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HomeMy WebLinkAboutRevised Drainage Report.. ~·· REVISED DRAINAGE REPORT FOR THE PROPOSED LAKESIDE VILLAGE SUBDIVISION COLLEGE STATION, TEXAS Prepared for MM&R Development, LLP c/o Lagrone Construction Company 4603 Caddie Court College Station, TX 77845 Submitted to City of College Station Development Services 1101 Texas Avenue College Station, Texas 77842 Prepared by CSC Engineering & Environmental Consultants, Inc. 3407 Tabor Road Bryan, Texas 77808 November 15, 2006 M. FrederiCkCOJ11;n~- Senior Engineer CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas TABLE OF CONTENTS Page 1.0 GENERAL DESCRIPTION OF SITE AND PROPOSED DEVELOPMENT ............................ 1 1.1 SOURCE OF PROJECT INFORMATION ....................................................................... 1 1.2 LOCATION OF PROPOSED PROJECT.......................................................................... 1 1.3 PROPOSED SUBDMSION DEVELOPMENT SCHEME ....... ... .. . . .. .. . .. . . . . . . .. . . .. . ... . . . . . ... . 1 2.0 MAJOR DRAINAGE BASIN AND SITE PRE-DEVELOPMENT SITE CONDITIONS AND DRAINAGE PATTERNS ................................................................................................. 3 3.0 SCOPE OF REPORT AND DRAINAGE DESIGN CRITERIA................................................. 4 4.0 GENERAL STORM WATER RUNOFF COMPUTATIONS..................................................... 5 4.1 USE OF THE RA TI ON AL FORMULA . .. .. .. .. .. .. .. .. . . ....... ............. .. . . . ... .. .. .. .. ... .. .. .. .. .. .. ..... 5 4.2 FACTORS IN THE RATIONAL FORMULA-DRAINAGE AREAS (A)........................ 6 4.3 FACTORS IN THE RATIONAL FORMULA-RUNOFF COEFFICIENTS (C) .............. 6 4.4 FACTORS IN THE RATIONAL FORMULA-TIME OF CONCENTRATION (Tc) ....... 11 4.5 FACTORS IN THE RATIONAL FORMULA-RAINFALL INTENSITY (I) .................. 11 4.6 STORM WATER RUNOFF QUANTITIES ..................................................................... 12 5.0 STORM WATER DRAINAGE SYSTEM COMPUTATIONS ................................................... 18 5.1 GENERAL ....................................................................................................................... 18 5 .2 STREET GUTTER OR WATER SPREAD CALCULATIONS ........................................ 18 5.3 INLET CALCULATIONS ................................................................................................ 18 5 .4 PIPING AND CHANNEL CALCULATIONS . . . . . . . . . . . .. ..................................................... 20 6.0 STORM WATER DETENTION COMPUTATIONS ................................................................. 23 6.1 GENERAL ....................................................................................................................... 23 6 .1.1 Eastern (Lakeside) or Phase I Portion of Development........................................... 23 6.1.2 Western (Creekside) or Phase II Portion of Development ....................................... 23 6.2 REQUIRED MINIMUM DETENTION STORAGE VOLUME FOR EASTERN OR PHASE I PORTION OF DEVELOPMENT ...................................................................... 24 6.3 DETENTION BASIN STORAGE AREA ......................................................................... 25 7.0 STORM WATER ROUTING COMPUTATIONS ..................................................................... 26 7.1 METHODOLOGY ........................................................................................................... 26 7.2 DETENTION BASIN OUTLET STRUCTURE................................................................ 26 7.3 DETENTION BASIN OUTLET STRUCTURE ................................................................ 26 7.4 ROUTING COMPUTATIONS AND CONCLUSIONS .................................................... 27 8.0 EROSION CONTROL MEASURES ......................................................................................... 28 8.1 GENERAL CONSIDERATIONS ..................................................................................... 28 9.0 CERTIFICATION ..................................................................................................................... 29 10.0 REFERENCES .......................................................................................................................... 30 11 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table la. Table lb. Tpble 2. Table3a. Table 3b. Table 4a. Table 4b. Table 5a. Table 5b. Table 6. Table 7. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11 . Figure 12. LIST OF TABLES Page Summary of All Drainage Sub-Basin Area Designations (See Figure 7), Calculated Areas, and Runoff Coefficients for Pre-Development Conditions ........................................ 7 Summary of All Drainage Sub-Basin Area Designations (See Figure 7), Calculated Areas, and Runoff Coefficients for Pre-Development Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Computed Rainfall Intensity Values for Defined Storm Return Period ................................ 12 Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eastern Storm Water Drainage System and Detention Basin Using the Rational Method for 10-Year Storm Return Period.............. 13 Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eastern Storm Water Drainage System and Detention Basin Using the Rational Method for 100-Year Storm Return Period............ 14 Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eagle A venue Roadway Ex1:ension (See Figure 7) Using the Rational Method for 10-Year Storm Return Period....................... 15 Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eagle A venue Roadway Extension (See Figure 7) Using the Rational Method for 100-Year Storm Return Period..................... 15 Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Western Storm Water Drainage System Using the Rational Method for the 10-Year Storm Return Period............................ 16 Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Western Storm Water Drainage System Using the Rational Method for the 100-Year Storm Return Period.......................... 17 Summary of Inlet Sizing Calculations ................................................................................ 20 Summary of Calculations for Storm Sewer Piping.............................................................. 22 LIST OF FIGURES Vicinity Map of Proposed Lakeside Village Subdivision General Site Map and Currently Planned Development Scheme Lick Creek Drainage Basin Aerial Photograph of General Area of Proposed Subdivision Pre-Development Site Surface Storm Water Runoff Flow Patterns Post-Development Site Grading Plan and Surface Storm Water Runoff Flow Patterns Post-Development Site Sub-Basin Drainage Areas Pre-Development and Post-Development Unit Hydrographs for 10-Year Storm Return Period Pre-Development and Post-Development Unit Hydrographs for 100-Year Storm Return Period Storage Volume Versus Depth for Lake Detention Basin Area Depth of Water in Outlet Pipe Box Versus Discharge Flows Inflow and Outflow Hydrographs Illustrating Routing for 100-Year Storm Event Through Detention Basin Ul CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas LIST OF APPENDICES Appendix A -Figures Appendix B -Nomographs Illustrating Water Spread in Streets Calculations Appendix C -Results of StormCAD Computer Runs Showing Water Level Elevations in Streets lV CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 1.0 GENERAL DESCRIPTION OF SITE AND PROPOSED DEVELOPMENT 1.1 SOURCE OF PROJECT INFORMATION Information concerning the project was provided by Mr. Ron Lagrone who is the representative of the developer of the proposed subdivision, MM&R Development, LLP. 1.2 LOCATION OF PROPOSED PROJECT The site of the proposed Lakeside Village Subdivision is situated northwest of the intersection of Longmire Drive and Eagle Avenue in the southern portion of College Station, Texas, as illustrated on Figure 1 -Vicinity Map of Proposed Lakeside Village Subdivision in Appendix A to this report. The site extends over a total area of approximately 13 .79 acres as illustrated on Figure 2 - General Stte Map and Currently Planned Development Scheme in Appendix A. The site is roughly rectangular in shape with approximate average plan dimensions of 412 ft by 1,362 ft. The site is roughly bisected by the right-of-way (ROW) for the planned extension of Eagle Avenue. The present end of the paved surface of Eagle A venue is approximately along the southeastern border of the proposed subdivision site. The site is bordered on the northeast by the recently completed Longmire Drive extension, and on the southeast by the previously discussed end of Eagle Avenue and also by Phase II of the Springbrook- Cypress Meadow Subdivision. The site is bounded on the southwest and northwest by undeveloped property and further to the southwest by the South Fork of Lick Creek. The currently undeveloped property to the northwest has already been platted and will ultimately be developed as the final phase of development of Dove Crossing. 1.3 PROPOSED SUBDIVISION DEVELOPMENT SCHEME The surface of the site of the proposed subdivision is currently used as undeveloped pastureland. The surface of the site is covered with tall native grasses, shrubs, and some isolated trees. The proposed development encompasses an area of approximately 13. 79 acres and consists of approximately 56 residential lots and accompanying street and utility infrastructure as illustrated on 1 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas F'gure 2. As can be seen from a review of Figure 2, the proposed development will be divided by an extension of Eagle Avenue to the west. In addition, the existing Springbrook-Cypress Meadow -Phase II, Block Ten subdivision borders the proposed development to the southeast and contains a 20-ft-wide drainage easement along the common border (but not through the existing Eagle Avenue ROW). An e~sting concrete drainage flume or channel is present within the two sections of the boundary drainage eas_ement and is connected with existing drainage systems on Longmire Drive, the existing Eagle A venue, or the existing South Fork of Lick Creek. The proposed development of the subject property on the northeastern side of the proposed e~ension of Eagle A venue was designated as the Lakeshore or eastern section of the development. This Lak:eshore section is also referred to as Phase I of the development and has approximately 27 lots that will be situated around a proposed lake. The roadways within the Lakeshore section have several proposed roadway names, such as Lakeshore Drive, Lakeshore Circle, and Lakeshore Court. The Lakeshore roadway network extends from the existing Longmire Drive and circles the proposed lake before ending in a cul-de-sac near the proposed Eagle Avenue extension. The western portion of the proposed development has been termed the Creekside or Phase II portion of the development. This Phase II portion of the proposed development is located on the southwestern side of the proposed Eagle Avenue extension and contains approximately 29 lots positioned around a street that will be known as Creekside Circle. As can be seen from Figure 2, Creekside Circle extends from Eagle A venue to the south and forms a circle or loop within the Phase II portion of the proposed development. 2 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 2.0 MAJOR DRAINAGE BASIN AND SITE PRE-DEVELOPMENT SITE CONDITIONS AND DRAINAGE PATTERNS As previously discussed, the site of the proposed development is located within the Lick Creek drainage basin. More specifically, the subject site is situated adjacent to the South Fork of Lick Creek. As illustrated on Figure 3 -Lick Creek Drain.age Basin in Appendix A, the subject site lies along Regulatory CJiannel Reach IV of the South Fork of the Lick Creek channel. The surface of the site of the proposed subdivision is currently used as undeveloped pastureland. As can be seen from a review of a recent aerial photograph of the area of the site presented in Figure 4 - Aerial Photograph of General Area of Proposed Subdivision, the surface of the site is covered with tall native grasses, shrubs, and some isolated trees. The existing topography across the site is relatively flat. The higher elevations are located along the northwestern boundary of the site and the ground surface generally slopes downward in an easterly direction toward the lower elevations around the previously referenced existing drainage flumes present along the southeastern boundary of the site. The higher elevations along the northwestern boundary range from approximately EL. 284 to EL. 286 and the lower elevations along the southeastern property boundary generally range from approximately EL. 282 to EL. 281.5 . The surface grade across the property generally ranges from approximately 0.5 percent to I percent. The major portion of the current or pre-development storm water runoff from the site appears to be by sheet-flow that follows the existing topography in an easterly or southeasterly direction toward the previously described drainage flumes along the southeastern boundary of the property as illustrated in Figure 5 -Pre-Development Site Surface Storm Water Runoff Flow Patterns. According to the Flood Insurance Maps for Brazos County and Incorporated Areas (Map Number 48041C0201 C dated February 9, 2000), no portion of the proposed development appears to lie within the 100-year floodplain or the floodway. 3 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 3.0 SCOPE OF REPORT AND DRAINAGE DESIGN CRITERIA This report addresses the design of drainage features including inlets and associated piping and channels located on the streets of the proposed subdivision and the required detention of increased storm Wflter runoff attributable to a portion of the proposed development. 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 (hereinafter referred to as DPDS Manual). The DPDS Manual is believed to have an issue date of 1997 . This report also discusses specific drainage control structures related to the detention of storm water runoff from a portion of the proposed subdivision and general erosion control measures. 4 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 4.0 GENERAL 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 fo~lowing 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 general grading plan for the proposed development, the patterns of post- development storm water runoff flows, and the location and approximate area of the proposed detention basin are illustrated on the accompanying Figure 6 -Post-Development Site Grading Plan and Surface Storm Water Runoff Flow Patterns. 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 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 dfainage 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. 5 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 4.2 FACTORS IN THE RATIONAL FORMULA-DRAINAGE AREAS (A) The site of the proposed subdivision was divided into 11 separate on-site and off-site drainage b').sins as depicted on Figure 7 -Site Sub-Basin Drainage Areas. A summary of the individual drainage arpas or subareas of the proposed development is presented in Tables la and lb. 4.3 FACTORS IN THE RATIONAL FORMULA -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 in accordance with information presented in Table 111-1 -Runoff Coefficients for Use in the Rational Formula of the DPDS Manual. The coefficient for the pre-development condition was determined based upon the land cover category listed in Table 111-1 as ''Natural Grasslands" for average slopes in the range of 1.0% to 3.5%. A range of C-values of 0.25 to 0.45 was listed in the referenced table for the ''Natural Grasslands" with the cited topographic conditions (slopes). The flat slopes across the site would fall within (or even below) the lower end of the previously indicated range in ground slopes. Therefore, a C-value of 0.25 from the lower end of the indicated range was also selected for use in charterizing pre-development cover of the entire site. Th post-development runoff coefficients used in the analysis were also obtained from Table IIl-1 of the DPDS. The land use associated with the proposed development could best be described as Medium Density Residential and Table 111-1 lists runoff coefficients in the range of 0.55 to 0.65 for finished or developed surface slopes in the range of 1.0% to 3.5%. Finished surface grades across the site will also be relatively flat. Consequently, a C-value of 0.55 from the lower end of the indicated range in values was employed to represent the developed condition for the proposed project. In addition to listing the sizes of the drainage subareas of the proposed development, Table 1 also summarizes the calculations for the various CA factors that were used with the Rational Method for the design of the drainage system for the proposed development, including the piping system and the inlets. The drainage areas and calculated CA factors are presented both for pre-development conditions (Table la) and for post-development conditions (Table lb). 6 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table la. Summary of All Drainage Sub-Basin Area Designations (See Figure 7), Calculated Areas, and Runoff Coefficients for Pre- Development Conditions DRAINAGE CALCULATED RUNOFF CA VALUE FOR AREA DRAINAGE COEFFICIENT, PRE-COMMENTS DESIGN A-AREA, A c DEVELOPMENT OR TION acres dimensionless CONDITIONS 1 REMARKS lA 2.44 acres 0.25 0.38 Off-site drainage area. Will drain to proposed detention pond (DP). 1B 1.09 acres 0.25 0.27 On-site drainage area. Will not be developed. Will drain to DP. 2A 0.94 acres 0.25 0.24 Off-site drainage area. Will drain to proposed DP. 2B 0.76 acres 0.25 0.19 On-site drainage area. Will not be developed. Will drain to DP. 3A 1.17 acres 0.25 0.29 Off-site drainage area. Will drain to proposed DP. 3B 1.08 acres 0.25 0.27 On-site drainage area. Will not be developed. Will drain to DP. 4 0.13 acres 0.25 0.03 On-site drainage area. Will drain to proposed DP. 5A 0.7 acres 0.25 0.18 Off-site drainage area. Will drain to Eagle A venue. 5B 0.94 acres 0.25 0.24 On-site drainage area. Will drain to Eagle A venue. 6 2.46 acres 0.25 0.86 On-site drainage area. Will drain to existing surface channel. Conservatively assumed to drain to proposed DP. 7A 0.40 acres 0.25 0.10 Off-site drainage area. Will drain to western portion of project. 7B 1.4 acres 0.25 0.35 On-site drainage area. Will drain to western portion of project. 8A 0.2 acres 0.25 0.05 Off-site drainage area. Will drain to Eagle Avenue. 8B 1.20 acres 0.25 0.30 On-site drainage area. Will drain to Eagle Avenue. 7 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table la (Continued). Summary of All Drainage Sub-Basin Area Designations (See Figure 7), Calculated Areas, and Runoff Coefficients for Pre-Development Conditions DRAINAGE CALCULATED RUNOFF CA VALUE FOR AREA DRAINAGE COEFFICIENT, PRE-COMMENTS DESIGNA-AREA, A c DEVELOPMENT OR TION acres dimensionless CONDITIONS 1 REMARKS 9A 0.07 acres 0.25 0.02 Off-site drainage area. Will drain to western portion of project. 9B 1.60 acres 0.25 0.40 On-site drainage area. Will drain to western portion of project. 10 2.01 acres 0.25 0.50 On-site drainage area. Will drain to existing surface channel. 11 0.80 acres 0.25 0.20 On-site drainage area. Will drain to proposed DP. Notes: 1. Calculations based upon a C-value of 0.25 for pre-development conditions. 8 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table lb. Summary of All Drainage Sub-Basin Area Designations (See Figure 7), Calculated Areas, and Runoff Coefficients for Pre- Development Conditions DRAINAGE CALCULATED RUNOFF CA VALUE FOR AREA DRAINAGE COEFFICIENT, PRE-COMMENTS DESIGNA-AREA, A c DEVELOPMENT OR TION acres dimensionless CONDITIONS 1 REMARKS IA 2.44 acres 0.25 0.38 Off-site non-developed drainage area. Will drain to proposed detention pond (DP). lB 1.09 acres 0.55 0.60 On-site drainage area. Will not be developed. Will drain to DP. 2A 0.94 acres 0.25 0.24 Off-site non-developed drainage area. Will drain to proposed DP. 2B 0.76 acres 0.55 0.42 On-site drainage area. Will not be developed. Will drain to DP. 3A 1.17 acres 0.25 0.29 Off-site non-developed drainage area. Will drain to proposed DP. 3B 1.08 acres 0.55 0.59 On-site drainage area. Will not be developed. Will drain to DP. 4 0.13 acres 0.55 0.07 On-site drainage area. Will drain to proposed detention pond. 5A 0.7 acres 0.25 0.18 Off-site non-developed drainage area. Will drain to Eagle Avenue. 5B 0.94 acres 0.55 0.52 On-site drainage area. Will drain to Eagle Avenue. 6 2.46 acres 0.55 1.35 On-site drainage area. Will drain to existing surface channel. Conservatively assumed to drain to proposed DP. 7A 0.40 acres 0.25 0.10 Off-site non-developed drainage area. Will drain to western portion of project. 7B 1.4 acres 0.55 0.77 On-site drainage area. Will drain to western portion of project. 8A 0.2 acres 0.25 0.05 Off-site non-developed drainage area. Will drain to Eagle Avenue. 8B 1.20 acres 0.55 0.66 On-site drainage area. Will drain to Eagle Avenue. 9 -CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table lb (Continued). Summary of All Drainage Sub-Basin Area Designations (See Figure 7), Calculated Areas, and Runoff Coefficients for Pre-Development Conditions DRAINAGE CALCULATED RUNOFF CA VALUE FOR AREA DRAINAGE COEFFICIENT, PRE-COMMENTS DESIGN A-AREA, A c DEVELOPMENT OR TION acres dimensionless CONDITIONS 1 REMARKS 9A 0.07 acres 0.25 0.02 Off-site drainage area. Will drain to western portion of project. 9B 1.60 acres 0.55 0.88 On-site drainage area. Will drain to western portion of project. 10 2.01 acres 0.55 1.11 On-site drainage area. Will drain to existing surface channel. 11 0.80 acres 0.55 0.44 On-site drainage area. Will drain to proposed DP. Notes: 1. Calculations based upon a C-value of0.25 for pre-development conditions and 0.55 for post-development conditions. 10 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 4.4 FACTORS IN THE RATIONAL FORMULA-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 off-site areas to the northwest of the subject development to the lower elevations along the southeastern boundary of the subject development where the storm water enters the existing concrete-lined drainage flume or channel. The referenced change in elevation is in the order of 7 ft (EL. 290 to 283), and the referenced distance is approximately 800 ft that produces a slope of approximately 0.9% for pre- development conditions. The slope for post-development conditions was determined from the proposed site grading plan and drainage patterns as illustrated on Figure 3. The surface slopes or grades and the velocities presented in Table ill-2 of the DPDS Manual were utilized to determine the appropriate storm water runoff velocity. For overland or sheet-flow over natural grasslands 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 2.5 feet per second (fps). Accordingly, an average velocity of 1.0 fps was conservatively selected for pre-development conditions since the measured slope of approximately 0. 9 percent is approximately 1/3 of the given range in slopes and 1/3 of the upper velocity range of 2.5 fps is approximately 0.83 fps . Thus, time of travel between the location of the higher elevations of the off-site properties northwest of the site proposed for development to the exit point at the existing concrete drainage channel was calculated to be approximately 800 seconds (800 ft distance/LO fps velocity) or approximately 13 .3 minutes for pre-development conditions. A conservative time of concentration of 10 minutes was used for pre-development conditions. Similarly, the post-development time of concentration was calculated over off-site natural grassland areas and the paved areas of the site without consideration of any detention and was determined to be a shorter time period. Consequently, 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. 4.5 FACTORS IN THE RATIONAL FORMULA -RAINFALL INTENSITY (I) The rainfall intensity values were computed using the intensity-duration-frequency curves developed by the Texas Department of Transportation and presented in the DPDS Manual. A minimum 11 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas time of concentration of 10 minutes was generally used for design of the storm sewer inlets, but the travel times in the proposed storm sewer piping network were also considered in determining the time of concentration for design of the pipes. The computed intensities calculated for storm events with "return periods" of 5, 10, 25 , 50, and 100 years baaed upon a 10-minute time of concentration are indicated in Table 2. Table 2. Computed Rainfall Intensity Values for Defined Storm Return Period Storm Return Period (Years) 5 10 25 50 100 4.6 STORM WATER RUNOFF QUANTITIES Rainfall Intensity (Inches/Hour) 7.7 8.6 9.9 11.1 12 .3 Storm water runoff quantities were calculated using the Rational Formula for three distinct areas of the proposed development that can be described as the eastern area, the central area (or Eagle Avenue), and the western area. The runoff quantities were determined for both the 10-year storm recurrence interval and also for the 100-year storm recurrence interval. As can be seen from a review of Figure 7, the eastern portion of the development that will flow into the proposed storm water detention basin consists of sub-basin areas IA, lB, 2A, 2B, 3A, 3B, 4, 6, and 11 . The calculated storm water runoff quantities for the eastern portion of the development where the storm water detention basin will be located are presented in Tables 3a and 3b for the 10-year and 100-year storm recurrence intervals, respectively. Similarly, the storm water runoff flows for the central or Eagle Avenue portion of the development can be associated with sub-basin areas 5A, 5B, 8A, and 8B for both the 10-year and the 100-year storm recurrence interval and are presented in Table 4a and 4b, respectively. Finally, the flows for the western portion of the proposed development, which consist of sub-basin areas 7A, 7B, 9A, 9B, and 10, were also computed for the 10-year and 100-year storm recurrence intervals and are presented in Tables 5a and 5b, respectively. 12 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table 3a. Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eastern Storm Water Drainage System and Detention Basin Using the Rational Method for 10-Year Storm Return Period PRE- Drainage DEVELOPMENT Area Area_ Intensity< CApre a Qpre Designation (acres) (inches/hr) (dlessb) (cfs) IA 2.44 8.6 0.61 5.25 lB 1.09 8.6 0.27 2.32 2A 0.94 8.6 0.24 2.06 2B 0.76 8.6 0.19 1.63 3A 1.17 8.6 0.29 2.49 3B 1.08 8.6 0.27 2.32 4 0.13 8.6 0.03 0.26 6 2.46 8.6 0.62 5.33 11 0.80 8.6 0.20 1.72 TOTALS 10.9 ac -23 .1 cfs Notes: •Average values ofC were obtained from Table III-I oftheDPDS Manual b dless = dimensionless 0 Values obtained from Table 2 of this report. 13 POST- DEVELOPMENT DIFFERENCE CApost• Qpost Qnur (dlessb) (cfs) (cfs) 0.61 5.25 0 0.60 5.16 2.84 0.24 2.06 0 0.42 3.59 1.96 0.29 2.49 0 0.59 5.11 2.79 0.07 0.61 0.35 1.35 11.64 6.31 0.44 3.78 2.06 -39.7 cfs -16.6 cfs CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table 3b. Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eastern Storm Water Drainage System and Detention Basin Using the Rational Method for 100-Year Storm Return Period PRE- Drainage DEVELOPMENT Area Area Intensityc CA pre a Qpre Designation (acres) (inches/hr) (dlessb) (cfs) lA 2.44 12.3 0.61 7.50 lB 1.09 12.3 0.27 3.35 2A 0.94 12.3 0.24 2.95 2B 0.76 12.3 0.19 2.34 3A 1.17 12.3 0.29 3.57 3B 1.08 12.3 0.27 3.32 4 0.13 12.3 0.03 0.37 6 2.46 12.3 0.62 7.63 11 0.80 12.3 0.20 2.46 TOTALS 10.9ac -33.5 cfs Notes: •Average values ofC were obtained from Table Ill-I of the DPDS Manual b dless = dimensionless 0 Values obtained from Table 2 of this report 14 POST- DEVELOPMENT DIFFERENCE CAPoSt 8 QPoSt Qnur (dlessb) (cfs) (cfs) 0.61 7.50 0 0.60 7.37 4.02 0.24 2.95 0 0.42 5.14 2.80 0.29 3.57 0 0.59 7.26 3.94 0.07 0.86 0.49 1.35 16.61 8.98 0.44 5.41 2.95 -56.7 cfs -23 .2 cfs CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table 4a. Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eagle Avenue Roadway Extension (See Figure 7) Using the Rational Method for 10-Year Storm Return Period PRE- Drainage DEVELOPMENT Area Area Intensityc CA pre a Qpre Designation (acres) (inches/hr) (dless1) (cfs) 5A 0.70 8.6 0.18 1.55 5B 0.94 8.6 0.24 2.06 Subtotal 3.61 8A 0.20 8.6 0.05 0.43 8B 1.20 8.6 0.30 2.58 Subtotal 3.20 TOTALS -6.81 cfs Notes: •Average values ofC were obtained from Table ill-1 o[theDPDS Manual b dless = dimensionless 0 Values obtained from Table 2 of this report. POST- DEVELOPMENT DIFFERENCE CA post a Qpost Qnur (dless1) (cfs) (cfs) 0.18 1.55 0 0.52 4.45 2.39 6.00 2.39 0.11 0.43 0 0.66 5.68 3.10 6.11 I 3.10 -12.1 -5.49 cfs cfs Table 4b. Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Eagle Avenue Roadway Extension (See Figure 7) Using the Rational Method for 100-Y ear Storm Return Period PRE- Drainage DEVELOPMENT Area Area Intensity< CApre8 Qpre Designation (acres) (inches/hr) (dlessb) (cfs) 5A 0.70 12.3 0.18 2.21 5B 0.94 12.3 0.24 2.95 Subtotal 5.16 8A 0.20 12.3 0.05 0.62 8B 1.20 12.3 0.30 3.69 Subtotal 4.31 TOTALS -9.47 cfs Notes: •Average values ofC were obtained from Table ill-I of the DPDS Manual b dless = dimensionless cValues obtained from Table 2 of this report. 15 POST- DEVELOPMENT DIFFERENCE CA post a Qpost On1rr (dlessb) (cfs) (cfs) 0.18 2.21 0 0.52 6.40 3.45 8.61 3.45 0.11 0.62 0 0.66 8.12 4.43 8.74 I 4.43 -17.4 cfs -7.88 cfs CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table 5a. Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Western Storm Water Drainage System Using the Rational Method for the 10-Y ear Storm Return Period PRE- Drainage DEVELOPMENT Area Area.. Intensityc CApre a Qpre Designation (acres) (inches/hr) (dlessb) (cfs) 7A 0.40 8.6 0.10 0.86 7B 1.4 8.6 0.35 3.01 Subtotal 3.87 9A 0.07 8.6 0.02 0.15 9B 1.6 8.6 0.40 3.45 Subtotal 3.60 10 2.01 8.6 0.50 4.32 Subtotal 4.32 TOTALS -11.8 cfs Notes: •Average values ofC were obtained from Table ITI-1 of the DPDS Manual b dless = dimensionless 0 Values obtained from Table 2 of this report 16 POST- DEVELOPMENT DIFFERENCE CApost a Qpost Qn11r (dlessb) (cfs) (cfs) 0.10 0.86 0 0.77 6.62 3.61 7.48 3.61 0.02 0.15 0 0.88 7.5 7 4.12 7.72 4.12 l.ll 9.51 5.19 9.51 I 5.19 -24.7 cfs -12.9 cfs CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table Sb. Calculation of Pre-and Post-Development Storm Water Runoff Quantities for Individual Drainage Areas Contributory to the Western Storm Water Drainage System Using the Rational Method for the 100-Y ear Storm Return Period PRE- Drainage DEVELOPMENT Area Area Intensityc CApre a Qpre Designation (acres) (inches/hr) (dlessb) (cfs) 7A 0.40 12.3 0.10 1.23 7B 1.4 12.3 0.35 4.31 Subtotal 5.54 9A 0.07 12.3 0.02 0.25 9B 1.60 12.3 0.40 4.92 Subtotal 5.17 10 2.01 12.3 0.50 6.15 Subtotal 6.15 TOTALS ~16.9 cfs Notes: •Average values ofC were obtained from Table III-1 of the DPDS Manual b dless = dimensionless 0Values obtained from Table 2 of this report 17 POST- DEVELOPMENT DIFFERENCE CA post a Qpost Qrnrr (dlessb) (cfs) (cfs) 0.10 1.23 0 0.77 9.47 5.16 10.7 5.16 0.02 0.25 0 0.88 10.8 5.83 11.0 5.83 1.11 13.7 7.50 13.7 I 7.50 ~35.4 cfs ~18 .5 cfs CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 5.0 STORM WATER DRAINAGE SYSTEM COMPUTATIONS 5.1 GENERAL Calculations were performed to check the water spread in the street, the inlet and associated piping capacities, and the detention capacity of the lake. Each of these calculations is presented in the following sections ofthis report and follows the guidelines outlined in the DPDS Manual. 5.2 STREET GUTTER OR WATER SPREAD CALCULATIONS The spread of water in the streets was calculated using Figure IV-1, Nomograph For Flow Jn Triangular Channels in the DPDS. The water spread criteria used in the analyses was than the flow of water in residential streets would be limited to the top of the lay-down curbs, and the flow of water in the collector street (Eagle Avenue) was limited to ensure that one 12-foot traffic lean at the center of the street would remain clean for the design storm event. The design storm had a return period of 10 years. The calculations were performed directly on the Figure IV-1 nomograph and are presented in Appendix B. One nomograph is presented for a typical residential street (Creekside Circle) and one nomograph is presented for the minor collector street (Eagle Avenue). The results of the calculations indicate that the capacities of the referenced streets under the previously stated limitations of water spread is greater that the project runoff flows to the streets. 5.3 INLET CALCULATIONS There are a total of four street curb inlet locations and four street drainage flumes (to lake) that are part of the planned development. The curb inlets were positioned in two pairs (on opposites sides of the street) along Eagle Avenue and along Creekside Circle as illustrated in Figure 3. The inlets are all planned to be curb inlets in sumps (or sags). The inlets were all designed as recessed or depressed inlets to increase their capture capacity. The inlets will all be standard 5-foot long depressed curb inlets with 5- foot extensions (for a total curb opening length of 10 feet). The inlets were all designed to be sufficiently long to be able to fully capture the storm runoff from a 10-year event and to not create excessive ponding of storm water runoff in the street for the design storm event. 18 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas As indicated in the Urban Drainage Design Manual, Hydraulic Circular No. 22 as published by the Federal Highway Administration, August 2001, Second Edition, the capacity of a curb-opening inlet in a sag location depends upon water depth at the curb, the curb opening length, and the height of the curb opening. The curb inlet will function as a weir to depths equal to the curb opening height and as an orifice at depths greater than 1.4 times the opening height. The flow will be in a transitional stage at water depths between 1. 0 and 1. 4 times the curb opening height. The inlets for the present project will not be submerged and can therefore be designed as rectangular weirs. The inlets capacities were calculated in accordance with the weir equation found on page 38 of the DPDSManual for "Curb Opening Inlets, Type A-1" ... Q = 3. 0 * L * y 312 , where Q = the capacity of the inlet in cfs, L = the length of the opening into which water enters into the inlet in feet, and y = total depth of water or head on the inlet in feet. An average depth of water of 7 inches (at the depressed opening of the inlet) was assumed for the Eagle A venue inlets in the vertical curb sections, and an average depth of 6 inches was assumed for the Creekside Circle inlets in the laydown curb sections. Table 4 summarizes the calculations for the design of the curb inlets in the streets. As indicated in Note b of Table 6, the calculated theoretical curb inlet capacity was reduced by 10% as discussed on page 39 of the DPDS Manual to account for possible clogging. The curb inlet capacities per foot presented in Table 4 are the reduced capacities. As can be seen from a review of Table 6, each inlet has been designed to capture all of the calculated runoff for a 10-year storm event without any excess flow or carry-over. 19 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table 6. Summary of Inlet Sizing Calculations FLOW TO Qa/La INLET INLET DESCRIPTION cfs Length (L) Length (L) NO. 0 10· OF INLET TYPE capture/foot b Required Provided Eagle 6.00 cfs Curb inlet (w/5 ' 1.20 5.00 ft 10 ft North Area5 extension) in sump (standard 5' with 5' ext) with depressed throat Eagle 6.1 lcfs Curb inlet (w/5 ' 1.20 5.09 ft 10 ft South Area8 extension) in sump (standard 5' with 5' ext) with depressed throat Creekside 7.72 cfs Curb inlet (w/5 ' 0.95 8.13 ft 10 ft North Area9 extension) in sump (standard 5' with 5' ext) with depressed throat Creekside 7.48 cfs Curb inlet (w/5 ' 0.95 7.87 ft 10 ft South Area 7 extension) in sump (standard 5' with 5' ext) with depressed throat Notes: a. Flows are for IO-year return period storm under post-development conditions; value assumes IO-minute minimum time of concentration. b. Value assumes a recessed inlet with a 6" vertical curb with a resulting average depth or head of7" along Eagle Avenue and a recessed inlet with a 4.5" laydown curb and an average depth or head of6" along Creekside Circle. Table value represents 10% reduction in calculated value to account for possible clogging of curb inlet. 5.4 PIPING AND CHANNEL CALCULATIONS Table 7 summarizes the calculations for the design of the pipes that are part of the storm sewer system. Each pipe was given a designation for the portion of the pipe extending between two drainage structures as illustrated on Figure 6. Each pipe was given a number and a word description in the table. For example, the pipe along Eagle Avenue between the proposed curb inlet structures along Eagle Avenue was termed the "Eagle Avenue Stm Swr Lateral Pipe" and was given a number designation of Line 1. Similarly, the down-gradient pipe which is proposed to transport storm water flows from the proposed collection curb inlet on the south side of Eagle A venue to the existing storm sewer channel collection structure for the existing drainage channel on south side of Eagle A venue at the property boundary was termed the "Eagle Avenue Stm Swr Discharge Pipe" and given a Line 2 designation on Figure 6. Similar descriptions and numerical line designations were also used for the Creekside Circle p1pmg. 20 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas The pipes designated as laterals (Pipe 1 on Eagle Avenue and Pipe 3 on Creekside Circle) will have to accommodate flows from only a single drainage area (Area 5 for Line 1 and Area 9 for Line 3). However, the discharge pipe for both inlet locations was designed for the cumulative drainage areas for both curb inlets (Areas 5 and 8 for Eagle Avenue and Areas 7 and 9 for Creekside Circle). The flows for the 10-year return interval storm for the referenced drainage areas are also listed in Table 7 under the column heading labeled as "Flows to Pipe." It should be noted that the flows to the Creekside Circle inlets were larger than the flows to the Eagle Avenue inlets. In addition, the surface grades at the Creekside Circle inlet locations are relatively flat and therefore it was necessary to use two lateral pipes of 18-inch diameter and two discharge pipes of 24-inch diameter at the Creekside Circle inlet locations. Table 7 also contains the diameters and slopes of the Pfoing required to handle the design flows. The calculated capacity of each pipe smaller than~ ~ c es in diameter was reduced by 25 percent as required by the DPDS Manual to account for possible clogging of the pipes with storm water debris. For example, the 18-inch diameter lateral line across Eagle Avenue had a computed capacity of approximately 8.0 cubic feet per second (cfs), but this value was reduced by 25 percent to approximately 6.0 cfs to account for possible closing. The clogging reduced flow values are listed in Table 7. The gravity flow pipe "networks" were analyzed using the StormCAD storm sewer design and analysis software (Bentley -formerly Haestad Methods). StormCAD employs a built-in numerical model which utilized both the direct step and standard step gradually varied flow methods. The purpose of the analysis was to determine if the water surface attributable to flows for the 10-year storm event would be contained with the curb or centerline elevation of the street and whether similar flows for the 100-year storm event could be contained with the roadway right-of-way. The computations were performed using the reduced capacity of the storm sewer pipes as a result of possible clogging. The results of the analyses are presented in Appendix C and indicate that the water surface elevation will remain within the defined limits during the specified storm events. 21 0 r ___ CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Table 7. Summary of Calculations for Storm Sewer Piping LINE STORM SEWER FLOWS TO STORM SEWER NO. LOCATION PIPE, Q10 PIPING DESIGN From Drainage To Upper Reduced Capacity Street Structure to Drainage End of Cumulative Diameter Slope Length Velocity Structure Pipe (See Note 1) cfs cfs inches percent feet cfs fps 1 Eagle A venue Lateral between curb 6.00 cfs 6.00 cfs 18" 0.49 41 6.0 cfs 4.5 inlets (non-reduced capacity lS 8.0 cfs) 2 Eagle A venue Discharge from 6.11 cfs 12.1 cfs 24" 0.43 214 12.1 cfs 5.1 downstream inlet (non-reduced capacity lS 16.1 cfs) 3 Creekside Circle Lateral between curb 7.72 cfs 7.72 cfs Two 18" 0.2 30 7.7 cfs 2.9 inlets (non-reduced capacity lS 10.2 cfs) 4 Creekside Circle Discharge from 7.48 cfs 15 .2 cfs Two 24" 0.28 117 19.5 cfs 4.2 downstream inlet (non-reduced capacity lS 26.0 cfs) Notes: 1. Flow represents computed capacity reduced by 25 percent for possible clogging. 22 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 6.0 STORM WATER DETENTION COMPUTATIONS 6.1 GENERAL 6.1.1 Eastern (Lakeside) or Phase I Portion of Development The proposed lake in the eastern or Phase I portion of the development was designed to create some detention storage in the area between the perimeter of the lake, which corresponds to the normal or "permanent" lake "pool" level, and the surrounding ROW of Lakeshore Circle. A concrete outfall structure is planned for the lake and will be connected with underground piping to the existing storm water inlet on the southern side of Longview Drive near the southeastern boundary of the Phase I portion of the development. Since the lake discharge will be routed to an existing storm water basin, the volume of the discharge will be limited by weir situated within the discharge structure such that the outflows do not exceed those of a 10-year storm return event. The additional storm water flows corresponding to storms greater than the 10-year event will be retained within the storage area between the lake and the street ROW and will be gradually released over time through the previously referenced weirs and outfall pipes in the outfall structure. The grades around the lake were established in the project grading plan such that once the storage capacity between the lake and the street ROW is exceeded, the ponded storm water will flow toward Longmire Drive and will not be discharged to proposed residential building sites. Due to the large storage volume within the "bowl-shaped" area S\JITOunding the lake, outflows from the lake that are not through the discharge structure are only expected to occur for storm events that have a return period well in excess of 100 years. The storage volume of the referenced detention area was calculated such that the peak discharge of the ultimate development hydrographs for the 100-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 100-year storm event peak, but since the discharge was to route into an existing storm drainage system along Longmire Drive, the discharge would actually be limited to the post-development flow for a 10-year storm event. 6.1.2 Western (Creekside) or Phase II Portion of Development Detention was determined not to be necessary for the western or Phase II portion of the development that lies adjacent to the existing South Fork of Lick Creek. The City of College Station 23 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas drainage ordinance lists the South Fork of Lick Creek as a primary drainage system or channel. The referenced ordinance encourages the rapid conveyance of stormwater runoff to the lower and middle reaches of these primary drainage channels in order to reduce the peak flows in the channels over the total duration of the design storms . We have determined that a direct discharge of stormwater from the western portion of the development to the drainageway would not produce significant impacts to flood elevations due to lags in peak flows. In addition, and as described in the following section of this report, the storage potential of the lake area in the eastern portion of the development (i.e., the volume defined by the elevations around the street ROW around the lake and the surface of the "permanent" water level of the lake) is significant and should be able to provide in excess of the minimum detention requirement for the eastern portion of the development. 6.2 REQUIRED MINIMUM DETENTION STORAGE VOLUME FOR EASTERN OR PHASE I PORTION OF DEVELOPMENT The required detention storage volume was determined as the difference in area between the pre- and post-development hydrographs for the eastern or Phase I portion of the planned development. The pre-and post-development flows were calculated for the sub-basins of the eastern drainage area for both a I 0-year recurrence interval storm and for a I 00-year recurrence interval storm and are presented in the previously referenced Tables 3a and 3b respectively. The Triangular Approximation method was used to determine the unit hydrographs. Graphical plots of the unit hydrographs based upon the data outlined in Tables 3A and 3B are illustrated on Figure 8 -Pre-and Post-Development Hydrographs for JO-Year Storm Return Period and on Figure 9 -Pre-and Post-Development Hydrographs for JOO-Year Storm Return Period. 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 14,940 cu ft for the IO-year event and approximately 20,880 cu ft for the 100-year event. 24 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas Runoff flows to the lake in the eastern portion of the project area will be generated from both on- site and off-site areas. The total area draining to the lake will be approximately 10.7 acres of which approximately 6 acres will be from on-site areas and 4.9 acres will be from off-site areas. Therefore, the actual 10.9-acre contributory drainage area for the lake will be a significant percentage of the 13.9-acre area of the planned development. 6.3 DETENTION BASIN STORAGE AREA As previously described, the developers propose to achieve the required storm detention within the area defined by the roadway ROW surrounding the proposed lake and the limits of the "permanent pool level" of the lake (EL 282) as depicted in Figure 6. The proposed detention area will be a combination of grass-lined areas and paved areas. The grass-lined areas will be present immediately surrounding the lake and also within the portions of the ROW that are outside of the paved streets. The proposed lake detention basin will be roughly rectangular in shape to conform to the space between the roadways known as Lakeshore Circle. The detention basin will have an approximate length of 400 ft and a width of approximately 200 ft as indicated in Figure 6. The total depth of the depressed basin area around the lake between the lake level of EL. 282 and the elevations along the ROW boundary will be approximately 1.5 ft to 2 ft. The "lowest" elevation along the ROW was determined to be approximately EL. 283 .75 . The volumes of water that could be stored within the area extending from the lake surface to the ROW boundary were computed electronically and are presented graphically on Figure 10. The approximate total volume provided by the proposed lake detention basin was electronically calculated to be approximately 87,000 cu ft. As previously stated, the required minimum storage volume of the detention basin would be approximately 14,940 cu ft for the IO-year event and approximately 20,880 cu ft for the 100-year event. As can be seen from the blue (IO-year) and red (100-year) dashed lines on Figure 10, the detention basin has more than adequate capacity for the indicated storm events . Both of the minimum required volumes are well less than the available storage capacity of 87,000 calculated for the proposed basin. 25 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 7.0 STORM WATER ROUTING COMPUTATIONS 7.1 METHODOLOGY The proposed detention basin was analyzed for flow routing through the area under the 100-year storm event. The purpose of the routing analysis was to simulate the performance of the detention basin in the form of inflow and outflow hydrographs. The storage-routing analysis was performed based upon the simplified 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 10. The storage volumes were assumed to be in the height interval above the "permanent" lake water surface elevation of EL. 282 to the elevation at the ROW boundaries at approximately EL. 284. The inflow and outflow rates described in the following sections of this report were utilized to model the routing through the detention basin. 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 do not diminish the impact of the peak flow. 7.2 DETENTION BASIN OUTLET STRUCTURE Flow rates into the detention basin were determined from the previously referenced unit hydrographs. 7.3 DETENTION BASIN OUTLET STRUCTURE The outlet structure for the detention basin is a concrete box positioned in the lake. The box will have solid walls except for control weirs formed into the four sides of the box to regulate the outflow from the lake and maintain the lake water level at EL. 282. The concrete box discharge structure will also have a grate inlet in the top of the box to accommodate excess flows and minimize ponding of water within the ROW. If flows cannot be accommodated by the discharge box, the grades around the lake were 26 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas established to encourage lake water to flow down Lakeshore Drive to Longmire Drive rather than to flow outside of the ROW. The concrete box outlet structure will have a discharge pipe that runs from the bottom of the box to the existing storm sewer inlet along Longmire Drive. The diameter and slope of the outlet pipe was established to provide a discharge from the lake detention basin that was approximately equal to the pre- development of approximately 33.5 cfs under maximum head conditions corresponding to the 100-year storm event. Flow out of the box discharge structure in the detention basin was calculated for various heights of water in the box and above the pipe invert and is depicted on Figure 11 -Depth of Water in Outlet Box Versus Discharge Flows. If it is ever required to drain the lake, the developers expressed a desire to use an independent pumping system to achieve drainage and not to provide the outlet structure with a drain valve for gravity drainage of at least a portion of the lake. 7.4 ROUTING COMPUTATIONS AND CONCLUSIONS Routing analysis was performed for the detention basin for the 100-year event which was determined to be the maximum design storm as discussed in the DPDS Manual. The results of the routing analyses are presented graphically on Figure 12 -Inflow and Outflow Hydrographs Illustrating Routing for JOO-Year Storm Event. Figure 12 illustrated plots of the inflow and outflow hydrographs. The difference between the two curves is the volume of storm flows that must be stored within the detention basin area. A review of Figure 12 for the 100-year event indicates that the detention basin has the capacity to store the difference between the inflow and outflow quantities without extending beyond the limits of the streets. The maximum calculated height of the stored water in the detention basin during the 100-year storm event is approximately 1.75 feet. 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 that the "peak discharges of the ultimate development hydrograph for the design storms ... [has been] ... limited to values less than target discharges ... [which are]... equal to or less than the peak discharges of the predevelopment hydrographs for the design storms" as called for in the DPDS Manual. The routing computations for other storm recurrence intervals indicated less storage requirements and lower water storage elevations. 27 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 8.0 EROSION CONTROL MEASURES 8.1 GENERAL CONSIDERATIONS The erosion control measures proposed at the site will consist of a combination of rock-surfaced construction entrances, silt fences, rock dams, hay bale barriers, and sedimentation traps. The locations of the proposed erosion control measures are depicted on Sheet EC-I of the construction plans. 28 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 10.0 REFERENCES Chow, Ven T., Maidment, David R., and Mays, Larry W. 1988. Applied Hydrology. McGraw-Hill Book Company. New York, NY. 1988. City of College Station, Texas. 1997. "Drainage Policy and Design Standards," part of the Storm Water Management Plan for the City of College Station. 1997. 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. Westaway, C.R. and Loomis, A. W. 1979 . Cameron Hydraulic Data. (16th Edition). Ingersoll-Rand. Woodcliff Lake, NJ. 1979. 30 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 9.0 CERTIFICATION "I hereby certify that this report for drainage design associated with the proposed Lakeside Village Subdivision development located northwest of the intersection of Longmire Drive and Eagle Avenue in College Station, Texas, was prepared under my supervision in accordance with the provisions of the City of College Station 'Drainage Policy and Design Standards ( 1997)' for the owners thereof." ~~~, .o~::e~''1 t ... J!'\ ··\l, .t: .............. · ... ~ MF CONLIN, JR. 21.... ~ ..•••.•............ • -o...·· i 44481 ... ~·it Q • • ,~,·~~l'l.~t~·· \\~'ONA\.~ ~ '~~~\() \\\\ if}\.~~ M. Frederick Conlin, Jr., P.E. / Registered Professional Engineer State of Texas P.E. Number 44481 29 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. Report of Drainage Study Lakeside Village Subdivision; College Station, Texas 10.0 REFERENCES Chow, Ven T., Maidment, David R., and Mays, Larry W. 1988 . Applied Hydrology. McGraw-Hill Book Company. New York, NY. 1988. City of College Station, Texas. 1997. "Drainage Policy and Design Standards," part of the Storm Water Management Plan for the City of College Station. 1997. 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. Westaway, C.R. and Loomis, A. W. 1979. Cameron Hydraulic Data. (16th Edition). Ingersoll-Rand. Woodcliff Lake, NJ. 1979. 30 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. APPENDIX A Figures Figure 1. Vicinity Map of Proposed Lakeside Village Subdivision Figure 2. General Site Map and Currently Planned Development Scheme Figure 3. Lick Creek Drainage Basin Figure 4. Aerial Photograph of General Area of Proposed Subdivision Figure 5. Pre-Development Site Surface Storm Water Runoff Flow Patterns Figure 6. Post-Development Site Grading Plan and Surface Storm Water Runoff Flow Patterns Figure 7. Post-Development Site Sub-Basin Drainage Areas Figure 8. Pre-Development and Post-Development Unit Hydrographs for 10-Year Storm Return Period Figure 9. Pre-Development and Post-Development Unit Hydrographs for 100-Year Storm Return Period Figure 10. Storage Volume Versus Depth for Lake Detention Basin Area Figure 11. Depth of Water in Outlet Pipe Box Versus Discharge Flows Figure 12. Inflow and Outflow Hydrographs Illustrating Routing for 100-Year Storm Event Through Detention Basin 11 c s c I 11gineenng <t I m·1ro11111el1ftJI CtnH11lta11tl . Inc. or: MM&R DEVELOPMENT, LLP ROCK PRAIRIE 0 VICINITY MAP OF PROPOSED LAKESIDE VILLAGE SUBDIVISION COLLEGE STATION, TEXAS PROJECT: 105085 LOCATION: COLLEGE STATION, TEXAS APPR: MFC REV. DATE: DRAWN BY: MOK SCALE: AS SHOWN DATE: 09/01/06 FIGURE NO.: 1 c s c UI -0 Vl ~ 0 .....I ..... I fl,'lllH'ill.' {,,, ,,,,,,,,,,,,,.,, 1 orn11//11•11\ b1i. 50 45 40 35 30 25 20 15 10 5 0 5 10 (600 sec.) PRE AND POST DEVELOPMENT HYDROGRAPHS FOR 10-YEAR STORM RETURN PERIOD LAKESIDE VILLAGE SUBDIVISION COLLEGE STATION TEXAS 15 TIME 20 (1200 sec.) Pl'e-o...lopmont and Poet Development Unit H,drogroplla f« 1 Q=Xtgr Sloan A.tum Period. Required Oeiention Basin Volume • Ji{l .800 oecondo)(J9.7 cfs-2.l.1 els) • 1'4,t40 cf• 25 PROJECT: 105085 30 min. (1800 sec.) LOCATION: COLLEGE STATION TEXAS M M&R DEVELOPMENT, LLP lt-'::'AP='P""'R"°': ,.,-M=:F,.,_C-=-===-----t"R::.'-:E:-:V-;.-. ='DA~T"'E,_,: ~,.,..,-,,...------ii DRAWN BY: MDK SCALE: ASSHO'M-1 DATE: 09/01.IJB FIGURE NO.: 8 I c s c UI ..... 0 (/) 3: g I.&.. I n~mi 111,,,.: ~ I,, """1111·111al ( onudtoftl\ f,. 100 90 80 70 60 50 40 30 20 10 0 5 10 (600 sec.) PRE AND POST DEVELOPMENT HYDROGRAPHS FOR 100-YEAR STORM RETURN PERIOD LAKESIDE VILLAGE SUBDIVISION ESTA ION TEXAS 15 TIME Pre-0-.lopment and Poet Dewfoi>menl UnR H)ldro9rapho '"' 100-xv Siem! -.m Period R9qulrod o.t.ntfon -Volume • JS{l,800 -)(~8.7 cfo-JJ.~ ef1) -20,880 cu. ft. 20 (1200 sec.) 25 PROJECT: 105085 30 min. (1800 sec.) LOCATION: COLLEGE SfATION TEXAS MM& R DEVELOPMENT, LLP lt":::"AP:::-P.,.,R.,.,: ,.,.M.,,,F,,..c-:-:::,,.,.-----rR="E~V.,._. ='DA~T"'E,_.,: ~.,.,.,.,,-------ii DRAWN BY: MDK SCALE: AS SHOV\.11J DATE: 09/01,00 FIGURE NO.: 9 . 0 0 Cl. .... c Q) c 0 E .... Q) ~ ~ ..0 <( .c .... a. Q) 0 Water Level Confined to Pork Area O.S -1----1---..~-1-,_....,...__-+----+----+----+-----+-----+-----+-----+----1 Around Lake Lake Surface El. 282.00 0 10,000 20.000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 100,000 I c s c I ngweerw,e, A l.ndronmental Co11s11/tont.l./11c or: MM&R DEVELOPMENT, LLP Storage Volume, cu. ft. STORAGE VOLUME VERSUS DEPTH FOR LAKE DETENTION BASION AREA LAKESIDE VILLAGE SUBDIVISION PROJECT: 105085 LOCATION: COLLEGE STATION, TEXAS APPR: MFC REV. DATE: DRAWN BY: MOK SCALE: AS SHOWN DATE: 09/01/06 FIGURE NO.: 10 -G) G) -x 0 a:i G) Q. a.. -G) :;: ::J 0 c .... G) -0 :r; -0 ~ -Q. G) 0 I <4-.5 <4-.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 c s c 10 l .t1l?UJeen11r: c\'. I m·zronmemol Co11~11/ra11B. !tu. MM&R DEVELOPMENT, LLP 20 30 ""° 50 Discharge Flow, cfs DISCHARGE FLOWS LAKESIDE VILLAGE SUBDIVISION COLLEGE STATION TEXAS PROJECT: 105085 LOCATION: COLLEGE STATION, TEXAS APPR: MFC REV. DATE: DRAWN BY: MOK SCALE: AS SHOWN DATE: 09/01/06 FIGURE NO.: 11 90 80 70 60 50 30 20 10 0 5 10 15 l.ngJ11eert11,f!. c.~ l.m·1ro11me111al Consulrmlf\. Inc. 3 t;:; !:! iJ' ~ 2 ~ VI .... 0 ~ (!) iij :I: ow 20 25 30 35 50 55 LLUSTRATING ROUTING FOR 100-YEAR STORM I INFLOW AND OUTFLOW HYDROGRAPHS . EVENT THROUGH DETENTION BASIN 1r============J~====~~or.~.=========i PROJECT: 105085 LOCATION: COLLEGE STATION, TEXAS APPR: MFC REV. DATE: MM&R DEVELOPMENT, LLP DRAWN BY: MOK SCALE: AS SHOWN DATE: 09/01/06 FIGURE NO.: 12 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. APPENDIXB Nomographs Illustrating Water Spread in Streets Calculations ~ .. 2 .... c QC topoo t,000 &,000 7,000 S,000 5,000 4/)00 too SO() 400 300 200 tOO tO IO 70 to so 40 30 zo 10 Z•flJ!QPNCAL O' l'RIMSVEftSE ~! n•OOEFA<XNT ~ ~s IN MAMolMS FQMLll.A 1•GIUOE O' CHANNEL IN FT./Ft y•OE:ftTH AT CUM °" OE!P£ST POINT IN FT. EXAMfl\..! (S.. Mlftff llMa) GIVEN• 1•0.0S Z•24 JI Z,A. •1200 n•.ot Q•l.O CF'S F1H01 J&0.22 -------------~----,-_-_-_---------............ _____ :_~ ... .,:,.--- "-------- w . .J '"-, ·., INIT!WCTIOHS I. COMCCT % MT10 WITH ~ (1) AM> COMCCT DCICMM• (Q) wm4 DO'Tl4 (J). n4D1 TWO LJtllO MUl'T .. T!MECT AT n.IN8 LINE Fat COl9l\.!TI IOUITION. L 'TO'*llRIM• WllM• Qi&• r<Mf at f6 CIWlt!L FIGURE m-1 HOMOGRAPH FOR FLOW IN TAtANGULAR CHANNEL S 2.0 .IO CI0%0.UO£) .oe .07 .oe ·°' .04 .OS ----·- .co. .ooe -'<>Gipe o..C.. :St""" et ; \ . . 004 '{Ji'<fE'c.L10 \ ~.::r:. -· ;_ ·' .OOI 1.0 .90 .10 .SO -~ .40 See_ o..c.c:o""'"'•"::>o .. :·t )-:: -.\r,o 3\~c=!.-.-' .. _ ~ -· ::.: 30Ae., ~'er~:~· J ~ " V\.o+ e,\f\C."'"\'<l <"-.C.1<---. ~ .zo .10 ~ .OI ~ .01 DI .OZ .01 0v--. ce.,.,..,,~" I Lo..n '2.... z L-~-~-_J. .. -· I ' I --~--· -~· -·+-~ i L. +-· .. j.. I ' J. "" -1 ~-. I I I ·t-L + I t __ _j___i·-+ --l. -f--J. ,1_+-3-0235 -50 SHEETS -5 SQUARES COMET 3-0236-100 SHEETS - 5 SQUARES 3-0237 -200 SHEETS - 5 SQUARES 3-0137-200 SHEETS -FILLER I I . I . ..t__t ! t-+· I. -,-,-· .. -,_ I -I _L • I . _.,.__ I : ; r·1 -~· r • I•_.. +--I· :. L.i..+--1 . .../ . -: . i--~· -~-' i :---T" 1-T --4 -·1 ""1·--' • --"' 4-4-J---L-L .....\..:;:.0',4.-'i-···-~6.o5t I , : I I • i l f -i--r-•":" --,--+-I < L I L f· '---~--~ _j ....._ ---·-··-·~_., ___ .. .. .) . ._. ~ I I -; I f --It.. -' + -- I i Kl,000 11')00 j l.,000 ('I 1,000 If) e,ooo I ~ 5poo .,..__, <? •l>OO. cf)t~ t en~ .. 3,000 ('/) 'l ,, t 'rf l too soo 400 ~ .. 2 300 ~ ~ II: zoo ; IOO tQ IO 70 to 90 40 30 • . ..J CREE'b.~e CrRcLE.. rf ;. ''. EQVATQtl Q•O.St <.J1 J2 '11"3 Z•~CIPNCAL 0# ~AHSVE"9E SLOPE n•OO€f'FICIENT 0# ~SIN MAHNMS FOMIULA 1•GIUOE OI 04AHNEL IN FT./F1'. y•OE:llTH AT CUM Oft DEEPEST POINT IN"· EX A.._,! (SM dcllftff lfnM) GIVEN• t•O.OS Z•24 JI ZAt•l200 -n•.Ol · Q•2.0 CF'S ·F'IH01 r•0.2Z INIT!!yCTIQ!!S 1 I. COMCC'T % MT10 WITH ~ (1) AM> COM! OCICMM• (Q) WITH DIP1l4 (r). THOE TWO ·u.s MUIT lilTEMECT AT,,,_ .... LINE FOR . Ca.uTI IOl.UT'IC*. =~ 1~:&J ~=:: ~; y' DE'Tl4 Ji OSTAIN ~ flOI' s ~ um7-Ae DE'TH1: no O,•Q~ FIGURE lll:-I HOMOGRAPH FOR FLOW IN TAtANGULAR CHANNELS 2.0 .IO (10%°"-'0£) .oe 1.0 .07 .oe .05 .oos .90 :ro .ISO .05 .01 CSC ENGINEERING & ENVIRONMENTAL CONSULTANTS, INC. APPENDIXC Results of StormCAD Computer Runs Showing Water Level Elevations in Streets Title: Lakeside Village Project Engineer: MFC/WRC Project Date: 11/03/06 Comments: Scenario Summary Scenario Base Physical Properties Alternat Base-Physical Properties Catchments Alternative Base-Catchments System Flows Alternative Base-System Flows Structure Headlosses Alterr Base-Structure Head losses Boundary Conditions Altern; Base-Boundary Conditions Design Constraints Alternati Base-Design Constraints Capital Cost Alternative Base-Capital Cost User Data Alternative Network Inventory Number of Pipes -Circular Pipes: -Box Pipes: -Arch Pipes: -Vertical Elliptical Pipes: -Horizontal Elliptical Pipes: Number of Junctions Number of Outlets Circular Pipes Inventory 18 inch Total Length Curb Inlet Inventory Dl-4A Title: Lakeside Village Base-User Data 2 2 0 0 0 0 0 1 44.29 ft 269.03 ft c:\ ... \stormcad\Jakesidevillageeagle1 Oyr.stm Number of Inlets -Grate Inlets: -Curb Inlets: -Combination Inlets: • Slot Inlets: • Grate Inlets in Ditch: • Generic Inlets: 24inch Dl-4E 2 0 2 0 0 0 0 Analysis Results Scenario: Base 224.74 ft CSCEng EA<SLE /\VENUE 11/10/06 02:23:03 PM © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Project Engineer: MFCIWRC StormCAD v5.6 (05.06.012.00] Page 1 of 2 Inlet elements for network with outlet: 0-1 Analysis Results Scenario: Base Label Inlet Total Total Total Bypass Capture HydraulicHydraulic Gravity Headless 1-1 1-2 Systemntercepte<Eypassedl"arget Efficiency Grade Grade Element Method Flow Flow Flow (%) Line In Line OutHeadloss (cfs) (cfs) (cfs) (ft) (ft) (ft) Curb Dl-L 6.33 Curb Dl-L 13.06 0.00 0.00 0.00 N/A 0.00 N/A Outlet: 0-1 100.0 281 .77 281.77 100.0 281.66 281 .66 0.00 Absolut 0.00 Absolut Label HydraulicHydraulic Gravity System System System System System System Grade Grade Element Additional Known Rational Intensity Flow Time CA Line In Line OutHeadloss Flow Flow Flow (in/hr) (min) (acres) (ft) (ft) (ft) (cfs) (cfs) (cfs) 0-1 279.41 279.41 0.00 6.53 6.53 0.00 0.00 0.88 0.00 Pipe elements for network with outlet: 0-1 Label Section Section Length NumbeiConstructed Energy Total AverageUpstrearfilownstreartliydraulicHydraulic Shape Size (ft) of Slope Slope SystemVeloclty Invert Invert Grade Grade Sections (ft/ft) (ft/ft) Flow (ft/s) Elevation Elevation Line In Line Out P-1 P-2 Circular 18 lnct 44.29 Circular 24 inct ~24.74 Title: Lakeside Village c:\ ... \stormcad\Jakesidevillageeagle1 Oyr.stm (cfs) (ft) (ft) (ft) (ft) 0.006773 002906 6.33 0.003159 003464 13.06 5.69 280.42 280.12 281 .77 281 .66 4.99 280.12 279.41 281 .66 280.71 CSCEng 11 /1 0/06 02:23:03 PM <!:! Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Project Engineer: MFCIWRC StormCAD v5.6 [05.06.012.00] Page 2 of 2 Scenario: Base Combined Pipe\Node Report Label Upstream Downstrearr Length Upstream Upstream lnle Upstrearb pstream Calculate ~pstream lnle Section Full Average Upstream bownstrearr Node Node (ft) Inlet Rational Inlet System CA Rational Flow Size Capacity Velocity Invert Invert Area Coefficient CA (acres) (cfs) (cfs) (ft/s) Elevation Elevation (acres) (acres) (ft) (ft) P-1 1-1 1-2 44.29 0.00 0.00 0.00 0.00 0.00 18 Inch 9.37 5.69 280.42 280.12 P-2 1-2 0-1 224.74 0.00 0.00 0.00 0.00 0.00 24inch 13.77 4.99 280.1 2 279.41 Title: Lakeside Village c:\ ... \stormcad\lakesidevillageeagle 1 Oyr.stm CSCEng 11/10/06 02:09:08 PM © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Constructec Description Slope (ft/ft) 0.006773 0.003159 Project Engineer: MFC/WRC StormCAD v5.6 [05.06.012.00) Page 1 of 1 44.29ft Profile Scenario: Base Profile: Profile - 1 Scenario: Base 1-1---~ 280.00 EllNOOon(lt) ~------------__i_-------------'----------------' 275.00 3+00 2+00 1+00 Stooon(lt) Title: Lakeside Village Project Engineer: MFC/WRC c:\. .. \stormcad\lakesidevillageeagle1 Oyr.stm CSC Eng StormCAD v5.6 [05.06.012.00] 11/10/06 02:02:4!i:lf!Mntley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 1 Title: Lakeside Village Project Engineer: MFCNVRC Project Date: 11 /03/06 Comments: Scenario Summary Scenario Base Physical Properties Alternat Base-Physical Properties Catchments Alternative Base-Catchments System Flows Alternative Base-System Flows Structure Head losses Alterr Base-Structure Headlosses Boundary Conditions Altem Base-Boundary Conditions Design Constraints Alternati Base-Design Constraints Capital Cost Alternative Base-Capital Cost User Data Alternative Base-User Data Network Inventory Number of Pipes -Circular P.ipes: -Box Pipes: -Arch Pipes: 2 2 0 0 -Vertical Elliptical Pipes: O -Horizontal Elliptical Pipes: 0 Number of Junctions O Number of Outlets Circular Pipes Inventory 18 inch Total Length Curb Inlet Inventory Dl-4A Title: Lakeside Village 44.29 ft 269.03 ft Number of Inlets -Grate Inlets: -Curb Inlets: -Combination Inlets: -Slot Inlets: -Grate Inlets in Ditch: -Generic Inlets: 24inch Dl-4E 2 0 2 0 0 0 0 Analysis Results Scenario: Base 224.74 ft c:\ ... \stormcad\Jakesidevillageeagle1 OOyr.stm CSC Eng 11/10/06 02:23:47 PM ~ Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1 -203-755-1666 Project Engineer: MFC/WRC StormCAD v5.6 [05.06.012.00] Page 1 of 2 Inlet elements for network with outlet: 0-1 Analysis Results Scenario: Base Label Inlet Total Total Total Bypass Capture HydraulicHydraulic Gravity Head loss 1-1 1-2 Systen1nterceptecBypassed'l"arget Efficiency Grade Grade Element Method Flow Flow Flow (%) Line In Line OutHeadloss (cfs) (cfs) (cfs) (ft) (ft) (ft) Curb 01-.t 9.1 O Curb 01-.t 18.45 0.00 0.00 0.00 NIA 0.00 NIA Outlet: 0-1 100.0 282.71 282.71 100.0 282.42 282.42 0.00 Absolut 0.00 Absolut Label Hydraulic Hydraulic Gravity System System System System System System Grade Grade ElementAddltlonalKnownRational lntensityFlow Time CA Line In Line OutHeadloss Flow Flow Flow (in/hr) (min) (acres) (ft) (ft) (ft) (cfs) (cfs) (cfs) 0 -1 279.41 279.41 0.00 9.10 9.35 0.00 0.00 0.78 0.00 Pipe elements for network with outlet: 0-1 Label Section Section Length Numbe!Constructed Energy Total AverageUpstrea~ownstrearliiydraullcHydraulic Shape Size (ft) of Slope Slope SystemVelocity Invert Invert Grade Grade P-1 P-2 Circular 18 inc~ 44.29 Circular 24 inc~ ?24. 7 4 Title: Lakeside Village Sections (ft/ft) (ft/ft) Flow (ft/s) Elevation Elevation Line In Line Out (cfs) (ft) (ft) (ft) (ft) 0.006773 006395 9.10 0.003159 005443 18.45 5.15 280.42 280.12 282.71 282.42 5.87 280.12 279.41 282.42 280.96 c:\ ... \stormcad\Jakesidevillageeagle1 OOyr.stm CSC Eng 11/10/06 02:23:47 PM © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1 -203-755-1666 Project Engineer: MFC/WRC StormCAD v5.6 [05.06.012.00) Page 2 of 2 Scenario: Base Combined Pipe\Node Report Label Upstream Jownstrearr Length Upstream Jpstream lnle Upstrearti pstream Calculate :lpstream lnle Section Full Average Upstream bownstrearr Node Node (ft) Inlet Rational Inlet System CA Rational Flov. Size Capacity Velocity Invert Invert Area Coefficient CA (acres) (cfs) (cfs) (ft/s) Elevation Elevation (acres) (acres) (ft) (ft) P-1 1-1 1-2 44.29 0.00 0.00 0.00 0.00 0.00 18 inch 9.37 5.15 280.42 280.12 P-2 1-2 0-1 224.74 0.00 0.00 0.00 0.00 0.00 24inch 13.77 5.87 280.12 279.41 Title: Lakeside Village c:\ ... \stormcad\Jakesidevillageeagle1 OOyr.stm CSC Eng 11/10/06 02:08:13 PM ©Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Constructec Description Slope (ft/ft) 0.006773 0.003159 Project Engineer: MFCIWRC StormCAD v5.6 (05.06.012.00] Page 1 of 1 I 11 l I P-1 44.29ft 'i ;.i.. -- 0+00 Title: Lakeside Village Profile Scenario: Base Profile: Profile - 1 Scenario: Base -=--- " -'·" .: ,, 1+00 2+00 Stooon(lt) c:\. .. \stonncadllakesidevillageeagle1 OOyr.stm CSC Eng 11/10/06 02:03:5:ia:1Mntley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA 11 I I 285.oo 280.00 Elev.iion (It) 275.00 3+00 Project Engineer: MFCN\/RC StormCAD v5.6 [05.06.012.00] +1-203-755-1666 Page 1 of1 Title: Lakeside Village Project Engineer: MFCM/RC Project Date: 11 /03/06 Comments: Scenario Summary Scenario Base Physical Properties Alternat Base-Physical Properties Catchments Alternative Base-Catchments System Flows Alternative Base-System Flows Structure Headlosses Alterr Base-Structure Headlosses Boundary Conditions Altern; Base-Boundary Conditions Design Constraints Alternati Base-Design Constraints Capital Cost Alternative Base-Capital Cost User Data Alternative Base-User Data Network Inventory Number of Pipes 2 Number of Inlets -Circular Pipes: 2 -Grate Inlets: -Box Pipes: 0 -Curb Inlets: -Arch Pipes: 0 -Combination Inlets: -Vertical Elliptical Pipes: 0 -Slot Inlets: -Horizontal Elliptical Pipes: 0 -Grate Inlets in Ditch: Number of Junctions 0 -Generic Inlets: Number of Outlets Circular Pipes Inventory 18 inch 62.00 1t 24inch Total Length 308.00 1t Curb Inlet Inventory Dl-4E 2 Title: Lakeside Village c:\ ... \stormcad\Jakesidevillagecreekside 1 OOyr.stm Analysis Results Scenario: Base c.'C""ee.:·~;cl.e.. -ioo 'r'~<' 2 0 2 0 0 0 0 246.00 1t CSC Eng 11 /10/06 02:26:32 PM ©> Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Project Engineer: MFCMIRC StormCAD v5.6 [05.06.012.00] Page 1 of 2 Inlet elements for network with outlet: 0-1 Analysis Results Scenario: Base Label Inlet Total Total Total Bypass Capture Hydraulic Hydraulic Gravity Headloss 1-1 1-2 SysternnterceptecBypassedrarget Efficiency Grade Grade Element Method Flow Flow Flow (%) Line In Line OutHeadloss (cfs) (cfs) (cfs) (ft) (ft) (ft) Curb 01-..: 12.06 Curb 01-..: 22.76 0.00 0.00 0.00 N/A 0.00 N/A Outlet: 0-1 100.0 282.76 282.76 100.0 282.68 282.68 0.00 Absolut 0.00 Absolut Label HydraulicHydraulic Gravity System System System System System System Grade Grade Element Additional Known Rational Intensity Flow Time CA Line In Line OutHeadloss Flow Flow Flow (in/hr) (min) (acres) (ft) (ft) (ft) (cfs) (cfs) (cfs) 0-1 280.00 280.00 0.00 12.06 10.70 0.00 0.00 0.68 0.00 Pipe elements for network with outlet: 0-1 Label Section Section Length Numbe!Constructed Energy Total Averagel.JpstrearfilownstrearliiydraulicHydraulic Shape Size (ft) of Slope Slope SystemVeloclty Invert Invert Grade Grade P-1 P-2 Circular 18 inct 31.00 Circular 24 inct 23.00 Title: Lakeside Village Sections (Mt) (Mt) Flow (ft/s) Elevation Elevation Line In Line Out (cfs) (ft) (ft) (ft) (ft) 2 0.001935 002468 12.06 2 0.001951 002918 22.76 3.41 281 .30 281 .24 282.76 282.68 3.90 281 .14 280.90 282.68 282.11 c:\. .. \stormcad\Jakesidevillagecreekside1 OOyr.stm CSC Eng 11/10/06 02:26:32 PM © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Project Engineer: MFC/WRC StormCAD v5.6 [05.06.012.00] Page 2 of 2 Scenario: Base Combined Pipe\Node Report Label Upstream Jownstrearr Length Upstream Jpstream lnle llpstreart pstream Calculate jpstream lnle Section Full Average Upstream Jownstrearr Node Node (ft) Inlet Rational Inlet System CA Rational Flow Size Capacity Velocity Invert Invert Area Coefficient CA (acres) (cfs) (cfs) (ft/s) Elevation Elevation (acres) (acres) (ft) (ft) P-1 1-1 1-2 31.00 0.00 0.00 0.00 0.00 0.00 18inch 10.01 3.41 281 .30 281 .24 P-2 1-2 0-1 123.00 0.00 0.00 0.00 0.00 0.00 24inch 21 .65 3.90 281.14 280.90 Title: Lakeside Village c :\ ... \stormcad\Jakesidevillagecreekside1 OOyr.stm CSC Eng 11 /10/06 02:26:48 PM © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 :::onstructed bescription Slope (ft/ft) 0.001935 0.001951 Project Engineer: MFC/WRC StormCAD v5.6 [05.06.012.00] Page 1 of 1 31.00 ft 0+00 Title: Lakeside Village Profile Scenario: Base Profile: Profile - 3 Scenario: Base 1+00 Station (ft) 285.00 280.00 2+00 c:\ ... \stormcadllakesidevillagecreekside1 OOyr.stm CSC Eng 11/10/06 02:27:17 PM <!:> Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666 Elevation (ft) Project Engineer: MFCIWRC StormCAD v5.6 (05.06.012.00) Page 1 of 1 Profile Scenario: Base c; , I ~\(S1cle · CLAii\~~ "°Ru\f\ Profile: Profile - 3 Scenario: Base 31.00 ft 0+00 1+00 Station (ft) 285.00 280.00 2+00 litle: Lakeside Village Pr' akesidevillagecreekside100yr25%reduction.stm CSC Eng Ston 11/10/06 04:15:04 PM © Bentley Systems, Inc. Haestad Methods Solution Center Watertown, CT 06795 USA +1-203-755-1666