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HomeMy WebLinkAboutDrainage ReportCERTIFICATION 1, Joseph P. Schultz, Licensed Professional Engineer No. 65889, State of Texas, certify that this report for the drainage design for the Graham Corner Plaza in College Station, Texas, was prepared by me in accordance with the provisions of the City of College Station Drainage Policy and Design Standards for the owners hereof, with the exception that storm water runoff detention is not being required for this project since the site discharges directly into an existing drainage and immediately into the 100- year floodplain limits. C� Ginger rso, P.E. Josep . S Zultz, P.E. -7 -23-03 TABLE OF CONTENTS GRAHAM CORNER PLAZA CERTIFICATION ...... TABLEOF CONTENTS............................----------......................._---............------........................................... ------............2 LISTOF TABLES ......................... ......................................................................................................................................... 2 INTRODUCTION.............................................._.........----......................-------......_.........................--------............................ 3 GENERAL LOCATION AND DESCRIPTION.................................................................................................................3 FLOOD HAZARD INFORMATION .................... ........................................................................................................ - ....3 DEVELOPMENT DRAINAGE PATTERNS ............................................ ..........................................................................3 DRAINAGEDESIGN CRITERIA .................................................... --............................---------------.....................-----......3 STORM WATER RUNOFF DETERMINATION...----...........................................................................-........_.-----.......4 STORM SEWER CULVERT DESIGN-------------------.......................----...............................-------............................--........5 STORM SEWER PIPE & INLET DESIGN--------..................................................................._....................-----............... CONCLUSIONS.............._._.._----...---------------------......---..............--------..........---......................_..............-------......... ------ 6 APPENDIXA......................................................................................................................................................................... 7 Calculations EXHIBITA------........................------------------------------------................._...............-------......................................................... 19 Time of Concentration Flow Path & Drainage Area Map EXHIBITB ...................-.................._..................................................-------.................. 21 Pre- and Post -Development Drainage Area Map EXHIBITC......................................................................................... ..------.............................--------------.............................. 23 Grading Plan LIST OF TABLES TABLE 1 — Rainfall Intensity & Runoff Data.......................................................................................... 4 TABLE 2 — Time of Concentration (tc) Equations.................................................................................. 5 DRAINAGE REPORT GRAHAM CORNER PLAZA INTRODUCTION The purpose of this report is to provide the hydrological effects of the construction of the infrastructure for the Graham Corner Plaza project, and to show that the storm water runoff will be controlled in such a manner so as to have minimal offsite or downstream impact. GENERAL LOCATION AND DESCRIPTION The project is located on 10.73 acres located in College Station, Texas. Most of the site is open land with grass. A 1.093 acre portion along the North Fork of Lick Creek is being dedicated to the City of College Station as greenway. This area is primarily wooded. The existing ground elevations range from elevation 276 to elevation 288. The general location of the project site is shown on the vicinity map in Exhibit A. FLOOD HAZARD INFORMATION The project site is located in the Lick Creek Drainage Basin. The site is located in a Zone X Area according to the Flood Insurance Rate Map (FIRM) prepared by the Federal Emergency Management Agency for Brazos County, Texas and incorporated areas dated February 9, 2000, panel number 48041CO201 D. Zone X Areas are determined to be outside of the 500-yr floodplain. This site is not within the limit of study for the FIRM. However, the approximate 100-year floodplain limits and the floodway were previously determined by Robertson Engineering for the City of College Station, and these limits were included on the Final Plat for the project. This floodplain area is also shown on Exhibit A. Most of the floodplain area and all of the floodway for this tract is located in the Greenways Dedication Area. DEVELOPMENT DRAINAGE PATTERNS The storm water runoff from the site flows into the North Fork of Lick Creek. The runoff from this development will be discharged into the creek and the 100-year floodplain; therefore, no detention is required for this project. The drainage area boundaries are shown on Exhibit A. DRAINAGE DESIGN CRITERIA The design parameters for the storm sewer are as follows: • The Rational Method is utilized to determine peak storm water runoff rates for the storm sewer design. • Design Storm Frequency Storm culverts 25-year storm event Stone sewer system 10 and 100-year storms events • Runoff Coefficients Undeveloped areas Developed areas Open space areas Impervious surfaces C = 0.30 C = 0.85 C = 0.40 C = 0.90 • Rainfall Intensity equations and values for Brazos County can be found in Table 1. • Time of Concentration, t, - Calculations for are based on the method found in the TR- 55 publication. Refer to Appendix A for the equations and calculations. The drainage runoff flow paths used for calculating the times of concentration for the design of Culvert No. I are shown in Exhibit B. For smaller drainage areas, a mininuull t, of 10 minutes is used to determine the rainfall intensity values. STORM WATER RUNOFF DETERMINATION The peak runoff values were determined in accordance with the criteria presented in the previous section for the 10-, 25- and 100-year storm events. The runoff coefficients are based on the development of this tract. The drainage areas are shown in Exhibit A. Runoff conditions are summarized in Table 1. The time of concentration equations are shown in Table 2. TABLE 1 - Rainfall Intensity & Runoff Data Area # Area (acres) C k (min) 10 year storm 25 year storm too year storm C, C C 0 Cana+ I10 (in/hr) Q+a (cfs) Ixs (in/hr) Qzs (cfs) tIN (in/hr) Q+m (cfs) A+ Ax Aa Total Area A 1.04 7.03 0.9 0.3 0.8 0.43 17.8 6.602 19.96 7.564 22.86 8.949 27.05 101 +236 2.36 t0.40 0.40 10 8.635 8.15 9.861 9.31 11.639 10A9 102 120 0.40 0.40 10 8.635 4.14 9.861 4.73 11.639 5.59 201 2.36 0.85 0.85 10 8.635 17.32 9.861 19.78 11.639 23.35 202 1.20_ 0.85 0.85 10 8.635 8.81 9.861 10.06 _11.639 11.87 _ 203 023 -- - _1.20 0.23 0.90 - _-- -- - - 0.90 _ 10 8.635 1.79 9.861 2.04 11.639 2.41 204 023 0.09 0.10 ... .. 0.23 0.90 .._. .. 0.90 10 8.635 1.79 9.861 9.861 2A4 0.80 _- 0.89 8.97 11.639 11.639 _. .. 11.639 11.639 2.47 0.94 1.05 70.59 205 _- 206 0.09 0.10 0.90 __- 0.90 0.90 10 .- 70 70 8.635 0.70 _.__ 0.90 0.85 8.635 8.635 0.78 7.85 .861 9.861 207 1.07 1.07 0. 55 9.861 The Rational Method: Q = CIA 1 = b I (tc+d)` Q = Flow (cfs) tc = Time of concentration (min) A = Area (acres) C = Runoff Coeff. I = Rainfall Intensity (in/hr) Brazos County. 10 year storm 25 year storm 100 year storm b=80 b=89 b=96 d=8.5 d=8.5 d=8.0 e = 0.763 e = 0.75 e = 0.730 tc = U(V`60) L = Length (ft) V = Velocity (ft/sec) TABLE 2 — Time of Concentration (t(:) Equations The time of concentration was determined using methods found in TR- 5, "Urban Hydrology for Small FVatershede. ' The equations are as follows: Time of Concentration: Tc = T,(,,,,.,, n,,,)+ where: T, = Travel Time, minutes For Shallow Concentrated Flow: T, = L / (60* V) where: T, = travel time, minutes V = Velocity, fps (See Fig 3-1, App. B) L = flow length, feet Refer to Appendix A for calculations. STORM SEWER CULVERT DESIGN A storm sewer culvert is proposed at the State Highway 6 West Frontage Road driveway for this development. This culvert will be designed for the 25-year storm event, and it will also pass the 100-year stone event without overtopping the driveway. Refer to Appendix A for the culvert calculator data sheets for the 25- and 100-year storm events. STORM SEWER PIPE & INLET DESIGN This project consists of the construction of the private driveway and stone sewer system and the public water and sanitary sewer lines for this development. No buildings or structures are proposed at this time. The private stone sewer system is designed to collect the developed condition runoff from Lots 1, 2, 4 & 5, and discharge it into the North Fork of Lick Creek. Lots 3 & 6 will have separate storm sewer systems that will discharge directly into the creek. The private driveway and the storm sewer curb inlets were designed for the existing conditions of the property. The storm sewer pipe system is designed for the future developed condition of the property. Pipes 1 & 2 will be constructed with the ends plugged until development of Lots 1, 4 or 5. Inlets and additional storm sewer piping will be required when the development plan for each lot is prepared. A drainage report shall be prepared for each lot before it is developed in order to verify that the calculated runoff values used in this report are not exceeded. As previously stated, the storm water runoff from this site will be collected by the proposed storm sewer system and then flow directly into the North Fork of Lick Creek. The storm sewer piping for this project has been selected to be Reinforced Concrete Pipe (RCP) meeting the requirements of ASTM C-76, Class III pipe meeting the requirements of ASTM C-789. The curb inlets will be cast -in -place concrete. Appendix A presents a summary of the storm sewer inlet design parameters and calculations. The inlets were designed based on a 10-year design storm. As per College Station guidelines, the capacities of inlets in sump were reduced by 10% to allow for clogglllg. Inlets were located to maintain a gutter flow depth of 6" or less. This design depth will prevent the spread of water from overtopping the curb of the road for the 10-year storm event. Refer to Appendix A for a summary of the gutter flow depths. The runoff intercepted by the proposed storm sewer inlets was calculated using the following equations. The depth of flow in the gutter was determined by using the Straight Crown Flow equation. The capacities for the inlets in sump (Inlets I & 2) were calculated using the Inlets in Sumps, Weir Flow equation with a maximum allowable depth of 7" (5" gutter flow plus 2" gutter depression). These equations and the resulting data are also summarized in Appendix A. There are no inlets on grade proposed for this development. Appendix A contains a summary of the storm sewer pipe design parameters and calculations. All pipes are 18" in diameter or larger. The pipes for the storm sewer system were designed based on the 10-year storm event, and they will also pass the 100-year storm event. Based on the depth of flow in the street determined for the 100-year storm event, this runoff will be contained within the street right-of-way until it enters the storm sewer system. The velocity of flow in the storm sewer pipe system is not lower than 2.5 feet per second, and it does not exceed 15 feet per second. As the data shows, even during low flow conditions, the velocity in the pipes will exceed 2.5 feet per second and prevent sediment build-up in the pipes. The maximum flow in the storm sewer pipe system will occur in Pipe No. 4. The maximum velocity for the pipe system in this development will be 8.9 feet per second and will occur in Pipe No. 4. A concrete headwall is proposed for the end of Pipe 4 to dissipate the energy of the discharge and control erosion. Appendix A contains a summary of the pipe calculations as well as a summary of the flows through the storm sewer system for the 10 and 100-year events. A grading plan for this site is provided as Exhibit C. The private driveway is designed so that it is above the base flood elevation for the North Fork of Lick Creek. The site will be graded so that if there is any flow that exceeds the capacity of the storm sewer system it would flow over the private driveway curb and immediately enter the floodplain area. The outlet of Pipe 4 is below the Base Flood Elevation so there will be a tailwater effect on the discharge of Pipe 4. However, due to the close proximity of this site to the stream channel and its location in the watershed, the peak runoff from this site will occur much sooner than the peak runoff for the stream. Therefore, the tailwater condition should have little effect on the capacity of the storm sewer pipe. As stated previously, the area adjacent to Storm Inlet 2 has been designed to allow excess runoff to flow directly into the floodplain area if the storm sewer pipes cannot carry the entire runoff from the site. This will limit the depth of water in the private drive during these circumstances. CONCLUSIONS The construction of this project will increase the storm water runoff from this site. However, the runoff will be carried through the proposed storm sewer system and immediately into the 100-year floodplain. The increased flow in this tributary should not have a significant impact on the surrounding property. No flood damage to downstream or adjacent landowners is expected as a result of this development. r� APPENDIX A Calculations l0 c ? i o < U N t o 'q � y O n T d 0 W 9 N O O_ L 2 C 0 p 'O O1 a aJ O N 9 c c n m n o E U la m O- c 0 `v y 3❑ c w m N m� 3 a S 3 0 0 O < U N O ry p t h o o _ O H I- tli Q t6 U m U N N N N N ^ L T a m s _T N Q C N L C ^ - p N U C U 00 C £ c O 3 cco � Q o 5 d � 0 x 0 W w n u u (7 u Time of Concentration Calculations Drainage Area for Proposed Culvert No. I Flow, along Pavement Segment #I: Flow length = 370' = L Slope = 0.8% For paved surface at 0.8%, Velocity V =1.8 fps (see Fig. 3-1) T,=U(60*V) = 370' / (60* L8) = 3.4 minutes Flow along Pavement Segment #2: Flow length = 615' = L Slope = 1.2% For paved surface at 1.2%, Velocity V =2.2 fps (fig 3-1) = 615' / (60*2.2) = 4.7 minutes Flow along Pavement Seginent #3: Flow length = 565' = L Slope = 1.0% For paved surface at 1.0%, Velocity V =2.0 fps (Fig 3-1) -4 = 565' / (60*2.0) = 4.7 minutes Flow thm Ditch Segment #4: (Refer to attached channel calculations) Trapezoidal channel with 1:5 sides, Bottom width = 24" Flow length = 690' = L Slope = 0.45% (Note: slope & length estimated from topography.) n = 0.035 Area = 7.03 acres (Drainage Area A) Q23 = 22.86 cfs (using tc = 17.8 minutes, C = 0.43) Upstream bypass from Existing Inlet A = 1.90 cfs Total Q25 = 24.8 cfs From Mannino's data, Velocity, V = 2.3 fps > t, = 300 sec = 5.0 minutes T, = 3.4 + 4.7 + 4.7 + 5.0 = 17.8 minutes s0 — 20 — .10 0 .06 N 02 — 01 — 005 — I I 1 1 ( l u l l 1 1 2 4 6 10 20 Average velocity, ft/sec Piqua ]-L—Avcra Kc vd++c itica (ec cAim atinK tr vd limo for xhalla.+ concantr tcd flow. :i'L (210-V I TR55. &,,md Ed.. Jun, 1986) Ditch for Tc Calculations.txt channel calculator Given Input Data: Shape........................... solving for ..................... Flowrate ........................ Slope........................... manning's n ..................... Height.......................... Bottom width .................... Left slope ...................... Right slope ..................... computed Results: Depth........................... velocity........................ Full Flowrate ................... Flow area ....................... Flow perimeter .................. Hydraulic radius ................ Topwidth ....................... Area............................ Perimeter ....................... Percent full .................... Trapezoidal Depth of Flow 24.9000 cfs 0.0045 ft/ft 0.0350 24.0000 in 24.0000 in 0.2000 ft/ft (v/H) 0.2000 ft/ft (v/H) 15.4741 in 2.2858 fps 71.5805 cfs 10.8932 ft2 181.8058 in 8.6280 in 178.7413 in 24.0000 ft2 268.7529 in 64.4755 E'age 1 E � ojojoo 0 E F I I I I rININm o F ,an E E Q � Nico!hm Q N N LL N 11 N e m Nm n:r i m N N O O N T I(")i(h Of O OJ U I _ I rn I o 0 o w N m W. O O M W N O I iaO C �!CN .- -: E Q O N OOOO O E � I of m O j r0 i01 O O N `m a minim m � y m N N 1 T T O O VI [O : N I Ol i�O N Ol m I 1 I I I I U n N C7 C) N N O o> O (O O m W O Cl!t0 c0 OI e- O v N j N N N N C ! CC! > N mph o� a w _gym m -Ej' �L' N r _> m n r n w it C N NN .N N 9 l o O �IO,O O C O O' m > 3 FO- rn _ i7- �!N U o C 6. N.� IO W�O OIto! ' N .(7 m C'1 X ♦1 a % > U r O V (O O t() (O to W M (O W 6 V' N N N M M V V' m y In r 0 h o r O N N N N N N n N N N n N n r h n n h N O N o N 0 N ` N N ` - O O IZ O O N O N O N O N O N O N N m N N N m N m N m N m N m N m N m m v m m m m m m v Q ¢ Q Q Q Q Q Q ¢ N M Q N c Oo N o r o � o ry o al 0 ry Ci 0 C7 0 a a t7 0 Ci OJ n N of M m (D � M W (O 7 OJ r m 0 m O M V O (p 6 N N M r 07 O N M r O O O C C N N N O O O O O N N N ` O Ota N N N O O O N N N O O O � QI f1I N N N ¢ ¢ m m N m m v m m N Z w v Q G Q Q N _I a C7 0 E 0 0 0 0-0 0 C7 U 0 0 Pipe 1 - 10 Year Storm Manning Pipe Calculator Given Input Data Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 18.0000 in Flowrate ........................ 7.8500 cfs Slope ........................... 0.0120 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 11.4659 in Area ............................ 1.7671 ft2 Wetted Area ..................... 1.1879 ft2 Wetted Perimeter ................ 33,2699 in Perimeter ....................... 56.5487 in Velocity ........................ 6.6083 fps Hydraulic Radius ................ 5.1415 in Percent Full .................... 63.6992 % Full flow Flowrate .............. 10.6850 cfs Full flow velocity .............. 6.0465 fps Pipe 1 - 100 Year Storm Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 16.0000 in Flowrate ........................ 10.5900 cfs Slope ........................... 0.0120 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 14.6100 in Area ............................ 1.7671 ft2 Wetted Area ..................... ............... 1.5363 ft2 Wetted Perimeter ................ 40.3883 in Perimeter ....................... 56.5437 in Velocity ........................ 6.8931 fps -Hydraulic Radius ................ 5.4775 in Percent Full .................... 81.1667 % Full flow Flowrate .............. 10.6850 cfs Full flow velocity .............. 6.0465 fps Graham Corner Plaza College Station, Texas Pipe 2 - 10 Year Storm Manning Pipe Calculator Given Input Data Shape ........................... Circular Solving for ..............:...... Depth of Flow Diameter ..................... — 30.0000 in Flowrate ........................ 25.1700 cfs Slope .........................- 0.0070 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 20.1101 in Area ... ........ ............... :. 4.9087 ft2 Wetted Area ..................... 3.4980 ft2 Wetted Perimeter ................ 57.5529 in Perimeter ....................... 94.2478 in Velocity ........................ s 7.1955 fps Hydraulic Radius ................ 8.7522 in Percent Full .................... 67.0336 % Full flow Flowrate .............. 31.8662 cfs Full flow velocity ........... — 6.4917 fps Pipe 2 - 100 Year Storm Manning Pipe Calculator Given Input Data Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 30.0000 in Flowrate ........................ 33.9300 cfs Slope ........................... 0.0070 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 26.9374 in Area ............................ 4.9087 ft2 Wetted Area ..................... 4.6454 ft2 Wetted Perimeter ................ 74.7349 in Perimeter .........- ............ 94.2478 in velocity 7.3040 fps Hydraulic Radius ................ 8.9508 in Percent Full .................... 89.7912 % Full flow Flowrate .............. 31.8662 cfs Full flow velocity .............. 6.4917 fps Graham Cornet: Plaza College Station, 're r:as Pipe 3 - 10 Year Storm Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 36.0000 in Flowrate ........................ 36-4700 cfs Slope ........................... 0-0070 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 22.2742 in Area ..........................:. 7.0686 ft2 Wetted Area ..................... 4.5927 ft2 Wetted Perimeter ................ 65.1795 in Perimeter ....................... 113-0973 in Velocity ........................ 7.9408 fps Hydraulic Radius ................ 10.1466 in Percent Full .................... 61.8728 % Full flow Flowrate .............. 51.8179 cfs Full flow velocity .............. 7.3307 fps Pipe 3 - 100 Year Storm Manning Pipe Calculator Given Input Data: Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 36.0000 in Flowrate ........................ 49.1600 cfs Slope ........................... 0.0070 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 27.9742 in Area ............................ 7.0686 ft2 Wetted Area ..................... 5.8936 ft2 Wetted Perimeter ................ 77.6919 in Perimeter ....................... 113.0973 in Velocity ........................ 8-3412 fps - Hydraulic Radius ................ 10.9237 in Percent Full .................... 77.7062 % Full flow Flowrate .............. 51.8179 cfs Full flow velocity -------------- 7.3307 fps Graham Corner Plaza Cc I.Iege Station, 4'ezae Pipe 4 - 10 Year Storm Manning Pipe Calculator Given Input Data Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 36.0000 in Flowrate ........................ 39.0300 cfs Slope ........................... 0.0080 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 22.2902 in Area ............................ 7.0686 ft2 Wetted Area ..................... 4.5966 ft2 Wetted Perimeter ................ 65.2126 in Perimeter ....................... 113.0973 in velocity ........................ 8.4910 fps Hydraulic Radius ................ 10.1501 in Percent Full .................... 61.9174 Full flow Flowrate .............. 55.3957 cfs Full flow velocity .............. 7.8369 fps Pipe 4 - 100 Year Storm Manning Pipe Calculator Given Input Data Shape ........................... Circular Solving for ..................... Depth of Flow Diameter ........................ 36.0000 in Flowrate ........................ 52.6100 cfs Slope ........................... 0.0080 ft/ft Manning's n ..................... 0.0140 Computed Results: Depth ........................... 28,0020 in Area ............................ 7.0686 ft2 Wetted Area ..................... 5.8994 ft2 Wetted Perimeter ................ 77.7587 in Perimeter ....................... 113.0973 in Velocity ........................ 8.9179 fps Hydraulic Radius ................ 10.9250 in Percent Full .................... 77,7834 % Full flow Flowrate .............. 55.3957 cfs Full flow velocity .............. 7.8369 fps Graham Corner Plaza College Station, Te::a:; Culvert 1 - 25 Year Storm Culvert Calculator Entered Data: Shape........................... Number of Barrels ............... Solving for ..................... Chart Number .................... Scale Number .................... Chart Description ............... Scale Description ............... Overtopping ..................... Flowrate ........................ Manning's n ..................... Roadway Elevation ............... Inlet Elevation ................. Outlet Elevation ................ Diameter ........................ Length.......................... Entrance Loss ................... Tailwater ....................... Computed Results: Headwater ....................... Slope velocity ........................ Circular 2 Headwater 1 3 CONCRETE PIPE CULVERT; NO BEVELED RING ENTRANCE GROOVE END ENTRANCE, PIPE PROJECTING FROM FILL Off 24.8000 cfs 0.0140 284.8500 ft 282.1400 ft 281.9000 ft 24.0000 in 48.0000 ft 0.2000 2.0000 ft 284.3570 ft Outlet Control 0.0050 ft/ft 3.9470 fps Culvert 1 - 100 Year Storm Culvert calculator Entered Data: Shape Number of Barrels ............... Solving for Chart Number .................... Scale Number .................... Chart Description ............... Scale Description ............... Overtopping ..................... Flowrate ........................ Manning's n ...................... Roadway Elevation ............... Inlet Elevation..... ............. Outlet Elevation ................ Diameter ........................ Length.......................... Entrance Loss ................... Tailwater ....................... Computed Results: Headwater ....................... Slope velocity ........................ Circular 2 Headwater 1 3 CONCRETE PIPE CULVERT; NO BEVELE➢ RING ENTRANCE GROOVE END ENTRANCE, PIPE PROJECTING FROM FILL Off 30.0000 cfs 0.0140 284.8500 ft 282.1400 ft 281.9000 ft 24.0000 in 48.0000 ft 0.2000 2.0000 ft 284.5919 ft Inlet Control 0.0050 ft/ft 4.7746 fps Graham Corner Plaza College SLarion. Texas N c O N CQ a � U d C O c Uc IT C U cu J L Q N 0 _ P m V O O o V m M NIA E Q N o R m N P O O r O Q R I I U o_ R O � IU tO ly N P NIA O J J c In m m h P 1 O `o OO OiO T CY O e w O m m P m n m r Tali. (J U mom N mm N CIO P W m I m U I N I Q u R cio 6 oo E G R N Pm y 3 R t7 NN L N R C m � m J it c f � (7 J m O 11 tr c � O � N t0 C E ^T Q N � � N m 3: m`O IL T - U Jp d X It 11 N O J JCy TE m U O U N hl O P m 3 11 � O r. � n M m e C 1v m T 1 � R m � J U C; .O_. b S N 9 N m N C N L O 11 W it V M' N - 71 ^ O j it II ^ O ^ U UI Cll � C N 2 (J 5 O O U C N 3 y u N mI 3 O N c O c U O N C U L P L m N 3 TtuI L p O 4 11 O. F LL N q m jr U) C) R p 11 11 11 11 R U U 11 Vl G7 c (n >. U C7 U S S >. w c EXHIBIT A Time of Concentration Flow Path & Drainage Area Map ID