The URL can be used to link to this page

Home My WebLink AboutFolderFOR OFFICE USE.'?_~ P&Z CASE NO.: _bU ____ • _y_ fl_ DATE SUBMITIE0:4' ( .C)(O C!TYOF COLLE 'E.c::· ATION P'4nning & D= 'Pmmt Sm;ica SITE PLAN APPLICATION MINIMUM SUBMITTAL REQUIREMENTS ./ Site plan application completed in full. \7 $200.00 App fication Fee. q~ ~ $200.00 Development Permit Application Fee. __ $600.00 Public Infrastructure Inspection Fee if applicable. {This fee is payable if construction of a pubfic V waterline, sewerline, sidewalk, street or drainage facilities is involved.) Eleven (11) folded copies of site plan · ~ One (1) folded copy of the landscape plan. -if One (1) copy of building elevation for all buildings. -T-A list of building materials for an facades and screening for non-residential buildings. __ Color samples for all non-residential buildings. __ Traffic Impact Analysis (if applicable for non-residential buildings). __ A copy of the attached site plan checklist with all items checked off or a brief explanation as to why they are not checked off. __ Parkland Dedication requirement approved by the Parks & Recreation Board, please provide proof of approval (if applicable). Date of Preappl ication Conference: __ _.cP.._.,./_1_3_,,L_0_5_--_-.--___________ _ NAMEOF PROJECT fJ/q,-z...:l..S ~+ !l..J)c.k.. '/J/'et.S t'c f?d . ADDRESS~------~------------------------- LEGAL DESCRIPTION ____________________________ _ Street Address --L!'-'--"--=-.LJ..!.'-'--'~;q::io....__,;-=~;:q::....,L--___ City Jk> u. t:;. f .!> "\ State T x E-Mail Address w; // @ v' ~· <;, 7et.. '1 () '-< s r~n . c .{)~ Phone Number Fax Number 2 fl/ ..-i J, /---0~ 2 0 PROPERTY OWNER'S INFORMATION: Name· jJ/'lZ. Cc. S ~ f t2:>c.k Jl/'a,f-;e /d. . ?.-/:t!... Street Address /I I?--£/dc,'dy~ Pal"i.,w7 City ~b~/£9"'"".,.u'-is;>o-'h~~~n__.___ ___ _ state 7X Zip Code 7 ]'os}: E-Mail Address ___________ _ Phone Number 2..'0 I-C31--s s~ Fax Number 2./o (-<;;;?,/ ~ <057 ~ ARCHITECT OR ENGINEER'S INFORMATION: Name L,Vl ~ /'f-~~Ol-i'<-iLS.. , TV\.c...., ) Street Address q-q Ir: Wes.~ }..(?.,,v.... State TX Zip Code "10 ~ S Phone Number ~ t'5 -?.. 1-f:> -'f $£?0 6/1 3/03 W; Jl; ~IM. t-d-fu' J City f/ cu. S fr9"" E-Mail Address .,.,;t(;~--l~fcrd@ w/kJe'j · L Oil' Fax Number --:fl~ -'!53 -"2.-S I S-- l of 6 DEVELOPMENT PERMIT PERMIT NO. 06-198 CITY OF COLLEGE STATION Planning cT Development &ruices FOR AREAS OUTSIDE THE SPECIAL FLOOD HAZARD AREA RE: CHAPTER 13 OF THE COLLEGE STATION CITY CODE SITE LEGAL DESCRIPTION: Plazas at Rock Prairie Lots 1-4 DATE OF ISSUE: 08/30/06 OWNER: Plazas at Rock Prairie LLC c/o Will Ogilvie 1117 Eldridge Parkway SITE ADDRESS: 3975 SH6 S DRAINAGE BASIN: Lick Creek VALID FOR 9 MONTHS CONTRACTOR: Houston, Texas 77057 TYPE OF DEVELOPMENT: Full Development Permit SPECIAL COND.ITIONS: All construction must be in compliance with the approved construction plans All trees required to be protected as part of the landscape plan must be completely barricaded in accordance with Section 7.5.E., Landscape/Streetscape Plan Requirements of the City's Unified Development Ordinance, prior to any operations of this permit. The cleaning of equipment or materials within the drip line of any tree or group of trees that are protected and required to remain is strictly prohibited. The disposal of any waste material such as, but not limited to, paint, oil, solvents, asphalt, concrete, mortar, or other harmful liquids or materials within the drip line of any tree required to remain is also prohibited. ****TCEQ PHASE II RULES IN EFFECT**** The Contractor shall take all necessary precautions to prevent silt and debris from leaving the immediate construction site in accordance with the approved erosion control plan as well as the City of College Station Drainage Policy and Design Criteria. If it is determined the prescribed erosion control measures are ineffective to retain all sediment onsite, it is the contractors responsibility to implement measures that will meet City, State and Federal requirements. The Owner and/or Contractor shall assure that all disturbed areas are sodden and establishment of vegetation occurs prior to removal of any silt fencing or hay bales used for temporary erosion control. The Owner and/or Contractor shall also insure that any disturbed vegetation be returned to its original condition, placement and state. The Owner and/or Contractor shall be responsible for any damage to adjacent properties, city streets or infrastructure due to heavy machinery and/or equipment as well as erosion, siltation or sedimentation resulting from the permitted work. In accordance with Chapter 13 of the Code of Ordinances of the City of College Station, measures shall be taken to insure that debris from construction, erosion, and sedimentation shall not be deposited in city streets, or existing drainage facilities. I hereby grant this permit for development of an area outside the special flood hazard area. All development shall be in accordance with the plans and specifications submitted to and approved by the City Engineer in the development permit application for the above named project and all of the codes and ordinances of the City of College Station that apply. 08-30 -<X, Date ¥2 ~/~ ate vr CITY OF COLLEGE STATION Planning & Development Strvica SITE LEGAL DESCRIPTION: Plazas at Rock Prairie Lots 1-4 DATE OF ISSUE: 06/29/06 OWNER: DEVELOPMENT PERMIT PERMIT NO. 06-19A FOR AREAS OUTSIDE THE SPECIAL FLOOD HAZARD AREA RE: CHAPTER 13 OF THE COLLEGE STATION CITY CODE SITE ADDRESS: 3975 SH6 S DRAINAGE BASIN: Lick Creek VALID FOR 3 MONTHS CONTRACTOR: Palzas at Rock Prairie LLC c/o Will Ogilvie 1117 Eldridge Parkway Houston , Texas 77057 TYPE OF DEVELOPMENT: SPECIAL CONDITIONS: Clearing and Grading Permit All construction must be in compliance with the approved construction plans All trees required to be protected as part of the landscape plan must be completely barricaded in accordance with Section 7.5.E., Landscape/Streetscape Plan Requirements of the City's Unified Development Ordinance, prior to any operations of this permit. The cleaning of equipment or materials within the drip line of any tree or group of trees that are protected and required to remain is strictly prohibited. The disposal of any waste material such as, but not limited to, paint, oil, solvents, asphalt, concrete, mortar, or other harmful liquids or materials within the drip line of any tree required to remain is also prohibited. ****TCEQ PHASE II RULES IN EFFECT**** The Contractor shall take all necessary precautions to prevent silt and debris from leaving the immediate construction site in accordance with the approved erosion control plan as well as the City of College Station Drainage Policy and Design Criteria. If it is determined the prescribed erosion control measures are ineffective to retain all sediment onsite, it is the contractors responsibility to implement measures that will meet City, State and Federal requirements. The Owner and/or Contractor shall assure that all disturbed areas are sodden and establishment of vegetation occurs prior to removal of any silt fencing or hay bales used for temporary erosion control. The Owner and/or Contractor shall also insure that any disturbed vegetation be returned to its original condition, placement and state. The Owner and/or Contractor shall be responsible for any damage to adjacent properties, city streets or infrastructure due to heavy machinery and/or equipment as well as eros ion , siltation or sedimentation resulting from the permitted work. In accordance with Chapter 13 of the Code of Ordinances of the City of College Station, measures shall be taken to insure that debris from construction , erosion, and sedimentation shall not be deposited in city streets, or existing drainage facilities. I hereby grant this permit for development of an area outside the special flood hazard area. All development shall be in accordance with the plans and specifications submitted to and approved by the City Engineer in the development permit application for the above named project and all of the codes and ordinances of the City of College Station that apply. William Langford From: Marc Macconnell [mmacconnell@ruskincorp.com] Sent: Thursday, August 10, 2006 3:20 PM To: Bill Langford Subject: Rock Prairie -Fire Hydrant & Tap Cost Bill, Here is the cost breakdown: 1 each 18" x 8" Tapping Sleeve and Valve with Box 1 each 8" x 2" Tee 1 each 8" Anchor Coupling 1 each 8" x 6" Reducer 3 each 6" Anchor Couplings leach Fire Hyrdrant Assembly Total Let me know if you need any additional information. Marc Macconnell Project Manager The Ruskin Corporation 5252 Westchester, Suite 160 Houston, Texas 77005 TEL (713) 629-9800 FAX (713) 663-6633 www.ruskincorp.com 8/10/2006 $4,500.00 $ 425.00 $ 275.00 $ 325.00 $ 750.00 ~ $Z,SOo.oo $8,775.00 Page 1 of 1 J Date: August 11, 2006 To: Carol Cotter From: William M. Langford, PE Project: Plazas at Rock Prairie WLB Project No: 9500502 !Quantity Description 1 Cost E.Stimate Public Fire Hydrant & Tap PRINCIPALS William V. Wright William M Langford P.E William L Black Jr. PE Comments: Carol, the attached cost estimate was determined by the contractor as part of the pricing of all site facilities. I have reviewed the estimate and concur that the estimates provided represent the cost of the public facilities proposed. 7915 Westglen Drive• Houston, Texas 77063 •Tel 713 278-9300 •Fax 713 953-2515 •e-mail wlb@wlbeng.com City of College Station Planning & Development Services P.O. Box 9960 College Station, TX 77840 MITCHELL MM MORGAN RE: Plazas at Rock Prairie Fireflow Analysis To Whom It May Concern : April 10, 2006 Below is the water analysis for the Plazas at Rock Prairie Road. Domestic flows were calculated using the Normal Flow method 2 as presented in the B/CS Unified Design Gui delines. The retail development is located on an approximately 1.805 acre site, requiring a peaked domestic flow of approximately 3. 76 gpm. The 2000 International Fire Code was used to calculate the fireflow required of the development. The retail center is approximately 18,661 sq uare feet and will be constructed of building type llB, requiring a fireflow of 3000 gpm (see Exhibit 1). This fireflow will be split between three hydrants: one to be constructed w ith the site, an existing hydrant on the Marriott Courtyard property, and the third located on SH6 frontage near the western corner of the proposed development. Please see Exhibit 2 for a hydrant location map. The updated City of Coll ege Station water system MikeNET model was checked against a hydrant flow test on the hydrant located nearest to the site on Marriott Courtyard property an d the hydrant located on SH6 frontage near the w estern corner of the proposed development. It was found that model results were approximately 15 psi greater than t hose found by flow tests under both static and residual conditions. Although the model is calculating higher pressures than observed, the difference between the static and residual in both calculated and observed results were similar. Because of this discrepancy, model pressures above 35 psi under fireflow conditions, instead of 20 psi, will be assumed sufficient. Please see Exhibit 3 for the hydrant flow test reports. ... ,. .< <\9 ,, ~ ~"- -, ~,'I" Flow Test and MikeNET_ Comparison '!'l @\" ,,:ffe, ~~, ,. '*' -{;.ey' Method Static Residua! Demand Flow Test -Marriot 89.0 psi 88.0 psi 1455 gpm Property (P-044) MikeNET (P-044) 102.4 psi 98.4 psi 1455 gpm Flow Test -SH6 88.0 psi 83.0 psi 1455 gpm Frontage (P-042) MikeNET (P-042) 102.4 psi 98.3 psi 1455 gpm 511 UNIVERSITY DRIVE EAST, SUITE 204 • COLLEGE STATION, TX 77840 • T 979.260.6963 • F 979 260.3564 CIVIL ENGINEERING • HYDRAULICS • HYDROLOGY • UTILITIES • STREETS • SITE PLANS • SUBDIVISIONS info@mitchellandmorgan.com • www.mitchellandmorgan.com It was found the existing waterlines and area hydrants will sufficiently serve the water needs of the Plazas at Rock Prairie. MikeNET analysis velocities were kept below 12 fps and pressure remained well above 35 psi . Please see Exhibit 4 for MikeNET analysis printouts. Once the above analysis was complete Mitchell & Morgan was informed that the shopping center building would include a fire wall, reducing the applicable square footage to 11,335 square feet. This reduction in area reduces the fire flow demand from 3000 gpm to 2250 gpm. The decreased demand still requires the flow to be split between three hydrants, as detailed earlier in this report. Because the MikeNET analysis shows sufficient pressures and velocities for the higher fire flow demand, a second analysis was not completed to illustrate the reduced flows and increased pressures. If you have any comments, or would like to discuss our findings further, please feel free to contact me. Veronica J.B. or Managing Partner cc: file Will Ogilvie, Vista 5:\Proj\0623-RPR_Fire_Flow\0623-fireflow-060406.doc II~( College station Utilities \WJ Reliable, Affordable, Community Owned 1601 GRAHAM ROAD COLLEGE STATION TEXAS 77845 Date: 4 APRIL 2006 From: Butch Willis Water Wastewater Division Phone: 979-764-3435 Fax: 979-764-3452 FLOW TEST REPORT Nozzle size: 2.5 inch Location: 3939 EARL RUDDER Flow hydrant number: P-042 Pitot reading: 75 (GPM): 1455 Static hydrant number: P-044 Static PSI: 88 Residual PSI: 83 EXHIBIT 3 l'i ~(College Station Utilities 'l#!J Reliable, Affordable, Community Owned 1601 GRAHAM ROAD COLLEGE STATION TEXAS 77845 Date: 4 APRIL 2006 From: Butch Willis Water Wastewater Division Phone: 979-764-3435 Fax: 979-764-3452 FLOW TEST REPORT Nozzle size: 2.5 inch Location: 3939 EARL RUDDER Flow hydrant number: P-044 Pitot reading: 75 (GPM): 1455 Static hydrant number: P-042 Static PSI: 89 Residual PSI: 88 EXHIBIT 3 EXHIBIT 4 fireflow.GDB Analysis Type: Peak Hour, Peak Day (multiplier of 4 on average day) Project Description: fireflow of 3000 gpm split on nodes 2244, 2238, and 2249 EXHIBIT 4 Results -Junctions J umber of Junctions: l l(Selection) I Junction ID Description Elevation Demand Grade Pressure I I [ftl lgpml [ft[ [psi[ 1492 J-4190 301.000 0.000 447.258 63.373 I 493 J-4180 302.000 0.000 446.699 62.698 I I 494 J-4170 295.000 77.536 449.032 66.742 I I 1298 292.000 21.108 445.975 66.717 I I 2238 P-042 314.000 1000.000 445.622 57.032 I 2239 310.000 0.000 445.425 58.680 I 2240 318.000 108.400 444.999 55.029 2241 312.000 0.000 443 .863 57.136 2244 P-044 314.000 1000.000 443.423 56.079 I 2249 312.000 1000.000 445.447 57.823 2250 296.500 22.240 447.004 65.214 Results -Pipes Number of Pipes: 11 (Selection) I Pipe ID Node 1 Node 2 Diameter Length Roughness Flow Velocity Head loss [inl [ft] I milliftl [gpm] [ft/sl [ft[ 1478 493 492 18.000 66 .171 130.000 -3565.638 -4.496 0.559 1479 494 492 18.000 274.117 130.000 4155.542 5.239 1.775 2348 1298 2250 12.000 999.7 12 120.000 -567.663 -1.610 1.030 264 1 493 2238 18.000 333.304 140.000 3565.638 4.496 1.076 2642 2238 2249 18.000 284.454 140.000 1457.238 1.837 0.175 2643 2238 2240 12.000 233 .182 140.000 1108.400 3.144 0.623 2644 2240 224 1 8.000 713.798 140.000 288.405 1.841 1.136 2645 2240 2244 8.000 185.863 140.000 711.595 4.542 1.576 2646 2244 2241 8.000 276.111 140.000 -288.405 -1.841 0.440 2649 2249 2239 18.000 309.873 140.000 457.238 0.576 0.022 2650 2250 492 12.000 229.083 120.000 -589.903 -1 .673 0.253 EXHIBIT 4 WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie DRAINAGE REPORT FOR PLAZAS AT ROCK PRAIRIE STATE HIGHWAY 6 ACCESS ROAD AT ROCK PRAIRIE DRIVE Prepared For: Vista Equities Group 111 7 Eldridge Parkway Houston, Texas Prepared By: WLB Associates, Inc. 7915 Westglen Houston, Texas 77063 March 28, 2006 (Rev. July 14, 2006) July 14, 2006 City of College Station 1101 Texas Avenue College Station, Texas 77842 Attention: Carol Cotter Re: Revised Drainage Report Submittal Plazas at Rock Prairie Retail Center at Highway 6 and Rock Prairie Road, WLB Project No. 9500502 Dear Ms. Cotter, .r /·I /-UM PR~Q~p~~ William V. Wright William M. Langford P. E. William L. Black Jr. P.E. tJ\J-lt\ The purpose of this letter is to submit the drainage report, which has been prepared for the referenced commercial project, for review and approval. The report, entitled "Drainage Report for Plazas at Rock Prairie State Highway 6 Access Road at Rock Prairie Drive" addresses existing Pre-Developed Condition, Post-Developed Conditions, and design of detention facilities as required by the Drainage Policy and Design Manual to offset development drainage impacts to downstream systems. This report has been revised to address City comments from our previous submittal. If you have any questions concerning this report, or require additional information, please do not hesitate to call the undersigned at (713) 278-9300. Your help has been greatly appreciated. Sincerely, '7 //'/Io (a Draiange Report Trans Ltr rEV 07-14-06.doc 7915 WestglenDrive •Houston, Texas 77063 •Tel 713 278-9300 •Fax 713 953-2515 • e-rnail wlb@wlbeng.com ·-· •. WLB AS SOCIA TES, INC. Drainage Report Plazas at Rock Prairie DRAINAGE REPORT FOR PLAZAS AT ROCK PRAIRIE STATE HIGHWAY 6 ACCESS ROAD AT ROCK PRAIRIE DRIVE Prepared For: Vista Equities Group 1117 Eldridge Parkway Houston, Texas Prepared By: WLB Associates, Inc. 7915 Westglen Houston, Texas 77063 March 28, 2006 (Rev. July 14, 2006) WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie TABLE OF CONTENTS PAGE NUMBER 1.0 GE ERAL LOCATION A D DESCRIPTION ................................... I 2.0 DRAINGE BASINS AND SUB-BASINS ...................................................... .1 3.0 DRAINAGE DESIGN CRITERIA ................................................... 2 4.0 DRAINAGE FACILITY DESIGN ................................................... 3 S.O CO CLUSIONS ........................................................................ 4 6.0 CERTIFICATIO ...................................................................... S LIST OF TABLES TABLE 1 PRE & POST-DEVELOPMENT STORMWATERRUNOFF RATES TABLE2 DESIG TRACT AND DETE TIO DISCHARGE SUMMARY TABLE 3 DETENTION POND SUMMARY LIST OF FIGURES FIGURE 1 GENERAL VICINITY MAP OF SUBJECT PROPERTY AND SURROUNDING AREAS FIGURE 2 SUBJECT PROPERTY AND ADJACENT PROPERTIES FIGURE 3 GENERAL SITE DEVELOPMENT SCHEME FIGURE 4 WATERSHED MAP OF SUBJECT PROPERTY AND SURROUNDING AREA FIGURE SA EXISTING DRAINAGE CONDITIONS FIGURE SB PHASE 1 DRAINAGE CONDITIONS FIGURE SC ULTIMATE DRAINAGE CONDITIONS WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie LIST OF FIGURES (continued) FIGURE 6 TYPES OF PROPOSED SITE COVER MATERIALS FIGURE 7A PRE-AND POST-DEVELOPME T HYDROGRAPHS FOR 5-YEAR STORM EVENT FIGURE 7B PRE-AND POST-DEVELOPME T HYDROGRAPHS FOR 10-YEAR STORM EVENT FIGURE 7C PRE-AND POST-DEVELOPMENT HYDROGRAPHS FOR 25-YEAR STORM EVE T FIGURE 7D PRE-AND POST-DEVELOPME T HYDROGRAPHS FOR 50-YEAR STORM EVENT FIGURE 7E PRE-A D POST-DEVELOPMENT HYDROGRAPHS FOR 100-YEAR STORM EVENT FIGURE 8 DETENTION POND SCHEMATIC AND VOLUME COMPUTATIONS FIGURE 9 DETENTION POND VOLUME VERSUS DEPTH GRAPH FIGURE 10 POND OUTLET DISCHARGE RA TE VERSUS DEPTH GRAPH FIGURE 11 SCHEMATIC EROSION CONTROL PLA 11 WLB AS SOCIA TES, INC. Drainage Report Plazas at Rock Prairie 1.0 GENERAL LOCATION AND DESCRIPTION The subject tract (Plazas at Rock Prairie development) is located at the northeast intersection corner of the northbound feeder road of State Highway 6 and Rock Prairie Road in the Carter's Creek Watershed. The general location of the tract is shown on the vicinity map included in this report as Figure 1, and the subject property and adjacent tracts are shown in more detail in Figure 2. The subject tract consists of two parcels comprising a total area of 3.592 acres. Parcel 1 consists 1.787 acres fronting Rock Prairie Road on the south, and State Highway 6 along the west side of the parcel. The second 1.805 acre parcel consists of Lot 2-C, Block One, of the Replat of 8.062 AC out of the Amending Plat of Cornerstone Commercial Subdivision Section One, which fronts State Highway 6 north of Parcel 1. The subject tract is bordered on the north by a shared private access drive to the Marriott Courtyard at Woodcreek Development, which is located east of the Lot 2-C portion of the tract, and north of the Parcel 1 portion. Parcel 1 is bordered on the east by an undeveloped tract. As can be seen from Figure No. 2 the site is roughly "L" shaped and extends along the SH6 and Rock Prairie Road frontage. Surface cover of Lot 2-C is comprised of grass, with a very few scattered trees, and has a small portion of paved access driveway along the north and east sides of the Lot which serve the Marriot development. Parcel 1 consists of a stand of cedar trees with scattered shrubs and grass cover. A portion of the Lot 2-C property currently drains via sheet flow to the roadside ditch alongside SH6. The remainder of Lot 2-C and all of Parcel 1 appears to drain to Rock Prairie Road via sheet flow and an onsite drainage swale located within Parcel 1, where it is collected by drainage inlets constructed with the Rock Prairie Road storm sewer system. The site is proposed to be developed as the Plazas at Rock Prairie Drive, an 18 ,661 SF commercial retail building with parking facilities to be constructed in Phase 1, along with two pad sites for future commercial retail construction. The General Site Development Scheme is shown on Figure No. 3. The building footprints and layouts shown for the future pads are preliminary and subject to change in the future. 2.0 DRAINAGE BASINS AND SUB-BASINS The 3.592 acre subject tract is shown by Figure o. 4 to be within the Carters Creek Drainage Basin near its' divide with the Lick Creek Drainage Basin. The 100-year flood plain/floodway is not on or immediately adjacent to the subject property, which is shown to be in Zone X on Flood Insurance Rate Map Number 4804C 0201D effective date February 9, 2000. On site detention will be utilized to limit post development discharges from the tract to the adjacent lateral drainage systems of SH6 and Rock Prairie Road to levels at, or below the pre-development discharge rates to avoid impact to these systems due to development. - 1 - WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie 3.0 DRAINAGE DESIGN CRITERIA Analysis and design of storm drainage facilities for this project is in accordance with design criteria contained within the publication "Drainage Policy and Design Standards Stormwater Management Plan for the City of College Station" hereinafter referred to as the DPDS Manual. A previous study entitled "Drainage Report For Courtyard Marriott At Woodcreek Development Cornerstone Properties State Highway 6 Access Road At Woodcreek Drive College Station, Texas" prepared by CSC Engineering & Environmental Consultants, Inc. dated June 26, 2000 was utilized to design stormwater and detention facilities for the Marriott development adjacent to a portion of the site. The detention facility, which receives discharges from a 2.5 acre area of the Marriott development, discharges to the SH6 Frontage Road ditch via a 12-inch concrete pipe sewer located within a 20-Ft Public Utility Easement crossing Lot 2-C along its' southern boundary. The spillway for the detention facility also discharges into a common access easement shared between the Marriott Development and Lot 2-C. The existing topography indicates that spillway discharges into the Access Easement area are collected within an existing swale which crosses the Parcel 1 area south to Rock Prairie Road. At this point it is picked up by the public storm sewer system via an opening in the back of a curb inlet which also drains the road paving. Development plans will need to leave the 12-inch outfall discharge pipe to SH6 in place, and maintain the emergency overflow from the pond for storms in excess of 25-yr frequency. The Rational Formula has been utilized to calculate stormwater discharges as the tract area is less than 50-acres in accordance with DPDS manual requirements. Manning's Formula has been utilized to analyze head losses and size storm sewer and drainage swales, and the triangular hydrograph method has been used to size detention facilities. Since detention is required for this development, the site storm sewer was designed to convey 100-year frequency discharges for the site to the detention pond location without exceeding allowable ponding elevations in parking lots or driveways as specified in DPDS Manual, Item 3 Storage Depths, on Page 74. 4.0 DRAINAGE FACILITY DESIGN The existing site is currently undeveloped with the exception of some minor amounts of paving for a shared common access drive along the northerly and easterly sides of the Lot 2-C portion of the project area. Figure SA -Existing Drainage Conditions shows the pre- development drainage pattern for the property, which has a small drainage area discharging to the SH 6 Frontage Road ditch, with the rest of the area discharging to Rock Prairie Road. In order to comply with City of College Station requirements concerning impact to downstream drainage systems, the proposed drainage system has -2 - WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie been designed to limit Phase 1 and Ultimate Conditions post-development S, 10, 2S , SO , and 100-year frequency discharges to at, or below the pre-development level discharges determined for the property utilizing methods prescribed in the DPDS Manual. The proposed Plazas at Rock Prairie Road project is to be constructed in phases. The first phase of development is shown in Figure SB -Phase 1 Drainage Conditions, which will include an 18,861 SF retail building with parking and driveways to Rock Prairie Road. Ultimate development conditions are shown on Figure SC -Ultimate Drainage Conditions, and assume development of the entire project as commercial retail. Proposed Phase 1 Storm Sewers and Detention Facilities are being sized to provide capacity for the ultimate drainage condition. Drainage discharges for S, 10, 2S , SO and 100-year frequencies were computed using the Rational Method as required by the DPDS Manual. A Runoff Coefficient (C=0.30) for existing conditions was determined from Table III-1 for natural woodlands with land slopes of 3.S to S.S percent for the Parcel 1 tract area, and also for the natural grassland area of Lot 2-C which has slopes of around 1 %. For ultimate developed conditions a value of C=0.8S was used for the Commercial Reserve Areas, and C=0.70 was used for the grassed detention reserve area which has a bottom area sloped steeply down to a concrete pilot. The Time of Concentration for Existing Conditions was determined to be less than 10 minutes using an average overland sheet flow velocity of 1.0 FPS per Table III-2 of the DPDS Manual. Per manual requirements a minimum time of concentration of Tc = 10 minutes was therefore utilized for both existing and developed conditions in accordance with DPDS Manual Section III Paragraph B3c3. Rainfall intensities for a Time of Concentration of 10-minutes were determined utilizing the DPDS Manual Intensity Duration Frequency Curves of Figure III-1. A complete listing of the runoff coefficients, intensity factors, and discharges computed for the Existing Pre-Developed, Phase 1 and Ultimate Post-Developed Conditions are included in this report as Table 1 - Pre & Post-Development Stormwater Runoff Rates. A summary of allowable rates of discharge from the detention facility, design detention discharge rates, and total post development tract discharge rates is included in Table 2: Design Tract and Detention Discharge Summary Table. Required detention capacity to offset downstream impacts due to development of the subject property was determined by taking the difference in volume beneath the pre and post-development hydrographs which were derived using the Triangular Approximation method of the DPDS Manual. The S, 10, 25 , 50, and 100-year hydrographs and required detention volume computations are presented in Figures 7 A thru 7E respectively. A summary of the required allowable discharge rates, actual design detention discharge rates, total tract post development discharge rates, and detention storage volume and elevations is included in Table 3: Detention Pond Summary. Figure No. 8 -Detention Pond Schematic and Volume Computation shows the general detention pond layout and lists storage volumes between the pond bottom elevation of 302 Ft (min. elevation of the top of concrete pilot channel) and the emergency overflow weir elevation of 306 Ft. to be approximately 27,918 CF. This is sufficient to provide for both the required S-year thru 100-year frequency detention volumes, and also for the 10% excess volumes required by -3 - WLB AS SOCIA TES, INC. Drainage Report Plazas at Rock Prairie the DPDS Manual to account for sedimentation. A graph of the proposed detention pond volume versus depth is shown in Figure No. 9. Table 2 shows the total allowable pre-development existing condition discharges to the public drainage systems in the right of ways of SH-6 and Rock Prairie Road. The table also shows the determination of both the allowable and design detention pond discharge, and the total post development design discharges from the tract to the public r-o-w for the 5, 10, 25 , 50, and 100-year frequency storm events. The net allowable detention pond discharges have been determined by subtracting the post-development discharges of the areas draining directly to the public systems in the adjacent roads from the total pre- project discharges for each of the storm frequencies investigated. Final design of the detention outfall limits pond discharges to a level equal to, or less than, the allowable detention discharge rates. Detention pond outflow is controlled by means of a 12-orifice installed in an 18-inch outfall discharge pipe which connects to the Rock Prairie Road Storm Sewer Inlet located at the southeasterly corner of the project area. Emergency and extreme event overflow capacity is provided by a 15-ft wide concrete weir structure with a weir elevation 306 feet. This structure directs overflow to Rock Prairie Road. Figure No. 10 is a graph of Pond Outlet Discharge Rate versus Pond Depth. The discharge rates shown indicate that at elevation 306.0 the discharge through the 12-inch orifice from the detention pond is 7.80 CFS, which is slightly below the 25-year frequency target rate of 7.98 CFS. Since the pond capacity below the emergency weir overflow elevation 306 exceeds the required detention volume for the 100-year frequency design storm, and design outflows for each of the storm frequencies investigated have been limited to the pre-development outflow rate, or less, the detention faci lity will prevent negative impact to the downstream public drainage systems for all frequencies examined. Above elevation 306 feet the emergency concrete weir has been sized to convey the 100-year frequency developed condition discharge of 30.07 cfs from the area which drains into the detention pond when the pond elevation reaches 306.75 feet. At this elevation the weir velocity is approximately 2.7 fps, and the storage surface provides 0.5 feet of freeboard below the minimum pond bank elevation of 307.25 feet. Emergency and Extreme Event Discharges from the Marriott Development detention pond discharge into the common access driveway behind the Phase 1 Building Structure and are to be conveyed south through the development via the driveway to Rock Prairie Road. Under normal conditions no flow is anticipated over the concrete spillway for storm frequencies up to the 100-year event. The detention pond is proposed to be a grassed lined facility with mm1mum 4-feet horizontal to 1-foot vertical rise side slopes, and a grassed maintenance berm on three sides. The fourth side will consist of a paved driveway and future paved parking area. The bottom of the pond is sloped at a minimum of 5% from the toe of the pond side slopes to the proposed concrete pilot channels. The pond area can be readily accessed for maintenance. Maximum ponding elevations within the gutters of private onsite driveways, parking areas, and at inlets are not expected to exceed 6-inches for the 100-year frequency event. -4 - WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie This meets the requirements for maximum ponding depth specified in the DPDS Manual Item 3-Storage Depths on page 74. Erosion controls during site construction will consist primarily of a combination of silt fences, hay bale barriers, and sedimentation traps. The locations of the proposed control measures are shown on Figure 11. 5.0 CONCLUSIONS The proposed development of the subject site will require provision of detention to offset impact to downstream drainage systems due to construction of buildings, paved parking and driveway areas, and associated storm drainage improvements. Onsite swales and storm sewer have been designed to convey the majority of the development to a detention facility to be located along the northeasterly boundary of the development. The storm drainage and detention system have been designed in accordance with requirements of the City of College Station DPDS Manual, and provide capacity to alleviate development impact for the required 5, 10, 25 , 50, and 100-year design storm frequencies. The detention and drainage systems have been designed to provide adequate capacity for the ultimate planned development of the site, and limit total ultimate post-development discharges from the site to a level slightly below the existing condition discharge rates computed for the pre-development conditions. 6.0 CERTIFICATION "I hereby certify that this report for the drainage design of the Plazas at Rock Prairie Road Development located at the northeasterly intersection corner of the northbound Frontage Road of State Highway 6 and Rock Prairie Road was prepared by me (or under my supervision) in accordance with the provisions of the City of College Station Drainage Policy and Design Standards for the owners thereof' William M. Langfi rd, PE Registered Professional Engineer State of Texas Registration No. 53170 -5 - WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie TABLES TABLE 1 -PRE & POST DEVELOPMENT STORMWATER RUNOFF RATES (CALCULATIONS USING RATIONAL METHOD) Q =CIA RAINFALL INTENSITY I (inches/hour) Per Figure Ill -1 Drainage Policy and Design Standards Manual at Time of Concentration T= 10 minutes Freauencvl 5-YR I 10-YR I 25-YR I 50-YR I 100-YR Rate I I 7.68 1 8.36 I 9.86 I 11.15 I 11.64 EXISTING CONDTIONS (PRE DEVELOPMENT) AREA AREA No. (ACRES) A1 l 0.51 81_ 3.21 3.72 c 0.3 0.3 0.30 5-YR CFS 1.18 7.40 8.57 10-YR CFS 1.28 8.05 9.33 25-YR CFS 1.51 9.50 PHASE 1 CONDTIONS (POST PHASE 1 DEVELOPMENT) AREA AREA No. (ACRES) A1 A2 0.17 0.03 c 0.75 0.3 5-YR CFS 0.98 0.07 10-YR CFS 1.07 0.08 25-YR CFS 1.26 0.09 50-YR 100-YR CFS CFS 1.71 1.78 10.74 11.21 12.44 12.99 50-YR 100-YR CFS CFS 1.42 0.10 1.48 0.10 rev.7-05-06 COMMENTS AREA TO SH6 ROAD DITCH AREA TO ROCK PRAIRIE ROAD COMMENTS A1-2 0.2 0.68 1.05 1.14 1.35 1.52 1.59 AREA TO SH6 ROAD DITCH 81 82 83 84 85 86 87 81-7 C1 C2 C3 C1-3 0.94 0.51 0.11 0.19 0.18 0.67 0.48 3.08 0.24 0.08 0.12 0.44 0.85 0.50 0.85 0.85 0.85 0.70 0.75 0.74 0.30 0.85 0.30 0.40 6.14 1.96 0.72 1.24 1.18 3.60 2.76 17.59 0.55 0.52 0.28 1.35 6.68 2.13 0.78 1.35 1.28 3.92 3.01 19.15 0.60 0.57 0.30 1.47 7.88 2.51 0.92 1.59 1.51 4.62 3.55 22.59 0.71 0.67 0.35 1.74 ULTIMATE CONDTIONS (POST FUTURE ULT. DEVELOPMENT) AREA AREA No. (ACRES) A1 A2 A1:2 81 82 83 84 85 86 87 88 89 C1 C2 C3 0.17 0.05 0.22 0.94 0.37 0.16 0.11 0.19 0.18 0.48 0.23 0.43 3.09 0.2 0.08 0.12 0.4 c 0.75 0.3 0.65 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.75 0.84 0.3 0.85 0.3 0.41 5-YR CFS 0.98 0.12 1.09 6.14 2.42 1.04 0.72 1.24 1.18 3.13 1.50 2.48 19.84 0.46 0.52 0.28 1.26 10-YR CFS 1.07 0.13 1.19 6.68 2.63 1.14 0.78 1.35 1.28 3.41 1.63 2.70 21.60 0.50 0.57 0.30 1.37 25-YR CFS 1.26 0.15 1.41 7.88 3.10 1.34 0.92 1.59 1.51 4.02 1.93 3.18 25.47 0.59 0.67 0.35 8.91 2.84 1.04 1.80 1.71 5.23 4.01 25.54 0.80 0.76 0.40 1.96 50-YR CFS 1.42 0.17 1.59 8.91 3.51 1.52 1.04 1.80 1.71 4.55 2.18 3.60 28.81 0.67 0.76 0.40 1.83 9.30 2.97 1.09 1.88 1.78 5.46 4.19 26.67 AREA TO DETENTION POND 0.84 0.79 0.42 2.05 AREA TO ROCK PRAIRIE ROAD 100-YR CFS 1.48 0.17 1.66 9.30 3.66 1.58 1.09 1.88 1.78 4.75 2.28 3.75 30.07 0.70 0.79 0.42 1.91 COMMENTS TABLE 2: DESIGN TRACT AND DETENTION DISCHARGE SUMMARY TABLE DESIGN STORM PRE-DEV EXIST. ULT.POST DEV. NET ALLOWABLE DESIGN TOTAL TRACT TOT AL TRACT PRE FREQUENCY CONDITIONS COND. TO R-0-W DETENTION POND DETENTION POND POST DEVELOPED DEV. ALLOWABLE (YEARS) DISCHARGE (CFS) DISCHARGE (CFS) DISCHARGE (CFS) DISCHARGE (CFS) DISCHARGE (CFS) DISCHARGE (CFS) 5 8.57 2.35 6.22 6.22 8.57 8.57 10 9.33 2.56 6.77 6.77 9.33 9.33 25 11 .01 3.03 7.98 6.82 9.85 11.01 50 12.44 3.42 9.02 7.32 10.74 12.44 100 12.99 3.57 9.42 7.8 11.37 12.99 Notes: Net alllowable det.pond discharge rate= pre-dev existing tract total discharge -ultimate post dev discharge direct to public r-o-w facilities Total tract post development discharge rate equals ult post developed discharge direct to public systems in r-o-w +design pond discharge Project: Plazas at Rock Prairie WLB Project No: 9500502 Time: 7/14/2006 14:57 TABLE 3: DETENTION POND SUMMARY DESIGN STORM ALLOWABLE DET. DESIGN DET POND VOLUME REQD. AT VOLUME PROVIDED DESIGN STORAGE FREQUENCY DISCHARGE RATE DISCHARGE RATE DESIGN DISCHARGE AT DESIGN DISCH. ELEVATION (YEARS (CFS) (CFS) (CF) (CF) (FEET) 5 6.22 6.22 12375 13484 304.48 10 6.77 6.77 13473 17511 304 .96 25 7.98 6.82 16785 18854 305.1 50 9.02 7.32 19341 22884 305.5 100 9.42 7.8 20043 27918 306 Note: Where the design discharge rate is lower than the allowable discharge rate, the required volume has been computed using the design discharge rate. This produces a higher required volume than would have been produced using the allowable rate of discharge (ref exhibits 7C-7E). Project: Plazas at Rock Prairie WLB Project No: 9500502 7/14/2006 14:57 WLB ASSOCIATES, INC. Drainage Report Plazas at Rock Prairie FIGURES 35 30 ~ 25 u 0 w C) 0::: <( ::r:: u (/) 0 Opost = 19.84 cfs 20-+-------- 15 10 5 5 10 ~-----REQUIRED VOLUME OF DETENTION STORAGE FOR 5 YEAR EVENT = DIFFERENCE IN AREA = 12,258 C.F. ~ POST-DEVELOPMENT / HYDROGRAPH ~E-DEVELOPMENT 15 20 25 TIME, minutes (/) Q) ...,, :l .~ E 0 I") II ..Y I") 30 FIGURE NUMBER 7 A PRE-AND POST- DEVELOPMENT HYDROGRAPH FOR 5-YEAR STORM EVENT PLAZAS AT ROCK PRAIRIE VISTA EQUITIES GROUP w Iii :g ABBOC:EA'l'EB. DIC. CXlllSA.'llllQ DIGllEElll 791 !I WESTGlDI HOUSTON, lEXAS n oel TD. 713-278-9300 FAX 713-9!13-2!115 PRo.ECT No: 9500!502 5 YEAR EXHIBIT (fJ '+-u 35 30 25 O Opost = 21 .60 cfs w ('.) O::'. <( ::r:: u (/) 0 20 15 10 5 5 10 ~-----REQUIRED VOLUM E OF DETENTION STORAGE FOR 10 YEAR EVENT = DIFFERENCE IN AREA = 13,347 C.F. r POST-DEVELOPMENT / HYDROGRAPH ~PRE-DEVf.LDPMENT HYDROGRAPH 15 20 TIM E, minutes 25 (/) Q) ..... ::l -~ E 0 I") 30 FIGURE NUMBER 78 PRE-AND POST- DEVELOPMENT HYDROGRAPH FOR 10-YEAR STORM EVENT PLAZAS AT ROCK PRAIRIE VISTA EQUITIES GROUP W Iii B ABBOCIA'l"BB. DIC. CIDMSA.'lllCI IJIGllEIRS 7915 WESTIUN HOUSTON, TEXAS 77083 1U. 713-2711-9300 fAX 713-953-2515 PROJECT Moo 9500502 10 YEAR EXHIBIT (/) '+- () a w (_') 0::: <t: ::r:: u (/) 0 35 30 25 20 15 10 5 Qpost = 25.4 7 cfs 5 10 I I I I I I I I I I I I / I I I I I I I I I I I I I I 15 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I ~ I REQUIRED VOLUME OF DETENTION STORAGE FOR 25 YEAR EVENT = DIFFERENCE IN AREA = 15,741 C.F. AT ALLOWABLE DISCHARGE RATE 7.98 CFS. FOR REDUCED DESIGN DISCHARGE RATE OF 6.82 CFS THE VOLUME REQUIRED INCREASES TO 16,785 C.F. / POST-DEVELOPMENT HYDROGRAPH I 20 25 E 0 n II ~ n 30 FIGURE NUMBER 7C PRE-AND POST- DEVELOPMENT HYDROGRAPH FOR 25-YEAR STORM EVENT PLAZAS AT ROCK PRAIRIE VISTA EQUITIES GROUP WL~ ABBOCIA"l"m:B. DSC. CCllllUL'llllO DIGIGRS TIME, minutes 7915 WESTGl.EN HOUSTON, TEXAS noel TEL 713-27&-9300 f'AX 713-953-2515 PRO.£CT No: 9S00502 25 YEAR EXHIBIT ({) 4-u 0 w (.'.) 0:::: <( ::r:: u (/) 0 35 30 Opost = 28.81 cfs 25 20 15 Opre = 9 02 cfs 10 (ALLOW LE DISCHARGE) Odes= 7.32 cfs 5 II (.) ..., 10 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I / I I I I I I ~ I I I I I I I I I I ,--REQUIRED VOLUME OF DETENTION STORAGE FOR 50 YE AR / EVENT = DIFFERENCE IN AREA = 17,811 C.F. AT / ALLOWABLE DISCHARGE RATE OF 9.02 CFS FOR REDUCED DESIGN DISCHARGE RATE OF 7.32 CFS THE VOLUME REQUIRED INCREASES TO 19,341 C.F. POST-DEVELOPMENT HYDROGRAPH E 0 I"') FIGURE NUMBER 70 PRE-AND POST- DEVELOPMENT HYDROGRAPH FOR 50-YEAR STORM EVENT PRE-DEVELOPMENT ~ HYDROGRAPH PLAZAS AT ROCK PRAIRIE DESIGN 50-YR DISCHARGE HYDROGRAPH 15 20 TIME, minutes 25 30 VISTA EQUITIES GROUP WLB A880C:IA'l"B8. IKC. COlllUl.1llO DICIMllll 7915 WESTCl.£N HOUSTON, 1EXAS 77083 lEL 713-27&-llJOO FAX 713-1153-2515 PRO.ECT Ncx 11500!!02 50 YEAR EXHIBIT (f) '+-0 w G er:: <( ::r:: u (/) 0 35 30 25 20 15 10 5 Opost = 30.07 cfs 5 10 I I I I I I / I I I I I I / I I I I I I I I I I I I I I I I I I I I I I I ,--REQUIRED VOLUME OF DETENTION STORAGE FOR 25 YEAR / EVENT = DIFFERENCE IN AREA = 18,585 C.F. AT / ALLOWABLE DISCHARGE RATE OF 9.42 CFS. I I I / FOR REDUCED DESIGN DISCHARGE RATE OF 7.80 CFS TH E / VOLUME REQUIRED INCREASES TO 20,040 C.F. / POST-DEVELOPMENT HYDROGRAPH I / FIGURE NUMBER 7E I I ~ PRE-DEVELOPMENT~ HYDROGRAPH DESIGN 100-YR DISCHARGE HYDROGRAPH 15 20 TIME, minutes 25 0 n II ..Y n 30 PRE-AND POST- DEVELOPMENT HYDROGRAPH FOR 100-YEAR STORM EVENT PLAZAS AT ROCK PRAIRIE VISTA EQUITIES GROUP w Iii g ABBOCIA'l'BB. DIC. CllllSIL11NQ DIGllEEltl 7915 WESTGUN HOUSTON, lEXAS n oel 1E.. 713-27&-9300 FAX 713-953-2515 PRO.ECT Nae 9500502 100 YEAR EXHIBIT c: 0 ~ 0 "' u "' iJ -0 ~ a.. w c I ~ I w ::Ii! ~ "' 0 I x ~ ~ m :c x 40,000 ................................................ . 35,000 ................................................ . 30,000 ........................................ . .......... LL. ~ 25,000 ................................... . w ~ => 20,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............... . _J 0 > w > 1-- <t:: _J => ~ => u 15,000 ................................................ . 10,000 . . . . . . . . . . . . . . . . . . . . ........................... . 5000 I POND aonou .....•.........•......... : ........ . 0 """-~~~~~~~~~~~~~~~~~~~~~~~--' 0 1 2 3 4 5 (EL. 302) (EL. 303) (EL. 304) (EL. 305) (EL. 306) (EL. 307) DEPTH OF STORAGE (FT.) REV. 07 05 06 ~ ~ FIGURE NUMBER 9 < 0:: a.. DETENTION POND ~ g VOLUME VERSUS ~ DEPTH GRAPH <( ~ PLAZAS AT ~ ROCK PRAIRIE ~ VISTA EQUITIES 8 GROUP 0 LO ~ ~~D ~ ABBOCIA"l"EB. DIC • ..., CCN9UL11NO DIQNEERS 6 7915 WESTGL£N HOUSTON, 1EXAS 77063 <C lEl 713-278-11300 f'AX 713-953-2515 ~ PROJECT No: 11500502 POND VOLUME EXHIBIT 6'-~~~~~~~~~~~~~~~~~~~~~~~~~~....i..~~~~....i..~~~~....i c 0 ~ 0 "' u "' 3' "O ~ c.. w 0 I ~ I ~ a:: < ::c (.) V) 9 0 i x ~ ~ iii ~ ~ w Ci: < a:: c.. ~ (.) 0 a:: I-< ,-.... (/) La... (_) ......_, ~ 0 _J La... .,__ w _J .,__ ::> 0 60 55 50 45 40 35 30 25 20 15 (/) z (!) ............................................... laJ CD 0:: ·········>········:·········:········<········~ I-• • L&.J ......... : ......... : ......... : ......... : ....... F. ::> 0 . . . . >-................................................ U z L&.J (!) . . . . 0:: ............................................... -~ L&.J . . . . 0:: . ··············································~ 0 == ................................................ g LL 10 .......................................................... . 6.82 : 5.67 . 5 0 ',fr"""-~~~~~~~~~~~~~~~~~~~~~~~~~~~--' (EL. 301.37) (EL. 302) (EL. 303) (EL. 304) (EL. 305) (EL. 306) (EL. 307) ELEVATION (FT) FIGURE NUMBER 10 POND OUTLET DISCHARGE RA TE VERSUS DEPTH GRAPH PLAZAS AT ROCK PRAIRIE VISTA EQUITIES GROUP ft' Iii :g ABBOCIA'l'BB. DIC. CON9UL11NQ ENQNEERS 71115 WESTGLEN HOUSTON, lEXAS nosJ lEl 713-278-9300 FAX 713-953-2515 PRo.E:CT No: 11500502 DISCHARGE RA lE EJOtlllT