeff., n (table 3-1) .. ©•�� � 3. Flow length, L (total L < 300 ft) .... ft goo, r 4. Two-yr 24-hr rainfall, P2 in 2. 5 5. Land slope, s .............................. ft/ft 0,04- 0.8 6. Tt 0.00075(nL0)4 Compute Tt ...... hr b,03 + P2 s VW Shallow concentrated flow Segment ID 7. Surface description (paved or unpaved) ..... Jt4e'vr:V 8. Flow length, L ............................. ft 6575 9. Watercourse slope, s ....................... ft/ft 0,o+ °a 10. Average velocity. V (figure 3-1) ........... ft/s 3- 2- 11. Tt ' 8600 V Compute Tt ...... hr ©.OS°� + 3.s"rur Channel flow Segment ID 12. Cross sectional flow area, a ............... ft 13. Wetted perimeter, p ft ur 14. Hydraulic radius, r - a Compute r ....... ft p w 15. Channel slope, s ..................... ...... ft/ft 16. Manning's roughness coeff., n .............. 2/3 1/2 n 17. V - 1.49 r s Compute V ....... ft/s 18. Flow length, L .......... ................... ft 19. Tt ' 3600 V Compute Tt ...... hr + 20. Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) .... ... hr 3 h +rr (210-VI-TR-55, Second Ed., June 1986) D-3 rr low Worksheet 3: Time of concentration (Tc) or travel time (Tt) Project 12t7t - 1 -1 By Date -' I M Location Qpc `jf. Checked Date Circle one: Present evelo 10 Circle one: Tc Tt through subarea NOTES: Space for as many as two segments per flow type can be used for each worksheet. so Include a map, schematic, or description of flow segments. Sheet flow (Applicable to Tc only) Segment ID Maw 1. Surface description (table 3-1) ............ 5V2f�,cc Q r Spic) +� 2. Manning's roughness coeff., n (table 3-1) .. 11, 3. Flow length, L (total L < 300 ft) .......... ft 200 4. Two-yr 24-hr rainfall, P ...., ZIS 2 ............. in 5. Land slope, s ....• ft/ft 0.0 a' 0.007 (nL)0.8 6. Tt 0.5 0.4 Compute Tt ...... hr P2 s Wx Shallow concentrated flow Segment ID (� 7. Surface description (paved or unpaved) .... . PAVei.- r 8. Flow length, L ft &75- 9. Watercourse slope, s ....................... ft/ft o,o4 10. Average velocity, V (figure 3-1) ........... ft/s 4,-o 11. Tt - 8600 V Compute Tt ...... hr •D4 + ►� rr Channel flow Segment ID 12. Cross sectional flow area, a 2 13. Wetted perimeter, p ....................... ft dw 14. Hydraulic radius, r - a Compute r ....... ft p w 15. Channel slope, s ..................... ...... ft/ft 16. Manning's roughness coeff., n ........ ...... 17. V - 1.49 r2/3 sl/2 Compute V fc/s n me 18. Flow length, L ............ ................. f 19. Tt - 3600 V Compute Tt „.... hr + 1W 20. Watershed or subarea T or T p 4 c t (add Tt in steps 6 11 and 19) .... ... hr rr (210-VI-TR-55, Second Ed., June 1986) D-3 Worksheet 3: Time of concentration (Tc) or travel time (Tt) VW Project 6AAPPE - PHASf- By Date Location �JALAIV- S-r, - "(Jet T- � Checked Date Circle one< resent Developed Circle one: Tc Tt through subarea ar NOTES: Space for as many as two segments per flow type can be used for each worksheet. rrr Include a map, schematic, or description of flow segments. Sheet flow (Applicable to Tc only) Segment ID Gmoov rw 1. Surface description (table 3-1) ............ i!2 9--Nm. Aac arr 2. Manning's roughness coeff., n (table 3-1) .. ®.O// 3. Flow length, L (total L < 300 ft) .......... ft 3©o sM 4. Two-yr 24-hr rainfall, P2 .................. in 2.5'0 5. Land slope, s .............................. ft/ft 000W] 0.007 0.8 + 6. Tt ( 0.5n0)4 Compute Tt ...... hr 0, 47 � 2.G►� P2 s Shallow concentrated flow Segment ID rr► 7. Surface description (paved or unpaved) ..... 8. Flow length, L ............................. ft err 9. Watercourse slope, s ....................... ft/ft *a10. Average velocity, V (figure 3-1) ........... ft/s 11. Tt ' 3600 V Compute Tt ...... hr + ' ie Channel flow Segment ID 12. Cross sectional flow area, a ............... ft AW 13. Wetted perimeter, pw ....................... ft wr 14. Hydraulic radius, r - a Compute r ....... ft p w 15. Channel slope, s ........................... ft/ft 16. Manning's roughness coeff., n .............. 2/3 1/2 17. V - 1.49 r s Compute V .. ..... ft/s n tirr 18. Flow length, L .......... ................... ft 19. Tt - 3600 V Compute Tt ...... hr + irr+ 20. Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) hr (210-VI-TR-55, Second Ed., June 1986) D-3 Worksheet 3: Time of concentration (Tc) or travel time (Tt) OR Project (4/-y;/ZAr - -fAy-r By Date NoLocation (,J=)&CNvr_ ST: - 1 �� 3T Checked Date Circle one: Present evelope Circle one: Tc Tt through subarea aw NOTES: Space for as many as two segments per flow type can be used for each worksheet. rr Include a map, schematic, or description of flow segments. Sheet flow (Applicable to Tc only) Segment ID ma 1. Surface description (table 3-1) ............ 2. Manning's roughness coeff., n (table 3-1) .. / ■r 3. Flow length, L (total L < 300 ft) .......... ft 300 r 4. Two-yr 24-hr rainfall, P2 in Z-S 5. Land slope, s .............................. ft/ft 0"O 7-5 0.8 6. Tt 0.000.5(n00.4 Compute Tt . ..... hr + P2 s Shallow concentrated flow Segment ID rrr 7. Surface description (paved or unpaved) ..... 8. Flow length, L ............................. ft do 9. Watercourse slope, s ....................... ft/ft err 10. Average velocity, V (figure 3-1) ........... ft/s _ 11. Tt 3600 V Compute Tt .... hr + AChannel flow Segment ID 12. Cross sectional flow area, a 2 ytr 13. Wetted perimeter, pw ....................... ft 14. Hydraulic radius, r a Compute r ....... ft P rrr w 15. Channel slope, s ........................... ft/ft 16. Manning's roughness coeff., n .............. 2/3 1/2 17. V - 1.49 r s Compute V ....... ft/s 00 18. Flow length, L ....... ............ .......... ft 19. Tt - 3600 V Compute Tt ...... hr + 20. Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) ....... hr +rr (210-VI-TR-55, Second Ed., June 1986) D-3 Worksheet 3: Time of concentration (Tc) or travel time (Tt) Project ��F}1<4rtVt, - � !t v By Date .. Locations�� S'T, — �A-,.-7- Checked Date Circle one: resenx Developed Circle one: Tc Tt through subarea NOTES: Space for as many as two segments per flow type can be used for each worksheet. rr Include a map, schematic, or description of flow segments. Sheet flow (Applicable to Tc only) Segment ID tx+T as 1. Surface description (table 3-1) .Kra ruv�z t c, ow 2. Manning's roughness coeff., n (table 3-1) .. 3. Flow length, L (total L < 300 ft) .......... ft r 4. Two-yr 24-hr rainfall, P2 .................. in Z-50 5. Land slope, s .............................. ft/ft 3.c� 0.8 ,n 6. Tt - 0.00 (n ) 0.5OO4 Compute Tt ...... hr P2 s Shallow concentrated flow Segment ID Aw 7. Surface description (paved or unpaved) ..... 8. Flow length, L ft .r 9. Watercourse slope, s ft/ft 10. Average velocity, V (figure 3-1) ft/s wr _ il. Tt 3600 V Compute Tt hr + err Channel flow Segment ID 12. Cross sectional flow area, a 2 AW 13. Wetted perimeter, p ....................... ft 14. Hydraulic radius, r Pa Compute r ....... ft ar w 15. Channel slope, s ........................... ft/ft 16. Manning's roughness coeff., n ......... ..... ar 17. V 1.49 r2/3 s1/2 n Compute V ....... ft/s +err 18. Flow length, L ft 19. Tt - 3600 V Compute Tt ...... hr + 20. Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) ..:.... hr wr (210-VI-TR-55, Second Ed., June 1986) D-3 Worksheet 3: Time of concentration (TC) or travel time (Tt) ow n Project _ ��1Ff�2e�C F`✓ft <,s By Date Location Checked Date wr. Circle one: PresentDevelo Circle one: Tc Tt through subarea yr NOTES: Space for as many as two segments per flow type can be used for each worksheet. we Include a map, schematic, or description of flow segments. Sheet flow (Applicable to Tc only) Segment ID <,-togi 1. Surface description (table 3-1) ............ f c.�LFizcr ( - 2. Manning's roughness coeff., n (table 3-1) .. C),01 rr 3. Flow length, L (total L < 300 ft) .......... ft lS-b rr► 4. Two-yr 24-hr rainfall, P2 in 2 Sb 5. Land slope, s .............................. ft/ft 2 50 6. T - 0.007 (nL)0.8 0 + t 0.5 0.4 Compute Tt ...... hr ��0 Zra .Q3 wt P2 s Shallow concentrated flow Segment ID No 7. Surface description (paved or unpaved) ..... 8. Flow length, L ft qW 9. Watercourse slope, s .................. ..... ft/ft ,No 10. Average velocity, V (figure 3-1) ...... ..... ft/s 11. T - L Compute Tt ...... hr + ' t 3600 V go Channel flow Segment ID 12. Cross sectional flow area, a ............... ft *W 13. Wetted perimeter, pw ft 14. Hydraulic radius, r - a Compute r ....... ft p aw w 15. Channel slope, s ........................... ft/ft 16. Manning's roughness coeff., n ......... ..... � 17. V - 1.49 r2/3 sl/2 Compute V ft/s n rr+ 18. Flow length, L ............................. ft 19. TL Compute Tt hr + t 3600 V F r 20. Watershed or subarea Tc or Tt (add Tt in steps 6, 11, and 19) ....... hr (210-VI-TR-55, Second Ed., June 1986) D-3 gaarde ., IF� 7TORNI OPTION: T'i`F'E-1A F..kIhiFt".LL C+IS'fRIBUTION NTER.; FF,.Eii(`t'EAR) , DURATION(HOUR), FRECIF(INCHES) 2. ry f4 Jtti4..:1..: :t7 is Tr*.-Ir.* 'l-*r T:}-i'A ti"£'F.I.- J.CaS. T'(F'E-1t+. DTtiTR.TB!_ITIUN w5-YEsaR 24-HOUR STORM 3.90" TOTAL PRECIP. - - - - - - - - ENTER: x(P ER ap), CN a.F'EF'.b(1, A(IMP ERV), CN CIMP ER V) , TC FOP. BASINNO�__1 ATS. FR.INT-OUT AP,EA(ACR.ES) PERVIOUS IMPER'-JIOUS TC(MINUTES) A CN A CN 3.5 21.E 35.0 2 93.0 4.G PEAI/,-Q( FS) T-F'E I,'.(HR.S) '03LCCU-FT1 ...62 7.67 34112 LATER [d:1(pathlfilenam [.ext1 FOR STOR.GiE OF COMPUTED H',`DROGRAPH. T gaard HIM P x� S.C.S. TYPE-1x RAINFALL DISTRIBUTION NTER.: FREQ 0,'EAF.), D iRATION(HOUR.), PRECIP CINCHES) 9 ------------------..------------------------------------------------...-- Y:Y^o:Y:YY:Y-T: S.C.S. TYPE-1N. DISTRIBUTION a:Y:n`Y•r:4:Y:'Y:r.a`ir Y:n`Y�f:Y:r.t:6:�: u5-'t EAR 24-HOUR STORM Y:Y:;Y 3.90" TOTAL PR.ECIP. ---------------------------------------------------------------------- ENTER: AOPER'a i, CN(PERV) , A(IMPER'-,l), CN(IMPERVl , TC FOR BASIN NO. I 1.54,5,0,93,5.3 BATA PRINT-OUT: AF'.E. OT,.-R.ES) PERVIOUS IMPERVIOUS TC(MINUTES) A CN x CN 31.5 3.E 65.0 .O 93.0 5.= PEAK.-C!( FS.) T-P Er+}:IHP,S) VUL CCU-FT) 4.25 7.67 30437 NTER [d:1[p thlfilename[.xt] FOR STOR 6E OF COMPUTED HYDR.OGR.WPH: $-;gaarde Auto " 'EF F+W�F'.Is4�tdCE: IhdFLO�' "tNd<;�aEl —CiL+"fFLC+�; N.i�TU�.L—OUTFLOR�' PK—�TF'+�E `_+TOk.r'.:�E ==;F'E!IF`�`s U — C++JlJP4EhdT, F. — RE'r'I E, >♦. — N01UsT ORIF, E — EhdLk.VE, ti — _TOF' FrEF'.FCERh4.k1°d�E: IPdFL04� Tr'F:�ET—Cil.�TFL0�4' hi�Te_I,�,L-01_ITFLO�t' F'iC—�T�rE tiTOF:.��E TR.IJ�TLIF'.E C+s<.T�.: F'.,•`G T.�hdY f,;FL�+.T �RNDEe+ _.I�EF:.—NE.s:L+ T.khdK—DIVAS TOR.—C7EF'TH Tw°d�'—LEhd�TH �TCERt+.GE-1�+�LUt4E ` 'TRIF`LE 11F°.IFI:.E F°.E TF:I�CT+�1R: C+I�(�N�=HE:;�1 HT+:.FEET_i Q—b4.k:�:Ci.F��J Da7TTOh4 +JF?.IFIi�E� 5.14 .O+J '1.��0 h4IC+C+LE QR.IFICE: �'.E:r '1.00 .5F10 ` 7.�t'aEi;FT:i DIS�_N.�iF:��ECrFS,si rT+JF?.NaE(:<<U—FTj F'ER.M—,�F?.E.K(5��.—F"i.? „� t ► • [ s i r APPENDIX C PIPE FLOW CHARACTERISTICS IA" ; /CENTURY WEST ENGINEERING CORPORATION lw PROJECT NAME 4AARDE STaEcT - 91tA5-E Z CALCULATED BY IJOC?i DATE PROJECT NO. 64Y or CHECKED BY DATE SUBJECT SHEET NO. OF C±,f)•Au TY 64" Ex= R'orLYt..owy Assume ooh Fr/Fr �/L = O, o l o p = IZ'` 4&,3 Iz 0,07m7 lot PC, CArAc4TY -- low 0,0-707 SSS r = = 0. 005 FT/pr- �2 = 0,010 P = lo ` So.r ` 0,0105 o.s = O,0707 1l ft= C-WA.-.4 t; C*0767 = a.(o5 &�S lo. aw APPENDIX D SUMMARY OF 2 - 10 YEAR DESIGN STORM MODELING TABLE 2a PEAK FLOWS AND DETENTION VOLUMES FROM 2-YEAR STORM : d= 2.50 inches Existing Proposed Detention Basin Subbasin Improvements Improvements Volume Tr (minute) Q (cfs) T(, (minute) Q (cfs) (ft3) West 2.6 0.23 3.0 0.33 ---- Walnut East 1 .7 0.20 1.8 0.26 ---- n/a 5.3 1 .02 4.6 1 .32 ---- Gaarde TABLE 2b PEAK FLOWS AND DETENTION VOLUMES FROM 5-YEAR STORM : d= 3.10 inches Existing Proposed Improvements Improvements Detention Basin Subbasin Volume Tr (minute) FQ (cfs) Tr (minute) Q (cfs) (ft3) West 2.6 0.32 3.0 0.42 ---- Walnut East 1 .7 0.28 1 .8 0.34 ---- n/a 5.3 1.52 4.6 1 .86 ---- Gaarde TABLE 2c PEAK FLOWS AND DETENTION VOLUMES FROM 10-YEAR STORM : d= 3.45 inches Existing Proposed Detention Basin Subbasin Improvements Improvements Volume T� (minute) Q (cfs) Tr (minute) Q (cfs) (ft3) West 2.6 0.37 3.0 0.48 ---- Walnut East 1 .7 0.32 1 .8 0.38 ---- n/a 5.3 1 .84 4.6 2.17 ---- Gaarde TABLE 3a PEAK FLOWS AND DETENTION VOLUMES FROM 2-YEAR STORM FOR COMBINING GAARDE AND WALNUT SYSTEMS Existing Proposed Detention Basin Subbasin Improvements Improvements Volume Tr ( minute) Q (cfs) T. (minute) Q (cfs) (ft3) West (3) 1 .22(1) (3) 1 .3012) --- Walnut/ Gaarde 1 . The combined system collects runoff from existing conditions on Walnut and Gaarde. 2. The combined system for proposed improvements reflects detention of runoff on Gaarde to predeveloped conditions which in turn empties into the Walnut Street West subbasin. 3. Time of Concentration for combined system was based upon overlay of the two hydrographs ( Gaarde and Walnut - West ) for the existing and future conditions. Program does not identify the composite value. TABLE 3b PEAK FLOWS AND DETENTION VOLUMES FROM 5-YEAR STORM FOR COMBINING GAARDE AND WALNUT SYSTEMS Existing Proposed Detention Basin Subbasin Improvements Improvements Volume T, (minute) Q (cfs) Tc (minute) Q (cfs) (ft3) West (3) 1 .78(" (3) 1 .88(2) --- Walnut/ Gaarde 1 . The combined system collects runoff from existing conditions on Walnut and Gaarde. 2. The combined system for proposed improvements reflects detention of runoff on Gaarde to predeveloped conditions which in turn empties into the Walnut Street West subbasin. 3. Time of Concentration for combined system was based upon overlay of the two hydrographs ( Gaarde and Walnut - West ) for the existing and future conditions. Program does not identify the composite value. TABLE 3c PEAK FLOWS AND DETENTION VOLUMES FROM 10-YEAR STORM FOR COMBINING GAARDE AND WALNUT SYSTEMS Existing Proposed Detention Basin Subbasin Improvements Improvements Volume Tr'(minute) Q (cfs) T� (minute) Q (cfs) (ft3) West (3) 2.1411) (3) 2.2412j --- Walnut/ Gaarde 1 . The combined system collects runoff from existing conditions on Walnut and Gaarde. 2. The combined system for proposed improvements reflects detention of runoff on Gaarde to predeveloped conditions which in turn empties into the Walnut Street West subbasin. 3. Time of Concentration for combined system was based upon overlay of the two hydrographs ( Gaarde and Walnut - West ) for the existing and future conditions. Program does not identify the composite value.