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Drainage ReportDRAINAGE REPORT FOR KOREAN MISSION CHURCH OF TEXAS A&M WORSHIP CENTER BUILDING COLLEGE STATION, TEXAS r-,% Prepared for Mike Lane Custom Builder P.O. Box 9905 College Station, Texas 77842 Submitted to City of College Station Development Services 1101 Texas Avenue College Station, Texas 77842 Prepared by 7- . •.ses sss• M F CONLIN, JR. 4 : 44481 ~'Q SS/ONALEN~ December, 2002 M. Frederick Conlin, P. Senior Engineer CSC Engineering & Environmental Consultants, Inc. 3407 Tabor Road Bryan, Texas 77808 '~2 William R. Cullen, P.E. Senior Engineer . \\\hhhh\ \hhA\ hA h \ \ \ \ \ \ _ _ \A\\A \\A\\ A \\Ah\ \ \ t t \ \ \ hh\\ A\t CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. k\4ti t... \4 \44...4 v k.?U n\\. \ \ \44\.. k\\1 \ \ \4...... \4..?Ah\N\ \\h 4 \ \4\4\\\+vvv4\h'4 +h\\\ +\\\\\\\\\\\\\\44Uih4NfMh4\4C+A\N.\4h\4\\44\\4+M\\4h\4\4\\44 \\44\4 ~Cv4\ Report of Drainage Study for Korean Mission Church of Texas A&M TABLE OF CONTENTS Page 1.0 GENERAL DESCRIPTION OF SITE AND PROPOSED DEVELOPMENT 3 2.0 PRE-DEVELOPMENT DRAINAGE PATTERNS AND MAJOR DRAINAGE BASINS 4 3.0 SCOPE OF REPORT AND DRAINAGE DESIGN CRITERIA 5 4.0 STORM WATER RUNOFF COMPUTATIONS 5 4.1 USE OF THE RATIONAL FORMULA 5 4.2 RUNOFF COEFFICIENTS (C) 6 4.3 TIME OF CONCENTRATION (Tc) 7 4.4 RAINFALL INTENSITY (I) 8 4.5 AREA OF SITE (A) 9 4.6 STORM WATER RUNOFF QUANTITIES 9 5.0 STORM WATER DETENTION COMPUTATIONS 9 5.1 REQUIRED MINIMUM DETENTION STORAGE VOLUME 9 5.2 DETENTION BASIN STORAGE AREA 10 5.3 DETENTION BASIN OUTLET STRUCTURE 11 6.0 STORMWATER ROUTING COMPUTATIONS 12 6.1 METHODOLOGY 12 6.2 ROUTING COMPUTATIONS AND CONCLUSIONS 12 7.0 EROSION CONTROL MEASURES 13 7.1 GENERAL CONSIDERATIONS 13 8.0 CERTIFICATION .....................................................................................................................13 9.0 REFERENCES 14 LIST OF TABLES Table 1. Summary of Determination of Runoff Coefficient (C) Values for Post-Development Conditions for Entire Site 7 Table 2. Computed Rainfall Intensity Values for Defined Storm Return Period 8 Table 3. Calculation of Pre- and Post-Development Storm Water Runoff Quantities Using the Rational Method 9 1 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drauiage Study for Korean Mission Church of Texas A&M LIST OF FIGURES Figure 1. General Site Vicinity Map Figure 2. Lick Creek Drainage Basin Figure 3. General Site Map and Currently Planned Development Scheme Figure 4. Pre-Development Surface Storm Water Runoff Flow Patterns Figure 5. Post-Development Site Grading Plan and Surface Storrn Water Runoff Flow Patterns Figure 6. Post-Development Site Drainage Basin and Sub-basin Boundaries Figure 7. Types of Site Cover Materials Figure 8. Pre- and Post-Development Hydrographs - 25 Year Event (for Determining Minimum Required Volume of Detention Basin) Figure 8. Stone Water Detention Basin Storage Depth versus Storage Volume Figure 9. Cumulative Outflow (Discharge) versus Depth of Storage Figure 10. Inflow and Outflow Hydrographs Illustrating Routing for 25-Year Storm Event Figure 11. Inflow and Outflow Hydrographs Illustrating Routing for 100-Year Storm Event 2 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage tit for Korean Mission Church of Texas A&M 1.0 GENERAL DESCRIPTION OF SITE AND PROPOSED DEVELOPMENT Information concerning the project was provided by Mr. Chad Grauke, AIA of Mike Lane Custom Builder. The site of the proposed church that is the subject of this report is located in the southern portion of College Station, Texas. The site is located on the western side of the State Highway 6 access road, approximatel} %3 mile south of the intersection with Southern Plantation Drive. The general location of the site is illustrated on Figure 1 of this report. The site is situated within the Spring Creek segment of the Lick Creek Drainage Basin (Figure 2). The subject tract of land is approximately 2.17 acres in area and is part of a larger 10.674 acres tract that has been referred to as Lot 1. Block 1 of the K.T.H. Commercial Addition Robert Stevenson League, A-54 (Figure 3). The smaller tract that is the subject of this report is the only portion of the 10.764-acre tract that is presently planned for development. The subject tract is roughly rectangular is shape and oriented in a northeastern-southwestern direction. The subject tract has approximate plan dimensions of 150 ft by 530 ft. However, a small access corridor within the adjacent lot along State Highway 6 is also part of the planned development (Figure 3). We understand that the Texas Department of Transportation (TxDOT) would not permit direct access of vehicles from State Highway 6 to the portion of the property planned for current development, and therefore, the referenced access corridor was a necessary addition to the proposed development. This corridor will provide access to State Highway 6 at a location acceptable to TxDOT. The proposed access corridor is aligned parallel to State Highway 6 and has approximately plan dimensions of 50 ft by 250 ft. Consequently, the entire tract of land planned for current development is roughly "L-shaped" (Figure 3) and extends over an area of approximately 2.17-acres. The site is bordered on the northeastern side by the access or service road of State Highway 6 and the Texas Department of Transportation's right-of-way for State Highway 6. The long southeastern boundary of the subject site is bordered by an approximately 14.28-acre tract of land owned by the K.S. Moss Capital Corporation. The short southwestern boundary of the subject property is bordered by a 40- ft-wide drainage easement and smaller natural drainage channel that is a tributary of Spring Creek. The 3 \ L \ \ \ \ , , \ . . . \ . \ \ ...•1 \ CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M general flow of the channel is toward Spring Creek to the northeast. The long northwestern boundary of the site borders the Nvestem portion of Lots 1 and 2 of the referenced commercial addition. The subject site is situated on a relatively heavily wooded tract of land. Some clearing of the land has been performed by others in the area of the proposed building location and the proposed parking lot in front of the building. The portion of the property adjacent to State Highway 6, which is the area of interest for the present study, has a relatively gentle slope from the higher elevations in the north and northeastern portions of the site to the lower elevations along the existing Spring Creek tributary that forms the southwestern boundary of the site (Figure 4). Existing ground surface elevations range from approximately El. 291 near the northwestern corner of the property to approximately El. 278 near the previously referenced tributary. The average surface grade across the site is approximately 2.5 percent, with slightly steeper grades being present in the northwestern corner of the site and shallower grades near the creek tributary. There do not appear to be any other significant surface features across the site. We understand that the proposed new worship center building will be a single-story structure and will have a footprint or ground floor area of approximately 15,000 square feet. We anticipate that the structure will be situated in the southwestern portion of the previously described property and northeast of the tributary creek that forms the southwestern boundary of the site. We further anticipate that the proposed development Avill have two parking areas, with one area along the previously described access corridor and the second area in front of the proposed building (Figure 1). We believe that the parking in the access corridor will accommodate approximately 19 vehicles and that the parking area in front of the church will have approximately 99 spaces. We anticipate that the paved drive and parking areas- associated with the new building will be constructed of a rigid pavement system with a Portland cement concrete (PCC) surface. Landscaping of the site will be done in the areas around the church building, behind the church, and the islands and areas bordering the parking lots. 2.0 PRE-DEVELOPMENT DRAINAGE PATTERNS AND MAJOR DRAINAGE BASINS As previously discussed, the subject 2.17-acre site is located in the Spring Creek sub-basin of the Lick Creek drainage basin. The subject site is situated near the sub-basin drainage divide between Spring Creek and the upper reaches of the south fork of Lick Creek as illustrated on Figure 2. 4 • 1\\t\\\~A\ \ \At\\ \ t\t \ \\\1t\ tt \\t\ \ \ \\\\ttt t11 \ \ \ \ \ t \ t \ • \ _ _ _ _ _ _ _ _ \t\\.... CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M There are no distinct drainage channels across the existing site. The major portion of current storm water runoff from the site appears to be by sheet-flow in a southerly or southwesterly direction towards the previously described existing tributary of Spring Creek (Figure 4). No portion of the 2.17- acre site appears to lie within the 100-year floodplain of Spring Creek or Lick Creek. 3.0 SCOPE OF REPORT AND DRAINAGE DESIGN CRITERIA This report addresses the need for retention of drainage from the subject site following the planned development of the church. The site and proposed development were evaluated in accordance with the criteria outlined in the "Drainage Policy and Design Standards (DPDS)" manual of the City of College Station, Texas. The DPDS manual is undated but contains a chapter on "Flood Hazard Protection" that has a revision date of October 1, 1990. This report also discusses specific drainage control structures related to the detention of storm water runoff from the new facility and general erosion control measures. 4.0 STORM WATER RUNOFF COMPUTATIONS 4.1 USE OF THE RATIONAL FORMULA The Rational Formula was used to compute the volume of storm water runoff prior to and following the planned development. Calculations based upon the Rational Formula were employed to assess the quantity of storm water that must be detained to "offset" the increased runoff associated with the new development. The generalized grading plan for the proposed development; the patterns of post- development storm water runoff flows, and the location and approximately area of the proposed detention basin are illustrated on the accompanying Figure 5. The approximate drainage basin and sub-basin boundaries of the drainage areas associated with post-development flow patterns across the site are illustrated on Figure 6. Use of the Rational Formula is reasonable for this project since the contributory area of runoff is less than 50 acres, an area sometimes referenced in the literature as an upper limit for use of the Rational Formula. In addition, the subject site is located within a Secondary Drainage System and not within a 5 ,~A\\\ \ _ _ \ \\1 \Q\\\ \ \\\\A\\\\ \ \ \ \ \ \ \ \ \ . CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M Primary Drainage System. The Rational Formula is not recommended for use within a Primary Drainage System. Therefore, the Rational Formula was used to determine the peak discharge for both pre- and post- development conditions. The general equation for the Rational Formula is well known: Q=CIA where Q = discharge of storm water in units of cubic feet per second (cfs) C = coefficient that represents the average runoff characteristics of the land cover within the drainage area of interest, i.e., the runoff coefficient, which is dimensionless I = rainfall intensity in units of inches per hour (in/hr), and A = area of the site that contributes to the storm water runoff in units of acres The numbers for each of the values used to compute the storm water runoff at the subject site are discussed in the following sections. 4.2 RUNOFF COEFFICIENTS (C) The runoff coefficients or "C" values were computed for both pre- and post-development conditions. Coefficients for the different types of surface covers were determined from Table III-1 of the DPDS manual. The coefficient for the pre-development condition was determined based upon the land cover category listed in Table III-1 as a combination of "Natural Woodlands" and "Natural Grasslands" for slopes in the range of 1% to 3.5%. A range of C-values of 0.18 to 0.25 was listed in the referenced table for the "Natural Woodlands" and a range of C-values of 0.35 to 0.45 was given for "Natural Grasslands" for the cited topographic conditions. Therefore, a conservative value of 0.4 was selected for use for pre- development cover of the entire 2.17-acre site. The post-development side grading plan and surface storm water runoff flow patterns are illustrated in Figure 5. As can be seen from Figure 5, the area incorporated in our analyses for post- development included the access corridor along the State Highway 6 service road as well as the site that is actually being developed for the church building. However, as indicated by the specific site drainage basin and sub-basin boundaries associated with development (Figure 6), not all of the developed site will 6 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. . . Report of Draniage,Stud.y for r Korean Mission Church of Texas A&M be draining directly to the planned detention basin. The portion of the paved area comprising the access corridor will drain onto the adjoining property owned by the developer through openings between the wheel stop structures that border the paved access corridor on the southwest. The post-development C-values were determined from the referenced table for the specific types of site cover associated with post-developed site conditions (Figure 7). The specific types of post- development cover materials illustrated in Figure 7 and the corresponding C-values from Table III-1 of the DPDS manual were used in the analysis listed in Table 1 to compute an average C-value for the post- developed site.. In general, a C-value of 0.9 was used for building roof and concrete covered pavements and sidewalks and a C-value of 0.5 was used for the landscaped or grassed areas. Table 1. Summary of Determination of Runoff Coefficient (C) Values for Post-Development Conditions for Entire Site Area of Coverage, Typical Extended Multiplication of Type of Ground Cover Square Feet C-Values C-Values X Area Concrete (sidewalks, streets, etc.) 14,500 0.90 13,050 Building roof 44,969 0.90 40,472 Grassed or landscaped areas 36,309 0.50 18,154 Summation 95,778 71,676 Therefore, the average C-value across the site can be determined by dividing the summation of the product of the individual areas times the respective C-values and dividing that summation by the overall area: Average C-value = 71,676 C-square feet/95,778 square feet = 0.75 4.3 TIME OF CONCENTRATION (Tc) The time of concentration at a site is used to determine the intensity of the rainfall event used for computing storm water flows and required detention volumes. The time of concentration is defined as "the time required for the runoff to be established and flow from the most remote part of the drainage area to the point under design." For pre-development conditions the time of concentration for the subject site was calculated based upon the elevation difference and the flow distance from the higher elevations in the northeastern portion of the property to the lower elevations where the storm water detention basin outlet 7 y, ca r_ _ r....♦ ♦ ♦r ♦ r err ~r err: ♦ ♦ r r ♦ r CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M structure is to be located. The referenced change in elevation is 9 ft and the referenced distance is approximately 460 ft which produces a slope of approximately 2% for pre-development conditions. The slope for post-development conditions was determined from the proposed site grading plan and drainage patterns as illustrated in Figure 5. The surface slopes or grades and the velocities presented in Table III-2 of the DPDS manual were utilized to determine the appropriate storm water runoff velocity. For overland or sheet-flow over land with slopes in the range of 0 to 3 percent, such as at the subject site, velocities of runoff flow are listed to be in the range of 0 to 1.5 feet per second (fps) for natural woodlands and in the range of 0 to 2.5 fps for natural grasslands. An average velocity of 1 fps was conservatively selected for pre-development conditions. Thus, time of travel between the location of the higher elevations of the site and the proposed detention basin outlet structure location was calculated to be approximately 460 seconds (460 ft distance/1 fps velocity) or approximately 7.7 minutes for pre- development conditions. The post-development time of concentration was calculated over the paved areas of the site without consideration of any detention and was determined to be a shorter time period. Therefore, a minimum time of concentration of 10 minutes (as specified in the DPDS manual) was used in the calculations for both pre- and post-development conditions. 4.4 RAINFALL INTENSITY (I) The rainfall intensity values were computed for the minimum 10-minute time of concentration previously discussed using the intensity-duration-frequency curves developed by the Texas Department of Transportation. The computed intensities calculated for storm events with "return periods" of 5, 10, 25, 50, and 100 years are indicated in Table 2. Table 2. Computed Rainfall Intensity Values for Defined Storm Return Period Storm Return Period Rainfall Intensity (Years) (Inches/Hour) 5 7.7 10 8.6 25 9.9 50 11.1 100 12.3 8 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M 4.5 AREA OF SITE (A) The area of the site used in the computation of storm water runoff is the original site area of 2.17 acres. 4.6 STORM WATER RUNOFF QUANTITIES Storm water runoff quantities were calculated using the Rational Formula. Runoff quantities were calculated for both pre- and post-development conditions for the 2.17-acre site and are presented in Table Table 3. Calculation of Pre- and Post-Development Storm Water Runoff Quantities Using the Rational Method Storm Area_ Intensity` PRE- DEVELOPMENT POST- DEVELOPMENT DIFFERENCE Event (acres) (inches (year) /hr) Cprea Qpre Cposta Qpost QD (dlessb) (cfs) (dlessb) (cfs) (cfs) 5 2.17 7.7 0.40 6.7 0.75 12.5 5.8 10 2.17 8.6 0.40 7.5 0.75 14.1 6.6 25 2.17 9.9 0.40 8.6 0.75 16.0 7.5 50 2.17 11.1 0.40 9.7 0.75 18.1 8.5 100 2.17 12.3 0.40 10.7 0.75 20.0 9.3 a Average values of C were obtained from Table III-1 of the DPDS Manual b dless = dimensionless c Values obtained from Table 2 of this report 5.0 STORM WATER DETENTION COMPUTATIONS 5.1 REQUIRED MINIMUM DETENTION STORAGE VOLUME The storage volume of the detention area was calculated such that the peak discharge of the ultimate development hydrographs for the 25-year design storm was limited to a discharge less than a defined target discharge. The defined target discharge was characterized by the DPDS manual to be the peak discharge of the pre-development hydrograph for the 25-year storm event. Since the entire 2.17-acre 9 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M site is being developed at the present time, the current developed condition and the ultimate developed condition were assumed to be the same. The required detention storage volume was determined as the difference in area between the pre- and post-development hydrographs, as depicted on Figure 8. The Triangular Approximation method was used to determine the hydrographs. The hydrographs were constructed by assuming that the peak discharge, as calculated from the Rational Formula, occurs at a time equal to the time of concentration and that one-third of the flow volume occurs before the peak discharge is reached and two-thirds occur following the peak discharge. The Triangular Approximation method of developing hydrographs is generally considered to be acceptable for analysis of Secondary Drainage Systems with an area of less than 50 acres, which is applicable to the drainage basin addressed in this report. The difference in area between the two hydrographs, or the required minimum volume of the detention storage area, was calculated to be approximately 6,740 ft3 for the 25-year event. 5.2 DETENTION BASIN STORAGE AREA We propose to construction the required detention basin on the southwestern side of the proposed building and adjacent to the existing Spring Creek tributary as depicted in Figure 5. The proposed detention basin will be an earthen structure that is created by a combination of excavation below the existing surface grades and construction of above-grade earthen berms to provide the required volume for storm water detention. The proposed detention basin will be roughly triangular in shape to conform to the space between the back of the building and the site boundaries along tributary creek. The detention basin will have an approximate length of 120 ft and a base width of approximately 45 ft as indicated in Figure 5. The total depth of the basin will be approximately 3 ft from the base of the structure to the bottom of the emergency overflow structure that will be built into the perimeter levee or embankment. The embankments for the detention basin will be formed with compacted clay soils, excavated as part of the proposed building development. The embankments will have side slope with inclinations of 4:1 (horizontal to vertical dimension) with a minimum crest or top width of 1 ft to provide resistance to erosion or damage from mowing equipmentThe slopes of the embankment will be sodded with grass following construction to minimize erosion of the embankment soils. The approximate volume provided by the proposed detention basin is illustrated on Figure 9. As can be seen from Figure 9, the full basin depth below the emergency overflow spillwau elevation would provide a potential storage volume of approximately 7,360 cu ft. With the addition of the 0.75 ft of 10 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. . Report of Drainage Study for Korean Mission Church of Texas A&M freeboard to the crest of the embankment, the proposed detention basin would have a storage volume of approximately 10,071 cu. ft. As previously stated, the required minimum storage volume of the detention basin would be approximately 6,740 cu ft in order to detain the difference between the 25-year event storm water runoff for pre- and post-development conditions. The minimum required volume of 6,740 cu ft is within the available storage capacity of the proposed basin. 5.3 DETENTION BASIN OUTLET STRUCTURE The outlet structures for the detention basin are composed of tow separate structures. A 8 in. diameter high density polyethylene (HDPE) pipe through the embankment will serves to drain the detention for "normal" discharges corresponding to a 25-year event. A 8-ft-wide concrete weir structure that is cut into the top of the detention basin embankment will provide for "emergency overflow" discharges for the 100-year event. The discharges from both structures will be routed to the previously referenced tributary of Spring Creek The diameter and slope of the HDPE outlet pipe was established to provide discharges from the detention basin during the 25-year storm event that were less than or equal to the 8.6 cfs runoff flows that were associated with the pre-development site conditions. As indicated by the graphical presentation of detention basin discharge versus depth illustrated on Figure 10, the planned pipe size and pipe grade provides for a discharge of approximately 3.5 cfs, from the detention basin with 3 ft depth of storm water detention, which is a flow that is less than the 8.6 cfs pre-development flow for the predevelopment 25- year storm event. The detention basin outlet pipe will discharge through the earthen side slope of the tributary stream and not at the base of the stream where the pipe outlet might become inundated for even common rainfall events. Erosion of the earthen side slopes of the "receiving" tributary- creek from detention basin discharges «-ill be minimized by providing rock-rip along the slope at the discharge point. The emergency overflow concrete Wier was sized to pass the outflow from a 100-year event. The length of the weir opening were calculated based upon the Francis formula for weirs: Q=3.33(L-0.2H)H'; where Q = flow rate through rectangular weir opening in cfs L = length of rectangular opening in feet H = head of water at a defined distance behind the wall in feet 11 • CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study for Korean Mission Church of Texas A&M A wier length of 8 feet was selected so that the cumulative flows from the emergency spillway and the outlet pipe of the detention basin exceeds the 100-year post-development in-flow of 20 cfs. 6.0 STORMWATER ROUTING COMPUTATIONS 6.1 METHODOLOGY The proposed detention basin in the southwestern portion of the project site was analyzed for flow routing through the areas under different storm events. The purpose of the routing analysis was to simulate the performance of the detention basins in the form of inflow and outflow hydrographs. The storage-routing analysis was performed based upon the Puls Method. The Puls Method is a procedure for graphically solving the continuity equation for storage reservoirs using the characteristic height-storage and height-discharge curves. As previously discussed, the depth-volume storage curve for the detention basin was developed graphically from the final grading plan and is graphically depicted on Figure 9. A height-discharge or discharge versus depth of storage curve was also developed and is illustrated in Figure 10. The routing time interval was selected to be slightly less than 10 percent of the time to peak of the inflow hydrograph to ensure that the numerical averaging procedures of the Puls Method does not diminish the impact of the peak flow. 6.2 ROUTING COMPUTATIONS AND CONCLUSIONS Routing analysis was performed for two storm events: the 25-year event, which represents the design storm; and the 100-year event called for in the DPDS. The results of the routing analyses are presented graphically on Figures 11 and 12 in the form in inflow and outflow hydrographs, the difference between the two curves being the volume that must be stored. A review of Figure 9 for the 25-year event indicates that the basin has the capacity to store the difference between the inflow and outflow quantities without overtopping. The maximum calculated height of the stored water in the detention basil during the 25-year storm event is approximately 2.9 ft. Therefore, it can be stated that the detention basis has the capacity to store the excess volume of storm water associated with the planned development of the site and [to] discharge the stored water at a rate that 12 ♦ \ \ \ U\\ \ \ \ \ \ \\\tiA r..... ~ CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Draniage Study for Korean Mission Church of Texas A&M is "equal to or less than the peak discharges of the pre-development hydrographs for the design [25-year] storm" as called for in the DPDS. As can be seen from Figure 12 for the 100-year event, the basin will contain a portion of the nmoff associated with the 100-year storm event but without any freeboard for the stored storm water. The remainder of the 100-year event flows will be routed via the previously discussed concrete spillway through the embankment to the tributary to Spring Creek. The detention basin should not be damaged at the point of overtopping due to the flume paving over the earthen slope. 7.0 EROSION CONTROL MEASURES 7.1 GENERAL CONSIDERATIONS The erosion control measures proposed at the site will consist of a combination of silt fences, hay bale barriers, and sedimentation traps. The locations of the proposed erosion control measures are depicted on Sheet C 4 of the plans. 8.0 CERTIFICATION "I hereby certify that this report for drainage design of the storm water detention basin at the 2.17-acre site of the proposed Korean Mission Church of Texas A&M located on the western side of the State Highway 6 service road south of Southern Plantation Drive in College Station, Texas, was prepared under my supervision in accordance with the previsions of the City of College Station "Drainage Policy and Design Standards (1990)" for the owners thereof" M. 2h a' ~ Y M. Frederick Conlin, Jr., P.E. Registered Professional Engineer State of Texas P.E. Number 44481 13 :.x, •a~~rrrr r r ti :rrr r r•:.r rr rrr rr rr •are r ~r ay. Fyn»~ e,~ t y~c, r~ ;fir rrrrti rr rrr r ♦ :;.:a r r~ rarrr.~,; err r r Vic, r ~y). _ . 7 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drauiage Studv for Korean Mission Church of Texas A&M 9.0 REFERENCES Chow, Ven T., Maidment, David R., and Mays, Larry W. 1988. Applied Hydroloy. McGraw-Hill Book Company. New York, NY. 1988. City of College Station, Texas. 1990. "Drainage Policy and Design Standards," part of the Stormwater Management Plan for the City of College Station. October, 1, 1990. Davis, Victor D., and Sorensen, Kenneth E. 1969. Handbook of Applied Hydraulics. McGraw-Hill Book Company. New York, NY. 1969. Hann, C. T., Barfield, B. J., and Hayes, C. J. 1994. Design Hydrology and Sedimentology for Small Catchments. Academic Press, Inc. San Diego, CA. 1994. Mason, John M. and Rhombrerg, Edward L. 1980. On-Site Detention. Prepared for Texas Engineering Extension Service, Texas A& M University. College Station, TX. 1980. Publication No. PWP: 03355-01. McCuen, Richard H. A Guide to Hydrologic Analysis Using SCS Methods. Prentice-Hall, Inc. Englewood Cliffs, NJ. 1982. United States Department of Agriculture. 1975. Urban Hydrology for Small Watersheds. Technical Release No. 55. Engineering Division, Soils Conservation Service, U.S. Department of Agriculture. January 1975. Wanielista, Martin P. 1978. Stormwater Management Quantity and Quality. Ann Arbor Science. Ann Arbor, MI. 1978. Westawav, C. R. and Loomis, A. W. 1979. Cameron Hydraulic Data. (16`h Edition). Ingersoll-Rand. Woodcliff Lake, NJ. 1979. 14 FIGURES z U ~ 0 f I r L Q S2 ~a SITE LOCATION 3 00 d ~ En a a • / ` or \ L Q W » ~ r • ~ u Ct 0 1n J. 9y PROJ. NO.: 102062 \ \ , DRAWN BY: DWA \ DATE: 12/12/02 REV. DATE: SCALE: NOTT0SCALE ,`,G7v~,i\^t~ r APPR: MFG FIGURE: i / ~v LICK ROCK PRAIRIE r~ RD. v.~ r cI <E0e N _ ~ srgT . Mgrs . II ` 0 \ LEGEND BASIN REFERENCE NUMBER ❑ REGULATORY CHANNEL REACHES PRIMARY DRAINAGE SYSTEM SECONDARY. DRAINAGE SYSTEM BASIN BOUNDARY SUB-BASIN BOUNDARY - - - LICK ROCK O PRq/ PROJECT 0 SITE ~pAK L1C O CO <F~ QT r\ Q~\ 5 Ac ~O pJ h LICK CREEK DRAINAGE BASIN P i Jar v/ i <<CK 5 i 1 1 ~ t 1 ~ l 1 ~ t l\ ~ / 10 Di 1 V~ t I I i FIGURE: 2 1 A ° z U o W ~ z b5 z a s a ~~0 z Uw 5 c~ A 0 rn BOUNDA I $ OF PARENT TRA T o ~r`_ f PRESENT ~EVEL'OPMENT --r-±- I ACCESS JI ~4REA OF PANNED OPMENT E E I I 0 D V L • V BOUND TES OF AREA OF PRESENT DEVELOPMENT F z ~i \Sp ~ •I Q 31: m 0 con W Aw ux w RiNc Q k l"*" ' AREA OF - B UNDARIES OF PRESENT`,DEVELORMENI ¢ w OUNDARI -S OF RENT TR>4 7 a ~ z rn ~w ■ Of PROJ. NO.: 102062 0 ' DRAWN BY: N7A DATE: 12712102 REV. DATE. 100 0 100 FEET lI SCALE: AS SHOWN APPR: MFC FIGURE: 3 Fff7 4 n } , 4r3Y41P w IJA1t W w U r~ i A ~ I ~ oW~O 1' ~ a ~ kN II ~ ~ I q ~y 3 W o ` co I I ~ z 50 0 50 FEET FLOW FROM ROOF DRAINS ,v _ I z r Xr ~ - q SOW w u i W I ~wr-1 1510 N12 \ 9~~ DETENTION OU L>ET PIPE i O U O l p NA(j~ N 0 I SPOUTS~(1YP p DOWN- I Per U i \ a \ /NG C KOREAN MI SIGN CHURCH iQ OFT~%ASABM ~ (1em~Yn14 ooq,0.) FF = X1.80 FROM ROOF,DRNNS ~ U 4'y3'4U PROJ. NO.: 102062 DRAWN BY: DWA a 4r4lros w 1147.w' ANDARD 5' CURBINLET 18' 1 ADS N-f2 WITH 10' EXTENSION DATE: 12H2102 DRAINAGE PIPE EXIST. CONTOURS OF ELEVATION REV. DATE: PROP. CONTOURS OF ELEVATION SCALE: AS SHOWN SW STORM WATER RUNOFF APPR: MFC --+r► \SURFACE $1V FLOW DIRECTION FIGURE: - SW FLOW DIRECTION IN PIPE 5 ~C E:l I-=-i-- 1 I 1q Ip I S 4r3W4C W WAr \ \ \ I / I ! i 1 \ 1 1 I 1 I 11 1 II I II I . I \ \ \ \ \ 1 ~ \ I I \ 13 \ / I \ \ \ \ 1 1 \ I~ / / / \ \ \ 1 1 1 f l / / / v V A 1 1 I I / / / v V A 1 1 I j j I T/ i 11 1 I I I 1 1 I , 11 ~ ~ 11 vvv 11 \I O ~ \I II I 11 1 I 1 I I I I I ~ 1 I 1 1 I I 1 I 1 1 1 1 I { 1 l f 1 \ 1 1 ~ 1 t \ t I ~ \ 1 I 50 0 50 FEET \ I \ 1 \ 1 \ \ 1 9 41'41'W W 11JE.17' SID,ib _ G~ A \ 0 \ 1 ~ I I 1 1 I I I I~ \ S AR' KOREAN MISSION CHURCH CP OF TEXAS A&M (1slory 114AW9q,8,) FF=281.80 - - \ DRAINAGE BASINS C~ AREA DRAINING FROM ACCESS CORRIDOR TO UNDEVELOPED PORTION OF SITE - AREA ASSUMED TO BE DRAINING TO DEIENSION BASIN DRAINAGE SUB-BASINS ® AREA DRAINING TO CURB INLET \ I L1 I I I I I ~I1 I I Ii1 II ~ I L t L I 1 I t 1 I T 1 I 1 I I I i III I I III I I III I I ;I 1 I II 1 I I `~I 1 I I I I I I 1. I I ; I I I I I I~ \ li ~~~If 11 I I ~ I I I I i I I ~ I I ~ I j I 1 I ~ f `I 1 I II I I I I 1 I I ! i Ir 1 ~ I I ,!II II II I I I I III I 11 I I I I I III I 1 I III II I L I;~ I I' III II 1 I '!I 1 I ;I ~ 1 II I''I! Il I I illl ~ I III I ; I III I '1 I III 1 I ~ll I II I ill i ' 1 I ~1 l I ~ I ~ ;III I I li' I I I I II 1 " I I I I I 1 I 1 I 'r 1 Q 3 S 0 w U> W N i 1 1 1 1 1 \ 1 1 t 1 I I I V i 1 I I 1 11 II 11 I 1 w w C7 L'G 1 O ^ ~O 00 ~v co O 0 0 s:4H~ ~4 0 AUW 0~0 0. U U 0 U m PROD. NO. 102062 6 A u MAY I I + L -r-- 1 COO 1 - - - - - - - - g0 1 w _ 014 I I w w Ii 1" I I O d 1 s 11'3CM' w sss.4r V1 ,L, 1 ! ~W I I~ \ _ I 1\ li it ~ I I 1 I I I \ \ \ \ 1 1 1 I 1 I I 1 \ \ 1 I I I 1`~ ~ \ \ \ ~ 11 I1 11 I I I G I° \ / \I \ 1 1 I J I~ I vv A A I 1 1 1 I' I / ~ ~ \ \ \1 11 11 \ I i i I i co I / / / \ \ I 1- I I Q ai 0 I ~ ~ / ~v v A I I I ill I, z ~ Z I / i A `v 11 I i 0 (9 ~ 11 I 11 1 11 ~ I I _ ~ N I 1 I I 1 A ! 1 I o I l 1 I 1 l I 1 I I 1 I \ I I I I I 4 I 1 1 1 \ 1 l I 1 \ 1 I l iII I I Ot \ i I \ 1\ I I W V ` I \ vv \V I I I I . U z 1v '~I I 1 vv v 50 0 50 FEET": II ! L 1a I 1\~ \1 I - 1v~ v ` I / I I I Q~0 \ I ~~I I ~ H H I +IVIror w n.x.sr I I \ T - - - - ; I I `I I r OW U CW7 \ 91)~ \ s I II I 0 Fa-1 1\ 0 q i i II 11 0 U 0 \ ~ N 1 1 I 1 Sp \ ~ \ ~ ~ I i i ; II I IA,- KOREAN MISSION CHURCH I III OF TEXAS ABM I I I 11I I,i I L Il t t Fk (Isloay114,400sq.n,) ` FF = 281.80 j q~ i I I I ' ~ I I U w ~ ~''9~ ~ ~ ~ ~ I •I I I ' ' A I ~ - - Lat - - t - II I I PROJ NO' 102062 - - - - - - - - - _ - - - - - - - - - - - - - - - - - Nim - - - - - r I 11 DRAWN BY: DWA 8 41*111W IN 1147.01• I ~ I l I DATE: 12/12102 REV. DATE: \ LANDSCAPED AREAS SCALE: SCALE: AS ~ AS SHOWN \ \ \ BUILDING ROOF AREA APPR MFC / \ 0 PCC PAVING AND FLATWORK AREAS I FIGURE'. 7 ~n DISCHARGE, Q, cfs o cn o cn o cNn (A A O~ m o 9D ol M D p 01 O o Z MDm N -oD tn O ;3 O v Z T - n MQ N = N 0 D m n0) 0 0- o =10 minutes tc ° v m v x Dja m D Z DC a o 00 T rz $v o ~ a 3 N '~D z~g ON w ~ a DADrX 5Si~0 m ~ n ' 3 Npp~Z~ 1 4 00 mZ m~ ap Z O z= ~c c~ M Ammv j o m o 0 3tc=30 minu tes co O 3 19 m 9 n v ~n n A O Zm0 -12 ~<fn D O~ Z ~ zm Apo m mz -n6O i; Or Z X~t Co Kt D Z Ge $N E:! m c OF O -w 1 J io Y aaIN v~ IW O IW U P I p ~o CUMULATIVE STORAGE VOLUME, cubic feet 3 0~0 Mme. ~ 25 25 25 ~n n X m D n z c (mc z 2 oom ;u ca O =O~ O ~ i m m cl) D W IIE111 I DISCHARGE FLOWS FROM DETENTION BASIN OUTLET, c.f.s. 0 of o O Zm Z`Z N Wm ~ m N Z 0 ME = N ~ N Z u 0 w it 0 O N .0. O1 co O N Lx Heig. Of ~LolIwq p97-7.75 Ft. - - - 16- 14- INFLOW 12 W 10- 9 Q 2 8- 6- 4- OUTFLOW 2- 0 0 5 10 15 20 25 30 TIME (minutes) PROJECT: KOREAN NdSSION CHURCH C P S LOCATION: COLLEGE STATION TEXAS . S H INFLOW AND OUTFLOW HYDROGRA APPR: MFC REV. DATE ILLUSTRATING ROUTING FOR 25-YEAR EVENT O SCALE: ASSHOWN DRAWN BY J C r DATE: 12/1902 FIGURE NO.: 11 25 - - 20 INFLOW 15 W ~ 10 0 OUTFLOW 5 0 0 5 10 15 20 25 30 TIME (minutes) PROJECT: KOREAN MISSION CHURCH C G PHS LOCATION: COLLEGE STATION TEXAS . S ® RA INFLOW AND OUTFLOW HYDRO BYO APPR: MFC REV. DATE ILLUSTRATING ROUTING FOR 1OD-YEAR EVENT eww. w~° DRAWN BY: JBF SCALE: AS SHOWN C DATE: 12/1 9M FIGURE N0.:12