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HomeMy WebLinkAboutDrainage Report January 2003DRAINAGE REPORT SEVENTH DAY ADVENTIST CHURCH 1350 EARL RUDDER FREEWAY 5.0 ACRES COLLEGE STATION, BRAZOS COUNTY, TEXAS DRAINAGE REPORT SEVENTH DAY ADVENTIST CHURCH 1350 EARL RUDDER FREEWAY COLLEGE STATION, BRAZOS COUNTY, TEXAS JANUARY, 2003 IN1RODUCTION: The proposed development is located along the west side of the Earl Rudder Freeway approximately 1200 feet north of University Oaks Drive and the tract is approximately 5 acres in size. The proposed improvements include pavement, drainage and utility improvements for the Seventh Day Adventist Church of College Station. The site consists of numerous trees and the terrain slopes in a southwesterly direction toward Glenhaven Drive at approximately 1 percent. The latest Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps ( 48041 CO 142C) shows that no portion of the site is in the regulatory 100-year flood plain. The site is zoned R-1 and R-5 and is being developed by Dr. Bill Davis, Seventh Day Adventist Church, 1218 Ettie Street, Bryan, TX 77803, 775-7362. EXISTING DRAINAGE BASIN DESCRIPTION: The drainage boundary for the site is Richard Carter Park to the north, Earl Rudder Freeway to the east, Cat Hollow Subdivision to the west and Dominik Drive to the south. Storm runoff from the site drains in three directions; Area A, 1.38 acres sheetflows northeast to the TXDOT right-of-way and discharges into a existing grate inlet and a 24" RCP storm sewer with a slope of 0.64%. Area B, 0.97 acres sheetflows west and then south along a ditch in the TXDOT right-of-way, and Area C, 1.95 acres sheetflows southeast towards Dominik Drive. See attached graphic, "DRAINAGE AREA MAP EXISTING CONDITIONS". PROPOSED DRAINAGE: The proposed grading of the site will route the storm water runoff in the same three directions. The area of Area A will be increased to 1.45 acres which will increase the runoff by 2.71 cfs. The capacity of the existing TXDOT grate inlet and the storm drain line was analyized and both have sufficient capacity to accept the increase in flow generated by the improvements. The area of Area B will be decreased to 0.83 acres but runoff will increase the by 1.58 cfs. The open ditch along the :frontage road that this area flows to was evaluated and has sufficient SEVENTH DAY ADVENTIST CHURCH -PAGE l OF 6 pages capacity to accept the increase in flow generated by the improvements. The area of Area C will decrease to 1. 72 acres and will be routed through the proposed detention basin. The runoff will be captured in the driveways and routed to the detention basin where it will be metered out to predevelopment conditions. There is an existing 18" RCP storm drain line at the southeastern comer of the tract that the detention basin outfall structure will connect to. The detention basin will maintain to predevelopment conditions the 2-100 year storm events. The basin was evaluated and modeled using the Haestad Methods "Pond Pack" computer program. Energy dissipation is considered and maintained with concrete and rock riprap at outfalls. The Rational Method was used to determine the peak storm water discharges for predevelopment and post development conditions. STORM WATER POLLUTION CONTROL PLAN: A SWPCP was not prepared because the area to be denuded is less than five acres however sediment from the construction activities will be maintained on the site with the use of silt fencing and this is shown on the construction plans. CONCLUSION: This project is in compliance with the City's Storm Water Design Standards. SEVENTH DAY ADVENTIST CHURCH -PAGE 2 OF 6 peges DRAJNAGE REPORT CHECK LIST Location: CJ Surrounding development: To the north is Richard Carter Park, to the west is Cat Hollow Subdivision a single family residential development, to the south is Dominik Drive with single-family residential homes and to the east is Earl Rudder Freeway. o Local streets, drainage systems shown The development will connect to the frontage road along Earl Rudder Freeway. The drainage system, existing and proposed are shown on the included graphics, "DRAINAGE AREA MAP EXISTING AND PROPOSED CONDITIONS". No portion of the site is in the 100-year flood plain. The runoff, existing and proposed will follow in the same general drainage pathways. Drainage Basins o Secondary system flow patterns and impact of development on existing system: Two areas will flow to TXDOT right-of-way. Area C will be captured and routed through a detention basin. The basin will discharge into an existing 18" RCP at the southwest comer of the tract and then into an existing storm sewer system along Glenhaven Drive. Design Criteria o There are no deviations from standard being requested. CJ Discussion of site constraints and capacities (streets, existing structures, etc.): Area A's existing grate inlet and RCP drain line in the TXDOT row is sized to accept the increase generated by the improvements as well as the open ditch along the frontage road. The existing 18" RCP that the detention basin will discharge into was evaluated and has sufficient capacity to accept the discharge from the improvements. o Discussion of any applicable previous drainage studies and how this plan will affect it: None that I am aware of. Hydrologic Criteria o RainfaU/runoff calculation method described and calculations provided The time of concentration method used is from the "URBAN HYDROLOGY FOR SMALL WATERSHEDS" USDA, Soil Conservation Service, Technical Release 55, June 1986. Chapter Three, "Time of Concentration and Travel Time". The rational method was used to determine the amount of runoff. CJ Detention discharge/storage calculation method/calculations The detention basin was designed using the Haestad Methods "Pond Pack" computer program. o Storm recurrence interval used 2-100 year storm for all analysis. o Discussion of other drainage facility design criteria used if not referenced in Standards Standard design criteria was met or exceeded for all proposed improvements. Hydraulic Criteria o Identify detention/retention outlet and routing The basin will discharge into an existing 18" RCP that has sufficient capacity. SEVENTH DAY ADVENTIST CHURCH -PAGE 3 OF 6 pages o Discussion of other drainage facility design criteria used not referenced in standards Standard design criteria was met or exceeded for all proposed improvements. Drainage Facility Design o Discuss drainage patterns/flow (pre vs. post) Please see attached graphics. o Are they draining water onto another property owner? -If so, is it where the water flowed before? and is it not more than what flowed there before? and no faster than it flowed before? Under existing conditions sheetflow from the tract flows to the lots along Dominik Drive and the Cathollow Subdivision residential section. The proposed improvements will reduce the runoff to the lots. o Discuss detention pond design (side slope, low flow channels, outlet works, freeboard, emergency spillway) Side slopes are 4:1 maximum, a low flow channel ("V") flume is provided in the basin, rock riprap and concrete aprons are provided as energy dissipaters, there is a 0.8 foot freeboard the basin will detain up to the 100 year storm, larger storms will be released through the opening in the top of the outfall structure that is a grate inlet. o Discuss Maintenance access and responsibilities The Owner will provide maintenance. Conclusions o Verify compliance with DPDS (signed and sealed certification) Standard design criteria was met or exceeded for all proposed improvements and the development permit application was submitted to the Planning Division. Explain effectiveness of improvements with regard to controlling discharges of 5-100 year storm by a) Detaining The improvements should decrease the sheet flow to the residential lots along Dominik Drive and the Cat Hollow Subdivision. b) Accommodation runoff in existing/proposed easements or ROW discharging into primary system Discharge increases are small enough that they will stay within the existing secondary systems. c.) Combination of a & b Appendices o References (all criteria and technical information used) The rational method was used for hydrologic determinations (Haestad Methods Quick TR-55) and Manning's formula was used for hydraulic determinations (Haestad Methods Pond Pack) Hydrologic computations o Land use assumptions for adjacent property Predevelopment was based on a coefficient of 0.3 and post-development was based on 0.90 for all pavement, sidewalk and buildings. Weighted coefficients are based on determinations of actual pervious versus impervious. SEVENTH DAY ADVENTIST CHURCH -PAGE 4 OF 6 pages o Minor/major storm runoff at specific points The outfalls are provided with concrete pads and splash walls to decrease the energy generated by the flows. o Hydrographs at critical points Peak flow is used for this project. Hydraulic computations o Culvert capacities (headwater and tail water assumptions) The capacity of the existing TXDOT culvert was evaluated using the Haestad Method FlowMaster program and is included for review. The existing TXDOT grate was evaluated using the grate inlet formula in the DPDS. The existing open ditch along the frontage road was evaluated using the Haestad Method FlowMaster program and is included for review. The existing 18" RCP pipe at the southwest corner of the tract was evaluated using the Haestad Methods StormCad program and is included for review. o Open channel design NA o Detention area/volume capacity/outlet capacity The effect of the detention basin on a given flood is determined by routing the flood hydrograph through the basin using the inflow hydrograph the pond characteristics and determining the outflow hydrograph. The pond characteristics are normally prescribed as stage-storage and stage-discharge (outfall) relationships. The stage represents the elevation of water surface in the pond measured from a horizontal datum and the storage is the volume of water in the pond. The stage-discharge relationship is governed by the hydraulics of the outlet structure. The basin was designed using level pool reservoir routing continuity principle equation S/t=I-0, where S=storage volume, t= time, !=inflow rate and O=outflow rate. The basin will maintain the predevelopment runoff conditions for all of the storm events In an attempt to maintain pre development outfall rates the Haestad Methods program "Pond-2" routes multiple storms through theoretical detention basins to determine storage volume and elevations. The input consists of hydrographs, elevation-vs-storage and outfall structure geometry. Hydrographs are determined using the Rational Method by input of the weighted coefficients as determined from the College Station Drainage Manual, intensity in inches per hour determined from the 1-D-F curves for this area and the acreage of the drainage area. The elevation- vs-storage rating curve is determined by the "Conic Method" to compute the incremental volume between pond contours and summed to create a volume rating table of cumulative pond volumes. The outfall structure input is based on the geometry of a rectangular weir with coefficients taken from Brater and King, "Handbook of Hydraulics". To determine storage volumes the program creates trapezoidal shaped hydrographs for all storm durations by using a duration (Td) and the corresponding peak Q. See attachment "Graphical Summary for Maximum Required Storage" Td is determined by the evaluating storage volumes at varying time increments to determine which time gives the largest storage volume. See SEVENTH DAY ADVENTIST CHURCH -PAGE 5 OF 6 pages attachment "Summary for Single Storm Frequency". From the hydrographs the storage volume is determined by overlaying the trapezoidal hydrograph with the outflow hydrograph that peaks at the allowable pre development outflow rate. o Attached Drawings The detail maps and drawings for this project are included in this drainage report. o Location map with drainage patterns See item above o Drainage Plan with topo (existing and proposed with arrow if needed) See item above TXDOT Permit Checklist A TXDOT permit is required. SEVENTH DAY ADVENTIST CHURCH -PAGE 6 OF 6 pages LOCATION O F SITE SEVENTH DAY ADVENTIST CHURCH SUMMARY OF RUNOFF CALCULATIONS PRE DEVELOPMENT CONDITIONS AREA A FLOW AREA SHEET SHALLOW Tc RUNOFF Q2 Q5 QlO Q25 QlOO (ACRES) FLOW :ONCENTRATEJ (MIN) :OEFFICIEN' (CFS) (CFS) (CFS) (CFS) (CFS) (MIN) FLOW (MIN) 1.38 24.6 5.4 30 0.3 1.45 1.79 2.05 2.35 2.79 POST DEVELOPMENT CONDITIONS AREA A 1.45 24.6 0 24.6 0.5 2.87 3.55 4.04 4.64 5.50 PRE DEVELOPMENT CONDITIONS AREA B FLOW AREA SHEET SHALLOW Tc RUNOFF Q2 Q5 QIO Q25 QIOO (ACRES) FLOW :ONCENTRATEJ (MIN) :OEFFICIEN' (CFS) (CFS) (CFS) (CFS) (CFS) (MIN) FLOW (MIN) 0.97 24.6 5.4 30 0.3 1.09 1.36 1.55 1.78 2.11 POST DEVELOPMENT CONDITIONS AREA B 0.83 0 0 IO 0.45 2.36 2.88 3.24 3.70 4.37 PRE DEVELOPMENT CONDITIONS AREA C FLOW AREA SHEET SHALLOW Tc RUNOFF Q2 Q5 QIO Q25 QlOO (ACRES) FLOW :ONCENTRATEJ (MIN) :OEFFICIEN' (CFS) (CFS) (CFS) (CFS) (CFS) (MIN) FLOW (MIN) 1.95 24.6 4.8 29.4 0.3 2.05 2.56 2.93 3.36 3.99 POST DEVELOPMENT CONDITIONS AREA C 1.72 0 0 10 0.45 3.76 4.65 5.29 6.07 7.20 DETENTION BASIN SUMMARY Basin Volwne = 12470 cubic feet Outfall Structure is a 4" wide vertical rectangular weir Storm Routing Q2 Q5 Q 10 Q25 Q 100 PeakOutflow(cfs) 1.79 2.17 2.44 2.8 3.25 Peak Elevation (MSL) 288.4 288.6 288.7 288.87 289.1 Peak Storage (CF) 2807 3660 4315 5090 6248 AREA A ANALYSIS OF THE EXISTING TXDOT GRATE INLET AND 24" STORM DRAIN LINE IN EARL RUDDER FREEWAY SEVENTII DAY ADVENTIST CHURCH -DRAINAGE REPORT Project Description Project File Worksheet Flow Element Method Solve For Input Data Mannings Coefficient Channel Slope Diameter Results Depth Discharge Flow Area Wetted Perimeter Top Width Critical Depth Percent Full Critical Slope Velocity Velocity Head Specific Energy Froude Number Maximum Discharge Full Flow Capacity Full Flow Slope Existing TXDOT 24" Storm Sewer Pipe Worksheet for Circular Channel c:\haestad\fmw\sdac. fm2 TXDOT Culvert Analysis Circular Channel Manning's Fonnula Full Flow Capacity 0.013 0.006400 ft/ft 24.00 in 24.0 in 18.10 cfs 3.14 ft2 6.28 ft 0.00 ft 1.53 ft 100.00 0.007332 ft/ft 5.76 tus 0.52 ft FULL ft FULL 19.47 cfs 18.10 cfs 0.006400 ft/ft ~~l'P1'. ~p fuu... Ft.ow Q,~~ ~ ~ f ¥t5.I u."' {2c p @ o. b4~1c:, t~ ls.to CPS ~~~e l~~bcSC To 72.cf c: f'l,1 f CFS Vt~ $uFf tCI ~v~:t C~J.>C (\""<. \ To \~c. r ~ ASc:... L n Ft.aw ~ W'\ 1H t. 01/23103 09:52:03 ftM ~>E:o 1 fY' pa.o v e ~ ~"'-i-S , Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 FlowMaster v5. 13 Page 1of1 Seventh Day Adventist Church GRATE INLET CAP A CITY Existing TXDOT Grate Inlet DEPTH OPEN OF WATER AREA AREA (FT.) (SQ. IN.) (SQ.Ff.) 921 6.40 0.10 0.20 0.30 0.40 0.50 0.60 0.70 Q (CFS) 9.75 13.79 16.89 19.50 21.80 23.88 25.79 TOP OF GRATE ELEVATION 294.75 294.9 295.0 295.1 295.2 295.3 295.4 295.5 Q=4.82 Ag yl/2 r ~r.~ Ffu>IJ'reGE, ~bD EXISTING TOP OF PAVEMENT IS AT ELEV. 296.20 WHICH IS 1.45 ABOVE THE GRATE INLET ?12~· D£vCL~p li?"~T ~\oo :::. P4>~7 O~-\f!J~p~ t ~tao ::. rnc~~ ~ 9~t-' rz,7Cf CFS '3.C?o CFS . ~ Zy:.1sT TxooT lNU:'T {-hd.j So;:-FtCl ~ C~.ilC )111 +o JS.c.c4Z:rt iUL ·tr.er~~~'-> (n F-cow ~W) T ~ 'PtJ.o F'~ t M p ~D vf m ~~ s . -~ J l -. ~ ' ; ,,. ' . P1010007.Jpg ( . 640x480x16M jpeg) AREAB FRONTAGE ROAD DITCH ANALYSIS SEVENTH DAY ADVENTIST CHURCH -DRAINAGE REPORT Project Description Project File Worksheet Flow Element Method Solve For Input Data An£~ B Frontage Road Ditch Sta. 10+00 Worksheet for Irregular Channel c:\haestad\fmw\sdac. fm2 Frontage Road Ditch Sta. 10+00 Irregular Channel Manning's Formula Water Elevation Channel Slope 0.020000 ft/ft Elevation range: 294.00 ft to 295.98 ft. Station (ft) Elevation (ft) 0.00 295.98 26.00 26.00 37.37 79.08 Discharge Results Wtd. Mannings Coefficient Water Surface Elevation Flow Area Wetted Perimeter Top Width Height Critical Depth 294.92 295.14 294.00 294.42 4.37 0.040 294.25 3.35 27.07 27.06 0.25 294.21 cfs ft ft2 ft ft ft ft Critical Slope 0.049537 ft/ft Velocity 1.30 ft/s Velocity Head 0.03 ft Specific Energy 294.27 ft Froude Number 0.65 Flow is subcritical. Start Station 0.00 26.00 End Station 26.00 79.08 Roughness 0.018 0.040 TH tS S E:_c TL c ri. l S LccJ.\ T'i D AT 'END © OF-l YY1 Pl2..e!>vt0 SW~<.Z A~uT L7o '';boUTl-I ceF SooTH 012.l VEwA<j. 'SZ.CTicO~ lNA-5 To S~w 7Ht: 0 lhCt-e'bS<:: lh d~h AL.on5 The fO-e>n -\-A' z. ~.0.0 Sw A L:E.. • G~E PST • G l nc.r-eAS-e I \'\ depfh = ~.' 1 FlowMaster v5.13 01/23/03 05:04:29 PM Haestad Methods, Inc. 37 Brookside Road waterbury, CT 06708 (203) 755-1666 Page 1 of 1 ~~ 'D1"ct-\ \ "F 3 /lf2£A-e,· Frontage Road Ditch Sta. 10+00 Rating Table for Irregular Channel Project Description Project File Worksheet Flow Element Method Solve For Constant Data Channel Slope Input Data Discharge Rating Table Discharge (cfs) 1.00 1.25 c:\haestad\fmw\sdac.fm2 Frontage Road Ditch Sta. 10+00 Irregular Channel Manning's Formula Water Elevation 0.020000 ft/ft Minimum Maximum Increment 1.00 5.00 0.25 cfs Water Surface Wtd. Mannings Elevation Coefficient (ft) 0.040 294.14 0.040 294.15 Velocity (ft/s) 0.90 0.95 'Az.e 1.50 ---~> 1.75 -- Q\oo 2.00 0.040 294.17 1.00 0.040-- - -... 294.18 -... -1.04 ::. ~ 2.25 ?-~I 2.50 '2 ,'7 'I c~.s 2.75 3.00 3.25 3.50 3.75 0.040 294.18 1.07 0.040 294.19 1.11 0.040 294 .20 1.13 0.040 294.21 1.16 0.040 294.22 1.19 0.040 294.22 1.21 0.040 294.23 1.23 0.040 294.23 1.26 .. PST ~lex> 4.00 0.040 294.24 1.28 >4.25 _...... 0.040 -· -- 4.50 --0.040 4.75 =~ 5.00 4. "37~F-..s 0.040 0.040 294.25 --- -~1.30 294.25 1.31 294.26 1.33 294.26 1.35 AP.EA-6 · W6. ttn... Su ti!. ~c e. tl_ 'i.v . Ch A f'!:)(a t Ftz.o 'VJ Pn. e ~ PST : · zq4,zs-2414, 1g FlowMaster v5.13 01/23/03 05:03:56PM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1 WM e:, 1)1-rw '2. -~ Project Description Project File Worksheet Flow Element Method Solve For Section Data A'(lg;A 6 Frontage Road Ditch Sta. 10+00 Cross Section for Irregular Channel c:\haestad\fmw\sdac. fm2 Frontage Road Ditch Sta. 10+00 Irregular Channel Manning's Formula Water Elevation Wtd. Mannings Coefficient Channel Slope 0.040 0.020000 ft/ft Water Surface Elevation Discharge 294.25 ft 4.37 cfs ,__295.21--~~~-+--~~__.,.+-~~~-+-_...~~-+-~~~-+-~~~-+-~~~-+~~~----l ¢:::'. ........ c .9295.0f--~~~+-~~~+--->,.-++-+-~~~-+-~~~-+-~~~-+~~~--+~~~--I ..... ro > Q) w 294.81--~~~+-~~~-+--~~~w--~~~-+-~~~-4-~~~~~~~-+~~~--1 01/23/03 05:10:03 PM 294.0L-~~~~~~~-'-~~~-'-~~.......:::...L.....~~~-'-~~~-'-~~~___.._~~~--' 0 .0 10.0 20.0 30.0 40.0 50.0 Station (ft) Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 60.0 70.0 80.0 FJowMaster v5.13 Page 1of1